Optical Densitometer Research Articles

Nuclear magnetic resonance imaging: a noninvasive analysis of moisture distributions in white oak lumber

Nuclear magnetic resonance (NMR) imaging is a valuable diagnostic tool that detects the presence of hydrogen protons or water in material studied. Recently the technique was successfully used to observe the occurrence of defects within logs. The present study examined the feasibility of using NMR imaging for analyzing moisture distributions within white oak (Quercusalba L.) lumber. At selected days during drying, three thicknesses of lumber were imaged to detect free water, using a clinical 0.5-T whole body NMR scanner. NMR was shown to provide a noninvasive image of the internal structure of lumber. Images revealed that growth ring orientation and rays may play an important role in the drying process. Moisture distributions (shell and core) were qualitatively observed. For a quantitative interpretation, images were measured with an optical densitometer. The average moisture content of the board was correlated successfully to the weighted average optical density for the shell and core regions combined.

Evaluation of freeze-substitution and conventional embedding protocols for routine electron microscopic processing of eubacteria

Freeze-substitution and more conventional embedding protocols were evaluated for their accurate preservation of eubacterial ultrastructure. Radioisotopes were specifically incorporated into the RNA, DNA, peptidoglycan, and lipopolysaccharide of two isogenic derivatives of Escherichia coli K-12 as representative gram-negative eubacteria and into the RNA and peptidoglycan of Bacillus subtilis strains 168 and W23 as representative gram-positive eubacteria. Radiolabeled bacteria were processed for electron microscopy by conventional methods with glutaraldehyde fixation, osmium tetroxide postfixation, dehydration in either a graded acetone or ethanol series, and infiltration in either Spurr or Epon 812 resin. A second set of cells were simultaneously freeze-substituted by plunge-freezing in liquid propane, substituting in anhydrous acetone containing 2% (wt/vol) osmium tetroxide, and 2% (wt/vol) uranyl acetate, and infiltrating in Epon 812. Extraction of radiolabeled cell components was monitored by liquid scintillation counting at all stages of processing to indicate retention of cell labels. Electron microscopy was also used to visually confirm ultrastructural integrity. Radiolabeled nucleic acid and wall components were extracted by both methods. In conventionally embedded specimens, dehydration was particularly damaging, with ethanol-dehydrated cells losing significantly more radiolabeled material during dehydration and subsequent infiltration than acetone-treated cells. For freeze-substituted specimens, postsubstitution washes in acetone were the most deleterious step for gram-negative cells, while infiltration was more damaging for gram-positive cells. Autoradiographs of specimens collected during freeze-substitution were scanned with an optical densitometer to provide an indication of freezing damage; the majority of label lost from freeze-substituted cells was a result of poor freezing to approximately one-half of the cell population, thus accounting for the relatively high levels of radiolabel detected in the processing fluids. These experiments revealed that gram-positive and gram-negative cells respond differently to freezing; these differences are discussed with reference to wall structure. It was apparent that the cells frozen first (ie., the first to contact the cryogen) retained the highest percentage of all radioisotopes, and the highest level of cellular infrastructure, indicative of better preservation. The preservation of these select cells was far superior to that obtained by more conventional techniques.

Nuclear medicine studies of aging—VIII. Bone to soft-tissue ratio of 99mTc labeled MDP and HMDP vs age

An objective approach to determine whether there was an advantage of using 99mTc-MDP or 99mTc-HMDP for bone imaging, particularly in elderly subjects, was evaluated by measuring the bone to soft-tissue ratio in relation to age. This was done by quantifying analog images of the femoral region by using an optical densitometer. A ratio (mean for right and left thighs) was determined for mid-femur to adjacent soft-tissue. These values were analyzed in relation to the age of patients studied with either MDP or HMDP. Little correlation with age was observed. An analysis at 10-year intervals of age indicated a decline in the ratio after 70 years, without any significant difference between MDP and HMDP.

