Screening effects on field emission from arrays of (5,5) carbon nanotubes: Quantum-mechanical simulation

The simulation of field electron emission from arrays of micrometer-long open-ended (5, 5) carbon nanotubes is performed in the framework of quantum theory of many electrons. It is found that the applied external field is strongly screened when the spacing distance is shorter than the length of the carbon nanotubes. The optimal spacing distance is two to three times of the nanotube length, slightly depending on the applied external fields. The electric screening can be described by a factor that is a exponential function of the ratio of the spacing distance to the length of the carbon nanotubes. For a given length, the field enhancement factor decreases sharply as the screening factor larger than 0.05. The simulation implies that the thickness of the array should be larger than a value but it does not help the emission much by increasing the thickness a great deal

Atomic decoration for improving the efficiency of field electron emission of carbon nanotubes

The field electron emission from the single-walled carbon nanotubes with their open ends terminated by -BH, -NH, and -O has been simulated. The apex-vacuum barrier and the emission current have been calculated. It has been found that -BH and -NH suppress the apex-vacuum barrier significantly and lead to higher emission current in contrast to the -O terminated structure in the same applied field. The calculated binding energy implies that the carbon nanotubes terminated with -BH and -NH are more stable than those saturated by oxygen atoms or by hydrogen atoms.Comment: 8 pages, 9 figures, LaTeX; content changed, typos corrected, references adde

Response and Remission Rates Following High-Frequency vs. Low-Frequency Repetitive Transcranial Magnetic Stimulation (rTMS) Over Right DLPFC for Treating Major Depressive Disorder (MDD): A Meta-Analysis of Randomized, Double-Blind Trials

Background: High-frequency (HF) repetitive transcranial magnetic stimulation (rTMS) over the left dorsolateral prefrontal cortex (L-DLPFC) is the most widely applied treatment protocol for major depressive disorder (MDD), while low-frequency (LF) rTMS over the right DLPFC (R-DLPFC) also exhibits similar, if not better, efficacy for MDD. Therefore, a meta-analysis is warranted to compare the efficacy of the two protocols for MDD.Method: We searched the literature from 1990 through to August 1, 2017 using MEDLINE, and the literature from 1995 through to August 1, 2017 using EMBASE, PsycINFO, the Cochrane Central Register of Controlled Trials (CENTRAL), SCOPUS, and ProQuest Dissertations and Theses (PQDT). We included randomized controlled trials (RCT) comparing the efficacy of HF rTMS over the L-DLPFC and LF rTMS over the R-DLPFC for MDD, which used response and/or remission rates as the primary endpoints, with and without sham-controlled.Results: (1) The meta-analysis of the response rates was based on 12 studies, including 361 patients with MDD (175 for HF (> 5 Hz) over the L-DLPFC, and 186 for LF (<5 Hz) over the R-DLPFC; odds ratio = 1.08; 95%, confidence interval = 0.88–1.34). (2) The meta-analysis of the remission rate was based on 5 studies, including 131 MDD patients (64 for HF over the L-DLPFC and 67 for LF over the R-DLPFC; odds ratio = 1.29; 95% confidence interval = 0.54–3.10).Conclusion: Both HF rTMS over the L-DLPFC and LF over the R-DLPFC demonstrated similar therapeutic efficacy for the treatment of patients with MDD. The results suggested that further investigation on treatment efficacy indicators before/during treatment is necessary and helpful for optimizing a personalized protocol for patients

Behavioral Manipulation by Optogenetics in the Nonhuman Primate

Given their neuroanatomical similarities to humans and their ability to perform complex behaviors, the nonhuman primate has been an important model for understanding complex systems such as sensory processing, motor control, social interaction, and nervous system disorders. Optogenetics offers cell-type specific neural control with millisecond precision, making it a powerful neural modulation technique. Combining optogenetics with the nonhuman primate model promises to lead to significant advances in both basic and applied research. In the past few years, optogenetics has made considerable progress in the nonhuman primate. Here, we systematically review the current state-of-art of optogenetics in the nonhuman primate with an emphasis on behavioral manipulation. Given its recent successes, we believe that the progress in the nonhuman primate will boost the translation of optogenetics to clinical applications in the near future

Aldol Condensation of Methyl Propionate and Formaldehyde: Thermodynamics, Reaction Process, and Network

The aldol condensation of methyl propionate (MP) and formaldehyde (FA) is an environmentally friendly and sustainable route to produce methyl methacrylate (MMA). However, the side reaction is a huge barrier to achieving high selectivity to the target product. To strengthen the regulation of selectivity for the main reaction, a reaction network was established based on the validation and analysis of side reactions in the system through a combination of experimental and computational methods. The thermodynamics was analyzed through the Gibbs free energy (Delta rGT theta) of reactions. On the basis of a rigorous material balance of all components, the sources and reaction equations of 15 products were identified. The multivariate nonlinear model between the yield of different products and reaction conditions was established to predict the yield of each product. The mean relative error of the actual yield and predicted yield was less than 5%. The key influencing condition for the synthesis of MMA was the liquid hourly space velocity (LHSV)

