Real-world utility of serological tests in patients with suspected scrub typhus in the Republic of Korea:A single-center,retrospective,observational study

Objective:Serological tests are widely used for scrub typhus diagnosis;however,their limitations are evident.This study aims to assess their practical value in clinical settings.Methods:We analyzed the data of adult patients with suspected scrub typhus who visited a tertiary care hospital in the Republic of Korea from September to December from 2019 to 2021.The included patients had an acute fever and at least one of the following ten secondary findings:myalgia,skin rash,eschar,headache,thrombocytopenia,increased liver enzyme levels,lymphadenopathy,hepatomegaly,splenomegaly,and pleural effusion.The diagnoses were grouped as scrub typhus or other diseases by two infectious disease physicians.Results:Among 136 patients who met the eligibility criteria,109 had scrub typhus and 27 had different diseases.Single and paired total antibodies using immunofluorescence assay(IFA),and total antibodies using immunochromatography-based rapid diagnostic testing(ICT)were measured in 98%,22%,and 75%of all patients,respectively.Confirmation using paired samples for scrub typhus was established at a median of 11[interquartile range(IQR)10-16]days following the first visit.Among the 82 admitted patients,the median admission time was 9(IQR 7-13)days.According to IFA,58(55%)patients with scrub typhus had total immunoglobulin titers≥1:320,while 23(85%)patients with other disease had titers<1:320.Positive ICT results were observed in 64(74%)patients with scrub typhus and 10(67%)patients with other diseases showed negative ICT results.Conclusions:Serological testing for scrub typhus is currently insufficient for decision-making in clinical practice.

A pilot clinical study to evaluate feasibility of using single patient classifier as a prognostic test in stage Ⅱ-Ⅲ gastric cancer patients

Objective:Precision medicine approaches emphasize the importance of reliable prognostic tools for guiding individualized therapy decisions.In this study,we evaluated the clinical feasibility of the single patient classifier(SPC)test,a new clinical-grade prognostic assay,in stageⅡ-Ⅲgastric cancer patients.Methods:A prospective multicenter study was conducted,involving 237 patients who underwent gastrectomy between September 2019 and August 2020 across nine hospitals.The SPC test was employed to stratify patients into risk groups,and its feasibility and performance were evaluated.The primary endpoint was the proportion of the cases in which the test results were timely delivered before selecting postoperative treatment.Furthermore,3-year disease-free survivals of risk groups were analyzed.Results:The SPC test met the primary endpoint criteria.The 99.5%of SPC tests were timely delivered to hospitals before the postoperative treatment started.In a clinical setting,the median time from the specimen transfer to laboratory to the result delivery to hospital was 4 d.Furthermore,3-year disease-free survivals were significantly different between risk groups classified with SPC tests.Conclusions:This study highlights the SPC test's feasibility in offering crucial information timely delivered for making informed decisions regarding postoperative treatment strategies.It also provides evidence to support the implementation of a future prospective clinical trial aimed at evaluating the clinical utility of the SPC test in guiding personalized treatment decisions for gastric cancer patients.

Comparative Study of the Widal Test against Stool Culture in the Diagnosis of Suspected Cases of Typhoid Fever in Some Low Income Communities in the Adamawa Region of Cameroon

