Investigating the minimum detectable activity concentration and contributing factors in airborne gamma-ray spectrometry

In this study,the theory of minimum detectable activity concentration(MDAC)for airborne gamma-ray spectrometry(AGS)was derived,and the relationship between the MDAC and the intrinsic effi-ciency of a scintillation counter,volume,and energy res-olution of scintillation crystals,and flight altitude of an aircraft was investigated.To verify this theory,experi-mental devices based on NaI and CeBr 3 scintillation counters were prepared,and the potassium,uranium,and thorium contents in calibration pads obtained via the stripping ratio method and theory were compared.The MDACs of AGS under different conditions were calculated and analyzed using the proposed theory and the Monte Carlo method.The relative errors found via a comparison of the experimental and theoretical results were less than 4%.The theory of MDAC can guide the work of AGS in probing areas with low radioactivity.

Effect of non-vacuum storage condition on minimum explosible concentration of aluminum dust

Non-vacuum storage condition has a great impact on the explosion characteristics of aluminum powders. In this paper, vacuum-packed flake and globular aluminum powders stored in a dryer after opening the vacuum package are selected as the experimental samples, and a 20 L spherical explosion device is chosen to test the minimum explosible concentration (MEC) values of aluminum dusts under different storage time. The results show that the MEC values of two types of unoxidized aluminum powders are 30 g/m^3. The MEC values of flake and globular aluminum powders firstly go up with the increase of storage time in the dryer and then reach the maximum values of 50 g/m^3 and 60 g/m^3 at respective storage time until finally they stabilize gradually. The main reason is that the oxidation rate is faster owing to the bigger specific surface area of globular aluminum powders. Hence, the storage time has more significant effect on the MEC of globular aluminum powder than that of flake aluminum powder. After a period of time, the outer surface is oxidized to generate a layer of film, which prevents the further oxidation of aluminum powder, resulting in the temporary stability of MEC.

INTRATHECAL GLYCINE SIGNIFICANTLY DECREASES THE MINIMUM ALVEOLAR CONCENTRATION OF ISOFLURANE IN RATS

To evaluate the effect of intrathecal administration of glycine on the minimum alveolar concentration （MAC） of isoflurane in rats. Methods Intrathecal catheters were implanted in 40 adult male rats anesthetized with isoflurane. Baseline MAC of isoflurane was measured during the infusion of artificial cerebrospinal fluid （CSF） alone. Subsequently, 10, 40, 80, 160, and 300 mmol/L of glycine dissolved in artificial CSF were infused for two hours at the same rate as under control conditions, and MAC for isoflurane was re-determined. Results Intrathecal administration of glycine produced a significant, dose-dependent decrease in MAC for isoflurane （up to -65.2% ± 16. 2% ）. Conclusions Intrathecal administration of glycine decreases anesthetic requirement. This result supports the idea that glycine receptors may be important to the immobilizing effect of anesthetics that enhance glycine receptor function such as isoflurane.

Treatment of methicillin-resistant Staphylococcus aureus infections:Importance of high vancomycin minumum inhibitory concentrations

Staphylococcus aureus(SA) infections remain a major cause of morbidity and mortality despite the availability of numerous effective anti-staphylococcal antibiotics.This organism is responsible for both nosocomial and community-acquired infections ranging from relatively minor skin and soft tissue infections to life-threateningsystemic infections.The increasing incidence of methicillin-resistant strains has granted an increasing use of vancomycin causing a covert progressive increase of its minimum inhibitory concentration(MIC)(dubbed the MIC "creep").In this way,the emergence of vancomycinintermediate SA(VISA) strains and heteroresistantVISA has raised concern for the scarcity of alternative treatment options.Equally alarming,though fortunately less frequent,is the emergence of vancomycin-resistant SA.These strains show different mechanisms of resistance but have similar problems in terms of therapeutic approach.Ultimately,various debate issues have arisen regarding the emergence of SA strains with a minimum inhibitory concentration sitting on the superior limit of the sensitivity range(i.e.,MIC = 2 μg/mL).These strains have shown certain resilience to vancomycin and a different clinical behaviour regardless of vancomycin use,both in methicillin-resistant SA and in methicillin-sensitive SA.The aim of this text is to revise the clinical impact and consequences of the emergence of reduced vancomycin susceptibility SA strains,and the different optimal treatment options known.

