Microbial communities are sensitive indicators for freshwater sediment copper contamination.

Anthropogenic activities, such as mining and agriculture, have resulted in many freshwater systems having elevated concentrations of copper. Despite the prevalence of this contamination, and the vital ecological function of prokaryotes, just three studies have investigated prokaryote community responses to copper concentration in freshwater sediments. To address this, the current study investigated these communities in outdoor mesocosms spiked with varying copper concentrations. We profiled the prokaryotic communities at the taxonomic level, using next-generation high-throughput sequencing techniques, as well as their function, using baiting with leaf analogues, and Biolog Ecoplates for community-level physiological profiling. Sediments containing just 46 mg kg-1 of copper, had distinctly different microbial communities compared with controls, as determined by both DNA and RNA 16S ribosomal RNA gene (rRNA) profiling. In addition to this, sediment communities displayed a greatly reduced utilisation of carbon substrates under elevated copper, while the communities recruited onto leaf analogues were also disparate from those of control ponds. Given the vital role of prokaryotes in ecosystem processes, including carbon cycling, these changes are potentially of great ecological relevance, and are seen to occur well below the 'low risk' sediment quality guideline values (SQGV) used by regulatory bodies internationally.

Health-related quality of life in long-term survivors of pediatric liver transplantation.

The purpose of this study is to measure the health-related quality of life (HRQOL) in children who are long-term survivors of liver transplantation and to pilot the Liver Transplant Disability Scale (LTDS), a newly developed 12-point scale that quantifies chronic medical disability related to liver transplantation. This study is a cross-sectional survey of 51 children surviving liver transplantation by at least 2 years, with a median age of 4.94 years. Functional capacity and utility scores were measured by the Health Utilities Index Mark II (HUI2), and chronic disease-specific medical disability was measured by the LTDS. HUI2 results were compared with a reference population. LTDS scores were compared with utility scores and patient survival 3 years later. Ninety percent of the study patients had functional deficits compared with 50% of controls. Functional impairment was typically mild. The resulting mean utility score, 0.86 +/- 0.13 (0 = dead, 1 = perfect health), was significantly less than that of the reference population, 0.95 +/- 0. 07 (P <.001). LTDS scores ranged from 0 (no disability) to 6 (moderate disability). Seventy-one percent of the children had mild disability (scores 0 to 3), and 29% had moderate disability (scores 4 to 6). LTDS scores did not correlate with utility scores but were predictive of survival. The majority of pediatric liver transplant recipients have mild functional deficits. Their utility scores reflected a high level of HRQOL but were significantly less than those of a reference population. The majority also had mild medical disability, predominantly delayed growth. Medical disability did not correlate with HRQOL but predicted survival 3 years later.

The Mirror syndrome.

This is a case report illustrating a patient who developed pre-eclampsia with non-immunological hydrops fetalis associated with fetal tachycardia. It illustrates how successful treatment of a fetal disorder can lead to resolution of the maternal disorder.

Recurrent cholestasis following ovarian hyperstimulation syndrome: case report.

This is a case report illustrating a patient who developed recurrent cholestasis during a twin pregnancy following in-vitro fertilization (IVF) treatment. On the first occasion cholestasis developed unusually in the first trimester, and on the second occasion, it presented in the way that obstetric cholestasis (OC) is commonly seen in the third trimester.

Effects of thyroxine and thyroparathyroidectomy on circadian wheel running in rats.

Thyroparathyroidectomized (TPX) and thyroidectomized male rats display shorter free-running activity periods and enhanced activity levels. These experiments were designed to determine whether this effect is due to the loss of thyroid hormones. The running wheel activity of 36 male rats, 19 TPX and 17 sham operated, was studied. The animals were kept in constant conditions for 7 weeks to obtain baseline data. Half the rats were then injected SC with capsules containing T4, while the other half were injected with blanks. All animals were then allowed to free-run undisturbed for another 8-9 weeks. TPX rats displayed significantly shorter baseline periods (average difference: 0.26 h) and heightened activity. Thyroxine treatment significantly lengthened TPX animals' cycles (average increase: 0.28 h) but did not affect intact rats' circadian rhythms. Thyroxine did, however, significantly decreased the activity levels of both TPX and sham-operated rats. These findings indicate that changes in TPX rats' activity cycles are caused by a reduction in thyroid hormones and that thyroxine acts on activity rhythms and levels by different mechanisms.

Clinical and pharmacological properties of ivermectin in rabbits and guinea pigs.

