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  • Oxford University Press  (32)
  • American Association for the Advancement of Science (AAAS)  (3)
  • 1
    Publication Date: 2015-08-08
    Description: We use star, galaxy and quasar spectra taken by the Sloan Digital Sky Survey to map out the distribution of diffuse interstellar bands (DIBs) induced by the Milky Way. After carefully removing the intrinsic spectral energy distribution of each source, we show that by stacking thousands of spectra, it is possible to measure statistical flux fluctuations at the 10 –3 level, detect more than 20 DIBs and measure their strength as a function of position on the sky. We create a map of DIB absorption covering about 5000 deg 2 and measure correlations with various tracers of the interstellar medium: atomic and molecular hydrogen, dust and polycyclic aromatic hydrocarbons (PAHs). After recovering known correlations, we show that each DIB has a different dependence on atomic and molecular hydrogen: while they are all positively correlated with $N_{\rm {H\scriptscriptstyle I}}$ , they exhibit a range of behaviours with $N_{\rm {H_2}}$ showing positive, negative or no correlation. We show that a simple parametrization involving only $N_{\rm {H\scriptscriptstyle I}}$ and $N_{\rm {H_2}}$ applied to all the DIBs is sufficient to reproduce a large collection of observational results reported in the literature: it allows us to naturally describe the relations between DIB strength and dust reddening (including the so-called skin effect), the related scatter, DIB pair-wise correlations and families, the affinity for /-type environments and other correlations related to molecules. Our approach allows us to characterize DIB dependencies in a simple manner and provides us with a metric to characterize the similarity between different DIBs.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 2
    Publication Date: 2016-05-06
    Description: Trimethylated histone H3 lysine 27 (H3K27me3) is linked to gene silencing, whereas H3K4me3 is associated with gene activation. These two marks frequently co-occupy gene promoters, forming bivalent domains. Bivalency signifies repressed but activatable states of gene expression and can be resolved to active, H3K4me3-prevalent states during multiple cellular processes, including differentiation, development and epithelial mesenchymal transition. However, the molecular mechanism underlying bivalency resolution remains largely unknown. Here, we show that the H3K27 demethylase UTX (also called KDM6A) is required for the resolution and activation of numerous retinoic acid (RA)-inducible bivalent genes during the RA-driven differentiation of mouse embryonic stem cells (ESCs). Notably, UTX loss in mouse ESCs inhibited the RA-driven bivalency resolution and activation of most developmentally critical homeobox ( Hox ) a–d genes. The UTX-mediated resolution and activation of many bivalent Hox genes during mouse ESC differentiation were recapitulated during RA-driven differentiation of human NT2/D1 embryonal carcinoma cells. In support of the importance of UTX in bivalency resolution, Utx -null mouse ESCs and UTX-depleted NT2/D1 cells displayed defects in RA-driven cellular differentiation. Our results define UTX as a bivalency-resolving histone modifier necessary for stem cell differentiation.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 3
    Publication Date: 2013-09-08
    Description: Genetic variation affecting absorption, distribution or excretion of essential trace elements may lead to health effects related to sub-clinical deficiency. We have tested for allelic effects of single-nucleotide polymorphisms (SNPs) on blood copper, selenium and zinc in a genome-wide association study using two adult cohorts from Australia and the UK. Participants were recruited in Australia from twins and their families and in the UK from pregnant women. We measured erythrocyte Cu, Se and Zn (Australian samples) or whole blood Se (UK samples) using inductively coupled plasma mass spectrometry. Genotyping was performed with Illumina chips and 〉2.5 m SNPs were imputed from HapMap data. Genome-wide significant associations were found for each element. For Cu, there were two loci on chromosome 1 (most significant SNPs rs1175550, P = 5.03 x 10 –10 , and rs2769264, P = 2.63 x 10 –20 ); for Se, a locus on chromosome 5 was significant in both cohorts (combined P = 9.40 x 10 –28 at rs921943); and for Zn three loci on chromosomes 8, 15 and X showed significant results (rs1532423, P = 6.40 x 10 –12 ; rs2120019, P = 1.55 x 10 –18 ; and rs4826508, P = 1.40 x 10 –12 , respectively). The Se locus covers three genes involved in metabolism of sulphur-containing amino acids and potentially of the analogous Se compounds; the chromosome 8 locus for Zn contains multiple genes for the Zn-containing enzyme carbonic anhydrase. Where potentially relevant genes were identified, they relate to metabolism of the element (Se) or to the presence at high concentration of a metal-containing protein (Cu).