Aspirin increases susceptibility of Helicobacter pylori to metronidazole by augmenting endocellular concentrations of antimicrobials

AIM： To investigate the increasing the susceptibility pylon） to metronidazole. mechanisms of aspirin of Helicobacter pylori （H METHODS： Hpylori reference strain 26695 and two metronidazole-resistant isolates of H pylori were included in this study. Strains were incubated in Brucella broth with or without aspirin （1 mmol/L）. The rdxA gene of Hpylori was amplified by PCR and sequenced. The permeability of Hpylori to antimicrobials was determined by analyzing the endocellular radioactivity of the cells after incubated with [7-^3H]-tetracycline. The outer membrane proteins （OMPs） of Hpylori 26695 were depurated and analyzed by SDS-PAGE. The expression of 5 porins （hopA, hopB, hopC, hopD and hopE） and the putative RND efflux system （hefABC） of H pylori were analyzed using real-time quantitative PCR. RESULTS： The mutations in rdxA gene did not change in metronidazole resistant isolates treated with aspirin. The radioactivity of H pylori increased when treated with aspirin, indicating that aspirin improved the permeability of the outer membrane of H pylori. However, the expression of two OMP bands between 55 kDa and 72 kDa altered in the presence of aspirin.The expression of the mRNA of hopA, hopB, hopC, hopD, hopE and herA, hefB, hefC of H pylori did not change when treated with aspirin. CONCLUSION： Although aspirin increases the susceptibility of H pylori to metronidazole, it has no effect on the mutations of rdxA gene of Hpylori. Aspirin increases endocellular concentrations of antimicrobials probably by altering the OMP expression.

In Vitro Anti-Bacterial and Anti-Fungal Activities of Extracts from Different Parts of 7 Zingiberaceae Plants

This study aimed to explore the anti-bacterial and anti-fungal activities of extracts from different parts of plants in the Zingiberaceae family.The inhibitory rate,minimum inhibitory concentration(MIC),and minimum bactericidal concentration(MBC)of leaf and stem,and root and rhizome extracts from Alpinia katsumadai Hayata,Alpinia oxyphylla Miq×Alpinia henryi K.Schumann,Alpinia oblongifolia Hayata,Alpinia nigra(Gaertn.)Burtt,Amomum villosum Lour,Alpinia zerumbet(Pers.)Burtt.et Smith and Alpinia oxyphylla Miq were determined using the fungus cake method and double dilution method.The seven Zingiberaceae plants exhibited characteristic antibacterial activities against pathogenic bacteria and fungi.At a 1.5 mg mL^(−1),A.zerumbet root and rhizome extracts exhibited strong inhibitory activity against S.aureus and E.coli,with 83.23%and 79.62%,respectively.In addition,A.zerumbet leaf and stem extracts had an inhibitory rate of 90.85%against P.aeruginosa.At the same concentration,the leaf and stem,root and rhizome extracts of A.katsumadai had the best anti-bacterial effect against F.oxysporum,with inhibition rates of 84.46%and 84.73%,respectively.Moreover,A.katsumadai and A.zerumbet leaf and stem extracts had the most significant antibacterial effect against S.aureus,with a MIC of 0.063 mg mL^(−1).Thus,both A.katsumadai and A.zerumbet extracts had significant antibacterial activity.In addition,by comparing the inhibitory effect of extracts from different parts,it was found that the inhibitory rate and average inhibitory rate of extracts from leaf and stem were higher than those from root and rhizome.The chemical constituents of A.katsumadai and A.zerumbet,determined by the high-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS),revealed that citric acid(CA),alpinetin,and pinocembrin(PNCB)were the functional constituents yielding the antibacterial activity.Overall,A.katsumadai and A.zerumbet have the potential to be developed as new plant fungicides and bactericides.

