bluuebunny/crossref_metadata_2025 huggingface dataset:
Injector‐internal thermal desorption from edible oils performed by programmed temperature vaporizing (PTV) injection
Authors: Fankhauser‐Noti Anja , Grob Koni
Published: September 2006

Injector‐internal thermal desorption is a promising technique for the analysis of a wide range of food components (e. g., flavors) or food contaminants (e. g., solvent residues, pesticides, or migrants from packaging materials) in edible oils and fats or fatty food extracts. Separation from the fatty matrix occurs during injection. Using programmed temperature vaporizing (PTV) injection, the oily sample or sample extract was deposited on a small pack of glass wool from which the components of interest were evaporated and transferred into the column in splitless mode, leaving behind the bulk of the matrix. Towards the end of the analysis, the oil was removed by heating out the injector and backflushing the precolumn. The optimization dealt with the gas supply configuration enabling backflush, the injector temperature program (sample deposition, desorption, and heating out), separation of the sample liquid from the syringe needle and positioning it on a support, deactivation of the support surface, holding the plug of fused silica wool by a steel wire, and the analytical sequence maintaining adsorptivity at the desorption site low. It was performed for a mixture of poly(vinyl chloride) (PVC) plasticizers in oil or fatty food. Using MS in SIM, the detection limit was below 0.1 mg/kg for plasticizers forming single peaks and 1 mg/kg for mixtures like diisodecyl phthalate. For plasticizers, RSDs of the concentrations were below 10%; for the slip agents, oleamide and erucamide, it was 12%. The method of incorporating PTV injection was used for about one year for determining the migration from the gaskets of lids for glass jars into oily foods.
Molecular weight of guar gum affects short‐chain fatty acid profile in model intestinal fermentation
Authors: Stewart Maria L. , Slavin Joanne L.
Published: September 2006

Dietary fiber exerts many beneficial physiological effects; however, not all types of dietary fiber display the same effects. Partially hydrolyzed guar gum (PHGG), a lower molecular weight form of guar gum, is more easily incorporated into food, but may have less pronounced physiological effects than the native form. The aim of this study was to identify differences in intestinal fermentability based on the molecular weight of guar gum. Guar gum of four molecular masses (15, 20, 400, and 1100 kDa) was fermented using a batch in vitro fermentation system. Human fecal inoculum was the source of microbes. The 400‐kDa fraction produced the greatest concentrations of total short‐chain fatty acid (SCFA) at 8 h and the highest amounts of butyrate at 24 h. At 24 h, the 400‐kDa fraction produced more total SCFA and propionate than the 15 kDa, but was not different than 20 kDa or 1100 kDa fractions. The molecular weight of guar gum was positively correlated with acetate production and negatively correlated with propionate production. This study concludes that 400‐kDa guar gum may be optimal for intestinal fermentability. In conclusion, the molecular weight of guar gum affects in vitro fermentability and should be considered when adding to a food or beverage.
Effect of cationic flaxseed protein hydrolysate fractions on the in vitro structure and activity of calmodulin‐dependent endothelial nitric oxide synthase
Authors: Omoni Adetayo O. , Aluko Rotimi E.
Published: September 2006

The objective of this study was to determine the in vitro effects of cationic flaxseed protein hydrolysate fractions on calmodulin (CaM) structure as well as the activity of CaM‐dependent endothelial nitric oxide synthase (eNOS). Flaxseed protein isolate was hydrolyzed with alcalase, and two peptide fractions were isolated by cation‐exchange chromatography. Fraction I, eluted first from the column, and fraction II contained 42% and 51% contents of basic amino acids, respectively. Fractions I and II reduced the activity of CaM‐dependent eNOS through a mostly mixed‐type inhibition mode. Fraction II was at least ten times more effective as an eNOS inhibitor when compared to fraction I, as evident from the IC50 (concentration of protein hydrolysate that reduced eNOS activity by 50%) values. Fluorescence spectroscopy showed that the tyrosine residues in CaM were increasingly exposed upon addition of fraction I, while the opposite was the case when fraction II was added. Circular dichroism studies showed that fractions I and II reduced the α‐helix content but increased the rigidity of the active calcium/CaM complex. We concluded that ability of the protein hydrolysate fractions to change the secondary and tertiary structures of CaM may explain their ability to reduce activity of CaM‐dependent eNOS.
Urinary retention and sympathetic sphincter obstruction in axonal Guillain–Barré syndrome
Authors: Sakakibara Ryuji , Uchiyama Tomoyuki , Tamura Noriko , Kuwabara Satoshi , Asahina Masato , Hattori Takamichi
Published: September 2006

A 62‐year‐old woman with axonal Guillain–Barré syndrome developed weakness and urinary retention simultaneously. The retention failed to recover for 10 months even after she regained the ability to walk. The patient exhibited no postural hypotension. Videourodynamics showed that the retention was caused not by the bladder paralysis but rather by internal (sympathetic) sphincter obstruction, which is extremely uncommon in peripheral neuropathies. We started the patient on an alpha‐adrenergic antagonist, urapidil, at 30 mg/day, and this led to successful relaxation of the urethra and reduced the postvoid residual from 200 ml to less than 30 ml. The underlying mechanisms of urinary retention in our patient appeared to involve hyperactive lumbosacral sympathetic nerves. Urinary retention and sympathetic sphincter obstruction can thus be features of axonal Guillain–Barré syndrome. Muscle Nerve, 2006
Hereditary neuropathy with liability to pressure palsy combined with schwannomas of the median and medial plantar nerves
Authors: Heckmann Josef G. , Dütsch Matthias , Buslei Ralf
Published: September 2006

