4,132 research outputs found
A 928 sq m (10000 sq ft) solar array
As the power requirements for space vehicles increases, the area of solar arrays that convert solar energy to usable electrical power increases. The requirements for a 928 sq m (10,000 sq ft) array, its design, and a full-scale demonstration of one quadrant (232 sq m (2500 sq ft)) deployed in a one-g field are described
The uniting of Europe and the foundation of EU studies: revisiting the neofunctionalism of Ernst B. Haas
This article suggests that the neofunctionalist theoretical legacy left by Ernst B. Haas is somewhat richer and more prescient than many contemporary discussants allow. The article develops an argument for routine and detailed re-reading of the corpus of neofunctionalist work (and that of Haas in particular), not only to disabuse contemporary students and scholars of the normally static and stylized reading that discussion of the theory provokes, but also to suggest that the conceptual repertoire of neofunctionalism is able to speak directly to current EU studies and comparative regionalism. Neofunctionalism is situated in its social scientific context before the theory's supposed erroneous reliance on the concept of 'spillover' is discussed critically. A case is then made for viewing Haas's neofunctionalism as a dynamic theory that not only corresponded to established social scientific norms, but did so in ways that were consistent with disciplinary openness and pluralism
One step multiderivative methods for first order ordinary differential equations
A family of one-step multiderivative methods based on Padé approximants to the exponential function is developed.
The methods are extrapolated and analysed for use in PECE mode.
Error constants and stability intervals are calculated and the combinations compared with well known linear multi-step combinations and combinations using high accuracy Newton-Cotes quadrature formulas as correctors.
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Warm gas towards young stellar objects in Corona Australis - Herschel/PACS observations from the DIGIT key programme
The effects of external irradiation on the chemistry and physics in the
protostellar envelope around low-mass young stellar objects are poorly
understood. The Corona Australis star-forming region contains the R CrA dark
cloud, comprising several low-mass protostellar cores irradiated by an
intermediate-mass young star. We study the effects on the warm gas and dust in
a group of low-mass young stellar objects from the irradiation by the young
luminous Herbig Be star R CrA. Herschel/PACS far-infrared datacubes of two
low-mass star-forming regions in the R CrA dark cloud are presented. The
distribution of CO, OH, H2O, [C II], [O I], and continuum emission is
investigated. We have developed a deconvolution algorithm which we use to
deconvolve the maps, separating the point-source emission from the extended
emission. We also construct rotational diagrams of the molecular species. By
deconvolution of the Herschel data, we find large-scale (several thousand AU)
dust continuum and spectral line emission not associated with the point
sources. Similar rotational temperatures are found for the warm CO (
K), hot CO ( K), OH ( K), and H2O ( K) emission,
respectively, in the point sources and the extended emission. The rotational
temperatures are also similar to what is found in other more isolated cores.
The extended dust continuum emission is found in two ridges similar in extent
and temperature to molecular mm emission, indicative of external heating from
the Herbig Be star R CrA. Our results show that a nearby luminous star does not
increase the molecular excitation temperatures in the warm gas around a young
stellar object (YSO). However, the emission from photodissociation products of
H2O, such as OH and O, is enhanced in the warm gas associated with these
protostars and their surroundings compared to similar objects not suffering
from external irradiation.Comment: 37 pages, accepted for publication in A&
Dynamic buckling and fragmentation in brittle rods
We present experiments on the dynamic buckling and fragmentation of slender
rods axially impacted by a projectile. By combining the results of Saint-Venant
and elastic beam theory, we derive a preferred wavelength lambda for the
buckling instability, and experimentally verify the resulting scaling law for a
range of materials including teflon, dry pasta, glass, and steel. For brittle
materials, buckling leads to the fragmentation of the rod. Measured fragment
length distributions show two clear peaks near lambda/2 and lambda/4. The
non-monotonic nature of the distributions reflect the influence of the
deterministic buckling process on the more random fragmentation processes.Comment: 4 pages, 5 figures, submitted to Physical Review Letter
Ultrafast Coulomb-induced dynamics of 2D magnetoexcitons
We study theoretically the ultrafast nonlinear optical response of quantum
well excitons in a perpendicular magnetic field. We show that for
magnetoexcitons confined to the lowest Landau levels, the third-order
four-wave-mixing (FWM) polarization is dominated by the exciton-exciton
