bluuebunny/crossref_metadata_2025 huggingface dataset:
Image coding based on wavelet feature vector
Authors: Lin Shinfeng D. , Shie Shih‐Chieh , Lee Kuo‐Yuan
Published: August 2005

In this article, an efficient image coding scheme that takes advantages of feature vector in wavelet domain is proposed. First, a multi‐stage discrete wavelet transform is applied on the image. Then, the wavelet feature vectors are extracted from the wavelet‐decomposed subimages by collecting the corresponding wavelet coefficients. And finally, the image is coded into bit‐stream by applying vector quantization (VQ) on the extracted wavelet feature vectors. In the encoder, the wavelet feature vectors are encoded with a codebook where the dimension of codeword is less than that of wavelet feature vector. By this way, the coding system can greatly improve its efficiency. However, to fully reconstruct the image, the received indexes in the decoder are decoded with a codebook where the dimension of codeword is the same as that of wavelet feature vector. Therefore, the quality of reconstructed images can be preserved well. The proposed scheme achieves good compression efficiency by the following three methods. (1) Using the correlation among wavelet coefficients. (2) Placing different emphasis on wavelet coefficients at different decomposing levels. (3) Preserving the most important information of the image by coding the lowest‐pass subimage individually. In our experiments, simulation results show that the proposed scheme outperforms the recent VQ‐based image coding schemes and wavelet‐based image coding techniques, respectively. Moreover, the proposed scheme is also suitable for very low bit rate image coding. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 123–130, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20045
A practical approach for estimating illumination distribution from shadows using a single image
Authors: Kim Taeone , Hong Ki‐Sang
Published: August 2005

This article presents a practical method that estimates illumination distribution from shadows using only a single image. The shadows are assumed to be cast on a textured, Lambertian surface by an object of known shape. Previous methods for illumination estimation from shadows usually require that the reflectance property of the surface on which shadows are cast be constant or uniform, or need an additional image to cancel out the effects of varying albedo of the textured surface on illumination estimation. But, our method deals with an estimation problem for which surface albedo information is not available. In this case, the estimation problem corresponds to an underdetermined one. We show that the combination of regularization by correlation and some user‐specified information can be a practical method for solving the underdetermined problem. In addition, as an optimization tool for solving the problem, we develop a constrained Non‐Negative Quadratic Programming (NNQP) technique into which not only regularization but also multiple linear constraints induced by user‐specified information are easily incorporated. We test and validate our method on both synthetic and real images and present some experimental results. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 143–154, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20047
Topographic guidance of endothelial cells on silicone surfaces with micro‐ to nanogrooves: Orientation of actin filaments and focal adhesions
Authors: Uttayarat Pimpon , Toworfe George K. , Dietrich Franziska , Lelkes Peter I. , Composto Russell J.
Published: August 2005

To mimic the uniformly elongated endothelium in natural linear vessels, bovine aortic endothelial cells (BAECs) are cultured on micro‐ to nanogrooved, model poly(dimethylsiloxane) (PDMS) substrates preadsorbed with about 300 ng/cm2 of fibronectin. BAEC alignment, elongation, and projected area were investigated for channel depths of 200 nm, 500 nm, 1 μm, and 5 μm, as well as smooth surfaces. Except for the 5 μm case, the ridge and channel widths were held nearly constant about 3.5 μm. With increasing channel depth, the percentage of aligned BAECs increased by factors of 2, 2, 1.8, and 1.7 for 1, 4, 24, and 48 h. Maximum alignment, about 90%, was observed for 1 μm deep channels at 1 h. The alignment of BAECs on grooved PDMS was maintained at least until cells reached near confluence. F‐actin and vinculin at focal adhesions also aligned with channel direction. Analysis of confocal microscopy images showed that focal adhesions localized at corners and along the sidewalls of 1‐μm deep channels. In contrast, focal adhesions could not form on the bottom of the 5‐μm deep channels. Cell proliferation was similar on grooved and smooth substrates. In summary, PDMS substrates engraved with micro‐ and nanochannels provide a powerful method for investigating the interplay between topography and cell/cytoskeletal alignment. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
The effect of combined cyclic mechanical stretching and microgrooved surface topography on the behavior of fibroblasts
Authors: Loesberg W. A. , Walboomers X. F. , van Loon J. J. W. A. , Jansen J. A.
Published: August 2005

Under the influence of mechanical stress, cultured fibroblasts have a tendency to orient themselves perpendicular to the stress direction. Similar cell alignment can be induced by guiding cells along topographical clues, like microgrooves. The aim of this study was to evaluate cell behavior on microgrooved substrates, exposed to cyclic stretching. We hypothesized that cellular shape is mainly determined by topographical clues. On basis of earlier studies, a 10‐μm wide square groove, and a 40‐μm wide V‐shaped groove pattern were used. Smooth substrates served as controls. Onto all substrates fibroblasts were cultured and 1‐Hz cyclic stretching was applied (0, 4, or 8%) for 3–24 h. Cells were prepared for scanning electron microscopy, immunostaining of filamentous actin, alignment measurements, and PCR (collagen‐I, fibronectin, α1‐ and β1‐integrins). Results showed that cells aligned on all grooved surfaces, and fluorescence microscopy showed similar orientation of intracellular actin filaments. After 3 h of stretch, cellular orientation started to commence, and after 24 h the cells had aligned themselves almost entirely. Image analysis showed better orientation with increasing groove depth. Statistical testing proved that the parameters groove type, groove orientation, and time all were significant, but the variation of stretch force was not. Substrates with microgrooves perpendicular to the stretch direction elicit a better cell alignment. The expression of β1‐integrin and collagen‐I was higher in the stretched samples. In conclusion, we can maintain our hypothesis, as microgrooved topography was most effective in applying strains relative to the long axis of the cell, and only secondary effects of stretch force were present. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Crosslinked chitosan: Its physical properties and the effects of matrix stiffness on chondrocyte cell morphology and proliferation
Authors: Subramanian Anuradha , Lin Hsin‐Yi
Published: August 2005

