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PubMed2006

Effect of deprotection extent on swelling and dissolution regimes of thin polymer films.

The response of unentangled polymer thin films to aqueous hydroxide solutions is measured as a function of increasing weakly acidic methacrylic acid comonomer content produced by an in situ reaction-diffusion process. Quartz crystal microbalance with energy dissipation and Fourier transform infrared spectroscopy measurements are used to identify four regimes: (I) nonswelling, (II) quasiequilibrium swelling, (III) swelling coupled with partial film dissolution, and (IV) film dissolution. These regimes result from chemical heterogeneity in local composition of the polymer film. The acid-catalyzed deprotection of a hydrophobic group to the methacrylic acid tends to increase the hydrophilic domain size within the film. This nanoscale structure swells in aqueous base by ionization of the methacrylic acid groups. The swollen film stability, however, is determined by the hydrophobic matrix that can act as physical cross-links to prevent dissolution of the polyelectrolyte chains. These observations challenge current models of photoresist film dissolution that do not include the effects of swelling and partial film dissolution on image quality.

Journal Article↗
PubMed2002

Bilayer films for mucosal (genetic) immunization via the buccal route in rabbits.

PURPOSE: The oral buccal mucosa may be an ideal site for mucosal immunization, allowing for the needle-free administration of cost-effective vaccines. A novel mucoadhesive bilayer film was developed to test the feasibility of this route of immunization in rabbits. METHODS: Bilayer films were developed using different ratios of Noveon and Eudragit S-100 as the mucoadhesive layer and a pharmaceutical wax as the impermeable backing layer. Optimal 3/8-inch films were post-loaded with 100 microg of plasmid DNA (CMV-beta-gal) or beta-galactosidase protein. The in vitro release rates and stability of the postloaded antigens were determined. The films were applied to the buccal pouch of rabbits on days 0. 7, and 14, and the humoral and splenocyte proliferative immune responses to beta-gal were determined through day 28 and compared to those responses after conventional subcutaneous injection of adjuvanted protein. RESULTS: The weight ratio of Noveon and Eudragit S-100 had a significant effect on adhesion time of bilayer films. Postloaded plasmid DNA and beta-gal remained stable after being released from bilayer films (release of -60-80% in 2 h for both). Buccal immunization using novel bilayer films (109 +/- 6-microm thickness) containing plasmid DNA led to comparable antigen-specific IgG titer to that of subcutaneous protein injection. All rabbits immunized with plasmid DNA via the buccal route but none by the subcutaneous route with protein antigen demonstrated splenocyte proliferative immune responses. CONCLUSION: The feasibility of buccal (genetic) immunization with these novel bilayer films was demonstrated.

Adhesives↗
PubMed2001

Crystallization kinetics of sol-gel derived hydroxyapatite thin films.

The crystallization kinetics of sol-gel derived hydroxyapatite (HA) and tricalcium phosphate (TCP) thin films were studied to determine whether viscous sintering could be used for densification. The films were approximately 900 nm thick, and were synthesized and processed on silicon substrates. The films were fired in air in a rapid thermal annealer (RTA) for various times and the degree of crystallinity was determined by measuring the intensity of characteristic X-ray diffraction lines. The growth kinetics of HA and TCP were measured between 420 and 550 degrees C, and between 840 and 920 degrees C, respectively. Films that were subjected to an accelerated aging step before firing, exhibited a significantly lower crystallization growth rate when compared to unaged films. The aged films also became harder, as measured by nanoindentation. At temperatures above 840 degrees C, HA transformed into both alpha-and beta-TCP, with the beta form being dominant at lower temperatures. The activation energies for both transformations (amorphous film to HA, and HA to TCP) were determined, as were the constants for the Avrami equation. Based on the rapid crystallization kinetics observed for the amorphous film to HA transformation, densification through viscous sintering is essentially precluded in this system.

Journal Article↗
PubMed2000

Applications of polyion films containing biomolecules to sensing toxicity.

