109 research outputs found
Two-fluid model for VLBI jets. I. Homogeneous and stationary synchrotron emission simulations
In this series of papers, we develop a two-fluid model for VLBI jets. The
idea is that the jet itself is non- or mildly-relativistic (electrons and
protons), while the radiating blobs are relativistic electron-positron `clouds'
moving on helical paths wrapped around the jet. In this work, the emphasis is
on the physical description of the clouds, and not on the structure or origin
of the trajectory. In the simple case where the magnetic field is uniform and
homogeneous accross the cloud, and the properties of the cloud are constant,
the present paper shows synthetic maps of VLBI jets in different
configurations, as well as the variation of different observational parameters
along the trajectory.Comment: to appear in A&A, 8 pages and 10 figure
Five-year follow-up of bilateral stimulation of the subthalamic nucleus in advanced Parkinson's disease
Background: Although the short-term benefits of bilateral stimulation of the subthalamic nucleus in patients with advanced Parkinson's disease have been well documented, the long-term outcomes of the procedure are unknown.
Methods: We conducted a five-year prospective study of the first 49 consecutive patients whom we treated with bilateral stimulation of the subthalamic nucleus. Patients were assessed at one, three, and five years with levodopa (on medication) and without levodopa (off medication), with use of the Unified Parkinson's Disease Rating Scale. Seven patients did not complete the study: three died, and four were lost to follow-up.
Results: As compared with base line, the patients' scores at five years for motor function while off medication improved by 54 percent (P<0.001) and those for activities of daily living improved by 49 percent (P<0.001). Speech was the only motor function for which off-medication scores did not improve. The scores for motor function on medication did not improve one year after surgery, except for the dyskinesia scores. On-medication akinesia, speech, postural stability, and freezing of gait worsened between year 1 and year 5 (P<0.001 for all comparisons). At five years, the dose of dopaminergic treatment and the duration and severity of levodopa-induced dyskinesia were reduced, as compared with base line (P<0.001 for each comparison). The average scores for cognitive performance remained unchanged, but dementia developed in three patients after three years. Mean depression scores remained unchanged. Severe adverse events included a large intracerebral hemorrhage in one patient. One patient committed suicide.
Conclusions: Patients with advanced Parkinson's disease who were treated with bilateral stimulation of the subthalamic nucleus had marked improvements over five years in motor function while off medication and in dyskinesia while on medication. There was no control group, but worsening of akinesia, speech, postural stability, freezing of gait, and cognitive function between the first and the fifth year is consistent with the natural history of Parkinson's disease
Editorial: Frontiers in astronomy and space sciences: Rising stars
Editorial on the Research Topic Frontiers in astronomy and space sciences: Rising star
Molecular interactions, characterization and photoactivity of Chlorophyll a/chitosan/2-HP-β-cyclodextrin composite films as functional and active surfaces for ROS production
Novel photosensitizing film based on the natural hybrid polymer Chitosan/2-hydroxy-propyl-β-Cyclodextrin (CH/CD) is synthesized introducing Chlorophyll a (CH/CD/Chla) as a photoactive agent for possible application in antimicrobial photodynamic therapy (PDT). The polymer absorbs visible light, in turn able to generate reactive oxygen species (ROS) and, therefore it can be used as environmental friendly and biodegradable polymeric photosensitizer (PS). The modified film is characterized by means of different spectroscopic, calorimetric, diffraction techniques and microscopic imaging methods including time-resolved absorption spectroscopy. UV–Vis, FTIR-ATR and X-ray Photoelectron Spectroscopy (XPS) analyses suggest that Chla shows a strong affinity toward Chitosan introducing interactions with amino groups present on the polymer chains. Nanosecond laser flash photolysis technique provides evidence for the population of the excited triplet state of Chla. Photogeneration of singlet oxygen is demonstrated by both direct detection by using infrared luminescence spectroscopy and chemical methods based on the use of suitable traps. Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Differential Scanning Calorimetry (DSC) analyses confirm also the occurrence of structural changes both on the film surface and within the film layer induced by the insertion of the pigment. Moreover, X-ray Diffraction data (XRD) shows the existence of an amorphous phase for the chitosan films in all the compared conditions
Kinetic Luminosity and Composition of Active Galactic Nuclei Jets
We present a new method how to discriminate the matter content of
parsec-scale jets of active galactic nuclei. By constraining the kinetic
luminosity of a jet from the observed core size at a single very long baseline
interferometry frequency, we can infer the electron density of a radio-emitting
component as a function of the composition. Comparing this density with that
obtained from the theory of synchrotron self-absorption, we can determine the
composition. We apply this procedure to the five components in the 3C~345 jet
and find that they are likely pair-plasma dominated at 11 epochs out of the
total 21 epochs, provided that the bulk Lorentz factor is less than 15
throughout the jet. We also investigate the composition of the 3C~279 jet and
demonstrate that its two components are likely pair-plasma dominated at three
epochs out of four epochs, provided that their Doppler factors are less than
10, which are consistent with observations. The conclusions do not depend on
the lower cutoff energy of radiating particles.Comment: 6 figures, 2 tables; accepted to Astroph.
