Aerial-terrestrial communications: terrestrial cooperation and energy-efficient transmissions to aerial-base stations

Hybrid aerial-terrestrial communication networks based on low-altitude platforms are expected to meet optimally the urgent communication needs of emergency relief and recovery operations for tackling large-scale natural disasters. The energy-efficient operation of such networks is important given that the entire network infrastructure, including the battery-operated ground terminals, exhibits requirements to operate under power-constrained situations. In this paper, we discuss the design and evaluation of an adaptive cooperative scheme intended to extend the survivability of the battery-operated aerial-terrestrial communication links. We propose and evaluate a real-time adaptive cooperative transmission strategy for dynamic selection between direct and cooperative links based on the channel conditions for improved energy efficiency. We show that the cooperation between mobile terrestrial terminals on the ground could improve energy efficiency in the uplink, depending on the temporal behavior of the terrestrial and aerial uplink channels. The corresponding delay in having cooperative (relay-based) communications with relay selection is also addressed. The simulation analysis corroborates that the adaptive transmission technique improves overall energy efficiency of the network whilst maintaining low latency, enabling real-time applications

Keep off the grass: Using herbivore exclusion cages to understand herbivory in seagrass meadows

Seagrasses provide important habitat that delivers ecosystem services and provides food to a wide diversity of herbivores globally. In the Great Barrier Reef (GBR) we find the full size spectrum of herbivores; from small mesograzers such as amphipods, to macrograzers such as fish and large megagrazers such as turtles and dugongs. These herbivores can structurally alter seagrass beds in either positive or negative ways depending on their size, feeding preferences and methods and grazing intensity. These structural changes can subsequently interact with the delivery of other ecosystem services, or the benefits to humans, provided by the seagrass meadow. In the tropics, we know little about the impact of herbivores and how different groups interact to structure seagrass meadows, despite the number and variety of herbivores present in tropical seagrass habitats. We carried out exclusion experiments that targeted each herbivore group individually and in combination in subtidal and intertidal seagrass meadows in Queensland, Australia to understand the role of herbivores in structuring meadows and the interaction between herbivore groups. Our results show different feeding strategies of herbivores in each habitat, especially megaherbivores, and these impact the meadow in different ways. The effects on biomass, shoot density and shoot height depended on the type of grazing observed. All herbivore groups acted to structure the seagrass and interacted to influence overall meadow properties. Grazer mediated changes in meadow structure will have important implications for the ecosystem services delivered by tropical seagrass ecosystems

Exclusion studies reveal the interactions between herbivores in structuring seagrass meadows their ecosystem services and the implications for effective management

Seagrasses provide important habitat that delivers ecosystem services and provides food to a wide diversity of herbivores globally. In the Great Barrier Reef we find large seagrass meadows that are grazed on by a diverse herbivore community. This presents a challenge for managers trying to conserve herbivores, the habitats they rely on and maintain ecosystem service delivery in coastal ecosystems. Herbivore communities can structurally alter seagrass meadows in positive or negative ways depending on their size, feeding methods and grazing intensity. These structural changes can alter the ecosystem services provided by the seagrass meadow. We carried out exclusion experiments targeting each herbivore group individually and in combination in subtidal and intertidal seagrass meadows in Queensland, to understand how herbivores can structure meadows and the interactions between herbivore groups. Our results show different feeding strategies of herbivores in each habitat, especially megaherbivores, which impact the meadow in different ways. The effects on biomass, shoot density and shoot height depended on the type of grazing observed. Grazer mediated changes in meadow structure will have important implications for the ecosystem services delivered by tropical seagrass ecosystems and the management of these ecosystems, including incorporating grazing dynamics into monitoring projects

Spatial and temporal patterns in macroherbivore grazing in a multi-species tropical seagrass meadow of the Great Barrier Reef

