1,308 research outputs found
Giant Spin Seebeck Effect through an Interface Organic Semiconductor
Interfacing an organic semiconductor C60 with a non-magnetic metallic thin
film (Cu or Pt) has created a novel heterostructure that is ferromagnetic at
ambient temperature, while its interface with a magnetic metal (Fe or Co) can
tune the anisotropic magnetic surface property of the material. Here, we
demonstrate that sandwiching C60 in between a magnetic insulator (Y3Fe5O12:
YIG) and a non-magnetic, strong spin-orbit metal (Pt) promotes highly efficient
spin current transport via the thermally driven spin Seebeck effect (SSE).
Experiments and first principles calculations consistently show that the
presence of C60 reduces significantly the conductivity mismatch between YIG and
Pt and the surface perpendicular magnetic anisotropy of YIG, giving rise to
enhanced spin mixing conductance across YIG/C60/Pt interfaces. As a result, a
600% increase in the SSE voltage (VLSSE) has been realized in YIG/C60/Pt
relative to YIG/Pt. Temperature-dependent SSE voltage measurements on
YIG/C60/Pt with varying C60 layer thicknesses also show an exponential increase
in VLSSE at low temperatures below 200 K, resembling the temperature evolution
of spin diffusion length of C60. Our study emphasizes the important roles of
the magnetic anisotropy and the spin diffusion length of the intermediate layer
in the SSE in YIG/C60/Pt structures, providing a new pathway for developing
novel spin-caloric materials
Required flows for aquatic ecosystems in Ma River, Vietnam
Ecological flow requirements for the Ma River in dry season were assessed in three reaches of Ma – Buoi, Ma – Len and Ma – Chu. 5 indictor fish species was chosen based on biodiversity survey and roles of those species in aquatic ecosystem as well as local communities. Biological and hydrological data (dry season of 2016- 2017) and 35 year recorded hydrological data were collected and analyzed as input data for a physical habitat model River HYdraulic and HABitat SImulation Model – RHYHABSIM. Model results shown that the optimal flows of the reaches were very much higher compare with the minimum annual low flow - MALF. In this study, MALF7day were applied to calculate the recommended minimum flows of the three reaches. The recommended required minimum flows for Ma – Buoi, Ma – Len and Ma – Chu reaches were 51 m3/s, 49 m3/s and 61 m3/s, respectively. It must be stressed that this study only assessed whether or not there is enough habitat available for the river to sustain a healthy ecosystem
Complete Fusion Enhancement and Suppression of Weakly Bound Nuclei at Near Barrier Energies
We consider the influence of breakup channels on the complete fusion of
weakly bound systems in terms of dynamic polarization potentials. It is argued
that the enhancement of the cross section at sub-barrier energies may be
consistent with recent experimental observations that nucleon transfer, often
leading to breakup, is dominant compared to direct breakup. The main trends of
the experimental complete fusion cross section for Li + Bi are
analyzed in the framework of the DPP approach.Comment: 12 pages, 2 figure
The Herschel view of the on-going star formation in the Vela-C molecular cloud
As part of the Herschel guaranteed time key program 'HOBYS', we present the
photometric survey of the star forming region Vela-C, one of the nearest sites
of low-to-high-mass star formation in the Galactic plane. Vela-C has been
observed with PACS and SPIRE in parallel mode between 70 um and 500 um over an
area of about 3 square degrees. A photometric catalogue has been extracted from
the detections in each band, using a threshold of 5 sigma over the local
background. Out of this catalogue we have selected a robust sub-sample of 268
sources, of which 75% are cloud clumps and 25% are cores. Their Spectral Energy
Distributions (SEDs) have been fitted with a modified black body function. We
classify 48 sources as protostellar and 218 as starless. For two further
sources, we do not provide a secure classification, but suggest they are Class
0 protostars.
From SED fitting we have derived key physical parameters. Protostellar
sources are in general warmer and more compact than starless sources. Both
these evidences can be ascribed to the presence of an internal source(s) of
moderate heating, which also causes a temperature gradient and hence a more
peaked intensity distribution. Moreover, the reduced dimensions of protostellar
sources may indicate that they will not fragment further. A virial analysis of
the starless sources gives an upper limit of 90% for the sources
gravitationally bound and therefore prestellar. We fit a power law N(logM) prop
M^-1.1 to the linear portion of the mass distribution of prestellar sources.
