Use of lambda DNA as a marker to assess DNA stability in olive oil during storage

Filtered olive oil samples spiked with three different concentrations of λDNA were stored at 25 °C under a 12 h photoperiod for up to a year. These samples were used for DNA extraction and PCR amplification of λDNA amplicons of 107, 415 and 691 bp length. The amplification signal was gradually decreased with longer storage periods, while the strength of the signal was related to the initial concentration of spiking λDNA particularly during longer storage periods. The 107 bp amplicon was the only one successfully amplified from all the samples, regardless of both concentration of spiking λDNA and storage period. The amplification of 415 and 691 bp amplicons was not successful for samples stored longer than a threshold period of 20 and 10 days, respectively. These results suggest that detection of polymorphic markers requiring DNA templates shorter than 100 bp might have a wider range of applications in DNA fingerprinting of olive oil. In addition, the DNA extracts were tested for the presence of inhibitors in PCR amplification reactions of yeast DNA amplicons. The inhibitory effect of olive DNA extracts was partial and gradually increased with the storage period of the olive oil samples used for the DNA extraction.     

切削和侵入作用下层理岩层破碎机理浅析

层理岩层是石油钻井中经常遇到的一类地层,特别是在页岩气开采过程中,所钻页岩属于典型的层理岩层。研究层理岩层在钻齿作用下的破碎机理对于控制井眼轨迹、优化钻进参数、提高钻进效率都有很大指导作用。在以往岩石破碎机理研究中,一般多假设岩石介质为各向同性;但是对于层理岩层,由于其表现出强烈的强度各向异性特征,各项同性假设不再适用。本文利用离散单元方法(PFC2D)建立了钻齿与层理岩层相互作用模型。研究了层理岩层在钻齿切削和侵入过程中的破碎情况、裂纹的扩展情况以及钻齿受力情况。研究表明:切削力根据层理倾角分为高切削力区和低切削力区;液柱压力的存在对裂纹扩展有抑制作用,增大切削力;在岩石侵入过程中,层理的存在改变了裂纹的走向,当主裂纹扩展至层理处时,裂纹不再向岩石内部扩展,而是朝着层理的方向扩展。     

Automatic quantification of mitochondrial fragmentation from two‐photon microscope images of mouse brain tissue

The morphology of mitochondria can inform about their functional state and, thus, about cell vitality. For example, fragmentation of the mitochondrial network is associated with many diseases. Recent advances in neuronal imaging have enabled the observation of mitochondria in live brains for long periods of time, enabling the study of their dynamics in animal models of diseases. To aid these studies, we developed an automatic method, based on supervised learning, for quantifying the degree of mitochondrial fragmentation in tissue images acquired via two‐photon microscopy from transgenic mice, which exclusively express Enhanced cyan fluorescent protein (ECFP) under Thy1 promoter, targeted to the mitochondrial matrix in subpopulations of neurons. We tested the method on images prior to and after cardiac arrest, and found it to be sensitive to significant changes in mitochondrial morphology because of the arrest. We conclude that the method is useful in detecting morphological abnormalities in mitochondria and, likely, in other subcellular structures as well.     

双曲线型聚焦战斗部破片的设计方法

为解决预制破片聚焦战斗部加工中存在效率低的问题,基于正反圆柱螺旋线相交性原理,通过局部淬火预制工艺提出了一种新的高效率战斗部破片设计方法,并给出了一种聚焦式战斗部的加工实例。结果表明,局部淬火工艺对战斗部破片的控制效果良好,破片形状规则、质量分布均匀,有效破片质量分数达90%,符合毁伤要求,验证了其设计原理的正确性和可行性。     

Synthesis of Gemini‐Like Methyl Acrylate‐Acrylic Acid‐Methyl Acrylate Triblock Copolymers Surfactants by RAFT Polymerization in Solution and Investigation of their Behavior at the Air–Water Interface

A series of methyl acrylate‐acrylic acid amphiphilic triblock copolymers (PMA‐PAA‐PMA) were prepared by solution polymerization using S,S′‐bis (α,α‐dimethy1acetic acid) trithiocarbonate (BDAT) as a reversible addition fragmentation chain transfer (RAFT) agent and methyl acrylate (MA) as the first monomer. The triblock copolymers and their common MA homopolymer precursors were characterized in terms of their compositions, molecular weights and behavior at the air–water interface using ¹H‐NMR spectroscopy, thermogravimetric analysis, gel permeation chromatography, surface tension, transmission electron microscopy (TEM) and dynamic light scattering respectively. The results indicated that PMA‐PAA‐PMA was successfully synthesized through RAFT polymerization. The polydispersity index (PDI) decreased when the molar ratio [n(MA)/n(AA)] increased, the lowest PDI was obtained at 5.23 wt% RAFT and the molecular weights were consistent with the theoretical value as the RAFT agent percentage varied. The polymer neutralized by sodium hydroxide solution shows a low critical micelle concentration (CMC), which was <10^?2 mol L^?1 in water. The A_min values increased and showed a maximum with decreased AA chain length. TEM showed that the neutralized polymer formed a special vesicle structure with large pore structure which led to a low CMC and surface tension of water.     

