Fracture mechanics analysis of row shear failure in dowelled timber connections

A quasi-nonlinear fracture mechanics model is presented for the analysis of row shear failure in timber connections with multiple fasteners in a row. A prerequisite for use of the model is a known distribution on the fasteners of the total applied load. It is shown that the ideal plastic and linear elastic fracture mechanics solutions appear as special cases of the quasi-nonlinear model. The model offers strength predictions that include the effect of among others the number of fasteners in a row, fastener spacing, row spacing, end-distance, edge-distance, fastener diameter, and material properties, such as shear strength, fracture energy, and modulus of elasticity. Simple explicit expressions are obtained from the analysis for any known fastener load distribution. For bolted connections, where bolt-hole gaps cause high loads on certain bolts at random, the model may be used in simulation procedures or in probabilistic models.     

Consumer perception of wood surfaces: the relationship between stated preferences and visual homogeneity

Information about people’s preferences as to wood products is of relevance to several decision makers in the forest sector. Studies revealing consumer preference provide information that can be used for marketing and manufacturing of wood products, but these also provide information of relevance to designers and decision makers involved in building design and construction processes. Previous studies show that the overall harmony of the visual surface is correlated with preference. In this study, perceived visual homogeneity is modeled for five copper-impregnated and five organic biocide-impregnated decking materials with different visual quality. The models are based on visual variables. Homogeneity is a function of material-dependent variables (dry knots, knot shape, and splay knot), production-dependent variables (stain), and surplus color, which is a combination of both wood property and treatment. The results imply that homogeneity is influenced by both wood properties and treatment. Producers of decking should, while maintaining a focus on using high-quality raw material, also focus on producing a product with an unstained appearance.     

Effect of β -glucanase and xylanase supplementation of barley- and rye-based diets on caecal microbiota of broiler chickens

1. The aim was to investigate the effect of grain type (barley or rye) and exogenous enzymes (β-glucanase or xylanase) on the composition of chicken caecal microbiota as examined by classical culturing and molecular techniques (fluorescent in-situ hybridisation (FISH) and terminal-restriction fragment-length polymorphism (T-RFLP)). 2. Plate counting revealed higher total numbers of anaerobic bacteria, lactic acid bacteria and yeasts in caecal contents of birds fed with rye-based diets than in birds fed with barley-based diets. 3. As assessed by FISH analysis, the most abundant bacterial groups in the broiler caeca were Clostridium coccoides-Eubacterium rectale followed by Bacteroides sp., Lactobacillus sp./Enterococcus sp., Bifidobacterium sp. and Enterobacteriaceae. For both cereal types, the enzyme supplementation significantly decreased the relative amount of Enterobacteriaceae. 4. The T-RFLP profiles indicated that the caecal microbiota of birds receiving rye-based diets was more diverse than that of birds fed on barley-based diets. 5. Irrespective of the method applied, the results indicate that the cereal type as well as the exogenous enzyme supplementation influence the microbiota in broiler chicken caeca, and may have the effect of reducing potentially pathogenic Enterobacteriaceae populations.     

Forage herbs improve mineral composition of grassland herbage

Provision of an adequate mineral supply in the diets of ruminants fed mainly on grassland herbage can present a challenge if mineral concentrations are suboptimal for animal nutrition. Forage herbs may be included in grassland seed mixtures to improve herbage mineral content, although there is limited information about mineral concentrations in forage herbs. To determine whether herbs have greater macro‐ and micromineral concentrations than forage legumes and grasses, we conducted a 2‐year experiment on a loamy‐sand site in Denmark sown with a multi‐species mixture comprised of three functional groups (grasses, legumes and herbs). Herb species included chicory (Cichorium intybus L.), plantain (Plantago lanceolata L.), caraway (Carum carvi L.) and salad burnet (Sanguisorba minor L.). We also investigated the effect of slurry application on the macro‐ and micromineral concentration of grasses, legumes and herbs. In general, herbs had greater concentrations of the macrominerals P, Mg, K and S and the microminerals Zn and B than grasses and legumes. Slurry application indirectly decreased Ca, S, Cu and B concentrations of total herbage because of an increase in the proportion of mineral‐poor grasses. Our study indicates that including herbs in forage mixtures is an effective way of increasing mineral concentrations in herbage.     

Insect larvae meal as an alternative source of nutrients in the diet of Atlantic salmon (Salmo salar) postsmolt

Two insect meal (IM) products were tested as ingredient in diets for Atlantic salmon weighing ~250 g. The modern control diet contained 200 g kg^?1 fish meal (FM100), which was stepwise replaced by insect meal A (IM A) as a 25% (A25), 50% (A50) or 100% (A100) FM replacement or insect meal B (IM B) as a 25% (B25) or 100% (B100) FM replacement. Selected nutrient parameters and contaminants were measured in the diets. After 15 weeks, fish length and weight were recorded and visceral and hepatic indices calculated. Fatty acid and amino acid digestibility was calculated. Morphology of the liver, kidney, mid‐ and hind intestine was evaluated. Finally, a sensory testing of the fillets was conducted. A25, A50 and A100 performed equally well as the FM100 diet. The feed intake decreased moderately with increasing IM A inclusion; however, food conversion ratio decreased, resulting in an equal net growth of the fish. Histology did not show any differences between any of the dietary groups, and sensory testing of fillets from FM100, A100 and B25 did not reveal any significant differences in odour, flavour/taste or texture between groups. IM A was suitable to replace up to 100% of dietary FM, whilst IM B did not perform equally well.     

