50 results on '"Zaitsev, Alexander"'
Search Results
2. Influence of the drag coefficient model on the dynamics of particle motion in the shock wave from the descent vehicle.
- Author
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Polyansky, Timofey and Zaitsev, Alexander
- Subjects
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SHOCK waves , *NAVIER-Stokes equations , *PARTICLE dynamics , *DRAG coefficient , *GAS flow , *DUST , *PARTICLE motion , *MOTION - Abstract
In this work results of numerical simulation of Martian dust particle movement and heat transfer in detached shock wave around descent vehicle are presented. Gas flow calculation was carried out in continual approach based on Navier Stokes equations. For particle simulation Lagrange method was used. Various models of drug coefficient calculation were considered and compared for different dust fractions. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
3. Combustion rate and ignition delay time of boron particles in flat-flame burner experiments.
- Author
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Ermolaev, Grigoriy V., Zaitsev, Alexander V., Azyazov, Valeriy N, and Mebel, Alexander M.
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FLUIDIZED-bed combustion , *COMBUSTION , *FLAME temperature , *HEAT release rates , *BORON , *SHOCK tubes - Abstract
The main part of available data on boron particles combustion was obtained in flat-flame burner experiments. Boron particles were injected into flat-flame burner post-flame zone with a transporting jet of cold nitrogen; the combustion process of boron particles was registered with a number of optical methods. Systematization of ignition delay and combustion times of boron particles obtained in that type of experiment was done. Combustion times are represented in the form of particles linear combustion speeds. Combustion speed shows classic dependence on temperature, at low temperatures the reaction is temperature dependent and seems to be kinetically controlled, at high temperatures the reaction is diffusion controlled one. Most of the combustion data was obtained in wet environment. Kinetically controlled combustion depends on surrounding gas temperature, so the heat generation doesn't significantly heat the particle above the ambient temperature, such an effect is possible if heat release of the reaction on the surface of the particle is reduced. Ignition delay time shows smooth decay with flame temperature growth in each of the individual experiment but random values between independent measurements. The particles of the same size at the same flame temperature can show 1 or 5 ms ignition delay in independent experiments, and are several orders higher than in shock tube experiments. Supposition of inner hidden influencing factor specific for flat-flame burner experiments is done. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
4. Intensity dependent features of the light-induced gasification of the waste-derived coal-water compositions.
- Author
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Egorov, Roman I., Zaitsev, Alexander S., Li, Hong, Gao, Xin, and Strizhak, Pavel A.
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RENEWABLE energy sources , *CONTINUOUS wave lasers , *BIOMASS gasification , *LIGHT intensity , *INDUSTRIAL wastes , *SYNTHESIS gas - Abstract
Nowadays, the recovery of combustible industrial waste is a very popular approach to supply cheap fuel to various consumers. However, due to the physical and chemical properties of the waste, it requires special preparation to be used effectively. The main features of the direct light-induced conversion of waste-derived coal-water compositions to syngas were investigated. Unlike classical techniques, the proposed method involves solar light, which is a renewable energy source. The fundamental intensity thresholds were shown when fuel was gasified by nanosecond pulses (8 J / c m 2 ) and continuous wave laser light (700 − 800 W / c m 2 ). Such light flow parameters are fully achievable by solar radiation. The dependencies of syngas component concentrations on the light intensity were shown as well as similar dependencies for the conversion rate and specific conversion energy (∼ 3.5 M J / k g for optimal gasification conditions). Image 1 • The efficiency of the gasification versus the light intensity was measured. • An effective gasification requires CW light intensity above 700 W/cm2. • Gasification by nanoisecond pulses starts if pulse energy is above 8 J/cm2. • Nanosecond pulses produce the finely dispersed fuel together with syngas. • CO2 wasn't observed during the laser processing of the coal-water slurry. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
5. Influence of Injection Parameters on Combustion Time of Boron Particle in Hot Gas Flow.
- Author
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Ermolaev, Grigory and Zaitsev, Alexander
- Abstract
The basic experimental studies on boron combustion are done with the same general scheme of the experiment. Boron particles are injected in to flat flame burner products with a help of the transporting jet of a cold nitrogen, boron particle combustion process is registered with a number of optical methods. It is proposed that boron particle is injected in to the main hot gas flow instantly, combustion takes place at flame temperature and predefined oxygen concentration, influence of the transporting cold nitrogen jet is ignored. Recent combustion models are based mostly on that type of experiment and characterized with high complexity and low prediction level. In our study we reconstruct particle injection conditions for several basic experimental papers. It is shown that in all experimental setups ignition, combustion and even total particle burn out takes place in a wake of cold nitrogen jet. This area is characterized with much lower gas temperature and oxygen concentration than the main flat burner flow. Total temperature decrease can be about several hundred degrees, oxygen concentration can be seriously 30-50% lower than used in previous analysis of experimental result. Ignition and transition to second stage of combustion temperatures are found with a help of the test particle trajectory and temperature tracking. It is shown that analysis of boron particles injection influence on gas temperature and oxygen concentration is obligatory for future combustion model. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
6. Influence of Injection Parameters on Combustion Time of Boron Particle in Hot Gas Flow.
- Author
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Ermolaev, Grigory and Zaitsev, Alexander
- Subjects
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BORON , *COMBUSTION , *PARTICLES , *JETS (Fluid dynamics) , *BURNERS (Technology) - Abstract
The basic experimental studies on boron combustion are done with the same general scheme of the experiment. Boron particles are injected in to flat flame burner products with a help of the transporting jet of a cold nitrogen, boron particle combustion process is registered with a number of optical methods. It is proposed that boron particle is injected in to the main hot gas flow instantly, combustion takes place at flame temperature and predefined oxygen concentration, influence of the transporting cold nitrogen jet is ignored. Recent combustion models are based mostly on that type of experiment and characterized with high complexity and low prediction level. In our study we reconstruct particle injection conditions for several basic experimental papers. It is shown that in all experimental setups ignition, combustion and even total particle burn out takes place in a wake of cold nitrogen jet. This area is characterized with much lower gas temperature and oxygen concentration than the main flat burner flow. Total temperature decrease can be about several hundred degrees, oxygen concentration can be seriously 30-50% lower than used in previous analysis of experimental result. Ignition and transition to second stage of combustion temperatures are found with a help of the test particle trajectory and temperature tracking. It is shown that analysis of boron particles injection influence on gas temperature and oxygen concentration is obligatory for future combustion model. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
7. Interfaces between Model Co-W-C Alloys with Various Carbon Contents and Tungsten Carbide.
- Author
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Konyashin, Igor, Zaitsev, Alexander, Meledin, Alexander, Mayer, Joachim, Loginov, Pavel, Levashov, Evgeny, and Ries, Bernd
- Subjects
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COBALT-tungsten alloys (Heat-resistant) , *INTERFACES (Physical sciences) , *TUNGSTEN carbide , *SINTERING , *PRECIPITATION (Chemistry) , *SIMULATION methods & models - Abstract
Interfaces between alloys simulating binders in WC-Co cemented carbides and tungsten carbide were examined on the micro-, nano-, and atomic-scale. The precipitation of fine WC grains and η-phase occurs at the interface of the alloy with the low carbon content. The precipitation of such grains almost does not occur in the alloy with the medium-low carbon content and does not take place in the alloy with the high carbon content. The formation of Co nanoparticles in the binder alloy with the medium-low carbon content was established. Interfaces in the alloy with the medium-low carbon content characterized by complete wetting with respect to WC and with the high carbon content characterized by incomplete wetting were examined at an atomic scale. The absence of any additional phases or carbon segregations at both of the interfaces was established. Thus, the phenomenon of incomplete wetting of WC by liquid binders with high carbon contents is presumably related to special features of the Co-based binder alloys oversaturated with carbon at sintering temperatures. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
8. Spanish Renaissance High Culture in Soviet Historiography: Interdisciplinary Aspect.
- Author
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Zaitsev, Alexander A. and Antonova, Natalia V.
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RENAISSANCE , *SOCIAL history , *SPANISH civics ,HISTORY of the Soviet Union - Abstract
The tradition of studying Spanish Renaissance in Russia is quite a complicated phenomenon, which requires a detailed analysis. The main questions which arise when referring to the issue are those of developmental patterns and interdisciplinary aspect of the letter. Spanish Renaissance culture is traditionally the subject to scrutiny for historians, philologists and art historians. The present article aims to outline a preliminary picture of interdisciplinary interaction, which gained momentum in the Soviet period of Russian Hispanism. Special attention is paid to the imminent figures of Spanish Renaissance historiography, as well as their ideas and concepts. The evolution of Spanish Renaissance studies is described against the background of the principal research areas. The present paper will be of interest to both intellectual historians and scholars investigating Renaissance and medieval history. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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9. Prospective directions for development of metallurgy and materials science of steel.
- Author
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Zaitsev, Alexander I.
- Subjects
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STEEL metallurgy , *MATERIALS science , *METAL inclusions , *RAW materials , *UNIFORMITY - Abstract
The features of current state of metallurgical technology and materials science of mass high-grade steels are viewed. A promising direction for principle improvement of the complex of properties and qualitative characteristics of steel including those, which are difficult to combine, is shown. It is the development of adequate physico-chemical methods of prediction and efficient technology methods of management of non-metallic inclusions, forms of presence of impurities, phases precipitations, structural state, including uniformity over the volume of metal. Additionally this approach allows reducing costs and expanding the raw material base. Its effectiveness is illustrated by the results of research carried out for a number of groups of mass high-quality steels. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
10. Temperature and chemical sensitivity of carbon films on quartz
- Author
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Kumar, Vivek and Zaitsev, Alexander M.
