Changes in Heartwood Chemistry of Dead Yellow-Cedar Trees that Remain Standing for 80 Years or More in Southeast Alaska

We measured the concentrations of extractable bioactive compounds in heartwood of live yellow-cedar (Chamaecyparis nootkatensis) trees and five classes of standing snags (1–5, averaging 4, 14, 26, 51, and 81 years-since-death, respectively) to determine how the concentrations changed in the slowly deteriorating snags. Three individuals from each of these six condition classes were sampled at four sites spanning a 260-km distance across southeast Alaska, and the influence of geographic location on heartwood chemistry was evaluated. Cores of heartwood were collected at breast height and cut into consecutive 5-cm segments starting at the pith. Each segment was extracted with ethyl acetate and analyzed by gas chromatography. Concentrations of carvacrol, nootkatene, nootkatol, nootkatone, nootkatin, and total extractives (a sum of 16 compounds) for the inner (0–5 cm from pith), middle (5–10 cm from pith), and surface (outer 1.1–6.0 cm of heartwood) segments from each core were compared within each tree condition class and within segments across condition classes. Heartwood of class 1 and 2 snags had the same chemical composition as live trees. The first concentration changes begin to appear in class 3 snags, which coincides with greater heartwood exposure to the external environment as decaying sapwood sloughs away, after losing the protective outer bark. Within core segments, the concentrations of all compounds, except nootkatene, decrease between snag classes 2 and 5, resulting in the heartwood of class 5 snags having the lowest quantities of bioactive compounds, although not different from the amounts in class 4 snags. This decline in chemical defense is consistent with heartwood of class 5 snags being less decay-resistant than heartwood of live trees, as observed by others. The unique heartwood chemistry of yellow cedar and the slow way it is altered after death allow dead trees to remain standing for up to a century with a profound impact on the ecology of forests in southeast Alaska where these trees are in decline.     

Structure-aided optimization of kinase inhibitors derived from alsterpaullone

In order to perform computer-aided design of novel alsterpaullone derivatives, the vicinity of the entrance to the ATP-binding site was scanned for areas that could be useful as anchoring points for additional protein-ligand interactions. Based on the alignment of alsterpaullone in a CDK1/cyclin B homology model, substituents were attached to the 2-position of the parent scaffold to enable contacts within the identified areas. Synthesis of the designed structures revealed three derivatives (3-5) with kinase-inhibitory activity similar to alsterpaullone. The novel 2-cyanoethylalsterpaullone (7) proved to be the most potent paullone described so far, exhibiting inhibitory concentrations for CDK1/ cyclin B and GSK-3beta in the picomolar range.     

实现多射频的软硬件方案

今天,忙碌穿梭的消费者也许觉得随身携带的不过是一台手机,而实际上,他们正带着七个以上射频,用于处理多频段蜂窝工作、Wi—Fi网络、蓝牙连接、辅助GPS（全球定位系统）等等功能。今后,他们还会拥有实现Adhoc式设备间通信的射频,     

开车和走路时不用电话

手机市场有巨大的潜力。高通公司首席运营官兼高通CDMA技术总裁sanjay K Jha在今年6月11日的设计自动化研讨会的主题演讲中称,今天的无线用户有20亿,而到2020年,将有90亿人成为潜在的客户（摩托罗拉后来雇用Jha为协作首席执行官）。Jha也指出了这个爆炸性市场的一个缺陷：90亿潜在用户中,很多人在手机上的花费不超过15美元或20美元。     

手工式模拟设计获得自动化辅助

模拟仿真器与设计捕捉工具在EDA市场已有长久的历史,这个市场一直在为数字仿真器增加某些Spice。不过,当仿真结果要转换为正弦波和硅片时,模拟EDA工具就会远远落后于数字EDA工具的水平。这种情况正在开始改变,传统数字EDA供应商正在出现以纳米尺度数字工艺支持模拟功能晶圆制作的工具。另外,代工厂专用工具包也正在简化用模拟工艺实现模拟、RF大电压功能的过程。     

Reduced‐scale test to assess the effect of fire barriers on the flaming combustion of cored composites: An upholstery‐material case study

Herein, we describe a reduced‐scale test (“Cube” test), measuring the fire performance of specimens including a fire barrier (FB) and a flammable core material, which acts as the main fuel load. The specimen is intended to reproduce a cross‐section of a composite product where heat/mass transfer occurs primarily in a direction perpendicular to the FB. The Cube test procedure and benefits are discussed in this work by adopting residential upholstery furniture as an exemplary study. One flexible polyurethane foam, one polypropylene cover fabric, and 10 commercially available FBs were selected. They were used to compare the fire performance of FBs, measured in terms of peak of heat release rate, in the ASTM E1474‐14 standard test and the newly developed Cube test. Edge effects severely affected the performance of FBs in the ASTM E1474‐14 standard test but not in the Cube test. Furthermore, appropriate test conditions were determined in the Cube test to measure the so‐called “wetting point,” that is, the time and value of heat release rate measured when flammable liquid products were first observed on the bottom of the specimen. The relevance of the “wetting point” in terms of full‐scale fire performance and failure mechanism of FBs is discussed.     