Introduction: Infectious diseases constitute a major concern of public health in developing countries. Facilities and well trained staff have been shown to be one of the major obstacles in the rapid and quality diagnosis of these diseases. As such, we carried out an analysis to compare the Widal test and stool culture to identify febrile patients with Salmonella infection. Method: A cross sectional study was conducted to diagnose salmonella infection with out-patients who demonstrated signs of salmonella infection. Serum was harvested from blood collected from 368 (Vina = 234, Mayo Banyo 65, and Djerem = 69) patients accompanied by stool, Widal test was conducted on the spot and stool was taken to a reference laboratory for culture using standard microbiological methods, sociological set up was calculated in percentages, prevalence was calculated using excel while statistical difference was calculated using SPSS. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated to compare the Widal test against stool culture. Results: A total of 368 (50.8% females and 49.2% males) participants took part in the survey. Salmonella prevalence (66.24%) in stool culture in the Vina division was significantly different (p 0.05). The sensitivity,specificity, PPV, and NPV of slide agglutination test against stool culture varied from different areas (Vina: 51.6%, 73.62%, 79.21% and 43.61%;Mayo Banyo: 60.53%, 77.78%, 79.31% and 58.33%;Djerem: 53.18%, 83.73% 73.91% and 67.39%) respectively. Slide agglutination test has a fair agreement with the stool culture (kappa, Vina = 0.202;Mayo Banyo = 0.37 and Djerem = 0.38). Conclusion: Generally, in the three areas of study, the Widal test had a fair correlation with the stool culture;This means the Widal test should not be used alone but in combination with stool culture in the detection of salmonella infections.

Application of fecal immunochemical test in colorectal cancer screening:A community-based,cross-sectional study in averagerisk individuals in Hainan

BACKGROUND The incidence of colorectal cancer(CRC)in China is steadily rising,with a high proportion of advanced-stage diagnoses.This highlights the significance of early detection and prevention measures to enhance survival rates.Fecal immunochemical testing(FIT)is a globally recommended CRC screening method;however,limited research has been conducted on its application in Hainan.AIM To assess the efficacy and adherence of FIT screening among average-risk individuals in Hainan,while also examining the risk factors associated with positive FIT results.METHODS This population-based cross-sectional study implemented FIT screening for CRC in 2000 asymptomatic participants aged 40-75 years from five cities and 21 community health centers in Hainan Province.The study was conducted from August 2022 to April 2023,employing a stratified sampling method to select participants.Individuals with positive FIT results subsequently underwent colonoscopy.Positive predictive values for confirmed CRC and advanced adenoma were calculated,and the relationship between relevant variables and positive FIT results was analyzed usingχ2 tests and multivariate logistic regression.RESULTS A total of 1788 participants completed the FIT screening,with a median age of 57 years(interquartile range:40-75).Among them,503(28.1%)were males,and 1285(71.9%)were females,resulting in an 89.4%compliance rate for FIT screening.The overall positivity rate of FIT was 4.4%[79 out of 1788;95%confidence interval(CI):3%-5%].The specific positivity rates for Haikou,Sanya,Orient City,Qionghai City,and Wuzhishan City were 9.6%(45 of 468;95%CI:8%-11%),1.3%(6 of 445;95%CI:0.1%-3.1%),2.7%(8 of 293;95%CI:1.2%-4.3%),3.3%(9 of 276;95%CI:1.0%-6.3%),and 4.2%(11 of 406;95%CI:1.2%-7.3%),respectively.Significant associations were found between age,dietary habits,and positive FIT results.Out of the 79 participants with positive FIT results,55 underwent colonoscopy,demonstrating an 82.2%compliance rate.Among them,10 had a clean gastrointestinal tract,43 had polyps or adenomas,and 2 were confirmed to have CRC,yielding a positive predictive value of 3.6%(95%CI:0.9%-4.2%).Among the 43 participants with polyps or adenomas,8 were diagnosed with advanced adenomas,resulting in an advanced adenoma rate of 14.5%(95%CI:10.1%-17.7%).CONCLUSION In the Hainan region,FIT screening for CRC among asymptomatic individuals at average risk is feasible and wellreceived.

Towards Improving the Quality of Requirement and Testing Process in Agile Software Development:An Empirical Study

