840 research outputs found
Magnetotransport studies of Superconducting PrFeAsTeO
We report a detailed study of the electrical transport properties of single
crystals of PrFeAsTeO, a recently discovered iron-based
superconductor. Resistivity, Hall effect and magnetoresistance are measured in
a broad temperature range revealing the role of electrons as dominant charge
carriers. The significant temperature dependence of the Hall coefficient and
the violation of Kohler's law indicate multiband effects in this compound. The
upper critical field and the magnetic anisotropy are investigated in fields up
to 16 T, applied parallel and perpendicular to the crystallographic c-axis.
Hydrostatic pressure up to 2 GPa linearly increases the critical temperature
and the resistivity residual ratio. A simple two-band model is used to describe
the transport and magnetic properties of PrFeAsTeO. The
model can successfully explain the strongly temperature dependent negative Hall
coefficient and the high magnetic anisotropy assuming that the mobility of
electrons is higher than that of holes
L4Fe2As2Te1-xO4-yFy (L = Pr, Sm, Gd): a layered oxypnictide superconductor with Tc up to 45 K
The synthesis, structural and physical properties of iron lanthanide
oxypnictide superconductors, L4Fe2As2Te1-xO4 (L = Pr, Sm, Gd), with transition
temperature at ~ 25 K are reported. Single crystals have been grown at high
pressure using cubic anvil technique. The crystal structure consists of layers
of L2O2 tetrahedra separated by alternating layers of chains of Te and of
Fe2As2 tetrahedra: -L2O2-Te-L2O2-Fe2As2-L2O2-Te-L2O2- (space group: I4/mmm, a ~
4.0, c ~ 29.6 {\AA}). Substitution of oxygen by fluorine increases the critical
temperature, e.g. in Gd4Fe2As2Te1-xOyF4-y up to 45 K. Magnetic torque
measurements reveal an anisotropy of the penetration depths of ~31.Comment: 8 figures, 4 table
Novel Scientific Evidence of Intoxication: Acoustic Analysis of Voice Recordings from the Exxon Valdez
Part of this article reports original research conducted under the direction of the second and third authors. The initial re search was supported by a contract to Indiana University from General Motors Research Laboratories. The specific analyses of voice recordings of Captain Joseph Hazelwood were conducted by them at the re quest of the National Transportation Safety Board, and are based on tapes and data supplied by the NTSB. The second author may be called as a witness in some of the lawsuits pending against the Exxon Corporation. The opinions expressed in this article concerning whether this evidence meets the legal standards of reliability and admissibility are those of the first author, who is not affiliated with the Speech Research Laboratory and has not participated in either the initial research nor the analysis of the Exxon Valdez tapes
Novel Scientific Evidence of Intoxication: Acoustic Analysis of Voice Recordings from the Exxon Valdez
Part of this article reports original research conducted under the direction of the second and third authors. The initial re search was supported by a contract to Indiana University from General Motors Research Laboratories. The specific analyses of voice recordings of Captain Joseph Hazelwood were conducted by them at the re quest of the National Transportation Safety Board, and are based on tapes and data supplied by the NTSB. The second author may be called as a witness in some of the lawsuits pending against the Exxon Corporation. The opinions expressed in this article concerning whether this evidence meets the legal standards of reliability and admissibility are those of the first author, who is not affiliated with the Speech Research Laboratory and has not participated in either the initial research nor the analysis of the Exxon Valdez tapes
Novel Scientific Evidence of Intoxication: Acoustic Analysis of Voice Recordings from the Exxon Valdez
A practice-related risk score (PRS): a DOPPS-derived aggregate quality index for haemodialysis facilities
Background. The Dialysis Outcomes and Practice Patterns Study (DOPPS) database was used to develop and validate a practice-related risk score (PRS) based on modifiable practices to help facilities assess potential areas for improving patient care.
Methods. Relative risks (RRs) from a multivariable Cox mortality model, based on observational haemodialysis (HD) patient data from DOPPS I (1996-2001, seven countries), were used. The four practices were the percent of patients with Kt/V >= 1.2, haemoglobin >= 11 g/dl (110 g/l), albumin >= 4.0 g/dl (40g/l) and catheter use, and were significantly related to mortality when modelled together. DOPPS II data (2002-2004, 12 countries) were used to evaluate the relationship between PRS and mortality risk using Cox regression.
Results. For facilities in DOPPS I and II, changes in PRS over time were significantly correlated with changes in the standardized mortality ratio (SMR). The PRS ranged from 1.0 to 2.1. Overall, the adjusted RR of death was 1.05 per 0.1 points higher PRS (P < 0.0001). For facilities in both DOPPS I and II (N = 119), a 0.2 decrease in PRS was associated with a 0.19 decrease in SMR (P = 0.005). On average, facilities that improved PRS practices showed significantly reduced mortality over the same time frame.
