基于“减抗、限抗”背景下猪场疾病防控的应对措施

随着国内外对滥用抗生素危害的进一步认识,抗生素将会逐渐在畜禽饲料中禁止添加。近年来,用于猪场疾病防控的各类抗生素替代品研究也取得一定进展,包括发酵饲料、中药活性物质,微生态制剂(复合益生菌)、植物提取物等。文章重点从抗生素在猪场疾病防控中的应用和存在问题,"减抗、限抗"对猪场疾病防控的影响和应对措施等方面进行综述,旨在为"减抗、限抗"时代猪场的疾病防控提供一些理论借鉴。

基于“减抗,限抗”背景下猪场疾病防控的对策研究

随着当前我国科学技术的不断发展,人们逐渐认识到抗生素对于动物产生的影响。在这一社会背景之下,产生了“减抗,限抗”的理念,也就是减少抗生素在畜禽养殖饲料中的添加计量。在此基础上,对于养猪场疾病防控过程中抗生素使用的替代品的研究取得了一定的成就。其中抗生素的替代品包括发酵饲料、活性物质等。基于此,文章探讨了当前“减抗,限抗”背景下对猪场疾病防控的措施。

黄山市兽用抗菌药减量化行动现状及建议

现代畜禽养殖与兽用抗菌药有着密切的关系,黄山市全力推进当地养殖场兽用抗菌药使用减量化行动,积极落实各项措施,强化“检打联动”机制,深入贯彻技术帮扶,认真实行“一场一策”,稳步推进“减抗”工作,兽用抗菌药减量工作取得实效。总结了黄山市兽用抗菌药减量化行动工作的经验和成效,分析在推进“减抗”过程中出现的问题和不足,并提出建议,明确下一步工作方向,为“减抗”工作持续深入推进提供参考。

安徽省兽用抗菌药使用减量化行动现状调查

为深入了解安徽省兽用抗菌药使用减量化行动的实施现状,结合达标养殖场验收工作,对该项行动的实施效果开展调查研究。通过召开座谈会、实地走访养殖场、现场验收申请达标的养殖企业等方式,全面了解兽用抗菌药使用减量化现状。结合调研信息,总结提炼主管部门开展减量化行动的经验做法,分析养殖企业“减抗”的技术路径,汇总减量化行动存在的问题,并针对性地提出科学合理的建议,旨在为深入开展兽用抗菌药使用减量化行动提供数据支撑。

科学应对“减抗”转变生猪疫病防控策略

笔者从加强饲养管理、改善养殖环境、科学使用疫苗免疫、使用抗菌药物替代品、加强生物安全措施控制、加强消毒、开展疫病净化和无疫小区建设、规范使用抗菌药物等方面阐述了转变生猪疫病防控策略,科学应对“减抗”的措施,以期指导生猪养殖场(户)做好生猪疫病防控工作。

Friction and wear performances of magnesium alloy against steel under lubrication of rapeseed oil with S-containing additive

A S-containing additive, sulfuration modified rapeseed oil （named as SRO）, was prepared by chemical modification of rapeseed oil with sulfur compounds. The results indicate that the friction and wear of the magnesium alloy-steel tribomates could be effectively reduced by formulating SRO into rapeseed oil lubricant. The friction coefficients and the wear volumes of magnesium alloy decrease with increasing contents of SRO. The surface lubricated with SRO-doped rapeseed oil was characterized by less wear as compared with that lubricated with neat rapeseed oil. The enhanced anti-wear and friction-reducing abilities of rapeseed oil by SRO in the lubrication of magnesium alloy against steel were ascribed to the formation of a composite boundary lubrication film due to the strong adsorption of SRO and rapeseed oil onto the lubricated surfaces and their tribochemical reactions with magnesium alloy.

