5,157 research outputs found
Practice Makes Perfect: The Volume-Outcome Association in Pediatric Stoma Closure Surgery
Children with anorectal malformations often receive a temporary colostomy or ileostomy before surgical repair of the anomaly to divert stool and allow their anatomy time to heal. Once their bodies have healed, the stoma is taken down, a standard procedure for pediatric general surgeons. However, for decades, stoma takedown surgery has been associated with a high risk of postoperative complications. This study seeks to determine if hospital prior-year stoma closure case volume influences pediatric patients\u27 quality outcome measures. Population. This study identified 340 pediatric patients having undergone stoma closure surgery during the study period at hospitals in a representative sample of seven states; Arkansas, Florida, Georgia, Maryland, Mississippi, New York, and Washington. Study Design. This study is a retrospective analysis of archival billing data for pediatric stoma closure patients. The billing data source is the 2016 - 2017 Agency for Healthcare Research and Quality\u27s (AHRQ) Healthcare Cost and Utilization Project (HCUP) database. Outcome Measures. This study uses generally accepted surrogate measures of a quality outcome. The quality outcome measures for this study are the rate of in-hospital mortality during the index admission, readmission to the hospital within 30 days of discharge, and length of stay (LOS) during the index admission. Results. One mortality occurred in the study population (.29%), while 39 patients were readmitted (11.5%). Logistic regression analysis found no significant volume-outcome association between volume and the outcome measures. However, when categorized into age groups, a statistically significant association exists between hospital prior-year volume and readmission (p \u3c .04) in the infant age group (Age \u3c 1). A similar association was found between hospital prior-year volume and LOS (p \u3c .002) in the infant group compared to the non-infant group. With each prior-year increase of 10 cases, the likelihood of readmission decreases by 52% and expected hospitalization days decreases by 25%. Conclusion. This study validates an inverse hospital volume-readmission association in infant stoma closure surgery and an inverse volume-LOS association among all pediatric patients, with the magnitude of the association being most significant in the infant population
Anomalous Hall Effect in three ferromagnets: EuFe4Sb12, Yb14MnSb11, and Eu8Ga16Ge30
The Hall resistivity (Rho_xy), resistivity (Rho_xx), and magnetization of
three metallic ferromagnets are investigated as a function of magnetic field
and temperature. The three ferromagnets, EuFe4Sb12 (Tc = 84 K), Yb14MnSb11 (Tc
= 53 K), and Eu8Ga16Ge30 (Tc = 36 K) are Zintl compounds with carrier
concentrations between 1 x 10^21 cm^-3 and 3.5 x 10^21 cm^-3. The relative
decrease in Rho_xx below Tc [Rho_xx(Tc)/Rho_xx(2 K)] is 28, 6.5, and 1.3 for
EuFe4Sb12, Yb14MnSb11, and Eu8Ga16Ge30 respectively. The low carrier
concentrations coupled with low magnetic anisotropies allow a relatively clean
separation between the anomalous (Rho_'xy), and normal contributions to the
measured Hall resistivity. For each compound the anomalous contribution in the
zero field limit is fit to alpha Rho_xx + sigma_xy rho_xx^2 for temperatures T
< Tc. The anomalous Hall conductivity, sigma_xy, is -220 +- 5 (Ohm^-1 cm^-1),
-14.7 +- 1 (Ohm^-1 cm^-1), and 28 +- 3 (Ohm^-1 cm^-1) for EuFe4Sb12,
Yb14MnSb11, and Eu8Ga16Ge30 respectively and is independent of temperature for
T < Tc if the change in spontaneous magnetization (order parameter) with
temperature is taken into account. These data are consistent with recent
theories of the anomalous Hall effect that suggest that even for stochiometric
ferromagnetic crystals, such as those studied in this article, the intrinsic
Hall conductivity is finite at T = 0, and is a ground state property that can
be calculated from the electronic structure.Comment: 22 pages, 13 figures Submitted to PR
Surveillance on the light-front gauge fixing Lagrangians
In this work we propose two Lagrange multipliers with distinct coefficients
for the light-front gauge that leads to the complete (non-reduced) propagator.
This is accomplished via terms in the
Lagrangian density. These lead to a well-defined and exact though Lorentz non
invariant light front propagator.Comment: 7 pages. This is an improved version of hep-th/030406
Rejuvenation in the Random Energy Model
We show that the Random Energy Model has interesting rejuvenation properties
in its frozen phase. Different `susceptibilities' to temperature changes, for
the free-energy and for other (`magnetic') observables, can be computed
exactly. These susceptibilities diverge at the transition temperature, as
(1-T/T_c)^-3 for the free-energy.Comment: 9 pages, 1 eps figur
Possible mechanism for achieving glass-like thermal conductivities in crystals with off-center atoms
In the filled Ga/Ge clathrate, Eu and Sr are off-center in site 2 but Ba is
on-center. All three filler atoms (Ba,Eu,Sr) have low temperature Einstein
modes; yet only for the Eu and Sr systems is there a large dip in the thermal
conductivity, attributed to the Einstein modes. No dip is observed for Ba. Here
we argue that it is the off-center displacement that is crucial for
understanding this unexplained difference in behavior. It enhances the coupling
between the "rattler" motion and the lattice phonons for the Eu and Sr systems,
and turns on/off another scattering mechanism (for 1K < T < 20K) produced by
the presence/absence of off-center sites. The random occupation of different
off-center sites produces a high density of symmetry-breaking defects which
scatters phonons. It may also be important for improving our understanding of
other glassy systems.Comment: 4 pages, 1 figure (2 parts) -- v2: intro broadened; strengthened
arguments regarding need for additional phonon scattering mechanis
Thermoelectric properties of Co, Ir, and Os-Doped FeSi Alloys: Evidence for Strong Electron-Phonon Coupling
The effects of various transition metal dopants on the electrical and thermal
transport properties of Fe1-xMxSi alloys (M= Co, Ir, Os) are reported. The
maximum thermoelectric figure of merit ZTmax is improved from 0.007 at 60 K for
pure FeSi to ZT = 0.08 at 100 K for 4% Ir doping. A comparison of the thermal
conductivity data among Os, Ir and Co doped alloys indicates strong
electron-phonon coupling in this compound. Because of this interaction, the
common approximation of dividing the total thermal conductivity into
independent electronic and lattice components ({\kappa}Total =
{\kappa}electronic + {\kappa}lattice) fails for these alloys. The effects of
grain size on thermoelectric properties of Fe0.96Ir0.04Si alloys are also
reported. The thermal conductivity can be lowered by about 50% with little or
no effect on the electrical resistivity or Seebeck coefficient. This results in
ZTmax = 0.125 at 100 K, still about a factor of five too low for solid-state
refrigeration applications
Symmetrical Temperature-Chaos Effect with Positive and Negative Temperature Shifts in a Spin Glass
The aging in a Heisenberg-like spin glass Ag(11 at% Mn) is investigated by
measurements of the zero field cooled magnetic relaxation at a constant
temperature after small temperature shifts . A
crossover from fully accumulative to non-accumulative aging is observed, and by
converting time scales to length scales using the logarithmic growth law of the
droplet model, we find a quantitative evidence that positive and negative
temperature shifts cause an equivalent restart of aging (rejuvenation) in terms
of dynamical length scales. This result supports the existence of a unique
overlap length between a pair of equilibrium states in the spin glass system.Comment: 4 page
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