Novel EIS postprocessing algorithm for breast cancer diagnosis

A new postprocessing algorithm was developed for the diagnosis of breast cancer using electrical impedance scanning. This algorithm automatically recognizes bright focal spots in the conductivity map of the breast. Moreover, this algorithm discriminates between malignant and benign/normal tissues using two main predictors: phase at 5 kHz and crossover frequency, the frequency at which the imaginary part of the admittance is at its maximum. The thresholds for these predictors were adjusted using a learning group consisting of 83 carcinomas and 378 benign cases. In addition, the algorithm was verified on an independent test group including 87 carcinomas, 153 benign cases and 356 asymptomatic cases. Biopsy was used as gold standard for determining pathology in the symptomatic cases. A sensitivity of 84% and a specificity of 52% were obtained for the test group.     

Sniffing the Unique “Odor Print” of Non‐Small‐Cell Lung Cancer with Gold Nanoparticles

A highly sensitive and fast‐response array of sensors based on gold nanoparticles, in combination with pattern recognition methods, can distinguish between the odor prints of non‐small‐cell lung cancer and negative controls with 100% accuracy, with no need for preconcentration techniques. Additionally, preliminary results indicate that the same array of sensors might serve as a better tool for understanding the biochemical source of volatile organic compounds that might occur in cancer cells and appear in the exhaled breath, as compared to traditional spectrometry techniques. The reported results provide a launching pad to initiate a bedside tool that might be able to screen for early stages of lung cancer and allow higher cure rates. In addition, such a tool might be used for the immediate diagnosis of fresh (frozen) tissues of lung cancer in operating rooms, where a dichotomic diagnosis is crucial to guide surgeons.     

Selective Quantitative Analysis and Interval Model Checking: Verifying Different Facets of a System

In this work we propose a verification methodology consisting of selective quantitative timing analysis and interval model checking. Our methods can aid not only in determining if a system works correctly, but also in understanding how well the system works. The selective quantitative algorithms compute minimum and maximum delays over a selected subset of system executions. A linear-time temporal logic (LTL) formula is used to select either infinite paths or finite intervals over which the computation is performed. We show how tableau for LTL formulas can be used for selecting either paths or intervals and also for model checking formulas interpreted over paths or intervals.To demonstrate the usefulness of our methods we have verified a complex and realistic distributed real-time system. Our tool has been able to analyze the system and to compute the response time of the various components. Moreover, we have been able to identify inefficiencies that caused the response time to increase significantly (about 50%). After changing the design we not only verified that the response time was lower, but were also able to determine the causes for the poor performance of the original model using interval model checking.     

Vacuity detection in temporal model checking

One of the advantages of temporal-logic model-checking tools is their ability to accompany a negative answer to the correctness query by a counterexample to the satisfaction of the specification in the system. On the other hand, when the answer to the correctness query is positive, most model-checking tools provide no witness for the satisfaction of the specification. In the last few years there has been growing awareness as to the importance of suspecting the system or the specification of containing an error also in the case model checking succeeds. The main justification of such suspects are possible errors in the modeling of the system or of the specification. Many such errors can be detected by further automatic reasoning about the system and the environment. In particular, Beer et al. described a method for the detection of vacuous satisfaction of temporal logic specifications and the generation of interesting witnesses for the satisfaction of specifications. For example, verifying a system with respect to the specification ϕ=AG(reqAFgrant) (“every request is eventually followed by a grant”), we say that ϕ is satisfied vacuously in systems in which requests are never sent. An interesting witness for the satisfaction of ϕ is then a computation that satisfies ϕ and contains a request. Beer et al. considered only specifications of a limited fragment of ACTL, and with a restricted interpretation of vacuity. In this paper we present a general method for detection of vacuity and generation of interesting witnesses for specifications in CTL^*. Our definition of vacuity is stronger, in the sense that we check whether all the subformulas of the specification affect its truth value in the system. In addition, we study the advantages and disadvantages of alternative definitions of vacuity, study the problem of generating linear witnesses and counterexamples for branching temporal logic specifications, and analyze the complexity of the problem. Published online: 22 January 2002     

Concurrent reachability games

We consider concurrent two-player games with reachability objectives. In such games, at each round, player 1 and player 2 independently and simultaneously choose moves, and the two choices determine the next state of the game. The objective of player 1 is to reach a set of target states; the objective of player 2 is to prevent this. These are zero-sum games, and the reachability objective is one of the most basic objectives: determining the set of states from which player 1 can win the game is a fundamental problem in control theory and system verification. There are three types of winning states, according to the degree of certainty with which player 1 can reach the target. From type-1 states, player 1 has a deterministic strategy to always reach the target. From type-2 states, player 1 has a randomized strategy to reach the target with probability 1. From type-3 states, player 1 has for every real ε>0$\epsilon >0$ a randomized strategy to reach the target with probability greater than 1−ε$1-\epsilon$. We show that for finite state spaces, all three sets of winning states can be computed in polynomial time: type-1 states in linear time, and type-2 and type-3 states in quadratic time. The algorithms to compute the three sets of winning states also enable the construction of the winning and spoiling strategies.     

