On effective properties of composites with coated cylindrically orthotropic fibers

Composite systems consisting of a matrix phase and coated inclusions with curvilinear anisotropy are considered, and a concise framework is established for analysis of their effective thermomechanical behavior. An exact relation between the effective thermal stress tensor and the purely mechanical influence functions of such media is derived. The presented analysis includes as a special case some previous work by the authors on composites with coated and cylindrically orthotropic fibers, e.g., carbon fibers. Furthermore, it allows to prove analytically certain symmetry and consistency properties of the effective thermomechanical tensors of such systems as approximated by the Mori—Tanaka micromechanical model.     

Consequences of gamma-irradiation on inflammatory cytokine regulation in human monocytes/macrophages

We have investigated mitochondrial DNA (mtDNA) mutagenesis in the laboratory mouse. Using a nested PCR method for quantification, the absolute frequency, tissue distribution and rate of increase of mitochondrial deletion mutations was determined. Multiple deletions arise in brain, cardiac muscle and kidney tissues: deletions occur most frequently at regions of directly repeated mtDNA homology. Deletion frequencies rose by 2.5 x 10(5), 6300- and 4000-fold in heart, brain and kidney, respectively, between young and old mice. The rates of mtDNA mutation accumulation in mouse and human hearts are modeled well by exponential equations, with r-values of 0.96 and 0.97, and mutations rose much faster in mouse than human mtDNA per unit time. Thus, maintenance of the human mitochondrial genome is much better than that of mice, consistent with the higher rate and final extent of total DNA repair in humans than mice, that has been observed by others and consistent with the predictions of the disposable soma model of aging. A comparison of mtDNA mutagenesis from cardiocytes vs. whole heart tissue was undertaken. Deletion mutations were observed to be 100-fold lower in DNA prepared from isolated cardiocytes than from whole heart homogenates, consistent with a model of uneven mtDNA mutation accumulation.     

The synchronous approach to reactive and real-time systems

The state of the art in real-time programming is briefly reviewed. The synchronous approach is then introduced informally and its possible impact on the design of real-time and reactive systems is discussed. The authors present and discuss the application fields and the principles of synchronous programming. The major concern of the synchronous approach is to base synchronous programming languages on mathematical models. This makes it possible to handle compilation, logical correctness proofs, and verification of real-time programs in a formal way, leading to a clean and precise methodology for design and programming     

Nucleocapsid protein zinc-finger mutants of simian immunodeficiency virus strain mne produce virions that are replication defective in vitro and in vivo

All retroviruses (except the spumaretroviruses) contain a nucleocapsid (NC) protein that encodes one or two copies of the Zn2+-finger sequence -Cys-X2-Cys-X4-His-X4-Cys-. This region has been shown to be essential for recognition and packaging of the genomic RNA during virion particle assembly. Additionally, this region has been shown to be involved in early infection events in a wide spectrum of retroviruses, including mammalian type C [e.g., murine leukemia virus (MuLV)], human immunodeficiency virus type 1 (HIV-1), Rous sarcoma virus, and other retroviruses. Mutations in the two Zn2+-fingers of the NC protein of simian immunodeficiency virus strain Mne [SIV(Mne)] have been generated. The resulting virions contained the normal complement of processed viral proteins with densities indistinguishable from wild-type SIV(Mne). All of the mutants had electron micrograph morphologies similar to those of immature particles observed in wild-type preparations. RNA packaging was less affected by mutations in the NC protein of SIV(Mne) than has been observed for similar mutants in the MuLV and HIV-1 systems. Nevertheless, in vitro replication of SIV(Mne) NC mutants was impaired to levels comparable to those observed for MuLV and HIV-1 NC mutants; replication defective NC mutants are typically 10(5)- to 10(6)-fold less infectious than similar levels of wild-type virus. One mutant, DeltaCys33-Cys36, was also found to be noninfectious in vivo when mutant virus was administered intravenously to a pig-tailed macaque. NC mutations can therefore be used to generate replication defective virions for candidate vaccines in the SIV macaque model for primate lentiviral diseases.     

Probability models of microcell coverage

Once a subscriber unit served by a microcell initiates a call, it must remain in the coverage area of the microcell long enough to complete call set up and hand-off functions. This restricts the minimum size attainable by a microcell. This paper derives the relationship between the microcell size, the call processing time, and the probability that a subscriber unit, initiating a call, will remain inside the microcell coverage area for at least the duration of call processing. Under simple assumptions, time spent in the coverage area of the microcellbefore andafter call initiation have the same cumulative density function, which is derived in this paper for traffic conditions encountered in highway and metropolitan settings.This paper is based on a contribution to the ETSI GSM2 Standards, Ronneby, Sweden, September 1991 [1].     

Sequential segmentation of nonstationary digital signals using spectral analysis

This paper is devoted to the sequential detection of abrupt changes in spectral characteristics of digital signals, as this problem occurs for the segmentation of real signals such as speech, EEG, ECG, or geophysical signals. The limitations of a classical test are emphasized and some new algorithms are presented. They are based upon the use of two autoregressive models and some distance measures between them, such as the log-likelihood ratio and Kullback's divergence between conditional probability laws. All these algorithms are compared both via a simulation study and from a theoretical point of view.     

Fault Detection and Diagnosis in Distributed Systems: An Approach by Partially Stochastic Petri Nets

We address the problem of alarm correlation in large distributed systems. The key idea is to make use of the concurrence of events in order to separate and simplify the state estimation in a faulty system. Petri nets and their causality semantics are used to model concurrency. Special partially stochastic Petri nets are developed, that establish some kind of equivalence between concurrence and independence. The diagnosis problem is defined as the computation of the most likely history of the net given a sequence of observed alarms. Solutions are provided in four contexts, with a gradual complexity on the structure of observations.     

One-dimensional wave propagation in materials with different moduli in tension and compression

One-dimensional wave propagation in compressible and incompressible elastic materials behaving differently in tension and compression is investigated. The constitutive equations of these materials are nonlinear even though small deformations are considered. The characteristic wavespeeds are derived, the hyperbolicity condition is investigated, and analytical simple wave solutions are obtained in a compressible and incompressible semi-infinite half-space. The presented solutions exhibit interesting phenomena of wave propagation, like that of a coupled shear-normal plane wave propagating steadily with a constant velocity in a compressible medium with different moduli in tension and compression.     

Design of adaptive algorithms for the tracking of time-varying systems

The design of adaptive algorithms for the tracking of slowly time-varying systems is investigated. A criterion for measuring the tracking capability of an algorithm in this situation was introduced in an earlier work; the domain of validity of this criterion is shown to be much wider than expected. On the other hand, multistep algorithms, introduced in the Soviet literature, are generalized and systematically studied; they are shown to provide significant improvements over the classical (one-step) methods for tracking. Finally, a complete design methodology for adaptive algorithms, used on time-varying systems is given.