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CARBON films , *TEMPERATURE effect , *QUARTZ , *ELECTRIC insulators & insulation , *ELECTRIC conductivity , *VACUUM , *AMMONIA , *SPUTTERING (Physics) - Abstract
Abstract: Insulating to conductive carbon films were obtained by controlled vacuum annealing of the disordered carbon films deposited on quartz by sputtering of carbon. The change of conductance of the films has been studied on exposure to the vapors of NH3 and NO2, chosen for their opposite donor–acceptor properties. The chemical sensitivity of conductance along with temperature sensitivity is discussed in terms of atomic ordering of the as-deposited films induced by heating at high temperatures and revealed by Raman scattering measurements. The observed dependence of conductance on temperature is explained by a model based on the charge tunneling through thermal vibrational barriers, the average height and width of which change with atomic ordering. Phenomenological description of chemical sensing by the films is given in terms of the time constant τ and the maximum relative change in conductance β, related to the surface and material properties of the films respectively. The expression σ = β/τ is considered a measure of the chemical sensitivity of the films and changes with modifications in the material structure of the films on annealing. [Copyright &y& Elsevier]
- Published
- 2012
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11. Classification of interstellar radio messages
- Author
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Zaitsev, Alexander
- Subjects
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INTERSTELLAR communication , *ASTROPHYSICS , *RADIO astronomy , *ASTRONOMY , *ASTRONOMICAL research , *TELECOMMUNICATION - Abstract
Abstract: Using the proposed classification criteria, all known interstellar radio messages are divided into two essentially different groups—scientifically based messages and pseudo-messages. Imitation of interstellar transmissions by most of the exo-civilizations can cause the Great Silence. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
12. Market mill dependence pattern in the stock market: Multiscale conditional dynamics
- Author
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Zaitsev, Sergey, Zaitsev, Alexander, Leonidov, Andrei, and Trainin, Vladimir
- Subjects
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STOCK exchanges , *NONLINEAR systems , *STATISTICAL correlation , *STOCK prices , *INFORMATION asymmetry , *DISTRIBUTION (Probability theory) - Abstract
Abstract: Market Mill is a complex dependence pattern leading to nonlinear correlations and predictability in intraday dynamics of stock prices. The present paper puts together previous efforts to build a dynamical model reflecting the market mill asymmetries. We show that certain properties of the conditional dynamics at a single time scale such as a characteristic shape of an asymmetry-generating component of the conditional probability distribution result in the “elementary” market mill pattern. This asymmetry-generating component matches the empirical distribution obtained from the market data. Multiple time scale considerations make the resulting “composite” mill similar to the empirical market mill patterns. Multiscale model also reflects a multi-agent nature of the market. Interpretation of variations of asymmetry patterns of individual stocks in terms of specific deformations of the fundamental market mill asymmetry patterns is described. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
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13. Sending and searching for interstellar messages
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Zaitsev, Alexander L.
- Subjects
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INTERSTELLAR communication , *EXTRATERRESTRIAL beings , *ASTRONOMICAL research , *EXTRATERRESTRIAL life , *SYNCHRONIZATION , *TIME measurements - Abstract
Abstract: There is a close interrelation between searching for extraterrestrial intelligence (SETI) and messaging to extraterrestrial intelligence (METI). For example, the answers to the questions “Where to search” and “Where to send” are equivalent, in that both require an identical selection from the same target star lists. Similar considerations lead to a strategy of time synchronization between sending and searching. Both SETI and METI use large reflectors. The concept of “magic frequencies” may be applicable to both SETI and METI. Efforts to understand an alien civilization''s interstellar messages (IMs), and efforts to compose our own IMs so they will be easily understood by unfamiliar extraterrestrials, are mutually complementary. Furthermore, the METI-question: “How can we benefit from sending IMs, if a response may come only thousands of years later?” begs an equivalent SETI-question: “How can we benefit from searching, if it is impossible now to perceive the motivations and feelings of those who may have sent messages in the distant past?” A joint consideration of the theoretical and the practical aspects of both sending and searching for IMs, in the framework of a unified, disciplined scientific approach, can be quite fruitful. We seek to resolve the cultural disconnect between those who advocate sending interstellar messages, and others who anathematize those who would transmit. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
14. Glueballs, hybrids, multiquarks: Experimental facts versus QCD inspired concepts
- Author
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Klempt, Eberhard and Zaitsev, Alexander
- Subjects
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QUANTUM chromodynamics , *LATTICE theory , *ENERGY levels (Quantum mechanics) , *PHYSICS - Abstract
Abstract: Glueballs, hybrids and multiquark states are predicted as bound states in models guided by quantum chromo dynamics (QCD), by QCD sum rules or QCD on a lattice. Estimates for the (scalar) glueball ground state are in the mass range from 1000 to 1800MeV, followed by a tensor and a pseudoscalar glueball at higher mass. Experiments have reported evidence for an abundance of meson resonances with and quantum numbers. In particular, the sector of scalar mesons is full of surprises starting from the elusive and mesons. The and , discussed extensively in the literature, are reviewed with emphasis on their Janus-like appearance as molecules, tetraquark states or mesons. Most exciting is the possibility that the three mesons , , and might reflect the appearance of a scalar glueball in the world of quarkonia. However, the existence of is not beyond doubt and there is evidence that both and are flavour octet states, possibly in a tetraquark composition. We suggest a scheme in which the scalar glueball is dissolved into the wide background into which all scalar flavour-singlet mesons collapse. There is an abundance of meson resonances with the quantum numbers of the . Three states are reported below whereas quark models expect only one, perhaps two. One of these states, , was the prime glueball candidate for a long time. We show that is the first radial excitation of the meson. Hybrids may have exotic quantum numbers which are not accessible by mesons. There are several claims for exotics, some of them with properties as predicted from the flux tube model interpreting the quark–antiquark binding by a gluon string. The evidence for these states depends partly on the assumption that meson–meson interactions are dominated by s-channel resonances. Hybrids with non-exotic quantum numbers should appear as additional states. Light-quark mesons exhibit a spectrum of (squared) masses which are proportional to the sum of orbital angular momentum and radial quantum numbers. Two states do not fall under this classification. They are discussed as hybrid candidates. The concept of multiquark states has received revived interest due to new resonances in the spectrum of states with open and hidden charm. The new states are surprisingly narrow and their masses and their decay modes often do not agree with simple quark-model expectations. Lattice gauge theories have made strong claims that glueballs and hybrids should appear in the meson spectrum. However, the existence of a scalar glueball, at least with a reasonable width, is highly questionable. It is possible that hybrids will turn up in complex multibody final states even though so far, no convincing case has been made for them by experimental data. Lattice gauge theories fail to identify the nonet of scalar mesons. Thus, at the present status of approximations, lattice gauge theories seem not to provide a trustworthy guide into unknown territory in meson spectroscopy. [Copyright &y& Elsevier]
- Published
- 2007
- Full Text
- View/download PDF
15. Nitrogen in CVD-Grown Diamond.
- Author
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Zaitsev, Alexander M., Kyaw Soe Moe, and Wuyi Wang
- Subjects
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DIAMONDS , *CHEMICAL vapor deposition - Abstract
The article presents a study of nitrogen-doped specimens grown in the chemical vapor deposition (CVD) diamond laboratory of the Gemological Institute of America (GIA) to gain a better understanding on how nitrogen behaves in CVD-grown diamond.
- Published
- 2018
16. Electron irradiation-induced paramagnetic and fluorescent defects in type Ib high pressure–high temperature microcrystalline diamonds and their evolution upon annealing.
- Author
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Nunn, Nicholas, Milikisiyants, Sergey, Danilov, Evgeny O., Torelli, Marco D., Dei Cas, Laura, Zaitsev, Alexander, Shenderova, Olga, Smirnov, Alex I., and Shames, Alexander I.
- Subjects
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ELECTRON beams , *NANODIAMONDS , *ELECTRON paramagnetic resonance , *ELECTRON paramagnetic resonance spectroscopy , *DIAMONDS , *HIGH temperatures , *OPTICAL engineering - Abstract
Defects introduced to synthetic type Ib diamond micrometer-size particles by electron-beam irradiation were studied by electron paramagnetic resonance and photoluminescence (PL) spectroscopy as a function of e-beam fluence and post-irradiation thermal annealing. Increasing electron-beam fluence causes a substantial reduction of the substitutional nitrogen (P1) content, accompanied by progressively higher concentrations of paramagnetic negatively charged vacancies (V−) and triplet interstitials (R1/R2). Annealing results in a drastic decrease in the V− and R1/R2 content and an increase in the negatively charged nitrogen-vacancies (NV− or W15). Analysis of PL spectra allows for identification of color centers in the irradiated diamond samples and following their evolution after annealing. These data facilitate understanding of different factors contributing to the formation of color centers in diamond and promote efforts toward controlled engineering of optical centers in fluorescent diamond particles. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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17. The Genetic Diversity of Horse Native Breeds in Russia.
