Electrical conductivity of plasmas of DB white dwarf atmospheres

The static electrical conductivity of non-ideal, dense, partially ionized helium plasma was calculated over a wide range of plasma parameters: temperatures $1\cdot 10^{4}\textrm{K} \lesssim T \lesssim 1\cdot 10^{5}\textrm{K}$ and mass density $1 \times 10^{-6} \textrm{g}/\textrm{cm}^{3} \lesssim \rho \lesssim 2 \textrm{g}/\textrm{cm}^{3}$. Calculations of electrical conductivity of plasma for the considered range of plasma parameters are of interest for DB white dwarf atmospheres with effective temperatures $1\cdot 10^{4}\textrm{K} \lesssim T_{eff} \lesssim 3\cdot 10^{4}\textrm{K}$. Electrical conductivity of plasma was calculated by using the modified random phase approximation and semiclassical method, adapted for the case of dense, partially ionized plasma. The results were compared with the unique existing experimental data, including the results related to the region of dense plasmas. In spite of low accuracy of the experimental data, the existing agreement with them indicates that results obtained in this paper are correct

Novel Meteor Simulation and Observation Techniques that Emerged from Big-Sky-Earth COST Action

The cooperation of scientists in Big-Sky-Earth COST Action creates an emergent group of researchers with relation to meteor science. Selected cases of development of novel approaches and techniques for meteor simulation and observation are presented

The Influence of Solar Spectral Lines on Electron Concentration in Terrestrial Ionosphere

One of the methods of detection and analysis of solar flares is observing the time variations of certain solar spectral lines. During solar flares, a raise of electron concentration occurs in Earth’s ionosphere which results in amplitude and phase variations of the recorded very low frequency (VLF) waves. We compared the data obtained by the analysis of recorded VLF signals and line spectra for different solar flares. In this paper we treated the DHO VLF signal transmitted from Germany at the frequency of 23.4 kHz recorded by the AWESOME system in Belgrade (Serbia) during solar flares in the period between 10:40 UT and 13:00 UT on 2011 April 22

Atom–Rydberg-atom chemi-ionization processes in solar and DB white-dwarf atmospheres in the presence of ( n – n ′)-mixing channels

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Models of Interactions of Laser Beams with Materials of Interest for Optical Components and Provoked Damages

Models of interactions of laser beams with materials of interest for optical components are presented in this paper. Special attention is paid to damages which appear within both active materials and optical components along the path of a propagating beam with theoretical treatment via various models

Models of Interactions of Laser Beams with Materials of Interest for Optical Components and Provoked Damages

Models of interactions of laser beams with materials of interest for optical components are presented in this paper. Special attention is paid to damages which appear within both active materials and optical components along the path of a propagating beam with theoretical treatment via various models

Ruby Laser Interaction with Austenite Structural Materials

The investigations were carried out on chrome nickel steel and nickel based superalloy samples thermo-mechanically treated to obtain optimal mechanical properties and surface stability. Chrome nickel steel and a few nickel based superalloys samples were exposed to the laser beam before creep deformation process. The second group of nickel based superalloy samples were exposed after the creep deformation. The damages occurred by exposing of chrome nickel steel and nickel base superalloy samples to the ruby laser were analyzed by scanning electron microscope and energy-dispersive X-ray spectrometry. In this paper, the influence of laser dynamical regime (MW/$mm^{2}$) to the microstructural changes of heat treated chrome nickel steel and nickel based superalloy are analyzed and discussed

Rendgensko ispitivanje prozračivanjem listova sa jedne umetnički oblikovane stolne lampe

For investigation of artistic components, generaly, there are many developed methods, but a lot of them still are not fully reliable or standardized. One of the available method for such investigation is radiographic testing, when the thickness of testing components does not represents a problem, whatever if the great or small thickness exists. Here is tested an artefact in the shape of desk lamp. The chemical composition of the body is analysed by using XRF spectrography while the radiographic transparent testing is applied through the whole body of the lamp. The body of this desk lamp is produced by casting, using the precise casting method, while other decorative ornaments were shaped by hammering. The fastening of those components is provided by brazing or mechanically. The plastic deformation is designated as method for shaping of thin elements – here leaves. The radiographic testing has revealed the existence of some indications only at leaves produced by hammering. The indications usualy mean discontinuity in material homogenity. Registration of indications and their locations are necessary steps in every further approach for removing such discontinuities. Chossing the repair method always is particular problem, however in entire technique, especially in sensitive artistic component(s). Every action in repairing or restauration may led to more or less visible traces. Unadequate actions may permanently change the appearance or usage of treated artefact.Za ispitivanje umetničkih predmeta, uopšte, razvijene su brojne metode ali sve te metode još uvek nisu potpuno pouzdane ili standardizovane. Jedna od primenljivih metoda za ovakva ispitivanje je radiografsko ispitivanje, kada debljina ispitivanih delova ne predstavlja problem, bilo da se radi o velikoj ili maloj debljini. Ovde je ispitivan jedan umetnički predmet u obliku stolne lampe. Hemijski sastav tela je analiziran korišćenjem rendgenske spektrografske analize (XRF) dok je rendgensko prozračivanje upotrebljeno za snimanje celog tela lampe. Telo lampe je proizvedeno livenjem, korišćenjem metode preciznog liva, dok su ostali dekorativni ornamenti oblikovani kovanjem. Pričvršćivanje ostalih komponenti je izvedeno lemljenjem ili mehanički. Plastično deformisanje je označeno kao metoda oblikovanja tankih elemenata – ovde su to listovi. Radiografsko ispitivanje je otkrilo prisustvo izvesnih indikacija samo na listovima izrađenih kovanjem. Indikacije obično označavaju prekid u homogenosti materijala. Registrovanje indikacija i njihovo lociranje su neophodni koraci u svakom daljem pristupu u cilju uklanjanja takvih diskontinuiteta. Izbor metode repariranja uvek je poseban problem, dakako u celoj tehnici a posebno pri ispitivanju umetničkih komponenti. Svaka akcija u reparaciji ili restauraciji može dovesti do manje ili više vidljivih tragova. Neadekvatne akcije mogu za stalno da promene izgled ili upotrebu tretiranog artefakta

Collapse of Xe polarized atomic states in magnetic fields

Ionization of two-photon excited states $$5p^{\mathrm {5}}(^{\mathrm {2}}P_{\mathrm {3/2}})6\hbox {p}[^{\mathrm {3}}/_{\mathrm {2}}$$, $$^{\mathrm {5}}/_{\mathrm {2}}]_{\mathrm {2}}$$, $$\hbox {M}=2$$ (jl-coupling) of xenon atoms by circularly polarized probe light was studied experimentally in a supersonic beam. The observed photoionization signals revealed oscillation structure due to the Larmor precession of atomic states in an external magnetic field. We derived analytical formulas for the photoelectron current and explained the diversity in the structure of the detected oscillations in terms of the principal lines among multiplet components of optical transitions. The obtained numerical data demonstrate collapse and revival (beating) behavior of the photocurrent due to nonlinearity of Zeeman shifts in the presence of the Paschen–Back effect. Our results indicate the possibility of implementing Doppler-free spectroscopy involving bound-free transitions