908 research outputs found
Real-time digital modelling in design education and practice
Real-time modelling represents the first thoroughgoing application of the digital realm to architecture and urban design, and as such marks a clear advance on the partial applications that were previously the norm. The authors have pooled their combined expertise in architecture and computer games to adapt the principles and techniques of real-time environments from computer games to designing buildings. The outcome is proprietary software called Cadai, which allows architectural and urban design proposals to be modelled in realistic detail, both externally and internally, and then be "walked" around in their entirety by viewers.
This paper argues that real-time modelling offers three advances on previous forms of 3D digital modelling: it enables digital modelling to be used from the earliest sketch stages of a design project; it allows collective online meetings of the project team inside the evolving design scheme, wherever the participants are in the world; and it enables greater user-participation in decisions about planning schemes, given that anyone familiar with computer game environments can now properly understand and experience architectural and urban design proposals. The paper explains the properties of Cadai and showcases some real-time models built by students at Oxford Brookes University and the University of Westminster, along with the first major commercial real-time model produced in Cadai for a brownfield development proposal in Northern England. Our contention is that real-time modelling will soon become the dominant way that computers operate in architectural and urban design, and will remain so for the foreseeable future
Numerical counterparts of GRB host galaxies
We explore galaxy properties in general and properties of host galaxies of
gamma-ray bursts (GRBs) in particular, using N-body/Eulerian hydrodynamic
simulations and the stellar population synthesis model, Starburst99, to infer
observable properties. We identify simulated galaxies that have optical star
formation rate (SFR) and SFR-to-luminosity ratio similar to those observed in a
well-defined sample of ten host galaxies. Each of the numerical counterparts
are found in catalogs at the same redshifts as the observed hosts. The
counterparts are found to be low-mass galaxies, with low mass-to-light ratio,
recent epoch of formation, and high ratio between the SFR and the average of
the SFR. When compared to the overall galaxy population, they have colors much
bluer than the high-mass star-forming galaxy population. Although their SFRs
span a range of values, the specific rates of the numerical counterparts are
equal to or higher than the median values estimated at the different redshifts.
We also emphasize the strong relationships between the specific star formation
rate (SFR) and quantities known to reflect the star formation history of
galaxies, i.e. color and mass-to-light ratio: At intermediate redshift, the
faintest and bluest galaxies are also the objects with the highest specific
rates. These results suggest that GRB host galaxies are likely to be drawn from
the high specific SFR sub-population of galaxies, rather than the high SFR
galaxy population. Finally, as indicated by our catalogs, in an extended
sample, the majority of GRB host galaxies is expected to have specific SFRs
higher than found in the magnitude-limited sample studied here.Comment: 11 pages, 11 figures. Accepted for publication in MNRA
Inducers of Friend leukaemic cell differentiation in vitro--effects of in vivo administration.
Studies were conducted of the in vivo therapeutic potential of compounds which induce the differentiation of Friend leukaemia cells (FLC) in vitro. DBA2/J mice were inoculated with Friend leukaemia cells grown in tissue culture and at various times thereafter were treated with either N-methylacetamide, dimethylacetamide, or tetramethylurea. While survival was only occasionally prolonged, in every study these agents significantly inhibited leukaemia cell proliferation in the spleen and to a lesser extent in the marrow. These agents had no effect on the rate of proliferation of FLC growing subcutaneously nor on the proliferation of myeloid leukaemia in RFMS mice. These studies indicate that the administration of inducing agents to mice bearing Friend leukaemia can alter the proliferation characteristics of the leukaemia cells and hence suggest that these agents may have therapeutic potential
Energy Injection in GRB Afterglow Models
We extend the standard fireball model, widely used to interpret gamma-ray
burst (GRB) afterglow light curves, to include energy injections, and apply the
model to the afterglow light curves of GRB 990510, GRB 000301C and GRB 010222.
