Synthetic Mechanochemical Molecular Swimmer

A minimal design for a molecular swimmer is proposed that is a based on a mechanochemical propulsion mechanism. Conformational changes are induced by electrostatic actuation when specific parts of the molecule temporarily acquire net charges through catalyzed chemical reactions involving ionic components. The mechanochemical cycle is designed such that the resulting conformational changes would be sufficient for achieving low Reynolds number propulsion. The system is analyzed within the recently developed framework of stochastic swimmers to take account of the noisy environment at the molecular scale. The swimming velocity of the device is found to depend on the concentration of the fuel molecule according to the Michaelis-Menten rule in enzymatic reactions.Comment: 4 pages, 3 figure

The use of field-programmable gate arrays for the hardware acceleration of design automation tasks

This paper investigates the possibility of using Field-Programmable Gate Arrays (Fr’GAS) as reconfigurable co-processors for workstations to produce moderate speedups for most tasks in the design process, resulting in a worthwhile overall design process speedup at low cost and allowing algorithm upgrades with no hardware modification. The use of FPGAS as hardware accelerators is reviewed and then achievable speedups are predicted for logic simulation and VLSI design rule checking tasks for various FPGA co-processor arrangements

The effects of recessions across demographic groups

The burdens of a recession are not spread evenly across demographic groups. As the public and media noticed, from the start of the current recession in December 2007 through June 2009 men accounted for more than three-quarters of net job losses. Other differences have garnered less attention but are just as interesting. During the same period, the employment of single people fell at more than twice the rate that it did for married people and the decline for black workers was one and a half times that for white workers. To provide a more complete understanding of the effect of recessions, this paper examines the different effects of this and previous recessions across a range of demographic categories: sex, marital status, race, age, and education level.Recessions ; Demography

A journal ranking for the ambitious economist

The authors devise an "ambition-adjusted" journal ranking based on citations from a short list of top general-interest journals in economics. Underlying this ranking is the notion that an ambitious economist wishes to be acknowledged not only in the highest reaches of the profession, but also outside his or her subfield. In addition to the conceptual advantages that they find in their ambition adjustment, they see two main practical advantages: greater transparency and a consistent treatment of subfields. They compare their 2008 ranking based on citations from 2001 to 2007 with a ranking for 2002 based on citations from 1995 to 2001.Research ; Economics ; Economists

Waveguide physical modeling of vocal tract acoustics: flexible formant bandwidth control from increased model dimensionality

Digital waveguide physical modeling is often used as an efficient representation of acoustical resonators such as the human vocal tract. Building on the basic one-dimensional (1-D) Kelly-Lochbaum tract model, various speech synthesis techniques demonstrate improvements to the wave scattering mechanisms in order to better approximate wave propagation in the complex vocal system. Some of these techniques are discussed in this paper, with particular reference to an alternative approach in the form of a two-dimensional waveguide mesh model. Emphasis is placed on its ability to produce vowel spectra similar to that which would be present in natural speech, and how it improves upon the 1-D model. Tract area function is accommodated as model width, rather than translated into acoustic impedance, and as such offers extra control as an additional bounding limit to the model. Results show that the two-dimensional (2-D) model introduces approximately linear control over formant bandwidths leading to attainable realistic values across a range of vowels. Similarly, the 2-D model allows for application of theoretical reflection values within the tract, which when applied to the 1-D model result in small formant bandwidths, and, hence, unnatural sounding synthesized vowels

Generalizations of the St\"ormer Problem for Dust Grain Orbits

We consider the generalized St\"ormer Problem that includes the electromagnetic and gravitational forces on a charged dust grain near a planet. For dust grains a typical charge to mass ratio is such that neither force can be neglected. Including the gravitational force gives rise to stable circular orbits that encircle that plane entirely above/below the equatorial plane. The effects of the different forces are discussed in detail. A modified 3rd Kepler's law is found and analyzed for dust grains.Comment: 21 pages LaTeX, 12 figure

The effects of recessions across demographic groups

The burdens of a recession are not spread evenly across demographic groups. The public and media, for example, noticed that, from the start of the current recession in December 2007 through June 2009, men accounted for more than three quarters of net job losses. Other differences have garnered less attention, but are just as interesting. During the same period, the employment of single people fell at more than twice the rate that it did for married people, while black employment fell at one-and-a-half times the rate that white employment did. To have a more complete understanding about what recessions mean for people, this paper examines the different effects of this and previous recessions on employment experiences across a range of demographic categories: sex, marital status, race, age, and education level.Recessions ; Demography