528 research outputs found
electron-positron-photon plasma around a collapsing star
We describe electron-positron pairs creation around an electrically charged
star core collapsing to an electromagnetic black hole (EMBH), as well as pairs
annihilation into photons. We use the kinetic Vlasov equation formalism for the
pairs and photons and show that a regime of plasma oscillations is established
around the core. As a byproduct of our analysis we can provide an estimate for
the thermalization time scale.Comment: 8 pages, 4 figures, to appear in the Proceedings of QABP200
Energy Extraction From Gravitational Collapse to Static Black Holes
The mass--energy formula of black holes implies that up to 50% of the energy
can be extracted from a static black hole. Such a result is reexamined using
the recently established analytic formulas for the collapse of a shell and
expression for the irreducible mass of a static black hole. It is shown that
the efficiency of energy extraction process during the formation of the black
hole is linked in an essential way to the gravitational binding energy, the
formation of the horizon and the reduction of the kinetic energy of implosion.
Here a maximum efficiency of 50% in the extraction of the mass energy is shown
to be generally attainable in the collapse of a spherically symmetric shell:
surprisingly this result holds as well in the two limiting cases of the
Schwarzschild and extreme Reissner-Nordstr\"{o}m space-times. Moreover, the
analytic expression recently found for the implosion of a spherical shell onto
an already formed black hole leads to a new exact analytic expression for the
energy extraction which results in an efficiency strictly less than 100% for
any physical implementable process. There appears to be no incompatibility
between General Relativity and Thermodynamics at this classical level.Comment: 7 pages, 2 figures, to appear on Int. Journ. Mod. Phys.
The cosmological constant and the relaxed universe
We study the role of the cosmological constant (CC) as a component of dark
energy (DE). It is argued that the cosmological term is in general unavoidable
and it should not be ignored even when dynamical DE sources are considered.
From the theoretical point of view quantum zero-point energy and phase
transitions suggest a CC of large magnitude in contrast to its tiny observed
value. Simply relieving this disaccord with a counterterm requires extreme
fine-tuning which is referred to as the old CC problem. To avoid it, we discuss
some recent approaches for neutralising a large CC dynamically without adding a
fine-tuned counterterm. This can be realised by an effective DE component which
relaxes the cosmic expansion by counteracting the effect of the large CC.
Alternatively, a CC filter is constructed by modifying gravity to make it
insensitive to vacuum energy.Comment: 6 pages, no figures, based on a talk presented at PASCOS 201
Plasma expansion in the geometry of a collapsing star
We describe the evolution of an electron-positron-photon plasma created by
Sauter--Heisenberg--Euler--Schwinger mechanism around a collapsing charged star
core in the Reissner-Nordstr\"{o}m geometry external to the core, in view of
the application in the framework of the EMBH theory for gamma ray bursts.Comment: 12 pages, 4 figures, to appear in the Proceedings of QABP200
Is the treatment of the tear trough deformity with hyaluronic acid injections a safe procedure? A systematic review
Among the various therapeutic options for the treatment of tear trough deformities, the use of hyaluronic acid-based fillers has constantly been increasing. The aim of this research is to conduct a systematic review of the published literature related to the use of hyaluronic acid-based dermal fillers for the treatment of tear trough deformities and possible related complications. A search of the published literature was conducted following the PRISMA guidelines, including PubMed, Cochrane Library, and Ovid databases. Text words and Medical Search Headings (MeSH terms) were used to identify nine articles included in our analysis. The most used filler was Restylane (Galderma). The injection technique was performed through the use of a cannula or, more frequently, with a needle, through the execution of boluses or retrograde release. The injection plane was predominantly the supra-periosteal layer. The most observed side effects were mild and included redness, edema, contour irregularities, bruising, and blue-gray dyschromia. The degree of patient satisfaction was high, with an optimal aesthetic result that was maintained for 6 to 12 months. Although the duration of treatment of tear trough deformities with HA fillers is not comparable to surgical treatment, this is a minimally invasive, safe procedure, quick to perform, and with a high degree of patient satisfaction
New perspectives in physics and astrophysics from the theoretical understanding of Gamma-Ray Bursts
If due attention is given in formulating the basic equations for the
Gamma-Ray Burst (GRB) phenomenon and in performing the corresponding
quantitative analysis, GRBs open a main avenue of inquiring on totally new
physical and astrophysical regimes. This program is one of the greatest
computational efforts in physics and astrophysics and cannot be actuated using
shortcuts. A systematic approach has been highlighted in three paradigms: the
relative space-time transformation (RSTT) paradigm, the interpretation of the
