664 research outputs found
Active Brownian Motion Tunable by Light
Active Brownian particles are capable of taking up energy from their
environment and converting it into directed motion; examples range from
chemotactic cells and bacteria to artificial micro-swimmers. We have recently
demonstrated that Janus particles, i.e. gold-capped colloidal spheres,
suspended in a critical binary liquid mixture perform active Brownian motion
when illuminated by light. In this article, we investigate in some more details
their swimming mechanism leading to active Brownian motion. We show that the
illumination-borne heating induces a local asymmetric demixing of the binary
mixture generating a spatial chemical concentration gradient, which is
responsible for the particle's self-diffusiophoretic motion. We study this
effect as a function of the functionalization of the gold cap, the particle
size and the illumination intensity: the functionalization determines what
component of the binary mixture is preferentially adsorbed at the cap and the
swimming direction (towards or away from the cap); the particle size determines
the rotational diffusion and, therefore, the random reorientation of the
particle; and the intensity tunes the strength of the heating and, therefore,
of the motion. Finally, we harness this dependence of the swimming strength on
the illumination intensity to investigate the behaviour of a micro-swimmer in a
spatial light gradient, where its swimming properties are space-dependent
Dynamics of conversion of supercurrents into normal currents, and vice versa
The generation and destruction of the supercurrent in a superconductor (S)
between two resistive normal (N) current leads connected to a current source is
computed from the source equation for the supercurrent density. This equation
relates the gradient of the pair potential's phase to electron and hole
wavepackets that create and destroy Cooper pairs in the N/S interfaces. Total
Andreev reflection and supercurrent transmission of electrons and holes are
coupled together by the phase rigidity of the non-bosonic Cooper-pair
condensate. The calculations are illustrated by snapshots from a computer film.Comment: 8 pages, 1 figure, accepted by Phys. Rev.
Effects of an Integrative Mind-Body-Medicine Group Program on Breast Cancer Patients During Chemotherapy: An Observational Study.
Background: Breast cancer is one of the leading cancers in women in the Western world. Cancer treatment, especially chemotherapy, is often associated with physical and psychosocial side effects.
Objective: To improve the quality of life and manage side effects, a new integrative mind-body-medicine group concept for breast cancer patients receiving chemotherapy was developed and pilot tested.
Methods: Breast cancer patients participated in a 66 hours mind-body-medicine group program tailored to the needs of cancer patients during chemotherapy. The program was integrated into standard care encompassing mindfulness training, yoga, moderate exercise, nutrition, complementary self-help strategies, cognitive restructuring, and acupuncture. Quality of life (EORTC QLQ-C30), depression and anxiety (HADS), stress (PSS-10), and fatigue (BFI) were assessed before and after the program, as well as satisfaction and safety. Analyses were carried out on exploratory basis with paired samples t-tests.
Results: Fifty-seven female patients, aged 51.3±10.5 years, with breast cancer diagnoses were enrolled. After completing the program, global EORTC quality of life was improved (D=9.5; 95%-CI=[2.9|16.1]; p=.005), although the EORTC-symptom scales assessing fatigue (D=9.9; 95%-CI=[1|18.8]; p=.030), nausea (D=7.1; 95%- CI=[0.6|13.6]; p=.031), and dyspnea (D=12.5; 95%-CI=[2.9|22.1]; p=.011) were found to be increased. Stress (D=-3.5; 95%-CI=[-5|-2.1]; p=.000), anxiety (D=-3.8; 95%-CI=[-4.9|-2.7]; p=.000) and depression (D=-3.9; 95%-CI=[-4.9|-2.8]; p=.000) were also found to be significantly reduced. Regarding the severity of (D=0.2; 95%- CI=[-0.8|0.5]; p=.644) and the impairment due to fatigue (D=0.1; 95%-CI=[-0.8|0.6]; p=.696), no significant worsening was observed. Patients were satisfied with the program. No serious adverse events were reported.