- Author
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Atroshchenko, Mikhail, Dementieva, Natalia, Shcherbakov, Yuri, Nikolaeva, Olga, Azovtseva, Anastasiia, Ryabova, Anna, Nikitkina, Elena, Makhmutova, Oksana, Datsyshin, Andrey, Zakharov, Viktor, and Zaitsev, Alexander
- Subjects
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HORSE breeding , *GENETIC variation , *HORSE breeds , *HORSE sports , *ANIMAL breeding , *ANIMAL breeds - Abstract
Horses were domesticated later than other farm animals. Horse breeds have been selectively developed by humans to satisfy different needs and purposes. The factory and indigenous breeds are of particular interest, having been bred in purity for many centuries without the addition of foreign blood. Data from 31 stud farms, as well as ranches, located in fifteen regions of the Russian Federation were used in this work. DNA was sampled from 102 stallions of 11 breeds: Arabian, Akhal-Teke, Don, Orlov Trotter, Vladimir Heavy Draft, Russian Heavy Draft, Soviet Heavy Draft, Kabardin, Yakut, Tuva, and Vyatka. Data on the origin of each animal from which the material was collected were taken into account. DNA genotyping was carried out using GGP Equine 70 k ® array chips (Thermo Fisher Scientific, USA). Genetic diversity of horse breeds was estimated using Admixture 1.3. and PLINK 1.9 software. FROH inbreeding was computed via the R detectRUNS package. The minimum length for ROH was set at 1 Mb to reduce the occurrence of false positives. We conducted PCA analysis using PLINK 1.9, and used the ggplot2 library in R for visualizing the results. Indigenous equine breeds, such as Vyatka, Tuva, and Yakut, are very hardy, and well adapted to local environmental and climatic conditions. They are employed as draft power, as well as for milk and meat. Both the Akhal-Teke breed and the Arabian breed have retained a minimum effective population size over many generations. We note significant accumulations of homozygosity in these breeds. In equestrian sports, performance is a top priority. ADMIXTURE and PCA analyses showed similarities between Don equine breeds and Kabardin, as well as some Arabian breed animals. Earlier research indicated the presence of thoroughbred traits in Don stallions. The Orlov Trotter breed stands out as a separate cluster in the structural and PCA analyses. Considering the small population size of this breed, our study found high FROH in all tested animals. The general reduction in the diversity of the horse breed gene pool, due to numerous crosses for breed improvement with thoroughbreds, has lead to a decline in the differences between the top sporting breeds. Our study presents new opportunities for exploring the genetic factors that influence the formation of adaptive traits in indigenous breeds, and for finding ways to preserve genetic diversity for effective population reproduction. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
18. High‐dynamic‐range transmission‐mode detection of synchrotron radiation using X‐ray excited optical luminescence in diamond.
- Author
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Stoupin, Stanislav, Antipov, Sergey, and Zaitsev, Alexander M.
- Subjects
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SYNCHROTRON radiation , *X-rays , *PHOTON flux , *NANODIAMONDS , *DIAMONDS , *ELECTRON beams , *HARD X-rays , *LUMINESCENCE - Abstract
Enhancement of X‐ray excited optical luminescence in a 100 µm‐thick diamond plate by introduction of defect states via electron beam irradiation and subsequent high‐temperature annealing is demonstrated. The resulting X‐ray transmission‐mode scintillator features a linear response to incident photon flux in the range 7.6 × 108 to 1.26 × 1012 photons s−1 mm−2 for hard X‐rays (15.9 keV) using exposure times from 0.01 to 5 s. These characteristics enable a real‐time transmission‐mode imaging of X‐ray photon flux density without disruption of X‐ray instrument operation. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
19. Microscale Simultaneous Measurement of Carbon and Nitrogen Isotopes on Natural Diamond.
- Author
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Ishida, Akizumi, Kitajima, Kouki, Hashizume, Ko, Spicuzza, Michael J., Zaitsev, Alexander, Schulze, Daniel J., and Valley, John W.
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CARBON isotopes , *NITROGEN isotopes , *PHOTOMULTIPLIERS , *DIAMONDS , *SECONDARY ion mass spectrometry , *CARBON analysis - Abstract
Simultaneous analysis of carbon and nitrogen isotope ratios by SIMS was applied for the first‐time to a natural diamond from the Kelsey Lake kimberlite, State Line Distinct, Colorado (UWD‐1). This in situ procedure is faster, reduces sample size for analysis, and measures both isotope ratios from a single ~ 10 μm diameter pit, a critical advantage for zoned diamonds. The carbon isotope ratio (expressed as δ13CVPDB) of the bulk UWD‐1 crystal, determined by the conventional combustion method in the present study, is ‐5.9‰ ± 0.2‰ (VPDB, 2s). Nitrogen mass fraction ([N]) and isotope ratio (expressed as δ15NAir) were determined by stepwise combustion and gas‐source mass‐spectrometry, resulting in 553 ± 64 μg g‐1 and ‐6.7‰ ± 1.1‰ (Air, 2s), respectively. Secondary ions of 12C2‐, 12C13C‐, 12C14N‐, and 12C15N‐ were simultaneously measured by SIMS using three Faraday cups and one electron multiplier. The spot‐to‐spot reproducibility of δ13C and δ15N values for the UWD‐1 (178 spots on sixteen chips, 10 μm spots), were 0.3‰ and 1.6‰, respectively (2s). While 12C14N‐/12C2‐ ratios, which are an indicator for [N], varied up to 12% among these sixteen chips, such variation did not correlate with either δ13C or δ15N values. We propose that UWD‐1 is a suitable reference sample for microscale in situ analysis of δ13C and δ15N values in diamond samples. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
20. Comparative Efficacy and Safety of Mycophenolate Mofetil and Azathioprine in Combination with Corticosteroids in the Treatment of Lymphocytic Myocarditis.
- Author
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Blagova, Olga, Rud', Ruslan, Kogan, Evgeniya, Zaitsev, Alexander, and Nedostup, Alexander
- Subjects
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MYCOPHENOLIC acid , *AZATHIOPRINE , *MYOCARDITIS , *SYSTOLIC blood pressure , *PARVOVIRUS B19 - Abstract
Aims: This paper aimed to study the efficacy and safety of mycophenolate mofetil (MM) in combination with corticosteroids in the treatment of lymphocytic myocarditis (LM) when compared to the standard combination of corticosteroids and azathioprine. Methods. The study included 50 adult patients (47.8 ± 10.8 y.o.) in a NYHA III functional class due to LM who were verified using endomyocardial biopsy. The main group included 29 patients who received MM at 2 g/day. The comparison group comprised 21 patients who received azathioprine at 150 [50; 150] mg/day. Both groups were administered with methylprednisolone. The average follow-up period was 30 [22; 35] months, but no less than 6 months. Results. The groups were comparable in the baseline parameters and standard drug therapy. In both groups, there was a comparable significant increase in the ejection fraction (from 30.6 ± 7.7% to 44.0 ± 9.4% vs. 29.2 ± 7.7% to 46.2 ± 11.8%, p < 0.001), and a decrease in systolic pressure in the pulmonary artery and the dimensions of the left ventricle and atrium. The frequency of death was two (6.9%) and two (9.5%), transplantation was one (3.4%) and one (4.8%) patient and the "death + transplantation" endpoint was three (10.3%) and three (14.3%) without differences between the groups. The presence of the parvovirus B19 in the myocardium in 6/5 patients did not affect the results. The incidence of infectious complications was comparable. The most severe infectious complications were pneumonia and fatal purulent encephalitis (both cases in the azathioprine group), leptospirosis meningitis (in the mycophenolate mofetil group). Conclusions. In the patients with LM, the combination of corticosteroids with MM at a dose of 2 g/day was at least no less effective than with azathioprine. There was a tendency toward a better tolerance using MM. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
21. On the way to mass-scale production of perfect bulk diamonds.
- Author
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Zaitsev, Alexander M.
- Subjects
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ANNEALING of crystals , *DIAMONDS , *LOW pressure (Science) , *CHEMICAL vapor deposition , *HYDROGEN plasmas , *NANOSTRUCTURED materials - Abstract
The article discusses the result of annealed diamonds through low-pressure/high-temperature (LPHT) without the application of stabilizing pressure. The LPHT annealing was run in hydrogen plasma and was examined on chemical vapor deposition (CVD) grown single crystals in temperatures ranging from 1,400 to 2,200 degree Centigrade. In addition, the LPHT annealing controls high-temperature treatment of diamond surfaces which is important for the micro- and nanostructuring of diamonds.
- Published
- 2008
- Full Text
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22. The Genetic Diversity of Stallions of Different Breeds in Russia.
- Author
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Dementieva, Natalia, Nikitkina, Elena, Shcherbakov, Yuri, Nikolaeva, Olga, Mitrofanova, Olga, Ryabova, Anna, Atroshchenko, Mikhail, Makhmutova, Oksana, and Zaitsev, Alexander
- Subjects
- *
HORSE breeding , *GENETIC variation , *HORSE breeds , *STALLIONS , *THOROUGHBRED horse , *HORSES , *GENETIC software - Abstract
The specifics of breeding and selection significantly affect genetic diversity and variability within a breed. We present the data obtained from the genetic analysis of 21 thoroughbred and warmblood horse breeds. The most detailed information is described from the following breeds: Arabian, Trakehner, French Trotter, Standardbred, and Soviet Heavy Horse. The analysis of 509,617 SNP variants in 87 stallions from 21 populations made it possible to estimate the genetic diversity at the genome-wide level and distinguish the studied horse breeds from each other. In this study, we searched for heterozygous and homozygous ROH regions, evaluated inbreeding using FROH analysis, and generated a population structure using Admixture 1.3 software. Our findings indicate that the Arabian breed is an ancestor of many horse breeds. The study of the full-genome architectonics of breeds is of great practical importance for preserving the genetic characteristics of breeds and managing breeding. Studies were carried out to determine homozygous regions in individual breeds and search for candidate genes in these regions. Fifty-six candidate genes for the influence of selection pressure were identified. Our research reveals genetic diversity consistent with breeding directions and the breeds' history of origin. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
23. LPHT annealing of brown-to-yellow type Ia diamonds.
- Author
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Eaton-Magaña, Sally, Ardon, Troy, and Zaitsev, Alexander M.
