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PubMed2005

Lethal effects of experimental warming approximating a future climate scenario on southern African quartz-field succulents: a pilot study.

Here we examine the response of succulents in a global biodiversity hot spot to experimental warming consistent with a future African climate scenario. Passive daytime warming (averaging 5.5 degrees C above ambient) of the natural vegetation was achieved with 18 transparent hexagonal open-top chamber arrays randomized in three different quartz-field communities. After 4-months summer treatment, the specialized-dwarf and shrubby succulents displayed between 2.1 and 4.9 times greater plant and canopy mortalities in the open-top chambers than in the control plots. Those surviving in cooler ventilated areas and shaded refuges in the chambers had lower starch concentrations and water contents; the shrubby succulents also exhibited diminished chlorophyll concentrations. It is concluded that current thermal regimes are likely to be closely proximate to tolerable extremes for many endemic succulents in the region, and that anthropogenic warming could significantly exceed their thermal thresholds. Further investigation is required to elucidate the importance of associated moisture deficits in these warming experiments, a potential consequence of supplementary (fog and dew) precipitation interception by open-top chambers and higher evaporation therein, on plant mortalities.

Africa, Southern↗
PubMed2005

Temperature rise induced by some light emitting diode and quartz-tungsten-halogen curing units.

Because of the risk of thermal damage to the pulp, the temperature rise induced by light-curing units should not be too high. LED (light emitting diode) curing units have the main part of their irradiation in the blue range and have been reported to generate less heat than QTH (quartz-tungsten-halogen) curing units. This study had two aims: first, to measure the temperature rise induced by ten LED and three QTH curing units; and, second, to relate the measured temperature rise to the power density of the curing units. The light-induced temperature rise was measured by means of a thermocouple embedded in a small cylinder of resin composite. The power density was measured by using a dental radiometer. For LED units, the temperature rise increased with increasing power density, in a statistically significant manner. Two of the three QTH curing units investigated resulted in a higher temperature rise than LED curing units of the same power density. Previous findings, that LED curing units induce less temperature rise than QTH units, does not hold true in general.

Composite Resins↗
PubMed1994

Quality assurance in mental health: the QUARTZ system.

This paper is concerned with how quality might be assured in mental health services. It includes an account of why a concern with quality and quality assurance procedures are now high on the agenda of the Health Service. A quality assurance programme requires a decision about what elements of a service to monitor, what information is relevant, how it can be collected, and a system for acting on the results. This paper provides a brief review of the kind of information that has been considered relevant and the methods that have been used to collect it. In addition, the principles underlying good and comprehensive quality assurance programmes will be outlined and the development of a particular system, known as QUARTZ, which has attempted to incorporate these principles, described briefly.

Humans↗
PubMed2001

Lagrangian effective material constants for the modeling of thermal behavior of acoustic waves in piezoelectric crystals. II. Applications and numerical values for quartz.

This paper presents a set of numerical values of temperature derivatives of Lagrangian effective elastic coefficients suitable for the modeling of small vibrations in quartz devices submitted to slow and homogeneous temperature variations. After a short description of the proper writing of vibration problems in practical applications with the help of this kind of coefficient, we determine the proposed set of numerical values from the frequency-temperature characteristics of an heterogeneous set of bulk and surface acoustic wave devices.

Journal Article↗
PubMed2002

Using adhesion to probe viscoelasticity of polymer film surfaces: a quartz crystal microbalance study.

We have used a quartz crystal microbalance to monitor the adhesion of small particles to the surface of polystyrene films. This technique is shown to provide a signature of viscoelastic relaxation processes at the polymer surface. For M(n) values less than 10(4) and greater than 10(5), this signature occurs at a temperature approximately 12.5 K above the measured bulk glass transition temperature, T(g). For intermediate values of M(n) however, the relaxation signature occurs at temperatures as low as 7 K above the bulk T(g). This observation suggests a slight decrease in the T(g) value near the polymer surface. A model incorporating the effects of enrichment of polymer chain ends at the free surface was considered and found to provide a quantitative description of the data.

Journal Article↗
PubMed1990

Latex piezoelectric immunoassay: detection of agglutination of antibody-bearing latex using a piezoelectric quartz crystal.

