Search

The transformation of renewable platform molecules to produce value-added fuels and fine-chemicals is a promising strategy to sustainably meet future demands. Owing to their finely modified electronic and geometric properties, carbon-based nanocatalysts have shown great capability to regulate their catalytic activity and stability. Their well-defined and uniform structures also provide both the opportunity to explore intrinsic reaction mechanisms and the site-requirement for valorization of renewable platform molecules to advanced fuels and chemicals. This Review highlights the progress achieved in carbon-based nanocatalysts, mainly by using effective regulation approaches such as heteroatom anchoring, bimetallic synergistic effects, and carbon encapsulation to enhance catalyst performance and stability, and their applications in renewable platform molecule transformations. The foundation for understanding the structure-performance relationship of carbon-based catalysts has been established by investigating the effect of these regulation methods on catalyst performance. Finally, the opportunities, challenges and potential applications of carbon-based nanocatalysts are discussed.

Background: China 's national-level anti-COVID-19 campaign has been going on for a month. With the development of the epidemic, it is found that COVID-19 severity in Hubei province (Hubei) is different from the rest of mainland China (Rest of China). It is necessary to compare the two areas, summarize experiences and lessons, analyze the epidemic trend and further point out the direction for the campaign. Methods: Prevent, quarantine and treat the disease according to The Novel Coronavirus Infected Pneumonia Diagnosis and Treatment Standards. Collect the numbers of total close contacts, daily observation cases, daily suspected cases, total conrmed cases, daily severe cases, total deaths from January 20 to February 19, input them into SPSS 25 and Microsoft ofce 2019 excel for data processing, statistical analysis and drawing. Findings: Total conrmed cases in Hubei account for 83.2% of the country. Daily suspected cases growth rates for both areas have become negative since February 9. Daily observation cases in Rest of China reached highest point on February 5 as opposed to February 13 in Hubei, and total close contacts growth rates for the last three days are declining steadily to 1.9% and 3.8% respectively. Total conrmed cases growth rate has hit the lowest levels in Rest of China at 0.34% by comparison with 0.57% in Hubei. Mean fatality rate and mean percentage of severe cases for the last three days in Rest of China are 0.67% and 5.83% in contrast to 3.12% and 18.2% in Hubei. There have been very signicant differences in fatality rate and percentage of severe cases existing in the two areas since January 23 and 24 respectively (P

Background: Mainland China has adopted the most decisive and proactive measures to contain the SARS-CoV-2 epidemic, which helps control the spread of the virus across the country. Objectives: Early epidemiological investigations found that the SARS-CoV-2 epidemic was more critical in Hubei province (Hubei) than in rest parts of mainland China (Rest of China). A cross-sectional study was conducted to answer this urgent question and provide implications for the world. Methods: Infected cases from Mainland China were divided into two groups: Hubei and the Rest of China. Prevention, quarantine, and treatment were based on The Novel Coronavirus Infected Pneumonia Diagnosis and Treatment Standards. Total confirmed cases, daily severe cases, total deaths, and total discharged cases were collected from January 20 to March 4 for statistical analysis. Results: Hubei accounted for 83.9% of China's total confirmed cases and 96.3% of China's total deaths. The percentage of severe cases and the rate of fatality in Hubei were higher than those in the Rest of China (P < 0.01). Daily severe cases in Hubei hit the peak at 11,246 cases on February 18, compared to 989 cases on February 10 in the Rest of China. The percentages of daily severe cases in both regions declined throughout the epidemic, from 23.3% to 8.6% in Hubei compared to 15.0% to 1.3% in the Rest of China. The latest fatality rate in Hubei was 4.30%, which was much higher than 0.85% in the Rest of China. Up to March 4, 64.7% of China's total confirmed cases were cured, 3.86% died, and 31.5% were under treatment. Conclusions: The implications for the world are cutting off the sources of infection and transmission routes, early detection, early isolation, and early treatment that can prevent the spread of SARS-CoV-2 and reduce the severity and fatality rate.

