Filar Micrometer Eyepiece Research Articles

Chemical composition of the primary cosmic rays near the top of the atmosphere

A stack of CR-39 (HCB 0.5%) passive solid-state nuclear track detectors were irradiated by primary cosmic rays near the top of the atmosphere. The stack of detectors were flown by balloons launched from Alice Springs, Australia in 1983. After 16 h 41 min flight exposure at an atmospheric pressure of 9.5 mb the plates were collected and chemically etched in 6.7 N NaOH aqueous solution at 70°C for 27 hours. The diameter distribution of the 1208 etch pits caused by the presence of heavy ions in primary cosmic rays was measured by a transmitted light Leitz Ortholux microscope having an objective×10 and a×15 filar micrometer eyepiece attachment. The diameter distribution was standardised and calibrated against the conventional cosmic-ray results found by Tasakaet al. The estimated charge spectrum is in accord with the nuclear emulsion data of Daniel and Durgaprasad, Kristianssonet al., Saito and Chohanet al.

Myogenic Tone of the Rat Testicular Subcapsular Artery has a Role in Autoregulation of Testicular Blood Supply

An in vitro method is described for the isolation, cannulation, and pressurization of a 10-mm segment of the adult rat testicular subcapsular artery by use of a 200-microns micropipette connected to an adjustable-height reservoir. External and internal arterial diameters were measured by a digital filar micrometer eyepiece calibrated with a Microcode scaler. Transmural pressure was increased stepwise by 20 mm Hg from 20 to 180 mm Hg at 10-min intervals. The following novel triphasic myogenic response was found: a 22.5% increase in lumen cross-sectional area from 20 to 40 mm Hg (p less than 0.05); a 37.3% decrease in lumen cross-sectional area from 40 to 100 mm Hg (p less than 0.05); and a 72.4% increase in lumen cross-sectional area from 100 to 180 mm Hg (p less than 0.05). Papaverine (0.1 mM) completely blocked the transmural pressure-induced vasoconstriction, indicating an active increase in vascular smooth muscle tone by transmural pressure. The calculated blood flow through the testicular subcapsular artery of the adult rat, from measured internal radii at various transmural pressures ranging from 20 to 180 mm Hg by Poiseuille's equation, was constant from 40 to 100 mm Hg and showed a progressive increase from 100 to 180 mm Hg. These data suggest that the myogenic response of the adult rat testicular subcapsular artery may have an important role in the autoregulation of the testicular blood supply.

An evaluation of sealing ability of calcium hydroxide sealers

Solid core filling material such as gutta-percha has been used to fill the root canal in conjunction with a sealer to prevent apical leakage. The purpose of this study was to compare apical seal of five different root canal sealers. Sixty roots of maxillary central incisors were cleansed and shaped and randomly assigned to one of six groups of ten roots each. The root canals were obturated with gutta-percha and one of the sealers by the lateral-vertical condensation technique. Groups I, II, III, IV, and V consisted of roots in which the canal was filled with gutta-percha along with either Roth's sealer, AH26, Sealapex, CRCS, or Nogenol sealer, respectively. Group VI was filled with gutta-percha and without sealer to serve as a control. The access opening was filled with amalgam. Each tooth was then placed in a capped vial containing 2 × 2 inch gauze pads saturated with distilled water, and the sealer was allowed to set at 37° C in the humidor for 48 hours. The roots, except for the apical 2 mm, were coated with two layers of nail polish. The roots were stained with india ink, decalcified, dehydrated, and then placed in methylsalicylate to make them transparent. The leakage was measured with a filar micrometer eyepiece under a dissecting microscope. The mean apical leakage of six groups was as follows: I = 0.45 mm, II = 0.277 mm, III = 0.343 mm, IV = 0.263 mm, V = 0.336 mm, and VI = 2.310 mm. Results showed no significant difference in the apical seal produced by gutta-percha and the tested root canal sealers. Canals that were obturated with gutta-percha and without sealer showed significantly greater apical leakage ( P < 0.01).

Hemodynamic changes in chick embryos precede heart defects after cardiac neural crest ablation.

