Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Simple

  • very simple

  • Terms modified by Simple

  • simple access
  • simple addition
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  • simple alcohol
  • simple algorithm
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  • simple analysis
  • simple analytical expression
  • simple analytical model
  • simple answer
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  • simple genetic control
  • simple geometry
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  • simple ketone
  • simple linear regression
  • simple linear regression analysis
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  • simple sequence repeat
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  • simple setting
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  • simple sol
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  • simple version
  • simple view
  • simple way

  • Selected Abstracts

    Mutational analysis of GJB1, MPZ, PMP22, EGR2, and LITAF/SIMPLE in Serbian Charcot-Marie-Tooth patients

    Milica Keckarevic-Markovic
    Abstract We report the results of mutational analysis in the following genes: GJB1, MPZ, PMP22, EGR2, and LITAF/SIMPLE in 57 Charcot-Marie-Tooth (CMT) patients of Serbian origin without the PMP22 duplication. We found 10 different mutations in 14 CMT patients: 6 mutations in GJB1, 3 in MPZ, and 1 in PMP22. Five of six GJB1 mutations are reported for the first time, and the most frequent one appears to be a founder mutation in the Serbian population. No mutations were found in EGR2 or LITAF. Thus, GJB1 mutation analysis should be done in patients without the PMP22 duplication and male-to-male transmission of CMT. [source]

    Linkage analysis with sequential imputation

    Zachary Skrivanek
    Abstract Multilocus calculations, using all available information on all pedigree members, are important for linkage analysis. Exact calculation methods in linkage analysis are limited in either the number of loci or the number of pedigree members they can handle. In this article, we propose a Monte Carlo method for linkage analysis based on sequential imputation. Unlike exact methods, sequential imputation can handle large pedigrees with a moderate number of loci in its current implementation. This Monte Carlo method is an application of importance sampling, in which we sequentially impute ordered genotypes locus by locus, and then impute inheritance vectors conditioned on these genotypes. The resulting inheritance vectors, together with the importance sampling weights, are used to derive a consistent estimator of any linkage statistic of interest. The linkage statistic can be parametric or nonparametric; we focus on nonparametric linkage statistics. We demonstrate that accurate estimates can be achieved within a reasonable computing time. A simulation study illustrates the potential gain in power using our method for multilocus linkage analysis with large pedigrees. We simulated data at six markers under three models. We analyzed them using both sequential imputation and GENEHUNTER. GENEHUNTER had to drop between 38,54% of pedigree members, whereas our method was able to use all pedigree members. The power gains of using all pedigree members were substantial under 2 of the 3 models. We implemented sequential imputation for multilocus linkage analysis in a user-friendly software package called SIMPLE. Genet Epidemiol 25:25,35, 2003. © 2003 Wiley-Liss, Inc. [source]

    Schwann cells and the pathogenesis of inherited motor and sensory neuropathies (Charcot-Marie-Tooth disease)

    GLIA, Issue 4 2006
    Philipp Berger
    Abstract Over the last 15 years, a number of mutations in a variety of genes have been identified that lead to inherited motor and sensory neuropathies (HMSN), also called Charcot-Marie-Tooth disease (CMT). In this review we will focus on the molecular and cellular mechanisms that cause the Schwann cell pathologies observed in dysmyelinating and demyelinating forms of CMT. In most instances, the underlying gene defects alter primarily myelinating Schwann cells followed by secondary axonal degeneration. The first set of proteins affected by disease-causing mutations includes the myelin components PMP22, P0/MPZ, Cx32/GJB1, and periaxin. A second group contains the regulators of myelin gene transcription EGR2/Krox20 and SOX10. A third group is composed of intracellular Schwann cells proteins that are likely to be involved in the synthesis, transport and degradation of myelin components. These include the myotubularin-related lipid phosphatase MTMR2 and its regulatory binding partner MTMR13/SBF2, SIMPLE, and potentially also dynamin 2. Mutations affecting the mitochondrial fission factor GDAP1 may indicate an important contribution of mitochondria in myelination or myelin maintenance, whereas the functions of other identified genes, including NDRG1, KIAA1985, and the tyrosyl-tRNA synthase YARS, are not yet clear. Mutations in GDAP1, YARS, and the pleckstrin homology domain of dynamin 2 lead to an intermediate form of CMT that is characterized by moderately reduced nerve conduction velocity consistent with minor myelin deficits. Whether these phenotypes originate in Schwann cells or in neurons, or whether both cell types are directly affected, remains a challenging question. However, based on the advances in systematic gene identification in CMT and the analyses of the function and dysfunction of the affected proteins, crucially interconnected pathways in Schwann cells in health and disease have started to emerge. These networks include the control of myelin formation and stability, membrane trafficking, intracellular protein sorting and quality control, and may extend to mitochondrial dynamics and basic protein biosynthesis. © 2006 Wiley-Liss, Inc. [source]

