Analysis Shows (analysis + shows)

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Analysis Shows

  • blot analysis shows
  • diffraction analysis shows
  • empirical analysis shows
  • mechanical analysis shows
  • phylogenetic analysis shows
  • regression analysis shows
  • sensitivity analysis shows
  • structural analysis shows
  • theoretical analysis shows
  • x-ray diffraction analysis shows

  • Selected Abstracts


    The de jure financial system in Korea has moved from mainly R (relationship)-mode financial contracts towards M (market)-mode contracts since the 1997 financial crisis, due largely to reforms introducing Anglo-American style corporate governance and the disintermediation of the larger business groups in corporate financing. Analysis shows that the effectiveness of this change in improving firms' performances has yet to be demonstrated. Unlike the disintermediation of the big-name firms, the affiliates of small and medium business groups and small and medium-sized independent firms have relied heavily on bank loans and internal finance. The impact of a more concentrated banking system and intensified competition on the type of corporate investment has yet to be analysed. [source]

    The role of organizational capabilities in cleaner technology adoption: an analysis of the response of the pharmaceutical manufacturing sector in Ireland to IPC licensing regulations

    Rachel M. Hilliard
    Abstract In introducing integrated pollution control licensing, regulators hope to achieve economic advantages as well as environmental benefits. The licensing is used as a vehicle for encouraging firms to adopt cleaner technology, potentially allowing firms to achieve economic advantages through process efficiencies and reduced environmental control costs. In Ireland, the regulatory approach has been to require firms to make managerial changes in the belief that this is a necessary precursor to the take-up of new technology. This paper examines how the pharmaceutical manufacturing sector has responded to environmental regulations that require cleaner technology adoption and managerial changes. Quantitative indicators are developed using data reported to the Irish Environmental Protection Agency. Analysis shows that firms were differentially able to implement both cleaner technology and the mandated managerial processes. The implications for policy are that regulatory instruments designed to stimulate cleaner technology may not be sufficient to promote change in firms, given that the influence of these instruments is mediated by the role of firm-specific, experience-based organizational capabilities. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment. [source]


    EVOLUTION, Issue 6 2006
    Xu-Sheng Zhang
    Abstract How phenotypic variances of quantitative traits are influenced by the heterogeneity in environment is an important problem in evolutionary biology. In this study, both genetic and environmental variances in a plastic trait under migration-mutation-stabilizing selection are investigated. For this, a linear reaction norm is used to approximate the mapping from genotype to phenotype, and a population of clonal inheritance is assumed to live in a habitat consisting of many patches in which environmental conditions vary among patches and generations. The life cycle is assumed to be selection-reproduction-mutation-migration. Analysis shows that phenotypic plasticity is adaptive if correlations between the optimal phenotype and environment have become established in both space and/or time, and it is thus possible to maintain environmental variance (VE) in the plastic trait. Under the special situation of no mutation but maximum migration such that separate patches form an effective single-site habitat, the genotype that maximizes the geometric mean fitness will come to fixation and thus genetic variance (VG) cannot be maintained. With mutation and/or restricted migration, VG can be maintained and it increases with mutation rate but decreases with migration rate; whereas VE is little affected by them. Temporal variation in environmental quality increases VG while its spatial variance decreases VG. Variation in environmental conditions may decrease the environmental variance in the plastic trait. [source]

    Unto Every One That Hath Shall Be Given: The Subject Areas Under The HEFCE Formula

    Geoffrey Whittington
    The Higher Education Funding Council for England and Wales (HEFCE) has recently revised its formulae for the distribution of teaching and research funds between universities. The new formulae are intended to increase the transparency of the allocation process and reduce the reliance on historical patterns of allocation. Analysis shows that the coefficients (costs and prices) on which the formulae depend are estimated from historical data, so that reliance on historical patterns has not been eliminated. Moreover, the process by which the coefficients were derived is not transparent and the data used are not necessarily the most appropriate. Thus, the new formulae, which lead to significant shifts in the allocation of funds between subject areas, cannot be shown to have the transparency and sound empirical basis to which HEFCE aspires. [source]

