NWChem: Past, present, and future
Journal of chemical physics online/The Journal of chemical physics/Journal of chemical physics,
05/2020
Journal Article
In this paper, the technique of two-dimensional parametric blade profile design is presented. Bezier curves are used to create the profile geometry. The main feature of the proposed method is an ...adaptive approach of curve fitting to given geometric conditions. Calculation of the profile shape is produced by multi-dimensional minimization method with a number of restrictions imposed on the blade geometry.The proposed method has been used to describe parametric geometry of known blade profile. Then the baseline geometry was modified by varying some parameters of the blade. The numerical calculation of obtained designs has been carried out. The results of calculations have shown the efficiency of chosen approach.
Currently, in order to decrease the negative effects caused by the presence of a discrete phase in the flow path of steam turbines stages operating in wet-steam area, different technical solutions ...are apply. These methods reduce the number of coarse droplets and wetness of working medium. The implementation of erosion reduction methods requires modifying surfaces of flow path, which can significantly affect the efficiency of the steam turbine. For example application of intrachanel moisture removing and steam injection needs changes of the stator blades surfaces. This article is a part of researches cycle about the efficiency of steam injection on the stator blade surface as the main method of coarse liquid particles diameters reduction in the last stages of high-power steam turbines. The paper presents the results of the analysis and comparison of experimental research unmodified profile to the profile of the stator blade changed by injection slot. The comparison of the profile losses considered blades is present. The analysis of the experimental results showed the feasibility and efficiency of this method of coarse liquid particles diameters reduction in the last stages of high-power steam turbines.
Fracture of an underground gas main with a diameter of 530 mm during the production of pneumatic tests along a factory longitudinal welded joint made by contact welding using high-frequency currents, ...is considered. Fracture research was carried out by analysis of the project and technical documentation of the object, visual and measuring control of the object, ultrasonic measurement of pipe wall thickness, fractographic, metallographic and chemical analyses, measurements of hardness and microhardness of pipe metal. It was established that fracture of the gas pipeline occurred as a result of the opening of one pipe along the entire length of the factory-made longitudinal welded joint during the propagation of cracks in the welded joint and the subsequent propagation of the main crack in both directions to adjacent pipes; the centers of fracture were numerous surface crack-like defects of the welded joint. It is shown that a fracture was caused by a violation of the welding technology of a longitudinal welded joint, a violation of heat treatment, an unacceptable thinning of the pipe wall in the weld zone.
Summary
The role of antisperm antibodies (ASA) in the aetiopathogenesis of varicocoele‐related male infertility remains unclear. The objective of this study was to determine whether varicocoele is ...associated with antisperm immune response and whether this factor provides additional affect on male fertility. We performed a multicentral, prospective study that included the clinical examination of 1639 male subjects from infertile couples and 90 fertile men, the evaluation of the absolute and relative risks of immune infertility associated with varicocoele and the impact of the autoimmune response on the semen quality. The methods used were as follows: standard examination of seminal fluid according to WHO criteria; ASA detection in seminal fluid using mixed antiglobulin reaction (MAR) and direct flow cytometry; measurement of spontaneous and ionophore‐induced acrosome reactions; oxidative stress evaluation with luminal‐dependent chemiluminescence method and evaluation of DNA fragmentation by sperm chromatin dispersion. The prevalence of varicocoele‐related immune infertility is about 15% and does not depend on the grade of vein dilatation both in primary and secondary fertility disorders. Varicocoele is not an immediate cause of autoimmune reactions against spermatozoa, but is a cofactor increasing ASA risk; the OR of immune infertility after a testicular trauma in varicocoele patients increases twofold. In varicocoele patients, the autoimmune antisperm reaction is accompanied by a more significant decrease in the semen quality (concentration and number of progressively motile and morphologically normal spermatozoa in the ejaculate), acrosome reaction disorders (presence of pre‐term spontaneous and lack of induced reactions) and an increase in the proportion of spermatozoa with DNA fragmentation. These disorders correlate with the level of sperm oxidative stress; reactive oxygen species (ROS) production in ASA‐positive varicocoele patients is 2.8 and 3.5 times higher than in ASA‐negative varicocoele patients and fertile men respectively. We did not find correlation between the grade of spermatic cord vein dilatation and ROS production.
A complex radiation diagnostics facility “DRAGON” has been constructed at the reactor IR-8. The facility includes 3 beams for measurements using neutron and gamma radiation. The parameters of the ...facility are presented; the main units of the facility are described. The results of radiographic and tomographic experiments on the setup are presented.
