A semi-Markov model with memory for price changes

We study the high frequency price dynamics of traded stocks by a model of returns using a semi-Markov approach. More precisely we assume that the intraday returns are described by a discrete time homogeneous semi-Markov which depends also on a memory index. The index is introduced to take into account periods of high and low volatility in the market. First of all we derive the equations governing the process and then theoretical results have been compared with empirical findings from real data. In particular we analyzed high frequency data from the Italian stock market from first of January 2007 until end of December 2010

Mesoporous matrices for quantum computation with improved response through redundance

We present a solid state implementation of quantum computation, which improves previously proposed optically driven schemes. Our proposal is based on vertical arrays of quantum dots embedded in a mesoporous material which can be fabricated with present technology. The redundant encoding typical of the chosen hardware protects the computation against gate errors and the effects of measurement induced noise. The system parameters required for quantum computation applications are calculated for II-VI and III-V materials and found to be within the experimental range. The proposed hardware may help minimize errors due to polydispersity of dot sizes, which is at present one of the main problems in relation to quantum dot-based quantum computation. (c) 2007 American Institute of Physics

Hao Bu Hao: A Survival Guide for Zhejiang University

In an ever-expanding global society, we must learn to embrace other cultures much different from our own. The University of Rhode Island’s International Engineering Program has opened several opportunities for students to work and live in an environment much different from that in Kingston, the most recent one being at Zhejiang University in Hangzhou, Zhejiang, China. The first group was sent to Hangzhou during the summer of 2006 for seven weeks to learn Mandarin and learn about the Far East. The fourteen of us lived in a dorm, studied Mandarin Chinese, visited cultural and historical sites, and took in all that China had to offer. Because we were the first group to go, we made some mistakes, as it was expected. I believe that future travelers to Hangzhou might benefit from stories of our experiences and lessons learned. My project is a get-by, survival guide for students from URI traveling to China. It will give participants an idea of what to expect from everything from food to weather to customs. It has words and phrases, as well as photos and explanations to make the transition from Kingston to Hangzhou smoother. It also has a brief history of China, as well as cultural differences, political and social expectations and ideas, and fun things to try. It is my hope that this guide will help students prepare for an amazing study abroad, or encourage others to apply. It is a wonderful program, with much more than just in-classroom learning. It brings students together from East and West, so that we may learn to communicate, cooperate, and understand each other

GMRT Discovery of A Millisecond Pulsar in a Very Eccentric Binary System

We report the discovery of the binary millisecond pulsar J0514-4002A, which is the first known pulsar in the globular cluster NGC 1851 and the first pulsar discovered using the Giant Metrewave Radio Telescope (GMRT). The pulsar has a rotational period of 4.99 ms, an orbital period of 18.8 days, and the most eccentric pulsar orbit yet measured (e = 0.89). The companion has a minimum mass of 0.9 M_sun and its nature is presently unclear. After accreting matter from a low-mass companion star which spun it up to a (few) millisecond spin period, the pulsar eventually exchanged the low-mass star for its more massive present companion. This is exactly the same process that could form a system containing a millisecond pulsar and a black hole; the discovery of NGC 1851A demonstrates that such systems might exist in the Universe, provided that stellar mass black holes exist in globular clusters.Comment: 12 pages (referee format), 3 figures, accepted for publication in Astrophysical Journal Letter

Discovery of short-period binary millisecond pulsars in four globular clusters

We report the discovery using the Parkes radio telescope of binary millisecond pulsars in four clusters for which no associated pulsars were previously known. The four pulsars have pulse periods lying between 3 and 6 ms. All are in circular orbits with low-mass companions and have orbital periods of a few days or less. One is in a 1.7-hour orbit with a companion of planetary mass. Another is eclipsed by a wind from its companion for 40% of the binary period despite being in a relatively wide orbit. These discoveries result from the use of improved technologies and prove that many millisecond pulsars remain to be found in globular clusters.Comment: 4 pages, 2 figs, 1 table - Accepted by Astrophysical Journal Letter

Equilibrium properties of highly asymmetric star-polymer mixtures

We employ effective interaction potentials to study the equilibrium structure and phase behavior of highly asymmetric mixtures of star polymers. We consider in particular the influence of the addition of a component with a small number of arms and a small size on a concentrated solution of large stars with a high functionality. By employing liquid integral equation theories we examine the evolution of the correlation functions of the big stars upon addition of the small ones, finding a loss of structure that can be attributed to a weakening of the repulsions between the large stars due to the presence of the small ones. We analyze this phenomenon be means of a generalized depletion mechanism which is supported by computer simulations. By applying thermodynamic perturbation theory we draw the phase diagram of the asymmetric mixture, finding that the addition of small stars melts the crystal formed by the big ones. A systematic comparison between the two- and effective one-component descriptions of the mixture that corroborates the reliability of the generalized depletion picture is also carried out.Comment: 26 pages, 9 figures, submitted to Phys. Rev.

Public Higher Education Funding, Budget Drivers, and Related Issues: The State Community College Director Perspective

This article presents results from the 2012 National Survey of Access and Finance Issues conducted by the National Council of State Directors of Community Colleges (NCSDCC), an affiliated council of the American Association of Community Colleges, and includes a comparison of survey results from previous years dating back to 2003, with the exception of 2005 and 2006 when the survey was not conducted

Detection of ionized gas in the globular cluster 47 Tucanae

We report the detection of ionized intracluster gas in the globular cluster 47 Tucanae. Pulsars in this cluster with a negative period derivative, which must lie in the distant half of the cluster, have significantly higher measured integrated electron column densities than the pulsars with a positive period derivative. We derive the plasma density within the central few pc of the cluster using two different methods which yield consistent values. Our best estimate of n_e = (0.067+-0.015)/cm^3 is about 100 times the free electron density of the ISM in the vicinity of 47 Tucanae, and the ionized gas is probably the dominant component of the intracluster medium.Comment: 5 pages, 3 included figures, accepted for publication by ApJ Letter

Timing of Millisecond Pulsars in NGC 6752: Evidence for a High Mass-to-Light Ratio in the Cluster Core

Using pulse timing observations we have obtained precise parameters, including positions with about 20 mas accuracy, of five millisecond pulsars in NGC 6752. Three of them, located relatively close to the cluster center, have line-of-sight accelerations larger than the maximum value predicted by the central mass density derived from optical observation, providing dynamical evidence for a central mass-to-light ratio >~ 10, much higher than for any other globular cluster. It is likely that the other two millisecond pulsars have been ejected out of the core to their present locations at 1.4 and 3.3 half-mass radii, respectively, suggesting unusual non-thermal dynamics in the cluster core.Comment: Accepted by ApJ Letter. 5 pages, 2 figures, 1 tabl

Coulomb interaction effects in spin-polarized transport

We study the effect of the electron-electron interaction on the transport of spin polarized currents in metals and doped semiconductors in the diffusive regime. In addition to well-known screening effects, we identify two additional effects, which depend on many-body correlations and exchange and reduce the spin diffusion constant. The first is the "spin Coulomb drag" - an intrinsic friction mechanism which operates whenever the average velocities of up-spin and down-spin electrons differ. The second arises from the decrease in the longitudinal spin stiffness of an interacting electron gas relative to a noninteracting one. Both effects are studied in detail for both degenerate and non-degenerate carriers in metals and semiconductors, and various limiting cases are worked out analytically. The behavior of the spin diffusion constant at and below a ferromagnetic transition temperature is also discussed.Comment: 9 figure