Software testing is a critical phase due to misconceptions about ambiguities in the requirements during specification,which affect the testing process.Therefore,it is difficult to identify all faults in software.As requirement changes continuously,it increases the irrelevancy and redundancy during testing.Due to these challenges;fault detection capability decreases and there arises a need to improve the testing process,which is based on changes in requirements specification.In this research,we have developed a model to resolve testing challenges through requirement prioritization and prediction in an agile-based environment.The research objective is to identify the most relevant and meaningful requirements through semantic analysis for correct change analysis.Then compute the similarity of requirements through case-based reasoning,which predicted the requirements for reuse and restricted to error-based requirements.Afterward,the apriori algorithm mapped out requirement frequency to select relevant test cases based on frequently reused or not reused test cases to increase the fault detection rate.Furthermore,the proposed model was evaluated by conducting experiments.The results showed that requirement redundancy and irrelevancy improved due to semantic analysis,which correctly predicted the requirements,increasing the fault detection rate and resulting in high user satisfaction.The predicted requirements are mapped into test cases,increasing the fault detection rate after changes to achieve higher user satisfaction.Therefore,the model improves the redundancy and irrelevancy of requirements by more than 90%compared to other clustering methods and the analytical hierarchical process,achieving an 80%fault detection rate at an earlier stage.Hence,it provides guidelines for practitioners and researchers in the modern era.In the future,we will provide the working prototype of this model for proof of concept.

Significance of oxidative stress and antioxidant capacity tests as biomarkers of premature ovarian insufficiency: A case control study

BACKGROUND Premature ovarian insufficiency(POI)is a condition that causes secondary amenorrhea owing to ovarian hypofunction at an early stage.Early follicular depletion results in intractable infertility,thereby considerably reducing the quality of life of females.Given the continuum in weakened ovarian function,progressing from incipient ovarian failure(IOF)to transitional ovarian failure and further to POI,it is necessary to develop biomarkers for predicting POI.The oxidative stress states in IOF and POI were comprehensively evaluated via oxidative stress[diacron-reactive oxygen metabolites(d-ROMs)]test and anti-oxidant capacity[biological antioxidant potential(BAP)].METHODS Females presenting with secondary amenorrhea over 4 mo and a follicle stimulating hormone level of>40 mIU/mL were categorized into the POI group.Females presenting with a normal menstrual cycle and a follicle stimulating hormone level of>10.2 mIU/mL were categorized into the IOF group.Healthy females without ovarian hypofunction were categorized into the control group.Among females aged<40 years who visited our hospital from January 2021 to June 2022,we recruited 11 patients into both POI and IOF groups.For the potential antioxidant capacity,the relative oxidative stress index(BAP/d-ROMs×100)was calculated,and the oxidative stress defense system was comprehensively evaluated.RESULTS d-ROMs were significantly higher in the POI and IOF groups than in the control group,(478.2±58.7 U.CARR,434.5±60.6 U.CARR,and 341.1±35.1 U.CARR,respectively)(U.CARR is equivalent to 0.08 mg/dL of hydrogen peroxide).However,no significant difference was found between the POI and IOF groups.Regarding BAP,no significant difference was found between the control,IOF,and POI groups(2078.5±157.4μmol/L,2116.2±240.2μmol/L,and 2029.0±186.4μmol/L,respectively).The oxidative stress index was significantly higher in the POI and IOF groups than in the control group(23.7±3.3,20.7±3.6,and 16.5±2.1,respectively).However,no significant difference was found between the POI and IOF groups.CONCLUSION High levels of oxidative stress suggest that evaluating the oxidative stress state may be a useful indicator for the early detection of POI.

Study on Key Biological Indicators of Diabetes Based on Statistical Tests

Normality testing is a fundamental hypothesis test in the statistical analysis of key biological indicators of diabetes.If this assumption is violated,it may cause the test results to deviate from the true value,leading to incorrect inferences and conclusions,and ultimately affecting the validity and accuracy of statistical inferences.Considering this,the study designs a unified analysis scheme for different data types based on parametric statistical test methods and non-parametric test methods.The data were grouped according to sample type and divided into discrete data and continuous data.To account for differences among subgroups,the conventional chi-squared test was used for discrete data.The normal distribution is the basis of many statistical methods;if the data does not follow a normal distribution,many statistical methods will fail or produce incorrect results.Therefore,before data analysis and modeling,the data were divided into normal and non-normal groups through normality testing.For normally distributed data,parametric statistical methods were used to judge the differences between groups.For non-normal data,non-parametric tests were employed to improve the accuracy of the analysis.Statistically significant indicators were retained according to the significance index P-value of the statistical test or corresponding statistics.These indicators were then combined with relevant medical background to further explore the etiology leading to the occurrence or transformation of diabetes status.

