PYY modulation of cortical and hypothalamic brain areas predicts feeding behaviour in humans

The ability to maintain adequate nutrient intake is critical for survival. Complex interrelated neuronal circuits have developed in the mammalian brain to regulate many aspects of feeding behaviour, from food-seeking to meal termination. The hypothalamus and brainstem are thought to be the principal homeostatic brain areas responsible for regulating body weight. However, in the current 'obesogenic' human environment food intake is largely determined by non-homeostatic factors including cognition, emotion and reward, which are primarily processed in corticolimbic and higher cortical brain regions. Although the pleasure of eating is modulated by satiety and food deprivation increases the reward value of food, there is currently no adequate neurobiological account of this interaction between homeostatic and higher centres in the regulation of food intake in humans. Here we show, using functional magnetic resonance imaging, that peptide YY3-36 (PYY), a physiological gut-derived satiety signal, modulates neural activity within both corticolimbic and higher-cortical areas as well as homeostatic brain regions. Under conditions of high plasma PYY concentrations, mimicking the fed state, changes in neural activity within the caudolateral orbital frontal cortex predict feeding behaviour independently of meal-related sensory experiences. In contrast, in conditions of low levels of PYY, hypothalamic activation predicts food intake. Thus, the presence of a postprandial satiety factor switches food intake regulation from a homeostatic to a hedonic, corticolimbic area. Our studies give insights into the neural networks in humans that respond to a specific satiety signal to regulate food intake. An increased understanding of how such homeostatic and higher brain functions are integrated may pave the way for the development of new treatment strategies for obesity.     

Intermediates in the transformation of phosphonates to phosphate by bacteria

Phosphorus is an essential element for all known forms of life. In living systems, phosphorus is an integral component of nucleic acids, carbohydrates and phospholipids, where it is incorporated as a derivative of phosphate. However, most Gram-negative bacteria have the capability to use phosphonates as a nutritional source of phosphorus under conditions of phosphate starvation. In these organisms, methylphosphonate is converted to phosphate and methane. In a formal sense, this transformation is a hydrolytic cleavage of a carbon-phosphorus (C-P) bond, but a general enzymatic mechanism for the activation and conversion of alkylphosphonates to phosphate and an alkane has not been elucidated despite much effort for more than two decades. The actual mechanism for C-P bond cleavage is likely to be a radical-based transformation. In Escherichia coli, the catalytic machinery for the C-P lyase reaction has been localized to the phn gene cluster. This operon consists of the 14 genes phnC, phnD, …, phnP. Genetic and biochemical experiments have demonstrated that the genes phnG, phnH, …, phnM encode proteins that are essential for the conversion of phosphonates to phosphate and that the proteins encoded by the other genes in the operon have auxiliary functions. There are no functional annotations for any of the seven proteins considered essential for C-P bond cleavage. Here we show that methylphosphonate reacts with MgATP to form α-D-ribose-1-methylphosphonate-5-triphosphate (RPnTP) and adenine. The triphosphate moiety of RPnTP is hydrolysed to pyrophosphate and α-D-ribose-1-methylphosphonate-5-phosphate (PRPn). The C-P bond of PRPn is subsequently cleaved in a radical-based reaction producing α-D-ribose-1,2-cyclic-phosphate-5-phosphate and methane in the presence of S-adenosyl-L-methionine. Substantial quantities of phosphonates are produced worldwide for industrial processes, detergents, herbicides and pharmaceuticals. Our elucidation of the chemical steps for the biodegradation of alkylphosphonates shows how these compounds can be metabolized and recycled to phosphate.     

Evidence for a spin-aligned neutron-proton paired phase from the level structure of (92)Pd

Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus (92)Pd. Gamma rays emitted following the (58)Ni((36)Ar,2n)(92)Pd fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.     

