90 research outputs found
Supramolecular polymerization of sulfated dendritic peptide amphiphiles into multivalent L-selectin binders
The synthesis of a sulfate-modified dendritic peptide amphiphile and its self-assembly into one-dimensional rod-like architectures in aqueous medium is reported. The influence of the ionic strength on the supramolecular polymerization was probed via circular dichroism spectroscopy and cryogenic transmission electron microscopy. Physiological salt concentrations efficiently screen the charges of the dendritic building block equipped with eight sulfate groups and trigger the formation of rigid supramolecular polymers. Since multivalent sulfated supramolecular structures mimic naturally occurring L-selectin ligands, the corresponding affinity was evaluated using a competitive SPR binding assay and benchmarked to an ethylene glycol-decorated supramolecular polymer
Fluorescent PolymerâSingleâWalled Carbon Nanotube Complexes with Charged and Noncharged Dendronized Perylene Bisimides for Bioimaging Studies
Fluorescent nanomaterials are expected to revolutionize medical diagnostic, imaging, and therapeutic tools due to their superior optical and structural properties. Their inefficient water solubility, cell permeability, biodistribution, and high toxicity, however, limit the full potential of their application. To overcome these obstacles, a waterâsoluble, fluorescent, cytocompatible polymerâsingleâwalled carbon nanotube (SWNT) complex is introduced for bioimaging applications. The supramolecular complex consists of an alkylated polymer conjugated with neutral hydroxylated or charged sulfated dendronized perylene bisimides (PBIs) and SWNTs as a general immobilization platform. The polymer backbone solubilizes the SWNTs, decorates them with fluorescent PBIs, and strongly improves their cytocompatibility by wrapping around the SWNT scaffold. In photophysical measurements and biological in vitro studies, sulfated complexes exhibit superior optical properties, cellular uptake, and intracellular staining over their hydroxylated analogs. A toxicity assay confirms the highly improved cytocompatibility of the polymerâwrapped SWNTs toward surfactantâsolubilized SWNTs. In microscopy studies the complexes allow for the direct imaging of the SWNTs' cellular uptake via the PBI and SWNT emission using the 1st and 2nd optical window for bioimaging. These findings render the polymerâSWNT complexes with nanometer size, dual fluorescence, multiple charges, and high cytocompatibility as valuable systems for a broad range of fluorescence bioimaging studies
Enhancement of fluorescent properties of near-infrared dyes using clickable oligoglycerol dendrons
Near-infrared (NIR) fluorescent dyes are gaining increased attention due to
their potential to serve as molecular probes for in vivo imaging. Here, we
demonstrate that oligoglycerol dendrons effectively enhance the fluorescence
properties of an NIR dye by increasing the solubility in water and the
prevention of aggregate formation. First- and second-generation oligoglycerol
dendrons were conjugated to an NIR dye via a dipolar-cycloaddition (click)
reaction. The two new dye conjugates exhibited enhanced NIR fluorescent
emission and considerably higher fluorescent quantum yields than the dye
alone. The high photostability measured for one of the oligoglycerol-linked
dyes, in comparison to commonly used fluorogenic dyes such as Cy5 and Cy7, was
validated using fluorescence microscopy of macrophages
Transient Monte Carlo Simulations for the Optimisation and Characterisation of Monolithic Silicon Sensors
An ever-increasing demand for high-performance silicon sensors requires
complex sensor designs that are challenging to simulate and model. The
combination of electrostatic finite element simulations with a transient Monte
Carlo approach provides simultaneous access to precise sensor modelling and
high statistics. The high simulation statistics enable the inclusion of Landau
fluctuations and production of secondary particles, which offers a realistic
simulation scenario. The transient simulation approach is an important tool to
achieve an accurate time-resolved description of the sensor, which is crucial
in the face of novel detector prototypes with increasingly precise timing
capabilities. The simulated time resolution as a function of operating
parameters as well as the full transient pulse can be monitored and assessed,
which offers a new perspective on the optimisation and characterisation of
silicon sensors.