    Temporal accuracy analysis of phase change convection simulations using the JFNK-SIMPLE algorithm

    Katherine J. Evans
    Abstract The incompressible Navier,Stokes and energy conservation equations with phase change effects are applied to two benchmark problems: (1) non-dimensional freezing with convection; and (2) pure gallium melting. Using a Jacobian-free Newton,Krylov (JFNK) fully implicit solution method preconditioned with the SIMPLE (Numerical Heat Transfer and Fluid Flow. Hemisphere: New York, 1980) algorithm using centred discretization in space and three-level discretization in time converges with second-order accuracy for these problems. In the case of non-dimensional freezing, the temporal accuracy is sensitive to the choice of velocity attenuation parameter. By comparing to solutions with first-order backward Euler discretization in time, it is shown that the second-order accuracy in time is required to resolve the fine-scale convection structure during early gallium melting. Qualitative discrepancies develop over time for both the first-order temporal discretized simulation using the JFNK-SIMPLE algorithm that converges the nonlinearities and a SIMPLE-based algorithm that converges to a more common mass balance condition. The discrepancies in the JFNK-SIMPLE simulations using only first-order rather than second-order accurate temporal discretization for a given time step size appear to be offset in time. Copyright © 2007 John Wiley & Sons, Ltd. [source]


    JOURNAL OF PHYCOLOGY, Issue 3 2008
    Euan D. Reavie
    Because diatom communities are subject to the prevailing water quality in the Great Lakes coastal environment, diatom-based indices can be used to support coastal-monitoring programs and paleoecological studies. Diatom samples were collected from Great Lakes coastal wetlands, embayments, and high-energy sites (155 sites), and assemblages were characterized to the species level. We defined 42 metrics on the basis of autecological and functional properties of species assemblages, including species diversity, motile species, planktonic species, proportion dominant taxon, taxonomic metrics (e.g., proportion Stephanodiscoid taxa), and diatom-inferred (DI) water quality (e.g., DI chloride [Cl]). Redundant metrics were eliminated, and a diatom-based multimetric index (MMDI) to infer coastline disturbance was developed. Anthropogenic stresses in adjacent coastal watersheds were characterized using geographic information system (GIS) data related to agricultural and urban land cover and atmospheric deposition. Fourteen independent diatom metrics had significant regressions with watershed stressor data; these metrics were selected for inclusion in the MMDI. The final MMDI was developed as the weighted sum of the selected metric scores with weights based on a metric's ability to reflect anthropogenic stressors in the adjacent watersheds. Despite careful development of the multimetric approach, verification using a test set of sites indicated that the MMDI was not able to predict watershed stressors better than some of the component metrics. From this investigation, it was determined that simpler, more traditional diatom-based metrics (e.g., DI Cl, proportion Cl-tolerant species, and DI total phosphorus [TP]) provide superior prediction of overall stressor influence at coastal locales. [source]


    ANZ JOURNAL OF SURGERY, Issue 6 2007
    FRACS, John P. Harris AM
    No abstract is available for this article. [source]

