Desorption of surfactant and sintering of surface-modified PdxNi1 − x nanoparticles

A series of Pd_xNi_1 − x nanoparticles in a diameter of 6-7 nm were prepared by wet chemical reduction. They were then modified with two surfactants, stearic acid (SA) and polyethylene glycol (PEG). Desorption of the surfactant was studied using a temperature programmed desorption technique, and the sintering behavior of surface-modified Pd_xNi_1 − x nanoparticles was examined. Since surface energy of the nanoparticles depends on the alloy composition, it can be correlated with the desorption temperature of surfactant from the nanoparticle surface. Because Ni has a higher surface energy, the surfactant desorption temperature increases as the Ni content increases. With the same stoichiometry, the desorption temperature of SA is always higher than that of PEG. The SA-modified nanoparticles have higher thermal stability and are less sintered than PEG-modified nanoparticles. The sintering and growth behavior of the nanoparticles can be correlated with variation of surface energy due to different surface modification.     

Structural and compositional heterogeneities in liquid aluminosilicate: insight from a grain structure model

Network structure as well as structural and compositional heterogeneities in aluminosilicate (Al₂O₃-2SiO₂) under compression is investigated by analysis and visualization of simulation data. Structural and compositional heterogeneities are clarified through analysis of topology structure and size distribution of TO _x -clusters (T = Si, Al; x = 3, 4, 5, 6) as well as OT _y -clusters (y = 2, 3, 4). The TO _x -cluster can be considered as TO _x -grains. It appears that the structure of aluminosilicate is the mixture of TO _x -grains with a different short-range order structure and this is the origin of structural heterogeneity. Regarding their composition, the OSi _y - and OAl _y -clusters can be considered as silica- and alumina-grains respectively, and the structure of aluminosilicate can thus be considered to be formed from silica- and alumina-grains. This results in compositional heterogeneity. Moreover, the degree of polymerization and polyamorphism as well as dynamic heterogeneity is also discussed in detail.     

Advances in theoretical and experimental XAFS studies of thermodynamic properties,anharmonic effects and structural determination of fcc crystals

Thermodynamic properties, anharmonic effects and structural determination of fcc crystals have been studied based on the theoretical and experimental Debye–Waller factors presented in terms of cumulant expansion up to the third order, thermal expansion coefficient, X-ray absorption fine structure (XAFS) spectra and their Fourier transform magnitudes. The advances in these studies are performed by the further development of the anharmonic correlated Einstein model primary only for approximating three first XAFS cumulants into the method using that all the considered theoretical and experimental XAFS parameters have been provided based on only the calculated and measured second cumulants. The obtained cumulants describe the anharmonic effects in XAFS contributing to the accurate structural determination. Numerical results for Cu are found to be in good agreement with the experimental values extracted by using the present advanced method and with those obtained by the other measurements.     

Tens of GHz Tantalum pentoxide‐based micro‐ring all‐optical modulator for Si photonics

A tantalum pentoxide‐based (Ta₂O₅‐based) micro‐ring all‐optical modulator was fabricated. The refractive index inside the micro‐ring cavity was modified using the Kerr effect by injecting a pumped pulse. The transmittance of the ring resonator was controlled to achieve all‐optical modulation at the wavelength of the injected probe. When 12 GHz pulses with a peak power of 1.2 W were coupled in the ring cavity, the transmission spectrum of the Ta₂O₅ resonator was red‐shifted by 0.04 nm because of the Kerr effect. The relationship between the modulation depth and gap of the Ta₂O₅ directional coupler is discussed. An optimized gap of 1100 nm was obtained, and a maximum buildup factor of 11.7 with 84% modulation depth was achieved. The nonlinear refractive index of Ta₂O₅ at 1.55 μm was estimated as 3.4 × 10^?14 cm²/W based on the Kerr effect, which is almost an order of magnitude higher than that of Si₃N₄. All results indicate that Ta₂O₅ has potential for use in nonlinear waveguide applications with modulation speeds as high as tens of GHz.

     

Der Einsatz von Sorbentien räumlich-globulrer Struktur zur Abtrennung radioaktiver Verunreinigungen aus Wasser

Abstract

Possibilities of using a new generation of sorbents have been investigated. Polymers of spatial-globular (spherulitic) structure (RGS polymers) have been tested to separate Cs, Sr and rare earth elements – which can also be radioactive contaminants – from different waters.

RGS polymers are both, solids and highly-disperse systems being extremely permeable to fluids and gases with low pressure decline. They were currently used to clean industrial waste-water.

