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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Ru-mediated ring-opening metathesis polymerization for the synthesis of complex polymer architectures

Scannelli, Samantha Jillian 30 May 2023 (has links)
Ring-opening metathesis polymerization (ROMP) has gained attention over the last few decades for its versatility and robustness. Through the use of highly active metal catalysts, such as Grubbs' first-generation catalyst [G1, (PCy3)2(Cl)2RuCHPh] and Grubbs' third-generation catalyst [G3, (H2IMes)(Cl)2(pyr)2RuCHPh], ROMP can exhibit living characteristics for some monomer classes, most commonly substituted norbornenes. The high livingness of ROMP makes it well-suited for the synthesis of complex polymer architectures (e.g., bottlebrush polymers, star polymers, and (multi)block copolymers, among others). However, compared to other living polymerizations, quantitative studies on the kinetic factors affecting living characteristics in ROMP are lacking. This work describes the effects of several reaction factors on the livingness in Ru-mediated ROMP of norbornene-based monomers. We performed thorough studies on the effects of the anchor group, the series of atoms directly attached to the norbornene, in the synthesis of both linear and bottlebrush polymers. Using small molecule norbornene monomers, we studied monomer HOMO energy, rate of propagation (kp), catalyst decomposition [a proxy for the termination rate constant (kt)], and livingness in ROMP as measured by the kp/kt ratio. HOMO energies were used to predict the reactivity of various monomers based on the hypothesis that high HOMO energy would lead to high monomer reactivity and high kp values. We observed a positive correlation between the HOMO energy and kp with both G1 and G3 catalysts, but we observed a plateau in kp for monomers with the highest HOMO energy when polymerized with G3 catalyst. These results suggested that above a certain level, HOMO energy no longer influenced the rate-determining step. Additionally, the anchor group had no apparent effect on catalyst decomposition with either catalyst. Therefore, when examining the livingness in ROMP of linear polymers, differences in the kp/kt ratios were primarily controlled by the kp value. When studying the synthesis of bottlebrush polymers, we found a similar positive correlation between HOMO energy and kp for five macromonomer (MM) species. To evaluate livingness of MMs, we targeted various backbone degrees of polymerization (Nbb), 100–2000, and found that MMs with high kp,obs values reached higher conversion with lower dispersities (Đ) at high target Nbb values than MMs with low kp,obs values. Finally, we investigated the synthesis of bottlebrush pseudo-pentablock copolymers using MMs with the highest and lowest kp anchor groups. This study revealed higher MM conversion and lower Đ values for each block for the MM with the highest kp anchor group, compared to the lowest kp MM. Furthering the anchor group study, we synthesized a small molecule monomer and two macromonomers containing a norbornene–benzoladderene structure. We found this anchor group had a higher HOMO energy than all other (macro)monomers previously studied. However, kp was not higher for the small molecule monomer compared to the other monomers studied, supporting the plateau in rate observed for monomers above a certain HOMO energy. The higher HOMO energy for MMs did increase kp for one of the MM compared to other MMs previously studied, however the MM with side-chains in the ortho position on the anchor group had a lower kp than expected. This low kp was attributed to the side-chains being in closer proximity to the reactive chain end, compared to the MM with side-chains in the meta position, hindering addition of new MM units. Altogether, these experiments revealed how the anchor group impacts kp and livingness in ROMP, two factors that are essential for the synthesis of precise bottlebrush (co)polymers. The final chapter of this dissertation evaluates the effect of reaction atmosphere on livingness in Ru-mediated ROMP. Here we envisioned that changing the atmosphere, from under air to on a Schlenk line under N2 to in an N2-filled glovebox, would reduce the rate of chain termination and improve livingness in ROMP of small molecule and macromonomers. We synthesized linear or bottlebrush pseudo-pentablock copolymers to evaluate the livingness of foud (macro)monomer structures in three different atmospheres. We found better agreement between Mn,expected and Mn,obs as well as lower overall and apparent Đ values for the bottlebrush polymers polymerized in N2 atmospheres. Interestingly, the effect was more prominent for low kp (macro)monomers; in other words, ROMP reactions of (macro)monomers with high kp values were successful under air, but for those with low kp values, a glovebox was required to observe good control. / Doctor of Philosophy / Ring-opening metathesis polymerization (ROMP) is a powerful chemical method used to make a wide variety of polymers. With use of ruthenium-based catalysts, ROMP can exhibit living characteristics for some monomer classes, making it well-suited for the synthesis of precise linear and bottlebrush polymers. However, compared to other living polymerizations, quantitative studies on the kinetic factors affecting living characteristics in ROMP are lacking. This work describes the effects of several reaction factors on the livingness in ROMP of norbornene-based monomers. We thoroughly studied the effects of the anchor group, the series of atoms directly attached to the norbornene, in the synthesis of both linear and bottlebrush polymers. Using small molecule norbornene monomers, we studied the monomer HOMO energy, rate of propagation (kp), catalyst decomposition, and the livingness in ROMP. We used HOMO energy to predict the reactivity of various monomers and found that high HOMO energy led to high kp values. Additionally, the anchor group had no apparent effect on catalyst decomposition; however, the large variations in kp meant that the anchor group influenced livingness in ROMP. When studying the synthesis of bottlebrush polymers, we found a similar positive correlation between HOMO energy and kp for five macromonomer (MM) species. Attaching a polymer side-chain to the norbornene decreases kp significantly, therefore our goal was to evaluate the livingness in ROMP under conditions that experience lower kp than linear polymers. We targeted large bottlebrush polymers, backbone degree of polymerization (Nbb) up to 2000, The final portion of this dissertation evaluates the effect of reaction atmosphere on the livingness in Ru-mediated ROMP. A large factor of livingness is kt, which in ROMP is typically decomposition of the catalyst chain end evidenced by low molecular weight tails in size exclusion chromatography traces. Here we envisioned changing the atmosphere, from air to inert, would prevent chain termination and improve the livingness in ROMP. We again used the synthesis of linear and bottlebrush pentablock copolymers to evaluate the livingness of six (macro)monomer structures in three different reaction atmospheres, air, N2, and in a glove box. Polymerizations under N2 or in the glove box produced more well-defined polymers than polymerizations in air by a marginal degree. Therefore, the livingness in ROMP improves when air is removed.
62