- Subjects
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DIAMONDS , *LOW pressure (Science) , *HIGH temperatures , *ABSORPTION , *ANNEALING of crystals - Abstract
Low-pressure, high-temperature (LPHT) annealing of yellow-to-brown type Ia natural diamonds was performed to monitor its effects on optical centers within diamond, changes in the observed color, and to assess the process's viability as a commercial gem treatment. With LPHT annealing only, the mostly brown diamonds showed a shift towards yellow coloration; Vis-NIR absorption spectra showed this change was due to a modest increase in H3 intensity. Even at long annealing times (24 h at 1800 °C) or annealing at high temperatures (2000 °C for five minutes), the diamonds did not significantly lose brown coloration. LPHT annealing showed itself as an ineffective means to break apart the vacancy clusters causing the brown color or causing nitrogen disaggregation, which resulted in only a small H3 generation. With LPHT annealing, “amber centers”—a group of several independent bands in the IR between 4200 and 4000 cm − 1 that disappear with HPHT annealing—were seen to anneal out gradually at various temperatures from 1700 to 2000 °C. In contrast, high-pressure, high-temperature (HPHT) annealing effectively removes brown color at similar time/temperature conditions. Without the high stabilizing pressure provided by HPHT annealing techniques, the LPHT annealing showed pronounced damage on inclusions and dramatic surface etching. In subsequent experiments, LPHT annealing was used as a follow-up to laboratory irradiation. The irradiation-related vacancies created greater concentrations of H3 and the vacancy-assisted disaggregation of nitrogen created donors which led to a high concentration of H2 centers. This combination of defects resulted in a pronounced and favorable shift towards saleable yellow colors due to an increase in H3 and a dramatic increase in the H2 center, which led to the suppression of the remaining brownish component. The annealing characteristics for many centers detected by Vis-NIR absorption spectroscopy, FTIR absorption spectroscopy, and photoluminescence spectroscopy were chronicled throughout the study and compared with other LPHT annealing studies and HPHT annealing experiments. [ABSTRACT FROM AUTHOR]
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- 2017
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24. B cell‐dependent subtypes and treatment‐based immune correlates to survival in stage 3 and 4 lung adenocarcinomas.
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Raju Paul, Susan, Valiev, Ivan, Korek, Skylar E., Zyrin, Vladimir, Shamsutdinova, Diana, Gancharova, Olga, Zaitsev, Alexander, Nuzhdina, Ekaterina, Davies, Diane L., Dagogo‐Jack, Ibiayi, Frenkel, Felix, Brown, Jessica H., Hess, Joshua M., Viet, Sarah, Petersen, Jason L., Wright, Cameron D., Ott, Harald C., Auchincloss, Hugh G., Muniappan, Ashok, and Shioda, Toshihiro
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B cells , *NON-small-cell lung carcinoma , *IMMUNE checkpoint inhibitors , *ADENOCARCINOMA , *PROGRESSION-free survival , *GENE expression - Abstract
Lung cancer is the leading cause of cancer‐related deaths worldwide. Surgery and chemoradiation are the standard of care in early stages of non‐small cell lung cancer (NSCLC), while immunotherapy is the standard of care in late‐stage NSCLC. The immune composition of the tumor microenvironment (TME) is recognized as an indicator for responsiveness to immunotherapy, although much remains unknown about its role in responsiveness to surgery or chemoradiation. In this pilot study, we characterized the NSCLC TME using mass cytometry (CyTOF) and bulk RNA sequencing (RNA‐Seq) with deconvolution of RNA‐Seq being performed by Kassandra, a recently published deconvolution tool. Stratification of patients based on the intratumoral abundance of B cells identified that the B‐cell rich patient group had increased expression of CXCL13 and greater abundance of PD1+ CD8 T cells. The presence of B cells and PD1+ CD8 T cells correlated positively with the presence of intratumoral tertiary lymphoid structures (TLS). We then assessed the predictive and prognostic utility of these cell types and TLS within publicly available stage 3 and 4 lung adenocarcinoma (LUAD) RNA‐Seq datasets. As previously described by others, pre‐treatment expression of intratumoral 12‐chemokine TLS gene signature is associated with progression free survival (PFS) in patients who receive treatment with immune checkpoint inhibitors (ICI). Notably and unexpectedly pre‐treatment percentages of intratumoral B cells are associated with PFS in patients who receive surgery, chemotherapy, or radiation. Further studies to confirm these findings would allow for more effective patient selection for both ICI and non‐ICI treatments. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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25. Manufacturing of Metal–Diamond Composites with High-Strength CoCrCu x FeNi High-Entropy Alloy Used as a Binder.
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Loginov, Pavel A., Fedotov, Alexander D., Mukanov, Samat K., Manakova, Olga S., Zaitsev, Alexander A., Akhmetov, Amankeldy S., Rupasov, Sergey I., and Levashov, Evgeny A.
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DIAMOND crystals , *MECHANICAL alloying , *POWDER metallurgy , *COPPER , *ALLOY powders , *TENSILE strength , *DIAMOND surfaces - Abstract
This paper focuses on the study of the structure and mechanical properties of CoCrCuxFeNi high-entropy alloys and their adhesion to single diamond crystals. CoCrCuxFeNi alloys were manufactured by the powder metallurgy route, specifically via mechanical alloying of elemental powders, followed by hot pressing. The addition of copper led to the formation of a dual-phase FCC + FCC2 structure. The CoCrCu0.5FeNi alloy exhibited the highest ultimate tensile strength (1080 MPa). Reductions in the ductility of the CoCrCuxFeNi HEAs and the tendency for brittle fracture behavior were observed at high copper concentrations. The equiatomic alloys CoCrFeNi and CoCrCuFeNi demonstrated high adhesion strength to single diamond crystals. The diamond surface at the fracture of the composites having the CoCrFeNi matrix had chromium-rich metal matrix regions, thus indicating that chromium carbide, responsible for adhesion, was formed at the composite–diamond interface. Copper-rich areas were detected on the diamond surface within the composites having the CoCrCuFeNi matrix due to the predominant precipitation of the FCC2 phase at the interfaces or the crack propagation along the FCC/FCC2 interface, resulting in the exposure of the Cu-rich FCC2 phase on the surface. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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26. Inclusion and point defect characteristics of Marange graphite-bearing diamonds after high temperature annealing.
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Eaton-Magaña, Sally, Ardon, Troy, and Zaitsev, Alexander M.
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POINT defects , *INCLUSIONS (Mineralogy & petrology) , *ANNEALING of crystals , *PHOTOLUMINESCENCE , *RAMAN spectroscopy - Abstract
This study gives an analysis of the effect of low-pressure, high-temperature annealing on the infrared, Raman, and photoluminescence (PL) features, as well as the inclusion characteristics, of cubo-octahedral diamond plates from the Marange deposits in Zimbabwe. The samples showed strong inclusion-related zoning which consists of micron-sized particles identified as graphite and these grew noticeably larger with annealing at temperatures of 300 °C to 1700 °C. Within the natural diamonds, the graphite inclusions (detected by Raman spectroscopy) had a grain size of approximately 1 μm, which increased to 3 μm after 1200 °C and 14 μm after 1700 °C annealing and their hexagonal morphology was discernible. From the geometry of these grains, we determined that they were oriented within the {111} family of planes. The infrared absorption and PL spatial maps were collected after every temperature step to study the effects of annealing on the defects, and photomicrographs and Raman spectra were collected to study the graphite inclusions. The graphitic inclusions grew much larger as the stressed diamond surrounding them converted to graphite. Many nitrogen-related optical centers, including NV − and H3 are no longer detected after high temperature annealing within the cuboid regions as these may have been transformed to hydrogen-bearing complexes such as NVH and N 2 VH. The presence of CH 4 is detected in the unannealed Marange diamonds, but was no longer observed in Raman spectra after 1200 °C annealing. This CH 4 disappearance along with changes in inclusion morphology could provide a method to detect heat treatment if these mixed-habit samples are sourced to create treated black gem diamond. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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27. MORE ON THE "FLUORESCENCE CAGE.".
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Zaitsev, Alexander and Dobrinets, Inga
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LETTERS to the editor , *FLUORESCENCE - Abstract
A response by Alexander Zaitsev and Inga Dobrinets to a letter to the editor about their article "'Fluorescence Cage': Visual Identification of HPHT-Treated Type I Diamonds" in the Fall 2009 issue is presented.
- Published
- 2009
28. Magnetic-field-dependent stimulated emission from nitrogen-vacancy centers in diamond.
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Hahl, Felix A., Lindner, Lukas, Vidal, Xavier, Tingpeng Luo, Takeshi Ohshima, Shinobu Onoda, Shuya Ishii, Zaitsev, Alexander M., Capelli, Marco, Gibson, Brant C., Greentree, Andrew D., and Jeske, Jan
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STIMULATED emission , *GEOMAGNETISM , *SUPERCONDUCTING quantum interference devices , *RABI oscillations , *SEMICONDUCTOR lasers , *DIAMONDS , *MAGNETIC field measurements , *NANODIAMONDS - Abstract
The article studies negatively charged nitrogen-vacancy (NV) centers in diamond and its importance in the field of medical and geological exploration. It discusses that best magnetic field sensitivities are reached by superconducting quantum interference devices (SQUIDs) and vapor cells; to achieve strong stimulated emission pumping of a high number of NV centers is needed, demonstration of strong light amplification, to investigate the magnetic field dependency of the measured amplification.
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- 2022
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29. Systemic chemotherapy decreases brain glucose metabolism.
