Search

NO3-(H2O)n clusters are a molecular model used to understand the solvation interaction between water and nitrate, an important anion in nature, industrial processes and biology. We demonstrate by ab initio molecular dynamics simulations that among the many isomeric structures at each cluster size with n = 1-6, thermal stability is an important consideration. The vibrational profile at a particular size, probed previously by infrared multiple photon dissociation (IRMPD) spectroscopy, can be accounted for by the isomers, which are both energetically and dynamically stable. Conversion and broadening due to the fluctuation of hydrogen bonds are important not only for the O-H stretching modes but also for the N-O stretching modes. Distinct patterns for the O-H stretching modes are predicted for the various solvation motifs. We also predict a surface structure for NO3-(H2O)n as n increases beyond 6, which can be verified by an early onset of strong libration bands for H2O in the IRMPD spectra and a flattening of the vertical detachment energy in the photoelectron spectra.

The strong volatility and randomness of wind power impact the grid and reduce the voltage quality of the grid when wind power is connected to the grid in large scale. The power sector takes the wind abandonment measures to ensure the grid voltage stability. The enhanced crow search algorithm optimization-extreme learning machine (ENCSA-ELM) model is proposed to accurately forecast short-term wind power to improve the utilization efficiency of clean energy. (1) The enhanced crow search algorithm (ENCSA) is proposed and applied to short-term wind power forecast. The convergence performance test revealed that the local development and global exploration capabilities of the ENCSA were enhanced, and the test result of the proposed ENCSA algorithm outperformed other well-known nature inspired algorithms and state-of-the-art CSA variants; (2) The output and input of the forecasting models were determined by analysis of the wind power impact factors and the wind power samples in autumn, winter and spring were forecasted by the ENCSA-ELM model; and (3) The forecast results were analyzed by multiple evaluation indexes. The simulation experiments revealed that the error interval and evaluation indexes of the ENCSA-ELM model outperformed the state-of-the-art wind power forecast methods, traditional machine learning models and ELM optimized by other algorithms. The RMSE value and MAPE value of the proposed model were controlled below 20% and 4%. Accurate wind power prediction maintains the voltage stability of power grid and increases the utilization efficiency of clean energy.

This study contributes to construct the mathematical model of hybrid dynamic economic emission dispatch (HDEED) considering renewable energy generation and propose a novel solving approach based on enhanced moth-flame optimization algorithm. Renewable energy power generation technology has an important impact on reducing pollutant emissions and promoting sustainable development. Therefore, this study aims to investigate the HDEED problem in consideration of renewable energy generation and improve the economic and environmental benefits of the power system. First, a moth-flame optimization algorithm based on position disturbance updating strategy (MFO_PDU) was proposed aiming at the non-convex, non-linear and high-dimensional characteristics of HDEED problem. Second, the mathematical model of HDEED on the basis of Wind-Solar-Thermal integrated energy was constructed, while taking into account the valve point effect, equality constraints and inequality constraints. Finally, three cases including test systems of different scales were formulated and employed to verify the proposed approach, and the compromise solution was determined through membership function. The results revealed that the fuel cost obtained by the MFO_PDU algorithm was 11.31%, 4.01% and 5.27% smaller than those of HHO, TSA and MFO algorithms for small-scale test system. Accordingly, the research outcomes contribute in reducing the fuel cost and pollutant emissions of power generation system, and further improving the utilization and penetration rate of renewable energy.

This study proposes improved tunicate swarm algorithm (ITSA) for solving and optimizing the dynamic economic emission dispatch (DEED) problem. The DEED optimization target is to reduce the fuel cost and pollutant emission of the power system. In addition, DEED is a complex optimization problem and contains multiple optimization goals. To strengthen the ability of the ITSA algorithm for solving DEED, the tent mapping is employed to generate initial population for improving the directionality in the optimization process. Meanwhile, the gray wolf optimizer is used to generate the global search vector for improving global exploration ability, and the Levy flight is introduced to expand the search range. Three test systems containing 5, 10 and 15 generator units are employed to verify the solving performance of ITSA. The test results show that the ITSA algorithm can provide a competitive scheduling plan for test systems containing different units. ITSA proposed algorithm gives the optimal economic and environmental dynamic dispatch scheme for achieving more precise dispatch strategy.