Holding wild caught red king crab,Paralithodes camtschaticus: effects of stocking density and feeding on survival and meat content

In this study, the effects of different stocking densities on survival, injury and meat content of captive male red king crab (mean weight = 2.6 kg) were examined. The first experiment was carried out in square plastic tanks with stocking densities of 100, 150 and 200 kg m^?3 for 56 days. In a second experiment, king crabs were kept at a stocking density of 60 kg m^?3 and were either fed or not fed. Both mortality and occurrence of injuries increased significantly with increasing stocking density. In the highest density groups, mortality and frequency of injury was 17% and 14% respectively, compared with 5% and 4% in the 150 kg m^?3 group. The percentage meat content was significantly lower at the final census compared with the initial census in all stocking density groups. In Experiment 2, there were no mortalities or injuries in either the fed or unfed treatments. The average percentage meat content increased in the fed treatment and decreased in the starved treatments. The results show that adult male king crab can maintain high survival rates at stocking densities up to 150 kg m^?3 in holding facilities of the design used in the present study for periods up to 2 months. However, to reduce mortality and frequency of injury over this period densities as low as 60 kg m^?3 and a holding system with a large bottom surface area are recommended.     

Replacement of the European wheat yellow rust population by new races from the centre of diversity in the near‐Himalayan region

Isolates of recently spreading races of yellow rust from wheat and triticale in Europe were analysed using virulence phenotypic data of 2605 isolates sampled in 12 countries between 2000 and 2014. A subset of 239 isolates was investigated by microsatellite markers. At least three races of non‐European origin, termed ‘Warrior’, ‘Kranich’ and ‘Triticale aggressive’, were identified in the post‐2011 population. The Warrior race was already present in high frequencies in the first year of detection in most European countries and to a large extent it replaced the pre‐2011 European population. In contrast, the two other exotic races were localized to certain regions and/or crop type. The presence already of at least six multilocus genotypes of the Warrior race and five genotypes of the Kranich race in the first year of detection and across large areas is consistent with a hypothesis of aerial spread from genetically diverse source populations. A comparison with reference isolates sampled from six continents suggested that the Warrior and Kranich races originated from sexually recombining populations in the centre of diversity of the yellow rust fungus in the near‐Himalayan region of Asia. However, the Triticale aggressive race was most similar to populations in the Middle East/Central Asia. The study illustrated the potential role of sexual Puccinia striiformis populations as a reservoir for new races replacing distant clonal populations.     

Population genetics of Phytophthora infestans in Denmark reveals dominantly clonal populations and specific alleles linked to metalaxyl‐M resistance

Control of the potato late blight pathogen Phytophthora infestans relies heavily on chemicals. The fungicide metalaxyl‐M (Mefenoxam) has played an important role in controlling the disease, but insensitivity to the fungicide in certain isolates is now of major concern. A genetic basis for resistance to metalaxyl suggests the possibility for linking resistance phenotypes to specific population genetic markers, but in order to do this, the population genetic structure and mode of reproduction in a population must first be well described. The dynamics of metalaxyl‐M resistance in the Danish population of P. infestans was characterized over the course of the 2013 growing season, as was the population genetic structure, using simple sequence repeat (SSR) genotypes and single nucleotide polymorphism (SNP)‐based mitochondrial haplotyping of over 80 isolates. Both mating types A1 and A2 were present in most fields, but tests for recombination showed that clonal reproduction dominates in Danish populations. Genotype was not linked to haplotype and no differentiation was observed at the haplotype level, but rather between fields. Resistance phenotypes were linked to specific SSR alleles, demonstrating the potential for a more precise SNP‐based marker system for predicting resistance to metalaxyl‐M.     

A Brave New World in Seafood Science and Technology

Arrowtooth flounder was found to be a suitable raw material for the production of surimi. Based on SDS-PAGE and autolysis tests, proteolytic activity was not observed during the production process itself, and the 12% residual activity in the mince after washing was effectively inhibited by bovine plasma powder, egg white and a2 macroglobulin. Plasma and egg white continued to increase gel strength values when added at levels higher than necessary to prevent proteolytic activity according to punch test results. Neither carrageenan nor whey protein concentrate were effective as either a protease inhibitor or gel enhancer.     

Influence of Dietary Lipid and Protein Sources on the Sensory Quality of Organic Rainbow Trout (Oncorhynchus mykiss) After Ice Storage

The influence of dietary protein and lipid sources on the quality of organic rainbow trout (Oncorhynchus mykiss) was studied. The protein and oil sources were fishmeal, fish oil, and organic vegetable protein and oils. Sensory profiling was performed during 3 to 14 days of ice storage along with lipid analyses of the fillet. Overall, the results showed that the sensory characteristics of the trout were affected in different ways during ice storage. The source of lipid seemed to affect the sensory quality at the beginning of the storage period, while the protein source seemed to have a more pronounced impact at the end of the storage period.