Hands-On Physical Science for In-Service Teachers

The initiation of the Virginia Commonwealth University B.S. in Science program was reported in this journal Fall 1999 as a program designed to meet the academic content major of a teacher preparation program for elementary and middle school mathematics and science teachers [1]. This paper reports the current status of the interdisciplinary B.S. in Science degree program including program enrollment data and trends. Also described are refinements in the required curriculum, which include a newly developed geometry, a mathematical computing course, and an emerging teaching technology course featuring graphing calculators, CBLs, and computer software applications

Performance of charge-injection-device infrared detector arrays at low and moderate backgrounds

Three 2 x 64 element charge injection device infrared detector arrays were tested at low and moderate background to evaluate their usefulness for space based astronomical observations. Testing was conducted both in the laboratory and in ground based telescope observations. The devices showed an average readout noise level below 200 equivalent electrons, a peak responsivity of 4 A/W, and a noise equivalent power of 3x10 sq root of W/Hz. Array well capacity was measured to be significantly smaller than predicted. The measured sensitivity, which compares well with that of nonintegrating discrete extrinsic silicon photoconductors, shows these arrays to be useful for certain astronomical observations. However, the measured readout efficiency and frequency response represent serious limitations in low background applications

Nanoscale intermittent contact-scanning electrochemical microscopy

A major theme in scanning electrochemical microscopy (SECM) is a methodology for nanoscale imaging with distance control and positional feedback of the tip. We report the expansion of intermittent contact (IC)-SECM to the nanoscale, using disk-type Pt nanoelectrodes prepared using the laser-puller sealing method. The Pt was exposed using a focused ion beam milling procedure to cut the end of the electrode to a well-defined glass sheath radius, which could also be used to reshape the tips to reduce the size of the glass sheath. This produced nanoelectrodes that were slightly recessed, which was optimal for IC-SECM on the nanoscale, as it served to protect the active part of the tip. A combination of finite element method simulations, steady-state voltammetry and scanning electron microscopy for the measurement of critical dimensions, was used to estimate Pt recession depth. With this knowledge, the tip-substrate alignment could be further estimated by tip approach curve measurements. IC-SECM has been implemented by using a piezo-bender actuator for the detection of damping of the oscillation amplitude of the tip, when IC occurs, which was used as a tip-position feedback mechanism. The piezo-bender actuator improves significantly on the performance of our previous setup for IC-SECM, as the force acting on the sample due to the tip is greatly reduced, allowing studies with more delicate tips. The capability of IC-SECM is illustrated with studies of a model electrode (metal/glass) substrate

An Impossibility Theorem for Von Neumann-Morgenstern Solutions

Recently two game theoretic interpretations of social choice procedures have been offered. First, Wilson (1970) and Plott, (1974) suggested that, for each environment, the value of a choice function might constitute a “solution” or stable set that could arise from the play of some underlying cooperative game. In this view, and important problem is to determine if and under what conditions a given solution concept (or notion of stability) can, for some game, characterize the behavior of a given social choice function. Secondly, social choice functions have been interpreted as collections of equilibria of an underlying noncooperative game (see Gibbard (1973), Peleg (1978), Maskin (1977), and Ferejohn and Grether (1979). In this framework, one major problem is to determine for a given equilibrium correspondence of a suitably chosen noncooperative game. A closely related problem is to determine which noncooperative games possess nonempty equilibrium correspondences of various sorts. In this paper, we pursue a cooperative game-theoretic interpretation of social choice. And in particular we show that, if a social choice function arises as a Von Neumann Morgenstern solution in each environment, then it is essentially oligarchical in exactly the same sense that “core” selecting choice functions are oligarchic. The conditions under which this conclusion is obtained are, in fact, slightly more restrictive than those for the results on core selecting choice functions but are still weak enough that our result applies to almost any commonly occurring voting scale

Implementation of Democratic Social Choice Functions

A social choice function is said to be implementable if and only if there exists a game form such that for all preference profiles an equilibrium strategy n-tuple exists and any equilibrium strategy n-tuples of the game yield outcomes in the social choice set. A social choice function is defined to be minimally democratic if and only if whenever there exists an alternative which is ranked first by n-1 voters and is no lower than second for the last voter, then the social choice must be uniquely that alternative. No constraints are placed on the social choice function for other preference profiles. Using the usual definitions of equilibria for n-person games—namely Nash and strong equilibria—it is shown here that over unrestricted preference domains, no minimally democratic social choice function is implementable. The same result holds in certain restricted domains of the type assumed by economists over public goods spaces. We then show that a different notion of equilibrium—namely that of sophisticated equilibrium—allows for implementation of democratic social choice functions also having further appealing properties. The implication is that models of democratic political processes cannot be based on the standard equilibrium notions of Nash or strong equilibria