1,121 research outputs found
High Temperature Electron Localization in dense He Gas
We report new accurate mesasurements of the mobility of excess electrons in
high density Helium gas in extended ranges of temperature and density to ascertain
the effect of temperature on the formation and dynamics of localized electron
states. The main result of the experiment is that the formation of localized
states essentially depends on the relative balance of fluid dilation energy,
repulsive electron-atom interaction energy, and thermal energy. As a
consequence, the onset of localization depends on the medium disorder through
gas temperature and density. It appears that the transition from delocalized to
localized states shifts to larger densities as the temperature is increased.
This behavior can be understood in terms of a simple model of electron
self-trapping in a spherically symmetric square well.Comment: 23 pages, 13 figure
Relationship among concentrations of milk urea nitrogen and plasma urea nitrogen and feeding time
Eight Holstein cows were used to determine the relationship among milk urea nitrogen (MUN), plasma urea nitrogen (PUN), and feeding time. We first established that MUN concentrations were similar in concentration among quarters by comparing milk samples from each quarter just before milking. In order to determine if collecting a sample of milk from a quarter influenced the MUN in samples taken later, samples were obtained from the right front quarter (RF) at 2, 4, 6, and 8 hr after the AM milking and from the left front quarter (LF), right rear (RR), and left rear (LR) at 4, 6, and 8 h after the AM milking, respectively. The MUN in samples obtained from RF at 4 hr was lower (P\u3c0.01) than corresponding samples taken from LF, but samples from RF at 6 and 8 hr did not differ from corresponding samples obtained from RR and LR. We concluded that by 6 hr, the effect of previous milking on MUN concentration disappeared because of dilution. To determine the influence of feeding time on MUN concentrations, cows were fed half of their normal PM feeding, injected with oxytocin at the subsequent AM milking to reduce residual milk, and offered surplus feed after the AM milking. Milk samples were collected at 2, 4, 6, 8, 10, and 12 hr after feeding from RF, LF, RR, LR, RF, and LF quarters, respectively. Blood samples were obtained from the coccygeal vein at hourly intervals after feeding with the last sample collected 12 hr after feeding. The MUN concentrations at 2, 4, 6, and 8 hr were similar. The MUN at 10 hr was similar to those at 2 and 8 hr, less than that at 4 and 6 hr, and greater than that for the 12 hr sample. Concentrations of PUN peaked at 2 hr postfeeding, then gradually declined through 12 hr postfeeding. The MUN peaked at 6 hr postfeeding and then declined. Time after feeding significantly influenced PUN and MUN concentrations.; Dairy Day, 2000, Kansas State University, Manhattan, KS, 2000
Intake and performance of dairy cows fed wet corn gluten feed during the periparturient period
Eight primiparous and nine multiparous Holstein cows were used in a randomized block design to determine the effect of wet corn gluten feed in the diet during the last 21 days of gestation on dry matter intake and early postpartum performance. Multilactation cows fed wet corn gluten feed maintained a higher dry matter intake and intake as a percentage of body weight during the last week before calving than cows fed the control diet. First-lactation cows fed wet corn gluten feed consumed less dry matter, both total and as a percentage of body weight, across calving than first-lactation cows fed the control diet. Milk, milk components, and blood metabolites were not influenced by diet. Wet corn gluten feed may help alleviate the depression in intake typically observed during late gestation for multiparous but not primiparous cows.; Dairy Day, 2000, Kansas State University, Manhattan, KS, 2000
Phase coherence phenomena in superconducting films
Superconducting films subject to an in-plane magnetic field exhibit a gapless
superconducting phase. We explore the quasi-particle spectral properties of the
gapless phase and comment on the transport properties. Of particular interest
is the sensitivity of the quantum interference phenomena in this phase to the
nature of the impurity scattering. We find that films subject to columnar
defects exhibit a `Berry-Robnik' symmetry which changes the fundamental
properties of the system. Furthermore, we explore the integrity of the gapped
phase. As in the magnetic impurity system, we show that optimal fluctuations of
the random impurity potential conspire with the in-plane magnetic field to
induce a band of localized sub-gap states. Finally, we investigate the
interplay of the proximity effect and gapless superconductivity in thin normal
metal-superconductor bi-layers.Comment: 13 pages, 8 figures include
Examining determinants of geographic variation in colorectal cancer mortality in North Carolina: A spatial analysis approach
Purpose: A recent study using national data from 2000 to 2009 identified colorectal cancer (CRC) mortality âhotspotsâ in 11 counties of North Carolina (NC). In this study, we used more recent, state-specific data to investigate the county-level determinants of geographic variation in NC through a geospatial analytic approach. Method: Using NC CRC mortality data from 2003 to 2013, we first conducted clustering analysis to confirm spatial dependence. Spatial economic models were then used to incorporate spatial structure to estimate the association between determinants and CRC mortality. We included county-level data on socio-demographic characteristics, access and quality of healthcare, behavioral risk factors (CRC screening, obesity, and cigarette smoking), and urbanicity. Due to correlation among screening, obesity and quality of healthcare, we combined these factors to form a cumulative risk group variable in the analysis. Results: We confirmed the existence of spatial dependence and identified clusters of elevated CRC mortality rates in NC counties. Using a spatial lag model, we found significant interaction effect between CRC risk groups and socioeconomic deprivation. Higher CRC mortality rates were also associated with rural counties with large towns compared to urban counties. Conclusion: Our findings depicted a spatial diffusion process of CRC mortality rates across NC counties, demonstrated intertwined effects between SES deprivation and behavioral risks in shaping CRC mortality at area-level, and identified counties with high CRC mortality that were also deprived in multiple factors. These results suggest interventions to reduce geographic variation in CRC mortality should develop multifaceted strategies and work through shared resources in neighboring areas
Magnetoinductance of Josephson junction array with frozen vortex diffusion
The dependence of sheet impedance of a Josephson junction array on the
applied magnetic field is investigated in the regime when vortex diffusion
between array plaquettes is effectively frozen due to low enough temperature.
