Lipid peroxidation in the freshwater shrimp Caridina nilotica as a biomarker of Roundup(?) herbicide pollution of freshwater systems in South Africa

Glyphosate-based herbicides used to control weeds and invading alien plant species in South Africa ultimately end up in freshwater ecosystems, but no South African environmental water quality guideline exists to regulate these bio-active chemicals. Ecotoxicological tests to assess the possibility of using lipid peroxidation (LPx) in Caridina nilotica as a potential biomarker of Roundup(?), a glyphosate-based herbicide, pollution were conducted. In two separate tests, 40 days post hatch shrimps were exposed to different concentrations of 4.3, 6.7, 10.5, 16.4, 25.6 and 40.0 mg/L in a 96 h acute toxicity test; and 2.2, 2.8, 3.4, 4.3 and 5.4 mg/L in a 21 d chronic toxicity test, using static-non renewal and static-renewal methods, respectively. Shrimp whole body LPx was estimated by thiobarbituric acid reactive species (TBARS) assay, performed by a malondialdehyde (MDA) reaction with 2-thiobarbituric acid (TBA) measured spectrophotometrically. Final MDA concentrations were expressed as nmol MDA produced/mg protein. Results showed that LPx was significantly lower in control animals than in animals exposed to different Roundup(?) concentrations, (p < 0.05). The present work provides an ecotoxicological basis for the possible use of LPx in Caridina nilotica as a biomarker for monitoring Roundup(?) pollution in freshwater ecosystems.     

Ultrasonic attenuation in commercial lead-silicate glasses

The ultrasonic attenuation of a range of commercial lead—silicate glasses has been studied over the temperature range 4.2 to 360 K. Measurements of shear-wave ultrasonic attenuation,A, over the frequency range 5 to 50 MHz have revealed peaks in the attenuation below room temperature and these are interpreted in terms of the resonant movement of oxygen ions in the silica networks. In some cases the effects of the peaks are seen to extend to room temperature in some of these glasses. Frequency dependence of the attenuation,A, can be fitted to a relation of the formA F ^N , whereF is the frequency andN is a constant. Shear-wave velocities are also measured to aid characterization of the glasses.     

Traffic signal light detection through sunglare filters of different Q factors

Recent guides for use of sunglare protection filters have introduced the concept of Q factors as a measure of colour appearance distortion in viewing traffic signal lights. The adoption of Q factor values was apparently arbitrary and not firmly based on experimental data. The manner in which changes in Q factor affect colour perception and detection of signal lights has been measured and shows that detection thresholds vary with the Q factor in a manner that can only partly be explained, but that is not independent of the colour of the signal as assumed in the guides. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 24–31, 1997.     

涠洲12-1油田天然气-水控制气窜实验研究

针对涠洲12-1油田涠四段油藏注天然气开发中气油比快速上升、气窜现象严重等问题,通过实验研究天然气-水控制气窜的效果及其驱替机理.利用细管装置测定原油的最小混相压力,对比天然气驱与天然气-水交替驱的实验效果;同时,利用可视化平面模型分析驱替机理及剩余油分布特征.研究结果表明:该油田天然气驱混相压力为36.35 MPa,...     

Studies on Starches from Nigerian Sorghum

Two varieties of white Nigerian sorghum have been examined for total lipid, protein and carbohydrate content. The levels of sucrose, raffinose, fructose and glucose in the ungerminated grain were measured and the starches have been isolated and purified. Amylose to amylopectin ratios, solubility properties, gelatinization temperatures and the size distribution of the granules were analyzed. Fractionation and chemical analyses of the large and small granules has revealed that the amylose to amylopectin ratios of both types of granules were similar.     

The aqueous chemistry of aluminum. A new approach to high-temperature solubility measurements

Predictions of changes in geothermal reservoir permeability and porosity during exploitation and reinjection, as well as aluminosilicate scale formation in wells and plant equipment, are currently limited by inaccuracies and discrepancies in our knowledge of the aqueous speciation of aluminum and the solubilities of aluminosilicates in high-temperature brines. To address this problem, the solubility of pure synthetic boehmite (AlOOH) has been measured in noncomplexing solutions over a wide range of pH (2–10), temperature (100–290°C), and ionic strength (0.03–1 mol·kg⁻¹ NaCl) in a hydrogen-electrode concentration cell (HECC) that provided continuous, in situ measurement of hydrogen ion molality. This represents the first such study ever reported of a pH-dependent mineral solubility profile across the entire pH range of natural waters at temperatures above 100°C.Samples of the solution were withdrawn after the pH reading stabilized for analysis of total aluminum content by ion chromatography. Acidic or basic titrants could then be metered into the cell to affect a change in the pH of the solution. The direction of approach to the equilibrium saturation state could be readily varied to ensure that the system was reversible thermodynamically. A least-squares regression of the results obtained at low ionic strength was used to determine the molal solubility products (Q_s0to Q_s4) of boehmite, which allowed comparison with those obtained from two recently-reported high-temperature studies of boehmite solubility, which relied on the conventional batch technique. Comparisons are also made with the low-temperature (<90°C) hydrolysis constants for aluminum obtained from solubility measurements with gibbsite as the stable phase. Based on these results, it is possible to draw some general conclusions concerning the relative importance of the aluminum species in solution and to reduce significantly the number of experiments needed to define this complex system. Finally, the application of this new technique to the study of the kinetics and thermodynamics of the dissolution and formation of more complex aluminosilicate minerals is discussed.     

Use of genetic algorithms to optimize fiber optic probe design for the extraction of tissue optical properties

This paper outlines a framework by which the optimal illumination/collection geometry can be identified for a particular biomedical application. In this paper, this framework was used to identify the optimal probe geometry for the accurate determination of tissue optical properties representative of that in the ultraviolet-visible (UV-VIS) spectral range. An optimal probe geometry was identified which consisted of a single illumination and two collection fibers, one of which is insensitive to changes in scattering properties, and the other is insensitive to changes in the attenuation coefficient. Using this probe geometry in conjunction with a neural network algorithm, the optical properties could be extracted with root-mean-square errors of 0.30 cm(-1) for the reduced scattering coefficient (tested range of 3-40 cm(-1)), and 0.41 cm(-1) for the absorption coefficient (tested range of 0-80 cm(-1)).     

In-Flight Absolute Radiometric Calibration of the Thematic Mapper

Ground spectral reflectance and atmospheric spectral optical depth measurements made at White Sands, New Mexico on January 3, 1983, were used with an atmospheric radiative transfer program to determine the spectral radiance at the entrance pupil of the Landsat-4 Thematic Mapper (TM). A comparison with the output digital counts of the TM, when imaging the measured ground area, provided an absolute calibration for five detectors in TM bands 2, 3, and 4. By reference to an adjacent, larger uniform area, the calibration was extended to all 16 detectors in each of the three bands. Pre-flight calibration results agreed with these inflight measurements to 6.6, 2.4, and 12.9 percent in bands 2, 3, and 4, respectively.