Home About us Contact
|
Home About us Contact | ||
|
|
||
Experimental Analysis (experimental + analysis)
Selected AbstractsCULTURAL DIVERSITY, DISCRIMINATION, AND ECONOMIC OUTCOMES: AN EXPERIMENTAL ANALYSISECONOMIC INQUIRY, Issue 2 2007PAUL J. FERRARO Does cultural diversity affect economic outcomes? We develop an experimental framework that complements ongoing research on this question. We vary the ethnic mix of bargaining sessions to study intercultural interactions among members of U.S. Hispanic and Navajo cultures. We control for demographic differences in our subject pools and elicit beliefs directly in order to differentiate between statistical discrimination and preference-based discrimination. Hispanic and Navajo subjects behave differently, and their behavior is affected by the ethnic composition of the experimental session. Our experimental framework can shed light on economic behavior and outcomes in societies of mixed ethnicity, race, and religion. (JEL C78, C90, Z10) [source] EXPERIMENTAL ANALYSIS OF THE DEFORMING MODE OF A SURFACE IN FUNCTION OF ITS ROUGHNESSEXPERIMENTAL TECHNIQUES, Issue 2 2000M. Dursapt First page of article [source] CONGRESSIONAL PARTISANSHIP, BIPARTISANSHIP AND PUBLIC OPINION: AN EXPERIMENTAL ANALYSISPOLITICS & POLICY, Issue 1 2001Jonathan Morris There has been extensive research concerning Congress and how partisan attachments and attitudes affect views toward it. In addition, a burgeoning area of research has developed concerning how media influences a person's attitudes and beliefs. In our study we test three hypotheses: viewing partisan House rhetoric will increase partisanship, negative attitudes toward Congress, and negative attitudes toward the federal government as a whole. We test these hypotheses with an experimental design in which we manipulate the independent variable at two levels: viewing partisan speeches and viewing bipartisan speeches. We find that direct exposure to congressional partisan rhetoric leads to lower levels of support and increased partisan polarization. Surprisingly, we also find that exposure to bipartisan floor rhetoric, while decreasing party polarization fails to generate increased levels of support for Congress or the government as whole. [source] Lattice Monte Carlo and Experimental Analyses of the Thermal Conductivity of Random-Shaped Cellular AluminumADVANCED ENGINEERING MATERIALS, Issue 10 2009Thomas Fiedler The effective thermal conductivity of open- and closed-cell aluminium foams with stochastic pore morphologies has been determined by numerical, analytical and experimental methods. A three dimensional analysis technique has been used where numerical calculation models are generated based on 3D computed tomographic (CT) reconstructions. The resulting three dimensional grid models are used for thermal Lattice Monte Carlo (LMC) analyses. The second part of this paper addresses experimental measurements of open-cell M-pore® and closed-cell Alporas® cellular aluminium. Finally, results obtained using both approaches are compared to classical analytic predictions. [source] Coordinated Development of Yeast Colonies: An Experimental Analysis of the Adaptation to Different Nutrient Concentrations , Part 1ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2005T. Walther Abstract The development of yeast colonies on solid agar substrates served as a model system to investigate the growth of higher fungi in a heterogeneous environment. Applying a new analytical technique , which was based on the estimation of the intensity of transmitted light from microscopic images taken along the colony radius , cell-density distributions inside fungal mycelia were measured at an extremely high spatial resolution. Using this method, the adaptation of yeast colonies to the limitation of different nutrients was investigated. Under conditions of carbon or nitrogen limitation, populations of the dimorphic model yeasts Yarrowia lipolytica and Candida boidinii underwent a transition in their morphology from solid colony to mycelial colony patterns. When grown under conditions that induced the mycelial morphology, colonies extended linearly at a constant rate irrespective of the initial nutrient concentration. In general, the cell density within the population declined at higher degrees of limitation. Nitrogen-limited colonies of both model yeasts, as well as carbon-limited Y.,lipolytica colonies proceeded to extend until the growth field was finally covered by the population. Under these conditions, areas of fairly constant cell densities were formed during the growth process. Only carbon-limited C.,boidinii colonies stopped extending at a final diameter which was small when compared to the size of the growth field, and formed a cell-density profile which was monotonically declining. The observed differences in the final colony diameter, and in the cell-density profile morphology indicated the presence of different regulatory mechanisms that ruled the colony development of the model yeasts. The presented monitoring technique for the biomass distribution inside fungal populations provided the basis for a quantitative and non-invasive description of mycelial development. [source] The Influence of Magnetic Fields on the Mechanical Behaviour of Granular Materials Used for Foundry Moulding: Numerical and Experimental Analysis,ADVANCED ENGINEERING MATERIALS, Issue 8 2006P.