This paper describes several applications of polyion-biomolecule films on electrodes related to future development of in vitro chemical toxicity sensors. In the first example, composite films of DNA and ionomers cast onto pyrolytic graphite (PG) electrodes are shown to be useful for detecting DNA damage during incubation with the carcinogen styrene oxide at pH 5.5. Single electrodes can be used to estimate relative damage rates by derivative square wave voltammetry. Films containing the ionomer Nafion gave better reproducibility than another ionomer, Eastman AQ38. In the second example, films containing redox proteins myoglobin (Mb) and cytochrome (cyt) P450cam were constructed in alternate layers with polyions including DNA on rough PG electrodes. Films with reversible protein FeIII/FeII electrochemistry with up to 7 electroactive layers were made. Amounts of electroactive protein on rough PG that were 7 to 17-fold larger than in similar films on smooth gold were achieved because many more layers were electroactive. Films of Mb/DNA also showed oxidation peaks after short incubations with styrene oxide that may be attributable to DNA damage. Results are relevant to the future design of enzyme-DNA films which convert pollutants and drugs to reactive metabolites, followed by electrochemical detection of the resulting DNA damage.

Anions↗
PubMed2003

The influence of surface forces on thin film drainage between a fluid drop and a flat solid.

An experiment is described in which a mica surface is driven towards a mercury drop immersed in aqueous electrolyte. Under appropriate conditions, hydrodynamic pressure in the aqueous film creates a classical dimple in the mercury drop. The use of optical interferometry and video recording to monitor the shape of the drop and the thickness of the aqueous film with sub-nanometre resolution yields a high density of precise data showing the formation and evolution of the dimple as the film drains. Variation of electrical potential applied to the mercury phase allows control of the surface forces acting between the drop and the mica surface, so that the effect of surface forces on the film drainage process is highlighted. It is found that the film thickness at the centre of the dimple and the lateral extent of the dimple are not significantly affected by surface forces. On the other hand, the minimum film thickness at the edge of the dimple is sensitive even to weak surface forces. Since this minimum film thickness is a major determinant of the film drainage rate, it is shown that surface forces have an important effect on the overall drainage process.

Journal Article↗
PubMed2004

Optical properties of nanostructured metal films.

Nanostructured metal films of platinum, gold and silver up to 675 nm thick we prepared by electrochemical deposition through templates of 700 nm diameter polystyrene spheres assembled as hexagonal close packed monolayer on an evaporated gold surface followed by removal of the template by dissolution in tetrahydrofuran. The reflection spectra of the films at normal incidence were recorded as a function of film thickness and the spectra correlated with the local visual appearance of the film and the surface structure from SEM. For thin films, below one quarter sphere height, the spectra show a single reflectivity dip at a wavelength just below the sphere diameter consistent with surface-plasmon grating-like behaviour. For the thicker films several reflectivity dips are observed which move towards longer wavelength with increasing film thickness. This behaviour is shown to be consistent with a model in which light reflected from the top of the structure interferes with light reflected from within the spherical segment cavities in the film.

Journal Article↗
PubMed2006

Effect of composition on the conductivity and morphology of poly(3-hexylthiophene)/gold nanoparticle composite Langmuir-Schaeffer films.

Ultrathin Langmuir-Schaeffer (LS) films were fabricated from blends of regioregular poly(3-hexylthiophene) (P3HT) and highly monodispersed dodecanethiolate-capped gold nanoparticles (Au NPs) mixed in varying weight ratios. The morphology of the ultrathin films was investigated by UV-visible absorption spectroscopy, atomic force microscopy (AFM) and field-emission scanning electron microscopy (FE-SEM). The results of the structural investigations were correlated with the lateral conductivity of the films, with P3HT in its unintentionally doped state, probed by scanning electrochemical microscopy (SECM), which proved to be a very sensitive technique. Control over the P3HT/Au NP ratio led to remarkable changes in the morphology and lateral conductivity of the films. Inclusion of Au NPs into P3HT was found to influence the ordering of P3HT, which ultimately determined the macroscopic charge transport characteristics of the films. Composite films with ca. 33% by weight of Au NPs were found to be the most ordered and exhibited the highest conductivity, substantially higher than P3HT alone. To provide insight into the film formation process, LS composite films comprising equal quantities of P3HT and Au NPs (by weight) were transferred at several surface pressures and investigated by SECM, AFM and FE-SEM.

Electrochemistry↗
PubMed2000

Decision-making models in the analysis of portal films: a clinical pilot study.

