Distribuição espacial e temporal da Biomassa Fitoplanctônica relacionada com Parâmetros Hidrológicos na Bacia do Pina (Recife – PE).
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Color Control in Sulfide Phosphors: Turning up the Light for Electroluminescent Displays
Manipulation of the defect chemistry in ZnS:Mn and SrS:Cu bulk and thin-film phosphors has resulted in specific and controllable emission colors across the entire visible spectrum. Saturated red emission is observed at exceptionally low threshold voltages in ac thin-film electroluminescent devices, while unsurpassed l…
Electrospray ionisation tandem mass spectrometry of poly [(R,S)-3-hydroxybutanoic acid] telechelics containing primary hydroxy end groups
Evaluation of polymer end-capping reactions with the aid of electrospray ionisation tandem mass spectrometry techniques (ESI-MS(n)) allows characterisation of novel poly[(R, S)-3-hydroxybutanoic acid]-(a-PHB) telechelics, containing primary hydroxyl groups at both polymer chain ends. The chemical structures of individ…
Localization of Residual Water in Alkali-Metal Cation-Exchanged X and Y Type Zeolites
The arrangements of residual water and alkali-metal cations in zeolites Y and X have been determined by Rietveld refinement in combination with Fourier analysis of X-ray powder patterns. The sodium forms NaY and NaX as well as partially cation exchanged forms MNaY and MNaX (M = K, Rb, Cs) were studied. It was shown th…
Thermally-Induced Phase Separation Mechanism Study for Membrane Formation
The thermally-induced phase separation mechanism was investigated for the system isotactic polypropylene and diphenyl ether. Droplet growth was monitored by using a thermo-optical microscope. The degree of supercooling for liquid-liquid phase separation affected the size and growth rate of the droplets. Increasing the…
<title>Projecting the performance of erbium-doped fiber devices in a space radiation environment</title>
The optical attenuation induced in two erbium-doped fibers by <SUP>60</SUP>Co (gamma) -ray exposures to 200 krad has been measured at 3 different dose rates, approximately, 35, 1000, and 20,500 rad/min. The growth of the induced loss was measured at 980, 1300, and 1500 nm. In some instances recovery of the loss after…
Synthesis of Viologens with Extended π−Conjugation and Their Photochromic Behavior on Near-IR Absorption
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTSynthesis of Viologens with Extended π−Conjugation and Their Photochromic Behavior on Near-IR AbsorptionMasato Nanasawa, Makio Miwa, Michiko Hirai, and Tetsuo KuwabaraView Author Information Department of Applied Chemistry and Biotechnology, Yamanashi University, Takeda 4, Kofu…
Thermal Behavior of 12-Molybdophosphoric Acid Supported on Zirconium-Loaded Silica
The thermal behavior of 12-molybdophosphoric acid (HPMo) supported on silica and Zr-loaded silica (Zr content from 1.6 to 17.0 wt %) was studied by X-ray diffraction, Fourier-transform infrared, in situ Raman, and X-ray photoelectron spectroscopic techniques. A silica support stabilizes the Keggin unit of HPMo up to 7…
On the Loops-to-Bridges Ratio in Ordered Triblock Copolymers: An Investigation by Dielectric Relaxation Spectroscopy and Computer Simulations
Dielectric relaxation spectroscopy and computer simulations have been used to elaborate on the loops/bridges population ratio in ordered poly(styrene- block - cis- isoprene- block -styrene), PS−PI−PS, triblock copolymer lamellae. The dynamics of the PI blocks are examined dielectrically for a PS−PI−PS copolymer having…
Temperature Dependence of Molecular Orientation on the Surfaces of Semifluorinated Polymer Thin Films
Near-edge X-ray absorption fine structure is used to investigate the temperature dependence of molecular orientation of semifluorinated liquid crystalline (SF-LC) mesogens, which are attached to the modified isoprene backbone of (i) a poly(1,2-isoprene) homopolymer and (ii) a diblock copolymer consisting of polystyren…
Hydroxylamine Seeding of Colloidal Au Nanoparticles. 3. Controlled Formation of Conductive Au Films