Chitosan [β(1‐4)‐2 amino‐2‐deoxy‐D‐glucose], the natural polyaminosaccharide derived from N‐deacetylation of chitin [β(1‐4)‐2 acetamide‐2‐deoxy‐D‐glucose], has been shown to possess attractive biological and cell interactive properties. Recently chitosan and chitosan analogs have also been shown to support the growth and continued function of chondrocytes. In the present study, chitosan substrates are crosslinked with a functional diepoxide (1,4 butanediol diglycidyl ether) to alter its mechanical property, and the viability and proliferation of the canine articular chondrocytes seeded on the crosslinked surface are further assayed. Of interest is the impact of substrate stiffness on the growth and proliferation of articular canine chondrocytes. Crosslinked scaffolds were also subjected to degradation by chitosanase to examine the impact of crosslinking on enzyme‐assisted degradation. The hydrophilicity and compression modulus of the crosslinked surfaces were measured via contact‐angle measurements and compression tests, respectively. Scanning electron microscopy (SEM) and fluorescent staining were used to observe the proliferation and morphology of chondrocyte cells on noncrosslinked and crosslinked surfaces. The crosslinked chitosan was found to be nontoxic to chondrocytes and more hydrophilic. Its compression modulus and stiffness increased, which may improve the scaffold resistance to wear and in vivo shrinkage once implanted. The increased stiffness also seemed to serve as an additional mechanical stimulus to promote chondrocyte growth and proliferation. The cell morphology on crosslinked scaffolds seen by SEM and fluorescent stain was the typical chondrocytic rounded shape. The method proposed provides a nontoxic way to increase the mechanical strength of the chitosan scaffolds. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Poly(lactide)‐poly(ethylene glycol) micelles as a carrier for griseofulvin
Authors: Pierri E. , Avgoustakis K.
Published: August 2005

In this work, the feasibility to develop micelle carriers of griseofulvin based on PLA‐PEG copolymers was investigated. With the use of the dialysis method of micelle formation, the micellization behavior of a range of PLA(X)‐PEG(5) copolymers was investigated. At copolymer concentrations in the organic solvent 10–20 mg/mL, stable micelles with 100% yield could only be prepared from PLA(X)‐PEG(5) copolymers with molar composition in the range 50–70% PEG. The copolymers exhibited sufficiently low CMC to provide stable micelles in vivo. The loading capacity of PLA(4)‐PEG(5) micelles with griseofulvin was 6.5 mg of drug/1 g of copolymer. The release of griseofulvin from the PLA‐PEG micelles in vitro in phosphate‐buffered saline (PBS) was sustained over 30 days. No burst effect was observed. Analysis of the release kinetics suggested that the release was erosion‐controlled. The release profile was biphasic. Micelle degradation data in PBS indicated that the second phase of release was induced by copolymer degradation. The PLA‐PEG micelles of griseofulvin were stable in simulated gastric and intestinal fluids for a long‐enough time for oral application. Overall, the PLA‐PEG micelles have suitable properties to be considered as potential oral or topical formulations of griseofulvin, provided that the drug‐loading capacity of the micelles is sufficiently improved. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Identification of Op18/stathmin as a potential target of ASK1‐p38 MAP kinase cascade
Authors: Mizumura Kenji , Takeda Kohsuke , Hashimoto Shu , Horie Takashi , Ichijo Hidenori
Published: August 2005

Apoptosis signal‐regulating kinase 1 (ASK1) is a mitogen‐activated protein (MAP) kinase kinase kinase that activates the JNK and p38 MAP kinase cascades and has a broad range of biological activities including cell differentiation and stress‐induced apoptosis. However, effector molecules of ASK1‐MAP kinase cascades that exert such activities have not been fully identified. Here we have identified oncoprotein 18 (Op18)/stathmin as a potential target of the ASK1‐p38 cascade. By two‐dimensional electrophoresis, phosphorylation of Op18/stathmin was found to be increased upon the expression of constitutively active ASK1 (ASK1ΔN) in PC12 cells. The ASK1‐dependent increase in the phosphorylation of Op18/stathmin was attenuated by the treatment with SB203580, suggesting that p38α and/or p38β contribute to the phosphorylation of Op18/stathmin. Consistently, we found that all four isoforms of p38 directly phosphorylated Op18/stathmin primarily at serine 25 in vitro. Taken together with the quantitative RT‐PCR data indicating that p38α was the dominantly expressed isoform in PC12 cells, ASK1‐induced phosphorylation of Op18/stathmin appears to be mediated mainly through p38α in these cells. Given that the microtubule‐destabilizing activity of Op18/stathmin is regulated by its phosphorylation, the ASK1‐p38 cascade may regulate microtubule dynamics through Op18/stathmin. J. Cell. Physiol. 206: 363–370, 2006. © 2005 Wiley‐Liss, Inc.
Overexpression of hyaluronan synthases alters vascular smooth muscle cell phenotype and promotes monocyte adhesion
Authors: Wilkinson Thomas S. , Bressler Steven L. , Evanko Stephen P. , Braun Kathleen R. , Wight Thomas N.
Published: August 2005

