6,580 research outputs found
Reactant pressure differential control for fuel cell gases
A pair of spool valves are described which are balanced between pressures of reactant gases supplied to a fuel cell power plant. The pressure differences are controlled between the gases so as to maintain those pressures substantially in the proportions necessary for operation of the fuel cell
Globalization of Capital Markets
Speech given at Session 1: The Global Capital Market: What\u27s Next. Richard Grasso spoke about the exciting changes that are transforming the global capital markets, particularly as seen from the perspective of 11 Wall Street. He also gave a brief review of some statistics, from markets past and present to show how dramatic these changes have been
The Sphaleron in a Magnetic Field and Electroweak Baryogenesis
The presence of a primordial magnetic field in the early universe affects the
dynamic of the electroweak phase transition enhancing its strength. This effect
may enlarge the window for electroweak baryogenesis in the minimal
supersymmetric extension of the standard model or even resurrect the
electroweak baryogenesis scenario in the standard model. We compute the
sphaleron energy in the background of the magnetic field and show that, due to
the sphaleron dipole moment, the barrier between topologically inequivalent
vacua is lowered. Therefore, the preservation of the baryon asymmetry calls for
a much stronger phase transition than required in the absence of a magnetic
field. We show that this effect overwhelms the gain in the phase transition
strength, and conclude that magnetic fields do not help electroweak
baryogenesis.Comment: 10 pages, 2 figure
Pair-transfer probability in open- and closed-shell Sn isotopes
Approximations made to estimate two-nucleon transfer probabilities in
ground-state to ground-state transitions and physical interpretation of these
probabilities are discussed. Probabilities are often calculated by
approximating both ground states, of the initial nucleus A and of the final
nucleus A\pm 2 by the same quasiparticle vacuum. We analyze two improvements of
this approach. First, the effect of using two different ground states with
average numbers of particles A and A\pm2 is quantified. Second, by using
projection techniques, the role of particle number restoration is analyzed. Our
analysis shows that the improved treatment plays a role close to magicity,
leading to an enhancement of the pair-transfer probability. In mid-shell
regions, part of the error made by approximating the initial and final ground
states by a single vacuum is compensated by projecting onto good particle
number. Surface effects are analyzed by using pairing interactions with a
different volume-to-surface mixing. Finally, a simple expression of the
pair-transfer probability is given in terms of occupation probabilities in the
canonical basis. We show that, in the canonical basis formulation, surface
effects which are visible in the transfer probability are related to the
fragmentation of single-particle occupancies close to the Fermi energy. This
provides a complementary interpretation with respect to the standard
quasiparticle representation where surface effects are generated by the
integrated radial profiles of the contributing wave functions.Comment: 12 pages, 7 figure
Diffuse cosmic rays shining in the Galactic center: A novel interpretation of H.E.S.S. and Fermi-LAT gamma-ray data
We present a novel interpretation of the -ray diffuse emission
measured by Fermi-LAT and H.E.S.S. in the Galactic center (GC) region and the
Galactic ridge (GR). In the first part we perform a data-driven analysis based
on PASS8 Fermi-LAT data: we extend down to few GeV the spectra measured by
H.E.S.S. and infer the primary cosmic-ray (CR) radial distribution between 0.1
and 3 TeV. In the second part we adopt a CR transport model based on a
position-dependent diffusion coefficient. Such behavior reproduces the radial
dependence of the CR spectral index recently inferred from the Fermi-LAT
observations. We find that the bulk of the GR emission can be naturally
explained by the interaction of the diffuse steady-state Galactic CR sea with
the gas present in the Central Molecular Zone. Although our results leave room
for a residual radial-dependent emission associated with a central source, the
relevance of the large-scale background prevents from a solid evidence of a GC
Pevatron.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
Hard Cosmic Ray Sea in the Galactic Center: a consistent interpretation of H.E.S.S. and Fermi-LAT -ray data
We present a novel interpretation of the gamma-ray diffuse emission measured
by H.E.S.S. in the Galactic Center (GC) region and the Galactic ridge. Our
starting base is an updated analysis of PASS8 Fermi-LAT data, which allows to
extend down to few GeV the spectra measured by H.E.S.S. and to infer the
primary CR radial distribution above 100 GeV. We compare those results with a
CR transport model assuming a harder scaling of the diffusion coefficient with
rigidity in the inner Galaxy. Such a behavior reproduces the radial dependence
of the CR spectral index recently inferred from Fermi-LAT measurements in the
inner GP. We find that, in this scenario, the bulk of the Galactic ridge
emission can be naturally explained by the interaction of the diffuse,
steady-state Galactic CR sea interacting with the gas present in the Central
molecular zone. The evidence of a GC PeVatron is significantly weaker than that
inferred adopting a conventional (softer) CR sea.Comment: Oral contribution to the International Cosmic Ray Conference (ICRC
2017), 12-20 July 2017, Bexco, Busan, Kore
Observation of explosive collisionless reconnection in 3D nonlinear gyrofluid simulations
