Hybrid and optical packet switching supporting different service classes in data center network

Photonic Network Communications - Optical packet switching is a prominent technology proposing not only a reduction in the energy consumption by the elimination of numerous...     

The effect of nitric oxide on cytokine-induced release of PGE2 by human cultured astroglial cells

Articles in this issue by A. C. Casiglia, A. LoCoco, and C. Zappulla; D. S. Crystal, H. Watanabe, K. Weinfurt, and C. Wu; M. Keller, N. Edelstein, C. Schmid, F. Fang, and G. Fang; and J. J. Han, M. D. Leichtman, and Q. Wang are discussed according to (a) the extent to which cultural variability can be reconciled with developmental theory and (b) the dimensions of cultural variability that matter most for development. It is argued that (a) cross-cultural research needs to be predicted on a model of how culture interacts with the forces that underlie and guide development and (b) the interpretation of cross-cultural research is severely limited without the direct measurement of the specific culture-related variables and processes that are hypothesized to account for diversity in development. Finally, within-culture variability needs to be studied in conjunction with between-culture variability so that a full model of diversity and development can be constructed.     

No, It Is Not Possible to Be Schizophrenic Yet Neuropsychologically Normal.

Cognitive impairment is well documented in schizophrenia, though some reports have been interpreted to suggest that it is possible to have schizophrenia without neuropsychological impairment. The authors tested this by comparing the neuropsychological profiles of closely matched patients with schizophrenia and healthy comparison participants. Sixty-four patients with schizophrenia and 64 healthy comparison cases, matched to within 3 Full-Scale IQ points, were tested using the Wechsler Adult Intelligence Scale (3rd ed.; D. Wechsler, 1997b) and the Wechsler Memory Scale (3rd ed.; D. Wechsler, 1997c). Neuropsychological profiles for these groups were markedly different, with the group of patients with schizophrenia exhibiting performance deficits in memory and speeded visual processing but superior verbal comprehension and perceptual organization relative to the group of healthy comparison participants matched on Full-Scale IQ. Thus, scoring in the normal range does not preclude neuropsychological abnormality in schizophrenia, confirming that neuropsychological impairment is a core feature of the illness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An experimental evaluation of cross-layer routing in a wireless mesh backbone

Over the latest few years, cross-layer design in wireless networks has drawn great attention from the research community. One of the main arguments in favor of such techniques is that the hop-count metric alone is not enough to capture the specificities of wireless links (e.g., interferences, collisions, fading). In this paper, we address a simple yet fundamental question: What are the real improvements that cross-layering can bring to routing performance when compared to the simple hop-count metric? In our experiments, we consider the backbone of a real wireless mesh network composed of 12 routers deployed in an office building. We focus on the stability of routes and their persistence. In spite of the nature of cross-layer metrics that take into account information from different layers, lets them be very reactive to changes, we observe that using these metrics, pairs of nodes tend to mainly use the same set of two or three routes between them.     

Four-wave mixing in traveling-wave semiconductor amplifiers

The traveling-wave equations of four-wave mixing in semiconductor amplifiers are solved analytically including saturation of the amplifier. Excellent agreement is obtained with numerical solutions of the traveling-wave equations. The analytical model is used to analyze a highly nondegenerate four-wave mixing experiment in a bulk semiconductor amplifier     

Multilevel coherent optical system based on Stokes parametersmodulation

A multilevel transmission system that allows efficient exploitation of a single-channel bandwidth in coherent optical communication systems is proposed. It is based on Stokes parameter modulation and a decision on the Poincare sphere. The block scheme of the transmitter, which is able to provide a generic output state of polarization (SOP) starting from a linearly polarized optical field, is shown and described. The propagation along the fiber is described in order to derive the expression of the optical field at the receiver input. The spectral characteristics of the transmitted and the received optical signals are analyzed     

Parallel file system performances in fusion data storage

High I/O flow rates, up to 10 GB/s, are required in large fusion Tokamak experiments like ITER where hundreds of nodes store simultaneously large amounts of data acquired during the plasma discharges. Typical network topologies such as linear arrays (systolic), rings, meshes (2-D arrays), tori (3-D arrays), trees, butterfly, hypercube in combination with high speed data transports like Infiniband or 10G-Ethernet, are the main areas in which the effort to overcome the so-called parallel I/O bottlenecks is most focused.The high I/O flow rates were modelled in an emulated testbed based on the parallel file systems such as Lustre and GPFS, commonly used in High Performance Computing. The test runs on High Performance Computing–For Fusion (8640 cores) and ENEA CRESCO (3392 cores) supercomputers. Message Passing Interface based applications were developed to emulate parallel I/O on Lustre and GPFS using data archival and access solutions like MDSPLUS and Universal Access Layer. These methods of data storage organization are widely diffused in nuclear fusion experiments and are being developed within the EFDA Integrated Tokamak Modelling – Task Force; the authors tried to evaluate their behaviour in a realistic emulation setup.     

A novel multilevel coherent optical system: 4-quadrature signaling

A novel multilevel coherent optical system is proposed. It is based on the exploitation of the property that the electromagnetic field propagating in a single-mode optical fiber can be represented by a four-dimensional vector whose components are the phase and quadrature terms of the two polarization components of the electrical field. This allows a wider use of the resources of the electromagnetic field for information transmission in order to obtain a spectrally efficient modulation format with a limited end. The net performance gain with respect to multilevel amplitude and phase modulation (N-APK) and N-PSK increases with an increase in the number of levels N. For instance, for N=32 the gain is 1.6 and 7.7 dB with respect to N-APK and N-PSK systems. The effect of laser phase noise on the system performance is evaluated     

Efficiency and noise performance of wavelength converters based onFWM in semiconductor optical amplifiers

All optical frequency converters are key devices for new-conception optical networks. A theoretical model is presented to evaluate performances of frequencies converters based on highly nondegenerate four-wave mixing (FWM) in semiconductor amplifiers. Conversion efficiency and noise performances are evaluated in generic saturation conditions and compared with experimental results     

High-speed DPSK coherent systems in the presence of chromaticdispersion and Kerr effect

The error probability for a single-channel coherent optical differential phase-shift keying (DPSK) transmission system based on repeaterless links in the presence of fiber chromatic dispersion and Kerr effect is evaluated. An accurate model for both the optical signal propagation and the probability distribution of the receiver decision variable is obtained by using a numerical solution of the nonlinear Shrodinger equation and the characteristic function method. The results show that the selection of an optimized IF filter bandwidth is crucial to obtaining the best system performance. When chromatic dispersion dominates, the best performance is achieved in the normal dispersion region whereas when the Kerr effect has the most limiting effect on system performances, the lowest error probability is attained in the anomalous regime. The maximum link length is limited by the presence of Kerr effect, independently of the amount of transmitted optical power, to be shorter than a threshold length if an error probability of 10^-9 is to be achieved