bluuebunny/crossref_metadata_2025 huggingface dataset:
Anterior cingulate integrity: Executive and neuropsychiatric features in Parkinson's disease
Authors: Lewis Simon J.G. , Shine James M. , Duffy Shantel , Halliday Glenda , Naismith Sharon L.
Published: August 2012

Patients with advanced Parkinson's disease (PD) commonly suffer with significant executive dysfunction and concomitant visual hallucinations. Although the underlying pathophysiology remains poorly understood, numerous studies have highlighted the strong association between these neuropsychiatric features, suggesting common neural pathways. Although previous neuroimaging studies have identified widespread volume loss across a number of cortical regions, to date, no studies have utilized proton magnetic resonance spectroscopy to provide insights into how neurometabolic changes may relate to such symptoms. Twenty patients with PD and 20 healthy controls underwent spectroscopy to determine the N‐acetyl aspartate/creatine (NAA/Cr) ratio, which reflects the degree of neuronal integrity in neurodegenerative diseases. Voxels were obtained from the anterior cingulate cortex (ACC), an area critical for a wide range of executive mechanisms as well as from a control volume in the posterior cingulate cortex (PCC). Compared to controls, patients with PD had lower NAA/Cr ratios in the ACC. In turn, lower NAA/Cr ratios significantly correlated with poorer executive function on tasks of attentional set‐shifting and response inhibition, as well as more‐severe psychotic symptoms and poorer performance on the Bistable Percept Paradigm, a neuropsychological probe of visual hallucinations. NAA/Cr ratios were significantly lower in hallucinators, compared to nonhallucinators, within the ACC, but did not differ in the PCC. These results suggest that loss of neuronal integrity within the ACC plays an important role in the pathophysiology underlying executive functioning and visual hallucinations in PD. © 2012 Movement Disorder Society
Tardive dyskinesia is caused by maladaptive synaptic plasticity: A hypothesis
Authors: Teo James T. , Edwards Mark J. , Bhatia Kailash
Published: August 2012

It has been 50 years since the first patients with tardive dyskinesia (TD) were described, but the pathophysiology is only partially understood and effective treatments have remained elusive. Newer atypical antipsychotics with less nonspecific activity at dopamine receptors have not heralded the end of tardive dyskinesia and merely highlight the incomplete understanding of the disorder.

We present an overview of the existing pathophysiology of the disorder and incorporate recent developments in genetics and the study of human synaptic plasticity in other hyperkinetic movement disorders. We propose a hypothesis that dopamine‐receptor sensitization and altered function of the N‐methyl‐D‐aspartate receptor produces maladaptive synaptic plasticity, which allows the encoding of abnormal motor programs, and propose studies that would falsify or support this hypothesis.

In conclusion, a maladaptive synaptic plasticity” hypothesis goes some way toward filling in the gaps of existing theories of TD with the pathophysiology of other hyperkinetic movement disorders. © 2012 Movement Disorder Society
The Canadian Airport Nowcasting System (CAN‐Now)
Authors: Isaac George A. , Bailey Monika , Boudala Faisal S. , Burrows William R. , Cober Stewart G. , Crawford Robert W. , Donaldson Norman , Gultepe Ismail , Hansen Bjarne , Heckman Ivan , Huang Laura X. , Ling Alister , Mailhot Jocelyn , Milbrandt Jason A. , Reid Janti , Fournier Marc
Published: August 2012

The Canadian Airport Nowcasting Project (CAN‐Now) has developed an advanced prototype all‐season weather forecasting and nowcasting system that can be used at major airports. This system uses numerical model data, pilot reports, ground in situ sensor observations (precipitation, icing, ceiling, visibility, winds), on‐site remote sensing (such as vertically pointing radar and microwave radiometer) and off‐site remote sensing (satellite and radar) information to provide detailed nowcasts out to approximately 6 h. The nowcasts, or short term weather forecasts, should allow decision makers such as pilots, dispatchers, de‐icing crews, ground personnel or air traffic controllers to make plans with increased margins of safety and improved efficiency. The system has been developed and tested at Toronto Pearson International Airport (CYYZ) and Vancouver International Airport (CYVR). A Situation Chart has been developed to allow users to have a high glance value product which identifies significant weather related problems at the airport. New products combining observations and numerical model output into nowcasts have been tested. Some statistical verifications of forecast products, with comparisons to persistence, covering both a winter (2009/2010) and summer (2010) period have been made. Problems with the prediction of relative humidity and wind direction are outlined. The ability to forecast categorical variables such as ceiling, visibility, as well as precipitation rate and type accurately are discussed. Overall, for most variables, the nowcast systems can outperform persistence after the first 1 or 2 h, and provide more accurate forecasts than individual Numerical Weather Prediction models out to 6 h.
Antihyperuricemic and nephroprotective effects of resveratrol and its analogues in hyperuricemic mice
Authors: Shi Yun‐Wei , Wang Cai‐Ping , Liu Lei , Liu Yang‐Liu , Wang Xing , Hong Ye , Li Zhen , Kong Ling‐Dong
Published: August 2012

Scope

Stilbenes, of which, resveratrol is a representative compound in foods and plants, possess a variety of bioactivities including antioxidation, anti‐inflammation, chemoprevention, and cardioprotection. This study was conducted to evaluate the antihyperuricemic and nephroprotective effects of resveratrol and its analogues and explore the possible mechanisms. The structure–activity relationships were analyzed.