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 4
    Publication Date: 2016-04-10
    Description: The central nervous system (CNS) is an immune-privileged organ with the capacity to prevent excessive inflammation. Aside from the blood-brain barrier, active immunosuppressive mechanisms remain largely unknown. We report that a neuron-specific molecule, synaptic adhesion-like molecule 5 (SALM5), is a crucial contributor to CNS immune privilege. We found that SALM5 suppressed lipopolysaccharide-induced inflammatory responses in the CNS and that a SALM-specific monoclonal antibody promoted inflammation in the CNS, and thereby aggravated clinical symptoms of mouse experimental autoimmune encephalomyelitis. In addition, we identified herpes virus entry mediator as a functional receptor that mediates SALM5’s suppressive function. Our findings reveal a molecular link between the neuronal system and the immune system, and provide potential therapeutic targets for the control of CNS diseases.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 5
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2015-10-24
    Description: Bellamya purificata is a widely distributed Chinese freshwater snail. It plays a significant role in ecosystem services. However, its natural habitats are under severe threat due to fragmentation and loss. In order to estimate the genetic diversity and population structure of B. purificata , 182 individuals from eight locations throughout its distribution across China were sampled. Seven microsatellite loci and the mitochondrial COI gene were genotyped. Our results showed that (1) the genetic diversity of B. purificata was high in all studied populations; (2) a low level of genetic differentiation existed among the eight populations with little restriction to gene flow; (3) no clear geographic structure was revealed by either Bayesian clustering, haplotype networks or AMOVA; (4) effective population size ( N e ) was moderate to high for all studied populations. The results of Bayesian Skyline plot analysis detected unstable population sizes through time for most populations. Passive dispersal during flooding events, zoochoric dispersal, possibly anthropogenic translocations and the large population sizes might be the major reasons for the lack of differentiation among Chinese B. purificata populations.
    Print ISSN: 0260-1230
    Electronic ISSN: 1464-3766
    Topics: Biology
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  • 7
    Publication Date: 2016-09-11
    Description: Hepatocellular carcinoma (HCC) is a malignant tumor originating in the liver. Previous studies have indicated that O-GlcNAc transferase (OGT) and histone deacetylase-1 (HDAC1) play important roles in the pathogenesis of HCC. In the present study, we investigated the physical link between OGT and HDAC1. The O-GlcNAcylation of HDAC1 is overexpressed in HCC. We found that HDAC1 has two major sites of O-GlcNAcylation in its histone deacetylase domain. HDAC1 O-GlcNAcylation increases the activated phosphorylation of HDAC1, which enhances its enzyme activity. HDAC1 O-GlcNAc mutants promote the p21 transcription regulation through affecting the acetylation levels of histones from chromosome, and then influence the proliferation of HCC cells. We also found that mutants of O-GlcNAcylation site of HDAC1 affect invasion and migration of HepG2 cells. E-cadherin level is highly up-regulated in HDAC1 O-GlcNAc mutant-treated liver cancer cells, which inhibit the occurrence and development of HCC. Our findings suggest that OGT promotes the O-GlcNAc modification of HDAC1in the development of HCC. Therefore, inhibiting O-GlcNAcylation of HDAC1 may repress the progression of HCC.
