bluuebunny/crossref_metadata_2025 huggingface dataset:
Source‐based morphometry: The use of independent component analysis to identify gray matter differences with application to schizophrenia
Authors: Xu Lai , Groth Karyn M. , Pearlson Godfrey , Schretlen David J. , Calhoun Vince D.
Published: February 2008

We present a multivariate alternative to the voxel‐based morphometry (VBM) approach called source‐based morphometry (SBM), to study gray matter differences between patients and healthy controls. The SBM approach begins with the same preprocessing procedures as VBM. Next, independent component analysis is used to identify naturally grouping, maximally independent sources. Finally, statistical analyses are used to determine the significant sources and their relationship to other variables. The identified “source networks,” groups of spatially distinct regions with common covariation among subjects, provide information about localization of gray matter changes and their variation among individuals. In this study, we first compared VBM and SBM via a simulation and then applied both methods to real data obtained from 120 chronic schizophrenia patients and 120 healthy controls. SBM identified five gray matter sources as significantly associated with schizophrenia. These included sources in the bilateral temporal lobes, thalamus, basal ganglia, parietal lobe, and frontotemporal regions. None of these showed an effect of sex. Two sources in the bilateral temporal and parietal lobes showed age‐related reductions. The most significant source of schizophrenia‐related gray matter changes identified by SBM occurred in the bilateral temporal lobe, while the most significant change found by VBM occurred in the thalamus. The SBM approach found changes not identified by VBM in basal ganglia, parietal, and occipital lobe. These findings show that SBM is a multivariate alternative to VBM, with wide applicability to studying changes in brain structure. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.
Dynamic neural responses to cue‐reactivity paradigms in heroin‐dependent users: An fMRI study
Authors: Yang Zheng , Xie Jun , Shao Yong‐Cong , Xie Chun‐Ming , Fu Li‐Ping , Li De‐Jun , Fan Ming , Ma Lin , Li Shi‐Jiang
Published: February 2008

Neuroimaging methods have been employed to study cue‐reactivity‐induced neural correlates in the human brain. However, very few studies have focused on characterizing the dynamic neural responses to the factorial interactions between the cues and the subjects. Fifteen right‐handed heroin‐dependent subjects and 12 age‐matched nondrug using subjects participated in this study. Cue‐reactivity paradigms were employed, while changes in blood oxygenation level‐dependent (BOLD) signals were acquired by functional MRI (fMRI). The fMRI datasets were analyzed with AFNI software and repeated two‐way ANOVA was employed for factorial analyses. Neural correlates of factorial interactions between cue‐factor and subject‐factor were identified in the regions of the ventral tegmental area (VTA), the left and right amygdala, the left and right fusiform cortex, and the precuneus in the mesocorticolimbic system, and in the superior frontal, dorsal lateral prefrontal, and orbitofrontal cortices in the prefrontal cortex system. The neural response patterns in the prefrontal systems are dynamic: decreased response to neutral‐cues and increased response to heroin‐cues. Further, heroin‐cue‐induced neural responses within the subregions in the PFC system are significantly intercorrelated. In conclusion, the cue‐reactivity paradigms significantly activated the dynamic neural activations in the prefrontal system. It is suggested that the dynamic response patterns in the PFC system characterize the impaired brain control functions in heroin‐dependent subjects. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.
The postprandial increase in blood triglycerides has no direct effect on the brain BOLD response
Authors: Slade Jill M. , Carlson Joseph J. , Forbes Sean C. , Stein Natalie J. , Moll Matthew R. , Wiseman Robert W. , Meyer Ronald A.
Published: February 2008

A previous study showed that ingestion of a liquid meal high in polyunsaturated lipids decreased the blood‐oxygenation‐level‐dependent (BOLD) response measured by functional magnetic resonance imaging (fMRI) during a finger‐tapping motor task, and suggested that this effect was due to a direct effect of blood lipids on the cerebral vasculature. This study compared the time course and magnitude of the BOLD response in fixed anatomic locations before and 3 h after ingestion of high versus low lipid content liquid meals (235 ml Ensure Plus [Abbot Labs] with or without 50 ml added canola oil). Blood triglyceride content peaked 3 h after the high lipid meal and was elevated by 33% compared with the low lipid meal. There was no significant effect of meal composition on the time course or magnitude of the BOLD response in fixed‐location clusters of voxels which were activated during either a motor (finger‐tapping), a visual (flashing checkerboard), or an integrative/cognitive (number addition) block‐design task paradigm. The results indicate that increased blood total triglyceride content after a meal with relatively high polyunsaturated fat does not directly alter the hemodynamic BOLD response to neural activity. However, the postprandial effect on BOLD response of other meals with varying fat types and amounts, as well as other nutrients and phytochemicals, remains to be determined. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.
Effect of forklift operation on lower back pain: An evidence‐based approach
Authors: Viruet Heriberto Barriera , Genaidy Ash , Shell Richard , Salem Sam , Karwowski Waldemar
Published: February 2008

