Acoustic ecology of Antarctic pinnipeds Van Opzeeland, Ilse; Van Parijs, Sofie; Bornemann, Horst ...
Marine ecology. Progress series,
09/2010, Volume:
414
Journal Article
Peer reviewed
Open access
In aquatic-mating pinnipeds, acoustic communication plays an important role in male competition and mate attraction. Vocal repertoire size and composition during the breeding season varies between ...species and is presumed to be a product of interspecific differences in sexual selection. In this study, we examine seasonal and diel patterns in acoustic repertoire size, composition and call activity of 4 Antarctic pinniped species: Weddell sealLeptonychotes weddellii, leopard sealHydrurga leptonyx, Ross sealOmmatophoca rossiiand crabeater sealLobodon carcinophaga. An 11 mo (Jan 2006 – Jan 2007, no recordings Jul and Nov 2006) near-continuous dataset was collected from the Perennial Acoustic Observatory in the Antarctic Ocean (PALAOA) located on the Ekström Iceshelf. The Weddell seal vocal repertoire consisted of 14 call types. Calls were present throughout the year except in February (11 mo), while repertoire composition varied considerably between months. The leopard seal vocal repertoire consisted of 7 call types. Calls were present between October and January (4 mo). All call types were used in a uniform manner throughout the entire call period. The Ross seal vocal repertoire consisted of 5 call types. Ross seal vocalizations were present from December until February (3 mo). Repertoire composition varied little between months. Crabeater seals produced one vocalization type, present from August to December (5 mo). Vocalizations in these species are likely produced in a breeding context. Inter-specific differences in behavioral ecology and interactions with abiotic and biotic environmental factors shape vocal behavior resulting in each species filling its own acoustic ecological niche.
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A hydraulically controllable mechanical seal for a nuclear reactor coolant pump (RCP) is under development. Its purpose is to correct excessive or insufficient leakage through RCP seals, a current ...expensive problem. The non-rotating seal face contains an annular cavity, filled with pressurized fluid. By changing the pressure within the cavity, the deformation and geometry of the face can be changed. Since the face geometry determines the thickness of the lubricating film between the two seal faces and the leakage rate, the leakage rate can be controlled. Simulations indicate that the hydraulically controllable seal provides sufficient control to address many abnormal leakage rate scenarios.
•New type of mechanical seal to correct excessive or insufficient leakage through RCP seals, is described.•Geometry of non-rotating seal face is controlled hydraulically.•Simulations show seal provides sufficient control to address many abnormal leakage rate scenarios.
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GEOZS, IJS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Individual behavioural specialisation has far‐reaching effects on fitness and population persistence. Theory predicts that unconditional site fidelity, that is fidelity to a site independent of past ...outcome, provides a fitness advantage in unpredictable environments. However, the benefits of alternative site fidelity strategies driving intraspecific variation remain poorly understood and have not been evaluated in different environmental contexts. We show that contrary to expectation, strong and weak site fidelity strategies in migratory northern elephant seals performed similarly over 10 years, but the success of each strategy varied interannually and was strongly mediated by climate conditions. Strong fidelity facilitated stable energetic rewards and low risk, while weak fidelity facilitated high rewards and high risk. Weak fidelity outperformed strong fidelity in anomalous climate conditions, suggesting that the evolutionary benefits of site fidelity may be upended by increasing environmental variability. We highlight how individual behavioural specialisation may modulate the adaptive capacity of species to climate change.
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Seal assemblies are critical elements in a variety of drilling and completion equipment such as wellhead casing hangers, packers, and liner hangers. Zonal isolation is accomplished by seal ...compression (energization) which generates contact pressure at the seal-pipe interface. The performance of a seal is evaluated based on its mechanical and hydraulic integrity as well as its resistance to failure mechanisms. Objective of this study is to evaluate the performance of a seal assembly at varying compressions, seal and pipe properties, and chemical swelling.
In this paper, numerical modeling approach validated by a lab-scale experimental work has been presented. Finite element model and experimental setup consisting of liner, casing, compression plates, and elastomer seal are used. In the model, seal performance was evaluated in terms of contact pressure generated at seal-pipe interface. Experimental setup was used to verify the modelling results. In experiments, sealability was evaluated by injecting gas and observing leakage.
Modelling results indicate that elastomer sealability is linearly dependent on amount of seal compression. Numerical model also demonstrated that pipe material can have notable impact on elastomer sealability. Simulation results show that seal-pipe friction has insignificant impact on seal performance. Exposure to surfactant caused volumetric swelling of investigated elastomer materials. Despite reduction in hardness, volumetric swelling was high enough to generate additional seal compression and provide improved sealability as demonstrated by model.
