1,719 research outputs found
Influence of vector interactions on the hadron-quark/gluon phase transition
The hadron-quark/gluon phase transition is studied in the two-phase model. As
a further study of our previous work, both the isoscalar and isovector vector
interactions are included in the Polyakov loop modified Nambu--Jona-Lasinio
model (PNJL) for the quark phase. The relevance of the exchange (Fock) terms is
stressed and suitably accounted for. The calculation shows that the isovector
vector interaction delays the phase transition to higher densities and the
range of the mixed phase correspondingly shrinks. Meanwhile the asymmetry
parameter of quark matter in the mixed phase decreases with the strengthening
of this interaction channel. This leads to some possible observation signals
being weakened, although still present. We show that these can be rather
general effects of a repulsion in the quark phase due to the symmetry energy.
This is also confirmed by a simpler calculation with the MIT--Bag model.
However, the asymmetry parameter of quark matter is slightly enhanced with the
inclusion of the isoscalar vector interaction, but the phase transition will be
moved to higher densities. The largest uncertainty on the phase transition lies
in the undetermined coupling constants of the vector interactions. In this
respect new data on the mixed phase obtained from Heavy Ion Collisions at
Intermediate Energies appear very important.Comment: submitted to Phys. Rev.
Instabilities in a Mean-field dynamics of Asymmetric Nuclear Matter
We discuss the features of instabilities in asymmetric nuclear matter, in
particular the relation between the nature of fluctuations, the types of
instabilities and the properties of the interaction. We show a chemical
instability appears as an instability against isoscalar-like fluctuations. Then
starting from phenomenological hadronic field theory (QHD), including exchange
terms, we discuss the symmetry energy and the relation to the dynamical
response inside the spinodal region.Comment: 8 pages, 5 Postscript figures, talk at Cortona 2000 Conference, Oct.
17 - Oct. 20, Italy, World Scientific (in press
Shells around black holes: the effect of freely specifiable quantities in Einstein's constraint equations
We solve Einstein's constraint equations in the conformal thin-sandwich
decomposition to model thin shells of non-interacting particles in circular
orbit about a non-rotating black hole. We use these simple models to explore
the effects of some of the freely specifiable quantities in this decomposition
on the physical content of the solutions. Specifically, we adopt either maximal
slicing or Kerr-Schild slicing, and make different choices for the value of the
lapse on the black hole horizon. For one particular choice of these quantities
the resulting equations can be solved analytically; for all others we construct
numerical solutions. We find that these different choices have no effect on our
solutions when they are expressed in terms of gauge-invariant quantities.Comment: 9 pages, 4 figure
Cholinergic suppression: A postsynaptic mechanism of long-term associative learning
Food avoidance learning in the mollusc Pleurobranchaea entails reduction in the responsiveness of key brain interneurons in the feeding neural circuitry, the paracerebral feeding command interneurons (PCNs), to the neurotransmitter acetylcholine (AcCho). Food stimuli applied to the oral veil of an untrained animal depolarize the PCNs and induce the feeding motor program (FMP). Atropine (a muscarinic cholinergic antagonist) reversibly blocks the food-induced depolarization of the PCNs, implicating AcCho as the neurotransmitter mediating food detection. AcCho applied directly to PCN somata depolarizes them, indicating that the PCN soma membrane contains AcCho receptors and induces the FMP in the isolated central nervous system preparation. The AcCho response of the PCNs is mediated by muscariniclike receptors, since comparable depolarization is induced by muscarinic agonists (acetyl-Ă -methylcholine, oxotremorine, pilocarpine), but not nicotine, and blocked by muscarinic antagonists (atropine, trifluoperazine). The nicotinic antagonist hexamethonium, however, blocked the AcCho response in four of six cases. When specimens are trained to suppress feeding behavior using a conventional food-avoidance learning paradigm (conditionally paired food and shock), AcCho applied to PCNs in the same concentration as in untrained animals causes little or no depolarization and does not initiate the FMP. Increasing the concentration of AcCho 10-100 times, however, induces weak PCN depolarization in trained specimens, indicating that learning diminishes but does not fully abolish AcCho responsiveness of the PCNs. This study proposes a cellular mechanism of long-term associative learning -- namely, postsynaptic modulation of neurotransmitter responsiveness in central neurons that could apply also to mammalian species
Relativistic Approach to Superfluidity in Nuclear Matter
Pairing correlations in symmetric nuclear matter are studied within a
relativistic mean-field approximation based on a field theory of nucleons
coupled to neutral ( and ) and to charged () mesons.
