Исследование конформации и электронной структуры N-метилмочевины методом функционала плотности

В настоящей работе методами DFT и HF с использованием пакета программ для квантово-химических расчетов Gaussian проведен конформационный анализ N-метилмочевины в растворе ДМСО. Окружение молекулы учитывалось в рамках модели непрерывной поляризуемой среды PCM. Выполнено исследование стереоэлектронных взаимодействий методом NBO, произведен расчет энергий граничных орбиталей

Low-temperature statistical mechanics of the QuanTizer problem: fast quenching and equilibrium cooling of the three-dimensional Voronoi Liquid

The Quantizer problem is a tessellation optimisation problem where point configurations are identified such that the Voronoi cells minimise the second moment of the volume distribution. While the ground state (optimal state) in 3D is almost certainly the body-centered cubic lattice, disordered and effectively hyperuniform states with energies very close to the ground state exist that result as stable states in an evolution through the geometric Lloyd's algorithm [Klatt et al. Nat. Commun., 10, 811 (2019)]. When considered as a statistical mechanics problem at finite temperature, the same system has been termed the 'Voronoi Liquid' by [Ruscher et al. EPL 112, 66003 (2015)]. Here we investigate the cooling behaviour of the Voronoi liquid with a particular view to the stability of the effectively hyperuniform disordered state. As a confirmation of the results by Ruscher et al., we observe, by both molecular dynamics and Monte Carlo simulations, that upon slow quasi-static equilibrium cooling, the Voronoi liquid crystallises from a disordered configuration into the body-centered cubic configuration. By contrast, upon sufficiently fast non-equilibrium cooling (and not just in the limit of a maximally fast quench) the Voronoi liquid adopts similar states as the effectively hyperuniform inherent structures identified by Klatt et al. and prevents the ordering transition into a BCC ordered structure. This result is in line with the geometric intuition that the geometric Lloyd's algorithm corresponds to a type of fast quench.Comment: 11 pages, 6 figure

Quark confinement and the bosonic string

Using a new type of simulation algorithm for the standard SU(3) lattice gauge theory that yields results with unprecedented precision, we confirm the presence of a $\gamma/r$ correction to the static quark potential at large distances $r$, with a coefficient $\gamma$ as predicted by the bosonic string theory. In both three and four dimensions, the transition from perturbative to string behaviour is evident from the data and takes place at surprisingly small distances.Comment: TeX source, 21 pages, figures include

Bimodal mesoporous titanium dioxide anatase films templated by a block polymer and an ionic liquid: influence of the porosity on the permeability

In the present paper, we report the synthesis of bimodal mesoporous anatase TiO2 films by the EISA (Evaporation-Induced Self-Assembly) method using sol-gel chemistry combining two porogen agents, a low molecular weight ionic template and a neutral block copolymer. The surfactant template (C(16)mimCl) generates non-oriented worm-like pores (8 to 10 nm) which connect the regularly packed ellipsoidal mesopores (15 to 20 nm diameter) formed by an amphiphilic block copolymer of the type poly(isobutylene)-b-poly(ethylene oxide) (PIB-PEO). The surfactant template can also significantly influence the size and packing of the ellipsoidal mesopores. The mesostructural organization and mesoporosity of the films are studied by Environmental Ellipsometry-Porosimetry (EEP), Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) and electron microscopy techniques. Electrochemical characterization is performed to study the permeability of the films to liquid solutions, using two types of probe moieties (K3FeIII(CN)(6) and Ru(bpy)(3)(2+)) by the wall-jet technique. An optimum ratio of C(16)mimCl/PIB-PEO provides anatase films with a continuous bimodal mesopore structure, possessing a permeability up to two times higher than that of the mesoporous films templated by PIB-PEO only (with partially isolated mesopores). When C(16)mimCl is used in large quantities, up to 20% weight vs. PIB-PEO, large overall porous volume and surface area are obtained, but the mesostructure is increasingly disrupted, leading to a severe loss of permeability of the bimodal films. A dye-sensitized solar cell set-up is used with anatase films as the photoelectrode. The photosensitizer loading and the total energy conversion efficiency of the solar cells using the mesoporous films templated by an optimal ratio of the two porogen agents C(16)mimCl and PIB-PEO can be substantially increased in comparison with the solar cells using mesoporous films templated by PIB-PEO only.DFG/SM 199/6-1DFG/OE 420/5-1BMBF/SOHyb/03X3525

Исследование структуры и свойств изделий, полученных методом порошковой металлургии из композиции Fe-C-Cr-Ni-W

