Three-dimensional structure of a low-Reynolds-number turbulent boundary layer

A low-Reynolds-number zero-pressure-gradient incompressible turbulent boundary layer was investigated using a volumetric imaging technique. The Reynolds number based on momentum thickness was 700. The flow was tagged with a passive scalar from two spanwise dye slots to distinguish between fluid motions originating in the inner and outer portions of the boundary layer. The resulting volumetric scalar field was interrogated using a laser sheet scanner developed for this study. Two- and three-dimensional time-dependent visualizations of a 50 volume time series are presented (equivalent to 17δ in length). In the outer portion of the boundary layer, scalar structures were observed to lie along lines in the (x, z)-plane, inclined to the streamwise (x-)direction in the range ±50°. The ejection of brightly dyed fluid packets from the near-wall region was observed to be spatially organized, and related to the passage of the large-scale scalar structures.Carl J Delo, Richard M Kelson and Alexander J Smit

Perceived discrimination, critical consciousness, and health in African-American women with HIV

Thesis (Ph.D.)--Boston UniversityPerceived racial discrimination (PRD), perceived gender discrimination (PGD), and discrimination-related stress (DS) have been shown to predict poor health and substance abuse in African-American women. They may contribute to racial disparities in both HIV infection and incarceration, which disproportionately affect African-American women. Critical consciousness (CC), the awareness of sociopolitical inequality, may provide a buffer against the effects of discrimination on health outcomes. This study examined (1) the effects of PGD, PRD, and DS on health and substance use and of CC as a moderator of these relationships in HIV-infected African-American women; and (2) the relationships of PRD, PGD, DS, and CC to HIV status and incarceration in HIV-infected and uninfected women. Seventy-three HIV-infected and 25 HIV-uninfected African-American women (ages 26 to 72 years) from the Chicago site of the Women's Interagency HIV Study completed self-report measures of PGD, PRD, DS, CC, depressive symptoms, quality oflife, cigarette smoking, anti-retroviral medication adherence and substance use. Blood pressure, body mass index, cholesterol, CD4+ cell count, and HIV viral load were also measured. Multiple linear and logistic regressions revealed that in HIV-infected women, PRD significantly related to higher and PGD related to lower blood pressure, likelihood of cigarette smoking, and likelihood of crack/cocaine/heroin and marijuana use. PRD significantly related to lower viral load when controlling for DS. Path analyses showed a significant direct relation of PRD to lower depressive symptoms, but a significant indirect relation to higher depressive symptoms as mediated by DS. Critical consciousness was found to relate to better HIV health markers in the context of high discrimination. At higher PGD, PRD, and DS, women with higher CC had higher CD4+ counts and lower viral load than women with lower CC. Partial correlations showed that in HIV-infected and uninfected women, there were significant positive relations of incarceration to PGD, PRD, DS, and CC. These results suggest that relationships of PGD, PRD and DS with health and substance use are complex, being protective for some outcomes but conferring risk for others. CC related to better health outcomes and provided a buffer against poor HIV health at high levels of discrimination

Quantum noise induced entanglement and chaos in the dissipative quantum model of brain

We discuss some features of the dissipative quantum model of brain in the frame of the formalism of quantum dissipation. Such a formalism is based on the doubling of the system degrees of freedom. We show that the doubled modes account for the quantum noise in the fluctuating random force in the system-environment coupling. Remarkably, such a noise manifests itself through the coherent structure of the system ground state. The entanglement of the system modes with the doubled modes is shown to be permanent in the infinite volume limit. In such a limit the trajectories in the memory space are classical chaotic trajectories.Comment: 14 page

The shifting landscape of prime ministerial accountability to parliament: an analysis of Liaison Committee scrutiny sessions

Prime ministerial power is always contingent, based on the utilisation of personal and institutional resources, subject to various formal and informal constraints. Parliament is both a political resource to be utilised, but also a veto-player. In the absence of formal mechanisms setting out the requirements for UK prime ministerial accountability to parliament, a fluid and essentially personalised relationship has developed. Regular prime ministerial appearances before the House of Commons Liaison Committee, begun in 2002, have added to parliament’s scrutiny toolkit. This article considers the accountability of the prime minister to parliament by analysing the emergence and development of the Liaison Committee evidence sessions, and draws on interviews with participants and examination of the session transcripts, in order to assess the value of this scrutiny mechanism within the broader framework of prime ministerial-legislative relation

Unifying Large- and Small-Scale Theories of Coordination

Coordination is a ubiquitous feature of all living things. It occurs by virtue of informational coupling among component parts and processes and can be quite specific (as when cells in the brain resonate to signals in the environment) or nonspecific (as when simple diffusion creates a source–sink dynamic for gene networks). Existing theoretical models of coordination—from bacteria to brains to social groups—typically focus on systems with very large numbers of elements (N→∞) or systems with only a few elements coupled together (typically N = 2). Though sharing a common inspiration in Nature’s propensity to generate dynamic patterns, both approaches have proceeded largely independent of each other. Ideally, one would like a theory that applies to phenomena observed on all scales. Recent experimental research by Mengsen Zhang and colleagues on intermediate-sized ensembles (in between the few and the many) proves to be the key to uniting large- and small-scale theories of coordination. Disorder–order transitions, multistability, order–order phase transitions, and especially metastability are shown to figure prominently on multiple levels of description, suggestive of a basic Coordination Dynamics that operates on all scales. This unified coordination dynamics turns out to be a marriage of two well-known models of large- and small-scale coordination: the former based on statistical mechanics (Kuramoto) and the latter based on the concepts of Synergetics and nonlinear dynamics (extended Haken–Kelso–Bunz or HKB). We show that models of the many and the few, previously quite unconnected, are thereby unified in a single formulation. The research has led to novel topological methods to handle the higher-dimensional dynamics of coordination in complex systems and has implications not only for understanding coordination but also for the design of (biorhythm inspired) computers

Multistability and metastability: understanding dynamic coordination in the brain

Multistable coordination dynamics exists at many levels, from multifunctional neural circuits in vertebrates and invertebrates to large-scale neural circuitry in humans. Moreover, multistability spans (at least) the domains of action and perception, and has been found to place constraints upon, even dictating the nature of, intentional change and the skill-learning process. This paper reviews some of the key evidence for multistability in the aforementioned areas, and illustrates how it has been measured, modelled and theoretically understood. It then suggests how multistability—when combined with essential aspects of coordination dynamics such as instability, transitions and (especially) metastability—provides a platform for understanding coupling and the creative dynamics of complex goal-directed systems, including the brain and the brain–behaviour relation