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Co/CoO multilayers are fabricated by means of radio-frequency magnetron sputtering. For the formation of each multilayer period, a Co layer is initially produced followed by natural oxidation. Platinum is used not only as buffer and capping layers, but also in the form of intermediate ultrathin layers to enhance perpendicular magnetic anisotropy. Three samples are compared with respect to the magnetic anisotropies and exchange bias between 4–300 K based on superconducting quantum interference device magnetometry measurements. Two of the multilayers are identical Co/CoO/Pt ones; one of them, however, is grown on a Co/Pt “magnetic substrate” to induce perpendicular magnetic anisotropy via exchange coupling through an ultrathin Pt intermediate layer. The third multilayer is of the form Co/CoO/Co/Pt. The use of a “magnetic substrate” results in the observation of loops with large remanence when the field applies perpendicular to the film plane. The CoO/Co interfaces lead to a significant exchange bias at low temperatures after field cooling. The largest exchange bias was observed in the film with double Co/CoO/Co interfaces. Consequently, significant perpendicular anisotropy coexists with large exchange bias, especially at low temperatures. Such samples can be potentially useful for applications related to spintronics and magnetic storage.

ZnO films and nanostructures were deposited on Si substrates by MOCVD using single source solid state zinc acetylacetonate (Zn(AA)) precursor. Doping by silver was realized in-situ via adding 1 and 10 wt. % of Ag acetylacetonate (Ag(AA)) to zinc precursor. Influence of Ag on the microstructure, electrical and optical properties of ZnO at temperature range 220–550 °C was studied by scanning, transmission electron and Kelvin probe force microscopy, photoluminescence and four-point probe electrical measurements. Ag doping affects the ZnO microstructure via changing the nucleation mode into heterogeneous and thus transforming the polycrystalline films into a matrix of highly c-axis textured hexagonally faceted nanorods. Increase of the work function value from 4.45 to 4.75 eV was observed with Ag content increase, which is attributed to Ag behaviour as a donor impurity. It was observed, that near-band edge emission of ZnO NS was enhanced with Ag doping as a result of quenching deep-level emission. Upon high doping of ZnO by Ag it tends to promote the formation of basal plane stacking faults defect, as it was observed by HR TEM and PL study in the case of 10 wt.% of Ag. Based on the results obtained, it is suggested that NS deposition at lower temperatures (220–300 °C) is more favorable for p-type doping of ZnO.

The catalytic efficiency and bench scale time on steam stability of Ni dispersed on three commercially available catalytic supports (ZrO 2 , La 2 O 3 –ZrO 2 and CeO 2 –ZrO 2 ) has been studied for the dry reforming of methane (DRM) in the temperature range of 500–800 °C and a CH 4 /CO 2 ratio equal to 1.5, simulating typical biogas quality. Ni supported on LaZr and CeZr carriers that obeyed enhanced basicity and oxygen ion lability values than Zr, exhibited superior catalytic efficiency and stability. A variety of techniques, namely N 2 physisorption-desorption (BET method), powder X-ray diffraction (XRD), hydrogen temperature programmed reduction (H 2 -TPR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, potentiometric titration and inductively coupled plasma emission spectroscopy (ICP), were applied for the characterization of particles morphology, textural, structural and other physical properties of the materials, as well as the type of carbon deposited on the catalytic surface after exposure to DRM reaction conditions. Post-reaction analysis of the deposited carbon on the catalysts surfaces showed that the prominent trend of the carbon deposits on the Ni/Zr and Ni/LaZr samples was to have a filamentous tube like morphology (graphite-2H). In contrast, on the Ni/CeZr used catalyst, the formation of small amount of carbon tube-like architectures was detected. The enhanced basicity and Ni dispersion of the Ni/LaZr and Ni/CeZr samples as well as the high oxygen ion lability of the lattice oxygen in the latter, were considered to be the major factors involved in the superior efficiency and durability of these samples in comparison to Ni/Zr sample.

Background: Vitamin D deficiency has been associated with increased colorectal cancer (CRC) incidence risk and mortality. Vitamin D mediates its action through binding of the vitamin D receptor (VDR) and polymorphisms of the VDR might explain these inverse associations. Methods: The aim of the study was the investigation of TaqI, ApaI, FokI and BsmI polymorphisms of the VDR gene for their relevance to colorectal carcinogenesis and progression. Peripheral blood was obtained from 397 patients with early operable stage II/III (n=202) and stage IV (n=195) CRC. Moreover, samples from 100 healthy donors and 40 patients with adenomatous polyps were also included as control groups. Genotyping in samples from patients and controls was performed using PCR-RFLP. Results: A significant association revealed between all four polymorphisms and cancer. Individuals with homozygous mutant (tt, aa, ff or bb) genotype are more susceptible to the disease (p

Among pollutants, nanoparticles (NPs) consist a potential environmental hazard, as they could possibly harm the aquatic and terrestrial ecosystems while having unpredictable repercussions on human health. Since monitoring the impact of NPs on aquatic and terrestrial life is challenging, due to the differential sensitivities of organisms to a given nanomaterial, the present study examines magnetite nanoparticles' mediated toxicity in different animal models, representing distinctive environments (terrestrial and aquatic). Oxidative, proteolytic and genotoxic effects were evaluated on the hemocytes of the snail Cornu aspersum; in addition to those, apoptotic effects were measured in gills and liver of the zebrafish Danio rerio, and the prussian carp Carassius gibelio. All biochemical parameters studied increased significantly in animals after 8 days exposure to NPs. Inter-species and inter-tissues differences in responses were evident. Our results suggest a common toxicity response mechanism functioning in the tissues of the three animals studied that is triggered by magnetite NPs. The simultaneous use of these parameters could be established after further investigation as a reliable multi-parameter approach for biomonitoring of terrestrial and aquatic ecosystems against magnetite nanoparticles. Additionally, the results of our study could contribute to the design of studies for the production and rational utilization of nanoparticles.