Influence of superplasticizers on the early-age crack resistance of concrete

In order to improve the early-age cracking resistance of concrete, different types of superplasticizers are used. Two types of polycarboxlic salt/acid superplasticizers and one retarding naphthalene superplasticizer are selected to investigate the influence of superplasticizers on the early-age cracking resistance of the concrete by using the slab test and the temperature-stress test. The results show that the polycarboxlic salt/acid superplasticizer cannot always improve the cracking resistance capacity of the concrete compared with the naphthalene superplasticizer, which is related to the chemical structure of the polycarboxlic salt/acid superplasticizer. High plastic tensile strength and dynamic elastic modulus at the early stage are beneficial to avoid cracking, and low hydration heat is also helpful. The evolutions of the drying shrilakage stress and the hydration heat temperature stress varying with time can be comprehensively evaluated by means of the slab test and the temperature stress test.

STUDY ON OPTIMIZATION OF HIGH PERFORMANCE CONCRETE ADMIXTURES

Influences of admixtures on the workability and strength of high performance concrete （HPC） are in- vestigated. The types of investigated admixtures include naphthalene series high range water reducing agent, polycarboxlic series high range water reduce agent and sodium sulfate hardening accelerating agent. Two kinds of curing condition, namely steam curing condition and standard curing condition, are adopted. The result shows that HPC, added with polycarboxlic series of high performance water reducer, has high workability and strength, while sodium sulfate accelerating agent causes poor workability and low strength. Thus for vapor-cured HPC and its formulations, naphthalene series high range water reducing agent with less sodium sulfate should be given pri- ority. Therefore, the differences of curing conditions should be considered when selecting HPC admixtures.

Reliability analysis of anti-pull piles under excavation

The impact of excavation on the reliability of anti- pull piles is studied, and three cases of reliability analysis, named reliability of ultimate limit state （ULS）, reliability of serviceability limit state （SLS） and reliability of system （SYS） are studied. The reduction factor of the pile capacity is used to calculate the reliability indices for the three cases. The ratio ξ of the pile capacity of SLS to the pile capacity of ULS has a significant influence on the reliability indices of SLS and SYS. The mean value μξ of the ratio ξ： is considered as a random variable to study the reliability indices of SLS and SYS. The numerical example demonstrates that the excavation depth and the excavation diameter are proved to have significant influences on the reduction factor of the pile capacity and the reliability indices. The reliability indices decrease with the increase in the excavation depth, and the excavation diameter has a considerable influence on the reliability index when the excavation is relatively deep. In addition, μξ has a significant influence on the reliability indices of SLS and SYS. For a more accurate estimation of μξ, further research should be conducted to study μξ.

Research on the dynamic performance of ship isolator system that use magnetorheological dampers

Isolator systems on ships should ideally be able to simultaneously reduce low frequency vibration response and high frequency shock response. Conventional isolator systems are unable to do so To solve the problem, a new style isolator system was created. This isolator system consists of a steel coil spring component and a magnetorheological （MR） damper component working in parallel. Experiments on this isolator system were carried out, including tests of vibration reduction and shock resistance. The vibration load frequencies were set from 1-15 Hz, and force amplitudes from 2.94-11.76kN. The maximum shock input acceleration was 20 g, and impulse width was lores. Both the vibration and shock loads were applied using MTS Systems Corporation＇s hydraulic actuators. The experimental results indicated that the isolator system performs well on system vibration response, with resonance humps of the vibration response obviously reduced after using the MR damper. For the shock experiment, the attenuation of shock response was much faster with increased MR damping. The MR damper＇s effect on shock moments was very different from its performance in vibration mode. The correlation between MR force and control current was not as evident as it was during vibration loads.