    Parallel DSMC method using dynamic domain decomposition

    J.-S. Wu
    Abstract A general parallel direct simulation Monte Carlo method using unstructured mesh is introduced, which incorporates a multi-level graph-partitioning technique to dynamically decompose the computational domain. The current DSMC method is implemented on an unstructured mesh using particle ray-tracing technique, which takes the advantages of the cell connectivity information. In addition, various strategies applying the stop at rise (SAR) (IEEE Trans Comput 1988; 39:1073,1087) scheme is studied to determine how frequent the domain should be re-decomposed. A high-speed, bottom-driven cavity flow, including small, medium and large problems, based on the number of particles and cells, are simulated. Corresponding analysis of parallel performance is reported on IBM-SP2 parallel machine up to 64 processors. Analysis shows that degree of imbalance among processors with dynamic load balancing is about ,,½ of that without dynamic load balancing. Detailed time analysis shows that degree of imbalance levels off very rapidly at a relatively low value with increasing number of processors when applying dynamic load balancing, which makes the large problem size fairly scalable for processors more than 64. In general, optimal frequency of activating SAR scheme decreases with problem size. At the end, the method is applied to compute two two-dimensional hypersonic flows, a three-dimensional hypersonic flow and a three-dimensional near-continuum twin-jet gas flow to demonstrate its superior computational capability and compare with experimental data and previous simulation data wherever available. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Identification of the inertia matrix of a rotating body based on errors-in-variables models

    Byung-Eul Jun
    Abstract This paper proposes a procedure for identifying the inertia matrix of a rotating body. The procedure based on Euler's equation governing rotational motion assumes errors-in-variables models in which all measurements, torque as well as angular velocities, are corrupted by noises. In order for consistent estimation, we introduce an extended linear regression model by augmenting the regressors with constants and the parameters with noise-contributed terms. A transformation, based on low-pass filtering, of the extended model cancels out angular acceleration terms in the regressors. Applying the method of least correlation to the model identifies the elements of the inertia matrix. Analysis shows that the estimates converge to the true parameters as the number of samples increases to infinity. Monte Carlo simulations demonstrate the performance of the algorithm and support the analytical consistency. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Adaptive secure multicast in wireless networks

    Yiliang Han
    Abstract Secure multicast is one of the majority services in the near future. The frameworks for IP multicast cannot be directly applied in wireless networks. To address the natural issues of wireless multicast and enhance the efficiency, an adaptive secure multicast framework based on a new primitive called multi-recipient generalized signcryption and a multi-recipient generalized signcryption scheme based on the gap Diffie,Hellman problem (MGSC-GDH) are proposed. The key technologies to construct a high-performance adaptive scheme including identification function, randomness reusing are investigated. The framework provides separate or joint encryption and signature functions according to users' identities and requirements transparently, and has the ability to aggregate multiple unicast besides the common multicast service. Therefore, overheads are reduced sharply for multiple functions which are provided with a single primitive. By the precise reduction, the gap-bridge between the security of a base scheme and the corresponding multi-recipient generalized signcryption scheme is built, which is a direct measure to quantify the security. Analysis shows that MGSC-GDH is a semantic secure multi-recipient generalized signcryption scheme and more efficient than other similar schemes in computational and communicational aspects. It is suitable for dynamic environment for rekeying is avoided when membership changes. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    An intelligent control concept for formation flying satellites

    S. R. Vadali
    Abstract This paper deals with the determination of initial conditions and the design of fuel-balancing orbit control laws for a formation of satellites. Hill's equations describe the linearized dynamics of relative motion between two satellites. They admit bounded relative orbit solutions as special cases. Predictably, these bounded solutions break down in the presence of nonlinearities and perturbations. A method for determining the initial conditions that result in quasi-periodic relative orbits over the short term, in the presence of J2 perturbation, is presented. The control acceleration or equivalently, the fuel required to cancel the perturbation on a satellite depends upon its orbital inclination with respect to that of the reference satellite. An intelligent control concept that exploits the physics of the relative motion dynamics is presented. Analysis shows that this concept minimizes the total fuel consumption of the formation and maintains equal, average fuel consumption for each satellite. The concept is implemented using a novel, disturbance accommodating control design process. Numerical simulations and analytical results are in excellent agreement with each other. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Aquatic Coleoptera Distribution and Environmental Relationships in a Large Patagonian River