Structures of APC/C(Cdh1) with substrates identify Cdh1 and Apc10 as the D-box co-receptor

The ubiquitylation of cell-cycle regulatory proteins by the large multimeric anaphase-promoting complex (APC/C) controls sister chromatid segregation and the exit from mitosis. Selection of APC/C targets is achieved through recognition of destruction motifs, predominantly the destruction (D)-box and KEN (Lys-Glu-Asn)-box. Although this process is known to involve a co-activator protein (either Cdc20 or Cdh1) together with core APC/C subunits, the structural basis for substrate recognition and ubiquitylation is not understood. Here we investigate budding yeast APC/C using single-particle electron microscopy and determine a cryo-electron microscopy map of APC/C in complex with the Cdh1 co-activator protein (APC/C(Cdh1)) bound to a D-box peptide at ～10 ? resolution. We find that a combined catalytic and substrate-recognition module is located within the central cavity of the APC/C assembled from Cdh1, Apc10--a core APC/C subunit previously implicated in substrate recognition--and the cullin domain of Apc2. Cdh1 and Apc10, identified from difference maps, create a co-receptor for the D-box following repositioning of Cdh1 towards Apc10. Using NMR spectroscopy we demonstrate specific D-box-Apc10 interactions, consistent with a role for Apc10 in directly contributing towards D-box recognition by the APC/C(Cdh1) complex. Our results rationalize the contribution of both co-activator and core APC/C subunits to D-box recognition and provide a structural framework for understanding mechanisms of substrate recognition and catalysis by the APC/C.     

火灾对混凝土结构性能影响的研究

通过对比大量文献资料,分析了火灾高温对混凝土强度的影响,抗拉强度随温度的变化规律,以及不同的冷却方式对高温后混凝土强度的影响;分析了影响钢筋与混凝土高温粘结性能的因素及粘结性能随温度变化的趋势;总结了不同温度对不同类型钢筋抗拉强度的影响,并对今后的研究提出了一些建议.     

Cramer法则在分式不等式证明中的应用

运用Cramer法则的工具,解决了一类分式不等式的证明问题,把数学知识进行高初的有机结合是对数学创新的一个重要目的.     

超支化不饱和聚(酰胺-酯)的改性及热分解动力学

采用不同链长的十四酰氯和十八酰氯对超支化不饱和聚(酰胺-酯)(MHBP)的端羟基进行原位端基改性,制备出2种改性超支化聚合物,用傅立叶红外光谱(FTIR)、热重分析(TGA)、黏度法等对其结构及性能进行表征,并研究了它们的热分解行为及其热分解动力学.结果表明,其热分解反应不是一级反应,改性超支化聚合物的热稳定性与末端烷烃链的长度有关,用Ozawa法求出了热分解表观活化能.     

Cryptic subarctic diversity: a new bumblebee species from the Yukon and Alaska (Hymenoptera: Apidae)

It is nearly 90 years since a bumblebee species has been described for the first time from Canada or the USA that was previously unrecognised by science. We describe and illustrate Bombus(Alpinobombus) kluanensis sp. nov. and begin to map its distribution. This species was discovered through analysis of Cytochrome c Oxidase subunit I barcodes and had been unsuspected on the basis of morphological and colour characteristics. So far, 247 female specimens considered to belong to this species are known from the subarctic mountains associated with the Denali Fault running from the Alaska Range (Alaska, USA) to Kluane in the Saint Elias Mountains (Yukon, Canada). A checklist of all species of the subgenus Alpinobombus worldwide is provided.

http://zoobank.org/urn:lsid:zoobank.org:pub:78D524DD-FFBA-4BC4-8D39-3EF4F6BDD39E     

On the Difficulty of Measuring Forecasting Skill in Financial Markets

The use of correlation between forecasts and actual returns is commonplace in the literature, often used as a measurement of investors' skill. A prominent application of this is the concept of the information coefficient (IC). Not only can the IC be used as a tool to rate analysts and fund managers but it also represents an important parameter in the asset allocation and portfolio construction process. Nevertheless, a theoretical understanding of it has typically been limited to the partial equilibrium context where the investing activities of each agent have no effect on other market participants. In this paper we show that this can be an undesirable oversimplification and we demonstrate plausible circumstances in which conventional empirical measurements of IC can be highly misleading. We suggest that improved understanding of IC in a general equilibrium setting can lead to refined portfolio decision making ex ante and more informative analysis of performance ex post. Copyright © 2015 John Wiley & Sons, Ltd.     

中频反应磁控溅射Al2O3薄膜的光学性质

采用中频反应磁控溅射技术在玻璃基片上制备了Al2O3薄膜,提出了一种利用透射光谱来简单有效地分析弱吸收薄膜的光学特性及与光学相关的其他物理特性的方法.对Al2O3薄膜进行透射谱测量,通过对薄膜折射率、吸收系数、膜厚度与入射光波长相互关系的分析,获得了Al2O3薄膜在400~1 100 nm区域内的折射率、吸收系数与入射光波长的关系式,以及Al2O3薄膜厚度的计算公式.