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At least 217 records · Page 12Linked to original sources
PubMed2005

Refractive index of thin films of SiO2, ZrO2, and HfO2 as a function of the films' mass density.

Series of amorphous SiO2, ZrO2 and HfO2 films were prepared by electron-beam evaporation at various oxygen pressures such that the packing density varied from 0.6 to 0.82. Transmittance spectra were evaluated with respect to thickness and refractive index by application of analytical formulas to the interference extrema and by dielectric modeling. The thickness of the films ranged from 150 to 1500 nm. The coefficients of Cauchy and Sellmeier dispersion curves were determined as a function of the packing density. The mass density of the compact amorphous grains was estimated by an effective-medium theory and a general refractivity formula. It is similar to those of the crystalline materials. We used the optical data to design multilayer coatings for laser applications in a broad spectral range, including the UV.

Journal Article↗
PubMed2003

Electroanalytical properties of aldehyde biosensors with a hybrid-membrane composed of an enzyme film and a redox Os-polymer film.

Aldehyde biosensors were constructed by cross-linking formaldehyde dehydrogenase (FDH) or aldehyde dehydrogenase (ADH) and bovine serum albumin on the surface of a redox Os-polymer-coated electrode. The prepared aldehyde biosensors responded rapidly (within 30 s) to aldehydes without the addition of a soluble mediator, because the inner redox Os-polymer film effectively mediated the electron transfer from NADH generated enzymatically into the outer enzyme film to a glassy carbon electrode. An FDH/Os-polymer electrode responded linearly over the concentration range of 2 x 10(-6)-5 x 10(-4) M for formaldehyde, while an ADH/Os-polymer electrode, though responding similarly to long chain aldehydes, such as propionaldehyde and butylaldehyde, responded linearly over the concentration range of 4 x 10(-6)-2 x 10(-4) M for acetaldehyde.

Aldehydes↗
PubMed1994

[Study of X-ray filter and peak kilovoltage in film-screen chest radiographs in regard to detection of simulated pulmonary nodules: comparison between film-screen combination and FCR].

We compared the ability of standard film-screen chest radiographs to detect simulated pulmonary nodules. The radiographs were taken with different X-ray filters and tube voltages. Detection capability was analyzed utilizing receiver operating characteristic (ROC) curves formed from the interpretation of six readers. Nodule detection was slightly better in images obtained with a tube voltage of 135 kVp than with one of 100 kVp (not statistically significant). Approximately equal detection performance was shown by a conventional film-screen system and FCR with three X-ray filter sets: a copper filter backed by aluminium, a tungsten filter backed by yttrium and aluminium, and a lead filter backed by yttrium and aluminium. Results showed less X-ray exposure with the two latter filter sets. Unenhanced FCR images taken with approximately the same X-ray exposure as conventional radiographs showed nearly equal ability to detect the simulated nodules.

Humans↗
PubMed1976

Photoelectrochemical effects in the electrolyte-pigment-metal system. I. Metal-free phthalocyanine film description of short-circuit photocurrents for thin films of pigment.

Using a semitransparent metallic electrode covered with a thin film of metal-free phthalocyanine, photoelectrochemical effects have been studied in the electrolyte-pigment-metal system. Measurement of the short-circuit photocurrent, produced by continuous illumination, allows description of a photodependent kinetic phase corresponding to the establishment of a stationary state in the charge separation region of the system after the creation of the current carriers.

Biological Transport↗
PubMed1976

Photoelectrochemical effects in the electrolyte-pigment-metal system. II. Metal-free phthalocyanine film action spectra of short-circuit photocurrents with increase of the film thickness.

The electrolyte-pigment-metal system can be described as analogous to a photosensitive junction region. When the thickness of the pigment film is increased, the action spectra of the maximum short-circuit photo-current under continuous illumination differ from the absorption spectra both in direct illumination (pigment-electrolyte) and in back illumination (metal-pigment). One is led to believe that there exist two photoactive regions in the system for the production of the short-circuit photocurrent; these two active regions are associated respectively with each interface. When the metallic semitransparent electrode is made of aluminum the two interfaces have opposite sign contributions to the photocurrent; this allows the determination of conditions in which one can observe specifically the contribution of the pigment-electrolyte interface, that is the interactions between excited pigment molecules and the redox system in the electrolyte.

Action Potentials↗
PubMed1979

Phospholipid monolayers at the hydrocarbon-electrolyte interface. The interrelation of film potential and film pressure.

