Commercial Emulsion Research Articles

The Resolving Power/Exposure Relation for Black-and-White Emulsion Layers

AbstractA theory of photographic resolving power similar to that of Selwyn has been developed for black-and-white emulsions. At the limit of resolution, commercial emulsions exposed to Cobb test charts of low contrast show a constant ratio of image density difference to image granularity over a wide range of exposures. Good agreement is obtained between resolving power/exposure curves determined by direct experiment and those derived from sensitometric and image structure data for the emulsions.

Bleached reflection holograms

By applying recently developed, low-noise, processing techniques, high quality, bleached, reflection holograms of three-dimensional objects have been produced with a commercial photographic emulsion. When illuminated with a compact, white light source, these holograms give bright, reconstructed images with a signal-to-noise ratio which compares very favourably with that for unbleached, transmission holograms.

Internal-Image Formation and Related Photographic Effects

In accordance with generally accepted views, it is shown that variations in degree of Clayden and Villard effects and in Solarizability can be broadly correlated with the surface/internal speed ratio. In particular it is shown that increase of surface/internal speed ratio by increase of digestion time, or simply by increase of exposure time, leads to a decrease in the Villard effect, and that solarizability can be greatly enhanced by kinking which increases internal sensitivity without much effect on surface response. However, among collections of commercial emulsions, correlations between surface/internal speed ratio and latent-image effects involving rehalogenation processes are masked by differences in the halogen-accepting properties of the emulsions. Observations on the Villard effect support the view that the grains which do not form surface image readily are the more sensitive ones for internal-image formation, and this should be recognised in attempting to deduce ratios of surface to internal speed.

Determination of Alpha Emitting Particle Size by the Autoradiography Using ZnS (Ag) Powder Screen

The autoradiography using ZnS (Ag) powder screen was studied for estimating the particle size of alphaemitting dust collected on an air sampling filter paper.The sensitivities of three commercial emulsion films for the detection of plutonium particles were compared by using a ZnS (Ag) powder screen. The effect of particle size of ZnS (Ag) powder on the sensitivity was examined and also the change of apparent particle size distribution with exposure time was examined.As the result the following were obtained;1) The sensitivity of a polaroid film is about 10 times higher than that of the X ray films.2) The minimum detectable activity for the polaroid film is 0.01 dpm for the exposure of 168 hours, which is equivalent to the diameter of 0.25μ for a 239PuO2 particle.

Extemporaneous Formulation Of Topical Corticosteroids

To the Editor.— As an industrial pharmacist I recognize the importance of proper formulation to insure drug availability and agree with Burdick et al ( 211 :462, 1970) that improper formulation of corticosteroids "may diminish or completely abolish the therapeutic activity." The authors correctly pointed out that triamcinolone is much less active in topical preparations than triamcinolone acetonide 1,2 and questioned whether the suggestion of Fischer 3 to crush triamcinolone tablets and compound them into a commercial emulsion base would give an active product. They showed that such preparations are inactive when compared to commercial triamcinolone acetonide preparations. However, they did not show that extemporaneous formulations are inferior to commercial formulations of the same compound. There are questions I would like to raise. (1) The identification of the active ingredient in the six prescriptions is very important, and I wondered about the "tentative identification." Do the authors plan additional testing or

Wiener Spectrum of Experimental Emulsions with Cubic Homogeneous Grains, Comparison of the Spectra with the Wiener Spectra of Commercial Emulsions

In this paper, the Wiener spectra of experimental emulsions with homogeneous cubic grains are compared with the Wiener spectra of commercial emulsions which have the same mean radius as the experimental emulsions but have a greater range of grain sizes. The experimental noise spectra are then compared with the theoretical noise spectrum of an ideal emulsion.

Fresh and Frozen Egg Yolk Protein Fractions: Emulsion Stabilizing Power, Viscosity, and Electrophoretic Patterns

INTRODUCTIONTHE protein and lipoprotein complexes present in the egg yolk are responsible for its ability to function as an excellent emulsifier in many food products (Snell et al., 1935). The two primary lipoprotein fractions of the yolk are lipovitellin (Alderton and Fevold, 1945) and lipovitellenin (Fevold and Lausten, 1946); livetin and phosvitin (Mecham and Olcott, 1949) are the water soluble egg yolk proteins. Vincent et al. (1966) found that the livetin and lipoprotein fractions of the yolk contribute to its low surface energy which in turn is necessary for emulsion formation but may not influence the emulsion stability.The use of frozen egg yolk increases efficiency in commercial emulsion production. However, the utility of freezing pure egg yolk is limited by the irreversible gelation reaction (Moran, 1925) which egg yolk undergoes as a result of freezing and thawing, resulting in a product of greatly increased viscosity which is difficult…

The Relationship between Surface and Internal Sensitivity of Individual Grains

By use of sensitometric and processing techniques it is shown that for typical commercial emulsions the grains which do not form surface image readily are the more sensitive ones for internal-image formation. From residual grain size data it is shown that this relationship between surface and internal sensitivities exists within individual size classes. Arguments are presented in favour of the view that the reciprocal relationship between surface and internal sensitivity is due in part to inherent differences among grains. The observations emphasize that the surface/internal sensitivity ratio for grains of high surface sensitivity can exceed considerably the corresponding ratio for the emulsion layer as a whole for production of small or moderate densities.

