Search results for "VOLUME"

Liquid chromatography detectors second, completely revised edition by R. P. W. Scott Perkin-Elmer Corporation, Instrument Group, Main Avenue, Norwalk…

1986

Gelchromatographische refraktionierung, 1. Ein verfahren zur korrektur von gelchromatogrammen

1979

A mathematical method is proposed for calculating the gel chromatogram w(v0) after correction with the instrument spreading function D(v, v0) and for calculating D(v,v0) using experimental data on the basis, that a gel chromatographic polymer fraction of the chromatogram e(v) is collected and injected again. The chromatogram of this fraction c(v) can be described by the integral equation: where v0 is the elution volume and v1 is the volume at which the fraction is collected. The solution of this equation simultaneously with Tung's equation by way of minimizing is suggested.

Description of the Retention and Peak Profile for Chromolith Columns in Isocratic and Gradient Elution Using Mobile Phase Composition and Flow Rate a…

2014

The effect of the modifier concentration and flow rate on the chromatographic performance of a second generation Chromolith® RP-18e column, under isocratic and gradient elution with acetonitrile-water mixtures, was examined using four sulphonamides as probe compounds. The acetonitrile concentration was varied between 5 and 55% (v/v), and the flow rate between 0.1 and 5.0 mL/min, keeping the other factors constant. The changes in both retention and peak profile were modelled, and used to build simple plots, where the logarithm of the retention factor was represented against the modifier concentration (in gradient elution, against the initial modifier concentration), and the half-widths or wi…

High-flow nasal therapy versus noninvasive ventilation in COPD patients with mild-to-moderate hypercapnic acute respiratory failure: study protocol f…

2019

Background Noninvasive ventilation (NIV) is indicated to treat respiratory acidosis due to exacerbation of chronic obstructive pulmonary disease (COPD). Recent nonrandomized studies also demonstrated some physiological effects of high-flow nasal therapy (HFNT) in COPD patients. We designed a prospective, unblinded, multicenter, randomized controlled trial to assess the noninferiority of HFNT compared to NIV with respect to the reduction of arterial partial pressure of carbon dioxide (PaCO2) in patients with hypercapnic acute respiratory failure with mild-to-moderate respiratory acidosis. Methods We will enroll adult patients with acute hypercapnic respiratory failure, as defined by arterial…

Critical single proximal left arterial descending coronary artery stenosis to mimic chronic myocardial ischemia: a new model induced by minimal invas…

2008

<i>Background/Aims:</i> The present report examines a new pig model for progressive induction of high-grade stenosis, for the study of chronic myocardial ischemia and the dynamics of collateral vessel growth. <i>Methods:</i> Thirty-nine Landrace pigs were instrumented with a novel experimental stent (GVD stent) in the left anterior descending coronary artery. Eight animals underwent transthoracic echocardiography at rest and under low-dose dobutamine. Seven animals were examined by nuclear PET and SPECT analysis. Epi-, mid- and endocardial fibrosis and the numbers of arterial vessels were examined by histology. <i>Results:</i> Functional analysis showed a…

Age at First Episode Modulates Diagnosis-Related Structural Brain Abnormalities in Psychosis.

2016

Brain volume and thickness abnormalities have been reported in first-episode psychosis (FEP). However, it is unclear if and how they are modulated by brain developmental stage (and, therefore, by age at FEP as a proxy). This is a multicenter cross-sectional case-control brain magnetic resonance imaging (MRI) study. Patients with FEP (n = 196), 65.3% males, with a wide age at FEP span (12-35 y), and healthy controls (HC) (n = 157), matched for age, sex, and handedness, were scanned at 6 sites. Gray matter volume and thickness measurements were generated for several brain regions using FreeSurfer software. The nonlinear relationship between age at scan (a proxy for age at FEP in patients) and…

Role of Data Communications in Hybrid Cloud Costs

2011

Rapid adoption of cloud services in recent years has been driven by multiple factors, such as faster time-to-market and improved scalability enabled by public cloud infrastructure. Hybrid clouds, combining the in-house capacities with on-demand capacity of public clouds, achieve both the increased utilization rate of the in-house infrastructure and the limited use of more expensive public cloud, thereby lowering the total costs for the cloud user. In this paper, an analytical model of hybrid cloud costs is introduced, wherein the costs of computing and data communication are taken into account. Using this model, the costefficient division of the computing capacity between the private and th…

Modelling the influence of nanoparticles in the phase behaviour of an epoxy/polystyrene mixture

2007

Abstract The cloud point temperatures of four series of epoxy/polystyrene blends have been experimentally determined as a function of polymer mass and system composition. The phase diagrams show an UCST behaviour, increasing incompatibility as the molar mass increases. The Flory–Huggins theory with a concentration-dependent interaction parameter has been developed to study the compatibility of two polymers in presence of spherical nanoparticles. This theory has been first compared with the experimental cloud point curve in absence of nanoparticles, and secondly it has been used to predict the thermodynamic behaviour in presence of different volume fraction of nanoparticles. Nanoparticles co…

Prediction of Ductile Fractures Occurrence in Deep Drawing of Square Boxes

1996

Abstract The authors propose a new approach for the prediction of tearing in the deep drawing process of square boxes. Such an approach is based on a damage mechanics formulation and in particular on the yield condition for damaging materials proposed by Tvergaard and Needleman and on a strain controlled nucleation model. The flow rule associated to the yield condition is introduced in a finite element explicit formulation founded on the solution of the dynamic equilibrium equation and on an explicit time integration scheme. By this way the developed model allows to calculate the void volume fraction value during the deep drawing process of square boxes and consequently to predict the insur…

Structuring of polymer blends in simple shear flow

1990

A simplified model for the formation of steady state structure of discrete domains in polymer blends is established for simple shear flow. It is assumed that the domain size distribution, which results from an equilibrium between breakup processes and coalescence processes, may be divided in small and stable spherical domains and large and unstable ellipsoidal domains. Based on simplified rate balances and an expression for domain deformation rate the volume fraction of large domains and the large and small semiaxes of the ellipsoids are expressed as functions of volume fraction and shear rate/shear stress. The ability of the model to simulate actual behaviour is tested against quantitative…