Search results for "Rite"
showing 10 items of 2726 documents
A clean method for flow injection spectrophotometric determination of cyclamate in table sweeteners
2005
Abstract A flow system based on the multicommutation is proposed for fast and clean determination of cyclamate. The procedure exploits the reaction of cyclamate with nitrite in acidic medium and the spectrophotometric determination of the excess of nitrite by iodometry. The flow system was designed with a set of solenoid micro-pumps to minimize reagent consumption and waste generation. The detection limit was estimated as 30 μmol L −1 (99.7% confidence level) with linear response ranging up to 3.0 mmol L −1 . The coefficient of variation was estimated as 1.7% for a solution containing 2.0 mmol L −1 cyclamate ( n = 20). About 60 samples can be analyzed per hour, consuming only 3 mg KI and 1…
Flow injection biamperometric determination of chloramphenicol and related nitro compounds by on-line chemical photodegradation
2000
Abstract An unsegmented continuous-flow assembly for the determination of chloramphenicol is proposed. The determination is based on the on-line photodegradation of the drug in an NH4+/NH3 buffer at pH 10.4 by using a photoreactor consisting of a 697 cm long × 0.8 mm ID piece of PTFE tubing coiled around an 8 W low-pressure mercury lamp. Photodegraded chloramphenicol is detected by photolytic cleavage of nitrite from the parent compound as well as by organic oxidizing photofragments, and their subsequent reaction with iodide ion, which is monitored biamperometrically. Triiodide thus formed is detected in excess iodide solution by polarizing two platinum electrodes at 100 mV. The calibration…
Indirect spectrophotometric determination of p-aminobenzoic acid in sunscreen formulations by sequential injection analysis
2003
Abstract A simple indirect sequential injection spectrophotometric method for the determination of the UV-filter p -aminobenzoic acid (PABA) in sunscreen formulations is proposed. The determination is based on the reaction of PABA with hypochlorite in acidic medium and the subsequent measurement of the residual chlorine by using the well-known reaction with o -tolidine. The experimental variables involved in the sequential injection analysis (SIA) system (sandwich arrangement, volumes of sample and reagents, propulsion flow rate, reaction coil length) and adequate concentrations of reagents were studied. The SIA method has a linear range up to 20 μg ml −1 (3 s y / x / b detection limit) of …
Determination of sulphonamides in human urine by azo dye precolumn derivatization and micellar liquid chromatography
1995
Abstract A high-performance liquid chromatographic method for the determination of sulphonamides in urine is reported. The drugs (sulphadiazine, sulphaguanidine, sulphamethizole, sulphamethoxazole, and sulphathiazole) were diazotized with nitrite and coupled with N-(1-naphthyl)ethylenediamine dihydrochloride in a sodium dodecyl sulphate (SDS) micellar medium. Separation of the sulphonamide azo dyes was performed on a C18 column with a 0.05 M SDS-2.4% pentanol mobile phase, which permitted the direct injection of the urine samples. The limits of detection were in the 0.1–0.3 μg/ml range.
Geographical Distribution of Cardiovascular Mortality in Comunidad Valenciana (Spain)
2002
Comunidad Valenciana is one of the seventeen autonomous regions into which Spain is divided. It is located on the east coast of Spain, next to the Mediterranean sea, with an area of 23,255 km2 and with 4,009,329 inhabitants in 1996. From an administrative point of view there are three levels of aggregation: provinces (3 units), health areas (20 units) and municipalities (541 units).
The Effective Sample Size
2013
Model selection procedures often depend explicitly on the sample size n of the experiment. One example is the Bayesian information criterion (BIC) criterion and another is the use of Zellner–Siow priors in Bayesian model selection. Sample size is well-defined if one has i.i.d real observations, but is not well-defined for vector observations or in non-i.i.d. settings; extensions of critera such as BIC to such settings thus requires a definition of effective sample size that applies also in such cases. A definition of effective sample size that applies to fairly general linear models is proposed and illustrated in a variety of situations. The definition is also used to propose a suitable ‘sc…
Contemporary practice and technical aspects in coronary intervention with bioresorbable scaffolds : a European perspective
2015
Aims Next to patient characteristics, the lack of a standardised approach for bioresorbable vascular scaffold (BVS) implantation is perceived as a potential explanation for the heterogeneous results reported so far. To provide some guidance, we sought to find a consensus on the best practices for BVS implantation and management across a broad array of patient and lesion scenarios. Methods and results Fourteen European centres with a high volume of BVS procedures combined their efforts in an informal collaboration. To get the most objective snapshot of different practices among the participating centres, a survey with 45 multiple choice questions was prepared and conducted. The results of th…
Hidden Markov random field model and Broyden–Fletcher–Goldfarb–Shanno algorithm for brain image segmentation
2018
International audience; Many routine medical examinations produce images of patients suffering from various pathologies. With the huge number of medical images, the manual analysis and interpretation became a tedious task. Thus, automatic image segmentation became essential for diagnosis assistance. Segmentation consists in dividing the image into homogeneous and significant regions. We focus on hidden Markov random fields referred to as HMRF to model the problem of segmentation. This modelisation leads to a classical function minimisation problem. Broyden-Fletcher-Goldfarb-Shanno algorithm referred to as BFGS is one of the most powerful methods to solve unconstrained optimisation problem. …
Low-pressure ferroelastic phase transition in rutile-type AX2 minerals: cassiterite (SnO2), pyrolusite (MnO2) and sellaite (MgF2)
2019
The structural behaviour of cassiterite (SnO2), pyrolusite (MnO2) and sellaite (MgF2), i.e. AX2-minerals, has been investigated at room temperature by in situ high-pressure single-crystal diffraction, up to 14 GPa, using a diamond anvil cell. Such minerals undergo a ferroelastic phase transition, from rutile-like structure (SG: P42/mnm) to CaCl2-like structure (SG: Pnnm), at ≈ 10.25, 4.05 and 4.80 GPa, respectively. The structural evolution under pressure has been described by the trends of some structure parameters that are other than zero in the region of the low-symmetry phase’s stability. In particular, three tilting-angles (ω, ω′, ABS) and the metric distortion of the cation-centred oc…
Structural and vibrational properties of CdAl2S4 under high pressure: Experimental and theoretical approach
2014
The behavior of defect chalcopyrite CdAl2S4 at high pressures and ambient temperature has been investigated in a joint experimental and theoretical study. High-pressure X-ray diffraction and Raman scattering measurements were complemented with theoretical ab initio calculations. The equation of state and pressure dependences of the structural parameters of CdAl2S4 were determined and compared to those of other AB(2)X(4) ordered-vacancy compounds. The pressure dependence of the Raman-active mode frequencies is reported, as well as the theoretical phonon dispersion curves and phonon density of states at 1 atm. Our measurements suggest that defect chalcopyrite CdAl2S4 undergoes a phase transit…