bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integration of VO2 Thin Films on Si(100) for Thermal Switching Devices Applications
Authors: Gupta Alok , Aggarwal Ravi , Narayan Jagdish 
Published: June 2009

AbstractThin films of vanadium dioxide (VO2) exhibit an interesting semiconductor to metal transition (SMT) when heated above ˜680C in which its resistivity changes by 3-4 orders of magnitude and its transmittance for IR wavelengths drops drastically. Integration of these thin films with Si (100) substrate is of immense technological importance due to its potential applications in sensor and memory based devices. Using pulsed laser deposition (PLD) we have demonstrated in this study that thin films of VO2 can be grown epitaxially on Si (100) substrate using an intermediate tetragonal Yttrium-Stabilized Zirconia (YSZ) layer without any further annealing. X-ray diffraction (XRD) and cross-section transmission electron microscopy studies were performed on the films and they are found to be of highly epitaxial nature. Electrical resistivity measurement were carried out using the four-point probe method and SMT parameters were extracted using Gaussian fit of the data. The S-M transition parameters are in close proximity with parameters obtained from vanadium oxide films deposited on oxide based substrates such as Al2O3 or TiO2.
Quantitative Investigation of the Factors Affecting the Hydrothermal Growth of Zinc Oxide Nanowires
Authors: Rachamim Aron Robert , Dalal Sharvari H. , Pfaendler Sieglinde M.-L. , Swanwick Michael E. , Flewitt Andrew , Milne William I. 
Published: June 2009

AbstractZinc oxide (ZnO) nanowires (NWs) are receiving significant industrial and academic attention for a variety of novel electronic, optoelectronic and MEMS device applications due to their unusual combination of physical properties, including being optically transparent, semiconducting and piezoelectric. Hydrothermal growth is possible at significantly lower temperatures (and hence lower thermal budgets) compared with other NW growth methods, such as chemical vapour deposition. In this context, the hydrothermal growth of ZnO NWs on seeded substrates immersed in equimolar zinc nitrate/HMTA aqueous solution was investigated. NWs were grown on polished silicon (001) substrates, and the solution concentrations, temperatures and growth times were varied. Importantly, the NW diameter was found to depend only on concentration during hydrothermal growth for times up to 4 hours. The average diameter was 14 nm in 0.005 M solution and increased up to a maximum 150 nm at 0.07 M, when the NWs formed a continuous polycrystalline film. Concentration and temperature were all found to affect the axial growth rate of NWs in the [0001] direction. The growth rate was constant up to 4 hours (200 nm hr-1) for constant conditions (81 oC, 0.025 M). The growth rate was found to increase approximately linearly with concentration at a rate of 7840 nm M-1 hr-1 up to 0.06 M (81 oC solution). The growth rate also increased linearly with temperature at a rate of 4.9 nm hr-1 K-1 (0.025 M solution). This indicates that growth takes place close to the equilibrium point, found by linear regression to be 36 oC for 0.025 M solution.
High-throughput top-down and bottom-up processes for forming single-nanotube based architectures for 3D electronics
Authors: Kaul Anupama B , Megerian Krikor G. , Allmen Paul von , Kowalczyk Robert , Baron Richard 
Published: June 2009

AbstractWe have developed manufacturable approaches to form single, vertically aligned carbon nanotubes, where the tubes are centered precisely, and placed within a few hundred nm of 1-1.5 m deep trenches. These wafer-scale approaches were enabled by chemically amplified resists and inductively coupled Cryo-etchers for forming the 3D nanoscale architectures. The tube growth was performed using dc plasma-enhanced chemical vapor deposition (PECVD), and the materials used for the pre-fabricated 3D architectures were chemically and structurally compatible with the high temperature (700 °C) PECVD synthesis of our tubes, in an ammonia and acetylene ambient. Tube characteristics were also engineered to some extent, by adjusting growth parameters, such as Ni catalyst thickness, pressure and plasma power during growth. Such scalable, high throughput top-down fabrication techniques, combined with bottom-up tube synthesis, should accelerate the development of PECVD tubes for applications such as interconnects, nano-electromechanical (NEMS), sensors or 3D electronics in general.
Composites of silver nanoparticles and poly(vinylidene fluoride-trifluoroethylene)copolymer: Preparation as well as structural and electrical characterization
Authors: Wegener Michael , Greco Tonino 
Published: June 2009

