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In the paper is demonstrated the use of positron lifetime spectroscopy (PLS) in a comparative study of the results in ferroelectrics. The first part is devoted to the application of PLS as a probe for measurements of ferroelectrics. In Triglycine Sulphate (TGS) (NH3CH2COOH)3H2SO4, Rochelle Salt (RS) NaKC4H4O64H2O and Potassium Dihydrogen Phosphate (KDP) KH2PO4 at different temperatures and gamma irradiation doses is established the existence of three positron lifetime components. This experimental results show that the second long lifetime component as a function of temperature in order-disorder ferroelectrics TGS, RS and KDP is due to the positron trapping in negatively charge defects of ferroelectric. The positron spectroscopy method is effective for measurements of extremely small defects and voids, which is important for the next exploitation period of the ferroelectrics. PLS measurements of ferroelectrics show that about the third lifetime component is due to the local formation of orhto-positronium state on the boundary between the domains. In the second part the PLS analysis has been applied for examination the electronic and defect structure in selected ferroelectrics materials. In gamma irradiated TGS positrons are trapped in the defect states of the oxygen ions of the two radicals CH2COO- and NH3CHCOO-. In RS positrons are trapped also in the defect states of the oxygen ions and OH groups.

Using recent data from photometric monitoring and data from the photographic plate archives we aim to study, the long-term photometric behavior of FUors. The construction of the historical light curves of FUors could be very important for determining the beginning of the outburst, the time to reach the maximum light, the rate of increase and decrease in brightness, the pre-outburst variability of the star. Our CCD photometric observations were performed with the telescopes of the Rozhen (Bulgaria) and Skinakas (Crete, Greece) observatories. Most suitable for long-term photometric study are the plate archives of the big Schmidt telescopes, as the telescopes at Kiso Observatory, Asiago Observatory, Palomar Observatory and others. In comparing our results with light curves of the well-studied FUors, we conclude that every new FUor object shows different photometric behavior. Each known FUor has a different rate of increase and decrease in brightness and a different light curve shape., Comment: 4 pages, 5 figures, accepted for publication in the International Astronomical Union Proceedings Series

We report the results of optical monitoring for a sample of 11 blazars including 10 BL Lacs and 1 Flat Spectrum Radio Quasar (FSRQ). We have measured the multiband optical flux and colour variations in these blazars on intra-day and short-term timescales of months and have limited data for 2 more blazars. These photometric observations were made during 2009 to 2011, using six optical telescopes, four in Bulgaria, one in Greece and one in India. On short-term timescales we found significant flux variations in 9 of the sources and colour variations in 3 of them. Intra-day variability was detected on 6 nights for 2 sources out of the 18 nights and 4 sources for which we collected such data. These new optical observations of these blazars plus data from our previous published papers (for 3 more blazars) were used to analyze their spectral flux distributions in the optical frequency range. Our full sample for this purpose includes 6 high-synchrotron-frequency-peaked BL Lacs (HSPs), 3 intermediate-synchrotron-frequency-peaked BL Lacs (ISPs) and 6 low-synchrotron-frequency-peaked BL Lacs (LSPs; including both BL Lacs and FSRQs). We also investigated the spectral slope variability and found that the average spectral slopes of LSPs show a good accordance with the Synchrotron Self-Compton (SSC) loss dominated model. Our analysis supports previous studies that found that the spectra of the HSPs and FSRQs have significant additional emission components. The spectra of all these HSPs and LSPs get flatter when they become brighter, while for FSRQs the opposite appears to hold. This supports the hypothesis that there is a significant thermal contribution to the optical spectrum for FSRQs.

