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At least 433 records · Page 24Linked to original sources
PubMed2004

Dynamic scale theory for characterizing surface morphology of layer-by-layer films of poly(o-methoxyaniline).

The dynamic scale theory and fractal concepts are employed in the characterization of surface morphological properties of layer-by-layer (LBL) films from poly(o-methoxyaniline) (POMA) alternated with poly(vinyl sulfonic acid) (PVS). The fractal dimensions are found to depend on the procedures to fabricate the POMA/PVS multilayers, particularly with regard to the drying procedures. LBL films obtained via drying in ambient air show a more homogeneous surface, compared to films dried under vacuum or a flow of nitrogen, due to a uniform rearrangement of polymer molecules during solvent evaporation.

Absorption↗
PubMed2006

Silica nanowires fabricated with layer-by-layer self-assembled nanoparticles.

In this paper we demonstrate an approach to fabricate silica nanowires by combining "top-down" e-beam lithography and "bottom-up" layer-by-layer (LbL) nano self-assembly techniques. The simple and low-cost LbL self-assembly technique is used to grow silica nanoparticle thin film, while the e-beam lithography based lift-off technique is implemented to pattern the self-assembled thin film to nanometer scale. The silica nanowires fabricated by this method have an average width of 90 nm, while the minimum width obtained is 63 nm. Our experimental results indicate a new approach to fabricate nanowires that can be used in nanoelectronic devices and circuits.

Crystallization↗
PubMed2006

pH sensitive organic-inorganic layered nanomaterials by self-assembly of indigocarmine between the inorganic layers.

New pH sensitive organic-inorganic intercalation compounds having different interlayer spacing were prepared. Zn-Al layered double hydroxide (LDH) is an anion exchangeable inorganic layered compound whose interlayer spacing is 0.76 nm. In the reactions of indigocarmine (IDC) with the calcined Zn-Al LDH at pH = 7 (LDH-IDC7), interlayer spacing increased to 2.25 nm. The interlayer spacing of LDH-IDC7 decreased to 1.89 nm by the treatment in basic solution. In the reaction of IDC with the calcined Zn-Al LDH at pH = 10 (LDH-IDC10), interlayer spacing of the intercalation compounds was 1.89 nm. The interlayer spacing of these intercalation compounds was changed reversibly by the treatments in acidic or basic solution.

Hydrogen-Ion Concentration↗
PubMed2006

Electrostatic layer-by-layer assembly of ultrathin films containing hexacyclen and p-sulfonatocalix[n]arene macrocycles.

Formation and characteristic properties of new layer-by-layer (LbL) assembled ultrathin films based on 1,4,7,10,13,16-hexaazacyclooctadecane (aza6) and p-sulfonatocalix[n]arenes with n=6 (calix6) and n=8 (calix8) are described. In particular, multilayered films of aza6 and polystyrenesulfonate (PSS), aza6 and calix8 or calix6, aza6 and hexacyanoferrate(II) (HCFII), calix8 and lanthanum(III), and calix8, 18-crown-6 and lanthanum(III) were investigated. The films were prepared upon alternating electrostatic adsorption of the cationic and anionic compounds from aqueous solution at charged substrates. Since the protonation of aza6 proceeds over a wide pH range, the film formation is strongly pH dependent. Linear growth of aza6/PSS films is found at pH 1.7 and 6.0, and superlinear growth at pH 0.9, 2.7, 3.7, and 5.0. The high affinity of aza6 towards inorganic ions favours the formation of LbL-assemblies of aza6 and HCFII counterions. Exposure of these films to Fe(III) leads to formation of Prussian Blue at the surface. The high affinity of p-sulfonato-calix[n]arenes towards La(III) favours the formation of LbL-assemblies of calix6 or calix8 and lanthanum. If additional 18-crown-6 is present in the La(III)-containing dipping solution, multilayered films of calix8, 18-crown-6 and La(III) are obtained.

