30,198 research outputs found
The cost of virtue : reward as well as feedback are required to reduce user ICT power consumption
This work was partly supported by the IU-AC project, funded by grant EP/J016756/1 from the Engineering and Physical Sciences Research Council (EPSRC).We show that students in a school lab environment will change their behaviour to be more energy efficient, when appropriate incentives are in place, and when measurement-based, real-time feedback about their energy usage is provided. Rewards incentivise `non-green' users to be `green' as well as encouraging those users who already claim to be `green'. Measurement-based feedback improves user energy awareness and helps users to explore and adjust their use of computers to become `greener', but is not sufficient by itself. In our measurements, weekly mean group energy use as a whole reduced by up to 16%; and weekly individual user energy consumption reduced by up to 56% during active use. The findings are drawn from our longitudinal study that involved 83 Computer Science students; lasted 48 weeks across 2 academic years; monitored a total of 26778 hours of active computer use; collected approximately 2TB of raw data.Publisher PD
Relativistic Conic Beams and Spatial Distribution of Gamma-Ray Bursts
We study the statistics of gamma-ray bursts, assuming that gamma-ray bursts
are cosmological and they are beamed in the form of a conical jet with a large
bulk Lorentz factor . In such a conic beam, the relativistic ejecta
may have a spatial variation in the bulk Lorentz factor and the density
distribution of gamma-ray emitting jet material. An apparent luminosity
function arises because the axis of the cone is randomly oriented with respect
to the observer's line of sight. The width and the shape of the luminosity
function are determined by the ratio of the beam opening angle of the conical
jet to the inverse of the bulk Lorentz factor, when the bulk Lorentz factor and
the jet material density is uniform on the photon emitting jet surface. We
calculate effects of spatial variation of the Lorentz factor and the spatial
density fluctuations within the cone on the luminosity function and the
statistics of gamma-ray bursts. In particular, we focus on the redshift
distribution of the observed gamma-ray bursts. The maximum distance to and the
average redshift of the gamma-ray bursts are strongly affected by the
beaming-induced luminosity function. The bursts with the angle-dependent
Lorentz factor which peaks at the center of the cone have substantially higher
average gamma-ray burst redshifts. When both the jet material density and the
Lorentz factor are inhomogeneous in the conical beam, the average redshift of
the bursts could be 5 times higher than that of the case in which relativistic
jet is completely homogeneous and structureless. Even the simplest models for
the gamma-ray burst jets and their apparent luminosity distributions have a
significant effect on the redshift distribution of the gamma-ray bursts.Comment: 15 pages, 4 figures, submitted to ApJ
Analysis of a conserved cellulase transcriptional regulator reveals inducer-independent production of cellulolytic enzymes in Neurospora crassa.
Cellulose is recalcitrant to deconstruction to glucose for use in fermentation strategies for biofuels and chemicals derived from lignocellulose. In Neurospora crassa, the transcriptional regulator, CLR-2, is required for cellulolytic gene expression and cellulose deconstruction. To assess conservation and divergence of cellulase gene regulation between fungi from different ecological niches, we compared clr-2 function with its ortholog (clrB) in the distantly related species, Aspergillus nidulans. Transcriptional profiles induced by exposure to crystalline cellulose were similar in both species. Approximately 50% of the cellulose-responsive genes showed strict dependence on functional clr-2/clrB, with a subset of 28 genes encoding plant biomass degrading enzymes that were conserved between N. crassa and A. nidulans. Importantly, misexpression of clr-2 under noninducing conditions was sufficient to drive cellulase gene expression, secretion, and activity in N. crassa, to a level comparable to wild type exposed to Avicel. However, misexpression of clrB in A. nidulans was not sufficient to drive cellulase gene expression under noninducing conditions, although an increase in cellulase activity was observed under crystalline cellulose conditions. Manipulation of clr-2 orthologs among filamentous fungi may enable regulated cellulosic enzyme production in a wide array of culture conditions and host strains, potentially reducing costs associated with enzyme production for plant cell wall deconstruction. However, this functionality may require additional engineering in some species
Holographic RG Flow in a New Sector of -Deformed Gauged Supergravity
We consider a certain supersymmetric,
invariant, subsector of the -deformed family of -gauged four-dimensional supergravities. The theory contains two scalar fields
and two pseudoscalar fields. We look for stationary points of the scalar
potential, corresponding to AdS vacua in the theory. One of these, which breaks
all supersymmetries but is nonetheless stable, is new. It exists only when
. We construct supersymmetric domain wall solutions in the
truncated theory, and we give a detailed analysis of their holographic dual
interpretations using the AdS/CFT correspondence. Domain walls where the
pseudoscalars vanish were studied previously, but those with non-vanishing
pseudoscalars, which we analyse numerically, are new. The pseudoscalars are
associated with supersymmetric mass deformations in the CFT duals. When
is zero, the solutions can be lifted to M-theory, where they approach
the Coulomb-branch flows of dielectric M5-branes wrapped on in the deep
IR.Comment: 40 pages, 10 figure
Thermodynamics of Magnetised Kerr-Newman Black Holes
The thermodynamics of a magnetised Kerr-Newman black hole is studied to all
orders in the appended magnetic field . The asymptotic properties of the
metric and other fields are dominated by the magnetic flux that extends to
infinity along the axis, leading to subtleties in the calculation of conserved
quantities such as the angular momentum and the mass. We present a detailed
discussion of the implementation of a Wald-type procedure to calculate the
angular momentum, showing how ambiguities that are absent in the usual
asymptotically-flat case may be resolved by the requirement of gauge
invariance. We also present a formalism from which we are able to obtain an
expression for the mass of the magnetised black holes. The expressions for the
mass and the angular momentum are shown to be compatible with the first law of
thermodynamics and a Smarr type relation. Allowing the appended magnetic field
to vary results in an extra term in the first law of the form
where is interpreted as an induced magnetic moment. Minimising the total
energy with respect to the total charge at fixed values of the angular
momentum and energy of the seed metric allows an investigation of Wald's
process. The Meissner effect is shown to hold for electrically neutral extreme
black holes. We also present a derivation of the angular momentum for black
holes in the four-dimensional STU model, which is supergravity
coupled to three vector multiplets.Comment: 27 page
- âŠ