Halide Plates Research Articles

Imaging the unimaginable: Medical imaging in the realm of photography

There is an almost innate urge in human beings to represent reality in a visual form. From rock art in the Paleolithic to images of galaxies, the quotidian and the extraordinary have been visually represented through the ages. Medical and scientific disciplines are no exception. Accurate representation of the human body structures and anatomy based on cadaver dissections was almost not possible up to the Renaissance due to ethical, social, and religious beliefs and objections. The works of Leonardo da Vinci (1452-1519) and others and, later, Andreas Vesalius (1514-1564), who produced De Humanis Corporis Fabrica, are considered landmarks in the history of medicine. During the following centuries medical and scientific illustration relied upon the expertise of physician-artists and scientist-artists until a new paradigm appeared in the realm of scientific (medical) illustration: the invention of photography in the 19th century. Two of the medical disciplines most rapidly influenced by photography were dermatology and pathology, both macro- and microscopic. Physicians rapidly started to use photographs as a tool for consultation, documentation, and education, and large collections of images were amassed by individuals and institutions for these purposes. Photographic images are produced by visible light impressing a light-sensitive material such as a silver halide plate, and nowadays a silicon chip. But photons are reflected by nontransparent objects, including the human skin. Developments in science and technology allowed the use of other types of radiation to reveal internal structures in the human body and, most interestingly, noninvasively. Thus today much of the medical diagnosis and treatment is guided by the so-called medical imaging with the use of these techniques, that is, medical photography, endoscopy, x-ray radiography, computer-aided tomography, magnetic resonance imaging, ultrasonography, thermography, and nuclear medicine functional imaging techniques as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Some of these techniques are being applied at the microscopic level to study cell structure and even functional changes in real time. All these advancements in science and technology applied to medicine and other disciplines pose the question as to what extent physicians are trading their capabilities as clinicians. Ethics issues add to the complexity of this new era governed by constant changes in scientific paradigms.

Wavelength selective holographic concentrator: Application to concentrated photovoltaics

In present investigation dependence of wavelength selectivity of holographic concentrators on depth of refractive index modulation have been reported through simulation and to validate with theoretical predictions, experimental curves have also been plotted with typically recorded three holographic concentrators on silver halide plate of different depth of refractive index modulations (n1=0.014, 0.018 and 0.024) at available wavelength sources (λ=488nm, 514.5nm, 532nm and 632.8nm) and are found to be in good agreement. In addition intensity distribution of different regions of the spectrum is measured and voltage generated due to incidence of different colors of the spectrum onto the Si solar cell is also being reported.

Bacteriorhodopsin as a high-resolution, high-capacity buffer for digital holographic measurements

Recent trends in optical metrology suggest that, in order for holographic measurement to become a widespread tool, it must be based on methods that do not require physical development of the hologram. While digital holography has been successfully demonstrated in recent years, unfortunately the limited information capacity of present electronic sensors, such as CCD arrays, is still many orders of magnitude away from directly competing with the high-resolution silver halide plates used in traditional holography. As a result, present digital holographic methods with current electronic sensors cannot record object sizes larger than several hundred microns at high resolution. In this paper, the authors report on the use of bacteriorhodopsin (BR) for digital holography to overcome these limitations. In particular, BR is a real-time recording medium with an information capacity (5000 line-pairs/mm) that even exceeds high resolution photographic film. As such, a centimetre-square area of BR film has the same information capacity of several hundred state-of-the-art CCD cameras. For digital holography, BR temporarily holds the hologram record so that its information content can be digitized for numeric reconstruction. In addition, this paper examines the use of BR for optical reconstruction without chemical development. When correctly managed, it is found that BR is highly effective, in terms of both quality and process time, for three-dimensional holographic measurements. Consequently, several key holographic applications, based on BR, are proposed in this paper.

Real-time color holographic interferometry.

