616 research outputs found
Control and femtosecond time-resolved imaging of torsion in a chiral molecule
We study how the combination of long and short laser pulses, can be used to
induce torsion in an axially chiral biphenyl derivative
(3,5-difluoro-3',5'-dibromo-4'-cyanobiphenyl). A long, with respect to the
molecular rotational periods, elliptically polarized laser pulse produces 3D
alignment of the molecules, and a linearly polarized short pulse initiates
torsion about the stereogenic axis. The torsional motion is monitored in
real-time by measuring the dihedral angle using femtosecond time-resolved
Coulomb explosion imaging. Within the first 4 picoseconds, torsion occurs with
a period of 1.25 picoseconds and an amplitude of 3 degrees in excellent
agreement with theoretical calculations. At larger times the quantum states of
the molecules describing the torsional motion dephase and an almost isotropic
distribution of the dihedral angle is measured. We demonstrate an original
application of covariance analysis of two-dimensional ion images to reveal
strong correlations between specific ejected ionic fragments from Coulomb
explosion. This technique strengthens our interpretation of the experimental
data.Comment: 11 pages, 9 figure
A new semi-solid casting technique for fabricating SiC-reinforced Mg alloys matrix composites
The capability of the newly developed rheocasting (RC) technique in combination with the RheoMetal process for producing SiC particulate-reinforced AM50 and AZ91D matrix composites (Mg-based MMCs) was investigated. The quality of the MMCs was studied by analyzing the fraction of casting pores, number density of SiC clusters and the uniformity of SiC particles. Solid fraction, particle size and oxidation of SiC particles had strong impacts on the overall quality of the MMCs. The MMCs produced by 40% solid fraction and oxidized micron-sized SiC particles exhibited an excellent casting quality. A low-quality MMC was obtained when non-oxidized sub-micron sized SiC particles were employed. The results showed the formation of various types intermetallic particles and carbides such as MgO, Mg2Si, Al2MgC2, Mg2C3, Al4C3 as the interfacial reaction products of SiC/Mg alloy's melts. Mg hydride (alpha-MgH2) was also identified in inter-dendritic regions of the MMCs for the first time
Sub-millimeter Observations of Giant Molecular Clouds in the Large Magellanic Cloud: Temperature and Density as Determined from J=3-2 and J=1-0 transitions of CO
We have carried out sub-mm 12CO(J=3-2) observations of 6 giant molecular
clouds (GMCs) in the Large Magellanic Cloud (LMC) with the ASTE 10m sub-mm
telescope at a spatial resolution of 5 pc and very high sensitivity. We have
identified 32 molecular clumps in the GMCs and revealed significant details of
the warm and dense molecular gas with n(H2) 10 cm and
Tkin 60 K. These data are combined with 12CO(J=1-0) and 13CO(J=1-0)
results and compared with LVG calculations. We found that the ratio of
12CO(J=3-2) to 12CO(J=1-0) emission is sensitive to and is well correlated with
the local Halpha flux. We interpret that differences of clump propeties
represent an evolutionary sequence of GMCs in terms of density increase leading
to star formation.Type I and II GMCs (starless GMCs and GMCs with HII regions
only, respectively) are at the young phase of star formation where density does
not yet become high enough to show active star formation and Type III GMCs
(GMCs with HII regions and young star clusters) represents the later phase
where the average density is increased and the GMCs are forming massive stars.
