bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous B homogenization and specific absorption rate hotspot suppression using a magnetic resonance phased array transmit coil
Authors: Van den Berg Cornelis A. T. , van den Bergen Bob , Van de Kamer Jeroen B. , Raaymakers Bas W. , Kroeze Hugo , Bartels Lambertus W. , Lagendijk Jan J. W.
Published: February 2007

In high‐field MRI severe problems with respect to B uniformity and specific absorption rate (SAR) deposition pose a great challenge to whole‐body imaging. In this study the potential of a phased array transmit coil is investigated to simultaneously reduce B nonuniformity and SAR deposition. This was tested by performing electromagnetic simulations of a phased array TEM coil operating at 128 MHz loaded with two different homogeneous elliptical phantoms and four dielectric patient models. It was shown that the wave interference of a circularly polarized RF field with an ellipse and a pelvis produces largely identical B and electric field patterns. Especially for obese patients, this results in large B nonuniformity and global areas with elevated SAR deposition. It is demonstrated that a phased array transmit coil can reduce these phenomena. The technique was especially successful in suppressing SAR hotspots with a decrease up to 50%. The application of optimized settings for an ellipse to the patient models leads to comparable results as obtained with the patient‐specific optimizations. This suggests that generic phase/amplitude port settings are possible, requiring no preinformation about patient‐specific RF fields. Such a scheme would, due to its simultaneous B homogenization and extra SAR margin, have many benefits for whole‐body imaging at 3 T. Magn Reson Med 57:577–586, 2007. © 2007 Wiley‐Liss, Inc.
Monitoring of brain potassium with rubidium flame photometry and MRI
Authors: Yushmanov Victor E. , Kharlamov Alexander , Boada Fernando E. , Jones Stephen C.
Published: February 2007

An animal model was developed to monitor [K+] in the brain using partial K+ replacement with Rb+ and 87Rb MRI. Fifty‐one rats were given 0–80 mM of RbCl in the drinking water for up to 90 days. Focal cerebral ischemia was produced in 15 of the animals. Na, K, and Rb content in precision‐guided submilligram samples of cortical brain were determined by emission flame photometry. Multinuclear 87Rb/23Na/1H MRI was performed on phantoms and rats at 3T using a twisted projection imaging (TPI) scheme for 87Rb/23Na, and custom‐built surface or parallel cosine transmit/receive coils. Brain [Rb+] was safely brought up to 17–25 mEq/kg within 2–3 weeks of feeding. The characteristic patterns of [K+] decrease (with a sharp drop at 3–4 hr of ischemia) and [Na+] increase (at a rate of 31%/hr) observed previously in animals without Rb/K substitution were reproduced in ischemic cortex. The Rb/(Rb+K) ratio increased over time in ischemic areas (R = 0.91, P < 0.001), suggesting an additional index of ischemia progression. Preliminary 87Rb MRI gave an estimate of 20–25 mEq Rb/kg brain weight (N = 2). In conclusion, brain Rb+ is detectable by 87Rb MRI and does not significantly interfere with ion dynamics in ischemic brain, which enables 87Rb MRI studies of K+ in ischemia. Magn Reson Med 57:494–500, 2007. © 2007 Wiley‐Liss, Inc.
Adiabatic refocusing pulses for volume selection in magnetic resonance spectroscopic imaging
Authors: Sacolick Laura I. , Rothman Douglas L. , de Graaf Robin A.
Published: February 2007

Because of their excellent slice profiles and high immunity to RF inhomogeneity, adiabatic full passage (AFP) pulses are ideal for use in spatial localization. The nonlinear, position‐dependent phase of a single AFP pulse generated during refocusing of transverse magnetization traditionally is eliminated by using identical pairs of AFP pulses, at the expense of increased RF power deposition and increased echo time (TE). Here it is shown that one can achieve significant phase refocusing by executing single AFP pulses along non‐equivalent spatial axes. When used for volume selection in MR spectroscopic imaging (MRSI) the remaining nonlinear phase becomes inconsequential when the phase across a spectroscopic volume is small. Selection of rectangular and octagonal volumes is demonstrated with half the number of AFP pulses used in the traditional approach. It is shown that octagonal volume selection in the human brain provides excellent suppression of extracranial lipids, and thus allows multislice 1H MRSI at 4 Tesla to be performed within the guidelines for RF power deposition. Magn Reson Med 57:548–553, 2007. © 2007 Wiley‐Liss, Inc.
Is the “biexponential diffusion” biexponential?
Authors: Kiselev Valerij G. , Il'yasov Kamil A.
Published: February 2007

Diffusion‐weighted signal from the brain,S, deviates from monoexponential dependence on theb‐factor. This property is often referred to as biexponential diffusion, since the corresponding model fits data well. The aim of this study is to examine the necessity of using the biexponential model in homogeneous voxels under isotropic diffusion weighting up tob= 2.5 ms/μm2. The model is compared to the cumulant expansion of lnSin a power series inb, which takes its origin in fundamental properties of the diffusion‐weighted signal, but diverges at largeb. The absence of statistically significant evidences for the biexponential diffusion is demonstrated in gray matter. The cumulant expansion terminated after the termb2describes data equally well with fewer adjustable parameters. The biexponential model is preferable in voxels with a partial volume of CSF. Magn Reson Med 57:464–469, 2007. © 2007 Wiley‐Liss, Inc.
Novel method for rapid, simultaneous T1, T*2, and proton density quantification
Authors: Warntjes J.B.M. , Dahlqvist O. , Lundberg P.
Published: February 2007

