Population dynamics and growth of the gastropod Oxystele variegata (Anton) on an exposed rocky shore

Oxystele variegata (Anton) was found to exhibit a gradient of increasing size up the shore with settlement of veliger larvae occurring primarily in the lower balanoid zone. This has a marked effect on biomass in different regions of the beach and, in combination with zone-dependent density, may be expected to affect the impact of the species as a grazer in different zones. Settlement was continuous during the sampling period but with a marked peak of recruitment in summer. Juvenile cohorts appear at 2-4 mm and grow to approximately 14 mm in their first year, after which growth declines, a mean size of 18 mm being reached after the second year. Growth of all size classes in the mid balanoid zone was markedly slower than in the lower balanoid zone because of greater snail densities and lower microphyte productivity. Low primary productivity in the upper balanoid, where large animals occur, may also be partially responsible for the slow growth rates recorded for these animals. Mean monthly mortality of adults was found to be 4.04% and that of juveniles 12,44%. Total population showed a decline of 30,80% over a period of 13 months. Decrease in numbers, however, occurred only on the lower shore and was related to high juvenile mortality rates     

Unemployed Job Seeker Attitudes towards Potential Travel‐to‐Work Times

The effectiveness of intra‐regional job search is influenced by how far people are willing to travel to new employment. While much has been written on the commuting patterns of those in work, relatively little research has been carried out on how far unemployed job seekers are prepared to commute. This paper presents and tests a model of factors influencing the maximum time unemployed job seekers would be willing to travel to a potential new job. Significant effects are found for a range of personal and demographic characteristics, including gender, years of education, type of job, and location. The evidence suggests support for the spatial mismatch hypothesis and shows differing accessibility to employment opportunities for certain types of unemployed people. The findings also suggest that models of the trade‐off between leisure and work time should fully include travel‐to‐work time as part of this trade‐off.     

An automated in-line clinical mastitis detection system using measurement of conductivity from foremilk of individual udder quarters

AIM: To assess a novel method for automatic in-line detection of clinical mastitis.

METHODS: For a brief period at the start of milking for each cow, electrical conductivity of foremilk was measured for each quarter in turn, using a single sensor installed in the long milk tube (LMT) about 1.5 m downstream from the milking-machine claw. Sequential separation of flow between udder quarters was achieved by control of pulsation to individual teatcups within a conventional cluster. The ratio of conductivity values between quarters was used as an indicator of mastitis status. The concept was evaluated initially in a pilot trial in a 200-cow herd milked in a 23-stall swing-over herringbone milking parlour. It was then tested rigorously in a field trial in a 640-cow herd milked in a 50-stall rotary milking parlour. Both trials were conducted in the Waikato region of New Zealand. In the latter trial, sensor results were compared with visual inspection of a commercial in-line mastitis filter fitted to each milking unit. These filters were inspected for clots immediately after every cow's milking, for 3 weeks. The dataset of approximately 27,000 individual milkings was tested against several published or potential alter- native ‘gold standards’ for diagnosing clinical mastitis.

RESULTS: In the pilot trial, 12–14 clinical events were detected out of 19 true clinical quarters, with a false-alert rate of between three and five false electrical-conductivity alerts per 1,000 individual milkings. In the more rigorous field trial, sensitivity ranged from 68 to 88%, and the false-alert rate (false-alert episodes per 1,000 individual milkings) ranged from 2.3 to 7.0.

CONCLUSION: The novel clinical mastitis detection system, based on separation of the flow and measurement of electrical conductivity from foremilk of individual udder quarters, has the potential to provide a new tool for helping farmers to monitor clinical mastitis in herds milked with conventional clusters.     

Human psittacosis associated with commercial processing of turkeys.

Between May 1 and Aug 1, 1974, 114 of approximately 1,000 employees in 7 turkey processing plants in Texas (5), Missouri (1), and Nebraska (1) had an illness compatible with psittacosis. The illness was characterized by fever, severe headache, and pneumonia. Treatment with tetracycline was effective in most cases. Psittacosis was confirmed in 41 (36%) of the cases by a fourfold change in complement-fixation titer to the Chlamydia group antigen. Investigations implicated several turkey flocks from Texas as the source of the disease. Control measured, including screening turkey flocks before slaughter and assuring treatment of infected birds, were instituted by a special task force of state and federal veterinarians.