Two cases of feline ectromelia: autopodium ectromelia associated with humero-ulnar synostosis and zeugopodium ectromelia     

Francesco Macrì  Massimo De Majo  Giuseppe Rapisarda  Giuseppe Mazzullo 《Journal of Feline Medicine and Surgery》2009,11(8):731-734

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Estimating the Risk of a Crop Epidemic From Coincident Spatio-temporal Processes     

Murali Haran  K. Sham Bhat  Julio Molineros  Erick De Wolf 《Journal of Agricultural, Biological & Environmental Statistics》2010,15(2):158-175

Fusarium Head Blight (FHB), or “scab,” is a very destructive disease that affects wheat crops. Recent research has resulted in accurate weather-driven models that estimate the probability of an FHB epidemic based on experiments. However, these predictions ignore two crucial aspects of FHB epidemics: (1) An epidemic is very unlikely to occur unless the plants are flowering, and (2) FHB spreads by its spores, resulting in spatial and temporal dependence in risk. We develop a new approach that combines existing weather-based probabilities with information on flowering dates from survey data, while simultaneously accounting for spatial and temporal dependence. Our model combines two space-time processes, one associated with pure weather-based FHB risks and the other associated with flowering date probabilities. To allow for scalability, we model spatiotemporal dependence via a process convolutions approach. Our sample-based approach produces a realistic assessment of areas that are persistently at high risk (where the probability of an epidemic is elevated for extended time periods), along with associated estimates of uncertainty. We conclude with the application of our approach to a case study from North Dakota.  相似文献   

An empirical equation to calculate soil solution electrical conductivity at 25°C from major ion concentrations     

F. Visconti  J. M. De Paz  J. L. Rubio 《European Journal of Soil Science》2010,61(6):980-993

The electrical conductivity at 25°C (EC₂₅) of soil solutions or irrigation waters is the standard property for assessing salinity. Many models for soil salinity prediction calculate the major ion composition of the soil solution. The electrical conductivity of a solution can be determined from its composition through several different empirical equations. An assessment of these equations is necessary to incorporate the most accurate and precise equations in such models. Twelve different equations for the EC₂₅ calculation were calibrated by means of regression analyses with data from 133 saturation extracts and another 135 1:5 soil‐to‐water extracts from a salt‐affected agricultural irrigated area. The equations with better calibration parameters were tested with another data set of 153 soil solutions covering a wide range of salt concentrations and compositions. The testing was conducted using the standardized difference t‐test, which is a rigorous validation test used in this study for the first time. The equations based on the ionic conductivity decrement given by Kohlrausch's law presented the poorest calibration parameters. The equations founded on the hypothesis that EC₂₅ is proportional to analytical concentrations had worse calibration and validation parameters than their counterparts based on free‐ion concentrations and ionic activities. The equations founded on simpler mathematical relationships generally gave improved validation parameters. The three equations based on the specific electrical conductivity definition presented a mean standardized difference between observations and predictions indistinguishable from zero at the 95% confidence level. The inclusion of the charged ion‐pair concentrations in the equation based on free‐ion concentrations improved its predictions, particularly at large electrical conductivities. This equation can be reliably used in conjunction with chemical speciation software to assess EC₂₅ from the ion composition of soil solutions.  相似文献   

Comparison between indirect and direct spray drift assessment methods     

D. Nuyttens  M. De Schampheleire  P. Verboven  B. Sonck 《Biosystems Engineering》2010,105(1):2-12

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Effect of a cross-flow opening on the performance of a centrifugal fan in a combine harvester: Computational and experimental study     

Mekonnen Gebreslasie Gebrehiwot  Josse De Baerdemaeker  Martine Baelmans 《Biosystems Engineering》2010,105(2):247-256

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A mathematical model linking tree sap flow dynamics to daily stem diameter fluctuations and radial stem growth     

Steppe K  De Pauw DJ  Lemeur R  Vanrolleghem PA 《Tree physiology》2006,26(3):257-273

To date, models for simulating sap flow dynamics in individual trees with a direct link to stem diameter variation include only the diameter fluctuation driven by a change in stem water storage. This paper reports results obtained with a comprehensive flow and storage model using whole-tree leaf transpiration as the only input variable. The model includes radial stem growth based on Lockhart's equation for irreversible cell expansion. It was demonstrated that including growth is essential to obtaining good simulation results. To model sap flow dynamics, capacitance of storage tissues was assumed either constant (i.e., electrical analogue approach) or variable and dependent on the water content of the respective storage tissue (i.e., hydraulic system approach). These approaches resulted in different shapes for the desorption curve used to calculate the capacitance of storage tissues. Comparison of these methods allowed detection of specific differences in model simulation of sap flow at the stem base (F(stem)) and stem diameter variation (D). Sensitivity analysis was performed to select a limited subset of identifiable parameters driving most of the variability in model predictions of F(stem) and D Both the electrical analogue and the hydraulic system approach for the flow and storage model were successfully calibrated and validated for the case of a young beech tree (Fagus sylvatica L.). Use of an objective model selection criterion revealed that the flow and storage model based on the electrical analogue approach yielded better predictions.  相似文献   