Most studies on the occupational hazards associated with forklift operation have examined risks of fatalities and traumatic injuries. Few studies have examined the magnitude of risk of lower back pain. This research deals with an evidence‐based approach designed to examine if there is a relationship between whole‐body vibration and driver postures with lower back pain among forklift operators and to offer some recommendations to minimize the risk of lower back pain. To accomplish the study goal, an evidence‐based approach was adopted from evidence‐based medicine. The basic steps of this evidence‐based approach were: (1) formulation of a clear research question from a worker‐occupational problem; (2) search of the literature for the best evidence with which to answer the question; (3) critically appraise the evidence; and (4) implement useful findings in occupational health and safety practices. In addition, the metarelative risk was calculated and the biological plausibility between whole body vibration (WBV) and operator posture with lower back pain was investigated. Six observational articles satisfied the inclusion criteria adopted in this research. The methodological qualities of the published studies ranged from marginal to average. The metarelative risk was 2.1, indicating that operators exposed to driving forklifts are greater than twice the risk of those not exposed to driving forklifts to experience lower back pain. There are biological mechanisms by which WBV and operator postures could develop lower back pain. Some aspects of the work environment that influenced vibration are seat, speed, track, and tires. Awkward postures and static postures are affected by cab design, seat, time spent seated, and the task performed. It appears that there is a causal relationship between forklift operation and lower back pain. The evidence examined shows a strong association and consistency between all studies and this relationship is biologically plausible. It is recommended that intervention studies be conducted to determine the effectiveness of ergonomic controls. © 2008 Wiley Periodicals, Inc.
Does lumbar fusion increase the risk of disc degeneration of the adjacent segment?
Authors: Flanagan Erica , Wiggermann Neal , Genaidy Ash , Stambough Jeffery , Shell Richard
Published: February 2008

Several reviews have attempted to establish whether there is an association between adjacent segment disorder and spinal fusion. None of these studies used an evidence‐based approach or solely focused on studies utilizing controls. The goal of this article is to identify any significant link between lumbar or lumbosacral spinal fusion and development of adjacent segment disease using literature with more than a 10‐year follow‐up, at least 15 subjects, and a control with no exposure to fusion. The published articles were obtained from a search of electronic databases and bibliographies of identified articles. The critical appraisal was performed using an epidemiological appraisal instrument. Five articles satisfied the inclusion criteria. From the literature, no definitive conclusion could be drawn regarding adjacent segment disorder as an outcome of spinal fusion. The failure of the literature to link adjacent segment disease to spinal fusion at least suggests the problem may not be widespread, but also fails to disprove the myriad of biomechanical concerns. Device manufacturers should address these concerns by furthering the development of motion preservation instrumentation and other innovations. Helping to drive this technology will be a larger data set of research with sound methodological quality and inclusion of accepted radiographic and functional outcomes. The reported findings underscore a need for information on spinal fusion and require a strategy for moving forward. © 2008 Wiley Periodicals, Inc.
Recovery of pyruvic acid with weakly basic polymeric sorbents
Authors: Huang Shaokai , Qin Wei , Dai Youyuan
Published: February 2008

BACKGROUND: Carboxylic acids are among the most important substances that can be manufactured from biomass. However, the recovery of carboxylic acids from fermentation broths presents a challenging separation problem. To avoid the production of waste salts and net consumption of chemicals in the calcium carboxylate salt process, the use of reversible chemical complexation with polymeric sorbents and extractants is attractive for carboxylic acid recovery. Pyruvic acid is widely used in the manufacture of medicines, pesticides and foodstuffs and can be produced by fermentation. Since the acidity of pyruvic acid (pKa = 2.49) is stronger than that of normal carboxylic acids, and as few reports on the recovery of pyruvic acid are available, the sorption of pyruvic acid from aqueous solution on two types of weakly basic polymeric sorbent, tertiary amine D301R and primary amine D392, was investigated over a wide pH range and at various salt (MgSO4) concentrations.

RESULTS: Overloading adsorption of pyruvic acid on both weakly basic polymeric sorbents occurred, with the overloading of D392 being greater than that of D301R. The adsorption of pyruvic acid on both sorbents was greatly affected by the solution pH and the salt concentration in the aqueous phase. An overloading model was able to predict the experimental uptake data very well.

CONCLUSION: Solution pH is one of the most important operating conditions, and both polymeric sorbents D392 and D301R can be used to recover pyruvic acid from dilute aqueous solution with high efficiency at a solution pH around 2. The uptake by D392 is greater than that by D301R owing to steric hindrance of the tertiary amine. Copyright © 2008 Society of Chemical Industry
Hydrophobically modified low molecular weight chitosans as efficient and nontoxic gene delivery vectors
Authors: Zhang Xin , Ercelen Sebnem , Duportail Guy , Schaub Emmanuel , Tikhonov Vladimir , Slita Alexander , Zarubaev Vladimir , Babak Valery , Mély Yves
Published: February 2008

Background

Chitosan derivatives are potential candidates for gene delivery because they are biocompatible and low toxic. However, their use has been limited by their moderate transfection efficiency and the rather large sizes of DNA complexes with high molecular weight chitosans. To circumvent these limitations, we used low molecular weight (approximately 5 kDa) chitosans grafted at 3 and 18 mol% with N‐/2(3)‐(dodec‐2‐enyl)succinoyl groups (HM‐LMW‐ch) that exhibit surfactant‐like properties.

Methods

The physico‐chemical properties of complexes of DNA with the two HM‐LMW‐ch derivatives and the nonmodified LMW‐ch were compared by electrophoresis, dynamic light scattering, fluorescence spectroscopy and fluorescence correlation spectroscopy. Moreover, their transfection efficiencies and cytotoxicity were evaluated and their intracellular trafficking was monitored by confocal microscopy. Finally, their ability to deliver genes in mice kidneys after systemic administration was investigated.

