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General Approach (general + approach)
Selected AbstractsA General Approach to the Synthesis of Substituted Isoxazolo[4,3- c]quinolines via Chalcones,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 26 2007Sudharshan Madapa Abstract A general and practical approach to the synthesis of substituted isoxazolo[4,3- c]quinolines from the substituted isoxazolines obtained by 1,3-dipolar cycloadditions between2-nitrobenzonitrile oxide and chalcones is described. SnCl2·2H2O-mediated reduction of the nitro group, followed by intramolecular cyclization involving the amino and the keto groups in these substrates, furnished mixtures ofisoxazolo[4,3- c]quinolines and 3,5-dihydroisoxazolo[4,3- c]quinolines. In contrast, the reduction of these substrates with Fe/AcOH unexpectedly yielded 3-benzoylquinolin-4-ylamine derivatives.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] A General Approach for Fabricating Arc-Shaped Composite Nanowire Arrays by Pulsed Laser DepositionADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Yue Shen Abstract Here, a new method is demonstrated that uses sideways pulsed laser deposition to deliberately bend nanowires into a desired shape after growth and fabricate arc-shaped composite nanowire arrays of a wide range of nanomaterials. The starting nanowires can be ZnO, but the materials to be deposited can be metallic, semiconductor, or ceramic depending on the application. This method provides a general approach for rational fabrication of a wide range of side-by-side or "core,shell" nanowire arrays with controllable degree of bending and internal strain. Considering the ZnO is a piezoelectric and semiconductive material, its electrical properties change when deformed. This technique has potential applications in tunable electronics, optoelectronics, and piezotronics. [source] A General Approach to Semimetallic, Ultra-High-Resolution, Electron-Beam ResistsADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Bao-Yu Zong Abstract Commercial electron-beam resists are modified into semimetallic resists by doping with 1,3,nm metal nanoparticles, which improve the resolution, contrast, strength, dry-etching resistance, and other properties of the resist. With the modified resists, fine resist nanopatterns from electron-beam lithography are readily converted into 5,50,nm, high-quality multilayers for metallic nanosensors or nanopatterns via ion-beam etching. This method solves the problem of the fabrication of fine (<50,nm) metallic nanodevices via pattern transferring. [source] A General Approach to First Order Phase Transitions and the Anomalous Behavior of Coexisting Phases in the Magnetic CaseADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Sergio Gama Abstract First order phase transitions for materials with exotic properties are usually believed to happen at fixed values of the intensive parameters (such as pressure, temperature, etc.) characterizing their properties. It is also considered that the extensive properties of the phases (such as entropy, volume, etc.) have discontinuities at the transition point, but that for each phase the intensive parameters remain constant during the transition. These features are a hallmark for systems described by two thermodynamic degrees of freedom. In this work it is shown that first order phase transitions must be understood in the broader framework of thermodynamic systems described by three or more degrees of freedom. This means that the transitions occur along intervals of the intensive parameters, that the properties of the phases coexisting during the transition may show peculiar behaviors characteristic of each system, and that a generalized Clausius,Clapeyron equation must be obeyed. These features for the magnetic case are confirmed, and it is shown that experimental calorimetric data agree well with the magnetic Clausius,Clapeyron equation for MnAs. An estimate for the point in the temperature-field plane where the first order magnetic transition turns to a second order one is obtained (the critical parameters) for MnAs and Gd5Ge2Si2 compounds. Anomalous behavior of the volumes of the coexisting phases during the magnetic first order transition is measured, and it is shown that the anomalies for the individual phases are hidden in the behavior of the global properties as the volume. [source] A General Approach to the Synthesis of ,2 -Amino Acid Derivatives via Highly Efficient Catalytic Asymmetric Hydrogenation of ,-AminomethylacrylatesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Yujuan Guo Abstract A new strategy was developed for the synthesis of a valuable class of ,-aminomethylacrylates via the Baylis,Hillman reaction of different aldehydes with methyl acrylate