Calixarenes↗
PubMed2006

Template-synthesized nanotubes through layer-by-layer assembly under charge interaction.

Aqueous polymer nanotubes can be assembled by combining the layer-by-layer (LbL) assembly and template technique under charge interaction. This method allows lots of species, especially in an aqueous system to form a tubular structure in the pores of the template. The tubes functions can be readily modified by introducing various functional components. Such assembled nanotubes are often mechanically stable and highly flexible. They have also numerous potential applications in delivering materials.

Aniline Compounds↗
PubMed2006

Fast numerical method for electromagnetic scattering by rough layered interfaces: propagation-inside-layer expansion method.

Electromagnetic scattering from a stack of two one-dimensional rough surfaces separating homogeneous media is modeled with a rigorous integral formulation solved by the method of moments. We present an efficient numerical method for computing the field scattered by such rough layers, in reflection as well as in transmission. We call this method propagation-inside-layer expansion (PILE) due to its straightforward physical interpretation. To our knowledge, it is the first method able to handle problems for this configuration with a huge number of unknowns. We study the convergence of this method versus a coupling condition and validate it by comparison with results from the literature.

Journal Article↗
PubMed2006

Optimization of star-oriented and layer-oriented wavefront sensing concepts for ground layer adaptive optics.

Multiconjugate adaptive optics is one of the major challenges in adaptive optics. It requires the measurement of the volumic distribution of the turbulence. Two wavefront sensing (WFS) concepts have been proposed to perform the wavefront analysis for such systems: the star-oriented and layer-oriented approaches. We give a performance analysis and a comparison of these two concepts in the framework of the simplest of the multi-guide-star adaptive optics systems, that is, ground layer adaptive optics. A phase-related criterion is proposed to assess analytically the performance of both concepts. This study highlights the main advantages and drawbacks of each WFS concept and shows how it is possible to optimize the concepts with respect to the signal to noise ratio on the phase measurement. A comparison of their optimized versions is provided and shows that one can expect very similar performance with the two optimized concepts.

Journal Article↗
PubMed2006

Virus-coated layer-by-layer colloids as a multiplex suspension array for the detection and quantification of virus-specific antibodies.

BACKGROUND: Suspension array technology has surpassed ELISA for automated, simultaneous detection and quantification of soluble biomarkers such as virus-specific antibodies. We describe assays in which antigens are attached to a lipid bilayer surrounding color-coded particles. METHODS: We used layer-by-layer technology to establish a multiplex suspension array with distinguishable microbeads coated with authentic viral surfaces to catch and quantify virus-specific antibodies in a flow cytometric analysis. Antigenic surfaces were generated by chimeric and wild-type baculoviruses plus 2 different influenza A virus subtypes fused to a lipid bilayer surrounding distinctly colored particles. Specificity of binding of chosen antibodies and sera was detected by immunofluorescence. Results of multiplex analysis were compared with results of ELISA. RESULTS: Titrations of virus-specific antibodies in the multiplex suspension array demonstrated specific binding to the viral surface proteins. The multiplex suspension array gave positive results for up to log 5-diluted primary antibodies with an approximately 5- to 10-fold reduced dynamic range compared with the respective ELISA. CONCLUSIONS: The bead-based multiplex suspension array is customizable and easy to establish. By displaying native influenza A virus surfaces and recombinant HIV-1 epitopes, the new assay provides a tool for the detection of major viral infections in humans.

Antibodies, Viral↗
PubMed2004

The many ways to sew up a uterus. "Single-layer" vs. "double-layer" cesarean repair: what's best?

