Assessment of pesticide residues in tomatoes and watermelons (fruits) from markets in Dar es Salaam, Tanzania

This study investigated the levels of pesticide residues in selected fruits from major markets in Dar es Salaam city. Samples of tomatoes and watermelons were analysed for eighteen organochlorine, organophosphorus and pyrethroid pesticide residues. Extraction was performed using acetone followed by dichloromethane: cyclohexane mixture and the extracts were cleanedup using florisil. The compounds were determined by gas chromatography–mass spectrometry (GC–MS). Pesticides and metabolites were detected in 95.8% of the samples. The compounds detected included chlorpyrifos, α-endosulfan, β-endosulfan and cypermethrin and their highest concentrations were 3810 ± 50, 370 ± 20, 120 ± 6 and 50 ± 4 ng/g, respectively. Others were p,p'- DDD, o,p'-DDD, p,p'-DDE and α-HCH with highest concentrations varying from 1 ± 0.5 to 20 ± 1.2 ng/g. There were no significant variations in concentrations of the pesticide residues between the fruits and among the sampling sites, indicating similarities in contamination patterns. The concentrations of the contaminants were above the maximum residue limits (MRLs) in 41.7% to 50% of the tomatoes and watermelons indicating risks and concerns for public health. The Tanzanian agrochemicals and food regulatory agencies (e.g. TPRI, TFDA and TBS) and the government in general should ensure strict applications of laws that regulate pesticides in the country and develop effective educational programmes for farmers to apply good agricultural practices such as reducing the use of pesticides, applying appropriate pesticides and doses, and restrict the spray before harvesting. The consumers should thoroughly wash or process the fruits to reduce the levels.Keywords: Pesticides, Fruits, Food, Contamination, Tanzani

The effect of plastic deformation upon the mechanical properties of carbon steels at ambient and low temperatures

SIGLELD:D48535/84 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Characterization of the probabilistic traveling salesman problem

We show that stochastic annealing can be successfully applied to gain new results on the probabilistic traveling salesman problem. The probabilistic "traveling salesman" must decide on an a priori order in which to visit n cities (randomly distributed over a unit square) before learning that some cities can be omitted. We find the optimized average length of the pruned tour follows E((L) over bar (pruned))=rootnp(0.872-0.105p)f(np), where p is the probability of a city needing to be visited, and f(np)-->1 as np-->infinity. The average length of the a priori tour (before omitting any cities) is found to follow E(L-a priori)=rootn/pbeta(p), where beta(p)=1/[1.25-0.82 ln(p)] is measured for 0.05less than or equal topless than or equal to0.6. Scaling arguments and indirect measurements suggest that beta(p) tends towards a constant for p<0.03. Our stochastic annealing algorithm is based on limited sampling of the pruned tour lengths, exploiting the sampling error to provide the analog of thermal fluctuations in simulated (thermal) annealing. The method has general application to the optimization of functions whose cost to evaluate rises with the precision required

Direkte Endlagerung ausgedienter Brennelemente DEAB. Aktives Handhabungsexperiment mit Neutronenquellen Abschlussbericht. Hauptband

