Stability and melting behavior of boron phosphide under high pressure

Boron phosphide(BP)has gained significant research attention due to its unique photoelectric and mechanical properties.In this work,we investigated the stability of BP under high pressure using x-ray diffraction and scanning electron microscope.The phase diagram of BP was explored in both B-rich and P-rich environments,revealing crucial insight into its behavior at 5.0 GPa.Additionally,we measured the melting curve of BP from 8.0 GPa to 15.0 GPa.Our findings indicate that the stability of BP under high pressure is improved within B-rich and P-rich environments.Furthermore,we report a remarkable observation of melting curve frustration at 10.0 GPa.This study will enhance our understanding of stability of BP under high pressure,shedding light on its potential application in semiconductor,thermal,and light-transmitting devices.

A new identification method for five species of oysters in genus Crassostrea from China based on high-resolution melting analysis

The high phenotypic plasticity in the shell of oysters presents a challenge during taxonomic and phylogenetie studies of these economically important bivalves. However, because DNA can exhibit marked differences among morphologically similar species, DNA barcoding offers a potential means for oyster identification. We analyzed the complete sequences of the cytochrome oxidase subunit I （COI） of five common Crassostrea species in China （including Hong Kong oyster C. hongkongensis, Jinjiang oyster C. ariakensis, Portuguese oyster C. angulata, Kumamoto oyster C. sikamea, and Pacific oyster C. gigas） and screened for distinct fragments. Using these distinct fragments on a high-resolution melting analysis platform, we developed an identification method that does not rely on species-specific PCR or fragment length polymorphism and is efficient, reliable, and easy to visualize. Using a single pair of primers （Oyster- COI-1）, we were able to successfully distinguish among the five oyster species. This new method provides a simple and powerful tool for the identification of oyster species.

Detection and Identification of Six Foodborne Bacteria by Two-tube Multiplex Real Time PCR and Melting Curve Analysis

Objective This study is aimed to develop a two-tube melting curve-based multiplex real time PCR assay （MCMRT-PCR） for the simultaneous detection of six common foodborne pathogenic bacteria （diarrhoeagenic Escherichia coli, Salmonella, and 5higella in tube 1, Staphylococcus aureus, Vibrio parahaemolyticus, and Listeria monocytogenes in tube 2）. Methods A two-tube MCMRT-PCR assay was performed on 7900HT Fast Real-Time PCR System {Applied Biosystems, USA）. Amplification by PCR was optimized to obtain high efficiency. The sensitivity and specificity of assays were investigated. Results The detection limit of optimized MCMRT-PCR assay was 3.9x102 CFU/mLfor S. aureus, 4.4x102 CFU/mL for L. monocytogenes, 3.0x102 CFU/mL for Salmonella, 2.5x102 CFU/mL for Shigella, 2.1x102 CFU/mL for V. parahaemolyticus, and 1.2x102 CFU/mL for E. coll. The feasibility of MCMRT-PCR was further evaluated using artificially contaminated milk, the sensitivity was at the level of 10s CFU/mL. Conclusion A two-tube MCMRT-PCR assay using six primer sets was developed for detection of multiple pathogens. Our findings demonstrates that the proposed two-tube assay is reliable, useful and rapid for simultaneous detection of six foodborne pathogenic bacteria with an intended application in provincial Centers for Diseases Control and Prevention （CDC）.

Effect of spermine on the melting curve and melting temperature of some tRNAs

Using purified bovine liver tRNA￣(Ile) and yeast tRNA￣(Phe), we studied the effects of spermine on the melting curve and melting temperature(Tm) of the tRNAs. The results showed that the absorbance at 260 nm of tRNAs decreases with the increase of temperature in the presence of 2 mmol/L spermine. We called this phenomenon hypochromism and reverse-Tm of the tRNAs. It is suggested that spermine binds to tRNAs and stabilizes the secondary structure of the tRNAs.

