1,313 research outputs found
Food spoilage in beeswax impregnated cotton cloth wraps compared to standard storage methods
Beeswax food wraps have gained popularity as a sustainable, natural alternative to single use options such as plastic bags, plastic wrap, and wax paper. Despite limited evidence, sellers advertise beeswax wraps as having antimicrobial benefits that help food stay fresh longer. The purpose of this investigation was to determine the ability of beeswax impregnated cotton cloth to inhibit food spoilage relative to traditional methods. We designed a prospective trial in which strawberry, bread, and cheese specimens were wrapped in one of the 3 materials: 1) beeswax impregnated cotton cloth, 2) wax paper, or 3) plastic bags alone and followed for 15 days at 65oF for progression of mold growth and other signs of deterioration. For most specimen/timepoint combinations (87%), we found no differences between storage methods. For the 13% of specimen/timepoint combinations where we did note a significant difference, beeswax wraps fared the worst. While beeswax wraps may be preferred as a natural food storage material, their ability to preserve food is no better than conventional options
The complex relationship between pediatric cardiac surgical case volumes and mortality rates in a national clinical database
ObjectiveWe sought to determine the association between pediatric cardiac surgical volume and mortality using sophisticated case-mix adjustment and a national clinical database.MethodsPatients 18 years of age or less who had a cardiac operation between 2002 and 2006 were identified in the Society of Thoracic Surgeons Congenital Heart Surgery Database (32,413 patients from 48 programs). Programs were grouped by yearly pediatric cardiac surgical volume (small, <150; medium, 150–249; large, 250–349; and very large, ≥350 cases per year). Logistic regression was used to adjust mortality rates for volume, surgical case mix (Aristotle Basic Complexity and Risk Adjustment for Congenital Heart Surgery, Version 1 categories), patient risk factors, and year of operation.ResultsWith adjustment for patient-level risk factors and surgical case mix, there was an inverse relationship between overall surgical volume as a continuous variable and mortality (P = .002). When the data were displayed graphically, there appeared to be an inflection point between 200 and 300 cases per year. When volume was analyzed as a categorical variable, the relationship was most apparent for difficult operations (Aristotle technical difficulty component score, >3.0), for which mortality decreased from 14.8% (60/406) at small programs to 8.4% (157/1858) at very large programs (P = .02). The same was true for the subgroup of patients who underwent Norwood procedures (36.5% [23/63] vs 16.9% [81/479], P < .0001). After risk adjustment, all groups performed similarly for low-difficulty operations. Conversely, for difficult procedures, small programs performed significantly worse. For Norwood procedures, very large programs outperformed all other groups.ConclusionThere was an inverse association between pediatric cardiac surgical volume and mortality that became increasingly important as case complexity increased. Although volume was not associated with mortality for low-complexity cases, lower-volume programs underperformed larger programs as case complexity increased
Nuclear Flow in Consistent Boltzmann Algorithm Models
We investigate the stochastic Direct Simulation Monte Carlo method (DSMC) for
numerically solving the collision-term in heavy-ion transport theories of the
Boltzmann-Uehling-Uhlenbeck (BUU) type. The first major modification we
consider is changes in the collision rates due to excluded volume and
shadowing/screening effects (Enskog theory). The second effect studied by us is
the inclusion of an additional advection term. These modifications ensure a
non-vanishing second virial and change the equation of state for the scattering
process from that of an ideal gas to that of a hard-sphere gas. We analyse the
effect of these modifications on the calculated value of directed nuclear
collective flow in heavy ion collisions, and find that the flow slightly
increases.Comment: 12 pages, REVTeX, figures available in PostScript from the authors
upon reques
Entropy production by resonance decays
We investigate entropy production for an expanding system of particles and
resonances with isospin symmetry -- in our case pions and mesons --
within the framework of relativistic kinetic theory. A cascade code to simulate
the kinetic equations is developed and results for entropy production and
particle spectra are presented.Comment: 17 pages, 10 ps-figures included, only change: preprint number adde
The SU(2) and SU(3) chiral phase transitions within Chiral Perturbation Theory
The SU(2) and SU(3) chiral phase transitions in a hot gas made of pions,
kaons and etas are studied within the framework of Chiral Perturbation Theory.
By using the meson meson scattering phase shifts in a second order virial
expansion, we are able to describe the temperature dependence of the quark
condensates. We have estimated the critical temperatures where the different
condensates melt. In particular, the SU(3) formalism yields a lower critical
temperature for the non-strange condensates than within SU(2), and also
suggests that the strange condensate may melt at a somewhat higher temperature,
due to the different strange and non-strange quark masses.Comment: 4 pages, two figures. Final version to appear in Phys Rev D. Complete
model independent calculation. Unitarized ChPt only used to check
extrapolation at high T. References added and numerical bug correcte
Kinetic Properties of a Bose-Einstein Gas at Finite Temperature
We study, in the framework of the Boltzmann-Nordheim equation (BNE), the
kinetic properties of a boson gas above the Bose-Einstein transition
temperature . The BNE is solved numerically within a new algorithm, that
has been tested with exact analytical results for the collision rate of an
homogeneous system in thermal equilibrium. In the classical regime (), the relaxation time of a quadrupolar deformation in momentum space is
proportional to the mean free collision time .
Approaching the critical temperature (), quantum statistic
effects in BNE become dominant, and the collision rate increases dramatically.
Nevertheless, this does not affect the relaxation properties of the gas that
depend only on the spontaneous collision term in BNE. The relaxation time
is proportional to , exhibiting a critical
slowing down. These phenomena can be experimentally confirmed looking at the
damping properties of collective motions induced on trapped atoms. The
possibility to observe a transition from collisionless (zero-sound) to
hydrodynamic (first-sound) is finally discussed.Comment: RevTeX, 5 figures. Submitted to Phys. Rev.
Fragment Flow and the Nuclear Equation of State
We use the Boltzmann-Uehling-Uhlenbeck model with a momentum-dependent
nuclear mean field to simulate the dynamical evolution of heavy ion collisions.
We re-examine the azimuthal anisotropy observable, proposed as sensitive to the
equation of state of nuclear matter. We obtain that this sensitivity is maximal
when the azimuthal anisotropy is calculated for nuclear composite fragments, in
agreement with some previous calculations. As a test case we concentrate on
semi-central collisions at 400 MeV.Comment: 12 pages, ReVTeX 3.0. 12 Postscript figures, uuencoded and appende
Relevant compounds of brazilian chardonnay wines and sparkling wines unveiled using comprehensive twodimensional gas chromatography.
This work employed HS-SPME, comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detector (GC × GC/TOFMS),statistical tools, andodor activity values (OAV) for the analysis of volatile compounds of Chardonnay wine, base wine and sparkling wines of Serra Gaúcha
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