Macroherbivory is an important process in seagrass meadows worldwide; however, the impact of macroherbivores on seagrasses in the Great Barrier Reef (GBR) has received little attention. We used exclusion cages and seagrass tethering assays to understand how the intensity of macroherbivory varies over space and time in the seagrass meadows around Green Island (Queensland), and what impact this has on overall meadow structure. Rates of macroherbivory were comparatively low, between 0.25–44% of daily seagrass productivity; however, rates were highly variable over a one-year period, and among sites. Loss of seagrass material to macroherbivory was predominantly due to fish; however, urchin herbivory was also taking place. Macroherbivory rates were of insufficient intensity to impact overall meadow structure. No macroherbivory events were identified on video cameras that filmed in the day, indicating that feeding may be occurring infrequently in large shoals, or at night. While relatively low compared to some meadows, seagrass macroherbivory was still an important process at this site. We suggest that in this highly protected area of the GBR, where the ecosystem and food webs remain largely intact, macroherbivory was maintained at a low level and was unlikely to cause the large-scale meadow structuring influence that can be seen in more modified seagrass systems

Ellipsometer nulling: convergence and speed

The process of nulling in ellipsometry is studied by a graphical presentation using the trajectories of two significant polarization states in the complex plane, XPC and XSA. These states are determined by (1) the polarizer and compensator (XPC) and (2) the specimen and the analyzer (XSA) in the polarizer-compensator-specimen-analyzer ellipsometer arrangement. As the azimuth angles of the ellipsometer elements are varied, XPC and XSA move closer to one another in a stepwise fashion until they coincide when a null is reached. Thus, at null, the polarization states are matched, and XPC = XSA. For an isotropic reflector, the trajectory of XSA is a straight line, which simplifies the development of a criterion for achieving the most rapid nulling for two nulling procedures

Exclusion studies reveal the interactions between herbivores in structuring seagrass meadows

Seagrasses provide important habitat that delivers ecosystem services and provides food to a wide diversity of herbivores globally. In the Great Barrier Reef we find large seagrass meadows that are grazed on by a diverse herbivore community. This presents a challenge for managers trying to conserve herbivores, the habitats they rely on and maintain ecosystem service delivery in coastal ecosystems. Herbivore communities can structurally alter seagrass meadows in positive or negative ways depending on their size, feeding methods and grazing intensity. These structural changes can alter the ecosystem services provided by the seagrass meadow. We carried out exclusion experiments targeting each herbivore group individually and in combination in subtidal and intertidal seagrass meadows in Queensland, Australia to understand how herbivores can structure meadows and the interactions between herbivore groups. Our results show different feeding strategies of herbivores in each habitat, especially megaherbivores, which impact the meadow in different ways. The effects on biomass, shoot density and shoot height depended on the type of grazing observed. Grazer mediated changes in meadow structure will have important implications for the ecosystem services delivered by tropical seagrass ecosystems and the management of these ecosystems, including incorporating grazing dynamics into monitoring projects

Ellipsometer nulling: convergence and speed

The process of nulling in ellipsometry is studied by a graphical presentation using the trajectories of two significant polarization states in the complex plane, XPC and XSA. These states are determined by (1) the polarizer and compensator (XPC) and (2) the specimen and the analyzer (XSA) in the polarizer-compensator-specimen-analyzer ellipsometer arrangement. As the azimuth angles of the ellipsometer elements are varied, XPC and XSA move closer to one another in a stepwise fashion until they coincide when a null is reached. Thus, at null, the polarization states are matched, and XPC = XSA. For an isotropic reflector, the trajectory of XSA is a straight line, which simplifies the development of a criterion for achieving the most rapid nulling for two nulling procedures