    María Laura Miserendino
    Abstract The benthic coleopteran assemblages of the Chubut River basin were studied in order to assess the main factors affecting species composition and distribution along the upper, middle and lower catchments. A total of 13 sampling sites were selected and sampled seasonally. Eight taxa and 1,601 individuals were collected during the study. Richness was higher in the main channel of Chubut River at the upper basin than at the middle basin. Beetles were completely absent at the lower basin. Mean monthly density per sites varied from 0 to 85 ind m,2. Stethelmis kaszabi had a more restricted distribution whereas Hemiosus dejeanii, Austrelmis sp. and Austrolimnius spp. were more frequent and abundant. Austrelmis sp. appears as the most tolerant species, especially to higher TSS, ammonia, and conductivity values. Luchoelmis cekalovici was absent in stations associated with urban areas. A Canonical Correspondence Analysis shows that conductivity, total suspended solids, wet width, water temperature and pH were the most important variables structuring beetle assemblages. Land use related variables such as NH4, TP, and NO3 were less important but still significant. An increase in TSS affected negatively the coleopteran community; this could be related to both hydrogeological characteristics and agricultural activities (including overgrazing). This is the first approach to the knowledge of the ecological range of distribution of the coleopteran species in Patagonian rivers. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    How light gets through periodically nanostructured metal films: a role of surface polaritonic crystals

    A. V. Zayats
    Summary The physical origin of the enhanced optical transmission of periodically structured films related to surface plasmon polaritons is discussed from first principles. The enhancement of transmission through smooth, randomly rough and periodically nanostructured films is considered. Analysis shows that any metal (or dielectric) nanostructured film can exhibit enhanced transmission in certain spectral ranges corresponding to surface plasmon (or phonon) polariton Bloch mode states on a periodic structure. Resonant tunnelling via these states is responsible for the transmission enhancement. The properties of surface polaritonic crystals are analogous to those of photonic crystals and can find numerous applications for scaling down optical devices to nanometric dimensions as well as for designing novel nanostructured materials whose optical properties are determined by surface polariton interaction in a periodic structure. [source]


    Michael J. Scott
    ABSTRACT: Using a case study of the Yakima River Valley in Washington State, this paper shows that relatively simple tools can be used to forecast the impact of the El Niño phenomenon on water supplies to irrigated agriculture, that this information could be used to estimate the significantly shifted probability distribution of water shortages in irrigated agriculture during El Niño episodes, and that these shifted probabilities can be used to estimate the value of exchanges of water between crops to relieve some of the adverse consequences of such shortages under western water law. Further, recently devised water-trading tools, while not completely free under western water law to respond to forecasted El Niño episodes (ocean circulation patterns), are currently being employed during declared drought to reduce the devastating effects of water shortages in junior water districts on high valued perennial crops. Additional institutional flexibility is needed to take full advantage of climate forecasting, but even current tools clearly could prove useful in controlling the effects of climate variability in irrigated agriculture. Analysis shows the significant benefit of temporarily transferring or renting water rights from low-value to high-value crops, based on El Niño forecasts. [source]

    Color centers in Yb:YAG crystals grown by temperature-gradient techniques

    Yongjun Dong
    Abstract Yb:YAG (Yb:Y3Al5O12) crystals have been grown by temperature-gradient techniques (TGT) and their color centers and impurity defects were investigated by means of gamma irradiations and thermal treatment. Two color centers located at 255 and 290 nm were observed in the as-grown TGT-Yb:YAG. Analysis shows that the 255 nm band may be associated with Fe3+ ions. Absorption intensity changes of the 290 nm band after gamma irradiation and thermal treatment indicate that this band may be associated with oxygen-vacancy defects. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    A coupled dispersion and exchange model for short-range dry deposition of atmospheric ammonia

    Benjamin Loubet
    Abstract The MODDAS-2D model (MOdel of Dispersion and Deposition of Ammonia over the Short-range in two dimensions) is presented. This stationary model couples a two-dimensional Lagrangian stochastic model for short-range dispersion, with a leaf-scale bi-directional exchange model for ammonia (NH3), which includes cuticular uptake and a stomatal compensation point. The coupling is obtained by splitting the upward and downward components of the flux, which can be generalized for any trace gas, and hence provides a way of simply incorporating bi-directional exchanges in existing deposition velocity models. The leaf boundary-layer resistance is parametrized to account for mixed convection in the canopy, and the model incorporates a stability correction for the Lagrangian time-scale for vertical velocity, which tends to increase the Lagrangian time-scale in very stable conditions compared with usual parametrizations. The model is validated against three datasets, where concentrations of atmospheric NH3 were measured at several distances from a line source. Two datasets are over grassland and one is over maize, giving a range of canopy structure. The model correctly simulates the concentration in one situation, but consistently overestimates it at further distances or underestimates it at small distances in the two other situations. It is argued that these discrepancies are mainly due to the lack of length of one of the line sources and non-aligned winds. Analysis shows that the surface exchange parameters and the turbulent mixing at the source level are the predominant factors controlling short-range deposition of NH3. Copyright © 2006 Royal Meteorological Society [source]