We report the results of quasi-simultaneous two filter optical monitoring of two high-energy peaked blazars, 1ES 1959+650 and 1ES 2344+514, to search for microvariability and short-term variability (STV). We carried out optical photometric monitoring of these sources in an alternating sequence of B and R pass-bands, and have 24 and 19 nights of new data for these two sources, respectively. No genuine microvariability (intra-night variability) was detected in either of these sources. This non-detection of intra-night variations is in agreement with the conclusions of previous studies that high-energy peaked BL Lacs are intrinsically less variable than low-energy peaked BL Lacs in the optical bands. We also report the results of STV studies for these two sources between July 2009 and August 2010. Genuine STV is found for the source 1ES 1959+650 but not for 1ES 2344+514. We briefly discuss possible reasons for the difference between the intra-night variability behaviour of high- and low-energy peaked blazars.

We present the results of our study of spectral energy distributions (SEDs) of a sample of ten low- to intermediate-synchrotron-peaked blazars. We investigate some of the physical parameters most likely responsible for the observed short-term variations in blazars. To do so, we focus on the study of changes in the SEDs of blazars corresponding to changes in their respective optical fluxes. We model the observed spectra of blazars from radio to optical frequencies using a synchrotron model that entails a log-parabolic distribution of electron energies. A significant correlation among the two fitted spectral parameters ($a$, $b$) of log-parabolic curves and a negative trend among the peak frequency and spectral curvature parameter, $b$, emphasize that the SEDs of blazars are fitted well by log-parabolic curves. On considering each model parameter that could be responsible for changes in the observed SEDs of these blazars, we find that changes in the jet Doppler factors are most important.

Results from optical photometric observations of the PMS star V 1735 Cyg are reported. The star is located in the IC 5146 dark cloud complex—a region of active star formation. On the basis of observed outburst and spectral properties, V 1735 Cyg was classified as a FUor object. We present data from BVRI CCD photometric observations of the star, collected from March 2003 to January 2009. Plates from the Rozhen Schmidt telescope archive were scanned for a brightness estimation of the star. A sequence of sixteen comparison stars in the field of V 1735 Cyg was calibrated in BVRI bands. The data from photographic observations made from 1986 to 1992 show a strong light variability (ΔV=1 ⋅ m 2). In contrast, the recent photometric data obtained from 2003 to 2009 show only small amplitude variations (ΔI=0 ⋅ m 3). The analysis of existing photometric data shows a very slow decrease in star brightness—1 ⋅ m 8 (R) for a 44 year period. The possibilities for future photometric investigations of V 1735 Cyg using the photographical plate archives is discussed briefly.

Hydrogen in nano-voids in neutron-irradiated nickel has been detected using positron annihilation lifetime spectroscopy (PALS). As positron lifetime is greatly affected by nano-voids bound with hyd...

The positron lifetime spectroscopy (PLS), a non-destructive characterization method, utilizes positronium (Ps; an electron–positron bound state) as a probe and measures its lifetime in polymer free volumes. For the first time the free volumes have been estimated by PLS in polyaniline (PANI) complexes with various inorganic and organic acids. It was found that the o -Ps lifetime increases and the intensity decreases with increasing ionic radius of the counter-ions in PANI complexes. Obviously, larger counter anions result in enhanced mean size of the voids corresponding to the free volume in the bulk polymer. Electrical conductivity has been measured by conventional four-probe technique. The glass transition temperature and temperature of removal of the absorbed water have been determined by using differential scanning calorimetry. It was established fairly well correlation of the mentioned polymer parameters with the o -Ps lifetime and the free volume of PANI complexes, respectively. The greater free-volume results in a decrease of conductivity, glass transition temperature and temperature of removal of the absorbed water.

Positron lifetime quantum-mechanical calculations were carried out for the investigation of defects in vanadium containing hydrogen atoms. The convergence of electronic structure calculations for supercell size is studied for vacancies, vacancy-clusters (nano-voids) and vacancy-clusters containing hydrogen. The electron wave functions have been obtained in the local density approximation (LDA) to the density functional theory (DFT). On the basis of the calculated results, the behaviours of empty nano-voids and nano-voids with hydrogen are discussed. It is found that hydrogen in larger three-dimensional vacancy-clusters change the annihilation characteristics drastically. The hydrogen atoms are trapped by lattice vacancies. These results provide physical insight for positron interactions with defects in vanadium and can be used for the prediction of hydrogen generation useful for the design of a fusion reactor.