An imaging method called “quantification of relaxation times and proton density by twin‐echo saturation‐recovery turbo‐field echo” (QRAPTEST) is presented as a means of quickly determining the longitudinal T1 and transverse T relaxation time and proton density (PD) within a single sequence. The method also includes an estimation of the B1 field inhomogeneity. High‐resolution images covering large volumes can be achieved within clinically acceptable times of 5–10 min. The range of accuracy for determining T1, T, and PD values is flexible and can be optimized relative to any anticipated values. We validated the experimental results against existing methods, and provide a clinical example in which quantification of the whole brain using 1.5 mm3 voxels was achieved in less than 8 min. Magn Reson Med 57:528–537, 2007. © 2007 Wiley‐Liss, Inc.
Inversion recovery prepared turbo spin echo sequences with reduced SAR using smooth transitions between pseudo steady states
Authors: Weigel Matthias , Zaitsev Maxim , Hennig Juergen
Published: February 2007

This study investigates the contrast behavior of 2D inversion recovery (IR) prepared turbo spin echo (TSE) sequences that use RF pulse schemes with variable low flip angles (hyperTSE) to reduce RF power deposition. A framework of equations and calculations for adapting the sequence parameters is presented by which equivalent image contrast is achieved compared to conventional IR‐TSE imaging. Although the inversion time (TI) and repetition time (TR) do not need to be changed, the echo time (TE) has to be prolonged such that the effective TE (TEeff) is preserved. Measurements in healthy volunteers confirmed this finding for IR‐TSE sequences using different TIs: fluid attenuated inversion recovery (FLAIR), gray matter (GM)‐white matter (WM)‐IR, and short tau IR (STIR). The results demonstrate that hyperTSE sequences enable high‐quality IR‐prepared imaging with a considerably reduced specific absorption rate (SAR). Magn Reson Med 57:631–637, 2007. © 2007 Wiley‐Liss, Inc.
Flow‐metabolism coupling in human visual, motor, and supplementary motor areas assessed by magnetic resonance imaging
Authors: Chiarelli Peter A. , Bulte Daniel P. , Gallichan Daniel , Piechnik Stefan K. , Wise Richard , Jezzard Peter
Published: February 2007

Combined blood oxygenation level‐dependent (BOLD) and arterial spin labeling (ASL) functional MRI (fMRI) was performed for simultaneous investigation of neurovascular coupling in the primary visual cortex (PVC), primary motor cortex (PMC), and supplementary motor area (SMA). The hypercapnia‐calibrated method was employed to estimate the fractional change in cerebral metabolic rate of oxygen consumption (CMRO2) using both a group‐average and a per‐subject calibration. The group‐averaged calibration showed significantly different CMRO2−CBF coupling ratios in the three regions (PVC: 0.34 ± 0.03; PMC: 0.24 ± 0.03; and SMA: 0.40 ± 0.02). Part of this difference emerges from the calculated values of the hypercapnic calibration constant M in each region (MPVC = 6.6 ± 3.4, MPMC = 4.3 ± 3.5, and MSMA = 7.2 ± 4.1), while a relatively minor part comes from the spread and shape of the sensorimotor BOLD–CBF responses. The averages of the per‐subject calibrated CMRO2−CBF slopes were 0.40 ± 0.04 (PVC), 0.31 ± 0.03 (PMC), and 0.44 ± 0.03 (SMA). These results are 10–30% higher than group‐calibrated values, and are potentially more useful for quantifying individual differences in focal functional responses. The group‐average calibrated motor coupling value is increased to 0.28 ± 0.03 when stimulus‐correlated increases in end‐tidal CO2 are included. Our results support the existence of regional differences in neurovascular coupling, and argue for the importance of achieving optimal accuracy in hypercapnia calibrations to resolve method‐dependent variations in published results. Magn Reson Med 57:538–547, 2007. © 2007 Wiley‐Liss, Inc.
Array‐optimized composite pulse for excellent whole‐brain homogeneity in high‐field MRI
Authors: Collins Christopher M. , Wang Zhangwei , Mao Weihua , Fang Jieming , Liu Wanzhan , Smith Michael B.
Published: February 2007

A number of methods to improve excitation homogeneity in high‐field MRI have been proposed, and some of these methods rely on separate control of radiofrequency (RF) coils in a transmit array. In this work we combine accurate RF field calculations and the Bloch equation to demonstrate that by using a sequence of pulses with individually optimized current distributions (i.e., an array‐optimized composite pulse), one can achieve remarkably homogeneous distributions of available signal intensity over the entire brain volume. This homogeneity is greater than that achievable using the same transmit array to produce either a single optimized (or RF shimmed) pulse or a single RF shimmed field distribution in a standard 90x‐90y composite pulse arrangement. Simulations indicate that with a very simple array‐optimized composite pulse, excellent whole‐brain excitation homogeneity can be achieved at up to 600 MHz. Magn Reson Med 57:470–474, 2007. © 2007 Wiley‐Liss, Inc.
Water‐ and fat‐suppressed proton projection MRI (WASPI) of rat femur bone
Authors: Wu Yaotang , Dai Guangping , Ackerman Jerome L. , Hrovat Mirko I. , Glimcher Melvin J. , Snyder Brian D. , Nazarian Ara , Chesler David A.
Published: February 2007

