bluuebunny/crossref_metadata_2025 huggingface dataset:
Compartmentalization in membrane rafts defines a pool of N‐cadherin associated with catenins and not engaged in cell–cell junctions in melanoma cells
Authors: Rossier‐Pansier Laetitia , Baruthio Frédérique , Rüegg Curzio , Mariotti Agnese
Published: July 2007

Melanoma progression is associated with changes in adhesion receptor expression, in particular upregulation of N‐cadherin which promotes melanoma cell survival and invasion. Plasma membrane lipid rafts contribute to the compartmentalization of signaling complexes thereby regulating their function, but how they may affect the properties of adhesion molecules remains elusive. In this study, we addressed the question whether lipid rafts in melanoma cells may contribute to the compartmentalization of N‐cadherin. We show that a fraction of N‐cadherin in a complex with catenins is associated with cholesterol/sphingolipid‐rich membrane microdomains in aggressive melanoma cells in vitro and experimental melanomas in vivo. Partitioning of N‐cadherin in membrane rafts is not modulated by growth factors and signaling pathways relevant to melanoma progression, is not necessary for cell–cell junctions' establishment or maintenance, and is not affected by cell–cell junctions' and actin cytoskeleton disruption. These results reveal that two independent pools of N‐cadherin exist on melanoma cell surface: one pool is independent of lipid rafts and is engaged in cell–cell junctions, while a second pool is localized in membrane rafts and does not participate in cell–cell adhesions. Targeting to membrane rafts may represent a previously unrecognized mechanism regulating N‐cadherin function in melanoma cells. J. Cell. Biochem. 103: 957–971, 2008. © 2007 Wiley‐Liss, Inc.
Raf kinase inhibitor protein positively regulates cell–substratum adhesion while negatively regulating cell–cell adhesion
Authors: Mc Henry Kevin T. , Montesano Roberto , Zhu Shoutian , Beshir Anwar B. , Tang Hui‐Hui , Yeung Kam C. , Fenteany Gabriel
Published: July 2007

Raf kinase inhibitor protein (RKIP) regulates a number of cellular processes, including cell migration. Exploring the role of RKIP in cell adhesion, we found that overexpression of RKIP in Madin‐Darby canine kidney (MDCK) epithelial cells increases adhesion to the substratum, while decreasing adhesion of the cells to one another. The level of the adherens junction protein E‐cadherin declines profoundly, and there is loss of normal localization of the tight junction protein ZO‐1, while expression of the cell–substratum adhesion protein β1 integrin dramatically increases. The cells also display increased adhesion and spreading on multiple substrata, including collagen, gelatin, fibronectin and laminin. In three‐dimensional culture, RKIP overexpression leads to marked cell elongation and extension of long membrane protrusions into the surrounding matrix, and the cells do not form hollow cysts. RKIP‐overexpressing cells generate considerably more contractile traction force than do control cells. In contrast, RNA interference‐based silencing of RKIP expression results in decreased cell–substratum adhesion in both MDCK and MCF7 human breast adenocarcinoma cells. Treatment of MDCK and MCF7 cells with locostatin, a direct inhibitor of RKIP and cell migration, also reduces cell–substratum adhesion. Silencing of RKIP expression in MCF7 cells leads to a reduction in the rate of wound closure in a scratch‐wound assay, although not as pronounced as that previously reported for RKIP‐knockdown MDCK cells. These results suggest that RKIP has important roles in the regulation of cell adhesion, positively controlling cell–substratum adhesion while negatively controlling cell–cell adhesion, and underscore the complex functions of RKIP in cell physiology. J. Cell. Biochem. 103: 972–985, 2008. © 2007 Wiley‐Liss, Inc.
Transcription factor access to promoter elements
Authors: Morse Randall H.
Published: July 2007

In eukaryotes, transcription factors, including both gene‐specific activators and general transcription factors (GTFs), operate in a chromatin milieu. Here, we review evidence from gene‐specific and genome‐wide studies indicating that chromatin presents an environment that is typically permissive for activator binding, conditional for pre‐initiation complex (PIC) formation, and inhibitory for productive PIC assembly within coding sequences. We also discuss the role of nucleosome dynamics in facilitating access to transcription factors (TFs) in vivo and indicate some of the principal questions raised by recent findings. J. Cell. Biochem. 102: 560–570, 2007. © 2007 Wiley‐Liss, Inc.
Foods design and ingredients for satiety: Promises and proof
Authors: Mela David J.
Published: July 2007

There is increasing interest in foods and ingredients claiming benefits for satiety and food intake control. Approaches to food product development include use of ‘traditional’ nutrients and reduced‐energy formulations, and possible ‘functional’ ingredients, for which the level and quality of supporting evidence varies. The underlying scientific principles and some examples are briefly reviewed here. Careful attention needs to be given to the quality of science and interpretations being used to develop and substantiate claims, especially for new innovations.
Analysis of fatty acids by mass spectrometry in the selected ion monitoring mode
Authors: Vetter Walter , Thurnhofer Saskia
Published: July 2007