-M. Geffroy Understanding the mechanical behaviour of granular materials is of financial importance in many industries, including the geotechnical [1], pharmaceutical and foundry sectors. In the latter, granular materials are used as mould elements for lost foam (sand) and magnetic moulding (steel shot) processes. This study focuses on optimising mould geometry and magnetic field characteristics (intensity and orientation) to obtain the desired dimensions of the final product. [source] Experimental Analysis on Performance and Durability of SOFC Demonstration UnitFUEL CELLS, Issue 3 2010M. Halinen Abstract A technical description and experimental analysis of a SOFC demonstration unit is presented. The unit contains most of the primary BoP-components of a complete SOFC system, except of air and fuel recirculation equipment or fuel system compressor. Natural gas is used as the fuel and electricity is supplied to the electric grid. A 5,kW power class planar SOFC stack from Research Centre Jülich is assembled to the demo unit and a long-term experiment is conducted to assess the characteristic performance and durability of different components of the unit (e.g. the SOFC stack, the fuel pre-reformer and air heat exchangers). The evolution of absolute voltage drop of the stack over time is found to be of the same magnitude when compared to short stack experiments. Thus, other system components are not observed to cause an increase in the characteristic voltage drop of the stack. Two BoP-components, the afterburner and the power conversion unit failed to operate as designed. The performance of other BoP-components i.e. fuel pre-reformer and heat exchangers were satisfactory during the test run, and no significant performance loss could be measured. [source] Experimental Analysis of Grazing by the Mayfly Meridialaris chiloeensis on Different Successional Stages of Stream PeriphytonINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2004Verónica Díaz Villanueva Abstract In this study we determined grazing effects of the South Andean endemic mayfly Meridialaris chiloeensis on periphyton at different stages of successional development. Grazing effects were studied through a two-factor experimental design (colonization stages X grazer density) in a stream-side channel in spring and winter. Our results showed an absence of proportionality between grazer density and periphyton decline in response to grazers at low and intermediate levels of periphytic biomass; however, when periphyton biomass was high a direct inverse relationship was observed between post-grazing biomass and grazer density. The relationship between periphytic algae (chlorophyll a concentration) and periphyton (total periphytic ash-free dry mass) (C/OM index) was used as an estimation of the autotrophic fraction in the total periphyton matrix. Grazing did not alter the C/OM index indicating that both autotrophic and heterotrophic fractions of the periphyton components were reduced in the same proportion. Ordination of samples using the relative abundance of diatom species showed that herbivore effect was less evident at intermediate and late stage of colonization than at early one. These results support the statement that the outcome of the herbivore-periphyton interaction may depend on the successional stage of the periphyton community. In spring Fragilaria pinnata relative abundance, on the basis of cell counts, was reduced by grazing and Nitzschia palea was enhanced. In the winter experiment, grazing decreased Achnanthes minutissima relative abundance. