Comment on "Novel Convective Instabilities in a Magnetic Fluid"

Comment on the paper "Novel Convective Instabilities in a Magnetic Fluid" by W. Luo, T. Du, and J. Huang, Phys. Rev. Lett., v.82, p.4134 (1999).Comment: 1 page, 1 figure, To appear in Phys. Rev. Lett. (2001

Using Performance Feedback to Teach Video Poker Players to Gamble Better

The present investigation reports two studies that examined the performance of non-pathological recreational video poker gamblers. In the first experiment, seven participants played three types of video poker games in a within partici-pants randomized sequence design. The percentage of errors made across games revealed the game variant “Deuces Wild” yielded more frequent mistakes than “Jacks or Better” or “Bonus Poker.” The second experiment consisted of a new sample of 11 participants being exposed to “Deuces Wild” poker to initially assess error percentages. Next, participants were all provided with performance feedback regarding their play, and finally the feedback was removed to assess performance maintenance. Results suggest that all poker players were able to improve performance above baseline level, and changes were maintained when the intervention was removed

Propagation of optical excitations by dipolar interactions in metal nanoparticle chains

Dispersion relations for dipolar modes propagating along a chain of metal nanoparticles are calculated by solving the full Maxwell equations, including radiation damping. The nanoparticles are treated as point dipoles, which means the results are valid only for a/d <= 1/3, where a is the particle radius and d the spacing. The discrete modes for a finite chain are first calculated, then these are mapped onto the dispersion relations appropriate for the infinite chain. Computed results are given for a chain of 50-nm diameter Ag spheres spaced by 75 nm. We find large deviations from previous quasistatic results: Transverse modes interact strongly with the light line. Longitudinal modes develop a bandwidth more than twice as large, resulting in a group velocity that is more than doubled. All modes for which k_mode <= w/c show strongly enhanced decay due to radiation damping.Comment: 26 pages, 7 figures, 2 tables. to appear in Phys. Rev.

A Case Study of Pathological Gambler Wagering at Golf

The present single case design explored the degree to which a pathological gambler’s golf performance would be affected by monetary consequences. Using an AB design, a twenty-three year old pathological gambler initially hit 10 golf balls on a computerized golfing game that interfaced with Playstation2’s “Tiger Woods PGA Tour 2006”. Following baseline, the participant was informed that he would be paid 20 dollars if his next 10 swings were closer to the golf hole than the prior 10 swings. The introduction of the monetary consequences resulted in the participant increasing shot variability and decreas-ing shot accuracy

AMPR/SSMI data comparisons

The AMPR was flown during CAPE and STORMFEST, during which some good data were gathered. Significant instrument noise problems were encountered in both deployments which appear to be temperature related. These are being fixed before the TOGA COARE deployment. New calibration loads have also been manufactured for the TOGA COARE configuration. Eric Smith at FSU had been analyzing the AMPR data and has written a journal article to be submitted early this summer. The emphasis of his work is on the interpretation of low resolution microwave data from space, based upon what we have learned from the high-resolution AMPR signatures

Cholinergic suppression: A postsynaptic mechanism of long-term associative learning

Food avoidance learning in the mollusc Pleurobranchaea entails reduction in the responsiveness of key brain interneurons in the feeding neural circuitry, the paracerebral feeding command interneurons (PCNs), to the neurotransmitter acetylcholine (AcCho). Food stimuli applied to the oral veil of an untrained animal depolarize the PCNs and induce the feeding motor program (FMP). Atropine (a muscarinic cholinergic antagonist) reversibly blocks the food-induced depolarization of the PCNs, implicating AcCho as the neurotransmitter mediating food detection. AcCho applied directly to PCN somata depolarizes them, indicating that the PCN soma membrane contains AcCho receptors and induces the FMP in the isolated central nervous system preparation. The AcCho response of the PCNs is mediated by muscariniclike receptors, since comparable depolarization is induced by muscarinic agonists (acetyl-ß -methylcholine, oxotremorine, pilocarpine), but not nicotine, and blocked by muscarinic antagonists (atropine, trifluoperazine). The nicotinic antagonist hexamethonium, however, blocked the AcCho response in four of six cases. When specimens are trained to suppress feeding behavior using a conventional food-avoidance learning paradigm (conditionally paired food and shock), AcCho applied to PCNs in the same concentration as in untrained animals causes little or no depolarization and does not initiate the FMP. Increasing the concentration of AcCho 10-100 times, however, induces weak PCN depolarization in trained specimens, indicating that learning diminishes but does not fully abolish AcCho responsiveness of the PCNs. This study proposes a cellular mechanism of long-term associative learning -- namely, postsynaptic modulation of neurotransmitter responsiveness in central neurons that could apply also to mammalian species

The Effects of Stopping Devices and Win Rate on Preference in Slot Machine Players

Using a between-subjects design, we evaluated the effect of structural features of slot machines in the form of stopping buttons and win rate on response allocation to two concurrently available simulated slot machines. Participants were randomly assigned to conditions that consisted of the slot machine with stopping buttons paying out substantially more, less, or equally to a slot machine that did not feature any stopping devices. Results indicated that win rate, rather than presence of stopping devices, played a primary role in determining to which slot machine participants allocated responses

Manipulating Contextual Control Over Simulated Slot Machine Gambling

Situational or contextual factors involved in slot machine gambling, such as colors, are assumed to play an important role in initiating and maintaining gambling. However, there is little empirical evidence for this assumption. The present study sought to investigate the effects of manipulating two contextual factors (the background colors of computer-simulated slot machines) on participants‟ responding to two concurrently available slot machines. Following a pretest, a nonarbitrary relational training and testing procedure was used to establish contextual functions of MORE-THAN and LESS-THAN for two cues. During posttest, participants allocated the majority of their responses to the slot machine that shared nonarbitrary properties with the contextual cue for MORE-THAN, despite the identical payout probabilities of the slot machines. Overall, the present findings demonstrate that participants‟ preferences for one of two concurrently available slot machines may come under contextual control. The advantages of the present approach to investigating the role played by situational factors such as colors in maintaining slot machine gambling are discussed

Direct measurement of superluminal group velocity and of signal velocity in an optical fiber

We present an easy way of observing superluminal group velocities using a birefringent optical fiber and other standard devices. In the theoretical analysis, we show that the optical properties of the setup can be described using the notion of "weak value". The experiment shows that the group velocity can indeed exceed c in the fiber; and we report the first direct observation of the so-called "signal velocity", the speed at which information propagates and that cannot exceed c.Comment: 5 pages, 5 figure

Cooling of cryogenic electron bilayers via the Coulomb interaction

Heat dissipation in current-carrying cryogenic nanostructures is problematic because the phonon density of states decreases strongly as energy decreases. We show that the Coulomb interaction can prove a valuable resource for carrier cooling via coupling to a nearby, cold electron reservoir. Specifically, we consider the geometry of an electron bilayer in a silicon-based heterostructure, and analyze the power transfer. We show that across a range of temperatures, separations, and sheet densities, the electron-electron interaction dominates the phonon heat-dissipation modes as the main cooling mechanism. Coulomb cooling is most effective at low densities, when phonon cooling is least effective in silicon, making it especially relevant for experiments attempting to perform coherent manipulations of single spins.Comment: 9 pages, 5 figure