    Averaged kick maps: less noise, more signal,and probably less bias

    Jure Pra, nikar
    Use of reliable density maps is crucial for rapid and successful crystal structure determination. Here, the averaged kick (AK) map approach is investigated, its application is generalized and it is compared with other map-calculation methods. AK maps are the sum of a series of kick maps, where each kick map is calculated from atomic coordinates modified by random shifts. As such, they are a numerical analogue of maximum-likelihood maps. AK maps can be unweighted or maximum-likelihood (,A) weighted. Analysis shows that they are comparable and correspond better to the final model than ,A and simulated-annealing maps. The AK maps were challenged by a difficult structure-validation case, in which they were able to clarify the problematic region in the density without the need for model rebuilding. The conclusion is that AK maps can be useful throughout the entire progress of crystal structure determination, offering the possibility of improved map interpretation. [source]

    X-Ray Structure Analyses of syn/anti -Conformers of N -Furfuroyl-, N -Benzoyl-, and N -Picolinoyl-Substituted (2R)-Bornane-10,2-sultam Derivatives

    Karolina Koszewska
    Abstract The synthesis and the X-ray structure of the three new N -(arylcarbonyl)-substituted derivatives 2a,2c of (2R)-bornane-10,2-sultam are presented and discussed. Direct comparison of the solid-state analyses shows that the dipole-directed SO2/CO anti- /syn- conformations may be very sensitive to weak electronic/electrostatic repulsions of the heteroatom lone pairs. The optimum interactions are reached when the lone pair of the , -positioned heteroatom is oriented in the O(3)C(11)N(1) plane. Such rare syn -conformations may be observed with at least up to 1.8,kcal/mol higher energy as compared to their ground states. Additionally, these anti/syn- conformations are also very sensitive to external influences such as, for example, the crystal-packing forces. [source]

    Investigation of the Influence of Overvoltage, Auxiliary Glow Current and Relaxation Time on the Electrical Breakdown Time Delay Distributions in Neon

    . A. Maluckov
    Abstract Results of the statistical analysis of the electrical breakdown time delay for neon-filled tube at 13.3 mbar are presented in this paper. Experimental distributions of the breakdown time delay were established on the basis of 200 successive and independent measurements, for different overvoltages, relaxation times and auxiliary glows. Obtained experimental distributions deviate from usual exponential distribution. Breakdown time delay distributions are numerically generated, usingMonte-Carlo method, as the compositions of the two independent random variables with an exponential and a Gaussian distribution. Theoretical breakdown time delay distribution is obtained from the convolution of the exponential and Gaussian distribution. Performed analysis shows that the crucial parameter that determines the complex structure of time delay is the overvoltage and if it is of the order of few percentage, then distribution of time delay must be treated as an convolution of two random variables. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Evaluating the Characteristics of Corporate Boards Associated with Layoff Decisions

    Alfred Yawson
    The paper evaluates the characteristics of corporate boards associated with layoff decisions using a large sample of UK firms suffering performance declines over the period 1994,2003. The results show that firms are less likely to respond to performance declines with employee layoffs when they have large boards. Further analysis shows that layoff decisions are positively associated with the proportion of outside directors and directors' remuneration. The findings provide some support to the recommendations of the Cadbury Report (1992) and Higgs Review (2003) on the importance of the structure and composition of board of directors in the corporate governance process. [source]


