Measurement of the refractive index and thermal refractive index coefficients of Nd:YAP crystal

The principal refractive indices of yttrium aluminate crystal doping with 1-wt.% neodymium (Nd:YAP) have been measured by a minimum deviation method for the wavelengths 0.5398, 0.6328, and 1.0795 microm in the temperature range of 289-435 K. The thermal refractive index coefficients have been obtained at these wavelengths, and they are all positive and slightly decrease with increased wavelength. The constants of the single term Sellmeier equation are also given for the 273-420 K temperature range. These constants are in linear relationship with temperature in the 4 x 10(-3) error range.

[The finite element analysis of the bicuspid and molar of mandible]

Recently, the finite element method has been adopted in the study of tooth structure as well as the stress distribution of dental prosthesis. In order to understand the loading state of the supporting tissues and the stress distribution of the teeth in various shapes under the pressure of loading, the author of this essay has applied the two-dimensional finite element method to the study of the stress distribution of the periodontal supporting tissues at the time when the second bicuspid and the second molar are vertically and obliquely loaded. Finally, the results of the quantitative analysis are obtained and a curve of the stress distribution of the teeth is also drawn up. The conclusion is as follows: 1. When the vertical loading is applied to the occlusal surface of the bicuspid and molar, the stress distribution of periodontal supporting tissues is uniform. 2. The stress concentration is on the marginal ridge and thedistal apex of bicuspid under the oblique loading. 3. When the oblique loading is applied to the occlusal surface of the molar, the stress concentration is only on the marginal ridge, and it is small.

Analysis of surface deposits on intrauterine contraceptive devices

Surface deposits on stainless steel contraceptive devices removed from the uterus after varying periods of insertion were examined and analyzed by means of scanning electron microscopy (SEM), X-ray energy dispersive analysis (XEDA), Augar electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and atomic absorption spectrophotometry for microquantitative analysis. The data obtained were compared with the data for copper-bearing IUDs (TCu200) obtained by the same method. The wire coils of stainless steel IUDs which had been in situ for 5 years showed no obvious changes, but copper wire coils showed varying degrees of erosion after the same period of time. Analysis clearly showed that the wire coils of both types of IUD were encrusted with deposits. Deposition began earlier on copper-bearing IUDs than on stainless steel IUDs (27 days and 3 months after insertion, respectively). This process began earlier than has previously been reported in the literature. The amount of deposit increased with duration of insertion, but there were large individual variations. The microanalysis showed that the principal component of the deposit on both types of IUD was calcium, which was present in the crystal form of calcium carbonate. The substances attaching to the crystals were similar to the nitrogenous organic compounds. We suggest that the mechanism regulating the deposited formation may be similar to that of calculus. The influence of these deposits on complications relating to IUD insertion, such as uterine bleeding and accidental pregnancy, is briefly discussed in this article. The subject should be studied in greater detail.

[Photodynamic therapy (PDT) of bladder cancer in the rat]

PDT of rat bladder cancer, induced by N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) was studied. All animals were divided at random into three groups. Group 2 and 3 were treated by hematoporphyrin derivative (HPD)-laser PDT while group 1, without treatment, served as control. The results showed that the malignant lesions could be selectively and obviously destroyed, if the whole tumor area were sufficiently exposed to the laser irradiation. However, the normal bladder epithelium and muscle layer showed no histologic change. Similar reactions were found in papilloma of bladder which was considered as precancerous lesion. Thus, PDT may be beneficial to cancer prevention. Its role in prevention and treatment of bladder cancer should be further studied experimentally and clinically.

A randomized comparative clinical evaluation of the Steel Ring, the VCu200 and the TCu220c IUDs

A randomized comparative clinical study of the Steel Ring, VCu200 and TCu220c IUDs was carried out in Beijing. Six-hundred subjects were recruited and each group of 200 was inserted with one of the three devices. The TCu220c and the VCu200 had statistically significantly lower pregnancy and expulsion rates at one and two years of use than the Steel Ring. However, the Steel Ring consistently had the lowest rate of removal for pain and/or bleeding. At two years, the early differences of use-related discontinuation and continuation between the higher rates of the Steel Ring and the lower rates of the VCu200 and TCu220c were significantly reduced. There were no statistically significant differences of net event rates between VCu200 and TCu220c.