The termination of tenured public school teachers for incompetence

Lewis, Wayne E. 04 October 2006 (has links)
The purpose of this study was to review state and federal court cases from 1982 through February 1998 in which tenured public school teachers were terminated for incompetence. This study provided a current analysis of judicial opinions of teacher incompetence as a follow-up to Shackleford's (1982) study in which she reviewed state and federal termination cases from 1958 through 1981. Four research questions guided the study based on the examination of 107 court cases. The study provided a current judicial definition regarding the term "incompetency" and also provided a legal frame of reference from which one could imply teacher incompetence. The following conclusions were derived from the analysis of court cases examined in this study. 1. The term "teacher incompetency" does not have a decisive judicial definition. Consequently, teachers may be terminated for multiple reasons of incompetency. 2. Courts have indicated that teachers should not be terminated for arbitrary or capricious reasons, but for just and reasonable cause. 3. The foremost purpose of teacher evaluation is remediation, not termination. Courts have indicated that teachers should be provided adequate time to 'find a solution to a problem. 4. Teachers must be provided adequate notice of the intent to terminate with a sufficiently detailed statement to inform the teacher of the allegations and charges so the teacher can prepare an adequate defense. 5. Teachers have a due process right to a fair hearing in which school officials must be able to exhibit a preponderance of evidence that the teacher is incompetent. 6. During hearings, teachers must be given an opportunity to crossexamine witnesses, testify, and present testimony of other witnesses and other relevant evidence. 7. A school board's termination of teachers for incompetence will not be sustained if a teacher's rights, guaranteed by the United States Constitution or state laws, are violated. 8. Teacher incompetency must be measured by the same standards required of others performing the same or similar duties. / Ph. D.
63

