2,725 research outputs found
Agonist-Specific Calcium Signaling and Phosphoinositide Hydrolysis in Human SK-N-MCIXC Neuroepithelioma Cells
Fura-2 digital imaging microfluorimetry was used to evaluate the Ca 2+ signals generated in single clonal human neuroepithelioma cells (SK-N-MCIXC) in response to agonists that stimulate phosphoinositide hydrolysis. Addition of optimal concentrations of either endothelin-1 (ET-1), ATP, oxotremorine-M (Oxo-M), or norepinephrine (NE) all resulted in an increase in the concentration of cytosolic calcium (Ca 2+ i ) but of different magnitudes (ET-1 = ATP> NE). The Ca 2+ signals elicited by the individual agonists also differed from each other in terms of their latency of onset, rate of rise and decay, and prevalence of a sustained phase of Ca 2+ influx. The Ca 2+ signals that occurred in response to ATP had a shorter latency and more rapid rates of rise and decay than those observed for the other three agonists. Furthermore, a sustained plateau phase of the Ca 2+ signal, which was characteristic of the response to Oxo-M, was observed in 94% of cells responded to ET-1 or ATP, whereas corresponding values for Oxo-M and NE were ∼74 and ∼48%. Sequential addition of agonists to cells maintained in a Ca 2+ -free buffer indicated that each ligand mobilized Ca 2+ from a common intracellular pool. When monitored as a release of a total inositol phosphate fraction, all four agonists elicited similar (four- to sixfold) increases in phosphoinositide hydrolysis. However, the addition of ET-1 or ATP resulted in larger increases in the net formation of inositol 1,4,5-trisphosphate than did either Oxo-M or NE. These results indicate that, in SK-N-MCIXC cells, the characteristics of both Ca 2+ signaling and inositol phosphate production are agonist specific.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66414/1/j.1471-4159.1994.63062099.x.pd
Phase Diagram of Pressure-Induced Superconductivity in EuFe2As2 Probed by High-Pressure Resistivity up to 3.2 GPa
We have constructed a pressuretemperature () phase diagram of
-induced superconductivity in EuFeAs single crystals, via
resistivity () measurements up to 3.2 GPa. As hydrostatic pressure is
applied, an antiferromagnetic (AF) transition attributed to the FeAs layers at
shifts to lower temperatures, and the corresponding resistive
anomaly becomes undetectable for 2.5 GPa. This suggests that the
critical pressure where becomes zero is about 2.5
GPa. We have found that the AF order of the Eu moments survives up to
3.2 GPa without significant changes in the AF ordering temperature
. The superconducting (SC) ground state with a sharp transition
to zero resistivity at 30 K, indicative of bulk
superconductivity, emerges in a pressure range from 2.5
GPa to 3.0 GPa. At pressures close to but outside the SC phase, the
curve shows a partial SC transition (i.e., zero resistivity is not
attained) followed by a reentrant-like hump at approximately
with decreasing temperature. When nonhydrostatic pressure with a uniaxial-like
strain component is applied using a solid pressure medium, the partial
superconductivity is continuously observed in a wide pressure range from 1.1
GPa to 3.2 GPa.Comment: 7 pages, 6 figures, accepted for publication in Physical Review B,
selected as "Editors' Suggestion
Proximal nested sampling with data-driven priors for physical scientists
Proximal nested sampling was introduced recently to open up Bayesian model
selection for high-dimensional problems such as computational imaging. The
framework is suitable for models with a log-convex likelihood, which are
ubiquitous in the imaging sciences. The purpose of this article is two-fold.
First, we review proximal nested sampling in a pedagogical manner in an attempt
to elucidate the framework for physical scientists. Second, we show how
proximal nested sampling can be extended in an empirical Bayes setting to
support data-driven priors, such as deep neural networks learned from training
data.Comment: 9 pages, 4 figure
Design and Vertical Tests of SPS-series Double-Quarter Wave (DQW) Cavity Prototypes for the HL-LHC Crab Cavity System
Crab crossing is essential for high-luminosity colliders. The High Luminosity
Large Hadron Collider (HL-LHC) will equip one of its Interaction Points (IP1)
with Double-Quarter Wave (DQW) crab cavities. A DQW cavity is a new generation
of deflecting RF cavities that stands out for its compactness and broad
frequency separation between fundamental and first high-order modes. The
deflecting kick is provided by its fundamental mode. Each HL-LHC DQW cavity
shall provide a nominal deflecting voltage of 3.4 MV, although up to 5.0 MV may
be required. A Proof-of-Principle (PoP) DQW cavity was limited by quench at 4.6
MV. This paper describes a new, highly optimized cavity, designated DQW
SPS-series, which satisfies dimensional, cryogenic, manufacturing and impedance
requirements for beam tests at SPS and operation in LHC. Two prototypes of this
DQW SPS-series were fabricated by US industry and cold tested after following
conventional SRF surface treatment. Both units outperformed the PoP cavity,
reaching a deflecting voltage of 5.3-5.9 MV. This voltage - the highest reached
by a DQW cavity - is well beyond the nominal voltage of 3.4 MV and may even
operate at the ultimate voltage of 5.0MVwith sufficient margin. This paper
covers fabrication, surface preparation and cryogenic RF test results and
implications
Galileo dust data from the jovian system: 2000 to 2003
The Galileo spacecraft was orbiting Jupiter between Dec 1995 and Sep 2003.