Hyaluronan (HA) accumulates in vascular disease but its functional role is not fully understood. To investigate the impact of HA enriched extracellular matrices (ECM) on cell phenotype, arterial smooth muscle cells (ASMCs) were transduced with retroviral constructs (LXSN) encoding murine has‐1, has‐2, and has‐3. HA synthesis was significantly elevated in has transduced ASMCs. Metabolically labeled HA from has‐1 and has‐2 transduced cells was present mostly in high molecular weight (HWA) fractions (2–10 × 106 Da), whereas HA produced by has‐3 and control cells was present in lower molecular weight fractions (∼2 × 106 Da). Both has‐1 and has‐3 transduced ASMCs accumulated more pericellular HA than has‐2 transduced ASMCs. All has transduced ASMCs had attenuated growth and migration rates, and a decreased detachment response. Affinity histochemistry revealed that has‐1 transduced ASMCs accumulated the greatest amount of HA containing ECM than the other transduced ASMCs. This ECM was hyaluronidase sensitive and bound a significantly greater number of monocytes than the ECM generated by has‐2 or has‐3 transduced ASMCs. Confocal microscopy showed CD44 positive monocytes bound to hyaluronidase sensitive ECM in has‐1 transduced ASMCs. These data implicate specific has isoforms in the formation of HA enriched pro‐inflammatory ECMs. J. Cell. Physiol. 206: 378–385, 2006. © 2005 Wiley‐Liss, Inc.
Microtubule‐dependent nuclear‐cytoplasmic shuttling of Runx2
Authors: Pockwinse Shirwin M. , Rajgopal Arun , Young Daniel W. , Mujeeb Khwaja A. , Nickerson Jeffrey , Javed Amjad , Redick Sambra , Lian Jane B. , van Wijnen Andre J. , Stein Janet L. , Stein Gary S. , Doxsey Stephen J.
Published: August 2005

RUNX/AML transcription factors are critical regulators of cell growth and differentiation in multiple lineages and have been linked to human cancers including acute myelogenous leukemia (RUNX1), as well as breast (RUNX2) and gastric cancers (RUNX3). RUNX proteins are targeted to gene regulatory micro‐environments within the nucleus via a specific subnuclear targeting signal. However, the dynamics of RUNX distribution and compartmentalization between the cytoplasm and nucleus is minimally understood. Here we show by immunofluorescence microscopy that RUNX2 relocates from the nucleus to the cytoplasm when microtubules are stabilized by the chemotherapeutic agent taxol. The taxol‐dependent cytoplasmic accumulation of RUNX2 is inhibited by leptomycin B, which blocks CRM‐1 dependent nuclear export, and is not affected by the protein synthesis inhibitor cycloheximide. Using biochemical assays, we show that endogenous RUNX2 associates with stabilized microtubules in a concentration‐dependent manner and that the RUNX2 amino terminus mediates the microtubule association. In soluble fractions of cells, RUNX2 co‐immunoprecipitates α tubulin suggesting that microtubule binding involves the α/β tubulin subunits. We conclude that RUNX2 associates with microtubules and shuttles between the nucleus and the cytoplasm. We propose that nuclear‐cytoplasmic shuttling of RUNX2 may modulate its transcriptional activity, as well as its ability to interface with signal transduction pathways that are integrated at RUNX2 containing subnuclear sites. It is possible that taxol‐induced acute depletion of the nuclear levels of RUNX2 and/or other cell growth regulatory factors may represent an alternative pathway by which taxol exerts its biological effects during cancer chemotherapies. J. Cell. Physiol. 206: 354–362, 2006. © 2005 Wiley‐Liss, Inc.
Dispersal of epithelial cancer cell colonies by lysophosphatidic acid (LPA)
Authors: Jourquin Jérôme , Yang Neng , Kam Yoonseok , Guess Cherise , Quaranta Vito
Published: August 2005

We describe a model system in which cancer cell colonies disperse into single, highly migratory cells in response to lysophosphatidic acid (LPA). Though LPA is known to stimulate chemotaxis and chemokinesis, a colony dispersal effect has not been reported, to our knowledge. Cancer colony dispersal by LPA is comprised of an ordered sequence of events: (1) stimulation of membrane ruffling and formation of lamellipodia, (2) dissolution of adherens junctions, (3) single cell migration in a mesenchymal‐like morphology we term “ginkgo‐leaf.” The net result is dispersal of carcinoma cells from a compact colony. We analyzed these three steps using live‐cell imaging and computer‐assisted quantification and measured the following parameters: onset of lamellipodia formation, lamellipodia velocity, colony dispersal, trans‐epithelial resistance, migrating cell number and speed. Because hepatocyte growth factor (HGF) was described as an epithelial scatter factor, we compared it to LPA in our system and found that HGF has no epithelial colony dispersal properties and that this effect is strictly related to LPA. Given its striking similarity to tumor cell budding observed in patients, we propose that LPA‐colony dispersal may provide a cellular mechanism underlying cancer invasion and as such deserves further studies. J. Cell. Physiol. 206: 337–346, 2006. © 2005 Wiley‐Liss, Inc.
Loss of mitochondrial membrane potential is associated with increase in mitochondrial volume: Physiological role in neurones
Authors: Safiulina Dzhamilja , Veksler Vladimir , Zharkovsky Alexander , Kaasik Allen
Published: August 2005