The Tamm Level and Reciprocity Failure

Early grain counts imply that the entry of two photo-electrons into a unique feature of the grain makes certain the formation of a development centre either internal or external, the site being decided afterwards. The unique feature is identified with the Tamm conducting surface level, lying between the crystal and a colloidal coating formed during digestion. The Tamm level separates order from disorder and is undisturbed by the external centre but is obstructed by the internal which interferes with the ordered crystal surface. The commercial emulsion favours the external image, the undigested emulsion the internal. Both are affected by recombination of the first electron, and the properties of the colloidal coating, which alone is sensitive to weak light, are deduced. The external centre is a new source of low intensity reciprocity failure for the internal image, and the internal centre a new source of high intensity reciprocity failure for the external image. The early grain counts are identified with those for an undigested emulsion developed “to completion”.

Characteristics of three nuclear emulsions for autoradiography at the electron microscope.

On account of their low grain size three commercial emulsions, Gevaert NUC 307, Ilford L4 and Kodak NTE have been investigated to assess their qualities for electron microscope microautoradiography. Grain size distribution curves were determined and a developer suitable for microautoradiography was selected after having tested different types of developers. In order to investigate the sensitivities of the three emulsions, monolayer preparations were irradiated in the electron microscope, using an energy of 5.7 keV corresponding to the mean β-energy of tritium. After exposure the specimens were developed but left unfixed. The sensitivity may then be determined using the percentage of developed grains. For the formation of one latent image the Ilford L4 emulsion must be hit on the average by 1 – 1.4 electrons per AgBr grain; the corresponding figures for Gevaert NUC 307 and Kodak NTE are 2 – 3 and 4 – 5 respectively. The problem of resolution of point and plane sources of radioactivity is discussed. Future advances in microautoradiography will depend on the development of emulsions with lower grain sizes, but such improvement must not be at the expense of sensitivity.

Latensification in Radiographic Emulsions*

Latensification by means of post-exposures to selected wavelengths of light or near infra-red will provide as much as three-fold enhancement of response of some commercial X-ray emulsions to ionizing photons. The sensitivity can be similarly enhanced by special development procedures. A combination of these techniques permits a five- or six-fold increase in sensitivity in the low-density region, for some emulsions. Spectral sensitivity changes in the X- and γ-ray response are small; no rate dependence is observed; variations in total density, however, are found with differences in delay period between exposure and post-exposure and between post-exposure and processing. The effects may be explained by the change in the size and location of development cent res resulting in an improvement of development activity, and therefore in a larger number of developed grains. In some instances, there may be an increase in developed grain size.

Rate Dependence in a Solarizing Commercial X-Ray Emulsion: Sensitometric Properties, Number, and Structure of Developed Grains*

A comparison was made of optical density, mass of developed silver, number, projected area, and structure of the grains of a solarizing radiographic bromo-iodide emulsion exposed to Co60 gamma radiation at two different intensities, and developed in a surface developer. In contrast to the optical density and the mass of silver developed for a given exposure, which show only little dependence on intensity, before solarization sets in, the dependence of the number of developed grains on intensity of exposure is quite marked. Another anomaly is observed in the re-reversal region for exposure to high-intensity radiation. There, mass of silver does not vary with exposure in the same direction as optical density.Associated with the changes in photometric behavior are marked changes in grain structure, while the changes in the projected area of developed silver are small. The photometric properties cannot be correlated uniquely with grain structure over the entire exposure range.

The Relationship between Covering Power at Saturation Density and Undeveloped Grain Size

AbstractExperimental values of covering power at diffuse saturation density of a range of commercial emulsions an energetic chemical development are compared with those expected on the basis of the Nutting expression for density. employing in the latter the grain-size characteristics of the undeveloped emulsions. For the size range investigated (0.07 to 2µ2) there is reasonable prediction of the variation of covering power with grain size, but the predicted values are too small. Apparently the average ratio of effective developed mean grain projective area to undeveloped mean area is about 2-6, this factor decreasing at a significant rate with increasing grain size. This ratio represents the product of two factors: the increase in geometric area of grains as a result of the development process, and the effective increase in size owing to light-scatter effects within the layer. Experimental observations indicate that the factorial increase of projective area on energetic chemical development is about 1-3 t...