    From Universal Laws of Cognition to Specific Cognitive Models

    Nick Chater
    Abstract The remarkable successes of the physical sciences have been built on highly general quantitative laws, which serve as the basis for understanding an enormous variety of specific physical systems. How far is it possible to construct universal principles in the cognitive sciences, in terms of which specific aspects of perception, memory, or decision making might be modelled? Following Shepard (e.g., 1987), it is argued that some universal principles may be attainable in cognitive science. Here, 2 examples are proposed: the simplicity principle (which states that the cognitive system prefers patterns that provide simpler explanations of available data); and the scale-invariance principle, which states that many cognitive phenomena are independent of the scale of relevant underlying physical variables, such as time, space, luminance, or sound pressure. This article illustrates how principles may be combined to explain specific cognitive processes by using these principles to derive SIMPLE, a formal model of memory for serial order (Brown, Neath, & Chater, 2007), and briefly mentions some extensions to models of identification and categorization. This article also considers the scope and limitations of universal laws in cognitive science. [source]

    Exposure Fusion: A Simple and Practical Alternative to High Dynamic Range Photography

    T. Mertens
    I.4.8 [Image Processing]: Scene Analysis , Photometry, Sensor Fusion Abstract We propose a technique for fusing a bracketed exposure sequence into a high quality image, without converting to High dynamic range (HDR) first. Skipping the physically based HDR assembly step simplifies the acquisition pipeline. This avoids camera response curve calibration and is computationally efficient. It also allows for including flash images in the sequence. Our technique blends multiple exposures, guided by simple quality measures like saturation and contrast. This is done in a multiresolution fashion to account for the brightness variation in the sequence. The resulting image quality is comparable to existing tone mapping operators. [source]

    "Halo" Grafting,A Simple and Effective Technique of Skin Grafting

    Sharad P. Paul, MD, M Phil, has indicated no significant interest with commercial supporters [source]

    A Simple, Pain-Free Treatment for Ingrown Toenails Complicated with Granulation Tissue

    BACKGROUND The treatment of ingrown toenail complicated with granulation tissue is usually partial or total nail avulsion with or without matricectomy. It costs loss of occupational power, however, because most patients cannot go to work or school for some time after surgery, and it is a costly and uncomfortable procedure for most patients. OBJECTIVE This study aimed to find an easy, painless, and inexpensive alternative. MATERIALS AND METHODS Seven patients with ingrown toenails complicated with granulation tissue are included. A small apparatus was applied on the nails, granulation tissue was chemically cauterized, and a foot bath was recommended twice daily. They were followed on a weekly basis or every other week until recovery. None of the patients received systemic treatment. RESULTS All seven patients were completely cured without requiring surgery and/or systemic treatment. The procedure did not have any effect on their daily life. The follow-up examination of the patients at 6 months revealed that they were totally cured, and there were no recurrences. CONCLUSION Patients with ingrown toenails complicated by granulation tissue might have an inexpensive and pain-free treatment alternative, although new studies with more patients are required. [source]

    A Contactless Impedance Probe for Simple and Rapid Determination of the Ratio of Liquids with Different Permittivities in Binary Mixtures

    ELECTROANALYSIS, Issue 1 2009
    Franti, ek Opekar
    Abstract Simple contactless cells with planar or tubular electrodes have been designed for measurement of the permittivity of solutions. The cells, connected to an integrated circuit of astable multivibrator, respond primarily to the capacitance component of the cell impedance, the multivibrator frequency depends in a defined manner on the solution permittivity and is readily used as the analytical signal in determinations of the ratios of components in binary liquid mixtures; water solution of methanol, ethanol and dioxane have been tested. The response of the cell with planar electrodes satisfies well the simple theoretical model and both the cells provide results with a sufficient sensitivity, a low LOD value (units of %vol) and a good precision (around 1%rel). The cell simplicity, small dimensions, long-term stability and the possibility of powering them from a battery make them suitable for hand-held meters. As an example of application in practice, the content of ethanol was determined in the car fuel petrol. [source]

    On-line sample preconcentration with chemical derivatization of bacterial biomarkers by capillary electrophoresis: A dual strategy for integrating sample pretreatment with chemical analysis

