ElfStore: A Resilient Data Storage Service for Federated Edge and Fog Resources

Edge and fog computing have grown popular as IoT deployments become wide-spread. While application composition and scheduling on such resources are being explored, there exists a gap in a distributed data storage service on the edge and fog layer, instead depending solely on the cloud for data persistence. Such a service should reliably store and manage data on fog and edge devices, even in the presence of failures, and offer transparent discovery and access to data for use by edge computing applications. Here, we present Elfstore, a first-of-its-kind edge-local federated store for streams of data blocks. It uses reliable fog devices as a super-peer overlay to monitor the edge resources, offers federated metadata indexing using Bloom filters, locates data within 2-hops, and maintains approximate global statistics about the reliability and storage capacity of edges. Edges host the actual data blocks, and we use a unique differential replication scheme to select edges on which to replicate blocks, to guarantee a minimum reliability and to balance storage utilization. Our experiments on two IoT virtual deployments with 20 and 272 devices show that ElfStore has low overheads, is bound only by the network bandwidth, has scalable performance, and offers tunable resilience.Comment: 24 pages, 14 figures, To appear in IEEE International Conference on Web Services (ICWS), Milan, Italy, 201

Sorption and Drug Release Studies from Semi-interpenetrating Polymer Networks of Chitosan and Xanthan Gum

Hydrogel films of Chitosan (CS) and Xanthan gum (XA) of compositions 100/0, 90/10, 80/20, 70/30, 60/40 and 50/50 (w/w) % were prepared and swollen in simulated gastric fluid (SGF) of pH 1.2 and simulated intestinal fluid (SIF) of pH 7.4. To impart stability in acidic environment, semi-interpenetrating polymer network (semi-IPNs) films were formed using glutaraldehyde (GA) as the crosslinking agent. With increase in XA concentration, equilibrium degree of swelling reduced in SGF as well as SIF indicating maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The swelling data was observed to follow second order kinetics. Spectroscopic and thermal analyses of these semi-IPN films also suggest maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The potential of using 50/50 semi-IPN in drug delivery was studied using amoxicillin. In-vitro drug release studies indicated higher drug release in SGF than in SIF suggesting dependence of amoxicillin release kinetics and diffusion coefficient on pH of the environment and drug loading. The results suggest that CS-based semi-IPNs with different crosslinker and XA concentration could be promising candidates for formulation in oral gastrointestinal delivery systems

