2,632 research outputs found
Time-dependent gravity in southern California, May 1974 - Apr 1979
Gravity measurements were coordinated with the long baseline three dimensional geodetic measurements of the Astronomical Radio Interferometric Earth Surveying project which used radio interferometry with extra-galactic radio sources. Gravity data from 28 of the stations had a single reading standard deviation of 11 microgal which gives a relative single determination between stations a standard deviation of 16 microgal. The largest gravity variation observed, 80 microgal, correlated with nearby waterwell variations and with smoothed rainfall. Smoothed rainfall data appeared to be a good indicator of the qualitative response of gravity to changing groundwater levels at other suprasediment stations, but frequent measurement of gravity at a station was essential until the quantitative calibration of the station's response to groundwater variations was accomplished
On the distillation and purification of phase-diffused squeezed states
Recently it was discovered that non-Gaussian decoherence processes, such as
phase-diffusion, can be counteracted by purification and distillation protocols
that are solely built on Gaussian operations. Here, we make use of this
experimentally highly accessible regime, and provide a detailed experimental
and theoretical analysis of several strategies for purification/distillation
protocols on phase-diffused squeezed states. Our results provide valuable
information for the optimization of such protocols with respect to the choice
of the trigger quadrature, the trigger threshold value and the probability of
generating a distilled state
Preparation of distilled and purified continuous variable entangled states
The distribution of entangled states of light over long distances is a major
challenge in the field of quantum information. Optical losses, phase diffusion
and mixing with thermal states lead to decoherence and destroy the
non-classical states after some finite transmission-line length. Quantum
repeater protocols, which combine quantum memory, entanglement distillation and
entanglement swapping, were proposed to overcome this problem. Here we report
on the experimental demonstration of entanglement distillation in the
continuous-variable regime. Entangled states were first disturbed by random
phase fluctuations and then distilled and purified using interference on beam
splitters and homodyne detection. Measurements of covariance matrices clearly
indicate a regained strength of entanglement and purity of the distilled
states. In contrast to previous demonstrations of entanglement distillation in
the complementary discrete-variable regime, our scheme achieved the actual
preparation of the distilled states, which might therefore be used to improve
the quality of downstream applications such as quantum teleportation
High quality anti-relaxation coating material for alkali atom vapor cells
We present an experimental investigation of alkali atom vapor cells coated
with a high quality anti-relaxation coating material based on alkenes. The
prepared cells with single compound alkene based coating showed the longest
spin relaxation times which have been measured up to now with room temperature
vapor cells. Suggestions are made that chemical binding of a cesium atom and an
alkene molecule by attack to the C=C bond plays a crucial role in such
improvement of anti-relaxation coating quality
PIF4 enhances DNA binding by CDF2 to co-regulate target gene expression and promote Arabidopsis hypocotyl cell elongation
How specificity is conferred within gene regulatory networks is an important problem in biology. The basic helix–loop–helix PHYTOCHROME-INTERACTING FACTORs (PIFs) and single zinc-finger CYCLING DOF FACTORs (CDFs) mediate growth responses of Arabidopsis to light and temperature. We show that these two classes of transcription factor (TF) act cooperatively. CDF2 and PIF4 are temporally and spatially co-expressed, they interact to form a protein complex and act in the same genetic pathway to promote hypocotyl cell elongation. Furthermore, PIF4 substantially strengthens genome-wide occupancy of CDF2 at a subset of its target genes. One of these, YUCCA8, encodes an auxin biosynthesis enzyme whose transcription is increased by PIF4 and CDF2 to contribute to hypocotyl elongation. The binding sites of PIF4 and CDF2 in YUCCA8 are closely spaced, and in vitro PIF4 enhances binding of CDF2. We propose that this occurs by direct protein interaction and because PIF4 binding alters DNA conformation. Thus, we define mechanisms by which PIF and CDF TFs cooperate to achieve regulatory specificity and promote cell elongation in response to light
Phenomenological constraints on Lemaitre-Tolman-Bondi cosmological inhomogeneities from solar system dynamics
We, first, analytically work out the long-term, i.e. averaged over one
orbital revolution, perturbations on the orbit of a test particle moving in a
local Fermi frame induced therein by the cosmological tidal effects of the
