99 research outputs found
Influence of the substrate-induced strain and irradiation disorder on the Peierls transition in TTF-TCNQ microdomains
The influence of the combined effects of substrate-induced strain, finite
size and electron irradiation-induced defects have been studied on individual
micron-sized domains of the organic charge transfer compound
tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) by temperature-dependent
conductivity and current-voltage measurements. The individual domains have been
isolated by focused ion beam etching and electrically contacted by focused ion
and electron beam induced deposition of metallic contacts. The
temperature-dependent conductivity follows a variable range hopping behavior
which shows a crossover of the exponent as the Peierls transition is
approached. The low temperature behavior is analyzed within the segmented rod
model of Fogler, Teber and Shklowskii, as originally developed for a
charge-ordered quasi one-dimensional electron crystal. The results are compared
with data obtained on as-grown and electron irradiated epitaxial TTF-TCNQ thin
films of the two-domain type
A new charge-transfer complex in UHV co-deposited tetramethoxypyrene and tetracyanoquinodimethane
UHV-deposited films of the mixed phase of tetramethoxypyrene and
tetracyanoquinodimethane (TMP1-TCNQ1) on gold have been studied using
ultraviolet photoelectron spectroscopy (UPS), X-ray-diffraction (XRD), infrared
(IR) spectroscopy and scanning tunnelling spectroscopy (STS). The formation of
an intermolecular charge-transfer (CT) compound is evident from the appearance
of new reflexes in XRD (d1= 0.894 nm, d2= 0.677 nm). A softening of the CN
stretching vibration (red-shift by 7 cm-1) of TCNQ is visible in the IR
spectra, being indicative of a CT of the order of 0.3e from TMP to TCNQ in the
complex. Characteristic shifts of the electronic level positions occur in UPS
and STS that are in reasonable agreement with the prediction of from DFT
calculations (Gaussian03 with hybrid functional B3LYP). STS reveals a HOMO-LUMO
gap of the CT complex of about 1.25 eV being much smaller than the gaps (>3.0
eV) of the pure moieties. The electron-injection and hole-injection barriers
are 0.3 eV and 0.5 eV, respectively. Systematic differences in the positions of
the HOMOs determined by UPS and STS are discussed in terms of the different
information content of the two methods.Comment: 20 pages, 6 figure
THE MODELING OF THE TECHOLOGY OF MEDICAL INFORMATION SEARCH IN THE INTERNET
During the research work the strengths and weaknesses of the horizontal and vertical search information were analyzed, the algorithmic model of vertical search information has been developed
Suzaku measurement of Abell 2204's intracluster gas temperature profile out to 1800 kpc
Context: Measurements of intracluster gas temperatures out to large radii are
important for the use of clusters for precision cosmology and for studies of
cluster physics. Previous attempts to measure robust temperatures at cluster
virial radii failed. Aims: The goal of this work is to measure the temperature
profile of the very relaxed galaxy cluster Abell 2204 out to large radii,
possibly reaching the virial radius. Methods: Taking advantage of its low
particle background due to its low-Earth orbit, Suzaku data are used to measure
the outer temperature profile of Abell 2204. These data are combined with
Chandra and XMM-Newton data of the same cluster in order to make the connection
to the inner regions, unresolved by Suzaku, and to determine the smearing due
to Suzaku's PSF. Results: The temperature profile of Abell 2204 is determined
from 10 kpc to 1800 kpc, close to an estimate of r200 (the approximation to the
virial radius). The temperature rises steeply from below 4 keV in the very
center up to more than 8 keV in the intermediate range and then decreases again
to about 4 keV at the largest radii. Varying the measured particle background
normalization artificially by +-10 percent does not change the results
significantly. Predictions for outer temperature profiles based on hydrodynamic
simulations show good agreement. In particular, we find the observed
temperature profile to be slightly steeper but consistent with a drop of a
factor of 0.6 from 0.3 r200 to r200, as predicted by simulations. Conclusions:
Temperature measurements up to the virial radius seem feasible with Suzaku,
when a careful analysis of the different background components and the effects
of the PSF is performed. The result obtained here indicates that numerical
simulations capture the intracluster gas physics well in cluster outskirts.Comment: 7 pages; Astronomy and Astrophysics, accepted; additional systematic
effects have been quantified, results unchanged; also available at
http://www.reiprich.ne
Коллоидно-химические свойства водной дисперсии прополиса, полученной методом замены растворителя