Neural crest cells are known to contribute to the normal architecture of the heart and aortic arch arteries. Ablation of neural crest cells over somites 1 to 3 in the chick embryo prevents conotruncal septation and results in persistent truncus arteriosus. To determine whether a deficiency of cardiac neural crest cells produces hemodynamic changes prior to the development of identifiable structural defects in the heart, we measured dorsal aortic blood velocity and vitelline artery blood pressure in lesioned and control embryos at a period of cardiac morphogenesis prior to septal formation. The internal diameter of the dorsal aorta at the level of the sinus venosus and the internal diameter of the aortic arch arteries at their midpoints were measured in embryos at Stage 18 of development using a filar micrometer eyepiece and a dissecting microscope. Embryos with neural crest lesions had significantly greater dorsal aortic blood flow velocity than control embryos. In addition, embryos lacking cardiac neural crest had significantly lower systolic and diastolic blood pressures than control embryos. There was no difference in heart rate, dorsal aortic diameter or internal diameter of the aortic arch arteries between lesioned and control embryos. Scanning electron micrographs revealed no gross morphological differences in cardiac looping or conotruncal wall development between lesioned and control embryos; however, embryos with cardiac neural crest ablations developed markedly hypoplastic 4th pharyngeal arches. This data suggests that hemodynamic changes precede the onset of structural heart defects in embryos with cardiac neural crest ablations.

Effect of conotruncal constriction on aortic-mitral valve continuity in the stage 18, 21 and 24 chick embryo

The effect of conotruncal constriction on the development of aortic-mitral valve continuity in stage 18, 21 and 24 chick embryos was studied. A 10-0 nylon suture was tied around the conotruncus, constricting the outflow tract of the heart. The loop was removed after 4 or 24 hours or left permanently in place in 3 subgroups of the 236 experimental embryos. The embryo hearts were harvested at stages after completion of cardiac morphogenesis, fixed in end-diastole and microdissected. The distance between the mitral and aortic anuli was measured from the base of the heart with a calibrated filar micrometer eyepiece. This measurement was compared with the mitral-aortic separation in 72 normal and 132 control embryos. The mitral-aortic separation was similar among normal, control and 4- and 24-hour experimental embryo hearts. However, the mitral-aortic separation increased from 0.34 ± 0.02 mm in normal hearts to 0.82 ± 0.25 mm in stage 18, 1.11 ± 0.36 mm in stage 21 and 0.75 ± 0.33 mm in stage 24 permanent loop experimental hearts (p < 0.01). In embryo hearts with an increased mitral-aortic separation, both great vessels arose from the right ventricle, the semilunar valves were at the same level and the ventricular septal defect was present beneath the aortic anulus. We conclude that conotruncal constriction modifies the relation of the aortic and the mitral valve. We speculate that conotruncal constriction alters the migration of mesenchymal tissue into the heart.

Comparison of stratum corneum thickness in children and adults

We compared the thickness of the stratum corneum from abdominal skin in infants less than 3 months of age, children between 3 months and 11 years, and adults. Measurements were made with a filar micrometer eyepiece on histologic sections obtained at autopsy. No significant differences were seen; therefore, a stratum corneum of different thickness cannot be used to explain differences in percutaneous absorption, supporting previous work which suggested that term infants and children have an efficient skin barrier. The greater toxicity from percutaneous absorption of topical compounds sometimes seen in children is more likely due to their increased surface to volume ratio and/or metabolic differences.

Regional Differences of Cell Sizes in the Human Stratum Corneum. Part I

Individual non-damaged horny cells can be removed from the human stratum corneum by a modification of the corneocyte count technique. Nine sites from four men were sampled and 50 cells from each specimen measured with a filar micrometer eyepiece. The longest and shortest diameters in micra and the surface area, calculated as an ellipse in square micra, were determined. Individual horny cells are much larger than previously described in the literature. Small cells, 34 μ to 36 μ in diameter were found on forehead and hand, larger cells, 41 μ to 44μ are typical for thigh axilla. Highly significant statistical differences for multiple sites of the human body were found when t-tests and the analysis of variance were applied. The regional differences in cell sizes are discussed.