A method for immunoassay of CRP (C-reactive protein) was developed using a piezoelectric quartz crystal. Previous immunoassays using a piezoelectric crystal have required the formation of a thin film on the crystal, to which an antibody is affixed. The occurrence of antigen-antibody reaction increases the weight attached to the crystal surface, which causes a reduction in the oscillation frequency. In our method, the frequency reduction was observed using antibody-bearing latex without any film. One possible mechanism of the frequency change is that the crystal acts as a sensing apparatus for viscosity or density change in the solution due to aggregation of latex particles. The detection limit was almost the same as that for latex photometric immunoassay (LPIA). The present method has been designated as latex piezoelectric immunoassay (LPEIA).

Agglutination Tests↗
PubMed1999

A kinetic study of protein binding to ecabet sodium using quartz-crystal microbalance.

To define the mechanism of the protection by ecabet sodium of the gastric mucosa, the characteristics of protein binding of this drug were investigated using a quartz-crystal microbalance (QCM) method. The binding rate constants (kb) and the binding amounts (delta m) were obtained from time courses of the frequency decrease (mass increase) of the QCM. The binding constants to proteins of two ecabet analogues (G1, ecabet type and G2, non-ionic ecabet type) were dependent on the pH, leading to large kb values at the acidic region. Furthermore, the kb values of G1 with the addition of bovine serum albumin (BSA) and bovine serum fibrinogen (BSF) at the acid region were larger than those of G2. The difference in kb values between G1 and G2 for porcine gastric mucin (PGM) is hardly discernible. Ecabet seems to be more heavily distributed in the ulcerous areas than in the intact mucosa, judging from the large binding constants of this drug to BSA and BSF compared with those to PGM. It is suggested that ecabet is bound to proteins by hydrophobic interaction, moreover, the electrostatic interaction between this drug and proteins (BSA and BSF) occurs at acidic pH region. On account of these interactions, ecabet sodium seems to have a more protective effect on an ulcer at intraluminal acidity than sucralfate. Finally, QCM was found to be a useful technique for detecting quantitatively the time course of binding proteins with drug.

Abietanes↗
PubMed2004

Exploiting quartz spectral signature for the detection of cloud-affected satellite infrared observations over African desert areas.

It is shown that IMG (interferometric monitoring of greenhouse gases) spectra recorded over African and Arabian deserts clearly contain the fingerprint of quartz-rich soils. We illustrate how this spectral signature can be exploited to devise a suitable cloud-detection scheme to identify which infrared observations are affected by clouds. As a by-product, the scheme also allows one to identify the most likely underlying emitting surface type and provides a suitable first guess for the surface emissivity to be used, e.g., for the retrieval of geophysical parameters from high-spectral-resolution infrared radiance from space. The analysis has focused on African deserts because of their intrinsic relevance to numerical weather prediction and Earth's climate. Desert areas, like oceans, are poorly covered by the world meteorological radiosonde network and therefore are geographical regions for which the global coverage capability of satellites soundings is expected to provide better initializations for numerical weather prediction than are now available. Application of the cloud-detection scheme to IMG spectra has been considered, which demonstrates the good performance of the method.

Journal Article↗
PubMed2004

Ammonia detection by use of quartz-enhanced photoacoustic spectroscopy with a near-IR telecommunication diode laser.

A gas sensor based on quartz-enhanced photoacoustic detection and a fiber-coupled telecommunication distributed-feedback diode laser was designed and characterized for trace NH3 monitoring at a 1.53-microm wavelength (overtone absorption region). Signal and noise dependence on gas pressure were studied to optimize sensor performance. The ammonia concentration resulting in a noise-equivalent signal was found to be 0.65 parts per million by volume with 38-mW optical excitation power and a lock-in amplifier time constant of 1 s. This corresponds to a normalized absorption sensitivity of 7.2 x 10(-9) cm(-1) W/Hz1/2, comparable with detection sensitivity achieved in conventional photoacoustic spectroscopy. The sensor architecture can be the basis for a portable gas analyzer.

Journal Article↗
PubMed2005

Use of Mie theory to analyze experimental data to identify infrared properties of fused quartz containing bubbles.

An improved method used to determine the absorption and scattering characteristics of a weakly absorbing substance containing bubbles is suggested. The identification procedure is based on a combination of directional-hemispherical measurements and predictions of Mie-scattering theory including approximate relations for a medium with polydisperse bubbles. A modified two-flux approximation is suggested for the calculation of directional-hemispherical transmittance and reflectance of a refracting and scattering medium. The complete identification procedure gives not only the spectral radiative properties but also the volume fraction of bubbles and the characteristics of possible impurity of the medium. This procedure is used to obtain new data on near-infrared properties of fused-quartz samples containing bubbles.