A 42‐year‐old woman was surgically treated for carpal tunnel syndrome, revealing schwannoma of the median nerve. A year later, she developed a tarsal tunnel syndrome. At time of this diagnosis, hereditary neuropathy with liability to pressure palsies (HNPP) was diagnosed genetically and a schwannoma of the medial plantar nerve was treated surgically. The occurrence of HNPP and schwannomas in the same patient might be purely coincidental, but it is tempting to speculate that they share a common genetic basis. Muscle Nerve, 2006
Weekly oral prednisolone improves survival and strength in male mdx mice
Authors: Keeling Richard M. , Golumbek Paul T. , Streif Elizabeth M. , Connolly Anne M.
Published: September 2006

Although corticosteroids alleviate weakness in mdx mice, no long‐term treatment has determined whether this benefit is maintained. We studied mdx mice forelimb grip strength and fatigue from 3 through 84 weeks and followed survival through 104 weeks. The mdx mice were given twice weekly oral prednisolone (5 mg/kg) beginning at 3 or 4 weeks. Treated mdx mice survived longer than untreated mice. Between 3 and 10 weeks, treated and untreated mdx mice had similar strength. Between 10 and 24 weeks, strength and strength per gram body weight declined more slowly in treated than untreated mdx mice. Between 24 and 84 weeks, treated and untreated mdx mice declined in strength at the same rate, although treated mice remained stronger. Forelimb grip fatigue was present in untreated mdx mice at all time‐points compared to wild‐type and was not changed significantly by treatment. We have demonstrated long‐term benefit of oral prednisolone in the mdx mouse model of Duchenne muscular dystrophy (DMD). As corticosteroids remain the most validated long‐term treatment of DMD, this work may allow for better prediction of synergistic treatments likely to translate to effective improvement for boys with this progressive muscular dystrophy. Muscle Nerve, 2006
Reliable surrogate outcome measures in multicenter clinical trials of Duchenne muscular dystrophy
Authors: Mayhew Jill E. , Florence Julaine M. , Mayhew Thomas P. , Henricson Erik K. , Leshner Robert T. , McCarter Robert J. , Escolar Diana M. ,   and The CINRG Investigators
Published: September 2006

We studied the reliability of a series of endpoints in an evaluation of subjects with Duchenne muscular dystrophy (DMD). The endpoints included quantitative muscle tests (QMTs), timed function tests, forced vital capacity (FVC), and manual muscle tests (MMT). Thirty‐one ambulatory subjects with DMD (mean age 8.9 years; range 5–16 years) were evaluated at eight sites by 15 newly trained evaluators as a test of interrater reliability of outcome measures. Both total QMT score [intraclass correlation coefficient (ICC) 0.96] and individual QMT assessments (ICC 0.85–0.96) were highly reliable. Forced vital capacity and all timed function tests were also highly reliable (ICC 0.97–0.99). MMT was the least reliable assessment method (ICC 0.61). These data suggest that primary surrogate outcome measures in large multicenter clinical trials in DMD should use QMT, FVC, or time function tests to obtain maximum power and greatest sensitivity. Muscle Nerve, 2006
Neuromuscular disorders in pregnancy
Authors: Sax Tracy Williams , Rosenbaum Richard B.
Published: September 2006

Many neuromuscular conditions occur more frequently during pregnancy and include carpal tunnel syndrome, Bell's palsy, lumbosacral radiculopathy, meralgia paresthetica, intercostal neuralgia, and other compression neuropathies. Preexisting or coincident neuromuscular diseases, including demyelinating polyneuropathies, inflammatory muscle disease, myasthenia gravis, and inherited nerve and muscle disease present specific problems during pregnancy. We review management of neuromuscular disorders during pregnancy, labor, delivery, and the early postpartum period. Muscle Nerve, 2006
Efficiency and fairness of system‐optimal routing with user constraints
Authors: Schulz Andreas S. , Stier‐Moses Nicolás E.
Published: September 2006

We study the route‐guidance system proposed by Jahn, Möhring, Schulz, and Stier‐Moses Operations Research 53 (2005), 600–616 from a theoretical perspective. As system‐optimal guidance is known to be problematic, this approach computes a traffic pattern that minimizes the total travel time subject to user constraints. These constraints are designed to ensure that routes suggested to users are not much longer than shortest paths for the prevailing network conditions. To calibrate the system, a certain measure—called normal length—must be selected. We show that when this length is defined as the travel time at equilibrium, the resulting traffic assignment is provably efficient and close to fair. To measure efficiency, we compare the output to the best solution without guidance and to user equilibria. To measure unfairness, we compare travel times of different users, and show that they do not differ too much. Inefficient or unfair traffic assignments cause users to travel too long or discourage people from accepting the system; either consequence would jeopardize the potential impact of a route‐guidance system. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(4), 223–234 2006
Extreme point characterizations for infinite network flow problems
Authors: Romeijn H. Edwin , Sharma Dushyant , Smith Robert L.
Published: September 2006

