Optimized ratiometric calcium sensors for functional in vivo imaging of neurons and T lymphocytes

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature Methods 11 (2014): 175-182, doi:10.1038/nmeth.2773.The quality of genetically encoded calcium indicators (GECIs) has improved dramatically in recent years, but high-performing ratiometric indicators are still rare. Here we describe a series of fluorescence resonance energy transfer (FRET)-based calcium biosensors with a reduced number of calcium binding sites per sensor. These ‘Twitch’ sensors are based on the C-terminal domain of Opsanus troponin C. Their FRET responses were optimized by a large-scale functional screen in bacterial colonies, refined by a secondary screen in rat hippocampal neuron cultures. We tested the in vivo performance of the most sensitive variants in the brain and lymph nodes of mice. The sensitivity of the “Twitch” sensors matched that of synthetic calcium dyes and allowed visualization of tonic action potential firing in neurons and high resolution functional tracking of T lymphocytes. Given their ratiometric readout, their brightness, large dynamic range and linear response properties, Twitch sensors represent versatile tools for neuroscience and immunology.2014-07-0

Evaluation of flight efficiency for Stockholm Arlanda Airport arrivals

Analysis of punctuality of airport arrivals, as well as identification of causes of the delays within transition airspace, is an important step in evaluating performance of the Terminal Maneuvering Area (TMA) Air Navigation Services: without knowing the current performance levels, it is difficult to identify which areas could be improved. Deviations from the flight plans is one of the major reasons for arrival delays. In this work, we quantified the impact of the deviations from the flight plans on the fuel burn. One of the main reasons of fuel waste is non- optimal vertical profiles during the descent phase. We calculated how much extra fuel is wasted due to vertical flight inefficiency within Stockholm TMA.Peer ReviewedPostprint (published version

Effects of Edge Oxidation on the Structural, Electronic, and Magnetic Properties of Zigzag Boron Nitride Nanoribbons

The effects of edge chemistry on the relative stability and electronic properties of zigzag boron nitride nanoribbons (ZBNNRs) are investigated. Among all functional groups considered, fully hydroxylated ZBNNRs are found to be the most energetically stable. When an in-plane external electric field is applied perpendicular to the axis of both hydrogenated and hydroxylated ZBNNRs, a spin-polarized half-metallic state is induced, whose character is different than that predicted for zigzag graphene nanoribbons. The onset field for achieving the half-metallic state is found to mainly depend on the width of the ribbon. Our results indicate that edge functionalization of ZBNNRs may open the way for the design of new nanoelectronic and nanospintronic devices

Selectivity of a Graphene Nanoribbon-Based Trinitrotoluene Detector: A Computational Assessment

A computational study investigating the suitability of zigzag graphene nanoribbons to serve as selective chemical detectors for trinitrotoluene is presented. Using lithium adatoms as surface anchoring sites, we find that chemisorption of different chemical precursors serving in the trinitrotoluene synthesis process induces unique and distinguishable fingerprints on the electronic structure of the underlying nanoribbon. Furthermore, mixed adsorption of trinitrotoluene and its various chemical precursors may allow the determination of the specific synthesis route used to produce this commonly used explosive material. The understanding of the contaminant adsorption process gained in this study suggests that lithium-decorated graphene nanoribbons may serve as selective chemical detectors

Edge Chemistry Effects on the Structural, Electronic, and Electric Response Properties of Boron Nitride Quantum Dots

The effects of edge hydrogenation and hydroxylation on the relative stability and electronic properties of hexagonal boron nitride quantum dots (<i>h</i>-BNQDs) are investigated. Zigzag edge hydroxylation is found to result in considerable energetic stabilization of <i>h</i>-BNQDs as well as a reduction of their electronic gap with respect to their hydrogenated counterparts. The application of an external in-plane electric field leads to a monotonous decrease of the gap. When compared to their edge-hydrogenated counterparts, significantly lower field intensities are required to achieve full gap closure of the zigzag edge hydroxylated <i>h</i>-BNQDs. These results indicate that edge chemistry may provide a viable route for the design of stable and robust electronic devices based on nanoscale hexagonal boron-nitride systems

Robust Superlubricity in Graphene/<i>h</i>‑BN Heterojunctions

The sliding energy landscape of the heterogeneous graphene/<i>h</i>-BN interface is studied by means of the registry index. For a graphene flake sliding on top of <i>h</i>-BN, the anisotropy of the sliding energy corrugation with respect to the misfit angle between the two naturally mismatched lattices is found to reduce with the flake size. For sufficiently large flakes, the sliding energy corrugation is expected to be at least an order of magnitude lower than that obtained for matching lattices regardless of the relative interlayer orientation. Therefore, in contrast to the case of the homogeneous graphene interface where flake reorientations are known to eliminate superlubricty, here, a stable low-friction state is expected to occur. Our results mark heterogeneous layered interfaces as promising candidates for dry lubrication purposes