bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of a Power Time Current to the Study of a Catalytic Mechanism in Chronopotentiometry and Reciprocal Derivative Chronopotentiometry. Advantages of a Cyclic Stationary Response
Authors: Molina Ángela , López‐Tenés Manuela , Soto Carmen M.
Published: May 2008

This paper develops the theory for a pseudo‐first order catalytic mechanism in chronopotentiometry with a power time current, I(t)=I0tu (u≥−1/2), applied to a spherical electrode of any size, and the advantages of the use of small electrodes and ultramicroelectrodes are discussed. The advantages of using a cyclic power time current to reach a stationary response suitable for characterizing a catalytic mechanism easily and accurately are reported. The reciprocal derivative (dt/dE−E) curves, which present peaks quantitatively related to the kinetic parameters of the chemical reaction, have been obtained from the potential‐time responses. The influence of the homogeneous kinetic, the electrode radius and the power of time current in the achievement of a stationary response is analyzed. Methods for determining thermodynamic and kinetic parameters of the chemical reaction are proposed.
Implementation of a protein profiling platform developed as an academic‐pharmaceutical industry collaborative effort
Authors: Végvári Ákos , Magnusson Mattias , Wallman Lars , Ekström Simon , Bolmsjö Gunnar , Nilsson Johan , Miliotis Tasso , Östling Jörgen , Kjellström Sven , Ottervald Jan , Franzén Bo , Hultberg Hans , Marko‐Varga György , Laurell Thomas
Published: May 2008

As much attention has devoted to the proteome research during the last few years, biomarker discovery has become an increasingly hot area, potentially enabling the development of new assays for diagnosis and prognosis of severe diseases. This is the field of research interest where efforts originating from both academic and industrial groups should jointly work on solutions. In this paper, we would like to demonstrate the fruitful combination of both research domains where the scientific crossroads sprout fresh ideas from the basic research domain and how these are refined and tethered to industrial standards. We will present an approach that is based on novel microfluidic devices, utilizing their benefits in processing small‐volume samples. Our biomarker discovery strategy, built around this platform, involves optimized samples processing (based on SPE and sample enrichment) and fast MALDI‐MS readout. The identification of novel biomarkers at low‐abundance level has been achieved by the utilization of a miniaturized sample handling platform, which offers clean‐up and enrichment of proteins in one step. Complete automation has been realized in the form of a unique robotic instrumentation that is able to extract and transfer 96 samples onto standard MALDI target plates with high throughput. The developed platform was operated with a 60 sample turnaround per hour allowing sensitivities in femtomol regions of medium‐ and low‐abundant target proteins from clinical studies on samples of multiple sclerosis and gastroesophageal reflux disease. Several proteins have been identified as new biomarkers from cerebrospinal fluid and esophagus epithelial cells.
Glycosylation analysis of glycoproteins and proteoglycans using capillary electrophoresis‐mass spectrometry strategies
Authors: Amon Sabine , Zamfir Alina D. , Rizzi Andreas
Published: May 2008

This review highlights recent developments in glycosylation analysis by modern MS in combination with CE based preseparation. Focused on CE‐MS strategies aimed for glycotyping, the review addresses the detailed glycoform analysis of glycoproteins, glycopeptides, and proteoglycans. Glycoform analysis in the context of modern glycoproteomics is briefly addressed, as well. CZE, CIEF, and frontal analysis CE approaches hyphenated to high‐resolution multistage MS for the detailed analysis of protein‐linked glycan structures are overviewed in a comprehensive way. Advantages and limitations of various methodological approaches and techniques as well as mass spectrometric instrumentation are discussed in the particular context of glycoanalysis.
Free and bound volatiles of rocket (Eruca sativa Mill.)
Authors: Blažević Ivica , Mastelić Josip
Published: May 2008

Volatile fractions of rocket (Eruca sativa Mill.) flowers and leaves with green beans were isolated by hydrodistillation in a Clevenger apparatus from fresh plant material prior to and after autolysis and from dried plant material. All isolates of volatile compounds were analysed by gas chromatography/gas chromatography–mass spectrometry (GC/GC–MS). Sulphur and/or nitrogen compounds, fatty acids and esters, aliphatic alcohols and carbonyl compounds and some other compounds in smaller percentages were identified. The main sulphur and/or nitrogen components were glucoerucin degradation volatiles: 4‐methylthiobutyl isothiocyanate (9.0–81.7%) and 5‐methylthiopentanenitrile (2.4–17.7%). Also, fatty acids and esters were identified as major components, such as: decanoic acid (1.2–32.8%), hexadecanoic acid (2.7–22.3%), dodecanoic acid (0.6–8.7%), (E,E)‐9,12‐octadecadienoic acid (6.5%), tetradecanoic acid (1.5–6.4%), methyl linolenate (0.4–5.1%) and methyl hexadecanoate (0.3–1.2%). The O‐glycosides of volatile compounds were isolated from fresh plant material of rocket flowers and leaves with green beans. After the enzymatic hydrolysis of glycosides and analysis by GC and GC–MS, 27 volatile aglycones were identified for the first time. The main aglycones were: 2‐phenylethyl alcohol (23.4–62.8%), methyl vanillate (5.4–12.4%), benzyl alcohol (5.4–8.6%), eugenol (1.2–7.5%), p‐anisyl alcohol (0.4–4.6%), 3‐oxo‐α‐ionol (0.4–3.2%), 4‐oxo‐β‐ionol (3.2%), o‐methoxy phenol (1.1–2.8%), phenol (0.3–2.8%) and trans‐carveol (0.2–2.3%). When compared, only (Z)‐3‐hexen‐1‐ol, 2‐methylbutanoic acid and 2‐phenylacetaldehyde were present in volatiles obtained by hydrodistillation and the volatile O‐aglycone fractions. Copyright © 2008 John Wiley & Sons, Ltd.
Human resources as a strategic partner: Sitting at the table with Six Sigma
Authors: Fazzari Alan J. , Levitt Kenneth
Published: May 2008

