Search results for "layer"

Efficient Degradation of 4-Nitrophenol by Using Functionalized Porphyrin TiO2 Photocatalysts Under Visible Irradiation

2007

Abstract The novel porphyrins 5,10,15,20-tetra-[4-(3-phenoxy)-propoxy]phenyl porphyrin, H2Pp(a) and 5,10,15,20-tetra-[2-(3-phenoxy)-propoxy]phenyl porphyrin, H2Pp(b) and their corresponding copper(II) complexes CuPp(a), CuPp(b) were synthesized and characterized by using various spectroscopic techniques. The photocatalytic activity of polycrystalline TiO2 samples impregnated with H2Pp(a), H2Pp(b), CuPp(a) and CuPp(b) as sensitizers have been investigated by carrying out the photo-degradation of 4-nitrophenol (4-NP) as a probe reaction in aqueous suspension and under visible light. The maximum photocatalytic activity was obtained using TiO2 loaded with a monolayer of the copper porphyrin CuP…

Defect incorporation in In-containing layers and quantum wells: Experimental analysis via deep level profiling and optical spectroscopy

2020

Abstract Recent studies demonstrated that the performance of InGaN/GaN quantum well (QW) light emitting diodes (LEDs) can be significantly improved through the insertion of an InGaN underlayer (UL). The current working hypothesis is that the presence of the UL reduces the density of non-radiative recombination centers (NRCs) in the QW itself: during the growth of the UL, surface defects are effectively buried in the UL, without propagating towards the QW region. Despite the importance of this hypothesis, the concentration profile of defects in the quantum wells of LEDs with and without the UL was never investigated in detail. This paper uses combined capacitance-voltage and steady-state pho…

Normalization of sphingomyelin levels by 2-hydroxyoleic acid induces autophagic cell death of SF767 cancer cells

2012

The very high mortality rate of gliomas reflects the unmet therapeutic need associated with this type of brain tumor. We have discovered that the plasma membrane fulfills a critical role in the propagation of tumorigenic signals, whereby changes in membrane lipid content can either activate or silence relevant pathways. We have designed a synthetic fatty acid, 2-hydroxyoleic acid (2OHOA), that specifically activates sphingomyelin synthase (SGMS), thereby modifying the lipid content of cancer cell membranes and restoring lipid levels to those found in normal cells. In reverting, the structure of the membrane by activating SGMS, 2OHOA inhibits the RAS-MAPK pathway, which in turn fails to acti…

Neural network approach to solving fuzzy nonlinear equations using Z-numbers

2020

In this article, the fuzzy property is described by means of the Z-number as the coefficients and variables of the fuzzy equations. This alteration for the fuzzy equation is appropriate for system modeling with Z-number parameters. In this article, the fuzzy equation with Z-number coefficients and variables is tended to be used as the models for the uncertain systems. The modeling issue related to the uncertain system is to obtain the Z-number coefficients and variables of the fuzzy equation. Nevertheless, it is extremely hard to get the Z-number coefficients of the fuzzy equations. In this article, in order to model the uncertain nonlinear systems, a novel structure of the multilayer neura…

Thin-layer affinity chromatography in analysis of protein-ligand affinity.

1996

The membrane environment modulates self-association of the human GpA TM domain--implications for membrane protein folding and transmembrane signaling.

2010

Abstract The influence of lipid bilayer properties on a defined and sequence-specific transmembrane helix–helix interaction is not well characterized yet. To study the potential impact of changing bilayer properties on a sequence-specific transmembrane helix–helix interaction, we have traced the association of fluorescent-labeled glycophorin A transmembrane peptides by fluorescence spectroscopy in model membranes with varying lipid compositions. The observed changes of the glycophorin A dimerization propensities in different lipid bilayers suggest that the lipid bilayer thickness severely influences the monomer–dimer equilibrium of this transmembrane domain, and dimerization was most effici…

Electronic and mechanical characterization of self-assembled alkanethiol monolayers by scanning tunneling microscopy combined with interaction-force-…

1993

We have used scanning tunneling microscopy to study self-assembled monolayers of mercaptohexadecanol in ultrigh vacuum. In addition to tunneling, the interaction force gradient acting between tip and sample was measured. Analysis of the force-gradient data shows that the tip is in mechanical contact with the surface of the monolayer which, in turn, is elastically compressed. The lateral dimensions of the mechanical contact are substantially (approximately five times) larger than the width of the tunneling-current filament. The results suggest that the compression of the monolayer constitutes an integral part of tunneling through the molecules

Linked Analysis of Large Cooperative, Allosteric Systems: The Case of the Giant HBL Hemoglobins

2008

Homotropic and heterotropic allosteric interactions are important mechanisms that regulate protein function. These mechanisms depend on the ability of oligomeric protein complexes to adopt different conformations and to transmit conformation-linked signals from one subunit of the complex to the neighboring ones. An important step in understanding the regulation of protein function is to identify and characterize the conformations available to the protein complex. This task becomes increasingly challenging with increasing numbers of interacting binding sites. However, a large number of interacting binding sites allows for high homotropic interactions (cooperativity) and thus represents the m…

Generation of proteoliposomes from subcellular fractions.

1998

Intracellular membranes are highly dynamic, yet they retain their identity and functional characteristics. Integral membrane proteins, which must confer this specific membrane identity, remain poorly characterized at the biochemical level, largely because detergent-mediated solubilization is required for purification and analysis, and several properties of integral membrane proteins can only be investigated when the molecule is properly embedded in a lipid bilayer. We present a method for the efficient reconstitution into proteoliposomes of integral membrane proteins from subcellular fractions. Integral membrane proteins were identified on high-resolution two-dimensional gels after selectiv…

Link adaptation with combined optimal frame size and rate selection in error-prone 802.11n networks

2008

In error-prone channel with low SNRs, the network throughput may drop significantly if the packet length becomes too large. On the other hand, too much protocol overhead will be introduced if the packet length is too small. In this paper, we study this tradeoff and propose an adaptive frame size algorithm for A-MPDU in 802.11n networks, which can maximize the throughput by selecting the optimized frame length under different channel conditions. When used together with rate selection, the network throughput can be further improved. Both analytical model and simulation results are presented, demonstrating that our algorithm outperforms the fixed length transmission scheme in 802.11n networks …