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Horky, Laura L., Gerbaudo, Victor H., Zaitsev, Alexander, Plesniak, Wen, Hainer, Jon, Govindarajulu, Usha, Kikinis, Ron, and Dietrich, Jörg
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CANCER chemotherapy , *GLUCOSE metabolism , *LUNG cancer patients , *LUNG cancer treatment , *FUNCTIONAL magnetic resonance imaging , *NEUROTOXICOLOGY - Abstract
Objective Cancer patients may experience neurologic adverse effects, such as alterations in neurocognitive function, as a consequence of chemotherapy. The mechanisms underlying such neurotoxic syndromes remain poorly understood. We here describe the temporal and regional effects of systemically administered platinum-based chemotherapy on glucose metabolism in the brain of cancer patients. Methods Using sequential FDG- PET/ CT imaging prior to and after administration of chemotherapy, we retrospectively characterized the effects of intravenously administered chemotherapy on brain glucose metabolism in a total of 24 brain regions in a homogenous cohort of 10 patients with newly diagnosed non-small-cell lung cancer. Results Significant alterations of glucose metabolism were found in response to chemotherapy in all gray matter structures, including cortical structures, deep nuclei, hippocampi, and cerebellum. Metabolic changes were also notable in frontotemporal white matter (WM) network systems, including the corpus callosum, subcortical, and periventricular WM tracts. Interpretation Our data demonstrate a decrease in glucose metabolism in both gray and white matter structures associated with chemotherapy. Among the affected regions are those relevant to the maintenance of brain plasticity and global neurologic function. This study potentially offers novel insights into the spatial and temporal effects of systemic chemotherapy on brain metabolism in cancer patients. [ABSTRACT FROM AUTHOR]
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- 2014
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30. Hydrogenation features of TiZrHfNbTa high-entropy alloy produced by calcium-hydride synthesis.
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Yudin, Sergey, Volodko, Sergey, Savvotin, Ivan, Berdonosova, Elena, Klyamkin, Semen, Bindyug, Denis, Zaitsev, Alexander, Yakushko, Egor, Moskovskikh, Dmitry, and Zadorozhnyy, Vladislav
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HYDROGEN as fuel , *ALLOYS , *HYDRIDES , *LATTICE constants , *UNIT cell , *TANTALUM - Abstract
A high-entropy alloy TiZrHfNbTa has been synthesized by a method of the mutual reduction of the higher oxides of corresponding metals with calcium hydride. The alloy structure was characterized and hydrogen absorption properties were studied. The alloy of overall equiatomic composition TiZrHfNbTa consists of two BCC phases with unit cell parameters of 3.419 and 3.328 Å. The distribution of the elements was established as follows: Ti 0.21 Zr 0.24 Hf 0.24 Nb 0.25 Ta 0.06 (BCC-I) and Ti 0.15 Zr 0.05 Hf 0.10 Nb 0.08 Ta 0.62 (BCC-II). The hydrogenation behavior of the alloy under different conditions was thoroughly studied. It was shown that complete hydrogenation resulted in the formation of FCC-type (H/M → 2) and BCT-type hydrides (H/M → 1) from BCC-I and BCC-II, respectively. Under low hydrogen pressure (< 212.8 Torr), BCC-I absorbed up to 0.33 at. H/M within a solid solution without changing the structural type. According the kinetic analysis, this process can be described as a second order reaction with activation energy of 102 kJ/mol. The BCC-I-based solid solution is capable of retaining hydrogen in a deep vacuum at a temperature of 430 °C. The fast kinetics of hydrogen absorption and high thermal stability allow us to suggest the studied two-phase TiZrHfNbTa alloy as a promising getter for vacuum devices. [Display omitted] • A TiZrHfNbTa HEA with a high rate of hydrogen sorption was produced from oxide raw materials. • The BCC phase with a large lattice parameter (3.419 Å) dissolves large amounts of hydrogen (up to 22 at%). • The Ti 0.21 Zr 0.24 Hf 0.24 Nb 0.25 Ta 0.06 phase forms an FCC dihydride through an intermediate orthorhombic hydride. • The activation energy of hydrogen dissolution in a BCC solution of HEA was determined and equal ⁓102 kJ/mol. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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31. Quantitative MRI analysis in children with multiple sclerosis: a multicenter feasibility pilot study.
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Chitnis, Tanuja, Guttmann, Charles R., Zaitsev, Alexander, Musallam, Alexander, Weinstock-Guttmann, Bianca, Yeh, Ann, Rodriguez, Moses, Ness, Jayne, Gorman, Mark, Healy, Brian C., Kuntz, Nancy, Chabas, Dorothee, Strober, Jonathan B., Waubant, Emmanuelle, Krupp, Lauren, Pelletier, Daniel, Erickson, Bradley, Bergsland, Niels, and Zivadinov, Robert
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MULTIPLE sclerosis , *GADOLINIUM , *MAGNETIC resonance imaging , *FEASIBILITY studies , *REGRESSION analysis - Abstract
Background Pediatric multiple sclerosis (MS) is a rare disorder with significant consequences. Quantitative MRI measurements may provide significant insights, however multicenter collaborative studies are needed given the small numbers of subjects. The goal of this study is to demonstrate feasibility and evaluate lesion volume (LV) characteristics in a multicenter cohort of children with MS. Methods A common MRI-scanning guideline was implemented at six member sites of the U.S. Network of Pediatric MS Centers of Excellence. We included in this study the first ten scans performed at each site on patients meeting the following inclusion criteria: pediatric RRMS within 3 years of disease onset, examination within 1 month of MRI and no steroids 1 month prior to MRI. We quantified T2 number, T2-LV and individual lesion size in a total of 53 MRIs passing quality control procedures and assessed gadolinium-enhancing lesion number and LV in 55 scans. We studied MRI measures according to demographic features including age, race, ethnicity and disability scores, controlling for disease duration and treatment duration using negative binomial regression and linear regression. Results The mean number of T2 lesions was 24.30 ± 19.68 (range:1-113) and mean gadoliniumenhancing lesion count was 1.85 ± 5.84, (range:0-32). Individual lesion size ranged from 14.31 to 55750.60 mm3. Non-white subjects had higher T2-LV (unadjusted pT2-LV = 0.028; adjusted pT2-LV = 0.044), and maximal individual T2-LV (unadjusted pMax = 0.007; adjusted pMax = 0.011) than white patients. We also found a trend toward larger mean lesion size in males than females (p = 0.07). Conclusion Assessment of MRI lesion LV characteristics is feasible in a multicenter cohort of children with MS. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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32. Characterization of pink diamonds of different origin: Natural (Argyle, non-Argyle), irradiated and annealed, treated with multi-process, coated and synthetic
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Deljanin, Branko, Simic, Dusan, Zaitsev, Alexander, Chapman, John, Dobrinets, Inga, Widemann, Annette, Del Re, Nicholas, Middleton, Tara, Deljanin, Elena, and De Stefano, Andrea
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DIAMONDS , *IRRADIATION , *GEMS & precious stones , *OPTICAL properties - Abstract
Abstract: One of the commercial challenges today in the gem industry is to quickly identify the origin of color in pink diamonds — natural, treated and synthetic by use of standard and advanced gemological instruments. An analytical technique that is used by many gem labs involves UV fluorescence. The principle factors in the technique are the excitation wavelengths and the emission spectra. No systematic study of fluorescence of pink natural diamonds, pink treated and pink synthetic diamonds has been undertaken. This study is mainly focused on using fluorescence techniques to characterize pink diamonds and to compile a reference library of emission spectra. Longwave (LW) and shortwave (SW) fluorescence of 365, 254 and 220 nm illumination were used in a custom built microscope with a fluorescence camera to record images and a spectrometer to record spectral data with which to establish a correlation with the cause of color. Other advanced instruments (CL imaging, UV–VIS–NIR, FTIR, PL spectroscopy and electrical conductance) were used to establish additional criteria for distinguishing natural, treated and synthetic pink diamonds and to find a correlation with the “EGL USA CIS (Cross-reference Identification System) fluorescence method”. [Copyright &y& Elsevier]
- Published
- 2008
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33. Market mill dependence pattern in the stock market: Modeling of predictability and asymmetry via multi-component conditional distribution
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Leonidov, Andrei, Trainin, Vladimir, Zaitsev, Alexander, and Zaitsev, Sergey
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DISTRIBUTION (Probability theory) , *PHYSICAL sciences , *STATICS , *GEOMETRY - Abstract
Abstract: Recent studies have revealed a number of striking dependence patterns in high frequency stock price dynamics characterizing probabilistic interrelation between two consequent price increments x (push) and y (response) as described by the bivariate probability distribution [A. Leonidov, V. Trainin, A. Zaitsev, On collective non-gaussian dependence patterns in high frequency financial data, ArXiv:physics/0506072, A. Leonidov, V. Trainin, A. Zaitsev, S. Zaitsev, Market mill dependence pattern in the stock market: asymmetry structure, nonlinear correlations and predictability, arXiv:physics/0601098, A. Leonidov, V. Trainin, A. Zaitsev, S. Zaitsev, Market mill dependence pattern in the stock market: distribution geometry, moments and gaussization, arXiv:physics/0603103, A. Leonidov, V. Trainin, A. Zaitsev, S. Zaitsev, Market mill dependence pattern in the stock market: distribution geometry. Individual portraits, arXiv:physics/0605138]. There are two properties, the market mill asymmetries of and predictability due to nonzero z-shaped mean conditional response, that are of special importance. Main goal of the present paper is to put together a model reproducing both the z-shaped mean conditional response and the market mill asymmetry of with respect to the axis . We develop a probabilistic model based on a multi-component ansatz for conditional distribution with push-dependent weights and means describing the both properties. In this paper we also introduce a quantitative measure of the relative weight of the asymmetric component of and show that the model reproduces a pattern observed in the market data. A relationship between the market mill asymmetry and predictability is discussed. A possible connection of the model to agent-based description of market dynamics is outlined. [Copyright &y& Elsevier]
- Published
- 2007
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34. Highly effective p-type doping of diamond by MeV-ion implantation of boron
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Vogel, Thomas, Meijer, Jan, and Zaitsev, Alexander
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ELECTRIC currents , *DIAMONDS , *TEMPERATURE , *AURORAL electrojet - Abstract
Boron ions (2 MeV) were implanted into type IIa natural diamond samples to create deep buried conducting layers. The implantation was carried out at room temperature, followed by furnace annealing at temperatures up to 1650 °C. Data of Hall effect and conductivity measurements are presented in a wide temperature range, which clearly show p-type conduction with an activation of up to 30% of the implanted boron atoms, which is the highest value yet reported for ion implanted diamond. [Copyright &y& Elsevier]
- Published
- 2004
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35. Phase Noise of an HTS Resonator Operated in the Nonlinear Regime.