followed by acetylation of the resulting allylic alcohols and SN2,-type amination of the allylic acetates. Asymmetric hydrogenation of these diverse olefinic precursors using rhodium(Et-Duphos) catalysts provided the corresponding ,2 -amino acid derivatives with excellent enantioselectivities and exceedingly high reactivities (up to >99.5% ee and S/C=10,000). The first hydrogenation of (Z)-configurated substrates was studied for the synthesis of ,2 -amino acid derivatives. The high influence of the substrate geometry and steric hindrance on the reactivity and enantioselectivity was also disclosed for this reaction. This protocol provides a highly practical, facile and scalable method for the preparation of optically pure ,2 -amino acids and their derivatives under mild reaction conditions. [source] Copper(II) Bromide/Boron Trifluoride Etherate-Cocatalyzed Cyclization of Ketene Dithioacetals and p -Quinones: a Mild and General Approach to Polyfunctionalized BenzofuransADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Yingjie Liu Abstract A new application of copper(II) bromide-activated ketene dithioacetals as nucleophiles in organic chemistry has been developed. Under the cocatalysis of copper(II) bromide (2.0,mol%) and boron trifluoride etherate (10,mol%), the conjugate addition and sequential cyclization of ,-electron-withdrawing group-substituted ketene dithioacetals with p -quinones in acetonitrile at room temperature gave a variety of benzofurans. This formal [3+2],cycloaddition provides a general method for catalytic synthesis of polyfunctionalized benzofurans with the advantages of readily available starting materials, cheap catalysts, mild reaction conditions, good yields and wide range of synthetic potential for the benzofuran products. Further transformations of the resulting benzofurans to 2-aminobenzofurans and benzofuro[2,3- d]pyrimidine derivatives are also investigated. [source] Evidence-Based Recommendations for the Assessment and Management of Sleep Disorders in Older PersonsJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 5 2009AGSF, Harrison G. Bloom MD Sleep-related disorders are most prevalent in the older adult population. A high prevalence of medical and psychosocial comorbidities and the frequent use of multiple medications, rather than aging per se, are major reasons for this. A major concern, often underappreciated and underaddressed by clinicians, is the strong bidirectional relationship between sleep disorders and serious medical problems in older adults. Hypertension, depression, cardiovascular disease, and cerebrovascular disease are examples of diseases that are more likely to develop in individuals with sleep disorders. Conversely, individuals with any of these diseases are at a higher risk of developing sleep disorders. The goals of this article are to help guide clinicians in their general understanding of sleep problems in older persons, examine specific sleep disorders that occur in older persons, and suggest evidence- and expert-based recommendations for the assessment and treatment of sleep disorders in older persons. No such recommendations are available to help clinicians in their daily patient care practices. The four sections in the beginning of the article are titled, Background and Significance, General Review of Sleep, Recommendations Development, and General Approach to Detecting Sleep Disorders in an Ambulatory Setting. These are followed by overviews of specific sleep disorders: Insomnia, Sleep Apnea, Restless Legs Syndrome, Circadian Rhythm Sleep Disorders, Parasomnias, Hypersomnias, and Sleep Disorders in Long-Term Care Settings. Evidence- and expert-based recommendations, developed by a group of sleep and clinical experts, are presented after each sleep disorder. [source] Modelling Long-memory Time Series with Finite or Infinite Variance: a General ApproachJOURNAL OF TIME SERIES ANALYSIS, Issue 1 2000Remigijus Leipus We present a class of generalized fractional filters which is stable with respect to series and parallel connection. This class extends the so-called fractional ARUMA and fractional ARMA filters previously introduced by e.g. Goncalves (1987) and Robinson (1994) and recently studied by Giraitis and Leipus (1995) and Viano et al. (1995). Conditions for the existence of the induced stationary S,S and L2 processes are given. We describe the asymptotic dependence structure of these processes via the codifference and the covariance sequences respectively. In the L2 case, we prove the weak convergence of the normalized partial sums. [source] A General Approach to Hedging Options: Applications to Barrier and Partial Barrier OptionsMATHEMATICAL FINANCE, Issue 3 2002Hans-Peter Bermin In this paper we consider a Black and Scholes economy