Mitochondrial volume homeostasis is a housekeeping cellular function, thought to help regulate oxidative capacity, apoptosis, and mechanical signaling. The volume is mainly regulated by potassium flux into and out of the matrix and controlled by the electrochemical potential. Mitochondrial depolarization will therefore affect this flux but studies showing how have not been consistent, and it is unclear what mitochondrial volume changes also occur. The aim of the present study was to investigate mitochondrial volume changes in permeabilized neurons under various bioenergetic conditions using deconvolution confocal microscopy. Under control conditions, mitochondria in situ appeared rod‐shaped with mean length, surface area, and volume values of 2.29 ± 0.10 µm, 1.41 ± 0.10 µm2, and 0.062 ± 0.006 µm3, respectively (n = 42). Valinomycin, a K+‐selective ionophore, increased mitochondrial volume by 63 ± 22%, although surface area was almost unchanged because mitochondrial shape became more spherical. Pinacidil, an opener of mitochondrial ATP‐dependent channels, produced similar effects, although some mitochondria were insensitive to its action. Mitochondrial depolarization with the protonophore FCCP, or with respiratory chain inhibitors antimycin and sodium azide was associated with a considerable increase in mitochondrial volume (by 75%–140%). Effects of mitochondrial modulators were also studied in intact neurones. Tracking of single mitochondria showed that during 65 ± 2% of their time, mitochondria were motile with an average velocity of 0.19 ± 0.01 µm/s. Antimycin, azide, and FCCP induced mitochondrial swelling and significantly decreased mitochondrial motility. In the presence of pinacidil, swollen mitochondria had reduced their motility, although mitochondria with normal volume stayed motile. These data show that mitochondrial depolarization was followed by significant swelling, which, in turn, impaired mitochondrial trafficking. J. Cell. Physiol. 206: 347–353, 2006. © 2005 Wiley‐Liss, Inc.
Nuclear envelope barrier leak induced by dexamethasone
Authors: Kastrup Lilian , Oberleithner Hans , Ludwig Yvonne , Schafer Claudia , Shahin Victor
Published: August 2005

Nuclear pore complexes (NPCs) are multiprotein channels that span the nuclear envelope. They strongly limit the efficiency of gene transfection by restriction of nuclear delivery of exogenously applied therapeutic macromolecules. NPC dilation could significantly increase this efficiency. Recently, it was shown in oocytes of Xenopus laevis that NPCs dilate from about 82 to 110 nm within min after injection of the glucocorticoid analog dexamethasone (dex). In the present paper we analyzed by means of atomic force microscopy the structural details of NPC dilation and correlated them with functional changes in nuclear envelope permeability. 5–11 min after Dex injection NPC dilation was found at its maximum (∼140 nm). In addition, a yet unknown configuration, so‐called giant pore, up to 300 nm in diameter, was visualized. Giant pore formation was paralleled by an increase in nuclear envelope permeability tested by electrophysiology and confocal fluorescence microscopy. Even large macromolecules lacking any nuclear localization signal (77 kDa FITC‐dextran, molecule diameter up to 36 nm) could gain access to the nucleus. We conclude that dex transiently opens unspecific pathways for large macromolecules. Dex treatment could be potentially useful for improving the efficiency of nuclear gene transfection. J. Cell. Physiol. 206: 428–434, 2006. © 2005 Wiley‐Liss, Inc.
Etoposide, vincristine, and cyclosporin A with standard‐dose radiation therapy in newly diagnosed diffuse intrinsic brainstem gliomas: A pediatric oncology group phase I study
Authors: Greenberg Mark L. , Fisher Paul G. , Freeman Carolyn , Korones David N. , Bernstein Mark , Friedman Henry , Blaney Susan , Hershon Linda , Zhou Tianni , Chen Zhengjia , Kretschmar Cynthia
Published: August 2005

Background

Brainstem gliomas (BSGs) are resistant to all therapy. Based on their imaging characteristics, we postulated that inhibition of P‐glycoprotein (P‐gp) associated with endothelial cells of the blood‐brain barrier might enhance penetration of xenobiotic antineoplastics.

Procedure

Seven patients were enrolled in a Phase I study of etoposide, continuous infusion cyclosporine A given with and escalating doses of vincristine and concomitant standard‐dose irradiation.

Results

Six patients were entered at the first level and one at the second. Closure of the study was mandated by dose‐limiting neurotoxicity, consisting of seizures associated with white‐matter changes, and alteration of consciousness with bulbar signs. One patient had tumor necrosis at 6 weeks, suggesting some tumor effect. Median survival for the group was 11 months, and for the patients who completed more than 1 month of therapy it was 11 months.

