Multilayer Graphene Synthesized by CVD Using Liquid Hexane as the Carbon Precursor

We produce multilayer graphene by the Chemical Vapor Deposition (CVD) method at atmospheric pressure and 1000 {\deg}C, using flexible copper substrates as catalyst and liquid hexane as the source of carbon. We designed an optical device to measure the transmittance of the carbon films; with this information we calculate that the approximate number of layers is 11.Comment: 6 pages, 5 figures. Accepted for publication in World Journal of Condensed Matter Physic

Modified Newtonian Dynamics as an entropic force

Under natural assumptions on the thermodynamic properties of space and time with the holographic principle we reproduce a MOND-like behaviour of gravity on particular scales of mass and length, where Newtonian gravity requires a modification or extension if no dark matter component is introduced in the description of gravitational phenomena. The result is directly obtained with the assumption that a fundamental constant of nature with dimensions of acceleration needs to be introduced into gravitational interactions. This in turn allows for modifications or extensions of the equipartion law and/or the holographic principle. In other words, MOND-like phenomenology can be reproduced when appropriate generalised concepts at the thermodynamical level of space and/or at the holographic principle are introduced. Thermodynamical modifications are reflected in extensions to the equipartition law which occur when the temperature of the system drops below a critical value, equals to Unruh's temperature evaluated at the acceleration constant scale introduced for the description of the gravitational phenomena. Our calculations extend the ones by Verlinde (2011) in which Newtonian gravity is shown to be an emergent phenomenon, and together with it reinforces the idea that gravity at all scales is emergent.Comment: 6 pages. Accepted for publication in Journal of Modern Physics (JMP

A direct primitive variable recovery scheme for hyperbolic conservative equations: the case of relativistic hydrodynamics

In this article we develop a Primitive Variable Recovery Scheme (PVRS) to solve any system of coupled differential conservative equations. This method obtains directly the primitive variables applying the chain rule to the time term of the conservative equations. With this, a traditional finite volume method for the flux is applied in order avoid violation of both, the entropy and "Rankine-Hugoniot" jump conditions. The time evolution is then computed using a forward finite difference scheme. This numerical technique evades the recovery of the primitive vector by solving an algebraic system of equations as it is often used and so, it generalises standard techniques to solve these kind of coupled systems. The article is presented bearing in mind special relativistic hydrodynamic numerical schemes with an added pedagogical view in the appendix section in order to easily comprehend the PVRS. We present the convergence of the method for standard shock-tube problems of special relativistic hydrodynamics and a graphical visualisation of the errors using the fluctuations of the numerical values with respect to exact analytic solutions. The PVRS circumvents the sometimes arduous computation that arises from standard numerical methods techniques, which obtain the desired primitive vector solution through an algebraic polynomial of the charges.Comment: 19 pages, 6 figures, 2 tables. Accepted for publication in PLOS ON

International Evidence on Fiscal Solvency: Is Fiscal Policy "Responsible"?

This paper looks at fiscal solvency and public debt sustainability in both emerging market and advanced countries. Evidence of fiscal solvency, in the form of a robust positive conditional relationship between public debt and the primary fiscal balance, is established in both groups of countries, as well as in the sample as a whole. Evidence of fiscal solvency is much weaker, however, at high debt levels. The debt-primary balance relationship weakens considerably in emerging economies as debt rises above 50 percent of GDP. Moreover, the relationship vanishes in high-debt countries when the countries are split into high- and low-debt groups relative to sample means and medians, and this holds for industrial countries, emerging economies, and in the combined sample. These findings suggest that many industrial and emerging economies, including several where fiscal solvency has been the subject of recent debates, appear to conduct fiscal policy responsibly. Yet our results cannot reject the hypothesis of fiscal insolvency in groups of countries with high debt ratios, where the response of the primary balance to increases in debt is not statistically significant.