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Mahon, Peter John, and mikewood@deakin edu au. "The determination of rate constants using microelectrodes." Deakin University. School of Science, 1992. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20050728.090033.
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An understanding of the rate and the mechanism of reaction is of fundamental importance in the many facets of chemistry. Electrochemical systems are further complicated by the heterogeneous boundary, between the solution and the electrode, that the electron passes through before any electrochemical reaction can take place.
This thesis concerns the development of methods for analysing electrode kinetics. One part involves the further development of the Global Analysis procedure to include electrodes with a spherical geometry which are traditionally the most popular form of electrodes. Simulated data is analysed to ascertain the accuracy of the procedure and then the known artifacts of uncompensated solution resistance and charging current are added to the simulated data so that the effects can be observed. The experimental analysis of 2-methyl-2-nitropropane is undertaken and comparisons are made with the Marcus-Hush electrochemical theories concerning electrode kinetics.
A related section explores procedures for the kinetic analysis of steady state voltammetric data obtained at microdisc electrodes. A method is proposed under the name of Normalised Steady State Voltammetry and is tested using data obtained from a Fast Quasi-Explicit Finite Difference simulation of diffusion to a microdisc electrode.
In a second area of work using microelectrodes, the electrochemical behaviour of compounds of the general formula M(CO)3(η3 - P2P1) where M is either Cr, Mo or W and P2P' is bis(2-diphenylphosphinoethyl)phenylphosphine) is elucidated. The development of instrumentation and mathematical procedures relevant to the measurement and quantitation of these systems is also investigated. The tungsten compound represents the first examples where the 17-electronfac+ and mer+ isomers are of comparable stability.
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Saw, Yoo-Sok. "Nonlinear rate control techniques for constant bit rate MPEG video coders." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/1381.
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Digital visual communication has been increasingly adopted as an efficient new medium in a variety of different fields; multi-media computers, digital televisions, telecommunications, etc. Exchange of visual information between remote sites requires that digital video is encoded by compressing the amount of data and transmitting it through specified network connections. The compression and transmission of digital video is an amalgamation of statistical data coding processes, which aims at efficient exchange of visual information without technical barriers due to different standards, services, media, etc. It is associated with a series of different disciplines of digital signal processing, each of which can be applied independently. It includes a few different technical principles; distortionrate theory, prediction techniques and control theory. The MPEG (Moving Picture Experts Group) video compression standard is based on this paradigm, thus, it contains a variety of different coding parameters which may result in different performance depending on their values. It specifies the bit stream syntax and the decoding process as its normative parts. The encoder details remain nonnormative and are configured by a specific design. This means that the MPEG video encoder has a great deal of flexibility in the aspects of performance and implementation. This thesis deals with control techniques for the data rate of compressed video, which determine the encoding efficiency and video quality. The video rate control is achieved by adjusting quantisation step size depending on the occupancy of a transmission buffer memory which stores the compressed video data for a specific period of time. Conventional video rate control techniques have generally been based either on linear predictive or on control theoretic models. However, this thesis takes a different view on digital video and MPEG video coding, and focuses on the non-stationary and nonlinear nature of realistic moving pictures. Furthermore, considering the MPEG encoding structure involved in the different disciplines, A series of improvements for video rate control are proposed, each of which enhances the performance of the MPEG encoder. A nonlinear quantisation control technique is investigated, which controls the buffer occupancy with the quantiser using a series of nonlinear functions. Linear and nonlinear feed-forward networks are also employed to control the quantiser. The linear combiner is used as a linear estimator and a radial basis function network as a nonlinear one. Finally, fuzzy rulebased control is applied to exploit the advantages of the nonlinear control technique which is able to provide linguistic judgement in the control mechanism. All these techniques are employed according to two global approaches (feedforward and feedback) applied to the rate control. The performance evaluation is carried out in terms of controllability over bit rate variation and video quality, by conducting a series of simulations.
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Howell, Leonard L. "An experimental analysis of rate constancy." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/29865.
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Bensaci, Abderrahmane. "Etude par RMN du sélénium 77 et du tellure 125 de la cinétique d'échange de dichalcogénures aromatiques." Rouen, 1987. http://www.theses.fr/1987ROUES008.
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Bijlsma, Sabina. "Estimating rate constants of chemical reactions using spectroscopy." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/81947.
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SUPO, KATHIA CECILIA LOPEZ. "DEVELOPMENT OF A CONSTANT RATE OF FLOW FIELD PERMEAMETER." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=13449@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
presente dissertação descreve o desenvolvimento de um equipamento destinado a determinar a condutividade hidráulica de meios porosos saturados in situ. O permeâmetro consiste em uma sonda que emprega o método da vazão constante. Após sua inserção pelo modo de cravação. Uma bomba de seringa instalada na superfície do terreno é utilizada para aplicar uma vazão constante enquanto que a carga hidráulica induzida no meio é medida através de um transdutor de pressão piezoresistivo instalado no corpo da sonda. O equipamento permite o escoamento das linhas de drenagem e de medição de carga hidráulica a partir da superfície possibilitando a saturação do meio poroso após a cravação da sonda bem como minimiza as incertezas associadas à medição de pressão. Esta última é alcançada através de um transdutor diferencial de pressão com uma faixa de trabalho de 10kPa que possibilita medições de poropressões bem próximas a zona de injeção. Esta característica permite a realização de ensaios num tempo curto e minimiza o problema de compatibilidade de fluidos decorrente do processo de injeção.
This thesis describes a piece of equipment developed to determine the hydraulic conductivity of saturated porous media. The permeameter consists of a pushed in probe and employs the constant flow rate method. A syringe pump installed on the surface is used to develop a constant rate of flow whereas a piezoelectric transducer installed in the probes body measures the induced change in hydraulic head. The great innovation in this device consists on its ability of saturating all of its drainage lines allowing the media to be saturated and minimizing the errors of pressure measurements. Pressure measurement is carried out using a 10kPa differential pressure transducer that enables porepressure to be measured close to the injection zone. This characteristic enables shorter tests to be carried out and minimize problems associated to fluid compability
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Lee, Yew Choong Patrick 1975. "Numerical modeling of constant rate of strain consolidation tests." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29564.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Includes bibliographical references (leaves 95-96).
Constant Rate of Strain Consolidation Testing (CRSC) is an effective testing method to determine cohesive soil properties including stress history, compressibility, hydraulic conductivity and coefficient of consolidation. However, testing at varying strain rates have resulted in inconsistent results with respect to expected soil behavior. This theoretical study develops at numerical model to simulate the important details of a CRSC test using a finite difference approach in a spreadsheet in Microsoft Excel. The model provides a tool which can be used to study the test interpolation errors. The model based on void ratio versus log of effective vertical stress and versus log of hydraulic conductivity relationship of soil and includes the pore pressure compressibility of base measuring system. Parametric studies are preformed on Resedimented Boston Blue Clay normally consolidated behavior to investigate the effects of apparatus compressibility and strain rate. Finally, the predicted base pore pressure from the model simulation are used with the conventional interpretation equations to quantify the errors in soil parameters due to apparatus compressibility. It was found that bottom drainage of the specimen into the measuring system in a pore pressure distribution such that the base excess pore water pressure is not equal to the maximum excess pore water pressure. The magnitude of this difference increases with strain rate and neutral plane location. When using the conventional interpretation, this causes a shift in the compression curve to higher effective vertical stress. The error is small when the pore water pressure ratio is less than 5%. The error in hydraulic conductivity is much more significant and causes an overestimate of the hydraulic conductivity. This research forms the basis for which future experimental validation, normally consolidated to overly consolidated and steady state to transient state analysis. It can form the basis of new theories for the interpretation of constant rate of strain consolidation tests.
by Yew Choong Patrick Lee.
