Concept and validation of a novel approach for producing large batches of reference material of ambient aerosols on filters

A novel method for preparing reference material of aerosol particulate matter (PM) on filters was developed by using the concept of very high volume, multiport sampling, and this was subsequently applied to produce more than 300 well-characterised units. The dedicated sampler built for this purpose features a 0.94-m-diameter, vacuum-tight main chamber with a total of 349 monitor ports, each holding a 37-mm-diameter, cellulose acetate–nitrate ester (CA) membrane filter with a nominal pore size of 0.8 m. At a pressure difference of about 130 hPa across the filter cassettes, the total initial air flow rate was 350 m³ h^–1 (1.0 m³ h^–1 per filter). Investigations into the variability of filter parameters showed that the flow resistance of CA filters is mostly determined by and proportional to their blank mass, with a mean uncertainty of about 5%. Total suspended particulate matter (TSP) was sampled for a total of 50 h using 349 selected filters with a relatively narrow spread in blank mass. The mean TSP mass per filter thus produced was 3.35 mg. Corrected for small differences in blank mass of the filters, the normalised aerosol masses per filter of 96% of the samples exhibited normal distributions with standard deviations of only 2.1 and 3.4%, depending on details of the normalisation procedure. Within the limits of the technique, a variation of aerosol mass with radial distance from the centre of the sampler is not clearly evident. The results provide evidence that the multiport approach allows large batches of particulate matter on filters to be produced in a reliable manner.     

Preparation,Homogeneity and Stability of Polar Pesticides in Freeze-Dried Water Interlaboratory Exercise

Abstract

An interlaboratory exercise was carried out to improve the state of the art of some polar pesticide determination in water (atrazine, simazine, carbaryl, propanil, linuron, fenamiphos and permethrin). The preparation, the homogeneity and the stability of freeze-dried water samples containing the above pesticides was studied. The final concentration of each pesticide in water was in the 50–80 μg.^?1 range with a salt content of 2.5 g.l^?1 of NaCl. After the lyophilization the residue was reho-mogenised, filled into amber glass bottles and stored at -20 °C and +20 °C. Every three months, one sample was analysed to verify the stability of the residue.

All pesticides were determined by high performance liquid chromatography with diode-array detection (HPLC-DAD) except permethrin which was determined by gas chromatography with electron capture detection (GC-ECD).

The results obtained show that the atrazine, carbaryl, propanil, linuron and fenamiphos samples were homogeneously distributed, whereas simazine and permethrin were not. With respect to the stability over three months, all pesticides were stable at ?20 °C. Atrazine, simazine, carbaryl, propanil and linuron are also stable for the maximum storage time at +20 °C but the concentration of fenamiphos decreased by about 70% after one month.

The results obtained in the interlaboratory study by the participants were in good agreement for many of the pesticides.     

Problems of traceability of total protein and catecholamine determinations in human urine

Some problems arising in the establishment of the traceabili- ty of the certified reference materi- al (CRM) CZ 6007a (total protein, creatinine and stress indicators) are discussed. Bovine serum albumin is recommended as a calibration standard for total protein determi- nation Received: 12 November 1999 Accepted: 16 August 2000     

Influence diagnostics in the varying coefficient model with longitudinal data

One or few observations can be highly influential on estimates of regression coefficients in the linear regression model. In this paper we derive influence diagnostics for the varying coefficients model with longitudinal data. We note that diagnostics in this context is quite different from the classical regression model in the sense that regression coefficients vary as time varies. A version of Cook’s distance is suggested to reflect this specific aspect of varying coefficient model. An algorithm to present some guidelines to determine influential observations deserving special attention is developed. An illustrative example based on the AIDS data is also given.     

