bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid phase behavior modeling of CO2 + molten polymer systems using cubic and theoretically based equations of state
Authors: Arce Pedro , Aznar Martin , Mattedi Silvana
Published: April 2008

Phase equilibrium data of CO2 + molten polymer systems are of great relevance for chemical engineers because these are necessary for the optimal design of polymer final‐treatment processes. This kind of processes needs information about gas solubilities in polymers at several temperatures and pressures. In this work, CO2 solubilities in molten polymers were modeled by the perturbed chain‐statistical associating fluid theory (PC‐SAFT) equation of state (EoS). For comparison, the solubilities were also calculated by the lattice gas theory (LGT) EoS, and by the well‐known Peng‐Robinson (PR) cubic EoS. To adjust the interactions between segments of mixtures, there were used classical mixing rules, with one adjustable temperature‐dependent binary parameter for the PC‐SAFT and PR EoS, and two adjustable binary parameters for the LGT EoS. The results were compared with experimental data obtained from literature. The results in terms of solubility pressure deviations indicate that the vapor–liquid behavior for CO2 + polymer systems is better predicted by the PC‐SAFT model than by LGT and PR models. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.
Electrospinning of polyamides with different chain compositions for filtration application
Authors: Heikkilä Pirjo , Taipale Aimo , Lehtimäki Matti , Harlin Ali
Published: April 2008

Electrospinning of several polyamides, PA6, PA66, PA612, PA614, PA1012, and PA1014, having different chain compositions and lengths of diacid and diamine segments, was demonstrated. Electrospinnability and fiber production rate of these polyamides were evaluated. Electrospun fibers were characterized with regard to their use in air filtration by measuring fiber diameter and filtration efficiency of fiber coating. Longer nonpolar chain segments of higher polyamides could in theory indicate higher dielectricity compared to PA6 and PA66, which would be an advantage in filtration applications. The solubility in polar formic acid and electrospinnability of higher polyamides, on the other hand, were clearly impaired with increased length of chain segments. Hence, PA66 is our best choice, and PA612 and PA6 our second options for commercial filtration applications if fiber electrospinnability, production rate, fiber diameter, and its distribution are concerned. Filtration efficiency of more than 95% of the particles having a diameter of 0.16 μm and above was achieved with 0.5 g/m2 coating of PA66 nanofibers. Further increase in coating weight mainly increased the pressure drop to an unusable range without a significant further improvement of filtration efficiency. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.
Rheological properties, flow visualization and extrudate swell of NR compound by rotating‐die rheometer
Authors: Intawong N.‐T. , Wongchaleo C. , Sombatsompop N.
Published: April 2008

An experimental apparatus coupled with a rotating die system was especially designed and manufactured to study the rheological properties, flow patterns and swelling behavior of natural rubber (NR) compound for different shear rates and die rotating speeds at a test temperature of 110°C, the results being compared with those by the static capillary die. It was found that NR compound used exhibited psuedoplastic non‐Newtonian behavior. The rotation of the capillary die could reduce the extrusion load. The wall shear stress for any given shear rates increased with increasing die rotating speed. The fluctuation of the entrance pressure drop increased with increasing die rotating speed. The flow pattern development in the rotating‐die rheometer was different from that observed in the static die. The flow patterns in the rotating die were clearly unstable and contained two flow components which included axial flow along the barrel and circumferential flow at the die entrance. The size and shape of the axial and circumferential flows were more dependent on the piston displacement. It was found that the swelling ratio of the NR compound decreased with increasing die rotating speed. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.
Super‐ductile PBT alloy with excellent heat resistance
Authors: Hashima Kazuhiro , Usui Kazuhiro , Fu Luxiang , Inoue Takashi , Fujimoto Ken‐ichiro , Segawa Kentaro , Abe Tomiya , Kimura Hitoshi
Published: April 2008

A super‐ductile PBT alloy with excellent heat resistance was successfully fabricated by reactive blending of poly(butylene terephthalate) (PBT) with poly(ethylene‐co‐glycidyl methacrylate) together with linear low density polyethylene (LLDPE) and hydrogenated styrene‐butadiene‐styrene block copolymer (SEBS). It possesses a unique tensile stress–strain curve with no yielding point and large elongation at break, moreover, the alloy did not show serious deterioration of the mechanical properties by high temperature annealing at 150°C for 96 h. The structure‐properties relationship is discussed on the basis of transmission electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, and wide‐angle X‐ray diffraction analysis. The outstanding ductile nature seems to come from the negative pressure effect of LLDPE (or LLDPE/SEBS) particles that dilates the PBT ligament matrix to enhance the local segment motions. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.
Preparation and thermo‐mechanical properties of heat‐resistant epoxy/silica hybrid materials
Authors: Yang Peng , Wang Guoqing , Xia Xue , Takezawa Yoshitaka , Wang Haitao , Yamada Shinji , Du Qiangguo , Zhong Wei
Published: April 2008

