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PubMed1989

[Effects of immunization on quartz resistance and phagocytic activity of macrophages].

The experiments on Wistar rats revealed that after their immunization by ram erythrocytes rats' peritoneal and alveolar macrophage possessed significantly higher resistance to cytotoxic effects of standard quartz in vitro compared to macrophage of control animals. Initial immunization greatly increases the capacity of peritoneal macrophage to absorb suspended polystyrene latex particles. Both immunized and nonimmunized rats had similar mobilization of phagocyte-able cells into respiratory tracts in response to intratracheal destruction product administration. Theoretical and applied aspects of the obtained results were discussed.

Animals↗
PubMed1989

Erythema induced by quartz-halogen sources.

The erythemal effect of 100-W quartz-halogen sources, previously predicted from radiation measurements, was directly measured on humans at a distance of 10 cm. Minimal erythema was produced in 15 min for skin type I. These data show that normal use of a desktop lamp should not usually lead to erythema in one day, but that long-term effects cannot be ignored, because for lifetime use at work, the relative risk for squamous cell carcinoma on the back of the hands is 3.4.

Carcinoma, Squamous Cell↗
PubMedDate not supplied

[Quartz--its relevance for dermatology].

Next to oxygen silicium is the most common substance of our environment. It occurs mostly in form of quartz (SiO2). In the past silica was usually mentioned in connection with foreign body granulomas in dermatological papers. Recently relations between occupational silica exposure and several diseases were reported. Silica exposure was related to the development of scleroderma, lupus erythematodes and sarcoidosis. Pathogenetic connections may be due to a stimulating effect on fibroblasts and due to immunmodulating properties of silica.

Dermatitis, Occupational↗
PubMedDate not supplied

[Quantitative evaluation of reflectance of some acrylic resins mixed with powdered enamel and/or natural quartz].

Autopolymerizing acrylic resins for temporary prothesis and crown veneering have been mixed with dental enamel and/or quartz in powder form in different percentages, to simulate optical properties of the tooth. The analysis of our measurements of apparent reflectance of those mixings show that is possible to approximate several of those values to the ones corresponding to natural tooth; being sufficient to follow the formulation given++ in this paper.

Acrylic Resins↗
PubMed1983

Experimental silicosis. II. Long-term effects of intratracheally instilled quartz on collagen metabolism and morphologic characteristics of rat lungs.

Rats received intratracheal instillations of 50 mg of silica (quartz, 0.5 mu particles). One, 2, 4, 5, 6, 9, and 12 months later, the lungs were evaluated histologically and by various biochemical measurements. The lung content of protein, proline, and hydroxyproline (collagen) were quantitated, as were the synthesis rates of lung collagen and the total lung protein (evaluated with lung minces in vitro. The ratio of newly synthesized and of total lung Type I to Type III collagen was also determined. These experiments were performed in parallel on rats free of chronic respiratory disease and a strain of conventional animals. The authors conclude that 1) the excess collagen deposited in granulomas and/or silicotic nodules as part of the fibrotic response of the lung is similar to normal lung collagen with respect to relative ratios of Types I and III present, in contrast to the response of the lung to oxidant pneumotoxins; 2) the response of the lung to silica continues for at least 1 year; 3) there are essentially no differences in the response of chronic respiratory disease-free Sprague-Dawley and conventional Wistar rats to intratracheally instilled silica. Both strains of rats develop silica-containing granulomas, mature silicotic nodules, and areas of alveolar lipoproteinosis associated with interstitial pneumonitis. Even 1 year after instillation of silica areas of granulomas, silicotic nodules and alveolar lipoproteinosis may be observed in most of the lungs studied; ie, these responses are not mutually exclusive.

Animals↗
PubMed1993

Microleakage of posterior composite resin restorations using beta quartz glass-ceramic inserts.

The effectiveness of using beta quartz glass-ceramic inserts in Class II composite resin restorations to prevent microleakage at the gingival cementum margins was investigated. Class II cavities were prepared on both mesial and distal sides of ten extracted teeth with the gingival margins placed on cementum. Both cavities were then restored with a composite resin in exactly the same manner, except that one received a glass ceramic insert and the other did not. The specimens were then thermocycled in basic fuchsin solution, embedded in epoxy resin and sectioned. The extent of dye penetration at the gingival cementum margins was then assessed and scored. The result indicated that the use of a glass-ceramic insert substantially reduced the microleakage of gingival cementum margins of composite resin restorations.

