On the release of metronidazole from natural rubber latex membranes

The controlled release of drugs can be efficient if a suitable encapsulation procedure is developed, which requires biocompatible materials to hold and release the drug. In this study, a natural rubber latex (NRL) membrane is used to deliver metronidazole (MET), a powerful antiprotozoal agent. MET was found to be adsorbed on the NRL membrane, with little or no incorporation into the membrane bulk, according to energy dispersive X-ray spectroscopy. X-ray diffraction and FTIR spectroscopy data indicated that MET retained its structural and spectroscopic properties upon encapsulation in the NRL membrane, with no molecular-level interaction that could alter the antibacterial activity of MET. More importantly, the release time of MET in a NRL membrane in vitro was increased from the typical 6-8 h for oral tablets or injections to ca. 100 h. The kinetics of the drug release could be fitted with a double exponential function, with two characteristic times of 3.6 and 29.9 h. This is a demonstration that the induced angiogenesis known to be provided by NRL membranes can be combined with a controlled release of drugs, whose kinetics can be tailored by modifying experimental conditions of membrane fabrication for specific applications. (C) 2010 Elsevier B.V. All rights reserved.

11B nuclear magnetic resonance study of boron nitride nanotubes prepared by mechano-thermal method

We reported ¹¹B nuclear magnetic resonance studies of boron nitride (BN) nanotubes prepared by mechano-thermal route. The NMR lineshape obtained at 192.493 MHz (14.7 T) was fitted with two Gaussian functions, and the ¹¹B nuclear magnetization relaxations were satisfied with the stretched–exponential function, exp[-(tlT₁)^(D+1)/6] (D: space dimension) at all temperatures. In addition, the temperature dependence of spin–lattice relaxation rates was well described by T_i^-1 = aT (a: constant, T: temperature) and could be understood in terms of direct phonon process. All the 11BNMR results were explained by considering the inhomogeneous distribution of the paramagnetic metal catalysts, such as α-Fe, Fe–N, and Fe₂ B, that were incorporated during the process of high-energy ball milling of boron powder and be synthesized during subsequent thermal annealing. X-ray powder diffraction as well as electron paramagnetic resonance (EPR) on BN nanotubes were also conducted and the results obtained supported these conclusions.

Modelling the cooling of coffee : insights from a preliminary study in Indonesia

This paper discusses an attempt to examine pre-service teachers’ mathematical modelling skills. A modelling project investigating relationships between temperature and time in the process of cooling of coffee was chosen. The analysis was based on group written reports of the cooling of coffee project and observation of classroom discussion. Findings showed that pre-service teachers were able to model the process of cooling of coffee as a decreasing exponential function. Difficulties with interpretation of the constant rate of cooling and reinterpretation of mathematical model were identified.

In-situ studies of X-ray diffraction line profiles from strained copper foils

The development of an in-situ tensometer is described along with preliminary results of x-ray line profiles from copper foils under tensile stress. The tensometer was designed and constructed on the high resolution diffraction instrument, Station 2.3 at the synchrotron radiation source (SRS) Daresbury Laboratory, and is capable of collecting data in either symmetric or asymmetric geometry including transmission and reflection modes. Experiments were carried out using 18 J..Lm thick copper foil up to strain levels of 5 % using both symmetric reflection and symmetric transmission diffraction. All profiles displayed diffraction broadening and asymmetry which increased with strain. In addition, the asymmetry observed in symmetric transmission was associated with extended tails on the low angle side of the profiles, but in symmetric reflection data the opposite asymmetry was observed. In the analysis, the measured profiles were fitted using the software TOPAS, a fundamental parameters approach to profile fitting. The instrumental profile function was characterised and modelled using annealed LaB6 powder. The diffraction broadening was then determined by refining the convolution of a Voigt function, an asymmetric exponential function and a fixed instrument function to reproduce the observed broadened profiles. The integral breadth and asymmetry results display a strong order dependence and increase almost linearly with strain. The results were interpreted by assuming crystallite size broadening in combination with dislocation broadening arising from fcc a/2( 110) {Ill } dislocations.

Relationships between inventory, sales and service in a retail chain store operation

Effective inventory management is critical to retailing success. Surprisingly, there islittle published empirical research examining relationships between retail inventory, sales andcustomer service. Based on a survey of 101 chain store units, this paper develops and tests aseries of hypotheses about retail inventory. Seventy-five percent of the store owners/managersresponded to the mail survey. As expected, significant positive relationships were found betweeninventory, service and sales. Specifically, support was found for the theory that inventory is afunction of the square root of sales. Also, greater product variety leads to higher inventory, andservice level is an exponential function of inventory. Finally, demand uncertainty was found tohave no apparent effect on inventory levels.

