Local-Line Single-Mode Optics--Viable Options for Today and Tomorrow

Introducing optical transmission into the local network poses a number of severe economic and technological problems. In this paper, we address these problems assuming a future requirement for a wholly monomode transmission network through long/short haul and local lines. The key considerations therefore involve the economic realization of systems in the 2-140 Mbit/s range. Specific laboratory designs at 2, 8, and 34 Mbits/s employing uni- and bidirectional operation are discussed. Field experience at 1.3 and 1.5 μm using very low cost unidirectional and bidirectional systems is reported, including systems based upon directional couplers, wavelength-duplex, and "piggyback" schemes.     

Noncontact methods of studying the parameters of particles in two-phase plasma flows

Journal of Engineering Physics and Thermophysics -     

Evolutionary dynamics of genetic variation in Epstein-Barr virus isolates of diverse geographical origins: evidence for immune pressure-independent genetic drift

The question whether immune pressure exerted by cytotoxic T lymphocytes (CTLs) can influence the long-term evolution of genetically stable viruses such as Epstein-Barr virus (EBV) has generated considerable scientific interest, primarily due to its important implications for the overall biology of the virus. While arguing for a role of CTLs in the evolution of viruses, it is important to differentiate between genetic variation in virus and immune recognition of these variant virus by CTLs. To assess the role of genetic selection in the long-term evolution of EBV, we have analyzed a large panel of type 1 EBV isolates from African, Southeast Asian, Papua-New Guinean (PNG), and Australian Caucasian individuals. Seven different regions of the EBV genome, which include nine CTL epitopes restricted through a range of HLA class I alleles, were sequenced and compared. Although numerous nucleotide changes were identified within these isolates, comparison of synonymous and nonsynonymous substitutions in the CTL epitope indicated that the genetic variation was generated mostly independently of immune selection pressure. Surprisingly, an inverse correlation between genetic variation within certain CTL epitopes and the frequency distribution of HLA alleles that present the CTL epitopes was seen, suggesting that the evolutionary pressures on the CTL epitopes of the virus may be toward their conservation rather than their inactivation. Furthermore, molecular evolutionary genetic analysis of nucleotide sequences revealed that viral isolates from PNG are evolving as a lineage distinct from isolates from African, Southeast Asian, and Australian Caucasian individuals.     

Water Affinity to Epitaxial Graphene: The Impact of Layer Thickness

The sensitivity to water vapour of one‐, two‐, and three‐layer epitaxial graphene (1, 2, and 3LG) is examined in this study. It is unambiguously shown that graphene's response to water, as measured by changes in work function and carrier density, is dependent on its thickness, with 1LG being the most sensitive to water adsorption and environmental concentration changes. This is furthermore substantiated by surface adhesion measurements, which bring evidence that 1LG is less hydrophobic than 2LG. Yet, surprisingly, it is found that other contaminants commonly present in ambient air have a greater impact on graphene response than water vapor alone. This study indicates that graphene sensor design and calibration to minimize or discriminate the effect of the ambient, in which it is intended to operate, are necessary to insure the desired sensitivity and reliability of sensors. The present work will aid in developing models for realistic graphene sensors and establishing protocols for molecular sensor design and development.     