Diglycidyl ether of bisphenol‐A (DGEBA) based epoxy/silica hybrid materials filled with various amounts of 3‐glycidoxypropyltrimethoxysilane (GPTMS) and silica nanoparticles were prepared, using 4,4′‐diaminodiphenyl sulfone (DDS) as curing agent. The obtained hybrid materials were analyzed by means of Fourier‐transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results indicated that the introduction of GPTMS and silica nanoparticles had synergistic effect. The addition of GPTMS not only ameliorated the compatibility between silica and the epoxy matrix but also increased the crosslinking density of the epoxy system; meanwhile the nano‐silica further reinforced the inorganic network of the hybrid system. Consequently, the hybrid materials showed much improved heat‐resistant properties. The storage modulus of the hybrid systems showed no obvious decrement in the glass transition region and kept at a high value even in the temperature region up to 300°C. The integral thermal stability of the resulting hybrid materials was also improved compared with the corresponding pure epoxy resin. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.
Polyurethane triblock copolymers with mono‐disperse hard segments. Influence of the hard segment length on thermal and thermomechanical properties
Authors: Arun Araichimani , Baack Kasper K.J. , Gaymans Reinoud J.
Published: April 2008

Polyurethane triblock copolymers were synthesized by reacting 4,4′‐methylenebis(phenyl isocyanate) (MDI)‐endcapped poly(tetramethylene oxide) (PTMO) with mono‐amine‐amide (MMA) units. Four different MMA units were used, i.e. no‐amide (6m), mono‐amide (6B), di‐amide (6T6m) and tri‐amide (6T6B), based on hexylamine (6m), 1,6‐hexamethylenediamine (6), terephthalic acid (T), and benzoic acid (B). The PTMO had a molecular weight of 2000 g/mol. Thermal and thermo‐mechanical properties were studied by means of differential scanning calorimetry and dynamic mechanical analysis, respectively. The structure of the carbonyl bond was explored by infra‐red analysis and the elastic behavior of the materials by compression set experiments. The triblock polyurethanes with mono‐disperse, hard end‐segments displayed low molecular weights (3200–3800 g/mol). The crystallinity of the MDI urethane‐urea group was found to depend on the structure of the amide. Increasing the number of amide bonds in the mono‐disperse hard segment increased the modulus and the hard segment melting temperature, and decreased the compression set values. The low temperature properties were hardly affected by the amide length. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.
Atom transfer radical polymerization of hexyl acrylate and preparation of its “all‐acrylate” block copolymers
Authors: Datta Haimanti , Singha Nikhil K.
Published: April 2008

This investigation reports the polymerization of hexyl acrylate (HA) using atom transfer radical polymerization technique and subsequently the preparation of its di‐ and triblock copolymers with methyl methacrylate. Atom transfer radical polymerization of HA was investigated using different initiators and CuBr or CuCl as catalyst in combination with varying ligands, e.g., 2,2′‐bipyridine and N,N,N′,N″,N″‐pentamethyl diethylenetriamine. Reaction parameters were adjusted to successfully polymerize HA with well‐defined molecular weights and narrow polydispersity indices. The polymerization was better controlled by the addition of polar solvents, which created a homogeneous catalytic system. UV–vis analysis showed that the polar solvent, acetone coordinated with copper (I), changes the nature of the copper catalyst, thereby influencing the dynamic equilibrium of activation–deactivation cycle. This resulted in improved control over polymerization as well as in lowering the polydispersity indices, but at the cost of polymerization rate compared with the bulk process. The presence of Br end group in the polymer chains was confirmed by 1H NMR as well as MALDI‐TOF mass analysis. In addition, poly(hexyl acrylate) was used as macroinitiator to prepare various “all‐acrylate” block (diblock, triblock) copolymers that were characterized by GPC and 1H NMR. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3499–3511, 2008
Thermally curable polyvinylchloride via click chemistry
Authors: Kiskan Baris , Demiray Güniz , Yagci Yusuf
Published: April 2008

Novel side‐chain benzoxazine functional polyvinylchloride (PVC‐Benzoxazine) was synthesized by using “Click Chemistry” strategy. First, approximately 10% of chloro groups of PVC were converted to azido groups by using NaN3 in N,N‐dimethylformamide. Propargyl benzoxazine was prepared independently by a ring closure reaction between p‐propargyloxy aniline, paraformaldehyde, and phenol. Finally, azidofunctionalized PVC was coupled to propargyl benzoxazine with high efficiency by click chemistry. The spectral and thermal analysis confirmed the presence of benzoxazine functionality in the resulting polymer. It is shown that PVC containing benzoxazine undergoes thermally activated curing in the absence of any catalyst forming PVC thermoset with high thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3512–3518, 2008
Aggregates of amphiphilic fluorinated copolymers and their encapsulating and unloading homopolymer behaviors
Authors: Xu Shouping , Liu Weiqu
Published: April 2008

Amphiphilic fluorinated block copolymers synthesized via reversible addition‐fragmentation chain transfer polymerization were used for the preparation of aggregates of various morphologies. First, dissolve the copolymer in 2‐butanone; second, add a precipitant solvent, which was the mixture of water and methanol, to induce the aggregation of the hydrophobic fluorinated block. With a hydrophilic tail and a very hydrophobic segment, these copolymers are likely to self‐assemble in solution and form aggregates. Observed by TEM, spheres, rods, and vesicles can be formed by changing the precipitant mixture contents. Besides, these aggregates were found to be able to carry hydrophobic fluorinated homopolymers, and two suggested processes have been proposed to explain their morphology changes from original spheres, rods and vesicles into larger size spheres. Finally, hollow bilayer spheres and tubules can be achieved after extracting homopolymers in the center of the newly formed spheres. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1000–1006, 2008
Effects of maternal retinoic acid administration in a congenital diaphragmatic hernia rabbit model
Authors: Gallot Denis , Coste Karen , Jani Jacques , Roubliova Xenia , Marceau Geoffroy , Velemir Luka , Verheyen An , Lemery Didier , Sapin Vincent , Deprest Jan
Published: April 2008