Nanoparticles with general formula CoFe2-xRExO4 (RE = Yb, Dy, Gd; x = 0.0–0.3) were synthesized by the co-precipitation and heat treated for potential application in magnetic hyperthermia. The influence of RE doping on structural, magnetic and thermal properties has been investigated. The RE cations enter the spinel lattice as detected by X-ray diffraction. Thermal treatment leads to thermodynamically stable and relaxed single-phase spinel structures only for lower RE content, x = 0.01–0.05. The annealed samples present higher mass magnetization values up to 83 Am2/kg. In the case of annealed samples saturation magnetization decreases linearly from 83 Am2/kg (x = 0.01) to about 60 Am2/kg (x = 0.30). Thermal treatment induces a reduction in coercivity from 60 to 100 mT for as-prepared samples to 18–33 mT for annealed samples. Heating efficiency, i.e., Specific Loss Power of all samples has been studied using both magnetometric and calorimetric method to examine the energy loss mechanisms.

Highlights • Anatomic variations of the origin of IMA and of its relationship with the AA are of paramount clinical importance as regards to diagnosis and surgical treatment. • Such variations might encumber high ligation of the IMA during surgery for rectal cancer, with subsequent implications or may pose a major risk factor of accidental injury and hemorrhage. • Such anatomic variations of the origin of the IMA and its relationship with AA, may be actually more common, than described in the literature., Introduction Identification and ligation of the inferior mesenteric artery (IMA) is a crucial surgical step when performing lower anterior resection (LAR) for rectal cancer. Anatomic variations of the relation between the IMA and the bifurcation point of abdominal aorta (AA) encumber surgical maneuvers and are of great clinical importance. Presentation of case An unusual anatomic variation of the relation between IMA and the bifurcation point of AA was unexpectedly detected during LAR to a 69-year-old Caucasian female patient. The operation was uneventful. A meticulous review of the recent literature was conducted as well. Discussion Variations of the mesenteric vascular supply are mainly identified incidentally, during the operation. In particular, variations of IMA are extremely uncommon in the literature. However, such kind of congenital variations, are not as rare as considered and their presence encumbers surgical maneuvers and increases the potentiality of intraoperative injury and hemorrhage. Conclusion Surgeons’ deep knowledge and unceasing awareness concerning probable anatomic variations of the relation between the IMA and AA, combined with detailed exposure of the operative field and of the relationship between these adjacent arteries constitute the cornerstone of a safe operation.

ZnO nanostructures were obtained by metal-organic chemical vapor deposition via Ag catalyst-assisted growth in a temperature range of 200-500 degrees C. Growth at temperatures above 500 degrees C resulted in vertically aligned ZnO nanorods (NLs). Ag incorporation into ZnO up to 0.4 at.% promoted creation of basal plane stacking fault (BSF) defects and corrugation of the side facets of the NLs. The presence of BSFs give rise to an additional photoluminescence peak with a wavelength of similar to 386 nm, which is slightly red-shifted compared to the commonly observed NBE emission at similar to 375 nm. The observed emission was found to be specifically observed from the side facets of the NLs. It is suggested that this emission is due to a high concentration of BSFs in the ZnO as a result of an incorporation of Ag as acceptor dopant. [GRAPHICS] SEM image of an Ag-doped ZnO nanorod with corrugated side facets. The observed corrugation is accompanied by a high concentration of basal plane stacking faults.

Baklavaridis, A., Tsiaoussis, I., Panayiotou, C., & Zuburtikudis, I. (2016). Effect of tungsten disulfide nanotubes on the thermomechanical properties of polypropylene‐graft‐maleic anhydride nanocomposites. Journal of Applied Polymer Science, 133(35)., In this work, the influence of tungsten disulfide nanotubes (INT-WS2) on the mechanical, thermal, structural, and morphological characteristics of Polypropylene-graft-maleic anhydride (PPGMA) nanocomposites is investigated. The addition of 5% INT-WS2 increases the Young's Modulus by 28.5% and the storage modulus by 196.5% (in the rubbery state). Furthermore, the nanocomposites' thermal stability increases (up to 10 °C) with the addition of INT-WS2. Transmission electron microscopy observations of the nanocomposites revealed that nanotubes' length is significantly reduced during processing and that nanotubes are well-dispersed inside the PPGMA matrix. DSC results indicated that INT-WS2 serve as nucleating agents in PPGMA. Moreover, AFM observations (coupled with DSC results) suggested the formation of fibrillar crystallites in the nanocomposites. This interfacial crystalline structure seems to interpose between the PPGMA and INT-WS2. Thus, it plays a crucial role in the load transfer from the amorphous part of the polymer to the rather stiff INT-WS2.

The magnetic properties of diluted films composed of nanocomposite Co-CoO nanoparticles (of ∼8 nm diameter) dispersed in a Cu matrix have been investigated. The nanoparticles were formed in an aggregation chamber by sputtering at different Ar/O2 partial pressures (0-0.015). The exchange-bias properties appear to be insensitive to the amount of O2 during their formation. However, the temperature dependence of the magnetization, M(T), exhibits two different contributions with relative intensities that correlate with the amount of O2. The magnetic results imply that two types of particles are formed, nanocomposite Co-CoO (determining the exchange-bias) and pure CoO, as confirmed by transmission electron microscopy observations. Importantly, as the O2 partial pressure during the sputtering is raised the number of nanocomposite Co-CoO nanoparticles (exhibiting exchange-bias properties) is reduced and, consequently, there is an increase in the relative amount of pure, antiferromagnetic CoO particles. © 2011 Springer Science+Business Media B.V.

