Pressure-induced phase transition and fracture in α-MoO3 nanoribbons.

MoO3 nanoribbons were studied under different pressure conditions ranging from 0 to 21GPa at room temperature. The effect of the applied pressure on the spectroscopic and morphologic properties of the MoO3 nanoribbons was investigated by means of Raman spectroscopy and scanning electron microscopy techniques. The pressure dependent Raman spectra of the MoO3 nanoribbons indicate that a structural phase transition occurs at 5GPa from the orthorhombic α-MoO3 phase (Pbnm) to the monoclinic MoO3-II phase (P21/m), which remains stable up to 21GPa. Such phase transformation occurs at considerably lower pressure than the critical pressure for α-MoO3 microcrystals (12GPa). We suggested that the applanate morphology combined with the presence of crystalline defects in the sample play an important role in the phase transition of the MoO3 nanoribbons. Frequencies and linewidths of the Raman bands as a function of pressure also suggest a pressure-induced morphological change and the decreasing of the nanocrystal size. The observed spectroscopic changes are supported by electron microscopy images, which clearly show a pressure-induced morphologic change in MoO3 nanoribbons.

Modelagem do transporte de cloreto proveniente de esgoto urbano em um aquífero sedimentar usando MT3D: o caso da bateria de poços de Juazeiro do Norte (CE) / Modeling of transport of chloride in a sedimentary aquifer using MT3D: the case of a well field in Juazeiro do Norte (CE)

Esse trabalho consiste em um estudo de caso, em que o modelo de transporte de soluto MT3D, associado ao modelo de fluxo MODFLOW, foi utilizado na avaliação da contaminação de um aquífero por água superficial de um riacho contaminado com esgoto urbano, utilizando o cloreto como traçador. Nessa área, as águas do aquífero são explotadas por uma bateria de poços alinhada ao riacho. A calibração do modelo de transporte foi executada para reproduzir os teores de cloretos observados nas águas dos poços em campanhas de monitoramento. Já a do modelo de fluxo procurou reproduzir as cargas hidráulicas observadas durante testes de bombeamentos realizados em cada poço. Os resultados obtidos nessas calibrações foram compatíveis com as observações. A partir dos modelos calibrados, foi realizada uma simulação futura (prognóstico), visando determinar o tempo necessário para a recuperação da qualidade de água subterrânea após interrupção do lançamento de esgoto no riacho. Os resultados da modelagem indicaram que: os rebaixamentos produzidos pelo bombeamento dos poços são maiores nas proximidades do riacho; o transporte de contaminante ocorre, predominantemente, na vertical, induzido pelo bombeamento dos poços e pela recarga do aquífero a partir do riacho; os níveis de cloretos relativamente elevados nas águas dos poços podem voltar aos valores naturais do aquífero em aproximadamente um ano, caso o lançamento de esgoto no riacho seja interrompido. Assim, para evitar um maior comprometimento dos aquíferos da área por poluição persistente, o esgoto deverá ter um destino adequado e a área de preservação permanente do riacho deverá ser respeitada.

This paper presents a case study in which the solute transport model MT3D, associated with the MODFLOW flow model, was used in the assessment of contamination of an aquifer by surface water from a creek contaminated with urban wastewater, using chloride as a tracer. In that area of the aquifer, groundwater is exploited through a field of wells along the creek. The calibration of the transport model was implemented in order to reproduce the levels of chloride in water from wells observed in monitoring campaigns. The flow model sought to reproduce the hydraulic loads observed during pumping tests conducted in each well. The results obtained from these calibrations were consistent with observations. Based on the calibrated models, we carried out a "future simulation" (prognosis), in order to determine the time required for recovery of groundwater quality after stopping sewage discharge into the creek. Modeling results indicate that: drawdowns produced by pumping the wells are higher in the proximity of the creek; contaminant transport occurs, predominantly, vertically induced by pumping of the wells and by aquifer recharge from the creek; elevated levels of chloride in the waters from the wells may return to natural values in about one year, if the release of sewage into the creek is stopped. In this context, in order to prevent further damage to the aquifer area through persistent pollution, sewage must have a suitable destination and the area of permanent protection of the creek must be respected.

