Home About us Contact
|
Home About us Contact | ||
|
|
||
Independent Estimates (independent + estimate)
Selected AbstractsA thermochemical boundary layer at the base of Earth's outer core and independent estimate of core heat fluxGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2008David Gubbins SUMMARY Recent seismological observations suggest the existence of a ,150-km-thick density-stratified layer with a P -wave velocity gradient that differs slightly from PREM. Such a structure can only be caused by a compositional gradient, effects of a slurry or temperature being too small and probably the wrong sign. We propose a stably stratified, variable concentration layer on the liquidus. Heat is transported by conduction down the liquidus while the light and heavy components migrate through the layer by a process akin to zone refining, similar to the one originally proposed by Braginsky. The layer remains static in a frame of reference moving upwards with the expanding inner core boundary. We determine the gradient using estimates of co, the concentration in the main body of the outer core, and cb, the concentration of the liquid at the inner core boundary. We determine the depression of the melting point and concentrations using ideal solution theory and seismologically determined density jumps at the inner core boundary. We suppose that co determines ,,mod, the jump from normal mode eigenfrequencies that have long resolution lengths straddling the entire layer, and that cb determines ,,bod, the jump determined from body waves, which have fine resolution. A simple calculation then yields the seismic, temperature, and concentration profiles within the layer. Comparison with the distance to the C-cusp of PKP and normal mode eigenfrequencies constrain the model. We explore a wide range of possible input parameters; many fail to predict sensible seismic properties and heat fluxes. A model with ,,mod= 0.8 gm cc,1, ,,bod= 0.6 gm cc,1, and layer thickness 200 km is consistent with the seismic observations and can power the geodynamo with a reasonable inner core heat flux of ,2 TW and nominal inner core age of ,1 Ga. It is quite remarkable and encouraging that a model based on direct seismic observations and simple chemistry can predict heat fluxes that are comparable with those derived from recent core thermal history calculations. The model also provides plausible explanations of the observed seismic layer and accounts for the discrepancy between estimates of the inner core density jumps derived from body waves and normal modes. [source] Illusion of confirmation from exposure to another's hypothesisJOURNAL OF BEHAVIORAL DECISION MAKING, Issue 1 2006Derek J. Koehler Abstract We examine the influence of exposure to an advisor's hypothesis, in the form of a point estimate of an uncertain quantity, on subsequent point estimates and confidence judgments made by advisees. In three experiments, a group of unexposed advisees produced their own estimates before being presented with that of the advisor, while a group of exposed advisees were presented with the advisor's estimate before making their own. Not surprisingly, exposed advisees deliberately incorporated the information conveyed by the advisor's estimate in producing their own estimates. But the exposure manipulation also had a contaminating influence that shifted what the advisees viewed as their own, independent estimates toward those of the advisor. Seemingly unaware of this influence, exposed advisees were subject to an illusion of confirmation in which they expressed greater confidence in the accuracy of the advisor's estimate than did unexposed advisees. Copyright © 2006 John Wiley & Sons, Ltd. [source] Temperature and prey quality effects on growth of juvenile walleye pollock Theragra chalcogramma (Pallas): a spatially explicit bioenergetics approachJOURNAL OF FISH BIOLOGY, Issue 3 2007M. M. Mazur A bioenergetics model for juvenile age-0 year walleye pollock Theragra chalcogramma was applied to a spatially distinct grid of samples in the western Gulf of Alaska to investigate the influence of temperature and prey quality on size-specific growth. Daily growth estimates for 50, 70 and 90 mm standard length (LS) walleye pollock during September 2000 were generated using the bioenergetics model with a fixed ration size. Similarities in independent estimates of prey consumption generated from the bioenergetics model and a gastric evacuation model corroborated the performance of the bioenergetics model, concordance correlation (rc) = 0·945, lower 95% CL (transformed) (L1) = 0·834, upper 95% CL (transformed) (L2) = 0·982, P < 0·001. A mean squared error analysis (MSE) was also used to partition the sources of error between both model estimates of consumption into a mean component (MC), slope component (SC), and random component (RC). Differences between estimates of daily consumption were largely due