and show how the Malliavin calculus approach can be extended to cover hedging of any square integrable contingent claim. As an application we derive the replicating portfolios of some barrier and partial barrier options. [source] General Approach to the Coupling of Organoindium Reagents with Imines via Copper Catalysis.CHEMINFORM, Issue 37 2006Daniel A. Black Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] A General Approach to (5S,6R)-6-Alkyl-5-benzyloxy-2-piperidinones: Application to the Asymmetric Syntheses of Neurokinin Substance P Receptor Antagonist (-)-L-733,061 and (-)-Deoxocassine.CHEMINFORM, Issue 1 2005Liang-Xian Liu Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: General Approach for the Synthesis of Sarpagine/Macroline Indole Alkaloids.CHEMINFORM, Issue 20 2002Enantiospecific Total Synthesis of the Indole Alkaloid Trinervine. Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] A General Approach to Fabricate Diverse Noble-Metal (Au, Pt, Ag, Pt/Au)/Fe2O3 Hybrid NanomaterialsCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2010Jun Zhang Dr. Abstract A novel, facile, and general one-pot strategy is explored for the synthesis of diverse noble-metal (Au, Pt, Ag, or Pt/Au)/Fe2O3 hybrid nanoparticles with the assistance of lysine (which is a nontoxic, user friendly amino acid that is compatible with organisms) and without using any other functionalization reagents. Control experiments show that lysine, which contains both amino and carboxylic groups, plays dual and crucial roles as both linker and capping agents in attaching noble metals with a small size and uniform distribution onto an Fe2O3 support. Considering the perfect compatibility of lysine with organism, this approach may find potentials in biochemistry and biological applications. Furthermore, this novel route is also an attractive alternative and supplement to the current methods using a silane coupling agent or polyelectrolyte for preparing hybrid nanomaterials. To demonstrate the usage of such hybrid nanomaterials, a chemical gas sensor has been fabricated from the as-synthesized Au/Fe2O3 nanoparticles and investigated for ethanol detection. Results show that the hybrid sensor exhibits significantly improved sensor performances in terms of high sensitivity, low detection limit, better selectivity, and good reproducibility in comparison with pristine Fe2O3. Most importantly, this general approach can be further employed to fabricate other hybrid nanomaterials based on different support materials. [source] Hypervideo application on an experimental control system as an approach to educationCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 1 2008Debevc, Matja Abstract Hypervideo, as an interactive tool with links within video frames, is becoming widely used in multimedia presentations for e-learning applications. Its concept of rich multimedia presentation together with temporal based link objects, gives a chance for use in engineering education courses, where many practical work and experiments are needed. In the article we present a strategy for the development and navigation of hypervideo application, to be used in engineering education. Example of magnetic suspension system experiment was built as hypervideo application. The system usability was tested with two methods, software usability measurement inventory (SUMI) evaluation and general approach to usability engineering. Test results have shown that hypervideo increases the users' motivation to work and helps students recognize, organize and present specific information. By applying some of the proposed improvements in future development, hypervideo could be a significant tool in the future of engineering education. © 2008 Wiley Periodicals, Inc. Comput Appl Eng Educ 16: 31,44, 2008; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20116 [source] Energy-Based Image DeformationCOMPUTER GRAPHICS FORUM, Issue 5 2009Z. Karni Abstract We present a general approach to shape deformation based on energy minimization, and applications of this approach to the problems of image resizing and 2D shape deformation. Our deformation energy generalizes that found in the prior art, while still admitting an efficient algorithm for its optimization. The key advantage of our energy function is the flexibility with which the set of "legal transformations" may be expressed; these transformations are the ones which are not considered to be distorting. This flexibility allows us to pose the problems of image resizing and 2D shape deformation in a natural way and generate minimally distorted results. It also allows us to strongly reduce undesirable foldovers or self-intersections. Results of both algorithms demonstrate the effectiveness of our approach. [source] Possibilism: An