Nuclear medicine studies of aging—IV.Femoral proximal to distal radionuclide uptake gradient

Analyses of radionuclide bone scans were carried out to determine if, with the aging process, there were measurable changes in the femoral gradient of activity from proximal to distal portions of bone. Images of the femoral region were obtained using a gamma camera 2-3 h after i.v. administration of 99mTc labeled MDP. Sixty patients (1-85 years old) were selected based on the criteria that their femoral images appeared normal and there was no history of limb disease. Radionuclide concentrations at the upper, middle, and lower regions of the femur were determined from the femoral scans by using an optical densitometer, and background corrected. Results were expressed as ratios of upper to middle, lower to middle, and upper to lower regions of the femur. The analysis showed that the lower to middle ratio declined with age.

An automated method for measuring thicknesses of layered sediments

Varves from many environments have been used as paleoclimatic indicators. Measurement of varve thicknesses has typically been done manually, but an automated procedure would provide more accurate measurements with considerable savings in time. An automated method described herein involves digitizing an x ray of the core with a high-resolution optical densitometer. The two-dimensional optical density field is filtered to enhance the varve signal, and the filtered series is then used to define a series of line segments representing varve boundaries. The distance between adjacent boundaries is then averaged across the core to obtain the mean thickness of each layer. A section of thin laminae from near the bottom of a long core from the Gulf of California (Deep Sea Drilling Project Hole 480) is analyzed to illustrate the technique.

Homogeneity and fissure determination in uranium bars with solid state nuclear track detectors

A simple and efficient method for determining fissure and concentration inhomogeneity in uranium bars is the alpha-radiographic technique. In our present work uranium bars made by ININ (Mexico) were studied by using CR-39 track detectors. The space inhomogeneity in track density was measured by an optical densitometer. The presence of fissure is determined by a microfiche reader. Such a study takes only few hours and does not require sophisticated instrumentation.

A scanning optical densitometer using deconvolution to measure soot concentrations in axisymmetric flames

Describes a sensitive dual-beam densitometer for measurement of soot concentrations in axisymmetric diffusion flames. The densitometer was designed to avoid interference from flame luminosity or schlieren effects, and had a noise level of 10-4 transmission. The flame being studied was traversed under automatic control through one light beam of the densitometer. This gave a set of absorption profiles at various heights above the burner. The local absorption coefficients (and hence soot concentrations) were then calculated by the deconvolution technique. The time taken to scan a complete flame, with soot measurements at about 150 points, was about 45 minutes. The authors discuss possible errors in the deconvolution process and give examples of typical soot concentration profiles. Possible improvements to the apparatus are also suggested.

Digital image processing of two dimensional echocardiograms: Identification of the endocardium

Digital computer image-processing techniques were applied to two dimensional echocardiograms to improve the accuracy of cardiac spatial measurements by enhancing endocardial recognition. Images were photographed from the two dimensional echocardiographic monitor and digitized using an optical densitometer. Image-processing algorithms were applied to the digitized images as follows: (1) Multiple images were averaged; (2) a gray level threshold was chosen to separate the image into tissue and cavity regions on the basis of amplitude (brightness) of the returning echoes; (3) endocardium was traced between the regions; (4) endocardial position was confirmed by matching this boundary with a contrast edge map of the original images; and (5) the endocardial boundaries were tested by comparison with simultaneous M mode echocardiograms. A linear correlation was found between M mode and computer-processed two dimensional echocardiographic measurements of ventricular septal thickness (r = 0.88); this was superior to the correlation between M mode and unprocessed two dimensional echocardiographic septal measurements (r = 0.55). The correlations between M mode and processed or unprocessed two dimensional echocardiographic measurements of left ventricular internal dimension were similar (r = 0.89 and 0.85, respectively), but the slope of the regression line for the processed data more closely approximated the line of identity (p <0.05). It is concluded that endocardial outlines derived with use of digital image-processing techniques lead to left ventricular measurements that correlate more closely with M mode measurements than do dimensions derived from unprocessed two dimensional echocardiography.

Low-drift optical-densitometer

A general purpose, optical densitometer has been constructed using inexpensive components. A drift rate of approximately 0.3% per hour, and a measurement accuracy of 0.1%, permit the instrument to detect small changes in the optical transmission of unknown samples.

