3,669 research outputs found
Linearity of charge measurement in laser filaments
We evaluate the linearity of three electric measurement techniques of the
initial electron density in laser filaments by comparing their results for a
pair of filaments and for the sum of each individual filament. The conductivity
measured between two plane electrodes in a longitudinal configuration is linear
within 2% provided the electric field is kept below 100 kV/m. Furthermore,
simulations show that the signal behaves like the amount of generated free
electrons. The slow ionic current measured with plane electrodes in a parallel
configuration is representative of the ionic charge available in the filament,
after several s, when the free electrons have recombined. It is linear
within 2% with the amount of ions and is insensitive to misalignment. Finally,
the fast polarization signal in the same configuration deviates from linearity
by up to 80% and can only be considered as a semi-qualitative indication of the
presence of charges, e.g., to characterize the filament length.Comment: 17 pages, 7 figure
1H, 13C, and 15N resonance assignments for the tandem PHD finger motifs of human CHD4
The plant homeodomain (PHD) zinc finger is a structural motif of about 40–60 amino acid residues found in many eukaryotic proteins that are involved in chromatin-mediated gene regulation. The human chromodomain helicase DNA binding protein 4 (CHD4) is a multi-domain protein that harbours, at its N-terminal end, a pair of PHD finger motifs (dPHD) connected by a ~30 amino acid linker. This tandem PHD motif is thought to be involved in targeting CHD4 to chromatin via its interaction with histone tails. Here we report the 1H, 13C and 15N backbone and side-chain resonance assignment of the entire dPHD by heteronuclear multidimensional NMR spectroscopy. These assignments provide the starting point for the determination of the structure, dynamics and histone-binding properties of this tandem domain pair
The Photoreaction of the Proton-Pumping Rhodopsin 1 From the Maize Pathogenic Basidiomycete Ustilago maydis
Microbial rhodopsins have recently been discovered in pathogenic fungi and have been postulated to be involved in signaling during the course of an infection. Here, we report on the spectroscopic characterization of a light-driven proton pump rhodopsin (UmRh1) from the smut pathogen Ustilago maydis, the causative agent of tumors in maize plants. Electrophysiology, time-resolved UV/Vis and vibrational spectroscopy indicate a pH-dependent photocycle. We also characterized the impact of the auxin hormone indole-3-acetic acid that was shown to influence the pump activity of UmRh1 on individual photocycle intermediates. A facile pumping activity test was established of UmRh1 expressed in Pichia pastoris cells, for probing proton pumping out of the living yeast cells during illumination. We show similarities and distinct differences to the well-known bacteriorhodopsin from archaea and discuss the putative role of UmRh1 in pathogenesis
Religious Extremism and Global Violence: What We Knew before September 11 and Why We Ignored It
Ancient Microbes from Halite Fluid Inclusions: Optimized Surface Sterilization and DNA Extraction
Fluid inclusions in evaporite minerals (halite, gypsum, etc.) potentially preserve genetic records of microbial diversity and changing environmental conditions of Earth's hydrosphere for nearly one billion years. Here we describe a robust protocol for surface sterilization and retrieval of DNA from fluid inclusions in halite that, unlike previously published methods, guarantees removal of potentially contaminating surface-bound DNA. The protocol involves microscopic visualization of cell structures, deliberate surface contamination followed by surface sterilization with acid and bleach washes, and DNA extraction using Amicon centrifugal filters. Methods were verified on halite crystals of four different ages from Saline Valley, California (modern, 36 ka, 64 ka, and 150 ka), with retrieval of algal and archaeal DNA, and characterization of the algal community using ITS1 sequences. The protocol we developed opens up new avenues for study of ancient microbial ecosystems in fluid inclusions, understanding microbial evolution across geological time, and investigating the antiquity of life on earth and other parts of the solar system
Anatomy of quantum chaotic eigenstates
The eigenfunctions of quantized chaotic systems cannot be described by
explicit formulas, even approximate ones. This survey summarizes (selected)
analytical approaches used to describe these eigenstates, in the semiclassical
limit. The levels of description are macroscopic (one wants to understand the
quantum averages of smooth observables), and microscopic (one wants
informations on maxima of eigenfunctions, "scars" of periodic orbits, structure
of the nodal sets and domains, local correlations), and often focusses on
statistical results. Various models of "random wavefunctions" have been
introduced to understand these statistical properties, with usually good
agreement with the numerical data. We also discuss some specific systems (like
arithmetic ones) which depart from these random models.Comment: Corrected typos, added a few references and updated some result
Wheat-barley hybridization – the last forty years
Abstract Several useful alien gene transfers have
been reported from related species into wheat (Triticum
aestivum), but very few publications have dealt
with the development of wheat/barley (Hordeum
vulgare) introgression lines. An overview is given
here of wheat 9 barley hybridization over the last
forty years, including the development of
wheat 9 barley hybrids, and of addition and translocation
lines with various barley cultivars. A short
summary is also given of the wheat 9 barley hybrids
produced with other Hordeum species. The meiotic
pairing behaviour of wheat 9 barley hybrids is presented,
with special regard to the detection of wheat–
barley homoeologous pairing using the molecular
cytogenetic technique GISH. The effect of in vitro
multiplication on the genome composition of intergeneric
hybrids is discussed, and the production and
characterization of the latest wheat/barley translocation
lines are presented. An overview of the agronomical
traits (b-glucan content, earliness, salt tolerance,
sprouting resistance, etc.) of the newly developed
introgression lines is given. The exploitation and
possible use of wheat/barley introgression lines for
the most up-to-date molecular genetic studies
(transcriptome analysis, sequencing of flow-sorted
chromosomes) are also discussed
Scaling of the surface vasculature on the human placenta
The networks of veins and arteries on the chorionic plate of the human placenta are analyzed in terms of Voronoi cells derived from these networks. Two groups of placentas from the United States are studied: a population cohort with no prescreening, and a cohort from newborns with an elevated risk of developing autistic spectrum disorder. Scaled distributions of the Voronoi cell areas in the two cohorts collapse onto a single distribution, indicating common mechanisms for the formation of the complete vasculatures, but which have different levels of activity in the two cohorts
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