Mitigation performance of the process protection system on the accident consequences of H2S-containing natural gas release and explosion

Toxic loads and explosion overpressure loads pose grave threats to the offshore oil and gas industry. Many safety measures are adopted to prevent and mitigate the adverse impacts caused by toxic loads and explosion overpressure loads. As a general safety barrier, the process protection system has been widely used but rarely evaluated. In order to assess the barrier ability, the mitigation performance of the process protection system is concerned in this study. Firstly, several chain accidents of H₂S-containing natural gas leakage and explosion are simulated by varying the response time of the process protection system with CFD code FLACS. Qualitative assessment is conducted based on the variation of the dangerous load profiles. Furthermore, the quantitative assessment of the mitigation performance is accomplished by considering its ability in reducing the probability of fatality. Emergency evacuation and no emergency evacuation are considered respectively in the quantitative assessment. The results prove that the process protection system takes effect on mitigating the toxic impact and explosion overpressure impact. The results also demonstrate that although the emergency evacuation may result in a severer explosion load to the operator, the process protection system can mitigate the adverse impacts regardless of whether the emergency evacuation is conducted or not.     

基于云平台的重庆环境监察移动执法系统集成研究

通过分析重庆市环境监察现场执法业务应用需求,结合现有的信息化现状及信息技术发展趋势,设计了“一个平台、一个中心、两个体系”的系统总体架构,提出了“移动端防控、链路安全、内网和服务器防护”的网络传输和信息安全系统设计,采用VPN专网,有效解决了符合三级等保安全的移动设备的传输网络,采用虚拟化的云服务平台,研发了市－区两级的重庆市环境监察移动执法系统,并在市局、涪陵和九龙坡区试点应用,取得了很好的应用效果。     

Nestmate recognition in three species of stenogastrine wasps (Hymenoptera,Vespidae)

The capacity to recognise a conspecific intruder was investigated in Parischnogaster jacobsoni, Liostenogaster flavolineata and L. vechti, three species of primitively social wasps of the subfamily Stenogastrinae. Results of behavioural experiments carried out in the field showed that females of all three species react pacifically if presented with female nestmates, but aggressively reject an intruder from a conspecific colony. As L. flavolineata and L. vechti both build large clusters of nests, often very close to each other, the recognition capacity among females from different nests, but in the same conspecific cluster, was also investigated. Females of both species were more aggressive towards females from a different colony in the same cluster than towards their female nestmates. Additional experiments on L. flavolineata showed that there was no difference in reaction towards females from colonies nearer or further from the tested colony but within the same cluster, nor towards females from a different cluster. The capacity to recognise an alien conspecific nest containing immature brood was investigated in P. jacobsoni. Adult females of this species, invited to land on an alien nest which had experimentally been exchanged for their own, accepted the new nest and partially destroyed the immature brood. The behaviour of the females when they land on an alien nest, however, suggests that they do recognise the nest as foreign. Acceptance of foreign nests coupled with low immature brood destruction is probably due to the high energetic costs of egg-deposition and larval rearing in stenogastrine wasps. These results suggest that nestmate recognition in these wasps is very efficient, even though they belong to the most primitive subfamily of social wasps. Received: 16 April 1996/Accepted after revision: 9 August 1996     

Multiple mate choice criteria and the importance of age for male mating success in the microhylid frog, Cophixalus ornatus

We examined multiple mate choice criteria in Cophixalus ornatus, a terrestrial breeding, microhylid frog. Mate choice consisted of three stages: mate attraction (male calling), courtship (male behavior between the call site and the nest), and nest site selection by the female. For male C. ornatus, the possession of a call with low dominant frequency relative to calling neighbors increased the probability that they would attract females. Dominant frequency was negatively correlated with age independent of male mass and snout vent length. When escorting the female from the call site to their nest, males traveled along more convoluted paths than when returning to the nest alone. The convolution of the path was, therefore, considered an aspect of courtship. Females released eggs into nests with structural characteristics typical of nests constructed by older males. Thus, females increased their chances of locating an acceptable nest by preferentially approaching males with lower dominant frequencies. This study is the first to demonstrate that age, independent of mass or snout-vent length, can influence call characteristics in anurans, and it is also the first to demonstrate the importance of male age to female mate choice in an amphibian.     

