Evaluating the profile of myofibrillar proteins and its relationship with tenderness among five styles of dry-cured hams

In order to investigate the relationship between profile of myofibrillar proteins and tenderness among 2 kinds of Chinese hams (Jinhua and Xuanwei) and 3 kinds of European hams (Iberian, Serrano and Parma), shear force, myofibril fragmentation index (MFI), SDS-PAGE, carbonyls content and Raman spectroscopy were investigated. The shear force and salt content of Chinese hams were significantly higher than that of European hams, while moisture content was lower than that of European hams (p < 0.05). MFI values and SDS-PAGE profile revealed that the degradation of myofibrillar proteins in Chinese hams was lower than in European hams. In addition, Chinese hams showed significantly higher carbonyls content and β-sheet content compared with European hams, indicated that proteins aggregation intensively inhibited the degradation of myofibrillar proteins in Chinese hams. These results indicated that the higher shear force in Chinese style hams could be attributed to the lower moisture content and limited proteolysis.     

HPLC-Q-TOF MS法研究3种银杏双黄酮成分的质谱裂解途径

本研究采用高效液相色谱-串联四极杆飞行时间质谱(HPLC-Q-TOF MS)在负离子模式下分析3种银杏双黄酮(7-去甲基银杏双黄酮、金松双黄酮、异银杏双黄酮)的质谱裂解途径。结果表明,3种化合物具有相似的裂解途径,均易丢失CH 3OH和CO 2,且该类成分在Ⅰ—C环和Ⅱ—C环发生多种Retro-Diels-Alder(RDA)裂解,可进一步失去取代基,得到相应的特征碎片离子。该结论可为银杏双黄酮类的结构鉴定提供依据。     

含芳香氨基酸三肽及其衍生物自由基离子的形成和解离机理研究

铜-配体(L)-三肽组成的三元复合物［Cu(L)M］²⁺，其中，L表示4′-氯-2,2′:6′,2″-三联吡啶(缩写为4Cl-tpy)；M表示酪氨酰-甘氨酰-色氨酸(YGW)及其修饰型三肽(CH₃CO-YGW-OCH₃，缩写 Ac-YGW-OMe)。使用该复合物，通过碰撞诱导解离 (collision-induced dissociation, CID)产生两种自由基离子 (［YGW］^·+和［Ac-YGW-OMe］^·+)。采用串联质谱结合密度泛函理论 (density functional theory, DFT)得到气相稳定结构，并研究其气相解离行为。研究结果表明，［YGW］^·+和［Ac-YGW-OMe］^·+的气相解离行为截然不同，［YGW］^·+主要产生［M-CO₂-116］⁺和［M-CO₂］^·+碎片离子；而［Ac-YGW-OMe］^·+在气相中主要产生［M-CH₃OH］^·+碎片离子。推测这两种离子的气相裂解机理分别为：［YGW］^·+羧基上的质子重排到多肽骨架中羰基氧上，经历 C_α-C键的断裂产生［M-CO₂］^·+、断裂色氨酸侧链 C_β-C_γ键产生［M-CO₂-116］⁺离子；［Ac-YGW-OMe］^·+则先经历质子重排到酯基氧上，然后经过C-O酯键的断裂形成［M-CH₃OH］^·+离子。参与重排的质子可能有3个来源：Ac-YGW-OMe中甘氨酸的C_α-H、色氨酸的C_α-H 或C_β-H，该机理有待进一步验证。本研究将为其他类型多肽及衍生物的结构及气相反应机理研究提供参考。     

The effect of various fire‐exposed surface dimensions on the spalling of concrete specimens

Concrete spalling due to fire exposure is often defined as the sudden detachment of fragments from a concrete surface. It can be quantified by various parameters of which weight loss and spalling depth are the most common ones. The risk of spalling is influenced by many factors such as concrete composition, heating rate and applied testing methods. A reduced scale testing method should be developed to analyse the spalling behaviour and to understand its effectiveness in more detail. As a subsection of this development, this study aimed to analyse the effect of different‐sized, circular heated areas in semi full‐scale fire tests. Therefore, vermiculite slabs with varying cut‐outs in their centre were placed between a specimen made of a spalling‐sensitive concrete and the combustion chamber. The combustion chamber was heated following a standard fire curve. Our experimental results show that the thermal expansion inside of equal‐sized specimens is strongly dependent on the size of the heated area. In addition, this area also affects thermal stresses. They decrease as a result of lower temperature gradients for tests with smaller unheated boundary areas. Apart from this, the analysis of fragments shows no correlation between their relative volume distribution and the heated area. Copyright © 2014 John Wiley & Sons, Ltd.     

