Microbial activities during the early stage of laboratory decomposition of tropical leaf litters: the effect of interactions between litter quality and exogenous inorganic nitrogen

The comparative decomposition of tropical leaf litters (e.g. Andropogon gayanus, Casuarina equisetifolia, Faidherbia albida) of different qualities was investigated under laboratory conditions during a 60-day incubation period conducted with a typical oxisol. Total CO₂-C, soil inorganic N, microbial biomass (fumigation-extraction), -glucosidase and dehydrogenase activities were determined over the incubation to assess how they responded to the addition of inorganic N (+N). Cumulative CO₂-C evolved from the litter-amended soils was higher than that recorded for the unamended control soil. For the unfertilized treatment (0 N), correlation coefficients calculated between initial chemical data and CO₂ flux during the first day of incubation were r =0.963 for water soluble-C and 0.869 for soluble carbohydrates (P <0.05). At the end of the incubation, the amounts of CO₂-C in the F. albida- and A. gayanus-amended soils were higher than that in the C. equisetifolia-amended treatment. Cumulative net N immobilization increased during the first 30 days of incubation, the amounts being similar for A. gayanus- and C. equisetifolia-amended soil and higher than that recorded in the F. albida-amended treatment. Soil microbial biomass and enzyme activities increased in the litter-amended soils during the first 15 days of incubation and decreased (except for the dehydrogenase activity) thereafter. The addition of inorganic N modified the patterns of CO₂-C respiration and net N immobilization. The magnitude of these modifications varied according to the litter quality. The use of an accurate indicator based on several litter components to predict the amplitude of organic material decomposition is discussed.     

2. In vivo nonvolatile release during eating of a model cheese: relationships with oral parameters

This study deals with the release kinetics of nonvolatile compounds (NVC) (leucine, phenylalanine, glutamic acid, citric acid, lactic acid, propanoic acid, sodium, potassium, calcium, magnesium, chloride, and phosphates) during the eating of a model cheese and the relationships to some oral (salivary and masticatory) parameters. The aroma release has previously been characterized in similar conditions [Pionnier, E.; Chabanet, C.; Mioche, L.; Le Quéré, J.-L.; Salles, C. J. Agric. Food Chem. 2004, 52, xxx-xxx (1)]. Saliva samples were collected from the tongues of eight assessors at different times during and after the chewing sequence. Atmospheric pressure ionization-mass spectrometry and/or high-performance liquid chromatography analyses have been performed on these samples in order to quantify the 12 NVC released in saliva. The maximum concentration (C(max)) in saliva varied significantly according to the compound. However, there was no significant effect of the compound on the time to reach maximum concentration (T(max)). Interindividual differences were observed for most of the parameters and for all of the NVC studied. The parameters extracted from the release profiles of the NVC were closely correlated. High T(max) and AUC (area under the curve) values could be related to high chewing time and low saliva flow rates, low chewing rates, low masticatory performances, and low swallowing rates.     

Effect of dose rate and mixtures of fungicides on selection for QoI resistance in populations of Plasmopara viticola

Resistance to QoI fungicides (strobilurins, famoxadone and fenamidone) in populations of Plasmopara viticola (Berk & Curt) Berlese & de Toni developed soon after their introduction in France and Italy. Current resistance management strategies include limitation of the number of applications, use of mixtures and alternation of fungicides with different modes of action. The selection pressure resulting from QoI fungicides applied alone or in mixtures with non-QoI fungicides was investigated in whole plant experiments under controlled conditions. QoI-resistant populations of P. viticola gradually reverted to full sensitivity following consecutive transfers to untreated plants, suggesting that resistant phenotypes were less competitive than sensitive ones. When cycled on QoI-treated plants, reduction in sensitivity was greater for the QoI fungicide which had greater intrinsic activity on P. viticola. Sensitivity decreased at each subsequent cycle, resulting in almost full resistance after four generations. Mixture experiments indicated that selection pressure was affected most by the dose of the QoI fungicide and the nature of the partner fungicide. Folpet delayed selection pressure most effectively when it was associated with famoxadone or azoxystrobin. Mancozeb was least effective at reducing the rate of selection compared with the QoI alone, and fosetyl-aluminium was intermediate. Higher rates of selection were recorded when the dose of the QoI fungicide, solo or in a mixture, was increased from 1 to 4 microg ml(-1). Increasing the dose of the non-QoI partner fungicide in the mixture from 10 to 30 microg ml(-1) resulted in reduced selection pressure. These results suggest that the choice of the fungicide partner and its dosage in the mixture can significantly affect the success of QoI resistance management strategies under practical conditions.     