Results

Complexes with HM(3%)‐LMW‐ch, but not with HM(18%)‐LMW‐ch and LMW‐ch, efficiently delivered genes in mice kidneys. HM(3%)‐LMW‐ch formed small positively charged particles that were resistant to DNases and nucleases and marginally interact with serum components. Moreover, these particles were efficiently internalized in cells and low toxic. By contrast, HM(18%)‐LMW‐ch formed large and weakly charged aggregates with DNA that were highly susceptible to DNases and nucleases.

Conclusions

HM(3%)‐LMW‐ch appears to be a promising nonviral vector with low cytotoxicity and efficient transfection properties. Copyright © 2008 John Wiley & Sons, Ltd.
The conservational heritage of wall paintings and buildings : an FT‐Raman spectroscopic study of prehistoric, Roman, mediaeval and Renaissance lime substrates and mortars
Authors: Edwards Howell G. M. , Farwell Dennis W.
Published: February 2008

Raman spectroscopic studies of ancient lime‐based plasters and mortars from periods ranging from prehistoric through Roman to mediaeval have revealed the potential application of the technique for the non‐destructive analysis of these ubiquitous substrates that are found in constructional and decorative work. Characteristic information obtained from the Raman spectra of these materials obtained with near infrared excitation at 1064 nm provides an insight into ancient technological practices and particularly the methodology of application of the associated pigments in wet fresco techniques in the transition towards gypsum plasters. The assignment of molecular features to the plasters and to their reaction product with moist air, calcium carbonate, facilitates the assessment of the extent of curing of the material that has taken place and is relevant to the conservation of buildings and fresco art works. Copyright © 2008 John Wiley & Sons, Ltd.
Physico‐chemical characterization of date varieties using multivariate analysis
Authors: Khan M. Nasiruddin , Sarwar Anila , Wahab M. Farooq , Haleem Roohi
Published: February 2008

BACKGROUND: The fruit of date palm is consumed as an ideal high‐energy food. It is also used for the treatment of colds, fever, liver and abdominal troubles. Its nutritional composition strongly depends upon variety and ripening stage. A number of varieties are available in Pakistan but little is known about their composition and nutritional characteristics. Inherent moisture, volatile matter, ash, fixed carbon, sugar and mineral metals of seven commercial date varieties (Aseel, Basra, Begun, Janshoor, Mazoee, Rabee and Zaidi) were investigated. The physical and chemical compositions with respect to maturation were also monitored for the Aseel variety.

RESULTS: The results showed significant varietal differences in moisture, ash and mineral metal composition when analysis of means was conducted at an alpha level of 0.05. The difference between means was insignificant (P > 0.05) for volatile matter, glucose, fructose and total reducing sugars. All varieties were found to be an excellent source of total reducing sugar (78%), potassium (403–632 mg per 100 g) and calcium (27.41–81.47 mg per 100 g). A gradual increase in total reducing sugar and minerals, especially potassium and copper, was observed with maturation. Variety Aseel was grouped on the basis of maturation using principal component analysis. Local date varieties were separated with 48.63% level of similarity from Iranian variety (29.17%) using Cluster analysis.

CONCLUSION: This study provides an overview of the physico‐chemical properties of date varieties. The sample varieties showed significant differences except for sugar and volatile matter. Multivariate analysis was found to be an important statistical tool for the separation of samples on the basis of geographical origin and maturations. Copyright © 2008 Society of Chemical Industry
Improving the resolution of neuropeptides in rat brain with on‐line HILIC‐RP compared to on‐line SCX‐RP
Authors: Mihailova Albena , Malerød Helle , Wilson Steven Ray , Karaszewski Bartosz , Hauser Roman , Lundanes Elsa , Greibrokk Tyge
Published: February 2008

Our two already established on‐line 2‐D LC systems, a strong cation exchange‐RP chromatography (SCX‐RP) system and a hydrophilic interaction LC (HILIC)‐RP 2‐D LC system, were compared to explore which system is best suited for our further studies of differences in cerebral neuropeptide expression as a function of hypoxia‐caused stress. The same mass spectrometer and database search parameters were applied in both systems. In total, 19 first dimension fractions were collected with the novel on‐line HILIC‐RP system, including a Hypercarb SPE column that was applied to trap the compounds not retained on a Kromasil C18 enrichment column. In contrast, six fractions were collected in the SCX‐RP method, due to practical limitations of this traditional on‐line 2‐D LC system. With the on‐line HILIC‐RP system three times more peaks were detected. It was observed that most of the compounds eluted in the first two fractions in the SCX‐RP method, while in the 2‐D HILIC‐RP method there seemed to be no correlation between peaks detected and fraction number. Thus, from this systematic study it seems that on‐line HILIC‐RP chromatography is the method of choice for comparative “peptidomics” of cerebral neuropeptides in future studies.
Analysis of calcineurin activity by capillary electrophoresis with laser‐induced fluorescence detection using peptide substrate
Authors: Enayetul Babar Sheikh Md. , Song Eun Joo , Yoo Young Sook
Published: February 2008