In this paper, a combination of electrostatic finite-element simulations
using 3D TCAD and transient Monte Carlo simulations with the Allpix Squared
framework are presented for a monolithic CMOS pixel sensor with a small
collection diode, that is characterised by a highly inhomogeneous, complex
electric field. The results are compared to transient 3D TCAD simulations that
offer a precise simulation of the transient behaviour but long computation
times. Additionally, the simulations are benchmarked against test-beam data and
good agreement is found for the performance parameters over a wide range of
different operation conditions
Amplified Cold Transduction in Native Nociceptors by M-Channel Inhibition
Topically applied camphor elicits a sensation of cool, but nothing is known about how it affects cold temperature sensing. We found that camphor sensitizes a subpopulation of menthol-sensitive native cutaneous nociceptors in the mouse to cold, but desensitizes and partially blocks heterologously expressed TRPM8(transient receptor potential cation channel subfamily M member 8). In contrast, camphor reduces potassium outward currents in cultured sensory neurons and, in cold nociceptors, the cold-sensitizing effects of camphor and menthol are additive. Using a membrane potential dye-based screening assay and heterologously expressed potassium channels, we found that the effects of camphor are mediated by inhibition of K(v)7.2/3 channels subtypes that generate the M-current in neurons. In line with this finding, the specific M-current blocker XE991 reproduced the cold-sensitizing effect of camphor in nociceptors. However, the M-channel blocking effects of XE991 and camphor are not sufficient to initiate cold transduction but require a cold-activated inward current generated by TRPM8. The cold-sensitizing effects of XE991 and camphor are largest in high-threshold cold nociceptors. Low-threshold corneal cold thermoreceptors that express high levels of TRPM8 and lack potassium channels are not affected by camphor. We also found that menthol-like camphor-potently inhibits K(v)7.2/3 channels. The apparent functional synergism arising from TRPM8 activation and M-current block can improve the effectiveness of topical coolants and cooling lotions, and may also enhance TRPM8-mediated analgesia
3D Hydrogels Containing Interconnected Microchannels of Subcellular Size for Capturing Human Pathogenic Acanthamoeba Castellanii
3D Hydrogels Containing Interconnected Microchannels of Subcellular Size for Capturing Human Pathogenic Acanthamoeba Castellani
Developing a Monolithic Silicon Sensor in a 65 nm CMOS Imaging Technology for Future Lepton Collider Vertex Detectors
Monolithic CMOS sensors in a 65 nm imaging technology are being investigated
by the CERN EP Strategic R&D Programme on Technologies for Future Experiments
for an application in particle physics. The appeal of monolithic detectors lies
in the fact that both sensor volume and readout electronics are integrated in
the same silicon wafer, providing a reduction in production effort, costs and
scattering material. The Tangerine Project WP1 at DESY participates in the
Strategic R&D Programme and is focused on the development of a monolithic
active pixel sensor with a time and spatial resolution compatible with the
requirements for a future lepton collider vertex detector. By fulfilling these
requirements, the Tangerine detector is suitable as well to be used as
telescope planes for the DESY-II Test Beam facility. The project comprises all
aspects of sensor development, from the electronics engineering and the sensor
design using simulations, to laboratory and test beam investigations of
prototypes. Generic TCAD Device and Monte-Carlo simulations are used to
establish an understanding of the technology and provide important insight into
performance parameters of the sensor. Testing prototypes in laboratory and test
beam facilities allows for the characterization of their response to different
conditions. By combining results from all these studies it is possible to
optimize the sensor layout. This contribution presents results from generic
TCAD and Monte-Carlo simulations, and measurements performed with test chips of
the first sensor submission.Comment: 7 pages, 8 figures, submitted to IEEE Xplore as conference record for
2022 IEEE NSS/MIC/RTS
Search for dark matter produced in association with bottom or top quarks in âs = 13 TeV pp collisions with the ATLAS detector
A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fbâ1 of protonâproton collision data recorded by the ATLAS experiment at âs = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements
The Crowdsourced Replication Initiative: Investigating Immigration and Social Policy Preferences. Executive Report.
In an era of mass migration, social scientists, populist parties and social movements raise concerns over the future of immigration-destination societies. What impacts does this have on policy and social solidarity? Comparative cross-national research, relying mostly on secondary data, has findings in different directions. There is a threat of selective model reporting and lack of replicability. The heterogeneity of countries obscures attempts to clearly define data-generating models. P-hacking and HARKing lurk among standard research practices in this area.This project employs crowdsourcing to address these issues. It draws on replication, deliberation, meta-analysis and harnessing the power of many minds at once. The Crowdsourced Replication Initiative carries two main goals, (a) to better investigate the linkage between immigration and social policy preferences across countries, and (b) to develop crowdsourcing as a social science method. The Executive Report provides short reviews of the area of social policy preferences and immigration, and the methods and impetus behind crowdsourcing plus a description of the entire project. Three main areas of findings will appear in three papers, that are registered as PAPs or in process
- âŠ