    Research Summary: This research examines how funding from the U.S. Department of Justice, Office of Community Oriented Policing Services (COPS), has affected violent and property crime rates in the United States from 1995 to 1999. Drawing on six years of panel data, we examine the effects of three types of awards made by COPS to 6,100 law enforcement agencies serving more than 145 million citizens. We estimate their impact on crime reduction over time in jurisdictions receiving funding and controlling for baseline levels of crime, socioeconomic characteristics, city size, and population diversity and mobility. Our analyses suggest that COPS hiring and innovative grant programs have resulted in significant reductions in local crime rates in cities with populations greater than 10,000 for both violent and nonviolent offenses. Multivariate analysis shows that in cities with populations greater than 10,000, an increase in one dollar of hiring grant funding per resident contributed to a corresponding decline of 5.26 violent crimes and 21.63 property crimes per 100,000 residents. Similarly, an increase in one dollar of innovative grant funding per resident has contributed to a decline of 12.93 violent crimes and 45.53 property crimes per 100,000 persons. In addition, the findings suggest that COPS grants have had no significant negative effect on violent and property crime rates in cities with less than 10,000 population. Policy Implications: The findings of this study imply that COPS program funding to medium- and large-size cities has been an effective force in reducing both violent and property crime. Federal government grants made directly to law enforcement agencies to hire additional officers and promote innovations may be an effective way to reduce crime on a national scale. [source]

    Crystal structure, thermal analysis and IR spectrometric investigation of bis (2-amino-6-methyl) pyridinium sulfate

    T. Guerfel
    Abstract The synthesis method, crystal structure determination, phase transitions studied by thermal analysis and IR spectrometric investigation of 2C6H9N2+.SO42, are reported. The compound crystallizes in the monoclinic space group C2/c (no. 15) with a = 10.5068(4) Å, b = 10.2225(5) Å, c = 14.0422(7) Å, and , = 104.489(3)°. The atomic arrangement can be described by layers built by all the components of the structure and centered by planes z = 1/4 and 3/4. The organic molecules form channels parallel to the c direction with dimensions of 4.163(1)Å and 5.148(4)Å. Thermal analysis shows that the anhydrous compound presents an irreversible weak phase transition. The IR study, based on theoretical analyses and on the literature data allows the interpretation of the IR spectrum. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Impact of magnetic field on the nucleation and morphology of calcium carbonate crystals

    K. V. Saban
    Abstract The influence of static magnetic field of strength 0.75 T on the nucleation of calcium carbonate crystals has been investigated. Particle size analysis shows that magnetic field can cause marked difference in distribution. One of the major impacts of magnetic exposure is the increase in number of the critical nuclei formed. Also, magnetic field promotes the formation of parallelepipedic calcite crystals and the dissolution of the smaller crystals by Ostwald ripening mechanism. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Protein methylation in full length Chlamydomonas flagella

    CYTOSKELETON, Issue 8 2009
    Roger D. Sloboda
    Abstract Post-translational protein modification occurs extensively in eukaryotic flagella. Here we examine protein methylation, a protein modification that has only recently been reported to occur in flagella [Schneider MJ, Ulland M, Sloboda RD.2008. Mol Biol Cell 19(10):4319,4327.]. The cobalamin (vitamin B12) independent form of the enzyme methionine synthase (MetE), which catalyzes the final step in methionine production, is localized to flagella. Here we demonstrate, using immunogold scanning electron microscopy, that MetE is bound to the outer doublets of the flagellum. Methionine can be converted to S-adenosyl methionine, which then serves as the methyl donor for protein methylation reactions. Using antibodies that recognize symmetrically or asymmetrically methylated arginine residues, we identify three highly methylated proteins in intact flagella: two symmetrically methylated proteins of about 30 and 40 kDa, and one asymmetrically methylated protein of about 75 kDa. Several other relatively less methylated proteins could also be detected. Fractionation and immunoblot analysis shows that these proteins are components of the flagellar axoneme. Immunogold thin section electron microscopy indicates that the symmetrically methylated proteins are located in the central region of the axoneme, perhaps as components of the central pair complex and the radial spokes, while the asymmetrically methylated proteins are associated with the outer doublets. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source]

