Obfuscation-based malware update: A comparison of manual and automated methods

Indexación: Scopus; Web of Science.This research presents a proposal of malware classification and its update based on capacity and obfuscation. This article is an extension of [4]a, and describes the procedure for malware updating, that is, to take obsolete malware that is already detectable by antiviruses, update it through obfuscation techniques and thus making it undetectable again. As the updating of malware is generally performed manually, an automatic solution is presented together with a comparison from the standpoint of cost and processing time. The automated method proved to be more reliable, fast and less intensive in the use of resources, specially in terms of antivirus analysis and malware functionality checking times.http://univagora.ro/jour/index.php/ijccc/article/view/2961/112

A deeper insight into quantum state transfer from an information flux viewpoint

We use the recently introduced concept of information flux in a many-body register in order to give an alternative viewpoint on quantum state transfer in linear chains of many spins.Comment: 6 pages, 3 figures, RevTeX

Four related benzazepine derivatives in a reaction pathway leading to a benzazepine carboxylic acid : hydrogen-bonded assembly in zero, one, two and three dimensions

The authors thank ‘Centro de Instrumentacion Cientıfico-Tecnica of Universidad de Jaen’ and the staff for data collection. AP, SAG and CMS thank Colciencias for financial support (grant No. 1102–521–28229). JC thanks the Consejerıa de Innovacion, Ciencia y Empresa (Junta de Andalucıa, Spain) and the Universidad de Jaen for financial support.(2R*,4S*)-Methyl 2,3,4,5-tetra­hydro-1,4-ep­oxy-1H-benz[b]azepine-2-carboxyl­ate, C12H13NO3, (I), and its reduction product (2R*,4S*)-methyl 4-hy­droxy-2,3,4,5-tetra­hydro-1H-benz[b]azepine-2-carboxyl­ate, C12H15NO3, (II), both crystallize as single enanti­omers in the space group P212121, while the hydrolysis product (2RS,4SR)-4-hy­droxy-2,3,4,5-tetra­hydro-1H-benz[b]azepine-2-carb­oxy­lic acid, C11H13NO3, (III), and the lactone (2RS,5SR)-8-(trifluoromethoxy)-5,6-dihydro-1H-2,5-methanobenz[e][1,4]oxazocin-3(2H)-one, C12H10F3NO3, (IV), both crystallize as racemic mixtures in the space group P21/c. The mol­ecules of compound (IV) are linked into centrosymmetric R22(10) dimers by N-HO hydrogen bonds, and those of compound (I) are linked into chains by C-H(arene) hydrogen bonds. A combination of O-HO and O-HN hydrogen bonds links the mol­ecules of com­pound (III) into sheets containing equal numbers of R44(14) and R44(26) rings, and a combination of C-H(arene) hydrogen bonds and three-centre O-H(N,O) hydrogen bonds links the mol­ecules of compound (II) into a three-dimensional frame­work structure. Comparisons are made with some related compounds.Publisher PDFPeer reviewe

Entanglement production by quantum error correction in the presence of correlated environment

We analyze the effect of a quantum error correcting code on the entanglement of encoded logical qubits in the presence of a dephasing interaction with a correlated environment. Such correlated reservoir introduces entanglement between physical qubits. We show that for short times the quantum error correction interprets such entanglement as errors and suppresses it. However for longer time, although quantum error correction is no longer able to correct errors, it enhances the rate of entanglement production due to the interaction with the environment.Comment: 7 pages, 3 figures, published versio

Avaliação da atividade antibacteriana de extratos metanólicos de diferentes espécies de algas e plantas halófitas

