Optical power meter using radiation pressure measurement

This paper describes a radiation pressure meter based on a diamagnetic spring. We take advantage of the diamagnetic property of pyrolytic carbon to make an elementary levitated system. It is equivalent to a torsional spring-mass-damper system consisting of a small pyrolytic carbon disc levitated above a permanent magnet array. There are several possible measurement modes. In this paper, only the angular response to an optical power single-step is described. An optical detection composed of a laser diode, a mirror and a position sensitive detector (PSD) allow measurement of the angular deflection proportional to the voltage delivered by the PSD. Once the parameters of the levitated system depending on its geometrical and physical characteristics have been determined regardless of any optical power, by applying a simple physical law, one can deduce the value of the optical power to be measured from the measurement of the first maximum of the output voltage amplitude

The career choice of first year occupational therapy students: A follow up study

This study replicated a survey of first-year occupational therapy students at Brunel University (Craik et al 2001) and 114 students (91.2%) responded. Their profile was similar to that of the students in the previous study, with 90% being female, 65% being over 21 years of age and 20% coming from minority ethnic groups. The most frequent way that the students had heard about occupational therapy remained through informal means, with variety and challenge continuing to be the most important factors in attracting potential students to the profession. The results of this study, taken with those of Craik et al (2001), provide data on 444 first-year students and further emphasise the importance of occupational therapists in encouraging recruitment to the professio

On the convergence of the Fitness-Complexity Algorithm

We investigate the convergence properties of an algorithm which has been recently proposed to measure the competitiveness of countries and the quality of their exported products. These quantities are called respectively Fitness F and Complexity Q. The algorithm was originally based on the adjacency matrix M of the bipartite network connecting countries with the products they export, but can be applied to any bipartite network. The structure of the adjacency matrix turns to be essential to determine which countries and products converge to non zero values of F and Q. Also the speed of convergence to zero depends on the matrix structure. A major role is played by the shape of the ordered matrix and, in particular, only those matrices whose diagonal does not cross the empty part are guaranteed to have non zero values as outputs when the algorithm reaches the fixed point. We prove this result analytically for simplified structures of the matrix, and numerically for real cases. Finally, we propose some practical indications to take into account our results when the algorithm is applied.Comment: 13 pages, 8 figure

Investigating the interplay between fundamentals of national research systems: performance, investments and international collaborations

We discuss, at the macro-level of nations, the contribution of research funding and rate of international collaboration to research performance, with important implications for the science of science policy. In particular, we cross-correlate suitable measures of these quantities with a scientometric-based assessment of scientific success, studying both the average performance of nations and their temporal dynamics in the space defined by these variables during the last decade. We find significant differences among nations in terms of efficiency in turning (financial) input into bibliometrically measurable output, and we confirm that growth of international collaboration positively correlate with scientific success, with significant benefits brought by EU integration policies. Various geo-cultural clusters of nations naturally emerge from our analysis. We critically discuss the possible factors that potentially determine the observed patterns

Liquidity crises on different time scales

We present an empirical analysis of the microstructure of financial markets and, in particular, of the static and dynamic properties of liquidity. We find that on relatively large time scales (15 min) large price fluctuations are connected to the failure of the subtle mechanism of compensation between the flows of market and limit orders: in other words, the missed revelation of the latent order book breaks the dynamical equilibrium between the flows, triggering the large price jumps. On smaller time scales (30 s), instead, the static depletion of the limit order book is an indicator of an intrinsic fragility of the system, which is related to a strongly nonlinear enhancement of the response. In order to quantify this phenomenon we introduce a measure of the liquidity imbalance present in the book and we show that it is correlated to both the sign and the magnitude of the next price movement. These findings provide a quantitative definition of the effective liquidity, which proves to be strongly dependent on the considered time scales

T-Duality in Sigma Models with Kaluza-Klein Metric as Electric-Magnetic Duality

It is shown that the T-duality in \sigma-model with Kaluza-Klein metric, without or with a torsion term, can be interpreted as electric-magnetic duality for some of their solitonic solutions. Actually Buscher's duality transformation interchanges the topological and Noether charges.Comment: 12 Pages, Late

How the Taxonomy of Products Drives the Economic Development of Countries

We introduce an algorithm able to reconstruct the relevant network structure on which the time evolution of country-product bipartite networks takes place. The significant links are obtained by selecting the largest values of the projected matrix. We first perform a number of tests of this filtering procedure on synthetic cases and a toy model. Then we analyze the bipartite network constituted by countries and exported products, using two databases for a total of almost 50 years. It is then possible to build a hierarchically directed network, in which the taxonomy of products emerges in a natural way. We study the influence of the structure of this taxonomy network on countries' development; in particular, guided by an example taken from the industrialization of South Korea, we link the structure of the taxonomy network to the empirical temporal connections between product activations, finding that the most relevant edges for countries' development are the ones suggested by our network. These results suggest paths in the product space which are easier to achieve, and so can drive countries' policies in the industrialization process.Comment: 16 pages, 8 figure