Authors' reply.     

Valérie Chetboul  Hervé P Lefebvre  Carolina Carlos Sampedrano  Vassiliki Gouni  Vittorio Saponaro  Francois Serres  Didier Concordet  Audrey P Nicolle  Jean-Louis Pouchelon 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2008,22(2):245-246

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Multi-element analysis of South African wines by ICP-MS and their classification according to geographical origin   总被引：5，自引：0，他引：5  

Coetzee PP  Steffens FE  Eiselen RJ  Augustyn OP  Balcaen L  Vanhaecke F 《Journal of agricultural and food chemistry》2005,53(13):5060-5066

Wines from three important wine-producing regions, Stellenbosch, Robertson, and Swartland, in the Western Cape Province of South Africa, were analyzed by ICP-MS and the elemental composition used in multivariate statistical analysis to classify the wines according to geographical origin. The method is based on the assumption that the provenance soil is an important contributor to the trace element composition of a wine. A total of 40 elements were determined in 40 wines. Of these, 20 elements: Li, B, Mg, Al, Si, Cl, Sc, Mn, Ni, Ga, Se, Rb, Sr, Nb, Cs, Ba, La, W, Tl, and U showed differences in their means across the three areas. In a stepwise discriminant analysis procedure, functions based on linear combinations of the log-transformed element concentrations of Al, Mn, Rb, Ba, W, and Tl were generated to correctly classify wines from each region. In an alternative approach, a pairwise discriminant analysis procedure, not previously used in wine provenance studies, was tested. In this procedure, the classification was done in three steps, with each step classifying a wine as coming from a certain region or not. The combination of elements characterizing wines from a particular region was different in each region. The discriminant functions were based on the following elements: Al, Mn, Rb, Ba, and W for Stellenbosch; Se, Rb, Cs, and Tl for Robertson; and Al, Mn, Rb, Sr, Ba, and Tl for Swartland. After this procedure, the classification of the wines into one of the groups was 100% successful.  相似文献   

A mathematical model of the effects of chronic carriers on the within-herd spread of contagious bovine pleuropneumonia in an African mixed crop-livestock system     

Lesnoff M  Laval G  Bonnet P  Chalvet-Monfray K  Lancelot R  Thiaucourt F 《Preventive veterinary medicine》2004,62(2):101-117

Contagious bovine pleuropneumonia (CBPP) is a respiratory disease of cattle; CBPP is caused by Mycoplasma mycoides subsp. mycoides small colony. CBPP is a major cause for concern for African countries (because of mortality, animal-production losses and cost of control). The clinical form of the disease is the more infectious (contagion occurs essentially through coughing). However, chronic lung lesions with viable mycoplasmas can persist in recovering cattle. Animals presenting these lesions might have a time-delimitated infectious phase. Such carriers are suspected to generate field outbreaks (although this hypothesis remains debated). We investigated the potential quantitative effects of these chronic carriers on the within-herd CBPP spread. Data were collected during a longitudinal field herd survey in a mixed crop-livestock system in the Ethiopian highlands. Two stochastic Markov-chain models' outputs (seroconversion dynamics, basic reproduction ratio R0, cumulative clinical incidence and risk of herd infection) were compared given different hypotheses on the carrier infectiousness. The late seroconversions observed in the field data were fitted correctly only for the highest carrier infectiousness we considered (mean chronic duration of 1 year and carriers 50-times less infectious than clinical cases). Although sensitivities (in terms of disease impact in the herd) were in general negligible when the carrier infectiousness was low (e.g. when carriers were assumed to be 1000-times less infectious than clinical cases), they rapidly became important when the infectiousness increased.  相似文献   

The variation of microfibril angle in South African grown Pinus patula and its influence on the stiffness of structural lumber     

C Brand Wessels  Francois S Malan  Martin Kidd  Tim Rypstra 《Southern Forests》2015,77(3):213-219

