bluuebunny/crossref_metadata_2025 huggingface dataset:
Density functional study on the reaction mechanism of palladium‐catalyzed addition of cyanoboranes to alkynes
Authors: Wang M. Y. , Cheng L. , Wu Z. J.
Published: March 2008

The B3LYP hybrid density functional method has been carried out to study theoretically the mechanism of Pd(0)‐catalyzed alkyne cyanoboration reaction. Both the intermolecular and intramolecular alkyne cyanoboration reactions were studied. For each reaction, three paths were proposed. In path A of each reaction, the first step is BCN bond oxidative addition to bisphosphine complex Pd(PH3)2, in path B of each reaction, the first step is alkyne coordination to bisphosphine complex Pd(PH3)2, and in path C of each reaction, the first step is the PH3 dissociation from Pd(PH3)2 to form monophosphine complex Pd(PH3). For both reactions, path B is favored. The dissociation and recoordination of phosphine ligand are found to be very important for the entire reaction, in agreement with the experiment. In both intermolecular and intramolecular cyanoboration reactions, cyano migration is preferred to take place compared with alkenylboryl migration for the formation of the final cis products. The rate‐determining step for both intermolecular and intramolecular cyanoboration reactions is found to be the insertion of carbon‐carbon triple bond into PdB bond with the activation energy of 38.4 and 34.3 kcal/mol relative to the initial reactants, respectively. These values suggest that intramolecular reaction is relatively easy to occur. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008
The intensity, location and structure of the tropical rainbelt over west Africa as factors in interannual variability
Authors: Nicholson Sharon E.
Published: March 2008

This study examines the nature of the tropical rainbelt over west Africa in 4 years corresponding to the four most common patterns of rainfall anomalies in the region. These include 2 years that were anomalously wet in the Sahel, 1955 and 1950, and 2 years, 1983 and 1984, that were anomalously dry. The year 1955 is ubiquitously wet, while a rainfall dipole prevails in 1950, with abnormally high rainfall in the Sahelian latitudes but drought conditions in the Guinea Coast latitudes to the south. The year 1983 is ubiquitously dry and 1984 is a year with a rainfall dipole but opposite in phase (i.e. Sahel dry, Guinea Coast wet). The main results of the study are that the contrast between wet and dry years is associated with a weakening and contraction of the tropical rainbelt. In addition, a north/south displacement of the rainbelt is associated with the dipole patterns, with a northward/southward shift bringing good rains to the Sahel/Guinea Coast. These shifts are associated with north/south shifts in the latitude of the African Easterly Jet (AEJ) over west Africa. The latitudinal position and extent of the rainbelt correspond to the latitudinal position and extent of an immense ‘tongue’ of strong ascending motion. The core of the ascending motion is bound by the axes of the AEJ on the north and the Tropical Easterly Jet (TEJ) in the south. This importance of these two jets in determining the character of the summer rainy season implies that the Sahelian region provides the link between the Sahel and global scale phenomena. Copyright © 2008 Royal Meteorological Society
Muscle satellite cell and atypical myogenic progenitor response following exercise
Authors: Parise Gianni , McKinnell Iain W. , Rudnicki Michael A.
Published: March 2008

Skeletal muscle satellite cells play an essential role in muscle regeneration and exercise adaptation. In recent years atypical myogenic progenitors (non–satellite‐cell muscle stem cells) have been identified in skeletal muscle and have been hypothesized to play an important role in the process of muscle regeneration. It remains unknown, however, whether any populations other than satellite cells play a significant role in repair and adaptation following exercise‐induced damage. We assessed the response of the satellite cell population and the CD45+:Sca‐1+ cell population, previously shown to support muscle regeneration following cardiotoxin‐induced injury, after acute eccentrically biased exercise in wild‐type mice. We observed evidence of focal muscle damage and repair following the exercise protocol using electron microscopy, hematoxylin–eosin staining, and single‐fiber analysis. In addition, we observed an approximately sixfold increase in the number of Myf5‐expressing cells by 48 h, which remained elevated until at least 96 h following exercise. We did not, however, observe any significant expansion of the CD45+:Sca‐1+ cell population or commitment of resident CD45+:Sca‐1+ cells to the myogenic lineage. Furthermore, expression of Wnt gene family members, previously associated with myogenic specification of CD45+:Sca‐1+ cells, did not differ following exercise. Therefore, we conclude that muscle satellite cells are the primary responders to exercise‐induced stress and that the CD45+:Sca‐1+ myogenic progenitors do not contribute to muscle repair/adaptation following exercise. Muscle Nerve, 2008
Cross‐sectional area reference values for nerve ultrasonography
Authors: Cartwright Michael S. , Passmore Leah V. , Yoon Joon‐Shik , Brown Martin E. , Caress James B. , Walker Francis O.
Published: March 2008

