Automated cellular sample preparation using a Centrifuge-on-a-Chip

The standard centrifuge is a laboratory instrument widely used by biologists and medical technicians for preparing cell samples. Efforts to automate the operations of concentration, cell separation, and solution exchange that a centrifuge performs in a simpler and smaller platform have had limited success. Here, we present a microfluidic chip that replicates the functions of a centrifuge without moving parts or external forces. The device operates using a purely fluid dynamic phenomenon in which cells selectively enter and are maintained in microscale vortices. Continuous and sequential operation allows enrichment of cancer cells from spiked blood samples at the mL min(-1) scale, followed by fluorescent labeling of intra- and extra-cellular antigens on the cells without the need for manual pipetting and washing steps. A versatile centrifuge-analogue may open opportunities in automated, low-cost and high-throughput sample preparation as an alternative to the standard benchtop centrifuge in standardized clinical diagnostics or resource poor settings.     

Isolated Pd Sites on the Intermetallic PdGa(111) and PdGa($\bar 1$$\bar 1$$\bar 1$) Model Catalyst Surfaces

Scratching the surface: The high selectivity of PdGa catalysts towards the partial hydrogenation of acetylene was previously attributed to the separation of Pd atomic sites at the surfaces. The atomic structures of PdGa surfaces are determined by means of a combined experimental and computational approach, allowing investigation of the catalytic dissociation of hydrogen. The two opposite (111) and ${{\left( {\bar 1\bar 1\bar 1} \right)}}$ surfaces show a very different arrangement of catalytic centers.     

Nanodiamonds in sugar rings: an experimental and theoretical investigation of cyclodextrin-nanodiamond inclusion complexes

We report on the noncovalent interactions of nanodiamond carboxylic acids derived from adamantane, diamantane, and triamantane with β- and γ-cyclodextrins. The water solubility of the nanodiamonds was increased by attaching an aromatic dicarboxylic acid via peptide coupling. Isothermal titration calorimetry experiments were performed to determine the thermodynamic parameters (K(a), ΔH, ΔG and ΔS) for the host-guest inclusion. The stoichiometry of the complexes is invariably 1:1. It was found that K(a), ΔG and ΔH of inclusion increase for larger nanodiamonds. ΔS is generally positive, in particular for the largest nanodiamonds. β-Cyclodextrin binds all nanodiamonds, γ-cyclodextrin clearly prefers the most bulky nanodiamonds. The interaction of 9-triamantane carboxylic acid shows one of the strongest complexation constants towards γ-cyclodextrin ever reported, K(a) = 5.0 × 10(5) M(-1). In order to gain some insight into the possible structural basis of these inclusion complexes we performed density functional calculations at the B97-D3/def2-TZVPP level of theory.     

Precipitation-driven self-sorting of imines

Judicious choice of precipitation conditions can lead to self-sorting of equilibrating mixtures of aromatic aldehydes and substituted anilines into a handful of imine products. The selectivity of this process is caused by the solubility differences among possible imines in the EtOH-H(2)O solvent mixtures used in precipitation.     

Use of anisotropic atom-atom potential functions in lattice-dynamical calculations for solid nitrogen

For solid nitrogen, a set of ‘anisotropic’ atom-atom semi-empirical potential functions, which are easily derived from the usual ‘6-exp’ or ‘12-6’, eliminates the difficulties encountered in demonstrating the stability of the γ-phase in lattice-dynamical calculations according to the Born-von Karman procedure.

Negative eigenvalues of the dynamical matrices in certain regions of the Brillouin zone disappear, the agreement with experimental data improves and the α-γ transition is foreseen.     

An algorithm to estimate anatomical connectivity between brain regions using diffusion MRI

The study of anatomical connectivity is essential for interpreting functional MRI data and for establishing how brain areas are linked together into networks to support higher-order functions. Diffusion-weighted MR images (DWI) and tractography provide a unique noninvasive tool to explore the connectional architecture of the brain. The identification of anatomical circuits associated with a specific function can be better accomplished by the joint application of diffusion and functional MRI. In this article, we propose a simple algorithm to identify the set of pathways between two regions of interest. The method is based upon running deterministic tractography from all possible starting positions in the brain and selecting trajectories that intersect both regions. We compare results from single-fiber tractography using diffusion tensor imaging and from multi-fiber tractography using reduced-encoding persistent angular structure (PAS) MRI on standard DWI datasets from healthy human volunteers. Our results show that, in comparison with single-fiber tractography, the multi-fiber technique reveals additional putative routes of connection. We demonstrate highly consistent results of the proposed technique over a cohort of 16 healthy subjects.     

Global compactness for a class of quasi-linear elliptic problems

We prove a global compactness result for Palais-Smale sequences associated with a class of quasi-linear elliptic equations on exterior domains.     

On the Dalgaard-Strulik Model with Logistic Population Growth Rate and Delayed-Carrying Capacity

Recently Dalgaard and Strulik have proposed (in Resour. Energy Econ. 33:782–797, 2011) an energy model of capital accumulation based on the mathematical framework developed by Solow-Swan and coupled with Cobb-Douglas production function (Solow in Q. J. Economics 70:65–94, 1956; Swan in Econ. Rec. 32(63):334–361, 1956). The model is based on a constant rate of population growth assumption. The present paper, according to the analysis performed by Yukalov et al. (Physica D 238:1752–1767, 2009), improves the Dalgaard-Strulik model by introducing a logistic-type equation with delayed carrying capacity which alters the asymptotic stability of the relative steady state. Specifically, by choosing the time delay as a bifurcation parameter, it turns out that the steady state loses stability and a Hopf bifurcation occurs when time delay passes through critical values. The results are of great interest in the applied and theoretical economics.