Ultrastructural findings in congenital anemia, dyskeratosis, and progressive alopecia in Polled Hereford calves.     

D J Steffen  H W Leipold  G S Elliott  J E Smith 《Veterinary pathology》1992,29(3):203-209

Ultrastructural evidence of dyserythropoiesis was found in ten calves (ages 1 to 16 months) previously diagnosed as having congenital anemia, dyskeratosis, and progressive alopecia. Morphologic abnormalities found in erythroid precursors of all calves were associated with the nucleus. Rubriblast nuclei were irregular with numerous blebs, indentations, and deep clefts. Elongated blebs appeared as satellite nuclei in some sections. Nuclear membranes had numerous defects or gaps, which were frequently present in, but not limited to, recently divided cells. Cytoplasmic material could be found within these gaps and extending into the nucleus. Rubricytes had chromatin that was abnormally condensed and hyperosmiophilic, with numerous translucent vacuoles present. Binucleate rubricytes occurred frequently in affected calves. These changes resemble those of type I congenital dyserythropoiesis in human beings, and we suggest congenital anemia, dyskeratosis, and progressive alopecia of Polled Hereford calves as the appropriate diagnostic terms to describe this disease.  相似文献   

Identification of broad-leaved dock (Rumex obtusifolius L.) on grassland by means of digital image processing     

Steffen Gebhardt  Jürgen Schellberg  Reiner Lock  Walter Kühbauch 《Precision Agriculture》2006,7(3):165-178

Digital image processing has the potential to support the identification of plant species required for site-specific weed control in grassland swards. The present study focuses on the identification of one of the most invasive and persistent weed species on European grassland, the broad-leaved dock (Rumex obtusifolius L., R.o.), in complex mixtures of perennial ryegrass with R.o. and other herbs.A total of 108 digital photographs were obtained from a field experiment under constant recording geometry and illumination conditions. An object-oriented image classification was performed. Image segmentation was done by transforming the red, green, blue (RGB) colour images to greyscale intensity images. Based on that, local homogeneity images were calculated and a homogeneity threshold (0.97) was applied to derive binary images. Finally, morphological opening was performed. The remaining contiguous regions were considered to be objects. Features describing shape, colour and texture were calculated for each of these objects. A Maximum-likelihood classification was done to discriminate between the weed species. In addition, rank analysis was used to test how combinations of features influenced the classification result.The detection rate of R.o. varied with the training dataset used for classification. Average R.o. detection rates ranged from 71 to 95% for the 108 images, which included more than 3,600 objects. Misclassifications of R.o. occurred mainly with Plantago major (P.m.). Between 9 and 16% R.o. objects were classified incorrectly as P.m. and 17–24% P.m. objects were misclassified as R.o. The classification result was influenced by the defined object classes (R.o., P.m., T.o., soil, residue vs. R.o., residue). For instance, classification rates were 86–91% and 65–82% for R.o. exclusively and R.o. against the remaining herb species, respectively.  相似文献   

Response of subsoil organic matter contents and physical properties to long-term,high-rate farmyard manure application     

Frederic Leuther  Maximilian Wolff  Klaus Kaiser  Lena Schumann  Ines Merbach  Robert Mikutta  Steffen Schlüter 《European Journal of Soil Science》2022,73(2):e13233

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Feline cerebrovascular disease: clinical and histopathologic findings in 16 cats     

Altay UM  Skerritt GC  Hilbe M  Ehrensperger F  Steffen F 《Journal of the American Animal Hospital Association》2011,47(2):89-97

Sixteen cats with cerebrovascular disease confirmed via histology to be of nontraumatic and nonneoplastic origins are described. In addition, the anatomy of the arterial supply of the cat's brain is reviewed. It is suggested that this unique arterial design may influence the incidence of cerebrovascular accidents in this species. Of the 16 cats reviewed, seven cats had ischemic infarctions, five had hemorrhagic infarctions, and four were diagnosed with intracranial hemorrhage. The median age was 8 yr and 9.5 yr in cats with infarctions and intracranial hemorrhages, respectively. Clinical signs were severe, acute, consistent with the localization of the cerebrovascular lesion, and influenced by underlying pathology. Four cats with infarction showed lateralized neurologic signs. Four cats with infarctions were diagnosed with pulmonary disease antemortem and three cats had hyperthyroidism. Cerebrospinal fluid analysis and computed tomography scans were available in two cats. None of the infarctions were grossly visible. All cats with hemorrhagic infarcts had severe liver pathology and nephritis was identified in four cats. Hypoxia was a feature in four cats and one cat suffered cardiac failure. In conclusion, the clinical picture is influenced by the type of cerebrovascular disease, the localization of the intracranial lesions, and any underlying pathology.  相似文献   

Independent Component Analysis for Three-Way Data With an Application From Atmospheric Science     

Steffen Unkel  Abdel Hannachi  Nickolay T. Trendafilov  Ian T. Jolliffe 《Journal of Agricultural, Biological & Environmental Statistics》2011,16(3):319-338

