275,900 research outputs found
An economical vent cover
Inexpensive formed-plastic vent cover has been developed that allows controlled purge of vent systems and also provides blowout protection. Cover can also be used in relief mode to allow normal system relief flows without disengaging from vent system. Cover consists of two parts made of plastics with varying densities to fit media used and desired pressures
Are the Kepler Near-Resonance Planet Pairs due to Tidal Dissipation?
The multiple-planet systems discovered by the Kepler mission show an excess
of planet pairs with period ratios just wide of exact commensurability for
first-order resonances like 2:1 and 3:2. In principle, these planet pairs could
have both resonance angles associated with the resonance librating if the
orbital eccentricities are sufficiently small, because the width of first-order
resonances diverges in the limit of vanishingly small eccentricity. We consider
a widely-held scenario in which pairs of planets were captured into first-order
resonances by migration due to planet-disk interactions, and subsequently
became detached from the resonances, due to tidal dissipation in the planets.
In the context of this scenario, we find a constraint on the ratio of the
planet's tidal dissipation function and Love number that implies that some of
the Kepler planets are likely solid. However, tides are not strong enough to
move many of the planet pairs to the observed separations, suggesting that
additional dissipative processes are at play.Comment: 20 pages, including 7 figures; accepted for publication in Ap
Scalar Quarkonium Masses and Mixing with the Lightest Scalar Glueball
We evaluate the continuum limit of the valence (quenched) approximation to
the mass of the lightest scalar quarkonium state, for a range of different
quark masses, and to the mixing energy between these states and the lightest
scalar glueball. Our results support the interpretation of as
composed mainly of the lightest scalar glueball.Comment: 14 pages of Latex, 5 PostScript figure
A Possible Origin of Dark Energy
We discuss the possibility that the existence of dark energy may be due to
the presence of a spin zero field , either elementary or composite. In
the presence of other matter field, the transformation
constant can generate a negative pressure, like the cosmological constant. In
this picture, our universe can be thought as a very large bag, similar to the
much smaller MIT bag model for a single nucleon.Comment: 4 pages, no figure, typos correcte
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Microbial mats of the Tswaing impact crater: results of a South African exobiology expedition and implications for the search for biological molecules on Mars
We describe microbial mats from the Tswaing impact crater in South Africa. The mats provide insights into the unique biological characteristics of impact craters and can help strategies for the search for biomolecules on Mars
Renormalization Group Study of the Electron-phonon Interaction in the High Tc Cuprates
We generalize the numerical renormalization group scheme to study the
phonon-mediated retarded interactions in the high Tc cuprates. We find that
three sets of phonon-mediated retarded quasiparticle scatterings grow under RG
flow. These scatterings share the following common features: 1) the initial and
final quasiparticle momenta are in the antinodal regions, and 2) the scattering
amplitudes have a symmetry. All three sets of retarded interaction
are driven to strong coupling by the magnetic fluctuations around .
After growing strong, these retarded interaction will trigger density wave
orders with d-wave symmetry. However, due to the d-wave form factor they will
leave the nodal quasiparticle unaffected. We conclude that the main effect of
electron-phonon coupling in the cuprates is to promote these density wave
orders.Comment: 4 pages, 3 figures, references added, added more details about
others' previous studie
Material Flow Analysis: Outcome Focus (MFA:OF) for Elucidating the Role of Infrastructure in the Development of a Liveable City
Engineered infrastructures (i.e., utilities, transport & digital) underpin modern society. Delivering services via these
is especially challenging in cities where differing infrastructures form a web of interdependencies. There must be a
step change in how infrastructures deliver services to cities, if those cities are to be liveable in the future (i.e., provide
for citizen wellbeing, produce less CO2 & ensure the security of the resources they use). Material Flow Analysis
(MFA) is a useful methodology for understanding how infrastructures transfer resources to, within and from cities
and contribute to the city’s metabolism. Liveable Cities, a five-year research programme was established to identify
& test radical engineering interventions leading to liveable cities of the future. In this paper, the authors propose an
outcome-focussed variation on the MFA methodology (MFA: OF), evidenced through work on the resource flows of
Birmingham, UK. These flows include water, energy, food & carbon-intensive materials (e.g., steel, paper, glass), as
well as their associated waste. The contribution MFA: OF makes to elucidating the interactions & interdependencies
between the flows is highlighted and suggestions are made for how it can contribute to the (radical) rethinking of the
engineered infrastructure associated with such flow
Temporal Aspects of Smart Contracts for Financial Derivatives
Implementing smart contracts to automate the performance of high-value
over-the-counter (OTC) financial derivatives is a formidable challenge. Due to
the regulatory framework and the scale of financial risk if a contract were to
go wrong, the performance of these contracts must be enforceable in law and
there is an absolute requirement that the smart contract will be faithful to
the intentions of the parties as expressed in the original legal documentation.
Formal methods provide an attractive route for validation and assurance, and
here we present early results from an investigation of the semantics of
industry-standard legal documentation for OTC derivatives. We explain the need
for a formal representation that combines temporal, deontic and operational
aspects, and focus on the requirements for the temporal aspects as derived from
the legal text. The relevance of this work extends beyond OTC derivatives and
is applicable to understanding the temporal semantics of a wide range of legal
documentation
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