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At least 145 records · Page 8Linked to original sources
PubMed2003

Dependence of film tension on the thickness of smectic films.

The film tension tau of free standing S(A) films has been measured for films with thicknesses between 2 and 150 layers. There is a clear increase of tau with the thickness for very thin films and a nonlinear slower increase for high thickness. The nonlinearity depends on the amount of liquid crystal accessible to the meniscus of the film during the drawing process. Several models are discussed that describe these effects.

Journal Article↗
PubMed1978

The measurement of the adhesion of film coatings to tablet surfaces: the effect of tablet porosity, surface roughness and film thickness.

The effect of tablet porosity, surface roughness and film thickness on the adhesion of hydroxypropyl methyl cellulose films to placebo tablet substrates have been studied using a specially designed tensile tester (Fisher & Rowe, 4976). There were direct relations between measured adhesion and tablet porosity and also surface roughness and tablet porosity. The effect of film thickness on the measured adhesion is complex with an initial decrease with thicknesses up to 35 micron and then a gradual increase with thicknesses up to 140 micron dut to differences in the strees distribution within the film during testing. A knowledge of these effects is necessary if results from various sources are to be compared. The findings illustrate the potential capability of the extrapolation of measured adhesion results to zero porosity and zero thickness values in order to obtain a measure of the true or intrinsic adhesion at any film/tablet interface without the confusing elements of tablet porosity, surface roughness and residual stresses in the film.

Adhesiveness↗
PubMed1981

The cracking of film coatings on film-coated tablets--a theoretical approach with practical implications.

A theoretical approach of film cracking is presented using equations which allow for the calculation of both the internal stress in a film coating due to shrinkage of the film on evaporation of the solvent and the thermal stress due to differences in the thermal expansion of the film coating and tablet substrate during changes in temperature arising out of the coating processes. The practical implications of this approach in film formulation are discussed with particular reference to the choice of tablet core formulation, the grade of polymer used, the type and concentration of both plasticizers and pigments and the solvent system used in the coating process.

Chemistry, Pharmaceutical↗
PubMed1983

The refractive indices of polymer film formers, pigments and additives used in tablet film coating: their significance and practical application.

The refractive indices of both the polymer film formers and additives are a fundamental factor in defining the appearance of the subsequent film coatings. The refractive indices of the polymer film formers are all in the region of 1.5 but those of pigments and additives vary between 1.5-3.2. Most pigments and additives are also anisotropic, i.e. they possess different refractive indices depending on their orientation. These observations have implications in the use of pigments and additives for the production of both opaque films with good hiding power and film-coated tablets with highlighted intagliations.

Chemistry, Pharmaceutical↗
PubMed2003

Diagnosis of Plasmodium falciparum malaria at delivery: comparison of blood film preparation methods and of blood films with histology.

We compared peripheral and placental blood films (made by different techniques) with placental histology for diagnosis of Plasmodium falciparum malaria in pregnancy. Samples from 464 women were examined, of whom 124 (26.7%) had active P. falciparum infection and 148 (31.9%) had past infection. Placental histology was more sensitive (91%) than peripheral blood film (47%) or placental blood film (63%) examination and also detected past infection. Few women had microscopically detectable infection without a positive histology. Infection detected by histology only and past infection were both associated with significantly lower infant birth weight and with lower hemoglobin concentrations compared to the results for uninfected women. Thick blood films were prepared with blood obtained by placental incision or scraping of the incision margin (263 samples) or by washing of placental tissue (235 samples). Each gave similar sensitivities (76 to 78%), specificities (98 to 99%), positive predictive values (92 to 98%), and negative predictive values (93 to 94%); but the median levels of parasitemia were lower for incision samples (840 parasites/ micro l) than scrapings (2,295 parasites/ micro l) (P = 0.02). Placental histology is the most sensitive method for the diagnosis of malaria in pregnancy. Methods for preparation of placental films may affect the density, but not the prevalence, of P. falciparum infection detected.

Animals↗
PubMed1989

Biomicroscopy of the tear film: the tear film of the pekingese dog.

Polarised light biomicroscopy was used to examine the normal pre-corneal tear film in 21 eyes of 12 pekingese dogs. The purpose of the study was to examine the influence of excessive exophthalmos on the pre-corneal tear film in the dog. The majority of the animals were found to have high levels of ocular surface contamination by particulate material and plaques of viscous mucus. Other abnormalities included surface lipid with an abnormal granular (three dogs) or 'curdled' (two dogs) appearance; excessive thinning of the lipid layer of the tear film; and the presence of dark globular structures in two dogs, which were presumed to be abnormal meibomian lipid. Break up of the tear film was observed in one dog. Grossly, a thread of viscous mucus was frequently observed along the margin of the lower eyelid. It is postulated that this thread forms because of the excessively exophthalmic conformation of the breed, which prevents the normal access of effete mucus and entrapped debris to the lower conjunctival fornix. The combination of the above factors in the pekingese is suggested as the mechanism whereby the tear film has a reduced stability, thus enhancing the risk from factors more usually considered to initiate corneal ulceration in the breed. The possible adverse effects of lid splitting for the mass removal of distichiae in exophthalmic dogs is discussed.