Uma análise dos leilões de partilha de produção do pré-sal através de simulação computacional

O presente trabalho consiste na aplicação da simulação computacional como método de aprofundamento do estudo de mecanismos de leilões aplicados na alocação do direito de exploração das reservas de petróleo da camada do pré-sal. A camada do pré-sal está localizada na costa brasileira e apresenta um grande potencial em termos de reserva de óleo e gás. A função lance aplicada para os participantes criados computacionalmente foi estimada com base em dados experimentais e segue uma função exponencial. A simulação possibilita reproduzir o modelo de leilão considerando todas as características e parâmetros dos experimentos sem incorrer no custo da realização de novas sessões de leilão com participantes reais. Os leilões estudados foram o leilão de valores privados de 1° preço e o leilão de valores privados de 2° preço. Através dos resultados obtidos identificou-se que o leilão de valores privados de 1° preço é menos arriscado que o leilão de valores privados de 2° preço; no leilão com simetria, o Princípio de Equivalência de Receita é válido; a eficiência observada é menor em leilões assimétricos; o leilão de 2° preço comparado com o de 1° preço apresenta um tradeoff entre a eficiência e a receita do governo; e que considerando o aprendizado dos participantes, não se observam alterações significativas nas estatísticas analisadas à medida que os participantes se tornam mais experientes.

Benthic foraminiferal distribution on the southeastern Brazilian shelf and upper slope

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Digital monitoring of mycelium growth kinetics and vigor of shiitake (Lentinula edodes (Berk.) Pegler) on agar medium

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

On the release of metronidazole from natural rubber latex membranes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrical load forecasting formulation by a fast neural network

The objective of this work is to develop a methodology for electric load forecasting based on a neural network. Here, backpropagation algorithm is used with an adaptive process that based on fuzzy logic and using a decaying exponential function to avoid instability in the convergence process. This methodology results in fast training, when compared to the conventional formulation of backpropagation algorithm. The results are presented using data from a Brazilian Electric Company, and shows a very good performance for the proposal objective.

Kinetics of photoinduced birefringence in the guest-host system of poly(methyl methacrylate) doped with azobenzene-containing crown ethers

The kinetics of the buildup and decay of photoinduced birefringence was examined in a series of host-guest systems: azobenzene-containing crown ethers, differing in the size of the crowns, dissolved in a poly (methyl methacrylate) matrix. In all samples, the kinetics of the buildup of the birefringence was reasonably described by a sum of two exponential functions, the time constants being inversely proportional to the intensity of the pumping light and the magnitudes of the signals at the saturation level depending on the pumping light intensity and sample thickness. The dark decays were best described by the stretched exponential function, with the characteristic parameters (time constant and stretch coefficient) being practically independent of the type of crown ether. The time constants of the signal decay were orders of magnitude shorter than the respective constants of the dark isomerization of the azo crown ethers, thus indicating that the process controlling the decay was a relaxation of the polymer matrix and/or a rearrangement of the flexible parts of the crowns. (C) 2007 Wiley Periodicals, Inc.

Synthesis of a functionalized europium complex and deposition of luminescent Langmuir-Blodgett (LB) films

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Measurement of the differential cross section d sigma/dt in elastic p(p)over-bar scattering at root s=1.96 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Magnetic resonance study of the crystallization behavior of InF3-based glasses doped with Cu2+, Mn2+ and Gd3+

The crystallization of fluoroindate glasses doped with Gd3+, Mn2+ and Cu2+ heat treated at different temperatures, ranging from the glass transition temperature (Tg) to the crystallization temperature (Tc), are investigated by electron paramagnetic resonance (EPR) and 19F nuclear magnetic resonance (NMR). The EPR spectra indicate that the Cu2+ ions in the glass are located in axially distorted octahedral sites. In the crystallized glass, the g-values agreed with those reported for Ba2ZnF6, which correspond to Cu2+ in a tetragonal compressed F- octahedron and to Cu2+ on interstitial sites with a square-planar F- co-ordination. The EPR spectra of the Mn2+ doped glasses exhibit a sextet structure due to the Mn2+ hyperfine interaction. These spectra suggest a highly ordered environment for the Mn2+ ions (close to octahedral symmetry) in the glass. The EPR spectra of the recrystallized sample exhibit resonances at the same position, suggesting that the Mn2+ ions are located in sites of highly symmetric crystalline field. The increase of the line intensity of the sextet and the decrease of the background line in the thermal treated samples suggest that the Mn2+ ions move to the highly ordered sites which contribute to the sextet structure. The EPR spectra of the Gd3+ doped glasses exhibit the typical U-spectrum of a s-state ion in a low symmetry site in disordered systems. The EPR of the crystallized glasses, in contrast, have shown a strong resonance in g ≈ 2.0, suggesting Gd3+ ions in environment close to cubic symmetry. The 19F NMR spin-lattice relaxation rates were also strongly influenced by the crystallization process that takes over in samples annealed above Tc. For the glass samples (doped or undoped) the 19F magnetization recoveries were found to be adjusted by an exponential function and the spin-lattice relaxation was characterized by a single relaxation time. In contrast, for the samples treated above Tc, the 19F magnetization-recovery becomes non-exponential. A remarkable feature of our results is that the changes in the Cu2+, Mn2+, Gd3+ EPR spectra and NMR relaxation, are always observed for the samples annealed above Tc. © 2006 Elsevier B.V. All rights reserved.

Geometrical logarithmic and trigonometric hypercomplex functions of quaternionic type

Quaternionic theory has greatly been developed in recent years [1-12]. Thus, in our view, the study of trigonometric and logarithmic type quaternionic functions is important for the determination and realization of a hyper complex theory. In this paper, we intend to give a geometrical foundation for both logarithmic and trigonometric hyper complex functions based on the exponential function of quaternionic type recently introduced by Borges, Marão and Machado in their paper entitled Geometrical octonions II: Hyper regularity and hyper periodicity of the exponential function appearing. © 2011 Pushpa Publishing House.