High-dose-rate remote afterloading intestinal radiotherapy employing the template technique for recurrent cancer in the pelvic area

Between December 1991 and August 1992, five patients with recurrent cancer in the pelvic area (four gynecological cancers and one rectal cancer) were treated at Osaka University Hospital with a remote afterloading interstitial implantation employing the template technique. External irradiation (40 to 50 Gy) was performed in four cases one to four weeks before brachytherapy. Interstitial high-dose-rate brachytherapy (24 to 40 Gy/four to eight fractions/two to four days) was performed twice a day. Three of the five patients achieved complete local tumor control. The remaining two patients obtained symptom relief. There were no complications serious enough to need surgical treatment. Moreover, this procedure is well tolerated and therefore an effective modality for elderly and frail patients.     

40-Gb/s X-cut LiNbO/sub 3/ optical modulator with two-step back-slot structure

We propose a newly designed X-cut lithium niobate (LiNbO/sub 3/) optical modulator. It has a two-step back-slot structure to satisfy the velocity-matching condition without the buffer layer of silicon dioxide (SiO/sub 2/). Accordingly, this modulator can achieve low drive voltage and low optical insertion loss. In addition, the dc-drift phenomena due to the buffer layer can be suppressed. This structure is fabricated with micromachining technology using excimer laser ablation. The optical 3-dB bandwidth of the fabricated modulator reaches 30 GHz, and the drive voltage is less than 3 V at 1 kHz. From the measurement of the optical eye diagram at 43.5-Gb/s, clear eye openings were obtained. This modulator is sufficient for 40-Gb/s optical transmission systems.     

Automated fault tree synthesis by semantic network modeling, rulebased development and recursive 3-value procedure

A concept of flow is introduced to represent any material, information, energy, activity, or phenomenon which can move or propagate along flow paths to cause events specific to the system to be analyzed. A graphical equipment library is given to represent typical types of ‘generation rate’ and ‘aperture’ controllers. The system is modeled by a semantic network with labeled arrows showing effect to cause (backward) relationships between flow and equipment nodes. A correspondence between the equipment library and the system components is established, and the semantic network is constructed by integrating network fragments in the library. Fixed and/or free boundary conditions can be specified explicitly for flow or equipment nodes. Forward-chaining event development rules locally trace the labeled arrows, while a 3-value procedure guides the FT generation by recursive rule applications. The rules are obtained from tables and equipment definitions. The 3-value logic is used to truncate FTs according to the boundary conditions. Different FTs are generated for different top events and boundary conditions, given a semantic network model. FT modules and their hierarchies can be identified by examining network theoretic properties of flow nodes. The proposed approach is demonstrated for a relay system, a hypothetical swimming pool reactor and a chemical reactor.     

Signal-Flow-Based Graphs for Failure-Mode Analysis of Systems with Control Loops

Control loops make failure-mode analysis via fault trees extremely difficult. This paper proposes a new approach based on signal flow graphs to model systems with control loops. Mason's Rule is applied to assess the effect of the loops. The top event of the system is defined by an inequality on a node-variable of the signal flow graph. Basic failures are modeled by source variables. Cut-off failures of the control loops are also considered. The method is useful for uncovering failure modes leading to the top event in complicated systems with control loops. General steps to apply the method to a system are: 1. Draw a SFG for the system. 2. Model basic failures by source variables. 3. Select a node-variable to define a top event. 4. Represent the top event in terms of the source variables, using Mason's Rule. 5. Discretize the source variables. 6. Classify loop states. 7. For each loop state, obtain system failure modes, using a search tree like Fig. 5. 8. Review the failure modes by more accurate simulation models. Any model is an approximation of an actual system. Thus, the resulting failure modes like those in Table 3 should be examined again, using past experience, more accurate simulation models, etc. The method should be viewed primarily as useful tool for uncovering failure modes in which complicated systems with the control loops fail.     

Pathogenesis of duct hyperplasia in the pancreas

Causative factors in duct hyperplasia were histologically examined by using 1,388 autopsied pancreases. Duct hyperplasia was frequent in pancreases having primary carcinoma and in those having necrotizing pancreatitis, but it was not frequent in those with interstitial pancreatitis, ductal pancreatitis, and other disorders. Duct hyperplasia was almost always found in ducts which connected with small ducts having a feature of adenomatous hyperplasia or ductular aggregation in foci of intralobular fibrosis. A histologic examination revealed that these fibrous foci are likely the vestiges of fat necrosis, mostly of a subclinical one.     