Investigators often study rats by μCT to investigate the pathogenesis and treatment of skeletal disorders in humans. However, μCT measurements provide information only on bone mineral content and not the solid matrix. CT scans are often carried out on cancellous bone, which contains a significant volume of marrow cells, stroma, water, and fat, and thus the apparent bone mineral density (BMD) does not reflect the mineral density within the matrix, where the mineral crystals are localized. Water‐ and fat‐suppressed solid‐state proton projection imaging (WASPI) was utilized in this study to image the solid matrix content (collagen, tightly bound water, and other immobile molecules) of rat femur specimens, and meet the challenges of small sample size and demanding submillimeter resolution. A method is introduced to recover the central region of k‐space, which is always lost in the receiver dead time when free induction decays (FIDs) are acquired. With this approach, points near the k‐space origin are sampled under a small number of radial projections at reduced gradient strength. The typical scan time for the current WASPI experiments was 2 hr. Proton solid‐matrix images of rat femurs with 0.4‐mm resolution and 12‐mm field of view (FOV) were obtained. This method provides a noninvasive means of studying bone matrix in small animals. Magn Reson Med 57:554–567, 2007. © 2007 Wiley‐Liss, Inc.
Optimized and combined T1 and B1 mapping technique for fast and accurate T1 quantification in contrast‐enhanced abdominal MRI
Authors: Treier Reto , Steingoetter Andreas , Fried Michael , Schwizer Werner , Boesiger Peter
Published: February 2007

Fast T1 mapping techniques are a valuable means of quantitatively assessing the distribution and dynamics of intravenously or orally applied paramagnetic contrast agents (CAs) by noninvasive imaging. In this study a fast T1 mapping technique based on the variable flip angle (VFA) approach was optimized for accurate T1 quantification in abdominal contrast‐enhanced (CE) MRI. Optimization methods were developed to maximize the signal‐to‐noise ratio (SNR) and ensure effective RF and gradient spoiling, as well as a steady state, for a defined T1 range of 100–800 ms and a limited acquisition time. We corrected B1 field inhomogeneities by performing an additional measurement using an optimized fast B1 mapping technique. High‐precision in vitro and abdominal in vivo T1 maps were successfully generated at a voxel size of 2.8 × 2.8 × 15 mm3 and a temporal resolution of 2.3 s per T1 map on 1.5T and 3T MRI systems. The application of the proposed fast T1 mapping technique in abdominal CE‐MRI enables noninvasive quantification of abdominal tissue perfusion and vascular permeability, and offers the possibility of quantitatively assessing dilution, distribution, and mixing processes of labeled solutions or drugs in the gastrointestinal tract. Magn Reson Med 57:568–576, 2007. © 2007 Wiley‐Liss, Inc.
Linear discriminant analysis of brain tumour 1H MR spectra: a comparison of classification using whole spectra versus metabolite quantification
Authors: Opstad K. S. , Ladroue C. , Bell B. A. , Griffiths J. R. , Howe F. A.
Published: February 2007

1H MRS is an attractive choice for non‐invasively diagnosing brain tumours. Many studies have been performed to create an objective decision support system, but there is not yet a consensus as to the best techniques of MRS acquisition or data processing to be used for optimum classification. In this study, we investigate whether LCModel analysis of short‐TE (30 ms), single‐voxel tumour spectra provide a better input for classification than the use of the original spectra. A total of 145 histologically diagnosed brain tumour spectra were acquired [14 astrocytoma grade II (AS2), 15 astrocytoma grade III (AS3), 42 glioblastoma (GBM), 41 metastases (MET) and 33 meningioma (MNG)], and linear discriminant analyses (LDA) were performed on the LCModel analysis of the spectra and the original spectra. The results consistently suggest improvement in classification when the LCModel concentrations are used. LDA of AS2, MNG and high‐grade tumours (HG, comprising GBM and MET) correctly classified 94% using the LCModel dataset compared with 93% using the spectral dataset. The inclusion of AS3 reduced the accuracy to 82% and 78% for LCModel analysis and the original spectra, respectively, and further separating HG into GBM and MET gave 70% compared with 60%. Generally MNG spectra have profiles that are visually distinct from those of the other tumour types, but the classification accuracy was typically about 80%, with MNG with substantial lipid/macromolecule signals being classified as HG. Omission of the lipid/macromolecule concentrations in the LCModel dataset provided an improvement in classification of MNG (91% compared with 76%). In conclusion, there appears to be an advantage to performing pattern recognition on the quantitative analysis of tumour spectra rather than using the whole spectra. However, the results suggest that a two‐step LDA process may help in classifying the five tumour groups to provide optimum classification of MNG with high lipid/macromolecule contributions which maybe misclassified as HG. Copyright © 2007 John Wiley & Sons, Ltd.
Multi‐path routing scheme for non‐interactive multicast communications
Authors: Srinivasan R. , Vaidehi V. , Ranjani N. , Sathya M. , Subramani D.
Published: February 2007

This paper proposes a multicast routing algorithm that makes use of multiple node‐disjoint distribution trees for its routing from the source to the multicast group members. The specialty of this scheme is that the different packets of a message between a source and destinations are routed through node‐disjoint paths to provide reliable and secure multicast communication. In this proposed routing scheme the computation of the node‐disjoint path for packet routing is done either at a centralized route moderator or in a distributed fashion at all destinations in order to avoid single point failure. An effective provision is made to enable new members to join the existing multicast trees and to prune leaving members. The performance parameters of the proposed reliable and secure multi‐path routing scheme are studied under various network conditions using GloMoSim. Copyright © 2006 John Wiley & Sons, Ltd.
Generalized midpoint integration algorithms for J2 plasticity with linear hardening
Authors: Artioli E. , Auricchio F. , Beirão da Veiga L.
Published: February 2007

