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Nitrogen-incorporated ultrananocrystalline diamond [(N)UNCD] pyramid tip cathode has been considered as a next-generation high peak current electron source for dielectric laser accelerators as well as other high peak current particle accelerator applications. In this work, we study non-linear photoemission from an (N)UNCD pyramid tip cathode using an ultrafast laser with the pulse length of 150 fs with the central wavelength of 800 nm in the peak intensity range of 10 9 – 10 10 W / cm 2. We demonstrated that as the incident laser intensity increases, the current emitted from the nano-tip first increases as a power function with an exponent of about 5 and then starts to roll over to an exponent of 3. This roll over is attributed to the Coulomb interaction between electrons emitted from the tip also known as the space charge. We also measured the photoemission electron energy spectra that show electrons with energies as high as ∼ 10 eV. Based on the shape of the electron energy spectra, we conclude that the high-energy electrons are thermally emitted electrons due to ultrafast laser heating at the tip of the (N)UNCD pyramid tip cathode. [ABSTRACT FROM AUTHOR]

Until recently, the Kara Sea was a stable ecosystem unaffected by alien species invasions. However, at the beginning of the twenty-first century, the snow crab (Chionoecetes opilio) was detected. Studies conducted between 2013 and 2022 in Blagopoluchiya Bay (Novaya Zemlya Archipelago, Kara Sea) provided an opportunity to observe the establishment of a population of this species and its influence on benthic communities. Various sampling methods, such as trawl and grab surveys, as well as video observations, were used to study two main seabed habitats, one in the deep inner basin and the other at the sill at the bay's exit. The study revealed significant changes in benthic ecosystems, including declines in integral benthic characteristics such as abundance, biomass, diversity, and shifts in dominant species. The response of megabenthos and macrobenthos varied between habitats, but in general, there was a sharp decline in the abundance of large bivalves and brittle stars. The observed changes were not related to environmental variability but most likely to the abundance and size structure of the snow crab. The taxonomic and size structure of the benthos changed as crab individuals increased in size, and the changes were faster and more pronounced in the area with higher crab abundance. These findings raise concerns about the potential long-term effects of the snow crab invasion on the Kara Sea ecosystem, including reduced biodiversity and changes in food webs. [ABSTRACT FROM AUTHOR]

The quantum efficiency and mean transverse energy of electrons emitted from a cathode determine the quality of beams generated from photoinjectors. The nitrogen-incorporated ultrananocrystalline diamond, (N)UNCD, is a new class of robust semiconductor photocathodes, which has been considered in photoinjectors for high peak current extraction. In this work, we measure the spectral response in quantum efficiency, photoemission energy spectra, and mean transverse energy of the (N)UNCD photocathode using a photoemission electron microscope. The observed quantum efficiency was comparable to that of copper photocathodes. Photoemission spectra showed the evidence of scattering of electrons before emission. This relaxation of electrons due to scattering is also observed in the spectral response of the mean transverse energy. The mean transverse energy is limited to ∼ 70 meV at the threshold. We attribute this to the physical and chemical roughness of the (N)UNCD photocathode and, hence, smoother films will be required to further reduce the mean transverse energy obtained from the (N)UNCD photocathode. [ABSTRACT FROM AUTHOR]

The elastic properties and solid solution strengthening of several Cu alloys that may be promising for high gradient applications were studied using ab initio calculations based on density functional theory. Specifically, the temperature and solute concentration dependence of elastic properties including bulk and shear moduli, thermal expansion coefficient, and heat capacity of these alloys were calculated. We found that the bulk and shear moduli are linearly dependent on the solute concentration in the dilute regime and change significantly for different Cu alloys. The thermal expansion coefficient and heat capacity are comparatively less sensitive to solute concentrations. Solid solution strengthening is observed to be linearly correlated with the change of lattice parameter of Cu. This work provides an in-depth understanding of the elastic properties of Cu alloys, which is key for predicting their performance at high gradient in normal conducting accelerating structures. [ABSTRACT FROM AUTHOR]