to differences in the means of estimates (MC= 0·45) and random sources (RC= 0·49) of error, and not differences in slopes (SC= 0·06). Similarly, daily growth estimates of 0·031,0·167 g day,1 generated from the bioenergetics model was within the range of growth estimates of 0·026,0·190 g day,1 obtained from otolith analysis of juvenile walleye pollock. Temperature and prey quality alone accounted for 66% of the observed variation between bioenergetics and otolith growth estimates across all sizes of juvenile walleye pollock. These results suggest that the bioenergetics model for juvenile walleye pollock is a useful tool for evaluating the influence of spatially variable habitat conditions on the growth potential of juvenile walleye pollock. [source] Phase-equilibrium constraints on titanite and rutile activities in mafic epidote amphibolites and geobarometry using titanite,rutile equilibriaJOURNAL OF METAMORPHIC GEOLOGY, Issue 7 2009P. KAPP Abstract Activities of titanite (Ttn, CaTiSiO5) and/or rutile (Rt, TiO2) phase components were calculated for 45 well-characterized natural titanite- or rutile-undersaturated epidote,amphibolites by using the equilibria: (i) 3 anorthite + 2 zoisite/clinozoisite + rutile + quartz = 3 anorthite + titanite + water (referred to as TZARS) and (ii) anorthite + 2 titanite = grossular + 2 rutile + quartz (referred to as GRATiS). In titanite-bearing and rutile-absent samples aRt is 0.75 ± 0.26. In titanite-absent, rutile-bearing samples aTtn is 0.89 ± 0.16. Mean values derived for aRt/aTtn are 0.92 ± 0.12 for rutile + titanite-bearing samples and 0.42 ± 0.27 for samples lacking both titanite and rutile. Use of these values with TZARS yields pressure estimates for epidote,amphibolites that differ on average by <0.5 kbar from those recorded by established mineral barometers, even where both titanite and rutile are lacking. Despite rather large uncertainties in the average values obtained for aRt, aTtn or aRt/aTtn, application of TZARS yields pressure estimates that agree with independent estimates to within ±0.5 kbar for titanite- and/or rutile-saturated samples, and to within ±0.8 kbar for samples that contain neither Ti-phase. The accuracy and precision of the TZARS barometer are comparable to that of many well-calibrated barometers. TZARS offers a much-needed barometer for mafic rocks metamorphosed at epidote-bearing amphibolite and blueschist facies conditions. In addition, the results provide a basis for application of other thermobarometers, such as Ti-in-zircon, where rutile activity is required as input. [source] Strain rates from snowball garnetJOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2003C. Biermeier Abstract Spiral inclusion trails in garnet porphyroblasts are likely to have formed due to simultaneous growth and rotation of the crystals, during syn-metamorphic deformation. Thus, they contain information on the strain rate of the rock. Strain rates may be interpreted from such inclusion trails if two functions are known: (1) The relationship between rotation rate and shear strain rate; (2) the growth rate of the crystal. We have investigated details of both functions using a garnetiferous mica schist from the eastern European Alps as an example. The rotation rate of garnet porphyroblasts was determined using finite element modelling of the geometrical arrangement of the crystals in the rock. The growth rate of the porphyroblasts was determined by using the major and trace element distributions in garnet crystals, thermodynamic pseudosections and information on the grain size distribution. For the largest porphyroblast size fraction (size L=12 mm) we constrain a growth interval between 540 and 590 °C during the prograde evolution of the rock. Assuming a reasonable heating rate and using the angular geometry of the spiral inclusion trails we are able to suggest that the mean strain rate during crystal growth was of the order of =6.6 × 10,14 s,1. These estimates are consistent with independent estimates for the strain rates during the evolution of this part of the Alpine orogen. [source] Summer predation rates on ungulate prey by a large keystone predator: how many ungulates does a large predator kill?JOURNAL OF ZOOLOGY, Issue 4 2008J. W. Laundré Abstract Estimates of predation rates by large predators can provide valuable information on their potential impact on their ungulate prey populations. This is especially the case for pumas Puma concolor and its main prey, mule deer Odocoileus hemionus. However, only limited information on predation rates of pumas exist where mule deer are the only ungulate prey available. I used VHF telemetry data collected over 24-h monitoring sessions and once daily over consecutive days to derive two independent estimates of puma predation rates on mule deer where they were the only large prey available. For the 24-h data, I had 48 time blocks on female pumas with kittens, 