Approach to Problem-Solving Derived from the Life and Work of Albert O. HirschmanDEVELOPMENT AND CHANGE, Issue 3 2008Philipp H. Lepenies ABSTRACT Albert O. Hirschman is the author of seminal, but prima facie unconnected contributions to the social sciences (,exit,voice', ,linkages'). Yet, his main originality lies in his general approach to problem-solving which is hidden behind the complexity of his oeuvre. This article intends to disentangle the intricacies of his work and to reveal his specific mode of investigation by making the multifaceted biographical influences on Hirschman's scholarly writings visible. Exhibiting the influence that decisive moments in his life had on his work not only allows us to identify and define his method of ,possibilism': it also shows that this approach remains a valid and useful multidisciplinary tool for unorthodox contemporary social analysis. [source] Deviations in the emergence of representations: a neuroconstructivist framework for analysing developmental disordersDEVELOPMENTAL SCIENCE, Issue 1 2000Andrew Oliver A common way of studying developmental disorders is to adopt a static neuropsychological deficit approach, in which the brain is characterized in terms of a normal brain with some parts or ,modules' impaired. In this paper we outline a neuroconstructivist approach in which developmental disorders are viewed as alternative developmental trajectories in the emergence of representations within neural networks. As a concrete instantiation of the assumptions underlying this general approach, we present a number of simulations in an artificial neural network model. The representations that emerge under different architectural, input and developmental timing conditions are then analysed within a multi-dimensional state space. We explore alternative developmental trajectories in these simulations, demonstrating how initial differences in the same parameter can lead to very different outcomes, and conversely how different starting states can sometimes result in similar end states (phenotypes). We conclude that the assumptions of the neuroconstructivist approach are likely to be more appropriate for analysing developmental deviations in complex dynamic neural networks, such as the human brain. [source] Optimal Nonparametric Estimation of First-price AuctionsECONOMETRICA, Issue 3 2000Emmanuel Guerre This paper proposes a general approach and a computationally convenient estimation procedure for the structural analysis of auction data. Considering first-price sealed-bid auction models within the independent private value paradigm, we show that the underlying distribution of bidders' private values is identified from observed bids and the number of actual bidders without any parametric assumptions. Using the theory of minimax, we establish the best rate of uniform convergence at which the latent density of private values can be estimated nonparametrically from available data. We then propose a two-step kernel-based estimator that converges at the optimal rate. [source] System peaks in micellar electrophoresis: I. Utilization of system peaks for determination of critical micelle concentrationELECTROPHORESIS, Issue 5 2008Jana Lokajová Abstract A new way to determine the critical micelle concentration (CMC) based on the mobilities of system peaks is presented. A general approach for the CMC determination is based on the change of the slope or on finding the inflection point in the plot of a physical property of solution as a function of surfactant concentration. The determination of CMC by system peaks in CE utilizes a "jump" instead of a continuous change in the measured quantity. This phenomenon was predicted by the program PeakMaster, which was modified for simulation of micellar systems. The simulation of the steep change in mobilities of the anionic system peaks showing the CMC value was verified experimentally in a set of measurements, where the concentration of the surfactant was varied while the ionic strength was kept constant. The experimental work fully proved our model. A comparative electric current measurement was carried out. The proposed method seems to offer easier CMC determination as compared to the standard methods. [source] Data processing in metabolic fingerprinting by CE-UV: Application to urine samples from autistic childrenELECTROPHORESIS, Issue 6 2007Ana C. Soria Abstract Metabolic fingerprinting of biofluids such as urine can be used to detect and analyse differences between individuals. However, before pattern recognition methods can be utilised for classification, preprocessing techniques for the denoising, baseline removal, normalisation and alignment of electropherograms must be applied. Here a MEKC method using diode array detection has been