Isotopic measurements of uranium using inductively coupled plasma cavity ringdown spectroscopy

Inductively coupled plasma cavity ringdown spectroscopy (ICP-CRDS) is applied to isotopic measurements of uranium. We have successfully obtained the isotopic-resolved spectra of uranium at three different atomic/ionic transition lines, 286.57, 358.49, and 409.01 nm. Of the three lines, the largest isotope shift of approximately 9 pm was measured at the 286.57 ionic line. Isotopic-resolved spectra were recorded in ratio of 1:1 (235U/238U, 2.5 micrograms/mL) and at the natural abundance ratio of 0.714% (235U/238U, 1.25 micrograms/mL 235U). The smallest measurable isotope shift of approximately 3 pm was determined for the 409.01 nm ion spectral line. Detection limits (DL) were obtained under optimized ICP operating conditions to be in the range of 70-150 ng/mL, except for the 238U component of the 286.57 nm line (300 ng/mL). This latter result was determined to be due to a strong, previously unreported, absorption interference from the argon plasma. The 235U isotope component (DL 70 ng/mL) was found to be unaffected. This work demonstrates the applicability of ICP-CRDS for uranium isotopic measurements. The potential of development of a field-deployable, on-line uranium isotope monitor using plasma-CRDS is discussed.     

Authentication and Authorization Mechanisms for Multi-Domain Grid Environments

This article discusses the authentication and the authorization aspects of security in grid environments spanning multiple administrative domains. Achievements in these areas are presented using the EU DataGrid project as an example implementation. It also gives an outlook on future directions of development.     

Bayesian relevance feedback for content-based image retrieval

Despite the efforts to reduce the so-called semantic gap between the user's perception of image similarity and the feature-based representation of images, the interaction with the user remains fundamental to improve performances of content-based image retrieval systems. To this end, relevance feedback mechanisms are adopted to refine image-based queries by asking users to mark the set of images retrieved in a neighbourhood of the query as being relevant or not. In this paper, the Bayesian decision theory is used to estimate the boundary between relevant and non-relevant images. Then, a new query is computed whose neighbourhood is likely to fall in a region of the feature space containing relevant images. The performances of the proposed query shifting method have been compared with those of other relevance feedback mechanisms described in the literature. Reported results show the superiority of the proposed method.     

Monitoring forest conditions in a protected Mediterranean coastal area by the analysis of multiyear NDVI data

The operational utilization of remote sensing techniques for monitoring terrestrial ecosystems is often constrained by problems of under-sampling in space and time, particularly in heterogeneous and unstable Mediterranean environments. The current work deals with the use of the NOAA-AVHRR and Landsat-TM/ETM+ images to produce long-term NDVI data series characterising coniferous and broadleaved forests in a protected coastal area in Tuscany (Central Italy). Two methods to extract NDVI values of relatively small vegetated areas from NOAA-AVHRR data were first evaluated by comparison to estimates from higher resolution Landsat-TM/ETM+images. The optimal method was then applied to multitemporal AVHRR data series to derive 10-day NDVI profiles of coniferous and broadleaved forests over a 15-year period (1986-2000). Trend analyses performed on these data series showed that notable NDVI decreases occurred during the study period, particularly for the coniferous forest in summer and early fall. Further analysis carried out on local meteorological measurements led to identify the likely causes of these negative trends in contemporaneous winter rainfall decreases which were significantly correlated with the found NDVI variations.     

Notes on theory and experimental conditions behind two-photon excitation microscopy

This report deals with the fundamental quantum physics behind two-photon excitation also providing a link to the experimental consequences exploited in microscopy. The optical sectioning effect is demonstrated as well as the distribution of excitation and of fluorescence emission.     

Assay of Sudan I contamination of foodstuff by atmospheric pressure chemical ionization tandem mass spectrometry and isotope dilution

Food safety represents one of the main issues of national and international agencies appointed to health control. In April 2003, a French agency disclosed that powdered or smashed hot chili pepper imported from India and Pakistan was heavily contaminated with a carcinogenic azo dye known as Sudan I. This paper deals with a modern approach for assaying the content of this colorant in foodstuff down to a limit of a few tens of parts per billion. The isotope dilution method combined with APCI tandem mass spectrometry was used. The internal standard, 1-(d5-phenylazo)-2-naphthalenol, was obtained by simple chemistry, and its structure was determined by 1H NMR spectroscopy. The mass spectrometric method is more sensitive than the HPLC approach by a factor of 20.     

A note on the identification of Rupicapra rupicapra species by polymerase chain reaction product sequencing

To identify meat samples suspected of containing a protected game species (Chamois-Rupicapra rupicapra) Polymerase Chain Reaction (PCR) product sequencing was performed. The amplicon was obtained with a pair of "universal" primers. The results confirm those of Isoelectric Focusing (IEF) on the same samples.     

Measurements of OH radicals in a low-power atmospheric inductively coupled plasma by cavity ringdown spectroscopy

Cavity ringdown spectroscopy is applied to line-of-sight measurements of OH radicals in an atmospheric-pressure argon inductively coupled plasma, operating at low power (200 W) and low gas flows (approximately 18 liters/min). Density populations of the single S21(1) rotational line in the OH A2sigma(+)-X2Pi (0-0) band are extracted from the measured line-of-sight absorbance. Plasma gas kinetic temperatures, derived from the recorded line shapes of the S21(1) line, ranged from 1858 to 2000 K with an average uncertainty of 10%. Assuming local thermodynamic equilibrium, an assumption supported by the comparison of the experimental and simulated spectra, the spatially averaged total OH number density at different observation heights was determined to be in the range of 1.7 x 10(20)-8.5 x 10(20) (m(-3)) with the highest OH density in the plasma tail. This work demonstrates that ringdown spectra of the OH radical may be used both as a thermometer for high-temperature environments and as a diagnostic tool to probe the thermodynamic properties of plasmas.     

Fusion of appearance-based face recognition algorithms

Although many algorithms have been proposed, face recognition and verification systems can guarantee a good level of performances only for controlled environments. In order to improve the performance and robustness of face recognition and verification systems, multi-modal and mono-modal systems based on the fusion of multiple recognisers using different or similar biometrics have been proposed, especially for verification purposes. In this paper, a recognition and verification system based on the combination of two well-known appearance-based representations of the face, namely, principal component analysis (PCA) and linear discriminant analysis (LDA), is proposed. Both PCA and LDA are used as feature extractors from frontal view images. The benefits of such a fusion are shown for different environmental conditions, namely, ideal conditions, characterised by a very limited variability of environmental parameters, and real conditions with a large variability of lighting, scale and facial expression.