The contribution is to propose a novel hybrid model based on modal reconstruction to predict short-term photovoltaic (PV) power. PV power generation large-scale grid connection causes the impact on the power system due to the instability and intermittence, and PV curtailment measures are taken to reduce the impact from voltage fluctuation. Accurate forecast is necessary to make a reasonable generation plan. A novel hybrid forecasting model is proposed, and an enhanced gray wolf optimization algorithm is proposed to improve the convergence ability and to solve the influence of extreme learning machine random parameters. The proposed algorithm has stronger convergence stability and higher convergence accuracy compared with the existing algorithms. The ensemble empirical mode decomposition algorithm is used to decompose the PV power under different weather conditions. The complexity of each component is calculated by the sample entropy, and the components are reconstructed to reduce the computational cost of forecasting models. The results revealed that mean absolute percentage error and root mean square error of the proposed model are smaller than 3% and 0.36 under various weather conditions. Meanwhile, the determination coefficient of the proposed model is more than 98%.

The finite analytic method is developed to solve the two-dimensional steady fluid flows in heterogeneous porous media with full tensor permeability on unstructured grids. The proposed FAM is constructed based upon the power-law analytic nodal solution in the angular domain with arbitrary shape. When approaching the grid node joining the subdomains, three different flow patterns may exist: power-law flow, linear flow or the stagnant flow. Based on the nodal analytic solution, the triangle-based FAM is proposed. Numerical examples show that the proposed numerical scheme makes the convergences much quickly than the traditional methods, typically the weighted harmonic mean method under the cell refinement. In practical applications, the grid refinement parameter n=2 or n=3 is recommended, and the relative error of the calculated equivalent permeability will below 4% independent of the heterogeneity. In contrast, when using the traditional numerical scheme the refinement ratio for the grid cell needs to increase dramatically to get an accurate result, especially for strong heterogeneous porous medium.

Objective To study the change of the contractile response of human umbilical artery smooth muscle cells (HUASMCs) during the heat stress, and explore the effect of the antioxidant on the changes. Methods HUASMCs were randomly divided into control group, heat stress group, antioxidant preprocessing group. Cells were stimulated by norepinephrine (NE) at a low concentration (0.05mg/L) and at a normal concentration (1.0mg/L) and cultured in the thermostatic water bath (41℃) for 0.5, 1, 1.5 or 2h, respectively. After stimulated by NE, proportion of the cell surface area contraction was measured to reflect the contractile response of each group. Results Compared with control group, regardless of the NE concentration: in heat stress group, contractile response at 1h increased significantly (P0.05), but in the antioxidant preprocessing group, the contractile response was more significant to the normal NE concentration than to the low NE concentration (P

Objective To investigate the effect of gradient heat stress on phagocytosis of hepatic Kupffer cells (KCs) in vitro in rats. Methods Rat Kupffer cells were isolated in vitro and the temperature for gradient heat stress was set at 37, 39, 41 and 43℃. After thermal stimulation, cell injury was detected by PI and Hochest33342 staining. CCK-8 assay was used to investigate difference in cellular proliferation rate over 24h between the groups. Flow cytometry was used to investigate the influence of heat stress on the phagocytosis of KCs. Results Compared to the normal control group, cells in each heat stress group exhibited varying degrees of damage, especially cells in 43℃ group. The ratio of damage cells increased with the increase of heat stress severity (P

Objective To examine the effects of ulinastatin (UTI) on cardiac dysfunction in mice with heat stroke and its possible mechanism. Methods 20 mice were divided into four groups randomly: room temperature plus normal saline (Sham+NS), room temperature plus UTI (Sham+UTI), heat stress plus normal saline (HS+NS), heat stress plus UTI (HS+UTI), 5 each. 105U/kg UTI was delivered by intraperitoneal injection before the onset of the heat stress. Room temperature groups were housed at room temperature (23.0±0.5℃), while heat stress groups were kept in an incubator at 36.5±0.5℃ and humidity of 65.0%±2.0%. The rectal temperature (Tr) reaching 42℃ was taken as severe heat stroke, and the time in two heat stress groups was recorded. The mice were transferred to the room temperature (23.0±0.5℃) for natural cooling after the heat stroke onset. 6 hours after the treatment, cardiac output (CO) was ultrasonographically detected, the myocardium was separated for histopathological examination and the expression of total p38 and phosphorylated p38 (p-p38) was determined by Western blotting. Results The time to reach 42℃ in HS+UTI group was significantly prolonged (P=0.044). Compared with the Sham+NS group, the CO in HS+NS and HS+UTI group decreased significantly (P=0.017), and the score of myocardial inflammation (P

Herein we report synthesis, structure and properties of a new type of twisted nanographene, which contains an [8]circulene moiety in a polycyclic framework of 96 sp2 carbon atoms. The key steps in this synthesis are the Diels-Alder reaction of a macrocyclic diyne and the subsequent Scholl reaction forming the [8]circulene moiety. Two incompletely cyclized products were isolated from the Scholl reaction, providing insight into the cyclization of the strained octagon. This nanographene is twisted along two directions with end-to-end twists of 142.4° and 140.2° as revealed by X-ray crystallography, and is flexible at room temperature as found from the computational and experimental studies.

