A Context-aware Trust Framework for Resilient Distributed Cooperative Spectrum Sensing in Dynamic Settings

Cognitive radios enable dynamic spectrum access where secondary users (SUs) are allowed to operate on the licensed spectrum bands on an opportunistic noninterference basis. Cooperation among the SUs for spectrum sensing is essential for environments with deep shadows. In this paper, we study the adverse effect of insistent spectrum sensing data falsification (ISSDF) attack on iterative distributed cooperative spectrum sensing. We show that the existing trust management schemes are not adequate in mitigating ISSDF attacks in dynamic settings where the primary user (PU) of the band frequently transitions between active and inactive states. We propose a novel context-aware distributed trust framework for cooperative spectrum sensing in mobile cognitive radio ad hoc networks (CRAHN) that effectively alleviates different types of ISSDF attacks (Always-Yes, Always-No, and fabricating) in dynamic scenarios. In the proposed framework, the SU nodes evaluate the trustworthiness of one another based on the two possible contexts in which they make observations from each other: PU absent context and PU present context. We evaluate the proposed context-aware scheme and compare it against the existing context-oblivious trust schemes using theoretical analysis and extensive simulations of realistic scenarios of mobile CRAHNs operating in TV white space. We show that in the presence of a large set of attackers (as high as 60% of the network), the proposed context-aware trust scheme successfully mitigates the attacks and satisfy the false alarm and missed-detection rates of $10^{-2}$ and lower. Moreover, we show that the proposed scheme is scalable in terms of attack severity, SU network density, and the distance of the SU network to the PU transmitter

Comparative effects of pure spirulina powder and other diets on larval growth and survival of green tiger shrimp, Peneaus semisulcatus

This experiment was carried out in Bandargah Station in Bushehr province. Peneaus semisulcatus larvae were fed on Spirulina platensis as supplementation microalgae. In order to use Spirulina platensis in this study, we have to produce biomass and dry production of this microalga. Determination of length and survival rate of Peneaus semisulcatus larvae was carried out as the objective of the study. Treatments including Z plus (as a supplementation without spirulina), M.C.F (as an imported enriched spirulina), the powder combination of Spirulina platensis with Z plus and Spirulina platensis as live food were compared to Cheatocerus microalgae as a control. The experiment was carried out from nauplii stage to early post larvae. The results of the experiment indicated that the powder combination of Spirulina platensis with Z plus treatment has the most survival rate (76.5%). The maximum of length (4.3mm) observed in control (Cheatocerus spp.). The maximum mortality was observed in zoa stage in spirulina microalgae treatment, because the spiral filamentous of Spirulina sp. was large

A comparative survey of abundance and biomass of Caspian Sea macrobenthos in coastal waters of Mazandaran Province

Caspian Sea macrobenthos was surveyed every two months from December 2007 to October 2008, in the west, east and central parts of Mazandaran province waters. Each area was sampled with 3 replicates at 2 depths of 5 and 10m by Van Veen grab. Five different classes were recognized, including Polychaeta (52.7%), Oligochaeta (27.8%), Bivalvia (12%), Cnistacea (7.5%) and Insects (0.07%). Total mean (LSD) abundance and biomass were 2727± 1303 individual/m2 and 88.9±22.93, respectively. The Polychaeta demonstrated the highest abundance and Bivalvia had the highest biomass. The highest abundance of macrobenthos was found in eastern and the highest biomass in western coasts of Mazandaran. In August 2008, macrobenthos abundance showed higher values. In October, remarkable difference was observed between the abundance of Polychaeta and other macrobenthos organisms. According to Kniskal-Wallis test, abundance and biomass of the entire macrobenthos classes except Insects, showed a significant difference between sampling months (P<0.05). Macrobenthos biomass had no significant difference among the three areas whereas abundance demonstrated a significant difference within these areas (P< 0.05)

Effect of malathion insecticide on liver tissue and enzymes of Rutilus rutilus caspicus of the Caspian Sea

Malathion is an organophosphate insecticide which uses to destroy insects and pests of fruit trees, ornamental plants and agricultural corps. In the present study, effect of Malathion on liver and selected enzymes (SGOT, SGPT and ALP) was studied in Caspian Roach (Rutilus rutilus caspicus). Four treatments with three replications were designed to carry out the survey. Four groups of experimental fish (containing 30 fish in each group) were exposed to different concentrations of Malathion. e. 0, 0.01, 0.05 and 0.1 ppm respectively for 23 days. Blood collection was done in 3rd, 13th and 23th after exposure to Malathion and also 30 days after recovery in clean water and enzymes were measured using standard kits. Also liver tissues were isolated to histological examination. Results showed that tissues of control group (0ppm) were normal and there were no damages, yet there were hepatocytes degeneration, picnotic in nuclear, hepatocytes vacuolization, vascular congestion and sinusoid congestion in liver of other groups. Tissue damages were increased in higher malathion concentration and over time. Results related to enzymes showed that there were no significant differences in SGOT of fish treated with low concentrations of malathion (0.01 and 0.05 ppm) and control group but it was increased in highest concentration (p<0.05). Yet, SGPT increased significantly after passing 23 days in all fish exposed to malathion But ALP changes trend was decreasing

Estimation growth parameters of Parastromateus niger in the coastal waters of Sistan and Baluchestan, Oman Sea

