PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Films”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed2006

Atomic layer deposition of tungsten(III) oxide thin films from W2(NMe2)6 and water: precursor-based control of oxidation state in the thin film material.

The atomic layer deposition of W2O3 films was demonstrated employing W2(NMe2)6 and water as precursors with substrate temperatures between 140 and 240 degrees C. At 180 degrees C, surface saturative growth was achieved with W2(NMe2)6 vapor pulse lengths of >/=2 s. The growth rate was about 1.4 A/cycle at substrate temperatures between 140 and 200 degrees C. Growth rates of 1.60 and 2.10 A/cycle were observed at 220 and 240 degrees C, respectively. In a series of films deposited at 180 degrees C, the film thicknesses varied linearly with the number of deposition cycles. Time-of-flight elastic recoil analyses demonstrated stoichiometric W2O3 films, with carbon, hydrogen, and nitrogen levels between 6.3 and 8.6, 11.9 and 14.2, and 4.6 and 5.0 at. %, respectively, at substrate temperatures of 160, 180, and 200 degrees C. The as-deposited films were amorphous. Atomic force microscopy showed root-mean-square surface roughnesses of 0.7 and 0.9 nm for films deposited at 180 and 200 degrees C, respectively. The resistivity of a film grown at 180 degrees C was 8500 microhm cm.

Journal Article↗
PubMed2004

Thin film interference of colloidal thin films.

A stairlike colloidal crystal thin film composed of poly(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-AA)) monodispersed colloids was fabricated on an inclined silicon substrate. Different bright colors were observed on the various parts of the film with different layers as white light irradiated perpendicularly on it. The relationship between the colors and layers of the film was investigated and discussed according to the principle of thin film interference. On the basis of the phenomenon of thin film interference, a one-layer colloidal film having uniform color was researched and it would display diverse colors before and after swollen by styrene (St). A circular stairlike colloidal film was achieved to mimic the colors of the peacock tail feather.

Acrylates↗
PubMed2004

Parametric study on electrochemical deposition of copper nanoparticles on an ultrathin polypyrrole film deposited on a gold film electrode.

Monoshaped and monosized copper nanostructured particles have been prepared by potentiostatic electrochemical deposition on an ultrathin polypyrrole (PPY) film, electrochemically grown on a Si(100) substrate sputter-coated with a thin gold film or gold-film electrode (GFE). The crystal size and the number density of the copper nanocrystals have been examined by varying several deposition parameters, including the thickness of the gold film, the PPY film thickness, the applied potential, and the Cu2+ and the electrolyte concentrations for copper deposition. Optimal conditions for uniform growth ofnanocrystals well-dispersed on the GFE have been determined, along with insight into the mechanism of crystal growth. A minimum gold film thickness of 80 nm is required to eliminate the effects of the gold-silicon interface. The PPY film thickness and homogeneity principally affect the shape uniformity of the nanocrystals, while the copper deposition potential could be used to regulate the size and number density of the nanocrystals. Both the Cu2+ and electrolyte concentrations are also found to play important roles in controlling the electrodeposition of nanocrystal growth.

Journal Article↗
PubMed2005

Heat-stabilized phospholipid films: film characterization and the production of protein-resistant surfaces.

Phospholipid films have been shown in a number of studies to exhibit potential as nonfouling surfaces for biomaterial applications. However, the practical application of such films has been hindered by instability in aqueous solutions and significant detachment under mild shear stresses. Methods for stabilizing lipid films have been investigated, but to date require the presence of specific functional groups or chemical modification of the lipid molecule. In contrast to these methods, we present a process for heat-stabilization of lipid films. These heat-stabilized films have been shown to be able to withstand repeated rinsing without significant detachment. Phosphatidylcholine monolayers were formed on hydrophobic self-assembled monolayers using the liposome fusion method and stabilized at 80 degrees C. The films were characterized using Fourier transform infrared spectroscopy, ellipsometry, and atomic force microscopy and were shown to be defect free after repeated rinsing. Further experiments using a quartz crystal microbalance showed that the heat-stabilized lipid films were highly resistant to nonspecific protein adhesion and compared very favorably with poly(ethylene glycol)-coated surfaces under identical exposure conditions.