    ELECTROPHORESIS, Issue 21 2005
    Adam S. Ptolemy
    Abstract Simple, selective yet sensitive methods to quantify low-abundance bacterial biomarkers derived from complex samples are required in clinical, biological, and environmental applications. In this report, a new strategy to integrate sample pretreatment with chemical analysis is investigated using on-line preconcentration with chemical derivatization by CE and UV detection. Single-step enantioselective analysis of muramic acid (MA) and diaminopimelic acid (DAP) was achieved by CE via sample enrichment by dynamic pH junction with ortho -phthalaldehyde/N -acetyl- L -cysteine labeling directly in-capillary. The optimized method resulted in up to a 100-fold enhancement in concentration sensitivity compared to conventional off-line derivatization procedures. The method was also applied toward the detection of micromolar levels of MA and DAP excreted in the extracellular medium of Escherichia coli bacterial cell cultures. On-line preconcentration with chemical derivatization by CE represents a unique approach for conducting rapid, sensitive, and high-throughput analyses of other classes of amino acid and amino sugar metabolites with reduced sample handling, where the capillary functions simultaneously as a concentrator, microreactor, and chiral selector. [source]

    Advances towards Highly Active and Stereoselective Simple and Cheap Proline-Based Organocatalysts,

    Francesco Giacalone
    Abstract Ten 4-acyloxy- L -prolines were screened as catalysts at loadings of 2,0.1 mol-% for the direct asymmetric aldol reaction in water by using variable amounts of water. Among them, a new catalyst, the L -proline carrying a trans -4-(2,2-diphenylacetoxy) group, and a catalyst previously synthesized by us, the L -proline carrying a trans -4-(4-phenylbutanoyloxy) group, were found to be excellent catalysts for the aldol reaction between cyclohexanone or cyclopentanone and substituted benzaldehydes when employed in only 1 and 0.5 mol-%,respectively, at room temperature without additives. For such catalysts, high turnover numbers were obtained, which are among the highest values obtained for enamine organocatalysis. Finally, these catalysts can be synthesized by direct O -acylation from inexpensive molecules and successfully used in scaled-up reactions. [source]

    Metal-Free Air Oxidation of Thiols in Recyclable Ionic Liquid: A Simple and Efficient Method for the Synthesis of Disulfides

    Devender Singh
    Abstract An efficient procedure for the oxidative coupling of alkyl, aryl and heteroaryl thiols with atmospheric oxygen is reported. The methodology utilizes BMIM-BF4 as a recyclable solvent and does not require support materials or metal salts. Symmetric disulfides are obtained in excellent yields. [source]

    On the Mechanism of the Puzzling "Endocyclic" Skeletal Rearrangement of 1,6-Enynes

    Noemí Cabello
    Abstract Skeletal rearrangements of simple 1,6-enynes have been studied in order to determine the factors that control the formation of five- or six-membered rings. Simple 1,6-enynes substituted only at C-4 preferentially give six-membered rings on skeletal rearrangement in the presence of gold(I) catalysts, whereas increasing electron-withdrawing character of substituents at C-4 leads to five-membered rings. Reactions of these simple enynes in the presence of PtCl4 as catalyst give exclusively exo - double skeletal rearrangements. Enynes substituted at the alkyne also react with AuI catalysts to give exclusively products of exo - double rearrangement. The different mechanisms have been analyzed by DFT calculations. Although a pathway for the formation of six-membered rings involving two steps in a ring-expansion/ring-contraction process was found, the activation energy of the first step is too high. Instead, this skeletal rearrangement appears to follow an exo - single skeletal rearrangement in which the initial cyclopropyl gold carbene opens to form a six-membered ring. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Access to Any Site-Directed Isotopomer of Methionine, Selenomethionine, Cysteine, and Selenocysteine , Use of Simple, Efficient Modular Synthetic Reaction Schemes for Isotope Incorporation

    Arjan H. G. Siebum
    Abstract Simple modular reaction schemes that allow access to any isotopomer of protected serine and homoserine have been worked out. These systems could be simply converted into cysteine, selenocysteine, homocysteine, homoselenocysteine, the essential amino acid methionine, and selenomethionine by Mitsunobu chemistry. These sulfur- and selenium-containing amino acids fulfil many essential roles in the living organism. In addition, homoserine could be converted in a few steps into optically active L -vinylglycine. As well as the stable isotopes 13C, 15N, 17O, and 18O, the radioactive isotopes of sulfur, selenium and carbon can also be easily introduced in a site-directed fashion. In view of the wide scope of the Mitsunobu reaction, we feel that many more important systems with the carbon skeleton of serine and homoserine should be preparable through this basic chemistry in any site-directed isotopically labeled form. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    A Simple and Innovative Route to Prepare a Novel Carbon Nanotube/Prussian Blue Electrode and its Utilization as a Highly Sensitive H2O2 Amperometric Sensor

