96 research outputs found

    Designing substitution boxes based on chaotic map and globalized firefly algorithm

    Get PDF
    Cipher strength mainly depends on the robust structure and a well-designed interaction of the components in its framework. A significant component of a cipher system, which has a significant influence on the strength of the cipher system, is the substitution box or S-box. An S-box is a vital and most essential component of the cipher system due to its direct involvement in providing the system with resistance against certain known and potential cryptanalytic attacks. Hence, research in this area has increased since the late 1980s, but there are still several issues in the design and analysis of the S-boxes for cryptography purposes. Therefore, it is not surprising that the design of suitable S-boxes attracts a lot of attention in the cryptography community. Nonlinearity, bijectivity, strict avalanche criteria, bit independence criteria, differential probability, and linear probability are the major required cryptographic characteristics associated with a strong S-box. Different cryptographic systems requiring certain levels of these security properties. Being that S- boxes can exhibit a certain combination of cryptographic properties at differing rates, the design of a cryptographically strong S-box often requires the establishment of a trade-off between these properties when optimizing the property values. To date, many S-boxes designs have been proposed in the literature, researchers have advocated the adoption of metaheuristic based S-boxes design. Although helpful, no single metaheuristic claim dominance over their other countermeasure. For this reason, the research for a new metaheuristic based S-boxes generation is still a useful endeavour. This thesis aim to provide a new design for 8 Ă— 8 S-boxes based on firefly algorithm (FA) optimization. The FA is a newly developed metaheuristic algorithm inspired by fireflies and their flash lighting process. In this context, the proposed algorithm utilizes a new design for retrieving strong S- boxes based on standard firefly algorithm (SFA). Three variations of FA have been proposed with an aim of improving the generated S-boxes based on the SFA. The first variation of FA is called chaotic firefly algorithm (CFA), which was initialized using discrete chaotic map to enhance the algorithm to start the search from good positions. The second variation is called globalized firefly algorithm (GFA), which employs random movement based on the best firefly using chaotic maps. If a firefly is brighter than its other counterparts, it will not conduct any search. The third variation is called globalized firefly algorithm with chaos (CGFA), which was designed as a combination of CFA initialization and GFA. The obtained result was compared with a previous S-boxes based on optimization algorithms. Overall, the experimental outcome and analysis of the generated S-boxes based on nonlinearity, bit independence criteria, strict avalanche criteria, and differential probability indicate that the proposed method has satisfied most of the required criteria for a robust S-box without compromising any of the required measure of a secure S-box

    A Salad of Block Ciphers

    Get PDF
    This book is a survey on the state of the art in block cipher design and analysis. It is work in progress, and it has been for the good part of the last three years -- sadly, for various reasons no significant change has been made during the last twelve months. However, it is also in a self-contained, useable, and relatively polished state, and for this reason I have decided to release this \textit{snapshot} onto the public as a service to the cryptographic community, both in order to obtain feedback, and also as a means to give something back to the community from which I have learned much. At some point I will produce a final version -- whatever being a ``final version\u27\u27 means in the constantly evolving field of block cipher design -- and I will publish it. In the meantime I hope the material contained here will be useful to other people

    The role of non-native plants in the integration of non-native phytophagous invertebrates in native food webs

