887 research outputs found
Nursing Ethics: Across the Curriculum and Into Practice Book Review
Spanning the nursing curriculum, Nursing Ethics: Across the Curriculum and Into Practice is derived from theoretical foundations, clinical evidence and case study. Based on the concept that compassionate relationships between nurses and patients form a vital element of humanistic nursing, this text provides foundational knowledge about ethics and decision-making strategies to prepare nurses for the moral issues they experience daily. Nursing Ethics includes decision-making approaches and models, rationale for decisions, and management of care for various topics
Single-particle excitations and the order parameter for a trapped superfluid Fermi gas
We reveal a strong influence of a superfluid phase transition on the
character of single-particle excitations of a trapped neutral-atom Fermi gas.
Below the transition temperature the presence of a spatially inhomogeneous
order parameter (gap) shifts up the excitation eigenenergies and leads to the
appearance of in-gap excitations localized in the outer part of the gas sample.
The eigenenergies become sensitive to the gas temperature and are no longer
multiples of the trap frequencies. These features should manifest themselves in
a strong change of the density oscillations induced by modulations of the trap
frequencies and can be used for identifying the superfluid phase transition.Comment: 5 pages, RevTeX, 2 eps figure
Accounting for data heterogeneity in integrative analysis and prediction methods: An application to Chronic Obstructive Pulmonary Disease
Epidemiologic and genetic studies in chronic obstructive pulmonary disease
(COPD) and many complex diseases suggest subgroup disparities (e.g., by sex).
We consider this problem from the standpoint of integrative analysis where we
combine information from different views (e.g., genomics, proteomics, clinical
data). Existing integrative analysis methods ignore the heterogeneity in
subgroups, and stacking the views and accounting for subgroup heterogeneity
does not model the association among the views. To address analytical
challenges in the problem of our interest, we propose a statistical approach
for joint association and prediction that leverages the strengths in each view
to identify molecular signatures that are shared by and specific to males and
females and that contribute to the variation in COPD, measured by airway wall
thickness. HIP (Heterogeneity in Integration and Prediction) accounts for
subgroup heterogeneity, allows for sparsity in variable selection, is
applicable to multi-class and to univariate or multivariate continuous
outcomes, and incorporates covariate adjustment. We develop efficient
algorithms in PyTorch. Our COPD findings have identified several proteins,
genes, and pathways that are common and specific to males and females, some of
which have been implicated in COPD, while others could lead to new insights
into sex differences in COPD mechanisms
Activity driven modeling of time varying networks
Network modeling plays a critical role in identifying statistical
regularities and structural principles common to many systems. The large
majority of recent modeling approaches are connectivity driven. The structural
patterns of the network are at the basis of the mechanisms ruling the network
formation. Connectivity driven models necessarily provide a time-aggregated
representation that may fail to describe the instantaneous and fluctuating
dynamics of many networks. We address this challenge by defining the activity
potential, a time invariant function characterizing the agents' interactions
and constructing an activity driven model capable of encoding the instantaneous
time description of the network dynamics. The model provides an explanation of
structural features such as the presence of hubs, which simply originate from
the heterogeneous activity of agents. Within this framework, highly dynamical
networks can be described analytically, allowing a quantitative discussion of
the biases induced by the time-aggregated representations in the analysis of
dynamical processes.Comment: 10 pages, 4 figure
Does Physical Activity Influence Semantic Memory Activation in Amnestic Mild Cognitive Impairment?