Nicotine Inhibits Anticoagulant Actions of Heparin

The lipid-clearing, anticoagulant actions of heparin, a sulfated mucopolysaccharide, can be inhibited by nicotine, according to Dr. Harold J. White of the Veterans Administration Hospital in Roxbury, Mass. In a paper "The Antagonism Between Nicotine and Heparin Activity," White observed that in white rats, injected with nicotine followed by heparin (and in reverse order), the normal lipid-clearing action of heparin decreased. In addition, the presence of nicotine inhibited the anticoagulant qualities of heparin, he said. When added to the blood, nicotine both accelerated (when present in minute amounts) and prolonged (when present in larger amounts) the normal clotting time. The accelerating effect could be reversed by prior incubation of nicotine with heparin. White's two-part study proceeded along these lines: <h3>In vitro.—</h3> Post-heparinized rat plasma (.5 ml) was incubated for one hour with varying amounts of nicotine in a commercial emulsion. The clearing factor activity (CFA) was measured as optical density

Studies of the Fine Structure of the Wax Layer of Sultana Grapes

The surface waxy bloom of sultana grapes has been studied using the carbon. replica technique in combination with electron microscopy. This layer consists of a series of overlapping wax platelets, each of which is about 0�1 f' wide. The air spaces between the wax platelets become filled with liquid when sultana berries are dipped in commercial emulsions known to accelerate their drying rate. Washing in distilled water removes this layer of dipping emulsion from the surface. The appearance of dipped and washed grapes is similar to that of untreated grapes.

High-resolution autoradiogaphy. II. The problem of resolution.

The resolution obtainable in electron microscopic autoradiographs, using a photographic emulsion consisting of a monolayer of silver bromide crystals, was investigated theoretically and experimentally. The expected distribution of exposed crystals around a point source was calculated from the geometry of the preparation and from the range distribution of the beta particles emitted by tritium. From such a distribution an autoradiographic resolution of the order of 1000 A can be predicted. From the point source distribution, the expected distribution of grains around bacteriophages labeled with tritium was calculated. This distribution was also measured experimentally in electron microscopic autoradiographs of bacteriophages T-2 labeled with thymidine-H(3). The two distributions agreed closely. It was also verified, using the nuclear region in thin cross-sections of Bacillus subtilis labeled with thymidine-H(3), that resolutions of the same order were obtained for extended sources. It was concluded that an autoradiographic resolution of 1000 A could be achieved with a presently available commercial emulsion, although emulsions with finer grains might be desirable in some circumstances.

A CONTROLLED ASSAY OF CLEARING FACTOR, AND ITS APPLICATION IN STUDIES OF THE ROLE OF HEPARIN IN CLEARING FACTOR PRODUCTION

A method for measuring clearing factor in vitro has been developed. This method makes use of a standard substrate–receptor system obtained by adding constant amounts of a commercial fat emulsion to stored plasma. Best results are obtained when plasma which has been heated to 56 °C for 5 minutes and stored at −20 °C is used at 50% concentration. A comparison of the production of clearing factor in different species using plasma from different species was made. With all clearing factors, the human and dog plasmas are superior to the other species studied. The results of intravenous and depot injections of heparin are compared.The intravenous injections cause maximum prolongation of clotting time almost immediately and maximum amounts of clearing factor within 30 minutes. Depot injections stimulate the production of maximum amounts of clearing factor as quickly as intravenous injections, but the maximum effect on the clotting mechanism is delayed for three to four hours.The implications of these results are discussed. The application of the method in the study of diseases associated with abnormalities in plasma proteins and fat metabolism is suggested.

Use of Commercial Sheet for Spectrochemical Analysis

Based on several years' experience, the substitution of commercial sheet film for glass plates is advocated for spectrochemical purposes. Advantages of sheet film are freedom from breakage, ease of cutting and filing, and ability to photograph wide spectral regions in one piece. Commercial emulsions are more uniformly coated and are much more free from blemishes. Holders for glass plates can be used for film with no structural changes. A list of available emulsions which can be used in place of spectroscopic plates is presented.

Estimation of the Critical τ Period in Latent-Image Formation by Intermittent Exposures*

Low-intensity reciprocity-law failure in photographic exposure represents an inefficiency arising from the regression of the latent image in its early stages of growth. Evidence has been given to show that the stable sublatent image requires for its formation the action of two or more quanta in a small critical time period, τ. A new method for evaluating this critical time period by intermittent exposures is described.Experiments carried out on four commercial emulsions showed approximately equal τ periods of the order of 3 seconds. Studies were also made on three experimental emulsions to determine the effect of certain types of chemical sensitization on the critical τ period. These experiments were carried out for both the surface and the internal latent image by means of varied development procedures. The critical τ period varied between 3 and 10 seconds for the surface image and remained essentially constant at about 4 seconds for the internal image. Results indicate that chemical sensitization increases the critical τ period of the surface latent image and slightly decreases the critical τ period of the internal image.

On the Mechanism of the Photographic Effect of Ultrasonic Waves

Experimental data are submitted indicating the existence of a direct action of ultrasonic waves on a photographic emulsion, contrary to the views of some other workers. All of the evidence obtained here indicates a closer correlation with the softness of the emulsion than with the known behavior of ultrasonically produced luminescence. Information is presented as to temperature dependence of the image, effect of ambient pressure, light shielding, and the behavior of various types of commercial emulsions.