Cohort study on the treatment of BRAF V600E mutant metastatic colorectal cancer with integrated Chinese and western medicine

BACKGROUND Patients with BRAF V600E mutant metastatic colorectal cancer(mCRC)have a low incidence rate,poor biological activity,suboptimal response to conventional treatments,and a poor prognosis.In the previous cohort study on mCRC conducted by our team,it was observed that integrated Chinese and Western medicine treatment could significantly prolong the overall survival(OS)of patients with colorectal cancer.Therefore,we further explored the survival benefits in the population with BRAF V600E mutant mCRC.AIM To evaluate the efficacy of integrated Chinese and Western medicine in the treatment of BRAF V600E mutant metastatic colorectal cancer.METHODS A cohort study was conducted on patients with BRAF V600E mutant metastatic colorectal cancer admitted to Xiyuan Hospital of China Academy of Chinese Medical Sciences and Traditional Chinese Medicine Hospital of Xinjiang Uygur Autonomous Region from January 2016 to December 2022.The patients were divided into two cohorts.RESULTS A total of 34 cases were included,with 23 in Chinese-Western medicine cohort(cohort A)and 11 in Western medicine cohort(cohort B).The median overall survival was 19.9 months in cohort A and 14.2 months in cohort B,with a statistically significant difference(P=0.038,hazard ratio=0.46).The 1-3-year survival rates were 95.65%(22/23),39.13%(9/23),and 26.09%(6/23)in cohort A,and 63.64%(7/11),18.18%(2/11),and 9.09%(1/11)in cohort B,respectively.Subgroup analysis showed statistically significant differences in median OS between the two cohorts in the right colon,liver metastasis,chemotherapy,and first-line treatment subgroups(P<0.05).CONCLUSION Integrated Chinese and Western medicine can prolong the survival and reduce the risk of death in patients with BRAF V600E mutant metastatic colorectal cancer,with more pronounced benefits observed in patients with right colon involvement,liver metastasis,combined chemotherapy,and first-line treatment.

Study on Inactivated Vaccine in Oil Emulsion Against Newcastle Disease and Fowl Cholera IV——Field Test of Vaccine

[ Objective] The aim of this study was to evaluate the clinical effect of the inactivated vaccine in oil emulsion against Newcastle disease and Fowl cholera, and provide conditions for combined prevention and control of Newcastle disease and Fowl cholera. [ Method] The mixture of avian pasteurella multocida （type A） virulent strain 1502 and Newcastle disease virus attenuated strain La Sota was prepared into five batches of the inactivated vaccine in oil emulsion to use in the field test for assessing its safety and effects on immune protection of chicken, duck and goose. [ Result] The field safety test showed that there was no adverse reaction in the vaccinated chickens, ducks and geese. The field test of immune effect for chickens suggested that the titers of hemagglutination inhibition antibody for Nescastle disease virus （ ND-HI ） in 7 - 14 day- old chickens and 60 -90 day-old young chickens were 2 -3 log2 higher than the control group after being vaccinated for 3 weeks, which could last for more than 4 months. The protection rate against avian pasteurella multocida was over 75.0% and its immune effect could last for 6 months. The field test of immune effect for duck and goose indicated that the titers of ND-HI antibody were all higher than 4.2 log2 in vaccinated ducks and geese while lower than 2 log2 in the control group after being vaccinated for 3 weeks. The protection rate against avian pasteurella multocida in vaccinated ducks and geese was higher than 75.0% and 62.5% respectively. [ Conclusion] The binary vaccine is safe for poultry and has good immune effects.