Strong metal-support interaction (SMSI) is crucial for supported catalysts in heterogeneous catalysis. Here is the first report on strong metal phosphide-phosphate support interaction (SMPSI). The key to SMPSI is the activation of P species on the support, which leads to simultaneously generate of metal phosphide NPs and core-shell nanostructures formed by support migration onto the NPs. The encapsulation state of metal phosphide and charge transfer are identical to those of classical SMSIs and can be optimally regulated. Furthermore, the strong interactions of Co2 PL /MnP-3 not only significantly enhance the anti-oxidation and anti-acid capability of non-noble metal but also exhibit excellent catalytic activity and stability toward hydrogenating a wide range of compounds into value-added fine chemicals with 100% selectivity, which is even better than Pd/C and Pt/C. The SMPSI construction can be generally extended to other systems such as Ni2 PL /Mn3 (PO4 )2 , Co2 PL /LaPO4 , and CoPL /CePO4 . This study provides a new approach for the rational design of advanced non-noble metal catalysts and introduce a novel paradigm for the strong interaction between NPs and support. This article is protected by copyright. All rights reserved.

Pulsed eddy current testing (PECT) has the advantages of rich information, efficiency and noncontact among defect nondestructive testing. Pulsed eddy current imaging technology also has a wide range of applications. However, the imaging method based on single feature is mostly adopted at this stage. In order to make better use of pulsed eddy current signals, signal slice based method was proposed for pulsed eddy current sequence imaging. Through the difference analysis of air-subtracted signal (ASS) and non-defect-subtracted signal (NDSS), sequence imaging in different ways is carried out. The influence of defects was explained by visualizing the diffusion of eddy currents in different specimens using a finite element model. ASS and NDSS image sequences were evaluated through image quality evaluation and quantitative identification. The result shows that there are some image frames in the image sequence that are better than the images generated by a single feature value in the image quality evaluation and quantitative analysis. It proves that the image sequence contains more defect information, which also illustrates the information richness of pulse eddy current detection.

Colorectal cancer (CRC) is the third‐most common cancer around the world, accounting for approximately 10% of cancer‐related mortality. Deeper molecular understanding of colorectal carcinogenesis will provide evidences for identification of early diagnostic indicators and novel therapeutic strategies for CRC treatment. The p21cdc42/rac1‐activated kinase 5 (PAK5) has been reported to be involved in a variety of tumor‐promoting behaviors, whereas the underlying mechanisms of PAK5 in CRC progression are still obscure. Our current study revealed an upregulated expression of PAK5 in human CRC tissues as compared with normal adjacent biopsies, which was associated with tumor progression and metastasis. We further unraveled that inhibition of PAK5 was correlated with restrained proliferation, migration, and invasion of CRC cells in vitro and in vivo. Moreover, we showed an indispensable role of PAK5 in interacting with Cdc42 and Integrin β1, β3, thus, to facilitate the migration and invasion of CRC cells. Collectively, we pointed out a potential of PAK5 to serve as a novel therapeutic target in restricting CRC proliferation and metastasis. The uncovered mechanisms will deepen the comprehension with regard to the mechanisms of CRC progression, as well as providing new insights for therapeutic intervention in colorectal cancer., PAK5 was highly expressed in human CRC samples, which was correlated with cancer progression and metastasis. Inhibition of PAK5 was associated with restrained tumor cell proliferation, migration, and invasion in vitro and in vivo models. Interacting with Cdc42 and integrin β1 and β3 was indispensable for PAK5 to facilitate the migration and invasion of CRC cells.

Objective: To determine whether the effectiveness of core stability exercises correlates with the severity of spinal stenosis in patients with degenerative lumbar spinal stenosis. Methods: Forty-two patients with degenerative lumbar spinal stenosis treated in the department of orthopedics of our hospital between May 2013 and January 2016 were included in the study. All the patients performed core stability exercises once daily for six weeks, and the clinical outcomes were evaluated using Japanese Orthopaedic Association (JOA) score and self-reported walking capacity. The anteroposterior osseous spinal canal diameter was measured to evaluate the severity of spinal stenosis. The correlation between the stenosis degree and the differences of Japanese Orthopaedic Association score or self-reported walking capacity at baseline and after treatment were analyzed. Results: The patients were divided into three groups according to the spinal stenosis degree. In the three groups, there was no significant difference in JOA or self-reported walking distance at baseline (p>0.05) and after treatment (p>0.05). The JOA scores and self-reported walking distance were significantly increased after treatment (p0.05) or self-reported walking distance (p>0.05). Conclusion: There was no significantcorrelation between the effectiveness of core stability exercises and the severity of spinal stenosis in patients with degenerative lumbar spinal stenosis.

