The Physical Principles of Quantum Mechanics. A critical review

The standard presentation of the principles of quantum mechanics is critically reviewed both from the experimental/operational point and with respect to the request of mathematical consistency and logical economy. A simpler and more physically motivated formulation is discussed. The existence of non commuting observables, which characterizes quantum mechanics with respect to classical mechanics, is related to operationally testable complementarity relations, rather than to uncertainty relations. The drawbacks of Dirac argument for canonical quantization are avoided by a more geometrical approach.Comment: Bibliography and section 2.1 slightly improve

Mark formation modeling in optical rewritable recording

In optical rewritable recording media, such as the Blu-ray Disc, amorphous marks are formed on a crystalline background of a phase-change layer, by means of short, high power laser pulses. In order to improve this data storage concept, it is of great importance to understand the mark formation process. Therefore, a rigorous numerical model is developed to study the influence of for instance the polarization of the incident laser light or the geometry and configuration of the recording stack on the size and shape of the mark. The mark formation process can be divided into three stages: the melting of the crystalline background, rapid solidification of the molten region and amorphization. The focus of this study is on the melting stage. In contrast to earlier work [1], the contribution of latent heat is taken into account in the computation of the temperature distribution in the optical recording disk. The corresponding three dimensional Stefan problem is numerically resolved using an adapted version of the discontinuous integration technique as described by for instance Fachinotti et al. [2]. Latent heat is incorporated as an added non-linear term to the heat conduction equation. Besides the inherent non-linear character of the considered partial differential equation, several other numerical challenges arise from the practical background of the problem: the phase-change layer forms an integral part a recording stack, consisting of various layers with possibly large jumps in physical parameters. In addition, there are variations in the geometry (i.e. grooved tracks). This makes that a finite element discretization is preferred. Finally, the accurate capturing of the free interface between the liquid and solid state requires high resolution meshes. In order to reduce computational load, an adaptive local mesh refinement code has been implemented.Electrical Engineering, Mathematics and Computer Scienc

Physiotherapy management of greater trochanteric pain syndrome (GTPS): an international survey of current physiotherapy practice

Objectives: This study aimed to establish and compare current physiotherapy management of GTPS in Australia, New Zealand (NZ) and Ireland. Design: Cross-sectional observational survey of physiotherapists. Methods: An online survey was distributed to registered musculoskeletal physiotherapists in Australia, NZ and Ireland. Ordinal and nominal data were analysed using frequency counts or mean ranks; median and interquartile ranges were calculated for numerical data. Inter-country comparisons were made using Chi-squared analyses for nominal/ordinal data and Kruskal–Wallis tests for numerical data. Statistical significance was set at P < 0.05. Results/findings: Valid responses were received from 361 physiotherapists, 61% were female and 80% worked in private practice. Overall, consistency in treatment of GTPS was observed across the three countries. All physiotherapists used education and exercise (most commonly strengthening and neuromuscular control) primarily targeting the gluteal muscles. Other interventions included massage (90%), stretching (53%), range of motion (40%), thermal modalities (50%), taping (38%) and electrotherapy (25%), whilst 40% commonly recommended up to 2 to 3 corticosteroid injections per patient/per annum. Physiotherapists used pain severity scales as their primary outcome measure (79%). Single leg stance was the most common physical measure used (68%), and global rating scores or standardised physical measures were less commonly used. Conclusion: This international survey established the physiotherapy management of GTPS. Education used in conjunction with exercise is in line with current evidence, but a proportion of clinicians use adjunct treatments without clear rationale or supporting evidence. Results indicate the need to further define optimal management of GTPS using robust methodologies such as randomised controlled trials

Heat current characteristics in nanojunctions with superconducting baths

As a fundamental requisite for thermotronics, controlling heat flow has been a longstanding quest in solid state physics. Recently, there has been a lot of interest in nanoscale hybrid systems as possible candidates for thermal devices. In this context, we study the heat current in the simplest hybrid device of a two level system weakly coupled to two heat baths. We use the reduced density matrix approach together with a simple Born-Markov approximation to calculate the heat current in the steady state. We consider different kinds of reservoirs and show that the nature of the reservoir plays a very important role in determining the thermal characteristics of the device. In particular, we investigate the effectiveness of a conventional superconductor as a reservoir with regard to manipulating the heat current. In the emergent temperature characteristics, we find that superconductivity in the reservoirs leads to enhanced thermal currents and that the superconducting phase transition is clearly visible in the heat current. We observe negative differential thermal conductance and a pronounced rectification of the heat current, making this 9 a good building block for a quantum thermal diode.Departamento Administrativo de Ciencia, Tecnología e Innovación [CO] Colciencias1115-569-34912n