    Get PDF
    This thesis brings together a series of studies, examining the role of non-native plants in the integration of non-native invertebrates in native food webs. I use data from comprehensive surveys of formally-planted gardens to investigate the efficacy of straightforward measures of non-native plant presence and/or landscape parameters, as reliable predictors of non-native invertebrate presence, finding that non-native invertebrate richness increases with non-native plant species richness, with invertebrates showing a clear preference for woody plants. I then use the context of metapopulation theory to explore the facilitative role of non-native plants in the ability of a non-native invertebrate to persist within a community, finding that where host-plant habitat patches are closer together, the likelihood of a patch being occupied is greater, especially if the patch is occupied but that this effect is not universal, with species-specific effects present also. I then explore the potential for apparent competition, in the form of negative indirect interactions between native and non-native plants mediated by a shared invertebrate enemy, with the indirect interactions biased by plant relatedness, finding that phylogenetically ranked pairwise native/non-native plant interactions are weakly correlated with observed shared invertebrate interactions, while a significant Mantel test result indicates a significant potential for apparent competition. Finally, I test for detectability of apparent competition in a gall wasp community, finding no evidence of apparent competition but potential evidence for the unexpected occurrence of apparent mutualism. Collectively, these findings provide original insight into how non-native plants and non-native invertebrates interact in an ecological community, and how these interactions help to structure the community. Additionally, they have implications for non-native invertebrate species management, from the practical application of ground-level planting decisions to the development of reliable predictive tools

    Fungal endophytic community associated with guarana (Paullinia cupana var. Sorbilis): diversity driver by genotypes in the centre of origin

    Get PDF
    Guarana plant is a native of the Amazon region. Due to its high amount of caffeine and tannins, the seed has medicinal and stimulating properties. The guarana industry has grown exponentially in recent years; however, little information is available about associated mycobiota, particularly endophytic fungi. The present study aimed to compare the distribution and diversity of endophytic fungi associated with the leaves and seeds of anthracnose-resistant and susceptible guarana plants produced in Maués and Manaus, Amazonas State, Brazil. A total of 7514 endophytic fungi were isolated on Potato Dextrose Agar, Sabouraud and Czapek media, and grouped into 77 morphological groups. Overall, fungal communities in guarana leaves and seeds were mainly composed by Colletotrichum and Fusarium genera, but also by Chondrostereum, Clonostachys, Curvularia, Hypomontagnella, Lentinus, Neopestalotiopsis, Nigrospora, Peroneutypa, Phyllosticta, Simplicillium and Tinctoporellus. Obtained results indicate that some members of Colletotrichum and Fusarium genera may have experienced dysbiosis during the guarana domestication process, suggesting that some individuals may behave as latent pathogens. The susceptible guarana genotype cultivated in Manaus presented higher fungal diversity. The relative abundance of taxa and diversity among samples suggests that communities are structured by genotype and geographic location. This is the first report of mycobiota in both guarana leaves and seeds.This research was funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior(CAPES) project Pró-Amazônia n◦3287/13. C.S. (Carla Santos) and N.L. were supported by FCT under the scopeof the strategic funding of UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004)funded by the European Regional Development Fund under the scope of Norte2020 - Programa OperacionalRegional do Norte. C.S. (Cledir Santos) was supported by the Universidad de La Frontera (Temuco, Chile) withpartial funding from the Project PIA19-0001.info:eu-repo/semantics/publishedVersio

    Lab-On-Chip for Ex-Vivo Study of Bio-Mechanical-Chemical Behavior of Tip Growing Plant Cells