Identification and antibiotic susceptibility evaluation of Mycoplasma synoviae isolated from chickens in central China

Mycoplasma synoviae(M.synoviae)infections have become an increasingly serious concern in China because they cause huge economic losses to the poultry industry.Antibiotic treatment is one of control strategies that can be used to contain clinical outbreaks in M.synoviae-free flocks,especially because the bacteria can be transmitted through eggs.To understand M.synoviae infection status in farms of central China and the antibiotic susceptibility of the circulating strains in vivo and in vitro,485 samples were collected from five provinces from 2019 to 2021.Fifty-two strains were isolated and identified.Determination of the minimum inhibitory concentration(MIC)of eight antibiotics(tylvalosin,tiamulin,tilmicosin,lincomycin,enrofloxacin,chlortetracycline,doxycycline and tylosin)for isolates showed that tylvalosin,doxycycline and tiamulin were effective against 52 clinical isolates(MIC values≤0.0625-0.25μg/mL,≤0.0625-1μg/mL,and 0.25-2μg/mL,respectively).Tilmicosin,enrofloxacin and lincomycin had high MICo values(>32μg/mL).An artificial M.synoviae infection model was established in chickens for evaluation of the short-term therapeutic effect of these antibiotics.After 5 days of medication,doxycycline(200 mg/L)showed a superior ability to inhibit M.synoviae compared with other groups,as did tylvalosin(200 mg/L).Furthermore,the therapeutic efficacy of tylvalosin(0.4μg/mL)on intra-embryo-injected M.synoviae was higher than that of tiamulin at the same dose.A combination of MiC values determined in vitro and therapeutic effects observed in vivo revealed that tylvalosin and doxycycline had the best therapeutic effects.Tylvalosin also showed better inhibitory effects on the vertical transmis-sion of M.synoviae than tiamulin.

Enhancing Accumulation and Penetration Efficiency of Next-Generation Antibiotics to Mitigate Antibiotic Resistance in Pseudomonas aeruginosa PAO1

This study explores the efficacy of advanced antibiotic compounds against P. aeruginosa, focusing on Antibiotic B, an enhanced derivative of Ceftriaxone. The study measured the intracellular uptake of Antibiotic B and introduced a novel adjuvant, Influximax, which augmented its antibacterial activity. Results showed a diminished potential for resistance emergence with Antibiotic B, particularly when used in combination with Influximax. The study suggests that optimizing antibiotic delivery into bacterial cells and leveraging syner-gistic adjuvant combinations can enhance drug resistance combat. .

基于杯式燃烧器测试系统的灭火性能评价研究进展

杯式燃烧器试验是消防领域用于测定气体灭火剂最小灭火浓度的经典方法。自哈龙灭火剂被淘汰以来,哈龙替代物经历了不同相态的发展,促使杯式燃烧器测试系统进行相应的改进,同时基于杯式燃烧器测试系统的灭火性能评价研究也在不断拓展。综述了国内外杯式燃烧器测试系统的使用和改进研究,重点介绍了适用于气相、液相、固相和复合相灭火剂的杯式燃烧器测试系统和测试方法,分别对气相、液相、含添加剂细水雾、干粉、复合灭火剂的灭火效率进行了总结和分析,综述了各相态灭火剂灭火性能评价研究。未来,杯式燃烧器测试系统仍将不断被改善,在灭火剂筛选和灭火性能评价等方面将发挥更重要的作用。

基于磁各向异性的管壁应力集中区域检测方法

针对应力集中导致管壁发生屈服失效的问题,提出了利用磁各向异性检测管壁应力集中区域的方法。从能量角度出发,研究了应力导致管壁产生磁各向异性的机理,建立了管壁当量应力与磁各向异性探头输出电压信号的数学模型,通过计算管壁的当量应力判断其是否发生屈服失效,搭建了应力检测实验平台。实验结果表明,应力会导致管壁产生磁各向异性,磁各向异性检测方法能够检测出管壁当量应力的变化趋势和主应力方向所在延长线的角度,进而判断管壁是否产生应力集中区域。

