检索结果-南通市图书馆

Abscisic Acid, High-Light, and Oxidative Stress Down-Regulate a Photosynthetic Gene via a Promoter Motif Not Involved in Phytochrome- Mediated Transcriptional Regulation

引用

Molecular Plant 2008年第1期1卷 75-83页

作者： Roberto j. Staneloni Maria j.se Rodriguez-Batiller j.rge j. Casal Fundacion Instituto Leloir and IIBBA-CONICET C1405BWE-Buenos Aires Argentina IFEVA Facultad de Agronomia Universidad de Buenos Aires and CONICET 1417 Buenos Aires Argentina

In etiolated seedlings, light perceived by phytochrome promotes the expression of light-harvesting chlorophyll a/b protein of photosystem Ⅱ （Lhcb） genes. However, excess of photosynthetically active radiation can reduce Lhcb expression. Here, we investigate the convergence and divergence of phytochrome, high-light stress and abscisic acid （ABA） signaling, which could connect these processes. Etiolated Arabidopsis thaliana seedlings bearing an Lhcb promoter fused to a reporter were exposed to continuous far-red light to activate phytochrome and not photosynthesis, and treated with ABA. We identified a cis-acting region of the promoter required for down-regulation by ABA. This region contains a CCAC sequence recently found to be necessary for ABI4-binding to an Lhcb promoter. However, we did not find a G-box-binding core motif often associated with the ABI4-binding site in genes promoted by light and repressed by ABI4. Mutations involving this motif also impaired the responses to reduced water potential, the response to high photosynthetic light and the response to methyl viologen but not the response to low temperature or to Norflurazon. We propose a model based on current and previous findings, in which hydrogen peroxide produced in the chloroplasts under high light conditions inter- acts with the ABA signaling network to regulate Lhcb expression. Since the mutation that affects high-light and methyl viologen responses does not affect phytochrome-mediated responses, the regulation by retrograde and phytochrome signaling can finally be separated at the target promoter level.

关键词： Abscisic Acid High-Light Oxidative Stress Down-Regulate Photosynthetic Gene

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Sodium lanthanide fluoride core-shell nanocrystals： A general perspective on epitaxial shell growth

引用

Nano Research 2013年第8期6卷 547-561页

作者： Noah j. j. j.hnson Frank C. j. M. van Veggel Department of Chemistry University ofVictoria P.O. Box3065 Victoria British Columbia Canada V8W 3V6

Understanding the structural characteristics and growth mechanism（s） are essen-tial for generating core-shell nano-heterostructures with distinctive properties. Especially in lanthanide-based nanocrystals, rational design of the core-shell composition can be utilized to enhance/tune the optical properties of the final nanostructure, or can be used to integrate multiple functional applications （e.g., luminescent/magnetic）. In this article, we review the progress in our current understanding of the epitaxial shell growth in sodium lanthanide fluoride （NaLnF4） nanocrystals. In order to understand epitaxial shell growth the core nanocrystals have to be uniform, and to date the synthesis of high quality near uniform size/shape dispersion controlled synthesis of lanthanide-based nanocrystals has been achieved mainly with this class of nanocrystals. The progress in core-shell synthesis and the epitaxial shell growth mechanism in this class of nanocrystals （NaLnF4） are reviewed, and a general perspective is provided on the core-shell morphology based on different characterization techniques. While there has been tremendous progress in studying the impact of core-shell structures in various functional applications, this review also highlights, in our view, the still limited understanding of ways to control the core-shell morphology and it emphasizes some important, unanswered questions that remain to be addressed to maximize their performance.

关键词： upconvertingnanocrystals core-shell lanthanides epitaxy

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

VARIABLE STEP-SIZE IMPLICIT-EXPLICIT LINEAR MULTISTEP METHODS FOR TIME-DEPENDENT PARTIAL DIFFERENTIAL EQUATIONS

引用

j.urnal of Computational Mathematics 2008年第6期26卷 838-855页

作者： DongWang Steven j. Ruuth Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign B231 Newmark Civil Engineering Laboratory Urbana IL 61801 USA Department of Mathematics Simon Fraser University Burnaby BC Canada V5A 1S6

Implicit-explicit （IMEX） linear multistep methods are popular techniques for solving partial differential equations （PDEs） with terms of different types. While fixed timestep versions of such schemes have been developed and studied, implicit-explicit schemes also naturally arise in general situations where the temporal smoothness of the solution changes. In this paper we consider easily implementable variable step-size implicit-explicit （VSIMEX） linear multistep methods for time-dependent PDEs. Families of order-p, pstep VSIMEX schemes are constructed and analyzed, where p ranges from 1 to 4. The corresponding schemes are simple to implement and have the property that they reduce to the classical IMEX schemes whenever constant time step-sizes are imposed. The methods are validated on the Burgers＇ equation. These results demonstrate that by varying the time step-size, VSIMEX methods can outperform their fixed time step counterparts while still maintaining good numerical behavior.