    Print ISSN: 0959-6658
    Electronic ISSN: 1460-2423
    Topics: Biology , Medicine
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  • 8
    Publication Date: 2015-04-12
    Description: Motivation: MicroRNAs (miRNAs) are short non-coding RNAs that play important roles in post-transcriptional regulations as well as other important biological processes. Recently, accumulating evidences indicate that miRNAs are extensively involved in cancer. However, it is a big challenge to identify which miRNAs are related to which cancer considering the complex processes involved in tumors, where one miRNA may target hundreds or even thousands of genes and one gene may regulate multiple miRNAs. Despite integrative analysis of matched gene and miRNA expression data can help identify cancer-associated miRNAs, such kind of data is not commonly available. On the other hand, there are huge amount of gene expression data that are publicly accessible. It will significantly improve the efficiency of characterizing miRNA’s function in cancer if we can identify cancer miRNAs directly from gene expression data. Results: We present a novel computational framework to identify the cancer-related miRNAs based solely on gene expression profiles without requiring either miRNA expression data or the matched gene and miRNA expression data. The results on multiple cancer datasets show that our proposed method can effectively identify cancer-related miRNAs with higher precision compared with other popular approaches. Furthermore, some of our novel predictions are validated by both differentially expressed miRNAs and evidences from literature, implying the predictive power of our proposed method. In addition, we construct a cancer-miRNA-pathway network, which can help explain how miRNAs are involved in cancer. Availability and implementation : The R code and data files for the proposed method are available at http://comp-sysbio.org/miR_Path/ Contact: liukeq@gmail.com Supplementary information: supplementary data are available at Bioinformatics online.
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
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  • 9
    Publication Date: 2015-04-28
    Description: Currently-proposed galaxy quenching mechanisms predict very different behaviours during major halo mergers, ranging from significant quenching enhancement (e.g. clump-induced gravitational heating models) to significant star formation enhancement (e.g. gas starvation models). To test real galaxies’ behaviour, we present an observational galaxy pair method for selecting galaxies whose host haloes are preferentially undergoing major mergers. Applying the method to central L * (10 10 M  〈  M *  〈 10 10.5 M ) galaxies in the Sloan Digital Sky Survey at z  〈 0.06, we find that major halo mergers can at most modestly reduce the star-forming fraction, from 59 to 47 per cent. Consistent with past research, however, mergers accompany enhanced specific star formation rates for star-forming L * centrals: ~10 per cent when a paired galaxy is within 200 kpc (approximately the host halo's virial radius), climbing to ~70 per cent when a paired galaxy is within 30 kpc. No evidence is seen for even extremely close pairs (〈30 kpc separation) rejuvenating star formation in quenched galaxies. For galaxy formation models, our results suggest: (1) quenching in L * galaxies likely begins due to decoupling of the galaxy from existing hot and cold gas reservoirs, rather than a lack of available gas or gravitational heating from infalling clumps, (2) state-of-the-art semi-analytic models currently overpredict the effect of major halo mergers on quenching, and (3) major halo mergers can trigger enhanced star formation in non-quenched central galaxies.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 10
    Publication Date: 2015-06-11
    Description: We investigate the variation of the ratio of the equivalent widths of the Fe ii 2600 line to the Mg ii 2796, 2803 doublet as a function of redshift in a large sample of absorption lines drawn from the Johns Hopkins University - Sloan Digital Sky Survey Absorption Line Catalog. We find that despite large scatter, the observed ratio shows a trend where the equivalent width ratio $\mathcal {R}\equiv W_{\rm Fe\,\small {II}}/W_{\rm Mg\,\small {II}}$ decreases monotonically with increasing redshift z over the range 0.55 ≤  z  ≤ 1.90. Selecting the subset of absorbers where the signal-to-noise ratio of the Mg ii equivalent width $W_{\rm Mg\,\small {II}}\ {\rm is} \ge 3$ and modelling the equivalent width ratio distribution as a Gaussian, we find that the mean of the Gaussian distribution varies as $\mathcal {R}\propto (-0.045\pm 0.005)z$ . We discuss various possible reasons for the trend. A monotonic trend in the Fe/Mg abundance ratio is predicted by a simple model where the abundances of Mg and Fe in the absorbing clouds are assumed to be the result of supernova (SN) ejecta and where the cosmic evolution in the SNIa and core-collapse SN rates is related to the cosmic star formation rate. If the trend in $\mathcal {R}$ reflects the evolution in the abundances, then it is consistent with the predictions of the simple model.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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