Search results for " polar"
showing 10 items of 1091 documents
Koherentas kustības uztveres izvērtēšanas metodes izstrāde
2021
Maģistra darbs ir uzrakstīts latviešu valodā. Satur 43 lapaspuses, 21 attēlu, 4 tabulas, 52 literatūras avotus. Darba mērķis: novērtēt faktoru (stimula fona kontrasta polaritāte, stimula ātrums, atkārtoti mērījumi, dalībnieks) ietekmi uz koherentas kustības uztveres slieksni. Rezultāti: Tika novērots, ka lielākai daļai dalībnieku, stimula fona polaritāte koherentas kustības uztveres slieksni neietekmē. Tomēr, atsevišķi dalībnieki uzrādīja būtiski zemāku koherences slieksni pie pozitīvas kontrasta polaritātes. Mainot stimula kustības ātrumu, atkārtotā mērījumā, pie stimula kustības ātruma 5 grādi/sekundē, koherentas kustības slieksnis samazinājās. Dalībnieki atšķirīgi reaģēja uz stimula fona…
Nonlinear relaxation phenomena in metastable condensed matter systems
2016
Nonlinear relaxation phenomena in three different systems of condensed matter are investigated. (i) First, the phase dynamics in Josephson junctions is analyzed. Specifically, a superconductor-graphene-superconductor (SGS) system exhibits quantum metastable states, and the average escape time from these metastable states in the presence of Gaussian and correlated fluctuations is calculated, accounting for variations in the the noise source intensity and the bias frequency. Moreover, the transient dynamics of a long-overlap Josephson junction (JJ) subject to thermal fluctuations and non-Gaussian noise sources is investigated. Noise induced phenomena are observed, such as the noise enhanced s…
Studies of host-guest thin films of corona-poled betaine-type polar molecules by kelvin probe technique and atomic force microscopy
2004
In this work betaine-type molecules were investigated. As a result of the asymmetry of charge distribution, molecules possess in the ground state a considerable permanent dipole moment. The decay of surface potential of poled polymer films is dependent at least on two relaxation processes. The influence of glass transition of PMMA on thermal dependence of the surface potential is shown. The transition temperature, where no changes of the surface potential appeared, is related to glass transition temperature of the host-guest system. The topography of the film surface was obtained by AFM.
Field-free two-direction alignment alternation of linear molecules by elliptic laser pulses
2005
We show that a linear molecule subjected to a short specific elliptically polarized laser field yields postpulse revivals exhibiting alignment alternatively located along the orthogonal axis and the major axis of the ellipse. The effect is experimentally demonstrated by measuring the optical Kerr effect along two different axes. The conditions ensuring an optimal field-free alternation of high alignments along both directions are derived.
Zvaigžņotā Debess: 2005, Vasara
2005
Contents: In memoriam Arturs Balklavs-Grīnhofs ; Parting Words to Arturs Balklavs ; List of Publications by Prof. Dr.phys. Arturs Balklavs-Grīnhofs ; Astronomy in 25 Years of Soviet Latvia ; Man in Space: Based on newspaper “Pravda” materials ; U.Dzērvītis. Centenary of the Theory of Relativity ; A.Balklavs. Gamma Emission from the Galactic Centre ; A.Alksnis, Z.Alksne. Fewer Brown Dwarfs, More Red Ones ; A.Alksnis. New Observations of the Eruptive Variable Star V838 Mon ; A.Balklavs. Cosmic Objects in Captivating Photos – 5 ; J. Freimanis. On Polarization of Continuous Solar Spectrum ; J.Jaunbergs. The Very First Contact with Titan ; A.Millers. Biological Effects of Cosmic Rays ; J.Jansons…
Measurement of the mixing-induced and CP-violating parameters of Bs -> phi gamma decays at LHCb
2018
En esta tesis se presenta la primera medida de los observables de violación de CP e inducidos por mezcla de la desintegración Bs -> phi gamma (los observables A, S y C), que aparecen en la fracción de desintegración en función del tiempo. Se han utilizado los datos tomados por el experimento LHCb durante los años 2011 y 2012, representando una luminosidad integrada de 3 fb-1 en total. El Modelo Estándar de física de partículas describe las propiedades de todas las partículas elementales y de las interacciones fuerte, débil y electromagnética. A pesar de su gran éxito predictivo, resulta necesaria una extensión del mismo puesto que no explica determinados fenómenos que han sido observados en…
Interface-Assisted Sign Inversion of Magnetoresistance in Spin Valves Based on Novel Lanthanide Quinoline Molecules
2018
Molecules are proposed to be an efficient medium to host spin-polarized carriers, due to their weak spin relaxation mechanisms. While relatively long spin lifetimes are measured in molecular devices, the most promising route toward device functionalization is to use the chemical versatility of molecules to achieve a deterministic control and manipulation of the electron spin. Here, by combining magnetotransport experiments with element-specific X-ray absorption spectroscopy, this study shows the ability of molecules to modify spin-dependent properties at the interface level via metal–molecule hybridization pathways. In particular, it is described how the formation of hybrid states determine…
Comments on 'formation and characterization of nanotubes of La(OH) 3 obtained using porous alumina membranes'
2010
New experimental evidence concerning the formation of La(OH)3 nanowires on anodic alumina membranes by cathodic polarization in 0.05 M lanthanum nitrate solution is provided to further support the conclusions previously reached in our work (Bocchetta et al 2007 Electrochem. Commun. 9 683-8) and recently criticized by González-Rovira et al (Nanotechnology 2008 19 495305). Some unconvincing aspects of the paper of González-Rovira et al, according to which the same electrochemical process should lead to the formation of hydroxycarbonate nanotubes, are also discussed.
Probing Lorentz invariance and other fundamental symmetries in3He/129Xe clock-comparison experiments
2011
We discuss the design and performance of a very sensitive low-field magnetometer based on the detection of free spin precession of gaseous, nuclear polarized 3He or 129Xe samples with a SQUID as magnetic flux detector. Characteristic spin precession times T*2 of up to 60 h were measured in low magnetic fields (about 1μT) and in the regime of motional narrowing. With the detection of the free precession of co-located 3He/129Xe nuclear spins (clock comparison), the device can be used as ultra-sensitive probe for non-magnetic spin interactions, since the magnetic dipole interaction (Zeeman-term) drops out in the weighted frequency difference, i.e., Δω = ωHe− γHe/γXe·ωXe. We report on searches …
Polar nanoregions in Pb(Mg1/3Nb2/3)O3 (PMN): insights from a supercell approach
2011
Abstract We report construction of a model of polar nanoregions in the PMN relaxor ferroelectric based on first-principles lattice dynamics for chemically ordered supercells [S.A. Prosandeev et al., Phys. Rev. B 70, 134110 (2004)], combined with invariance under permutations and dipole-dipole interaction as a source supporting randomly oriented residual polarization. Representative analytical estimates of polar nanore-gion — supercell mapping reproduce both nonzero local and zero macroscopic polarization of the structure, as well as the temperature change of the supercell anisotropy at cooling and field cooling.