Sorting Second-Grade Students: Differentiating Those Retained From Those Promoted.

A cohort of 2nd-grade students provided comparisons of academic and social competence based on school retention/promotion decisions. Sample groups were (a) retained, (b) at risk for retention, (c) special education, and (d) promoted. Findings suggested most children with academic deficiencies are identified by schools early and are sorted into educational treatments differing in intensity that represent a continuum of competence. The authors provide empirical evidence counter to the assumptions that retained students have the requisite ability to catch up and have more problem behaviors than other low-achieving students. The relevance of high-stakes test scores for promotion/retention decisions and the parallels between schools' implementation of retention policy and implementation of regulations for identifying children with disabilities are included in the discussion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Molecular correlations in sheared thermotropic copolyesters showing banded textures

Banded textures produced in a thermotropic liquid crystal polymer by shearing between glass slides are examined by using both transmission electron and polarized light microscopy. The periodic variation in director orientation about the shear axis, as measured by light microscopy, is shown to be distinctly different from that indicated by electron diffraction. Measurements of birefringence and observation of Zernicke phase contrast indicate periodic variations in optical properties of the polymer, in step with the bands. Such effects are accounted for in terms of a synchronous rotation of the planar aromatic groups about the molecular chain axes. Evidence for an out-of-plane component of molecular orientation is also presented.     

The effect of temperature on crazing mechanisms in polystyrene

At room temperature scission is the dominant mechanism for the modification of the entanglement network required for craze formation in polystyrene, but as the temperature is increased towardsT _g, there is the possibility that disentanglement processes may contribute. These will be most important for short chains. If disentanglement can occur, a molecular weight dependence of the crazing stress as a function of temperature will result. This prediction is tested by straining thin films of a range of monodisperse samples of polystyrene at temperatures between 40 and 90° C. The nature of the ensuing deformation has been characterized by transmission electron microscopy. It is observed that whereas only crazing occurs over the entire temperature range for the lowest molecular weight sample, shear processes become important for higher molecular weight materials. For the longest chains, crazing is almost entirely suppressed at 80° C, with the preferential formation of shear deformation zones occurring. These observations are consistent with the idea that disentanglement is playing a significant role in craze formation at sufficiently high temperatures.     

Evaluating hyperspectral imaging of wetland vegetation as a tool for detecting estuarine nutrient enrichment

Nutrient enrichment and eutrophication are major concerns in many estuarine and wetland ecosystems, and the need is urgent for fast, efficient, and synoptic ways to detect and monitor nutrients in wetlands and other coastal systems across multiple spatial and temporal scales. We integrated three approaches in a multi-disciplinary evaluation of the potential for using hyperspectral imaging as a tool to assess nutrient enrichment and vegetation responses in tidal wetlands. For hyperspectral imaging to be an effective tool, spectral signatures must vary in ways correlated with water nutrient content either directly, or indirectly via such proxies as vegetation responses to elevated nitrogen. Working in Elkhorn Slough, central California, where intensive farming practices generate considerable runoff of fertilizers and pesticides, we looked first for long- and short-term trends among temporally ephemeral point data for nutrients and other water quality characters collected monthly at 18 water sampling stations since 1988. Second, we assessed responses of the dominant wetland plant, Salicornia virginica (common pickleweed) to two fertilizer regimes in 0.25 m² experimental plots, and measured changes in tissue composition (C, H, N), biomass, and spectral responses at leaf and at canopy scales. Third, we used HyMap hyperspectral imagery (126 bands; 15–19 nm spectral resolution; 2.5 m spatial resolution) for a synoptic assessment of the entire wetland ecosystem of Elkhorn Slough. We mapped monospecific Salicornia patches (～ 56–500 m²) on the ground adjacent to the 18 regular water sampling sites, and then located these patches in the hyperspectral imagery to correlate long-term responses of larger patches to water nutrient regimes. These were used as standards for correlating plant canopy spectral responses with nitrogen variation described by the water sampling program. There were consistent positive relationships between nitrogen levels and plant responses in both the field experiment and the landscape analyses. Two spectral indices, the Photochemical Reflectance Index (PRI) and Derivative Chlorophyll Index (DCI), were correlated significantly with water nutrients. We conclude that hyperspectral imagery can be used to detect nutrient enrichment across three spatial and at least two temporal scales, and suggest that more quantitative information could be extracted with further research and a greater understanding of physiological and physical mechanisms linking water chemistry, plant properties and spectral imaging characteristics.     

