Magnetoelectric effects in the spiral magnets CuCl2 and CuBr2

The nature and symmetry of transition mechanisms in the spin-spiral copper halides CuCl₂ and CuBr₂ are analyzed theoretically. The magnetoelectric effects observed in the two multiferroic compounds are described and their phase diagram at zero and applied magnetic fields are worked out. The emergence of the electric polarization at zero field below the paramagnetic phase is shown to result from the coupling of two distinct spin-density waves and to be only partly related to the Dzialoshinskii-Moriya interactions. Applying a magnetic field along the two-fold monoclinic axis of CuCl₂ yields a decoupling of the spin-density waves modifying the symmetry of the phase and the spin-spiral orientation. The remarkable periodic dependences of the magnetic susceptibility and polarization, on rotating the field in the monoclinic plane, are described theoretically.

Dielectric investigation of the Sr3WO6 double perovskite at RF/microwave frequencies

This work reports the dielectric properties of Sr₃WO₆ (SWO) double perovskite at radio frequencies as a function of the temperature and a study in microwaves range to evaluate the material as a novel dielectric resonator.

Increased bioavailability of primaquine using poly(ethylene oxide) matrix extended-release tablets administered to beagle dogs

Primaquine (PQ) is used for the radical cure of Plasmodium vivax malaria and can cause serious side effects in some individuals. The development of an extended-release dosage with poly(ethylene oxide) as a hydrophilic polymer has been investigated to improve drug efficacy and tolerability. The aim of this study was to evaluate in vivo a new extended-release formulation of PQ (60 mg). The formulation was administered to beagle dogs and plasma PQ concentrations were compared to a conventional immediate-release formulation of PQ (60 mg). The evaluation was carried out using a validated high-performance liquid chromatography method using solid-phase extraction. Total PQ exposure in beagle dogs was 2.2 times higher (area under curve of 12 193 versus 5678 ng h/ml) and the elimination half-life of PQ was a 19-fold greater (12.95 hours versus 0.68 hours) with the extended-release tablets compared with the immediate-release tablets. These findings suggest that the extended-release formulation of PQ merits further evaluation for the treatment of P. vivax malaria and/or chemoprophylaxis.

Development, validation and stability study of pediatric atenolol syrup

Atenolol [4-(2-hydroxy-isopropylaminopropoxy)-phenylacetamide], is a cardioselective beta1-adrenergic receptor blocking agent prescribed for treatment of hypertension, angina pectoris and cardiac arrhythmias. However, most of these medicines are not formulated for easy or accurate administration to children. Atenolol is unstable in solutions and therefore the development of a liquid dosage form is a significant challenge. Studies showed that the degradation rate of atenolol is dependent on the temperature, indicating higher stability at 4 degrees C. Atenolol syrup is stable for 9 days, with acceptable apearance. A second order model adequately described atenolol decomposition when stored as syrup. A stability-indicating method was developed and validated in order to evaluate these studies.

Transcriptome characterization of the dimorphic and pathogenic fungus Paracoccidioides brasiliensis by EST analysis

Paracoccidioides brasiliensis is a pathogenic fungus that undergoes a temperature-dependent cell morphology change from mycelium (22 degrees C) to yeast (36 degrees C). It is assumed that this morphological transition correlates with the infection of the human host. Our goal was to identify genes expressed in the mycelium (M) and yeast (Y) forms by EST sequencing in order to generate a partial map of the fungus transcriptome. Individual EST sequences were clustered by the CAP3 program and annotated using Blastx similarity analysis and InterPro Scan. Three different databases, GenBank nr, COG (clusters of orthologous groups) and GO (gene ontology) were used for annotation. A total of 3,938 (Y = 1,654 and M = 2,274) ESTs were sequenced and clustered into 597 contigs and 1,563 singlets, making up a total of 2,160 genes, which possibly represent one-quarter of the complete gene repertoire in P. brasiliensis. From this total, 1,040 were successfully annotated and 894 could be classified in 18 functional COG categories as follows: cellular metabolism (44%); information storage and processing (25%); cellular processes-cell division, posttranslational modifications, among others (19%); and genes of unknown functions (12%). Computer analysis enabled us to identify some genes potentially involved in the dimorphic transition and drug resistance. Furthermore, computer subtraction analysis revealed several genes possibly expressed in stage-specific forms of P. brasiliensis. Further analysis of these genes may provide new insights into the pathology and differentiation of P. brasiliensis.