热带果树在云南热区农林复合生态农业技术中的应用     

张德  段曰汤  沙毓沧  罗敬萍  马开华  何璐  瞿文林 《西南农业学报》2006,19(Z1):331-336

根据云南热区的自然资源概况,探讨热带果树在本区农林复合生态农业技术中的应用.  相似文献   

Influence of fertilization on acrylamide formation during frying of potatoes harvested in 2003   总被引：3，自引：0，他引：3  

De Wilde T  De Meulenaer B  Mestdagh F  Govaert Y  Vandeburie S  Ooghe W  Fraselle S  Demeulemeester K  Van Peteghem C  Calus A  Degroodt JM  Verhé R 《Journal of agricultural and food chemistry》2006,54(2):404-408

The quality of the potato has been found to vary, when grown under different agricultural and environmental conditions, such as the level of fertilization. Consequently these factors may influence the acrylamide formation during the preparation of French fries. These assumptions were studied on three varieties: Bintje, Ramos, and Saturna from the harvest of 2003. Decreasing N fertilization caused increases in the reducing sugar concentration from 60% up to 100% on DM for all varieties studied. Due to a high correlation between the reducing sugar content and the generation of acrylamide during frying, this resulted in a parallel increase in the acrylamide concentration of the French fries. Thus by lowering the amount of N fertilizer, an increase of 30-65% of the acrylamide generation during frying could be observed. It seems of extreme importance to find an appropriate balance between the level of N fertilizer in order to diminish acrylamide formation but on the other hand to obtain an acceptable tuber and to consider the environmental impact. All results reported should be seen in the perspective of the warm growing season of 2003.  相似文献   

Speciation of phytate ion in aqueous solution. Sequestering ability toward mercury(II) cation in NaClaq at different ionic strengths     

De Stefano C  Milea D  Porcino N  Sammartano S 《Journal of agricultural and food chemistry》2006,54(4):1459-1466

As a contribution to understanding the speciation of mercury in the environment and to the study of the sequestering ability of phytate (Phy) toward heavy metal and organometal cations, this paper describes the results of an investigation (at t = 25 degrees C by potentiometry, ISE-H+ glass electrode) of its interactions with mercury(II) cation in NaCl aqueous solutions at different ionic strengths (I = 0.15 and 1.0 mol L(-1)), in the pH range 2.5 < or = pH < or = 9.5 and considering metal-to-ligand ratios of 1:1 < or = Hg/Phy < or = 4:1. The formation of 11 HgiHjPhy(12-2i-j)(- species with i = 1 and 0 < or = j < or = 7 and i = 2 and 0 < or = j < or = 2 was observed. Their complex formation constant values proved to be fairly dependent on ionic strength. The speciation of phytic acid and mercury(II) is also dependent on the metal-to-ligand ratio; the dependence of the stability of phytate-mercury(II) species on the phytate protonation step was modeled, and an empirical predictive relationship was proposed. From the results obtained, phytate has very good sequestering ability toward Hg2+, even in the presence of considerable excesses of chloride ion, that is, another ligand strongly interacting with mercury; this supports future studies both on the use of plants that naturally synthesize it for phytoremediation purposes and on its direct application in remediation techniques.  相似文献   

The chicken pituitary-specific transcription factor PIT-1 is involved in the hypothalamic regulation of pituitary hormones     

Van As P  Janssens K  Pals K  De Groef B  Onagbesan OM  Bruggeman V  Darras VM  Denef C  Decuypere E 《Acta veterinaria Hungarica》2006,54(4):455-471

Pit-1 is a pituitary-specific POU-domain DNA binding factor, which binds to and trans-activates promoters of growth hormone- (GH), prolactin- (PRL) and thyroid stimulating hormone-beta- (TSHbeta) encoding genes. Thyrotropin-releasing hormone (TRH) is located in the hypothalamus and stimulates TSH, GH and PRL release from the pituitary gland. In the present study, we successfully used the cell aggregate culture system for chicken pituitary cells to study the effect of TRH administration on the ggPit-l* (chicken Pit-1), GH and TSHbeta mRNA expression in vitro. In pituitary cell aggregates of 11-day-old male broiler chicks the ggPit-l * mRNA expression was significantly increased following TRH administration, indicating that the stimulatory effects of TRH on several pituitary hormones are mediated via its effect on the ggPit-l* gene expression. Therefore, a semiquantitative RT-PCR method was used to detect possible changes in GH and TSHbeta mRNA levels. TRH affected both the GH and TSHbeta mRNA levels. The results of this in vitro study reveal that ggPit-1 * has a role in mediating the stimulatory effects of TRH on pituitary hormones like GH and TSHbeta in the chicken pituitary.  相似文献