For nearly three decades, the quality management philosophy known as Six Sigma has brought competitive advantage to organizations implementing it. The typical approach, however, has been to have leaders from operations, engineering, quality, and marketing manage this strategic initiative. Human resource's role has been to default to the administrative tasks of organizing the required training, keeping records, and assisting in the selection of candidates for the program. Yet for the past two decades human resources has also been struggling to gain a seat at the executive table. This paper gives an overview of Six Sigma and shares insights on how human resources is a natural fit to lead a breakthrough change initiative as strategically focused as Six Sigma in small and midsize organizations. By so doing, HR can be assured value‐added status.
SEM analysis of enamel surface treated by Er:YAG laser: Influence of irradiation distance
Authors: Souza‐Gabriel A.E. , Chinelatti M.A. , Borsatto M.C. , Pécora J.D. , Palma‐Dibb R.G. , Corona S.A.M.
Published: May 2008

Background:

Depending on the distance of laser tip to dental surface a specific morphological pattern should be expected. However, there have been limited reports that correlate the Er:YAG irradiation distance with dental morphology.

Purpose:

To assess the influence of Er:YAG laser irradiation distance on enamel morphology, by means of scanning electron microscopy (SEM).

Methods:

Sixty human third molars were employed to obtain discs (≅1 mm thick) that were randomly assigned to six groups (n = 10). Five groups received Er:YAG laser irradiation (80 mJ/2 Hz) for 20 s, according to the irradiation distance: 11, 12, 14, 16, or 17 mm and the control group was treated with 37% phosphoric acid for 15 s. The laser‐irradiated discs were bisected. One hemi‐disc was separated for superficial analysis without subsequent acid etching, and the other one, received the phosphoric acid for 15 s. Samples were prepared for SEM.

Results:

Laser irradiation at 11 and 12 mm provided an evident ablation of enamel, with evident fissures and some fused areas. At 14, 16 and 17 mm the superficial topography was flatter than in the other distances. The subsequent acid etching on the lased‐surface partially removed the disorganized tissue.

Conclusions:

Er:YAG laser in defocused mode promoted slight morphological alterations and seems more suitable for enamel conditioning than focused irradiation. The application of phosphoric acid on lased‐enamel surface, regardless of the irradiation distance, decreased the superficial irregularities. Microsc. Res. Tech., 2008. © 2008 Wiley‐Liss, Inc.
Shannon's entropy and fractal dimension provide an objective account of bone tissue organization during calvarial bone regeneration
Authors: Rocha Lenaldo B. , Adam Randall L. , Leite Neucimar J. , Metze Konradin , Rossi Marcos A.
Published: May 2008

The regeneration of compact bone involves the deposition of a poorly organized connective tissue template that remodels into compact lamellar bone. An objective description of this process is difficult because classical histomorphometry is unable to correctly characterize qualitative changes in tissue complexity. In this study, we demonstrated the use of two distinct methods of image texture analysis, the Shannon's entropy [standard error (SE)], and the fractal dimension (FD) to characterize the formation and remodeling of newly formed compact bone within two different polyanionic collagen‐elastin matrices. The matrices were implanted in defects created into parietal bones of rats. The SE and FD were calculated for histological images of the experimental groups collected 3, 7, 15, 30, 60, and 365 days postsurgery and for the original bone only at day 365. Results showed that the SE and the FD initially increased and then diminished for all groups from day 3 to day 365 approaching the values of the original bone. These results are consistent with poor tissue organization during early osteogenesis that remodels into an organized lamellar structure, showing that these methods can be valuable tools to describe bone tissue remodeling during the regeneration process of compact bones. Microsc. Res. Tech., 2008. © 2008 Wiley‐Liss, Inc.
Preparation of a sorbitol methacrylate grafted silica as stationary phase for hydrophilic interaction chromatography
Authors: Persson Jonas , Hemström Petrus , Irgum Knut
Published: May 2008

A new highly hydrophilic stationary phase based on graft polymerization of sorbitol methacrylate from the surface of Kromasil silica particles is described. Polymerization was initiated by thermal cleavage of tert‐butyl hydroperoxide covalently attached to the silica particle surface. Due to the highly amphiphilic properties of the monomer, an extensive search was needed to find solvent conditions that enabled surface‐initiated polymerization. This was finally solved by using a mixture of solvents that only partially dissolved the monomer. The graft polymerization was confirmed by Fourier transform infrared spectroscopy and elemental analysis. The resulting stationary phase was evaluated by HPLC and exhibited a selectivity markedly different from that of commercially available columns and of neat silica.
Effect of external cueing on gait in Huntington's disease
Authors: Delval Arnaud , Krystkowiak Pierre , Delliaux Marie , Blatt Jean‐Louis , Derambure Philippe , Destée Alain , Defebvre Luc
Published: May 2008

