58,724 research outputs found
N=2 Conformal Superspace in Four Dimensions
We develop the geometry of four dimensional N=2 superspace where the entire
conformal algebra of SU(2,2|2) is realized linearly in the structure group
rather than just the SL(2,C) x U(2)_R subgroup of Lorentz and R-symmetries,
extending to N=2 our prior result for N=1 superspace. This formulation
explicitly lifts to superspace the existing methods of the N=2 superconformal
tensor calculus; at the same time the geometry, when degauged to SL(2,C) x
U(2)_R, reproduces the existing formulation of N=2 conformal supergravity
constructed by Howe.Comment: 43 pages; v2 references added, acknowledgments update
Timing by Stellar Pulsations as an Exoplanet Discovery Method
The stable oscillations of pulsating stars can serve as accurate timepieces,
which may be monitored for the influence of exoplanets. An external companion
gravitationally tugs the host star, causing periodic changes in pulsation
arrival times. This method is most sensitive to detecting substellar companions
around the hottest pulsating stars, especially compact remnants like white
dwarfs and hot subdwarfs, as well as delta Scuti variables (A stars). However,
it is applicable to any pulsating star with sufficiently stable oscillations.
Care must be taken to ensure that the changes in pulsation arrival times are
not caused by intrinsic stellar variability; an external, light-travel-time
effect from an exoplanet identically affects all pulsation modes. With more
long-baseline photometric campaigns coming online, this method is yielding new
detections of substellar companions.Comment: 9 pages, 2 figures: Invited review to appear in 'Handbook of
Exoplanets,' Springer Reference Works, edited by Hans J. Deeg and Juan
Antonio Belmont
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Minimizing the Cost of Innovative Nuclear Technology Through Flexibility: The Case of a Demonstration Accelerator-Driven Subcritical Reactor Park
Presented is a methodology to analyze the expected Levelised Cost Of Electricity (LCOE) in the face of technology uncertainty for Accelerator-Driven Subcritical Reactors (ADSRs). It shows that flexibility in the design and deployment strategy of an ADSR park demonstrator significantly reduces its expected LCOE. The methodology recognizes in the conceptual design a range of possible technological outcomes for the ADSR accelerator system. It identifies flexibility âonâ and âinâ the design to modify the future development path in light of such uncertain scenarios. Uncertainty and flexibility are incorporated in the ADSR valuation. The resulting economic assessment is more realistic than typical discounted cash flow analysis that does not consider a range of development outcomes, or the flexibility to change development path
Uniting mathematics and biology for control of visceral leishmaniasis
The neglected tropical disease (NTD) visceral leishmaniasis (VL) has been targeted by the WHO for elimination as a public health problem on the Indian subcontinent by 2017 or earlier. To date there is a surprising scarcity of mathematical models capable of capturing VL disease dynamics, which are widely considered central to planning and assessing the efficacy of interventions. The few models that have been developed are examined, highlighting the necessity for better data to parameterise and fit these and future models. In particular, the characterisation and infectiousness of the different disease stages will be crucial to elimination. Modelling can then assist in establishing whether, when, and how the WHO VL elimination targets can be met
Reconciling a significant hierarchical assembly of massive early-type galaxies at z<~1 with mass downsizing
Hierarchical models predict that massive early-type galaxies (mETGs) are the
latest systems to be in place into the cosmic scenario (at z<~0.5), conflicting
with the observational phenomenon of galaxy mass downsizing, which poses that
the most massive galaxies have been in place earlier that their lower-mass
counterparts (since z~0.7). We have developed a semi-analytical model to test
the feasibility of the major-merger origin hypothesis for mETGs, just
accounting for the effects on galaxy evolution of the major mergers strictly
reported by observations. The most striking model prediction is that very few
present-day mETGs have been really in place since z~1, because ~90% of the
mETGs existing at z~1 are going to be involved in a major merger between z~1
and the present. Accounting for this, the model derives an assembly redshift
for mETGs in good agreement with hierarchical expectations, reproducing
observational mass downsizing trends at the same time.Comment: 2 pages, 1 figure, Proceedings of Symposium 2 of JENAM 2010,
"Environment and the Formation of Galaxies: 30 years later", ed. I. Ferreras
and A. Pasquali, Astrophysics & Space Science Proceedings, Springe
Interfacial adhesion of laser clad functionally graded materials
Specially designed samples of laser clad AlSi40 functionally graded materials (FGM) are made for evaluating the interfacial adhesion. To obtain the interfacial bond strength notches are made right at the interface of the FGMs. In-situ microstructural observations during straining in a field-emission gun environmental scanning electron microscopy reveal different failure modes of the FGMs and substrate. Mapping of strain fields using digital imaging correlation shows a gradual transition of deformation over the interface region and softening effects in the heat-affected zones of the FGM tracks. The strengthening of the FGM is dominated by the size of the Al halos around the particles, in accordance with a dislocation pile-up model.
The coastal marine mollusc fauna of King Island, Tasmania
The findings of a week-long survey of coastal marine molluscs around King Island are documented. In total, 408 species were recorded, 78 for the first time. King Island appears to be the only Tasmanian outpost for 44 species. Only two non-native species were found. A number of usually distinct species-pairs or groups appear to form intergrades around King Island. Along the islandâs east coast, beached shells belonging to Quaternary-era sub-fossils were found, not all of which are represented in the contemporary local fauna. Following critical examination of published sources and museum specimens, a checklist of King Islandâs coastal marine mollusc fauna is presented, comprising 619 species. It is likely that many more local species await discovery and documentation
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