Analysis of sensitivity to hydrate blockage risk in natural gas gathering pipeline

During the operational process of natural gas gathering and transmission pipelines,the formation of hydrates is highly probable,leading to uncontrolled movement and aggregation of hydrates.The continuous migration and accumulation of hydrates further contribute to the obstruction of natural gas pipelines,resulting in production reduction,shutdowns,and pressure build-ups.Consequently,a cascade of risks is prone to occur.To address this issue,this study focuses on the operational process of natural gas gathering and transmission pipelines,where a comprehensive framework is established.This framework includes theoretical models for pipeline temperature distribution,pipeline pressure distribution,multiphase flow within the pipeline,hydrate blockage,and numerical solution methods.By analyzing the influence of inlet temperature,inlet pressure,and terminal pressure on hydrate formation within the pipeline,the sensitivity patterns of hydrate blockage risks are derived.The research indicates that reducing inlet pressure and terminal pressure could lead to a decreased maximum hydrate formation rate,potentially mitigating pipeline blockage during natural gas transportation.Furthermore,an increase in inlet temperature and terminal pressure,and a decrease in inlet pressure,results in a displacement of the most probable location for hydrate blockage towards the terminal station.However,it is crucial to note that operating under low-pressure conditions significantly elevates energy consumption within the gathering system,contradicting the operational goal of energy efficiency and reduction of energy consumption.Consequently,for high-pressure gathering pipelines,measures such as raising the inlet temperature or employing inhibitors,electrical heat tracing,and thermal insulation should be adopted to prevent hydrate formation during natural gas transportation.Moreover,considering abnormal conditions such as gas well production and pipeline network shutdowns,which could potentially trigger hydrate formation,the installation of methanol injection connectors remains necessary to ensure production safety.

故障模式下斜盘式轴向柱塞泵的流体振动传递路径分析

轴向柱塞泵是液压系统中的核心元件,其性能直接决定了整个系统的安全性和可靠性。而轴向柱塞泵故障也时常发生,最为常见的是三大摩擦副及轴承的失效故障。常常出现压力脉动、流量不达标、油液泄漏量大、壳体振动异常等多征兆问题,致使工作人员对其故障的溯源难以精准判别。但是轴向柱塞泵发生故障时壳体的异常振动对于各故障模式下其表现出来的时/频域曲线均不一致,所以本文对轴向柱塞泵正常及各种故障模式下进行流体振动产生机理及传递规律分析;建立柱塞泵流体振动传递路径模型及振动微分方程;利用MATLAB求解得到柱塞泵各模式下前、中、后壳体振动响应时/频域曲线,并提取典型故障特征信号。为轴向柱塞泵各故障模式下诊断提供理论依据。

Detection and identification of intestinal pathogenic bacteria by hybridization to oligonucleotide microarrays

AIM： To detect the common intestinal pathogenic bacteria quickly and accurately.METHODS： A rapid （〈3 h） experimental procedure was set up based upon the gene chip technology, Target genes were amplified and hybridized by oligonucleotide microarrays.RESULTS： One hundred and seventy strains of bacteria in pure culture belonging to 11 genera were successfully discriminated under comparatively same conditions, and a series of specific hybridization maps corresponding to each kind of bacteria were obtained. When this method was applied to 26 divided cultures, 25 （96.2%） were identified.CONCLUSION： Salmonella sp., Escherichia coli, Shigella sp., Listeria monocytogenes, Vibrio parahaemolyticus, Staphylococcus aureus , Proteus sp., Bacillus cereus, Vibrio cholerae, Enterococcus faecalis, Yersinia enterocolitica, and Campylobacter jejuni can be detected and identified by our microarrays. The accuracy, range, and discrimination power of this assay can be continually improved by adding further oligonudeotides to the arrays without any significant increase of complexity or cost.

