Martin Luther University of Halle-Wittenberg

About: Martin Luther University of Halle-Wittenberg is a education organization based out in Halle, Germany. It is known for research contribution in the topics: Population & Liquid crystal. The organization has 20232 authors who have published 38773 publications receiving 965004 citations. The organization is also known as: MLU & University of Wittenberg.

Real-space grids and the Octopus code as tools for the development of new simulation approaches for electronic systems

Abstract: Real-space grids are a powerful alternative for the simulation of electronic systems. One of the main advantages of the approach is the flexibility and simplicity of working directly in real space where the different fields are discretized on a grid, combined with competitive numerical performance and great potential for parallelization. These properties constitute a great advantage at the time of implementing and testing new physical models. Based on our experience with the Octopus code, in this article we discuss how the real-space approach has allowed for the recent development of new ideas for the simulation of electronic systems. Among these applications are approaches to calculate response properties, modeling of photoemission, optimal control of quantum systems, simulation of plasmonic systems, and the exact solution of the Schrodinger equation for low-dimensionality systems.

Cyclooxygenase-2: a novel target for cancer chemotherapy?

Abstract: Epidemiologic studies have documented a 40-50% reduction in incidence of colorectal cancer in individuals taking nonsteroidal antiinflammatory drugs (NSAIDs). Since NSAIDs are known to inhibit cyclooxygenases (COX-1, COX-2), the basic mechanism of their antitumor effects is conceivably the altered metabolism of arachidonic acid and, subsequently, prostaglandins (PGs). Although COX-2, the inducible isoform, is regularly expressed at low levels in colonic mucosa, its activity increases dramatically following mutation of the APC (adenomatous polyposis coli) gene suggesting that beta-catenin/T-cell factor mediated Wnt-signaling activity may regulate COX-2 gene expression. In addition, hypoxic conditions and sodium butyrate exposure may also contribute to COX-2 gene transcription in human cancers. The development of selective COX-2 inhibitors has made it possible to further evaluate the role of COX-2 activity in colorectal carcinogenesis. To date, at least five mechanisms by which COX-2 contributes to tumorigenesis and the malignant phenotype of tumor cells have been identified, including: (1) inhibition of apoptosis; (2) increased angiogenesis; (3) increased invasiveness; (4) modulation of inflammation/immuno-suppression; and (5) conversion of procarcinogens to carcinogens. A clear positive correlation between COX-2 expression and inhibition of apoptosis has been established, associated with increased PGE2 levels resulting in modulation of pro- and anti-apoptotic factors (e.g., bcl-2, MAKs/ras, caspase-3, Par-4). In terms of angiogenesis and invasiveness, COX-2 activity was found to increase the expression of growth factors (e.g., VDEG, PDGF, bFGF) and matrix metalloproteinases (MMPs). Since COX-2 inhibitors have been demonstrated to interfere with tumorigenesis and apoptosis, COX-2 and its gene product may be attractive targets for therapeutic and chemoprotective strategies in colorectal cancer patients. This may lead to new perspectives that by controlling the cancer phenotype, rather than attempting to eradicate all affected cells, may provide significant benefits to the cancer patient.

Biochar stability in soil: Decomposition during eight years and transformation as assessed by compound-specific 14C analysis

