39,107 research outputs found
The measurement of biaxial strains in coated fabric materials using the disc-replica method
A method of measuring biaxial strains in coated fabric type materials
is presented whereby the strain is deduced from the distortion of a circular
impression made on the material. The impression is placed on the material
when loaded, enabling all measurements to be made with the material in its
relaxed, unloaded, state
Multi-wavelength Observations of Blazar AO 0235+164 in the 2008-2009 Flaring State
The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to Îł-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the Îł-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 R_g. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus
The effect of parallel static and microwave electric fields on excited hydrogen atoms
Motivated by recent experiments we analyse the classical dynamics of a
hydrogen atom in parallel static and microwave electric fields. Using an
appropriate representation and averaging approximations we show that resonant
ionisation is controlled by a separatrix, and provide necessary conditions for
a dynamical resonance to affect the ionisation probability.
The position of the dynamical resonance is computed using a high-order
perturbation series, and estimate its radius of convergence. We show that the
position of the dynamical resonance does not coincide precisely with the
ionisation maxima, and that the field switch-on time can dramatically affect
the ionisation signal which, for long switch times, reflects the shape of an
incipient homoclinic. Similarly, the resonance ionisation time can reflect the
time-scale of the separatrix motion, which is therefore longer than
conventional static field Stark ionisation. We explain why these effects should
be observed in the quantum dynamics.
PACs: 32.80.Rm, 33.40.+f, 34.10.+x, 05.45.Ac, 05.45.MtComment: 47 pages, 20 figure
Observational evidence for the shrinking of bright maser spots
The nature of maser emission means that the apparent angular size of an
individual maser spot is determined by the amplification process as well as by
the instrinsic size of the emitting cloud. Highly sensitive MERLIN radio
interferometry images spatially and spectrally resolve water maser clouds
around evolved stars. We measured the properties of clouds around the red
supergiant S Per and the AGB stars IK Tau, RT Vir, U Her and U Ori, to test
maser beaming theory. Spherical clouds are expected to produce an inverse
relationship between maser intensity and apparent size, which would not be seen
from cylindrical or slab-like regions. We analysed the maser properties, in
order to estimate the saturation state, and investigated the variation of
observed spot size with intensity and across the spectral line profiles.
Circumstellar masers emanate from discrete clouds from about one to 20 AU in
diameter depending on the star. Most of the maser features have negative
excitation temperatures close to zero and modest optical depths, showing that
they are mainly unsaturated. Around S Per and (at most epochs) RT Vir and IK
Tau, the maser component size shrinks with increasing intensity. In contrast,
the masers around U Ori and U Her tend to increase in size, with a larger
scatter. The water masers from S Per, RT Vir and IK Tau are mainly beamed into
spots with an observed angular size much smaller than the emitting clouds and
smallest of all at the line peaks. This suggests that the masers are
amplification-bounded, emanating from approximately spherical clouds. Many of
the masers around U Her and U Ori have apparent sizes which are more similar to
the emitting clouds and have less or no dependence on intensity, suggesting
that these masers are matter-bounded. This is consistent with an origin in
flattened clouds and these two stars have shown other behaviour indicating the
presence of shocks.Comment: 17 pages, 26 figure files, accepted by A&A 2010 Oct 2
Print Advertisement Characteristics and Apple Variety Attraction: A Mimic Model Approach
A structural latent variable model of apple variety demand is used to analyze the effect of variety specific newspaper advertisement characteristics on variety attraction (preferences), and in turn on variety demand. The influence of advertisement size, the use of color and the Washington apple logo were analyzed. The estimated variety attraction variable is important in explaining demand. Model specifications which exclude this variable tend to understate demand elasticities. Advertisement size has a positive impact on Granny Smith, Fuji, and Gala sales. Red Delicious sales are positively influenced by color ads, but negatively affected by ads with the Washington apple logo.Apple demand, newspaper advertisements, structural latent variable model, Marketing,
DYNAMIC COMPLEMENTARITY IN EXPORT PROMOTION: THE MARKET ACCESS PROGRAM IN FRUITS AND VEGETABLES
Government-supported promotion in foreign markets may justified when market failures exist, such as spillover externalities, where promotion of one commodity positively influences exports of another, or when market uncertainties cause planning horizons to be shorter than the persistent effects of promotion. A dynamic model of U.S. apple, almond, grape, and wine export supply is developed to test for these market failures. Promotion is viewed as an investment in establishing and maintaining a productÂ’'s image. Evidence supporting the existence of each market failure is found. Exporters and program administrators may fail to account for them in export promotion planning.International Relations/Trade,
A BILATERAL COMPARISON OF FRUIT AND VEGETABLE CONSUMPTION: U.S AND CANADA
A structural latent variable model tests the role quality and information play in explaining observed differences in Canadian and U.S. produce consumption (5.0 vs. 3.5 servings/day). Dietary health information is significant in expanding demands. Quality promotes fruit consumption in Canada, consistent with the Alchian-Allen prediction.Food Consumption/Nutrition/Food Safety,
THE ECONOMIC VALUE OF PUBLIC RELATIONS EXPENDITURES: FOOD SAFETY AND THE STRAWBERRY CASE
Food safety has become an important issue affecting public health and grower profits. Outbreaks of foodborne illnesses are typically accompanied by press accounts of the incident and a decrease in demand. This study estimates the short- and long-run impacts of adverse and positive information delivered through print media on strawberry grower profits. Positive information may arise as apart of the promotional efforts of grower associations. It is found that adverse information reduces grower profits, but that positive information can partially offset their effects. It is suggested that grower groups could redirect funds used for promotion to food safety initiatives.Food Consumption/Nutrition/Food Safety,
Strategic Interaction With Multiple Tools: A New Empirical Model
The Lanchester model of strategic interaction typically considers only two-firm rivalry and one strategic tool. This paper presents an alternative that considers rivalry among several firms using multiple tools. Marketing decisions are dynamically optimal and use equations of motion for market share that are consistent with optimal consumer choice. Using a single-market case study that consists of five years of monthly data on ready to eat cereal sales, advertising, product development investments and new product introductions, we test our model against a similar Lanchester specification. Non-nested specification tests fail to reject the proposed model, but reject the Lanchester alternative.advertising, brands, cereal, dynamic, Lanchester, oligopoly, strategic interaction., Marketing,
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