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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1181

Experiment & Trix : Ett utvecklingsprojekt om naturvetenskap med fokus på experiment

Duman, Daniella January 2014 (has links)
Syftet med detta utvecklingsprojekt är att stärka naturvetenskapens roll i grundskolans tidigare åldrar. Att väcka intresse och lust för de naturvetenskapliga ämnena samt för att arbeta praktiskt så att eleverna är delaktiga i undervisningen. Det handlar även om att bekanta sig med naturvetenskapen i vardagen och inse att den är enkel att arbeta med. Materialet består av experiment som eleverna får och lärarhandledningar som följer med varje experiment till lärarna. Materialet är konstruerat till elever och lärare i årskurs 1-3 i grundskolan. Varje experiment har ett mål som ska nås från kursplanerna i naturvetenskap (biologi, fysik och kemi) för år 1-3 och där kan läraren bestämma hur/om eleverna har nått det målet. Lärarhandledningarna är uppbyggda med ”tips innan experimentet”, ”förklaring”, ”resultat”, ”undersök mer” och centralt innehåll”. För att utvärdera materialet fick två lärare i naturvetenskap titta på materialet och säga vad de tyckte om det. Upplevelsen av lärarnas tänkande kring arbetet var väldigt positivt och målet för att arbetet skulle vara lättillgängligt nåddes. En av lärarna skrev ”Du kommer säkert att locka många elever till större och vidare nyfikenhet med ditt material”. Lärarna ville gärna använda materialet och behålla det och det ses som något positivt. Möjlighet till skapande och elevernas intresse tas omhand och detta är förhoppningsvis bara början till att naturvetenskapen lyfts och används mer i skolan. / The purpose of this development is to strengthen scientific role in schools earlier ages. To arouse interest and desire for the natural sciences, as well as to work so that students are involved in teaching. It is also about to become acquainted with natural sciences in everyday life, and realize that it is easy to work with. The material consists of experiments that students and a teacher's guide as follows with each experiment to teachers. The material is designed to students and teachers in grade 1-3 in primary school. Each experiment has a target to be reached from the curriculum in science for years 1-3 and where trainer can determine how/if pupils have reached the goal. A teacher's guide is built with "tips before the experiment", "Explanation", "results", "explore more" and central content". In order to evaluate the material had two teachers in science look at the material and say what they thought about it. Experience of teachers' thinking around the work was very positive and the objective of the work would be accessible was reached. One of the teachers wrote "You will certainly attract many students to larger and further curiosity with your material". Teachers wanted to use the material and keep it and it is seen as something positive. An opportunity for the creation and students' interest will be looked after and this is hopefully just the beginning of that life sciences lifts and is used more in the school.
1182

Parity violating asymmetries in the Gº experiment: Pion photoproduction on the Δ resonance

Coppens, Alexandre Francois Constant 13 September 2010 (has links)
Symmetry tests and more precisely parity violation experiments using the properties of the weak interaction give us unique insight into the internal hadronic structure of matter. The Gº experiment at Jefferson Laboratory used parity violating electron scattering to probe the strange quark contribution to the electromagnetic nucleon form factors, (GMs and GEs) as well as the axial contribution, (GAe). The data taken during the experiment provide further information on the axial transition form factor of the N - $\Delta$ transition, (GANΔ), as well as the scale of the low energy constant (dΔ) characterizing the parity violating γNΔ coupling. The analysis of backward angle Gº data taken with a liquid deuterium target to deduce the parity violating asymmetry for pion photoproduction on the Δ resonance, and the first experimental constraint on the value of dΔ, are reported in this thesis. The results showed that dΔ = (8.3 ± 25.3) gπ where the uncertainty is dominated by statistics, and that 75 percent of the theory range would be excluded by this measurement at 1 sigma.
1183

