Phase relationship between the long-time beats of free induction decays and spin echoes in solids

Recent theoretical work on the role of microscopic chaos in the dynamics and relaxation of many-body quantum systems has made several experimentally confirmed predictions about the systems of interacting nuclear spins in solids, focusing, in particular, on the shapes of spin echo responses measured by nuclear magnetic resonance (NMR). These predictions were based on the idea that the transverse nuclear spin decays evolve in a manner governed at long times by the slowest decaying eigenmode of the quantum system, analogous to a chaotic resonance in a classical system. The present paper extends the above investigations both theoretically and experimentally. On the theoretical side, the notion of chaotic eigenmodes is used to make predictions about the relationships between the long-time oscillation phase of the nuclear free induction decay (FID) and the amplitudes and phases of spin echoes. On the experimental side, the above predictions are tested for the nuclear spin decays of F-19 in CaF2 crystals and Xe-129 in frozen xenon. Good agreement between the theory and the experiment is found.Comment: 20 pages, 9 figures, significant new experimental content in comparison with version

Phase separation in the vicinity of "quantum critical" doping concentration: implications for high temperature superconductors

A general quantitative measure of the tendency towards phase separation is introduced for systems exhibiting phase transitions or crossovers controlled by charge carrier concentration. This measure is devised for the situations when the quantitative knowledge of various contributions to free energy is incomplete, and is applied to evaluate the chances of electronic phase separation associated with the onset of antiferromagnetic correlations in high-temperature cuprate superconductors. The experimental phenomenology of lanthanum- and yittrium-based cuprates was used as input to this analysis. It is also pointed out that Coulomb repulsion between charge carriers separated by the distances of 1-3 lattice periods strengthens the tendency towards phase separation by accelerating the decay of antiferromagnetic correlations with doping. Overall, the present analysis indicates that cuprates are realistically close to the threshold of phase separation -- nanoscale limited or even macroscopic with charge density varying between adjacent crystal planes

Geographical variation in sound production in the anemonefish <i>Amphiprion akallopisos</i>

Because of pelagic-larval dispersal, coral-reef fishes are distributed widely with minimal genetic differentiation between populations. Amphiprion akallopisos, a clownfish that uses sound production to defend its anemone territory, has a wide but disjunct distribution in the Indian Ocean. We compared sounds produced by these fishes from populations in Madagascar and Indonesia, a distance of 6500?km. Differentiation of agonistic calls into distinct types indicates a complexity not previously recorded in fishes' acoustic communication. Moreover, various acoustic parameters, including peak frequency, pulse duration, number of peaks per pulse, differed between the two populations. The geographic comparison is the first to demonstrate ‘dialects’ in a marine fish species, and these differences in sound parameters suggest genetic divergence between these two populations. These results highlight the possible approach for investigating the role of sounds in fish behaviour in reproductive divergence and speciation

Population Differences in Death Rates in HIV-Positive Patients with Tuberculosis.

SETTING: Randomised controlled clinical trial of Mycobacterium vaccae vaccination as an adjunct to anti-tuberculosis treatment in human immunodeficiency virus (HIV) positive patients with smear-positive tuberculosis (TB) in Lusaka, Zambia, and Karonga, Malawi. OBJECTIVE: To explain the difference in mortality between the two trial sites and to identify risk factors for death among HIV-positive patients with TB. DESIGN: Information on demographic, clinical, laboratory and radiographic characteristics was collected. Patients in Lusaka (667) and in Karonga (84) were followed up for an average of 1.56 years. Cox proportional hazard analyses were used to assess differences in survival between the two sites and to determine risk factors associated with mortality during and after anti-tuberculosis treatment. RESULTS: The case fatality rate was 14.7% in Lusaka and 21.4% in Karonga. The hazard ratio for death comparing Karonga to Lusaka was 1.47 (95% confidence interval [CI] 0.9-2.4) during treatment and 1.76 (95%CI 1.0-3.0) after treatment. This difference could be almost entirely explained by age and more advanced HIV disease among patients in Karonga. CONCLUSION: It is important to understand the reasons for population differences in mortality among patients with TB and HIV and to maximise efforts to reduce mortality

Extracting Lyapunov exponents from the echo dynamics of Bose-Einstein condensates on a lattice

