Size effect and the quadratic temperature dependence of the transverse magnetoresistivity in "size-effect" tungsten single crystals

The transverse magnetoresistivity of pure tungsten single crystals with a residual resistivity ratio ρ293K/ρ4.2K of about 75000 was measured from 4.2 to 20 K and in magnetic fields of up to 15 T. The size effect, i.e. the linear dependence of the magnetoconductivity on the inverse cross sample dimensions, was studied in detail at high fields. We show that the size effect can be used for the separation of the contributions from the electron-surface and the electron-phonon scattering mechanisms to the full conductivity. We demonstrate that the electron-phonon scattering leads to the exponential temperature dependence of the conductivity, and the interference between the electron-phonon and the electron-surface processes leads to a new scattering mechanism "electron-phonon-surface" with a quadratic temperature dependence of the magnetoconductivity. © Published under licence by IOP Publishing Ltd

Covariant theory of particle-vibrational coupling and its effect on the single-particle spectrum

The Relativistic Mean Field (RMF) approach describing the motion of independent particles in effective meson fields is extended by a microscopic theory of particle vibrational coupling. It leads to an energy dependence of the relativistic mass operator in the Dyson equation for the single-particle propagator. This equation is solved in the shell-model of Dirac states. As a result of the dynamics of particle-vibrational coupling we observe a noticeable increase of the level density near the Fermi surface. The shifts of the single-particle levels in the odd nuclei surrounding 208-Pb and the corresponding distributions of the single-particle strength are discussed and compared with experimental data.Comment: 27 pages, 8 figure

Quantifying residual finiteness of arithmetic groups

The normal Farb growth of a group quantifies how well-approximated the group is by its finite quotients. We show that any S-arithmetic subgroup of a higher rank Chevalley group G has normal Farb growth n^dim(G).Comment: 18 page

On compatibility between isogenies and polarisations of abelian varieties

We discuss the notion of polarised isogenies of abelian varieties, that is, isogenies which are compatible with given principal polarisations. This is motivated by problems of unlikely intersections in Shimura varieties. Our aim is to show that certain questions about polarised isogenies can be reduced to questions about unpolarised isogenies or vice versa. Our main theorem concerns abelian varieties B which are isogenous to a fixed abelian variety A. It establishes the existence of a polarised isogeny A to B whose degree is polynomially bounded in n, if there exist both an unpolarised isogeny A to B of degree n and a polarised isogeny A to B of unknown degree. As a further result, we prove that given any two principally polarised abelian varieties related by an unpolarised isogeny, there exists a polarised isogeny between their fourth powers. The proofs of both theorems involve calculations in the endomorphism algebras of the abelian varieties, using the Albert classification of these endomorphism algebras and the classification of Hermitian forms over division algebras

A system for restoring production energy management after emergencies

Almost a third of Russia's regions are located in areas that can be affected by natural and industrial disasters, which can in turn trigger further damages and losses. This situation can be also described by the lack of any theoretical, methodological and scientific basis for making forecasts covering the possible destruction of assets belonging to hazardous and highly hazardous facilities and to regional infrastructure and for the recovery measures that should be taken under emergency conditions. Analysis was performed to determine the possible problems occurring at the design, construction, and restoration stages in recovery. A set of risk forecast map cards were developed, that can be applied to determine the chances of uncontrolled natural or industrial energy releases and to design the corresponding mitigation measures in the form of extreme response projects. © 2014 WIT Press.International Journal of Safety and Security Engineering;International Journal of Sustainable Development and Planning;WIT Transactions on Ecology and the Environmen

Control of electron dynamics in mesoscopic quantum circuits

Future electronics faces a transition from conventional technology with progress predicted by Moore’s law to a quantum technology where quantum tunneling or coherent ballistic transport plays a significant role. This thesis concentrates on several applications of quantum technology. We start with demonstrating an alternative method for engineering the potential landscape in two-dimensional electron systems embedded in GaAs/AlGaAs heterostructures in the first chapter. We present a characterization of this design using field effect, Hall effect, and Aharonov- Bohm measurements to study electrostatic, dynamic and coherence properties and also show the general feasibility of our approach for future quantum applications. In the second chapter, we examine optimization of the electron transport between two distant quantum point contacts. We present a technique to measure the angular distribution of electrons emitted from a quantum point contact by deflecting it with an external magnetic field. In the second chapter, we also demonstrate coupling enhancement between two distant quantum point contacts by electrostatic focusing of ballistic electrons. Our observations favor electron dynamics according to a Gaussian beam optics model assuming Hermite functions rather than the frequently used plane electron wave model. In the third chapter, we discuss the coherent coupling of a quantum point contact with an open hemispherical resonator. We present a method to determine the electron phase coherence length based on Gaussian-Hermite modes of both quantum point contact and a cavity. Finally, the last chapter introduces a Lissajous rocking ratchet realized in the quantum dot embedded in the semiconductor heterostructure. It creates directed motion of electrons and breaks time-reversal symmetry on-chip. At the end of the thesis, we discuss results of performed experiments in the context of quantum technology

Problematični izvori. Devetnaestostoljetna istraživanja ruskih ljekovitih izvora

Traditional Russian worldviews explained healing from water sources in terms both Protestants and Catholics would have used elsewhere in Europe: as the grace of God or as the intervention of saints through associated relics or wonder-working icons. Holy wells were freely venerated within parishes until the eighteenth century when Peter the Great and the Holy Synod (the Russian Orthodox Church’s highest governing body) forbade pilgrimage to holy wells in a reformist drive to eradicate religious “superstitions.” This essay employs primary sources to consider how nineteenth-century developments at Russian holy wells and mineral springs related to social class, economics and those eighteenth-century reforms that merged the church with government structures. While liturgical activities at holy wells and the designation of new holy wells was criminalized, mineral springs gained appeal for “scientific” cures and as resort enterprises for the upper classes.Tradicionalni ruski svjetonazori objašnjavali su iscjeljenje vodom u terminima koje su drugdje u Europi koristili i protestanti i katolici: kao božju milost ili intervenciju svetaca putem relikvija ili čudotvornih ikona. Sveti bunari slobodno su se štovali u župama sve do 18. stoljeća kada su Petar Veliki i Sveta sinoda (najviše upravno tijelo Ruske pravoslavne crkve) zabranili hodočašća na svete izvore u reformističkoj težnji da iskorijene vjerska “praznovjerja”. Koristeći se primarnim izvorima, u članku se razmatra kako su devetnaestostoljetni događaji vezani uz ruske svete bunare i mineralne izvore bili povezani s društvenom klasom, ekonomijom i već spomenutim osamnaestostoljetnim reformama koje su dovele do fuzije Crkve sa strukturama vlasti. I dok su liturgijske aktivnosti povezane sa svetim bunarima kao i imenovanje novih svetih bunara bili kriminalizirani, mineralni su izvori postali privlačni zbog svoje “znanstvene” ljekovitosti te kao odmarališta i poslovni pothvati viših klasa