GC/EI‐MS‐SIM (gas chromatography / electron ionisation – mass spectrometry with selected ion monitoring) can be easily applied to the determination of fatty acids as methyl esters (FAME). SIM masses should have a high relative abundance and for this reason we suggest m/z 74 and m/z 87 for saturated and monoenoic fatty acids as well as m/z 79 and m/z 81 for FAME with more than one double bond. The relevance and ratio of these fragment ions along with GC retention times enables a good identification of a FAME represented by a peak detected in the chromatograms. Compared to GC with a flame ionisation detector, this simple method provides a higher selectivity and better sensitivity. It also offers the possibilities of using a wide range of internal standards which enables the individual quantification of FAME instead of the determination of their contributions to the fatty acid pattern.
Corrosion resistance of hot‐dipped zinc and zinc alloy coated sheet steels under offshore atmospheric environment
Authors: Li Y. , Liu J. , Li Y. , Chu S.
Published: July 2007

The application of hot‐dipped zinc and zinc‐aluminum alloy coatings were introduced. Exposure tests of the steels with these coatings were conducted in the offshore atmosphere in Qingdao and Xiamen for 12 years separately. Effects of the coating thickness, alloy composition and atmospheric environment on the corrosion performance were studied. Results of the onsite exposure tests were compared with the results of a previous indoor salt spray accelerated corrosion tests. The study supports that zinc‐aluminum alloy coatings are useful in providing better corrosion resistance and can be further developed for future applications.
Failure of package boilers in a petrochemical plant
Authors: Gaur B.
Published: July 2007

The paper deals with the failure investigation of furnace‐tubes of a few medium capacity (86 T/H steam generation) package boilers in a petrochemical plant. As a consequence of damage, the boilers required major tube‐repair on urgent basis, and complete tube replacement within a period of two years. Failure of different boilers took place at varying service durations, though all of them had the same design and criteria of operation. The study included metallurgical characterization of the failed components; analysis of operation and process (historical) data; review of inspection and maintenance records; evaluation of design and water‐treatment practices; etc. As a result, water‐side corrosion was attributed to be the cause of tube‐leakage via general and localized corrosion mechanism, while, no metallurgical defects and changes were noticed in the failed components. On the other hand, process and operational abnormalities were diagnosed as the root cause of trouble initiation and propagation. In order to avoid the recurrence of such failures, various preventive measures (inspection, maintenance, operation and process) have been recommended.
Effects of Tafel slope, exchange current density and electrode potential on the corrosion of steel in concrete
Authors: Ge J. , Isgor O.B.
Published: July 2007

A parametric study is carried out to investigate the effect of variations in anodic and cathodic Tafel slopes, exchange current densities and electrode potentials on the rate of steel corrosion in concrete. The main goal of this investigation is to identify the parameters that have significant influence on steel corrosion rate. Since there is a degree of uncertainty associated with the selection of these parameters, particularly during modelling exercises, it is intended that the results of this study will provide valuable information to engineers and researchers who simulate steel corrosion in concrete. To achieve this goal, the effect of a parameter on the corrosion rate of steel is studied while all other parameters are kept constant at a predefined base case. For each parameter, two extreme cases of anode‐to‐cathode ratio are studied. The investigation revealed that the variations in the anodic electrode potential have the greatest impact on the corrosion rate, followed by the variations in the cathodic Tafel slope.
Anti‐tarnish treatment of brass for coinage
Authors: Wang P. , Liang C. H. , Zhang J.
Published: July 2007

The anti‐tarnish film was formed on brass for coinage by 1‐phenyl‐5‐mercaptotetrazole (PMTA), which was studied by accelerated corrosion test (metallic coatings‐thioacetamide corrosion test), polarization curves and electrochemical impedance spectroscopy (EIS) in synthetic sweat solution. The accelerated corrosion test showed that PMTA exhibited better anti‐tarnish performance on brass than that of traditional anti‐tarnish agent benzotriazole (BTA). The polarization measurements showed that PMTA could be classified as a mixed inhibitor for it could restrain both anodic and cathodic reactions. EIS measurements indicated that the inhibition efficiency of PMTA on brass was over 98.4% in synthetic sweat solution. All these results showed that PMTA was an excellent anti‐tarnish agent of the brass for coinage, the optimum treating conditions of which were 0.5 gL−1, pH = 3, 55°C–85°C, 7 min.
SCC of X‐52 and X‐60 weldements in diluted NaHCO3 solutions with chloride and sulfate ions
Authors: Gonzalez‐Rodriguez J.G. , Espinosa‐Medina M.A. , Angeles‐Chavez C. , Zeferino‐Rodriguez T.
Published: July 2007

Stress corrosion cracking tests were performed in both X‐52 and X‐60 weldments in sodium bicarbonate (NaHCO3) solutions at 50°C using the Slow Strain Rate Testing (SSRT) technique. Solution concentrations varied between 0.1 to 0.0001 M, and to simulate the NS‐4 solution, chloride (Cl−) and/or sulfate ($\rm SO_{4}^{2-}$) ions were added to the 0.01 M solution. Tests were complemented with hydrogen permeation measurements and polarization curves. It was found that the corrosion rate, taken as the corrosion current, Icorr, was maximum in 0.01 M NaHCO3 and with additions of $\rm SO_{4}^{2-}$ ions. Higher or lower solution concentrations or additions of Cl− alone decreased the corrosion rate of the weldment. The SSC susceptibility, measured as the percentage reduction in area, was maximum in 0.01M NaHCO3. Higher or lower solution concentrations of additions of Cl− or $\rm SO_{4}^{2-}$ decreased the SCC susceptibility of the weldment. The amount of hydrogen uptake for the weldment was also highest in 0.01 M NaHCO3 solution, but it was minimum with the addition of Cl− or $\rm SO_{4}^{2-}$ ions. Thus, the most likely mechanism for the cracking susceptibility of X‐52 and X‐60 weldments in diluted NaHCO3 solutions seems to be hydrogen‐assisted anodic dissolution.
Degradation of Poly(methyl methacrylate) Model Compounds at Constant Elevated Temperature Studied via High Resolution Electrospray Ionization Mass Spectrometry (ESI‐MS)
Authors: Bennet Francesca , Lovestead Tara M. , Barker Philip J. , Davis Thomas P. , Stenzel Martina H. , Barner‐Kowollik Christopher
Published: July 2007

