Search

A novel ring-on-ring test setup was developed for investigating the biaxial flexural strength of small circular soda–lime–silica glass specimens at high loading rates in a high-speed test rig. Such rate effects becomes important when designing for extreme events such as impact and blast, which are highly relevant for glass used in e.g. façades. The investigation focused on two groups of specimens with different surface conditions: as-received and pre-damaged with a well-defined flaw. A total of 151 specimens were tested in order to evaluate the influence of loading rate and surface condition on the flexural strength. Quasi-static and dynamic experiments were performed at loading rates ranging between 2 and 5.6 × 106 MPa/s. An 85% increase in strength with loading rate was observed for the ‘as-received’ specimens and 52% for the ‘pre-damaged’.

The tempering process introduces a residual stress field to the glass that only allows a drilling depth of approximately 20% of the thickness (compressive zone) before fragmentation will be initiated. The present paper investigates post-drilled holes in tempered glass that can be used for a novel assembling technique leading to an increased accuracy in the connection and avoiding custommade solutions with holes drilled prior to tempering. The partly drilling is first studied experimentally measuring the change in strains (stresses) on the surface close to the hole as function of drilling depth. These data are then further used to validate a finite element model capable of describing the redistribution of residual stresses around the hole for several geometric variations such as depth, diameter, rounding and inclination. Above all, the numerical study shows an increase in the apparent strength (The term “apparent strength” is used for the strength originating from both the material strength and the residual stress state) of the hole. Furthermore, it is seen that drilling into the compressive zone only, will not lead to any tensile stresses at the surface of the hole. As the drilling process will damage the glass around and inside the hole, hence decreasing the strength, an etching technique is finally given to post-improve the quality of the hole surface locally. After 6 h of local etching with ammonium hydrogen fluoride (NH4HF2), an increase in strength of about 310% is observed. Increasing the etching time further, with the given acid and concentration, is shown not to yield any further (significant) increase in the strength.

Contains fulltext : 98924.pdf (preprint version ) (Open Access)

Contains fulltext : 98990.pdf (preprint version ) (Open Access)

In the last decade the main goals of organic dairying have been to attain acceptable levels of milk production, increase opportunities for animals to perform species own behaviour, resulting in improved animal welfare and animal health, and minimize the use of therapeutic interventions, including the reduction of the (preventive) use of antibiotics. Maintaining animal health without the use of therapeutic interventions is a major challenge for organic dairy farmers. In particular, udder health remains a major problem in both conventional and organic farming. In the QualityLowInputFood (QLIF) project udder health status and management were assessed in different production systems and European regions. These studies suggest that good udder health can be maintained in organic or low-input farming management systems. Novel strategies to control mastitis were evaluated and the potential of using internal teat sealers for the control of environment-associated pathogens was shown. Also oral application of a herd profile based single homeopathic remedy combined with homeopathic silica had a significant effect on cows with a relative low somatic cell count before drying-off. Suckling systems in calf rearing, as an integrated management approach, did not result in better udder health. None of the studies presented identified new variables affecting udder health. QLIF studies also demonstrated the importance of comparing udder health parameters in contrasting organic, low input and conventional production systems, since clear differences in antibiotic use against mastitis could be identified not only between organic and conventional systems, but also among dairy systems used in different EU-countries. Although alternative treatments used in organic systems could not be shown to be fully effective, results suggest that the use of individual or combined alternative strategies to improve udder health on organic or low-input farms warrants further investigation. Based on the resul

In the last decade the main goals of organic dairying have been to attain acceptable levels of milk production, increase opportunities for animals to perform species own behaviour, resulting in improved animal welfare and animal health, and minimize the use of therapeutic interventions, including the reduction of the (preventive) use of antibiotics. Maintaining animal health without the use of therapeutic interventions is a major challenge for organic dairy farmers. In particular, udder health remains a major problem in both conventional and organic farming. In the QualityLowInputFood (QLIF) project udder health status and management were assessed in different production systems and European regions. These studies suggest that good udder health can be maintained in organic or low-input farming management systems. Novel strategies to control mastitis were evaluated and the potential of using internal teat sealers for the control of environment-associated pathogens was shown. Also oral application of a herd profile based single homeopathic remedy combined with homeopathic silica had a significant effect on cows with a relative low somatic cell count before drying-off. Suckling systems in calf rearing, as an integrated management approach, did not result in better udder health. None of the studies presented identified new variables affecting udder health. QLIF studies also demonstrated the importance of comparing udder health parameters in contrasting organic, low input and conventional production systems, since clear differences in antibiotic use against mastitis could be identified not only between organic and conventional systems, but also among dairy systems used in different EU-countries. Although alternative treatments used in organic systems could not be shown to be fully effective, results suggest that the use of individual or combined alternative strategies to improve udder health on organic or low-input farms warrants further investigation. Based on the resul