Ultrasound allows for a non‐invasive structural assessment of nerves, muscles, and surrounding tissues, and therefore it is increasingly being used as a supplement to traditional electrodiagnostic studies. As investigators have begun to use ultrasound to explore peripheral nerves, it has become clear that conditions such as entrapment, hereditary neuropathies, acquired neuropathies, trauma, and nerve tumors result in an increase in nerve cross‐sectional area. Reference values have not been published for the cross‐sectional area of many nerves commonly studied in diseases of the peripheral nervous system, so our goal was to obtain reference values for the nerve cross‐sectional area at the following sites: radial at antecubital fossa; radial at distal spiral groove; musculocutaneous in upper arm; trunks of the brachial plexus; vagus at carotid bifurcation; sciatic in distal thigh; tibial in popliteal fossa; tibial in proximal calf; tibial at ankle; peroneal in popliteal fossa; peroneal at fibular head; and sural in distal calf. Mean cross‐sectional area, as well as side‐to‐side differences, are reported for each site, and qualitative data are provided to guide imaging at each site. The information provided in this study should serve as the starting point for quantitatively evaluating these nerve sites with ultrasound. Muscle Nerve, 2008
Implementation of the finite element method in the three‐dimensional discontinuous deformation analysis (3D‐DDA)
Authors: Grayeli Roozbeh , Hatami Kianoosh
Published: March 2008

A modified three‐dimensional discontinuous deformation analysis (3D‐DDA) method is derived using four‐noded tetrahedral elements to improve the accuracy of current 3D‐DDA algorithm in practical applications. The analysis program for the modified 3D‐DDA method is developed in a C++ environment and its accuracy is illustrated through comparisons with several analytical solutions that are available for selected problems. The predicted solutions for these problems using the modified 3D‐DDA approach all show satisfactory agreement with the corresponding analytical results. Results presented in this paper demonstrate that the modified 3D‐DDA method with discontinuous modeling capabilities offers a useful computational tool to determine stresses and deformations in practical problems involving fissured elastic media with reasonable accuracy. Copyright © 2008 John Wiley & Sons, Ltd.
External urethral sphincter activity in diabetic rats
Authors: Liu Guiming , Lin Yi‐Hao , Yamada Yasuhiro , Daneshgari Firouz
Published: March 2008

Aim

To examine the temporal effects of diabetes on the bladder and the external urethral sphincter (EUS) activity in rats.

Methods

Female Sprague‐Dawley rats (n = 24) were divided into two groups: streptozotocin‐induced diabetic rats and age‐matched controls. Cystometrograms (CMGs) were taken under urethane anesthesia and electromyograms (EMG) of the EUS were evaluated in all rats at 6 and 20 weeks after diabetes induction. After EMG assessment, the tissues of the urethra were harvested for morphological examination.

Results

Diabetes caused reduction of body weight, but an increase in bladder weight. CMG measurements showed diabetes increased threshold volume, contraction duration, high‐frequency oscillations (HFO), and residual volume. Peak contraction amplitude increased in 6‐week but not 20‐week diabetic rats. EUS‐EMG measurements showed increased frequency of EUS‐EMG bursting discharge during voiding in 6‐week diabetic rats (8.1 ± 0.2 vs. 6.9 ± 0.6/sec) but not in 20‐week (5.8 ± 0.3 vs. 6.0 ± 0.2/sec) diabetic rats compared with controls. EUS‐EMG bursting periods were also increased in both 6‐week and 20‐week diabetic rats compared with controls. EUS‐EMG silent periods were reduced in 6‐week diabetic rats, but were not changed in 20‐week diabetic rats compared with controls. Active periods did not change in 20‐week diabetic rats, but increased in 6‐week diabetic rats compared with controls. Morphometric analysis showed atrophy of the EUS after 20 week but not 6 weeks of DM induction.

Conclusions

Our data indicates diabetes causes functional and anatomical abnormalities of the EUS. These abnormalities may contribute to the time‐dependent bladder dysfunction in diabetic rats. Neurourol. Urodynam. 27:429–434, 2008. © 2008 Wiley‐Liss, Inc.
A numerical study on the generation of impulsive noise by complex flows discharging from a muzzle
Authors: Bin Jonghoon , Kim Minwoo , Lee Soogab
Published: March 2008

A numerical study on impulsive noise generation produced by complex flows discharging from a muzzle is achieved and the basic structures generating impulsive noise are analyzed. Complex flow features by a muzzle flow and noise generation mechanisms by several sources of noise are discussed from numerical simulations. Two‐dimensional axisymmetric Euler equations are used for governing equations. High‐order dispersion relation preserving finite difference method and an optimized four‐level marching method are used for spatial discretization and time integration, respectively. In order to show the capability of this method to capture blast waves and to examine the basic generation mechanism of acoustic waves from a muzzle, the interaction between a shock/blast wave and a vortex ring is implemented. From the numerical simulation of the 7.62‐mm NATO rifle G3 with a DM‐41 round in the near field, complex blast waves, jet flow, various vortices and their interaction phenomena are described and noise generation mechanism due to the interaction of complex flow structures is observed. The present results demonstrate that numerical simulation using computational aeroacoustic methods provides not only a reliable way to determine the blast wave dynamics of the muzzle flow but also allows an opportunity to study the physics and detailed mechanisms of the noise generation and propagation due to the interaction of complex flow structures generated from a muzzle system. Copyright © 2008 John Wiley & Sons, Ltd.
Optimal control problems with delays in state and control variables subject to mixed control–state constraints
Authors: Göllmann L. , Kern D. , Maurer H.
Published: March 2008