小型猪气管插管时异氟醚半数有效剂量的探索

目的本研究拟探讨小剂量舒泰(1.5 mg/kg)肌注复合异氟烷吸入用于保留自主呼吸的小型猪气管插管时50%和95%有效的异氟烷最小肺泡气浓度(50%and 95%minimum alveolar concentrations effective inhaled,MAC EI50and MAC EI95),为小型猪提供安全的麻醉插管方法。方法44例全身麻醉的巴马小型猪,肌注舒泰镇静后,面罩吸入异氟烷进行麻醉诱导,监测心率、血压、呼吸、体温、氧饱和度、呼末二氧化碳浓度和呼末异氟烷浓度。初始呼末异氟烷浓度设置为2.0%,采用Cooper’s评分评价气管插管满意度,采用Dixon’s改良序贯法测算剂量-效应关系。Probit回归法计算MAC EI50和MAC EI95及95%可信区间(confidence interval,CI)。结果小剂量舒泰复合异氟烷吸入诱导直接喉镜气管插管时,小型猪肺泡气浓度的MAC EI503.10%(95%CI 2.79%~3.56%),MAC EI953.77%(95%CI 3.41%~6.42%);在做好监测和气道管理预案的基础上,肺泡异氟烷浓度3.10%~3.75%,均能保证小型猪生命体征稳定。结论舒泰复合异氟烷吸入用于保留自主呼吸的小型猪气管插管是建立小型猪经口气道较好且安全的麻醉方法,具有推广价值。

中医体质分型对全麻诱导时七氟醚MAC值的影响

目的:探讨气管插管全麻诱导时,在常见的四种中医体质分型患者中,吸入七氟醚使意识消失的最低肺泡有效浓度的半数有效浓度(EC_(50))的差异。方法:研究纳入80例拟择期行气管插管全麻手术患者,根据《中医体质分类与判定》标准分为平和质(A组)、血瘀质(B组)、阴虚质(C组)、阳虚质(D组)共四组,每组20例。以吸入麻醉药七氟醚诱导麻醉,使患者意识消失,设定起始七氟醚的呼气末浓度为1.72%,并计算出5个阶梯的七氟醚呼吸末浓度值,分别为0.84%、1.21%、1.72%、2.45%和3.50%,最终用序贯法测定患者意识消失时七氟醚最低肺泡浓度的EC_(50)。结果:四组病人意识消失时七氟醚EC_(50)及对应的95%可信区间(CI)分别是:A组EC_(50)为2.37%(95%CI:1.97%~2.85%);B组EC_(50)为2.21%(95%CI:1.88%~2.58%):C组EC_(50)为2.83%(95%CI:2.63%~3.03%);D组EC_(50)为1.85%(95%CI:1.57%~2.18%)。结论:七氟醚最低肺泡有效浓度在不同中医体质患者中的存在一定差异性,阳虚患者七氟醚EC_(50)比阴虚患者明显降低。

MRMR-SA-EGA-ELM的叶绿素a浓度预测模型研究

为提高叶绿素a浓度的预测精度,以南太湖区域-湖州市新塘港2020年5月至11月份的水质监测数据为原始样本数据,使用最大相关最小冗余算法(MRMR)从原始样本数据中选取效果更优的特征值,作为预测模型的输入数据,将精英遗传算法(EGA)与模拟退火算法(SA)组合优化极限学习机(ELM)网络的初始参数,最终构建MRMR-SA-EGA-ELM叶绿素a浓度预测模型。实验结果表明,MRMR-SA-EGA-ELM模型预测叶绿素a浓度的平均绝对误差(MAE)、均方误差(MSE)、决定系数(R^(2))分别为1.009、1.607、0.903,而ELM模型预测结果的MAE、MSE、R^(2)分别为2.078、8.249、0.562,MRMR-SA-EGA-ELM模型的效果得到显著提升,可实现对叶绿素a浓度的准确预测。

