Showing papers by "Technion – Israel Institute of Technology published in 1991"

Proofs that yield nothing but their validity or all languages in NP have zero-knowledge proof systems

Abstract: In this paper the generality and wide applicability of Zero-knowledge proofs, a notion introduced by Goldwasser, Micali, and Rackoff is demonstrated. These are probabilistic and interactive proofs that, for the members of a language, efficiently demonstrate membership in the language without conveying any additional knowledge. All previously known zero-knowledge proofs were only for number-theoretic languages in NP fl CONP. Under the assumption that secure encryption functions exist or by using "physical means for hiding information, '' it is shown that all languages in NP have zero-knowledge proofs. Loosely speaking, it is possible to demonstrate that a CNF formula is satisfiable without revealing any other property of the formula, in particular, without yielding neither a satis@ing assignment nor properties such as whether there is a satisfying assignment in which xl = X3 etc. It is also demonstrated that zero-knowledge proofs exist "outside the domain of cryptography and number theory. " Using no assumptions. it is shown that both graph isomorphism and graph nonisomor- phism have zero-knowledge interactive proofs. The mere existence of an interactive proof for graph nonisomorphism is interesting, since graph nonisomorphism is not known to be in NP and hence no efficient proofs were known before for demonstrating that two graphs are not isomorphic.

The dialectics of sketching

Abstract: The generation of architectural form is by definition a creative activity. As a rule, architects engage in intensive, fast, freehand sketching when they first tackle a design task. This study investigated the process of sketching and revealed that by sketching, the designer does not represent images held in the mind, as is often the case in lay sketching, but creates visual displays which help induce images of the entity that is being designed. Sketching partakes in design reasoning and it does so through a special kind of visual imagery. A pattern of pictorial reasoning is revealed which displays regular shifts between two modalities of arguments, pertaining to both figural and nonfigural aspects of candidate forms at the time they are being generated, as part of the design search. The dialectics of sketching is the oscillation of arguments which brings about gradual transformation of images, ending when the designer judges that sufficient coherence has been achieved.

Maximum-rank array codes and their application to crisscross error correction

Abstract: A mu -(n*n,k) array code C over a field F is a k-dimensional linear space of n*n matrices over F such that every nonzero matrix in C has rank >or= mu . It is first shown that the dimension of such array codes must satisfy the Singleton-like bound k >

Selective increase of iron in substantia nigra zona compacta of parkinsonian brains.

Abstract: Histochemical and biochemical determinations of total iron, iron (II), and iron (III) contents in brain regions from Parkinson's and Alzheimer's diseases have demonstrated a selective increase of total iron content in parkinsonian substantia nigra zona compacta but not in the zona reticulata. The increase of iron content is mainly in iron (III). The ratio of iron (II):iron (III) in zona compacta changes from almost 2:1 to 1:2. This change is thought to be relevant and may contribute to the selective elevation of basal lipid peroxidation in substantia nigra reported previously. Iron may be available in a free state and thus can participate in autooxidation of dopamine with the resultant generation of H2O2 and oxygen free radicals.

An information retrieval approach for automatically constructing software libraries

Abstract: A technology for automatically assembling large software libraries which promote software reuse by helping the user locate the components closest to her/his needs is described. Software libraries are automatically assembled from a set of unorganized components by using information retrieval techniques. The construction of the library is done in two steps. First, attributes are automatically extracted from natural language documentation by using an indexing scheme based on the notions of lexical affinities and quantity of information. Then a hierarchy for browsing is automatically generated using a clustering technique which draws only on the information provided by the attributes. Due to the free-text indexing scheme, tools following this approach can accept free-style natural language queries. >