Optimal control problems with delays in state and control variables are studied. Constraints are imposed as mixed control–state inequality constraints. Necessary optimality conditions in the form of Pontryagin's minimum principle are established. The proof proceeds by augmenting the delayed control problem to a nondelayed problem with mixed terminal boundary conditions to which Pontryagin's minimum principle is applicable. Discretization methods are discussed by which the delayed optimal control problem is transformed into a large‐scale nonlinear programming problem. It is shown that the Lagrange multipliers associated with the programming problem provide a consistent discretization of the advanced adjoint equation for the delayed control problem. An analytical example and numerical examples from chemical engineering and economics illustrate the results. Copyright © 2008 John Wiley & Sons, Ltd.
PROSPECT lost: when a pilot project does not look to learn
Authors: Mattingly Michael
Published: March 2008

If a development project is destined to reach only a selection of its intended beneficiaries or to give them only momentary or uncertain benefits, there is a strong rationale for making it instead a project of trials from which lessons can be taken for obtaining the impact that it may not otherwise have. Because the fundamental problems and opportunities of development are very complex by their nature, interventions that seek to test practice knowledge and to learn above all else may have the greatest potential for benefit in the long term. A project that wishes to create experience from which others can learn will engage in research, so it must be conceived, led and conducted as such. This means it must be designed with knowledge of research. It must be led with an appreciation and understanding of research method. Specific research activities must be conducted that produce knowledge and promote its up‐take, so that learning is a principle project outcome. The large urban anti‐poverty project, PROSPECT, conducted in Lusaka, Zambia, illustrates this argument. Copyright © 2008 John Wiley & Sons, Ltd.
New insights on the role of CXCR4 in cancer metastasis
Authors: Zlotnik A
Published: March 2008

The evolutionarily conserved chemokine superfamily encodes small peptide molecules that bind G‐protein‐coupled receptors. In humans, this superfamily includes at least 46 ligands and 18 receptors. In general, chemokines and their receptors form a chemotactic network that regulates the migration of cells to specific micro‐anatomical destinations within an organism in an organized and non‐random manner. Recent studies place chemokine‐chemokine receptor pairs at the centre of not only physiological cell migration, but also pathological processes such as metastasis. This mini review considers some recent data on how chemokines regulate tumour cells during metastasis. These observations suggest novel ways for pharmacological intervention. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Fracture prediction in tough polyethylene pipes using measured craze strength
Authors: Davis P. , Burn S. , Gould S.
Published: March 2008

In this study, an empirical model is developed that predicts the time to failure for PE pipes under combined pressure and deflection loads. The time‐dependent craze strength of different PE materials is measured using the circumferentially deep‐notched tensile (CDNT) test. In agreement with previous research, results indicate that bimodal materials with comonomer side‐chain densities biased toward high‐molecular‐weight PE molecules exhibit significantly higher long‐term craze strengths. A comparison of currently available PE materials with CDNT samples taken from a PE pipe that failed by slow crack growth in service clearly indicates the superior performance of new‐generation materials. Using measured craze strength data from the CDNT test, a simplified model for predicting failure in buried PE pipes is developed. Extending previous research, the reference stress concept is used to calculate an equivalent craze stress for a pipe subjected to combined internal pressure and deflection loads. Good agreement is obtained between the model predictions and observed failure times in an experimental test‐bed study of pipes under in‐service loading conditions. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Semi‐empirical, squeeze flow and intermolecular diffusion model. I. Determination of model parameters
Authors: Grewell David , Benatar Avraham
Published: March 2008

This article reviews the development of molecular healing models that couple squeeze flow and intermolecular diffusion. Historically there are a few studies that combine these processes for fusion bonding of thermoplastic composites. The motivation of this work was to develop similar models for welding of polymer films and films to substrates. These models are theoretically developed and experimentally verified. It was found that the time dependence for squeeze flow is of the same order of magnitude as that for intermolecular diffusion, making models for these processes indistinguishable experimentally, and therefore, they were assumed to occur simultaneously. Furthermore, it was found that healing of the weld can be better defined as a function of time and temperature instead of temperature alone, as historically done for welding applications. Comparison of the weld strength predictions with experimental data for impulse welds showed that the developed models were able to predict weld strength over a wide range of parameters. In Part 2, moving heat source heat transfer models together with the coupled squeeze flow and intermolecular diffusion model are used to predict healing during laser microwelding. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Synthesis and photopolymerization kinetics of polymeric one‐component type II photoinitiator containing benzophenone moiety and tertiary amine
Authors: Xiao Pu , Wang Ying , Dai Mingzhi , Shi Suqing , Wu Gangqiang , Nie Jun
Published: March 2008