PHYSIOLOGICAL AND ECOLOGICAL DRIVERS AND AGRONOMICAL CONSEQUENCES OF THE OZONE-LIKE SYNDROME IN WHEAT

Tropospheric ozone (O3) is known to adversely affect the productivity of a wide range of crops including wheat. However different species, can exhibit different responses to ozone exposure. Since the Triticum genus (wheat) is one of the most cultivated and consumed cereal on the global scale and also considered an O3-sensitive crop, research on its protection against ozone damages can contribute to the improvement of its productivity and thus the worldwide food security. The first part of this research was focused on a varietal screening experiment carried out in 2013 to assess the ozone sensitivity of 3 Italian and 2 Spanish cultivars of durum wheat (Triticum durum), applying two different levels of ozone (50% increment and 50% decrement of the ambient ozone concentration ) to plants grown in Open-Top Chambers. The durum wheat sensitivity to ozone was based on the assessment of leaf visible injuries, histochemical observations, physiological parameters, yield and yield quality analysis. Two Italian cultivars (Colombo and Sculptur) resulted more sensitive to ozone than the others, according to the physiological parameters tested and to the grain yield and quality analysis. However, they also showed different levels of leaf visible and microscopic injuries. The flag-leaves of cv Colombo resulted clearly more damaged by ozone exposure than the flag-leaves of cv Sculptur at both visible and microscopic levels. The second part of the research tried to analyze to a deeper extent the response to ozone exposure of the two most sensitive cultivars selected from the previous experiment. A second experiment was performed in 2014 using four ozone levels: -5% and -50% of ambient ozone concentration in non-filtered and charcoal-filtered OTCs, respectively; +30 and +60% of ambient ozone concentration in ozone-enriched OTCs (OZ+ and OZ++ OTC). In order to test the effectiveness of an antitranspirant compound in protecting durum wheat from ozone oxidative stress, a chitosan solution was weekly applied as leaf spraying during the growing season in 2014. The chitosan treatments were applied at 3 levels: tap-water (CTRL, no chitosan), 40kDa chitosan solution (CHI40) and 300kDa chitosan solution (CHI300). Both durum wheat cultivars confirmed their sensitivity to ozone as observed in the previous experiment. Grain yield losses observed in ozonated treatments were related to a decrease of stomatal conductance that is due to damages to the Rubisco and Calvin cycle. No protective effect due to chitosan treatments was observed in both cultivars. However, chitosan improved slightly the grain yield and the aboveground biomass production in plants grown in charcoal-filtered and non-filtered OTCs. Biomass data were also used for the definition of dose-effect relationships based on the ozone exposure (AOT40), the phytotoxic ozone dose (POD6) and the yield losses. The grain yield losses were plotted against AOT40 and POD6 in order to test the linear regression of these two indices. Each increase of AOT40 3000 ppb.h caused a grain yield loss of about 1.8%, while for the POD6, an increase of 1mmol O3 m-2 caused 1.3% reduction. Both AOT40 and POD6 resulted appropriated for assessment of durum wheat yield losses. However, the dose-effect relationship based on POD6 showed a better fit compared to the AOT40. During the 2014 experiment an important part of the research regarded the ultrastructural analysis of ozone-like symptoms on flag-leaves carried out by transmission electron microscopy (TEM), and the assessment of the levels of some antioxidant molecules (ascorbate and glutathione) involved in the ozone-detoxifying process, to understand the mechanisms underlying the different ozone sensitivity of Colombo and Sculptur in terms of visible and microscopic symptoms. Results from TEM demonstrated that visible symptoms in Colombo are due to the presence of damaged stomata and plasmolyzed mesophyll cells around the sub-stomatal cavity. On other hand, no damage on stomata, mesophyll cells and chloroplasts were observed in Sculptur cultivar explaining the absence of the visible symptoms. In general Sculptur showed higher levels of ascorbate content than Colombo, suggesting a higher capacity ascorbate biosynthesis. No significant difference in ascorbate content was found between plants exposed and not exposed to elevated ozone. The total and the oxidized glutathione content increased in the Colombo cultivar grown in elevated ozone conditions indicating that plant ability to maintain glutathione in the reduced form was decreased by the ozone stress

ParIC : A Family of Parallel Incomplete Cholesky Preconditioners

A class of parallel incomplete factorization preconditionings for the solution of large linear systems is investigated. The approach may be regarded as a generalized domain decomposition method. Adjacent subdomains have to communicate during the setting up of the precon­ ditioner, and during the application of the preconditioner. Overlap is not necessary to achieve high performance. Fill­in levels are considered in a global way. If necessary, the technique may be implemented as a global re­ordering of the unknowns. Experimental results are reported for two­dimensional problems

Spatial and temporal variation of hydraulic conductivity and vegetation growth in green infrastructures using infiltrometer and visual technique

Hydraulic conductivity of a vegetated soil (i.e., mixed grass cover) is an important parameter governing the hydrological performance of green infrastructure (GI). This paper focuses on GI with mixed grass cover in the presence of trees. Due to shading effects (interception of radiant energy) of tree canopy, mixed grass cover in the vicinity of trees may not receive direct photosynthetically active radiation (PAR). This can hinder the growth rates resulting in the low grass cover (i.e., in density). The hydraulic conductivity and the performance of GI can be further affected. Several field studies were conducted to investigate hydraulic conductivity in different types of vegetated covers. However, any variation in growth and hydraulic conductivity of mixed grass cover in the vicinity of trees was rarely investigated. The objective of this study is to quantify spatial and temporal variation of vegetation growth and hydraulic conductivity in a mixed grass cover in the vicinity of a tree. Field monitoring of a mixed grass cover in the vicinity of a tree in a GI was conducted for about six months. Hydraulic conductivity tests were carried out using mini disk infiltrometer (MDI) at 149 locations in a selected site once every month. Vegetation density was quantified using image analysis and the images were captured by a DJI Phantom drone. The growth of mixed grass cover around tree vicinity (within 5 m radial distance) was found to be more uniform during months characterized by high rainfall depth. Spatial heterogeneity in both vegetation density and hydraulic conductivity is found to be more significant during a dry period than wet period. Variation of hydraulic conductivity with respect to the change in vegetation density is found to be significant in a wet period than dry period. It is also found that hydraulic conductivity is higher at the portions where shredded leaves are present. The obtained dynamic spatio-temporal relationship of soil, vegetation and atmospheric parameters can support the design of green infrastructures and contribute to a better understanding of the maintenance practices