used for high-resolution separation of both charged and neutral metabolites. Novel and generic algorithms have been developed for use prior to multivariate data analysis. Alignment is achieved by combining the use of reference peaks with a method that uses information from multiple wavelengths to align electropherograms to a reference signal. This metabolic fingerprinting approach by MEKC has been applied for the first time to urine samples from autistic and control children in a nontargeted and unbiased search for markers for autism. Although no biomarkers for autism could be determined using MEKC data here, the general approach presented could also be applied to the processing of other data collected by CE with UV,Vis detection. [source] High-throughput screening of kinase inhibitors by multiplex capillary electrophoresis with UV absorption detectionELECTROPHORESIS, Issue 1-2 2003Yan He Abstract Protein kinases play a major role in the transformation of cells and are often used as molecular targets for the new generation of anticancer drugs. We present a novel technique for high-throughput screening of inhibitors of protein kinases. The technique involves the use of multiplexed capillary electrophoresis (CE) for the rapid separation of the peptides, phosphopeptides, and various inhibitors. By means of UV detection, diversified peptides with native amino acid sequences and their phosphorylated counterparts can be directly analyzed without the need for radioactive or fluorescence labeling. The effects of different inhibitors and their IC50 value were determined using three different situations involving the use of a single purified kinase, two purified kinases, and crude cell extracts, respectively. The results suggest that multiplexed CE/UV may prove to be a straightforward and general approach for high-throughput screening of compound libraries to find potent and selective inhibitors of the various protein kinases. [source] Advances in sol-gel based columns for capillary electrochromatography: Sol-gel open-tubular columnsELECTROPHORESIS, Issue 22-23 2002Abdul Malik Abstract The development of sol-gel open-tubular column technology in capillary electrochromatography (CEC) is reviewed. Sol-gel column technology offers a versatile means of creating organic-inorganic hybrid stationary phases. Sol-gel column technology provides a general approach to column fabrication for microseparation techniques including CEC, and is amenable to both open-tubular and monolithic columns. Direct chemical bonding of the stationary phase to the capillary inner walls provides enhanced thermal and solvent stability to sol-gel columns. Sol-gel stationary phases inherently possess higher surface area, and thus provide an effective one-step alternative to conventional open-tubular column technology. Sol-gel column technology is applicable to both silica-based and transition metal oxide-based hybrid stationary phases, and thus, provides a great opportunity to utilize advanced material properties of a wide range of nontraditional stationary phases to achieve enhanced selectivity in analytical microseparations. A wide variety of stationary phase ligands can be chemically immobilized on the capillary inner surface using a single-step sol-gel procedure. Sol-gel chemistry can be applied to design stationary phases with desired chromatographic characteristics, including the possibility of creating columns with either a positive or a negative charge on the stationary phase surface. This provides a new tool to control electroosmotic flow (EOF) in the column. Column efficiencies on the order of half a million theoretical plates per meter have been reported for sol-gel open-tubular CEC columns. The selectivity of sol-gel stationary phases can be easily fine-tuned by adjusting the composition of the coating sol solution. Open-tubular columns have significant advantages over their packed counterparts because of the simplicity in column making and hassle-free fritless operation. Open-tubular CEC columns possess low sample capacity and low detection sensitivity. Full utilization of the analytical potential of sol-gel open-tubular columns will require a concomitant development in the area of high-sensitivity detection technology. [source] New plant protection information system in Hungary,EPPO BULLETIN, Issue 1 2000A. Pákozdi Data on the occurrence and spread of pests has been supplied by the Hungarian Plant Protection Organization for over 40 years. Since the 1970s, this service has been operated by the central station and the 20 county stations of the Plant Protection Organization. Data recorded on pest occurrence and developmental stage of pests and plants has been used to run a forecasting system at local and national levels. However, because