Field-based liquefaction evaluation procedures include the stress-based, strain-based, and energybased based approaches. The existence of a volumetric threshold shear strain, γtv, under which there is no development of excess pore pressures, and the unique relationship between pore pressure ratio and cyclic shear strain, γc, make a compelling argument for using a strain-based approach. However, the cyclic strain approach has not yet been standardized for field evaluations. The primary objective of this thesis is to use published databases of 415 shear-wave velocity and 230 Standard Penetration Test liquefaction field case histories to investigate the performance of the cyclic strain approach for the evaluation of initial liquefaction relative to the cyclic stress approach. Additionally, the concept of the γtv is expressed in terms of the peak ground surface acceleration and defined as the threshold amax. Computing (amax)t could provide a fast and simple evaluation for initial liquefaction, where no liquefaction is expected for a minimum computed (amax)t determined from the case histories. The variant of the strain-based procedure proposed herein avoids the direct need for laboratory cyclic testing by employing pore pressure generation models that are functions of cyclic shear strain, number of equivalent cycles, and relative density to predict initial liquefaction. The results from the proposed procedure are compared with those of the stress-based approach to determine which better matches the field observations of the case histories. It was found that the cyclic strain approach resulted in 70% to 77% correct predictions. In contrast, the cyclic stress approach yielded 87% to 90% correct predictions. The reasons why the predictions were not always correct with the cyclic strain approach are due to inherent limitations of the cyclic strain approach. Most significantly, an inherent and potentially fatal limitation of the strain-based procedure is it ignoring the softening of the soil stiffness due to excess pore pressure in representing the earthquake loading in terms of γc and neqγ. / Master of Science / Earthquakes can cause heavy damage when they occur. One of the ways in which this happens is when the earthquake shaking causes the soil to behave like a liquid. This is the phenomenon known as liquefaction. An example of liquefaction is a person sinking in quicksand. Relating this to earthquakes, liquefaction can be thought of as a building sinking in quicksand that formed as a consequence of earthquake shaking. Destructive cases of liquefaction have been reported in almost all major earthquakes. When cases of liquefaction are properly documented, they can provide information that will help engineers and scientists assess the efficacy of existing liquefaction evaluation procedures and/or to develop new procedures. There are different methods to evaluate the occurrence of liquefaction, with the cyclic stress approach being the most widely used. This study assesses the efficacy of an alternative approach to see if it yields better predictions of liquefaction triggering than the cyclic stress approach. The approach under consideration is called the cyclic strain approach. To examine the effectiveness of the cyclic strain approach, sites that experienced liquefaction in the past were analyzed to see if the predictions made with the approach matched the past field observations. Due to potential shortcomings in implementing the strain based procedure, as well as inherent limitations of the procedure, the strain-based procedure yielded predictions that were inferior to the more widely used stress-based procedure.

No / Vascular relaxation induced by 3′,5′-cyclic adenosine monophosphate (cAMP) is both endothelium-dependent and endothelium-independent, although the underlying signaling pathways are not fully understood. Aiming to uncover potential mechanisms, we performed contraction–relaxation experiments on endothelium-denuded and intact rat aorta rings and measured NO levels in isolated human endothelial cells using single cell fluorescence imaging. The vasorelaxant effect of forskolin, an adenylyl cyclase activator, was decreased after selective inhibitor of protein kinase A (PKA), a cAMP-activated kinase, or L-NAME, an endothelial nitric oxide synthase (eNOS) inhibitor, only in intact aortic rings. Both selective activation of PKA with 6-Bnz-cAMP and exchange protein directly activated by cAMP (Epac) with 8-pCPT-2′–O-Me-cAMP significantly relaxed phenylephrine-induced contractions. The vasorelaxant effect of the Epac activator, but not that of the PKA activator, was reduced by endothelium removal. Forskolin, dibutyryl cAMP (a cAMP analogue), 6-Bnz-cAMP and 8-pCPT-2′–O-Me-cAMP increased NO levels in endothelial cells and the forskolin effect was significantly inhibited by inactivation of both Epac and PKA, and eNOS inhibition. Our results indicate that the endothelium-dependent component of forskolin/cAMP-induced vasorelaxation is partially mediated by an increase in endothelial NO release due to an enhanced eNOS activity through PKA and Epac activation in endothelial cells. / This work was supported by grants from the Ministerio de Ciencia e Innovación, Spain (SAF2010-22051) and Xunta de Galicia, Spain (INCITE08PXIB203092PR)

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25308号 / 工博第5267号 / 新制||工||2002(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 佐藤 啓文, 教授 跡見 晴幸, 教授 梶 弘典 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Ph. D.