Performance evaluation of liner hangers is considered a challenge for industry and regulators because of limited testing protocols, standards, or regulatory guidelines for evaluating this type of barrier system. Information generated in this work will help further advance performance evaluation and qualification guidelines for liner hanger seal assembly.
•Finite element modeling of liner hanger seal assembly.•Experimental setup to test seal assembly.•Review of Sealing mechanisms and failure modes of liner hanger seal assembly.•Parameters influencing contact pressure.•Elastomer performance under chemical swelling.
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Individual variation in reproductive ability is a key component of natural selection within populations, driving the evolution of life histories and population responses to changing environmental ...conditions. Evidence that population density affects individual‐level fitness in wild populations is limited, particularly for long‐lived animals, which are difficult to observe on a biologically relevant scale. We tested for individual heterogeneity in reproductive performance in female grey seals (Halichoerus grypus) using 35 yr of mark–resighting data at Sable Island, Canada (43.93° N 59.91° W). We used Bayesian generalized linear mixed‐effect models and multistate open robust design mark–resight models to investigate whether population size negatively influences individual reproductive performance. We measured reproductive performance in two ways: reproductive frequency (the probability of returning to the island to breed) and annual provisioning performance (the probability of successfully weaning a pup given a female bred). Sighting histories of 1,655 known‐aged females with a total of 22,961 pupping events were used for analysis. After accounting for effects of female age, parity, and random year effects, we found that both provisioning performance and reproductive frequency demonstrated a strong, positive correlation with population size. Among‐individual variance in reproductive traits and responses to population size indicated considerable heterogeneity in overall reproductive performance. As population size grew, “robust” females increased their reproductive performance more than their more “frail” conspecifics in both reproductive traits, resulting in an amplification of differences among individuals. Consequently, simulations from posterior distributions revealed a large fitness consequence of heterogeneity in this population, with “frail” individuals having 47.1% fewer successful pups than more “robust” females (mean reproductive output ± SD: 9.12 ± 3.77 pups for frail individuals, 16.97 ± 2.94 for robust individuals). Repeatability of overall reproductive performance across environments indicates individual quality may be more influential to lifetime reproductive success than costs associated with reproductive investment. This quantification of relative fitness and its dynamics is crucial to understanding broad evolutionary processes in natural populations.
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The enzyme-linked immunosorbent assay (ELISA) was applied to detect antibodies against Brucella abortus in serum samples from four seal species at nine coastal locations of Hokkaido, Japan. These ...antibodies were detected in 27% (32/118) of Western Pacific harbor seals (Phoca vitulina stejnegeri) at Cape Erimo. The antibodies were observed in spotted seals (P. largha) in one out of six at Nemuro, in two out of three at Rebun Island, in one out of two at Bakkai, and in examined one at Soya. They were also found in respective examined one ribbon seal (Histriophoca fasciata) and one ringed seal (Pusa hispida) at Akkeshi. Harbor seals that tested positive were mostly yearlings (35%, 20/57) and juveniles (45%, 10/22), while only one pup (1/13) and one subadult (1/5) tested positive with low titers of the antibody; no antibodies were observed in adults (n=21). These results suggest that Brucella mainly infected harbor seals from the environment while weaning, and the bacteria were cleared during the early life stage of the seals. In spotted seals, however, antibodies were also detected in adults, suggesting that spotted seals could become infected with Brucella even as adults. It is also possible that a different, more persistent strain of Brucella may have infected the spotted seals.
Gaskets play a significant role in the thermal insulation of refrigerators. Previous studies mainly focused on how to obtain the heat and moisture transfer load of a given gasket, but lacked ...appropriate structural improvement measures and their effect on the heat leakage load and energy consumption of refrigerators. In this paper, the heat transfer analysis of an original gasket was conducted via numerical simulation. It was found that the main thermal insulation weaknesses of the original gasket are gasket-cold air, gasket-outer shell of the cabinet, gasket-inner lining of door and gasket-hot air. Thus, adding an auxiliary-airbag to the original gasket and a comprehensive new-design gasket were proposed to improve the thermal insulation. Compared with the original gasket, the numerical simulation results showed the heat leakage loads of the auxiliary-airbag and new-design gasket were reduced by 18.44 % and 27.49 %. The total heat leakage loads of refrigerators equipped with improved gaskets were reduced by 4.46 % and 6.64 %. The effect of two structurally improved gaskets on the refrigerator energy consumption was experimentally studied. The repetitively measured results showed the energy consumption of refrigerators with the auxiliary-airbag and the new-designed gasket were reduced by 0.93 % and 3.19 %. The reason why the reduction in refrigerator energy consumption is lower than the reduction in heat leakage load is due to the difficulty in achieving the designed assembly state of the gasket during actual installation. Based on the holdings of refrigerators around the world, it is estimated that the refrigerators energy consumption can be reduced by 106.776 billion kWh per year and carbon emissions can be reduced by 12.74 million tons per year when using the new-design gasket proposed in this study.