Songdo: urban autopoiesis

Hunter, Meaghan 15 October 2010 (has links)
This project examines the term autopoiesis and contextualizes it into the realm of Landscape Architecture. Autopoiesis is defined as self-generating, self-producing, self-maintaining organization, used to describe the resilience of a living system. This practicum presents autopoiesis as a process condition that describes incidences of phenomena and the resulting emergent behaviors. Through illustration, photography, simulation and experimental studies, an understanding of autopoiesis through visual representations was attained. This practicum creates a space that uses the dynamics of autopoiesis to both inform and form the design of an urban condition. Located along the coast of Incheon, South Korea, a 1.6km2 site of reclaimed tidal-flat land was investigated. Autopoiesis was understood through phenomena and emergent behaviors that resulted by integrating the fluctuating tidal system into the creation, realization and functioning of the site. The intention of this project is to articulate the notions of autopoiesis through the design of a flexible condition that responds, reacts and engages with contingencies and disturbances, allowing these types relationships to become integral component to the overall development and functioning of the designed site.
1184

Robust designs for field experiments with blocks

Mann, Rena Kaur 28 July 2011 (has links)
This thesis focuses on the design of field experiments with blocks to study treatment effects for a number of treatments. Small field plots are available but located in several blocks and each plot is assigned to a treatment in the experiment. Due to spatial correlation among the plots, the allocation of the treatments to plots has influence on the analysis of the treatment effects. When the spatial correlation is known, optimal allocations (designs) of the treatments to plots have been studied in the literature. However, the spatial correlation is usually unknown in practice, so we propose a robust criterion to study optimal designs of the treatments to plots. Neighbourhoods of correlation structures are introduced and a modified generalized least squares estimator is discussed. A simulated annealing algorithm is implemented to compute optimal/robust designs. Various results are obtained for different experimental settings. Some theoretical results are also proved in the thesis. / Graduate
1185

Search for new spin-0 particles near π⁰ mass produced in association with τ pairs at BABAR

Beaulieu, Alexandre 29 August 2013 (has links)
This research project searches for new physics in the τ sector that would resolve the tension between BABAR measurement for the pion-photon transition form factor Fπ0(Q^2)and the standard model asymptotic prediction. This behaviour could be explained by a new light pseudo-scalar state that mixes with the π 0 and enhances its coupling to the c and b quarks or the τ lepton, or by a new spin-0 particle with mass very close to the π 0 . We examine one channel to test for existence of such objects: their creation in association with τ pairs in e+ e− collisions. The analysis uses a typical cut-based approach as the large predicted cross-sections and the kinematics of the final states allow for a direct selection of signal events and background suppression. Current simulation studies predict a 90% CL limit on the production cross-section on the order of 100 fb in case of no signal, while the theory predicts production cross-sections on the order of 1 pb to 100 pb depending on the model. / Graduate / 0798 / beaa@uvic.ca
1186

Social Preferences and Voting on Reform: An Experimental Study

Paetzel, Fabian, Sausgruber, Rupert, Traub, Stefan 04 1900 (has links) (PDF)
Debating over efficiency-enhancing but inequality-increasing reforms accounts for the routine business of democratic institutions. Fernandez and Rodrik (1991) hold that anti-reform bias can be attributed to individual-specific uncertainty regarding the distribution of gains and losses resulting from a reform. In this paper, we experimentally demonstrate that anti-reform bias arising from uncertainty is mitigated by social preferences. We show that, paradoxically, many who stand to lose from reforms vote in favor because they value efficiency, while many who will potentially gain from reforms oppose them due to inequality aversion. (authors' abstract) / Series: Department of Economics Working Paper Series
1187

Progress Toward a Redetermination of the Neutron Lifetime Through the Absolute Determination of Neutron Flux

Yue, Andrew T 01 December 2011 (has links)
The reported lifetime in an in-beam neutron lifetime experiment performed at NIST was tn = (886.3 ± 3.4) s. The largest source of uncertainty was the efficiency of the neutron flux monitor (0.3% relative uncertainty). The flux monitor operates by counting charged particles produced when neutrons impinge on a 6Li foil. Its efficiency was calculated from the 6Li thermal neutron cross section, the solid angle subtended by the charged particle detectors, and the amount of neutron-absorbing material present on the foil. An absolute black neutron detector for cold neutron beams has been developed to measure the efficiency without the need to know these quantities. The flux monitor efficiency is measured to a precision of 0.052% using this direct calibration technique. This calibration removes the largest barrier to a 1 s neutron lifetime measurement with the beam technique. It is hoped that this data can also be used to re-evaluate the current NIST neutron lifetime value, reduce its uncertainty, and remove the dependence on evaluated nuclear data files. There is also the possibility for a direct measurement of the 6Li thermal neutron cross section.
1188