中药混合液对耐甲氧西林金黄色葡萄球菌的体外抗菌作用的研究

目的探究中药混合液对耐甲氧西林金黄色葡萄球菌(Methicillin-resistant Staphylococcus Sureus,MRSA)的体外抗菌作用。方法选取2022年1月—2023年6月江苏省启东市中医院检验科临床分离的40株MRSA。万古霉素、中药混合液对MRSA的体外最低抑菌浓度(Minimum Inhibitory Concentration,MIC)值采用微量肉汤稀释法测定;用K-B纸片扩散法测定万古霉素和中药混合液对MRSA的抑菌效果,探究不同药物浓度对MRSA抑菌活性的影响。结果万古霉素MIC值为(1.56±0.55)mg/L,低于中药混合液的(1.63±0.62)mg/mL,差异有统计学意义(P<0.05)。万古霉素抑菌圈直径为(20.56±0.87)mm,优于中药混合液的(19.89±0.73)mm,差异有统计学意义(P<0.05)。抑菌圈直径大小随浓度增加而增大且中药混合液各浓度抑菌圈直径均大于万古霉素,差异有统计学意义(P均<0.05)。结论中药混合液对MRSA的体外最低抑菌浓度极低,可以有效抑制耐甲氧西林金黄色葡萄球菌的生长。

微生物源溶菌酶的抑菌及抗炎活性

为研究微生物源溶菌酶对14种供试菌的体外抑菌活性及对脂多糖(lipopolysaccharide,LPS)诱导的小鼠巨噬细胞RAW264.7细胞炎症的抑制作用,该文采用二倍稀释法测定微生物源溶菌酶对供试菌的最小抑菌浓度(minimum inhibitory concentration,MIC),评价其体外抑菌活性,通过构建LPS诱导的小鼠巨噬细胞RAW264.7炎症模型,以细胞中一氧化氮(nitric oxide,NO)及肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)的分泌量为指标,评价微生物源溶菌酶的抗炎活性。结果表明,微生物源溶菌酶对大肠杆菌、枯草芽孢杆菌、金黄色葡萄球菌、沙门氏菌、单增李斯特菌、耐热芽孢杆菌、酿酒酵母、酪丁酸梭菌、产黄青霉、黑曲霉和根霉11种菌均表现出良好的抑菌效果,具有较强的广谱抑菌性;在试验浓度范围内,对保加利亚乳杆菌、嗜热链球菌、乳酸乳球菌乳亚种3种益生菌无抑制效果,反而具有生长促进效果。微生物源溶菌酶对LPS诱导的小鼠巨噬细胞RAW264.7炎症模型表现出明显的抗炎作用,可显著降低NO及TNF-α的分泌,且与微生物源溶菌酶的作用浓度呈正相关。在试验浓度范围内,与模型组相比NO分泌量最高可降低57.92%,TNF-α分泌量最高可降低36.75%。微生物源溶菌酶具有良好的抑菌和抗炎活性,为其作为食品添加剂在抑制腐败菌生长、促进益生菌增殖等方面应用提供了理论基础。

几种天然植物精油的抑菌活性及协同增效研究

采用打孔法、倍数稀释法测定丁香等12种植物精油对常见食品病原菌大肠杆菌、金黄色葡萄球菌、沙门氏菌的抑菌圈,最低抑菌质量浓度(MIC)和最低杀菌质量浓度(MBC)以评估抑菌效果。选择较强抑菌活性的精油复配,利用倍数稀释法研究协同指数(SI),选取一种复配精油对冷鲜鸡胸肉进行保鲜,研究菌落总数、大肠杆菌、金黄色葡萄球菌、沙门氏菌计数和风味变化。结果表明:12种植物精油对3种病原菌的抑菌圈直径为0.3~7.3 cm,MIC为0.98~125 g/L,MBC为3.91~500 g/L。筛选出4种精油两两复配,得到4种对大肠杆菌、金黄色葡萄球菌或沙门氏菌的协同增效组合,SI最低值分别为0.750、0.375和0.375,其中牛至-松针精油组合明显抑制了鸡胸肉冷藏期间菌落总数、大肠杆菌、金黄色葡萄球菌和沙门氏菌的上升幅度,货架期延长了5 d。该研究筛选的植物精油对食品病原菌有良好的抑制活性,复配增效可有效降低MIC,牛至-松针精油组合对冷鲜鸡胸肉保鲜效果良好,可用于天然食品保鲜剂研发。

