排序方式: 共有59条查询结果,搜索用时 46 毫秒
31.
Kathryn M. Irvine Alix I. Gitelman Jennifer A. Hoeting 《Journal of Agricultural, Biological & Environmental Statistics》2007,12(4):450-469
In a spatial regression context, scientists are often interested in a physical interpretation of components of the parametric
covariance function. For example, spatial covariance parameter estimates in ecological settings have been interpreted to describe
spatial heterogeneity or “patchiness” in a landscape that cannot be explained by measured covariates. In this article, we
investigate the influence of the strength of spatial dependence on maximum likelihood (ML) and restricted maximum likelihood
(REML) estimates of covariance parameters in an exponential-with-nugget model, and we also examine these influences under
different sampling designs—specifically, lattice designs and more realistic random and cluster designs—at differing intensities
of sampling (n=144 and 361). We find that neither ML nor REML estimates perform well when the range parameter and/or the nugget-to-sill
ratio is large—ML tends to underestimate the autocorrelation function and REML produces highly variable estimates of the autocorrelation
function. The best estimates of both the covariance parameters and the autocorrelation function come under the cluster sampling
design and large sample sizes. As a motivating example, we consider a spatial model for stream sulfate concentration. 相似文献
32.
Le Gall M Guéguen J Séve B Quillien L 《Journal of agricultural and food chemistry》2005,53(8):3057-3064
The effects of three particle sizes with two types of grindings and two thermal treatments on pea protein extraction (PE) and susceptibility to in vitro enzymatic hydrolysis (pepsin plus trypsin) were studied. Degrees of hydrolysis (DH) were calculated. Remaining peptides were detected by SDS-PAGE and identified by immunoblotting and MS/MS spectrometry. The increase in particle size decreased PE and DH due to a restricted access of solvents and enzymes to proteins. The thermal treatment induced a decrease in PE but did not modify DH. Heating improved legumin (alphaM) and convicilin pepsin hydrolyses but reduced the pea albumin 2 (PA2) hydrolysis. After pepsin and trypsin hydrolysis, only peptides from vicilin and lectin were identified by LC-MS/MS analyses, whatever the treatment. 相似文献
33.
Jérémy Cottes Alix Saquet Ludovic Palayret Olivier Husson Robin Beghin Deonie Allen 《Archives of Agronomy and Soil Science》2020,66(4):473-487
ABSTRACTSoil redox potential (Eh) and pH are fundamentals parameters for plants growth. Measuring soil Eh is essential but complex due to the lack of measurement reliability resulting from high temporal variability and metrological challenges. This paper proposes practical advancements for measuring Eh in aerobic soils using combined electrodes (improvements in methodology specific to cleaning electrodes, measurement time, cleaning the dataset). The study of soil Eh and pH on sunflower and wheat in pot experiments has highlighted the relationship between Ehcumul (Eh associated with a dimension of time) and the portion of porosity that is accessible to air. For reduced soil conditions, sunflower positively reacts to better aeration. Strong correlations exist between the duration of each potential range and the growth of sunflower. The study of sunflower growth in soil reveals extremely harmful impact resulting from too high and/or too low Eh values. 相似文献
34.
Emilie Trehiou-Sechi DVM Luc Behr DVM PhD Valérie Chetboul DVM PhD Jean-Louis Pouchelon DVM PhD Maud Castaignet DVM Vassiliki Gouni DVM Charlotte Misbach DVM Amandine M.P. Petit DVM Nicolas Borenstein DVM PhD 《Journal of Veterinary Cardiology》2011,13(3):219-225
Surgical treatment of mitral stenosis (MS) usually consists of open mitral commissurotomy (MC) or percutaneous balloon MC, which require a cardiopulmonary bypass or transseptal approach, respectively. We describe here the first surgical management of congenital MS in a dog using a less invasive procedure, a surgical closed MC under direct echo guidance. A 5-year-old female Cairn terrier was referred for ascites, weakness, and marked exercise intolerance for 2 months, which was refractory to medical treatment. Diagnosis of severe MS associated with atrial fibrillation (AF) was confirmed by echo-Doppler examination and electrocardiography. Poor response to medical treatment suggested a corrective procedure on the valve was indicated. However, due to the cost and high mortality rate associated with cardiopulmonary bypass, a hybrid MC was recommended. A standard left intercostal thoracotomy was performed and three balloon valvuloplasty catheters of differing diameters were sequentially inserted through the left atrium under direct echo guidance. Transesophageal echocardiography revealed a 62% reduction in the pressure half-time compared to the pre-procedure. Thirteen months after surgery the dog is still doing well with resolution of ascites and a marked improvement of most echo-Doppler variables. 相似文献
35.