    Get PDF
    This thesis presents design, modeling, fabrication, and testing of different Lab-on-chip (LOC) devices to study static and dynamic behavior of pollen tubes in bio-mechanical-chemical environments. The main components of microfluidic platform include microfluidic network for manipulation, trapping and growing of a series of pollen tubes in a controlled environment, actuating channels in order to introduce chemicals and drugs toward the pollen tube, microstructural elements such as microgaps and microcantilevers to provide Ex-Vivo environment for characterizing static and dynamic responses of pollen tubes. A Lab-On-Chip (LOC), called, TipChip was developed as a flexible platform that can simplify sophisticated functions such as chemical reactions, drug development, by integrating them within a single micro-device. The configuration of the microfluidic network was developed in such a way that it allows observation under chemical or mechanical manipulation of multiple pollen tubes. The growth of pollen tubes under different flow rates and geometrical dimensions of microfluidic network has been studied and the challenges have been identified. The microfluidic platform design was enhanced to deal with the challenges by adapting the dimensions of the microfluidic network and the inlet flow. It provides identical growth environments for growing pollen tubes along each microchannel and improves the performance of microfluidic device, through varying the dimensions and geometries of the microfluidic network. The thesis identifies the static response of pollen tube to chemical stimulation which was used to determine the role of a few of the growth regulators such as sucrose and calcium ions as they regulate tube turgor pressure and cell wall mechanical properties of pollen tube. New experimental platforms were fabricated to treat locally the pollen tube at the tip in order to characterize its static response to local treatment in reorienting the growth direction. The device is also used to locally stimulate the cylindrical region of pollen tube. Using these LOC devices we attempted to answer some questions regarding the role of regulators in pollen tube growth. The thesis explores in detail the dynamic growth of pollen tube in normal condition and also under chemical stimulation. Waveform analysis is employed in order to extract primary and secondary oscillation frequencies of pollen tube as significant indicators of dynamic growth of pollen tube. The dynamic response of pollen tubes is implemented as a whole-plant cell sensor for toxicity detection in order to detect toxic materials in concentration-based manner. Aluminum ions were tested as the toxic substance. The degree of toxicity was defined by measuring the reduction in growth rate as well as peak oscillation frequencies in the case of static and dynamic response of pollen tube, respectively. The thesis addresses the quantification of mechanical properties of pollen tube cell wall using the Bending LOC (BLOC) platform. The flexural rigidity of the pollen tube and the Young’s modulus of the cell wall are estimated through finite element modeling of the observed fluid-structure interaction. The thesis also explores the feasibility of studying the pollen tube response to the mechanical stimulation. The microfluidic device also enables integrating mechanical force obstructing pollen tube growth in order to characterize the interaction of pollen tube and mechanical structures which are similar to the in-vivo interaction between a pollen tube and the growth matrix during the course of growth toward the ovule. The behavior of the pollen tube while passing through microgap was also explored in detail. The deflection of microgap under growth force and the changes in diameter of the pollen tube under reaction force from microgap were evaluated. This part explores the role of mechanical forces in bursting the pollen tube tip which could explain the contribution of mechanical signal in the bursting of tube near the vicinity of the ovule. In addition, the configuration of microgap enabled the estimation of the maximum invasive force exerted by pollen tube. Thus, the proposed microfluidic platform is highly suitable for cellular analysis, pollen tube biology and detection of toxicity

    Modelling cytosolic flow and vesicle transport in the growing pollen tube

    Get PDF
    Scientific interest in the mathematical modelling of pollen tube growth has increased steadily over the last few decades. The highly localized and rapid nature of this growth necessitates large--scale actomyosin transport of cellular material throughout the cell cytoplasm. This directed movement of cellular material induces a flow in the cytosol, also known as 'cyclosis'. The extent to which inclusion of this flow is important to modelling the distribution of elements in the cytoplasm is currently unclear, with its effect often conflated with that of actomyosin transport. In this thesis, a finite volume method (FVM) is developed for the numerical evaluation of transport equations describing vesicle distribution in the pollen tube cytoplasm. This is coupled with a novel method of regularized ringlets, derived via analytical azimuthal integration of the regularized Stokeslet, for obtaining numerical solutions to axisymmetric Stokes flows. Using this method of regularized ringlets, we present an axisymmetric velocity profile for cytosolic flow in the pollen tube based on the drag induced by actomyosin vesicle transport. When used in the transport equation for vesicle distribution, we find that recreation of the apical `inverted vesicle cone' requires the use of an enlarged effective fluid viscosity amongst other results

    Abstracts of Papers, 86th Annual Meeting of the Virginia Academy of Science

    Get PDF
    Abstracts for the 86th Annual Meeting of the Virginia Academy of Science, May 20-23, 2008, Hampton University, Hampton, VA

    Annual Report of the Clemson Board of Trustees, 1984-1985

    Get PDF
    • …
    corecore