Derailing individualized ovarian stimulation

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A Relative Position Code for Saccades in Dorsal Premotor Cortex

Spatial computations underlying the coordination of the hand and eye present formidable geometric challenges. One way for the nervous system to simplify these computations is to directly encode the relative position of the hand and the center of gaze. Neurons in the dorsal premotor cortex (PMd), which is critical for the guidance of arm-reaching movements, encode the relative position of the hand, gaze, and goal of reaching movements. This suggests that PMd can coordinate reaching movements with eye movements. Here, we examine saccade-related signals in PMd to determine whether they also point to a role for PMd in coordinating visual–motor behavior. We first compared the activity of a population of PMd neurons with a population of parietal reach region (PRR) neurons. During center-out reaching and saccade tasks, PMd neurons responded more strongly before saccades than PRR neurons, and PMd contained a larger proportion of exclusively saccade-tuned cells than PRR. During a saccade relative position-coding task, PMd neurons encoded saccade targets in a relative position code that depended on the relative position of gaze, the hand, and the goal of a saccadic eye movement. This relative position code for saccades is similar to the way that PMd neurons encode reach targets. We propose that eye movement and eye position signals in PMd do not drive eye movements, but rather provide spatial information that links the control of eye and arm movements to support coordinated visual–motor behavior

An Analysis of Pricing Strategy and Price Dispersion on the Internet

Using prices obtained from shopbots, we test several hypotheses regarding the economics of information and optimal search. We find that price dispersion is positively (negatively) related to product price and the number of sellers in cross-sectional (time series) analysis. Price dispersion increases over time when the sample includes new entrants, but decreases in the absence of entry. Controlling for shipping charges and seller heterogeneity reduces, but does not eliminate, price dispersion. Finally, prices appear to be correlated across products and over time – low price sellers for one product (time period) generally charge low prices for all items (time periods).

Assessing An Economics Programme: Hansen Proficiencies, ePortfolio, and Undergraduate Research

Numerous sources calling for more accountability in higher education are putting increased pressure on many economics departments to develop assessment plans. This paper discusses a set of principles for programmatic assessment gleaned from the assessment literature, while highlighting one US economic department's journey to develop an assessment of student learning outcomes based on Hansen's proficiencies. We explain the curriculum reforms that culminate with independent undergraduate research as suggested by the highest level of Hansen's proficiencies. We describe ePortfolios which showcase student abilities and integrate evidence of student learning across the curriculum. For departments without direct guidance from accreditation boards or other agencies, we put forth a process of forming programmatic assessment in economics.

The Divine Clockwork: Bohr's correspondence principle and Nelson's stochastic mechanics for the atomic elliptic state

We consider the Bohr correspondence limit of the Schrodinger wave function for an atomic elliptic state. We analyse this limit in the context of Nelson's stochastic mechanics, exposing an underlying deterministic dynamical system in which trajectories converge to Keplerian motion on an ellipse. This solves the long standing problem of obtaining Kepler's laws of planetary motion in a quantum mechanical setting. In this quantum mechanical setting, local mild instabilities occur in the Kelperian orbit for eccentricities greater than 1/\sqrt{2} which do not occur classically.Comment: 42 pages, 18 figures, with typos corrected, updated abstract and updated section 6.

Redistricting on Beacon Hill and Political Power on Capitol Hill: Ancient Legacies and Present-Day Perils

This article discusses legislative reapportionment and past efforts to manipulate district lines as far back as the legendary Elbridge Gerry in the early nineteenth century. Specifically, it deals with what political history has to tell us about the current furor over House Speaker Thomas Finneran’s proposed congressional redistricting. More than any other state in the Union, the Massachusetts lawmakers in the U.S. House of Representatives have enjoyed disproportionate power as a result of a bipartisan strategy of incumbency protection dating back to the 1940s. That power may be in jeopardy if Speaker Finneran implements his plans to create a new 5th District in southeastern Massachusetts while merging districts represented by two incumbent Democratic congressmen, Marty Meehan of Lowell and John Tierney of Salem. The speaker broke with a tradition of deference to incumbency and collegial consensus building that normally prevails during the decennial redrawing of district lines and may have risked diminishing Massachusetts’s political power for at least a decade

Optical Communications Using Gallium Arsenide Injection Lasers

A synthesis is presented which illustrates the applicability of gallium arsenide injection lasers as the source in high data rate optical communication systems. The synthesized system is a data link between two synchronous relay satellites separated by 45,500 statute miles. Requirements of the system were a data rate of 25 megabits per second and an information error rate of less than 10~5 . The system is synthesized using the parameters of commercially available injection lasers and photodetectors. A greater information capacity is shown when optimistic parameter values are used

Dorsal Premotor Neurons Encode the Relative Position of the Hand, Eye, and Goal during Reach Planning

When reaching to grasp an object, we often move our arm and orient our gaze together. How are these movements coordinated? To investigate this question, we studied neuronal activity in the dorsal premotor area (PMd) and the medial intraparietal area (area MIP) of two monkeys while systematically varying the starting position of the hand and eye during reaching. PMd neurons encoded the relative position of the target, hand, and eye. MIP neurons encoded target location with respect to the eye only. These results indicate that whereas MIP encodes target locations in an eyecentered reference frame, PMd uses a relative position code that specifies the differences in locations between all three variables. Such a relative position code may play an important role in coordinating hand and eye movements by computing their relative position