Platinum-Catalyzed Reactions of 2,3-Bis(diisopropylsilyl)thiophene with Alkynes.

The reactions of 2,3-bis(diisopropylsilyl)thiophene (1) with diphenylacetylene, phenylacetylene, trimethylsilylacetylene, and mesitylacetylene have been reported. The reactions of 1 with diphenylacetylene and phenylacetylene in the presence of a catalytic amount of tetrakis(triphenylphosphine)platinum(0) at 80 °C gave [1,4]disilino[2,3-b]thiophene derivatives. With trimethylsilylacetylene, 1 afforded two types of products arising from sp-hybridized C-H bond activation of the acetylene, together with [1,3]disilolo[4,5-b]thiophene derivatives. A similar treatment of 1 with mesitylacetylene produced two regioisomers of products arising from the C-H bond activation of mesitylacetylene. Theoretical calculations for the intramolecular reactions of 10a and 10b are also discussed.

The chemistry of benzodisilacyclobutenes and benzobis(disilacyclobutene)s: new development of transition-metal-catalyzed reactions, stereochemistry and theoretical studies.

The synthesis and reactions of 3,4-benzo-1,2-disilacyclobut-3-enes and benzo[1,2:4,5]bis(1,2-disilacyclobut-3-ene)s developed by our group are reported in this review. The palladium-, platinum- and nickel-catalyzed reactions of benzodisilacyclobutenes and benzobis(disilacyclobutene)s with unsaturated compounds afford various types of products. The structures of the products are dependent upon the nature of the transition metal used as a catalyst. The reactions of cis- and trans-benzodisilacyclobutenes with alkenes and alkynes in the presence of a transition-metal catalyst proceed with high stereospecificity to give the respective adducts. The thermal reactions of cis- and trans-benzodisilacyclobutenes with various substrates also proceed stereospecifically to give adducts. The results of theoretical calculations for the platinum-catalyzed reaction of disilacyclobutene with acetylene, the nickel-catalyzed reaction of benzodisilacyclobutene and the thermal reaction of benzobis(disilacyclobutene) are discussed in this review.

[Physical characteristics of anti-scatter grids according to old and new JIS standards].

JIS Z 4910 (anti-scatter grids) of the JIS standards was revised in 2000. Major points of revision were the provision of general-purpose and mammographic anti-scatter grids and changes in the diameter of the measuring field and difference in the manufacturing allowance. We measured the physical characteristics (grid selectivity, contrast improvement ratio, and grid exposure factor) of [general-purpose anti-scatter grids] referring to the methods of measurement [JIS Z 4910:2000] and [JIS Z 4910:1983] using an inverter-type high-voltage generator. Physical characteristics indicated a lower value for [JIS Z 4910:2000] than for [JIS Z 4910:1983]. [JIS Z 4910:2000] was able to measure primary radiation and scattered radiation more accurately than [JIS Z 4910:1983] because of the diameter of the measuring field and the measurement arrangement. Moreover, the physical characteristic values were influenced by radiation quality, e.g., differences in high-voltage generators. In the method of measuring stipulated by JIS, strict conditions regarding the arrangement of the measurement tools and the stability and other factors of the power output of the X-ray generator are provided for the type approval test conducted by the manufacturer.

[Report based on Fiscal 2000 Diagnostic X-ray Equipment Questionnaire Survey (conditions of X-ray units and similar equipment)].

The X-ray Systems Study Group, in an attempt to determine the current status and changes in the state of X-ray equipment, reception systems, and equipment control, conducted investigational research by distributing a questionnaire survey to 400 facilities. The rate of recovery was 33%. The capacity of transformers has been increasing in spite of the three-phase 415 V decrease in the power supply of X-ray equipment. Among high-voltage generators, inverter-type X-ray equipment accounted for 81.3% of units. The ratio of the X-ray tube of a conventional rotational system to that of a high-speed rotational system was 1:3, and 54.9% had target angles of 12 . Many X-ray tubes had a heat capacity of less than 200-300 kHU. The body parts that had the shortest times on radiography were adult chest and pediatric chest. In many cases, the shortest time used was 10 msec. Facilities in which the shortest time was less than 10 msec accounted for almost half of the total number. Facilities where the radiation dose of radiography had decreased showed 1/4 of the digitalization whole. Measurement was carried out when the equipment was bought in 94.9% of facilities, and measurement when the service contract was finished was done in 77.1% of the responding facilities.

[Report based on fiscal 2000 diagnostic x-ray equipment questionnaire survey(conditions of radiography)].

