Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 162-173). Also available on the World Wide Web.

Thesis (M.E. 1975) from the Department of Electrical Engineering, University of Adelaide.

The effect of decompression stress on circulating microparticles (MPs) from leukocytes (LMP), platelets (PMP), and endothelial cells (EMP) was investigated in fifteen male naval clearance divers. Venous blood samples were obtained 30 min before and 75 min after exposure to 81msw for 20 min. MPs were isolated by differential centrifugation and immunophenotyped using multiparameter flow cytometry. Venous gas emboli (VGE) were assessed using Doppler ultrasound every 40 min post-dive and subsequently graded using the Kisman Integrated Severity Score (mean KISS=21.92, indicating moderate level of VGE). Following the dive there was increased expression of CD41a, CD106, CD62P and CD31 on MPs, while CD45 and CD141 expression decreased. A positive correlation was found between KISS and CD41a expression post-dive. These results indicate that decompression stress activated platelets, producing PMPs and resulting in potential vascular disruption or injury. The inclusion of MP measures in future DCS-related research may help identify biomarkers of DCS.

The effect of decompression stress on circulating microparticles (MPs) from leukocytes (LMP), platelets (PMP), and endothelial cells (EMP) was investigated in fifteen male naval clearance divers. Venous blood samples were obtained 30 min before and 75 min after exposure to 81msw for 20 min. MPs were isolated by differential centrifugation and immunophenotyped using multiparameter flow cytometry. Venous gas emboli (VGE) were assessed using Doppler ultrasound every 40 min post-dive and subsequently graded using the Kisman Integrated Severity Score (mean KISS=21.92, indicating moderate level of VGE). Following the dive there was increased expression of CD41a, CD106, CD62P and CD31 on MPs, while CD45 and CD141 expression decreased. A positive correlation was found between KISS and CD41a expression post-dive. These results indicate that decompression stress activated platelets, producing PMPs and resulting in potential vascular disruption or injury. The inclusion of MP measures in future DCS-related research may help identify biomarkers of DCS.

The incidence of lumbar spinal stenosis (LSS) is steadily rising, mostly because of a noticeably older age structure. In Sweden, LSS surgery has increased continuously over the years and is presently the most common argument to undergo spine surgery. The purpose of the surgery is to decompress the neural elements in the stenotic spinal canal. To avoid instability, there has been a tradition to do the decompression with a complementary fusion, especially if degenerative spondylolisthesis is present preoperatively. The overall aims of this thesis were to evaluate which method of surgery that generally can be considered to give sufficiently good clinical results with least cost to society and risk of complications and to determine whether there is a difference in outcome between smokers and non-smokers. The Swespine Register was used to collect data on clinical outcome after LSS surgery. In two of the studies, large cohorts were observed prospectively with follow-up after 2 years. Data were analysed in a multivariate model and logistic regression. In a randomised controlled trial (RCT, the Swedish Spinal Stenosis Study), 233 patients were randomised to either decompression with fusion or decompression alone and then followed for 2 years. The consequence of preoperative degenerative spondylolisthesis on the results was analysed and a health economic evaluation performed. The three-dimensional CT technique was used in a radiologic biomechanical pilot study to evaluate the stabilising role of the segmental midline structures in LSS with preoperative degenerative spondylolisthesis by comparing laminectomy with bilateral laminotomies. Smokers, in comparison with non-smokers, showed less improvement after surgery for LSS. Decompression with fusion did not lead to better results compared with decompression alone, no matter if degenerative spondylolisthesis was present preoperatively or not; nor was decompression with fusion found to be more cost-effective than decomression alone. The instability caused by a decompression proved to be minimal and removal of the midline structures by laminectomy did not result in increased instability compared with the preservation of these structures by bilateral laminotomies. In LSS surgery, decompression without fusion should generally be the treatment of choice, regardless of whether preoperative degenerative spondylolisthesis is present or not. Special efforts should be targeted towards smoking cessation prior to surgery.