A framework for defining seagrass habitat for the Great Barrier Reef, Australia

This report describes a framework to define seagrass habitat and seagrass desired state for the Great Barrier Reef (GBR). We developed this by defining assessment zones using key physical attributes for the GBR. The assessment zones were developed with two main objectives: (1) to assess the representativeness of existing seagrass data throughout the GBR; and (2) to provide a framework in which to develop seagrass desired state (i.e. condition targets). We defined assessment zones using spatial data that reflect environmental and benthic condition likely to affect seagrass distribution, diversity and density. These include: (1) latitude, defined as regions using 6 Natural Resource Management (NRM) boundaries, (2) influence from and proximity to land (estuarine, coastal, reef, and offshore water bodies), and (3) water depth (intertidal, shallow subtidal 10m) resulting in 68 zones for the GBR. The largest assessment zone was the offshore water body in every region. Deep subtidal was the largest depth zone in coastal, reef, and offshore waters in each region. The estuarine deep subtidal zone was limited. Zones are seagrass-centric and not analogous to the Great Barrier Reef Marine Park zoning. Data from extensive seagrass surveys and long-term monitoring across the GBR since the early 1980s provides information on seagrass presence/absence, species composition, abundance, and spatial extent. Data rich areas include coastal and estuarine intertidal and shallow subtidal zones. Data from reef and offshore zones, and in deep subtidal zones, are more limited as it comes from sporadic one-off surveys and few meadows have been mapped. Available seagrass data ranges from sporadic large-scale survey data with low to medium spatial and low temporal resolution, to high spatial and high temporal resolution data collected seasonally at discrete sites. Defining these assessment zones is a critical first step in defining habitat types and quantifying desired state for GBR seagrasses. Habitat attributes not included in the zones, such as sediment type and exposure to wind and waves, as well as new seagrass biomass data will be used to update the framework, turning it into a full habitat assessment for defining desired state. A case study based in Cleveland Bay, as well as previous research, will be used to identify how this framework will be updated. Seagrass desired state is an ecological target that can be used to assess the effectiveness of management strategies to protect seagrass of the GBR. Desired state analysis requires data with medium to high spatial and temporal resolution that allows assessment in the context of disturbance events, recovery trajectories, and seasonal fluctuations. Robust analysis will be restricted to locations within zones where continuous data collection has occurred, e.g. the Marine Monitoring Program (MMP) and Queensland Ports Seagrass Monitoring Program (QPSMP), and for an adequate time span (generally >10 years)

Molecular Detection of Virulence Factors (Adhesion Genes) in Some Staphylococcus Epidermidis Locally Isolated From Different Clinical Sources

The icaA and icaD genes are found in bacterial cells. The icaA and icaD genes allow a bacterium to produce biofilm. Biofilms are an important virulence determinant in bacteria because biofilm formation significantly increases resistance to antibiotics and promotes host defenses. The ability of biofilm production can be determined by two phenotypic methods and genotypic methods of some adhesion factors (icaA and icaD). The phenotypic methods included the Congo-red agar (CRA) and Microtiter plate (Mtp). The results showed that 58 (69%) from 84 isolates were positive for producing biofilm on (CRA) plates and the 55 (65%) from 84 isolates were positive for adhesion and biofilm formation by (Mtp) on the O.D. 490nm. The extraction of DNA is subjected to use for polymerase chain reaction (PCR) which is used to amplify specific genes. The production of viscous layer of Staphylococcus epidermidis was investigated by using Molecular analysis (PCR) monoplex to amplify the virulence factor (icaA, icaD) genes (adhesion factors) with the amplicon sizes 188 bp and 198 bp, respectively. The results of the genes icaA and icaD represented as sixty for (46) 54.8% and thirty (30) 35.7%, respectively. The conclusion to these study detection to icaA and icaD genesis important virulence factor

Effective action for the field equations of charged black holes

In this article, we consistently reduce the equations of motion for the bosonic N = 2 supergravity action, using a multi-centered black hole ansatz for the metric. This reduction is done in a general, non-supersymmetric setup, in which we extend concepts of BPS black hole technology. First of all we obtain a more general form of the black hole potential, as part of an effective action for both the scalars and the vectors in the supergravity theory. Furthermore, we show that there are extra constraints specifying the solution, which we calculate explicitly. In the literature, these constraints have already been studied in the one-center case. We also show that the effective action we obtain for non-static metrics, can be linked to the "entropy function" for the spherically symmetric case, as defined by Sen and Cardoso et al.Comment: 18 pages, (v2: small corrections, version to be published in CQG