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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.
261

Determination of silver using cyclic epithermal neutron activation analysis

Pun, Tin-Hei 26 October 2010 (has links)
A fast pneumatic transfer facility was installed at the Nuclear Engineering Teaching Laboratory (NETL) of the University of Texas at Austin for the purpose of cyclic thermal and epithermal neutron activation analysis. In this work efforts were focused on the evaluation of cyclic epithermal neutron activation analysis (CENAA). Various NIST and CANMET certified materials were analyzed by the system. Experiment results showed 110Ag as one of the isotopes favored by the system. Thus, the system was put into practical application for identifying silver concentration in the Arctic atmospheres in air filters collected in 2009, and traces in metallic ores Comparison of silver concentrations via CENAA with the CANMET certified reference materials gave very good results. / text
262

DIRECT PRODUCTS AND THE INTERSECTION MAP OF CERTAIN CLASSES OF FINITE GROUPS

Chifman, Julia 01 January 2009 (has links)
The main goal of this work is to examine classes of finite groups in which normality, permutability and Sylow-permutability are transitive relations. These classes of groups are called T , PT and PST , respectively. The main focus is on direct products of T , PT and PST groups and the behavior of a collection of cyclic normal, permutable and Sylow-permutable subgroups under the intersection map. In general, a direct product of finitely many groups from one of these classes does not belong to the same class, unless the orders of the direct factors are relatively prime. Examples suggest that for solvable groups it is not required to have relatively prime orders to stay in the class. In addition, the concept of normal, permutable and S-permutable cyclic sensitivity is tied with that of Tc, PTc and PSTc groups, in which cyclic subnormal subgroups are normal, permutable or Sylow-permutable. In the process another way of looking at the Dedekind, Iwasawa and nilpotent groups is provided as well as possible interplay between direct products and the intersection map is observed.
263

Synthesis of polycyclic hydantoin derivitaves and peptides.

Albasheer, Mohamed Saadaldin Altaib. January 2008 (has links)
Cyclic cage compounds have attracted much attention in pharmaceutical studies. The lipophilic nature of these compounds plays an important role in facilitating the crossing of the cellular membranes, including the blood brain barrier (BBB) and the central nervous system (CNS). Several adamantane and pentacyclo[5.4.0.02,6.03,10.05,9]undecane (PCU) derivatives have shown great potential as antiviral, antibacterial and neuroprotective compounds. The aim of this study includes the synthesis of hydantoin derivatives of adamantane and PCU as anticonvulsant compounds. Fosphentoin sodium (Cerebyx) 48 is a commercial anticonvulsant drug. Structurally, compound 51 and 52 are similar to Cerebyx 48, where the two phenyl groups have been replaced with PCU or adamantane skeleton respectively. The cage skeleton should increase the lipophilic character of the drug whilst the phosphate group should retain the water solubility of the substrate. The attempted synthesis of these compounds is described in Chapter 2. The PCU hydantoin is readily converted to the PCU amino acid. The synthesis of the PCU amino acid 41 and its Fmoc derivative 106 is described in Chapter 3. This compound was incorporated into small peptides, namely Ala-Ala-Ala-PCU-Ala-Ala-Ala-Fmoc and Ala-Val- PCU-Ile for future testing as a potential anti-cancer agent. NMR studies of these peptides are also reported. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2008.
264

