Moulting southern elephant seals, Mirounga leonina (L.), were counted in 17 discrete wallows at Walker Bay on Livingston Island in the South Shetland Islands between 2 January and 16 February 1994. Daily weather conditions were also recorded. It was also found that, although there were no overall correlations between wind scale, air temperature, sunshine, precipitation, sea roughness and cloud cover with seal numbers, there were conditions on specific days that affected the movements of seals between wallows. Most notably, it was found that numbers of seals decreased when they were exposed to winds, and that they often sought out more sheltered sites nearby.
Twelve mineral elements and total ash were examined in regard to the possible use as the estimators of digestibility of natural food in Antarctic seals. Four of them: phosphorus, calcium, copper and zinc have proved to give most reliable results. The estimated total dry mass and organic matter digestibilities of fish food in Weddell seals (Leptonychotes weddelli (Lesson)) averaged 82 and 91%, while the corresponding values for krill eaten by crabeaters (Lobodon carcinophagus (Hombron and Jaequinot)) and leopard seals (Hydrourga leptonyx (Blainville)) reached approximately 87 and 91%, respectively.
A common problem encountered in hydraulic valves is a progressing deterioration of tightness of their water flow cutting-off seats. The seats are provided usually with a copper-alloy insert joined mechanically with cast-iron valve housing. The problem of unreliability of such joints can be solved by providing surface of the seat with a coating, deposited with the use of HVOF method and resistant to abrasive and cavitation wear. The tests were carried out for a sealing-draining seat insert made of CuZn39Pb2Al brass used to date and a specimen taken from the cast-iron valve housing which was the substrate for a plasma-sprayed coating of powder containing 86.1% Cr, 7.2% Ni, and 6.7% C. The coating, 345 ± 15 μm thick, was characterized with good quality of bonding with cast-iron substrate and high compactness of the material. The cavitation wear test on materials used in the study were carried out with the use of Vibra-Cell ultrasonic liquid processor (Sonics) equipped with a piezoelectric probe operating at the frequency of 20 kHz. Based on profilograms taken along a line crossing centers of cavitation craters, measurements of the height parameter Rt, and microscopic observations of surfaces it has been found that the coating plasma-sprayed onto substrate of nodular cast iron demonstrated higher resistance to cavitation compared to copper-alloy inserts used so far in cast-iron hydraulic valves. Cavitation craters on the material used typically for valve seats to date were more distinctly outlined and deeper compared to craters observed on the coating. Larger were also sizes of local tear-outs which resulted in larger difference between the peaks line and the valleys line.
This study describes the seasonal and annual changes in the diet of non-breeding male Antarctic fur seals (Arctocephalus gazella) through the analysis of faeces collected on shore during four summer seasons (1993/94-1996/97) in the area of Admiralty Bay (King George Island, South Shetlands). Krill was the most frequent prey, found in 88.3% of the 473 samples. Fish was present in 84.7% of the samples, cephalopods and penguins in 12.5% each. Of the 3832 isolated otoliths, 3737 were identified as belonging to 17 fish species. The most numerous species were: Gymnoscopelus nicholsi, Electrona antarctica , Chionodraco rastrospinosus, Pleuragramma antarcticum, and Notolepis coatsi. In January, almost exclusively, were taken pelagic Myctophidae constituting up to 90% of the total consumed fish biomass. However, in February and March, the number of bentho-pelagic Channichthyidae and Nototheniidae as well as pelagic Paralepididae increased significantly, up to 45% of the biomass. In April the biomass of Myctophidae increased again. The frequency of squid and penguin occurrence was similar and low, but considering the greater individual body mass of penguins, their role as a food item may be much greater. In March and April, penguins could be as important prey item as fish. The amount of krill in the diet of Antarctic fur seals declined with a concomitant decrease in the mature krill availability. This appears to have been compensated by an increased frequency of the fur seal to eat fish and penguins.
The aim of this paper was to test currently available on the market products for sealing anodic oxide coatings as well as to test the use of other alternative substances improving the sealing process. The ability to seal in 10 different solutions and the quality of the seal has been tested. The influence of the applied preparations on corrosion resistance and resistance to strongly alkaline environment was also investigated.
Based on the results obtained, satisfactory results were archived for the sample sealed in a IMN-OML (Institute of Non-Ferrous Metals in Gliwice, Light Metals Division) solution sealant and in solution of nickel acetate in a medium-temperature process. Sealing by means of nickel acetate solutions is economically justified, and its use allows the process temperature to be lowered. When it comes to resistance to alkalis, samples sealed in IMN-OML sealant are the best. Commercial solutions have also achieved positive results in all tests.