The finite analytic numerical method for 3D quasi-Laplace equation with conductivity in full tensor form is constructed in this article. For cubic grid system, the gradient of the potential variable will diverge when tending to the common edge joining the four grids with different conductivities. However, the potential gradient along the tangential direction is of limited value. As a consequence, the 3D quasi-Laplace equations will behave as a quasi-2D one. An approximate analytical solution of the 3D quasi-Laplace equation can be found around the common edge, which is expressed as a combination of a power-law function and a linear function. With the help of this approximate analytical solution, a 3D finite analytical numerical scheme is then constructed. Numerical examples show that the proposed numerical scheme can provide rather accurate solutions only with 3 × 3 × 3 or 4 × 4 × 4 subdivisions. More important, the convergent speed of the numerical scheme is independent of the conductivity heterogeneity. In contrast, when using the traditional numerical schemes, typically such as the MPFA method, the refinement ratio for the grid cell needs to increase dramatically to get an accurate result for the strong heterogeneous case.© 2017 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2017

Robotics has become a crucial domain in technology education, helping students to improve their abilities in assembly and programming. Despite the considerable research that has gone into the learning performance associated with robotics, little work has been done on the cognitive processes involved in learning this subject. The purpose of this study was to develop an instrument (based on the theoretical framework of MSLQ), with which to evaluate the motivation of high school students to learn robotics and the strategies they employ. Fifty participants in the open category competition of the World Robot Olympiad 2010 completed the self-reported questionnaire (RMSLQ-HS). Thirteen factors and fifty one items were extracted using exploratory factor analysis. Implications for the educational application of robotics and research suggestions related to RMSLQ are also discussed.

A series of nanostructures of Zinc Sulfide (ZnS), including the small Zn n S n ( n = 1–15) clusters, the magic cage-like Zn 12 S 12 and its derivants (Zn 12 S 12 -based dimers, trimers, nanowires and monolayer) were systematically investigated by using a first-principles bottom-up calculation. The results show that the Zn 12 S 12 cage-like structure with six isolated four-membered rings (4NRs) and eight six-membered rings (6NRs) has T h symmetry and a large HOMO-LUMO gap, indicating that the Zn 12 S 12 cluster would be ideal building blocks for the synthesis of new cluster-assembled materials. Via the aggregation of Zn 12 S 12 , we find that the Zn 12 S 12 cages can bind into various porous materials with different dimensionality by the most stable bonding H H 1 . Interestingly, all of these cluster-assembled structures are found to be more stable than the individual Zn 12 S 12 cage and rock salt (RS) phase of ZnS. These fascinating findings will be advantageous for promoting the potential applications of the inorganic ZnS-based nanosystems in the new type of electronic nanodevices and high-performance semiconductor materials.

Convection-dominated diffusion problems usually develop multiscaled solutions and adaptive mesh is popular to approach high resolution numerical solutions. Most adaptive mesh methods involve complex adaptive operations that not only increase algorithmic complexity but also may introduce numerical dissipation. Hence, it is motivated in this paper to develop an adaptive mesh method which is free from complex adaptive operations. The method is developed based on a range-discrete mesh, which is uniformly distributed in the value domain and has a desirable property of self-adaptivity in the spatial domain. To solve the time-dependent problem, movement of mesh points is tracked according to the governing equation, while their values are fixed. Adaptivity of the mesh points is automatically achieved during the course of solving the discretized equation. Moreover, a singular point resulting from a nonlinear diffusive term can be maintained by treating it as a special boundary condition. Serval numerical tests are performed. Residual errors are found to be independent of the magnitude of diffusive term. The proposed method can serve as a fast and accuracy tool for assessment of propagation of steep fronts in various flow problems.

In order to assess the digestive physiological capacity of the American shad Alosa sapidissima and to establish feeding protocols that match larval nutritional requirements, we investigated the ontogenesis of digestive enzymes (trypsin, amylase, lipase, pepsin, alkaline phosphatase, and leucine aminopeptidase) in larvae, from hatching to 45 days after hatching (DAH). We found that all of the target enzymes were present at hatching, except pepsin, which indicated an initial ability to digest nutrients and precocious digestive system development. Trypsin rapidly increased to a maximum at 14 DAH. Amylase sharply increased until 10 DAH and exhibited a second increase at 33 DAH, which coincided with the introduction of microdiet at 30 DAH, thereby suggesting that the increase was associated with the microdiet carbohydrate content. Lipase increased until 14 DAH, decreased until 27 DAH, and then increased until 45 DAH. Pepsin was first detected at 27 DAH and then sharply increased until 45 DAH, which suggested the formation of a functional stomach. Both alkaline phosphatase and leucine aminopeptidase markedly increased until 18 DAH, which indicated intestinal maturation. According to our results, we conclude that American shad larvae possess the functional digestive system before mouth opening, and the significant increases in lipase, amylase, pepsin, and intestinal enzyme activities between 27 and 33 DAH suggest that larvae can be successfully weaned onto microdiets around this age.

