674 research outputs found
XMM-Newton observation of a sample of four close dSph galaxies
We present the results of the analysis of deep archival \sat\ observations
towards the dwarf spheroidal galaxies Draco, Leo I, Ursa Major II and Ursa
Minor in the Milky Way neighbourhood. The X-ray source population is
characterized and cross-correlated with available databases with the aim to
infer their nature. We also investigate if intermediate-mass black holes are
hosted in the center of these galaxies. In the case of Draco, we detect 96
high-energy sources, two of them being possibly local stars, while no evidence
for any X-ray emitting central compact object is found. Towards the Leo I and
UMa II field of view we reveal 116 and 49 X-ray sources, respectively. None of
them correlates with the putative central black holes and only one is likely
associated with a UMa II local source. The study of the UMi dwarf galaxy shows
54 high-energy sources and a possible association {with a source at the dSph
center}. We put an upper limit to the central compact object luminosity of
4.0210 erg/s. Furthermore, via the correlation with a radio
source near the galactic center, we get that the putative black hole should
have a mass of and be
radiatively inefficient. This confirms a previous result obtained by using
Chandra data alone.Comment: MNRAS, in press, tables available on lin
Totally implantable middle ear device for rehabilitation of sensorineural hearing loss: preliminary experience with the Esteem†, Envoy
Conclusion. According to the first series of implanted patients, Esteem 2†technology can be regarded as a safe and reliable system for hearing restoration in case of moderate to severe sensorineural hearing loss. Objectives. To assess the benefit deriving from implantation of a totally implantable middle ear device in subjects affected by moderate to severe sensorineural hearing loss, the Esteem 2†(Envoy Medical), as measured through pure tone audiometry testing carried out during the different postoperative fitting sessions. Patients and methods. Six patients have been operated on since July 2007. Selection was carried out via preoperative audiometric tests and thorough counseling, which considered information on previous experience with conventional hearing aids as well as each patient’s motivation to undergo a surgical application. Specific surgical training is needed to accommodate routine surgical steps along with less familiar steps, such as placement of cement material and overall fixation of the system. Results. The surgical procedure took a long time, but a reduced duration was recorded in the last procedure compared with the first one. The implantation process induced a deterioration in hearing thresholds, which fully recovered after activation of the device. A postoperative hearing gain could be measured in all three patients: in this regard, the perceived quality of sound was shown to be better than could be expected by the measurable hearing gain
Spontaneous self-ordered states of vortex-antivortex pairs in a Polariton Condensate
Polariton condensates have proved to be model systems to investigate
topological defects, as they allow for direct and non-destructive imaging of
the condensate complex order parameter. The fundamental topological excitations
of such systems are quantized vortices. In specific configurations, further
ordering can bring the formation of vortex lattices. In this work we
demonstrate the spontaneous formation of ordered vortical states, consisting in
geometrically self-arranged vortex-antivortex pairs. A mean-field generalized
Gross-Pitaevskii model reproduces and supports the physics of the observed
phenomenology
Spin-to-Orbital Angular Momentum Conversion in Semiconductor Microcavities
We experimentally demonstrate a technique for the generation of optical beams
carrying orbital angular momentum using a planar semiconductor microcavity.
Despite being isotropic systems, the transverse electric - transverse magnetic
(TE-TM) polarization splitting featured by semiconductor microcavities allows
for the conversion of the circular polarization of an incoming laser beam into
the orbital angular momentum of the transmitted light field. The process
implies the formation of topological entities, a pair of optical half-vortices,
in the intracavity field
Correlation between morphological and functional retinal impairment in multiple sclerosis patients
PURPOSE. TO assess whether a correlation exists between optic nerve fiber layer (NFL) thickness and the retinal or visual pathway function in multiple sclerosis (MS) patients previously affected by optic neuritis. METHODS. Fourteen patients with a diagnosis of definite,MS were examined. All had been affected by optic neuritis (,MSON) with complete recovery of visual acuity (14 eyes included in study). These were compared with 14 eyes from 14 age-matched control subjects. NFL thickness was measured by optical coherence tomography (OCT). Three different measurements in each quadrant (superior, inferior, nasal, and temporal) were taken and averaged. The data in all quadrants (12 values averaged) were identified as NFL Overall, whereas the data obtained ill the temporal quadrant only (3 values averaged) were identified as NFL Temporal. Retinal and visual pathway function was assessed by simultaneously recording pattern electroretinograms (PERGs) and visual evoked potentials (VEPs) using high-contrast (80%) checkerboard stimuli subtending ii minutes anti 60 minutes of the visual are (min are) and reversed at the rate of two reversals per second. RESULTS. III MSON eyes there was a significant (P 0.01) between NFL values and the other electrophysiological data (PERG recorded with 60-min are checks and VEP recorded with 15-min arc and 60-min are checks) were found. CONCLUSIONS. There is a correlation between PERG changes and NFL thickness in MS patients previously affected by optic neuritis, but there is no correlation between VEP changes and NFL thickness
Retinal functional changes measured by frequency-doubling technology in patients treated with hydroxychloroquine.
