bluuebunny/crossref_metadata_2025_split huggingface dataset:
Resistance switching properties of epitaxial Pr0.7Ca0.3MnO3 thin films with different electrodes
Authors: Lau H. K. , Leung C. W. , Chan Y. K. 
Published: July 2009

AbstractResistance switching effect caused by external electric field was investigated in Pr0.7Ca0.3MnO3 (PCMO) thin films grown on (001)‐oriented LaAlO3, by using different metallic (Al, Pt, Au, Ti) electrodes. When Al was used as one or both of the electrodes, PCMO thin films exhibited resistance changes upon reversing voltage polarities. Nonlinear, hysteretic current–voltage loops were observed. Our measurements showed that the total resistance of the samples were dominated by interfacial resistance. Such kind of device structure can find applications in non‐volatile memory devices.
Dependence on substrate temperature of the conformation and structure of a poly[3‐(4‐octyloxyphenyl)thiophene] (POOPT) thin film obtained by matrix assisted pulsed laser evaporation (MAPLE)
Authors: Califano Valeria , Bloisi Francesco , Vicari Luciano , Cassinese Antonio , Barra Mario , Carella Antonio , Roviello Antonio 
Published: July 2009

AbstractIn this paper, the substrate temperature influence on the structural and main opto‐electronic properties of poly[3‐(4‐octyloxyphenyl)thiophene] (POOPT) films, deposited by matrix assisted pulsed laser evaporation (MAPLE), was analyzed. Fourier transform infrared analysis of films was performed to verify that laser irradiation has not induced polymer modifications or decomposition, confirming the reliability and high control of the MAPLE deposition technique. UV–Visible spectroscopy allowed gaining insights about films conformation and packing, while conductivity values have been measured by basic current–voltage measurements. In agreement with the experimental observations reported for other growth techniques, our results highlight the substrate temperature effect in promoting the film structural organization and improving their charge transport capability. At substrate temperature of 453 K, films deposited by MAPLE show a higher conjugation length in comparison with spin‐coated films. The substrate temperature increase also favors side‐chains commutation to different steric configurations.
Electrical, structural and optical characterization of copper oxide thin films as a function of post annealing temperature
Authors: Figueiredo V. , Elangovan E. , Gonçalves G. , Franco N. , Alves E. , Park S.H.K. , Martins R. , Fortunato E. 
Published: July 2009

AbstractCopper oxide thin films were obtained by annealing (temperature ranging between 100 and 450 °C) the metallic Cu films deposited on glass substrates by e‐beam evaporation. XRD studies confirmed that the cubic Cu phase of the as‐deposited films changes into single cubic Cu2O phase and single monoclinic CuO phase, depending on the annealing conditions. The crystallite size is varied between ∼12 and 31 nm. The lattice parameters of cubic Cu and Cu2O phases are estimated to ∼3.60 and ∼4.26 Å, respectively. The films with Cu2O phase showed p‐type characteristics. The conductivity is decreased linearly with the decreasing temperature (1/T), which has confirmed the semiconductor nature of the deposited films. The calculated activation energy is varied between 0.10 and 0.16 eV. The surface microstructure is changed depending on the variation in the annealing temperature. The poor transmittance of the as‐deposited films (<1%) is increased to a maximum of ∼80% (800 nm) on annealing at 200 °C. The estimated direct allowed band gap is varied between 1.73 and 2.89 eV.
Spatially resolved contact‐resistance measurements on crystalline silicon solar cells
Authors: Kontermann Stefan , Hörteis Matthias , Ruf Alexander , Feo Sergio , Preu Ralf 
Published: July 2009

AbstractThis paper demonstrates a method for quantitatively determining the spatially resolved contact resistance of silicon solar cells. Contact‐resistance maps obtained by this technique on screen‐printed industrial silicon solar cells are presented and discussed. Extending the contact‐resistance map to a series‐resistance map by adding contributions from the rear, bulk, emitter, and metallization shows this map to qualitatively agree well with photoluminescence (PL) series‐resistance imaging. Compared to existing approaches, our technique enables the spatially resolved measurement of the contact resistance separately from any other series‐resistance contributions.
Role of oxygen additive on hydrogen impurity incorporation in nanocrystalline diamond films fabricated by microwave plasma chemical vapor deposition
Authors: Tang C. J. , Gu L. P. , Grácio J. , Ribeiro J. L. 
Published: July 2009