The Galileo dust detector monitored the jovian dust environment between about 2
and 370 R_J (jovian radius R_J = 71492 km). We present data from the Galileo
dust instrument for the period January 2000 to September 2003. We report on the
data of 5389 particles measured between 2000 and the end of the mission in
2003. The majority of the 21250 particles for which the full set of measured
impact parameters (impact time, impact direction, charge rise times, charge
amplitudes, etc.) was transmitted to Earth were tiny grains (about 10 nm in
radius), most of them originating from Jupiter's innermost Galilean moon Io.
Their impact rates frequently exceeded 10 min^-1. Surprisingly large impact
rates up to 100 min^-1 occurred in Aug/Sep 2000 when Galileo was at about 280
R_J from Jupiter. This peak in dust emission appears to coincide with strong
changes in the release of neutral gas from the Io torus. Strong variability in
the Io dust flux was measured on timescales of days to weeks, indicating large
variations in the dust release from Io or the Io torus or both on such short
timescales. Galileo has detected a large number of bigger micron-sized
particles mostly in the region between the Galilean moons. A surprisingly large
number of such bigger grains was measured in March 2003 within a 4-day interval
when Galileo was outside Jupiter's magnetosphere at approximately 350 R_J
jovicentric distance. Two passages of Jupiter's gossamer rings in 2002 and 2003
provided the first actual comparison of in-situ dust data from a planetary ring
with the results inferred from inverting optical images.Comment: 59 pages, 13 figures, 6 tables, submitted to Planetary and Space
Scienc
A novel epilepsy mutation in the sodium channel SCN1A identifies a cytoplasmic domain for {beta} subunit interaction
A mutation in the sodium channel SCN1A was identified in a small Italian family with dominantly inherited generalized epilepsy with febrile seizures plus (GEFS+). The mutation, D1866Y, alters an evolutionarily conserved aspartate residue in the C-terminal cytoplasmic domain of the sodium channel {alpha} subunit. The mutation decreased modulation of the {alpha} subunit by {beta}1, which normally causes a negative shift in the voltage dependence of inactivation in oocytes. There was less of a shift with the mutant channel, resulting in a 10 mV difference between the wild-type and mutant channels in the presence of {beta}1. This shift increased the magnitude of the window current, which resulted in more persistent current during a voltage ramp. Computational analysis suggests that neurons expressing the mutant channels will fire an action potential with a shorter onset delay in response to a threshold current injection, and that they will fire multiple action potentials with a shorter interspike interval at a higher input stimulus. These results suggest a causal relationship between a positive shift in the voltage dependence of sodium channel inactivation and spontaneous seizure activity. Direct interaction between the cytoplasmic C-terminal domain of the wild-type{alpha} subunit with the {beta}1or {beta}3 subunit was first demonstrated by yeast two-hybrid analysis. The SCN1A peptide K1846-R1886 is sufficient for {beta} subunit interaction. Coimmunoprecipitation from transfected mammalian cells confirmed the interaction between the C-terminal domains of the {alpha} and {beta}1 subunits. The D1866Y mutation weakens this interaction, demonstrating a novel molecular mechanism leading to seizure susceptibility
Genome size and ploidy of Paracoccidioides brasiliensis reveals a haploid DNA content: Flow cytometry and GP43 sequence analysis
The aim of this study was to evaluate genome size and ploidy of the dimorphic pathogenic fungus Paracoccidioides brasiliensis. The cell cycle analysis of 10 P. brasiliensis isolates by flow cytometry (FCM) revealed a genome size ranging from 26.3+/-0.1Mb (26.9+/-0.1fg) to 35.5+/-0.2Mb (36.3+/-0.2fg) per uninucleated yeast cell. The DNA content of conidia from P. brasiliensis ATCC 60855-30.2+/-0.8Mb (30.9+/-0.8fg) -showed no significant differences with the yeast form, possibly excluding the occurrence of ploidy shift during morphogenesis. The ploidy of several P. brasiliensis isolates was assessed by comparing genome sizing by FCM with the previously described average haploid size obtained from electrophoretic karyotyping. The analysis of intra-individual variability of a highly polymorphic P. brasiliensis gene, GP43, indicated that only one allele seems to be present. Overall, the results showed that all analysed isolates presented a haploid, or at least aneuploid, DNA content and no association was detected between genome size/ploidy and the clinical-epidemiological features of the studied isolates. This work provides new knowledge on P. brasiliensis genetics/genomics, important for future research in basic cellular/molecular mechanisms and for the development/design of molecular techniques in this fungus
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