Results from optical photometric observations of the pre-main sequence star GM Cep are reported in the paper. The star is located in the field of the young open cluster Trumpler 37 - a region of active star formation. GM Cep shows a large amplitude rapid variability interpreted as a possible outburst from EXor type in previous studies. Our data from BVRI CCD photometric observations of the star are collected from June 2008 to February 2011 in Rozhen observatory (Bulgaria) and Skinakas observatory (Crete, Greece). A sequence of sixteen comparison stars in the field of GM Cep was calibrated in the BVRI bands. Our photometric data for a 2.5 years period show a high amplitude variations (Delta V ~ 2.3m) and two deep minimums in brightness are observed. The analysis of collected multicolor photometric data shows the typical of UX Ori variables a color reversal during the minimums in brightness. On the other hand, high amplitude rapid variations in brightness typical for the Classical T Tauri stars also present on the light curve of GM Cep. Comparing our results with results published in the literature, we conclude that changes in brightness are caused by superposition of both: (1) magnetically channeled accretion from the circumstellar disk, and (2) occultation from circumstellar clouds of dust or from features of a circumstellar disk., Comment: 7 pages, 3 figures, accepted for publication in Ap&SS

Context. 3C 454.3 is a very active flat spectrum radio quasar (blazar) that has undergone a recent outburst in all observed bands, including the optical. Aims. In this work we explore the short-term optical variability of 3C 454.3 during its outburst by searching for time delays between different optical bands. Finding one would be important for understanding the evolution of the spectrum of the relativistic electrons, which generate the synchrotron jet emission. Methods. We performed photometric monitoring of the object by repeating exposures in different optical bands (BVRI). Occasionally, different telescopes were used to monitor the object in the same band to verify the reliability of the smallest variations we observed. Results. Except on one occasion, where we found indications of a lag of the blue wavelengths behind the red ones, the results are inconclusive for most of the other cases. There were either no structures in the light curves to be able to search for patterns, or else different approaches led to different conclusions., Comment: 4 pages, 4 figures. Accepted for publication in A&A

We have measured multi-band optical flux and colour variations for a sample of 12 low energy peaked blazars on short, day-to-month, timescales. Our sample contains six BL Lacertae objects and six flat spectrum radio quasars. These photometric observations, made during September 2008 to June 2009, used five optical telescopes, one in India and four in Bulgaria. We detected short term flux variations in eleven of these blazars and colour variability in eight of them. Our data indicate that six blazars (3C 66A, AO 0235+164, S5 0716+714, PKS 0735+178, OJ 287 and 3C 454.3) were observed in preor post-outburst states, that five (PKS 0420 014, 4C 29.45, 3C 279, PKS 1510 089 and BL Lac) were in a low state, while one (3C 273) was in an essentially steady state. The duty cycles for flux and colour variations on short timescales in these low energy peaked blazars are �92 per cent and � 33 per cent, respectively. The colour vs magnitude correlations seen here support the hypothesis that BL Lac objects tend to become bluer with increase in brightness; however, flat spectrum radio quasars may show the opposite trend, and there are exceptions to these trends in both categories of blazar. We briefly discuss emission models for active galactic nuclei that might explain our results.

We observed the prototype blazar, BL Lacertae, extensively in optical and radio bands during an active phase in the period 2010--2013 when the source showed several prominent outbursts. We searched for possible correlations and time lags between the optical and radio band flux variations using multifrequency data to learn about the mechanisms producing variability. During an active phase of BL Lacertae, we searched for possible correlations and time lags between multifrequency light curves of several optical and radio bands. We tried to estimate any possible variability timescales and inter-band lags in these bands. We performed optical observations in B, V, R and I bands from seven telescopes in Bulgaria, Georgia, Greece and India and obtained radio data at 36.8, 22.2, 14.5, 8 and 4.8 GHz frequencies from three telescopes in Ukraine, Finland and USA. Significant cross-correlations between optical and radio bands are found in our observations with a delay of cm-fluxes with respect to optical ones of ~250 days. The optical and radio light curves do not show any significant timescales of variability. BL Lacertae showed many optical 'mini-flares' on short time-scales. Variations on longer term timescales are mildly chromatic with superposition of many strong optical outbursts. In radio bands, the amplitude of variability is frequency dependent. Flux variations at higher radio frequencies lead the lower frequencies by days or weeks. The optical variations are consistent with being dominated by a geometric scenario where a region of emitting plasma moves along a helical path in a relativistic jet. The frequency dependence of the variability amplitude supports an origin of the observed variations intrinsic to the source., Comment: 10 pages, 9 figures, Accepted for publication in A&A

