Metathesis is a valuable reaction for the production of new alkenes. In the last 50 years, heterogeneous as well as homogeneous catalysts have been used for this reaction. In the homogeneous category are the very successful catalysts designed by the Grubbs group. The first generation Grubbs precatalyst (Gr1) bearing two phosphine ligands was followed after extensive studies by the more active second generation Grubbs precatalyst (Gr2). In Gr2, one of the phosphine ligands is replaced with an N-heterocyclic carbene. Grubbs type precatalysts bearing pyridynyl-alcoholato chelating ligands are pertinent to this study. Scheme 1: The synthesis of Grubbs type precatalysts bearing a pyridynyl-alcoholato ligand. In two previous studies, both supported by computational methods, Grubbs type precatalysts with N^O chelating ligands were synthesised. These investigations were motivated by the fact that chelating ligands bearing different donor atoms can display hemilability. The loosely bound donor atom can de-coordinate to make available a coordination site to an incoming substrate “on demand”, whilst occupying the site otherwise and hence preventing decomposition via open coordination sites. In the first investigation, the incorporation of an O,N-ligand with both R1 and R2 being phenyl groups into the Gr2 precatalyst, resulted in an increase in activity, selectivity and lifetime of the precatalyst in comparison to Gr2 in the metathesis reaction with 1- octene. In the second study, three synthesised complexes were found to be active for the metathesis of 1-octene. This computational study sought to better understand the structural differences and thermodynamic properties of these Grubbs type precatalysts with bidentate/hemilabile ligands. A large number of structures were constructed in Materials Studio by varying the R groups of the bidentate/hemilabile ligand attached to both the Gr1 and Gr2 catalysts. The majority of structures were Gr1-type complexes. For each ligand selected, a group of structures consisting of closed precatalyst, open precatalyst, and where applicable a precatalyst less PCy3, closed metallacycle, open metallacycle and where applicable a metallacycle less PCy3, was constructed and optimised using DMol3. Bond lengths, bond angles, HOMO and LUMO energies and Hirshveld charges of structures were compared with one another. PES scans were performed on the metallacycles of four groups. The purpose of the PES scans was to ascertain whether these bidentate ligands were hemilabile and to illuminate the preferred reaction mechanism for these types of precatalysts. The major finding of this study was that the possibility of an associative mechanism cannot be ruled out for some Gr2-type precatalysts with bidentate ligand. For some precatalysts hemilability is energetically expensive and possibly not viable. No evidence of a concerted mechanism was found. The dissociative mechanism was found to be the preferred mechanism for most of the structures that were subjected to PES scans. The HOMO-LUMO energies of a complex can be used, as a predictive tool, to assess the reactivity and stability of a complex, as well as its preference for substrates. / Thesis (MSc (Chemistry))--North-West University, Potchefstroom Campus, 2013.

Preventative interventions often demand that resources be consumed in the present in exchange for future benefits. Cost-effectiveness analysis is a tool to understand these trade-offs, and inform decision-making under resource constraints. Targeted testing and treatment (TTT) for latent tuberculosis infection (LTBI) consists in identifying people at high risk for LTBI for preventive treatment to decrease the risk of active tuberculosis disease (ATBD). The state of Tennessee began conducting TTT statewide in 2001. This study uses a decision tree to evaluate the cost and outcomes of TTT for LTBI in Tennessee, compared to passive ATBD case finding (PACF). Key probabilities were obtained from the Tennessee TTT program and the literature. Outcomes are measured in terms of Quality Adjusted Life Years (QALY). The cost-effectiveness threshold was $100,000/QALY saved. One-way sensitivity analyses around factors related to study design, the program’s environment, and program performance were conducted, as was probabilistic sensitivity analysis (PSA) which takes into account the uncertainty in multiple parameters simultaneously. The base case, with a 25-year analytic horizon and 3% discount rate, shows that TTT prevents 47 ATBD cases, and saves 31 QALYs per 100,000 patients screened at a societal cost of $12,579 per QALY saved. Sensitivity analyses identified value thresholds that would trigger a change in preferred policy. PSA shows that the likelihood that TTT would be cost-effective is low. Decision makers should carefully assess the characteristics of the local TB epidemic and expected program performance to determine whether TTT is preferable over PACF from a cost-effectiveness viewpoint.