Adsorption↗
PubMed2000

Glass transitions and dynamics in thin polymer films: dielectric relaxation of thin films of polystyrene

The glass transition temperature T(g) and the temperature T(alpha) corresponding to the peak in the dielectric loss due to the alpha process have been simultaneously determined as functions of film thickness d through dielectric measurements for polystyrene thin films supported on glass substrate. The dielectric loss peaks have also been investigated as functions of frequency for a given temperature. A decrease in T(g) was observed with decreasing film thickness, while T(alpha) was found to remain almost constant for d>d(c) and to decrease drastically with decreasing d for d<d(c). Here, d(c) is a critical thickness dependent on molecular weight. The relaxation time tau(alpha) of the alpha process, which was measured as the frequency at which the dielectric loss realizes its peak value at a given temperature, was found to have a d dependence similar to that of T(alpha). The relaxation function for the alpha process was obtained by using the observed frequency dependence of the peak profile of the dielectric loss. The exponent beta(KWW), which was obtained from the relaxation functions, decreases as thickness decreases. This suggests that the distribution of relaxation times for the alpha process broadens with decreasing thickness. The thickness dependence of T(g) is directly related to the distribution of relaxation times for the alpha process, not to the relaxation time itself. The value of the thermal expansion coefficient normal to the film surface was found to increase with decreasing film thickness below T(g), but to decrease with decreasing film thickness above T(g). These experimental results are discussed in the context of a three-layer model in which within thin films there are three layers with different mobilities and glass transition temperatures.

Journal Article↗
PubMed1975

The influence of chromatin compactness on the stoichiometry of the Feulgen-Schiff procedure studied in model films. II. Investigations on films containing condensed or swollen chicken erythrocyte nuclei.

As models for different states of chromatin compactness, nuclei from chicken erythrocytes were isolated and either osmotically swollen or kept as condensed as possible. Both types of nuclei were then fixed and incorporated into polyacrylamide films. Hydrolysis with 5 N HCl and staining with Schiff's reagent of these model films were studied using several parameters. The phosphate content of the films was analyzed as a parameter for the depolymerization losses and the staining with Schiff's reagent as a parameter for the apurinic acid (APA) content. The loss of ultraviolet absorbance from the films and the accumulation of ultraviolet absorbing substances in the hydrolyzing acid were monitored as parameters for the progress of hydrolysis. Conversion of the generated aldehyde groups to APA-Schiff chromophore is shown to take place with the same stoichiometry for both types of nuclei as well as for DNA in model films. It is further shown that the nuclei- and DNA-films are suitable models for investigating the influence of chromatin compactness on the course of the Feulgen-Schiff reaction. For the most compact form of chromatin studied, a very high reduction in staining intensity of up to 40% could be demonstrated after certain normally applied hydrolysis times. This is due primarily to a decrease with a factor of 2.3 of the depurination rate constants of these models (from 0.030/min to 0.013/min). Therefore prolonged hydrolysis periods are required to obtain the same APA concentrations, but then depolymerization processes cause losses of nuclear material. The differences in depurination rates could be explained by a decrease in [H3O]+ in the neighborhood of the purine-sugar linkages, caused by the presence of fixed positive charges form the protein components of the chromatin. These findings may explain the cytophotometrically determined differences in chromophore yield of 10-20% found in the nuclei of cells with different states of compactness of their chromatin. The descending part of the Feulgen hydrolysis curve represents the depolymerization of APA and loss by diffusion of the reaction products. In the Appendix, cytophotometric data of cells have been analyzed to show that this part of the hydrolysis curve may be used to estimate the acid stability of chromatin complexes. The depurination and depolymerization rates found closely correspond with the data obtained from the model films.

Animals↗
PubMed1993

Film-based chest radiography: AMBER vs asymmetric screen-film systems.

