Der Einfluß der freien Ladungsträger auf die optischen Konstanten des Bi2Se3 im Wellenlängengebiet von 2 bis 23 μm

The influence of free carriers on the optical constants of Bismuthtriselenide Bi₂Se₃ was investigated in the infrared (2–23 μm). The reflection and transmission ofn-type Bi₂Se₃ single crystals was measured at approximately 30, 80 and 300 °K. Up till now,p-type Bi₂Se₃ is not known. The dependence of the refraction index and the absorption constant on the wavelength was calculated from the results of the measurements. It was found that the optical constants strongly depend on the carrier concentration. The crystals were prepared according the bridgman method. They normally have a carrier concentration of about 10¹⁹ cm^?3, which can be diminished by annealing in Selenium vapour of various pressure up to 10¹⁸ cm^?3. Bismuthtriselenide is a degenerated semiconductor. We obtained for the optical energy band gap by extrapolation the value 0,21 eV. It increases with increasing carrier concentration. This is known as the Burstein-Moss-effect.     

Systematic analysis of the total proteins of a mammalian organism: principles, problems and implications for sequencing the human genome

High-resolution two-dimensional electrophoresis (2-DE) has reached a technological level that allows us to resolve most of the numerous unknown protein species of a mammalian organism if appropriate strategies are used. We will discuss the problems of classification and characterization of proteins and propose a systematic approach to the analysis of the total protein complex. Both a comprehensive as well as a pragmatic approach towards systematic analysis have been considered. A "complex protein database" is suggested and considered with regard to various uses. A systematic analysis of the mouse proteins has been started and some of the preliminary results are summarized here. In particular, genetic properties of the proteins were investigated and are presented in order to demonstrate the significance of a systematic analysis of proteins for research and practical application (e.g. mutagenicity testing). A concept is presented for sequencing the coding DNA of mouse and man, starting with a systematic analysis of mouse proteins and then using two recently developed methods - microsequencing of proteins from spots of 2-DE protein patterns, and utilization of the relatively short N-terminal sequences obtained - to produce the corresponding cDNA's of these proteins.     

Tissue specific resonance frequencies of water and metabolites within the human brain

Chemical shift imaging (CSI) without water suppression was used to examine tissue-specific resonance frequencies of water and metabolites within the human brain. The aim was to verify if there are any regional differences in those frequencies and to determine the influence of chemical shift displacement in slice-selection direction. Unsuppressed spectra were acquired at 3T from nine subjects. Resonance frequencies of water and after water signal removal of total choline, total creatine and NAA were estimated. Furthermore, frequency distances between the water and those resonances were calculated. Results were corrected for chemical shift displacement. Frequency distances between water and metabolites were consistent and greater for GM than for WM. The highest value of WM to GM difference (14ppb) was observed for water to NAA frequency distance. This study demonstrates that there are tissue-specific differences between frequency distances of water and metabolites. Moreover, the influence of chemical shift displacement in slice-selection direction is showed to be negligible.     

Self-Assembly and Phase Behavior of Short Chain Phosphonic Acid-Water Systems in a Wide Concentration Range Microscopic,NMR, and X-ray Diffraction Studies

The phase behavior of n-octane and n-hexane phosphonic acid-D₂O systems was studied in the concentration range from 0.1 to 90 wt.% and in a temperature range from 10° to 130°C by polarizing and dark field microscopy and by ¹H, ²D and, ³¹P NMR. Further, electron microscopy, X-ray diffraction and surface tension measurements were performed. For the first time, a widely spaced lamellar phase was observed over large concentration and temperature ranges in an essentially two-component system. By using the sonication or injection methods, unilamellar liposomes were obtained below 1 wt.%. At high temperatures, the clouding phenomenon was observed. The importance of hydrogen bond formation between polar groups for building up stable lamellae even at high dilution is stressed. The results are discussed with respect to some existing points of view concerning the possibility of lamellar structure formation from single short chain amphiphilic compounds including lipids.     

Die chemische Verschiebung der Exomethylenprotonen von α-Methylen-cycloketonen,Konformation der Keto-Exomethylengruppe

Die durch die Anisotropie der Bindungen bedingte innere chemische Verschiebung der Exomethylenprotonen wurde in Abhängigkeit vom Rotationswinkel zwischen der Keto- und Exomethylengruppe in Dipolnäherung berechnet. Aus dem Vergleich der theoretischen Werte mit den für eine Reihe von α-Methylen-cycloketonen und 16) experimentell erhaltenen folgt, daß die Keto-Exomethylengruppe bei den Verbindungen mit n = 5, 6, 7 und 8 in einer s-cis-Konformation und bei denen mit n = 9 und 10 in einer s-trans-Konformation vorliegt. Beim α-Methylen-cyclohexadecanon (n = 16) findet eine teilweise freie Rotation statt.     

Analysis of some greedy algorithms for the single-sink fixed-charge transportation problem

The single-sink fixed-charge transportation problem (SSFCTP) consists of finding a minimum cost flow from a number of nodes to a single sink. Beside a cost proportional to the amount shipped, the flow cost encompass a fixed charge. The SSFCTP is an important subproblem of the well-known fixed-charge transportation problem. Nevertheless, just a few methods for solving this problem have been proposed in the literature. In this paper, some greedy heuristic solutions methods for the SSFCTP are investigated. It is shown that two greedy approaches for the SSFCTP known from the literature can be arbitrarily bad, whereas an approximation algorithm proposed in the literature for the binary min-knapsack problem has a guaranteed worst case bound if adapted accordingly to the case of the SSFCTP.     

Identification of phosphorylation and acetylation sites in αA-crystallin of the eye lens (<Emphasis Type="Italic">mus musculus</Emphasis>) after two-dimensional gel electrophoresis

Posttranslational modifications are of great interest because of their relevance in biological systems as proteins are commonly activated or deactivated by phosphorylation, glycation and acetylation [1, 2]. During eye lens aging the number of the A-crystallin isoproteins increases. This could be observed by the use of 2D-PAGE (two-dimensional gel electrophoresis). The number of A-crystallin spots in the gel increased during eye lens aging. For further analysis the spots of 2D-PAGE were cut out and the identification of the proteins was done using nanoLC-ESI-MS/MS (liquid chromatography electrospray ionization tandem mass spectrometry). The created MS/MS-data were analyzed using the Sequest algorithm. Searches with different parameters were done to preferably get the complete sequence coverage and to identify posttranslational modifications of the A-crystallin. The acetylated N-terminus of this protein could be detected. Furthermore, phosphorylation of serine 122 and 148 was identified in two different spots.     

Zur Theorie von Oberflächenzuständen an Festkörpern

A theory of surface states for one and two surfaces is formulated using a Green function method. The formalism is applied to a one dimensional model of a two band system.