508 research outputs found
Collective excitations of a trapped degenerate Fermi gas
We evaluate the small-amplitude excitations of a spin-polarized vapour of
Fermi atoms confined inside a harmonic trap. The dispersion law
is obtained for the vapour in the
collisional regime inside a spherical trap of frequency , with
the number of radial nodes and the orbital angular momentum. The low-energy
excitations are also treated in the case of an axially symmetric harmonic
confinement. The collisionless regime is discussed with main reference to a
Landau-Boltzmann equation for the Wigner distribution function: this equation
is solved within a variational approach allowing an account for
non-linearities. A comparative discussion of the eigenmodes of oscillation for
confined Fermi and Bose vapours is presented in an Appendix.Comment: 14 pages, no figures, accepted for publication in Eur.Phys.Jour.
Kinetic energy of a trapped Fermi gas interacting with a Bose-Einstein condensate
We study a confined mixture of bosons and fermions in the regime of quantal
degeneracy, with particular attention to the effects of the interactions on the
kinetic energy of the fermionic component. We are able to explore a wide region
of system parameters by identifying two scaling variables which completely
determine its state at low temperature. These are the ratio of the
boson-fermion and boson-boson interaction strengths and the ratio of the radii
of the two clouds. We find that the effect of the interactions can be sizeable
for reasonable choices of the parameters and that its experimental study can be
used to infer the sign of the boson-fermion scattering length. The interplay
between interactions and thermal effects in the fermionic kinetic energy is
also discussed.Comment: REVTEX, 8 pages, 6 figures included. Small corrections to text and
figures, accepted for publication in EPJ
Temperature-dependent density profiles of trapped boson-fermion mixtures
We present a semiclassical three-fluid model for a Bose-condensed mixture of
interacting Bose and Fermi gases confined in harmonic traps at finite
temperature. The model is used to characterize the experimentally relevant
behaviour of the equilibrium density profile of the fermions with varying
composition and temperature across the onset of degeneracy, for coupling
strengths relevant to a mixture of
K and K atoms.Comment: 9 pages, 2 postscript figures, accepted for publication in Eur. Phys.
Jour.
effect of intrathecal baclofen botulinum toxin type a and a rehabilitation programme on locomotor function after spinal cord injury a case report
Objective: a few studies have reported the use of botulinum toxin injections after spinal cord injury, as this is the gold standard to treat focal spasticity. We report such a case here. Case report: a 38-year-old woman who had become paraplegic and care-dependent secondary to cervico-thoracic intramedullary ependymoma, presented 8 months later with painful lower limb spasticity, which was being treated with oral anti-spastic and benzodiazepine drugs with no therapeutic effect. We treated the patient with intrathecal baclofen to reduce her spasticity and in order to avoid the major side-effects of high dosages of oral baclofen. after motor rehabilitation programmes, which included functional ele
Static Properties of Trapped Bose-Fermi Mixed Condensate of Alkali Atoms
Static properties of a bose-fermi mixture of trapped potassium atoms are
studied in terms of coupled Gross-Pitaevskii and Thomas-Fermi equations for
both repulsive and attractive bose-fermi interatomic potentials. Qualitative
estimates are given for solutions of the coupled equations, and the parameter
regions are obtained analytically for the boson-density profile change and for
the boson/fermion phase separation. Especially, the parameter ratio
is found that discriminates the region of the large boson-profile change. These
estimates are applied for numerical results for the potassium atoms and checked
their consistency. It is suggested that a small fraction of fermions could be
trapped without an external potential for the system with an attractive
boson-fermion interaction.Comment: 8 pages,5 figure
Collective dynamics of fermion clouds in cigar-shaped traps
The propagation of zero sound in a spin-polarized Fermi gas under harmonic
confinement is studied as a function of the mean-field interactions with a
second Fermi gas. A local-density treatment is compared with the numerical
solution of the Vlasov-Landau equations for the propagation of density
distortions in a trapped two-component Fermi gas at temperature T=0.2 Tf. The
response of the gas to the sudden creation of a sharp hole at its centre is
also studied numerically.Comment: 15 pages, 6 figure
A Web Infrastructure for Certifying Multimedia News Content for Fake News Defense
In dealing with altered visual multimedia content, also referred to as fake
news, we present a ready-to-deploy extension of the current public key
infrastructure (PKI), to provide an endorsement and integrity check platform
for newsworthy visual multimedia content. PKI, which is primarily used for Web
domain authentication, can directly be utilized with any visual multimedia
