Efektivitas Penggunaan Media Peraga Ikonik Jangka Sorong dan Mikrometer Sekrup Terhadap Pemahaman Konsep Pengukuran Siswa

The limited number of measuring devices generally becomes an obstacle of learning on measurement using Vernier caliper and micrometer screw in class. This situation causes students’ achievement on measurement have not been maximum. Iconic vernier calipers and micrometer screw are needed in the learning as more flexible alternative auxiliary media to increase students’ understanding on measurement concepts. The objective of this research is to determine the increase of students' understanding on the measurement concept after using the vernier calipers and micrometer screw iconic media. The research method used was an experimental method with the design of Pretest-Postest Control Group Design. The research was conducted in class VII of a junior high school in Banjarharjo. The experimental group was class VII A, while the control group is class VII B. The data of students’ understanding on the concept of measurement was taken from the results of the posttest of both groups. The analysis results shows average score of experimental group understanding is 69.58 with 69,44% of individual completeness and 0.51 gain factor. Meanwhile, the average score of control group understanding is 59.72, with 41.67% individual completeness and 0.45 gain factor score. This study indicates that the use of vernier calipers and micrometer screw iconic media is effective in increasing the students’ understanding on measurement concept of students.

The Effects of Carbocaine Hydrochloride on Isolated Porcine Corneas In Vitro: A Comparison of Opacity, Hydration and Thickness

— Several concentrations of carbocaine hydrochloride, a local anaesthetic, were applied to isolated porcine corneas and stromas for periods of 1, 2, 3 and 4 hours. Increases in opacity (manifested as decreases in the intensity of a beam of light passed through the cornea from the epithelium to the endothelium), hydration (determined by the loss of water on drying to constant weight), and thickness (measured with a micrometer screw gauge) were determined. Small, time-related increases in opacity, associated with increases in hydration and thickness, were observed in control preparations and in preparations treated with 0.5–2% carbocaine hydrochloride over a 4-hour incubation period. However, only those increases resulting from incubation for 4 hours with 2% carbocaine hydrochloride differed significantly from control values. Higher concentrations (8% and 16%) also caused opacity, but decreased hydration and thickness, probably because of the hypertonicity of these solutions.

A new calibration method for gravity meters

Current calibration methods give gravity meter accuracies of 3 to 5 μGal [Formula: see text] over 10 mGal intervals. The new calibration method should extend the accuracies to 100 mGal intervals. The new method nulls with both a micrometer screw and an electrostatic feedback nuller. The screw is calibrated and used only at discrete points and the electrostatic nuller completes the nulling to obtain gravity readings. Determining the calibration curve itself rather than measuring and integrating calibration (interval) factors avoids approximations. Circular errors (periods of the order of a turn of the screw) are completely taken into account at the discrete points. Calibration only at discrete points makes calibration time reasonable.

Modified Method of Krejnin and Murri for the Determination of Absolute Declinations

Krejnin and Muni's method (1973) enablesenables one to derive absolute declinations of stars in a narrow equatorial zone |δ| < 10′ from observations near the Earth's equator |ϕ| < 10′. Some systematic effects, including the errors of the value of the micrometer screw for two equatorial instruments (or the scale error if one of the instruments is a PZT), might be determined if a global reduction is used for the original observations from the equator and from those of an astrolabe at latitude |ϕ| ∼ 20° to 23°. Astrolabes—especially photoelectric ones (Hu 1988) are considered to be the most efficient for determination of absolute declinations of stars and absolute latitudes of the instruments in Tolchel'nikova-Murri (1985).In Izv. GAO No. 206 the method will be published as well as the criterion for estimating the efficiency of different programs, which is required to improve planning in astrometry.