Many applications, such as compact accelerators and electron microscopy, demand high brightness electron beams with small source size and ultralow emittance. Diamond emitters manufactured with semiconductor processes can be employed in such compact beam sources. The micrometer-scale pyramid structure of the emitter allows enhancement of the external field compared to that at the substrate, leading to electron emission with small beam size. We investigate the dependence of the field enhancement on the shape of the emitter and the resulting emission characteristics. The beam formation and dynamics are simulated with the LSP [D. Welch, D. Rose, R. Clark, T. Genoni, and T. Hughes, Comput. Phys. Commun. 164, 183 (2004)] particle-in-cell code to obtain the macroscopic observables. To account for the semiconductor charge transport in the bulk material and the tunneling through the surface, a first-principle semiclassical Monte Carlo emission model is developed and applied to the diamond pyramid. Using this Monte Carlo emission model and the result from the geometric field enhancement calculation, we construct a simple model to qualitatively explain the measured emission characteristics. A comparison between our model and experiments indicates that the beam current is mostly emitted at the apex of the emitter. [ABSTRACT FROM AUTHOR]

Biodiversity in the Laptev Sea was assessed for gutless marine worms of the family Siboglinidae (Annelida), whose metabolism is provided by symbiotic bacteria that oxidize hydrogen sulfide and methane. Seven siboglinid species were found within the geographical boundaries of the Laptev Sea, and another species was found in an adjacent sector of the Arctic Basin. The largest number of finds and the greatest biological diversity of siboglinids were observed in the eastern part of the Laptev Sea in a field of numerous methane flares. One find was made in the estuary area of the Lena River at a depth of 25 m. A possible association of siboglinids with methane seepage areas is discussed. [ABSTRACT FROM AUTHOR]

Diamond field emitter array field emission cathodes (DFEA FECs) are attractive for the next generation of injectors due to their ability to produce transversely shaped beams without the need for complex masking or laser schemes. However, reliability of this cathode technology remains a challenging issue as principal mechanisms guiding and allowing for output beam shaping remained poorly understood. This paper reports the results of testing two DFEA FECs with the same pattern and emitter tip geometry. Although both cathodes were able to sustain gradients of 44 MV/m and produce maximum output integral charge of 0.5 nC per radio frequency pulse, their emission patterns were different. One cathode did not produce a shaped beam, while the other one did. This difference was explained by the extent of the local variations of the diamond material across the arrays as discovered by spatially resolved Raman spectroscopy. The main practical takeaways were (i) tip sharpness was not a prerequisite for producing a shaped beam and instead (ii) material characteristics resulting in different cathode ballast resistance affected emission spatial uniformity across the array and hence the beam shaping. [ABSTRACT FROM AUTHOR]

We report the high gradient testing results of two single-cell off-axis coupled standing wave accelerating structures. Two brazed standing wave off-axis coupled structures with the same geometry were tested: one made of pure copper (Cu) and one made of a copper–silver (CuAg) alloy with a silver concentration of 0.08%. A peak surface electric field of 450 MV/m was achieved in the CuAg structure for a klystron input power of 14.5 MW and a 1 μs pulse length, which was 25% higher than the peak surface electric field achieved in the Cu structure. The superb high gradient performance was achieved because of the two major optimizations in the cavity's geometry: (1) the shunt impedance of the cavity was maximized for a peak surface electric field to accelerating gradient ratio of ∼2 for a fully relativistic particle, and (2) the peak magnetic field enhancement due to the input coupler was minimized to limit pulse heating. These tests allow us to conclude that C-band accelerating structures can operate at peak fields similar to those at higher frequencies while providing a larger beam iris for improved beam transport. [ABSTRACT FROM AUTHOR]