Test and Study of the Rock Pressure Sensitivity for KeLa-2 Gas Reservoir in the Tarim Basin

KeLa-2 gas reservoir is the largest uncompartimentalized gas field so far discovered in China, with a reserve of hundreds of billions of cubic meters of dry gas. It has such features as extremely long interval (550m), high pressure (74.5MPa) and pressure coefficient (2.022). Gas reservoirs with a pressure coefficient of over 2.0 are not commonly found. The abnormal high-pressure reservoirs are quite different in characteristic and performance during the process of depletion exploitation. Therefore, it is necessary to know the property of pressure sensitivity for this abnormal high-pressure reservoir. The aim of this paper is to test the reservoir pressure sensitivity and to analyze its effect on the deliverability of gas. Through some experiments, the permeability change with the confining pressure of rock samples from KeLa-2 abnormal high-pressure gas reservoir is measured. A power function is used to match the measured data, and to derive an empirical equation to describe the change of permeability through the change of the reservoir pressure or effective overburden pressure. Considering the permeability change during the development of reservoirs, a conventional deliverability equation is modified, and the deliverability curve for KeLa-2 gas reservoir is predicted. The research indicates that the extent of the pressure sensitivity of rock samples from KeLa-2 is higher than that from the Daqing oilfield. KeLa-2 reservoir rock has the feature of an undercompaction state. The pressure sensitivity of a reservoir may decrease the well deliverability. It is concluded that for KeLa-2 reservoir the predicted absolute open flow (AOF), when the pressure sensitivity is taken into account, is approximately 70% of the AOF when permeability is constant and does not change with pressure.

Comparable study on typhoon and strong northern wind characteristics of the Runyang Suspension Bridge based on field tests

The strong wind characteristics of the Runyang Suspension Bridge（ RSB） including the wind speed and direction, the turbulence intensity, the turbulence integral length and power spectrum are analyzed based on measurement data from the wind environment monitoring subsystem of the structural health monitoring system （SHMS）of the RSB and field tests during strong winds. The differences between the typhoon and the strong northern wind are especially studied. It is found that the mean wind speed of the strong northern wind is a little smaller and the mean wind direction is more stable than that of the typhoon. The turbulence intensity of both the typhoon and the strong northern wind is greater than the values suggested in Chinese code, and the turbulence integral length difference between the typhoon and a strong northern wind is not clear. As for the along-wind turbulence power spectrum, the spectrum of the strong northern wind can fit the Kaimal spectrum better than that of the typhoon. The obtained results can provide measurement data for founding a strong wind characteristic database and determining the strong wind characteristic parameter values of the RSB.

CENTRIFUGAL TEST STUDY ON THE BEHAVIOR OF SOFT CLAY AT SEA BOTTOM UNDER THE ACTION OF WAVE FORCE

The importance of studying the behavior of the soil at the sea bottom under the action of wave force has arisen with the development of offshore engineering.In this paper,the behavior of the soft clay under the action of wave forces is studied by performing centrifugal tests.The soil profile and the wave characters were simulated in the centrifugal model cell according to the typical environmental conditions of the oil fields in the Bohai gulf.Test results show that the soft clay layer will be seriously softened near the upper surface under the maximum wave height and slightly affected in the deeper layer,and that no liquefaction was recorded in the silty sand sublayer during the test.It is proven that the centrifugal test is a valid technique for simulating the interaction between soil and wave.

Study on mechanical properties of composite materials by in-situ tensile test

The mechanical properties of the SiC fiber-reinforced Mg-Al metal matrix composite materials have been studied on internal microstructure by (scanning electron microscopy) SEM in-situ tensile test. The emergence and propagation of the crack, and the fracture behavior in materials have been observed and studied. It is found that in the case of the tensile test, the crack emerged in SiC fiber initially. In the case of the strong cohesion of the fiber-metal interface, the crack propagated in the fiber, meanwhile the fibers in the neighborhood of the cracked fiber began to crack and the Mg-Al metal deformed plastically, and at last the material fractured. Otherwise the toughness of the materials grows in the case of the lower cohesion of the fiber-metal matrix interface.

