13 research outputs found
Monitoring Reversible Tight Junction Modulation with a CurrentâDriven Organic Electrochemical Transistor
AbstractThe barrier functionality of a cell layer regulates the passage of nutrients into the blood. Modulating the barrier functionality by external chemical agents like polyâlâlysine (PLL) is crucial for drug delivery. The ability of a cell layer to impede the passage of ions through it and therefore to act as a barrier, can be assessed electrically by measuring the resistance across the cell layer. Here, an organic electrochemical transistor (OECT) is used in a currentâdriven configuration for the evaluation of reversible modulation of tight junctions in Cacoâ2 cells over time. Exposure to low and medium concentrations of PLL initiates reversible modulation, whereas a too high concentration induces an irreversible barrier disruption due to nonfunctional tight junction proteins. The results demonstrate the suitability of OECTs to in situ monitor temporal barrier modulation and recovery, which can offer valuable information for drug delivery applications
Current-Driven Organic Electrochemical Transistors for Monitoring Cell Layer Integrity with Enhanced Sensitivity
AbstractIn this progress report an overview is given on the use of the organic electrochemical transistor (OECT) as a biosensor for impedance sensing of cell layers. The transient OECT current can be used to detect changes in the impedance of the cell layer, as shown by Jimison et al. To circumvent the application of a high gate bias and preventing electrolysis of the electrolyte, in case of small impedance variations, an alternative measuring technique based on an OECT in a currentâdriven configuration is developed. The ionâsensitivity is larger than 1200 mV Vâ1decâ1 at low operating voltage. It can be even further enhanced using an OECT based complementary amplifier, which consists of a pâtype and an nâtype OECT connected in series, as known from digital electronics. The monitoring of cell layer integrity and irreversible disruption of barrier function with the currentâdriven OECT is demonstrated for an epithelial Cacoâ2 cell layer, showing the enhanced ionâsensitivity as compared to the standard OECT configuration. As a stateâofâtheâart application of the currentâdriven OECT, the in situ monitoring of reversible tight junction modulation under the effect of drug additives, like polyâlâlysine, is discussed. This shows its potential for in vitro and even in vivo toxicological and drug delivery studies
Michelson interferometer with diffractively-coupled arm resonators in second-order Littrow configuration
Michelson-type laser-interferometric gravitational-wave (GW) observatories
employ very high light powers as well as transmissively- coupled Fabry-Perot
arm resonators in order to realize high measurement sensitivities. Due to the
absorption in the transmissive optics, high powers lead to thermal lensing and
hence to thermal distortions of the laser beam profile, which sets a limit on
the maximal light power employable in GW observatories. Here, we propose and
realize a Michelson-type laser interferometer with arm resonators whose
coupling components are all-reflective second-order Littrow gratings. In
principle such gratings allow high finesse values of the resonators but avoid
bulk transmission of the laser light and thus the corresponding thermal beam
distortion. The gratings used have three diffraction orders, which leads to the
creation of a second signal port. We theoretically analyze the signal response
of the proposed topology and show that it is equivalent to a conventional
Michelson-type interferometer. In our proof-of-principle experiment we
generated phase-modulation signals inside the arm resonators and detected them
simultaneously at the two signal ports. The sum signal was shown to be
equivalent to a single-output-port Michelson interferometer with
transmissively-coupled arm cavities, taking into account optical loss. The
proposed and demonstrated topology is a possible approach for future
all-reflective GW observatory designs
Metal-Free Intermolecular CâH Borylation of N-Heterocycles at BâB Multiple Bonds
Carbene-stabilized diborynes of the form LBBL (L = NHC or CAAC) induce rapid, high yielding, intermolecular ortho-CâH borylation at N-heterocycles at room temperature. A simple pyridyldiborene is formed when an NHC-stabilized diboryne is combined with pyridine, while a CAAC-stabilized diboryne leads to activation of two pyridine molecules to give a tricyclic alkylideneborane, which can be forced to undergo a further H-shift resulting in a zwitterionic, doubly benzo-fused 1,3,2,5-diazadiborinine by heating. Use of the extended N-heteroaromatic quinoline leads to a borylmethyleneborane under mild conditions via an unprecedented boron-carbon exchange process
