1,824 research outputs found
Preliminary vegetation map of the Espenberg Peninsula, Alaska, based on an Earth Resources Technology Satellite image
There are no author-identified significant results in this report
Simple technologies for fabrication of low-loss silica waveguides
A simple and reproducible technology is developed for the fabrication of low-loss silica waveguides on silicon substrates. The guiding layer is formed by changing the Si-O ratio composition of the SiO/sub 2/ layer. The waveguides can be made to have a good match to either optical fibres or guided-wave devices in III-V compound semiconductor
Individual scatterers as microscopic origin of equilibration between spin- polarized edge channels in the quantum Hall regime
The equilibration length between spin-polarized edge states in the Quantum
Hall regime is measured as a function of a gate voltage applied to an electrode
on top of the edge channels. Reproducible fluctuations in the coupling are
observed and interpreted as a mesoscopic fingerprint of single spin-flip
scatterers which are turned on and off. A model to analyze macroscopic edge
state coupling in terms of individual scatterers is developed, and
characteristic values for these scatterers in our samples are extracted. For
all samples investigated, the distance between spin-flip scatterers lies
between the Drude and the quantum scattering length.Comment: 4 pages, 2 figure
Ubiquitin-specific protease-like 1 (USPL1) is a SUMO isopeptidase with essential, non-catalytic functions.
Isopeptidases are essential regulators of protein ubiquitination and sumoylation. However, only two families of SUMO isopeptidases are at present known. Here, we report an activity-based search with the suicide inhibitor haemagglutinin (HA)-SUMO-vinylmethylester that led to the identification of a surprising new SUMO protease, ubiquitin-specific protease-like 1 (USPL1). Indeed, USPL1 neither binds nor cleaves ubiquitin, but is a potent SUMO isopeptidase both in vitro and in cells. C13orf22lâan essential but distant zebrafish homologue of USPL1âalso acts on SUMO, indicating functional conservation. We have identified invariant USPL1 residues required for SUMO binding and cleavage. USPL1 is a low-abundance protein that colocalizes with coilin in Cajal bodies. Its depletion does not affect global sumoylation, but causes striking coilin mislocalization and impairs cell proliferation, functions that are not dependent on USPL1 catalytic activity. Thus, USPL1 represents a third type of SUMO protease, with essential functions in Cajal body biology
Signals for Lorentz Violation in Post-Newtonian Gravity
The pure-gravity sector of the minimal Standard-Model Extension is studied in
the limit of Riemann spacetime. A method is developed to extract the modified
Einstein field equations in the limit of small metric fluctuations about the
Minkowski vacuum, while allowing for the dynamics of the 20 independent
coefficients for Lorentz violation. The linearized effective equations are
solved to obtain the post-newtonian metric. The corresponding post-newtonian
behavior of a perfect fluid is studied and applied to the gravitating many-body
system. Illustrative examples of the methodology are provided using bumblebee
models. The implications of the general theoretical results are studied for a
variety of existing and proposed gravitational experiments, including lunar and
satellite laser ranging, laboratory experiments with gravimeters and torsion
pendula, measurements of the spin precession of orbiting gyroscopes, timing
studies of signals from binary pulsars, and the classic tests involving the
perihelion precession and the time delay of light. For each type of experiment
considered, estimates of the attainable sensitivities are provided. Numerous
effects of local Lorentz violation can be studied in existing or near-future
experiments at sensitivities ranging from parts in 10^4 down to parts in
10^{15}.Comment: 46 pages two-column REVTeX, accepted in Physical Review
Transient deSUMOylation of IRF2BP proteins controls early transcription in EGFR signaling
Molecular switches are essential modules in signaling networksand transcriptional reprogramming. Here, we describe a role forsmall ubiquitin-related modifier SUMO as a molecular switch inepidermal growth factor receptor (EGFR) signaling. Using quantita-tive mass spectrometry, we compare the endogenous SUMOproteomes of HeLa cells before and after EGF stimulation. Thereby,we identify a small group of transcriptional coregulators includingIRF2BP1, IRF2BP2, and IRF2BPL as novel players in EGFR signaling.Comparison of cells expressing wild type or SUMOylation-deficientIRF2BP1indicates that transient deSUMOylation of IRF2BP proteinsis important for appropriate expression of immediate early genesincludingdual specificity phosphatase1(DUSP1, MKP-1) and thetranscription factor ATF3. We find that IRF2BP1is a repressor,whose transient deSUMOylation on the DUSP1promoter allowsâand whose timely reSUMOylation restrictsâDUSP1transcription.Our work thus provides a paradigm how comparative SUMOproteome analyses serve to reveal novel regulators in signal trans-duction and transcription
Evidence for Ubiquitous, High-EW Nebular Emission in z~7 Galaxies: Towards a Clean Measurement of the Specific Star Formation Rate using a Sample of Bright, Magnified Galaxies
Growing observational evidence now indicates that nebular line emission has a
significant impact on the rest-frame optical fluxes of z~5-7 galaxies observed
with Spitzer. This line emission makes z~5-7 galaxies appear more massive, with
lower specific star formation rates. However, corrections for this line
emission have been very difficult to perform reliably due to huge uncertainties
on the overall strength of such emission at z>~5.5. Here, we present the most
direct observational evidence yet for ubiquitous high-EW [OIII]+Hbeta line
emission in Lyman-break galaxies at z~7, while also presenting a strategy for
an improved measurement of the sSFR at z~7. We accomplish this through the
selection of bright galaxies in the narrow redshift window z~6.6-7.0 where the
IRAC 4.5 micron flux provides a clean measurement of the stellar continuum
light. Observed 4.5 micron fluxes in this window contrast with the 3.6 micron
fluxes which are contaminated by the prominent [OIII]+Hbeta lines. To ensure a
high S/N for our IRAC flux measurements, we consider only the brightest
(H_{160}<26 mag) magnified galaxies we have identified in CLASH and other
programs targeting galaxy clusters. Remarkably, the mean rest-frame optical
color for our bright seven-source sample is very blue, [3.6]-[4.5]=-0.9+/-0.3.
