Silver Cluster Interactions with Tyrosine: Towards Amino Acid Detection

Tyrosine (Tyr) is involved in the synthesis of neurotransmitters, catecholamines, thyroid hormones, etc. Multiple pathologies are associated with impaired Tyr metabolism. Silver nanoclusters (Ag NCs) can be applied for colorimetric, fluorescent, and surface-enhanced Raman spectroscopy (SERS) detection of Tyr. However, one should understand the theoretical basics of interactions between Tyr and Ag NCs. Thereby, we calculated the binding energy (E_b) between Tyr and Ag_n^q (n = 1–8; q = 0–2) NCs using the density functional theory (DFT) to find the most stable complexes. Since Ag NCs are synthesized on Tyr in an aqueous solution at pH 12.5, we studied Tyr⁻¹, semiquinone (SemiQ⁻¹), and Tyr⁻². Ag₃²⁺ and Ag₅⁺ had the highest E_b. The absorption spectrum of Tyr⁻² significantly red-shifts with the attachment of Ag₃²⁺, which is prospective for colorimetric Tyr detection. Ag₃²⁺ interacts with all functional groups of SemiQ⁻¹ (phenolate, amino group, and carboxylate), which makes detection of Tyr possible due to band emergence at 1324 cm⁻¹ in the vibrational spectrum. The ground state charge transfer between Ag and carboxylate determines the band emergence at 1661 cm⁻¹ in the Raman spectrum of the SemiQ⁻¹–Ag₃²⁺ complex. Thus, the prospects of Tyr detection using silver nanoclusters were demonstrated.     

Effect of Low-Dose Ionizing Radiation on the Expression of Mitochondria-Related Genes in Human Mesenchymal Stem Cells

The concept of hormesis describes a phenomenon of adaptive response to low-dose ionizing radiation (LDIR). Similarly, the concept of mitohormesis states that the adaptive program in mitochondria is activated in response to minor stress effects. The mechanisms of hormesis effects are not clear, but it is assumed that they can be mediated by reactive oxygen species. Here, we studied effects of LDIR on mitochondria in mesenchymal stem cells. We have found that X-ray radiation at a dose of 10 cGy as well as oxidized fragments of cell-free DNA (cfDNA) at a concentration of 50 ng/mL resulted in an increased expression of a large number of genes regulating the function of the mitochondrial respiratory chain complexes in human mesenchymal stem cells (MSC). Several genes remained upregulated within hours after the exposure. Both X-ray radiation and oxidized cfDNA resulted in upregulation of FIS1 and MFN1 genes, which regulated fusion and fission of mitochondria, within 3–24 h after the exposure. Three hours after the exposure, the number of copies of mitochondrial DNA in cells had increased. These findings support the hypothesis that assumes oxidized cell-free DNA as a mediator of MSC response to low doses of radiation.     

n‐GaAs/InGaP/p‐GaAs Core‐Multishell Nanowire Diodes for Efficient Light‐to‐Current Conversion

Heterostructure n‐GaAs/InGaP/p‐GaAs core‐multishell nanowire diodes are synthesized by metal‐organic vapor‐phase epitaxy. This structure allows a reproducible, selective wet etching of the individual shells and therefore a simplified contacting of single nanowire p‐i‐n junctions. Nanowire diodes show leakage currents in a low pA range and at a high rectification ratio of 3500 (at ±1V). Pronounced electroluminescence at 1.4 eV is measured at room temperature and gives evidence of the device quality. Photocurrent generation is demonstrated at the complete area of the nanowire p‐i‐n junction by scanning photocurrent microscopy. A solar‐conversion efficiency of 4.7%, an open‐circuit voltage of 0.5 V and a fill factor of 52% are obtained under AM 1.5G conditions. These results will guide the development of nanowire‐based photonic and photovoltaic devices.     

A Probabilistic‐Statistical Model of Change of Particle Size Distribution in Settlers and Tanks

A probabilistic and statistical model of changes in the particle size distribution of the dispersed phase of low‐concentrated suspensions has been developed. The applicability of the method is theoretically substantiated. It is demonstrated that changes in the particle size distribution, in particular in the field of gravity, can be described by the Fokker‐Planck‐Kolmogorov equation.     

Improvement of sound absorption and flexural compliance of porous alumina-mullite ceramics by engineering the microstructure and segmentation into topologically interlocked blocks

Ceramic plates composed of topologically interlocked osteomorphic blocks with mono- and bimodal pore size distributions are fabricated by combining freeze gelation and sacrificial templating and trialled for sound absorption. These blocks present a concavo-convex geometry that constrains their movement solely by the contact with the neighbors. Our studies show that by using porous osteomorphic blocks, enhanced sound absorption coefficient (α) of 0.97 at 420 Hz can be reached, indicating that the gaps between blocks have a significant effect on the sound absorption at frequencies lower than 600 Hz, whereas the bimodal porosity of the block material enhances sound absorption for higher frequencies. Indentation tests confirm the advantages of the topologically interlocked structures, such as a spectacularly high flexural compliance, as compared to monolithic parts made from the same material. We concluded that materials design based on topological interlocking leads to an excellent combination of mechanical and sound absorption properties.     

Low-temperature microwave sintering of TiN–SiC nanocomposites

Densification kinetics study during microwave sintering of titanium nitride-based nanocomposite has been conducted. A series of TiN–SiC compositions with 1, 3, 5 wt% of silicon carbide were microwave sintered at relatively low sintering temperatures (900–1,300 °C) for 0–30 min. The SiC content influenced on heating uniformity and final density and grain-size achieved. Densification process during microwave sintering obeyed the mechanism of grain-boundary diffusion with activation energy of 235 kJ mol⁻¹. Microwave sintering resulted in fine microstructure (~300 nm) and hence high values of micro hardness (~20 GPa).     

纳米流体驱提高原油采收率的三维孔隙尺度模拟

基于不同渗透率岩心的三维微观模型,采用流体体积法对纳米流体驱油进行数值模拟;利用实验测得的含SiO2纳米颗粒的悬浮液界面张力、接触角和黏度,针对质量分数为0～1％、具有不同粒径的SiO2纳米颗粒的水基悬浮液,研究了纳米颗粒质量分数和粒径、驱替液流速、原油黏度和岩心渗透率对纳米流体驱油效率的影响.研究表明:采收率随着颗粒...     

LSV models with stochastic interest rates and correlated jumps

Pricing and hedging exotic options using local stochastic volatility models drew a serious attention within the last decade, and nowadays became almost a standard approach to this problem. In this paper we show how this framework could be extended by adding to the model stochastic interest rates and correlated jumps in all three components. We also propose a new fully implicit modification of the popular Hundsdorfer and Verwer and Modified Craig–Sneyd finite-difference schemes which provides second-order approximation in space and time, is unconditionally stable and preserves positivity of the solution, while still has a linear complexity in the number of grid nodes.