Conclusions. The PRS assesses modifiable HD practices that are linked to improved patient survival. Further refinements might lead to improvements in the PRS and will address regional variations in the PRS/mortality relationship
Upper critical field, pressure-dependent superconductivity and electronic anisotropy of SmFeAsTeOF
We present a detailed study of the electrical transport properties of a
recently discovered iron-based superconductor:
SmFeAsTeOF. We followed the temperature
dependence of the upper critical field by resistivity measurement of single
crystals in magnetic fields up to 16 T, oriented along the two main
crystallographic directions. This material exhibits a zero-temperature upper
critical field of 90 T and 65 T parallel and perpendicular to the FeAs
planes, respectively. An unprecedented superconducting magnetic anisotropy
is observed near Tc, and it decreases
at lower temperatures as expected in multiband superconductors. Direct
measurement of the electronic anisotropy was performed on microfabricated
samples, showing a value of that raises up to
19 near Tc. Finally, we have studied the pressure and temperature dependence of
the in-plane resistivity. The critical temperature decreases linearly upon
application of hydrostatic pressure (up to 2 GPa) similarly to overdoped
cuprate superconductors. The resistivity shows saturation at high temperatures,
suggesting that the material approaches the Mott-Ioffe-Regel limit for metallic
conduction. Indeed, we have successfully modelled the resistivity in the normal
state with a parallel resistor model that is widely accepted for this state.
All the measured quantities suggest strong pressure dependence of the density
of states
High- and Low-Performing Adult Cochlear Implant Users on High-Variability Sentence Recognition:Differences in Auditory Spectral Resolution and Neurocognitive Functioning
Background Postlingually deafened adult cochlear implant (CI) users routinely display large individual differences in the ability to recognize and understand speech, especially in adverse listening conditions. Although individual differences have been linked to several sensory ("bottom-up'') and cognitive ("top-down'') factors, little is currently known about the relative contributions of these factors in high- and low-performing CI users. Purpose The aim of the study was to investigate differences in sensory functioning and neurocognitive functioning between high- and low-performing CI users on the Perceptually Robust English Sentence Test Open-set (PRESTO), a high-variability sentence recognition test containing sentence materials produced by multiple male and female talkers with diverse regional accents. Research Design CI users with accuracy scores in the upper (HiPRESTO) or lower quartiles (LoPRESTO) on PRESTO in quiet completed a battery of behavioral tasks designed to assess spectral resolution and neurocognitive functioning. Study Sample Twenty-one postlingually deafened adult CI users, with 11 HiPRESTO and 10 LoPRESTO participants. Data Collection and Analysis A discriminant analysis was carried out to determine the extent to which measures of spectral resolution and neurocognitive functioning discriminate HiPRESTO and LoPRESTO CI users. Auditory spectral resolution was measured using the Spectral-Temporally Modulated Ripple Test (SMRT). Neurocognitive functioning was assessed with visual measures of working memory (digit span), inhibitory control (Stroop), speed of lexical/phonological access (Test of Word Reading Efficiency), and nonverbal reasoning (Raven's Progressive Matrices). Results HiPRESTO and LoPRESTO CI users were discriminated primarily by performance on the SMRT and secondarily by the Raven's test. No other neurocognitive measures contributed substantially to the discriminant function. Conclusions High- and low-performing CI users differed by spectral resolution and, to a lesser extent, nonverbal reasoning. These findings suggest that the extreme groups are determined by global factors of richness of sensory information and domain-general, nonverbal intelligence, rather than specific neurocognitive processing operations related to speech perception and spoken word recognition. Thus, although both bottom-up and top-down information contribute to speech recognition performance, low-performing CI users may not be sufficiently able to rely on neurocognitive skills specific to speech recognition to enhance processing of spectrally degraded input in adverse conditions involving high talker variability
The Global Impact of the COVID-19 Pandemic on In-Center Hemodialysis Services:An ISN-Dialysis Outcomes Practice Patterns Study Survey
Charge-Stripe Order and Superconductivity in
A combined resistivity and hard x-ray diffraction study of superconductivity
and charge ordering in , as a function of Pt
substitution and externally applied hydrostatic pressure, is presented.
Experiments are focused on samples near the critical composition where competition and switching between charge order and
superconductivity is established. We show that charge order as a function of
pressure in is preempted - and hence
triggered - by a structural transition. Charge ordering appears uniaxially
along the short crystallographic (1,0,1) domain axis with a
modulation. Based on these results we
draw a charge-order phase diagram and discuss the relation between stripe
ordering and superconductivity.Comment: 8 pages, 4 figures: Accepted in Scientific Report
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