Synthesis of Nitrogen-Doped Graphene via Thermal Annealing Graphene with Urea

Chemical doping is an effective method to intrinsically modify the chemical and electronic property of graphene. We propose a novel approach to synthesize the nitrogen-doped graphene via thermal annealing graphene with urea, in which the nitrogen source can be controllably released from the urea by varying the annealed temperature and time. The doped N content and the configuration N as well as the thermal stabilities are also evaluated with X-ray photoelectron spectroscopy and Raman spectra. Electrical measurements indi- cate that the conductivity of doped graphene can be well regulated with the N content. The method is expected to produce large scale and controllable N-doped graphene sheets for a variety of potential applications.

An efficient formulation based on the Lagrangian method for contact–impact analysis of flexible multi-body system

In this paper,an efficien formulation based on the Lagrangian method is presented to investigate the contact–impact problems of f exible multi-body systems.Generally,the penalty method and the Hertz contact law are the most commonly used methods in engineering applications.However,these methods are highly dependent on various non-physical parameters,which have great effects on the simulation results.Moreover,a tremendous number of degrees of freedom in the contact–impact problems will influenc thenumericalefficien ysignificantl.Withtheconsideration of these two problems,a formulation combining the component mode synthesis method and the Lagrangian method is presented to investigate the contact–impact problems in fl xible multi-body system numerically.Meanwhile,the finit element meshing laws of the contact bodies will be studied preliminarily.A numerical example with experimental verificatio will certify the reliability of the presented formulationincontact–impactanalysis.Furthermore,aseries of numerical investigations explain how great the influenc of the finit element meshing has on the simulation results.Finally the limitations of the element size in different regions are summarized to satisfy both the accuracy and efficien y.

Contact-impact formulation for multi-body systems using component mode synthesis

The efficiency and accuracy are two most concerned issues in the modeling and simulation of multi-body systems involving contact and impact. This paper proposed a formulation based on the component mode synthesis method for planar contact problems of flexible multi-body systems. A flexible body is divided into two parts： a contact zone and an un-contact zone. For the un-contact zone, by using the fixed-interface substructure method as reference, a few low-order modal coordinates are used to replace the nodal coordinates of the nodes, and meanwhile, the nodal coordinates of the local impact region are kept unchanged, therefore the total degrees of freedom （DOFs） are greatly cut down and the computational cost of the simulation is significantly reduced. By using additional constraint method, the impact constraint equations and kinematic constraint equations are derived, and the Lagrange equations of the first kind of flexible multi-body system are obtained. The impact of an elastic beam with a fixed half disk is simulated to verify the efficiency and accuracy of this method.

A new subregion mesh method for the investigation of the elastic-plastic impact in flexible multibody systems

Impact processes between flexible bodies often lead to local stress concentration and wave propagation of high frequency. Therefore, the modeling of flexible multibody systems involving impact should consider the local plastic deformation and the strict requirements of the spatial discretization. Owing to the nonlinearity of the stiffness matrix, the reduction of the element number is extremely important. For the contact-impact problem, since different regions have different requirements regarding the element size, a new subregion mesh method is proposed to reduce the number of the unnecessary elements. A dynamic model for flexible multibody systems with elastic-plastic contact impact is established based on a floating frame of reference formulation and complete Lagrange incremental nonlinear finite-element method to investigate the effect of the elastic-plastic deformation as well as spatial discretization. Experiments on the impact between two bodies are carried out to validate the correctness of the elastic-plastic model. The proposed formulation is applied to a slider-crank system with elastic-plastic impact.

Investigation on the choice of boundary conditions and shape functions for flexible multi-body system

The objective of this investigation is to examine the correctness and efficiency of the choice of boundary conditions when using assumed mode approach to simulate flexible multi-body systems. The displacement field due to deformation is approximated by the Rayleigh-Ritz assumed modes in floating frame of reference （FFR） formulation. The deformations obtained by the absolute nodal coordinate （ANC） formulation which are transformed by two sets of reference coordinates are introduced as a criterion to verify the accuracy of the simulation results by using the FFR formulation. The relationship between the deformations obtained from different boundary conditions is revealed. Nu- merical simulation examples demonstrate that the assumed modes with cantilevered-free, simply-supported and free- free boundary conditions without inclusion of rigid body modes are suitable for simulation of flexible multi-body system with large over all motion, and the same physical deformation can be obtained using those mode functions, differ only by a coordinate transformation. It is also shown that when using mode shapes with statically indeterminate boundary conditions, significant error may occur. Furthermore, the slider crank mechanism with rigid crank is accurate enough for investigating boundary condition problem of flexible multi-body system, which cost significant less simulating time.

