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PubMed1989

The effect of gas permeability of film dressings on wound environment and healing.

We have determined the effect of oxygen and carbon dioxide permeability of thin film dressings on wound exudate P O2, P CO2, pH, and epithelialization in shallow wounds on domestic pigs. Three kinds of films were compared: polyvinylidine chloride, a low gas permeability film; polyurethane, a medium gas permeability film; and poly(dimethyl silicone), a high gas permeability film. Exudate under the silicone film had the highest P O2 and the lowest P CO2; exudate under the polyurethane had intermediate P O2 and P CO2; and exudate under the polyvinylidine chloride had the lowest P O2 and highest P CO2. Values for pH under the films correlated inversely with P CO2. The gas tensions and pH are a reflection of the ability of the films to control the diffusion of oxygen into and the loss of carbon dioxide from the wound exudate. Mean epithelialization values at 2 and 3 d were not significantly different under polyvinylidine chloride and polyurethane, but both were higher than under the silicone film. We infer from the data that the use of oxygen and carbon dioxide impermeable film dressings do not affect epithelialization in well-perfused, shallow wounds. The use of the silicone film (highly permeable to both oxygen and carbon dioxide) led to a loss of carbon dioxide. The resulting relatively high pH may have been responsible for the reduced rate of epithelialization which occurred beneath the silicone film.

Animals↗

PubMed1985

The adhesion characteristics of some pigmented and unpigmented aqueous-based film coatings applied to aspirin tablets.

The adhesion of pigmented (with talc and titanium dioxide) and unpigmented aqueous-based films, derived from hydroxypropyl methylcellulose, to aspirin tablets and the effect of ageing on the measured adhesion have been assessed. The adhesion of hydroxypropyl methylcellulose film attained maximum values at polyethylene glycol 400 and polyvinyl alcohol levels of 10 and 20 wt%, respectively. Above these concentrations, adhesion decreased. For solid loaded films it is proposed that the effect of pigments on film adhesion is dependent on the balance between their influence on the internal stress of the film coating and the strength of the film-tablet interface. Adhesion was enhanced when a pigment increased the strength of the interface faster than it increased internal stress, and vice versa. A simple relation between the measured adhesion and the incidence of edge splitting of film-coated tablets was not observed. Generally, film adhesion fell when the tablets were aged at 37 degrees C and 75% r.h. as a result of swelling-induced stresses in the film and at the film tablet interface. The effect of ageing on the adhesion of the system plasticized with polyethylene glycol 400 was eased when the film was pigmented. Adhesion was largely unaffected with film-coated tablets stored in tightly closed bottles at 20 degrees C for five months.

Aspirin↗

PubMed2004

Cell-adhesive and blood-coagulant properties of ultrathin poly(methyl methacrylate) stereocomplex films.

Isotactic (it) and syndiotactic (st) poly(methyl methacrylate)s (PMMAs) were assembled on a poly(ethylene terephthalate) cell disk (as a solid substrate), which is normally used for cell culture, to produce ultrathin stereocomplex films. Static contact angles of the films using air bubbles in aqueous phase revealed the stepwise assembly of both polymers. More L929 fibroblast cells adhered and were flattened on the ultrathin stereocomplex films, compared to homogeneous PMMA films and to spin-coated films comprised of a mixed solution of it- and st-PMMAs with a molar ratio of 1 : 2, which is the stoichiometry of a stereocomplex. The difference in the number of adherent cells was greatest after the first 3 h of incubation. Pre-adsorption of proteins, which are related to cell adhesion, onto the stereocomplex film potentially modulated the cell-adhesive properties. Fresh whole human blood did not coagulate on the complex film for 20 min, although blood coagulated after 15 min on the homogeneous films and on the 1 : 2 mixed film. Platelets did not adhere onto the complex films after 15 min of incubation, which was consistent with the results of blood coagulation. These observations indicate that the stereocomplex formation of PMMAs on the surface of films strongly affects the bioactivity of these films.