    E2f6 and Bmi1 cooperate in axial skeletal development

    Maria Courel
    Abstract Bmi1 is a Polycomb Group protein that functions as a component of Polycomb Repressive Complex 1 (PRC1) to control axial skeleton development through Hox gene repression. Bmi1 also represses transcription of the Ink4a-Arf locus and is consequently required to maintain the proliferative and self-renewal properties of hematopoietic and neural stem cells. Previously, one E2F family member, E2F6, has been shown to interact with Bmi1 and other known PRC1 components. However, the biological relevance of this interaction is unknown. In this study, we use mouse models to investigate the interplay between E2F6 and Bmi1. This analysis shows that E2f6 and Bmi1 cooperate in the regulation of Hox genes, and consequently axial skeleton development, but not in the repression of the Ink4a-Arf locus. These findings underscore the significance of the E2F6,Bmi1 interaction in vivo and suggest that the Hox and Ink4a-Arf loci are regulated by somewhat different mechanisms. Developmental Dynamics 237:1232-1242, 2008. © 2008 Wiley-Liss, Inc. [source]

    Two Na,K-ATPase ,2 subunit isoforms are differentially expressed within the central nervous system and sensory organs during zebrafish embryogenesis

    Johannes R. Rajarao
    Abstract We have identified cDNAs encoding a second zebrafish ortholog of the human Na,K-ATPase ,2 subunit. The ,2b cDNA encodes a 292 amino acid-long polypeptide with 74% identity to the previously characterized zebrafish ,2a subunit. By using a zebrafish meiotic mapping panel, we determined that the ,2b gene (atp1b2b) was tightly linked to markers on linkage group 5, whereas the ,2a gene was located on linkage group 23. In situ hybridization analysis shows that in developing zebrafish embryos, atp1b2a and atp1b2b are predominantly expressed in the nervous system. ,2a transcripts were abundantly expressed throughout brain as well as spinal cord neurons and lateral line ganglia. In contrast, ,2b mRNA expression was primarily detected in sensory organs, including retina, otic vesicles, and lateral line neuromast cells. These results suggest that the ,2a and ,2b genes play distinct roles in developing brain and sensory organs, and raise the possibility that the functions encoded by the single mammalian ,2 gene may be partitioned between the two zebrafish ,2 orthologs. © 2002 Wiley-Liss, Inc. [source]

    Modelling increased soil cohesion due to roots with EUROSEM

    S. De Baets
    Abstract As organic root exudates cause soil particles to adhere firmly to root surfaces, roots significantly increase soil strength and therefore also increase the resistance of the topsoil to erosion by concentrated flow. This paper aims at contributing to a better prediction of the root effects on soil erosion rates in the EUROSEM model, as the input values accounting for roots, presented in the user manual, do not account for differences in root density or root architecture. Recent research indicates that small changes in root density or differences in root architecture considerably influence soil erosion rates during concentrated flow. The approach for incorporating the root effects into this model is based on a comparison of measured soil detachment rates for bare and for root-permeated topsoil samples with predicted erosion rates under the same flow conditions using the erosion equation of EUROSEM. Through backwards calculation, transport capacity efficiencies and corresponding soil cohesion values can be assessed for bare and root-permeated topsoils respectively. The results are promising and present soil cohesion values that are in accordance with reported values in the literature for the same soil type (silt loam). The results show that grass roots provide a larger increase in soil cohesion as compared with tap-rooted species and that the increase in soil cohesion is not significantly different under wet and dry soil conditions, either for fibrous root systems or for tap root systems. Power and exponential relationships are established between measured root density values and the corresponding calculated soil cohesion values, reflecting the effects of roots on the resistance of the topsoil to concentrated flow incision. These relationships enable one to incorporate the root effect into the soil erosion model EUROSEM, through adapting the soil cohesion input value. A scenario analysis shows that the contribution of roots to soil cohesion is very important for preventing soil loss and reducing runoff volume. The increase in soil shear strength due to the binding effect of roots on soil particles is two orders of magnitude lower as compared with soil reinforcement achieved when roots mobilize their tensile strength during soil shearing and root breakage. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Sedimentological, modal analysis and geochemical studies of desert and coastal dunes, Altar Desert, NW Mexico