In recent years, memory has shown to be a constraining factor in many workloads. Memory is an expensive necessity in many situations, from embedded devices with a few kilobytes of SRAM to warehouse-scale computers with thousands of terabytes of DRAM. Memory compression has existed in all major operating systems for many years. However, while faster than swapping to a disk, memory decompression adds latency to data read operations. Companies and research groups have investigated hardware compression to mitigate these problems. Still, open-source low-latency hardware compressors and decompressors do not exist; as such, every group that studies hardware compression must re-implement. Importantly, because the devices that can benefit from memory compression vary so widely, there is no single solution to address all devices' area, latency, power, and bandwidth requirements. This work intends to address the many issues with hardware compressors and decompressors. This work implements hardware accelerators for three popular compression algorithms; LZ77, LZW, and Huffman encoding. Each implementation includes a compressor and decompressor, and all designs are entirely parameterized. There are a total of 22 parameters between the designs in this work. All of the designs are open-source under a permissive license. Finally, configurations of the work can achieve decompression latencies under 500 nanoseconds, much closer than existing works to the 255 nanoseconds required to read an uncompressed 4 KB page. The configurations of this work accomplish this while still achieving compression ratios comparable to software compression algorithms. / Master of Science / Computer memory, the fast, temporary storage where programs and data are held, is expensive and limited. Compression allows for data and programs to be held in memory in a smaller format so they take up less space. This work implements a hardware design for compression and decompression accelerators to make it faster for the programs using the compressed data to access it. This work includes three hardware compressor and decompressor designs that can be easily modified and are free for anyone to use however they would like. The included designs are orders of magnitude smaller and less expensive than the existing state of the art, and they reduce the decompression time by up to 6x. These smaller areas and latencies result in a relatively small reduction in compression ratios: only 13% on average across the tested benchmarks.

Si le phénomène bullaire reste le primum movens à l’origine de l’obstruction vasculaire lors de la décompression, les plaquettes sanguines jouent un rôle déterminant dans la physiopathologie de l’accident de décompression (ADD). L’objectif de ces travaux était d’étudier les mécanismes à l’origine de cette agrégation plaquettaire induit par le phénomène bullaire. La première étape a permis de valider un modèle animal d’ADD chez le rat et de confirmer que le degré d’agrégation constituait un indice fiable de sévérité de l’ADD. La seconde a eu pour but d’étudier différents marqueurs spécifiques de l’activation plaquettaire. La troisième étape a étudié les effets de différents anti-agrégants plaquettaires administrés avant l’exposition. Les résultats confirment que le clopidogrel, un inhibiteur spécifique des récepteurs à l’ADP, a un effet protecteur sur le risque de survenue et la sévérité des ADD en réduisant l’importance de l’agrégation plaquettaire. Ces résultats sont en faveur d’un mécanisme d’agrégation ADP-dépendant conséquence des interactions entre les plaquettes et les bulles circulantes. La génération de thrombine, un autre puissant agoniste plaquettaire, interviendrait dans la genèse d’un état pro-thrombotique loco-régional conséquence des lésions induites par le passage des bulles au contact de l’endothélium vasculaire. Enfin, les résultats montrent le rôle joué par les micro-particules dans la diffusion à distance de cet état pro-thrombotique. Des études à venir devront confirmer l’intérêt d’une utilisation du clopidogrel dans le traitement de l’ADD ainsi que le rôle de l’oxyde nitric, de la prostacycline PGI2 et du shear-stress dans l’effet protecteur des vibrations et de l’exercice physique sur le risque de survenue de l’ADD en réduisant l’agrégation plaquettaire et en optimisant la cinétique d’élimination des bulles circulantes. / If bubble-induced mechanical obstruction of vessels is the central event during decompression, blood platelets play a key role in the pathogenesis of decompression sickness (DCS). But bubble-induced platelet aggregation (BIPA) mechanisms are unknown. In a previous study, we highlighted a post-dive decrease in platelet count in divers. The aims of this study was therefore to validate an experimental model of DCD in rat to clarify relationship between blood platelet and bubble formation, investigate platelet activation by measuring different platelet markers, and to study the effects of different antithrombotic pre-treatments. First, the results clearly indicate that clopidogrel, a powerful ADP-inhibitor, has a protective effect on decompression risk improving significantly DCS outcome and reducing DCS severity. The results point to the predominant involvement of the ADP release in the BIPA mechanism. Second, we showed the participation of thrombin generation, a powerful platelet agonist, in the thrombotic event. If local BIPA seems to be the direct consequence of bubble-blood component interactions in vascular bed, the regional thrombotic event could be the consequence of bubble-induced vessel wall injury with a key role played by micro-particles in the general extend. Further human studies should be aimed at demonstrating that clopidogrel can offer a benefit as an adjuvant in DCS treatment and the role played by nitric oxyd and prostacyclin in the protective effect of vibrations and physical exercise on DCS risk reducing bubble-induced platelet aggregation