X-ray equipment has seen advances in inverters and the digitalization of reception systems. The X-ray Systems Study Group, in order to examine changes in the conditions of radiography, including pediatric radiography, variations in shortest irradiation time, and standardization of the conditions of radiography, carried out investigative research using a questionnaire survey that was sent to 400 facilities. The recovery rate was 33%. In terms of the reception system, half of the general radiography systems were using computed radiography (CR). Seventy percent of respondents used an intensifying screen and film(S EF)in stomach double-contrast radiography. About 80% used digital radiography (DR) and digital subtraction angiography (DSA) in aorta abdominalis angiography. At least 70% of high-voltage generators were of the inverter type. The conditions of radiography were not greatly influenced by changes in reception systems and X-ray equipment. Many pediatric radiographies were carried out by radiological technologists. We consider it useful to conduct such survey investigations.

[Measurement of depth dose distribution using plastic scintillator].

We propose a new method to measure the depth dose distribution in matter. The method is to use organic plastic scintillator as a phantom, which has the effective atomic number close to that of human soft tissue, and to measure the position distribution of the scintillation light by a wavelength analyzer through a thread of plastic optical fiber. The purpose of this study is to examine possibility to measure the depth dose distribution with the proposed method. We carried out the following three measurements. First, we measured the effective field of view (FOV); the plastic optical fiber accepts the light from the FOV. Then, we measured the dose dependence of the amount of emission light. Finally, the light distribution in the depth direction by the present method was compared to the depth dose distribution by the ionization chamber. The results are as follows. The angular range of FOV is 7.03 degrees +/- 0.21 degrees The dose dependence shows a good linearity. In other words, the amount of emission light is proportional to the absorbed dose. Both of the light and the dose distributions are proportional each other, and they show the same attenuation in the region deeper than 15 mm. From these results, we conclude that the present method can be used for the measurement of the depth dose distribution in matter.

[Characteristics of specifications of transportable inverter-type X-ray equipment].

Our X-ray systems study group measured and examined the characteristics of four transportable inverter-type X-ray equipments. X-ray tube voltage and X-ray tube current were measured with the X-ray tube voltage and the X-ray tube current measurement terminals provided with the equipment. X-ray tube voltage, irradiation time, and dose were measured with a non-invasive X-ray tube voltage-measuring device, and X-ray output was measured by fluorescence meter. The items investigated were the reproducibility and linearity of X-ray output, error of pre-set X-ray tube voltage and X-ray tube current, and X-ray tube voltage ripple percentage. The waveforms of X-ray tube voltage, the X-ray tube current, and fluorescence intensity draw were analyzed using the oscilloscope gram and a personal computer. All of the equipment had a preset error of X-ray tube voltage and X-ray tube current that met JIS standards. The X-ray tube voltage ripple percentage of each equipment conformed to the tendency to decrease when X-ray tube voltage increased. Although the X-ray output reproducibility of system A exceeded the JIS standard, the other systems were within the JIS standard. Equipment A required 40 ms for X-ray tube current to reach the target value, and there was some X-ray output loss because of a trough in X-ray tube current. Owing to the influence of the ripple in X-ray tube current, the strength of the fluorescence waveform rippled in equipments B and C. Waveform analysis could not be done by aliasing of the recording device in equipment D. The maximum X-ray tube current of transportable inverter-type X-ray equipment is as low as 10-20 mA, and the irradiation time of chest X-ray photography exceeds 0.1 sec. However, improvement of the radiophotographic technique is required for patients who cannot move their bodies or halt respiration. It is necessary to make the irradiation time of the equipments shorter for remote medical treatment.

[Characteristics of a new non-invasive x-ray output analyzer].

The X-ray systems study group used the Victoreen NERO mAx model 8000, a new non-invasive X-ray output analyzer, to measure the tube voltage, tube voltage waveform, tube current, and irradiation time for conditions corresponding to general radiography and mammography. The measurement results were then compared with those obtained using a conventional invasive measuring instrument. The peak values of the tube voltage measured by the NERO mAx and the invasive measuring instrument were compared. The NERO mAx had a good measurement error range of -1.2 to +0.9 kV. For tube current measurement by the NERO mAx, the maximum error for general radiography conditions was +11 mA and that for mammography conditions was +6 mA. For irradiation time measurement, the value for general radiography conditions was slightly greater and the value for mammography conditions was slightly less than the corresponding values obtained by the invasive measuring instrument. If radiation quality is changed during measurement of the characteristics, measurement values change. Since the NERO mAx incorporates two types of X-ray detectors, it shows good measurement reproducibility. The NERO mAx has been shown to have suitable characteristics for use as a measuring instrument for constancy tests. In the future, constancy tests should be used to quantitatively control the factors determining clinical image quality.