    J. J. Kasper-Zubillaga
    Abstract Sedimentological, compositional and geochemical determinations were carried out on 54 desert and coastal dune sand samples to study the provenance of desert and coastal dunes of the Altar Desert, Sonora, Mexico. Grain size distributions of the desert dune sands are influenced by the Colorado River Delta sediment supply and wind selectiveness. The desert dune sands are derived mainly from the quartz-rich Colorado River Delta sediments and sedimentary lithics. The dune height does not exert a control over the grain size distributions of the desert dune sands. The quartz enrichment of the desert dune sands may be due to wind sorting, which concentrates more quartz grains, and to the aeolian activity, which has depleted the feldspar grains through subaerial collisions. The desert dune sands suffer from little chemical weathering and they are chemically homogeneous, with chemical alteration indices similar to those found in other deserts of the world. The desert sands have been more influenced by sedimentary and granitic sources. This is supported by the fact that Ba and Sr concentration values of the desert sands are within the range of the Ba and Sr concentration values of the Colorado River quartz-rich sediments. The Sr values are also linked to the presence of Ca-bearing minerals. The Zr values are linked to the sedimentary sources and heavy mineral content in the desert dunes. The Golfo de Santa Clara and Puerto Peñasco coastal dune sands are influenced by long shore drift, tidal and aeolian processes. Coarse grains are found on the flanks whereas fine grains are on the crest of the dunes. High tidal regimens, long shore drift and supply from Colorado Delta River sediments produce quartz-rich sands on the beach that are subsequently transported into the coastal dunes. Outcrops of Quaternary sedimentary rocks and granitic sources increase the sedimentary and plutonic lithic content of the coastal dune sands. The chemical index of alteration (CIA) values for the desert and coastal dune sands indicate that both dune types are chemically homogeneous. The trace element values for the coastal dune sands are similar to those found for the desert dune sands. However, an increase in Sr content in the coastal dune sands may be due to more CaCO3 of biogenic origin as compared to the desert dune sands. Correlations between the studied parameters show that the dune sands are controlled by sedimentary sources (e.g. Colorado River Delta sediments), since heavy minerals are present in low percentages in the dune sands, probably due to little heavy mineral content from the source sediment; grain sizes in the dune sands are coarser than those in which heavy minerals are found and/or the wind speed might not exert a potential entrainment effect on the heavy mineral fractions to be transported into the dune. A cluster analysis shows that the El Pinacate group is significantly different from the rest of the dune sands in terms of the grain-size parameters due to longer transport of the sands and the long distance from the source sediment, whereas the Puerto Peñasco coastal dune sands are different from the rest of the groups in terms of their geochemistry, probably caused by their high CaCO3 content and slight decrease in the CIA value. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Spectral analysis and design approach for high force-to-volume extrusion damper-based structural energy dissipation

    Geoffrey W. Rodgers
    Abstract High force-to-volume extrusion damping devices can offer significant energy dissipation directly in structural connections and significantly reduce seismic response. Realistic force levels up to 400,kN have been obtained experimentally validating this overall concept. This paper develops spectral-based design equations for their application. Response spectra analysis for multiple, probabilistically scaled earthquake suites are used to delineate the response reductions due to added extrusion damping. Representative statistics and damping reduction factors are utilized to characterize the modified response in a form suitable for current performance-based design methods. Multiple equation regression analysis is used to characterize reduction factors in the constant acceleration, constant velocity, and constant displacement regions of the response spectra. With peak device forces of 10% of structural weight, peak damping reduction factors in the constant displacement region of the spectra are approximately 6.5,×, 4.0,×, and 2.8,× for the low, medium, and high suites, respectively. At T,=,1,s, these values are approximately 3.6,×, 1.8,×, and 1.4,×, respectively. The maximum systematic bias introduced by using empirical equations to approximate damping reduction factors in design analyses is within the range of +10 to ,20%. The seismic demand spectrum approach is shown to be conservative across a majority of the spectrum, except for large added damping between T,=,0.8 and 3.5,s, where it slightly underestimates the demand up to a maximum of approximately 10%. Overall, the analysis shows that these devices have significant potential to reduce seismic response and damage at validated prototype device force levels. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Modeling the effect of high dead-space syringes on the human immunodeficiency virus (HIV) epidemic among injecting drug users