An approach to enlarge preformed colloidal Au nanoparticles in solution based on the Au colloidal surface-catalyzed reduction of Au 3+ by NH 2 OH (“seeding”) has been adapted to 12-nm-diameter colloidal Au nanoparticles immobilized in monolayers and multilayers. Bulk characterization of the ensuing films was carried o…
Monolithic Mesoporous Silica Templated by Microemulsion Liquid Crystals
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTMonolithic Mesoporous Silica Templated by Microemulsion Liquid CrystalsPingyun Feng, Xianhui Bu, Galen D. Stucky, and David J. PineView Author Information Department of Chemical Engineering and Department of Chemistry, University of California Santa Barbara, California…
Functional Poly(ethylene oxide) Multiarm Star Polymers: Core-First Synthesis Using Hyperbranched Polyglycerol Initiators
Hyperbranched polyglycerol as well as polyglycerol modified with short apolar oligo(propylene oxide) segments (DP n = 23−52; M w / M n = 1.2−1.4) was deprotonated with diphenylmethylpotassium and used as polyfunctional initiators for the anionic polymerization of ethylene oxide to prepare poly(ethylene oxide) (PEO) mu…
Theory of Orbital Ordering, Fluctuation and Resonant X-ray Scattering in Manganites
A theory of resonant x-ray scattering in perovskite manganites is developed by applying the group theory to the correlation functions of the pseudospin operators for the orbital degree of freedom. It is shown that static and dynamical informations of the orbital state are directly obtained from the elastic, diffuse an…
Gap to Transition Temperature Ratio in Density Wave Ordering: a Dynamical Mean Field Study
We use the dynamical mean-field method to determine the origin of the large ratio of the zero temperature gap to the transition temperature observed in most charge density wave materials. The method is useful because it allows an exact treatment of thermal fluctuations. We establish the relation of the dynamical mean-…
Seeding of Colloidal Au Nanoparticle Solutions. 2. Improved Control of Particle Size and Shape
New fields of research in chemistry and physics require improved synthetic techniques for colloidal metal particles. This paper reports a generally applicable technique for synthesizing colloidal Au particles of mean diameters between 20 and 100 nm that exhibit improved monodispersity relative to previously published…
Concentration Dependence of Solution Viscosities of Rigid Rod Polymers
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTConcentration Dependence of Solution Viscosities of Rigid Rod PolymersT. K. Kwei, M. Nakazawa, S. Matsuoka, M. K. Cowman, and Y. OkamotoView Author Information Polymer Research Institute, Polytechnic University, Six Metrotech Center…
Addition of Ammonia to AlH3and BH3. Why Does Only Aluminum Form 2:1 Adducts?
The electronic structures of the mono- and bisammonia adducts EH3NH3 and EH3(NH3)2, E = B and Al, have been investigated using ab initio electronic structure methods. Geometries were optimized at the MP2/cc-pVTZ level. Higher-level correlated methods (MP4(SDTQ), QCISD(T), CCSD(T)), as well as the G2 and CBS-Q methods,…
Synthesis, Characterization, and Ion-Exchange Properties of Zinc and Magnesium Manganese Oxides Confined within MCM-41 Channels
Zinc− and magnesium−manganese oxide particles have been grown in the pores of MCM-41 using a procedure adapted from a mild synthesis for layered manganese oxides. The Mn-modified silicates were analyzed by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), N 2…
The Stepwise Four- and Six-Electron Reduction of Carbon Monoxide to Oxyalkylidyne, to Carbide and Oxide, Then to Carbide over an Nb−Oxo Surface Modeled by Calix[4]arene1
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTThe Stepwise Four- and Six-Electron Reduction of Carbon Monoxide to Oxyalkylidyne, to Carbide and Oxide, Then to Carbide over an Nb−Oxo Surface Modeled by Calix[4]arene1Alessandro Caselli, Euro Solari, Rosario Scopelliti, and Carlo FlorianiView Author Information Insti…