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The Impact of Insurance Prices on Decision Making Biases: An Experimental AnalysisJOURNAL OF RISK AND INSURANCE, Issue 2 2003Susan K. Laury This article tests whether the use of endogenous risk categorization by insurers enables consumers to make better-informed decisions even if they do not choose to purchase insurance. We do so by adding a simple insurance market to an experimental test of optimal (Bayesian) updating. In some sessions, no insurance is offered. In others, actuarially fair insurance prices are posted, and a subset of subjects is allowed to purchase this insurance. We find significant differences in the decision rules used depending on whether one observes insurance prices. Although the majority of choices correspond to Bayesian updating, the incidence of optimal decisions is higher in sessions with an insurance option. Most subjects given the option to purchase actuarially fair insurance choose to do so. However, fewer subjects purchase insurance when the probability of a loss is higher. [source] Tax Evasion and Voting: An Experimental AnalysisKYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 2 2002Lars P. Feld The authors would like to thank Gerald Hosp and Hannelore Weck-Hannemann for valuable comments and suggestions. The usual disclaimer applies. [source] An Experimental Analysis of the Impact of Intermediaries on the Outcome of Bargaining GamesREAL ESTATE ECONOMICS, Issue 2 2001Abdullah Yavas We conduct an experimental analysis of the bargaining between a buyer and a seller of the exchange of a single good by means of an intermediary or broker. We examine how an intermediary affects the price, the likelihood of a successful negotiation, and the time it takes to complete a negotiation. We first examine the impact of the intermediary as a pure middleman, and then as an information source about the distribution of seller and buyer reservation prices. The results show that an intermediary, whether or not informed, increases the sale price, reduces the likelihood of an agreement, and increases the time to reach an agreement (though the number of bargaining rounds declines). The results suggest that the benefits of brokerage may be predominantly in the matching of buyers and sellers rather than in facilitating bargaining. [source] Numerical and Experimental Analysis of an Axial Flow Left Ventricular Assist Device: The Influence of the Diffuser on Overall Pump PerformanceARTIFICIAL ORGANS, Issue 7 2005Alexandrina Untaroiu Abstract:, Thousands of adult cardiac failure patients may benefit from the availability of an effective, long-term ventricular assist device (VAD). We have developed a fully implantable, axial flow VAD (LEV-VAD) with a magnetically levitated impeller as a viable option for these patients. This pump's streamlined and unobstructed blood flow path provides its unique design and facilitates continuous washing of all surfaces contacting blood. One internal fluid contacting region, the diffuser, is extremely important to the pump's ability to produce adequate pressure but is challenging to manufacture, depending on the complex blade geometries. This study examines the influence of the diffuser on the overall LEV-VAD performance. A combination of theoretical analyses, computational fluid (CFD) simulations, and experimental testing was performed for three different diffuser models: six-bladed, three-bladed, and no-blade configuration. The diffuser configurations were computationally and experimentally investigated for flow rates of 2,10 L/min at rotational speeds of 5000,8000 rpm. For these operating conditions, CFD simulations predicted the LEV-VAD to deliver physiologic pressures with hydraulic efficiencies of 15,32%. These numerical performance results generally agreed within 10% of the experimental measurements over the entire range of rotational speeds tested. Maximum scalar stress levels were estimated to be 450 Pa for 6 L/min at 8000 rpm along the blade tip surface of the impeller. Streakline analysis demonstrated maximum fluid residence times of 200 ms with a majority of particles exiting the pump in 80 ms. Axial fluid forces remained well within counter force generation capabilities of the magnetic suspension design. The no-bladed configuration generated an unacceptable hydraulic performance. The six-diffuser-blade model produced a flow rate of 6 L/min against 100 mm Hg for 6000 rpm rotational speed, while the three-diffuser-blade model produced the same flow rate and pressure rise for a rotational speed of 6500 rpm. The three-bladed diffuser configuration was selected over the six-bladed, requiring only an incremental adjustment in revolution per minute to compensate for and ease manufacturing constraints. The acceptable results of the computational simulations and experimental testing encourage final prototype manufacturing for acute and chronic animal studies. [source] How Can Rotaxanes Be Modified by Varying Functional Groups at the Axle?,A Combined Theoretical and Experimental Analysis of Thermochemistry and Electronic EffectsCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2010Christian Spickermann Dipl.