Many important biomarkers for disease diagnosis are present at low concentrations in human serum. These biomarkers are masked in proteomic analysis by highly abundant proteins such as human serum albumin (HSA) and immunoglobulins (IgGs) which account for up to 80% of the total protein content of serum. Traditional depletion methods using macro-scale LC-columns for highly abundant proteins involve slow separations which impart considerable dilution to the samples. Furthermore, most techniques lack the ability to process multiple samples simultaneously. We present a method of protein depletion using superparamagnetic beads coated in anti-HSA, Protein A, and Protein G, manipulated by digital microfluidics (DMF). The depletion process was capable of up to 95% protein depletion efficiency for IgG and HSA in 10 min for four samples simultaneously, which resulted in an approximately 4-fold increase in signal-to-noise ratio in MALDI-MS analysis for a low abundance protein, hemopexin. This rapid and automated method has the potential to greatly improve the process of biomarker identification.

A systematic analysis of defect textures in faceted nanoparticles with polygonal configurations embedded in a nematic matrix is performed using the Landau-de Gennes model, homeotropic strong anchoring in a square domain with uniform alignment in the outer boundaries. Defect and textures are analyzed as functions of temperature T, polygon size R, and polygon number N. For nematic nanocomposites, the texture satisfies a defect charge balance equation between bulk and surface (particle corner) charges. Upon decreasing the temperature, the central bulk defects split and together with other -1/2 bulk defects are absorbed by the nanoparticle's corners. Increasing the lattice size decreases confinement and eliminates bulk defects. Increasing the polygon number increases the central defect charge at high temperature and the number of surface defects at lower temperatures. The excess energy per particle is lower in even than in odd polygons, and it is minimized for a square particle arrangement. These discrete modeling results show for first time that, even under strong anchoring, defects are attached to particles as corner defects, leaving behind a low energy homogeneous orientation field that favors nanoparticle ordering in nematic matrices. These new insights are consistent with recent thermodynamic approaches to nematic nanocomposites that predict the existence of novel nematic/crystal phases and can be used to design nanocomposites with orientational and positional order.

Two dimensional texture simulations, based on the Landau-de Gennes equations of nematodynamics in the absence of flow, were carried out for nematics with embedded faceted binary and multiple particles using temperature, size, and density as topological control variables. The stable modes obtained from kinetic simulations are summarized in texture phase diagrams in terms of temperature, particle separation and particle size. The key novelty in 2D faceted particles is the presence of corners that are sources/sinks of disclination lines or active corner defects. Under close corner-to-corner proximity, disclination lines form inter-or intra-particle links, while under larger distances, surface defects decorate the corners. This generic geometric behaviour is modulated by temperature since the line tension of disclinations decreases with increasing temperature. The characteristic texture diagrams show that for nanoparticles, increasing particle separation results in a disclination mode sequence of linked particles, cross-linked particles, and intra-particle disclinations. For colloidal particles, increasing size results in a mode sequence of linked particles and isolated particles with corner defects. For intermediate particle size, a continuous evolution of the phase diagrams from the former to the latter is demonstrated. At low temperatures, increasing interparticle distances leads to a defect breakage at a critical value independent of particle size. Multimer particle assemblies form stable filaments via a corner-to-corner interparticle disclination linkage mechanism. The stability of the multimers to bending is characterized using curvature as a topological control variable. As stretchingdriven instabilities in binary particles give rise to surface defects modes, bending-driven instabilities give rise also to multi-particle rings with corner decorated surface defects. The integrated texture phase diagrams, topological transitions, tension and bending-driven instabilities demonstrate the potential functionality of faceted particle liquid crystal nanocomposites.

Introduction: both natural and anthropogenic activities add mercury (Hg) to the atmosphere. The speciation and chemical transformation of mercury in the atmosphere can significantly influence how it is deposited on the earth’s surface. Methods: To better understand the impact of urban emissions on global mercury cycling, we developed an inexpensive technique for the reliable measurement of gaseous oxidized mercury (GOM) in air. This simple technique is based on a thermal decomposition-difference method previously developed by others for aircraft studies of gom in the remote troposphere. measurements of total atmospheric mercury (TAM) were made by decomposing all forms of mercury in ambient air to gaseous elemental mercury (GEM) at 500°c prior to detection using cold vapour atomic fluorescence spectroscopy (CVAFS). The amount of gom was determined through the difference between TAM and GEM values. results and discussion: a diurnal pattern was found for GEM, with the highest concentrations of Hg species found ranging from 2:00 to 5:00 pm and the lowest and most stable values from 9:00 pm to 6:00 am. The amount of GOM was estimated on the 5th floor balcony of pavillon prépresident-Kennedy at université de Québec à montréal to be 14.7 ± 10.3 ng∙m-3 (arithmetic mean from eight groups of Tam-gem differences in the afternoons of july 12 and 14, 2011 and 95% confidence interval). The inconsistent GOM result, in addition to a large error value, suggests the need for further investigation, and to compare the efficiency of this method to previously established methods to identify and quantify the mercury species in urban gom.