The high kinetic temperature correlated with \Halpha flux suggests that FUV
heating is dominant in the molecular gas of the LMC.Comment: 74 pages, including 41 figures, accepted for publication in ApJ
The Goblet Cell Protein Clca1 (Alias mClca3 or Gob-5) Is Not Required for Intestinal Mucus Synthesis, Structure and Barrier Function in Naive or DSS- Challenged Mice
The secreted, goblet cell-derived protein Clca1 (chloride channel regulator,
calcium-activated-1) has been linked to diseases with mucus overproduction,
including asthma and cystic fibrosis. In the intestine Clca1 is found in the
mucus with an abundance and expression pattern similar to Muc2, the major
structural mucus component. We hypothesized that Clca1 is required for the
synthesis, structure or barrier function of intestinal mucus and therefore
compared wild type and Clca1-deficient mice under naive and at various time
points of DSS (dextran sodium sulfate)-challenged conditions. The mucus
phenotype in Clca1-deficient compared to wild type mice was systematically
characterized by assessment of the mucus protein composition using proteomics,
immunofluorescence and expression analysis of selected mucin genes on mRNA
level. Mucus barrier integrity was assessed in-vivo by analysis of bacterial
penetration into the mucus and translocation into sentinel organs combined
analysis of the fecal microbiota and ex-vivo by assessment of mucus
penetrability using beads. All of these assays revealed no relevant
differences between wild type and Clca1-deficient mice under steady state or
DSS-challenged conditions in mouse colon. Clca1 is not required for mucus
synthesis, structure and barrier function in the murine colon
Mis-reporting, previous health status and health status of family may seriously bias the association between food patterns and disease
Genetic association of CDC2 with cerebrospinal fluid tau in Alzheimer's disease
We have recently reported that a polymorphism in the cell division cycle (CDC2) gene, designated Ex6 + 7I/D, is associated with Alzheimer's disease (AD). The CDC2 gene is located on chromosome 10q21.1 close to the marker D10S1225 linked to AD. Active cdc2 accumulates in neurons containing neurofibrillary tangles (NFT), a process that can precede the formation of NFT. Therefore, CDC2 is a promising candidate susceptibility gene for AD. We investigated the possible effects of the CDC2 polymorphism on cerebrospinal fluid (CSF) biomarkers in AD patients. CDC2 genotypes were evaluated in relation to CSF protein levels of total tau, phospho-tau and beta-amyloid (1-42) in AD patients and control individuals, and in relation to the amount of senile plaques and NFT in the frontal cortex and in the hippocampus in patients with autopsy-proven AD and controls. The CDC2 Ex6 + 7I allele was associated with a gene dose-dependent increase of CSF total tau levels (F-2,F- 626 = 7.0, p = 0.001) and the homozygous CDC2Ex6 +7II genotype was significantly more frequent among AD patients compared to controls (p = 0.006, OR = 1.57, 95% CI 1.13-2.17). Our results provide further evidence for an involvement of cdc2 in the pathogenesis of AD. Copyright (C) 2005 S. Karger AG, Basel
Luftföroreningar vid svetsning
PIXE-analyser kan utföras med utvecklad analysuppställning med noggrannhet och precision av c:a 10 % och med hög analyskapacitet. Ett dataprogram för evaluering av räntgenspektra presenteras. Inverkan av provtjocklek vid PIXE-analys av inhomogena prov har studerats och korrektioner föreslås. Fluorinnehållet i filterprov har bestämts, samtidigt med PIXE-analys, genom utnyttjande av en kärnfysikalisk reaktion som ger resultat med god noggrannhet och precision. Svetsaerosoler har karakteriserats m.h.a. PIXE, ESCA och TEM/EDAX. En uppställning för insamling av svetsaerosoler under utveckling och hittillsvarande resultat indikerar representativ provinsamling med god reproducerbarhet
Influence of the magnetic sublattices in the double perovskite LaCaNiReO6
The magnetism of double perovskites is a complex phenomenon, determined from intra- or interatomic magnetic moment interactions, and strongly influenced by geometry. We take advantage of the complementary length and timescales of the muon spin rotation, relaxation, and resonance (μ+SR) microscopic technique and bulk ac/dc magnetic susceptibility measurements to study the magnetic phases of the LaCaNiReO6 double perovskite. As a result, we are able to discern and report ferrimagnetic ordering below TC=102K and the formation of different magnetic domains above TC. Between TC<T<270K, the following two magnetic environments appear, a dense spin region and a static-dilute spin region. The paramagnetic state is obtained only above T>270K. An evolution of the interaction between Ni and Re magnetic sublattices, in this geometrically frustrated fcc perovskite structure, is revealed as a function of temperature through the critical behavior and thermal evolution of microscopic and macroscopic physical quantities
IdeS: A Bacterial Proteolytic Enzyme with Therapeutic Potential
Background: IdeS, a proteinase from Streptococcus pyogenes, cleaves immunoglobulin (Ig)G antibodies with a unique degree of specificity. Pathogenic IgG antibodies constitute an important clinical problem contributing to the pathogenesis of a number of autoimmune conditions and acute transplant rejection. To be able to effectively remove such antibodies is therefore an important clinical challenge. Methodology/Principal Findings: IdeS was found to specifically and efficiently cleave IgG in human blood in vitro (20 mg of IdeS caused a complete degradation of IgG in one ml of human whole blood in 15 minutes) and to clear IgG from the blood stream of rabbits in vivo (no IgG was detected six hours following an intravenous injection of 5 mg of IdeS) without any side effects. In a mouse model of immune thrombocytopenic purpura (ITP), polyclonal IgG antibodies against platelet surface antigens were used to induce a lethal disease. These profoundly thrombocytopenic animals were treated and cured by a single injection of IdeS. Conclusions/Significance: Novel information is provided concerning the IgG-cleaving activity of IdeS in vitro and in vivo. The highly specific and rapid elimination of IgG in vivo, the dramatic effect in a mouse model of ITP, and the lack of sid
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