Some clinicians have used a single, poorly-designed, retrospective study of single-layer vs. double-layer repair of the uterus during cesarean surgery to justify denying women the option of a trial of labor on subsequent pregnancies. This paper reviews the latest research and suggests the adoption of four new protocols for women after a cesarean. Women should receive a full summary of the repair methods used during their surgery; Women should be counseled as to the risk of delivering another child less than two years after uterine surgery; On subsequent pregnancies after cesarean birth, women should have an ultrasound near the end of the pregnancy looking for evidence of placental growth in the area of the scar and implications of this should be explained; and Vicryl sutures should be used for sewing up the uterus.

Adult↗
PubMed2005

[Reliability of an improved measurement system used in three-dimensional reconstruction of stomatognathic system by cutting and scanning layer-by-layer].

OBJECTIVE: To reconstruct 3D shape of edentulous jaw by using improved measurement system and to analyze the precision of this method. METHODS: Standard edentulous jaw models were measured with a improved measurement system by cutting and scanning layer-by-layer, and the 3D shape of the models was reconstructed by image processing with specialty software. Ten cubic plaster modes were reconstructed by the same way, data of every border before and after reconstruction were measured and analyzed. RESULTS: Data of edentulous jaw models were obtained. The errors in ten cubic before and after reconstruction were not significantly different (P > 0.05), data measured in horizontal plane were not significantly different (P > 0.05), and data measured in altitude direction were significantly different (P < 0.01), data measured after reconstruction were less than before, the error was (0.09 +/- 0.08) mm. CONCLUSION: The improved cutting and scanning measurement system can be fit for the 3D reconstruction of stomatognathic system with high precision.

Humans↗
PubMed1993

Comparison of continuous single layer polypropylene anastomosis with double layer and stapled anastomoses in elective colon resections.

The documented leak rate of the continuous single layer polypropylene (CSLP) anastomosis in elective colon resection is 0-6 per cent. It is more cost effective than stapling (S), and should be faster and easier to perform than the double-layer (DL) technique. However, there have been no reported series comparing the outcome of the CSLP anastomosis with the DL and S techniques. We reviewed the charts of 100 patients with elective colon resections. Eighty-four had data sufficient for analysis. There were 44 CSLP, 21 DL, and 19 S. The groups were comparable with respect to 12 preoperative variables. Proportionately more large-small bowel anastomoses were performed in the S group, and no patient in the S group was actively taking steroids. Clinical outcome was assessed. All leaks were clinically apparent and documented with contrast enema or laparotomy. The leak rate for the CSLP was 6.8 per cent (3/44). Two of the three patients with leaks were taking steroids. There were two leaks in the DL group (9.5%), one of which was taking steroids, and no leaks in the S group. The difference in leak rate between the three groups was not statistically significant. The average cost for CSLP at our institution is $4.00 compared with $8.00 and $35.00 for the DL and S, respectively. We conclude that the CSLP is a reasonable and safe alternative to DL and S anastomoses.

Anastomosis, Surgical↗
PubMed1975

Use of combined chromatographic methods including thin-layer chromatography for analysis of complex polymer systems. Determination of the polydispersity of block copolymers of styrene and methyl methacrylate by gel permeation, thin-layer and pyrolysis gas chromatography.

A combination of gel permeation chromatography (GPC), thin-layer chromatography (TLC) and pyrolysis gas chromatography (PGC) has been used for investigations of a polymethyl methacrylate-polystyrene-polymethyl methacrylate block copolymer. Continuous distribution of the polymer (40-mg sample) was attained according to the content of the styrene and methyl methacrylate units and of the block copolymer and according to the composition of the copolymer as functions of the hydrodynamic radius of the macromolecules. The polymer was subjected to a preliminary fractionation with an analytical gel chromatograph. The fractions were investigated by TLC, which permitted the separation of the block copolymer and the homopolymers. The composition of the fractions obtained by GPC and TLC was determined by PGC. As a result, it was possible to establish the composition of the block copolymer and its ratio to polymethyl methacrylate in each fraction. This investigation was based on a combination of highly effective fractionation by chromatographic methods with precise quantitative ratios obtained from Benoit's universal calibration graph and from determinations of the composition of the polymer fractions by PGC. The mechanism of the TLC of polymers, including the appearance of artefacts that distort the results of analysis, is also discussed.