High Resolution Melting Curve Analysis for Rapid Detection of Pyrazinamide Resistance in Mycobacterium tuberculosis Clinical Isolates

Background: Pyrazinamide (PZA) is one of the most important drugs for tuberculosis (TB) treatment, however, its susceptibility is not routinely tested. High-resolution melting (HRM) curve analysis has been widely used for many applications. In this study, HRM assay was developed and evaluated for the detection of PZA resistance in Mycobacterium tuberculosis clinical isolates. Methods: Ninety five M. tuberculosis clinical isolates with different susceptibility patterns to anti-TB drugs were used to evaluate this assay. Isolates were phenotypically (Bactec MGIT 960) and genotypically (HRM and pncA gene sequencing) analysed for PZA resistance. Results: Bactec MGIT 960 analysis revealed that 29 of the 95 M. tuberculosis isolates were PZA resistant. In comparison to the Bactec MGIT 960, HRM showed a sensitivity of 47.7% and specificity of 74.6%, and the overall agreement between the two methods was 68.4%. Based on DNA sequencing, a correlation of 0.67 (significant at p-value pncA mutations was observed. PZA resistance was strongly associated with multi-drug resistant (MDR)-TB as it was shown in 79.3% of the MDR isolates included in the study. Conclusion: HRM is simple and useful for screening clinical M. tuberculosis isolates for PZA resistance, however, further modifications to improve its performance are required.

Rheological Behaviour for Polymer Melts and Concentrated SolutionsPart Ⅱ: Material Function with Nagai Chain Constraints and Determination of Their Parameters from Flow Curves

An integral constitutive equation and a set of material functions for describing the strain history of polymer melts were formulated in terms of the Cauchy-Green and Finger tensors. A simple memory function and the dependence of ηo and τt on M3.4 were derived from the theory of non-linear viscoelasticity with constraints of entanglements for polymer melts and substituted into the Oldroye-Walters-Fredickson constitutive equation. An integral constitutive equation for polymer melts was consequently obtained. Some material functions of the constitutive equation related to certain 'test flow' are examined as follows : (1) simple steady shear flow; (2) steady elongation flow; (3) small-amplitude oscillatory shear flow; (4) stress growth upon the inception of steady shear elongation flow; (5) stress relaxation (modulus and compllance). These theoretical relations for simple steady shear flow were compared with experimental data from our laboratory and references for various polymer melts and concentrated solutions. A good agreement between the theory and experiment was achieved.

Simulation of Melting Behavior of the MgSi03 Perovskite Under Lower Mantle Conditions

The melting curve of MgSiO3 perovskite was simulated using molecular dynamics method combining with the effective pair potentials under the lower mantle conditions. It was shown that the state equation simulated for MgSiO3 perovskite is very successful in reproducing accurately the experimental data over a wide range of pressure. The pressure dependence of the simulated melting temperature of MgSiO3 perovskite is in agreement with the recent experimental data. The melting curve simulated for MgSiO3 is very steep at pressures below 60 GPa first, then it becomes smooth with increasing pressure. At the core mantle boundary pressure 135 GPa, MgSiO3 perovskite melts at 6500 K, which is significantly lower than that of the extrapolations of the experimental data from Zerr and Boehler.

不同成形方式对WE43镁合金组织和力学性能的影响

采用激光选区熔化成形(SLM)、铸造及挤压方式制备了WE43镁合金试样,通过维氏硬度计、密度测试计、光学显微镜、扫描电镜以及拉伸试验机等设备分析了不同制备方式下WE43镁合金的宏微观组织和力学性能变化规律;设计了基于指数函数的模型对不同成形方式的WE43应力–应变曲线进行统一拟合,为WE43材料未来增材、减材以及等材工艺复合制造复杂零件打下基础。结果表明,SLM成形WE43有明显的各向异性,铸态和挤压态不明显。SLM成形WE43镁合金的强度最高,抗拉强度达到313 MPa,是铸态的183%;挤压态WE43镁合金塑性最好,伸长率达到10.2%,是铸态的232%;此外,SLM态镁合金密度只有1.731 g/cm^(3),仅为挤压态的85.7%和铸态的95.2%。在断裂特性上,SLM态和挤压态为韧性断裂,而铸造态为脆性断裂。在内部存在20μm左右孔洞形缺陷的情况下,SLM成形镁合金依然具有最高的强度,主要原因是SLM成形WE43镁合金平均晶粒尺寸仅为2.6μm,基体内存在大量的稀土相沉淀以及纳米级亚稳相。由此可知,通过进一步的后处理方法焊合SLM态镁合金内部孔洞形缺陷后,材料力学性能可以大幅提高。