Zielsetzung des aktiven Handhabungsexperimentes war, die radiologischen Aspekte aufgrund Neutronenrueckstreuung zu untersuchen, die bei der Handhabung von Brennelementen bzw. hochaktivem Abfall in den Strecken eines untertaegigen Endlagers in Salzformation auftreten. Da Neutronen eine wichtige Rolle bei der Option der direkten Endlagerung spielen, wurde der Schwerpunkt der Untersuchung auf ihren Beitrag zu der totalen Aequivalenzdosisleistung gelegt. Die Aequivalenzdosisleistungen der von direkten und an Salzgestein gestreuten Neutronen bei Handhabung von Pollux-Behaeltern und Einzelabschirmbehaeltern wurde durch einen Versuchsbehaelter, der mit einer Cf-252-Neutronenquelle beladen war, simuliert und experimentell analysiert, um die radiologische Exposition des Betriebspersonals abschaetzen zu koennen. Die Ergebnisse des AHE-Experiments lieferten wertvolle Beitraege zum besseren Verstaendnis der radiologischen Aspekte bzgl. Neutronenrueckstreuung bei der Handhabung von ausgedienten Brennelementen bzw. hochaktivem Abfall in einem Endlager im Salz. Validierte Computerprogramme stehen nun zur Verfuegung, die eine Minimierung der Personendosen des Betriebspersonals ermoeglichen. (orig.)The objective of the Active Handling Experiment with Neutron Soruces was to investigate radiological aspects due to backscattered neutrons when spent fuel and high level waste will be handled in the drifts of an underground repository located in a salt dome. As neutrons play an important role in the direct disposal option, main emphasis was laid on their contribution to the total dose equivalent rate. The radiological exposure caused by direct neutrons and neutrons scattered by the salt rock during handling processes of POLLUX packages and shipping packages was simulated and experimentally analysed with the help of the AHE package. The AHE shielding cask was filled with one Cf-252 line source in order to simulate the neutron fields of a loaded POLLUX cask and a shipping cask loaded with a fuel element canister with respect to neutron energy distributions and local dose equivalent rates. The results of the AHE experiment provided valuable contributions for a better understanding of radiological aspects during handling spent fuel/high level waste in an underground repository. Validated computer codes are available now which make it possible to minimize the occupational dose. (orig.)Available from TIB Hannover: RO 6452(66)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); European Union (Euro), Brussels (Belgium)DEGerman

Active handling experiment with neutron sources (AHE) Final report

The objective of the Active Handling Experiment with Neutron Soruces was to investigated radiological aspects due to backscattered neutrons when spent fuel and high level waste will be handled in the drifts of an underground repository located in a salt dome. As neutrons play an important role in the direct disposal option, main emphasis was laid on their contribution to the total dose equivalent rate. The radiological exposure caused by direct neutrons and neutrons scattered by the salt rock during handling processes of POLLUX packages and transfer packages was simulated and experimentally analysed with the help of the AHE package. The AHE shielding cask was filled with one Cf-252 line source in order to simulate the neutron fields of a loaded POLLUX cask and a transfer cask loaded with a fuel element canister with respect to neutron energy distributions and local dose equivalent rates. The results of the AHE experiment provided valuable contributions for a better understanding of radiological aspects during handling spent fuel/high level waste in an underground repository. Validated computer codes are available now which make it possible to minimize the occupational dose. (orig.)SIGLEAvailable from TIB Hannover: F96B1477+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); Commission of the European Communities (CEC), Brussels (Belgium)DEGerman

Statistical consulting at German universities: Results of a survey

Statistical consulting, Survey,

Direkte Endlagerung ausgedienter Brennelemente DEAB. Aktives Handhabungsexperiment mit Neutronenquellen. Berechnung der Ortsdosisleistung und Neutronenspektren vom POLLUX-Behaelter, Einzelabschirmbehaelter und Versuchsbehaelter in einem Salzbergwerk (TA 1)

