宁夏彭阳县退耕还林还草研究

运用了生态学、经济学的办法,在彭阳县退耕还林还草的大前提下,对于彭阳县的各种状况进行了分析,探讨了以农林牧复合体系为指导的生了一条果园复合经营脱贫致富的新路子。态农业,并论证了其可行性,分析了三种模式综合所能带来的生态经济效益,开创     

基于高重频固体激光信号的快速采集系统

采用积分电路的方法对高重频固体激光的窄脉冲信号进行捕捉,对积分电路的原理构成、周期窄脉冲信号采集放大电路的设计、测量误差来源及处理做了分析和讨论。以W77E58为采集电路的CPU,以FT245BM为核心构成USB接口电路,实现了窄脉冲信号的快速采集与传输,较好地解决了对多路探测器实时快速采集和向上位机传送的问题,达到了比较满意的效果。     

Schrödinger and Dirac equations for the hydrogen atom, and Laguerre polynomials

It is usually claimed that the Laguerre polynomials were popularized by Schrödinger when creating wave mechanics; however, we show that he did not immediately identify them in studying the hydrogen atom. In the case of relativistic Dirac equations for an electron in a Coulomb field, Dirac gave only approximations, Gordon and Darwin gave exact solutions, and Pidduck first explicitly and elegantly introduced the Laguerre polynomials, an approach neglected by most modern treatises and articles. That Laguerre polynomials were not very popular before their use in quantum mechanics, probably because they had been little used in classical mathematical physics, is confirmed by the fact that, as we show, they had been rediscovered independently several times during the nineteenth century, in published or unpublished studies of Abel, Murphy, Chebyshev, and Laguerre.     

Dynamics of collapsing and exploding Bose-Einstein condensates.

When atoms in a gas are cooled to extremely low temperatures, they will-under the appropriate conditions-condense into a single quantum-mechanical state known as a Bose-Einstein condensate. In such systems, quantum-mechanical behaviour is evident on a macroscopic scale. Here we explore the dynamics of how a Bose-Einstein condensate collapses and subsequently explodes when the balance of forces governing its size and shape is suddenly altered. A condensate's equilibrium size and shape is strongly affected by the interatomic interactions. Our ability to induce a collapse by switching the interactions from repulsive to attractive by tuning an externally applied magnetic field yields detailed information on the violent collapse process. We observe anisotropic atom bursts that explode from the condensate, atoms leaving the condensate in undetected forms, spikes appearing in the condensate wavefunction and oscillating remnant condensates that survive the collapse. All these processes have curious dependences on time, on the strength of the interaction and on the number of condensate atoms. Although the system would seem to be simple and well characterized, our measurements reveal many phenomena that challenge theoretical models.     

Phot1 and phot2 mediate blue light regulation of stomatal opening.

The stomatal pores of higher plants allow for gaseous exchange into and out of leaves. Situated in the epidermis, they are surrounded by a pair of guard cells which control their opening in response to many environmental stimuli, including blue light. Opening of the pores is mediated by K(+) accumulation in guard cells through a K(+) channel and driven by an inside-negative electrical potential. Blue light causes phosphorylation and activation of the plasma membrane H(+)-ATPase that creates this potential. Thus far, no blue light receptor mediating stomatal opening has been identified, although the carotenoid, zeaxanthin, has been proposed. Arabidopsis mutants deficient in specific blue-light-mediated responses have identified four blue light receptors, cryptochrome 1 (cry1), cryptochrome 2 (cry2), phot1 and phot2. Here we show that in a double mutant of phot1 and phot2 stomata do not respond to blue light although single mutants are phenotypically normal. These results demonstrate that phot1 and phot2 act redundantly as blue light receptors mediating stomatal opening.     

Prediction from the One‐Way Error Components Model with AR(1) Disturbances

In this paper we extend the works of Baillie and Baltagi (1999, in Analysis of Panels and Limited Dependent Variables Models, Hsiao C et al. (eds). Cambridge University Press: Cambridge, UK; 255–267) and generalize certain results from the Baltagi and Li (1992, Journal of Forecasting 11 : 561–567) paper accounting for AR(1) errors in the disturbance term. In particular, we derive six predictors for the one‐way error components model, as well as their associated asymptotic mean squared error of multi‐step prediction in the presence of AR(1) errors in the disturbance term. In addition, we also provide both theoretical and simulation evidence as to the relative efficiency of our alternative predictors. The adequacy of the prediction AMSE formula is also investigated by the use of Monte Carlo methods and indicates that the ordinary optimal predictor performs well for various accuracy criteria. Copyright © 2011 John Wiley & Sons, Ltd.     

New Astragalus (Leguminosae) from the Goose Creek Drainage, Utah - Nevada

A new species, Astragalus anserinus Atwood, Goodrich, & Welsh, is described from specimens taken from tuffaceous outcrops in the Goose Creek drainage of Box Elder County, Utah and Elko County Nevada.        

Atomic structure holography using thermal neutrons.

The idea of atomic-resolution holography has its roots in the X-ray work of Bragg and in Gabor's electron interference microscope. Gabor's lensless microscope was not realized in his time, but over the past twelve years there has been a steady increase in the number of reports on atomic-resolution holography. All of this work involves the use of electrons or hard X-rays to produce the hologram. Neutrons are often unique among scattering probes in their interaction with materials: for example, the relative visibility of hydrogen and its isotopes is a great advantage in the study of polymers and biologically relevant materials. Recent work proposed that atomic-resolution holography could be achieved with thermal neutrons. Here we use monochromatic thermal neutrons, adopting the inside-source concept of Sz?ke, to image planes of oxygen atoms located above and below a single hydrogen atom in the oxide mineral simpsonite.