When 400 micrograms ivermectin/kg was administered subcutaneously to rabbits infected with the ear mite Psoroptes cuniculi it significantly reduced the clinical score, and when 500 micrograms ivermectin/kg was administered subcutaneously to guinea pigs with mange due to Trixacaurus caviae it resulted in a clinical cure. In rabbits a subcutaneous dose of 400 micrograms/kg produced high and sustained concentrations of ivermectin in the tissues and body fluids for at least 13 days and its rate of depletion from tissues was similar to that observed in sheep and rats. The mean (+/- sem) maximum concentration in plasma was 42.0 +/- 9.7 ng/ml 37.2 +/- 5.0 hours after administration and the area under the concentration-time curve was 3543 +/- 580 ng/ml hours. After the administration of 500 micrograms ivermectin/kg to guinea pigs orally, subcutaneously or topically the drug could be detected in the plasma only after subcutaneous administration. The mean concentration 72 hours after its administration to four guinea pigs was 0.7 +/- 0.3 ng/ml.

A review of pH measurement at high temperatures.

Measurement of pH in aqueous solutions at up to 300 degrees and 150-300 bar is reviewed. Potentiometric membrane electrodes are identified as the sensors giving the most immediate hope of being practical. Zirconia membranes work well above 200 degrees and in alkaline solution, whereas glass membranes are best up to 150 degrees and in acidic solutions. Both membranes are largely free from interferences. Metal-metal oxide electrodes offer poor prospects, deviating from the ideal Nernstian response at all temperatures and being susceptible to interference from many redox and complexing agents, but systems based on iridium oxide have some promise. The hydrogen electrode remains the standard for pH measurement, but its analytical application is limited by the need to know the hydrogen partial pressure. A practical solution to this problem has yet to be found, except in restricted and artificial circumstances. Palladium hydride electrodes may be useful up to about 200 degrees , but in hydrogen-saturated waters revert to being hydrogen electrodes in any case. Non-potentiometric pH measurements with semiconducting oxides have been shown to be possible, but there are many unanswered questions about possible interferences. Considerable extra instrumentation is required, compared with potentiometry. Fibre-optic sensors based on indicator dyes have been investigated at room temperature, and have the great merit of not requiring a reference electrode. They seem, however, prone to many interferences and have an inherently limited working range of approximately 2 pH. No measurements at high temperature have been reported. Improved reference electrodes for potentiometric systems are still needed, although there have been advances in the design of external pressure-compensated electrodes working at room temperature. The silver-silver chloride system is still the one most favoured. There has been little rigorous work on standard buffer solutions at above 100 degrees and none at above 200 degrees . Neutral and alkaline buffers are especially needed. The establishment of proper pH standards for high-temperature work would make the testing of sensors both speedier and more reliable. Doubtless because of the experimental difficulties involved, few measurements have actually been made at high temperature, and those in a rather restricted range of conditions. In particular, measurements in dilute, poorly buffered, solutions, which provide the most rigorous test of a system's capability, are completely lacking.

Non-linearity of calibration in the determination of anions by ion-chromatography with suppressed conductivity detection.

Traces of simple inorganic anions may be determined by chromatographic separation with an alkaline eluent and conductimetric detection, which involves "suppressing" the background conductivity of the eluent by neutralization to form a sparingly dissociated species. Over a wide range of determinand concentration, e.g., two decades, non-linearity of the calibration may become evident, leading to errors of up to 100% at lower concentrations if linearity is assumed (a linear fit of the data usually gives a correlation coefficient >0.99, which may lead to false confidence). The curvature arises from displacement of eluent ions by the determinand and the consequent re-equilibration of the conjugate acid in the suppressed eluate. Even if the distribution of determinand in the peak is ideally Gaussian, the observed conductivity peak may be distorted and calibration will then be non-linear. The best linearity is obtained with the most strongly basic eluent, but other characteristics must also be considered, e.g., run time, peak separation. With a carbonate eluent, the curvature is demonstrated empirically for chloride, nitrate and sulphate calibrations. A second-order fit gives errors of < 10%. With a more strongly basic borate eluent, the deviation from linearity is negligible, but elution times are longer and may be inconvenient in some circumstances.

Combination pH electrodes of special design: Temperature characteristics and performance in poorly-buffered waters.

The performance of 5 combination pH electrodes with special design features has been assessed. Two electrodes were intended for measurements in low-conductivity waters, two were designed to have a rapid and stable temperature response and one electrode shared both features. The performance in low-conductivity waters was either poor or merely acceptable; better results have been obtained with separate glass and reference electrodes. The electrodes designed to have good temperature response were better in this respect than conventional combination electrodes, but the same or better performance can be obtained by use of separate glass and remote-junction reference electrodes. It should be noted that the temperature coefficients of these combination electrodes were the same as for almost all pH electrodes: any improvement was only in the rate and stability of response.