In Huntington's disease (HD) patients, gait is characterized by a timing disorder with marked intraindividual variability in temporal gait parameters (caused by the presence of both hyperkinetic and hypokinetic features). We sought to determine the influence of use of a metronome on gait parameters in patients simultaneously performing motor or cognitive tasks that required attentional resources. The objective is to evaluate the influence of rhythmic cues on gait interference during self‐regulated walking and a dual task paradigm in HD. Fifteen HD patients and 15 paired controls were asked to walk and simultaneously perform another motor task (carrying a tray with four full glasses) or a cognitive task (counting backwards). We evaluated the effect of a metronome (set at 100% and 120% of the subject's self‐determined cadence) in three different task conditions (gait alone, gait + motor task, gait + cognitive task). The use of auditory cues during free gait and dual tasks did not improve kinematic parameters in HD patients, in contrast to the situation for control subjects (improvement in gait speed and cadence but not stride length when the metronome was set at 120% in all conditions). HD patients have difficulty in synchronizing their footsteps with a metronome, mainly due to attentional deficits. © 2008 Movement Disorder Society
Evaluating Parkinson's disease patients at home: Utility of self‐videotaping for objective motor, dyskinesia, and ON–OFF assessments
Authors: Goetz Christopher G. , Leurgans Sue , Hinson Vanessa K. , Blasucci Lucia M. , Zimmerman Jennifer , Fan Wenqing , Nguyen Tiffany , Hsu Ann
Published: May 2008

The objective is to test feasibility and utility of home‐based videos for assessing Parkinson's disease (PD) patients. As part of a clinical trial, patients opted between coming to the study sites or learning to videotape assessments at home. Those opting for at‐home filming completed training on videotape techniques. Ten‐minute films were taken at 30‐minute intervals over 8.5 hours, 2 and 4 weeks after study entry using a protocol covering most items of the UDPRS motor examination and all Rush Dyskinesia Rating Scale items. After each filming, patients marked their ON/OFF status, based on prior training. We determined the number of patients who elected self‐taping and the quality of video segments obtained. To assess ON/OFF patient accuracy, we compared the rater's and patient's assessment of ON/OFF at each time point. Of 12 participants, 10 elected self‐videotaping and only 1 time point was missed (99.5% taping compliance). All self‐recorded video segments were clear with all protocol elements included. With the exception of one missed ON/OFF rating, patient‐based self‐ratings occurred on time. Rating ON/OFF, UPDRS, and RDRS assessments for 8.5 hours required 170 minutes by the blinded rater. In spite of patient training, mean ON/OFF concordance between rater and patients was only 64%. At home video‐based self‐recordings are feasible and allow accurate rater‐based ON/OFF assessments. In this group of patients with no or mild fluctuations, in spite of pretrial training, patients were inaccurate in separating ON vs. OFF status. © 2008 Movement Disorder Society
Human scFv SIgA expressed on Lactococcus lactis as a vector for the treatment of mucosal disease
Authors: Yuvaraj Saravanan , Lahham Saed , Marreddy Ravi K. R. , Dijkstra Gerard , Wolken Wout A. M. , Lolkema Juke S. , Helfrich Wijnand , Johansen Finn‐Erik , Peppelenbosch Maikel P. , Bos Nicolaas A.
Published: May 2008

The gastrointestinal tract is a complex niche and the main port of entry of many pathogens that trigger a wide range of diseases like inflammatory bowel disease (IBD) and colon cancer. Antibodies are effective for treating such diseases, but a system capable of local delivery at the site of the pathology, thus avoiding systemic side effects, is not yet available. Here we report a novel recombinant scFvSIgA1 protein produced by Lactococcus lactis, anchored to the bacterial membrane, which retains its full immuno‐recognizing potential. This scFv fragment employed was specific for a colon cancer epitope, epithelial glycoprotein protein‐2 (EGP‐2). Accordingly L. lactis expressing this chimeric protein was capable of binding cells expressing this epitope. Expression of specific antibodies on bacteria may allow local delivery of anticancer agents produced by such bacteria in conjunction with the antibody and provides a new avenue in the quest for targeted drug delivery.
Polyunsaturated fatty acids, inflammatory processes and inflammatory bowel diseases
Authors: Calder Philip C.
Published: May 2008

With regard to inflammatory processes, the main fatty acids of interest are the n‐6 PUFA arachidonic acid (AA), which is the precursor of inflammatory eicosanoids like prostaglandin E2 and leukotriene B4, and the n‐3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA and DHA are found in oily fish and fish oils. EPA and DHA inhibit AA metabolism to inflammatory eicosanoids. They also give rise to mediators that are less inflammatory than those produced from AA or that are anti‐inflammatory. In addition to modifying the lipid mediator profile, n‐3 PUFAs exert effects on other aspects of inflammation like leukocyte chemotaxis and inflammatory cytokine production. Some of these effects are likely due to changes in gene expression, as a result of altered transcription factor activity. Fish oil has been shown to decrease colonic damage and inflammation, weight loss and mortality in animal models of colitis. Fish oil supplementation in patients with inflammatory bowel diseases results in n‐3 PUFA incorporation into gut mucosal tissue and modification of inflammatory mediator profiles. Clinical outcomes have been variably affected by fish oil, although some trials report improved gut histology, decreased disease activity, use of corticosteroids and relapse.
Effects of Eg5 knockdown on human prostate cancer xenograft growth and chemosensitivity
Authors: Hayashi Norihiro , Koller Erich , Fazli Ladan , Gleave Martin E.
Published: May 2008

OBJECTIVES

Microtubular inhibitors, including docetaxel, are active cytotoxics in many cancers, including prostate cancer (CaP). The Eg5 gene, a member of the kinesin‐5 family, plays critical roles in proper mitotic spindle function, and is a potential microtubule‐related target for proliferating cancer cells. To investigate the functional activities of Eg5 in CaP, we used an antisense oligonucleotide (ASO) targeting Eg5 to assess the potency and anti‐cancer activity of Eg5 ASO treatment for androgen‐independent CaP cells in vitro and in vivo.