Toll样受体和白细胞介素-17单核苷酸多态性与口腔扁平苔藓易感性的相关性研究

目的探讨Toll样受体(TLR)和白细胞介素-17(IL-17)基因的遗传多态性及与口腔扁平苔藓(OLP)的相关性。方法选取病例组(OLP组)患者与对照组(未患OLP人群)外周血提取的DNA为研究对象,选取TLR与IL-17上的7个单核苷酸多态性(SNP)位点,分别是TLR3中的rs5743312、TLR2中的rs121917864和IL-17A中的5个SNP位点(rs4711998、rs3819024、rs8193036、rs3748067和rs17878530)。采用高分辨率熔解曲线分析法进行外周血细胞PCR产物基因多态性检测,并与DNA测序结果比对。统计分析SNP位点与OLP发生的相关性。结果rs5743312(TLR3)、rs3819024(IL-17A)与OLP的发生相关,并有统计学意义(P<0.05)。其余5个SNP位点未检测出与OLP相关。结论rs5743312(TLR3)和rs3819024(IL-17A)可能与OLP的易感性相关。

高分辨率熔解曲线快速检测结核分枝杆菌对链霉素耐药情况的研究

探讨高分辨率熔解曲线(HRM)技术检测结核分枝杆菌对链霉素耐药性的可行性。用传统药物敏感性试验进行结核分枝杆菌链霉素耐药性检测;以Rpsl和rrs的耐药决定区为靶点设计引物进行HRM分析,判断菌株是否对链霉素耐药;以药敏结果为标准,应用SPSS17.0分析两种检测结果之间的符合率;Kappa检验分析两种结果的一致性。药敏结果显示,84株菌株中有20株对链霉素耐药,64株为敏感株;HRM检测结果显示,24株菌株对链霉素耐药,60株为敏感株;以药敏结果为参照,HRM检测结核分枝杆菌对链霉素耐药性的敏感性为75%,特异性为85.9%,经Kappa检验显示,两种方法检测结果具有中度一致性。本研究结果表明HRM可快速检测结核分枝杆菌对链霉素的耐药性,具有较好的灵敏度,在耐药结核病的早期辅助诊断方面具有一定的应用价值。

高分辨率熔解曲线检测结核分枝杆菌对氧氟沙星耐药性研究

评价高分辨率熔解曲线法在结核分枝杆菌氧氟沙星耐药性检测的有效性。采用传统比例法、DNA测序法、高分辨率熔解曲线法对84株结核分枝杆菌临床分离株进行氧氟沙星耐药性检测,分别以药敏结果和DNA测序结果为参照,应用卡方检验分析各检测结果之间的差异性,Kappa检验分析检测结果一致性。药敏结果显示,12株菌对氧氟沙星耐药,72株敏感。DNA测序结果显示,10株菌存在gyrA基因耐药相关突变,74株菌不存在gyrA基因耐药相关突变。高分辨率熔解曲线检测结果显示,有14株耐药株,70株敏感株。以比例法药敏结果为参照,DNA测序检测菌株耐药性的敏感性为83.3%、特异性为100%、符合率为97.6%,检测结果具有高度一致性;高分辨率熔解曲线法检测菌株耐药性的敏感性为75%、特异性为93.1%、符合率为90.5%,检测结果具有中度一致性。以DNA测序结果为参照,高分辨率熔解曲线法检测gyrA基因耐药突变的敏感性为80%,特异性为91.9%,符合率为90.4%,检测结果具有中度一致性。本研究结果表明高分辨率熔解曲线法对结核分枝杆菌氧氟沙星耐药性检测的效能良好,可用于氧氟沙星耐药结核分枝杆菌的快速辅助筛查,为早期治疗方案制定提供重要依据。