Aldol Condensation of Methyl Propionate and Formaldehyde: Thermodynamics, Reaction Process, and Network

The aldol condensation of methyl propionate (MP) and formaldehyde (FA) is an environmentally friendly and sustainable route to produce methyl methacrylate (MMA). However, the side reaction is a huge barrier to achieving high selectivity to the target product. To strengthen the regulation of selectivity for the main reaction, a reaction network was established based on the validation and analysis of side reactions in the system through a combination of experimental and computational methods. The thermodynamics was analyzed through the Gibbs free energy (Delta rGT theta) of reactions. On the basis of a rigorous material balance of all components, the sources and reaction equations of 15 products were identified. The multivariate nonlinear model between the yield of different products and reaction conditions was established to predict the yield of each product. The mean relative error of the actual yield and predicted yield was less than 5%. The key influencing condition for the synthesis of MMA was the liquid hourly space velocity (LHSV)

Influence of Al Oxides on Cs-SiO(2 )Catalysts for Vapor Phase AldolCondensation of Methyl Acetate and Formaldehyde

A novel Al-promoted Cs-SiO2catalyst was synthesized via impregnation methods and applied in the aldolcondensation reaction of methyl acetate (Ma) with formaldehyde (FA) to synthesize methyl acrylate (MA). Promotion effects of Aloxides on Cs-SiO2catalysts were systematically investigated. The physical-chemical properties of synthesized catalysts werecharacterized through XRD, FT-IR, EDS mapping, N2physical adsorption, NH3-/CO2-TPD, Py-IR, XPS, solid-state MAS NMR,and TG. Subsequently, the catalytic performance of fabricated catalysts was evaluated in afixed-bed microreactor. Reactionparameters, Cs2O and Al2O3contents, as well as calcination temperature were optimized. The evaluation of catalytic stability wasconducted under optimal reaction conditions. As a result, the introduction of Al species into Cs-SiO2endowed the Al-Cs-SiO2catalyst with superior catalytic performance and good reusabilityA novel Al-promoted Cs-SiO2catalyst was synthesized via impregnation methods and applied in the aldolcondensation reaction of methyl acetate (Ma) with formaldehyde (FA) to synthesize methyl acrylate (MA). Promotion effects of Aloxides on Cs-SiO2catalysts were systematically investigated. The physical-chemical properties of synthesized catalysts werecharacterized through XRD, FT-IR, EDS mapping, N2physical adsorption, NH3-/CO2-TPD, Py-IR, XPS, solid-state MAS NMR,and TG. Subsequently, the catalytic performance of fabricated catalysts was evaluated in afixed-bed microreactor. Reactionparameters, Cs2O and Al2O3contents, as well as calcination temperature were optimized. The evaluation of catalytic stability wasconducted under optimal reaction conditions. As a result, the introduction of Al species into Cs-SiO2endowed the Al-Cs-SiO2catalyst with superior catalytic performance and good reusability

Research on the Visual Guidance System of Zoning Casting Grinding Based on Feature Points

Compared to traditional rough casting grinding (RCG), the individualization of castings is very different, which makes it difficult to realize the automation of casting grinding. At this stage, the primary method is manual grinding. In this study, the regional casting grinding system based on feature points is adopted to achieve the personalized grinding of castings and improve the grinding efficiency and the automation level of the manufacturing process. After preprocessing the point cloud, the fast point feature histogram (FPFH) descriptor is used to describe the features of each region and construct the local template. The position of the local region is obtained by template matching. The random sample consensus (RANSAC) algorithm is used to calculate the plane and fit the point cloud to obtain the contact point trajectory of the grinding head. Then, according to different polishing methods, different polishing poses are generated. The simulation experimental results show that the system has good adaptability, and the consistency of finished products is good

Research on the Visual Guidance System of Zoning Casting Grinding Based on Feature Points

Compared to traditional rough casting grinding (RCG), the individualization of castings is very different, which makes it difficult to realize the automation of casting grinding. At this stage, the primary method is manual grinding. In this study, the regional casting grinding system based on feature points is adopted to achieve the personalized grinding of castings and improve the grinding efficiency and the automation level of the manufacturing process. After preprocessing the point cloud, the fast point feature histogram (FPFH) descriptor is used to describe the features of each region and construct the local template. The position of the local region is obtained by template matching. The random sample consensus (RANSAC) algorithm is used to calculate the plane and fit the point cloud to obtain the contact point trajectory of the grinding head. Then, according to different polishing methods, different polishing poses are generated. The simulation experimental results show that the system has good adaptability, and the consistency of finished products is good