Theoretical and Empirical Essays on the Effects of Proposed and Existing Environmental Policies

Jones, Luke Robert 01 December 2011 (has links)
This dissertation consists of three chapters that explore environmental policy. Chapter 1 empirically investigates the potential for incentives to encourage the adoption of low-emission alternatives to gasoline motorcycles. Hanoi, Vietnam, like many Asian cities, is experiencing rapid growth in the ownership of personal gasoline-powered motorcycles and scooters, and along with this heightened air quality issues. Electric scooters have the potential to reduce air pollution as an alternative to gasoline-powered motorcycles; however, electric scooters have yet to penetrate the Vietnamese and other large Asian markets. This study uses a choice experiment survey to elicit the demand for electric scooters, with focus on the effects that economic incentives and technology improvements have on adoption. Chapter 2 takes the first steps toward incorporating point sources into the theoretical discussion on nonpoint pollution ambient taxes. Previous investigations into the use of ambient taxes for nonpoint source pollution have not addressed the role of point sources, even though many watersheds have both source types. This paper examines the use of taxes for jointly regulating point and nonpoint sources. A model of point-nonpoint pollution is developed, and within this framework taxes are applied to achieve different regulatory objectives, including implementing optimal emissions reductions, as well as meeting exogenously specified environmental goals at least cost. Discussion centers on comparison of the point and nonpoint taxes in each scenario. Chapter 3 is an experimental economics examination of the design of markets for water quality trading. Water quality trading is endorsed by policymakers as a tool for reducing pollution in watersheds in a cost-effective manner, and many watersheds in the U.S. have established water quality trading programs. As a whole, these programs have not been successful. It is hypothesized that common features of these programs, such as the market institutions in place, may contribute to the limited success. As a first step in empirically investigating water quality trading markets, this study uses laboratory experiments to isolate how different institutions affect economic efficiency. In particular, we compare cap-and-trade, two forms of baseline-and-credit institution, and a tax/subsidy regulation, and examine the effect of introducing fixed technology costs with these four institutions.
1189

Generation and detection of lamb waves for the characterization of plastic deformation

Pruell, Christoph 24 August 2007 (has links)
In this thesis ultrasonic Lamb wave measurements are performed to detect material nonlinearity in aluminum sheets. When a Lamb wave propagates, higher harmonic wave fields are generated and under certain conditions the second harmonic is cumulative. When these conditions hold the Lamb waves are serviceable for material nonlinearity measurements. For generation, a wedge transducer combination is used. The detection of the Lamb wave are performed with either a laser interferometer or a second wedge transducer combination and the results are benchmarked. A short time Fourier transformation (STFT) is applied to the detected signal to extract the amplitudes of the first and second harmonics. A relative ratio of the first and second harmonics is deduced from nonlinear wave theory to assign the nonlinearity of the material. To verify the capability of the measurement setup and to show that cumulative second harmonics are generated, measurements for different propagation distances are performed. Further measurements on plasticly deformed specimens are carried out to examine the change of the material nonlinearity as a function of plasticity.
1190

Efectes de l'ostracisme i del gen de la monoamino-oxidasa A en una tasca experimental d'agressió en humans