Reversible protein phosphorylation and dephosphorylation are very important activities in understanding cellular signaling networks. In this paper we described a CE‐LIF‐based assay method of calcineurin (CN), a protein phosphatase important in cardiac hypertrophy, in which a fluorescence‐labeled 19‐amino acid phosphopeptide was used as a substrate. The substrate was converted to a dephosphorylated product by CN and both the substrate and product were detected by the LIF detector. This assay method was tested for various separation parameters as well as reaction parameters. It was found that 100 mM of a boric acid buffer with a pH of 9.00 produced optimum separation at 10 kV of applied voltage using a 47 cm capillary. After obtaining the suitable reaction conditions the method was used to detect and quantify the CN activity in HL‐1 cell extracts where the picogram level of CN activity was obtained per microgram total protein. It was also observed that immunosuppressive drugs like okadaic acid and cyclosporine A inhibit in vitro CN activity.
Mass spectrometry strategies applied to the characterization of proline‐rich peptides from secretory parotid granules of pig (Sus scrofa)
Authors: Fanali Chiara , Inzitari Rosanna , Cabras Tiziana , Fiorita Antonella , Scarano Emanuele , Patamia Maria , Petruzzelli Raffaele , Bennick Anders , Messana Irene , Castagnola Massimo
Published: February 2008

Basic proline‐rich proteins (bPRPs) are a class of proteins widely present in saliva of humans and other mammals. They are synthesized as preproproteins and enzymatically cleaved into small peptides before secretion from the salivary glands. Recently, we characterized two proline‐rich peptides (SP‐A and SP‐B) in parotid secretory granules of pig (Sus Scrofa) that are derived from three isoforms of a PRP proprotein (Swiss‐Prot data bank: Q95JC9‐1, Q95JC9‐2 and Q95JC9‐3). Together the coding regions for SP‐A and SP‐B, which are repeated many times, account for 52–70% of the coding regions of the PRP proproteins. This study was undertaken to identify peptides encoded by unassigned regions of the PRP proproteins. RP‐HPLC‐ESI‐IT‐MS analysis of enriched granule preparations from pig parotid glands by two different analytical strategies identified ten new proline‐rich peptides derived from the three proproteins. Together with the coding regions for SP‐A and SP‐B already identified it was possible to assign 68–75% of the proproteins coding regions. The peptide sequences indicated a number of unusual proteolytic cleavage sites suggesting the presence of unknown proprotein convertases.
Peptidomics: The integrated approach of MS, hyphenated techniques and bioinformatics for neuropeptide analysis
Authors: Boonen Kurt , Landuyt Bart , Baggerman Geert , Husson Steven J. , Huybrechts Jurgen , Schoofs Liliane
Published: February 2008

MS is currently one of the most important analytical techniques in biological and medical research. ESI and MALDI launched the field of MS into biology. The performance of mass spectrometers increased tremendously over the past decades. Other technological advances increased the analytical power of biological MS even more. First, the advent of the genome projects allowed an automated analysis of mass spectrometric data. Second, improved separation techniques, like nanoscale HPLC, are essential for MS analysis of biomolecules. The recent progress in bioinformatics is the third factor that accelerated the biochemical analysis of macromolecules. The first part of this review will introduce the basics of these techniques. The field that integrates all these techniques to identify endogenous peptides is called peptidomics and will be discussed in the last section. This integrated approach aims at identifying all the present peptides in a cell, organ or organism (the peptidome). Today, peptidomics is used by several fields of research. Special emphasis will be given to the identification of neuropeptides, a class of short proteins that fulfil several important intercellular signalling functions in every animal. MS imaging techniques and biomarker discovery will also be discussed briefly.
Microstructured Reactors for Polymer Synthesis: A Renaissance of Continuous Flow Processes for Tailor‐Made Macromolecules?
Authors: Wilms Daniel , Klos Johannes , Frey Holger
Published: February 2008

Organic synthesis in microfluidic devices has attracted increasing interest in recent years. However, little efforts had been undertaken to exploit this novel technology for polymer chemistry until several recent studies demonstrated the interesting potential of microreactors for the synthesis and modification of polymers. In fact, anionic polymerizations in continuous capillary flow‐tube systems were established already in 1962 in pioneering work by Szwarc. Subsequent work focused on detailed kinetic analyses in such reactors. The present article explores different current strategies developed by several research groups to realize bulk and solution polymerizations using continuous flow microreactors. Inherent benefits and limitations of these systems compared to traditional laboratory set‐ups are discussed. We present a variety of recent pioneering and advanced approaches to realize free radical, controlled radical, cationic and anionic polymerizations in microtechnological reaction devices. In some cases, surprisingly narrow molecular weight distributions have been obtained, demonstrating the promising potential of this approach for the tailoring of polymer structures.

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Herz spaces and summability of Fourier transforms
Authors: Feichtinger Hans G. , Weisz Ferenc
Published: February 2008

A general summability method is considered for functions from Herz spaces Kαp,r (ℝd ). The boundedness of the Hardy–Littlewood maximal operator on Herz spaces is proved in some critical cases. This implies that the maximal operator of the θ ‐means σθ T f is also bounded on the corresponding Herz spaces and σθ T f → f a.e. for all f ∈ K–d /p p,∞ (ℝd ). Moreover, σθ T f (x) converges to f (x) at each p ‐Lebesgue point of f ∈ K–d /p p,∞ (ℝd ) if and only if the Fourier transform of θ is in the Herz space Kd /p p ′,1 (ℝd ). Norm convergence of the θ ‐means is also investigated in Herz spaces. As special cases some results are obtained for weighted Lp spaces. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solutions of Volterra integral equations with infinite delay
Authors: Franco Daniel , O'Regan Donal
Published: February 2008