M.Eng.
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Tao, Jianping. "PULSE SHAPED CONSTANT ENVELOPE 8-PSK MODULATION STUDY." International Foundation for Telemetering, 1997. http://hdl.handle.net/10150/609753.
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International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, NevadaThe most bandwidth-efficient communication methods are imperative to cope with the congested frequency bands. Pulse Shaping methods have excellent effects on narrowing bandwidth and increasing band utilization. The position of the baseband filters for the pulse shaping is crucial. Filters after the modulator will have non-constant envelope and before the modulator will have constant envelope. These two types have different effects on narrowing the bandwidth and producing bit errors. The constant envelope 8 PSK is used throughout the simulations and is compared with the non-constant envelope results. This work provides simulation results of spectrum analysis and measure of bit errors produced by pulse shaping in an AWGN channel.
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McIntyre, Dennis O. "The effect of temperature on uptake rate constants, depuration rate constants, and bioconcentration factors (BCF) for six organochlorines in the aquatic insect, Chironomus riparius /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487596807823978.
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Hariharakumar, Pradeep. "Constant displacement rate experiments and constitutive modeling of asphalt mixtures." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3066.
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The focus of this dissertation is on constant displacment rate experiments on asphalt concrete and on developing continuum models in a general thermo-mechanical setting which will corroborate with the experimental results. Modeling asphalt concrete and predicting its response is of great importance to the pavement industry. More than 90 percent of the US Highways uses asphalt concrete as a pavement material.
Asphalt concrete exhibits nonlinear response even at small strains and the response of asphalt concrete to different types of loading is quite different. The properties of asphalt concrete are highly influenced by the type and amount of the aggregates and the asphalt used. The internal structure of asphalt concrete keeps on evolving during the loading process. This is due to the influence of different kinds of activities at the microlevel and also due to the interaction with the environment. The properties of asphalt concrete depend on its internal structure. Hence we need to take the evolution of the internal structure in modeling the response of asphalt concrete.
Experiments were carried out at different confinement pressures and displacement rates on cylindrical samples of asphalt concrete. Two different aggregates were used to make the sample -limestone and granite. The samples were tested at a constant displacement rate at a given confinement pressure. The force required to maintain this constant displacement rate is measured and recorded.
The frame-work has been developed using the idea of multiple natural configurations that was introduced recently to study a variety of non-linear dissipative response of materials. By specifying the forms of the stored energy and rate of dissipation function of the material, specific models were developed using this frame work. In this work both a compressible and an incompressible model were developed by choosing appropriate forms of stored energy and rate of dissipation function. Finally the veracity of the models were tested by corroborating with the experimental results.
It is anticipated that the present work will aid in the development of better constitutive equations which in turn will accurately model asphalt concrete in laboratory and in field.
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González, Jorge H. (Jorge Hugo) 1971. "Experimental and theoretical investigation of constant rate of strain consolidation." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8985.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references (leaves 212-216).
The Constant Rate of Strain (CRS) test provides an efficient and a relatively rapid method to determine properties (stress history, compressibility, hydraulic conductivity, and rate of consolidation) of a cohesive soil and possess many advantages over the incremental oedometer test. Ease of operation and the ability to take frequent readings provides tremendous labor savings and a better definition of the compression curve. However, the test has some disadvantages including, pore pressure measurement errors, initial transient conditions, and strain rate dependent soil behavior. There is also no set standard for the method of analysis to be used for interpretation of the CRS data. This experimental and theoretical study evaluates parameters that affect CRS test results, including strain rate sensitivity, testing device effects, and different methods used to interpret the data. An extensive program was conducted on Resedimented Boston Blue Clay (RBBC) and Resedimented Vicksburg Buckshot Clay (RVBC) to study the behavior during constant rate of strain consolidation. Strain rate sensitivity was measured using the Wissa Constant rate of strain device. Two special CRS tests were performed to evaluate the pore pressure measuring system and to. assess transient conditions. Two analysis methods proposed by Wissa et al. (1971) were scrutinized using a numerical simulation on a model soil. The stiffness of the pore pressure system relative to the soil stiffness is extremely important in tests with high ... Both soils were found to be strain rate sensitive. The softer RVBC had little sensitivity in compression and c, behavior. However, the k, decreased with increasing hydraulic gradient. Stiffer RBBC had a high sensitivity in compression and cv behavior. kv was insensitive to gradient but this observation is believed to be an error caused by the system stiffness. The findings support the use of either the linear or nonlinear theory provided the ... is kept below 0.15. The system stiffness, relative to the soil stiffness, is very important and negatively impacts results as the ... increases. The transient duration is well predicted by Wissa's F3 = 0.4 limit. Based on numerical simulation, it was shown that the established equations to compute k, and c, should be modified to account for large deformations.
by Jorge H. Gonzalez.
S.M.
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Nakamura, Hisao. "Quantum Dynamics Study on State Resolved Rate Constants in Unimolecular Reactions." 京都大学 (Kyoto University), 2000. http://hdl.handle.net/2433/181456.
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McCoy, Tammy Michelle. "Extension of the master sintering curve for constant heating rate modeling." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22532.
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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Joe K. Cochran; Committee Co-Chair: Dr. Thomas H. Sanders; Committee Member: Dr. John Elton; Committee Member: Dr. Meilin Liu; Committee Member: Dr. Robert F. Speyer.
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Berutti, Neto Renato. "Investiga??o Te?rica de Rea??es Unimoleculares da Formamida em Fase Gasosa." Universidade Federal Rural do Rio de Janeiro, 2012. https://tede.ufrrj.br/jspui/handle/jspui/2221.
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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior, CAPES, Brasil.
This work has been performed at the Laboratory of Chemical Kinetics, located in the Chemistry Department of Universidade Federal Rural do Rio de Janeiro, for the study of unimolecular reactions of formamide in gas phase and on the ground state: (1) CHONH2? CO + NH3 (2) CHONH2? H2 + HNCO and (3) CHONH2? HCO + NH2. Theoretical calculations including geometry optimizations and frequencies, have been performed at CASSCF level, with corrections at MRMP2 level for the electronic energy. The cc-pVDZ, cc and cc-pVTZ basis sets as well as the aug-cc-pVDZ have been used for comparative purposes. The unimolecular reactions were differently treated, depending on the specific topology of the potential energy surface. For the decompositions, corresponding saddle points have been located and the lowest energy paths have been calculated with the intrinsic reaction coordinate (IRC) method. The dissociation reaction has been described in terms of a scanning on the potential curve considering partial geometry optimizations of the fragments NH2 and HCO, keeping the CN distances frozen, those assumed as the internal reaction coordinate. Ab initio calculations were performed with the package GAMESS. The results show that the best description of the molecule has been obtained at CAS(10,9)/CCT level, yielding minimum deviations for the calculated molecular properties in relation to the experimental data available in the literature. The critical energies for the reactions of the decomposition have been determined, being (1): 77.60 kcal / mol and (2): 73.56 kcal / mol, both at level MRMP2/CAS(10,9)/CCT. For these results, it has been observed that the corrections MRMP2 are very important, bringing data calculated values very close to the literature values. From the analysis of the reaction pathways, it can be inferred that the dynamics of decomposition CHONH2 ? CO + NH3 is initiated by the torsional movement along the axis molecular by slightly rotating the fragment HCO in relation to the NH2, while the distance CN extends and the HC distance increases, with decreasing of HCN angle; the hydrogen atom bonds to the nitrogen atom and, with progressive increase of the distance CN, the fragments NH3 and CO are formed, achieving relaxed geometries. The decomposition CHONH2? HNCO + H2, by its turn, is initiated by increasing the distance HC at the HCO fragment, and further hydrogen abstraction of the atom at the NH2 fragment to form H2, which progressively separates from the HNCO, after the saddle point, generating the two products of this reaction. Dissociation is interpreted as the stretching of the CN bond, which promotes the separation of the NH2 and HCO fragments, whose geometries are relaxed along the curve of potential. The dissociation limit, determined at level MRMP2/CAS(10,9)/CCT is 91.52 kcal/mol. The canonical variational constant were calculated in the range of 300 - 2000K, being the values, in s-1, obtained at 1600K: (1) k = 5.62 x 103, (2) k = 1.07 x 103 and (3) k = 3.45. It follows that the channel (1) is privileged at a temperature of 1600K, and the decompositions are faster than the dissociation.