AbstractIn this work, we study the influence of oxygen additive in the gas phase on hydrogen impurity incorporation into thick nanocrystalline diamond (NCD) films. Various diamond samples were grown on large silicon wafers of 5.08 cm diameter by adjusting the amount of oxygen and nitrogen additives into a conventional CH4/H2 plasma while keeping the other parameters constant using a 5‐kW microwave plasma‐assisted chemical vapor deposition (MPCVD) reactor. The morphology, crystalline quality, and hydrogen impurity content of the produced diamond samples were characterized using scanning electron microscopy, micro‐Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy, respectively. The Raman and the FTIR spectra of the diamond samples indicate that on increasing the amount of oxygen additive in the gas phase, the crystalline quality of the NCD films is significantly enhanced, while their bonded hydrogen content decreases drastically. We conclude that a small amount of oxygen addition has an enhancement effect on the overall quality of diamond films ranging from polycrystalline to nanocrystalline in two ways: improving the diamond crystalline quality and suppressing hydrogen impurity incorporation.
Fabrication and optical properties of thin silica‐coated CdSe/ZnS quantum dots
Authors: Sun Ye , Masia Francesco , Langbein Wolfgang , Borri Paola 
Published: July 2009

AbstractWe demonstrate the fabrication of thin silica‐coated CdSe/ZnS colloidal quantum dots using a reverse microemulsion method. Spherical particles of <20 nm diameter with a single dot in the centre of a thin silica shell of good morphology are achieved, promising for biophotonic applications where hydrophilic bio‐compatible and small luminescent nanoparticles are needed. We characterize the spectrally‐ and time‐resolved photoluminescence of these silica‐coated dots, from which we identify the influence of each step of the coating procedure on their emission quantum yield. Optimization of the growth parameters eventually results in a less than two‐fold reduction of the quantum yield after silica‐coating.
Photoplastic effects in chalcogenide glasses: A review
Authors: Yannopoulos S. N. , Trunov M. L. 
Published: July 2009

AbstractA synopsis of various photoinduced changes of rheological, mechanical and elastic properties is presented in the first part of the article. After a critical appraisal of a large body of experimental data, it is suggested that the photoviscous effect, that is, the athermal decrease of viscosity of a non‐crystalline chalcogenide upon illumination, is the key for a plethora of photoinduced effects reported so far in the literature under different names. Morphic effects (shape or surface morphology) may appear either in the presence or absence of external mechanical stimuli leading to the fabrication of a variety of technologically important photoprocessed structures. A few representative examples of photoplastic effects are described in some detail in the second part of the paper, based on information provided by in situ Raman scattering and nanoindentation experiments.
On the atomic structure of thin amorphous Ge–Sb–Te films
Authors: Frumar Miloslav , Kohoutek Tomas , Prikryl Jan , Orava Jiri , Wagner Tomas 
Published: July 2009

AbstractThe structure of thin films of Ge2Sb2Te5 was studied by high‐resolution transmission electron microscopy (HRTEM) and by X‐ray diffraction (XRD). The as‐evaporated films prepared by flash evaporation were amorphous. Nearly, all the atoms were randomly distributed but even in as‐evaporated films small areas with some ordering were noticeable. The number and size of the ordered areas increased with thermal treatment of films to temperatures ∼80 °C, i.e., ∼70 °C below the crystallization temperature of amorphous Ge2Sb2Te5. After thermal treatment, small embryos of nucleation centers (size <8 nm) were formed. According to XRD measurements the films as a whole were still fully amorphous. The crystallite model of the structure of amorphous solids is then partly valid, at least for Ge2Sb2Te5. We expect that it can be applied also for other Ge–Sb–Te‐based films, as well as for the other amorphous chalcogenides. The possible impact of the formation of nucleation “embryos” on storage time of data in optical and electrical phase‐change memory materials and devices is discussed.
Garcinia mangostana L.: a phytochemical and pharmacological review
Authors: Obolskiy Dmitriy , Pischel Ivo , Siriwatanametanon Nisarat , Heinrich Michael 
Published: July 2009

