Home About us Contact
|
Home About us Contact | ||
|
|
||
Experimental Study (experimental + study)
Selected AbstractsTHE MIRACLE OF THE CELLS: AN EXPERIMENTAL STUDY OF INTERVENTIONS TO INCREASE PAYMENT OF COURT-ORDERED FINANCIAL OBLIGATIONS,CRIMINOLOGY AND PUBLIC POLICY, Issue 1 2008DAVID WEISBURD Research Summary: In this article, we present findings from an experimental study of an innovative program in fine enforcement developed by the Administrative Office of the Courts (AOC) of New Jersey, termed Project MUSTER (MUST Earn Restitution). The project was initiated by the New Jersey AOC as a response to concerns among probation personnel that probationers sentenced to monetary penalties often failed to meet their financial obligations. The program sought to increase payment of court-ordered financial obligations among probationers who are seriously delinquent in paying fines, penalties, and restitution, and was designed to "strengthen the effectiveness of restitution and fine sanctions by forcing those offenders who have the ability to make regular payments to do so." Project MUSTER relied on a combination of intensive probation, threats of violation to court and incarceration, and community service. We find that probationers sentenced to Project MUSTER were significantly more likely to pay court-ordered financial obligations than were those who experienced regular probation supervision. However, probationers sentenced to a second treatment group, in which the only intervention was violation of probation (one part of the MUSTER program), had similar outcomes to the MUSTER condition. These findings suggest that the main cause of fine payment was a deterrent threat of possible incarceration, which is often termed the "miracle of the cells." Policy Implications: Our study shows that it is possible to gain greater compliance with court-ordered financial obligations and that such compliance may be gained with a relatively simple and straightforward criminal justice intervention. Threats of violation of probation are an effective tool for gaining compliance with financial obligations. Given the growing interest in monetary penalties as an alternative to incarceration, these findings have particular policy importance. [source] LIMITED DISPERSAL, BUDDING DISPERSAL, AND COOPERATION: AN EXPERIMENTAL STUDYEVOLUTION, Issue 4 2009Rolf Kümmerli Numerous theoretical studies have investigated how limited dispersal may provide an explanation for the evolution of cooperation, by leading to interactions between relatives. However, despite considerable theoretical attention, there has been a lack of empirical tests. In this article, we test how patterns of dispersal influence the evolution of cooperation, using iron-scavenging in the bacterium Pseudomonas aeruginosa as our cooperative trait. We found that relatively limited dispersal does not favor cooperation. The reason for this is that although limited dispersal increases the relatedness between interacting individuals, it also leads to increased local competition for resources between relatives. This result supports Taylor's prediction that in the simplest possible scenario, the effects of increased relatedness and local competition exactly cancel out. In contrast, we show that one way for cooperation to be favored is if individuals disperse in groups (budding dispersal), because this maintains high relatedness while reducing local competition between relatives (relatively global competition). [source] AN EXPERIMENTAL STUDY ON THE RIDE COMFORT OF THE KOREAN HIGH-SPEED TRAINEXPERIMENTAL TECHNIQUES, Issue 6 2009Y.-G. Kim First page of article [source] Experimental Study and Modelling of Formation and Decay of Active Species in an Oxygen DischargeCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005A.-M. Diamy Abstract A microwave (2.45 GHz) oxygen discharge (3 hPa, 150 W, 50 mL.min,1) is studied by optical emission spectroscopy of O(5P) (line 777.4 nm) and of the atmospheric system of O2(head-line 759.4 nm). Calibration of the spectral response of the optical setup is used to determine the concentrations of O(5P) and O2(b). The concentration of the O(5P) atoms is in the range 108,109 cm,3 and the concentration of the O2(b) molecules is in the range 1014 , 2 × 1014 cm,3 along the discharge tube. An attempt is made to simulate the experimental results by using coupling the Boltzmann equation, homogeneous energy transfer V-V and V-T, heterogeneous reactions on the walls (energy transfer and recombination of atoms) and a kinetic scheme (electronic transfer and chemical reactions). The Boltzmann equation includes momentum transfer, inelastic and superelastic processes and e-e collisions. V-V and V-T transfer equations are obtained from the SSH theory and the kinetic scheme includes 65 reactions with 17 species [electrons e, ions O, and O2,, fundamental electronic neutral species O(3P), O2, O2(X,v), O3 and excited neutral species O2(a), O2(b), O2(A), O(1D), O(1S), O(5P), O(4d 5Do), O(5s 5So), O(3d 5Do) and O(4s 5So)]. A fair agreement between experimental results and modelling is obtained with the following set of fitting values: , heterogeneous deactivation coefficient for O2(b) , = 2.6 × 10,2; , rate constant of reaction [O(1D) + O(3P) , 2 O(3P)] k34 = 1.4 × 10,11 cm3.s,1; , electron concentration in the range 1010 , 1011 cm,3. Modelling shows that the recombination coefficient for oxygen atoms on the silica wall (range 1.4 × 10,3 , 0.2 × 10,3) is of the same order as the values obtained in a previous paper and that the ratio ([O] / 2 [O2]initial) is about 33,50%. