Are Public Housing Projects Good For Kids?

One goal of federal housing policy is to improve the prospects of children in poor families. But little research has been conducted into the effects on children of participation in housing programs, perhaps because it is difficult to find data sets with information about both participation and interesting outcome measures. This paper combines data from several sources to provide a first look at the effects of participation in public housing projects on housing quality and on the educational attainment of children. We first use administrative data from the Department of Housing and Urban Development to impute the probability that a Census household lives in a public housing project. We find that a higher probability of living in a project is associated with poorer outcomes. We then use a two-sample instrumental variables (TSIV) technique to combine information on the probability of living in a project, obtained from the 1990 to 1995 Current Population Surveys, with information on outcomes obtained from the 1990 Census. The instrument common to both samples is an indicator equal to one if the household is entitled to a larger housing project unit because of the sex composition of the children in the household. Families entitled to a larger unit because of sex composition are 24 percent more likely to live in projects. When we control for omitted variables bias using TSIV, we find that project households are less likely to suffer from overcrowding and less likely to live in high-density complexes. Project children are also 12 to 17 percentage points less likely to have been held back in school one or more grades, although this effect is confined to boys. Thus, most families do not face a tradeoff between housing quality and child outcomes—the average project improves both.

The impact of a new regional air ambulance service on a large general hospital

Background: Helicopter air ambulance crews are influenced in their selection of the destination hospital for their patients by several factors including: distance from the scene; facilities, on site specialties, and senior cover of the receiving hospital; and the proximity of the helicopter landing area to the emergency department (ED). Only a limited number of hospitals have landing sites adjacent to the ED from which patients can be taken directly into the department (primary landing sites). Helicopter crews will often elect to over fly hospitals that do not have primary landing sites because secondary land transfers will add delays in delivering patients. Birmingham Heartlands Hospital has an elevated helideck adjacent to the ED. In October 2003, the Warwickshire and Northamptonshire Air Ambulance (WNAA) service was launched; the hospital sits on the western periphery of the area served by the service. Methods: Prospective data was collated on all patients brought by WNAA to Heartlands Hospital between 1 October 2003 and 31 August 2004. Results: In the 10 month period after the launch of the service, the helicopter delivered 83 patients to the ED; 74 of these were "off patch". This additional workload generated 163 ward days, 19 operative procedures, and 85 intensive care unit, high dependency unit, or coronary care unit days. The direct costs of this additional workload approached £160 000. Conclusions: In future discussions on the cost effectiveness of air ambulances, it will be important to consider both the direct and indirect costs to the receiving hospitals arising from the redistribution of emergency workload. Abbreviations: ED, emergency department; HDU, high dependency unit; HEMS, helicopter emergency medical service; ICU, intensive care unit; ISS, injury severity score; WNAA, Warwickshire and Northamptonshire Air Ambulance; WMCAA, West Midlands County Air Ambulance

Contingent plan structures for spacecraft

Most current AI planners build partially ordered plan structures which delay decisions on action ordering. Such structures cannot easily represent contingent actions. A representation which can is presented. The representation has some other useful features: it provides a good account of the causal structure of a plan, can be used to describe disjunctive actions, and it offers a planner the opportunity of even less commitment than the classical partial order on actions. The use of this representation is demonstrated in an on-board spacecraft activity sequencing problem. Contingent plan execution in a spacecraft context highlights the requirements for a fully disjunctive representation, since communication delays often prohibit extensive ground-based accounting for remotely sensed information and replanning on execution failure

Introduction to the special issue: Social construct within an information society

Managing Information Systems (IS) is increasingly complex, as multiple stakeholders try to communicate, act, and interact for social and business gain. Understanding and managing these complex stakeholder relations and the contingencies of successful communication among culturally diverse stakeholder groups are some of the major challenges for professional communicators in the third millennium. Such challenges have important implications for communication between user and developer groups as training and education of the users becomes more complex. In an effort to connect information system practice with communication theory, this special issue of IEEE Transactions on Professional Communication looks at information systems as social constructs of an information societ

Tablet computers in assessing performance in a high stakes exam : opinion matters

The authors would like to thank Dr Craig brown, University of Aberdeen for assistance with data analysis.Peer reviewedPublisher PD

Ubiquitous energy storage

This paper presents a vision of a future power system with "ubiquitous energy storage", where storage would be utilized at all levels of the electricity system. The growing requirement for storage is reviewed, driven by the expansion of distributed generation. The capabilities and existing applications of various storage technologies are presented, providing a useful review of the state of the art. Energy storage will have to be integrated with the power system and there are various ways in which this may be achieved. Some of these options are discussed, as are commercial and regulatory issues. In two case studies, the costs and benefits of some storage options are assessed. It is concluded that electrical storage is not cost effective but that thermal storage offers attractive opportunities