We present several new existence results for a Volterra integral equation with infinite delay. We discuss periodic and bounded solutions. Sufficient conditions for the existence of positive periodic solutions are also provided. The techniques we employ have not been used for this equation before. Our results generalize and complement those in the literature and several examples are presented to show their applicability. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The alternative Daugavet property of C *‐algebras and JB *‐triples
Authors: Martín Miguel
Published: February 2008

A Banach space X is said to have the alternative Daugavet property if for every (bounded and linear) rank‐one operator T: X → X there exists a modulus one scalar ω such that ∥Id+ωT ∥ = 1 + ∥T ∥. We give geometric characterizations of this property in the setting of C *‐algebras, JB *‐triples, and of their isometric preduals. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Small sets for Neumann boundary conditions
Authors: Voigt Jürgen
Published: February 2008

For an open set D ⊆ ℝn and a relatively closed subset E ⊆ D of Lebesgue measure zero, we investigate conditions for the property that Brownian motion with reflexion at the boundary on D and D \ E are the same. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A semi‐analytical approach for modelling heat transfer during salt‐cavern leaching process
Authors: Rouabhi A. , Tijani M. , Stab O. , Charnavel Y. , You T.
Published: February 2008

The use of gas‐storage caverns in salt formations is a growing industry that continues to gain momentum because it allows gas to be injected and withdrawn at high rates compared with other underground gas‐storage systems such as porous rock systems.

In order to predict cavern production performances, cavern thermodynamics behaviour must be studied by higher accuracy approaches. This behaviour is extremely related to the temperature distribution in the surrounding formations. During the leaching process, the thermal equilibrium of the rock salt surrounding the cavern is extensively disrupted. The purpose of this paper is to study the heat transfer problem during the leaching process and to develop a thermal model that can be easily used in field applications. The results of this work will be the input data for the prediction of the gas temperature and pressure during cavern gas‐storage operation phase. Moreover, the developed model can find its use in the design of salt caverns since it can be coupled with geometrical modelling of salt dissolution codes. Copyright © 2008 John Wiley & Sons, Ltd.
A semi‐algebraic approach that enables the design of inter‐grid operators to optimize multigrid convergence
Authors: Navarrete Michelini Pablo , Coyle Edward J.
Published: February 2008

We study the effect of inter‐grid operators—the interpolation and restriction operators—on the convergence of two‐grid algorithms for linear models. We show how a modal analysis of linear systems, along with some assumptions on the normal modes of the system, allows us to understand the role of inter‐grid operators in the speed and accuracy of a full‐multigrid step.

We state an assumption that generalizes local Fourier analysis (LFA) by means of a precise description of aliasing effects on the system. This assumption condenses, in a single algebraic property called the harmonic aliasing property, all the information needed from the geometry of the discretization and the structure of the system's eigenvectors. We first state a harmonic aliasing property based on the standard coarsening strategies of 1D problems. Then, we extend this property to a more aggressive coarsening typically used in 2D problems with the help of additional assumptions on the structure of the system matrix.

Under our general assumptions, we determine the exact rates at which groups of modal components of the error evolve and interact. With this knowledge, we are then able to design inter‐grid operators that optimize the two‐grid algorithm convergence. By different choices of operators, we verify the classic heuristics based on Fourier harmonic analysis, show a trade‐off between the rate of convergence and the number of computations required per iteration, and show how our analysis differs from LFA. Copyright © 2008 John Wiley & Sons, Ltd.
Multigrid Methods
Authors: Falgout Robert D.
Published: February 2008

This special issue contains papers from the Thirteenth Copper Mountain Conference on Multigrid Methods, held in the Colorado Rocky Mountains on March 19–23, 2007, co‐chaired by Van Henson and Joel Dendy. The papers address a variety of applications and cover a breadth of topics, ranging from theory to high‐performance computing. Copyright © 2008 John Wiley & Sons, Ltd.
New analysis of the optimization of electromagnetic shielding properties using conducting polymers and a multi‐objective approach
Authors: Schütze Oliver , Jourdan Laetitia , Legrand Thomas , Talbi El‐Ghazali , Wojkiewicz Jean‐Luc
Published: February 2008

Recently, an approach was proposed to optimize multi‐layer shields of polyaniline–polyurethane (PAni/PU) conducting composites in the microwave band. Though by this method shields for different applications can be obtained which are light‐weight and offer a low percolation threshold, the full potential of the design process could not be tapped since the underlying optimization problem includes only one objective. In this work we go one step beyond and re‐formulate the design problem as a multi‐objective optimization problem (MOP). To be more precise, we involve simultaneously the shielding efficiency as well as the weight and the cost of the material—i.e. all the requirements for modern shielding materials—within the optimization process. After having stated the model we present two possible ways to approximate the solution set—the so‐called Pareto set—and address the related and important decision‐making problem. All steps are demonstrated on a particular three‐layered composite in order to show the applicability of the novel approach. Copyright © 2008 John Wiley & Sons, Ltd.
Café‐au‐lait macules and pediatric malignancy caused by biallelic mutations in the DNA mismatch repair (MMR) gene PMS2
Authors: Jackson Carl‐Christian , Holter Spring , Pollett Aaron , Clendenning Mark , Chou Shirley , Senter Leigha , Ramphal Raveena , Gallinger Steven , Boycott Kym
Published: February 2008