We consider four schemes based on generalized midpoint rule and return map algorithm for the integration of the classical J2 plasticity model with linear hardening. The comparison, aiming to establish which is the preferable scheme among the four considered, is both theoretical and numerical. On one side, extending and completing the existing results in the literature, we investigate the four schemes from the theoretical viewpoint, addressing in particular the existence of solution, long‐term behaviour, accuracy and stability. On the other hand, we develop an extensive set of numerical tests, based on pointwise stress–strain loading histories, iso‐error maps and initial boundary‐value problems. Copyright © 2007 John Wiley & Sons, Ltd.
Properties of a novel thermal sensitive polymer based on poly(vinyl alcohol) and its layer‐by‐layer assembly
Authors: Lu Hong , Zheng Anna , Xiao Huining
Published: February 2007

Structurally modified poly(vinyl alcohol) (PVA) was prepared as novel thermally sensitive polymers by partially acetalyzing and/or ionizing the commercially available PVA. Their aqueous solutions experience completely reversible polymer aggregation and dissolution above and below the lower critical solution temperature (LCST), respectively. The LCST of a partially acetalyzed PVA (APVA) can be readily controlled by the degree of acetalysis or the molecular weight of the starting PVA. Introduction of a small amount of cationic group onto the APVA backbone increases the LCST obviously, while the LCST is highly sensitive to NaCl concentration. Then APVA and cationic APVA multilayers are assembled on rayon to make a thermal responsive fiber. The atomic force microscopy (AFM) images of the surface reveal the increment of roughness stimulated by temperature. Copyright © 2007 John Wiley & Sons, Ltd.
Hybrid proton exchange membranes based on sulfonated poly(phthalazinone ether ketone) and zirconium hydrogen phosphate
Authors: Zhang Hong‐wei , Du Chun‐hui , Xu You‐yi , Zhu Bao‐ku
Published: February 2007

Sulfonated poly(phthalazinone ether ketone)s (SPPEKs) and zirconium hydrogen phosphate (ZrP) hybrid membranes for direct methanol fuel cells (DMFCs) were prepared by the impregnation method and direct blending method. The physicochemical properties of these hybrid membranes were studied by means of field‐emission scanning electron microscope (FSEM), X‐ray diffraction (XRD) analysis, and thermogravimetry analysis (TGA). For the hybrid membranes prepared from impregnation procedure, the highest proton conductivity could reach 0.074 S/cm at 80°C under 100% relative humidity and the methanol permeability at room temperature is more than 10 times lower than that of Nafion 117. Copyright © 2007 John Wiley & Sons, Ltd.
Co‐prescriptions with itraconazole and fluconazole as a signal for possible risk of drug–drug interactions: a four‐year analysis from Italian general practice
Authors: Galatti Laura , Mazzaglia Giampiero , Greco Antonella , Sessa Emiliano , Cricelli Claudio , Schito Gian Carlo , Nicoletti Giuseppe , Spina Edoardo , Caputi Achille P.
Published: February 2007

Purpose

To determine the prevalence of concomitant use of drugs potentially responsible for interactions among itraconazole and fluconazole users in general practice.

Methods

During the years 1999–2002, we obtained information from the ‘Health Search Database’, (HSD) an Italian general practice research database. Among a total sample of 457 672 eligible patients, we included those aged >16 years, and whose diagnoses could be classified as mycosis. Itraconazole and fluconazole users were then selected. A potentially drug–drug interaction (DDI) occurred when the use of concomitant drugs were recorded within ±30 days from the date of the first azoles prescription. Interacting drugs were classified according to the summary of product characteristics (SPC) as provided by the Italian Pharmaceutical Repertory (REFI).

Results

From 18 323 cases of mycosis, we selected 4843 itraconazole and 1446 fluconazole users. Potentially interacting drugs were prescribed in 8.7% of itraconazole and 6.1% of fluconazole users. For itraconazole, calcium channel blockers were the most common interacting drugs (3.3%), followed by statins (1.7%) and clarithromycin (1.3%), whereas gestoden + ethynylestradiol (2.5%) and benzodiazepines (1.8%) resulted as the most common interacting drugs among fluconazole users.

Conclusion

Data indicate a relevant prevalence of concomitant use of medications potentially leading to drug interactions among azoles users. Because of the wide use of these medications in general practice, they should be used with clinical monitoring in view of their known side effects as well as their potential risk for drug interaction. Copyright © 2007 John Wiley & Sons, Ltd.
Roboter lernen Fußball spielen: Autonome Roboter
Authors: Lauer Martin , Hafner Roland
Published: February 2007

Seit zehn Jahren gibt es jährlich die Weltmeisterschaft Robocup für autonome, fußballspielende Roboter. Inzwischen sind der mechanische Aufbau der Roboter, die Sensorauswertung und Verhaltenssteuerung per Bordrechner so weit entwickelt, dass ein echtes Fußballspiel entstehen kann. Allerdings erfordert die Übertragung der Techniken von radbasierten Robotern auf zweibeinige, humanoide Roboter noch intensive Forschung. Das gilt auch für eine technische Ausstattung, die die Entwicklung eines umfassenden taktischen Spiels ermöglicht. Trotz des ermutigenden Fortschritts ist der Weg noch weit, bis ein Fußballroboter mit menschlichen Spielern mithalten kann.
SCIAMACHY – Neue Ansichten der Erdatmosphäre: Atmosphären‐ und Klimaforschung aus dem All
Authors: Gottwald Manfred , Bovensmann Heinrich
Published: February 2007