Conclusion

This regimen proved excessively toxic. © 2005 Wiley‐Liss, Inc.
Co‐activation effect of chlorine on the physical properties of CdS thin films prepared by CBD technique for photovoltaic applications
Authors: Amanullah F. M. , Al‐Shammari A. S. , Al‐Dhafiri A. M.
Published: August 2005

A simple chemical bath deposition (CBD) technique with ultrasonication has been developed and successfully used to deposit cadmium sulfide (CdS) thin films onto glass substrates from a bath containing cadmium salt and thiourea. The structural and electrical properties of the CdS films were investigated. From the X‐ray diffraction pattern, the CdS films were found in both hexagonal and cubic phases. Electrical resistivity, carrier concentration and carrier mobility of the films have been reported. The electrical resistivity of the as‐deposited–annealed films was in the range 106–108 Ω cm and low for chlorine‐doped‐annealed films (10–2–102 Ω cm). From the Hall measurements, the films showed n‐type conductivity. All the results are presented and discussed. The results of the obtained films are promising to find application in optoelectronic devices as well as window material in heterojunction solar cell fabrication. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Superconductivity in boron‐doped homoepitaxial (001)‐oriented diamond layers
Authors: Kačmarčik J. , Marcenat C. , Cytermann C. , Ferreira da Silva A. , Ortega L. , Gustafsson F. , Marcus J. , Klein T. , Gheeraert E. , Bustarret Etienne
Published: August 2005

The crystallinity and built‐in strain of diamond epilayers grown by MPCVD with boron contents nB varying from 2 × 1020 to 2 × 1021 cm–3 as evaluated by SIMS are assessed by HR‐XR Diffraction. Both ac transport and ac susceptibility measurements show that the critical concentration for the onset of superconductivity in (001)‐oriented single crystalline films is about 5 × 1020 cm–3. This is also the critical hole concentration for the metal–non metal transition in this system, as evaluated by two types of theoretical calculations and by low temperature resistivity experiments. We report also preliminary results of point contact spectroscopy on an epilayer with a critical transition temperature Tc = 2.1 K, which yield a superconducting gap around 0.3 meV compatible with a conventional BCS‐type description of superconductivity in this system. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
QND theory of long range forces in AFM on Au(111)
Authors: Drakova D. , Doyen G.
Published: August 2005

The nature of the long range forces in atomic force microscopy (AFM) between a tungsten tip and the Au(111) surface is studied within Quantum Nano Dynamics (QND), treating many‐particle interactions and long range screening effects. A new mechanism of long range forces between a neutral tip and a metal surface is suggested due to the interaction with the image potential in the tip and the sample of a single electron localized on the Au(111) surface in front of the tip, in the presence of the AFM tip, and the image screening it provides.

magnified image

Force between a W‐tip and Au(111) – measured in AFM (circles and crosses, left‐hand axis, Ref. [1]) and calcu‐lated within QND theory (full curve, right‐hand axis).

(© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Early stages of continuous wave experiments on cavity‐polaritons
Authors: Houdré R.
Published: August 2005

This chapter presents a basics description of cavity‐polariton physics and highlights the historical context of the early stages of continuous wave experiments performed on cavity‐polaritons with M. Ilegems during the period 1992–2000. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Alignment and Assembly of Adsorbed Collagen Molecules Induced by Anisotropic Chemical Nanopatterns
Authors: Denis Frédéric A. , Pallandre Antoine , Nysten Bernard , Jonas Alain M. , Dupont‐Gillain Christine C.
Published: August 2005

Collagen, a protein widely used to control cell–material interactions, is known to self‐assemble in solution. Supramolecular structures also form on material surfaces following collagen adsorption. Herein, we report the use of anisotropic, flat, surface chemical nanopatterns, which consist of alkyl‐terminated tracks drawn in an oligo(ethylene glycol)‐terminated matrix, to direct collagen adsorption. As revealed by atomic force microscopy, the spontaneous collagen adsorption performed on such patterned substrates results in the accumulation of collagen on the hydrophobic tracks. Moreover, the width of the tracks (30–90 nm), which is much smaller than the length of the collagen molecule (≈300 nm), is the origin of preferential alignment of the molecules and of their assembly into continuous bundles of adsorbed collagen. This chemical guidance effect due to self‐confinement of proteins upon adsorption may bring novel and valuable applications, specifically in biomaterials science and cell growth control.
Real presence: contemporaneity in Bonhoeffer's Christology
Authors: Jenson Matt
Published: August 2005

Dietrich Bonhoeffer delivered his lectures on Christology in the midst of his academic career but only shortly after becoming a Christian. They thus give us a window into the mind of a theologian wrestling with fundamental questions of faith and scholarship. In particular, the theme of contemporaneity with Christ in Bonhoeffer's Christology gives proper place to the ‘Who?’ question over the ‘How?’, reveals a nuanced account of the relation of historical inquiry to the rule of faith, and offers an amplification of the Reformers' emphasis on the God who is for us.
Influence of particle characteristics on granular friction
Authors: Anthony Jennifer L. , Marone Chris
Published: August 2005

We report on laboratory experiments designed to illuminate grain‐scale deformation mechanisms within fault gouge. We vary particle size distribution, grain and surface roughness, and gouge layer thickness to better understand how grain sliding, rolling, dilation, and compaction affect the strength and stability of granular fault gouge. The experiments employed the double direct shear testing geometry and were run at room temperature, controlled humidity, and shearing rates from 0.1 to 3000 μm/s. Experiments were carried out under constant normal stress of 5 and 10 MPa and thus within a nonfracture loading regime where sliding friction for smooth, spherical particles is measurably lower than for rough, angular particles. We compare results from shear between smooth boundaries, where we hypothesize that grain boundary sliding is the dominant deformation mechanism, and roughened surfaces, where rolling and granular dilation contribute to shear deformation. We find that particle angularity and bounding surface roughness increase the frictional strength within sheared layers, indicating differences in particle reorganization due to these factors. In gouge material composed of <30% angular grains we observe repetitive stick‐slip sliding where stress drop decreases while preinstability creep increases with increasing gouge layer thickness. Our data show significant differences in stick‐slip characteristics as a function of gouge layer thickness and particle size, which we interpret in terms of the mechanics of grain bridges that support forces on the layers. We suggest that force chains exhibit qualitative differences as a function of grain angularity and bounding surface roughness.
Stratification and turbulence in subtidal channels through intertidal mudflats
Authors: Ralston David K. , Stacey Mark T.
Published: August 2005