A 14‐year‐old male presented with a T4 sigmoid adenocarcinoma, <10 colonic adenomas and multiple café‐au‐lait macules. Family history was not suggestive of a dominant hereditary form of colorectal cancer. Evaluation of the tumor revealed abnormal immunohistochemical staining of the PMS2 protein and high frequency microsatellite instability. Germline analysis identified biallelic PMS2 missense mutations. A new cancer syndrome caused by biallelic mutations in the mismatch repair genes, including PMS2, is now emerging and is characterized by café‐au‐lait macules, colonic polyps and a distinctive tumor spectrum. Pediatr Blood Cancer 2008;50:1268–1270. © 2008 Wiley‐Liss, Inc.
Synthesis, light emission, and photovoltaic properties of perylene‐containing polyacetylenes
Authors: Hua Jianli , Lam Jacky Wing Yip , Yu Xiaoming , Wu Lijun , Kwok Hoi Sing , Wong Kam Sing , Tang Ben Zhong
Published: February 2008

Perylene (Py)‐containing polyacetylenes with different skeleton structures [HCC(C6H4)CO2Py]n (P1), [HCC(CH2)8CO2Py]n (P2), and {[(C6H5) CC(CH2)9NH2]co[(C6H5)CC(CH2)9Py]}n (P3) are synthesized in satisfactory yields by Rh‐catalyzed polymerization (for P1 and P2) and polymer reaction (for P3). All the polymers are soluble and possess high molecular weights (Mw up to 2.8 × 105). Their structures and properties are characterized and evaluated by IR, NMR, UV, TGA, PL, and photovoltaic (PV) analyses. The polymers are thermally stable, losing little of their weights when heated to 330 °C. When their solutions are irradiated, their perylene pendants emit intense red fluorescence at 610 nm. PV cells with a configuration of ITO/PEDOT:PSS/polymer/LiF/Al are fabricated, which show maximum current density of 10.3 μA/cm2. The external quantum efficiency is sensitive to the polymer structure, with P3 exhibiting the highest value of 0.23%. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2025–2037, 2008
Metal nanocomposite films prepared in situ from PVA and silver nitrate. Study of the nanostructuration process and morphology as a function of the in situ routes
Authors: Clémenson S. , Léonard D. , Sage D. , David L. , Espuche E.
Published: February 2008

Cast‐hybrid films composed of polyvinyl alcohol (PVA) and silver nitrate were treated according to three different ways, thermal annealing, UV‐irradiation, and chemical reduction by a borohydride solution, to obtain PVA/silver nanocomposite films. The nanostructuration process was studied as a function of the treatment conditions, and discussed as a function of the mobility state of the polymer chains in the nanocomposite matrix during treatment. A homogeneous dispersion of crystalline silver nanoparticles was obtained by thermal annealing above Tg and below Tm and UV‐lamp irradiation below Tg. For these two treatments, the major processing parameters were the annealing temperature and time and the UV‐exposure time, respectively. For low‐conversion rate in Ag(0), the films evolved upon ageing at room temperature. Totally different morphology and Ag(0) conversion were achieved by chemical reduction in a borohydride solution. All the silver ions were reduced into Ag(0), and crystalline silver nanoparticles layers parallel to the film surface were observed after the treatment. This morphology was related to the high‐swollen state of the polymer matrix during treatment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2062–2071, 2008
Preparation and property of two soluble oxadiazole‐containing functional polyacetylenes
Authors: Wang Xin , Wu Jincui , Xu Hongyao , Wang Pei , Tang Ben Zhong
Published: February 2008

Two novel high‐molecular weight functional polyacetylenes (PA) bearing oxadiazole group as a pendant, poly(2‐(4‐octoxyphenyl)‐5‐(4‐ethynylphenyl)‐1,3,4‐oxadiazole) (P1) and poly(2‐(4′‐octoxyphenyl)‐5‐(4′‐propynyloxyphenyl)‐1,3,4‐oxadiazole) (P2) were synthesized by [Rh(nbd)Cl]2‐Et3N catalysts. Both polymers were soluble in common organic solvents such as CHCl3 and tetrahydrofuran. Their structures and properties were characterized and evaluated with FTIR, NMR, UV, thermogravimetric analysis, GPC, optical‐limiting and nonlinear optical analyses, respectively. The results show that linkage of oxadiazole chromophore to PA main chain has improved the nonlinear optical (NLO) property of PA, and endowed PA with novel optical limiting properties and enhanced thermal stability. Simultaneously, the optical‐limiting and NLO properties of the polymers were sensitive to their molecular structures. P1 with oxadiazole directly incorporated into PA main chain as a pendant showed better performances and larger third‐order nonlinear optical susceptibility than P2 with oxadiazole incorporated into PA main chain via a spacer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2072–2083, 2008
Poly(1,4‐cyclohexylenedimethylene 1,4‐cyclohexanedicarboxylate): Influence of stereochemistry of 1,4‐cyclohexylene units on the thermal properties
Authors: Berti Corrado , Binassi Enrico , Celli Annamaria , Colonna Martino , Fiorini Maurizio , Marchese Paola , Marianucci Elisabetta , Gazzano Massimo , Di Credico Francesco , Brunelle Daniel J.
Published: February 2008

