773 resultados para DDoS attacks


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Multidimensional scaling is applied in order to visualize an analogue of the small-world effect implied by edges having different displacement velocities in transportation networks. Our findings are illustrated for two real-world systems, namely the London urban network (streets and underground) and the US highway network enhanced by some of the main US airlines routes. We also show that the travel time in these two networks is drastically changed by attacks targeting the edges with large displacement velocities. (C) 2011 Elsevier By. All rights reserved.

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The relationship between the structure and function of biological networks constitutes a fundamental issue in systems biology. Particularly, the structure of protein-protein interaction networks is related to important biological functions. In this work, we investigated how such a resilience is determined by the large scale features of the respective networks. Four species are taken into account, namely yeast Saccharomyces cerevisiae, worm Caenorhabditis elegans, fly Drosophila melanogaster and Homo sapiens. We adopted two entropy-related measurements (degree entropy and dynamic entropy) in order to quantify the overall degree of robustness of these networks. We verified that while they exhibit similar structural variations under random node removal, they differ significantly when subjected to intentional attacks (hub removal). As a matter of fact, more complex species tended to exhibit more robust networks. More specifically, we quantified how six important measurements of the networks topology (namely clustering coefficient, average degree of neighbors, average shortest path length, diameter, assortativity coefficient, and slope of the power law degree distribution) correlated with the two entropy measurements. Our results revealed that the fraction of hubs and the average neighbor degree contribute significantly for the resilience of networks. In addition, the topological analysis of the removed hubs indicated that the presence of alternative paths between the proteins connected to hubs tend to reinforce resilience. The performed analysis helps to understand how resilience is underlain in networks and can be applied to the development of protein network models.

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1,3-beta-Glucan depolymerizing enzymes have considerable biotechnological applications including biofuel production, feedstock-chemicals and pharmaceuticals. Here we describe a comprehensive functional characterization and low-resolution structure of a hyperthermophilic laminarinase from Thermotoga petrophila (TpLam). We determine TpLam enzymatic mode of operation, which specifically cleaves internal beta-1,3-glucosidic bonds. The enzyme most frequently attacks the bond between the 3rd and 4th residue from the non-reducing end, producing glucose, laminaribiose and laminaritriose as major products. Far-UV circular dichroism demonstrates that TpLam is formed mainly by beta structural elements, and the secondary structure is maintained after incubation at 90 degrees C. The structure resolved by small angle X-ray scattering, reveals a multi-domain structural architecture of a V-shape envelope with a catalytic domain flanked by two carbohydrate-binding modules. Crown Copyright (C) 2011 Published by Elsevier Inc. All rights reserved.

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Sugarcane is an important crop that has recently become subject to attacks from the weevil Sphenophorus levis, which is not efficiently controlled with chemical insecticides. This demands the development of new control devices for which digestive physiology data are needed. In the present study, ion-exchange chromatography of S. levis whole midgut homogenates, together with enzyme assays with natural and synthetic substrates and specific inhibitors, demonstrated that a cysteine proteinase is a major proteinase, trypsin is a minor one and chymotrypsin is probably negligible. Amylase, maltase and the cysteine proteinase occur in the gut contents and decrease throughout the midgut; trypsin is constant in the entire midgut, whereas a membrane-bound aminopeptidase predominates in the posterior midgut. The cysteine proteinase was purified to homogeneity through ion-exchange chromatography. The purified enzyme had a mass of 37 kDa and was able to hydrolyze Z-Phe-Arg-MCA and Z-Leu-Arg-MCA with k(cat)/K(m) values of 20.0 +/- 1.1 mu M(-1) s(-1) and 30.0 +/- 0.5 mu M(-1) s(-1), respectively, but not Z-Arg-Arg-MCA. The combined results suggest that protein digestion starts in the anterior midgut under the action of a cathepsin L-like proteinase and ends on the surface of posterior midgut cells. All starch digestion takes place in anterior midgut. These data will be instrumental to developing S. levis-resistant sugarcane. (C) 2011 Elsevier Ltd. All rights reserved.