Chromatography↗
PubMed1975

Improvements in the thin-layer chromatography of natural products. I. Thin-layer chromatography of the aflatoxins.

During the period which has elapsed since the aflatoxins were first isolated, one of the main problems has been the separation of the individual aflatoxins in pure form from aflatoxin-containing extracts. This separation has been best effected by thin-layer chromatography, and in this paper we describe how some of the difficulties may be overcome by using an appropriate combination of solvent system and silica gel preparation. For the examination of aflatoxin-containing extracts from the mycelia of Aspergillus flavus moulds, an initial freeze-drying step has been found to improve appreciably the quality of the chromatograms obtained.

Acetates↗
PubMed1975

An improved technique for the analysis of amino acids and related compounds on thin layers of cellulose. X. The characterization of some methionyl, phenylalanyl, tyrosyl and other peptides by thin-layer and ion-exchange chromatography.

This paper is a continuation of previous work (Parts VI, VIII, and IX) designed to identify small peptides in biological fluids by a combination of ion-exchange and thin-layer chromatography. Several series of peptides, mainly dipeptides, with methionine, phenylalanine, tyrosine, aspartic acid, serine, or glutamic acid as the N-terminal amino acid, have been examined.

Amino Acids↗
PubMed1977

Quantitation with high-performance thin-layer chromatography and programmed multiple development with high-performance micro-thin-layer material for drug analyses in biological fluids.

The programmed multiple development thin-layer chromatography (PMD-TLC) technique was compared with the conventional chromatographic technique on both normal and HPTLC plates. The potency of this high-performance TLC is illustrated and discussed by means of the data obtained with the determination of digitoxin in human serum. Improvement of the efficiency of TLC, resulting in a better resolution and sensitivity with PMD-TLC using using HPTLC plates, makes this high-performance TLC technique comparable to high-performance liquid chromatography. This TLC approach might lead to a sensitive, rapid, selective and simply assay for routine serial analyses and, because of its specificity and flexibility, it may facilitate drug interaction studies.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Layer by layer analysis of commissural hippocampal evoked potentials during glutamate microiontophoresis.

Commissural evoked potentials (EP) in hippocampal area CA1 were investigated during microiontophoretic application of sodium glutamate (SG) in experiments on unanesthetized rats immobilized with diplacin. EP were recorded by the central barrel of a five-barreled microiontophoretic microelectrode before and during application of SG. The effect of SG in the region of EP reversal was characterized by depression of the initial positive phase of the response and an increase in negativity. In the radial layer SG caused a substantial increase in the commissural response recorded at a depth. At a distance of 100 mu from the tip of the iontophoretic pipet no changes in EP were found. An increase in the intensity of transhippocampal stimulation was accompanied by a marked increase in the amplitude and a change in shape of the individual phases of EP and it abolished the effect of the microiontophoretically applied SG. During paired stimulation with an interval of 20--200 msec different effects of SG on the testing response were recorded depending on the length of the interval.

Animals↗
PubMed1988

Experimental demonstration of lateral cohesion in a layer of adsorbed protein and in layers of gold-antibody complexes bound to surface immobilised antigen.

The spatial distribution of ferritin molecules adsorbed on quartz surfaces and the spatial distribution of antibody-coated colloidal gold particles over an antigen-coated surface was studied by electron microscopy. Ferritin molecules were found to initially adsorb in small clusters at 2.5 X 10(9) sites/cm2. The initial nucleation was followed by growth of the clusters. Gold antibody complexes were initially bound to the antigen-coated surface as single particles, and formation of clusters was a secondary event at higher particle densities. The results indicate that lateral cohesion between macromolecules may play a role in the stability of adsorbed layers of protein and surface immobilised antigen-antibody complexes.

Animals↗