Showing papers by "Fraunhofer Society published in 1981"

Morphology and Fine Structure of Hair

Abstract: Studing the coats of fur animals gives insight into nature’s solutions to problems of thermal protection in environmental conditions. Within one species of fur animal living in open country, the respective adaption to the climate occurs by means of programmed and subtle modification of the texture of the hair coat, and efficient alterations in the keratinic structure of the hair. Winter fur is composed of very fine, relatively stiff and short, tightly packed crimped hairs. Thermal insulation is achieved by a large volume of air trapped in the hair coat between fine fibers. In summer there is less packing density. The steady movement of long and flexible hairs prevents the formation of air pockets in the coat and provides more efficient cooling. In the spring hair grows rapidly, producing long and coarse hairs. In the autumn numerous secondary follicles form complementary short and stiff hairs, mostly with a pronounced crimp. The increase in hair diameter that occurs in the spring causes a remarkable change in the scale pattern on the hair surface (Fig. 1). Examinations of ultrathin sections of different keratin fibers and hairs by electron microscopy showed that many scale patterns on hair surfaces had their origins in the molding of the shape of the epidermicular cells of the inner root sheath onto the surface of the cuticle.

The Influence of Material and Device Parameters on the Optical Characteristics of Liquid Crystal Displays

Abstract: A review of the influence of material and cell parameters on the optical characteristics of TN-displays is given. The optical response is dependent on the elastic constants, the dielectric constants, the viscosities, and the combination of cell thickness and refractive index anisotropy. Model calculations of the optical characteristics of TN-cells for different combinations of material and cell parameters are presented.

On the ultrasonic absorption and dispersion in amorphous superconductors

Abstract: We explain the unexpected behaviour of the ultrasonic absorption observed in the amorphous superconductor Pd30Zr70. It is assumed that the relaxation of the tunnelling states present in amorphous metals, is determined by their strong coupling to electrons as well as to thermal phonons. The distribution of the corresponding coupling strengths as invoked in the tunnelling model leads to a smooth temperature dependence of the absorption when passing through the superconducting transition temperature Tc. In contrast, the dispersion should exhibit a change of slope at Tc.

Quantitative esr analysis of deep defects in LEC-grown GaP

Abstract: Defects in LEC GaP have been analyzed quantitatively using an ESR method. Transition-metal impurities and native defects were studied in as-grown crystals. The antisite defect, PGa, and the isolated gallium vacancy, VGa, were emphasized since no other method has given definite, quantitative information on these defects. PGa antisites are present in some Cr-doped and some Zn-dopeii samples in concentrations high enough to affect their electrical properties. VGa was not detected in as-grown crystals indicating that VGa concentrations are smaller than the antisite concentrations at least in p-type material. Typical ESR detection., limits for transition-metal impurities are in the middle 1014 cm−3 range. The method is especially sensitive to Fe traces which were observed in all the samples studied.

Identification and microanalysis of mineral fibers by LAMMA

Abstract: Analysis of asbestos and glass fibers obtained by either environmental sampling or after longer periods of deposition in human and animal tissue revealed that the latter undergo changes of their chemical composition. Electron microscopy and LAMMA were used in these investigations. The extent of fiber dissolution could be assessed. Some fibers remained chemically unchanged. In certain fibers only some elements were partially leached out whereas in other fibers the majority of metallic elements were eluted.

On the conversion of solar radiation with fluorescent planar concentrators /FPCs/

Abstract: Though experimental results obtained with FPCs in the visible region are encouraging, the utilization of the near infrared region of the solar spectrum is still involving great problems due to low fluorescence quantum yields of dyes, strongly overlapping bands and bad stability. Our investigation of 30 infrared laser dyes (Eastman, Lambda Physik) shows, that quantum yields decrease statistically with increasing wavelength and that they depend strongly on solvent viscosity and temperature in several cases. The suppression of radiation-less processes by deuteration of NH2-groups in oxazine dyes enhances quantum yields substantially.

Photoacoustic detection of ferro and paramagnetic resonance

Abstract: A commercial ESR spectrometer was modified to detect the photoacoustic signal of modulated magnetic resonance absorption, operating at room temperature and at atmospheric pressure. Both magnetically ordered materials (YIG and FeBO3) and paramagnetic substances were investigated. The measurements include various phenomena of ferromagnetic resonance: uniform precession, magnetostatic modes and spin-wave instabilities. Paramagnetic resonance was observed in the concentrated system MnF2 and in the diluted system ZnS : Mn (1%), with well resolved hyperfine splitting.

Fehlermöglichkeiten bei der quantitativen Analyse polycyclischer aromatischer Kohlenwasserstoffe aus Luftstaubextrakten mit der Capillar-Gas-Chromatographie

Abstract: Ein vielfach angewandtes capillargas-chromatographisches Verfahren zur Bestimmung von polycyclischen aromatischen Kohlenwasserstoffen (PAH) in der Atmosphare wurde auf seine Zuverlassigkeit bei der Gewinnung von quantitativen Analysendaten hin gepruft. Eine PAH-Fraktion, die in unserem Labor routinemasig durch Extraktion von atmospharischem Schwebstaub mit Methanol, Flussig-Flussig-Verteilung (Cyclohexan/Methanol-Wasser) und zwei saulenchromatographischen Trennungen (SiO2/Cyclohexan und Sephadex LH-20/Propanol-2) gewonnen wird, wurde bei dem letzten chromatographischen Schritt (Sephadex LH-20/Propanol-2) weiter fraktioniert. Durch Untersuchung der so erhaltenen Fraktionen mit Hilfe der Capillar-Gas-Chromatographie und der GC-MS-Kopplung wurden fur 14 ausgewahlte PAH Uberlagerungen durch Storsubstanzen qualitativ und quantitativ ermittelt. Dabei zeigte sich, das ein Teil der Fehler vermieden werden kann, wenn die PAH mit zwei und drei Ringen exakt von den interessierenden PAH mit vier und mehr Ringen abgetrennt werden. Fur einige PAH sind die quantitativen Ergebnisse jedoch auch bei richtiger Schnittpunktwahl mit Vorsicht zu bewerten; zu diesen Verbindungen gehort auch das oftmals als Mas fur die cancerogene Potenz einer PAH-Fraktion angesehene Benzo(a)pyren.

Determination of vapour pressure curves by automated headspace analysis

Abstract: The application of headspace analysis techniques for the evaluation of vapour pressure curves is described. As representative examples the vapour pressure curves of n-octane, benzene, bis-(2-chloroethyl)-sulphide and 2-nitrophenol are determined and compared with data from literature. The method gives reliable results down to vapour pressures of about 1 Pa and allows the evaluation of a vapour pressure curve within one working day or less.

Successful application of automatic assembly in the German Federal Republic

Abstract: West Germany is one of Europe's leading users of assembly automation techniques. This report classifies the types of systems now being installed and gives examples of some successful applications.