A chromium-free environmental protection aluminum surface treatment technology was developed by theoretical analysis and a large number of experiments. Add zirconium ions and cerium ions to the treatment solution, besides adding fluoride, aluminum and hydrogen peroxide, etc. According to the orthogonal test obtained a non-chromate film-formation process of environmental friendly aluminum. The characterization methods including SEM, XPS and XRD were applied to study and analyze the morphology, composition, phase, and corrosion resistance of phosphate film, then discussed the film-forming reaction mechanism. Results showed that chemical conversion film formed on the aluminum surface was uniform, compact and stronger anti-corrosion could replace the traditional, more toxic chromate conversion film.

Using a gridded ionization chamber, angular distributions for the 64 Zn(n,α) 61 Ni reaction were measured at 5.0, 5.7, and 6.5 MeV. The neutrons were produced through the D(d, n ) 3 He reaction. The neutron flux was determined through the 238 U(n, f) reaction. The results show a backward peak in the center-of-mass reference system for 5.7 and 6.5 MeV. The cross sections are 72.5, 72.0, and 70.8 mb for 5.0, 5.7, and 6.5 MeV, respectively.

The differential cross sections of the {sup 6}Li(n,t){sup 4}He reaction were measured at 1.85 and 2.67 MeV by using a gridded ionization chamber. Neutrons were produced through the T(p,n){sup 3}He reaction. The absolute neutron flux was determined through the {sup 238}U(n,f) reaction. Results are compared with existing data.

The differential cross sections of the 10 B(n, α) 7 Li reaction were measured at 4.17, 5.02, 5. 74, and 6.52 MeV by using a gridded ionization chamber. Neutrons were produced through the D(d,n) 3 He reaction. The absolute neutron flux was determined through the 238 U(n,f) reaction. The experiment shows that as the neutron energy increases from 4.17 to 6.52 MeV, the differential cross section changes from almost 90-deg symmetry to obviously backward peaked in the center-of-mass reference system.

The experiment of determination of the 64Zn(n, α)61Ni reaction cross section in the 5.0 - 6.75 MeV neutron energy range was performed at the 4.5 MV Van de Graaff accelerator at the Institute of Heavy Ion Physics, Peking University, Beijing. A double section ionization chamber with grids was used for direct registration of the reaction products. The cross sections and angular distributions were extracted from the experimental data. The obtained values were compared with the results of other authors and theoretical estimations. The analysis of the experimental data and model calculations were carried out.

A gridded ionization chamber was used to measure the differential cross sections for tritons from the {sup 6}Li(n,t){sup 4}He reaction at 3.67 and 4.42 MeV. Neutrons were produced via the D(d,n){sup 3}He reaction. The absolute neutron flux was determined through the {sup 238}U(n,f) and H(n,p) reactions. At 3.67 MeV the result is almost 90 deg symmetric, but it is obviously forward peaked at 4.42 MeV in the center-of-mass reference system.

Cross sections, angular distributions, and double-differential cross sections were measured for 39 K(n,α) 36 Cl reactions at E n = 4.5,'5.5, and 6.5 MeV and for 40 Ca(n,α) 37 Ar reactions at E n = 5.0 to 6.0 MeV, using a twin-gridded ionization chamber, and the experimental data were analyzed with the UNF code. The results indicate that the optical model parameters employed in the calculation are appropriate in the energy region. The energy level densities used in our calculations are a little different from the findings of Gilbert and Cameron, and the pair corrections of some nuclei are much smaller than what was determined by them. The experiment and model calculation results indicate that in the energy region below 7 MeV, the compound nuclear mechanism is predominant; at 6.5 MeV, the preequilibrium emission is ∼12%.

