Search results for "VS."

Zvaigžņotā Debess: 2011, Pavasaris (211)

2011

Contents: “ZVAIGŽŅOTĀ DEBESS” FORTY YEARS AGO: A.Alksnis. XIV General Assembly of the International Astronomical Union (abridged) ; H.Strods. Jaunlaicene’s Watchmaker (abridged) ; I.Daube. At the Radioastrophysical Observatory of the Latvian Academy of Sciences (abridged). 50 YEARS SINCE GAGARIN’S SPACE FLIGHT: R.Misa. Dream about Cosmos ; A.Zalcmane. Konstantin Tsiolkovsky Astronautics Museum in Kaluga; E.Bērziņa. Outer Space in Pauls Stradins Museum of History of Medicine. NEWS: A.Alksnis. Different Faces of Whirpool Galaxy ; A.Alksnis. The Kleopatra’s Trio and other Minor Planets Groups. SPACE RESEARCH and EXPLORATION: V.Kalniņš. NASA Preparing Solar Probe Plus to Plunge into Sun's Atmos…

Uguņošanas laikā radušos aerosolu daļiņu sastāva analīze

2019

Literatūras apskatā apkopota informācija par aerosoliem un to pētīšanas metodēm, salūta epizožu laikā radīto gaisa piesārņojuma ietekmi gan cilvēka organismam, gan klimatam un iekārtām, kuras izmanto paraugu ņemšanā un analīzē. Darba eksperimentālajā daļā veikta gaisa aerosolu daļiņu ņemšana uguņošanas laikā un ikdienā, frakcionējot smalkās un rupjās aerosolu daļiņas. Smalkajām un rupjajām aerosolu daļiņām noteikta masas koncentrācija un metālisko elementu saturs, izmantojot ICP-MS un TXRF analīzes.

Study of optical and magneto processes in Rb atomic vapor layer of nanometric thickness

2012

Using a narrow-band resonant fluorescence spectra from a nano-cell with a thickness of L= [lambda]/2, and VSOP resonances formed at a thickness L =[lambda] ([lambda] is the wavelength of the resonant radiation), for the first time it was experimentally investigated the behaviour of the frequency and intensity (transition probabilities) of the atomic hyperfine structure transitions between the 85Rb, 87Rb, D1 and D2 lines Zeeman sublevels in external magnetic fields in range 5 - 7000G. The behaviour of tens of previously unstudied atomic transitions was analyzed and it is demonstrated that the intensities of these lines can both greatly increase, and decrease (tenfold). For the first time it …

Quantum chemical modelling of polarons and perovskite solid solutions

2001

Abstract Following our previous study [J. Phys.: Condens. Matter 10 (1998) 6271] of a single Nb impurity and Nb clusters in KTaO 3 , we present results of the calculations for a series of perovskite KNb x Ta 1− x O 3 (KTN) solid solutions ( x =0, 0.125, 0.25, 0.75, 1). The quantum chemical method of the intermediate neglect of the differential overlap (INDO) combined with the large unit cell (LUC) periodic model is used. According to the INDO calculations, Nb impurity becomes off-center in KTaO 3 already at the lowest studied concentrations ( x =0.125), in a good agreement with XAFS measurements. We compare our results with previous ab initio FP-LMTO calculations. Quantum chemical calculati…

Computer modelling of point defects in ABO3 perovskites and MgO

2004

We present results for basic intrinsic defects: F-type electron centers (O vacancy which trapped one or two electrons) and hole polarons bound to Mg or K vacancy in ionic MgO and partly covalent KNbO3 perovskite, respectively. We demonstrate that a considerable covalency of the perovskite chemical bonding makes the F-type centers therein much more similar to defects in partly-covalent quartz-type oxides rather than the conventional F centers in alkali halides and ionic MgO. Both one-site (atomic) and two-site (molecular) polarons are expected to coexist in KNbO3 characterized by close absorption energies. Our calculations confirm existence of the self-trapped electron polarons in KNbO3, KTa…

Atomic and electronic structure of perfect and defective PbZrO3 perovskite: Hybrid DFT calculations of cubic and orthorhombic phases

2007

Abstract The structural and electronic properties of pure cubic and low-temperature orthorhombic PbZrO3 (antiferroelectric phase), as well as cubic PbZrO3 containing single F-centers (neutral oxygen vacancies) have been simulated by means of ab initio hybrid density functional calculations. We observed a substantial increase of the Pb–O bond covalency in ideal orthorhombic PbZrO3 with respect to its cubic phase. Relatively large displacement of four Pb atoms nearest to the F-center (0.25 A towards the defect) could affect the PbZrO3 ferroelectric properties. An O vacancy in the bulk PbZrO3 attracts ≈0.7 e, and the remaining electron density from the missing O2− is localized mostly on four n…

Preface to Special Issue of Energy Technology on Perovskite Optoelectronics

2017

This Editorial introduces one of two companion Special Issues on “Halide Perovskites for Optoelectronics Applications” in Energy Technology and ChemSusChem following the ICMAT 2017 Conference in Singapore. More information on the other Special Issue can be found in the Editorial published in ChemSusChem.

Preparation and Characterization of Mixed Halide MAPbI 3− x Cl x Perovskite Thin Films by Three‐Source Vacuum Deposition

2019

Modified Operators Interpolating at Endpoints

2021

Some classical operators (e.g., Bernstein) preserve the affine functions and consequently interpolate at the endpoints. Other classical operators (e.g., Bernstein–Durrmeyer) have been modified in order to preserve the affine functions. We propose a simpler modification with the effect that the new operators interpolate at endpoints although they do not preserve the affine functions. We investigate the properties of these modified operators and obtain results concerning iterates and their limits, Voronovskaja-type results and estimates of several differences.

Dominant-negative FADD rescues the in vivo fitness of a cytomegalovirus lacking an anti-apoptotic viral gene

2008

ABSTRACT Genes that inhibit apoptosis have been described for many DNA viruses. Herpesviruses often contain even more than one gene to control cell death. Apoptosis inhibition by viral genes is postulated to contribute to viral fitness, although a formal proof is pending. To address this question, we studied the mouse cytomegalovirus (MCMV) protein M36, which binds to caspase-8 and blocks death receptor-induced apoptosis. The growth of MCMV recombinants lacking M36 (ΔM36) was attenuated in vitro and in vivo. In vitro, caspase inhibition by zVAD-fmk blocked apoptosis in ΔM36-infected macrophages and rescued the growth of the mutant. In vivo, ΔM36 infection foci in liver tissue contained sign…