Animals↗

PubMed1996

Determination of lubricating film thickness for permeable hydrogel and non-permeable polyurethane layers bonded to a rigid substrate with particular reference to cushion form hip joint replacements.

The lubricating film thickness in a model of compliant layered bearings, using both permeable hydrogels and non-permeable polyurethane elastomers for total hip joint replacements, has been measured using optical interferometry, under both entraining and squeeze-film motion. The film thickness in the lubricated contact was measured for both water and a 40 per cent glycerol solution in water as a function of entraining velocity and squeeze-film time. The measured lubricating film thickness for the permeable hydrogel was compared to that of the non-permeable polyurethane elastomer and little difference was found when the lubricating film thickness was sufficiently large (greater than 150 nm). Comparison of the experimental results and the theoretical predictions based upon elastohydrodynamic lubrication analysis showed good agreement in the entraining experiments where the film thickness was greater than 150 nm. In the squeeze-film experiments the experimental measurements were greater than the theoretical predictions for all squeeze times due to the formation of a central pocket of fluid which was not predicted by the simple theory used. This also occurred for the hydrogels for films greater than 150 nm. For longer squeeze times the film thickness for the hydrogel fell below the theoretical prediction. This was considered to be due to the permeability of the hydrogel reducing the film thickness when the film thickness was less than 150 nm. The permeability of the hydrogel was not modelled in the theoretical lubrication analysis used in this study.

Biomechanical Phenomena↗

PubMed2006

Determination of properties of wedged, nonuniformly thick, and absorbing thin films by using a new numerical method.

Nonuniformity in the thickness of thin films can severely distort their transmission spectra as compared with those of flat, smooth films. Methods that extract properties such as refractive index, thickness, and extinction coefficient of such films can suffer inaccuracies when they are applied to wedged or nonuniformly thick films. To accurately extract optical properties of nonuniform films, we have developed a novel numerical method and efficient constitutive relations that can determine film properties from just the transmission spectrum for films that are locally smooth with negligible scattering loss. This optimum parameter extraction (OPE) method can accommodate films with two-dimensional thickness variation that would result in significant errors in the values of refractive index and film thickness if not considered. We show that for carefully chosen test cases and for actual pulsed-laser-deposition AlN thin films, properties such as refractive index, extinction coefficient, and film thickness were very accurately determined by using our OPE method. These results are compared with previous techniques to determine the properties of thin films, and the accuracy of and applicable conditions for all these methods are discussed.

Journal Article↗

PubMed2004

Use of UV-protective windows and window films to aid in the prevention of skin cancer.

People are exposed to ambient solar ultraviolet (UV) radiation throughout their daily routine, intentionally and unintentionally. Cumulative and excessive exposure to UV radiation is the behavioral cause to skin cancers, skin damage, premature skin aging, and sun-related eye disorders. More than one million new cases of skin cancer were diagnosed in the United States this year. UV radiates directly and diffusely scattered by the various environmental and atmospheric conditions and has access to the skin from all directions. Because of this diffuse UV radiation, a person situated under a covering, such as the roof of a car or house, is not completely protected from the sun's rays. Because shade structures do not protect effectively against UV radiation, there have been major advances in photoprotection of glass by the development of specially designed photoprotective windows and films. It is the purpose of this collective review to highlight the photoprotective windows and films that should be incorporated into residential, commercial, and school glass windows to reduce sun exposure. Low-emittence (low-E) coatings are microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface to reduce the U-factor by suppressing radiative heat flow as well as to limit UV radiation. The exclusive Thermaflect coating uses the most advanced, double-layer soft coat technology to continue to deliver top performance for UV protection as well as prevent heat loss in the home. This product blocks 87% of UV radiation and has an Energy Star certification in all climate zones. Tints and films have been another important advance in glass photoprotection, especially in automobiles. Quality widow film products are high-tech laminates of polyester and metallized coatings bonded by distortion-free adhesives. The International Window Film Association provides members with accreditation in solar control films, safety films, and automotive films in an effort to increase consumer awareness and demand for all professionally installed film window products. The Skin Cancer Foundation has also played a leadership role in certifying window films that limit UV transmission. The Panorama Designer and Safety Films are currently recommended for UV photoprotection by The Skin Cancer Foundation. On the basis of these innovative scientific and industrial advances in window and film photoprotective products, we recommend that they be used in all residential, commercial, and school facilities to provide photoprotection in an effort to reduce skin cancer.