Metallfreie intermolekulare C-H-Borylierung von N-Heterocyclen an B-B-Mehrfachbindungen
Carbenstabilisierte Diborine der Form LBBL (L=N-heterocyclisches Carben (NHC) oder cyclisches Alkyl(amino)carben (CAAC)) induzieren bei Raumtemperatur eine schnelle, ertragreiche, intermolekulare ortho-C-H-Borylierung an N-Heterocyclen. Ein einfaches Pyridyldiboren wird gebildet, wenn ein NHC-stabilisiertes Diborin mit Pyridin kombiniert wird, wĂ€hrend ein CAAC-stabilisiertes Diborin zur Aktivierung von zwei PyridinmolekĂŒlen fĂŒhrt, um ein tricyclisches Alkylidenboran zu bilden, das durch Erhitzen zu einem zwitterionischen, zweifach benzokondensierten 1,3,2,5-Diazadiborinin mittels einer weiteren H-Verschiebung umgelagert werden kann. Die Verwendung des verlĂ€ngerten N-heteroaromatischen Chinolins fĂŒhrt unter milden Bedingungen ĂŒber einen bisher unbekannten Bor-Kohlenstoff-Austauschprozess zu einem Borylmethylenboran
Comprehensive study on the formation of grain boundary serrations in additively manufactured Haynes 230 alloy
Recently, grain boundary serrations have been introduced in conventionally processed Haynes 230 through a slow-cooling heat treatment. The aim of this work was to utilize these heat treatments to introduce serrations in additively manufactured (Laser Metal Deposition) Haynes 230. Contrary to expectations, serrations already formed during the fast-cooling of the Laser Metal Deposition process. Electron Backscatter Diffraction was used to elucidate the underlying phenomenon for the emergence of serrations during fast-cooling. As a result, a hypothesis regarding a new mechanism responsible for the formation of grain boundary serrations was formulated. Additionally, specific characteristics of the Laser Metal Deposition process have been identified. This includes a columnar-to-equiaxed transition (CET) for slower feed rates, leading to smaller grains despite lower cooling rates; the observation of an abrupt increase in grain growth for a raised solution annealing temperature; the fact that serrations hinder uncontrolled grain growth and finally that the LMD-process leads to a finer carbide morphology compared to conventional manufacturing methods, potentially leading to an increased precipitation strengthening effect
Stepwise and selective synthesis of chelating, multimetallic and mixed-metal Ï-diborene complexes
The reaction of a pyridyl-substituted, doubly Lewis base-stabilised diborene with different amounts of copper(I) precursors led to the formation of the first chelating Ï-diborene complexes, the first Ï-diborene complexes in which metals are bound to both faces of the B=B bond, and the first mixed-metal Ï-diborene species
Added value by hybrid additive manufacturing and advanced manufacturing approaches
In order to lead to a competitive advantage there is the need to carefully consider the pros and cons of state of the art manufacturing techniques. This is frequently carried out in a competitive manner but can also be done in a complementary way. This complementary approach is often used for the processing of difficult-to-machine materials with particular regard to high tech parts or components. Hybrid machining processes (HMPs) or - more general â advanced machining processes (AMPs) can be brought to the point that the results would not be possible with the individual constituent processes in isolation. Hence, the controlled interaction of process mechanisms and/or energy sources is frequently applied for a significant increase of the process performance and will be addressed within the present paper. A via Electron Beam Melting (EBM) manufactured gamma titanium aluminide (Îł-TiAl) nozzle is extended and adapted. This is done via hybrid Laser Metal Deposition (LMD). The presented approach considers critical impacts like processing temperatures, temperature gradients and solidification conditions with particular regard to crucial material properties like the phenomena of lamellar interface cracking. Furthermore, selected destructive and non-destructive testing is performed in order to prove the material properties. Finally, the results will be evaluated. This will also be done in the perspective of other applications