205 research outputs found
A multi-scale multi-frequency deconvolution algorithm for synthesis imaging in radio interferometry
Aims : We describe MS-MFS, a multi-scale multi-frequency deconvolution
algorithm for wide-band synthesis-imaging, and present imaging results that
illustrate the capabilities of the algorithm and the conditions under which it
is feasible and gives accurate results.
Methods : The MS-MFS algorithm models the wide-band sky-brightness
distribution as a linear combination of spatial and spectral basis functions,
and performs image-reconstruction by combining a linear-least-squares approach
with iterative minimization. This method extends and combines the
ideas used in the MS-CLEAN and MF-CLEAN algorithms for multi-scale and
multi-frequency deconvolution respectively, and can be used in conjunction with
existing wide-field imaging algorithms. We also discuss a simpler hybrid of
spectral-line and continuum imaging methods and point out situations where it
may suffice.
Results : We show via simulations and application to multi-frequency VLA data
and wideband EVLA data, that it is possible to reconstruct both spatial and
spectral structure of compact and extended emission at the continuum
sensitivity level and at the angular resolution allowed by the highest sampled
frequency.Comment: 17 pages, 11 figure
On the Calibration of Full-polarization 86GHz Global VLBI Observations
We report the development of a semi-automatic pipeline for the calibration of
86 GHz full-polarization observations performed with the Global Millimeter-VLBI
array (GMVA) and describe the calibration strategy followed in the data
reduction. Our calibration pipeline involves non-standard procedures, since
VLBI polarimetry at frequencies above 43 GHz is not yet well established. We
also present, for the first time, a full-polarization global-VLBI image at 86
GHz (source 3C 345), as an example of the final product of our calibration
pipeline, and discuss the effect of instrumental limitations on the fidelity of
the polarization images. Our calibration strategy is not exclusive for the
GMVA, and could be applied on other VLBI arrays at millimeter wavelengths. The
use of this pipeline will allow GMVA observers to get fully-calibrated datasets
shortly after the data correlation.Comment: 10 pages, 10 figures. Accepted for publication in A&
On the Tort of Light Pollution
光污染是现代社会的新公害。光污染,在英美被称为“干扰光”,在日本则称其为“光害”,在德国则被视为“不可量物”的一种,而在我国,有学者援用“噪音”的说法,将其称“噪光”。光污染是指因不当使用人为照明或其它设备造成光的入侵而引起的不良影响。对于光污染,根据不同的标准可以作不同的分类。例如根据光污染发生时间的不同,可以将光污染分为昼光光污染和夜光光污染。国际上一般将光污染分成三类,即白亮污染、人工白昼和彩光污染。光污染对环境、生物和人都危害甚巨。 我国现行涉及光污染侵权的立法主要体现在宪法、民法通则、物权法、侵权责任法、环境保护法和地方立法之中。我国现行涉及光污染侵权的立法,无论是中央立法还是地方...Light pollution is a new form of environment pollution in modern society. It was called "interference of light" in Britain and America. It was called "light nuisance" in Japan. In Germany, light pollution is considered to be a kind of "non-amount of matter". Light pollution is due to the improper use of artificial lighting and the adverse effects caused by the invasion of light. According to the d...学位:法律硕士院系专业:法学院法律系_法律硕士(JM)学号:1302009115036
The effect of systematics on polarized spectral indices
We study four particularly bright polarized compact objects (Tau A, Virgo A,
3C273 and Fornax A) in the 7-year WMAP sky maps, with the goal of understanding
potential systematics involved in estimation of foreground spectral indices. We
estimate the spectral index, the polarization angle, the polarization fraction
and apparent size and shape of these objects when smoothed to a nominal
resolution of 1 degree FWHM. Second, we compute the spectral index as a
function of polarization orientation, alpha. Because these objects are
approximately point sources with constant polarization angle, this function
should be constant in the absence of systematics. However, computing it for the
K- and Ka-band WMAP data we find strong index variations for all four sources.
For Tau A, we find a spectral index beta=-2.59+-0.03 for alpha=30 degrees, and
beta=-2.03+-0.01 for alpha=50 degrees. On the other hand, the spectral index
between Ka and Q band is found to be stable. A simple elliptical Gaussian toy
model with parameters matching those observed in Tau A reproduces the observed
signal, and shows that the spectral index is in particular sensitive to the
detector polarization angle. Based on these findings, we first conclude that
estimation of spectral indices with the WMAP K-band polarization data at 1
degree scales is not robust. Second, we note that these issues may be of
concern for ground-based and sub-orbital experiments that use the WMAP
polarization measurements of Tau A for calibration of gain and polarization
angles.Comment: 5 pages, 6 figures, submitted to ApJ; new figure and expanded
conclusio
Properties of Interfaces in the two and three dimensional Ising Model
To investigate order-order interfaces, we perform multimagnetical Monte Carlo
simulations of the and Ising model. Following Binder we extract the
interfacial free energy from the infinite volume limit of the magnetic
probability density. Stringent tests of the numerical methods are performed by
reproducing with high precision exact results. In the physically more
interesting case we estimate the amplitude of the critical
interfacial tension to be . This
result is in good agreement with a previous MC calculation by Mon, as well as
with experimental results for related amplitude ratios. In addition, we study
in some details the shape of the magnetic probability density for temperatures
below the Curie point.Comment: 25 pages; sorry no figures include
Renormalized spin coefficients in the accumulated orbital phase for unequal mass black hole binaries
We analyze galactic black hole mergers and their emitted gravitational waves.
Such mergers have typically unequal masses with mass ratio of the order 1/10.