Conclusion: Breast cancer patients benefit from an integrative mind-body-medicine group program during chemotherapy regarding the quality of life and psychological symptoms. Randomized controlled trials are warranted
Gaussian Wavefunctional Approach in Thermofield Dynamics
The Gaussian wavefunctional approach is developed in thermofield dynamics. We
manufacture thermal vacuum wavefunctional, its creation as well as annihilation
operators,and accordingly thermo-particle excited states. For a
(D+1)-dimensional scalar field system with an arbitrary potential whose Fourier
representation exists in a sense of tempered distributions, we calculate the
finite temperature Gaussian effective potential (FTGEP), one- and
two-thermo-particle-state energies. The zero-temperature limit of each of them
is just the corresponding result in quantum field theory, and the FTGEP can
lead to the same one of each of some concrete models as calculated by the
imaginary time Green function.Comment: the revised version of hep-th/9807025, with one equation being added,
a few sentences rewritten, and some spelling mistakes corrected. 7 page,
Revtex, no figur
Renormalization of Hamiltonian Field Theory; a non-perturbative and non-unitarity approach
Renormalization of Hamiltonian field theory is usually a rather painful
algebraic or numerical exercise. By combining a method based on the coupled
cluster method, analysed in detail by Suzuki and Okamoto, with a Wilsonian
approach to renormalization, we show that a powerful and elegant method exist
to solve such problems. The method is in principle non-perturbative, and is not
necessarily unitary.Comment: 16 pages, version shortened and improved, references added. To appear
in JHE
Optical absorption spectra of finite systems from a conserving Bethe-Salpeter equation approach
We present a method for computing optical absorption spectra by means of a
Bethe-Salpeter equation approach, which is based on a conserving linear
response calculation for electron-hole coherences in the presence of an
external electromagnetic field. This procedure allows, in principle, for the
determination of the electron-hole correlation function self-consistently with
the corresponding single-particle Green function. We analyze the general
approach for a "one-shot" calculation of the photoabsorption cross section of
finite systems, and discuss the importance of scattering and dephasing
contributions in this approach. We apply the method to the closed-shell
clusters Na_4, Na^+_9 and Na^+_(21), treating one active electron per Na atom.Comment: 9 pages, 3 figure
Ionic and electronic structure of sodium clusters up to N=59
We determined the ionic and electronic structure of sodium clusters with even
electron numbers and 2 to 59 atoms in axially averaged and three-dimensional
density functional calculations. A local, phenomenological pseudopotential that
reproduces important bulk and atomic properties and facilitates structure
calculations has been developed. Photoabsorption spectra have been calculated
for , , and to
. The consistent inclusion of ionic structure considerably
improves agreement with experiment. An icosahedral growth pattern is observed
for to . This finding is supported by
photoabsorption data.Comment: To appear in Phys. Rev. B 62. Version with figures in better quality
can be requested from the author
Structure and properties of small sodium clusters
We have investigated structure and properties of small metal clusters using
all-electron ab initio theoretical methods based on the Hartree-Fock
approximation and density functional theory, perturbation theory and compared
results of our calculations with the available experimental data and the
results of other theoretical works. We have systematically calculated the
optimized geometries of neutral and singly charged sodium clusters having up to
20 atoms, their multipole moments (dipole and quadrupole), static
polarizabilities, binding energies per atom, ionization potentials and
frequencies of normal vibration modes. Our calculations demonstrate the great
role of many-electron correlations in the formation of electronic and ionic
structure of small metal clusters and form a good basis for further detailed
study of their dynamic properties, as well as structure and properties of other
atomic cluster systems.Comment: 47 pages, 16 figure
A Self-Consistent Microscopic Theory of Surface Superconductivity
The electronic structure of the superconducting surface sheath in a type-II
superconductor in magnetic fields is calculated
self-consistently using the Bogoliubov-de Gennes equations. We find that the
pair potential exhibits pronounced Friedel oscillations near the
surface, in marked contrast with the results of Ginzburg-Landau theory. The
role of magnetic edge states is emphasized. The local density of states near
the surface shows a significant depletion near the Fermi energy due to the
development of local superconducting order. We suggest that this structure
could be unveiled by scanning-tunneling microscopy studies performed near the
edge of a superconducting sample.Comment: 12 pages, Revtex 3.0, 3 postscript figures appende
Short-range and tensor correlations in the O(e,epn) reaction
The cross sections for electron induced two-nucleon knockout reactions are
evaluated for the example of the O(e,epn)N reaction leading to
discrete states in the residual nucleus N. These calculations account
for the effects of nucleon-nucleon correlations and include the contributions
of two-body meson exchange currents as the pion seagull, pion in flight and the
isobar current contribution. The effects of short-range as well as tensor
correlations are calculated within the framework of the coupled cluster method
employing the Argonne V14 potential as a model for a realistic nucleon-nucleon
interaction. The relative importance of correlation effects as compared to the
contribution of the meson exchange currents depends on the final state of the
residual nucleus. The cross section leading to specific states, like e.g. the
ground state of N, is rather sensitive to the details of the correlated
wave function.Comment: 16 pages, 9 figures include
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