AbstractGarcinia mangostana L. (mangosteen, Clusiaceae) has a long history of use as a medical plant, mostly in Southeast Asia. This is a review of the phytochemistry and pharmacology of mangosteen. Traditionally mangosteen is famous for its antiinflammatory properties and is used in the treatment of skin infections and wounds. Other applications include the therapy of various conditions such as dysentery, different urinary disorders, cystitis and gonorrhoea. This review highlights the development of this botanical drug into a widely used nutraceutical. Products derived from G. mangostana are now distributed increasingly all over the world. This has given rise to a concomitant increase in research on the phytochemical constituents and biological activity of mangosteen. Central to the biological activity of the species are xanthones which are reviewed in detail. A comprehensive assessment of the biological activities of individual xanthones as well as extracts of G. mangostana is included. In addition, its potential in terms of developing novel drug leads is assessed. Products containing its fruits are now sold widely as ‘liquid botanical supplements’, but evidence for the health benefits of these products is still lacking. As shown here, a serious weakness in our knowledge is the lack of clinical data and it is not yet clear to what extent the findings about pharmacological activities are of potential clinical relevance. Copyright © 2009 John Wiley & Sons, Ltd.
A comparison of CUSUM, EWMA, and temporal scan statistics for detection of increases in poisson rates
Authors: Han Sung Won , Tsui Kwok‐Leung , Ariyajunya Bancha , Kim Seoung Bum 
Published: July 2009

AbstractVarious control chart methods have been used in healthcare and public health surveillance to detect increases in the rates of diseases or their symptoms. Although the observations in many health surveillance applications are often discrete, few efforts have been made to ex‐ plore the behavior of detection methods in discrete distributions. Joner et al. (Statist. Med. 2008; 27:2555–2575) investigated and compared the performance of the scan statistic methods with the cumulative sum (CUSUM) charts under a Bernoulli distribution. In this paper we compare the performance of three detection methods: temporal scan statistic, CUSUM, and exponential weighted moving average (EWMA) when the observations follow the Poisson distribution. A simulation study showed that the Poisson CUSUM and EWMA charts generally outperformed the Poisson scan statistic methods. In comparisons between CUSUM and EWMA, the CUSUM charts were superior in dealing with a large shift with a later change in time. However, the EWMA charts outperformed the CUSUM charts in situations with a small shift and an early change in time. The methods were also compared with thyroid cancer using a real data set. Copyright © 2009 John Wiley & Sons, Ltd.
Similarity Based Descriptors – Useful for Classification of Substrates of the Human Multidrug Transporter P‐Glycoprotein?
Authors: Schwaha Rita , Ecker Gerhard F. 
Published: July 2009

AbstractAs part of the ATP‐binding cassette transporter superfamily P‐glycoprotein (ABCB1) acts as xenotoxic exporter and consequently is strongly involved in multidrug resistance (MDR) and drug‐drug interactions. In this work we focus on our in‐house developed SIBAR approach for prediction of ABCB1 substrates. SIBAR values were calculated on basis of three different descriptor sets: 2D‐MOE descriptors, VSA descriptors and 3D Autocorrelation vectors using in total four reference sets. In order to compare linear with non‐linear classification methods we used binary QSAR and a support vector machine (SVM), respectively. Results demonstrate that with 2D‐MOE and VSA‐descriptors prediction of non substrates performs better, whereas autocorrelation vectors show higher accuracy for substrates. With respect to the different reference sets used in this case selection on basis of maximum diversity yielded better results than a set derived from the training set compounds. In general, the models show distinct differences in their performance depending on the combination of method and descriptor type.
Development and validation of a gas chromatography/mass spectrometry method for the assessment of genomic DNA methylation
Authors: Rossella Federica , Polledri Elisa , Bollati Valentina , Baccarelli Andrea , Fustinoni Silvia 
Published: July 2009