Das Atmosphäreninstrument SCIAMACHY auf ENVISAT ermöglicht einzigartige Untersuchungen unserer Erdatmosphäre. Erstmals können weltweit die Luftschadstoffe und Ozonvorläufersubstanzen Stickstoffdioxid, Kohlenmonoxid, Schwefeldioxid, Formaldehyd und Glyoxal global mit einer räumlichen Auflösung vermessen werden, die Aussagen über die Luftqualität einzelner Großstädte und Ballungszentren sowie die Verifikation von Emissionskatastern erlaubt. Auch wichtige Treibhausgase wie Methan und Kohlenstoffdioxid werden erstmals erfasst. Zudem sind viele bedeutende Atmosphärenparameter von der Erdoberfläche bis in die Mesosphäre zugänglich. Dazu zählt insbesondere Ozon zusammen mit global bestimmbaren dreidimensionalen Verteilungen wichtiger ozonzerstörender Substanzen wie etwa Stick‐ und Halogenoxiden.
Schnittfeste Saucenwürfel – kleckerfreie Sauce
Authors: Vilgis Thomas
Published: February 2007

Die Diskussion bei der Nachsitzung des physikalischen Kolloquiums ist angeregt. Das Fleisch geschnitten, zum Mund geführt, und schwupp, landet ein Saucenspritzer mitten auf der neuen Krawatte. Inspiriert durch neue Trends in der Avantgardeküche ließe sich dieses Missgeschick vermeiden: kleckerfreie Saucen, schnittfest und trotzdem heiß, das wär's. Tatsächlich sind schmackhaft warme, feste Gele in der haute cuisine keine Utopie. Und aus physikalischer Sicht ist der feste Saucenwürfel ein interessantes Beispiel für einen Sol‐Gel‐Übergang.
Schwingende Nanoschichten im Röntgen‐Stroboskop
Authors: Bargheer Matias , v. Korff Schmising Clemens , Wörner Michael , Elsässer Thomas
Published: February 2007

Eine Arbeitsgruppe am Max‐Born‐Institut (MBI) in Berlin verwendet mit Hochleistungslasern erzeugte ultrakurze Röntgenimpulse, um atomare Bewegungen in Nanostrukturen stroboskopisch abzubilden. Die Methode ermöglicht simultan eine Zeitauflösung von 100 Femtosekunden und eine Ortsauflösung von 100 Femtometern.
Eine schwebende Lichtkugel in einer Kugelleuchte
Authors: Schlichting H. Joachim
Published: February 2007

Gläserne Kugelleuchten können zu Hohlspiegeln werden und von den im Innern befindlichen Lampen reelle, frei schwebende Bilder erzeugen. Dem unvorbereiteten Beobachter erscheint ein solches Bilder wie ein glühendes Plasma.
Gesucht: Monsieur Le Blanc
Authors: Loos Andreas
Published: February 2007

In den Straßen von Paris tobt die Revolution: Die Bastille wird gestürmt, Plätze verwandeln sich in Schlachtplätze, Guillotinen haben Hochkonjunktur. Von alldem bekommt die schüchterne 13‐Jährige wenig mit. In der väterlichen Bibliothek sitzt sie mit verstaubten Wälzern im Schoß. Angeblich beeindruckt sie besonders die Geschichte vom Tod des Archimedes.
Deposition of “Polysiloxane” Thin Films Containing Silver Particles by an RF Asymmetrical Discharge
Authors: Despax Bernard , Raynaud Patrice
Published: February 2007

The aim of the present work is to produce silver‐containing SiCxOyHz thin films by using simultaneous sputtering of silver and plasma polymerization in an HMDSO plasma. The ratio of plasma polymerization to sputtering was adjusted by using a pulsed flow rate of the hexamethyldisiloxane precursor, which permitted an accurate control of the co‐deposition process. The presence of silver in the gas phase was detected by optical emission spectroscopy. The silver volume fraction was controlled over a wide range by superimposing physical sputtering onto the polymerization process taking place simultaneously within a very low and narrow range of HMDSO plasma pressure. The polymer matrix structures were analyzed by several techniques. FTIR spectra revealed the presence of SiOSi, SiCSi, SiCH3 and CC groups whose amount varied with the silver content. TEM analysis showed Ag nanoparticles with sizes varying from 4 to 70 nm depending on the silver volume fraction.

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Dielectric Barrier Discharge at Atmospheric Pressure as a Tool to Deposit Versatile Organic Coatings at Moderate Power Input
Authors: Heyse Pieter , Dams Roel , Paulussen Sabine , Houthoofd Kristof , Janssen Kris , Jacobs Pierre A. , Sels Bert F.
Published: February 2007

Plasma coating technologies have been demonstrated as being promising for the fabrication of bioactive and biocompatible materials, among others. Reported efforts are exclusively focused on the two‐step approaches, in which the bioactive component is first immobilized on a substrate, followed by a (vacuum) plasma polymerization treatment or vice versa. However, we believe that upon minimizing the plasma energy, numerous bioactive substances such as enzymes and nucleic acids can be immobilized directly in plasmas via copolymerization with organic precursors, or by direct entrapment in the organic polymer. Therefore, a dielectric barrier discharge was employed at atmospheric pressure and ambient temperature to deposit organic coatings with reasonable growth rates at power input and frequency values as low as possible. Two promising precursors, acetylene and pyrrole, were selected out of 22 organic monomers for full physicochemical characterization. While the acetylene polymer film shows resemblance with its vacuum plasma analogue, polypyrrole coatings produced in vacuum and atmospheric plasmas differ significantly.

