Search results for "optical"

showing 10 items of 7671 documents

Iodine and mercury resonance lamps for kinetics experiments and their spectra in the far ultraviolet

2000

Electrodeless iodine and mercury iodide radio-frequency discharge lamps have been made to provide intense sources of resonance radiation of iodine and mercury in the 183-253 nm region. Production technology and emission spectra in the ultraviolet and vacuum ultraviolet regions are described. Both lamps (iodine and mercury iodide) are designed and used for monitoring the iodine 2P1/2 (206.163 nm) and 2P3/2 (183.038 nm) level population kinetics after flash photolysis of I2 or other precursor molecules in laboratory experiments. The technique is suitable for the investigation of the gas phase reaction kinetics following the photolysis of I2 in the presence of O3.

chemistry.chemical_classificationGas-discharge lampAcoustics and UltrasonicsKineticsPhotodissociationIodideAnalytical chemistrychemistry.chemical_elementCondensed Matter PhysicsIodinemedicine.disease_causeSurfaces Coatings and FilmsElectronic Optical and Magnetic Materialslaw.inventionMercury (element)chemistrylawmedicineFlash photolysisUltravioletJournal of Physics D: Applied Physics
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Methods for Separating Native Enzymes

1994

In the course of electrophoresis the stability of an enzyme depends on such conditions as (a) pH-value, (b) ion strength and ion species, (c) effector molecules, (d) temperature and (e) properties of the separation matrix. These parameters were empirically optimized for starch gel electrophoresis [1–3] and cellulose acetate electrophoresis [4, 5] when analyzing predominantly animal and human specimen. A major advantage of these types of separation media is that practically every buffer system can be used to separate enzymes whereas in disc-gel electrophoresis [6–8] the number of applicable buffer systems is limited. When using isoelectric focusing to separate native enzymes no buffer choice…

chemistry.chemical_classificationGel electrophoresisElectrophoresisStarch gel electrophoresisIsoelectric pointChromatographyEnzymeMolecular massChemistryIsoelectric focusingBuffer (optical fiber)
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Multifunctional polymer-derivatized γ-Fe2O3 nanocrystals as a methodology for the biomagnetic separation of recombinant His-tagged proteins

2008

Abstract Multifunctional polymer-derivatized superparamagnetic iron oxide (γ-Fe2O3) nanoparticles were prepared for biomagnetic separation of histidine-tagged recombinant proteins building up a faster and efficient method for protein separation by making use of their intrinsic magnetic properties. Using polymer bound γ-Fe2O3 nanocrystals, a 6× histidine-tagged recombinant protein (silicatein) with a molecular weight of 24 kDa has been isolated and purified. The supermagnetic iron oxide nanocrystals were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), SQUID and Mossbauer and the polymer functionalization of the γ-Fe2O3 nanocrystals was monitored by UV–vi…

chemistry.chemical_classificationGel electrophoresisMaterials scienceIron oxideNanoparticlePolymerCondensed Matter PhysicsElectronic Optical and Magnetic Materialschemistry.chemical_compoundNuclear magnetic resonancechemistryChemical engineeringProtein purificationMicroscopyHigh-resolution transmission electron microscopySuperparamagnetismJournal of Magnetism and Magnetic Materials
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Properties and interactions – melting point of tri­bromo­benzene isomers

2021

The melting points of tri­bromo­benzene isomers are correlated with the number, nature and distribution of intermolecular interactions in their structures.

chemistry.chemical_classificationHalogen bondtribromobenzene isomersChemistryIntermolecular forcemelting pointMetals and AlloysClose-packing of equal spheresResearch PapersAtomic and Molecular Physics and OpticsElectronic Optical and Magnetic MaterialsCrystalmolecular symmetryCrystallographynoncovalent interactionsMaterials ChemistryMelting pointMolecular symmetrystructure-property relationshipNon-covalent interactionsMoleculehalogen bondActa Crystallographica Section B-Structural Science Crystal Engineering and Materials
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Effects of isotopic substitution on the conformational properties of polymeric aqueous solutions

2000

Abstract This work deals with a side-by-side comparison between the PEO conformational properties in H 2 O and D 2 O. The gyration radius, evaluated by SANS, the hydrodynamic radius, evaluated by PCS, and the Raman D-LAM band analysis furnish valuable information on the structural arrangement of the molecules. The findings clearly show different behavioural properties of the polymer in H 2 O and D 2 O.

chemistry.chemical_classificationHydrodynamic radiusMaterials scienceRadiusPolymerCondensed Matter PhysicsGyrationSmall-angle neutron scatteringElectronic Optical and Magnetic Materialssymbols.namesakechemistrysymbolsMoleculePhysical chemistryElectrical and Electronic EngineeringRaman spectroscopyRaman scattering
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Diferrocenyl tosyl hydrazone with an ultrastrong NHFe hydrogen bond as double click switch.