Friction and Wear Behaviors of Nano-Silicates in Water

Nano-metric magnesium silicate and zinc silicate with particle size of about 50-70nm were prepared in water by the method of chemical deposition. The antiwear and friction reducing abilities of the nano-silicates, as well as their composites with oleic acid tri-ethanolamine （OATEA）, were evaluated on a four-ball friction tester. The topographies and tribochemical features of the worn surfaces were analyzed by scanning electron microscope （SEM） and X-ray photoelectron spectroscope （XPS）. Results show that nano-silicates alone provide poor antiwear and friction reducing abilities in water, but exhibits excellent synergism with OATEA in reducing friction and wear. The synergism in reducing friction and wear between nano- silicates and OATEA does exist almost regardless of particte sizes and species, and may be attributed, on one hand, to the formation of an adsorption film of OATEA, and, on the other hand, to the formation oftribochemical species of silicon dioxide and iron oxides on the friction surfaces. Tribo-reactions and tribo-adsorptions of nano-silicates and OATEA would produce hereby an effective composite boundary lubrication film, which could efficiently enhance the anti-wear and friction-reducing abilities of water.

Application of dynamic analysis of strength reduction in the slope engineering under earthquake

At present,the methods of analyzing the stability of slope under earthquake are not accurate and reasonable because of some limitations. Based on the real dynamic tensile-shear failure mechanism of slope,the paper proposes dynamic analysis of strength reduction FEM (finite element method) and takes the reduction of shear strength parameters and tensile strength parameters into consideration. And it comprehensively takes the transfixion of the failure surface,the non-convergence of calculation and mutation of displacement as the criterion of dynamic instability and failure of the slope. The strength reduction factor under limit state is regarded as the dynamic safety factor of the slope under earthquake effect and its advantages are introduced. Finally,the method is applied in the seismic design of anchors supporting and anti-slide pile supporting of the slope. Calculation examples show that the application of dynamic analysis of strength reduction is feasible in the seismic design of slope engineering,which can consider dynamic interaction of supporting structure and rock-soil mass. Owing to its preciseness and great advantages,it is a new method in the seismic design of slope supporting.

Does gemcitabine-based combination therapy improve the prognosis of unresectable pancreatic cancer?

AIM:To assess whether gemcitabine-based combination therapy improves the prognosis of unresectable pancreatic cancer compared with gemcitabine treatment alone.METHODS:A quantitative up-to-date meta-analysis was undertaken to investigate the efficacy of gemcitabine-based combination treatment compared with gemcitabine monotherapy in locally advanced or metastatic pancreatic cancer.Inclusion was limited to highquality randomized clinical trials.RESULTS:Twenty-six studies were included in the present analysis,with a total of 8808 patients recruited.The studies were divided into four subgroups based on the different kinds of cytotoxic agents,including platinum,fluoropyrimidine,camptothecin and targeted agents.Patients treated with gemcitabine monotherapy had significantly lower objective response rate [risk ratio(RR),0.72;95% confidence interval(CI):0.63-0.83;P < 0.001],and lower 1-year overall survival(RR,0.90;95%CI:0.82-0.99;P = 0.04).Gemcitabine monotherapy caused fewer complications,including fewer grade 3-4 toxicities:including vomiting(RR,0.75;95%CI:0.62-0.89;P = 0.001),diarrhea(RR,0.66;95%CI:0.49-0.89;P = 0.006),neutropenia(RR,0.88;95%CI:0.72-1.06;P = 0.18),anemia(RR,0.96;95%CI:0.82-1.12;P = 0.60),and thrombocytopenia(RR,0.76;95%CI:0.60-0.97;P = 0.03) compared with gemcitabine combination therapies.CONCLUSION:Gemcitabine combination therapy provides a modest improvement of survival,but is associated with more toxicity compared with gemcitabine monotherapy.