Insulated Gate Bipolar Transistor (IGBT) is the core power device in the fields of railways, new energy sources, and automobiles. The safe and reliable operation of IGBT is the basis to ensure the sustained and steady development of all walks of life. The junction-to-case thermal resistance of the IGBT power modules can manifest the fatigue degree of the solder layer. The saturation voltage drop manifests the aging degree of the IGBT bonding wire. Therefore, the IGBT reliability can be judged by a certain rule along with the external parameters such as the junction-to-case thermal resistance Rth and the saturation voltage drop Vce. In order to grasp this rule, this study illustrates the correlations between the external parameters of IGBT and the number of power cycles. As a result, the functional relationships between the average change rate of junction-to-case thermal resistance and the number of power cycles ( Δ R ¯ th —n) as well as the average saturation voltage drop rate of change and the number of power cycles ( Δ V ¯ ce —n) have been gained from IGBT test samples. After obtaining these functional relationships, for any IGBT of the same model in working condition, a proposition of judging the aging degree can be obtained. Here, the aging degree of the IGBT is represented by a real number in the interval [0, 1] and the reliability of the above proposition is calculated from the standard deviation of the working lifetime of each test sample. The method proposed in this study can not only be used to judge the aging degree of IGBT, but also to estimate the remaining lifetime.

Infrared spectra of the neutral dimethylamine-methanol cluster, DMA-CH3OH, were measured in the spectral range of 2800-3900 cm-1 using an infrared-vacuum ultraviolet (IR-VUV) scheme. Quantum chemical calculations and ab initio molecular dynamic (AIMD) simulations were carried out to understand the experimental spectral features. Experimental and theoretical results reveal the coexistence of N···HO and O···HN hydrogen-bonded structures. AIMD simulations show that the methyl group in methanol internally rotates around the N···O axis, addressing the dynamic effect of the fluctuation of hydrogen bonds on the vibrational features. The bonding analysis was performed to elucidate the nature of the intermolecular interaction between DMA and CH3OH. The present work provides the fundamental understanding of hydrogen-bonding networks in the amine-alcohol complexes.

We report on the gas phase vibrational spectroscopy of the hexahydrated sulfate dianion, SO42-(H2O)6, and its fully deuterated isotopologue, SO42-(D2O)6, using infrared photodissociation (IRPD) spectroscopy of the D2-tagged dianions in combination with density-functional-theory calculations on minimum-energy structures as well as finite temperature ab initio molecular dynamics (AIMD) simulations. The IRPD spectra were recorded at an ion trap temperature of 12 K and in the spectral range from 650 to 3800 cm-1, covering the intramolecular modes of the solvent (OH/OD stretches and H2O/D2O bends) at higher energies, those of the solute (sulfate stretches) at intermediate energies and the intermolecular solute librational modes at the lowest energies. Isomer-specific double resonance in combination with messenger-tag dependent IRPD spectra show that only a single isomer is contributing significantly and that this isomer is not the highly symmetric Td but rather the lower symmetry C3 isomer. Temperature-dependent IR multiple photon dissociation spectra of bare SO42-(H2O)6 suggest that the C3 isomer remains the most stable one up to 200 K. The AIMD simulations reveal that the IRPD spectra can only be fully understood when anharmonic effects as well as entropy-driven hydrogen bond network fluctuations are considered.

With a p K

Under environmental excitation and based on observability, an online model to predict the state of heavy-duty machine tool–foundation systems is proposed aimed to address the difficulties of directly measuring machine tool displacement states. The aim of the model is to address the difficulties associated with directly measuring machine tool displacements in real time. In this paper, to accurately obtain contact parameters of the joint surface, three states—elasticity, plasticity, and fracture—of concrete micro-bumps were studied. To obtain the equivalent elastic modulus of the secondary pouring material and reinforced concrete material, a composite foundation constitutive model is proposed to determine the equivalent elastic modulus of the concrete foundation. Surface topography features were reconstructed by truncating the peaks of curves, force balance relationships were defined at the joint surfaces, and a metal–concrete joint contact model based on fractal theory was deduced. Based on the joint contact model, a dynamic model of the heavy-duty machine tool–foundation system was established. The dynamic parameters were detected in real time and used to reconstruct the above dynamic model based on observation theory. Further, an estimation model was established to describe the state of a heavy-duty machine tool–foundation system, and online estimation of the machine tool displacement was realized. Finally, the estimation model was validated using an experimental setup of the heavy-duty machine tool–foundation system that considers joint surface factors. In conclusion, the model provides a theoretical basis for stable online control of heavy-duty machine tools.