In order to explore various factors to the aluminum surface self-assembly process on film forming properties, this study tested a large number of single-factor method to determine the optimal experimental conditions: film-forming time was 3min; pH was 6; PESA was 2.5mL/L; organic phosphorus compounds was 5mL/L; nitrilotriacetic acid was 5g/L; fluoride was 10g/L; processing time was 3min. Results showed that under these conditions the SAMs had good overall performance with strong adhesion.

In order to explore non-chrome aluminum conversion coating on the surface of various factors on the film properties, this study through a large number of single factor tests to determine the best material into a film former ratio and process conditions: sulfuric acid (1∶2) 3.4mL/100mL, cerium sulfate 1.2g/100mL, alum 0.6g/100mL, zirconium tetrafluoride 1.5g/100mL, potassium fluoroborate 0.6g / 100mL, hydrogen peroxide (1∶2) 1.5mL/100mL, temperature of 40 °C, deposition time 20min. On the basis of the analysis of various influencing factors, this study have a better understanding in the various factors which play a role in the film in the process, and optimize its manufacturing process which make the film corrosion resistance, appearance and comprehensive performance are in the best situation.

Differential scattering cross-section data have been measured at 43 angles from ${11}^{\ifmmode^\circ\else\textdegree\fi{}}$ to ${160}^{\ifmmode^\circ\else\textdegree\fi{}}$ for 37-MeV neutrons incident on $^{209}\mathrm{Bi}$. The primary motivation for the measurements is to address the scarcity of neutron scattering data above 30 MeV and to improve the accuracy of optical-model predictions at medium neutron energies. The high-statistics measurements were conducted at the China Institute of Atomic Energy using the $^{3}\mathrm{H}$($d,n$)$^{4}\mathrm{He}$ reaction as the neutron source, a pulsed deuteron beam, and time-of-flight (TOF) techniques. Within the resolution of the TOF spectrometer, the measurements included inelastic scattering components. The sum of elastic and inelastic scattering cross sections was computed in joint optical-model and distorted-wave Born approximation calculations under the assumption of the weak particle-core coupling. The results challenge predictions from well-established spherical optical potentials. Good agreement between data and calculations is achieved at 37 MeV provided that the balance between surface and volume absorption in a recent successful model [A. J. Koning and J. P. Delaroche, Nucl. Phys. A 713, 231 (2003)] is modified, thus suggesting the need for global optical-model improvements at medium neutron energies.

The {ital p}-{sup 40}Ca mean field is derived from an optical-model (OM) analysis that explicitly incorporates the dispersion relation connecting the real and imaginary parts of the mean field. This analysis is based on differential cross-section, analyzing power, and reaction cross-section data available in the energy range between 20 and 180 MeV. The extrapolation of the OM potential from positive to negative energies provides the shell-model potential. This extrapolation is guided by known single-particle energies. The deeply bound 1{ital p} and 1{ital s} orbits clearly indicate the need for a linear rather than an exponential energy dependence of the Hartree-Fock potential at large negative energies. The analysis also provides root-mean-square radii, occupation probabilities, spectral functions, and absolute spectroscopic factors for proton single-particle orbits in {sup 40}Ca. Our calculated 15% depletion of the hole states in {sup 40}Ca is lower than that suggested for {sup 208}Pb from theoretical and experimental studies. We also find that a substantial amount of single-particle strength in {sup 40}Ca is located at rather high excitation energy.