A polymeric one‐component type II photoinitiator (PDABPP) based on 4,4′‐dihydroxybenzophenone (DHBP), acryloyl chloride, and piperazine was synthesized, and its structure was confirmed by GPC and 1H NMR. The photopolymerization kinetics of the photoinitiator was studied by real‐time infrared spectroscopy. It indicated that PDABPP was a more effective photoinitiator than that of benzophenone (BP)/triethylamine (TEA). The rate of polymerization and final conversion increased, and the induction period shortened with increase of PDABPP concentration, light intensity, and amine concentration. The kinetics of photopolymerization for tripropylene glycol diacrylate (TPGDA) incorporating PDABPP in the presence of different tertiary amines as the initiating system indicated that the PDABPP/TEA combination exhibited the highest polymerization rates among the PDABPP/amines combinations. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Effect of weakly interacting nanofiller on the morphology and viscoelastic response of polyolefins
Authors: Kalfus Jan , Jancar Josef , Kucera Jaroslav
Published: March 2008

Effect of silica nanofiller on the deformation response and morphology of low‐ and high‐density polyethylene (HDPE, LDPE) and isotactic polypropylene (PP) modified with fumed silica was investigated. The dynamic‐mechanical thermal spectroscopy, differential scanning calorimetry, optical microscopy, and density measurements were carried out to determine the temperature dependence of storage and loss moduli as well as nanocomposite morphology. It was demonstrated that the degree of matrix reinforcement is considerably affected by the extent of matrix crystallinity, especially, in the temperature range from (Tm–130°C) to Tm. Based on experimental evidence and literature review, it is proposed that this phenomenon may be attributed to the alpha‐mechanical relaxation process occurring above matrix Tg. As a result of adding silica into the melted matrix, mobility of chains in contact with silica particles became reduced. This caused substantial changes in morphology of these semicrystalline nanocomposites. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Effect of PMMA addition on characterization and morphology of PVDF
Authors: Elashmawi I.S. , Hakeem N.A.
Published: March 2008

Polyvinylidene fluoride and polymethylmethacrylate (PVDF/PMMA) films were blended with different concentrations by casting method. Structural, spectroscopic, and morphological characteristics of both the interface and the surface of the films have been investigated. The blends were characterized using X‐ray diffraction (XRD), Fourier transform infrared (FTIR), UV–visible, differential thermal analysis (DTA), and scanning electron microscopy (SEM). All measurements reveal that the blends take place based on the influence of PMMA content on PVDF. FTIR results indicate the possible interactions between carbonyl group of PMMA and CH2 groups of PVDF which indicates the formation of blends. Optical absorption spectra suggested the presence of an optical gap (Eg) which decreased with increasing PMMA content. UV/VIS spectra were characterized by a sharp edge and a window of wavelength range 290–350 nm for some blends. The optical window can be used as an optical sensor or band pass filter. The degree of crystallinity was found to decrease with increasing PMMA content, which was confirmed by XRD and DTA analysis. SEM micrograph shows spherulites which increase with the addition of PMMA and it becomes sharper and contains a longitudinal shape. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Novel phenylethynyl‐endcapped polyimide oligomers: Synthesis and characterization
Authors: Chen Jiansheng , Qu Ximing , Liu Jingang , Yang Haixia , Fan Lin , Yang Shiyong
Published: March 2008

A series of novel phenylethynyl‐endcapped polyimide oligomers were prepared by polycondensation of an aromatic diamine mixture of 1,3‐bis(4‐aminophenoxy) benzene (1,3,4‐APB) and 3,4′‐oxydianiline (3,4′‐ODA) with different aromatic dianhydrides including 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐(hexafluoro isopropylidene)diphthalic anhydride (6FDA), 4,4′‐oxydiphthalic anhydride (ODPA), and 4,4′‐[2,2,2‐trifluoro‐1‐(3′,5′‐bis‐(trifluoro‐methyl)phenyl)ethylidene]diphthalic anhydride (9FDA) in the presence of 4‐phenyl‐ethynylaniline (PEA) as endcapping agent in aprotic solvent at elevated temperature. The chemical structures, thermal behavior, and melt rheological properties of the synthesized polyimide oligomers were investigated. Experimental results indicated that the fluorinated polyimide oligomers derived from 6FDA (PI‐2) and 9FDA (PI‐4) are amorphous solid resins and exhibited lower melt viscosities than those prepared from the unfluorinated aromatic dianhydrides such as BPDA and ODPA. The BPDA‐based polyimide oligomers with a molar ratio of 1,3,4‐APB/3,4′‐ODA = 50:50 (PI‐5) showed lower melt viscosity than those derived from a mixture of 1,3,4‐APB and 3,4′‐ODA with molar ratios of 75:25 and 100:0, respectively. In addition, the melt viscosity of the polyimide oligomers increased obviously with increasing of the polymer calculated molecular weights. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Flexural creep of all‐polypropylene composites: Model analysis
Authors: Banik K. , Karger‐Kocsis J. , Abraham T.
Published: March 2008

In this article, simple viscoelastic and empirical models are presented to predict and analyze the flexural creep behavior of all‐poly(propylene) (all‐PP) composites. Results of the successful application of these models to the actual creep behavior of unidirectional (UD) and cross‐ply (CP) all‐PP composites tested by short‐term flexural creep measurements over a temperature range of 20–80°C are presented. Analysis of the momentary creep behavior of all‐PP composites with different tape lay‐ups are made to understand their deformation mechanism. Further to the main theme of the article, an interesting discrepancy while predicting the long‐term creep behavior of these composites based on the time‐temperature superposition (TTS) principle and Findley power law model is visualized which has also been illustrated here. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Effect of orientation and crystallinity on the photodegradation of poly(ethylene terephthalate) fibers
Authors: Fashandi H. , Zadhoush A. , Haghighat M.
Published: March 2008