Microcomputer-controlled digitizer and image analyzer

An automatic digitizer has been developed that employs a microcomputer-controlled photosensor to detect and digitize analog curves from strip-chart paper, drawings, photographs of oscilloscope traces, negatives, etc. The control and data acquisition programs are coded in BASIC enabling real-time interactive control of the system. Movement of the photosensor is accomplished under program control and is selectable in either a curve-follower or raster-scan mode. Use of visible-LED photodetectors permits curves drawn with different colored inks to be discriminated and separately digitized. The system is simple to use and highly versatile with capabilities that extended beyond curve digitization. In the raster-scan mode, operation of the apparatus as an optical densitometer is possible enabling detailed image analysis and digital image reconstruction to be performed (e.g., quantitative measurement of intensity distribution and mode structure from photographs of laser output beams.)

Insulin does not enhance uptake of 14C-deoxyglucose in the ventromedial nucleus of the hypothalamus

The effect of insulin on glucose metabolism in the ventromedial nucleus of the hypothalamus (VMH) was examined using 14C-deoxyglucose autoradiography. Unilateral VMH microinjections (0.5 μl) of 10 mU of regular insulin and contralateral VMH saline as control were accomplished through cannulae in diabetic and non-diabetic rats. Visual examination of autoradiograms of brain sections taken from these rats after the intracardial injection of 14C-deoxyglucose revealed no assymmetry in VMH optical densities (O.D.). Similarly, intraventricular injection of 0.2 U of insulin in 10 μl of saline did not produce any obvious darkening of the VMH autoradiogram of a non-diabetic rat. O.D. was quantified using an optical densitometer in another experiment. The average VMH O.D. taken from autoradiograms of diabetic rats which received 10 U/kg insulin and 50 μ Ci 14C-deoxyglucose intracardially was equivalent to that of diabetics which received saline and deoxyglucose. Autoradiographic O.D. of diaphragm muscle taken from insulin-treated rats was twice that of controls. These observations demonstrate that glucose metabolism in the VMH is not insulin-dependent.

Thermography as a Means of Blood Perfusion Measurement

The scanning infrared camera has been used to verify an analytical model relating blood perfusion rate to skin temperature. The blood perfusion rates were measured with both the mercury strain gage and the volume plethysmograph on the human forearm. Thermograms were taken of the forearm and temperature measured using an optical densitometer. Comparison of the volume plethysmograph with the strain gage, and the thermograms with the strain gage indicate thermography to be a useful means of measuring blood flow. Thermography has the advantages of being noninvasive and can be used to measure blood perfusion in parts of the body not easily monitored with occlusive techniques.

A fast precision scanning microscope stage

A servomechanism capable of moving a microscope slide in a plane to precision of better than 1/8 mu m over a field of up to 50 mu m square is described. Its purpose is to provide a scanning movement for an optical densitometer with a fixed, on-axis light spot. The scanning velocity can reach a maximum of 10 mm s-1. The instrument is designed to be controlled remotely (by computer) and to be both compact and lightweight.

古紙及び脱墨パルプ中のカーボンの簡易測定

The Quantitative analysis of carbon derived from black printing ink in waste paper or deinked pulp has been made by microscopic measurements of its numbers and dimensions in a hand sheet pulp. However, this method has several disadvantages; the contents of carbon thus determined contain some non-carbon dirts, and this must be carried out on the pulp sheets and is usually accompanied by some observational errors. In order to solve these disadvantages, a new determination method, what is called, wet decomposition method has been developed. The principle of this method is as follows.(1) Dissolve materials except carbon in waste paper or deinked pulp by wet oxidation, and filter off dissolved materials. (2) The collected residue consisting mainly of carbon is washed, dried and measured for its blackness with an optical densitometer. A constant ratio has been observed between the carbon contents and the blackness density for the residue. Therefore, the carbon contents can be determined by measuring the density of blackness. Decomposition of non-carbon materials containing wood cellulose, lignin and others is done with a boiling concentrated nitric acid and perchloric acid for about one and half hour in a Kjeldahl flask. In this study, the carbon contents were compared on the samples before and after deinking waste news by the floatation method. By means of employing both the new and the conventional method, carbon and other non-carbon dirts in deinking pulp can be determined separately. This method, however, can not be applied for waste paper with the high content in ash because of their ash weight exceeding those of carbon in waste paper or deinked pulp. Therefore, the new method is suitable for samples with the low content in ash and applicable only for printed papers with black ink such as newspaper.

