3,412 research outputs found
Role of ZIP14 (SLC39A14) gene histidine rich regions in neural tube defects
Neural tube defects (NTDs) comprise a group of congenital malformations that includes spina bifida, anencephaly, meningomyelocele and encephalocele. Reports have implicated zinc deficiency as one of the causative factors of NTDs. Both environmental and genetic factors are involved in the etiology of NTDs. Inadequate folate intake and nutritional deficiency are important environmental risk factors. The aim of this study was to determine the relation of a zinc related gene ZRT and IRT like protein 14 (ZIP14) and neural tube defects in Turkish patients. The case control study included seventy Turkish mothers who gave birth to NTD infants. Two hundred and thirty-nine healthy controls were consecutively selected without any congenital defects or familial NTD history. Following DNA extraction, PCR, SSCP and DNA sequencing analysis of exons of the ZIP14 gene were performed. Our data revealed that no relation of neural tube defects and ZIP14 was detected in Turkish NTD patients. Zinc deficiency have been reported as a risk factor for Turkish population and other possible zinc related gene defects may have importance.Keywords: Neural tube defects (NTDs); Zinc; ZIP1
Associative memory design using overlapping decompositions
Cataloged from PDF version of article.This paper discusses the use of decomposition techniques in the design of associative memories via arti"cial neural networks. In
particular, a disjoint decomposition which allows an independent design of lower-dimensional subnetworks and an overlapping
decomposition which allows subnetworks to share common parts, are analyzed. It is shown by a simple example that overlapping
decompositions may help in certain cases where design by disjoint decompositions fails. With this motivation, an algorithm is
provided to synthesize neural networks using the concept of overlapping decompositions. Applications of the proposed design
procedure to a benchmark example from the literature and to a pattern recognition problem indicate that it may improve the
e!ectiveness of the existing methods. ( 2001 Published by Elsevier Science Ltd
Exact Analysis of Offset-based Service Differentiation in Single-channel Multi-class OBS
Cataloged from PDF version of article.We study a multi-class optical burst switching (OBS)
node using the horizon reservation scheme. Multiple traffic
classes are differentiated using different offset times per class.
Assuming Poisson burst arrivals and phase-type distributed burst
lengths, we exactly solve for per-class blocking probabilities using
the well-known theory of feedback Markov fluid queues
Wavelength converter sharing in asynchronous optical packet/burst switching: An exact blocking analysis for markovian arrivals
Cataloged from PDF version of article.In this paper, we study the blocking probabilities
in a wavelength division multiplexing-based asynchronous
bufferless optical packet/burst switch equipped with a bank of
tuneable wavelength converters dedicated to each output fiber
line. Wavelength converter sharing, also referred to as partial
wavelength conversion, corresponds to the case of a number
of converters shared amongst a larger number of wavelength
channels. In this study, we present a probabilistic framework for
exactly calculating the packet blocking probabilities for optical
packet/burst switching systems utilizing wavelength converter
sharing. In our model, packet arrivals at the optical switch are
first assumed to be Poisson and later generalized to the more
general Markovian arrival process to cope with very general
traffic patterns whereas packet lengths are assumed to be exponentially
distributed. As opposed to the existing literature based
on approximations and/or simulations, we formulate the problem
as one of finding the steady-state solution of a continuous-time
Markov chain with a block tridiagonal infinitesimal generator. To
find such solutions, we propose a numerically efficient and stable
algorithm based on block tridiagonal LU factorizations. We show
that exact blocking probabilities can be efficiently calculated
even for very large systems and rare blocking probabilities, e.g.,
systems with 256 wavelengths per fiber and blocking probabilities
in the order of 10−40. Relying on the stability and speed of the
proposed algorithm, we also provide a means of provisioning
wavelength channels and converters in optical packet/burst
switching systems
A novel MEFV gene mutation (A511V) in a Chilean FMF patient
Familial Mediterranean fever (FMF) is an autosomal recessive disease which is characterized by recurrent fever and inflammation of serous membranes. A Chilean FMF patient was investigated for MEFV mutations. After DNA extraction, exons 3, 5, 10 and 30UTR region of MEFV gene were analyzed by DNA sequencing while E148Q and R202Q mutations of exon 2 weredetected by RFLP. A novel missense mutation, A511V (c.1532C>T, p.Ala511Val), was found in a heterozygous state in exon 5 of MEFV gene. Also, R202Q (c.605G>A, p.Arg202Gln) was detected in heterozygous state. R202Q was of clinical value in the diagnosis of FMF when combined with adisease causing mutation. In this patient, A511V was detected in compound heterozygous state with R202Q and this association may play an important role in FMF
