741 research outputs found
Turbulence and suspended sediment measurements in an urban environment during the Brisbane River flood of January 2011
In urbanized areas, flood flows constitute a hazard to populations and infrastructure, as illustrated during major floods in 2011. During the 2011 Brisbane River flood, some turbulent velocity data were collected using acoustic Doppler velocimetry in an inundated street. The field deployment showed some unusual features of flood flow in the urban environment. That is, the water elevations and velocities fluctuated with distinctive periods between 50 and 100 s linked with some local topographic effects. The instantaneous velocity data were analyzed using a triple decomposition. The velocity fluctuations included a large energy component in the slow fluctuation range, whereas the turbulent motion components were much smaller. The suspended sediment data showed some significant longitudinal flux. Altogether, the results highlighted that the triple decomposition approach originally developed for periodic flows is well-suited to complicated flows in an inundated urban environment
Recognition and blocking of innate immunity cells by Candida albicans chitin
Peer reviewedPublisher PD
Coincident brane nucleation and the neutralization of \Lambda
Nucleation of branes by a four-form field has recently been considered in
string motivated scenarios for the neutralization of the cosmological constant.
An interesting question in this context is whether the nucleation of stacks of
coincident branes is possible, and if so, at what rate does it proceed. Feng et
al. have suggested that, at high ambient de Sitter temperature, the rate may be
strongly enhanced, due to large degeneracy factors associated with the number
of light species living on the worldsheet. This might facilitate the quick
relaxation from a large effective cosmological constant down to the observed
value. Here, we analyse this possibility in some detail. In four dimensions,
and after the moduli are stabilized, branes interact via repulsive long range
forces. Because of that, the Coleman-de Luccia (CdL) instanton for coincident
brane nucleation may not exist, unless there is some short range interaction
which keeps the branes together. If the CdL instanton exists, we find that the
degeneracy factor depends only mildly on the ambient de Sitter temperature, and
does not switch off even in the case of tunneling from flat space. This would
result in catastrophic decay of the present vacuum. If, on the contrary, the
CdL instanton does not exist, coindident brane nucleation may still proceed
through a "static" instanton, representing pair creation of critical bubbles --
a process somewhat analogous to thermal activation in flat space. In that case,
the branes may stick together due to thermal symmetry restoration, and the pair
creation rate depends exponentially on the ambient de Sitter temperature,
switching off sharply as the temperature approaches zero. Such static instanton
may be well suited for the "saltatory" relaxation scenario proposed by Feng et
al.Comment: 38 pages, 6 figures. Replaced with typos correcte
Time-of-flight mass measurements of neutron-rich chromium isotopes up to N = 40 and implications for the accreted neutron star crust
We present the mass excesses of 59-64Cr, obtained from recent time-of-flight
nuclear mass measurements at the National Superconducting Cyclotron Laboratory
at Michigan State University. The mass of 64Cr is determined for the first
time, with an atomic mass excess of -33.48(44) MeV. We find a significantly
different two-neutron separation energy S2n trend for neutron-rich isotopes of
chromium, removing the previously observed enhancement in binding at N=38.
Additionally, we extend the S2n trend for chromium to N=40, revealing behavior
consistent with the previously identified island of inversion in this region.
We compare our results to state-of-the-art shell-model calculations performed
with a modified Lenzi-Nowacki-Poves-Sieja interaction in the fp shell,
including the g9/2 and d5/2 orbits for the neutron valence space. We employ our
result for the mass of 64Cr in accreted neutron star crust network calculations
and find a reduction in the strength and depth of electron-capture heating from
the A=64 isobaric chain, resulting in a cooler than expected accreted neutron
star crust. This reduced heating is found to be due to the >1-MeV reduction in
binding for 64Cr with respect to values from commonly used global mass models.Comment: Accepted to Physical Review
Autonomic impairment of patients in coma with different Glasgow coma score assessed with heart rate variability
Primary objective: The objective of this study is to assess the functional state of the autonomic nervous system in healthy individuals and in individuals in coma using measures of heart rate variability (HRV) and to evaluate its efficiency in predicting mortality. Design and Methods: Retrospective group comparison study of patients in coma classified into two subgroups, according to their Glasgow coma score, with a healthy control group. HRV indices were calculated from 7 min of artefact-free electrocardiograms using the Hilbert–Huang method in the spectral range 0.02–0.6 Hz. A special procedure was applied to avoid confounding factors. Stepwise multiple regression logistic analysis (SMLRA) and ROC analysis evaluated predictions. Results: Progressive reduction of HRV was confirmed and was associated with deepening of coma and a mortality score model that included three spectral HRV indices of absolute power values of very low, low and very high frequency bands (0.4-0.6 Hz). The SMLRA model showed sensitivity of 95.65%, specificity of 95.83%, positive predictive value of 95.65%, and overall efficiency of 95.74%. Conclusions: HRV is a reliable method to assess the integrity of the neural control of the caudal brainstem centres on the hearts of patients in coma and to predict patient mortality
New Herbig Ae/Be stars confirmed via high-resolution optical spectroscopy
We present FEROS high-resolution (R~45000) optical spectroscopy of 34 Herbig
Ae/Be star candidates with previously unknown or poorly constrained spectral
types. Within the sample, 16 sources are positionally coincident with nearby
(d<250 pc) star-forming regions (SFRs). All the candidates have IR excess. We
determine the spectral type and luminosity class of the sources, derive their
radial and rotational velocities, and constrain their distances employing
spectroscopic parallaxes. We confirm 13 sources as Herbig Ae/Be stars and find
one classical T Tauri star. Three sources are emission line early-type giants
and may be Herbig Ae/Be stars. One source is a main-sequence A-type star.
