1,326 research outputs found
The influence of gas expulsion and initial mass-segregation on the stellar mass-function of globular star clusters
Recently de Marchi, Paresce & Pulone (2007) studied a sample of twenty
globular clusters and found that all clusters with high concentrations have
steep stellar mass-functions while clusters with low concentration have
comparatively shallow mass-functions. No globular clusters were found with a
flat mass-function and high concentration. This seems curious since more
concentrated star clusters are believed to be dynamically more evolved and
should have lost more low-mass stars via evaporation, which would result in a
shallower mass-function in the low-mass part.
We show that this effect can be explained by residual-gas expulsion from
initially mass-segregated star clusters, and is enhanced further through
unresolved binaries. If gas expulsion is the correct mechanism to produce the
observed trend, then observation of these parameters would allow to constrain
cluster starting conditions such as star formation efficiency and the
time-scale of gas expulsion.Comment: accepted for publication in MNRAS, 10 pages, 6 figure
Pulsed Plasma Lubrication Device and Method
Disclosed herein is a lubrication device comprising a solid lubricant disposed between and in contact with a first electrode and a second electrode dimensioned and arranged such that application of an electric potential between the first electrode and the second electrode sufficient to produce an electric arc between the first electrode and the second electrode to produce a plasma in an ambient atmosphere at an ambient pressure which vaporizes at least a portion of the solid lubricant to produce a vapor stream comprising the solid lubricant. Methods to lubricate a surface utilizing the lubrication device in-situ are also disclosed
Histamine plasma levels and elimination diet in chronic idiopathic urticaria
Abstract: Objective: The aim of this study was to evaluate the effects of an oligoantigenic and histamine-free diet on patients affected with chronic idiopathic urticaria (CIU).
Design: Ten patients with chronic idiopathic urticaria were prescribed an oligoantigenic and histamine-free diet for 21 days, followed by serial and controlled reintroduction of foods during a further 70 days. Modification in clinical illness as well as histamine plasma levels, post-heparin plasma diamine oxidase (DAO) and intestinal permeability were evaluated.
Results: The oligoantigenic and histamine-free diet induced a significant improvement of symptoms (P < 0.05). Moreover, CIU patients on free diet showed higher histamine plasma levels (P < 0.05 vs post-diet and vs controls) that fell to control levels during the oligoantigenic and histamine-free diet. Post-heparin plasma diamine oxidase values were slightly reduced and were unchanged during the diet as well as intestinal permeability, which was always normal in all patients.
Conclusions: These data suggest that histamine plays a major role in chronic idiopathic urticaria. The finding of normal intestinal permeability suggests that a morphological damage of intestinal mucosa should be excluded in these patients. However, the presence of low levels of post-heparin plasma diamine oxidase may indicate a subclinical impairment of small bowel enterocyte function that could induce a higher sensitivity to histamine-rich or histamine-producing food
Estimate of average freeze-out volume in multifragmentation events
An estimate of the average freeze-out volume for multifragmentation events is
presented. Values of volumes are obtained by means of a simulation using the
experimental charged product partitions measured by the 4pi multidetector INDRA
for 129Xe central collisions on Sn at 32 AMeV incident energy. The input
parameters of the simulation are tuned by means of the comparison between the
experimental and simulated velocity (or energy) spectra of particles and
fragments.Comment: To be published in Phys. Lett. B 12 pages, 5 figure
Yield scaling, size hierarchy and fluctuations of observables in fragmentation of excited heavy nuclei
Multifragmentation properties measured with INDRA are studied for single
sources produced in Xe+Sn reactions in the incident energy range 32-50 A MeV
and quasiprojectiles from Au+Au collisions at 80 A MeV. A comparison for both
types of sources is presented concerning Fisher scaling, Zipf law, fragment
size and fluctuation observables. A Fisher scaling is observed for all the
data. The pseudo-critical energies extracted from the Fisher scaling are
consistent between Xe+Sn central collisions and Au quasi-projectiles. In the
latter case it also corresponds to the energy region at which fluctuations are
maximal. The critical energies deduced from the Zipf analysis are higher than
those from the Fisher analysis.Comment: 30 pages, accepted for publication in Nuclear Physics A, references
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Bimodality: a possible experimental signature of the liquid-gas phase transition of nuclear matter
We have observed a bimodal behaviour of the distribution of the asymmetry
between the charges of the two heaviest products resulting from the decay of
the quasi-projectile released in binary Xe+Sn and Au+Au collisions from 60 to
100 MeV/u. Event sorting has been achieved through the transverse energy of
light charged particles emitted on the quasi-target side, thus avoiding
artificial correlations between the bimodality signal and the sorting variable.
Bimodality is observed for intermediate impact parameters for which the
quasi-projectile is identified. A simulation shows that the deexcitation step
rather than the geometry of the collision appears responsible for the bimodal
behaviour. The influence of mid-rapidity emission has been verified. The two
bumps of the bimodal distribution correspond to different excitation energies
and similar temperatures. It is also shown that it is possible to correlate the
bimodality signal with a change in the distribution of the heaviest fragment
charge and a peak in potential energy fluctuations. All together, this set of
data is coherent with what would be expected in a finite system if the
corresponding system in the thermodynamic limit exhibits a first order phase
transition.Comment: 30 pages, 31 figure
Liquid-gas phase transition in hot nuclei studied with INDRA
Thanks to the high detection quality of the INDRA array, signatures related
to the dynamics (spinodal decomposition) and thermodynamics (negative
microcanonical heat capacity) of a liquid-gas phase transition have been
simultaneously studied in multifragmentation events in the Fermi energy domain.