In this research, photodegradation of poly(ethylene terephthalate) (PET) fibers was investigated with emphasis on the morphological state of yarns. Two kinds of yarns, FDY (Fully Drawn Yarn) and POY (Partially Oriented Yarn), with different molecular orientation and crystallinity were applied in this research. FDY is spun in the same way as POY and subsequently drawn at high speed and then entangled before winding up. This sample has higher molecular orientation and crystallinity than the POY sample. Several analytical methods were applied in this study: viscometry, X‐ray diffraction, FTIR spectroscopy, UV–Visible spectrophotometry, and mechanical testing. Viscometry was used to determine molecular weight as a monitoring factor for degradation. X‐ray diagrams showed higher crystallinity for FDY samples during weathering process by irradiation. Results of mechanical testing indicated that the tenacity of the FDY fibers had less deterioration in comparison with the POY ones. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Numerical simulation of tunnel diodes for multi‐junction solar cells
Authors: Hermle M. , Létay G. , Philipps S. P. , Bett A. W.
Published: March 2008

This work presents efforts to simulate numerically the current voltage (IV) curve of a III–V based Esaki tunnel diode. Using a tunneling model, which takes into account the full nonlocality of the barrier, a good agreement between measured and simulated IV curves of a GaAs tunnel diode was achieved. The influence of a series resistance effect as well as the importance of trap assisted tunneling (TAT) could be shown. In addition, we present a two‐dimensional model of a III–V multi‐junction solar cell including the numerical model of the investigated Esaki tunnel diode. Copyright © 2008 John Wiley & Sons, Ltd.
Optical properties of TiO2 films made by air oxidation of Ti
Authors: Svitasheva S. N. , Gritsenko V. A. , Kolesov B. A.
Published: March 2008

In this work spectral behaviour of complex refractive index of thermal oxidized titanium films deposited onto Si (100) substrate were investigated by spectroscopic ellipsometry in the range of 1.5‐4.77 eV. The films were subjected to annealing in air at temperature 750 °C for 7 and 25 hours. As it follows from our studies, air oxidation of titanium resulted in coexisting of different phases in the film, and dependence of their optical and structural properties upon z‐coordinate (upon film depth). The spectral dependences of complex refractive index and the changing of film thickness due to cumulative annealing were determined from pseudodielectric function (PDF) ‐ ε(E) spectra, for which data acquisition was performed by Spectroscopic Phase Modulated Ellipsometer (SPME). Complicated phase composition of films was revealed by using multi‐layers conception of investigated film and applying oscillator's model and EMA approximation for description of spectral dependence of dielectric function of film or its separate layers. Raman spectra were used to distinguish phase components in the films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ellipsometric characterization of photo‐resist gratings using artificial neural network
Authors: Gereige I. , Robert S. , Stchakovsky M. , Jamon D. , Celle F. , Reynaud S. , Pommier J. C. , Jourlin Y.
Published: March 2008

In this work, we report on the control of patterned photoresist structures used as a mask in the photolithographic process. This control is crucial in order to detect any defect before the final etching step on the substrate or sublayer. Scatterometry is an optical method that has true potential for critical dimension and profile analysis.

Spectroscopic ellipsometry is employed to measure the diffracted signature, and followed by a neural treatement to extract the geometrical parameters. Experimental results are validated on 2‐μm‐period gratings, with various geometrical profiles, transfered on a glass substrate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐situ observation of photodoping phenomena in chalcogenide glass by spectroscopic ellipsometry
Authors: Murakami Y. , Wakaki M. , Kawabata S.
Published: March 2008

Anormalous diffusion process of Ag into an As2S3 film induced by illumination of light with photon energy larger than optical gap was examined in‐situ by spectroscopic ellipsometry in the wavelength regions between 450 and 850 nm. Two steps of doping called as the first and second stage were derived through the analyses of the optical constants, which is difficult to obtain by the monochromatic ellipsometry. The features of photodoping were clearly observed through the analysis of the results of spectroscopic ellipsometry, which suggests the superiority of the method to treat for such complex phenomenon. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fréedericksz transition in homeotropically aligned liquid crystals: a photopolarimetric characterization
Authors: Vena C. , Versace C. , Strangi G. , D'Elia St. , Bartolino R.
Published: March 2008

This work is aimed to the photopolarimetric characterization of the disorder evolution occurring in homeotropically aligned nematic liquid crystal films during the Fréedericksz transition. This order‐disorder transition is studied by monitoring the depolarization effects of the transmitted light. Depolarization mainly occurs because light undergoes random and local phase displacements. The measurements reveal unexpected depolarization effects at the transition, which we interpret in terms of director field unhomogeneity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Real‐time spectroscopic ellipsometry for protein adsorption study and pH effect
Authors: Lousinian S. , Logothetidis S.
Published: March 2008