of significant staff reductions in the Plant Protection Organization and the disappearance of independent forecasting groups, the reliability of the system, which was based on very specific data, has decreased. It has become necessary to develop a more reliable and flexible computer-aided system (Plant Protection Information System, PPIS), better adjusted to the political and economic changes that have occurred. A major element of the new system, introduced in 1997, is that excessively detailed recording was replaced by a more practical general approach with fewer subjective errors. Specialists from the county stations of the Plant Protection Organization monitor infestation levels of 73 pests in 20 crops using five qualification categories. The results obtained are input into the PPIS program, which processes them into user-friendly charts and maps showing the plant health situation in each county and in the country as a whole, as a basis for taking decisions on plant protection measures. [source] Straightforward Strategy for the Stereoselective Synthesis of Spiro-Fused (C-5)Isoxazolino- or (C-3)Pyrazolino-(C-3)quinolin-2-ones from Baylis,Hillman Adducts by 1,3-Dipolar Cycloaddition and Reductive Cyclization,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 32 2008Virender Singh Abstract A straightforward and general approach for the stereoselective synthesis of spiro-fused (C-5)isoxazolino- or (C-3)pyrazolino-(C-3)quinolin-2-ones from the adducts offorded from the Baylis,Hillman reaction of 2-nitrobenzaldehyde and ethyl acrylate by sequential 1,3-dipolar cycloaddition and reductive cyclization is presented. It was found that the reductive cyclization of the isoxazoline derivatives proceeded efficiently in the presence of In/HCl, whereas similar reductions of pyrazolines gave better yields when carried out in the presence of an Fe/AcOH mixture. However, similar attempts employing the Baylis,Hillman adduct of 2-nitrobenzaldehyde and methyl vinyl ketone did not yield the desired compounds.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Tensile and compressive damage coupling for fully-reversed bending fatigue of fibre-reinforced compositesFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 6 2002W. Van Paepegem ABSTRACT Due to their high specific stiffness and strength, fibre-reinforced composite materials are winning through in a wide range of applications in automotive, naval and aerospace industry. Their design for fatigue is a complicated problem and a large research effort is being spent on it today. However there is still a need for extensive experimental testing or large safety factors to be adopted, because numerical simulations of the fatigue damage behaviour of fibre-reinforced composites are often found to be unreliable. This is due to the limited applicability of the theoretical models developed so far, compared to the complex multi-axial fatigue loadings that composite components often have to sustain in in-service loading conditions. In this paper a new phenomenological fatigue model is presented. It is basically a residual stiffness model, but through an appropriate choice of the stress measure, the residual strength and thus final failure can be predicted as well. Two coupled growth rate equations for tensile and compressive damage describe the damage growth under tension,compression loading conditions and provide a much more general approach than the use of the stress ratio R. The model has been applied to fully-reversed bending of plain woven glass/epoxy specimens. Stress redistributions and the three stages of stiffness degradation (sharp initial decline , gradual deterioration , final failure) could be simulated satisfactorily. [source] A Generalized System for Photoresponsive Membrane Rupture in PolymersomesADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Neha P. Kamat Abstract Polymersomes are vesicles whose membranes comprise self-assembled block copolymers. It has recently been shown that co-encapsulating conjugated multiporphyrin dyes in a polymersome membrane with ferritin protein in the aqueous lumen confers photolability to the polymersome. In the present study, the photolability is shown to be extendable to vesicles containing dextran, an inert and inexpensive polysaccharide, as the luminal solute. How structural features of the polymersome/porphyrin/dextran composite affect its photoresponse is explored. Increasing dextran molecular weight, decreasing block copolymer molecular weight, and altering fluorophore-membrane interactions results in increasing the photoresponsiveness of the polymersomes. Amphiphilic interactions of the luminal encapsulant with the membrane coupled with localized heat production in the hydrophobic bilayer likely cause differential