Gallardo Pujol, David 22 October 2009 (has links)
L'any 2002, Caspi et al. informaren per primer cop d'una interacció entre un factor genètic concret (el gen de la monoamino-oxidasa A o MAOA) i un factor ambiental concret, el maltractament infantil, i de llurs efectes sobre el comportament antisocial en l'edat adulta. Aquest treball seminal originà posteriors recerques que tractaren de replicar aquesta interacció amb diferents mostres i metodologies. Tots aquests treballs, però, tenen en comú la utilització de dissenys correlacionals. És a dir, cap d'ells pot assegurar la causalitat dels efectes de la interacció genotip-ambient en el comportament antisocial. L'objectiu d'aquest treball és, principalment, replicar les troballes de Caspi et al. (2002) de forma experimental, mitjançant la utilització d'anàlegs de laboratori. Per una altra banda, la majoria de treballs no han trobat una relació directa entre el gen de la MAOA i l'agressió, però fins ara no havia estat estudiat el paper dels trets de personalitat com a possibles endofenotips que estiguin mediant en aquesta relació. Les hipòtesis d'aquest treball són dues, 1) que els subjectes portadors de l'al·lel de baixa activitat del gen de la MAOA sota una condició d'adversitat ambiental respondran de forma significativament més elevada en una tasca d'agressió experimental. Per contra, no hi haurà diferències entre aquells subjectes que no hagin estat exposats a adversitat ambiental en funció del seu genotip MAOA. 2) Els trets de personalitat "agressivitat" i "impulsivitat" tindran un paper significatiu en la relació entre genotip i fenotip (MAOA i agressió respectivament), essent els portadors de l'al·lel de baixa activitat del gen de la MAOA més agressius i impulsius i puntuant així més alt en la tasca d'agressió de laboratori. Per tal d'induir l'adversitat ambiental o ostracisme utilitzem la tasca Cyberball, genotipem als subjectes mitjançant procediments estàndard i com a variable dependent utilitzem una tasca d'agressió experimental anomenada Point Subtraction Aggression Paradigm (PSAP). Per tal de posar a prova la primera hipòtesi utilitzem una Anàlisi Multivariant de la Variància, i per tal de posar a prova la segona hipòtesi, un Model d'Equacions Estructurals. Els resultats ens indiquen que el gen de la MAOA no té cap efecte sobre la agressió mesurada segons el PSAP, mentre que l'ostracisme i la interacció entre ambdós sí, explicant un 30% de la variabilitat de l'agressió gràcies a les variables independents. Els resultats avalen la rèplica de les troballes de Caspi et al. en una situació controlada de laboratori. Així doncs, mitjançant un disseny experimental, aquest treball ha reproduït una interacció entre el gen de la MAOA i l'ostracisme i els seus efectes sobre l'agressió. D'altra banda, hem contrastat parcialment la segona hipòtesi del treball, trobant efectes indirectes del gen de la MAOA en l'agressió en el PSAP a través del tret de personalitat "impulsivitat". Com a conclusions generals, podem afirmar que el tipus de disseny que hem utilitzat en aquest treball podria generalitzar-se a d'altres formes d'interacció genotip-ambient que han estat detectades. Sens dubte, creiem que pot ésser una eina molt útil per a d'altres investigadors. També hem observat com és possible d'emprar variables de personalitat com a endofenotips. De fet, no només és possible sinó que creiem que és desitjable, per tal de reduir la distancia entre el genotip i el fenotip. / In 2002, Caspi et al. reported for the first time an interaction between a specific genetic factor (monoamine-oxidase A or MAOA gene) and a specific environmental factor, child abuse, and their effects on antisocial behavior in adulthood. This seminal work originated research that tried to replicate this interaction with different samples and methodologies. All these studies, however, have in common the use of correlational designs. The main aim of this study is mainly to replicate the findings of Caspi et al. (2002) experimentally. The hypotheses of this study are two, 1) that subjects carrying the low-activity allele of the MAOA gene under adverse environmental condition will respond significantly higher in the aggression experimental task. However, there won't be differences between those subjects that have not been exposed to environmental adversity regardless of their MAOA genotype. 2) Personality traits "aggressiveness" and "impulsiveness" will show a significant role in the relationship between genotype and phenotype (MAOA and aggression, respectively), being carriers of the low-activity allele of the MAOA gene more aggressive and impulsive, and thus scoring higher in the aggression task. We induced environmental adversity (ostracism) using the Cyberball task, genotype was obtained following standard procedures. As dependent variable we used the experimental aggression task Point Subtraction Aggression Paradigm (PSAP). Results indicate that MAOA gene has no effect on PSAP aggression, while the interaction between ostracism does have, explaining up to 30% of the variance. Thus, using an experimental design, this study has reproduced an interaction between the MAOA gene and environmental adversity and its effects on aggression. Furthermore, we found partial support for the second hypothesis, finding indirect effects of the MAOA gene on PSAP aggression via "impulsiveness". As a general conclusion, we can state that the type of design that we used in this study could be generalized to other forms of genotype-environment interaction that have been detected. Undoubtedly, we can be a useful tool for other researchers. We have also observed how it is possible to use variables as personality endofenotips. In fact, not only possible but believe it is desirable to reduce the gap between genotype and phenotype.

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