Novel polymorphs of the anti-Trypanosoma cruzi drug benznidazole.

Benznidazole (N-benzyl-2-(2-nitro-1H-imidazol-1-yl)acetamide), is a nitro-heterocyclic drug used in the treatment of Chagas disease. Despite the fact that this drug was released more than 30 years ago, little information about its solid state properties is available in the literature. In this study, it was verified that this drug exhibits three polymorphs, which were characterized in situ by X-ray powder diffraction, thermal analysis, hot stage microscopy and infrared spectroscopy. The thermodynamic relationships among these polymorphs were also discussed.

The encapsulation of ß-lapachone in 2-hydroxypropyl-ß-cyclodextrin inclusion complex into liposomes: a physicochemical evaluation and molecular modeling approach.

The aim of this study was to encapsulate lapachone (ß-lap) or inclusion complex (ß-lap:HPß-CD) in liposomes and to evaluate their physicochemical characteristics. In addition, the investigation of the main aspects of the interaction between ß-lap and 2-hydroxypropyl-ß-cyclodextrin (HPß-CD), using both experimental and molecular modeling approaches was discussed. Furthermore, the in vitro drug release kinetics was evaluated. First, a phase solubility study of ß-lap in HPß-CD was performed and the ß-lap:HPß-CD was prepared by the freeze-drying technique. A 302-fold increase of solubility was achieved for ß-lap in HPß-CD solution with a constant of association K(1:1) of 961 M(-1) and a complexation efficiency of ß-lap of 0.1538. (1)H NMR, TG, DSC, IR, Raman and SEM indicated a change in the molecular environment of ß-lap in the inclusion complex. Molecular modeling confirms these results suggesting that ß-lap was included in the cavity of HPß-CD, with an intermolecular interaction energy of -23.67 kJ mol(-1). ß-lap:HPß-CD and ß-lap-loaded liposomes presented encapsulation efficiencies of 93% and 97%, respectively. The kinetic rate constants of 183.95±1.82 µg/h and 216.25±2.34 µg/h were calculated for ß-lap and ß-lap:HPß-CD-loaded liposomes, respectively. In conclusion, molecular modeling elucidates the formation of the inclusion complex, stabilized through hydrogen bonds, and the encapsulation of ß-lap and ß-lap:HPß-CD into liposomes could provide an alternative means leading eventually to its use in cancer research.

Functionalization of single-wall carbon nanotubes through chloroform adsorption: theory and experiment.

The interaction of chloroform (CHCl(3)) with single-wall carbon nanotubes (SWCNT) is investigated using both first principles calculations based on Density Functional Theory and vibrational spectroscopy experiments. CHCl(3) adsorption on pristine, defective, and carboxylated SWCNTs is simulated, thereby gaining a good understanding of the adsorption process of this molecule on SWCNT surfaces. The results predict a physisorption regime in all cases. These calculations point out that SWCNTs are promising materials for extracting trihalomethanes from the environment. Theoretical predictions on the stability of the systems SWCNT-CCl(2) and SWCNT-COCCl(3) are confirmed by experimental TGA data and Fourier Transform Infrared Spectroscopy (FT-IR) experiments. Results from resonance Raman scattering experiments indicate that electrons are transferred from the SWCNTs to the attached groups and these results are in agreement with the predictions made by ab initio calculations.

New crystals in the lithium sulfate family.

The preparation and structures of caesium lithium sulfate, Cs(1.15)Li(2.85)(SO(4))(2), and caesium lithium rubidium sulfate, Cs(0.90)Li(2.88)Rb(0.22)(SO(4))(2), are described and discussed in the context of simple and double sulfate polymorphism. The latter structure is related to the former through the substitution of Rb for Cs. In both crystals, the sulfate ions occupy two non-equivalent sites, but the ions are disordered in Cs(1.15)Li(2.85)(SO(4))(2).