The products of the thermal degradation at 95 °C over 10 months of ω‐saturated and non‐saturated poly(methyl methacrylate) (pMMA) model compounds were identified with high accuracy via quadrupole ion trap and quadrupole ion trap‐time of flight (Q‐ToF) mass spectrometry. Analysis of the samples taken via these techniques indicated that degradation of vinyl terminated pMMA proceeds via the incorporation of oxygen via the formation of ethylene oxide type end groups, which subsequently rearrange under the expulsion of formaldehyde and 2‐oxo‐propionic acid methyl ester. The corresponding saturated model compounds were demonstrated to be stable over the same time period. The present findings highlight for the first time that poly(methyl methacrylate) degradation does not necessarily and exclusively proceed via radical intermediates.

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Morphological Analysis of Telechelic Ureidopyrimidone Functional Hydrogen Bonding Linear and Star‐Shaped Poly(ethylene‐co‐propylene)s
Authors: Mather Brian D. , Elkins Casey L. , Beyer Frederick L. , Long Timothy E.
Published: July 2007

Ureidopyrimidone (UPy) end‐functionalized linear and star‐shaped poly(ethylene‐co‐propylene)s (hydrogenated polyisoprene) with molecular weights between 12K and 90K and narrow molecular weight distributions (PDI = $\overline M _{\rm w} /\overline M _{{\rm n},}$ < 1.10) were studied with SAXS and AFM. These hydrogen bond end‐functionalized polymers (0.45–1.14 mol.‐% UPy end‐groups) unexpectedly exhibited microphase separated domains with interdomain spacings of approximately 10–15 nm suggesting a solid‐state clustering of the hydrogen bonding end‐groups beyond simple dimerization. The interdomain spacings that were obtained from SAXS measurements systematically increased with molecular weight and decreased for monofunctional oligomers relative to telechelic analogs of the identical molecular weight. Variable temperature AFM measurements confirmed the presence of microphase separation at the surface for the star‐shaped UPy end‐functional poly(ethylene‐co‐propylene) and revealed a decrease in phase contrast upon heating to 130 °C with retention of the microphase separated texture.

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Non‐price rigidity and cost of adjustment
Authors: Müller Georg , Bergen Mark , Dutta Shantanu , Levy Daniel
Published: July 2007

There has been increasing interest in understanding how firms undertake non‐price adjustment activities, especially in situations where prices may be rigid despite changes in market conditions. Using scanner price data for over 4500 different food products from a large US supermarket chain, we document periods of rigidity in product additions and deletions: new products are less likely to be introduced, and existing products are less likely to be discontinued during holiday periods than throughout the rest of the year. We argue that this is due to higher costs of undertaking these kinds of product assortment activities during holiday periods. We discuss how this relates to the exiting literature on non‐price adjustment and price rigidity. Copyright © 2007 John Wiley & Sons, Ltd.
Search for new antagonist ligands for adenosine receptors from QSAR point of view. How close are we?
Authors: González Maykel Pérez , Terán Carmen , Teijeira Marta
Published: July 2007

In view of the large libraries of nucleoside analogues that are now being handled in organic synthesis, the identification of drug biological activity is advisable prior to synthesis and this can be achieved by employing predictive biological property methods. In this sense, Quantitative Structure–Activity Relationships (QSAR) or docking approaches have emerged as promising tools. Although a large number ofin silicoapproaches have been described in the literature for the prediction of different biological activities, the use of QSAR applications to develop adenosine receptor (AR) antagonists is not common as for the case of the antibiotics and anticancer compounds for instance. The intention of this review is to summarize the present knowledge concerning computational predictions of new molecules as adenosine receptor antagonists. © 2007 Wiley‐Periodicals, Inc. Med Res Rev, 28, No. 3, 329–371, 2008
Mediated electron transfer from lithium investigated voltammetrically in tetrahydrofuran: why are some mediators more effective reducing reagents than others?
Authors: Wood Natasha C. L. , Paddon Christopher A. , Bhatti Farrah L. , Donohoe Timothy J. , Compton Richard G.
Published: July 2007

