Critical parameters in the production of ceramic pot filters for household water treatment in developing countries.

The need to improve the access to safe water is generally recognized for the benefit of public health in developing countries. This study's objective was to identify critical parameters which are essential for improving the performance of ceramic pot filters (CPFs) as a point-of-use water treatment system. Defining critical production parameters was also relevant to confirm that CPFs with high-flow rates may have the same disinfection capacity as pots with normal flow rates. A pilot unit was built in Cambodia to produce CPFs under controlled and constant conditions. Pots were manufactured from a mixture of clay, laterite and rice husk in a small-scale, gas-fired, temperature-controlled kiln and tested for flow rate, removal efficiency of bacteria and material strength. Flow rate can be increased by increasing pore sizes and by increasing porosity. Pore sizes were increased by using larger rice husk particles and porosity was increased with larger proportions of rice husk in the clay mixture. The main conclusions: larger pore size decreases the removal efficiency of bacteria; higher porosity does not affect the removal efficiency of bacteria, but does influence the strength of pots; flow rates of CPFs can be raised to 10-20 L/hour without a significant decrease in bacterial removal efficiency.

Low urinary oestrogen excretion during pregnancy, due to an impairment of fetal adrenocorticotrophic hormone secretion.

Four cases of newborn infants whose mothers had a low urinary oestrogen excretion during pregnancy are reported. Placental sulphatase deficiency in placental insufficiency were excluded by a dehydroepiandrosterone sulphate loading test. Postnatally, they developed a clinical picture characterized by an inappropriate secretion of cortisol which, by the results of an adrenocorticotrophic hormone stimulation test, appeared to be due to an impairment of adrenocorticotrophic hormone secretion. The prenatal and postnatal steroid metabolism is discussed.

The origin of plasma creatine kinase 1, detected in patients during and following open heart surgery.

Plasma creatine kinase 1 (CK-1) was detected intra-operatively in 6 out of 6 patients and postoperatively in 15 out of 22 patients, undergoing cardiac surgery. A transient increase in plasma levels of creatine kinase 2 (CK-2) and total creatine kinase (CK-tot.) activity was observed in all patients. The disappearance rates for the 2 isoenzymes in the circulation were CK-1: Kd = 4.7 X 10(-3) min-1, and CK-2: Kd = 0.60 X 10(-1) min-3. Analysis of vessel and heart tissue showed that the saphenous vein contained mainly CK-1; high activities of all three isoenzymes were found in the parts of the heart investigated. Most probably, both CK-1 and CK-2 are liberated from injured cardiac tissue.

Bacteria and virus removal effectiveness of ceramic pot filters with different silver applications in a long term experiment.

In 2012 more than 4 million people used a ceramic pot filter (CPF) as household water treatment system for their daily drinking water needs. In the normal production protocol most low cost filters are impregnated with a silver solution to enhance the microbial removal efficiency. The aim of this study was to determine the role of silver during the filtration and subsequent storage. Twenty-two CPFs with three different silver applications (non, only outside and both sides) were compared in a long-term loading experiment with Escherichia coli (K12 and WR1) and MS2 bacteriophages in natural challenge water under highly controlled laboratory circumstances. No significant difference in Log Removal Values were found between the filters with different silver applications. The results show that the storage time in the receptacle is the dominant parameter to reach E. coli inactivation by silver, and not the contact time during the filtration phase. The hypothesis that the absence of silver would enhance the virus removal, due to biofilm formation on the ceramic filter element, could not be confirmed. The removal effectiveness for viruses is still of major concern for the CPF. This study suggests that the ceramic pot filter characteristics, such as burnt material content, do not determine E. coli removal efficacies, but rather the contact time with silver during storage is the dominant parameter to reach E. coli inactivation.

99mTc bone scanning agents--III. Preparation and gel chromatography of 99mTc(Sn)MDP complexes.

The preparation of 99mTc(Sn)MDP was investigated as a function of pH, MDP concentration and Sn(II) concentration. The labeling efficiency was over 90% in the majority of the experiments and remained constant over the range pH 2-9. The MDP concentration had little effect, while the Sn(II) concentration had a significant positive influence. The complex formation appeared to be partly reversible. The formation of different complexes was investigated by means of gel chromatography under various experimental conditions. Altogether six complexes were found. At acid conditions two major complexes were found and at neutral pH one major complex. The presence or absence of a particular complex was mainly determined by the pH and by the MDP concentration. The Sn(II) concentration had very little effect. The results are compared with previous results of similar experiments with 99mTc(Sn)pyrophosphate.

99mTc bone scanning agents--I. Influence of experimental conditions on the formation and gel chromatography of 99mTc(Sn)pyrophosphate complexes.

The conversion of 99mTcO4- to 99mTc(Sn)pyrophosphate complexes was investigated under various experimental conditions. An increase of the Sn(II) concentration had a beneficial effect, whereas the ligand concentration had little effect. The pH had only a small influence over the range 2-8. Raising the pH to 10 resulted in the partial decomposition of the complexes, which could be reversed by lowering the pH. Furthermore, the occurrence of various complexes was investigated by means of gel chromatography on Biogel P-4 as a function of pH and of the Sn(II) and pyrophosphate concentrations. Four major fractions were found. A single preparation contained, however, no more than two major fractions. The formation of the different complexes was mainly governed by the pH and the ligand concentration. The influence of the eluent on the decomposition and interconversion of the complexes during chromatography was also studied. It appeared to be necessary that the eluent should have the same composition (except for 99mTcO4-) as the reaction mixture.

99mTc bone scanning agents--IV. Chemical characterization of 99mTc(Sn)-pyrophosphate complexes.

Various reaction mixtures for the preparation of 99Tc(Sn)-pyrophosphate were investigated by means of gel chromatography. All components were radioactively labeled. The most likely composition of the complexes, which also appear in "no carrier added" preparations, was determined. At pH 7 one complex is found with the composition TcPyp2. Two complexes are found at pH 4: TcPyp and TcPyp2. Further, at pH 7 a polymeric technetium compound is found not containing tin or pyrophosphate.

99mTc bone scanning agents--II. Adsorption of 99mTc(Sn)pyrophosphate complexes on the mineral phase of bone.

The adsorption of pyrophosphate, tin-pyrophosphate and 99mTc(Sn)pyrophosphate on Ca3(PO4)2 was investigated at pH 4.0 and pH 7.4. All components were radioactively labeled. Tin and reduced technetium were in most cases almost completely bound. The adsorption of pyrophosphate, tin(II) and technetium-99m at pH 4.0 was higher than at pH 7.4. The presence of tin gave rise to an increase of the pyrophosphate adsorption that was much larger than can be accounted for by a stoichiometric adsorption of tin-pyrophosphate. It is concluded that tin and technetium are bound as negatively charged complexes with pyrophosphate. Finally it is argued that the fraction of the bone scanning agent that reaches the bone surface is adsorbed completely by the mineral phase.

99mTc bone scanning agents--V. Influence of experimental conditions on the labeling efficiency and gel chromatography of 99mTc(Sn)HMDP.

The preparation of 99mTc(Sn)HMDP was investigated as a function of pH, Sn(II) and ligand concentration. HMDP could be labeled efficiently from pH 2-9. The Sn(II) and the ligand concentrations had a beneficial influence. The composition of the radiopharmaceutical under various experimental conditions was studied by means of gel chromatography on Biogel P-4. Six different complexes were found. A preparation consisted of maximally three major complexes. The presence of a particular complex was mainly determined by pH and ligand concentration. The Sn(II) concentration had little influence.