“When words become unclear”: unmasking ICT through visual methodologies in participatory ICT4D

AI & SOCIETY - Across the globe, our work and social lives are increasingly integrated with Information and Communication Technologies (ICT), yet massive disparities in the values, uses and...     

A viewpoint on material and design considerations for oesophageal stents with extended lifetime

Journal of Materials Science - Oesophageal stents are meshed tubular implants designed to maintain patency of the oesophageal lumen and attenuate the symptoms of oesophageal cancer. Oesophageal...     

DBS-IC: An adaptive Data Bundling System for Intermittent Connectivity

As mobile and wireless technologies become more pervasive in our society, people begin to depend on network connectivity, regardless of their location. Their mobility, however, implies a dynamic topology where routes to a destination cannot always be guaranteed. The intermittent connectivity that results from this lack of end-to-end connection is a dominant problem that leads to user frustration. Existing research to provide the mobile user with a facade of constant connectivity generally presents mechanisms to handle disconnections when they occur. In contrast, the system we propose in this paper provides ways to handle disconnections before they occur. We present a Data Bundling System for Intermittent Connections (DBS-IC) comprised of a Stationary Agent (SA) and a Mobile Agent (MA). The SA pro-actively gathers data the user has previously specified, and opportunistically sends this data to the MA. The SA groups the user-requested data into one or more data bundles, which are then incrementally delivered to the MA during short periods of connectivity. We fully implement DBS-IC and evaluate its performance via live tests under varying network conditions. Results show that our system decreases data retrieval time by a factor of two in the average case and by a factor of 20 in the best case.     

Investigation into Photoconductivity in Single CNF/TiO<Subscript>2</Subscript>-Dye Core–Shell Nanowire Devices

A vertically aligned carbon nanofiber array coated with anatase TiO₂ (CNF/TiO₂) is an attractive possible replacement for the sintered TiO₂ nanoparticle network in the original dye-sensitized solar cell (DSSC) design due to the potential for improved charge transport and reduced charge recombination. Although the reported efficiency of 1.1% in these modified DSSC’s is encouraging, the limiting factors must be identified before a higher efficiency can be obtained. This work employs a single nanowire approach to investigate the charge transport in individual CNF/TiO₂ core–shell nanowires with adsorbed N719 dye molecules in dark and under illumination. The results shed light on the role of charge traps and dye adsorption on the (photo) conductivity of nanocrystalline TiO₂ CNF’s as related to dye-sensitized solar cell performance.     

Chemoselective Immobilization of Proteins by Microcontact Printing and Bio‐orthogonal Click Reactions

Herein, a combination of microcontact printing of functionalized alkanethiols and site‐specific modification of proteins is utilized to chemoselectively immobilize proteins onto gold surfaces, either by oxime‐ or copper‐catalyzed alkyne–azide click chemistry. Two molecules capable of click reactions were synthesized, an aminooxy‐functionalized alkanethiol and an azide‐functionalized alkanethiol, and self‐assembled monolayer (SAM) formation on gold was confirmed by IR spectroscopy. The alkanethiols were then individually patterned onto gold surfaces by microcontact printing. Site‐specifically modified proteins—horse heart myoglobin (HHMb) containing an N‐terminal α‐oxoamide and a red fluorescent protein (mCherry‐CVIA) with a C‐terminal alkyne—were immobilized by incubation onto respective stamped functionalized alkanethiol patterns. Pattern formation was confirmed by fluorescence microscopy.     

Impact of DNA-surface interactions on the stability of DNA hybrids

The structure and stability of single- and double-stranded DNA hybrids immobilized on gold are strongly affected by nucleotide-surface interactions. To systematically analyze the effects of these interactions, a set of model DNA hybrids was prepared in conformations that ranged from end-tethered double-stranded to directly adsorbed single-stranded (hairpins) and characterized by surface plasmon resonance (SPR) imaging, X-ray photoelectron spectroscopy (XPS), fluorescence microscopy, and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The stabilities of these hybrids were evaluated by exposure to a series of stringency rinses in solutions of successively lower ionic strength and by competitive hybridization experiments. In all cases, directly adsorbed DNA hybrids are found to be significantly less stable than either free or end-tethered hybrids. The surface-induced weakening and the associated asymmetry in hybridization responses of the two strands forming hairpin stems are most pronounced for single-stranded hairpins containing blocks of m adenine (A) nucleotides and n thymine (T) nucleotides, which have high and low affinity for gold surfaces, respectively. The results allow a qualitative scale of relative stabilities to be developed for DNA hybrids on surfaces. Additionally, the results suggest a route for selectively weakening portions of immobilized DNA hybrids and for introducing asymmetric hybridization responses by using sequence design to control nucleotide-surface interactions--a strategy that may be used in advanced biosensors and in switches or other active elements in DNA-based nanotechnology.