Maternal retinoid administration has beneficial effects on lung development in the nitrofen rodent toxic model of congenital diaphragmatic hernia (DH). We wanted to investigate the effects in a surgical model, where the retinoid signaling pathway is not primarily disrupted by the toxic agent. We created DH in fetal rabbits at day 23 of gestation, administrated to the does all trans‐retinoic acid (ATRA) or vehicle (VHC) intramuscularly for 8 consecutive days and harvested normal and operated (DH) fetuses at 31 d (n = 7 in each group). Normal lungs exposed to ATRA had increased surfactant protein mRNA levels without change in type II pneumocyte density. There was no measurable effect on lung‐to‐body weight ratio and airway morphometry by ATRA. In DH lungs (DH/VHC) surfactant protein mRNA levels were increased, as well as the density of type II pneumocytes. When supplemented with ATRA (DH/ATRA) these parameters returned to normal (VHC). Cell proliferation or apoptosis were not influenced by ATRA supplementation. In conclusion, maternal ATRA supplementation does not affect gross anatomic, morphologic or proliferation indices in hypoplastic lungs related to surgically induced DH in rabbit. However, ATRA lowers surfactant protein expression and normalizes type I/II pneumocyte ratio to what is observed in normal lungs. Pediatr Pulmonol. 2008; 43:594–603. © 2008 Wiley‐Liss, Inc.
Obesity: what role for general practice in management?
Authors: Mayor Susan
Published: April 2008

Susan Mayor reports on two opposing views on whether or not the ever‐growing problem of obesity can be tackled by GPs. Copyright © 2008 Wiley Interface Ltd
The challenge of treating chronic constipation in children
Authors: Malakounides Georgina , Clayden Graham
Published: April 2008

Our series Prescribing in children gives practical advice for successful management of childhood problems in general practice. Here, the authors describe the diagnosis and recommended treatment of constipation and highlight other prescribing issues in this patient group. Copyright © 2008 Wiley Interface Ltd
Determination of the 15N/14N, 17O/16O, and 18O/16O ratios of nitrous oxide by using continuous‐flow isotope‐ratio mass spectrometry
Authors: Komatsu Daisuke D. , Ishimura Toyoho , Nakagawa Fumiko , Tsunogai Urumu
Published: April 2008

We developed a rapid, sensitive, and automated analytical system to determine the δ15N, δ18O, and Δ17O values of nitrous oxide (N2O) simultaneously in nanomolar quantities for a single batch of samples by continuous‐flow isotope‐ratio mass spectrometry (CF‐IRMS) without any cumbersome and time‐consuming pretreatments. The analytical system consisted of a vacuum line to extract and purify N2O, a gas chromatograph for further purification of N2O, an optional thermal furnace to decompose N2O to O2, and a CF‐IRMS system. We also used pneumatic valves and pneumatic actuators in the system so that we could operate it automatically with timing software on a personal computer. The analytical precision was better than 0.12‰ for δ15N with >4 nmol N2O injections, 0.25‰ for δ18O with >4 nmol N2O injections, and 0.20‰ for Δ17O with >20 nmol N2O injections for a single measurement. We were also easily able to improve the precision (standard errors) to better than 0.05‰ for δ15N, 0.10‰ for δ18O, and 0.10‰ for Δ17O through multiple analyses with more than four repetitions with 190 nmol samples using the automated analytical system. Using the system, the δ15N, δ18O, and Δ17O values of N2O can be quantified not only for atmospheric samples, but also for other gas or liquid samples with low N2O content, such as soil gas or natural water. Here, we showed the first ever Δ17O measurements of soil N2O. Copyright © 2008 John Wiley & Sons, Ltd.
Can crude oils be distinguished by different component distribution obtained by laser desorption ionization mass spectrometry and evaluated by chemometrics?
Authors: Smaniotto Anna , Montanari Luciano , Flego Cristina , Rizzi Andrea , Ragazzi Eugenio , Seraglia Roberta , Traldi Pietro
Published: April 2008

Fourteen different crude oil samples were analyzed as collected by mass spectrometry. For two of them the results obtained by means of different techniques, i.e. electrospray ionization, atmospheric pressure chemical ionization, laser desorption/ionization, were compared. The latter technique leads to the best results: even if unable to give specific information on heteroatom‐containing components, it allows a general view to be obtained of the panorama of the oil composition in terms of molecular weight distribution. The statistical evaluation of the mass spectrometry data by multivariate techniques, such as cluster analysis (Average Linkage) and correspondence analysis, allows evidence for the differences and similarities among the crude oils under study. Copyright © 2008 John Wiley & Sons, Ltd.
Three‐dimensional ultrasound‐guided robotic needle placement: an experimental evaluation
Authors: Boctor Emad M. , Choti Michael A. , Burdette Everette C. , Webster III Robert J.
Published: April 2008

Background

Clinical use of image‐guided needle placement robots has lagged behind laboratory‐demonstrated robotic capability. Bridging this gap requires reliable and easy‐to‐use robotic systems.