A study of a range of aromatic molecules is investigated electrochemically to determine what makes an effective reducing mediator. With the aim of developing a better understanding of electron transfers (ETs) mediated from lithium in functional group reduction, a series of single ET reactions are reported in this paper. Typical reaction conditions involved the use of aromatic mediators such as naphthalene, anthracene, 4,4′‐di‐tert‐butyl‐1,1′‐biphenyl (DBB) with lithium metal in tetrahydrofuran (THF) at −78 °C. The results of these experiments showed that some mediators were more effective reducing reagents than others. Cryoelectrochemical procedures are used to mimic the conditions of the SET reactions in order to investigate the exact nature and role of the mediator formed upon ET. It is demonstrated that electro‐generated and stabilized radical anions of anthracene at −78 °C mediate the reduction of organic substrates, whereas the more reactive dianion is quickly protonated and therefore unable to act as an ET reagent; direct electrochemical reduction of the sulfide, phenyl 3‐phenylpropylsulfide (RSPh) gives the thiol, thiophenol, and propyl benzene whereas mediated reduction gives the dimer, diphenyl disulfide and propyl benzene. The possibility to selectively reduce a substrate with either a single electron or with two electrons is possible by using either the radical anion (mediated) or via the direct electroreduction. DBB and naphthalene (both single electron accepting species only) have been found to be the most effective reducing reagents in this study. Anthracene and other two‐electron accepting species only showed effective reducing ability when a stoichiometric amount of lithium was used therefore preventing the ‘over‐reduction’ to the dianion. Copyright © 2007 John Wiley & Sons, Ltd.
Nucleobases modified azo‐polysiloxanes, materials with potential application in biomolecules nanomanipulation
Authors: Hurduc Nicolae , Enea Ramona , Scutaru Dan , Sacarescu Liviu , Donose Bogdan C. , Nguyen Anh V.
Published: July 2007

Here we show the possibility to obtain azopolysiloxanes modified with nucleobases (adenine and thymine) with potential application in immobilization and nanomanipulation of biomolecules. We propose a photofluidization mechanism based on the concept of the conformational instability, which can explain the presence of the fluid state below the glass transition. The azopolymers were characterized by 1H NMR, GPC, DSC, DTG, UV spectroscopy, AFM analysis, and molecular simulations. Depending on the type of nucleobase used, the surface of the azopolysiloxane film can be structured in different ways under UV irradiation. Photoisomerization studies in solid state were carried out to demonstrate the influence of the operational conditions (presence or absence of natural visible light) on the polymeric film UV response. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4240–4248, 2007
Nanocomposites through copolymerization of a polyhedral oligomeric silsesquioxane and methyl methacrylate
Authors: Amir Noa , Levina Anastasia , Silverstein Michael S.
Published: July 2007

The mechanical properties and thermal stability of polymers can be enhanced through the formation of nanocomposites. Nanocomposites consisting of hybrid copolymers of methacrylcyclohexyl polyhedral oligomeric silsesquioxane (POSS‐1) and methyl methacrylate (MMA) with up to 92 wt % (51 mol %) POSS‐1 and with superior thermal properties were synthesized using solution polymerization. The POSS‐1 contents of the copolymers were similar to or slightly higher than those in the feeds, the polydispersity indices were relatively low, and the degree of polymerization decreased with increasing POSS‐1 content. POSS‐1 enhanced the thermal stability, increasing the degradation temperature, reducing the mass loss, and preventing PMMA‐like degradation from propagating along the chain. The mass loss was reduced in a high POSS‐1 content copolymer since the polymerization of POSS‐1 with itself reduced sublimation. Exposure to 450 °C produced cyclohexyl‐POSS‐like remnants in the POSS‐1 monomer and in all the copolymers. The degradation of these remnants, for the copolymers and for the POSS‐1 monomer, yielded 75% SiO2 and an oxidized carbonaceous residue. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4264–4275, 2007
Synthesis, characterization, and crosslinking of methacrylate‐telechelic PDMAAm‐b‐PDMS‐b‐PDMAAm copolymers
Authors: Karunakaran Radhakrishnan , Kennedy Joseph P.
Published: July 2007

The synthesis and molecular characterization of a new amphiphilic conetwork (APCN) designed for silicone hydrogel use is described. The synthesis strategy, outlined in Scheme 1, calls for the preparation, by the RAFT technique, of a new methacrylate‐telechelic amphiphilic pentablock, MA‐PHEA‐b‐PDMAAM‐b‐PDMS‐b‐PDMAAm‐b‐PHEA‐MA, and its crosslinking to the target APCN. The sketch shows the architecture of the APCN (dotted lines, PDMAAm; solid lines, PDMS; clusters, MA‐based crosslinking sites; see Fig. 3). All six synthesis steps proceed smoothly and efficiently, and the products are optically clear, colorless membranes exhibiting properties appropriate for ophthalmic use. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4284–4290, 2007
Remote Plasma Deposited Silicon Dioxide‐Like Film Densification by Means of RF Substrate Biasing: Film Chemistry and Morphology
Authors: Milella Antonella , Creatore Mariadriana , Blauw Michiel A. , van de Sanden Marius C. M.
Published: July 2007

Silicon dioxide‐like films were deposited from a mixture of O2/hexamethyldisiloxane injected in an Ar‐fed expanding thermal plasma. In order to increase the film density, a radiofrequency (rf, 13.56 MHz) external substrate biasing was applied during deposition, thus delivering ion bombardment during film growth. Fourier transform infrared spectroscopy shows that the film densification at increasing substrate bias occurs via condensation of silanol groups to form SiOSi bridges, accompanied by a decrease of the disorder in the film network. Ion bombardment leads also to the smoothening of film surface as quantified by atomic force microscopy measurements, which point out to a decrease in film root mean square roughness by as much as 80% (0.19 nm).

