INNOVACIÓN EN LOS SISTEMAS DE PAGOS: EL CASO DEL MERCADO DE TRANSFERENCIAS DE CRÉDITO EN EL PERU

El presente trabajo es una primera aproximación al análisis de los factores que explican el menor desarrollo del mercado de transferencias de crédito en el Perú, a pesar de las ventajas que tiene respecto al uso del efectivo y del cheque. Siguiendo la literatura sobre el tema de innovación, el análisis parte de la concepción de que los sistemas de pago son una industria de red y en ese contexto se busca identificar incentivos y limitantes que tienen los agentes para el desarrollo del mercado. Se concluye que entre los factores limitantes se tiene a: • La estructura de comisiones a nivel del servicio de compensación y de los clientes del sistema financiero. • El incentivo de los bancos por invertir en sus propias redes, en lugar de hacerlo en la red común. • La falta de cultura financiera. • Presencia de mecanismos de pago de obligaciones que limitan el desarrollo de los sistemas de pagos. De esta forma, existe una tarea de difusión y de coordinación para que el mercado de transferencias de crédito se desarrolle, beneficiándose los agentes económicos por el menor riesgo y mayor eficiencia para el pago de sus transacciones.

Tables of the Equally Correlated Multivariate Normal Probability Integral

1 online resource (PDF, 193 pages

The Casimir Problem of Spherical Dielectrics: Quantum Statistical and Field Theoretical Approaches

The Casimir free energy for a system of two dielectric concentric nonmagnetic spherical bodies is calculated with use of a quantum statistical mechanical method, at arbitrary temperature. By means of this rather novel method, which turns out to be quite powerful (we have shown this to be true in other situations also), we consider first an explicit evaluation of the free energy for the static case, corresponding to zero Matsubara frequency ($n=0$). Thereafter, the time-dependent case is examined. For comparison we consider the calculation of the free energy with use of the more commonly known field theoretical method, assuming for simplicity metallic boundary surfaces.Comment: 31 pages, LaTeX, one new reference; version to appear in Phys. Rev.

Casimir effect for the scalar field under Robin boundary conditions: A functional integral approach

In this work we show how to define the action of a scalar field in a such a way that Robin boundary condition is implemented dynamically, i.e., as a consequence of the stationary action principle. We discuss the quantization of that system via functional integration. Using this formalism, we derive an expression for the Casimir energy of a massless scalar field under Robin boundary conditions on a pair of parallel plates, characterized by constants $c_1$ and $c_2$. Some special cases are discussed; in particular, we show that for some values of $c_1$ and $c_2$ the Casimir energy as a function of the distance between the plates presents a minimum. We also discuss the renormalization at one-loop order of the two-point Green function in the $\lambda\phi^4$ theory submitted to Robin boundary condition on a plate.Comment: 16 pages, 2 figures. Version 2: contains a new section on the renormalization of the two-point Green function in the presence of a flat boundary. Accepted for publication in J. Phys.

Biomechanical corneal changes induced by different flap thickness created by femtosecond laser

OBJECTIVE: To evaluate the impact of the creation of corneal flaps at different thicknesses on the biomechanical properties of swine corneas. METHOD: Twelve swine eyes were obtained to form two groups: 100 μm flap thickness and 300 μm flap thickness. Each eye was submitted to the following examinations: raster topography to investigate corneal curvature alterations, ocular response analyzer to investigate corneal hysteresis change, optical coherence tomography to measure central corneal and flap thickness and sonic wave propagation velocity as a measure of stiffness, before and immediately after flap creation. After flap amputation, surface wave velocity measurements were repeated. RESULTS: Measured flap thicknesses were statistically different for thin and thick flap groups, with an average of 108.5 + 6.9 and 307.8 + 11.5 μm respectively. Hysteresis and corneal resistance factor did not change significantly after flap creation in the thin flap group. With thicker flaps, both parameters decreased significantly from 8.0 +1.0 to 5.1 +1.5 mmHg and from 8.2 + 1.6 to 4.1 +2.5 mmHg respectively. Simulated keratometry values increased in the thick flap group (from 39.5 + 1 D to 45.9+1.2 D) after flap creation but not in the thin flap group (from 40.6 + 0.6 D to 41.4+ 1.0 D). Regarding surface wave velocity analysis, the surgical procedures induced statistically lower results in some positions. CONCLUSION: In the experimental conditions established by this model, thicker flaps presented a greater biomechanical impact on the cornea.National Institutes of Health (NIH)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Characterization and Evaluation of Gum Arabic Coated Sand as Proppants for Hydraulic Fracturing Applications

Luwa sand was characterized and used to design a proppant for reservoir stimulation/hydraulic fracturing applications. This involves describing the sand in terms of its physicochemical properties, including Sieve analysis, proppant sphericity and roundness measurement, acid solubility measurement, turbidity test, bulk density measurement, proppant crush-resistance test and loss on ignition test (LOI). Additional tests on hardness and elemental (XRF) were also conducted. X-ray fluorescence analysis of the sand indicates that the sand contains higher percentages of Aluminium oxide (Al2O3) than Silicon oxide (SiO2). The hardness test on the Mohs scale confirmed the sand materials as topaz, i.e. not purely corundum (a crystalline form of aluminium oxide) or purely quartz with a hardness value of 8. This value is more complex than silicon oxide, with a hardness value of 7, and less than corundum, with a hardness value of 9. The Luwa sand is uniformly graded; more than 90% of the sand falls within the specified particle range of 20/40 mesh size. The 20/40 mesh-designed proppant shows favourable qualities for consideration as a proppant. However, the sand exhibits low crush resistance at pressures of 3000 psi and, therefore, cannot be applied in reservoirs with closure stress of up to 3000 psi. Because of the low crush strength of Luwa sand, gum Arabic resin was used to coat the sand for improved mechanical and chemical stability. The new resin-coated sand was further tested for crush resistance and acid solubility. The result shows a significant improvement in the crush resistance above 3000 psi with less than 5% fines generated. Generally, the uncoated sand produces less than 10% fines at stresses less than 3000 psi and is considered to have a 2 K value, while the resin-coated proppant generates 10% fines above 6000 psi. The resin coated can be classified as having a 5K value and can be applied in reservoirs with closure stress of up to 5000 psi or less

Casimir Force on a Micrometer Sphere in a Dip: Proposal of an Experiment

The attractive Casimir force acting on a micrometer-sphere suspended in a spherical dip, close to the wall, is discussed. This setup is in principle directly accessible to experiment. The sphere and the substrate are assumed to be made of the same perfectly conducting material.Comment: 11 pages, 1 figure; to appear in J. Phys. A: Math. Ge