bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of restart simulation: Theoretical basis and sensitivity study
Authors: Villén‐Altamirano Manuel , Villen‐Altamirano Jose 
Published: September 2008

AbstractRESTART (Repetitive Simulation Trials After Reaching Thresholds) is a widely applicable accelerated simulation technique that allows the evaluation of extremely low probabilities. This paper revisits the theoretical basis of RESTART in a more general and rigorous way. The unbiasedness of the estimator is proved and its variance is derived without need of making any assumption on the simulated system. From this analysis, the gain obtained with RESTART as well as the optimal parameter values that maximise the gain are derived. The sensitivity of the method to the choice of the importance function, threshold values and number of retrials for each threshold is studied, providing simple bounds on me impact on the gain of each of these choices.
Quantum simulation — rare event simulation by means of cloning, thinning and distortion
Authors: Addie R. G. 
Published: September 2008

AbstractA method of rare event simulation, termed herequantum simulation, and known also (with some variations) aspopulation Monte Carlo, andSequential Markov Chain simulation, is applied in this paper torare event simulationof communication systems. The technique described in this paper generalizesimportance sampling, importance splittingand die Monte Carlo method which uses a collection (population) of particles. The termquantum simulationis used for the rare‐event simulation technique presented in this paper because the entire ensemble of simulations resembles the parallel universes model of quantum mechanics. By using cloning, thinning and distortion it is possible to design simulations with the speed of importance sampling and the flexibility of importance splitting. A particularly difficult system is investigated in this paper by means of quantum simulation, namely a buffer fed by a Poisson‐Pareto Burst Process. The simulations are able to confirm an analytic approximation for this model to a degree not previously achievable. Furthermore, this approximation was originally developed as a consequence of the investigation of this model by means of quantum simulation.
On steady‐state simulation of some weak regenerative networks
Authors: Morozov Evsei , Aminova Irina 
Published: September 2008

AbstractWe discuss the possibilities of the so‐called weak regeneration in the steady‐state analysis of multiserver queues and some Jackson‐type and multiclass queueing networks when classical regenerative simulation is ineffective. A few constructions of weak regeneration for open Jackson‐type and multiclass queueing networks are given in an explicit form. Conditions are found when efficiency of weak regeneration (expressed in the simulation time needed for confidence estimation with a given precision) stays very high while the efficiency of classical regeneration is rapidly decreasing. Numerical results are also considered which illustrate an advantage of the weak regeneration in simulation of some tandem queueing networks.
Orthogonal multicarrier CDMA and its detection on frequency‐selective channels
Authors: Sari Hikmet 
Published: September 2008

AbstractMulticarrier code‐division multiple access (MC‐CDMA) first appeared in the literature in 1993. It combines conventional code‐division multiple access (CDMA) and orthogonal frequency‐division multiplexing (OFDM), and has several variants that depend on how this combination is done. Although there have been a significant number of publications on MC‐CDMA since its introduction, the literature is still very fragmented, and the terminologies used by different authors are inconsistent. In addition, there are also a number of confusions concerning the detection of MC‐CDMA signals on frequency‐selective channels. As an attempt to achieve mis goal, this paper gives a comprehensive review of MC‐CDMA, describes its different variants, and reviews the receiver techniques for orthogonal MC‐CDMA. It also discusses the relative merits of MC‐CDMA and of multicarrier time‐division multiple access (MC‐TDMA) and orthogonal frequency‐division multiple access (OFDMA) which are the two omer multiple access techniques usable in conjunction with multicarrier transmission.
Development and implementation of an advanced airport data link based on multi‐carrier communications
Authors: Haas Erik , Lang Helmuth , Schnell Michael 
Published: September 2008

