Lattice Boltzmann for Binary Fluids with Suspended Colloids

A new description of the binary fluid problem via the lattice Boltzmann method is presented which highlights the use of the moments in constructing two equilibrium distribution functions. This offers a number of benefits, including better isotropy, and a more natural route to the inclusion of multiple relaxation times for the binary fluid problem. In addition, the implementation of solid colloidal particles suspended in the binary mixture is addressed, which extends the solid-fluid boundary conditions for mass and momentum to include a single conserved compositional order parameter. A number of simple benchmark problems involving a single particle at or near a fluid-fluid interface are undertaken and show good agreement with available theoretical or numerical results.Comment: 10 pages, 4 figures, ICMMES 200

Using the Discrete Lindley Distribution to Deal with Over-dispersion in Count Data

Count data in environmental epidemiology or ecology often display substantial over-dispersion, and failing to account for the over-dispersion could result in biased estimates and underestimated standard errors. This study develops a new generalized linear model family to model over-dispersed count data by assuming that the response variable follows the discrete Lindley distribution. The iterative weighted least square is developed to fit the model. Furthermore, asymptotic properties of estimators, the goodness of fit statistics are also derived. Lastly, some simulation studies and empirical data applications are carried out, and the generalized discrete Lindley linear model shows a better performance than the Poisson distribution model

Intrinsic tunneling spectroscopy: A look from the inside at HTSC

Layered structure of Bi-2212 high $T_c$ superconductor (HTSC), provides a unique opportunity to probe quasiparticle density of states inside a bulk single crystal by means of intrinsic (interlayer) tunneling spectroscopy. Here I present a systematic study of intrinsic tunneling characteristics of Bi-2212 as a function of doping, temperature, magnetic field and intercalation. An improved resolution made it possible to simultaneously trace the superconducting gap (SG) and the normal state pseudo-gap (PG) in a close vicinity of $T_c$ and to analyze closing of the PG at $T^*$. The obtained doping phase diagram exhibits a critical doping point for appearance of the PG and a characteristic crossing of the SG and the PG close to the optimal doping. All this points towards coexistence of two different and competing order parameters in Bi-2212.Comment: 4 pages, 5 figures, Presentation at M2S-Rio (May 2003), Subm. to Physica C. Note: A discussion of magnetic field dependencies is adde

Magnetoresistance and dephasing in a two-dimensional electron gas at intermediate conductances

We study, both theoretically and experimentally, the negative magnetoresistance (MR) of a two-dimensional (2D) electron gas in a weak transverse magnetic field $B$. The analysis is carried out in a wide range of zero-$B$ conductances $g$ (measured in units of $e^2/h$), including the range of intermediate conductances, $g\sim 1$. Interpretation of the experimental results obtained for a 2D electron gas in GaAs/In$_x$Ga$_{1-x}$As/GaAs single quantum well structures is based on the theory which takes into account terms of higher orders in $1/g$, stemming from both the interference contribution and the mutual effect of weak localization (WL) and Coulomb interaction. We demonstrate that at intermediate conductances the negative MR is described by the standard WL "digamma-functions" expression, but with a reduced prefactor $\alpha$. We also show that at not very high $g$ the second-loop corrections dominate over the contribution of the interaction in the Cooper channel, and therefore appear to be the main source of the lowering of the prefactor, $\alpha\simeq 1-2/\pi g$. We further analyze the regime of a "weak insulator", when the zero-$B$ conductance is low $g(B=0)<1$ due to the localization at low $T$, whereas the Drude conductance is high, $g_0>>1.$ In this regime, while the MR still can be fitted by the digamma-functions formula, the experimentally obtained value of the dephasing rate has nothing to do with the true one. The corresponding fitting parameter in the low-$T$ limit is determined by the localization length and may therefore saturate at $T\to 0$, even though the true dephasing rate vanishes.Comment: 36 pages, 16 figure

Vortex structure in d-density wave scenario of pseudogap

We investigate the vortex structure assuming the d-density wave scenario of the pseudogap. We discuss the profiles of the order parameters in the vicinity of the vortex, effective vortex charge and the local density of states. We find a pronounced modification of these quantities when compared to a purely superconducting case. Results have been obtained for a clean system as well as in the presence of a nonmagnetic impurity. We show that the competition between superconductivity and the density wave may explain some experimental data recently obtained for high-temperature superconductors. In particular, we show that the d-density wave scenario explains the asymmetry of the gap observed in the vicinity of the vortex core.Comment: 8 pages, 10 figure

Properties of layer-by-layer vector stochastic models of force fluctuations in granular materials