AbstractComposites comprising of polymers and metal nanoparticles are of great interest in regard to electronic and opto-electronic applications. The preparation of such nanocomposites with homogenously dispersed particles usually cannot be solved by mixing the polymer and the desired isolated colloids due to strong agglomeration tendency of the metallic nanoparticles. Consequently, nanocomposites with colloids have been prepared by synthesis of the inorganic particles in situ, for instance in solution, and then mixed with the polymer solution.Extensive attention has been given to the study of the plasmonic properties of noble metal nanoparticles as a result of their potential application as waveguides, photonic circuits, and sensors [1]. Surface plasmon polaritons are excited when electromagnetic radiation causes coherent oscillations of the conducting electrons of noble metal nanoparticles such as gold, silver or copper. The selective photon absorption and scattering allow the monitoring of the optical properties of the nanoparticles by conventional spectroscopic methods like UV-vis spectroscopy. Previous investigations show that the surface plasmon resonance frequency is extremely sensitive to the size, shape, and the surrounding dielectric environment of the nanoparticles [2].In order to obtain multifunctional composites electro-active polymers (EAP) can be chosen as matrix materials. EAPs such as polyvinylidene fluoride (PVDF) and its copolymer with trifluoroethylene (P(VDF-TrFE)) show a ferroelectric polarization accompanied with piezo- and pyroelectric properties. Both polymers are suitable for composite preparation as earlier studies have shown, e.g. performed on ceramic-polymer composites in order to optimize their piezo- and pyroelectric properties and to adjust their dielectric properties, respectively. Recently, PVDF with embedded metallic nanoparticles was studied regarding the kinetics of film preparation, dispersion and resulting properties [3].In this work, the influence of homogenously dispersed silver-nanoparticles in electro-active polymers such as PVDF and P(VDF-TrFE) has been investigated over a broad range of mass fractions of silver. For low silver nanoparticle content (up to 3wt.%) the surface plasmon polariton resonance peak can be observed in the blue spectral region. From the infrared spectra it is concluded that no significant degradation of the polymers occurs. Higher silver amounts cause the formation of fractal-like agglomerates. Thus, a high extinction cross section in the visible and infrared spectral range is found. Furthermore, the influence of the silver mass fraction to the thermal, electrical and dielectric properties of the nanocomposites is discussed in detail.[1] S. A. Maier, H. A. Atwater, J. Appl. Phys. 2005, 98, 011101-10. [2] J. J. Mock, et al, J. Chem. Phys. 2002, 116, 6755-6759.[3] J. Compton, et al, Makromol. Symp. 2007, 247, 182-189.
On the defect induced ferromagnetic ordering above room-temperature in undoped and Mn doped ZnO thin films
Authors: Kapilashrami Mukes , Xu Jun , Ström Valter , Rao K V , Belova Lyubov 
Published: June 2009

AbstractEvidence for long range ferromagnetic order above room-temperature, RTFM, in pristine ZnO, In2O3, TiO2 nanoparticles and thin films, containing no nominal magnetic elements have been reported recently. This could question the origin of RTFM in doped dilute alloys if for example the ZnO matrix itself develops a defect induced magnetic order with a significant moment per unit cell. In this presentation we report a systematic study of the film thickness dependence of RTFM in pure ZnO deposited by DC Magnetron Sputtering. We observe a maximum in the saturation magnetization, MS, value of 0.62 emu/g (0,018 μB/unit cell), for a ˜480 nm film deposited in an oxygen ambience of appropriate pressure. Above a thickness of around 1 μm the films are diamagnetic as expected. We thus see a sequential transition from ferromagnetism to para- and eventual diamagnetism as a function of film thickness in ZnO. We also find that in such a ZnO matrix with a maximum intrinsic defect induced moment, on doping with Mn the maximum enhanced MS value of 0.78 emu/g is obtained for 1at.% Mn doping. With this approach of appropriate doping in a defect tailored matrix, we routinely obtain RTFM in both undoped and Mn- doped ZnO thin films.
Four Stable Magnetization States Formed in the Single Layer of GaMnAs Ferromagnetic Film
Authors: Lee Sanghoon , Liu X. , Furdyna J. K. 
Published: June 2009