O presente trabalho foi realizado no Laborat?rio de Cin?tica, situado no Departamento de Qu?mica da Universidade Federal Rural do Rio de Janeiro, visando o estudo das Rea??es Unimoleculares da Formamida em Fase Gasosa e no Estado Fundamental: (1) CHONH2? CO + NH3, (2) CHONH2? HNCO + H2 e (3) CHONH2? HCO + NH2. C?lculos te?ricos, incluindo otimiza??es de geometria e frequ?ncias, foram procedidos em n?vel CASSCF com corre??es em n?vel MRMP2 para a energia eletr?nica. Bases cc-pVDZ e cc-pVTZ, assim como aug-ccpVDZ foram utilizados para fins comparativos. As rea??es unimoleculares foram tratadas diferentemente, dependendo da topologia espec?fica da superf?cie de energia potencial. Para as decomposi??es, pontos de sela correspondentes foram localizados e caminhos de menor energia foram calculados com o m?todo da coordenada de rea??o intr?nseca (IRC). A rea??o de dissocia??o foi descrita a partir do levantamento da curva de potencial considerando otimiza??es parciais de geometria dos fragmentos NH2 e HCO, mantendo fixas as dist?ncias CN, coordenada interna esta, assumida como a coordenada de rea??o. Os c?lculos ab initio foram realizados com o pacote GAMESS. Os resultados mostram que a melhor descri??o da mol?cula de formamida foi obtida em n?vel CAS(10,9)/CCT, promovendo menores desvios das propriedades moleculares calculadas em rela??o as experimentais dispon?veis na literatura. As energias cr?ticas para as rea??es de decomposi??o foram determinadas, sendo (1): 77,60kcal/mol e (2): 73,56 kcal/mol, ambas em n?vel MRMP2/CAS(10,9)/CCT. Para esses resultados, observou-se que as corre??es MRMP2 foram muito importantes, trazendo esses dados calculados a valores muito pr?ximos aos recomendados na literatura. A partir da an?lise dos caminhos de rea??o, pode-se inferir que a din?mica da decomposi??o CHONH2? CO + NH3 ? iniciada pelo movimento de tor??o ao longo do eixo molecular, fazendo girar levemente o fragmento NH2 em rela??o ao HCO, ao mesmo tempo em que o eixo CN se alonga e a dist?ncia HC aumenta, com a diminui??o do ?ngulo HCN, o ?tomo de hidrog?nio se liga ao nitrog?nio e, a partir do aumento progressivo da dist?ncia CN, os fragmentos NH3 e CO se formam, tendo lentamente suas geometrias relaxadas. J? a decomposi??o CHONH2? HNCO + H2 ? iniciada pelo aumento da dist?ncia HC no radical HCO e posterior abstra??o de um dos ?tomos de hidrog?nio do fragmento NH2 para a forma??o de H2, que se distancia progressivamente, ap?s a regi?o do ponto de sela, do fragmento HNCO, gerando os dois produtos desta rea??o. A dissocia??o, interpretada como o estiramento da liga??o CN, promove a separa??o dos fragmentos NH2 e HCO, cujas geometrias s?o otimizadas ao longo da curva de potencial. O limite de dissocia??o, calculado em n?vel MRMP2/CAS(10,9)/CCT foi determinado como 91,52 kcal/mol. As constantes variacionais can?nicas foram calculadas na faixa de 300 - 2000K com o programa kcvt, sendo os valores, em s-1, obtidos a 1600K: (1) k = 5,62 x 103, (2) k = 1,07 x 103 e (3) k = 3,45. Conclui-se que o canal (1) ? privilegiado na temperatura de 1600K, e que as decomposi??es s?o mais r?pidas que a dissocia??o.
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Turnidge, Martin Laurence. "Vibrational energy transfer at low temperatures and the use of infrared laser excitation for trace detection." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337427.
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Li, Vincent Yiu Fai. "An artificial intelligence approach to the processing of radar return signals for target detection." Thesis, University of Plymouth, 1999. http://hdl.handle.net/10026.1/2814.
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Most of the operating vessel traffic management systems experience problems, such as track loss and track swap, which may cause confusion to the traffic regulators and lead to potential hazards in the harbour operation. The reason is mainly due to the limited adaptive capabilities of the algorithms used in the detection process. The decision on whether a target is present is usually based on the magnitude of the returning echoes. Such a method has a low efficiency in discriminating between the target and clutter, especially when the signal to noise ratio is low. The performance of radar target detection depends on the features, which can be used to discriminate between clutter and targets. To have a significant improvement in the detection of weak targets, more obvious discriminating features must be identified and extracted. This research investigates conventional Constant False Alarm Rate (CFAR) algorithms and introduces the approach of applying ar1ificial intelligence methods to the target detection problems. Previous research has been unde11aken to improve the detection capability of the radar system in the heavy clutter environment and many new CFAR algorithms, which are based on amplitude information only, have been developed. This research studies these algorithms and proposes that it is feasible to design and develop an advanced target detection system that is capable of discriminating targets from clutters by learning the .different features extracted from radar returns. The approach adopted for this further work into target detection was the use of neural networks. Results presented show that such a network is able to learn particular features of specific radar return signals, e.g. rain clutter, sea clutter, target, and to decide if a target is present in a finite window of data. The work includes a study of the characteristics of radar signals and identification of the features that can be used in the process of effective detection. The use of a general purpose marine radar has allowed the collection of live signals from the Plymouth harbour for analysis, training and validation. The approach of using data from the real environment has enabled the developed detection system to be exposed to real clutter conditions that cannot be obtained when using simulated data. The performance of the neural network detection system is evaluated with further recorded data and the results obtained are compared with the conventional CFAR algorithms. It is shown that the neural system can learn the features of specific radar signals and provide a superior performance in detecting targets from clutters. Areas for further research and development arc presented; these include the use of a sophisticated recording system, high speed processors and the potential for target classification.
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Jönsson, Daniel. "Evaluation of Rate Constants from Protein-Ligand Interactions with Weak Affinity Chromatography." Thesis, Linnéuniversitetet, Institutionen för naturvetenskap, NV, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-19974.
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The paradigm of drug discovery have been to find the strongest possible binder to the target by high-throughput screening (HTS) but high affinity interactions are related to low kinetic off rates and thus result in severe side-effects and non-approved drugs. Lead molecules working in a transient manner (KD > µM) will allow for rapid off rates and possibly less side-effects. In this study the peak profile method applied to weak affinity chromatography (WAC) was evaluated as a simple way to provide the kinetics of the interaction and thereby allowing for high-throughput determinations. In the peak profile formula all band-broadening effects except the stationary mass transfer is subtracted which simplifies the calculations for the kinetics of the interaction tremendously. The technique was evaluated by screening of 3 different benzamidines at 3 linear flow-rates using zonal chromatography and human α-thrombin as immobilized target protein. The kinetics of the interaction could unfortunately not be determined. This was possibly due to the flow-rates not being high enough as indicated by a low critical ratio (η < 1). Higher flow-rates would increase the contribution to band-broadening due to kinetic effects but would also require more precise estimation of peak variance.
