Antarctic subglacial lakes have, over the past few years, been hypothesised to house unique forms of life and hold detailed
sedimentary records of past climate change. Testing this hypothesis requires in situ examinations. The direct measurement
of subglacial lakes has been considered ever since the largest and best-known lake, named Lake Vostok, was identified as having
a deep water-column. The Subglacial Antarctic Lake Environments (SALE) programme, set up by the Scientific Committee on Antarctic
Research (SCAR) to oversee subglacial lakes research, state that prior exploration of smaller lakes would be a “prudent way
forward”. Over 145 subglacial lakes are known to exist in Antarctica, but one lake in West Antarctica, officially named Ellsworth
Subglacial Lake (referred to hereafter as Lake Ellsworth), stands out as a candidate for early exploration. A consortium of
over 20 scientists from seven countries and 14 institutions has been assembled to plan the exploration of Lake Ellsworth.
An eight-year programme is envisaged: 3 years for a geophysical survey, 2 years for equipment development and testing, 1 year
for field planning and operation, and 2 years for sample analysis and data interpretation. The science experiment is simple
in concept but complex in execution. Lake Ellsworth will be accessed using hot water drilling. Once lake access is achieved,
a probe will be lowered down the borehole and into the lake. The probe will contain a series of instruments to measure biological,
chemical and physical characteristics of the lake water and sediments, and will utilise a tether to the ice surface through
which power, communication and data will be transmitted. The probe will pass through the water column to the lake floor. The
probe will then be pulled up and out of the lake, measuring its environment continually as this is done. Once at the ice surface,
any water samples collected will be taken from the probe for laboratory analysis (to take place over subsequent years). The
duration of the science mission, from deployment of the probe to its retrieval, is likely to take between 24 and 36 h. Measurements
to be taken by the probe will provide data about the following: depth, pressure, conductivity and temperature; pH levels;
biomolecules (using life marker chips); anions (using a chemical analyzer); visualisation of the environment (using cameras
and light sources); dissolved gases (using chromatography); and morphology of the lake floor and sediment structures (using
sonar). After the probe has been retrieved, a sediment corer may be dropped into the lake to recover material from the lake
floor. Finally, if time permits, a thermistor string may be left in the lake water to take time-dependent measurements of
the lake’s water column over subsequent years. Given that the comprehensive geophysical survey of the lake will take place
in two seasons during 2007–2009, a two-year instrument and logistic development phase from 2008 (after the lake’s bathymetry
has been assessed) makes it possible that the exploration of Lake Ellsworth could take place at the beginning of the next
decade. 相似文献
Industrial Control Systems and Supervisory Control and Data Acquisition (ICS/SCADA) systems are profound backbones of the national critical infrastructures and are essential to the sustainability of society since they help monitoring and controlling the cyber-enable services, such as energy, transportation, healthcare, etc. Modern SCADA systems continue to use the legacy communication protocols that lack adequate security mechanisms to provide trusted device authentication and ensure data flow integrity. Furthermore, advent of state-of-the-art network-capable sensor technology exposes many unique vulnerabilities to the adversaries. Thus, integrity of the data originated from field sensors along with their identity must be managed carefully in order to enhance reliability of ICS/SCADA ecosystems. In this paper, we present a blockchain-based SRAM PUF Authentication and Integrity (BloSPAI) protocol that aims to ensure a continuous authentication of field sensors and provide a robust data flow integrity process by leveraging distributed ledger and hardware security primitives. The prototype of the protocol has been implemented in a sensor-integrated Raspberry PI testbed that is interfaced with a permissioned blockchain network. We discuss the performance and overhead aspects of the proposed BloSPAI protocol and compare with state-of-art cybersecurity solutions. Through experimental evaluation demonstrates the relationship between the size of the blockchain network impacts the throughput in terms of time to commit transactions and overall systems setup time.
