3,515 research outputs found
Renormalization of a gapless Hartree-Fock approximation to a theory with spontaneously broken O(N)-symmetry
The renormalization of a gapless Phi-derivable Hartree--Fock approximation to
the O(N)-symmetric lambda*phi^4 theory is considered in the spontaneously
broken phase. This kind of approach was proposed by three of us in a previous
paper in order to preserve all the desirable features of Phi-derivable
Dyson-Schwinger resummation schemes (i.e., validity of conservation laws and
thermodynamic consistency) while simultaneously restoring the Nambu--Goldstone
theorem in the broken phase. It is shown that unlike for the conventional
Hartree--Fock approximation this approach allows for a scale-independent
renormalization in the vacuum. However, the scale dependence still persists at
finite temperatures. Various branches of the solution are studied. The
occurrence of a limiting temperature inherent in the renormalized Hartree--Fock
approximation at fixed renormalization scale mu is discussed.Comment: 11 pages, 14 figures / Version accepted by Phys. Rev. D: title and
one reference change
An Overview of Individualized Management of Neuropsychiatric Symptoms in Dementia
Background: It is estimated that about 11% of adults 65 and older have dementia in the United States. Neuropsychiatric symptoms are common in the presentation of dementia. These symptoms often result in increased morbidity and mortality, negative patient outcomes, caregiver burden, institutionalized care, and diminished quality of life. The focus of this paper is to analyze the therapeutic effectiveness of nonpharmacologic interventions in the management of neuropsychiatric symptoms of dementia.
Methods: A literature review was conducted to critique current evidence on the use of nonpharmacologic interventions in managing neuropsychiatric symptoms in older adults with dementia. Searches were performed using PubMed, UpToDate, and Google Scholar.
Results: Pharmacotherapy should be cautiously considered in treating neuropsychiatric symptoms of dementia due to adverse effects and black box warnings. Although further studies are needed, music therapy, tailored bathing routines, bright light therapy, multisensory stimulation, and eliminating the use of elderspeak language are nonpharmacologic interventions that contain some evidence in improving quality of life in dementia. The validation technique is still an ethically controversial approach to communication. As a result of the COVID-19 pandemic, social isolation has worsened in people with dementia.
Conclusion: Dementia is a disease that requires multifactorial care in approaching management. Nonpharmacologic interventions are the first-line plan of treatment in managing neuropsychiatric symptoms of dementia and present with fewer side effects and are person-centered in implementing. Future research in developing measures for quality of life is needed to study effectiveness of nonpharmacologic therapy
Soft Modes, Resonances and Quantum Transport
Effects of the propagation of particles, which have a finite life-time and an
according width in their mass spectrum, are discussed in the context of
transport description. First, the importance of coherence effects
(Landau-Pomeranchuk-Migdal effect) on production and absorption of field quanta
in non-equilibrium dense matter is considered. It is shown that classical
diffusion and Langevin results correspond to re-summation of certain
field-theory diagrams formulated in terms of full non-equilibrium Green's
functions. Then the general properties of broad resonances in dense and hot
systems are discussed in the framework of a self-consistent and conserving
Phi-derivable method of Baym at the examples of the rho-meson in hadronic
matter and the pion in dilute nuclear matter. Further we address the problem of
a transport description that properly accounts for the damping width of the
particles. The Phi-derivable method generalized to the real-time contour
provides a self-consistent and conserving kinetic scheme. We derive a
generalized expression for the non-equilibrium kinetic entropy flow, which
includes corrections from fluctuations and mass-width effects. In special cases
an H-theorem is proved. Memory effects in collision terms give contributions to
the kinetic entropy flow that in the Fermi-liquid case recover the famous
bosonic type T^3 ln T correction to the specific heat of liquid Helium-3. At
the example of the pion-condensate phase transition in dense nuclear matter we
demonstrate important part played by the width effects within the quantum
transport.Comment: submitted to Phys. At. Nucl. (Rus.), the volume dedicated to the
memory of A.B. Migdal. 31 pages, 5 figure
Soft Modes, Quantum Transport and Kinetic Entropy
The effects of the propagation of particles which have a finite life-time and
an according width in their mass spectrum are discussed in the context of
transport descriptions. In the first part the coupling of soft photon modes to
a source of charged particles is studied in a classical model which can be
solved completely in analytical terms. The solution corresponds to a
re-summation of certain field theory diagrams. The general properties of broad
resonances in dense finite temperature systems are discussed at the example of
the -meson in hadronic matter. The second part addresses the problem of
transport descriptions which also account for the damping width of the
particles. The Kadanoff--Baym equation after gradient approximation together
with the -derivable method of Baym provides a self-consistent and
conserving scheme. Memory effects appearing in collision term diagrams of
higher order are discussed. We derive a generalized expression for the
nonequilibrium kinetic entropy flow, which includes corrections from
fluctuations and mass-width effects. In special cases an -theorem is proved.