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This Master’s Thesis examines transnational conflicts and Christian-Muslim relations in Nigeria between the years 2001 and 2006. It focuses on two major transnational conflicts: The September 11, 2001 attacks in the United States and the Danish cartoon controversy of 2005/2006. It discusses the impact of these transnational conflicts on Christian-Muslim relations in Nigeria in the light of the implementation of the Sharia Law in some northern Nigerian states and the improved access to the broadcast media and mobile telephone communication in Nigeria. By underscoring the relationship between transnational conflicts and the local context, this study provides a new perspective for understanding Christian-Muslim relations in Nigeria

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The rapid development of data transfer through internet made it easier to send the data accurate and faster to the destination. There are many transmission media to transfer the data to destination like e-mails; at the same time it is may be easier to modify and misuse the valuable information through hacking. So, in order to transfer the data securely to the destination without any modifications, there are many approaches like cryptography and steganography. This paper deals with the image steganography as well as with the different security issues, general overview of cryptography, steganography and digital watermarking approaches.  The problem of copyright violation of multimedia data has increased due to the enormous growth of computer networks that provides fast and error free transmission of any unauthorized duplicate and possibly manipulated copy of multimedia information. In order to be effective for copyright protection, digital watermark must be robust which are difficult to remove from the object in which they are embedded despite a variety of possible attacks. The message to be send safe and secure, we use watermarking. We use invisible watermarking to embed the message using LSB (Least Significant Bit) steganographic technique. The standard LSB technique embed the message in every pixel, but my contribution for this proposed watermarking, works with the hint for embedding the message only on the image edges alone. If the hacker knows that the system uses LSB technique also, it cannot decrypt correct message. To make my system robust and secure, we added cryptography algorithm as Vigenere square. Whereas the message is transmitted in cipher text and its added advantage to the proposed system. The standard Vigenere square algorithm works with either lower case or upper case. The proposed cryptography algorithm is Vigenere square with extension of numbers also. We can keep the crypto key with combination of characters and numbers. So by using these modifications and updating in this existing algorithm and combination of cryptography and steganography method we develop a secure and strong watermarking method. Performance of this watermarking scheme has been analyzed by evaluating the robustness of the algorithm with PSNR (Peak Signal to Noise Ratio) and MSE (Mean Square Error) against the quality of the image for large amount of data. While coming to see results of the proposed encryption, higher value of 89dB of PSNR with small value of MSE is 0.0017. Then it seems the proposed watermarking system is secure and robust for hiding secure information in any digital system, because this system collect the properties of both steganography and cryptography sciences.

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Vilhelm Ekelund och den fransk-italienska kultursfären: Några nedslag i de tidiga prosaverken – från Antikt ideal (1909) till Attiskt i fågelperspektiv (1919). (Vilhelm Ekelund and the French and Italian cultural heritage: A study of his early prose – from Antikt ideal (1909) to Attiskt i fågelperspektiv (1919)). The Swedish poet, essayist and aphorist Vilhelm Ekelund was not only influenced by German literature and philosophy, he also wrote extensive literary criticism on the subject of Romance language authors. This article discusses Ekelund’s relationship to some of the most influential French and Italian writers – as it can be seen in his work during the period 1909-1919. This relationship was ambiguous: he paid homage to French authors such as Montaigne, Montesquieu, Stendhal and Comte – as well as to the Italian poet and philosopher Leopardi – but he also severely criticized such distinguished writers as Baudelaire, Rousseau and Maupassant. One conclusion of this article is that the authors praised by Ekelund all venerate the Greek and Roman cultural heritage, whereas the despised novelists and poets were, in his opinion, either too “modern” or too “feminine” – both highly pejorative adjectives in the author’s terminology. It is also noted that Ekelund’s most ferocious attacks date from the first part of the decade, before he entered a more harmonic period with the works Metron (1918) and Attiskt i fågelperspektiv (1919).

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The theme of family in literature and in popular discourse occurs at times when the family as an institution is under attack. Attacks against the family coupled with defence of the family are viewed as the barometer of people’s satisfaction with the society in which they live. This outpouring of emotion, whether it is in defence of or attacking the family, is the result of the family’s position on the bridge between nature and society – a fortunate (or a detrimental) link between an individual and the units that make up a society. Across the United States and much of the western world, the battle for gay marriage and inclusive civil unions has revealed the fissures in our collective moral view of the family. The conservative concern about the absence of ‘family values’ is magnified by our situation in a world of flux. Inflation, war, terrorist threats, and the depletion of natural resources are but a few examples. When so much is unknown, how do we position ourselves? What anchors us to the past, gives us comfort in the present, and supports us in the future if not the family? Alternatively, what coddles us more in the past, shackles us more to the present, and lulls us more into a fixed conception of the future than the family? My research is not a sociological survey into the family nor does it stake any claims to understanding the present state of the family in society. The study seeks, however, to shed light on the rhetorical uses of the family by analysing two novels that are inextricably concerned with the theory of the family in times of heightened social change. In particular, my research focuses upon the social role and political meaning of the family in Anna Karenina and Jia.