We report the discovery of a large amplitude outburst from the young star HBC 722 (LkHA 188 G4) located in the region of NGC 7000/IC 5070. On the basis of photometric and spectroscopic observations, we argue that this outburst is of the FU Orionis type. We gathered photometric and spectroscopic observations of the object both in the pre-outburst state and during a phase of increase in its brightness. The photometric BVRI data (Johnson-Cousins system) that we present were collected from April 2009 to September 2010. To facilitate transformation from instrumental measurements to the standard system, fifteen comparison stars in the field of HBC 722 were calibrated in the BVRI bands. Optical spectra of HBC 722 were obtained with the 1.3-m telescope of Skinakas Observatory (Crete, Greece) and the 0.6-m telescope of Schiaparelli Observatory in Varese (Italy). The pre-outburst photometric and spectroscopic observations of HBC 722 show both low amplitude photometric variations and an emission-line spectrum typical of T Tau stars. The observed outburst started before May 2010 and reached its maximum brightness in September 2010, with a recorded Delta V~4.7 mag. amplitude. Simultaneously with the increase in brightness the color indices changed significantly and the star became appreciably bluer. The light curve of HBC 722 during the period of rise in brightness is similar to the light curves of the classical FUors - FU Ori and V1057 Cyg. The spectral observations during the time of increase in brightness showed significant changes in both the profiles and intensity of the spectral lines. Only H alpha remained in emission, while the H beta, Na I 5890/5896, Mg I triplet 5174, and Ba II 5854/6497 lines were in strong absorption., 4 pages, 6 figures, accepted for publication in A&A

Lattice defects containing hydrogen and helium in Pd have been studied by positron model calculations using Density Functional Theory [DFT] in its local density approximation [LDA] [1] implementation. A correlation between the positron lifetime, positron ground stage energy and number atoms of H and He has been established. It was found that the value of positron lifetime for perfect Pd lattice is 106 ps and for mono vacancy is 184 ps which corresponds to the experimental values.

Reflection High Energy Electron Diffraction (RHEED) has been used for investigating the surfaces of natural PbS single crystals before and after their covering with absorbed Hg. The aim has been the clarification of the sorption mechanism of Hg on PbS, a system fur preconcentration of Hg from air for further analysis.

Es werden die Wachstumsformen kugelformiger Casiumeinkristalle aus der Dampfphase bei einem Ubersattigungsverhaltnis s von 1,02 bis 56 untersucht. Bei diesen Ubersattigungen treten an der Anfangswachstumsform nur die Flachen {110} auf. An den Endwachstumsformen erscheinen auch die Flachen {211}. {100}- und {111}-Flachen wurden nicht beobachtet. Die Ergebnisse werden vom Standpunkt der Theorie von STRANSKI und KAISCHEW diskutiert und gedeutet. [Russian Text Ignored]