Such blue colors cannot be explained by the stellar continuum light and require
that the rest-frame EW of [OIII]+Hbeta be greater than 637 Angstroms for the
average source. The bluest four sources from our seven-source sample require an
even more extreme EW of 1582 Angstroms. Our derived lower limit for the mean
[OIII]+Hbeta EW could underestimate the true EW by ~2x based on a simple
modeling of the redshift distribution of our sources. We can also set a robust
lower limit of >~4 Gyr^-1 on the specific star formation rates based on the
mean SED for our seven-source sample. (abridged)Comment: 9 pages, 6 figures, 1 table, submitted to the Astrophysical Journa
CLASH: z ~ 6 young galaxy candidate quintuply lensed by the frontier field cluster RXC J2248.7-4431
We present a quintuply lensed z ~ 6 candidate discovered in the field of the
galaxy cluster RXC J2248.7-4431 (z ~ 0.348) targeted within the Cluster Lensing
and Supernova survey with Hubble (CLASH) and selected in the deep HST Frontier
Fields survey. Thanks to the CLASH 16-band HST imaging, we identify the
quintuply lensed z ~ 6 candidate as an optical dropout in the inner region of
the cluster, the brightest image having magAB=24.81+-0.02 in the f105w filter.
We perform a detailed photometric analysis to verify its high-z and lensed
nature. We get as photometric redshift z_phot ~ 5.9, and given the extended
nature and NIR colours of the lensed images, we rule out low-z early type and
galactic star contaminants. We perform a strong lensing analysis of the
cluster, using 13 families of multiple lensed images identified in the HST
images. Our final best model predicts the high-z quintuply lensed system with a
position accuracy of 0.8''. The magnifications of the five images are between
2.2 and 8.3, which leads to a delensed UV luminosity of L_1600 ~ 0.5L*_1600 at
z=6. We also estimate the UV slope from the observed NIR colours, finding a
steep beta=-2.89+-0.38. We use singular and composite stellar population SEDs
to fit the photometry of the hiz candidate, and we conclude that it is a young
(age <300 Myr) galaxy with mass of M ~ 10^8Msol, subsolar metallicity
(Z<0.2Zsol) and low dust content (AV ~ 0.2-0.4).Comment: 21 pages, 13 figures, 6 tables, submitted to MNRAS on 11 Aug 2013,
accepted on 23 Nov 201
Difference Image Analysis of Galactic Microlensing I. Data Analysis
This is a preliminary report on the application of Difference Image Analysis
(DIA) to galactic bulge images. The aim of this analysis is to increase the
sensitivity to the detection of gravitational microlensing. We discuss how the
DIA technique simplifies the process of discovering microlensing events by
detecting only objects which have variable flux. We illustrate how the DIA
technique is not limited to detection of so called ``pixel lensing'' events,
but can also be used to improve photometry for classical microlensing events by
removing the effects of blending. We will present a method whereby DIA can be
used to reveal the true unblended colours, positions and light curves of
microlensing events. We discuss the need for a technique to obtain the accurate
microlensing time scales from blended sources, and present a possible solution
to this problem using the existing HST colour magnitude diagrams of the
galactic bulge and LMC. The use of such a solution with both classical and
pixel microlensing searches is discussed. We show that one of the major causes
of systematic noise in DIA is differential refraction. A technique for removing
this systematic by effectively registering images to a common airmass is
presented. Improvements to commonly used image differencing techniques are
discussed.Comment: 18 pages, 8 figures, uses AAS LaTEX 4.0, To appear in Astrophysical
Journa
The influence of anesthetics, neurotransmitters and antibiotics on the relaxation processes in lipid membranes
In the proximity of melting transitions of artificial and biological
membranes fluctuations in enthalpy, area, volume and concentration are
enhanced. This results in domain formation, changes of the elastic constants,
changes in permeability and slowing down of relaxation processes. In this study
we used pressure perturbation calorimetry to investigate the relaxation time
scale after a jump into the melting transition regime of artificial lipid
membranes. This time corresponds to the characteristic rate of domain growth.
The studies were performed on single-component large unilamellar and
multilamellar vesicle systems with and without the addition of small molecules
such as general anesthetics, neurotransmitters and antibiotics. These drugs
interact with membranes and affect melting points and profiles. In all systems
we found that heat capacity and relaxation times are related to each other in a
simple manner. The maximum relaxation time depends on the cooperativity of the
heat capacity profile and decreases with a broadening of the transition. For
this reason the influence of a drug on the time scale of domain formation
processes can be understood on the basis of their influence on the heat
capacity profile. This allows estimations of the time scale of domain formation
processes in biological membranes.Comment: 12 pages, 6 figure
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