Methods

Our system for image‐guided needle placement requires only simple, low‐cost components and minimal, entirely off‐line calibration. It rapidly aligns needles to planned entry paths using 3D ultrasound (US) reconstructed from freehand 2D scans. We compare system accuracy against clinical standard manual needle placement.

Results

The US‐guided robotic system is significantly more accurate than single manual insertions. When several manual withdrawals and reinsertions are allowed, accuracy becomes equivalent. Inex vivoexperiments, robotic repeatability was 1.56 mm, compared to 3.19 and 4.63 mm for two sets of manual insertions. In anin vivoexperiment with heartbeat and respiratory effects, robotic system accuracy was 5.5 mm.

Conclusions

A 3D US‐guided robot can eliminate error bias and reduce invasiveness (the number of insertions required) compared to manual needle insertion. Remaining future challenges include target motion compensation. Copyright © 2008 John Wiley & Sons, Ltd.
Afferent influences on striatal development in organotypic cocultures
Authors: Snyder‐Keller Abigail , Tseng Kuei Y. , Lyng Gregory D. , Graber David J. , O'Donnell Patricio
Published: April 2008

Organotypic cocultures of striatum, cortex, and ventral mesencephalon were used to study the anatomical and physiological development of striatal neurons in the presence or absence of cortical and nigral (SN/VTA) inputs. Striatum and cortex were dissected from prenatal (E18–E22) or early postnatal (P0–P2) rats, and SN/VTA was dissected from E14–15 fetuses; pieces were maintained up to 3 weeks in static slice culture. Triple cocultures containing SN/VTA exhibited rapid and robust dopamine (DA) innervation of the striatum in a patchy pattern, and homogeneous distribution within the cortical piece, regardless of the orientations of the three pieces. DA fibers within the striatal piece overlapped striatal patch neurons, marked by DARPP‐32 immunoreactivity, in striatal cultures prepared from all age rats, but development most analogous to that seen in vivo was observed with the use of late prenatal (E20–E22) striatum. The patch/matrix organization was maintained in cultures prepared from late prenatal striatum in the presence of cortical and nigrostriatal DA afferents. In addition, a more complete transition to a patchy organization was observed in E18/19 striatal cultures in the presence of cortical and DA innervation. Electrophysiological recording demonstrated the presence of both spontaneous and cortically evoked activity in striatal medium spiny neurons; this activity was greatly influenced by the presence of DA innervation. These findings demonstrate the importance of afferent innervation in the maturation of striatal neurons in organotypic cultures. Synapse 62:487–500, 2008. © 2008 Wiley‐Liss, Inc.
Cerebellar modulation of frontal cortex dopamine efflux in mice: Relevance to autism and schizophrenia
Authors: Mittleman Guy , Goldowitz Daniel , Heck Detlef H. , Blaha Charles D.
Published: April 2008

Cerebellar and frontal cortical pathologies have been commonly reported in schizophrenia, autism, and other developmental disorders. Whether there is a relationship between prefrontal and cerebellar pathologies is unknown. Using fixed potential amperometry, dopamine (DA) efflux evoked by cerebellar or, dentate nucleus electrical stimulation (50 Hz, 200 μA) was recorded in prefrontal cortex of urethane anesthetized lurcher (Lc/+) mice with 100% loss of cerebellar Purkinje cells and wildtype (+/+) control mice. Cerebellar stimulation with 25 and 100 pulses evoked prefrontal cortex DA efflux in +/+ mice that persisted for 12 and 25 s poststimulation, respectively. In contrast, 25 pulse cerebellar stimulation failed to evoke prefrontal cortex DA efflux in Lc/+ mice indicating a dependency on cerebellar Purkinje cell outputs. Dentate nucleus stimulation (25 pulses) evoked a comparable but briefer (baseline recovery within 7 s) increase in prefrontal cortex DA efflux compared to similar cerebellar stimulation in +/+ mice. However, in Lc/+ mice 25 pulse dentate nucleus evoked prefrontal cortex DA efflux was attenuated by 60% with baseline recovery within 4 s suggesting that dentate nucleus outputs to prefrontal cortex remain partially functional. DA reuptake blockade enhanced 100 pulse stimulation evoked prefrontal cortex responses, while serotonin or norepinephrine reuptake blockade were without effect indicating the specificity of the amperometric recordings to DA. Results provide neurochemical evidence that the cerebellum can modulate DA efflux in the prefrontal cortex. Together, these findings may explain why cerebellar and frontal cortical pathologies co‐occur, and may provide a mechanism that accounts for the diversity of symptoms common to multiple developmental disorders. Synapse 62:544–550, 2008. © 2008 Wiley‐Liss, Inc.
Transmission power adjustment of wireless sensor networks using fuzzy control algorithm
Authors: Zhang Jianhui , Chen Jiming , Sun Youxian
Published: April 2008