Measurements of surface pressure of surface potential are reported for films of distearoyl phosphatidylcholine (density range: 0.15--2.65 . 10(18) molecules/m2) spread at the interface between 2,2,4-trimethylpentane and 100 mM NaCl. Low density behavior of the surface pressure is explained using classical viral theory. The behavior of the surface potential is qualitatively explained for all densities in terms of the dipole moments associated with the carboxyl groups and headgroups of the phosphatidylcholine.

Electrolytes↗
PubMed1996

Portable chest radiology in intensive care: a comparison of a new dual characteristic film-screen system (Insight) incorporating a flexible grid with a standard film-screen system.

Insight (Insight, Kodak, UK) is a new dual image receptor system which utilizes an asymmetric film screen combination. Conventional radiography was compared with the Insight system, in combination with a cassette incorporating a flexible grid, in fifty patients on the intensive care unit. Radiographs were analysed by intensive care junior medical staff, nursing staff and two groups of radiologists. Insight provided better visualization of lung parenchyma, mediastinal detail and position of endotracheal tubes than conventional radiography. Central venous catheters were generally seen better on conventional radiographs than on Insight. Insight system produces a significant improvement in plain chest radiography in the intensive care unit. In the absence of digital radiography it is a suitable technique for routine radiography in the intensive care unit.

Aged↗
PubMed2001

Variations in coupled water, viscoelastic properties, and film thickness of a Mefp-1 protein film during adsorption and cross-linking: a quartz crystal microbalance with dissipation monitoring, ellipsometry, and surface plasmon resonance study.

We have measured the time-resolved adsorption kinetics of the mussel adhesive protein (Mefp-1) on a nonpolar, methyl-terminated (thiolated) gold surface, using three independent techniques: quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance, and ellipsometry. The QCM-D and ellipsometry data shows that, after adsorption to saturation of Mefp-1, cross-linking of the protein layer using NaIO4 transforms it from an extended (approximately 20 nm), water-rich, and hydrogel-like state to a much thinner (approximately 5 nm), compact, and less water-rich state. Furthermore, we show how quantitative data about the thickness, shear elastic modulus, and shear viscosity of the protein film can be obtained with the QCM-D technique, even beyond the Sauerbrey regime, if frequency (f) and energy dissipation (D) measurements measured at multiple harmonics are combined with theoretical simulations using a Voight-based viscoelastic model. The modeling result was confirmed by substituting H2O for D2O. As expected, the D2O substitution does not influence the actual adsorption behavior, but resulted in expected differences in the estimated effective density and shear viscosity. These results provide new insight and understanding about the adsorption kinetics and crosslinking behavior of Mefp-1. They also demonstrate how the above three techniques complement each other for biomolecule adsorption studies.

Adsorption↗
PubMed2002

Conformation transition in silk protein films monitored by time-resolved Fourier transform infrared spectroscopy: effect of potassium ions on Nephila spidroin films.

We used time-resolved Fourier transform infrared spectroscopy (FTIR) to follow a conformation transition in Nephila spidroin film from random coil and/or helical structures to beta-sheet induced by the addition of KCl from 0.01 to 1.0 mol/L in D(2)O. Time series difference spectra showed parallel increases in absorption at 1620 and 1691 cm(-)(1), indicating formation of beta-sheet, together with a coincident loss of intensity of approximately 1650 cm(-)(1), indicating decrease of random coil and/or helical structures. Increase in KCl concentration produced an increased rate of the conformation transition that may attributable to weakening of hydrogen bonds within spidroin macromolecules. The conformation transition was a biphasic process with [KCl] > or = 0.3 mol/L but monophasic with [KCl] < or = 0.1 mol/L. This suggests that, at high KCl concentrations, segments of the molecular chain are adjusted first and then the whole molecule undergoes rearrangement. We discuss the possible significance of these findings to an understanding of the way that spiders spin silk.

Animals↗
PubMed2005

Thin-film transistors based on Langmuir-Blodgett films of heteroleptic bis(phthalocyaninato) rare earth complexes.