Coverage metrics for temporal logic model checking*

In formal verification, we verify that a system is correct with respect to a specification. Even when the system is proved to be correct, there is still a question of how complete the specification is, and whether it really covers all the behaviors of the system. In this paper we study coverage metrics for model checking. Coverage metrics are based on modifications we apply to the system in order to check which parts of it were actually relevant for the verification process to succeed. We introduce two principles that we believe should be part of any coverage metric for model checking: a distinction between state-based and logic-based coverage, and a distinction between the system and its environment. We suggest several coverage metrics that apply these principles, and we describe two algorithms for finding the non-covered parts of the system under these definitions. The first algorithm is a symbolic implementation of a naive algorithm that model checks many variants of the original system. The second algorithm improves the naive algorithm by exploiting overlaps in the variants. We also suggest a few helpful outputs to the user, once the non-covered parts are found.

Fairness and hyperfairness in multi-party interactions

Summary In this paper, a new fairness notion is proposed for languages withmulti-party interactions as the sole interprocess synchronization and communication primitive. The main advantage of this fairness notion is the elimination of starvation occurring solely due to race conditions (i.e., ordering of independent actions). Also, this is the first fairness notion for such languages which is fully adequate with respect to the criteria presented in [2]. The paper defines the notion, proves its properties, and presents examples of its usefulness. Orna Grumberg received her B.Sc. degree, M.Sc. and Ph.D. in the Computer Science Department at the Technion—Israel Institute of Technology. Since 1984 she is a faculty member in the Computer Science Department at the Technion. Her research interests include verification of distributed systems, computer-aided verification, model checking, temporal logics and automata. Paul Attie received a B.A. degree in engineering science from the University of Oxford, and an M.Sc. degree in computer science from the University of London. Since 1986, Paul has been with the Microelectronics and Computer Technology Corporation, where he is currently a member of technical staff. He is also a candidate for the Ph.D. in computer science degree at the University of Texas at Austin. His research interests include temporal logic, fairness, algebraic process theory, formal semantics, and concurrent program verification.The photograph and autobiography of Dr. Nissim Francez were published in Volume 2, Issue No. 4, 1988 on page 226     

Latticed-LTL synthesis in the presence of noisy inputs

In the classical synthesis problem, we are given a specification ψ over sets of input and output signals, and we synthesize a finite-state transducer that realizes ψ: with every sequence of input signals, the transducer associates a sequence of output signals so that the generated computation satisfies ψ. In recent years, researchers consider extensions of the classical Boolean setting to a multi-valued one. We study a multi-valued setting in which the truth values of the input and output signals are taken from a finite lattice, and so is the satisfaction value of specifications. We consider specifications in latticed linear temporal logic (LLTL). In LLTL, conjunctions and disjunctions correspond to the meet and join operators of the lattice, respectively, and the satisfaction values of formulas are taken from the lattice too. The lattice setting arises in practice, for example in specifications involving priorities or in systems with inconsistent viewpoints. We solve the LLTL synthesis problem, where the goal is to synthesize a transducer that realizes the given specification in a desired satisfaction value. For the classical synthesis problem, researchers have studied a setting with incomplete information, where the truth values of some of the input signals are hidden and the transducer should nevertheless realize ψ. For the multi-valued setting, we introduce and study a new type of incomplete information, where the truth values of some of the input signals may be noisy, and the transducer should still realize ψ in the desired satisfaction value. We study the problem of noisy LLTL synthesis, as well as the theoretical aspects of the setting, like the amount of noise a transducer may tolerate, or the effect of perturbing input signals on the satisfaction value of a specification. We prove that the noisy-synthesis problem for LLTL is 2EXPTIME-complete, as is traditional LTL synthesis.     

Another Look at LTL Model Checking

We show how LTL model checking can be reduced to CTL model checking with fairness constraints. Using this reduction, we also describe how to construct a symbolic LTL model checker that appears to be quite efficient in practice. In particular, we show how the SMV model checking system developed by McMillan [16] can be extended to permit LTL specifications. The results that we have obtained are quite surprising. For the specifications which can be expressed in both CTL and LTL, the LTL model checker required at most twice as much time and space as the CTL model checker. We also succeeded in verifying non-trivial LTL specifications. The amount of time and space that is required is quite reasonable. Based on the examples that we considered, it appears that efficient LTL model checking is possible when the specifications are not excessively complicated.