Fast Positive Feedback Between the Adrenocortical Stress Response and a Brain Mechanism Involved in Aggressive Behavior.

Aggressive behavior induces an adrenocortical stress response, and sudden stressors often precipitate violent behavior. Experiments in rats revealed a fast, mutual, positive feedback between the adrenocortical stress response and a brain mechanism controlling aggression. Stimulation of the aggressive area in the hypothalamus rapidly activated the adrenocortical response, even in the absence of an opponent and fighting. Hypothalamic aggression, in turn, was rapidly facilitated by a corticosterone injection in rats in which the natural adrenocortical stress response was prevented by adrenalectomy. The rapidity of both effects points to a fast, mutual, positive feedback of the controlling mechanisms within the time frame of a single conflict. Such a mutual facilitation may contribute to the precipitation and escalation of violent behavior under stressful conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanical properties of freely suspended semiconducting graphene-like layers based on MoS2

We fabricate freely suspended nanosheets of molybdenum disulphide (MoS₂) which are characterized by quantitative optical microscopy and high-resolution friction force microscopy. We study the elastic deformation of freely suspended nanosheets of MoS₂ using an atomic force microscope. The Young''s modulus and the initial pre-tension of the nanosheets are determined by performing a nanoscopic version of a bending test experiment. MoS₂ sheets show high elasticity and an extremely high Young''s modulus (0.30 TPa, 50% larger than steel). These results make them a potential alternative to graphene in applications requiring flexible semiconductor materials.PACS, 73.61.Le, other inorganic semiconductors, 68.65.Ac, multilayers, 62.20.de, elastic moduli, 81.40.Jj, elasticity and anelasticity, stress-strain relations.     

推动电视观赏体验新革命

随着价格合理、以硬盘为基础的个人录像机(PVRs)的出现,以及宽带IP(网络协议)连接的全面普及,人们的电视观赏体验也在彻底改变.消费者不必再按照电视公司设定的时间表收看节目.他们可以透过"时空转换(Timeshift)",选择自己方便的时段播放节目,或从影片点播服务器下载节目,并且确保数字影片格式丝毫不会影响观赏效果.     

网络化环境中的内容共享

融合与互连继续推动着消费类电子产业.与以前相比,当今的电子设备具有更多功能、更大内存和更高级的通信性能.因此,在越来越多的设备上,消费者可以采集、存储和播放音频、视频以及静态图像.     

驾御新技术浪潮的印刷业

●变革的冲击 20世纪80年代下半叶当数字技术开始进入印刷业时,我们曾经一度大谈过技术变革浪潮的来临.比如,我们许多人都记得当时有一个简捷的提法,即用以描述通用印前平台取代传统专用系统的所谓"第三次浪潮".     

Interactions between simultaneously activated behavioral systems in the rat.

Interactions between electrically induced attack and teeth-chattering from 1 electrode and grooming from another were examined in male albino rats. The interaction between electrically induced attacks and deprivation-induced feeding, as well as the effect of food deprivation on attack, was also studied. Results indicate that attack appears to be a dominant response, for it suppressed grooming and feeding at a low level of activation. On the other hand, it was not affected by simultaneously induced grooming or feeding. However, food deprivation decreased the threshold for attack, leaving attack latency, attack form, or bite targets unaffected. Teeth-chattering, suggested to be related to attack and flight, was also a dominant response. Results suggest that interactions between behavioral systems are in favor of the systems that must act acutely on activation in order to survive. Apparently, the regulations governing these interactions are represented in the functional organization of the brain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modifications in Booth's method for the spectrophotometric determination of?-carotene in vegetables

Summary Booth's method for the spectrophotometric determination ofß-carotene gives reliable results, but the extraction method is very laborious and tedious. Removal of the acetone from the extract and elution of the acetone-free extract on the adsorption column also require much time and attention. The authors describe the modifications made to these three parts of Booth's method for the determination of carotene. The simultaneous application of Booth's original method and of the modified method to samples of carrots, five leafy vegetables and four brassicas gave, in general, corresponding results. With brassicas a tendency was observed for the modified method to yield lower carotene contents. Using the modified method, with pureß-carotene added to samples of carrots and spinach, the authors found recoveries of 98%–100% and 86%–88% respectively.

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Modifikationen der spektrophotometrischenß-Carotin-Bestimmung nach Booth in Gemüse

Zusammenfassung Die Ergebnisse der spektrophotometrischenß-Carotin-Bestimmung nach Booth sind zuverlässig, aber die damit verbundene Extraktionsmethode ist arbeitsintensiv und strapaziös. Auch das Entfernen von Aceton aus dem Extrakt und das Eluieren des acetonfreien Extrakts auf der Säule erfordert viel Zeit und Aufmerksamkeit. Die Autoren beschreiben die von ihnen angebrachten Modifikationen dieserß-Carotin-Bestimmung in den drei Stufen. Die gleichzeitige Anwendung der ursprünglichen Methode nach Booth und deren Modifikation brachte bei Karotten, fünf Blattgemüsen und vier Kohlarten im allgemeinen ähnliche Ergebnisse. Bei den Kohlarten war die Tendenz zu beobachten, daß mit der modifizierten Methode dieß-Carotingehalte etwas niedriger waren. Die modifizierte Methode hatte eine Rückgewinnungsquote von 98–100% bzw. 86–88% bei einem Zusatz von reinemß-Carotin zu Karotten- und Spinatproben.

     

Shallow and Undoped Germanium Quantum Wells: A Playground for Spin and Hybrid Quantum Technology

Buried‐channel semiconductor heterostructures are an archetype material platform for the fabrication of gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface; however, nearby surface states degrade the electrical properties of the starting material. Here, a 2D hole gas of high mobility (5 × 10⁵ cm² V^?1 s^?1) is demonstrated in a very shallow strained germanium (Ge) channel, which is located only 22 nm below the surface. The top‐gate of a dopant‐less field effect transistor controls the channel carrier density confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The high mobility leads to mean free paths ≈ 6 µm, setting new benchmarks for holes in shallow field effect transistors. The high mobility, along with a percolation density of 1.2 × 10¹¹cm^?2, light effective mass (0.09m_e), and high effective g‐factor (up to 9.2) highlight the potential of undoped Ge/SiGe as a low‐disorder material platform for hybrid quantum technologies.     

Femtogram doubly clamped nanomechanical resonators embedded in a high-Q two-dimensional photonic crystal nanocavity

We demonstrate a new optomechanical device system which allows highly efficient transduction of femtogram nanobeam resonators. Doubly clamped nanomechanical resonators with mass as small as 25 fg are embedded in a high-finesse two-dimensional photonic crystal nanocavity. Optical transduction of the fundamental flexural mode around 1 GHz was performed at room temperature and ambient conditions, with an observed displacement sensitivity of 0.94 fm/Hz(1/2). Comparison of measurements from symmetric and asymmetric double-beam devices reveals hybridization of the mechanical modes where the structural symmetry is shown to be the key to obtain a high mechanical quality factor. Our novel configuration opens the way for a new category of "NEMS-in-cavity" devices based on optomechanical interaction at the nanoscale.