BACKGROUND:
Antimalarial drugs such as chloroquine (CQ) and hydroxychloroquine (HCQ) are mainly used in the treatment of rheumatologic diseases, and their use may be associated with irreversible retinal toxicity. Previous studies indicate early paracentral visual field loss (Humphrey 10-2) in patients taking HCQ". These paracentral defects appear before changes in other clinical parameters as visual acuity and fundoscopy. The mechanism of CQ toxicity remains unclear. It was reported that toxic doses of CQ administered for as long as 4.5 years to Rhesus monkeys caused an initial dramatic effect on ganglion cells, followed later by photoreceptors and RPE degeneration. The purpose of this study is to explore early retinal functional changes measured by frequency-doubling technology (FDT) in patients treated with hydroxychloroquine (HCQ).
METHODS:
Forty-eight eyes of 48 subjects treated with hydroxychloroquine (HCQ), with no signs of retinal toxicity, and 36 eyes of 36 age and sex-matched healthy subjects were enrolled in this cross-sectional, prospective, observational, case control study. Functional testing included frequency-doubling Humphrey-matrix perimetry (FDP), white-on-white Humphrey visual field perimetry (HFA), using the 24-2 and 10-2 threshold programs, multifocal electroretinogram (mfERG, Veris 4.9) and low contrast sensitivity (CS) measurement.
RESULTS:
FDP mean deviation (MD) was found to be significantly reduced in HCQ-treated patients compared to controls both in the 24-2 (-1.38 ± 2.41 dB vs 0.21 ± 1.83 dB, p < 0.01) and in the 10-2 program (-0.97 ± 2.88 dB vs 0.15 ± 1.72 dB, p < 0.01). FDP pattern standard deviation (PSD) was found to be significantly worse in HCQ-treated patients compared to controls both in the 24-2 (2.70 ± 0.65 dB vs 2.41 ± 0.31 dB, p < 0.01 and in the 10-2 program (2.86 ± 0.48 dB vs 2.48 ± 0.39 dB, p < 0.01). HFA PSD and CS was also significantly reduced in HCQ patients, while response amplitude densities (RAD) were similar between patients and controls. A statistically significant difference in the ratio of the 5°-10° RAD and the 0°-2.5° RAD (0.31 ± 0.08 vs 0.36 ± 0.07 respectively, p < 0.05) was found between groups.
CONCLUSION:
Frequency doubling perimetry could be useful to detect early retinal impairment in patients treated with hydroxychloroquine
Probing the Dynamics of Spontaneous Quantum Vortices in Polariton Superfluids
The experimental investigation of spontaneously created vortices is of utmost
importance for the understanding of quantum phase transitions towards a
superfluid phase, especially for two dimensional systems that are expected to
be governed by the Berezinski-Kosterlitz-Thouless physics. By means of time
resolved near-field interferometry we track the path of such vortices, created
at random locations in an exciton-polariton condensate under pulsed
non-resonant excitation, to their final pinning positions imposed by the
stationary disorder. We formulate a theoretical model that successfully
reproduces the experimental observations
Polariton Condensation in a One-Dimensional Disordered Potential
We study the coherence and density modulation of a non-equilibrium
exciton-polariton condensate in a one-dimensional valley with disorder. By
means of interferometric measurements we evidence a modulation of the
first-order coherence function and we relate it to a disorder-induced
modulation of the condensate density, that increases as the pump power is
increased. The non-monotonous spatial coherence function is found to be the
result of the strong non-equilibrium character of the one-dimensional system,
in the presence of disorder
Citicoline in ophthalmological neurodegenerative disease: A comprehensive review
Cytidine 5'-diphosphocholine has been widely studied in systemic neurodegenerative diseases, like Alzheimer's disease, Parkinson's disease, and brain ischemia. The rationale for the use of citicoline in ophthalmological neurodegenerative diseases, including glaucoma, anterior ischemic optic neuropathy, and diabetic retinopathy, is founded on its multifactorial mechanism of action and the involvement in several metabolic pathways, including phospholipid homeostasis, mitochondrial dynamics, as well as cholinergic and dopaminergic transmission, all being involved in the complexity of the visual transmission. This narrative review is aimed at reporting both pre-clinical data regarding the involvement of citicoline in such metabolic pathways (including new insights about its role in the intracellular proteostasis through an interaction with the proteasome) and its effects on clinical psychophysical, electrophysiological, and morphological outcomes following its use in ophthalmological neurodegenerative diseases (including the results of the most recent prospective randomized clinical trials)
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