Optimal computation with non-unitary quantum walks

Quantum versions of random walks on the line and the cycle show a quadratic improvement over classical random walks in their spreading rates and mixing times, respectively. Non-unitary quantum walks can provide a useful optimisation of these properties, producing a more uniform distribution on the line, and faster mixing times on the cycle. We investigate the interplay between quantum and random dynamics by comparing the resources required, and examining numerically how the level of quantum correlations varies during the walk. We show numerically that the optimal non-unitary quantum walk proceeds such that the quantum correlations are nearly all removed at the point of the final measurement. This requires only O(logT)$O(logT)$ random bits for a quantum walk of T$T$ steps.     

How old is the Web? Characterizing the age and the currency of the European scientific Web

The aim of this paper is to model and study the age of the Web using a sample of about four million of web pages from the 16 European Research Area countries obtained during 2004 and 2005. Web page time-stamp (date when the web pages were created or last changed for last time), format and size in bytes data have been analysed. Several indicators are introduced to measure longitudinal aspects of the Web. Half-age is proposed as a measure of the age distribution because this is found to be exponential. “Web Update Index” and “Lifespan Index” are introduced to measure the changing rate of a small sample over time. Results show that the British Web space has the youngest Web pages while the Greek and Belgian ones have the oldest. The study also compared Web pages topics and found that Biology pages are more stable than Physics pages.     

Comparing traditional and Rasch analyses of the Mississippi PTSD Scale: revealing limitations of reverse-scored items

This study examined whether Rasch analysis could provide more information than true score theory (TST) in determining the usefulness of reverse-scored items in the Mississippi Scale for Posttraumatic Stress Disorder (M-PTSD). Subjects were 803 individuals in inpatient PTSD units at 10 VA sites. TST indicated that the M-PTSD performed well and could be improved slightly by deleting one item. Factor analysis using raw scores indicated that the reverse-scored items formed the second factor and had poor relationships with normally scored items. However, since item-total correlations supported their usefulness, they were kept. The subsequent Rasch analysis indicated that five of the seven worst fitting items were reverse-scored items. We concluded that using reversed items with disturbed patients can cause confusion that reduces reliability. Deleting them improved validity without loss of reliability. The study supports the use of Rasch analysis over TST in health research since it indicated ways to reduce respondent burden while maintaining reliability and improving validity.     

Electromagnetic and fluid flow phenomena in a mercury model system of the electromagnetic casting of aluminum

A mathematical formulation has been developed to represent the electromagnetic force field and the velocity field in the melt for the electromagnetic casting of aluminum. The theoretical predictions based on fundamental considerations are compared with experimental measurements obtained on a physical model system. The measurements and predictions were found to be in good agreement, regarding both the velocity fields and the electromagnetic force fields. The principal conclusion emerging from this work is of critical importance in achieving the dual objective, that is providing a restraining force, while minimizing the melt velocity perpendicular to the free surface. The mathematical formulation presented in the paper provides the theoretical framework for quantitatively defining these conditions in terms of the coil and the shield parameters. J.L. Meyer, formerly with the Department of Materials Science and Engineering at Massachusetts Institute of Technology N. EL-KADDAH, formerly with the Department of Materials Science and Engineering at MIT     

Fluid flow phenomena in a single phase coreless induction furnace

New measurement techniques for local velocity, magnetic field, and current density have been applied to the study of electromagnetic and hydrodynamic phenomena in a coreless induction furnace containing an aluminum alloy. The action of electromagnetic shields on the intensity and the structure of the liquid metal flow is reported. It is shown that the direction of the fluid flow and the number and sizes of the recirculating cells may be significantly modified; the electromagnetic stirring may also be practically canceled. The influence of the dimensions of the screens on the structure of the liquid metal flow is examined. Finally, the modification of the fluid flow phenomena is explained by the evolution of the electromagnetic force patterns.     

Discussion in large classes via public-address system.

Describes a format for a large introductory psychology lecture course that uses a public address system to facilitate communication between the lecturer and students. (0 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Toluene steam reforming over nickel based catalysts

Steam reforming of toluene (SRT) has been studied initially in eight nickel-based catalysts where nickel (10 wt%) was incorporated in different supports (olivine, Al2O3, MgO, LDH, ZrO₂, CeO₂ and natural sepiolite) by the incipient wetness impregnation method. Among them, nickel catalyst based on sepiolite exhibited a promising catalytic performance, with a high conversion of toluene (16%), high selectivity to hydrogen (68.4%) and low production of undesired by-products (CO, CH₄, ethylene and benzene) at low temperature (500 °C). On the other hand, the incorporation of Ni in the sepiolitic material by precipitation (PP) has been considered as alternative method to the incipient wetness impregnation method (IWI). PP method allowed to prepare a Ni-based catalyst with a very high activity (conversion of toluene ~100%), high selectivity to hydrogen (73%) and lower production of undesirable by-products (5% CO, 2% CH₄ and 0% C₆H₆) at 575 °C. In addition, catalytic deactivation due to coke deposition and nickel sinterization was clearly lower for the catalyst synthesized by PP. Characterization by different physicochemical techniques (XRD, TEM, BET surface area, ICP-OES, TPR and EA) showed that PP method allowed to obtain a sepiolite-based catalyst containing Ni with larger external surface area and smaller, highly dispersed and easily reducible Ni metal particles. The results here discussed show that the Ni incorporation method has a clear influence in the preparation of nickel catalyst supported on sepiolite with improved catalytic performance in the steam reforming of toluene.     

Mobile learning vs. traditional classroom lessons: a comparative study

Different methods can be used for learning, and they can be compared in several aspects, especially those related to learning outcomes. In this paper, we present a study in order to compare the learning effectiveness and satisfaction of children using an iPhone game for learning the water cycle vs. the traditional classroom lesson. The iPhone game includes multiple interaction forms and combined augmented reality (AR) mini‐games with non‐AR mini‐games. The traditional classroom lesson had the same learning content as the iPhone game. Thirty‐eight children participated in the study. The analyses showed that the children made significant learning gains about the water cycle, regardless of the method used. Even though the results showed that the iPhone method achieved higher knowledge results than the traditional classroom lesson, no statistically significant differences were found between the iPhone and the classroom lesson. When analysing the motivational outcomes, the results showed that the children found the iPhone game to be more satisfying than the classroom lessons. Since the iPhone game achieved similar learning results and a higher motivational effect than the classroom lesson, this suggests that games of this kind could be used as a tool in primary schools to reinforce students' lessons.