Ball-milling of magnetite powder is studied as a potential method to produce large quantities of nanostructured particles for As(III) and As(V) adsorption. Surfactant-assisted milling resulted in 30 nm isolated nanoparticles with high specific surface area but limited adsorption capacity. On the opposite, when no surfactant is added, large aggregates (300 nm) surrounded by a thick α-Fe 2 O 3 shell were formed. Hematite-coated particles appear to be very effective in the removal of As(III) and As(V) from aqueous solutions being able to adsorb around 1.0 and 2.1 μg/mg, respectively, while keeping the residual arsenic below the regulation limits for drinking water. In addition, the existence of a magnetic core facilitates their application in a magnetic separation system.

The aim of this work was the fabrication of Nd 2 Fe 14 B nanoparticles, through a “top-down” technique like surfactant-assisted high-energy ball-milling, and the monitoring of the milling-process stages with respect to the structure and magnetism. The ball-milling of a 40 μm powder under Ar atmosphere, in an organic solution of oleic acid/oleylamine, resulted in 15 nm isolated nanoparticles after 20 h, presenting improved magnetocrystalline anisotropy compared to the initial material. By extending the mechanical process up to 100 h a gradual formation of elongated nanoparticles followed by structural amorphization was observed.

We have developed a modified synthetic protocol for the growth of monodispersed, superparamagnetic, flower-like colloidal nanoclusters (CNCs), which are consisted of smaller iron oxide nanocrystals with adjustable size. We show that their optical properties can be tuned by applying an external magnetic field. The latter controls the subtle balance of the CNCs’ mutual interactions (magnetic versus electrostatic) and drives their assembly in aqueous media. Spectrophotometric measurements reveal that a diffuse reflectance maximum, in the visible range, is related to the CNCs organization. As the strength of the external magnetic field increases, in the range 160–600 G, the spectral weight of this feature shifts towards the blue region of the spectrum. The induced photonic crystal-like response entails a remarkable magneto-optical behavior, closely associated with the size-dependent characteristics of the CNCs ensemble. Such materials pave the way for promising technological implementations in photonics.

In core–shell systems with non-magnetic core and magnetic shell, the electron transport and magnetic properties are expected to show enhanced behavior due to the particular morpho-structural features of the conductive and magnetic regions. This may lead to novel advanced GMR materials and spin valves. This is the case of core–shell Ag–Co colloidal nanoscale particles that organize into regular arrays. An insight on the structure and morphology of the newly synthesized Ag–Co nanoparticles deposited on different substrates will be presented. The influence of the substrate on different morphologies and organization dynamics is discussed. It is shown that the magnetic behavior of the Ag–Co nanoparticles is highly influenced by the corona-like morphology of Co shell, chemical environment of the magnetic atoms and by the fact that they exhibit strongly reduced coordination due to the surface states.

Spherical 4 nm FePt nanoparticles were synthesized by the simultaneous decomposition of Fe(CO)5 and the polyol reduction of Pt(acac)2. The final Fe-to-Pt composition was tuned between 15-55 at.% by varying the ingredient precursor ratios. The effect of composition and structural ordering on the macroscopic magnetic features of final FePt nanoparticles was examined via post-synthetic annealing stages at different conditions. Structural ordering is promoted in all cases, though samples approximating equiatomic Fe/Pt ratios eventually transform to fct-FePt phase while the FePt3-phase is favored for the Pt-richer samples. Consequently, the magnetic features of the annealed nanoparticles may be categorized; the hard magnetic FePt region dominating for Fe content between 40-55 at.% and the soft magnetic FePt3 region dominating in the region 20-30 at.% while Fe content less than 20 at.% results in Pt-richer phases with diminishing ferromagnetic behavior.

The controllable synthesis of relatively large nickel nanoparticles via thermal decomposition of nickel acetate tetrahydrate in oleylamine in the presence of 1-adamantane carboxylic acid (ACA) and trioctylphosphine oxide (TOPO) is reported. High crystalline hcp nanoparticles of different sizes have been prepared at 290 °C, whereas at relative lower temperatures fcc are favored. The particle size was varying between 50 and 150 nm by properly adjusting the proportion of the capping ligands. TOPO-to-ACA ratio was also found to have an influence on the magnetic properties through the potential formation of a NiO shell. Pure hcp Ni nanoparticles over 50 nm in size served as models to illuminate the magnetic behavior of this metastable hexagonal Ni phase. Contrary to the net ferromagnetic characteristics of fcc Ni nanoparticles in the same size range, hexagonal structured particles exhibit superparamagnetic behavior at room temperature and a weak ferromagnetic contribution below 15 K.

ZnO single crystal nanohexagons have been grown heteroepitaxially on p-type Si-face 4H-SiC substrates with 8 degrees miscut from to [0 0 0 1] by catalyst-free atmospheric pressure metalorganic chemical vapor deposition and characterized by x-ray diffraction, scanning and transmission electron microscopy as well as energy disperse x-ray and cathodoluminescence analyses. The as-grown ZnO nanohexagons have a pillar shape terminated by a and c plane facets, and are aligned along the growth direction with the epitaxial relation [0 0 0 1](ZnO) parallel to[0 0 0 1](4H-SiC) and [1 0 (1) over bar 0](ZnO) parallel to[1 0 (1) over bar 0](4H-SiC). The ZnO nanohexagons demonstrate intense UV emission (lambda(NBE)=376 nm) and negligible defect-related luminescence.