Validation Study on Listening Test in Newly Reformed CET- 6： A Case Study of CET-6 Official Sample

Listening Comprehension test of CET-6 has a great adjustment in its item types and weighting of score since December,2015, however, there have been few researches concerning the validity of newly innovated CET-6 listening comprehension test.This paper tries to explore the construct validity and content validity of it. Based on the comparison between the test contents of lis-tening and the test requirements in CET syllabus,it is found that CET-6 listening shows good content relevance. Structural equa-tion modeling(SEM) was used to investigate the construct validity of CET-6 listening, which demonstrates that it mainly tests stu-dents' ability to understand details and inference, while ignoring socio-linguistic competence and psych-physiological compe-tence. Therefore, certain changes are desirable to increase the validity of the listening part of CET-6.

A Study of the English Oral Tests in Light of the Communicative Language Testing Theory

Speaking,as a productive skill,is a priority for many foreign-language learners.They often evaluate their success in language learning on the basis of how much they feel they have improved in their spoken language proficiency.Consequently,testing of oral skills has hardly been neglected in college English examination.The communicative testing theory in 1970s greatly influenced language testing,especially the oral tests.This essay briefly explores the theory of communicative language testing and discusses the methods of TOEFL oral test and college English oral test and proposes ways to the latter one for further improve ment.

A Study on Washback Effect of CET-6 Translation Test Towards College English Teaching and Learning

CET-6 is a nationwide and standardized test to evaluate college students' English levels. Now more than 10 million college students take part in the exam every year. On August 14, 2013, the CET-4 and CET-6 examination committee reformed the structure of the CET-6 papers. After that the sentence translation was changed into paragraph translation,the scores of translation section also increased to 15 points which is more difficult and more important than before. There is no doubt that CET-6will exert a great impact on the teaching and learning of College English in China. This thesis focuses on the washback effect of CET-6 translation test towards college English teaching and learning.First of all, this paper introduces the CET-6 translation test requirements, and the score requirements of translation part. The author also illustrates some significant language testing research of both domestic and foreign scholars, and explains the concept of reliability and validity. Secondly, through the survey method of interviews and questionnaire the author study the characteristics of teaching in college classroom, the effect of translation teaching, and how do students to study translation. The author makes a further research on the interaction between the translation test and the teaching and learning based on the relevant theories. At last, the author finds that the negative washback effect of the CET-6 translation test is greater than the positive one. The author reflects on the current translation teaching and learning in China, and hopes to minimize the negative effects of CET-6 translation test.

Study on liquefaction of saturated loess by in-situ explosion test

Liquefaction testing at a saturated loess site was performed under the simulated earthquake ground motion induced by artificial explosions with micro-time intervals.The time histories of ground acceleration,pore water pressure and the ultimate value of residual strain were recorded and measured.The modified FEQdrain computation software was used to analyze the liquefaction.Both the test and the analysis confirm the objective occurrence of loess liquefaction.Furthermore,the reliability of the method of the loess liquefaction analysis based on FEQdrain and the model of pore water pressure development of saturated loess are examined.

Application of transparent soil model tests to study the soil-rock interfacial sliding mechanism

When transparent soil technology is used to study the displacement of a slope, the internal deformation of the slope can be visualized. We studied the sliding mechanism of the soil-rock slope by using transparent soil technology and considering the influence of the rock mass Barton joint roughness coefficient, angle of the soil mass, angle of the rock mass and soil thickness factors on slope stability. We obtained the deformation characteristics of the soil and rock slope with particle image velocimetry and the laser speckle technique. The test analysis shows that the slope sliding can be divided into three parts: displacements at the top, the middle, and the bottom of the slope; the decrease in the rock mass Barton joint roughness coefficient, and the increase in soil thickness, angles of the rock mass and soil mass lead to larger sliding displacements. Furthermore, we analyzed the different angles between the rock mass and soil thickness. The test result shows that the displacement of slope increases with larger angle of the rock mass. Conclusively, all these results can help to explain the soil-rock interfacial sliding mechanism.

