Calculations on the production and use of superfine holographic X-ray gratings for astrophysical observations

Superfine holograhic X-ray gratings may be produced by transferring onto metal an interference pattern generated by two branches of a sufficiently coherent X-ray beam, emitted in the form of synchrotron radiation from high energy electron storage rings. Generation of the coherent beam requires restrictions on the beam size. A calculation is presented which allows an exact evaluation of this restriction. The effect of defocusing optics on the expected resolution is also studied

Feasibility of coherent X-ray production by X-ray pumping

It is suggested that coherent X-rays can be produced by inverting the electron population in a suitable target, such as Li, through irradiation with X-rays generated by fast electrons traversing an electromagnetic field (as in a storage ring). Conditions to be satisfied by target and radiation parameters are stated, and examples given

Huge negative differential conductance in Au-H2 molecular nanojunctions

Experimental results showing huge negative differential conductance in gold-hydrogen molecular nanojunctions are presented. The results are analyzed in terms of two-level system (TLS) models: it is shown that a simple TLS model cannot produce peaklike structures in the differential conductance curves, whereas an asymmetrically coupled TLS model gives perfect fit to the data. Our analysis implies that the excitation of a bound molecule to a large number of energetically similar loosely bound states is responsible for the peaklike structures. Recent experimental studies showing related features are discussed within the framework of our model.Comment: 9 pages, 8 figure

EFFECTS OF LOAD CARRIAGE ON CURVATURE OF THE SPINE

The purpose of this study was to measure the curvature of the spine during load carriage in a rested and mildly fatigued condition. Twelve female subjects walked around an indoor track wearing a 9 kg backpack, in which fifteen spring loaded rods protruded from the back of the pack. The rods were separated by 1.9 cm and were designed to measure the curvature of the spine. The subjects walked for 21 minutes at a rate of 1.79 m/s. Fifteen samples were recorded over 2.5 s at 3 minutes and again at 18 minutes. The means of the two curves were derived from the data to achieve the mean rested and fatigued curves. With fatigue, the cervical to thoracic cavity was thrust forward, causing a significant increase in lordosis of the thoracic to lumbar region. With load carriage, increased lordosis was present to counter balance the weight of the backpack

Emergence of bound states in ballistic magnetotransport of graphene antidots

An experimental method for detection of bound states around an antidot formed from a hole in a graphene sheet is proposed by measuring the ballistic two terminal conductances. In particularly, we consider the effect of bound states formed by magnetic field on the two terminal conductance and show that one can observe Breit-Wigner like resonances in the conductance as a function of the Fermi level close to the energies of the bound states. In addition, we develop a new numerical method in which the computational effort is proportional to the linear dimensions, instead of the area of the scattering region beeing typical for the existing numerical recursive Green's function method.Comment: 7 pages, 6 figure