Ceramics↗
PubMed1993

[Simultaneous determination of vitamin B1 and vitamin C in aqueous solution with piezoelectric crystal quartz sensors].

According to the response properties of piezoelectric crystal quartz sensors to the solution conductivity the frequency shift response was derived to show a linear dependence on the concentrations of vitamin B1 (VB1) and vitamin C (VC). This was experimentally verified and a calibration model for simultaneous determinations of the two vitamins was established. The usefulness of the technique was evaluated by quantitation of mixtures of unknown composition using common multiple linear regression (MLR) and partial least squares (PLS). The average relative standard deviations for six samples were 4.46% for VB1 and 6.63% for VC with MLR; and 1.97% for VB1 and 2.74% for VC with PLS, respectively.

Ascorbic Acid↗
PubMed2000

A combined electrochemical quartz-crystal microbalance probe beam deflection (EQCM-PBD) study of solvent and ion transfers at a poly

The oxidative polymerisation of the complex2,3-dimethyl-N,N'-bis-(salicylidene)butane-2,3-diaminatonick-el(II), [Ni(saltMe)], was monitored by the electrochemical quartz microbalance (EQCM) and crystal impedance techniques. Polymerisation efficiency was maintained throughout deposition of a film, which behaved rigidly, on the electrode. A combined EQCM-PBD (probe beam deflection) study of the redox process of the film exposed to a monomer-free solution of 0.1 M tetraethylammonium perchlorate (TEAP) in acetonitrile showed an electroneutrality mechanism dominated by anion movement accompanied by co-transfer of solvent above 0.8 V. The individual contributions of all the mobile species involved in the redox switching of the poly[Ni(saltMe)] film were determined quantitatively by temporal convolution analysis; the estimated solution-phase diffusion coefficient of the exchanged species was 1.24 x 10(-5) cm2s-1.

Journal Article↗
PubMed2000

Dynamic analyses on induced-fit gaseous guest binding to organic crystals with a quartz-crystal microbalance

The inclusion behavior of gaseous guest molecules in a solid apohost, an orthogonal anthracene-bis(resorcinol)tetraol (1), was investigated with a quartz-crystal microbalance (QCM). Compound 1 forms crystals composed of molecular sheets bound together by an extensive hydrogen-bonded network. An apohost of 1 was cast onto a QCM and the binding of gaseous guest molecules was followed as a function of time by observing the decrease in the oscillation frequency, which is directly related to the increase in mass. Ethyl acetate and methyl ethyl ketone were significantly included into the apohost, whereas benzene and cyclohexane were simply adsorbed onto the surface of the solid; all these guests have similar vapor pressures at 25 degrees C. On the other hand, a host analogue 2, a tetramethoxy derivative of 1, barely included these guest molecules. The inclusion amount and the rate of inclusion of ethyl acetate or methyl ethyl ketone showed a drastic increase above a threshold concentration of guests in the gas phase. Thus, the structure of the apohost changed cooperatively in order to bind guest molecules above the threshold guest concentration. This cooperativity of the binding behavior was kinetically analyzed.

Journal Article↗
PubMed2002

Preparation and self-assembly of chiral porphyrin diads on the gold electrodes of quartz crystal microbalances: a novel potential approach to the development of enantioselective chemical sensors.

Porphyrin diad 1 was synthesized by reaction of the acyl chloride of porphyrin 2 and trans-1,2-dithiane-4,5-diol. The Co complex of this diad was studied as a potential enantioselective receptor for chiral recognition in solution and in the solid state. In solution both enantiomers of limonene induce significant changes in the visible and circular dichroism (CD) spectra of [Co2(1)], while a different behavior is observed in the case of the enantiomeric pair of trans-1,2-diaminocyclohexane. A different efficiency of [Co2(1)] chiral recognition is obtained for these compounds, with a remarkable degree of enantiodiscrimination observed in the case of limonene. Self-assembled monolayers of [Co2(1)] were deposited onto the gold electrodes of quartz crystal microbalances to be used as sensing materials of nanogravimetric sensors operating in the gas phase. The enantiodiscrimination properties of these sensors towards the enantiomeric pairs of chiral analytes have been studied. While in the case of analytes bearing donor ligand atoms we did not observe a remarkable enantioselectivity, a significant degree of chiral discrimination was observed in the case of limonene; this result is particularly encouraging for the potential development of enantioselective chemical sensors for use in an array configuration.