In the present study, different series of high-density polyethylene (HDPE) nanocomposites were prepared by melt mixing on a Haake-Buchler Reomixer, containing 2.5 wt % of multiwall carbon nanotubes, pristine and modified montmorillonite, surface-treated and -untreated SiO2 nanoparticles. From transmission electron micrographs, it was found that beyond a fine dispersion of nanoparticles into HDPE matrix, there are also some aggregates easily discriminated. As a result, there was a decrease in the tensile and impact strength of most of nanocomposites except Young's modulus, which was increased. Storage modulus as recorded from dynamic mechanical analysis was also increased in all nanocomposites, because HDPE becomes stiffer due to the incorporation of nanoparticles. The nucleation behavior of nanoparticles during crystallization was found to have no obvious effect on melting and crystallization temperature of HDPE. However, a small decrease in the heat of fusion in all nanocomposites was evidenced. Gas permeability of HDPE matrix in O2, N2, and CO2 was reduced in all nanocomposites compared with neat polymer. Thermal stability of HDPE was also enhanced due to the incorporation of different nanoparticles. From the kinetic analysis of thermal decomposition of HDPE, it was concluded that to describe the thermal degradation of HDPE and the studied nanocomposites, two consecutive mechanisms of nth-order autocatalysis have to be considered. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

In this work, we study the influence of Pt underlayer in Pt/Sm–Co/Pt trilayers and in Pt/Sm–Co multilayers. In both cases, Pt underlayer seems to impose better crystallinity to Sm–Co layer and certainly promotes the evolution of the hard-magnetic SmCo 5 phase. Particularly, in the case of multilayer form, where multiple interlayers of Pt each one serving as a dedicated underlayer for the deposition of a specific Sm–Co layer, enhanced crystallinity is observed. Moreover, post-deposition annealing facilitates these features at relatively lower temperatures (∼400 °C) than those met in thin-film cases. This behavior is also followed by enhancement of saturation magnetization, while higher temperature post-deposition thermal treatment seems to deteriorate structural and magnetic features. If annealing temperature gets over 550 °C macroscopic magnetic features depress, probably due to domination of annealing-activated processes such as Sm oxidation and formation of non-magnetic phases since Pt diffuses throughout the whole magnetic layer.

Co x Pt 1− x nanostructures with varying composition and controllable morphologies have been synthesized through the thermal decomposition of appropriate platinum and cobalt precursors in organic solvents. The employment of several different surfactants facilitated the production of nanostructures with various sizes and shapes including nanowires, flower-like structures and spherical particles. The composition of the as-prepared nanomaterials ranged between Pt-rich and stoichiometric CoPt alloy, mainly depending on the starting ratio of the precursors. Three-dimensional structures such as the ‘flower-like’ ones showed a net ferromagnetic behavior, even at room temperature. In certain cases, the alloy nanostructures were annealed in order to obtain the ‘hard’ fct-CoPt phase, which displayed high coercivity values.

Ni nanoparticles were prepared via thermal decomposition of nickel acetate tetrahydrate in the presence of long-chain amines, which acted as both solvents and reducing agents. By tuning the reaction temperature, Ni nanostructures with either hcp or fcc crystal structure were obtained. In principle, higher temperatures favored the formation of hcp nanoparticles. The employment of additional surfactants such as 1-adamantanecarboxylic acid and trioctylphosphine-oxide facilitated the tuning of the particles’ growth limit. The size of the particles varied between 5 and 120 nm. The magnetic features of fcc-Ni nanoparticles were quite similar to the corresponding ‘bulk’ ones. On the other hand, the hcp-Ni particles showed weak magnetic features, reflected by low magnetization values, the absence of saturation magnetization and by blocking temperatures far below room temperature.

The electronic structure of in-grown 8H stacking faults in 4H-SiC matrix has been investigated in detail. After assessment of the structural properties by high resolution transmission electron microscopy, we focus on the electronic structure. We show that one unit cell of 8H does not behave like a single type-II quantum well but, rather, like two type-II quantum wells of 3C coupled by a thin hexagonal barrier. Using a transfer matrix method, we compute the corresponding transition energies, taking into account the effect of the valence band offset and built-in electric field. A good agreement is found with the experimental data collected from low temperature photoluminescence spectroscopy.

The combination of transparent conductive oxides with high-barrier films deposited onto flexible polymeric substrates is of considerable importance in order to improve the efficiency, lifetime and stability of flexible electronic devices. In this work, ZnO thin films have been deposited onto high-barrier hybrid/PET flexible substrates by pulsed DC magnetron sputtering, at room temperature and by applying different power values on the target. The employment of in situ and real-time Vis-fUV (1.5-6.5 eV) spectroscopic ellipsometry allowed the investigation of the growth mechanisms of ZnO thin films as well as the modification procedure in the hybrid's surface. Island growth is dominant during the initial stages of deposition concerning low target power regime, whereas layer-by-layer deposition prevails at the high target power regime. The hybrid's modified layer of approximately 10nm was confirmed by the transmission electron microscopy measurements which additionally revealed a columnar structure of the film with a nanocrystalline morphology. The estimated size of the nanocrystals ( approximately 15 nm and above) was compatible with atomic force microscopy (AFM) measurements. Finally, the evolution of the optical parameters (energy gap and absorption peaks) of the ZnO films during the deposition was similar.

Boron nitride (BN) thin films grown on Si (100) substrates by radio frequency magnetron sputtering, with varying growth parameters, are studied by high-resolution transmission electron microscopy (HRTEM). The HRTEM study reveals the presence of several interesting nanostructures in the BN films. Nanotube-like configurations, nanoarches and nanohorns are observed, as well as well-orientated cubic BN nanocrystals. It is found that several configurations of the turbostratic BN planes (properly orientated or curved) can act, in the same film, as nucleation sites for the growth of the cubic phase.