Properties of stellar generations in Globular Clusters and relations with global parameters
ABRIDGED) We revise the formation of Galactic GCs by adding the detailed
chemical composition of their different stellar generations (from 1200 giants
in 19 GCs) to their global parameters. We propose to identify as GCs those
showing the Na-O anticorrelation, and we classify the GCs according to
kinematics and location in the Galaxy in disk/bulge, inner, and outer halo. We
find that the LF of GCs is fairly independent of their population, suggesting
that it is imprinted by the formation mechanism, and only marginally affected
by the ensuing evolution. We show that a large fraction of the primordial
population should have been lost by the proto-GCs. The extremely low Al
abundances found for the primordial population of massive GCs indicate a very
fast enrichment process before the formation of the primordial population. We
suggest a scenario for the formation of GCs including at least 3 main phases:
i) the formation of a precursor population (likely due to the interaction of
cosmological structures similar to those leading to dwarf spheroidals, but
residing at smaller Rgc, with the early Galaxy or with other structures), ii)
which triggers a large episode of star formation (the primordial population),
and iii) the formation of the current GC, mainly within a cooling flow formed
by the slow winds of a fraction of the primordial population. The precursor
population is very effective in raising the metal content in massive and/or
metal poor (mainly halo) clusters, while its role is minor in small and/or
metal rich (mainly disk) ones. Finally, we use PCA and multivariate relations
to study the phase of metal-enrichment from 1st to 2nd generation. Most of the
chemical signatures of GCs may be ascribed to a few parameters, the most
important being [Fe/H], mass, and age of the cluster, with the location within
the Galaxy also playing some role.Comment: 24 pages (+2 pages of bibliography and 5 of Appendix), 19 figures,
accepted for publication on Astronomy and Astrophysic
Long-term effects of STN DBS on mood: psychosocial profiles remain stable in a 3-year follow-up
<p>Abstract</p> <p>Background</p> <p>Deep brain stimulation of the subthalamic nucleus significantly improves motor function in patients with severe Parkinson's disease. However, the effects on nonmotor aspects remain uncertain. The present study investigated the effects of subthalamic nucleus deep brain stimulation on mood and psychosocial functions in 33 patients with advanced Parkinson's disease in a three year follow-up.</p> <p>Methods</p> <p>Self-rating questionnaires were administered to 33 patients prior to surgery as well as three, six, twelve and 36 months after surgery.</p> <p>Results</p> <p>In the long run, motor function significantly improved after surgery. Mood and psychosocial functions transiently improved at one year but returned to baseline at 36 months after surgery. In addition, we performed cluster and discriminant function analyses and revealed four distinct psychosocial profiles, which remained relatively stable in the course of time. Two profiles featured impaired psychosocial functioning while the other two of them were characterized by greater psychosocial stability.</p> <p>Conclusion</p> <p>Compared to baseline no worsening in mood and psychosocial functions was found three years after electrode implantation. Moreover, patients can be assigned to four distinct psychosocial profiles that are relatively stable in the time course. Since these subtypes already exist preoperatively the extent of psychosocial support can be anticipatory adjusted to the patients' needs in order to enhance coping strategies and compliance. This would allow early detection and even prevention of potential psychiatric adverse events after surgery. Given adequate psychosocial support, these findings imply that patients with mild psychiatric disturbances should not be excluded from surgery.</p
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