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Tissue Integration of Polyacrylamide Hydrogel: An Experimental Study of Periurethral, Perivesical, and Mammary Gland Tissue in the PigDERMATOLOGIC SURGERY, Issue 2008DMSC, LISE H. CHRISTENSEN MD BACKGROUND Polyacrylamide hydrogel (PAAG) is a nondegradable water-based polymer with high viscoelasticity. The gel is used as a tissue filler, the only risk being prolonged infection with anaerobic, contaminating microorganisms if not treated early with broad-spectrum antibiotics. OBJECTIVE With silicone gel as reference, PAAG tissue integration and migration was studied in a longitudinal study of the pig. MATERIALS AND METHODS Forty-one pigs were used. PAAG and silicone gel were injected into mammary tissue, and PAAG was injected into urethral or bladder wall or the anal canal. Tissues and regional lymph nodes were examined at 1, 1 1/2, 3, 3 1/2, 6, 12, and 14 months, and other lymph nodes and organs were examined at 1, 6, 12, and 14 months. RESULTS PAAG was invaded by macrophages and giant cells that were gradually replaced by a network of fibrous tissue. Silicone gel was seen inside these cells or as large vacuoles, surrounded by a fibrous capsule. Regional lymph nodes contained PAAG only at 1 1/2 months and silicone gel at 12 months. CONCLUSION PAAG is a stable, viscoelastic bulking agent, which unlike silicone gel is slowly integrated within its host tissue via a thin fibrous network. Long-term risk of fibrosis and migration is minimal. [source] Cognition and Behavior in Normal-Form Games: An Experimental StudyECONOMETRICA, Issue 5 2001Miguel Costa-Gomes This paper reports experiments designed to study strategic sophistication, the extent to which behavior in games reflects attempts to predict others' decisions, taking their incentives into account. We study subjects' initial responses to normal-form games with various patterns of iterated dominance and unique pure-strategy equilibria without dominance, using a computer interface that allowed them to search for hidden payoff information, while recording their searches. Monitoring subjects' information searches along with their decisions allows us to better understand how their decisions are determined, and subjects' deviations from the search patterns suggested by equilibrium analysis help to predict their deviations from equilibrium decisions. [source] Merging of E2 and E1cb Reaction Mechanisms: A Combined Theoretical and Experimental StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 32 2009Edoardo Mosconi Abstract By combining the results of kinetic measurements with DFT calculations we provide a clear-cut evidence of the merging between the E2 and E1cb reaction mechanisms for a large series of leaving groups. Our results solve a long-debated issue in chemical reactivity with profound implications both from a fundamental and biological point of view, thus paving the way to further investigations with different substrates.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] The Formation of Silylated ,-Lactams from Silylketenes through Lewis Acid Promoted [2+2] Cycloaddition: A Combined Theoretical and Experimental StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2005Béatrice Pelotier Abstract The stereoselective formation of silylated cis -,-lactams from (trimethylsilyl)ketene and an ,-imino ester by Lewis acid catalysis is described. Theoretical results suggest that the reaction between (trimethylsilyl)ketene and trans -(methoxycarbonyl)- N -methylformaldimine would proceed most favourably with the BF3 catalyst coordinated to the ketene. Moreover, the calculated energy barriers account for the cis:trans ratio found experimentally. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Aliphatic Thiocarbonyl Ylides and Thiobenzophenone: Experimental Study of Regiochemistry and Methylene Transfer in CycloadditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2005Rolf Huisgen Abstract 1,3-Dipolar cycloadditions of aliphatic or alicyclic thiocarbonyl ylides 3A-D , sterically hindered at least at one terminus , with thiobenzophenone produce both regioisomeric 1,3-dithiolanes 4 and 5. According to quantum-chemical calculations (preceding paper), a concerted cycloaddition furnishing 2,4-substituted dithiolanes 4 competes with the formation of an intermediate C,C -biradical 9 which cyclizes to the more crowded 4,5-substituted dithiolanes 5. When steric hindrance of 3 increases, the cycloaddition is superseded by ,methylene transfer', i.e., the transfer of the less hindered terminus of 3E-J to the S-atom of thiobenzophenone. The thiobenzophenone S -alkylide 11, thus formed, rapidly reacts with a second molecule ofthiobenzophenone to generate the 4,4,5,5-tetraphenyl-1,3-dithiolane 12 via the highly stabilized C,C -biradical 10. Methylene transfer occurs when the cyclization of the mixed C,C -biradical 9 requires a higher activation barrier than its dissociation to aliphatic thioketone + 11; the threshold is surprisingly well reproduced by calculations. The structural assignment of sixteen 1,3-dithiolanes is based on their formation from corresponding reactant pairs as well as on 1H and 13C chemical shifts. X-ray diffraction analyses of three spiro-1,3-dithiolanes reveal the van der Waals strain in non-bonded interactions, folding angles, shearing forces, and bond lengths. Comparison of the mass spectra of many 1,3-dithiolanes allows the reconstruction of major fragmentation pathways. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Theoretical and Experimental Study of the Regioselectivity of Michael AdditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2004David C. Chatfield Abstract Nucleophilic attack at an ,,,-unsaturated carbonyl moiety usually results in conjugate addition at the ,-carbon atom (1,4 or Michael addition) or, occasionally, in addition at the carbonyl carbon atom (1,2 addition). Recently, however, addition at the ,-carbon atom has been observed when strongly electron-withdrawing groups are positioned at the carbon atom , relative to the carbonyl group [e.g., methyl 3,3-bis(trifluoromethyl)propenoate (8) and ethyl 3-(2,4-dinitrophenyl)propenoate (24)]. We have performed theoretical calculations [HF/6,31+G(d) and B3LYP//HF/6,31+G(d)] for the addition of cyanide anion to model ,,,-unsaturated carbonyl compounds to determine trends in the regioselectivity with respect to properties of the substituents. The difference between the reaction barriers for ,- vs. ,-addition decreases as the strength of electron-withdrawing groups increases until, for sufficiently strong electron-withdrawing groups, ,-addition becomes favored. The calculations are in agreement with the experimental results. We show that the regioselectivity can be predicted from partial atomic charges and properties of the frontier orbitals of the reactants. We also report new experimental evidence of ,-addition to polysubstituted cinnamates and cinnamaldehydes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] An Experimental Study of an Empowerment-Based Intervention for African American Head Start FathersFAMILY RELATIONS, Issue 3 2002Jay Fagan This study examined the effects of an empowerment intervention, Men as Teachers, on African American Head Start fathers. Fathers were randomly assigned to the empowerment program or to a control group in which participants viewed a five-part videotape series on parenting. The results revealed a significant improvement in fathers' attitudes about their ability to teach their preschool-age children for the experimental group only. There was no significant improvement in these fathers' attitudes about racial oppression socialization practices. Resident fathers in the experimental group showed significant gains in self-esteem and parenting satisfaction. [source] Combined First-Principle Calculations and Experimental Study on Multi-Component Olivine Cathode for Lithium Rechargeable BatteriesADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Hyeokjo Gwon Abstract The electrochemical properties and phase stability of the multi-component olivine compound LiMn1/3Fe1/3Co1/3PO4 are studied experimentally and with first-principles calculation. The formation of a solid solution between LiMnPO4, LiFePO4, and LiCoPO4 at this composition is confirmed by XRD patterns and the calculated energy. The experimental and first-principle results indicate that there are three distinct regions in the electrochemical profile at quasi-open-circuit potentials of ,3.5,V, ,4.1,V, and ,4.7,V, which are attributed to Fe3+/Fe2+, Mn3+/Mn2+, and Co3+/Co2+ redox couples, respectively. However, exceptionally large polarization is observed only for the region near 4.1,V of Mn3+/Mn2+ redox couples, implying an intrinsic charge transfer problem. An ex situ XRD study reveals that the reversible one-phase reaction of Li extraction/insertion mechanism prevails, unexpectedly, for all lithium compositions of LixMn1/3Fe1/3Co1/3PO4 (0,,,x,,,1) at room temperature. This is the first demonstration that the well-ordered, non-nanocrystalline (less than 1% Li,M disorder and a few hundred nanometer size particle) olivine electrode can be operated solely in a one-phase mode. [source] On the Interaction of Risk and Time Preferences: An Experimental StudyGERMAN ECONOMIC REVIEW, Issue 3 2001Vital Anderhub Experimental studies of risk and time