OBJECTIVE: Contrast-to-noise ratios were measured on radiographs from two types of state-of-the-art chest imaging systems (an Advanced Multiple Beam Equalization Radiography [AMBER] system and an asymmetric screen-film system) to facilitate an objective comparison of image quality. MATERIALS AND METHODS: Radiographs of a chest phantom were obtained by using the AMBER system with a medium-latitude screen-film image recorder (Kodak T-MAT L film and Lanex regular screens) and a commercially available asymmetric, zero-crossover screen-film system optimized for chest radiography (Kodak InSight and InSight HC). Conventionally acquired radiographs (T-MAT L/Lanex regular) were also evaluated as a reference. Films were digitized, radiographic contrast and noise were measured in the lung-, mediastinum-, and subdiaphragm-equivalent regions of each image, and contrast-to-noise ratios were computed. RESULTS: Radiographic contrast and contrast-to-noise values were found to be higher on AMBER images in all chest regions when compared with radiographs obtained with the asymmetric screen-film systems (InSight contrast-to-noise ratio approximately 77% of AMBER contrast-to-noise in the lung-equivalent region, 57% in the mediastinum-equivalent region, and 43% in the subdiaphragm-equivalent region). On conventional radiographs, the contrast and contrast-to-noise values were higher than on all other image types in the lung-equivalent region and lower than on all other image types in the less well penetrated chest areas. CONCLUSION: Image quality was higher, most notably in dense phantom regions, on radiographs obtained with the AMBER system than on radiographs obtained with the new asymmetric screen-film systems. Clinical studies are needed to determine whether this level of image improvement justifies the additional expense of the exposure equalization system.

Humans↗
PubMed2004

[Preparation of liposome podophyllotoxin chitosan film and determination the podophyllotoxin content in the film by ultraviolet spectrophotometry].

OBJECTIVE: To optimize the formula of liposome podophyllotoxin chitosan film and accurately determine the podophyllotoxin content in the film. METHODS: Liposome podophyllotoxin chitosan films were prepared according to different formula derived from the results of orthogonal design by selecting chitosan, acetic acid and gelatin as the 3 factors for preparation, each factor including 3 levels with liposome podophyllotoxin as the blank factor. Comprehensive evaluation of the formulas was performed on the basis of the conglutination and solubility of the prepared film to select the optimal formula. The content of podophyllotoxin was determined by ultraviolet spectrophotometry at 292 nm. RESULTS: The conglutination and solubility were optimal of the film prepared from 2% chitosan, 1% acetic acid, 2% gelatin and 2.8% liposome podophyllotoxin chitosan, showing good linearity within podophyllotoxin concentration range of 5-25 microg/ml (r=0.999 89) with an average recovery rate of 99.7% (n=5) and RSD of 1.11%. CONCLUSION: The film prepared according to the orthogonal design results conforms to the requirements in terms of conglutination and solubility, and the method we adopted is fast and accurate, yielding qualified film with censored podophyllotoxin content that distributes homogeneously.

Animals↗
PubMed2006

[The research of film formation properties of the aerosol of biodegradable multi-function film].

The aerosol of biodegradable multi-function film were prepared, whose properties, affective factors and hemostasis effect were studied. Film formation properties were investigated in different lots of aerosols, including film formation time, uniformity, film particle size and film thickness. Young's modulus was about 0. 0373GPa, and elongation at break was 0. 89% by means of tensile method. It is proved that the aerosol of biodegradable multi-function film is easy to form films and its hemostasis effect is well.

Aerosols↗
PubMed2002

Corresponding dose response of radiographic film with layered gafchromic film.

This note investigates the dose response of layered HS Gafchromic film compared to Kodak EDR-2 radiographic film. Using five layers of HS type Gafchromic film a dose response greater than EDR-2 film is achieved at the peak wavelength (0.55 OD/Gy versus 0.3 OD/Gy for EDR-2 film). Even over a broader waveband of 30 nm, which is similar to that found in ultra bright LED scanners, the response was found to be 0.38 OD/Gy as opposed to 0.29 OD/Gy. Measurements averaged over the entire visible spectrum produce a relative dose response of 0.165 OD/Gy for five layer HS and 0.29 OD/Gy for EDR-2 film. Due to this high dose response that is achievable, the five layer HS could be used in applications where small doses are delivered to certain areas and a low dependence of energy response is required for measurement.

Dose-Response Relationship, Radiation↗
PubMed1996

Evaluating sol-gel ceramic thin films for metal implant applications. I. Processing and structure of zirconia films on Ti-6AI-4V.

