The effect of magnification on student performance in pediatric operative dentistry

Previous research has shown that accurate student self-evaluation is related to higher quality dental products. Variance in student performance still remains. Enhancement of visual perception could contribute to product improvement. Only one study has evaluated the effects of magnification on simulated dental patient care. The present study sought to determine if magnification had a positive effect on student-generated products in pediatric amalgam preparations. Fifty-two third-year students were randomly assigned to experimental (magnification) or control (no magnification) groups. Members of the experimental group used magnification in their daily work in the pediatric dentistry clinic. No significant differences between the groups' preparations or evaluations of standard preparations were found. Further study should address these issues: 1) possible effects of specific training in the use of magnification devices; 2) whether the tolerance for error in dental preparations is so great that finer vision contributes little to product improvement; 3) the role of tactile sensation in evaluation and preparation; and 4) the possible benefits of magnification for effect of age. Based on this study, it seems that requiring students to purchase magnification devices may not be justified.     

Application of longitudinal magnification effect to magnification stereoscopic angiography: a new method of cerebral angiography

A new method of stereoscopic cerebral angiography has been developed which employs 2X radiographic magnification. In order to obtain the same depth perception in the object as with conventional contact stereoscopic angiography, one can made the x-ray exposures at two focal spot positions which are separated by only 1 inch (2.5 cm), whereas the contact technique requires a separation of 4 inches (10 cm). The smaller distance is possible because, with 2X magnification, the transverse detail in the object is magnified by a factor of two, but the longitudinal detail, which is related to the stereo effect, is magnified by a factor of four, due to the longitudinal magnification effect. The small focal spot separation results in advantages such as improved stereoscopic image detail, better image quality, and low radiation exposure to the patient.     

Aberrations of spherocylindrical spectacle lenses

A procedure has been developed for tracing a bundle of rays through and ophthalmic lens and a schematic eye with its primary line of sight pointed through various parts of the lens. A bundle of eight rays can provide data for assessing the quality of the image formed by such a system. To test the procedure and to generate data which can help in selecting a method for evaluating image quality, we selected a single lens as an example. The lens selected has a spherical back surface (-5.00 diopters) and a toric front surface (+15.00 diopters in the vertical and /10.00 diopters in the horizontal). It has a center thickness of 5 mm and glass of index 1.523. Spot diagrams were generated with the eye pointed in various directions through the ophthalmic lens. The data generated showed that peripheral bundles which fall between the principal meridians emerge as astigmatic bundles. This leads to the proposal that blur circle theory can be used for evaluating the quality of the optical image and that it suffices in the case of a spherocylindrical ophthalmic lens to base the tolerances for refractive power on measurements made in the principal meridians.     

The leaching of nickel from new and used metal spectacle frames

Hyperthermia is a promising method for increasing the efficacy of radiation therapy of colorectal cancer. To study the histological aspects of healing of an anastomosis in the colon, after combined preoperative (sham) irradiation and (sham) hyperthermia treatment, 48 male Wistar rats were divided randomly into four groups. In each animal, a segment of the colon was treated successively by (sham) irradiation (single dose of 25 Gy X rays) and/or (sham) hyperthermia (44 degrees C, 30 min). After 5 days, a resection of the colon was performed by construction of an anastomosis: The distal limb consisted of (sham-) irradiated and/or (sham-) hyperthermia-treated bowel. Rats were killed 3 or 7 days after the surgical procedure. Evaluation of healing of the anastomosis was made by: (1) histological analysis of sections stained with hematoxylin and eosin, (2) semiquantitative measurement of collagen in the area of the anastomosis and (3) semiquantitative analysis of the number of macrophages by immunocytochemistry. Healing of the anastomoses in animals receiving irradiation or hyperthermia alone and in control animals was relatively uneventful. There were no differences between groups in formation of collagen or infiltration by macrophages in the area of the anastomosis. Animals treated with both radiation and hyperthermia showed marked necrosis, infiltration by polymorphonuclear leukocytes and rupture of the anastomosis. It is concluded that preoperative irradiation with a single dose of 25 Gy in combination with local hyperthermia at 44 degrees C for 30 min leads to disturbed repair of anastomoses.     

The relative position priming effect depends on whether letters are vowels or consonants.

