An analysis of mental imagery versus the memory of pictures in grades seven and eight.

Thesis (Ed.M.)--Boston Universit

In the Beginning...Was the Act!: Zizek, Marx, and the Question of Form

In almost all commentary on the work Slavoj iek the question of his relationship to the thought of Karl Marx is either ignored or indirectly addressed in terms of his relationship to contemporary thinkers. This is best exemplified in discussions of what is ieks most significant contribution to todays growing swell of left-wing political theory: the critique of ideology. Against those who find its root elsewhere and who consequently offer various critiques of the positions iek takes, understanding the root of ideology to be the material practice of commodity exchange enables one to see the overall coherence of his work. After differentiating ieks position from many of his contemporaries and arguing that ieks parallax view can be best understood as a development of Marxs commodity fetishism the author goes on to use this as a means to get at the idea of form as it appears in Marx and iek. On this basis the last half of the study takes up contemporary history and theory on the formation of psychoanalytic associations and radical party politics to substantiate the claim that while both owe their existence to capitalism, capitalism could owe to them its destruction

Video Guidance, Landing, and Imaging system (VGLIS) for space missions

The feasibility of an autonomous video guidance system that is capable of observing a planetary surface during terminal descent and selecting the most acceptable landing site was demonstrated. The system was breadboarded and "flown" on a physical simulator consisting of a control panel and monitor, a dynamic simulator, and a PDP-9 computer. The breadboard VGLIS consisted of an image dissector camera and the appropriate processing logic. Results are reported

Proton-induced noise in digicons

The Space Telescope, which carries four Digicons, will pass several times per day through a low-altitude portion of the radiation belt called the South Atlantic Anomaly. This is expected to create interference in what is otherwise anticipated to be a noise-free device. Two essential components of the Digicon, the semiconductor diode array and the UV transmitting window, generate noise when subjected to medium-energy proton radiation, a primary component of the belt. These trapped protons, having energies ranging from 2 to 400 Mev and fluences at the Digicon up to 4,000 P+/sec-sq cm, pass through both the window and the diode array, depositing energy in each. In order to evaluate the effect of these protons, engineering test models of Digicon tubes to be flown on the High Resolution Spectrograph were irradiated with low-flux monoenergetic proton beams at the University of Maryland cyclotron. Electron-hole pairs produced by the protons passing through the diodes or the surrounding bulk caused a background count rate. This is the result of holes diffusing over a distance of many diode spacings, causing counts to be triggered simultaneously in the output circuits of several adjacent diodes. Pulse-height spectra of these proton-induced counts indicate that most of the bulk-related counts overlap the single photoelectron peak. A geometrical model will be presented of the charge collection characteristics of the diode array that accounts for most of the observed effects

Convergence rates in expectation for Tikhonov-type regularization of Inverse Problems with Poisson data

In this paper we study a Tikhonov-type method for ill-posed nonlinear operator equations \gdag = F( ag) where \gdag is an integrable, non-negative function. We assume that data are drawn from a Poisson process with density t\gdag where $t>0$ may be interpreted as an exposure time. Such problems occur in many photonic imaging applications including positron emission tomography, confocal fluorescence microscopy, astronomic observations, and phase retrieval problems in optics. Our approach uses a Kullback-Leibler-type data fidelity functional and allows for general convex penalty terms. We prove convergence rates of the expectation of the reconstruction error under a variational source condition as $t\to\infty$ both for an a priori and for a Lepski{\u\i}-type parameter choice rule

Including changes in security of supply in cost benefit analysis – an application to oil prices in the transport sector

This paper contains a tentative suggestion of how to take into account changes in security of supply in real world cost-benefit analysis. Assuming that consumers are risk avers, security of supply can be viewed as a matter of avoiding oscillations in consumption originating from volatile prices of for in- stance oil. When the government makes transport related choices on behalf of the consumers, the effect on oscillations in general consumption should be included in the policy assessment taking into account the most significant correlations between prices on alternative fuels and between fuel prices and consumption in general. In the paper, a method of valuing changes in security of supply based on portfolio theory is applied to some very simple transport related examples. They indicate that includ- ing the value of changes in security of supply often makes very little difference to the results of cost benefit analysis, but more work has to be done on quantifying, among other things, consumers’ risk aversion and the background standard deviation in total consumption before firm conclusions can be drawn

Molecular dynamics studies of the melting of butane and hexane monolayers adsorbed on the basal‐plane surface of graphite

doi:10.1063/1.465067The effect of molecular steric properties on the melting of quasi‐two‐dimensional solids is investigated by comparing results of molecular dynamics simulations of the melting of butane and hexane monolayers adsorbed on the basal‐plane surface of graphite. These molecules differ only in their length, being members of the n‐alkane series [CH3(CH2)n−2CH3] where n=4 for butane and n=6 for hexane. The simulations employ a skeletal model, which does not include the hydrogen atoms explicitly, to represent the intermolecular and molecule-substrate interactions. Nearest‐neighbor intramolecular bonds are fixed in length, but the molecular flexibility is preserved by allowing the bend and dihedral torsion angles to vary. The simulations show a qualitatively different melting behavior for the butane and hexane monolayers consistent with neutron and x‐ray scattering experiments. The melting of the low‐temperature herringbone (HB) phase of the butane monolayer is abrupt and characterized by a simultaneous breakdown of translational order and the orientational order of the molecules about the surface normal. In contrast, the hexane monolayer exhibits polymorphism in that the solid HB phase transforms to a rectangular‐centered structure with a short coherence length in coexistence with a fluid phase. A significant result of the simulations is that they demonstrate the importance of molecular flexibility on the nature of the melting transition. The formation of gauche molecules is essential for the melting process in the hexane monolayer but unimportant for butane. The effect of molecular length on the qualitative nature of the melting process is discussed for both monolayers.This work was supported by The Danish Natural Science Research Council Grant No. M 11-7015, the U.S. NSF Grants No. DMR-8704938 and No. DMR-9011069,and the Pittsburgh Supercomputing Center Grant No. DMR-880008P