Using length frequency information collected for Parastromateus niger catch in the coastal waters of Sistan and Baluchestan, Oman Sea, we estimated growth parameters of the fish. The data were collected of the fork length of around 887 fish each month during 2001. The length infinity (L∞), growth coefficient (K) and the length at age zero (t0) of the fish measured as 57.8 cm, 0.3 per year and -0.003 respectively. The relationship between the length and weight of the fish was estimated as 0.0469 for “a” , 2.829 for "b" and 0.914 for the correlation coefficient. The average length of the fish in different months of the year calculated and a Tukey test showed that this was significantly different

Fake News Detection on Twitter Using Propagation Structures

The growth of social media has revolutionized the way people access information. Although platforms like Facebook and Twitter allow for a quicker, wider and less restricted access to information, they also consist of a breeding ground for the dissemination of fake news. Most of the existing literature on fake news detection on social media proposes user-based or content-based approaches. However, recent research revealed that real and fake news also propagate significantly differently on Twitter. Nonetheless, only a few articles so far have explored the use of propagation features in their detection. Additionally, most of them have based their analysis on a narrow tweet retrieval methodology that only considers tweets to be propagating a news piece if they explicitly contain an URL link to an online news article. By basing our analysis on a broader tweet retrieval methodology that also allows tweets without an URL link to be considered as propagating a news piece, we contribute to fill this research gap and further confirm the potential of using propagation features to detect fake news on Twitter. We firstly show that real news are significantly bigger in size, are spread by users with more followers and less followings, and are actively spread on Twitter for a longer period of time than fake news. Secondly, we achieve an 87% accuracy using a Random Forest Classifier solely trained on propagation features. Lastly, we design a Geometric Deep Learning approach to the problem by building a graph neural network that directly learns on the propagation graphs and achieve an accuracy of 73.3%

Environmental factors affecting agar extraction from Gracilaria corticata in the coastal areas of Persian Gulf, Bandar-e-Lengeh

The effects of environmental factors and season on agar extraction from Gracilaria corticata were investigated for the period 1993-94 in the coastal areas of Persian Gulf. Water temperature, water salinity and ammonia and phosphate ions were measured monthly. Mean temperature was found to be 27.8 centigrade, mean salinity was 36.38 PPT., mean ammonia ions was 0.154mg/l and mean phosphate ions was 0.029mg/l . After harvesting, Gracilaria were dried and weighed and subjected to the alkali agar extraction method. Maximum and minimum agar yield were obtained in August and December with 10.01% and 5.44% respectively. There was a significant correlation between agar yield, biomass and ammonium fertility. Results showed that the maximum agar yield from Gracilaria was obtained in March and August

The effects of creosote on mortality rate and blood biochemical factors of stellate sturgeon (Acipenser stellatus)

The effects of creosote on stellate sturgeon (Acipenser stellatus) juveniles each weighing 3.6 ±1 grams was evaluated. Acute toxicity test was undertaken in static water quality at 22 degree C plus or minus 1 according to the OECD method at the Caspian Sea Ecology Institute in 2005. The effect was assessed based on the results of the acute toxicity test. For the test, the hematological and biochemical properties of one control and five experimental groups of the fish juveniles what were exposed to creosote were compared. The acute toxicity test lasting 96 h was performed in fully static water condition with aeration

A novel, eco-friendly and green synthesis of PPAC-ZnO and PPAC-nZVI nanocomposite using pomegranate peel: Cephalexin adsorption experiments, mechanisms, isotherms and kinetics

In the present work, powdered activated carbon coated by nanoparticles ZnO and nZVI was derived from pomegranate peel extracts and finally applied for removal of cephalexin (CEX (from aqueous solutions. This experimental research was conducted discontinuously. The effects of pH of solution, reaction time, PPAC-nZVI and PPAC-ZnO composites dose, and initial concentration of cephalexin and composite recovery on process efficiency were investigated. The removal efficiency in optimal conditions for cephalexin with PPAC-nZVI and PPAC-ZnO (CEX = 50 mg L�1, composite dose = 1.25 g L�1, reaction time = 45 min and pH = 5) was obtained 96.06 and 94.17, respectively. The results of the study of isotherm and absorption kinetics for both composites showed that the absorption process follows Langmuir isotherm and pseudo second-order kinetics. The present study showed that the composites could be used as an effective and bio-friendly absorbent to remove cephalexin from aqueous solutions. © 2020 The Society of Powder Technology Japa

Trust-aware Consensus-inspired Distributed Cooperative Spectrum Sensing for Cognitive Radio Ad Hoc Networks

Cooperation among cognitive radios for spectrum sensing is deemed essential for environments with deep shadows. In this paper, we study cooperative spectrum sensing for cognitive radio ad hoc networks where there is no fusion center to aggregate the information from various secondary users. We propose a novel consensus-inspired cooperative sensing scheme based on linear iterations that is fully distributed and low-cost. In addition, the tradeoffs on the number of consensus iterations are explored for scenarios with different shadow fading characteristics. Furthermore, we model insistent spectrum sensing data falsification (ISSDF) attack aimed at consensus-based iterative schemes and show its destructive effect on the cooperation performance which accordingly results in reduced spectrum efficiency and increased interference with primary users. We propose a trust management scheme to mitigate these attacks and evaluate the performance improvement through extensive Monte Carlo simulations for large-scale cognitive radio ad hoc networks in TV white space. Our proposed trust management reduces the harm of a set of collusive ISSDF attackers up to two orders of magnitude in terms of missed-detection and false alarm error rates. Moreover, in a hostile environment, integration of trust management into cooperative schemes considerably relaxes the sensitivity requirements on the cognitive radio devices