The paper provides a thermodynamic insight into the metastable nature of InN and In-rich InGaN alloys, based on experimental studies of their plasma-assisted MBE growth and high-temperature ...decomposition, as well as on theoretical modeling of nitrogen vacancy behavior. This instability may easily result in occurrence of metallic In nanoparticles in the bulk of In(Ga)N films and in the vicinity of extended defects at high enough In content, which makes us consider this material as a metal–semiconductor composite. An overview of a wide set of experimental studies performed by us on the epitaxial films grown in many laboratories all around the world is given which proves an existence of such In nanoparticles in the films and shows how they affect optical and electrical properties of the epilayers. Possible applications of epitaxial InN layers for THz emitters and magnetic field sensors are discussed.
•InN and In-rich InGaN need to be regarded as metal-semiconductor composites.•Thermodynamic insight into the metastable nature of InN is provided.•Overview of experimental proofs of complex structures of InN epilayers is presented.•In metal nanoparticles act via particle plasmons and highly conductive inhomogeneities.
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Steel 45 surface is aluminized by electroexplosive alloying. The aluminized surface is treated by an electron beam. The structure and mechanical properties of the surface layer are studied. The ...electroexplosive is shown to lead to the formation of a high-porous coating on the steel surface. The subsequent electron-beam treatment in a mode of melting the surface layer is accompanied by the formation of a smooth surface, the increase in the microhardness in a layer thickness of 45–50 µm by a factor of 3.5 as compared to that of the initial material. The physical nature of the increase in the strength properties of a steel surface layer is explained.
We determine the response of a uniformly rotating star to tidal perturbations due to a companion. General periodic orbits and parabolic flybys are considered. We evaluate energy and angular momentum ...exchange rates as a sum of contributions from normal modes allowing for dissipative processes. We consider the case when the response is dominated by the contribution of an identifiable regular spectrum of low-frequency modes, such as rotationally modified gravity modes. We evaluate this response in the limit of very weak dissipation, where individual resonances can be significant and also when dissipative effects are strong enough to prevent wave reflection from the neighbourhood of either the stellar surface or stellar centre, making radiation conditions more appropriate. The former situation may apply to Sun-like stars with radiative cores and convective envelopes and the latter to more massive stars with convective cores and radiative envelopes. We provide general expressions for transfer of energy and angular momentum that can be applied to an orbit with any eccentricity.
Detailed calculations require knowledge of the mode spectrum and evaluation of the mode overlap integrals that measure the strength of the tidal interaction. These are evaluated for Sun-like stars in the slow rotation regime where centrifugal distortion is neglected in the equilibrium and the traditional approximation is made for the normal modes. We use both a Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) procedure and a direct numerical evaluation which are found to be in good agreement for regimes of interest. The former is used to provide expressions for the mode spectrum and overlap integrals as a function of mode frequency and stellar rotation rate. These can be used to find the tidal energy and angular momentum exchange rates and hence the orbital evolution.
Finally we use our formalism to determine the evolution time scales for an object, in an orbit of small eccentricity, around a Sun-like star in which the tidal response is assumed to occur. Systems with either no rotation or synchronous rotation are considered. Only rotationally modified gravity modes are taken into account under the assumption that wave dissipation proceeds close to the stellar centre. It is noted that inertial waves excited in the convective envelope may produce a comparable amount of tidal dissipation in the latter case for sufficiently large orbital periods.
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•Few-layer graphene nanoflakes with domain size less than 50 nm were used as supports.•Supports with different types of dominating nitrogen species were synthesized.•Stability of ...nitrogen functional groups was investigated.•Catalysts supported on oxidized both pristine and doped supports were the most active.
Nitrogen-doped carbon nanomaterials show unique properties in catalysis both as an active component and as a support. The oxidized and N-doped graphene nanoflakes (GNFs) of low domain size (10–30 nm) have been studied in present work as supports for cobalt-based Fischer-Tropsch catalysts. Three supports with different types of dominating nitrogen species were synthesized and the effect of both the nature and localization of nitrogen species in the support on the structure and performance of 10 wt.% Co catalysts was investigated. Varying the synthesis technique and post-synthesis treatment, the cobalt particle size and hence the activity of catalyst can be tuned. The catalysts supported on oxidized pristine and N-doped GNFs were found to be the most active. Transformations of N-groups during catalyst preparation and reduction were observed. In the case of edge localization of N-groups the cross-linking of support particles was detected that led to the diffusion hindering and low CO conversion over corresponding catalyst.
We report on pseudomorphic MBE growth of CdTe/Zn(Mg)(Se)Te quantum dot (QD) structures on InAs(100) substrates and studies of their structural and optical properties. The QDs were fabricated by using ...a thermal activation technique comprising deposition of a strained CdTe 2D layer, covering it with amorphous Te, followed by fast thermal desorption of the Te layer, which results in a 2D-3D RHEED pattern transition. The QDs exhibit the surface density as low as ~1010cm−2. The influence of MBE growth parameters and the structure design on photoluminescence properties of the QDs are discussed. Single QD photoluminescence was observed at T=8K from the 200-nm-wide mesa-structures made of the CdTe QD structures, and the antibunching effect with g(2)(0)=0.16±0.04 was demonstrated. The peculiarities of MBE growth of ZnTe/MgTe/MgSe short-period superlattices nearly lattice-matched to InAs, which could serve as wide gap barriers for efficient electron and hole confinement in the CdTe/Zn(Mg)(Se)Te QDs, are also described.
