Search results for "Pulse"

High Accuracy Modelling of Hybrid Power Supplies

2011

This chapter proposes a modelling approach based on the PSIM/Simulink co-simulation toolbox for hybrid power supplies, featuring high accuracy. Hybrid source performances are fully tested during behavioural simulations. The importance of high-accuracy modelling is investigated and modelling guidelines for both power sources and load are given for further applications. The Simulink model is analyzed and the efficiency of the proposed approach is verified by the comparison between simulation and experimental results. In the last few years, hybrid power supplies are investigated for a wide variety of application areas: two primary sources are coupled to take advantages of both, overcoming thei…

An analytical model of heat transfer and fluid dynamic performances of an unconventional NTR engine for manned interplanetary missions

2009

Abstract An analytical model of fluid flow and heat transfer of a Nuclear Thermal Rocket (NTR) engine concept is presented. The engine is based on the direct conversion of the kinetic energy of the fission fragments (FFs) into the propellant enthalpy. The FFs can escape from an extremely thin layer of fissionable material: a sufficiently large surface coated with few micrometers of Americium 242m, confined by a neutron moderator–reflector, may become a critical reactor. Three dimensional coupled CFD-Monte Carlo simulations have already been presented in Di Piazza and Mulas (2006) . In this paper, an analytical integral 1-D model of fluid dynamics and heat transfer is built in order to fores…

Refolding of the integral membrane protein light-harvesting complex II monitored by pulse EPR

2009

The major light-harvesting chlorophyll a / b complex (LHCII) of the photosynthetic apparatus in plants self-organizes in vitro. The recombinant apoprotein, denatured in dodecyl sulfate, spontaneously folds when it is mixed with its pigments, chlorophylls, and carotenoids in detergent solution, and assembles into structurally authentic LHCII in the course of several minutes. Pulse EPR techniques, specifically double-electron-electron resonance (DEER), have been used to analyze protein folding during this process. Pairs of nitroxide labels were introduced site-specifically into recombinant LHCII and shown not to affect the stability and function of the pigment-protein complex. Interspin dist…

Osteogenic commitment and differentiation of human mesenchymal stem cells by low‐intensity pulsed ultrasound stimulation

2018

Low-intensity pulsed ultrasound (LIPUS) as an adjuvant therapy in in vitro and in vivo bone engineering has proven to be extremely useful. The present study aimed at investigating the effect of 30 mW/cm(2) LIPUS stimulation on commercially available human mesenchymal stem cells (hMSCs) cultured in basal or osteogenic medium at different experimental time points (7d, 14d, 21d). The hypothesis was that LIPUS would improve the osteogenic differentiation of hMSC and guarantying the maintenance of osteogenic committed fraction, as demonstrated by cell vitality and proteomic analysis. LIPUS stimulation (a) regulated the balance between osteoblast commitment and differentiation by specific network…

Multidimensional pseudo-random pulse signals and their coincidence properties

1996

Arterial Stiffness is Associated With Moderate to Vigorous Physical Activity Levels in Post-Myocardial Infarction Patients.

2019

Arterial stiffness has shown independent predictive value for all-cause and cardiovascular mortalities, as well as fatal and nonfatal coronary events. Physical activity (PA) is associated with reduced cardiovascular morbidity and mortality. The study aims to analyze the cross-sectional association of arterial stiffness with objectively measured PA in patients following acute myocardial infarction.One hundred patients were consecutively recruited after experiencing an acute myocardial infarction. Central arterial stiffness was measured through carotid-femoral pulse wave velocity (cf-PWV) and daily PA was assessed objectively during 7 consecutive days with accelerometers. To be valid, data re…

Usefulness of transcutaneous PCO2to assess nocturnal hypoventilation in restrictive lung disorders

2016

Background and objectiveNocturnal hypoventilation is now an accepted indication for the initiation of non-invasive ventilation. Nocturnal hypoventilation may be an under diagnosed condition in chronic respiratory failure. The most appropriate strategy to identify sleep hypoventilation is not yet clearly defined. In clinical practice, it is indirectly assessed using nocturnal pulse oximetry (NPO) and morning arterial blood gases (mABG). Even though continuous transcutaneous carbon dioxide partial pressure (TcPCO2) monitoring is theoretically superior to NPO plus mABG, it is not routinely used. We aimed to prospectively compare NPO plus mABG with nocturnal TcPCO2 for the detection of alveolar…

Observation of ventilation-induced Spo(2) oscillations in pigs: first step to noninvasive detection of cyclic recruitment of atelectasis?

2010

High arterial partial oxygen pressure (Pao(2)) oscillations within the respiratory cycle were described recently in experimental acute lung injury. This phenomenon has been related to cyclic recruitment of atelectasis and varying pulmonary shunt fractions. Noninvasive detection of Spo(2) (oxygen saturation measured by pulse oximetry) as an indicator of cyclic collapse of atelectasis, instead of recording Pao(2) oscillations, could be of clinical interest in critical care. Spo(2) oscillations were recorded continuously in three different cases of lung damage to demonstrate the technical feasibility of this approach. To deduce Pao(2) from Spo(2), a mathematical model of the hemoglobin dissoci…

Target oxygen levels in preterm neonates

2013

To achieve postnatal adaptation newly born infant need to aerate the lungs, reduce pulmonary vascular resistance, and initiate oxygen and carbon dioxide exchange. The cornerstone of newborn resuscitation resides therefore in the establishment of a functional residual capacity and an adequate oxygenation. Recent guidelines have established guidelines concerning oxygen supplementation in preterm infants in the delivery room (DR); however, they are vague and unspecific. Herewith, we will address available information regarding the use of oxygen supplementation in the DR in preterm infants to satisfactorily overcome postnatal adaptation. Introduction: Resuscitation of the newborn is considered …

Arterial stiffness in symptomatic smokers with normal lung function

2017

Chronic obstructive pulmonary disease (COPD) is associated with cardiovascular morbidity and mortality. Arterial stiffness and endothelial dysfunction index are validated surrogate cardiovascular markers and are increased in subjects with COPD. We tested whether increased arterial stiffness and endothelial dysfunction occur in symptomatic smokers with no evidence of bronchial obstruction. Clinical and lung functional assessments were conducted in smoker subjects with chronic respiratory symptoms and in COPD patients. Pulse wave velocity (PWV), aortic augmentation index (AIx) and reactive hyperaemia index (RHI) were measured to estimate the cardiovascular risk. 48 smokers (male n=37, female …