Geometric thermodynamics: black holes and the meaning of the scalar curvature

In this paper we show that the vanishing of the scalar curvature of Ruppeiner-like metrics does not characterize the ideal gas. Furthermore, we claim through an example that flatness is not a sufficient condition to establish the absence of interactions in the underlying microscopic model of a thermodynamic system, which poses a limitation on the usefulness of Ruppeiner's metric and conjecture. Finally, we address the problem of the choice of coordinates in black hole thermodynamics. We propose an alternative energy representation for Kerr-Newman black holes that mimics fully Weinhold's approach. The corresponding Ruppeiner's metrics become degenerate only at absolute zero and have non-vanishing scalar curvatures.Comment: LaTeX file, no figure

Inquiry based learning: why buying a car with a tree included? Enhancing science and mathematic learning

International reports reveal a deficient situation in relation to science and mathematics learning, which can be considered as an obstacle for the education of literate and informed citizens and the qualification and the preparation of future scientists and engineers. This situation may be partly attributed to the way science and mathematics are taught at school. Research on effective teaching approaches shows that inquiry based learning (IBL) improves students’ engagement and motivation for science and mathematics learning and promotes the development of process skills, critical thinking and conceptual understanding of some science and mathematics topics. The present work describes the design and implementation of an instructional approach for enhancing science and mathematics learning through IBL. The instructional approach is based on the design of an interdisciplinary task which starts by challenging students through the analysis of an advertisement. The initial scenario engages students in an investigation process to look for evidence and understanding while acquiring meaningful learning of key science topics and mathematical tools. The task also takes advantage of current technological resources to facilitate and support the overall inquiry process. (Orig.

Relative efficiency and validity properties of a visual analogue vs a categorical scaled version of the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index: Spanish versions

AbstractObjective: To compare the performance of visual analogue (VAS) vs categorical (CT) scaled versions of the three subscales (pain, stiffness and difficulty) of the WOMAC Index in patients with knee osteoarthritis.Material and methods: Patients with knee OA (at least grade II of Kellgren & Lawrence classification) were treated for a 6-weeks period with an NSAID. The following measures were applied at baseline and after treatment: VAS and CT WOMAC scales, Lequesne Index, pain on VAS, and global assessment by patient and observer. Construct Validity was determined by correlation of each of the subscale scores with the other outcomes both at baseline and after treatment (Pearson’s test); responsiveness comparing baseline vs final status by Wilcoxon’s test; reliability by analysis of the internal consistency using Cronbach’s alpha at baseline and after the treatment period; and test–retest reliability by Kendall’s Tau-c statistics. Finally, correlation and analysis of the relative efficiency (RE) between the subscales of both formats were tested.Results: Seventy-three (8 men and 65 women) patients with a mean disease duration from first diagnosis of 69 months (3 to 254) completed the study. The following were the observed values for the instruments’ psychometric properties: (1) construct validity: correlations ranged from 0.30 to 0.84 for VAS and 0.27 to 0.77 for CT subscales; (2) responsiveness: achieved P values for the pain, stiffness and difficulty scales were P<0.0001, P=0.002 and P<0.0001 in VAS and P=0.003, P<0.0001 and P=0.001 in CT format respectively; (3) internal consistency: the obtained Cronbach’s alpha coefficients ranged from 0.71 to 0.97 for the VAS and 0.64 to 0.95 for the CT subscales; (4) test–retest reliability: correlation coefficients ranged from 0.36 to 0.76 for VAS and 0.34 to 0.52 for CT subscales; and (5) the relative efficiency of the subscales in VAS vs CT format were 2.20, 0.91 and 1.91 for pain, stiffness and difficulty respectively. Significant correlations between subscales in both formats ranging from 0.72 to 0.86 were observed.Conclusion: We have shown that both the VAS version of WOMAC have adequate evaluative and discriminative properties. We found the pain and physical function scales in VAS format and the stiffness scale in CT format to have a slightly better performance in this sample

Tribo-Corrosion behaviour of TiCxOy thin films in bio fluids

In recent years, the development of thin film systems for decorative applications has attracted significant attention in scientific research. These decorative coatings require, not only an attractive appearance for market applications, but also an ability to protect the surface underneath. Because of this, corrosion, wear and their combined effects (termed tribo-corrosion) are particularly important for lifetime prediction. The tribo-corrosion behaviour of a range of single layered titanium oxycarbide, TiCxOy,coatings, produced by DC reactive magnetron sputtering, has been studied and reported as a function of electrode potential (-0.9 V, -0.5 V, 0.0 V and +0.5 V) and applied load (3, 6 and 9 N). The study was conducted in a reciprocating sliding tribosystem (Plint TE 67/E) in a bio fluid (an artificial perspiration solution) at room temperature. During the wear tests, both the open-circuit potential and the corrosion current were monitored. The results showed that electrode potential and load have a significant influence on the total material loss. The variations in Rp (polarization resistance) and Cf(capacitance) before and after sliding, obtained by Electrochemical Impedance Spectroscopy (EIS) were evaluated in order to provide an understanding of the resistance of the film in such conditions. Tribo-corrosion maps were generated, based on the results, indicating the change in mechanisms of the tribological and corrosion parameters for such coatings

Pengaruh Career Development Terhadap Succession Dengan Efek Mediasi Organizational Justice Pada PT Sumberdaya Sewatama

This research was conducted in order to determine whether the Organizational Justice has a mediating effect in the influence of Career Development to Succession in a family enterprise in the research, namely PT SumberdayaSewatama. The sampling method used is convenience sampling. This research took a sample of 38 employees at managerial level. Methods of data analysis used in this research is the analysis of the effect of mediation (OJ) and test effect of independent variables (CD) to the dependent variable (S). The results of data processing using SPSS 22 for windows with macros and hayes 2013. The result shows that managerial level employees at PT Sumberdaya Sewatama have career development, organizational justice, and succession were already good, but organizational justice can not mediate the effect of career development to succession

Biomechanics of the Cornea Assessed by the CorVis ST ® Device: a Numerical Approach

To evaluate by means of finite element modeling the influence of tissue properties of the cornea on its deformation response when an air jet is applied onto its surface and, according to this, to discuss the clinical interpretation of these measurements in terms of corneal biomechanical behaviour

Cultivos urbanos en un aula de matemáticas inclusiva

En el presente trabajo se describe un proyecto de aula en curso en un aula inclusiva-, el cual hace referencia a la realización de cultivos urbanos, este trabajo se describe en 4 fases en las cuales se desarrollan conceptos y nociones matemáticas