1,318 research outputs found
The C. elegans Thermosensory Neuron AFD Responds to Warming
AbstractThe mechanism of temperature sensation is far less understood than the sensory response to other environmental stimuli such as light, odor, and taste. Thermotaxis behavior in C. elegans requires the ability to discriminate temperature differences as small as âŒ0.05°C and to memorize the previously cultivated temperature [1, 2]. The AFD neuron is the only major thermosensory neuron required for the thermotaxis behavior [3]. Genetic analyses have revealed several signal transduction molecules that are required for the sensation and/or memory of temperature information in the AFD neuron [4â7], but its physiological properties, such as its ability to sense absolute temperature or temperature change, have been unclear. We show here that the AFD neuron responds to warming. Calcium concentration in the cell body of AFD neuron is increased transiently in response to warming, but not to absolute temperature or to cooling. The transient response requires the activity of the TAX-4 cGMP-gated cation channel, which plays an essential role in the function of the AFD neuron [5]. Interestingly, the AFD neuron further responds to step-like warming above a threshold that is set by temperature memory. We suggest that C. elegans provides an ideal model to genetically and physiologically reveal the molecular mechanism for sensation and memory of temperature information
XMM-Newton observations of the hot spot galaxy NGC 2903
We report on the first deeper X-ray broad-band observation of the hot spot
galaxy NGC 2903 obtained with XMM-Newton. X-ray imaging and spectra of the
spiral barred galaxy were obtained from XMM-Newton archival data to study its
X-ray population and the conditions of the hot gas in its central region. We
investigate the spectral properties of the discrete point-source population and
give estimates of their X-ray spectral parameters. By analysing the RGS
spectra, we derive temperature and abundances for the hot gas located in its
central region. A total of six X-ray point sources (four of them ULX
candidates) were detected in the energy range of 0.3-10.0 keV located within
the galaxy D25 optical disk. Three of these sources are detected for the first
time, and one of them with a luminosity of higher than 10^39 erg/s. After
fitting three different models, we were able to estimate their luminosities,
which are compatible with those of binaries with a compact object in the form
of black holes (BHs) rather than neutron stars (NSs). We extracted the combined
first-order RGS1 and RGS2 spectra of its central region, which display several
emission lines. Both O\,{\sc vii} and lines seem to be of similar
strength, which is consistent with the presence of the collisionally ionized
gas that is typical of starburst galaxies. We fitted the spectrum to a model
for a plasma in collisional ionization equilibrium (CIE) and the continuum was
modelled with a power law, resulting in a plasma temperature of T = 0.31 \pm
0.01 keV and an emission measure EM \equiv n_Hn_eV =6.4_{-0.4}^{+0.5}\times
10^{61}^{-3}. We also estimated abundances that are consistent with solar
values.Comment: 5 pages, 2 figures, accepted for publication in A&A, resubmission
corrects typographical errors and improves exposition according to the
referee's suggestion
X-ray reflection in a sample of X-ray bright Ultraluminous X-ray sources
We apply a reflection-based model to the best available XMM-Newton spectra of
X-ray bright UltraLuminous X-ray (ULX) sources (NGC 1313 X-1, NGC 1313 X-2, M
81 X-6, Holmberg IX X-1, NGC 5408 X-1 and Holmberg II X-1). A spectral drop is
apparent in the data of all the sources at energies 6-7 keV. The drop is
interpreted here in terms of relativistically-blurred ionized reflection from
the accretion disk. A soft-excess is also detected from these sources (as
usually found in the spectra of AGN), with emission from O K and Fe L, in the
case of NGC 5408 X-1 and Holmberg II X-1, which can be understood as features
arising from reflection of the disk. Remarkably, ionized disk reflection and
the associated powerlaw continuum provide a good description of the broad-band
spectrum, including the soft-excess. There is no requirement for thermal
emission from the inner disk in the description of the spectra. The black holes
of these systems must then be highly spinning, with a spin close to the maximum
rate of a maximal spinning black hole. The results require the action of strong
light bending in these sources. We suggest that they could be strongly
accreting black holes in which most of the energy is extracted from the flow
magnetically and released above the disc thereby avoiding the conventional
Eddington limit.Comment: Accepted for publication in MNRA
Discovery of interstellar mercapto radicals (SH) with the GREAT instrument on SOFIA
We report the first detection of interstellar mercapto radicals, obtained
along the sight-line to the submillimeter continuum source W49N. We have used
the GREAT instrument on SOFIA to observe the 1383 GHz Doublet Pi 3/2 J = 5/2 -
3/2 lambda doublet in the upper sideband of the L1 receiver. The resultant
spectrum reveals SH absorption in material local to W49N, as well as in
foreground gas, unassociated with W49N, that is located along the sight-line.
