7,052 research outputs found
THE REAL RATE OF PROTECTION: THE STABILIZING EFFECT OF PRICE POLICIES AND DIRECT PAYMENTS
Traditional indicators of protection refer to the level effect of price policies on income and ignore the stabilizing effect. We derive a measure of the real rate of protection which incorporates these dual dimensions. The income stabilizing effects of price policy protection lead to a greater level of real protection than would be measured conventionally. Computed real protection rates for the European Union wheat market over the pre- and post-MacSharry reform periods were found to be some 3-5 percent greater than traditional indicators. Moreover, the compensatory payments to farmers following the 1992 reforms had a major risk reducing impact.International Relations/Trade,
Experimental Analysis of Turbulent Structures and the Effects of Non-Equilibrium on an Axial Vortex
Examples of the axial vortex include, dust devils, trailing line aircraft wake vortices, and tornadoes. Some of these vortices can prove hazardous to individuals and property. This necessitates that studies be conducted to understand their structure and to attempt to develop mathematical models of the flow physics involved. A wide variety of experimental techniques have been used in the past to study the vortex, with flow visualization and hotwire anemometry being chosen for this experiment. There have been many inadequate mathematical models proposed in the past. The experimental results obtained were compared to the work of Ash, Zardadkhan and Zuckerwar (2011) taking into account the effects of non-equilibrium pressure forces on the flow. Their work used an eddy viscosity model to satisfy closure of the Navier-Stokes equation. The applicability of this model was further accessed in the experiment.
For the purpose of this experiment a bi-wing vortex generator was constructed. The vortex generator was designed without a central body in an attempt to minimize the velocity deficit created by its wake. This was instead replaced with a small cylinder containing a bevel gear system to link the movement of one wing to the other so prices adjustments could be made simultaneously. In the experiment Flow Visualization via smoke injection into the wind tunnel was used to observe the structure of the vortex. These observations were used to determine which vortex generator and wind tunnel setting yielded the largest most stable vortex. With the vortex generator set at an angle of attack of ±12º hotwire surveys employing a TSI 300 anemometer paired with an X-wire hot-film probe were then conducted on vortices at tunnel settings of 30 m/s and 40 m/s
Velocity profiles consistent with axial vortices were observed in the hotwire surveys. These profiles, when compared to the profiles generated taking into account non-equilibrium pressure effects, indicated that pressure relaxation and therefore non-equilibrium forces had a meaningful effect on the axial vortices. The Reynolds stress data obtained in the experiment also indicated that the Reynolds stress follow a trend consistent with the eddy viscosity model though it was impossible to obtain fully conclusive results due to the x-films inability to obtain the “axial-azimuthal” Reynolds stress correlation. Further study is required to give a more comprehensive view of the effects of non-equilibrium conditions on axial vortices
Validation of a novel scoring system for changes in skeletal manifestations of hypophosphatasia in newborns, infants, and children: The Radiographic Global Impression of Change scale
Hypophosphatasia (HPP) is the heritable metabolic disease characterized by impaired skeletal mineralization due to low activity of the tissue-nonspecific isoenzyme of alkaline phosphatase. Although HPP during growth often manifests with distinctive radiographic skeletal features, no validated method was available to quantify them, including changes over time. We created the Radiographic Global Impression of Change (RGI-C) scale to assess changes in the skeletal burden of pediatric HPP. Site-specific pairs of radiographs of newborns, infants, and children with HPP from three clinical studies of asfotase alfa, an enzyme replacement therapy for HPP, were obtained at baseline and during treatment. Each pair was scored by three pediatric radiologists ( raters ), with nine raters across the three studies. Intrarater and interrater agreement was determined by weighted Kappa coefficients. Interrater reliability was assessed using intraclass correlation coefficients (ICCs) and by two-way random effects analysis of variance (ANOVA) and a mixed-model repeated measures ANOVA. Pearson correlation coefficients evaluated relationships of the RGI-C to the Rickets Severity Scale (RSS), Pediatric Outcomes Data Collection Instrument Global Function Parent Normative Score, Childhood Health Assessment Questionnaire Disability Index, 6-Minute Walk Test percent predicted, and Z-score for height in patients aged 6 to 12 years at baseline. Eighty-nine percent (8/9) of raters showed substantial or almost perfect intrarater agreement of sequential RGI-C scores (weighted Kappa coefficients, 0.72 to 0.93) and moderate or substantial interrater agreement (weighted Kappa coefficients, 0.53 to 0.71) in patients aged 0 to 12 years at baseline. Moderate-to-good interrater reliability was observed (ICC, 0.57 to 0.65). RGI-C scores were significantly (p ≤ 0.0065) correlated with the RSS and with measures of global function, disability, endurance, and growth in the patients aged 6 to 12 years at baseline. Thus, the RGI-C is valid and reliable for detecting clinically important changes in skeletal manifestations of severe HPP in newborns, infants, and children, including during asfotase alfa treatment. © 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc
A Multiscale Investigation of Habitat Use and Within-river Distribution of Sympatric Sand Darter Species
The western sand darter Ammocrypta clara, and eastern sand darter Ammocrypta pellucida are sand-dwelling fishes of conservation concern. Past research has emphasized the importance of studying individual populations of conservation concern, while recent research has revealed the importance of incorporating landscape scale processes that structure habitat mosaics and local populations. We examined habitat use and distributions of western and eastern sand darters in the lower Elk River of West Virginia. At the sandbar habitat use scale, western sand darters were detected in sandbars with greater area, higher proportions of coarse grain sand and faster bottom current velocity, while the eastern sand darter used a wider range of sandbar habitats. The landscape scale analysis revealed that contributing drainage area was an important predictor for both species, while sinuosity, which presumably represents valley type also contributed to the western sand darter’s habitat suitability. Sandbar quality (area, grain size, and velocity) and fluvial geomorphic variables (drainage area and valley type) are likely key driving factors structuring sand darter distributions in the Elk River. This multiscale study of within-river species distribution and habitat use is unique, given that only a few sympatric populations are known of western and eastern sand darters