Enhanced Flight Termination System Study Overview and Status

Cronk, Steven G., Tobin, Maria A., Sakahara, Robert D. 10 1900 (has links)
International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The Range Commanders Council (RCC) Range Safety Group (RSG) is conducting a study into the next generation of ground-based flight termination technology, known as the Enhanced Flight Termination System (EFTS) study. The study was initiated by the RCC in April 2000 and scheduled to be complete in March 2002. The Government is performing the study with support from contractors and academia. In addition to the RSG, the Telemetry Group, Frequency Management Group, Telecommunications and Timing Group of the RCC support the study. Additionally, the National Security Agency is providing key support along with vendors who design, build, and test range safety systems. This paper will describe the background, goals, and current status of the study.
64

Therapist (Dis)Continuity, Therapeutic Relationship, and (Premature) Termination in a Psychology Training Clinic

Al-Jabari, Rawya M. 08 1900 (has links)
Premature termination is a substantial problem with significant adverse effects for clients, therapists, and treatment organizations. Unfortunately, it is also a relatively common phenomenon within mental healthcare settings. Across varied mental healthcare settings, rates of premature termination have reportedly ranged from 19.7 % to 40 %. Perhaps not surprisingly, the rate of premature termination in training clinics is substantially higher than in community mental health settings and private practice, with 75 to 80 % of clients ending treatment services prematurely. The purpose of this study was to explore the combined effect of intake therapist continuity or discontinuity, and quality of the therapeutic relationship on premature termination. Intake therapist continuity, measures of working alliance, and termination outcome from 524 clients at the University of North Texas Psychology Clinic were utilized for adults receiving individual therapy services between August 2008 and August 2013. Results of the study suggest intake therapist continuity did not predict subjective termination status (X2(2, n = 524) = 1.61, p = 0.45), nor did it predict change in symptomology status (X2(3, n = 453) = 1.14, p = 0.77). Additionally, working alliance predicted subjective termination status (X2(6, n = 212) = 21.17, p < 0.01), but not change in symptomology status (X2(9, n = 208) = 6.27, p = 0.71). The findings of the current study are discussed, as well as suggestions for further research related to client, therapist, treatment, and procedural variables and their impact on premature termination.
65

Výpověď z pracovního poměru, komparace ČR a SR / The notice of termination of employment, comparation ČR and SR

Kalužáková, Mária January 2014 (has links)
The purpose of my thesis is to compare the legal regulation of notice of termination of employment in the legal systems of the Czech Republic and Slovakia. The thesis consists of the introduction, conclusion and six chapters, each of which contains a comparison of various aspects of the two regulations. The introduction sets out the reasons for which I chose this topic and the method of processing my thesis. The first chapter characterises notice in general, its cancellation and requirements, i.e. the written form and the delivery of the notice. The second chapter focuses on the notice given by an employee and on particularities of the Czech regulation of the notice related to the transfer of rights and obligations arising from the employment relationship and the counterpart of such notice in Slovak labour law, which is the termination by agreement. Notice given by the employer is discussed in the third chapter. This chapter consists of three parts. The first part highlights the comparison of individual reasons of the notice, the second focuses on cases in which the notice is prohibited, and the third on the substantive conditions of the notice. The fourth chapter is divided into two parts. The first part discusses the differences in the regulation of redundancy payment accordance to the Labour...
66

Výpověď z pracovního poměru ve vybraných členských státech EU / Notice of termination of employment in selected EU member states

Tichý, Ondřej January 2016 (has links)
Notice of termination of employment in selected EU member states The diploma thesis analyses the legal regulation of notice of termination from employer's side in the Czech Republic and its comparison with Austrian and German legal regulation of the same institute. Thanks to the comparison it will be possible to reach the aim of the thesis which is to find out how social is the Czech attitude regarding this topic and to discover all the possible differences and similarities among all the three legal regulations. The first chapter serves as an introduction to the particular national labour legal provisions including the development and describes the main sources of law concerning the labour law. The pivotal chapter concentrates on individual reasons for dismissal under section 52 of the Czech Labour Code to which the thesis searches for the same or similar legal regulation within the other two legal systems. This chapter is divided into the subchapters as every of them focuses on one group of reasons for dismissal. At the end of each subchapter examples from Austria and Germany are given which prove differences and similarities among the three legal systems. This logic of subchapter arrangement enables easier understanding of individual reasons for dismissal and their examples in all the three...
67