Global change study is an interdisciplinary and comprehensive research activity with international cooperation, arising in 1980s, with the largest scopes. The interaction between land use and cover change, as a research field with the crossing of natural science and social science, has become one of core subjects of global change study as well as the front edge and hot point of it. It is necessary to develop research on land use and cover change in urbanization process and build an analog model of urbanization to carry out description, simulation and analysis on dynamic behaviors in urban development change as well as to understand basic characteristics and rules of urbanization process. This has positive practical and theoretical significance for formulating urban and regional sustainable development strategy. The effect of urbanization on land use and cover change is mainly embodied in the change of quantity structure and space structure of urban space, and LUCC model in urbanization process has been an important research subject of urban geography and urban planning. In this paper, based upon previous research achievements, the writer systematically analyzes the research on land use/cover change in urbanization process with the theories of complexity science research and intelligent computation; builds a model for simulating and forecasting dynamic evolution of urban land use and cover change, on the basis of cellular automation model of complexity science research method and multi-agent theory; expands Markov model, traditional CA model and Agent model, introduces complexity science research theory and intelligent computation theory into LUCC research model to build intelligent computation-based LUCC model for analog research on land use and cover change in urbanization research, and performs case research. The concrete contents are as follows: 1. Complexity of LUCC research in urbanization process. Analyze urbanization process in combination with the contents of complexity science research and the conception of complexity feature to reveal the complexity features of LUCC research in urbanization process. Urban space system is a complex economic and cultural phenomenon as well as a social process, is the comprehensive characterization of urban society, economy and culture, and is a complex space system formed by society, economy and nature. It has dissipative structure characteristics, such as opening, dynamics, self-organization, non-balance etc. Traditional model cannot simulate these social, economic and natural driving forces of LUCC including main feedback relation from LUCC to driving force. 2. Establishment of Markov extended model of LUCC analog research in urbanization process. Firstly, use traditional LUCC research model to compute change speed of regional land use through calculating dynamic degree, exploitation degree and consumption degree of land use; use the theory of fuzzy set to rewrite the traditional Markov model, establish structure transfer matrix of land use, forecast and analyze dynamic change and development trend of land use, and present noticeable problems and corresponding measures in urbanization process according to research results. 3. Application of intelligent computation research and complexity science research method in LUCC analog model in urbanization process. On the basis of detailed elaboration of the theory and the model of LUCC research in urbanization process, analyze the problems of existing model used in LUCC research (namely, difficult to resolve many complexity phenomena in complex urban space system), discuss possible structure realization forms of LUCC analog research in combination with the theories of intelligent computation and complexity science research. Perform application analysis on BP artificial neural network and genetic algorithms of intelligent computation and CA model and MAS technology of complexity science research, discuss their theoretical origins and their own characteristics in detail, elaborate the feasibility of them in LUCC analog research, and bring forward improvement methods and measures on existing problems of this kind of model. 4. Establishment of LUCC analog model in urbanization process based on theories of intelligent computation and complexity science. Based on the research on abovementioned BP artificial neural network, genetic algorithms, CA model and multi-agent technology, put forward improvement methods and application assumption towards their expansion on geography, build LUCC analog model in urbanization process based on CA model and Agent model, realize the combination of learning mechanism of BP artificial neural network and fuzzy logic reasoning, express the regulation with explicit formula, and amend the initial regulation through self study; optimize network structure of LUCC analog model and methods and procedures of model parameters with genetic algorithms. In this paper, I introduce research theory and methods of complexity science into LUCC analog research and presents LUCC analog model based upon CA model and MAS theory. Meanwhile, I carry out corresponding expansion on traditional Markov model and introduce the theory of fuzzy set into data screening and parameter amendment of improved model to improve the accuracy and feasibility of Markov model in the research on land use/cover change.

Cross sections and differential cross sections of ${}^{39}\mathrm{K}(n,\ensuremath{\alpha}{)}^{36}\mathrm{Cl}$ at $En=4.5,$ 5.5, and 6.5 MeV, and that of ${}^{40}\mathrm{Ca}(n,\ensuremath{\alpha}{)}^{37}\mathrm{Ar}$ at $En=5$ and 6 MeV were measured. These data and other available experimental data were used in optical model calculations which contain a dispersion relation term. One set of parameters for dispersive optical potentials of ${}^{39}\mathrm{K}(n,n),$ $(n,p),$ and $(n,\ensuremath{\alpha})$ reactions is determined, and subsequently used in the dispersive optical model (DOM) calculations for ${}^{40}\mathrm{Ca}(n,n),$ $(n,p),$ and $(n,\ensuremath{\alpha})$ reactions. A good description of the experimental data with DOM is achieved, and the results are compared with that of the spherical optical model.