Quantitative test of thermal field theory for Bose-Einstein condensates II

We have recently derived a gapless theory of the linear response of a Bose-condensed gas to external perturbations at finite temperature and used it to explain quantitatively the measurements of condensate excitations and decay rates made at JILA [D. S. Jin et.al., Phys. Rev. Lett. 78, 764 (1997)]. The theory describes the dynamic coupling between the condensate and non-condensate via a full quasiparticle description of the time-dependent normal and anomalous averages and includes all Beliaev and Landau processes. In this paper we provide a full discussion of the numerical calculations and a detailed analysis of the theoretical results in the context of the JILA experiment. We provide unambiguous proof that the dipole modes are obtained accurately within our calculations and present quantitative results for the relative phase of the oscillations of the condensed and uncondensed atom clouds. One of the main difficulties in the implementation of the theory is obtaining results which are not sensitive to basis cutoff effects and we have therefore developed a novel asymmetric summation method which solves this problem and dramatically improves the numerical convergence. This new technique should make the implementation of the theory and its possible future extensions feasible for a wide range of condensate populations and trap geometries.Comment: 23 pages, 11 figures, revtex 4. Submitted to PRA. Sequel to: S. A. Morgan et al, PRL, 91, 250403 (2003

Gesture and speech integration: an exploratory study of a man with aphasia

Background: In order to fully comprehend a speaker’s intention in everyday communication, we integrate information from multiple sources including gesture and speech. There are no published studies that have explored the impact of aphasia on iconic co-speech gesture and speech integration. Aims: To explore the impact of aphasia on co-speech gesture and speech integration in one participant with aphasia (SR) and 20 age-matched control participants. Methods & Procedures: SR and 20 control participants watched video vignettes of people producing 21 verb phrases in 3 different conditions, verbal only (V), gesture only (G) and verbal gesture combined (VG). Participants were required to select a corresponding picture from one of four alternatives: integration target, a verbal only match, a gesture only match, and an unrelated foil. The probability of choosing the integration target in the VG that goes beyond what is expected from the probabilities of choosing the integration target in V and G was referred to as multi-modal gain(MMG). Outcomes & Results: SR obtained a significantly lower multi-modal gain score than the control participants (p<0.05). Error analysis indicated that in speech and gesture integration tasks, SR relied on gesture in order to decode the message, whereas the control participants relied on speech in order to decode the message. Further analysis of the speech only and gesture only tasks indicated SR had intact gesture comprehension but impaired spoken word comprehension. Conclusions & Implications: The results confirm findings by Records (1994) which reported that impaired verbal comprehension leads to a greater reliance on gesture to decode messages. Moreover, multi-modal integration of information from speech and iconic gesture can be impaired in aphasia. The findings highlight the need for further exploration of the impact of aphasia on gesture and speech integration

Vibration-Induced Conductivity Fluctuation (VICOF) Testing of Soils

In this Letter, we propose and experimentally demonstrate a simple method to provide additional in-formation by conductivity measurements of soils. The AC electrical conductance of the soil is measured while it is exposed to a periodic vibration. The vibration-induced density fluctuation implies a corresponding conductivity fluctuation that can be seen as combination frequency components, the sum and the difference of the mean AC frequency and the double of vibration frequency, in the current response. The method is demonstrated by measurements on clayey and sandy soils

Effect of vacuum exhaust pressure on the performance of MHD ducts at high B-field

The effect of area ratio variation on the performance of a supersonic Hall MHD duct is investigated. Results indicate that for a given combustion pressure there exists an area ratio below which the power generating region of the duct is shock free and the power output increases linearly with the square of the magnetic field. For area ratios greater than this, a shock forms in the power generating region which moves upstream with increasing magnetic field strength resulting in a less rapid raise in the power output. The shock can be moved downstream by either increasing the combustion pressure of decreasing the exhaust pressure. The influence of these effects upon duct performance is presented

TRADABLE PERMITS FOR CONTROLLING NITRATES IN GROUNDWATER AT THE FARM LEVEL: A CONCEPTUAL MODEL

Nitrate contamination of municipal and domestic well water supplies is becoming an increasing problem in many rural and urban areas, raising the cost of providing safe drinking water. The objective of this paper is to describe a marketable permit scheme that can effectively manage nitrate pollution of groundwater supplies for communities in rural areas without hindering agricultural production in watersheds. They key to implementing this scheme is being able to link nitrate leaching from nitrogen fertilizer applied to crops at a farm to nitrate levels measured at a drinking water well.agriculture, groundwater pollution, leaching, nitrates, pollution trading, Environmental Economics and Policy,

Oyster Demand Adjustments to Counter-Information and Source Treatments in Response to Vibrio vulnificus

A web-based contingent behavior analysis is developed to quantity the effect of both negative and positive information treatments and post harvest processes (PHP) on demand for oysters. Results from a panel model indicate that consumers of raw and cooked oysters behave differently after news of an oyster-related human mortality. While cooked oyster consumers take precautionary measures against risk, raw oyster consumers exhibit optimistic bias and increase their consumption level. Further, by varying the source of a counter-information treatment, we find that source credibility impacts behavior. Oyster consumers, and in particular, raw oyster consumers, are most responsive to information provided by a not-for-profit, non-governmental organization. Finally, post harvest processing of oysters has no impact on demand. Key Words: Oyster demand; consumer behavior; non-market valuation; Vibrio vulnificus; information treatments; source credibility; optimistic bias

High B-field, large area ratio MHD duct experiments

Studies of the effect of area ratio variation on the performance of a supersonic Hall MHD duct were extended up to area ratios of 6.25/1. It is shown that for a given area ratio there is a combustion pressure above which the power generating region of the duct is shock free and the power output increases linearly with the square of the magnetic field. Below this pressure a shock forms in the duct which moves upstream with increasing magnetic field strength and results in a less rapid rise in power output

Oyster Demand Adjustments to Counter-Information and Source Treatments in Response to Vibrio vulnificus

A web-based contingent behavior analysis was developed to quantify the effect of both negative and positive information treatments and post harvest processes on demand for oysters. Results from a panel model indicate that consumers of raw and cooked oysters behave differently after news of an oyster-related human mortality. While cooked oyster consumers take precautionary measures against risk, raw oyster consumers exhibit optimistic bias and increase their consumption level. Further, by varying the source of a counter-information treatment, we find that source credibility impacts behavior. Oyster consumers, and in particular, raw oyster consumers, are most responsive to information provided by a not-for- profit, nongovernmental organization. Finally, post harvest processing of oysters has no impact on demand.consumer behavior, information treatments, non-market valuation, optimistic bias, Oyster demand, source credibility, Vibrio vulnificus, Agribusiness, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, Institutional and Behavioral Economics, Q18, Q13, Q58,

Practical quantum key distribution over a 48-km optical fiber network

The secure distribution of the secret random bit sequences known as "key" material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is a new technique for secure key distribution with single-photon transmissions: Heisenberg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non-orthogonal photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. Here we report the most recent results of our optical fiber experiment in which we have performed quantum key distribution over a 48-km optical fiber network at Los Alamos using photon interference states with the B92 and BB84 quantum key distribution protocols.Comment: 13 pages, 7 figures, .pdf format submitted to Journal of Modern Optic