540 research outputs found
Non-Fermi liquid normal state of the Heavy Fermion superconductor UBe13
Non-Fermi liquid (NFL) behavior in the normal state of the heavy-fermion
superconductor UBe13 is studied by means of low-temperature measurements of the
specific heat, C, and electrical resistivity, \rho, on a high-quality single
crystal in magnetic fields up to 15.5 T. At B=0, unconventional
superconductivity forms at Tc=0.9 K out of an incoherent state, characterized
by a large and strongly temperature dependent \rho(T). In the magnetic field
interval 4 T \leq B \leq 10 T, \rho(T) follows a T^3/2 behavior for Tc(B)\leq T
\leq 1 K, while \rho is proportional to T at higher temperatures. Corresponding
Non-Fermi liquid behavior is observed in C/T as well and hints at a nearby
antiferromagnetic (AF) quantum critical point (QCP) covered by the
superconducting state. We speculate that the suppression of short-range AF
correlations observed by thermal expansion and specific heat measurements below
T_L \simeq 0.7 K (B=0) yields a field-induced QCP, T_L \to 0, at B=4.5 T.Comment: Presented at the M2S-2003 conference in Rio / Brazi
Recommended from our members
A delta configured auxiliary resonant snubber inverter
A delta ({Delta}) configured auxiliary resonant snubber inverter is developed to overcome the voltage floating problem in a wye (Y) configured resonant snubber inverter. The proposed inverter is to connect auxiliary resonant branches between phase outputs to avoid a floating point voltage which may cause over-voltage failure of the auxiliary switches. Each auxiliary branch consists of a resonant inductor and a reverse blocking auxiliary switch. Instead of using an anti-paralleled diode to allow resonant current to flow in the reverse direction, as in the Y-configured version, the resonant branch in the {Delta}-configured version must block the negative voltage, typically done by a series diode. This paper shows single-phase and three-phase versions of {Delta}-configured resonant snubber inverters and describes in detail the operating principle of a single-phase version. The extended three-phase version is proposed with non-adjacent state space vector modulation. For hardware implementation, a single-phase 1-kW unit and a three-phase 100-kW unit were built to prove the concept. Experimental results show the superiority of the proposed topology
Pressure and linear heat capacity in the superconducting state of thoriated UBe13
Even well below Tc, the heavy-fermion superconductor (U,Th)Be13 has a large
linear term in its specific heat. We show that under uniaxial pressure, the
linear heat capacity increases in magnitude by more than a factor of two. The
change is reversible and suggests that the linear term is an intrinsic property
of the material. In addition, we find no evidence of hysteresis or of latent
heat in the low-temperature and low-pressure portion of the phase diagram,
showing that all transitions in this region are second order.Comment: 5 pages, 4 figure
Gammaretrovirus-mediated correction of SCID-X1 is associated with skewed vector integration site distribution in vivo
We treated 10 children with X-linked SCID (SCID-X1) using gammaretrovirus-mediated gene transfer. Those with sufficient follow-up were found to have recovered substantial immunity in the absence of any serious adverse events up to 5 years after treatment. To determine the influence of vector integration on lymphoid reconstitution, we compared retroviral integration sites (RISs) from peripheral blood CD3(+) T lymphocytes of 5 patients taken between 9 and 30 months after transplantation with transduced CD34(+) progenitor cells derived from 1 further patient and I healthy donor. Integration occurred preferentially in gene regions on either side of transcription start sites, was clustered, and correlated with the expression level in CD34(+) progenitors during transduction. In contrast to those in CD34(+) cells, RISs recovered from engrafted CD3(+)T cells were significantly overrepresented within or near genes encoding proteins with kinase or transferase activity or involved in phosphorus metabolism. Although gross patterns of gene expression were unchanged in transduced cells, the divergence of RIS target frequency between transduced progenitor cells and post-thymic T lymphocytes indicates that vector integration influences cell survival, engraftment, or proliferation
The HI/OH/Recombination line survey of the inner Milky Way (THOR): data release 2 and Hi overview
Context. The Galactic plane has been observed extensively by a large number of Galactic plane surveys from infrared to radio wavelengths at an angular resolution below 40". However, a 21 cm line and continuum survey with comparable spatial resolution is still missing. Aims. The first half of THOR data (l = 14.0 37.9, and l = 47.1 51.2, |b| < 1.25) has been published in our data release 1 paper (Beuther et al. 2016). With this data release 2 paper, we publish all the remaining spectral line data and Stokes I continuum data with high angular resolution (1000–4000) including a new H i dataset for the whole THOR survey region (l = 14.0 67.4 and |b| < 1.25). As we have published the results of OH lines and continuum emission elsewhere, we concentrate on the H i analysis in this paper. Methods. With the Karl G. Jansky Very Large Array (VLA) in C-configuration, we observed a large portion of the first Galactic quadrant achieving an angular resolution of < 40. At L Band, the WIDAR correlator at the VLA was set to cover the 21 cm H i line, four OH transitions, a series of Hn↵ radio recombination lines (RRLs; n = 151 to 186), and eight 128 MHz wide continuum spectral windows (SPWs) simultaneously. Results. We publish all OH and RRL data from the C-configuration observations, and a new H i dataset combining VLA C+D+GBT (VLA D-configuration and GBT data are from the VLA Galactic Plane Survey, Stil et al. 2006) for the whole survey. The H i emission shows clear filamentary substructures at negative velocities with low velocity crowding. The emission at positive velocities is more smeared-out likely due to higher spatial and velocity crowding of structures at the positive velocities. Comparing to the spiral arm model of the Milky Way, the atomic gas follows the Sagittarius and Perseus Arm well but with significant