Carbon based thin films, such as amorphous carbon (a‐C) and amorphous hydrogenated diamond‐like carbon (a‐C:H) are considered as excellent candidates for biomedical applications. Protein adsorption is an important aspect for the improvement of many applications, such as medical implants, biosensor design, etc. The density, orientation, and conformation of surface‐bound proteins are believed to be key factors in controlling subsequent cellular adhesion. Aim of this work is the study of the pH effect on fibrinogen adsorption on a haemocompatible a‐C:H thin film developed by rf reactive magnetron sputtering. For this purpose, Vis–UV Spectroscopic Ellipsometry (SE) has been used. It is a non destructive, surface sensitive technique, with the capability of performing real‐time measurements in air as well as in liquid environment, with great potential in biomedical studies. An appropriate ellipsometric model has been developed, in order to describe accurately the protein adsorption mechanisms in real‐time. SE results reveal the differences in the rate of fibrinogen thickness increase and transition rate of fibrinogen from liquid to adsorbed state. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Random errors and optimum estimation of measurements photometric ellipsometers
Authors: Dron O. S.
Published: March 2008

A method of calculation of ellipsometric parameters, which allows to minimize random errors and simultaneously obtain their covariance matrix, is developed for photometric ellipsometry and polarimetry systems on the basis of Generalized least‐squares method (GLSM). As examples of application for rotating compensator ellipsometer the optimum value of retardation of the compensator equal to 132° is calculated, and also the technique of determination of the spectral range is offered. For shot‐noise limited systems the basic equation R = D (R)U is obtained, where R is the vector of measured parameters, D (R) is the covariance matrix of these parameters, and U is a constant vector describing the measuring system. All the results are applicable both for Stokes‐ and for Muller‐ellipsometry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wide angle beam ellipsometry for extremely large samples
Authors: Major C. , Juhász G. , Horváth Z. , Polgar O. , Fried M.
Published: March 2008

Our aim was to make possible to use ellipsometry for mapping purposes during one measuring cycle even on large wafers or panels (several dm2 area). The new technique (Patent pending: P0700366, 2007 [1]) (based on our wide‐angle beam ellipsometry solution) uses non‐collimated illumination with special mirror arrangement giving multiple‐angle‐of‐incidence information. The prototype uses a so called RGB‐laser (658, 532, 474 nm) as light source. The detection is almost without background. One rapid measuring cycle is enough to determine the polarization state at all the points inside the illuminated area. The collected data can be processed very fast providing nearly real‐time thicknesses and/or refractive index maps over a large (several dm2) area of the sample surface even in the case of multi‐layer samples. The method can be used for mapping (quality) control purposes in the case of large area solar cell table production lines even in vacuum chamber with 5‐10 mm lateral resolution. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of Ru and RuO2 thin films prepared by pulsed metal organic chemical vapor deposition
Authors: Roeder G. , Manke C. , Baumann P. K. , Petersen S. , Yanev V. , Gschwandtner A. , Ruhl G. , Petrik P. , Schellenberger M. , Pfitzner L. , Ryssel H.
Published: March 2008

Ultra‐thin ruthenium (Ru) layers were fabricated by pulsed metal organic chemical vapor deposition in an Aixtron Tricent reactor using a metal‐organic Ru precursor. Layer deposition was performed on different metal barrier combinations and on Al2O3 dielectric layers used in the fabrication of advanced Metal‐Insulator‐Metal (MIM) capacitor structures and on thermal SiO2 as reference structure. Ru layers with a thickness of 10 nm were characterized by Spectroscopic Ellipsometry (SE) and additional reference methods such as Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and X‐Ray Reflectometry (XRR). As deposited and in situ annealed Ru layers were characterized by SE applying Drude‐Lorentz‐ and Effective Medium Approximation (EMA) models. It was shown that the deposited layers consist of a Ru‐RuO2 bilayer structure. By in situ annealing, the RuO2 layer thickness is reduced and highly pure Ru films are obtained. On the metal barriers the formation of a metal oxide interface, which is related to the deposition process, was determined. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical modeling and XRR/AFM characterization of highly conductive thin Ag layers
Authors: Ulrich S. , Pflug A. , Schiffmann K. , Szyszka B.
Published: March 2008

Thin silver layers (≈ 12 nm) are widely used in low‐E architectural glass coatings. For these and other applications thin Ag films with high conductivity are desired. We prepared Glass/ZnO:Al/Ag layer stacks with Ag thicknesses in the range of 7 – 40 nm by means of magnetron sputtering. The ZnO:Al Layer was RF/DC sputtered from a ceramic target and serves as seed layer for growth of strongly (111) oriented silver with high conductivity (M. Arbab, Thin Solid Films 381, 15 (2001) [1]). Layer thicknesses, top surface and interface roughnesses were determined by XRR and compared with AFM rough ness for the top layer. We present a dielectric function model for thin silver films with which the optical measurements are excellently described. The hereby determined layer thicknesses correspond precisely to those determined by XRR. The best agreement was found when only reflectance and transmittance measurements were used. The model for the dielectric function assumes a constant charge density and uses the electron mobility as free parameter. For the Ag resistivity ρ we found a strong decrease with increasing Ag thickness. A value of ρ‐Ag = 3.83 µΩcm was interpolated for an Ag thickness of 12 nm for pure DC plasma excitation during ZnO:Al seed layer deposition. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First‐order phase transitions of spin‐crossover and charge transfer solids probed by spectroscopic ellipsometry
Authors: Boukheddaden K. , Loutete‐Dangui E.D. , Koubaa M. , Eypert C.
Published: March 2008