We study capacitated network flow problems with demands defined on a countably infinite collection of nodes having finite degree. This class of network flow models includes, for example, all infinite horizon deterministic dynamic programs with finite action sets, because these are equivalent to the problem of finding a shortest path in an infinite directed network. We derive necessary and sufficient conditions for flows to be extreme points of the set of feasible flows. Under an additional regularity condition met by all such problems with integer data, we show that a feasible solution is an extreme point if and only if it contains neither a cycle nor a doubly‐infinite path consisting of free arcs (an arc is free if its flow is strictly between its upper and lower bounds). We employ this result to show that the extreme points can be characterized by specifying a basis. Moreover, we establish the integrality of extreme point flows whenever node demands and arc capacities are integer valued. We illustrate our results with an application to an infinite horizon economic lot‐sizing problem. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(4), 209–222 2006
On the spanningw‐wide diameter of the star graph
Authors: Lin Cheng‐Kuan , Huang Hua‐Min , Hsu D. Frank , Hsu Lih‐Hsing
Published: September 2006

Letuandvbe any two distinct nodes of an undirected graphG, which isk‐connected. A containerC(u,v) betweenuandvis a set of internally disjoint paths {P1,P2,…,Pw} betweenuandvwhere 1 ≤w≤k. The width ofC(u,v) iswand the length ofC(u,v) {written aslC(u,v) is max {l(Pi) ∣ 1 ≤i≤w}. Aw‐containerC(u,v) is a container with widthw. Thew‐wide distance betweenuandv,dw(u,v), is min {l(C(u,v)) ∣C(u,v) is aw‐container}. Aw‐containerC(u,v) of the graphGis aw*‐container if every node ofGis incident with a path inC(u,v). That means that thew‐containerC(u,v) spans the whole graph. LetSnbe then‐dimensional star graph withn≥ 5. It is known thatSnis bipartite. In this article, we show that, for any pair of distinct nodesuandvin different partite sets ofSn, there exists an (n− 1)*‐containerC(u,v) and the (n− 1)‐wide distanced(n− 1)(u,v) is less than or equal to${n!\over n-2}+1$. In addition, we also show the existence of a 2*‐containerC(u,v) and the 2‐wide distanced2(u,v) is bounded above by${n!\over 2}+1$. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(4), 235–249 2006
Heterograft copolymers of poly(ε‐caprolactone) prepared by combination of ATRA “grafting onto” and ATRP “grafting from” processes
Authors: Riva R. , Rieger J. , Jérôme R. , Lecomte PH.
Published: September 2006

This paper aims at reporting on the synthesis of a heterograft copolymer by combining the “grafting onto” process based on atom transfer radical addition (ATRA) and the “grafting from” process by atom transfer radical polymerization (ATRP). The statistical copolymerization of ε‐caprolactone (εCL) and α‐chloro‐ε‐caprolactone (αClεCL) was initiated by 2,2‐dibutyl‐2‐stanna‐1,3‐dioxepane (DSDOP), followed by ATRA of parts of the chlorinated units of poly(αClεCL‐co‐εCL) on the terminal double bond of α‐MeO,ω‐CH2CHCH2CO2‐poly(ethylene oxide) (PEO). The amphiphilic poly(εCL‐g‐EO) graft copolymer collected at this stage forms micelles as supported by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The unreacted pendant chloro groups of poly(εCL‐g‐EO) were used to initiate the ATRP of styrene with formation of copolymer with two populations of randomly distributed grafts, that is PEO and polystyrene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6015–6024, 2006
Viscoelastic dewetting of constrained polymer thin films
Authors: Gabriele Sylvain , Damman Pascal , Sclavons Séverine , Desprez Sylvain , Coppée Séverine , Reiter Günter , Hamieh Moustafa , Akhrass Samer Al , Vilmin Thomas , Raphaël Elie
Published: September 2006

Thin films of fluids are playing a leading role in countless natural and industrial processes. Here we study the stability and dewetting dynamics of viscoelastic polymer thin films. The dewetting of polystyrene close to the glass transition reveals unexpected features: asymmetric rims collecting the dewetted liquid and logarithmic growth laws that we explain by considering the nonlinear velocity dependence of friction at the fluid/solid interface and by evoking residual stresses within the film. Systematically varying the time so that films were stored below the glass‐transition temperature, we studied simultaneously the probability for film rupture and the dewetting dynamics at early stages. Both approaches proved independently the significance of residual stresses arising from the fast solvent evaporation associated with the spin‐coating process. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3022–3030, 2006
Thickness of the soft layer on glassy polystyrene surfaces
Authors: Gasemjit Pattrawin , Johannsmann Diethelm
Published: September 2006

The flow behavior of the near‐surface region of polystyrene films was studied via the decay kinetics of imprinted corrugation gratings at elevated temperatures. The speed of the decay is the result of a balance between surface tension, on the one hand, and viscous drag, on the other. Depth profiling is possible because the penetration depth of a surface wave is proportional to its wavelength. From the dependence of the decay rate on the penetration depth one concludes that the surface region displays an increased molecular mobility. The soft surface layer has a thickness of about 20 nm. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3031–3036, 2006
WAKE UP! The effectiveness of a student response system in large packaging classes
Authors: Auras Rafael , Bix Laura
Published: September 2006