RESULTS

PC3 cells express higher Eg5 protein and mRNA levels compared to LNCaP cells. In both cell lines, Eg5 ASO treatment reduced mRNA and protein levels in a dose‐dependent manner and a complete reduction of Eg5 protein levels was observed at 100 nM. Dose‐dependent inhibition in cell growth, potent G2/M phase arrest, and increases in apoptotic sub‐G1 fraction were also observed using Eg5 ASO. Surprisingly, low dose Eg5 ASO significantly antagonized cytotoxic effects of paclitaxel. In vivo, Eg5 ASO monotherapy significantly reduced both LNCaP and PC‐3 tumor growth but combination treatment with paclitaxel did not yield additive benefits.

CONCLUSIONS

These findings suggest that while Eg5 is a potential target to delay androgen‐independent CaP growth, combination treatment with paclitaxel may not be desirable. Prostate 68:1283–1295, 2008. © 2008 Wiley‐Liss, Inc.
Structural characterization of AlGaN/AlN Bragg reflector grown by metalorganic chemical vapor deposition
Authors: Ji X. L. , Jiang R. L. , Liu B. , Xie Z. L. , Zhou J. J. , Li L. , Han P. , Zhang R. , Zheng Y. D. , Zheng J. G.
Published: May 2008

A thirty‐pair AlGaN/AlN distributed Bragg reflector (DBR) targeted at a center wavelength of 320 nm was grown on a 2‐inch sapphire substrate by metalorganic chemical vapor deposition (MOCVD). It is free of cracks in the main area of the wafer except for a ∼4 mm periphery observed under optical microscope. The measured reflectance spectrum shows a peak reflectivity of 93% at 313 nm and a bandwidth of 13 nm. Further investigation into the interfaces was performed using Auger electron spectroscopy (AES), scanning transmission electron microscope (STEM) and energy dispersive X‐ray fluorescence spectrometer (EDX). It was found that the constitutional change is abrupt when AlGaN is deposited on an AlN layer but gradual in reverse, which resulted in a stack of quasi‐three‐layer periods and high Al composition and therefore both the center reflectivity and the bandwidth were depressed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical properties of chlorine‐doped ZnO thin films grown by MOCVD
Authors: Chikoidze E. , Modreanu M. , Sallet V. , Gorochov O. , Galtier P.
Published: May 2008

Chlorine‐doped ZnO thin films were grown by MOCVD on sapphire and fused silica. Chlorine is incorporated in substitution for oxygen and acts as a donor, leading to an increase of electron concentration. Transport properties were studied for samples with different chlorine content. Hall effect measurements show the increase of electron carrier concentration and decrease of electron mobility on increasing the amount of chlorine incorporated in ZnO. Carrier concentrations as high as 6.5 × 1020 cm–3 has been achieved with a resistivity of ρ = 1.4 × 10–3 Ω cm for layers deposited on sapphire substrate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improved quality nonpolar a ‐plane GaN/AlGaN UV LEDs grown with sidewall lateral epitaxial overgrowth (SLEO)
Authors: Imer Bilge , Schmidt Matt , Haskell Ben , Rajan Siddharth , Zhong Barry , Kim Kwangchoong , Wu Feng , Mates Tom , Keller Stacia , Mishra Umesh K. , Nakamura Shuji , Speck James S. , DenBaars Steven P.
Published: May 2008

High quality nonpolar a ‐plane GaN templates were grown by utilizing sidewall lateral epitaxial overgrowth (SLEO) technique with threading dislocation density of ∼106–107 cm–2. 360 nm GaN/AlGaN multiple quantum well ultraviolet light emitting diodes were grown with metalorganic chemical vapor deposition. Reduced defect density SLEO a‐ plane, planar a ‐plane, and planar c ‐plane templates were co‐loaded for device growth and processed together in order to make relative device performance comparison. For SLEO a ‐plane LEDs E EL peak position was measured at 360 nm and it was independent of drive current. The linewidth of the emission was 7 nm. The series resistance of these diodes was as low as 16.5 Ω and the forward voltage was measured as 4.08 V at 20 mA. The external quantum efficiency of the high quality SLEO a ‐plane devices was ∼275× higher than planar a ‐plane devices. The highest output power was realized at 200 mA as 65 μW. The effect of contact geometry on electrical and optical characteristics of the devices was also discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural properties of GaN and Ga1–xMnx N layers grown by sublimation sandwich method
Authors: Kaminski M. , Podsiadlo S. , Dominik P. , Mizera J. , Wozniak M. , Gebicki W. , Kamler G.
Published: May 2008

The structural properties of GaN and Ga1–x Mnx N layers are reported. The GaN and Ga1–x Mnx N layers were obtained by the sublimation sandwich method (SSM). Electron microprobe measurements detected high Mn concentration of up to 4.0 at% in Ga1–x Mnx N materials. Raman investigations demonstrated that the prepared layers had a well‐ordered structure. The densities of dislocations in the template MOCVD layer, SSM GaN layers and SSM Ga1–x Mnx N layers were 3.9 × 108 cm–2, 1.4 × 108 cm–2 and 3.0 × 109 cm–2, respectively. The AFM studies demonstrated that the GaN RMS roughness increased with the increase in thickness. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shape effect of microtwins on high‐resolution transmission electron microscope images
Authors: Kuramochi K. , Yamazaki T. , Nakanishi N. , Hashimoto I. , Watanabe K.
Published: May 2008

The shape effect of microtwins on high‐resolution transmission electron microscopy (HRTEM) images is demonstrated with the help of a detailed comparison between experimental HRTEM images of recrystallized silicon (including many microtwins) and corresponding dynamical simulations. The analysis points to an important fact: The shape effect of microtwins leads to artificial contrasts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of deuterium and tritium on formation and annealing of vacancy‐type defects in deformed nickel
Authors: Druzhkov A. P. , Arbuzov V. L. , Danilov S. E.
Published: May 2008