An ordered molecular assembly of heteroleptic bis(phthalocyaninato) rare earth complexes M(Pc)[Pc(OC8H17)8] [M = Tb, Lu; H2Pc = phthalocyanine; H2Pc(OC8H17)8 = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyanine] has been fabricated by the Langmuir-Blodgett (LB) technique and characterized by surface pressure-area isotherms, electronic absorption and polarized electronic absorption spectroscopy, low-angle X-ray diffraction, and atomic force microscopy. The molecular ordering in the LB multilayer film on SiO2 substrate was made into a p-channel field effect transistor (FET), which was generally operated in the enhanced mode. The energy levels of the highest occupied molecular orbital and the lowest unoccupied molecular orbital as well as the energy band diagram can be deduced from the electrochemical measurement results. The charge mobilities of Tb(Pc)[Pc(OC8H17)8] and Lu(Pc)[Pc(OC8H17)8] were calculated to be about 6.4 x 10(-4) and 1.7 x 10(-3) cm2 V(-1) s(-1), respectively.

Journal Article↗
PubMed2006

Optical sum-frequency emission from langmuir-blodgett films of variable thickness: effects of the substrate and polar orientation of fatty acids in the films.

The nonlinear optical response arising from a model multilayer structure, i.e., Langmuir-Blodgett (LB) films comprised of different numbers of per-protonated (H) and per-deuterated (D) fatty acid layers on solid substrates, has been evaluated by sum-frequency generation (SFG) spectroscopy. The SFG signals depend significantly on the absolute polar orientation of the fatty acids in the individual layers and on the nonlinear optical response of the substrate. The SFG spectra on gold and fused quartz substrates demonstrate a totally different dependence on the number of the contributing H layers, which it is possible to analyze quantitatively. The results provide important information for understanding the origin of the nonlinear optical responses from ordered systems composed of multiple interfaces and therefore for extracting exact structural information about each interface from the observed SFG signals.

Journal Article↗
PubMed2004

Stability of thin nematic films. Commentary on "Morphology and structure of thin liquid-crystalline films at nematic-isotropic transition" by P. Ziherl and S. Zumer.

We discuss the peculiarity of thin nematic films on solid substrates with a free surface, underlining the differences with what is usually seen in dewetting. We review the thermodynamic basis of the coupled phase/thickness separation that has previously been shown experimentally. We give new experimental evidences for the origin of the coupling force chosen in our previous theoretical model. This additional information contributes to the discussion raised by the article of Ziherl and Zumer in this issue.

Comment↗
PubMed1975

The influence of chromatin compactness on the stoichiometry of the Feulgen-Schiff procedure studied in model films. I. Theoretical kinetics and experiments with films containing isolated deoxyribonucleic acid.

Theoretical considerations on the expected kinetics of the course of the Feulgen-Schiff reaction show that the leveling off of the first part of the Feulgen hydrolysis curve can be explained by the gradual conversion of deoxyribonucleic acid (DNA) to apurinic acid (APA). In addition, depolymerization of DNA caused by the acid used for hydrolysis can account for the decline after a maximum is reached in this curve. With the aid of polyacrylamide model films containing DNA, a detailed study was made both of the process of purine liberation which results in the formation of APA and of the depolymerization processes which cause losses of stainable material. The liberation of purine bases was analyzed by ultraviolet absorbance measurements and by gel chromatography of the neutralized hydrolysing acid. APA concentration was monitored by following the loss of ultraviolet absorbance associated with the purine losses. The depolymerization process was followed by phosphorus determinations. The experimental results were found to be in accordance with the kinetics expected from the theoretical model.

Chemical Phenomena↗
PubMedDate not supplied

[Photovoltaic effect in pigment films in contact with an electrolytes. V. Theory of the Becquerel photovoltaic effect in porous films of phthalocyanine].

In accordance with literature and our experimental data a theoretical analysis of the model system metal-porous film of the pigment-electrolyte was carried out at stationary illumination in the regimes of photocurrent and photopotential. The main properties and positions of the model are supported experimentally. Specific behaviour of the photovoltaic system considered resides in the discovered dependence of the transfer mechanism on the value of catode potential of the electrode.

Electrochemistry↗
PubMed1985

[Spray film coating of spherical microgranules with non-aqueous varnish film-formers].

To coat crystals and spherical microgranules with polymer films, the influence of different components of the spray on the release behaviour of the coating product has been tested by means of a spray coating process. The examinations which had been based on cellulose acetatephthalate and various polyacrylate types, were aimed at technological lab parameters of the process as well as at the choice of the solvents, the polymer type and the plasticiser admixture. The liberation test has been made in artificial digestives. The results show that the knowledge of the effects of varied dispensing components will enable as well an optimization of the technological process as a purposeful control of the required retarded effects of the final product.

Drug Compounding↗