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Vitusevich, Svetlana A., Klein, Norbert, Zaitsev, Alexander G., and Geerk, Jochen
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HIGH temperature superconductors , *RESONATORS , *ELECTRONIC noise , *NONLINEAR systems - Abstract
Nonlinear properties of high-temperature superconducting (HTS) strongly coupled resonators at different input power have been investigated by measurements of the quality factor as a function of input power as well as by generation of the intermodulation distortion (IMD). The double-sided YBCO films on CeOs buffered sapphire demonstrate advanced performance with the microwave surface resistance of ∼ 0.3 mΩ at 8.5 GHz at 77 K and an IMD third-order interception point estimated at P[sub circ] ≈ 70 W. A parallel feedback oscillator was assembled using a transmission type HTS resonator cooled with liquid nitrogen and a room temperature low noise amplifier. Results on the phase noise investigation of the 2.3 GHz oscillator based on HTS resonator operated in the nonlinear regime demonstrated a deviation from the simple model of the phase noise, which predicts an up-conversion of 1/f noise of the amplifier to oscillator phase noise. The later can be explained by the phase noise introduced additionally due to the nonlinear response of the HTS resonator. [ABSTRACT FROM AUTHOR]
- Published
- 2003
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36. Near‐Infrared Fluorescence from Silicon‐ and Nickel‐Based Color Centers in High‐Pressure High‐Temperature Diamond Micro‐ and Nanoparticles.
- Author
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Shames, Alexander I., Dalis, Adamos, Greentree, Andrew D., Gibson, Brant C., Abe, Hiroshi, Ohshima, Takeshi, Shenderova, Olga, Zaitsev, Alexander, and Reineck, Philipp
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NANODIAMONDS , *TIME-resolved spectroscopy , *ELECTRON paramagnetic resonance spectroscopy , *NICKEL (Coin) , *HIGH temperatures , *FLUORESCENCE , *ARTIFICIAL diamonds - Abstract
Fluorescent color centers in diamond are invaluable room temperature quantum systems in fundamental scientific studies and vital for many emerging applications from inertial navigation to quantum sensing in biology. Yet, controlled production of specific color centers in synthetic diamond at scale remains challenging. Characteristics of silicon‐ and nickel‐based defects with strong fluorescence in the 700–950 nm spectral region formed in Si‐ and Ni‐doped diamond, created via high‐pressure high‐temperature synthesis in commercial quantities without irradiation, are reported. Using electron paramagnetic resonance spectroscopy and fluorescence spectroscopy, the presence of defects including the negatively charged silicon‐vacancy (SiV−), silicon‐boron (SiB) and positively charged substitutional nickel center (Nis+) in micrometer‐sized particles is identified and quantified. The color centers' optical properties are investigated via time‐resolved and steady‐state fluorescence spectroscopy below 10 K and at room temperature. In ensemble measurements, the particles show no detectable signals from nitrogen‐vacancy (NV−) defects. The particles' relative fluorescence brightness is quantified and compared to particles containing ≈1 ppm NV− centers. It is demonstrated that the Nis+ center fluorescence characteristics are preserved in 50 nm nanoparticles. The work paves the way for the use of fluorescent nanodiamonds in the first near‐infrared biological window between 700 nm and 950 nm in biomedical applications. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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37. Diagnostic Value of Different Noninvasive Criteria of Latent Myocarditis in Comparison with Myocardial Biopsy.
- Author
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Blagova, Olga, Osipova, Yuliya, Nedostup, Alexander, Kogan, Evgeniya, Zaitsev, Alexander, and Fomin, Victor
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MYOCARDITIS , *CARDIOMYOPATHIES , *DILATED cardiomyopathy , *HEART diseases , *ARRHYTHMIA , *VIRAL genomes , *CORONARY angiography - Abstract
Purpose: The aim of this study was to quantify the value of various clinical, laboratory, and instrumental signs in the diagnosis of myocarditis in comparison with morphological studies of the myocardium. Methods: In 100 patients (65 men, 44.7 ± 12.5 years old) with "idiopathic" arrhythmias (n = 20) and dilated cardiomyopathy (DCM; n = 80), we performed the following: 71 endomyocardial biopsies (EMB), 13 intraoperative biopsies, 5 studies of explanted hearts, and 11 autopsies with virus investigation (real-time PCR) of the blood and myocardium. Antiheart antibodies (AHA) were also measured as well as cardiac CT (n = 45), MRI (n = 25), and coronary angiography (n = 47). The comparison group included 50 patients (25 men, 53.7 ± 11.7 years old) with noninflammatory heart diseases who underwent open heart surgery. Results: Active/borderline myocarditis was diagnosed in 76.0% of the study group and in 21.6% of patients in the comparison group (p < 0.001). The myocardial viral genome was observed more frequently in patients in the comparison group than in the study group (65.0 and 40.2%; p < 0.01). We evaluated the diagnostic value of noninvasive markers of myocarditis. The panel of AHA had the greatest importance in the identification of myocarditis: sensitivity was 81.5%, and the positive and negative predictive values were 75.0 and 60.5%. This defined the diagnostic value of noninvasive markers of myocarditis and established a diagnostic algorithm providing an individual assessment of the likelihood of myocarditis development. Conclusion: AHA have the greatest significance in the diagnosis of latent myocarditis in patients with "idiopathic" arrhythmias and DCM. The use of a complex of noninvasive criteria allows the probability of myocarditis to be estimated and the indications for EMB to be determined. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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38. Genetic analysis of maternal and paternal lineages in Kabardian horses by uniparental molecular markers.
- Author
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Khaudov, Aliy-bek D., Duduev, Astemir S., Kokov, Zaur A., Amshokov, Khazhismel K., Zhekamukhov, Mohamed Kh., Zaitsev, Alexander M., and Reissmann, Monika
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HAPLOTYPES , *ALLELES , *GENETICS , *GENOMES , *NUCLEOTIDE sequence - Abstract
Studies of mitochondrial DNA (mtDNA) as well as the non-recombining part of the Y chromosome help to understand the origin and distribution of maternal and paternal lineages. The Kabardian horse from Northern Caucasia which is well-known for strength, stamina and endurance in distance riding has a large gap in its breeding documentation especially in the recent past. A 309 bp fragment of the mitochondrial D-loop (156 Kabardian horses) and six mutations in Y chromosome (49 Kabardian stallions), respectively, were analyzed to get a better insight into breeding history, phylogenetic relationship to related breeds, maternal and paternal diversity and genetic structure. We found a high mitochondrial diversity represented by 64 D-loop haplotypes out of 14 haplogroups. The most frequent haplogroups were G (19.5%), L (12.3%), Q (11.7%), and B (11.0%). Although these four haplogroups are also frequently found in Asian riding horses (e.g. Buryat, Kirghiz, Mongolian, Transbaikalian, Tuvinian) the percentage of the particular haplogroups varies sometimes remarkable. In contrast, the obtained haplogroup pattern from Kabardian horse was more similar to that of breeds reared in the Middle East. No specific haplotype cluster was observed in the phylogenetic tree for Kabardian horses. On Kabardian Y chromosome, two mutations were found leading to three haplotypes with a percentage of 36.7% (haplotype HT1), 38.8% (haplotype HT2) and 24.5% (haplotype HT3), respectively. The high mitochondrial and also remarkable paternal diversity of the Kabardian horse is caused by its long history with a widely spread maternal origin and the introduction of Arabian as well as Thoroughbred influenced stallions for improvement. This high genetic diversity provides a good situation for the ongoing breed development and performance selection as well as avoiding inbreeding. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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39. Passive charge state control of nitrogen-vacancy centres in diamond using phosphorous and boron doping.
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Groot‐Berning, Karin, Raatz, Nicole, Dobrinets, Inga, Lesik, Margarita, Spinicelli, Piernicola, Tallaire, Alexandre, Achard, Jocelyn, Jacques, Vincent, Roch, Jean‐François, Zaitsev, Alexander M., Meijer, Jan, and Pezzagna, Sébastien
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PASSIVE states , *NITROGEN , *DIAMONDS , *PHOSPHORUS , *BORON , *DOPING agents (Chemistry) , *QUANTUM plasmas - Abstract
The control and stabilisation of the charge state of nitrogen-vacancy centres in diamond is an important issue for the achievement of reliable processing of spin-based quantum information. The effect of phosphorous and boron doping of diamond on the charge state of nitrogen-vacancy (NV) centres is shown here. Ensembles of NV centres are produced at a depth of 60 nm in ultrapure diamond by implantation of nitrogen ions. Overlapping with the NV ensembles, donor and acceptor doped regions of different doping levels are prepared by ion implantation of phosphorus and boron followed by annealing in vacuum at 1500 °C. We show how the charge state of NV centres is controlled by the presence of phosphorous or boron atoms in their neighbourhood. For the lowest doping level, spectral measurements on the ensemble of NV centres reveal a higher amount of NV0 in the case of boron and a higher amount of NV− in the case of phosphorus, as compared with undoped regions. This behaviour is strengthened when the doping level is increased. Interestingly, the charge state control of native silicon-vacancy centres is also evidenced. Finally, we discuss the role of the surface termination of diamond on the average charge state of the NV ensemble (still dominant even at a depth of 60 nm) and confirm that the surface 2D-hole-gas (H-termination) can be compensated by nitrogen itself. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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40. Disconnection Mechanism and Regional Cortical Atrophy Contribute to Impaired Processing of Facial Expressions and Theory of Mind in Multiple Sclerosis: A Structural MRI Study.