preference typically focus on one of the two phenomena. The goal of this paper is to investigate the (possible) correlation between subjects' attitude to risk and their time preference. For this sake we ask 61 subjects to price a simple lottery in three different scenarios. At the first, the lottery premium is paid ,now'. At the second, it is paid ,later'. At the third, it is paid ,even later,. By comparing the certainty equivalents offered by the subjects for the three lotteries, we test how time and risk preferences are interrelated. Since the time interval between ,now' and ,later' is the same as between ,later' and ,even later', we also test the hypothesis of hyperbolic discounting. The main result is a statistically significant negative correlation between subjects' degrees of risk aversion and their (implicit) discount factors. Moreover, we show that the negative correlation is independent of the method used to elicit certainty equivalents (willingness to pay versus willingness to accept). [source] Learning and Noisy Equilibrium Behavior in an Experimental Study of Imperfect Price Competition*INTERNATIONAL ECONOMIC REVIEW, Issue 3 2002C. Monica Capra We consider a duopoly pricing game with a unique Bertrand,Nashequilibrium. The high-price firm has a nonvanishing market share, however, and intuition suggests that observed prices may be positively related to this market share. This relationship is implied by a model in which players make noisy (logit) best responses to expected payoff differences. The resulting logit equilibrium model was used to design an experiment in which the high-price firm's market share varies. The model accurately predicts the final-period price averages. A naive learning model predicts the observed differences in the time paths of average prices. [source] Experimental Study of the Aging and Self-Healing of the Glass/Ceramic Sealant Used in SOFCsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2010Wenning N. Liu High operating temperatures of solid oxide fuel cells (SOFCs) require that the sealant must function at a high temperature between 600°C and 900°C and in the oxidizing and reducing environments of fuel and air. This paper describes tests to investigate the temporal evolution of the volume fraction of ceramic phases, the evolution of micro-damage, and the self-healing behavior of the glass,ceramic sealant used in SOFCs. It was found that after the initial sintering process, further crystallization of the glass,ceramic sealant does not stop, but slows down and reduces the residual glass content while boosting the ceramic crystalline content. Under a long-term operating environment, distinct fibrous and needle-like crystals in the amorphous phase disappeared, and smeared/diffused phase boundaries between the glass phase and ceramic phase were observed. Meanwhile, the micro-damage was induced by the cooling down process from the operating temperature to room temperature, which can potentially degrade the mechanical properties of the glass/ceramic sealant. The glass/ceramic sealant exhibited self-healing upon reheating to the SOFC operating temperature, which can restore the mechanical performance of the glass/ceramic sealant. [source] Experimental Study on the Diet of Mosquitofish (Gambusia holbrooki) under Different Ecological Conditions in a Shallow LakeINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2004Saúl Blanco Abstract We studied the diet of the eastern mosquitofish Gambusia holbrooki with in situ experimental mesocosms located in a shallow lake. Different nutrient concentrations (phosphorus and nitrogen) and fish population densities were tested. Our results confirm that it is a planktivorous species, with also a great ingestion of algae and detritus. Nutrient fertilization caused almost no changes in this species feeding behavior, but larger mosquitofish stocks induced a shift to zooplanktivory and a decline in detritivory. When macrophytes were present, the predation effect focused on zooplankton and plant-associated animals, otherwise predation on bottom macroinvertebrates increased. Females preyed upon almost all groups more intensely, including detritus. Males and juveniles did not overlap diet, the former being more selective on ostracods, while juveniles consumed detritus, rotifers and cladoceran. Our data support the idea that mosquitofish can cause important top-down effects in shallow lakes under a wide variety of ecological conditions, being an important zooplanktivore in both turbid and plant-dominated shallow lakes especially in the Mediterranean zone, where high temperatures and absence of piscivores promote maintenance of its populations during the whole year. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Implicit Theories of Organizational Power and Priming Effects on Managerial Power-Sharing Decisions: An Experimental Study,JOURNAL OF APPLIED SOCIAL PSYCHOLOGY, Issue 2 2004Peter T. Coleman Over 60 years of research on participative leadership has documented the many benefits of power sharing in organizations. However, a common obstacle to power sharing is the unwillingness of those with power to share it. An experimental study is presented that investigated the effects of managers' implicit theories of power in organizations on their willingness to share power with subordinates. The study proposed that chronic differences in implicit power theories (the degree of competitive vs. cooperative beliefs and ideals regarding organizational power relations) would affect managers' decisions to share or withhold power. Subliminal priming was predicted to temporarily enhance the accessibility of these differences in implicit power theories, thereby fostering or inhibiting spontaneous decisions to share power. Results indicate that the subliminal priming of competitive theories of organizational power negatively influenced managers' immediate, spontaneous decisions to share power, whereas chronic differences in their implicit theories similarly affected their more systematic decisions to share power. The theoretical and applied contributions of the study are discussed. [source] Rock Stars in Anti-Drug-Abuse Commercials: An Experimental Study of Adolescents' Reactions,JOURNAL OF APPLIED SOCIAL PSYCHOLOGY, Issue 6 2000Michael D Newcomb Two studies examined adolescents' perceptions and effectiveness of rock stars in antidrug-abuse public-service announcements (PSAs). In the pilot study (N= 24 teenagers), adolescents expected rock musicians, and in particular heavy metal musicians, to be drug users. In our experimental study (N= 78 high school students aged 15 to 16 years), one group was shown 4 PSAs produced by Rock Against Drugs, using rock stars Jon Bon Jovi, Aimee Mann, Gene Simmons, and Belinda Carlysle as spokespersons. The comparison group was shown 4 equivalent PSAs that were created using unknown actors selected for their similarity to the rock stars in terms of age, ethnicity, and gender, but without any reference to rock music. PSA ratings were taken on 4 scales: attractiveness, expertness, trustworthiness, and overall PSA rating. Pretest and posttest measures of drug attitudes supported our hypotheses that countermessages from rock stars denormalize the connection between rock music and drugs, and that adolescents respond more positively to PSAs with rock stars than to PSAs without rock stars. [source] An Experimental Study of Auditor Analytical Review JudgementsJOURNAL OF BUSINESS FINANCE & ACCOUNTING, Issue 9-10 2000Kenny Z. Lin This paper provides evidence as to how five factors highlighted in the current UK auditing standard are taken into account by auditors in analytical review (AR) judgements. While the relative importance of particular cues was generally found to be consistent with the standard, certain factors were taken into account only to a marginal extent. Little evidence of configural cue usage was identified. The study also provides evidence of a tendency towards conservatism in the way auditors approach AR. The results suggest both that the potential to substitute AR for other substantive procedures may be realised only imperfectly and that the issue of configural reasoning should be addressed in the auditing standard. [source] An Experimental Study of Auditor Analytical Review JudgementsJOURNAL OF BUSINESS FINANCE & ACCOUNTING, Issue 7-8 2000Kenny Z. Lin This paper provides evidence as to how five factors highlighted in the current UK auditing standard are taken into account by auditors in analytical review (AR) judgements. While the relative importance of particular cues was generally found to be consistent with the standard, certain factors were taken into account only to a marginal extent. Little evidence of configural cue usage was identified. The study also provides evidence of a tendency towards conservatism in the way auditors approach AR. The results suggest both that the potential to substitute AR for other substantive procedures may be realised only imperfectly and that the issue of configural reasoning should be addressed in the auditing standard. [source] Testing the Long-Term Effects of the Go Sun Smart Worksite Health Communication Campaign: A Group-Randomized Experimental StudyJOURNAL OF COMMUNICATION, Issue 3 2008Peter A. Andersen This study examined the long-term effects of the Go Sun Smart (GSS) campaign, a large-scale health communication intervention designed to promote sun safety to employees at 26 ski areas in western North America. Employees were enrolled in a pair-matched group-randomized pretest,posttest controlled design with 2 follow-up surveys. Half of the ski areas were randomly assigned to implement GSS in the winter. This article reports analyses of a hierarchical linear design with responses from 1,463 employees who completed the second follow-up survey at the end of the following summer (69% of those who completed the first posttest). GSS continued to have positive effects on employees who