AbstractIn this paper, both the concept and the demonstrator implementation of an advanced airport data link is described which is used for data exchange between pilots and controllers in future surface movement guidance and control systems on airports. To fulfil future airport capacity requirements, the proposed data link has to be a high capacity, high rate data link. Therefore, the data link design is based on multi‐carrier code‐division multiple‐access which is a flexible and highly efficient multiple‐access transmission technique suitable for mobile communications in fading conditions. Both simulation results with typical aeronautical channel scenarios and bit error rate measurements using the demonstrator hardware show the suitability of multi‐carrier code‐division multiple‐access for aeronautical communications within the airport and its vicinity. Moreover, implementation effects which degrade the performance are identified and countermeasures are proposed and investigated. The results show that a reduction of the implementation loss of up to 2 dB is achievable by applying appropriate countermeasures.
Maximum a posteriori multipath fading channel estimation for ofdm systems
Authors: Panayirci Erdal , Çirpan Hakan A. 
Published: September 2008

AbstractIn this paper, a non‐data‐aided maximum a posteriori (MAP) channel estimation technique for OFDM systems employing M‐PSK modulation scheme is proposed. The technique requires a convenient representation of the discrete multipath fading channel based on the Karhunen‐Loeve orthogonal expansion and estimates the complex channel parameters of each subcarriers iteratively in frequency domain using the Expectation‐Maximization (EM) algorithm. Pilot symbols are employed to choose reliable initial values of the unknown channel parameters. An analytical expression is derived for the exact Cramer‐Rao lower bound of the proposed MAP channel estimator. Moreover, robustness of estimator to changes in channel correlation and signal‐to‐noise ratio is also analyzed. The performance is presented in terms of the mean‐square error and the uncoded symbol error rate for a system employing QPSK signaling. Computer simulations demonstrate that the performance of OFDM systems using coherent demodulation based on our channel estimation can be significantly improved.
Delay analysis of a probabilistic priority discipline
Authors: Jiang Yuming , Tham Chen‐Khong , Ko Chi‐Chung 
Published: September 2008

AbstractIn computer networks, the Strict Priority (SP) discipline is perhaps the most common and simplest method to schedule packets from different classes of applications, each with diverse performance requirements. With this discipline, however, packets at higher priority levels can starve packets at lower priority levels. To resolve this starvation problem, we propose to assign a parameter to each priority queue in the SP discipline. The assigned parameter determines the probability or extent by which its corresponding queue is served when the queue is polled by the server. We thus form a new packet service discipline, referred to as the Probabilistic Priority (PP) discipline. By properly adjusting the assigned parameters, not only is the performance of higher priority classes satisfied, but also the performance of lower priority classes can be improved. This paper analyzes the delay performance of the PP discipline. A decomposition approach is proposed for calculating the average waiting times and their bounds are studied. Two approximation approaches are proposed to estimate the waiting times. Simulation results that validate the numerical analysis are presented and examined. A numerical example which demonstrates the use of the PP discipline to achieve service differentiation is presented. This example also shows how the assigned parameters can be determined from the results of analysis mentioned above.
An analytical expression for the acquisition time and optimal designing graph for a frequency detector of OFDM systems
Authors: Pinchas Monika , Hasson Jaime , Bobrovsky Ben Zion 
Published: September 2008

AbstractIn this paper we introduce an analytical expression for the acquisition time of a frequency detector used in OFDM systems. We present a useful “designing graph” which eliminates the need to simulate the whole system in order to obtain the optimal number of guard interval samples, that should be used by the frequency detector.
Study of an european all optical transport transparent network based on the 16×2.5 Gbit/S transmission
Authors: Joindot Michel , Matera Francesco , Settembre Marina , Weinert Carl 
Published: September 2008

AbstractIn this work we report a transmission study on the possibility of implementing an all optical transparent network based on WDM 16×2.5 Gbit/s systems, which connects the main cities of Europe. We show that severe transmission problems are present and that they are due to the impact of the fibre nonlinear Kerr effect in terms of cross phase modulation. Numerical results shows that such an impairment can be strongly limited by the use of the dispersion management with fibre gratings and good performance can be achieved for the longest paths of the order of 2000 km.
Performance comparison of square root raised‐cosine and lerner filters for the MDFT‐TMUX filter bank
Authors: Madhu Rao A. Sudana , Prabhu K. M. M. 
Published: September 2008