We attempt to describe the stress distributions of granular packings using lattice-based layer-by-layer stochastic models that satisfy the constraints of force and torque balance and non-tensile forces at each site. The inherent asymmetry in the layer-by-layer approach appears to lead to an asymmetric force distribution, in disagreement with both experiments and general symmetry considerations. The vertical force component probability distribution is robust and in agreement with predictions of the scalar q model while the distribution of horizontal force components is qualitatively different and depends on the details of implementation.Comment: 18 pages, 12 figures (with subfigures), 1 table. Uses revtex, epsfig,subfigure, and cite. Submitted to PRE. Plots have been bitmapped. High-resolution version is available. Email [email protected] or download from http://rainbow.uchicago.edu/~mbnguyen/research/vm.htm

Do fishing education programs effectively transfer 'catch-and-release' best practices to youth anglers yielding measurable improvements in fish condition and survival?

There is growing interest in educating anglers on catch-and-release (C&R) best practices, yet there is little information on whether angler education programs yield measurable improvements in fish condition and survival. As such, we conducted a study focused on mixed-gender youth groups (aged 8-10) and contrasted three levels of training intervention. Treatment 1 training had no mention of C&R best practices. Treatments 2 and 3 trainings involved visual aids to illustrate best practices, while Treatment 3 added a hands-on demonstration. When caught by the most highly trained participants, fish experienced the least amount of air exposure, but were handled for longer periods, as trained anglers were more careful. Higher levels of training led to a higher likelihood that anglers wet their hands and used a bucket filled with water while handling fish but all treatment groups yielded similar incidences of deep hooking and bleeding. Overall, mortality (initial and after ∼12 h) was low across all treatments. Our findings suggest that a short (∼20 min) fishing workshop can transfer information on C&R practices, at least in the short-term, that can lead to some improved conditions for angler-caught fish. It is unclear the extent to which this information is retained in the long-term or how different target populations or training strategies might influence knowledge transfer and adoption and thus biological outcomes. With growing interest in sharing C&R best practices with anglers, we suggest that there is need for additional research on outreach strategies to ensure that such efforts are effective and yield meaningful benefits to fish welfare and conservation

Pouch-Related Symptoms and Quality of Life in Patients with Ileal Pouch-Anal Anastomosis

Background: Restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) has become the standard surgical treatment for the majority of patients with inflammatory bowel disease (IBD) who require colectomy. We evaluated the prevalence of pouch-related symptoms among the Crohn's and Colitis Foundation of America Partners cohort and the effect of pouch-related symptoms on Patient-Reported Outcome Measurement Information System measures. Methods: We performed analyses nested in the Crohn's and Colitis Foundation of America Partners cohort. We used bivariate analyses to compare demographics and medication use among patients with ulcerative colitis or indeterminate colitis and pouch-related symptoms and those with IPAA without symptoms. We also compared Patient-Reported Outcome Measurement Information System domains (measured in T-scores) and short IBD questionnaire quality of life scales between symptomatic pouch patients (over the past 6 mo) and those without symptoms. Results: Among 243 patients reporting a history of IPAA, 199 (82%) reported a history of pouch symptoms. Patients with recent pouch symptoms demonstrated higher mean T-scores in pain interference (53.0 versus 45.3; P < 0.001), depression (51.0 versus 46.4; P = 0.002), and fatigue (56.3 versus 47.0; P < 0.001). Symptomatic pouch patients reported lower mean scores in social role satisfaction (47.4 versus 54.6) and short IBD questionnaire (4.8 versus 5.8) (both P < 0.001). These differences were all clinically meaningful. Conclusions: In a large sample of patients with IBD, nearly all patients with IPAA reported a history of pouch symptoms. Patients experiencing symptoms within the 6 months before the survey assessment demonstrated clinically meaningful decrements in patient-reported outcomes in multiple domains of physical and psychosocial functioning

Envisioning the future of aquatic animal tracking: Technology, science, and application

Electronic tags are significantly improving our understanding of aquatic animal behavior and are emerging as key sources of information for conservation and management practices. Future aquatic integrative biology and ecology studies will increasingly rely on data from electronic tagging. Continued advances in tracking hardware and software are needed to provide the knowledge required by managers and policymakers to address the challenges posed by the world's changing aquatic ecosystems. We foresee multiplatform tracking systems for simultaneously monitoring the position, activity, and physiology of animals and the environment through which they are moving. Improved data collection will be accompanied by greater data accessibility and analytical tools for processing data, enabled by new infrastructure and cyberinfrastructure. To operationalize advances and facilitate integration into policy, there must be parallel developments in the accessibility of education and training, as well as solutions to key governance and legal issues