Energy constraint is the most conspicuous characteristic in wireless sensor networks (WSN). Node deployment, dynamic topology control, and data transmission in WSN all consume a large amount of energy. Therefore, proper adjustment of transmission power (TP) contributes much energy saving. In this paper, a new TP adjustment method based on Fuzzy Control Theory, called FCTP, is proposed for the dynamic topology control. The simulation results show that this method is more robust to tolerate accidental interfere, more rapidly convergent, and more energy efficient than other TP adjustment approaches, which lead to longer network lifetime. Copyright © 2008 John Wiley & Sons, Ltd.
Overproduction of non‐translatable mRNA silences. The transcription of Ty1 retrotransposons in S. cerevisiae via functional inactivation of the nuclear cap‐binding complex and subsequent hyperstimulation of the TORC1 pathway
Authors: Wu Xiaofeng , Jiang Yi Wei
Published: April 2008

Co‐suppression is high gene copy number‐triggered homology‐dependent gene silencing, and co‐suppression may have evolved in eukaryotes to counter invasive molecular parasites, such as viruses and transposons. We previously reported ‘Ty1 transcriptional co‐suppression’—high Ty1 copy number‐triggered transient transcriptional silencing of Ty1 retrotransposons in S. cerevisiae. We report here that this phenomenon is unlikely to be homology‐dependent, despite the copy number dependence. The Ty1 mRNA is an extremely poor template for translation, and overproduction of non‐translatable mRNA without Ty1 homology is sufficient to initiate the transient Ty1 transcriptional silencing. We present genetic evidence that overproduction of non‐translatable mRNA may functionally inactivate the nuclear cap‐binding complex (CBC), and inactivation of CBC may then hyperstimulate the TORC1 pathway to mediate Ty1 transcriptional silencing. Our results point to a potent regulatory function of non‐translatable mRNA in vivo (via CBC and TORC1) to potentially modulate a variety of intracellular activities, such as Ty1 transcription. Although overproduction of non‐translatable mRNA causes transient Ty1 transcriptional silencing, it does not play a detectable role in controlling Ty1 retrotransposition. Copyright © 2008 John Wiley & Sons, Ltd.
23S RNA‐derived replicon as a ‘molecular tag’ for monitoring inoculated wine yeast strains
Authors: Esteban Rosa , Rodríguez‐Cousiño Nieves
Published: April 2008

In this study we have developed a useful method to identify a particular yeast strain within a mixture of strains during must fermentation, based on the presence or absence of a stable genetic element derived from Saccharomyces cerevisiae 23S RNA autonomous replicon. 23S RNA is a natural virus‐like RNA replicon present in some S. cerevisiae strains, which encodes only its own RNA‐dependent RNA polymerase named p104. A modified version of 23S RNA (23S‐tagged RNA) was generated after transformation of S. cerevisiae wine strains with a launching plasmid, where six nucleotides were changed in the 23S RNA cDNA sequence without modifying the amino acid sequence of p104 RNA polymerase. Once generated, the 23S‐tagged RNA can replicate autonomously (without the plasmid), is very stable, is present in high copy number in stationary phase or nitrogen‐starved cells and confers no phenotype to the host, like the endogenous 23S RNA replicon. However, it can be distinguished from endogenous 23S RNA by reverse transcription followed by polymerase chain reaction (RT–PCR) with specific oligonucleotide primers. 23S RNA‐derived replicon can be used to tag wine yeast strains in order to monitor easily their prevalence over endogenous strains during wine fermentation. Copyright © 2008 John Wiley & Sons, Ltd.
Atomistic simulation of CeO2 surface hydroxylation: implications for glass polishing
Authors: Stanek Christopher R. , Tan Averyl H. H. , Owens Scott L. , Grimes Robin W.
Published: April 2008

Atomistic simulation techniques have been used to investigate the dissociative adsorption of water on the (110), (111), and (100) low index surfaces of CeO2, as well as a so-called “trench” surface configuration. Several different coverages of water have been considered to better understand how the hydroxylation process progresses. Hydroxylation energies and surface energies of CeO2 calculated via atomistic simulations are compared to similar results for other fluorite oxides. Finally, the modification of CeO2 crystallite morphology in the presence of water is predicted from the changes in surface energy and the implications of these morphological changes for glass polishing are discussed.
Nicotine dependence criteria and nicotine withdrawal symptoms in relation to pain among an adult general population sample
Authors: John Ulrich , Meyer Christian , Rumpf Hans‐Jürgen , Hapke Ulfert
Published: April 2008

Background: Evidence has shown that people who have smoked at any point in life have a higher probability of pain than those who have never smoked. The goal of this study was to analyze whether there are associations between nicotine dependence including nicotine withdrawal with pain and the number of pain locations.

Methods: Data stems from a cross‐sectional survey study with a probability sample of residents of a northern German area with 4075 study participants, aged 18–64 years (participation rate 70.2%). Face‐to‐face in‐home computer‐aided interviews (Composite International Diagnostic Interview) were used to assess single pain locations, the diagnostic criteria of nicotine dependence, alcohol dependence, depressive, and anxiety disorders according to the Diagnostic and Statistical manual of the American Psychiatric Association (DSM‐IV).

