Search results for "vessels"

Influence of polymer content in Ca-deficient hydroxyapatite–polycaprolactone nanocomposites on the formation of microvessel-like structures

2009

Calcium phosphate (CaP) ceramics are widely used in bone tissue engineering due to their good osteoconductivity. The mechanical properties of CaP can be modified by the addition of small volume fractions of biodegradable polymers such as polycaprolactone (PCL). Nevertheless, it is also important to evaluate how the polymer content influences cell-material or cell-cell interactions because of potential consequences for bone regeneration and vascularization. In this study we assessed the general biocompatibilty of Ca-deficient hydroxyapatite (CDHA)-PCL disks containing nominally 11 and 24% polycaprolactone using human umbilical vein endothelial cells and human primary osteoblasts. Confocal mi…

The control of the residual lifetimes of carbon fibre-reinforced composite pressure vessels

2015

International audience; The understanding of the degradation of carbon fibre composites, with emphasis on the use of these composites in filament-wound pressure vessels, is explored. Earlier studies by many researchers have led to a general appreciation of the mechanisms involved; however, only recently have both computational power and experimental techniques become sufficiently developed to allow for the use of quantitative analyses. It is shown that damage is controlled by fibre failure, and that initially this occurs randomly within the structure. In monotonic loading, the development of clusters of fibre breaks causes rapid failure; however, under maintained loads the kinetics of damag…

The effects of linearly increasing flip angles on 3D inflow MR angiography

1994

As recently demonstrated, spin saturation effects in 3D time-of-flight (TOF) MR angiography (MRA) can be reduced by using RF pulses with linearly increasing flip angles (ramp pulses) in the main direction of flow. We developed a model for calculating the signal distribution of proton flow within the excitation volume (slab) for different ramp slopes and compared the results with the measured distribution for the lower-leg arteries. The ramp pulses were generated using the Fourier transformation of the desired excitation profiles. With a bandwidth of 6 kHz and a pulse length of 2.56 ms satisfactory ramps with variable slopes were generated and applied in a standard flow-compensated 3D FISP s…

Effect of the loading rate on ultimate strength of composites. Application: Pressure vessel slow burst test

2013

International audience; The strength of unidirectional elastic fibre composites is shown to depend on the loading rate as the viscoelastic nature of the matrix results in a fall in breaking load as the rate is reduced. The simulation of the accumulation of fibre breaks leading to failure, takes into account all physical phenomena involved fibre failure, including the stochastic nature of fibre strength, stress transfer through the matrix between reinforcements, interfacial debonding and the viscoelastic nature of the matrix. The kinetics of composite failure are seen to involve the initial formation of random fibre breaks which at higher loads coalesce into clusters of broken fibres. The ra…

Health monitoring of high performance composite pressure vessels,

2018

International audience; The most important form of damage in carbon fiber reinforced composite pressure vessels is the failure of the fibers however the rate of fiber failure is controlled by the viscoelastic nature of the matrix, which determines overall in-service lifetimes. This type of damage is very different from that encountered with metal pressure vessels and requires a detailed understanding in order to ensure reliability. Innovative proof testing methods based on these processes are necessary. The damage processes and the means of quantifying them are discussed. Their reliability under pressure over periods of decades is analyzed. Intrinsic safety factors linked directly to the pr…

Free vortex shape in Uncovered Unbaffled Stirred Tanks (UUST) agitated by Rushton turbines

2012

The main feature of unbaffled stirred tanks is the highly swirling liquid motion, which leads to the formation of a central vortex on the liquid free surface, when the vessel is operated without top-cover (Uncovered Unbaffled Stirred Tanks, UUST). In this work, original data on fluid dynamics characteristics of (UUST) agitated by a Rushton turbine are presented. In particular, digital image analysis is employed to accurately assess vortex shape and validate an original model for its description. The model describes vortex shape in the case of sub-critical systems (when vortex bottom is placed above the impeller plane) as well as in the case of super-critical systems (when vortex bottom fall…

Nipple-sparing mastectomy and breast reconstruction with a deep inferior epigastric perforator flap using thoracodorsal recipient vessels and a low l…

2018

Background Nipple-sparing mastectomy poses challenges in providing esthetically-pleasing immediate autologous breast reconstruction. This study was to investigate the outcomes of nipple-sparing mastectomy with breast reconstruction using free abdominal flaps between two different recipient sites. Methods Between 2010 and 2016, 79 patients who underwent nipple-sparing mastectomy with autologous breast reconstruction using thoracodorsal (TD) vessels in 30 cases or internal mammary (IM) vessels in 49 cases were investigated. Demographics, intraoperative findings, complications, and quality of life using Breast-Q questionnaire were compared between two groups. Results All flap survived. There w…

Involvement of PKC and NF-κB in Nitric Oxide Induced Apoptosis in Human Coronary Artery Smooth Muscle Cells

2001

Apoptosis of vascular smooth muscle cells is critically involved in progression of atherosclerosis and may prevent intimal hyperplasia in restenosis and vascular remodeling. Nitric oxide (NO) is known to induce apoptosis, but the signaling pathways still remain unclear. We investigated p53 accumulation, protein kinase C (PKC) activation and nuclear transcription factor (NF-kappaB) binding activity as possible signaling mechanisms of NO-induced apoptosis. Apoptosis was induced dose-dependently with the NO-donors sodiumnitroprusside (SNP: 232+/-48%) and SIN-1 (241+/-90% of actinomycin D induced apoptosis; means +/- SEM, *por =0.05 vs. control) in HSMC. Inhibition of PKC significantly attenuat…

NUMERICAL SIMULATION OF SEDIMENT RESUSPENSION IN MECHANICALLY STIRRED VESSEL

2008

Relations of Metabolically Healthy and Unhealthy Obesity to Digital Vascular Function in Three Community‐Based Cohorts: A Meta‐Analysis

2017

Background Microvascular dysfunction is a marker of early vascular disease that predicts cardiovascular events. Whether metabolically healthy obese individuals have impaired microvascular function remains unclear. The aim of this study was to evaluate the relation of obesity phenotypes stratified by metabolic status to microvascular function. Methods and Results We meta‐analyzed aggregate data from 3 large cohorts (Brazilian Longitudinal Study of Adult Health, the Framingham Heart Study, and the Gutenberg Heart Study; n=16 830 participants, age range 19–90, 51.3% men). Regression slopes between cardiovascular risk factors and microvascular function, measured by peripheral arterial tonometr…