•A method to determine the thermal insulation weaknesses of the gasket is proposed.•Comprehensive structural improvements to reduce gasket heat load are proposed.•Thermal insulation improvement of gaskets will decrease refrigerator temperature.•Energy consumption of refrigerators with new-design gaskets is reduced by 3.19 %.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
With the growing emphasis on minimization of global plastic waste, flexible fibre‐based packaging has gained significant interest over the past few years. Heat‐sealing technology is commonly applied ...for vertical form‐fill‐seal machine to provide tight closure of packages for maintaining food quality and shelf life. Several different seal bar geometries and adequate heat‐seal parameters are required to improve the seal tightness of the packages. This study aims to compare the heat sealability of thermoplastic film (OPP/PE) and paper‐based materials in vertical form‐fill‐seal machine using various seal bar profiles. The investigation includes seal strength measurement, understanding the causes of leak formation, seal tightness and inspection of the seal using scanning electron microscopy. Results reveal that OPP/PE material has exceptional seal strength and leakproof ability compared with paper‐based materials. However, it has limited operating window because the material shrinks and coarsens at approximately 140°C. Sealing temperature and dwell time are found to be the major factors affecting the seal strength of paper‐based material. Results reveal the PE‐coated papers exhibit nearly twice the seal strength compared with the dispersion‐coated paper. It was difficult to achieve good hot‐tack values with dispersion‐coated paper. During testing, all the paper‐based materials experience delamination and fibre tear, and its severity increases with the increasing material grammage. As plateau temperature is reached, the fibre delamination remains relatively constant. The serrated geometry of seal bar design plays a significant role in providing a satisfactory airtight seal, particularly around the pouch's layer jump. However, flat seal bar designs are not recommended for gas tight applications for paper‐based materials.
The objective of this paper was to evaluate and compare the seal strength and seal tightness of the dispersion‐coated paper material and PE‐extrusion‐coated paper‐based material with different thicknesses and grammages using different seal bars in the VFFS machine. Study concluded that the serrated seal bar had the highest possible seal strength and tightness. Additionally, unlike the flat seal bar, the grooved angle from the serrated seal bar developed an intact seal at the layer jump area.
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The behavior of colony-based marine predators is the focus of much research globally. Large telemetry and tracking data sets have been collected for this group of animals, and are accompanied by many ...empirical studies that seek to segment tracks in some useful way, as well as theoretical studies of optimal foraging strategies. However, relatively few studies have detailed statistical methods for inferring behaviors in central place foraging trips. In this paper we describe an approach based on hidden Markov models, which splits foraging trips into segments labeled as "outbound", "search", "forage", and "inbound". By structuring the hidden Markov model transition matrix approximately, the model naturally handles the sequence of behaviors within a foraging trip. Additionally, by structuring the model in this way, we are able to develop realistic simulations from the fitted model. We demonstrate our approach on data from southern elephant seals (Mirounga leonina) tagged on Kerguelen Island in the Southern Ocean. We discuss the differences between our 4-state model and the widely used 2-state model, and the advantages and disadvantages of employing a more complex model.
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Over the past several decades, the Gulf of Maine has experienced significant socio‐ecological change. Coastlines have become more densely populated and developed, rapid and dramatic climate change ...has affected coastal ocean environments, and seal populations have grown as a result of federal protections. Long‐term data sets from marine mammal stranding networks represent a valuable resource for investigating indicator species for coastal ocean health during this period of change. Using data collected from stranded harbor (Phoca vitulina), harp (Pagophilus groenlandicus), and gray (Halichoerus grypus) seals from 2002 to 2017 in Massachusetts, New Hampshire, and Maine, we tested for spatiotemporal correlations between stranding density and human population density, size of and proximity to seal haul‐outs, sea surface temperature, North Atlantic Oscillation, snowfall, and sea ice extent. We found that in the Gulf of Maine proximity to coastal human population centers and large seal haul‐outs are the greatest drivers of reported seal stranding density. Environmental factors played an important role only for harp seals, which do not breed in the study area, although recent shifts in the environmental seascape have the potential to affect all seal species in the Gulf of Maine.
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