Byzantine Attack and Defense in Cognitive Radio Networks: A Survey

The Byzantine attack in cooperative spectrum sensing (CSS), also known as the spectrum sensing data falsification (SSDF) attack in the literature, is one of the key adversaries to the success of cognitive radio networks (CRNs). In the past couple of years, the research on the Byzantine attack and defense strategies has gained worldwide increasing attention. In this paper, we provide a comprehensive survey and tutorial on the recent advances in the Byzantine attack and defense for CSS in CRNs. Specifically, we first briefly present the preliminaries of CSS for general readers, including signal detection techniques, hypothesis testing, and data fusion. Second, we analyze the spear and shield relation between Byzantine attack and defense from three aspects: the vulnerability of CSS to attack, the obstacles in CSS to defense, and the games between attack and defense. Then, we propose a taxonomy of the existing Byzantine attack behaviors and elaborate on the corresponding attack parameters, which determine where, who, how, and when to launch attacks. Next, from the perspectives of homogeneous or heterogeneous scenarios, we classify the existing defense algorithms, and provide an in-depth tutorial on the state-of-the-art Byzantine defense schemes, commonly known as robust or secure CSS in the literature. Furthermore, we highlight the unsolved research challenges and depict the future research directions.Comment: Accepted by IEEE Communications Surveys and Tutoiral

Nanobiomotors of archaeal DNA repair machineries:current research status and application potential

Nanobiomotors perform various important functions in the cell, and they also emerge as potential vehicle for drug delivery. These proteins employ conserved ATPase domains to convert chemical energy to mechanical work and motion. Several archaeal nucleic acid nanobiomotors, such as DNA helicases that unwind double-stranded DNA molecules during DNA damage repair, have been characterized in details. XPB, XPD and Hjm are SF2 family helicases, each of which employs two ATPase domains for ATP binding and hydrolysis to drive DNA unwinding. They also carry additional specific domains for substrate binding and regulation. Another helicase, HerA, forms a hexameric ring that may act as a DNA-pumping enzyme at the end processing of double-stranded DNA breaks. Common for all these nanobiomotors is that they contain ATPase domain that adopts RecA fold structure. This structure is characteristic for RecA/RadA family proteins and has been studied in great details. Here we review the structural analyses of these archaeal nucleic acid biomotors and the molecular mechanisms of how ATP binding and hydrolysis promote the conformation change that drives mechanical motion. The application potential of archaeal nanobiomotors in drug delivery has been discussed

Validating Candidate Congenital Heart Disease Genes in Drosophila.

Genomic sequencing efforts can implicate large numbers of genes and de novo mutations as potential disease risk factors. A high throughput in vivo model system to validate candidate gene association with pathology is therefore useful. We present such a system employing Drosophila to validate candidate congenital heart disease (CHD) genes. The protocols exploit comprehensive libraries of UAS-GeneX-RNAi fly strains that when crossed into a 4×Hand-Gal4 genetic background afford highly efficient cardiac-specific knockdown of endogenous fly orthologs of human genes. A panel of quantitative assays evaluates phenotypic severity across multiple cardiac parameters. These include developmental lethality, larva and adult heart morphology, and adult longevity. These protocols were recently used to evaluate more than 100 candidate CHD genes implicated by patient whole-exome sequencing (Zhu et al., 2017)

The archaeal ATPase PINA interacts with the helicase Hjm via its carboxyl terminal KH domain remodeling and processing replication fork and Holliday junction.

PINA is a novel ATPase and DNA helicase highly conserved in Archaea, the third domain of life. The PINA from Sulfolobus islandicus (SisPINA) forms a hexameric ring in crystal and solution. The protein is able to promote Holliday junction (HJ) migration and physically and functionally interacts with Hjc, the HJ specific endonuclease. Here, we show that SisPINA has direct physical interaction with Hjm (Hel308a), a helicase presumably targeting replication forks. In vitro biochemical analysis revealed that Hjm, Hjc, and SisPINA are able to coordinate HJ migration and cleavage in a concerted way. Deletion of the carboxyl 13 amino acid residues impaired the interaction between SisPINA and Hjm. Crystal structure analysis showed that the carboxyl 70 amino acid residues fold into a type II KH domain which, in other proteins, functions in binding RNA or ssDNA. The KH domain not only mediates the interactions of PINA with Hjm and Hjc but also regulates the hexameric assembly of PINA. Our results collectively suggest that SisPINA, Hjm and Hjc work together to function in replication fork regression, HJ formation and HJ cleavage