Evaporation of particle-stabilised emulsion sunscreen films
We recently showed (Binks et al., ACS Appl. Mater. Interfaces, 2016, DOI: 10.1021/acsami.6b02696) how evaporation of sunscreen films consisting of solutions of molecular UV filters leads to loss of UV light absorption and derived sun protection factor (SPF). In the present work, we investigate evaporation-induced effects for sunscreen films consisting of particle-stabilized emulsions containing a dissolved UV filter. The emulsions contained either droplets of propylene glycol (PG) in squalane (SQ), droplets of SQ in PG or droplets of decane in PG. In these different emulsion types, the SQ is involatile and shows no evaporation, the PG is volatile and evaporates relatively slowly, whereas the decane is relatively very volatile and evaporates quickly. We have measured the film mass and area, optical micrographs of the film structure, and the UV absorbance spectra during evaporation. For emulsion films containing the involatile SQ, evaporation of the PG causes collapse of the emulsion structure with some loss of specular UV absorbance due to light scattering. However, for these emulsions with droplets much larger than the wavelength of light, the light is scattered only at small forward angles so does not contribute to the diffuse absorbance and the film SPF. The UV filter remains soluble throughout the evaporation and thus the UV absorption by the filter and the SPF remain approximately constant. Both PG-in-SQ and SQ-in-PG films behave similarly and do not show area shrinkage by dewetting. In contrast, the decane-in-PG film shows rapid evaporative loss of the decane, followed by slower loss of the PG resulting in precipitation of the UV filter and film area shrinkage by dewetting which cause the UV absorbance and derived SPF to decrease. Measured UV spectra during evaporation are in reasonable agreement with spectra calculated using models discussed here
Spectrophotometry of thin films of light absorbing particles
Thin films of dispersions of light absorbing solid particles or emulsions containing a light absorbing solute all have a non-uniform distribution of light absorbing species throughout the sample volume. This results in non-uniform light absorption over the illuminated area which causes the optical absorbance, as measured using a conventional specular UV-vis spectrophotometer, to deviate from the Beer-Lambert relationship. We have developed a theoretical model to account for the absorbance properties of such films which are shown to depend on the size and volume fraction of the light absorbing particles plus other sample variables. We have compared model predictions with measured spectra for samples consisting of emulsions containing a dissolved light absorbing solute. Using no adjustable parameters, the model successfully predicts the behaviour of non-uniform, light absorbing emulsion films with varying values of droplet size, volume fraction and other parameters
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Liquid Titanium Solute Diffusion Measured by Pulsed Ion-Beam Melting
The diffusivities of Sri, Mo, Zr, and Hf in liquid Ti were determined by pulsed ion-beam melting of thin liquid layers. Time-resolved optical reflectance and one-dimensional heat-flow simulations were employed to determine the melt duration. The broadening of nearly Gaussian solute concentration-depth profiles was determined ex situ using Rutherford backscattering spectrometry. Solute diffusivities in the range of 5 to 9 X 10-5 cm2/s were determined at temperatures in the range of 2200 to 2500 K. Calculations of buoyancy and Marangoni convection indicate that convective contamination is unlikely.Engineering and Applied Science
Analysis of Observed Contamination Through SAGE III's First Year on Orbit
SAGE III is a payload on the International Space Station that conducts measurements of ozone and other atmospheric constituents through the use of a moderate resolution spectrometer with an operating wavelength range of 290 nm to 1550 nm. Because of the optically sensitive nature of the payload, a suite of eight Thermoelectric Quartz Crystal Microbalances (TQCMs) were included to monitor the operating environment. During the rst year of operation, the SAGE III TQCMs were instrumental in detecting several periods of higher contamination and localizing their sources. A clear window made from quartz crystal covers the instrument assembly's aperture. Under nominal operating conditions, this window is only open during science gathering activities. However, if the rates of contamination accumulation are detected to be above the background rate, the window will be kept closed during science gathering to protect the optically sensitive instrument mirror. An analysis of the signal transmissions through the window for the wavelengths of 290 nm to 1550 nm has been conducted to determine any possible degradation of the window and potential in uence on science data collected to date, and established a baseline for future analysis
Shear-dependent apparent slip on hydrophobic surfaces: The Mattress Model
Recent experiments (Zhu & Granick (2001) Phys. Rev. Lett. 87 096105) have
measured a large shear dependent fluid slip at partially wetting fluid-solid
surfaces. We present a simple model for such slip, motivated by the recent
observations of nanobubbles on hydrophobic surfaces. The model considers the
dynamic response of bubbles to change in hydrodynamic pressure due to the
oscillation of a solid surface. Both the compression and diffusion of gas in
the bubbles decrease the force on the oscillating surface by a ``leaking
mattress'' effect, thereby creating an apparent shear-dependent slip. With
bubbles similar to those observed by atomic force microscopy to date, the model
is found to lead to force decreases consistent with the experimental
measurements of Zhu & Granick
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