Mixing-induced anisotropic correlations in molecular crystalline systems

We investigate the structure of mixed thin films composed of pentacene (PEN) and diindenoperylene (DIP) using X-ray reflectivity and grazing incidence X-ray diffraction. For equimolar mixtures we observe vanishing in-plane order coexisting with an excellent out-of-plane order, a yet unreported disordering behavior in binary mixtures of organic semiconductors, which are crystalline in their pure form. One approach to rationalize our findings is to introduce an anisotropic interaction parameter in the framework of a mean field model. By comparing the structural properties with those of other mixed systems, we discuss the effects of sterical compatibility and chemical composition on the mixing behavior, which adds to the general understanding of interactions in molecular mixtures.Comment: 5 pages, 5 figures, accepted by Phys. Rev. Let

ASTRONOMICAL GLASS PLATE NEGATIVES: MONITORING OF EMULSION LAYER DETERIORATION

One of the techniques for making photographic negatives most used in the history of photography were gelatin glass plates. This technique was used not only in the artistic field but also and mainly in the scientific field. The main period when glass plate negatives were used in astronomy was between 1890–1980. There are over 7 million of these negatives all over the word and they carry valuable historical scientific data. However, during the long-term storage of this material, deterioration of the emulsion (picture) layer and/or the support (glass) layer has occurred. In this paper we report on our preliminary results from an analysis of the yellowing of the emulsion layer and of gold micro-spots. Both phenomena worsen the readability of the information in the photograph, and it is necessary to prevent their formation, which is why we need to know as much as possible about their origin

Determination of the Lithosphere-Asthenosphere Boundary (LAB) beneath the Nógrád-Gömör Volcanic Field by combined geophysical (magnetotellurics) and geochemical methods

Understanding the fundamental role of LAB is substantial for the investigation of the geodynamic evolution of the Earth. The LAB depths can be estimated by different geophysical methods (seismology, magnetotellurics), however these depths are controversial. It has been emphasized in the literature that combined geophysical and geochemical approach may lead to better understanding of these depths. The magnetotellurics (MT) is very powerful method because it indicates the sudden increase in conductivity at the LAB. The mantle xenoliths (small fragments of the lithospheric mantle) provide the information to reconstruct their P-T paths. In the Carpathian-Pannon region (CPR) five, well-studied occurrences of mantle xenoliths-bearing Plio-Pleistocene alkali basalts are known, which makes the CPR a very promising area for investigating the inconsistency in the LAB estimates. As a test area Nógrád-Gömör Volcanic Field (NGVF) has been chosen. The host basalt erupted at the NGVF collected mantle xenoliths from a small volume of the upper mantle in a depth of about 40-50 km. The major element geochemistry of the studied xenoliths indicates that most of them represent common lherzolitic mantle, whereas others show strong wehrlitisation process. This metasomatism is supposed to be caused by a migrating mafic melt agent, resulting in the transformation of a large portion of lherzolite to wehrlite beneath the NGVF, possibly just below the crust mantle boundary. In aim to detect the LAB at the research area and find the correlation with petrologic and geochemical results we carried out MT deep soundings. The campaign contained 12 long period MT stations with 3-5 km average spacing along 60 km long profile SSE to NNW direction. This presentation summarizes the preliminary results of the combined geophysical and geochemical approaches to determine the LAB depths

Electronic structure of ferromagnetic semiconductor Ga1-xMnxAs probed by sub-gap magneto-optical spectroscopy

We employ Faraday and Kerr effect spectroscopy in the infrared range to investigate the electronic structure of Ga1-xMnxAs near the Fermi energy. The band structure of this archetypical dilute-moment ferromagnetic semiconductor has been a matter of controversy, fueled partly by previous measurements of the unpolarized infrared absorption and their phenomenological impurity-band interpretation. The infrared magneto-optical effects we study arise directly from the spin-splitting of the carrier bands and their chiral asymmetry due to spin-orbit coupling. Unlike the unpolarized absorption, they are intimately related to ferromagnetism and their interpretation is much more microscopically constrained in terms of the orbital character of the relevant band states. We show that the conventional theory of the disordered valence band with dominant As p-orbital character and coupled by kinetic-exchange to Mn local moments accounts semi-quantitatively for the overall characteristics of the measured infrared magneto-optical spectra.Comment: 4 pages 3 figure

The role of cytokinins in clubroot disease

Clubroot (Plasmodiophora brassicae) is a pathogen of Brassicaceae that causes significant reductions in yield as a consequence of gall formation in the root and hypocotyl of infected plants. The pathogen hijacks host vascular cambium development, and cytokinins are implicated in this process. This paper uses transcriptomics and metabolomics to investigate changes in cytokinin metabolism during gall formation of clubroot-infected Arabidopsis thaliana. RNASeq analysis of infected tissue showed that host cytokinin metabolism was strongly down-regulated both at the onset and late stages of gall formation. Expression of host genes associated with cytokinin biosynthesis, signalling, degradation and conjugation was strongly repressed. Analysis of cytokinin precursors, active components and conjugates by microanalytical techniques was consistent with these transcriptional responses. Two isopentenyltransferase genes associated with cytokinin biosynthesis are present in the P. brassicae genome and are expressed throughout gall formation. The impact of pathogen-derived cytokinins on the total cytokinin content of infected tissue and host gene expression was minimal in wild type plants. However, infection of ipt1;3;5;7 mutants that are severely restricted in their ability to synthesise active cytokinins led to an increase in expression of host cytokinin-responsive genes. We interpret these results as indicating that P. brassicae can synthesise small amounts of cytokinin, but this has little impact on the host plant as the ipt1;3;5;7 phenotype is not rescued. Intriguingly, plasmodial development was slowed and spore viability reduced in these mutants indicating a potential role for cytokinins in plasmodial development