worked at intervention ski areas into the summer. Employees exposed to GSS reported less sunburning, engaged in more sun safety behaviors, were more aware of the program, and had more discussions of sun safety at home than employees at matched control group resorts. The long-term effects of GSS support recommending that sun protection programs be implemented at workplaces, but such programs should be implemented with high fidelity to achieve maximum benefits. Despite limitations due to nonresponse, geography, measurement, and ethnicity, the hierarchical clustered design improved the internal validity and generalizability of the findings. [source] Judges' Use of Examinee Performance Data in an Angoff Standard-Setting Exercise for a Medical Licensing Examination: An Experimental StudyJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 4 2009Brian E. Clauser Although the Angoff procedure is among the most widely used standard setting procedures for tests comprising multiple-choice items, research has shown that subject matter experts have considerable difficulty accurately making the required judgments in the absence of examinee performance data. Some authors have viewed the need to provide performance data as a fatal flaw for the procedure; others have considered it appropriate for experts to integrate performance data into their judgments but have been concerned that experts may rely too heavily on the data. There have, however, been relatively few studies examining how experts use the data. This article reports on two studies that examine how experts modify their judgments after reviewing data. In both studies, data for some items were accurate and data for other items had been manipulated. Judges in both studies substantially modified their judgments whether the data were accurate or not. [source] How Law Changes the Environmental Mind: An Experimental Study of the Effect of Legal Norms on Moral Perceptions and Civic EnforcementJOURNAL OF LAW AND SOCIETY, Issue 4 2009Yuval Feldman This paper examines how different legal instruments affect people's moral intuitions and willingness to engage in social enforcement in the field of environmental law. These instruments vary in terms of their governance technique, the process through which they were enacted, and their allocation of enforcement responsibilities. Their effect on citizens' moral evaluation and emotional reaction to corporate polluting behaviour are examined, based on an experimental survey of a representative sample of 1400 individuals in Israel. Our findings demonstrate that their design influences people's level of moral and emotional resentment when faced by environmentally problematic behaviour, as well as their motivation to engage in private enforcement. The design of the regulatory instrument could thus generate biases in social reactions to polluting behaviour, irrespective of its actual ecological adverse effect. We analyse the moral and psychological mechanisms which underlie these effects and explore their various policy implications. [source] Experimental Study on Phase Transformation Between MgB2 and MgB4JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2007S. C. Yan Using X-ray diffraction (XRD), scanning electron microscope (SEM), and differential scanning calorimetry (DSC), we have investigated the reaction between MgB4 and Mg in its solid, liquid, and gas physical states. The XRD results indicate that the reaction of MgB4+Mg=2MgB2 always occurs independently of the different states of Mg. DSC measurements show that the solid,solid reaction MgB4(s)+Mg(s)=2MgB2(s), the Mg melting Mg(s),Mg(l), and the Mg volatilization occur in turn with increasing temperature for mixed (MgB4+Mg) powder with a nominal stoichiometry of MgB2. SEM observations indicate that the resulting synthesized MgB2 samples, obtained from the MgB4+Mg mixtures, have a denser microstructure than those obtained directly from Mg+B mixtures. On the basis of XRD, DSC, and SEM results, a kinetic model for the reaction between MgB4 and Mg is proposed. [source] Integrating Formal and Functional Approaches to Language Teaching in French Immersion: An Experimental StudyLANGUAGE LEARNING, Issue 2001Elaine M. Day This experimental study was designed to evaluate the effect on French language proficiency of an integrated formal, analytic and functional, communicative approach (experiential) to second-language teaching in the immersion classroom. The impetus for the study arises from previous research indicating that immersion children show persistent weaknesses in their grammatical skills despite the fluent, functional proficiency they achieve in their second language. The experimental materials, which were custom-designed for our study, highlight form-function relations, promote noticing, encourage metalin-guistic awareness, and provide opportunities for language practice and thus relate to some of the theoretical issues that Rod Ellis (this volume) has indicated are important