A hepatitis B virus mutant associated with an epidemic of fulminant hepatitis

Abstract: Background. A nosocomial outbreak of fulminant hepatitis B occurred in five patients in Haifa, Israel. Previous investigations identified the suspected source as a carrier of hepatitis B surface antigen who was positive for antibodies to hepatitis B e antigen and had chronic liver disease. We examined the strain of hepatitis B virus (HBV) that caused this epidemic, in order to identify specific mutations in the precore or core region. Methods. The presence of HBV was identified by polymerase-chain-reaction amplification of viral DNA in serum from the source patient, the five patients with fulminant hepatitis B, and five controls with acute, self-limited hepatitis B. The amplified viral HBV DNA samples were then cloned and sequenced. Results. Sequence analysis of viral DNA established that the same HBV mutant with two mutations in the precore region was present in the source patient and the five patients with fulminant hepatic failure. This HBV mutant had significant sequence divergence from other known HB...

Two simple proofs of the Kochen-Specker theorem

Abstract: A new proof of the Kochen-Specker theorem uses 33 rays, instead of 117 in the original proof. If the number of dimensions is increased from 3 to 4, only 24 rays are needed.

Learning decision trees using the Fourier spectrum

Abstract: This work gives apolynomial time algorithm for learning decision trees with respect to the uniform distribution (This algorithm uses membership queries) The decision tree model that is considered is an extension of the traditional boolean decision tree model that allows linear operations in each node (ie, summation of a subset of the input variables over GF(2)) This paper shows how to learn in polynomial time any function that can be approximated (in norm L2) by a polynomially sparse function (ie, a function with only polynomially many nonzero Fourier coefficients) The authors demonstrate that any functionf whose L -norm (ie, the sum of absolute value of the Fourier coefficients) is polynomial can be approximated by a polynomially sparse function, and prove that boolean decision trees with linear operations are a subset of this class of functions Moreover, it is shown that the functions with polynomial L -norm can be learned deterministically The algorithm can also exactly identify a decision tree of depth d in time polynomial in 2 a and n This result implies that trees of logarithmic depth can be identified in polynomial time

Estimation and classification of polynomial-phase signals

Abstract: The measurement of the parameters of complex signals with constant amplitude and polynomial phase, measured in additive noise, is considered. A novel new integral transform that is adapted for signals of this type is introduced. This transform is used to derive estimation and classification algorithms that are simple to implement and that exhibit good performance. The algorithms are extended to constant amplitude and continuous nonpolynomial phase signals. >

Degradation of nuclear oncoproteins by the ubiquitin system in vitro.

Abstract: Nuclear oncoproteins are among the most rapidly degraded intracellular proteins. Previous work has implicated the ubiquitin-mediated proteolytic system in the turnover of short-lived intracellular proteins. In the present study, we have evaluated the potential role of the ubiquitin system in the degradation of the specific nuclear oncoproteins encoded by the N-myc, c-myc, c-fos, p53 and E1A genes. Each of these nuclear oncoproteins was synthesized in vitro by transcription of the appropriate cDNA and translation of the resulting mRNA in the presence of [35S]methionine. Degradation of labeled proteins was monitored in the ubiquitin cell-free system. ATP stimulated the degradation of all the proteins between 3- and 10-fold. The degradation was completely inhibited by neutralizing antibody directed against the ubiquitin-activating enzyme, E1, the first enzyme in the ubiquitin-mediated proteolytic cascade. Moreover, degradation in E1-depleted lysates could be restored in each case by the addition of affinity-purified E1. These data suggest that the ubiquitin system mediates the degradation of these oncoproteins in vitro. Degradation of other proteins, such as superoxide dismutase, cytochrome c, enolase, RNase A, and ornithine decarboxylase, is not mediated by the ubiquitin cell-free system. This suggests that the nuclear oncoproteins studied here possess specific signals that target them for rapid turnover by this proteolytic pathway. Furthermore, the relative sensitivity to degradation of various E1A mutants in vivo is also maintained in the cell-free system, suggesting that the ubiquitin pathway may play a role in the cellular degradation of these proteins as well.

