657 research outputs found
State Aggregation-based Model of Asynchronous Multi-Fiber Optical Switching with Shared Wavelength Converters
Cataloged from PDF version of article.This paper proposes new analytical models to study optical packet switching architectures
with multi-fiber interfaces and shared wavelength converters. The multi-fiber
extension of the recently proposed Shared-Per-Input-Wavelength (SPIW) scheme is
compared against the multi-fiber Shared-Per-Node (SPN) scheme in terms of cost and
performance for asynchronous traffic. In addition to using Markov chains and fixed-point
iterations for modeling the mono-fiber case, a novel state aggregation technique is
proposed to evaluate the packet loss in asynchronous multi-fiber scenario. The accuracy
of the performance models is validated by comparison with simulations in a wide variety
of scenarios with both balanced and imbalanced input traffic. The proposed analytical
models are shown to remarkably capture the actual system behavior in all scenarios we
tested. The adoption of multi-fiber interfaces is shown to achieve remarkable savings in
the number of wavelength converters employed and their range. In addition, the SPIW
solution allows to save, in particular conditions, a significant number of optical gates
compared to the SPN solution. Indeed, SPIW allows, if properly dimensioned, potential
complexity and cost reduction compared to SPN, while providing similar performance.
(C) 2013 Elsevier B.V. All rights reserved
Evaluation of the Precision-Privacy Tradeoff of Data Perturbation for Smart Metering
Abstract:
Smart grid users and standardization committees require that utilities and third parties collecting metering data employ techniques for limiting the level of precision of the gathered household measurements to a granularity no finer than what is required for providing the expected service. Data aggregation and data perturbation are two such techniques. This paper provides quantitative means to identify a tradeoff between the aggregation set size, the precision on the aggregated measurements, and the privacy level. This is achieved by formally defining an attack to the privacy of an individual user and calculating how much its success probability is reduced by applying data perturbation. Under the assumption of time-correlation of the measurements, colored noise can be used to even further reduce the success probability. The tightness of the analytical results is evaluated by comparing them to experimental data
Shared-per-wavelength asynchronous optical packet switching: A comparative analysis
Cataloged from PDF version of article.This paper compares four different architectures for sharing wavelength converters in
asynchronous optical packet switches with variable-length packets. The first two architectures
are the well-known shared-per-node (SPN) and shared-per-link (SPL) architectures,
while the other two are the shared-per-input-wavelength (SPIW) architecture, recently
proposed as an optical switch architecture in synchronous context only, which is extended
here to the asynchronous scenario, and an original scheme called shared-per-output-wavelength
(SPOW) architecture that we propose in the current article. We introduce novel analytical
models to evaluate packet loss probabilities for SPIW and SPOW architectures in
asynchronous context based on Markov chains and fixed-point iterations for the particular
scenario of Poisson input traffic and exponentially distributed packet lengths. The models
also account for unbalanced traffic whose impact is thoroughly studied. These models are
validated by comparison with simulations which demonstrate that they are remarkably
accurate. In terms of performance, the SPOW scheme provides blocking performance very
close to the SPN scheme while maintaining almost the same complexity of the space
switch, and employing less expensive wavelength converters. On the other hand, the SPIW
scheme allows less complexity in terms of number of optical gates required, while it substantially
outperforms the widely accepted SPL scheme. The authors therefore believe that
the SPIW and SPOW schemes are promising alternatives to the conventional SPN and SPL
schemes for the implementation of next-generation optical packet switching systems.