Reinforced Concrete (RC) structures are common in earthquake-prone areas. During an earthquake, the steel reinforcement is subjected to cyclic strain histories which lead to inelastic response. In the case of rare, strong earthquakes, inelastic buckling and even rupture due to low-cycle fatigue can also occur. The understanding and characterization of the performance of RC structures under earthquake hazards requires the accurate simulation of the inelastic hysteretic behavior of steel reinforcement by means of appropriate constitutive models. Several uniaxial material models have been developed for reinforcing steel. Existing material models sacrifice efficiency for accuracy or vice versa. Conceptually simple and numerically efficient models do not accurately capture the hysteretic response and ignore rupture or buckling. On the other hand, more refined material models are characterized by iterative stress update procedures which can significantly increase the computational cost of an analysis. Additionally, experience suggests that refined models attempting for the effect of inelastic buckling tend to lead to numerical convergence problems in the stress update procedure. The goal of the present study is the formulation and implementation of an accurate and computationally efficient constitutive model for steel reinforcement under cyclic loading. A previously developed model, capable of capturing the inelastic hysteretic response of reinforcing steel in the absence of buckling and rupture, is used as a starting point in this study. The model is enhanced by replacing its original, iterative stress update procedure with an equally accurate, non-iterative one. Additionally, the model is enhanced to capture the effects of inelastic buckling and of rupture. The accuracy of the model and the efficiency of the non-iterative stress update algorithm are demonstrated by means of validation analyses. / Master of Science

Soil liquefaction during earthquakes is a phenomenon that can cause tremendous damage to structures such as bridges, roads, buildings, and pipelines. The objective of this research is to develop an energy-based approach for evaluating the potential for liquefaction triggering. The current state-of-practice for the evaluation of liquefaction triggering is the "simplified" stressbased framework where resistance to liquefaction is correlated to an in situ test metric (e.g., normalized standard penetration test N-value, N1,60cs, normalized cone penetration tip resistance, qc1Ncs, or normalized small strain shear wave velocity, Vs1). Although rarely used in practice, the strain-based procedure is commonly cited as an attractive alternative to the stress-based framework because excess pore pressure generation (and, in turn, liquefaction triggering) is more directly related to strains than stresses. However, the method has some inherent and potentially fatal limitations in not being able to appropriately define both the amplitude and duration of the induced loading in a total stress framework. The energy-based method proposed herein builds on the merits of both the stress- and strain-based procedures, while circumventing their inherent limitations. The basis of the proposed energy-based approach is a macro-level, low cycle fatigue theory in which dissipated energy (or work) per unit volume is used as the damage metric. Because dissipated energy is defined by both stress and strain, this energy-based method brings together stress- and strain-based concepts. To develop this approach, a database of liquefaction and nonliquefaction case histories was assembled for multiple in situ test metrics. Dissipated energy per unit volume associated with each case history was estimated and a family of limit-state curves were developed using maximum likelihood regression for different in situ test metrics defining the amount of dissipated energy required to trigger liquefaction. To ensure consistency between these limit-state curves and laboratory data, a series of cyclic tests were performed on samples of sand. These laboratory-based limit-state curves were reconciled with the field-based limit-state curves using a consistent definition of liquefaction. / Doctor of Philosophy / Soil liquefaction during earthquakes is a phenomenon that can cause tremendous damage to structures such as bridges, roads, buildings, and pipelines. The objective of this research is to develop an energy-based approach for evaluating the potential for liquefaction triggering. Current procedures to evaluate liquefaction triggering include stress-based and strain-based procedures. However, these procedures have some inherent and potentially fatal limitations. The energy-based method proposed herein builds on the merits of both the stress- and strain-based procedures, while circumventing their inherent limitations. The proposed energy-based approach uses dissipated energy (or work) per unit volume to evaluate the potential for liquefaction. Because dissipated energy is defined by both stress and strain, this energy-based method brings together stress- and strain-based concepts. To develop this approach, a database of case histories in which liquefaction was either observed or not observed was assembled. Dissipated energy per unit volume associated with each case history was estimated and a family of relationships was regressed to define the amount of dissipated energy required to trigger liquefaction. Results from a series of cyclic laboratory tests performed on samples of sand were reconciled with the field-based relationships using a consistent definition of liquefaction. This research proposes a method that is based on a robust mechanistic framework that will make it easier to evaluate liquefaction for circumstances that are not well represented in current liquefaction evaluation procedures. The components of the proposed energy-based procedure are developed consistently and are presented in such a way that this procedure can be readily adopted by practitioners who are already familiar with existing liquefaction evaluation procedures. The broader impacts of this work will help to minimize losses from earthquakes by improving the way engineers evaluate liquefaction.