关键词： Implicit-explicit (IMEX) linear multistep methods Variable step-size Zero-stability Burgers' equation.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Arc erosion of AgSnO_2 electrical contacts at different stages of a break operation

引用

Rare Metals 2010年第3期29卷 248-254页

作者： j. Swingler A. Sumption School of Engineering Sciences University of Southampton

Arc erosion studies are conducted on AgSnO2 contact materials at different stages in the break operation. A resistive load arrangement is used with up to 42 V DC at 24 A and a constant contact opening velocity. The arc current is terminated at different stages as the arc is drawn between the contacts enabling a study of the arcing phenomena up to that point. Surface profiling of the contacts is conducted to determine the extent of erosion at the different stages as the arc is drawn. Spectral analysis is also conducted on the arc and then related to the extent of erosion. The results show that particular features occur at different stages as the arc is drawn. As the arc is initially established, it goes through an ＂Arc Generation＂ regime where the arc roots are small and immobile on both the anode and the cathode. Material transfer occurs mainly from anode to cathode. The spectral analysis indicates that Sn and O species dominate the arc followed by the Ag species. As the arc is drawn further and enters the ＂Arc Degeneration＂ regime, the anode undergoes significantly larger erosion than the cathode. Also, both contacts indicate that multiple arc roots have formed, which are highly mobile in the later stages of the discharge. The spectral analysis indicates that Ag and N species are in high concentrations compared to other species. The mechanisms of erosion and deposition are discussed in relation to the species within the arc discharge. For the complete break operation, it is found that the anode undergoes maj.r erosion, and it is thought that the gaseous ions species do not dominate the arc under these conditions of short arcs and voltage 〈42 V to cause cathode erosion.

关键词： contact materials electrical contacts arc erosion 3D surface profiles spectral analysis

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Small Zeros of Additive Forms in Several Variables

引用

Acta Mathematica Sinica,English Series 1998年第1期14卷 57-66页

作者： j. S. Hwang Institute of Mathematics Academia Sinica Taipei Taiwan 11529 China

Let f（X） be an additive form defined by f（X）=f（x1. x2,…,xs）=σ1α1x1k+σα2x2k+…+σsαsxsk, where αo≠0 is integer, i=1, 2,…, s. In 1979, Schmidt proved that if ε>0 then there is a large constant C（k, ε） such that for s≥C（k, ε） the equation f（X）=0 has a nontrivial integer solution in σ1. σ2,…σs, x1, x2…,xs satisfying σi=±1 and |xi|≤Aε, i=1, 2.…,s where A=max|ai|. Schmidt did not estimate this constant C（k. ε） since it would be extremely large. In this paper, we prove the following result: Theorem 1 If log A≤1/ε,then C（k,ε）≤max （2/ε,20）; if log A>1/ε,A is sufficiently larye and 1/2A≤5≤|ai|≤A,i=1. 2,…, s, then C（k,ε）≤c1c2p and if the last condition is omitted, then C（k. ε）≤[4/ε]c1c2,where c1={2k+1 for≤k≤11 [5k2log k] for k≥12, c2=100c1k22k+c12 and p=2[log 2c1/ε]. We note that the inequality in the first case is sharp but not in the second case.

关键词： Additive form Subset sums Small zeros

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

ON THE ALGORITHMIC COMPLEXITY OF STATIC STRUCTURES

引用

j.urnal of Systems Science & Complexity 2010年第6期23卷 1037-1053页

作者： j.el RATSABY j. CHASKALOVIC j.el RATSABY Dept. of Electrical and Electronics Engineering Ariel University Center of Samaria Ariel Israel Department of Mathematics Ariel University Center of Samaria Ariel Israel and IJLRDA University Pierre and Marie Curie-Paris VI France.

This paper provides a first indication that this is true for a system comprised of a static structure described by hyperbolic partial differential equations and is subj.cted to an external random input force. The system deforms the randomness of an input force sequence in proportion to its algorithmic complexity. The authors demonstrate this by numerical analysis of a one-dimensional vibrating elastic solid （the system） on which we apply a maximally-random force sequence （input）. The level of complexity of the system is controlled via external parameters. The output response is the field of displacements observed at several positions on the body. The algorithmic complexity and stochasticity of the resulting output displacement sequence is measured and compared against the complexity of the system. The results show that the higher the system complexity, the more random-deficient the output sequence.

关键词： Data compression descriptional complexity randomness static structure.