Large classes present many challenges in higher education. New digital technologies, such as interactive student response systems (SRSs), are promising tools for large classes. SRSs facilitate interaction between faculty members and students on an on‐going basis by allowing instructors to ask multiple‐choice, true/false and numerical questions during class and then analyse and display the student responses in real time. In general, SRSs consist of three basic components: a student input device (clicker), operating system software loaded onto the classroom computer, and an overhead projection system to display the questions asked and the distribution of student responses. SRSs have already been used in classrooms in a variety of fields; however, to our knowledge, they have not been used previously in packaging education. This article describes the introduction of an SRS in two packaging classes at the School of Packaging at Michigan State University. The SRS implementation is discussed and faculty and student comments and responses regarding the SRS are reported. The system motivated student participation and attendance for both classes: 75% of student respondents stated that the SRS motivated them to attend class; 57% of student respondents reported that the SRS enhanced their classroom experience; and 56% of the student respondents indicated that the system helped them to comprehend the material better. These numbers are supported by the vast majority of research studies, which indicate improved attendance, participation and comprehension when using SRSs for large classrooms. Copyright © 2006 John Wiley & Sons, Ltd.
Neighborhood Behavior: Validation of Two‐Dimensional Molecular Similarity as a Predictor of Similar Biological Activities and Docking Scores
Authors: Perekhodtsev Gleb D.
Published: September 2006

We have used four large datasets to determine the extent to which Two‐Dimensional (2D) structural similarity of chemical compounds predicts how similarly they bind to proteins. Structures of 1750, 1853, 1377, and 407 inhibitors for trypsin, thrombin, factor Xa (fXa), and urokinase‐type Plasminogen Activator (uPA), respectively, with their observed binding affinities were collected from various literature sources. We also obtained calculated binding affinities for the datasets using an in‐house docking program. Plots of the differences in affinity for all pairs of compounds versus their 2D similarity values were generated. All datasets with both observed and calculated affinities clearly exhibit structure–activity relationships (neighborhood behavior), though notable differences among plots are also observed. Guidelines for application of 2D similarity in structure‐based virtual screening are discussed in the context of the results obtained.
Protein profile of osteoarthritic human articular cartilage using tandem mass spectrometry
Authors: Garcia Benjamin A. , Platt Mark D. , Born Timothy L. , Shabanowitz Jeffrey , Marcus Norman A. , Hunt Donald F.
Published: September 2006

Articular cartilage contains both chondrocyte cells and extracellular matrix (ECM) components. Currently, comprehensive information concerning the protein composition of human articular cartilage tissue is somewhat lacking. In this report we detail the use of tandem mass spectrometry (MS/MS) for a preliminary global identification of proteins from human articular knee cartilage tissue from patients diagnosed with osteoarthritis. Knee cartilage supernatant was fractionated using one‐dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (1D‐SDS‐PAGE), in‐gel digested and peptide sequences were then determined by performing on‐line nano‐liquid chromatography (LC)/MS/MS experiments using an ion trap mass spectrometer. Altogether, over 100 different proteins from nearly 700 unique peptide sequences were detected by MS/MS. The majority of the proteins identified are involved in ECM organization (35%), signal transduction and cell communication (14%), immune response (11%) and metabolism and energy pathways (11%). Proteins observed included several well‐known cartilage components as well as lower abundant lesser known ECM proteins. Possible degradation products in the cartilage sample, such as from cartilage link protein, could also be detected by our mass spectrometry methods. We show here that mass spectrometry can be utilized as a tool for a fast, accurate and sensitive analysis of a complex mixture of cartilage proteins. It is believed that this type of proteomic analysis will aid future work centered on investigating the pathology of this and other related joint diseases. Copyright © 2006 John Wiley & Sons, Ltd.
A study of the elimination of water from lithium‐cationized tripeptide methyl esters by means of tandem mass spectrometry and isotope labeling
Authors: Talaty Erach R. , Cooper Travis J. , Piland Debra L. , Bateman David J. , Syed Adeel , Stevenson William , Van Stipdonk Michael J.
Published: September 2006

Extensive isotope labeling (2H, 13C and 15N), collision‐induced dissociation (CID) and multiple‐stage tandem mass spectrometry were used to investigate the elimination of H2O from a series of model, metal‐cationized tripeptide methyl esters. The present results corroborate our earlier suggestion that loss of water from lithiated peptides is initiated by a nucleophilic attack from the N‐terminal side upon an amide carbonyl carbon atom to form a five‐membered ring as an intermediate followed by 1,2‐elimination of water. We show that the nucleophilic atom is the oxygen atom of the N‐terminal amide group in the fragmentation of [AcGGGOMe+Li]+ as well as [GGGOMe+Li]+. However, the subsequent fragmentation is markedly different in the two cases as a result of the absence and presence of a free amino group. In particular, extensive scrambling of protons in the α‐positions of GGGOMe is observed, presumably as a consequence of intervention of the basic amino group. Copyright © 2006 John Wiley & Sons, Ltd.
Simultaneous quantification of fexofenadine and pseudoephedrine in human plasma by liquid chromatography/tandem mass spectrometry with electrospray ionization: method development, validation and application to a clinical study
Authors: Nirogi Ramakrishna V. S. , Kandikere Vishwottam N. , Shukla Manoj , Mudigonda Koteshwara , Maurya Santosh , Komarneni Prashanth
Published: September 2006

