Surface modification of poly(ε-caprolactone) using a dielectric barrier discharge in atmospheric pressure glow discharge mode

The role of roughening and functionalization processes involved in modifying the wettability of poly(e-caprolactone) (PCL) after treatment by an atmospheric pressure glow discharge plasma is discussed. The change in the ratio of Cdouble bond; length as m-dashO/C–O bonds is a significant factor influencing the wettability of PCL. As the contact angle decreases, the level of Cdouble bond; length as m-dashO bonds tends to rise. Surface roughness alterations are the driving force for lasting increases in wettability, while the surface functional species are shorter lived. We can approximate from ageing that the increase in wettability for PCL after plasma treatment is 55–60% due to roughening and 40–45% due to surface functionalization for the plasma device investigated.

Scheme for enhancing efficiency in resonant-cavity Schottky photodetectors

It is shown that structuring the top layers of a resonant cavity Schottky photodetector in a way that allows coupling between the wavevector of incident radiation and that of electron-collective oscillations (plasmons) at the surface of the metallic electrode leads to practically zero reflectance in the case of front illuminated devices. This is expected to result in a consequential enhancement in the quantum efficiency in these photodetectors. (C) 2001 Elsevier Science Ltd. All rights reserved.

Involvement of MAPKs in endostatin-mediated regulation of blood-retinal barrier function

Purpose: This study aimed to evaluate the effects of endostatin on tight junction (TJ) integrity in retinal microvascular endothelial cells (RMECs) in vitro and in vivo. Moreover, it was hypothesized that endostatin-induced occludin upregulation regulated VEGF(165)-mediated increases in endothelial cell permeability and involved activation of the MAPK signaling cascade. Endostatin is a 20-kDa fragment of collagen XVIII that has been shown to be efficacious in the eye by preventing retinal neovascularization. Endostatin is a specific inhibitor of endothelial cell proliferation, migration, and angiogenesis and has been reported to reverse VEGF-mediated increases in vasopermeability and to promote integrity of the blood-retinal barrier (BRB). In order to determine the mechanism of endostatin action on BRB integrity, we have examined the effects of endostatin on a number of intracellular pathways implicated in endothelial cell physiology. Methods: C57/Bl6 mice were injected with VEGF(165) and/or endostatin, and the distribution of occludin staining was determined using retinal flatmounts. Western blot analysis of RMECs treated with VEGF(165) and/or endostatin was used to determine changes in occludin expression and p38 MAPK and extracellular regulated kinase (ERK1/ERK2 MAPK) activation, while FD-4 flux across the RMEC monolayer was used to determine changes in paracellular permeability. Results: Endostatin prevented the discontinuous pattern of occludin staining observed at the retinal blood vessels of mice administered an intraocular injection of VEGF(165). It was shown that endostatin activated p38 MAPK 5 min after addition to RMECs and continued to do so for approximately 30 min. Endostatin was also shown to activate ERK1/ERK2 5 min after addition and continued to do so, albeit with less potency, up to and including 15 min after addition. Inhibition of p38 MAPK and ERK1/ERK2 prevented endostatin's ability to upregulate levels of occludin expression. Inhibition of these key signaling molecules was shown to prevent endostatin's ability to protect against VEGF(165)- mediated increases in paracellular permeability in vitro. However, it appears that p38 MAPK may play a more important role in VEGF-mediated permeability, as inhibition of ERK1/ERK2 will not prevent VEGF(165)- mediated permeability compared with control ( untreated) cells or cells treated with both a p38 MAPK inhibitor and VEGF(165). Conclusions: Occludin is important for the maintenance of tight junction integrity in vivo. In a p38 MAPK and ERK1/ERK2 dependent manner, endostatin was shown to upregulate the levels of expression of the tight junction protein occludin. Inhibition of these key MAPK components may prevent endostatin's ability to decrease VEGF(165)-induced paracellular permeability.

Causality, apparent 'superluminality' and reshaping in barrier penetration

We consider tunneling of a nonrelativistic particle across a potential barrier. It is shown that the barrier acts as an effective beam splitter which builds up the transmitted pulse from the copies of the initial envelope shifted in the coordinate space backward relative to the free propagation. Although along each pathway causality is explicitly obeyed, in special cases reshaping can result an overall reduction of the initial envelope, accompanied by an arbitrary coordinate shift. In the case of a high barrier the delay amplitude distribution (DAD) mimics a Dirac delta function, the transmission amplitude is superoscillatory for finite momenta and tunneling leads to an accurate advancement of the (reduced) initial envelope by the barrier width. In the case of a wide barrier, initial envelope is accurately translated into the complex coordinate plane. The complex shift, given by the first moment of the DAD, accounts for both the displacement of the maximum of the transmitted probability density and the increase in its velocity. It is argued that analyzing apparent

Morphology, barrier, and mechanical properties of biaxially deformed poly(ethylene terephthalate)-mica nanocomposites

Nanocomposites of poly(ethylene terephthalate) PET with a partially synthetic fluoromica were prepared by melt mixing and extruded into sheet and subjected to large-scale biaxial stretching. Transmission electron microscopy (TEM) analysis of the mica tactoids showed that biaxial stretching had caused the tactoids to be more orientated and with improved exfoliation. The moduli of the nanocomposites were enhanced with increasing mica loading and the reinforcement effect was higher when the stretch ratio was 2 or 2.5, accommodated by having more aligned tactoids and reduced agglomeration. Enhancement in modulus was less pronounced for a stretch ratio of 3. Storage modulus was enhanced more significantly above the glass transition temperature. The barrier properties were enhanced by addition of mica before and after stretching. The Halpin-Tsai theory underpredicted the relative modulus of the PET nanocomposites, whereas the Nielsen model over-predicted the relative permeability. POLYM. ENG. SCI., 2012. (c) 2011 Society of Plastics Engineers