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91.
As water moves inside the wood, the gluelines might act as barriers that are potentially leading to local moistening. Even low amounts of water may influence the mechanical performance of glued wood products. Dynamic vapor sorption analysis was performed to assess the sorption processes of six commercial wood adhesives. Vapor sorption isotherms were compared with vapor uptake dynamics. Phenol–resorcinol–formaldehyde showed high moisture uptake of 18 %, while vapor diffusion speed was low. Fish glue showed a water uptake of 45 % at otherwise moderate vapor uptake speed. Melamine–formaldehyde resin gained 22 % water, and polyvinyl acetate absorbed 10 %. The latter was also the fastest vapor absorbing adhesive. Polyurethane only absorbed 3.5 % of moisture at medium uptake speed. Mechanisms of water diffusion seem to be driven by (1) the available free volume in the polymer and (2) the interacting ionic groups of the polymer chain. While the free volume could be linked to the accumulated moisture, the ionic group interaction might determine the measured vapor diffusion dynamics. 相似文献
92.
Oliver Tendayi Zishiri Schalk Willem Cloete Johannes Jacobus Olivier Kennedy Dzama 《Tropical animal health and production》2013,45(2):517-524
Genetic trends were constructed to monitor the genetic change for subjectively assessed and objectively measured traits using data emanating from complete records from the National Small Stock Improvement Scheme database and performance records accumulated by a single breeder over a period of 24 years. The objectively measured production traits considered were weaning weight, post-weaning weight (PWW), yearling weight, average daily weight gain to weaning (ADGW), average daily weight gain during post-weaning phase (ADGPW) and average daily weight gain up to yearling age. The subjectively assessed traits (scored on a five-point scale) were conformation, fat distribution, size, type and colour. Direct genetic trends for live weight and growth traits (with the exception of ADGPW) were positive. All the objectively measured traits where maternal effects were significant, except PWW, registered small declines in maternal breeding values. The fastest genetic progress was attained by ADGW, which amounted to 0.29 % of the overall phenotypic mean per annum. Conformation and type exhibited positive but slow increments in direct breeding values at an equivalent annual rate amounting to 0.12 and 0.09 % of the overall phenotypic mean, respectively. Size demonstrated a negative genetic trend of ?0.14 % of the overall phenotypic mean per annum. Genetic trends for fat distribution and colour were negligible. It was concluded that breeders should focus more on the performance recording of objective traits as they are likely to respond favourably to selection pressure. 相似文献
93.
A-MB Oliver DM Leathwick TS Waghorn CM Miller DS Atkinson 《New Zealand veterinary journal》2013,61(6):383-387
Abstract AIM: To determine whether the fungicide, carbendazim, as applied to pastures for controlling facial eczema (FE), would inhibit development of the free-living stages of the gastrointestinal nematode parasite Trichostrongylus colubriformis. METHODS: Two studies were conducted, using sheep faeces containing eggs of T. colubriformis. In the first, the faeces were either exposed or not to an application of carbendazim sprayed at the recommended rate for FE control. After spraying, dishes containing the faeces were incubated at 20°C for 14 days, and the resulting third-stage infective larvae (L3) extracted by baermannisation and counted. In addition, naturally infested pasture was also sprayed, and the number of L3 present 7 days later was assessed by cutting herbage samples and extracting larvae by soaking in water and baermannisation. In the second, the faeces were incubated at 20°C for 0, 3 or 7 days before being exposed to no, one or two applications of carbendazim. After further incubation for 14, 11 or 7 days, L3 were similarly extracted by baermannisation and counted. RESULTS: In the first study, there was a 74% reduction in the number of T. colubriformis larvae recovered from faeces exposed to carbendazim compared with faeces not exposed, but there was no reduction in the number of L3 recovered from herbage. In the second study, faeces incubated for 0 or 3 days prior to exposure to a single application of carbendazim yielded 98% or 89% fewer larvae, respectively, than faeces not exposed. Faeces incubated for 7 days prior to exposure yielded similar numbers of larvae to faeces not exposed. CONCLUSION: Treatment of pastures with carbendazim for FE control is likely to result in reduced development of the larvae of T. colubriformis, and by inference those of other species, where the application coincides with the presence of freshly deposited faeces containing eggs and developing larvae. However, no effect of treatment on L3 was indicated. The significance of this for on-farm nematode parasite control remains to be determined, as does any potential for strategic applications of carbendazim to pasture aimed at reducing numbers of parasite larvae on pasture. The latter should not be contemplated without due consideration of the implications for the development of anthelmintic resistance. 相似文献
94.