The focus of the research is on investigations of various methods for obtaining sensible heat flux (H) for estimating evaporation. The key for this approach is the application of the shortened energy balance equation, and in the case of methods based on the Monin-Obukhov similarity theory (MOST), such as surface-layer scintillometrv and temperature variance with adjusted for stability using air temperature skewness, and surface renewal (SR), die iterative procedures. The application of the shortened energy balance requires that errors associated with measurement of net irradiance (Rnet) and soil heat flux (S) are kept to a minimum To this end. methodology for the calibration of net radiometers for both the infrared and short wave irradiances receive attention. A field study attempts to quantify the error in soil heat flux measurement for a mesic grassland. A standard, convenient and accurate method for calibrating net radiometers would assist in unravelling reasons for the perplexing lack of surface energy balance closure when employing the eddy covariance (EC) flux estimation method as well as improve on the accuracy of the energy balance residual method for estimating evaporation. A relatively inexpensive, accurate and quick laboratory method, based on physical theory, for non-steady radiative conditions above a large water-heated or water-cooled radiator containing circulated water, with surface-embedded thermocouples is used to obtain reproducible net radiometer calibration factor's for the infrared waveband for a wide range in net irradiance. When applied, the method would reduce error m the most important term of the shortened energy balance and assist in energy balance closure aspects of EC measurements. The SLS method, reliant on MOST, is used for estimating a really-averaged H for a mesic grassland for a 30-month period. Comparisons with EC measurements feature prominently in this unique study. These comparisons include using different MOST procedures and the influence of the Bowen ratio on SLS measurement: of if is investigated. Furthermore, since there are reports in the literature that the EC method may underestimate H and or latent energy flux (LE), resulting in the shortened energy balance not being closed, effort is devoted to this aspect. Other methods used for comparison purposes are the traditional Bowen ratio energy balance (BREB), SR, TV and ETo (grass reference) methods. The TV and SLS and/or EC measurements of H are compared above three contrasting canopy surfaces. It is shown that other high frequency air temperature-based methods, for example, for the first time the TV method with adjustment for skewness, may pave the way for evaporation stations from which real-time and sub-hourly estimates may be obtained relatively inexpensively. Another area of research that receives attention is the placement height of EC instruments above short-canopy surfaces and a spectral analysis of the vertical wind speed and some temperature measurement: for close-canopv placement heights. The SR method is used to estimate, for the first time, open-water evaporation. The ideal SR method applied above canopies is the most inexpensive micrometeorological method for estimating H, but the SR weighting factor a needs to be determined using EC and for this reason, the TV method with adjustment for skewness was investigated. Finally, a unique implementation of SR uses an iterative method for calculating H. A similar iterative procedure is applied for MOST and ETo calculations. / Thesis (DScAgric)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Inconsistencies in alcohol use measurement across studies and broad conceptualizations of post-secondary education experiences of young adults impede the comparison of research findings and our understanding of age-related shifts in alcohol use during emerging adulthood. This dissertation uses data from the Victoria Health Youth Survey (V-HYS), a 5 wave longitudinal study following 662 Canadian youth across the ages of 12-27. Study 1 examined the longitudinal associations among four measures of alcohol consumption (frequency, quantity, frequency of heavy episodic drinking and volume) from ages 15-25 and compared the ability of these measures to predict alcohol-related problems in emerging adulthood. Levels and rates of change across alcohol dimensions were moderately associated over time. However, measures of alcohol involvement significantly differed in their average rate of growth and in the prediction of alcohol-related problems in emerging adulthood. Heavy episodic drinking