1,353 research outputs found
Innate talents: reality or myth?
Talents that selectively facilitate the acquisition of high levels of skill are said to be present in some children but not others. The evidence for this includes biological correlates of specific abilities, certain rare abilities in autistic savants, and the seemingly spontaneous emergence of exceptional abilities in young children, but there is also contrary evidence indicating an absence of early precursors of high skill levels. An analysis of positive and negative evidence and arguments suggests that differences in early experiences, preferences, opportunities, habits, training, and practice are the real determinants of excellence
History of depression and survival after acute myocardial infarction
Objective: To compare survival in post-myocardial (MI) participants from the Enhancing Recovery In Coronary Heart Disease (ENRICHD) clinical trial with a first episode of major depression (MD) and those with recurrent MID, which is a risk factor for mortality after acute MI. Recent reports suggest that the level of risk may depend on whether the comorbid MD is a first or a recurrent episode. Methods: Survival was compared over a median of 29 months in 370 patients with an initial episode of MD, 550 with recurrent MD, and 408 who were free of depression. Results: After adjusting for an all-cause mortality risk score, initial Beck Depression Inventory score, and the use of selective serotonin reuptake inhibitor antidepressants, patients with a first episode of MD had poorer survival (18.4% all-cause mortality) than those with recurrent MD (11.8%) (hazard ratio (HR)=1.4; 95% Confidence Interval (CI)=1.0-2.0; p=.05). Both first depression (HR=3.1; 95% CI=1.6-6.1; p=.001) and recurrent MD (HR=2.2; 95% CI=1.1-4.4; p=.03) had significantly poorer survival than did the nondepressed patients (3.4%). A secondary analysis of deaths classified as probably due to a cardiovascular cause resulted in similar HRs, but the difference between depression groups was not significant. Conclusions: Both initial and recurrent episodes of MD predict shorter survival after acute MI, but initial MD episodes are more strongly predictive than recurrent episodes. Exploratory analyses suggest that this cannot be explained by more severe heart disease at index, poorer response to depression treatment, or a higher risk of cerebrovascular disease in patients with initial MD episodes
Gauged Dimension Bubbles
Some of the peculiar electrodynamical effects associated with gauged
``dimension bubbles'' are presented. Such bubbles, which effectively enclose a
region of 5d spacetime, can arise from a 5d theory with a compact extra
dimension. Bubbles with thin domain walls can be stabilized against total
collapse by the entrapment of light charged scalar bosons inside the bubble,
extending the idea of a neutral dimension bubble to accommodate the case of a
gauged U(1) symmetry. Using a dielectric approach to the 4d dilaton-Maxwell
theory, it is seen that the bubble wall is almost totally opaque to photons,
leading to a new stabilization mechanism due to trapped photons. Photon
dominated bubbles very slowly shrink, resulting in a temperature increase
inside the bubble. At some critical temperature, however, these bubbles
explode, with a release of radiation.Comment: 14 pages, no figures; to appear in Phys.Rev.
Fermionic and Bosonic Stabilizing Effects for Type I and Type II Dimension Bubbles
We consider two types of "dimension bubbles", which are viewed as 4d
nontopological solitons that emerge from a 5d theory with a compact extra
dimension. The size of the extra dimension varies rapidly within the domain
wall of the soliton. We consider the cases of type I (II) bubbles where the
size of the extra dimension inside the bubble is much larger (smaller) than
outside. Type I bubbles with thin domain walls can be stabilized by the
entrapment of various particle modes whose masses become much smaller inside
than outside the bubble. This is demonstrated here for the cases of scalar
bosons, fermions, and massive vector bosons, including both Kaluza-Klein zero
modes and Kaluza-Klein excitation modes. Type II bubbles expel massive particle
modes but both types can be stabilized by photons. Plasma filled bubbles
containing a variety of massless or nearly massless radiation modes may exist
as long-lived metastable states. Furthermore, in contrast to the case with a
"gravitational bag", the metric for a fluid-filled dimension bubble does not
exhibit a naked singularity at the bubble's center.Comment: 17 pages, no figs; to appear in Phys.Rev.
Relativistic effects in electromagnetic nuclear responses in the quasi-elastic delta region
A new non-relativistic expansion in terms of the nucleon's momentum inside
nuclear matter of the current for isobar electro-excitation from the nucleon is
performed. Being exact with respect to the transferred energy and momentum,
this yields new current operators which retain important aspects of relativity
not taken into account in the traditional non-relativistic reductions. The
transition current thus obtained differs from the leading order of the
traditional expansion by simple multiplicative factors. These depend on the
momentum and energy transfer and can be easily included together with
relativistic kinematics in non-relativistic, many-body models of isobar
electro-excitation in nuclei. The merits of the new current are tested by
comparing with the unexpanded electromagnetic nuclear responses in the isobar
peak computed in a relativistic Fermi gas framework. The sensitivity of the
relativistic responses to the isobar's magnetic, electric and Coulomb form
factors and the finite width of the isobar is analyzed.Comment: 26 pages plus 6 figure
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