Ultraviolet discharges from a radio-frequency system for potential biological/chemical applications

In this work, we describe a new electrode-less radio-frequency(RF) excitation technique for generating excimers in the vacuum ultraviolet(VUV) and ultraviolet(UV) spectral regions for potential biological/chemical applications. Spectra data of Xe~*_2, XeI~*, and KrI~* generated by this new technique are presented. Optical efficiency of the lamp system ranges from 3% to 6% for KrI~*, 7% to 13% for XeI~*, and 15% to 20% for Xe~*_2. Also, results of irradiating E-coli with XeI~*discharge from this lamp system is presented to show one of the promising applications of such electrode-less apparatus.This new RF lamp system offers an interesting addition to the already existing technologies for generating VUV and UV light for various biological, physical, and chemical processes especially those requiring large area for high productivity.     

Topology-Preserving Geodesic Active Contours for Segmentation of High Content Fluorescent Cellular Images

In this paper a method for segmentation of fluorescent cellular images is introduced, which uses geodesic active contours. After segmentation of the nuclei by a thresholding algorithm, the appropriate whole cells are detected by inflation of the nuclei masks and gradient information. Because the implicit level set formulation provides topological changes and the topology of the nuclei and the whole cells is equal, a topology–preserving modification is necessary. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Particle tracking velocimetry of the flow field around a collapsing cavitation bubble

The velocity field in the vicinity of a laser-generated cavitation bubble in water is investigated by means of particle tracking velocimetry (PTV). Two situations are explored: a bubble collapsing spherically and a bubble collapsing aspherically near a rigid wall. In the first case, the accuracy of the PTV method is assessed by comparing the experimental data with the flow field around the bubble as obtained from numerical simulations of the radial bubble dynamics. The numerical results are matched to the experimental radius–time curve extracted from high-speed photographs by tuning the model parameters. Trajectories of tracer particles are calculated and used to model the experimental process of the PTV measurement. For the second case of a bubble collapsing near a rigid wall, both the bubble shape and the velocity distribution in the fluid around the bubble are measured for different standoff parameters γ at several instants in time. The results for γ > 1 are compared with the corresponding results of a boundary-integral simulation. For both cases, good agreement between simulation and experiment is found.     

Kinetic study of semifluorinated arylene vinylene ether polymers

Fluorinated arylene vinylene ether (FAVE) polymers were prepared from the base‐promoted addition of commercial 2,2‐bis(4‐hydroxyphenyl)hexafluoropropane (6F bisphenol A) to aryl trifluorovinyl ether (TFVE), 2,2′‐bis(4‐trifluorovinyloxybiphenyl)‐1,1,1,3,3,3‐hexafluoropropane. The step‐growth polymerization kinetics by using stoichiometric NaH and catalytic Cs₂CO₃ were investigated by monitoring the ¹⁹F NMR signals of the aryl TFVEs. The nth order kinetic model was used to determine rate constants over a series of programmed temperatures. Polymerization using stoichiometric NaH resulted in second‐order kinetics with an activation energy of 59 kJ/mol. This model kinetic study provided insight into the mechanistic pathways of the FAVE polymer system that has recently shown a lot of interest in many areas of materials science. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Experimental investigation of steel spheres as a passive enhancement technique for flash boiling of HCFC-22

An experimental investigation was conducted to study the influence of a layer of 3.6-mm-diameter steel spheres on the mass flow during flash boiling in a glass pressure vessel. It was observed that the steel spheres added numerous heterogeneous nucleation sites within the liquid and promoted abundant vapor bubble growth during depressurization. The steel spheres were in contact with each other and with the interior of the glass vessel. The data from these experiments were compared with baseline experimental results primarily with regard to the mass flow. Each test was run for 60 s, using controlled variables of orifice diameters (1.59 and 5.56 mm), initial refrigerant amounts (0.23, 0.45, and 0.68 kg), initial pressures (575 and 840 kPa), and vessel geometries (665 and 1110 ml). Pressures, temperatures, and mass flow rates, along with calculated saturation temperatures, amount of superheat, mass flux, and total mass flashed, were used to compare the baseline experiments with the enhanced boiling method. Results showed an increase in the total mass flashed at each test condition, ranging from an average of 22% to 81% with respect to baseline experiments.     

Electronic spectroscopy of the previously unknown arsenic carbide (AsC) free radical

The previously unknown arsenic carbide (AsC) free radical has been identified in the gas phase through a combination of laser-induced fluorescence (LIF), single vibronic level emission, and stimulated emission pumping (SEP) spectroscopy in a supersonic expansion. The As(12)C and As(13)C isotopologues have been detected as products of an electric discharge in mixtures of arsine (AsH(3)) and carbon dioxide ((12)CO(2) or (13)CO(2)) in high pressure argon. The B (2)Σ(+)-X (2)Σ(+) band system was recorded by LIF spectroscopy and emission transitions from the B state down to the ground state and to the low-lying A (2)Π(i) state were observed. High resolution studies of the B-X 0-0 band by LIF and the B-A 0-0 band by SEP spectroscopy enabled a determination of the molecular structures in the three states. Although CN, CP, and AsC have similar X (2)Σ(+) and A (2)Π(i) states, the B (2)Σ(+) state molecular orbital configuration of CP and AsC differs from that of the CN free radical.     