Abstract: Stability and transformation products of incomplete combustion of vegetation or fossil fuel, frequently called pyrogenic or black carbon and of biochar in soil, remains unknown mainly because of their high recalcitrance compared to other natural substances. Therefore, direct estimations of biochar decomposition and transformations are difficult because 1) changes are too small for any relevant experimental period and 2) due to methodological constraints (ambiguity of the origin of investigated compounds). We used 14C-labeled biochar to trace its decomposition to CO2 during 8.5 years and transformation of its chemical compounds: neutral lipids, glycolipids, phospholipids, polysaccharides and benzenepolycarboxylic acids (BPCA). 14C-labeled biochar was produced by charring 14C-labeled Lolium residues. We incubated the 14C-labeled biochar in a Haplic Luvisol and in loess for 8.5 years under controlled conditions. In total only about 6% of initially added biochar were mineralized to CO2 during the 8.5 years. This is probably the slowest decomposition obtained experimentally for any natural organic compound. The biochar decomposition rates estimated by 14CO2 efflux between the 5th and 8th years were of 7 × 10−4 % per day. This corresponds to less than 0.3% per year under optimal conditions and is about 2.5 times slower as reported from the previous shorter study (3.5 years). After 3.5 years of incubation, we analyzed 14C in dissolved organic matter, microbial biomass, and sequentially extracted neutral lipids, glycolipids, phospholipids, polysaccharides and BPCA. Biochar-derived C (14C) in microbial biomass ranged between 0.3 and 0.95% of the 14C input. Biochar-derived C in all lipid fractions was less than 1%. Over 3.5 years, glycolipids and phospholipids were decomposed 1.6 times faster (23% of their initial content per year) compared to neutral lipids (15% year−1). Polysaccharides contributed ca. 17% of the 14C activity in biochar. The highest portion of 14C in the initial biochar (87%) was in BPCA decreasing only 7% over 3.5 years. Condensed aromatic moieties were the most stable fraction compared to all other biochar compounds and the high portion of BPCA in biochar explains its very high stability and its contribution to long-term C sequestration in soil. Our new approach for analysis of biochar stability combines 14C-labeled biochar with 14C determination in chemical fractions allowed tracing of transformation products not only in released CO2 and in microbial biomass, but also evaluation of decomposition of various biochar compounds with different chemical properties.

Transancestral GWAS of alcohol dependence reveals common genetic underpinnings with psychiatric disorders

Abstract: Liability to alcohol dependence (AD) is heritable, but little is known about its complex polygenic architecture or its genetic relationship with other disorders. To discover loci associated with AD and characterize the relationship between AD and other psychiatric and behavioral outcomes, we carried out the largest genome-wide association study to date of DSM-IV-diagnosed AD. Genome-wide data on 14,904 individuals with AD and 37,944 controls from 28 case-control and family-based studies were meta-analyzed, stratified by genetic ancestry (European, n = 46,568; African, n = 6,280). Independent, genome-wide significant effects of different ADH1B variants were identified in European (rs1229984; P = 9.8 × 10-13) and African ancestries (rs2066702; P = 2.2 × 10-9). Significant genetic correlations were observed with 17 phenotypes, including schizophrenia, attention deficit-hyperactivity disorder, depression, and use of cigarettes and cannabis. The genetic underpinnings of AD only partially overlap with those for alcohol consumption, underscoring the genetic distinction between pathological and nonpathological drinking behaviors.

Adipophilin is a specific marker of lipid accumulation in diverse cell types and diseases

Abstract: We report the human DNA and protein sequence of adipophilin and its association with the surface of lipid droplets. The amino acid sequence of human adipophilin has been determined by using cDNA clones from several tissues and confirmed by the reverse transcription/polymerase chain reaction method and Edman sequencing. The open reading frame of adipophilin encodes a polypeptide with a calculated molecular weight of 48.1 kDa and an isoelectric point of 6.72. By immunofluorescence and electron-microscopic localization with newly raised specific poly- and monoclonal antibodies, we show that this protein is not restricted to adipocytes as previously indicated by studies of the mouse homologous protein, adipose-differentiation-related protein. Adipophilin occurs in a wide range of cultured cell lines, including fibroblasts and endothelial and epithelial cells. In tissues, however, expression of adipophilin is restricted to certain cell types, such as lactating mammary epithelial cells, adrenal cortex cells, Sertoli and Leydig cells of the male reproductive system, and steatosis or fatty change hepatocytes in alcoholic liver cirrhosis. Our results reveal adipophilin as a possible new marker for the identification of specialized differentiated cells containing lipid droplets and for diseases associated with fat-accumulating cells.