Dissertação de mest., Engenharia Biológica, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2011Os organismos marinhos são uma fonte fundamental de novos compostos bioativos com potencial interesse para a indústria farmacêutica e com diversas atividades biológicas. Sendo o tratamento de infeções bacterianas cada vez mais dificultado pela capacidade das bactérias de desenvolverem resistência aos agentes antimicrobianos é necessário a contínua descoberta e desenvolvimento de novos compostos antibacterianos para assegurar um futuro sustentável do ponto de vista da saúde pública. Deste modo, este trabalho teve como objetivo avaliar a atividade antibacteriana de extratos de metanol de diferentes espécies de macro- e microalgas, ervas marinhas e plantas halófitas contra estirpes bacterianas potencialmente patogénicas, pelo método de difusão em agar. As diferentes espécies de macroalgas foram colhidas na praia de Olhos d’Água (Albufeira) entre julho e novembro de 2009. As amostras de microalgas foram fornecidas pelo Laboratório Experimental de Organismos Aquáticos (LEOA, UAlg) e pela NECTON S.A. As plantas halófitas foram colhidas em maio de 2010 na Praia de Faro e Ludo. A atividade antibacteriana foi determinada segundo os protocolos padronizados pelo Clinical and Laboratory Standards Institute, através do método de difusão em agar. Foram utilizadas 4 estirpes bacterianas nomeadamente B. cereus NCTC 7464, S. aureus NCTC 6571 (Gram-positivas), E. coli NCTC 9001 e P. aeruginosa NCTC 10662 (Gram-negativas). Não foram observadas zonas de inibição nos controlos negativos (metanol) e todos os antibióticos utilizados (ácido nalidíxico, gentamicina, penicilina G e tetraciclina) resultaram em inibição do crescimento bacteriano respetivo. Observaram-se zonas de inibição em Staphylococcus aureus na presença dos extratos metanólicos de Cystoseira nodicaulis (8,44 ± 0,53 mm) e C. tamariscifolia (11,12 ± 0,78 mm). Os restantes extratos metanólicos de algas e ervas marinhas foram inativos em relação às estirpes estudadas. Os extratos de microalgas e de plantas halófitas testados não demonstraram atividade antibacteriana contra as estirpes estudadas. Os resultados obtidos neste trabalho indicam que os extratos de C. nodicaulis e C. tamariscifolia apresentam atividade antibacteriana. Os restantes extratos não demonstraram, porém, qualquer atividade

Josephson oscillation linewidth of ion-irradiated YBa2_2Cu3_3O7_7 junctions

We report on the noise properties of ion-irradiated YBa$_2$Cu$_3$O$_7$ Josephson junctions. This work aims at investigating the linewidth of the Josephson oscillation with a detector response experiment at $\simeq$132 GHz. Experimental results are compared with a simple analytical model based on the Likharev-Semenov equation and the de Gennes dirty limit approximation. We show that the main source of low-frequency fluctuations in these junctions is the broadband Johnson noise and that the excess ($\frac{1}{f}$) noise contribution does not prevail in the temperature range of interest, as reported in some other types of high-T$_c$ superconducting Josephson junctions. Finally, we discuss the interest of ion-irradiated junctions to implement frequency-tunable oscillators consisting of synchronized arrays of Josephson junctions

Cluster Algorithm Renormalization Group Study of Universal Fluctuations in the 2D Ising Model

In this paper we propose a novel method to study critical systems numerically by a combined collective-mode algorithm and Renormalization Group on the lattice. This method is an improved version of MCRG in the sense that it has all the advantages of cluster algorithms. As an application we considered the 2D Ising model and studied wether scale invariance or universality are possible underlying mechanisms responsible for the approximate "universal fluctuations" close to a so-called bulk temperature $T^*(L)$. "Universal fluctuations" was first proposed in [1] and stated that the probability density function of a global quantity for very dissimilar systems, like a confined turbulent flow and a 2D magnetic system, properly normalized to the first two moments, becomes similar to the "universal distribution", originally obtained for the magnetization in the 2D XY model in the low temperature region. The results for the critical exponents and the renormalization group flow of the probability density function are very accurate and show no evidence to support that the approximate common shape of the PDF should be related to both scale invariance or universal behavior.Comment: 6 pages, 4 figures and 3 table

Entangled states maximize the two qubit channel capacity for some Pauli channels with memory

We prove that a general upper bound on the maximal mutual information of quantum channels is saturated in the case of Pauli channels with an arbitrary degree of memory. For a subset of such channels we explicitly identify the optimal signal states. We show analytically that for such a class of channels entangled states are indeed optimal above a given memory threshold. It is noteworthy that the resulting channel capacity is a non-differentiable function of the memory parameter.Comment: 4 pages no figure

Brane World Cosmology, the CMB and the Radion

Recent developments in the theory of extra dimensions have opened up avenues to confront such theories with cosmological tests. We discuss a brane-world model with a bulk scalar field, motivated by supergravity. The low-energy effective action is derived and physical constraints on the parameters of the model discussed. The cosmological evolution of the brane-world moduli is investigated and it is shown that one of the moduli is a quintessence field. The CMB predictions are computed. Finally, the possibility that the radion field in brane-worlds could be a chameleon field is investigated.Comment: 11 pages, 6 figures, to appear in the proceedings of the DPU Workshop: The Density Fluctuations in the Universe: Beyond the Inflaton Paradigm (Athens, June 2004