It is the experimental report by using 17cm, 19cm in thickness water-phantom to investigate optimum tube voltage in taking skull roentgenography. The obtained results are as follows: 1. An adequate kVp for P-A projection is range from 80-90. 2. An adequate kVp for lateral projection is range from 75-85.

The tube voltage in radiographic technique factors of the extremities was studied to use the acryl phantom and aluminum step wedge. It was the proper tube voltage that was over 55-60kV in the finger, over 65kV in the forearm and over 75kV in the knee joint.

In an attempt to provide optimum kVp for four spot films of stomach examinations, we measured experimentally film density and scatter radiation with field size. And to investigate the effect of concentrations in barium sulphite and kVp in spot films of stomach fluoroscopy were carried out and the following results were obained. 1. The entire density of film by field size has the sharpest increase from $10cm^2$ to $100cm^2$, and relatively flattened curve beyond $500cm^2$ in field size. 2. The quantity of scatter radiation reaching an X-ray film depends upon field size: the larger the fields, the more scatter radiation. 3. It is necessary for increasing 3 to 5kVp as for the absence of barium sulphite and 5 to 7 kVp in the case of 20 per cent and 25 per cent in barium sulphite concentrations to produce uniform density in the four spot films for stomach fluoroscopy.

An experimental study was carried out to make a comparison between tube voltage and density of barium sulphate in the stomach radiography. The results were summarized as follows: 1. The percentage of density on concentrations of barium sulphate as contrast media could not show in differences with changes of voltages applied X-ray tube. 2. The changes of density visualized on X-ray film mainly depend upon with thickness of stomach filled barium sulphate than the ratio of barium sulphite and plain water volume. 3. The lesions positioned in upper part within stomach exhibited their best discrimination performanance with depth in the low tube voltage, followed in order by the middle part and lower part. However, the discrimination performanance at the high tension radiography uniformly visualized over X-ray film without density in change.

To know the effect of tube voltage to X-ray film image, authors made an experimental study on the exponential value of applied voltage and the effect of scattered ray in photographic contrast, and obtained the results as follows: 1. The exponential value of tube voltage was under the control of the applied voltage, the kinds of screens and grids, and its existence. The range of its value was from 1.03 to 5.3. 2. The efficiency of X-ray production was directly proportional to the applied voltage, and to oftain the same density, the tube current(mAs) was inversely proportional to applied voltage 3. The production of scattered rays was in proportion to the tube voltage, and the photographic contrast was mainly influenced by the scattered rays.

X-ray grid is the most important means to reduce the scattered ray from patients, but alternative way is air gap technique that is another name of Groedel technique. This technique is mainly used in chest radiography. Authors performed an experimental study on the air gap technique for chest radiography and obtained the results as follows; 1. In using the high voltage air technique, scattered ray could be reduced effectively, while the percentage of scattered ray was slightly increased than conventional grid technique. 2. In film contrast, 30cm air gap technique was inferior to 12:1 grid technique and contrast improvement was increased when the object was thicker and higher voltage was used. 3. The patient exposure dose was reduced about $25{\sim}45%$ compared with conventional grid technique by air gap technique used.

To shield the radiation, we can make use of various materials, but the scattered rays can be caused by the shielding materials. The degree of the scattered rays production is influenced by the nature of the shielding materials and the energy of the radiation, therefore to choose the proper shielding material is the most important matter in radiation protection. Authors made an experimental study on the scattered rays generated from the shielding materials, and obtained the results as follows: 1. In the ranking of the scattered rays production: Cement bricks, black colored fire bricks, and red colored fire bricks were marked the first the second, and the third ranking respectly, and the last order was lead plates. 2. In the relative ranking of the scattered rays production by energy increase: Lead plates were marked the first order, the next and third order were red colored fire bricks and black colored fire bricks respectly, and cement bricks were marked the last order. 3. The scattered ray ratio of lateral-back point per lateral point were generally decreased by energy increment. The diminishing orders were that lead plates were the first order, and the next and the third order were red colored fire bricks and black colored fire bricks respectly, cement bricks were marked the last order.

We studied about dosimetry according to the X-ray tube voltage, radiation field object thickness and obtained results as follow. 1. Secondary ray involing rate in the penetrated radiation increased proportion to the tube voltage, but its rate is more larger at the small radiation fields. than large fields. 2. Secondary ray involving rate in the penetrated radiation increased at thick object and large exposure fields. But saturated phenomenon appeared at limited field. 3. Secondary involving rate of acryl phantom is more top place than water, paraffin and aluminum phantom.

To compare three-phase 12-pulse full-wave X-ray generators with single-phase full-wave X-ray generators on their performance of outputs, authors studied the generating X-ray by means of exposure dose and radiographic density. The results were as follows; 1. The exposure doses of three-phase full-wave X-ray generators showed a 30%-60% increase as compared against of single-phase full-wave generators. 2. The transmitted doses of three-phase full-wave generators were more increased than single-phase full-wave X-ray generators. 3. To obtain the same density, 60kVp in three-phase full-wave generators were equivalent to $60{\sim}65kVp$ in single-phase full-wave generators, and 100kVp in those generators were equivalent to $100{\sim}125kVp$ in these generators.

흰불나방(Hyphantria cunea Drury)의 각(各) 변태단계(變態段階)에 따라 $1.75{\sim}7krad$의 Cobalt-60 $\gamma$선(線)을 전신조사(全身照射)하여 $\gamma$선조사(線照射)에 의(依)한 중장세포(中腸細胞)의 조직학적(組織學的) 변화(變化)를 광학현미경(光學顯微鏡)으로 정상군(正常群)과 비교(比較) 관찰(觀察)하였던 바, 다음과 같은 결과(結果)를 얻었다. 1. 중장(中腸)의 상피세포(上皮細胞)는 원주세포(圓柱細胞), 배상세포(杯狀細胞), 신생세포(新生細胞)로 구성(構成)되어 있었다. 2. 조사(照射)의 영향(影響)은 조사(照射)된 선량(線量)과 변태시기(變態時期)에 따라 변화(變化)되었다. 3. 조직학적(組織學的) 변화(變化)의 정도(程度)는 조사선량(照射線量)이 많을수록 증대(增大)되었다. 4. 방사선(放射線)의 감수성(感受性)은 종령유충(終齡幼蟲), 용8일(日)에서 가장 높았다.

The concentration of total protein during the metamorphosis of the Indian meal moth, Plodia interpunctella $H\ddot{u}bner$ was measured using micro-Kjeldahl method by Oser(1965). Healthy specimens were chosen as samples at each developmental stages: the 1st instar larva, the 3rd inster larva, final instar larva, pupae 2, 6, 10 days and the adult 1 day. The total protein concentration decreased gradually until the two day pupal stage and increased at the six day pupal stage. In the one day dault stage, the concentration reached a maximum. In conclusion, changes of total protein concentation through the course of the physiological cycle form a U-shaped curve when graphed against the histolysis of larval organs and the histogenesis of adult organs. In view of controlling pest, the U-shaped pattern of physiological activity indicates that control will be the most effective at the time of the most physiological weakness manifested at the two day pupal stage.