Gutless marine worms of the family Siboglinidae have been found in the estuaries of the largest Arctic rivers Yenisei, Lena, and Mackenzie. Siboglinid metabolism is provided by symbiotic chemoautotrophic bacteria. Strong salinity stratification is characteristic of the estuaries of the largest Arctic rivers and ensures a high salinity at depths of 25–36 m, where siboglinids were found. High methane concentrations, which are necessary for siboglinid metabolism, result from dissociation of permafrost gas hydrates under the influence of river runoff in the conditions of Arctic warming. [ABSTRACT FROM AUTHOR]

Operation of normal conducting accelerator structures at high accelerating gradients is beneficial for many accelerator applications in basic science, industry, medicine, and National Security. RF breakdown is the major factor that limits the achievable accelerating gradients. Previous experiments on copper (Cu) have demonstrated that RF breakdown probability can be significantly decreased by hardening the material and alloying Cu with solutes such as silver (Ag). In this paper, we propose a figure-of-merit (FOM) that characterizes the ability of Cu alloys to withstand high-gradients. The FOM represents a trade-off between hardening through solid solution strengthening and the additional thermal stress induced by incremental RF pulse heating resulting from changes in electronic properties induced by alloying. We performed high-throughput ab initio calculations and computed the FOM for a large number of binary Cu alloys. Several promising candidate alloys for high-gradient accelerating structures were identified, such as CuAg, CuCd, CuHg, CuAu, CuIn, and CuMg. CuAg alloys have previously exhibited low RF breakdown rates in experiments. The results provide guidance for selecting alloys for the future high-gradient normal conducting accelerating structures operating at very high gradients. [ABSTRACT FROM AUTHOR]

Only seven frenulate species are currently known along the Eurasian coast of the Arctic Ocean. We describe a new genus and a new species of frenulates Crispabrachia yenisey , gen. nov. et sp. nov. The morphological analysis involved standard anatomical techniques, semithin sections and scanning electron microscopy (SEM). The molecular study included four markers (partial COI , 16S , 18S and 28S) and implemented Bayesian and Maximum likelihood phylogenetic approaches. The description of Crispabrachia gen. nov. is the first documented finding of frenulates in the Kara Sea at the estuary of the Yenisey River in rather shallow water (28 m). The establishment of a new genus is warranted based on the composition of morphological characters and several specific features including free, comparatively short curly tentacles, a triangular cephalic lobe with amplate base, the valvate extension of the posterior part of the forepart and prominent papillae on the nonmetameric region. The tube structure with prominent frills and the worm's numerous tentacles, metameric papillae with cuticular plaques and segmental furrow on the forepart indicate that the new genus belongs to the polybrachiid group. Although the type locality in the Yenisey River estuary is unusual for siboglinids in general, the physical conditions here are common for other frenulates habitats, i.e. salinity ~30–33, bottom water temperature –1.5°C. This finding was made in the Yenisey Gulf in the region with the highest methane concentrations in the southern part of the Kara Sea that reflects permafrost degradation under the influence of river flow. Further study of the region would help to understand the factors influencing frenulate distributions and improve our knowledge of their biodiversity. Only seven frenulate species are currently known along the Eurasian coast of the Arctic Ocean. In this paper, we describe a new genus and a new species of frenulates – Crispabrachia yenisey , gen. nov. et sp. nov. Here we present the morphological analysis of new genus. The molecular study included four markers (partial COI , 16S , 18S and 28S) and implemented Bayesian and Maximum likelihood phylogenetic approaches. The description of Crispabrachia gen. nov. is the first documented finding of frenulates in the Kara Sea at the estuary of the Yenisey River in rather shallow water (28 m). [ABSTRACT FROM AUTHOR]

