19 research outputs found
TTF-TCNQ-based thin films and microcrystals - growth and charge transport phenomena
Organische Materialien haben bis zur Mitte des 20. Jahrhunderts hinsichtlich ihrer elektronischen Eigenschaften keine besondere Aufmerksamkeit auf sich gezogen. GrƶĆeres Interesse an diesen Materialien entstand erst durch die Entdeckung einer ungewƶhnlich hohen elektrischen LeitfƤhigkeit des organischen Perylen-Bromin Ladungstransfer-Komplexes durch Inokuchi et al. im Jahr 1954. Diese neue Klasse von Materialien besteht typischerweise aus Donor- und Akzeptor-MolekĆ¼len, die in einer bestimmten Stƶchiometrie aneinander gebunden sind. Elektrische Ladung wird zwischen den Donor- und Akzeptor-MolekĆ¼len transferiert. Um diesen Prozess zu beschreiben, entwickelte Robert Mulliken in den 60er Jahren ein theoretisches GerĆ¼st. AbhƤngig von der Anordnung der MolekĆ¼le und transferierten elektrischen Ladung kann der Ladungstransfer-Komplex (oder Salz) ein Isolator, ein Halbleiter, ein Metall oder sogar ein Supraleiter sein. Noch mehr Aufmerksamkeit erhielten Ladungstransfer-Materialien mit der Entdeckung des ersten quasi-eindimensionalen organischen Metalls TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane) im Jahr 1973. ..
Influence of the substrate-induced strain and irradiation disorder on the Peierls transition in TTF-TCNQ microdomains
The influence of the combined effects of substrate-induced strain, finite
size and electron irradiation-induced defects have been studied on individual
micron-sized domains of the organic charge transfer compound
tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) by temperature-dependent
conductivity and current-voltage measurements. The individual domains have been
isolated by focused ion beam etching and electrically contacted by focused ion
and electron beam induced deposition of metallic contacts. The
temperature-dependent conductivity follows a variable range hopping behavior
which shows a crossover of the exponent as the Peierls transition is
approached. The low temperature behavior is analyzed within the segmented rod
model of Fogler, Teber and Shklowskii, as originally developed for a
charge-ordered quasi one-dimensional electron crystal. The results are compared
with data obtained on as-grown and electron irradiated epitaxial TTF-TCNQ thin
films of the two-domain type
Annexins induce curvature on free-edge membranes displaying distinct morphologies
Annexins are a family of proteins characterized by their ability to bind anionic membranes in response to Ca2+-activation. They are involved in a multitude of cellular functions including vesiculation and membrane repair. Here, we investigate the effect of nine annexins (ANXA1-ANXA7, ANXA11, ANXA13) on negatively charged double supported membrane patches with free edges. We find that annexin members can be classified according to the membrane morphology they induce and matching a dendrogam of the annexin family based on full amino acid sequences. ANXA1 and ANXA2 induce membrane folding and blebbing initiated from membrane structural defects inside patches while ANXA6 induces membrane folding originating both from defects and from the membrane edges. ANXA4 and ANXA5 induce cooperative roll-up of the membrane starting from free edges, producing large rolls. In contrast, ANXA3 and ANXA13 roll the membrane in a fragmented manner producing multiple thin rolls. In addition to rolling, ANXA7 and ANXA11 are characterized by their ability to form fluid lenses localized between the membrane leaflets. A shared feature necessary for generating these morphologies is the ability to induce membrane curvature on free edged anionic membranes. Consequently, induction of membrane curvature may be a significant property of the annexin protein family that is important for their function
Hydrodynamic loading and viscous damping of patterned perforations on microfabricated resonant structures
We examined the hydrodynamic loading of vertically resonating microfabricated plates immersed in liquids with different viscosities. The planar structures were patterned with focused ion beam, perforating various shapes with identical area but varying perimeters. The hydrodynamic loading of various geometries was characterized from resonant frequency and quality factor. In water, the damping increased linearly with the perimeter at 45.4 Ć 10 -3 Ns/m 2, until the perforation\u27s radius was 123% Ā± 13% of the depth of penetration of fluid\u27s oscillation. The added mass effect decreased with perforations and recovered to the level of un-perforated structures when the perforation\u27s radius became smaller than the depth of penetration. Ā© 2012 American Institute of Physics
Fractional CO2 laser ablation leads to enhanced permeation of a fluorescent dye in healthy and mycotic nails-An imaging investigation of laser-tissue effects and their impact on ungual drug delivery
PURPOSE: Conventional oral antifungal therapies for onychomycosis (OM) often do not achieve complete cure and may be associated with adverse effects, medical interactions, and compliance issues restricting their use in a large group of patients. Topical treatment can bypass the systemic side effects but is limited by the physical barrier of the nail plate. Ablative fractional laser (AFL) treatment can be used to improve the penetration of topical drugs into the nail. This study visualized the effects of laser ablation of nail tissue and assessed their impact on the biodistribution of a fluorescent dye in healthy and fungal nail tissue. METHODS: For the qualitative assessment of CO(2) AFL effects on healthy nail tissue, scanning electron microscopy (SEM), coherent antiāStokes Raman scattering microscopy (CARSāM), and widefield fluorescence microscopy (WFM) were used. To quantitate the effect of laserāpretreatment on the delivery of a fluorescent dye, ATTOā647N, into healthy and fungal nail tissue, ablation depth, nail plate thickness, and ATTOā647N fluorescence intensity in three nail plate layers were measured using WFM. A total of 30 nail clippings (healthy nā=ā18, fungal nā=ā12) were collected. An aqueous ATTOā647N solution was directly applied to the dorsal surface of 24 nail samples (healthy nā=ā12, fungal nā=ā12) and incubated for 4āhours, of which half (healthy nā=ā6, fungal nā=ā6) had been pretreated with AFL (30āmJ/mb, 15% density, 300āHz, pulse duration <1āms). RESULTS: Imaging revealed a threeālayered nail structure, an AFLāinduced porous ablation crater, and changes in autofluorescence. While intact fungal samples showed a 106% higher ATTOā647N signal intensity than healthy controls, microporation led to a significantly increased fluorophore permeation in all samples (pā<ā0.0001). AFL processing of nail tissue enhanced topical delivery of ATTOā647N in all layers, (average increase: healthy +108%, fungal +33%), most pronounced in the top nail layer (healthy +122%, fungal +68%). While proportionally deeper ablation craters correlated moderately with higher fluorescence intensities in healthy nail tissue, fungal samples showed no significant relationship. CONCLUSION: Fractional CO(2) laser microporation is a simple way of enhancing the passive delivery of topically applied ATTOā647N. Although the impaired nail plate barrier in OM leads to greater diffusion of the aqueous solution, AFL can increase the permeability of both structurally deficient and intact nails