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Twenty Years of Hakone Symposia: From Basic Plasma Chemistry to Billion Dollar Markets
Authors: Kogelschatz Ulrich
Published: July 2007

The progress of atmospheric‐pressure non‐thermal plasma technology since the first Hakone symposium in 1987, later referred to as Hakone I, is summarized. Advances in the fundamental understanding of the discharge physics of corona discharges and of dielectric barrier discharges led to a number of technical developments that resulted in improved industrial processes and novel products including excimer‐based ultraviolet sources and fluorescent lamps, and flat large‐area plasma display panels using Xe vacuum ultraviolet radiation. The newly established markets surpass the original market of ozone generators by two orders of magnitude. Recent research activities devoted to microcavity plasma devices address an entirely new realm of discharge physics with fascinating new applications.

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Ensemble averaged coherent state path integral for disordered bosons with a repulsive interaction (Derivation of mean field equations)
Authors: Mieck B.
Published: July 2007

We consider bosonic atoms with a repulsive contact interaction in a trap potential for a Bose‐Einstein condensation (BEC) and additionally include a random potential. The ensemble averages for two models of static (I) and dynamic (II) disorder are performed and investigated in parallel. The bosonic many body systems of the two disorder models are represented by coherent state path integralson the Keldysh time contour which allow exact ensemble averages for zero and finite temperatures. These ensemble averages of coherent state path integrals therefore present alternatives to replica field theories or super‐symmetric averaging techniques. Hubbard‐Stratonovich transformations (HST) lead to two corresponding self‐energies for the hermitian repulsive interaction and for the non‐hermitian disorder‐interaction. The self‐energy of the repulsive interaction is absorbed by a shift into the disorder‐self‐energy which comprises as an element of a larger symplectic Lie algebrasp(4M) the self‐energy of the repulsive interaction as a subalgebra (which is equivalent to the direct product ofM×sp(2); ‘M’ is the number of discrete time intervals of the disorder‐self‐energy in the generating function). After removal of the remaining Gaussian integral for the self‐energy of the repulsive interaction, the first order variations of the coherent state path integrals

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result in the exact mean field or saddle point equations, solely depending on the disorder‐self‐energy matrix. These equations can be solved by continued fractions and are reminiscent to the `Nambu‐Gorkov' Green function formalism in superconductivity because anomalous terms or pair condensates of the bosonic atoms are also included into the selfenergies. The derived mean field equations of the models with static (I) and dynamic (II) disorder are particularly applicable for BEC ind= 3 spatial dimensions because of the singularity of the density of states at vanishing wavevector. However, one usually starts out from restricted applicability of the mean field approach ford= 2; therefore, it is also pointed out that one should consider different HST's ind= 2 spatial dimensions with the block diagonal densities as ‘hinge’ functions and that one has to introduce a coset decompositionSp(4M)\U(2M) into densities and anomalous terms of the total disorder‐self‐energysp(4M) for deriving a nonlinear sigma model.
Misfit dislocations in highly mismatched oxide interfaces, an X‐ray diffraction study
Authors: Conchon F. , Boulle A. , Guinebretière R.
Published: July 2007

We present here a detailed study describing the strain relaxation mechanisms occurring in the highly mismatched ZrO2/MgO system. Especially, we show using reciprocal space mapping that the ZrO2islands epitaxially grown on the MgO substrate are fully relaxed implying the formation of misfit dislocations at the interface. Furthermore, an analysis of transverse scans performed through symmetrical ZrO2reflections for several azimuthal positions of the sample lets us conclude that dislocations form a square network parallel to ZrO2cell axes. Finally, an accurate analysis of the diffraction data evidences the existence of two subsets of misfit dislocations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐temperature induced nano‐crystal formation in ion beam‐induced amorphous silicon ripples
Authors: Grenzer J. , Mücklich A. , Grigorian S. , Pietsch U. , Datta D. P. , Chini T. K. , Hazra S. , Sanyal M. K.
Published: July 2007

We report on in‐situ investigations of a recrystallization process of amorphous and damaged crystalline parts generated during ion‐beam induced rippling on a Si(100) surface. The ripple structure was created by 60 keV 40Ar+ irradiation with a dose of ∼5 × 1017 ions/cm2 at ion incident angle of 60° with respect to the surface normal. At this dose the ripples have an average spatial periodicity of about 715 nm and surface undulations with an amplitude of about 40 nm. Structure and morphology of ripples were studied by two types of X‐ray scattering (grazing incidence diffraction and amorphous scattering) methods, transmission electron microscopy and atomic force microscopy. X‐ray grazing‐incidence amorphous scattering pattern were recorded in‐situ for a temperature range from 250 to 750 °C. Up to about 500 °C mainly we found a single broad scattering maximum corresponding to the Si(111) inter‐planar distances. At higher temperature these peaks become sharp and intense indicating the onset of a re‐crystallization process in the amorphous top layer.