Reduction in the rotation ages of softwood saw-log plantations in South Africa is causing increased proportions of low stiffness sawn lumber at final harvest. It has been shown for some species that the microfibril angle (MFA) of the S2 layer of tracheids is strongly related to the modulus of elasticity (MOE) of wood, even more so than wood density, especially in wood formed during juvenile growth. The objectives of this study were to describe the variation in MFA in young Pinus patula trees and to determine the relationship between MFA and the dynamic MOE of sawn P. patula lumber. Thirty 16- to 20-year-old trees from six compartments from the Mpumalanga escarpment were processed into discs and lumber. The MFA, density and ring width were measured at two height levels using Silviscan 3. The average annual ring MFA varied between 7° and 29°; the pattern of variation depended mainly on height level and the ring number from the pith. The MFA in P. patula followed the same within-tree variation trends as in New Zealand-grown Pinus radiata but the average MFA was lower in absolute terms and differences between height levels were less pronounced. The MFA and density exhibited highly significant Pearson correlations of 0.73 and 0.70, respectively, with board dynamic MOE. A multiple regression model, which included MFA, density and ring width, explained 71% of the variation in the dynamic MOE of boards. A sensitivity analysis on the model showed that MFA and density had approximately similar influences on predicting the dynamic MOE of Pinus patula boards.  相似文献   

Phyllosilicate diversity and past aqueous activity revealed at Mawrth Vallis, Mars     

Bishop JL  Dobrea EZ  McKeown NK  Parente M  Ehlmann BL  Michalski JR  Milliken RE  Poulet F  Swayze GA  Mustard JF  Murchie SL  Bibring JP 《Science (New York, N.Y.)》2008,321(5890):830-833

Observations by the Mars Reconnaissance Orbiter/Compact Reconnaissance Imaging Spectrometer for Mars in the Mawrth Vallis region show several phyllosilicate species, indicating a wide range of past aqueous activity. Iron/magnesium (Fe/Mg)-smectite is observed in light-toned outcrops that probably formed via aqueous alteration of basalt of the ancient cratered terrain. This unit is overlain by rocks rich in hydrated silica, montmorillonite, and kaolinite that may have formed via subsequent leaching of Fe and Mg through extended aqueous events or a change in aqueous chemistry. A spectral feature attributed to an Fe2+ phase is present in many locations in the Mawrth Vallis region at the transition from Fe/Mg-smectite to aluminum/silicon (Al/Si)-rich units. Fe2+-bearing materials in terrestrial sediments are typically associated with microorganisms or changes in pH or cations and could be explained here by hydrothermal activity. The stratigraphy of Fe/Mg-smectite overlain by a ferrous phase, hydrated silica, and then Al-phyllosilicates implies a complex aqueous history.  相似文献   

不同光截获下番茄形态结构的动态模拟与比较   总被引：2，自引：0，他引：2  

董乔雪  王一鸣Jean Francois Barczi 贺超兴 《中国农业大学学报》2005,10(5):26-31

为研究不同光截获对番茄植株形态结构的影响，基于结构-功能互反馈建模原理建立了番茄结构-功能模型。采用基于番茄拓扑结构的多目标估算方法，利用实验观测数据对模型进行多目标校准和验证。对局部遮阴和无遮阴栽培条件下番茄植株的生长过程进行动态模拟，并对不同生长阶段番茄植株的形态结构、器官周期累积生物量以及器官三维形态输出进行比较，结果表明：无遮阴栽培条件下，番茄植株茎杆节间短粗，叶片和果实较大。而局部遮阴栽培条件下番茄植株茎杆细长，叶片稀薄，果实较小。不同光截获下模型的输出结果与观测数据拟合较好，验证了模型的有效性。  相似文献   

Methyltransferase recruitment and DNA hypermethylation of target promoters by an oncogenic transcription factor   总被引：1，自引：0，他引：1  

