Search results for "Ultra"

Valence bands of poly(methylmethacrylate) and photoion emission in vacuum ultraviolet region

1992

Photoion and photoelectron yields were measured for poly(methylmethacrylate) in the photon energy region of 8–40 eV using synchrotron radiation. Further, the valence‐band structure was investigated with ultraviolet photoelectron spectra and valence effective Hamiltonian calculations. A significant difference was observed between the photon energy dependencies of photoion and photoelectron yields. The threshold energy for photoion emission was found to be 10.5 eV, while that for photoelectron emission was 8.5 eV, indicating holes created near the valence‐band top do not contribute to the ion emission. At the higher‐energy region, the ion emission efficiency was found to be enhanced in the ph…

Cuando la izquierda quiere ser de centro

2002

Electrochemical study of intramolecular charge transfer complexes derived from 1,4-naphthoquinone Part 1. Electroreduction

1995

Abstract Electrochemical investigations (polarography, cyclic voltammetry, rotating ring-disk electrode voltammetry) of intramolecular charge transfer complexes (AC) derived from 1,4-naphthoquinone were performed in acetonitrile. It is concluded that in the first one-electron stage of its electrochemical reduction the AC is in a complexed form. At the same time the amino moiety, which shows a marked inductive (−I) effect, acts as an electron donor in the donor-acceptor (D-A) interaction. Facilitation of the reduction of the quinone part by the aryl amine residue is compensated by the D-A interaction, which makes the electroreduction more difficult. By using ultramicroelectrodes it was shown…

Multi-functional hindered amine light stabilizers-functionalized carbon nanotubes for advanced ultra-high molecular weight Polyethylene-based nanocom…

2015

Hindered Amine Light Stabilizer (HAS) molecules have been covalently linked on the outer surface of multi-walled carbon nanotubes (CNTs), and the so-obtained multi-functional fillers (HAS-f-CNTs) have been compounded with Ultra High Molecular Weight Polyethylene (UHMWPE) to get composite films. The success of the grafting reaction of the HAS molecules has been confirmed through spectroscopic and thermo-gravimetric analyses. Morphological analyses reveal a segregated microstructure, in which CNT-rich channels surround the polymer domains. This morphology results in improved mechanical properties and appreciable electrical conductive features. More importantly, the addition of only 1 wt.% of …

Studies on the structure of coumarin-modified dextran nanoparticles by fluorescence spectroscopy.

2012

The photophysical and photochemical characteristics of nano-scaled particles obtained via solvent displacement from coumarin-modified dextrans were studied by means of absorption- and fluorescence-spectroscopy. The environment-dependent fluorescence emission of the pendant 4-methyl-7-alkoxy coumarin groups was exploited as a probe to gain information about the inner structure of the polysaccharide based nanoparticles. Time-resolved fluorescence measurements showed that the particles had two domains of different polarity and it could be confirmed that the core of the nano-assemblies contained water. Moreover, preliminary experiments were carried out demonstrating the possibility to control t…

BIOADHESIVE PROPERTIES OF A POLYAMINOACIDIC HYDROGEL: EVALUATION BY ATR FT-IR SPECTROSCOPY

2005

The bioadhesive properties of a novel chemical hydrogel based on a polymer of protein-like structure, have been investigated by using ATR FT-IR spectroscopy. In particular, the copolymer PHG obtained by partial derivatization of PHEA with GMA was chemically crosslinked by UV irradiation at 313 nm. Crosslinked PHG was treated with water to obtain a swelled sample, named PHG-UV gel, that was brought into contact with a phosphate buffer/citric acid solution at pH 7.0 in the absence or in the presence of mucin at various concentrations (0.01, 0.1 and 1 wt.-%). Preliminary dynamic swelling studies have evidenced the occurrence of an interaction between the PHG-UV gel and the glycoprotein. This r…

UV-photocrosslinking of inulin derivatives to produce hydrogels for drug delivery application.

2005

In this work, INU, a natural polysaccharide, has been chemically modified in order to obtain new photocrosslinkable derivatives. To reach this goal, INU has been derivatized with MA thus obtaining four samples (INU-MA derivatives) as a function of the temperature and time of reaction. An aqueous solution of the derivative INU-MA1 was irradiated by using a UV lamp with an emission range from 250 to 364 nm and without using photoinitiators. The obtained hydrogel showed a remarkable water affinity but it underwent a partial degradation in simulated gastric fluid. To overcome this drawback, INU-MA 1 was derivatized with SA thus obtaining the INU-MA1-SA derivative designed to produce a hydrogel …

Plasma Polymer Membranes for Immobilising Metalloporphyrins

2013

Atmospheric pressure dielectric barrier discharge formation of organosilicon thin films loaded with zinc 5,10,15,20-tetraphenylporphyrin (Zn(TPP)) was investigated for different deposition conditions. UV–visible spectroscopy and scanning electron microscopy revealed the effects of the metalloporpyhrins injection parameters and the plasma polymerisation conditions can affect the dispersion of the metalloporphyrins and the morphology of the coatings. The stability of the embedded Zn(TPP) molecules was investigated by orbitrap mass spectrometry.

CONTROLLED RELEASE OF IgG BY NOVEL UV INDUCED POLYSACCHARIDE/POLY(AMINO ACID)HYDROGELS

2009

The development of new protein and peptide drugs needs new delivery systems able to entrap such drugs in safe conditions without affecting their structure and biological activity. In this context, the present work reports a new approach to load IgG, used as a model of therapeutic proteins such as anti-TNF-alpha monoclonal antibodies, into a polymeric system able to release the entrapped IgG in a controlled manner. In particular, new polysaccharide/poly(amino acid) UV induced hydrogels are proposed as colon delivery systems for human IgG. The poly(amino acid), alpha,beta-poly[N-(2-hydroxyethyl)-D,L-aspartamide], has been functionalized with methacrylic anhydride, while the polysaccharide, in…

Copper carbonate as a solid-bed reactor for spectrophotometric determination of doxycycline and oxytetracycline in an unsegmented continuous flow ass…

1993

The FIA-spectrophotometric determination of doxycycline was carried out by reaction of the drug with cupric ions entrapped in a polymeric material in a packed-bed reactor: the complex formed was then injected into a manifold with an alkaline solution as carrier. The developed colour was monitored at 395.0 nm. The method was applied to the determination of doxycycline in different pharmaceutical formulations. The calibration graph for doxycycline hyclate was linear over the range 10.0-80.0 mg ml-1 (n = 8) with a relative standard deviation of 1.4% (at 25 mg ml-1) and a sample throughput of 128 h-1. The proposed procedure was also applied to the determination of oxytetracycline in pharmaceuti…