Notch pathway inhibitor DAPT enhances Atoh1 activity to generate new hair cells in situ in rat cochleae

Atoh1 overexpression in cochlear epithelium induces new hair cell formation. Use of adenovirus-mediated Atoh1 overexpression has mainly focused on the rat lesser epithelial ridge and induces ectopic hair cell regeneration. The sensory region of rat cochlea is difficult to transfect, thus new hair cells are rarely produced in situ in rat cochlear explants. After culturing rat cochleae in medium containing 10% fetal bovine serum, adenovirus successfully infected the sensory region as the width of the supporting cell area was significantly increased. Adenovirus encoding Atoh1 infected the sensory region and induced hair cell formation in situ. Combined application of the Notch inhibitor DAPT and Atoh1 increased the Atoh1 expression level and decreased hes1 and hes5 levels, further promoting hair cell generation. Our results demonstrate that DAPT enhances Atoh1 activity to promote hair cell regeneration in rat cochlear sensory epithelium in vitro.

Impact of pond and fence aquaculture on reservoir environment

With the rapid development of aquaculture in lakes and reservoirs, its negative effects on water quality and aquatic organisms are clearly emerging. Toward a better understanding of these effects, chemical and biological monitoring was conducted in the Fangbian Reservoir to study the relationship between aquaculture and eutrophication. As a domestic water supply source, this reservoir has reached the mesotrophic level. The concentrations of total nitrogen （TN） and total phosphorus （TP） in the Fangbian Reservoir have frequently exceeded the prescriptive level according to the Environmental Quality Standardgfor SurJace Water （GB3838-2002）. Pond and fence aquaculture feeding is the main cause of high levels of nitrogen and phosphorus, accounting for nearly half of the total pollution, and causing the reservoir environmental capacity to be exceeded. The amounts of nitrogen and phosphorus that went directly to the reservoir through the residual bait and fish droppings in fence aquaculture were 42 768 kg per year and 10 856 kg per year respectively, from 2007 to 2009. About 2 913 kg of nitrogen and 450 kg of phosphorus were imported to the reservoir through the exchange of water from the culturing ponds at the same time. Therefore, controlling the aquaculture scale and promoting eco-aquaculture are key measures for lessening the eutrophication degree and improving the water quality.

mi R-29a promotes hepatitis B virus replication and expression by targeting SMARCE1 in hepatoma carcinoma

AIM To investigate the functional role and underlying molecular mechanism of mi R-29 a in hepatitis B virus(HBV) expression and replication.METHODS The levels of mi R-29 a and SMARCE1 in HBV-infected Hep G2.2.15 cells were measured by quantitative real-time PCR and western blot analysis. HBV DNA replication was measured by quantitative PCR and Southern blot analysis. The relative levels of hepatitis B surface antigen and hepatitis B e antigen were detected by enzyme-linked immunosorbent assay. The Cell Counting Kit-8(CCK-8) was used to detect the viability of Hep G2.2.15 cells. The relationship between mi R-29 a and SMARCE1 were identified by target prediction and luciferase reporter analysis.RESULTS mi R-29 a promoted HBV replication and expression, w h i le S MA R C E 1 r e p r e s s e d H B V r e p lic a t io n a n d expression. Cell viability detection indicated that mi R-29 a transfection had no adverse effect on the host cells. Moreover, SMARCE1 was identified and validated to be a functional target of mi R-29 a. Furthermore, restored expression of SMARCE1 could relieve the increased HBV replication and expression caused by mi R-29 a overexpression.CONCLUSION mi R-29 a promotes HBV replication and expression through regulating SMARCE1. As a potential regulator of HBV replication and expression, mi R-29 a could be a promising therapeutic target for patients with HBV infection.

Impacts of Passive Smoking on Learning and Memory Ability of Mouse Offsprings and Intervention by Antioxidants