To support the pharmacokinetic and bioavailability study of a once‐daily fexofenadine/pseudoephedrine combination, a high‐performance liquid chromatography/positive ion electrospray tandem mass spectrometry (HPLC/ESI‐MS/MS) method for the simultaneous quantification of fexofenadine and pseudoephedrine was developed and validated with 500 µL human plasma using mosapride as an internal standard (IS). Following solid‐phase extraction, the analytes were separated using an isocratic mobile phase on a reversed‐phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M+H]+ions,m/z502/466 for fexofenadine,m/z166/148 for pseuoephedrine andm/z422/198 for the IS. The method exhibited linear dynamic ranges of 1–500 ng/mL and 2–1000 ng/mL for fexofenadine and pseudoephedrine, respectively, in human plasma. The lower limits of quantification were 1 and 2 ng/mL with a relative standard deviation of less than 10% for fexofenadine and pseudoephedrine, respectively. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The total chromatographic run time was 2 min and more than 400 human plasma samples could be analyzed in one day by running the system overnight. The method is precise and sensitive enough for its intended purpose. Copyright © 2006 John Wiley & Sons, Ltd.
A high‐throughput, fully automated liquid/liquid extraction liquid chromatography/mass spectrometry method for the quantitation of a new investigational drug ABT‐869 and its metabolite A‐849529 in human plasma samples
Authors: Rodila Ramona C. , Kim Joseph C. , Ji Qin C. , El‐Shourbagy Tawakol A.
Published: September 2006

ABT‐869 is a novel ATP‐competitive inhibitor for all the vascular endothelial growth factor (VEGF) and platelet‐derived growth factor (PDGF) receptor tyrosine kinases (RTKs). It is one of the oncology drugs in development at Abbott Laboratories and has great potential for enhanced anti‐tumor efficacy as well as activity in a broad range of human cancers. We report here an accurate, precise and rugged liquid chromatography/mass spectrometry (LC/MS/MS) assay for the quantitative measurement of ABT‐869 and its acid metabolite A‐849529. A fully automated 96‐well liquid/liquid extraction method was achieved utilizing a Hamilton liquid handler. The only manual intervention required prior to LC/MS/MS injection is to transfer the 96‐well plate to a drying rack to dry the extracts then transfer the plate back to the Hamilton for robotic reconstitution. The linear dynamic ranges were from 1.1 to 598.8 ng/mL for ABT‐869 and from 1.1 to 605.8 ng/mL for A‐849529. The coefficient of determination (r2) for all analytes was greater than 0.9995. For the drug ABT‐869, the intra‐assay coefficient of variance (CV) was between 0.4% and 3.7% and the inter‐assay CV was between 0.9% and 2.8%. The inter‐assay mean accuracy, expressed as percent of theoretical, was between 96.8% and 102.2%. For the metabolite A‐849529, the intra‐assay CV was between 0.5% and 5.1% and the inter‐assay CV was between 0.8% and 4.9%. The inter‐assay mean accuracy, expressed as percent of theoretical, was between 96.9% and 100.6%. Copyright © 2006 John Wiley & Sons, Ltd.
JSetL: a Java library for supporting declarative programming in Java
Authors: Rossi G. , Panegai E. , Poleo E.
Published: September 2006

In this paper we present a Java library—called JSetL—that offers a number of facilities to support declarative programming such as those usually found in logic or functional declarative languages: logical variables, list and set data structures (possibly partially specified), unification and constraint solving over sets, non‐determinism. The paper describes the main features of JSetL and it shows, through a number of simple examples, how these features can be exploited to support a real declarative programming style in Java. Copyright © 2006 John Wiley & Sons, Ltd.
Efficient plagiarism detection for large code repositories
Authors: Burrows Steven , Tahaghoghi S. M. M. , Zobel Justin
Published: September 2006

Unauthorized re‐use of code by students is a widespread problem in academic institutions, and raises liability issues for industry. Manual plagiarism detection is time‐consuming, and current effective plagiarism detection approaches cannot be easily scaled to very large code repositories. While there are practical text‐based plagiarism detection systems capable of working with large collections, this is not the case for code‐based plagiarism detection. In this paper, we propose techniques for detecting plagiarism in program code using text similarity measures and local alignment. Through detailed empirical evaluation on small and large collections of programs, we show that our approach is highly scalable while maintaining similar levels of effectiveness to that of the popular JPlag and MOSS systems. Copyright © 2006 John Wiley & Sons, Ltd.
Investigating service‐oriented system performance: a systematic study
Authors: Woodall Philip , Brereton Pearl , Budgen David
Published: September 2006