This work concentrates on the influence of synthetic mechanisms of FePt nanoparticles on their self-arrangement and some structural and magnetic properties as studied by means of different electron microscopy techniques and SQUID magnetometry. High-reflux points associated with long boiling durations seem adequate to increase the iron precursor's decomposition yield and facilitate the simultaneous cubic to tetragonal FePt transformation, in single-phase FePt nanoparticles. Nevertheless, such conditions also result in the loss of long-range arrangement and in the appearance of coalescence effects. A core–shell structure comprising of FePt and Fe3O4 is favored under mild thermal conditions during synthesis, which seems to confront the undesirable atomic diffusion. Additionally, particle isolation due to the surfactant coating leads in an hcp-symmetry self-assembly. Moreover, working at lower temperatures allows a homogeneous mixture between different phases producing binary composite arrays.

In boron-substituted melt-spun Sm(Co,Fe,Cu,Zr) 7.5 -type alloys a nanocomposite microstructure and high coercivities in both as-spun and short-time annealed ribbons can be obtained. In the present study three different compositions, namely Sm(Co 0.73 Fe 0.1 Cu 0.09 Zr 0.04 B 0.04 ) 7.5 , Sm(Co 0.70 Fe 0.1 Cu 0.12 Zr 0.04 B 0.04 ) 7.5 and Sm(Co 0.70 Fe 0.1 Ni 0.12 Zr 0.04 B 0.04 ) 7.5 have been examined in order to investigate the influence of composition on the magnetic properties and the microstructure. Melt-spun ribbons have been obtained and annealing has been followed under argon atmosphere for 30–75 min at 600–870 °C. For the as-spun ribbons the TbCu 7 -type of structure and fcc-Co as a secondary phase have been identified in the X-ray diffraction patterns. For the annealed ribbons above 700 °C the 1:7 phase transforms into 2:17 and 1:5 phases. The TEM studies have shown a homogeneous nanocrystalline microstructure with average grain size of 30–80 nm. Coercivity values of 15–27 kOe have been obtained from hysteresis loops traced in non-saturating fields. The coercivity decreases with temperature, but it is sufficiently large to maintain values higher than 5 kOe at 380 °C.

Ultra-thin nanocrystalline silicon films with varying thickness from 5 to 36nm were grown on quartz by low pressure chemical vapor deposition (LPCVD) of Si. Observations on cross-sectional transmission electron microscopy (TEM) specimens revealed that the films had a columnar growth, i.e. the third dimension of the nanocrystals, perpendicular to the SVSi0 2 interface, was approximately equal to the film thickness, while the lateral size of nanocrystals was defined during the initial stage of growth and was not very much affected by the film thickness. The observed columnar growth gives the possibility to obtain two-dimensional nanocrystal arrays on quartz with well defined size in the z-direction. Plane view images showed that the lateral distribution of nanocrystal size presents a well-defined maximum in all the films. The mean lateral size of the nanocrystals did not change very much with the film thickness, being in the range of 11-13 nm. The num- :: ber of grains with size larger than the mean one tended to increase with the thickness of the film.

ZnO thin films were deposited onto flexible Poly-Ethylene Terephthalate and Poly-Ethylene Naphthalate substrates in an ultra-high vacuum chamber by Pulsed DC Magnetron Sputtering. The process took place at room temperature and in argon atmosphere with fixed pressure, by applying two different power values on the target, in order to investigate their effect on the growth, optical, nanostructural and topographical properties of the films. In-situ and real-time Spectroscopic Ellipsometry in the 1.5–6.5 eV energy region has been employed to monitor the ZnO deposition, which revealed information about the growth mechanisms, interface phenomena and optical properties of the films. Transmission Electron Microscopy was used in order to investigate the structural characteristics of the films and to examine the film/polymer interface properties. The X-ray Diffraction measurements revealed the changes in films structure caused by the change of the target power, nevertheless all films were preferentially grown along the (002) axis. Finally, with Atomic Force Microscopy the surface roughness of the films was defined correlated also with the target power applied. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

CoPt-based hard–soft sputtered bilayers with (1 1 1) texture have been produced by appropriate heat treatment of the bottom layer. Two samples with different degrees of chemical ordering of the hard layer are compared. The anisotropy of the hard layer determines its robustness against destabilization from the soft one. Detailed measurements of the soft layer minor hysteresis loop features as a function of the magnetic state of the hard layer are proposed as a means to study the nature of interfacial exchange interactions and the mechanism of magnetization reversal. When hard layer anisotropy is not robust enough, the reversed soft layer can induce irreversible changes to the magnetic structure at the interface leading to a decoupling of exchange field from the magnetic state of the hard layer.

This work proposes a large-scale synthesis methodology for engineered and functional magnetic nanoparticles (i.e. ferrites, sulfides) designed towards the principles of green and sustainable production combined with biomedical applicability. The experimental setup consists of a two-stage continuous-flow reactor in which single-crystalline nanoparticles are formed by the coprecipitation of metal salts in an aqueous environment. A series of optimized iron-based nanocrystals (Fe3O4, Fe3S4, CoFe2O4 and MnFe2O4) with diameters between 18 and 38 nm has been obtained. The samples were validated as potential magnetic hyperthermia agents by their heating efficiency as determined by specific loss power (SLP) in calorimetric experiments. In an effort to enhance colloidal stability and surface functionality, nanoparticles were coated by typical molecules of biomedical interest in a single step process. Finally, two-phase particle systems have been produced by a two-stage procedure to enhance the heating rate by the effective combination of different magnetic features. Results indicate relatively high SLP values for uncoated nanoparticles (420 W g−1 for Fe3O4) and a reduction of 20–60% in the heat dissipation rate upon covering by functional groups. Eventually, such effect was more than counterbalanced by the magnetic coupling of different phases in binary systems, since SLP was multiplied up to ∼1700 W g−1 for MnFe2O4/Fe3O4 suggesting a novel route to tune the efficiency of magnetic hyperthermia agents.