Glass↗

PubMed1995

Functional properties and applications of edible films made of milk proteins.

Edible films and coatings based on milk proteins have been developed to be used as a protective layer on foods or between food components. The most important functionalities of an edible film or coating include control of mass transfers, mechanical protection, and sensory appeal. Control of mass transfers involves preventing foods from desiccation, regulating microenvironments of gases around foods, and controlling migration of ingredients and additives in the food systems. Adequate mechanical strength of an edible film is necessary to protect the integrity of packaging throughout distribution. The sensory properties of an edible coating or film are a key factor for acceptance of final products. Simple milk protein films are good barriers to gas transfers because of their complex intermolecular bindings. Lipid is frequently incorporated into protein films to improve their properties as barriers to moisture vapor. Protein films are distinctly different in mechanical profiles from those films made of other materials. Approaches traditionally used in material sciences have been adapted and modified for studying the functionality of edible films. Potential uses of innovative processing technologies in film making to alter the film functionality are briefly discussed. A survey of potential applications of edible film based on milk protein is presented.

Chemical Phenomena↗

PubMed2006

Mechanical properties and antibacterial efficacy of chitosan films.

Chitin, chitosan and quaternary chitosan films were prepared, and the mechanical properties and the antibacterial activities of chitosan and quaternary chitosan films were evaluated. The tensile strength of chitin films was 30-40% lower than that of chitosan films, but the crystallinity of the former was much higher than those of the latter. A detailed analysis of the crystallinity and orientation of crystallites of chitosan films revealed that the cast film prepared with acetic acid provided a little lower crystallinity than the others. The antibacterial activities of quaternary chitosan films against Staphylococcus aureus and Escherichia coil were stronger than those of chitosan films. The antibacterial activities of neutralized chitosan films may be slightly inferior to those of un-neutralized chitosan films. The improvement in the antibacterial activity of chitosan films against E. coli was slightly inferior to that against S. aureus. This phenomenon was particularly observed on the neutralized chitosan films. Though the antibacterial activity of chitosan was slightly inferior to that of the organic antibacterial compounds, we emphasize that chitosan would be a useful and suitable material with regard to its effect on the environmental ecosystem.

Acetic Acid↗

PubMedDate not supplied

Influence of storage conditions and type of plasticizers on ethylcellulose and acrylate films formed from aqueous dispersions.

PURPOSE: To investigate the influence of storage conditions and types of plasticizers on the properties and stability of ethylcellulose and polymethacrylate films and to elucidate the mechanism for the changes observed. METHODS: Films were prepared from Surelease, Aquacoat and Eudragit L 30D dispersions by the casting method. The effects of different plasticizers on the morphology, transparency, mechanical property and water vapour permeability of the prepared films were studied. The film samples were exposed to storage conditions of 30 degrees C and 50 or 75 %RH. Samples were removed at pre-determined time intervals for mechanical testing and analysis of plasticizer content in the films. RESULTS: It was found that films prepared from aqueous ethylcellulose dispersions were relatively weaker and more brittle than acrylate films. Acrylate films did not show any significant change in mechanical property when stored at high humidity. However, the properties of ethylcellulose films stored at high humidity varied depending on the type of plasticizers present. CONCLUSIONS: The changes in mechanical property of ethylcellulose films on storage were mainly attributed to the loss of plasticizers during storage, causing further coalescence of ethylcellulose films and to a smaller extent, reduction in moisture content of the film.

Acrylates↗

PubMed1983

[The lacrimal film, structure and stability].