Pure nickel and nickel loaded with deuterium or tritium were examined during deformation at 270–300 K to 3–45% and subsequent annealing up to 850 K using the measurements of the electrical resistivity and positron annihilation spectroscopy. Three‐dimensional vacancy clusters were formed during deformation in nickel loaded with the hydrogen isotopes unlike in pure nickel. Vacancy clusters decorated with deuterium or tritium atoms created at room temperature, i.e. below a temperature at which monovacancies, are mobile in nickel. Vacancy clusters decorated with deuterium atoms have two types of atomic configurations or degrees of decoration with the binding energy of 0.73 eV and 1.05 eV, respectively. Only one configuration having the binding energy of 1.05 eV was detected for vacancy clusters decorated with tritium atoms. Possible reasons for different behaviors of vacancy clusters in T‐ and D‐loaded nickel are also discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermoelectric properties of n‐type Mg2Si0.6–ySby Sn0.4 compounds
Authors: Zhang Q. , Yin H. , Zhao X. B. , He J. , Ji X. H. , Zhu T. J. , Tritt T. M.
Published: May 2008

The thermoelectric properties of n‐type Mg2Si0.6–y Sby Sn0.4 solid solutions with a small Sb‐doping ratio on the Si‐site (y = 0.0–0.015) were prepared by an induction melting/hot‐pressing method. The electrical conductivity, Seebeck coefficient and thermal conductivity have been measured as a function of temperature from 300 K to 820 K. A power factor ∼2.28 × 10–3 Wm–1 K–2 at 574 K for y = 0.01, and a dimensionless figure of merit ZT ∼0.68 at 724 K for y = 0.005 are attained. Given the potential of these materials for utilization in thermoelectric devices in a medium temperature range, the thermoelectric compatibility of Mg2Si0.6–y Sby Sn0.4 samples has been also addressed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new architecture for self‐organized silicon nanowire growth integrated on a 〈100〉 silicon substrate
Authors: Buttard D. , David T. , Gentile P. , Hertog M. Den , Baron T. , Ferret P. , Rouvière J. L.
Published: May 2008

A lithography‐independent method for achieving self‐organized growth of silicon nanowires by means of a Chemical‐Vapor‐Deposition process is investigated using a nanoporous alumina template on a 〈100〉 oriented silicon substrate. The position of the nanowires is determined by the location of gold colloids, acting as catalysts, which are initially deposited at the bottom of the pores over large areas of the sample. The direction of growth is guided by the pore axis, which is perpendicular to the silicon substrate surface. Results from scanning and transmission electron microscopy are presented and discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of V addition on magnetic, transport, and microstructural properties of La0.7Sr0.3MnO3
Authors: Zhao T.‐S. , Li B. H. , Han G.
Published: May 2008

The microstructural, magnetic, and magnetotransport properties of polycrystalline samples with nominal composition of La0.7Sr0.3Mn1–x Vx O3 (0 ≤ x ≤ 0.25) sintered in air have been investigated. It is found that V could not substitute for Mn to form La0.7Sr0.3Mn1–x Vx O3. The samples contain several phases such as (La, Sr)Mn1–δ O3, LaSr3V3O12, Mn3O4 etc. and constitute multi‐phase composites. The Sr–V‐rich phase form a liquid phase during sintering process and the sintering be long to liquid‐phase sintering, which may effectively promote grain growth of (La, Sr)Mn1–δ O3 phase. The Curie temperature TC and saturation magnetization of the composites decrease with increasing the V content x. The addition of V may effectively improve the low‐field MR response at low temperatures due to the variation in the microstructure of the composites. The MR ratio at a low field of 2 kOe reaches 25% for the x = 0.15 sample at 84 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of electroplated, thick permalloy films
Authors: Getlawi S. , Theis M. , Friedrich S. , Koblischka‐Veneva A. , Koblischka M. R. , Saumer M. , Hartmann U.
Published: May 2008

Permalloy (Ni81Fe19) films and foils were fabricated by means of electroplating. Two different types of samples were produced, (i) a patterned permalloy film on a Si wafer (type 1) and (ii) a NiFe foil (type 2), which was separated from the substrate after deposition. The samples were characterized employing magnetic force microscopy (MFM), transmission electron microscopy (TEM) and electron‐backscatter diffraction (EBSD). On the foil type sample, MFM reveals a maze domain pattern, and on the structured samples (type 1), a Landau domain pattern is obtained. EBSD enables the identification of the permalloy Kikuchi pattern without the effect of a substrate. The analysis reveals randomly oriented grains with a narrow size distribution. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear‐laser χ(3)‐ and χ(2)‐effects in fine‐grained highly transparent optical Ba(Mg,Zr,Ta)O3 ceramics and their microhardness
Authors: Kaminskii A. A. , Akchurin M. Sh. , Tanaka N. , Eichler H. J. , Rhee H. , Ueda K. , Takaichi K. , Shirakawa A. , Tokurakawa M. , Dong J. , Kintaka Y. , Kuretake S. , Sakabe Y.
Published: May 2008

We report on laser‐induced χ(3)‐ and χ(2)‐nonlinear generation in novel optical ceramics, Ba(Mg,Zr,Ta)O3, with “disordered” O5h structure, namely high‐order Stokes and anti‐Stokes lasing, third‐ and second‐harmonic generation under one‐micrometer picosecond pumping. Microhardness and fracture toughness were also measured. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of ZnFe2O4 and In‐doped ZnFe2O4 nanoparticles
Authors: Maletin M. , Moshopoulou E. G. , Srdic V. V.
Published: May 2008