Fire resistance of earthquake damaged reinforced concrete frames

Ab. Kadir, Mariyana Aida January 2013 (has links)
The topic of structural damage caused by fires following an earthquake (FFE) has been discussed extensively by many researchers for over a decade in order to bring the two fields closer together in the context of performance based structural engineering. Edinburgh University, Heriot-Watt University, Indian Institute of Technology Roorkee (IIT Roorkee) and Indian Institute of Science initiated a collaboration to study this problem under a UK-India Engineering Research Initiative (UKIERI) funded project. The first construction of a single-storey reinforced concrete frame at IIT Roorkee was completed in summer 2011; this is known as the Roorkee Frame Test 1 throughout this thesis. This thesis presents the modelling of the Roorkee Frame Test 1 using the finite element method and assesses the capability of the numerical methodologies for analysing these two sequential events. Both two and three dimensional finite element models were developed. Beam and shell elements were chosen for the numerical modelling, which was carried out using the general purpose finite element package ABAQUS (version 6.8). The variation in material properties caused by these two types of loading, including strength and stiffness degradation, compressive hardening, tension stiffening, and thermal properties, is implemented in the numerical modelling. Constitutive material calculations are in accordance with EC4 Part 1.1, and all loading is according to IS 1893:2002 Part 1 (Indian Standard). The time-temperature curve used in the analysis is based on data from the test carried out. The behaviour of the Roorkee Frame Test 1 when subjected to monotonic, cyclic lateral loading followed by fire is presented. The capacity of the frame when subjected to lateral loading is examined using a static non-linear pushover method. Incremental lateral loading is applied in a displacement-controlled manner to induce simulated seismic damage in the frame. The capacity curve, hysteresis loops and residual displacements are presented, discussed and compared with the test results. The heat transfer analysis using three dimensional solid elements was also compared against temperature distributions recorded during the Roorkee frame fire test. Based on the smoke layer theory, two emissivity values were defined. In this study, the suitability of numerical modelling using ABAQUS to capture the behaviour of Roorkee frame test is examined. The results from this study show that the 3D ABAQUS model predicted more reliable hysteresis curves compared to the 2D ABAQUS model, but both models estimated the lateral load capacity well. However neither model was able to simulate the pinching effect clearly visible in the hysteresis curves from the test. This was due to noninclusion of the bond slip effect between reinforcing bars and concrete. The residual displacement obtained at the end of the cyclic lateral loading analysis from the 2D ABAQUS model is higher than that seen in the test. However, the result in the 3D ABAQUS model matched the trend obtained in the test. The both columns appear to stiffen under the heating and the residual displacement seems to recover slightly. Lateral displacements, obtained in the thermo-mechanical analysis of the numerical models, show that thermal expansion brings the frame back towards its initial position. Finally, correlation studies between analytical and experimental results are conducted with the objective to establish the validity of the proposed model and identify the significance of various effects on the local and global response of fire resistance earthquake damaged of reinforced concrete frames. These studies show that the effect of tension stiffening and bond-slip are very important and should always be included in finite element models of the response of reinforced concrete frame with the smeared crack model when subjected to lateral and thermal loading. The behaviour of reinforced concrete frames exposed to fire is usually described in terms of the concept of the fire resistance which defined in terms of displacement limit. This study shows the global displacement of the frame subjected to fire recover slightly due to the thermal expansion during the heating.
265

Copper Electrodeposition on Iridium, Ruthenium and Its Conductive Oxide Substrate

Huang, Long 12 1900 (has links)
The aim of this thesis was to investigate the physical and electrochemical properties of sub monolayer and monolayer of copper deposition on the polycrystalline iridium, ruthenium and its conductive oxide. The electrochemical methods cyclic voltammetry (CV) and chronocoulometry were used to study the under potential deposition. The electrochemical methods to oxidize the ruthenium metal are presented, and the electrochemical properties of the oxide ruthenium are studied. The full range of CV is presented in this thesis, and the distances between the stripping bulk peak and stripping UPD peak in various concentration of CuSO4 on iridium, ruthenium and its conductive oxide are shown, which yields thermodynamic data on relative difference of bonding strength between Cu-Ru/Ir atoms and Cu-Cu atoms. The monolayer of UPD on ruthenium is about 0.5mL, and on oxidized ruthenium is around 0.9mL to 1.0mL. The conductive oxide ruthenium presents the similar properties of ruthenium metal. The pH effect of stripping bulk peak and stripping UPD peak of copper deposition on ruthenium and oxide ruthenium was investigated. The stripping UPD peak and stripping bulk peak disappeared after the pH ≥ 3 on oxidized ruthenium electrode, and a new peak appeared, which means the condition of pH is very important. The results show that the Cl- , SO42- , Br- will affect the position of stripping bulk peak and stripping UPD peak: the stripping bulk peak will shift and decrease if the concentration of halide ions is increasing, and the monolayer of UPD will increase at the same time.
266

Effect of Catecholamines, Methylxanthines and Cyclic Nucleotides on the Morphogenesis of Verticillium Dahliae