The acidic complexation of tetracycline with sucralfate for its mucoadhesive preparation

The complex of antibiotics with sucralfate (SF) was prepared with acid. The mechanism of the complexation and some factors concerning the preparation, which influence the mucoadhering property, were studied. The complexation was confirmed by the change in color and instrumental analysis. The acidic complex appeared to be produced by reagglomeration of SF preliminary particles. It was suggested that the amide or amine groups of tetracycline (TC) and aluminum moieties of SF serve as the binding sites. The potential of multiple binding sites and a priority in them were suggested by the Scatchard plot analysis. The additional amounts of acid and the increase in the surface area increased the number of sites. The amount of the additional acid appeared to be the most important factor during the preparation of the acidic complex. The appropriate amount of acid added appeared to produce a complex rich in TC. However, an excess amount might cause the excess dissociation of aluminum moieties, which destroys the mucoadhesive paste-forming property.     

Dependence of sonoluminescence intensity on the geometrical configuration of a reactor cell

Dependence of sonoluminescence (SL) intensity on the geometrical configuration of a reactor cell is studied theoretically and experimentally. The model is a rectangular glass cell set in a water-cooling bath. Ultrasound is irradiated from the bottom of bath into the cell. Theoretical analysis of transmitted acoustic energy assuming a plane acoustic wave clarified the influences of distance between the transducer and the cell bottom, thickness of the cell bottom, and water depth in the cell. The theory is examined through intensity measurement of SL emitted in the cell using a photomultiplier tube. Dependence of SL intensity on the above parameters agreed with the theory very well. Distributions of SL are also observed using a high sensitivity CCD camera and are compared with optically visualized sound fields to show the relationship between the sound field and the SL     

State-Transition Monte Carlo for Evaluating Large, Repairable Systems

This paper presents a new Monte Carlo method to estimate unreliabilities of large, repairable systems which can be modeled by a stationary Markov transition diagram. Sequences of state transitions ending at absorbing states are generated, using random numbers. Times to transitions related to the state-sequences are not generated. Next, the probability of system failure occurring in a mission time along each state-sequence is calculated. Finally, the arithmetic mean of these probabilities estimates the system unreliability. This state transition Monte Carlo method yields better estimates in fewer trials than direct Monte Carlo methods. A cold-standby problem with non-identical units is also solved as a by-product of this paper.     

Nitride formation by the carbothermal reduction of a zeolite-polyacrylonitrile inclusion compound

An inclusion compound between zeolite and polyacrylonitrile has been applied as a precursor for the carbothermal reduction process. By heat treatment at 1400 to 1600° C in N₂, -sialon was mainly obtained. The X phase, -Si₃N₄, the 15R-AlN phase, AIN, and mullite also formed under certain firing conditions. On the other hand, -Si₂N₄ was detected as the principal crystalline phases as well as -sialon in the products from zeolite-carbon mixtures. Hence, the use of the inclusion compound was advantageous for -sialon production in the conversion of zeolite to nitrides.     

Preparation of lithium aluminosilicate glass-ceramic monolith from metal alkoxide solution

Glass-ceramic monoliths with a composition of Li₂O·Al₂O₃·4SiO₂ have been synthesized by the sol-gel technique using metal alkoxides as starting materials. Heating dried gel monoliths of about 36 mm diameter and height to appropriate temperatures gave glass-ceramic monoliths of about 20 mm diameter and height without the occurrence of cracks, while a melt-derived glass body of the same composition was cracked or softened on heating. The glass-ceramic monoliths obtained by heating gel monoliths at 1000 C for 40 h were a porous body, whose bulk density and porosity were 1.62 g cm^–3 and 34%, respectively. On heating gel monoliths, -eucryptite crystals were first precipitated around 750 C, followed by precipitation of -spodumene crystals at 830 C. At higher temperatures the latter grew at the expense of the former phase. The crystallized specimens exhibited very low thermal expansion coefficient ranging from –13-12×10^–7 C^–1 at temperatures from room temperature to 700 C depending on the heat-treatment temperature of gels, indicating that a porous glass-ceramic monolith with ultra-low thermal expansion can be prepared using the present sol-gel method.