-Chem No abstract is available for this article. [source] Multimode Project Scheduling Based on Particle Swarm OptimizationCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2006Hong Zhang This article introduces a methodology for solving the MRCPSP based on particle swarm optimization (PSO) that has not been utilized for this and other construction-related problems. The framework of the PSO-based methodology is developed. A particle representation formulation is proposed to represent the potential solution to the MRCPSP in terms of priority combination and mode combination for activities. Each particle-represented solution should be checked against the nonrenewable resource infeasibility and will be handled by adjusting the mode combination. The feasible particle-represented solution is transformed to a schedule through a serial generation scheme. Experimental analyses are presented to investigate the performance of the proposed methodology. [source] Thermoregulation of the Escherichia coli O157:H7 pO157 ecf operon and lipid A myristoyl transferase activity involves intrinsically curved DNAMOLECULAR MICROBIOLOGY, Issue 2 2004Jang W. Yoon Summary Escherichia coli O157:H7 survives in diverse environments from the ruminant gastrointestinal tract to cool nutrient-dilute water. We hypothesized that the gene regulation required for this flexibility includes intrinsically curved DNA that responds to environmental changes. Three intrinsically curved DNAs were cloned from the E. coli O157:H7 virulence plasmid (pO157), sequenced and designated Bent 1 through Bent 3 (BNT1, BNT2 and BNT3). Compared to BNT1 and BNT3, BNT2 had characteristics typical of intrinsically curved DNA including electrophoretic gel retardation at 4°C, six partially phased adenine:thymine tracts and transcriptional activation. BNT2::lacZ operon fusions showed that BNT2 activated transcription at 24°C compared to 37°C and was partially repressed by a bacterial nucleoid-associated protein H-NS. BNT2 regulated the E. coli attaching and effacing gene-positive conserved fragments 1,4 (ecf1,4) that are conserved in Shiga toxin-producing E. coli associated with human disease. Experimental analyses showed that ecf1,4 formed an operon. ecf1, 2 and 3 encoded putative proteins associated with bacterial surface polysaccharide biosynthesis and invasion and ecf4 complemented a chromosomal deletion of lpxM encoding lipid A myristoyl transferase. Mass spectrometric analysis of lipid A from ecf and lpxM single and double mutants showed that myristoylation was altered at lower temperature. [source] Experimental analysis of a mass storage systemCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 15 2006Shahid Bokhari Abstract Mass storage systems (MSSs) play a key role in data-intensive parallel computing. Most contemporary MSSs are implemented as redundant arrays of independent/inexpensive disks (RAID) in which commodity disks are tied together with proprietary controller hardware. The performance of such systems can be difficult to predict because most internal details of the controller behavior are not public. We present a systematic method for empirically evaluating MSS performance by obtaining measurements on a series of RAID configurations of increasing size and complexity. We apply this methodology to a large MSS at Ohio Supercomputer Center that has 16 input/output processors, each connected to four 8 + 1 RAID5 units and provides 128 TB of storage (of which 116.8 TB are usable when formatted). Our methodology permits storage-system designers to evaluate empirically the performance of their systems with considerable confidence. Although we have carried out our experiments in the context of a specific system, our methodology is applicable to all large MSSs. The measurements obtained using our methods permit application programmers to be aware of the limits to the performance of their codes. Copyright © 2006 John Wiley & Sons, Ltd. [source] Experimental analysis of Mn segregation in Bridgman-grown gallium antimonide: Dependency on the ampoule radiusCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2004J. L. Plaza Abstract This work considered the segregation of manganese in vertical Bridgman-grown GaSb crystals for different ampoule diameters. Experimental data of the impurity distribution were obtained from atomic absorption spectrometry and also Hall measurements. It was demonstrated that the radial segregation is more pronounced in the case of thick ampoule diameters. Furthermore the manganese effective segregation coefficient, resistivity, carrier mobility and density were obtained in each case. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Experimental analysis of the impact of peer-to-peer applications on traffic in commercial IP networksEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 6 2004Nadia Ben Azzouna To evaluate the impact of peer-to-peer (P2P) applications on traffic in wide area networks, we analyze measurements from a high speed IP backbone link carrying TCP traffic towards several ADSL areas. The first observations are that the prevalent part of traffic is due to P2P applications (almost 80% of total traffic) and that the usage of network becomes symmetric in the sense that customers are not only clients but also servers. This latter point is observed by the significant proportion of long flows mainly composed of ACK segments. When analyzing the bit rate created by long flows, it turns out that the TCP connections due to P2P applications have a rather small bit rate and that there is no evidence for long range dependence. These facts are intimately related to the way P2P protocols are running. We separately analyze signaling traffic and data traffic. It turns out that by adopting a suitable level of aggregation, global traffic can be described by means of usual tele-traffic models based on M/G/, queues with Weibullian service times. Copyright © 2004 AEI [source] Experimental analysis of compaction of concrete and mortarINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 15 2001Nicolas Burlion Abstract Compaction of concrete is physically a collapse of the material porous microstructure. It produces plastic strains in the material and, at the same time, an increase of its bulk modulus. This paper presents two experimental techniques aimed at obtaining the hydrostatic response of concrete and mortar. The first one is a uniaxial confined compression test which is quite simple to implement and allows to reach hydrostatic pressures of about 600 MPa. The specimen size is large enough so that concrete with aggregate sizes up to 16 mm can be tested. The second one is a true hydrostatic test performed on smaller (mortar) specimens. Test results show that the hydrostatic response of the material is elasto-plastic with a stiffening effect on both the tangent and unloading bulk moduli. The magnitude of the irreversible volumetric strains depends on the initial porosity of the material. This porosity can be related in a first approximation to the water/cement ratio. A comparison of the hydrostatic responses obtained from the two testing techniques on the same material show that the hydrostatic response of cementitious materials cannot be uncoupled from the deviatoric response, as opposed to the standard assumption in constitutive relations for metal alloys. This feature should be taken into account in the development of constitutive relations for concrete subjected to high confinement pressures which are needed in the modelling of impact problems. Copyright © 2001 John Wiley & Sons, Ltd. [source] Experimental analysis of capillary tubes behaviour with some HCFC-22 alternative refrigerantsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2001Samuel M. Sami Abstract In this paper, an experimental study is presented to enhance our understanding of the capillary tube behaviour using some new alternative refrigerants to HCFC-22. An experimental setup fully instrumented was used to gather the behaviour of three different capillary tube geometries with R-410B, R-407C, and R-410A under various conditions; saturated, sub-cooled and two-phase. Experimental data showed that R-410B has the highest pressure drop along the capillary tubes compared to the alternatives under question and also has the highest temperature drop along the capillary tube. The data also showed that R-407C has similar capillary behaviour to that of R-22. The results clearly demonstrated that the pressure drop is significantly influenced by the diameter of the capillary tube, the type of refrigerant and inlet conditions to the capillary tube. The data also showed that the capillary pressure drop decreases with the increase of the capillary diameter. There is clear evidence that the component concentration of the refrigerant mixture significantly affects the capillary tube behaviour and particularly the pressure drop along the capillary tube length. Copyright © 2001 John Wiley & Sons, Ltd. [source] Experimental analysis of specific treatment factors: Efficacy and practice implicationsJOURNAL OF CLINICAL PSYCHOLOGY, Issue 7 2005Jeffrey M. Lohr Interest in the empirical demonstration of the clinical efficacy of psychosocial treatments has been rekindled by societal concerns over accountability and cost effectiveness of mental health services. The result has been the identification of specific treatments for specific disorders. The prescription of treatment content should be based on the theory of therapeutic action and/or the disorder to which it is applied. The demonstration of specific treatment efficacy requires experimental evidence showing the influence of specific