This is in between that typical of CO clumps and those of cores in nearby
star-forming regions. We interpret this as a result of the inhomogeneity of our
sample, which is composed of comparable fractions of clumps and cores.Comment: 9 pages, 7 figures, accepted by A&
Consistency of cosmic microwave background temperature measurements in three frequency bands in the 2500-square-degree SPT-SZ survey
We present an internal consistency test of South Pole Telescope (SPT)
measurements of the cosmic microwave background (CMB) temperature anisotropy
using three-band data from the SPT-SZ survey. These measurements are made from
observations of ~2500 deg^2 of sky in three frequency bands centered at 95,
150, and 220 GHz. We combine the information from these three bands into six
semi-independent estimates of the CMB power spectrum (three single-frequency
power spectra and three cross-frequency spectra) over the multipole range 650 <
l < 3000. We subtract an estimate of foreground power from each power spectrum
and evaluate the consistency among the resulting CMB-only spectra. We determine
that the six foreground-cleaned power spectra are consistent with the null
hypothesis, in which the six cleaned spectra contain only CMB power and noise.
A fit of the data to this model results in a chi-squared value of 236.3 for 235
degrees of freedom, and the probability to exceed this chi-squared value is
46%.Comment: 21 pages, 4 figures, current version matches version published in
JCA
Expression of somatostatin receptors 2 and 5 in circulating tumour cells from patients with neuroendocrine tumours.
BACKGROUND: Neuroendocrine tumours (NET) overexpress somatostatin receptors (SSTR) that can be targeted for therapy. Somatostatin receptor expression is routinely measured by molecular imaging but the resolution is insufficient to define heterogeneity. We hypothesised that SSTR expression could be measured on circulating tumour cells (CTCs) and used to investigate heterogeneity of expression and track changes during therapy. METHODS: MCF-7 cells were transfected with SSTR2 or 5 and spiked into donor blood for analysis by CellSearch. Optimum anti-SSTR antibody concentration and exposure time were determined, and flow cytometry was used to evaluate assay sensitivity. For clinical evaluation, blood was analysed by CellSearch, and SSTR2/5 immunohistochemistry was performed on matched tissue samples. RESULTS: Flow cytometry confirmed CellSearch was sensitive and that detection of SSTR was unaffected by the presence of somatostatin analogue up to a concentration of 100 ng ml(-l). Thirty-one NET patients were recruited: grade; G1 (29%), G2 (45%), G3 (13%), primary site; midgut (58%), pancreatic (39%). Overall, 87% had SSTR-positive tumours according to somatostatin receptor scintigraphy or 68-Ga-DOTATE PET/CT. Circulating tumour cells were detected in 21 out of 31 patients (68%), of which 33% had evidence of heterogeneous expression of either SSTR2 (n=5) or SSTR5 (n=2). CONCLUSIONS: Somatostatin receptors 2 and 5 are detectable on CTCs from NET patients and may be a useful biomarker for evaluating SSTR-targeted therapies and this is being prospectively evaluated in the Phase IV CALMNET trial (NCT02075606)
A Comparison of Maps and Power Spectra Determined from South Pole Telescope and Planck Data
We study the consistency of 150 GHz data from the South Pole Telescope (SPT)
and 143 GHz data from the Planck satellite over the patch of sky covered by the
SPT-SZ survey. We first visually compare the maps and find that the residuals
appear consistent with noise after accounting for differences in angular
resolution and filtering. We then calculate (1) the cross-spectrum between two
independent halves of SPT data, (2) the cross-spectrum between two independent
halves of Planck data, and (3) the cross-spectrum between SPT and Planck data.
We find the three cross-spectra are well-fit (PTE = 0.30) by the null
hypothesis in which both experiments have measured the same sky map up to a
single free calibration parameter---i.e., we find no evidence for systematic
errors in either data set. As a by-product, we improve the precision of the SPT
calibration by nearly an order of magnitude, from 2.6% to 0.3% in power.