The field dependent contribution to sheet inductance is found to be
proportional to f*ln(1/f), where f<<1 is the magnitude of the field expressed
in terms of flux quanta per plaquette.Comment: 5 pages, no figure
Tilt order parameters, polarity and inversion phenomena in smectic liquid crystals
The order parameters for the phenomenological description of the smectic-{\it
A} to smectic-{\it C} phase transition are formulated on the basis of molecular
symmetry and structure. It is shown that, unless the long molecular axis is an
axis of two-fold or higher rotational symmetry, the ordering of the molecules
in the smectic-{\it C} phase gives rise to more than one tilt order parameter
and to one or more polar order parameters. The latter describe the indigenous
polarity of the smectic-{\it C} phase, which is not related to molecular
chirality but underlies the appearance of spontaneous polarisation in chiral
smectics. A phenomenological theory of the phase transition is formulated by
means of a Landau expansion in two tilt order parameters (primary and
secondary) and an indigenous polarity order parameter. The coupling among these
order parameters determines the possibility of sign inversions in the
temperature dependence of the spontaneous polarisation and of the helical pitch
observed experimentally for some chiral smectic-{\it } materials. The
molecular interpretation of the inversion phenomena is examined in the light of
the new formulation.Comment: 12 pages, 5 figures, RevTe
Quantitative conditional quantum erasure in two-atom resonance fluorescence
We present a conditional quantum eraser which erases the a priori knowledge
or the predictability of the path a photon takes in a Young-type double-slit
experiment with two fluorescent four-level atoms. This erasure violates a
recently derived erasure relation which must be satisfied for a conventional,
unconditional quantum eraser that aims to find an optimal sorting of the system
into subensembles with particularly large fringe visibilities. The conditional
quantum eraser employs an interaction-free, partial which-way measurement which
not only sorts the system into optimal subsystems with large visibility but
also selects the appropriate subsystem with the maximum possible visibility. We
explain how the erasure relation can be violated under these circumstances.Comment: Revtex4, 12pages, 4 eps figures, replaced with published version,
changes in Sec. 3, to appear in Physical Review
Development and validation of a 5-year mortality prediction model using regularized regression and Medicare data
Purpose: De-implementation of low-value services among patients with limited life expectancy is challenging. Robust mortality prediction models using routinely collected health care data can enhance health care stakeholders' ability to identify populations with limited life expectancy. We developed and validated a claims-based prediction model for 5-year mortality using regularized regression methods. Methods: Medicare beneficiaries age 66 or older with an office visit and at least 12 months of pre-visit continuous Medicare A/B enrollment were identified in 2008. Five-year mortality was assessed through 2013. Secondary outcomes included 30-, 90-, and 180-day and 1-year mortality. Claims-based predictors, including comorbidities and indicators of disability, frailty, and functional impairment, were selected using regularized logistic regression, applying the least absolute shrinkage and selection operator (LASSO) in a random 80% training sample. Model performance was assessed and compared with the Gagne comorbidity score in the 20% validation sample. Results: Overall, 183 204 (24%) individuals died. In addition to demographics, 161 indicators of comorbidity and function were included in the final model. In the validation sample, the c-statistic was 0.825 (0.823-0.828). Median-predicted probability of 5-year mortality was 14%; almost 4% of the cohort had a predicted probability greater than 80%. Compared with the Gagne score, the LASSO model led to improved 5-year mortality classification (net reclassification index = 9.9%; integrated discrimination index = 5.2%). Conclusions: Our claims-based model predicting 5-year mortality showed excellent discrimination and calibration, similar to the Gagne score model, but resulted in improved mortality classification. Regularized regression is a feasible approach for developing prediction tools that could enhance health care research and evaluation of care quality
Approximate k-state solutions to the Dirac-Yukawa problem based on the spin and pseudospin symmetry
Using an approximation scheme to deal with the centrifugal
(pseudo-centrifugal) term, we solve the Dirac equation with the screened
Coulomb (Yukawa) potential for any arbitrary spin-orbit quantum number
{\kappa}. Based on the spin and pseudospin symmetry, analytic bound state
energy spectrum formulas and their corresponding upper- and lower-spinor
components of two Dirac particles are obtained using a shortcut of the
Nikiforov-Uvarov method. We find a wide range of permissible values for the
spin symmetry constant C_{s} from the valence energy spectrum of particle and
also for pseudospin symmetry constant C_{ps} from the hole energy spectrum of
antiparticle. Further, we show that the present potential interaction becomes
less (more) attractive for a long (short) range screening parameter {\alpha}.
To remove the degeneracies in energy levels we consider the spin and pseudospin
solution of Dirac equation for Yukawa potential plus a centrifugal-like term. A
few special cases such as the exact spin (pseudospin) symmetry Dirac-Yukawa,
the Yukawa plus centrifugal-like potentials, the limit when {\alpha} becomes
zero (Coulomb potential field) and the non-relativistic limit of our solution
are studied. The nonrelativistic solutions are compared with those obtained by
other methods.Comment: 21 pages, 6 figure
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