Two processes were found, a formation of crystalline islands on top of the former amorphous surface ripples and a growth of polycrystalline twins close to the former amorphous‐crystalline interface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First order phase transition in MnAs nanodisks
Authors: Jenichen B. , Kaganer V. M. , Takagaki Y. , Herrmann C. , Ploog K. H. , Dudzik E. , Feyerherm R.
Published: July 2007

The first order phase transition between ferromagnetic α‐MnAs and paramagnetic β‐MnAs in nanoscale disks etched out of an epitaxial MnAs film on GaAs(001) is studied by means of X‐ray diffraction and magnetic force microscopy. The temperature hysteresis loop is observed to be expanded with decreasing disk size. The hysteresis is absent in the original continuous epitaxial film from which the disks are fabricated. The hysteresis is explained as a competition between the energy gain due to the phase transition and the energy loss due to the elastic strain. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase contrast X‐ray imaging of large samples using an incoherent laboratory source
Authors: Kottler C. , Pfeiffer F. , Bunk O. , Grünzweig C. , Bruder J. , Kaufmann R. , Tlustos L. , Walt H. , Briod I. , Weitkamp T. , David C.
Published: July 2007

An interferometric method to record quantitative X‐ray phase contrast images has been developed that can be used at polychromatic and incoherent X‐ray sources such as laboratory tubes. With respect to previously presented results, in this work we report on recent developments and results that have been achieved in view of potential future applications such as in medicine or biology. In particular, due to improvements in the fabrication process large area diffraction gratings with high aspect ratio were achieved. Thereby, the field of view of the interferometer has been drastically increased to 64 × 64 mm2 and the design value of the photon energy for the gratings could be increased up to 28 keV. Moreover, the use of a Medipix2 single photon‐counting pixel detector shows a considerable improvement in image quality and sensitivity over the integrating detector used so far. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐resolution X‐ray diffraction study of CZ‐grown GaAsP crystals
Authors: Kowalski G. , Gronkowski J. , Czyżak A. , Słupiński T. , Borowski J.
Published: July 2007

We report results of X‐ray investigations of tellurium‐doped GaAs1–x Px (with 0.07 ≤ x ≤ 0.20) single crystals, conducted in order to support finding proper growth parameters which would yield a material of sufficient homogeneity of the lattice parameter for prospective applications. Our samples were studied using high‐resolution diffractometry which allowed to obtain both rocking curves and reciprocal space maps of the diffracted intensity, as well as using plane‐wave topography in the reflection mode. Weak reflections were also used to study the influence of Te atoms on the compound lattice. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐plane lattice parameter determination of Zn:LiNbO3 thin films epitaxially grown on x‐cut LiNbO3 substrates using X‐ray diffraction methods
Authors: Kräußlich J. , Dubs C. , Lorenz A. , Tünnermann A.
Published: July 2007

As a precursor material for electrooptical applications in the integrated optics, nominal pure as well as Zn‐doped stoichiometric LiNbO3 thin films of a few µm thickness were grown by liquid phase epitaxy on congruent LiNbO3 substrates. The crystalline perfection and lattice parameters of the epitaxially grown films were investigated by means of high‐resolution X‐ray diffraction methods. The symmetric θ /2θ ‐diffractograms show a lattice parameter increase perpendicular to the sample surface (Δd /d)⊥ up to 10–3 with increasing Zn content. X‐ray diffraction reciprocal space measurements taken up with asymmetric reflections are well suited to determine the in‐plane lattice parameters of the grown films. Despite different Zn contents, the Zn:LiNbO3 thin films reveal a distinctly pseudomorphous growth. Using the generalized Hooke's law in matrix way of writing and taking the measured values into account, the relaxed lattice parameters of the grown films as well as the in‐plane strain and tension components have been numerically calculated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observation of interference fringes due to lattice distortion by resonant scattering X‐ray topography
Authors: Negishi Riichirou , Fukamachi Tomoe , Yoshizawa Masami , Hirano Keiichi , Kawamura Takaaki
Published: July 2007

The interference fringe caused by lattice distortion around a defect is observed in the resonant scattering X‐ray topography for the GaAs 200 reflection in the Laue case. The amplitude of the fringe can be maximized when the Fourier transform of the imaginary part of X‐ray polarizability χhi is zero. The fringe position relative to the defect shifts when the incident angle is varied, and the fringe spacing changes as a function of the distance from the defect. A kinematical image can be distinguished from a dynamical one by observing the image position when the incident angle is varied in the case of χhi = 0. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of SR thermal load studied by FEA
Authors: Áč V. , Korytár D.
Published: July 2007

This work deals with analysis of the thermal effects and inherent mechanical deformations under absorption of the X‐ray beam heat. The work is motivated by recent research concentrated on the development of optics for high‐flux synchrotron radiation sources. We present the analyses of the static thermal load effects on the surface deformation field for a monocrystalline silicon target, which is the basic material for crystal X‐ray optics. The surface and bulk thermal load induces the gradient of temperature and mechanical deformations of the target that are affecting the reflection and diffraction properties of the target. The paper presents the finite‐element analyses (FEA) and simulation results of mechanical deformation of flat and slotted silicon targets. The hints for improved target geometry and physical limits for an actual cooling system can be obtained from the presented analyses. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gerhard Borrmann (1908–2006) and Gerhard Hildebrandt (1922–2005): their life stories and their contribution to the revival of dynamical theory in the 1950's
Authors: Authier A. , Klapper H.
Published: July 2007

G. Borrmann and his former student and co‐worker G. Hildebrandt passed way a few months ago. Both have given major contributions to the development of the dynamical theory of diffraction and to X‐ray imaging topography. Their career and their scientific achievements are reviewed briefly, with emphasis on Borrmann's very early work (Kossel lines, the discovery of anomalous absorption and of the Borrmann fan). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of stress distribution in III–V single crystal layers for heterogeneous integration applications
Authors: Jackson M. , Goorsky M. S. , Noori A. , Hayashi S. , Sandhu R. , Poust B. , Chang‐Chien P. , Gutierrez‐Aitken A. , Tsai R.
Published: July 2007