Decentralized Adaptive Robust Tracking and Model Following for Large-Scale Systems Including Delayed State Perturbations in the Interconnections

The problem of decentralized robust tracking and model following is considered for a class of uncertain large-scale systems including delayed state perturbations in the interconnections. In this paper, it is assumed that the upper bounds of the delayed state perturbations, uncertainties, and external disturbances are unknown. A modified adaptation law with σ-modification is introduced to estimate such unknown bounds, and on the basis of the updated values of these unknown bounds, a class of decentralized local memoryless state feedback controllers is constructed for robust tracking of dynamical signals. The proposed decentralized adaptive robust tracking controllers can guarantee that the tracking errors between each time-delay subsystem and the corresponding local reference model without time-delay decrease uniformly asymptotically to zero. Finally, a numerical example is given to demonstrate the validity of the results.     

Cobalt thin films on gold: A new reference material for the quantification of cobalt phthalocyanine and cobalt porphyrin modified gold electrodes with synchrotron radiation micro X-ray fluorescence spectroscopy

New reference materials consisting of cobalt thin films on gold were prepared by sputter deposition. The thickness and homogeneity of the films were characterized using synchrotron radiation micro-XRF. The samples can be used as reference materials to quantify cobalt phthalocyanine and cobalt porphyrin modified gold electrodes which have been analyzed with synchrotron radiation micro-XRF.     

Design and Performance of an AlGaN-Based p-i-n Ultraviolet Photodetector

An AlGaN-based back-illuminated ultra- violet p-i-n detector is designed and its performance is analysed both simulately and experimentally. The width of p- and i-regions has been optimized to the best theoretic values. It is indicated that the changing of responsivity with increase of bias can not be attributed to the expansion of depletion layer as it is believed, but to two reasons: 1) the effect of GaN/AlGaN heterojunction barrier to block the electrons decreases with higher bias and 2) the recombination rate of excess carriers decreases due to the building up of an electric field in depletion region. At zero bias, the simulated responsivity reaches its maximum of 0.12 A/W with quantum efficiency of 55.1%. The measured peak responsivity is more than 0.09 A/W with quantum efficiency greater than 41.6%. The experimental data are almost consistent with the results of the simulation.     

Some remarks on Bayesian inference for one-way ANOVA models

We consider the standard one-way ANOVA model; it is well-known that classical statistical procedures are based on a scalar non-centrality parameter. In this paper we explore both marginal likelihood and integrated likelihood functions for this parameter and we show that they exactly lead to the same answer. On the other hand, we prove that a fully Bayesian testing procedure may provide different conclusions, depending on what is considered to be the real quantity of interest in the model or, said differently, which are the competing hypotheses. We illustrate these issues via a real data example.     

KEF Reference Model 205／2音箱

虽然我们仍然习惯于以“新Reference”来形容KEF的这一旗舰系列，但实际上大家都知道，那是2007年的产品了。好在，Hi—Fi音响与手机、数码相机等快速消费品有所不同，厂家的升级换代通常都至少需要一年以上的间隔。对于Hi—End器材，有时更是“十年磨一剑”。多半，要等上三五年才会见到有新款面世。更有甚者，真的可能需要花上10年功夫来完成。那么，这个“新”又来自哪里呢？其实，这是相对旧款Reference系列而言的。     

Gradient of reference difference based matching algorithm for image feature point

During matching on feature point, gray correlation matching technology is utilized to extract multi-peaks as a coarse matching set. A pair of given corresponding reference points within the left and right images is used to calculate gradients of reference difference between the reference points and each feature point within the multi-peaks set. The unique correspondence is determined by criterion of minimal gradients of reference difference. The obtained correspondence is taken as a new pair of reference points to update the reference points continuously until all feature points in the left (or right) image being matched with the right (or left) image. The gradients of reference difference can be calculated easily by means of pre-setting a pair of obvious feature points in the left and right images as a pair of corresponding reference points. Besides,the efficiency of matching can be improved greatly by taking the obtained matching point as a new pair of reference points, and by updating the reference point continuously. It is proved that the proposed algorithm is valid and reliable by 3D reconstruction on two pairs of actual natural images with abundant and weak texture, respectively.