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Bird, Nicholas James. "Use of the terminal rate constant in the assessment of glomerular filtration rate by clearance of injected tracers." Thesis, University of Surrey, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436077.
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Boyd, Laura E. "Heterogeneous electron transfer rate constants of ferrocene/ ferrocenium in room-temperature ionic liquids /." Full text available from ProQuest UM Digital Dissertations, 2009. http://0-proquest.umi.com.umiss.lib.olemiss.edu/pqdweb?index=0&did=1913291371&SrchMode=1&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1278437152&clientId=22256.
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Short, Hayden B. "Chemically Accurate Calculations of Rate Constants of Spin Trap-Hydroxyl Radical Addition Reactions." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/honors/252.
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The DMPO type spin trap 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) and the exceptionally similar spin trap 2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-l-oxide (EMPO) are widely studied in computational and theoretical works. This particular study examines the addition reactions that both these molecules undergo with the carcinogenic hydroxyl radical. This work used a relatively new approximation method, called the correlation consistent composite approach or ccCA, for carrying out quantum mechanical calculations to give the free energies of the products and reactants of the reactions. The free energies are to be used to extrapolate the rate constants of the reactions from the Arrhenius equation. Though both the spin traps studied have been widely examined and assessed in both theoretical and experimental work, accurately calculated rate constants have not been previously obtained using computational methods. The results obtained here will help to assess the efficiency and the accuracy of the ccCA method, as well as lead to the design of better, more novel spin traps.
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Lai, Yeh-Hung. "The constrained blister - a nearly constant strain energy release rate test for adhesives." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/44077.
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This study developed and analyzed a modification of the blister test permitting nearly constant strain energy release rate testing of adhesive bonds. The work consisted of three parts; (1) development of the testing technique to evaluate strain energy release rate and to record the time dependent nature of the fracture process, (2) numerical analysis of the constrained blister test to determine the applicability of an approximate solution for several materials, and (3) development of an. analytical technique to evaluate the strain energy release rate for relatively stiff specimens.
Master of Science
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Yandek, Lindsay E. "MULTIPLE SUBSTRATE KINETICS OF RIBONUCLEASE P: RELATIVE RATE CONSTANT DETERMINATION THROUGH INTERNAL COMPETITION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1371041699.
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Adams, Amy Lynn. "Laboratory evaluation of the constant rate of strain and constant head techniques for measurement of the hydraulic conductivity of fine grained soils." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66859.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 185-187).
This thesis evaluates the constant rate of strain and constant head techniques for measurement of the hydraulic conductivity of fine grained soils. A laboratory program compares hydraulic conductivity measurements made using both measurement techniques on a total of 12 specimens. Both resedimented and intact materials covering a wide range of plasticity are investigated. Specific material types include Boston Blue Clay, San Francisco Bay Mud, Maine Clay, Ugnu Clay and Kaolinite. Constant rate of strain (CRS) and constant head tests were conducted in a standard Trautwein CRS device modified to allow control of the base pore pressure for constant head testing. A flexible wall permeameter device was used to perform constant head hydraulic conductivity testing on two specimens; this allowed for comparison with the constant head measurements made in the CRS device. A bottom seating error was found in the CRS device. Bottom seating error occurs during set up when the top of the base porous stone is not flush with the bottom of the rigid specimen ring, causing a gap to form between the specimen and the porous stone. A bottom seating error translates into a strain error, which affects both the measured CRS compression and hydraulic conductivity results. Bottom seating error can be avoided using a modified set up procedure. Void ratio errors are sometimes noted between the void ratio measured in the CRS device and that measured upon removal from the CRS device. These errors are likely resultant from specimen swelling following load removal. Based on comparison to the results of an interlaboratory study into the reproducibility of the saturated hydraulic conductivity measured in a flexible wall permeameter, the CRS and constant head techniques were found to measure the same hydraulic conductivity. This conclusion is independent of specimen origin, i.e. resedimented or intact. The CRS and constant head techniques measure the same average hydraulic conductivity even when non uniformities are present, provided the non uniformities are continuous and oriented perpendicular to the axial loading direction.
by Amy Lynn Adams.
S.M.
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Minakata, Daisuke. "Development of aqueous phase hydroxyl radical reaction rate constants predictors for advanced oxidation processes." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37127.
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Emerging contaminants are defined as synthetic or naturally occurring chemicals or microorganisms that are not currently regulated but have the potential to enter the environment and cause adverse ecological and/or human health effects. With recent development in analytical techniques, emerging contaminants have been detected in wastewater, source water, and finished drinking water. These environmental occurrence data have raised public concern about the fate and ecological impacts of such compounds. Concerns regarding emerging contaminants and the many chemicals that are in use or production necessitate a task to assess their potential health effects and removal efficiency during water treatment.
Advanced oxidation processes (AOPs) are attractive and promising technologies for emerging contaminant control due to its capability of mineralizing organic compound via reactions with highly active hydroxyl radicals. However, the nonselective reactivity of hydroxyl radicals and the radical chain reactions make AOPs mechanistically complex processes. In addition, the diversity and complexity of the structure of a large number of emerging contaminants make it difficult and expensive to study the degradation pathways of each contaminant and the fate of the intermediates and byproducts. The intermediates and byproducts that are produced may pose potential effects to human and aquatic ecosystems. Consequently, there is a need to develop first-principle based mechanistic models that can enumerate reaction pathway, calculate concentrations of the byproducts, and estimate their human effects for both water treatment and reuse practices.
This dissertation develops methods to predict reaction rate constants for elementary reactions that are identified by a previously developed computer-based reaction pathway generator. Many intermediates and byproducts that are experimentally identified for HO* induced reactions with emerging contaminants include common lower molecular weight organic compounds on the basis of several carbons. These lower carbon intermediates and byproducts also react with HO* at relatively smaller reaction rate constants (i.e., k < 109 M-1s-1) and may significantly affect overall performance of AOPs. In addition, the structures of emerging contaminants with various functional groups are too complicated to model. As a consequence, the rate constant predictors are established based on the conventional organic compounds as an initial approch.
A group contribution method (GCM) predicts the aqueous phase hydroxyl radical reaction rate constants for compounds with a wide range of functional groups. The GCM is a first comprehensive tool to predict aqueous phase hydroxyl radical reaction rate constants for reactions that include hydrogen-atom abstraction from a C-H bond and/or a O-H bond by hydroxyl radical, hydroxyl radical addition to a C=C unsaturated bond in alkenes and aromatic compounds, and hydroxyl radical interaction with sulfur-, nitrogen-, or phosphorus-atom-containing compounds. The GCM shows predictability; factor of difference of 2 from literature-reported experimental values. The GCM successfully predicts the hydroxyl radical reaction rate constants for a limited number of emerging contaminants.
Linear free energy relationships (LFERs) bridge a kinetic property with a thermochemical property. The LFERs is a new proof-of-concept approach for Ab initio reaction rate constants predictors. The kinetic property represents literature-reported and our experimentally obtained hydroxyl radical reaction rate constants for neutral and ionized compounds. The thermochemical property represents quantum mechanically calculated aqueous phase free energy of activation. Various Ab initio quantum mechanical methods and solvation models are explored to calculate the aqueous phase free energy of activation of reactantas and transition states. The quantum mechanically calculcated aqueous phase free energies of activation are within the acceptable range when compared to those that are obtained from the experiments. These approaches may be applied to other reaction mechanisms to establish a library of rate constant predictions for the mechanistic modeling of AOPs. The predicted kinetic information enables one to identify important pathways of AOP mechanisms that are initiated by hydroxyl radical, and can be used to calculate concentration profiles of parent compounds, intermediates and byproducts. The mechanistic model guides the design of experiments that are used to examine the reaction mechanisms of important intermediates and byproducts and the application of AOPs to real fields.
