A note on the development of the thermocline in temperate lakes

An exact solution has been obtained for a non-linear partial differential equation governing the vertical transport of heat in a lake. The equation, derived and analyzed numerically by Sundaram and Rehm (1971, 1973) is based on a balance between thermal buoyany forces and wind induced turbulence. The exact solution displays the qualitative features of the numerical solution and its representation of the seasonal descent of the thermocline is accurate.     

RESIDENTIAL WATER DEMAND: A POOLED,TIME SERIES,CROSS SECTION STUDY OF MALMÖ, SWEDEN1

Shortcoming associated with past water demand studies are evaluated. To overcome these shortcomings, pooled, time series, cross section data from -6, Sweden, are used in an ordinary Least squares analysis to estimate the demand for residential water. Elasticities for five variables, including price and income, are estimated. An approach for the conduct of future water demand studies is suggested.     

First-trimester maternal serum human thyroid-stimulating hormone in chromosomally normal and Down syndrome pregnancies

Maternal serum human thyroid-stimulating hormone (TSH) levels were investigated in chromosomally normal and Down syndrome pregnancies to determine whether TSH can be used as a marker for Down syndrome in the first trimester. Measurements were conducted on stored serum samples collected from 23 Down syndrome pregnancies and 115 unaffected pregnancies before chorionic villus sampling (CVS), between 9 and 11 completed weeks of pregnancy. The samples were matched for gestational age, maternal age, maternal weight and duration of storage of the serum sample. Maternal TSH concentration was slightly decreased in Down syndrome pregnancies, with a median of 0.84 multiples of the median (MoM). Maternal serum human chorionic gonadotropin (hCG) concentration was slightly elevated in Down syndrome pregnancies, with a median of 1.03 MoM. Both differences were not significant applying matched rank analysis (p=0.50 for TSH and p=0.43 for hCG). The association between TSH and hCG in unaffected pregnancies was also measured. The Spearman correlation coefficient between TSH and hCG was −0.21 which was statistically significant (p=0.02, 95% confidence interval −0.38 to −0.03). However, it was concluded that TSH is not a useful marker for distinguishing Down syndrome-affected pregnancies from normal pregnancies in the first trimester. Copyright © 2001 John Wiley & Sons, Ltd.     

Movements between coral colonies in Trapezia ferruginea (Crustacea: Brachyura), an obligate symbiont of scleractinian corals

Trapezia ferruginea appears to depend entirely on its coral host (Pocillopora spp.) for shelter and food. Field and laboratory experiments have shown that the brightly colored crabs move between colonies at night. Analysis of movements in crabs randomly distributed among randomized Pocillopora damicornis colonies under laboratory conditions showed that after 6 days there was a significant increase in the number of heterosexual pairs (P<0.001) and a significant correlation between the number of crabs and the size of colonies (P=0.003), as well as between the size of crabs and the size of colonies (P=0.020) — conditions which are also observed in the field. No such correlations were obtained (P>0.05) in a similar experiment where very intense predation by carnivorous fishes was present. This host selection by adults appears to be elicited by the lack of a suitable partner and the inadequate size of their established territory in the colony.     

Pressurised liquid-liquid extraction. An approach to the removal of inorganic non-metal species from used industrial oils

Modified pressurised hot water is used for the development of a high pressure liquid-liquid extraction method for the decontamination of used industrial oils from inorganic non-metal species (chlorine, fluorine and sulphur). The oils were subjected to dynamic extraction with water modified with 5% v/v HNO3 at 200 degrees C as extractant. Under these working conditions the analytes were transferred to the aqueous phase. Spontaneous separation of the two immiscible liquid phases (the used oil and extract) takes place in the collection flask after extraction. The treated and untreated oil samples were oxidised and the chloride, fluoride and sulphate thus formed were determined by ion-chromatography. The method was applied to four oil samples from different locations in Spain. A residence time of approximately =10 min provided oil samples from which 88.3%, 89.4% and 89.4% of chloride, fluoride and sulphate, respectively, have been removed with respect to the initial concentration of each analyte in the oil. The repeatability, expressed as relative standard deviation (RSD), was of 11.9%, 13.7% and 7.2% for Cl(-), F(-) and SO4(2-), respectively; whilst the within-laboratory reproducibility yielded RSDs of 6.2%, 7.9% and 6.2% for the same analytes. The proposed approach has proved to be efficient, simple, easily transferable to industrial scale, cheap, fast and environmentally friendly.     

Uranium-thorium disequilibrium in north-east Atlantic waters

In this paper we report and compare the concentrations of 234Th and 238U measured in surface and subsurface waters collected in the course of a sampling campaign in the north east Atlantic in June-July 1998. Dissolved 234Th concentrations in surface waters ranged from 5 to 20 Bq m(-3), showing a large deficiency relative to 238U concentrations (typically 42 Bq m-3). This disequilibrium is indicative of active 234Th scavenging from surface waters. Observed 234Th/238U activity ratios, together with corresponding 234Th particulate concentrations, were used to calculate mean residence times for 234Th with respect to scavenging onto particles (tau(diss)) and subsequent removal from surface waters (tau(part)). Residence times in the range 5-30 days were determined for tau(diss) and 4-18 days for tau(part) (n=14). In addition, ultrafiltration experiments at six stations in the course of the same expedition revealed that in north-east Atlantic surface waters a significant fraction (46+/-17%; n=6) of the thorium in the (operationally-defined) dissolved phase (<0.45 microm) is in colloidal form. These observations are consistent with the 'colloidal pumping' model in which it is assumed that 234Th is rapidly absorbed by colloidal particles, which then aggregate, albeit at a slower rate, into larger filterable particles. In essence, colloids act as intermediaries in the transition from the fully dissolved to the filter-retained (>0.45 microm) phase. Thus, the time (tau(c)) for fully dissolved 234Th to appear in the filter-retained fraction is dependent on the rate of colloidal aggregation. Here, we determined tau(c) values in the range 3-17 days.     

Global-scale vs. regional-scale scenario assumptions: implications for estimating future water withdrawals in the Elbe River basin

In this paper, we explore how scenarios of future water withdrawals in a river basin are influenced by scale-dependent quantifications of the driving forces for two global-scale storylines. Either global-scale information or region-specific information is used to do the quantifications. In addition, we analyze the impact of including or not some restricted regional-scale information in the employed water use model. To develop scenarios of water withdrawals in the German part of the Elbe River basin, we applied the modules for domestic, thermoelectric power and manufacturing water use of the global water model WaterGAP, using scale-dependent driving forces scenarios and other scale-dependent model input. In the global-scale quantitative interpretations of the storylines of the IPCC SRES scenarios A1 and B2, all major driving forces of water withdrawals in the basin—population, thermoelectric power production and industrial gross domestic product—show vigorous increases between 2000 and 2025, while from the regional perspective, smaller increases but mostly decreases appear to be plausible. These discrepancies are partly due to the fact that for the global-scale interpretations only the historic developments until 1990 were taken into account, and not until 2000 as in the regional case. The resulting scenarios of sectoral water withdrawals in 2025 differ strongly between the two scale-dependent interpretations of the storylines, with the global one leading to much higher absolute water withdrawals and much lower withdrawal decreases between 2000 and 2025. Therefore, for regional assessments of water withdrawals, we recommend to embed the scenario analysis in global-scale storylines by performing regional-scale quantifications of the global qualitative driving forces scenarios, based on a limited amount of region-specific information.