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Important Quantities (important + quantity)
Selected AbstractsSemiparametric Bayesian inference for dynamic Tobit panel data models with unobserved heterogeneityJOURNAL OF APPLIED ECONOMETRICS, Issue 6 2008Tong Li This paper develops semiparametric Bayesian methods for inference of dynamic Tobit panel data models. Our approach requires that the conditional mean dependence of the unobserved heterogeneity on the initial conditions and the strictly exogenous variables be specified. Important quantities of economic interest such as the average partial effect and average transition probabilities can be readily obtained as a by-product of the Markov chain Monte Carlo run. We apply our method to study female labor supply using a panel data set from the National Longitudinal Survey of Youth 1979. Copyright © 2008 John Wiley & Sons, Ltd. [source] Fluctuating Helium Emission in Optically Thick Divertor PlasmasCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-3 2008F. B. Rosmej Abstract Simulations of the helium radiative properties carried out with the recently developed multi-level meta-stable resolved collisional-radiative code SOPHIA discovered new unique emission lines to analyze optically thick divertor plasmas relevant for ITER. The comparison of their time dependent line emission obtained from the NAGDIS-II plasma simulator experiments with time dependent temperature probe measurements shows a strong correlation. This indicates that line intensity fluctuations can be transformed to the important quantities of density and temperature fluctuations. A transformation method based on integral line intensity ratios which can be recorded with high time resolution is discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Freshwater and marine virioplankton: a brief overview of commonalities and differencesFRESHWATER BIOLOGY, Issue 6 2008STEVEN W. WILHELM Summary 1. Viruses are a pervasive component of microbial food webs in both marine and freshwater systems. The abundance of viruses in individual aquatic systems appears to be independent of salinity but related to the biomass of primary and secondary producers as well as seasonal effects. Burst size, virus production rate and the percentage of microbial cells carrying a viral burden also appear to be more closely correlated to trophic status than to salinity. 2. In marine environments, the roles of planktonic viruses as regulators of carbon and nutrient cycling as well as microbial community structure have been a focus of numerous studies, yet the roles of freshwater virioplankton remain much less studied. Nevertheless, a survey of published freshwater studies demonstrates that virioplankton recycle important quantities of growth-limiting nutrients from hosts via generation of dead particulate and dissolved organic matter during cell lysis, and suggests that both the chemical speciation and concentration of these organic compounds and nutrients may have important influences on the microbial community. 3. Parallel observations on the spatial patterns and dynamics of microbial mortality due to viruses or grazing are more advanced in freshwaters than in marine environments. However, the constraints that determine whether virus- or grazer-mediated mortality dominates are not yet understood in either environment. 4. Application of molecular approaches has facilitated the examination of the diversity and ecological dynamics of specific viral populations and entire communities. The depth of detail achieved in marine environments towards characterizing these populations and communities is just beginning to be matched in freshwater systems. The few available data suggest that viruses targeting-related hosts in freshwater and marine systems may be genetically distinct. 5. Although the role of viruses in aquatic systems is complex and remains insufficiently studied, our survey of the literature indicates that, despite some differences, many of the controls on virioplankton activity and diversity are similar in marine and freshwater environments. [source] A nuclear microprobe study of the distribution and concentration of carbon and nitrogen in Murchison and Tagish Lake meteorites, Antarctic micrometeorites, and IDPs: Implications for astrobiologyMETEORITICS & PLANETARY SCIENCE, Issue 11 2003G. Matrajt We observed that IDPs are richest in both elements. All the MMs studied contain carbon, and all but the coarse-grained and 1 melted MM contained nitrogen. We also observed a correlation in the distribution of carbon and nitrogen, suggesting that they may be held in an organic material. The implications for astrobiology of these results are discussed, as small extraterrestrial particles could have contributed to the origin of life on Earth by delivering important quantities of these 2 bio-elements to the Earth's surface and their gas counterparts, CO2 and N2, to the early atmosphere. [source] Thermal vacancies and self-diffusion energy in 2024 Al-alloy by positron annihilation lifetime techniquePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2009Emad A. Badawi Abstract Positron annihilation lifetime technique (PALT) is one of the most important nuclear non-destructive techniques. It was used to study the thermal vacancies in one of the most important engineering aluminum alloys , the 2024 Al-alloy. Quenching experiments were usually performed on thin specimens to ensure a uniform quenching rate throughout the specimen. The specimens were prepared with dimensions of 0.15 × 1.5 × 1.5 cm3. After grinding, polishing and etching, samples of 2024 were homogenized for 12 h at 673 K and annealed for 90-min., before being quenched in water (277 K). Positron lifetime measurements followed. From such measurements, it is possible to deduce the vacancy formation enthalpy, which in combination with the results of self-diffusion measurements, gives a value for migration enthalpy of the vacancy. These are very important quantities in the study of the annealing of irradiation induced defects. The use of the quenching technique in the positron annihilation study has the advantage that it allows a distinction between vacancy and dislocation. