32 research outputs found
Measurement of the Strange Quark Contribution to Proton Structure through Parity Violating Electron-Proton Scattering
The G0 (G-Zero) forward angle experiment completed in Hall C of the Thomas Jefferson National Accelerator Facility (TJNAF) has measured the parity violating asymmetries in elastic electron-proton scattering over a Q2 range of 0.12 < Q2 < 1.0 (GeV/c)2. A linear combination of the strange electric (GsE) and magnetic (GsM) form factors calculated from these asymmetries indicate a non-zero contribution of the strange quark to the charge and magnetization structure of the proton in the above kinematic range at a 89% confidence level. The results show a previously unmeasured Q2 dependence of the strange form factors. Combining the G0 results with previous parity violating experiments show that at Q2 = 0.1 (GeV/c)2 GsM = 0.62+-0.31 GsE = -0.013+-0.028 At intermediate Q2 of about 0.23 (GeV/c)2, a consistent value of GsM is seen compared to previous experiments, together with a measurement that may imply a negative value of GsE. For Q2 above 0.5 (GeV/c)2 a consistently positive value for the linear combination of the strange form factors is seen
Enhanced ultrafast X-ray diffraction by transient resonances
Diffraction-before-destruction imaging with single ultrashort X-ray pulses
has the potential to visualise non-equilibrium processes, such as chemical
reactions, at the nanoscale with sub-femtosecond resolution in the native
environment without the need of crystallization. Here, a nanospecimen partially
diffracts a single X-ray flash before sample damage occurs. The structural
information of the sample can be reconstructed from the coherent X-ray
interference image. State-of-art spatial resolution of such snapshots from
individual heavy element nanoparticles is limited to a few nanometers. Further
improvement of spatial resolution requires higher image brightness which is
ultimately limited by bleaching effects of the sample. We compared snapshots
from individual 100 nm Xe nanoparticles as a function of the X-ray pulse
duration and incoming X-ray intensity in the vicinity of the Xe M-shell
resonance. Surprisingly, images recorded with few femtosecond and
sub-femtosecond pulses are up to 10 times brighter than the static linear model
predicts. Our Monte-Carlo simulation and statistical analysis of the entire
data set confirms these findings and attributes the effect to transient
resonances. Our simulation suggests that ultrafast form factor changes during
the exposure can increase the brightness of X-ray images by several orders of
magnitude. Our study guides the way towards imaging with unprecedented
combination of spatial and temporal resolution at the nanoscale
Measurement of the strange quark contribution to proton structure through parity violating electron-proton scattering
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Data from: Amphibian chytridiomycosis in Japan: distribution, haplotypes, and possible entry into Japan
A serious disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis was first found in Japan in December 2006 in imported pet frogs. This was the first report of chytridiomycosis in Asia. To assess the risk of pandemic chytridiomycosis to Japanese frogs, we surveyed the distribution of the fungus among captive and wild frog populations. We established a nested PCR assay that uses two pairs of PCR primers to amplify the internal transcribed spacer (ITS) region of a ribosomal RNA cassette to detect mild fungal infections from as little as 0.001 pg (1 fg) of B. dendrobatidis DNA. We collected swab samples from 265 amphibians sold at pet shops, 294 bred at institutes, and 2,103 collected at field sites from northern to southwestern Japan. We detected infections in native and exotic species, both in captivity and in the field. Sequencing of PCR products revealed 26 haplotypes of the B. dendrobatidis ITS region. Phylogenetic analysis showed that 3 of these haplotypes were specific to the Japanese giant salamander (Andrias japonicus) and appeared to have established a commensal relationship with this native amphibian. Many other haplotypes were carried by alien amphibians. The highest genetic diversity of B. dendrobatidis was found in the American bullfrog (Rana catesbeiana). Some strains of B. dendrobatidis appeared to be endemic to Japanese native amphibians, but many alien strains are being introduced into Japan via imported amphibians. To improve chytridiomycosis risk management, we must consider the risk of B. dendrobatidis changing hosts as a result of anthropogenic disturbance of the host-specific distribution of the fungus
Phylogenic tree of BD080526
Phylogenic tree of BD08052