Integrating Nonindigenous Aquatic Plant Control with Protection of Snail Kite Nests in Florida

The endangered snail kite (Rostrhamus sociabilis) feeds primarily on the freshwater apple snail (Pomacea paludosa) in Florida. The nonindigenous, floating water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) impede kites from finding snails. Effective control of these aquatic plants in the littoral zone of central and south Florida lakes benefits kites by maintaining open foraging habitat. However, incidental herbicide spraying of nesting substrates result in nest collapse when kites breed in nonwoody, emergent plants [cattail (Typha spp.) and giant bulrush (Scirpus validus)] in the outer littoral zone during lower lake levels. Many endangered species recovery plans and their implementation have experienced problems due to inaction and/or noncooperation by various governmental agencies and their personnel. Herein, we describe the development and implementation of a buffer zone strategy to prevent secondary impacts from an aquatic plant control program to snail kites nesting on lakes in central and south Florida. A strategy was jointly developed by personnel of five state and federal agencies to control herbicide application near kite nesting areas during the normal breeding season. Although requiring various modifications during its implementation, this cooperative effort successfully integrated aquatic plant control objectives with snail kite conservation on Lake Okeechobee during 1988. The program was expanded the following year to lakes Kissimmee and Tohopekaliga. Since the implementation of the snail kite impact preclusion program, no nest loss was attributed to incidental herbicide applications on lakes Okeechobee, Kissimmee, and Tohopekaliga.     

Cannibalize or care? The role of perceived paternity in the sand goby, <Emphasis Type="Italic">Pomatoschistus minutus</Emphasis>

Parental care is a costly part of reproduction. Hence, natural selection should favor males which avoid caring for unrelated young. However, the decision to abandon or reduce care requires cues which are evaluated to give information on potential reproductive value of the offspring. The prediction that male sand gobies, Pomatoschistus minutus, care for foreign eggs as long as they were spawned in their own nest and at least some of such cues are fulfilled was tested. Egg-guarding males that had recently taken part in a spawning event were given a clutch of eggs that was sired either by themselves or another male, in either their own or another male’s aquarium. Males that had not taken part in a spawning event were used as controls and were given eggs sired by another male. We measured the amount of filial cannibalism and nest building. Control group males did not care for eggs and ate them all before rebuilding the nest. In the other treatments, there were no significant effects of paternity, though males moved to another male’s aquarium increased their clutch area threshold and completely consumed larger clutches than males that were not moved. There was no intermediate response in any treatment in the form of increased partial filial cannibalism or less well-constructed nests. Our results suggest that egg-guarding males cannot distinguish between eggs sired by themselves and those sired by other males but are able to react to cues indicating paternity state. Males do not adopt eggs to attract females in P. minutus.     

Are nest characters of importance when choosing a male in the fifteen-spined stickleback (Spinachia spinachia)?

Male fifteen-spined sticklebacks (Spinachia spinachia) build their nests by wrapping epiphytic algae around macroalgae and securing them with secretional threads. In this study, I show that female fifteen-spined stickleback prefer males which have built their nests above the surrounding vegetation. High-located nests are safer, because they are less likely to attract egg-predators such as shore crabs (Carcinus maenas). Thus, I found that shore crabs more rapidly find eggs in nests built close to the bottom than in nests well above the it. Moreover, male-male competition could be an additional explanation as to why males build nests high up. Thus, my field results suggest that the closer the males were to a neighbour, the higher they built. Larger males were also found to have larger territories but male size did not correlate with the height of the nest above the surrounding vegetation. Females showed no preference for nest size, regardless of the presence of egg-predators. However, they tended to choose nests that had no egg-predators in the vicinity over nests with egg-predators close by. Female choosiness for certain nest characters may provide one explanation for the evolution of male care in this species. Received: 29 December / 1999 Revised: 18 April 2000 / Accepted: 28 May 2000     

