Quasi-non-linear fracture mechanics analysis of splitting failure in simply supported beams loaded perpendicular to grain by dowel joints

A quasi-non-linear fracture mechanics model based on beam on elastic foundation theory is applied for analysis of the splitting failure of dowel joints loaded perpendicular to grain. Simply supported beams symmetrically loaded by two dowels are considered, and the effects of edge distance, dowel spacing, and distance between dowels and supports are accounted for. The foundation modulus used in the beam on elastic foundation model is chosen so that the perpendicular-to-grain tensile strength and fracture energy properties of the wood are correctly represented. This ensures that a conventional stress analysis and failure criterion lead to the same solution as the compliance method of fracture mechanics. A semiempirical efficiency factor is proposed to account for the influence of the total beam depth, which does not enter the beam on elastic foundation model, but the effect of which is evident from tests. It is shown that the so-called Van der Put/Leijten model, which recently has been adopted in Eurocode 5, appears as a special case of the model presented. Tests on simply supported beams with a single dowel joint at midspan are compared with the theoretical predictions. Various edge distances, beam depths, and spans were tested.     

The antimicrobial susceptibility of Staphylococcus species isolated from canine dermatitis

In a retrospective study, 1538 strains of -haemolysin-producing Staphylococcus species isolated from dermatitis in dogs at three veterinary clinical microbiology laboratories in Norway during 1986–87 and 1993–94 were investigated for their antimicrobial susceptibility. None of the strains was resistant to cloxacillin, cephalexin or the quinolones enrofloxacin and ciprofloxacin. More than 96% of the strains were susceptible to trimethoprim-sulphonamide, bacitracin and fucidic acid. Between 67% and 89% of the strains were susceptible to erythromycin, lincosamides, tetracycline, neomycin and chloramphenicol. Only 37.9% of the strains were susceptible to penicillin. The frequency of penicillin resistance increased significantly between the first and second periods, from 46.0% to 58.6%. The frequency of resistance to lincomycin, clindamycin and erythromycin also increased significantly between the first and second periods, from 3.0%, 2.1% and 3.3% to 25.5%, 19.5% and 24.8%, respectively. A moderate increase in resistance to tetracycline was also noted, from 20.4% in the first to 27.6% in the second period. On the other hand, the frequency of resistance to trimethoprim-sulphonamide decreased significantly from 4.1% in the first to 0.9% in the second period. Many different resistance patterns were observed in each period. However, the proportion of multiresistant strains increased from 2.1% in the first to 10.2% in the second period. There was a decrease in resistance to the combination of trimethoprim-sulphonamide and penicillin from the first to the second period. Resistance to the combination of lincosamides and pencillin increased. For the combinations penicillin-tetracycline-lincosamides, pencillin-lincosamides-erythromycin, and pencillin-tetracycline-lincosamides-erythromycin, there was a striking increase in resistance between the first and the second periods.Abbreviations CVL Central Veterinary Laboratory - NCVM Norwegian College of Veterinary Medicine - NVL Norwegian Veterinary Laboratory     

Catalog of Micro-Tom tomato responses to common fungal, bacterial, and viral pathogens

Lycopersicon esculentum cultivar Micro-Tom is a miniature tomato with many advantages for studies of the molecular biology and physiology of plants. To evaluate the suitability of Micro-Tom as a host plant for the study of pathogenesis, Micro-Tom plants were inoculated with 16 well-known fungal, bacterial, and viral pathogens of tomato. Athelia rolfsii, Botryotinia fuckeliana, Oidium sp., Phytophthora infestans, and Sclerotinia sclerotiorum caused typical symptoms and sporulated abundantly on Micro-Tom. Micro-Tom was resistant to Alternaria alternata, Corynespora cassiicola, and Fusarium oxysporum. When Micro-Tom was inoculated with 17 isolates of Ralstonia solanacearum, many isolates induced wilt symptoms. Agrobacterium tumefaciens also was pathogenic, causing crown galls on stem tissue after needle prick inoculation. In Micro-Tom sprayed with Pseudomonas syringae pv. tomato, P. s. pv. tabaci, or P. s. pv. glycinea, bacterial populations did not increase, and yellow lesions appeared only on leaves sprayed with P. s. pv. tomato. Tomato mosaic virus, Tomato aspermy virus, and Cucumber mosaic virus systemically infected Micro-Tom, which developed symptoms characteristic of other cultivars of tomato after infection with the respective virus. These results indicated that Micro-Tom was generally susceptible to most of the important tomato pathogens and developed typical symptoms, whereas certain pathogens were restricted by either hypersensitive resistance or nonhost resistance on Micro-Tom. Therefore, an assortment of Micro-Tom–pathogen systems should provide excellent models for studying the mechanism of susceptible and resistant interactions between plants and pathogens.     

