The ultimate strength assessment of steel tubular members is of the utmost importance to the design and maintenance of many structures including large offshore platforms. Ultimate strength assessments I using numerical solutions must model both nonlinear material and geometric behaviour. The latter must consider large displacements, very often large rotations, and possibly even large strains. These numerical solutions must be computationally efficient and be capable of running on generally available computer hardware, i.e. minicomputers. To achieve this efficiency, attention must be paid to programming considerations, and a new suite of data management modules has been developed and is described in this thesis, which minimise disk storage and speed program development. In addition, the structural modelling was carried out almost exclusively using the Semiiaaf thin shell element. The work described in this thesis considers most of the components which contribute to the numerical ultimate strength analysis of steel tubular members. Theoretically, attention has been focused in two areas, namely the geometric nonlinearity and the automatic solution of the resulting nonlinear equations. A detailed study has been carried out to understand fully the main methods of accounting for geometric nonlinearity from fundamentals of continuum mechanics. The study has considered both the Green-Lagrange and Logarithmic strain measures with a Total Lagrangian, Updated Lagrangian and Eulerian description of motion. These formulations have been included in the Semiiaaf shell element, firstly using a continuum mechanics based approach, and secondly using the more orthodox stress resultant approach. At all stages within the thesis attention is drawn to the effects of the approximations which have been made and their resulting limitations in the respective formulations. The solution of the nonlinear equations is also covered in detail using Newton-type algorithms coupled with line searches. The solution algorithms have been derived for a constrained environment where a modified version of the generalised arc-length constraint has been used. The inclusion of material nonlinearity has been well developed previously but has been included for completeness. To demonstrate the performance and limitations of the theory presented, several carefully chosen numerical examples have been included which include the analysis of tubular steel T and X joints connections and residual strength assessment of a dented pipeline riser. Where possible, results have been compared with experimental tests. The thesis concludes that for general engineering structures, the Total Lagrangian approach based on the stress resultant model gives good engineering results, even in the presence of moderately large rotations. Of the alternative formulations the Updated Lagrangian layered approach is probably the most effective for large rotations and small to moderate strains.

No description available.

Introducció: La cirurgia bariátrica és el tractament més eficaç pels pacients amb obesitat mòrbida i que compleixin els criteris establerts per a ser tributaris de tractament. Estudis que han demostrat que la grelina és un factor important en la regulació de la ingesta ha fet que s'hagin realitzat treballs que relacionessin els nivells de grelina i les diferents tècniques quirúrgiques bariàtriques, donat que la major part de grelina es sintetitza al fundus gàstric. En el cas de la gastrectomia tubular, hi ha una exèresi de quasi la totalitat del fundus gàstric, amb el que els nivells de grelina teòricament han d'estar baixos després de la intervenció. La pèrdua de pes tan bona després de la gastrectomia tubular pot ser deguda en part a la disminució brusca de la grelina, que faria disminuir la ingesta. La gastrectomia tubular i les implicacions metabòliques que la intervenció quirúrgica produiria, es veurien reflectides en les variacions en els nivells plasmàtics de Grelina, GLP-1, Insulina i Glucèmia, així com en els canvis ponderals i de la ingesta depenent de les situacions fisiopatològiques en les quals s'aplica la intervenció quirúrgica.Aquestes situacions són: 1.- Situació de no obesitat. 2.- Obesitat exògena degut a una excessiva ingesta calòrica. 3.- Obesitat determinada genèticament. 4.- Obesitat determinada genèticament i Diabetis Mellitus tipus 2.Objectius: Analitzar l'efecte de la gastrectomia tubular sobre el pes per a cada model experimental. Analitzar l'efecte de la gastrectomia tubular sobre el volum d'ingesta per cada model experimental i la seva relació amb els canvis ponderals. Analitzar l'efecte de la gastrectomia tubular sobre els nivells de glucèmia per cada model experimental i la seva relació amb els canvis ponderals i els volum d'ingesta. Analitzar l'efecte de la gastrectomia tubular sobre els nivells de Grelina, GLP-1 i Insulina plasmàtica per cada model experimental.Mètodes: Gastrectomia tubular als diferents models experimentals: 1-rates Sprague Dawley no obeses, 2- rates Sprague Dawley obeses per dieta cafeteria, 3- rates Zucker obeses genéticament i 4- rates obeses i diabétiques genéticament (ZDF). El model 2 té un grup control que no serà intervingut i tan sols se li retira la dieta cafeteria.Resultats globals/ Conclusions: La gastrectomia tubular te un efecte metabòlic i ponderal diferent si l'apliquem a rates no obeses o a rates amb obesitat exògena. Mentre en el grup no obès es produeixen pocs canvis passades dues setmanes de la intervenció, en el model d'obesitat exògena la gastrectomia tubular aconsegueix la normalització del pes i igualar tots els paràmetres endocrino-metabòlics estudiats als obtinguts per les rates no obeses. La única excepció d'aquest comportament és el GLP- 1 que com sabem te un efecte anorexígen, i persisteix més alt en aquest en el grup de les rates obeses a pesar que el pes ja s'ha normalitzat.La gastrectomia tubular practicada en rates genèticament obeses (Model 3) té un efecte poc important tan pel que fa a la ingesta calòrica com pel que fa al pes. Aquest model es l'únic en el que es produeixen augments de pes post-intervenció encara que la intervenció fa que es situïn per sota del pes teòric per l' edat. També s'ha observat una tendència a la disminució de l'hiperinsulinisme i de la hiperglucèmia.En el model 4 de rates obeses i diabètiques, la gastrectomia tubular produeix una disminució de la ingesta amb una estabilització del pes que arriba a valors pròxims al pes ideal per la edat. La repercussió sobre l'estat metabòlic és escassa però hem pogut constatar, a diferencia dels altres grups, augments d'insulina postintervenció que no aconsegueixen corregir l'estat d'hiperglucèmia. / Introduction: Bariatric surgery is the most effective treatment for patients who have morbid obesity and who comply with the criteria established to be eligible for treatment. Studies have shown that ghrelin is an important factor in regulating intake, and this has led to further studies into ghrelin levels and the various bariatric surgical techniques, because most grelin is synthesized in the gastric fundus. We should point out that sleeve gastrectomy involves the exeresis of almost the entire gastric fundus, which means that the ghrelin levels should theoretically be low after the intervention. Such good weight loss after sleeve gastrectomy may be partly due to the sudden decrease in ghrelin, which would clearly decrease intake. Sleeve gastrectomy and the metabolic implications of surgical intervention would be reflected in variations in the plasma levels of ghrelin, GLP-1, insulin and glycaemia, as well as changes in weight and calorie intake, which would depend on the physiopathological situations in which the surgical intervention takes place.These situations are: 1. Non-obese situations. 2. Exogenous obesity due to excessive calorie intake. 3. Genetically determined obesity. 4. Genetically determined obesity and type 2 diabetis mellitus.Aims: To analyse the effect of sleeve gastrectomy on weight for each experimental model. To analyse the effect of sleeve gastrectomy on intake volume for each experimental model and its relation to weight change. To analyse the effect of sleeve gastrectomy on glycaemia levels for each experimental model and its relation to weight change and intake volume. To analyse the effect of sleeve gastrectomy on levels of ghrelin, GLP-1 and plasma insulin for each experimental model.Methods: Sleeve gastrectomy in the various experimental models described. Model 2 has a control group that will not be intervened and they are only withdrawn from the cafeteria diet.Overall results/Conclusions: Sleeve gastrectomy affects metabolism and weight differently in non-obese rats (model 1) and rats with exogenous obesity (cafeteria diet model 2). While the non-obese group undergoes few changes during the first two weeks after the intervention, the weight of the exogenous obesity model normalises and all the endocrine-metabolic parameters studied are the same as those for non-obese rats. The only exception to this is GLP-1 which, as is well known, has an anorectic effect, and it remains high in the group of obese rats even though weight has normalised.Sleeve gastrectomy in genetically obese rats (model 3) has little effect on both calorie intake and weight. This is the only model in which weight increases after the intervention even though the intervention positions them below the theoretical weight for their age. It has also been observed that hyperinsulinism and hyperglycaemia tend to decrease after the gastrectomyIn model 4 (obese and diabetic rats), sleeve gastrectomy decreases intake and stabilizes weight at values that are close to the ideal weight for the age in this type of rats. The effect on the metabolic state is only slight but, unlike other animals, we have found increases in insulin after the intervention that do not manage to correct the state of hyperglycaemia.