AbstractA GaMnAs ferromagnetic semiconductor film under compressive strain has strong biaxial in-plane anisotropy, which generates four stable magnetization directions at a zero magnetic field. This feature results in a double switching behavior in the main loop of planar Hall resistance (PHR) spectrum. The minor scan of PHR measurement exhibited staggered asymmetric loops due to the formation of the stable muti-domain structures. We demonstrated the observed four stable PHR states can be served as quaternary logic states for spin memory device.
Electronic Structure and Magnetic Properties of Ti-doped ZnO
Authors: Lardjane Soumia , Merad Ghouti , Faraoun Houda Imane 
Published: June 2009

AbstractRecent experiments suggest that Ti doped ZnO can be a promising room temperature dilute magnetic semiconductor (DMS) and a potentially useful material for spintronic devices. Furthermore, the fact that Ti doped ZnO shows ferromagnetic behaviour despite it contains no magnetic element makes this system good candidate for theoretical investigation regarding the controversies about the origin of ferromagnetic ordering in TM-doped ZnO. In this work, the density functional theory (DFT) is used to calculate the electronic and magnetic structures of Ti-doped ZnO. The obtained results are used to discuss the origin of the ferromagnetism, and the contribution of different atoms in the magnetic moment.
Multifunctional Cellular Materials
Authors: De Gliniasty Michel , Bouchet Régis 
Published: June 2009

AbstractIn many industrial fields, structural materials play a key role in the increase of performance, but new requirements in terms of energy saving, safety, materials economy… lead to more stringent requirements on materials properties.
The two usual strategies –microstructure optimisation and shape optimisation-, which act at two different scales, the micrometer scale and above the centimetre scale, become less and less efficient with this new strong demand for multi-functional properties. The largely unexplored millimetre scale, domain of the so called “structural materials”, is a possible answer. Structural materials benefit of an extra degree of freedom well suited for multi-functionality: they allow using combination of materials from different classes, allow geometrical optimisation, and can be naturally integrated in structures such as sandwiches and various stiffened plate geometries.
The price to pay for this extra-richness is the extraordinary wide variety of potential solutions to investigate for a given problem. Hence modelling plays a crucial role for selecting and optimising such innovative materials.
This paper is an overview of a project, named MAPO (“Materiaux Poreux”), aiming at designing high-temperature materials with acoustical and structural properties.
Generalizing the Evaluation of Medical Image Processing Tools by Use of Gabor Patterns
Authors: Strasburger H. , Rascher-Friesenhausen R. , Klein J. , Preim B. , Apelt D. 
Published: June 2009

Summary
Objective: Tools for medical image processing are usually evaluated by observers with radiological experience and with complex tasks. For easing evaluation of filtering and enhancement tools, the observer’s task can be generalized.
Methods: By describing aspects of the MCS method (Mammographic Contrast Sensitivity) we illustrate issues of selecting a metric for assessing visual performance, the observer’s task and the image material to be used, aiming at a generalization of the design of studies for the evaluation of medical image processing tools. Concerning the metric, we distinguish acuity from contrast sensitivity. With respect to the observer’s task, we distinguish tasks of discrimination from those at a higher level of recognition. Finally, we show the advantage of using medical images for evaluating image processing tools by comparing the results for measurements on homogeneous background and mammographic images.
Results: The perceptual level of the observer’s task and the complexity of the used image material influences the outcome of observer studies, particularly also from crowding effects. The design of a study should minimize the impact of the observer’s experience on the outcome. This can be achieved by using non-anatomical, standardized perceptual targets like Gabor patterns, used in the context of medical images.
Conclusions: Understanding the concepts of perception helps designing observer studies that are as complex as required, but at the same time as simple and general as possible. Performing an observer study may be simplified by a study design which does not require radiological experience of the observers, if the study aims at the evaluation of tools that shall support basic perception tasks, such as e.g. contrast enhancement.
High resolution fate map of the zebrafish diencephalon
Authors: Russek‐Blum Niva , Nabel‐Rosen Helit , Levkowitz Gil 
Published: June 2009

