Manipulation and control of droplets on surfaces in a homogeneous electric field

A method to manipulate and control droplets on a surface is presented. The method is based on inducing electric dipoles inside the droplets using a homogeneous external electric field. It is shown that the repulsive dipole force efficiently suppresses the coalescence of droplets moving on a liquid-infused surface (LIS). Using a combination of experiments, numerical computations and semi-analytical models, the dependence of the repulsion force on the droplet volumes, the distance between the droplets and the electric field strength is revealed. The method allows to suppress coalescence in complex multi-droplet flows and is real-time adaptive. When the electric field strength exceeds a critical value, tip streaming from the droplets sets in. Based on that, it becomes possible to withdraw minute samples from an array of droplets in a parallel process.

Quantum unitary dynamics of a charged fermionic field and Schwinger effect

In quantum field theory, particle creation occurs, in general, when an intense external field, such as an electromagnetic field, breaks time translational invariance. This leads to an ambiguity in the definition of the vacuum state. In cosmological backgrounds this ambiguity has been reduced by imposing that the quantization preserves the symmetries of the system and that the dynamics is unitarily implemented. In this work, we apply these requirements to the quantization of a massive charged fermionic field coupled to a classical time-dependent homogeneous electric field, extending previous studies done for a scalar field. We characterize the quantizations fulfilling the criteria above and we show that they form a unique equivalence class of unitarily related quantizations, which provide a well-defined number of created particles at all finite times.

Non-canonical outcomes of break-induced replication produce complex, extremely long-tract gene conversion events in yeast

Long-tract gene conversions (LTGC) can result from the repair of collapsed replication forks, and several mechanisms have been proposed to explain how the repair process produces this outcome. We studied LTGC events produced from repair collapsed forks at yeast fragile site FS2. Our analysis included chromosome sizing by contour-clamped homogeneous electric field (CHEF) electrophoresis, next-generation whole genome sequencing, and Sanger sequencing across repair event junctions. We compared the sequence and structure of LTGC events in our cells to the expected qualities of LTGC events generated by proposed mechanisms. Our evidence indicates that some LTGC events arise from half-crossover during BIR, some LTGC events arise from gap repair, and some LTGC events can be explained by either gap repair or “late” template switch during BIR. Also based on our data, we propose that models of collapsed replication forks be revised to show not a one-end double-strand break (DSB), but rather a two-end DSB in which the ends are separated in time and subject to gap repair.

Absence of embedded eigenvalues for Hamiltonian with crossed magnetic and electric fields

In the presence of the homogeneous electric field [Formula: see text] and the homogeneous perpendicular magnetic field [Formula: see text], the classical trajectory of a quantum particle on [Formula: see text] moves with drift velocity [Formula: see text] which is perpendicular to the electric and magnetic fields. For such Hamiltonians, the absence of the embedded eigenvalues of perturbed Hamiltonian has been conjectured. In this paper, one proves this conjecture for the perturbations [Formula: see text] which have sufficiently small support in the direction of drift velocity.

Pore Structures for High-Throughput Nanopore Devices

Nanopore devices are expected to advance the next-generation of nanobiodevices because of their strong sensing and analyzing capabilities for single molecules and bioparticles. However, the device throughputs are not sufficiently high. Although analytes pass through a nanopore by electrophoresis, the electric field gradient is localized inside and around a nanopore structure. Thus, analytes located far from a nanopore cannot be driven by electrophoresis. Here, we report nanopore structures for high-throughput sensing, namely, inverted pyramid (IP)-shaped nanopore structures. Silicon-based IP-shaped nanopore structures create a homogeneous electric field gradient within a nanopore device, indicating that most of the analytes can pass through a nanopore by electrophoresis, even though the analytes are suspended far from the nanopore entrance. In addition, the nanostructures can be fabricated only by photolithography. The present study suggests a high potential for inverted pyramid shapes to serve as nanopore devices for high-throughput sensing.