Nájem bytu / Residential lease

Kotrba, Radim January 2012 (has links)
Residential lease The thesis examines residential lease. For the reason of limited length the paper does not deal with the topic in general but focuses primarily on the aspects of residential lease termination. This particular topic was chosen because of the fact that it is one of the significant legal relations occurring among the subjects of law, many people fulfil their accommodation requirements through it and almost everyone gets in touch with it in his/her life, in a way. Taking into consideration the social implications of rental housing the topic goes beyond the legal area. It is politically sensitive and it involves frequent disputes between the parties that are on the opposite sides of the political spectrum, mainly because of the different levels of regulation. The goal of the thesis is to explore and evaluate the effective legal regulation in the light of practice of the Supreme Court of the Czech Republic. Moreover, the thesis tries to be proactive and predict possible questionable aspects and it aims to provide the readers with practical advice and recommendations at the same time. From the structural point of view the thesis is divided into chapters, each of them dealing with different features. Firstly, chapter one briefly describes what the residential lease is, furthermore, it explains its...
68

Výpověď z pracovního poměru / The notice of termination

Škopek, Petr January 2013 (has links)
The purpose of the thesis is to provide a summary of the legal regulation and to point out legal problems connected with the Notice of termination in the Czech Republic. The thesis is composed of eleven chapters, the introduction and the conclusion. Chapter One is introductory and defines concept and position of Labour law in the system of law in the Czech Republic and function of Labour law. Chapter Two examines, in general relation, between Civil law and Labour law. In chapter Three, author tries to explain legal regulation of legal acts. The chapter consists of two parts. Part one focuses on legal regulation of legal acts in the Civil Code and Part two focuses on legal regulation of legal acts in the Labour Code. Chapter Four describes basic principles of Labour law. In chapter Five is short excursion to the history of labour legislation in our territory. This chapter is divided into three subchapters according to some important historical events of our labour legislation. Chapter Six concentrates on domestic source of law in the area of notice of termination. This chapter is divided into three parts. First part is about constitutional acts, second part is about statutes and third part is about case law in the Czech Republic. In chapter Seven are described international source of law in the area...
69

Výpověď z pracovního poměru / Notice of termination of employment

Šmídová, Klára January 2018 (has links)
This diploma thesis deals with the topic of the notice of termination of employment in the Czech labour law. The thesis sets out multiple primary goals. The first goal is to introduce the reader to the context of the legal framework of the notice of termination of employment, including an analysis of selected case law relevant to the topic. The second goal is to provide a comparative outline via the exploration of Belgian labour law and its legal regulation of the notice of termination of employment. Thirdly, the author reflects the findings gathered throughout the thesis and offers some amendments de lege ferenda. The diploma thesis is divided into eleven parts. The first three parts relate to the general description of the matter - the first is devoted to the labour law in the context of the legal system of the Czech Republic, the second is devoted to specific characteristics of an employment relationship and its subject and object. The third part discusses the termination of employment in general and it also takes into account the strategy of flexicurity. The fourth part aims at enlightening the effect of the international law and the law of the European Union on the legal regulation of the notice of termination of employment. The fifth part is devoted to the notice of termination of employment...
70

Důvody výpovědi z pracovního poměru / Reasons for termination of employment

Karlová, Zuzana January 2019 (has links)
Reasons for termination of employment Abstract The topic of the diploma thesis concerns the reasons for the termination of the employment relationship. The aim of the thesis is to analyse thoroughly the reasons for termination in the light of legal regulation as well as the case law, but the aim of the thesis is also to reveal possible legal deficiencies and possible proposals for its de lege ferenda solutions. The actual text of the work outside of the introduction and the conclusion is divided into 4 chapters. The first chapter defines the basic concepts of labour law, its function and its position within the system of law, especially its relation to civil law. The second chapter deals with general employment and termination of employment. At the beginning there is a brief discussion about the employment relationship and its origin, including its subjects, and a list of all ways of terminating the employment relationship and more precisely characterized selected ways of termination of employment, including the termination of employment contract, the probationary period, the immediate cancellation of the employment relationship and, last but not least, the collective redundancies. The third, most extensive, chapter is the core of the entire thesis and is divided into several subchapters. These deal with...

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