13,620 research outputs found
Cooperative effect of phonons and electronic correlations for superconductivity in cobaltates
We propose that unconventional superconductivity in hydrated sodium cobaltate
results from an interplay of electronic correlations and
electron-phonon interactions. On the basis of the model plus phonons we
found evidences for a) unconventional superconductivity, b) realistic values of
and c) the dome shape existing near . This picture is
obtained for close to the critical Coulomb repulsion which separates
the uniform Fermi liquid from CDW ordered phase.Comment: 4 pages, 3 figure
Letter to the editor: autoimmune pathogenic mechanisms in amyotrophic lateral sclerosis
The innate immune system may affect the function and survival of motor neurons in ALS by at least three mechanisms. First, there is evidence to suggest that aggregates of mutant SOD1—which is derived from microglial and astroglial cells—activate neighbouring microglia by binding to TLR2, TLR4, and CD14, and subsequently promote neuronal cell death [9]. Second, the release of pro- inflammatory cytokines may drive motor neuron damage. Third, although poorly understood, a mechanism has been suggested on the basis of the functional analysis of microglial cells that express mutant SOD1 [10]. These cells showed impaired overall motility and a reduced capacity to clear neuronal cell debris. Impairment of microglial cell phagocytosis may therefore contribute to the accumulation of further immunostimulatory proteins, including mutant SOD1, chromogranin A, and dsRNA, thereby resulting in disease progression
Social geography of rhinoscleroma and qualitatively and quantitatively abnormal cell-mediated immunity
Rhinoscleroma is a progressive chronic granulomatous disease of the upper respiratory tract that may extend to the tracheobronchial tract. It is common belief that the pathology is determined by Klebsiella Rhinoscleromatis. In the authors' opinion, the infection with Klebsiella Rhinoscleromatis may not represent the only etiopathogenic factor of the disease. Rhinoscleroma is reported in many countries, but has a peculiar social and geographic distribution, in that it assumes an endemic character only in some regions of the Middle East, West Russia, North Africa, Indonesia, Central and South America. In Europe, most of the cases are reported in Poland, Hungary and Romania. In Italy, Rhinoscleroma is almost exclusively located in the southern and island regions. Rhinoscleroma is predominantly reported in rural areas, in the presence of poor socio-economic conditions, which according to many authors would be a co-factor triggering the disease. In this article, the authors review some inconsistencies in etiology, histology and epidemiology of Rhinoscleroma. Based on the overall picture, they propose that intrinsic factors, possibly of genetic origin, may give rise to the disease, and suggest possible lines of research to distinguish between extrinsic and intrinsic factors as determinants for Rhinoscleroma
Dynamical properties of a strongly correlated model for quarter-filled layered organic molecular crystals
The dynamical properties of an extended Hubbard model, which is relevant to
quarter-filled layered organic molecular crystals, are analyzed. We have
computed the dynamical charge correlation function, spectral density, and
optical conductivity using Lanczos diagonalization and large-N techniques. As
the ratio of the nearest-neighbour Coulomb repulsion, V, to the hopping
integral, t, increases there is a transition from a metallic phase to a charge
ordered phase. Dynamical properties close to the ordering transition are found
to differ from the ones expected in a conventional metal. Large-N calculations
display an enhancement of spectral weight at low frequencies as the system is
driven closer to the charge ordering transition in agreement with Lanczos
calculations. As V is increased the charge correlation function displays a
plasmon-like mode which, for wavevectors close to (pi,pi), increases in
amplitude and softens as the charge ordering transition is approached. We
propose that inelastic X-ray scattering be used to detect this mode. Large-N
calculations predict superconductivity with dxy symmetry close to the ordering
transition. We find that this is consistent with Lanczos diagonalization
calculations, on lattices of 20 sites, which find that the binding energy of
two holes becomes negative close to the charge ordering transition.Comment: 22 pages, 16 eps figures; caption of Fig. 5 correcte
Therapeutic approaches with intravitreal injections in geographic atrophy secondary to age-related macular degeneration: current drugs and potential molecules
The present review focuses on recent clinical trials that analyze the efficacy of
intravitreal therapeutic agents for the treatment of dry age-related macular degeneration (AMD),
such as neuroprotective drugs, and complement inhibitors, also called immunomodulatory or
anti-inflammatory agents. A systematic literature search was performed to identify randomized
controlled trials published prior to January 2019. Patients affected by dry AMD treated with
intravitreal therapeutic agents were included. Changes in the correct visual acuity and reduction in
geographic atrophy progression were evaluated. Several new drugs have shown promising results,
including those targeting the complement cascade and neuroprotective agents. The potential action
of the two groups of drugs is to block complement cascade upregulation of immunomodulating
agents, and to prevent the degeneration and apoptosis of ganglion cells for the neuroprotectors,
respectively. Our analysis indicates that finding treatments for dry AMD will require continued
collaboration among researchers to identify additional molecular targets and to fully interrogate the
utility of pluripotent stem cells for personalized therapy
Electroweak 2 -> 2 amplitudes for electron-positron annihilation at TeV energies
The non-radiative scattering amplitudes for electron-positron annihilation
into quark and lepton pairs in the TeV energy range are calculated in the
double-logarithmic approximation. The expressions for the amplitudes are
obtained using infrared evolution equations with different cut-offs for virtual
photons and for W and Z bosons, and compared with previous results obtained
with an universal cut-off.Comment: Revtex4, 17 pages, 7 figures. Some minor changes made, more refs
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Non-Fermi liquid behavior in nearly charge ordered layered metals
Non-Fermi liquid behavior is shown to occur in two-dimensional metals which
are close to a charge ordering transition driven by the Coulomb repulsion. A
linear temperature dependence of the scattering rate together with an increase
of the electron effective mass occur above T*, a temperature scale much smaller
than the Fermi temperature. It is shown that the anomalous temperature
dependence of the optical conductivity of the quasi-two-dimensional organic
metal alpha-(BEDT-TTF)2MHg(SCN)4, with M=NH4 and Rb, above T*=50-100 K, agrees
qualitatively with our predictions for the electronic properties of nearly
charge ordered two-dimensional metals.Comment: accepted in Phys. Rev. Let
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