19,980 research outputs found
Obfuscation-based malware update: A comparison of manual and automated methods
IndexaciĂłn: 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 âCentro de Instrumentacion Cientıfico-Tecnica of Universidad de Jaenâ and the staff for data collection. AP, SAG and CMS thank Colciencias for financial support (grant No. 1102â521â28229). 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-tetraÂhydro-1,4-epÂoxy-1H-benz[b]azepine-2-carboxylÂate, C12H13NO3, (I), and its reduction product (2R*,4S*)-methyl 4-hyÂdroxy-2,3,4,5-tetraÂhydro-1H-benz[b]azepine-2-carboxylÂate, C12H15NO3, (II), both crystallize as single enantiÂomers in the space group P212121, while the hydrolysis product (2RS,4SR)-4-hyÂdroxy-2,3,4,5-tetraÂhydro-1H-benz[b]azepine-2-carbÂoxyÂlic 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 molÂecules 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 molÂecules of comÂpound (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 molÂecules of compound (II) into a three-dimensional frameÂwork 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 BiolĂłgica, Faculdade de CiĂȘncias e Tecnologia, Univ. do Algarve, 2011Os organismos marinhos sĂŁo uma fonte fundamental de novos compostos bioativos com potencial interesse para a indĂșstria farmacĂȘutica e com diversas atividades biolĂłgicas. Sendo o tratamento de infeçÔes bacterianas cada vez mais dificultado pela capacidade das bactĂ©rias de desenvolverem resistĂȘncia aos agentes antimicrobianos Ă© necessĂĄrio a contĂnua descoberta e desenvolvimento de novos compostos antibacterianos para assegurar um futuro sustentĂĄvel do ponto de vista da saĂșde pĂșblica. Deste modo, este trabalho teve como objetivo avaliar a atividade antibacteriana de extratos de metanol de diferentes espĂ©cies de macro- e microalgas, ervas marinhas e plantas halĂłfitas contra estirpes bacterianas potencialmente patogĂ©nicas, pelo mĂ©todo de difusĂŁo em agar. As diferentes espĂ©cies de macroalgas foram colhidas na praia de Olhos dâĂgua (Albufeira) entre julho e novembro de 2009. As amostras de microalgas foram fornecidas pelo LaboratĂłrio Experimental de Organismos AquĂĄticos (LEOA, UAlg) e pela NECTON S.A. As plantas halĂłfitas 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, atravĂ©s do mĂ©todo de difusĂŁo 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). NĂŁo foram observadas zonas de inibição nos controlos negativos (metanol) e todos os antibiĂłticos utilizados (ĂĄcido nalidĂxico, gentamicina, penicilina G e tetraciclina) resultaram em inibição do crescimento bacteriano respetivo. Observaram-se zonas de inibição em Staphylococcus aureus na presença dos extratos metanĂłlicos de Cystoseira nodicaulis (8,44 ± 0,53 mm) e C. tamariscifolia (11,12 ± 0,78 mm). Os restantes extratos metanĂłlicos de algas e ervas marinhas foram inativos em relação Ă s estirpes estudadas. Os extratos de microalgas e de plantas halĂłfitas testados nĂŁo 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 nĂŁo demonstraram, porĂ©m, qualquer atividade
Josephson oscillation linewidth of ion-irradiated YBaCuO junctions
We report on the noise properties of ion-irradiated YBaCuO
Josephson junctions. This work aims at investigating the linewidth of the
Josephson oscillation with a detector response experiment at 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 () noise contribution
does not prevail in the temperature range of interest, as reported in some
other types of high-T 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 . "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
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