Animals↗
PubMed1994

Comparison of a new dual characteristic film-screen system (insight) with a standard film-screen system for chest radiology.

A new dual image receptor screen-film combination has been developed by Kodak with the objective of improving mediastinal and retro-cardiac detail whilst retaining good contrast and detail in the lung fields. This system was compared with our standard chest system. The study population was 36 patients with sarcoidosis. A postero-anterior (PA) chest film using our standard system was followed by a PA chest film using the new system--both using high kVp technique. The pairs of radiographs were assessed for (1) presence or absence of lymphadenopathy; (2) visibility of anterior and posterior mediastinal and azygo-esophageal lines; (3) visibility of vessels in the outer and inner thirds of the lungs and (4) visibility of infiltrates, if present. The new film-screen combination was judged to show the mediastinal structures better in almost all instances. However, our standard combination was preferred for lung detail visualization in most cases. No significant difference was found between the two systems in their ability to demonstrate lymphadenopathy. The results were almost unchanged when the observers were given the option to score the criteria as equally well demonstrated on both films as opposed to not having this option available. We feel the advantages of the Insight system do not compensate for the significant loss of parenchymal detail resulting from the use of this system.

Adult↗
PubMedDate not supplied

[Sensitometric characteristics of medical roentgenographic and fluorographic films. Sensitivity of the amplifying screens combined with a film].

Factors affecting the degree of sensitivity of roentgenographic and radiofluorographic films and of their combinations with fluorescent screens are considered. A method of films exposure with a roentgenosensitometer permitting it to determine the sensitivity in conditions closely approaching the ones used in practice and corresponding to the minimum of the isoopaque is suggested. A way for determining the sensitivity of films in m2-mJ1 and lx-1-c-1 is indicated. Numerical values for the sensitivity of the films and their combinations with the screens are given. It is shown that with Eef = 38 keV, T = 20 degrees C, exposure time of 0.4--1 sec and optical density 1.00 over general focusing the lower limit of the X-ray RM-1film sensitivity to the light of CaWO4-screens is 38 m2-mJ-1 and of the fluorographic film Pphi-3 to the light of the Zn0-68Cd0-32S--Ag-screens -- 14.6 m2-mJ-1 or 30 lx-1-c-1.

Fluoroscopy↗
PubMed2001

Detection of interproximal caries using methods applicable to a field environment: digital radiography, manually processed film, and self-developing film.

The purpose of this study was to determine if the alternatives to conventional dental radiography are diagnostically equivalent to conventional film in a field setting. These alternatives, digital radiography and self-developing film, could significantly decrease the weight and cubic size of a field X-ray set. Five radiographic methods were evaluated: self-developing film, manually processed film, film developed in an automatic processor, digital images on a liquid crystal diode, and digital images on a cathode ray tube screen. The results indicate that the liquid crystal diode system adversely affected the ability of the dentist to detect small interproximal lesions. The other methods were statistically equivalent. A recommendation for an "image acquisition" system to be included in a field dental treatment facility should be based on clinical factors as well as nonclinical factors such as cost, reliability, and logistical support requirements.

Analysis of Variance↗
PubMed1991

[Portal films and daylight film developing].

Automatic daylight film handling systems in radiotherapeutic departments are useful to process simulation films. Plastic film cassettes with two polished stainless steel screens (2 mm at the front and 0.5 mm at the back) instead of the fluorescent intensifying screens are used. Regular diagnostic films are exposed with five monitor units. Loading and unloading of the cassettes are performed automatically. Exposed films are rapidly available with sufficient quality.

Automation↗
PubMed1990

Evaluation of image quality in individual films of double film packets.

A total of 47 double film packets were exposed of a radiographic standard (step-wedge), a clinical model (dried skull), and a clinical situation (endodontic therapy). Dentists were employed as expert observers to compare detail and definition between front and back films within each packet. Front films (those closest to the source) had significantly superior image quality compared to back films (those further from the source). In vitro radiographic trials were significantly similar to in vivo radiographic results.

Chi-Square Distribution↗
PubMed1998

Characteristics of a commercially available film digitizer and their significance for film dosimetry.

Dosimetric detectors used in high-energy photon radiation dosimetry mainly perform a zero- or one-dimensional measurement. These low-dimensional methods are not always adequate in the context of conformal radiotherapy. Therefore, two-dimensional film dosimetry has attracted attention. We studied a 12-bit CCD-based film digitizer (Vidar VXR-12) with regard to accurate film dosimetry. We investigated the stability, linearity, noise, effects of aberrant light scatter and built-in conversion tables. A digitizing resolution of 75 dpi and a digitizing speed of 20 ms/line result in an optimal signal-to-noise ratio. At optical densities above 2.0, the reading accuracy of the digitizer is limited by noise. The results of various experiments prove both the capabilities and limitations of the digitizer studied. We also propose a method to acquire and process film data using such a digitizer.