The relative position priming effect is a type of subset priming in which target word recognition is facilitated as a consequence of priming the word with some of its letters, maintaining their relative position (e.g., csn as a prime for casino). Five experiments were conducted to test whether vowel-only and consonant-only subset primes contribute equally to this effect. Experiment 1 revealed that this subset priming effect emerged when primes were composed exclusively of consonants, compared with vowel-only primes (csn-casino vs. aia-animal). Experiment 2 tested the impact of letter frequency in this asymmetry. Subset priming effects were obtained for both high- and low-frequency consonants but not for vowels, which rules out a letter frequency explanation. Experiment 3 tested the role of phonology and its contribution to the priming effects observed, by decreasing the prime duration. The results showed virtually the same effects as in the previous experiments. Finally, Experiments 4 and 5 explored the influence of repeated letters in the primes on the magnitude of the priming effects obtained for consonant and vowel subset primes (iuo-dibujo and aea-madera vs. mgn-imagen and rtr-frutero). Again, the results confirmed the priming asymmetry. We propose that a functional distinction between consonants and vowels, mainly based on the lexical constraints imposed by each of these types of letters, might provide an explanation for the whole set of results. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The relative effect of dietary fats and carbohydrates on lipid metabolism in the albino rat

This study is concerned with the effect of two carbohydrates, cane-sugar and corn starch, at four different levels in the presence of two dietary fats, on the serum and the tissue lipids (cholesterol, phospholipid and fatty acid patterns). Keeping the dietary fats (coconut safflower seed oil) at 20% level, diets containing (a) startch (54%) + cane sugar (0%), (b) starch (44%) + cane sugar 10%), (c) starch (10%) + cane sugar (44%) and (d) only cane sugar (54%) were administered to rats for 8 weeks. The lipid levels were determined at the end of the feeding period. The beneficial effect of the unsaturated fat in lowering the serum cholesterol level is nullified by an excess of cane sugar in the diet. In liver, there is an increase of 40-50% of cholesterol, as the cane sugar level in the diet is raised, irrespective of the type of dietary fat. The fatty acid pattern of the serum and tissue lipids is influenced by dietary fats as well as carbohydrates.     

我院城市规划设计现状与展望

回顾我院城市规划发展历程和现状,展望我院在世纪之交城市规划设计任务,并针对我院城市规划设计的发展提出了建议.     

Impact resistance of Transitions Plus spectacle lenses

Although it has been shown that photochromic glass industrial lenses do not provide adequate occupational impact protection, they are frequently requested by outdoor workers wanting sunglasses. The recent introduction of Transitions Plus (TP), a photochromic plastic lens, may meet the needs of these workers. The impact resistance of 60 TP lenses of dress thickness was studied using a ballistic test. Lenses were edged and mounted in metal industrial frames. The completed spectacles were placed on a headform for ballistic testing using a 6.5 mm (1/4 in) steel ball propelled from an airgun. The lenses were divided into test groups that received: (1) a single impact at the geometrical center by a ball traveling at 18 m/s (59 ft/s) and (2) 50 consecutive impacts at 18 m/s, or (3) a single impact at 46.5 m/s (152 ft/s). All lenses passed the single impact test at 18 m/s. Four lenses broke under repeated impact. All lenses subjected to the high-speed impact test failed, either breaking or being dislodged from the frame. These findings show that dress thickness TP lenses provide impact protection from small blunt missiles traveling at moderate speed, and that they are durable under repeated low energy impact. However, thicker lenses must be used when the wearer has a high risk of ocular exposure to small high-speed missiles in the workplace. It can be concluded that TP lenses may be used in occupational eyewear for many outdoor workers who want photochromic sunglass lenses, provided that other needs for vision and occupational safety are also satisfied.     

Effects of magnification on a subminiature assembly operation.

This experiment was designed to investigate the effects of magnification on the duration of elements of a subminiature assembly operation. The task consisted of grasping a metal dot .010 in. in diameter wtih a tweezers, transporting it to a hole, and dropping it into the hole. Ss used a binocular type industrial microscope and performed under 3 magnifications, 20X, 30X, and 40X. Precision of the task was varied by changing the diameter of the hole into which the dot was assembled. Results indicated that no single magnification was optimum for all elements. For pick up and travel loaded, 30X was optimum while for travel unloaded, 20X was optimum. Results for the assemble element were inconclusive. There was no evidence that the optimum magnification is dependent upon the precision requirements of the task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Simon effect occurs relative to the direction of an attention shift.

We investigated whether the Simon effect depends on the orienting of attention. In Experiment 1, participants were required to execute left-right discriminative responses to 2 patterns that were presented to the left or right of fixation. The 2 patterns were similar, and the discrimination was difficult. A letter at fixation signaled whether the current trial was a catch trial. The results showed a reversal of the Simon effect. That is, spatially noncorresponding responses were faster than spatially corresponding responses. In Experiment 2, the discrimination of the relevant stimulus attribute was easy. In Experiment 3, the discrimination of the relevant stimulus attribute was difficult, but the stimulus exposure time was long. In either experiment, the regular Simon effect was reinstated. In Experiment 4, the letter that signaled a catch trial appeared to the left or right of the imperative stimulus. The Simon effect occurred relative to the position of the letter. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of relative crystal orientation on the liquid metal induced grain boundary fracture of aluminum bicrystals

