Liquid bridging of cylindrical colloids in near-critical solvents.

Within mean field theory, we investigate the bridging transition between a pair of parallel cylindrical colloids immersed in a binary liquid mixture as a solvent that is close to its critical consolute point Tc. We determine the universal scaling functions of the effective potential and of the force between the colloids. For a solvent that is at the critical concentration and close to Tc, we find that the critical Casimir force is the dominant interaction at close separations. This agrees very well with the corresponding Derjaguin approximation for the effective interaction between the two cylinders, while capillary forces originating from the extension of the liquid bridge turn out to be more important at large separations. In addition, we are able to infer from the wetting characteristics of the individual colloids the first-order transition of the liquid bridge connecting two colloidal particles to the ruptured state. While specific to cylindrical colloids, the results presented here also provide an outline for identifying critical Casimir forces acting on bridged colloidal particles as such and for analyzing the bridging transition between them.

Prognostic significance of pre-transplant quality of life in allogeneic hematopoietic cell transplantation recipients.

Quality of life (QOL) is an important outcome for hematopoietic cell transplantation (HCT) recipients. Whether pre-HCT QOL adds prognostic information to patient and disease related risk factors has not been well described. We investigated the association of pre-HCT QOL with relapse, non-relapse mortality (NRM), and overall mortality after allogeneic HCT. From 2003 to 2012, the Functional Assessment of Cancer Therapy-Bone Marrow Transplant Scale instrument was administered before transplantation to 409 first allogeneic HCT recipients. We examined the association of the three outcomes with (1) individual QOL domains, (2) trial outcome index (TOI) and (3) total score. In multivariable models with individual domains, functional well-being (hazard ratio (HR) 0.95, P=0.025) and additional concerns (HR 1.39, P=0.002) were associated with reduced risk of relapse, no domain was associated with NRM, and better physical well-being was associated with reduced risk of overall mortality (HR 0.97, P=0.04). TOI was not associated with relapse or NRM but was associated with reduced risk of overall mortality (HR 0.93, P=0.05). Total score was not associated with any of the three outcomes. HCT-comorbidity index score was prognostic for greater risk of relapse and mortality but not NRM. QOL assessments, particularly physical functioning and functional well-being, may provide independent prognostic information beyond standard clinical measures in allogeneic HCT recipients.

Effective interaction between a colloid and a soft interface near criticality.

Within mean-field theory we determine the universal scaling function for the effective force acting on a single colloid located near the interface between two coexisting liquid phases of a binary liquid mixture close to its critical consolute point. This is the first study of critical Casimir forces emerging from the confinement of a fluctuating medium by at least one shape responsive, soft interface, instead of by rigid walls only as studied previously. For this specific system, our semi-analytical calculation illustrates that knowledge of the colloid-induced, deformed shape of the interface allows one to accurately describe the effective interaction potential between the colloid and the interface. Moreover, our analysis demonstrates that the critical Casimir force involving a deformable interface is accurately described by a universal scaling function, the shape of which differs from that one for rigid walls.

Obtaining effective pair potentials in colloidal monolayers using a thermodynamically consistent inversion scheme.

The structure and stability of colloidal monolayers depends crucially on the effective pair interaction potential u(r) between colloidal particles. In this study, we construct a novel method for extracting u(r) from the two-dimensional (2D) radial distribution function g(r) of dense colloidal monolayers. The method is based on the Ornstein-Zernike relation and the HMSA closure first proposed by Zerah and Hansen (Zerah, G.; Hansen, J.-P. Self-consistent integral equations for fluid pair distribution functions: Another attempt. J. Chem. Phys. 1986, 84(4), 2336-2343). The HMSA closure contains a single fitting parameter which is determined by requiring thermodynamic consistency between the virial and compressibility equations of state. The accuracy of the HMSA inversion scheme is compared to a 2D predictor corrector scheme based on hard-disk fluids (HDPC) previously proposed by us (Law, A. D.; Buzza, D. M. A. Determination of interaction potentials of colloidal monolayers from the inversion of pair correlation functions: A two-dimensional predictor-corrector method. J. Chem. Phys. 2009, 131, 094704) and the conventional "one-step" inversion methods of HNC and Percus-Yevick (PY). The accuracy of all these schemes is tested against Monte Carlo simulation data for g(r) from monolayers interacting via a range of commonly encountered potentials, including both purely repulsive potentials and potentials containing an attractive well. For all the potentials studied, we find that the accuracy of the HMSA and HDPC schemes is superior to HNC and PY, especially as we go to higher densities. The HDPC and HMSA schemes are particularly accurate for hard-core and soft-core fluids, respectively, at high density and are therefore complementary to each other. Finally, we find that, even in the presence of experimentally realistic levels of noise in the input g(r) data, both HMSA and HDPC schemes are able to faithfully extract the salient features of the underlying interaction potentials. Both these schemes therefore provide convenient and accurate methods for extracting u(r) from experimental g(r) data for general 2D monolayers.

Determination of interaction potentials of colloidal monolayers from the inversion of pair correlation functions: a two-dimensional predictor-corrector method.

The structure and stability of colloidal monolayers depend crucially on the effective pair potential u(r) between colloidal particles. In this paper, we develop a two-dimensional (2D) predictor-corrector method for extracting u(r) from the pair correlation function g(r) of dense colloidal monolayers. The method is based on an extension of the three-dimensional scheme of Rajagopalan and Rao [Phys. Rev. E 55, 4423 (1997)] to 2D by replacing the unknown bridge function B(r) with the hard-disk bridge function B(d)(r); the unknown hard-disk diameter d is then determined using an iterative scheme. We compare the accuracy of our predictor-corrector method to the conventional one-step inversion schemes of hypernetted chain closure (HNC) and Percus-Yevick (PY) closure. Specifically we benchmark all three schemes against g(r) data generated from Monte Carlo simulation for a range of 2D potentials: exponential decay, Stillinger-Hurd, Lennard-Jones, and Derjaguin-Landau-Verwey-Overbeek. We find that for all these potentials, the predictor-corrector method is at least as good as the most accurate one-step method for any given potential, and in most cases it is significantly better. In contrast the accuracy of the HNC and PY methods relative to each other depends on the potential studied. The proposed predictor-corrector scheme is therefore a robust and more accurate alternative to these conventional one-step inversion schemes.