The Hartree-Fock and the pairing fields are calculated in a self-consistent
way. The energy gap is the result of a strong cancellation between the scalar
and vector components of the pairing field. We find that the pair amplitude
vanishes beyond a certain value of momentum of the paired nucleons. This fact
determines an effective cutoff in the gap equation. The value of this cutoff
gives an energy gap in agreement with the estimates of non relativistic
calculations.Comment: 21 pages, REVTEX, 8 ps-figures, to appear in Phys.Rev.C. e-mail:
[email protected]
Pharmacological management of COVID-19 patients with ARDS (CARDS): A narrative review
Coronavirus disease 2019 (COVID-19) is highly infectious. It has been highlighted that if not expertly and individually managed with consideration of the vasocentric features, a COVID-19 patient with an acute respiratory distress syndrome (CARDS) may eventually develop multiorgan failure. Unfortunately, there is still no definite drug for CARDS that is capable of reducing either short-term or long-term mortality and no specific treatments for COVID-19 exist right now. In this narrative review, based on a selective literature search in EMBASE, MEDLINE, Scopus, The Cochrane Library, Web of Science, and Google Scholar and ClinicalTrials.gov, we have examined the emerging evidence on the possible treatment of CARDS. Although numerous pharmacologic therapies to improve clinical outcomes in CARDS have been studied also in clinical trials, none have shown efficacy and there is great uncertainty about their effectiveness. There is still no recommendation for the therapeutic use of any specific agent to treat CARDS because no drugs are validated to have significant efficacy in clinical treatment of COVID-19 patients in large-scale trials. However, there exist a number of drugs that may be useful at least in some patients. The real challenge now is to link the right patient to the right treatment
Disposal of green roofs: A contribution to identifying an âAllowed by legislationâ endâofâlife scenario and facilitating their environmental analysis
The rapid and widespread deployment of green roofs requires the need to address their disposal and to assess the environmental impact of this phase of their life cycle to understand whether their current large-scale application may pose a problem. A review of the literature on green roofs environmental performance (particularly Life Cycle Assessment studies) has highlighted the lack of a standardized, commonly adopted, procedure for determining the treatments, recovery and/or disposal, to be assigned to waste from the removal of green roofs. In this regard, it should be mentioned that there is a lack of ad hoc legislation on the disposal of this technology (to the best of the authorsâ knowledge, even at the international level). In this paper, an attempt procedure is introduced to identify the end-of-life scenario of green roofs that does not conflict with the current regulations regarding wastes. Specifically, the procedure relies on an âattempt classificationâ of the waste from individual green roof elements and the priority criterion for intervention. This procedure might thus be used temporarily by technicians, pending the issuance of guidelines specifically dedicated to green roofs disposal, to model their end-of-life and thus assess the environmental impact of this phase of the life cycle. The feasibility of this proposal was verified through a field application. Besides the methodological proposal, the results of the work indicated the need to review the current waste legislation and update it -at least the Italian one - to also consider new materials used in green transition technologies
Active Rules for Runtime Adaptivity Management
The trend over the last years clearly shows that modern Web
development is evolving from traditional, HTML-based Web sites to fullfledged, complex Web applications, also equipped with active and/or adaptive application features. While this evolution unavoidably implies higher development costs and times, such implications are contrasted by the dynamics of the modern Web, which demands for even faster application development and evolution cycles.
In this paper we address the above problem by focusing on the case of adaptive Web applications. We illustrate an ECA rule-based approach, intended to facilitate the management and evolution of adaptive application features. For this purpose, we stress the importance of decoupling the active logic (i.e. the adaptivity rules) from the execution of the actual application by means of a decoupled rule engine that is able to capture events and to autonomously enact adaptivity actions
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