Robotics has become a crucial domain in technology education, helping students to improve their abilities in assembly and programming. Despite the considerable research that has gone into the learning performance associated with robotics, little work has been done on the cognitive processes involved in learning this subject. The purpose of this study was to develop an instrument (based on the theoretical framework of MSLQ), with which to evaluate the motivation of high school students to learn robotics and the strategies they employ. Fifty participants in the open category competition of the World Robot Olympiad 2010 completed the self-reported questionnaire (RMSLQ-HS). Thirteen factors and fifty one items were extracted using exploratory factor analysis. Implications for the educational application of robotics and research suggestions related to RMSLQ are also discussed.

The Scholl-type cyclodehydrogenation generating up to four cycloheptatriene rings around a fenestrindane core leads to novel, saddle-shaped polyaromatic hydrocarbon derivatives. In this article, we present the results of in-depth experimental and computational works on the oxidative cyclization of various 1,4,9,12-tetraarylfenestrindanes. In particular, the kinetic control of the four-step cyclization of the electronically activated tetrakis(3,4-dimethoxyphenyl) derivative is elucidated. The reasons for the exclusive emergence of one single among the three possible doubly cyclized intermediates and for the nonappearance of the singly and triply cyclized intermediates are clarified. In addition, the origin of the concomitant bridgehead hydroxylation is studied. The reactivity of a set of fifteen symmetrically and unsymmetrically substituted 1,4,9,12-tetraarylfenestrindanes towards Scholl-type cyclodehydrogenation is presented, pinpointing the structural factors that underlie this reaction and demonstrating the potential and limitations of this synthetic approach. A particularly surprising finding of this study is that the electronically nonactivated 1,4,9,12-tetraphenylfenestrindane can also undergo the fourfold Scholl-type cyclization process and can be transformed to the parent saddle hydrocarbon. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

White adipose tissue (WAT) browning is a potential strategy to treat obesity, and is characterized by the formation of brown adipocytes induced by cold or β-3 adrenergic receptor (β-3AR) agonist treatment. The hedgehog (Hh) signaling at the primary cilium is closely related to obesity, and plays a key role in the differentiation and adipogenesis of adipocytes. However, little is known about its effects on WAT browning. In this study, browning models were used to evaluate the activity and effect of Hh signaling on WAT browning using Hh antagonists, agonist, and small-interfering RNAs (siRNAs) specific for glioma-associated oncogene homologue 1 (Gli1), smoothened (Smo), and suppressor of fused (Sufu). We observed that Hh signaling activity was inhibited during the browning process both in vivo and in vitro. Further, Hh signaling inhibition enhanced WAT browning, while its activation attenuated norepinephrine-induced browning. Thus, the inhibition of Hh signaling promotes WAT browning and therefore, Hh signaling may be a therapeutic target against obesity and associated comorbidities.

Herein, we report two new types of twisted polycyclic arenes (2 a, b and 3 a, b) with constitutionally isomeric π-backbones, which are synthesized by controlling the Scholl reaction of 1,2,4,5-tetra(naphth-2-yl)-3,6-diphenylbenzene (1) with properly positioned electron-donating substituents. With a polycyclic backbone containing two [5]helicene and four [4]helicene moieties, 2 a and b are new members of multiple helicenes with interesting stereochemistries. The as-synthesized 2 a and b are the twisted isomers, and thermal isomerization of twisted-2 b results in anti-2 b, a more stable stereoisomer. Both twisted- and anti-2 b have been fully characterized, and the thermal isomerization of twisted-2 b has been studied with 1H NMR spectroscopy and DFT calculations. Compounds 3 a and b are new members of twistacenes, the benzannulated pentacene backbone of which exhibits an end-to-end twist as found from the crystal structure. Twisted- and anti-2 b are also found to function as p-type semiconductors in solution-processed thin film transistors, whereas the thin films of 3 b appear insulating presumably due to the lack of π–π interactions.