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Buras, Zachary J. (Zachary James). "Measuring rate constants and product branching for reactions relevant to combustion and atmospheric chemistry." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/117862.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages [383]-406).
Over the last century there have been countless experimental measurements of the overall reaction kinetics of gas-phase radicals, often with the aid of lasers. In more recent decades, ab initio predictions of product branching using quantum chemical calculations combined with modem rate theories have become common. However, there are few experimental measurements against which to validate predicted product branching, even for an important reaction system such as hydroxyl radical addition to acetylene that is critical to oxidation chemistry both in the atmosphere and in combustion. As a result, many of the kinetic parameters that appear in commonly used combustion mechanisms are based purely on predictions. The few experiments that do attempt to quantify product branching generally fall into two categories, each with unique advantages/disadvantages: crossed molecular beams (CMB) that simulate single collision conditions, or end-product analysis of a complex, thermalized process, such as pyrolysis. Laser flash photolysis (LFP) with molecular beam mass spectrometry (MBMS) offers a compromise between CMB and end-product experiments: the reaction conditions are thermalized but still simple enough that primary products can be quantified with confidence. This thesis describes a unique apparatus, and the improvements made to it, that combines LFP and MBMS for primary product branching quantification, as well as multiple-pass laser absorbance spectrometry (LAS) for accurate measurements of overall kinetics. The full capability of this LFP/MBMS/LAS apparatus is demonstrated for the chemically interesting phenyl radical + propene reaction system, which has been implicated as a potential source of second aromatic ring formation under combustion conditions. Overall kinetic measurements are also reported in this work either for systems that involve a newly discovered reactive species (various cycloaddition reactions of the simplest Criegee Intermediate formed in atmospheric ozonolysis) or that was disputed in the literature (vinyl radical + 1,3-butadiene, which has been implicated as a potential source of benzene in combustion). Finally, this thesis shows how detailed chemical insights made either experimentally or theoretically can be translated into applications via the Reaction Mechanism Generator (R4G). The application discussed is natural gas high temperature pyrolysis for the production of C2 commodity chemicals.
by Zachary J. Buras.
Ph. D.
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Casey, Lee S. "Kinetic rate constants for the formation of trihalomethanes in chlorinated ammonia containing ground water." FIU Digital Commons, 1985. http://digitalcommons.fiu.edu/etd/2026.
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It is well established that trihalomethanes, in drinking water are byproducts of chlorine disinfection. A method to predict the distribution and concentration of trihalornethanes is important because of health risks associated with chronic exposure to these compounds. A literature review has provided information on the chemistry of water chlorination and a data base developed in the laboratory has provided data on trihalomethane formation under various conditions. These data were used to generate rate constants for the formation of trihalomethanes.
Trihalornethane formation kinetics appeared to be influenced primarily by the presence of ammonia. The influence of pH is not as profound as indicated in literature. The rate of formation is low at and before breakpoint, whereas it increases after breakpoint.
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Clarke, Jo Aine. "A Constant Struggle: Renegotiating Identity in the Aftermath of Rape." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002371.
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Saghaian, Nejad Esfahani Sayed Mahdi. "STATISTICAL MODELS FOR CONSTANT FALSE-ALARM RATE THRESHOLD ESTIMATION IN SOUND SOURCE DETECTION SYSTEMS." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/46.
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Constant False Alarm Rate (CFAR) Processors are important for applications where thousands of detection tests are made per second, such as in radar. This thesis introduces a new method for CFAR threshold estimation that is particularly applicable to sound source detection with distributed microphone systems. The novel CFAR Processor exploits the near symmetry about 0 for the acoustic pixel values created by steered-response coherent power in conjunction with a partial whitening preprocessor to estimate thresholds for positive values, which represent potential targets.
To remove the low frequency components responsible for degrading CFAR performance, fixed and adaptive high-pass filters are applied. A relation is proposed and it tested the minimum high-pass cut-off frequency and the microphone geometry.
Experimental results for linear, perimeter and planar arrays illustrate that for desired false alarm (FA) probabilities ranging from 10-1 and 10-6, a good CFAR performance can be achieved by modeling the coherent power with Chi-square and Weibull distributions and the ratio of desired over experimental FA probabilities can be limited within an order of magnitude.
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Karaca, Ümit Özen Serdar. "Constant False Alarm Rate (cfar) Detection Based Estimators With Applications to Sparse Wireless Channels/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/elektrikveelektronikmuh/T000586.pdf.
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Liang, Y., C. Zeng, J. J. Wang, M. W. Liu, Yeh T. C. Jim, and Y. Y. Zha. "Constant Gradient Erosion Apparatus for Appraisal of Piping Behavior in Upward Seepage Flow." AMER SOC TESTING MATERIALS, 2017. http://hdl.handle.net/10150/625214.
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Seepage direction is crucial for understanding the critical state and development of piping erosion. A stress-controlled apparatus was designed to investigate the piping behavior of cohesionless soil under upward flow condition. The components of the new apparatus included a loading chamber, a vertical and confining loading system, an upstream water supply device, a soil-water separating system, and a water collecting system. The loading chamber provides space for a soil specimen setting and loading. The combination of a vertical and a confining loading system was designed to apply complex stresses to a soil specimen. Under the stresses, the specimen was then eroded by the gradually increasing hydraulic head supplied by the water supply system. The eroded particle and spilling water were collected and detected by the soil-water separating system and the water collecting system. A series of experiments were carried out using the new apparatus. Results demonstrated the repeatability experiments and usefulness of the apparatus. The new apparatus allowed us to investigate the piping behavior under different stress states and hydraulic gradients. With this new apparatus and experiments, we found that lower and high critical hydraulic gradients (CHGs) should be included as the criteria of piping development based on the relationship between the hydraulic gradient and the seepage response. In addition, the stress state on the CHG and the particle erosion rate played important roles in the piping development. The outer pressure on the specimen can retard the development of erosion. In contrast, the hydraulic gradient was found to be positively correlated to the erosion rate. Results also indicated that a specimen would collapse once the amount of eroded small particles exceeds the critical value of 46.5 % of the soil.
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Pradie, Noriberto Araujo. "Mecanismo da decomposição e reações com radicais em acetatos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-18082011-104220/.