A new optical technique based on real-time color holographic interferometry has been developed for analyzing unsteady aerodynamic wakes in fluid mechanics or for measuring displacements and deformations in solid mechanics. The technique's feasibility is demonstrated here. It uses three coherent wavelengths produced simultaneously by a cw laser (mixed argon and krypton). Holograms are recorded on single-layer panchromatic silver halide (Slavich PFG 03C) plates. Results show the optical setup can be adjusted to obtain a uniform background color. The interference fringe pattern visualized is large and colored and exhibits a single central white fringe, which makes the zero order of the interferogram easy to identify. An application in a subsonic wind tunnel is presented, in which the unsteady wake past a cylinder is recorded at high rate.

Post-heat treatment applied to correlation filters recorded on silver halide plates

Recently, a post-heat treatment to improve the diffraction efficiency of silver halide amplitude holograms for display has been presented. We show that the post-heat treatment can also be applied to different kinds of matched filters used in pattern recognition tasks. The post-heat treatment increases the diffraction efficiency of filters and preserves their information content at the same time. Thus its effect can be considered as a bleaching procedure. Experimental results are presented.

Silver halide noise gratings recorded in dichromated gelatin

It is shown that high efficiency noise gratings may be recorded in dichromated gelatin when a single beam traverses a silver halide plate held in contact with a dichromated gelatin plate. A replay beam, in the same direction as the recording beam, will then reconstruct the noise radiation and will itself be depleted. Owing to swelling of the dichromated gelatin plate at processing maximum depletion occurs at a shorter wavelength. A model using geometrical constructions on the Ewald sphere is shown to be able to predict the optimum wavelength.

Reflection holograms replayed at infrared and ultraviolet

The transmission characteristics of reflection holograms recorded in commercially available silver halide plates at δ = 514.5 nm are investigated. It is shown that they can be replayed up to infrared, and relying on second harmonic modulation, down to ultraviolet wavelengths. A simple coupled wave theory is found to give good agreement with the experimental results.

Reactions of salts of hexakis(pyridine N-oxide)M(II) complexes (M = Co, Ni, Zn) and alkali halides used in infrared spectroscopy

A number of salts of hexakis(pyridine N-oxide)zinc(II) complexes decompose in alkali halide pellets. Initially ion exchange occurs, often followed by the formation of Zn(pyno) 3X 2 (pyno = pyridine N-oxide; X = Br, Cl). The analogous cobalt and nickel compounds are nearly always stable. A mull between alkali halide plates gives greater amounts of the same product Washing this product with toluene gives Zn(pyno) 2X 2. Examples of i.r. and far i.r. spectra are given. Energetical and structural effects are discussed. Far i.r. spectra of M(pyno) 3X 2(M = Co, Zn) confirm the structure [M(pyno) 6][MX 4] for these compounds. New compounds are [Zn(pyno) 2(NO 3) 2], [Zn(pyno- d 5) 2[NO 3) 2], [Zn(pyno- d 5) 6](NO 3) 2 and [Zn(pyno) 6]I 2.

Holographic Recording Materials-A Review

Holographic recording materials in current use are examined along with a few of their applications. Some experimental media are also studied. No effort is made to rank the commercial materials, since satisfactory results can be obtained with any of them. The discussion covers silver halide plates and films, photoresists, thermoplastics, photopolymers, dichromated gelatin, photochromic materials, electrooptical crystals, styryl free radical film, and TEP film. A convenient summation of some material properties is presented in tabular form.

A Micro-Extraction Technique with Compounds Isolated from Thin-Layer Chromatograms

A micro-apparatus is described for the extraction of drugs and related compounds from thin-layer or paper chromatograms by continuous elution with 1ml. solvent. The sample, after extraction, is ground with KBr, mounted on a micro potassium halide plate, and placed in the center of a paper frame with a window area for infrared analysis. Spectra can be determined on 5- or 10-mcg. samples without beam condensers, ordinate expanders, or micro-dies.