Methods and results

Potassium oxonate‐induced hyperuricemic mice were dosed by gavage with eight stilbenes. Uric acid, creatinine, and blood urea nitrogen (BUN) levels in serum and urine, clearance rate of creatinine and BUN, 24‐h urate excretion, and fractional excretion of uric acid, uromodulin levels in urine and kidney were determined to evaluate renal urate handling and function. Renal protein levels of organic ion transporters were detected to elucidate the possible mechanisms. Resveratrol, trans‐4‐hydroxystilbene, pterostilbene, polydatin, and mulberroside A were found to have antihyperuricemic activities. These compounds together with trans‐2‐hydroxystilbene provided nephroprotection. Trans‐3,4′,5‐trimethoxystilbene and cis‐combretastatin A‐4 had no effects.

Conclusion

The uricosuric and nephroprotective actions of resveratrol and its analogues were mediated by regulating renal organic ion transporters in hyperuricemic mice, supporting their beneficial effects for the prevention of hyperuricemia. The number and position, methoxylation and glycosylation of hydroxyl groups in these trans‐stilbenes were required for their effects.
Xanthones from the stems of Cratoxylum cochinchinense
Authors: Duan Yinghui , Dai Yi , Chen Liuyuan , Liu Mingli , Li Yaolan , Yao Xinsheng
Published: August 2012

Four new xanthones, 1‐methoxy‐3,7,8‐trihydroxyxanthone (1), 1‐methoxy‐4,7,8‐trihydroxyxanthone (2), 1‐methoxy‐4,7‐dihydroxyxanthone (3), and 1,4‐dimethoxy‐2,7‐dihydroxyxanthone (4) were isolated from the stems of Cratoxylum cochinchinense along with four known xanthones (5–8). The structures of new compounds were determined by extensive spectroscopic analyses, mainly 1D and 2D NMR and HRESIMS data. Copyright © 2012 John Wiley & Sons, Ltd.
Neuromuscular and metabolic comparisons between ramp and step incremental cycle ergometer tests
Authors: Zuniga Jorge M. , Housh Terry J. , Camic Clayton L. , Bergstrom Haley C. , Traylor Daniel A. , Schmidt Richard J. , Johnson Glen O.
Published: August 2012

Introduction

We compared peak and submaximal mean values for neuromuscular and metabolic parameters between ramp (15 W·min−1) and step (30 W increments every 2 min) incremental cycle ergometer tests.

Methods

Thirteen healthy adults (7 men and 6 women; mean ± SD age = 23.4 ± 3.3 years) performed randomly ordered ramp or step incremental tests. Two‐way repeated measures analyses of variance were used to analyze the data.

Results

The ramp incremental test resulted in lower mean EMG amplitude, O2, and HR values at the common power outputs, with no differences for MMG amplitude values.

Conclusions

It is possible that the cumulative effect of producing an increased amount of work during the step (total work = 75.83 kJ) vs. ramp (total work = 65.60 kJ) incremental cycle ergometer tests at the common power outputs may have contributed to the greater fatigue‐induced increase in muscle recruitment and/or firing rate, oxygen consumption, and heart rate. Muscle Nerve, 2013
Intracranial Arteriovenous Malformations as a Possible Cause of Endocranial Bone Lesions and Associated Neurological Disorder
Authors: Janovic A. , Milovanovic P. , Sopta J. , Rakocevic Z. , Filipovic V. , Nenezic D. , Djuric M.
Published: August 2012

Endocranial bone lesions have attracted intensive scientific debate on their aetiology. In recent literature, the lesions were almost exclusively interpreted as of infectious origin. In this paper, we give new insight into the aetiology of endocranial lesions, distinguishing the lesions of vascular origin from those caused by tuberculosis or other conditions. The analysis is based on a rare case of a young female individual who displayed multiple endocranial lesions with ‘serpens endocrania symmetrica’ morphology. The lesions were associated with an uncommon branching pattern of the middle meningeal artery and marked side differences in teeth pathology. Postcranial skeleton showed signs of the left upper limb weakness. The macroscopic finding of the endocranial lesions along with the skeletal evidence of neurological damage, together with characteristic radiological and histological features, can lead to diagnosis of arteriovenous malformations. This study aims to improve understanding of the aetiology of endocranial bone lesions. Copyright © 2012 John Wiley & Sons, Ltd.
Viscoelastic properties of poly(ε‐caprolactone) – hydroxyapatite micro‐ and nano‐composites
Authors: Leung Linus H. , Naguib Hani E.
Published: August 2012

Various composites have been proposed in the literature for the fabrication of bioscaffolds for bone tissue engineering. These materials include poly(ε‐caprolactone) (PCL) with hydroxyapatite (HA). Since the biomaterial acts as the medium that transfers mechanical signals from the body to the cells, the fundamental properties of the biomaterials should be characterized. Furthermore, in order to control the processing of these materials into scaffolds, the characterization of the fundamental properties is also necessary. In this study, the physical, thermal, mechanical, and viscoelastic properties of the PCL‐HA micro‐ and nano‐composites were characterized. Although the addition of filler particles increased the compressive modulus by up to 450%, the thermal and viscoelastic properties were unaffected. Furthermore, although the presence of water plasticized the polymer, the viscoelastic behavior was only minimally affected. Testing the composites under various conditions showed that the addition of HA can strengthen PCL without changing its viscoelastic response. The results found in this study can be used to further understand and approximate the time‐dependent behavior of scaffolds for bone tissue engineering. Copyright © 2012 John Wiley & Sons, Ltd.
Preparation of magnetically doped multilayered functional silica particles via surface modification with organic polymer
Authors: Rahman M. A. , Miah M. A. J. , Minami H. , Ahmad H.
Published: August 2012

