755 research outputs found
RAPIDLY-LABELLED, ACIDIC PHOSPHOLIPIDS OF THE GOLDFISH BRAIN 1
Homogenates and particulate fractions of goldfish brain incorporated radioactivity from Γ-[ 32 P]ATP selectively into acidic phospholipids during brief periods of incubation. Phosphatidate and lysophosphatidate became strongly labelled and activity was also found in phosphatidyl inositol phosphate and in phosphatidyl inositol diphosphate. When tetraphenylborate (a K + -complexing agent) was added, a selective stimulation of incorporation of 32 P into phosphatidate occurred. The addition of perchlorate (also known to bind K + ) did not produce a similar stimulation, nor did the addition of K + block the stimulation by tetraphenylborate. The stimulation of the labelling of phospholipids by tetraphenylborate appeared to be the result of multiple actions. Besides the evidence that it acted by stimulating the phosphoinositide phosphodiesterase of brain, data were obtained suggesting that it stimulated diglyceride kinase and blocked endogenous destruction of ATP as well. The stimulation by tetraphenylborate was blocked by addition of atropine but not of arecoline.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65711/1/j.1471-4159.1970.tb03374.x.pd
Relationship between high sodium levels in municipally softened drinking water and elevated blood pressure
A recent study in Massachusetts found that a group of high school sophomores exposed to 107 mg/l sodium in their drinking water had significantly higher blood pressures than a control group exposed to a lower level of sodium (8 mg/l). The present study was undertaken in Illinois to determine if these findings could be repeated with a group of high school juniors and seniors from two communities, LaGrange and Westchester, located in the Chicago metropolitan area. The concentration of sodium in LaGrange's municipal drinking water is 405 mg/l as compared to 4 mg/l for Westchester. Of the 386 eligible students in LaGrangeI.84%volunteered to have their blood pressures taken. In Westchester, 78% of the 401 eligible students volunteered. Results of the survey indicated that male and female systolic blood pressures in the high sodium community were not higher than those in the low-sodium community (p > 0.05). In contrast, the male and female diastolic blood pressures were significantly higher in the high-sodium community (p < 0.05). However, the increases in diastolic blood pressures were not as large as those observed in the Massachusetts study. The long-term significance of these findings is unknown. However, they do indicate a need for further follow-up study to determine if there is an association with the development of hypertension.U.S. Department of the InteriorU.S. Geological SurveyOpe
The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems
We present VLA HI spectral line imaging of 5 sources discovered by ALFALFA.
These targets are drawn from a larger sample of systems that were not uniquely
identified with optical counterparts during ALFALFA processing, and as such
have unusually high HI mass to light ratios. These candidate "Almost Dark"
objects fall into 4 categories: 1) objects with nearby HI neighbors that are
likely of tidal origin; 2) objects that appear to be part of a system of
multiple HI sources, but which may not be tidal in origin; 3) objects isolated
from nearby ALFALFA HI detections, but located near a gas-poor early-type
galaxy; 4) apparently isolated sources, with no object of coincident redshift
within ~400 kpc. Roughly 75% of the 200 objects without identified counterparts
in the .40 database (Haynes et al. 2011) fall into category 1. This
pilot sample contains the first five sources observed as part of a larger
effort to characterize HI sources with no readily identifiable optical
counterpart at single dish resolution. These objects span a range of HI mass
[7.41 < log(M) < 9.51] and HI mass to B-band luminosity ratios (3 <
M/L < 9). We compare the HI total intensity and velocity
fields to SDSS optical imaging and to archival GALEX UV imaging. Four of the
sources with uncertain or no optical counterpart in the ALFALFA data are
identified with low surface brightness optical counterparts in SDSS imaging
when compared with VLA HI intensity maps, and appear to be galaxies with clear
signs of ordered rotation. One source (AGC 208602) is likely tidal in nature.
We find no "dark galaxies" in this limited sample. The present observations
reveal complex sources with suppressed star formation, highlighting both the
observational difficulties and the necessity of synthesis follow-up
observations to understand these extreme objects. (abridged)Comment: Astronomical Journal, in pres
Electro-extractive fermentation for efficient biohydrogen production
Electrodialysis, an electrochemical membrane technique, was found to prolong and enhance the production of biohydrogen and purified organic acids via the anaerobic fermentation of glucose by Escherichia coli. Through the design of a model electrodialysis medium using cationic buffer, pH was precisely controlled electrokinetically, i.e. by the regulated extraction of acidic products with coulombic efficiencies of organic acid recovery in the range 50–70% maintained over continuous 30-day experiments. Contrary to\ud
previous reports, E. coli produced H2 after aerobic growth in minimal medium without inducers and with a mixture of organic acids dominated by butyrate. The selective separation of organic acids from fermentation provides a potential nitrogen-free carbon source for further biohydrogen production in a parallel photofermentation. A parallel study incorporated this fermentation system into an integrated biohydrogen refinery (IBR) for the conversion of organic waste to hydrogen and energy
C2D Spitzer-IRS spectra of disks around T Tauri stars V. Spectral decomposition
(Abridged) Dust particles evolve in size and lattice structure in
protoplanetary disks, due to coagulation, fragmentation and crystallization,
and are radially and vertically mixed in disks. This paper aims at determining
the mineralogical composition and size distribution of the dust grains in disks
around 58 T Tauri stars observed with Spitzer/IRS. We present a spectral
decomposition model that reproduces the IRS spectra over the full spectral
range. The model assumes two dust populations: a warm component responsible for
the 10\mu m emission arising from the disk inner regions and a colder component
responsible for the 20-30\mu m emission, arising from more distant regions. We
