Controlling Polymer Capture and Translocation by Electrostatic Polymer-Pore Interactions

Polymer translocation experiments typically involve anionic polyelectrolytes such as DNA molecules driven through negatively charged nanopores. Quantitative modelling of polymer capture to the nanopore followed by translocation therefore necessitates the consideration of the electrostatic barrier resulting from like-charge polymer-pore interactions. To this end, in this work we couple mean-field level electrohydrodynamic equations with the Smoluchowski formalism to characterize the interplay between the electrostatic barrier, the electrophoretic drift, and the electro-osmotic liquid flow. In particular, we find that due to distinct ion density regimes where the salt screening of the drift and barrier effects occur, there exists a characteristic salt concentration maximizing the probability of barrier-limited polymer capture into the pore. We also show that in the barrier-dominated regime, the polymer translocation time increases exponentially with the membrane charge and decays exponentially fast with the pore radius and the salt concentration. These results suggest that the alteration of these parameters in the barrier-driven regime can be an efficient way to control the duration of the translocation process and facilitate more accurate measurements of the ionic current signal in the pore

Joint Interference Alignment and Bi-Directional Scheduling for MIMO Two-Way Multi-Link Networks

By means of the emerging technique of dynamic Time Division Duplex (TDD), the switching point between uplink and downlink transmissions can be optimized across a multi-cell system in order to reduce the impact of inter-cell interference. It has been recently recognized that optimizing also the order in which uplink and downlink transmissions, or more generally the two directions of a two-way link, are scheduled can lead to significant benefits in terms of interference reduction. In this work, the optimization of bi-directional scheduling is investigated in conjunction with the design of linear precoding and equalization for a general multi-link MIMO two-way system. A simple algorithm is proposed that performs the joint optimization of the ordering of the transmissions in the two directions of the two-way links and of the linear transceivers, with the aim of minimizing the interference leakage power. Numerical results demonstrate the effectiveness of the proposed strategy.Comment: To be presented at ICC 2015, 6 pages, 7 figure

Inhomogeneous critical current in nanowire superconducting single-photon detectors

A superconducting thin film with uniform properties is the key to realize nanowire superconducting single-photon detectors (SSPDs) with high performance and high yield. To investigate the uniformity of NbN films, we introduce and characterize simple detectors consisting of short nanowires with length ranging from 100nm to 15{\mu}m. Our nanowires, contrary to meander SSPDs, allow probing the homogeneity of NbN at the nanoscale. Experimental results, endorsed by a microscopic model, show the strongly inhomogeneous nature of NbN films on the sub-100nm scale.Comment: 10 pages, 4 figure

Phonon Softening and Direct to Indirect Bandgap Crossover in Strained Single Layer MoSe2

Motivated by recent experimental observations of Tongay et al. [Tongay et al., Nano Letters, 12(11), 5576 (2012)] we show how the electronic properties and Raman characteristics of single layer MoSe2 are affected by elastic biaxial strain. We found that with increasing strain: (1) the E' and E" Raman peaks (E1g and E2g in bulk) exhibit significant red shifts (up to 30 cm-1), (2) the position of the A1' peak remains at 180 cm-1 (A1g in bulk) and does not change considerably with further strain, (3) the dispersion of low energy flexural phonons crosses over from quadratic to linear and (4) the electronic band structure undergoes a direct to indirect bandgap crossover under 3% biaxial tensile strain. Thus the application of strain appears to be a promising approach for a rapid and reversible tuning of the electronic, vibrational and optical properties of single layer MoSe2 and similar MX2 dichalcogenides.Comment: http://link.aps.org/doi/10.1103/PhysRevB.87.12541

The economic importance of migrant entrepreneurship: An application of data envelopment analysis in the Netherlands

In the Anglo-Saxon literature in the past decade, much attention has been paid to the economic importance of ethnic (migrant) entrepreneurship. This type of self-employment appears to provide a vital and creative contribution to the urban economy. The rising size and importance of ethnic entrepreneurship has recently prompted much policy and research interest regarding migrant business in Europe. Also in The Netherlands this new phenomenon is increasingly recognised and regarded as an interesting focus for the city’s Small and Medium Enterprise (SME) policy. Migrant entrepreneurs do not only have a substantial impact on the urban economy, but they also act as role models for socio-economic integration. They often operate in interesting market niches and provide a positive stimulus for creative business-making in modern cities. The present article offers first an overview of the literature on this issue and investigates next empirically the economic performance of Turkish migrant entrepreneurs in the highly skilled and hightech sector in the Netherlands through the use of data envelopment analysis (DEA)

Cultural diversity and urban innovativeness: Personal and business characteristics of urban mirgrant entrepreneurs

This article studies the driving forces for successful migrant entrepreneurship in Amsterdam. Three categories of migrants are investigated: Moroccans, Surinamese and Turks. Particular attention is paid to their personal and business characteristics. An extensive field survey was undertaken to identify the main background factors which influence the success or failure of migrant entrepreneurs. It turns out that personality, work discipline and business ambition are the critical success factors for a good business performance on the part of migrant entrepreneurs. Contrary to our assumption, migrant networks and support systems have no positive or negative influence on business performance. © 2009 Interdisciplinary Centre for Comparative Research in the Social Sciences and ICCR Foundation