Objective: To explore the intraocular pressure and corneal endothelial cells integrity changes in cataract phacoemulsification after anti-glaucoma surgery. Methods: Phacoemulsification was performed in 102 patients (118 eyes) with cataract after anti-glaucoma surgery and the intraocular pressure and corneal endothelial cell integrity changes of patients were observed at Day 1 and 3, first week and first month before and after surgery, including central corneal endothelial cell density, average cell area (AVE), cell area of coefficient of variation (CV) and central corneal thickness (CCT). Results: The intraocular pressure was elevated, the central endothelial cell density was reduced, the AVE, the CV and CTT thicken were increased at Day 1 and 3, first week and first month after surgery. The difference compared with preoperative was statistically significant. The intraocular pressure and CTT almost recovered to preoperative levels in 1 month after cataract phacoemulsification and the difference was not statistically significant; while the central endothelial cell density was still decreased and AVE and CV were still increased and the difference of these indexes and the coefficient of the patients was statistically significant compared with before surgery. Conclusions: For the patients with antiglaucoma after cataract phacoemulsification, intraocular pressure and endothelial cell integrity change was initially observed at Day 1 after surgery, whereas they can almost return to the preoperative level in a month after surgery.

Septic encephalopathy (SE) is a diffuse cerebral dysfunction resulting from a systemic inflammatory response, and is associated with an increased risk of mortality. The pathogenesis of SE is complex and multifactorial, but unregulated immune imbalance may be an important factor. The current retrospective study examined the clinical data of 86 patients with severe sepsis who were admitted to the Intensive Care Unit at Zhongshan Hospital, Xiamen University (Xiamen, China) from January, 2014 to January, 2015. The patients were assigned to SE and non-SE patient groups according to the presence or absence of SE. The proportion of T-lymphocyte subsets and natural killer (NK) cells in the immune cell population, representing the function of the immune system, were analyzed for their association with SE and compared with other clinical predictors and biomarkers. The incidence of SE in the patients was 39.5%, and this group demonstrated higher mortality rates (38 vs. 10% in non-SE patients; P=0.001). Univariate analysis revealed that the SE patients reported a lower percentage of cluster of differentiation 4+(CD4+) T-lymphocytes (51.67±7.12 vs. 60.72±3.70% in non-SE patients; P0.05). The present results confirm that SE leads to higher mortality in patients with severe sepsis, and demonstrate that immune imbalance is important in the development of SE. The proportion of CD4+ T-lymphocytes present were revealed in the current study to be a powerful predictor of SE in patients with severe sepsis.

The phosphine complexes of Ru dihydride are model catalysts for CO2 hydrogenation. Despite many theoretical studies, important questions remain unresolved regarding the underlying catalytic mechanisms. We report a comparative study by using density functional theory on two catalysts, (PMe3)4RuH2 and (dmpe)2RuH2, with dmpe = Me2PCH2CH2PMe2, for which very different mechanisms have been suggested in previous studies. By comparing their energy profiles along all possible reaction paths side by side, we are able to clarify the similarity and difference between them, and provide a consistent account for all the experimental observations reported, including the kinetic models, the cis to trans transformation of (dmpe)2RuH2, and the significant enhancement of the catalytic rate in supercritical CO2 for (PMe3)4RuH2 and its lack thereof for (dmpe)2RuH2. The crucial difference between the two mechanisms involves the formation of an intermediate, in which a formate ion binds to Ru as a bidentate ligand. When this step results in the dissociation of a ligand, the reaction rate is enhanced under supercritical conditions, due to the increase in entropy, which should be a valid consideration for other catalytic reactions as well.

We herein report an efficient synthesis of dibenzo[a,m]rubicene, a new member of nonplanar cyclopenta-fused polycyclic aromatic hydrocarbon, and its derivatives. It is found that the conformation and molecular packing of dibenzo[a,m]rubicenes in the solid state can be tuned by the substituting groups, and the silylethynylated derivatives of dibenzo[a,m]rubicenes function as p-type organic semiconductors in solution-processed thin film transistors with field effect mobility of up to 1.0 cm(2) V(-1) s(-1).

Three new acylated aminooligosaccharide (1&ndash, 3), along with five known congeners (4&ndash, 8), were isolated from the marine-derived Streptomyces sp. HO1518. Their structures were fully elucidated by extensive spectroscopic analysis, mainly based on 1D-selective and 2D TOCSY, HSQC-TOCSY, and HRESIMS spectrometry measurements, and by chemical transformations. All of the compounds were evaluated for their &alpha, glucosidase and pancreatic lipase inhibitory activities. Among the isolates, D6-O-isobutyryl-acarviostatin II03 (3) and D6-O-acetyl-acarviostatin II03 (8), sharing acarviostatin II03-type structure, showed the most potent &alpha, glucosidase and lipase inhibitory effects, far stronger than the antidiabetic acarbose towards &alpha, glucosidase and almost equal to the anti-obesity orlistat towards lipase in vitro. This is the first report on inhibitory activities against the two major digestive enzymes for acylated aminooligosaccharides. The results from our investigation highlight the potential of acylated aminooligosaccharides for the future development of multi-target anti-diabetic drug.