Magnetically modified functional particles are emerging as one of the most promising candidate in numerous multidisciplinary applications. In this research, a simple process has been developed to prepare magnetically modified aminated silica (SiO2) particles. Herein, submicron‐sized SiO2 particles were modified with poly(methylmethacrylate‐methacrylic acid) by seeded polymerization without any stabilizer. The carboxyl groups localized near the particles surface were then covalently linked with ethylene diamine to prepare aminated composite particles. Iron ions were then precipitated on the surface of aminated composite particles to obtain magnetically doped functional SiO2 particles. The preparation of such particles was confirmed by scanning electron microscopy, Fourier transform infrared, 1H NMR, X‐ray photoelectron spectroscopy and thermogravemetric analyses. Relative measurement of adsorption study of different biomolecules suggested that magnetically doped functional silica particles are comparatively hydrophobic. Copyright © 2012 John Wiley & Sons, Ltd.
Experience with microarray‐based comparative genomic hybridization for prenatal diagnosis in over 5000 pregnancies
Authors: Shaffer Lisa G. , Dabell Mindy P. , Fisher Allan J. , Coppinger Justine , Bandholz Anne M. , Ellison Jay W. , Ravnan J. Britt , Torchia Beth S. , Ballif Blake C. , Rosenfeld Jill A.
Published: August 2012

Objective

To demonstrate the usefulness of microarray testing in prenatal diagnosis based on our laboratory experience.

Methods

Prenatal samples received from 2004 to 2011 for a variety of indications (n = 5003) were tested using comparative genomic hybridization‐based microarrays targeted to known chromosomal syndromes with later versions of the microarrays providing backbone coverage of the entire genome.

Results

The overall detection rate of clinically significant copy number alterations (CNAs) among unbiased, nondemise cases was 5.3%. Detection rates were 6.5% and 8.2% for cases referred with abnormal ultrasounds and fetal demise, respectively. The overall rate of findings with unclear clinical significance was 4.2% but would reduce to 0.39% if only de novo CNAs were considered. In cases with known chromosomal rearrangements in the fetus or parent, 41.1% showed CNAs related to the rearrangements, whereas 1.3% showed clinically significant CNAs unrelated to the karyotype. Finally, 71% of the clinically significant CNAs found by microarray were below the resolution of conventional karyotyping of fetal chromosomes.

Conclusions

Microarray analysis has advantages over conventional cytogenetics, including the ability to more precisely characterize CNAs associated with abnormal karyotypes. Moreover, a significant proportion of cases studied by array will show a clinically significant CNA even with apparently normal karyotypes. © 2012 John Wiley & Sons, Ltd.
Kinetics of Michael addition polymerizations of n,n′‐bismaleimide‐4,4′‐diphenylmethane with barbituric acid
Authors: Yu Fu‐En , Hsu Jung‐Mu , Pan Jing‐Pin , Wang Tsung‐Hsiung , Chern Chorng‐Shyan
Published: August 2012

With the addition of sufficient hydroquinone to completely suppress the free radical polymerization, the kinetics of Michael addition polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane (BMI) and barbituric acid (BTA) with BMI/BTA = 2/1 (mol/mol) in 1‐methyl‐2‐pyrrolidone was investigated independently. A mechanistic model was developed to adequately predict the polymerization kinetics before a critical conversion (ca. 60%), at which point the diffusion‐controlled polymer reactions started to predominate in the latter stage of polymerization. The Michael addition polymerization rate constants and activation energy in the temperature range 383–423 K were determined accordingly. Beyond the critical conversion, a relatively stationary limiting conversion (ca. 69%) independent of the reaction temperature was achieved. A diffusion‐controlled polymerization model taken from the literature satisfactorily predicted the limiting conversion data. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Influence of two compatibilizers on clay/PP nanocomposites properties
Authors: Potarniche Catalina‐Gabriela , Vuluga Zina , Christiansen Jesper de Claville , Radovici Constantin , Kristensen Peter Kjaer
Published: August 2012

This article investigates the influence on mechanical properties of using a two compatibilizer system. Cloisite‐Na Clay (ClNa) was organically modified in different ways with a polyethermonoamine and maleated polypropylene (MA‐g‐PP) added as a second compatibilizer. A corotating twin‐screw extruder was used to obtain nanocomposites based on polypropylene via the melt intercalation technique. X‐ray diffraction and differential scanning calorimetric results showed that intercalated nanocomposites with improved thermal stability were obtained. Increases of 8% in tensile strength, 34% in modulus, and 20% in crystallinity were observed. Also an increase of 23% in creep properties was observed when using these two compatibilizer system and 1% clay. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Studies on the synthesis of low molecular weight, one‐dimensional polyanilines prepared by fast emulsion polymerization using (n‐dodecylbenzenesulfonic acid)/HCl emulsifiers
Authors: Wu Yi‐Jhen , Ho Ko‐Shan , Cheng Yu‐Wei , Chao Liang , Wang Yen‐Zen , Hsieh Tar‐Hwa , Ho Tsung‐Han , Han Yu‐Kai
Published: August 2012