file. Unlike many other fake news researches that focus on technical multimedia
data processing and verification, we enable various news organizations to use
our developed program to certify/endorse a multimedia news content when they
believe this news piece is truthiness and newsworthy. Our program digitally
signs the multimedia news content with the news organization's private key, and
the endorsed news content can be posted not only by the endorser, but also by
any other websites. By installing a web browser extension developed by us, an
end user can easily verify whether a multimedia news content has been endorsed
and by which organization. During verification, our browser extension will
present to the end user a floating logo next to the image or video. This logo,
in the shape of a shield, will show whether the image has been endorsed, by
which news organization, and a few more pieces of essential text information of
the news multimedia content. The proposed system can be easily integrated to
other closed-web system such as social media networks and easily applied to
other non-visual multimedia files.Comment: 7 pages, 6 figure
Subextensive singularity in the 2D Ising spin glass
The statistics of low energy states of the 2D Ising spin glass with +1 and -1
bonds are studied for square lattices with , and =
0.5, where is the fraction of negative bonds, using periodic and/or
antiperiodic boundary conditions. The behavior of the density of states near
the ground state energy is analyzed as a function of , in order to obtain
the low temperature behavior of the model. For large finite there is a
range of in which the heat capacity is proportional to .
The range of in which this behavior occurs scales slowly to as
increases. Similar results are found for = 0.25. Our results indicate that
this model probably obeys the ordinary hyperscaling relation , even though . The existence of the subextensive behavior is
attributed to long-range correlations between zero-energy domain walls, and
evidence of such correlations is presented.Comment: 13 pages, 7 figures; final version, to appear in J. Stat. Phy
Miscibility in a degenerate fermionic mixture induced by linear coupling
We consider a one-dimensional mean-field-hydrodynamic model of a
two-component degenerate Fermi gas in an external trap, each component
representing a spin state of the same atom. We demonstrate that the
interconversion between them (linear coupling), imposed by a resonant
electromagnetic wave, transforms the immiscible binary gas into a miscible
state, if the coupling constant, , exceeds a critical value, . The effect is predicted in a variational approximation, and
confirmed by numerical solutions. Unlike the recently studied model of a binary
BEC with the linear coupling, the components in the immiscible phase of the
binary fermion mixture never fill two separated domains with a wall between
them, but rather form anti-locked ( -phase-shifted) density waves.
Another difference from the bosonic mixture is spontaneous breaking of symmetry
between the two components in terms of numbers of atoms in them, and
. The latter effect is characterized by the parameter (only is a conserved quantity), the
onset of miscibility at meaning a transition
to . At , features damped
oscillations as a function of . We also briefly consider an asymmetric
model, with a chemical-potential difference between the two components.Comment: 9 pages, 12 figures, PRA (in press
Lactobacillus johnsonii LJO02 (DSM 33828) Cell-Free Supernatant and Vitamin D Improve Wound Healing and Reduce Interleukin-6 Production in Staphylococcus aureus-Infected Human Keratinocytes
Methicillin-resistant biofilm-forming Staphylococcus spp. are found in about 25% of the overall cases of chronic wounds, which can undergo malignant degeneration and be associated with skin cancer. Although antimicrobial agents are clinically used to counteract pathogens and promote wound healing, they are increasingly ineffective against multi-drug resistant bacteria. Moreover, they can induce dysbiosis, which favors opportunistic pathogen infections and alters immune responses. Consequently, research on pathogen containment strategies is crucial. We aimed to evaluate the potential beneficial effect of Lactobacillus johnsonii LJO02 cell-free supernatant (CFS) and vitamin D, as single treatments or in combination, on cell viability, wound healing, and the pro-inflammatory interleukin-6 (IL-6) production of a Staphylococcus aureus-infected human immortalized keratinocyte cell line (HaCaT) in vitro model. The analysis showed that LJO02 CFS 20% v/v ratio and 100 nM vitamin D promoted infected cell viability and wound healing and significantly reduced IL-6 production. However, their effect was not synergic, since no significant difference between the single and combined treatments was observed. LJO02 CFS topic application and vitamin D supplementation could provide a valuable strategy for attenuating S. aureus-induced pathogenesis, promoting wound healing and opening new therapeutic strategies supporting the conventional approaches
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