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Mike, Andrea, Strammer, Erzsebet, Aradi, Mihaly, Orsi, Gergely, Perlaki, Gabor, Hajnal, Andras, Sandor, Janos, Banati, Miklos, Illes, Eniko, Zaitsev, Alexander, Herold, Robert, Guttmann, Charles R. G., and Illes, Zsolt
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FACIAL expression , *MULTIPLE sclerosis , *MAGNETIC resonance imaging , *THEORY of mind , *BRAIN imaging , *CORPUS callosum , *ENTORHINAL cortex - Abstract
Successful socialization requires the ability of understanding of others’ mental states. This ability called as mentalization (Theory of Mind) may become deficient and contribute to everyday life difficulties in multiple sclerosis. We aimed to explore the impact of brain pathology on mentalization performance in multiple sclerosis. Mentalization performance of 49 patients with multiple sclerosis was compared to 24 age- and gender matched healthy controls. T1- and T2-weighted three-dimensional brain MRI images were acquired at 3Tesla from patients with multiple sclerosis and 18 gender- and age matched healthy controls. We assessed overall brain cortical thickness in patients with multiple sclerosis and the scanned healthy controls, and measured the total and regional T1 and T2 white matter lesion volumes in patients with multiple sclerosis. Performances in tests of recognition of mental states and emotions from facial expressions and eye gazes correlated with both total T1-lesion load and regional T1-lesion load of association fiber tracts interconnecting cortical regions related to visual and emotion processing (genu and splenium of corpus callosum, right inferior longitudinal fasciculus, right inferior fronto-occipital fasciculus, uncinate fasciculus). Both of these tests showed correlations with specific cortical areas involved in emotion recognition from facial expressions (right and left fusiform face area, frontal eye filed), processing of emotions (right entorhinal cortex) and socially relevant information (left temporal pole). Thus, both disconnection mechanism due to white matter lesions and cortical thinning of specific brain areas may result in cognitive deficit in multiple sclerosis affecting emotion and mental state processing from facial expressions and contributing to everyday and social life difficulties of these patients. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
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41. Quantitative MRI analysis in children with multiple sclerosis: a multicenter feasibility pilot study.
- Author
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Chitnis, Tanuja, Guttmann, Charles R, Zaitsev, Alexander, Musallam, Alexander, Weinstock-Guttman, Bianca, Yeh, Ann, Rodriguez, Moses, Ness, Jayne, Gorman, Mark P, Healy, Brian C, Kuntz, Nancy, Chabas, Dorothee, Strober, Jonathan B, Waubant, Emmanuelle, Krupp, Lauren, Pelletier, Daniel, Erickson, Bradley, Bergsland, Niels, Zivadinov, Robert, and U.S. Network of Pediatric MS Centers of Excellence
- Abstract
Background: Pediatric multiple sclerosis (MS) is a rare disorder with significant consequences. Quantitative MRI measurements may provide significant insights, however multicenter collaborative studies are needed given the small numbers of subjects. The goal of this study is to demonstrate feasibility and evaluate lesion volume (LV) characteristics in a multicenter cohort of children with MS.Methods: A common MRI-scanning guideline was implemented at six member sites of the U.S. Network of Pediatric MS Centers of Excellence. We included in this study the first ten scans performed at each site on patients meeting the following inclusion criteria: pediatric RRMS within 3 years of disease onset, examination within 1 month of MRI and no steroids 1 month prior to MRI. We quantified T2 number, T2-LV and individual lesion size in a total of 53 MRIs passing quality control procedures and assessed gadolinium-enhancing lesion number and LV in 55 scans. We studied MRI measures according to demographic features including age, race, ethnicity and disability scores, controlling for disease duration and treatment duration using negative binomial regression and linear regression.Results: The mean number of T2 lesions was 24.30 ± 19.68 (range:1-113) and mean gadolinium-enhancing lesion count was 1.85 ± 5.84, (range:0-32). Individual lesion size ranged from 14.31 to 55750.60 mm3. Non-white subjects had higher T2-LV (unadjusted pT2-LV = 0.028; adjusted pT2-LV = 0.044), and maximal individual T2-LV (unadjusted pMax = 0.007; adjusted pMax = 0.011) than white patients. We also found a trend toward larger mean lesion size in males than females (p = 0.07).Conclusion: Assessment of MRI lesion LV characteristics is feasible in a multicenter cohort of children with MS. [ABSTRACT FROM AUTHOR]- Published
- 2013
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- View/download PDF
42. Radio-colouration of diamond: a spectroscopic study.
- Author
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Nasdala, Lutz, Grambole, Dieter, Wildner, Manfred, Gigler, Alexander, Hainschwang, Thomas, Zaitsev, Alexander, Harris, Jeffrey, Milledge, Judith, Schulze, Daniel, Hofmeister, Wolfgang, and Balmer, Walter
- Subjects
- *
DIAMONDS , *RADIATION damage , *GEOLOGY , *IRRADIATION , *RADIOACTIVE substances , *PHOTOLUMINESCENCE - Abstract
We have undertaken a study of the common green or orange-brown spots at the surface of rough diamond specimens, which are caused by alpha particles emanating from radioactive sources outside the diamond. Richly coloured haloes represent elevated levels of structural damage, indicated by strong broadening of the main Raman band of diamond, intense strain birefringence, and up-doming of spots due to their extensive volume expansion. Green radio-colouration was analogously generated through the irradiation of diamond with 8.8 MeV helium ions. The generation of readily visible radio-colouration was observed after irradiating diamond with ≥10 He ions per cm. The accumulation of such a high number of alpha particles requires irradiation of the diamond from a radioactive source over long periods of time, presumably hundreds of millions of years in many cases. In the samples irradiated with He ions, amorphisation was observed in volume areas where the defect density exceeded 5 × 10 Å (or 0.03 dpa; displacements per target atom). In contrast, graphitisation as a direct result of the ion irradiation was not observed. The green colouration transformed to brown at moderate annealing temperatures (here 450 °C). The colour transformation is associated with only partial recovery of the radiation damage. The colour change is mainly due to the destruction of the GR1 centre, explained by trapping of vacancies at A defects to form the H3 centre. An activation energy of ~2.4 ± 0.2 eV was determined for the GR1 reduction. The H3 centre, in turn, causes intense yellowish-green photoluminescence under ultraviolet illumination. Radio-colouration and associated H3 photoluminescence are due to point defects created by the ions irradiated, whereas lattice ionisation is of minor importance. This is concluded from the depth distribution of the colouration and the photoluminescence intensity (which corresponds to the defect density but not the ionisation distribution pattern). The effect of the implanted He ions themselves on the colour and photoluminescence seems to be negligible, as radio-colouration and H3 emission were analogously produced through irradiation of diamond with C ions. The photoluminescence emission becomes observable at extremely low defect densities on the order of 10 Å (or 0.000006 dpa) and is suppressed at moderate defect densities of ~5 × 10 Å (or ~0.003 dpa). Intensely brown-coloured diamond hence does not show the H3 emission anymore. Anneals up to 1,600 °C has reduced considerably irradiation damage and radio-colouration, but the structural reconstitution of the diamond (and its de-colouration) was still incomplete. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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- View/download PDF
43. Formation of carbon nanofilms on diamond for all-carbon based temperature and chemical sensor application
- Author
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Kumar, Vivek, Bergman, Alexandra A., Gorokhovsky, Anshel A., and Zaitsev, Alexander M.
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CARBON nanotubes , *TEMPERATURE effect , *CHEMICAL vapor deposition , *THIN films , *SURFACE chemistry , *CHEMICAL detectors , *ATOMIC force microscopy - Abstract
Abstract: The objective of the present study is to investigate temperature and chemical sensitivity of carbon nanofilms made on diamond surface by high temperature surface modification followed by plasma treatment. The carbon nanofilms made this way were characterized by electrical measurements, Raman spectroscopy and atomic force microscopy. The nanofilms were found amorphous in nature. They showed significant sensitivity of their electrical conductance to temperature and exposure to vapors of different organic compounds. The fast response and recovery of the conductance make the carbon nanofilms on diamond substrates promising for development of all-carbon chemical sensors which could be suitable for biological and medical applications. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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44. Heat capacity and T–p phase diagram of Cs2NH4GaF6 elpasolite
- Author
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Gorev, Mikhail V., Flerov, Igor N., Tressaud, Alain, Zaitsev, Alexander I., and Durand, Etienne
- Subjects
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TEMPERATURE , *PHASE transitions - Abstract
Cs2NH4GaF6 prepared by solid-state reaction exhibits at room temperature a cubic Fm
m elpasolite structure with3 a0=9.167 A˚. Calorimetric measurements have shown the presence of a first order phase transition atT0=161 K. Pressure dependence of the phase transition temperature has been studied by DTA under pressure. The data are analyzed in the framework of orientational disordering of [NH4]+ and [GaF6]3− ions. [ABSTRACT FROM AUTHOR]- Published
- 2002
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45. Immunosuppressive therapy of biopsy proved immune-mediated lymphocytic myocarditis in the virus-negative and virus-positive patients.