Low molecular weight polyaniline nanotubes were prepared by fast emulsion polymerization in the presence of both n‐dodecylbenzenesulfonic acid (DBSA) and HCl(aq). The anilinium monomers associated with DBSA emulsifiers were found to self‐arrange into strands of associated cylindrical micelles before polymerization, as monitored by their optical activity and optical image. In the presence of some HCl(aq), the monomer‐associated cylindrical micelles expanded and the polymerization rate could be speeded up. It was found that the low molecular weight (viscosity‐averaged molecular weight) polyaniline obtained can easily lead to the formation of highly conductive, one‐dimensional nanotubes or nanofibers monitored by the variation of optical activities and λmax of the UV–visible–near IR spectra during polymerization. The DBSA/HCl ratio played an important role in the eventual properties and morphologies of the one‐dimensional polyanilines, which can be illustrated by conductivity, SEM and transmission electron microscopy measurements. The resultant one‐dimensional polyaniline nanotubes can be arranged into a layered structure by orientation, illustrated by AFM and wide‐angle X‐ray diffraction. © 2012 Society of Chemical Industry
Facile synthesis of processable aromatic polyamides containing thioether units
Authors: Huang Guangshun , Zhang Suixin , Li Dongsheng , Zhang Meilin , Zhang Gang , Yang Jie
Published: August 2012

Aromatic polyamides containing thioether units were synthesized by interfacial polycondensation of 4,4′‐thiodibenzoyl chloride (or 4,4′‐bis(4‐chloroformylphenylthio)benzene) with aromatic diamines containing a nitrile unit. Their structure was established using 1H NMR and Fourier transform infrared spectroscopy. The inherent viscosities of the polyamides prepared with optimum synthesis conditions were in the range 0.71–0.84 dL g−1. These polyamides showed excellent thermal properties with glass transition temperatures of 210.5–219.6 °C, melting temperatures of 313.8–315.0 °C and initial degradation temperatures of 440–459 °C. They could be processed by melting due to their relatively wide processing window. Their tensile strengths were 71.3–79.1 MPa, water absorption was 0.17–0.22 wt%, and melt flowability was in the range 64.5 to 315.2 Pa s and 68.5 to 422.3 Pa s at different shear rates. At the same time, they were soluble in aprotic solvents such as N‐methyl‐2‐pyrrolidone, dimethylformamide and dimethylsulfoxide. The results suggest that these aromatic polyamides containing thioether units represent a promising type of heat‐resistant and processable engineering plastic. © 2012 Society of Chemical Industry
Synthesis of a new 2‐amino‐glycan, poly‐(1→6)‐α‐D‐mannosamine, by ring‐opening polymerization of 1,6‐anhydro‐mannosamine derivatives
Authors: Hattori Kazuyuki , Yoshida Takashi
Published: August 2012

A stereoregular 2‐amino‐glycan composed of a mannosamine residue was prepared by ring‐opening polymerization of anhydro sugars. Two different monomers, 1,6‐anhydro‐2‐azido‐mannose derivative (3) and 1,6‐anhydro‐2‐(N, N‐dibenzylamino)‐mannose derivative (6), were synthesized and polymerized. Although 3 gave merely oligomers, 6 was promptly polymerized into high polymers of the number‐average molecular weight (Mn) of 2.3 × 104 to 2.9 × 104 with 1,6‐α stereoregularity. The differences of polymerizability of 3 and 6 from those of the corresponding glucose homologs were discussed. It was found that an N‐benzyl group is exceedingly suitable for protecting an amino group in the polymerization of anhydro sugars of a mannosamine type. The simultaneous removal of O‐ and N‐benzyl groups of the resulting polymers was achieved by using sodium in liquid ammonia to produce the first 2‐amino‐glycan, poly‐(1→6)‐α‐D‐mannosamine, having high molecular weight through ring‐opening polymerization of anhydro sugars.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Biocompatible poly(ethylene glycol)‐poly(γ‐cholesterol‐L‐glutamate) copolymers: Synthesis, characterization, and in vitro studies
Authors: Wu Yang , Ma Qing , Song Xiangrong , Zheng Yu , Ren Wen , Zhang Jinkun , Ouyang Liang , Wu Fengbo , He Gu
Published: August 2012

A novel amphiphilic poly(ethylene glycol)‐block‐poly(γ‐cholesterol‐L‐glutamate) (mPEG–PCHLG) diblock copolymer has been synthesized. The mPEG–PCHLG copolymer has good biocompatibility and low toxicity. The mPEG–PCHLG copolymers could aggregate into nanoparticles with PCHLG blocks as the hydrophobic core and PEG blocks as the hydrophilic shell through emulsion solvent evaporation method. The copolymers were characterized by nuclear magnetic resonance spectroscopy, mass spectrum, Fourier transform infrared spectroscopy, and gel permeation chromatography. The particle sizes, size distributions, and zeta potentials of nanoparticles can also be determined by dynamic light scattering and transmission electron microscopy. This work provides a new and facile approach to prepare amphiphilic block copolymer nanoparticles with controllable performances. This novel copolymer may have potential applications in drug delivery and bioimaging applications.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Thermokarst Lakes on the Arctic Coastal Plain of Alaska: Spatial and Temporal Variability in Summer Water Temperature
Authors: Hinkel Kenneth M. , Lenters John D. , Sheng Yongwei , Lyons Evan A. , Beck Richard A. , Eisner Wendy R. , Maurer Eric F. , Wang Jida , Potter Brittany L.
Published: August 2012

