Automated performance attack discovery in distributed system implementations

Security and performance are critical goals for distributed systems. The increased complexity in design, incomplete expertise of developers, and limited functionality of existing testing tools often result in implementations with vulnerabilities and make the debugging process difficult and costly. The deployed vulnerabilities are often exploited by adversaries preventing the system from achieving its design goals. We refer to attacks that slow down the performance of a system as performance attacks. In the past, finding performance attacks has been a painstaking manual process that involved an expert of the target implementation. Given the cost associated with each vulnerability that occurs in the production, there is a need for tools to automatically check that the implementation of a protocol achieves its performance goals with respect to malicious components in the system. In this dissertation, we find performance attacks automatically from implementations of distributed systems. We do not try to show that an implementation is free from all attacks. Our goal is to find attacks and report them to the user in a timely manner. We first investigate how to find attacks automatically from implementations under a simulated environment. A simulated approach, however, has a fundamental limitation in terms of applicable target systems, as certain assumptions are made about languages, operating systems or libraries used. Therefore, we next investigate challenges and requirements to automatically find attacks in implementations of distributed systems under an emulated environment where no limiting assumptions are made

Exploration of Clothing Pressure for Compression Pants Measuring Blood Flow and Velocity

Older adults are staying active in health care and wearing compression products during exercise. Since most available products are developed for young people, it is necessary to develop those suitable for older adults. This study aimed to explore the optimum level of clothing pressure at each part of the lower limb for designing compression pants with positive effects on the blood flow of older adults. Calf sleeve (CS) and thigh sleeve (TS) were produced using the prototype pattern. Three types of CS and TS were produced to three levels of pressure: L1, L2, and L3. Eighteen participants in their 50 s and 60 s were given 12 experimental sleeves: three types of TS and nine combined types of CS and TS. The experimental sleeves were evaluated for pressure, blood flow, blood velocity, and perceived fit. The TS alone at ~ 9.8 mmHg thigh pressure led to increased blood flow and velocity with an outstanding perceived fit. Wearing CS and TS led to a significant increase in blood flow and velocity at the following pressure: ankle ~ 8.3 mmHg, calf ~ 10.5 mmHg, and thigh ~ 9.8 mmHg, with a significantly positive perceived fit. These results are meaningful in providing valuable data for the design of compression pants

Development of Grading Rules Based on Lower Body Type for Leg Guard Production

The purpose of this study was to classify the body types of Korean men based on measurement and suggest a grading rule chart by body type to improve the fit of leg guards

Global stability of Vegas-like TCP flow

A TCP Vegas flow adapts its sending rate to maintain a constant backlog in its path. The stability of nonlinear adaptation has been analyzed based on linearization and only accounted for a small signal. We extend the error model of TCP-like flow to a state-dependent coefficient form with nonlinear state feedback. The nonlinear feedback is here approximated by a saturation function. Using a quadratic Lyapunov function approach, we find a domain of attraction to show that the unique equilibrium point of the system is asymptotically stable in the domain

High adaptability of the omega loop underlies the substrate-spectrum-extension evolution of a class A β-lactamase, PenL

The omega loop in β-lactamases plays a pivotal role in substrate recognition and catalysis, and some mutations in this loop affect the adaptability of the enzymes to new antibiotics. Various mutations, including substitutions, deletions, and intragenic duplications resulting in tandem repeats (TRs), have been associated with β-lactamase substrate spectrum extension. TRs are unique among the mutations as they cause severe structural perturbations in the enzymes. We explored the process by which TRs are accommodated in order to test the adaptability of the omega loop. Structures of the mutant enzymes showed that the extra amino acid residues in the omega loop were freed outward from the enzyme, thereby maintaining the overall enzyme integrity. This structural adjustment was accompanied by disruptions of the internal α-helix and hydrogen bonds that originally maintained the conformation of the omega loop and the active site. Consequently, the mutant enzymes had a relaxed binding cavity, allowing for access of new substrates, which regrouped upon substrate binding in an induced-fit manner for subsequent hydrolytic reactions. Together, the data demonstrate that the design of the binding cavity, including the omega loop with its enormous adaptive capacity, is the foundation of the continuous evolution of β-lactamases against new drugs

Enabling online geospatial isotopic model development and analysis

In recent years, there has been a rapid growth in the amount of environmental data collected over large spatial and temporal scales. It presents unprecedented opportunities for new scientific discovery, while in the same time poses significant challenges to the research community on how to effectively identify and integrate these datasets into their research models and tools. In this paper, we describe the design and implementation of IsoMAP- a gateway for Isoscapes (isotopic landscapes) modeling, analysis and prediction. IsoMAP provides an online workspace that helps researchers access and integrate a number of disparate and diverse datasets, develop Isoscapes models over selected spatio-temporal domains using geo-statistical algorithms, and predict maps for the stable isotope ratios of water, plants, and soils. The IsoMAP system leverages the computation resources available on the TeraGrid to perform geospatial data operations and geostatistical model calculations. It builds on a variety of open source technologies for GIS, geospatial data management and processing, grid computing, and gateway development. The system was successfully used to teach a tutorial in the 2011 conference on the Roles of Stable Isotopes in Water Cycle Research. A post-tutorial survey was conducted. We review the users ’ feedback and present a future development plan based on that

Patient Descriptions of Rectal Effluents May Help to Predict the Quality of Bowel Preparation With Photographic Examples

Background/AimsPrevious studies have suggested a weak correlation between self-reported rectal effluent status and bowel preparation quality. We aim to evaluate whether photographic examples of rectal effluents could improve the correlation between patient descriptions of rectal effluents and bowel preparation quality.MethodsBefore colonoscopy, patients were asked to describe the nature of their last three rectal effluents. Photographic examples of rectal effluents were provided as a reference for scoring. Bowel preparation was subsequently assessed by a single endoscopist using a global preparation assessment scale. Preparation outcomes were grouped into two levels (excellent to good vs. fair to inadequate). Both univariate and multivariate logistic regression models were used to find any association between bowel preparation quality and patient characteristics.ResultsA total of 138 patients completed the questionnaires. The mean age was 56.5±10.4 years. The mean sum of the last three rectal effluent scores was 5.9±2.0. Higher rectal effluent scores (odds ratio [OR], 0.82; P=0.043) and the presence of diverticula (OR, 0.16; P<0.001) were risk factors for suboptimal preparation.ConclusionsPhotographic example-guided patient descriptions of rectal effluents showed a statistically significant association with bowel preparation quality. However, clinical significance seemed to be low. The presence of diverticula was an independent predictive factor for suboptimal bowel preparation quality