43 blocks on females without kittens and 30 blocks on males. For the daily consecutive data, the average number of consecutive days followed was 51.5±4.2 days. There were data on five female pumas with kittens, five pregnant females and nine females without kittens. Predation rates over an average month of 30 days from the 24-h monitoring sessions were 2.0 mule deer per puma month for males (15.1 days per kill), 2.1 mule deer per puma month (14.3 days per kill) for females without kittens and 2.5 mule deer per puma month (12.0 days per kill) for pregnant females and females with kittens. For the consecutive daily data, females without kittens had an estimated predation rate of 2.1±0.14 mule deer per puma month (14.9±0.90 days per kill). Pregnant and females with kittens had predation rates of 2.7±0.18 and 2.6±0.21 mule deer per puma month, respectively (11.4±0.72 and 12.0±1.1 days per kill, respectively). Predation rates estimated in this study compared with those estimated by energetic demand for pumas in the study area but were lower than other field derived estimates. These data help increase our understanding of predation impacts of large predators on their prey. [source] Splitting the Baby: An Empirical Test of Rules of Thumb in Regulatory Price SettingKYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 3 2005T. Randolph Beard Summary This article provides an empirical evaluation of a recent and important exercise in regulatory price setting in the United States. The 1996 Telecommunications Act required incumbent local phone companies to sell components of their network to rival firms at regulated prices, and the prices for these ,unbundled network elements' were based primarily on independent estimates of forward-looking economic costs. Our econometric analysis reveals that, while cost is a primary determinant of element prices, the prices also reflect foregone retail profits for incumbent firms. Statistical tests suggest that ,splitting the baby' is an accurate positivist description of public agency behavior. [source] PRIMER NOTE: Primers for amplifying the hypervariable, male-transmitted COII-COI junction region in amblemine freshwater mussels (Bivalvia: Unionoidea: Ambleminae)MOLECULAR ECOLOGY RESOURCES, Issue 3 2007JENNIFER M. WALKER Abstract Freshwater bivalves in the superfamily Unionoidea possess distinct male (M)- and female (F)-transmitted mitochondrial DNA (mtDNA). The former evolves independently of and at a significantly faster rate than the latter. Thus, population genetic and phylogenetic analyses of M sequences facilitate the generation of independent estimates of genetic variation and evolutionary relationships which are often more robust than those provided by analyses of F sequences alone. However, M mtDNA's rapid substitution rate often renders polymerase chain reaction (PCR) amplification difficult with ,universal' primers. Herein, we report on three pairs of PCR primers that consistently amplify the hypervariable M COII-COI gene junction region in 25 bivalve genera (Unionoidea: Ambleminae). [source] What can we learn on the thermal history of the Universe from future cosmic microwave background spectrum measurements at long wavelengths?MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2003C. Burigana ABSTRACT We analyse the implications of future observations of the cosmic microwave background (CMB) absolute temperature at centimetre and decimetre wavelengths, where both ground, balloon and space experiments are currently under way to complement the accurate COBE/FIRAS data available at ,, 1 cm. Our analysis shows that forthcoming ground and balloon measurements will allow a better understanding of free,free distortions but will not be able to significantly improve the constraints already provided by the FIRAS data on the possible energy exchanges in the primeval plasma. The same holds even for observations with sensitivities up to ,10 times better than those of forthcoming experiments. Thus, we have studied the impact of very high-quality data, such as those, in principle, achievable with a space experiment such as the Diffuse Microwave Emission Survey (DIMES) planned to measure the CMB absolute temperature at 0.5 ,,, 15 cm with a sensitivity of ,0.1 mK, close to that of FIRAS. We have demonstrated that such high-quality data would improve by a factor of ,50 the FIRAS results on the fractional energy exchanges, ,,/,i, associated with dissipation processes possibly occurred in a wide range of cosmic epochs, at intermediate and high redshifts (yh, 1), and that the energy dissipation epoch could also be significantly constrained. By jointly considering two dissipation processes occurring at different epochs, we demonstrated that the sensitivity and frequency coverage of a DIMES -like experiment would allow one to accurately recover the epoch and the amount of energy possibly injected into the radiation field at