Study of Low-intensity 2450-MHz Microwave Exposure Enhancing the Genotoxic Effects of Mitomycin C Using Micronucleus Test and Comet Assay in vitro

Objective To determine the interaction between 2450-MHz microwaves (MW) radiation and mitomycin C (MMC). Methods The synergistic genotoxic effects of low-intensity 2450-MHz microwave and MMC on human lymphocytes were studied using single cell gel electrophoresis (SCGE) assay (comet assay) and cytokinesis-blocked micronucleus (CBMN) test in vitro. The whole blood cells from a male donor and a female donor were either only exposed to 2450-MHz microwaves (5.0 mW/cm2) for 2 h or only exposed to MMC (0.0125 μ/mL, 0.025 μg/mL, 0.05μg/mL and 0.1 μg/mL) for 24 h; and the samples were exposed to MMC for 24 h after exposure to MW for 2 h. Results In the comet assay, the comet lengths ( 29.1 μm and 25.9 μm) of MW were not significantly longer than those (26.3 μrn and 24.1 μm) of controls (P>0.05). The comet lengths (57.4 μm, 68.9 μm, 91.4 μm, 150.6μm and 50.6 μm, 71.7μm, 100.1 μm, 145.1 μm) of 4 MMC groups were significantly longer than those of controls (P<0.01). The comet lengths (59.1 μm, 92.3 μm, 124.5 μm, 182.7 μm and 57.4 μm, 85.5 μm, 137.5 μm, 178.3 μm) of 4 MW plus MMC groups were significantly longer than those of controls too (P<0.01). The comet lengths of MW plus MMC groups were significantly longer than those of the corresponding MMC doses (P<0.05 or P<0.01) when the doses of MMC were ≥50.025 μg/mL. In the CBMN, the micronucleated cell (MNC) rates of MW were 5% and 6%, which showed no difference compared with those (4‰ and 4‰) of controls (P>0.05). The MNC rates of 4 MMC groups were 8‰, 9‰, 14‰, 23‰ and 8‰, 8‰, 16‰, 30‰ respectively. When the doses of MMC were 3≥0.05 μg/mL, MNC rates of MMC were higher than those of controls (P<0.05). MNC rates of 4 MW plus MMC groups were 12‰, 13‰, 20‰, 32‰ and 8‰, 9‰, 23‰, 40‰. When the doses of MMC were 5≥0.05 μg/mL, MNC rates of MW plus MMC groups were much higher than those of controls (P<0.01). MNC rates of 4 MW plus MMC groups were not significantly higher than those of the corresponding MMC doses. Conclusion The low-intensity 2450-MHz microwave radiation can not induce DNA and chromosome damage, but can increase DNA damage effect induced by MMC in comet assay.

Particle flow study on strength and meso-mechanism of Brazilian splitting test for jointed rock mass

A discrete element method （DEM） called particle flow code （PFC2D） was used to construct a model for Brazilian disc splitting test in the present study. Based on the experimental results of intact Brazilian disc of rock-like material, a set of micro-parameters in PFC2D that reflected the macro-mechanical behavior of rock-like materials were obtained. And then PFC2D was used to simulate Brazilian splitting test for jointed rock mass specimens and specimen containing a central straight notch. The effect of joint angle and notch angle on the tensile strength and failure mode of jointed rock specimens was detailed analyzed. In order to reveal the meso-mechanical mechanism of crack coalescence, displacement trend lines were applied to analyze the displacement evolution during the crack initiation and propagation. The investigated conclusions can be described as follows. （1） The tensile strength of jointed rock mass disc specimen is dependent to the joint angle. As the joint angle increases, the tensile strength of jointed rock specimen takes on a nonlinear variance. （2） The tensile strength of jointed rock mass disc specimen containing a central straight notch distributes as a function of both joint angle and notch angle. （3） Three major failure modes, i.e., pure tensile failure, shear failure and mixed tension and shear failure mode are observed in jointed rock mass disc specimens under Brazilian test. （4） The notch angle roles on crack initiation and and joint angle play important propagation characteristics of jointed rock mass disc specimen containing a central straight notch under Brazilian test.