Abstract AIM: To examine the effect of an anthelmintic treatment to lambs, followed immediately by a shift onto pastures with differing levels of larval contamination, on the development of anthelmintic resistance, in order to support recommendations to farmers regarding drench-and-shift practices for sustainable worm control. METHODS: Newly weaned Romney lambs (n=72) were dosed with third-stage infective larvae (L3) of two nematode parasite species, Teladorsagia (=Ostertagia) circumcincta and Trichostrongylus colubriformis, comprising benzimidazole-resistant and -susceptible isolates, calculated to yield, after treatment with albendazole, a 95% reduction in faecal nematode egg count (FEC). Once infections became patent (Day 0), lambs were randomised into nine groups of eight animals, treated with albendazole at the manufacturer's recommended dose rate, and moved to individual pastures each previously prepared to have one of three different levels of parasite larval infestation (Treatment 1 = low contamination, Treatment 2 = medium contamination, and Treatment 3 = high contamination), and grazed on those pastures before receiving a second treatment with albendazole at Day 47. Anthelmintic resistance status in each group of lambs was measured using FEC reduction (FECR) and egghatch assays (EHA) after the first anthelmintic treatment, and FECR after the second treatment. RESULTS: Egg-hatch assays demonstrated significant differences between treatments. The concentration of anthelmintic required to kill 50% of the eggs (LC50) for Treatment 1, comprising the least contaminated pastures, was significantly higher than for Treatments 2 and 3 on Days 33 and 40. Treatment 1 also had a significantly lower FECR at the final anthelmintic treatment, and significantly lower FEC than the other two treatments from Days 26 to 47. CONCLUSIONS: The results demonstrated that the populations of T. circumcincta and T. colubriformis in lambs treated with anthelmintic had significantly higher levels of albendazole resistance at the end of the grazing period in lambs moved onto pastures with relatively low levels of parasite contamination than those moved onto pastures with relatively higher contamination, confirming drench-and-shift onto ‘clean’ pasture as a high-risk practice for the selection for anthelmintic resistance. While this does not necessarily preclude the use of this practice it does emphasise the importance of taking appropriate remedial action to minimise the risk. 相似文献
95.
R.E. Oliver B.V.Sc. G.W. Horner B.V.Sc. M.Sc. R. Hunter F.I.M.L.T. W. Niederer B.V.Sc. 《New Zealand veterinary journal》2013,61(7):135-137
Abstract Extract Parainfluenza type 3(Pl3) virus has been associated with upper respiratory disease of cattle in many countries (Hoerlein et al., 1959; Bögel, 1961; Reisinger, 1962; Jolly and Ditchfield, 1965). However, PI3 virus has not been isolated from cattle with respiratory disease in New Zealand although a serological study found that 89.3% of cows had significant levels of antibody against PI3 virus (Pastier and Hansen, 1966). In most cases infections are subclinical, and there is little evidence to suggest that PI3 virus is an important cause of disease in New Zealand cattle (Jolly, 1967). This communication records an outbreak of upper respiratory disease in cattle from which PI3 virus was isolated. 相似文献
96.
DM Leathwick TS Waghorn CM Miller DS Atkinson NA Haack A-M Oliver 《New Zealand veterinary journal》2013,61(6):305-312
AIM: To determine whether drenching regimes for lambs by which a proportion (10%) of the heaviest animals was selectively left untreated, or animals are only drenched ‘on demand’ when faecal nematode egg counts (FEC) exceeded a threshold level, would result in measurable increases in parasite larval challenge in the autumn and/or decreases in the performance of lambs. METHODS: A replicated study compared three drenching strategies in which mobs of lambs (n=360 in total) received either: a five-drench preventive programme, administered to all animals (Treatment 1); a five-drench preventive programme, but the 10% heaviest animals left untreated each time (Treatment 2); or drench treatments administered only when FEC exceeded 500 eggs per gram of faeces (epg) (Treatment 3). After the five-drench programme, animals in Treatments 1 and 2 were treated according to FEC as for Treatment 3. A triple-combination drench containing ivermectin, oxfendazole and levamisole, administered orally, was used for all treatments. There were nine farmlets, allowing three replicates of each treatment, in a completely randomised design. Parasite infestations on pasture were measured in autumn by pasture plucks, and worm burdens were monitored in tracer lambs, while the performance of lambs was assessed by liveweight gains, fleece weights, and body condition and dag scores. RESULTS: Increased numbers of Haemonchus contortus and Trichostrongylus colubriformis larvae on pasture were found in the autumn on farmlets treating selectively or on-demand (Treatments 2 and 3). No differences were detected in other parasite species. Mean liveweight gains did not differ between treatments but some differences were detected between drenched and undrenched lambs in Treatment 2. Mean body condition and mean dag scores of lambs in Treatment 3 tended to be lower and higher, respectively, than those of lambs in Treatment 1; Treatment 2 was generally intermediate. CONCLUSIONS: Drenching strategies for lambs designed to slow the development of anthelmintic resistance, by increasing the pool of susceptible worms available to dilute resistant survivors after treatment, resulted in increased numbers of H. contortus and T. colubriformis but not other species of parasite on pasture. The increased parasite challenge to lambs in the autumn was associated with small production losses, which may be acceptable to farmers wishing to implement such strategies. It is clear that further work is required on the interaction between management practices and the population dynamics of parasites, especially with regard to creating pools of susceptible genotypes to slow the development of drench resistance. 相似文献
97.