material in the inter-arm regions. With the C-configuration-only H i+continuum data, we produced a H i optical depth map of the THOR areal coverage from 228 absorption spectra with the nearest-neighbor method. With this ⌧ map, we corrected the H i emission for optical depth and the derived column density is 38% higher than the column density with optically thin assumption. The total H i mass with optical depth correction in the survey region is 4.7⇥108 M, 31% more than the mass derived assuming the emission is optically thin. If we apply this 31% correction to the whole Milky Way, the total atomic gas mass would be 9.4–10.5⇥109 M. Comparing the H i with existing CO data, we find a significant increase in the atomic-to-molecular gas ration from the spiral arms to the inter-arm regions. Conclusions. The high sensitivity and resolution THOR H i dataset provides an important new window on the physical and kinematic properties of gas in the inner Galaxy. Although the optical depth we derive is a lower limit, our study shows that the optical depth correction is significant for H i column density and mass estimation. Together with the OH, RRL and continuum emission from the THOR survey, these new H i data provide the basis for high angular-resolution studies of the interstellar medium (ISM) in different phases
Atomic and molecular gas properties during cloud formation
Context: Molecular clouds, which harbor the birthplaces of stars, form out of the atomic phase of the interstellar medium (ISM). To understand this transition process, it is crucial to investigate the spatial and kinematic relationships between atomic and molecular gas. Aims: We aim to characterize the atomic and molecular phase of the ISM and set their physical properties into the context of cloud formation processes. Methods: We study the cold neutral medium (CNM) by means of H self absorption (HISA) toward the giant molecular filament GMF20.0-17.9 (distance=3.5 kpc, length ∼170 pc) and compare our results with molecular gas traced by CO emission. We fit baselines of HISA features to H emission spectra using 1st and 2nd order polynomial functions. Results: The CNM identified by this method spatially correlates with the morphology of the molecular gas toward the western region. However, no spatial correlation between HISA and CO is evident towards the eastern part of the filament. The distribution of HISA peak velocities and line widths agrees well with CO within the whole filament. The column densities of the CNM probed by HISA are on the order of 1020 cm while those of molecular hydrogen traced by CO are an order of magnitude higher. The column density probability density functions (N-PDFs) of HISA (CNM) and H emission (tracing both the CNM and the warm neutral medium, WNM) have a log-normal shape for all parts of the filament, indicative of turbulent motions as the main driver for these structures. The HN-PDFs show a broad log-normal distribution with a power-law tail suggesting the onset of gravitational contraction. The saturation of H column density is observed at ∼25 M_\bigodotpc. Conclusions: We conjecture that different evolutionary stages are evident within the filament. In the eastern region we witness the onset of molecular cloud formation out of the atomic gas reservoir while the western part is more evolved as it reveals pronounced H2 column density peaks and signs of active star formation
Multimessenger astronomy with the Einstein Telescope
Gravitational waves (GWs) are expected to play a crucial role in the
development of multimessenger astrophysics. The combination of GW observations
with other astrophysical triggers, such as from gamma-ray and X-ray satellites,
optical/radio telescopes, and neutrino detectors allows us to decipher science
that would otherwise be inaccessible. In this paper, we provide a broad review
from the multimessenger perspective of the science reach offered by the third
generation interferometric GW detectors and by the Einstein Telescope (ET) in
particular. We focus on cosmic transients, and base our estimates on the
results obtained by ET's predecessors GEO, LIGO, and Virgo.Comment: 26 pages. 3 figures. Special issue of GRG on the Einstein Telescope.
Minor corrections include
Plasma NGAL levels in stable kidney transplant recipients and the risk of allograft loss
BACKGROUND: The object of this study was to investigate the utility of Neutrophil gelatinase-associated lipocalin (NGAL) and Calprotectin (CPT) to predict long-term graft survival in stable kidney transplant recipients (KTR). METHODS: 709 stable outpatient KTR were enrolled >2 months post-transplant. The utility of plasma and urinary NGAL (pNGAL, uNGAL) and plasma and urinary CPT at enrollment to predict death-censored graft loss (GL) was evaluated during a 58-month follow-up. RESULTS: Among biomarkers, pNGAL showed best predictive ability for graft loss and was the only biomarker with an AUC > 0.7 for GL within 5 years. Patients with GL within 5 years (n=49) had a median pNGAL of 304[IQR 235-358] versus 182[IQR 128 -246]ng/ml with surviving grafts (p<0.001). Time-dependent Receiver operating characteristic analyses at 58 months indicated an Area-Under-the-Curve (AUC) for pNGAL of 0.795, serum creatinine (sCr) based estimated glomerular filtration rate (eGFR) CKD EPI had an AUC of 0.866. pNGAL added to a model based on conventional risk factors for GL with death as competing risk (age, transplant age, presence of donor specific antibodies, presence of proteinuria, history of delayed graft function) had a strong independent association with GL (subdistribution Hazard ratio (sHR) for binary log transfomed pNGAL (log2 (pNGAL)) (3.4 95% CI 2.24-5.15), p<0.0001). This association was substantially attenuated when eGFR was added to the model (sHR for log2 (pNGAL) 1.63 95% CI 0.92-2.88, p=0.095). Category-free net reclassification improvement of a risk model including log2(pNGAL) additionally to conventional risk factors and eGFR was 54.3% (95% CI 9.2 to 99.3%) but C-statistic did not improve significantly. CONCLUSIONS: pNGAL was an independent predictor of renal allograft loss in stable KTR from one transplant center but did not show consistent added value when compared to baseline predictors including the conventional marker eGFR. Future studies in larger cohorts are warranted
- …