show evidence for a significant size distribution flattening compared to the
typical MRN distribution, providing an explanation for the usual boxy 10\mu m
feature profile generally observed. We reexamine the crystallinity paradox,
observationally identified by Olofsson et al. (2009), and we find a
simultaneous enrichment of the crystallinity in both the warm and cold regions,
while grain sizes in both components are uncorrelated. Our modeling results do
not show evidence for any correlations between the crystallinity and either the
star spectral type, or the X-ray luminosity (for a subset of the sample). The
size distribution flattening may suggests that grain coagulation is a slightly
more effective process than fragmentation in disk atmospheres, and that this
imbalance may last over most of the T Tauri phase. This result may also point
toward small grain depletion via strong stellar winds or radiation pressure in
the upper layers of disk. The non negligible cold crystallinity fractions
suggests efficient radial mixing processes in order to distribute crystalline
grains at large distances from the central object, along with possible nebular
shocks in outer regions of disks that can thermally anneal amorphous grains
Hot debris dust around HD 106797
Photometry of the A0 V main-sequence star HD 106797 with AKARI and
Gemini/T-ReCS is used to detect excess emission over the expected stellar
photospheric emission between 10 and 20 micron, which is best attributed to hot
circumstellar debris dust surrounding the star. The temperature of the debris
dust is derived as Td ~ 190 K by assuming that the excess emission is
approximated by a single temperature blackbody. The derived temperature
suggests that the inner radius of the debris disk is ~ 14 AU. The fractional
luminosity of the debris disk is 1000 times brighter than that of our own
zodiacal cloud. The existence of such a large amount of hot dust around HD
106797 cannot be accounted for by a simple model of the steady state evolution
of a debris disk due to collisions, and it is likely that transient events play
a significant role. Our data also show a narrow spectral feature between 11 and
12 micron attributable to crystalline silicates, suggesting that dust heating
has occurred during the formation and evolution of the debris disk of HD
106797.Comment: Accepted to ApJ Letters, 8 pages, 2 figure
Correction: Peak plasma interleukin-6 and other peripheral markers of inflammation in the first week of ischaemic stroke correlate with brain infarct volume, stroke severity and long-term outcome
In table 3, the correlation coefficient between peak plasma cortisol and mRS at 3 months (column 4, row 5), should read 0.48, not 0 [1]
Mid-IR spectroscopy of T Tauri stars in Chamealeon I: evidence for processed dust at the earliest stages
We present mid-IR spectroscopy of three T Tauri stars in the young Chamealeon
I dark cloud obtained with TIMMI2 on the ESO 3.6m telescope. In these three
stars, the silicate emission band at 9.7 micron is prominent. We model it with
a mixture of amorphous olivine grains of different size, crystalline silicates
and silica. The fractional mass of these various components change widely from
star to star. While the spectrum of CR Cha is dominated by small amorphous
silicates, in VW Cha (and in a lesser degree in Glass I), there is clear
evidence of a large amount of processed dust in the form of crystalline
silicates and large amorphous grains. This is the first time that processed
dust has been detetected in very young T Tauri stars (~ 1 Myr).Comment: 5 pages, 4 Postscript figures. accepted for A&A Letter
Left-right symmetry at LHC and precise 1-loop low energy data
Despite many tests, even the Minimal Manifest Left-Right Symmetric Model
(MLRSM) has never been ultimately confirmed or falsified. LHC gives a new
possibility to test directly the most conservative version of left-right
symmetric models at so far not reachable energy scales. If we take into account
precise limits on the model which come from low energy processes, like the muon
decay, possible LHC signals are strongly limited through the correlations of
parameters among heavy neutrinos, heavy gauge bosons and heavy Higgs particles.
To illustrate the situation in the context of LHC, we consider the "golden"
process . For instance, in a case of degenerate heavy neutrinos
and heavy Higgs masses at 15 TeV (in agreement with FCNC bounds) we get
fb at TeV which is consistent with muon
decay data for a very limited masses in the range (3008 GeV, 3040 GeV).
Without restrictions coming from the muon data, masses would be in the
range (1.0 TeV, 3.5 TeV). Influence of heavy Higgs particles themselves on the
considered LHC process is negligible (the same is true for the light, SM
neutral Higgs scalar analog). In the paper decay modes of the right-handed
heavy gauge bosons and heavy neutrinos are also discussed. Both scenarios with
typical see-saw light-heavy neutrino mixings and the mixings which are
independent of heavy neutrino masses are considered. In the second case heavy
neutrino decays to the heavy charged gauge bosons not necessarily dominate over
decay modes which include only light, SM-like particles.Comment: 16 pages, 10 figs, KL-KS and new ATLAS limits taken into accoun
Grain growth in the inner regions of Herbig Ae/Be star disks
We present new mid-infrared spectroscopy of
the emission from warm circumstellar dust grains
in Herbig Ae/Be stars. Our survey significantly
extends the sample that was studied by Bouwman et
al. (2001). We find a correlation between the
strength of the silicate feature and its shape.
We interpret this as evidence for the removal of
small (0.1 mu m) grains from the disk surface
while large (1-2 mu m) grains persist. If the
evolution of the grain size distribution is
dominated by gravitational settling, large grains
are expected to disappear first, on a timescale
which is much shorter than the typical age of our
programme stars. Our observations thus suggest a
continuous replenishment of micron sized grains
at the disk surface. If the grain replenishment
is due to the dredge-up of dust from the disk
interior, the mineralogy we observe is
representative of the bulk composition of dust in
these stars. Based on observations obtained at
the European Southern Observatory (ESO), La
Silla, and on observations with ISO, an ESA
project with instruments funded by ESA Member
States (especially the PI countries: France,
Germany, The Netherlands and the UK) and with the
participation of ISAS and NASA
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