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Estudos do mecanismo de reações unimoleculares, das moléculas de acetato de metila e etila, induzidas por absorção multifotônica e de reações bimoleculares com os radicais OH e Cl, usando cálculos ab initio e de funcional de densidade foram realizados neste trabalho. A análise dos cálculos das barreiras de energia e das constantes de velocidade microcanônicas das reações unimoleculares com o formalismo da teoria RRKM, permitiu prever algumas reações cujos produtos não foram determinados experimentalmente. Além disso, semelhanças das geometrias e dos valores de energia de algumas estruturas entre diferentes superfícies de energia, analisadas com cálculos de IRC, permitiram a explicação da viabilidade de determinada via de reação em detrimento de outra. Em outro método, relatado por Forst(1), na determinação das constantes de velocidade variacionais, comparadas com a variação da energia de Gibbs, verificou-se constantes de velocidade microcanônicas menores e a localização dos estados de transição em comprimentos de ligação, também, menores. Nas reações com o radical OH e Cl, a via predominante de reação é o ataque aos hidrogênios do grupo ligado diretamente ao oxigênio da molécula, responsável pelo valor da constante final de mais de 93% nas reações com OH e 99% nas reações com Cl, a 298K, em concordância com os resultados experimentais, em detrimento do ataque ao grupo CH3 da porção carboxilato da molécula. Nas reações com OH, os valores de constante de velocidade calculados mais próximos dos valores experimentais foram obtidos a partir dos resultados com os funcionais mPW1B95-41, para o acetato de metila, e mPW1B95-44, para o acetato de etila, enquanto que nas reações com Cl foram obtidos com o os métodos CCSD(T)//B3LYP para o acetato de metila e CCSD(T)//MP2 para o acetato de etila. Os valores de constante de velocidade da reação com cloro são cerca de dez vezes maiores que aquelas para as reações com radicais OH. As reações com OH e Cl ocorrem em uma única etapa, sem estabilização do intermediário e sem efeito de tunelamento significante. Por sua vez, cálculos da constante de velocidade, pelo método da relação estrutura reatividade (SAR), sobreestimam a reatividade dos hidrogênios dos grupos CH3 na porção carboxilato, em ambos os acetatos, e na porção etóxido do acetato de etila. Este método falha ao descrever a participação de cada grupo na reação com Cl, pois prevê que a reação no grupo CH3 da porção alcóxido passa a ser predominante sobre a reação ao grupo CH2 nas reações do acetato de etila, oposto aos nossos cálculos onde a reação com o grupo CH2 é a predominante. Outra falha do método é na previsão de mesma reatividade para ambos os grupos CH3 no acetato de metila, pois por nossos cálculos a reação ocorre predominantemente no grupo CH3 na porção alcóxido da molécula.Computational studies on methyl and ethyl acetates molecules using ab initio and density functional calculations exploring the unimolecular mechanism, induced by multiphoton absorption, and the bimolecular reactions with OH and Cl radicals, have been performed in this work. Analysis of the calculated energy barriers and rate constants of unimolecular reactions with the RRKM microcanonical theory, predicts the occurrence of some reactions whose products were not determined experimentally. Furthermore, similarities on geometrical and energetic of some structures between different energy surfaces, analyzed with IRC calculations, allowed the explanation of the viability of a particular reaction pathway over another. Forst\'s method, used to determine variational rate constants, when compared with the variation of Gibbs energy, generates microcanonical rate constants with smaller values and location of transition states in smaller bond lengths. With OH and Cl, the predominant reaction route is the attack on the hydrogens of the group bonded directly to oxygen in the molecule, responsible for more than 93% of the final constant value in reactions with OH and 99% in reactions with Cl , at 298 K, in agreement with the experimental results, while the attack to the CH3 group in the carboxylate portion of the molecule is the less likely to occur. In reactions with OH, the values of the rate constant calculated closer to the experimental values were obtained from the results with functional mPW1B95-41, for methyl acetate, and mPW1B95-44 for ethyl acetate, whereas in reactions with Cl, were obtained with the CCSD(T)//B3LYP method for the methyl acetate and the CCSD(T)//MP2 method for ethyl acetate. The rate constant for the reaction with chlorine are about ten times larger than those for reactions with OH radicals. Reactions with OH and Cl occur in a single step, without stabilization of the intermediary and without significant tunneling effect. The rate constant obtained by the structure-reactivity relationship (SAR) overestimates the reactivity of the hydrogens of the CH3 groups at the carboxylate portion, in both acetates, and at the ethoxide portion of ethyl acetate. This method fails to describe the participation of each group in the reaction with Cl, predicting that the reaction on the CH3 portion of the alkoxide becomes predominant over the reaction on the CH2 group of ethyl acetate, relative to our calculations where the reaction with the CH2 group is predominant. Another flaw by providing the same reactivity for both the CH3 in methyl acetate, is in disagreement with our calculations which indicate that the reaction occurs predominantly in the CH3 group at the alkoxide portion of the molecule.
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Pezacki, John Paul. "Rate constants and mechanisms for reactions of carbenes and cations from oxadiazolines and other precursors." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0028/NQ51008.pdf.
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Pezacki, John Paul. "Rate constants and mechanisms for reactions of carbenes and cations from oxadiazolines and other precursors /." *McMaster only, 1998.
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Betts, Nicholas B. "Laboratory studies of gas phase ion-neutral reaction rate constants relevant to the interstellar medium." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1439438.
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Holm, Daniélle. "Influence of strain rate in CRS tests : A laboratory study of three Swedish clays." Thesis, KTH, Jord- och bergmekanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192212.
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The Constant Rate of Strain (CRS) test is currently the most widely used method for determination of consolidation parameters in Sweden. These parameters are used to calculate the probable settlements and behavior of soils. With the Swedish standard strain rate, the duration of a single the test is about 24h, but a higher strain rate would allow for more tests to be performed in the same amount of time. For all clays in Sweden, the Swedish standard for the CRS test suggests a fixed rate of strain that is independent of soil properties, while the North American standard proposes a strain rate that generates a pore pressure ratio of 3-15%. Soil properties such as water content, liquid limit, sensitivity and shear strength vary greatly between different regions of Sweden. It would be beneficial if these properties could be used to find the ideal strain rate for the CRS test. Performing the tests at a higher strain rate, and thus performing more tests within a shorter amount of time, would save both time and money. In this report, 24 CRS tests are performed on three different clays with distinctive properties. Each clay is tested with three different strain rates: the Swedish standard rate of 0.680%/h, a higher rate of 3.00%/h and a lower rate of 0.154%/h. The results are evaluated according to both standards, and are compared and analyzed to determine whether there is any indication that the strain rate can be selected based on the soil properties. The results indicate that the selection of the strain rate is dependent on the soil properties. In addition, the majority of the tests can be conducted with higher strain rates than what is required by the Swedish standard and still manage to lie within the 3-15% limit of the pore pressure ratio, which is acceptable for the North American standard. However, the preconsolidation pressure does rise with increased strain rates, which can generate problems and erroneous results when calculating the settlements. A more extensive testing program with CRS tests and full-scale field tests must be carried out before any recommendation of a higher strain rate can be made.
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Karlsson, Mikael. "Determination of antibody affinity and kinetic binding constants in Gyrolab Bioaffy microfluidic CD." Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11616.
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Studies of binding reactions are of highest importance in a vast number of areas of biomedicine and biotechnology. A demand for fast and accurate small-volume measurements grows stronger, partly due to the development of therapeutic antibodies. In this report, a novel method for studies of binding reactions of antibodies is described. The use of a microfluidic platform shows promising results in determination of affinity binding constants.
Affinities between 1E-09 and 1E-11 M have been determined for four TSH antibodies. Reproducibility tests give a CV below 10%, using different Gyrolab instruments and microfluidic CD:s. The method carries the advantages of using solution-based measurements of unmodified molecules. Also an initial proof-of-concept for measurement of binding reaction rate constants shows further usage of the method. The kinetic association rate constant has been determined to 2E+06 M-1s-1 for one antibody. The possibility of using this method for screening of antibody libraries is also discussed.
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Chun, Geumju 1965. "Critical strain for dynamic recrystallization during the constant strain rate hot deformation of Nb steels." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81532.
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The presence of peak points in constant strain rate flow curves is generally considered to indicate the onset of dynamic recrystallization (DRX). However, not all materials display clear peaks when tested under these conditions. It has been suggested that DRX is initiated when the strain reaches a critical value epsilonc that is related to the peak strain epsilonp and that this critical strain can be detected from the inflection point in plots of the strain hardening rate theta against stress sigma, regardless of the presence or absence of peaks. This is of importance because many works regarding DRX have been carried out by physical simulation using laboratory torsion tests.However, one of the main problems in laboratory simulation is that the inflection point for DRX is not easily determined, particularly in microalloyed steels. This problem is rendered more difficult in torsion testing because of the strain gradient along the radius of the specimen. As an alternative, compression testing can provide more accurate data regarding the initiation of DRX.
