Cooperation between the fog and the cloud in mobile cloud computing environments could offer improved offloading services to smart mobile user equipment (UE) with computation intensive tasks. In this ...paper, we tackle the computation offloading problem in a mixed fog/cloud system by jointly optimizing the offloading decisions and the allocation of computation resource, transmit power, and radio bandwidth while guaranteeing user fairness and maximum tolerable delay. This optimization problem is formulated to minimize the maximal weighted cost of delay and energy consumption (EC) among all UEs, which is a mixed-integer non-linear programming problem. Due to the NP-hardness of the problem, we propose a low-complexity suboptimal algorithm to solve it, where the offloading decisions are obtained via semidefinite relaxation and randomization, and the resource allocation is obtained using fractional programming theory and Lagrangian dual decomposition. Simulation results are presented to verify the convergence performance of our proposed algorithms and their achieved fairness among UEs, and the performance gains in terms of delay, EC, and the number of beneficial UEs over existing algorithms.
Ocean acidification is predicted to have widespread implications for marine bivalve mollusks. While our understanding of its impact on their physiological and behavioral responses is increasing, ...little is known about their reproductive responses under future scenarios of anthropogenic climate change. In this study, we examined the physiological energetics of the Manila clam Ruditapes philippinarum exposed to CO2-induced seawater acidification during gonadal maturation. Three recirculating systems filled with 600 L of seawater were manipulated to three pH levels (8.0, 7.7, and 7.4) corresponding to control and projected pH levels for 2100 and 2300. In each system, temperature was gradually increased ca. 0.3°C per day from 10 to 20°C for 30days and maintained at 20°C for the following 40days. Irrespective of seawater pH levels, clearance rate (CR), respiration rate (RR), ammonia excretion rate (ER), and scope for growth (SFG) increased after a 30-day stepwise warming protocol. When seawater pH was reduced, CR, ratio of oxygen to nitrogen, and SFG significantly decreased concurrently, whereas ammonia ER increased. RR was virtually unaffected under acidified conditions. Neither temperature nor acidification showed a significant effect on food absorption efficiency. Our findings indicate that energy is allocated away from reproduction under reduced seawater pH, potentially resulting in an impaired or suppressed reproductive function. This interpretation is based on the fact that spawning was induced in only 56% of the clams grown at pH 7.4. Seawater acidification can therefore potentially impair the physiological energetics and spawning capacity of R. philippinarum.
•Effects of pH on molluscan physiology during gonadal maturation were investigated.•Feeding physiology is sensitive to seawater acidification.•Reduced seawater pH compromises the energy budget of clams.•Seawater acidification potentially impairs molluscan spawning capacity.
Today, billions of communication devices connecting to wireless networks impose serious challenges to network deployment, management, and data processing. Among all emerging technologies tackling ...these challenges, SDNs decouple the control plane from the data plane to provide network programmability, and virtualization can share network and radio resources among various applications. On the other hand, fog computing offloads computing services from the cloud to the edge of networks, offering real-time data services to nearby data terminals. In this article, we present an integrated architecture for software defined and virtualized radio access networks with fog computing. We propose a design of software as a service called OpenPipe, which enables network-level virtualization. To integrate SDNs and network virtualization with fog computing, we adopt a hybrid control model with two hierarchical control levels, where an SDN controller forms the higher level and local controllers comprise the lower level. Typical use cases of the proposed network architecture are validated through laboratory demonstrations.
In this paper, the energy-spectral efficiency (ESE) benefiting from the joint optimization of coordinated multi-point (CoMP) transmission and base station (BS) deployment is evaluated in the context ...of dense large-scale cellular network. We first derive a closed-form network ESE expression for a large-scale CoMP-enhanced network, which allows us to quantify the influence of key network parameters on the achievable network ESE, including the BS density and the cooperation activation probability, characterized by a CoMP activation factor as well as the users' behaviors, such as their geographical mobile-traffic intensity and average user rate. With the aid of this tractable ESE expression and for a given BS density, we next formulate a cellular-scenario-aware CoMP activation optimization problem while considering the users' outage probability as constraints to maximize the network's ESE. We then jointly optimize the CoMP activation factor and the BS density to maximize the network ESE, again under the constraint of the users' outage probability. Our simulation results confirm the accuracy of our analysis and verify the impact of several key parameters on the network ESE. Finally, the ESE improvement of our proposed strategies is evaluated under diverse scenarios, which provides valuable insight into the joint CoMP and BS deployment optimization in dense large-scale cellular networks.
