Sizing and Eddy currents in magnetic core nanoparticles: An optical extinction approach

Optical extinction is a handy and ubiquitous technique that allows us to study colloidal nanoparticles in their native state. The typical analysis of the extinction spectrum can be extended in order to obtain structural information of the sample such as the size distribution of the cores and the thickness of the coating layers. In this work the extinction spectra of Fe3O4, Fe3O4@Au, and Fe3O4@SiO2@Au single and multilayer nanoparticles are obtained by solving full Mie theory with a frequency dependent susceptibility derived from the Gilbert equation and considering the effect of Eddy currents. The results are compared with non-magnetic Mie theory, magnetic dipolar approximation and magnetic Mie theory without Eddy currents. The particle size-wavelength ranges of validity of these different approaches are explored and novel results are obtained for Eddy current effects in optical extinction. These results are used to obtain particle size and shell thickness information from the experimental extinction spectra of Fe3O4 and Fe3O4@Au nanoparticles in good agreement with TEM results, and to predict the plasmon peak parameters for Fe3O4@SiO2@Au three layer nanoparticles.Fil: Mendoza Herrera, Luis Joaquin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Bruvera, Ignacio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Scaffardi, Lucia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; ArgentinaFil: Schinca, Daniel Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Ópticas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones Ópticas. Universidad Nacional de La Plata. Centro de Investigaciones Ópticas; Argentin

La macroeconomía de una economía abierta en el corto plazo: del modelo Mundell - Fleming a la demanda agregada

In this paper the Mundell - Fleming model is used to derive the curve of the aggregate demand for regimens of fixed and flexible exchange rates, in a context of perfect capital mobility. A curve of perfectly elastic aggregate supply will be supposed. Though, all increment of the aggregate demand will be translated in a variation of the production of the same magnitude to return to the equilibrium, while the price level stays constant. The price level will be introduced in an explicit way, since the analysis requires that one works in the plane of the demanded production and the price level. The form of incorporating it will be through the real exchange rate, in the market for goods; and through the nominal demand of money, in the monetary market.

Green accounting in Colombia: a case study of the mining sector

The environmental crisis involves several responsible parties, and industries are one of them. Therefore, it is important to interrelate the environment and economy to generate an environmental commitment by industries. Green accounting arises with the aims of providing quantitative and qualitative information on the company’s environmental aspects. This paper describes the current state of green accounting in the leading mining companies in Colombia according to the Ministry of Energy and Mines of Colombia. Findings show that 80% of the selected mining companies integrate green accounting in their management system. However, the underlying procedures are not always put into practice. Therefore, accounting studies must lead to the development of an environmental accounting model and the implementation of mandatory regulations for green accounting

La macroeconomí­a de una economí­a abierta: el mercado de trabajo y la oferta agregada

In this paper we study the operation of the labor market, and a curve of aggregate supply is derived, for the cases of closed and open economy, in the short, medium and long term. In an open economy, an important part of the production costs is derived of the use of imported inputs in the fabrication of the products. Therefore, the domestic price level, besides depending on the level of the nominal wage, is also associated to factors like the exchange rate or to the international price of imported inputs. In the short term, since the nominal wage and the exchange rate are independent of the activity level, the price level is constant and therefore the aggregate supply is perfectly elastic. In the medium term, an increment of the level of economic activity, reduces the unemployment rate and produces an increment of the wages, that elevates the costs of production of the companies and the price level of the economy. Therefore, firms are willing to offer a larger production but at a higher price level. In the long term, prices do not affect the level of economic activity, which implies that the aggregate supply is perfectly inelastic. After presenting the different versions of the aggregate supply, we carry out exercises of comparative static to show the effects on aggregate supply of a technological change and an increment of the international price of petroleum.

El mercado de bienes y los mercados financieros en economías con sistema bancario dolarizado

The private commercial banking and a widespread foreign currency market are the central institutions that characterize the financial system of many Latin American countries. In these economies, the stock markets still don't have a great macroeconomic importance and the markets for government issued bonds are is in the middle of their development. In this paper a macroeconomic model is presented where the core of the financial system is constituted by banks. Banks accept deposits and grant credits as much in domestic currency as in foreign currency, and the flows of short term capitals have their origin in the external indebtedness of the local banks. The starting point of this type of models is the old Mundell-Fleming, which allows us to link the real sector with the financial system, in a world opened to the international trade of goods and financial capitals. In an economy where the firms and the families have their debt in foreign currency, if we consider that the real load of the debt influences private expenditure, a devaluation, under a fixed exchange rate regime, or under an expanding monetary policy in a regimen of flexible exchange rate, can increase the real exchange rate, elevate the real load of the debt and, if this effect is more important than the Marshall-Lerner effect, the devaluation or the expansive monetary policy can have a recessive effect on the level of economic activity.