Influence of processing time on nanoparticle generation during picosecond-pulsed fundamental and second harmonic laser ablation of metals in tetrahydrofuran

The influence of fundamental and second harmonic wavelength on ablation efficiency and nanoparticle properties is studied during picosecond laser ablation of silver, zinc, and magnesium in polymer-doped tetrahydrofuran. Laser ablation in stationary liquid involves simultaneously the fabrication of nanoparticles by ablation of the target material and fragmentation of dispersed nanoparticles by post irradiation. The ratio in which the laser pulse energy contributes to these processes depends on laser wavelength and colloidal properties. For plasmon absorbers (silver), using the second harmonic wavelength leads to a decrease of the nanoparticle productivity over process time along with exponential decrease in particle diameter, while using the fundamental wavelength results in a constant ablation rate and linear decrease in particle diameter. For colloids made of materials without plasmon absorption (zinc, magnesium), laser scattering is the colloidal property that limits nanoparticle productivity by Mie-scattering of dispersed nanoparticle clusters.     

Treatment of roughness and concentration gradients in total Reflection X-ray fluorescence analysis of surfaces

Total Reflection X-ray fluorescence (TXRF) spectrometry, a new technique for surface and layer analysis, was originally confined to ideal smooth interfaces. In practice, however, one has to cope with more or less rough surfaces. Therefore, modelling calculations have been conducted to consider the consequences of residual roughness on the fluorescence signal at grazing incidence. The model used was verified experimentally on surfaces which exhibit peak-to-valley roughnesses ranging from 5 to 4000 nm. In addition, concentration changes occurring in the zone of roughness in the surface layer of a high grade steel after exposure to nitric acid were determined.     

Impaired pulmonary blood flow distribution in congestive heart failure assessed using synchrotron radiation microangiography

Synchrotron radiation microangiography is a powerful tool for assessing adverse changes in pulmonary vessel density associated with primary pulmonary hypertension (PH). Congestive heart failure (CHF) leads to a `secondary' onset of PH, yet it is unknown whether secondary PH is also associated with reduced vessel density. This study utilized synchrotron radiation to assess both pulmonary vessel density and endothelial function in a Dahl rat model of CHF with secondary PH. High salt‐fed Dahl salt‐sensitive (Dahl‐S) and salt‐resistant (Dahl‐R) rats were anesthetized and microangiography was performed to assess the pulmonary vessel density and vascular responses to (i) sodium nitroprusside (5.0 µg kg^?1 min^?1), (ii) acetylcholine (3.0 µg kg^?1 min^?1) and (iii) ET‐1_A receptor blockade, BQ‐123 (1 mg kg^?1). Dahl‐S rats developed CHF and secondary PH as evident by endothelial dysfunction, impaired vasodilatory responses to acetylcholine, enhanced vasodilatory responses to BQ‐123 and extensive pulmonary vascular remodeling. Consequently, the pulmonary vessel density was adversely reduced. Interestingly, the etiology of secondary PH manifests with structural and functional changes that are comparable with that previously reported for primary PH. One important discrepancy, however, is that ET‐1 modulation of pulmonary vessels is most striking in vessels with a diameter range of 100–200 µm in secondary PH, in contrast to a range of 200–300 µm in primary PH. Such discrepancies should be considered in future studies investigating primary and secondary forms of PH.     

Benchmark calculations of the complete configuration-interaction limit of Born-Oppenheimer diagonal corrections to the saddle points of isotopomers of the H + H2 reaction

We present a detailed ab initio study of the effect that the Born-Oppenheimer diagonal correction (BODC) has on the saddle-point properties of the H3 system and its isotopomers. Benchmark values are presented that are estimated to be within 0.1 cm(-1) of the complete configuration-interaction limit. We consider the basis set and correlation treatment requirements for accurate BODC calculations, and both are observed to be more favorable than for the Born-Oppenheimer energies. The BODC raises the H + H2 barrier height by 0.1532 kcal/mol and slightly narrows the barrier--with the imaginary frequency increasing by approximately 2%.     

Trace element enrichment on a quartz glass surface used as a sample support of an X-ray spectrometer for the subnanogram range

Summary A procedure for trace element enrichment on a quartz glass surface by matrix removal is described. It is applied for sample preparation on quartz glass flats which are used as sample supports for an X-ray fluorescence spectrometer yielding minimum detectable limits of about 20 pg. Measurements on the elements Cr, Fe, Co, Ni, Cu, Zn, As, Hg, and Pb gave recovery efficiencies between 97 and 100%.