    Edson Nossol
    Abstract The utilization of iron-based species (mainly metallic iron, hematite and magnetite) encapsulated into multi-walled carbon nanotubes (CNTs) as reactants in an electrochemical synthesis is reported for the first time in this work. Prussian blue (PB) is electrosynthesized in a heterogeneous reaction between ferricyanide ions in aqueous solution and the iron-species encapsulated into CNTs, resulting in novel CNT/PB paste electrodes. This innovative preparation route produces an intimate contact between the PB and the CNTs, which improves the stability and redox properties of PB. The PB formation and the chemical interaction between the PB and the CNTs are confirmed by Raman spectroscopy. The electrode is employed as a hydrogen peroxide amperometric sensor, resulting in a very low limit of detection (1.94,×,10,8,mol L,1) and very high sensitivity (15.3,A cm,2M,1). [source]

    Influences of habitat complexity on the diversity and abundance of epiphytic invertebrates on plants

    FRESHWATER BIOLOGY, Issue 4 2003
    Hiromi Taniguchi
    SUMMARY 1. The compound influence of habitat complexity and patch size on stream invertebrate assemblages associated with submerged macrophytes was investigated through field sampling of two natural macrophyte species with contrasting leaf morphologies (complex, Ranunculus yezoensis; simple, Sparganium emersum) and an experiment with two artificial plants with different levels of morphological complexity. 2. The artificial plant experiment was designed to separate the effects of habitat area (patch size) and habitat complexity, thus enabling a more rigorous assessment of complexity per se than in previous studies where only a single patch size was used. Simple and complex artificial plants were established with five different patch sizes corresponding to the range found in natural plants. 3. Invertebrates occurred on both complex and simple forms of natural and artificial plants at similar abundances with dipterans and ephemeropterans being predominant. Taxon richness was higher on structurally complex Ranunculus than on simple Sparganium and was similarly higher on the complex artificial plant than on the simple one, over the entire range of habitat patch sizes. Thus, architectural complexity affected the taxon richness of epiphytic invertebrates, independently of habitat scale. 4. On the natural plants there was no difference in the abundance (both number of individuals and biomass) of invertebrates between simple and complex forms, while on artificial plants more invertebrates occurred on complex than on simple forms. The amount of particulate organic matter, >225 ,m (POM) and chlorophyll a showed mixed patterns on natural and artificial plants, suggesting that the availability of these resources is not an overriding proximate factor controlling invertebrate abundance on plants. The difficulty of extrapolating from experimental results involving use of artificial plants is discussed, especially when considering the relationship between habitat structure and the occurrence of epiphytic invertebrates on natural plants. [source]

    Simple and Efficient Generation of White Light Emission From Organophosphorus Building Blocks

    Carlos Romero-Nieto
    Abstract This paper describes a structure,property study using two dithieno[3,2- b;2,,3,- d]phosphole building blocks for the generation of white light emission and the incorporation of these units in a single polystyrene material. The emission of one of the light-emitting organophosphorus building blocks can efficiently be switched from orange to green by simple protonation of the amino functional groups that are part of the , -conjugated scaffold. The resulting three components (blue, green, and orange) exhibit photophysical properties that allow for an efficient fluorescence resonance energy transfer (FRET) in the mixture/polymer and provide intense white fluorescence upon excitation of the blue component; the fluorescence is close to pure white in solution and similar to the emission of an incandescent light bulb in the thin film. The results nicely illustrate the intriguing features that can be obtained by exclusively using organophosphorus-based organic electronic materials. [source]

    Simple and Generalized Synthesis of Semiconducting Metal Sulfide Nanocrystals

    Sang-Hyun Choi
    Uniform-sized semiconducting nanocrystals of binary metal sulfides are synthesized from the thermolysis of metal-oleate complexes in alkanethiol. The size of the Cu2S nanocrystals can be tuned from 7 to 20,nm by varying the reaction conditions. Various shaped nanocrystals of CdS, ZnS, MnS, and PbS are synthesized from the thermal reaction of metal-oleate complex in alkanethiol. [source]