We report on the application of a single layer graphene substrates for the growth of polycrystalline ZnO films with advanced light emission properties. Unusually high ultraviolet (UV) and visible (VIS) photoluminesce was observed from the ZnO/Gr/SiC structures in comparison to identical samples without graphene. The photoluminescence intensity depends non-monotonically on the films thickness, reaching its maximum for 150 nm thick films. The phenomena observed is explained as due to the dual graphene role: i) the dangling bond free substrate, providing growth of relaxed thin ZnO layers ii) a back reflector active mirror of the Fabry-Perot cavity that is formed. The reported results demonstrate the potential of two-dimensional carbon materials integration with light emitting wide band gap semiconductors and can be of practical importance for the design of future optoelectronic devices. Funding agencies: Linkoping Linnaeus Initiative for Novel Functional Materials (LiLi-NFM); Angpanneforeningens Forskningsstiftelse [14-517]; European Union [604391]

Co70Cr30 alloyed layers are combined with extremely thin Pt layers in order to produce novel face-centered-cubic multilayered films to be considered as a potential perpendicular magnetic recording medium. The films were grown on Si, glass and polyimide substrates by e-beam evaporation at a temperature slightly higher than room temperature. The multilayered structure of the films was verified by X-ray diffraction experiments. Plane-view transmission electron microscopy images have revealed the formation of very small grains in the range of 7–9 nm. Hysteresis loops as a function of temperature were recorded via the magneto-optic Kerr effect in the polar geometry configuration. The system exhibits perpendicular magnetic anisotropy, which enhances with decreasing temperature. Hysteresis loops with a squareness of 1 and a coercivity of 1.45 kOe were obtained at 10 K. Furthermore, complete magneto-optic spectra of the films are recorded, showing a strong magneto-optic enhancement in the ultraviolet region at around 4.5 eV.

Monodisperse FeCo nanoparticles were synthesized via thermal decomposition of appropriate organometallic complexes in heated toluene containing surfactants, aiming to a soft magnetic nanomaterial with a high metal percent. The particles were characterized by X-ray powder diffraction, electron microscopy, and static magnetometry techniques. The effect of air exposure on the structural and magnetic properties was examined. Portions of the dried nanoparticles were mixed with additional surfactants or polyvinylpyrrolidone, followed by redispersion into tetrahydrofuran, so as to study arrangement features in the first case, while the use of polyvinylpyrrolidone intended to the expansion of the interparticle distances in order to get more "isolated" nanoparticles.

Pd thin films, grown on Si-rich 6H-SiC(0 0 0 1) substrates, were studied by atomic force microscopy, electron diffraction and high-resolution transmission electron microscopy. It is concluded that the growth is successful only when all the growth process takes place at room temperature. Under these conditions a very good epitaxial growth of Pd is achieved, despite the large misfit (about 8.6%) between Pd and the substrate and the existence of a semi-amorphous layer between the thin film and the substrate. A large number of twins appear in these films.

Silicon nanocrystals (nc-Si) have gained great interest due to their excellent optical and electronic properties and their applications in optoelectronics. The aim of this work is the study of growth mechanism of nc-Si into a-SiO 2 matrix from SiO/SiO 2 multilayer annealing, using non-destructive and destructive techniques. The multilayer were grown by e-beam evaporation from SiO and SiO 2 materials and annealing at temperatures up to 1100 °C in N 2 atmosphere. X-rays reflectivity (XRR) and high resolution transmission electron microscopy (HRTEM) were used for the structural characterization and spectroscopic ellipsometry in IR (FTIRSE) energy region for the study of the bonding structure. The ellipsometric results gave a clear evidence of the formation of an a-SiO 2 matrix after the annealing process. The XRR data showed that the density is being increased in the range from 25 to 1100 °C. Finally, the HRTEM characterization proved the formation of nc-Si. Using the above results, we describe the growth mechanism of nc-Si into SiO 2 matrix under N 2 atmosphere.

In a Pd thin film grown on a 6H-SiC (0001) substrate, several twin interfaces have been observed, classified as (1) {111}Sigma = 3 twin interfaces and (2) {221}Sigma = 3 twin interfaces. The first ones are coherent twin interfaces and in some cases exhibit steps of one or more atomic layers in height. The second ones are perpendicular to the first ones. They usually appear with a rigid-body displacement, but in some cases no displacement was observed. Models for the interfaces are proposed.

CrN–TiN thin films were deposited as successive, alternating layers on Si(100) substrates using a closed field unbalanced reactive magnetron sputtering method (CF-UBRMS) at various substrate biases ( V b ) and substrate rotation speeds. High resolution electron microscopy (HREM) study showed that the nanostructural characteristics of the films depend on the growing conditions. For the case of substrate bias V b = − 50 V and high rotation speed of the substrate, the film is polycrystalline with no preferential growth mode, while for lower speeds two nanocrystalline layers are formed with preferential growth orientations: [100] nitrides //[100] Si in the first zone and [111] nitrides //[100] Si in the second one. Epitaxial growth is observed sometimes locally in grains of the first zone. The multilayer character of the films was partially preserved only for films grown with the substrate at floating potential and low substrate rotation speed. For a higher speed, the growth takes place also with the two-zone growth mode.