James F X Wellehan Lisa L Farina Curry G Keoughan Maud Lafortune Amy M Grooters Leonel Mendoza Murray Brown Scott P Terrell Elliott R Jacobson Darryl J Heard 《Journal of zoo and wildlife medicine》2004,35(4):564-568
A 4.5-yr-old male dromedary camel (Camelus dromedarius) was evaluated for a mass on the right side of the face. A complete blood count and blood chemistry revealed anemia and hypoproteinemia. Radiographs did not reveal bony involvement. The mass was resected and Pythium insidiosum was cultured. The camel was treated with an experimental immunotherapeutic vaccine and with sodium iodide and ceftiofur. The camel began to lose weight postoperatively and died 6 mo later. At necropsy, the camel was found to have gastritis of the third compartment of the stomach with intralesional hyphae of this oomycete pathogen. 相似文献
36.
37.
Xavier Portell Ophélie Sauzet María Balseiro-Romero Pascal Benard Rémi Cardinael Estelle Couradeau Dieudonné D. Danra Daniel L. Evans Ellen L. Fry Edith C. Hammer Danielle Mamba Luis Merino-Martín Carsten W. Mueller Marcos Paradelo Frédéric Rees Lorenzo M. W. Rossi Hannes Schmidt Laura S. Schnee Charlotte Védère Alix Vidal 《European Journal of Soil Science》2021,72(1):31-34
38.
Thomas Steglich Diana Bernin Annelie Moldin Daniel Topgaard Maud Langton 《Cereal Chemistry》2015,92(6):617-623
Whole wheat pasta offers improved nutritional value compared with regular pasta but lacks appeal to many consumers owing to its negative organoleptic properties, such as texture and taste. Various approaches have been studied to improve these properties in whole wheat products. Optimizing bran particle size showed its potential in noodles, but studies of its effects in pasta are scarce. Therefore, we produced spaghetti enriched with bran fractions similar in chemical composition but with varying median particle sizes of 90, 160, 370, and 440 µm. The effect of bran particles and their median size on dried and cooked pasta was studied by light microscopy and three‐dimensional magnetic resonance imaging. In general, bran particle size did not influence the macrostructure in cooked spaghetti. However, larger bran particles created a more heterogeneous microstructure in contrast to smaller particles and affected starch granule swelling. Sensory analysis indicated a preference for pasta containing smaller particles. Our results give new insight into the microstructural features responsible for the negative consumer appeal, and they could be used to guide future efforts in designing improved pasta formulations. 相似文献
39.
Maud VP Charron Georgette Kluiters Michel Langlais Henri Seegers Matthew Baylis Pauline Ezanno 《Veterinary research》2013,44(1):44
Bluetongue (BT) can cause severe livestock losses and large direct and indirect costs for farmers. To propose targeted control strategies as alternative to massive vaccination, there is a need to better understand how BT virus spread in space and time according to local characteristics of host and vector populations. Our objective was to assess, using a modelling approach, how spatiotemporal heterogeneities in abundance and distribution of hosts and vectors impact the occurrence and amplitude of local and regional BT epidemics. We built a reaction–diffusion model accounting for the seasonality in vector abundance and the active dispersal of vectors. Because of the scale chosen, and movement restrictions imposed during epidemics, host movements and wind-induced passive vector movements were neglected. Four levels of complexity were addressed using a theoretical approach, from a homogeneous to a heterogeneous environment in abundance and distribution of hosts and vectors. These scenarios were illustrated using data on abundance and distribution of hosts and vectors in a real geographical area. We have shown that local epidemics can occur earlier and be larger in scale far from the primary case rather than close to it. Moreover, spatial heterogeneities in hosts and vectors delay the epidemic peak and decrease the infection prevalence. The results obtained on a real area confirmed those obtained on a theoretical domain. Although developed to represent BTV spatiotemporal spread, our model can be used to study other vector-borne diseases of animals with a local to regional spread by vector diffusion. 相似文献
40.
Abel Bernadou Régis Céréghino Hugues Barcet Maud Combe Xavier Espadaler Vincent Fourcassié 《Landscape Ecology》2013,28(7):1387-1400
Of particular importance in shaping species assemblages is the spatial heterogeneity of the environment. The aim of our study was to investigate the influence of spatial heterogeneity and environmental complexity on the distribution of ant functional groups and species diversity along altitudinal gradients in a temperate ecosystem (Pyrenees Mountains). During three summers, we sampled 20 sites distributed across two Pyrenean valleys ranging in altitude from 1,009 to 2,339 m by using pitfall traps and hand collection. The environment around each sampling points was characterized by using both physical and land-cover variables. We then used a self-organizing map algorithm (SOM, neural network) to detect and characterize the relationship between the spatial distribution of ant functional groups, species diversity, and the variables measured. The use of SOM allowed us to reduce the apparent complexity of the environment to five clusters that highlighted two main gradients: an altitudinal gradient and a gradient of environmental closure. The composition of ant functional groups and species diversity changed along both of these gradients and was differently affected by environmental variables. The SOM also allowed us to validate the contours of most ant functional groups by highlighting the response of these groups to the environmental and land-cover variables. 相似文献