The quality of organic milk is affected by feed composition, and especially the high use of legumes has been identified as the reason for high levels of polyunsaturated fatty acids, carotenoids and tocopherols in organic milk. Four different pastures composed of mainly white clover (WCL), red clover (RCL), lucerne (LUC) or chicory (CIK), respectively, were established to investigate the influence of sward composition on the milk quality of grazing cows. On three occasions during the grazing period (May, June and August), groups of 12 Holstein cows were grazing the pastures for two weeks. About 70% of the daily dry matter intake was pasture, and the remaining dry matter intake was a mixture of oats, hay and minerals (82%, 16%, 2%, respectively). The swards were sampled, and their feed quality as well as their composition of carotenoids, tocopherols and fatty acids was analysed. On each occasion, milk was sampled after two weeks of grazing, and the content of tocopherols and carotenoids as well as the composition of fatty acids was analysed. The overall feed quality expressed as IVOMD (in vitro organic matter disappearance) and NDF (neutral detergent fibre) was affected by period and to a lesser extent by forage type. The content of carotenoids was higher in RCL compared to the other forages, while no effect of period was observed. Alpha-tocopherol was neither affected by period nor by forage type. Fatty acid content, in particular content of linolenic acid, decreased during the grazing period, and it was highest in RCL, intermediate in CIK and lowest in WCL and LUC. Milk yield was neither affected by period nor by forage type. Milk fatty acid composition and content of alpha-tocopherol and carotenoids showed minor differences between forage types and sampling occasions. However, multivariate analysis of these data showed grouping according to sampling occasion, but no clear grouping according to forage types. Despite the differences in composition of forage and in co

To investigate the effect of the dietary intake of the cow on milk composition, bulk-tank milk was collected on 5 occasions from conventional (n = 15) and organic (n = 10) farms in Denmark and on 4 occasions from low-input nonorganic farms in the United Kingdom, along with management and production parameters. Production of milk based on feeding a high intake of cereals, pasture, and grass silage resulted in milk with a high concentration of α-linolenic acid (9.4 ± 0.2 mg/ kg of fatty acids), polyunsaturated fatty acids (3.66 ± 0.07 mg/kg of fatty acids), and natural stereoisomer of α-tocopherol (RRR-α-tocopherol, 18.6 ± 0.5 mg/kg of milk fat). A milk production system using a high proportion of maize silage, by-products, and commercial concentrate mix was associated with milk with high concentrations of linoleic acid (LA; 19.7 ± 0.4 g/kg of fatty acids), monounsaturated fatty acids (27.5 ± 0.3 mg/kg of fatty acids), and a high ratio between LA and α-linolenic acid (4.7 ± 0.2). Comparing these 2 production systems with a very extensive nonorganic milk production system relying on pasture as almost the sole feed (95 ± 4% dry matter intake), it was found that the concentrations of conjugated LA (cis-9,trans-11; 17.5 ± 0.7 g/kg of fatty acids), trans-11-vaccenic acid (37 ± 2 g/kg of fatty acids), and monounsaturated fatty acids (30.4 ± 0.6 g/kg of fatty acids) were higher in the extensively produced milk together with the concentration of antioxidants; total α-tocopherol (32.0 ± 0.8 mg/kg of milk fat), RRR-α-tocopherol (30.2 ± 0.8 mg/kg of milk fat), and β-carotene (9.3 ± 0.5 mg/kg of milk fat) compared with the organic and conventional milk. Moreover, the concentration of LA (9.2 ± 0.7 g/kg of fatty acids) in milk from the extensive milk production system was found to approach the recommended unity ratio between n-6 and n-3, although extensive milk production also resulted in a lower daily milk yield.

Contains fulltext : 99113.pdf (publisher's version ) (Open Access)

Contains fulltext : 99122.pdf (preprint version ) (Open Access)

Contains fulltext : 99112.pdf (preprint version ) (Open Access)

Contains fulltext : 99121.pdf (publisher's version ) (Closed access)

Because of its high saturated fatty acid (FA) content milk fat is considered hypercholesterolemic. Intake of unsaturated FA (UFA) reduces the plasma cholesterol concentrations. Especially conjugated linoleic acids (CLA) have shown positive effects on cardiovascular diseases, prevention of cancer and obesity. The aim of our project is to investigate how grazing can enhance the content of these beneficiary FA in milk. For bith types of cow races we observed no direct effect of increased grazing in the diet on the short chain FA (SCFA) content in milk, implying that the de novo synthesis of these FA remained unaffected. Regarding the content of CLA c9,t11 there was a strong positive effect on Holstein milk (R2 = 0,88), but almost none on Jersey milk when the percentage of grazing increases in the diet, thus suggesting that the mammary gland D9-desaturase acitivities of these two cow races react differently to increasing pasture grazing.

Udgivelsesdato: 2008/6

Udgivelsesdato: JUL

Milk from cows fed high concentration of synthetic all-rac-a-tocopheryl acetate (2-3 g day-1) were shown not to have improved oxidative stability, when oxidation were initiated by light exposure or Cu(II) addition. For milk with high fraction of unsaturated lipids as obtained through feed with toasted soybeans, the high a-tocopherol content even acted prooxidative. Stereo-selective analysis of the milk showed that among the 8 stereo-isomers of all-rac-a-tocopherol, only the 2R-stereo-isomers were excreted into the milk and among these mainly the native RRR-stereo-isomer. Feeding studies of dairy cows should accordingly be reevaluated in two respect: (i) the use of high level supplementation of a-tocopherol, as it may induce lipid oxidation, (ii) the use of synthetic, none-resolved a-tocopherol as mainly the native RRR-stereo-isomer, only partly the three other 2R-stereo-isomers, and none of the three 2S-stereo-isomers are excreted into the milk.

Udgivelsesdato: 2007/11

Pancreatic beta cells, proliferation, growth factors, growth hormone