Double crystal X‐ray diffraction imaging and a variable temperature stage are employed to determine the stress distribution in heterogeneous wafer bonded layers though the superposition of images produced at different rocking curve angles. The stress distribution in InP layers transferred to a silicon substrate at room temperature exhibits an anticlastic deformation, with different regions of the wafer experiencing different signs of curvature. Measurements at elevated temperatures (≤125 °C) reveals that differences in thermal expansion coefficients dominate the stress and that interfacial particulates introduce very high local stress gradients that increase with increased temperature. For thinned GaAs substrates (100 μm) bonded using patterned metal interlayers to a separate GaAs substrate at ≈200 °C, residual stresses are produced at room temperature due to local stress points from metallization contacts and vias and the complex stress patterns can be observed using the diffraction imaging technique. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Features of dislocation images reconstructed from step‐scanned white X‐ray section topographs
Authors: Kajiwara Kentaro , Kawado Seiji , Iida Satoshi , Suzuki Yoshifumi , Chikaura Yoshinori
Published: July 2007

We have observed dislocations in a CZ‐silicon crystal using step‐scanning white X‐ray section topography and examined the feature of the dislocation images reconstructed by stacking 200 shots of sec‐ tion topographs. These topographs were obtained from symmetric 004‐reflection in the Laue case using 20, 30, and 60 keV X‐rays. Direct images, intermediary images, and dynamical images of dislocations were observed in a tomogram, i.e., a sliced image obtained from the stacked section topographs, and the contrast of the dynamical images was reduced with increasing X‐ray energy. The stacked section topographs provided three‐dimensional images of the dislocations based on the direct images, and the sliced image enabled us to observe the dislocations separately in a highly dislocated region of the CZ‐silicon crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamical theory of X‐ray diffraction by multilayered structures with microdefects
Authors: Molodkin V. B. , Olikhovskii S. I. , Kislovskii E. N. , Fodchuk I. M. , Skakunova E. S. , Pervak E. V. , Molodkin V. V.
Published: July 2007

The dynamical recurrence relation for amplitudes of coherent waves in the multilayered structure with Coulomb‐type defects (2D and 3D defects or microdefects) has been derived and the expression for the diffuse component of reflection coefficient of this structure has been obtained with account for the dynamical redistribution of intensities of transmitted and diffracted coherent waves in each layer. The derived formulas, which self‐consistently take into account both the diffuse scattering contribution to the diffracted intensity and its extinction due to diffuse scattering, have been applied to analyze the rocking curve of InGaAs/GaAs multilayered structure with quantum well. Layer thicknesses and chemical compositions as well as strains and concentration profiles of chemical elements in layers have been found. Additionally, characteristics of dislocation loops in the substrate of the multilayered structure have been determined. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of phase contrast hard X‐ray microscopy using planar sets of refractive crossed linear parabolic lenses made from SU‐8 polymer
Authors: Reznikova E. , Weitkamp T. , Nazmov V. , Last A. , Simon M. , Saile V.
Published: July 2007

Planar X‐ray refractive lenses with parabolic surface profile, and in crossed geometry to provide 2D focusing, are fabricated from SU‐8 polymer using the LIGA process and deep X‐ray lithography technology. A transmission X‐ray microscope (TXM) using a condenser and an objective lens based on this type of X‐ray optics was set up at the ESRF beamline BM 5, for photon energies of 17.1 and 18 keV. Test structures made of gold and SU‐8, with different thicknesses, were imaged with this TXM using in‐line phase‐contrast, with X‐ray magnification factors of 13–20, spatial resolution between 0.2 and 0.3 µm and exposure times around 1 s. The advantages of a TXM based on refractive SU‐8 planar crossed condenser and objective and the optimisation of the optical scheme and of the condenser focusing profile are discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A magnetron sputter deposition chamber for in‐situ investigation of multilayer film growth using a state of the art Laboratory Diffractometer
Authors: Ringpfeil Clemens , Lützenkirchen‐Hecht Dirk , Frahm Ronald
Published: July 2007

An Fe2O3–Al2O3 bilayer film was prepared on a Si(111)‐wafer by sputter deposition in a vacuum chamber with two integrated small magnetron sources and in‐situ investigated using grazing incidence X‐ray reflectivity, X‐ray scattering and X‐ray diffraction experiments. We will present details of the new cell and present first results of the prepared Fe2O3–Al2O3 thin films, which exhibit an amorphous film structure with a reduced density and a roughness increasing with film thickness. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect structure of silicon crystals implanted with H2+ ions
Authors: Shalimov Artem , Shcherbachev Kirill D. , Bak‐Misiuk Jadwiga , Misiuk Andrzej
Published: July 2007