Portal films continue to play an important role in the verification of radiotherapy treatment. There is still some discussion, however, as to what action should be taken after a port film has shown a radiation field deviation from the prescribed volume. It was the aim of the present pilot study to investigate the performance of three decision-making models ('Amsterdam', 'Quebec' and 'Newcastle') and an expert panel basing their decision on intuition rather than formal rules after portal film acquisition in a clinical setting. Portal films were acquired on every day during the first week of treatment for five head and neck and five prostate cancer patients (diagnostic phase). If required, the field position was modified according to our normal practice following the recommendation of the expert panel. In order to analyse the results of the models, however, additional port films were taken in the following 3 treatment weeks with the patient moved as required by the different models (intervention phase). The portal films were taken over 4 consecutive days, positioning the patient according to each of the different models on one day each. None of the models diagnosed a field misplacement in the head and neck patients, while the 'Amsterdam' and 'Quebec' models predicted a move in one prostate patient. The 'Newcastle' model, which is based on Hotelling's T2 statistic, proved to be more sensitive and diagnosed a systematic displacement for three prostate patients. The intervention phase confirmed the diagnosis of the model, even if the three portal films taken with the patient position adjusted as required by the model proved to be insufficient to demonstrate an improvement. The 'Newcastle' model does not rely on assumptions about the random movement of patients and requires five portal films before a decision can be reached. This approach lends itself well to incorporation into electronic portal imaging 'packages', where repeated image acquisitions present no logistical difficulty.

Decision Support Techniques↗
PubMed2000

[History of scientific and popular educational films in neurology and psychiatry in Germany 1985-1929].

Based on a survey of a variety of sources from medical and film history, an account is given of the history of scientific and popular educational films in neurology and psychiatry in Germany in the era of the silent film 1895-1929. A central event for the centralization of the production and distribution of medical scientific educational films was the foundation, in 1918, of the 'cultural department' of the Ufa film company which established, under the direction of the neurologist Curt Thomalla, a large medical film archive. Curt Thomalla was also the first who developed a dramatic type of popular educational film amalgamating medical and melodramatical features, thereby greatly increasing its mass impact, but also anticipating central elements of its later misuse by the Nazi film propaganda.

Germany↗
PubMed1984

[Complex evaluation of film mammographic imaging systems. 2. Comparison of 18 systems using a signal-noise matrix].

The concept of the signal-noise matrix with physiological optical noise measurements for defining visibility thresholds provides a quantitative means for comparing film mammographic systems (9). Eighteen such systems were compared. A graded list can be produced relating the integrated signal-noise ratio to area and detail contrast (image quality) and to the required radiation dose (dose efficiency). For this, maximal dose (industrial film) and minimal image quality can be taken into consideration. In this list, in agreement with other publications (12) high resolution film-screen combinations, using industrial film (eg. Cronex 70/screen) come top. In combination with a grid technique, this system achieves a greatly superior image quality. Amongst commercial film-screen systems, only the Trimax mammography system with high resolution screens is comparable. All other commercial systems (single or double coated films) are unsatisfactory with respect to their dose efficiency and image quality. Some industrial films without screens (Mamoray M4) are intermediate between high definition and other commercial systems. Ninety-second, screenless films offered for mammography appear unsuitable for this purpose, both in view of their dose efficiency and image quality.

Evaluation Studies as Topic↗
PubMed1985

The impact of routine admission chest x-ray films on patient care.

We evaluated the impact of routine chest x-ray films, obtained on admission, on the treatment of patients on internal medicine wards of the Veterans Administration Medical Center, Long Beach, California--a population known to have a high prevalence of cardiopulmonary disease. The reasons for ordering chest films were determined prospectively, and three Department of Medicine faculty members reviewed the charts of admitted patients to determine the impact of chest-film results on patient care. Routine chest x-ray films were ordered for 294 (60 per cent) of the 491 patients studied. Abnormalities were noted in 106 (36 per cent) of these 294 patients. The findings were previously known, chronic, and stable in 86 patients; they were new in only 20. Treatment was changed because of chest-film results in only 12 (4 per cent) of the patients. In only one of these patients would appropriate treatment probably have been omitted if a chest film had not been obtained, and the patient's outcome was not improved by the treatment instituted. We conclude that the impact of routine admission chest x-ray films on patient care is very small, even in a population with a high prevalence of cardiopulmonary disease. We recommend that such films not be ordered solely because of admission.

Adult↗
PubMed2004

Phase behavior in thin films of cylinder-forming ABA block copolymers: experiments.

