Electron attachment to gas-phase uracil.

We present results about dissociative electron attachment (DEA) to gas-phase uracil (U) for incident electron energies between 0 and 14 eV using a crossed electron/molecule beam apparatus. The most abundant negative ion formed via DEA is (U-H)-, where the resonance with the highest intensity appears at 1.01 eV. The anion yield of (U-H)- shows a number of peaks, which can be explained in part as being due to the formation of different (U-H)- isomers. Our results are compared with high level ab initio calculations using the G2MP2 method. There was no measurable amount of a parent ion U-. We also report the occurrence of 12 other fragments produced by dissociative electron attachment to uracil but with lower cross sections than (U-H)-. In addition we observed a parasitic contaminating process for conditions where uracil was introduced simultaneously with calibrant gases SF6 and CCl4 that leads to a sharp peak in the (U-H)- cross section close to 0 eV. For (U-H)- and all other fragments we determined rough measures for the absolute partial cross section yielding in the case of (U-H)- a peak value of sigma (at 1.01 eV)=3 x 10(-20) m2.

Electron attachment to uracil: effective destruction at subexcitation energies.

We demonstrate that electrons at energies below the threshold for electronic excitation (<3 eV) effectively decompose gas phase uracil generating a mobile hydrogen radical and the corresponding closed shell uracil fragment anion (U-H)(-). The reaction is energetically driven by the large electron affinity of the (U-H) radical. This observation has significant consequences for the molecular picture of radiation damage, i.e., genotoxic effects or damage of living cells due to the secondary component of high energy radiation.

Optical properties of atmospheric particles: complete parameter sets obtained through polar photometry and an improved inversion technique.

Complete sets of optical parameters of dry particles sampled on a Nuclepore filter are derived through interpretation of photometric data with an improved inversion technique. The parameters are the volume-extinction and absorption coefficients, the single-scattering albedo, the asymmetry parameter of the volume scattering function, the apparent complex refractive index, and the apparent soot content. They may serve as input data for solar radiation-budget considerations. Results from preliminary measurements taken in Central Europe and Italy show an extreme variability of the optical parameters. Both large regional and temporal variabilities have been observed caused by the fluctuating midlatitude weather systems and human activities.

Calorimetric measurement of optical absorption.

Airborne particles are drawn into a chamber. After closing the chamber the particles are irradiated with broadband shortwave radiation. The mean shortwave volume absorption coefficient of the particles is calculated from the measured pressure change with time within the chamber. The method has been calibrated using water vapor. The detection limit is +/-2 x 10(-6)/m in terms of the volume absorption coefficient. There is very good agreement between the calorimetric and a new photometric absorption measurement. Advantages and disadvantages of both methods are discussed at the end of the paper.

Single scattering albedo, asymmetry parameter, apparent refractive index, and apparent soot content of dry atmospheric particles.

Mean shortwave values of the single scattering albedo and the asymmetry parameter of dry atmospheric particles have been measured photometrically. From the single scattering albedo the mean shortwave value of the apparent complex refractive index and the apparent volume fraction of soot within the particulate matter are derived. From 275 measurements the mean value of the single scattering albedo is 0.835, the mean value of the apparent complex refractive index is 1.51-0.026i, and the mean value of the apparent volume fraction of soot is 5.8%. For seventy-seven cases of mostly urban particles the mean value of the asymmetry parameter is 0.39. The term apparent stands for appearing (but not necessarily) real or true. Reasons for this attribute are the idealizations necessary to get a value of the refractive index of atmospheric particles. Consequently the use of an apparent refractive index for modeling purposes is restricted as described in the concluding section.

Light absorption measurements: new techniques.

A new radiometer is described which simplifies measurement of the radiation supply of solar wavelengths. Two methods of measuring the radiant energy absorbed by aerosol particles are described: A photometric technique is used for particles collected on filters, and a calorimetric technique is used for in situ measurements. Data collected with the radiometer and the light absorption techniques yield the heating rate of the atmosphere due to light absorption by the particles. Sample measurements show substantial atmospheric temperature increases due to absorption, especially in industrial regions.

[Functional analysis and reproducible technic for the radiography of the temporomandibular joint]. / Funktionsanalyse und reproduzierbare Kiefergelenk-Röntgenaufnahmetechnik

An improved x-ray machine is presented with which it is possible, for the first time, to take and exactly reproduce roentgenograms of the temporo-mandibular joint focussed bilaterally on to the transverse hinge-axis. This technique permits the accurate radiological comparisons required for diagnosis and therapy, in the asymmetric skull.

[Age dependence of visual acuity after incomplicated cataractoperation (author's transl)]. / Altersabhängigkeit der Sehschärfe nach unkomplizierten Kataraktoperationen

The results of visual acuity in 1523 cataract-extractions were evaluated; comparing the visual acuity of the 7th to the 9th postoperative days, when the patients left the hospital. 73,1% of the patients had a supplemental disease of the eye or another general disease. 76,6% of the patients had a postoperative visual acuity between 5/4 and 5/15, clearly depending on the age of the patients. General diseases influence scarcely surgery, but the older the patients the more we find a reduced visual acuity that is reduced by generative senile macula disease. On an average they stayed in hospital for 9,4 days.