We propose theoretically an experimentally realizable method to demonstrate the Lyapunov instability and to extract the value of the largest Lyapunov exponent for a chaotic many-particle interacting system. The proposal focuses specifically on a lattice of coupled Bose-Einstein condensates in the classical regime describable by the discrete Gross-Pitaevskii equation. We suggest to use imperfect time-reversal of system's dynamics known as Loschmidt echo, which can be realized experimentally by reversing the sign of the Hamiltonian of the system. The routine involves tracking and then subtracting the noise of virtually any observable quantity before and after the time-reversal. We support the theoretical analysis by direct numerical simulations demonstrating that the largest Lyapunov exponent can indeed be extracted from the Loschmidt echo routine. We also discuss possible values of experimental parameters required for implementing this proposal

Bell's theorem as a signature of nonlocality: a classical counterexample

For a system composed of two particles Bell's theorem asserts that averages of physical quantities determined from local variables must conform to a family of inequalities. In this work we show that a classical model containing a local probabilistic interaction in the measurement process can lead to a violation of the Bell inequalities. We first introduce two-particle phase-space distributions in classical mechanics constructed to be the analogs of quantum mechanical angular momentum eigenstates. These distributions are then employed in four schemes characterized by different types of detectors measuring the angular momenta. When the model includes an interaction between the detector and the measured particle leading to ensemble dependencies, the relevant Bell inequalities are violated if total angular momentum is required to be conserved. The violation is explained by identifying assumptions made in the derivation of Bell's theorem that are not fulfilled by the model. These assumptions will be argued to be too restrictive to see in the violation of the Bell inequalities a faithful signature of nonlocality.Comment: Extended manuscript. Significant change

Towards a Conceptualization of Sociomaterial Entanglement

In knowledge representation, socio-technical systems can be modeled as multiagent systems in which the local knowledge of each individual agent can be seen as a context. In this paper we propose formal ontologies as a means to describe the assumptions driving the construction of contexts as local theories and to enable interoperability among them. In particular, we present two alternative conceptualizations of the notion of sociomateriality (and entanglement), which is central in the recent debates on socio-technical systems in the social sciences, namely critical and agential realism. We thus start by providing a model of entanglement according to the critical realist view, representing it as a property of objects that are essentially dependent on different modules of an already given ontology. We refine then our treatment by proposing a taxonomy of sociomaterial entanglements that distinguishes between ontological and epistemological entanglement. In the final section, we discuss the second perspective, which is more challenging form the point of view of knowledge representation, and we show that the very distinction of information into modules can be at least in principle built out of the assumption of an entangled reality

Towards a new theory of practice for community health psychology

The article sets out the value of theorizing collective action from a social science perspective that engages with the messy actuality of practice. It argues that community health psychology relies on an abstract version of Paulo Freire’s earlier writing, the Pedagogy of the Oppressed, which provides scholar-activists with a ‘map’ approach to collective action. The article revisits Freire’s later work, the Pedagogy of Hope, and argues for the importance of developing a ‘journey’ approach to collective action. Theories of practice are discussed for their value in theorizing such journeys, and in bringing maps (intentions) and journeys (actuality) closer together

The utilization of an ultrasound-guided 8-gauge vacuum-assisted breast biopsy system as an innovative approach to accomplishing complete eradication of multiple bilateral breast fibroadenomas

<p>Abstract</p> <p>Background</p> <p>Ultrasound-guided vacuum-assisted breast biopsy technology is extremely useful for diagnostic biopsy of suspicious breast lesions and for attempted complete excision of appropriately selected presumed benign breast lesions.</p> <p>Case presentation</p> <p>A female patient presented with 16 breast lesions (eight within each breast), documented on ultrasound and all presumed to be fibroadenomas. Over a ten and one-half month period of time, 14 of these 16 breast lesions were removed under ultrasound guidance during a total of 11 separate 8-gauge Mammotome^®excision procedures performed during seven separate sessions. Additionally, two of these 16 breast lesions were removed by open surgical excision. A histopathologic diagnosis of fibroadenoma and/or fibroadenomatous changes was confirmed at all lesion excision sites. Interval follow-up ultrasound imaging revealed no evidence of a residual lesion at the site of any of the 16 original breast lesions.</p> <p>Conclusion</p> <p>This report describes an innovative approach of utilizing ultrasound-guided 8-gauge vacuum-assisted breast biopsy technology for assisting in achieving complete eradication of multiple bilateral fibroadenomas in a patient who presented with 16 documented breast lesions. As such, this innovative approach is highly recommended in similar appropriately selected patients.</p