The Polymer Stress Tensor in Turbulent Shear Flows

The interaction of polymers with turbulent shear flows is examined. We focus on the structure of the elastic stress tensor, which is proportional to the polymer conformation tensor. We examine this object in turbulent flows of increasing complexity. First is isotropic turbulence, then anisotropic (but homogenous) shear turbulence and finally wall bounded turbulence. The main result of this paper is that for all these flows the polymer stress tensor attains a universal structure in the limit of large Deborah number \De\gg 1. We present analytic results for the suppression of the coil-stretch transition at large Deborah numbers. Above the transition the turbulent velocity fluctuations are strongly correlated with the polymer's elongation: there appear high-quality "hydro-elastic" waves in which turbulent kinetic energy turns into polymer potential energy and vice versa. These waves determine the trace of the elastic stress tensor but practically do not modify its universal structure. We demonstrate that the influence of the polymers on the balance of energy and momentum can be accurately described by an effective polymer viscosity that is proportional to to the cross-stream component of the elastic stress tensor. This component is smaller than the stream-wise component by a factor proportional to \De ^2 . Finally we tie our results to wall bounded turbulence and clarify some puzzling facts observed in the problem of drag reduction by polymers.Comment: 11 p., 1 Fig., included, Phys. Rev. E., submitte

Toward a structural understanding of turbulent drag reduction: nonlinear coherent states in viscoelastic shear flows

Nontrivial steady flows have recently been found that capture the main structures of the turbulent buffer layer. We study the effects of polymer addition on these "exact coherent states" (ECS) in plane Couette flow. Despite the simplicity of the ECS flows, these effects closely mirror those observed experimentally: Structures shift to larger length scales, wall-normal fluctuations are suppressed while streamwise ones are enhanced, and drag is reduced. The mechanism underlying these effects is elucidated. These results suggest that the ECS are closely related to buffer layer turbulence.Comment: 5 pages, 3 figures, published version, Phys. Rev. Lett. 89, 208301 (2002

Neandertal Mandibular Molars from Hortus Cave, France: A Comparison of Crown Shapes Using Elliptical Fourier Analysis

Neandertal permanent mandibular molars are well represented at Hortus Cave, France, Sub-Phase IVb and Vb, providing an opportunity to assess intrapopulation and intersite shape variation. We expected the mandibular molars from Hortus cave, comprising Hortus II, Hortus IV, Hortus V and Hortus VI to cluster together, compared to Neandertals close in proximity, such as Malarnaud and La Quina 5 as well as those more distantly located such as Arcysur- Cure 1, Engis 2 and Scladina 4A-1. A single Neolithic cave burial from Maurenne Caverne de la Cave, Belgium (n = 11) is used to contextualize the degree of variation in the Hortus assemblage. From photographic images of the permanent molars, crown shapes were digitized and binarized. The resulting images were processed in R using elliptical Fourier analysis and the resulting amplitudes of the harmonics were subjected to principal components analysis and hierarchical clustering. Hortus II and Hortus V, both from Sub-Phase Vb, are relatively similar to one another in M1 crown shape, and are secondarily grouped with Hortus IV from Sub-Phase IVb. Maurenne Caverne de la Cave has a larger degree of variation in crown shape than the Hortus assemblage, and the Neandertals imperfectly cluster together and apart from the Neolithic sample for some multivariate comparisons. Variance in Neandertal molar crown shape can be primarily explained as the result of chronology. Hortus consistently groups with other MIS 3 Neandertals such as La Quina 5 and Engis 2, while those from MIS 5, represented by Scladina 4A-1 and Malarnaud are distinct as is Arcy-sur-Cure 1 from late MIS 3. Across the molars, the Hortus assemblage is most similar to La Quina 5 from Charente, Southwest France

Multi-Zone Shell Model for Turbulent Wall Bounded Flows

We suggested a \emph{Multi-Zone Shell} (MZS) model for wall-bounded flows accounting for the space inhomogeneity in a "piecewise approximation", in which cross-section area of the flow, $S$, is subdivided into "$j$-zones". The area of the first zone, responsible for the core of the flow, $S_1\simeq S/2$, and areas of the next $j$-zones, $S_j$, decrease towards the wall like $S_j\propto 2^{-j}$. In each $j$-zone the statistics of turbulence is assumed to be space homogeneous and is described by the set of "shell velocities" $u_{nj}(t)$ for turbulent fluctuations of the scale $\propto 2^{-n}$. The MZS-model includes a new set of complex variables, $V_j(t)$, $j=1,2,... \infty$, describing the amplitudes of the near wall coherent structures of the scale $s_j\sim 2^{-j}$ and responsible for the mean velocity profile. Suggested MZS-equations of motion for $u_{nj}(t)$ and $V_j(t)$ preserve the actual conservations laws (energy, mechanical and angular momenta), respect the existing symmetries (including Galilean and scale invariance) and account for the type of the non-linearity in the Navier-Stokes equation, dimensional reasoning, etc. The MZS-model qualitatively describes important characteristics of the wall bounded turbulence, e.g., evolution of the mean velocity profile with increasing Reynolds number, \RE, from the laminar profile towards the universal logarithmic profile near the flat-plane boundary layer as \RE\to \infty.Comment: 27 pages, 17 figs, included, PRE, submitte