Cobalt↗
PubMed2003

High-speed electrophoretic analysis of 1-phenyl-3-methyl-5-pyrazolone derivatives of monosaccharides on a quartz microchip with whole-channel UV detection.

1-Phenyl-3-methyl-5-pyrazolone (PMP) derivatives of monosaccharides were analyzed by electrophoresis on a quartz microchip with whole-channel UV detection. Rapid separation of PMP derivatives of aldopentoses was achieved by plain-zone electrophoresis in a neutral phosphate buffer with the height equivalent to a theoretical plate at the micrometer level. Zone electrophoresis as borate complexes was also successful for the separation of PMP derivatives of a few aldoses, which were separated within 1 min. Separation by microchip electrophoresis was compared to that by capillary electrophoresis, and the difference was discussed in terms of column efficiency and sample column capacity.

Antipyrine↗
PubMed2004

Calculation of the vibration frequencies of alpha-quartz: the effect of Hamiltonian and basis set.

The central-zone vibrational spectrum of alpha-quartz (SiO2) is calculated by building the Hessian matrix numerically from the analytical gradients of the energy with respect to the atomic coordinates. The nonanalytical part is obtained with a finite field supercell approach for the high-frequency dielectric constant and a Wannier function scheme for the evaluation of Born charges. The results obtained with four different Hamiltonians, namely Hartree-Fock, DFT in its local (LDA) and nonlocal gradient corrected (PBE) approximation, and hybrid B3LYP, are discussed, showing that B3LYP performs far better than LDA and PBE, which in turn provide better results than HF, as the mean absolute difference from experimental frequencies is 6, 18, 21, and 44 cm(-1), respectively, when a split valence basis set containing two sets of polarization functions is used. For the LDA results, comparison is possible with previous calculations based on the Density Functional Perturbation Theory and usage of a plane-wave basis set. The effects associated with the use of basis sets of increasing size are also investigated. It turns out that a split valence plus a single set of d polarization functions provides frequencies that differ from the ones obtained with a double set of d functions and a set of f functions on all atoms by on average less than 5 cm(-1).

Journal Article↗
PubMed2001

Optimization of quartz tube pyrolysis atmospheric pressure ionization mass spectrometry for the generation of bacterial biomarkers.

Experimental procedures were investigated to improve the efflux of biomolecule pyrolyzates from quartz tube pyrolysis under atmospheric pressure ionization mass spectrometry conditions. Heating regimes, airflows, and ion focusing parameters were optimized to increase the informative mass spectral signals generated from the pyrolysis of Gram-positive bacterial spores and vegetative cells. Dipicolinic acid (DPA) is found in 5-15% by weight in Gram-positive Bacillus spores, and the parameter optimization procedures provided an intense mass spectral signature of the m/z 168 protonated DPA molecule with a minimization of pyrolytic and ionization fragments. Moreover, mass spectral information from the optimization protocols yielded peaks and mass patterns characteristic of DNA and RNA nitrogen bases, protein diketopiperazines, and amino sugars.

Bacillus↗
PubMedDate not supplied

Monte Carlo analysis of the detection of clay occlusion of respirable quartz particles using multiple voltage scanning electron microscopy.

The electron incident-energy dependence of the relative intensities of Al and Si x-rays produced in a respirable-sized quartz particle by scanning electron microscopy is sensitive to the inhomogeneity of the distribution of Al and Si in the particle. Realistic Monte Carlo calculations of this energy dependence validate the proposal to use this effect for the detection of particles in which an aluminosilicate coating occludes the surface of a silica core.

Journal Article↗
PubMed2001

Charge-dependent sidedness of cytochrome P450 forms studied by quartz crystal microbalance and atomic force microscopy.

