Elektronenmikroskopische Untersuchungen an den epitheloiden Zellen der Hoyer-Grosserschen Organe

The Science of Nature -     

Determination and assessment of the characteristic values for the evaluation of the thermal safety of chemical processes

Experience gained in the chemical industry in testing and assessing the thermal safety of chemical processes is published in this paper. Isothermal and adiabatic tests, which are the most important methods for both small and large quantities, are described and discussed. Methods for testing the thermal hazards of primary or desired reactions are also included, e.g. reaction calorimetry, adiabatic methods, investigations using a sampling method. More important are the criteria for assessing the test results. On the basis of energies produced by primary and secondary reactions and the temperature ranges within which they take place, thermal hazards can be predicted. If the rules for the safe design of batch and semi-batch reactions are observed, it is possible to control the thermal behaviour of reactions.     

Flocculants—an Ecofriendly Approach

Although water-soluble synthetic polymers find wide applications as flocculants, the potential problem associated with their use is lack of biodegradability and high cost. Polysaccharides owing to their distinctive features like ability to undergo different chemical reactions, biodegradability and sustainability inspire hope to obtain effective, economical viable and safe substitute of the synthetic flocculants. In this regard, chemical modification of Cassia tora and guar gum was carried out through different substitution and grafting reactions. The modified products were tested against kaolin under laboratory conditions vis-a-vis polyacrylamide based synthetic flocculant.     

Action and composition of the alarm pheromone of the bedbugCimex lectularius L.

The Science of Nature -     

Physiologische Anpassungen eines marinen insekts. II. Die Eigenschaften von schwimmenden und absinkenden Eigelegen

The gelatinous egg-masses of Clunio marinus (Diptera; Chironomidae) consist of a tube of jelly containing up to 175 eggs. The swimming egg-mass of the Atlantic populations (Race A) and the sinking egg-mass of the Baltic populations (Race B) have a higher density than the sea water, on which the female spawns; salinity is not important to the swimming or sinking of the egg-masses. Density and sinking velocity of gelatinous egg-masses from Atlantic midges are significantly higher than those from Baltic midges if the eggs are laid on water of the same salinity. The density of the eggs and the quantitative relation of eggs to jelly are the same in both races. The jelly of the egg-masses from the Baltic Sea race swells more than that from the Atlantic Sea race (increase of volume by absorption of water = 3-fold and 2.4-fold, respectively). During swelling the jelly alters from a trough-like shape into a tube-like from which closes around the eggs. If the surface tension of the spawning medium is lowered by use of detergents, the A-spawn will sink. A- and B-spawns occupy different positions at an oil-water interface. Interference contrast microscopy revealed that the A-jelly forms a well-defined outer line in relationship to the surrounding aqueous medium; this line is missing in the B-jelly. The morphological fine surface structures, as seen by the scanning electron microscope, do not explain the different properties of the A- and B-spawn. Extracts and hydrolysates of jelly material were separated by thin-layer chromatography. The results indicate that the spawn jelly of C. marinus consists of a polysaccharide-protein-complex, similar to the jellies of other invertebrates. It is rather probable that the chemical structure or the components of the jellies from A- and B-populations are not exactly the same; this would explain the different properties described. The ecological significance of swimming and sinking gelatinous egg-masses and the taxonomical position of both midge populations are discussed.     

Cadmium accumulation in Allium schoenoprasum L. grown in an aqueous medium

The ability of Allium schoenoprasum L. (chives) to accumulate and tolerate cadmium in aqueous Hoagland medium at 50microM and 250microM was tested under continuous growth or several successive harvests of shoots. After 28 days of continuous growth, chives accumulated the metal up to 0.2% and 0.5% of its dry weight, when grown in 50microM and 250microM, respectively. In experiments that the leaves were successively harvested every 16 days, there were no obvious stress symptoms after six harvests during a period of 96 days at 50microM Cd. At 250microM, after 64 days and four harvests, inhibition of growth occurred. In each treatment, a total of 1.2g kg(-1) DW and 2.4g kg(-1) DW was accumulated in the leaves, respectively. Total SH compounds concentration in leaf was found significantly higher by 3 and 7.4 times in plants treated with Cd at 50microM and 250microM in comparison to the control, respectively, while no difference in the concentration of glutathione (GSH+GSSG) was found. Thus, it is assumed that sulphur-containing compounds, yet unknown, are involved in defensive mechanisms against heavy metals in chives. The results presented, point to chives phytoremediation potential, but also on the potential risk in accumulation of heavy metals in a commonly edible plant.