We study the charge transfer in multilayer graphene from first principles. We find that highly oriented (Bernal) and misoriented (turbostratic) multilayers show similar charge distributions despite their different electronic structure. We quantify the charge transfer and doping distribution in turbostratic graphene layers, where the screening is affected by vanishing density of states near the Fermi level. The results are in good agreement with an analytic model accounting for the electrostatic interaction and the band filling and point out the importance of system-specific interactions between the surface and the first layer. We find that graphene is an outstanding material for ultrathin electrodes, as most of the benefits of multilayer graphene can be captured with bilayers.

Inkjet printing deposits droplets with a well-controlled narrow size distribution. This paper aims at improving experimental and numerical methods for the optimization of drop formation. We introduce a method to extract the one-dimensional velocity profile inside a single droplet during drop formation. We use a novel experimental approach to capture two detailed images of the very same droplet with a small time delay. The one-dimensional velocity within the droplet is resolved by accurately determining the volume distribution of the droplet. We compare the obtained velocity profiles to a numerical simulation based on the slender jet approximation of the Navier-Stokes equation and we find very good agreement.

Listening is a complex sound selection process thought to be located in the auditory cortex. A biophysically motivated Hopf model of the mammalian cochlea reveals that pitch, a main characteristic in the perception of sound, is already materialized at the level of the mammalian hearing sensor. Here, we provide evidence that major elements of listening may similarly be implemented at the auditory periphery by means of efferent connections to the cochlea that tune the hearing sensor towards an auditory object of interest. The cochlea model we use in our investigations is advocated by its performance quality, the simplicity by which efferent control can be implemented, and by the closeness of the control results compared to the biological data. We tune the Hopf parameters to target on a sound, using pitch as the guiding feature. How well we achieve our goal is tested on real-world sounds and measured by a specifically developed tuning-error measure. The results provide a first estimate of how much the peripheral hearing system can assist a listener in focusing on an auditory signal and, thus, what is contributed by the auditory cortex.

The refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, the refractive index contains rich information related to the metabolism of cells at the cellular and subcellular levels. Here, we report a no-moving-parts approach that provides three-dimensional refractive-index maps of biological samples continuously flowing in a microfluidic channel. Specifically, we use line illumination and off-axis digital holography to record the angular spectra of light scattered from flowing samples at high speed. Applying the scalar diffraction theory, we obtain accurate refractive-index maps of the samples from the measured spectra. Using this method, we demonstrate label-free three-dimensional imaging of live RKO human colon cancer cells and RPMI8226 multiple myeloma cells, and obtain the volume, dry mass, and density of these cells from the measured three-dimensional refractive-index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, shows promise as a quantitative tool for stain-free characterization of a large number of cells.

We present a method by which first-principles calculations are linked quite naturally to experimental observables, which determine and characterize the state of an electrochemical system. The method is based on the formation energies of ions in solution and utilizes a grand canonical framework. This is particularly well suited to use in conjunction with ab initio calculations, since it allows charged defects to be treated individually, rather than requiring the consideration of full charge-neutral reactions. It allows the identification of a region of water stability, the $p\mathrm{H}$ scale, and the electrode potential. We discuss and demonstrate the possibilities and capabilities of the approach by the extraction of ion-hydration energies from the Nernst equation and the construction of a $\text{potential}/p\mathrm{H}$ diagram for zinc by an alternative route deviating from the standard approach used to obtain Pourbaix diagrams.