    A Simple, One-Step Approach to Durable and Robust Superhydrophobic Textiles,

    Jan Zimmermann
    Abstract Superhydrophobic textile fabrics are prepared by a simple, one-step gas phase coating procedure by which a layer of polymethylsilsesquioxane nanofilaments is grown onto the individual textile fibers. A total of 11 textile fabrics made from natural and man made fibers are successfully coated and their superhydrophobic properties evaluated by the water shedding angle technique. A thorough investigation of the commercially relevant poly(ethylene terephthalate) fabric reveals an unparalleled long-term water resistance and stability of the superhydrophobic effect. Because of the special surface geometry generated by the nanoscopic, fibrous coating on the microscopic, fibrous textiles, the coated fabric remains completely dry even after two months of full immersion in water and stays superhydrophobic even after continuous rubbing with a skin simulating friction partner under significant load. Furthermore, important textile parameters such as tensile strength, color, and haptics are unaffected by the silicone nanofilament coating. For the first time, an in-depth characterization of the wetting properties, beyond simple contact angle measurements, as well as a thorough evaluation of the most important textile parameters is performed on a superhydrophobic fabric, which reveals a true potential for application. [source]

    Simple and efficient integration of rigid rotations suitable for constraint solvers

    Tomasz Koziara
    Abstract Simple and efficient way of integrating rigid rotations is presented. The algorithm is stable, second-order accurate, and in its explicit version involves evaluation of only two exponential maps per time step. The semi-explicit version of the proposed scheme improves upon the long-term stability, while it retains the explicitness in the force evaluation. The algebraic structure of both schemes makes them suitable forthe analysis of constrained multi-body systems. The explicit algorithm is specifically aimed at the analysis involving small incremental rotations, where its modest computational cost becomes the major advantage. The semi-explicit scheme naturally broadens the scope of possible applications. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Simple and Efficient Near-Infrared Organic Chromophores for Light-Emitting Diodes with Single Electroluminescent Emission above 1000,nm,

    ADVANCED MATERIALS, Issue 1 2009
    Gang Qian
    A series of NIR organic chromophores with donor,,,acceptor,,,donor structure are synthesized. Good thermal stability and strong photoluminescence in solid state render them suitable for application in light-emitting diodes. Exclusive near-infrared emission at 1080,nm with external quantum efficiency of 0.28% is obtained from the nondoped OLEDs. The longest electroluminescence wavelength is 1220,nm. [source]

    Cytoplasmic melanoma-associated antigen (CYT-MAA) serum level in patients with melanoma: A potential marker of response to immunotherapy?

    Sandra R. Reynolds
    Abstract Simple, noninvasive methods are needed to follow effectiveness of new treatments in patients with melanoma. In our study, we examined cytoplasmic melanoma-associated antigen (CYT-MAA) serum level in melanoma patients during immunotherapy. Sera of 117 patients were assayed for CYT-MAA by double-sandwich ELISA before and during treatment with a polyvalent, shed antigen, melanoma vaccine. Vaccine-treated patients included 30 with American Joint Committee on Cancer (AJCC) stage IIb or IIIa, 30 with stage IIc, IIIb or IIIc, 30 with resected stage IV and 27 with measurable stage IV disease. Prior to vaccine therapy, 63% of patients had elevated serum CYT-MAA with high levels of antigen in all disease stages. After initiation of therapy, the level declined in more than 90% of the positive patients and fell below the positive cut-off in 56% of these patients within 5 months. By contrast, there was no decline in CYT-MAA serum level in 11 patients who served as untreated controls with melanoma. Multivariate analysis of the treated patients using accelerated failure time Weibull models adjusted for stage and age showed that patients whose CYT-MAA serum level remained elevated during treatment were ,3 times more likely to recur or progress than patients who were consistently below the positive cut-off (hazard ratio = 3.42, 95% CI [1.38, 8.47], p = 0.0079). Measurement of CYT-MAA serum level appears to show potential as an early marker of prognosis in patients with stages IIb to IV melanoma. Measurement of CYT-MAA serum level during therapy could provide an intermediate marker of response in these patients. © 2006 Wiley-Liss, Inc. [source]