The initial use of a service‐oriented system, which collates information from three databases, highlighted a performance problem with query response time for queries that selected more than ten attributes from a single data source. Our aim was to find the cause of the performance problem within the service‐oriented system. The challenges that were encountered when attempting to locate such a problem are described. Our approach to finding the performance problem, while addressing these challenges, was based on systematically devising and applying measurements to the system. We developed strategies that addressed the challenges and the inherent difficulty of measuring performance in a service‐oriented system. The cause of the performance problem was a buffer used by a JDBC‐ODBC driver to connect Java code to a Microsoft Access database. Three strategies successfully addressed the challenges of measuring performance in the service‐oriented system. In particular, routing queries to a local data source eliminated networking problems. Creating a model of the system allowed performance measurements to continue concurrently with demonstrations of the system, and with its further development. Finally, porting the system identified the part that had a detrimental effect on performance. Copyright © 2006 John Wiley & Sons, Ltd.
Dynamic refresh‐rate scaling via frame buffer monitoring for power‐aware LCD management
Authors: Kim Hyoseung , Cha Hojung , Ha Rhan
Published: September 2006

In recent years, there has been wide‐spread use of large and high‐resolution liquid‐crystal displays (LCDs) on handheld devices. The portion of LCD power consumption in the overall system has gradually increased. While most of the previous research on LCD power management has focused on the hardware level, practical mechanisms at the software level are hardly known. This paper presents a power‐aware LCD management mechanism, based on dynamic refresh‐rate scaling and frame buffer monitoring. The proposed mechanism guarantees the display quality of service, which is inherently specified by content types. The mechanism does not require additional hardware or modifications to applications. The experiment results—on a commercial PDA with a $320\times240$ resolution—show that the proposed mechanisms effectively reduce the power consumption by up to 10%, while satisfying the display quality requirements for the LCD screen. Copyright © 2006 John Wiley & Sons, Ltd.
Design and implementation of UMTS session management in the user equipment
Authors: Gan Chai‐Hien , Lin Yi‐Bing , Chen Shi‐Hi
Published: September 2006

In universal mobile telecommunications system (UMTS), session management (SM) maintains a communication session between a user equipment (UE) and the core network. 3GPP TS 24.008 specifies the SM functions and the communication protocols between the UE and the core network. However, the interaction between the SM and other entities in the UE are not specified in detail. This paper designs and implements the SM software. We use a finite state machine (FSM) to model the SM functions. Based on the FSM and the primitives, we describe how to set up the development steps to implement the SM at the UE. Copyright © 2006 John Wiley & Sons, Ltd.
Security in wireless sensor networks
Authors: Giruka Venkata C. , Singhal Mukesh , Royalty James , Varanasi Srilekha
Published: September 2006

With sensor networks on the verge of deployment, security issues pertaining to the sensor networks are in the limelight. Though the security in sensor networks share many characteristics with wireless ad hoc networks, the two fields are rapidly diverging due to the fundamental differences between the make‐up and goals of the two types of networks. Perhaps the greatest dividing difference is the energy and computational abilities. Sensor nodes are typically smaller, less powerful, and more prone to failure than nodes in an ad hoc network. These differences indicate that protocols that are valid in the context of ad‐hoc networks may not be directly applicable for sensor networks. In this paper, we survey the state of art in securing wireless sensor networks. We review several protocols that provide security in sensor networks, with an emphasis on authentication, key management and distribution, secure routing, and methods for intrusion detection. Copyright © 2006 John Wiley & Sons, Ltd.
Pervasive data access in wireless and mobile computing environments
Authors: Lee Ken C. K. , Lee Wang‐Chien , Madria Sanjay
Published: September 2006

The rapid advance of wireless and portable computing technology has brought a lot of research interests and momentum to the area of mobile computing. One of the research focus is onpervasive data access. With wireless connections, users can access information at any place at any time. However, various constraints such as limited client capability, limited bandwidth, weak connectivity, and client mobility impose many challenging technical issues. In the past years, tremendous research efforts have been put forth to address the issues related to pervasive data access. A number of interesting research results were reported in the literature. This survey paper reviews important works in two important dimensions of pervasive data access:data broadcastandclient caching. In addition, data access techniques aiming at various application requirements (such astime,location,semanticsandreliability) are covered. Copyright © 2006 John Wiley & Sons, Ltd.
Analytical modeling of MAC protocol in ad hoc networks
Authors: Chen Yunli , Zeng Qing‐An , Agrawal Dharma P.
Published: September 2006

In ad hoc networks, CSMA/CA is a widely used MAC layer protocol. There has been considerable work on the performance evaluation of this protocol. But most work is confined to saturation performance of single‐hop ad hoc networks. In this paper, we employ a linear feedback model to evaluate the performance for CSMA/CA according to the Poisson distributed traffic in both single‐hop and multi‐hop ad hoc networks. To the best of our knowledge, this is the first attempt to analytically evaluate the performance for CSMA/CA protocol under a general assumption about the traffic. This paper also gives analytical results, showing the impact of RTS/CTS. Although RTS/CTS do add the overhead to the system, they become essential when either the hidden terminal problem is dominant, or the traffic is heavy, or the packet length is very large. This paper also shows that the performance degrades dramatically in multi‐hop ad hoc networks when the number of competing nodes increases, which implies that the scalability is still a major problem in ad hoc networks. To validate our analytical results, we have done extensive simulations, and it is observed that the simulation results match the analytical results very well. Copyright © 2006 John Wiley & Sons, Ltd.
Sustained service lookup in areas of sudden dense population
Authors: Aly Sherif G. , Elnahas Amal A.
Published: September 2006