Observational studies and clinical trials suggest nut intake, including almonds, is associated with an enhancement in antioxidant defense and a reduction in the risk of cancer and cardiovascular disease. Almond skins are rich in polyphenols (ASP) that may contribute to these putative benefits. To assess their potential mechanisms of action, we tested the in vitro effect of ASP extracted with methanol (M) or a gastrointestinal juice mimic (GI) alone or in combination with vitamins C (VC) or E (VE) (1-10 micromol/L) on scavenging free radicals and inducing quinone reductase (QR). Flavonoid profiles from ASP-M and -GI extracts were different from one another. ASP-GI was more potent in scavenging HOCl and ONOO (-) radicals than ASP-M. In contrast, ASP-M increased and ASP-GI decreased QR activity in Hepa1c1c7 cells. Adding VC or VE to ASP produced a combination- and dose-dependent action on radical scavenging and QR induction. In comparison to their independent actions, ASP-M plus VC were less potent in scavenging DPPH, HOCl, ONOO (-), and O 2 (-) (*). However, the interaction between ASP-GI plus VC promoted their radical scavenging activity. Combining ASP-M plus VC resulted in a synergistic interaction, inducing QR activity, but ASP-GI plus VC had an antagonistic effect. On the basis of their total phenolic content, the measures of total antioxidant activity of ASP-M and -GI were comparable. Thus, in vitro, ASP act as antioxidants and induce QR activity, but these actions are dependent upon their dose, method of extraction, and interaction with antioxidant vitamins. 相似文献
98.
Hardsetting soil properties are undesirable in agricultural soils because they hamper crop production by limiting seedling emergence and root growth via increased mechanical soil resistance at low moisture contents. The objective of this study was to determine the effect of additions of organic matter on the penetration resistance of a hardsetting soil for the entire water tension range. Investigations were carried out on Saalian glacial till, which is used as a reclamation substrate in post-lignite-mining reclamation. Proportions of 0%, 1%, 2%, 3% and 4% by mass of organic matter (OM) were used. The remoulded samples were saturated under a constant load of 2.4 kPa to achieve bulk densities equivalent to a soil depth of 15–20 cm via water-induced consolidation. Subsequently, the mixtures were adjusted to water tensions between 100 and 107 hPa and penetrated using a small cone penetrometer. Compared to 0% OM, the addition of 1% OM led to a very small but significant (P < 0.01) increase in the bulk density, while between 1% and 4% OM bulk density was seen to decrease in a linear fashion. At moisture contents greater than field capacity, penetration resistance values were consistent with the observed changes in bulk density, leading to an increase in the samples containing 0–1% OM to critical values for root-growth and a decrease for samples containing 2% and more organic matter reaching to values non-critical for roots. At moisture contents smaller than field capacity, penetration resistance values were inversely related to the bulk density, supporting the concept that the type of organic matter added contributed to soil cohesion. Modeling the relation between water tension and penetration resistance using a sigmoidal equation showed a high consistency between the observed data and the model. 相似文献
99.
100.
Booker CW Abutarbush SM Morley PS Guichon PT Wildman BK Jim GK Schunicht OC Pittman TJ Perrett T Ellis JA Appleyard G Haines DM 《The Canadian veterinary journal. La revue veterinaire canadienne》2008,49(3):253-260
The aim of this study was to investigate the effect of bovine viral diarrhea virus (BVDV) infections (unapparent acute infections and persistent infections) on the overall health and performance of feedlot cattle. Calves from 25 pens (7132 calves) were enrolled in the study. Overall and infectious disease mortality rates were significantly higher (P < 0.05) in pens categorized at arrival as positive for type I BVDV and lower in pens that were positive for type II BVDV than in negative pens. Mortality attributed to BVDV infection or enteritis was significantly more common (P < 0.05) in the pens containing persistently infected (PI) calves than in pens not containing PI calves (non-PI pens). There were no statistically detectable (P > or = 0.05) differences in morbidity, overall mortality, average daily gain, or the dry matter intake to gain ratio between PI and non-PI pens. Although type-I BVDV infections in feedlots appear to contribute to higher mortality rates, the presence of PI calves alone does not appear to have a strong impact on pen-level animal health and feedlot performance. 相似文献