Analysis of volatile contaminants in vegetable oils by headspace solid-phase microextraction with carboxen-based fibres

The headspace solid-phase microextraction (HS-SPME) efficiencies from vegetable oil of the recently available Carboxen-poly(dimethylsiloxane) (PDMS) and divinylbenzene-Carboxen-PDMS fibres were found to be much greater than those of the PDMS fibre for a number of volatile contaminants. Using these Carboxen-based fibres, the commonly used HS-SPME equilibration times for aqueous matrices of 30-45 min at room temperature for a number of halogenated and aromatic analytes with volatilities ranging from 1,1-dichloroethylene to hexachlorobenzene were found to be insufficient for the effective extraction of the less volatile analytes from vegetable oil. HS-SPME at 100 degrees C for 45 min, followed by rapid cooling to 0 degrees C with a 10 min continuing extraction, however, significantly increased the SPME efficiencies for the less volatile analytes. Spiking solutions were prepared in vegetable oil instead of methanol as the latter was found to displace analytes from the Carboxen material. Using either of the Carboxen-based fibres and SPME at 100 degrees C, all the target analytes could be determined at low or sub-microg kg(-1) with repeatability < or =10%, even though an equilibrium SPME of the less volatile analytes was not achieved.     

Compleximetric determination of calcium in impure calcium carbonate and limestone

Calcium is determined in impure calcium carbonate and limestone samples by titrating with 0.01 M disodium EGTA at pH 12 in the presence of at least 0.6 mg of magnesium and a maximum of 500 μg of iron(III), using a pH 12.5 sodium hydroxide-potassium cyanide-sodium sulfide buffer and Calcon indicator. The results of such titrations are compared with those obtained by titrating at pH 10 the calcium perchlorate solutions derived from calcium oxalate, and with those of a modified LEWIS AND MELNICK method. The results for magnesium (% MgO) obtained by difference are in fair agreement. Magnesium can be titrated compleximetrically as magnesium perchlorate, but the reagent blank must be determined.     

Gamma-ray spectroscopy of 192–195Po

Prompt and delayed γ-rays have been observed from very neutron deficient ^192–195Po nuclei by using the recoil-decay tagging (RDT) and recoil gating techniques. The yrast levels up to the (10⁺) state in the ¹⁹²Po were identified for the first time. Comprehensive data for ¹⁹⁴Po rendered it possible to extend the yrast line and to observe several positive and negative parity non-yrast states. In the odd-mass isotopes ¹⁹³Po and ¹⁹⁵Po, favoured and unfavoured states on top of the 13/2⁺ state have been identified. The results are discussed within the simple vibrator and rotor pictures as well as in the framework of coexisting spherical and deformed-intruder structures. Received: 5 July 1999 / Revised version: 7 September 1999     

Infrared imagery of an air/CO2 axisymmetric jet

This experiment uses an infrared imaging system to investigate a subsonic, non-isoenergetic, air/CO₂ axisymmetric jet. The classical limitations of using IR imagery with hot gases are presented and a novel approach to overcome these limitations is proposed. The results suggest that radial and axial irradiant profiles measured with the IR imager, when non-dimensionalized, collapse onto curves of similarity. This behavior could allow temperature, velocity, and concentration profiles to be deduced from the IR image.     

First observation of excited states in 184Pb: spectroscopy beyond the neutron mid-shell

Excited states have been identified for the first time in ¹⁸⁴Pb, the first even-even Pb isotope beyond the 82 < N < 126 mid-shell, using the recoil-decay tagging (RDT) technique. A collective band built on the first-excited 2⁺ state has been observed. This resembles those seen in ^186,188Pb and the Hg isotones, and can thus be associated with a prolate-deformed shape. Variable moment of inertia (VMI) fits of the prolate 0⁺ level energies in ^184,186,188Pb indicate that the minimum appears at N= 103, the same neutron number at which the corresponding minimum in Hg isotopes is observed. Received: 19 May 1998 / Revised version: 1 July 1998     

On atomization of uranium in plutonium matrix using ETA-AAS

Atomization processes for uranium in aqueous media and in the presence of a plutonium matrix have been studied and a chemical mechanism is proposed. These studies have been utilized for the determination of uranium in plutonium by Electrothermal Atomization- Atomic Absorption Spectrometry (ETA-AAS) within the constraints of its stable carbide forming tendency and complexity caused by formation of plutonium suboxide at high temperatures. In spite of these limitations the analytical range obtained for determination of uranium is 2.5–100 ng with a sample aliquot of 5 μL containing 5 mg/mL plutonium concentration. The precision of the method is evaluated as 9% RSD. Received: 9 September 1997 / Revised: 29 December 1997 / Accepted: 31 December 1997     

In-beam gamma-ray spectroscopy of 190, 197Po

γ -ray transitions in the neutron-deficient nuclei ^{190, 197}Po have been identified using the JUROGAM Ge detector array coupled to the RITU gas-filled separator and the GREAT spectrometer. The yrast band of ¹⁹⁰Po has been firmly established through γ -γ coincidences and extended up to a spin and parity of 14⁺. It displays similar behaviour to its isotones ¹⁸⁶Hg and ¹⁸⁸Pb above the 4⁺ level, thus confirming its prolate nature. In ¹⁹⁷Po the band built upon the 13/2⁺ isomer has been extended up to a spin and parity of 33/2⁺, while the non-yrast band has been observed for the first time. The behaviour of ¹⁹⁷Po is found to be similar to that of the nearby even-mass isotopes, which is consistent with the model in which the i _13/2 neutron is weakly coupled to the states in the even-even core.     

3D reconstruction of road surfaces using an integrated multi-sensory approach

In this paper, we present our experience in building a mobile imaging system that incorporates multi-modality sensors for road surface mapping and inspection applications. Our proposed system leverages 3D laser-range sensors, video cameras, global positioning systems (GPS) and inertial measurement units (IMU) towards the generation of photo-realistic, geometrically accurate, geo-referenced 3D models of road surfaces. Based on our summary of the state-of-the-art systems for a road distress survey, we identify several challenges in the real-time deployment, integration and visualization of the multi-sensor data. Then, we present our data acquisition and processing algorithms as a novel two-stage automation procedure that can meet the accuracy requirements with real-time performance. We provide algorithms for 3D surface reconstruction to process the raw data and deliver detail preserving 3D models that possess accurate depth information for characterization and visualization of cracks as a significant improvement over contemporary commercial video-based vision systems.     

New Einstein-Sasaki spaces in five and higher dimensions

We obtain infinite classes of new Einstein-Sasaki metrics on complete and nonsingular manifolds. They arise, after Euclideanization, from BPS limits of the rotating Kerr-de Sitter black hole metrics. The new Einstein-Sasaki spaces L(p,q,r) in five dimensions have cohomogeneity 2 and U(1) x U(1) x U(1) isometry group. They are topologically S(2) x S(3). Their AdS/CFT duals describe quiver theories on the four-dimensional boundary of AdS(5). We also obtain new Einstein-Sasaki spaces of cohomogeneity n in all odd dimensions D = 2n + 1 > or = 5, with U(1)(n + 1) isometry.