procedures beyond nonspecific factors of treatment. We provide an analysis of these factors and their effects in evaluating the specific efficacy of prescriptive psychosocial treatments. Experimental procedures and designs that test the validity of specific treatments are described and applied to cognitive-behavioral treatments of generalized anxiety disorder. The empirical and professional implications of specific treatment efficacy in evidence-based practice are discussed. © 2005 Wiley Periodicals, Inc. J Clin Psychol 61: 819,834, 2005. [source] Modeling an active conformation for linear peptides and design of a competitive inhibitor for HMG-CoA reductaseJOURNAL OF MOLECULAR RECOGNITION, Issue 4 2008Valeriy V. Pak Abstract This study presents an approach that can be used to search for lead peptide candidates, including unconstrained structures in a recognized sequence. This approach was performed using the design of a competitive inhibitor for 3-hydroxy-3-methylglutaryl CoA reductase (HMGR). In a previous design for constrained peptides, a head-to-tail cyclic structure of peptide was used as a model of linear analog in searches for lead peptides with a structure close to an active conformation. Analysis of the conformational space occupied by the peptides suggests that an analogical approach can be applied for finding a lead peptide with an unconstrained structure in a recognized sequence via modeling a cycle using fixed residues of the peptide backbone. Using the space obtained by an analysis of the bioactive conformations of statins, eight cyclic peptides were selected for a peptide library based on the YVAE sequence as a recognized motif. For each cycle, the four models were assessed according to the design criterion ("V" parameter) applied for constrained peptides. Three cyclic peptides (FGYVAE, FPYVAE, and FFYVAE) were selected as lead cycles from the library. The linear FGYVAE peptide (IC50,=,0.4,µM) showed a 1200-fold increase the inhibitory activity compared to the first isolated LPYP peptide (IC50,=,484,µM) from soybean. Experimental analysis of the modeled peptide structures confirms the appropriateness of the proposed approach for the modeling of active conformations of peptides. Copyright © 2008 John Wiley & Sons, Ltd. [source] Odontocete suction feeding: Experimental analysis of water flow and head shapeJOURNAL OF MORPHOLOGY, Issue 12 2006Alexander J. WerthArticle first published online: 13 NOV 200 Abstract The role of cranial morphology in the generation of intraoral and oropharyngeal suction pressures in odontocetes was investigated by manipulating the jaw and hyolingual apparatus of submerged heads of three species presenting varied shapes. Hyoid and gular muscles were manually employed to depress and retract the tongue. Pressures were recorded at three locations in the oral cavity, as gape and site, speed, and force of pull were varied. A biomechanical model was also developed to evaluate pressure data. The species with the shortest, bluntest head and smallest mouth opening generated greater negative pressures. Suction generation diminished sharply as gape increased. Greatest negative pressures attained were around ,45 mmHg (,6,000 Pa), a magnitude deemed suitable for capture of small live prey. Odontocetes utilizing this bidirectional flow system should profit by evolution of a rounder mouth opening through progressive shortening and widening of the rostrum and jaws, a trend evident in cranial measurements from fossil and recent odontocetes. Blunt heads correlate with anatomical, ecological, and behavioral traits associated with suction feeding. Small-gape suction (with minimally opened jaws) could be used by odontocetes of all head and oral shapes to draw prey sufficiently close to the mouth for suction ingestion or grasping via dentition. Principal limitations of the experimental and mathematical simulations include assumption of a stationary odontocete with static (open or closed) jaws and potential scaling issues with differently sized heads and gapes. J. Morphol., 2006. © 2006 Wiley-Liss, Inc. [source] Untersuchungen hinsichtlich der Dauerhaftigkeit von Wärmedämmverbundsystemen (WDVS) mit HolzfaserdämmplattenBAUPHYSIK, Issue 4 2009Norbert Rüther Dipl. Wärme; Versuche; thermal insulation and heat; experimental set-up Abstract Der Schutz der Dämmstoffe von WDVS vor Umwelteinflüssen wird hauptsächlich durch das Putzssystem sichergestellt. Haftet dieses nicht mehr am Dämmstoff, so sind umfangreiche Sanierungsmaßnahmen erforderlich. Mit Hilfe von Haftzugprüfungen aus künstlich gealterten Proben sollten Prognosen über die Dauerhaftigkeit unter realen Bedingungen abgeleitet werden. Es wurde festgestellt, dass die Festigkeit von Platten mit hoher Anfangsfestigkeit über