Cerium dioxide (CeO2) exhibits exceptional electronic properties such as optical transparency and high refractive index (n) and high dc dielectric constant (k). Therefore, it is an attractive material for ultra-thin gate oxide in CMOS technology, where high-k dielectrics are required. We study the electronic properties of nanostructured and porous cerium oxide (CeOx) films, 110-500 nm thick, grown on Si by electron beam evaporation (EBE) and ion beam assisted deposition (IBAD). The film microstructure and morphology (grain size, porosity, defect concentration, surface and interface roughness) are controlled by varying the process parameters appropriately. They have been studied by high-resolution and transmission electron microscopy (HRTEM). The optical properties have been studied by spectroscopic ellipsometry (SE) and k was determined by capacitance measurements. We have found that the values of k and n (1.6-2.5 depending on porosity) are affected by the electronic transitions, which are strongly correlated with the microstructure and morphology of the films. We investigate how the microstructure and morphology variations affect the absolute values of the dc dielectric constant and of the dielectric function at the UV-Vis and IR spectral regions. In addition, we investigate the very important role of the defects, which have the form of grain boundaries, trivalent Ce3+ and O vacancies. As a result we were able to tailor n and k of CeOx films controlling their porosity and defect density. (C) 2003 Elsevier B.V. All rights reserved. Materials Science and Engineering B-Solid State Materials for Advanced Technology

Recent developments of lithographic techniques as well as improved chemical synthesis methods allow researchers to engineer novel nanostructured materials consisting of arrays of self-organized nanocrystals and multilayers grown as patterns on different substrates. In our case, the magnetic nanostructures consist either of multilayers directly deposited on pre-patterned substrates to form regular arrays of stripes and grooves or colloidal solutions of self-organized bimetallic Ag/Co nanoparticles on patterned and nonpatterned substrates. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed in order to study the surface morphology of the 2D patterning arrays and the 3D nanostructures. The development of periodic arrays of magnetic patterns of micrometer size is strongly dependent on technological parameters such as: film thickness, distances, size and shape of the patterns. Moreover, it is shown that the substrate morphology significantly affects the colloidal crystallization of magnetic nanoparticles and leads to different growth modes. This will ultimately affect the overall magnetic behavior of the nanostructures. Consequently, the combination of self-assembly and patterning allows for the controlled fabrication of the novel magnetic nanostructures at a macroscopic level and the study of fundamental aspects in magnetism such as quantum tunneling magnetization and magneto-transport properties along well-defined nanosized patterns.

The main challenge in fabrication of ZnO-based devices is the absence of reliable p-type material. This is mostly caused by insufficient crystalline quality of the material and not well-enough-developed native point defect control of ZnO. At present high-quality ZnO wafers are still expensive and ZnO heteroepitaxial layers on sapphire are the most reasonable alternative to homoepitaxial layers. But it is still necessary to improve the crystalline quality of the heteroepitaxial layers. One of the approaches to reduce defect density in heteroepitaxial layers is to introduce a strained-layer superlattice (SL) that could stop dislocation propagation from the substrate-layer interface. In the present paper we have employed fifteen periods of a highly strained SL structure. The structure was grown on a conventional double buffer layer comprising of high-temperature MgO/low-temperature ZnO on sapphire. The influence of the SLs on the properties of the heteroepitaxial ZnO layers is investigated. Electrical measurements of the structure with SL revealed very high values of the carrier mobility up to 210 cm 2 /Vs at room temperature. Structural characterization of the obtained samples showed that the dislocation density in the following ZnO layer was not reduced. The high mobility signal appears to come from the SL structure or the SL/ZnO interface.

The aim of this study was to investigate any possible relation between the severity of anorectal dysfunction in diabetes mellitus and duration of disease and presence of microangiopathy or neuropathy or both.Standard multiport anorectal manometry was performed in 25 healthy control subjects (10 males; age (mean +/- 1 standard deviation), 62 +/- 14 years) and 38 patients with diabetes mellitus. Patients were divided into two groups according to the duration of the disease: Group A (19 patients) with a duration less than 10 years (7.2 +/- 2.5; 8 males; age, 57 +/- 18) and Group B (19 patients) with a duration longer than 10 years (19.8 +/- 5.6; 6 males; age, 62 +/- 15).Results are reported as mean +/- one standard deviation. Patients showed lower resting and squeeze anal pressures (P0.01), impaired rectoanal inhibitory and anocutaneous reflexes, and reduced sensitivity in rectal distention (P = 0.004) as compared with controls. In addition, Group B showed a significantly increased incidence of microangiopathy (P = 0.04) and autonomic and peripheral neuropathy (P = 0.002), significantly reduced basal and squeeze anal pressures (52 +/- 16 vs. 64 +/- 24 mmHg; P = 0.03 and 98 +/- 39 vs. 124 +/- 54 mmHg; P = 0.04, respectively), reduced amplitude of slow waves (7.3 +/- 3 ts. 9.5 +/- 3.7 mmHg; P = 0.03), anal leak in smaller rectal volumes (P = 0.003), and reduced response of the anal sphincter at the anocutaneous reflexes (29 +/- 14 vs. 39 +/- 14 mmHg; P = 0.05) compared with Group A. The former group of patients exhibited a significantly higher incidence of fecal incontinence (P = 0.008).Patients with long-standing diabetes mellitus have increased incidence of fecal incontinence and severely impaired function of both the anal sphincters and the rectum. These findings could be attributed to the increased incidence of microangiopathy and autonomic and peripheral neuropathy observed in this subset of diabetic patients.

Zinc oxide quantum dots were prepared in diethyleneglycol using zinc acetate as a precursor compound and the particle size of the dried powders was determined using the X-ray diffraction method (XRD). It was found that quantum dot size ranges from 4 to 9 nm and is influenced by the initial zinc acetate concentration and the centrifugation speed. Theoretical predictions concerning quantum dot size by the potential morphing method showed good agreement with the measurements from XRD.

