Dissipative Dynamics of Collisionless Nonlinear Alfven Wave Trains

The nonlinear dynamics of collisionless Alfven trains, including resonant particle effects is studied using the kinetic nonlinear Schroedinger (KNLS) equation model. Numerical solutions of the KNLS reveal the dynamics of Alfven waves to be sensitive to the sense of polarization as well as the angle of propagation with respect to the ambient magnetic field. The combined effects of both wave nonlinearity and Landau damping result in the evolutionary formation of stationaryOA S- and arc-polarized directional and rotational discontinuities. These waveforms are freqently observed in the interplanetary plasma.Comment: REVTeX, 6 pages (including 5 figures). This and other papers may be found at http://sdphpd.ucsd.edu/~medvedev/papers.htm

Two dimensional modulational instability in photorefractive media

We study theoretically and experimentally the modulational instability of broad optical beams in photorefractive nonlinear media. We demonstrate the impact of the anisotropy of the nonlinearity on the growth rate of periodic perturbations. Our findings are confirmed by experimental measurements in a strontium barium niobate photorefractive crystal.Comment: 8 figure

Inflammation, amyloid, and atrophy in the aging brain: relationships with longitudinal changes in cognition

Amyloid deposition occurs in aging, even in individuals free from cognitive symptoms, and is often interpreted as preclinical Alzheimer's disease (AD) pathophysiology. YKL-40 is a marker of neuroinflammation, being increased in AD, and hypothesized to interact with amyloid-B (AB ) in causing cognitive decline early in the cascade of AD pathophysiology. Whether and how A and YKL-40 affect brain and cognitive changes in cognitively healthy older adults is still unknown. We studied 89 participants (mean age: 73.1 years) with cerebrospinal fluid samples at baseline, and both MRI and cognitive assessments from two time-points separated by two years. We tested how baseline levels of AB 42 and YKL-40 correlated with changes in cortical thickness and cognition. Thickness change correlated with AB 42 only in AB 42+ participants (<600 pg/mL, n = 27) in the left motor and premotor cortices. AB 42 was unrelated to cognitive change. Increased YKL-40 was associated with less preservation of scores on the animal naming test in the total sample (r = -0.28, p = 0.012) and less preservation of a score reflecting global cognitive function for AB 42+ participants (r = -0.58, p = 0.004). Our results suggest a role for inflammation in brain atrophy and cognitive changes in cognitively normal older adults, which partly depended on AB accumulation

Berry phases for the nonlocal Gross-Pitaevskii equation with a quadratic potential

A countable set of asymptotic space -- localized solutions is constructed by the complex germ method in the adiabatic approximation for the nonstationary Gross -- Pitaevskii equation with nonlocal nonlinearity and a quadratic potential. The asymptotic parameter is 1/T, where $T\gg1$ is the adiabatic evolution time. A generalization of the Berry phase of the linear Schr\"odinger equation is formulated for the Gross-Pitaevskii equation. For the solutions constructed, the Berry phases are found in explicit form.Comment: 13 pages, no figure

Modulational instability, solitons and beam propagation in spatially nonlocal nonlinear media

We present an overview of recent advances in the understanding of optical beams in nonlinear media with a spatially nonlocal nonlinear response. We discuss the impact of nonlocality on the modulational instability of plane waves, the collapse of finite-size beams, and the formation and interaction of spatial solitons.Comment: Review article, will be published in Journal of Optics B, special issue on Optical Solitons, 6 figure

Hamiltonian form and solitary waves of the spatial Dysthe equations

The spatial Dysthe equations describe the envelope evolution of the free-surface and potential of gravity waves in deep waters. Their Hamiltonian structure and new invariants are unveiled by means of a gauge transformation to a new canonical form of the evolution equations. An accurate Fourier-type spectral scheme is used to solve for the wave dynamics and validate the new conservation laws, which are satisfied up to machine precision. Traveling waves are numerically constructed using the Petviashvili method. It is shown that their collision appears inelastic, suggesting the non-integrability of the Dysthe equations.Comment: 6 pages, 9 figures. Other author's papers can be downloaded at http://www.lama.univ-savoie.fr/~dutykh

Maintaining a balance: a focus group study on living and coping with chronic whiplash-associated disorder

<p>Abstract</p> <p>Background</p> <p>There is little qualitative insight into how persons with chronic Whiplash-Associated Disorder cope on a day to day basis. This study seeks to identify the symptoms persons with Whiplash-Associated Disorder describe as dominating and explore their self-initiated coping strategies.</p> <p>Methods</p> <p>Qualitative study using focus groups interviews. Fourteen Norwegian men and women with Whiplash-Associated Disorder (I or II) were recruited to participate in two focus groups. Data were analyzed according to a phenomenological approach, and discussed within the model of Cognitive Activation Theory of Stress (CATS).</p> <p>Results</p> <p>Participants reported neck and head pain, sensory hypersensitivity, and cognitive dysfunction following their whiplash injury. Based on the intensity of symptoms, participants divided everyday life into good and bad periods. In good periods the symptoms were perceived as manageable. In bad periods the symptoms intensified and took control of the individual. Participants expressed a constant notion of trying to balance their three main coping strategies; rest, exercise, and social withdrawal. In good periods participants experienced coping by expecting good results from the strategies they used. In bad periods they experienced no or negative relationships between their behavioral strategies and their complaints.</p> <p>Conclusions</p> <p>Neck and head pain, sensory hypersensitivity, and cognitive dysfunction were reported as participants' main complaints. A constant notion of balancing between their three main coping strategies; rest, exercise, and social withdrawal, was described.</p

The implications of autonomy: Viewed in the light of efforts to uphold patients dignity and integrity

This article focuses on Danish patients’ experience of autonomy and its interplay with dignity and integrity in their meeting with health professionals. The aim is to chart the meanings and implications of autonomy for persons whose illness places them in a vulnerable life situation. The interplay between autonomy and personal dignity in the meeting with health care staff are central concepts in the framework. Data collection and findings are based on eight qualitative semi-structured interviews with patients. Patients with acute, chronic, and life threatening diseases were represented including surgical as well as medical patients. The values associated with autonomy are in many ways vitalising, but may become so dominant, autonomy seeking, and pervasive that the patient's dignity is affected. Three types of patient behaviour were identified. (1) The proactive patient: Patients feel that they assume responsibility for their own situation, but it may be a responsibility that they find hard to bear. (2) The rejected patient: proactive patients take responsibility on many occasions but very active patients are at risk of being rejected with consequences for their dignity. (3) The knowledgeable patient: when patients are health care professionals, the patient's right of self-determination was managed in a variety of ways, sometimes the patient's right of autonomy was treated in a dignified way but the opposite was also evident. In one way, patients are active and willing to take responsibility for themselves, and at the same time they are “forced” to do so by health care staff. Patients would like health professionals to be more attentive and proactive