In summer 2010, water temperature profile measurements were made in 12 thermokarst lakes along a 150‐km long north–south transect across the Arctic Coastal Plain of northern Alaska. In shallow lakes, gradual warming of the water column to 1–4°C begins at the lake bed during decay of the ice cover in spring. Rapid warming follows ice‐off, with water temperature responding synchronously to synoptic weather variations across the area. Regionally, ice‐off occurs 2–4 weeks later on lakes near the coast. Inland lakes are warmer (13°C) in mid‐summer than those near the coast (7°C), reflecting the regional climate gradient and the maritime effect. All lakes are well mixed and largely isothermal, with some thermal stratification (< 2°C) occurring during calm, sunny periods in deeper lakes. In deep (6–9 m) lake‐bed depressions that are likely ice‐wedge troughs, water cools by conduction to the colder sediments below, while concurrent warming occurs in the upper water column. A spatially dense sample of near‐surface temperature measurements was collected from one lake over a short period and shows warmer (2–3°C) temperatures on the upwind, sheltered end of the lake. This study demonstrates that climatic gradients, meteorological conditions and basin characteristics impact lake temperature dynamics. Copyright © 2012 John Wiley & Sons, Ltd.
Virulence of Verticillium lecanii (Z.) against cereal aphids; does timing of infection affect the performance of parasitoids and predators?
Authors: Aqueel Muhammad A , Leather Simon R
Published: August 2012

BACKGROUND: Entomopathogenic fungi such as Verticillium lecanii (Z.) (Mycotal®) are used for pest control as an alternative to chemical control. In this study, the effect of V. lecanii on cereal aphids is assessed. In addition, an investigation is carried out to determine whether the use of V. lecanii affects the performance of two natural enemies of aphids, the predator Harmonia axyridis (P.) and the parasitoid Aphidius colemani (V.), in no‐choice experiments under laboratory conditions.

RESULTS: The number of Rhopalosiphum padi (L.) and Sitobion avenae (F.) killed was increased by increasing the concentration of V. lecanii. The timing of application of fungus to aphids affected the efficacy of other biocontrol agents, a parasitoid and a predator. Parasitation by A. colemani (V.) in both cereal aphids (S. avenae and R. padi) was not affected by V. lecanii when aphids were first treated with V. lecanii and then exposed to A. colemani. The emergence of adults from parasitised mummies was, however, lower in infected aphids than in uninfected aphids when the aphids were first exposed to the parasitoids and then treated with fungus. The female sex ratio in the emerging adults was lower in V. lecanii‐treated aphids in both species. When aphids were first treated with V. lecanii, 72 h before predation, fewer aphids of both species were consumed by H. axyridis (P.).

CONCLUSION: Use of entomopathogenic fungus as a biological control agent could be a complementary strategy in an integrated pest management programme against cereal aphids, but it can reduce the efficiency of other biocontrol agents (parasitoids and predators) when applied simultaneously. © 2012 Society of Chemical Industry
Antibacterial activity of two chitosan solutions and their effect on rice bacterial leaf blight and leaf streak
Authors: Li Bin , Liu Baoping , Shan Changlin , Ibrahim Muhammad , Lou Yihan , Wang Yangli , Xie Guanlin , Li Hong‐ye , Sun Guochang
Published: August 2012

BACKGROUND: Bacterial leaf blight and leaf streak are the two most damaging bacterial diseases of rice. However, few bactericidal chemicals are available for controlling both diseases. The antibacterial properties of two kinds of chitosan with different molecular weights and degrees of N‐deacetylation and their effect on rice bacterial leaf blight and leaf streak were evaluated.

RESULTS: Results showed that the two kinds of chitosan solution possess a strong antibacterial activity against both rice bacterial pathogens and significantly reduced disease incidence and severity by comparison with the control under greenhouse conditions. However, the interaction between chitosan and rice pathogens was affected by the type and concentration of chitosan, the bacterial species and the contact time between chitosan and bacteria. The direct antibacterial activity of chitosan may be attributed to both membrane lysis and the destruction of biofilm. In addition, both chitosan solutions significantly increased the activities of phenylalanine ammonia lyase, peroxidase and polyphenol oxidase in rice seedlings following inoculation of two rice pathogens by comparison with the control.

CONCLUSION: The role of chitosan in protection of rice against bacterial pathogens has been shown to involve direct antibacterial activity and indirect induced resistance. Copyright © 2012 Society of Chemical Industry
Finite‐time formation control of multiple nonholonomic mobile robots
Authors: Ou Meiying , Du Haibo , Li Shihua
Published: August 2012

This paper considers finite‐time formation control problem for a group of nonholonomic mobile robots. The desired formation trajectory is represented by a virtual dynamic leader whose states are available to only a subset of the followers and the followers have only local interaction. First of all, a continuous distributed finite‐time observer is proposed for each follower to estimate the leader's states in a finite time. Then, a continuous distributed cooperative finite‐time tracking control law is designed for each mobile robot. Rigorous proof shows that the group of mobile robots converge to the desired geometric formation pattern in finite time. At the same time, all the robots can track the desired formation trajectory in finite time. Simulation example illustrates the effectiveness of our method. Copyright © 2012 John Wiley & Sons, Ltd.
Randomly coloring constant degree graphs
Authors: Dyer Martin , Frieze Alan , Hayes Thomas P. , Vigoda Eric
Published: August 2012