Memory effects in collision terms provide contributions to the kinetic entropy
flow that in the Fermi-liquid case recover the famous bosonic type
correction to the specific heat of liquid Helium-3.Comment: Contribution to Proc. of Int. Workshop "Kadanoff-Baym Equations -
Progress and Perspectives for Many-Body Physics" Rostock (Germany), September
20-24 1999, ed. M.Bonitz, World Scientific (2000
Submicrometric Films of Surface-Attached Polymer Network with Temperature-Responsive Properties
Temperature-responsive properties of surface-attached
poly(N-isopropylacrylamide) (PNIPAM) network films with well-controlled
chemistry are investigated. The synthesis consists of cross-linking and
grafting preformed ene-reactive polymer chains through thiol--ene click
chemistry. The formation of surface-attached and cross-linked polymer films has
the advantage of being wellcontrolled without any caution of no-oxygen
atmosphere or addition of initiators. PNIPAM hydrogel films with same
cross-link density are synthesized on a wide range of thickness, from
nanometers to micrometers. The swelling-collapse transition with temperature is
studied by using ellipsometry, neutron reflectivity, and atomic force
microscopy as complementary surface-probing techniques. Sharp and high
amplitude temperature-induced phase transition is observed for all
submicrometric PNIPAM hydrogel films. For temperature above LCST,
surface-attached PNIPAM hydrogels collapse similarly but without complete
expulsion of water. For temperature below LCST, the swelling of PNIPAM
hydrogels depends on the film thickness. It is shown that the swelling is
strongly affected by the surface attachment for ultrathin films below 150
nm. For thicker films above 150 nm (to micrometers), surface-attached polymer
networks with the same cross-link density swell equally. The density profile of
the hydrogel films in the direction normal to the substrate is confronted with
in-plane topography of the free surface. It results that the free interface
width is much larger than the roughness of the hydrogel film, suggesting
pendant chains at the free surface.Comment: in Langmuir, American Chemical Society, 2015, LANGMUIR, 31 (42),
pp.11516-1152
Manipulating plasma turbulence in cross-field plasma sources using unsteady electrostatic forcing
Unsteady electrostatic forcing is investigated as a method for manipulating turbulent plasma behaviour within Hall effect thrusters and similar cross-field plasma devices using a simplified 1D-3V azimuthal electrostatic particle-in-cell simulation. A wide range of axial electric field forcing frequencies from 1 MHz up to 10 GHz at amplitudes of 10 V/cm, 50 V/cm and 100 V/cm are applied to the plasma and the response is evaluated against a baseline case defined by community benchmark LANDMARK Test Case 1. 'Tailoring' of plasma parameters such as the electron cross-field mobility is demonstrated via manipulation of the electron drift instability using unsteady forcing. Excitation of the unstable electron cyclotron modes of the electron drift instability is shown to be able to produce a reduction of the resultant electron cross-field mobility of the plasma by up to 50% compared to the baseline value. Additionally, forcing at the electron cyclotron frequency appears to be capable of increasing cross-field mobility by up to 2000%. Implications of the results for direct drive electric propulsion systems and improved current utilisation efficiencies for Hall effect thrusters are discussed
Gapless Hartree-Fock Resummation Scheme for the O(N) Model
A modified selfconsistent Hartree-Fock approximation to the lambda*phi^4
theory with spontaneously broken O(N) symmetry is proposed. It preserves all
the desirable features, like conservation laws and thermodynamic consistency,
of the selfconsistent Dyson scheme generated from a 2PI functional, also known
as the Phi-derivable scheme, while simultaneously respecting the
Nambu-Goldstone theorem in the chiral-symmetry broken phase. Various
approximate resummation schemes are discussed.Comment: 13 pages, 10 figures / Version accepted by Phys. Rev. D: the
introduction has been expanded by a few remarks in order to further clarify
the goal of the pape
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