and volume showed the strongest associations in developmental trends and were similarly predictive of alcohol-related problems. The findings from this study support using measures of heavy episodic drinking or volume for assessing alcohol use and alcohol-related problems during emerging adulthood. Building on Study 1, Study 2 compared the trajectories of heavy episodic drinking during adolescence and emerging adulthood among youth in four different educational pathways: two-year college students, four-year university students, transfer students, and terminal high school graduates. This study also examined whether individual level factors could account for group differences in heavy drinking among the education groups. Terminal high school graduates consistently had the highest levels of alcohol use over time compared to all three post-secondary groups. Two-year college students had significantly higher levels of heavy drinking than university or transfer students when they enrolled, but university students had the greatest increases in heavy drinking after enrollment. However, differences in heavy drinking between post-secondary groups were completely accounted for by variations in the age at the time of enrollment. Taken together, the current findings illustrate that enrolling in post-secondary education, regardless of the type of institution, is associated with an increase in the frequency of heavy drinking during emerging adulthood and that this increase is greatest for younger students. However, the rates of drinking never exceeded that of the terminal high school graduates over time. These studies illustrate that the conclusions drawn about alcohol use trends during emerging adulthood may be contingent on the alcohol consumption measure used and conceptualizations of educational experiences. The results of the current studies provide recommendations to researchers about which measures of alcohol involvement to select for inclusion in future studies, and inform the optimal timing, targets, and contexts for alcohol prevention and intervention efforts during emerging adulthood. / Graduate / 0620

Intelligent tutoring systems and computer-supported collaborative environments have been designed to enhance human learning in various domains. While a number of solid techniques have been developed in the Artificial Intelligence in Education (AIED) field to foster human learning in fundamental science domains, there is still a lack of evidence about how to support learning in so-called ill-defined domains that are characterized by the absence of formal domain theories, uncertainty about best solution strategies and teaching practices, and learners' answers represented through text and argumentation. This dissertation investigates how to support students' learning in the ill-defined domain of professional ethics through a computer-based learning system. More specifically, it examines how to support students in the analysis of case studies, which is a common pedagogical practice in the ethics domain. This dissertation describes our design considerations and a resulting system called Umka. In Umka learners analyze case studies individually and collaboratively that pose some ethical or professional dilemmas. Umka provides various types of support to learners in the analysis task. In the individual analysis it provides various kinds of feedback to arguments of learners based on predefined system knowledge. In the collaborative analysis Umka fosters learners' interactions and self-reflection through system suggestions and a specifically designed visualization. The system suggestions offer learners the chance to consider certain helpful arguments of their peers, or to interact with certain helpful peers. The visualization highlights similarities and differences between the learners' positions, and illustrates the learners' level of acceptance of each other's positions. This dissertation reports on a series of experiments in which we evaluated the effectiveness of Umka's support features, and suggests several research contributions. Through this work, it is shown that despite the ill-definedness of the ethics domain, and the consequent complications of text processing and domain modelling, it is possible to build effective tutoring systems for supporting students' learning in this domain. Moreover, the techniques developed through this research for the ethics domain can be readily expanded to other ill-defined domains, where argument, qualitative analysis, metacognition and interaction over case studies are key pedagogical practices.