Field observations in San Francisco Bay of subtidal channels that drain through intertidal mudflats indicate that substantial periodic stratification develops in very shallow flows with distinct asymmetries between flood and ebb conditions. The greatest variability in salinity and stratification occurs during the wet winter months. Very strong longitudinal salinity gradients develop across the intertidal zone, between salty subtidal water and fresher water draining into the marsh upstream. Tidal straining of the longitudinal gradient creates the periodic stratification, stratifying through ebbs and destratifying through floods. The stratification can be very strong in very shallow flows, with N2 > 0.1 s−2 in about 0.5 m water depth. Analysis of the data with dimensionless numbers shows that at times the stratification is strong enough to suppress turbulence and mixing. The asymmetry in stratification between ebbs and floods results in asymmetries in eddy viscosity and eddy diffusivity, with lower values during the stratified ebbs. Because of the intertidal elevation of the system, the strong longitudinal salinity gradient is regenerated each time the mudflats and marsh drain. The system approaches a tidally periodic steady state where the flow dynamics are dominated by the sharp front of salty water that advects into the intertidal zone on the rising tide and exits the system by each lower low water. The field data are supported by a numerical model with simple mudflat/channel bathymetry. Both the field and numerical work indicate that the shallow, low energy flows in mudflat channels transition between strongly stratified suppressed turbulence and relatively unstratified active turbulence each tidal cycle.
A base flow separation algorithm based on the linearized Boussinesq equation for complex hillslopes
Authors: Huyck Annelies A. O. , Pauwels Valentijn R. N. , Verhoest Niko E. C.
Published: August 2005

The separation of base flow from discharge records is an important issue in hydrology. The objective of this paper is to develop a base flow separation algorithm, based on groundwater theory, in which the shape of the aquifer is taken into account and for which the parameters can be estimated from river discharge measurements. For this purpose, an analytical solution to the linearized Boussinesq equation for realistic aquifer shapes and temporally variable recharge rates is derived. This solution is combined with a mass balance at the land surface in order to construct the base flow separation algorithm. The parameters of the base flow filter are calculated on the basis of the same analytical solution. Comparison of the results of the new algorithm to existing base flow separation methods shows the need for a physical basis for base flow filters.
Fossil bryophytes as recorders of ancient CO2 levels: Experimental evidence and a Cretaceous case study
Authors: Fletcher Benjamin J. , Beerling David J. , Brentnall Stuart J. , Royer Dana L.
Published: August 2005

Biological and geochemical CO2 proxies provide critical constraints on understanding the role of atmospheric CO2 in driving climate change during Earth history. As no single existing CO2 proxy is without its limitations, there is a clear need for new approaches to reconstructing past CO2 concentrations. Here we develop a new pre‐Quaternary CO2 proxy based on the stable carbon isotope composition (δ13C) of astomatous land plants. In a series of CO2‐controlled laboratory experiments, we show that the carbon isotope discrimination (Δ13C) of a range of bryophyte (liverwort and moss) species increases with atmospheric CO2 across the range 375 to 6000 ppm. Separate experiments establish that variations in growth temperature, water content and substrate type have minor impacts on the Δ13C of liverworts but not mosses, indicating the greater potential of liverworts to faithfully record past variations in CO2. A mechanistic model for calculating past CO2 concentrations from bryophyte Δ13C (White et al., 1994) is extended and calibrated using our experimental results. The potential for fossil liverworts to record past CO2 changes is investigated by analyzing the δ13C of specimens collected from Alexander Island, Antarctica dating to the “greenhouse” world of the mid‐Cretaceous. Our analysis and isotopic model yield mid‐Cretaceous CO2 concentrations of 1000–1400 ppm, in general agreement with independent proxy data and long‐term carbon cycle models. The exceptionally long evolutionary history of bryophytes offers the possibility of reconstructing CO2 concentrations back to the mid‐Ordovician, pre‐dating all currently used quantitative CO2 proxies.
Local climate sensitivity of the Three Gorges Dam
Authors: Miller Norman L. , Jin Jiming , Tsang Chin‐Fu
Published: August 2005

Two simulations, control and land use change, were performed for an eight week period (2 April–16 May 1990) to determine the net sensitivity of the local climate around the Three Gorges Dam. The analysis indicates that the large reservoir acts as a potential evaporating surface that decreases the surface temperature, cools the lower atmosphere, decreasing upward motion, and increasing sinking air mass. Such sinking results in low level moisture divergence, decreasing cloudiness, and increasing net downward radiation, which increases the surface temperature. However, results indicate that evaporative cooling dominates radiative warming in this initial study. The strong evaporation also supplies moisture to the atmosphere, suggesting an increase in precipitation, but the sinking moist air diverges away from the TGD region with no net change in precipitation. This numerical study represents an initial methodology for quantification of the impact of the Three Gorges Dam on the local climate and a more comprehensive, fine‐scale set of multi‐season simulations with additional observational data is needed for a more complete analysis.
Width of the North Cape Current and location of the Polar Front in the western Barents Sea
Authors: Ingvaldsen Randi B.
Published: August 2005

