5,475 research outputs found
The 2D/3D dynamics of wall-bounded low-Rm magnetohydrodynamic (MHD) turbulence
No full textWith this experimental study, we give evidence that the dynamics of low-Rm MHD turbulence depends on the diffusion length l_z, which corresponds to the distance over which the Lorentz force is able to diffuse momentum before it is balanced by inertia
Estudo comparativo da clonidina com a dexmedetomidina para a sedação do paciente crítico sob ventilação mecânica
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde. Programa de Pós-Graduação em Ciências MédicasObjetivo: Comparar a segurança e efetividade da clonidina com a dexmedetomidina para a sedação de pacientes críticos. Estabelecer a relação entre essas duas drogas e o desenvolvimento de Delirium bem como seu impacto no sistema imune. Método: Ensaio clínico, aberto, randomizado, aprovado pela Comissão de Ética da Instituição. Foram analisados pacientes que necessitassem de ventilação mecânica por um período mínimo de 24 horas, sem doença neurológica prévia, hipotensão ou bradiarritmia. A segurança dos fármacos foi avaliada pelo seu impacto nos níveis de pressão arterial média (PAM) e freqüência cardíaca (FC). CAM-ICU e níveis de cortisol foram avaliados no começo e 24hs após o início da infusão para mensurar impacto no Delirium e no sistema imune. A efetividade foi analisada pelo tempo em que os pacientes mantiveram-se sob sedação ideal (Ramsay2/4, RASS-3/+1). Para análise estatística foram utilizados os testes t de Student e ?2 (significante p?0,05). Resultados: Foram avaliados 29 pacientes, 14 receberam clonidina (G1) e 15 dexmedetomidina (G2). As características clínicas e demográficas foram semelhantes nesses grupos. A dose média administrada de clonidina foi 0,82µg/kg/h e de dexmedetomidina foi 0,62µg/kg/h. As duas drogas causaram redução na PAM e FC, com exceção da PAM na sexta e vigésima quarta hora do G2. Houve uma tendência que os pacientes do G2 permanecessem mais tempo com sedação ideal (Rass: G1=58,5%, G2=71,9%, Ramsay: G1=54,7%, G2=68,4%) (p=NS). Os níveis de cortisol embora elevados nos dois grupos, não sofreram variação significativa após 24hs de infusão das drogas (G1:34,0/35,2µg/dL, G2:40,9/62,0µg/dL). Houve uma tendência de que Delirium fosse mais freqüentemente diagnosticado no G2 ao final do protocolo (28,6% vs. 45,5% p=NS). Conclusão: A dexmedetomidina e a clonidina mostraram-se efetivas e seguras para a sedação dos pacientes críticos sob ventilação mecânica deste estudo
Triangular Constellations in Flows
No full textParticles advected on the surface of a fluid can exhibit fractal clustering. The local structure of a fractal set is described by its dimension , which is the exponent of a power-law relating the mass in a ball to its radius : . It is desirable to characterise the {\em shapes} of constellations of points sampling a fractal measure, as well as their masses. The simplest example is the distribution of shapes of triangles formed by triplets of points, which we investigate for fractals generated by chaotic dynamical systems. The most significant parameter describing the triangle shape is the ratio of its area to the radius of gyration squared. We show that the probability density of has a phase transition: is independent of and approximately uniform below a critical flow compressibility , which we estimate. For the distribution appears to be described by two power laws: when , and when
Exact two-dimensionalization of low-magnetic-Reynolds-number flows subject to a strong magnetic field
No full textWe investigate the behavior of flows, including turbulent flows, driven by a horizontal body-force and subject to a vertical magnetic field, with the following question in mind: for very strong applied magnetic field, is the flow mostly two-dimensional, with remaining weak three-dimensional fluctuations, or does it become exactly 2D, with no dependence along the vertical? We restrict attention to low-magnetic-Reynolds number (Rm) flow. Because liquid metals have low magnetic Prandtl number, such low- flows can have a kinetic Reynolds number as large as one million and therefore be strongly turbulent. We first focus on the quasi-static approximation, i.e. the asymptotic limit of vanishing magnetic Reynolds number Rm << 1: we prove that the flow becomes exactly 2D asymptotically in time, regardless of the initial condition and provided the interaction parameter N is larger than a threshold value. We call this property absolute two-dimensionalization: the attractor of the system is necessarily a (possibly turbulent) 2D flow. We then consider the full-magnetohydrodynamic equations and we prove that, for low enough Rm and large enough N, the flow becomes exactly two-dimensional in the long-time limit provided the initial vertically-dependent perturbations are infinitesimal. We call this phenomenon linear two-dimensionalization: the (possibly turbulent) 2D flow is an attractor of the dynamics, but it is not necessarily the only attractor of the system. Some 3D attractors may also exist and be attained for strong enough initial 3D perturbations. These results shed some light on the existence of a dissipative anomaly for magnetohydrodynamic flows subject to a strong external magnetic field