Fourteen sources are post-main-sequence giant and supergiant stars. Two sources
are extreme emission-line stars. Most of the sources appear to be background
stars at distances over 700 pc. We show that high-resolution optical
spectroscopy is a crucial tool for distinguishing young stars from post-main
sequence stars in samples taken from emission-line star catalogs based on
low-resolution spectroscopy. Within the sample, 3 young stars (CD-38 4380, Hen
3-1145, and HD 145718) and one early-type luminosity class III giant with
emission lines (Hen 3-416) are at distances closer than 300 pc and are
positionally coincident with a nearby SFR. These 4 sources are likely to be
nearby young stars and are interesting for follow-up observations at
high-angular resolution. Furthermore, seven confirmed Herbig Ae/Be stars at
d>700 pc (Hen 2-80, Hen 3-1121 N&S, HD 313571, MWC 953, WRAY 15-1435, and Th
17-35) are inside or close (<5') to regions with extended 8 micron continuum
emission and in their 20' vicinity have astronomical sources characteristic of
SFRs. These 7 sources are likely to be members of SFRs. These regions are
attractive for future studies of their stellar content.Comment: 24 pages, 6 Figures, accepted by Astronomy and Astrophysics, in
press
Beta-delayed proton emission in the 100Sn region
Beta-delayed proton emission from nuclides in the neighborhood of 100Sn was
studied at the National Superconducting Cyclotron Laboratory. The nuclei were
produced by fragmentation of a 120 MeV/nucleon 112Sn primary beam on a Be
target. Beam purification was provided by the A1900 Fragment Separator and the
Radio Frequency Fragment Separator. The fragments of interest were identified
and their decay was studied with the NSCL Beta Counting System (BCS) in
conjunction with the Segmented Germanium Array (SeGA). The nuclei 96Cd, 98Ing,
98Inm and 99In were identified as beta-delayed proton emitters, with branching
ratios bp = 5.5(40)%, 5.5+3 -2%, 19(2)% and 0.9(4)%, respectively. The bp for
89Ru, 91,92Rh, 93Pd and 95Ag were deduced for the first time with bp = 3+1.9
-1.7%, 1.3(5)%, 1.9(1)%, 7.5(5)% and 2.5(3)%, respectively. The bp = 22(1)% for
101Sn was deduced with higher precision than previously reported. The impact of
the newly measured bp values on the composition of the type-I X-ray burst ashes
was studied.Comment: 15 pages, 14 Figures, 4 Table
Low-lying level structure of Cu and its implications on the rp process
The low-lying energy levels of proton-rich Cu have been extracted
using in-beam -ray spectroscopy with the state-of-the-art -ray
tracking array GRETINA in conjunction with the S800 spectrograph at the
National Superconducting Cyclotron Laboratory at Michigan State University.
Excited states in Cu serve as resonances in the
Ni(p,)Cu reaction, which is a part of the rp-process in
type I x-ray bursts. To resolve existing ambiguities in the reaction Q-value, a
more localized IMME mass fit is used resulting in ~keV. We derive
the first experimentally-constrained thermonuclear reaction rate for
Ni(p,)Cu. We find that, with this new rate, the
rp-process may bypass the Ni waiting point via the Ni(p,)
reaction for typical x-ray burst conditions with a branching of up to
40. We also identify additional nuclear physics uncertainties that
need to be addressed before drawing final conclusions about the rp-process
reaction flow in the Ni region.Comment: 8 pages, accepted for Phys. Rev.
- …