8,676 research outputs found
The deuteron: a mini-review
We review some recent results for elastic electron deuteron scattering
(deuteron form factors) and photodisintegration of the deuteron, with emphasis
on the recent high energy data from Jefferson Laboratory (JLab).Comment: 14 pages, 11 figures, Invited talk given to the Conference on Mesons
& Light Nuclei, held in Prague, Czech Republic, July 2- 6, 200
Electromagnetic structure of the deuteron
Recent measurements of the deuteron electromagnetic structure functions A, B,
and extracted from high energy elastic scattering, and the cross
sections and asymmetries extracted from high energy photodisintegration
, are reviewed and compared to theory. The theoretical
calculations range from nonrelativistic and relativistic models using the
traditional meson and baryon degrees of freedom, to effective field theories,
to models based on the underlying quark and gluon degrees of freedom of QCD,
including nonperturbative quark cluster models and perturbative QCD. We review
what has been learned from these experiments, and discuss why elastic
scattering and photodisintegration seem to require very different theoretical
approaches, even though they are closely related experimentally.Comment: review paper; 93 pages, 35 figure
Global shallow water magnetohydrodynamic waves in the solar tachocline
We derive analytical solutions and dispersion relations of global magnetic
Poincar\'e (magneto-gravity) and magnetic Rossby waves in the approximation of
shallow water magnetohydrodynamics. The solutions are obtained in a rotating
spherical coordinate system for strongly and weakly stable stratification
separately in the presence of toroidal magnetic field. In both cases magnetic
Rossby waves split into fast and slow magnetic Rossby modes. In the case of
strongly stable stratification (valid in the radiative part of the tachocline)
all waves are slightly affected by the layer thickness and the toroidal
magnetic field, while in the case of weakly stable stratification (valid in the
upper overshoot layer of the tachocline) magnetic Poincar\'e and fast magnetic
Rossby waves are found to be concentrated near the solar equator, leading to
equatorially trapped waves. However, slow magnetic Rossby waves tend to
concentrate near the poles, leading to polar trapped waves. The frequencies of
all waves are smaller in the upper weakly stable stratification region than in
the lower strongly stable stratification one
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Silicon Alley: A Framework for New York City’s Entrepreneurship Ecosystem and its Public Policy Considerations
As cities like New York emerge as hubs of innovation resolved in using technology and engaging non-governmental actors, this white paper pursues an analysis of the actors in the urban innovation ecosystem to pinpoint what makes these ecosystems distinct from their suburban counterparts. New York is unique in the way it describes innovation and entrepreneurs, pursuing an open and loose definition, enabling it to engage stakeholders and actors in a way that other places cannot. By bringing multiple perspectives and stakeholders into the fold, New York is able to pursue entrepreneurship hand in hand with civic duties, fostering an environment that centers public and social good in many cases. Actors then blur the boundaries between being entrepreneurs, public servants, and civil society members.
This paper explores the urban dynamics of innovation ecosystems, focusing on the role of New York in fostering and orchestrating them. Section I analyzes the disruptive role of emerging technologies in society, focusing on workforce and skills. Section II defines urban innovation ecosystems, assesses the forces that are propelling this new spatial geography of innovation, and provides insights into redefining the new dynamics and while arguing that the urban innovation ecosystem remains distinct from traditional “innovation ecosystems.” Section III provides a case study of New York’s innovation ecosystem and lists the multiple assets of the city as an innovation district. Finally, it puts forward policy considerations for a diverse set of stakeholders, including policy makers, technology companies, and civil society on how leveraging technology and entrepreneurship ecosystems can catalyze innovation; and illustrates policy actions applied to a number of challenges
Socioeconomic status and anxiety as predictors of antidepressant treatment response and suicidal ideation in older adults.
BACKGROUND: Separate reports from the maintenance treatment for late-life depression (MTLD) trials have shown that low socioeconomic status (SES) and anxiety symptoms at the time of treatment initiation predict lower levels of response to antidepressant treatment and higher levels of suicidal ideation in older adults. AIM: To determine whether SES and anxiety independently contribute to worse treatment outcomes, as indicated by persistence of depressive symptoms during treatment and the persistence of suicidal ideation. Consistent with prior evidence that sociodemographic factors and clinical history are both prognostic of depression treatment efficacy, we hypothesized that SES and pre-existing anxiety symptoms will both predict lower levels of response to treatment and higher levels of suicidal ideation. METHOD: Secondary analyses of data from the MTLD trials. RESULTS: Regression analyses which controlled for comorbid anxiety indicated that residents of middle- and high-income census tracts were more likely to respond to treatment (HR, 1.63; 95%CI, 1.08-2.46) and less likely to report suicidal ideation during treatment (OR, 0.51; 95%CI, 0.28-0.90) than residents of low income census tracts. The same regression models indicated that pre-existing anxiety symptoms were independently related to lower treatment response (HR, 0.73; 95%CI, 0.60-0.89) and higher risk of suicidal ideation (OR, 1.45; 95%CI, 0.98-2.14). CONCLUSION: These findings demonstrate the importance of treating anxiety symptoms during the course of treatment for late-life depression and, at the same time, addressing barriers to treatment response related to low SES
Seabird Bycatch in Pelagic Longline Fisheries Is Grossly Underestimated when Using Only Haul Data
Hundreds of thousands of seabirds are killed each year as bycatch in longline fisheries. Seabirds are predominantly caught during line setting but bycatch is generally recorded during line hauling, many hours after birds are caught. Bird loss during this interval may lead to inaccurate bycatch information. In this 15 year study, seabird bycatch was recorded during both line setting and line hauling from four fishing regions: Indian Ocean, Southern Ocean, Coral Sea and central Pacific Ocean. Over 43,000 albatrosses, petrels and skuas representing over 25 species were counted during line setting of which almost 6,000 seabirds attempted to take the bait. Bait-taking interactions were placed into one of four categories. (i) The majority (57%) of bait-taking attempts were “unsuccessful” involving seabirds that did not take the bait nor get caught or hooked. (ii) One-third of attempts were “successful” with seabirds removing the bait while not getting caught. (iii) One-hundred and seventy-six seabirds (3% of attempts) were observed being “caught” during line setting, with three albatross species – Laysan (Phoebastria immutabilis), black-footed (P. nigripes) and black-browed (Thalassarche melanophrys)– dominating this category. However, of these, only 85 (48%) seabird carcasses were retrieved during line hauling. Most caught seabirds were hooked through the bill. (iv) The remainder of seabird-bait interactions (7%) was not clearly observed, but likely involved more “caught” seabirds. Bait taking attempts and percentage outcome (e.g. successful, caught) varied between seabird species and was not always related to species abundance around fishing vessels. Using only haul data to calculate seabird bycatch grossly underestimates actual bycatch levels, with the level of seabird bycatch from pelagic longline fishing possibly double what was previously thought
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