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Spurenelementanreicherung an der Quarzglasoberfläche von Probenträgern eines Röntgenfluorescenzspektrometers für den Subnanogramnibereich

Zusammenfassung Es wird ein Verfahren zur Spurenelementanreicherung durch Entfernen der Matrix auf einer Quarzglasoberfläche beschrieben. Das Verfahren wird zur Probenherstellung auf hochebenen Quarzglasblöcken angewendet, die als Probenträger für ein Röntgenfluorescenzspektrometer dienen, das im Subnanogramnibereich arbeiten kann. Für die Elemente Cr, Fe, Co, Ni, Cu, Zn, As, Hg und Pb wurden Ausbeuten zwischen 97 und 100% gemessen.

     

Total reflection X-ray fluorescence spectrometry for quantitative surface and layer analysis

Measurements of X-ray fluorescence spectra versus grazing incident angles provide information on elemental composition as well as density and thickness of near surface layers. Calculations of fluorescence intensities are presented, which are used for the evaluation of data obtained by total reflection X-ray fluorescence (TXRF) spectrometry. The calculation is based on a matrix formalism to account for standing wave phenomena due to transmission and reflection in layered material. For the determination of concentrations the model makes additional use of the fundamental parameter technique in order to include absorption and enhancement effects of the fluorescence radiation. On the basis of experimental data some capabilities of this nondestructive and contactless probing technique are presented.     

Converged calculations of vibrational energy transfer probabilities for the collision of two HF(v=1) molecules

We present converged quantum mechanical calculations of state-to-state transition probabilities for the collision of two hydrogen fluoride molecules with zero total angular momentum. The potential energy surface is obtained by adding a vibrational dependence to the interaction potential of Alexander and DePristo. We have calculated converged transition probabilities for vibration-to-vibration and vibration-to-translation-and-rotation energy transfer including full vibration-rotation coupling. The calculations include up to 948 coupled channels. Final production runs were carried out with a highly vectorized code on the Minnesota Supercomputer Institute's Control Data Corporation Cyber 205 computer.     

Behaviour of a protein isolate from rapeseed (Brassica napus) and its main protein components - globulin and albumin - at air/solution and solid interfaces, and in emulsions

The behaviour of a rapeseed protein isolate (RI) and its main protein components - globulin (RG) and albumin (RA) - in adsorbed and spread monolayers, as well as in emulsions was investigated. Tensiometry, film-pressure area and Langmuir-Blodgett-techniques, and emulsion parameters were used to characterise the behaviour of the rapeseed proteins at various interfaces. The adsorption isotherms for albumin showed a plateau value for the surface pressure (Pi(e)) of 11.6 mN/m at the low critical association concentration (CAC) of 5.6x10(-8) g/ml. Both values were found to be distinctly higher for the globulin and the protein isolate. The isotherms of a mixture of RG and RA, which corresponds to the composition of RI, seems to be a superimposition of the isotherms of RA and RG. Contact angle measurements showed that all samples used were able to form LB-layers and to make hydrophilic glass surfaces more hydrophobic and vice versa. The changes in contact angle were more pronounced on hydrophobic glass surfaces. Monolayer and emulsion characteristics are dominated by the interfacial properties of albumin. The maximum film pressure reached by globulin was only about 8 mN/m. The globulin also possesses the lowest emulsifying activity. From the mean molecular area calculated for spread globulin, it is concluded that the globulin maintains its globular conformation at surfaces, which explains the low surface activity. Albumin and the protein isolate were highly surface active in monolayers and emulsion formation. The slightly different interfacial behaviour of the protein isolate compared with the corresponding mixture is probably due to additional effects of non-protein components and a partially denatured state of the protein.     

Anab initio potential energy surface and dynamics calculations for vibrational excitation of I2 by He

We present newab initio calculations of the interaction potential and the elastic and inelastic cross sections for He scattering by I₂. The electronic structure calculations of the interaction potential are based on an extensive one-electron basis set (triple zeta plus ad set on each I, ans function plus ap set at the I₂ bond center, and quadruple zeta plus twop sets on He), a two-configuration-SCF orbital set, and a configuration interaction calculation based on all single and double excitations out of the two-configuration reference space. The calculations are performed at 16He-I₂ distances for nine combinations of I₂ vibrational displacement and orientation. A new form of analytic representation is presented that is particularly well suited to efficient and accurate fitting ofab initio interaction potentials that include vibrational displacements. Scattering calculations are performed by the vibrational close-coupling, rotational-infinite-order-sudden approximation with a converged vibrational basis.