Some formal properties of stratified feature grammars

In this paper, we investigate the formal expressive properties of Stratified Feature Grammar (SFG), a new logic-based linguistic framework motivated by relational grammar and metagraph grammar, as well as by Kasper-Rounds logic. The driving force behind SFG is the generalization of the conceptfeature from an unanalyzable atomic one to a sequence of so-called R-signs. The linguistic interpretation of thesestratified features is that each R-sign in such a sequence denotes a primitive grammatical relation such as subject or direct object in different syntactic “strata”. This generalization permits the specification of a rigorous feature-structure-based formalism for natural-language grammars based on the view that syntax is “multistratal” and “relational”. The introduction of stratified features leads to several other innovations, two of which might have utility in other frameworks. One is the idea of imposing a partial order on features. The other is the concept of(data) justification: essentially, this is a stipulation that for an S-graph to be well-formed with respect to some grammarG it must, in addition to satisfying the rules ofG, have each of its “core” data (each feature occurrence, each node-label occurrence and each instance of so-called structure-sharing) justified in a formally precise manner by some rule of Justification ensures that. Justification ensures that satisfying S-graphs do not have more structure than absolutely necessary and so makes it appealing to a notion of “minimal model” otiose. Justification plays a key role in a number of our proofs. The formal results presented here include the following. First, it is proved that in the unrestricted SFG framework, every type 0 (r.e.) language is generated by some SFG. Then, we restrict the framework to so-calledbounded SFG with two linguistically motivated principles: Lexical Anchoring and Boundedness. Anchoring requires, in essence, that each core datum of an S-graph be justified by aword in its yield. Boundedness insures that S-graph features are short. Although these restrictions together put the class of bounded SFG languages well within the class of recursive languages, we go on to demonstrate that the recognition problem for bounded SFG is NP-hard. Further, we establish that a bounded SFG language need not be semi-linear. On the matter of upper bounds, we show that every bounded SFL can be recognized by a nondeterministic Turing machine inn logn space and polynomial time and that the recognition problem for bounded SFL's is NP-complete.     

Identification of variegated coloring in skin tumors: neuralnetwork vs. rule-based induction methods

The use of neural networks for automatic identification of variegated coloring, which is believed to be one of the most predictive features for malignant melanoma, is described. The Nestor development system (NDS) was chosen for neural network implementation. At the heart of NDS is a three-layer neural network called a restricted Coulomb energy (RCE) network. The learning scheme and the database for detection of variegated coloring are discussed. Results are reported     

Access to word meanings during spoken language comprehension: Effects of sentential semantic context.

In 3 cross-modal priming experiments, the authors investigated whether access to a word's meaning is affected by the semantic context in which it is heard or is exhaustive and context-independent. The access of nonassociated semantic properties and normatively associated words before and after prime offset was probed. Whereas associated targets were primed context-independently, access to semantic property targets was affected by the sentential context. Semantic property targets showed greater priming in a sentence biasing to a specific semantic property than in a neutral condition, even when this bias made the target property irrelevant rather than relevant. These results cannot be accounted for by current exhaustive access or context-dependency theories of lexical access. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sorting human beta-cells consequent to targeted expression of green fluorescent protein

Pancreatic islets of Langerhans are composed of four major endocrine cell types with a smaller number of nonendocrine cells. To study the molecular constituents and function of just one subpopulation of islet cells, it is necessary to sort them from the other cell types. While rat beta-cells can be sorted by autofluorescence-activated flow cytometry, this has not proved possible on a routine and reproducible basis for human beta-cells. In the present study, we have selectively labeled human beta-cells with green fluorescent protein (GFP), allowing for their sorting by flow cytometry. Human islet cells were infected with replication-defective (attenuated) recombinant adenovirus expressing GFP driven by the rat insulin I promoter (Ad-RIP-GFP) for targeted expression in beta-cells, or beta-galactosidase driven by the promiscuous cytomegalovirus (CMV) promoter (Ad-CMV-beta-gal) as control. Whereas the majority of islet cells can be infected by adenovirus, as shown by control infection with Ad-CMV-beta-gal, increased fluorescence after infection with Ad-RIP-GFP was limited to insulin-containing beta-cells. Infection of islet cells with Ad-RIP-GFP resulted reproducibly in the appearance of a population of intensely fluorescent cells, when analyzed by flow cytometry. These cells were sorted using a fluorescence-activated cell sorter (FACS) and shown by immunofluorescence to consist of >95% beta-cells. The targeted expression of GFP thus allows for preparation of human beta-cells purified close to homogeneity. This method should be readily applicable in any laboratory with FACS capability.