Earlier results have shown that stronger southwesterly winds give higher temperatures, stronger velocities and higher transports in the North Cape Current (NCaC) in the western Barents Sea. This investigation shows that the wind field causing the stronger southwesterlies also causes a wider NCaC, i.e., the NCaC becomes warmer and wider at the same time. In warm periods, the NCaC seems to be a two‐core current system, while it has only one wider core in cold periods. The reason for the fluctuations in the width of the NCaC is a non‐uniform wind field across the current. The varying width of the NCaC affects the location of the Polar Front south of Bear Island. The location of this front is not as stationary as earlier believed and in warm periods with strong wind, the front is located further upslope than in cold periods.
The impact of management development on perceptions of organizational performance in European firms
Authors: Mabey Christopher , Gooderham Paul N
Published: August 2005

Management development is generally regarded as a key element in a strategic approach to human resource management. Yet there is still little empirical evidence that it actually contributes significantly to superior firm performance, and if it does, precisely which aspects of management development policy and practice lead to these positive outcomes. The purpose of this paper is to test these relationships. Based on interviews with human resource development and line managers in 499 European firms, contextual factors like sales turnover, size and country explained some variance in perceptions of performance. However, the degree of variance explained is considerably enhanced when variables are introduced, which capture the way management development is conceived and implemented. Causal path analysis shows that a favorable strategic fit and organizational fit significantly predicts line manager perceptions of the importance given to management development, which in turn, distinguishes high‐ from low‐performing companies.
Often called for but rarely chosen: alliance research that directly studies process
Authors: Salk Jane E
Published: August 2005

Every so often, alliance scholars make cogent arguments for why the alliance field needs more process research. Rather than plea this case yet again, this paper explores why the field of alliance research continues to be overwhelmingly cross‐sectional and structural in nature. Looking at research published since the mid‐1990s, it appears that reflexive ‘calls for future process research’ crop up frequently. Even in cross‐sectional, structural research, authors evoke stories about processes, even if these processes depend on assumptions about actors and behaviors that lie outside of what is observable with their data and methods. What impedes the development of process research are norms and taken‐for‐granted routines within the mainstream scholarly community. I discuss implications of this reflexivity and how it might be challenged to rejuvenate and advance alliance research.
Faraday rotation in an electron-positron plasma containing a fraction of ions
Authors: Hall J. O. , Shukla P. K.
Published: August 2005

The Faraday rotation in a magnetized electron-positron plasma containing a fraction of ions is investigated by using a multifluid description. It is shown that the Faraday rotation for circularly polarized electromagnetic waves with frequencies much larger than the electron/positron plasma and electron gyrofrequencies is proportional to the ion number density and the magnitude of the ambient magnetic-field strength. The results are relevant for astrophysical observations and diagnostics of laboratory electron-positron-ion magnetoplasmas.
Exchange coupling in transition-metal complexes via density-functional theory: Comparison and reliability of different basis set approaches
Authors: Ruiz Eliseo , Rodríguez-Fortea Antonio , Tercero Javier , Cauchy Thomas , Massobrio Carlo
Published: August 2005

Theoretical methods based on density-functional theory with Gaussian, plane waves, and numerical basis sets were employed to evaluate the exchange coupling constants in transition-metal complexes. In the case of the numerical basis set, the effect of different computational parameters was tested. We analyzed whether and how the use of pseudopotentials affects the calculation of the exchange coupling constants. For the three different basis sets, a comparison of the exchange coupling constants and spin distributions shows that both the plane-wave and the numerical basis set approaches are accurate and reliable alternatives to the more established Gaussian basis functions.
Ground-state and vibrationally assisted tunneling in the formic acid dimer
Authors: Mil’nikov G. V. , Kühn O. , Nakamura H.
Published: August 2005

The previously developed instanton theory [G. V. Mil’nikov and H. Nakamura, J. Chem. Phys. 122, 124311 (2005)] is applied to the calculation of vibrationally assisted tunneling splitting of the deuterated formic acid dimer (DCOOH)2 with all the degrees of freedom taken into account. The ground-state tunnel splitting is determined by the density-functional theory combined with coupled cluster level of quantum chemistry to be 0.0038cm−1 which is comparable to the experimental value of 0.0029cm−1. Further, the tunnel splittings of fundamental excitations are estimated for frequencies below 300cm−1. In this energy range it is found that the excitation modes may either enhance or suppress tunneling as compared to the ground state. For the higher-frequency modes a rapid growth of the tunnel splitting is observed. At frequencies above 1000cm−1 the semiclassical solution becomes unstable and no reliable tunneling splittings can be obtained. This is in vast contrast to the adiabatic approximation to the instanton theory in which the tunnel splittings can be retrieved up to 3000cm−1. We discuss this disparity from the viewpoint of the multidimensional character of tunneling in hydrogen bonds and the adiabatic approximation is concluded to be inaccurate.
The polymerization of actin: Extent of polymerization under pressure, volume change of polymerization, and relaxation after temperature jumps
Authors: Matthews Jermey N. A. , Yim Peter B. , Jacobs Donald T. , Forbes Jeffrey G. , Peters Neçois D. , Greer Sandra C.
Published: August 2005

