Numerical test of the Cardy-Jacobsen conjecture in the site-diluted Potts model in three dimensions

We present a microcanonical Monte Carlo simulation of the site-diluted Potts model in three dimensions with eight internal states, partly carried out in the citizen supercomputer Ibercivis. Upon dilution, the pure model's first-order transition becomes of the second-order at a tricritical point. We compute accurately the critical exponents at the tricritical point. As expected from the Cardy-Jacobsen conjecture, they are compatible with their Random Field Ising Model counterpart. The conclusion is further reinforced by comparison with older data for the Potts model with four states.Comment: Final version. 9 pages, 9 figure

Low temperature phase diagram of condensed para-Hydrogen in two dimensions

Extensive Path Integral Monte Carlo simulations of condensed para-Hydrogen in two dimensions at low temperature have been carried out. In the zero temperature limit, the system is a crystal at equilibrium, with a triangular lattice structure. No metastable liquid phase is observed, as the system remains a solid down to the spinodal density, and breaks down into solid clusters at lower densities. The equilibrium crystal is found to melt at a temperature close to 7 K

On the possibility to supercool molecular hydrogen down to superfluid transition

Recent calculations by Vorobev and Malyshenko (JETP Letters, 71, 39, 2000) show that molecular hydrogen may stay liquid and superfluid in strong electric fields of the order of $4\times 10^7 V/cm$. I demonstrate that strong local electric fields of similar magnitude exist beneath a two-dimensional layer of electrons localized in the image potential above the surface of solid hydrogen. Even stronger local fields exist around charged particles (ions or electrons) if surface or bulk of a solid hydrogen crystal is statically charged. Measurements of the frequency shift of the $1 \to 2$ photoresonance transition in the spectrum of two-dimensional layer of electrons above positively or negatively charged solid hydrogen surface performed in the temperature range 7 - 13.8 K support the prediction of electric field induced surface melting. The range of surface charge density necessary to stabilize the liquid phase of molecular hydrogen at the temperature of superfluid transition is estimated.Comment: 5 pages, 2 figure

PI-controlled bioreactor as a generalized Lienard system

It is shown that periodic orbits can occur in Cholette's bioreactor model working under the influence of a PI-controller. We find a diffeomorphic coordinate transformation that turns this controlled enzymatic reaction system into a generalized Lienard form. Furthermore, we give sufficient conditions for the existence and uniqueness of limit cycles in the new coordinates. We also perform numerical simulations illustrating the possibility of the existence of a local center (period annulus). A result with possible practical applications is that the oscillation frequency is a function of the integral control gain parameterComment: 15 pages, 5 figures, accepted version at Computers & Chem. En

Microcanonical finite-size scaling in specific heat diverging 2nd order phase transitions

A Microcanonical Finite Site Ansatz in terms of quantities measurable in a Finite Lattice allows to extend phenomenological renormalization (the so called quotients method) to the microcanonical ensemble. The Ansatz is tested numerically in two models where the canonical specific-heat diverges at criticality, thus implying Fisher-renormalization of the critical exponents: the 3D ferromagnetic Ising model and the 2D four-states Potts model (where large logarithmic corrections are known to occur in the canonical ensemble). A recently proposed microcanonical cluster method allows to simulate systems as large as L=1024 (Potts) or L=128 (Ising). The quotients method provides extremely accurate determinations of the anomalous dimension and of the (Fisher-renormalized) thermal $\nu$ exponent. While in the Ising model the numerical agreement with our theoretical expectations is impressive, in the Potts case we need to carefully incorporate logarithmic corrections to the microcanonical Ansatz in order to rationalize our data.Comment: 13 pages, 8 figure

Scaling the drop size in coflow experiments

We perform extensive experiments with coflowing liquids in microfluidic devices and provide a closed expression for the drop size as a function of measurable parameters in the jetting regime that accounts for the experimental observations; this expression works irrespective of how the jets are produced, providing a powerful design tool for this type of experiment

Paper based narrations: a study of the types of narrative texts used in early childhood education classrooms in Madrid

En este artículo se realiza un estudio sobre los distintos libros empleados en las aulas de 0 a 6 años en España con el objetivo de conocer el tipo de texto narrativo más empleado según el curso escolar, el tipo de centro (público, privado o concertado) y la percepción de utilidad de la formación académica del profesorado. La investigación se ha llevado a cabo a través un estudio cualitativo asociativo a partir de una encuesta online a 111 docentes en activo. Los principales resultados muestran que el profesorado percibe, en general, que la formación académica ha influido a la hora de manejar determinados tipos de cuentos como los relatos clásicos. Además, este trabajo evidencia que la formación académica sobre Literatura Infantil y Juvenil (LIJ) necesita ser reforzada dentro de los distintos planes de estudio.Artikulu honetan Espainian 0 eta 6 urte bitarteko ikasgeletan erabiltzen diren hainbat liburu aztertu dira, gehien erabiltzen diren narrazio testuak zein diren jakiteko. Horretarako, irizpide hauek erabili dira: eskolako ikasmailak, ikastetxe mota (publikoa, pribatua, kontzertatua), eta irakasleei prestakuntza akademikoa erabilgarria iruditzen zaien edo ez kontuan hartuta. Ikerketa azterketa kualitatibo baten bidez egin da, jardunean dauden 111 irakasleri egindako online galdetegi batetik abiatuta. Emaitza nagusiek diote irakasleek, oro har, uste dutela prestakuntza akademikoak eragina izan duela zenbait ipuin motarekin lan egitean, hala nola ipuin klasikoekin. Gainera, lan honek agerian jartzen du Haur eta Gazte Literaturari (HGL) buruzko prestakuntza akademikoa indartu egin behar dela.The aim of this article is to carried out a study about the different tales that are used in classrooms from 0 to 6 years old in Spain. The objective was to know the type of narrative text which are used according to the academic year, the type of centre (public, private, or subsided), and the perception of the usefulness of the academic education of teachers. The research has been developed through a qualitative associative study based on an online survey of 111 teachers. The main results show how teachers generally perceive that their academic education has influenced the use of certain types of tales such as classic stories. On the other hand, the specific education that teachers have about Children’s and Youth Literature needs to be reinforced within the different study plans

Surgical Options for the Refractive Correction of Keratoconus: Myth or Reality

Keratoconus provides a decrease of quality of life to the patients who suffer from it. The treatment used as well as the method to correct the refractive error of these patients may influence on the impact of the disease on their quality of life. The purpose of this review is to describe the evidence about the conservative surgical treatment for keratoconus aiming to therapeutic and refractive effect. The visual rehabilitation for keratoconic corneas requires addressing three concerns: halting the ectatic process, improving corneal shape, and minimizing the residual refractive error. Cross-linking can halt the disease progression, intrastromal corneal ring segments can improve the corneal shape and hence the visual quality and reduce the refractive error, PRK can correct mild-moderate refractive error, and intraocular lenses can correct from low to high refractive error associated with keratoconus. Any of these surgical options can be performed alone or combined with the other techniques depending on what the case requires. Although it could be considered that the surgical option for the refracto-therapeutic treatment of the keratoconus is a reality, controlled, randomized studies with larger cohorts and longer follow-up periods are needed to determine which refractive procedure and/or sequence are most suitable for each case