The manganese(IV) oxide electrode as a manganese(II) sensor.

Manganese(IV) oxide electrodes formed with a graphite/PTFE substrate are shown to have near-theoretical response to manganese(II) ions in pH-4 acetate medium and a sub-Nernstian response in 0.1M nitric acid medium. Lead and iron(III) ions interfere, and iron(II) ions even more so, but other bivalent transition metal ions have little effect. The main drawback of this type of electrode is its long response time (~ 20 min). Some attempts to use manganese(IV) oxide electrodes as the basis for phosphate electrodes by use of MnHPO(4).3H(2)O and MnNH(4)PO(4).H(2)O are also described.

Linear titration plots for the analysis of mixtures of three weak acids or bases.

Linearly related functions have been derived which enable mixtures of three weak acids or bases in solution to be analysed by means of pH-titration data. This theory has been tested with data from the titration of a variety of mixtures of acids. The data required for the functions are pH, volume of titrant, the equilibrium constants relevant to the mixture, and an independently determined equivalence volume. This may be the equivalence volume for one of the components of the mixture or the sum of the equivalence volumes for any two or all three of the components. It is immaterial how this equivalence volume is obtained, but it is usually possible to obtain the total equivalence volume from data in another part of the same titration curve (when a large excess of titrant has been added).

A bromide-selective electrode-redox electrode cell for the potentiometric determination of bromine and free residual chlorine.

A potentiometric cell consisting of a bromide-selective electrode and a platinum redox electrode is sensitive to free residual chlorine (FRC) when the sample solution is treated before measurement with reagents to give pH 5 and a bromide content of 0.1M. The calibration graph of e.m.f. vs. log [FRC] is linear over the [FRC] range from about 0.05 to 50 mg l . (the highest level tested). Not all forms of bromide-selective electrode prove suitable, but one with a silver bromide single-crystal membrane has been found to give a theoretical calibration slope, whereas one with an Ag(3)SBr compressed pellet membrane gave a sub-Nernstian response. The response to combined residual chlorine (CRC) is negligible but if both FRC and CRC are present, the sample treatment is likely to cause a reduction in FRC concentration. Tests have shown that a similar bias can be found with the commonly used DPD colorimetric method.

Performance of the Orion 97-70 total residual chlorine electrode at low concentrations and its application to the analysis of cooling waters.

The performance characteristics of the Orion 97-70 total residual chlorine electrode have been determined and the electrode has been found to give a near-theoretical response down to chlorine concentrations in the range 1-5 mug/1. Within-batch relative standard deviations are about 6-8% at concentrations above 50 mug/1. and 10-15% at lower levels. The method is virtually free from interferences (only strong oxidizing agents such as permanganate interfere) but large variations in salinity affect the calibration by changing the conditional standard potential. The best performance at low concentrations (<50 mug/1.) is achieved only if the manufacturer's recommended procedure is changed, namely by using a more dilute iodide reagent, stirring constantly, adding the iodide reagent before the buffer solution and using chloramine-T as a standard.

Solid-state ion-selective electrodes for the potentiometric determination of phosphate.

A number of solid-state ion-selective electrodes for the potentiometric determination of phosphate have been made and their properties investigated. The most successful of these electrodes, which had a membrane comprising silver sulphide, lead sulphide and lead hydrogen phosphate, had a theoretical Nernstian response to orthophosphate ion at concentrations down to 5 mug/ml total phosphate at pH 8.3. The electrode had a slow response and its standard potential changed with time. Anions such as sulphate, bicarbonate and nitrate did not interfere; chloride had a transient effect, but even at its worst the interference was less serious than with other phosphate electrodes. The electrode was used as an indicator in the potentiometric precipitation titration of phosphate and lanthanum.

Linear titration plots for polyfunctional weak acids and bases.

Procedures are derived for obtaining the equivalence volumes in the potentiometric titrations of polyfunctional weak acids and weak bases by a linear titration plot method. The effect of errors in the equilibrium constants on the accuracy is considered. A Fortran program is available to do the calculations.

Improved linear titration plots for weak-acid titrations.

Linear titration plot functions are derived for the following types of titration: weak monobasic acid-strong base, weak dibasic acid-strong base weak acid-weak base. These functions are compared with the corresponding Gran functions, where possible, and the effects of the following sources of error are discussed: the neglect of activity coefficients, errors in equilibrium constants and the presence of a hydrolysable salt.