thermal expansion in the membrane and the subsequent membrane rupture. This study suggests a general approach to impart photoresponsiveness to any biomimetic vesicle system without chemical modification, as well as a simple, bio-inert method for constructing photosensitive carriers for controlled release of encapsulants. [source] Domain Engineering of Lead-Free Li-Modified (K,Na)NbO3 Polycrystals with Highly Enhanced PiezoelectricityADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Ke Wang Abstract Aging and re-poling induced enhancement of piezoelectricity are found in (K,Na)NbO3 (KNN)-based lead-free piezoelectric ceramics. For a compositionally optimized Li-doped composition, its piezoelectric coefficient d33 can be increased up to 324 pC N,1 even from a considerably high value (190 pC N,1) by means of a re-poling treatment after room-temperature aging. Such a high d33 value is only reachable in KNN ceramics with complicated modifications using Ta and Sb dopants. High-angle X-ray diffraction analysis reveals apparent changes in the crystallographic orientations related to a 90° domain switching before and after the aging and re-poling process. A possible mechanism considering both defect migration and rotation of spontaneous polarization explains the experimental results. The present study provides a general approach towards piezoelectric response enhancement in KNN-based piezoelectric ceramics. [source] The life cycles of the temperate lactococcal bacteriophage ,LC3 monitored by a quantitative PCR methodFEMS MICROBIOLOGY LETTERS, Issue 1 2000Merete Lunde Abstract We present here a new and general approach for monitoring the life cycles of temperate bacteriophages which establish lysogeny by inserting their genomes site-specifically into the bacterial host chromosome. The method is based on quantitative amplification of specific DNA sites involved in various cut-and-join events during the life cycles of the phages (i.e. the cos, attP, attB, attL and attR sites) with the use of sequence-specific primers. By comparing the amounts of these specific DNA sites at different intervals, we were able to follow the development of the lytic and lysogenic life cycles of the temperate lactococcal bacteriophage ,LC3 after infection of its bacterial host Lactococcus lactis ssp. cremoris IMN-C18. [source] A General Approach for Fabricating Arc-Shaped Composite Nanowire Arrays by Pulsed Laser DepositionADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Yue Shen Abstract Here, a new method is demonstrated that uses sideways pulsed laser deposition to deliberately bend nanowires into a desired shape after growth and fabricate arc-shaped composite nanowire arrays of a wide range of nanomaterials. The starting nanowires can be ZnO, but the materials to be deposited can be metallic, semiconductor, or ceramic depending on the application. This method provides a general approach for rational fabrication of a wide range of side-by-side or "core,shell" nanowire arrays with controllable degree of bending and internal strain. Considering the ZnO is a piezoelectric and semiconductive material, its electrical properties change when deformed. This technique has potential applications in tunable electronics, optoelectronics, and piezotronics. [source] Spontaneous Lamellar Alignment in Thickness-Modulated Block Copolymer FilmsADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Bong Hoon Kim Abstract Here, spontaneous lamellar alignment in a thickness-modulated block copolymer film is presented as a facile, scalable, and general approach for creating a highly aligned lamellar morphology. Thickness-modulated block copolymer films are prepared on neutral surfaces by various methods, such as solution dropping, dewetting-induced self-organized patterning, and thermal imprinting. Regardless of the film preparation method, the self-assembled lamellar domains become spontaneously aligned along the thickness gradient after sufficient thermal annealing. Real-time AFM imaging reveals that spontaneous alignment occurs through the directional growth of well-ordered domains along the thickness gradient, which is accompanied by defect dynamics, with vertical linear defects moving from thicker parts of the film towards the thinner ones, reducing their length and thus the associated energy. The mechanism underlying this interesting self-aligning behavior is provided by a ,geometric anchoring' phenomenon, originally envisioned to account for the liquid crystal alignment under a non-flat geometry of confinement. This novel self-aligning principle offers a valuable opportunity to control nanoscale alignment in block copolymer films by manipulating the, much larger, microscale morphology. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||