The magnetic behaviour of ZnFe2O4 and Zn0.85In0.15Fe2O4 nanoparticles with diameters of about 4.1 and 3 nm respectively was investigated by dc magnetisation measurements. Both materials are at superparamagnetic state above a blocking temperature of about 25 K and exhibit the collective behaviour of an assembly of single domain ferromagnets below this temperature. In‐doping results in a decrease of the magnetisation and increase of coercitivity of the nanoparticles. This observation implies that, besides size, doping causes also significant structural rearrangements which in turn induce changes in the strength and the number of Fe3+(A)–O–Fe3+(B) superexchange interactions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermionic and tunneling transport mechanisms in graphene field‐effect transistors
Authors: Ryzhii Victor , Ryzhii Maxim , Otsuji Taiichi
Published: May 2008

We present an analytical device model for a graphene field‐effect transistor (GFET) on a highly conducting substrate, playing the role of the back gate, with relatively short top gate which controls the source–drain current The equations of the GFET device model include the Poisson equation in the weak nonlocality approximation. Using this model, we find explicit analytical formulae for the spatial distributions of the electric potential along the channel and for the voltage dependences of the thermionic and tunneling currents. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Properties of post‐annealed ZnO films grown with O3
Authors: Kim H. S. , Lugo F. , Pearton S. J. , Norton D. P. , Ren F.
Published: May 2008

The properties of ZnO thin films grown with ozone are examined. Annealing studies were performed on ZnO films grown by pulsed‐laser deposition using either O2 and an O2/O3 gas mixture as the oxidant. The carrier density of ZnO films grown with pure O2 generally decreases upon annealing in 1 atm O2. In contrast, the n‐type carrier density for ZnO films grown with O2/O3 mixture gas increased with O2 annealing. The results indicate that acceptor states, created via growth in ozone, are annihilated with post‐annealing. This suggests that the ozone‐related acceptor states are metastable. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis of ZnO whiskers with different aspect ratios by a facile solution route
Authors: Xie Juan , Li Ping , Wang Yanji , Wei Yu
Published: May 2008

Monodispersed zinc oxide (ZnO) whiskers with different aspect ratios were successfully prepared via a simple solution route at low temperature. It is found that the diameter and aspect ratio of ZnO whiskers depend critically on the structure and type of ionic surfactant added in the reaction solution. To further understand the effect of the surfactants on the formation process of ZnO whiskers, concentration measurements of Zn(II) remaining in the solution as well as scanning electron microscopy (SEM) and X‐ray powder diffraction (XRD) analyses of the solid product have been made at regular intervals throughout the reaction with and without the surfactants. A possible formation process has been reasonably suggested based on these systematic experimental results. It is believed that anion surfactants are capable of slowing down the nucleation and growth rate of ZnO crystallite, which is favorable for the anisotropic growth habit of ZnO crystal to form needle‐like whiskers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A morphological and microstructural study of flame‐sprayed zinc coatings on low‐alloyed steels as a contribution to explaining their corrosion resistance
Authors: Chaliampalias D. , Vourlias G. , Pistofidis N. , Stergioudis G. , Polychroniadis E. K.
Published: May 2008

Zinc is an ideal coating material for steels because it offers simultaneously cathodic and barrier protection. Several processes have been developed to provide zinc coatings. Thermal spraying is widely used due to the fact that it is simple, quick and effective. The present work deals with the morphology, the structure and the corrosion performance of zinc coatings deposited with thermal spraying. The study was performed with scanning electron microscopy and X‐ray diffraction, while microstructural characterization was accomplished with transmission electron microscopy. Finally, corrosion tests were performed with exposure of the coated samples in a salt‐spray chamber. From the microstructural investigation it was deduced that before corrosion the as‐produced coatings are mainly composed of zinc, while zinc oxide nanoparticles are dispersed in their mass. After corrosion tests it was found that zinc flame‐sprayed coatings provide adequate corrosion protection because the corrosive elements did not penetrate the coating or reach the substrate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magneto‐capacitance study of an n‐AlGaAs/GaAs heterojunction supporting a sizable dc current
Authors: Kawazu T. , Sakaki H.
Published: May 2008

The magneto‐capacitance between the gate and the two‐dimensional electron gas (2DEG) channel has been investigated in a selectively doped n‐AlGaAs/GaAs heterojunction with feeding a sizable current to the 2DEG channel. By measuring and analyzing the differential capacitance Cmeas and longitudinal resistance Rxx, we found that Cmeas includes extrinsic oscillatory components resulting from Rxx and showed how the intrinsic component Cint of the capacitance is extracted from Cmeas. The capacitance Cint was examined as a function of the magnetic field B around BL = 3.75 T, which corresponds to the filling factor ν = 4 of the Landau levels. We found that Cint gets very close to the zero‐field capacitance C0 when the deviation ΔB = |B ‐BL | exceeds ∼ 0.1 T, while Rxx remains zero over a wider range of B (between 3.6 and 3.9 T). This suggests that an incompressible region percolates through the channel and forms a path, even when compressible regions spread over the most region of the sample. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Site‐controlled InGaAs quantum dots grown on a GaAs multi‐faceted microstructure for single photon emissions
Authors: Chang Hsiang‐Szu , Hsu Chieh‐Ming , Yang Ming‐Hui , Hsieh Tung‐Po , Chyi Jen‐Inn , Hsu Tzu‐Min
Published: May 2008