Epidemiological and clinical characteristics of 65 hospitalized patients with COVID-19 in Liaoning, China

BACKGROUND Coronavirus disease 2019(COVID-19)has spread rapidly to multiple countries through its infectious agent severe acute respiratory syndrome coronavirus 2.The severity,atypical clinical presentation,and lack of specific anti-viral treatments have posed a challenge for the diagnosis and treatment of COVID-19.Understanding the epidemiological and clinical characteristics of COVID-19 cases in different geographical areas is essential to improve the prognosis of COVID-19 patients and slow the spread of the disease.AIM To investigate the epidemiological and clinical characteristics and main therapeutic strategy for confirmed COVID-19 patients hospitalized in Liaoning Province,China.METHODS Adult patients(n=65)with confirmed COVID-19 were enrolled in this retrospective study from January 20 to February 29,2020 in Liaoning Province,China.Pharyngeal swabs and sputum specimens were collected from the patients for the detection of severe acute respiratory syndrome coronavirus 2 nucleic acid.Patient demographic information and clinical data were collected from the medical records.Based on the severity of COVID-19,the patients were divided into nonsevere and severe groups. All patients were followed until March 20,2020.RESULTSThe mean age of 65 COVID-19 patients was 45.5 ± 14.4 years, 56.9% were men,and 24.6% were severe cases. During the 14 d before symptom onset, 25 (38.5%)patients lived or stayed in Wuhan, whereas 8 (12.3%) had no clear history ofexposure. Twenty-nine (44.6%) patients had at least one comorbidity;hypertension and diabetes were the most common comorbidities. Compared withnonsevere patients, severe patients had significantly lower lymphocyte counts[median value 1.3 × 10^(9)/L (interquartile range 0.9-1.95) vs 0.82 × 10^(9)/L (0.44-1.08),P < 0.001], elevated levels of lactate dehydrogenase [450 U/L (386-476) vs 707 U/L(592-980), P < 0.001] and C-reactive protein [6.1 mg/L (1.5-7.2) vs 52 mg/L (12.7-100.8), P < 0.001], and a prolonged median duration of viral shedding [19.5 d (16-21) vs 23.5 d (19.6-30.3), P = 0.001]. The overall median viral shedding time was19.5 d, and the longest was 53 d. Severe patients were more frequently treatedwith lopinavir/ritonavir, antibiotics, glucocorticoid therapy, immunoglobulin,thymosin, and oxygen support. All patients were discharged following treatmentin quarantine.CONCLUSIONOur findings may facilitate the identification of severe cases and inform clinicaltreatment and quarantine decisions regarding COVID-19.

Fabrication of Highly Conductive Pd Nanowires using PDMS Transfer Method on DNA Scaffolds through Ethanol-Reduction

We have developed a simple, productive, and ettectlve poly（cllmetnysltoxane） rranu fer method to fabricate highly conductive Pd nanowires following DNA scaffolds on various substrates, based on ethanolreduction at low temperature. Pd nanoparticles were selectively deposited and confined onto the DNA templates on a PDMS sheet to form Pd nanowires and then the nanowires were transferred to other various substrates with a low occurrence of par asitic nanoparticles. The structure, morphology and the conductance of Pd nanowires were characterized with transmission electron microscopy, field emission scanning electron mi croscopy, and electrical transport measurement, respectively. Moreover, the growth process of the Pd nanowires was investigated by varying the incubation time and reaction temper ature. The present strategy provides a new method to fabricate extremely dense, highly conductive, and well aligned Pd nanowires on various substrates, which make it promising for building nanosensors and nanoelectronic devices.

Epidemiological and clinical characteristics of fifty-six cases of COVID-19 in Liaoning Province, China

BACKGROUND Pneumonia of uncertain cause has been reported in Wuhan,China since the beginning of early December 2019.In early January 2020,a novel strain ofβ-coronavirus was identified by the Chinese Center for Disease Control and Prevention from the pharyngeal swab specimens of patients,which was recently named severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).There is evidence of human-to-human transmission and familial cluster outbreak of SARSCoV-2 infection.The World Health Organization(WHO)recently declared the SARS-CoV-2 epidemic a global health emergency.As of February 17,2020,71329 laboratory-confirmed cases(in 25 countries,including the United States and Germany)have been reported globally.Other than its rapid transmission,the epidemiological and clinical characteristics of coronavirus disease 2019(COVID-19)remain unclear.In December 2019,coronavirus disease(named COVID-19 by the WHO)associated with the SARS-CoV-2 emerged in Wuhan,China and spread quickly across the country.AIM To analyze the epidemiological and clinical characteristics of confirmed cases of this disease in Liaoning province,a Chinese region about 1800 km north of Wuhan.METHODS The clinical data of 56 laboratory-confirmed COVID-19 cases due to 2019-nCoV infection were analyzed.The cases originated from eight cities in Liaoning province.RESULTS The median age of the patients was 45 years,and 57.1%of them were male.No patient had been in direct contact with wild animals.Among them,23 patients(41.1%)had resided in or traveled to Wuhan,27 cases(48.2%)had been in contact with confirmed COVID-19 patients,5 cases(8.9%)had been in contact with confirmed patients with a contact history to COVID-19 patients,and 1 case(1.8%)had no apparent history of exposure.Fever(75.0%)and cough(60.7%)were the most common symptoms.The typical manifestations in lung computed tomography(CT)included ground-glass opacity and patchy shadows,with 67.8%of them being bilateral.Among the patients in the cohort,78.6%showed reduction in their lymphocyte counts,57.1%showed increases in their C-reactive protein levels,and 50.0%showed decreases in their blood albumin levels.Eleven patients(19.6%)were admitted to intensive care unit,2 patients(3.5%)progressed to acute respiratory distress syndrome,4 patients(7.1%)were equipped with non-invasive mechanical ventilation,and 1 patient(1.8)received extracorporeal membrane oxygenation support.There were 5 mild cases(5/56,8.9%),40 moderate cases(40/56,71.4%),10 severe cases(10/56,17.9%),and 1 critical case(1/56,1.8%).No deaths were reported.CONCLUSION SARS-CoV-2 can be transmitted among humans.Most COVID-19 patients show symptoms of fever,cough,lymphocyte reduction,and typical lung CT manifestations.Most are moderate cases.The seriousness of the disease(as indicated by blood oxygen saturation,respiratory rate,oxygenation index,blood lymphocyte count,and lesions shown in lung CT)is related to history of living in or traveling to Wuhan,underlying diseases,admittance to intensive care unit,and mechanical ventilation.