基于MLPA结合熔解曲线法鉴别山药及其常见混伪品

目的:利用MLPA技术结合熔解曲线法建立一种能鉴别山药及其常见混伪品的新方法。方法:以山药、参薯、木薯、番薯为研究对象,针对四个物种的matK序列分别设计MLPA特异性探针,通过DNA变性、杂交、连接、扩增及熔解反应等步骤,建立MLPA-熔解曲线鉴别体系,利用各样品熔解曲线中特异性峰(Tm值)的差异实现不同物种的鉴定。结果:27份样品中,山药Tm值为78.3℃,参薯Tm值为79.9℃,木薯Tm值为81.2℃,番薯Tm值为82.9℃,且相互之间没有交叉干扰。该法对山药、参薯、木薯、番薯各自单独的最低检测限为0.1 ng/μL;对相互混淆掺伪的最低有效检出率为5%。27份样品的检测结果均与测序结果一致。结论:MLPA技术结合熔解曲线法具有特异性强、灵敏度高、操作简单等优点,具有进一步推广应用的潜力。

115462例新生儿葡萄糖-6-磷酸脱氢酶缺乏症筛查及基因突变分析

目的了解贵阳地区葡萄糖-6-磷酸脱氢酶(glucose-6-phosphate dehydrogenase,G6PD)缺乏症发病情况和基因突变特点,为贵阳地区G6PD缺乏症的防治提供科学参考。方法募集该地区2020年8月至2023年1月出生的新生儿,应用荧光分析法对其血斑样本进行G6PD酶活性筛查,召回初筛阳性儿,完成G6PD酶活性诊断及多色探针荧光PCR熔解曲线法(Multicolor probe melting curve analysis method,MMCA)基因突变分析。结果共募集115462例新生儿,G6PD酶活性筛查血斑样本共筛出阳性1606例,筛查阳性率为1.39%(1606/115462),其中男性为1.83%(1130/61801)、女性0.89%(476/53661),男女新生儿G6PD酶活性初筛阳性率差异有统计学意义(P<0.01);召回初筛阳性患儿,G6PD基因突变检出率87.07%(909/1044),其中男性为90.09%(764/848),女性为73.98%(145/196),男女间G6PD基因突变检出率差异有统计学意义(P<0.01)。本研究共检出13种类型G6PD基因单一突变型(c.1024 G>T、c.1388 G>A、c.95 A>G、c.1376 G>T、c.592C>T、c.871 G>A、c.519 C>T、c.392G>T、c.493 A>G、c.1004C>A、c.1360C>T、c.383T>C、c.517T>C)和6种复合突变型(c.1376 G>T杂合复合c.95A>G杂合突变、c.1024 G>T杂合复合c.95A>G杂合突变、c.1024 C>T杂合复合c.1388 G>A杂合突变、c.1024 C>T杂合复合c.519C>T杂合突变、c.1376 G>T杂合复合c.1024 C>T杂合突变、c.95A>G杂合复合c.1388 G>A杂合突变)。贵阳地区G6PD缺乏症基因突变类型复杂多样,G6PD突变常见类型为c.1024 C>T、c.1388G>A、c.95 A>G、c.1376G>T这四种类型。结论贵阳地区G6PD基因突变位点具有明显地域性特征,开展G6PD酶活性筛查及相关诊断检测,有利于本地区G6PD缺乏症的筛查、确诊、治疗和防控,有效提高出生人口素质。

Development of a multiplex polymerase chain reaction assay for detection of hepatitis C virus,hepatitis B virus,and human immunodeficiency virus 1

