Positologica: A Positron ECT Device with a Continuously Rotating Detector Ring

A rotary positron emission computed tomography device is developed for human brain and animal studies. The device utilizes 64 rectangular BGO detectors arranged at unequal spacing on a circular ring. The detector ring is continuously rotated at a constant speed of 60 rpm or less. This single continuous motion of the ring with the detector array provides excellent sampling characteristics and high detector redundancy. The device has a field of view 24 cm in diameter with a slice thickness adjustable from 1 cm to 2 cm. Measured width of system response to a 2 mm diameter line source is 5.8 mm FWHM at the center and less than 9 mm FWHM within a circle 16 cm in diameter. Measured sensitivity including scattered coincidence events is about 17 kcps/pCi/ml for a 20 cm diameter water phantom and 2 cm thick slice.     

Dip-coating conditions and modifications of lead titanate and lead zirconate titanate films

The modifications of dip-coated lead titanate (PT) and lead zirconate titanate (PZT) films strongly depend on the film thickness and the substrate in addition to the heat-treatment temperature. At 500 to 600 ° C, metastable paraelectric pyrochlore grew on glass plates (amorphous plates) when the thickness of the coated films produced by one coating cycle was below 100 nm, while ferroelectric perovskite formed on crystalline substrates or when thick films were coated on amorphous plates. This tendency is discussed in terms of an inhomogeneous reaction and the epitaxial effect. The perovskite PT films coated on single-crystal SrTiO₃ plate at 700 ° C were strongly oriented to thec-axis.     

Suppression of tin whisker formation on fine pitch connectors by surface roughening

In the electronics industry, lead-free solder processes such as the terminal plating of electronic components, fine pitch connectors, and flexible printed circuits (FPCs) are invariably hampered by the serious problem of tin whisker formation. Here, a new and simple method, the JVC Micro Island (JMI) process, is proposed for the prevention of tin whisker formation in fine pitch connectors. Briefly, the base copper terminal was acid etched to afford a roughened surface, which was then tin plated. The contact test with Knoop indentation proved the effectiveness of the present process. The maximum length of the as-formed tin whiskers was less than 50 μm. The solderability of the JMI FPCs was not influenced by the present process. Thus, the new JMI process is shown to have a great advantage for the prevention of tin whisker formation in fine pitch connectors.     

Dependence of Output Power on Cavity Length in a Gyrotron Backward Wave Oscillator

A relativistic electron beam (500 keV, 200 A, 10 ns) generated magnetically tunable microwave radiation in a frequency range of 9-13 GHz when it is injected into an X-band rectangular waveguide immersed in a uniform axial magnetic field (4-10 kG). The mechanism of the microwave radiation was identified as the gyrotron backward wave interaction. The output power of the radiated microwave increased exponentially with the increase of the cavity length.     

Sonication‐Induced Formation of Size‐Controlled Self‐Assemblies of Amphiphilic Janus‐Type Polymers as Optical Tumor‐Imaging Agents

In this study, amphiphilic Janus‐type polymers were synthesized via ring‐opening metathesis polymerization (ROMP), multiple vicinal diol formation, and grafting of poly(ethylene glycol) monomethyl ether (mPEG). These amphiphilic polymers formed self‐assemblies, which were a mixture of micelles and multimicellar aggregates, in water. By choosing suitable Janus‐type polymers and irradiating an aqueous solution of polymers using a sonicator, either small micelles or large multimicellar aggregates were obtained selectively. Hydrophobic substituents controlled the aggregation–disaggregation behavior, leading to the formation of metastable self‐assemblies by sonication. The formation of self‐assemblies with a uniform size was affected by ultrasonic frequency, rather than power. In vivo optical tumor imaging revealed that the large‐size multimicellar aggregates persisting for a long time in blood circulation slowly accumulated in tumor tissues. In contrast, the tumor site was rapidly, clearly visualized using the small‐size micelles.     