The food spectra of a local group of snow crabs Chionoecetes opilio was studied by the analysis of stomach content. This abundant group of crabs settled in the vicinity of the Blagopoluchiya Bay (the Kara Sea coast of the Novaya Zemlya archipelago) in 2013–2014. By September 2018, the mass cohort reached the VI instar, the average carapace width of males was 28 mm and of females, 27 mm. The stomachs of more than 60% of the crabs were filled with food by 50% or more. Snow crabs behave as non-selective epibenthic feeders, consuming both plant and animal food (exclusively invertebrates), with some degree of cannibalism. The highest frequency of occurrence was observed for brittle stars (68.9%, which also accounted for more than a third of the volume of the virtual food lump), detritus (63.8%), and plant residues (60.7%), followed by bivalves and polychaetes. The average number of prey per stomach (Froerman coefficient) was 2.86, which was typical for gathering predators. Snow crabs used almost all of the abundant and available macrobenthos resources as food items. Snow crabs from open shelf areas do not usually eat macrophytes and detritus (possibly originating partially from macrophytes). These characteristics are peculiarities of the feeding of snow crabs in deep fjords, abundant on the eastern coast of the Novaya Zemlya archipelago. [ABSTRACT FROM AUTHOR]

Pogonophora or siboglinid tubeworms (Annelida, Siboglinidae) have been found in the East Siberian Sea for the first time. On the basis of the results of molecular phylogenetic analysis, the found specimens are presumably assigned to the genus Oligobrachia. The stations where the siboglinid tubeworms have been found are located in the area of methane seeps. This confirms the previously stated hypothesis about relationship of siboglinid tubeworm distribution with the areas of underwater methane seeps. [ABSTRACT FROM AUTHOR]

A new modal method for controlling the deformation of a linear elastic structure under conditions of quasi-static loading is proposed. The advantage of the new method is independent control of orthogonal modes, which increases the accuracy and speed of control. To illustrate the proposed method, compensation of the deformation error in a rotary table with a high tilt accuracy is considered. [ABSTRACT FROM AUTHOR]

—During 79th cruise of R/V Akademik Mstislav Keldysh twelve trawl hauls were collected in Powell Basin and adjacent area at depths 370–3771 m. The structure of the benthic assemblages was highly variable when considered at the macrotaxon level. The main factors shaping the taxonomical structure of the sampled assemblages were depth, near-bottom current velocities and proportion of the hard fraction of the sediment. Hard substrate assemblages of the Antarctic peninsula slope and Philip Ridge with high percentage of filter-feeders (mainly sponges) were associated with the highest values of the near-bottom tide currents (up to 55.6 cm/s). In several trawl hauls indicator species of vulnerable marine ecosystems—mainly Demospongiae sponges, deep-sea corals Stylasteridae (Hydrozoa) and Primnoidae (Octocorallia)—were collected. [ABSTRACT FROM AUTHOR]

Diamond field-emitter arrays (DFEAs) are arrays of diamond pyramids with exquisitely sharp tips and micrometer-scale bases that produce high current densities. These arrays can be fabricated in arbitrary shapes, ranging from single tips to many millions of tips, so that they produce an inherently shaped electron beam. Each tip emits a modest current, but the large dense array can produce many Amps. We are investigating these cathodes for use in dielectric wakefield accelerators; however, they may also be applicable to vacuum microwave tubes. Recently, shaped beam production and transport have been demonstrated in the 1.3-GHz RF gun at the Argonne Cathode Test Stand at the Argonne National Laboratory. The charge was measured on a Faraday cup and the beam imaged on a YAG screen with peak electric field gradients on the cathode ranging from 12 to 35 MV/m. Three cathode geometries were tested: one 1-mm equilateral triangle with 7- $\mu \text{m}$ base pyramids and 10- $\mu \text{m}$ pitch, one 1-mm equilateral triangle with 10- $\mu \text{m}$ base and 25- $\mu \text{m}$ pitch, and one sparse $5\times 5$ square array with 20- $\mu \text{m}$ base and 400- $\mu \text{m}$ pitch. The two triangular arrays emitted 35 nC in an RF macropulse at 35 MV/m and 13-nC charge at 27 MV/m, respectively, while the sparse array emitted 0.060-nC charge at 15 MV/m. This article presents the results of the triangular array experiments, including damage due to breakdown in the RF gun and initial models of tip-to-tip shielding. [ABSTRACT FROM AUTHOR]