AbstractThis paper deals with prototype filters, namely, square root raised — cosine (SRC) and Lerner filters in the modified discrete Fourier transform (MDFT) transmultiplexer (TMUX) filter bank. The error obtained in the reconstruction of the original signal is compared for various filter orders. These filters can be employed in multicarrier modulation system‐ overlapped discrete multitone (overlapped DMT) or discrete wavelet multitone (DWMT) system. However, with the SRC filter, a large number of computations are required. By employing Lerner filter, we can reduce this by atleast 3‐ folds. We have carried out simulation studies for an 8‐channel MDFT‐ TMUX filter bank and the results obtained are presented.
A Bayesian model averaging approach for cost‐effectiveness analyses
Authors: Conigliani Caterina , Tancredi Andrea 
Published: September 2008

AbstractWe consider the problem of assessing new and existing technologies for their cost‐effectiveness in the case where data on both costs and effects are available from a clinical trial, and we address it by means of the cost‐effectiveness acceptability curve. The main difficulty in these analyses is that cost data usually exhibit highly skew and heavy‐tailed distributions so that it can be extremely difficult to produce realistic probabilistic models for the underlying population distribution, and in particular to model accurately the tail of the distribution, which is highly influential in estimating the population mean. Here, in order to integrate the uncertainty about the model into the analysis of cost data and into cost‐effectiveness analyses, we consider an approach based on Bayesian model averaging: instead of choosing a single parametric model, we specify a set of plausible models for costs and estimate the mean cost with a weighted mean of its posterior expectations under each model, with weights given by the posterior model probabilities. The results are compared with those obtained with a semi‐parametric approach that does not require any assumption about the distribution of costs. Copyright © 2008 John Wiley & Sons, Ltd.
Physical inactivity and its impact on healthcare utilization
Authors: Sari Nazmi 
Published: September 2008

AbstractPhysically inactive people are expected to use more healthcare services than active people. This inactivity imposes costs on the collectively funded health insurance programs. In this paper, excess utilization of healthcare services due to physical inactivity is examined using count data models and the Canadian Community Health Survey. The aim of the paper is to estimate utilization of healthcare services associated with inactivity and to estimate its impact on the Canadian healthcare system. The results suggest that physical inactivity increases hospital stays, and use of physician and nurse services. On average, an inactive person spends 38% more days in hospital than an active person. S/he also uses 5.5% more family physician visits, 13% more specialist services, and 12% more nurse visits than an active individual. The subsequent social cost of inactivity for the healthcare system is substantial. Copyright © 2008 John Wiley & Sons, Ltd.
Early phase of maternal skin carcinogenesis recruits long‐term engrafted fetal cells
Authors: Huu Sau Nguyen , Khosrotehrani Kiarash , Oster Michèle , Moguelet Philippe , Espié Marie‐Josée , Aractingi Sélim 
Published: September 2008

AbstractDuring pregnancy, fetal cells enter the maternal circulation. These may be mesenchymal stem cells, haematopoietic or endothelial progenitors, which may persist for decades and be recruited to damaged maternal tissues. Recently, fetal cells were also identified in tumour tissues such as cervical cancer and breast carcinomas. However, the timing of malignant tumour infiltration was not demonstrated. In this study, we used two step carcinogenesis to assess the presence of fetal cells in early phases of skin tumour formation in previously pregnant mice. Wild‐type female C57/BL6 mice were bred to transgenic mice for EGFP. After delivery, skin papillomas were induced by two‐step carcinogenesis. The tumours were dissected 9 months after gestation. Fetal cells were identified in 75% of cutaneous papillomas (9/12 tumours), but never in normal skin from the same mice. Fetal cells expressed von‐Willebrand factor, and less frequently CD45 or cytokeratin but did not express the tumoral epidermal keratins. Our study shows that long‐term engrafted fetal cells home to early stage skin tumours where they participate in formation of the stroma. © 2008 Wiley‐Liss, Inc.
A pooled analysis of melanocytic nevus phenotype and the risk of cutaneous melanoma at different latitudes
Authors: Chang Yu‐mei , Newton‐Bishop Julia A. , Bishop D. Timothy , Armstrong Bruce K. , Bataille Veronique , Bergman Wilma , Berwick Marianne , Bracci Paige M. , Elwood J. Mark , Ernstoff Marc S. , Green Adèle C. , Gruis Nelleke A. , Holly Elizabeth A. , Ingvar Christian , Kanetsky Peter A. , Karagas Margaret R. , Marchand Loïc Le , Mackie Rona M. , Olsson Håkan , Østerlind Anne , Rebbeck Timothy R. , Reich Kristian , Sasieni Peter , Siskind Victor , Swerdlow Anthony J. , Titus‐Ernstoff Linda , Zens Michael S. , Ziegler Andreas , Barrett Jennifer H. 
Published: September 2008