early and intermediate epochs even in the presence of a possible late distortion, while the constraints on the energy possibly dissipated at late epochs can be improved by a factor of ,2. In addition, such measurements can provide an independent and very accurate cross-check of FIRAS calibration. Finally, a DIMES -like experiment will be able to provide indicative independent estimates of the baryon density: the product ,bH20 can be recovered within a factor of ,2,5 even in the case of (very small) early distortions with ,,/,i, (5,2) × 10,6. On the other hand, for ,b (H0/50)2, 0.2, an independent baryon density determination with an accuracy at , per cent level, comparable to that achievable with CMB anisotropy experiments, would require an accuracy of ,1 mK or better in the measurement of possible early distortions but up to a wavelength from , few × dm to ,7 dm, according to the baryon density value. [source] Hedonic Price Indexes and the Matched Models ApproachTHE MANCHESTER SCHOOL, Issue 1 2004Mick Silver We consider three approaches to estimating quality-adjusted price changes: (i) the dummy variable approach from a hedonic regression, (ii) a superlative or exact hedonic index and (iii) a matching technique,a technique akin to that used by statistical offices. The dummy variable approach is prevalent in the literature and has been used for independent estimates of quality changes when commenting on sources of error in consumer price indexes. However, the availability of scanner data provides an opportunity to utilize data on the prices (unit values), volumes and quality characteristics of a much wider range of transactions and to consider methods less restrictive than the dummy variable approach. The practical use of superlative or exact hedonic index and matching techniques using scanner data is explored, and the results from all three methods are compared. A feature of the paper is the breadth of the empirical work. It not only encompasses three different approaches, but extends across four different types of consumer durables. The manner in which the three approaches relate to each other is explored and the implications for quality-adjusted price changes is discussed. [source] The diabatic heat budget of the upper troposphere and lower/mid stratosphere in ECMWF reanalysesTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 638 2009S. Fueglistaler Abstract We present an analysis of the diabatic terms in the thermodynamic energy equation from ERA-40 and the ECMWF reanalysis ERA-Interim. We analyse the clear-sky radiative heating, the cloud radiative effects, and the impact from latent heat exchange and mixing. The diabatic heat budget is closed with the calculation of the temperature assimilation increment. The previously noted excessive tropospheric circulation at low latitudes in ERA-40 is also reflected in the diabatic heat budget. The temperature increment acts to cool the excessive model heating. Conversely, ERA-Interim requires heating from the assimilation increment at low latitudes, suggesting too little convection. In the tropical tropopause layer (TTL), both reanalyses show a strong heating from the interaction of clouds with radiation, but lack of reliable independent estimates renders the role of clouds uncertain. Both reanalyses show cooling in the TTL by the assimilation increment, suggesting that the models may overestimate the cloud radiative heating, or that the convective parametrization scheme has difficulties in capturing the thermal effects of deep convection. In the stratosphere, ERA-40 shows unrealistic radiative heating due to problems in the temperature profile. The diabatic heat balance is dominated by the assimilation increment, and the residual circulation is much faster than in ERA-Interim. Conversely, ERA-Interim is better balanced and requires a substantially smaller temperature increment. Its structure and magnitude of radiative heating/cooling at low/high latitudes is quite realistic. Overall, ERA-Interim provides a much improved residual circulation, but uncertainties in the magnitude of terms in particular around the tropical tropopause remain large. Copyright © 2009 Royal Meteorological Society [source] Commentary: Discount Rates in Disarray , Evidence on Flawed Goodwill Impairment TestingAUSTRALIAN ACCOUNTING REVIEW, Issue 3 2010Michael E. Bradbury Carlin and Finch (2009)compare the reported goodwill impairment discount rates to their own ,independent' estimate for a sample of 105 Australian firms. On the basis of this comparison they claim (but do not show) that the discretion in determining the discount rate ,could be used opportunistically' and ,fundamental questions must be asked about the quality of reported earnings , produced in conformity with the IFRS regime'. This commentary points out that the research design does not permit the assessment of either of these claims. [source] | ||||||||||||||||