节理倾角对岩石隧道掘进机破岩特性影响的数值研究

为研究节理特征对岩石隧道掘进机（TBM）盘形滚刀破岩特性的影响,采用颗粒离散元法（PFC）建立了不同节理倾角下双滚刀破岩模型并进行数值仿真,研究不同节理倾角对应的岩石破碎模式、裂纹数目和破岩比能。结果表明:（1）倾斜节理的存在改变了裂纹扩展规律,裂纹呈现不对称性扩展模式。节理的存在改变了裂纹的延伸方向,限制主裂纹向下扩展。节理倾角越大,对主裂纹的萌生与扩展起到的阻碍作用越明显。节理倾角较小时,裂纹沿节理倾向延伸,有利于双滚刀间裂隙的贯通,有利于岩石碎屑的剥落;（2）节理倾角对剪切裂纹的影响较小,主要影响拉裂纹数目。总裂纹数随节理倾角的增大先增大后减小,当节理倾角为30°时达到最大。从滚刀破岩效率来看,节理岩体存在一个最优节理倾角。当节理倾角在30°附近时,破岩比能最小,破岩效率最高。基于颗粒离散元法PFC2D可以较好地模拟节理岩体双滚刀破岩过程,弥补室内试验无法进行细观特性研究的缺陷。     

动载诱发冲击地压的实验研究

运用自主研发的冲击岩爆实验系统,进行了动载诱发冲击地压实验研究,提出了一种判别动载是否诱发冲击地压的实验方法。实验采用对加载至500 m深度应力状态下的带圆柱形贯穿孔洞的立方体砂岩试样,在σv方向逐级施加扰动波,σh保持在恒定应力水平的加载方式,模拟了500 m深度砂岩巷道,由于顶板垮落产生垂直向冲击扰动,由此诱发冲击地压破坏的过程。通过数据采集系统实时采集力和位移数据,获得应力应变曲线;通过图像采集系统实时拍摄动载诱发冲击地压过程,获得颗粒弹射、碎屑剥落等特征现象。实验发现,动载诱发冲击地压过程经历了平静期、颗粒弹射、碎屑剥落和冲击地压剧烈破坏4个阶段。对巷道围岩应力状态进行计算,得出动载诱发冲击地压时巷道围岩最大切向应力大于其单轴抗压强度。对碎屑特征及微观结构分析发现,动载诱发冲击地压产生的碎屑呈现出明显的片状特征,以中、细粒碎屑为主,通过电镜扫描可见穿晶裂纹。计算碎屑块度分形维数表明,动载诱发冲击地压破碎程度较单轴压缩破坏高。     

爆炸荷载下建筑玻璃的破坏研究综述

恐怖主义爆炸袭击和各种爆炸事件的发生,给人类及建筑物造成极大的伤害和破坏,其中大多数人员伤亡是由建筑玻璃破碎的碎片造成的。因此,抗爆玻璃性能的研究成为人们关注的热点。本文对抗爆玻璃结构、研究分析方法及爆炸荷载下建筑玻璃的破坏研究现状做了较全面的综述。     

One‐step synthesis of triarm block copolymers via simultaneous reversible‐addition fragmentation chain transfer and ring‐opening polymerization

One‐step synthesis of star copolymers by reversible addition–fragmentation chain transfer (RAFT) and ring‐opening polymerization (ROP) by using a novel dual initiator is reported. Triarm block copolymers comprising one polystyrene (or polyacrylamide) arm and two poly(β‐butyrolactone) arms were synthesized in one‐step by simultaneous RAFT polymerization of styrene (St) (or acrylamide, designated as AAm) and ROP of β‐butyrolactone (BL) in the presence of a novel trifunctional initiator, 1,2‐propanediol ethyl xanthogenate (RAFT‐ROP agent). This dual initiator was obtained through the reaction of 3‐chloro‐1,2‐propanediol with the potassium salt of ethyl xanthogenate. The principal parameters such as monomer concentration, initiator concentration, and polymerization time that affect the one‐step polymerization reaction were evaluated. The characterization of the products was achieved using Fourier‐transform infrared spectroscopy (FTIR), ¹H‐nuclear magnetic resonance (¹H‐NMR), ¹³C‐nuclear magnetic resonance (¹³C‐NMR), Gas chromatography–mass spectrometry (GC–MS), gel‐permeation chromatography (GPC), thermogravimetric analysis (TGA), and fractional precipitation (γ) techniques. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

基于图像分析的大米形状识别

提出了一种基于计算机图像分析的大米米胚脱落与颗粒破碎识别新方法。首先,将边缘曲线变换为极坐标形式,采用椭圆模板定位目标,获得一组与目标平移、旋转和尺度无关的形状描述数据;再运用小波变换提取奇异点及特征参数。取100颗样品进行验证,结果表明,该方法用于目标定位与识别时的鲁棒性强,可信度高。对米胚脱落、米粒破碎的判定正确率分别为98.9%、100%。