The protein actin can polymerize from monomeric globular G-actin to polymeric filamentary F-actin, under the regulation of thermodynamic variables such as temperature, pressure, and compositions of G-actin and salts. We present here new measurements of the extent of polymerization (ϕ) of actin under pressure (P), for rabbit skeletal muscle actin in H2O buffer in the presence of adenosine triposphate and calcium ions and at low (5–15mM) KCl concentrations. We measured ϕ using pyrene-labeled actin, as a function of time (t) and temperature (T), for samples of fixed concentrations of initial G-actin and KCl and at fixed pressure. The ϕ(T,P) measurements at equilibrium have the same form as reported previously at 1atm: low levels of polymerization at low temperatures, representing dimerization of the actin; an increase in ϕ at the polymerization temperature (Tp); a maximum in ϕ(T) above Tp with a decrease in ϕ(T) beyond the maximum, indicating a depolymerization at higher T. From ϕ(T,P) at temperatures below Tp, we estimate the change in volume for the dimerization of actin, ΔVdim, to be −307±10ml∕mol at 279K. The change of Tp with pressure dTp∕dP=(0.3015±0.0009)K∕MPa=(30.15±0.09)mK∕atm. The ϕ(T,P) data at higher T indicate the change in volume on propagation, ΔVprop, to be +401±48ml∕mol at 301K. The ϕ(t) measurements yield initial relaxation times rp(T) that reflect the behavior of ϕ(T) and support the presence of a depolymerization temperature. We also measured the density of polymerizing actin with a vibrating tube density meter, the results of which confirm that the data from this instrument are affected by viscosity changes and can be erroneous.
Fundamentals of micromechanical thermoelectric sensors
Authors: Dürig U.
Published: August 2005

The thermal and electrical properties of a thin heater strip made of silicon, consisting of a low-doped electrical resistor connected to highly doped long legs, are discussed based on analytical models for the heat and the electrical current transport. Such heater strips are used, for example, as sensitive position and height sensors in local-probe storage applications. The aim of the paper is to provide a thorough understanding of the important physical mechanisms and scaling laws, and thus to establish a solid basis for the directed engineering of such sensors. In particular, the dynamic response is treated in full generality, including the intricate electrothermal coupling arising from the highly temperature-dependent resistivity of the Si heater element.
dc modulation in field-effect transistors operating under microwave irradiation for quantum readout
Authors: Ferrari Giorgio , Fumagalli Laura , Sampietro Marco , Prati Enrico , Fanciulli Marco
Published: August 2005

With a view to using microwaves to excite the single-spin resonance of an electron trapped in a defect at the Si∕SiO2 interface of a metal-oxide-semiconductor field-effect transistor (MOSFET), we report on the experimental evidence for a stationary current in such devices operated under microwave radiation. The stationary current is examined as a function of the microwave power and of the operating voltage of the MOSFET. The transistor behavior is reproduced by a model exploiting the nonlinearity of the MOSFET channel resistance as a component of the circuit coupled with the electromagnetic field. We conclude that, in operating a MOSFET under microwaves, one has to pay attention to the generation of spurious stationary currents that may alter the likelihood to observe spin-dependent phenomena in the random telegraph signal observed in a MOSFET.
Activation and protonation of dinitrogen at the FeMo cofactor of nitrogenase
Authors: Kästner Johannes , Hemmen Sascha , Blöchl Peter E.
Published: August 2005

The protonation of N2 bound to the active center of nitrogenase has been investigated using state-of-the-art density-functional theory calculations. Dinitrogen in the bridging mode is activated by forming two bonds to Fe sites, which results in a reduction of the energy for the first hydrogen transfer by 123kJ∕mol. The axial binding mode with open sulfur bridge is less reactive by 30kJ∕mol and the energetic ordering of the axial and bridged binding modes is reversed in favor of the bridging dinitrogen during the first protonation. Protonation of the central ligand is thermodynamically favorable but kinetically hindered. If the central ligand is protonated, the proton is transferred to dinitrogen following the second protonation. Protonation of dinitrogen at the Mo site does not lead to low-energy intermediates.
Influence of ZrO2 addition on the microstructure and discharge properties of Mg–Zr–O protective layers in alternating current plasma display panels
Authors: Guo Bingang , Liu Chunliang , Song Zhongxiao , Liu Liu , Fan Yufeng , Xia Xing , Fan Duowang
Published: August 2005

Mg–Zr–O protective layers for alternating current plasma display panels were deposited by e-beam evaporation. The effect of the ZrO2 addition on both the discharge properties [firing voltage Vf, minimum sustaining voltage Vs, and memory coefficient (MC)] and the microstructure of deposited Mg–Zr–O films were investigated. The results show that the film microstructure changes and the electron emission enhancement due to the ZrO2 addition are the main reasons for the improvements of the discharge properties of Mg–Zr–O films. A small amount of Zr solution in MgO under its solid solubility can effectively increase the outer-shell valence electron emission yield so as to decrease Vf and Vs compared with using a pure MgO protective layer. The ZrO2∕(MgO+ZrO2) ratio has a great effect on the film surface conditions. Proper surface morphologies make a good contribution to obtain large MC in accordance with lower firing voltage.