We show that discrete energy injections can cause temporal variations in the
optical light curves and present fits to the light curves of GRB 000301C as an
example. A continuous injection may be required to interpret other bursts such
as GRB 010222. The extended model accounts reasonably well for the observations
in all bands ranging from X-rays to radio wavelengths. In some cases, the radio
light curves indicate that additional model ingredients may be needed.Comment: Accepted for publication in the Astrophysical Journa
Multiple melt plumes observed at the Breioamerkurjokull ice face in the upper waters of Jokulsarlon lagoon, Iceland
Breioamerkurjokull flows from the Vatnajokull ice cap and calves into the Jokulsarlon proglacial lagoon. The lagoon is connected to the North Atlantic Ocean through a 6 m deep narrow channel. Four hydrographic surveys in spring 2012, and a 2011 4-month long temperature and salinity time series of lagoon inflow show that the lake has significantly changed since 1976. Warm saline ocean water enters each tidal cycle and descends below the maximum sampled depths. The lagoon has a surface layer of ice melt, freshwater and Atlantic derived water. Beneath 10 m depth an advective/diffusive balance is responsible for determining the temperature and salinity of the lagoon waters down to ~90 m. To maintain the observed hydrographic structure, we calculate an upwelling of deep water of ~0.2 m d−1. A survey within 30 m of Breioamerkurjokull showed that the warmest and most saline waters sampled within the lagoon below 10 m depth were adjacent to the glacier face, along with multiple interleaved warm and cold layers. A heat and salt balance model shows that submarine melting along the ice face generates multiple meltwater plumes that are mixed and diluted within 200 m of the ice face
Self-Organized Criticality in Compact Plasmas
Compact plasmas, that exist near black-hole candidates and in gamma ray burst
sources, commonly exhibit self-organized non-linear behavior. A model that
simulates the non-linear behavior of compact radiative plasmas is constructed
directly from the observed luminosity and variability. The simulation shows
that such plasmas self organize, and that the degree of non-linearity as well
as the slope of the power density spectrum increase with compactness. The
simulation is based on a cellular automaton table that includes the properties
of the hot (relativistic) plasmas, and the magnitude of the energy
perturbations. The plasmas cool or heat up, depending on whether they release
more or less than the energy of a single perturbation. The energy release
depends on the plasmas densities and temperatures, and the perturbations
energy. Strong perturbations may cool the previously heated plasma through
shocks and/or pair creation.
New observations of some active galactic nuclei and gamma ray bursters are
consistent with the simulationComment: 9 pages, 5 figures, AASTeX, Submitted to ApJ
Gravity and elevation changes at Askja, Iceland
Ground tilt measurements demonstrate that Askja is in a state of unrest, and that in the period 1988 - 1991 a maximum 48 +/- 3 µrad tilt occurred down towards the centre of the caldera. This is consistent with 126 mm of deflation at the centre of the caldera with a 2.5 - 3.0 km depth to the source of deformation. The volume of the subsidence bowl is 6.2 x 106 m3. When combined with high precision microgravity measurements, the overall change in sub-surface mass may be quantified. After correction for the observed elevation change using the free air gradient of gravity measured for each station, the total change in mass is estimated to be less than 109 kg. A small residual ground inflation and net gravity increase in the eastern part of the caldera may be caused by dyke intrusion in this region. The minimum dimensions of such an intrusion or complex of intrusions are 1m width, up to 100m deep and up to several hundred metres thick
Modelling variable glacier lapse rates using ERA-Interim reanalysis climatology: an evaluation at Vestari- Hagafellsjökull, Langjökull, Iceland
The near-surface air temperature lapse rate is an important tool for spatially distributing temperatures in snow- and ice-melt models, but is difficult to parameterize, as it is not simply correlated with boundary-layer meteorological variables, such as temperature itself. This contribution quantifies spring-autumn lapse rate variability over 5 years at Vestari-Hagafellsjökull, a southerly outlet of Langjökull in Iceland. It is observed that summer lapse rates (0.57 °C 100 m) are significantly lower than non-summer rates, and are also lower than the Saturated Adiabatic Lapse Rate (SALR), which is often adopted in melt models. This is consistent with reduced near-surface temperature sensitivity to free-atmosphere temperature change during the occurrence of melting. A Variable Lapse Rate (VLR) regression model is calibrated with standardized, 750 hPa temperature anomalies derived from ERA-Interim climatology, which is shown to be highly significantly correlated with near-surface temperatures. The modelled VLR overestimates cumulative June-September Positive Degree Days (PDDs) by 3% when used to extrapolate temperatures from 1100 to 500 m a.s.l. on the glacier, whereas the SALR overestimates cumulative PDDs by 14%. ERA-Interim data therefore appear to offer a good representation of free-atmosphere temperature variability over Vestari-Hagafellsjökull, and the modelling approach offers a simple means of improving lapse rate parameterizations in melt models. © 2012 Royal Meteorological Society
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