The precorneal tear film is important in preserving the integrity of the corneal epithelium. One of several quantitative and qualitative clinical evaluation of the tear film is the determination of break-up time (BUT). Although controversial, this test is an important index of tear film physiology. The test depends upon the viscosity, surface tension and geometry of the tear film. The system is therefore ill-defined and current practices of bio-microscopic examination do not take into account the real nature of the called "dry spot". In this paper, we describe an innovative method of microscopic examination of the wetting film formed on the eye. The method is based on physico-chemical studies of thin wetting film (thin liquid film formed on solid surface). A freshly enucleated eye is immerged in a physiological solution and a thin wetting film is formed by bringing an air bubble into contact with a corneal epithelium. The examination of the wetting film is done using a specially-constructed device which simultaneously enables the deliver of an air bubble and the ability to observe the formed bubble. The observed interference colours provide information about the thickness and homogeneity of the liquid film. One can also observe the nature of lipid droplets floating at the surface of the tear aqueous phase by this technique. The study of the stability and rupture of thin films formed on freshly enucleated normal rabbit or rat eyes shows that the corneal epithelium is perfectly wettable as long as the epithelial cells had not suffered any irreversible damage. "Dry spot" are in reality microscopically thin fluid films with a thickness of several hundred nanometers.

Animals↗

PubMed1994

[Clinical evaluation of asymmetric film-screen system for thoracic lesions].

We investigated the clinical usefulness of the asymmetric film-screen system on postero-anterior chest roentgenograms for thoracic lesions. The asymmetric film-screen system, the so-called Kodak Insight thoracic imaging system, records a different image on each side of double-emulsion film. An image displaying the lung field is captured on the anterior side of the film, while one displaying the mediastinal, retrocardiac and retrodiaphragmatic structures is captured on the posterior side. The clinical usefulness of the asymmetric film was evaluated in 20 patients for visibility of the anatomical structures and abnormal lesions in comparison with conventional film. In the asymmetric film-screen system, the front and rear screens were HC (high contrast) and Regular, respectively. Chest radiography was performed at 200mA and 100kVp. As conventional film, we used SRC film (Konica, orthotype film), and chest radiography was performed at 100mA and 130kVp. The chest roentgenograms obtained with the asymmetric film-screen system provided better information on normal structures and abnormal lesions in the lung field, but slightly inferior information on mediastinal structures. In conclusion, it was considered that the asymmetric film-screen system was useful for thoracic lesions.

Aged↗

PubMed2004

Matchline dosimetry in step and shoot IMRT fields: a film study.

The Varian millennium 120 multileaf collimator has curved leaf ends. Transmission through the leaf ends generates a small asymmetric penumbral dose effect. This design can lead to hot spots between neighbouring beam segments during step and shoot IMRT dose delivery. We have observed some matchlines with film for clinical beams optimized using the pinnacle radiotherapy treatment planning system; hence we sought to verify the optimum leaf offset required to minimize the matchline effect. An in-house program was created to control the MLC leaf banks in 2 cm steps with a 2 cm gap. The gap was varied by the following offset values from 0.0 to 0.1 cm. Two types of radiographic films (Kodak EDR and XV films) and a radiochromic film (Gafchromic MD-55-2) were used to measure the optical density maps. The films were positioned in a solid water phantom perpendicular to the beam axis and irradiated at d(max) using a 6 MV photon beam. An ion chamber (IC4) was used to measure point doses for normalization in a beam umbral minima position. The relative mean peak to valley dose ratios measured with no leaf offset were 1.31, 1.30 and 1.31 for the XV, EDR2 and Gafchromic films, respectively. For a 0.07 cm gap per leaf and a performance of end leaf repeatability of 0.01 cm, the central matchline was reduced to about 1.0 for all dosimeters, with two mini-peaks measured as 1.05, 1.05 and 1.08 each side of the matchline, for XV, EDR2 and Gafchromic, respectively. The average relative dose across the umbra for this offset was XO-mat V = 1.01, EDR = 1.01 and radiochromic film = 1.02, respectively. While we expected the beam penumbral tails from segment neighbours to cause overprediction of the dose in the central valley regions due to the energy response of radiographic films, by normalizing all dosimeters to an ion chamber reading in the minimum we could not observe any major shape distortion between the radiographic film and radiochromic film results. In conclusion, relative doses measured by radiographic and radiochromic films agree well with IC4 within +/-2%.

