Miniaturization to the micrometer and nanometer scale opens up the possibility to probe biology on a length scale where fundamental biological processes take place, such as the epigenetic and genetic control of single cells. To study single cells the necessary devices need to be integrated on a single chip; and, to access the relevant length scales, the devices need to be designed with feature sizes of a few nanometers up to several micrometers. We will give a few examples from the literature and from our own research in the field of miniaturized chip-based devices for DNA analysis, including dielectrophoresis for purification of DNA, artificial gel structures for rapid DNA separation, and nanofluidic channels for direct visualization of single DNA molecules.

A new magnetic separation idea utilizing several ideas from microfabrication and nanomagnetics is presented. The basic idea comes from our earlier work using asymmetry in obstacles and Brownian motion to effect separation of objetcs [10] by moving them in streams whose angle to the hydrodynamic average velocity is a function of the diffusion coefficient of the object. The device we propose here is not technically a Brownian ratchet device but uses the idea of force which acts at angle to the hydrodynamic flow. In our case, the force is generated by a magnetic field gradient which comes from an array of magnetized wires which lie at an angle 0 to a hydrodynamic field flow. The sum of the hydrodynamic force and the magnetic force create a new vector which as in the case of the Brownian ratchet moves the cell out of the main stream direction.

We revisit the scalar O(N ) model in the dimension range 4 < d < 6 and study the effects caused by its metastability. As shown in previous work, this model formally possesses a fixed point where, perturbatively in the 1/N expansion, the operator scaling dimensions are real and above the unitarity bound. Here, we further show that these scaling dimensions do acquire small imaginary parts due to the instanton effects. In d dimensions and for large N , we find that they are of order e −N f (d) , where, remarkably, the function f (d) equals the sphere free energy of a conformal scalar in d − 2 dimensions. The non-perturbatively small imaginary parts also appear in other observables, such as the sphere free energy and two and three-point function coefficients, and we present some of their calculations. Therefore, at sufficiently large N , the O(N ) models in 4 < d < 6 may be thought of as complex CFTs. When N is large enough for the imaginary parts to be numerically negligible, the five-dimensional O(N ) models may be studied using the techniques of numerical bootstrap.Dedicated to the memory of Steve Gubser

We show that a careful analysis of the Navier-Stokes equation in the low Reynolds number limit has two distinct solutions, one valid for a deep, thin curtain of flow and the other for a thin wide flow. We derive a solution to the latter situation and use the results to develop a new way to control fluid flows in thin, wide sheet flow.