Rheology of natural fibers thermoplastic compounds: Flow length and fiber distribution

The presented study investigates the flow length and the corresponding fiber content distribution in the injection‐moulded natural fiber reinforced thermoplastics and its relation to fiber type and processing parameters such as injection pressure, temperature, injection rate and mould tempering by increasing die temperature. In this research, polypropylene compounds with nominally 30 wt % hemp and sisal fibers are investigated. The influence of the injection pressure (500 and 1000 bar), melt temperature (180°C, 200°C, and 220°C), and die temperature (23°C and 80°C) on the fiber content distribution all over the sample is investigated. An increasing linear trend of fiber content along the spiral length is observed as an evidence of a fiber/polymer multiflow system. A pattern for fiber content distribution with respect to the fiber length along the injected spiral can be distinguished, where the longer fibers are usually found at the end of the injected part and the shorter fibers remain near mould entrance point. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39861.     

添加碳纳米管对选区激光熔化AlSi10Mg合金缺陷的影响

利用选区激光熔化成形技术制备了纯AlSi10Mg合金及碳纳米管(carbon nanotubes,CNTs)-AlSi10Mg复合材料。当添加CNTs含量为0.05%(质量分数)时具有一定增强效果,但随着CNTs添加量增大,复合材料性能却因为缺陷的增加而明显下降。木实验利用纳米CT技术对纯合金及CNTs(0.5%)-AlSi10Mg复合材料进行缺陷的三维重构。结果表明,添加0.5%的CNTs后,成形缺陷体积所占比例由12%增加至46%;气孔型缺陷数量明显增加,并且等效直径相对较大。CNTs在粉体中的团聚及对气体的吸附作用是两种类型缺陷增加的根本原因。     

Early Herbivore Alert: Insect Eggs Induce Plant Defense

Plants are able to “notice” insect egg deposition and to respond by activating direct and indirect defenses. An overview of these defenses and the underlying mechanisms is given from a tritrophic perspective. First, the interface between plant and eggs is addressed with respect to the mode of attachment of eggs on the plant surface. It is elucidated which plant cells might respond to components from insect eggs or the egg deposition. The scarce knowledge on the elicitors associated with the eggs or the egg-laying female is outlined. Since endosymbiotic microorganisms are often present on the eggs, and microorganisms are also abundant on the leaf surface, the role of these hidden players for eliciting oviposition-induced plant responses is considered. Furthermore, the question of which physiological and molecular processes are induced within the plant in response to egg deposition is addressed. Second, studies on the response of the herbivorous insect to oviposition-induced plant defenses are outlined. Third, the importance of oviposition-induced plant volatiles and contact cues for host and prey location of parasitoids and predators is discussed in the context of other informative chemicals used by carnivores when searching for food. Finally, physiological and ecological costs of oviposition-induced plant responses are addressed.     

Condensation Detection Using a Wirelessly Powered RF-Temperature Sensor

The formation of condensation on windshields can be counteracted and even prevented through the concerted use of an automobile heating, ventilation, and air-conditioning (HVAC) system. By anticipating the formation of dew, through the temperature of the windshield and dew point in the cabin, a condensation-free windshield can be ensured. A new approach toward a system for condensation detection is reported. It uses an actively powered humidity sensor, as well as a remotely and wirelessly powered temperature sensor system. The wirelessly powered temperature detector, which may be embedded in the windshield of an automobile, obtains its energy via an inductively coupled magnetic field and simultaneously transmits data through a load-modulation technique. Such a system approach offers advantages in terms of cost, system life, and maintenance, in comparison with existing wired systems and other wireless solutions. The system is implemented using off-the-shelf components and is discretely designed around application-specific resonant tanks. The resonant tanks were mathematically characterized and compared with measured values. The read range of the wirelessly powered condensation detector at a frequency of 13.56 MHz is more than 4 cm while consuming a maximum power of approximately 2 mW. The application of this technology as part of a climate-control system is discussed in this paper. System concept, design considerations, and prototype characterization are also included.     