Quantifying patch distribution at multiple spatial scales: Applications to wildlife-habitat models

Multiscale analyses are widely employed for wildlife-habitat studies. In most cases, however, each scale is considered discrete and little emphasis is placed on incorporating or measuring the responses of wildlife to resources across multiple scales. We modeled the responses of three Arctic wildlife species to vegetative resources distributed at two spatial scales: patches and collections of patches aggregated across a regional area. We defined a patch as a single or homogeneous collection of pixels representing 1 of 10 unique vegetation types. We employed a spatial pattern technique, three-term local quadrat variance, to quantify the distribution of patches at a larger regional scale. We used the distance at which the variance for each of 10 vegetation types peaked to define a moving window for calculating the density of patches. When measures of vegetation patch and density were applied to resource selection functions, the most parsimonious models for wolves and grizzly bears included covariates recorded at both scales. Seasonal resource selection by caribou was best described using a model consisting of only regional scale covariates. Our results suggest that for some species and environments simple patch-scale models may not capture the full range of spatial variation in resources to which wildlife may respond. For mobile animals that range across heterogeneous areas we recommend selection models that integrate resources occurring at a number of spatial scales. Patch density is a simple technique for representing such higher-order spatial patterns.     

Finding best exotic breed proportion in crossbred lactating sheep kept under farmers’ conditions in Ethiopia determined by use of nested Legendre polynomials with limited data

ABSTRACT

The present study was conducted to estimate milk production performance and fit lactation curves for groups of ewes of Local and of Awassi crosses, with a variable blood level, reared under farmer’s environment. The Weigh-Suckle-Weigh method plus hand milking was used to estimate milk yield for ewes. A total of 466 observations from 115 ewes were used. Estimated least-squares adjusted means for the milk production over 120 days were 0.56?kg day^?1 (Local), 0.67 (<30% Awassi), 0.86 (30–50% Awassi), and 0.96 (>50% Awassi). Groups with 30–50% Awassi and >50% Awassi ewes produced significantly (p?<?0.05) more milk than Local ewes. Significant differences were observed between <30% Awassi and >50% Awassi crossbred groups. The best crosses (>50% Awassi) produced over 70% more milk than the local ewes which demonstrates the potential that exists in increasing milk production through the initiated crossbreeding programme with sheep in Ethiopia.     

Effects of three short-term pasture allocation methods on milk production,methane emission and grazing behaviour by dairy cows

Two short-term grazing experiments were conducted with Norwegian Red cows. In Exp 1, 24 cows were randomly assigned to one of the following three pasture allocation methods (PAM): weekly pasture allowance (7RG), grazing 1/7 of 7RG each day (1SG), or grazing as 1SG but had access to grazed part of the paddock within one week (1FG). In Exp 2, 7RG was shortened to 5 days (5RG). We hypothesized that PAM will affect sward quality, quantity, intake and production differently. Pasture chemical composition changed with advancing grazing days but were not different between treatments. Pasture intake, milk yield, and methane emission were not affected by PAM. In Exp 1, 7RG cows spent less time on grazing, whereas in Exp 2, 1FG cows spent longer on grazing than others. Patterns observed in sward quality, and behavioural and physiological adaptations of cows to short-term changes in nutrient supply may explain the observed effects.     

Effects of oral supplementation of probiotic strains of Lactobacillus rhamnosus and Enterococcus faecium on diarrhoea events of foals in their first weeks of life

Foal first diarrhoea is one of the most prominent problems in the early life of horses. Probiotics might have the potency to prevent or at least diminish neonatal diarrhoea. We hypothesised that the treatment of foals with probiotic strains of Lactobacillus rhamnosus and Enterococcus faecium starting early after birth and then daily over 2 weeks would prevent or mitigate foal heat diarrhoea. The influence of this probiotic treatment on diarrhoea incidence and growth and health performance of young foals was investigated. Thirty‐four foals were randomly allocated to two groups. From day 1 to 14 of life, the foals received either placebo (PG, n = 16) or the probiotic treatment (TG, n = 18). Clinical examination was performed, and the faeces consistency score (FCS, 1–5; with diarrhoea defined by ≤3) was recorded once per day in weeks 1 and 2 and once weekly in weeks 3–8 of life (WL). The body height was measured at birth and after two and eight WL. Diarrhoea occurred in the 1st WL in 19% and 61% of PG and TG foals respectively. In the 1st WL, diarrhoea lasted 0.3 ± 0.8 and 1.6 ± 1.4 days in PG and TG foals respectively. In the 2nd WL, diarrhoea occurred in 94% and 84% of PG and TG foals, respectively, and lasted for 3.0 ± 1.5 and 3.7 ± 1.6 days respectively. At least two periods of diarrhoea developed in 33% and 65% of PG and TG foals respectively. The TG foals grew slightly slower than the PG foals. The results indicated that the probiotic treatment of neonatal foals as performed in this study was not suitable to reduce diarrhoea within the first two WL, because contrary to the hypothesis, the TG foals suffered more frequently and for longer periods from diarrhoea than the PG foals.