The conversion of natural habitats to human land uses often increases local temperatures, creating novel thermal environments for species. The variable responses of ectotherms to habitat conversion, where some species decline while others persist, can partly be explained by variation among species in their thermal niches. However, few studies have examined thermal niche variation within species and across forest‐land use ecotones, information that could provide clues about the capacity of species to adapt to changing temperatures. Here, we quantify individual‐level variation in thermal traits of the tropical poison frog, Oophaga pumilio,in thermally contrasting habitats. Specifically, we examined local environmental temperatures, field body temperatures (Tb), preferred body temperatures (Tpref), critical thermal maxima (CTmax), and thermal safety margins (TSM) of individuals from warm, converted habitats and cool forests. We found that frogs from converted habitats exhibited greater mean Tb and Tpref than those from forests. In contrast, CTmax and TSM did not differ significantly between habitats. However, CTmax did increase moderately with increasing Tb, suggesting that changes in CTmax may be driven by microscale temperature exposure within habitats rather than by mean habitat conditions. Although O. pumilio exhibited moderate divergence in Tpref, CTmax appears to be less labile between habitats, possibly due to the ability of frogs in converted habitats to maintain their Tb below air temperatures that reach or exceed CTmax. Selective pressures on thermal tolerances may increase, however, with the loss of buffering microhabitats and increased frequency of extreme temperatures expected under future habitat degradation and climate warming. Abstract in Spanish is available with online material. 相似文献
Regional climate change in Antarctica would favor the carbon assimilation of Antarctic vascular plants, since rising temperatures are approaching their photosynthetic optimum (10–19°C). This could be detrimental for photoprotection mechanisms, mainly those associated with thermal dissipation, making plants more susceptible to eventual drought predicted by climate change models. With the purpose to study the effect of temperature and water availability on light energy utilization and putative adjustments in photoprotective mechanisms of Deschampsia antarctica Desv., plants were collected from two Antarctic provenances: King George Island and Lagotellerie Island. Plants were cultivated at 5, 10 and 16°C under well‐watered (WW) and water‐deficit (WD, at 35% of the field capacity) conditions. Chlorophyll fluorescence, pigment content and de‐epoxidation state were evaluated. Regardless of provenances, D. antarctica showed similar morphological, biochemical and functional responses to growth temperature. Higher temperature triggered an increase in photochemical activity (i.e. electron transport rate and photochemical quenching), and a decrease in thermal dissipation capacity (i.e. lower xanthophyll pool, Chl a/b and β carotene/neoxanthin ratios). Leaf mass per unit area was reduced at higher temperature, and was only affected in plants exposed to WD at 16°C and exhibiting lower electron transport rate and amount of chlorophylls. D. antarctica is adapted to frequent freezing events, which may induce a form of physiological water stress. Photoprotective responses observed under WD contribute to maintain a stable photochemical activity. Thus, it is possible that short‐term temperature increases could favor the photochemical activity of this species. However, long‐term effects will depend on the magnitude of changes and the plant's ability to adjust to new growth temperature. 相似文献
Vallinoto, M., Sequeira, F., Sodré, D., Bernardi, J. A. R., Sampaio, I. & Schneider, H. (2009). Phylogeny and biogeography of the Rhinella marina species complex (Amphibia, Bufonidae) revisited: implications for Neotropical diversification hypotheses. —Zoologica Scripta, 39, 128–140. A number of distinct hypotheses have been proposed to account for the origin of the considerable biological diversity found in the Neotropics, which is still a matter of intense debate. Here, we conducted a phylogenetic analysis of the Rhinella marina complex, a group of species widely distributed in Central and South America, combining published data with new sequences of three mtDNA genes (12S, 16S and cyt b) in order to clarify the evolutionary relationships and biogeographical history of the group. We included eight of the ten currently recognized R. marina group species and several outgroups. Maximum parsimony, maximum likelihood, and Bayesian inference analyses produced similar topologies, with two well‐supported main clades, each characterized by a deep subdivision. One of these major clades includes the samples of R. marina from Central America and Ecuador (west of the Andes), whereas the other comprises the remaining species of the group and samples of R. marina from the Amazon basin and other areas east of the Andes. A Bayesian coalescent‐based method (BEAST) dated the divergence between the two major clades, and between the Central American and Ecuadorian clades to the Miocene, matching the timing of other Central‐South American faunal divergences. Taken together, the results highlight the importance of Tertiary events such as the Pebas/marine incursions into the Amazon basin and Andean uplift for the diversification and historical biogeography of R. marina, making such taxa paraphyletic, and provide new perspectives on the debate on its species status. 相似文献