interaction effects. For repulsive interactions, we identify two regimes in the
time-evolution of the optical polarization characterized by exponential and
{\em power law} decay of the FWM signal. We describe these regimes by deriving
an analytical solution for the memory kernel of the two-exciton wave-function
in strong magnetic field. For strong exciton-exciton interactions, the decay of
the FWM signal is governed by an antibound resonance with an
interaction-dependent decay rate. For weak interactions, the continuum of
exciton-exciton scattering states leads to a long tail of the time-integrated
FWM signal for negative time delays, which is described by the product of a
power law and a logarithmic factor. By combining this analytic solution with
numerical calculations, we study the crossover between the exponential and
non-exponential regimes as a function of magnetic field. For attractive
exciton-exciton interaction, we show that the time-evolution of the FWM signal
is dominated by the biexcitonic effects.Comment: 41 pages with 11 fig
The Figure in Art: Selections from the Gettysburg College Collection
The Figure in Art: Selections from the Gettysburg College Collection is the second annual exhibition curated by students enrolled in the Art History Methods class. This exhibition is an exciting academic endeavor and provides an incredible opportunity for engaged learning, research, and curatorial experience. The eleven student curators are Diane Brennan, Rebecca Duffy, Kristy Garcia, Megan Haugh, Dakota Homsey, Molly Lindberg, Kathya Lopez, Kelly Maguire, Kylie McBride, Carolyn McBrady and Erica Schaumberg. Their research presents a multifaceted view of the representation of figures in various art forms from different periods and cultures.https://cupola.gettysburg.edu/artcatalogs/1017/thumbnail.jp
Asthma and treatment with inhaled corticosteroids: associations with hospitalisations with pneumonia
Background: Pneumonia is an important cause of morbidity and mortality. COPD patients using inhaled corticosteroids (ICS) have an increased risk of pneumonia, but less is known about whether ICS treatment in asthma also increases the risk of pneumonia. The aim of this analysis was to examine risk factors for hospitalisations with pneumonia in a general population sample with special emphasis on asthma and the use of ICS in asthmatics. Methods: In 1999 to 2000, 7340 subjects aged 28 to 54 years from three Swedish centres completed a brief health questionnaire. This was linked to information on hospitalisations with pneumonia from 2000 to 2010 and treatment with ICS from 2005 to 2010 held within the Swedish National Patient Register and the Swedish Prescribed Drug Register. Results: Participants with asthma (n=587) were more likely to be hospitalised with pneumonia than participants without asthma (Hazard Ratio (HR 3.35 (1.97-5.02)). Other risk factors for pneumonia were smoking (HR 1.93 (1.22-3.06)), BMI 30 kg/m2 (HR 2.54 (1.39-4.67)). Asthmatics (n=586) taking continuous treatment with fluticasone propionate were at an increased risk of being hospitalized with pneumonia (incidence risk ratio (IRR) 7.92 (2.32-27.0) compared to asthmatics that had not used fluticasone propionate, whereas no significant association was found with the use of budesonide (IRR 1.23 (0.36-4.20)). Conclusion: Having asthma is associated with a three times higher risk of being hospitalised for pneumonia. This analysis also indicates that there are intraclass differences between ICS compounds with respect to pneumonia risk, with an increased risk of pneumonia related to fluticasone propionate
Theory of exciton-exciton correlation in nonlinear optical response
We present a systematic theory of Coulomb interaction effects in the
nonlinear optical processes in semiconductors using a perturbation series in
the exciting laser field. The third-order dynamical response consists of
phase-space filling correction, mean-field exciton-exciton interaction, and
two-exciton correlation effects expressed as a force-force correlation
function. The theory provides a unified description of effects of bound and
unbound biexcitons, including memory-effects beyond the Markovian
approximation. Approximations for the correlation function are presented.Comment: RevTex, 35 pages, 10 PostScript figs, shorter version submitted to
Physical Review
Excavations and the afterlife of a professional football stadium, Peel Park, Accrington, Lancashire: towards an archaeology of football
Association football is now a multi-billion dollar global industry whose emergence spans the post-medieval to the modern world. With its professional roots in late 19th-century industrial Lancashire, stadiums built for the professionalization of football first appear in frequency in the North of England. While many historians of sport focus on consumerism and âtopophiliaâ (attachment to place) regarding these local football grounds, archaeological research that has been conducted on the spectator experience suggests status differentiation within them. Our excavations at Peel Park confirm this impression while also showing a significant afterlife to this stadium, particularly through childrenâs play
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