Oyofo, Buhari Anthony 01 August 1981 (has links)
The purpose of this investigation is to study the effects of methylxanthines, catecholamines, and cyclic nucleotides on melanin synthesisand conidiation using the technique of phase contrast microscopy. Verticillium wild type (T9) strain was grown in both sucrose nitrate liquid medium and polygalacturonic acid media (SNLM and PGAM). These media allowed rapid production of conidia and synchronous development of microsclerotia respectively. Even though caffeine has a greater effect on conidiation, both caffeine and theophylline promoted melanization. Dibutyl cyclic AMP to lesser extent inhibited conidiation, while cyclic AMP had little to no effect on conidiation. Dibutyl cyclic AMP inhibited melanin production. Cyclic AMP had a stimulatory effect on melanin production. Isoproterenol a stimulant of adenylate cyclase activity, inhibited conidiation the first two days, but had no apparent effect after day 3. Isoproterenol also induced melanin production in the flask. Propranolol, an antagonist of hormonally induced adenylate cyclase activity, did not repress conidiation when compared to the drug-free SNLM. Melanin was not formed in either SNLM and PGAM, suggesting that the effect of propranolol was opposite that of isoproterenol. Propranolol, a beta blocking agent, reversed the isoproterenol induced inhibition of conidiation. This reversal indicates that there is a receptor which isoproterenol attached itself to - the binding beta receptor site. The isoproterenol effect on conidiation and melanin synthesis indicates that, there might be cyclic AMP involvement in development, since this agent affects cyclic AMP level. Since melanin is known to be associated with microsclerotia, it is possible that cyclic AMP might be involved in this development. In this study, the effects of methylxanthines, catecholamines and cyclic nucleotides on melanin synthesis and conidiation was determined. There is every possibility that cyclic AMP might be involved in the regulation of conidiation process and melanin synthesis.
267

Lap splice in glass fiber reinforced polymer‐reinforced concrete rectangular columns subjected to cyclic‐reversed loads

Naqvi, Syed 27 October 2016 (has links)
This study presents the experimental results of nine full-scale lap spliced glass-fiber reinforced polymer (GFRP) reinforced concrete (RC) columns, and one additional reference steel-RC column with lap splices, under axial and cyclic-reversed loads. The test parameters included type of reinforcement, lap splice length of longitudinal reinforcement, transverse reinforcement spacing, and the effect of using steel fiber-reinforced concrete (SFRC). Test results indicated that a splice length of 60 times the diameter of the longitudinal column bar was adequate in transferring the full bond forces along the splice length and were able to maintain the lateral load carrying capacity when subjected to higher levels of axial loads and drift ratios. In addition, lap spliced GFRP-RC columns with closely spaced transverse reinforcement achieved high levels of deformability. Furthermore, the use of SFRC in columns with inadequate splice increased the peak lateral strength and the energy dissipation of the specimens. / February 2017
268

Disrupting the INCENP-Aurora B interaction with genetically-encoded cyclic peptides

Gohard, Florence Helen January 2015 (has links)
The chromosome passenger complex (CPC) is an essential mitotic regulator with key roles in mitotic processes such as chromosome condensation, spindle dynamics, chromosome bi-orientation, the spindle checkpoint and cytokinesis. The Aurora B kinase is the CPC’s catalytic subunit. Its targeting and activation are dependent on interactions with the other components of the complex: inner centromere protein (INCENP), survivin and borealin/Dasra B. INCENP serves both as a scaffolding subunit for the CPC as a whole and as an activator of Aurora B via its highly conserved INbox domain. Aurora B is a putative anti‐cancer target; several inhibitors of the kinase are currently in clinical trials. All these are ATP-analogues targeting the kinase active site. The protein-­protein interaction between Aurora B and the INCENP INbox is also essential for CPC function. Earlier studies have demonstrated that INCENP INbox mutants unable to bind and/or activate Aurora B cannot rescue lethality in the absence of endogenous INCENP. The first goal of this study was to test the in vivo effects of disrupting the interaction between endogenous wild type INCENP and Aurora B. For this, a cell-based CPC function assay was developed in HeLa cells. Using this assay, I show that expression of soluble INbox in HeLa cells produces a significant increase in multinucleated and micronucleated cells: both effects consistent with Aurora B loss of function. Expression of soluble INbox bearing the mutations W845G and/or F881A does not elicit this effect suggesting that those mutants cannot bind to Aurora B and occlude INCENP binding. The result concerning the F881A mutant contrasts with earlier reports that equivalent mutants could bind, but not activate, Aurora B. Expression of an INbox mutant lacking the C-­terminal TSS motif reported to be involved in Aurora B activation but not binding has effects similar to those of the wild type INbox. Using the INbox/Aurora B interaction as a model, a secondary goal of this study was to develop and evaluate a novel approach to identify small peptides capable of dissociating intracellular protein‐protein interactions. For this, a library of small (5-­9 residues long) circular peptides (CPs) mimicking the INbox was generated using the split intein circular ligation of proteins and peptides (SICLOPPS) methodology and assayed using the cell-­based CPC function assay. Over two successive rounds of screening, a small number of CPs were identified that caused a significant increase in rates of multinucleated and micronucleated cells. Although statistically significant, these increases were very modest. Furthermore, due to high heterogeneity in SICLOPPS processing efficiencies, it was not practicable to compare the effects of different peptides side-­by-side by transfection. The level of variation in processing efficiency – thus, CP production – was unexpectedly high and puts into question the functional complexity of more commonly used combinatorial cyclic peptide libraries derived using current SICLOPPS methodology. The results of this study are divided into three sections. The first is a methods section concerning the testing of SICLOPPS in HeLa cells and the development of a cell­‐based CPC function assay. In the second, the effects of expressing soluble INbox and mutants thereof in HeLa cells are presented. The final results section presents the results of the feasibility study of the rationally-­designed genetically encoded library approach.
269