    Moisture sorption isotherm and xerophilic moulds associated with dried cocoyam chips in storage in Nigeria

    J. Obeta Ugwuanyi
    Summary Extended storage of cocoyams (Colocasia antiquorum and Colocasia esculenta) is achieved in parts of Nigeria by processing them into smoked and dried chips. In this study, cocoyam chips were collected from parts of Nigeria at the end of drying, at various periods of storage and from markets, and analysed for moisture content, moisture sorption characteristics and xerophilic moulds. Moisture content of chips ranged from 7.07 ± 1.1% for freshly dried samples to 16 ± 2.2% for samples stored up to 8 months. Six mould species from four groups of the genus Aspergillus (including five xerophiles) identified as Aspergillus fumigatus, Eurotium repens, Eurotium amstelodami, Eurotium chevalieri and Aspergillus flavus and Aspergillus niger and Mucor sp. were isolated. The variety of moulds increased with storage and moisture content of samples. Moisture sorption in dried chips showed type II sigmoidal behaviour. Wood smoke significantly protected chips from mould colonization, but in cooperation with reduced water activity. Simple and inexpensive storage of freshly dried samples in airtight bags led to prolonged storage of up to 14 months without deterioration. [source]

    Simple Chiral Diaminobinaphthyl Dilithium Salts for Intramolecular Catalytic Asymmetric Hydroamination of Amino-1,3-dienes

    Julia Deschamp
    Abstract Simple and easily accessible chiral lithium amide salts are reported as efficient (pre)catalysts for the diastereo- [up to (E:Z)=92:8] and enantioselective [up to 72% ee (E)] hydroamination/cyclisation of conjugated primary aminodienes. These chiral lithium salts are straightforwardly prepared by in situ combination of an N -substituted (R)-(+)-1,1,-binaphthyl-2,2,-diamine ligand and a commercial methyllithium solution. Information on the solid-state structure of these salts was obtained by X-ray analysis of a single crystal. [source]

    Copper(I) Acetate: A Structurally Simple but Highly Efficient Dinuclear Catalyst for Copper-Catalyzed Azide-Alkyne Cycloaddition

    Changwei Shao
    Abstract In this article, the structurally well-defined dinuclear complex copper(I) acetate was studied in detail and was developed as a highly practical and efficient catalyst for the copper(I)-catalyzed azide-alkyne cycloaddition. The "bare" phenylethynylcopper(I) (i.e., with no exogeneous ligands) was isolated as an intermediate, which can be converted into an active catalytic species by treatment with acetic acid (in situ produced in the reaction) to efficiently catalyze the azide-alkyne cycloaddition under mild conditions. [source]

    A Simple, Effective Boron-Halide Ethoxylation Catalyst

    Abstract Boron esters B(OR)3, readily derived from boric acid and alcohols, combine with iodide or bromide to catalyze the ethoxylation of alcohols and phenols, giving good rates and narrow product distributions. The combined action of a weak electrophile [B(OR)3] and a weak nucleophile (halide) allows for the ethoxylation of base-sensitive alcohols. Experiment suggests a new mechanism for this commercially important reaction proceeding through key ,-haloalkoxy intermediates. [source]

    Simple yet powerful techniques for optimization of horizontal recursion steps in Gaussian-type two-electron integral evaluation algorithms

    Marcin Makowski
    Abstract Simple heuristic rules are given that allow optimization of the performance of horizontal recursion steps present in schemes for calculation of two electron integrals are given. The number of floating point operations and computer timings are compared with the other algorithmic approaches to the problem. It is shown that the presented rules lead to substantial computational savings when compared with the standard implementation and may be also used succesfully instead of the algorithms based on full tree search techniques. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source]

    Accurate and simple synthesis formulas for coplanar waveguides

    Ali Akdagli
    Abstract Simple and accurate closed-form formulas obtained by using a differential evolution algorithm are presented for the synthesis of coplanar waveguides (CPW). The results of the synthesis formulas proposed in this article are compared with those of the quasi-static analysis, the synthesis formulas reported by the other researchers and also the experimental works available in the literature. The accuracy of the proposed synthesis formulas is found to be better than 0.75% for 9256 CPWs samples. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008. [source]