The viability of subcarrier modulation for enhancing the performance of installed-base MMF links

The technique of Subcarrier Modulation is assessed by statistical analysis as a viable solution to broadband data transmission over dispersion limited multimode fibre. It is shown that a suitable passband region for transmission of 2.5 Gb/s channels exists at 5 GHz in greater than 80% of worst-case fibres under standard SMF/MMF launch conditions. ©2002 Optical Society of America.

Tag-reporting levels for red drum (Sciaenops ocellatus) caught by anglers in South Carolina and Georgia estuaries

A total of 1784 legal-size (≥356 mm TL) hatchery-produced red drum (Sciaenops ocellatus) were tagged and released to estimate tag-reporting levels of recreational anglers in South Carolina (SC) and Georgia (GA). Twelve groups of legal-size fish (~150 fish/group) were released. Half of the fish of each group were tagged with an external tag with the message “reward” and the other half of the fish were implanted with tags with the message “$100 reward.” These fish were released into two estuaries in each state (n=4); three replicate groups were released at different sites within each estuary (n=12). From results obtained in previous tag return experiments conducted by wildlife and fisheries biologists, it was hypothesized that reporting would be maximized at a reward level of $100/tag. Reporting level for the “reward” tags was estimated by dividing the number of “reward” tags returned by the number of “$100 reward” tags returned. The cumulative return level for both tag messages was 22.7 (±1.9)% in SC and 25.8 (±4.1)% in GA. These return levels were typical of those recorded by other red drum tagging programs in the region. Return data were partitioned according to verbal survey information obtained from anglers who reported tagged fish. Based on this partitioned data set, 14.3 (±2.1)% of “reward” tags were returned in SC, and 25.5 (±2.3)% of “$100 reward” tags were returned. This finding indicates that only 56.7% of the fish captured with “reward” tags were reported in SC. The pattern was similar for GA where 19.1 (±10.6)% of “reward” message tags were returned as compared with 30.1 (±15.6)% for “$100 reward” message tags. This difference yielded a reporting level of 63% for “reward” tags in GA. Currently, 50% is used as the estimate for the angler reporting level in population models for red drum and a number of other coastal finfish species in the South Atlantic region of the United States. Based on results of our study, the commonly used reporting estimate may result in an overestimate of angler exploitation for red drum.

Mechanisms of erosion of unfilled elastomers by solid particle impact

The mechanisms of material removal were studied during the erosion of two unfilled elastomers (natural rubber and epoxidised natural rubber). The effects of impact velocity and of lubrication by silicone oil were investigated. The development of surface features due to single impacts and during the early stages of erosion was followed by scanning electron microscopy. The basic material removal mechanism at impact angles of both 30° and 90° involves the formation and growth of fine fatigue cracks under the tensile surface stresses caused by impact. No damage was observed after single impacts; it was found that many successive impacts are necessary for material removal. It was found that the erosion rate has a very strong dependance on impact velocity above about 50 ms-1.

云南中甸尼西鸡的血液蛋白多态性研究

　采用水平式淀粉胶凝胶电泳技术和垂直式聚丙烯酰胺凝胶电泳技术检测了云南中 甸尼西鸡的血液蛋白多态，对33个样本的37个基因座位进行了分析，共有9个座位出现多态，分 别为ES-1、ES-2、AKP-1、AKP-2、LAP、PGM、CK、Tf及6PGD。多态位点百分比P=0.2432,平 均杂合度=0.1015,每个座位等位基因的平均数A=1.3784,结果表明尼西鸡的血液蛋白多态程度较 高，在蛋白质水平上的遗传多样性较为丰富。同时发现Amy-1座位只出现杂合子AB型。