We experimentally establish a phase diagram of thin films of concentrated solutions of a cylinder forming polystyrene-block-polybutadiene-block-polystyrene triblock copolymer in chloroform. During annealing the film forms islands and holes with energetically favored values of film thickness. The thin film structure depends on the local thickness of the film and the polymer concentration. Typically, at a thickness close to a favored film thickness parallel orientation of cylinders is observed, while perpendicular orientation is formed at an intermediate film thickness. At high polymer concentration the cylindrical microdomains reconstruct to a perforated lamella structure. Deviations from the bulk structure, such as the perforated lamella and a wetting layer are stabilized in films thinner than approximately 1.5 domain spacings.

Journal Article↗
PubMed2004

Structure formation in films of weakly charged block polyelectrolyte solutions.

A mean-field dynamic density functional theory is used to describe a phase diagram of concentrated solutions of weakly charged flexible block polyelectrolytes in a film. Electrostatics is taken into account by applying the local electroneutrality constraint (the Donnan membrane equilibrium approach). In the Donnan limit it is assumed that a salt added to the solution perfectly screens long-range electrostatic interactions. The phase diagram of a solution of a triblock polyelectrolyte in a film as a function of the solvent concentration and the charge of the polyelectrolyte (solvophilic) block is calculated for a given film thickness. The phase behavior of the block polyelectrolyte film arises from the interplay between surface-induced alignment and the electrostatically-driven structure formation. The observed mesoscopic structures (lamellar, perforated lamellar, cylindrical, micellar, and mixed phases) are oriented parallel to the surfaces for the considered case of morphologies unfrustrated by the film thickness. Structures with connections between parallel layers (bicontinuous, etc.) are not formed. As a result of surface-induced ordering, the region of ordered phases in a film is wider than in bulk and the phase boundary between ordered and disordered phases is more diffuse. As in the case of unconfined block polyelectrolyte solution, the solution in a film does not follow the lyotropic sequence of phases of such a block copolymer upon increase in the charge of the polyelectrolyte block. Upon changing the charge of the solvophilic copolymer block, transformations of copolymer morphology take place via change in curvature of polymeric domains. Due to confinement of a polyelectrolyte film, no swelling of solvophilic domains is observed.

Journal Article↗
PubMed2005

The structure and crystallization of thin water films on Pt(111).

When water is adsorbed on Pt(111) above 135 K several different ice structures crystallize, depending on the thickness of the ice layer. At low coverage water forms extended islands of ice with a (square root(37) x square root(37))R25(o) unit cell, which compresses as the monolayer saturates to form a (square root(39) x square root(39))R16(o) structure. The square root(39) low-energy electron diffraction (LEED) pattern becomes more intense as the second layer grows, remaining bright for films up of 10-15 layers and then fading and disappearing for films more than ca. 40 layers thick. The ice multilayer consists of an ordered square root(39) wetting layer, on which ice grows as a crystalline film which progressively loses its registry to the wetting layer. Ice films more than ca. 50 layers thick develop a hexagonal LEED pattern, the entire film and wetting layer reorienting to form an incommensurate bulk ice. These changes are reflected in the vibrational spectra which show changes in line shape and intensity associated with the different ice structures. Thin amorphous solid water films crystallize to form the same phases observed during growth, implying that these structures are thermodynamically stable and not kinetic phases formed during growth. The change from a square root(39) registry to incommensurate bulk ice at ca. 50 layers is associated with a change in crystallization kinetics from nucleation at the Pt(111) interface in thin films to nucleation of incommensurate bulk ice in amorphous solid water films more than 50 layers thick.

Journal Article↗
PubMed2006

A comparative study of the polyaniline thin films produced by the cluster beam deposition and laser ablation methods.

Polyaniline (PANI) thin films have been prepared by applying the novel neutral and ionized cluster beam deposition (NCBD and ICBD) methods and the pulsed laser deposition (PLD) technique to the PANI samples of half-oxidized emeraldine base (EB-PANI) and protoemeraldine base forms in a high-vacuum condition. Characterization of the oxidation states and structural changes of pristine and doped thin films has been performed by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and x-ray photoelectron spectroscopy. Spectroscopic measurements demonstrate that the dominant structure of NCBD and ICBD thin films corresponds to the reduced leucoemeraldine base state, whereas the chemical composition of PLD thin films depends critically on the laser fluence and the molecular weight of PANI target. The congruent deposition is only obtained for the PLD films deposited by the laser-induced decomposition of the low-molecular-weight targets in the low to intermediate fluence regime (below 100 mJ/cm2 with a pulse duration of 7 ns). The surface morphology examined by atomic force microscopy measurements shows that the cluster and laser beams are effective in producing smooth, uniform polymeric thin films. After I2 and HCl doping, the electrical conductivities of the NCBD, ICBD, and particularly PLD thin films are increased significantly. The higher conductivity of PLD films is ascribed to higher amounts of quinoid di-imine doping sites in the EB-PANI state, and the overall structure-conductivity characteristics are consistent with the spectroscopic observations.

