83 research outputs found
Perfect Fluid Quantum Anisotropic Universe: Merits and Challenges
The present paper deals with quantization of perfect fluid anisotropic
cosmological models. Bianchi type V and IX models are discussed following
Schutz's method of expressing fluid velocities in terms of six potentials. The
wave functions are found for several examples of equations of state. In one
case a complete wave packet could be formed analytically. The initial
singularity of a zero proper volume can be avoided in this case, but it is
plagued by the usual problem of non-unitarity of anisotropic quantum
cosmological models. It is seen that a particular operator ordering alleviates
this problem.Comment: 13 pages, 4 figures; Accepted for publication in Gen Relativ Gravi
Modeling the quantum evolution of the universe through classical matter
It is well known that the canonical quantization of the
Friedmann-Lema\^itre-Robertson-Walker (FLRW) filled with a perfect fluid leads
to nonsingular universes which, for later times, behave as their classical
counterpart. This means that the expectation value of the scale factor
never vanishes and, as , we recover the classical expression for
the scale factor. In this paper, we show that such universes can be reproduced
by classical cosmology given that the universe is filled with an exotic matter.
In the case of a perfect fluid, we find an implicit equation of state (EoS). We
then show that this single fluid with an implict EoS is equivalent to two
non-interacting fluids, one of them representing stiff matter with negative
energy density. In the case of two non-interacting scalar fields, one of them
of the phantom type, we find their potential energy. In both cases we find that
quantum mechanics changes completely the configuration of matter for small
values of time, by adding a fluid or a scalar field with negative energy
density. As time passes, the density of negative energy decreases and we
recover the ordinary content of the classical universe. The more the initial
wave function of the universe is concentrated around the classical big bang
singularity, the more it is necessary to add negative energy, since this type
of energy will be responsible for the removal of the classical singularity.Comment: updated version as accepted by Gen. Relativ. Gravi
Cardiac risk assessment by gated single-photon emission computed tomography in asymptomatic end-stage renal disease patients at the start of dialysis
Efeito do extrato aquoso de Sida cordifolia na regeneração hepática após hepatectomia parcial
Introdução: O uso de plantas medicinais para o tratamento de patologias humanas tem aumentado em todo mundo. Muitas
delas são usadas por administração oral, e após a absorção podem afetar muitos órgãos. Objetivo: Esse estudo, tem como
objetivo verificar o efeito do extrato aquoso de Sida cordifolia, popularmente conhecida no Brasil como “malva-branca”,
na regeneração hepática. Métodos: Vinte ratos foram divididos em 4 grupos: controle, Sida 100, Sida 200 e Sida 400. Os
animais foram submetidos a administração oral de água destilada, 100, 200 e 400 mg/kg de extrato aquoso de Sida cordifolia,
respectivamente. Imediatamente após, foi realizada hepatectomia parcial 67%. Vinte quatro horas após, os fígados foram
removidos. A regeneração hepática foi avaliada por imunohistoquímica (PCNA), usando o anticorpo monoclonal PC-10.
Resultados: Os grupos Sida100 e Sida200 mostraram índices de regeneração hepática maiores que o grupo controle
(p<0.001 e p<0.05, respectivamente). Conclusão: O extrato aquoso de Sida cordifolia estimula a regeneração hepática
após hepatectomia parcial a 67% em ratos. _________________________________________________________________________________________ ABSTRACT: Purpose: The use of medicinal plants for the treatment of human diseases has increased worldwide. Many of them are
used by oral administration and, after absorption, may affect many organs. Therefore, this study aimed at assessing the
effects of the aqueous extract of Sida cordifolia leaves, popularly known in Brazil as “malva-branca”, on liver regeneration.
Methods: Twenty rats were divided into four groups: control, Sida100, Sida200 and Sida400 groups. All animals were
submitted to oral administration of distilled water, 100, 200 and 400 mg/kg of the aqueous extract of Sida cordifolia,
respectively. Immediately after this, they underwent 67% partial hepatectomy. Twenty four hours later, their livers were
removed. Hepatic regeneration was assessed by immunohistochemical staining for proliferating cell nuclear antigen
(PCNA) using the PC-10 monoclonal antibody. Results: Sida100 and Sida200 groups disclosed higher liver regeneration
indices than control group (p<0.001 and p<0.05, respectively). Conclusion: The aqueous extract of Sida cordifolia
stimulates liver regeneration after 67% partial hepatectomy in rats
Testing of aspect-oriented programs: difficulties and lessons learned based on theoretical and practical experience
Aspectos clínicos, histológicos e de microscopia eletrônica dos granulomas de intubação das pregas vocais
Effect of sitagliptin on cardiovascular outcomes in type 2 diabetes
BACKGROUND: Data are lacking on the long-term effect on cardiovascular events of adding sitagliptin, a dipeptidyl peptidase 4 inhibitor, to usual care in patients with type 2 diabetes and cardiovascular disease. METHODS: In this randomized, double-blind study, we assigned 14,671 patients to add either sitagliptin or placebo to their existing therapy. Open-label use of antihyperglycemic therapy was encouraged as required, aimed at reaching individually appropriate glycemic targets in all patients. To determine whether sitagliptin was noninferior to placebo, we used a relative risk of 1.3 as the marginal upper boundary. The primary cardiovascular outcome was a composite of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for unstable angina. RESULTS: During a median follow-up of 3.0 years, there was a small difference in glycated hemoglobin levels (least-squares mean difference for sitagliptin vs. placebo, -0.29 percentage points; 95% confidence interval [CI], -0.32 to -0.27). Overall, the primary outcome occurred in 839 patients in the sitagliptin group (11.4%; 4.06 per 100 person-years) and 851 patients in the placebo group (11.6%; 4.17 per 100 person-years). Sitagliptin was noninferior to placebo for the primary composite cardiovascular outcome (hazard ratio, 0.98; 95% CI, 0.88 to 1.09; P<0.001). Rates of hospitalization for heart failure did not differ between the two groups (hazard ratio, 1.00; 95% CI, 0.83 to 1.20; P = 0.98). There were no significant between-group differences in rates of acute pancreatitis (P = 0.07) or pancreatic cancer (P = 0.32). CONCLUSIONS: Among patients with type 2 diabetes and established cardiovascular disease, adding sitagliptin to usual care did not appear to increase the risk of major adverse cardiovascular events, hospitalization for heart failure, or other adverse events
Spatial variation in the structure and composition of the herbaceous community in a semiarid region of northeastern Brazil
- …