Southern elephant male seals (Mirounga leonina Linnaeus, 1758) were studied at King George Island (62°14´S, 58°40´W) from September to December 1999. The first males came ashore at the beginning of September. Twenty-five adults were immobilized, hot iron branded, and measured. Thirteen out of the 25 marked males spent an average of 66 (+/-8) days on land. Early arrival was positively correlated with the time spent ashore (r = 0.88, P < 0.05). Nine harems were formed in the study area. At the maximum haul-out of females (28 October) mean harem size was 32ą42 females (range 3–107). During the course of harem development, 10 changes in male harem dominance were observed. These changes were more frequent during the early (1–20 October, n = 6) than during the mid (21 October – 10 November, n = 2) and late (11–29 November, n = 2) periods of harem development. Overall, there were 14 dominant males; five of these in two different harems and nine in one harem. Of the 25 marked males, 44% were resighted in the following breeding or moulting season, and 16% seemed to improve their potential breeding success.
A population survey of southern elephant seals (Mirounga leonina Linnaeus, 1758) was conducted at Nelson Island, South Shetland Islands, Antarctica, during the 2001 breeding season. Two breeding sites were identified, one of which had not been previously reported. The largest breeding site was located at Duthoit Point, with a total of 128 females, 111 pups and 7 weanlings distributed in 6 harems along 3 km of coast. The new breeding group was observed at Harmony Point, where 3 females with their pups were found. This is the first report on southern elephant seal numbers during the breeding period for the Nelson Island coast.
The cephalopod diet of the gentoo penguin, Pygoscelis papua and the Antarctic fur seal, Arctocephalus gazella was comparatively analyzed at Laurie Island, South Orkney Islands. A total of 125 stomach samples were collected by the water off-loading method from gentoo penguins during the autumns of 1993, 1995 and 1996, and 39 fur seal scats were collected from mid March to April 1988. Cephalopods preyed upon by gentoo penguins were represented by 1974 beaks (1628 lower, 346 upper) which occurred in 50.4% of the samples. Lower beaks identified belonged exclusively to the squid Psychroteuthis glacialis. The mean lower rostral length (LRL) of these beaks was 1.1 mm (range 0.4– 1.8 mm). From the Antarctic fur seal scats 103 beaks (41 lower, 62 upper) were removed from 60.6% of scats which contained prey remains. The cephalopod species identified were Slosarczykovia circumantarctica and P. glacialis which constituted 78.8% and 21.1% in terms of numbers, respectively. The mean lower rostral length for S. circumantarctica was 2.7 mm (range 2.0–3.5 mm), while that of P. glacialis was 1.6 mm (range 1.0–2.5 mm). The foraging behaviour of the two top predators was analyzed and discussed according to the composition and size of their cephalopod prey.
The mine seals in coal mines with a good impact resistance and air tightness are mainly used to isolate abandoned mining areas from active workings. For one thing, it can prevent the leakage of harmful gases, such as toxic gas from abandoned areas. For another, once an underground mine explosion happens, it can effectively block the spread of the explosion between the abandoned mining areas and the active workings. Hence, it is of great significance to study the explosion-proof performance and mechanical properties of the mine seals. First of all, the effect of slotting on the stability of the seals in coal mines under explosion load was explored in this study. By numerical simulations, the mechanical response characteristics of the seals with or without cutting a slot under the explosion load were compared in detail. The results show that slotting improved the stress concentration at the contact surface of surrounding rock by transferring partial impact received by mine seals to the surrounding rocks, thus, to achieve the effect of buffering explosion impact. Besides, such effect will be enhanced with increasing cutting depth into rock, and will stabilize when the depth is 20 cm. On this basis, the mechanical properties and damage of the seals constructed by different materials (standard brick and #C40 concrete) under the explosion load were compared. It was found that once a slot was set, the maximum deformation of the concrete seal was reduced, while the maximum deformation of the brick seal increased. Since the non-deformability of the concrete seal is obviously stronger than that of the brick seal, with the impact resistance stronger than that of the brick seal, the concrete seal is more suitable for slotting. Moreover, the damage of the seals in underground coal mines under the strata ground pressure was studied; the results of which show that the damage state under the ground pressure can be divided into 3 levels, i.e. no damage, minor damage and rapid development of damage. Meanwhile, it was found that the prestressed structure formed by the ground pressure at the level of no damage can enhance the protective effect of the seals in coal mines. However, when the ground pressure was further developed, the seal itself was destroyed and the protective effect was lost. In addition, the influence of roof to floor moving convergence, a deformation parameter of the roadway, on the seals was also investigated. The results show that the ground pressure and roof-to-floor convergence act on the seals in coal mines in the same way, thus roof to floor moving convergence can replace the ground pressure to analyze other related mechanical properties of the seals in coal mines in the future researches.