The correlation between both types of signals strongly supports the existence
of a first order phase transition for hot nuclei.Comment: 9 pages, 2 figures, Invited talk to Nucleus-nucleus 2003 Moscow June
200
Fragment properties of fragmenting heavy nuclei produced in central and semi-peripheral collisions
Fragment properties of hot fragmenting sources of similar sizes produced in
central and semi-peripheral collisions are compared in the excitation energy
range 5-10 AMeV. For semi-peripheral collisions a method for selecting compact
quasi-projectiles sources in velocity space similar to those of fused systems
(central collisions) is proposed. The two major results are related to
collective energy. The weak radial collective energy observed for
quasi-projectile sources is shown to originate from thermal pressure only. The
larger fragment multiplicity observed for fused systems and their more
symmetric fragmentation are related to the extra radial collective energy due
to expansion following a compression phase during central collisions. A first
attempt to locate where the different sources break in the phase diagram is
proposed.Comment: 23 pages submitted to NP
Antimicrobial and Antibiofilm Activities of Carvacrol, Amoxicillin and Salicylhydroxamic Acid Alone and in Combination vs. Helicobacter pylori: Towards a New Multi-Targeted Therapy
The World Health Organization has indicated Helicobacter pylori as a high-priority pathogen whose infections urgently require an update of the antibacterial treatments pipeline. Recently, bacterial ureases and carbonic anhydrases (CAs) were found to represent valuable pharmacological targets to inhibit bacterial growth. Hence, we explored the underexploited possibility of developing a multiple-targeted anti-H. pylori therapy by assessing the antimicrobial and antibiofilm activities of a CA inhibitor, carvacrol (CAR), amoxicillin (AMX) and a urease inhibitor (SHA), alone and in combination. Minimal Inhibitory (MIC) and Minimal Bactericidal (MBC) Concentrations of their different combinations were evaluated by checkerboard assay and three different methods were employed to assess their capability to eradicate H. pylori biofilm. Through Transmission Electron Microscopy (TEM) analysis, the mechanism of action of the three compounds alone and together was determined. Interestingly, most combinations were found to strongly inhibit H. pylori growth, resulting in an additive FIC index for both CAR-AMX and CAR-SHA associations, while an indifferent value was recorded for the AMX-SHA association. Greater antimicrobial and antibiofilm efficacy of the combinations CAR-AMX, SHA-AMX and CAR-SHA against H. pylori were found with respect to the same compounds used alone, thereby representing an innovative and promising strategy to counteract H. pylori infections
A rare case of cerebral venous thrombosis and disseminated intravascular coagulation temporally associated to the covid-19 vaccine administration
Globally, at the time of writing (20 March 2021), 121.759.109 confirmed COVID-19 cases have been reported to the WHO, including 2.690.731 deaths. Globally, on 18 March 2021, a total of 364.184.603 vaccine doses have been administered. In Italy, 3.306.711 confirmed COVID-19 cases with 103.855 deaths have been reported to WHO. In Italy, on 9 March 2021, a total of 6.634.450 vaccine doses have been administered. On 15 March 2021, Italian Medicines Agency (AIFA) decided to temporarily suspend the use of the AstraZeneca COVID-19 vaccine throughout the country as a precaution, pending the rulings of the European Medicines Agency (EMA). This decision was taken in line with similar measures adopted by other European countries due to the death of vaccinated people. On 18 March 2021, EMAâs safety committee concluded its preliminary review about thromboembolic events in people vaccinated with COVID-19 Vaccine AstraZeneca at its extraordinary meeting, confirming the benefits of the vaccine continue to outweigh the risk of side effects, however, the vaccine may be associated with very rare cases of blood clots associated with thrombocytopenia, i.e., low levels of blood platelets with or without bleeding, including rare cases of cerebral venous thrombosis (CVT). We report the case of a 54-year-old woman who developed disseminated intravascular coagulation (DIC) with multi-district thrombosis 12 days after the AstraZeneca COVID-19 vaccine administration. A brain computed tomography (CT) scan showed multiple subacute intra-axial hemorrhages in atypical locations, including the right frontal and the temporal lobes. A plain old balloon angioplasty (POBA) of the right coronary artery was performed, without stent implantation, with restoration of distal flow, but with persistence of extensive thrombosis of the vessel. A successive thorax angio-CT added the findings of multiple contrast filling defects with multi-vessel involvement: at the level of the left upper lobe segmental branches, of left interlobar artery, of the right middle lobe segmental branches and of the right interlobar artery. A brain magnetic resonance imaging (MRI) in the same day showed the presence of an acute basilar thrombosis associated with the superior sagittal sinus thrombosis. An abdomen angio-CT showed filling defects at the level of left portal branch and at the level of right suprahepatic vein. Bilaterally, it was adrenal hemorrhage and blood in the pelvis. An evaluation of coagulation factors did not show genetic alterations so as the nasopharyngeal swab ruled out a COVID-19 infection. The patient died after 5 days of hospitalization in intensive care
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