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Conservation laws for energy and momentum in curved spaces

引用

j.urnal of Zhej.ang University-Science A(Applied Physics & Engineering) 2007年第4期8卷 665-668页

作者： LóPEZ-BONILLA j. MORALES j. OVANDO G. Section of Postgraduate Studies and Research Superior School of Mechanical and Electrical EngineeringNational Polytechnic InstituteCP 07738Mexico Division of Basic Sciences and Engineering Autonomous Metropolitan UniversityCP 02200Mexico

In arbitrary Riemannian 4-spaces, continuity equations are constructed which could be interpreted as conservation laws for the energy and momentum of the gravitational field. Special attention is given to general relativity to obtain, of natural manner, the pseudotensors of Einstein, Landau-Lifshitz, Moeller, Goldberg and Stachel, and also the conservation equations of Komar, Trautman, DuPlessis and Moss.

关键词： Noether theorem Lagrangians in curved spaces Energy and momentum in Riemannian spaces Rund-Lovelock identities

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Acoustic Measurements for Determination of the Materials Damping Using A Sound Source Localisation System

引用

Acta Metallurgica Sinica(English Letters) 2013年第2期26卷 113-121页

作者： j. Gken j. Swiostek H. Hurdelbrink U. Keil Faculty of Maritime Studies University of Applied Sciences Emden/Leer Bergmannstr. 36 26789 LeerGermany Stalomax TM Company of High-Precision Mechanics ul. Parkingowa 45 37450 Stalowa WolaPoland

Noise measurements are especially a problem when the obj.ct under investigation is largely dimensioned and can only be measured from the distance. To obtain information about the location of noise generation, a measurement technique which makes sound visible in order to introduce further specific technical measures is advantageous. The question is if the time dependence of the signal got from such a non touching and non destructive acoustic method has the potential to calculate the materials damping from. Using a small sound source localization system （Microflown^TM probe）, specimens of magnesium alloys with different grain sizes obtained by hydrostatic extrusion were investigated. It has been demonstrated that the fine grained microstructure led to a lower damping and its dependence on the strain was reduced. In this context, acoustic measurements by a sound source localisation system which makes materials characterization possible could be used as a quality tool to detect changes in highly stressed components. This approach allows to promote a selective substitution of conventional materials by more innovative ones. The offshore sector is considered to be a field of application： Wind turbines produce noise emission which stems mainly from turbulences at the tips of the rotor blades and vibrations of components inside the nacelle （e.9. gearbox, generator, ...）. If the vibration amplitudes are too high, microcracks of components can lead to failure over the long term. The monitoring of microstructural changes using a larger type of a sound source localisation system is considered as an innovative technical approach with respect to maintenance activities.

关键词： Magnesium Noise measurements MicroflownTM Damping

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Inherent robust stability of driver support systems

引用

Science China(Technological Sciences) 1999年第4期42卷 437-448页

作者：王龙 j. Ackermann Robust Control Group Institute of Robotics and System Dynamics German Aerospace Research CenterD-82230 Wessling Germany)

Presented are the fact that the transfer function from the front steering angle to yaw rate is strictly positive real, irrespective of the uncertain mass and uncertain velocity, how to determine the positivity margin for this transfer function (some stabilization results are obtained), and how to check the positivity of a controller family. Furthermore,by exploiting the intrinsic structure of system equations and uncertainties, a nonconservative PID stabilization criterion for driver support systems is established. Some interesting results on positivity and connections of PID controllers are shown. Finally, some extreme point results on PID α-stabilization are obtained. These results give certain explanations and j.stifications for the simulation results performed at German Aerospace Research Center.

关键词： driver support systems PID controllers positivity uncertain parameters stabilization car steering systems parameter space extreme point results.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Large open-circuit voltage polymer solar cells by poly(3-hexylthiophene) with multi-adducts fullerenes

引用

Science China Chemistry 2012年第5期55卷 743-748页

作者： HEEGER Alan j. Department of Physics University of California Santa Barbara USA

Polymer solar cells (PSCs) made by poly(3-hexylthiophene) (P3HT) with multi-adducts fullerenes, [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM), PC61BM-bisadduct (bisPC61BM) and PC61BM-trisadduct (trisPC61BM), were reported. Electrochemistry studies indicated that PC61BM, bisPC61BM and trisPC61BM had step-up distributional lowest unoccupied molecular orbital (LUMO) energy. PSCs made by P3HT with above PC61BMs show a trend of enlarged open-circuit voltages, which is in good agreement with the energy difference between the LUMO of PC61BMs and the HOMO of P3HT. On the contrary, reduced short-circuit currents (j.c) were observed. The investigation of photo responsibility, dynamics analysis based on photo-induced absorption of composite films, P3HT:PC61BMs and n-channel thin film field-effect transistors of PC61BMs suggested that the short polaron lifetimes and low carrier mobilities were response for reduced j.c. All these results demonstrated that it was important to develop an electron acceptor which has both high carrier mobility, and good compatibility with the electron donor conj.gated polymer for approaching high performance PSCs.

关键词： fullerene derivative large open circuit voltage polaron lifetime charge carrier mobility

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：