Identification of temperature-dependent water quality changes during a deep well injection experiment in a pyritic aquifer

Artificial recharge is a technique used increasingly to supplement drinking water supplies. To assess the potential water quality changes that occur during subsurface passage, a comprehensive deep-well injection experiment was carried out for a recharge scheme, where pretreated, aerobic surface water was injected at 300 m depth into an anaerobic aquifer. Water quality parameters were recorded over the 854-days long injection phase. The evolution of the major ion and redox chemistry was analyzed with a three-dimensional reactive multicomponent transport model. It was found that the oxidation of pyrite was the main driverforwater quality changes and that reaction rates depended significantly on the spatially/temporally varying groundwater temperature. With the temperature-dependency of the oxidation reactions incorporated into the model, the simulations give an accurate picture of the temporal and spatial evolution of the hydrochemical changes that occurred during the experiment. To delineate the influence of physical and chemical processes on local concentration changes the results of the reactive transport model simulations were compared with the corresponding results from nonreactive simulations. The study emphasizes the suitability of mechanistic multicomponent reactive transport modeling as an integrative tool for data analysis when physical transport and chemical processes interact.     

Life stage specific impact of dimethoate on the predatory mite Hypoaspis aculeifer canestrini (Gamasida: Laelapidae)

Toxicants may affect juveniles more than adults because of physiological and behavioral aspects. When developing toxicity tests, this issue is often not addressed, and the most sensitive end point may be ignored. The topic was raised by a European working group aiming to develop a standard toxicity test with the predatory mite, Hypoaspis (Geolaelaps) aculeifer Canestrini, as this species was included in the EU Guidance documentfortesting of pesticides. To assess whether the juvenile life stages are the most susceptible, we examined the acute toxicity of dimethoate on larvae, protonymphs, deutonymphs, males, and females of H. aculeifer. The mites were exposed to 0, 2, 4, and 6 mg dimethoate kg(-1) for 7 days in an OECD artificial soil (5% organic matter). Total juvenile biomass, reproduction, mortality, and population growth rate (pgr) lambda were assessed at the end of the test. A comparison of mortality ranked the sensitivity of the life stages: Larvae (LC50 = 3.8 mg kg(-1)) > protonymphs (LC50 = 5.3 mg kg(-1)) > males (LC50 = 5.6 mg kg(-1)) > deutonymphs (LC50 = 7.1 mg kg(-1)) > females (LC50 = 7.6 mg kg(-1)). Effects on reproduction and pgr were significant at 2 mg dimethoate kg(-1), with population decline starting at this concentration. Thus, a test system with H. aculeifer including reproduction as end point is a rational approach, as reproduction will encompass juvenile mortality, at least with respect to dimethoate. Moreover, we suggest that pgr should be included in chronic standard tests because of high ecological relevance and the feasibility of applying it.     

Temperature-induced pressure gradient in the clearance between screw flight and barrel of a single screw extruder

The effect of temperature-induced pressure gradients occurring in drag flow in a narrow gap between parallel walls, when a viscosity gradient in flow direction is present is described and analyzed. The effect dominates the technologically important clearance flow problem, where the viscosity gradient originates from temperature changes. The polymer layer in the clearance between screw flight and barrel of a single screw extruder supposedly has to separate the metallic surfaces from each other. In certain operating conditions this bearing function breaks down and dry friction between metallic surfaces occurs. This failure, which has not yet been explained, is reasoned to be caused by the temperature-induced pressure flow in the clearance.     

Polysaccharidzus?tze in eiwei?reichen Lebensmitteln

Zusammenfassung Aus der Literatur bekannte Verfahren zur Isolierung von Polysacchariden aus eiweißreichen Lebensmitteln, insbesondere Frischkäsen, erwiesen sich im praktisch interessanten Bereich (0,01–0,2% Bindemittelzusatz) als wenig brauchbar. Stattdessen wird folgende Probenaufbereitung vorgeschlagen: 1. Entfettung der Proben mit einem Gemisch von Äthanol, Diäthyläther und Petroläther; 2. vollständige Hydrolyse der Proteine mit Pepsin, Pronase E und einem Gemisch von Aminopeptidase M und Prolidase; 3. Abtrennung der Polysaccharide von den niedermolekularen Substanzen und von Enzymresten durch Gelfiltration an Biogel P-2; 4. Konzentrierung der polysaccharidhaltigen Fraktion durch Gefriertrocknung, Ultrafiltration oder Eindampfen.- Das Verfahren wurde am Beispiel von Speisequark und Doppelrahmfrischkäse erprobt, ist im Prinzip aber verallgemeinerungsfähig.

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Polysaccharide additives in foods rich in proteinsI. Sample preparation for estimation, especially in fresh cheese

Summary Published procedures for the isolation of polysaccharides from foods rich in proteins, especially fresh cheese, proved not very useful for the concentration in question (0,01–0.2%). We, instead, propose the following sample preparation: 1. Removal of lipids by an ethanol - ethyl ether - petrol ether mixture; 2. complete hydrolysis of proteins with pepsin, pronase E and a mixture of Amnopeptidase M and prolidase; 3. separation of the polysaccharides from the low molecular substances and from enzyme residues by gel filtration on Biogel P-2; 4. concentration of the polysaccharides containing fraction by freeze drying, ultrafiltration or evaporation. - The method was tested with quarg and double cream fresh cheese, it can, however, be adopted to use in other products.

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Deutsches Wollforschungsinstitut, Aachen.     

39 GHz monolithic coplanar waveguide amplifier using doped channel HFET technology on InP

A single-state amplifier has been designed and fabricated using 0.25 mu m gate length, doped-channel HFET technology on InP substrates. Coplanar waveguide (CPW) was used for impedance matching. A gain of 14.4 dB was measured at 39 GHz.<>