Dependence of Exchange Bias on Interparticle Interactions in Co/CoO Core/Shell Nanostructures

This article reports the dependence of exchange bias (EB) effect on interparticle interactions in nanocrystalline Co/CoO core/shell structures, synthesized using the conventional sol-gel technique. Analysis via powder X-Ray diffraction (PXRD) studies and transmission electron microscope (TEM) images confirm the presence of crystalline phases of core/shell Co/CoO with average particle size ≈ 18 nm. Volume fraction (φ) is varied (from 20% to 1%) by the introduction of a stoichiometric amount of non-magnetic amorphous silica matrix (SiO2) which leads to a change in interparticle interaction (separation). The influence of exchange and dipolar interactions on the EB effect, caused by the variation in interparticle interaction (separation) is studied for a series of Co/CoO core/shell nanoparticle systems. Studies of thermal variation of magnetization (M−T) and magnetic hysteresis loops (M−H) for the series point towards strong dependence of magnetic properties on dipolar interaction in concentrated assemblies whereas individual nanoparticle response is dominant in isolated nanoparticle systems. The analysis of the EB effect reveals a monotonic increase of coercivity (HC) and EB field (HE) with increasing volume fraction. When the nanoparticles are close enough and the interparticle interaction is significant, collective behavior leads to an increase in the effective antiferromagnetic (AFM) CoO shell thickness which results in high HC and HE. Moreover, in concentrated assemblies, the dipolar field superposes to the local exchange field and enhances the EB effect contributing as an additional source of unidirectional anisotropy

Mining And Validating Localized Frequent Itemsets With Dynamic Tolerance

We cast the frequent itemset mining problem as a criterion guided optimization problem instead of one based on exact counting. This opens several interesting possibilities, including modification of the criterion function to take into account (i) error tolerance, (ii) locality, (iii) unsupervised estimation of the error tolerance, and (iv) search strategy. We also propose a new validation procedure that takes into account the completeness and accuracy of the discovered patterns. Experiments with real Web transaction data are presented

Detecting Obfuscated Viruses Using Cosine Similarity Analysis

Virus writers are getting smarter by the day. They are coming up with new, innovative ways to evade signature detection by anti-virus software. One such evasion technique used by polymorphic and metamorphic viruses is their ability to morph code so that signature based detection techniques fail. These viruses change form such that every new infected file has different strings, rendering string based signature detection practically useless against such viruses. Our work is based on the premise that given a variant of morphed code, we can detect any obfuscated version of this code with high probability using some simple statistical techniques. We use the cosine similarity function to compare two files based on static analysis of the portable executable (PE) format. Our results show that for certain evasion techniques, it is possible to identify polymorphic/metamorphic versions of files based on cosine similarity

Detecting Obfuscated Viruses Using Cosine Similarity Analysis

Virus writers are getting smarter by the day. They are coming up with new, innovative ways to evade signature detection by anti-virus software. One such evasion technique used by polymorphic and metamorphic viruses is their ability to morph code so that signature based detection techniques fail. These viruses change form such that every new infected file has different strings, rendering string based signature detection practically useless against such viruses. Our work is based on the premise that given a variant of morphed code, we can detect any obfuscated version of this code with high probability using some simple statistical techniques. We use the cosine similarity function to compare two files based on static analysis of the portable executable (PE) format. Our results show that for certain evasion techniques, it is possible to identify polymorphic/metamorphic versions of files based on cosine similarity

Dependence of Exchange Bias on Interparticle Interactions in Co/CoO Core/Shell Nanostructures

This article reports the dependence of exchange bias (EB) effect on interparticle interactions in nanocrystalline Co/CoO core/shell structures, synthesized using the conventional sol-gel technique. Analysis via powder X-Ray diffraction (PXRD) studies and transmission electron microscope (TEM) images confirm the presence of crystalline phases of core/shell Co/CoO with average particle size ≈ 18 nm. Volume fraction (φ) is varied (from 20% to 1%) by the introduction of a stoichiometric amount of non-magnetic amorphous silica matrix (SiO2) which leads to a change in interparticle interaction (separation). The influence of exchange and dipolar interactions on the EB effect, caused by the variation in interparticle interaction (separation) is studied for a series of Co/CoO core/shell nanoparticle systems. Studies of thermal variation of magnetization (M−T) and magnetic hysteresis loops (M−H) for the series point towards strong dependence of magnetic properties on dipolar interaction in concentrated assemblies whereas individual nanoparticle response is dominant in isolated nanoparticle systems. The analysis of the EB effect reveals a monotonic increase of coercivity (HC) and EB field (HE) with increasing volume fraction. When the nanoparticles are close enough and the interparticle interaction is significant, collective behavior leads to an increase in the effective antiferromagnetic (AFM) CoO shell thickness which results in high HC and HE. Moreover, in concentrated assemblies, the dipolar field superposes to the local exchange field and enhances the EB effect contributing as an additional source of unidirectional anisotropy

Woodfordia Fruticosa: Traditional Uses and Recent Findings

Woodfordia fruticosa Kurz of the family Lythraceae is a plant of tropical and subtropical region with a long history of medicinal use. A wide range of chemical compounds including tannins (especially those of macrocyclic hydrolysable class), flavonoids, anthraquinone glycosides, and polyphenols have been isolated from this species in recent times. Extracts and metabolites of this plant, particularly those from flowers and leaves, possess useful pharmacological activities. A comprehensive account of the chemical constituents and the biological activities is presented and a critical appraisal of the ethnopharmacological issues is included in view of the many recent findings of importance on this plant

Anti-Helicobacter Pylori Potential of Artemisinin and Its Derivatives

The antimalarial drug artemisinin from Artemisia annua demonstrated remarkably strong activity against Helicobacter pylori, the pathogen responsible for peptic ulcer diseases. In an effort to develop a novel antimicrobial chemotherapeutic agent containing such a sesquiterpene lactone endoperoxide, a series of analogues (2 natural and 15 semisynthetic molecules), including eight newly synthesized compounds, were investigated against clinical and standard strains of H. pylori. The antimicrobial spectrum against 10 H. pylori strains and a few other bacterial and fungal strains indicated specificity against the ulcer causing organism. Of five promising molecules, a newly synthesized ether derivative �-artecyclopropylmether was found to be the most potent compound, which exhibited MIC range, MIC90, and minimum bactericidal concentration range values of 0.25 to 1.0 �g/ml, 1.0 �g/ml, and 1 to 16 �g/ml, respectively, against both resistant and sensitive strains of H. pylori. The molecule demonstrated strong bactericidal kinetics with extensive morphological degeneration, retained functional efficacy at stomach acidic pH unlike clarithromycin, did not elicit drug resistance unlike metronidazole, and imparted sensitivity to resistant strains. It is not cytotoxic and exhibits in vivo potentiality to reduce the H. pylori burden in a chronic infection model. Thus, �-artecyclopropylmether could be a lead candidate for anti-H. pylori therapeutics. Since the recurrence of gastroduodenal ulcers is believed to be mainly due to antibiotic resistance of the commensal organism H. pylori, development of a candidate drug from this finding is warrante