AbstractA method for the determination of DNA global methylation, taken as the ratio (%) of 5‐methylcytosine (5mCyt) versus the sum of cytosine (Cyt) and 5mCyt, via gas chromatography/mass spectrometry (GC/MS), was developed and validated. DNA (2.5 µg) was hydrolyzed with aqueous formic acid 88%, spiked with cytosine‐2,4‐13C2,15N3 and 5‐methyl‐2H3‐cytosine‐6‐2H1 as internal standards, and derivatized with N‐methyl‐N‐(tert‐butyldimethylsilyl)trifluoroacetamide and 1% tert‐butyldimethylchlorosilane, in the presence of acetonitrile and pyridine. GC/MS, operating in single ion monitoring mode, separated and specifically detected all nucleobases as tert‐butyldimethylsilyl derivatives, without interferences, with the exception of guanosine. The method was linear throughout the range of clinical interest and had good sensitivity, with a limit of quantification of 3.2 pmol for Cyt and 0.056 pmol for 5mCyt, the latter corresponding to a methylation level of 0.41%. Intra‐ and inter‐day precision and accuracy were below 4.0% for both analytes and methylation. The matrix absolute effect, process efficiency and coefficient of variation ranged from 96.5 to 101.2%. The matrix relative effect was below 1%. The method was applied to the analysis of different human DNAs, including: nonmethylated DNA from PCR (methylation 0.00%), hypermethylated DNA prepared using M.SssI CpG methyltransferase (methylation 18.05%), DNA from peripheral blood leukocytes of healthy subjects (N = 6, median methylation 5.45%), DNA from bone marrow of leukemia patients (N = 5, 3.58%) and DNA from myeloma cell lines (N = 4, 2.74%). Copyright © 2009 John Wiley & Sons, Ltd.
Optimal preparation methods for automated matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry profiling of low molecular weight proteins and peptides
Authors: Penno Megan A. S. , Ernst Matthias , Hoffmann Peter 
Published: July 2009

AbstractMass spectrometry (MS) profiling of the proteome and peptidome for disease‐associated patterns is a new concept in clinical diagnostics. The technique, however, is highly sensitive to external sources of variation leading to potentially unacceptable numbers of false positive and false negative results. Before MS profiling can be confidently implemented in a medical setting, standard experimental methods must be developed that minimize technical variance. Past studies of variance have focused largely on pre‐analytical variation (i.e., sample collection, handling, etc.). Here, we examined how factors at the analytical stage including the matrix and solid‐phase extraction influence MS profiling. Firstly, a standard peptide/protein sample was measured automatically by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) MS across five consecutive days using two different preparation methods, dried droplet and sample/matrix, of four types of matrix: α‐cyano‐4‐hydroxycinnamic acid (HCCA), sinapinic acid (SA), 2,5‐dihydroxybenzoic acid (DHB) and 2,5‐dihydroxyacetophenone (DHAP). The results indicated that the matrix preparation greatly influenced a number of key parameters of the spectra including repeatability (within‐day variability), reproducibility (inter‐day variability), resolution, signal strength, background intensity and detectability. Secondly, an investigation into the variance associated with C8 magnetic bead extraction of the standard sample prior to automated MS profiling demonstrated that the process did not adversely affect these same parameters. In fact, the spectra were generally more robust following extraction. Thirdly, the best performing matrix preparations were evaluated using C8 magnetic bead extracted human plasma. We conclude that the DHAP prepared according to the dried‐droplet method is the most appropriate matrix to use when performing automated MS profiling. Copyright © 2009 John Wiley & Sons, Ltd.
Practical assessment of hardware limitations on power aware wireless sensor networks—An anti‐windup approach
Authors: Walsh M. J. , Alavi S. M. Mahdi , Hayes M. J. 
Published: July 2009

AbstractThis work considers the effect of hardware constraints that typically arise in practical ‘power‐aware’ wireless sensor network systems. A rigorous methodology is presented that quantifies the effect of output power limit and quantization constraints on bit error rate performance. The approach uses a novel, intuitively appealing means of addressing the output power constraint, wherein the attendant saturation block is mapped from the output of the plant to its input and compensation is then achieved using a robust anti‐windup scheme. A priori levels of system performance are attained using a quantitative feedback theory approach on the initial, linear stage of the design paradigm. This hybrid design is assessed experimentally using a fully compliant 802.15.4 testbed where mobility is introduced through the use of autonomous robots. A benchmark comparison between the new approach and a number of existing strategies is also presented. Copyright © 2009 John Wiley & Sons, Ltd.
Minimal data rate stabilization of nonlinear systems over networks with large delays
Authors: De Persis C. 
Published: July 2009