2014

The intramolecular NH⋯Fe hydrogen bond in diferrocenyl hydrazone 2 raises the barrier for intramolecular electron transfer in its mixed-valent cation 2+ and is only disrupted by double oxidation to 22+.

chemistry.chemical_classificationHydrogen bondMetals and AlloysHydrazoneGeneral ChemistryPhotochemistryCatalysisSurfaces Coatings and FilmsElectronic Optical and Magnetic Materialschemistry.chemical_compoundElectron transferchemistryTosylIntramolecular forceMaterials ChemistryCeramics and CompositesChemical communications (Cambridge, England)
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The effect of disorder on optical spectra of conjugated polymers

1993

Abstract Using the semi-empirical parametrization of the Pariser-Parr-Pople model we determine the excitonic states in conjugated polymers. The employed parameters correspond to a moderate strength of the long-range Coulomb interaction. In order to take the disorder into account, the nearest-neighbour transfer matrix elements are chosen according to a random distribution. Averaging the results over a large number of chains of 100 sites, which are known to be sufficiently long so that finite-size effects become negligible, we obtain the linear and third-order nonlinear optical susceptibilities. With increasing disorder the linear absorption, the two-photon absorption and the third-harmonic g…

chemistry.chemical_classificationImaginationChemistryMechanical Engineeringmedia_common.quotation_subjectMetals and AlloysPolymerCondensed Matter PhysicsAsymmetryMolecular physicsTransfer matrixSpectral lineElectronic Optical and Magnetic MaterialsNuclear magnetic resonanceMechanics of MaterialsMaterials ChemistryCoulombAbsorption (electromagnetic radiation)Parametrizationmedia_commonSynthetic Metals
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Maghemite polymer nanocomposites with modulated magnetic properties

2007

A method is presented for the production of maghemite polymer nanocomposites with modulated magnetic properties. Magnetic nanocomposites prepared using this method show regular variation in the magnetic blocking temperature from 2 K to 300 K, and variation in the saturation magnetization from 0 to 50 emu g � 1 (Fe2O3). The method is based on the in situ formation of maghemite nanoparticles in nitrogen-base polymer matrixes. The particle size can be varied regularly from 1.5 nm to 16 nm by changing the ratio of iron loading in the polymer and/or the Fe(II)/Fe(III) ratios. The particles are isolated and uniformly distributed within the matrix. The mate

chemistry.chemical_classificationIn situNanocompositeMaterials sciencePolymers and PlasticsPolymer nanocompositeMetals and AlloysMaghemiteNanoparticlePolymerengineering.materialElectronic Optical and Magnetic MaterialsNuclear magnetic resonancechemistryChemical engineeringCeramics and CompositesengineeringParticle sizeActa Materialia
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Crystal structures, infrared-spectra, and thermal behavior of calcium hydrogenselenite monohydrate, Ca(HSeO3)2 · H2O, and dicalcium diselenite bis(hy…

1986

Abstract Calcium hydrogenselenite monohydrate and dicalcium diselenite bis(hydrogenselenite) were synthesized and their crystal structures determined. Crystal data for Ca(HSeO3)2 · H2O: a = 6.911(2), b = 7.369(2), c = 6.739(2) A, α = 90.51(3)°, β = 90.93(3)°, γ = 107.46(2)°, V = 327.3(2) A3, space group P 1 (No. 2), dcalcd = 3.19 M gm−3, Z = 2, and R = 0.036 for 1503 reflections. Data for Ca2(HSeO3)2(Se2O5): a = 14.719(4), b = 7.059(2), c = 11.793(2) A, β = 117.96(2)°, V = 1082.3(4) A3, space group C2 c (No. 15), dcalcd = 3.52 Mg m−3, Z = 4, and R = 0.047 for 1251 reflections. Both structures form a three-dimensional network. The coordination polyhedron around calcium is a monocapped trigon…

chemistry.chemical_classificationInfraredInfrared spectroscopychemistry.chemical_elementCrystal structureCalciumCondensed Matter PhysicsElectronic Optical and Magnetic MaterialsInorganic ChemistryCrystallographyTrigonal prismchemistryCrystal dataX-ray crystallographyMaterials ChemistryCeramics and CompositesPhysical and Theoretical ChemistryInorganic compoundJournal of Solid State Chemistry
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Synthesis, characterization and thermal properties of small R2R′2N+X−-type quaternary ammonium halides

2005

Twenty-one R {sub 2} R {sup '} {sub 2}N{sup +} X {sup -} -type (R=methyl or ethyl, R {sup '}=alkyl, X=Br or I) quaternary ammonium (QA) halides have been prepared by using a novel one-pot synthetic route in which a formamide (dimethyl-, diethylformamide, etc.) is treated with alkyl halide in the presence of sodium or potassium carbonate. The formation of QA halides was verified with {sup 1}H-NMR, {sup 13}C-NMR, MS and elemental analysis. The crystal structures of four QA halides (two bromide and two iodide) were determined using X-ray single crystal diffraction, and the powder diffraction method was used to study the structural similarities between the single crystal and microcrystalline bu…

chemistry.chemical_classificationInorganic chemistryHalideCrystal structureCondensed Matter PhysicsElectronic Optical and Magnetic MaterialsInorganic ChemistryCrystallographychemistry.chemical_compoundchemistryIonic liquidX-ray crystallographyMaterials ChemistryCeramics and CompositesMelting pointPhysical and Theoretical ChemistrySingle crystalAlkylPowder diffractionJournal of Solid State Chemistry
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