Coastal eutrophication is an indisputable reality and becoming a worldwide concern. However, whether and how eutrophication affects metal bioaccumulation in marine bivalves have not yet been ...elucidated. Here, we present the potential influence of coastal eutrophication on metal bioaccumulation in the Manila clam Ruditapes philippinarum. The degree of coastal eutrophication was examined monthly over a 1-year period at three sampling sites. The bioconcentration factor (BCF), biosediment accumulation factor (BSAF) and metal pollution index (MPI) were applied to evaluate the efficiency of metal bioaccumulation in R. philippinarum. BCF and BSAF indicated that eutrophication did not significantly affect the bioaccumulation of Cr, Cu, Zn, Cd, Pb, Hg, and As in R. philippinarum. However, up to 56% of MPI variation can be related to the level of eutrophication. Therefore, further research should address the synergistic effects of eutrophication and metal pollution on coastal ecosystems.
•BCF, BSAF and MPI are employed to evaluate metal accumulation in Manila clams.•Up to 56% of MPI can be related to the degree of coastal eutrophication.•Eutrophication likely prompts metal accumulation in edible bivalves.
This paper studies the performance of cache-enabled dense small cell networks consisting of multi-antenna sub-6 GHz and millimeter-wave (mm-wave) base stations. Different from the existing works ...which only consider a single antenna at each base station, the optimal content placement is unknown when the base stations have multiple antennas. We first derive the successful content delivery probability by accounting for the key channel features at sub-6 GHz and mm-wave frequencies. The maximization of the successful content delivery probability is a challenging problem. To tackle it, we first propose a constrained cross-entropy algorithm which achieves the near-optimal solution with moderate complexity. We then develop another simple yet effective heuristic probabilistic content placement scheme, termed two-stair algorithm, which strikes a balance between caching the most popular contents and achieving content diversity. Numerical results demonstrate the superior performance of the constrained cross-entropy method and that the two-stair algorithm yields significantly better performance than only caching the most popular contents. The comparisons between the sub-6 GHz and mm-wave systems reveal an interesting tradeoff between caching capacity and density for the mm-wave system to achieve similar performance as the sub-6 GHz system.
Ocean acidification can negatively impact marine bivalves. Pivotal to projecting their fate is the ability to acclimate and adapt to shifts in seawater chemistry. Transgenerational plasticity enables ...marine bivalves to acclimate, yet the underlying mechanisms at different levels of biological organization remain poorly understood. Here, we performed a transgenerational experiment to understand biochemical responses of the Manila clam, Ruditapes philippinarum, following exposure to moderately reduced seawater pH (from 8.1 to 7.7). Activities of tissue calcification-relevant enzymes, such as carbonic anhydrase (CA), acid phosphatase (ACP) and alkaline phosphatase (ALP), energy-metabolizing enzymes, such as Na+/K+-ATPase (NKA) and Ca2+/Mg2+-ATPase (CMA), as well as tissue energy reserves (glycogen, lipid and protein) were assayed. With decreasing seawater pH, adult R. philippinarum exhibited significantly increased CA activity, and especially the clams with a history of transgenerational exposure displaying significantly higher CA activity than those spawned from parents exposed to ambient seawater pH. Yet, ACP and ALP activities remained unaffected. Transgenerational exposure to reduced seawater pH led to significant increases of NKA activity, while no transgenerational response of CMA activity was observed. Tissue glycogen and lipid contents were significantly depleted under acidified conditions regardless of transgenerational exposure. Yet, transgenerational alleviation in the net protein degradation was found. These findings suggest that our current understanding of transgenerational responses is still limited by the achievable time-window possible in the laboratory. While the energetic budget is lower under acidified conditions, there is no evidence of transgenerational recovery in term of energetic budget. Therefore, this work demonstrates that the critical basis of ocean acidification resilience can most likely be explained in energetic terms.
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•Transgenerational exposure to seawater acidification significantly increased the activity of carbonic anhydrase.•A significant decrease of Na+/K+-ATPase activity was seen in transgenerationally acclimated clams under acidified conditions.•Tissue protein degradation was alleviated following transgenerational exposure to seawater acidification.
•Neither pH nor transgeneration elicited lipid peroxidation.•Antioxidant responses occurred in CO2-exposed mussels.•Transgenerational effects alleviated oxidative stress responses.•Transgenerational ...immunity may occur rapidly in an acidifying ocean.