In low permeability reservoirs with conductive fractures, there is large capillary pressure contrast between the matrix and the fracture. It may cause very sharp changes in physical quantities near the matrix-fracture interface, which makes it difficult to calculate the matrix-fracture exchange flux accurately in the traditional embedded fracture model (EDFM). The strong capillary pressure contrast between the matrix and the fracture results in three flow patterns near the matrix-fracture interface and creates difficulty in calculation of the matrix-fracture exchange flux. In this article, a modified embedded discrete fracture model is proposed, where the analytical solutions for the three different patterns are employed to construct the numerical scheme for calculating the matrix-fracture exchange flux. The numerical tests show that the calculated results of the proposed model are in agreement with the reference model in which both the fracture cells and also the matrix cells near the fracture are subdivided sufficiently.

Photovoltaic power generation is greatly affected by weather conditions while the photovoltaic power has a certain negative impact on the power grid. The power sector takes certain measures to abandon photovoltaic power generation, thus limiting the development of clean energy power generation. This study is to propose an accurate short-term photovoltaic power prediction method. A new short-term photovoltaic power output prediction model is proposed Based on extreme learning machine and intelligent optimizer. Firstly, the input of the model is determined by correlation coefficient method. Then the chicken swarm optimizer is improved to strengthen the convergence. Secondly, the improved chicken swarm optimizer is used to optimize the weights and the extreme learning machine thresholds to improve the prediction effect. Finally, the improved chicken swarm optimizer extreme learning machine model is used to predict the photovoltaic power under different weather conditions. The testing results show that the average mean absolute percentage error and root mean square error of improved chicken swarm optimizer - extreme learning machine model are 5.54% and 3.08%. The proposed method is of great significance for the economic dispatch of power systems and the development of clean energy.

A new trefoil-shaped molecular architecture consisting of three conjugated macrocycles was synthesized through an unprecedented 3-fold copper catalyzed [4 + 2] benzannulation. DFT calculations indicate that the most stable conformation of this trefoil macrocycle is D3-symmetric. In agreement with the calculated results, the trefoil macrocycle in single crystals exists as a pair of enantiomers with D3-symmetry and exhibits interesting honeycomb-like supramolecular structures.

NO3-(H2O)n clusters are a molecular model used to understand the solvation interaction between water and nitrate, an important anion in nature, industrial processes and biology. We demonstrate by ab initio molecular dynamics simulations that among the many isomeric structures at each cluster size with n = 1-6, thermal stability is an important consideration. The vibrational profile at a particular size, probed previously by infrared multiple photon dissociation (IRMPD) spectroscopy, can be accounted for by the isomers, which are both energetically and dynamically stable. Conversion and broadening due to the fluctuation of hydrogen bonds are important not only for the O-H stretching modes but also for the N-O stretching modes. Distinct patterns for the O-H stretching modes are predicted for the various solvation motifs. We also predict a surface structure for NO3-(H2O)n as n increases beyond 6, which can be verified by an early onset of strong libration bands for H2O in the IRMPD spectra and a flattening of the vertical detachment energy in the photoelectron spectra.

By ab initio molecular dynamics simulations, we examined the variation in the oxygen reduction reaction pathways on Pt(1 1 1) in the presence of H, HBr or HClO4, with dozens of explicit water molecules. The free energy changes and barriers were calculated by thermodynamic integration. Significant variations among the three models were observed, indicating the importance of considering the effect of an anion. The dissociation of adsorbed O2* and the association of a proton with an adsorbed O2* were often coupled with each other due to the reactivity of an adsorbed O* atom towards both H2O and solvated H+.