Finally, we compare all three cross-spectra to the full-sky Planck power
spectrum and find marginal evidence for differences between the power spectra
from the SPT-SZ footprint and the full sky. We model these differences as a
power law in spherical harmonic multipole number. The best-fit value of this
tilt is consistent among the three cross-spectra in the SPT-SZ footprint,
implying that the source of this tilt is a sample variance fluctuation in the
SPT-SZ region relative to the full sky. The consistency of cosmological
parameters derived from these datasets is discussed in a companion paper.Comment: 15 pages, 9 figures. Published in The Astrophysical Journal. Current
arxiv version matches published versio
A Comparison of Cosmological Parameters Determined from CMB Temperature Power Spectra from the South Pole Telescope and the Planck Satellite
The Planck cosmic microwave background (CMB) temperature data are best fit
with a LCDM model that is in mild tension with constraints from other
cosmological probes. The South Pole Telescope (SPT) 2540 SPT-SZ
survey offers measurements on sub-degree angular scales (multipoles ) with sufficient precision to use as an independent check of
the Planck data. Here we build on the recent joint analysis of the SPT-SZ and
Planck data in \citet{hou17} by comparing LCDM parameter estimates using the
temperature power spectrum from both data sets in the SPT-SZ survey region. We
also restrict the multipole range used in parameter fitting to focus on modes
measured well by both SPT and Planck, thereby greatly reducing sample variance
as a driver of parameter differences and creating a stringent test for
systematic errors. We find no evidence of systematic errors from such tests.
When we expand the maximum multipole of SPT data used, we see low-significance
shifts in the angular scale of the sound horizon and the physical baryon and
cold dark matter densities, with a resulting trend to higher Hubble constant.
When we compare SPT and Planck data on the SPT-SZ sky patch to Planck full-sky
data but keep the multipole range restricted, we find differences in the
parameters and . We perform further checks, investigating
instrumental effects and modeling assumptions, and we find no evidence that the
effects investigated are responsible for any of the parameter shifts. Taken
together, these tests reveal no evidence for systematic errors in SPT or Planck
data in the overlapping sky coverage and multipole range and, at most, weak
evidence for a breakdown of LCDM or systematic errors influencing either the
Planck data outside the SPT-SZ survey area or the SPT data at .Comment: 14 pages, 7 figures. Updated 1 figure and expanded on the reasoning
for fixing the affect of lensing on the power spectrum instead of varying
Alen
A Measurement of the Cosmic Microwave Background Damping Tail from the 2500-square-degree SPT-SZ survey
We present a measurement of the cosmic microwave background (CMB) temperature
power spectrum using data from the recently completed South Pole Telescope
Sunyaev-Zel'dovich (SPT-SZ) survey. This measurement is made from observations
of 2540 deg of sky with arcminute resolution at GHz, and improves
upon previous measurements using the SPT by tripling the sky area. We report
CMB temperature anisotropy power over the multipole range . We
fit the SPT bandpowers, combined with the seven-year Wilkinson Microwave
Anisotropy Probe (WMAP7) data, with a six-parameter LCDM cosmological model and
find that the two datasets are consistent and well fit by the model. Adding SPT
measurements significantly improves LCDM parameter constraints; in particular,
the constraint on tightens by a factor of 2.7. The impact of
gravitational lensing is detected at , the most significant
detection to date. This sensitivity of the SPT+WMAP7 data to lensing by
large-scale structure at low redshifts allows us to constrain the mean
curvature of the observable universe with CMB data alone to be
. Using the SPT+WMAP7 data, we measure the
spectral index of scalar fluctuations to be in the LCDM
model, a preference for a scale-dependent spectrum with .
The SPT measurement of the CMB damping tail helps break the degeneracy that
exists between the tensor-to-scalar ratio and in large-scale CMB
measurements, leading to an upper limit of (95%,C.L.) in the LCDM+
model. Adding low-redshift measurements of the Hubble constant () and the
baryon acoustic oscillation (BAO) feature to the SPT+WMAP7 data leads to
further improvements. The combination of SPT+WMAP7++BAO constrains
in the LCDM model, a detection of , ... [abridged]Comment: 21 pages, 10 figures. Replaced with version accepted by ApJ. Data
products are available at http://pole.uchicago.edu/public/data/story12
- …