A series of poly(1,4‐cyclohexylenedimethylene 1,4‐cyclohexanedicarboxylate) (PCCD) samples, characterized by different cis/trans ratio of the 1,4‐cyclohexanedicarbonyl unit, have been synthesized and analyzed by thermogravimetry (TGA), calorimetry (DSC), and X‐ray diffraction (WAXD). The thermal stability results are good and are not affected by the stereochemistry of the 1,4‐cyclohexylene units. On the other hand, the thermal transitions are notably influenced by the cis/trans content. With the increment of the trans content the polymer changes from completely amorphous to semicrystalline material. Tg, Tm, and crystallinity increase. These results suggest that the trans configuration induces a better chain packing and higher symmetry, improving the crystallizability of the samples. The effect of the molecular structure on the thermal properties is analyzed by using a statistical approach. From the effective correlations found between stereochemistry of the C6 rings and transition temperatures it is possible to extrapolate that the configuration of 1,4‐cyclohexylene ring deriving from 1,4‐cyclohexanedicarboxylic acid or dimethyl 1,4‐cyclohexanedicarboxylate results to be the main element responsible for the thermal properties. This is due to the high rigidity of the 1,4‐cyclohexanedicarbonyl unit with respect to 1,4‐cyclohexanedimethyleneoxy unit, deriving from the diol. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 619–630, 2008
Energetic Materials: Crystallization, Characterization and Insensitive Plastic Bonded Explosives
Authors: van der Heijden Antoine E. D. M. , Creyghton Yves L. M. , Marino Emanuela , Bouma Richard H. B. , Scholtes Gert J. H. G. , Duvalois Willem , Roelands Marc C. P. M.
Published: February 2008

The product quality of energetic materials is predominantly determined by the crystallization process applied to produce these materials. It has been demonstrated in the past that the higher the product quality of the solid energetic ingredients, the less sensitive a plastic bonded explosive containing these energetic materials becomes. The application of submicron or nanometric energetic materials is generally considered to further decrease the sensitiveness of explosives. In order to assess the product quality of energetic materials, a range of analytical techniques is available. Recent attempts within the Reduced‐sensitivity RDX Round Robin (R4) have provided the EM community a better insight into these analytical techniques and in some cases a correlation between product quality and shock initiation of plastic bonded explosives containing (RS‐)RDX was identified, which would provide a possibility to discriminate between conventional and reduced sensitivity grades.
Characterization of Polymer‐Coated RDX and HMX Particles
Authors: da Costa Mattos Elizabeth , Moreira Enézio D. , Diniz Milton F. , Dutra Rita C. L. , da Silva Gilson , Iha Koshun , Teipel Ulrich
Published: February 2008

Fourier transform‐infrared spectroscopy (FT‐IR) in transmission and photoacoustic detection (PAS) techniques have been used for the characterization of polymeric coating of cyclotrimethylenetrinitramine (RDX) using a fluoroelastomer (Viton®). Although the bands of the polymer were indicated by two different techniques, the transmission (casting film) showed better evidence of absorption of fluoroelastomer for the polymer coating of the energetic material. Also attenuated total reflectance (ATR), another FT‐IR technique, has been used to analyze a cyclotetramethylenetetramine (HMX)/Viton system for the characterization of Viton bands and it showed excellent results without sample preparation.
A simple method for monitoring the cysteine content in synthetic peptides
Authors: Horváti Kata , Bõsze Szilvia , Hudecz Ferenc , Medzihradszky‐Schweiger Hedvig
Published: February 2008

A new method for the determination of the cysteine content of synthetic peptides is described. For this purpose the classical amino acid analysis is not suitable, as cysteine may undergo oxidative dimerisation to cystine during the hydrolysis or evaporation. The intact peptide was reacted with N‐ethylmaleimide (NEM) yielding a stable S‐(N‐ethylsuccinimido)‐cysteine derivative, which could be separated by RP‐HPLC and characterised by mass spectrometry. For the quantitative determination less than 0.1 µM peptide was sufficient. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.
Comparison of InGaN/GaN light emitting diodes grown on m ‐plane and a ‐plane bulk GaN substrates
Authors: Yamada Hisashi , Iso Kenji , Saito Makoto , Hirasawa Hirohiko , Fellows Natalie , Masui Hisashi , Fujito Kenji , Speck James S. , DenBaars Steven P. , Nakamura Shuji
Published: February 2008

InGaN/GaN‐based light emitting diodes (LEDs) grown on m ‐plane, a ‐plane and off‐axis between m ‐ and a ‐plane GaN bulk substrates were investigated. A smooth surface was obtained when a ‐plane substrate was applied; however, large amounts of defects were observed. Photoluminescence measurements of the LEDs with a well thickness of 2.5 nm revealed that all the LEDs showed the peak emission wavelength at 389 nm. The PL intensity of the a ‐plane LED is one order of magnitude lower than that of the m ‐plane LED. The a ‐plane LEDs showed significant lower electroluminescence output powers than m ‐plane LEDs, suggesting that excitons are trapped by the defects, which act as non‐radiative recombination centers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Differentiation of heterocyclic regioisomers: a combined tandem mass spectrometry and computational study of N‐acridin‐4‐ylbenzylamide and N‐acridin‐2‐yl‐benzylamide
Authors: Tintaru Aura , Benchabane Yohann , Boyer Gérard , Humbel Stéphane , Charles Laurence
Published: February 2008