Objective To determine the impact of passive smoking and the protective effect of antioxidants such as vitamin E and quercetin on learning and memory ability of mouse offsprings. Methods A passive smoking model of pregnant mice was established. Learning and memory ability was evaluated by the water maze test and long term potentiation （LTP）. Nitric oxide （NO）, content, nitric oxide synthase （NOS）, acetylcholinesteras （Ache） activity in brain, vitamin E concentration, and reactive oxygen species （ROS） in serum were determined. The latency period （the time during which the mice swim from the starting position to the ending position） and errors （the number of mice entering the blind end） in control and antioxidant intervention groups were compared with those in the smoke exposure group after 6 days. Results The latency period as well as errors in the air, control diet, tobacco smoke （TS）, and vitamin E diet groups were decreased significantly as compared with the TS and control diet groups （P〈O.05）. LTP was restrained in the TS and control diet groups. LTP in all the antioxidant diet groups was significantly increased compared with the TS and control diet groups. In addition, NOS and acetylcholinesteras （Ache） activitiy was significantly higher in the TS and control diet groups than in the air and control diet group. NO content was not significantly different among the different groups, and significantly lower in the TS and vitamin E diet groups than in the TS group, control diet group, quercetin diet group, and mixture diet group （P〈0.05）. Vitamin E concentration and ROS activity in serum were correlated with the outcome of water maze and LTP. Conclusion Passive smoking reduces LTP formation by disturbing the hippocampus function of mice, by decreasing NOS （especially vitamin E） partially improve the learning and memory smoke during pregnancy. and Ache activity and increasing NO content. Antioxidants ability of offsprings whose mothers are exposed to tobacco

Seroprevalence and evolutionary dynamics of genotype 4 hepatitis E virus in Shandong Province,China

AIM: To investigate the seroprevalence and evolutionary dynamics of hepatitis E virus (HEV) and assess the ancestor of HEVs in China’s Shandong Province.

Optimal control based coordinated taxiing path planning and tracking for multiple carrier aircraft on flight deck

Coordinated taxiing planning for multiple aircraft on flight deck is of vital importance which can dramatically improve the dispatching efficiency.In this paper,first,the coordinated taxiing path planning problem is transformed into a centralized optimal control problem where collision-free conditions and mechanical limits are considered.Since the formulated optimal control problem is of large state space and highly nonlinear,an efficient hierarchical initialization technique based on the Dubins-curve method is proposed.Then,a model predictive controller is designed to track the obtained reference trajectory in the presence of initial state error and external disturbances.Numerical experiments demonstrate that the proposed“offline planningþonline tracking”framework can achieve efficient and robust coordinated taxiing planning and tracking even in the presence of initial state error and continuous external disturbances.

Study on the mechanism of hydrodesulfurization of tetrahydrothiophene catalyzed by nickel phosphide

Hydrodesulfurization(HDS)reaction can significantly reduce the viscosity and sulfur content of heavy oil,while the HDS reaction mechanism of tetrahydrothiophene as the main sulfide in heavy oil is still unclear.The HDS experiment of tetrahydrothiophene catalyzed by nickel phosphide(Ni_(2)P)is carried out at 200-300°C.The results indicate that the H_(2)S production under the catalysis of Ni_(2)P increases obviously within 200-250°C.The main gas products of HDS reaction are butane,butene and H_(2)S.Meanwhile,the mechanism of tetrahydrothiophene catalyzed by Ni_(2)P is analyzed based on Density Functional Theory(DFT).It is revealed that the adsorption model is most stable when tetrahydrothiophene is vertically adsorbed on the V-Ni-Hcp1 site of Ni_(2)P(001).The C-S bond is elongated and the C-C bond is shortened after adsorption.Hydrogenation(HYD)is the most possible reaction route of tetrahydrothiophene on Ni_(2)P(001)surface.There are two routes with the lowest activation energy,which are C_(4)H_(8)S→C_(4)H_(8)SH^(*)→C_(4)H_(9)SH^(*)→C_(4)H_(10)+H_(2)S and C_(4)H_(8)S→C_(4)H9S^(*)→C_(4)H_(9)^(*)+SH^(*)→C_(4)H_(10)+H_(2)S.Butane and H_(2)S are produced in the reaction,corresponding to the experimental results.This study provides a basis for understanding of the HDS mechanism of tetrahydrothiophene catalyzed by Ni_(2)P.

Chiral Bronsted acid-catalyzed conjugate addition of indoles to azadienes:Enantioselective synthesis of hetero-triarylmethanes

An efficient chiral Br?nsted acid-catalyzed conjugate addition of indoles to azadienes has been successfully developed,which enables a facile approach to optically active hetero-triarylmethanes with excellent enantioselectivities and broad substrate scope.This chiral Br?nsted acid catalytic system provides a new opportunity for the development of asymmetric reactions of azadienes.