The emitted gravitational waves carry the inprint of spins and mass quadrupoles
of the binary components. Among these contributions, we consider here the
quasi-precessional evolution of the spins. A method of taking into account
these third post-Newtonian (3PN) effects by renormalizing (redefining) the 1.5
PN and 2PN accurate spin contributions to the accumulated orbital phase is
developed.Comment: 10 pages, to appear in Class. Quantum Grav. GWDAW13 Proceedings
Special Issue, v2: no typos conjectur
Ca2+ monitoring in Plasmodium falciparum using the yellow cameleon-Nano biosensor
Calcium (Ca2+)-mediated signaling is a conserved mechanism in eukaryotes, including the human malaria parasite, Plasmodium falciparum. Due to its small size (300?nM). We determined that the mammalian SERCA inhibitor thapsigargin and antimalarial dihydroartemisinin did not perturb SERCA activity. The change of the cytosolic Ca2+ level in P. falciparum was additionally detectable by flow cytometry. Thus, we propose that the developed YC-Nano-based system is useful to study Ca2+ signaling in P. falciparum and is applicable for drug screening.We are grateful to Japanese Red Cross Blood Society for providing human RBC and plasma. We also thank Tanaka R, Ogoshi (Sakura) M and Matsumoto N for technical assistance and Templeton TJ for critical reading. This study was conducted at the Joint Usage / Research Center on Tropical Disease, Institute of Tropical Medicine, Nagasaki University, Japan. KP was a Tokyo Biochemical Research Foundation (TBRF, http://www.tokyobrf.or.jp) post-doctoral fellow and PEF was a Japanese Society of Promotion Sciences (JSPS) post-doctoral fellow. This work was supported in part by the TBRF (K.P.), JSPS (P.E.F.), Takeda Science Foundation (K.Y.), Grants-in-Aids for Scientific Research 24590509 (K.Y.), 22390079 (O.K.), and for Scientific Research on Innovative Areas 23117008 (O.K.), MEXT, Japan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Default Pathway of var2csa Switching and Translational Repression in Plasmodium falciparum
Antigenic variation is a subtle process of fundamental importance to the survival of a microbial pathogen. In Plasmodium falciparum malaria, PfEMP1 is the major variable antigen and adhesin expressed at the surface of the infected erythrocyte, which is encoded for by members of a family of 60 var-genes. Peri-nuclear repositioning and epigenetic mechanisms control their mono-allelic expression. The switching of PfEMP1 depends in part on variable transition rates and short-lived immune responses to shared minor epitopes. Here we show var-genes to switch to a common gene that is highly transcribed, but sparsely translated into PfEMP1 and not expressed at the erythrocyte surface. Highly clonal and adhesive P. falciparum, which expressed distinct var-genes and the corresponding PfEMP1s at onset, were propagated without enrichment or panning. The parasites successively and spontaneously switched to transcribe a shared var-gene (var2csa) matched by the loss of PfEMP1 surface expression and host cell-binding. The var2csa gene repositioned in the peri-nuclear area upon activation, away from the telomeric clusters and heterochromatin to transcribe spliced, full-length RNA. Despite abundant transcripts, the level of intracellular PfEMP1 was low suggesting post-transcriptional mechanisms to partake in protein expression. In vivo, off-switching and translational repression may constitute one pathway, among others, coordinating PfEMP1 expression
Glycogen Synthase Kinase-3 regulates multiple myeloma cell growth and bortezomib-induced cell death
BACKGROUND:
Glycogen Synthase Kinase-3 (GSK-3) \u3b1 and \u3b2 are two serine-threonine kinases controlling insulin, Wnt/\u3b2-catenin, NF-\u3baB signaling and other cancer-associated transduction pathways. Recent evidence suggests that GSK-3 could function as growth-promoting kinases, especially in malignant cells. In this study, we have investigated GSK-3\u3b1 and GSK-3\u3b2 function in multiple myeloma (MM).
METHODS:
GSK-3 \u3b1 and \u3b2 expression and cellular localization were investigated by Western blot (WB) and immunofluorescence analysis in a panel of MM cell lines and in freshly isolated plasma cells from patients. MM cell growth, viability and sensitivity to bortezomib was assessed upon treatment with GSK-3 specific inhibitors or transfection with siRNAs against GSK-3 \u3b1 and \u3b2 isoforms. Survival signaling pathways were studied with WB analysis.
RESULTS:
GSK-3\u3b1 and GSK-3\u3b2 were differently expressed and phosphorylated in MM cells. Inhibition of GSK-3 with the ATP-competitive, small chemical compounds SB216763 and SB415286 caused MM cell growth arrest and apoptosis through the activation of the intrinsic pathway. Importantly, the two inhibitors augmented the bortezomib-induced MM cell cytotoxicity. RNA interference experiments showed that the two GSK-3 isoforms have distinct roles: GSK-3\u3b2 knock down decreased MM cell viability, while GSK-3\u3b1 knock down was associated with a higher rate of bortezomib-induced cytotoxicity. GSK-3 inhibition caused accumulation of \u3b2-catenin and nuclear phospho-ERK1, 2. Moreover, GSK-3 inhibition and GSK-3\u3b1 knockdown enhanced bortezomib-induced AKT and MCL-1 protein degradation. Interestingly, bortezomib caused a reduction of GSK-3 serine phosphorylation and its nuclear accumulation with a mechanism that resulted partly dependent on GSK-3 itself.
CONCLUSIONS:
These data suggest that in MM cells GSK-3\u3b1 and \u3b2 i) play distinct roles in cell survival and ii) modulate the sensitivity to proteasome inhibitors
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