Film Dosimetry↗

PubMed2004

Predicting energy response of radiographic film in a 6 MV x-ray beam using Monte Carlo calculated fluence spectra and absorbed dose.

The advantage of radiographic film is that it allows two-dimensional, high-resolution dose measurement. While there is concern over its photon energy dependence, these problems are considered acceptable within small fields, where the scatter component is small. The application of film dosimetry to intensity modulated radiotherapy (IMRT) raises additional concern since the primary fluence may vary significantly within the field. The varying primary fluence in combination with a large scatter fraction, present for large fields and large depths, causes the spectrum at various points within the IMRT field to differ from the spectrum in the uniform fields typically used for calibrating the film. As a result, significant artifacts are introduced in the measured dose distribution. The purpose of this work is to quantify and develop a method to correct for these artifacts. Two approaches based on Monte Carlo (MC) simulations are examined. In the first method, the film artifact, as quantified by film and ion chamber output measurements in uniform square fields, is derived from the MC calculated ratio of absorbed doses to film and to water. In the second method, the measured film artifact is correlated with MC calculated photon spectra, revealing a strong correlation between the measured artifact and the "scatter"-to-"primary" ratio, defined by the ratio of the number of photons below to the number of photons above 0.1 MeV, independent of field size and depth. These methods are evaluated in high- and low-dose regions of a large intensity-modulated field created with a central block. The spectral approach is also tested with a clinical IMRT field. The absorbed dose method accurately corrects the measured film dose in the open part of the field and in points under the block and outside the field. The dose error is reduced from as much as 16% of the open field dose to less than 1%, as verified with an ion chamber. The spectral method accurately corrects the measured film dose in the open region of the centrally blocked field, but does not fully correct for the film artifact for points under the block and outside the field, where the spectrum is substantially different. Applied to the clinical field, the corrected film measurement shows good agreement with data obtained with a two-dimensional diode array.

Dose-Response Relationship, Radiation↗

PubMed2005

The calibration of experimental self-developing Gafchromic HXR film for the measurement of radiation dose in computed tomography.

A prototype, self-developing Gafchromic HXR film has sensitivity an order of magnitude larger than that of the commercially available Gafchromic XR film used in interventional radiological applications. The higher sensitivity of the HXR film allows the possibility of acquisition of high-resolution calibrated dose profiles within the diagnostic range of exposure levels, below 10 R (87.7 mGy). We employed a commercially available, optical flatbed scanner for digitization of the film and image analysis software to determine the response of the HXR films to ionizing radiation. Spatial uniformity and temporal repeatability of the flatbed scanner were determined and used in optimization of the digitization protocol. The HXR film postexposure density growth and sensitivity to ambient light were determined using multiple scans of two simultaneously exposed sheets, one stored in light-tight conditions and the other continuously illuminated with white light. A calibrated step wedge of the HXR film was obtained by simultaneous irradiation of a portion of a film strip and a calibrated ionization chamber using a radiographic x-ray tube with beam characteristics matched to a typical CT scanner (8 mm Al HVL, 120 kVp). Repeated digitization of the calibration film was used to determine the precision of the film response measurements. The precision, as measured by the standard deviation of multiple measurements, was better than 1% over the full dynamic range of film response. This precision was measured using exposures ranging from 0.5 to 12 R (4.4 to 105.3 mGy). This exposure range is highly relevant to x-ray computed tomography. Preliminary radiation dose profiles demonstrate the utility of this technique.

Abdomen↗

PubMed2005

Energy dependence of response of new high sensitivity radiochromic films for megavoltage and kilovoltage radiation energies.

