In this dissertation, I enumerate several privacy problems in online social networks (OSNs) and describe a system called Footlights that addresses them. Footlights is a platform for distributed social applications that allows users to control the sharing of private information. It is designed to compete with the performance of today's centralised OSNs, but it does not trust centralised infrastructure to enforce security properties. Based on several socio-technical scenarios, I extract concrete technical problems to be solved and show how the existing research literature does not solve them. Addressing these problems fully would fundamentally change users' interactions with OSNs, providing real control over online sharing. I also demonstrate that today's OSNs do not provide this control: both user data and the social graph are vulnerable to practical privacy attacks. Footlights' storage substrate provides private, scalable, sharable storage using untrusted servers. Under realistic assumptions, the direct cost of operating this storage system is less than one US dollar per user-year. It is the foundation for a practical shared filesystem, a perfectly unobservable communications channel and a distributed application platform. The Footlights application platform allows third-party developers to write social applications without direct access to users' private data. Applications run in a confined environment with a private-by-default security model: applications can only access user information with explicit user consent. I demonstrate that practical applications can be written on this platform. The security of Footlights user data is based on public-key cryptography, but users are able to log in to the system without carrying a private key on a hardware token. Instead, users authenticate to a set of authentication agents using a weak secret such as a user-chosen password or randomly-assigned 4-digit number. The protocol is designed to be secure even in the face of malicious authentication agents.

Memory models typically assume that recall is a two-stage process with learning affecting both processes to the same degree. This equal learning assumption is difficult to reconcile with studies of the 'testing effect', which reveal different forgetting rates following learning from test practice versus learning from restudy. Here we present a new memory model, termed Primary and Convergent Retrieval (PCR) that assumes successful recall leads to a selective enhancement for the second stage of recall (Convergent Retrieval). We applied this model to existing testing effect data. In two new experiments, we confirmed novel predictions of the PCR model for transfer between retrieval cues and for recall latencies. This is the first formally specified model of the testing effect and it has broad implications for the nature of learning and retrieval.

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The College Adjustment Scales (CAS) are a multidimensional psychological measure designed specifically for use in college and university settings. The purpose of this study was to assess the ability of the College Adjustment Scales (CAS) to function as outcome measures in university counseling centers. Study 1 assessed the ability of the CAS to track change following brief therapy using a nonequivalent control group design. Study 2 assessed the convergent validity of the CAS by correlating two of the nine CAS scales with two established measures. The results of a three-factor MANOV A revealed that the CAS were able to track change very well for undergraduate students. Results for graduate students showed that three of the CAS scales tracked change quite well, two scales did not track change, and four scales did not track change for graduate males. Convergent validity results were mixed for the two scales assessed. The Self-Esteem scale was determined to be a fairly good measure of global self-esteem. The CAS Anxiety scale did not correlate well with an instrument that is a good measure of anxiety characterized by physiological symptoms. Recommendations for future research are discussed.

Final publication is available at http://www.plosgenetics.org/article/related/info%3Adoi%2F10.1371%2Fjournal.pgen.1005802 / 京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19627号 / 医博第4134号 / 新制||医||1016(附属図書館) / 32663 / 京都大学大学院医学研究科医学専攻 / (主査)教授 萩原 正敏, 教授 松田 秀一, 教授 瀬原 淳子 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Vertebrate development is regulated by cellular communication by mechanisms of cell fate and cell behavior. These crucial mechanisms are regulated by cellular signaling and in the case of cell fate, cellular signaling results in transcription of developmentally important genes. Communication between cells can also result in regulation of cell behavior by acting on cytoskeletal elements rather than nuclear factors. One of the cellular signals that regulate both cell fate and cell behavior is the family of Wnt signaling molecules. Wnt5a is one of 19 Wnt molecules and has been previously demonstrated to play critical roles in many important processes in embryonic development as well tumor suppression. Despite many studies that lend credence to a pathway that regulates cell behavior for Wnt5a rather than cell fate, the identity of the pathway(s) Wnt5a impinges upon remains unclear. Despite the possibility of Wnt5a signaling through multiple pathways, here, focus is given to the non-canonical Wnt signaling pathway, a pathway that regulates cell behavior, also known as the Wnt/Planar Cell Polarity (PCP) pathway. The involvement of Wnt5a in the Wnt/PCP pathway was demonstrated with a genetic approach: crossing Wnt5a heterozygous mice with mice heterozygous for a component of the Wnt/PCP pathway to uncover genetic interactions in vivo. Hence, Wnt5a X Looptail (Lp) (Wnt/PCP) heterozygous crosses have been performed. Double heterozygotes for this intercross did not exhibit a decrease in viable progeny as compared to the decreased numbers of Lp heterozygotes. These observations demonstrated a lack of genetic interaction between Wnt5a and the PCP pathway. Wnt5a mutants possess phenotypes associated with deficits in the Wnt/PCP pathway, namely convergent extension (CE) defects and neural tube closure defects. However, upon further investigation of the increased penetrance of craniorachischisis in Wnt5a-/-;Lp+/-, Wnt5a mutants do not display the characteristic broadening of the neural floor plate commonly associated with Lp-/-. This supports that Wnt5a and PCP signaling are parallel pathways that have converged to regulate different aspects of CE and neural tube closure. Despite the complexity of Wnt5a and its potential involvement in multiple pathways, dissection of this will explain the broad range of phenotypes observed.

No / The results of computational fluid dynamics simulation for convective heat transfer of turbulent flow in a cooled convergent-divergent nozzle are reported. The importance of the heat transfer coefficient is to find the most suitable metals for the nozzle wall as well as its application for producing nano-particles. ansys-icem and ansys-cfx 13.0 are used to mesh and simulate fluid flow in the nozzle, respectively. Effects of grid resolution and different turbulence models on the heat transfer coefficient are investigated. Three turbulence models of k-omega, k-epsilon and shear stress transport are applied to calculate the heat transfer coefficient. Stagnation absolute pressure and temperature are 10.3 bara and 840 K, respectively, the same as those in the experimental work. The heat transfer coefficients obtained from simulation are compared with the available experimental data in literature to find out the best suitable mesh grid and the turbulence model. Under the selected operating conditions, k-epsilon and k-omega models have shown the best agreement with the experimental data with the average error of 6.5% and 10%, respectively, while shear stress transport under predicts the values with 16% error.

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