The effect of refractive index of the mounting medium on the apparent diameter of latex particles and glass fibres.

SUMMARYThe diameters of latex particles were measured in different media with a light microscope. The microscope was fitted with a filar micrometer eyepiece and, for measurement, the cross‐wire was set on the centre of the dark line forming the edge of the image. Electron microscopy was used for comparison. Good agreement between light and electron microscopy was obtained using media of relative refractive index (nd object/nd medium) between 1·06 and 1·08. With higher relative refractive indices the light microscope underestimates dimensions for particles 4·17 μ diameter and overestimates for particles 2·7 μ diameter.

SOME EXPERIMENTS CONCERNING THE LIMITATIONS AND ERRORS IN SIZE MEASUREMENT OF SMALL OBJECTS BY VISUAL MICROSCOPY

SYNOPSISThe systematic errors which arise in the measurement of small, non‐periodic objects by visual microscopy are discussed, together with a method for reducing these errors by calibration with objects of known size. Such a calibration is described for the case where the diameters of circular holes and opaque disks are measured using a filar micrometer eyepiece, an oil‐immersion objective, and full‐cone illumination. Examples are given showing the influence of the numerical apertures of the condenser and objective upon the sizing errors. The results are used to derive size correction factors applicable to the measurement of any thin, high contrast object when the same sizing technique is used. Values are also given for the useful lower limits of measurement. Further experimental evidence emphasizes the difficulty of accurate measurement where the objects are of finite thickness.

A new micrometer microscope.

THE usual method of measuring the dimensions of microscopic objects is to compare them against an eye-piece scale or to use a calibrated filar micrometer eye-piece. Such methods are not capable of great accuracy and are inherently slow and poorly adapted to statistical problems. In order to plot the size distribution of a large number of particles, it is necessary to bring each in turn to the centre of the field and to set it against the scale.

Particle-Size Distribution of Pulverized Snow

Abstract A microscopic method for the determination of particle-size distribution of pulverized snow was worked out. The method gives satisfactory distribution curves, presenting the number of particles as a function of their cross-sectional “areas”. The measurements were made by means of a filar micrometer eyepiece, the snow particles being placed on a ruled glass slide, which was submerged in silicone oil to prevent evaporation. The time for the determination of a distribution can be appreciably shortened by estimating the size of the particles instead of measuring them, though the accuracy is not so high in this case.

Particle-Size Distribution of Pulverized Snow

AbstractA microscopic method for the determination of particle-size distribution of pulverized snow was worked out. The method gives satisfactory distribution curves, presenting the number of particles as a function of their cross-sectional “areas”. The measurements were made by means of a filar micrometer eyepiece, the snow particles being placed on a ruled glass slide, which was submerged in silicone oil to prevent evaporation. The time for the determination of a distribution can be appreciably shortened by estimating the size of the particles instead of measuring them, though the accuracy is not so high in this case.

Dual Objective Optical Micrometer for Strain Measurements

A dual objective optical micrometer for strain measurements of up to 8% is described. In this instrument the images of two reference marks on a specimen are brought to a focus in one field on the reticle scale of a filar micrometer eyepiece. The relative displacement of the images is measured by the eyepiece and the readings are reduced to strain by the use of a calibrated magnification factor. Since only the separation distance of the images is of interest, the exact position of the images in the field is not critical. No external point of reference on the instrument mount is necessary, hence alignment problems are minimized and the instrument may be moved between readings. The described calibration procedure shows that the least count of the instrument with a 2.64-in. gauge length is 42×10−6 in./in. and measurements can be made with an accuracy of ±13×10−6 in./in.

Semi-automatic recorder for filar micrometer eyepiece and its application to track measurement

A differential transformer has been mounted on a filar micrometer eyepiece and has been coupled to a recording circuit, to make possible automatic recording of the hairline positions. The apparatus greatly reduces the time required to make measurements with a filar eyepiece; e.g., as when measuring the multiple Coulomb scattering of tracks in nuclear emulsions.

A Mechanism for Reducing Vibration in the Use of the Filar Micrometer Eyepiece

A Mechanism for Reducing Vibration in the Use of the Filar Micrometer Eyepiece