Rhodium

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Eine variante der simplexmethode mit gleichzeitigem austausch mehrerer basisvariablen pro iterationsschritt

Zusammenfassung Das Iterationsverfahren der Simplexmethode besteht bekanntlich darin, von einer (gegebenen, aber noch nicht optimalen) Basislösung eine Variable auszuwählen und diese gegen eine Nichtbasisvariable auszutauschen, so daß hierbei eine im Sinne des Extremalwertes der Zielfunktion günstigere Basislösung entsteht. Die hier dargestellte Variante gestattet es, gegebenenfalls mehrere Basisvariable gegen eine gleiche Anzahl von Nichtbasisvariablen bei einem Iterationsschritt auszutauschen. Dieses Verfahren kürzt beispielsweise den Lösungsprozeß des Transportproblems im allgemeinen beträchtlich ab.

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Summary Solving a linear programming problem by the Simplexmethod the usual procedure is as follows: from a (given not yet optimal) basic solution one basic variable is chosen for being changed with a non-basic variable to get a better approximation to the extremum of the given linear equation. The described method sometimes allows exchanging several basic variables in each Simplex-step. Using this method usually the solution process of the transportation problem for example may be abbreviated efficiently.

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Vorgel. v.:H. P. Künzi     

Binding the tobacco mosaic virus to inorganic surfaces

We studied the adsorption behavior and surface chemistry of the tobacco mosaic virus (TMV) on well-defined metal and insulator surfaces. TMV serves as a tubular supramolecular model system with precisely known surface termination. We show that if the surface chemistry of the substrate and the pH-dependent chemistry of the molecular surface match, for example, by hydrogen bonding, a strong adsorption occurs, and lateral movement is impeded. Due to the immobilization, the virion can be imaged by atomic force microscopy (AFM) in contact mode. We also used self-assembled monolayers with an acyl chloride group to induce covalent bonding via ester formation. Noncontact AFM proved that TMV keeps its cylindrical cross section only under weak adsorption conditions, that is, on hydrophobic surfaces, while on hydrophilic substrates a deformation occurs to maximize the number of interacting chemical groups.     

NONLINEAR LASERSPECTROSCOPIC INVESTIGATIONS OF THE PIGMENT-PIGMENT INTERACTION WITHIN THE LIGHT-HARVESTING COMPLEX OF PHOTOSYSTEM II

Using a pump and test beam technique in the frequency domain with pump pulses in the nanosecond time range, the nonlinear transmission properties were investigated at room temperature in photosystem (PS) II membrane fragments and isolated light-harvesting chlorophyll a/b-protein preparations (LHC II preparations). In LHC II preparations and PS II membrane fragments, respectively, pump pulses of 620 nm and 647 nm cause a transmission decrease limited to a wavelength region in the nearest vicinity of the pump pulse wavelength (full width at half maximum ' 0.24 nm). In contrast, at 670 nm neither a transmission decrease nor a narrow band feature were observed. The data obtained for PS II membrane fragments and LHC II preparations at shorter wavelengths (620 nm, 647 nm) were interpreted in terms of excited state absorption of whole pigment-protein clusters within the light-harvesting antenna of photosystem II. The interpretation of the small transmission changes as homogeneously broadened lines led to a transversal relaxation time for chlorophyll in the clusters of about 4 ps.     

Optical and X-ray emission spectroscopy of high-power laser-induced dielectric breakdown in molecular gases and their mixtures

Large-scale plasma was created in molecular gases (CO, CO2, N2, H2O) and their mixtures by high-power laser-induced dielectric breakdown (LIDB). Compositions of the mixtures used are those suggested for the early earth's atmosphere of neutral and/or mildly reducing character. Time-integrated optical spectra emitted from the laser spark have been measured and analyzed. The spectra of the plasma generated in the CO-containing mixtures are dominated by emission of both C2 and CN radicals. A vibrational temperature of approximately 10(4) K was determined according to an intensity distribution in a vibronic structure of the CN (B2Sigma(+)u-X2Sigma(+)g) violet band. For comparison, the NH3-CH4-H2-H2O mixture has been irradiated as a model of the strongly reducing version of the early earth's atmosphere. In this mixture, excited CN seems to be significantly less abundant than C2. The LIDB experiments were in the molecular gases carried out not only in the static cell but also using a large, double stream pulse jet (gas puff target) placed in the vacuum interaction chamber. The obtained soft X-ray emission spectra indicate the presence of highly charged atomic ions in the hot core of high-power laser sparks.     

IR-device Grade (Hg,Cd)Te Crystals Grown by a Modified Bridgman Method

Electrical and photoelectrical properties of IR-devices manufactured on (Hg, Cd)Te-wafers cut from single crystals grown by modified Bridgman method are reported and compared to those of devices made on THM-(Hg, Cd)Te. MIS-structures and photodiodes were used in order to investigate the different materials. The influence of material parameters and device technology respectively is involved in our discussion of device properties. The quality of modified Bridgman-(Hg, Cd)Te was found to be comparable to that of the THM-(Hg, Cd)Te. At T = 80 K and FOV = 60° background limited detectivity of photodiodes with a cut-off wavelength of λ_co = 10.7 μm was achieved.     

Zur jodometrischen Analyse eines Gemenges von Sulfid; Sulfit und Thiosulfat

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Zur Eiwei?bestimmung in Fleisch

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