Class-based first-fit spectrum allocation with fragmentation avoidance for dynamic flexgrid optical networks
Cataloged from PDF version of article.A novel Class-Based First Fit (CBFF) spectrum allocation policy is proposed for dynamic flexgrid optical networks. The effectiveness of the proposed CBFF policy is compared with that of the First Fit (FF) policy for single-link and network scenarios. Throughput is shown to be consistently improved under the proposed CBFF policy with throughput gains of up to 15%, compared with the FF policy for the network scenarios we studied. The reduction in bandwidth blocking probability with CBFF with respect to FF increases as the link capacities increase. Throughput gains of CBFF compared with those of FF are more significant under alternate routing as opposed to fixed routing. © 2014 Elsevier B.V. All rights reserved
TCP flow aware adaptive path switching in diffserv enabled MPLS networks
Cataloged from PDF version of article.We propose an adaptive flow-level multi-path routing-based traffic engineering solution for an IP backbone network
carrying TCP/IP traffic. Incoming TCP flows are switched between two explicitly routed paths, namely the primary and
secondary paths (PP and SP), for resilience and potential goodput improvement at the TCP layer. In the proposed
architecture, PPs receive a preferential treatment over SPs using differentiated services mechanisms. The reason for this
choice is not for service differentiation but for coping with the detrimental knock-on effect stemming from the use of longer
SP that is well known for conventional network load balancing algorithms. Moreover, both paths are congestion-controlled
using Explicit Congestion Notification marking at the core and Additive Increase Multiplicative Decrease rate adjustment
at the ingress nodes. The delay difference between PP and SP is estimated using two per-egress rate-controlling buffers
maintained at the ingress nodes for each path, and this delay difference is used to determine the path over which a new TCP
flow will be routed. We perform extensive simulations using ns-2 in order to demonstrate the viability of the proposed
distributed adaptive multi-path routing method in terms of per-flow TCP goodput. The proposed solution consistently
outperforms the single-path routing policy and provides substantial per-flow goodput gains under poor PP conditions.
Moreover, highest goodput improvements under the proposed scheme are achieved by flows that receive the lowest
goodputs with single-path routing, while the performance of the flows with high goodputs with single-path routing does not
deteriorate with the proposed path switching technique. Copyright # 2011 John Wiley & Sons, Ltd
Kinetic and thermodynamic investigations of strontium ions retention by natural kaolinite and clinoptilolite minerals
The current study was devoted to the determination of various thermodynamic and kinetic parameters resulting from the fixation of Sr2+ by natural samples of kaolinite and clinoptilolite minerals. The sorption process followed pseudo second order kinetics, with faster sorption on kaolinite compared to clinoptilolite, where the uptake is affected by intraparticle diffusion. Freundlich and Dubinin-Radushkevich isotherm models described the data more adequately than Langmuir model, and clinoptilolite showed a higher strontium sorption capacity than kaolinite. Thermodynamically, the activation energy of Sr2+ sorption by kaolinite and clinoptilolite were respectively, -8.5 and -18.4 kJ/mol. The sorption process on both minerals was spontaneous and endothermic at all the studied concentrations, with ΔH° being 11.3 and 9.8 kJ/mol, for sorption on kaolinite and clinoptilolite, respectively. The findings of this study were compared with those of an earlier study on the uptake of Cs+ by the same minerals.İYTE: 2003 İYTE 0
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
Rate-distortion optimization for stereoscopic video streaming with unequal error protection
We consider an error-resilient stereoscopic streaming system that uses an H.264-based multiview video codec and a rateless Raptor code for recovery from packet losses. One aim of the present work is to suggest a heuristic methodology for modeling the end-to-end rate-distortion (RD) characteristic of such a system. Another aim is to show how to make use of such a model to optimally select the parameters of the video codec and the Raptor code to minimize the overall distortion. Specifically, the proposed system models the RD curve of video encoder and performance of channel codec to jointly derive the optimal encoder bit rates and unequal error protection (UEP) rates specific to the layered stereoscopic video streaming. We define analytical RD curve modeling for each layer that includes the interdependency of these layers. A heuristic analytical model of the performance of Raptor codes is also defined. Furthermore, the distortion on the stereoscopic video quality caused by packet losses is estimated. Finally, analytical models and estimated single-packet loss distortions are used to minimize the end-to-end distortion and to obtain optimal encoder bit rates and UEP rates. The simulation results clearly demonstrate the significant quality gain against the nonoptimized schemes
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