Nest concealment and parental behaviour interact in affecting nest survival in the blackcap (Sylvia atricapilla): an experimental evaluation of the parental compensation hypothesis

Nest concealment varies strongly within populations of many species. Although some studies have revealed the beneficial effects of concealment in mitigating predation pressure on nests, other studies were unable to find similar effects. One potential reason for the mixed results is that parental behaviour may compensate for the effects of nest cover, and specifically designed experimental studies are needed to reveal this compensation. I studied the effects of concealment on the probability of nest survival in the blackcap (Sylvia atricapilla), by experimentally manipulating the degree of nest-foliage cover. There was a significant effect of the treatment depending on nest type and the phase of nesting. Whereas there was no effect of concealment on nest survival in natural nests, there was a positive effect in real nests baited with plasticine clutches (i.e. without parental activity). Parents probably behaviourally compensated for poor concealment in natural nests (nest guarding, defence). In line with this, there was no effect of concealment on nest survival during incubation, whereas there was probably a positive effect in the nestling phase. Parents spent more time on the nest during incubation (80%) than during the care of nestlings (40%) and, consequently, had more opportunities to compensate for poor cover. In general, we cannot use single measures of behaviours or states (nest concealment) as an indication of predation risk because of the capacity for compensation in other behaviours.Communicated by C. Brown     

Self-organized digging activity in ant colonies

Many ant species adjust the volume of their underground nest to the colony size. We studied whether the regulation of the volume of excavated sand could result from an interplay between recruitment processes and ant density. Experiments were performed with different group sizes of workers in the ant Messor sancta. When presented with a thin homogeneous sand disk, these groups excavated networks of galleries in less than 3 days. The excavation dynamics were logistic shaped, which suggests the existence of a double feedback system: a positive one resulting in an initial exponential growth phase, and a negative one leading the dynamics to a saturation phase. The total volume of excavated sand was almost proportional to the number of workers. We then developed a model in which we incorporated the quantitative behavioral rules of the workers digging activity. A positive feedback was introduced in the form of a recruitment process mediated by pheromones. The model predicts that the excavation dynamics should be logistic shaped and the excavation should almost stop despite the absence of any explicit negative feedback. Moreover, the model was able to reproduce the positive linear relationship between nest volume and colony size.Communicated by K. Ross     

Cues used by shiny cowbirds (Molothrus bonariensis) to locate and parasitise chalk-browed mockingbird (Mimus saturninus) nests

Unlike other birds, shiny cowbirds (Molothrus bonariensis) must locate host nests where to lay their eggs and then decide whether to parasitise them. They should also synchronise their laying with that of the host to increase the survival of parasite egg and young. Shiny cowbirds can discover nests using host behaviour as a cue, or by searching the habitat without need for the presence of a host. Besides, they can synchronise parasitism with host laying by monitoring nests during building and laying, or directly by assessing the degree of development of embryos through the puncture of host eggs. Alternatively, synchronization can arise by lower nest attentiveness during host laying. We determined the extent of synchronization between laying of shiny cowbirds and chalk-browed mockingbirds (Mimus saturninus) and estimated if parasitism was negatively associated with host nest attentiveness. We also conducted an experiment to test if host activity was necessary to locate nests, and if puncture of host eggs was a cue for deciding parasitism. Shiny cowbirds synchronised parasitism with host laying in 75% of the cases and synchronization was not explained by lower host nest attentiveness during laying. Shiny cowbirds located nests without need for presence of a host, but the decision of parasitising the nest depended on host activity at the nest. The information that shiny cowbirds could obtain through egg punctures was not necessary for deciding parasitism. Our results indicate that shiny cowbirds rely on the precise timing of their eggs and avoid laying in unsuitable nests.