Polarization memory of luminescence from photo-generated carriers in aSixC1−x:H (x∼0.2)

Photoluminescence of aSi_xC_1?x:H (x～0.2) is studied with a particular interest on the localization of carriers. Taking the polarization memory of luminescence as a probe, we clarify the localized character of photo-generated carriers as functions of excitation photon energy, emitted photon energy, temperature and time. The picosecond time-resolved measurement of the polarization memory is shown useful to study dynamical relaxation processes of carriers in disordered systems.     

Highly planar amphiphilic porphyrins

A first synthesis of an asymmetric and amphiphilic β-substituted porphyrin is reported. The porphyrin can be integrated into various types of nanostructures with the amphiphilic characters in hydrophilic solvents. The one-dimensional integration may induce a magnetic interaction between the central metals.     

Total Synthesis of Lajollamycin B

The first total synthesis of lajollamycin B, a structurally novel nitro-tetraene spiro-β-lactone/γ-lactone antibiotic, is described. The convergent synthesis involves the construction of the C8′–C11′ nitrodienylstannane and its coupling with the segment prepared from the C1′–C7′ ω-iodoheptadienoic acid and the right-hand heterocyclic fragment, which has been utilized for our previous syntheses of oxazolomycin A. The revision of the geometry of the terminal Δ^{10′, 11′}-double bond from E to Z is also described for the structure of natural lajollamycin B.     

Development of high-radiation-sensitive polymer gel for magnetic resonance imaging in three-dimensional dosimetry

We developed a high radiation sensitive polymer gel by modifying the amounts of the gel components and the temperature for the gel preparation. We evaluated its relaxation time linearity against dose and compared the measured dose distribution with the calculated one. For the relaxation time-dose linearity, irradiations were carried out with a linear accelerator using 6 MV photons and doses ranging from 0-5.0 Gy. The relationship between dose and R(2) value (reciprocal of T(2) relaxation time) was measured and it had good linearity over a wide range (0.3-5 Gy). The measured dose distributions were in good agreement with calculated ones. Since the present gel has higher sensitivity and it is synthesized more easily at lower cost than conventional polymer gels, we expect to see improved three-dimensional (3D) dosimetry using it.     

Coherent combination of high-power, zigzag slab lasers

We demonstrate a scalable architecture for a high-power, high-brightness, solid-state laser based on coherent combinations of master oscillator power amplifier chains. A common master oscillator injects a sequence of multikilowatt Nd:YAG zigzag slab amplifiers. Adaptive optics correct the wavefront of each amplified beamlet. The beamlets are tiled side by side and actively phase locked to form a single output beam. The laser produces 19 kW with beam quality <2x diffraction limited. To the best of our knowledge, this is the brightest cw solid-state laser demonstrated to date.     

Multibubble sonoluminescence enhancement by fluid flow

Forced fluid flow can cause the enhancement of multibubble sonoluminescence (SL) under suitable conditions. The effect of directional flow with a circulator is similar to that of rotating flow with a stirrer. The mechanism of the enhancement is that both flows prevent cavitation bubbles from coalescing and clustering, which are responsible for the quenching of SL. The intensity of sonochemiluminescence (SCL) in an aqueous luminol solution increases with flow speed at higher ultrasonic powers more significantly than that of SL in distilled water. However, in the range of low ultrasonic power, the intensities of SL and SCL decrease with flow speed. Therefore, an optimum flow speed exists in relation to ultrasonic power and frequency.