Quartz crystal microbalance (QCM) resonance measurements were used to examine the surface charge characteristics of cytochrome P450 forms and the influence of charge on the docking of redox partners like cytochrome b5. The distal surface of cytochrome P450 (CYP)101 (pI = 4.5), relative to the heme, is fairly anionic, as is the proximal surface. The latter, however, also has two cationic clusters. A considerably greater extent of CYP101 binding was seen to the cationic, polyethylene-surfaced resonators. CYP2B4 (pI = 8.5) preferentially bound to the polyanionic, polystyrene sulfonate-surfaced resonators. Cytochrome b5 is an acidic protein that had a preferential binding to the poly(ethyleneimine (PEI)-surfaced resonators. When binding to CYP2B4-surfaced films, cytochrome b5 preferentially bound to those cytochrome P450 molecules that were adsorbed to cationic (PEI) films. It is suggested that adsorption of CYP2B4 to an anionic poly(styrenesulfonate) (PSS) surface is with cationic clusters that include the cytochrome b5 docking domain. This diminishes the extent of docking of the cytochrome b5. In contrast, when CYP2B4 is adsorbed to a cationic film the proximal surface with the cytochrome b5-docking site is available for cytochrome b5 binding. A film of the polycation PEI was adsorbed to the silver QCM surface. It formed polymer islands when viewed with atomic force microscopy. Polyanionic PSS was adsorbed intermittently with the PEI. By the third and fourth layer of polyions the polymer islands were essentially merged and protein adsorption as a fourth or fifth layer formed a nearly continuous film. CYP101 was seen to adsorb as globules with a molecular diameter of about 10 nm. CYP2B4 adsorbed to the polyionic films had a slightly elliptical globular shape, also with a molecular diameter of about 10 nm.

Adsorption↗
PubMed2000

Detection and analysis of Bacillus subtilis growth with piezoelectric quartz crystal impedance based on starch hydrolysis.

A piezoelectric quartz crystal (PQC) impedance method based on the alpha-amylase-catalyzed hydrolysis of starch present in a culture medium has been developed for in situ monitoring of the whole growth process of Bacillus subtilis and the variation in the activity of alpha-amylase during bacterial growth. An S-shaped response behavior was observed for Deltaf(0), and simultaneously inverse S-shaped responses were found for DeltaR(1) and DeltaL(1). The ratio of DeltaR(1) to Deltaf(0) or DeltaL(1) coincided well with that calculated from Martin's equations reflecting the solution density-viscosity effect, suggesting that the continuing change in liquid loading onto the PQC surface causes significant variation in Deltaf(0), DeltaR(1), and DeltaL(1). Bacterial growth equations were derived from the kinetics of the enzyme-catalyzed hydrolysis of starch, which fit well with the experimental responses of Deltaf(0), DeltaR(1), and DeltaL(1). Kinetic parameters of bacterial growth, including the asymptote (A), the maximum specific growth rate (microm), and the lag time (lambda), were obtained and were in good agreement with those obtained from the pour plate count method. The variation in the activity of alpha-amylase exhibited peak-type behavior with its maximum value at the later stage of the log phase. In addition, the influence of initial bacterial concentration was also investigated.

Algorithms↗
PubMed2000

Study on colloidal Au-enhanced DNA sensing by quartz crystal microbalance.

Colloidal Au is reported for enhancement the immobilization capacity and ultimately detection limit of DNA using quartz crystal microbalance (QCM). Immobilization of approximately 12 nm-diameter colloidal Au on to an Au-coated QCM resulted in an easier attachment of oligonucleotide, with a mercaptohexyl group at the 5'-phosphate end and an increased capacity for nucleic acid detection. DNA immobilization and hybridization was monitored from QCM frequency changes. Hybridization was induced by exposure of the DNA-containing films to complementary DNA in solution. A much higher sensitivity was obtained for the analyte. The Au nanoparticle films on the Au plate provide a novel means for the fabrication of DNA sensor.

Animals↗
PubMed1998

Measurements Using the Quartz Crystal Microbalance Technique of Ferritin Monolayers on Methyl-Thiolated Gold: Dependence of Energy Dissipation and Saturation Coverage on Salt Concentration.

The adsorption kinetics of ferritin as a function of ionic strength has been studied with a new quartz crystal microbalance technique, allowing simultaneous measurement of the frequency shift (proportional to the mass uptake under certain conditions) and of changes in the energy dissipation caused by the adlayer. The measurements were performed with methyl-terminated (hydrophobic) thiol-covered gold surfaces, at pH 7.0 and ionic strengths in the range 1-200 mM KCl. The saturation uptake increases rapidly with increasing ionic strength in the range 20-50 mM and is then independent of ionic strength at >100 mM. The dissipation factor reveals, in the low coverage regime, distinct differences in the adlayer properties at low and high ionic strength, respectively. These results are briefly discussed in terms of the screening properties of the solvent and its influence on the protein-protein interaction in solution and on the surface. Copyright 1998 Academic Press.

Journal Article↗