Hamiltonian Formulation of Two Body Problem in Wheeler-Feynman electrodynamics

A Hamiltonian formulation for the classical problem of electromagnetic interaction of two charged relativistic particles is found.Comment: 22 pages, 8 Uuencoded Postscript figure

Magmatic expressions of continental lithosphere removal

Gravitational lithosphere removal in continental interior has been inferred from various observations, including anomalous surface deflections and magmatism. We use numerical models and a simplified theoretical analysis to investigate how lithosphere removal can be recognized in the magmatic record. One style of removal is a Rayleigh-Taylor-type instability, where removal occurs through dripping. The associated magmatism depends on the lithosphere thermal structure. Four types of magmatism are predicted: (1) For relatively hot lithosphere (e.g., back arcs), the lithosphere can be conductively heated and melted during removal, while the asthenosphere upwells and undergoes decompression melting. If removal causes significant lithospheric thinning, the deep crust may be heated and melted. (2) For moderately warm lithosphere (e.g., average Phanerozoic lithosphere) in which the lithosphere root has a low density, only the lithosphere may melt. (3) If the lithosphere root has a high density in moderately warm lithosphere, only asthenosphere melt is predicted. (4) For cold lithosphere (e.g., cratons), no magmatism is induced. An alternate style of removal is delamination, where dense lithosphere peels along Moho. In most cases, the lithosphere sinks too rapidly to melt. However, asthenosphere can upwell to the base of the crust, resulting in asthenospheric and crustal melts. In delamination, magmatism migrates laterally with the detachment point; in contrast, magmatism in Rayleigh-Taylor-type instability has a symmetric shape and converges toward the drip center. The models may explain the diversity of magmatism observed in areas with inferred lithosphere removal, including the Puna Plateau and the southern Sierra Nevada

Crustal deformation induced by mantle dynamics: insights from models of gravitational lithosphere removal

Mantle-based stresses have been proposed to explain the occurrence of deformation in the interior regions of continental plates, far from the effects of plate boundary processes. We examine how the gravitational removal of a dense mantle lithosphere root may induce deformation of the overlying crust. Simplified numerical models and a theoretical analysis are used to investigate the physical mechanisms for deformation and assess the surface expression of removal. Three behaviours are identified: (1) where the entire crust is strong, stresses from the downwelling mantle are efficiently transferred through the crust. There is little crustal deformation and removal is accompanied by surface subsidence and a negative free-air gravity anomaly. Surface uplift and increased free-air gravity occur after the dense root detaches. (2) If the mid-crust is weak, the dense root creates a lateral pressure gradient in the crust that drives Poiseuille flow in the weak layer. This induces crustal thickening, surface uplift and a minor free-air gravity anomaly above the root. (3) If the lower crust is weak, deformation occurs through pressure-driven Poiseuille flow and Couette flow due to basal shear. This can overthicken the crust, producing a topographic high and a negative free-air gravity anomaly above the root. In the latter two cases, surface uplift occurs prior to the removal of the mantle stress. The modeling results predict that syn-removal uplift will occur if the crustal viscosity is less than ∼10^(21) Pa s, corresponding to temperatures greater than ∼400–500 °C for a dry and felsic or wet and mafic composition, and ∼900 °C for a dry and mafic composition. If crustal temperatures are lower than this, lithosphere removal is marked by the formation of a basin. These results can explain the variety of surface expressions observed above areas of downwelling mantle. In addition, observations of the surface deflection may provide a way to constrain the vertical rheological structure of the crust

Confirmation of the planet around HD 95086 by direct imaging

VLT/NaCo angular differential imaging at L' (3.8 microns) revealed a probable giant planet comoving with the young and early-type HD 95086 also known to harbor an extended debris disk. The discovery was based on the proper motion analysis of two datasets spanning 15 months. However, the second dataset suffered from bad atmospheric conditions, which limited the significance of the redetection at the 3 sigma level. In this Letter, we report new VLT/NaCo observations of HD 95086 obtained on 2013 June 26-27 at L' to recover the planet candidate. We unambiguously redetect the companion HD 95086 b with multiple independent pipelines at a signal-to-noise ratio greater than or equal to 5. Combined with previously reported measurements, our astrometry decisively shows that the planet is comoving with HD 95086 and inconsistent with a background object. With a revised mass of 5 pm 2 Jupiter masses, estimated from its L' photometry and "hot-start" models at 17 pm 4 Myr, HD 95086 b becomes a new benchmark for further physical and orbital characterization of young giant planets.Comment: accepted for publication to AP