Journal Article↗
PubMed2004

Application of a widely electrically tunable diode laser to chemical gas sensing with quartz-enhanced photoacoustic spectroscopy.

A near-infrared diode laser with sample-grating distributed Bragg reflectors was used as a widely tunable spectroscopic source for multispecies chemical sensing. Quartz-enhanced photoacoustic spectroscopy was utilized to obtain high absorption sensitivity in a compact gas cell. CO2, H2O C2H2, and NH3 were monitored. A noise equivalent sensitivity of 8 x 10(-9) cm(-1) W(-1) Hz(-1/2)for NH3 detection was achieved, which corresponds to a NH3 mixing ratio of 4.4 parts in 10(6) by volume (ppmv) with a 1-s time constant and available 5.2-mW optical power in the gas cell.

Journal Article↗
PubMed2005

Organic and inorganic fouling at quartz-liquid interface in ultraviolet photoreactors during on-line sterilization of cheese whey.

This article reports on lamp fouling during on-line ultraviolet (UV) sterilization of cheese whey. The extent of fouling as well as the composition of fouling materials was studied after the operation of three tubular UV reactors of different flow thicknesses (18, 13, and 6 mm) for 48 h at a 2-h residence time. Lamp fouling, which significantly affected the sterilization efficiency, was realized after an extended period of operation. The extent of lamp fouling increased with a decrease in the thickness of the flowing cheese whey (14.42, 15.31, and 25.25 g for 18-, 13-, and 6-mm thickness, respectively). A strong relationship between the extent of fouling and the steady-state outlet temperature was observed. The fouling material contained 63.51 to 77.19% protein, 12.57 to 16.49% fat, and 6.51 to 9.47% minerals on dry weight bases compared with 1% protein, 0.5% fat, and 0.4% minerals in raw cheese whey. The organic and inorganic material concentrations in the fouling material increased with a decrease in the flow thickness. The fouling mechanism was owing to adsorption and direct ion exchange, which were enhanced by the high temperature and low pH attained in the study. Improved designs of UV reactors in which the contact between the flowing material and the quartz surface should be developed.

Bioreactors↗
PubMed2001

A comparative study on the viscoelasticity and morphology of polyaniline films galvanostatically grown on bare and 4-aminothiophenol-modified gold electrodes using an electrochemical quartz crystal impedance system and SEM.

The equivalent-circuit parameters of the 9-MHz piezoelectric quartz crystal (PQC) resonance were measured in situ during the galvanostatic polymerization of aniline on 4-aminothiophenol(4-ATP)-modified and bare Au electrodes for ca. 2000 s, respectively. Two polymerization media, 0.100 mol L-1 aniline in 1.0 mol L-1 H2SO4 and in 2.0 mol L-1 HClO4 aqueous solutions, and two values of the current density, 12 and 36 microA cm-2, were used. At identical levels of the resonant frequency shifts in the solutions, obviously greater increases in the motional resistance (R1) were found after aniline polymerization on bare Au electrodes, though the absolute values of delta f0/delta R1 were all large; also, the resonant frequency shifts in air (delta f0g) were considerably smaller for PANI films grown on bare Au electrodes. It is thus concluded that, under identical polymerization conditions, (1) the PANI film grown on a bare gold electrode is rougher, less compact, and can entrap solution more notably; (2) the deposition efficiency of PANI is higher on a 4-ATP-modified Au electrode, owing to a significantly greater observed "dry" frequency shift, and thus a greater "net" mass value of the polyaniline backbone. SEM observations have confirmed that PANI films on 4-ATP-modified Au electrodes were smoother and more compact than those grown on bare Au ones under identical polymerization conditions. In addition, a technique of simultaneous measurements of the electroacoustic admittance of the PQC resonance and the electrochemical impedance was used to monitor the adsorption of 4-ATP onto a PQC gold electrode.

Journal Article↗
PubMed2004

Effect of the size of molecularly imprinted polymers sensing materials on piezoelectric quartz crystal sensor performance.

The effect of the size of the molecularly imprinted polymers (MIPs) on the piezoelectric quartz crystal (PQC) sensor performance was investigated. Erythromycin imprinted polymers microspheres with different sizes were synthesized by precipitation polymerization. The size of the MIPs was characterized by using transmission electron microscope (TEM) analysis. Being coated with a poly(vinyl chloride) (PVC) membrane containing MIPs, the proposed PQC sensor can selectively adsorb the template molecule. Investigation of the performance of sensors modified with different sizes of MIPs showed that PQC sensor modified with smaller size MIPs exhibited better performance and excellent selectivity. Other influencing factors on sensor functions modified with different sizes MIPs were also investigated.