Size- and speed-dependent mechanical behavior in living mammalian cytoplasm

Active transport in the cytoplasm plays critical roles in living cell physiology. However, the mechanical resistance that intracellular compartments experience, which is governed by the cytoplasmic material property, remains elusive, especially its dependence on size and speed. Here we use optical tweezers to drag a bead in the cytoplasm and directly probe the mechanical resistance with varying size a and speed V. We introduce a method, combining the direct measurement and a simple scaling analysis, to reveal different origins of the size- and speed-dependent resistance in living mammalian cytoplasm. We show that the cytoplasm exhibits size-independent viscoelasticity as long as the effective strain rate V/a is maintained in a relatively low range (0.1 s −1 < V/a < 2 s −1 ) and exhibits size-dependent poroelasticity at a high effective strain rate regime (5 s −1 < V/a < 80 s −1 ). Moreover, the cytoplasmic modulus is found to be positively correlated with only V/a in the viscoelastic regime but also increases with the bead size at a constant V/a in the poroelastic regime. Based on our measurements, we obtain a full-scale state diagram of the living mammalian cytoplasm, which shows that the cytoplasm changes from a viscous fluid to an elastic solid, as well as from compressible material to incompressible material, with increases in the values of two dimensionless parameters, respectively. This state diagram is useful to understand the underlying mechanical nature of the cytoplasm in a variety of cellular processes over a broad range of speed and size scales. Keywords: cell mechanics; poroelasticity; viscoelasticity; cytoplasmic state diagra

Spectrum sharing and aggregation for future wireless networks, part II

The papers in this special issue represent the second one in the sequel of three special issues on spectrum sharing and aggregation for future wirelessn networks

Effects of food restriction on growth, body composition and gene expression related in regulation of lipid metabolism and food intake in grass carp

It is well known that most fish would prefer to use body lipid stores for energy expenditure when receiving a long-term food restriction. However, the mechanism of this is still not clear. In the present study, a growth experiment was carried out to investigate the effects of food restriction on growth performance, gene expression related in regulation of lipid metabolism and food ingestion in grass carp (Ctenopharyngodon idellus). Four rations, satiation (S), 80% S, 60% S and 40% S, were adopted in this study. Each treatment was randomly assigned to triplicate net cages of 15 fish (177.3 +/- 3.3 g) per cage. The experiment lasted for 49 days at 30.0 +/- 3.0 degrees C. The experimental results showed that a significant increase in feeding rate and weight gain was found in grass carp with the increased ration level. The body lipid and energy content of the grass carp exhibited a significant decrease when receiving food restriction. The transcriptional levels of the genes involved in lipogenesis (srebp-1c, fas, ppar gamma) were down-regulated at the rations of food restriction. The relative expression of hepatic fas (fatty acid synthetase) and srebp-1c (sterol regulatory element-binding protein 1c) in the fish at satiation were significantly higher than the restricted-fed groups. Similarly, the expressions of hepatic ppar. (peroxisome proliferator-activated receptor-gamma) in the fish at the ration of satiation and 80% S were significantly higher than the group at the low ration of 40% S. However, the expression of hepatic cpt-1a (carnitine palmitoyl transferase I) involved in fatty acid beta-oxidation in fish was significantly up-regulated when receiving food restriction. Other hepatic lipolysis genes of ppar alpha (peroxisome proliferators-activated receptor alpha) and hl (hepatic lipase) didn&#39;t show any significant changes in restricted-fed fish. The transcriptional levels of hepatic leptin and hypothalamus pomc (proopiomelanocortin) were significantly down-regulated in fish fed with restricted rations. But the hypothalamus npy (neuropeptide Y) and lepr (leptin receptor) had no change. The present results indicated that a long-term food restriction could cause less accumulation of lipid and could be through a way of down-regulating lipogenesis genes and up-regulating lipolysis genes. Long-term restriction could also activate the appetite of grass carp by down-regulating some anorexigenic genes. Statement of relevance: Food restriction for some time could lead to a suitable lipid storage, in case of accumulation of fatty acid profile and lipid, in cultured grass carp. (C) 2016 Elsevier B.V. All rights reserved.</p