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Improvements of Permeation Barrier Coatings Using Encapsulated Parylene Interlayers for Flexible Electronic Applications
Authors: Chen Tsai‐Ning , Wuu Dong‐Sing , Wu Chia‐Cheng , Chiang Cheng‐Chung , Chen Yung‐Pei , Horng Ray‐Hua
Published: February 2007

A multilayer barrier structure composed of silicon nitride, silicon oxide, and encapsulated parylene on a polycarbonate substrate has been investigated for flexible electronic applications. The organic buffer is commonly used as the smoothing, strengthening and defect‐decoupling layer. However, a lateral leakage problem was observed in the organic interlayer, and resulted in increased permeation and poor adhesion between organic and inorganic layers. It was found that an encapsulated, thermal‐treated parylene interlayer can be used to efficiently reduce the water vapor and oxygen permeation. After 75 d, the water vapor transmission rate (WVTR) can reach 2.5 × 10−7 (g · m−2) d−1, as calculated by the calcium test. After being flexed for 5 000 times, the WVTR value almost keeps around 2.1 × 10−6 (g · m−2) d−1. The performance of the proposed multilayer barrier structure has a high potential for flexible solar cell and organic light‐emitting diode applications.

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Chemical and Physical Properties of Copper and Nitrogen Plasma‐Implanted Polyethylene
Authors: Zhang Wei , Ji Junhui , Zhang Yihe , Yan Qing , Chu Paul K.
Published: February 2007

Plasma immersion ion implantation (PIII) is a new technique used to modify the surface physical and chemical properties of polymers for antibacterial purposes. Our previous research work has shown that copper and nitrogen PIII can give rise to excellent antibacterial properties on polyethylene (PE) substrates. In this paper, the effects of the PIII conditions on the chemical and physical properties of the Cu and N plasma‐implanted PE are investigated. Elemental depth profiles show that Cu and N PIII results in the formation of CN, CN bonds in the surface region, and that the implanted Cu does not bond with the polymer matrix elements. A longer PIII time increases the concentrations of CN, CN and CN bonds formed in the near‐surface region, but the elemental chemical states deeper into the sample remain about the same for different PIII time durations. However, if N‐PIII and Cu‐PIII are not carried out simultaneously, for example, N‐PIII following Cu‐PIII, the retained Cu dose is affected due to nitrogen sputtering, but the Cu chemical state is not altered. In addition, more CN and CN bonds are formed in the outer surface region. A longer N‐PIII implantation time further enriches these chemical functional groups.

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Toxicity of extracts and isobutyl amides from Piper tuberculatum: potent compounds with potential for the control of the velvetbean caterpillar, Anticarsia gemmatalis
Authors: Navickiene Hosana M Debonsi , Miranda José E , Bortoli Sérgio A , Kato Massuo J , Bolzani Vanderlan S , Furlan Maysa
Published: February 2007

The isobutyl amides pellitorine (compound 1) and 4,5‐dihydropiperlonguminine (compound 2) were extracted from the seeds of Piper tuberculatum Jacq. (Piperaceae) in yields of 6.10 and 4.45% respectively. The acute toxicities to the velvetbean caterpillar, Anticarsia gemmatalis (Hübner) (Lepidoptera: Noctuidae), of extracts of seeds, leaves and stems of P. tuberculatum, and of compounds 1 and 2, were evaluated by means of contact bioassays. The extracts caused 80% mortality when doses higher than 800.00 µg insect−1 of extract of seeds, leaves and stems were administered to the velvetbean caterpillars. Compounds 1 and 2 showed 100% mortality at doses of 200 and 700 µg insect−1 respectively. The LD50 and LD90 values were respectively 31.3 and 104.5 µg insect−1 for compound 1, and 122.3 and 381.0 µg insect−1 for compound 2. The potential value of extracts and amides derived from P. tuberculatum as efficient insecticides against velvetbean caterpillars is discussed. Copyright © 2007 Society of Chemical Industry
Screening of the antibacterial effects of a variety of essential oils on microorganisms responsible for respiratory infections
Authors: Fabio A. , Cermelli C. , Fabio G. , Nicoletti P. , Quaglio P.
Published: February 2007

The aim of this study was to examine the cytotoxicity and the antibacterial effects of a variety of essential oils on major respiratory tract pathogens. The cytotoxicity of 13 essential oils was evaluated on Vero cells. The antibacterial activity was evaluated by the Kirby Bauer paper method, minimum inhibitory and bactericidal concentration against Streptococcus pyogenes, agalactiae, pneumoniae and Klebsiella pneumoniae, Haemophilus influenzae, Staphylococcus aureus and Stenotrophomonas maltophilia isolated from clinical specimens. The antibiotic sensitivity of these isolates was examined. Some oils showed inhibition of bacterial growth against most of the organisms examined. Cinnamon and thyme showed the strongest action followed by clove. The results reported in this paper indicate that thyme can be considered as a potential antimicrobial agent for the treatment of some respiratory tract infections in man. Copyright © 2007 John Wiley & Sons, Ltd.
Composition and cytotoxic activity of the leaf essential oil of Comptonia peregrina (L.) Coulter
Authors: Sylvestre Muriel , Pichette André , Lavoie Serge , Longtin Angélique , Legault Jean
Published: February 2007

Comptonia peregrina (L.) Coulter, a native plant from Canada used in traditional medicine against cancer, was extracted by hydrodistillation. Two fractions were collected, one over 0–30 min and one over 30–60 min, to assess the influence of time of hydrodistillation on the composition of essential oil. The chemical composition of these two extracts was determined by GC and GC‐MS analyses. Fifty five components were identified: β‐caryophyllene (23.69% and 15.16%) and α‐humulene (9.67% and 7.43%) were the major components in the 0–30 min and 30–60 min fractions, respectively, while β‐myrcene was detected in a higher amount in the 0–30 min fraction (12.58%) than in the 30–60 min fraction (0.15%). The cytotoxic activities of these fractions were assessed against human lung carcinoma cell line A‐549 and human colon adenocarcinoma cell line DLD‐1. Only the 30–60 min fraction was found to be active against both tumor cell lines, with GI50 values of 66 ± 12 µg/mL for A‐549 and of 46 ± 7 µg/mL for DLD‐1. Two sesquiterpenes present in the oil, α‐humulene and (E)‐nerolidol, have been found to be cytotoxic against both tumor cell lines. Copyright © 2007 John Wiley & Sons, Ltd.
An approach to estimate the energy and strength of the intramolecular hydrogen bond in different conformers of 4‐methylamino‐3‐penten‐2‐one
Authors: Raissi Heidar , Moshfeghi Effat , Jalbout Abraham F. , Saeid Hosseini Mohammad , Fazli Mustapha
Published: February 2007