The nonlinear dynamics of collisionless reconnecting modes is investigated,
in the framework of a three-dimensional gyrofluid model. This is the relevant
regime of high-temperature plasmas, where reconnection is made possible by
electron inertia and has higher growth rates than resistive reconnection. The
presence of a strong guide field is assumed, in a background slab model, with
Dirichlet boundary conditions in the direction of nonuniformity. Values of ion
sound gyro-radius and electron collisionless skin depth much smaller than the
current layer width are considered. Strong acceleration of growth is found at
the onset to nonlinearity, while at all times the energy functional is well
conserved. Nonlinear growth rates more than one order of magnitude higher than
linear growth rates are observed when entering into the small- regime
Towards an expanded model of litigation
Introduction: The call for contributions for this workshop describes the important new challenges for the legal search
community this domain brings. Rather than just understanding the challenges this domain poses in terms of
their technical properties, we would like to suggest that understanding these challenges as socio-technical
challenges will be important. That is, as well as calling for research on a technical level to address these
challenges we are also calling for work to understand the social practices of those involved in e-discovery
(ED) and related legal work. A particularly interesting feature of this field is that it is likely that search
technologies will (at least semi-)automate responsiveness review in the relatively near term and this will
change the way that the work is organised and done in many ways â offering new possibilities for new
ways of organising the work. As well as designing those technologies for automating responsiveness
review we need to be envisioning how the work will be done in the future, how these technologies will
impact the organisation of the case and so on. In this position paper we therefore outline the importance of
understanding the wider social context of ED when designing tools and technologies to support and change
the work. We would like to reinforce and expand on Conradâs call for IR researchers to understand just
what ED entails [2], include the stages that come both before and after core retrieval activities.
The importance of considering the social aspects of work in the design of the technology has been
established for some time. Ushering in this âturn to the social,â and focusing on interface design, Gentner
and Grudin [4] described how the GUI has already changed from an interface for engineers, representing
the engineering model of the machine to one that supported single âeverymanâ users (based on ideas from
psychology). From then onwards the interface has evolved to support groups of users, taking into account
the social and organisational contexts of use. This has particular resonance for the design of ED
technologies: during ED in particular and the wider legal process there are often many lawyers involved â
reviewing documents, determining issues, etc. Even if the way that their work is organised currently is not
seen as collaborative in the traditional sense â with individual lawyers working on individual document sets
to review them - their work needs to be coordinated and it seems likely that their work could be enhanced
by, for example, knowledge of what their colleagues had found, how the case was shaping up, new key
terms and facts turned up and so on. Work is often modelled for the purposes of design using process
models, but this misses out on the richness and variety actually found when one examines how the work is
carried out [3]. Technologies which strictly enforce the process models can often hinder the work, or end
up being worked around as was the case with workflow systems since people interpret processes very
flexibly to get the work done ([1], [3]). Other studies in other fields have found similar problems when
systems are designed on for example cognitive models of how the work is done; they often do not take into
account the situated nature of the work and thus they can be very difficult to use [5]. We believe, like [2],
that a clear understanding of the social practices of ED is vital for the creation of high-quality, meaningful
tools and technologies. We furthermore propose that work practice studies, to be used in combination with
other methods, are a central part of getting the detailed understanding of the work practices central to
designing useful and intelligent tools. Work practice studies would involve ethnographies, consisting
primarily of observation, undertaken of practitioners engaging in the work of ED
A common solution to the cosmic ray anisotropy and gradient problems
Multichannel Cosmic Ray (CR) spectra and the large scale CR anisotropy can
hardly be made compatible in the framework of conventional isotropic and
homogeneous propagation models. These models also have problems explaining the
longitude distribution and the radial emissivity gradient of the -ray
galactic interstellar emission. We argue here that accounting for a well
physically motivated correlation between the CR escape time and the spatially
dependent magnetic turbulence power can naturally solve both problems. Indeed,
by exploiting this correlation we find propagation models that fit a wide set
of CR primary and secondary spectra, and consistently reproduce the CR
anisotropy in the energy range 10^2 - 10^4 \GeV and the -ray
longitude distribution recently measured by Fermi-LAT.Comment: 4 pages, 3 figures. v2: Accepted in Phys. Rev. Let
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