This study demonstrates the single photon emissions form site‐controlled InGaAs quantum dots (QDs) grown on an apex plane of a GaAs multifaceted structure by pattern‐growth techniques, multifaceted structure comprises the top (001) plane, and {111} and {011} side wall facets. The QDs formed on the apex plane rather than the side wall facet because the growth rate of apex plane is exceeded that of side wall facet. Microphotoluminescence (μ PL), μ PL excitation (μ PLE) and theoretical calculations are adopted to estimate the growth rate of the {111} ({011}) facets as ∼82% (∼69%) lower than that of the (001) plane. Since the (001) plane growth rate is higher than that of the side wall facets, the QDs can be carefully controlled. This method is effective in the fabrication of a single photon source. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control of shell filling with Coulomb interaction in quantum dots side‐coupled to quantum wires
Authors: Otsuka Tomohiro , Abe Eisuke , Iye Yasuhiro , Katsumoto Shingo
Published: May 2008

We report the control of the orbital occupation by using the intra‐orbital Coulomb interaction in quantum dots Tcoupled to quantum wires. With the change of the confinement potential, intra‐orbital Coulomb interaction exceeds orbital level spacing and influences the orbital occupation. We realize such potential modification by changing either the gate design or the voltages applied to the gates. The rearrangement of the orbital occupation is confirmed from the response of the addition energy spectroscopy to the magnetic field. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Isotropic interface roughness of pseudomorphic In0.74Ga0.26As/In0.52Al0.48As quantum wells grown on (411)A InP substrates by molecular beam epitaxy
Authors: Kitada T. , Kusuonki S. , Kinouchi M. , Morita K. , Isu T. , Shimomura S.
Published: May 2008

Anisotropy of the interface roughness has been investigated for pseudomorphic In0.74Ga0.26As/In0.52Al0.48As modulation doped quantum wells (MD‐QWs) grown on (411)A and (100) InP substrates by molecular beam epitaxy. Significant difference of low‐temperature electron mobility between two different in‐plane current directions ([0$ \bar 1 $1] and [011]) was observed for the (100) MDQW with a well width of 4 nm, while it was not observed for the (411)A MD‐QW.

The observed electron mobility was analyzed by the theory of interface roughness scattering. Lateral size of the roughness along the [0$ \bar 1 $1] direction (Λ = 5.8 nm) is 29% larger than that of the [011] direction (Λ = 4.5 nm) for the (100) interface. On the other hand, the (411)A interface shows isotropic roughness (Λ ∼ 4.5 nm) with much smaller amplitude (Δ = 0.24 nm) comparing to the (100) interface (Δ = 0.33 nm). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
n‐Channel GaAs MESFETs for cryogenic application
Authors: Chen Y. G. , Itatani T. , Ohkubo M.
Published: May 2008

Some normally‐on n‐channel GaAs MESFETs with large size gates are designed and fabricated for low‐noise, low power consumption application at cryogenic temperatures. Low‐doping n‐type GaAs (Si‐doped) epitaxial wafers are used to fabricate n‐channel MESFETs. The comparison of DC characteristics of the MESFETs at room temperature and at 4.2 K is reported. The maximum consumption power of the fabricated MESFETs is calculated to be 0.8mW. With the increasing of gate length, the power consumption and transconductance of MESFETs reduce consequently. The specific contact resistance of the metal/GaAs ohmic contacts determined from circular transfer line model and four‐point probe method at 4.2K is at the order of 10–7 Ωcm2, which is available for low noise application at cryogenic temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman scattering study of BxGa1–xN growth on AlN template substrate
Authors: Ould Saad Hamady S. , Baghdadli T. , Gautier S. , Bouchaour M. , Martin J. , Ougazzaden A.
Published: May 2008

In this study, Raman scattering measurements are reported on the BxGa1–xN layers grown on AlN‐on‐sapphire templates by MOVPE. The boron content covered the composition range from 0% (pure GaN) to 1.75%. The Raman spectra were recorded at 300 K with a confocal micro‐Raman spectrometer in the backscattering geometries. Raman cartography at a lateral resolution of 1 µm was performed to study the spatial variation of the phonon peaks characteristics. The homogeneity of BGaN layers was studied and the phonon modes characteristics are determined as a function of composition, with respect to the laser polarisation. The E2 and A1(LO) modes frequencies are shifted with respect to the pure GaN. The A1(LO) mode behaviour correlates well with the free carriers concentration measured by Hall Effect method, indicating a phonon‐plasmon coupling decreasing with increasing boron content in alloy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InGaN growth on ZnO (0001) substrate by metalorganic vapor phase epitaxy
Authors: Kawai Y. , Ohsuka S. , Iwaya M. , Kamiyama S. , Amano H. , Akasaki I.
Published: May 2008

InGaN growth has been performed on nearly lattice‐matched ZnO (0001) substrates by metalorganic vapor phase epitaxy at relatively low temperatures below 600 °C. The grown layers were confirmed to be single crystalline by X‐ray diffraction and reflection high energy electron diffraction analyses. By annealing the ZnO substrate under oxygen atmosphere prior to the growth, scratches due to polishing were completely removed, as observed by atomic force microscopy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sub‐100 nm gate‐length SiGe/Si MIS‐HFET using Cat‐CVD SiN
Authors: Onojima N. , Kasamatsu A. , Hirose N. , Mimura T. , Matsui T.
Published: May 2008