We propose a new method for the precise measurement of dielectric permittivity of ceramics and polymers at millimeter-wave frequencies that employs the TE01 mode of a circular waveguide. At higher frequencies, accurately measuring the dielectric permittivity of materials becomes extremely challenging by using the fundamental TE10 mode of a rectangular waveguide. As the frequency increases, the dimensions of the dielectric sample that has to be fit into the waveguide become very small. Therefore, small fabrication imperfections that produce air gaps between the sample and the wall of the waveguide result in significant errors during measurements. In contrast, the TE01 mode of the circular waveguide that does not have an electric field at the surface of the waveguide is insensitive to small imperfections during fabrication. We measured the dielectric permittivity in small samples of alumina (Al2O3), magnesium calcium titanate (MCT) ceramics, and Teflon placed in a circular waveguide. The results showed that the method was very robust with respect to manufacturing imperfections: when dimensions of the alumina and Teflon samples varied by as much as 10% and 20%, the differences in the computed dielectric permittivity of the alumina were only 1.26% and 3.06%, respectively, and those of Teflon were 1.98% and 2.12%. In addition, when the high-dielectric permittivity material MCT samples were deformed by 5% and 10%, the differences were just 0.04% and 0.14% each, respectively. We believe that this new proposed method is also applicable to even higher frequencies in the THz regime and at a very high relative dielectric permittivity of larger than 10. [ABSTRACT FROM AUTHOR]

We have demonstrated generation and transport of a patterned electron beam from a Diamond Field-Emitter Array (DFEA) cathode in a radio frequency (rf) gun. DFEAs are arrays of micrometer-scale pyramids with nanometer-scale tips. They can be fabricated with base widths ranging from 3 μm to 25 μm and pitches as small as 5 μm. They have an inherent 1:0.7 base to height ratio. DFEAs operate as field-emitter cathodes and potentially produce intrinsically shaped electron beams, which are of interest for a number of accelerator applications. We report on the results of a recent experiment in which a beam, consisting of several beamlets, was produced from a DFEA cathode in an rf gun and transported 2.54 m along a beam line. A macrobunch charge of 60 pC was measured at a cathode field gradient of 15.1 MV/m. [ABSTRACT FROM AUTHOR]

This paper describes the design, fabrication, and initial testing of a Ka-band dielectric-loaded traveling-wave tube (TWT) with very high bandwidth. Applications for high-power mm-wave sources span radar (including imaging), biology, medicine, communications, national security, and other areas. Specifically, to achieve long-range, cm-scale imaging using synthetic aperture radar techniques, a radio-frequency (RF) source with an average power level of 1 kW and a bandwidth of 10 GHz will be required. We developed a novel Ka-band TWT architecture that approaches these requirements. To achieve a very wide bandwidth, we proposed to use a dielectric-lined waveguide slow-wave structure. A dielectric constant of larger than 13 is needed for the resonance with a 20-keV electron beam. In our design, we have used $\varepsilon = 20$ magnesium–calcium–titanate (MCT) ceramics. The two halves of the dielectric are shaped to ensure that the TM11-like mode has a flat electric field profile along the beam slot to accommodate transport of a 5-A sheet electron beam. The gain for the structure peaks at 33.25 GHz and is predicted to be 2.3 dB/cm with a total gain of 30 dB. The structure was fabricated and cold tested. Although the results of the cold test were inconclusive, we discuss possible reasons for discrepancies between simulations and measurements and propose simplifications to the tube’s geometry for future studies. [ABSTRACT FROM AUTHOR]

Here we report the first finding of a frenulate pogonophoran (Annelida, Siboglinidae) in the southern part of the Kara Sea. This finding was made in the Yenisei Gulf in the region of the highest methane concentrations, resulting from the degradation of permafrost under the influence of river flow. It has been suggested that pogonophorans are indicators of hydrocarbon manifestations of various genesis. [ABSTRACT FROM AUTHOR]