Statistical modelling for effect of mix-parameters on properties of high-flowing sand-concrete

The high-flowing sand-concrete （HFSC） containing natural sands as aggregate was carried out. The high fluidity and stability of HFSC can be achieved by tailoring the mix design parameters, such as fine to coarse sand ratio, dosage of additions, water to binder ratio and dosage of admixtures. Mini-cone slump test, v-fl.mnel time test and viscosity model parameters were used to characterize the behaviour of HFSC in fresh state. The mechanical compressive strength in 28 d was also determined. A factorial design approach was used to establish models highlighting the effect of each mix-parameter on measured properties of HFSC. The derived models are valid for mixtures made with 0 to 0.3 of dune sand to total sand ratio, 82 to 418 kg/m3 of marble powder, 0.42 to 0.46 of water/binder ratio and 1.3% to 1.9% of superplasticizer high water-reducer. The results show that the derived models constitute very efficient means for understanding the influence of key mix-parameters on HFSC properties and are useful in selecting the optimum mix proportions, by simulating their impact on fluidity, stability and compressive strength.

New method of designing anti-slide piles——the strength reduction FEM

At present,the thrust of an anti-slide pile can be worked out with some calculation methods. However,the resistance in front of the pile,the distributions of resistance and thrust,and appropriate pile length cannot be easily obtained. In this paper,the authors applied the strength-reduction finite element method (FEM) to several design cases of anti-slide piles. Using this method,it is possible to take the pile-soil interactions into consideration,obtain reasonable resistance in front of pile and the distributions of thrust and resistance,and reasonable lengths of anti-slide piles. In particular,the thrust and resistance imposed on embedded anti-slide piles can be calculated and composite anti-slide pile structures such as anchored piles and braced piles can be optimized. It is proved through the calculation examples that this method is more reliable and economical in the design of anti-slide pile.

Performance improvement of car body structure in 100% frontal impact

During the 100%front impact,all the parts of front car will participate in the course;the crash stiffness of bodywork will also reach the peak.During the crash,rational structure of bodywork can resist the distortion,absorb more energy and get better mode of distortion and low deceleration rate,so as to meet the performance of crash safety.The paper mainly makes optimization analysis based on the problems of front side rails,subframe,firewall,and optimization cases are confirmed which can decrease the intrusion and deceleration rate of the whole car.The structure of bodywork after optimization can meet the performance of crash safety.

Research progress in the SO2 resistance of the catalysts for selective catalytic reduction of NOx

The selective catalytic reduction （SCR） of NOx with NH3 has been proven to be an efficient technology for NOx conversion to N2. However, the catalysts used for SCR usually suffer from the problem of sulfur poisoning which seriously limits their practical application. This review summarized sulfur poisoning mechanisms of various SCR deNG catalysts and strategies to reduce deactivation caused by SO2 such as doping metals, controlling the structures and morphologies of the catalysts, and selecting appropriate supports. The methods and procedures of catalysts preparation and the reaction conditions also have effect on SO2-resistance of the catalysts. Several novel catalyst systems that exhibited good SO2 resistance are also introduced. This paper could provide guidance for the development of highly efficient sulfur-tolerant deNOx catalysts.

Seismic hazard mitigation for nuclear power plant

The seismic safety of nuclear power plan(tNPP)has always been a major consideration in the site selection,design,operation,and more recently recertification of existing installations. In addition to the actual NPP and all their operational and safety related support systems,the storage of spent fuel in temporary or permanent storage facilities also poses a seismic risk. This seismic risk is typically assessed with state-of-the-art modeling and analytical tools that capture everything from the ground rupture or source of the earthquake to the site specific ground shaking,taking geotechnical parameters and soilfoundationstructureinteraction (SFSI) into account to the non-linear structural response of the reactor core,the containment structure,the core cooling system and the emergency cooling system(s),to support systems,piping systems and non-structural components,and finally the performance of spent fuel storage in the probabilistically determined operational basis earthquake (OBE) or the safe shutdown earthquake (SSE) scenario. The best and most meaningful validation and verification of these advanced analytical tools is in the form of full or very large scale experimental testing,designed and conducted in direct support of model and analysis tool calibration. This paper outlines the principles under which such calibration testing should be conducted and illustrates with examples the kind of testing and parameter evaluation required.