Thesis (Ph. D.)--Lehigh University, 1999. / Includes vita. Includes bibliographical references (leaves 160-162).

The warp knitting machine market has long been dominated by large-scale flat models, which have been steadily developed. Tubular fabrics are generally made in a special version of flat warp knitting machines containing two needle bars, one for each side of the tube, joined on the sides by yarns knitting alternatively on each bar. Warp knitting technology has failed to enter the circular knitting industry, dominated by weft knitting, due to its complexity in achieving warp knit structures in circular form. This thesis presents the design, synthesis, manufacture and test of an innovative method of producing tubular warp knitting fabrics, using a circular format rather than flat needle bars. This novel concept opens up many industrial applications from medical textiles to fruit packaging.

No description available.

No / This paper summarises the data from 1819 tests on concrete-filled steel tube columns and compares their failure load with the prediction of Eurocode 4. The full data is given on the website http://web.ukonline.co.uk/asccs2 . The comparison with Eurocode 4 is discussed and shows that Eurocode 4 can be used with confidence and generally gives good agreement with test results, the average Test/EC4 ratio for all tests being 1.11. The Eurocode 4 limitations on concrete strength could be safely extended to concrete with a cylinder strength of 75 N/mm2 for circular sections and 60 N/mm2 for rectangular sections.

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

Organic cations (OC's) are actively secreted by the renal proximal tubules in a number of species. The transepithelial transport of OC's involves a secondary active OC/H+ exchange process at the brush border (luminal) membrane. This study employed rabbit renal brush border membrane vesicles (BBMV) to investigate the structural requirements associated with substrate recognition at the OC transporter. A number of compounds (an N-alkylammonium series, an N1-alkylpyridinium series and some clinically important organic bases) were tested for their ability to competitively block the uptake of radioactively labelled tetraethylammonium (TEA) into BBMV. The inhibitory effectiveness of these compounds was correlated to the degree of hydrophobicity surrounding the positively-charged nitrogenous nucleus common to all the inhibitors. Preloading BBMV with N1-substituted pyridines trans-stimulated the uptake of TEA, suggesting that these compounds are translocated substrates for the OC transporter. The activity of the OC transport inhibitor and neurotoxin 1-methyl-4-phenylpyridinium was of special interest, and thus its transport characteristics were fully evaluated.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.