in SLA in the 90s. This classroom-based study on the conditional is one of a series of studies undertaken in Canadian French immersion to investigate the effectiveness of form-focused instruction in classrooms (see Swain, 2000). The results of our study, which was conducted in grade 7 early immersion, showed that the Experimental group performed significantly higher in writing than the Control group, in both the post- and the follow-up testing. Although this was not found for speaking, an examination of the individual class data revealed greater and more consistent growth in speaking for the Experimental than for the Control classes, suggesting that they benefited somewhat from the experi- mental treatment in this domain as well. Although Ellis (this volume) notes that research on form-focused instruc- tion in the 90s has tended to split pedagogy from theory, the immersion research in this area does not seem t o reflect this shift. In a recent article, Swain (2000) reviews the French Immersion (FI) studies and summarizes their re- sults as follows: "Overall, the set of experiments conducted in FI classes suggest that there is value in focusing on language form through the use of pre-planned curriculum materials in the context of content-based language learn- ing" (Swain, 2000, p. 205). Her reference to curriculum materials and to the specific context of content-based lan- guage learning should signal to the reader the orientation t o pedagogical considerations that characterize this research. As Ellis notes, hybrid research using both experimental and qualitative methods is becoming more common in SLA. Recently, the experimental materials in our study were implemented in a grade 8 immersion classroom, and the children's collaborative language activity was observed by a researcher working from a sociocultural theoretical per- spective (Spielman-Davidson, 2000). The uptake of our research by a researcher working in another paradigm introduces another kind of hybridity that we hope will also shed further light on questions in form-focused instruction and lead to appropriate changes in pedagogy and in the design of immersion curricula. [source] An Experimental Study on the Free-Radical Copolymerization Kinetics with Crosslinking of Styrene and Divinylbenzene in Supercritical Carbon DioxideMACROMOLECULAR REACTION ENGINEERING, Issue 1 2009Pedro R. García-Morán Abstract A study on the effect of process conditions and composition of the reacting mixture on the kinetics and particle properties in the copolymerization of styrene and divinylbenzene in supercritical carbon dioxide is presented. Polystyrene -block- polydimethylsiloxane and Krytox 257 FSL (Dupont) were used as stabilizers, and their performance compared. A 38 mL, high-pressure view cell, equipped with one frontal and two lateral sapphire windows, was used as the reacting vessel. The polymer product was characterized for total monomer conversion, gel content, molecular weight averages of the sol fraction and particle size distribution. Acceptable polymerization rates and partially-agglomerated spherical particles were produced under the conditions tested. [source] Thermal Degradation Kinetics of Nylon 66: Experimental Study and Comparison with Model PredictionsMACROMOLECULAR REACTION ENGINEERING, Issue 5 2007Mark A. Schaffer Abstract An experimental investigation of nonoxidative thermal degradation kinetics of nylon 66 melt under high temperature (280,300,°C) and low water content (0.02,0.14 wt.-%) conditions is presented. Experimental data for the time evolution of polymer end-group concentrations and degradation-product generation rates were compared with the predictions of the only published kinetic model. The omitted influence of water content is a plausible partial explanation for the considerable discrepancy between model predictions and some data. Several previously unreported or unquantified degradation products were identified and measured. Potential additional reactions to account for these results in future kinetic models are proposed. [source] Mapping of Atrial Activation Patterns After Inducing Contiguous Radiofrequency Lesions: An Experimental StudyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2001FRANCISCO J. CHORRO CHORRO, F.J., et al.: Mapping of Atrial Activation Patterns After Inducing Contiguous Radiofrequency Lesions: An Experimental Study. High resolution mapping techniques are used to analyze the changes in atrial activation patterns produced by contiguous RF induced lesions. In 12 Langendorff-perfused rabbit hearts, left atrial activation maps were obtained before and after RF induction of epicardial lesions following a triple-phase sequential protocol: (phase 1) three separate lesions positioned vertically in the central zone of the left atrial wall; (phase 2) the addition of two lesions located between the central lesion and the upper and lower lesions; and (phase 3) the placement of four additional lesions between those