Bistable molecular conductors with a field-switchable dipole group

A class of bistable "stator-rotor" molecules is proposed, where a stationary bridge (stator) connects the two electrodes and facilitates electron transport between them. The rotor part, which has a large dipole moment, is attached to an atom of the stator via a single sigma bond. Hydrogen bonds formed between the rotor and stator make the symmetric orientation of the dipole unstable. The rotor has two potential minima with equal energy for rotation about the sigma bond. The dipole orientation, which determines the conduction state of the molecule, can be switched by an external electric field that changes the relative energy of the two potential minima. Both orientation of the rotor correspond to asymmetric current-voltage characteristics that are the reverse of each other, so they are distinguishable electrically. Such bistable stator-rotor molecules could potentially be used as parts of molecular electronic devices.Comment: 8 pages, 7 figure

An Adversarial Algorithm for Delegation

Postprin

Prospects for rapid deceleration of small molecules by optical bichromatic forces

We examine the prospects for utilizing the optical bichromatic force (BCF) to greatly enhance laser deceleration and cooling for near-cycling transitions in small molecules. We discuss the expected behavior of the BCF in near-cycling transitions with internal degeneracies, then consider the specific example of decelerating a beam of calcium monofluoride molecules. We have selected CaF as a prototype molecule both because it has an easily-accessible near-cycling transition, and because it is well-suited to studies of ultracold molecular physics and chemistry. We also report experimental verification of one of the key requirements, the production of large bichromatic forces in a multi-level system, by performing tests in an atomic beam of metastable helium.Comment: 11 pages, 6 figures, revised version, to be published in Physical Review

Dynamic Models of Reputation and Competition in Job-Market Matching

A fundamental decision faced by a firm hiring employees - and a familiar one to anyone who has dealt with the academic job market, for example - is deciding what caliber of candidates to pursue. Should the firm try to increase its reputation by making offers to higher-quality candidates, despite the risk that the candidates might reject the offers and leave the firm empty-handed? Or should it concentrate on weaker candidates who are more likely to accept the offer? The question acquires an added level of complexity once we take into account the effect one hiring cycle has on the next: hiring better employees in the current cycle increases the firm's reputation, which in turn increases its attractiveness for higher-quality candidates in the next hiring cycle. These considerations introduce an interesting temporal dynamic aspect to the rich line of research on matching models for job markets, in which long-range planning and evolving reputational effects enter into the strategic decisions made by competing firms. We develop a model based on two competing firms to try capturing as cleanly as possible the elements that we believe constitute the strategic tension at the core of the problem: the trade-off between short-term recruiting success and long-range reputation-building; the inefficiency that results from underemployment of people who are not ranked highest; and the influence of earlier accidental outcomes on long-term reputations. Our model exhibits all these phenomena in a stylized setting, governed by a parameter q that captures the difference in strength between the two top candidates in each hiring cycle. We show that when q is relatively low the efficiency of the job market is improved by long-range reputational effects, but when q is relatively high, taking future reputations into account can sometimes reduce the efficiency

B190 computer controlled radiation monitoring and safety interlock system

The Center for Accelerator Mass Spectrometry (CAMS) in the Earth and Environmental Sciences Directorate at Lawrence Livermore National Laboratory (LLNL) operates two accelerators and is in the process of installing two new additional accelerators in support of a variety of basic and applied measurement programs. To monitor the radiation environment in the facility in which these accelerators are located and to terminate accelerator operations if predetermined radiation levels are exceeded, an updated computer controlled radiation monitoring system has been installed. This new system also monitors various machine safety interlocks and again terminates accelerator operations if machine interlocks are broken. This new system replaces an older system that was originally installed in 1988. This paper describes the updated B190 computer controlled radiation monitoring and safety interlock system

The Self-Administered Witness Interview Tool (SAW-IT): Enhancing witness recall of workplace incidents

Given the often crucial role of witness evidence in Occupational Health and Safety investigation, statements should be obtained as soon as possible after an incident using best practice methods. The present research systematically tested the efficacy of a novel Self-Administered Witness Interview Tool (SAW-IT); an adapted version of the Self-Administered Interview (SAI©) designed to elicit comprehensive information from witnesses to industrial events. The present study also examined whether completing the SAW-IT mitigated the effect of schematic processing on witness recall. Results indicate that the SAW-IT elicited significantly more correct details, as well as more precise information than a traditional incident report form. Neither the traditional report from, nor the SAW-IT mitigated against biasing effects of contextual information about a worker’s safety history, confirming that witnesses should be shielded from extraneous post-event information prior to reporting. Importantly, these results demonstrate that the SAW-IT can enhance the quality of witness reports

Bi-stable tunneling current through a molecular quantum dot

An exact solution is presented for tunneling through a negative-U d-fold degenerate molecular quantum dot weakly coupled to electrical leads. The tunnel current exhibits hysteresis if the level degeneracy of the negative-U dot is larger than two (d>2). Switching occurs in the voltage range V1 < V < V2 as a result of attractive electron correlations in the molecule, which open up a new conducting channel when the voltage is above the threshold bias voltage V2. Once this current has been established, the extra channel remains open as the voltage is reduced down to the lower threshold voltage V1. Possible realizations of the bi-stable molecular quantum dots are fullerenes, especially C60, and mixed-valence compounds.Comment: 5 pages, 1 figure. (v2) Figure updated to compare the current hysteresis for degeneracies d=4 and d>>1 of the level in the dot, minor corrections in the text. To appear in Phys. Rev.

Differences in cognitive and emotional processes between persecutory and grandiose delusions

Cognitive models propose that cognitive and emotional processes, in the context of anomalies of experience, lead to and maintain delusions. No large-scale studies have investigated whether persecutory and grandiose delusions reflect differing contributions of reasoning and affective processes. This is complicated by their frequent cooccurrence in schizophrenia. We hypothesized that persecutory and grandiose subtypes would differ significantly in their associations with psychological processes

Quantum computing with antiferromagnetic spin clusters

We show that a wide range of spin clusters with antiferromagnetic intracluster exchange interaction allows one to define a qubit. For these spin cluster qubits, initialization, quantum gate operation, and readout are possible using the same techniques as for single spins. Quantum gate operation for the spin cluster qubit does not require control over the intracluster exchange interaction. Electric and magnetic fields necessary to effect quantum gates need only be controlled on the length scale of the spin cluster rather than the scale for a single spin. Here, we calculate the energy gap separating the logical qubit states from the next excited state and the matrix elements which determine quantum gate operation times. We discuss spin cluster qubits formed by one- and two-dimensional arrays of s=1/2 spins as well as clusters formed by spins s>1/2. We illustrate the advantages of spin cluster qubits for various suggested implementations of spin qubits and analyze the scaling of decoherence time with spin cluster size.Comment: 15 pages, 7 figures; minor change