19,100 research outputs found
Observational Constraints on Silent Quartessence
We derive new constraints set by SNIa experiments (`gold' data sample of
Riess et al.), X-ray galaxy cluster data (Allen et al. Chandra measurements of
the X-ray gas mass fraction in 26 clusters), large scale structure (Sloan
Digital Sky Survey spectrum) and cosmic microwave background (WMAP) on the
quartessence Chaplygin model. We consider both adiabatic perturbations and
intrinsic non-adiabatic perturbations such that the effective sound speed
vanishes (Silent Chaplygin). We show that for the adiabatic case, only models
with equation of state parameter are allowed: this
means that the allowed models are very close to \LambdaCDM. In the Silent case,
however, the results are consistent with observations in a much broader range,
-0.3<\alpha<0.7.Comment: 7 pages, 12 figures, to be submitted to JCA
Porous bioactive composites from marine origin based in chitosan and hydroxylapatite particles
An optimal carrier for bone tissue engineering should be both a controlled release system
and a scaffold. In the former role, the carrier must prevent rapid factor clearance and ideally meter
out the growth factor in a predictable manner, allowing therapeutic doses to stimulate target cells for
the appropriate duration. In the latter role, the material should act as a permissive environment into
which bone cells would be attracted to migrate and begin the process of depositing bone matrix.
Therefore the direct incorporation of growth factor in porous scaffolds should be a desirable goal.
The inclusion of a bioactive ceramic on the scaffold design will confer to the systems a bone
bonding behaviour that will guide bone formation. This work reports the development of composite
chitosan/HA (from algal origin) porous structures produced by means of freeze-drying processing
routes that can be further loaded with a biologically active agent. The developed bioactive 3D
structures (completely from marine origin) have potential application as tissue engineering scaffolds
and drug delivery systems due to their morphological and bioactive properties.(undefined
Tratamiento de reflujo vesicoureteral
Abstract
OBJECTIVES: Vesicoureteral reflux (VUR) is a frequent pathology, with an incidence of 29/50% in children studied for urinary tract infection (UTI) and 20% of newborns with the diagnosis of prenatal hydronephrosis. Over the years, the treatment has been the subject of many meetings, many research studies, and continues being a topic under discussion. The number of candidates for surgical treatment increased with the development of minimally invasive endoscopic techniques by subureteral injection of bulking agents. We present the results of the surgical treatment of VUR between 2001 and 2006.
METHODS: We performed a retrospective study of the endoscopic treatment of VUR by subureteral injection of Dextranomer and hyaluronic acid copolymer (Copol-Dx/AH). All children undergoing treatment between July 1st 2001 and December 30th 2006 were included in this study. Treatment was performed in children with VUR grade II or greater. All patients presenting no reflux or grade I VUR on control VCUG were considered cured; stopping antibiotic prophylaxis was proposed in these cases.
RESULTS: 661 children underwent treatment, 607 endoscopic and 54 with the Cohen technique. Among children treated endoscopically, 437 where females and 170 males. VUR was bilateral in 37.7% of the cases, with grade II being the most frequent (40% in males and 57% in females). Overall success rate was 70% after first treatment, 75% after second treatment and increased to 78% after the third.
CONCLUSIONS: Subureteral injection of dextranomer and hyaluronic acid copolymer is on effective treatment in children with VUR, independently of the grade. It is a simple, safe, well tolerated procedure with low associated morbidity. Currently, it is the surgical treatment of choice in most patients with VUR
Universal velocity distributions in an experimental granular fluid
We present experimental results on the velocity statistics of a uniformly
heated granular fluid, in a quasi-2D configuration. We find the base state, as
measured by the single particle velocity distribution , to be universal
over a wide range of filling fractions and only weakly dependent on all other
system parameters. There is a consistent overpopulation in the distribution's
tails, which scale as . More
importantly, the high probability central region of , at low velocities,
deviates from a Maxwell-Boltzmann by a second order Sonine polynomial with a
single adjustable parameter, in agreement with recent theoretical analysis of
inelastic hard spheres driven by a stochastic thermostat. To our knowledge,
this is the first time that Sonine deviations have been measured in an
experimental system.Comment: 13 pages, 15 figures, with minor corrections, submitted to Phys. Rev.
Impactos do fenômeno ENOS sobre a temperatura no Brasil.