BACKGROUND Hepatitis C virus(HCV),hepatitis B virus(HBV),and human immunodeficiency virus 1(HIV-1)are the most epidemic blood-borne viruses,posing threats to human health and causing economic losses to nations for combating the infection transmission.The diagnostic methodologies that depend on the detection of viral nucleic acids are much more expensive,but they are more accurate than sero-logical testing.AIM To develop a rapid,cost-effective,and accurate diagnostic multiplex polymerase chain reaction(PCR)assay for simultaneous detection of HCV,HBV,and HIV-1.METHODS The design of the proposed PCR assay targets the amplification of a short conserved region featured with a distinguishable melting profile and electro-phoretic molecular weight inside each viral genome.Therefore,this diagnostic method will be appropriate for application in both conventional(combined with electrophoresis)and real-time PCR facilities.Confirmatory in silico investigations were conducted to prove the capability of the approached PCR assay to detect variants of each virus.Then,Egyptian isolates of each virus were subjected to the wet lab examination using the given diagnostic assay.RESULTS The in silico investigations confirmed that the PCR primers can match many viral variants in a multiplex PCR assay.The wet lab experiment proved the efficiency of the assay in distinguishing each viral type through high-resolution melting analysis.Compared to related published assays,the proposed assay in the current study is more sensitive and competitive with many expensive PCR assays.CONCLUSION This study provides a simple,cost-effective,and sensitive diagnostic PCR assay facilitating the detection of the most epidemic blood-borne viruses;this makes the proposed assay promising to be substitutive for the mistakable and cheap serological-based assays.

基于探针熔解曲线分析的多重PCR同步鉴定6种腹泻病原菌

目的基于多重聚合酶链反应(PCR)和探针熔解曲线分析技术,建立可同时鉴定6种常见急性感染性腹泻病原菌的高灵敏度诊断方法,并验证其检测性能。方法采用熔解曲线分析6种常见急性感染性腹泻病原菌熔解温度(Tm)值,建立基于探针熔解曲线分析的多重PCR检测方法,并评价其灵敏度、特异性和重复性。采用该方法检测175例疑似感染性腹泻患者粪便样本,比较该方法鉴定结果与细菌培养法和荧光PCR法鉴定结果的差异,不一致结果通过测序进行确认。结果建立的多重PCR检测方法可实现单次PCR同步检测6种肠道病原菌,检测限为1×10^(3)~1×10^(4)拷贝·mL^(-1),不同病原菌间无交叉反应,特异性高。175例腹泻患者粪便样本中共检出91例(52%)阳性样本。6种病原菌的检测内变异系数(CV)均<0.1%。与细菌培养法相比,该方法检测沙门菌、志贺菌的符合率分别为94.85%(kappa=0.894)、100.00%(kappa=1.000);与荧光PCR相比,该方法检测艰难梭菌的符合率为98.28%(kappa=0.900)。结论建立的基于探针熔解曲线分析的多重PCR方法同时鉴定6种腹泻病原菌具有较高的灵敏度和特异性,可为急性感染性腹泻的临床诊断及时提供实验室依据。

龟甲配方颗粒的高分辨熔解曲线技术鉴别研究

目的建立一种龟甲配方颗粒高分辨熔解曲线(HRM)技术鉴别方法。方法根据乌龟Chinemys reevesii及其混伪品的细胞色素C氧化酶亚基Ⅰ(cytochrome oxidase subunitⅠ,COI)基因序列上的单核苷酸多态性(single nucleotide polymorphisms,SNP)位点设计鉴别引物,扩增产物直接进行HRM分析,并优化反应体系,根据最佳条件进行适用性验证。结果在模板DNA质量浓度为0.62~374.88 ng/μL、引物浓度为0.1~0.4μmol/L、退火温度为62℃、循环数为45个的条件下,龟甲饮片和配方颗粒的熔解曲线为单峰,其Tm均值分别为(82.39±0.09)、(82.38±0.05)℃,而混伪品和醋龟甲配方颗粒未有扩增。结论该研究建立的高分辨熔解曲线鉴别方法可快速鉴别龟甲原料和配方颗粒的真伪,以及区分其生品和炮制品配方颗粒,为龟甲配方颗粒的质量标准研究提供了理论依据。