Journal Article↗
PubMed2004

Estimation of kinetics parameters for the adsorption of human serum albumin onto hydroxyapatite-modified silver electrodes by piezoelectric quartz crystal impedance analysis.

The adsorption of human serum albumin onto hydroxyapatite-modified silver electrodes has been in situ investigated by utilizing the piezoelectric quartz crystal impedance technique. The changes of equivalent circuit parameters were used to interpret the adsorption process. A kinetic model of two consecutive steps was derived to describe the process and compared with a first-order kinetic model by using residual analysis. The experimental data of frequency shift fitted to the model and kinetics parameters, k1, k2, psi1, psi2 and qr, were obtained. All fitted results were in reasonable agreement with the corresponding experimental results. Two adsorption constants (7.19 kJ mol(-1) and 22.89 kJ mol(-1)) were calculated according to the Arrhenius formula.

Adsorption↗
PubMed2005

Surface plasmon resonance spectroscopy and quartz crystal microbalance study of MutS binding with single thymine-guanine mismatched DNA.

MutS is a DNA mismatch binding protein that recognizes heteroduplex DNA containing mispaired or unpaired bases. In this study, we employ a quartz crystal microbalance (QCM) and a surface plasmon resonance (SPR) device for the study of MutS binding with DNA containing a single Thymine-Guanine (T-G) mismatch at different sites. Multi-step surface binding reactions are involved in the study, including probe DNA immobilization on the sensor surface through biotin-streptavidin-biotin bridge chemistry, target DNA hybridization to form T-G heteroduplexes, and MutS recognition of the mutation sites. The QCM frequency (d f) and motional resistance (d R, an impedance parameter reflective of QCM damping), as well as the SPR angle shift (d q ) are recorded for the binding reactions. The combined SPR and QCM data collection and analysis allow for an assessment of not only the amount of bound biopolymer but provide also information on also the structural properties of the streptavidin, DNA and MutS/DNA complexes. The affinity of the MutS/T-G heteroduplex assembly is determined by both the QCM and SPR methods through titration of the surface bound DNA with increasing MutS concentration. It is found that if the T-G mismatch is in the center of the DNA fragment, the MutS/DNA complex is more stable than if the mismatch is located near the end of the fragment.

Base Pair Mismatch↗
PubMed2005

In vitro and in vivo efficacy of new blue light emitting diode phototherapy compared to conventional halogen quartz phototherapy for neonatal jaundice.

High intensity light emitting diodes (LEDs) are being studied as possible light sources for the phototherapy of neonatal jaundice, as they can emit high intensity light of narrow wavelength band in the blue region of the visible light spectrum corresponding to the spectrum of maximal bilirubin absorption. We developed a prototype blue gallium nitride LED phototherapy unit with high intensity, and compared its efficacy to commercially used halogen quartz phototherapy device by measuring both in vitro and in vivo bilirubin photodegradation. The prototype device with two focused arrays, each with 500 blue LEDs, generated greater irradiance than the conventional device tested. The LED device showed a significantly higher efficacy of bilirubin photodegradation than the conventional phototherapy in both in vitro experiment using microhematocrit tubes (44+/-7% vs. 35+/-2%) and in vivo experiment using Gunn rats (30+/-9% vs. 16+/-8%). We conclude that high intensity blue LED device was much more effective than conventional phototherapy of both in vitro and in vivo bilirubin photodegradation. Further studies will be necessary to prove its clinical efficacy.

Animals↗
PubMed2001

[Determination of lead in water depuration agent with single-slotted quartz tube by atom-trapping atomic absorption spectrometry].

The determination of lead in water depuration agent with single-slotted quartz tube by the fuel-lean flame trapping and pulsed fuel-rich flame discharge atom-trapping atomic absorption spectrometry have been investigated. The optimum conditions for the determination and the tolerance of interfering elements are studied. A simple and rapid method is proposed. The linear relationship holds in the range 0-100 micrograms.L-1, the recovery is between 97%-103% and the relative standard deviation is 2.6%-2.8%. The proposed method has been applied to the determination of lead in water depuration agent samples with satisfactory results.

Lead↗