inhomogeneous Lemaitre-Tolman-Bondi (LTB) model. The LTB solution has recently
attracted attention, among other things, as a possible explanation of the
observed cosmic acceleration without resorting to dark energy. Then, we
phenomenologically constrain both the parameters K_1 = -\ddot R/R and K_2 =
-\ddot R^'/R^' of the LTB metric in the Fermi frame by using different kinds of
solar system data. The corrections to the standard
Newtonian/Einsteinian precessions of the perihelia of the inner planets
recently estimated with the EPM ephemerides, compared to our predictions for
them, yield K_1 = (4+8) 10^-26 s^-2, K_2 = (3+7) 10^-23 s^-2. The residuals of
the Cassini-based Earth-Saturn range, compared with the numerically integrated
LTB range signature, allow to obtain K_1/2 = 10^-27 s^-2. The LTB-induced
distortions of the orbit of a typical object of the Oort cloud with respect to
the commonly accepted Newtonian picture, based on the observations of the comet
showers from that remote region of the solar system, point towards K_1/2 <=
10^-30-10^-32 s^-2. Such figures have to be compared with those inferred from
cosmological data which are of the order of K1 \approx K2 = -4 10^-36 s^-2.Comment: LaTex2e, 18 pages, 3 tables, 3 figures. Minor changes. Reference
added. Accepted by Journal of Cosmology and Astroparticle Physics (JCAP
Development of Fast Helium Beam Emission Spectroscopy for Plasma Density and Temperature Diagnostics
Melanin in Fonsecaea pedrosoi: a trap for oxidative radicals
<p>Abstract</p> <p>Background</p> <p>The pathogenic fungus <it>Fonsecaea pedrosoi </it>constitutively produces the pigment melanin, an important virulence factor in fungi. Melanin is incorporated in the cell wall structure and provides chemical and physical protection for the fungus.</p> <p>We evaluated the production of nitric oxide (NO) in macrophages, the oxidative burst and the inducible nitric oxide synthase (i-NOS) activity in interactions between activated murine macrophages and <it>F. pedrosoi</it>. Experiments were carried out with or without tricyclazole (TC) treatment, a selective inhibitor of the dihydroxynaphthalene (DHN)-melanin biosynthesis pathway in <it>F. pedrosoi</it>. The paramagnetisms of melanin and the TC-melanin were analysed by electron spin resonance. The fungal growth responses to H<sub>2</sub>O<sub>2 </sub>and to S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide donor, were also evaluated.</p> <p>Results</p> <p>Melanised <it>F. pedrosoi </it>cells were more resistant to both H<sub>2</sub>O<sub>2 </sub>and NO. Nitrite was not detected in the supernatant of macrophages incubated with melanised fungal cells. However, i-NOS expression was unaffected by the presence of either untreated control <it>F. pedrosoi </it>or TC-treated <it>F. pedrosoi</it>. In addition, the inhibition of the DHN-melanin pathway by TC improved the oxidative burst capability of the macrophages.</p> <p>Conclusion</p> <p>The NO-trapping ability of <it>F. pedrosoi </it>melanin is an important mechanism to escape the oxidative burst of macrophages.</p
Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology
The best European locality for complete Eocene mammal skeletons is Grube Messel, near Darmstadt, Germany. Although the site was surrounded by a para-tropical rain forest in the Eocene, primates are remarkably rare there, and only eight fragmentary specimens were known until now. Messel has now yielded a full primate skeleton. The specimen has an unusual history: it was privately collected and sold in two parts, with only the lesser part previously known. The second part, which has just come to light, shows the skeleton to be the most complete primate known in the fossil record.We describe the morphology and investigate the paleobiology of the skeleton. The specimen is described as Darwinius masillae n.gen. n.sp. belonging to the Cercamoniinae. Because the skeleton is lightly crushed and bones cannot be handled individually, imaging studies are of particular importance. Skull radiography shows a host of teeth developing within the juvenile face. Investigation of growth and proportion suggest that the individual was a weaned and independent-feeding female that died in her first year of life, and might have attained a body weight of 650-900 g had she lived to adulthood. She was an agile, nail-bearing, generalized arboreal quadruped living above the floor of the Messel rain forest.Darwinius masillae represents the most complete fossil primate ever found, including both skeleton, soft body outline and contents of the digestive tract. Study of all these features allows a fairly complete reconstruction of life history, locomotion, and diet. Any future study of Eocene-Oligocene primates should benefit from information preserved in the Darwinius holotype. Of particular importance to phylogenetic studies, the absence of a toilet claw and a toothcomb demonstrates that Darwinius masillae is not simply a fossil lemur, but part of a larger group of primates, Adapoidea, representative of the early haplorhine diversification
- …