Spontaneous imbibition in a slit pore: a lattice-gas dynamic mean field study

We present a theoretical study of spontaneous imbibition in a slit pore using a lattice-gas model and a dynamic mean-field theory. Emphasis is put on the influence of the precursor films on the speed of the imbibition front due to liquid mass conservation. This work is dedicated to Bob Evans for his 65th birthday in recognition of his seminal contributions to the theory of fluids in confining geometries.Comment: 17 pages, 13 figure

Physics and application of photon number resolving detectors based on superconducting parallel nanowires

The Parallel Nanowire Detector (PND) is a photon number resolving (PNR) detector which uses spatial multiplexing on a subwavelength scale to provide a single electrical output proportional to the photon number. The basic structure of the PND is the parallel connection of several NbN superconducting nanowires (100 nm-wide, few nm-thick), folded in a meander pattern. PNDs were fabricated on 3-4 nm thick NbN films grown on MgO (TS=400C) substrates by reactive magnetron sputtering in an Ar/N2 gas mixture. The device performance was characterized in terms of speed and sensitivity. PNDs showed a counting rate of 80 MHz and a pulse duration as low as 660ps full width at half maximum (FWHM). Building the histograms of the photoresponse peak, no multiplication noise buildup is observable. Electrical and optical equivalent models of the device were developed in order to study its working principle, define design guidelines, and develop an algorithm to estimate the photon number statistics of an unknown light. In particular, the modeling provides novel insight of the physical limit to the detection efficiency and to the reset time of these detectors. The PND significantly outperforms existing PNR detectors in terms of simplicity, sensitivity, speed, and multiplication noise

High performance NbN nanowire superconducting single photon detectors fabricated on MgO substrates

We demonstrate high-performance nanowire superconducting single photon detectors (SSPDs) on ultrathin NbN films grown at a temperature compatible with monolithic integration. NbN films ranging from 150nm to 3nm in thickness were deposited by dc magnetron sputtering on MgO substrates at 400C. The superconducting properties of NbN films were optimized studying the effects of deposition parameters on film properties. SSPDs were fabricated on high quality NbN films of different thickness (7 to 3nm) deposited under optimal conditions. Electrical and optical characterizations were performed on the SSPDs. The highest QE value measured at 4.2K is 20% at 1300nm

QCA as an approach to make sense of micro-level data-centric practices for policy innovation: a walk-through

The paper explores the potentialities and challenges of using a comparative research method — Qualitative Comparative Analysis (QCA) — as a methodological approach for researching policy innovation. The paper argues for QCA to constitute a rigorous and systematic way to explore policy innovation using micro-level experimental and innovative practices in the public sector as the empirical base. Conceptually, we propose considering the importance of policy workers in policy innovation processes. This proposal addresses a gap in policy innovation research that appears to have mostly focused on entrepreneurship while under-appreciating other individual agency explanations of change (e.g., policy workers). Policy innovation researchers should therefore reframe the concept of policy innovation from an out-based view to a process-based view, while avoiding the development of ideographic knowledge. To address this issue, we provide a walk-through of using QCA as a methodological approach to investigate data-centric practices in the public sector. In the walk-through, we simulate the execution of the first three steps of approaching different cases of data-centric practices through QCA, identifying variables and calibrating them. Other researchers might find this approach useful to investigate similar innovative practices in the public sector in the perspective of policy innovation

C1,γ regularity for singular or degenerate fully nonlinear equations and applications

In this note, we prove C1,γ regularity for solutions of some fully nonlinear degenerate elliptic equations with “superlinear” and “subquadratic” Hamiltonian terms. As an application, we complete the results of Birindelli et al. (ESAIM Control Optim Calc Var, 2019. https://doi.org/10.1051/cocv/2018070) concerning the associated ergodic problem, proving, among other facts, the uniqueness, up to constants, of the ergodic function

Boundary asymptotics of the ergodic functions associated with fully nonlinear operators through a liouville type theorem

We prove gradient boundary blow up rates for ergodic functions in bounded domains related to fully nonlinear degenerate/singular elliptic operators. As a consequence, we deduce the uniqueness, up to constants, of the ergodic functions. The results are obtained by means of a Liouville type classification theorem in half-spaces for infinite boundary value problems related to fully nonlinear, uniformly elliptic operators

A novel bacterial l-arginine sensor controlling c-di-GMP levels in Pseudomonas aeruginosa

Nutrients such as amino acids play key roles in shaping the metabolism of microorganisms in natural environments and in host–pathogen interactions. Beyond taking part to cellular metabolism and to protein synthesis, amino acids are also signaling molecules able to influence group behavior in microorganisms, such as biofilm formation. This lifestyle switch involves complex metabolic reprogramming controlled by local variation of the second messenger 3′, 5′-cyclic diguanylic acid (c-di-GMP). The intracellular levels of this dinucleotide are finely tuned by the opposite activity of dedicated diguanylate cyclases (GGDEF signature) and phosphodiesterases (EAL and HD-GYP signatures), which are usually allosterically controlled by a plethora of environmental and metabolic clues. Among the genes putatively involved in controlling c-di-GMP levels in P. aeruginosa, we found that the multidomain transmembrane protein PA0575, bearing the tandem signature GGDEF-EAL, is an l-arginine sensor able to hydrolyse c-di-GMP. Here, we investigate the basis of arginine recognition by integrating bioinformatics, molecular biophysics and microbiology. Although the role of nutrients such as l-arginine in controlling the cellular fate in P. aeruginosa (including biofilm, pathogenicity and virulence) is already well established, we identified the first l-arginine sensor able to link environment sensing, c-di-GMP signaling and biofilm formation in this bacterium

Low field magnetotransport in strained Si/SiGe cavities

Low field magnetotransport revealing signatures of ballistic transport effects in strained Si/SiGe cavities is investigated. We fabricated strained Si/SiGe cavities by confining a high mobility Si/SiGe 2DEG in a bended nanowire geometry defined by electron-beam lithography and reactive ion etching. The main features observed in the low temperature magnetoresistance curves are the presence of a zero-field magnetoresistance peak and of an oscillatory structure at low fields. By adopting a simple geometrical model we explain the oscillatory structure in terms of electron magnetic focusing. A detailed examination of the zero-field peak lineshape clearly shows deviations from the predictions of ballistic weak localization theory.Comment: Submitted to Physical Review B, 25 pages, 7 figure