6,457 research outputs found
The equation of state of neutron star matter and the symmetry energy
We present an overview of microscopical calculations of the Equation of State
(EOS) of neutron matter performed using Quantum Monte Carlo techniques. We
focus to the role of the model of the three-neutron force in the high-density
part of the EOS up to a few times the saturation density. We also discuss the
interplay between the symmetry energy and the neutron star mass-radius
relation.
The combination of theoretical models of the EOS with recent neutron stars
observations permits us to constrain the value of the symmetry energy and its
slope. We show that astrophysical observations are starting to provide
important insights into the properties of neutron star matter.Comment: 7 pages, 3 figure, talk given at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
Plastron properties of a superhydrophobic surface
Most insects and spiders drown when submerged during flooding or tidal inundation, but some are able to survive and others can remain submerged indefinitely without harm. Many achieve this by natural adaptations to their surface morphology to trap films of air, creating plastrons which fix the water-vapor interface and provide an incompressible oxygen-carbon dioxide exchange surface. Here the authors demonstrate how the surface of an extremely water-repellent foam mimics this mechanism of underwater respiration and allows direct extraction of oxygen from aerated water. The biomimetic principle demonstrated can be applied to a wide variety of man-made superhydrophobic materials
Scattering induced dynamical entanglement and the quantum-classical correspondence
The generation of entanglement produced by a local potential interaction in a
bipartite system is investigated. The degree of entanglement is contrasted with
the underlying classical dynamics for a Rydberg molecule (a charged particle
colliding on a kicked top). Entanglement is seen to depend on the structure of
classical phase-space rather than on the global dynamical regime. As a
consequence regular classical dynamics can in certain circumstances be
associated with higher entanglement generation than chaotic dynamics. In
addition quantum effects also come into play: for example partial revivals,
which are expected to persist in the semiclassical limit, affect the long time
behaviour of the reduced linear entropy. These results suggest that
entanglement may not be a pertinent universal signature of chaos.Comment: Published versio
The role of electromagnetic trapped modes in extraordinary transmission in nanostructured materials
We assert that the physics underlying the extraordinary light transmission
(reflection) in nanostructured materials can be understood from rather general
principles based on the formal scattering theory developed in quantum
mechanics. The Maxwell equations in passive (dispersive and absorptive) linear
media are written in the form of the Schr\"{o}dinger equation to which the
quantum mechanical resonant scattering theory (the Lippmann-Schwinger
formalism) is applied. It is demonstrated that the existence of long-lived
quasistationary eigenstates of the effective Hamiltonian for the Maxwell theory
naturally explains the extraordinary transmission properties observed in
various nanostructured materials. Such states correspond to quasistationary
electromagnetic modes trapped in the scattering structure. Our general approach
is also illustrated with an example of the zero-order transmission of the
TE-polarized light through a metal-dielectric grating structure. Here a direct
on-the-grid solution of the time-dependent Maxwell equations demonstrates the
significance of resonances (or trapped modes) for extraordinary light
transmissioComment: 14 pages, 6 figures; Discussion in Section 4 expanded; typos
corrected; a reference added; Figure 4 revise
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Exploring content and psychometric validity of newly developed assessment tools for itch and skin pain in atopic dermatitis.
BackgroundAtopic dermatitis (AD) is a common skin disorder characterized by chronic inflammation, altered skin barrier function, and inflammatory cell skin infiltration that decreases health-related quality of life (HRQoL). The study objective was to understand the patient perspective of AD burden and determine suitable patient-reported outcome (PRO) measures.MethodsThis mixed methods study involved the collection of qualitative and quantitative information from adults (≥ 18 years old) and adolescents (12 - 17 years old) with clinician-confirmed AD regarding their experiences of AD symptoms and its impact on HRQoL. The first part of the study included three stages: in-person concept elicitation (CE) interviews, a 2-week daily electronic diary (eDiary) study, and in-person cognitive debriefing (CD) interviews. An Itch numeric rating scale (NRS) (v1.0) and a Skin Pain NRS (v1.0) evaluation during CD interviews required participants to think about their 'worst' itch and 'worst' skin pain in the past 24 h. Other PRO measures allowed for psychometric testing. The second part of the study involved telephone-depth interviews (TDIs) and qualitative feedback from participants who had not participated in the CD interviews. Qualitative data were thematically analyzed. Psychometric evaluation of NRS measures was performed using eDiary data.ResultsIn the CE interviews, itch and/or itching and skin pain were the most prevalent symptoms consistently discussed by participants. Both NRS measures demonstrated strong psychometric reliability and were applicable across ages with suitable concurrent validity. During the CD interviews, some participants focused their answers on their 'average' itch/itching in the past 24 h, rather than their 'worst' itch. Some participants answered the Skin Pain NRS thinking about general pain or other types of pain, rather than skin pain specifically. Consequently, modifications to both measures addressed these issues and re-tested as paper-and-pen versions in subsequent TDIs. Itch NRS (v2.0) modifications helped participants focus on their worst itching. Most participants preferred Skin Pain NRS v2.0b, which included skin pain descriptors.ConclusionsItching and skin pain are the most important and relevant AD symptoms. The Itch NRS (v2.0) and Skin Pain NRS (v2.0b) appear to be appropriate endpoints for the assessment of itching and skin pain severity for clinical trials with adults and adolescents with AD
Time delay for one-dimensional quantum systems with steplike potentials
This paper concerns time-dependent scattering theory and in particular the
concept of time delay for a class of one-dimensional anisotropic quantum
systems. These systems are described by a Schr\"{o}dinger Hamiltonian with a potential converging to different limits
and as and respectively. Due to the
anisotropy they exhibit a two-channel structure. We first establish the
existence and properties of the channel wave and scattering operators by using
the modern Mourre approach. We then use scattering theory to show the identity
of two apparently different representations of time delay. The first one is
defined in terms of sojourn times while the second one is given by the
Eisenbud-Wigner operator. The identity of these representations is well known
for systems where vanishes as (). We show
that it remains true in the anisotropic case , i.e. we prove
the existence of the time-dependent representation of time delay and its
equality with the time-independent Eisenbud-Wigner representation. Finally we
use this identity to give a time-dependent interpretation of the
Eisenbud-Wigner expression which is commonly used for time delay in the
literature.Comment: 48 pages, 1 figur
Spin in relativistic quantum theory
We discuss the role of spin in Poincar\'e invariant formulations of quantum
mechanics.Comment: 54 page
Dynamics of quantum systems
A relation between the eigenvalues of an effective Hamilton operator and the
poles of the matrix is derived which holds for isolated as well as for
overlapping resonance states. The system may be a many-particle quantum system
with two-body forces between the constituents or it may be a quantum billiard
without any two-body forces. Avoided crossings of discrete states as well as of
resonance states are traced back to the existence of branch points in the
complex plane. Under certain conditions, these branch points appear as double
poles of the matrix. They influence the dynamics of open as well as of
closed quantum systems. The dynamics of the two-level system is studied in
detail analytically as well as numerically.Comment: 21 pages 7 figure
Atmospheric and oceanic dust fluxes in the northeastern tropical Atlantic Ocean: how close a coupling?
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