Erfahrungen mit der Leybold ScrewLine in industriellen Anwendungen. ScrewLine Vacuum Pumps in Industrial Applications

Die Beispiele aus verschiedenen ?industriellen”? Applikationen zeigen, dass sich das Konzept der ScrewLine SP630 auch unter härtesten Bedingungen hervorragend bewährt. Die Pumpe ist eine echte ?Universalpumpe”? und kann durch ihr Zubehör auch an viele Prozesse im Randbereich der Chemischen Industrie oder in der Halbleiterindustrie angepaßt werden. In allen Fällen überzeugen vor allem die sehr niedrigen ?Cost of Ownership”? und die hohe Robustheit der Pumpe. Außerdem präsentiert sie sich als sehr modernes Produkt und setzt bei Vakuumleistung, Schallpegel und Wartungsfreundlichkeit neue Maßstäbe. Leybold Vacuum bietet mit der ScrewLine also wieder ein echtes ?Arbeitspferd”? und setzt so eine Tradition mit Produkten wie TRIVAC, SOGEVAC und RUVAC nahtlos fort.     

Compositional analysis of pattern-plated permalloy films

The combination of scanning electron microscopy (SEM)—energy-dispersive spectroscopy (EDS) and secondary ion mass spectrometry (SIMS) is a powerful approach for the characterization of the lateral and depth homogeneity of pattern-electroplated permalloy (Ni_0.80Fe_0.20) films. SEM-EDS is particularly useful for providing highly accurate data on a large number of analysis points for lateral homogeneity characterization. SIMS proved particularly useful in providing depth profiles with high depth resolution.     

SNR enhancement in radial SSFP imaging using partial k-space averaging

The steady-state free precessing (SSFP) sequences, widely used in MRI today, acquire data only during a short fraction of the repetition time (TR). Thus, they exhibit a poor scan efficiency. In this paper, a novel approach to extending the acquisition window for a given TR without considerably modifying the basic sequence is explored for radial SSFP sequences. The additional data are primarily employed to increase the signal-to-noise ratio, rather than to improve the temporal resolution of the imaging. The approach is analyzed regarding its effect on the image SNR (signal to noise ratio) and the reconstruction algorithm. Results are presented for phantom experiments and cardiac functions studies. The gain in SNR is most notable in rapid imaging, since SNR enhancement for a constant repetition time may be used to compensate for the increase in noise resulting from angular undersampling.     

Gramicidin channels

Gramicidin channels are mini-proteins composed of two tryptophan-rich subunits. The conducting channels are formed by the transbilayer dimerization of nonconducting subunits, which are tied to the bilayer/solution interface through hydrogen bonds between the indole NH groups and the phospholipid backbone and water. The channel structure is known at atomic resolution and the channel's permeability characteristics are particularly well defined: gramicidin channels are selective for monovalent cations, with no measurable permeability to anions or polyvalent cations; ions and water move through a pore whose wall is formed by the peptide backbone; and the single-channel conductance and cation selectivity vary when the amino acid sequence is varied, even though the permeating ions make no contact with the amino acid side chains. Given the amount of experimental information that is available-for both the wild-type channels and for channels formed by amino acid-substituted gramicidin analogues-gramicidin channels provide important insights into the microphysics of ion permeation through bilayer-spanning channels. For the same reason, gramicidin channels constitute the system of choice for evaluating computational strategies for obtaining mechanistic insights into ion permeation through the complex channels formed by integral membrane proteins.     

The melting of sponge iron spheres in their own melt

Explanation of the model. Computation of melting behaviour of sponge iron pellets as a function of initial temperature of the pellet, the superheat of the melt, the heat transfer coefficient and thermal conductivity of the pellet. Dimensionless melting time. Experiments in an induction furnace.     

Assessment of pheromone production and response in fission yeast by a halo test of induced sporulation

We describe a rapid, sensitive and semi-quantitative plate assay for monitoring pheromone activity in the fission yeast Schizosaccharomyces pombe. It is based on the observation that meiosis requires stimulation by pheromone and exploits diploid strains that will only sporulate after addition of exogenous pheromone. The tester strains are heterozygous for mating type, are non-switching, and are mutated in one of the early subfunctions (either mat1-Mc or mat1-Pc), so that meiosis is only induced after exposure to exogenous pheromone (M-factor or P-factor, respectively). Pheromone activity is assessed as an iodine-positive halo of sporulation surrounding the pheromone source, and the width of the halo is related to the amount of pheromone being produced. The assay is sufficiently sensitive to monitor the low amount of M-factor produced by an M mam1 strain, and its sensitivity towards P-factor is greatly increased by using a hyper-sensitive tester strain lacking the Sxa2 protease that is believed to degrade this pheromone. We also demonstrate that the production of P-factor is very much stimulated by exposure of P cells to M-factor.