Spectroscopic investigation of the function of aqueous 2-hydroxyethylmethacrylate/glutaraldehyde solution as a dentin desensitizer

Fourier-transform (FT)-Raman and -infrared (IR) spectroscopy were employed to investigate the function of the aqueous 2-hydroxyethylmethacrylate/glutaraldehyde solution (Gluma) as a desensitizer. 2-Hydroxyethylmethacrylate (HEMA), glutaraldehyde (GA), and the mixture of HEMA/GA (i.e. Gluma) were used to interact with dentin, collagen, hydroxyapatite (HAP), and bovine serum albumin (BSA) individually. All the interactions were monitored by an FT-Raman spectrometer. FT-IR spectroscopy was also used in this study. The results show that HEMA could be absorbed by dentin and collagen; GA could cross-link collagen and BSA; and when BSA was added to Gluma, polymerization of HEMA occurred. The results suggest that Gluma acts as a desensitizer whereby, first, GA reacts with part of the serum albumin in dentinal fluid, which induces a precipitation of serum albumin, then, second, a reaction of GA with serum albumin induces polymerization of HEMA. The function of Gluma as a desensitizer to block dentinal tubules occurs via these two reactions.

Determination of ethenzamide and acetoaminophen in quaternary powdered samples by near infrared spectroscopy and searching combination moving window partial least squares algorithm: effects of spectral resolution and signal-to-noise ratio

The present study reports an application of the searching combination moving window partial least squares (SCMWPLS) algorithm to the determination of ethenzamide and acetoaminophen in quaternary powdered samples by near infrared (NIR) spectroscopy. Another purpose of the study was to examine the instrumentation effects of spectral resolution and signal-to-noise ratio of the Buchi NIRLab N-200 FT-NIR spectrometer equipped with an InGaAs detector. The informative spectral intervals of NIR spectra of a series of quaternary powdered mixture samples were first located for ethenzamide and acetoaminophen by use of moving window partial least squares regression (MWPLSR). Then, these located spectral intervals were further optimised by SCMWPLS for subsequent partial least squares (PLS) model development. The improved results are attributed to both the less complex PLS models and to higher accuracy of predicted concentrations of ethenzamide and acetoaminophen in the optimised informative spectral intervals that are featured by NIR bands. At the same time, SCMWPLS is also demonstrated as a viable route for wavelength selection.

Coating nano-hemalite on (Y,Gd)BO3 : Eu3+ phosphors by a facile method

(Y, Gd) BO3:Eu3+ particles coated with nano-hematite were prepared by a facile method I for example (humid) solid phase reaction at room temperature. The resulted hematite-coated (Y, Gd)BO3:Eu3+ particles were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) analysis, X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and photoluminescence spectra (PL). The SEM and EDS analyses indicate that the particles are coated with a very thin layer of iron oxide. XPS results further confirmed that the coating was hematite, and the coating thickness was in nanometer range. XRD patterns showed that either the hematite coating was too thin or the content of hematite was too small, so that the XRD cannot detect it. The emission spectra illustrate that the peak near 580 nm disappears due to the coating of iron oxide, and when the coating is very thin, the ratio of D-5(0)-> F-7(2) to D-5(2)-> F-7(1) of coated particles is higher than that of uncoated ones, which indicates that the color purity of the phosphor is increased by coating nano-hematite.

Coating of Y2O3 : Eu3+ particles with alumina by a humid solid state reaction at room temperature

Humid solid state reaction at room temperature was utilized for the first time to coat Y2O3 : Eu3+ particles with alumina. The particles were studied with an X-ray photoelectron spectrometer (XPS), a scanning electron microscope (SEM), and an energy dispersive spectrometer (EDS). XPS results show that the yttrium and europium contents are decreased and that the aluminum content is the highest except for that of oxygen after coating. SEM and EDS results show that particles are coated with a thin shell of alumina.

Study on the biodegradation process of poly (3-hydroxybutyrate)

Poly (3-hydroxybutyrate) (PHB) films were biodegraded by DS9701. The degradation process was monitored by using SEM. It was shown that the PHB degradation occurred firstly in the amorphous part of PHB and then in the crystalline part, especially from the center of PHB spherulites. PHB deplymerase produced by DS9701 mainly attacked the second ester bond of PHB and the degraded product was dimmer, determined by using mass spectrometer.