    ADDICTION, Issue 8 2010
    Georgiy V. Bobashev
    ABSTRACT Aims To illustrate the impact of different proportions of injecting drug users (IDUs) sharing high dead-space syringes (HDSS) or low dead-space syringes (LDSS) on the probability of human immunodeficiency virus (HIV) transmission; and thus the impact on injection-related HIV prevalence and incidence. Design A stochastic mathematical model was used to evaluate the impact of HDSS use in high- and low-risk IDU populations. Model parameters were obtained from peer-reviewed publications. Analytical solutions of a simplified deterministic model were obtained to explain the effect of HDSS on HIV endemic states. Findings Simulation analysis shows that the HIV epidemic could be sustained even when a small percentage of sharing (10%) involved HDSS. The effect is much stronger in high-risk compared with low-risk populations. Steady state HIV prevalence increases with the proportion of HDSS, and for high- and low-risk populations reaches around 80% and 20%, respectively. For low-risk populations, the use of LDSS could result in the virtual elimination of HIV. These results are dependent upon an evidence-supported assumption of a significant difference in HIV transmission risk associated with HDSS versus LDSS. Conclusions Our models suggest that injection-related HIV epidemics may not occur when most (e.g. 95% or more) IDUs use LDSS. While these results are based on indirect risk measures and a number of simplifying assumptions, the effect of blood retained in high dead-space syringes on HIV prevalence seems to be very strong, even using relatively conservative assumptions. The findings have potential implications for needle exchange programs and the types of syringes produced and distributed world-wide. [source]

    Parental Separation and Children's Educational Attainment: A Siblings Analysis on Swedish Register Data

    ECONOMICA, Issue 292 2006
    This paper analyses whether the commonly found negative relationship between parental separation in childhood and educational outcomes is causal or due mainly to selection. We use data on about 100,000 Swedish full biological siblings, born in 1948,63, and perform cross-section and sibling-difference estimations. Outcomes are measured as educational attainment in 1996. Our cross-section analysis shows the expected negative and significant relationship, while the relationship is not significant, though precisely estimated, in the sibling-difference analysis. This finding was robust to the sensitivity tests performed and is consistent with selection, rather than causation, being the explanation for the negative relationship. [source]


    EDUCATIONAL THEORY, Issue 5 2009
    Eric Bredo
    In Moderating the Debate: Rationality and the Promise of American Education, Michael Feuer raises concerns about the consequences of basing educational policy on the model of rational choice drawn from economics. Policy making would be better and more realistic, he suggests, if it were based on a newer procedural model drawn from cognitive science. In this essay Eric Bredo builds on Feuer's analysis by offering a more systematic critique of the traditional model of rationality that Feuer criticizes, a more critical evaluation of the procedural model that he favors, and a recommendation that the situational model he does not consider may have some benefits over both. This analysis shows that the traditional model presupposes an actor that cannot learn or develop. While the actor in the procedural model can learn, Bredo contends that it cannot develop, that is, it cannot outgrow its initial assumptions and values. Only the situational model allows for learning and development, important in a model to be used in the field of education. Bredo also considers in his analysis the social-relational assumptions built into the traditional, procedural, and situational models and the likely ethical consequences of acting on them. [source]

    The genome of Syntrophomonas wolfei: new insights into syntrophic metabolism and biohydrogen production

    Jessica R. Sieber
    Summary Syntrophomonas wolfei is a specialist, evolutionarily adapted for syntrophic growth with methanogens and other hydrogen- and/or formate-using microorganisms. This slow-growing anaerobe has three putative ribosome RNA operons, each of which has 16S rRNA and 23S rRNA genes of different length and multiple 5S rRNA genes. The genome also contains 10 RNA-directed, DNA polymerase genes. Genomic analysis shows that S. wolfei relies solely on the reduction of protons, bicarbonate or unsaturated fatty acids to re-oxidize reduced cofactors. Syntrophomonas wolfei lacks the genes needed for aerobic or anaerobic respiration and has an exceptionally limited ability to create ion gradients. An ATP synthase and a pyrophosphatase were the only systems detected capable of creating an ion gradient. Multiple homologues for ,-oxidation genes were present even though S. wolfei uses a limited range of fatty acids from four to eight carbons in length.Syntrophomonas wolfei, other syntrophic metabolizers with completed genomic sequences, and thermophilic anaerobes known to produce high molar ratios of hydrogen from glucose have genes to produce H2 from NADH by an electron bifurcation mechanism. Comparative genomic analysis also suggests that formate production from NADH may involve electron bifurcation. A membrane-bound, iron,sulfur oxidoreductase found in S. wolfei and Syntrophus aciditrophicus may be uniquely involved in reverse electron transport during syntrophic fatty acid metabolism. The genome sequence of S. wolfei reveals several core reactions that may be characteristic of syntrophic fatty acid metabolism and illustrates how biological systems produce hydrogen from thermodynamically difficult reactions. [source]