An In Vitro Comparison of Cyclic Fatigue of Profile® Vortex™ and Endosequence™ Rotary Nickel-Titanium Files

Al-Foraih, Fawaz 07 April 2011 (has links)
The purpose of this study was to determine the number of rotations to fracture (cyclic fatigue) of the Profile® Vortex™ files (Dentsply Tulsa Dental Specialties, Tulsa, OK) compared to the EndoSequence™ files (Brasseler USA, Savannah, GA) using an in-vitro apparatus simulating a curved canal. Two hundred Profile® Vortex™ files of 25mm length were divided equally into ten groups, one for each of the Profile® Vortex™ files 20/0.04, 20/0.06, 25/0.04, 25/0.06, 30/0.04, 30/0.06, 35/0.04, 35/0.06, 40/0.04, and 40/0.06. Two hundred EndoSequence™ files of 25mm length were divided equally into ten groups of the same tip and taper sizes analogous to the Profile® Vortex™ file groups. Files were rotated at 500 rpm in a fixed groove in the metal block of the apparatus. The angle of deflection for all files was fixed at 33 degrees, determined using the Schneider method. The time from initiation of rotation to fracture was recorded and rotations to fracture were calculated. The data collected was analyzed using a multi-way ANOVA, followed by specific post-hoc contrasts comparing the two brands for each tip and taper combination. The results demonstrated that the Profile® Vortex™ files required significantly greater rotations to fracture than the EndoSequence™ (p < 0.001) in all tip sizes in both 0.04 and 0.06 tapers. Profile® Vortex™ files exhibited a greater resistance to cyclic fatigue than the EndoSequence™ files.
270

Cyklická voltametrie jako detekční technika ve vysokoúčinné kapalinové chromatografii / Cyclic Voltammetry as a Detection Technique in High Performance Liquid Chromatography

Burešová, Helena January 2014 (has links)
The aim of the thesis was to study the possibility of employment of cyclic voltammetry as a detection technique in liquid chromatography. The phenothiazine derivatives (chlorpromazine hydrochloride, diethazine hydrochloride, and thioridazine hydrochloride) were used as model compounds. Firstly, the comparison of two potential detectors (tubular detector and bulk "wall-jet" detector) was accomplished. Only bulk "wal-jet" detector satisfied. Next, the conditions for the separation and detection of studied phenothiazines on RP-select B LiChrospher® 60 (250×4 mm) column with cyclic voltammetry as the detection techniques were optimized. The best separation is achieved in mobile phase consisted from the solution of 0.1 mol dm-3 sodium perchlorate in acetonitrile-water (80:20) mixture. The effect of flow rate of mobile phase and scan rate of polarization of the electrode on the symmetry of chromatographic peak was also followed, and optimal values of 0.5 ml min-1 for flow rate, and of 0.5 V s-1 for scan rate, were found. Under optimized conditions the calibration dependences of studied phenothiazines were measured in the range from 5×10-5 to 1×10-3 mol dm-3 for chlorpromazine, and in the range from 8×10-5 to 1×10-3 mol dm-3 for diethazine and thioridazine. The developed method was applied to...

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