Kinematic improvement after the external-application herbs combine rehabilitation in upper-limb spasticity due to stroke

Background: Spasm is one of the most serious physical impairment after stroke. the external-application herbs have showed some effects on the spasm. This study was conducted to evaluate the comparative effectiveness of the external-application herbs and physical therapy in upper limb spasticity after stroke. Methods: A total of 100 patients with upper limb spasm after stroke (stroke time less than 1 month), have been recruited in Shun-yi Hospital of Beijing Traditional Chinese Medicine Hospital. Patients will be randomly allotted to one of two groups (N = 50, respectively): the TCM external application group, and the usual rehab (conventional physical therapy and medication treatment) group. The two groups will be administered once a month for three months. The primary outcome will be Modified Athworth Scale (MAS) and the simplified scale (Fugl-Meyer assessment, FMA) for upper limb. Results: Muscle tension and motor function were evaluated before and 4 weeks after treatments. There was a significant improvement in muscle tension and motor function in patients with stroke after the external-application herbs and physical therapy (P < 0.05). Conclusion: There was a significant improvement in kinematics in patients with stroke.

Study on the in situ desulfurization and viscosity reduction of heavy oil over MoO_(3)–ZrO_(2)/HZSM-5 catalyst

Heavy oil is characterized by high viscosity.High viscosity makes it challenging to recover and transport.HZSM-5,MoO_(3)/HZSM-5,ZrO_(2)/HZSM-5 and MoO_(3)–ZrO_(2)/HZSM-5 catalysts were developed to promote in situ desulfurization and viscosity reduction of heavy oil.The physical and chemical properties of catalysts were characterized by XPS,XRD,TEM,NH3-TPD,etc.The effects of temperature,catalyst type and addition amount on viscosity and composition of heavy oil were evaluated.The results showed that the presence of MoO_(3)–ZrO_(2)/HZSM-5 nanoparticles during aquathermolysis could improve the oil quality by reducing the heavy fractions.It reduced viscosity by 82.56%after the reaction at 280℃ and catalyst addition of 1 wt%.The contents of resins and asphaltic in the oil samples were 5.69%lower than that in the crude oil.Sulfur content decreased from 1.45%to 1.03%.The concentration of H2S produced by the reaction was 2225 ppm.The contents of sulfur-containing functional groups sulfoxide and sulfone sulfur in the oil samples decreased by 19.92%after the catalytic reaction.The content of stable thiophene sulfur increased by 5.71%.This study provided a basis for understanding the mechanism of heavy oil desulfurization and viscosity reduction.

Air target recognition method against ISRJ for radio frequency proximity sensors using chaotic stream encryption

The interrupted-sampling repeater jamming(ISRJ)can cause false targets to the radio-frequency proximity sensors(RFPSs),resulting in a serious decline in the target detection capability of the RFPS.This article proposes a recognition method for RFPSs to identify the false targets caused by ISRJ.The proposed method is realized by assigning a unique identity(ID)to each RFPS,and each ID is a periodically and chaotically encrypted in every pulse period.The processing technique of the received signal is divided into ranging and ID decryption.In the ranging part,a high-resolution range profile(HRRP)can be obtained by performing pulse compression with the binary chaotic sequences.To suppress the noise,the singular value decomposition(SVD)is applied in the preprocessing.Regarding ID decryption,targets and ISRJ can be recognized through the encryption and decryption processes,which are controlled by random keys.An adaptability analysis conducted in terms of the peak-to-side lobe ratio(PSLR)and bit error rate(BER)indicates that the proposed method performs well within a 70-k Hz Doppler shift.A simulation and experimental results show that the proposed method achieves extremely stable target and ISRJ recognition accuracies at different signal-to-noise ratios(SNRs)and jamming-to-signal ratios(JSRs).

Growth of high-crystallinity uniform GaAs nanowire arrays by molecular beam epitaxy

The self-catalyzed growth of Ga As nanowires(NWs)on silicon(Si)is an effective way to achieve integration between group III–V elements and Si.High-crystallinity uniform Ga As NW arrays were grown by solid-source molecular beam epitaxy(MBE).In this paper,we describe systematic experiments which indicate that the substrate treatment is crucial to the highly crystalline and uniform growth of one-dimensional nanomaterials.The influence of natural oxidation time on the crystallinity and uniformity of Ga As NW arrays was investigated and is discussed in detail.The Ga As NW crystallinity and uniformity are maximized after 20 days of natural oxidation time.This work provides a new solution for producing high-crystallinity uniform III–V nanowire arrays on wafer-scale Si substrates.The highly crystalline uniform NW arrays are expected to be useful for NW-based optical interconnects and Si platform optoelectronic devices.