AbstractControl systems over networks with a finite data rate can be conveniently modeled as hybrid (impulsive) systems. For the class of nonlinear systems in feedfoward form, we design a hybrid controller, which guarantees stability, in spite of the measurement noise due to the quantization,andof an arbitrarily large delay, which affects the communication channel. The rate at which feedback packets are transmitted from the sensors to the actuators is shown to be arbitrarily close to the infimal one. Copyright © 2009 John Wiley & Sons, Ltd.
Stabilizability for nonlinear systems of difference equations
Authors: Medina Rigoberto 
Published: July 2009

AbstractThe stabilization problem for a class of infinite‐dimensional discrete‐time nonlinear systems is discussed. Under an appropiate growth condition on the nonlinear perturbation combined with the ‘freezing’ method to discrete‐time systems on Banach spaces, we establish explicit conditions for global feedback exponential stabilizability, and these conditions are easy to construct and to verify. This approach will allow us to avoid the construction of Lyapunov's functions in some situations. Copyright © 2009 John Wiley & Sons, Ltd.
Invertebrate communities in Compensation Creek, a man‐made stream in boreal Newfoundland: The influence of large woody debris
Authors: Gabriel Celina M. , Clarke Keith D. , Campbell Christine E. 
Published: July 2009

AbstractBenthic invertebrate communities were examined in Compensation Creek, a man‐made stream in south‐central Newfoundland, Canada. Samples taken in September 2006 and September 2007 from large woody debris (LWD) were compared with samples from benthic environments to determine whether LWD supported a more diverse and abundant invertebrate community. Benthic habitats in a nearby natural stream were also sampled. Taxa composition was similar between the man‐made and the natural stream, highlighting successful colonization for the majority of taxa. Within Compensation Creek, taxa richness was higher in benthic habitats than on LWD, likely influenced by the successional age of the stream and surrounding habitat. The more complex benthic substrate provided refugia and allowed for the accumulation of fine detritus as a food source. Scrapers were almost completely absent from LWD and collector‐gatherer abundance was greater in the benthos. Collector‐filterer abundance was more than six times greater near the pond outflow than farther downstream when discharge was high, but abundances were almost equal when discharge was reduced. Riparian vegetation has not fully established around the man‐made stream, whereas it is overhanging and extensive at the natural stream, leading to more leaf‐litter input for shredders. As the morphology of Compensation Creek changes, the invertebrate community will continue to develop and likely increase utilization of accumulated detritus at LWD. Copyright © 2009 John Wiley & Sons, Ltd.
Coloring uniform hypergraphs with few edges
Authors: Kostochka A.V. , Kumbhat M. 
Published: July 2009

AbstractA hypergraph is b‐simple if no two distinct edges share more than b vertices. Let m(r, t, g) denote the minimum number of edges in an r‐uniform non‐t‐colorable hypergraph of girth at least g.Erdős and Lovász proved that

A result of Szabó improves the lower bound by a factor of r2−ϵ for sufficiently large r. We improve the lower bound by another factor of r and extend the result to b‐simple hypergraphs. We also get a new lower bound for hypergraphs with a given girth. Our results imply that for fixed b, t, and ϵ > 0 and sufficiently large r, every r‐uniform b‐simple hypergraph $\cal {H}$ with maximum edge‐degree at most trr1−ϵ is t‐colorable. Some results hold for list coloring, as well. © 2009 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Sustainable development in the uplands of Lao PDR
Authors: Alexander Kim Suzanne , Millar Joanne , Lipscombe Neil 
Published: July 2009

AbstractSmallholder farmers resident in marginalized communities in the uplands of Lao People's Democratic Republic (Lao PDR) have been subject to agricultural reforms and policies requiring adaptation of their rural livelihood systems and adoption of new agricultural technologies. Structured interviews with farmers explored their perspectives and experiences when developing economically viable, locally adapted and diversified livelihood and farming system strategies. Agricultural productivity was dependent on cultivatable land and forest biodiversity, while agricultural strategies embedded knowledge, information and ideas to enable farmers to adapt to changing conditions. Political, social, economic and environmental factors have influenced smallholder farmers in their preference and uptake of new technologies and activities. Opportunities to trial new technologies and further support, advice and information from extension officers and projects, combined with market opportunities and access to credit, will enable some farmers to find sustainable production alternatives. Copyright © 2009 John Wiley & Sons, Ltd and ERP Environment.