X-ray absorption measurements on an ultrasonic spray aerosol.

Spray deposition of thin films and coatings is a widely used manufacturing process owing to its low cost, versatility and simple implementation. The objective of the presented experiments was to investigate whether X-ray absorption measurements on solutes carried by aerosols are possible, and what count rates can be achieved depending on solution flow through and the resulting mass density in the interrogation volume. The investigated prototypical spray aerosol was InCl(3) dissolved in water or ethanol dispersed via an ultrasonic nebulizer. InCl(3) spray is essential for the ion layer gas reaction process used for the deposition of In(2)S(3) buffer layers for highly efficient chalcopyrite solar cells. The discussed experiments demonstrate that measurements are possible, but that the achievement of good signal-to-noise ratios requires extended sampling times and concentrated solutions.

Comprehensive comparison of various techniques for the analysis of elemental distributions in thin films.

The present work shows results on elemental distribution analyses in Cu(In,Ga)Se2 thin films for solar cells performed by use of wavelength-dispersive and energy-dispersive X-ray spectrometry (EDX) in a scanning electron microscope, EDX in a transmission electron microscope, X-ray photoelectron, angle-dependent soft X-ray emission, secondary ion-mass (SIMS), time-of-flight SIMS, sputtered neutral mass, glow-discharge optical emission and glow-discharge mass, Auger electron, and Rutherford backscattering spectrometry, by use of scanning Auger electron microscopy, Raman depth profiling, and Raman mapping, as well as by use of elastic recoil detection analysis, grazing-incidence X-ray and electron backscatter diffraction, and grazing-incidence X-ray fluorescence analysis. The Cu(In,Ga)Se2 thin films used for the present comparison were produced during the same identical deposition run and exhibit thicknesses of about 2 µm. The analysis techniques were compared with respect to their spatial and depth resolutions, measuring speeds, availabilities, and detection limits.

[Use of transesophageal echocardiography during implantation of aortic endoprosthesis (stent). Initial experience].

OBJECTIVE: To report the role played by transesophageal echocardiography during implantation of self-expanding aortic endoprostheses (stent) at a hemodynamics laboratory. METHODS: Thirteen patients underwent stent implantation in the descending thoracic aorta with the aid of transesophageal echocardiography during the entire procedure. Indications for stenting were as follows: 8 aortic dissections, 2 true aneurysms, 2 penetrating atherosclerotic ulcers, and 1 traumatic pseudoaneurysm. RESULTS: No complications resulting from the use of transesophageal echocardiography were observed. In 12 patients, the initial result was considered appropriate, with total or partial resolution of the major lesion confirmed by a posterior examination. In 1 patient, the procedure was suspended after transesophageal echocardiography and angiography showed that the proximal aortic diameter was inappropriate. Transesophageal echocardiography contributed to clarifying relevant points, such as aortic diameter, anatomic detail of the intimal lesion, and location and size of the communicating orifice. In addition, it facilitated placing the stent in the target lesion, reduced the time of exposure to radiation and the use of contrast medium, and provided rapid identification of intercurrent events, possibly reducing the total duration of the procedure. CONCLUSION: The use of transesophageal echocardiography during placement of aortic stents seems appropriate. The actual advantages of the procedure will be defined in a comparative prospective study.

[Quantification of mitral prosthesis failure by different methods of evaluation by transesophageal echocardiography]. / Quantificação de insuficiência protética mitral por diferentes métodos de avaliação pela ecocardiografia transesofágica.

