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

Probing individual split Cooper-pairs using the spin qubit toolkit

A superconductor is a natural source of spin-entangled spatially separated electron pairs. Although the first Cooper-pair splitter devices have been realized recently, an experimental confirmation of the spin state and the entanglement of the emitted electron pairs is lacking up to now. In this paper a method is proposed to confirm the spin-singlet character of individual split Cooper pairs. Two quantum dots (QDs), each of them holding one spin-prepared electron, serve as the detector of the spin state of a single Cooper pair that is forced to split when it tunnels out from the superconductor to the QDs. The number of charges on the QDs, measured at the end of the procedure, carries information on the spin state of the extracted Cooper pair. The method relies on the experimentally established toolkit of QD-based spin qubits: resonant spin manipulation, Pauli blockade, and charge measurement.Comment: 15 pages, 7 figure

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

Minimization number of measured data for magnetostatic field mapping

Balalářská práce se zabývá problematikou mapování statického magnetického pole a metod analýzy měřených dat. Práce je zaměřená na vyhodnocení mapy magnetického pole v pracovním prostoru MR tomografu z dat změřených na povrchu zvoleného objemu. Pro uvedenú problematiku je zde uvedeno řešení a vyhodnocení výsledků.Výsledkem bakalářskej práce je navrhnutí vhodné matematické metody pro mapování statického magnetického pole, a v programu MATLAB sestavit algoritmus pro vyhodnocení mapy magnetického pole. V práci je dále zahrnutý výpočet výsledné hodnoty koeficientů pro výpočet indukce magnetického pole v libovolném bode zvoleného objemu. Měřením byly experimentálne ověřeni hodnoty, tj. zadané hodnoty, ze kterýho práce vychází, pomocí MR tomografu. Výslednou navrženou metodu je možné využít na výpočet koeficientů pro magnetické indukce v jakémkoli bode zvoleného objemu, ze zadaných hodnot indukce zvolého objemuThis work deals with questions of mapping statical magnetical field and methods analyses plumbed dates. There is mentioned solving of problems and interpretation of results. Work is centered on evaluation map of magnetic field in workspace of MR tomography from data measured on surface shere. Imposition of submission is proposition acceptable mathematical method and trought program MATLAB compile algorithm for interpretation map magnetic field. In work is further included calculation resulting values of coefficients for induction of magnetic field for selected parts of sphere. By force of admeasurement were experimentally verifyded values wich from the work proceed. Designed method is possible to use for calculation of coefficeints for magnetic induction at any point on sphere from booked up dates.

Les sens inuit de l’histoire et leurs divergences au Groenland de l’Ouest et au Nunavut

On ne peut nier que les sens que les Inuit et les Qallunaat ont de leur propre «histoire» (et de celle des autres) sont loin de concorder. Mais au-delà de quelques stéréotypes conçus comme des oppositions entre l’écrit et l’oral, l’histoire et le mythe, etc., on ne sait pas grand-chose sur les historicités inuit. Selon l’argument développé dans cet article, les changements récents des historicités inuit ne représentent pas un progrès, d’un intérêt limité pour les questions historiques, à une conscience historique éclairée. Il faut plutôt considérer ces changements comme concomitants aux récentes transitions rapides de leurs sociétés, de leurs visions du monde, et de leurs identités. Les différences entre les historicités au Groenland de l’Ouest et au Nunavut peuvent être attribuées au fait que les visions du passé y sont l’aboutissement de développements historiques divergents à l’intérieur d’un cadre (post-) colonial.No one will dispute that Inuit and Qallunaat senses of their own (and others') “history” are different. But, beyond a few stereotypes framed as oppositions between written and oral, history and myth, etc., one actually knows little about Inuit historicities. This paper argues that recent changes in Inuit historicities do not represent a progress from limited interest in historical questions, to some enlightened historical consciousness. Rather, these changes should be seen as parallelling the recent rapid transitions of their societies, world views and identities. Differences between West Greenlandic and Nunavut historicities may be attributed to the fact that today’s visions of the past are the outcome of divergent historical developments within a (post-)colonial framework