Atomically thin layers of two-dimensional materials can be assembled in vertical stacks that are held together by relatively weak van der Waals forces, enabling coupling between monolayer crystals ...with incommensurate lattices and arbitrary mutual rotation
. Consequently, an overarching periodicity emerges in the local atomic registry of the constituent crystal structures, which is known as a moiré superlattice
. In graphene/hexagonal boron nitride structures
, the presence of a moiré superlattice can lead to the observation of electronic minibands
, whereas in twisted graphene bilayers its effects are enhanced by interlayer resonant conditions, resulting in a superconductor-insulator transition at magic twist angles
. Here, using semiconducting heterostructures assembled from incommensurate molybdenum diselenide (MoSe
) and tungsten disulfide (WS
) monolayers, we demonstrate that excitonic bands can hybridize, resulting in a resonant enhancement of moiré superlattice effects. MoSe
and WS
were chosen for the near-degeneracy of their conduction-band edges, in order to promote the hybridization of intra- and interlayer excitons. Hybridization manifests through a pronounced exciton energy shift as a periodic function of the interlayer rotation angle, which occurs as hybridized excitons are formed by holes that reside in MoSe
binding to a twist-dependent superposition of electron states in the adjacent monolayers. For heterostructures in which the monolayer pairs are nearly aligned, resonant mixing of the electron states leads to pronounced effects of the geometrical moiré pattern of the heterostructure on the dispersion and optical spectra of the hybridized excitons. Our findings underpin strategies for band-structure engineering in semiconductor devices based on van der Waals heterostructures
.
Summary
Antisperm antibodies (ASA) are a cause of male infertility. ASA are often found in varicocele patients. The study objective was to assess the ASA role in fertility recovery after ...varicocelectomy. The longitudinal study involved 99 patients with varicocele. Patients were examined according to the WHO recommendations; ASA level was measured using the direct method of Sperm MAR test: 66 patients were ASA‐negative, 33 had MAR‐IgG ≥ 10%. All patients underwent microsurgical varicocelectomy. Student's t‐test, Wilcoxon test, Chi‐squared test and signed rank test were used for data analysis. The retrospective analysis of all operated patients data showed that the patients without spermiogram improvement after varicocelectomy had higher ASA levels. 3 months after the surgery, the initially ASA‐negative varicocele patients demonstrated 2.5 times increase in number of progressive motile spermatozoa in the ejaculate (p < 0.001), accompanied by 6% decrease in abnormal sperm count (p < 0.05); the spermiogram parameters improved in 77% of cases (p < 0.01). After the surgery, ASA developed in 16% of cases (Max ‐ MAR‐IgG = 12%). The patients who were initially ASA‐positive demonstrated ASA decrease only in half of the cases (16 of 33; p > 0.05). The main outcome in this group was a favourable response to the surgery (ASA level decrease) vs. no reduction in autoimmune process. The improvement in the ASA‐positive group was demonstrated in the patients with higher varicocele grade (median – 2 vs. 1; p < 0.05) and lower ASA level (MAR‐IgG = 48% vs. 92%; p < 0.01). The pregnancy rate within a year after surgery was 2.8 times more frequent in couples with ASA‐negative men: 39% (25 of 65) in the ASA‐negative group compared to 14% (4 of 28) in the ASA‐positive group (p < 0.05). Thus, antisperm immune response decreases the varicocelectomy efficacy for reproductive function recovery: the higher percentage of ASA and lower grade of varicocele are associated with an unfavourable prognosis.
Interactions between the gut microbiota and the host are important for health, where dysbiosis has emerged as a likely component of mucosal disease. The specific constituents of the microbiota that ...contribute to mucosal disease are not well defined. The authors sought to define microbial components that regulate homeostasis within the intestinal mucosa. Using an unbiased, metabolomic profiling approach, a selective depletion of indole and indole-derived metabolites was identified in murine and human colitis. Indole-3-propionic acid (IPA) was selectively diminished in circulating serum from human subjects with active colitis, and IPA served as a biomarker of disease remission. Administration of indole metabolites showed prominent induction of IL-10R1 on cultured intestinal epithelia that was explained by activation of the aryl hydrocarbon receptor. Colonization of germ-free mice with wild-type Escherichia coli, but not E. coli mutants unable to generate indole, induced colonic epithelial IL-10R1. Moreover, oral administration of IPA significantly ameliorated disease in a chemically induced murine colitis model. This work defines a novel role of indole metabolites in anti-inflammatory pathways mediated by epithelial IL-10 signaling and identifies possible avenues for utilizing indoles as novel therapeutics in mucosal disease.
Abstract
Energy relaxation of photo-excited charge carriers is of significant fundamental interest and crucial for the performance of monolayer transition metal dichalcogenides in optoelectronics. ...The primary stages of carrier relaxation affect a plethora of subsequent physical mechanisms. Here we measure light scattering and emission in tungsten diselenide monolayers close to the laser excitation energy (down to ~0.6 meV). We reveal a series of periodic maxima in the hot photoluminescence intensity, stemming from energy states higher than the A-exciton state. We find a period ~15 meV for 7 peaks below (Stokes) and 5 peaks above (anti-Stokes) the laser excitation energy, with a strong temperature dependence. These are assigned to phonon cascades, whereby carriers undergo phonon-induced transitions between real states above the free-carrier gap with a probability of radiative recombination at each step. We infer that intermediate states in the conduction band at the Λ-valley of the Brillouin zone participate in the cascade process of tungsten diselenide monolayers. This provides a fundamental understanding of the first stages of carrier–phonon interaction, useful for optoelectronic applications of layered semiconductors.
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