Si(001) single crystal was implanted with hydrogen ions with energy 135 keV and dose 5 × 1016 cm–2. After implantation, Si:H samples were annealed at 450 and 650 °C under atmospheric and enhanced hydrostatic pressure (1.1 GPa). Defect structure of as‐implanted and processed Si:H was determined by X‐ray scattering methods. Two types of defect clusters contributing to diffuse scattering were revealed: (i) the defects produced by hydrogen diffusion, characterized by small dimensions, with concentration dependent on annealing temperature; (ii) rather large bubbles and platelets produced due to hydrogen agglomeration at defects with negative dilatation. The samples annealed under high pressure contain large defects with the double force tensor equivalent to the dislocation loops one. It is found that the high pressure heat treatment retards the hydrogen diffusion. Distribution of diffuse scattering around the 004 reciprocal lattice point for each type of defects is simulated and compared with the experimental data. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oxidation as an assistant tool for structural analysis of inhomogeneous nanoscale InAs/AlAs(001) island system
Authors: Zolotaryov A. , Bolz A. , Schramm A. , Hansen W. , Johnson R. L.
Published: July 2007

In the paper we present the structural and morphological investigation of an InAs/AlAs(001) island system under growth conditions where partial island coalescence takes place. To provide the structural analysis of elastically strained islands, new experimental X‐ray diffraction technique based on effect of islands oxidation is proposed and verified. It is found that both elastically strained and plastically relaxed islands coexist and have distinctly different sizes and chemical composition what can be explained by differences in their formation mechanisms. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transport and mobility properties of wurtzite InN and GaN
Authors: Yarar Zeki
Published: July 2007

The results of an ensemble Monte Carlo model of the electron transport in wurtzite gallium nitride (GaN) and indium nitride (InN) are presented. There is a controversy over the material parameters of InN, therefore the recently reported and the traditionally accepted parameter values for InN are used in simulations and the results are compared. The steady‐state and transient electron transport characteristics are analyzed and the valley populations of electrons are determined as a function of electric field. The low‐field mobility of electrons is also obtained as a function of temperature and over a wide range of carrier concentrations. It is seen that with the recently published material parameters the peak velocity of carriers in InN increases significantly, while the field at which it is attained decreases. The calculated maximum low field mobility at 300 K in InN with the recent material parameters is about 10000 cm2/V s for low carrier concentrations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐pressure behavior of Ni‐filled and Fe‐filled multiwalled carbon nanotubes
Authors: Poswal H. K. , Karmakar S. , Tyagi Pawan K. , Misra D. S. , Busetto E. , Sharma Surinder M. , Sood A. K.
Published: July 2007

The high‐pressure behavior of Ni‐filled and Fe‐filled multiwalled carbon nanotubes has been investigated up to 27 GPa and 19 GPa, respectively, with the help of synchrotron‐based angle‐dispersive X‐ray diffraction. These nanotubes do not show any structural transformation up to the highest pressures studied. These results are similar to that of Co‐filled nanotubes [1], but are in sharp contrast to the earlier results on Fe‐filled tubes [2], where the tubes were found to undergo a sudden collapse of intertube separation. Our present observations suggest that the occurrence of an isostructural phase transition in Fe3C, observed in our earlier study, may be responsible for the structural transition in nanotubes in that case. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of interstitial hydrogen on the electronic structure of the B2 FeAl alloy
Authors: González Estela A. , Jasen Paula V. , Brizuela Graciela , Juan Alfredo , Nieminen Risto
Published: July 2007

The electronic structure and bonding in a B2 Fe–Al alloy with and without hydrogen as an interstitial atom were studied within the framework of the density functional theory and the findings compared with previous results in Fe an Al. The hydrogen absorption turns out to be a favorable process. The hydrogen was found near an Al octahedral site, the Al–H distance being shorter than that of Fe–H. The density of states (DOS) curves show several peaks below the d metal band which is made up mostly of hydrogen based states (>50% H1s) while the metal contribution includes mainly s‐ and p‐orbitals. An electron transfer of nearby 0.14 e– comes from the metal to the H. The overlap population values reveal metal–metal bond breaking, the intermetallic bond being the most affected. The H bond mainly with the Al atoms and the reported Fe–H overlap population is much lower than that corresponding to FePd alloys and BCC Fe. The changes in the overlap population show the Fe–Al bond is weakening nearly 53% after H absorption, while the Fe–Fe bond is only weakened 23%. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase diagrams of the kinetic metamagnetic spin‐3/2 Blume–Capel model in an oscillating external field
Authors: Keskin M. , Canko O. , Kırak M.
Published: July 2007

Dynamic phase diagrams are calculated, within a mean‐field approach, for the kinetic metamagnetic spin‐3/2 Blume–Capel model in the presence of a time‐dependent oscillating external magnetic field using Glauber‐type stochastic dynamics and six fundamental types of phase diagrams are found in the reduced temperature (T) and magnetic‐field amplitude parameter (h) plane. The phase diagrams exhibit one, two or three dynamic tricritical points, and besides the paramagnetic (P), the antiferromagnetic‐3/2 (AF3/2), the antiferromagnetic‐1/2 (AF1/2) phases, three coexistence phase regions, namely AF3/2 + P, AF1/2 + P, AF3/2 + AF1/2, exist depending upon the interaction parameters. The dynamic phase boundaries between the P and AF3/2 phases are always second‐order lines, but between the P and AF1/2 phases are second‐ or/and first‐order lines. All other dynamic phase boundaries among the disordered, ordered phases and coexistence phase regions are first‐order lines. We have investigated the influence of the crystal field interaction (D) and we obtain five different phase diagram topologies in (d, T) plane, d = D /𝒥′ We have also studied the influence of the frequency on the phase boundaries as well as the dynamic tricritical point and found that the topologies of the phase diagrams slightly change. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)