一株类芽孢杆菌的鉴定及抗菌活性探究

为了筛选产新型天然抗菌物质微生物,本研究利用共培养的方法筛选目的菌株;通过16S rDNA、生理生化性质和全基因组测序鉴定菌株种属;利用抗菌物质稳定性、菌株基因组次级代谢产物预测和最小抑菌浓度研究抗菌物质的生物学特性。从土壤中筛选了一株类芽孢杆菌Paenibacillus elgii CL-1,该菌所产抗菌物质具有广谱抗菌性能,且耐受过氧化氢酶、胃蛋白酶、胰蛋白酶、蛋白酶K和酸碱,高温不稳定;利用antiSMASH分析发现Paenibacillus elgii CL-1含有penisin和octapeptin C4等17种次级代谢产物基因簇;进一步的分析发现,通过高效液相色谱从该菌发酵液中分离纯化出的抗菌物质抗菌谱广,抗菌活性好,最小抑菌浓度值可达1μg/mL。通过质谱分析发现类芽孢杆菌Paenibacillus elgii CL-1能够产生抗菌谱广、稳定性好和抗菌活性强的抗菌物质pelgipeptin B。本研究为挖掘天然抗菌药物pelgipeptin B提供底盘菌株,为其研发和应用奠定基础。

亚抑菌浓度抗菌药物影响金黄色葡萄球菌生物膜形成的研究进展

金黄色葡萄球菌(SA)是引起医院获得性感染的常见病原体之一,极易黏附在导管或植入物表面形成生物膜导致耐药性增加,给临床治疗带来极大挑战。近年研究表明,抗菌药物处于亚抑菌浓度时可影响SA生物膜形成。因此,本文阐述SA生物膜的形成过程及基因调控,不同抗菌药物在亚抑菌浓度下对SA生物膜形成的影响及其作用机制,以期为有效控制及治疗SA生物膜相关感染提供一定依据。

基于PIPSBOX测量气态14C流出物装置的设计

14C作为环境影响评价中的重要核素,现有测量技术很难实现核设施气态14C流出物的在线测量。基于PIPSBOX测量技术研制了气态14C流出物在线测量装置的原理样机,模拟了PIPSBOX测量14C的探测效率,理论证明测量的可行性。通过将不同形式的14C气体转化为14CO_(2)形态,以便进行低温分离14CO_(2)提高14C浓度,最后实现PIPSBOX测量14C气体。最终在3 h内,该系统测量14C的最小可探测活度浓度达到0.99 Bq/m3,小于现在连续取样一周的探测下限10 Bq/m^(3),这项工作建立了14C测量新方法,实现了气态14C流出物的在线测量,也为大气中14C在线测量提供参考。

树舌灵芝深层发酵产物抑菌作用的研究

以分离自广西乐业天坑群的树舌灵芝的深层发酵产物(菌丝体、发酵液)为试材,采用滤纸片法、二倍稀释法,研究了树舌灵芝发酵产物提取物的抑菌作用,以期为开发防腐、食品保鲜产品提供参考依据。结果表明:树舌灵芝菌丝体提取物和发酵液提取物中均含有抗菌活性物质,发酵液乙酸乙酯提取物的抑菌能力最强,对10种供试菌均有较好的抑菌效果;发酵液乙酸乙酯提取物梯度洗脱、分离纯化后得到的30%乙酸乙酯组分(B5)的抑菌能力最高,对10种供试菌的抑菌圈直径基本上均最大;B5对藤黄微球菌的最低抑菌浓度(MIC)值为25 mg·mL^(-1),对大肠杆菌等5种菌的MIC值为50 mg·mL^(-1),对酿酒酵母的MIC值为200 mg·mL^(-1),对黑曲霉、米曲霉和绿色木霉的MIC值为400 mg·mL^(-1)。