We present a quantitative and comparative ellipsometric study of two switchable solids, undergoing a first‐order transition around ambient temperature: the spin‐crossover (SC), [Fe(NH2‐trz)3]Br2 and the cooperative Jahn‐Teller (JT) switch, RbMn[Fe(CN)6]. Ellipsometric spectra have been recorded in the optical range 240‐1000nm and temperature interval 260‐380 K for both solids. We found that absorption spectra of the SC show temperature invariant isobestic point, while that of the JT clearly indicates a thermally induced energy shift, in relation with the structural transition of this material. Integrating the absorption spectra, we derived the thermal dependence of the fractions of the high‐temperature phases for both solids, and found them in excellent agreement with that of magnetic data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic ellipsometry and vector network analysis for determination of the electromagnetic response in two wavelength regions
Authors: Åkerlind C. , Jänis A. , Kariis H. , Arwin H. , Järrendahl K.
Published: March 2008

In this work, spectroscopic ellipsometry and vector network analysis are used to determine the electromagnetic response of three samples, an epoxy polymer, a sample with ferrit‐based nanoparticles in a polymer matrix and silicon, in the wavelength ranges 0.4‐30 μm and 0.75‐7.59 cm. Both methods measure amplitude and phase changes due to interaction with a sample and can be used to measure the full complex‐valued dielectric response to electromagnetic radiation. The data from the two methods show similar levels of the response at the two ends of the spectral gap between the ranges of the two methods. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dielectric and magnetic birefringence in low‐chlorine‐doped n ‐type Zn1–xMnxSe
Authors: Saenger M. F. , Hetterich M. , Hofmann T. , Kirby R. D. , Sellmyer D. J. , Schubert M.
Published: March 2008

Generalized spectroscopic ellipsometry over the spectral range from 1.24 to 3.34 eV is used to investigate a set of molecular beam epitaxy grown lowchlorine‐doped n ‐type Zn1–x Mnx Se films on (001)‐oriented GaAs for x = 0.0, 0.02, 0.14 and 0.28. We present evidence for intrinsic optical anisotropy in dependence of the Mn concentration caused by wurtzitestructure domain formation. We employ a previously established dielectric function model that accounts for band‐gap transition energy splitting in cubic semiconductors [Phys. Rev. B 60, 16618 (1999)]. Room temperature magneto‐optic generalized ellipsometry in the Kerrconfiguration reveals the sp‐d exchange energy splitting parameters upon expanding our anisotropy model by inclusion of chiral spin‐polarized band‐to‐band transition contributions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrooptic ellipsometry study of piezoelectric BaTiO3‐ZnO heterostructures
Authors: Voora V. M. , Hofmann T. , Brandt M. , Lorenz M. , Grundmann M. , Schubert M.
Published: March 2008

We report on electrooptic reflection‐type spectroscopic ellipsometry investigations of a wurtzite structure (ZnO) and perovskite structure (BaTiO3) thin film heterostructure between Pt contacts. The ZnO spontaneous polarization biases the ferroelectric polarization domain switching in BaTiO3, and causes a strong asymmetric electrooptic hysteresis behavior, reflected by an overall change of sample effective thickness and effective index of refraction. This hysteresis behavior is concordant with our previously observed electric hysteresis behavior of the same sample structure.We explain the hysteresis behavior by piezoelectric strain within the ferroelectric layer, by interface lattice charge coupling between the BaTiO3 and ZnO layer, and the previously identified depletion layer formation within the n ‐type doped ZnO layer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positionality of African Americans and a theoretical accommodation of it: Rethinking science education research
Authors: Parsons Eileen R. Carlton
Published: March 2008

This essay addresses a call for research involving African Americans to interpret data from the historical, contemporary, and cultural experiences of African Americans. The essay argues for a science education research approach that explicitly considers the positionality of African Americans in the United States. This positionality involves the negotiation of three distinct and conflicting realms of experience that pertain to oppression, African‐rooted Black culture, and the dominant culture in the United States. The theoretical tool proposed in this essay accommodates the positionality of African Americans by superimposing it upon a model that synthesizes the ideas of Michael Cole (cultural‐historical activity theory) and Urie Bronfenbrenner (ecology of human development). © 2008 Wiley Periodicals, Inc.Sci Ed92:1127–1144, 2008
Neurobiological perspectives of free will and freedom of choice
Authors: Drubach Daniel A.
Published: March 2008