Identification of high-lying odd energy levels of uranium by resonant ionization mass spectrometry

Single-colour and two-colour multiphoton resonant ionization spectra of uranium atom were studied extensively with a Nd: YAG laser-pumped dye laser atomic beam apparatus time-of-flight mass spectrometer in our laboratory. The energy locations of high-lying odd-parity levels in the region 33 003-34 264 cm(-1),mearured by a two-colour three-step ionization technique, were reported here. The angular momentum quantum number J was uniquely assigned for these levels by using angular momentum selection rules.

The multicolour three-photon resonant ionization spectrum studies in uranium atom

The multicolour three-photon resonant ionization spectra of U-238 were measured by using the pulsed dye lasers system synchronously pumped by a frequency doubled Nd:YAG-laser 532 nm output(operated at 10 Hz),a device for atomic beam of U, time-of-flight mass spectrometer and boxcar integrator. The dye laser pulses have a 6 ns duration. Beams from the dye lasers, which have the same polarization direction and are focused by lenses, entered an interaction chamber through opposite windows on a common axis and spatialy overlapped the U atomic beam. The optical pulse from dye laser DL2 was delayed to arrive at the interaction region 8 ns after the pulse from dye laser DL1; in the same way,the pulse from DL3 was delayed 8 ns after from DL2. The atomic beam device was made from stainless steel. We generated the U vapor by heating solid U in a graphite crucible by e-type electron -field on first excited states were studied in uranium atom. The question how to determine single-colour, two-colour and three-colour three-photon resonant ionization peak in the three-colour three-photon resonant ionization spectra diagram were solved.

New high-lying odd-parity excited levels of atomic uranium

We report the measurement of 112 new high-lying odd-parity excited levels of U I in the energy region 35 678-36 696 cm(-1). These levels were obtained with a setup composed of a Nd:YAG-laser-pumped pulsed dye laser system, an atomic beam device, a time-of-flight mass spectrometer, and a boxcar integrator. (C) 2000 Optical Society of America [S0740-3224(99)02309-7] OCIS code: 300.0300.

Gas-phase ion-molecule reactions of C-60 with the plasma of methyl acrylate

The gas-phase ion-molecule reactions of C-60 with the plasma generated from methyl acrylate under self-chemical ionization conditions were studied by use of a triple-quadrupole mass spectrometer. The adduct cation [C60C3H3O](+) and protonated molecular ion [C60H](+) were observed as the major product ions. The former adduct ion is formed by electrophilic reaction of C-60 with the ion [CH2=CHCO](+), a main fragment ion resulting from the methyl acrylate molecular ion [CH2=CHCOOCH3](+) through alpha cleavage. The latter ion is generated by proton transfer from protonated methyl acrylate to C-60. Semi-empirical quantum chemical calculations have been performed for the eight possible isomers of [C60C3H3O](+) at the Hartree-Fock level by use of the AMI method. The results show three types of cycloadducts as the most stable structures among the possible isomers.

Functionalization of isotactic polypropylene with maleic anhydride by reactive extrusion: mechanism of melt grafting

In this work, chemical structures and molecular parameters of grafted materials of PP-g-MAH prepared by melt reactive extrusion were studied by using electrospray ionization-mass spectrometer and gel permeation chromatography. It was found that the initial radicals, due to homolitic scission of dicumyl peroxide could be combined with maleic anhydride (MAH) monomers as well as polypropylene (PP) molecular chains. The homopolymerization of MAH cannot occur and the MAH radicals undergo a dismutational reaction under the processing condition (180-190 degreesC). A modified mechanism of melt grafting MAH onto PP has been proposed tentatively on the basis of our experimental results and other experimental findings published in the literature. (C) 2001 Elsevier Science Ltd. All rights reserved.