Geometric nonlinear formulation for thermal-rigid-flexible coupling system

This paper develops geometric nonlinear hybrid formulation for flexible multibody system with large deformation considering thermal effect. Different from the conventional formulation, the heat flux is the function of the rotational angle and the elastic deformation, therefore, the coupling among the temperature, the large overall motion and the elastic deformation should be taken into account. Firstly, based on nonlinear strain-displacement relationship, varia- tional dynamic equations and heat conduction equations for a flexible beam are derived by using virtual work approach, and then, Lagrange dynamics equations and heat conduction equations of the first kind of the flexible multibody system are obtained by leading into the vectors of Lagrange multiplier associated with kinematic and temperature constraint equations. This formulation is used to simulate the thermal included hub-beam system. Comparison of the response be- tween the coupled system and the uncoupled system has re- vealed the thermal chattering phenomenon. Then, the key parameters for stability, including the moment of inertia of the central body, the incident angle, the damping ratio and the response time ratio, are analyzed. This formulation is also used to simulate a three-link system applied with heat flux. Comparison of the results obtained by the proposed formulation with those obtained by the approximate nonlinear model and the linear model shows the significance of con- sidering all the nonlinear terms in the strain in case of large deformation. At last, applicability of the approximate non- linear model and the linear model are clarified in detail.

Treatment of Adult Hirschsprung's Disease by Botulinum Toxin A through Anorectal Injection

To the Editor:The patient was a 16-year-old adolescent boy who was diagnosed with congenital megacolon.He had difficulty with defecating for more than 10 years.His bowel movements stopped more than 1 week ago.He was admitted to the hospital with incomplete intestinal obstruction.The patient showed signs of moderate nutrition,poor mental health,and full abdominal bulging and had an abdominal circumference of 104 cm. Rectal examination showed blasting exhaust and defecation, and the anal pressure measurement value was 89 mmHg.The total abdominal augmentation computed tomography and total colorectal sputum angiography showed that the upper and middle rectum,descending colon,transverse colon,and ascending colon were dilated,the maximum diameter of the intestine was 23 cm,and the intestine was filled with feces, suggesting that the lower rectum and sigmoid colon were narrow [Figure 1a and 1b].

A combinatorial strategy to identify various types of QTLs for quantitative traits using extreme phenotype individuals in an F_(2)population

Theoretical and applied studies demonstrate the difficulty of detecting extremely over-dominant and smalleffect genes for quantitative traits via bulked segregant analysis(BSA)in an F_(2)population.To address this issue,we proposed an integrated strategy for mapping various types of quantitative trait loci(QTLs)for quantitative traits via a combination of BSA and whole-genome sequencing.In this strategy,the numbers of read counts of marker alleles in two extreme pools were used to predict the numbers of read counts of marker genotypes.These observed and predicted numbers were used to construct a new statistic,G_(w),for detecting quantitative trait genes(QTGs),and the method was named dQTG-seq1.This method was significantly better than existing BSA methods.If the goal was to identify extremely over-dominant and smalleffect genes,another reserved DNA/RNA sample from each extreme phenotype F_(2)plant was sequenced,and the observed numbers of marker alleles and genotypes were used to calculate G_(w)to detect QTGs;this method was named dQTG-seq2.In simulated and real rice dataset analyses,dQTG-seq2 could identify many more extremely over-dominant and small-effect genes than BSA and QTL mapping methods.dQTGseq2 may be extended to other heterogeneous mapping populations.The significance threshold of G_(w)in this study was determined by permutation experiments.In addition,a handbook for the R software dQTG.seq,which is available at https://cran.r-project.org/web/packages/dQTG.seq/index.html,has been provided in the supplemental materials for the users’convenience.This study provides a new strategy for identifying all types of QTLs for quantitative traits in an F_(2)population.