Journal Article↗
PubMed1975

Perceiving the language of films.

Children appear to be familiar with the language of film makers or at least to perceive and remember films less well when the rules of this cinematic language are broken. In this experiment a simple action sequence filmed from a static viewpoint was made up into two films of four shots. One film was edited according to the rules of directional continuity specified by Hollywood cinema, that is the four shots were presented so as to preserve the subject's direction of movement across cuts. The other film was edited disregarding these rules. Apart from this difference both films were identical. Children aged seven, nine, and thirteen years watched either of these films and reconstructed the action using pictures representing the four shots. The children who saw the conventional version were better able to reconstruct what they had seen than those who saw the unconventional version.

Adolescent↗
PubMed2001

Migration of 4-nonylphenol from polyvinyl chloride food packaging films into food simulants and foods.

Migration of 4-nonylphenol (NP) from polyvinyl chloride (PVC) films for food packaging into food simulants and foods has been studied in domestic applications such as wrapping of food and reheating in a microwave oven. The migration of NP from the PVC films was determined by high-performance liquid chromatography with electrochemical coulometric-array detection (LC/ED). Twelve PVC films intended for commercial use and ten for domestic applications (total: 22 samples) were analysed. Some of the PVC films (two home-use and ten retail-use) contained NP at concentrations of between 500 and 3300 microg/g. Migration of NP from the films was influenced by the test conditions (n-heptane at 25 degrees C for 60 min, distilled water at 60 degrees C for 30 min and 4% acetic acid at 60 degrees C for 30 min). The amount of NP migrating from the PVC films into n-heptane (0.33-1.6 microg/cm2) was higher than the amount migrating into distilled water or 4% acetic acid (up to 9.7 ng/cm2) for the 11 films in which NP was detected. Up to 0.23% of the NP migrated into distilled water and 4% acetic acid and up to 62.5% into n-heptane. In addition, we investigated NP migration into cooked rice samples wrapped in PVC film. Using spiked samples the method gave an average recovery of 83.7% (n = 5) with a standard deviation of 2.5%. Migration of NP ranged from not detectable (< 1.0 ng/g) to 410.0 ng/g by reheating samples in a microwave oven for 1 min and from not detectable to 76.5 ng/g by keeping samples at room temperature for 30 min.

Chromatography, High Pressure Liquid↗
PubMed2004

Can computed tomography scout radiography replace plain film in the evaluation of patients with acute urinary tract colic?

PURPOSE: To determine the sensitivity of computed tomography (CT) scout view in detecting ureteral stones and whether CT scout radiography can replace plain film in the evaluation of patients with acute urinary tract colic. MATERIAL AND METHODS: Between January 2000 and 2002, 110 patients with ureterolithiasis were prospectively evaluated for the detection of ureteral stones on CT scout radiographs. The findings were compared with those of plain films. All patients were examined with plain film, CT scout radiography, and unenhanced helical CT. CT scans were performed within 24 h of plain films. Each CT scout radiograph was interpreted without knowledge of the findings on plain film. RESULTS: 111 stones were detected by unenhanced helical CT. Mean stone size was 3.9 mm (range 1-10 mm). Of all stones, 57 (52%) were visible on plain film; 44 (40%) were seen on CT radiographs. The sensitivity of 79 small stones (< 5 mm) on CT scout radiography was 29% and of abdominal radiography 37%. For 32 big stones (> 5 mm), the sensitivity of CT scout radiography was 66% and of abdominal radiography 87.5%. CONCLUSION: In this study, plain film was more sensitive than CT scout radiography in revealing ureteral calculi. However, the detection of stones 5 mm or larger had a sensitivity of 66% on CT scout radiographs; 77% (44/57) of the stones visible on plain films were also seen on CT scout radiographs. We therefore believe that CT scout radiography can be used as a baseline study in most patients with big ureteral stones.

Acute Disease↗