A falha por descompressão rápida de gás (Rapid Gas Decompression, RGD) de o’rings elastoméricos assume a forma de trincas, bolhas e cisões, apresentandose após a queda da pressão à qual o selo está exposto. A resistência à RGD tem um papel fundamental nas especificações dos materiais elastoméricos para a indústria do petróleo e gás. No presente trabalho foi desenvolvida uma bancada para ensaios de qualificação de o’rings elastoméricos para testes de resistência por RGD seguindo a norma ISO 23936-2. Para avaliar o desempenho da bancada, quatro ensaios foram realizados utilizando o’rings comerciais com e sem certificado para RGD. A análise das curvas de ensaio evidencia que os parâmetros de ensaio foram atingidos satisfatoriamente. Além disso, taxas lineares de descompressão foram atingidas utilizando um método manual, não obstante uma relevante proposta de melhora é apresentada. / Rapid gas decompression (RGD) damage of elastomeric o’ring seals is the structural failure in the form of blistering, internal cracking and splitting caused upon the release of the pressure the seals are exposed to. RGD resistance plays a key role in the specifications of these components for the oil & gas industry. During this work a test bench was developed for qualification of o’rings RGD resistance according to wellknown international standard ISO 23936-2. In order to evaluate the test bench’s performance, four tests were carried out using o’rings with and without RGD qualification certificates. Analysis of test curves show that test parameters were attained satisfactorily. Furthermore, adequate linear decompression processes were achieved using a manual method, nonetheless a relevant improvement is proposed.

A falha por descompressão rápida de gás (Rapid Gas Decompression, RGD) de o’rings elastoméricos assume a forma de trincas, bolhas e cisões, apresentandose após a queda da pressão à qual o selo está exposto. A resistência à RGD tem um papel fundamental nas especificações dos materiais elastoméricos para a indústria do petróleo e gás. No presente trabalho foi desenvolvida uma bancada para ensaios de qualificação de o’rings elastoméricos para testes de resistência por RGD seguindo a norma ISO 23936-2. Para avaliar o desempenho da bancada, quatro ensaios foram realizados utilizando o’rings comerciais com e sem certificado para RGD. A análise das curvas de ensaio evidencia que os parâmetros de ensaio foram atingidos satisfatoriamente. Além disso, taxas lineares de descompressão foram atingidas utilizando um método manual, não obstante uma relevante proposta de melhora é apresentada. / Rapid gas decompression (RGD) damage of elastomeric o’ring seals is the structural failure in the form of blistering, internal cracking and splitting caused upon the release of the pressure the seals are exposed to. RGD resistance plays a key role in the specifications of these components for the oil & gas industry. During this work a test bench was developed for qualification of o’rings RGD resistance according to wellknown international standard ISO 23936-2. In order to evaluate the test bench’s performance, four tests were carried out using o’rings with and without RGD qualification certificates. Analysis of test curves show that test parameters were attained satisfactorily. Furthermore, adequate linear decompression processes were achieved using a manual method, nonetheless a relevant improvement is proposed.

A falha por descompressão rápida de gás (Rapid Gas Decompression, RGD) de o’rings elastoméricos assume a forma de trincas, bolhas e cisões, apresentandose após a queda da pressão à qual o selo está exposto. A resistência à RGD tem um papel fundamental nas especificações dos materiais elastoméricos para a indústria do petróleo e gás. No presente trabalho foi desenvolvida uma bancada para ensaios de qualificação de o’rings elastoméricos para testes de resistência por RGD seguindo a norma ISO 23936-2. Para avaliar o desempenho da bancada, quatro ensaios foram realizados utilizando o’rings comerciais com e sem certificado para RGD. A análise das curvas de ensaio evidencia que os parâmetros de ensaio foram atingidos satisfatoriamente. Além disso, taxas lineares de descompressão foram atingidas utilizando um método manual, não obstante uma relevante proposta de melhora é apresentada. / Rapid gas decompression (RGD) damage of elastomeric o’ring seals is the structural failure in the form of blistering, internal cracking and splitting caused upon the release of the pressure the seals are exposed to. RGD resistance plays a key role in the specifications of these components for the oil & gas industry. During this work a test bench was developed for qualification of o’rings RGD resistance according to wellknown international standard ISO 23936-2. In order to evaluate the test bench’s performance, four tests were carried out using o’rings with and without RGD qualification certificates. Analysis of test curves show that test parameters were attained satisfactorily. Furthermore, adequate linear decompression processes were achieved using a manual method, nonetheless a relevant improvement is proposed.