The molecular structure and intramolecular hydrogen bond energy of 32 conformers of 4‐methylamino‐3‐penten‐2‐one were investigated at MP2 and B3LYP levels of theory using the standard 6–31G** basis set and AIM analyses. Furthermore, calculations for all the possible conformations of 4‐methylamino‐3‐penten‐2‐one in water solution were also carried out at B3LYP/6–31G** level of theory. The calculated geometrical parameters and conformational analyses in gas phase and water solution show that the ketoamine conformers of this compound are more stable than the other conformers (i.e., enolimine and ketoimine). This stability is mainly due to the formation of a strong NH···O intramolecular hydrogen bond, which is assisted by π‐electrons resonance. Hydrogen bond energies for all conformers of 4‐methylamino‐3‐penten‐2‐one were obtained from the related rotamers method. The nature of intramolecular hydrogen bond existing within 4‐methylamino‐3‐penten‐2‐one has been investigated by means of the Bader theory of atoms in molecules, which is based on topological properties of the electron density. The results of these calculations support the results which obtained by related rotamers method. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Predictor‐based repetitive learning control for a class of remote control nonlinear systems
Authors: Pan Ya‐Jun , Sheng Long
Published: February 2007

In this paper, a repetitive learning control (RLC) approach is proposed for a class of remote control nonlinear systems satisfying the global Lipschitz condition. The proposed approach is to deal with the remote tracking control problem when the environment is periodic or repeatable over infinite time domain. Since there exist time delays in the two transmission channels: from the controller to the actuator and from the sensor to the controller, tracking a desired trajectory through a remote controller is not an easy task. In order to solve the problem caused by time delays, a predictor is designed on the controller side to predict the future state of the nonlinear system based on the delayed measurements from the sensor. The convergence of the estimation error of the predictor is ensured. The gain design of the predictor applies linear matrix inequality (LMI) techniques developed by Lyapunov Kravoskii method for time delay systems. The RLC law is constructed based on the feedback error from the predicted state. The overall tracking error tends to zero asymptotically over iterations. The proof of the stability is based on a constructed Lyapunov function related to the Lyapunov Kravoskii functional used for the proof of the predictor's convergence. By well incorporating the predictor and the RLC controller, the system state tracks the desired trajectory independent of the influence of time delays. A numerical simulation example is shown to verify the effectiveness of the proposed approach. Copyright © 2007 John Wiley & Sons, Ltd.
The performance and efficacy of a two‐person operated portable PIT‐antenna for monitoring spatial distribution of stream fish populations
Authors: Linnansaari Tommi P. , Cunjak Richard A.
Published: February 2007

Passive Integrated Transponder (PIT) technology has enabled the tracking of individual fish by using data‐logging stations and one‐person operated portable tracking units. Whereas data‐logging stations are fixed at a certain location, the portable units have traditionally been used in studies that require tracking operations at small spatial scales (<1000 m2) due to the time investment necessary to fully scan the stream channel. We developed a two‐person operated portable antenna that is stretched between the operators and the area in between is scanned for PIT‐tags. The antenna was five metres wide but can be customized to fit stream‐specific needs. The antenna can be used with existing Texas Instruments Series 2000 tracking units, and the detection distance ranged between 46 and 61 cm when using 23‐ or 32‐mm PIT‐tags, respectively (tag held parallel to the plane of the open coil inductor loop). To assess antenna performance in field trial, we compared the efficacy (% tags found) and time‐efficiency (time used to track a study site) between one‐ and two‐person antennae in three separate stream sites. The new antenna type proved to be very efficient (95.2–100%) for locating tags in all trials. However, the new antenna type might not perform adequately in areas with high structural complexity (e.g. logjams, overhanging vegetation) and a follow‐up with one‐person operated antenna is recommended in such complex habitats. The time consumption was always lower (10–53%) with the new antenna and significant time savings can be assumed especially in areas with a low density of PIT‐tagged individuals. Further, we have successfully used the new antenna type to track juvenile Atlantic salmon both in winter conditions (ice‐free) and warmer water (14°C) without causing fright responses. The new antenna type makes the use of PIT‐technology feasible not only at the micro/mesohabitat scale but also at the segment/reach scale and can thus be used to monitor behavioural responses of fish at the population level in wadable streams. Copyright © 2007 John Wiley & Sons, Ltd.
Dementia: nurturing the spirit
Authors: Hudson Rosalie
Published: February 2007

Cries of dementia commonly heard in residential aged‐care homes call for nothing less than a person‐to‐person response. Spiritual nurture is not to be located in some esoteric, disembodied, otherworldly realm, nor does it belong exclusively in the chaplain's domain. The answer lies in the everyday lived experience of those who have dementia and those who care for them; in the particularity of interpersonal relationships rather than in a generalized problem‐solving process. This involves the professional carer entering the life narrative of the person with dementia, in the context of family and community. In a life‐giving community the cries of dementia will be heard as genuine, rather than being ignored as irrational and unworthy of response. The surprising outcome of spiritual nurturance in the context of dementia is that the health professional, in responding to the cries of dementia, may also discover his or her true self. Copyright © 2007 John Wiley & Sons, Ltd.
Influence of rotary inertia on the fiber dynamics in homogeneous creeping flows
Authors: Altenbach H. , Naumenko K. , Pylypenko S. , Renner B.
Published: February 2007