在未来勘探开发中研发的推动作用

在过去的20年里,尽管油价和经营环境不断发生着变化,但勘探开发的产量和经济效益持续增长着,科学研究和先进技术起了关键作用。未来的勘探开发将更加依赖于先进的技术和科学的研究开发。 随着变化的经营环境和关键的先进科学技术强有力的结合,出现了新的研发模式和发展趋势。在这里我们     

Understanding the role of impulsivity and externalizing psychopathology in alcohol abuse: Application of the UPPS Impulsive Behavior Scale.

The present study explores the relation among 4 personality traits associated with impulsive behavior and alcohol abuse. Personality traits were measured using the 4 subscales of the UPPS Impulsive Behavior Scale (UPPS: S. P. Whiteside & D. R. Lynam. 2001). The UPPS and measures of psychopathology were administered to clinical samples of alcohol abusers high in antisocial personality traits (AAPD), alcohol abusers low in antisocial personality traits (AA), and a control group (total N = 60). Separate analyses of variance indicated that AAPDs had significant elevations on all 4 UPPS scales, whereas the AAs and controls differed only on the Urgency subscale. However, when controlling for psychopathology, group differences on the UPPS scales disappeared. The results suggest that personality traits related to impulsive behavior are not directly related to alcohol abuse but rather are associated with the elevated levels of psychopathology found in a subtype of alcohol abusers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrical/electronic effects of titanium and iron impurities in EFG and FZ solar cell silicon: SPV/EBIC analysis

In this paper results on surface photovoltage (SPV) and electron beam induced conductivity (EBIC) studies of edge-defined film-fed growth (EFG) and floating zone (FZ) silicon solar cell materials (both p-type) are presented. A systematic comparison based on minority carrier diffusion length and carrier recombination is made between: (i) samples contaminated with Ti and/or Fe, (ii) samples gettered by phosphorous diffusion, and (iii) as-received samples. Deep level transient spectroscopy (DLTS) measurements, together with the iron-boron (FeB) pairing kinetics [1] have successfully been used to detect the presence of Fe in the samples. Even though this process is effective in revealing Fe impurities in p-type FZ silicon it is evidently not suitable for Fe identification in p-type EFG silicon. Ti, like Fe, is found to be a prominent lifetime-limiting metallic impurity in both EFG and FZ silicon. Phosphorous diffusion is proven to be an effective external gettering technique for fast-diffusing impurities such as Fe, but not for Ti.     

Layout-Specific Circuit Evaluation in 3-D Integrated Circuits

In this paper, we describe a comprehensive layout methodology for bonded three-dimensional integrated circuits (3D ICs). In bonded 3D integration technology, parts of a circuit are fabricated on different wafers, and then, the wafers are bonded with a glue layer of Cu or polymer based adhesive. Using our layout methodology, designers can layout such 3D circuits with necessary information on inter-wafer via/contact and orientation of each wafer embedded in the layout. We have implemented the layout methodology in 3DMagic. Availability of 3DMagic has led to interesting research with a wide range of layout-specific circuit evaluation, from performance comparison of 2D and 3D circuits to layout-specific reliability analyses in 3D circuits. Using 3DMagic, researchers have designed and simulated an 8-bit encryption processor mapped into 2D and 3D FPGA layouts. Moreover, the layout methodology is an essential element of our ongoing research for the framework of a novel Reliability Computer Aided Design tool, ERNI-3D.