die Zeit um etwa 25 % geringer wird, dann jedoch auf dem Festigkeitsniveau verbleibt. Bei Platten mit niedriger Anfangsfestigkeit wurde kein relevanter Festigkeitsabfall ermittelt. Experimental analysis of the durability of external thermal insulation compound systems (ETICS) using wood fibre insulating boards. The insulation of external thermal insulation compound systems has to be protected by the rendering system. The failure of the rendering system, e.g. due to the loss of bonding strength to the insulation can lead to a failure of the hole system. Forecasts of the durability should be done by using test results of tensile bond strength from samples which were stressed by artificial weathering. Boards with a relatively high strength lose nearly 25 % of their strength and continue in a while at that level. Boards with a relatively low strength do not lose there strength any more. [source] Increasing accuracy of causal inference in experimental analyses of biodiversityFUNCTIONAL ECOLOGY, Issue 6 2004L. BENEDETTI-CECCHI Summary 1Manipulative experiments are often used to identify causal linkages between biodiversity and productivity in terrestrial and aquatic habitats. 2Most studies have identified an effect of biodiversity, but their interpretation has stimulated considerable debate. The main difficulties lie in separating the effect of species richness from those due to changes in identity and relative density of species. 3Various experimental designs have been adopted to circumvent problems in the analysis of biodiversity. Here I show that these designs may not be able to maintain the probability of type I errors at the nominal level (, = 0·05) under a true null hypothesis of no effect of species richness, in the presence of effects of density and identity of species. 4Alternative designs have been proposed to discriminate unambiguously the effects of identity and density of species from those due to number of species. Simulations show that the proposed experiments may have increased capacity to control for type I errors when effects of density and identity of species are also present. These designs have enough flexibility to be useful in the experimental analysis of biodiversity in various assemblages and under a wide range of environmental conditions. [source] The impact of groundwater,surface water interactions on the water balance of a mesoscale lowland river catchment in northeastern GermanyHYDROLOGICAL PROCESSES, Issue 2 2007Stefan Krause Abstract The glacially formed northeastern German lowlands are characterized by extensive floodplains, often interrupted by relatively steep moraine hills. The hydrological cycle of this area is governed by the tight interaction of surface water dynamics and the corresponding directly connected shallow groundwater aquifer. Runoff generation processes, as well as the extent and spatial distribution of the interaction between surface water and groundwater, are controlled by floodplain topography and by surface water dynamics. A modelling approach based on extensive experimental analyses is presented that describes the specific water balance of lowland areas, including the interactions of groundwater and surface water, as well as reflecting the important role of time-variable shallow groundwater stages for runoff generation in floodplains. In the first part, experimental investigations of floodplain hydrological characteristics lead to a qualitative understanding of the water balance processes and to the development of a conceptual model of the water balance and groundwater dynamics of the study area. Thereby model requirements which allow for an adequate simulation of the floodplain hydrology, considering also interactions between groundwater and surface water have been characterized. Based on these analyses, the Integrated Modelling of Water Balance and Nutrient Dynamics (IWAN) approach has been developed. This consists of coupling the surface runoff generation and soil water routines of the deterministic, spatially distributed hydrological model WASIM-ETH-I with the three-dimensional finite-difference-based numerical groundwater model MODFLOW and Processing MODFLOW. The model was applied successfully to a mesoscale subcatchment of the Havel River in northeast Germany. It was calibrated for two small catchments (1·4 and 25 km2), where the importance of the interaction processes between groundwater and surface waters and the sensitivity of several controlling parameters could be quantified. Validation results are satisfying for different years for the entire 198 km2 catchment. The model approach was further successfully tested for specific events. The experimental area is a typical example of a floodplain-dominated landscape. It was demonstrated