Rolling of asymmetric disks on an inclined plane

In a recent papers, Turner and Turner (2010 {\em Am. J. Phys.} {\bf 78} 905-7) and Jensen (2011 {\em Eur. J. Phys.} {\bf 32} 389-397) analysed the motion of asymmetric rolling rigid bodies on a horizontal plane. These papers addressed the common misconception that the instantaneous point of contact of the rolling body with the plane can be used to evaluate the angular momentum $\mathbf L$ and the torque $\boldsymbol\tau$ in the equation of motion $d\mathbf L/dt = \boldsymbol\tau$. To obtain the correct equation of motion, the "phantom torque" or various rules that depend on the motion of the point about which $\mathbf L$ and $\boldsymbol\tau$ are evaluated were discussed. In this paper, I consider asymmetric disks rolling down an inclined plane and describe the most basic way of obtaining the correct equation of motion; that is, to choose the point about which $\mathbf L$ and $\boldsymbol\tau$ are evaluated that is stationary in an inertial frame

World city network integration in the Eurasian realm

A team of authors from the Globalization and World Cities (GaWC) research network explores the main empirical features of the global economic integration of Eurasia through an analysis of the (shifting) position of that macroregion's key cities. More specifically, they examine the gateway roles played by key cities in four major subregions-China, the former Eastern Bloc (FEB, i.e., Central and Eastern Europe), former Soviet Union (FSU), and India-in the channeling of transnational flows of capital, goods, knowledge, and people in 2000-2008, focusing on the globalization of firms in the financial and business service sectors. Although cities in the four subregions share a common recent history of transition from closed and state-centered to open and market-based economies, the study reveals the persistence of distinctive geographical idiosyncrasies in their connections across the globe

Post-selection-free preparation of high-quality physical qubits

Rapidly improving gate fidelities for coherent operations mean that errors in state preparation and measurement (SPAM) may become a dominant source of error for fault-tolerant operation of quantum computers. This is particularly acute in superconducting systems, where tradeoffs in measurement fidelity and qubit lifetimes have limited overall performance. Fortunately, the essentially classical nature of preparation and measurement enables a wide variety of techniques for improving quality using auxiliary qubits combined with classical control and post-selection. In practice, however, post-selection greatly complicates the scheduling of processes such as syndrome extraction. Here we present a family of quantum circuits that prepare high-quality |0> states without post-selection, instead using CNOT and Toffoli gates to non-linearly permute the computational basis. We find meaningful performance enhancements when two-qubit gate fidelities errors go below 0.2%, and even better performance when native Toffoli gates are available.Comment: Source code and data behind this paper can be found at https://github.com/riverlane/purification-without-post-selectio

Goodbye Reykjavik: international banking centres and the global financial crisis

This empirical paper analyses how leading international banking centres (IBCs) have been faring under the 2008 global financial crisis. We aggregate data derived from The Banker’s annual list of the world’s leading banks at the city level to map changing levels of Tier 1 capital between 2007 and 2008 and returns on capital in 2008. The results point to a general but nonetheless variegated shift ‘from West to East’ in the world of IBCs. The paper concludes with a brief review of the implications for future research on financial geographies in general and the geographies of the financial crisis in particular

The network dimension

There is now a considerable literature on the role of cities as key nodes in an increasingly globalized economy. One expression of this can be found in recent large edited volumes such as this one: for instance, Scott (2001), Brenner and Keil (2006), Taylor et al. (2007, 2011, 2013) and Derudder et al. (2012) have mustered over 300 chapters between them but still represent only the tip of this particular iceberg. Within this literature, the research in the context of the Globalization and World Cities (GaWC, http://www.lboro.ac.uk/gawc) research network has pioneered a relational approach to understanding cities in globalization as a ‘world city network’ (WCN). One area of focus has been the formal analysis of inter-city relations of cities based on a precise specification of the WCN as an ‘interlocking network’ (e.g. Taylor, 2001; Taylor et al. 2011). In the initial specification of this model and in much of the subsequent empirical WCN research, it is put forward that globalized producer services firms are the key ‘network makers’: drawing on the work of Sassen (1991) and Castells (1996), it is posited that these firms 'interlock' cities through their global, city-centred location strategies

Life and Death at the Edge of a Windy Cliff

The survival probability of a particle diffusing in the two dimensional domain $x>0$ near a ``windy cliff'' at $x=0$ is investigated. The particle dies upon reaching the edge of the cliff. In addition to diffusion, the particle is influenced by a steady ``wind shear'' with velocity $\vec v(x,y)=v\,{\rm sign}(y)\,\hat x$, \ie, no average bias either toward or away from the cliff. For this semi-infinite system, the particle survival probability decays with time as $t^{-1/4}$, compared to $t^{-1/2}$ in the absence of wind. Scaling descriptions are developed to elucidate this behavior, as well as the survival probability within a semi-infinite strip of finite width $|y|<w$ with particle absorption at $x=0$. The behavior in the strip geometry can be described in terms of Taylor diffusion, an approach which accounts for the crossover to the $t^{-1/4}$ decay when the width of the strip diverges. Supporting numerical simulations of our analytical results are presented.Comment: 13 pages, plain TeX, 5 figures available upon request to SR (submitted to J. Stat. Phys.

