2,099 research outputs found
Action Principle for the Classical Dual Electrodynamics
The purpose of this paper is to formulate an action principle which allows
for the construction of a classical lagrangean including both electric and
magnetic currents. The lagrangean is non-local and shown to yield all the
expected (local) equations for dual electrodynamics.Comment: latex, 8 pages, no figure
Interface optical phonons in spheroidal dots: Raman selection rules
The contribution of interface phonons to the first order Raman scattering in
nanocrystals with non spherical geometry is analyzed. Interface optical phonons
in the spheroidal geometry are discussed and the corresponding Frohlich-like
electron-phonon interaction is reported in the framework of the dielectric
continuum approach. It is shown that the interface phonon modes are strongly
dependent on the nanocrystal geometry, particularly on the ellipsoid's
semi-axis ratio. The new Raman selection rules have revealed that solely
interface phonon modes with even angular momentum are allowed to contribute to
the first order phonon-assisted scattering of light. On this basis we are able
to give an explanation for the observed low frequency shoulders present in the
Raman cross-section of several II-VI semiconductor nanostructures.Comment: 8 pages, 2 figure
Multimodal Highlighting of Structural Abnormalities in Diabetic Rat and Human Corneas.
PURPOSE: This study aimed to highlight structural corneal changes in a model of type 2 diabetes, using in vivo corneal confocal microscopy (CCM). The abnormalities were also characterized by transmission electron microscopy (TEM) and second harmonic generation (SHG) microscopy in rat and human corneas.
METHODS: Goto-Kakizaki (GK) rats were observed at age 12 weeks (n = 3) and 1 year (n = 6), and compared to age-matched controls. After in vivo CCM examination, TEM and SHG microscopy were used to characterize the ultrastructure and the three-dimensional organization of the abnormalities. Human corneas from diabetic (n = 3) and nondiabetic (n = 3) patients were also included in the study.
RESULTS: In the basal epithelium of GK rats, CCM revealed focal hyper-reflective areas, and histology showed proliferative cells with irregular basement membrane. In the anterior stroma, extracellular matrix modifications were detected by CCM and confirmed in histology. In the Descemet's membrane periphery of all the diabetic corneas, hyper-reflective deposits were highlighted using CCM and characterized as long-spacing collagen fibrils by TEM. SHG microscopy revealed these deposits with high contrast, allowing specific detection in diabetic human and rat corneas without preparation and characterization of their three-dimensional organization.
CONCLUSION: Pathologic findings were observed early in the development of diabetes in GK rats. Similar abnormalities have been found in corneas from diabetic patients.
TRANSLATIONAL RELEVANCE: This multidisciplinary study highlights diabetes-induced corneal abnormalities in an animal model, but also in diabetic donors. This could constitute a potential early marker for diagnosis of hyperglycemia-induced tissue changes
Anti-vascular endothelial growth factor acts on retinal microglia/macrophage activation in a rat model of ocular inflammation.
PURPOSE: To evaluate whether anti-vascular endothelial growth factor (VEGF) neutralizing antibodies injected in the vitreous of rat eyes influence retinal microglia and macrophage activation. To dissociate the effect of anti-VEGF on microglia and macrophages subsequent to its antiangiogenic effect, we chose a model of acute intraocular inflammation.
METHODS: Lewis rats were challenged with systemic lipopolysaccharide (LPS) injection and concomitantly received 5 µl of rat anti-VEGF-neutralizing antibody (1.5 mg/ml) in the vitreous. Rat immunoglobulin G (IgG) isotype was used as the control. The effect of anti-VEGF was evaluated at 24 and 48 h clinically (uveitis scores), biologically (cytokine multiplex analysis in ocular media), and histologically (inflammatory cell counts on eye sections). Microglia and macrophages were immunodetected with ionized calcium-binding adaptor molecule 1 (IBA1) staining and counted based on their differential shapes (round amoeboid or ramified dendritiform) on sections and flatmounted retinas using confocal imaging and automatic quantification. Activation of microglia was also evaluated with inducible nitric oxide synthase (iNOS) and IBA1 coimmunostaining. Coimmunolocalization of VEGF receptor 1 and 2 (VEGF-R1 and R2) with IBA1 was performed on eye sections with or without anti-VEGF treatment.