that the lateral flow processes and the interactions between groundwater and surface water have a major importance for the water balance and periodically superimposed on the vertical runoff generation. Copyright © 2006 John Wiley & Sons, Ltd. [source] Feasibility Study of a Thick-Film PZT Resonant Pressure Sensor Made on a PreFired 3D LTCC StructureINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2009Marina Santo Zarnik This paper discusses the feasibility of a piezoelectric resonant pressure sensor made of lead,zirconate,titanate (PZT) thick films on a preprocessed 3D low-temperature co-fired ceramic structure with a deformable diaphragm. Numerical and experimental analyses were carried out. Two different thick-film PZT compositions were characterized. Using experimentally evaluated material properties, a finite-element analysis showed the trends and facilitated the decisions in the design phase of the sensor. [source] A macroscopic traffic model for highway work zones: Formulations and numerical resultsJOURNAL OF ADVANCED TRANSPORTATION, Issue 3 2006Gang-len Chang This study presents a multilane model for analyzing the dynamic traffic properties of a highway segment under a lane-closure operation that often incurs complex interactions between mandatory lane-changing vehicles and traffic at unblocked lanes. The proposed traffic flow formulations employ the hyperbolic model used in the non-Newtonian fluid dynamics, and assume the lane-changing intensity between neighboring lanes as a function of their difference in density. The results of extensive simulation experiments indicate that the proposed model is capable of realistically replicating the impacts of lane-changing maneuvers from the blocked lanes on the overall traffic conditions, including the interrelations between the approaching flow density, the resulting congestion level, and the exiting flow rate from the lane-closure zone. Our extensive experimental analyses also confirm that traffic conditions will deteriorate dramatically and evolve to the state of traffic jam if the density has exceeded its critical level that varies with the type of lane-closure operations. This study also provides a convenient way for computing such a critical density under various lane-closure conditions, and offers a theoretical basis for understanding the formation as well as dissipation of traffic jam. [source] Mast cells in the amphibian brain during developmentJOURNAL OF ANATOMY, Issue 3 2010Claudia Pinelli Abstract This is the first descriptive study of ontogenesis and anatomical distribution of mast cells in the developing brain of three different amphibian species. In the toad and the green frog, mast cells are preferentially located in: (i) the meningeal lining (pia mater), (ii) the choroid plexuses, both anterior and posterior, and (iii) the neuropil, in close association with the epithelial cell lining of blood vessels. It is only in the perennially aquatic African clawed frog that mast cells never appear inside brain ventricles and within the neuropil. Mast cells first become identifiable in brain of different species in different stages of development. While there are differences in the number of mast cells in different species at different stages of development, the number nearly doubles in all three species during the transition from pro-metamorphic stage of larval development to the peak of metamorphic climax. Furthermore, the number of mast cells is comparatively higher in the toad and remarkably lower in the fully aquatic Xenopus laevis, in which species the first appearance of identifiable mast cells during larval development occurs much later than in equivalent stages of development of the toad and the green frog. The secretory nature of mast cells can be assumed by the presence of cytoplasmic granules, which may show species-specific texture. Further experimental analyses are required to unveil the usefulness of mast cells in the amphibian brain. [source] Local structure of vanadium in doped LiFePO4JOURNAL OF SYNCHROTRON RADIATION, Issue 5 2010Ting Zhao LiFePO4 composites with 5,at.% vanadium doping are prepared by solid state reactions. X-ray absorption fine-structure spectroscopy is used as a novel technique to identify vanadium sites. Both experimental analyses and theoretical simulations show that vanadium does not enter into the LiFePO4 crystal lattice. When the vanadium concentration is lower then 1,at.%, the dopant remains insoluble. Thus, a single-phase vanadium-doped LiFePO4 cannot be formed and the improved electrochemical properties of vanadium-doped LiFePO4 previously reported cannot be associated with crystal structure changes of the LiFePO4via vanadium doping. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||