Aqueous solubility and n-octanol/water partition coefficient correlations

Studies of the fate of chemicals require the knowledge of numerous parameters, among which of utmost importance are the water solubility and the n-octanol/water partition coefficient.

Numerous writers have demonstrated that there is a close correlation between these two parameters. The literature offers about fifteen cases of correlations between solubility and n-octanol/water partition coefficient with, for some of them, and for solids, a third variable: the fusion point. Unfortunately, the coefficients are often the results of theoretical considerations and the size of the data base is often small.

A study carried out on 300 products shows clearly the importance of the size of the data base. It is demonstrated that the coefficients obtained in practice are different from those which had been calculated theoretically. In particular, the introduction of a fusion point correction appears to be justified only to a limited extent.

This analysis has shown that there is a need to reexamine the theoretical approach and determine why the coefficients of the regression equation do not appear to adopt the values excepted from theoretical considerations.     

Assessment of labile phosphorus fractions and adsorption characteristics in relation to soil properties of West African savanna soils

A large proportion of total P in the soils of the area is unavailable to plants and consequently P is the second most limiting nutrient. The labile and moderately labile phosphorus fractions and adsorption characteristics of surface and subsurface horizons of eleven soil profiles in the derived savanna (DS) and the northern Guinea savanna (NGS) of West Africa were assessed. The labile P fractions are the resin and HCO₃-extractable inorganic (Pi) and organic (Po) P. The moderately labile fractions are the NaOH-extractable portion of soil P in the Hedley sequential procedure. In the DS soils, the resin P, considered the most readily available fraction, varied from 1 to 14 mg kg⁻¹, HCO₃-Pi ranged from 3.3 to 11, and HCO₃-PO was between 4 and 12 mg kg⁻¹ in the surface horizon. In the NGS, the topsoil contained 1.5–3 mg kg⁻¹ of resin P, 5–8 mg kg⁻¹ of HCO₃-Pi, and 7.5–9.7 mg kg⁻¹ of HCO₃-Po. Sodium hydroxide-Po was the largest of the fractions in all the soils studied. It ranged from 23 to 55 mg kg⁻¹ in the topsoil. In general, the labile P levels were higher in soils of the DS than of the NGS and were related to the oxalate-extractable Fe (Fe_ox), and Al (Al_ox) as well as to soil texture. The subsoil of Kasuwan Magani (profile KS 9–21 cm) required 153 mg P kg⁻¹ to maintain 0.2 mg P l⁻¹ in solution (standard P requirement), and Danayamaka (profile DD 7–32 cm) required 145 mg P kg⁻¹. These could translate to 214 and 200 kg P ha⁻¹ if a plow layer of 10 cm is assumed. Because these are within the plow layer, more P fertilizer would be needed for crop production than in the other soils. The standard P requirement and the adsorption maxima were related to Fe_ox and Al_ox, dithionite-Fe (Fe_d), and texture. The increase in labile P content with decreasing Fe_ox and Al_ox could imply that management practices capable of reducing the activities of Fe and Al in solution might improve P availability.     

Residual benefits of promiscuous soybean to maize (Zea mays L.) grown on farmers’ fields around Minna in the southern Guinea savanna zone of Nigeria

Biological nitrogen fixation (BNF) by promiscuous cultivars of soybeans (Glycine max (L.) Merr.) in cereal-based cropping systems of Nigeria’s moist savanna zone offers a potential for minimizing the investment made by resource-poor farmers on nitrogen fertilizers. A 3-year trial was conducted on five farmers’ fields in the southern Guinea savanna zone of Nigeria to assess the residual effects of two successive crops of promiscuous soybean cultivars on the yield of a following maize (Zea mays L.) crop. The soybean cultivars, TGX1456-2E (medium maturity) and TGX1660-19F (late maturity), were grown in 1996 and 1997. Treatments, imposed only in the first year of the trial, were: (i) uninoculated, (ii) inoculated with a mixture of two Bradyrhizobium strains, and (iii) fertilized with 60 kg N ha⁻¹. A fourth treatment was a plot left to fallow. In 1998, all the previous soybean and fallow plots were sown to maize without any fertilizer application. Results in 1996 and 1997 showed a soybean response to inoculation in the first year, but differences due to the residual effect of inoculation in the second year were not significant. Both cultivars showed a similar response to inoculation but responses at the five sites were varied. Soybean cultivar 1456-2E fixed 43–52% of its N amounting to 56–70 kg N ha⁻¹ and cultivar 1660-19F derived 39–54% of its N from N₂-fixation which amounted to 51–78 kg N ha⁻¹. Both cultivars had a high N harvest index resulting in a net removal of 52–95 kg N ha⁻¹ when both grain and stover were exported. Even when the stover was returned, there was a depletion of 23–65 kg N ha⁻¹, with 1456-2E removing more N than 1660-19F. Arbuscular-mycorrhizal infection on maize roots was 11–27% and dependent on previous soybean treatments and farmers’ fields. Plant height, shoot biomass, grain yield, and N uptake of maize were significantly greater in plots previously sown to soybean than in the fallow plots. In general, plots sown to the late maturing cultivar 1660-19F exhibited better residual effect, producing larger yield parameters than the plots planted with medium maturing 1456-2E.     

