On the theory of elasticity of the orthotropic material wood

Summary Aim of this study is to determine the basic equations concerning the second boundary value problem of the theory of elasticity in particular for construction wood. For rhombic orthotropic materials, as represented for example by straight grained wooden constructions, the equations are calculated in Cartesian co-ordinates. For cylindrical orthotropic materials, as represented for example by curved laminated beams, the equations are calculated in cylindrical co-ordinates. In both cases the equations are determined for space stress problems. Assuming the plain stress condition the basic equations of plain stress problems can then be derived from the spatial equations.     

Laser rangefinder-based measuring of crop biomass under field conditions

Knowledge of site-specific crop parameters such as plant height, coverage and biomass density is important for optimising crop management and harvesting processes. Sensors for measuring crop parameters are essential pre-requisites to gather this information. In recent years, laser rangefinder sensors have been adopted in many industrial applications. In agricultural engineering, the potential of laser rangefinders for measuring crop parameters has been little exploited. This paper reports the design and the performance of a measuring system based on a triangulation and a time-of-flight laser rangefinder for estimating crop biomass density in representative crops under field conditions. It was shown that the mean height of reflection point is a suitable parameter for non-contact indirect measurement of crop biomass by laser rangefinder sensors. The main parameters for potential assessment were the coefficient of determination (R ² ) and the standard error (RMSE) for the relation between crop biomass density and the mean height of the reflection point in crop stands from oilseed rape, winter rye, winter wheat and grassland during the vegetation period in 2006. For the triangulation sensor, R ² was in the range from 0.87 to 0.98 and for the time-of-flight sensor in the range from 0.75 to 0.99 for both fresh matter and dry matter density. The triangulation sensor had a reduced suitability caused by masking effects of the reflected beam and because of limited measuring range. Based on the results of experiments and technical data, it was concluded that the time-of-flight principle has good potential for site-specific crop management.     

Contact structure and potential risk factors for avian influenza transmission among open-sided chicken farms in Kamalia, an important poultry rearing area of Pakistan

Since 1994, the domestic poultry in Pakistan has experienced several outbreaks due to avian influenza viruses of subtypes H7N3, H5N1, and H9N2. This paper reveals horizontal contacts and potential risk factors for the spread of avian influenza infection between open-sided chicken farms in Kamalia, a sub-district of Punjab province. Between April and June 2009, an interview-based questionnaire was administered to a sample of 78 growers. The survey identified the following potential biosecurity risks for outbreak propagation: i) short buffer distances between farms, ii) disposal of carcasses and other organic wastes into the environment, iii) entry of feral birds into poultry sheds, iv) visits of poultry farmers to possible cross-contamination sites, v) absence of boundary walls, vi) incomplete biosecurity on high-risk visitors (i. e. those going inside the poultry houses), essential vehicles and equipment used by vaccination crews vii) visits of intermediaries and service providers and, viii) sharing of egg trays between farms at production. For most of the variables, there was no significant difference between the broiler and layer type of farms (p < or = 0.05). The risk of an extensive outbreak in Kamalia was concluded to be due to its high poultry density, ubiquitous small-scale, market-oriented poultry production with medium to low biosecurity, and the affiliation of the farmers to multiple service providers. To reduce the risk of having an outbreak, farm-specific biosecurity gaps should be identified and appropriate action taken to close these gaps. Improvement in biosecurity and targeted surveillance are therefore considered critical to limit the spread of infection should an outbreak occur.     

Depth transfer of fecal indicator organisms in an arable clayey soil

In clayey soils, shrinking cracks formed during dry periods in the summer are the most important form of macropores. They may contribute under disadvantageous conditions to the movement of fecal microorganisms and therefore to the contamination of groundwater. For this reason, a field experiment was carried out on a highly clayey arable soil to investigate the effect of the factors slurry addition, sampling date, depth, and season. Under worst case conditions, i.e. a soil at field capacity, irrigated directly after application of fresh cattle slurry with high rates of water, the numbers of spores, total coliforms, fecal coliforms and fecal streptococci were not significantly increased at depths of 15 cm, 45 cm and 75 cm in spring (with less shrinking cracks) or in autumn (with more shrinking cracks). The close correlations between the numbers of spores, total coliforms, aerobic bacteria and microbial biomass C indicate that spore forming organisms and most total coliforms belong to the autochthonous soil microflora and cannot indicate fecal pollution.     

An approach to extrapolate categorical agricultural soil data to nonmapped areas using majority vote

Soil maps are indispensable base material for planning processes and risk analyses. For many studies, however, area‐wide uniformly scaled soil maps are not available. Our objective was to develop a GIS‐based method for providing information for NoData areas of the Medium‐Scale Agricultural Site Mapping (MMK). NoData areas represent nonagricultural zones, in this case especially forests. A grid‐based methodology for extrapolating soil mapping units of agricultural areas to the entire landscape was developed and tested in Mecklenburg–Western Pomerania (total area 23,170 km²). The principle of the extrapolation method is based on a statistical neighborhood analysis implemented by the moving‐window technology considering selected site features as geology, altitude, and relief energy. Results were illustrated exemplarily for soil‐moisture conditions, which are expressed as “hydromorphy association types”. Four different indicators were derived to ensure a spatially differentiated evaluation of the extrapolation quality. The precision with which it is possible to extrapolate already mapped MMK units in terms of the hydromorphy association type was used to validate the extrapolation method. Evaluation of the results was based on the percentage of Correctly Extrapolated Pixels (CEP), which were derived from a confusion matrix. The percentage of CEP was 26% when the 15 single classes of the hydromorphy association type were considered separately. The percentage of CEP rose up to 65% after grouping the hydromorphy association types into three practically combined categories. It could be demonstrated that the extrapolation technique applied represented an objective and relatively fast and cost‐effective method to obtain an area‐wide MMK mapping.     

Climate and the collapse of Maya civilization

In the anoxic Cariaco Basin of the southern Caribbean, the bulk titanium content of undisturbed sediment reflects variations in riverine input and the hydrological cycle over northern tropical South America. A seasonally resolved record of titanium shows that the collapse of Maya civilization in the Terminal Classic Period occurred during an extended regional dry period, punctuated by more intense multiyear droughts centered at approximately 810, 860, and 910 A.D. These new data suggest that a century-scale decline in rainfall put a general strain on resources in the region, which was then exacerbated by abrupt drought events, contributing to the social stresses that led to the Maya demise.     

COMPUTED TOMOGRAPHIC DETERMINATION OF TIBIAL TORSION IN THE DOG

The goal of this study was to develop a method for computed tomographic (CT) measurement of tibial torsion, and to compare this technique with direct anatomic measurement of tibial torsion in cadaveric canine tibiae. Paired hind limbs of 10 cadaveric dogs were mounted on a custom-designed limb holding apparatus. One-millimeter thick, contiguous, transverse CT slices were obtained from the distal femur to the proximal tibia and 2 mm CT slices were obtained from the distal tibia to the proximal tarsus. The tibiae were freed of soft tissues and digital photographic images of the proximal and distal articular surfaces were obtained with the camera lens aligned perpendicular to the long axis of the tibia. Multiple proximal and distal tibial axes were identified on the images; two proximal and two distal axes were found to be repeatable in all specimens in both the direct and CT methods. The torsion angle was calculated by determining the difference between the axis angles for each pair of proximal and distal axes. There was no significant difference in torsion angle identified between the direct photographic and CT method for any pair of proximal and distal axes. CT determination of tibial torsion is a rapid and accurate method, and warrants investigation in clinical patients.     

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