The issue of free will and freedom of choice has been debated by countless theologians and philosophers throughout the history of mankind, but only recently have neuroscientists begun to address the subject from a neurobiological perspective. In this paper we explore the potential contributions of neurosciences towards answering the question of whether free will exists in humans and its potential neurobiological correlate. To accomplish this, we discuss the neural mechanisms of free will from two perspectives: that of voluntary movement and the stimulus response paradigm. We also address the role of awareness in free will and propose the existence of an underlying ‘volitional system’ contained within the central nervous system. Copyright © 2008 John Wiley & Sons, Ltd.
Healing as a creative art: opportunities to provide for the spiritual health of families when children need critical care
Authors: Macnab Andrew
Published: March 2008

In an Intensive Care Unit (ICU) of a Children's Hospital science, wisdom and compassion must be interwoven into the fabric of everyday in order for the children and their families to heal and the staff caring for them to remain healthy. The challenge is to practise both the art and science of medicine and to respond to the different cultural and spiritual beliefs of those brought together by a child's illness.

This paper summarizes the special needs of parents and children in the ICU, the obstacles and opportunities encountered by staff, and research from Vancouver which helps those who provide holistic and spiritually oriented care. Copyright © 2008 John Wiley & Sons, Ltd.
Adsorption and diffusion property of a hydrogen atom on a Pd3Ag(111) surface
Authors: Ozawa N. , Arboleda N. B. , Nakanishi H. , Shimoji N. , Kasai H.
Published: March 2008

The behavior of a hydrogen atom on a Pd3Ag(111) surface is investigated by calculating the quantum states of the hydrogen atom via the first principles calculation methods. The calculation results show that the ground state wave function for the motion of hydrogen atom is localized on the fcc hollow site surrounded by three Pd atoms. Moreover, activation energies for the diffusion of the hydrogen atom on the whole Pd3Ag(111) surface are estimated as 394 and 520 meV via quantum and classical methods, respectively. Compared with our previous study on the behavior of hydrogen atom on the Pd(111) surface, the adsorption energy of hydrogen atom becomes smaller, while the activation energy becomes larger as a result of Ag alloying. Copyright © 2008 John Wiley & Sons, Ltd.
Uniformalization of AT cut quartz crystal wafer thickness using open‐air type plasma CVM process
Authors: Yamamura Kazuya , Morikawa Tetsuya , Shibahara Masafumi , Zettsu Nobuyuki , Mori Yuzo
Published: March 2008

Improvement of thickness variation of the AT cut quartz crystal wafer is very important to advance the performance of the quartz resonator and to improve the productivity. However, conventional machining cannot exceed its technical limit any more, because quartz crystal is brittle and the wafer having thickness less than several tens of micrometers is required. We have newly developed the chemical finishing process to correct the thickness variation of the quartz crystal wafer, which utilizes localized atmospheric pressure plasma without gas replacing process. In the case of the atmospheric pressure plasma, high‐density plasma region is localized in the vicinity of the electrode because of its small mean free path. Removal volume is proportional to the dwelling time of the plasma on the workpiece surface. Therefore, free figuring without mask pattern is realized by numerically controlled scanning of the localized reactive area. By applying our proposed correcting process, thickness variation of the commercially available AT cut quartz crystal wafer was improved from 270 to 40 nm. Copyright © 2008 John Wiley & Sons, Ltd.
Towards interoperability: a wrapper model for integrating remote laboratories in a collaborative discovery learning environment
Authors: Martínez‐Carreras M. Antonia , Gómez‐Skarmeta Antonio F.
Published: March 2008

Collaborative theories in learning are playing a vital role in the way learners interact with each other. More concretely, in collaborative learning the communication between learners is considered the most important element in their knowledge building. Regarding experimental subjects, the discovery learning discipline has emerged, in which students construct their knowledge through experimentation. In this sense, platforms such as Pedagogica, Web‐based inquiry science environment, SimQuest, Interactive Physics, Working Models and Co‐Lab provide support of this kind of learning. Regarding experimentation, one of the resources that may enrich the learning of students is the use of remote laboratories. However, the majority of these learning systems lack interfaces and models to provide interoperability with remote laboratories. Regarding interoperability issues, service‐oriented architecture (SOA) is the most well‐known paradigm for this issue. In this paper, we describe a wrapper model based on SOA for interoperability between Co‐Lab and existing remote laboratories. Moreover, we explain how we have integrated the existing remote laboratories in Co‐Lab using this model and we show the general pattern for including external experiments. Copyright © 2008 John Wiley & Sons, Ltd.
Mobility handling in MAC for wireless ad hoc networks
Authors: Raja Anjali , Su Xiao
Published: March 2008

Wireless Sensor Networks (WSNs) are becoming popular in a wide variety of applications. In a WSN, sensor nodes can be static or mobile, depending on applications. Handling mobility in a sensor network can pose interesting challenges in sensor protocol design, and special algorithms are needed to adapt to mobility in the network. In this paper, we survey the current state of art in handling mobility in sensor networks. We first study how mobility affects the design of different layers in the sensor network architecture, and then take a closer look at mobility handling in the MAC layer. We also describe the results of simulations that we conducted to compare and analyze existing mobility‐aware MAC protocols. Finally, we discuss open issues in dealing with mobility in sensor networks. Copyright © 2008 John Wiley & Sons, Ltd.