Mixing an alcoholic extract of propolis with distilled water or aqueous solution, which model seawater composition, give rise to aqueous dispersions with or without emulsifier. High dispersion stability is attained at hydrophylic-lipophylic balance equaled 13.9 using sorbitan oleate and polyoxyethylene sorbitan monooleate (Polysorbate-80) as a binary emulsifier. The initial particle size of dispersions is almost identical regardless of the presence of the emulsifier or water salinity. However, in the latter case a dispersion with essentially narrow size distribution is formed and, as a result, the dispersion is more resistant to coagulation and phase separation. Apparently, the main contribution to the stability of the aqueous propolis dispersion is made by the structural-mechanical barrier, which is formed by a thick adsorption layer of the hydrated nonionic surfactant.Смешением спиртового раствора прополиса с дистиллированной водой или водным раствором, моделирующим состав морской воды, получены его дисперсии, в том числе в присутствии эмульгатора. Наибольшая устойчивость дисперсии достигается при использовании в качестве эмульгатора смеси сорбитанолеат/полисорбат-80 со значением гидрофильно-липофильного баланса 13.9. Исходный размер частиц дисперсии практически одинаков вне зависимости от присутствия ПАВ и минерализации среды, однако в последнем случае получается более монодисперсная и потому более устойчивая к коагуляции и расслоению дисперсия. Основной вклад в устойчивость водной дисперсии прополиса, по-видимому, вносит структурно-механический барьер, который образован толстым адсорбционным слоем неионогенного ПАВ, сольватированного водой
Morphology, phylogeny, and taxonomy of Microthlaspi (Brassicaceae: Coluteocarpeae) and related genera
The genus Thlaspi has been variously subdivided since its description by Linnaeus in 1753, but due to similarities in fruit shape several segregates have still not gained broad recognition, despite the fact that they are not directly related to Thlaspi. This applies especially to segregates now considered to belong to the tribe Coluteocarpeae, which includes several well-studied taxa, e.g., Noccaea caerulescens (syn. Thlaspi caerulescens), and the widespread Microthlaspi perfoliatum (syn. Thlaspi perfoliatum). The taxonomy of this tribe is still debated, as a series of detailed monographs on Coluteocarpeae was not published in English and a lack of phylogenetic resolution within this tribe was found in previous studies. The current study presents detailed phylogenetic investigations and a critical review of morphological features, with focus on taxa previously placed in Microthlaspi. Based on one nuclear (ITS) and two chloroplast (matK, trnL-F) loci, four strongly supported major groups were recovered among the Coluteocarpeae genera included, corresponding to Ihsanalshehbazia gen. nov., Friedrichkarlmeyeria gen. nov., Microthlaspi s.str., and Noccaea s.l. In addition, two new species of Microthlaspi, M. sylvarum-cedri sp. nov. and M. mediterraneo-orientale sp. nov., were discovered, which are well supported by both morphological and molecular data. Furthermore, M. erraticum comb. nov. (diploid) and M. perfoliatum s.str. (polyploid) were shown to be distinct species, phylogenetically widely separate, but with some overlap in several morphological characters. Detailed descriptions, notes on taxonomy, geographical distribution, and line drawings for the new species and each species previously included in Microthlaspi are provided. In addition, the current taxonomic state of the tribe Coluteocarpeae is briefly discussed and it is concluded that while several annual taxa are clearly distinct from Noccaea, many perennial taxa, after thorough phylogenetic and morphological investigations, may have to be merged with this genus. © International Association for Plant Taxonomy (IAPT) 2016
Prof. Alexey V. Konarev (celebrating the 75th birthday)
On January 16, 2023 we celebrated the 75th birthday of Professor Alexey V. Konarev, Doctor of Biological Sciences, a renowned scientist in the sphere of plant biochemistry and molecular biology, one of the eldest staff members of VIR
Clusters of galaxies : observational properties of the diffuse radio emission
Clusters of galaxies, as the largest virialized systems in the Universe, are
ideal laboratories to study the formation and evolution of cosmic
structures...(abridged)... Most of the detailed knowledge of galaxy clusters
has been obtained in recent years from the study of ICM through X-ray
Astronomy. At the same time, radio observations have proved that the ICM is
mixed with non-thermal components, i.e. highly relativistic particles and
large-scale magnetic fields, detected through their synchrotron emission. The
knowledge of the properties of these non-thermal ICM components has increased
significantly, owing to sensitive radio images and to the development of
theoretical models. Diffuse synchrotron radio emission in the central and
peripheral cluster regions has been found in many clusters. Moreover
large-scale magnetic fields appear to be present in all galaxy clusters, as
derived from Rotation Measure (RM) studies. Non-thermal components are linked
to the cluster X-ray properties, and to the cluster evolutionary stage, and are
crucial for a comprehensive physical description of the intracluster medium.
They play an important role in the cluster formation and evolution. We review
here the observational properties of diffuse non-thermal sources detected in
galaxy clusters: halos, relics and mini-halos. We discuss their classification
and properties. We report published results up to date and obtain and discuss
statistical properties. We present the properties of large-scale magnetic
fields in clusters and in even larger structures: filaments connecting galaxy
clusters. We summarize the current models of the origin of these cluster
components, and outline the improvements that are expected in this area from
future developments thanks to the new generation of radio telescopes.Comment: Accepted for the publication in The Astronomy and Astrophysics
Review. 58 pages, 26 figure
- …