Study of fragmentation in cBN powders under ultra-high pressure

Studying the fragmentation law and refinement of cubic boron nitride powder under ultra-high pressure is crucial to producing a high-strength, high-density polycrystalline cubic boron nitride. In this paper, brown and black cBN crystalline powders with different micron sizes were selected as initial raw materials for an ultra-high-pressure simulation experiment. Single and mixed particles were extruded under 80MPa low pressure and 5.5GPa ultra-high pressure at ambient temperature for 1 min. The crushing behavior and particle size distribution of cBN powders with different particle sizes and ratios were investigated using a laser particle size analyzer and scanning electron microscopy. Results revealed no particle breakage or deformation at low pressure, and the compaction density was low. However, under ultra-high pressure, the cBN particles showed cracks, plastic deformation, and fragmentation, resulting in crushed fine particles filling in the voids of coarse particles, which led to a higher pressing density. Small-sized or mixed cBN particles with high density ratios were not easily crushed; the coarser the particle size, the more severe the ultra-high-pressure extrusion and crushing. The pressing density also declined, and brown cBN crystal particles with higher impact toughness demonstrated a lower particle breakage rate. The ultra-high-pressure crushing law should be considered and appropriate binders should be selected to improve the sintering performance of PcBN materials; ultra-high-pressure crushing of cBN powder contributes to cBN-cBN and cBN-M-cBN bonds under high temperatures and ultra-high pressure.     

崩落矿石块度对放矿的影响分析

从散体力学的角度，分析了矿石块度大小、粗颗粒矿石含量对抗剪强度的影响。通过室内模拟试验，深入研究了放矿过程中崩落矿石块度对放矿规律及放出体大小的影响，得出了矿石块度组成是影响放出体形状和大小的重要因素的结论，对现场生产具有指导意义。     

放顶煤工作面顶煤破碎机理研究

结合我国放顶煤开采的实践，对放顶煤工作面顶煤的破碎和移动规律及上覆岩层的活动规律进行了研究，指出了开采深度、煤层强度、支架支护强度及煤层厚度等是影响顶煤破碎和放顶煤效果的主要因素。同时指出了顶煤的破碎是顶煤与上覆岩层相互作用的结果，而支架仅起辅助破煤的作用。并在此提出了顶煤破碎分区。     

爆炸冲击能和膨胀能破岩作用机理研究

为研究岩石破碎过程中爆炸应力波与爆生气体膨胀的作用，进行了耦合装药爆破实验。结果表明，耦合装药爆破时爆炸冲击能（Ｅｓ）和部分膨胀能（Ｅｂ）进行冲击加载，在介质中依次激起原生和次生爆炸应力波。不同Ｅｓ／Ｅｂ比值条件下，介质爆破致裂效果与破碎质量出现明显差异的主要原因，是这两个应力波加载水平发生了变化，进而影响到介质的爆破破裂行为。由此认为，Ｅｓ和部分Ｅｂ在破岩过程中所起的主要作用，是通过应力波与缺陷相互作用使岩石产生破裂的方式进行的；以（准）静态形式存在的部分Ｅｂ的主要作用，是促使爆破块度与岩体分离。     

新型广谱金刚石破碎岩石工具的研制

新型广谱金刚石钻头由钻头钢体和金刚石刀头组成。金刚石刀头由若干含金刚石孕镶层和纯合金层相间组成。该新型金刚石钻头破碎岩石是以金刚石破碎为主、以破碎穴效应为辅的方式进行的。其特点是破碎岩石效率较高，对岩石的适应性较强，使用寿命高，钻头的导向性及工作稳定性较好，钻进效果与钻进质量明显提高。