Ocean acidification and marine biofouling, which may interact in the future, pose two major threats to global coastal ecosystems. Yet, the fate of highly invasive fouling species in a rapidly acidifying ocean remains poorly understood, due to lack of information on multigenerational consequences at different levels of biological organization. Here, we investigated antioxidant responses of the mussel, Musculista senhousia, a swiftly spreading invasive fouling species in global coastal waters, following transgenerational exposure to elevated pCO2. In the face of seawater acidification, M. senhousia without a prior history of transgenerational exposure to elevated pCO2 showed resistance to lipid peroxidation, but significantly increased activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), indicated oxidative stress responses. However, enhanced transgenerational immunity occurred, as exemplified by observations that mussels originating from parents exposed to elevated pCO2 exhibited significantly lower activities of SOD, CAT and GPx in comparison to those spawn from parents exposed to ambient pCO2. Rapid transgenerational acclimation of M. senhousia in terms of reduced oxidative stress responses can likely be linked to the enhanced capacity of maintaining acid-base homeostasis previously demonstrated. These findings provide the first evidence of transgenerational plasticity at the biochemical level in highly invasive fouling bivalve species, and represent a step forward in understanding how they respond and acclimate in an acidifying ocean.
Marine biofouling by the swiftly spreading invasive mussel (Musculista senhousia) has caused serious ecological and economic consequences in the global coastal waters. However, the fate of this ...highly invasive fouling species in a rapidly acidifying ocean remains unknown. Here, we demonstrated the impacts of ocean acidification within and across generations, to understand whether M. senhousia has the capacity to acclimate to changing ocean conditions. During the gonadal development, exposure of mussels to elevated pCO2 caused significant decreases of survival, growth performance and condition index, and shifted the whole-organism energy budget by inflating energy expenses to fuel compensatory processes, eventually impairing the success of spawning. Yet, rapid transgenerational acclimation occurred during the early life history stage and persisted into adulthood. Eggs spawned from CO2-exposed mussels were significantly bigger compared with those from non-CO2-exposed mussels, indicating increased maternal provisioning into eggs and hence conferring larvae resilience under harsh conditions. Larvae with a prior history of transgenerational exposure to elevated pCO2 developed faster and had a higher survival than those with no prior history of CO2 exposure. Transgenerational exposure significantly increased the number of larvae completing metamorphosis. While significant differences in shell growth were no longer observed during juvenile nursery and adult grow-out, transgenerationally exposed mussels displayed improved survival in comparison to non-transgenerationally exposed mussels. Metabolic plasticity arose following transgenerational acclimation, generating more energy available for fitness-related functions. Overall, the present study demonstrates the remarkable ability of M. senhousia to respond plastically and acclimate rapidly to changing ocean conditions.
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•Asian date mussels are sensitive to elevated pCO2 during gonadal ripening.•Transgenerational phenotypic plasticity occurred through all life history stages.•Maternal provisioning and metabolic adaptation serve as key mechanisms.•Mussels hold the great ability to rapidly adapt to changing ocean conditions.
Ocean acidification may interfere with the calcifying physiology of marine bivalves. Therefore, understanding their capacity for acclimation and adaption to low pH over multiple generations is ...crucial to make predictions about the fate of this economically and ecologically important fauna in an acidifying ocean. Transgenerational exposure to an acidification scenario projected by the end of the century (i.e., pH 7.7) has been shown to confer resilience to juvenile offspring of the Manila clam, Ruditapes philippinarum. However, whether, and to what extent, this resilience can persist into adulthood are unknown and the mechanisms driving transgenerational acclimation remain poorly understood. The present study takes observations of Manila clam juveniles further into the adult stage and observes similar transgenerational responses. Under acidified conditions, clams originating from parents reproductively exposed to the same level of low pH show a significantly faster shell growth rate, a higher condition index and a lower standard metabolic rate than those without prior history of transgenerational acclimation. Further analyses of stable carbon isotopic signatures in dissolved inorganic carbon of seawater, individual soft tissues and shells reveal that up to 61% of shell carbonate comes from metabolic carbon, suggesting that transgenerationally acclimated clams may preferentially extract internal metabolic carbon rather than transport external seawater inorganic carbon to build shells, the latter known to be energetically expensive. While a large metabolic carbon contribution (45%) is seen in non-acclimated clams, a significant reduction in the rate of shell growth indicates it might occur at the expense of other calcification-relevant processes. It therefore seems plausible that, following transgenerational acclimation, R. philippinarum can implement a less costly and more efficient energy-utilizing strategy to mitigate the impact of seawater acidification. Collectively, our findings indicate that marine bivalves are more resilient to ocean acidification projected for the end of the century than previously thought.
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•Rapid transgenerational acclimation can persist into adulthood.•Stable carbon isotope analysis deciphers carbon sources of the shell.•Transgenerational exposure elicits a large metabolic carbon contribution to shell carbonate.
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