Biophysical Phenomena↗
PubMed1990

Potential use of a 100-mm film digitizer and image processor for film archiving.

The present study was undertaken to examine experimentally and clinically whether a 100-mm roll-film digitizer and image processing device could preserve or increase the diagnostic accuracy of 100-mm roll films used in the mass screening of patients for lung cancer and provide picture archives of high enough image quality to replace the original films. The quality of the processed digitized CRT image was found to be only slightly less than that of the original films. There was only a slight decrease in diagnostic accuracy, and the system was judged to be potentially useful as a miniature picture archiving and reference system.

Equipment Design↗
PubMed2006

Sensitivity of linear CCD array based film scanners used for film dosimetry.

Film dosimetry is commonly performed by using linear CCD array transmission optical densitometers. However, these devices suffer from a variation in response along the detector array. If not properly corrected for, this nonuniformity may lead to significant overestimations of the measured dose as one approaches regions close to the edges of the scanning region. In this note, we present measurements of the spatial response of an AGFA Arcus II document scanner used for radiochromic film dosimetry. Results and methods presented in this work can be generalized to other CCD based transmission scanners used for film dosimetry employing either radiochromic or radiographic films.

Computer Peripherals↗
PubMed1996

Short communication: portal imaging with film-cassette combinations: what film should we use?

A large number of commercially available X-ray films were obtained to assess their suitability for megavoltage radiotherapy portal imaging. The speed (represented by optimum film dose), gamma (gamma) and latitude of all these films were determined. Films with high gamma values are recommended for clinical use to maximize the low levels of radiation contrast produced by a megavoltage beam.

Humans↗
PubMed2004

Thick film traps with an irregular film. Preparation and evaluation.

A new method for preparation of sorbent-based ultra-thick film traps for concentration of trace volatile components from gaseous matrices is described. The procedure is based on blowing a prepolymer (polydimethylsiloxane) through a capillary tube, forming an irregular film of stationary phase. Subsequently, the prepolymer is immobilized in a few seconds by heating to 200 degrees C. Evaluation of the performance of the new traps showed that the loss of efficiency, compared to regular smooth film traps is only on the order of 20-30%. In terms of breakthrough volume, this loss in performance is rather insignificant. The technology is extremely simple and allows a rapid and cheap production of a large number of ultra-thick film traps, even in non-specialized laboratories. The method can be applied to any type of cross-linkable stationary phase, thereby expanding the scope of sorbent-based trapping and preconcentration concept. Many applications are anticipated in trace and ultra-trace analysis in a wide range of fields, such as environmental chemistry, polymers, food and process analysis.

Dimethylpolysiloxanes↗
PubMed2003

Phospholipid black foam films: dynamic contact angles and gas permeability of DMPC+DMPG black films.

The behavior of black foam films from aqueous dispersions of dimyristoylphosphatidyl-choline (DMPC) with addition of the soluble phospholipid dimyristoylphosphatidylglycerol (DMPG) has been studied in dynamic conditions. The dynamic contact angles theta and the gas permeability coefficient K have been measured using the diminishing bubble method. The DMPC vesicle suspension in water is obtained through sonication and DMPG is dissolved in it. Two solutions with different NaCl concentrations (0.1 M and 0.5 M) have been studied. The behavior of the dynamic contact angles is very different for DMPC black films with, and without DMPG, respectively. They follow very different time dependence during spontaneous or forced variations of the bubble size. The gas permeability coefficient is significantly reduced by the DMPG addition. The NaCl concentration also influences this specific behavior. It seems that the electrically charged DMPG anions, which determine a significant electrostatic disjoining pressure, play an important role for this specific behavior. The results are discussed in connection with data regarding the thickness and structure of these black foam films. Films from DMPC+DMPG solutions in ethanol plus water mixed solvent have been studied as well, but no quantitative results could be obtained.

Biophysical Phenomena↗
PubMed2006

Surface- and bulk-modified galactoglucomannan hemicellulose films and film laminates for versatile oxygen barriers.

The objective of this study was to create oxygen barrier films based on the hemicellulose O-acetylgalactoglucomannan (AcGGM) that show high resistance toward moisture-rich conditions. We have applied Williamson benzylation, a classic derivatization method of carbohydrates, as well as two different methods for surface grafting, and, finally, lamination of unmodified hemicellulose films with the synthesized hydrophobic benzylgalactoglucomannan (BnGGM). It was found that the thermoplastically behaving BnGGM could form independent transparent and strong films that were easy to handle. As expected, their resistance toward water was very high, and the oxygen barrier properties showed drastically lower sensitivity toward moisture than films from the corresponding unmodified material. The surface grafting and lamination methods were approached in order to try and combine excellent barrier properties with moisture tolerance. It was found that the grafting methods applied had a positive effect in this direction; however, lamination turned out to be an even more promising option.

Carbohydrate Conformation↗