An integral part in the field of soft robotics is the ability to tune material stiffness. This adaptability is inspired from the natural ability of organisms to alter their stiffness to perform various tasks. The most common approach to mimic this ability is through granular jamming, where a granular material switches between fluid and solid-like states based on density alterations caused by vacuum pressure. In this thesis, a cuboid composite material is introduced, containing internal cylindrical chambers arranged in distinct matrix configurations (2x2, 3x3, and 4x4). A custom-designed pneumatic system enables precise control over this transition, allowing for selective modulation of stiffness across different regions of the material by applying differing pressures to specific regions of the composite material. This approach not only allows for rapid changes in stiffness, but enables stiffness to be adjusted uniformly throughout the material or localized to specific areas. This approach also allows for predictive modeling of granular composites to better understand its mechanical response under differential pressures. / Master of Science / Soft robotics is a field that mimics the flexibility of living organisms such as octopi, geckos, etc., to create machines that can adapt to various tasks and environments. One of the unique features of these robots is their ability to change how stiff or soft they are, much like an octopus can alter the rigidity of its tentacles when gripping an object. A method called granular jamming is at the heart of this technology. It involves using materials made up of tiny particles, like coffee grounds or sand, that can switch between flowing freely like a liquid and locking together like a solid. This switch is controlled by changing the space between the particles, usually by sucking out air to pack them tightly. The research in this thesis introduces a special type of material designed as a rubber-like cube containing multiple small cylindrical compartments arranged in different patterns, such as 2x2 or 4x4 grids. Each compartment is filled with these unique particle-based materials, in this particular instance, the material is coffee grounds. We use a specially designed air pressure system to selectively adjust the air pressure in these compartments, making the material stiffer or softer as needed. This allows us to control the stiffness with great precision, either uniformly across the whole block or in specific areas. The experiments conducted in this thesis show a clear pattern: the more air pressure is decreased (making it more negative), the stiffer the material becomes. This finding confirms that granular jamming is a promising strategy for rapidly and precisely controlling material stiffness for future soft robotic applications.

No description available.

The application of microanalytical techniques was used to elucidate the enzyme profiles of adenylate cyclase and cAMP-dependent protein kinase within a series of malignant and benign human mammary tumors. The methods allow for determination of enzyme activity in histologically-confirmed neoplastic areas within individual tumors which permits comparisons to be made with particle and cytosolic fractions prepared from mammary tumors. The potential for cAMP formation by adenylate cyclase and mediation of cAMP effects by cAMP-dependent protein kinase were studied to provide information on the levels of enzyme activity and the extent and type(s) of regulation of these enzymes in a cell-free system. Adenylate cyclase (AC) activity levels were higher in benign than malignant tumor tissue on a dry wt basis. A 2 to 3-fold activation by Gpp(NH)p and a 4 to 5-fold stimulation by fluoride was demonstrated. Calmodulin activation of tumor-associated AC was not observed. Membrane-associated AC could be stimulated by PGE₁, prolactin and TSH. Thermal stability studies suggested that AC from malignant tissue was more labile than that from benign tissue. Cyclic AMP-dependent protein kinase associated with human mammary tumors was primarily type II kinase based upon DEAE-Sephacel chromatography and demonstrated a preference for histone VS as a substrate. Cyclic AMP-dependency was supported by enzyme activation by cAMP, by cAMP binding, and inhibition by protein kinase inhibitors and regulatory subunit. The activity ratio was slightly higher in benign than malignant tissue. Histone kinase activity was higher in benign than malignant tumor microsections. Cyclic AMP-binding activity was higher in malignant than benign tumor cytosolic fractions, although cAMP affinity was similar. Catalytic subunit was prepared from tumor histone kinase by cAMP affinity chromatography. Reassociation of tumor catalytic subunit and heterologous regulatory subunit was shown. A cAMP-independent casein kinase was also partially characterized in human mammary tumors. Endogenous phosphorylation in tumor cytosolic fractions was examined and polypeptides identified which showed phosphorylation differences in the presence of cAMP. / Ph. D.

Cyclic AMP functions as the chemotactic signal during aggregation of single-celled amoebae of the cellular slime mold Dictyostelium discoideum. Evidence suggests that cyclic AMP also acts as a regulatory molecule during Dictyostelium multicellular differentiation. Biochemical characterization of adenylate cyclase, the cyclic AMP synthetic enzyme, was accomplished using a sensitive radioimmunoassay. The enzyme was found to be pellet-bound. The non-ionic detergents, Triton X-100 and Lubrol PX, were not effective for solubilizing this activity. Magnesium or manganese could serve as the required divalent cation, with the Mn-supported activity over 4-fold greater than the Mg-supported activity. Typical mammalian adenylate cyclase modulators such as guanyl nucleotides, fluoride, and cholera toxin did not activate the Dictyostelium enzyme. Calcium, in conjunction with its protein receptor calmodulin, did not appear to regulate the enzyme. An endogenous extracellular, heat-stable substance was found to inhibit Dictyostelium adenylate cyclase. By use of ultramicrotechniques adenylate cyclase activity was localized in the pre-spore cells of the culminating individual with no activity detected in the pre-stalk region. Lack of detectable activity in the pre-stalk cells may be due to a masking by the endogenous inhibitor. An increasing gradient of activity was found in the pre-spore mass with activity increasing from the uppermost area to the base. No striking localization was seen prior to the pre-culmination stage of development. Two peaks in cyclic AMP levels, as measured in individuals were found during development. One coincided with aggregation, the other occurred at the culmination stage. A gradient of cyclic AMP within the culminating individual paralleled the gradient of adenylate cyclase activity. The tip of the individual had greater levels of cyclic AMP than the middle pre-spore region, and the upper stalks had higher levels than the lower stalks. These data indicate an enzymatic potential for establishing a gradient of cyclic AMP. At the culmination stage of development this molecule could act to direct the chemotactic movements of the pre-stalk cells as well as provide positional information for the terminal differentiation of the pre-spore cells into mature spores. / Ph. D.