2010 Elsevier B.V. All rights reserved
Analytical model of asynchronous shared-per-wavelength multi-fiber optical switch
In this paper, a buffer-less shared-per-wavelength optical switch is equipped with multi-fiber interfaces and operated in asynchronous context. An analytical model to evaluate loss performance is proposed using an approximate Markov-chain based approach and the model is validated by simulations. The model is demonstrated to be quite accurate in spite of the difficulty in capturing correlation effects especially for small switch sizes. The model is also applied to calculate the number of optical components needed to design the optical switch according to packet loss requirements. The impact of the adoption of multiple fiber interfaces is outlined in terms of the remarkable saving in the number of wavelength converters employed, while increasing at the same time the number of optical gates needed by the space switching subsystem. The numerical results produced are a valuable basis to optimize overall switch cost. © 2011 IEEE
Oxygen-isotope effect on the in-plane penetration depth in underdoped Y_{1-x}Pr_xBa_2Cu_3O_{7-delta} as revealed by muon-spin rotation
The oxygen-isotope (^16O/^18O) effect (OIE) on the in-plane penetration depth
in underdoped Y_{1-x}Pr_xBa_2Cu_3O_{7-delta} was studied by
muon-spin rotation. A pronounced OIE on was observed
with a relative isotope shift of
=-5(2)% for x =0.3 and -9(2)% for
x=0.4. It arises mainly from the oxygen-mass dependence of the in-plane
effective mass . The OIE exponents of T_{c} and of
exhibit a relation that appears to be generic for
cuprate superconductors.Comment: 4 pages, 4 eps figures, RevTex
Packet loss analysis of synchronous buffer-less optical switch with shared limited range wavelength converters
Application of synchronous optical switches in Optical Packet/Burst switched networks is considered. The shared per node architectural concept, where wavelength converters are shared among all input and output channels, is applied for contention resolution in the wavelength domain. A semi-analytical traffic model suitable to represent the different contributions to packet loss is proposed and validated. Full and limited range wavelength conversion capabilities are considered, and loss results obtained to support switch design. An approximated fully analytical approach for the limited range case is also described and comparison with simulation results is presented to assess the capability to capture the main aspects of packet loss behavior. ©2007 IEEE
\u3cem\u3ePhaeophleospora vochysiae\u3c/em\u3e Savi & Glienke sp. nov. Isolated from \u3cem\u3eVochysia divergens\u3c/em\u3e Found in the Pantanal, Brazil, Produces Bioactive Secondary Metabolites
Microorganisms associated with plants are highly diverse and can produce a large number of secondary metabolites, with antimicrobial, anti-parasitic and cytotoxic activities. We are particularly interested in exploring endophytes from medicinal plants found in the Pantanal, a unique and widely unexplored wetland in Brazil. In a bio-prospecting study, strains LGMF1213 and LGMF1215 were isolated as endophytes from Vochysia divergens, and by morphological and molecular phylogenetic analyses were characterized as Phaeophleospora vochysiae sp. nov. The chemical assessment of this species reveals three major compounds with high biological activity, cercoscosporin (1), isocercosporin (2) and the new compound 3-(sec-butyl)-6-ethyl-4,5-dihydroxy-2-methoxy-6-methylcyclohex-2-enone (3). Besides the isolation of P. vochysiae as endophyte, the production of cercosporin compounds suggest that under specific conditions this species causes leaf spots, and may turn into a pathogen, since leaf spots are commonly caused by species of Cercospora that produce related compounds. In addition, the new compound 3-(sec-butyl)-6-ethyl-4,5-dihydroxy-2-methoxy-6-methylcyclohex-2-enone showed considerable antimicrobial activity and low cytotoxicity, which needs further exploration
Genetic variation of CYP2C19 affects both pharmacokinetic and pharmacodynamic responses to clopidogrel but not prasugrel in aspirin-treated patients with coronary artery disease
The metabolic pathways leading to the formation of prasugrel and clopidogrel active metabolites differ. We hypothesized that decreased CYP2C19 activity affects the pharmacokinetic and pharmacodynamic response to clopidogrel but not prasugrel. Ninety-eight patients with coronary artery disease (CAD) taking either clopidogrel 600 mg loading dose (LD)/75 mg maintenance dose (MD) or prasugrel 60 mg LD/10 mg MD were genotyped for variation in six CYP genes. Based on CYP genotype, patients were segregated into two groups: normal function (extensive) metabolizers (EM) and reduced function metabolizers (RM). Plasma active metabolite concentrations were measured at 30 min, 1, 2, 4, and 6 h post-LD and during the MD period on Day 2, Day 14, and Day 29 at 30 min, 1, 2, and 4 h. Vasodilator-stimulated phosphoprotein (VASP) and VerifyNow (TM) P2Y12 were measured predose, 2, and 24 +/- 4 h post-LD and predose during the MD period on Day 14 +/- 3 and Day 29 +/- 3. For clopidogrel, active metabolite exposure was significantly lower (P = 0.0015) and VASP platelet reactivity index (PRI, %) and VerifyNow (TM) P2Y(12) reaction unit (PRU) values were significantly higher (P < 0.05) in the CYP2C19 RM compared with the EM group. For prasugrel, there was no statistically significant difference in active metabolite exposure or pharmacodynamic response between CYP2C19 EM and RM. Variation in the other five genes demonstrated no statistically significant differences in pharmacokinetic or pharmacodynamic responses. Variation in the gene encoding CYP2C19 in patients with stable CAD contributes to reduced exposure to clopidogrel's active metabolite and a corresponding reduction in P2Y(12) inhibition, but has no significant influence on the response to prasugrel
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