Efficient Dynamic Access Analysis Using JavaScript Proxies

JSConTest introduced the notions of effect monitoring and dynamic effect inference for JavaScript. It enables the description of effects with path specifications resembling regular expressions. It is implemented by an offline source code transformation. To overcome the limitations of the JSConTest implementation, we redesigned and reimplemented effect monitoring by taking advantange of JavaScript proxies. Our new design avoids all drawbacks of the prior implementation. It guarantees full interposition; it is not restricted to a subset of JavaScript; it is self-maintaining; and its scalability to large programs is significantly better than with JSConTest. The improved scalability has two sources. First, the reimplementation is significantly faster than the original, transformation-based implementation. Second, the reimplementation relies on the fly-weight pattern and on trace reduction to conserve memory. Only the combination of these techniques enables monitoring and inference for large programs.Comment: Technical Repor

Type-based Dependency Analysis for JavaScript

Dependency analysis is a program analysis that determines potential data flow between program points. While it is not a security analysis per se, it is a viable basis for investigating data integrity, for ensuring confidentiality, and for guaranteeing sanitization. A noninterference property can be stated and proved for the dependency analysis. We have designed and implemented a dependency analysis for JavaScript. We formalize this analysis as an abstraction of a tainting semantics. We prove the correctness of the tainting semantics, the soundness of the abstraction, a noninterference property, and the termination of the analysis.Comment: Technical Repor

TreatJS: Higher-Order Contracts for JavaScript

TreatJS is a language embedded, higher-order contract system for JavaScript which enforces contracts by run-time monitoring. Beyond providing the standard abstractions for building higher-order contracts (base, function, and object contracts), TreatJS's novel contributions are its guarantee of non-interfering contract execution, its systematic approach to blame assignment, its support for contracts in the style of union and intersection types, and its notion of a parameterized contract scope, which is the building block for composable run-time generated contracts that generalize dependent function contracts. TreatJS is implemented as a library so that all aspects of a contract can be specified using the full JavaScript language. The library relies on JavaScript proxies to guarantee full interposition for contracts. It further exploits JavaScript's reflective features to run contracts in a sandbox environment, which guarantees that the execution of contract code does not modify the application state. No source code transformation or change in the JavaScript run-time system is required. The impact of contracts on execution speed is evaluated using the Google Octane benchmark.Comment: Technical Repor

Contact Surface Area: A Novel Signal for Heart Rate Estimation in Smartphone Videos

We consider the problem of smartphone video-based heart rate estimation, which typically relies on measuring the green color intensity of the user's skin. We describe a novel signal in fingertip videos used for smartphone-based heart rate estimation: fingertip contact surface area. We propose a model relating contact surface area to pressure, and validate it on a dataset of 786 videos from 62 participants by demonstrating a statistical correlation between contact surface area and green color intensity. We estimate heart rate on our dataset with two algorithms, a baseline using the green signal only and a novel algorithm based on both color and area. We demonstrate lower rates of substantial errors (>10 beats per minute) using the novel algorithm (4.1%), compared both to the baseline algorithm (6.4%) and to published results using commercial color-based applications (>6%)

Symbolic Solving of Extended Regular Expression Inequalities

This paper presents a new solution to the containment problem for extended regular expressions that extends basic regular expressions with intersection and complement operators and consider regular expressions on infinite alphabets based on potentially infinite character sets. Standard approaches deciding the containment do not take extended operators or character sets into account. The algorithm avoids the translation to an expression-equivalent automaton and provides a purely symbolic term rewriting systems for solving regular expressions inequalities. We give a new symbolic decision procedure for the containment problem based on Brzozowski's regular expression derivatives and Antimirov's rewriting approach to check containment. We generalize Brzozowski's syntactic derivative operator to two derivative operators that work with respect to (potentially infinite) representable character sets.Comment: Technical Repor

