3,365 research outputs found
Constraining decaying dark matter with neutron stars
The amount of decaying dark matter, accumulated in the central regions in
neutron stars together with the energy deposition rate from decays, may set a
limit on the neutron star survival rate against transitions to more compact
objects provided nuclear matter is not the ultimate stable state of matter and
that dark matter indeed is unstable. More generally, this limit sets
constraints on the dark matter particle decay time, . We find that
in the range of uncertainties intrinsic to such a scenario, masses or and lifetimes s and
s can be excluded in the bosonic or fermionic
decay cases, respectively, in an optimistic estimate, while more
conservatively, it decreases by a factor . We
discuss the validity under which these results may improve with other current
constraints.Comment: 6 pages, 1 figure, matches published versio
Recommended from our members
Trade Preferences: Economic Issues and Policy Options
[Excerpt] Since 1974, Congress has created multiple trade preference programs designed to foster economic growth, reform, and development in less developed countries. These programs give temporary, non-reciprocal, duty-free U.S. market access to select exports of eligible countries. Congress conducts regular oversight of these programs, repeatedly revising and extending them. Two major issues face the 111th Congress: (1) the expiration of two preference programs by December 31, 2010; and (2) possible legislative action on broader reform of the preference programs based on comprehensive reviews in hearings held in both the House and the Senate earlier in this Congress.
This report discusses the major U.S. trade preference programs, their possible economic effects, stakeholder interests, and legislative options
Rotation symmetry axes and the quality index in a 3D octahedral parallel robot manipulator system
The geometry of a 3D octahedral parallel robot manipulator system is specified in terms of two rigid octahedral structures (the fixed and moving platforms) and six actuation legs. The symmetry of the system is exploited to determine the behaviour of (a new version of) the quality index for various motions. The main results are presented graphically
Race and Health Disparities Among Seniors in Urban Areas in Brazil
White seniors report better health than Black seniors in urban areas in Sao Paulo, Brazil. This is the case even after controlling for baseline health conditions and several demographic, socio-economic and family support characteristics. Furthermore, adjusted racial disparities in self-reported health are larger than the disparities found using alternative measures of functional health. Our empirical research in this paper suggests that the two most important factors driving racial disparities in health among seniors (in our sample) are historical differences in rural living conditions and current income. Present economic conditions are more relevant to racial disparities among poor seniors than among rich seniors. Moreover, racial differences in health not attributable to observable characteristics are more important when comparing individuals in the upper half of the income distribution.
- …