Generic theory of colloidal transport

We discuss the motion of colloidal particles relative to a two component fluid consisting of solvent and solute. Particle motion can result from (i) net body forces on the particle due to external fields such as gravity; (ii) slip velocities on the particle surface due to surface dissipative phenomena. The perturbations of the hydrodynamic flow field exhibits characteristic differences in cases (i) and (ii) which reflect different patterns of momentum flux corresponding to the existence of net forces, force dipoles or force quadrupoles. In the absence of external fields, gradients of concentration or pressure do not generate net forces on a colloidal particle. Such gradients can nevertheless induce relative motion between particle and fluid. We present a generic description of surface dissipative phenomena based on the linear response of surface fluxes driven by conjugate surface forces. In this framework we discuss different transport scenarios including self-propulsion via surface slip that is induced by active processes on the particle surface. We clarify the nature of force balances in such situations.Comment: 22 pages, 1 figur

Thermodynamics of the half-filled Kondo lattice model around the atomic limit

We present a perturbation theory for studying thermodynamic properties of the Kondo spin liquid phase of the half-filled Kondo lattice model. The grand partition function is derived to calculate chemical potential, spin and charge susceptibilities and specific heat. The treatment is applicable to the model with strong couplings in any dimensions (one, two and three dimensions). The chemical potential equals zero at any temperatures, satisfying the requirement of the particle-hole symmetry. Thermally activated behaviors of the spin(charge) susceptibility due to the spin(quasiparticle) gap can be seen and the two-peak structure of the specific heat is obtained. The same treatment to the periodic Anderson model around atomic limit is also briefly discussed.Comment: 5 pages, 3 figures, to appear in Phys. Rev.

Linear stability analysis of transverse dunes

Sand-moving winds blowing from a constant direction in an area of high sand availability form transverse dunes, which have a fixed profile in the direction orthogonal to the wind. Here we show, by means of a linear stability analysis, that transverse dunes are intrinsically unstable. Any along-axis perturbation on a transverse dune amplify in the course of dune migration due to the combined effect of two main factors, namely: the lateral transport through avalanches along the dune's slip-face, and the scaling of dune migration velocity with the inverse of the dune height. Our calculations provide a quantitative explanation for recent observations from experiments and numerical simulations, which showed that transverse dunes moving on the bedrock cannot exist in a stable form and decay into a chain of crescent-shaped barchans.Comment: 8 pages, 4 figure

Modifiable Risk Factors for Hospital Readmission among Patients with Inflammatory Bowel Disease in a Nationwide Database

Background: Previous studies suggest that disease activity alone does not reliably predict hospital readmission among patients with inflammatory bowel diseases (IBDs). Using a national database, we aimed to further describe the burden of readmissions for IBD and identify modifiable risk factors. Methods: We performed a retrospective cohort study using 2013 data from the Nationwide Readmission Database (NRD). Using International Classification of Diseases, ninth Revision, Clinical Modification (ICD-9-CM) codes, we identified adult patients with discharge diagnoses of ulcerative colitis or Crohn's disease and ascertained diagnoses of anxiety, depression, chronic pain, tobacco use, and other comorbidities during index admission. Logistic regression was used to estimate factors associated with hospital readmission. Results: Among 52,498 hospitalizations of patients with IBD (63% Crohn's disease and 37% ulcerative colitis), 12,407 (24%) were readmitted within 90 days of the index hospitalization, resulting in roughly $576 million in excess charges. In multivariable analysis of patients with Crohn's disease, anxiety (odds ratio [OR] 1.31, 95% confidence interval [CI], 1.21-1.43), depression (OR 1.27, 95% CI, 1.07-1.50), chronic pain (OR 1.31, 95% CI, 1.18-1.46), and tobacco abuse (OR 1.13, 95% CI, 1.06-1.22) were associated with a significant increase in odds of readmission. Among patients with ulcerative colitis, anxiety (OR 1.28, 95% CI, 1.14-1.45), depression (OR 1.35, 95% CI, 1.07-1.70), and chronic pain (OR 1.44, 95% CI, 1.21-1.73) were associated with a significant increase in odds of readmission. Conclusions: Readmission occurs frequently in patients with IBD and is costly. Anxiety, depression, and chronic pain may represent targets for interventions to prevent 90-day hospital readmission in this population

The Burden of Hospital Readmissions among Pediatric Patients with Inflammatory Bowel Disease

Objective To evaluate the burden and predictors of hospital readmissions among pediatric patients with inflammatory bowel disease using the Nationwide Readmissions Database. Study design We performed a retrospective cohort study using 2013 Nationwide Readmissions Database. International Classification of Diseases, Ninth Revision, Clinical Modification codes were used to identify patients 7 days was associated with increased readmissions (aOR 1.69, 95% CI 1.09-2.62). Conclusions Readmission occurs frequently in children with inflammatory bowel disease and is associated with significant cost and resource burdens. Among patients with CD, psychiatric comorbidities such as anxiety and depression are apparent drivers of readmission

Simulating (electro)hydrodynamic effects in colloidal dispersions: smoothed profile method

Previously, we have proposed a direct simulation scheme for colloidal dispersions in a Newtonian solvent [Phys.Rev.E 71,036707 (2005)]. An improved formulation called the ``Smoothed Profile (SP) method'' is presented here in which simultaneous time-marching is used for the host fluid and colloids. The SP method is a direct numerical simulation of particulate flows and provides a coupling scheme between the continuum fluid dynamics and rigid-body dynamics through utilization of a smoothed profile for the colloidal particles. Moreover, the improved formulation includes an extension to incorporate multi-component fluids, allowing systems such as charged colloids in electrolyte solutions to be studied. The dynamics of the colloidal dispersions are solved with the same computational cost as required for solving non-particulate flows. Numerical results which assess the hydrodynamic interactions of colloidal dispersions are presented to validate the SP method. The SP method is not restricted to particular constitutive models of the host fluids and can hence be applied to colloidal dispersions in complex fluids