AbstractAn abnormal nevus phenotype is associated with an increased risk of melanoma. We report a pooled analysis conducted using individual nevus data from 15 case‐control studies (5,421 melanoma cases and 6,966 controls). The aims were to quantify the risk better and to determine whether relative risk is varied by latitude. Bayesian unconditional logistic random coefficients models were employed to study the risk associated with nevus characteristics. Participants with whole body nevus counts in the highest of 4 population‐based categories had a greatly increased risk of melanoma compared with those in the lowest category (pooled odds ratio (pOR) 6.9 (95% confidence interval (CI): 4.4, 11.2) for those aged <50 years and pOR 5.1 (95% CI: 3.6, 7.5) for those aged ≥50). The pOR for presence compared with absence of any clinically atypical nevi was 4.0 (95% CI: 2.8, 5.8). The pORs for 1–2 and ≥3 large nevi on the body compared with none were 2.9 (95% CI: 1.9, 4.3) and 7.1 (95% CI: 4.7, 11.6), respectively. The relative heterogeneities among studies were small for most measures of nevus phenotype, except for the analysis of nevus counts on the arms, which may have been due to methodological differences among studies. The pooled analysis also suggested that an abnormal nevus phenotype is associated most with melanomas on intermittently sun‐exposed sites. The presence of increased numbers of nevi, large nevi and clinically atypical nevi on the body are robust risk factors for melanoma showing little variation in relative risk among studies performed at different latitudes. © 2008 Wiley‐Liss, Inc.
Comparison of cytotoxic and inflammatory responses of photoluminescent silicon nanoparticles with silicon micron‐sized particles in RAW 264.7 macrophages
Authors: Choi Jonghoon , Zhang Qin , Reipa Vytas , Wang Nam Sun , Stratmeyer Melvin E. , Hitchins Victoria M. , Goering Peter L. 
Published: September 2008

AbstractPhotoluminescent silicon nanoparticles have a bright and stable fluorescence and are promising candidates for bio‐imaging, cell staining and drug delivery. With increasing development of nanotechnology applications for biomedicine, an understanding of the potential toxicity of nanoparticles is needed to assess safety concerns for clinical applications. The objective of this study was to compare biological responses of silicon nanoparticles (SNs, 3 nm diameter) with silicon microparticles (SMs, ∼100–3000 nm diameter) in cultured murine macrophages (RAW 264.7) using standard protocols for assessing cytotoxicity/cell viability and inflammatory responses developed for micron‐sized particles. SNs and SMs were exposed to macrophages with and without addition of endotoxin lipopolysaccharide (LPS), a positive inducer of tumor necrosis factor‐alpha (TNF‐α), interleukin 6 (IL‐6), and nitric oxide (NO). Cytotoxicity was assayed using the dye exclusion and MTT assays. Cell supernatants were assayed for production TNF‐α, IL‐6 and NO. SNs at concentrations ≤20 µg ml−1 exhibited no cytotoxicity or inflammatory responses; however, SNs and SMs >20 and 200 µg ml−1, respectively, increased cytotoxicity compared with controls. SMs induced concentration‐related increases in TNF‐α and IL‐6 production; in contrast, the production of these cytokines was shown to decrease with increasing concentrations of SNs. NO production was not induced by SNs or SMs alone. Fluorescence microscopy demonstrated that SNs were associated with the macrophages, either internalized or attached to cell membranes. In conclusion, evaluating differences in biological responses for nanoparticles compared with microparticles of the same material may help improve tests to assess biological responses of nanoparticles that may be used in biomedical applications. Copyright © 2008 John Wiley & Sons, Ltd.
Characterization of Pseudomonas sp. BCNU 171 tolerant to organic solvents
Authors: Choi Hye Jung , Kim Seon‐A , Kim Dong Wan , Moon Ja Young , Jeong Yong Kee , Joo Woo Hong 
Published: September 2008

