Increasing productivity in recent European oak trees?

As an attempt to analyze the role of the biosphere in the disturbed carbon cycle, as far as the standing biomass is concerned, a search for growth trends in tree ring series was started. A group of 27 cut oak trees from various locations in Europe and with ages between 25 and 262 years was analyzed in the following way: (1) A two-parameter smoothing function applied to each single tree cancelled out the year-to-year noise of ring widths; (2) this function containing the growth information over the whole life span of a tree was used to compute the (smoothed) width of the 40th and the 80th ring for each tree; (3) each ring width derived from a single tree in this way was plotted vs time, i.e., over the particular year of its formation. A statistical analysis of these plots shows that the variation of ring widths (delta r) in time (t) is best represented by an exponential function of the form delta rn(t) = delta r0n + aebt (n = 40; 80). The pre-industrial value, delta r0n (for t approximately less than 1,800), turns out to be identical with the 2,700 years average of European oak trees, as found by Hollstein (1979) in his dendrochronological work. Several possibilities are discussed what might have caused such growth trend.

[Gas-chromatographic determination of chloramphenicol residues in animal material]. / Gaschromatographische Bestimmung von Chloramphenicol-Rückständen in tierischem Material.

On the basis of the relevant literature and of their own experimental work, the authors describe extraction, cleaning and derivatization procedures for the determination of chloramphenicol in milk, muscular substance, urine and bile. Chloramphenicol was determined as bis-(trimethylsilyl)-ether using a gas chromatograph fitted with an electron capture detector. To evaluate the analytical techniques, the authors estimated the sensitivity, accuracy and precision for residue amounts of 0.1 and 0.05 mg of chloramphenicol/kg of material under investigation. The limit of detection was 0.02 mg/kg for meat, and 0.01 mg/kg for milk, urine and bile.

[Measurement of emulsion stability]. / Zur Stabilitätsmessung von Emulsionen

For the routine assessment of the stability of water-in-oil emulsions, the authors suggest to determine the beginning of de-emulsification or to measure the stability constant at 38 degrees C., since these methods yield fairly reproducible results and require but little time and laboratory outfit. More accurate results will be obtained only by conductance measurements.