Estimation of uncertainty in routine pH measurement

A procedure for estimation of measurement uncertainty of routine pH measurement (pH meter with two-point calibration, with or without automatic temperature compensation, combination glass electrode) based on the ISO method is presented. It is based on a mathematical model of pH measurement that involves nine input parameters. Altogether 14 components of uncertainty are identified and quantified. No single uncertainty estimate can be ascribed to a pH measurement procedure: the uncertainty of pH strongly depends on changes in experimental details and on the pH value itself. The uncertainty is the lowest near the isopotential point and in the center of the calibration line and can increase by a factor of 2 (depending on the details of the measurement procedure) when moving from around pH 7 to around pH 2 or 11. Therefore it is necessary to estimate the uncertainty separately for each measurement. For routine pH measurement the uncertainty cannot be significantly reduced by using more accurate standard solutions than ±0.02 pH units – the uncertainty improvement is small. A major problem in estimating the uncertainty of pH is the residual junction potential, which is almost impossible to take rigorously into account in the framework of a routine pH measurement.¹ Received: 11 August 2001 Accepted: 22 February 2002     

An automated monitoring system for VOC ozone precursors in ambient air: development,implementation and data analysis

An automated system for the monitoring of volatile organic compound (VOC) ozone precursors in ambient air is described. The measuring technique consists of subambient preconcentration on a cooled trap followed by thermal desorption and GC/FID analysis. First, the technical development, which permits detection limits below 0.05 ppbv to be reached, proceeded in two steps: (1) the determination of optimum sampling parameters (trap composition and conditioning, outlet split, desorption temperature); (2) the development of a reliable calibration method based on a highly accurate standard. Then, a 4-year field application of the hourly measuring chain was carried out at two urban sites. On the one hand, quality control procedures provided the best VOC identification (peak assignment) and quantification (reproducibility, blank system control). On the other hand, the success and performances of the routine experience (88% of the measurements covered more than 40 target compounds) indicated the high quality and suitability of the instrumentation which is actually applied in several French air quality monitoring networks. Finally, an example of data analysis is presented. Data handling identified important organic compound sources other than vehicle exhaust.     

济南地区表层土壤及沉积物中饱和烃分布特征及源解析

研究了济南地区不同功能区的表层土壤及沉积物中饱和烃的组成和分布特征,在此基础上初步分析了其来源.结果表明,饱和烃主要有正构烷烃、类异戊二烯、环烷烃等组成,正构烷烃碳数分布范围为n-C10-n-C34,类异戊二烯类主要是姥姣烷、植烷及甲基C13-C17烷等,同时还检出烷基环己烷,甾烷、三萜烷及藿烷等环烷烃.饱和烃总体含量分布为北高南低,北部化工区、高速入口处等饱和烃主要来源于原油或成品油等化石燃料及其燃烧产物;南部山区、水库沉积物及农田土壤等饱和烃主要来源于化石燃料的燃烧及高等植物.     

Production of low- and high-energy radioactive-ion beams by fragmentation

The physics opportunities made possible by beams of rare isotopes are among the richest available in nuclear science. The rare-isotope accelerator (RIA) now under development is an innovative accelerator that will define the state of the art for all such facilities. A novel aspect of the RIA project is the conversion of the most intense high-energy heavy-ion beams into both fast and reaccelerated exotic beams. Along with target fragmentation in next-generation high-power ISOL targets, RIA will use projectile fragmentation in a high-energy separator/gas-filled ion collector system to provide an extensive range of thermalized ions for reacceleration. In addition, a second high-energy separator will provide the same or larger range of ions for high-energy experiments. A brief overview of the RIA accelerator concept, the layout of the facility, and production techniques will be given along with information on the present R&D efforts in gaseous-ion collection. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: morrissey@nscl.msu.edu     

(Im-)possible ISOL beams

Refractory elements, i.e. elements with very high melting point and low vapor pressure, cannot be released in atomic form from an ISOL target. Therefore most of these elements are presently not available as ISOL beams. However, when reactive gases are introduced into the target, they may form volatile compounds with the refractory elements, allowing for an easier transport to the ion source. Particularly useful are high-temperature stable fluorides and oxides. By these chemical evaporation methods so far ISOL beams of the refractory elements C, Zr, Hf and Ta have been produced. We discuss how ISOL beams of B, Ti, Nb, Mo, Tc, Ru, W, Re, Os and Ir could be produced in a similar way.     

On-line production of neutron rich isotopes from uranium carbide targets

Experiments done using on-line mass separation of neutron-rich nuclei produced by 1 GeV proton beam on natural U by spallation reactions are performed to study the characteristics of different UCx targets. Special attention is devoted to reliably extract isotopic yields in case of complex decay schemes and to the valuation of release efficiency of some isotopic chains. New gamma-branching measuremet for ⁹²Rb are obtained. In addition, a formalism is developed to disantangle the contribution of β-decay in the target from direct production by fission and to provide more consistent data for the interpretation of release curves. Some results are shown for the Cs and Rb isotopic chains.     

Ochratoxin A non-conventional exposure sources — A review

Ochratoxin A (OTA) is one of the most studied mycotoxins, with great public health and agroeconomic significance. The exposure of both humans and animals to this fungal toxin has been associated to food matrices since its discovery. However, according to recent reports, OTA may also represent a potential airborne hazard, in water-damaged buildings, or occupational contamination, in workplaces with high mould exposure, such as agricultural, farm and alimentary industries. Further, in addition to the conventional studied food matrices, worldwide consumed, there are increasing reports on different and less obvious sources of alimentary exposure. These include traditional and home-made food products, highly consumed by specific groups of populations that thus might be at risk. This paper aims to spotlight the current knowledge on these non-conventional OTA exposure sources.     

Acoustic source terms study for non-isothermal flows using an aeroacoustic hybrid approach

This paper presents a numerical study of noise source term in non-isothermal flows in the context of an aeroacoustic hybrid technique at low Mach numbers. Asymptotic analysis applied to the fully compressible Navier–Stokes equations provides separated sets of equations for the dynamic of the flow and the production and propagation of acoustic waves. Comparisons with analytical dipole and quadrupole distributions are performed, confirming the dipole type of non-isothermal source distribution. This paper is a preliminary work for some more extensive studies on the topic. To cite this article: F. Golanski, C. Prax, C. R. Mecanique 333 (2005).     

Analytical model for thermal resistance due to multiple moving circular contacts on a coated bodyModèle analytique pour la résistance thermique due à des contacts circulaires mobiles multiples à la surface d'un solide revêtu

The heat transfer at the interface of two solids in sliding/rolling contact depends on the constriction phenomenon which occurs at the vicinity of asperities. In order to study this problem, the micro-contacts are represented by multiple moving circular heat sources on the surface of a body. The studied body is constituted of a substrate and a surface coating. The thermal constriction resistance due to those contacts is determined analytically in this paper. The solution is developed by using the integral Fourier transforms, and it is valid regardless of the velocity and the relative contact size values. To cite this article: A. Baïri, C. R. Mecanique 331 (2003).     

ISO spectroscopy: the study of low-mass star formation

Summary The current observational scenario pertaining to the study of low-mass star formation is discussed together with the evolutionary sequence that such a scenario seems to suggest. The opportunities offered by the spectrometers on board of the ISO satellite for improving our understanding of the involved physical processes are then discussed. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.