Unrelated toxin–antitoxin systems cooperate to induce persistence

Persisters are drug-tolerant bacteria that account for the majority of bacterial infections. They are not mutants, rather, they are slow-growing cells in an otherwise normally growing population. It is known that the frequency of persisters in a population is correlated with the number of toxin–antitoxin systems in the organism. Our previous work provided a mechanistic link between the two by showing how multiple toxin–antitoxin systems, which are present in nearly all bacteria, can cooperate to induce bistable toxin concentrations that result in a heterogeneous population of slow- and fast-growing cells. As such, the slow-growing persisters are a bet-hedging subpopulation maintained under normal conditions. For technical reasons, the model assumed that the kinetic parameters of the various toxin–antitoxin systems in the cell are identical, but experimental data indicate that they differ, sometimes dramatically. Thus, a critical question remains: whether toxin–antitoxin systems from the diverse families, often found together in a cell, with significantly different kinetics, can cooperate in a similar manner. Here, we characterize the interaction of toxin–antitoxin systems from many families that are unrelated and kinetically diverse, and identify the essential determinant for their cooperation. The generic architecture of toxin–antitoxin systems provides the potential for bistability, and our results show that even when they do not exhibit bistability alone, unrelated systems can be coupled by the growth rate to create a strongly bistable, hysteretic switch between normal (fast-growing) and persistent (slow-growing) states. Different combinations of kinetic parameters can produce similar toxic switching thresholds, and the proximity of the thresholds is the primary determinant of bistability. Stochastic fluctuations can spontaneously switch all of the toxin–antitoxin systems in a cell at once. The spontaneous switch creates a heterogeneous population of growing and non-growing cells, typical of persisters, that exist under normal conditions, rather than only as an induced response. The frequency of persisters in the population can be tuned for a particular environmental niche by mixing and matching unrelated systems via mutation, horizontal gene transfer and selection.     

Statistical reasoning in diagnostic problem-solving—The case of flow-rate measurements

There are various methods for measuring flow rates in rivers, but all of them have practical issues and challenges. A period of exceptionally high water levels revealed substantial discrepancies between two measurement setups in the same waterway. Finding a causal explanation of the discrepancies was important, as the problem might have ramifications for other flow-rate measurement setups as well. Finding the causes of problems is called diagnostic problem-solving. We applied a branch-and-prune strategy, in which we worked with a hierarchy of hypotheses, and used statistical analysis as well as domain knowledge to rule out options. We were able to narrow down the potential explanations to one main suspect and an alternative explanation. Based on the analysis, we discuss the role of statistical techniques in diagnostic problem-solving and reasoning patterns that make the application of statistics powerful. The contribution to theory in statistics is not in the individual techniques but in their application and integration in a coherent sequence of studies – a reasoning strategy.     

夏普 对应“迅驰”的平板电脑登场

2003年1月9日,英特尔(Intel)发表了全新的无线上网技术--迅驰。迅驰技术的发布,使我们的网络生活开始改变,随时随地、无拘无束的上网冲浪成为了今后发展的一个重点。目前开始在市场上应用迅驰技术的产品有笔记本电脑和平板电脑(Tablet PC)两种,本质上两种产品基本上相同。相比传统笔记本电脑,平板电脑时尚的色彩更浓厚一些。记得3月份的时候,宏基推出了全球首款基于迅驰技术的平板电脑,推出后的反响十分强烈。     

Analysis of computational problems expressing the overall uncertainties: photons, neutrons and electrons

In the frame of the EU Coordination Action CONRAD (coordinated network for radiation dosimetry), WP4 was dedicated to work on computational dosimetry with an action entitled 'Uncertainty assessment in computational dosimetry: an intercomparison of approaches'. Participants attempted one or more of eight problems. This paper presents the results from problems 4-8-dealing with the overall uncertainty budget estimate; a short overview of each problem is presented together with a discussion of the most significant results and conclusions. The scope of the problems discussed here are: the study of a (137)Cs calibration irradiator; the manganese bath technique; the iron sphere experiment using neutron time-of-flight technique; the energy response of a RADFET detector and finally the sensitivity and uncertainty analysis for the recoil-proton telescope discussed in the companion paper.