Di Croce L  Raker VA  Corsaro M  Fazi F  Fanelli M  Faretta M  Fuks F  Lo Coco F  Kouzarides T  Nervi C  Minucci S  Pelicci PG 《Science (New York, N.Y.)》2002,295(5557):1079-1082

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Effects of salinity on germination,growth and yield of cowpea   总被引：1，自引：0，他引：1  

D. W. Wests  L. E. Francois 《Irrigation Science》1982,3(3):169-175

Summary Adequate information on salt tolerance is lacking for cowpea (Vigna unguiculata (L.) Walp.), a crop grown under both dryland and irrigated conditions. A two-year field plot study was conducted to determine the responses of both the vegetative and dry seed yield of cowpea to a range of soil salinities. Four salinity levels were imposed each year on a Pachappa fine sandy loam (mixed, thermic, Mollic Haploxeralf). Vegetative growth, dry seed yield, and several components of seed yield were measured.Vegetative yield was decreased more by increasing soil salinity than was dry seed yield. Vegetative growth was reduced 9.0% for each unit increase in electrical conductivity of the soil saturation extract beyond a threshold value of 1.6 dS/m. Dry seed yield was reduced 12% for each unit increase beyond 4.9 dS/m. Fewer pods per plant accounted for nearly all of the seed yield reduction associated with increasing salinity levels.Germination was significantly reduced when electrical conductivity in sand cultures exceeded 12.0 dS/m.  相似文献   

Leaf volatile compounds of six citrus somatic allotetraploid hybrids originating from various combinations of lime, lemon, citron, sweet orange, and grapefruit     

Gancel AL  Ollitrault P  Froelicher Y  Tomi F  Jacquemond C  Luro F  Brillouet JM 《Journal of agricultural and food chemistry》2005,53(6):2224-2230

Volatile compounds were extracted by a pentane/ether (1:1) mixture from the leaves of six citrus somatic allotetraploid hybrids resulting from various combinations of lime, lemon, citron, sweet orange, and grapefruit. Extracts were examined by gas chromatography-mass spectrometry (GC-MS) and compared with those of their respective parents. All hybrids having an acid citrus parent exhibit the same relative contents in hydrocarbons and oxygenated compounds as the acid citrus, while the (grapefruit + orange) hybrid behaves similarly to its two parents. When volatile compound contents (microg g(-1)) are examined in detail, several behaviors are encountered in hybrids and seem to depend on the presence/absence of the considered parental compound and on the corresponding hybrid combination. Meanwhile, the sesquiterpene hydrocarbons are present in all hybrids at concentrations systematically lower than those of the highest parental producers. Statistical analyses show that hybrids exhibit hardly discriminable aromatic profiles, meaning that no strong dominance of one or the other parent was observed in hybrids with regards to the leaf volatile compound production.  相似文献   

Immobilization of nitrogen from urea and plant residues in a ferrallitic soil: Laboratory experiments and study by size-fractionation     

C. Francois  C. Feller  G. Guiraud  J. Loury  J. -P. Boudot 《Biology and Fertility of Soils》1991,12(3):182-188

Summary The fate of N when incorporated in a ferrallitic soil was investigated during a 3-month incubation, using either ¹⁵N-labelled urea or ¹⁵N-labelled crop residues (sugarcane roots and leaves). The organic matter was characterized by particle-size fractionation. The urea-derived organic ¹⁵N was mainly found in the clay-sized fractions and was ascribed to biological activity. The plant-derived ¹⁵N was observed both in the sand-sized and in the clay-sized fractions; the former pool was ascribed to the persistence of crops residues, the latter to biological immobilization. The relative proportions of organic ¹⁵N recovered in the various clay fractions (coarse, fine, and very fine) were similar, irrespective of the nature of the added ¹⁵N. The very fine clay fraction (F<0.05 m) showed the highest isotopic excess, and thus gave rise to the highest turnover rate.  相似文献