The reaction of Pd thin films evaporated in ultrahigh vacuum on a clean and Si-rich 6H-SiC(0001)(3×3) surface has been investigated in situ by low-energy electron diffraction (LEED) and photoelectron spectroscopy (UPS and XPS), and ex situ by atomic force microscopy (AFM) and glancing-incidence X-ray diffraction (GIXRD). For studying the interface formation, submonolayer amounts of Pd were sequentially deposited up to ∼20 A on the substrate maintained at room temperature. This deposit was subsequently annealed to 600–800 °C. At room temperature, Pd starts to react with SiC when the thickness attains ∼2.5 A, giving an interface Pd2Si silicide. Under annealing the film is transformed into Pd2Si islands standing on the SiC (1×1) surface. No extra-structure of C 1s is observed in the two cases; only an energy shift of about 0.25 eV is detected during the metal deposition, which is attributed to a change in the band bending. Further deposition of ∼100 A of Pd on this annealed surface gives an epitaxial Pd(111) film, despite a lattice mismatch of more than 10% between the metal and the semiconductor. The film is disrupted after annealing at 600–800 °C. The combination of XPS, AFM and GIXRD analyses indicates that the film annealed at 800 °C is discontinuous and formed of sharp epitaxial Pd2Si islands and graphite which probably surrounds the islands.

Zinc thermal spraying is widely used for steel coatings. In the present work, the morphology and the corrosion performance of the as-formed coatings is investigated. Initial observations took place with a low magnification stereoscope equipped with a CCD camera, while Scanning Electron Microscopy (SEM) was used for more detailed observation. Selected samples were also examined with High Resolution Electron Microscopy (HREM) in order to investigate the oxygene distribution which was detected by EDS analysis. Corrosion tests were accomplished in a Salt Spray Chamber (SSC) and the corroded samples were also examined with SEM. From this investigation it was deduced that the ascast coatings are mainly composed by pure zinc. However, zinc oxide inclusions were also encoutered in the form of nanoparticles. Regarding corrosion, the samples exposed in the SSC were uniformly attacked. Nevertheless the substrate was effectively protected.

It has been recently shown that erythromycin, amacrolide antibiotic, exhibits prokinetic properties, byenhancing gastric emptying in health and disease and byinducing gallbladder contraction. The aim of the study was to further investigate theeffect of intravenous erythromycin on gallbladdermotility during fasting and postprandial states. In 10healthy male subjects gallbladder emptying was assessed by ultrasonography on three differentoccasions, each in a random sequence, as follows: (1)after giving 300 ml of fresh milk and infusing normalsaline as placebo (postprandial emptying), (2) afterinfusing 200 mg of erythromycin during the fastingstate, and (3) after infusing 200 mg of erythromycinalong with ingestion of 300 ml of fresh milk. Infusionof erythromycin and placebo lasted 10 min. From the emptying curves, the duration of the lag phaseof emptying, the ejection fraction of emptying, and thetime by which maximal emptying was achieved werecalculated. Infusion of erythromycin induced animmediate contraction [lag phase (±SD): 1.3± 2.6 SD min] of the gallbladder by 42.1 ±22% of its initial volume. Infusion of erythromycinduring the postprandial state significantly decreasedthe duration of the lag phase (1.3 ± 3.5 min after erythromycinplus test meal versus 3.6 ± 4.2 min after testmeal only, P < 0.04) and significantly increased theejection fraction (78 ± 8.5% after erythromycinplus test meal versus 60.6 ± 8.5% after test meal only, P

Multilayered structures with a 40 nm period composed of titanium and two different titanium oxides, TiO and TiO 2 , were accurately produced by DC magnetron sputtering using the reactive gas pulsing process. These multilayers were sputtered onto Al 2 O 3 sapphire to avoid substrate compound diffusion during flash annealing (ranging from 350 °C to 550 °C). Structure and composition of these periodic TiO 2 /TiO/Ti stacks were investigated by X-ray diffraction, X-ray photoemission spectroscopy and transmission electronic microscopy techniques. Two crystalline phases α-Ti and fcc-TiO were identified in the metallic-rich sub-layers whereas the oxygen-rich ones were composed of a mixture of amorphous and rutile TiO 2 phase. DC electrical resistivity ρ measured for temperatures ranging from 25 to 200 °C was influenced by the thermal treatments. The temperature coefficients of resistance of these periodic TiO 2 /TiO/Ti multilayers were modified from 11.7 × 10 − 04 to − 8.81 × 10 − 04 K − 1 . Local changes of crystallinity were reported and the resistivity responses of these annealed films could be linked to the typical electrical behavior of a metal–oxide mixture.

Alloys with nominal stoichiometry Sm 9 (Co 1− x Zr x ) 4 , x =0–0.1, have been produced by arc melting and then annealed under vacuum at temperature range of 700°C–1000°C for 19–65 h. Powder diffraction patterns were analyzed by the Rietveld method. Sample Sm 9 Co 4 , annealed at 700°C for 25 h, crystallizes in the monoclinic Mn 5 C 2 - type of structure (space group C2/ c ) with a =1.6268(9) nm, b =0.64112(37) nm, c =0.70467(39) nm, β =96.52(3) degrees and Z =4. Crystal structure of Sm 9 (Co 0.98 Zr 0.02 ) 4 was described using the Fe 3 C structure type (s.g. Pnma) with a =0.70613(25) nm, b =0.9621(34) nm and c =0.6341(23) nm. In zirconium substituted samples the dominant phase is Fe 3 C structure type. Magnetic phase transitions were observed in thermomagnetic curves traced in the range of 10–300 K, covering both the magnetically ordered and paramagnetic regions. The microstructure, observed by SEM and TEM, drastically changes with Zr substitution for Co.