Search results for "INDEX"
showing 10 items of 5395 documents
High Plasma Concentration of Non-Esterified Polyunsaturated Fatty Acids Is a Specific Feature of Severe COVID-19 Pneumonia
2020
Background: The pathogenesis of severe COVID-19 is frequently associated with an uncontrolled inflammatory response. Severe forms of COVID-19 appear to be more frequent in obese patients, but an association with metabolic disorders is not established. Here, we focused on lipoprotein metabolism in patients hospitalized for severe pneumonia, depending on COVID-19 status. Methods: Thirty-four non-COVID-19 and 27 COVID-19 patients with severe pneumonia were enrolled. Most of them required intensive care. Plasma lipid levels, lipoprotein metabolism, and clinical and biological features were assessed. Findings: Despite similar initial metabolic comorbidities and respiratory severity, COVID-19 pat…
Static measurements of refractive index increments at 633 nm with a modified refractive index detector
1985
A R 401 Waters Assoc. differential refractometer has been modified to obtain the variation of refractive index increments, dn/dc, of polymer solutions at 633 nm. The introduced modifications were in the sample injection system and in the light source. The performance of the modified refractometer both with aqueous and organic solutions is analyzed. In order to localize a conformational transition in lysozyme, the dependence of dn/dc on temperature for lysozyme solutions in phosphate buffer is studied. Similarly, (dn/dc)k values for the ternary n-alkane/butanone/poly(dimethyl siloxane) systems over the whole composition range of the binary solvent mixtures are evaluated.
Gas-liquid chromatography and lipophilicity of esters of benzoic acids
1987
Abstract The use of gas-liquid chromatographic (GLC) retention indices for the determination of lipophilicity was studied for a series of alkyl and arylalkyl esters of substituted benzoic acids. The regression relationships between the logarithms of the partition coefficients and the retention characteristics measured on two cpillary columns, SE-30 and OV-351, were evaluated. The behaviour of arylalkyl esters and of alkyl esters cannot be expressed in terms of a single regression equation. This is probably a consequence of the effect of the intramolecular hydrophobic interaction upon the retention of arylalkyl esters under GLC conditions. An analysis of the isokinetic relationships revealed…
Determination of indoor air quality of a phytosanitary plant.
2011
A new methodology has been developed to determine volatile organic compounds (VOCs) and pesticides in ambient air using membrane based devices as passive samplers. Pesticides were determined by gas chromatography with mass spectrometry detection (GC-MS) after their microwave-assisted extraction (MAE) from the passive sampler and the required clean-up. On the other hand, VOCs were also caught with the same samplers and directly determined by head space (HS) coupled to GC-MS. The use of samplers filled with florisil and activated carbon allows us to catch with a simple device both, VOCs and pesticides, with a high vapor pressure. Results obtained in the deployment of samplers in different sit…
Gas chromatography of homologous esters
1984
Abstract The gas chromatographic retention behaviour of the butanoyl and 2-, 3- and 4-chlorobutanoyl esters of C 3 —C 5 saturated aliphatic branched-chain and unsaturated C 3 —C 6 alcohols on SE-30 and OV-351 glass capillary columns operated iso-thermally at several temperatures is reported. Retention index increments at 80, 120 and 160°C show the effects of chain branching and the olefinic and acetylenic unsaturation in the alkyl chain and the effect of the position of the chlorine substituent in the acyl chain. The results are compared with the behaviour of the corresponding n -alkyl esters and the chlorinated propanoyl esters.
Gaschromatographisch-massenspektrometrische identifizierung der durch umsetzung von aminen mit isocyanaten gebildeten harnstoffderivate
1977
Abstract Gas chromatographic-mass spectrometric identification of urea derivatives formed by the reaction of amines with isocyanates N,N′-Di- and N,N′,N′-trisubstituted ureas constitute suitable derivatives for the gas chromatographic (GC) determination of primary and secondary amines. The GC identification of N- tert. -butyl-,N′,N′-alkyl urea derivatives presented in the first communication has been succesfully confirmed by mass spectrometry (MS) and mass fragmentometry. The reproduced mass spectra of six N- tert. -butyl-,N′,N′-alkyl ureas were interpreted according to the decomposition mechanisms of less complicated alkyl ureas known from the literature. Using combined GC-MS the detection…
Allylated cyclodextrins as effective affinity materials in chemical sensing of volatile aromatic hydrocarbons using an optical planar Bragg grating s…
2013
We report on the application of perallyl-substituted α-, β- and γ-cyclodextrins to an optical planar Bragg grating refractive index sensor for the effective sensitization of the sensor for airborne volatile aromatic hydrocarbons. Thereby, the emphasis of this work lies on the comparison of the different cyclodextrin types regarding their suitability as affinity material assessed by the sensors sensitivity and response behavior. The opto-chemical sensor device showed an immediate and quick response to the application of the investigated analytes benzene, toluene and m-xylene as well as a linear dependence on the concentration of those analytes. Studies on the sensors sensitivity depending on…
Infrared spectroscopy on lead silicate glass
1993
The reflectance spectra of some lead silicate glasses of general formula (PbO)x(SiO2)y have been measured in the infrared frequency range from 50 to 4000 cm−1. The dispersion and absorption spectra in the range 50–2000 cm−1 have been calculated from the reflectance data using the Kramers-Kronig relations. The band at ∼ 135 cm−1 is assigned to the stretching vibration of lead-oxygen bonds. The shoulder band of the silicon-oxygen stretching mode at ∼900 cm−1 shows a weak coupling of those bonds to the Pb2+ modifier. The vibration strength of those bands shows that the number of the Pb2+ modifier increases first up approximately to 50 Mol% with the increase of PbO content and then decreases ra…
Hybrid silicon on insulator/polymer electro-optical intensity modulator operating at 780 nm
2014
Currently inorganic materials prevail as the nonlinear active medium for light modulation in electro-optical (EO) device technology. A recent promising trend is to consider organic nonlinear optical materials for application in EO modulators due to their multiple advantages including low costs and high EO coefficients. In this paper, we proposed a new type of polymer EO modulator whose fabrication is compatible with the currently used silicon on insulator technology. Our numerical optimization of the proposed structure demonstrates that it is theoretically possible to achieve a half-wave voltage as low as 1.56 V for a 1 cm long modulator structure operating at 780 nm. Based on the results o…
Effect of stress and temperature on the thermomechanical degradation of a PE-LD/OMMT nanocomposites
2014
Thermomechanical degradation of nanocomposites is a topical issue that has not been fully investigated as demonstrated by the low number of papers available in the literature regarding this spe- cific aspect. In particular, with regards to low density polyethylene/clay nanocomposites, the degrada- tion behavior is very complex since it involves the degradation paths of both the polymer matrix and the organomodified nanoclay. In the present work, the effects of mechanical stress and temperature on the thermomechanical behavior of PE-LD/organomodified clay nanocomposites and the degradation paths were investigated by rheological, FT-IR and mechanical methods. The results have shown that the t…