Zielsetzung des aktiven Handhabungsexperimentes war, die radiologischen Aspekte aufgrund Neutronenrueckstreuung zu untersuchen, die bei der Handhabung von Brennelementen bzw. hochaktivem Abfall in den Strecken eines untertaegigen Endlagers in Salzformation auftreten. Da Neutronen eine wichtige Rolle bei der Option der direkten Endlagerung spielen, wurde der Schwerpunkt der Untersuchung auf ihren Beitrag zu der totalen Aequivalenzdosisleistung gelegt. Die Aequivalenzdosisleistungen der von direkten und an Salzgestein gestreuten Neutronen bei Handhabung von Pollux-Behaeltern und Einzelabschirmbehaeltern wurde durch einen Versuchsbehaelter, der mit einer Cf-252-Neutronenquelle beladen war, simuliert und experimentell analysiert, um die radiologische Exposition des Betriebspersonals abschaetzen zu koennen. Die Ergebnisse des AHE-Experiments lieferten wertvolle Beitraege zum besseren Verstaendnis der radiologischen Aspekte bzgl. Neutronenrueckstreuung bei der Handhabung von ausgedienten Brennelementen bzw. hochaktivem Abfall in einem Endlager im Salz. Validierte Computerprogramme stehen nun zur Verfuegung, die eine Minimierung der Personendosen des Betriebspersonals ermoeglichen. (orig.)The objective of the Active Handling Experiment with Neutron Soruces was to investigated radiological aspects due to backscattered neutrons when spent fuel and high level waste will be handled in the drifts of an underground repository located in a salt dome. As neutrons play an important role in the direct disposal option, main emphasis was laid on their contribution to the total dose equivalent rate. The radiological exposure caused by direct neutrons and neutrons scattered by the salt rock during handling processes of POLLUX packages and shipping packages was simulated and experimentally analysed with the help of the AHE package. The AHE shielding cask was filled with one Cf-252 line source in order to simulate the neutron fields of a loaded POLLUX cask and a shipping cask loaded with a fuel element canister with respect to neutron energy distributions and local dose equivalent rates. The results of the AHE experiment provided valuable contributions for a better understanding of radiological aspects during handling spent fuel/high level waste in an underground repository. Validated computer codes are available now which make it possible to minimize the occupational dose. (orig.)Available from TIB Hannover: RO 6452(67)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); European Union (Euro), Brussels (Belgium)DEGerman

Direkte Endlagerung ausgedienter Brennelemente DEAB. Aktives Handhabungsexperiment mit Neutronenquellen. Experimentelle Ermittlung der Spektren und Aequivalentdosisleistungen der Neutronen und Photonen an dem AHE-Gebinde ohne und mit Salzumgebung (TA 3)

The objective of the Active Handling Experiment with Neutron Soruces was to investigate radiological aspects due to backscattered neutrons when spent fuel and high level waste will be handled in the drifts of an underground repository located in a salt dome. As neutrons play an important role in the direct disposal option, main emphasis was laid on their contribution to the total dose equivalent rate. The radiological exposure caused by direct neutrons and neutrons scattered by the salt rock during handling processes of POLLUX packages and shipping packages was simulated and experimentally analysed with the help of the AHE package. The AHE shielding cask was filled with one Cf-252 line source in order to simulate the neutron fields of a loaded POLLUX cask and a shipping cask loaded with a fuel element canister with respect to neutron energy distributions and local dose equivalent rates. The results of the AHE experiment provided valuable contributions for a better understanding of radiological aspects during handling spent fuel/high level waste in an underground repository. Validated computer codes are available now which make it possible to minimize the occupational dose. (orig.)Zielsetzung des aktiven Handhabungsexperimentes war, die radiologischen Aspekte aufgrund Neutronenrueckstreuung zu untersuchen, die bei der Handhabung von Brennelementen bzw. hochaktivem Abfall in den Strecken eines untertaegigen Endlagers in Salzformation auftreten. Da Neutronen eine wichtige Rolle bei der Option der direkten Endlagerung spielen, wurde der Schwerpunkt der Untersuchung auf ihren Beitrag zu der totalen Aequivalenzdosisleistung gelegt. Die Aequivalenzdosisleistungen der von direkten und an Salzgestein gestreuten Neutronen bei Handhabung von Pollux-Behaeltern und Einzelabschirmbehaeltern wurde durch einen Versuchsbehaelter, der mit einer Cf-252-Neutronenquelle beladen war, simuliert und experimentell analysiert, um die radiologische Exposition des Betriebspersonals abschaetzen zu koennen. Die Ergebnisse des AHE-Experiments lieferten wertvolle Beitraege zum besseren Verstaendnis der radiologischen Aspekte bzgl. Neutronenrueckstreuung bei der Handhabung von ausgedienten Brennelementen bzw. hochaktivem Abfall in einem Endlager im Salz. Validierte Computerprogramme stehen nun zur Verfuegung, die eine Minimierung der Personendosen des Betriebspersonals ermoeglichen. (orig.)Available from TIB Hannover: RO 6452(69)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); European Union (Euro), Brussels (Belgium)DEGerman