The Decay of Wall Bounded MHD Turbulence at Low RM
No full textWe have developed a new spectral method to simulate flows with very fine boundary layers present. We apply it to calculate the evolution of freely decaying MHD turbulence between isolating walls. By comparison them with results obtained in fully periodic domain we quantify the influence of the channel walls on the character of freely decaying MHD turbulence
Constraining hadronization mechanisms with /D production ratios in Pb-Pb collisions at TeV
No full textInternational audienceThe production of prompt baryons at midrapidity () was measured in central (0-10%) and mid-central (30-50%) Pb-Pb collisions at the center-of-mass energy per nucleon-nucleon pair TeV with the ALICE detector. The production yield, the /D production ratio, and the nuclear modification factor are reported. The results are more precise and more differential in transverse momentum () and centrality with respect to previous measurements. The /D ratio, which is enhanced with respect to the pp measurement for GeV/, is described by theoretical calculations that model the charm-quark transport in the quark-gluon plasma and include hadronization via both coalescence and fragmentation mechanisms
Estudo comparativo do propofol com o midazolam para a sedação, a curto prazo, de pacientes sob ventilação mecanica internada em UTI
No full textDissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro de Ciencias da SaudeFoi realizado um estudo clínico aberto, controlado e randomizado em 30 pacientes adultos, com o objetivo de comparar a segurança e a eficácia do propofol a do midazolam para sedação, a curto prazo, de pacientes interndos na UTI e sob ventilação mecânica. Os pacientes foram distribuídos aleatoriamente em dois grupos. A taxa de mortalidade foi 46.6 % em ambos os grupos. As variáveis bioquímicas, determinadas nas amostras colhidas no início e no final do estudo, foram similares nos dois grupos. Não houve aumento significativo nos níveis séricos de triglicerídeos e tampouco evidências de supressão adrenal. Foi constatada uma queda, estatisticamente significativa, da FC em ambos os grupos, e da PAM intergrupos. Para a sedação, a curto prazo (£24h), de pacientes sob ventilação mecânica, o propofol e o midazolam são drogas seguras e eficazes. O propofol é mais eficaz, já que possibilita uma sedação mais superficial e um despertar mais rápido, enquanto que o midazolam interfere menos com a estabilidade hemodinâmica
A basis of a certain module for the hyperalgebra and some applications
No full textIn the hyperalgebra of the -th Frobenius kernel of the algebraic group , we construct a basis of the
-module generated by a certain element which was given by the
author before. As its applications, we also prove some results on the
-modules and the algebra .Comment: 30 page
Borromini tuscolano
No full textLa pubblicazione propone, in versione ampliata e aggiornata, la chiave di lettura già avanzata dall’autore alcuni anni or sono in relazione all’intervento seicentesco voluto dalla famiglia Falconieri sulla più antica delle Ville Tuscolane, la Rufina, ritenendone valida la consolidata attribuzione al Borromini.
Nel volume viene data un’ampia dimostrazione dell’efficacia dell’interazione “documenti storici-rilievo architettonico”, nella ricostruzione delle fasi evolutive di una fabbrica e di come questo momento d’analisi, ove insufficientemente approfondito, possa indurre a considerazioni erronee.
Infatti, l’ipotesi diffusa in vari contributi sull’argomento riguardo alla forma dell’originario Casino della Rufina – e in particolare alla posizione della loggia verso Roma – è suffragata soltanto da incisioni d’epoca e non è mai stata scientificamente comprovata dal riscontro di un rilievo, né dal confronto attento con la pianta del nucleo originario della fabbrica conservata nelle Carte Strozzi presso l’Archivio di Stato di Firenze, ignorata o considerata – con una certa superficialità – come inattendibile.
L’ipotesi qui sostenuta valuta la “logica” dell’addizione alla Villa Rufina basandosi su considerazioni relative sia ai vari documenti iconografici sia all’attendibilità di ciascuno; il tutto è inoltre riferito al completo rilevamento dell’opera nel suo stato attuale.
Discutendo ipotesi diverse (anche attributive) emerse nel frattempo e sviluppando le considerazioni precedentemente avanzate grazie anche a un nuovo apparato iconografico che vede sfruttate le potenzialità della modellazione 3D applicate ai criteri del rilievo filologico, il lavoro tende a ribadire l’efficacia di tale metodo d’indagine, basato sul rilievo delle attuali condizioni dell’opera in associazione all’imprescindibile analisi storico-documentale.
