992 research outputs found
Passive broadband full Stokes polarimeter using a Fresnel cone
Light's polarisation contains information about its source and interactions,
from distant stars to biological samples. Polarimeters can recover this
information, but reliance on birefringent or rotating optical elements limits
their wavelength range and stability. Here we present a static, single-shot
polarimeter based on a Fresnel cone - the direct spatial analogue to the
popular rotating quarter-wave plate approach. We measure the average angular
accuracy to be 2.9 (3.6) degrees for elliptical(linear) polarisation states
across the visible spectrum, with the degree of polarisation determined to
within 0.12(0.08). Our broadband full Stokes polarimeter is robust,
cost-effective, and could find applications in hyper-spectral polarimetry and
scanning microscopy.Comment: 6 Pages, 4 Figure
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Overview and status of the 0.5NA EUV microfield exposure tool at Berkeley Lab
A 0.5-NA extreme ultraviolet micro-field exposure tool has been installed and commissioned at beamline 12.0.1.4 of the Advanced Light Source synchrotron facility at Lawrence Berkeley National Laboratory. Commissioning has demonstrated a patterning resolution of 13 nm half-pitch with annular 0.35-0.55 illumination; a patterning resolution of 8 nm half-pitch with annular 0.1-0.2 illumination; critical dimension (CD) uniformity of 0.7 nm 1σ on 16 nm nominal CD across 80% of the 200 um x 30 um aberration corrected field of view; aerial image vibration relative to the wafer of 0.75 nn RMS and focus control and focus stepping better than 15 nm
A low-energy limit of Yang-Mills theory on de Sitter space
We consider Yang-Mills theory with a compact structure group G on four-dimensional de Sitter space dS4. Using conformal invariance, we transform the theory from dS4 to the finite cylinder I × S3, where I = (−π/2, π/2) and S3 is the round three-sphere. By considering only bundles P → I × S3 which are framed over the temporal boundary ∂I × S3, we introduce additional degrees of freedom which restrict gauge transformations to be identity on ∂I × S3. We study the consequences of the framing on the variation of the action, and on the Yang-Mills equations. This allows for an infinite-dimensional moduli space of Yang-Mills vacua on dS4. We show that, in the low-energy limit, when momentum along I is much smaller than along S3, the Yang-Mills dynamics in dS4 is approximated by geodesic motion in the infinite-dimensional space Mvac of gauge-inequivalent Yang-Mills vacua on S3. Since Mvac ≅ C∞(S3, G)/G is a group manifold, the dynamics is expected to be integrable
Wheat take-all (1997)
Take-all is a disease of the roots, crown, and stem base of wheat. It interrupts plant development and may seriously suppress yields. A common problem of winter wheat in North America, Take-all occurs in Missouri especially under cool, damp conditions. The name originated in Australia in the middle of the last century when the disease 'took all' seedlings it attacked. In Missouri the disease seldom affects seedlings but more commonly attacks wheat plants at the tillering stage. This publication provides a description of the disease as well as some tips on how to control it
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The fate of hydrophobic organic compounds in soil systems : a kinetic model and sensitivity analysis
A mathematical model was developed using
finite difference numerical techniques to examine the
effects of kinetic parameters on the fate of
hydrophobic organic compounds in soil systems. The
model included advection; dispersion; bacterial
metabolism; and sorption and desorption to soil solids
and bacteria, and degradation by bacteria. The most
important processes governing the eventual fate of
organic compounds were surface sorption and
degradation by soil bacteria. It was concluded that
future research should be focused in these areas
Changes in Habitat Use of Montezuma Quail in Response to Tree Canopy Reduction in the Capitan Mountains of New Mexico
Montezuma quail (Cyrtonyx montezumae) are unique among quail with respect to clutch size, diet, covey dynamics, and habitat use. With the exception of a few notable early studies, there is relatively little information on the ecology of Montezuma quail. Pervious research has indicated that one of the primary habitats utilized by Montezuma quail is pinyon–juniper (Pinus spp.–Juniperus spp.) woodlands. Throughout many areas of the southwestern United States, pinyon–juniper woodlands are often targeted for thinning projects. Many studies have been conducted on the amount of canopy cover needed by other quail species. However, data on characteristics of their preferred habitat in many of the mountains they inhabit is limited in the literature and no data are currently published on their response to thinning projects. Therefore, studies are warranted to fill in these missing data, which will increase our knowledge about the habitat requirements of Montezuma quail and allow us to make informed decisions about thinning projects in areas occupied by Montezuma quail. The goal of this research was to evaluate Montezuma quail responses to common silvicultural practices, specifically pinyon–juniper thinning in the Capitan Mountains of New Mexico. Results of our project indicated that Montezuma quail selected for sites that had been thinned to reduce canopy cover to a 30–40% mosaic. Selection for this habitat was much higher than selection for the surrounding area, which consisted of ≥70% canopy cover (Manly–Chesson Selectivity Index = 1.68). Overall, this study yields vital information for managers considering implanting thinning projects in Montezuma quail habitat
Automated synthesis of radiopharmaceuticals for positron emission tomography: an apparatus for labelling with [11C] methyl iodide (MIASA)
A fully automated apparatus for the routine synthesis and
formulation of short-lived 11C (t1/2 = 20 min) labelled radiopharmaceuticals
for positron emission tomography (PET) has
been developed. [11C]Carbon dioxide is converted to [11C]methyl
iodide, which can be used to label a wide variety of substrates by
methylation at C, N, O, or S electron rich centres. The apparatus,
MIASA (methyl iodide automated synthesis apparatus), was
designed to operate as part of an automated labelling system in a
shielded ‘hot’ laboratory. The apparatus was designed without the
size constraints of typical instrumentation used in hot cells, although
it is compact where necessary. Ample use of indicators and sensors,
together with compact design of the reaction flasks for small dead
space and efficient evaporation, led to good reliability and
performance. The design of the hardware and software is described
in this paper, together with a preparation of 3-N-[11C]methylspiperone
as a sterile injectable solution in physiological saline
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