•CdTe/Zn(Mg)(Se)Te QD structures lattice-matched to InAs were grown by MBE.•CdTe/ZnTe QDs formed by thermal activation technique demonstrate antibunching effect.•MBE growth of ZnTe/MgTe/MgSe short-period superlattices pseudomorphic to InAs is reported.
Background
Cognitive impairment is an irreversible, aging-associated condition that robs people of their independence. The purpose of this study was to investigate possible causes of this condition ...and propose preventive options.
Methods
We assessed cognitive status in long-living adults aged 90+ (
n
= 2,559) and performed a genome wide association study using two sets of variables: Mini-Mental State Examination scores as a continuous variable (linear regression) and cognitive status as a binary variable (> 24, no cognitive impairment; <10, impairment) (logistic regression).
Results
Both variations yielded the same polymorphisms, including a well-known marker of dementia, rs429358in the APOE gene. Molecular dynamics simulations showed that this polymorphism leads to changes in the structure of alpha helices and the mobility of the lipid-binding domain in the APOE protein.
Conclusion
These changes, along with higher LDL and total cholesterol levels, could be the mechanism underlying the development of cognitive impairment in older adults. However, this polymorphism is not the only determining factor in cognitive impairment. The polygenic risk score model included 45 polymorphisms (ROC AUC 69%), further confirming the multifactorial nature of this condition. Our findings, particularly the results of PRS modeling, could contribute to the development of early detection strategies for predisposition to cognitive impairment in older adults.
Treatment options for adenoid cystic carcinoma (ACC) of the salivary gland, a slowly growing tumor with propensity for neuroinvasion and late recurrence, are limited to surgery and radiotherapy. ...Based on expression analysis performed on clinical specimens of salivary cancers, we identified in ACC expression of the neurotrophin-3 receptor TrkC/NTRK3, neural crest marker SOX10, and other neurologic genes. Here, we characterize TrkC as a novel ACC marker, which was highly expressed in 17 out of 18 ACC primary-tumor specimens, but not in mucoepidermoid salivary carcinomas or head and neck squamous cell carcinoma. Expression of the TrkC ligand NT-3 and Tyr-phosphorylation of TrkC detected in our study suggested the existence of an autocrine signaling loop in ACC with potential therapeutic significance. NT-3 stimulation of U2OS cells with ectopic TrkC expression triggered TrkC phosphorylation and resulted in Ras, Erk 1/2 and Akt activation, as well as VEGFR1 phosphorylation. Without NT-3, TrkC remained unphosphorylated, stimulated accumulation of phospho-p53 and had opposite effects on p-Akt and p-Erk 1/2. NT-3 promoted motility, migration, invasion, soft-agar colony growth and cytoskeleton restructuring in TrkC-expressing U2OS cells. Immunohistochemical analysis demonstrated that TrkC-positive ACC specimens also show high expression of Bcl2, a Trk target regulated via Erk 1/2, in agreement with activation of the TrkC pathway in real tumors. In normal salivary gland tissue, both TrkC and Bcl2 were expressed in myoepithelial cells, suggesting a principal role for this cell lineage in the ACC origin and progression. Sub-micromolar concentrations of a novel potent Trk inhibitor AZD7451 completely blocked TrkC activation and associated tumorigenic behaviors. Pre-clinical studies on ACC tumors engrafted in mice showed efficacy and low toxicity of AZD7451, validating our in vitro data and stimulating more research into its clinical application. In summary, we describe in ACC a previously unrecognized pro-survival neurotrophin signaling pathway and link it with cancer progression.
•Co25.4Cr15Fe37.9Mn3.5Ni16.8Si1.4 alloy was produced by wire arc additive technology.•The microstructure consists mainly of FCC phase but also has CoCr nano phase.•The alloy has good mechanical ...properties.•The chemical are distributed homogeneously.
This study employed wire arc additive manufacturing (WAAM) to fabricate non-equiatomic Co25.4Cr15Fe37.9Mn3.5Ni16.8Si1.4 high-entropy alloy (HEA). Microstructure, elemental distribution, and mechanical properties were investigated. The fabricated HEA has a dendrite structure composed mainly of the FCC phase and CoCr nanoparticles with 1.5–2.5 nm sizes. Energy-dispersive X-ray spectrometry analysis showed that elements are distributed homogeneously in the alloy. Transmission electron microscopy demonstrated the presence of randomly oriented residual dislocations with the density of 1.2∙1010 cm−2. Compressive and tensile tests showed ductile deformation behavior. The yield strength of the alloy is ∼ 279 MPa; ultimate tensile strength is ∼ 500 MPa, and elongation is ∼ 63%.
On the basis of low-temperature (5 K) microphotoluminescence measurements in a wide ZnSe/ZnMgSSe quantum well, the existence of isolated quantum emitters in this heterostructure is demonstrated. ...Characteristically, the corresponding emission lines experience stepwise spectral shifts by a few meV on a time scale of 1–10 min. The unconventional properties of the observed emitters are explained by considering the picture of a system with a large dipole moment in the ground state, such as a single donor–acceptor pair or a similar system located near an extended defect.
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