AbstractAn organic solvent‐tolerant bacterium, designated as Pseudomonas sp. BCNU 171, was isolated from industrial wastewater in Korea, on the basis of its ability to survive in the presence of benzene, toluene, propylbenzene and xylenes. Its tolerance limits were 8 mM in phenol, 20 mM in benzene and 60 M in toluene. The log P value of phenol was approximately 1.5, which indicates that Pseudomonas sp. BCNU 171 exhibits the highest tolerance to organic solvents. Pseudomonas sp. BCNU 171, a relative of P. putida, P. mosselii and P. moteillii based on phylogenetic analyses using 16S rRNA sequences, was designated as a new sp. that is tolerant to a wide spectrum of organic solvents, especially xylene isomers. These findings may facilitate the understanding of organic solvent tolerance in bacterial cells. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synergistic effect of beneficial rhizosphere microflora in biocontrol and plant growth promotion
Authors: Kannan Vijayaragahavan , Sureendar Raman 
Published: September 2008

AbstractBiological systems are getting more relevance than chemical control of plant pathogens as they are not only eco‐friendly and economic in approach but are also involved in improving the soil consistency and maintenance of natural soil flora. Plant growth promoting rhizosphere microorganisms were isolated from three different tree rhizospheres using selective culture media. Five microorganisms were selected from each rhizosphere soil based on their efficiency and screened for their ability to promote plant growth as a consortium. Each of the developed consortium has a phosphate solubilizer, nitrogen fixer, growth hormone producer, heterotrophic member and an antagonist. The plant growth promoting ability of the microbial members present in the consortium was observed by estimating the IAA production level and also by the nitrogenase activity of the nitrogen fixers. The biocontrol potentiality of the consortium and the antagonist present in the consortium were checked by both dual plate assay and cross‐streaking technique. Consortial treatments effected very good growth promotion in Lycopersicon esculentum Mill and the treated plants also developed resistance against wilt pathogen, Fusarium oxysporum f. sp. lycopersici though the effect was well pronounced with consortium developed from Santalum album. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Acquisition of deeper knowledge on the human plasma fatty acid profile exploiting comprehensive 2‐D GC
Authors: Quinto Tranchida Peter , Costa Rosaria , Donato Paola , Sciarrone Danilo , Ragonese Carla , Dugo Paola , Dugo Giovanni , Mondello Luigi 
Published: September 2008

AbstractThe present research is focused on the use of comprehensive 2‐D GC (GC×GC) for the elucidation of the human plasma fatty acid (FA) profile. The enhanced sensitivity, increased separation power and the formation of group‐type patterns provided by GC×GC enabled the identification and quantification of a high number of both well known and unexpected FAs, for a total of 65 components. Peak assignment was, in most cases, supported by using pure standard compounds. The results attained demonstrated the usefulness of the multidimensional GC method in this fundamental field of research.
Post‐traumatic stress in survivors of an airplane crash‐landing: A clinical and exploratory research intervention
Authors: Sloan Patrick 
Published: September 2008

AbstractPost‐traumatic stress in 30 male survivors of an airplane crash‐landing was studied through interviews and questionnaires based on a nonpathological model of preventive psychological intervention and monitoring. Five questionnaires were given initially 12 days after the event and repeated at 2, 5, 10, and 12 months. Two of the brief measures were given weekly from 2 to 8 weeks after the event. As a group, the survivors experienced high levels of stress initially, which decreased rapidly and leveled off over time. There was, however, significant variability among individuals in this seemingly homogeneous group of college basketball players and supportive personnel in their experience of stress to the same traumatic event. There was also a marked contrast between group questionnaire results and individual verbal descriptions of their reaction to an unrelated, fatal airplane crash on the campus of the survivors 1 month after their own crash‐landing. Questionnaire data are presented descriptively and discussed in relation to other normative data in the literature and to the methods of observation in this study. Recommendations are offered for professionals attempting this type of field study.