In der vorliegenden Arbeit wird das Wachstum von Rubidium-Einkristallkugeln aus der Gasphase untersucht. Bei kleinen Ubersattigungen treten auf der Anfangswachstumsform die Flachen {110} und {100} auf; bei grosen Ubersattigungen erscheinen nur die Flachen {110}. Bei fortgeschrittenen Wachstumsformen erscheinen auch die Flachen {211} als schmale Streifen zwischen den Rhombendodekaederflachen; Temperaturschwankungen vergrosern die Ausmase der {211}-Flachen. Die Versuchsergebnisse werden vom Standpunkt der Theorie von Stranski und Kaischew diskutiert und gedeutet. The growth of rubidium monocrystalline spheres from the vapour phase is studied. Weak supersaturation leads to the formation of the faces {110} and {100} in the initial growth-habit, whereas strong supersaturation leads to the faces {110} only. The narrow faces {211} are observed only in the final growth-habit on the edges between the rhombic dodecahedral faces. Temperature variations increase the dimensions of the faces {211}. The experimental results are discussed on the basis of the theory of Stransky and Kaischew.

A total of 116 patients with various degrees of chronic renal insufficiency were studied. The most frequent cause that led to its development was the chronic pyelinephritis, followed by chronic glomerulonephritis, and the other chronic renal disease, as--renal polycystosis, diabetic nephropathy, endemic nephropathy, etc. The dynamic and static pulmonary volumes volumes and capacities were investigated in order to achieve the task set and on their base--the type of ventilation disorder was determined. Certain changes of the indices were found in parallel with the intensification of the chronic renal insufficiency. They were best manifested in the patients with advanced renal insufficiency from II and IV group. Ventilation disorders were present in 50% of the patients examined. The restrictive type ventilation insufficiency was most often found (22.4%), second--the mixed type of ventilation defect (16.4%) and third--the obstructive type ventilation insufficiency (11.2%).

Lung ventilation was determined in 116 patients with various degrees of chronic renal insufficiency. The patients examined were subdivided into 4 groups according to the values of serum creatinine and glomerular filtration. Lung ventilation was increased in all patient groups, mainly on the account of the increased inspiration reserve volume. The changes in respiration rate were insignificant. PaCO2 values in arterial blood were adopted, by the author, as a sign of an existing hyperventilation. A high correlation interdependence was established between CO2 pressure in arterial blood (PaCO2) and the active blood reaction (pH). Considerably less was the correlation dependence between hyperventilation syndrome and the values of serum creatinine and blood urea.

The authors observed two cases with crossed renal dystopia, to which venous urography, renal scintigraphy, echographic and gamma-chamber investigations were performed. The venous urography, in case of the appropriate symptomatics, is stressed to be able to establish the presence of heterolateral dystopia by as far as the distributional function of the anomaly is concerned--the gamma-chamber investigation is with the highest information value.

The results are reported from the carried out 701 shortterm therapeutic courses in 527 patients with exacerbated chronic pyelonephritis. The results are considered as "very good" in realization of a full clinical remission (normalization of temperature and ESR), disappearance of leucocyturia and bacteriuria), "good" - in normalization of three of those indices and "withfut effect". Co-trimoxazol (88.3 per cent of the patients), gentamycin (61.7%), ampicillin (58.8%), nelidix acid (57.4%), nitrfuran (55.0%) and choloramphenicol (53.1%) have manifested the highest effectiveness (very good and good effect). In a small number of the treated patients with cephalosporins effect was obtained in 50.0 per cent, with urovalidin - 44.4 per cent and with carbenicillin - 62.5 per cent. According to the authors' opinion the therapeutic schemes for a long-term treatment must include chlorampheniacal, nelidix acid, co-trimoxazol and nitrofuran sometives -amplicillin. Gentamycin, ampicillin and cephalosporins and with indications - some other uroantiseptics must be used in the coping with severe exacerbation of the disease. The authors recommend the chronic intermittent uroantiseptic treatment.

The analytical diffusion capacity of the lungs was determined in 63 patients with various stages of chronic renal insufficiency. On the base of the values of serum creatinine and glomerular filtration the patients were subdivided into four groups. Considerable changes in all the three values of alveolar-capillary diffusion (DLCO, Dm, Vc) were established, with a definite parallelism between those changes and the chronic renal insufficiency stage. The most serious changes concern the membrane component. The correlation analysis confirms the presence of high reverse correlation interdependence, both with the values of serum creatinine and blood urea and with the diastolic arterial pressure.