Stretching of polymers in a random three-dimensional flow

Behavior of a dilute polymer solution in a random three-dimensional flow with an average shear is studied experimentally. Polymer contribution to the shear stress is found to be more than two orders of magnitude higher than in a laminar shear flow. The results indicate that the polymer molecules get strongly stretched by the random motion of the fluid.Comment: 4 pages, 3 figure

Short-term psychodynamic psychotherapy for functional somatic disorders: a systematic review and meta-analysis of within-treatment effects

OBJECTIVE: A recent meta-analysis of 17 randomized, controlled trials (RCTs) showed that Short-term Psychodynamic Psychotherapy (STPP) for functional somatic disorders (FSD) reduced somatic symptoms compared to wait list, minimal treatment, and treatment-as-usual controls. A clinically important yet unanswered question is how much improvement patients experience within STPP treatment. METHODS: Following a systematic search, we identified STPP trials presenting data at baseline and post-treatment/follow-up. Meta-analyses determined the magnitude of changes in somatic symptoms and other outcomes from before to after STPP, and analyses examined effect sizes as a function of study, therapy, and patient variables. RESULTS: We identified 37 trials (22 pre-post studies and 15 RCTs) totaling 2094 patients treated an average of 13.34 sessions for a range of FSD. Across all studies, somatic symptoms improved significantly from pre-treatment to short-term follow-up with a large effect size (SMD = −1.07), which was maintained at long-term follow-up (SMD = −0.90). After excluding two outlier studies, effects at short- and medium-term follow-up remained significant but were somewhat reduced in magnitude (e.g., short-term SMD = −0.73). Secondary outcomes including anxiety, depression, disability, and interpersonal problems had medium to large effects. Effects were larger for studies of STPP that were longer than 12 sessions or used an emotion-focused type of STPP, and for chronic pain or gastrointestinal conditions than for functional neurological disorders. CONCLUSIONS: STPP results in moderate to large improvements in multiple outcome domains that are sustained in long-term follow-up. STPP is an effective treatment option for FSD and should be included in treatment guidelines

Polymer transport in random flow

The dynamics of polymers in a random smooth flow is investigated in the framework of the Hookean dumbbell model. The analytical expression of the time-dependent probability density function of polymer elongation is derived explicitly for a Gaussian, rapidly changing flow. When polymers are in the coiled state the pdf reaches a stationary state characterized by power-law tails both for small and large arguments compared to the equilibrium length. The characteristic relaxation time is computed as a function of the Weissenberg number. In the stretched state the pdf is unstationary and exhibits multiscaling. Numerical simulations for the two-dimensional Navier-Stokes flow confirm the relevance of theoretical results obtained for the delta-correlated model.Comment: 28 pages, 6 figure

The diet of young Neandertals from France, Pech de l’Azé I and Hortus II, reconstructed using dental microwear texture analysis

