11,346 research outputs found
The homotopy fixed point spectra of profinite Galois extensions
Let E be a k-local profinite G-Galois extension of an E_infty-ring spectrum A
(in the sense of Rognes). We show that E may be regarded as producing a
discrete G-spectrum. Also, we prove that if E is a profaithful k-local
profinite extension which satisfies certain extra conditions, then the forward
direction of Rognes's Galois correspondence extends to the profinite setting.
We show the function spectrum F_A((E^hH)_k, (E^hK)_k) is equivalent to the
homotopy fixed point spectrum ((E[[G/H]])^hK)_k where H and K are closed
subgroups of G. Applications to Morava E-theory are given, including showing
that the homotopy fixed points defined by Devinatz and Hopkins for closed
subgroups of the extended Morava stabilizer group agree with those defined with
respect to a continuous action and in terms of the derived functor of fixed
points.Comment: 60 Page
The Charge of Glass and Silica Surfaces
We present a method of calculating the electric charge density of glass and
silica surfaces in contact with aqueous electrolytes for two cases of practical
relevance that are not amenable to standard techniques: surfaces of low
specific area at low ionic strength and surfaces interacting strongly with a
second anionic surface.Comment: 7 pages, including 3 figure
Solid-state combustion synthesis of ceramics and alloys in reduced gravity
Possible microgravity effects are explored in the combustion synthesis of ceramics and alloys from their constituent elements. Molten intermediates are typically present during the combustion process, thereby offering the chance for natural convection to take place. Numerical simulations suggest that the combustion front in concert with gravity may act as a partial zone-refinement mechanism which is attempting to sweep out porosity in the sample. Contrary to suggestions by dimensional analysis, no effects on the combustion rate are seen. An analytical model of the combustion velocity as a function of the gravitational field and the spreading rate of molten material gives the correct order of magnitude of the gravity effect as measured by centrifuge experiments
Traditional male circumcision : Balancing cultural rights and the prevention of serious, avoidable harm.
PKThe right to participate in cultural practices should be protected. However, it is a limited right, and does not entail a right to activities that cause serious and avoidable harms. I argue that the harms currently resulting from traditional circumcision are very serious, and that we have an obligation to ensure that the practice is effectively regulated so as to minimise the
Models for pushing objects with a mobile robot using single point contact
In many mobile robotic manipulation tasks it is desirable to interact with the robots surroundings without actually grasping the object being manipulated. Non-prehensile manipulation allows a robot to interact in situations which would otherwise be impossible due to size or weight. This paper presents the derivation of a mathematical model of an object pushed by a single point and sliding in the presence of friction where the dynamic effects of mass and inertia are significant. This model is validated using numerical simulation. The derived dynamic model is also compared with a kinematic approximation from literature, showing that under certain conditions, the motion of a pushed object is similar to the motion of a non-holonomic vehicle. Finally, the results of experimental investigations are discussed and promising directions for further work are proposed. ©2010 IEEE
Probing Low Energy Neutrino Backgrounds with Neutrino Capture on Beta Decaying Nuclei
We study the interaction of low energy neutrinos on nuclei that spontaneously
undergo beta decay showing that the product of the cross section times neutrino
velocity takes values as high as 10^{-42} cm^2 c for some specific nuclei that
decay via allowed transitions. The absence of energy threshold and the value of
the cross section single out these processes as a promising though very
demanding approach for future experiments aimed at a direct detection of low
energy neutrino backgrounds such as the cosmological relic neutrinos.Comment: Includes a discussion of local relic neutrino density effect on
neutrino capture rate. Accepted for publication in JCA
High-resolution quantitative profiling of tRNA abundance and modification status in eukaryotes by mim-tRNAseq
Measurements of cellular tRNA abundance are hampered by pervasive blocks to cDNA synthesis at modified nucleosides and the extensive similarity among tRNA genes. We overcome these limitations with modification-induced misincorporation tRNA sequencing (mim-tRNAseq), which combines a workflow for full-length cDNA library construction from endogenously modified tRNA with a comprehensive and user-friendly computational analysis toolkit. Our method accurately captures tRNA abundance and modification status in yeast, fly, and human cells and is applicable to any organism with a known genome. We applied mim-tRNAseq to discover a dramatic heterogeneity of tRNA isodecoder pools among diverse human cell lines and a surprising interdependence of modifications at distinct sites within the same tRNA transcript
Combined analysis of KamLAND and Borexino neutrino signals from Th and U decays in the Earth's interior
The KamLAND and Borexino experiments have detected electron antineutrinos
produced in the decay chains of natural thorium and uranium (Th and U
geoneutrinos). We analyze the energy spectra of current geoneutrino data in
combination with solar and long-baseline reactor neutrino data, with
marginalized three-neutrino oscillation parameters. We consider the case with
unconstrained Th and U event rates in KamLAND and Borexino, as well as cases
with fewer degrees of freedom, as obtained by successively assuming for both
experiments a common Th/U ratio, a common scaling of Th+U event rates, and a
chondritic Th/U value. In combination, KamLAND and Borexino can reject the null
hypothesis (no geoneutrino signal) at 5 sigma. Interesting bounds or
indications emerge on the Th+U geoneutrino rates and on the Th/U ratio, in
broad agreement with typical Earth model expectations. Conversely, the results
disfavor the hypothesis of a georeactor in the Earth's core, if its power
exceeds a few TW. The interplay of KamLAND and Borexino geoneutrino data is
highlighted.Comment: 12 pages, including 6 figure
Potential of a Neutrino Detector in the ANDES Underground Laboratory for Geophysics and Astrophysics of Neutrinos
The construction of the Agua Negra tunnels that will link Argentina and Chile
under the Andes, the world longest mountain range, opens the possibility to
build the first deep underground labo- ratory in the Southern Hemisphere. This
laboratory has the acronym ANDES (Agua Negra Deep Experiment Site) and its
overburden could be as large as \sim 1.7 km of rock, or 4500 mwe, providing an
excellent low background environment to study physics of rare events like the
ones induced by neutrinos and/or dark matter. In this paper we investigate the
physics potential of a few kiloton size liquid scintillator detector, which
could be constructed in the ANDES laboratory as one of its possible scientific
programs. In particular, we evaluate the impact of such a detector for the
studies of geoneutrinos and galactic supernova neutrinos assuming a fiducial
volume of 3 kilotons as a reference size. We emphasize the complementary roles
of such a detector to the ones in the Northern Hemisphere neutrino facilities
through some advantages due to its geographical location.Comment: 20 pages, 16 figures and 9 table
Two-Body B Meson Decays to η and η': Observation of B → η'K
In a sample of 6.6×10^6 produced B mesons we have observed decays B→η′K, with branching fractions B(B^+→η′K^+) = (6.5_(-1.4)^(+1.5)±0.9)×10^(-5) and B(B^0→η′K^0) = (4.7_(-2.0)^(+2.7)±0.9)×10^(-5). We have searched with comparable sensitivity for 17 related decays to final states containing an η or η′ meson accompanied by a single particle or low-lying resonance. Our upper limits for these constrain theoretical interpretations of the B→η′K signal
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