As mobility became the norm rather than the exception, location‐based services are playing more of a key role in assisting mobile users. In this paper, we address the challenges of providing location‐based services to users in areas of sudden population increases, such as stadiums and traffic jams. A sudden increase in the number of mobile users leads to an increasing demand for the already scarce wireless bandwidth, thus causing dramatical throughput degradation and an increase in connectivity failures. We propose a hybrid model within which a peer‐to‐peer mode is deployed to assist the cellular‐based network whenever a sudden increase in population density is sensed by the base station. Location‐based data is migrated to selected elite nodes, thus allowing other peer nodes to get their information locally. This approach is proven, through experimental results, to decrease the query response time and number of query failures. Copyright © 2006 John Wiley & Sons, Ltd.
Power control and scheduling for guaranteeing quality of service in cellular networks
Authors: Wu Dapeng , Negi Rohit
Published: September 2006

Providing quality of service (QoS) guarantees is important in the third generation (3G) and the fourth generation (4G) cellular networks. However, large‐scale fading and non‐stationary small‐scale fading can cause severe QoS violations. To address this issue, we design QoS provisioning schemes, which are robust against time‐varying large scale path loss, shadowing, non‐stationary small scale fading, and very low mobility. In our design, we utilize our recently developed effective capacity technique and the time‐diversity dependent power control proposed in this paper. The key elements of our QoS provisioning schemes are channel estimation, power control, dynamic channel allocation, and adaptive transmission. The advantages of our QoS provisioning schemes are (1) power efficiency, (2) simplicity in QoS provisioning, (3) robustness against large‐scale fading and non‐stationary small‐scale fading. Simulation results demonstrate that the proposed algorithms are effective in providing QoS guarantees under various channel conditions. Copyright © 2006 John Wiley & Sons, Ltd.
Bit error rate for rectangular QAM with arbitrary constellation mapping in Nakagami‐mchannels
Authors: Xu Hong , Benjillali Mustapha , Szczeciński Leszek
Published: September 2006

We present closed‐form expressions for the bit error rate (BER) of rectangular quadrature amplitude modulation (QAM) in Nakagami‐mfading channels. The presented formulas, which are valid for arbitrary bits‐to‐symbols mapping, thus may be used when non‐Gray mapping is employed, are particularly useful in the low signal‐to‐noise ratio (SNR) range and/or for small values of the parameterm. The advantage of the proposed expressions over the known bounding techniques is illustrated through numerical simulations. Copyright © 2006 John Wiley & Sons, Ltd.
A mutual authentication and privacy mechanism for WLAN security
Authors: Jiang Yixin , Lin Chuang , Yin Hao , Chen Zhen
Published: September 2006

IEEE 802.11 wireless local area networks (WLAN) has been increasingly deployed in various locations because of the convenience of wireless communication and decreasing costs of the underlying technology. However, the existing security mechanisms in wireless communication are vulnerable to be attacked and seriously threat the data authentication and confidentiality. In this paper, we mainly focus on two issues. First, the vulnerabilities of security protocols specified in IEEE 802.11 and 802.1X standards are analyzed in detail. Second, a new mutual authentication and privacy scheme for WLAN is proposed to address these security issues. The proposed scheme improves the security mechanisms of IEEE 802.11 and 802.1X by providing a mandatory mutual authentication mechanism between mobile station and access point (AP) based on public key infrastructure (PKI), offering data integrity check and improving data confidentiality with symmetric cipher block chain (CBC) encryption. In addition, this scheme also provides some other new security mechanisms, such as dynamic session key negotiation and multicast key notification. Hence, with these new security mechanisms, it should be much more secure than the original security scheme. Copyright © 2006 John Wiley & Sons, Ltd.
Increasing network lifetime by balancing node energy consumption in heterogeneous sensor networks
Authors: Du Xiaojiang , Xiao Yang , Dai Fei
Published: September 2006

Sensor nodes are powered by battery and have severe energy constraints. The typical many‐to‐one traffic pattern causes uneven energy consumption among sensor nodes, that is, sensor nodes near the base station or a cluster head have much heavier traffic burden and run out of power much faster than other nodes. The uneven node energy dissipation dramatically reduces sensor network lifetime. In a previous work, we presented the chessboard clustering scheme to increase network lifetime by balancing node energy consumption. To achieve good performance and scalability, we propose to form a heterogeneous sensor network by deploying a few powerful high‐end sensors in addition to a large number of low‐end sensors. In this paper, we design an efficient routing protocol based on the chessboard clustering scheme, and we compute the minimum node density for satisfying a given lifetime constraint. Simulation experiments show that the chessboard clustering‐based routing protocol balances node energy consumption very well and dramatically increases network lifetime, and it performs much better than two other clustering‐based schemes. Copyright © 2006 John Wiley & Sons, Ltd.
Web browsing optimization over 2.5G and 3G: end‐to‐end mechanisms vs. usage of performance enhancing proxies
Authors: Gomez C. , Catalan M. , Viamonte D. , Paradells J. , Calveras A.
Published: September 2006