Actigraphic home-monitoring sleep-disturbed and control infants and young children: a new method for pediatric assessment of sleep-wake patterns.

Abstract: Two studies were conducted to evaluate actigraphic home-monitoring for the assessment of infants' and children's sleep patterns. In the first study, 11 children (aged 12 to 48 months) were monitored in the laboratory by traditional polysomnography and by actigraphy for one night. Actigraphic automatic sleep-wake scorings were compared with those of the polysomnograph; total agreement rate was 85.3%. In the second study, sleep patterns of 63 sleep-disturbed and 34 control healthy children (aged 9 to 27 months) were compared. These children were home-monitored by actigraph for a mean of 4.45 nights (total 482 nights). Actigraphic data were analyzed by an automated scoring procedure. Sleep quality of the sleep-disturbed children, measured by actigraphically derived sleep percent and number of longer-than-5-minute wakings, was significantly lower than that of the control subjects (P less than .0001). Sleep measures showed significant night-to-night stability in both groups. The stability of specific measures and their age trends were different between the groups. Actigraphic sleep measures alone could discriminate between sleep-disturbed and control children with a highly correct assignment rate of 79.4% and 91.2%, respectively.

Construction of asymptotically good low-rate error-correcting codes through pseudo-random graphs

Abstract: A novel technique, based on the pseudo-random properties of certain graphs known as expanders, is used to obtain novel simple explicit constructions of asymptotically good codes. In one of the constructions, the expanders are used to enhance Justesen codes by replicating, shuffling, and then regrouping the code coordinates. For any fixed (small) rate, and for a sufficiently large alphabet, the codes thus obtained lie above the Zyablov bound. Using these codes as outer codes in a concatenated scheme, a second asymptotic good construction is obtained which applies to small alphabets (say, GF(2)) as well. Although these concatenated codes lie below the Zyablov bound, they are still superior to previously known explicit constructions in the zero-rate neighborhood. >

The MADS box gene family in tomato: temporal expression during floral development, conserved secondary structures and homology with homeotic genes from Antirrhinum and Arabidopsis.

Abstract: Summary Five genes with homology to the floral homeotic genes deficiens of Antirrhinum and agamous of Arabidopsis were isolated from tomato. Each of the five genes is unique in the genome and could be localized to a different chromosome by RFLP mapping. Four of the tomato genes (hereafter TM) are flower-specific with distinguishable temporal expression. TM4 and TM8 are ‘early’, while TM5 and TM6 are ‘late’ genes. TM4 is homologous to squamosa and TM6 is similar to deficiens, which are, respectively, ‘early’ and ‘late’ bona fide homeotic genes in Antirrhinum. The proteins encoded by the five tomato genes, like several known homeotic genes from other plants, contain within their N-terminus a highly conserved DMA-binding domain, the MADS box. All known plant MADS box genes also share, however, other properties. They all contain a central, moderately conserved, and rather basic domain, and a highly divergent or even missing C-terminal domain. Furthermore, molecular modelling predicts the presence of a conserved amphipatic alpha helix, at a constant distance from the MADS box in each of these proteins. The common properties of eight MADS box proteins from three plant families indicate that all their domains were coded for by the same ancestor gene. The sequence homology between pairs of MADS genes from different species indicates that the MADS ancestor gene multiplied and diverged in an ancestor plant common to several dicotyledon families.

Rare decays of the top quark in the standard and two-Higgs-doublet models.