In this paper, a new approach to independent component analysis (ICA) for three-way data is considered. The rotational freedom of the three-mode component analysis (Tucker3) model is exploited to implement ICA in one mode of the data. The performance of the proposed approach is evaluated by means of numerical experiments. An illustration with real data from atmospheric science is presented, where the first mode is spatial location, the second is time and the third is a set of different meteorological variables representing geopotential heights at various vertical pressure levels. The results show that the three-mode decomposition finds spatial patterns of climate anomalies which can be interpreted in a meteorological sense and as such gives an insightful low-dimensional representation of the data.  相似文献   

Soil‐structure development including seasonal dynamics in a long‐term fertilization experiment     

Steffen Schlüter  Ulrich Weller  Hans‐Jörg Vogel 《植物养料与土壤学杂志》2011,174(3):395-403

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Megacity emissions and lifetimes of nitrogen oxides probed from space     

Beirle S  Boersma KF  Platt U  Lawrence MG  Wagner T 《Science (New York, N.Y.)》2011,333(6050):1737-1739

Megacities are immense sources of air pollutants, with large impacts on air quality and climate. However, emission inventories in many of them still are highly uncertain, particularly in developing countries. Satellite observations allow top-down estimates of emissions to be made for nitrogen oxides (NO(x) = NO + NO(2)), but require poorly quantified a priori information on the NO(x) lifetime. We present a method for the simultaneous determination of megacity NO(x) emissions and lifetimes from satellite measurements by analyzing the downwind patterns of NO(2) separately for different wind conditions. Daytime lifetimes are ~4 hours at low and mid-latitudes, but ~8 hours in wintertime for Moscow. The derived NO(x) emissions are generally in good agreement with existing emission inventories, but are higher by a factor of 3 for the Saudi Arabian capital Riyadh.  相似文献   

BRCA1 tumor suppression depends on BRCT phosphoprotein binding, but not its E3 ligase activity     

Shakya R  Reid LJ  Reczek CR  Cole F  Egli D  Lin CS  deRooij DG  Hirsch S  Ravi K  Hicks JB  Szabolcs M  Jasin M  Baer R  Ludwig T 《Science (New York, N.Y.)》2011,334(6055):525-528

Germline mutations of the breast cancer 1 (BRCA1) gene are a major cause of familial breast and ovarian cancer. The BRCA1 protein displays E3 ubiquitin ligase activity, and this enzymatic function is thought to be required for tumor suppression. To test this hypothesis, we generated mice that express an enzymatically defective Brca1. We found that this mutant Brca1 prevents tumor formation to the same degree as does wild-type Brca1 in three different genetically engineered mouse (GEM) models of cancer. In contrast, a mutation that ablates phosphoprotein recognition by the BRCA C terminus (BRCT) domains of BRCA1 elicits tumors in each of the three GEM models. Thus, BRCT phosphoprotein recognition, but not the E3 ligase activity, is required for BRCA1 tumor suppression.  相似文献   

Surface melt-induced acceleration of Greenland ice-sheet flow   总被引：2，自引：0，他引：2  

Zwally HJ  Abdalati W  Herring T  Larson K  Saba J  Steffen K 《Science (New York, N.Y.)》2002,297(5579):218-222

Ice flow at a location in the equilibrium zone of the west-central Greenland Ice Sheet accelerates above the midwinter average rate during periods of summer melting. The near coincidence of the ice acceleration with the duration of surface melting, followed by deceleration after the melting ceases, indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice-bedrock interface. Interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting, with larger increases accompanying higher amounts of summer melting. The indicated coupling between surface melting and ice-sheet flow provides a mechanism for rapid, large-scale, dynamic responses of ice sheets to climate warming.  相似文献   

A new algorithm for automatic Rumex obtusifolius detection in digital images using colour and texture features and the influence of image resolution     

Steffen Gebhardt  Walter Kühbauch 《Precision Agriculture》2007,8(1-2):1-13

In Gebhardt et al. (2006) an object-oriented image classification algorithm was introduced for detecting Rumex obtusifolius (RUMOB) and other weeds in mixed grassland swards, based on shape, colour and texture features. This paper describes a new algorithm that improves classification accuracy. The leaves of the typical grassland weeds (RUMOB, Taraxacum officinale, Plantago major) and other homogeneous regions were segmented automatically in digital colour images using local homogeneity and morphological operations. Additional texture and colour features were identified that contribute to the differentiation between grassland weeds using a stepwise discriminant analysis. Maximum-likelihood classification was performed on the variables retained after discriminant analysis. Classification accuracy was improved by up to 83% and Rumex detection rates of 93% were achieved. The effect of image resolution on classification results was investigated. The eight million pixel images were upscaled in six stages to create images with decreasing pixel resolution. Rumex detection rates of over 90% were obtained at almost all resolutions, and there was only moderate misclassification of other objects to RUMOB. Image processing time ranged from 45 s for the full resolution images to 2.5 s for the lowest resolution ones.  相似文献