A Thin Film Radiation Dosimeter System

A laser based optical densitometer system has been developed for scanning thin film dosimeters (T.F.D.'s). The system utilizes a laser beam whose wave length occurs in the maximum optical attenuation spectral range of the dosimeter film dye. A split beam comparitor technique allows accurate determination of radiation induced changes in the dosimeter film optical density.

Dispersed density distribution and extent of agglomeration in a polydisperse fine particle suspension flowing turbulently upwards in a duet

Measurements are reported of the mean dispersion density of a suspension of 0–40 pm zinc particles flowing upwards in a 3 in. diam. tube. Due to electrostatic charging of the particles the dispersion density increases markedly towards the wall. A special null-comparator optical densitometer has been developed for taking these measurements. The design and behaviour of this instrument is described in detail. These results also indicate that only a limited degree of particle agglomeration occurs in the centre of the pipe but that this increases towards the wall.

Study of Homogeneity and Water Absorption Behavior of Double Layer Silver Gray Tiles Using Film Neutron Radiography Technique

Neutron radiography (NR) technique has been adopted to study homogeneity and water absorption behavior of building materials, like double layer silver gray tiles obtained from Concord Real Estate &amp; Building Products, Unit II, Salna, Gazipur, Dhaka, Bangladesh. Measurements of optical density differences between the film background and radiographic images of the dry/wet samples were used for investigation of the present work. The optical density was measured by using the digital optical densitometer (Model 07-424, S-23285, Victoreen Inc. USA). Large variation in optical density values of the radiographic image was observed. From this observation it shows that the rate of water absorption of the tiles increases with increase of immersion time. Through the investigation of radiographic image and subsequently analyzing the optical density we observed that distribution of the elements in the tiles are inhomogeneous. Key words: Homogeneity, Water absorption, Silver gray, Neturon radiography.DOI: 10.3329/bjsir.v43i2.963 Bangladesh J. Sci. Ind. Res. 43(2), 197-206, 2008

Determination of the molecular-weight distribution of polyethylene glycols by thin-layer chromatography coupled with densitometry

Thin-layer chromatography with multiple one-dimensional elution was used to determine the molecular-weight distribution of polyethylene of the general formula HO(CH 2CH 2O) n H after conversion into their dichloro derivatives. The adsorbent was silica gel, the developer was based on a mixture of 2-butanone and water, and the spots were visualised with iodine vapour, and then evaluated with the aid of an optical densitometer. This method permitted the quantitative fractionation of polyethylene glycols with degrees of polymerisation ( n) of up to 21.

Angular Distribution of Sublimed and Sputtered Particles from Ag Single Crystals

When silver (100) and (110) single crystals were sputtered by 160–200-eV argon ions from an arc the well-known spot patterns appeared when the sputtered particles were collected as a thin film on glass plates. To determine whether similar spot patterns would result from sublimation, the same crystals were sublimed at temperatures between 642° and 815°C under high-vacuum conditions. Optical transmission densitometer measurements on the resulting thin films indicated that during sublimation the emission was approximately cosine, and no evidence of preferential ejection of silver particles during sublimation was detected. It is estimated that if preferential ejection is taking place along the close-packed directions of the crystal during sublimation in this temperature range, this emission produced a thickness change of the collected silver films such that the transmitted light intensity varied from a cosinelike curve by less than 5% at those angles.

Red Blood Cell Destruction by Cavitating Sound Fields

Work is in progress on an investigation of the breakdown of erythrocytes subjected to cavitating radio-frequency sound fields. These fields are produced by three bowl-shaped barium titanate ceramic transducers, each having a different resonant frequency. The bowls are driven as much as an octave off resonance by a special electronic generator; a range of 60 kc to 1 mc is covered. Acoustic pressures of greater than 1 atmos rms in water are obtained, and are measured with a barium titanate ceramic probe-type hydrophone. A 300 to 1 dilution of whole blood in saline is placed in a test tube and suspended in the sound field. A built-in optical densitometer measures the density of unbroken cells, and the result is plotted versus time on a graphic recorder. Breakdown rate is calculated from the curves thus obtained. Preliminary studies have been made with erythrocytes of man, cow, sheep, and rat. Results show a definite dependence of red cell breakdown rate upon frequency. This relationship varies from one species to another, and definite resonances are observed for all. This investigation is being supported by a research grant, H-1769 from the National Heart Institute, of the National Institutes of Health, Public Health Service.