Population dynamics during startup of thermophilic anaerobic digesters: The mixing factor

Two thermophilic digesters were inoculated with manure and started-up under mixed and stagnant conditions. The Archaea in the mixed digester (A) were dominated by hydrogenotrophic Methanobateriaceae (61%) with most of the methane being produced via syntrophic pathways. Methanosarcinales (35%) were the only acetoclastic methanogens present. Acetate dissipation seems to depend on balanced hydrogenotrophic-to-acetotrophic abundance, which in turn was statistically correlated to free ammonia levels. Relative abundance of bacterial community was associated with the loading rate. However, in the absence of mixing (digester B), the relationship between microbial composition and operating parameters was not discernible. This was attributed to the development of microenvironments where environmental conditions are significantly different from average measured parameters. The impact of microenvironments was accentuated by the use of a non-acclimated seed that lacks adequate propionate degraders. Failure to disperse the accumulated propionate, and other organics, created high concentration niches where competitive and inhibiting conditions developed and favored undesired genera, such as Halobacteria (65% in B). As a result, digester B experienced higher acid levels and lower allowable loading rate. Mixing was found necessary to dissipate potential inhibitors, and improve stability and loading capacity, particularly when a non-acclimated seed, often lacking balanced thermophilic microflora, is used.     

Identification of 1-methyloctyl butanoate as the major sex pheromone component from females of the saddle gall midge,Haplodiplosis marginata (Diptera: Cecidomyiidae)

The saddle gall midge, Haplodiplosis marginata (von Roser) (Diptera: Cecidomyiidae), has undergone a resurgence recently as a pest of cereals in Belgium and other European countries. An effective monitoring tool of saddle gall midge flights is needed to understand the enigmatic population dynamics of this pest, and to design an integrated management strategy. Therefore, volatile compounds emitted by females (alkan-2-ols and alk-2-yl butanoates) were identified, and the chirality of the emitted esters was determined to be the R absolute configuration. In field-trapping experiments, racemic non-2-yl butanoate attracted substantial numbers of H. marginata males. Thus, this compound will be useful in baited traps for monitoring seasonal flight patterns, and improving integrated management of the saddle gall midge in agricultural systems.     

Prenatal molecular diagnosis in RASA1-related disease

RASA1-related disease is a rare autosomal dominant disease characterized by capillary malformations, arteriovenous malformations (AVMs), and/or arteriovenous fistulas (AFVs). Penetrance is nearly complete and vascular malformations may cause serious complications such as organ injury due to oxygenation disorder, brain abscess, hemorrhage, and stroke. Early diagnosis is useful in order to discuss optimal management, including AVMs/AVFs embolization or surgical procedures, and try to prevent some of the complications. In this context, molecular testing of RASA1 gene mutation in relatives may help to better manage the family. All arteriovenous malformations are however not accessible to such procedures. In addition, these therapeutic procedures may result in potential side effects and complications. A couple was referred to our genetics unit and asked us for prenatal genetic testing about a RASA1 mutation. Here, we discuss about arguments that led our team to accept prenatal testing. To the best of our knowledge, no molecular prenatal diagnosis was reported until now in RASA1-related diseases. This first report of prenatal diagnosis in RASA1-related diseases may also offer perspectives for a more general discussion in the field of inherited arteriovenous malformations.     

Contamination of Clams with Human Norovirus and a Novel Hepatitis A Virus in Cameroon

Food and Environmental Virology - Shellfish constitute an important protein source but may be contaminated by viruses from various origins. A study performed on clams collected in Cameroon showed a...