656 research outputs found
Modified McLeod pressure gage eliminates measurement errors
Modification of a McLeod gage eliminates errors in measuring absolute pressure of gases in the vacuum range. A valve which is internal to the gage and is magnetically actuated is positioned between the mercury reservoir and the sample gas chamber
Device for measuring pressure Patent
Improved McLeod gage for pressure measuremen
Relationship of Weed Control and Soil pH to No-Tillage Corn Yields
Atrazine and simazine are used for selective control of a broad spectrum of weeds in corn. Over 80% of the U.S. corn production is treated with one or the other of these two s-triazine herbicides. In Kentucky they are used annually on over 800,000 acres of corn, including over 200,000 acres of no-tillage corn. When added to the soil these compounds are ultimately degraded to non-phytotoxic compounds. The rate of degradation is dependent upon the physical, chemical, and biological properties of the soil. Although atrazine and simazine are chemically similar, simazine is considered to degrade slightly slower than atrazine after application to the soil and as a result will remain in the soil for a longer period of time
Multi-wavelength Observations of Dusty Star Formation at Low and High Redshift
This paper examines what can be learned about high-redshift star formation
from the small fraction of high-redshift galaxies' luminosities that is emitted
at accessible wavelengths. We review and quantify empirical correlations
between bolometric luminosities produced by star formation and the UV, mid-IR,
sub-mm, and radio luminosities of galaxies in the local universe. These
correlations suggest that observations of high-redshift galaxies at any of
these wavelengths should constrain their star-formation rates to within
0.2--0.3 dex. We assemble the limited evidence that high-redshift galaxies obey
these locally calibrated correlations. The characteristic luminosities and dust
obscurations of galaxies at z ~ 0, z ~ 1, and z ~ 3 are reviewed. After
discussing the relationship between the high-redshift populations selected in
surveys at different wavelengths, we calculate the contribution to the 850um
background from each. The available data show that a correlation between
star-formation rate and dust obscuration L_dust/L_UV exists at low and high
redshift. This correlation plays a central role in the major conclusion of this
paper: most star formation at high redshift occurred in galaxies with 1 <
L_dust/L_UV < 100 similar to those that host the majority of star formation in
the local universe and to those that are detected in UV-selected surveys.
(abridged)Comment: Scheduled for publication in ApJ v544 Dec 2000. Significant changes
to section 4. Characteristic UV and dust luminosities of star-forming
galaxies at redshifts z~0, z~1, and z~3 presented. Existence of extremely
obscured galaxies more clearly acknowledged. Original conclusions reinforced
by the observed correlation between bolometric luminosity and dust
obscuration at 0<z<
The modular S-matrix as order parameter for topological phase transitions
We study topological phase transitions in discrete gauge theories in two
spatial dimensions induced by the formation of a Bose condensate. We analyse a
general class of euclidean lattice actions for these theories which contain one
coupling constant for each conjugacy class of the gauge group. To probe the
phase structure we use a complete set of open and closed anyonic string
operators. The open strings allow one to determine the particle content of the
condensate, whereas the closed strings enable us to determine the matrix
elements of the modular -matrix, also in the broken phase. From the measured
broken -matrix we may read off the sectors that split or get identified in
the broken phase, as well as the sectors that are confined. In this sense the
modular -matrix can be employed as a matrix valued non-local order parameter
from which the low-energy effective theories that occur in different regions of
parameter space can be fully determined.
To verify our predictions we studied a non-abelian anyon model based on the
quaternion group of order eight by Monte Carlo simulation. We
probe part of the phase diagram for the pure gauge theory and find a variety of
phases with magnetic condensates leading to various forms of (partial)
confinement in complete agreement with the algebraic breaking analysis. Also
the order of various transitions is established.Comment: 37 page
Zero-voltage conductance peak from weak antilocalization in a Majorana nanowire
We show that weak antilocalization by disorder competes with resonant Andreev
reflection from a Majorana zero-mode to produce a zero-voltage conductance peak
of order e^2/h in a superconducting nanowire. The phase conjugation needed for
quantum interference to survive a disorder average is provided by particle-hole
symmetry - in the absence of time-reversal symmetry and without requiring a
topologically nontrivial phase. We identify methods to distinguish the Majorana
resonance from the weak antilocalization effect.Comment: 13 pages, 8 figures. Addendum, February 2014: Appendix B shows
results for weak antilocalization in the circular ensemble. (This appendix is
not in the published version.
M\"ossbauer Antineutrinos: Recoilless Resonant Emission and Absorption of Electron Antineutrinos
Basic questions concerning phononless resonant capture of monoenergetic
electron antineutrinos (M\"ossbauer antineutrinos) emitted in bound-state
beta-decay in the 3H - 3He system are discussed. It is shown that lattice
expansion and contraction after the transformation of the nucleus will
drastically reduce the probability of phononless transitions and that various
solid-state effects will cause large line broadening. As a possible
alternative, the rare-earth system 163Ho - 163Dy is favoured.
M\"ossbauer-antineutrino experiments could be used to gain new and deep
insights into several basic problems in neutrino physics
First search for gravitational waves from the youngest known neutron star
We present a search for periodic gravitational waves from the neutron star in the supernova remnant Cassiopeia
A. The search coherently analyzes data in a 12 day interval taken from the fifth science run of the Laser
Interferometer Gravitational-Wave Observatory. It searches gravitational-wave frequencies from 100 to 300 Hz
and covers a wide range of first and second frequency derivatives appropriate for the age of the remnant and
for different spin-down mechanisms. No gravitational-wave signal was detected. Within the range of search
frequencies, we set 95% confidence upper limits of (0.7–1.2) × 10^(−24) on the intrinsic gravitational-wave
strain, (0.4–4) × 10^(−4) on the equatorial ellipticity of the neutron star, and 0.005–0.14 on the amplitude of
r-mode oscillations of the neutron star. These direct upper limits beat indirect limits derived from energy
conservation and enter the range of theoretical predictions involving crystalline exotic matter or runaway r-modes.
This paper is also the first gravitational-wave search to present upper limits on the r-mode amplitude
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