Electrospray ionization (ESI) tandem mass spectrometry (MS/MS) has been used to differentiate two positional isomers of acridine derivatives, N‐acridin‐4‐ylbenzylamide and N‐acridin‐2‐ylbenzylamide. The study revealed that the isomeric ion structures produced by these heterocycles could be distinguished upon collision‐induced dissociations (CID). In particular, the loss of a water molecule was shown to be a regiospecific reaction of the protonated N‐acridin‐4‐ylbenzylamide, in which the location of the benzylamide substituent with respect to the acridinic nitrogen greatly assists proton migration by allowing the creation of intramolecular hydrogen bonds. To a lesser extent, the two isomers could also be distinguished by the difference in the abundance of the benzoyl cation in the MS/MS spectra of the [M+H]+ ions, as this ion is produced with a much higher rate from N‐acridin‐4‐ylbenzylamide. Calculations based on quantum‐mechanical models have been performed to evaluate the stability of the ion structures and to support mechanisms proposed for these two dissociation reactions. Copyright © 2008 John Wiley & Sons, Ltd.
Complexation of diazaperylene and bisisoquinoline with transition metal ions in the gas phase studied by electrospray ionization mass spectrometry
Authors: Starke Ines , Kammer Stefan , Grunwald Nicolas , Schilde Uwe , Holdt Hans‐Jürgen , Kleinpeter Erich
Published: February 2008

The complex formation of the ligands 1,12‐diazaperylene (dap), 1,1′‐bisisoquinoline (bis), 2,2′‐bipyridine (bpy) and 1,10‐phenanthroline (phen) with transition metal ions (M = Fe, Co, Ni, Cu, Zn, Ru, Os, Re, Pd, Pt, Ag and Cd) in the gas phase has been studied by electrospray ionization mass spectrometry. With the exception of Ru, Os, Fe, Ni and Cu, singly charged complexes [MLn]+ (n = 1,2) were observed. The complexes of dap and bis with Ru, Os, Fe and Ni ions, and the mixed ligand complexes with bpy and phen, are preferably of the doubly charged type [ML3]2+. In addition, collision‐induced dissociation (CID) measurements were employed to evaluate the relative stabilities of these complexes. The CID experiments of mixed‐ligand complexes which contain both dap and phen or dap and bpy exhibit preferential elimination of bpy, indicating that bpy is a weaker ligand than phen and dap. Copyright © 2008 John Wiley & Sons, Ltd.
Effect of alloy composition on the selective oxidation of ternary FeSiCr, FeMnCr model alloys
Authors: Swaminathan Srinivasan , Spiegel Michael
Published: February 2008

In order to understand the effect of Si and Mn concentration on the selective oxidation of Cr, the model alloys of Fe–1% Si–0.8% Cr, Fe–2% Si–0.8% Cr, Fe–1% Mn–0.8% Cr and Fe–2% Mn–0.8% Cr (all in wt%) were studied. The specimens were annealed at 820 °C in N2–5%H2 gas atmospheres with the different dew points (DPs) of − 80, − 40 and − 29 °C, respectively. Surface analyses were carried out by using the XPS and field emission (FE)‐SEM. Only binary oxides of the alloying elements were observed on the surface of all the ternary model alloys annealed at a low DP of − 80 °C. Increasing the DP to − 40 °C leads to maximum external oxidation of the alloying elements. In the Fe–1% Si–0.8% Cr alloy, annealing at the higher DP of − 29 °C promotes internal oxidation of Cr. On the other hand, increasing the Si concentration in the FeCr alloy (i.e. Fe–2% Si–0.8% Cr), the maximum external oxidation of Cr was observed due to the decrease of surface oxygen potential by Si. Moreover, the oxidation kinetics seems to play a decisive role, i.e. the oxygen competition between Si and Cr leads to partial oxidation of these elements. In both FeMnCr alloys, the effect of Mn concentration on the selective oxidation of Cr is indistinguishable, however, apart from their binary oxides (MnO/Mn3O4, Cr2O3), the MnCr chemical interaction causes the formation of ternary oxide (MnCr2O4) at the DP of − 40 and − 29 °C. Copyright © 2008 John Wiley & Sons, Ltd.
Emulating Access Grid features at Web endpoints: a developer's view
Authors: Sendín‐Raña Pablo , Otero‐Alonso Nicolás , Goyanes de Miguel Vicente , González‐Castaño Francisco J. , Rodríguez‐Hernández Pedro S. , Gil‐Castiñeira Felipe , Costa‐Montenegro Enrique
Published: February 2008

This paper presents the development experience and the evaluation of a system to emulate interactive features of Access Grid virtual rooms (venues) at Web endpoints. The system includes a toolset to demultiplex Access Grid sources, transcode them to adequate formats for Internet distribution and store the resulting multimedia streams in repositories in real time. A specialized server asynchronously delivers those streams to standard Web browsers, which synchronize them and emulate typical Access Grid interactive features such as multiple windows or dynamic video selection. Web browsers can compose multiple independent streams. We call the resulting paradigm Presentations on Demand. From the point of view of software practice, the system relies on a combination of SMIL scripts, CSS and Javascript. Copyright © 2008 John Wiley & Sons, Ltd.
From spontaneous play and hanging out to out‐of‐school time programming: An American perspective
Authors: VanderVen Karen
Published: February 2008

Two‐parent working families, safety factors, shifts in gender roles, and many other factors have led to rapid development of out‐of‐school‐time programming to provide youngsters with the kinds of experiences they might have historically received at home and in the neighborhood. This article elaborates on key issues in quality, the quality of relationships with both peers and staff, opportunity for youth voice, and the activities provided.