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Blagova, Olga, Nedostup, Alexander, Kogan, Evgeniya, Zaitsev, Alexander, and Fomin, Victor
- Subjects
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MYOCARDITIS , *PARVOVIRUS B19 , *VIRAL genomes , *BIOPSY , *MYOCARDIUM - Abstract
• The histological activity did not differ depending on the presence of the virus in the myocarditis. • The immune activity in virus-positive patients was as high as that of virus-negative patients. • Immunosupressive therapy is effective both in virus-negative and virus-positive patients. • The virus-positive patients in the absence of IST had no clinical improvement. to study the effect of immunosupressive therapy (IST) in the virus-negative and virus-positive patients with immune-mediated myocarditis. in 60 patients (45 male, 46.7 ± 11.8 years, mean LV EDD, 6.7 ± 0.7 cm, EF 26.2 ± 9.1%) active/borderline myocarditis was verified by endomyocardial biopsy (n = 38), intraoperative biopsy (n = 10), examination of explanted heart (n = 3) and autopsy (n = 9). Indications for IST determined based on histological, immune activity. The follow-up was 19.0 [7.25; 40.25] months. The viral genome in the myocardium was detected in 32 patients (V + group), incl. parvovirus B19 in 23. The anti-heart antibody level was equally high in the V + and V- patients. Antiviral therapy was administered in 24 patients. IST (in 22 V + and 24 V- patients) include steroids (n = 40), hydroxychloroquine (n = 20), azathioprine (n = 21). The significant decrease of LV EDD (6.7 ± 0.7 to 6.4 ± 0.8), PAP (48.9 ± 15.5 to 39.4 ± 11.5 mm Hg, р<0,01), increase of EF (26.5 ± 0.9 to 36.0 ± 10.8), and lower lethality (23.9% and 64.3%; RR 0.37, 95% CI 0.19–0.71), p <0.01, were found only in IST group. Significant improvement due to IST were achieved not only in V-, but also in V + patients. IST in patients with immune-mediated lymphocytic myocarditis is effective and is associated with lower lethality both in virus-negative and virus-positive patients. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
46. Toward production of diamond particles with improved fluorescence uniformity.
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Shenderova, Olga A., Nunn, Nicholas A., Torelli, Marco D., McGuire, Gary E., Shames, Alexander I., and Zaitsev, Alexander M.
- Subjects
- *
NANODIAMONDS , *RAPID thermal processing , *FLUORESCENCE , *ARTIFICIAL diamonds , *NEUTRON irradiation , *PARTICLES , *DIAMONDS - Abstract
Recent advancements in high temperature rapid thermal annealing (RTA) of irradiated diamond particles has made possible the production of the particles with fluorescence based on complexes of nitrogen and vacancies in a broad range of colors: blue, green, red/NIR as well as their mixtures, depending on the temperature and irradiation fluence. Still, the production of fluorescent diamond particles suffers from fluorescence inhomogeneity among particles. The goal of the current study is improvement of the fluorescence uniformity among the treated particles. Experiments were performed using as-grown 40 μm in diameter type Ib synthetic diamond particulate assuming that nitrogen uniformity among the as-grown particles should be higher versus milled ones used in previous studies. Particles were irradiated under mild conditions with 1 MeV electrons to a fluence 3 × 1018 e/cm2 without overheating during irradiation which resulted in relatively uniform green fluorescence among particles treated via RTA at temperatures corresponding to H3 centers formation. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
47. Reproductive Characteristics of Thawed Stallion Sperm.
- Author
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Atroshchenko, Mikhail M., Arkhangelskaya, Ekaterina, Isaev, Dmitry A., Stavitsky, Sergey B., Zaitsev, Alexander M., Kalaschnikov, Valery V., Leonov, Sergey, and Osipov, Andreyan N.
- Subjects
- *
SPERMATOZOA , *STALLIONS , *HORSE breeding , *SEMEN , *SEMEN analysis , *DNA damage , *SPERM motility - Abstract
Simple Summary: It is very important to evaluate correctly the fertilizing capacity of frozen sperm before carrying out the artificial insemination of mares. It is not always possible to perform complex laboratory tests under the stud farm's conditions. The purpose of our study was to determine the minimum set of relatively simple laboratory tests sufficient to confirm the feasibility of frozen/thawed sperm for insemination and to predict the pregnancy rate in mares. We found that sperm characteristics such as activity, survival at low temperature, and DNA damage are sufficient to determine the quality of frozen/thawed sperm. These characteristics can be determined by simple tests and assays that can be used for increasing the effectiveness of artificial insemination not only in horse breeding but also in other areas of livestock and even in reproductive medicine. The main goal of our study was to determine a set of thawed stallion sperm characteristics that have predictive value for the pregnancy rate (PR) of mares after artificial insemination (AI). DNA fragmentation and survival of sperm during hypothermic storage were studied in addition to routinely determined semen characteristics such as concentration, percentage of motile spermatozoa, and morphology. To estimate DNA fragmentation, a modified hallo assay was applied. Sperm survival was determined within hours as the ability of spermatozoa to maintain progressive motility (PM) during the storage of ejaculate diluted with lactose-chelate-citrate-yolk (LCCY) medium at +4 °C. Strong positive correlation between PR and thawed sperm motility (r = 0.90, p < 0.05) as well as between PR and sperm survival (r = 084, p < 0.05) was revealed. There was also a strong negative correlation between PR and DNA damages in spermatozoa (r = −0.94, p < 0.05). We found no dependence of PR on normal morphology spermatozoa percentage in thawed semen. We concluded that the sperm activity, survival, and DNA fragmentation should be considered as the sufficient reproductive characteristics of semen to evaluate the quality of frozen/thawed sperm and prediction of PR. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
48. Fluorescent Diamond Particles: From Fancy Blue to Red: Controlled Production of a Vibrant Color Spectrum of Fluorescent Diamond Particles (Adv. Funct. Mater. 19/2019).
- Author
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Dei Cas, Laura, Zeldin, Steven, Nunn, Nicholas, Torelli, Marco, Shames, Alexander I., Zaitsev, Alexander M., and Shenderova, Olga
- Subjects
- *
VISIBLE spectra , *DIAMONDS spectra , *DIAMONDS , *RAPID thermal processing , *PARTICLES , *IMAGINATION - Published
- 2019
- Full Text
- View/download PDF
49. From Fancy Blue to Red: Controlled Production of a Vibrant Color Spectrum of Fluorescent Diamond Particles.
- Author
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Dei Cas, Laura, Zeldin, Steven, Nunn, Nicholas, Torelli, Marco, Shames, Alexander I., Zaitsev, Alexander M., and Shenderova, Olga
- Subjects
- *
RAPID thermal processing , *ARTIFICIAL diamonds , *DIAMONDS spectra , *VISIBLE spectra , *TEMPERATURE control , *PARTICLES - Abstract
The current study reports a breakthrough method for production of multicolor diamond particulates using a rapid thermal annealing (RTA) approach with precise temperature and time control, enabling annealing of diamond particulates up to 2100 °C without extensive graphitization. The RTA method generates conditions which allow formation of one‐, two‐, and three‐atom nitrogen complexes with vacancies in electron irradiated type Ib synthetic diamond, providing vibrant luminescence in the red, green, and blue spectral ranges, correspondingly. Controlled and highly reproducible formation of specific color centers previously not possible in type Ib synthetic diamond particles opens new opportunities for particulate diamond in a plethora of fluorescence imaging applications in biological and industrial fields. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
50. Study of Fancy-Color and Near-Colorless HPHT-grown Synthetic Diamonds from Advanced Optical Technology Co., Canada.
- Author
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Deljanin, Branko, Simic, Dusan, Epelboym, Marina, and Zaitsev, Alexander M.
- Subjects
- *
DIAMONDS , *HIGH temperature chemistry , *JEWELRY , *COLOR , *LUMINESCENCE , *ARTIFICIAL gems & precious stones - Abstract
Laboratory-created diamonds now on the market are grown under high-pressure, high-temperature (HPHT) conditions, and in the last few years, they have become more available in the jewelry trade. EGL USA has studied yellow-to-orange synthetic diamonds from Chatham Created Gems and the Gemesis Corporation (Woodring and Deljanin, 2004), and as a result of this research is offering a laboratory service of testing and certifying synthetic diamonds. This is the first study of synthetic diamonds created by Advanced Optical Technologies Corp. (AOTC), based in Ottawa, Canada. They are producing as-grown yellow-to-orange, blue, and near-colorless synthetic diamonds, as well as pink-to-purple ones that are produced by the irradiation and annealing of as-grown yellows. Produced in Europe using Russian BARS-type presses, the crystals typically weigh 1-4 ct, and the polished samples are 0.50-2 ct. Recently AOTC has started commercially selling their synthetic diamonds for jewelry purposes in North America under the name "Adia Created Diamonds." All of the faceted stones are certified and laser inscribed as "AOTC-created" at EGL in Vancouver, Canada. Since the color of AOTC-created diamonds is stable, EGL is grading them with the same terminology that is used for natural diamonds. We examined the following AOTC synthetic diamonds: 247 yellow to orange (Fancy Light to Fancy Vivid), 68 blue (light to Fancy Vivid), eight pink to purple (Fancy Intense to Fancy Deep), and five near colorless (D to I). Some contained gray metallic inclusions that were irregular in shape and very different from crystals seen in natural diamonds. Their clarity grades ranged from VVS to I, with the majority (59%) in the VVS to VS categories. Most synthetic diamonds from other producers can be identified by a characteristic cross-shaped UV luminescence pattern that is stronger in short-wave than in long-wave UV radiation. The majority of the AOTC-created diamonds did not show characteristic color zoning nor any fluorescence pattern when illuminated with a standard UV lamp, so we used UV sources with higher intensity such as the DiamondView and a custom-made EGL instrument (at wavelengths of 220, 254, and 365 nm). With this UV illumination, we could observe the cubo-octahedral color zoning that is typical of HPHT-grown synthetic diamonds. These new AOTC-created synthetic diamonds can be separated from their natural counterparts based on careful observation with the microscope, and through the use of crossed polarizers, the DiamondView, and advanced spectroscopy. [ABSTRACT FROM AUTHOR]
- Published
- 2006
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