Home  About us  Contact
 

Edge Area (edge + area)

Distribution by Scientific Domains
Life Sciences40%

Selected Abstracts

Comparative phylogeography of five avian species: implications for Pleistocene evolutionary history in the Qinghai-Tibetan plateau

MOLECULAR ECOLOGY, Issue 2 2010
Y. QU
Abstract Pleistocene climate fluctuations have shaped the patterns of genetic diversity observed in extant species. In contrast to Europe and North America where the effects of recent glacial cycles on genetic diversity have been well studied, the genetic legacy of the Pleistocene for the Qinghai-Tibetan (Tibetan) plateau, a region where glaciation was not synchronous with the North Hemisphere ice sheet maxima, remains poorly understood. Here, we compared the phylogeographical patterns of five avian species on the Qinghai-Tibetan plateau by three mitochondrial DNA fragments: the Tibetan snow finch (Montifringilla adamsi), the Blanford's snow finch (Pyrgilauda blanfordi), the horned lark (Eremophila alpestris), the twite (Carduelis flavirostris) and the black redstart (Phoenicurus ochruros). Our results revealed the three species mostly distributed on the platform region of the plateau that experienced population expansion following the retreat of the extensive glaciation period (0.5,0.175 Ma). These results are at odds with the results from avian species of Europe and North America, where population expansions occurred after Last Glacial Maximum (LGM, 0.023,0.018 Ma). A single refugium was identified in a restricted semi-continuous area around the eastern margin of the plateau, instead of multiple independent refugia for European and North American species. For the other two species distributed on the edges of the plateau (the twite and black redstart), populations were maintained at stable levels. Edge areas are located on the eastern margin, which might have had little or no ice cover during the glaciation period. Thus, milder climate may have mitigated demographic stresses for edge species relative to the extremes experienced by platform counterparts, the present-day ranges of which were heavily ice covered during the glaciation period. Finally, various behavioural and ecological characteristics, including dispersal capacities, habitat preference and altitude specificity along with evolutionary history might have helped to shape different phylogeographical structures appearing in these five species. [source]

Numerical analysis on thermal characteristics for chip scale package by integrating 2D/3D models

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1 2009
Ping Yang
Abstract The objective of this paper is to investigate stress and strain of a special scale package-substrate on chip for reliability evaluation or manufacture strategy in deep-seated situation. A two-dimensional model with one-half of cross-section (2D model) and a three-dimensional model with one-fourth of whole package (3D model) were built, respectively, to simulate the thermal stress and strain of CSP-SOC under the condition of the standard industry thermal cycling temperature ,40 to125°C. The different locations can be processed by using the two models, respectively, based on different modeling simplified modes. By using 2D model, the numerical simulation shows that the maximum deformation of the prototype occurs in printed circuit board (PCB), the maximum stress and strain occurs in the outer solder balls. In the meantime, by the results of 3D model, the simulation shows that the maximum elastic strain occurs in the interface between the solder balls and PCB, the minimum strain occurs in the underfill tape, the maximum packaging stress occurs in the edge area of the chip. The result from 3D model maybe more impersonal to reflect the stress and strain characteristics because the third direction is considered in modeling. The analysis by integrating the 2D model and 3D model can get a more comprehensive profile for the thermal investigation of chip scale package (CSP) than by using any single model. The investigation built a basis for improving reliability in engineering design of CSP product. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A luminescent solar concentrator with 7.1% power conversion efficiency

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 6 2008
L. H. Slooff
Abstract The Luminescent Solar Concentrator (LSC) consists of a transparent polymer plate, containing luminescent particles. Solar cells are connected to one or more edges of the polymer plate. Incident light is absorbed by the luminescent particles and re-emitted. Part of the light emitted by the luminescent particles is guided towards the solar cells by total internal reflection. Since the edge area is smaller than the receiving one, this allows for concentration of sunlight without the need for solar tracking. External Quantum Efficiency (EQE) and current,voltage (I ,V) measurements were performed on LSC devices with multicrystalline silicon (mc-Si) or GaAs cells attached to the sides. The best result was obtained for an LSC with four GaAs cells. The power conversion efficiency of this device, as measured at European Solar Test Installation laboratories, was 7.1% (geometrical concentration of a factor 2.5). With one GaAs cell attached to one edge only, the power efficiency was still as high as 4.6% (geometrical concentration of a factor 10). To our knowledge these efficiencies are among the highest reported for the LSC. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Analysis of Meox - 2 mutant mice reveals a novel postfusion-based cleft palate

DEVELOPMENTAL DYNAMICS, Issue 2 2006
Jiu-Zhen Jin
Abstract Cleft palate represents a common human congential disease involving defects in the development of the secondary palate. Major steps in mammalian palatogenesis include vertical growth, elevation, and fusion of the palate shelves. Our current study with the homeobox gene Meox - 2 during mouse secondary palate development reveals a novel postfusion-based mechanism for cleft palate. Meox - 1 and Meox - 2 are two functionally related homeobox genes playing important roles in somitogenesis and limb muscle differentiation. We found that the expression of Meox - 2, not Meox - 1, marks the specification of early mouse palatal mesenchymal cells in the maxillary processes at embryonic day 11.5 (E11.5). From E12.5 to E15.5, the expression of Meox - 2 occupies only the posterior part of the palate, providing an early molecular marker for the anterior,posterior polarity in mouse secondary palate formation. A total of 35.3% of Meox - 2,/, (n = 17) and 25.5% of Meox - 2+/, (n = 55) mouse embryos display a cleft palate phenotype at E15.5, indicating that the reduction of Meox - 2 function is associated with susceptibility to cleft palate. Unlike previously reported clefts, none of the clefts found in Meox - 2 mutants contain any epithelial sheets in the medial edge areas, and detailed examination revealed that the clefts resulted from the breakdown of newly fused palates. This article is the first report of a gene required to maintain adherence of the palatal shelves after fusion. Developmental Dynamics 235:539,546, 2006. © 2005 Wiley-Liss, Inc. [source]

How Does Structural Reform Affect Regional Development?

ECONOMIC GEOGRAPHY, Issue 4 2000
Resolving Contradictory Theory with Evidence from India
Abstract: Regional theory offers little coherent guidance on the prospects for interregional development after structural reform in developing nations. In this paper I suggest a basic set of hypotheses in which the neoliberal nation-state is simultaneously a reduced state (less concerned about promoting regional balance) and an enlarged state (directing development toward selected regions). Under the new regulatory structure the location of post-reform investments may be expected to favor the coast, advanced regions, and existing metropolises (especially the edge areas); these expectations may be more true for foreign direct investments than domestic investments (especially the direct investments of the state). I use disaggregated pre- and post-reform industrial data from India to test the hypotheses. The results offer partial to full support for all hypotheses, providing evidence of the return of cumulative causation, and raising concerns about the political economy of future development in the lagging regions. [source]