We consider the main effects of beam emittance on W-band traveling-wave tube (TWT) performance and gain. Specifically, we consider a representative dielectric TWT structure with ~5 dB/cm of gain driven by a 5-A, 20-keV, sheet electron beam that is focused by a wiggler magnetic field. The normalized beam transverse emittance must be about 1 \mu \textm or lower to ensure that both the transport is stable and the gain is not degraded by the effective energy spread arising from the emittance. This emittance limit scales roughly inversely with frequency. [ABSTRACT FROM AUTHOR]

We present results from cryogenic tests of the multi-cell superconducting radio frequency (SRF) cavity with a photonic band gap (PBG) coupler cell. Achieving high average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery-linacs (ERLs). Beam current in ERLs is limited by the beam break-up instability, caused by parasitic higher order modes (HOMs) interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The multi-cell cavity was designed and fabricated of niobium. Two cryogenic (vertical) tests were conducted. The high unloaded Q-factor was demonstrated at a temperature of 4.2K at accelerating gradients up to 3 MV/m. The measured value of the unloaded Q-factor was 1.55×108, in agreement with prediction. [ABSTRACT FROM AUTHOR]

A multi-meter long collinear dielectric wakefield accelerator is considered, and it is shown that a single bunch breakup instability is a major limiting factor for obtaining highly efficient energy transfer from the drive bunch to the main bunch. Different methods for instability suppression are studied. Numerical simulations using a 6D particle tracking computer code are performed and tolerances to various errors are defined. [ABSTRACT FROM PUBLISHER]

We report results from recent 2.1GHz superconducting radio frequency (SRF) photonic band gap (PBG) resonator experiments at Los Alamos. Two 2.1GHz PBG cells with elliptical rods were fabricated and tested at high power in a liquid helium bath at the temperatures of 4K and below 2K. The described SRF PBG cells were designed with a particular emphasis on changing the shape of the PBG rods to reduce peak surface magnetic fields and at the same time to preserve its effectiveness at damping higher-order-modes. The superconducting PBG cavities have great potential for damping long-range wakefields in SRF accelerator structures without affecting the fundamental accelerating mode. The cells performed in accordance with simulation's predictions and the maximum achieved accelerating gradient was 18.3 MV/m. This represents a 30% increase over gradients previously demonstrated in superconducting PBG cavities with round rods. [ABSTRACT FROM AUTHOR]

Materials science needs to study dynamic properties of high-Z materials lead to a unique and challenging set of requirements for future X-ray free-electron lasers (XFELs), with single-pulse fluxes of up to 1012 50 keV X-rays that are both transversely and longitudinally coherent. These parameters cannot be met through an extension of the beam and FEL technologies used at existing and currently planned X-ray FEL facilities. We describe a novel technique to achieve higher fluxes by reducing the transverse beam emittance of high bunch charges and another to achieve longitudinal coherency by pre-modulating the electron beam current before it reaches the undulator. These techniques are investigated numerically and analytically, and also hold potential for increasing performance and decreasing cost of soft X-ray FELs. [ABSTRACT FROM AUTHOR]

We have designed, fabricated, and tested a novel photonic band gap (PBG) channel-drop filter (CDF) operating at around 240 GHz. A PBG CDF is a device that allows the channeling of selected frequencies from continuous spectra into separate waveguides through select defects in a PBG structure. It is compact and configurable, and thus, it can be employed for millimeter-wave spectrometry with applications in communications, radio astronomy, and radar receivers for remote sensing and nonproliferation. In this paper we present the design, modeling, and fabrication methods used to produce a silicon-based PBG CDF, and demonstrate its ability to filter the frequency of 240 GHz with a linewidth of approximately 1 GHz and transmission of 25 dB above background. [ABSTRACT FROM AUTHOR]