induced in the previous phases. In six additional experiments a pathological analysis of the individual RF lesions was performed. In phase 1 (lesion diameter = 2.8 ± 0.2 mm, gap between lesions = 3 ± 0.8 mm), the activation process bordered the lesions line in two (2.0-ms cycles) and four experiments (1.0-ms cycles). In phase 2, activation bordered the lesions line in eight (2.0-ms cycles, P < 0.01 vs control) and nine experiments (1.0-ms cycles, P < 0.001), and in phase 3 this occurred in all experiments except one (both cycles, P < 0.001 vs control). In the experiments with conduction block, the increment of the interval between activation times proximal and distal to the lesions showed a significant correlation to the length of the lesions (r = 0.68, P < 0.05, 100-ms cycle). In two (17%) experiments, sustained regular tachycardias were induced with reentrant activation patterns around the lesions line. In conclusion, in this acute model, atrial RF lesions with intact tissue gaps of 3 mm between them interrupt conduction occasionally, and conduction block may be frequency dependent. Lesion overlap is required to achieve complete conduction block lines. Tachycardias with reentrant activation patterns around a lesions line may be induced. [source] Opposite Effects of Myocardial Stretch and Verapamil on the Complexity of the Ventricular Fibrillatory Pattern: An Experimental StudyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2000FRANCISCO J. CHORRO CHORRO, F.J., et al.: Opposite Effects of Myocardial Stretch And Verapamil on The Complexity of The Ventricular Fibrillatory Pattern: An Experimental Study. An experimental model is used to analyze the effects of ventricular stretching and verapamil on the activation patterns during VF. Ten Langendorff-perfused rabbit hearts were used to record VF activity with an epicardial multiple electrode before, during, and after stretching with an intraventricular balloon, under both control conditions and during verapamil (Vp) infusion (0.4,0.8 ,mol). The analyzed parameters were dominant frequency (FrD) spectral analysis, the median (MN) of the VF intervals, and the type of activation maps during VF (I = one wavelet without block lines, II = two simultaneous wavelets with block lines, III = three or more wavelets with block lines). Stretch accelerates VF (FrD: 22.8 ± 6.4 vs 15.2 ± 1.0 Hz, P < 0.01; MN: 48 ± 13 vs 68 ± 6 ms, P < 0.01). On fitting the FrD time changes to an exponential model after applying and suppressing stretch, the time constants (stretch: 101.2 ± 19.6 s; stretch suppression: 97.8 ± 33.2 s) do not differ significantly. Stretching induces a significant variation in the complexity of the VF activation maps with type III increments and type I and II decrements (control: I = 17.5%, II = 50.5%, III = 32%; stretch: I = 7%, II = 36.5%, III = 56.5%, P < 0.001). Vp accelerates VF (FrD: 20.9 ± 1.9 Hz, P < 0.001 vs control; MN: 50 ± 5 ms, P < 0.001 vs control) and diminishes activation maps complexity (I = 25.5%, II = 60.5%, III = 14%, P < 0.001 vs control). On applying stretch during Vp perfusion, the fibrillatory process is not accelerated to any greater degree. However, type I and II map decrements and type III increments are recorded, though reaching percentages similar to control (I = 16.5%, II = 53%, III = 30.5%, NS vs control). The following conclusions were found: (1) myocardial stretching accelerates VF and increases the complexity of the VF activation pattern; (2) time changes in the FrD of VF during and upon suppressing stretch fit an exponential model with similar time constants; and (3) although stretching and verapamil accelerate the VF process, they exert opposite effects upon the complexity of the fibrillatory pattern. [source] Experimental Study on Particle Size Distribution and Concentration Using Transmission Fluctuation Spectrometry with the Autocorrelation TechniquePARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2005Xiaoai Guo Abstract Based on the statistical characteristics of the transmission fluctuations in the particle suspension, transmission fluctuation spectrometry with autocorrelation (TFS-AC) is described theoretically, with the assumptions of geometric ray propagation and completely absorbent particles in the suspension. The experiments presented here are realized in a focused Gaussian beam with the TFS-AC technique. The acquisition of transmission fluctuation signals is achieved by using a high-resolution digital oscilloscope. The transition function of TFS-AC is obtained by varying the autocorrelation time. With a modified iterative Chahine inversion algorithm, solving a linear equation retrieves information on the particle size distribution and particle concentration. Some experimental results on spherical and non-spherical particles are presented and discussed. The experiments cover a particle size range from 1,m to 1000,,m and a particle concentration of up to 12,%. [source] | |||||||||||||||||||||||||||||||||||||