Mechanically tuned conductivity in piezoelectric semiconductors

In this work, different ZnO interfaces were studied with respect to their performance in piezotronic applications. The electrical conductivity across metal – ZnO Schottky contacts as well as varistor-type ZnO-ZnO interfaces was measured as a function of uniaxial compressive stress. In addition, temperature-dependent measurements of the direct piezoelectric response of ZnO single crystals with and without the existence of a highly resistive space charge region were performed. The electrical conductivity across potential barriers at metal – ZnO Schottky contacts on either the Zn- or O-terminated surface of a bulk ZnO single crystal was measured under increasing uniaxial compressive stress. The generation of negative or positive piezoelectric polarization charges was found to increase or decrease the Schottky barrier height depending on the sign of the piezoelectric charge. The evolution of potential barrier height with increasing amount of positive piezoelectric charge was determined from I-V deconvolution techniques and allowed a comparison of the experimental data with different theoretical models. Measurements were performed on bulk ZnO single crystals to overcome shortcomings in existing literature in which studies are mainly based on metal-ZnO nanostructure contacts. Thereby the fundamental concept of the piezotronic effect could be confirmed and the current understanding is extended. Direct piezoelectric measurements on bulk ZnO single crystals with and without the existence of a highly resistive space charge region were performed as a function of temperature and loading frequency. A decreasing number of free charge carriers with decreasing temperature revealed a correlation between free charge carrier density and screening of the piezoelectric potential. An increase in attainable piezoelectric polarization with decreasing temperature was evident for the crystals with and without space charge region. In addition, the generation of a highly resistive space charge region in the vicinity of a Schottky contact allowed a measurement of the piezoelectric potential already at room temperature and for low loading frequencies. The shift of the attainable piezoelectric response to higher temperatures and lower loading frequencies due to the existence of a depletion region is of great importance for piezotronic applications. Besides metal-ZnO contacts, ZnO bicrystal interfaces were prepared by epitaxial solid-state transformation. The preparation process allows for both, a defined orientation of the polarization vector as well as tailoring of the defect state density at the ZnO-ZnO interface. Consequently, the interaction between positive and negative piezoelectric charges and the electrostatic potential barrier at the bicrystal interface could be systematically investigated. Stress-dependent conductivity measurements revealed a decreasing barrier for positive piezoelectric charges and an increasing potential barrier for negative piezoelectric charges. The magnitude of this coupling was compared to theoretical models as well as to experimental results obtained on metal-ZnO Schottky contacts. In comparison to the Schottky contact, potential barriers at ZnO-ZnO interfaces featured a much higher stress sensitivity. For the lowering case by positive piezoelectric charges an almost complete extinction of the electrostatic potential barrier could be achieved. The obtained results demonstrate the potential of individual ZnO-ZnO interfaces as promising alternative to metal-ZnO Schottky contacts in future piezotronic applications. By interrupting the epitaxial solid-state transformation process at different times during the high temperature treatment, single crystal – polycrystal structures with varying amount of remaining polycrystalline material in between two well oriented single crystals were prepared. Temperature-dependent conductivity measurements were applied to determine the influence of the high temperature treatment on the potential barrier height at varistor-type interfaces during bicrystal fabrication by epitaxial solid-state transformation. Furthermore, stress-dependent I-V measurements revealed extremely high stress sensitivities for structures with intermediate times of high temperature treatment. These measurements close the gap between piezotronic systems based on polycrystalline varistor ceramics and individual bicrystal interfaces and reveal the future potential of microstructural engineering for the development of varistor-based piezotronic devices

Prostate lymphoscintigraphy and radio-guided surgery for sentinel lymph node identification in prostate cancer - Technique and results of the first 350 cases

Introduction: Having in mind the promising results of lymphoscintigraphy and intraoperative gamma probe application for the detection of sentinel lymph nodes (SLN) in malignant melanoma, breast and penis cancer, we tried to identify the SLN in prostate cancer by applying a comparable technique. Materials and Method. 350 patients with prostate cancer were examined after providing informed consent. The day before pelvic lymphadenectomy technetium-99m nanocolloid was transrectally injected into the prostate under ultrasound guidance. A single central application was done per prostate lobe in most cases. Activity attained 90400 MBq, and the total injected volume was about 2-3 ml. Hereafter, lymphoscintigraphy was carried out. Those lymph nodes having been identified as SLN by means of gamma probe detection and lymphoscintigraphy were removed intraoperatively. Later, most of the cases had different types of pelvic lymphadenectomy. SLN received serial sections and immunohistochemistry, non-SLN step sections. Results: 335 patients showed at least 1 SLN in lymphoscintigraphy. 24.7% had lymph node metastases. In 2 patients, metastases in non-SLN were found without at least one SLN being affected (false-negative patient). Conclusion:Our experience suggests that the SLN identification is not only feasible in breast cancer and malignant melanoma, but also in prostate cancer with a comparable technique. Copyright (C) 2003 S. Karger AG, Basel