Attraverso il medesimo impianto scientifico procedurale è inoltre sviluppata la ricostruzione filologica del fronte settentrionale, basata anche su documentazione fotografica d’epoca parzialmente inedita. Si intende così offrire un iniziale – seppur parziale – contributo alla rilettura dell’ultima fase (quella novecentesca) che ha contrassegnato la fabbrica, vedendola già alterata ai primi del XX secolo, quindi compromessa dagli eventi bellici e infine trasformata dalle operazioni di restauro/ripristino del complesso, che hanno riproposto solo parzialmente e in modo generico la precedente morfologia del manufatto.This publication proposes, in an expanded and updated version, the key that the Author had already advanced in an earlier essay which was published ten years ago, concerning the 17th century intervention on the Villa Rufina: the first one of the Ville Tuscolane (summer residences for the papal circle that rose, in the late Renaissance, on the hills at the south of Rome). The Authors assumes also to be valid the well-established attribution of this work to Francesco Borromini.
In this volume a wide demonstration is offered of the efficacy, for the aim of a reliable reconstruction of the evolutionary phases of a certain building, of the interaction between the historical documents and the architectural survey, showing also how this time of analysis can lead to incorrect or misleading considerations, when it is not carried out enough deeply.
In the second phase (the expansion of the 17th century) which characterized all the Ville Tuscolane, the Rufina, at the time owned by the Falconieri (family), was the subject of an extensive renewal. With this intervention the first bulding that had initiated the “modern rediscovery” of building activity in these places (being, in fact, the originator of the Complex) was considerably transformed with regard to its material structure, appearance and relationship with the environment. For the devising of the general plan, it is commonly ascribed to Francesco Borromini, on the basis more of archive documents than of its style.
If the decoration of the Villa has been extensively and reliably studied, the same cannot be said about the transformations that the old building underwent, especially with regard to the lost loggia towards Rome. The hypothesis that has gradually taken root, about the location of this lodge, in the various papers published on the subject, is in fact supported only by some engravings of the time (in which the Villa is depicted in a pseudo-perspectival view and only as an element amongst the many others of the Complex). It has never been scientifically proved by the check of a survey, or by a careful comparison with the plan of the original nucleus of the original factory map stored in the “Carte Strozzi” at the State Archives of Florence, that has been ignored or considered – with some superficiality – as unreliable.
The hypothesis the Author suggested since the previous essay, evaluates the “logic” of the addition Borromini made to the Villa Rufina detaching itself from these assumptions and basing itself on some specific considerations concerning the iconographic documents that have been published over the years in various contributions, evaluating the reliability of each of them. These considerations were also related to a comprehensive survey of the work in its current state, as the so far published surveys are partial or were carried out on the structure as extensively damaged by the war.
In the volume are also discussed several different hypotheses that emerged in the meantime, also on the allocation of the project, as the attribution to Borromini – which in the past had seen ups and downs, from the header of the engraving by Alessandro Specchi to the evidences provided by Paolo Portoghesi and by Angela Negro, taken from the Falconieri-Carpegna archive – has recently been the subject of a new attempt of denial.
Developing the considerations already advanced before, and using a new display of subsidiary iconography that sees the exploitation of the potential of 3d modeling when applied to the criteria of the philological surveying, this study aims at a confirmation of the effectiveness of this method of investigation, which is based on a survey of the work in its positive state in conjunction with an unavoidable historical-documentary analysis.
On the basis of this same scientific procedural system, taking as well in account many historical photographic documents, so far unpublished, is also developed a philological reconstruction of the northern front, that is proposed in the last chapter. The aim is to provide a first – although partial – contribution to the re-reading of the last phase (the 20th century), which marked the building, that had already been altered in the early years of the 20th century, then compromised by the war and finally transformed by the restoration and rehabilitation of the complex, which reconstructed the pre-existing morphology only in a partial and general way
Measuring KK interactions using Pb-Pb collisions at TeV
No full textWe present the first ever measurements of femtoscopic correlations between the KS0 and K ± particles. The analysis was performed on the data from Pb–Pb collisions at sNN=2.76 TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding via the a0(980) resonance. The extracted kaon source radius and correlation strength parameters for KS0K− are found to be equal within the experimental uncertainties to those for KS0K+ . Comparing the results of the present study with those from published identical-kaon femtoscopic studies by ALICE, mass and coupling parameters for the a0 resonance are tested. Our results are also compatible with the interpretation of the a0 having a tetraquark structure instead of that of a diquark.We present the first ever measurements of femtoscopic correlations between the K and K particles. The analysis was performed on the data from Pb-Pb collisions at TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding via the resonance. The extracted kaon source radius and correlation strength parameters for KK are found to be equal within the experimental uncertainties to those for KK. Comparing the results of the present study with those from published identical-kaon femtoscopic studies by ALICE, mass and coupling parameters for the resonance are constrained. Our results are also compatible with the interpretation of the having a tetraquark structure over that of a diquark
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