探针熔解曲线在耐药结核病快速筛查中的临床应用研究

目的研究探针熔解曲线在耐药结核病快速筛查中的临床应用价值。方法选取2020年1月—2021年3月镇江市第三人民医院收治的378例肺结核患者为研究对象,依次完成传统罗氏固体药物敏感性检测(比例法)、探针熔解曲线技术检测常用的6种药物耐药结果,包含利福平、异烟肼、乙胺丁醇、链霉素、氧氟沙星、阿米卡星,和比例法进行对比,计算探针熔解曲线技术检测6种药物的敏感度、特异度、阳性预测值、阴性预测值、符合率与约登指数。结果与比例法作比较,熔解曲线技术检测利福平耐药性的敏感度、特异度、阳性预测值、阴性预测值、符合率、约登指数分别为91.70%、98.10%、61.10%、99.70%、97.90%、0.898;异烟肼是87.90%、94.20%、59.20%、98.80%、93.65%、0.821;乙胺丁醇是87.50%、97.03%、38.89%、99.72%、96.83%、0.845;链霉素是91.30%、98.19%、87.50%、98.79%、97.35%、0.895;氧氟沙星是94.74%、98.89%、81.82%、99.72%、98.68%、0.936;阿米卡星是80.00%、99.46%、66.67%、99.73%、99.21%、0.795。结论探针熔解曲线在耐药结核病快速筛查中应用,具有较高敏感度及特异度,有利于临床早期识别耐药现象。

公路用融雪剂理论用量研究

文章提出了采用融雪剂冰点标准曲线,确定不同气温条件下融雪剂理论用量的方法。研究认为,以冰点标准曲线确定融雪剂用量,需综合考虑温度和需要融化的冰雪量。在融雪剂应用过程中,实际用量亦受其他次要因素影响,如融雪剂融化冰雪时的热效应、光照、风速、蒸发、撒布时机、交通量、交通开放要求等。同时提出确定融雪剂理论用量的方法,从而最大限度地发挥融雪剂融雪化冰的作用,为融雪剂的科学使用提供案例参考。

Rapid screening for Klinefelter syndrome with a simple high-resolution melting assay： a multicenter study

Klinefelter syndrome （KS） is the set of symptoms that result from the presence of an extra X chromosome in males. Postnatal population-based KS screening will enable timely diagnosis of this common chromosomal disease, providing the opportunity for early intervention and therapy at the time point when they are most effective and may prevent later symptoms or complications. Therefore, through this study, we introduced a simple high-resolution melting （HRM） assay for KS screening and evaluated its clinical sensitivity and specificity in three medical centers using 1373 clinical blood samples. The HRM assay utilized a single primer pair to simultaneously amplify specific regions in zinc finger protein, X-linked （ZFX） and zinc finger protein, Y-linked （ZFY）. In cases of KS, the ratios of ZFX/ZFYare altered compared to those in normal males. As a result, the specific melting profiles differ and can be differentiated during data analysis. This HRM assay displayed high analytical specificity over a wide range of template DNA amounts （5 ng-50 ng） and reproducibility, high resolution for detecting KS mosaicism, and high clinical sensitivity （100%） and specificity （98.1%）. Moreover, the HRM assay was rapid （2 h per run）, inexpensive （0.2 USD per sample）, easy to perform and automatic, and compatible with both whole blood samples and dried blood spots. Therefore, this HRM assay is an ideal postnatal population-based KS screening tool that can be used for different age groups.

High-resolution melting-based TILLING of γ ray-induced mutations in rice

Targeting Induced Local Lesions IN Genomes （TILLING） is a reverse genetics strategy for the high-throughput screening of induced mutations.γ, radiation, which often induces both insertion/deletion （Indel） and point mutations, has been widely used in mutation induction and crop breeding. The present study aimed to develop a simple, high-throughput TILLING system for screening γ ray-induced mutations using high-resolution melting （HRM） analysis. Pooled rice （Oryza sativa） samples mixed at a 1：7 ratio of Indel mutant to wild-type DNA could be distinguished from the wild-type controls by HRM analysis. Thus, an HRM-TILLING system that analyzes pooled samples of four M2 plants is recommended for screening γ, ray-induced mutants in rice. For demonstration, a γ, ray-mutagenized M2 rice population （n=4560） was screened for mutations in two genes, OsLCT1 and SPDT, using this HRM-TILLING system. Mutations including one single nucleotide substitution （G→A） and one single nucleotide insertion （A） were identified in OsLCT1, and one tdnucleotide （TTC） deletion was identified in SPDT. These mutants can be used in rice breeding and genetic studies, and the findings are of importance for the application of γ, ray mutagenesis to the breeding of rice and other seed crops.