Ductile crack growth in pre-cracked CVN specimens: numerical studies

This study describes plane strain, finite element analyses to model ductile crack extension in pre-cracked Charpy specimens subjected to static and impact loading. The Gurson–Tvergaard (GT) dilatant plasticity model for voided materials describes the degradation of material stress capacity. Fixed-size, computational cell elements defined over a thin layer along the crack plane provide an explicit length scale for the continuum damage process. Outside of this layer, the material remains undamaged by void growth, consistent with metallurgical observations. The finite strain constitutive models include the effects of high strain rates on the material flow properties. Parametric studies focusing on numerically generated R-curves quantify the relative influence of impact velocity, material strain rate sensitivity, and properties of the computational cells (thickness and the initial cell porosity). In all cases, impact loading elevates significantly the R-curve by increasing the amount of background plasticity. The strong effects of impact loading on the driving force for cleavage fracture are illustrated through evolution of the Weibull stress. The analyses suggest a negligible, additional effect of tearing on the Weibull stress under impact loading. Validation of the computational cell approach to predict loading rate effects on R-curves is accomplished by comparison to static and impact experimental sets of R-curves for three different steels.     

Disbudding of red deer stag calves to prevent antler growth

Red deer stag calves aged five to seven months were disbudded with a standard cattle disbudding iron as a means of preventing antler growth and development. Two sizes of iron, one 2.2 cm in diameter and one 1.5 cm in diameter, were compared at disbudding in November or January. Disbudding in November and January with the 2.2 cm iron had success rates of 97 per cent and 92 per cent, respectively. Treatment with the 1.5 cm iron was less effective at both times. There was no significant difference between the liveweights of the treated groups and a non-disbudded control group at turnout in the spring or at slaughter in November when the stags were 16 months of age.     

Effect of progesterone on the expression of estrus at the first postpartum ovulation in dairy cattle.

Fifty-two lactating Holstein cows were randomly assigned to receive either a progesterone-releasing (2 g of progesterone) or a control-releasing intravaginal device (0 g of progesterone). Intravaginal devices were inserted on d 10 and removed on d 15 postpartum. Daily blood samples were collected from d 10 to 90 postpartum for subsequent determination of progesterone concentrations. Observations for estrus were conducted three times daily in a dirt paddock containing a testosterone-treated cow. Serum concentrations of progesterone in the progesterone-releasing intravaginal device group were elevated on d 11, 12, 13, 14, and 15 compared with those of the control group. The days to first post-partum ovulation were similar between the treated and control groups, respectively (30.6 vs. 30.5 d). Also similar was the proportion of cows expressing estrus at first, second, and third postpartum ovulations (9/27 vs. 3/24, 14/23 vs. 15/21, and 14/21 vs. 9/15, respectively), length of the first postpartum estrous cycle (17.9 vs. 18.3 d), and peak serum concentrations of progesterone during the first estrous cycle (3.5 vs. 2.9 ng/ml). These data indicate that administration of progesterone early postpartum did not increase the proportion of cows expressing estrus at the first ovulation.     

Phosphites in polyolefin process stabilization

The use of stabilizer systems containing phosphites in polyolefins is well-established in the technical and patent literature. In addition to the known effects of improved heat and color stability for polyolfins, we have recently found that phosphite-containing stabilizer systems impart a process stabilizing effect as evidenced by melt flow analysis. By monitoring the poly-olefin melt flow after multiple extrusions with increasing temperature, it was found that the combination of phenolics and phosphites has a marked influence on the control of melt flow of polyolefins and the effect appears to be synergistic in operation.     

Convenient access both to highly antimalaria-active 10-arylaminoartemisinins, and to 10-alkyl ethers including artemether, arteether, and artelinate

An economical phase-transfer method is used to prepare 10-arylaminoartemisinins from DHA and arylamines, and artemether, arteether, and artelinate from the corresponding alcohols. In vivo sc screens against Plasmodium berghei and P. yoelii in mice reveal that the p-fluorophenylamino derivative 5 g is some 13 and 70 times, respectively, more active than artesunate; this reflects the very high sc activity of 10-alkylaminoartemisinins. However, through the po route, the compounds are less active than the alkylaminoartemisinins, but still approximately equipotent with artesunate.     

Uncertainty in octanol-water partition coefficient: implications for risk assessment and remedial costs

The assessment of human health and ecological risks at chemically contaminated sites often includesthe use of models to assess chemical transport, fate, and exposure/toxicity. These models require input data on a variety of physical and chemical properties for each compound of concern. Small changes in some of these parameters may result in significant differences in estimated human health or ecological risks and in the extent of required remediation efforts. The octanol-water partition coefficient (Kow) for hydrophobic organic compounds is one such parameter, particularly because it is often used to estimate additional partitioning and bioaccumulation parameters. Unfortunately, there is considerable variability among tabulated Kow values for many compounds of concern. This paper assesses the implications of using various values of Kow to calculate health-protective polychlorinated biphenyl (PCB) sediment quality objectives (SQOs) in a case study using a simplified food chain model and the range of Kow values available from or recommended by the U. S. EPA. For the site and Kow values considered in this study, which are a snapshot of values available in the spring of 2004, the SQOs differ by as much as a factor of 5. This range of SQOs is estimated to correspond to a difference in remediation costs of $48 million.     

Quantification of the Bactericidal,Fungicidal, and Sporicidal Efficacy of the JLA Ltd. Ozone Laundering System

The objective of this study was to demonstrate the bactericidal, fungicidal, and sporicidal efficacy of the in-use concentration of ozone in solution generated continuously by the JLA Limited OTEX validated ozone laundering system against a range of typical microorganisms associated with laundering applications. The study used the JLA HC 100 laundering machine as the containment vessel. Test microbial suspensions were introduced directly into the drum of the laundering machine containing a known level of water in the presence of soluble ozone. Using standard microbiological techniques, the numbers of surviving bacteria, mold spores or bacterial spores were determined, and reductions in viable counts were calculated. The following test organisms were employed: Pseudomonas aeruginosa, Methicillin-Resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, E. coli, Acinetobacter baumannii, Aspergillus niger (spores), and Clostridium difficile (spores). All tests used multiple contact times of 0, 1, 3, 5, 7, 11 and 15 minutes at 20 °C±2 °C. Levels of ≤0.25 mg/L of dissolved ozone had minimal effect on the bacteria. Levels of >0.45 mg/L ozone showed good biocidal activity, except against Acinetobacter baumannii, which showed strong resistance to ozone. Against fungal spores, dissolved ozone levels of >1.2 mg/L were required to obtain a 2.8 log reduction. For Clostridium difficile spores, a dissolved ozone level between 0.90 and 1.20 mg/L gave >1.6 log reduction with no discernable spore recovery. In every instance, the control tests (no ozone) recovered levels of microorganisms that proved that the action of the laundering machine has no antimicrobial activity, and that the log reductions obtained are solely due to the effects of dissolved ozone.