393 research outputs found
Genetic engineering of baker’s and wine yeasts using formaldehyde hyperresistance-mediating plasmids
Yeast multi-copy vectors carrying the for maldehyde-resistance marker gene SFA have proved to be a valuable tool for research on industrially used strains of Saccharomyces cerevisiae. The genetics of these strains is often poorly understood, and for various reasons it is not possible to simply subject these strains to protocols of genetic engineering that have been established for laboratory strains of S. cerevisiae. We tested our vectors and protocols using 10 randomly picked baker’s and wine yeasts all of which could be transformed by a simple protocol with vectors conferring hyperresistance to formaldehyde. The application of formaldehyde as a selecting agent also offers the advantage of its biodegradation to CO2 during fermentation, i.e., the selecting agent will be consumed and therefore its removal during down-stream processing is not necessary. Thus, this vector provides an expression system which is simple to apply and inexpensive to use. Key words: · Yeast · Transformation · Hyperresistance to formaldehyd
Spin waves cause non-linear friction
Energy dissipation is studied for a hard magnetic tip that scans a soft
magnetic substrate. The dynamics of the atomic moments are simulated by solving
the Landau-Lifshitz-Gilbert (LLG) equation numerically. The local energy
currents are analysed for the case of a Heisenberg spin chain taken as
substrate. This leads to an explanation for the velocity dependence of the
friction force: The non-linear contribution for high velocities can be
attributed to a spin wave front pushed by the tip along the substrate.Comment: 5 pages, 9 figure
Spin waves cause non-linear friction
Energy dissipation is studied for a hard magnetic tip that scans a soft
magnetic substrate. The dynamics of the atomic moments are simulated by solving
the Landau-Lifshitz-Gilbert (LLG) equation numerically. The local energy
currents are analysed for the case of a Heisenberg spin chain taken as
substrate. This leads to an explanation for the velocity dependence of the
friction force: The non-linear contribution for high velocities can be
attributed to a spin wave front pushed by the tip along the substrate.Comment: 5 pages, 9 figure
Topological phase transitions and chiral inelastic transport induced by the squeezing of light
We show how the squeezing of light can lead to the formation of topological
states. Such states are characterized by non-trivial Chern numbers, and exhibit
protected edge modes which give rise to chiral elastic and inelastic photon
transport. These topological bosonic states are not equivalent to their
fermionic (topological superconductor) counterparts and cannot be mapped by a
local transformation onto topological states found in particle-conserving
models. They thus represent a new type of topological system. We study this
physics in detail in the case of a Kagome lattice model, and discuss possible
realizations using nonlinear photonic crystals or superconducting circuits.Comment: 11 pages, 4 figure
Thermoconditional modulation of the pleiotropic sensitivity phenotype by the Saccharomyces cerevisiae PRP19 mutant allele pso4-1
The conditionally-lethal pso4-1 mutant allele of the spliceosomal-associated PRP19 gene allowed us to study this gene’s influence on pre-mRNA processing, DNA repair and sporulation. Phenotypes related to intron-containing genes were correlated to temperature. Splicing reporter systems and RT–PCR showed splicing efficiency in pso4-1 to be inversely correlated to growth temperature. A single amino acid substitution, replacing leucine with serine, was identified within the N-terminal region of the pso4-1 allele and was shown to affect the interacting properties of Pso4-1p. Amongst 24 interacting clones isolated in a two-hybrid screening, seven could be identified as parts of the RAD2, RLF2 and DBR1 genes. RAD2 encodes an endonuclease indispensable for nucleotide excision repair (NER), RLF2 encodes the major subunit of the chromatin assembly factor I, whose deletion results in sensitivity to UVC radiation, while DBR1 encodes the lariat RNA splicing debranching enzyme, which degrades intron lariat structures during splicing. Characterization of mutagen-sensitive phenotypes of rad2{Delta}, rlf2{Delta} and pso4-1 single and double mutant strains showed enhanced sensitivity for the rad2{Delta} pso4-1 and rlf2{Delta} pso4-1 double mutants, suggesting a functional interference of these proteins in DNA repair processes in Saccharomyces cerevisiae
Spin excitations in a monolayer scanned by a magnetic tip
Energy dissipation via spin excitations is investigated for a hard
ferromagnetic tip scanning a soft magnetic monolayer. We use the classical
Heisenberg model with Landau-Lifshitz-Gilbert (LLG)-dynamics including a
stochastic field representing finite temperatures. The friction force depends
linearly on the velocity (provided it is small enough) for all temperatures.
For low temperatures, the corresponding friction coefficient is proportional to
the phenomenological damping constant of the LLG equation. This dependence is
lost at high temperatures, where the friction coefficient decreases
exponentially. These findings can be explained by properties of the spin
polarization cloud dragged along with the tip.Comment: 6 pages, 5 figure
- …