The biological effects of photodynamic therapy on normal skin in mice--I. A light microscopic study

A light microscopic investigation of the biological effects of photodynamic therapy using hematoporphyrin derivative and red light irradiation has been carried out. HpD alone, even used at a dose of 50 mg/kg, did not cause histologically discernible changes. The irradiation alone used in this experiment caused only slight or moderate dilatation and congestion of blood vessels, which disappeared completely within several hours after light exposure. In the PDT treated mouse ears severe degeneration and necrosis of skin tissue occurred within 1-2 days. The importance of adequate drug and light doses and proper interval chosen for obtaining best therapeutic effects and protection of surrounding normal tissues was pointed out. The possible mechanism of the PDT action in vivo was briefly discussed.

The biological effects of photodynamic therapy on normal skin in mice--II. An electron microscopic study

In the present study it has been demonstrated that the ultrastructural changes in mouse ear skin after PDT action occurred much more distinct and earlier than those observed in the histological study. Various types of cells in the skin respond to the photodynamic action differently. The endothelial cells, fibroblasts and nerve fibers are most sensitive. In contrast, the keratinocytes and chondrocytes often remain rather well preserved after PDT treatment. The possible mechanism of PDT action was briefly discussed.

Influence of vitamin deficiency and level of dietary protein on the incidence of leg problems in broiler chicks

Diets containing either 22 or 30% protein were supplemented with a vitamin mix where one of 11 added vitamins were singly eliminated from the mix. Male, day-old broilers were fed these diets to 3 weeks of age, and weight gains, feed utilization, and leg problems were recorded. In general, the higher protein diet did not result in a greater incidence of leg problems; however, it did alter performance of several of the vitamin-deficient diets as compared to the lower protein diet. Of the 11 vitamins studied only nonsupplementation of riboflavin markedly reduced weight gain and feed utilization during the 3-week feeding period. However, deletions of vitamin D3 and niacin also resulted in reduced performance. Riboflavin deficiency resulted in paralysis in a high percentage of the birds while the niacin-deficient diet gave a high percentage of birds with deformed legs and problems of mobility. The results demonstrate that a high incidence of leg problems may be present in a flock with little or no signs of reduced gain or feed utilization. The data suggest that under practical conditions the elimination of a particular vitamin from a diet for a short period of time would probably have a negligible effect on performance.

Alterations in levels of thyrotrophin releasing hormone and rates of hormone degradation in hypothalamic tissue of the developing rat

Developmental changes in levels of hypothalamic thyrotrophin releasing hormone (TRH) and the role that hypothalamic degrading enzymes may play in these alterations were investigated. Levels of TRH in male and female fetal rats and in male neonatal rats were measured by radioimmunoassay. The hormone content of the hypothalamus was shown to increase from less than 1 ng at 1--4 days of age to approximately 10 ng at 20 days of age. Thereafter, the content of TRH declined to the adult level of about 5 ng. The ability of fractionated hypothalamic homogenates to degrade TRH was measured over the same time. The 27 000 g supernatant fraction contained a degrading activity that yielded only radiolabelled deamido-TRH upon incubation with [L-proline 2,3-3H]TRH. The corresponding particulate fraction contained at least two distinct TRH degrading activities as determined by the number of metabolites present. Changes in rates of degradation were not large enough to account for the differences observed in levels of TRH.

A flow calorimetric method of determining electron beam energy

The construction of an adiabatic flow calorimeter using water as the working substance is described. It is shown that at high dose rates the heat defect due to chemical reactions in water is small (of the order of 0-3%) and that under high dose rate conditions flow calorimetry can be used as a method of measuring the energy of high intensity electron beams. Measurements made with a 15 MeV linear accelerator are reported and compared with magnetic measurements.