439 research outputs found
Thermo-magnetic hysteretic properties resembling superconductivity in the normal state of La1.85Sr0.15CuO4
We have performed detailed magnetic and thermal hysteresis experiments in the
normal-state magnetization of La1.85Sr0.15CuO4 single crystal. Using a
combination of in-field and in-zero-magnetic-field measurements at different
stages of thermal history of the sample, we identified subtle effects
associated with the presence of magnetic signatures which resemble those below
the superconducting transition temperature (Tc=36 K) but survive up to 250 K.Comment: One file including text and figure
The Bean-Livingston barrier at a superconductor/magnet interface
The Bean-Livingston barrier at the interface of type-II
superconductor/soft-magnet heterostructures is studied on the basis of the
classical London approach. This shows a characteristic dependence on the
geometry of the particular structure and its interface as well as on the
relative permeability of the involved magnetic constituent. The modification of
the barrier by the presence of the magnet can be significant, as demonstrated
for a cylindrical superconducting filament covered with a coaxial magnetic
sheath. Using typical values of the relative permeability, the critical field
of first penetration of magnetic flux is predicted to be strongly enhanced,
whereas the variation of the average critical current density with the external
field is strongly depressed, in accord with the observations of recent
experiments.Comment: RevTeX 4; revised version; accepted in Journal of Physics: Condensed
Matte
MiRonTop: mining microRNAs targets across large scale gene expression studies
Summary: Current challenges in microRNA (miRNA) research are to improve the identification of in vivo mRNA targets and clarify the complex interplay existing between a specific miRNA and multiple biological networks. MiRonTop is an online java web tool that integrates DNA microarrays or high-throughput sequencing data to identify the potential implication of miRNAs on a specific biological system. It allows a rapid characterization of the most pertinent mRNA targets according to several existing miRNA target prediction approaches. It also provides useful representations of the enrichment scores according to the position of the target site along the 3′-UTR, where the contribution of the sites located in the vicinity of the stop codon and of the polyA tail can be clearly highlighted. It provides different graphs of miRNA enrichment associated with up- or down-regulated transcripts and different summary tables about selections of mRNA targets and their functional annotations by Gene Ontology
Influence of field penetration ratios and filamentation on end-effect related hysteretic loss reductions for superconducting strips
There are a few key conductor-specific factors which influence the power loss of
superconductors; these include critical current, geometry, and normal metal resistivity. This
paper focuses on the influence of sample geometry on the power loss of superconducting strips
and the effect of filamentation and sample length as a function of the field penetration state of
the superconductor. We start with the analytical equations for infinite slabs and strips and then
consider the influence of end effects for both unstriated and striated conductor. The loss is then
calculated and compared as a function of applied field for striated and unstriated conductors.
These results are much more general than they might seem at first glance, since they will be
important building blocks for analytic loss calculations for twisted geometries for coated
conductors, including helical (Conductor on Round Core, CORC), and twisted (e.g., twist stack
cables) geometries. We show that for relatively low field penetration, end effects and reduced
field penetration both reduce loss. In addition, for filamentary samples the relevant ratio of length
scales becomes the filament width to sample length, thus modifying the loss ratios.Funding was provided by the U.S. Department of Energy, Office of High Energy Physics, under
Grants No. DE-SC0011721 and the Chinese Scholarship Council.This paper investigates the influence of sample geometry on the loss of superconducting strips and the
effect of filamentation and sample length as a function of the field penetration state of the
superconductor. The loss for finite segments is calculated as a function of applied field for striated and
unstriated conductors. These results are much more general than they might seem at first glance, since
they will be important building blocks for analytic loss calculations for twisted geometries for coated
conductors, including helical (Conductor on Round Core, CORC), and twisted (e.g., twist stack cables)
geometries. For high levels of flux penetration, the end effects are those for superconducting slabs, while
for relatively low field penetration, end effects and reduced field penetration both reduce loss. However,
for filamentary samples the ratio of length scales becomes filament width to sample length, thus
modifying the loss ratios. This leads to an apparent reduction in the end effects, since the relevant ratio
which controls them is the filament width to sample length, rather than the whole conductor width to
sample length.
Acknowledgment
Diffusion of Alexa Fluor 488-Conjugated Dendrimers in Rat Aortic Tissue
In this study, the distribution of labeled dendrimers in native and aneurysmal rat aortic tissue was examined. Adult male rats underwent infrarenal aorta perfusion with generation 5 (G5) acetylated Alexa Fluor 488-conjugated dendrimers for varying lengths of time. In a second set of experiments, rats underwent aortic elastase perfusion followed by aortic dendrimer perfusion 7 days later. Aortic diameters were measured prior to and postelastase perfusion, and again on the day of harvest. Aortas were harvested 0, 12, or 24 h postperfusion, fixed, and mounted. Native aortas were harvested and viewed as negative controls. Aortic cross-sections were viewed and imaged using confocal microscopy. Dendrimers were quantified (counts high-powered field). Results were evaluated by repeated measures ANOVA and Student's t -test. We found that in native aortas, dendrimers penetrated the aortic wall in all groups. For all perfusion times, fewer dendrimers were present as time between dendrimer perfusion and aortic harvest increased. Longer perfusion times resulted in increased diffusion of dendrimers throughout the aortic wall. By 24 h, the majority of the dendrimers were through the wall. Dendrimers in aneurysmal aortas, on day 0 postdendrimer perfusion, diffused farther into the aortic wall than controls. In conclusion, this study documents labeled dendrimers delivered intra-arterially to native rat aortas in vivo , and the temporal diffusion of these molecules within the aortic wall. Increasing perfusion time and length of time prior to harvest resulted in continued dendrimer diffusion into the aortic wall. These preliminary data provide a novel mechanism whereby local inhibitory therapy may be delivered locally to aortic tissue.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72448/1/annals.1383.004.pd
Modeling the Evolution of Regulatory Elements by Simultaneous Detection and Alignment with Phylogenetic Pair HMMs
The computational detection of regulatory elements in DNA is a difficult but important problem impacting our progress in understanding the complex nature of eukaryotic gene regulation. Attempts to utilize cross-species conservation for this task have been hampered both by evolutionary changes of functional sites and poor performance of general-purpose alignment programs when applied to non-coding sequence. We describe a new and flexible framework for modeling binding site evolution in multiple related genomes, based on phylogenetic pair hidden Markov models which explicitly model the gain and loss of binding sites along a phylogeny. We demonstrate the value of this framework for both the alignment of regulatory regions and the inference of precise binding-site locations within those regions. As the underlying formalism is a stochastic, generative model, it can also be used to simulate the evolution of regulatory elements. Our implementation is scalable in terms of numbers of species and sequence lengths and can produce alignments and binding-site predictions with accuracy rivaling or exceeding current systems that specialize in only alignment or only binding-site prediction. We demonstrate the validity and power of various model components on extensive simulations of realistic sequence data and apply a specific model to study Drosophila enhancers in as many as ten related genomes and in the presence of gain and loss of binding sites. Different models and modeling assumptions can be easily specified, thus providing an invaluable tool for the exploration of biological hypotheses that can drive improvements in our understanding of the mechanisms and evolution of gene regulation
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