Direct detection of the asteroidal YORP effect

The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect is believed to alter the spin states of small bodies in the solar system. However, evidence for the effect has so far been indirect. We report precise optical photometric observations of a small near-Earth asteroid, (54509) 2000 PH5, acquired over 4 years. We found that the asteroid has been continuously increasing its rotation rate omega over this period by domega/dt = 2.0 (+/-0.2) x 10(-4) degrees per day squared. We simulated the asteroid's close Earth approaches from 2001 to 2005, showing that gravitational torques cannot explain the observed spin rate increase. Dynamical simulations suggest that 2000 PH5 may reach a rotation period of approximately 20 seconds toward the end of its expected lifetime.     

Assessment of strawberry aroma through SPME/GC and ANN methods. Classification and discrimination of varieties

To provide an efficient and running analytical tool to strawberry plant breeders who have to characterize and compare the aromatic properties of new cultivars to those already known, a HS-SPME/GC-MS analysis method has been coupled with a statistical treatment method issued from the current development of artificial neuron networks (ANN), and more specifically, the unsupervised learning systems called Kohonen self-organizing maps (SOMs). So, 70 strawberry samples harvested at CIREF from 17 known varieties have been extracted by using a DVB/Carboxen/PDMS SPME fiber according to the headspace procedure, and then chromatographed. A panel of 23 characteristic aromatic constituents has been selected according to published results relative to strawberry aroma. The complex resulting matrix, collecting the relative abundance of the 23 selected constituents for each sample, has been input into the SOM software adapted and optimized from the Kohonen approach described by one of the authors. After a period of training, the self-organized system affords a map of virtual strawberries to which real samples are compared and plotted in the best matching unit (BMU) of the map. The efficiency for discriminating the real samples according to their variety is dependent on the number of units selected to define the map. In this case, a 24-unit map allowed the complete discrimination of the 17 selected varieties. Moreover, to test the validity of this approach, two additional samples were blind-analyzed and the results were computed according to the same procedure. At the end of this treatment, both samples were plotted into the same unit as those of the same variety used for training the map.     

Investigation of Nitrification and Denitrification in the Sediment of Wastewater Stabilization Ponds

Kinetic studies of nitrification and denitrification were carried out on reconstituted cores of sediments taken from wastewater stabilization ponds. This study aims to quantify the nitrification and denitrification in the sediment and to offer kinetic models to describe the processes. Sediment cores were collected, and laboratory studies were performed. The result showed that nitrification and denitrification processes are absent in the water column of stabilization ponds of the Bertrix (Belgium) wastewater treatment plant. On the contrary, nitrification and denitrification rates measured on 18 cores of sediment are, respectively, in the range of 0.12?C1.56 g N-NH ₄ ⁺ /m² day and 0.1?C1.2 g N/m² day. In order to describe nitrification and denitrification processes, two kinetic models were developed using the Monod standard equation.     

Computed tomography or rhinoscopy as the first-line procedure for suspected nasal tumor: A pilot study

There are no evidence-based guidelines as to whether computed tomography (CT) or endoscopy should be selected as the first-line procedure when a nasal tumor is suspected in a dog or a cat and only one examination can be performed. Computed tomography and rhinoscopic features of 17 dogs and 5 cats with a histopathologically or cytologically confirmed nasal tumor were retrospectively reviewed. The level of suspicion for nasal neoplasia after CT and/or rhinoscopy was compared to the definitive diagnosis. Twelve animals underwent CT, 14 underwent rhinoscopy, and 4 both examinations. Of the 12 CT examinations performed, 11 (92%) resulted in the conclusion that a nasal tumor was the most likely diagnosis compared with 9/14 (64%) for rhinoscopies. Computed tomography appeared to be more reliable than rhinoscopy for detecting nasal tumors and should therefore be considered as the first-line procedure.     

Direct detection of the Yarkovsky effect by radar ranging to asteroid 6489 Golevka

Radar ranging from Arecibo, Puerto Rico, to the 0.5-kilometer near-Earth asteroid 6489 Golevka unambiguously reveals a small nongravitational acceleration caused by the anisotropic thermal emission of absorbed sunlight. The magnitude of this perturbation, known as the Yarkovsky effect, is a function of the asteroid's mass and surface thermal characteristics. Direct detection of the Yarkovsky effect on asteroids will help constrain their physical properties, such as bulk density, and refine their orbital paths. Based on the strength of the detected perturbation, we estimate the bulk density of Golevka to be 2.7(+0.4)(-0.6) grams per cubic centimeter.