RESULTS: Neutralizing rat anti-VEGF antibodies significantly decreased ocular VEGF levels but did not decrease the endotoxin-induced uveitis (EIU) clinical score or the number of infiltrating cells and cytokines in ocular media (interleukin [IL]-1β, IL-6, tumor necrosis factor [TNF]-α, and monocyte chemoattractant protein [MCP]-1). Eyes treated with anti-VEGF showed a significantly decreased number of activated microglia and macrophages in the retina and the choroid and decreased iNOS-positive microglia. IBA1-positive cells expressed VEGF-R1 and R2 in the inflamed retina.
CONCLUSIONS: Microglia and macrophages expressed VEGF receptors, and intravitreous anti-VEGF influenced the microglia and macrophage activation state. Taking into account that anti-VEGF drugs are repeatedly injected in the vitreous of patients with retinal diseases, part of their effects could result from unsuspected modulation of the microglia activation state. This should be further studied in other ocular pathogenic conditions and human pathology
On The Low Frequency Quasi Periodic Oscillations of X-ray Sources
Based on the interpretation of the twin kilohertz Quasi Periodic Oscillations
(kHz QPOs) of X-ray spectra of Low Mass X-Ray Binaries
(LMXBs) to the Keplerian and the periastron precession frequencies at the
magnetosphere-disk of X-ray neutron star (NS) respectively, we ascribe the low
frequency Quasi Periodic Oscillations (LFQPO) and HBO (15-60 Hz QPO for Z
sources or Atoll sources) to the periastron precession at some outer disk
radius.
The obtained conclusions include: all QPO frequencies increase with
increasing the accretion rate. The obtained theoretical relations between HBO
(LFQPO) frequency and the kHz QPO frequency are similar to the measured
empirical formula. Further, the possible dynamical mechanism for QPO production
is discussed.Comment: 6 pages, 2 figures, accepted by APSS, 200
Electronic Raman scattering and photoluminescence from LaSrMnO exhibiting giant magnetoresistance
Raman and Photoluminescence (PL) experiments on correlated metallic
LaSrMnO have been carried out using different excitation
wavelengths as a function of temperature from 15 K to 300 K. Our data suggest a
Raman mode centered at 1800 cm and a PL band at 2.2 eV. The intensities
of the two peaks decrease with increasing temperature. The Raman mode can be
attributed to a plasmon excitation whose frequency and linewidths are
consistent with the measured resistivities. The PL involves intersite
electronic transitions of the manganese ions.Comment: 10 pages + 4 eps figures, Revtex 3.0, figures available on reques
Shadowing Effects on Vector Boson Production
We explore how nuclear modifications to the nucleon structure functions,
shadowing, affect massive gauge boson production in heavy ion collisions at
different impact parameters. We calculate the dependence of , and
production on rapidity and impact parameter to next-to-leading order in
Pb+Pb collisions at 5.5 TeV/nucleon to study quark shadowing at high . We
also compare our Pb+Pb results to the rapidity distributions at 14 TeV.Comment: 25 pages ReVTeX, 12 .eps figures, NLO included, version accepted for
publication in Physical Review
Non-Fermi liquid behavior and scaling of low frequency suppression in optical conductivity spectra of CaRuO
Optical conductivity spectra of paramagnetic CaRuO are
investigated at various temperatures. At T=10 K, it shows a non-Fermi liquid
behavior of , similar to the case
of a ferromagnet SrRuO. As the temperature () is increased, on the other
hand, in the low frequency region is progressively
suppressed, deviating from the 1/{\omega}^{\frac 12%}-dependence.
Interestingly, the suppression of is found to scale with
at all temperatures. The origin of the scaling
behavior coupled with the non-Fermi liquid behavior is discussed.Comment: 4 pages, 3 figure
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