We study a simple Markov chain, known as the Glauber dynamics, for generating a random k ‐coloring of an n ‐vertex graph with maximum degree Δ. We prove that, for every ε > 0, the dynamics converges to a random coloring within O(nlog n) steps assuming k ≥ k0(ε) and either: (i) k/Δ > α* + ε where α*≈︁ 1.763 and the girth g ≥ 5, or (ii) k/Δ >β * + ε where β*≈︁ 1.489 and the girth g ≥ 7. Our work improves upon, and builds on, previous results which have similar restrictions on k/Δ and the minimum girth but also required Δ = Ω (log n). The best known result for general graphs is O(nlog n) mixing time when k/Δ > 2 and O(n2) mixing time when k/Δ > 11/6. Related results of Goldberg et al apply when k/Δ > α* for all Δ ≥ 3 on triangle‐free “neighborhood‐amenable” graphs.© 2012 Wiley Periodicals, Inc. Random Struct. Alg., 2013
Random doubly stochastic tridiagonal matrices
Authors: Diaconis Persi , Wood Philip Matchett
Published: August 2012

Let
\documentclass{article}\usepackage{mathrsfs}\usepackage{amsmath, amssymb}\pagestyle{empty}\begin{document}\begin{align*}{\mathcal T}\end{align*} \end{document}n be the compact convex set of tridiagonal doubly stochastic matrices. These arise naturally in probability problems as birth and death chains with a uniform stationary distribution. We study ‘typical’ matrices T∈
\documentclass{article}\usepackage{mathrsfs}\usepackage{amsmath, amssymb}\pagestyle{empty}\begin{document}\begin{align*}{\mathcal T}\end{align*} \end{document}n chosen uniformly at random in the set
\documentclass{article}\usepackage{mathrsfs}\usepackage{amsmath, amssymb}\pagestyle{empty}\begin{document}\begin{align*}{\mathcal T}\end{align*} \end{document}n. A simple algorithm is presented to allow direct sampling from the uniform distribution on
\documentclass{article}\usepackage{mathrsfs}\usepackage{amsmath, amssymb}\pagestyle{empty}\begin{document}\begin{align*}{\mathcal T}\end{align*} \end{document}n. Using this algorithm, the elements above the diagonal in T are shown to form a Markov chain. For large n, the limiting Markov chain is reversible and explicitly diagonalizable with transformed Jacobi polynomials as eigenfunctions. These results are used to study the limiting behavior of such typical birth and death chains, including their eigenvalues and mixing times. The results on a uniform random tridiagonal doubly stochastic matrices are related to the distribution of alternating permutations chosen uniformly at random.© 2012 Wiley Periodicals, Inc. Random Struct. Alg., 42, 403–437, 2013
The disconfirmatory interview as a strategy for the assessment of system dynamics models
Authors: Andersen Deborah Lines , Luna‐Reyes Luis Felipe , Diker Vedat G. , Black Laura , Rich Eliot , Andersen David F.
Published: August 2012

System dynamics requires the intense use of qualitative data and human judgment in all stages of model development. Most approaches to the formal inclusion of qualitative data have been employed with the purpose of knowledge elicitation during the conceptualization or formulation stages of modeling. In recent years, a small community of practice has explored the creation of interviewing tools to assess system dynamics models. We present the disconfirmatory assessment interview as a specific technique to be used during model assessment. This paper explores the use of interviews as a research and knowledge acquisition technique and more fully describes disconfirmatory assessment as an interview strategy. Based on a comparison of four applications of disconfirmatory interviews as a tool to assess system dynamics models, we present seven features that should form the core of the disconfirmatory interview. Copyright © 2012 System Dynamics Society.
Thickness dependence of the structural, mechanical and electrical properties of Ni films deposited on polyimide by ion beam‐assisted deposition (IBAD)
Authors: Xu Jun , Shao Tianmin
Published: August 2012

Ni thin films with different thicknesses were deposited on pre‐treated polyimide substrates by ion beam‐assisted deposition. Dependence of structural, mechanical and electrical properties of the Ni films on their thickness was investigated. The results showed a clear correlation between film properties and film thickness. The inter‐diffusion at the interface regions of the films with different deposition time were demonstrated by transmission electron microscopy and X‐ray photoelectron spectroscopy. With increasing film thickness, surface roughness of the Ni films firstly decreased and then increased, while the grain size gradually increased. Residual stress of the Ni thin films decreased with increasing Ni film thickness up to 202 nm and then slightly increased as the film thickness further increased. Resistivity decreased, and temperature coefficient of resistivity (TCR) increased with increasing film thickness due to the enhancement of crystallization degree and the increase in grain size. The decrease in surface roughness and residual stress also contributed to the decrease of resistivity and the increase of TCR of the films. An optimal film thickness is suggested, which yielded a relatively high TCR value and low levels of both surface roughness and residual stress. Copyright © 2012 John Wiley & Sons, Ltd.
Backscattered electrons from gold surface films deposited on silicon substrates: a joint experimental and computational investigation to add new potentiality to electron microscopy
Authors: Dapor Maurizio , Bazzanella Nicola , Toniutti Laura , Miotello Antonio , Crivellari Michele , Gialanella Stefano
Published: August 2012

This paper addresses the problem of the thickness determination of thin gold overlayers deposited on silicon bulk substrates by looking at the electron backscattering coefficient involved in scanning electron microscopy (SEM). A Monte Carlo code, used to calculate the backscattering coefficient, together with a simple experimental setup, which uses a conventional SEM, allow to determine thin film thickness (in the range 25–200 nm) with an estimated accuracy of 20%. This adds obviously new potentiality to SEM. Copyright © 2012 John Wiley & Sons, Ltd.
Study of the self‐assembling of n‐octylphosphonic acid layers on aluminum oxide from ethanolic solutions
Authors: Hauffman Tom , Hubin Annick , Terryn Herman
Published: August 2012