Infrared emission spectra of quantities of pesticides in the microgram range

Infrared emission spectra of DDT, Sevin, Malathion, and Dieldrin have been measured with a multiple-scan interference spectrometer near ambient temperatures. Sample preparation was simple and nondestructive, the materials being supported on halide plates or first surface mirrors, thus avoiding the difficulties introduced by solvents, mulling, or pelleting techniques. The exploratory experiments indicate that quantities of pesticides in the microgram ranges can be examined by means of their self-emitted infrared radiation, thus showing the method to be potentially valuable for the examination of ultramicroscopic samples.

Absolute Infrared Intensity Measurements in Thin Films. II. Solids Deposited on Halide Plates

When a thin film of an absorbing substance is deposited on a halide plate, because of various reflection effects, the absorption coefficient measured experimentally in transmission will not correspond to the true absorption coefficient. This paper examines the relationship between this apparent absorption coefficient (α′) and the true absorption coefficient (α). Starting with a rigorous expression for the observed transmission, a relationship is established between α′ and α expressed as an infinite series in powers of d/λ (film thickness divided by wavelength). The result is valid for small d/λ. In the limit as d→0, a very simple relationship connects α and α′. For finite (but not too large) d, higher-order correction terms are derived. The theory is applied to the data of Wieder and Dows on SF6(s) deposited on AgCl and to the data of Yamada and Person on CS2(s) deposited on AgCl. For comparison and to calculate the higher-order correction terms, the data are also fit and analyzed using the damped oscillator model (DOM). The DOM results agree well with the theory. A marked change in band shape due to reflection effects is predicted for the two SF6 fundamentals. Some general suggestions are made concerning experimental procedures. It seems likely that the methods developed in this work will permit reliable corrections for reflection effects in thin film absorption measurements. In the final section, a rigorous method of treating the entire problem is outlined which is applicable, in principle, in all cases. This method depends on the fact that the transmission and phase shift can be related by a Kramers—Kronig-type dispersion relation. It is thus possible, in principle, to calculate α (and the refractive index) under any circumstances without any reference to a physical model. A preliminary application of this method to the SF6 data is presented.

Near Infrared Spectra of Crystalline Alkali Hydroxides

The technique of melting alkali hydroxides between alkali halide plates has been used to obtain the near infrared absorption spectra of LiOH, LiOD, NaOH, NaOD, KOH, and KOD. Complicated combination band structure is observed in NaOH similar to that observed previously in LiOH, Ca(OH)2 and Mg(OH)2. The deuterated spectra of LiOH and NaOH indicate that both translational and librational (or rotational) modes couple to the fundamental OH— ion vibrations. Fundamental frequencies of 3611±4 cm—1 and 2654±2 cm—1 are observed for KOH and KOD, respectively. Reactions of the alkali hydroxides with certain alkali halides are observed.

Studies in photographic sensitivity VII. The action of hydrogen peroxide on single-layer silver halide plates

1. (1) Single-grain-layer silver halide plates are only very slightly affected by hydrogen peroxide, no matter what the concentration of H 2O 2 or time of treatment, unless they have been given a previous light exposure. In this case the number of grains showing developability seems to be greater than the sum of those produced by light and hydrogen peroxide separately. 2. (2) The reason suggested for this is that not only developable latent image, but also undevelopable image is produced by light and that the hydrogen peroxide carries this over into developable latent image as well as makes its own proportion of grains developable. 3. (3) It is shown that Clark's hypotheses ( a) that the so-called sensitivity of specks consists of silver oxide or hydroxide, ( b) that the action of hydrogen peroxide is a purely chemical one on this oxide or hydroxide, reducing this to silver, which then makes the plate developable, are untenable, not being supported by experimental facts, and ( c) that reversal is due to peptization of the silver by the hydrogen peroxide, is still open to question. (4) It is further shown that while our original hypothesis that the action of H 2O 2 is one of chemiluminescence is not completely substantiated, it is at least not strongly contraverted except by one fact, namely, that acid H 2O 2 seems to be slightly more effective than alkaline H 2O 2 in producing a latent image. On the other hand, alkaline H 2O 2 may cause peptization of the sensitivity specks and hence work against the formation of developable centres.