Neste trabalho, a variabilidade das temperaturas máximas e mínimas mensais de 265 estações convencionais, componentes do Banco de Dados Meteorológicos para Ensino e Pesquisa (BDMEP do INMET), nos últimos 50 anos, foi relacionada com as variações do Oceanic Niño Index do NOAA Climate Prediction Center através do treinamento de uma rede neural artificial. Os resultados da pesquisa mostram a relação quase que direta entre ENOS (El Niño-Oscilação Sul) e as temperaturas máximas e mínimas mensais no Brasil. Foram escolhidas algumas localidades para demonstrar os resultados da pesquisa: Manaus, Recife, Cuiabá, Brasília, São Paulo e Porto Alegre. Os eventos de El Niño contribuem para o aumento das temperaturas máximas e mínimas enquanto o inverso ocorre em eventos de La Niña, exceto para a região Amazônica. Em anos de La Niña ocorrem diminuição das temperaturas do ar em quase todas as regiões do Brasil. O impacto do fenômeno ENOS no país se faz mais presente nos meses de inverno e primavera.bitstream/item/76849/1/Impactos-fenomeno.pd
Bilayered chitosan-based scaffolds for osteochondral tissue engineering : influence of hydroxyapatite on in vitro cytotoxicity and dynamic bioactivity studies in a specific double-chamber bioreactor
Osteochondral tissue engineering presents a current research challenge due to the necessity of combining both bone and cartilage
tissue engineering principles. In the present study, bilayered chitosan-based scaffolds are developed based on the optimization of both
polymeric and composite scaffolds. A particle aggregation methodology is proposed in order to achieve an improved integrative
bone–cartilage interface needed for this application, since any discontinuity is likely to cause long-term device failure. Cytotoxicity
was evaluated by the MTS assay with the L929 fibroblast cell line for different conditions. Surprisingly, in composite scaffolds using
unsintered hydroxyapatite, cytotoxicity was observed in vitro. This work reports the investigation that was conducted to overcome
and explain this behaviour. It is suggest that the uptake of divalent cations may induce the cytotoxic behaviour. Sintered hydroxyapatite
was consequently used and showed no cytotoxicity when compared to the controls. Microcomputed tomography (micro-CT) was carried
out to accurately quantify porosity, interconnectivity, ceramic content, particle and pore sizes. The results showed that the developed
scaffolds are highly interconnected and present the ideal pore size range to be morphometrically suitable for the proposed applications.
Dynamical mechanical analysis (DMA) demonstrated that the scaffolds are mechanically stable in the wet state even under dynamic compression.
The obtained elastic modulus was, respectively, 4.21 ± 1.04, 7.98 ± 1.77 and 6.26 ± 1.04 MPa at 1 Hz frequency for polymeric,
composite and bilayered scaffolds. Bioactivity studies using both a simulated body fluid (SBF) and a simulated synovial fluid (SSF) were
conducted in order to assure that the polymeric component for chondrogenic part would not mineralize, as confirmed by scanning electron
microscopy (SEM), inductively coupled plasma-optical emission spectroscopy (ICP) and energy-dispersive spectroscopy (EDS) for
different immersion periods. The assays were carried out also under dynamic conditions using, for this purpose, a specifically designed
double-chamber bioreactor, aiming at a future osteochondral application. It was concluded that chitosan-based bilayered scaffolds produced
by particle aggregation overcome any risk of delamination of both polymeric and composite parts designed, respectively, for chondrogenic
and osteogenic components that are mechanically stable. Moreover, the proposed bilayered scaffolds could serve as alternative,
biocompatible and safe biodegradable scaffolds for osteochondral tissue engineering applications
Optimization of chitosan-based composite and bi-layered scaffolds produced by particles aggregation for osteochondral tissue engineering: Influence of hydroxylapatite
[Excerpt] Osteochondral tissue engineering presents a challenge to the present research due to requirements’ combination of both bone and cartilage tissue engineering. In the present study, bilayered
chitosan scaffolds are proposed based in the optimization of polymeric and composite scaffolds. µ-CT was carried out for accurate morphometric characterization quantifying porosity, interconnectivity,
ceramic content, particles and pores size. The results showed that the developed scaffolds are highly interconnected and present ideal pore size range, being morphometrically adequate for
the proposed applications. [...]info:eu-repo/semantics/publishedVersio
Caging dynamics in a granular fluid
We report an experimental investigation of the caging motion in a uniformly
heated granular fluid, for a wide range of filling fractions, . At low
the classic diffusive behavior of a fluid is observed. However, as
is increased, temporary cages develop and particles become increasingly
trapped by their neighbors. We statistically analyze particle trajectories and
observe a number of robust features typically associated with dense molecular
liquids and colloids. Even though our monodisperse and quasi-2D system is known
to not exhibit a glass transition, we still observe many of the precursors
usually associated with glassy dynamics. We speculate that this is due to a
process of structural arrest provided, in our case, by the presence of
crystallization.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
- …