For the foreground material at velocities in the range 37 - 44 km/s with
respect to the local standard of rest, we infer a total SH column density ~ 2.6
E+12 cm-2, corresponding to an abundance of ~ 7 E-9 relative to H2, and
yielding an SH/H2S abundance ratio ~ 0.13. The observed SH/H2S abundance ratio
is much smaller than that predicted by standard models for the production of SH
and H2S in turbulent dissipation regions and shocks, and suggests that the
endothermic neutral-neutral reaction SH + H2 -> H2S + H must be enhanced along
with the ion-neutral reactions believed to produce CH+ and SH+ in diffuse
molecular clouds.Comment: Accepted for publication in Astronomy and Astrophysics (SOFIA/GREAT
special issue
PDGFRα plays a crucial role in connective tissue remodeling.
Platelet derived growth factor (PDGF) plays a pivotal role in the remodeling of connective tissues. Emerging data indicate the distinctive role of PDGF receptor-α (PDGFRα) in this process. In the present study, the Pdgfra gene was systemically inactivated in adult mouse (α-KO mouse), and the role of PDGFRα was examined in the subcutaneously implanted sponge matrices. PDGFRα expressed in the fibroblasts of Pdgfra-preserving control mice (Flox mice), was significantly reduced in the sponges in α-KO mice. Neovascularized areas were largely suppressed in the α-KO mice than in the Flox mice, whereas the other parameters related to the blood vessels and endothelial cells were similar. The deposition of collagen and fibronectin and the expression of collagen 1a1 and 3a1 genes were significantly reduced in α-KO mice. There was a significantly decrease in the number and dividing fibroblasts in the α-KO mice, and those of macrophages were similar between the two genotypes. Hepatocyte growth factor (Hgf) gene expression was suppressed in Pdgfra-inactivated fibroblasts and connective tissue. The findings implicate the role of PDGFRα-dependent ECM and HGF production in fibroblasts that promotes the remodeling of connective tissue and suggest that PDGFRα may be a relevant target to regulate connective tissue remodeling
BaFe12O19 single-particle-chain nanofibers : preparation, characterization, formation principle, and magnetization reversal mechanism
BaFe12O19 single-particle-chain
nanofibers have been successfully prepared by
an electrospinning method and calcination
process, and their morphology, chemistry,
and crystal structure have been characterized
at the nanoscale. It is found that individual
BaFe12O19 nanofibers consist of single nanoparticles which are found to stack along the
nanofiber axis. The chemical analysis shows that the atomic ratio of Ba/Fe is 1:12, suggesting a
BaFe12O19 composition. The crystal structure of the BaFe12O19 single-particle-chain nanofibers
is proved to be M-type hexagonal. The single crystallites on each BaFe12O19 single-particlechain
nanofibers have random orientations. A formation mechanism is proposed based on
thermogravimetry/differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and transmission
electron microscopy (TEM) at six temperatures, 250, 400, 500, 600, 650, and 800 ïżœC.
The magnetic measurement of the BaFe12O19 single-particle-chain nanofibers reveals that the
coercivity reaches a maximum of 5943 Oe and the saturated magnetization is 71.5 emu/g at
room temperature. Theoretical analysis at the micromagnetism level is adapted to describe the
magnetic behavior of the BaFe12O19 single-particle-chain nanofibers
Nomenclature of the gadolinite supergroup
The newly defined gadolinite supergroup approved by the IMA CNMNC (vote 16-A) includes mineral species that have the general chemical formula A2MQ2T2O8\u20192 and belong to silicates, phosphates and arsenates. Each site is occupied by: A Ca, REE (Y and lanthanoids), actinoids, Pb, Mn2\ufe, Bi; M Fe, \u25a1 (vacancy), Mg, Mn, Zn, Cu, Al; Q B, Be, Li; T Si, P, As, B, Be, S; and\u2019 O, OH, F. The classification of the gadolinite supergroup is based on the occupancy of A, M, Q, T and\u2019 sites and application of the dominant-valency and dominant-constituent rules. The gadolinite supergroup is divided into two groups defined by prevailing charge occupancy at the T site Si4\ufe in gadolinite group and P5\ufe or As5\ufe in herderite group. The gadolinite group is divided into the gadolinite and datolite subgroups. The A site is dominantly occupied by divalent cations in the datolite subgroup and by trivalent cations in the gadolinite subgroup. Accordingly, the Q site is dominantly occupied by B3\ufe in the datolite subgroup and by Be2\ufe in the gadolinite subgroup. The herderite group is divided into two subgroups. The herderite subgroup is defined by the dominant divalent cation (usually Ca2\ufe) in the A site and Be2\ufe in the Q site, while the M site is vacant. The drugmanite subgroup is defined by the dominance of divalent cations (usually Pb2\ufe) in the A site, vacancy in the Q site and the occupation of the M site. Moreover, \u201cbakerite\u201d is discredited as mineral species because it does not meet the conditions of the dominant-constituent rule
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