Results: Ever smokers with three or more nicotine dependence criteria after controlling for alcohol dependence, depressive, anxiety disorders, age and gender revealed an odds ratio (OR) of 4.2 (95% confidence interval, CI, 2.0–9.0) compared to ever smokers without nicotine dependence criteria, and ever smokers with four or more nicotine withdrawal symptoms displayed an OR of 3.6 (CI 1.5–8.7) compared to ever smokers who had not experienced withdrawal symptoms. Current smokers who used 20 or more cigarettes per day had an OR of 0.5 (CI 0.3–0.8) of experiencing pain in three or more locations compared to former smokers.

Conclusion: Nicotine dependence criteria are associated with a higher probability of pain than having no nicotine dependence criteria in this general population sample.
A study of visual and tactile terrain classification and classifier fusion for planetary exploration rovers
Authors: Halatci Ibrahim , Brooks Christopher A. , Iagnemma Karl
Published: April 2008

Knowledge of the physical properties of terrain surrounding a planetary exploration rover can be used to allow a rover system to fully exploit its mobility capabilities. Terrain classification methods provide semantic descriptions of the physical nature of a given terrain region. These descriptions can be associated with nominal numerical physical parameters, and/or nominal traversability estimates, to improve mobility prediction accuracy. Here we study the performance of multisensor classification methods in the context of Mars surface exploration. The performance of two classification algorithms for color, texture, and range features are presented based on maximum likelihood estimation and support vector machines. In addition, a classification method based on vibration features derived from rover wheel–terrain interaction is briefly described. Two techniques for merging the results of these “low-level” classifiers are presented that rely on Bayesian fusion and meta-classifier fusion. The performance of these algorithms is studied using images from NASA's Mars Exploration Rover mission and through experiments on a four-wheeled test-bed rover operating in Mars-analog terrain. Also a novel approach to terrain sensing based on fused tactile and visual features is presented. It is shown that accurate terrain classification can be achieved via classifier fusion from visual and tactile features.
A structural approach to the automatic adjudication of word sense disagreements
Authors: NAVIGLI ROBERTO
Published: April 2008

The semantic annotation of texts with senses from a computational lexicon is a complex and often subjective task. As a matter of fact, the fine granularity of the WordNet sense inventory [Fellbaum, Christiane (ed.). 1998.WordNet: An Electronic Lexical DatabaseMIT Press], ade factostandard within the research community, is one of the main causes of a low inter-tagger agreement ranging between 70% and 80% and the disappointing performance of automated fine-grained disambiguation systems (around 65% state of the art in the Senseval-3 English all-words task). In order to improve the performance of both manual and automated sense taggers, either we change the sense inventory (e.g. adopting a new dictionary or clustering WordNet senses) or we aim at resolving the disagreements between annotators by dealing with the fineness of sense distinctions. The former approach is not viable in the short term, as wide-coverage resources are not publicly available and no large-scale reliable clustering of WordNet senses has been released to date. The latter approach requires the ability to distinguish between subtle or misleading sense distinctions. In this paper, we propose the use of structural semantic interconnections – a specific kind of lexical chains – for the adjudication of disagreed sense assignments to words in context. The approach relies on the exploitation of the lexicon structure as a support to smooth possible divergencies between sense annotators and foster coherent choices. We perform a twofold experimental evaluation of the approach applied to manual annotations from the SemCor corpus, and automatic annotations from the Senseval-3 English all-words competition. Both sets of experiments and results are entirely novel: structural adjudication allows to improve the state-of-the-art performance in all-words disambiguation by 3.3 points (achieving a 68.5% F1-score) and attains figures around 80% precision and 60% recall in the adjudication of disagreements from human annotators.
Disparities in pension systems and financial flows among European countries
Authors: CHATEAU JEAN , CHOJNICKI XAVIER , MAGNANI RICCARDO
Published: April 2008

We present a quantitative analysis of the impact of differential ageing and pension reforms on capital and labor market and, in particular, on intra-European capital flows. To this end, we develop a stylized general equilibrium model with overlapping generations of heterogeneous agents for the three largest European countries: France, Germany and the United Kingdom. The model presents a structure halfway between pure general equilibrium models with rigorous microeconomic foundations and accounting models where the macroeconomic environment remains exogenous. We show that the dynamics of capital accumulation and pension system sustainability are totally different depending on the assumption concerning economic openness. Finally, in the long run, resorting to debt financing seems to be a dead end to finance retirement systems.
Mast cells can contribute to axon–glial dissociation and fibrosis in peripheral nerve
Authors: Monk Kelly R. , Wu Jianqiang , Williams Jon P. , Finney Brenda A. , Fitzgerald Maureen E. , Filippi Marie-Dominique , Ratner Nancy
Published: April 2008

Expression of the human epidermal growth factor receptor (EGFR) in murine Schwann cells results in loss of axon–Schwann cell interactions and collagen deposition, modeling peripheral nerve response to injury and tumorigenesis. Mast cells infiltrate nerves in all three situations. We show that mast cells are present in normal mouse peripheral nerve beginning at 4 weeks of age, and that the number of mast-cells in EGFR+ nerves increases abruptly at 5–6 weeks of age as axons and Schwann cells dissociate. The increase in mast cell number is preceded and accompanied by elevated levels of mRNAs encoding the mast-cell chemoattractants Rantes, SCF and VEGF. Genetic ablation of mast cells and bone marrow reconstitution in W41 × EGFR+ mice indicate a role for mast cells in loss of axon−Schwann cell interactions and collagen deposition. Pharmacological stabilization of mast cells by disodium cromoglycate administration to EGFR+ mice also diminished loss of axon−Schwann cell interaction. Together these three lines of evidence support the hypothesis that mast cells can contribute to alterations in peripheral nerves.
Events at the transition between cell cycle exit and oligodendrocyte progenitor differentiation: the role of HDAC and YY1
Authors: He Ye , Sandoval Juan , Casaccia-Bonnefil Patrizia
Published: April 2008