Two-color DNA nanoprobe of intracellular dynamics

We have developed a correlation microscopy technique to follow the dynamics of quantum dot labeled DNA within living cells. The temporal correlation functions of the labels reflect the fluctuations of the DNA nanoprobe as a result of its interactions with the cellular environment. They provide a sensitive measure for the length of the probe on the scale of a persistence length (～50 nm) and reveal strong nonthermal dynamics of the cell. These results pave the way for dynamic observations of DNA conformational changes in vivo.     

On the role of DNA biomechanics in the regulation of gene expression

DNA is traditionally seen as a linear sequence of instructions for cellular functions that are expressed through biochemical processes. Cellular DNA, however, is also organized as a complex hierarchical structure with a mosaic of mechanical features, and a growing body of evidence is now emerging to imply that these mechanical features are connected to genetic function. Mechanical tension, for instance, which must be felt by DNA within the heavily constrained and continually fluctuating cellular environment, can affect a number of regulatory processes implicating a role for biomechanics in gene expression complementary to that of biochemical regulation. In this article, we review evidence for such mechanical pathways of genetic regulation.     

木聚糖酶固态罐发酵及尾气在线测定

建立了可对 4个各自独立的 2L玻璃发酵罐同时通气培养和尾气检测的固态发酵系统(SSF) ,以 1 0 0g麸皮和 1 0 0g木屑及 1 5 0mLMandels营养盐溶液为培养基进行木霉T6培养 ,在实验条件范围内找出了最佳产木聚糖酶的环境条件 ,即温度为 3 0℃ ,pH6.0 ,接种量 2 5mL/罐 ( 2× 1 0 8～ 4×1 0 8个孢子 /mL) ,通过对木聚糖酶活力和尾气中CO2 变化的连续测定显示 ,菌体CO2 的释放与木聚糖酶合成具有一定的相关性 ,木聚糖酶的合成与尾气中CO2 含量之间存在着滞后关系 ,尾气CO2浓度在发酵 2 6h达到最高值 ,木聚糖酶活力在 3 9h才达峰值。通过对SSF尾气中CO2 的在线测定 ,能够初步了解SSF中菌丝体生长和产物合成之间的动力学关系     

Analysis of Volatiles Induced by Oviposition of Elm Leaf Beetle Xanthogaleruca luteola on Ulmus minor

Egg deposition of the elm leaf beetle Xanthogaleruca luteola causes the emission of volatiles from its food plant, Ulmus minor. These volatiles are exploited by the egg parasitoid, Oomyzus gallerucae, to locate its host. In contrast to other tritrophic systems, the release of volatiles is not induced by feeding but by egg deposition. Previous investigations showed that the release is systemic and can be triggered by jasmonic acid. Comparison of headspace analysis revealed similarities in the blend of volatiles emitted following egg deposition and feeding. The mixture consists of more than 40 compounds; most of the substances are terpenoids. Leaves next to those carrying eggs emit fewer compounds. When treated with jasmonic acid, leaves emit a blend that consists almost exclusively of terpenoids. Dichloromethane extracts of leaves treated with jasmonic acid were also investigated. After separation of extracts of jasmonate induced elm leaves on silica, we obtained a fraction of terpenoid hydrocarbons that was attractive to the parasitoids. This indicates that jasmonic acid stimulates the production of terpenoid hydrocarbons that convey information of egg deposition to the parasitoid.     

Sequence analysis of Tn10 insertion sites in a collection of Escherichia coli strains used for genetic mapping and strain construction

The chromosomal insertion sites of Tn10-containing Escherichia coli strains were amplified by inverse PCR, and the nucleotide sequences of the junctions were determined. In 95 strains analyzed, 88 unique Tn10 positions were determined and matched to the E. coli chromosome sequence. Two gaps in insertion site positions were noted, one including the terminus of DNA replication and another bounded by recombination hot spots RhsA and RhsB.