1,318 research outputs found
Anomalies in Auction Choice Behavior
No full textIvanova-Stenzel and Salmon (2004a) established some interesting yet puzzling results regarding bidders’ preferences between auction formats. The finding is that bidders strongly prefer the ascending to the first price sealed bid auction on a ceteris paribus basis but they are not willing to pay up to an entry price for entering into an ascending auction instead of a first price that would equalize the profits between the two. While it was found that risk aversion on the part of the bidders could resolve this anomaly the claim that risk aversion drives overbidding in first price auctions is somewhat controversial. In this study we examine two competing explanations for the observed behavior; loss aversion and “clock aversion”, i.e. a dislike for some aspect of the clock based bidding mechanism. We find that neither alternative explanation can account for bidders’ auction choice behavior leaving risk aversion as the only un-falsified hypothesis
Revenue Equivalence Revisited
No full textThe conventional wisdom in the auction design literature is that first price sealed bid auctions tend to make more money while ascending auctions tend to be more efficient. We re-examine these issues in an environment in which bidders are allowed to endogenously choose in which auction format to participate. Our findings are that more bidders choose to enter the ascending auction than the first price sealed bid auction and this extra entry is enough to make up the revenue difference between the formats. Consequently, we find that both formats raise approximately the same amount of revenue. They also generate efficiency levels and bidder earnings that are roughly equivalent across mechanisms though the earnings in the ascending might be slightly higher. In expected utility terms though, we find that the expected utility of entering a first price sealed bid auction is greater than entering an ascending for any risk averse bidder suggesting that we are seeing “overentry” into the ascending auctions
Revenue Equivalence Revisited
No full textThe conventional wisdom in the auction design literature is that first price sealed bid auctions tend to make more money while ascending auctions tend to be more efficient. We re-examine these issues in an environment in which bidders are allowed to endogenously choose in which auction format to participate. Our findings are that more bidders choose to enter the ascending auction than the first price sealed bid auction and this extra entry is enough to make up the revenue difference between the formats. Consequently, we find that both formats raise approximately the same amount of revenue. They also generate efficiency levels and bidder earnings that are roughly equivalent across mechanisms though the earnings in the ascending might be slightly higher. In expected utility terms though, we find that the expected utility of entering a first price sealed bid auction is greater than entering an ascending for any risk averse bidder suggesting that we are seeing “overentry†into the ascending auctions.bidder preferences; private values; sealed bid auctions; ascending auctions; endogenous entry
The joint Simon effect depends on perceived agency, but not intentionality, of the alternative action
No full textA co-actor’s intentionality has been suggested to be a key modulating factor for joint action effects like the joint Simon effect (JSE). However, in previous studies intentionality has often been confounded with agency defined as perceiving the initiator of an action as being the causal source of the action. The aim of the present study was to disentangle the role of agency and intentionality as modulating factors of the JSE. In Experiment 1, participants performed a joint go/nogo Simon task next to a co-actor who either intentionally controlled a response button with own finger movements (agency+/intentionality+) or who passively placed the hand on a response button that moved up and down on its own as triggered by computer signals (agency-/intentionality-). In Experiment 2, we included a condition in which participants believed that the co-actor intentionally controlled the response button with a Brain-Computer Interface while placing the response finger clearly besides the response button, so that the causal relationship between agent and action effect was perceptually disrupted (agency-/intentionality+). As a control condition, the response button was computer controlled while the co-actor placed the response finger besides the response button (agency-/intentionality-). We observed a JSE when the co-actor responded intentionally and the causal relationship between co-actor and action effect could be perceived, but not when the co-actor did not respond intentionally and the causal relationship was disrupted (Experiment 1). When the intentionality of the co-actor was maintained but the perception of the causal relationship between co-actor and action effect destroyed, the JSE was absent (Experiment 2). Our findings clearly indicate a vital role of a co-actor’s agency for the JSE and suggest that the ascription of agency is strongly perceptually grounded
Reply [to “Comment on ‘Magnetic field line reconnection experiments,’ Parts 1–4 by R. L. Stenzel, W. Gekelman, and N. Wild”]
No full textFacile access to chain length dependent termination rate coefficients via reversible addition-fragmentation chain transfer (RAFT) polymerization: Influence of the RAFT agent structure