Heavy atom nitroxyl radicals. V. An experimental and ab initio study of the previously unknown H2PS free radical

The B?(2)A(')-X?(2)A(') transition of the prototypical thiophosphoryl radical, H(2)PS, was observed for the first time using laser-induced fluorescence and single vibronic level emission spectroscopy. H(2)PS and its deuterated isotopologues, D(2)PS and HDPS, were produced in a pulsed supersonic discharge jet from a precursor mixture of Cl(3)PS and H(2) or D(2) or an H(2)/D(2) mixture in high-pressure argon. High level ab initio calculations of the lowest three doublet electronic states helped in the definitive assignment of the B?-X? transition, which involves electron promotion from the π to the π? orbital. Vibrational frequencies were determined for several modes of each isotopologue in the X? and B? states and found to be in accord with theoretical predictions. Although a line-by-line rotational analysis was not possible, the observed band contours are consistent with the geometries obtained from our ab initio calculations. Theory indicates that PS bond length increases upon electronic excitation, while the pyramidalization of the radical does not change significantly.     

The electronic spectrum of the previously unknown HAsO transient molecule

The A?(1)A(')-X?(1)A(') electronic spectrum of the jet-cooled transient molecule HAsO and its deuterated isotopologue has been observed for the first time by pulsed discharge jet laser spectroscopy. The techniques of laser-induced fluorescence and single vibronic level emission were employed to probe the electronic properties of the species. The bending and AsO stretching frequencies have been determined in both states. A rotational analysis of the 0(0)(0) bands of both HAsO and DAsO has been completed and the following effective (r(0)) structures were derived: r(")(HAs) = 1.576(3) ?, r(")(AsO) = 1.8342(5) ?, and θ(") = 101.5(4)°; and r(')(HAs) = 1.569(4) ?, r(')(AsO) = 1.7509(9) ?, and θ(') = 93.1(10)°. In the rotational analysis, lines induced by axis-tilting were observed, and calculated spectra with an axis tilting angle of 3.0(5)° reproduced the intensity of these lines. The change in geometry on electronic excitation is similar to that observed for the molecule HPO, with an increase in the X-O bond length and a decrease in the HXO angle, but contrary to the predictions of the Walsh diagram for generic HAB triatomic molecules. Our ab initio calculations show that the correlation between orbital energy and bond angle changes upon electronic excitation, resulting in the atypical angle change.     

Non-phosgene route to unsymmetrical ureas from N-Cbz-α-amino acid amides

A convenient method toward the synthesis of α-amino acid-derived unsymmetrical ureas 2 is described herein. This route involves an interesting rearrangement of amides of N-Cbz-α-amino acids 1, which presumably entails the intermediacy of hydantoins that is followed by hydrolysis to afford unsymmetrical ureas 2 in quantitative yields and high purity.     

Agglomerative hierarchical clustering analysis of twenty-six rice samples analysed by instrumental neutron activation analysis and other techniques

As part of the ongoing work on the safety and security of foods grown locally and imported into Jamaica, twenty five rice brands available on the Jamaican market and one sample of locally grown brown rice were collected and analysed for 36 elements using a combination of instrumental neutron activation analysis, total reflection X-ray fluorescence, flame atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry. Quality control for each of the techniques was provided by analysis of reference materials and inter-comparisons of common elements. Agglomerative hierarchical clustering analysis performed on the raw data set identified white, parboiled and brown rice as the major clusters. The element and cluster median concentration in μg/g (for polished, parboiled and brown respectively) for each of the three clusters were Al (8.7, 11.3, 14.9), As (0.20, 0.21, 0.15), Br (12.1, 0.9, 3.4), Ca (60.4, 409.1, 112.5), Co (0.1, 0.09, 0.11), Cr (0.11, 0.10, 0.11), Cs (0.012, 0.004, 0.018), Eu (0.004, 0.004, 0.003), Cu (2.2,2.7, 3.6), Fe (13, 17, 20), K (894,1,815,2,538), La (0.009, 0.014, 0.015), Mg (340, 504, 1,303), Mn (9.7, 14.9, 28.5), Mo (0.7, 1.1, 0.8), Na (5.1, 9.9, 16.9), P (936, 2,328, 3,670), Rb (4.5, 6.1, 7.3), S (1,088,1,308, 1,321), Sb (0.004, 0.006, 0.005), Sc (0.001, 0.002, 0.002), Se (0.09, 0.17, 0.16), Sm (0.001, 0.003, 0.001), Sr (2.0, 1.9, 2.9), V (0.036, 0.041, 0.058), Zn (17.9, 15.3, 22.8). The use of agglomerative hierarchical clustering has proven to be a rapid method for the analysis of the dataset, correctly clustering rice by process that is, polished, parboiled and brown, with sub-clusters that further identified location, cultivars and an adulterated sample. The data validated here has been used to estimate the elemental contribution of rice to the Jamaican diet.