The effect of physical activity (PA) on functional brain activation for semantic memory in amnestic mild cognitive impairment (aMCI) was examined using event-related functional magnetic resonance imaging during fame discrimination. Significantly greater semantic memory activation occurred in the left caudate of High- versus Low-PA patients, (P=0.03), suggesting PA may enhance memory-related caudate activation in aMCI
Stability of a vortex in a small trapped Bose-Einstein condensate
A second-order expansion of the Gross-Pitaevskii equation in the interaction
parameter determines the thermodynamic critical angular velocity Omega_c for
the creation of a vortex in a small axisymmetric condensate. Similarly, a
second-order expansion of the Bogoliubov equations determines the (negative)
frequency omega_a of the anomalous mode. Although Omega_c = -omega_a through
first order, the second-order contributions ensure that the absolute value
|omega_a| is always smaller than the critical angular velocity Omega_c. With
increasing external rotation Omega, the dynamical instability of the condensate
with a vortex disappears at Omega*=|omega_a|, whereas the vortex state becomes
energetically stable at the larger value Omega_c. Both second-order
contributions depend explicitly on the axial anisotropy of the trap. The
appearance of a local minimum of the free energy for a vortex at the center
determines the metastable angular velocity Omega_m. A variational calculation
yields Omega_m=|\omega_a| to first order (hence Omega_m also coincides with the
critical angular velocity Omega_c to this order). Qualitatively, the scenario
for the onset of stability in the weak-coupling limit is the same as that found
in the strong-coupling (Thomas-Fermi) limit.Comment: 8 pages, RevTe
Limits to Sympathetic Evaporative Cooling of a Two-Component Fermi Gas
We find a limit cycle in a quasi-equilibrium model of evaporative cooling of
a two-component fermion gas. The existence of such a limit cycle represents an
obstruction to reaching the quantum ground state evaporatively. We show that
evaporatively the \beta\mu ~ 1. We speculate that one may be able to cool an
atomic fermi gas further by photoassociating dimers near the bottom of the
fermi sea.Comment: Submitted to Phys. Rev
Exact Eignstates for Trapped Weakly Interacting Bosons in Two Dimensions
A system of N two-dimensional weakly interacting bosons in a harmonic trap is
considered. When the two-particle potential is a delta function Smith and
Wilkin have analytically proved that the elementary symmetric polynomials of
particle coordinates measured from the center of mass are exact eigenstates. In
this study, we point out that their proof works equally well for an arbitrary
two-particle potential which possesses the translational and rotational
symmetries. We find that the interaction energy associated with the eigenstate
with angular momentum L is equal to aN(N-1)/2+(b-a)NL/2, where a and b are the
interaction energies of two bosons in the lowest-energy one-particle state with
zero and one unit of angular momentum, respectively. Additionally, we study
briefly the case of attractive quartic interactions. We prove rigorously that
the lowest-energy state is the one in which all angular momentum is carried by
the center of mass motion.Comment: 4 pages, minor changes made, to appear in PRA Brie
Phase diagram of quantized vortices in a trapped Bose-Einstein condensed gas
We investigate the thermodynamic stability of quantized vortices in a dilute
Bose gas confined by a rotating harmonic trap at finite temperature.
Interatomic forces play a crucial role in characterizing the resulting phase
diagram, especially in the large Thomas-Fermi regime. We show that the
critical temperature for the creation of stable vortices exhibits a maximum as
a function of the frequency of the rotating trap and that the corresponding
transition is associated with a discontinuity in the number of atoms in the
condensate. Possible strategies for approaching the vortical region are
discussed.Comment: Revtex, 4 pages, 2 figure
Scattering of short laser pulses from trapped fermions
We investigate the scattering of intense short laser pulses off trapped cold
fermionic atoms. We discuss the sensitivity of the scattered light to the
quantum statistics of the atoms. The temperature dependence of the scattered
light spectrum is calculated. Comparisons are made with a system of classical
atoms who obey Maxwell-Boltzmann statistics. We find the total scattering
increases as the fermions become cooler but eventually tails off at very low
temperatures (far below the Fermi temperature). At these low temperatures the
fermionic degeneracy plays an important role in the scattering as it inhibits
spontaneous emission into occupied energy levels below the Fermi surface. We
demonstrate temperature dependent qualitative changes in the differential and
total spectrum can be utilized to probe quantum degeneracy of trapped Fermi gas
when the total number of atoms are sufficiently large . At smaller
number of atoms, incoherent scattering dominates and it displays weak
temperature dependence.Comment: updated figures and revised content, submitted to Phys.Rev.
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