Выпускная квалификационная работа 89с., 12рис., 17 табл., 21 источников литературы. Ключевые слова: порошковая металлургия, механическая активация, спекание, пористость, размер зерен и пор, микротвёрдость, металлографический и фазовый анализ. Цель работы – Исследовать структуру и свойства изделий, полученных методом порошковой металлургии из композиции Fe-C-Cr-Ni-W. В работе проводили подготовку поверхности образца (шлифовка, полировка, травление), оценку пористости, металлографический и рентгеноструктурный анализ, а также была измерена микротвердость. Основные характеристики спеченной стали 03Х17Н12В: пористость – 10%; микротвердость – 82 кг/см3; структура - аустенитная.Final qualifying work is presented with 89 pages,12pictures, 17tables，21literature sources. Keywords: powder metallurgy, mechanical activation, sintering, porosity, grain size and pore, micro-hardness, metallographic analysis, phase analysis. Research purpose: study the structure and the properties of the products obtained by powder metallurgy from the composition Fe-C-Cr-Ni-W. In the work, conducted preparation of the sample surface (grinding, polishing and etching) ，evaluation of porosity, metallographic and X-ray analysis, even micro-hardness was measured. The main characteristics of the sintered steel 03Cr17Ni12W: porosity - 10%; micro-hardness - 82 kg /cm3; structure - austenitic

Scalable Focused Ion Beam Creation of Nearly Lifetime-Limited Single Quantum Emitters in Diamond Nanostructures

The controlled creation of defect center---nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here, we demonstrate direct, maskless creation of atom-like single silicon-vacancy (SiV) centers in diamond nanostructures via focused ion beam implantation with $\sim 32$ nm lateral precision and $< 50$ nm positioning accuracy relative to a nanocavity. Moreover, we determine the Si+ ion to SiV center conversion yield to $\sim 2.5\%$ and observe a 10-fold conversion yield increase by additional electron irradiation. We extract inhomogeneously broadened ensemble emission linewidths of $\sim 51$ GHz, and close to lifetime-limited single-emitter transition linewidths down to $126 \pm13$ MHz corresponding to $\sim 1.4$-times the natural linewidth. This demonstration of deterministic creation of optically coherent solid-state single quantum systems is an important step towards development of scalable quantum optical devices

Casimir scaling as a test of QCD vacuum

Recent accurate measurements of static potentials between sources in various representations of the gauge group SU(3) performed by G.Bali provide a crucial test of the QCD vacuum models and different approaches to confinement. The Casimir scaling of the potential observed for all measured distances implies strong suppression of higher cumulant contributions. The consequences for the instanton vacuum model and the spectrum of the QCD string are also discussed.Comment: LaTeX, 15 pages, 1 figur

Investigating photo-catalytic activity of metal-ceramic composites in eosin degradation using complex iron compounds

Iron-containing metal-ceramic composites based on silicon nitrides, titanium, and sialon were investigated in terms of their phase composition, as well as identification and evaluation of acid-base surface centers. It is shown that the base Lewis centers and the acid centers of Brensted are prevalent on the surface of the materials. The photocatalytic activity of composites was examined in the process of eosin degradation in presence of Н[2]О[2] and EDTA. The composites based on nitrides of silicon and titanium demonstrate the highest activity under ferric complex system conditions

Who and when should we screen for prostate cancer? Interviews with key opinion leaders

Prostate cancer screening using prostate-specific antigen (PSA) is highly controversial. In this Q & A, Guest Editors for BMC Medicine's 'Spotlight on Prostate Cancer' article collection, Sigrid Carlsson and Andrew Vickers, invite some of the world's key opinion leaders to discuss who, and when, to screen for prostate cancer. In response to the points of view from the invited experts, the Guest Editors summarize the experts' views and give their own personal opinions on PSA screening

Two Dimensional Triptycene End‐Capping and Its Influence on the Self‐Assembly of Quinoxalinophenanthrophenazines †

In this report we investigated two-dimensionally triptycene end-capped QPPs in terms of their solution and solid-state behavior. For this purpose, a triphenylene based ortho-diamine decorated with two triptycenyl units as well as a phenylene diamine with two non-annulated triptycene units have been synthesized. Sequences of condensation reactions with a pyrene-based tetraketone and ortho-diamines yielded a series of QPPs and UV/Vis investigations of the corresponding compounds led to the conclusion, that the QPPs form dimers in solution, which was further supported by MALDI-TIMS-TOF-MS. Single-crystal X-ray analysis of the triply and quadruply triptycene end-capped QPPs furthermore showed short π-π-distances of 3.3—3.4 Å and a perfect shape match during the dimerization of the triply triptycenyl end-capped QPP making it possible synthon fo