AbstractThe diencephalon acts as an interactive site between the sensory, central, and endocrine systems and is one of the most elaborate structures in the vertebrate brain. To better understand the embryonic development and morphogenesis of the diencephalon, we developed an improved photoactivation (uncaging)‐based lineage tracing strategy. To determine the exact position of a given diencephalic progenitor domain, we used a transgenic line driving green fluorescent protein (GFP) in cells expressing the proneural protein, Neurogenin1 (Neurog1), which was used as a visible neural plate landmark. This approach facilitated precise labeling of defined groups of cells in the prospective diencephalon of the zebrafish neural plate. In this manner, we labeled multiple overlapping areas of the diencephalon, thereby ensuring both accuracy and reproducibility of our lineage tracing regardless of the dynamic changes of the developing neural plate. We present a fate map of the zebrafish diencephalon at a higher spatial resolution than previously described. Developmental Dynamics 238:1827–1835, 2009. © 2009 Wiley‐Liss, Inc.
Resonance Raman Studies of Bis(terpyridine)ruthenium(II) Amino Acid Esters and Diesters
Authors: Heinze Katja , Hempel Klaus , Tschierlei Stefanie , Schmitt Michael , Popp Jürgen , Rau Sven 
Published: June 2009

AbstractResonance Raman (rR) spectroscopy in combination with DFT calculations was used to elucidate the nature of the 1metal‐to‐ligand charge‐transfer states (1MLCT) of ester derivatives of homo‐ and heteroleptic bis(terpyridine)ruthenium(II) complexes [RuII(tpy–COOC2H5)(tpy–R)](PF6)2 with R = NH2 (1a), R = COOC2H5 (1b) and R = NHCOCH3 (1c). The rR spectra provide evidence that the 1MLCT states of 1b and 1c are well described by the expected 1[(“t2g”)5{π*(tpy–COOC2H5)}1] electron configuration, while the 1MLCT state of the donor/acceptor‐substituted complex 1a also involves the amine‐substituted terpyridine ligand. The excited state of 1a can be described by a 1[{dyz/π(tpy–NH2)}1{π*(tpy–COOC2H5)}1] electron configuration with ligand‐to‐ligand charge‐transfer (1LLCT) character. The mixed MLCT/LLCT character of the singlet excited state of 1a is characterized by a low‐energy absorption maximum (λmax = 500 nm). The π‐donor character of the tpy–NH2 ligand is also corroborated by DFT calculations on model compounds (small HOMO/LUMO gap, short C–N bond, longer Ru–N bond). The emitting triplet state features a low‐energy emission maximum (λmax = 744 nm) as well as a longer lifetime of the emitting state (τ = 33.7 ns) at room temperature in acetonitrile as compared to the data of 1b and 1c.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
The spatial and temporal patterns of aggradation in a temperate, upland, gravel‐bed river
Authors: Raven Emma K. , Lane Stuart N. , Ferguson Rob I. , Bracken Louise J. 
Published: June 2009

AbstractIntensive field monitoring of a reach of upland gravel‐bed river illustrates the temporal and spatial variability of in‐channel sedimentation. Over the six‐year monitoring period, the mean bed level in the channel has risen by 0·17 m with a maximum bed level rise of 0·5 m noted at one location over a five month winter period. These rapid levels of aggradation have a profound impact on the number and duration of overbank flows with flood frequency increasing on average 2·6 times and overbank flow time increasing by 12·8 hours. This work raises the profile of coarse sediment transfer in the design and operation of river management, specifically engineering schemes. It emphasizes the need for the implementation of strategic monitoring programmes before engineering work occurs to identify zones where aggradation is likely to be problematic. Exploration of the sediment supply and transfer system can explain patterns of channel sedimentation. The complex spatial, seasonal and annual variability in sediment supply and transfer raise uncertainties into the system's response to potential changes in climate and land‐use. Thus, there is a demand for schemes that monitor coarse sediment transfer and channel response. Copyright © 2009 John Wiley & Sons, Ltd.
Nutrient solution concentration and growing season affect yield and quality of Lactuca sativa L. var. acephala in floating raft culture
Authors: Fallovo Carlo , Rouphael Youssef , Rea Elvira , Battistelli Alberto , Colla Giuseppe 
Published: June 2009