In this work, the DRX behavior of three Nb microalloyed steels was investigated using compression testing. Continuous deformation by axisymmetric compression was employed in the temperature range 850 to 1050°C at strain rates of 0.01, 0.1 and 1/sec. Stress-strain curves were obtained and then the critical strains for initiation were calculated using a method based on the presence of an inflection point at the moment of initiation. The critical strain was observed to increase when the deformation temperature was decreased or when the strain rate was increased. No significant effect of the level of microalloying addition on the DRX behavior was detected within the range studied.
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Cai, Wei. "Discrete element modelling of constant strain rate and creep tests on a graded asphalt mixture." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/29249/.
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This thesis investigates the use of Discrete Element Modelling (DEM) to simulate the elastic and viscoelastic deformation behaviour of an asphalt mixture. A numerical specimen preparation procedure has been developed to produce specimens with an isotropic stress and correct volumetrics. Stone mastic asphalt has been chosen in this project because of its high content of coarse aggregate and binder-rich mortar. A range of uniaxial compression tests have been undertaken in the laboratory under various loading speeds and stresses. The axial stress, axial strain and radial strain were recorded during the tests. The peak stress is found to be as a power-law function of the strain rates for the asphaltic material. Elastic contact properties have been used to investigate the effect of particle number and location, loading speed, normal and shear contact stiffness. The Poisson's ratio was found to increase with the ratio of normal to shear contact stiffness but was independent of the stiffnesses. The Young's modulus was found to be dependent on both normal and shear stiffnesses, in agreement with previous work on idealised asphalt mixtures. The Burger's model was introduced to give time-dependent stiffness for the viscoelastic modelling. The Burger's model was implemented to give moment and torsional resistance as well as in direct tension and compression. To reduce the computational time in the creep simulations, the effect of scaling both viscosities in the Burger's model to simulate a shorter time, have been investigated. The effects of each parameter on the deformation of asphalt mixture were also investigated. The stress-strain response for the laboratory tests and the simulations were recorded. The results show good agreement when the bond strengths in the model are made to be a function of strain rate for both constant strain rate and creep conditions. Both normal and Weibull distributions have been used for the bond strengths between the aggregate particles. The constant strain rate tests results were proved to be independent of the bond strength variability and position of particles, while the creep tests results were dependent on the hand strength variability and position of particles. This is in good agreement with experimental tests: different specimens at the same stress level gave variability in the creep behaviour, at higher stress levels. Bond breakages were recorded during the simulations to investigate the micromechanical deformation behaviour of asphalt mixtures. It was found that a well-defined rupture at higher stress levels coincided with the maximum rate of bond breakage. The modified Burger's model has therefore proven to be a useful tool in modelling the moment and torsional resistance at particle contacts in an asphalt mixtures, in order to correctly predict observed behaviour.
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Wang, Xipeng. "CONSTANT FALSE ALARM RATE PERFORMANCE OF SOUND SOURCE DETECTION WITH TIME DELAY OF ARRIVAL ALGORITHM." UKnowledge, 2017. http://uknowledge.uky.edu/ece_etds/105.
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Time Delay of Arrival (TDOA) based algorithms and Steered Response Power (SRP) based algorithms are two most commonly used methods for sound source detection and localization. SRP is more robust under high reverberation and multi-target conditions, while TDOA is less computationally intensive. This thesis introduces a modified TDOA algorithm, TDOA delay table search (TDOA-DTS), that has more stable performance than the original TDOA, and requires only 4% of the SRP computation load for a 3-dimensional space of a typical room. A 2-step adaptive thresholding procedure based on a Weibull noise peak distributions for the cross-correlations and a binomial distribution for combing potential peaks over all microphone pairs for the final detection. The first threshold limits the potential target peaks in the microphone pair cross-correlations with a user-defined false-alarm (FA) rates. The initial false-positive peak rate can be set to a higher level than desired for the final FA target rate so that high accuracy is not required of the probability distribution model (where model errors do not impact FA rates as they work for threshold set deep into the tail of the curve). The final FA rate can be lowered to the actual desired value using an M out of N (MON) rule on significant correlation peaks from different microphone pairs associated is a point in the space of interest. The algorithm is tested with simulated and real recorded data to verify resulting FA rates are consistent with the user-defined rates down to 10-6.
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Quillon, Aurélia Leroux Caroline Piau Didier. "Prédiction markovienne in silico des régions constantes et variables des lentivirus." [s.l.] : [s.n.], 2006. http://hal.archives-ouvertes.fr/docs/00/12/41/42/PDF/these_BoissinQuillon.pdf.
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Dawson, Casey A. "Children's Use of Race in Drawing Inferences Based on Their Understanding of Race Constancy." TopSCHOLAR®, 2007. http://digitalcommons.wku.edu/theses/10.
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Children’s understanding of race constancy and their subsequent use of race as a means of drawing inductive inferences were investigated. Race constancy was determined by children’s tendency to say that people could change category membership by changing their outside appearance. A second phase of the study measured how many race-based inferences children made relative to other social categories such as age or sex. The results indicated that children who had a better understanding of race constancy were also more likely to use race as a means of drawing inductive inferences. These findings support a developmental progression of race constancy and give insight to the development of potential bias and stereotypes.
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Cochran, Kellie. "Prediction of the Degradation of Emerging Contaminants During Oxidative Treatment via Analysis of Reaction Rate Constants." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1890.
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Globally, water supplies are diminishing in quality while demand is continually increasing. The municipal water and wastewater sector has been paying increased attention to unregulated emerging organic contaminants. Advanced oxidation processes (AOPs), which produce hydroxyl radicles (•OH), have been developed and implemented to remove recalcitrant emerging contaminants left by conventional treatment processes. The current understanding of the removal efficacy of AOPs for emerging contaminants is limited. This study analyzes the ability of an AOP involving ozone and multi-walled carbon nanotubes (MWCNTs) in removing three specific emerging contaminants: caffeine, atrazine, and phenytoin, which were selected based on their persistence and ubiquity in the environment and their potential to serve as AOP efficacy indicator compounds. Reaction rate constants were determined from batch reactor data and compared to the degradation trends observed for the different compounds after exposure to treatment. During exposure to ozone alone, caffeine degraded quickly (KO3 = 334 ± 67 M-1 s-1), atrazine degraded slightly (KO3 = 8.3 ± 1.0 M-1 s-1), and phenytoin did not respond to the treatment. Atrazine and phenytoin were exposed to •OH in the AOP treatment process, and the contaminants displayed greater removal compared to ozone only. To simulate more realistic water systems, a mixture of caffeine and atrazine was subjected to ozone only and the AOP with ozone and CNTs. Competition for ozone and •OH resulted in lower atrazine degradation. This result reflects the expected degradation of these compounds based on their individually determined reaction rate constants. Atrazine behaved as expected when exposed to ozone and the AOP, and the reaction rate constants determined for atrazine reflect the observed degradation trend which qualifies atrazine as a potential indicator compound. Overall, this study demonstrates the ability of the AOP combining ozone and CNTs to degrade recalcitrant compounds, the potential for atrazine to serve as an indicator compound for AOPs, and the reliability of reaction rate constants to predict the degradation of contaminants in increasingly complex water systems.
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Alves, Tiago Vinicius. "Estudo teórico da reação do radical metila com nitrogênio atômico (4S): aspectos estruturais, energéticos, espectroscópicos e cinéticos." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/46/46132/tde-19052008-134755/.