PURPOSE: To evaluate the different methods for grading mitral regurgitation (MR) by transesophageal echocardiography (TEE) in patients with clinical suspicion of mitral prosthesis dysfunction. METHODS: Cardiac catheterization (Cath) was performed in 15 patients for grading the severity of prosthetic MR, divided in two groups based on the presence or absence of severe MR. Prosthetic MR was quantified by TEE using methods commonly used for MR of native valves: subjective assessment by color Doppler, objective assessment based on absolute jet area and on its relative area (jet area/left atrial area) and assessment based on the presence of systolic flow reversal in pulmonary vein. RESULTS: Prosthetic MR was mostly transprosthetic (14 patients) and eccentric (11 patients). There was significant correlation (p < 0.05) between Cath and TEE for identification of severe MR based on subjective assessment and on the presence of systolic flow reversal in pulmonary vein. Identification based on absolute (jet area > 7 cm2) and relative (jet area > 35% of left atrial area) jet areas did not reveal significant correlation with the angiographic grade and showed clear underestimation by TEE when the last method was used. However, there was good correlation (p < 0.05) if relative jet areas > 30% were considered as cut point. CONCLUSION: TEE correctly identified angiographic severe mitral prosthesis regurgitation, mainly by the presence of systolic flow reversal in pulmonary vein and subjective assessment. The estimation of severity of the prosthetic MR by absolute or relative jet area seems to be limited and should be used with caution due to eccentricity of the regurgitant jet, frequently seen in mitral prosthesis dysfunction.

Hot spot kinetics of the sonolysis of aqueous acetate solutions.

Water and acetate solutions were irradiated under argon by 300 kHz ultrasonic waves. Oxygen was found to be generated besides the products H2 and H2O2, already known. In the presence of acetate the O2 yield decreased rapidly while that of H2O2 decreased more slowly. Succinic acid was found as a product of the attack of OH radicals on acetate. Appreciable amounts of glyoxylic and glycolic acid and smaller amounts of formaldehyde and carbon dioxide were also detected. They resulted from the reaction of sonolytically generated oxygen with CH2CO2- radicals, produced upon attack of OH on acetate. Methane was a minor product of sonolysis. At acetate concentrations above 0.4 mol dm-3 CO2 and CO became the predominant products of sonolysis. This is explained by a second kind of action of ultrasound on dissolved acetate, i.e. by a thermal decomposition. This decomposition is possibly facilitated by radical attack on acetate. The results are discussed in terms of a 'structured hot spot' model, in which three regions for the occurrence of chemical reactions are postulated: a hot gaseous nucleus, an interfacial region with radial gradient in temperature and local radical density; and the bulk solution at ambient temperature.

Critical discussion of previous experience and new approaches in the development of composite filling materials.

Following the 1975 report in Chicago, an attempt is made to discover the present position with regard to the development of composite filling materials, and to determine whether further development is necessary or even possible. The reasons for considering clinical trials important are given, and the problem of the chemical bond to hard dental tissues is discussed. The influence of the thermal coefficient of expansion on the marginal seal is discussed in relation to border discolouration, and a critical assessment given of acid etching and remineralization. The significance of wear for the maintenance of contours is pointed out, in particular in connection with occlusal surface fillings in the cheek teeth, as well as the problem of contact-point characterization and fracture strength after repair of an old filling. Improvements in UV light polymerization are described. A critical discussion of the different opinions on the significance of histological findings in relation to pulp tolerance is presented, and finally the significance of water uptake and radiological opacity is discussed. In conclusion indications in relation to the present state of development are listed.

[Critical considerations on the development of composite filling materials]. / Kritische Betrachtungen über die Entwicklung von kompositefüllungsmaterialien

Following the report given at the FDI congress in Chicago in 1975, the question is raised about the present state of acrylic filling materials, i.e. whether further developments are necessary or even possible. The importance of clinical testing is emphasized and the problems involved in chemical binding to the dental hard substances discussed. The influence of the thermal coefficient of expansion on the marginal seal is discussed in connection with marginal discoloration, and acid cauterization as well as remineralization are critically evaluated. The significance of wear and tear for maintaining the contours is emphasized, especially in connection with occlusal fillings of lateral teeth, as well as the problem of shaping a contact point and tensile strength after repair of an old filling. Improvements in UV light polymerisation are described. The different opinions on the importance of histological findings regarding pulp tolerance are critically discussed and finally the significance of water uptake and radiological opacity is delt with. In conclusion, the indication for acrylic filling materials at the present time is defined.