The complexity of the adult brain is the result of an integrated series of developmental events that depends on appropriate timing of differentiation. The importance of transcriptional regulatory networks and epigenetic mechanisms of regulation of gene expression is becoming increasingly evident. Among these mechanisms, previous work has revealed the importance of histone deacetylation in oligodendrocyte differentiation. In this manuscript we define the region of interaction between transcription factor Yin-Yang 1 (YY1) and histone deacetylase 1, and characterize the functional consequences of YY1 overexpression on the differentiation of oligodendrocyte progenitors.
Reduced EGFR signaling in progenitor cells of the adult subventricular zone attenuates oligodendrogenesis after demyelination
Authors: Aguirre Adan , Gallo Vittorio
Published: April 2008

Neural progenitor cells that express the NG2 proteoglycan are present in different regions of the adult mammalian brain where they display distinct morphologies and proliferative rates. In the developing postnatal and adult mouse, NG2+ cells represent a major cell population of the subventricular zone (SVZ). NG2+ cells divide in the anterior and lateral region of the SVZ, and are stimulated to proliferate and migrate out of the SVZ by focal demyelination of the corpus callosum (CC). Many NG2+ cells are labeled by GFP-retrovirus injection into the adult SVZ, demonstrating that NG2+ cells actively proliferate under physiological conditions and after demyelination. Under normal physiological conditions and after focal demyelination, proliferation of NG2+ cells is significantly attenuated in wa2 mice, which are characterized by reduced signaling of the epidermal growth factor receptor (EGFR). This results in reduced SVZ-to-lesion migration of NG2+ cells and oligodendrogenesis in the lesion. Expression of vascular endothelial growth factor (VEGF) and EGFR ligands, such as heparin binding-EGF and transforming growth factor α, is upregulated in the SVZ after focal demyelination of the CC. EGF-induced oligodendrogenesis and myelin protein expression in wild-type SVZ cells in culture are significantly attenuated in wa2 SVZ cells. Our results demonstrate that the response of NG2+ cells in the SVZ and their subsequent differentiation in CC after focal demyelination depend on EGFR signaling.
Supportive or information-processing functions of the mature protoplasmic astrocyte in the mammalian CNS? A critical appraisal
Authors: Kimelberg Harold K.
Published: April 2008

It has been proposed that astrocytes should no longer be viewed purely as support cells for neurons, such as providing a constant environment and metabolic substrates, but that they should also be viewed as being involved in affecting synaptic activity in an active way and, therefore, an integral part of the information-processing properties of the brain. This essay discusses the possible differences between a support and an instructive role, and concludes that any distinction has to be blurred. In view of this, and a brief overview of the nature of the data, the new evidence seems insufficient to conclude that the physiological roles of mature astrocytes go beyond a general support role. I propose a model of mature protoplasmic astrocyte function that is drawn from the most recent data on their structure, the domain concept and their syncytial characteristics, of an independent rather than integrative functioning of the ends of each process where the activities that affect synaptic activity and blood vessel diameter will be concentrated.
Do glial cells control pain?
Authors: Suter Marc R. , Wen Yeong-Ray , Decosterd Isabelle , Ji Ru-Rong
Published: April 2008

Management of chronic pain is a real challenge, and current treatments that focus on blocking neurotransmission in the pain pathway have resulted in limited success. Activation of glial cells has been widely implicated in neuroinflammation in the CNS, leading to neurodegeneration in conditions such as Alzheimer's disease and multiple sclerosis. The inflammatory mediators released by activated glial cells, such as tumor necrosis factor-α and interleukin-1β not only cause neurodegeneration in these disease conditions, but also cause abnormal pain by acting on spinal cord dorsal horn neurons in injury conditions. Pain can also be potentiated by growth factors such as brain-derived growth factor and basic fibroblast growth factor, which are produced by glia to protect neurons. Thus, glial cells can powerfully control pain when they are activated to produce various pain mediators. We review accumulating evidence that supports an important role for microglial cells in the spinal cord for pain control under injury conditions (e.g. nerve injury). We also discuss possible signaling mechanisms, in particular mitogen-activated protein kinase pathways that are crucial for glial-mediated control of pain. Investigating signaling mechanisms in microglia might lead to more effective management of devastating chronic pain.
Measurement of methanol emissions from Australian wildfires by ground‐based solar Fourier transform spectroscopy
Authors: Paton‐Walsh Clare , Wilson Stephen R. , Jones Nicholas B. , Griffith David W. T.
Published: April 2008

