A microfabricated electrical SPLITT system

A growing need for methods to analyze and prepare monodisperse nanoparticles on an industrial scale exists and may be solved by the application of split flow thin fractionation (SPLITT) at the microscale. Microfluidic systems of this type have the ability to separate nanoparticles with high precision in a continuous manner. A miniaturized SPLITT system can be fabricated using standard microfabrication technologies, works in a continuous mode, and can be used as a sample preparation instrument in a micro-total-analysis-system (micro-TAS). In this paper, a miniaturized electrical SPLITT system, which separates particles continuously based on electrophoretic mobility, has been characterized. The advantages of miniaturization have been elucidated. The various aspects of the micro SPLITT system discussed in this paper can be broadly classified into: micro SPLITT system design, fluidics modeling to refine the splitter arrangements, and experimental characterization of the SPLITT system. The design of the micro SPLITT system has been elucidated focusing on the two designs that were implemented. Fluid modeling, used to arrive at a new SPLITT design, was done using a commercially available CFD package to investigate behavior of the fluid in the microchannel with various splitter arrangements. Testing was done with nanoparticles of varying diameter and electrophoretic mobilities to verify the modeling results and demonstrate functionality of the SPLITT system. Particles eluted from both outlets of the SPLITT system were characterized using AFM and SEM to verify the function of the system.     

trans‐Bis­[1‐methyl‐3‐(p‐nitro­phenyl)­triazenido 1‐oxide‐κ2N3,O]­di­pyridine­nickel(II)

In the centrosymmetric title complex, [Ni(C₇H₇N₄O₃)₂(C₅H₅N)₂], the coordination geometry about the Ni²⁺ ion is octahedral, with two deprotonated 1‐methyl‐3‐(p‐nitro­phenyl)­triazenide 1‐oxide ions, viz. [O₂N­C₆H₄­NNN(O)­CH₃]^?, acting as bidentate ligands (four‐electron donors). Two neutral pyridine (py) mol­ecules complete the coordination sphere in positions trans to each other. The triazenide 1‐oxide ligand is almost planar, the largest interplanar angle of 8.80 (12)° being between the phenyl ring of the p‐nitro­phenyl group and the plane defined by the N₃O moiety. The Ni—N_triazenide, Ni—O and Ni—N_py distances are 2.0794 (16), 2.0427 (13) and 2.1652 (18) Å, respectively.     

Finite element approximation of a model for phase separation of a multi-component alloy with a concentration-dependent mobility matrix

We consider a model for phase separation of a multi-componentalloy with a concentration-dependent mobility matrix and logarithmicfree energy. In particular we prove that there exists a uniquesolution for sufficiently smooth initial data. Further, we provean error bound for a fully practical piecewise linear finiteelement approximation in one and two space dimensions. Finallynumerical experiments with three components in one space dimensionare presented.     

An alternative procedure for approximating hyperbolic systems of conservation laws

This work presents an alternative numerical procedure for simulating a class of nonlinear hyperbolic systems, using Glimm's method for advancing in time. The standard procedure to implement this methodology suffers from the disadvantage of requiring a complete solution of the associated Riemann problem—a task, in general, not easily reached. The alternative procedure introduced in this article consists in approximating the solution of the associated Riemann problem by piecewise constant functions always satisfying the jump condition—thus circumventing the difficulty of solving the Riemann problem and giving rise to an approximation easier to implement with lower computational cost. In order to illustrate the good performance of the alternative methodology proposed, two problems are considered—namely the transport of a pollutant in the atmosphere and the dynamics of the filling up of a rigid porous medium, modeled under a mixture theory viewpoint. Comparison with the standard procedure, employing the complete solution of the associated Riemann problem for implementing Glimm's scheme, has shown good agreement.     

Nilpotent pseudogroups of functions on an interval

A near-identity nilpotent pseudogroup of order m 1 is a family f ₁, . . . , f _n : (-1, 1) of C ² functions for which: for some small positive real number < 1/10 ^m+1 and commutators of the functions f _i of order at least m equal the identity. We present a classification of near-identity nilpotent pseudogroups: our results are similar to those of Plante, Thurston, Farb and Franks. As an application, we classify certain foliations of nilpotent manifolds.