It is shown that these polymers can be used successfully to separate radionuclides. Polymers RGS-81 and RGS-112 have high distribution coefficients for CS, Sr, Sc, the lanthanide series and Hf in weakly acid solutions. In HF solutions, Sc and Hf can be separated from Cs, Sr and the lanthanides.     

Photophysics of Silicon Phthalocyanines in Aqueous Media

Phthalocyanines have been used as photodynamic therapy (PDT) agents because of their uniquely favorable optical properties and high photostability. They have been shown to be highly successful for the treatment of cancer through efficient singlet‐oxygen (¹O₂) production. However, due to their hydrophobic properties, the considerations of solubility and cellular location have made understanding their photophysics in vitro and in vivo difficult. Indeed, many quantitative assessments of PDT reagents are undertaken in purely organic solvents, presenting challenges for interpreting observations during practical application in vivo. With steady‐state and time‐resolved laser spectroscopy, we show that for axial ligated silicon phthalocyanines in aqueous media, both the water:lipophile ratio and the pH have drastic effects on their photophysics, and ultimately dictate their functionality as PDT drugs. We suggest that considering the presented photophysics for PDT drugs in aqueous solutions leads to guidelines for a next generation of even more potent PDT agents.     

Comparison of Yield,Chemical Composition and Antimicrobial Activity of Distichochlamys citrea Rhizome Essential Oils Obtained by Different Extraction Methods

Moscow University Chemistry Bulletin - Hydrodistillation (HD), steam distillation (SD) and microwave-assisted hydrodistillation (MAHD) extraction methods were assessed for their effects on yield,...     

AQP4 Attenuated TRAF6/NFκB Activation in Acrylamide-Induced Neurotoxicity

Acrylamide (ACR) is present in high-temperature-processed high-carbohydrate foods, cigarette smoke, and industrial pollution. Chronic exposure to ACR may induce neurotoxicity from reactive oxygen species (ROS); however, the mechanisms underlying ACR-induced neurotoxicity remain unclear. We studied 28-day subacute ACR toxicity by repeatedly feeding ACR (0, 15, or 30 mg/kg) to rats. We conducted RNA sequencing and Western blot analyses to identify differences in mRNA expression in the blood and in protein expression in the brain tissues, respectively, of the rats. AQP4 transient transfection was performed to identify potential associations with protein regulation. The rats treated with 30 mg/kg ACR exhibited hind-limb muscle weakness. Matrix metalloproteinase (MMP9) expression was higher in the ACR-treated group than in the control group. ACR induced MMP-9 and AQP4 protein expression in the brain tissues of the rats, which subsequently presented with neurotoxicity. In the in vitro study, Neuro-2a cells were transiently transfected with AQP4, which inhibited MMP-9 and TNF receptor-associated factor 6 (TRAF6) expression, and inhibited ACR induced expression of TRAF6, IκBα, and nuclear factor κB (NFκB). Using a combination of in vivo and in vitro experiments, this study revealed that depressive symptoms associated with ACR-induced neurotoxicity are associated with downregulation of AQP4 and induction of the TRAF6 pathway.     

Combining Complex and Radial Slave Boson Fields within the Kotliar–Ruckenstein Representation of Correlated Impurities

The gauge symmetry group of any slave boson representation allows to gauge away the phase of bosonic fields. One benefit of this radial field formulation is the elimination of spurious Bose condensations when saddle-point approximation is performed. Within the Kotliar–Ruckenstein representation, three of the four bosonic fields can be radial while the last one has to remain complex. In this work, the procedure to carry out the functional integration involving constrained fermionic fields, complex bosonic fields, and radial bosonic fields is presented. The correctness of the representation is verified by exactly evaluating the partition function and the Green's function of the Hubbard model in the atomic limit.     

Numerical study of InGaN tandem solar cells with intermediate bands

Theoretical investigations of InGaN tandem solar cells with intermediate bands (IBs) have been conducted through calculating the diode equation taking into account the radiative and nonradiative recombination currents. The calculated maximum ef?ciencies of the double‐junction cell with one IB in each subcell are 57.85% and 68.37% under AM1.5G one‐sun and 46000‐sun illuminations, respectively. It has also been observed that the combined device with the top‐cell bandgaps of 2.9–3.4 eV (2.6–3.4 eV for full concentration) may have an opportunity to realize the application of over 50% efficiency. We suggest that the optimized width of the IB layer be designed in the range of 1–6 μm if its absorption coefficient is 10⁴–10⁵ cm^–1 in the IB region.