Excretion and detection of SARS coronavirus and its nucleic acid from digestive system

AIM： To study whether severe acute respiratory syndrome coronavirus （SARS-CoV） could be excreted from digestive system.METHODS： Cell culture and semi-nested RT-PCR were used to detect SARS-CoV and its RNA from 21 stool and urine samples, and a kind of electropositive filter media particles was used to concentrate the virus in 10 sewage samples from two hospitals receiving SAILS patients in Beijing in China. RESULTS： It was demonstrated that there was no live SARS-CoV in all samples collected, but the RNA of SARS-CoV could be detected in seven stool samples from SARS patients with any one of the symptoms of fever, malaise, cough, or dyspnea, in 10 sewage samples before disinfection and 3 samples after disinfection from the two hospitals. The RNA could not be detected in urine and stool samples from patients recovered from SARS.CONCLUSION： Nucleic acid of SARS-CoV can be excreted through the stool of patients into sewage system, and the possibility of SARS-CoV transmitting through digestive system cannot be excluded.

Meta analysis of Masquelet technology and Llizarov technology in the treatment of infectious bone defects

Objective: To systematically evaluate the clinical efficacy and safety of Masquelet technology and Llizarov group technology in the treatment of infectious bone defects by meta-analysis. Methods: The computer searched China Knowledge Network (CNKI), Wanfang, VIP, Chinese Biomedical Literature Database (CBM), Pubmed, Medline, Cochrane Llibrary databases. The retrieval time was from the time of the establishment of the database to January 2020. According to the inclusion and exclusion criteria, randomized controlled trials on the treatment of infectious bone defects using Masquelet technology and Llizarov technology were collected, and the retrieved literature was independently screened, evaluated, and data extracted by two researchers, and then RevMan5.3 software was used so for meta-analysis. Results: A total of 10 RCT documents were included, with a total of 496 patients, including 242 in the Masquelet group and 254 in the Llizarov group. The results of the meta-analysis showed that: in terms of bone defect healing time, total weight bearing time, treatment cost, and complication rate, the Masquelet group was significantly different from the Llizarov group, and the Masquelet group was better than the Llizarov group (P <0.05);In terms of knee joint Lowa score and SF-36 score, Masquelet group has significant differences compared with Llizarov group, Llizarov group is better than Masquelet group (P <0.05);in excellent rate, number of operations, ankle Lowa score, infection control rate In terms of excellent rate of affected limb function, there was no significant difference between Masquelet group and Llizarov group (P> 0.05). Conclusion:Compared with Llizarov technology, Masquelet technology has obvious advantages in the treatment of infectious bone defects in terms of bone defect healing time, total weight-bearing time, treatment cost, and complication rate. In terms of scoring, it has advantages over Masquelet technology, but in terms of excellent treatment rate, number of operations, and ankle lowa score. In terms of infection control rate and excellent function of affected limbs, there was no significant difference between Masquelet technology and Llizarov technology,However, due to the low quality of the included studies and the small sample size, the exact efficacy still needs to be confirmed by higher quality RCT studies.