In many studies, choice based conjoint analysis is used to build a market simulator to develop marketing strategies; i.e., shares-of-preference are taken as market share forecasts. However, conjoint data are collected in interview situations, which may differ considerably from real shopping behavior. In this paper, we test the internal and external validity of four commercial choice based conjoint pricing studies including a total of 43 brands. We use conjoint and sales data to assess the relative performance of two modern approaches to estimate conjoint parameters: the segmentation based Latent Class model and the individual level Hierarchical Bayes approach. Our paper confirms previous results of the internal superiority of the Hierarchical Bayes approach. The main result of our investigation is that internal validity does not predict external validity and that Latent Class shows the same real world performance as Hierarchical Bayes. Both models show an average error of 4.2% in market share level prediction and a correlation of 69% between conjoint forecasts and real market shares. (author's abstract) / Series: Working Papers SFB "Adaptive Information Systems and Modelling in Economics and Management Science"

In this paper we head for a fully Bayesian analysis of the latent class model with a priori unknown number of classes. Estimation is carried out by means of Markov Chain Monte Carlo (MCMC) methods. We deal explicitely with the consequences the unidentifiability of this type of model has on MCMC estimation. Joint Bayesian estimation of all latent variables, model parameters, and parameters determining the probability law of the latent process is carried out by a new MCMC method called permutation sampling. In a first run we use the random permutation sampler to sample from the unconstrained posterior. We will demonstrate that a lot of important information, such as e.g. estimates of the subject-specific regression coefficients, is available from such an unidentified model. The MCMC output of the random permutation sampler is explored in order to find suitable identifiability constraints. In a second run we use the permutation sampler to sample from the constrained posterior by imposing identifiablity constraints. The unknown number of classes is determined by formal Bayesian model comparison through exact model likelihoods. We apply a new method of computing model likelihoods for latent class models which is based on the method of bridge sampling. The approach is applied to simulated data and to data from a metric conjoint analysis in the Austrian mineral water market. (author's abstract) / Series: Working Papers SFB "Adaptive Information Systems and Modelling in Economics and Management Science"

Karvių slaptojo mastito etiologija, gydymas ir prevencija Raktiniai žodžiai: Slaptas mastitas, karvių, etiologija, gydymas, prevencija Darbą atliko: Darbo vadovas: Darbo apimtis: 45 puslapiai, 5 lentelės, 17 paveikslėlių, 34 naudotos literatūros šaltiniai. Darbo tikslas: Įvertinti mikroorganizmų paplitimą karvių mastito etiologijoje ir nustatyti jų atsparumą antimikrobinėms medžiagoms Darbo uždaviniai: 5. Nustatyti mikroorganizmų, sukėlusių karvėms slaptąjį mastitą paplitimą; 6. Nustatyti mikroorganizmų atsparumą antimikrobinėms medžiagoms; 7. Išanalizuoti ryšį tarp mikroorganizmų rūšių ir somatinių ląstelių skaičiumi 8. Įvertinti preparatų gydomąjį efektyvumą slaptuoju mastitu sergančioms karvėms; Mokslinis - tiriamasis darbas buvo atliekamas 2012 – 2014 metais Lazdijų raj. esančiame X ūkyje. Šiuo metu ūkyje kiekviena dieną melžiama ~ 500 karvių. X ūkyje melžiamos karvės yra laikomos šaltojo tipo tvarte naudojant palaidą sistemą. Tyrimams buvo atrinktos 62 karvės sergančios subklinikiniu mastitu, kurios suskirstytos į 2 grupes po 31 karvę. Grupėms buvo skirtas skirtingas gydymas, 1 –oji grupė gydyta kombinuotu gydymu- „SYNULOX RTU“ injekcinė suspensija kartu su „SYNULOX LC“ intramaminė suspensija galvijams laktacijos metu, o 2 – jai grupei skirtas paprastas gydymas „SYNULOX LC“ intramaminė suspensija. Prieš gydymą ir po gydymo buvo stebėtas SLS kitimas piene, sukėlėjų diagnozavimas, primilžio kitimas, ketvirčių užkrėstumas. X ūkyje nustatėme, kad subklinikiniu... [toliau žr. visą tekstą] / Key Words: latent mastitis, cows, etiology, treatment, prevention Work done by: Supervisor: Volume: 45 pages, 5 tables, 17 images, 34 sources of used literature Aim and goals: Aim: To evaluate spreading of microorganisms in the etiology of cow mastitis and to establish antimicrobal drug resistance Goals: 1. To establish spreading of microorganisms causing latent mastitis of cows; 2. To establish antimicrobal microorganisms resistance; 3. To analyse the relation between the types of microorganisms and number of somatic cells; 4. To evaluate the effectiveness of preparations applied to treat the cows on latent mastitis; The scientific research was carried out in the years 2012 – 2014 in the farm X located in Lazdijai district. Currently, ~ 500 of cows are milked every day in this farm. The milch - cows in the farm X are being kept in the cold type of cow - shed applying a loose system. 