Les adultes néandertaliens présentent des différences de régime alimentaire en fonction de leur paléohabitat. Nous examinons si les jeunes enfants néandertaliens de France datant du stade isotopique marins 3 montrent également ces distinctions alimentaires à partir de l’étude de la texture des micro-usures dentaires des deuxièmes molaires déciduales des individus Pech de l’Azé I, datant d’une phase froide-tempérée, et Hortus II, datant d’une phase froid-aride extrême. L’échantillon comparatif (n=76) comprend des molaires déciduales d’agriculteurs-cueilleurs provenant de trois grottes néolithiques de Belgique, dont Caverne de la Cave à Maurenne (n=5), Sclaigneaux (n=7) et Bois Madame (n=6), ainsi que des agriculteurs de l’époque romaine d’Herculanum (n=15) et médiévaux de Canterbury, Angleterre (n=43). Lorsque la complexité est comparée à l’anisotropie, Pech de l’Azé I présente une valeur élevée provenant de la mastication de plantes à parties dures ou de particules adhérentes, ou de la consommation d’aliments mal transformés ou chargés de silicates abrasifs. En revanche, Hortus II a une valeur faible, peut-être en raison de l’accès limité aux parties dures des plantes comme les graines et les noix. Toutefois, Pech de l’Azé I et Hortus II se ressemblent en présentant une faible valeur d’anisotropie qui est révélatrice de mouvements complexes des mâchoires lors de la mastication et sont différents des enfants humains néolithiques, romains et médiévaux qui ont tendance à avoir des valeurs plus élevées. Les régimes alimentaires des enfants néandertaliens diffèrent en fonction du paléohabitat et sont généralement plus diversifiés que ceux des producteurs d’aliments, qu’ils habitent des environnements boisés ou ouverts.Neandertal adults show differences in diet with respect to paleohabitat. To examine whether Neandertal children of France during Marine Isotope Stage 3 also show these dietary distinctions, the deciduous second molars of Pech de l’Azé I, from a cold-temperate period, and Hortus II from Sub-Phase Vb, an extreme cold-arid interval, were examined using dental microwear texture analysis. The comparative sample (n=76) includes deciduous molars from Neolithic forager-farmers of Belgium, including Caverne de la Cave at Maurenne (n=5), Sclaigneaux (n=7) and Bois Madame (n=6), Roman-era farmers from Herculaneum (n=15) and Medieval agriculturalists from Canterbury, England (n=43). When complexity is compared to anisotropy, Pech de l’Azé I exhibits an elevated value from the mastication of plants with hard parts or adherent particles, or the consumption of foods that were poorly processed or grit-laden, whereas Hortus II presents a low value, perhaps from limited access to hard plant parts such as seeds and nuts. However, Pech de l’Azé I and Hortus II resemble each other in having a low value for anisotropy, which is indicative of complicated movements of the jaws during mastication and are dissimilar to Neolithic, Roman and Medieval human children who tend to have higher values. The diets of Neandertal children differ with respect to paleohabitat and typically were more diverse than those of food producers regardless of whether they inhabited wooded or open environments

Drug-gene interactions of antihypertensive medications and risk of incident cardiovascular disease: a pharmacogenomics study from the CHARGE consortium

Background Hypertension is a major risk factor for a spectrum of cardiovascular diseases (CVD), including myocardial infarction, sudden death, and stroke. In the US, over 65 million people have high blood pressure and a large proportion of these individuals are prescribed antihypertensive medications. Although large long-term clinical trials conducted in the last several decades have identified a number of effective antihypertensive treatments that reduce the risk of future clinical complications, responses to therapy and protection from cardiovascular events vary among individuals. Methods Using a genome-wide association study among 21,267 participants with pharmaceutically treated hypertension, we explored the hypothesis that genetic variants might influence or modify the effectiveness of common antihypertensive therapies on the risk of major cardiovascular outcomes. The classes of drug treatments included angiotensin-converting enzyme inhibitors, beta-blockers, calcium channel blockers, and diuretics. In the setting of the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium, each study performed array-based genome-wide genotyping, imputed to HapMap Phase II reference panels, and used additive genetic models in proportional hazards or logistic regression models to evaluate drug-gene interactions for each of four therapeutic drug classes. We used meta-analysis to combine study-specific interaction estimates for approximately 2 million single nucleotide polymorphisms (SNPs) in a discovery analysis among 15,375 European Ancestry participants (3,527 CVD cases) with targeted follow-up in a case-only study of 1,751 European Ancestry GenHAT participants as well as among 4,141 African-Americans (1,267 CVD cases). Results Although drug-SNP interactions were biologically plausible, exposures and outcomes were well measured, and power was sufficient to detect modest interactions, we did not identify any statistically significant interactions from the four antihypertensive therapy meta-analyses (Pinteraction > 5.0×10−8). Similarly, findings were null for meta-analyses restricted to 66 SNPs with significant main effects on coronary artery disease or blood pressure from large published genome-wide association studies (Pinteraction ≥ 0.01). Our results suggest that there are no major pharmacogenetic influences of common SNPs on the relationship between blood pressure medications and the risk of incident CVD

Turbulence anisotropy and the SO(3) description

We study strongly turbulent windtunnel flows with controlled anisotropy. Using a recent formalism based on angular momentum and the irreducible representations of the SO(3) rotation group, we attempt to extract this anisotropy from the angular dependence of second-order structure functions. Our instrumentation allows a measurement of both the separation and the angle dependence of the structure function. In axisymmetric turbulence which has a weak anisotropy, this more extended information produces ambiguous results. In more strongly anisotropic shear turbulence, the SO(3) description enables one to find the anisotropy scaling exponent. The key quality of the SO(3) description is that structure functions are a mixture of algebraic functions of the scale with exponents ordered such that the contribution of anisotropies diminishes at small scales. However, we find that in third-order structure functions of homogeneous shear turbulence the anisotropic contribution is always large and of the same order of magnitude as the isotropic part. Our results concern the minimum instrumentation needed to determine the parameters of the SO(3) description, and raise several questions about its ability to describe the angle dependence of high-order structure functions