AbstractBACKGROUND: There is growing interest among consumers in baby leaf vegetables, mostly requested for mixed salads, both as fresh market products and ready‐to‐use vegetables. Fertilisation is one of the most practical and effective ways of controlling and improving the yield and nutritional quality of crops for human consumption. The optimal fertiliser concentration for baby leaf vegetables depends on the environmental conditions. The aim of the present work was to determine the effects of nutrient solution concentration (2, 18, 34, 50 or 66 mequiv L−1) during two consecutive growing seasons (spring and summer) on the yield and leaf quality of Lactuca sativa L. var. acephala grown in a floating system.RESULTS: Marketable fresh yield, total dry biomass, leaf area index, macroelement (N, P, K and Mg) concentrations and nitrate and total chlorophyll contents increased in response to an increase in nutrient solution concentration, while the opposite trend was observed for root/shoot ratio and glucose, fructose, starch, total carbohydrate and protein contents. Plants grown in the spring season exhibited lower yield and growth (total dry biomass and leaf area index) but higher leaf quality (higher carbohydrate content and lower nitrate content) than those grown in the summer season.CONCLUSION: The use of nutrient solution concentrations of 37 and 44 mequiv L−1 for the spring and summer seasons respectively could be adopted in the present conditions to improve marketable fresh yield and leaf mineral content, but with a slight reduction in some nutritional parameters. Copyright © 2009 Society of Chemical Industry
NMR metabolomics and drug discovery
Authors: Powers Robert 
Published: June 2009

AbstractNMR is an integral component of the drug discovery process with applications in lead discovery, validation, and optimization. NMR is routinely used for fragment‐based ligand affinity screens, high‐resolution protein structure determination, and rapid protein‐ligand co‐structure modeling. Because of this inherent versatility, NMR is currently making significant contributions in the burgeoning area of metabolomics, where NMR is successfully being used to identify biomarkers for various diseases, to analyze drug toxicity and to determine a drug's in vivo efficacy and selectivity. This review describes advances in NMR‐based metabolomics and discusses some recent applications. Copyright © 2009 John Wiley & Sons, Ltd.
A novel approach for the homogenization of cellulose to use micro‐amounts for stable isotope analyses
Authors: Laumer W. , Andreu L. , Helle G. , Schleser G. H. , Wieloch T. , Wissel H. 
Published: June 2009

AbstractClimate reconstructions using stable isotopes from tree‐rings are steadily increasing. The investigations concentrate mostly on cellulose due to its high stability. In recent years the available amount of cellulose has steadily decreased, mainly because micro‐structures of plant material have had to be analyzed. Today, the amounts of cellulose being studied are frequently in the milligram and often in the microgram range. Consequently, homogeneity problems with regard to the stable isotopes of carbon and oxygen from cellulose have occurred and these have called for new methods in the preparation of cellulose for reliable isotope analyses. Three different methods were tested for preparing isotopically homogenous cellulose, namely mechanical grinding, freezing by liquid nitrogen with subsequent milling and ultrasonic breaking of cellulose fibres. The best precision of isotope data was achieved by freeze‐milling and ultrasonic breaking. However, equipment for freeze‐milling is expensive and the procedure is labour‐intensive. Mechanical grinding resulted in a rather high loss of material and it is also labour‐intensive. The use of ultrasound for breaking cellulose fibres proved to be the best method in terms of rapidity of sample throughput, avoidance of sample loss, precision of isotope results, ease of handling, and cost. Copyright © 2009 John Wiley & Sons, Ltd.