We report the first atmospheric column measurements of methanol made by ground‐based solar Fourier transform infrared spectroscopy. The measurements were made through smoke plumes over South Eastern Australia during the Austral summers of 2001/2002 and 2002/2003. There is a strong correlation between the measured column amounts of methanol and simultaneous and co‐located measurements of aerosol optical depth. An emission factor for methanol from Australian forest fires of 2.3 ± 0.8 grams per kilogram of dry fuel consumed is estimated by use of the correlations of methanol and carbon monoxide with aerosol optical depth and literature values for the emission factor of carbon monoxide. This agrees well with literature values for emissions measured from extra‐tropical forest fires elsewhere in the world. Methanol is clearly an important volatile organic product of forest fires with an emission factor similar to formaldehyde's and approximately half that of methane.
Cluster observations of an ion‐scale current sheet in the magnetotail under the presence of a guide field
Authors: Nakamura R. , Baumjohann W. , Fujimoto M. , Asano Y. , Runov A. , Owen C. J. , Fazakerley A. N. , Klecker B. , Rème H. , Lucek E. A. , Andre M. , Khotyaintsev Y.
Published: April 2008

We report on Cluster observations of a thin current sheet interval under the presence of a strong ∣BY∣ during a fast earthward flow interval between 1655 UT and 1703 UT on 17 August 2003. The strong ∣BY∣ in the tail could be associated with a strong IMF ∣BY∣, but the large fluctuations in BY, not seen in the IMF, suggest that a varying reconnection rate causes a varying transport of BY‐dominated magnetic flux and/or a change in BY due to the Hall‐current system. During the encounter of the high‐speed flow, an intense current layer was observed around 1655:53 UT with a peak current density of 182 nA/m2, the largest current density observed by the Cluster four‐spacecraft magnetic field measurement in the magnetotail. The half width of this current layer was estimated to be ∼290 km, which was comparable to the ion‐inertia length. Its unique signature is that the strong current is mainly field‐aligned current flowing close to the center of the plasma sheet. The event was associated with parallel heating of electrons with asymmetries, which suggests that electrons moving along the field lines can contribute to a strong dawn‐to‐dusk current when the magnetotail current sheet becomes sufficiently thin and active in a strong guide field case.
Mantle melting beneath the Tibetan Plateau: Experimental constraints on ultrapotassic magmatism
Authors: Holbig Eva S. , Grove Timothy L.
Published: April 2008

Phase equilibrium experiments on primitive Miocene olivine leucitite (Bb‐107) from the Qiangtang terrane of the Tibetan Plateau were performed from 1.0 to 2.2 GPa and 1270 to 1440°C. The composition is multiply saturated with olivine and clinopyroxene from 1.2 to 2.2 GPa and 1340°C under nominally anhydrous conditions. Phase assemblages in the experiments have been used to model the effects of high‐pressure fractional crystallization. The results are consistent with an origin of Bb‐107 as a modified mantle melt produced by fractional crystallization in the lithospheric mantle or lower continental crust. Liquids from spinel + garnet peridotite melting experiments are compositionally similar to the primitive fractionation corrected melt. If metasomatized mantle contained H2O when melting began, the depth of melting approaches the base of the Moho and is 1300°C at 2 GPa for 5 wt % H2O in the melt and 1360°C at 2.2 GPa for 2 wt % H2O, and 1420°C at 2.4 GPa for a dry melt. Major and trace element evidence from Bb‐107 and other primitive Tibetan shoshonitic lavas indicates that these magmas may be derived as low‐extent melts (1–3 wt %) of a metasomatized mantle in the spinel and garnet stability fields. The depth of melting and the geochemical characteristics of the Tibetan lavas are correlated. Increased extents of melting correlate with increasing depth of melting. This correlation is to be expected if melting occurred during lithospheric thinning during downward convective flow at the margin of the lithosphere–asthenosphere boundary.
Mechanisms for recent warming of the North Atlantic: Insights gained with an eddy‐permitting model
Authors: Marsh Robert , Josey Simon A. , de Cuevas Beverly A. , Redbourn Lisa J. , Quartly Graham D.
Published: April 2008

The role of ocean heat transport variations in recent warming of the North Atlantic is investigated using an eddy‐permitting global ocean model with prescribed atmospheric boundary conditions for 1985–2003. Variability of the model sea surface temperature compares favorably with satellite and in situ observations. Each data set reveals a similar pattern of significant surface warming over 1985–2003, across much of the North Atlantic. Significant warming trends exceed 0.1°C a−1 across a large area of the northwest Atlantic in the model simulation. Warming of the tropics and midlatitudes are considered separately. In both regions, long‐term rises in temperature coincide with increasing ocean heat content in the upper few hundred meters, consistent with recent observations. The strongest link between surface temperature and heat content is found in midlatitudes. Averaged within each region, model surface heat fluxes do not show any major trends and are within the range of uncertainty in observational estimates. In midlatitudes, heat content increases are largely explained by changes in ocean heat transport across regional boundaries. While meridional heat transport is strongly linked to the meridional overturning circulation in the subtropics, such a link is weak in midlatitudes, where heat transport variability appears to be more strongly linked to fluctuations in gyre transport and eddy fluxes. It is concluded that the pattern of recent warming in the midlatitude North Atlantic is related to anomalous convergence of ocean heat transport, associated with changes in overturning and horizontal components of the circulation, in the northern subtropics and the subpolar gyre respectively.