The purpose of this paper is to evaluate the energy dependence of the response of two new high sensitivity models of radiochromic films EBT and XR-QA. We determined the dose response curves of these films for four different radiation sources, namely, 6 MV photon beams (6 MVX), Ir-192, I-125, and Pd-103. The first type (EBT) is designed for intensity modulated radiation therapy (IMRT) dosimetry, and the second type (XR-QA) is designed for kilovoltage dosimetry. All films were scanned using red (665 nm) and green (520 nm) light sources in a charge-coupled device-based densitometer. The dose response curves [net optical density (NOD) versus dose] were plotted and compared for different radiation energies and light sources. Contrary to the early GAFCHROMIC film types (such as models XR, HS, MD55-2, and HD810), the net optical densities of both EBT and XR-QA were higher with a green (520 nm) than those with a red (665 nm) light source due to the different absorption spectrum of the new radiochromic emulsion. Both film types yield measurable optical densities for doses below 2 Gy. EBT film response is nearly independent of radiation energy, within the uncertainty of measurement. The NOD values of EBT film at 1 and 2 Gy are 0.13 and 0.25 for green, and 0.1 and 0.17 for red, respectively. In contrast, the XR-QA film sensitivity varies with radiation energy. The doses required to produce NOD of 0.5 are 6.9, 5.4, 0.7, and 0.9 Gy with green light and 19, 13, 1.7, and 1.5 Gy with red light, for 6 MVX, Ir-192, I -125, and Pd-103, respectively. EBT film was found to have minimal photon energy dependence of response for the energies tested and is suitable for dosimetry of radiation with a wide energy spectrum, including primary and scattered radiation. XR-QA film is promising for kilovoltage sources with a narrow energy spectra. The new high sensitivity radiochromic films are promising tools in radiation dosimetry.

Densitometry↗

PubMed2000

A new verification film system for routine quality control of radiation fields: Kodak EC-L.

BACKGROUND: The use of modern irradiation techniques requires better verification films for determining set-up deviations and patient movements during the course of radiation treatment. This is an investigation of the image quality and time requirement of a new verification film system compared to a conventional portal film system. MATERIAL AND METHODS: For conventional verifications we used Agfa Curix HT 1000 films which were compared to the new Kodak EC-L film system. 344 Agfa Curix HT 1000 and 381 Kodak EC-L portal films of different tumor sites (prostate, rectum, head and neck) were visually judged on a light box by 2 experienced physicians. Subjective judgement of image quality, masking of films and time requirement were checked. RESULTS: In this investigation 68% of 175 Kodak EC-L ap/pa-films were judged "good", only 18% were classified "moderate" or "poor" 14%, but only 22% of 173 conventional ap/pa verification films (Agfa Curix HT 1000) were judged to be "good". CONCLUSIONS: The image quality, detail perception and time required for film inspection of the new Kodak EC-L film system was significantly improved when compared with standard portal films. They could be read more accurately and the detection of set-up deviation was facilitated.

Humans↗

PubMed1982

Sensitometric comparison of dental films of groups D and E.

In early 1981 Kodak introduced into the market Ektaspeed dental film of speed group E, which is more sensitive than Ultra-Speed film of speed group D. This investigation compared the sensitometric properties of Kodak dental films of speed groups D and E. By plotting a graph of density against log relative exposure, the characteristic curves were drawn for the two types of films. The curves showed that film E was approximately twice as fast as film D. A table derived from a mathematical description of the characteristic curves permitted the formulation of exact exposure-multiplying factors for changing from one type of film to another. Both films had almost the same useful density range, but film D had higher average film contrast and lower latitude than film E.

Radiography, Dental↗

PubMed1990

Sensitometric comparison of unexpired and expired duplicating films used in dentistry.

This investigation compared the sensitometric properties of unexpired and expired duplicating films. The characteristic curve derived for a duplicating film is the negative slope of a solarization curve; that is, it is different in direction to that of a regular x-ray film. An expired duplicating film is slower than an unexpired duplicating film. Unlike a negative working film, which gains fog past its expiration date, a positive working film (for example, a duplicating film) gains contrast past its expiration date. An expired duplicating film has a narrower latitude than that of an unexpired duplicating film for a useful density range. Clinically, a duplicating film can be used years after its expiration date even though there is a change in its speed and contrast.

Copying Processes↗