Pathways of change : shifting connectivities in the world city network, 2000-08

This is an empirical paper that measures and interprets changes in intercity relations at the global scale in the period 2000-08. It draws on the network model devised by the Globalization and World Cities (GaWC) research group to measure global connectivities for 132 cities across the world in 2000 and 2008. The measurements for both years are adjusted so that a coherent set of services/cities is used. A range of statistical techniques is used to explore these changes at the city level and the regional scale. The most notable changes are: the general rise of connectivity in the world city network; the loss of global connectivity of US and sub-Saharan African cities (Los Angeles, San Francisco and Miami in particular); and, the gain in global connectivity of south Asian, Chinese and eastern European cities (Shanghai, Beijing and Moscow in particular)

26856 Proliferative nodule resembling angiomatoid Spitz with pronounced degenerative atypia arising within a giant congenital nevus

Proliferative nodules arising within congenital melanocytic nevi present a diagnostic challenge for dematopathologists given their close resemblance to melanoma. In difficult cases, ancillary molecular tests can be used to better exclude the possibility of malignancy. We report case of a biopsy and subsequent excision of an unusual proliferative nodule with overlapping features of angiomatoid Spitz tumor and ancient melanocytic nevus which demonstrated normal findings on both chromosomal microarray and a gene expression profiling assay. Our case is noteworthy given its striking resemblance to what has been reported for an angiomatoid Spitz tumor. To our knowledge, this particular morphologic subset of Spitz has been described primarily in the context of spontaneous melanocytic tumors arising de novo outside the context of a congenital lesion. The pathology showed bizarre cytological features along with a myxoid and highly vascularized stroma which is thought to represent degenerative atypia characteristic of an “ancient nevus.” The lesions described as ancient nevi have some overlapping stromal features with angiomatoid Spitz tumors. A low proliferation index and paucity of mitotic figures is characteristic of these neoplasms. We hypothesize that continued host response to the lesion may be responsible for inducing the observed cytological and stromal derangement. Interestingly, these changes increased from the time of biopsy to the excision. Future studies should aim to define the genetic and immunologic signature of these lesions to help predict prognosis. The relationship between angiomatoid Spitz tumor, ancient change, and regressing nevi should also be investigated

The global capacity of Belgium’s major cities: Antwerp and Brussels compared

The paper has two purposes: (i) to outline a methodology for systematically measuring economic relations between the world’s major cities and (ii) to provide a general assessment of the position of Belgium’s major cities in this global urban network. In the first section, we stress that research on Brussels and Antwerp under conditions of contemporary globalization lacks a systematic account of their global relational patterns, a knowledge lacuna that can at least partly be traced back to the dearth of suitable data. In a second section, we outline the methodology for measuring the networked context of the world’s major cities. In a third section, we provide a systematic overview of Antwerp’s and Brussels’ position in this global urban network. Apart from the rather common sensical observation that Brussels is more strongly connected than Antwerp, it is also shown that Brussels’ «global» relations contrast with Antwerp’s more intense «local» relations. In relative terms, Brussels is strongly connected to East Asia and North America, while the most thorough links of Antwerp are exclusively with nearby European (especially German) cities.Deze bijdrage heeft twee doelstellingen: (i) het beschrijven van een methodologie die toelaat om de economische relaties tussen steden te meten, en (ii) een algemene analyse van de twee belangrijkste Belgische steden gebaseerd op deze methodologie. In een eerste deel wordt geargumenteerd dat in het bestaande onderzoek over Antwerpen en Brussel een systematische analyse van hun mondiale relationele patronen ontbreekt. In een tweede deel wordt de methodologie uiteengezet die toelaat om economische relaties tussen steden in te schatten. In een derde deel, ten slotte, geven we een overzicht van de voornaamste conclusies over de positie van Brussel en Antwerpen in dit mondiale stedennetwerk. Naast de voor de hand liggende vaststelling dat Brussel sterker geconnecteerd is dan Antwerpen, kan ook vastgesteld worden dat Brussel een echte wereldstad is in de zin dat de connecties «globaal» zijn, terwijl de belangrijkste relaties van Antwerpen eerder «lokaal» georiënteerd zijn. Brussel is bijvoorbeeld sterk geconnecteerd met Pacifisch Azië en Noord-Amerika, terwijl de belangrijkste relaties van Antwerpen die zijn met naburige Europese (vooral Duitse) steden