1,429 research outputs found
Optical control of an atomic inner-shell x-ray laser
X-ray free-electron lasers have had an enormous impact on x-ray science by
achieving femtosecond pulses with unprecedented intensities. However,
present-day facilities operating by the self-amplified spontaneous emission
(SASE) principle have a number of shortcomings, namely, their radiation has a
chaotic pulse profile and short coherence times. We put forward a scheme for a
neon-based atomic inner-shell x-ray laser (XRL) which produces temporally and
spatially coherent subfemtosecond pulses that are controlled by and
synchronized to an optical laser with femtosecond precision. We envision that
such an XRL will allow for numerous applications such as nuclear quantum optics
and the study of ultrafast quantum dynamics of atoms, molecules, and condensed
matter.Comment: 8 pages, 5 figures, RevTeX4.1, revise
Cytological and molecular characterization of wheat lines with Thinopyrum intermedium chromosome additions, substitutions and translocations resistant to barley yellow dwarf virus
Barley yellow dwarf virus (BYDV) is the most serious viral disease affecting wheat and genes for BYDV resistance have not been found in wheat. BYDV-resistant alien addition and alien substitution lines produced from a wheat × Thinopyrum intermedium (species of Agropyron complex) cross were characterized. Chromosome pairing in the hybrids between two substitution lines showed that they had the same Th. intermedium chromosome. Likewise, two addition lines involved the same alien chromosome. In situ hybridization of chromosomes, confirmed that line P29 is a disomic substitution line. Double monosomic seeds and self-pollinated seeds from monosomic addition plants were irradiated to induce translocations between wheat and Th. intermedium chromosomes. Putative translocations were selected on the basis of BYDV resistance and studied by chromosome analysis, Southern hybridization using Thinopyrum specific probe and RFLP markers. A BYDV-resistant translocation was identified
Long rainbow cycles in proper edge-colorings of complete graphs
We show that any properly edge-colored Kn contains a rainbow cycle with
at least (4=7 − o(1))n edges. This improves the lower bound of n=2 − 1 proved
in [1]
Interaction corrections at intermediate temperatures: dephasing time
We calculate the temperature dependence of the weak localization correction
in a two dimensional system at arbitrary relation between temperature, and
the elastic mean free time. We describe the crossover in the dephasing time
between the high temperature, ,
and the low temperature behaviors. The prefactors in
these dependences are not universal, but are determined by the Fermi liquid
constant characterising the spin exchange interaction.Comment: 4 pages, to appear in PRB, minor errors corrected, added reference
Noncommutative Common Cause Principles in Algebraic Quantum Field Theory
States in algebraic quantum field theory "typically" establish correlation
between spacelike separated events. Reichenbach's Common Cause Principle,
generalized to the quantum field theoretical setting, offers an apt tool to
causally account for these superluminal correlations. In the paper we motivate
first why commutativity between the common cause and the correlating events
should be abandoned in the definition of the common cause. Then we show that
the Noncommutative Weak Common Cause Principle holds in algebraic quantum field
theory with locally finite degrees of freedom. Namely, for any pair of
projections A, B supported in spacelike separated regions V_A and V_B,
respectively, there is a local projection C not necessarily commuting with A
and B such that C is supported within the union of the backward light cones of
V_A and V_B and the set {C, non-C} screens off the correlation between A and B
Accurate ab initio potential energy surface, thermochemistry, and dynamics of the F- + CH<inf>3</inf>F S<inf>N</inf>2 and proton-abstraction reactions
The inter-relationship of ascorbate transport, metabolism and mitochondrial, plastidic respiration.
Abstract Significance: Ascorbate, this multifaceted small molecular weight carbohydrate derivative, plays important roles in a range of cellular processes in plant cells, from the regulation of cell cycle, through cell expansion and senescence. Beyond these physiological functions, ascorbate has a critical role in responses to abiotic stresses, such as high light, high salinity, or drought. The biosynthesis, recycling, and intracellular transport are important elements of the balancing of ascorbate level to the always-changing conditions and demands. Recent Advances: A bidirectional tight relationship was described between ascorbate biosynthesis and the mitochondrial electron transfer chain (mETC), since L-galactono-1,4-lactone dehydrogenase (GLDH), the enzyme catalyzing the ultimate step of ascorbate biosynthesis, uses oxidized cytochrome c as the only electron acceptor and has a role in the assembly of Complex I. A similar bidirectional relationship was revealed between the photosynthetic apparatus and ascorbate biosynthesis since the electron flux through the photosynthetic ETC affects the biosynthesis of ascorbate and the level of ascorbate could affect photosynthesis. Critical Issues: The details of this regulatory network of photosynthetic electron transfer, respiratory electron transfer, and ascorbate biosynthesis are still not clear, as are the potential regulatory role and the regulation of intracellular ascorbate transport and fluxes. Future Directions: The elucidation of the role of ascorbate as an important element of the network of photosynthetic, respiratory ETC and tricarboxylic acid cycle will contribute to understanding plant cell responses to different stress conditions. Antioxid. Redox Signal. 00, 000-000
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