Optical metropolitan DWDM networks an overview

The paper deals with the subject of how to build a core network in the current technology scenario. We start with an overview ofwhat we consider a core network, not in an abstract way but referring to real country situations, and pointing out the differentaspects conditioning its realisation – population distribution, territory shape, traffic characteristics. In the next section asummary of different network topologies is presented and briefly analysed – rings, meshes, loosely or tightly interconnected,with particular attention to the resilience aspect in case of faults. The following section is dedicated to a short presentation of thecurrent technology scenario and how it reflects on the network elements (NEs) offered on the market (OXC, OADM, PXC, etc).Finally, the question is posed: “What is the best way to implement a core network?” with the conclusion being that there is nosingle answer – each situation must be pursued on a case-by-case basis. This paper describes some important aspects of next-generation metropolitan networking, with special focus on market driversand applications, upcoming standards like GFP and GMPLS, required functionalities like optical switching and protection, and ageneric view on a next-generation platform.     

Analysis of plane-wave light normally incident to an axially excited structurally chiral half-space

We analyse electromagnetic radiation normally incident to a structurally chiral half-space. We adopt two strategies based respectively on the exact electromagnetic solution to the problem, and a more phenomenological approach based on coupled-wave analysis. We find good agreement between the two methods.     

Explicit expressions for spectral remittances of axially excited chiral sculptured thin films

Abstract

A theory of reflection and transmission of normally incident plane waves to a chiral sculptured thin film (CSTF) is presented. It is based on a coupled wave approach, in which the handedness-reversing reflections at the medium's interfaces are combined with the handedness-preserving distributed reflection inside the CSTF. Explicit formulas for the various reflection and transmission coefficients are derived. The method is shown to provide acceptable quantitative agreement with the exact full electromagnetic analysis.     

Polarization-dependent narrowband spectral filtering by chiral sculptured thin films

Abstract

We analyse theoretically transmission through two layers of different thin-film helicoidal bianisotropic mediums (TFHBMs), wherein the pitch of each layer bears a precisely determined relation to the overall thickness of the bi-layer. A spectral hole emerges from the interaction of the circular Bragg regimes of both TFHBM layers. Our results generalize a recently discovered scheme for producing spectral holes in fibre-Bragg gratings, with which comparison is made. The proposed TFHBM bi-layers may be useful for the simultaneous production of oppositely polarized beams with narrow bandwidths and a specific amplitude splitting ratio.     

Preparation and characterization of poly(vinyl alcohol) nanocomposites made from cellulose nanofibers

A method using a combination of ball milling, acid hydrolysis, and ultrasound was developed to obtain a high yield of cellulose nanofibers from flax fibers and microcrystalline cellulose (MCC). Poly(vinyl alcohol) (PVA) nanocomposites were prepared with these additives by a solution‐casting technique. The cellulose nanofibers and nanocomposite films that were produced were characterized with Fourier transform infrared spectrometry, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. Nanofibers derived from MCC were on average approximately 8 nm in diameter and 111 nm in length. The diameter of the cellulose nanofibers produced from flax fibers was approximately 9 nm, and the length was 141 nm. A significant enhancement of the thermal and mechanical properties was achieved with a small addition of cellulose nanofibers to the polymer matrix. Interestingly, the flax nanofibers had the same reinforcing effects as MCC nanofibers in the matrix. Dynamic mechanical analysis results indicated that the use of cellulose nanofibers (acid hydrolysis) induced a mechanical percolation phenomenon leading to outstanding and unusual mechanical properties through the formation of a rigid filler network in the PVA matrix. X‐ray diffraction showed that there was no significant change in the crystallinity of the PVA matrix with the incorporation of cellulose nanofibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Generalization from single sentence to multisentence production in severely aphasic patients

Multisentence production was examined in three nonfluent aphasic patients who had undergone a single sentence production training program using a computerized visual communication system (C-VIC). Patients were required to describe videotaped vignettes in English and using C-VIC. C-VIC allowed for an investigation of production abilities previously impossible to measure in severely aphasic patients, since C-VIC does not require internal generation of appropriate lexical items or phonological and articulatory realization. Results are discussed in the context of language production models in an attempt to determine the breakdown(s) in the production system that result in difficulty in trying to produce multiple sentences.     

Expression of leptin receptor isoforms in rat brain microvessels

Current evidence suggests that host defense in respiratory mycoplasmosis is dependent on both innate and humoral immunity. To further delineate the roles of innate and adaptive immunity in antimycoplasmal defenses, we intranasally infected C3H/HeSnJ-scid/scid (C3H-SCID), C3H/HeSnJ (C3H), C57BL/6J-scid/scid (C57-SCID), and C57BL/6N (C57BL) mice with Mycoplasma pulmonis and at 14 and 21 days postinfection performed quantitative cultures of lungs and spleens, quantification of lung lesions, and histopathologic assessments of all other major organs. We found that numbers of mycoplasmas in lungs were associated with genetic background (C3H susceptible, C57BL resistant) rather than functional state of adaptive immunity, indicating that innate immunity is the main contributor to antimycoplasmal defense of the lungs. Extrapulmonary dissemination of mycoplasmas with colonization of spleens and histologic lesions in multiple organs was a common occurrence in all mice. The absence of adaptive immune responses in severe combined immunodeficient (SCID) mice resulted in increased mycoplasmal colonization of spleens and lesions in extrapulmonary sites, particularly spleens, hearts, and joints, and also reduced lung lesion severity. The transfer of anti-M. pulmonis serum to infected C3H-SCID mice prevented extrapulmonary infection and disease, while the severity of lung lesions was restored by transfer of naive spleen cells to infected C3H-SCID mice. Collectively, our results strongly support the conclusions that innate immunity provides antimycoplasmal defense of the lungs and humoral immunity has the major role in defense against systemic dissemination of mycoplasmal infection, but cellular immune responses may be important in exacerbation of mycoplasmal lung disease.