One of the molecules which has been noted to form self‐assembled monolayers on aluminium oxide is the phosphonic acid molecule. A variety of chain lengths and solvents have been discussed in state of the art literature. No global consensus about the adsorption mechanism and its limitations has been found yet. In this study, we present the continuation of previous analysis of the adsorption of n‐octylphosphonic acids on chemically and morphologically optimised aluminium oxides. An ex situ analysis approach, using atomic force microscopy, X‐ray photoelectron spectroscopy and Visible Ellipsometry (VISE) is presented. It can be seen that from ethanol, the molecules adsorb on the surface. This occurs in a very unstable way, creating defects at the surface. Through modeling of ellipsometry data, it is found that the oxide film itself is attacked by the acids, resulting in non homogeneous organic overlayers. It seems that, from an ex situ point of view, ethanol is not suitable for the creation of n‐octylphoshonic acid monolayers. The reaction of the phosphonic acids with the aluminium hydroxyls creates local aqueous environments, which are, in combination with dissolved acids, hazardous for the oxide surface. Copyright © 2012 John Wiley & Sons, Ltd.
A simple method for estimating the odds ratio in matched case‐control studies with incomplete paired data
Authors: Miller Kelly M. , Looney Stephen W.
Published: August 2012

Paired data from matched case‐control studies are commonly used to estimate the association between the exposure to a risk factor and the occurrence of a disease. The odds ratio is typically used to quantify this association. Difficulties in estimating the true odds ratio with matched pairs arise, however, when the exposure status is unknown for one of the individuals in one or more pairs. In this article, we propose a simple method for estimating the odds ratio when the sample consists of a combination of complete and incomplete matched pairs; that is, some of the pairs have exposure data for both the case and the control, some of the pairs have exposure data just for the case, and the remaining pairs have exposure data just for the control. This method uses a weighted average of the odds ratio estimator that is most commonly used when the sample consists entirely of complete paired observations and the odds ratio estimator that is most commonly used when the sample consists entirely of unpaired observations. The proposed estimator has simple closed‐form expressions for the estimate of the odds ratio and its approximate variance. We compare our method to existing methods via simulation and show that our method is comparable to or better than the other methods in terms of bias, mean squared error, and confidence interval coverage probability and width. Copyright © 2012 John Wiley & Sons, Ltd.
Two‐stage designs for Phase 2 dose‐finding trials
Authors: Ivanova Anastasia , Xiao Changfu , Tymofyeyev Yevgen
Published: August 2012

We propose a Bayesian adaptive two‐stage design for the efficient estimation of the maximum dose or the minimum effective dose in a dose‐finding trial. The new design allocates subjects in stage two according to the posterior distribution of the target dose location. Simulations show that the proposed two‐stage design is superior to equal allocation and to a two‐stage strategy where only one dose is left in the second stage. Copyright © 2012 John Wiley & Sons, Ltd.
A three‐level mixed‐effects location scale model with an application to ecological momentary assessment data
Authors: Li Xue , Hedeker Donald
Published: August 2012

In studies using ecological momentary assessment (EMA), or other intensive longitudinal data collection methods, interest frequently centers on changes in the variances, both within‐subjects and between‐subjects. For this, Hedeker et al. (Biometrics 2008; 64: 627–634) developed an extended two‐level mixed‐effects model that treats observations as being nested within subjects and allows covariates to influence both the within‐subjects and between‐subjects variance, beyond their influence on means. However, in EMA studies, subjects often provide many responses within and across days. To account for the possible systematic day‐to‐day variation, we developed a more flexible three‐level mixed‐effects location scale model that treats observations within days within subjects, and allows covariates to influence the variance at the subject, day, and observation level (over and above their usual effects on means) using a log‐linear representation throughout. We provide details of a maximum likelihood solution and demonstrate how SAS PROC NLMIXED can be used to achieve maximum likelihood estimates in an alternative parameterization of our proposed three‐level model. The accuracy of this approach using NLMIXED was verified by a series of simulation studies. Data from an adolescent mood study using EMA were analyzed to demonstrate this approach. The analyses clearly show the benefit of the proposed three‐level model over the existing two‐level approach. The proposed model has useful applications in many studies with three‐level structures where interest centers on the joint modeling of the mean and variance structure. Copyright © 2012 John Wiley & Sons, Ltd.
Design and analysis of non‐pharmacological treatment trials with multiple therapists per patient
Authors: Roberts Chris , Walwyn Rebecca
Published: August 2012

In trials of physical and talking therapies, nesting of patients within therapists has statistical implications analogous to those of cluster randomised trials. Nevertheless, the clustering effect may be more complex, as it interacts with treatment. For some therapies, individual patients may receive care from multiple therapists of the same type, so that patients are no longer strictly nested within therapists, creating a ‘multiple‐membership’ relationship between patients and therapists.

This paper considers methods of analysis and sample size estimation for trials with multiple‐membership clustering effects. It is motivated by a trial of a psychotherapy for the treatment of adolescent depression with cognitive behavioural therapy. We tested methods and issues in a Monte Carlo simulation study, simulating trials with multiple membership. Results demonstrate satisfactory performance in terms of convergence and give estimates of the intra‐cluster correlation coefficient and empirical test size similar to a simple hierarchical design.