Chemical and electrochemical syntheses of a series of the zinc(II) and cadmium(II) complexes were carried out on the basis of sterically hindered Schiff bases, which are the condensation products of 4,6-ditert-butyl-2-aminophenol with the salicylaldehyde derivatives (H2L, H2L1). The structures and compositions of the synthesized binuclear complexes M2L2 and M2L21 where M = Zn(II) and Cd(II), were proved by the data of elemental analysis, IR spectroscopy, and ¹H NMR spectroscopy. The structures of the Zn2L2 ⋅ 2Py and Zn2L2 2DMF dimers were proved by X-ray diffraction analysis. The electrochemical dissolution of zero-valence zinc and cadmium in methanol in the presence of equimolar amounts of H2L and H2L1 made it possible to isolate dimeric complexes of the corresponding metals of the composition M2L2 and M2L21. [ABSTRACT FROM AUTHOR]

The chemical and electrochemical synthesis of cobalt(II), nickel(II), and copper(II) complexes based on sterically hindered tridentate Schiff bases obtained by the coupling of 2-amino-4,6-di- tert-butylphenol with salicylaldehyde derivatives (H2L, H2L’) was performed. The resulting dinuclear complexes were characterized by elemental analysis, IR spectroscopy, and magnetochemical measurements in the 300–2 K temperature range. The structures of the dinuclear nickel(II) and copper(II) complexes with the composition Ni2L2·2AcOH·2MeOH and Cu2L2, respectively, were established by X-ray diffraction. The copper chelates are characterized by the presence of antiferromagnetic exchange interactions. The mononuclear copper(II) complexes (DMSO)bis[2-(5,7-di- tert-butyl-4-hydroxybenzoxazol-2-yl)phenolato]copper(II) and (DMF)2bis[2-(5,7-di- tert-butyl-4-hydroxybenzoxazol-2-yl)phenolato]copper(II) were isolated upon electrochemical dissolution of copper(0) and were structurally characterized. [ABSTRACT FROM AUTHOR]

The reaction of di( tert-butyl) derivatives of pyrocatechol with 2,6-dihydroxyaniline afforded 2,4,6,8-tetra( tert-butyl)-9-hydroxyphenoxazin-1-one. The chemical properties of the reaction product and its ability to form complexes with metal salts as the tridentate ligand were investigated. The structure of hydroxyphenoxazinone was established by X-ray diffraction. [ABSTRACT FROM AUTHOR]

Alkylation of o-(N-sulfonylamino)phenylimino derivatives of indol-2-one and cyclohepta[c]furan with phenacyl bromides is accompanied by cyclization to previously unknown tetrahydroquinoxalines having spiro-fused oxoindole and cyclohepta[c]furan fragments. The structure of the latter includes a nitrogen-oxygen triangular system typical of most natural cytotoxic compounds. [ABSTRACT FROM AUTHOR]

Alkylation of N-benzylidene-N'-R-sulfonyl-o-phenylenediamines with phenacyl bromides is accompanied by diastereoselective cyclization to afford tetrahydroquinoxaline derivatives. No cyclization occurs in the alkylation of the same compounds with p-nitrobenzyl bromide or chloroacetamide derivatives because of reduced reactivity of the N-methylene protons. [ABSTRACT FROM AUTHOR]

Unsuccessful attempts of producing crystalline hydrogen predicted in [1] based on electronic theory do not reduce interest in this hydrogen state in connection with its possible formation in solid-state hydrogen accumulators. The hydrogen density in these materials can approach the value reported in [1]. However, the nonequilibrium state and the presence of defects in the matrix can lead to the formation of nanostructural hydrogen comprising small-sized crystallites with boundaries rather than of a single crystal. The electronic structure of this state has been unknown even in a general form; there is no information on possible mechanisms governing the interaction between nanostructural elements. It is clear only that hydrogen forms a band of weakly hybridized electronic states in hydrides of transition metals [2]. In the zero-order approximation, the elements of hydrogen nanostructure can be represented as cluster fragments of a grain and the intergranular boundary. In this case, the electronic spectra of these fragments can be used to estimate the individual properties of nanostructure elements and (with the use of phenomenological models) the effects of their interaction. [ABSTRACT FROM AUTHOR]