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A busca de uma melhor compreensão dos ciclos químicos que ocorrem na atmosfera de Titan, um dos satélites naturais de Saturno, tem posto em relevância a importância de reações químicas envolvendo nitrogênio atômico e hidrocarbonetos, principalmente o radical metila. Além desta ênfase astroquìmica, essa reação tem também um papel importante no estudo da decomposição de metano em plasma pós-descarga de nitrogênio e no entendimento de processos de combustão. Neste trabalho, dando continuidade a estudos teóricos envolvendo reações de espécies atômicas com hidrocarbonetos realizados por este grupo e utilizando o estado da arte em termos de cálculos de estrutura eletrônica, realizou-se uma ampla investigação da superfície tripleto de energia potencial 3[H3, C, N] com ênfase nos aspectos estruturais, energéticos e espectroscópicos dos pontos estacionários e na cinética global da reação. Nesta superfície de energia potencial, foram caracterizados 7 pontos estacionários, sendo 3 estados de transição e 4 mínimos. No melhor nível de cálculo, CCSD(T)/CBS, o mínimo global corresponde à formação do radical metilnitreno, 71,01 kcal/mol mais estável do que o canal de entrada N(4S) + CH3 (2A2\"). Entretanto, via caminhos distintos, a reação prossegue formando H2CN + H como o principal produto, resultado esse que não confirma uma suposição anterior de que HCN seria o produto principal. No aspecto cinético, verificou-se que a etapa determinante da reação é regida pelo canal de entrada bimolecular, sem barreira, e que o valor para a constante de velocidade global, na melhor descrição deste trabalho, de 1,93 x 10-10 cm3 molécula?1 s-1, é bem superior à de estudo teórico anterior. Além da boa concordância com dados experimentais, nossos resultados também mostram um aumento da constante de velocidade com a temperatura, o que não foi previsto nesse estudo anterior.The search for a better understanding of chemical cycles in Titan´s atmosphere, one of Saturn´s largest natural satellite, has emphasized the importance of chemical reactions between atomic nitrogen and hydrocarbons, especially methyl radical. Besides this astrochemical relevance, this reaction also plays a key role in the study of methane decomposition in after-glow nitrogen plasma, and in combustion processes. In this work, as another step towards theoretical studies of reactions involving atomic species with hydrocarbons carried out by this group, and using state-of-the-art electronic structure calculations, a wide investigation of the triplet potential energy surface 3[H3, C, N] was made with emphasis on structural, energetic, and spectroscopic aspects of the stationary points, and on the global kinetic description of the reaction. In this potential energy surface, 7 stationary points were characterized: 3 transition states and 4 minima. In our best description, CCSD(T)/CBS, the global minimum corresponds to the formation of the methylnitrene radical, 71.01 kcal/mol more stable than the entrance channel N(4S) + CH3 (2A2\"). However, by different paths, the reaction proceeds leading to the formation of H2CN + H as the major product, a result that does not confirm a previous supposition that HCN would be the major product. Kinetically, we have shown that the rate determining step is the barrierless bimolecular collision of CH3 and N(4S), and that the global rate constant, in the best estimate of this work, 1.93 x 10-10 cm3 molecule-1 s-1, is well superior to that of a previous theoretical study. Besides the good agreement with the experimental data, our results also show an increase of the rate constant with the temperature, a result not predicted by that previous study.
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Fritsch, LeaAnn Thompson. "Effects of chronic suboptimal energy intake on constant-load exercise in young women." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-09182008-063227/.
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Dean, Valarie Nichole. "Time Constant Analysis of Initial 'Jump' in Firing Rate of Human Motor Units During Isometic Contraction." Thesis, The University of Arizona, 2010. http://hdl.handle.net/10150/146201.
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Ongoing research studying the underlying mechanism and prevalence of Persistent Inward Currents (PICs) has posed a challenge to the conventional view that the firing rate of a motor unit is proportional to the amount of synaptic input it receives. Near the time of human motor unit recruitment during isometric muscle contraction, a sudden steep rise in firing rate is observed, which is suggested to result from rapid triggering of PICs, an intrinsic property of motor neurons. In evaluating the time constants associated with these steep rises in firing rate across different contractile speeds, it has been found that the time course of the steep rise is dependent on the time course of muscle contraction. This evidence suggests that the mechanism underlying this steep rise in firing rate is not PIC-associated, but rather depends on an alternate, unknown mechanism.
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Phan, Anthony. "Development of a rate of injection bench and constant volume combustion chamber for diesel spray diagnostics." [Ames, Iowa : Iowa State University], 2009.
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Green, Dale. "A probabilistic approach to reaction coordinate and rate constant modeling applied to epoxide ring-opening reactions." Kansas State University, 2012. http://hdl.handle.net/2097/15085.
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Master of ScienceDepartment of Chemical Engineering
Keith Hohn
The study will utilize a probabilistic reaction modeling method for ring-opening reactions of epoxide. In particular, to elucidate the reaction mechanism by the methods presented, focus will be placed on the nucleophillic attack of ethylene oxide by ammonia and its anion. This focus was chosen because of the potential to gain significant advantage in computational intensity required to model the epoxy-amino macromolecular curing reactions and resulting thermochemical and physical properties of the cured resin. The method employed utilizes the combinatorial probability that 1. Two molecules will approach a transition state with sufficient energy to drive reaction 2. Any reaction will occur for a given penetration into the potential energy surface. The concept of a transition state is relaxed to allow a dynamic probability that any reaction will proceed given a position on the intrinsic reaction coordinate (IRC) rather than searching for a specific transition state of theoretical reaction probability. 3. The reaction that occurs yields a desired stable or semi-stable molecular complex This study will focus on identifying possible stable and semi-stable products and corresponding rate constants. The technique developed here is novel in that it provides an unsupervised method to identify all structures corresponding to minima on the potential energy surface. The technique provides a pragmatic and efficient approach to sample a molecular system for different reaction mechanisms and provides a relative energy requirement to achieve these mechanisms with no presupposition of the mechanism, product, or transition state. It is possible from this data to derive rate constants for a reacting system, however, the rate constant derived for the EO/NH2 molecular system yielded significantly understated reaction probabilities and therefore rate constants.
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Shao, Kejun. "Kinetic Study of the Reactions of Chlorine Atoms with Fluoromethane and Fluoromethane-d3 in the Gas Phase." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011808/.
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The kinetics of the gas-phase reactions of chlorine atoms with fluoromethane (CH3F) and fluoromethane-d3(CD3F) were tested experimentally. The relative rate method was applied by using CH4 as the reference compound for fluoromethane (CH3F) and CH4 and CH3F as the reference compound for fluoromethane-d3(CD3F). The rate constants for H-abstraction from CH3F and D-abstraction from CD3F were measured at room temperature and a total pressure of 920 Torr using Ar as a diluent. The rate constants are described by the expressions: kH= (3.50±0.52) x 10-13 cm3 molecule-1 s-1 and kD=(5.0±0.51) x 10-14 cm3 molecule-1 s-1. The kinetic isotope effect, equal to the ratio kH/kD, was found to be 7.0±1.2 at room temperature.
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Sherrell, Ian M. "Development of a Flotation Rate Equation from First Principles under Turbulent Flow Conditions." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29943.
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A flotation model has been proposed that is applicable in a turbulent environment. It is the first turbulent model that takes into account hydrodynamics of the flotation cell as well as all relevant surface forces (van der Waals, electrostatic, and hydrophobic) by use of the Extended DLVO theory. The model includes probabilities for attachment, detachment, and froth recovery as well as a collision frequency. A review of the effects fluids have on the flotation process has also been given. This includes collision frequencies, attachment and detachment energies, and how the energies of the turbulent system relate to them. Flotation experiments have been conducted to verify this model. Model predictions were comparable to experimental results with similar trends. Simulations were also run that show trends and values seen in industrial flotation systems. These simulations show the many uses of the model and how it can benefit the industries that use flotation.Ph. D.
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Jani, Parth K. "Experimental Investigation of Influence of Liquid Physicochemical Properties on Adiabatic Bubble Growth from Submerged Capillary Orifice under Constant Flow Rate Conditions." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1623169715636338.
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