No full textA recently developed methodology for determining chain length dependent termination rate coefficients, (k(t)(i,i)), via reversible addition-fragmentation chain transfer (RAFT) polymerizations has been extended and validated for 1-phenylethyl phenyldithioacetate (PEPDA) and 3-benzylsulfanylthiocarbonylsulfanylpropionic acid (BSPA) mediated styrene (bulk) free radical polymerizations at 80 degreesC. While the use of cumyl phenyldithioacetate (CPDA) enables a highly precise mapping of the chain length dependence of the termination rate coefficient, employment of PEPDA and BSPA leads to considerable information loss for short chain lengths (i < 10). Careful simulations demonstrate that such behavior is caused by a substantial decrease in the initial transfer effectiveness of the RAFT agents when going from CPDA to BSPA, leading to hybrid behavior between conventional and living free radical polymerization. The observed hybrid behavior is quantifiable via (overall) transfer rate coefficients for the individual RAFT agents in the preequilibrium step [CPDA (k(tr,R) = 5.0 x 10(5) L mol(-1) s(-1)), PEPDA (k(tr,R) = 2.0 x 10(5) L mol(-1) s(-1)), and BSPA (k(tr,R) = 1.0 x 10(4) L mol(-1) s(-1)) at 80 degreesC] The underlying structural cause is the change from a tertiary (CPDA), via a secondary (PEPDA), to a primary (BSPA) leaving group in the initial RAFT agent. Further, the presented simulations open an efficient pathway for approximating overall preequilibrium transfer rate coefficients for the employed RAFT agents
Experimental Studies Of Magnetic Reconnection
No full textLaboratory magnetic reconnection experiments have been performed for nearly 20 years. Elegant experiments by Stenzel and Gekelman [R. L. Stenzel and W. Gekelman, Phys. Rev. Lett. 42, 1055 (1979); W. Gekelman and R. L. Stenzel, Phys. Rev. Lett. 54, 2414 (1985)] focused on the measurement of field quantities with a single movable probe in a highly reproducible plasma. Observations included a very thin current sheet (on the order of c/ωpe), accelerated electrons, and whistler waves. The argon ions were unmagnetized in these experiments. Recent magnetohydrodynamic (MHD) experiments by Yamada and Ono have used merging plasmoids [M. Yamada, Y. Ono, A. Hayakawa, M. Katsurai, and F. W. Perkins, Phys. Rev. Lett. 65, 721 (1990); Y. Ono, M. Yamada, T. Akao, T. Tajima, and R. Matsumoto, Phys. Rev. Lett. 76, 3328 (1996)] and have measured three dimensional effects and ion acceleration. We have observed correlations between magnetic reconnection and energetic ion flow events with merging force free spheromaks at the Swarthmore Spheromak Experiment (SSX) [T. W. Kornack, P. K. Sollins, and M. R. Brown, Phys. Rev. E 58, R36 (1998)]. The reconnection layer is measured with linear and two dimensional probe arrays and ion flow is directly measured with a retarding grid energy analyzer. Flow has been measured both in the plane of the reconnection layer and out of the plane. The outflow velocity is nearly Alfvénic in the reconnection plane and the scale of the magnetic structures is consistent with collisionless reconnection theories (on the order of c/ωpi). Results from the two dimensional array show the formation of magnetic islands correlated with super-Alfvénic ions accelerated normal to the layer
Pulsed currents carried by whistlers. VIII. Current disruptions and instabilities caused by plasma erosion
No full textIn a large magnetized laboratory plasma (nӍ10 12 cm Ϫ3 , kT e у1 eV, B 0 у10 G, 1 m ϫ 2.5 m͒, the transient processes of switch-on currents to electrodes are investigated experimentally. The current rise time lies between the ion and electron cyclotron periods ͑electron magnetohydrodynamics͒. The initial current scales linearly with applied voltage and is not limited by the electron saturation current of the positive electrode, but by the ion saturation current of the return electrode. The collection of electrons in the flux tube of the positive electrode gives rise to a space charge electric field, which expels the unmagnetized ions, erodes the density, and disrupts the current. Repeated current oscillations arise from a feedback between current, density, and potential oscillations. The dependence of the transient and unstable electrode currents on externally variable parameters is investigated in the present paper. A companion paper ͓Urrutia and Stenzel, Phys. Plasmas 4, 36 ͑1997͔͒ presents in situ measurements of plasma currents, plasma parameters, and microinstabilities. These results are relevant to the physics of pulsed Langmuir probes, current collection from tethered electrodes in space, and plasma erosion switches
Well-defined diblock glycopolymers from RAFT polymerization in homogeneous aqueous medium
No full textReversible addition-fragmentation chain transfer polymerization was applied to the synthesis of well-defined diblock glycopolymers carrying different cyclic carbohydrates on the two blocks. The macroRAFT agents poly(methyl 6-O-methacryloyl-α-D-glucoside) dithiobenzoate and poly(2- methacryloxyethyl glucoside) dithiobenzoate were prepared by RAFT polymerization of the corresponding glycomonomers with (4-cyanopentanoic acid)-4- dithiobenzoate as the chain transfer agent. The reactions were stopped around 85% conversion in order to preserve the highest possible end-of-chain- functionality and the glycopolymers were isolated by precipitation in methanol. Chain extension with 2-methacryloxyethyl glucoside and methyl 6-O-methacryloyl-α-D-mannoside afforded poly(methyl 6-O-methacryloyl- α-D-glucoside-block-2-methacryloxyethyl glucoside) and poly(2-methacryloxyethyl glucoside-block-methyl 6-O-methacryloyl-α-D- mannoside), respectively, having a predetermined molecular weight and narrow polydispersity (PDI ≤ 1.20). The structure of the prepared polymers was confirmed by proton and carbon NMR and their thermal properties investigated via DSC. © 2005 American Chemical Society
Solvent and oxygen effects on the free radical polymerization of 6-O-vinyladipoyl-D-glucopyranose
No full textThe vinyl ester-type glycomonomer 6-O-vinyladipoyl-d-glucopyranose was polymerized in water and alcohol solutions. In all cases, long polymerization times were necessary to achieve reasonable conversions. Depending on the nature of the solvent, polydisperse glycopolymers were obtained possessing a molecular weight ranging between 10,000 and 122,000 Da (PS equivalent). Higher alcohols appeared to act as chain transfer agents and oligomers with DPn between 2 and 6 were indeed obtained when 2-propanol was the solvent. Also, thorough oxygen removal from the reaction mixture proved to be essential for the success of the experiment, plain nitrogen sparging being ineffective in most cases. © 2005 Elsevier Ltd. All rights reserved
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