新型冠状病毒肺炎患者肝功能损伤的危险因素分析

背景肝功能损伤情况在新型冠状病毒肺炎(coronavirus disease-2019,COVID-19)患者中较为常见,具体原因不甚清楚.本研就回顾性分析COVID-19患者的临床资料,探讨肝功能损伤的危险因素,期望为新型冠状病毒感染相关的肝功能损伤的防治提供理论依据.目的本研究旨在探讨COVID-19患者肝功能损伤的相关危险因素.方法整理2020-02-04/2020-02-29日于武汉火神山医院诊治的100例COVID-19患者的临床病历资料.分析性别、年龄、基础疾病、饮食情况和入院前服药情况等临床参数与各项肝功能指标表达的关系.结果在100例新型冠状病毒肺炎患者中,54例为男性,其平均年龄为59.89岁±13.07岁.新型冠状病毒肺炎的常见临床症状为发热(81%)、咳嗽(64%)、乏力(52%).在100例患者中,38例患者观察到肝功能的异常,包括28例有丙氨酸氨基转移酶(alanine aminotransferase,ALT)升高,10例有天门冬氨酸氨基转移酶(aspartate aminotransferase,AST)升高,20例有谷氨酰转肽酶(gamma-glutamyl transferase,γ-GGT)升高,7例有碱性磷酸酶升高,6例有总胆红素升高,15例有乳酸脱氢酶升高.男性患者更易出现ALT(P<0.001)、AST(P=0.006)和γ-GGT(P<0.001)的升高.入院前抗病毒药或中成药应用与COVID-19患者的各项肝功能指标之间无统计学意义.结论男性新冠病毒性肺炎患者更易出现肝功能损伤.

Molecular mechanism of a coastal cyanobacterium Synechococcus sp.PCC 7002 adapting to changing phosphate concentrations

Phosphorus concentration on the surface of seawater varies greatly with different environments,especially in coastal.The molecular mechanism by which cyanobacteria adapt to fluctuating phosphorus bioavailability is still unclear.In this study,transcriptomes and gene knockouts were used to investigate the adaptive molecular mechanism of a model coastal cyanobacterium Synechococcus sp.PCC 7002 during periods of phosphorus starvation and phosphorus recovery(adding sufficient phosphorus after phosphorus starvation).The findings indicated that phosphorus deficiency affected the photosynthesis,ribosome synthesis,and bacterial motility pathways,which recommenced after phosphorus was resupplied.Even more,most of the metabolic pathways of cyanobacteria were enhanced after phosphorus recovery compared to the control which was kept in continuous phosphorus replete conditions.Based on transcriptome,54 genes potentially related to phosphorusdeficiency adaptation were selected and knocked out individually or in combination.It was found that five mutants showed weak growth phenotype under phosphorus deficiency,indicating the importance of the genes(A0076,A0549-50,A1094,A1320,A1895)in the adaptation of phosphorus deficiency.Three mutants were found to grow better than the wild type under phosphorus deficiency,suggesting that the products of these genes(A0079,A0340,A2284–86)might influence the adaptation to phosphorus deficiency.Bioinformatics analysis revealed that cyanobacteria exposed to highly fluctuating phosphorus concentrations have more sophisticated phosphorus acquisition strategies.These results elucidated that Synechococcus sp.PCC 7002 have variable phosphorus response mechanisms to adapt to fluctuating phosphorus concentration,providing a novel perspective of how cyanobacteria may respond to the complex and dynamic environments.

Dissolution kinetics and reaction mechanism of Al_(2)O_(3) in molten CaF_(2)-CaO-Al_(2)O_(3) slag

The dissolution behavior of Al_(2)O_(3) in molten CaF_(2)-CaO-Al_(2)O_(3) slag,a basic slag system of electroslag remelting process,was investigated by rotating cylinder method using corundum rods to simulate Al_(2)O_(3) inclusions in steel.The experimental results show that the dissolution rate of Al_(2)O_(3);rods in CaF_(2)-CaO-Al_(2)O_(3) slag increases with the increase in rotating speed and temperature,and the rate-controlling step is the mass transfer in the slag.The dissolution rate of Al_(2)O,in CaF_(2)-CaO-Al_(2)O_(3) slag increases with the increase in the ratio of CaO to Al_(2)O_(3),which is due to the increase in dissolution driving force and the decrease in slag viscosity.The apparent activation energy of the mass transfer of AlOs in slag C is calculated to be 222.86 kJ mol^(-1).During the dissolution of Al_(2)0,inclusions in the slag,it reacts with F in liquid slag at first,then reacts with CaO to form the intermediate compounds of xCaO-yAl_(2)O_(3) system,and finally dissolves in molten slag.The dissolution rate of Al_(2)O_(3) inclusions in CaF_(2)-CaO-Al_(2)O_(3) slag for electroslag remelting is positively correlated with the ratio of the dissolution driving force and slag viscosity,and the correlation coeficient is 2.487×10^(-11).