Costs and effects of microsurgery versus radiosurgery in treating acoustic neuroma

This study analyses costs and effects of treating acoustic neuroma patients by using microsurgery compared to radiosurgery. Radiosurgery is the stereotactic application of radiotherapy and an innovative medical technology. Cost and effect estimates of conventional treatment were based on a retrospective study in the Netherlands. Similar data for a comparable group of patients in Sweden were collected for radiosurgery, as this treatment option is currently not available in the Netherlands. Fifty-three acoustic neuroma patients who had been operated on the University Hospital Rotterdam between November 1990 and February 1995 were included. This group was compared with 92 acoustic neuroma patients treated with radiosurgery (Gamma Knife. Stockholm, Sweden) in the same period. Data on health care use were collected from patient files. To obtain data on production losses and quality of life, a questionnaire was sent by mail in February 1995. This booklet consisted of the Health and Labour-questionnaire (HLQ), the Short Form-36 (SF36) and the EuroQol. The response rate was 92%. Direct costs for microsurgery amounted to Dfl. 20.072,- and for radiosurgery to Dfl. 14.272,-. Indirect costs were respectively Dfl. 16.400,- and Dfl. 1.020,-. General health rating was better for radiosurgery than for microsurgery. On the whole, differences in clinical outcomes between the two patient groups were small. Assuming a reasonable occupancy rate of the expensive radiosurgery equipment, we demonstrated that for the short term treating patients with acoustic neuroma with an extra-meatal tumour diameter of less than 3 centimeters, radiosurgery is more cost-effective than microsurgery.     

Extrinsic base optimization for high-performance RF SiGeheterojunction bipolar transistors

A comprehensive study on the effect of extrinsic base optimization on the RF performance of an advanced SiGe HBT is presented. An optimized extrinsic poly base with its interface to the epi-base passivated by boron ions is demonstrated to enhance the f_max and the current gain almost two times and to reduce the low-frequency 1/f noise ten times and noise figure (NF) 0.5 dB, achieving f_max of 45 GHz, 1/f noise corner frequency of 700 Hz at I_B=1.0 μA, NF⩽1.0 dB at 900 MHz. Early voltage V_A of ⩾200 V is achieved, while maintaining a BV_CEO of ⩾8.0 V     

500 mW coherent large aperture ring oscillators

A large aperture ring laser having a diffraction limited output measuring 0.2 degrees *0.2 degrees is described. The design uses angled incidence onto monolithic gratings for feedback and mode selectivity. Devices of this design have exhibited threshold current density less than 300 A/cm/sup 2/ and over 500 mW of single frequency output power.<>     

THE RELATION BETWEEN THE FINENESS AND OTHER PROPERTIES OF CALCINED GYPSUM1

Experimental methods.—The normal consistency was measured by the Southard viscosimeter. the time of set by the Vicat needle, and the plasticity by spreading upon a porous porcelain plate. Conclusions.—(1) Normal consistency is obtained with less water the coarser the calcined gypsum, (2) the finer the material the shorter the time of set, (3) the finer the calcined gypsum the stronger is the set material until the degree of fineness beyond that of size 6 (A. S. T. M. spec.) after which increase in fineness is accompanied by decrease in strength, (4) the finer the calcined gypsum the more sand it will carry.     

EFFECTS OF ACCELERATORS AND RETARDERS ON CALCINED GYPSUM1

Theories on the setting and the effects of accelerators and retarders on calcined gypsum are outlined. Accelerators and retarders as found by the writer and several other investigators are given, with comparative effect and any noticeable advantages or disadvantages of such instruments.