We derive formulae for sample size and power for multiple‐membership trial designs. We then compare estimates of power from this formula with empirical power derived from the simulation study. Finally, we show that we can easily extend formulae for sample size and power to allow consideration of power and sample size for certain types of more complex interventions. These include situations where therapists of different types deliver separate components of the intervention, creating a cross‐classified relationship, or where several therapists deliver a group‐administered treatment, creating further levels. Copyright © 2012 John Wiley & Sons, Ltd.
A conditional error function approach for subgroup selection in adaptive clinical trials
Authors: Friede T. , Parsons N. , Stallard N.
Published: August 2012

Growing interest in personalised medicine and targeted therapies is leading to an increase in the importance of subgroup analyses. If it is planned to view treatment comparisons in both a predefined subgroup and the full population as co‐primary analyses, it is important that the statistical analysis controls the familywise type I error rate. Spiessens and Debois (Cont. Clin. Trials, 2010, 31, 647–656) recently proposed an approach specific for this setting, which incorporates an assumption about the correlation based on the known sizes of the different groups, and showed that this is more powerful than generic multiple comparisons procedures such as the Bonferroni correction. If recruitment is slow relative to the length of time taken to observe the outcome, it may be efficient to conduct an interim analysis. In this paper, we propose a new method for an adaptive clinical trial with co‐primary analyses in a predefined subgroup and the full population based on the conditional error function principle. The methodology is generic in that we assume test statistics can be taken to be normally distributed rather than making any specific distributional assumptions about individual patient data. In a simulation study, we demonstrate that the new method is more powerful than previously suggested analysis strategies. Furthermore, we show how the method can be extended to situations when the selection is not based on the final but on an early outcome. We use a case study in a targeted therapy in oncology to illustrate the use of the proposed methodology with non‐normal outcomes. Copyright © 2012 John Wiley & Sons, Ltd.
Linear combinations of biomarkers to improve diagnostic accuracy with three ordinal diagnostic categories
Authors: Kang Le , Xiong Chengjie , Crane Paul , Tian Lili
Published: August 2012

Many researchers have addressed the problem of finding the optimal linear combination of biomarkers to maximize the area under receiver operating characteristic (ROC) curves for scenarios with binary disease status. In practice, many disease processes such as Alzheimer can be naturally classified into three diagnostic categories such as normal, mild cognitive impairment and Alzheimer's disease (AD), and for such diseases the volume under the ROC surface (VUS) is the most commonly used index of diagnostic accuracy. In this article, we propose a few parametric and nonparametric approaches to address the problem of finding the optimal linear combination to maximize the VUS. We carried out simulation studies to investigate the performance of the proposed methods. We apply all of the investigated approaches to a real data set from a cohort study in early stage AD. Copyright © 2012 John Wiley & Sons, Ltd.
Sample size in cluster‐randomized trials with time to event as the primary endpoint
Authors: Jahn‐Eimermacher Antje , Ingel Katharina , Schneider Astrid
Published: August 2012

In cluster‐randomized trials, groups of individuals (clusters) are randomized to the treatments or interventions to be compared. In many of those trials, the primary objective is to compare the time for an event to occur between randomized groups, and the shared frailty model well fits clustered time‐to‐event data. Members of the same cluster tend to be more similar than members of different clusters, causing correlations. As correlations affect the power of a trial to detect intervention effects, the clustered design has to be considered in planning the sample size. In this publication, we derive a sample size formula for clustered time‐to‐event data with constant marginal baseline hazards and correlation within clusters induced by a shared frailty term. The sample size formula is easy to apply and can be interpreted as an extension of the widely used Schoenfeld's formula, accounting for the clustered design of the trial. Simulations confirm the validity of the formula and its use also for non‐constant marginal baseline hazards. Findings are illustrated on a cluster‐randomized trial investigating methods of disseminating quality improvement to addiction treatment centers in the USA. Copyright © 2012 John Wiley & Sons, Ltd.
A general binomial regression model to estimate standardized risk differences from binary response data
Authors: Kovalchik Stephanie A. , Varadhan Ravi , Fetterman Barbara , Poitras Nancy E. , Wacholder Sholom , Katki Hormuzd A.
Published: August 2012

Estimates of absolute risks and risk differences are necessary for evaluating the clinical and population impact of biomedical research findings. We have developed a linear‐expit regression model (LEXPIT) to incorporate linear and nonlinear risk effects to estimate absolute risk from studies of a binary outcome. The LEXPIT is a generalization of both the binomial linear and logistic regression models. The coefficients of the LEXPIT linear terms estimate adjusted risk differences, whereas the exponentiated nonlinear terms estimate residual odds ratios. The LEXPIT could be particularly useful for epidemiological studies of risk association, where adjustment for multiple confounding variables is common. We present a constrained maximum likelihood estimation algorithm that ensures the feasibility of risk estimates of the LEXPIT model and describe procedures for defining the feasible region of the parameter space, judging convergence, and evaluating boundary cases. Simulations demonstrate that the methodology is computationally robust and yields feasible, consistent estimators. We applied the LEXPIT model to estimate the absolute 5‐year risk of cervical precancer or cancer associated with different Pap and human papillomavirus test results in 167,171 women undergoing screening at Kaiser Permanente Northern California. The LEXPIT model found an increased risk due to abnormal Pap test in human papillomavirus‐negative that was not detected with logistic regression. Our R package blm provides free and easy‐to‐use software for fitting the LEXPIT model. Published 2012. This article is a US Government work and is in the public domain in the USA.