The rotation of an inertialess ellipsoidal particle in a Newtonian fluid has been firstly analyzed by Jeffery [1]. He found that in the shear flow the particle rotates such that the end of its axis of symmetry describes a closed periodic orbit. The aim of this paper is to discuss the effects of particle inertia on the rotary motion of a fiber in uniform flow fields. We recall the equations of motion and the constitutive equation for the hydrodynamic moment in the case of a slender fiber. These equations are solved numerically for several flow fields. We demonstrate that for the plane flow fields with dominant vorticity (elliptic and rotational flows) the effect of inertia is the slow particle drift toward the flow plane.
Adhesive elastic plastic contact: theory and numerical simulation
Authors: Gilabert F.A. , Quintanilla M.A.S. , Castellanos A. , Valverde J.M.
Published: February 2007

We examine the adhesive contact of an elastic‐plastic sphere and a rigid plane. We assume that the contact is normal and frictionless. First, a Molecular Dynamics (MD) simulation of the contact of an amorphous van der Waals solid is performed. Next, a simple model (EP) for the elastic plastic contact is presented, which has as asymptotic limit the singular model (SS) developed by Mesarovic and Johnson in [1]. Finally, the numerical results are quantitatively compared and discussed in relation to the EP and SS models, and qualitatively with Tomas' model [2]. Acknow This work has been supported by the Ministerio de Educación y Ciencia of the Spanish Government under contract number BFM2003‐1739, and by the Junta de Andalucía under project FQM‐421. A significant technical part of this work has been additionally performed under the Project HPC‐EUROPA (RII3‐CT‐2003‐506079), with the support of the European Community – Research Infrastructure Action under the FP6 “Structuring the European Research Area” Programme.
How to improve gait and balance function in elderly individuals—compliance with principles of training
Authors: Oddsson Lars I. E. , Boissy Patrick , Melzer Itshak
Published: February 2007

Most balance training regimens for elderly individuals focus on self-controlled exercises, although automatic postural responses after a balance perturbation are not under direct volitional control. We critically review the literature on this topic, and notice that several studies fail to comply with basic principles of training and therefore show little improvement in function. Some present the view that physical function in the too frail and too fit cannot be improved, which we instead argue would be the effect of nonspecific training programs. We propose a concept for balance training that incorporates voluntary exercises as well as perturbation and dual-task exercises to improve balance control. The program is performed on five different levels where levels 1–4 exercises focus on the skill to maintain balance and level 5 adds perturbation exercises that focus on the skill to recover balance as well as dual task exercises providing a cognitive load during execution of a balance motor task. Functional requirements for muscle strength and power are directly incorporated into the program. The feasibility of the concept has been demonstrated on elderly fallers. A randomized control trial is underway to investigate the effects on healthy elderly individuals. Further intervention studies using this concept are encouraged.
Oxygen consumption of equine articular chondrocytes: Influence of applied oxygen tension and glucose concentration during culture
Authors: Schneider Nicole , Mouithys‐Mickalad Ange , Lejeune Jean‐Philippe , Duyckaerts Claire , Sluse Francis , Deby‐Dupont Ginette , Serteyn Didier
Published: February 2007

We investigated the oxygen (O2) uptake of equine articular chondrocytes to assess their reactions to anoxia/re‐oxygenation. They were cultured under 5% or 21% gas phase O2 and at glucose concentrations of 0, 1.0 or 4.5 g/L in the culture medium (n = 3). Afterwards, the O2 consumption rate of the chondrocytes was monitored (oxymetry) before and after an anoxia period of 25 min. The glucose consumption and lactate release were measured at the end of the re‐oxygenation period. The chondrocytes showed a minimal O2 consumption rate, which was hardly changed by anoxia. Independently from the O2 tension, glucose uptake by the cells was about 30% of the available culture medium glucose, thus higher for cells at 4.5 g/L glucose (n= 3). Lactate release was also independent from O2 tension, but lower for cells at 4.5 g/L glucose (n= 3). Our observations indicated that O2 consumption by equine chondrocytes was very low despite a functional mitochondrial respiratory chain, and nearly insensitive to anoxia/re‐oxygenation. But the chondrocytes metabolism was modified by an excess of O2 and glucose.
Copper induces permeability transition through its interaction with the adenine nucleotide translocase
Authors: García Noemí , Martínez‐Abundis Eduardo , Pavón Natalia , Correa Francisco , Chávez Edmundo
Published: February 2007

In this work we examined the effect of low concentrations of Cu2+ on the opening of the mitochondrial non‐specific pore. The purpose was addressed to further contribute to the knowledge of the mechanisms that regulate the open/closed cycles of the permeability transition pore. Membrane leakage was established by measuring matrix Ca2+ efflux and mitochondrial swelling. The experimental results indicate that Cu2+ at very low concentrations promoted the release of accumulated Ca2+, as well as mitochondrial swelling, provided 1,10‐phenanthroline has been added. Carboxyatractyloside and Cu2+ exhibited additive effects on these parameters. After Cu2+ titration of membrane thiols, it might be assumed that the blockage of 5.9 nmol of SH/mg protein suffices to open the non‐specific pore. Taking into account the reinforcing effect of carboxyatractyloside, the increasing ADP concentrations, and that N‐ethylmaleimide inhibited the Cu2+‐induced Ca2+ efflux, it is proposed that the target site for Cu2+ is located in the ADP/ATP carrier.