An Organic–Inorganic Hybrid Composite as a Coating Agent

An organic–inorganic hybrid composite for use as a coating agent was prepared by mixing linseed oil with hydrophobic octylsilyl titanium dioxide particles having an average diameter of 35 nm (OSI-TIO2-35) in volatile silicone. The weight ratio of linseed oil with OSI-TIO2-35 was varied from 2:8 to 8:2 and the mixture was spread on a glass plate by dragging an applicator across it. After storing in the oven at 60 °C for 2 days, the composite having the weight ratio of OSI-TIO2-35 with linseed oil at 8:2 exhibited very high water-repellent properties having a water contact angle of 148°. Variation of the water contact angle during storage at 60 °C was monitored. It decreased by 10° in the initial 8 h and then increased by 45° over the next 2 days. Composites containing silicone resin, TMSS BY11-018, instead of linseed oil were also prepared. The sample having a weight ratio of OSI-TIO2-35 with TMSS BY11-018 at 8:2 also exhibited very high water-repellent properties with a water contact angle of 152°. The highly hydrophobic surface thus prepared by the coating and drying of those organic-inorganic hybrid composites was easily transferred to highly hydrophilic surfaces by calcination at 500 °C for 3 h.     

Novel retrovirus protease inhibitors, RPI-856 A, B, C and D, produced by Streptomyces sp. AL-322

Four kinds of retrovirus protease inhibitors (RPI-856 A, B, C and D) were isolated as white powder from the culture filtrate of a soil isolate, Streptomyces sp. AL-322 by column chromatography using Diaion HP-20, Sephadex LH-20, ODS reversed phase HPLC and SP-2SW ion exchange HPLC. The structures of these inhibitors were elucidated by physico-chemical properties, chemical reactions and spectral analyses, as valyl-ADPAA-leucyl-AOPBA-valyl-valyl-aspartic acid (RPI-856 A and B) and valyl-ADPAA-leucyl-AOPBA-valyl-valine (RPI-856 C and D) [ADPAA = 2-amino-2-(3,5-dihydroxyphenyl)acetic acid, AOPBA = 3-amino-2-oxo-4-phenylbutyric acid]. RPI-856 A and B, and RPI-856 C and D were both determined to be diasteromers each other on the asymmetric carbon in AOPBA. These four inhibitors strongly inhibited in vitro HIV-1 protease and HTLV-I protease both derived from recombinant Escherichia coli with IC50 of 10(-7) approximately 10(-8) M.     

A high-speed-retry banyan switch architecture for giga-bit-rate BISDN networks

This paper proposes a high-speed ATM switch architecture for handling cell rates of several Gb/s in a broadband communication switching system or cross-connect system. The proposed switch architecture, named the high-speed-retry banyan switch, employs a bufferless banyan network between input and output buffers; a cell is repeatedly transmitted from an input buffer until it can be successfully transmitted to the desired output buffer. A simple cell-retransmission algorithm, is employed as is a ring-arbitration algorithm for cell conflict. They are suitable for FIFO type buffers and bufferless highspeed devices. Good traffic characteristics which are independent of switch size are achieved for an internal speed ratio of only four times the input line speed. A prototype system with the internal speed of 1·2 Gb/s is constructed in order to confirm the basic operation of the high-speed-retry banyan switch. The prototype system, even in its present state, could be used to realize a giga-bit-rate BISDN switching system.     

Synthesis of anti-rheumatic agent epoxyquinomicin B

Anti-rheumatic agent (+/-)-epoxyquinomicin B was synthesized for a 22% overall yield in eight steps from commercially available 3-hydroxy-4-nitrobenzaldehyde via the intermediate quinone 6 prepared by selective phenol oxidation of 5 by use of Fremy's salt as the key step.     

Inhibition of the growth of cariogenic bacteria in vitro by plant flavanones

Phytoalexins, defensive compounds produced by plants against microbial infections, were purified from Sophora exigua (Leguminosae) and their growth inhibitory effects on oral cariogenic bacteria were determined in vitro. Among three isolated compounds, 5,7,2',4'-tetrahydroxy-8-lavandulylflavanone completely inhibited the growth of oral bacteria including primary cariogenic mutans streptococci, other oral streptococci, actinomycetes, and lactobacilli, at concentrations of 1.56 to 6.25 micrograms/ml.