Thin ceramic films or coatings over metallic bone-interfacing implant surfaces have the potential to improve implant performance with respect to implant fixation, wear, or corrosion. In this study, zirconia (ZrO2) thin films formed on Ti-6AI-4V using a polymeric alkoxide-based solgel process were investigated. ZrO2 films of uniform thickness on the order of 100 nm were obtained by dip coating Ti-6AI-4V samples into a zirconium propoxide containing solution using a substrate withdrawal speed ranging from 2 to 8 cm/min and a sol of nominal viscosity approximately 6 cps. These films were essentially free of surface macrodefects but had random submicron "pinholes." X-ray diffraction studies suggested that the films were at least partially crystalline, with some "metastable" cubic and/or tetragonal phases after annealing for 1 h at 500 degrees C. The demonstrated reproducibility of this approach for producing good quality ZrO2 films on Ti-6AI-4V warrants further studies to optimize processing conditions for implant applications.

Alloys↗
PubMed2002

Thin films of Ag nanoparticles prepared from the reduction of AgI nanoparticles in self-assembled films.

A novel method for the preparation of thin films of Ag nanoparticles is reported. Using mercaptoacetic acid as the stabilizing agent, AgI nanoparticles were prepared in aqueous solution. And based on electrostatic interactions, the thiol-passivated AgI nanoparticles were assembled in a self-assembled film by alternative deposition with a cationic polyelectrolyte. Then the AgI nanoparticles in the composite film were reduced by NaBH(4), which resulted in the formation of a thin film of Ag nanoparticles. UV-visible spectra and X-ray photoelectron spectroscopy data confirmed the transformation from AgI to Ag. Atomic force microscopy (AFM) showed that the formed Ag nanoparticles distributed on the film homogeneously. Surface-enhanced Raman spectroscopy (SERS) measurement indicated that the prepared thin films could be used as effective SERS substrates. The reduction process was also carried out by UV light at selective surface regions, which resulted in the formation of patterned nanoparticle arrays.

Journal Article↗
PubMed1995

The role of synovial fluid filtration by cartilage in lubrication of synovial joints--IV. Squeeze-film lubrication: the central film thickness for normal and inflammatory synovial fluids for axial symmetry under high loading conditions.

The axially symmetric problem of synovial film filtration and synovial gel formation at normal approach of cartilage surfaces in the human hip joint loaded by a compressive force has been solved numerically in Part III of this paper [Hlavácek and Novák, J. Biomechanics 28, 1193-1198 (1995)] for the Newtonian viscous phase of the biphasic synovial fluid and for low loads only. Because of a high non-linearity of the problem the method used there breaks down for higher loads. On anticipating that for a high step loading the fluid pressure in the central part of the squeezed synovial film is close to the pressure in a dry frictionless contact, the synovial film filtration at the film centre is governed by two ordinary differential equations that are easy to solve. The central gel film thickness thus obtained, i.e. the film thickness at the moment, when the filtered fluid turns into a stable gel is about 1 micron for the normal synovial fluid (with a non-Newtonian viscous phase of the synovial fluid) and changes very little if the geometric, material and loading parameters of the problem vary within the physiological range. The inflammatory case (with a more or less Newtonian viscous phase) yields values by one order lower at least. The results of stress analysis in the cartilage for this mixture model suggest the reason for vertical cracking at the free cartilage surface and horizontal splitting at the tide mark observed in osteoarthritic joints.

Biomechanical Phenomena↗
PubMed2004

Grafting of poly(ethylene oxide) to the surface of polyaniline films through a chlorosulfonation method and the biocompatibility of the modified films.

Poly(ethylene oxide) (PEO) could be grafted on the surface of polyaniline (PANI) films by chlorosulfonating the films with chlorosulfonic acid followed by reacting the modified films with PEO in a pyridine solution. The modified PANI films were examined by X-ray photoelectron spectroscopy and water droplet contact angles. The surface of the PEO grafted to hydrophobic PANI films became hydrophilic and the amounts of bovine serum albumin and human blood plasma platelet adsorbed onto it were decreased by more than 80%. For comparison purposes, and because the water wetting angle can be used as a measure of biocompatibility, wetting angle experiments have been also carried out for Pluronic triblock copolymer grafted to PANI and PEO or Pluronic molecules entrapped on the surfaces of PANI films. PANI was selected as substrate because one can easily change its surface properties by PEO grafting and because being conductive can be used as a sensor.

Adsorption↗