Clinical observation of raltitrexed/bevacizumab combined with irinotecan or oxaliplation for advanced colorectal cancer

Objective： The aim of the study was to investigate the efficacy and safety of raltitrexed/bevacizumab in combination with irinotecan or oxaliplation for advanced colorectal cancer as the second-line and second-line above treatments. Metho ods： Fifteen cases of advanced colorectal cancer were enrolled to receive regimens including raltitrexed/bevacizumab combined with irinotecan or oxaliplation. Two cases were treated with raltitrexed ＋ bavacizumab regimen, 9 cases with raltitrexed ＋ bavacizumab ＋ irinotecan regimen, and 4 cases with raltitrexed ＋ bevacizumab ＋ oxaliplation regimen. The doses of the drugs were as follows： bevacizumab 5 mg/kg ivgtt, d 1; raltitrexed 2.0 mg/m2 ivgtt 15 min, d2; irinotecan 180 mg/m2 ivgtt 1 h, d2; and oxaliplatin 85 mg/m2 ivgtt 2 h, d2. Two weeks was a cycle for each regimen. Results： The efficacy of the 15 patients could be evaluated. Two cases were in PR ,10 cases in SD, 3 cases in PD, the response rate was 13.3%, and the disease control rate was 80.0%. The median progress-free survival was 5.1 months （95% CI： 3.404-6.813 months）, and the median overall survival was 11.5 months （95% CI： 8.985-13.930 months）. The adverse effects included anorexia, nausea/vomiting, fatigue, leucopenia, thrombocytopenia, etc, and the main 3-4 grades adverse effects were anorexia, nausea/vomiting, fatigue, and thrombocytopenia. Conclusion： Raltitrexed/bevacizumab combined with irinotecan or oxaliplatin as the secondline and second-line above treatments for advanced colorectal cancer has high disease control rates, and the adverse effect is well tolerated. The combined regimen can be recommended as a phase III clinical research and second-line and secondlines above treatments for advanced colorectal cancer.

Production and Properties of Superplasticized Concrete

The objective of this research is to study the effect of grinding powdered superplasticizer, Portland cement, sand, and silica fume on the properties of fresh and hardened concrete. Lose Angeles Machine was used to grind these constituents. The program was arranged to determine the effect of cycles＇ number, superplasticizer type and dosage, silica fume dosage and condition, and gravel to sand ratio on properties of concrete. Naphthalene sulphonated formaldehyde （NSF） superplasticizers in the forms of liquid and powdered were used. Silica fume may be grinded with the other constituents （grinded）, or added to concrete mixer （normal）. The water/cement （w/c） ratio varied from 0.35 to 0.55 to achieve a constant slump （50-90 mm）. Slumps, bulk density and mechanical properties of concrete were measured. Scanning electron microscope （SEM） was also used to show the differences between traditional and superplasticized concrete. The results showed that grinding the mixture enhances fresh and hardened concrete properties. It is also observed that grinding the mixture for 500 cycles is more effective than other numbers of grinding. In addition, superplasticized concrete exhibits compressive strength higher than traditional one at varied ages. Moreover, using powdered superplasticizer has a remarkable effect on enhancing concrete properties rather than using it in a liquid form. A dosage of 1% by weight of cement gave the highest results of compressive strength. Silica fume has an essential role in improving concrete strength and durability since it acts as very efficient void filler and as a super pozzolana. SEM observations illustrate that grinding the mixture enhances transition zone （TZ） properties and makes it denser. On the other hand, grinded mixture can be packaged in bags and transported for use in crowded cities, and so, enhances quality control, since the only requirement to obtain superplasticized concrete is to add water and gravel. This technique has many benefits such as; saving cement, labor and noise, high quality control, and enhancing concrete permeability and durability. There are many fields of application of superplasticized concrete such as; in locations which are not easily accessible by ordinary concreting techniques, in repairing and strengthen, thin coating, and for small projects when ready mix supply is not feasible.