The effects of relative crystal orientation on liquid metal induced intergranular fracture were studied to: 1) verify the existence of the theoretically and experimentally predicted orientation dependence of this process; and 2) determine which crystallographically related property produced such dependence. A base metal of 99.993 pct pure aluminum and a liquid metal of Hg-3 at. pct Ga were chosen as the embrittlement couple. Bicrystals of aluminum were grown with symmetric <110> tilt boundaries so that: 1) individual boundaries could be tested; and 2) the resulting embrittlement susceptibility of each boundary could be correlated with a controlled crystallographic variable, the tilt angle. A fracture mechanics testing method was developed which enabled the crack propagation resistance of each grain boundary in the Hg-3 at. pct Ga atmosphere to be determined by yielding the crack extension force of a propagating crack. The variation in crack extension force with symmetric <110> tilt angle was analyzed to determine what crystallographically related property produced the observed variations. Consideration of the crystallographically related properties of: 1) slip compatibility between adjacent grains; 2) grain boundary atomic density; and 3) grain boundary energy led to the conclusion that the observed variations were caused by variations in grain boundary energy, and a mathematical relationship was developed that expressed the dependency.     

Depression and the magnification of failure.

Theory and observation suggest that depressed individuals minimize the importance of successes while magnifying the significance of failures. An experimental test of these predictions was performed. Depressed and nondepressed college students were given predetermined success or failure feedback on an ostensible test of social perceptiveness. Prior to taking the test, subjects indicated the degree to which they possessed various personality traits (including social perceptiveness) and the importance of those traits. After subjects received the feedback, the trait scales were readministered. The results indicated that depressed subjects inflated the importance of social perceptiveness after learning they had done poorly on a test presumed to measure that trait. In contrast, nondepressed subjects inflated the importance of social perceptiveness after succeeding on the test. Depressed subjects also displayed a tendency to overgeneralize from the social perceptiveness test results by lowering their estimates of their general proficiency following failure. The results suggest that depressed individuals evaluate personal feedback in a manner that tends to be self-derogating. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Method of objective determination of secondary aniseikonia in preschool and school-age children

Smoking a single cigarette can reduce digital blood flow. Sarin (1974) showed a 42% reduction in digital blood flow in his series, and other investigators have shown similar findings (Ludbrook 1974, Rottenstein 1960). The focus of this paper is on the pharmacological effects of the various components of cigarette smoke and their potentials effects on wound healing in the hand. A case is described to illustrate the effect of stopping smoking upon a non-healing fingertip ulcer.     

Mathematical analysis and experiment on the corneal reflex test in spectacle wearers

An experimental study and mathematical analysis of the corneal reflex test was undertaken in spectacle wearers. In the experimental study, photographs were taken of the corneal reflex through spectacles and the conversion ratios determined as measured in degrees/mm. In the mathematical analysis, the magnification effect of the lens was elucidated by three methods: geometrical analysis; real measurement of magnification factor; and ray tracing analysis. The real measurement of the conversion ratios was in good agreement with the conversion ratios determined by the three mathematical analyses. These results clearly showed that the corneal reflex test can be clinically useful even in wearers of spectacles.     

Pediatric skeletal scintigraphy: applications of pinhole magnification

Pinhole magnification scintigraphy is an effective means of evaluating the pediatric skeleton because it provides optimal high-resolution images. This technique is indicated when diagnostic uncertainty persists after high-resolution imaging with parallel hole collimation. Pinhole magnification scintigraphy requires approximately 20 minutes of acquisition time per image and meticulous attention to details such as choice of pinhole insert, collimator positioning, and patient immobilization. However, the technique is superior to planar imaging in demonstrating acute osteomyelitis in bone adjacent to growth centers and epiphyseal involvement that is either primary or the result of local spread of infection. In addition, pinhole imaging has proved highly reliable in the early diagnosis of Legg-Calvé-Perthes disease and is useful in depicting osteonecrosis related to specific causes such as corticosteroid treatment or trauma. Scintigraphic manifestations of femoral head ischemia or infarction and findings indicative of osteomyelitis associated with a hip effusion are well demonstrated with pinhole imaging. This technique also helps characterize osteoid osteomas and may be used intraoperatively to confirm the complete excision of this benign tumor. Finally, pinhole magnification scintigraphy clearly depicts fractures of the femoral neck and allows a high degree of confidence in diagnosing injuries to the small bones of the hands and feet.     

Improvement of detectability of microcalcifications by magnification digital mammography

Our aim in this study was to evaluate the potential utility of magnification mammography with a CR system by investigating the basic imaging parameters and detectability of microcalcifications in comparison with those of conventional screen-film systems. The basic imaging parameters were evaluated by measuring scatter fraction, modulation transfer function (MTF), Wiener spectrum, and incident dose for the various magnification factors. The detection of simulated microcalcifications in radiographs of a mammographic phantom and breast specimens were evaluated subjectively and quantitatively for screen-film and CR techniques with various magnification factors. The scatter fraction of digital magnification mammography decreased with increasing magnification factor. MTF of magnification digital mammography improved with increasing magnification factor. The detectability of microcalcifications with the CR system was significantly improved by magnification technique. From the above results, it is expected that the use of magnification mammography with a CR system will improve the detectability of microcalcification.