Abstract: The decays $t\ensuremath{\rightarrow}\mathrm{cV}$, where $V=\ensuremath{\gamma}, g, or Z$, and $t\ensuremath{\rightarrow}\mathrm{cH}$ are calculated, keeping all masses, in the standard model (SM) for all possible values of the top-quark mass that are consistent with present data. We find that the branching fractions for these processes are small, the largest being $B(t\ensuremath{\rightarrow}cH)\ensuremath{\sim}{10}^{\ensuremath{-}7}$ and $B(t\ensuremath{\rightarrow}cg)\ensuremath{\sim}{10}^{\ensuremath{-}10}$. Our calculations are then extended to include the possible contributions of charged Higgs bosons to the transitions $t\ensuremath{\rightarrow}\mathrm{cV}$ in the context of general two-Higgs-doublet models. These new contributions can enhance the SM branching fractions by as much as 3-4 orders of magnitude, e.g., $B(t\ensuremath{\rightarrow}cg)\ensuremath{\sim}{10}^{\ensuremath{-}7}\ensuremath{-}{10}^{\ensuremath{-}6}$, for various values of the parameters. General expressions for flavor-changing neutral-current decays of heavy quarks including all masses and momenta, in the SM and in the two-Higgs-doublet models, are also given.

The Cramer-Rao lower bound for signals with constant amplitude and polynomial phase

Abstract: The authors derive the Cramer-Rao lower bound (CRLB) for complex signals with constant amplitude and polynomial phase, measured in additive Gaussian white noise. The exact bound requires numerical inversion of an ill-conditioned matrix, while its O(N/sup -1/) approximation is free of matrix inversion. The approximation is tested for several typical parameter values and is found to be excellent in most cases. The formulas derived are of practical value in several radar applications, such as electronic intelligence systems (ELINT) for special pulse-compression radars, and motion estimation from Doppler measurements. Consequently, it is of interest to analyze the best possible performance of potential estimators of the phase coefficients, as a function of signal parameters, the signal-to-noise ratio, the sampling rate, and the number of measurements. This analysis is carried out. >

The Landscapes of Childhood: The Reflection of Childhood's Environment in Adult Memories and in Children's Attitudes

Abstract: This article deals with children's relation to the environment from actual and retrospective points of view, delineated by empirical research and by theoretical analysis. The empirical research investigated the environmental preferences and the nature of the experiences of being outdoors as reflected in adult's (N = 198) recollections and in children's (N = 174) actual approach. Among the findings was that almost all adults identify the most significant place in their childhood with the outdoors. The children's preference of place is dependent on their personal needs on one hand, and on the properties of the place associated with these needs on the other. Children experience the natural environment in a deep and direct manner, not as a background for events, but, rather, as a factor and stimulator. There is a connection between the quality of the child's experience and the way it is engraved in memory as he or she matures: (a) An experience in which the child is actively involved, with his body, his sense...

Linear FM signal parameter estimation from discrete-time observations

Abstract: The authors consider the problem of estimating the parameters of a complex linear FM signal from a finite number of noisy discrete-time observations An estimation algorithm is proposed, and its asymptotic (large sample) performance is analyzed The algorithm is computationally simple, consisting of two fast Fourier transforms (FFTs) accompanied by one-dimensional searches for maxima The variance of the estimates is shown to be close to the Cramer-Rao lower bound when the signal-to-noise ratio is 0 dB and above The authors applied the algorithm to the problem of estimating the kinematic parameters of an accelerating target by pulse-Doppler radar A representative test case was used to exhibit the usefulness of the algorithm for this problem, and to verify the analytical results by Monte Carlo simulations >

Two Languages Are More Informative Than One

Abstract: This paper presents a new approach for resolving lexical ambiguities in one language using statistical data on lexical relations in another language. This approach exploits the differences between mappings of words to senses in different languages. We concentrate on the problem of target word selection in machine translation, for which the approach is directly applicable, and employ a statistical model for the selection mechanism. The model was evaluated using two sets of Hebrew and German examples and was found to be very useful for disambiguation.

Modern signals and systems

Abstract: Overview of signals and systems an introduction to signals an introduction to systems difference and differential systems state description of systems expansion theory and Fourier series Fourier transforms the z- and laplace transforms applications to signal processing and digital filtering applications to communication feedback and applications to automatic control supplement reviews and SIGSYS tutorial.