We fabricated sub‐100 nm gate‐length SiGe/Si n‐channel metal‐insulator‐semiconductor (MIS) heterostructure field‐effect transistors (HFETs) using a SiN gate insulator formed by catalytic chemical vapor deposition (Cat‐CVD). The Cat‐CVD SiN thin film (5 nm) was found to be an effective gate insulator with good gate controllability and dielectric properties. Due to the MIS structure, large gate bias swing was achieved from ‐3 to 3 V, and the maximum drain current density exceeded 450 mA/mm. The maximum transconductance (gm) was 220 mS/mm at VGS = 3 V, which was larger than that for a Schottky‐gate device. RF measurements of the MIS‐gate device, however, showed a relatively lower current gain cutoff frequency (fT) compared with the Schottky‐gate device, suggesting that two electron transport channels existed for the MIS‐gate structure, one at the SiGe/Si buried channel and the other at the SiN/Si surface channel. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shallow Li‐acceptor levels in ZnO films codoped with Li and F atoms
Authors: Kobayashi K. , Tomita Y. , Maeda Y. , Haneda H.
Published: May 2008

Li,F‐codoped ZnO films have been prepared by simultaneous evaporation of LiF at 780 °C during the ZnO growth. The codoped ZnO film has the resistivity of 79 Ωcm and the electron density of 6.8 ×1016 cm–3. Photoluminescence spectra of the codoped ZnO film in the range of 14 to 120 K show new emissions at 3.3136 and 3.3270 eV, besides bound excitonic emissions. The emission at 3.3136 eV disappears at a temperature higher than 40 K, and is assigned to donor‐acceptor pair emission. The emission at 3.3270 eV is ascribed to free‐electron to acceptor transition. The Li‐acceptor levels are estimated to be 0.11 eV from free‐electron to acceptor transition. As excitation intensity increases, the photon energy of the donor‐acceptor pair emission remains unchanged. These results lead to the interpretation that Li and F atoms are located at nearest neighbour sites in the ZnO lattice and that the presence of Li‐F complexes suppresses the formation of interstitial Li. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Molecular‐beam epitaxy fabrication and analysis of GaN nanorods on patterned silicon‐on‐insulator substrate
Authors: Seo J. U. , Hasegawa S. , Asahi H.
Published: May 2008

GaN nanorods field emission arrays (FEAs) were fabricated on patterned silicon‐on‐insulator substrates with 10×10 μm2 and 1×1 μm2 periodic‐windows by molecular beam epitaxy. Their morphologies and field emission characteristics were investigated. FEAs fabricated on the 1×1 μm2 periodic‐window substrates exhibited lower threshold electric field of 2.6 V/μm, higher field emission current density of 10–3 A/cm2 and higher field enhancement factor of 1685 than those for the FEAs fabricated on the 10×10 μm2 periodic‐window substrates in spite of the reduced active areas. The improved field emission characteristics for the FEAs with smaller area periodic‐window are considered to be due to the edge effect at the patterned area. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical conductivity of carbon nanotubes and polystyrene composites
Authors: Kažukauskas V. , Kalendra V. , Bumby C. W. , Ludbrook B. M. , Kaiser A. B.
Published: May 2008

We report investigation of electrical conductivity of high resistivity polystyrene/carbon nanotube composites. The films consisted of a thiol‐bonded network of wrapped MWNTs within a polystyrene matrix with mass ratios ranging from 0% to 1%. The electrical conductivity and its thermal activation energy were systematically depending on the CNT doping level. A number of phenomena could be explained by the presence of CNT ‘islands’ in the polystyrene matrix at doping levels below the percolation threshold. At higher levels of CNTs an interconnected conducting network is formed. The results appear consistent with fluctuation‐assisted tunnelling through barriers between conducting carbon nanotubes for medium and large voltages. However, at low voltages there is a sharper decrease in conductance as voltage decreases that could arise from Coulomb blockade effects or other small barriers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and optical properties of Er doped GaN with various Er concentrations
Authors: Chen Shaoqiang , Seo Jongwon , Sawahata Junji , Akimoto Katsuhiro
Published: May 2008

Luminescence properties of Er in GaN combined with the structural properties were studied by photoluminescence measurements and X‐ray diffraction measurements. It was found that Er atoms occupy two kinds of incorporation sites in GaN and only one kind of site is suggested to be active for the light emission. The maximum luminescence intensity was obtained with the Er concentration at around 4 at%. The concentration quenching was observed and the cause of the quenching is related to the degradation of crystal quality rather than the formation of the segregation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Metalorganic chemical vapor deposition of ZnO(0001) thin films on GaN(0001) templates and ZnO(0001) substrates
Authors: Ive T. , Ben‐Yaacov T. , Murai A. , Asamizu H. , Van de Walle C. G. , Mishra U. , DenBaars S. P. , Speck J. S.
Published: May 2008

We investigated the properties of ZnO layers grown by metalorganic chemical vapor deposition on GaN(0001) templates and ZnO(0001) bulk substrates. Steps and hexagonal pits were observed on the surfaces of the ZnO/GaN films as revealed by atomic force microscopy. The root‐mean‐square roughness was 2.6 nm over 20×20 mm2. The surfaces of the homoepitaxially grown ZnO films were smooth and featureless with a rootmean‐square roughnesses of 0.12 nm over 6×6 mm2. Full width at half maximums of ω‐scans for the on‐axis (0002) and the off‐axis (20$ \bar 2 $1) reflections were 0.091° and 0.159°, respectively. The corresponding values for the ZnO/ZnO films were 0.025° and 0.035°, respectively. Reciprocal space maps for the (10$ \bar 1 $5) reflection revealed that the ZnO films grown on GaN were fully relaxed and that the peaks of the homoepitaxially grown ZnO layers were indistinguishable from the ZnO substrate peaks. Ga‐doped ZnO layers were grown at 300 °C on (In,Ga)N light emitting diodes as transparent electrodes and for wafer bonding to ZnO substrates in order to enhance the light extraction. The forward voltage was 4.5 V at 20 mA. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)