Cardiovascular dysfunction is a common complication among heatstroke patients, but its underlying mechanism is unclear. This study was designed to investigate the role of calpain-2 and its downstream signal pathway in heat stress-induced cardiomyocyte apoptosis and heart dysfunction. In cultured primary mouse neonatal cardiomyocytes (MNCs), heat stress (43°C for 2 hr) induced a heat-shock response, as indicated by upregulated heat-shock protein 27 (HSP27) expression and cellular apoptosis, as indicated by increased caspase-3 activity, DNA fragmentation and decreased cell viability. Meanwhile, heat stress decreased calpain activity, which was accompanied by downregulated calpain-2 expression and increased phosphorylation of p38, extraceIIuIar signaI-reguIated protein kinase (ERK1/2) and c-Jun N-terminaI kinase (JNK). Calpain-2 overexpression abrogated heat stress-induced apoptosis and phosphorylation of p38 and JNK, but not of ERK1/2. Blocking only p38 prevented heat stress-induced apoptosis in MNCs. In cardiac-specific calpain-2 overexpressing transgenic mice, p38 phosphorylation and cardiomyocyte apoptosis were decreased in the heart tissue of heatstroke mice, as revealed by western blot and terminal deoxynucleotidyl transferase dUTP nick end labelling assays, respectively. M-mode echocardiography also demonstrated that calpain-2 overexpression significantly improved heatstroke-induced decreases in ventricular end-diastolic volume and cardiac output. In conclusion, our study suggests that heat stress reduces calpain-2 expression, which then activates p38, leading to cardiomyocyte apoptosis and heart dysfunction.

The bolted joint provides more than half of the stiffness and nearly all of the damping of the whole machine tool. It is necessary to study the dynamics mechanism and establish accurate model of joint surface. The paper proposes the model of nonlinear virtual material based on fractal theory and Hertz contact theory, the contact surface can be divided into several sections based on the pressure distribution, the elastic modulus and stress of each section can be calculated. An L-shaped specimen is designed to validate the accuracy of presented model. The maximum errors of natural frequencies between theoretical and experimental is 8.8%, suggesting that nonlinear virtual material method is appropriate for the bolted joint.

HCO3−(H2O)n clusters provide a model system to understand the solvation interaction between the bicarbonate ion and water. Based on harmonic analysis, ab initio molecular dynamics simulations, and comparison with infrared multiple photon dissociation spectra and with previous results on H2PO4−(H2O)n, the solvation effects on the vibrational modes of HCO3−(H2O)n are analyzed. Hydrogen bond interactions have a significant impact on the vibration, especially when a hydrogen atom is directly involved in a particular mode. The COH bending mode is flattened, when the COH group is solvated by water molecules. The emergence of broad water libration modes indicates the aggregation of water molecules and the formation of a surface structure with bicarbonate on the surface.

In the wake of big data and Internet plus era, continuous infiltration of digital technology has been happening in various fields of social and economic development. As the most important material carrier of historical culture, the historical value of historical buildings is produced and accumulated in its historical evolution, and it can only be protected from being created again. Based on the background of digitization of cultural resources, this paper summarizes the relevant digital technologies for the digital translation of information on buildings of historical and cultural heritage, as a means to promote the spread of the PDA+APPS mobile terminal, so as to achieve the purpose of preservation, protection, management and publicity. Meanwhile, this paper analyzes the application of digital technology in this field and the prospect of its function.

We describe organogenesis at a histological level in American shad (Alosa sapidissima) larvae from 0 until 45 days after hatching (DAH). Larval development was divided into four stages based on the feeding mode, external morphological features, and structural changes in the organs: stage 1 (0–2 DAH), stage 2 (3–5 DAH), stage 3 (6–26 DAH) and stage 4 (27–45 DAH). At early stage 2 (3 DAH), American shad larvae developed the initial digestive and absorptive tissues, including the mouth and anal opening, buccopharyngeal cavity, oesophagus, incipient stomach, anterior and posterior intestine, differentiated hepatocytes, and exocrine pancreas. The digestive and absorptive capacity developed further in stages 2 to 3, at which time the pharyngeal teeth, taste buds, gut mucosa folds, differentiated stomach, and gastric glands could be observed. Four defined compartments were discernible in the heart at 4 DAH. From 3 to 13 DAH, the excretory systems started to develop, accompanied by urinary bladder opening, the appearance and development of primordial pronephros, and the proliferation and convolution of renal tubules. Primordial gills were detected at 2 DAH, the pseudobranch was visible at 6 DAH, and the filaments and lamellae proliferated rapidly during stage 3. The primordial swim bladder was first observed at 2 DAH and started to inflate at 9 DAH; from then on, it expanded constantly. The spleen was first observed at 8 DAH and the thymus was evident at 12 DAH. From stage 4 onwards, most organs essentially manifested an increase in size, number, and complexity of tissue structure.

One-on-one online English tutoring provides equal educational opportunities for students living in remote areas. This study examines the learning satisfaction, attitudes, and grades of e-tutees receiving online English tutoring. Ten e-tutees and ten e-tutors participated in the study. The study found that the e-tutees were satisfied with their one-on-one online English tutoring and that they performed well on online English tests. In addition, evaluations made by e-tutors show their e-tutees learning attitudes were positive. Online English distance education not only overcomes the limitations of space and time but also facilitates e-tutees' learning and development.