2.5 Generation (2.5G) and Third Generation (3G) cellular wireless networks allow mobile Internet access with bearers specifically designed for data communications. However, Internet protocols under‐utilize wireless wide area network (WWAN) link resources, mainly due to large round trip times (RTTs) and request‐‐reply protocol patterns. Web browsing is a popular service that suffers significant performance degradation over 2.5G and 3G. In this paper, we review and compare the two main approaches for improving web browsing performance over wireless links: (i) using adequate end‐to‐end parameters and mechanisms and (ii) interposing a performance enhancing proxy (PEP) between the wireless and wired parts. We conclude that PEPs are currently the only feasible way for significantly optimizing web browsing behavior over 2.5G and 3G. In addition, we evaluate the two main current commercial PEPs over live general packet radio service (GPRS) and universal mobile telecommunications system (UMTS) networks. The results show that PEPs can lead to near‐ideal web browsing performance in certain scenarios. Copyright © 2006 John Wiley & Sons, Ltd.
Proxy‐RED: an AQM scheme for wireless local area networks
Authors: Yi Sungwon , Kappes Martin , Garg Sachin , Deng Xidong , Kesidis George , Das Chita R.
Published: September 2006

Wireless access points (APs) act as bridges between wired and wireless networks. Since the actually available bandwidth in wireless networks is much smaller than the bandwidth in wired networks, there is a disparity in channel capacity which makes the access point a significant network congestion point in the downstream direction. A current architectural trend in wireless local area networks (WLAN) is to move functionality from APs to a centralized gateway in order to reduce cost and improve features. In this paper, we study the use of RED, a well known active queue management (AQM) scheme, and explicit congestion notification (ECN) to handle bandwidth disparity between the wired and the wireless interface of an access point. Then, we propose the Proxy‐RED scheme, as a solution for reducing the AQM overhead from the access point. Simulations‐based performance analysis indicates that the proposed Proxy‐RED scheme improves the overall performance of a network. In particular, the Proxy‐RED scheme significantly reduces packet loss rate and improves goodput for a small buffer, and minimizes delay for a large buffer size. Copyright © 2006 John Wiley & Sons, Ltd.
Effect of elevated CO2levels on leaf starch, nitrogen and photosynthesis of plants growing at three natural CO2springs in Japan
Authors: Onoda Yusuke , Hirose Tadaki , Hikosaka Kouki
Published: September 2006

Plant communities around natural CO2springs have been exposed to elevated CO2levels over many generations and give us a unique opportunity to investigate the effects of long‐term elevated CO2levels on wild plants. We searched for natural CO2springs in cool temperate climate regions in Japan and found three springs that were suitable for studying long‐term responses of plants to elevated levels of CO2: Ryuzin‐numa, Yuno‐kawa and Nyuu. At these CO2springs, the surrounding air was at high CO2concentration with no toxic gas emissions throughout the growth season, and there was natural vegetation around the springs. At each site, high‐CO2(HC) and low‐CO2(LC) plots were established, and three dominant species at the shrub layers were used for physiological analyses. Although the microenvironments were different among the springs, dicotyledonous species growing at the HC plots tended to have more starch and less nitrogen per unit dry mass in the leaves than those growing at the LC plots. In contrast, monocotyledonous species growing in the HC and LC plots had similar starch and nitrogen concentrations. Photosynthetic rates at the mean growth CO2concentration were higher in HC plants than LC plants, but photosynthetic rates at a common CO2concentration were lower in HC plants. Efficiency of water and nitrogen use of leaves at growth CO2concentration was greatly increased in HC plants. These results suggest that natural plants growing in elevated CO2levels under cool temperate climate conditions have down‐regulated their photosynthetic capacity but that they increased photosynthetic rates and resource use efficiencies due to the direct effect of elevated CO2concentration.
Topological accessibility shows a distinct asymmetry in the folds of βα proteins
Authors: Taylor William R.
Published: September 2006

A novel measure, called “topological accessibility” quantifies how easy it is to reconstruct a protein structure using only local contacts when starting at any point on the chain. Plotting this measure for all points in the chain gives a picture of how accessible the fold is. Simple folds are accessible from all positions, others are accessible only from limited positions while the most complex folds are not accessible from any position. The distribution of topological accessibility along the chain was found to be completely symmetric for the all‐α and all‐β protein classes. However, for the βα class, a distinct asymmetry was found (with probability 10−30 of being due to chance). Examination of the proteins contributing to this signal indicated many that have an ancient origin. This suggests that the folds of these proteins may have become fixed under the influence of amino‐terminal folding before the advent of chaperone assisted folding.
Stereoisomeric bio‐inversion key to biosynthesis of firefly d‐luciferin
Authors: Niwa Kazuki , Nakamura Mitsuhiro , Ohmiya Yoshihiro
Published: September 2006

The chirality of the luciferin substrate is critical to the luciferin–luciferase reaction producing bioluminescence. In firefly, the biosynthetic pathway of d‐luciferin is still unclear, although it can be synthesized in vitro from d‐cysteine. Here, we show that the firefly produces both d‐ and l‐luciferin, and that the amount of active d‐luciferin increases gradually with maturation stage. Studies of firefly body extracts indicate the possible conversion of l‐cysteine via l‐luciferin into d‐luciferin, suggesting that the biosynthesis is enzymatically regulated by stereoisomeric bio‐inversion of l‐luciferin. We conclude that the selection of chirality in living organisms is not as rigid as previously thought.