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Multipolar Ordering in Electro- and Magnetostatic Coupled NanosystemsCHEMPHYSCHEM, Issue 9 2008Elena Y. Vedmedenko Dr. habil. Abstract Electric and magnetic multipole moments and polarizabilities are important quantities in studies of intermolecular forces, non-linear optical phenomena, electrostatic, magnetostatic or gravitational potentials and electron scattering. The experimental determination of multipole moments is difficult and therefore the theoretical prediction of these quantities is important. Depending on purposes of the investigation several different definitions of multipole moments and multipole,multipole interactions are used in the literature. Because of this variety of methods it is often difficult to use published results and, therefore, even more new definitions appear. The first goal of this review is to give an overview of mathematical definitions of multipole expansion and relations between different formulations. The second aim is to present a general theoretical description of multipolar ordering on periodic two-dimensional lattices. After a historical introduction in the first part of this manuscript the static multipole expansion in cartesian and spherical coordinates as well as existing coordinate transformations are reviewed. On the basis of the presented mathematical description multipole moments of several symmetric charge distributions are summarized. Next, the established numerical approach for the calculation of multipolar ground states, namely Monte Carlo simulations, are reviewed. Special emphasis is put on the review of ground states in multipolar systems consisting of moments of odd or even order. The last section is devoted to the magnetization reversal in dense packed nanomagnetic arrays, where the magnetic multipole,multipole interactions play an important role. Comparison between the theory and recent experimental results is given. [source] Exciton Diffusion Measurements in Poly(3-hexylthiophene),ADVANCED MATERIALS, Issue 18 2008Paul E. Shaw The problem of making reliable measurements of exciton diffusion lengths in organic semiconductors is addressed. The exciton diffusion length is an extremely important quantity in the operation of organic solar cells. We focus on the polymer P3HT because of its widespread use in solar cells and are able to fit the exciton diffusion in a range of films with a single diffusion constant, showing that our approach is particularly robust. [source] A comparison of the physicochemical, microbiological and aromatic composition of Traditional and Industrial Leben in TunisiaINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 1 2010OLFA SAMET-BALI Traditional Tunisian Leben (TL) was produced according to the traditional method. Physicochemical and microbiological characteristics and major aromatic compounds were studied and compared to industrial Leben (IL) and experimental Leben (EL). The results show a decrease in lactose content and pH value and an increase in lactic acid during spontaneous fermentation. TL and EL were characterised by higher protein, lactose and ash contents but were less fatty and acidic than IL. Lactic acid bacteria (LAB) and yeasts present in TL were responsible for lactic acid fermentation and aroma development. The LAB and yeast counts in TL were higher than that in EL and IL. Dynamic headspace extraction procedure shows the existence of four major volatile compounds: acetaldehyde, ethanol, diacetyl and acetoin in TL, IL and EL. However, TL has the most important quantity of aroma. [source] Molecular polarizability of fullerenes and endohedral metallofullerenesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2002Francisco Torrens Abstract The interacting induced dipoles polarization model implemented in our program POLAR is used for the calculation of the molecular dipole µ and tensor quadrupole moments and also the dipole,dipole polarizability . The method is tested with Scn, Cn (fullerene and graphite) and endohedral Scn@Cm clusters. The polarizability is an important quantity for the identification of clusters with different numbers of atoms and even for the separation of isomers. The results for the polarizability are of the same order of magnitude as from reference calculations performed with our version of the program PAPID. The bulk limit for the polarizability is estimated from the Clausius,Mossotti relationship. The polarizability trend for these clusters as a function of size is different from what one might have expected. The clusters are more polarizable than what one might have inferred from the bulk polarizability. Previous theoretical work yielded the same trend for Sin, Gen and GanAsm small clusters. However, previous experimental work yielded the opposite trend for Sin, GanAsm and GenTem larger clusters. At present, the origin of this difference is problematic. One might argue that smaller clusters need not behave like those of intermediate size. The high polarizability of small clusters is attributed to dangling bonds at the surface of the cluster. In this respect, semiconductor clusters resemble metallic clusters. Copyright © 2002 John Wiley & Sons, Ltd. [source] Temperature measurements in combustion,not only with CARS: a look back at one aspect of the European CARS WorkshopJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2003W. Stricker Abstract Temperature is perhaps the most important quantity in combustion research and technology. The potential and state of the art of various laser-based diagnostics used for the determination of temperature in laboratory flames and practical combustion devices are discussed and illustrated with a few representative examples from our laboratory. The emphasis is on coherent anti-Stokes Raman scattering (CARS), the main topic of the European CARS Workshop in the past. As a result, CARS is today the most matured and proven technique for technical applications. In addition to CARS, however, linear laser spectroscopic methods also deliver valuable and supplementary information on temperature in combustion. Copyright © 2003 John Wiley & Sons, Ltd. [source] The effects of model parameter deviations on the variance of a linearly filtered time seriesNAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 5 2010Daniel W. Apley Abstract We consider a general linear filtering operation on an autoregressive moving average (ARMA) time series. The variance of the filter output, which is an important quantity in many applications, is not known with certainty because it depends on the true ARMA parameters. We derive an expression for the sensitivity (i.e., the partial derivative) of the output variance with respect to deviations in the model parameters. The results provide insight into the robustness of many common statistical methods that are based on linear filtering and also yield approximate confidence intervals for the output variance. We discuss applications to time series forecasting, statistical process control, and automatic feedback control of industrial processes. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010 [source] | |||||||||||||