62 cows with subclinical mastitis were selected for research. 2 groups were formed, each consisting of 31 cow. Special treatments were applied for both groups. A combined treatment was delivered to the Ist group of cows - injection suspension „SYNULOX RTU“ together with Intramammary suspension „SYNULOX LC“ to cattles during lacation period. Meanwhile, a simple treatment was delivered to the IInd group of cows - Intramammary suspension „SYNULOX LC“. SLS change in milk, diagnosis of agents of desease, change of milk yield, infection of the quarters has been observed before and... [to full text]

The phrase "opportunities to learn" (OTL) is most commonly interpreted in institutional, or inter-individual, terms but it can also be viewed as a cognitive, or intra-individual, phenomenon. How student learning heterogeneity (LH) - learning differences manifested when children's understanding is later assessed - is understood varies by OTL interpretation. In this study, I argue that the cognitive underpinning of learning disability, learning difficulty, typical achievement, and gifted achievement in mathematics is not well understood in part because of the ambiguity of LH assumptions in previous studies. Data from 104,315 Ontario students who had responded to provincially-mandated mathematics tests in grades 3, 6, and 9 dataset were analyzed using latent trait analysis (LTM) and latent class analysis (LCA). The tests were constructed to distinguish four achievement levels per grade and, either five curriculum strands (grades 3 and 6), three strands (grade 9 applied) or four strands (grade 9 academic). Best-fitting LTM models reflected 3- or 4-factors (grade 9 applied and grades 3, 6, 9 academic, respectively). Best-fitting LCA solutions reflected 4- or 5-classes (grade 3, 6 and grade 9 applied, academic, respectively). There were differences in relative proportions of students who were distributed across levels and classes. Moreover, grade 9 models were more complex than the reported four achievement levels. To explore intrinsic modeled results further, latent factors were plotted against latent classes. Implications of institutional versus cognitive interpretations are discussed.

This study uses latent class analysis and latent transition analysis to model and compare patterns of offending over time for males and females by: (1) identifying qualitative dimensions of offending; (2) modeling how patterns of offending change over time; and (3) exploring factors related to patterns of offending. This is a secondary analysis of data from the Edinburgh Study of Youth Transition and Crime, a longitudinal study consisting of a cohort of about 4,000 young people from secondary schools in the City of Edinburgh who responded to questionnaires administered between 1988 and 2001, when they were about 12, 13, 14, and 15 years old. Previous studies of offending have used trajectory modeling to explore the course of offending from onset to termination, but the models are generally based on a count of types of offences aggregated across individuals over time, making it difficult to determine whether individuals exhibit more versatility or specialization in offending or switch offences from one point in time to another. In addition, most of the studies on patterns of offending have focused primarily on males. An understanding of patterns of offending over time for both males and females is important for the design and selection of developmentally appropriate prevention/treatment strategies. The present study adds to the literature by (1) further exploring the small and understudied literature on offence transitions; (2) examining more closely the development of female offending separately from and in relation to male offending; and (3) exploring a range of factors (criminogenic and non-criminogenic) related to the development of offending for both males and females. While the same number of qualitative dimensions (latent classes) characterised male and female offending in this study, there were some structural differences. There was also evidence of shifts in the qualitative dimensions for males and females over time. Finally, those factors classified as criminogenic were more likely to differentiate among the latent classes than those classified as non-criminogenic.