burst structure (IBS) paradigm, the GRB-supernova time sequence (GSTS)
paradigm. In fundamental physics new regimes are explored: (1) the process of
energy extraction from black holes; (2) the quantum and general relativistic
effects of matter-antimatter creation near the black hole horizon; (3) the
physics of ultrarelativisitc shock waves with Lorentz gamma factor . In astronomy and astrophysics also new regimes are explored: (i) the
occurrence of gravitational collapse to a black hole from a critical mass core
of mass M\agt 10M_\odot, which clearly differs from the values of the
critical mass encountered in the study of stars ``catalyzed at the endpoint of
thermonuclear evolution" (white dwarfs and neutron stars); (ii) the extremely
high efficiency of the spherical collapse to a black hole, where almost 99.99%
of the core mass collapses leaving negligible remnant; (iii) the necessity of
developing a fine tuning in the final phases of thermonuclear evolution of the
stars, both for the star collapsing to the black hole and the surrounding ones,
in order to explain the possible occurrence of the "induced gravitational
collapse". A new class of space missions to acquire information on such extreme
new regimes are urgently needed.Comment: RevTeX4, 93 pages, 50 figures, to appear in the "Proceedings of the
Xth Brazilian School of Cosmology and Gravitation", M. Novello, editor, AIP,
in pres
Observational signatures of an electromagnetic overcritical gravitational collapse
We present theoretical predictions for the spectral, temporal and intensity
signatures of the electromagnetic radiation emitted during the process of the
gravitational collapse of a stellar core to a black hole, during which
electromagnetic field strengths rise over the critical value for pair
creation. The last phases of this gravitational collapse are studied, leading
to the formation of a black hole with a subcritical electromagnetic field,
likely with zero charge, and an outgoing pulse of initially optically thick
-photon plasma. Such a pulse reaches transparency at Lorentz gamma
factors of --. We find a clear signature in the outgoing
electromagnetic signal, drifting from a soft to a hard spectrum, on very
precise time-scales and with a very specific intensity modulation. The
relevance of these theoretical results for the understanding of short gamma-ray
bursts is outlined.Comment: 11 pages, 3 figures, to appear on Int.J.Mod.Phys.
Botulinum toxin type a reconstituted with lidocaine: A report of 1000 consecutive cases
(1) Background: There is an increasing demand for a reversal of the aging process and, nowadays, more patients are seeking minimally invasive methods instead of surgery to meet this goal. The purpose of this paper is to evaluate the predictability of the off-label aesthetic use of botulinum toxin type A (BoNTA) reconstituted with lidocaine. (2) Methods: One thousand treatments, between January 2010 and January 2020, with BoNTA reconstituted with lidocaine for the rejuvenation of the upper third of the face, were performed and retrospectively evaluated. (3) Results: A few seconds after the BoNTA injections, the effect of muscle paralysis was seen in all cases; this allowed providing an optimal symmetric result with no need for a touch-up procedure at the control after three weeks. A burning sensation during the injections was claimed by almost all patients. Major complications were not registered. No touch-up procedures were required. (4) Conclusions: The results of this study show how the reconstitution of BoNTA with lidocaine may avoid imperfect results after the injections; the immediate feedback on the extent of paralysis to be expected from the chemodenervation action of BoNTA allows the physician to have immediate control of the final result
Chronic endometritis and altered embryo implantation: a unified pathophysiological theory from a literature systematic review
Purpose: Chronic endometritis (CE) is a frequent hysteroscopic and histological finding which affects embryo transfer implantation during IVF-ICSI cycles. In particular, CE impairs proper decidualization and, subsequently, implantation. Although this correlation has been clearly clarified, a pathophysiological explanation assembling all the studies performed has not been elucidated yet. For this reason, we have structured a systematic review considering all the original articles that evaluated a pathological element involved in CE and implantation impairment. Methods: The authors searched electronic databases and, after screening, collected 15 original articles. These were fully scanned and used to create a summary pathway. Results: CE is primarily caused by infections, which lead to a specific cytokine and leukocyte pattern in order to prepare the uterus to fight the noxa. In particular, the immunosuppression requested for a proper semi-allogenic embryo transfer implantation is converted into an immunoreaction, which hampers correct embryo implantation. Moreover, endometrial vascularization is affected and both irregular vessel density and luminal thickening and thrombosis reduce what we have first identified as endometrial flow reserve. Finally, incorrect uterine wave propagation could affect embryo contact with decidua. Conclusion: This is the first summary of evidence on CE pathophysiology and its relationship with infertility. Understanding the CE pathophysiology could improve our knowledge in embryo transfer success
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