Preparation and properties of nanocrystalline Yb2O3

Nanocrystalline Yb2O3 of various particle sizes was prepared using sol-gel method. XRD analysis shows that the prepared nanocrystalline Yb2O3 is cubic in structure with space group Ia3. TEM photographs indicate that Yb2O3 nanoparticles are basically spherical in shape. Calculation of crystallite size indicates that the average crystallite size of Yb2O3 increases with increasing calcination temperature, but the average crystal lattice distortion rate decreases with increasing calcination temperature and crystallite size. This result shows that the smaller the crystallite size, the bigger the crystal lattice distortion, and the worse crystal growth. Solubility test of Yb2O3 in nitric acid shows that the surface activity of Yb2O3 increases with decreasing crystallite size. Fourier Transform Infrared Spectrometer (FTIR) spectra reveal that nanocrystalline Yb2O3 has higher surface activity; than that of ordinary Yb2O3. Absorbance intensity of Yb-O bond of nanocrystalline Yb2O3 is weaker than that of ordinary Yb2O3, and the absorbance of Yb-O bond of nanocrystalline Yb2O3 is small blue-shifted.

Gas-phase ion - Molecule reactions of neutral C-60 with the plasmas of alkyl methyl ethers and primary alcohols

The gas-phase ion-molecule reactions of C-60 with the methoxymethyl ion [CH3O=CH2](+) and the 1-hydroxyethyl ion [CH3CH=OH](+) generated under the self-chemical-ionization (self-CI) conditions of alkyl methyl ethers and primary alcohols were studied in the ion source of a mass spectrometer. The adduct ions [C60C2H5O](+) and protonated molecules [C60H](+) were observed as the major products of C-60 with the plasma of alkyl methyl ethers. On the contrary, the reactions of C-60 With the plasmas of primary alcohols produced few corresponding adduct ions. The AM1 semiempirical molecular orbital calculations were carried out on 14 possible structures. The calculated results showed that the most stable structure among the possible isomers of [C60C2H5O](+) is the [3+2] cycloadduct. According to experimental and theoretical results, the pathway for the formation of the adduct was presented.

Application of acetone and dimethyl ether chemical ionization reagent gases to structural analysis

Acetone and dimethyl ether( DME) have been shown to be reagent gases of exceptional utitlity and versatility for the characterization of a variety of class of organic compounds. The fragmentation mechanisms of the adduct product ions, formed by ion/molceule reaction of the substrate with the ionized gases, have been studied and substantiated by experiments with acetone-d(6) and DME-d(6).

The rheological and extrusion behaviour of blends based on phenolphthalein poly(ether-ether-sulfone) and thermotropic liquid crystalline polymer

A novel engineering thermoplastic, phenolphthalein poly (ether-ether-sulfone) (PES-C) was blended with a commercial thermotropic liquid crystalline polymer(TLCP), Vectra A950, up to 30 weight percent of TLCP. A rheometrics dynamic spectrometer (RDS-I) and a CEAST capillary rheometer, a rheoscope 1000 were employed to investigate the melt rheology and extrusion behaviour at both the low and high shearing rates. The morphologies of the blends under different shearing were observed with a scanning electron microscope(SEM) and correlated to the observed rheology. The principal normal stress differences measured with cone-and-plate geometry give a temperature-independent correlation for both blend and PES-C when they are plotted against shear stress. But the extrudate swell of the blends showed a strong temperature dependence at each shear stress. The concentration dependence of extrudate swell shows a contrary behaviour to that of the inorganic filled system. A reasonable hypothesis based on the relaxation and disorientation of TLCP during flowing in the capillary and exiting was given to explain it. The melt fracture was checked after extrusion from capillary and was discussed.

Gas-phase ion-molecule reactions of C-60 with methyl ethers CH3OCnH2n+1

Gas-phase ion-molecule reactions of buckminsterfullerene (C-60) with the ion systems generated from the self-chemical-ionization of alkyl methyl ethers(CH3OCnH2n+1, n =2 , 3, 4) were studied in the ion source of a mass spectrometer. The adduct cation [C60C2H5O](+) and protonated molecular ion [C60H](+) were observed as the major products, The former was produced by the reactions.of C-60 with the methoxymethyl ion [CH3O = CH2](+) , the latter corresponded to the proton transfer reactions from the protonated alkyl methyl ethers to C60 It is suggested that the [3+2] cycloadduct is the most favorable structure among the probable isomers with special chemical properties, Our investigation provides the guidance for the synthesis of this compound in condensed phase.