Carrier mobility of photochromic diarylethene amorphous films

Photochromic diarylethenes (DAEs) have gained attention as attractive current switching materials by light irradiation in the organic electronics field. We investigated the hole mobility of amorphous films consisting of three types of DAEs using a space-charge-limited current method and a better chemical structure to achieve high mobility. The hole mobility of open-ring (colorless) DAE having benzothiophene rings substituted with triphenylamine (TPA) as an aryl group was 2 × 10⁴ times (2 × 10⁻⁶ cm²/V s) larger than that of DAE containing thiophene rings without TPA. When the DAE film was irradiated with ultraviolet (UV) light, the hole mobility decreased temporarily at 4% of closed-ring (colored) isomers and then increased to two-three times of the initial colorless state at 85% of the closed-ring isomers. The temporary decrease in the hole mobility originated in the hole trapping effect of the closed-ring molecules in a matrix consisting of open-ring isomers.     

Planar Radiating Oscillator Using Butterfly-Shaped Patch Element and Spatial Power-Combining Array

A planar radiating oscillator using a butterfly-shaped patch element is described. To obtain an injection-locking range that can be changed and low cross-polarization, we used a butterfly-shaped patch. The patch element was able to change the injection-locking range while maintaining low cross-polarization, and two types of patch were compared. As one application, we designed and fabricated 1x2, 2x1 and 2x2 spatial power-combining arrays by using radiative mutual coupling. The 2x2 array was successfully operated with a single-bias supply without using a 3-D (three-dimensional) Fabry-Perot cavity. An equivalent isotropic radiated power of 2.5 W was measured at X-band.     

Molecular cloning and nucleotide sequences of cDNA and gene encoding endo-inulinase from Penicillium purpurogenum

A cDNA and a gene encoding endo-inulinase from Penicillium purpurogenum were isolated, and were cloned for the first time. Two oligonucleotide probes, which were synthesized based on the partial amino acid sequences of the purified endo-inulinase, were used to screen a cDNA library. A 1.7-kb DNA fragment encoding endo-inulinase was isolated and analyzed. A single open reading frame, consisting of 1548-bp, was found to encode a polypeptide that comprised a 25-amino acid signal peptide and 490-amino acid mature protein. All the partial amino acid sequences of the purified enzyme were discovered in the deduced ones. The deduced amino acid sequences of endo-inulinase had similar sequences to those of fructan hydrolases. A 3.5-kb chromosomal DNA fragment encoding endo-inulinase was also isolated and analyzed. The same ORF with cDNA clone as identified. There were no introns in the endo-inulinase gene.     

A technique of parallel connections of pulsewidth-modulated NPC inverters by using current-sharing reactors

The neutral-point-clamped (NPC) PWM inverters have many advantages such as the ability to operate the motor with nearly sinusoidal current waveforms. For this reason, in larger-capacity inverter systems, NPC PWM inverters using the GTOs, etc., have also been put into practical use because of great advantages to large-capacity ac motor drives such as lower ripple currents and higher output voltages. With the spread of applications, still larger-capacity inverters also are expected. However, since the capacities of such switching devices are insufficient, a certain technique and controlling method are proposed for the parallel connections of NPC inverters. The output voltage waveforms of the proposed inverter have certain voltage levels, and thus it is anticipated that it will be difficult to analyze the output harmonics. For such waveforms of output voltage and current-sharing reactor, a frequency analysis approach is described whose results are verified by experiments.     

Degradation of PL characteristics in strained layer multi-quantum well structure with atomic ordering structure

Clarification of the degradation mechanism of photoluminescence (PL) charac-teristics of InGaAsP compressively strained layer multi-quantum well (SL-MQW) structures on an InP substrate is studied to realize highly strained SL-MQW lasers with a large number of well layers. An unusual temperature-dependence of the PL peak wavelength is observed in the SL-MQW structure: the shift of the PL peak wavelength is reduced with change in measurement temperature. The degradation of PL characteristics is evaluated by the reduc-tion in the PL shift as well as an increase in PL linewidth and a decrease in PL peak intensity. The extent of the PL degradation increases with an increase in the number of well layers and an increase in strain. In the SL-MQW structure with degraded PL characteristics, the structure of CuPt-type atomic ordering is clearly observed for the first time in each barrier layer by high-resolution transmission electron microscope (HR-TEM) measurements. In the SL-MQW structure, neither dislocation nor three-dimensional nucleation is observed by TEM measurements. By increasing the growth temperature, elimination of the ordering structure as well as improvement in the PL characteristics have been confirmed even in the SL-MQW structure with a large amount of strain and a large number of well layers.     

Heterogeneous zonal distribution of sulfotransferase isoenzymes in rat liver

By employing dual-digitonin-pulse perfusion technique, the cytosolic fractions were prepared from periportal (PP) and perivenous (PV) hepatocytes of male and female rat livers. Sulfotransferase (ST) activities toward 2-naphthol (2NAP) (at pH 5.5 and 7.4), 4-nitrophenol, dehydroepiandrosterone (DHEA), and cortisol were measured in each fraction. DHEA-ST activity was mainly localized in PP fraction in males, while in females it was slightly higher in PP fraction than in PV samples. In contrast, phenol ST activities were higher in PV fraction in both sexes. With anti-HS-ST and anti-P-ST antisera, the levels of immunoreactive ST polypeptides were compatible with the levels of ST activities except that in female PP fraction the level of immunoreactive P-ST polypeptide was low in spite of comparatively high levels of P-ST activities. Chromatofocusing of PP and PV fractions separated P-ST activities into three major fractions (I-III), which have distinct catalytic and electrochemical properties. Fraction I was localized only in the PP samples in both sexes and revealed ST activities toward 2NAP at pH 5.5 and 7.4, while fraction II was localized in the PP and PV samples in both sexes with 2NAP-ST activity only at pH 7.4. Fraction III which had ST activities at pH 5.5 and 7.4 was present only in the PV samples in female rats, whereas in male rats it was present in both PP and PV samples. With anti-P-ST antiserum, the immunoreactive polypeptide was present in fraction III, but no immunoreactive band was detected in fractions I and II, suggesting the presence of immunochemically and electrochemically different P-ST(s) in these fractions.     

Chain Shuffling: Investigations into the Specificity and Selectivity of Antibody Catalysis

The antibody phage display system has been investigated as a vehicle for the potential altering of a catalytic antibody's specificity and chemical reactivity. Using previously identified catalytic antibodies, heavy and light “chain shuffling” experiments have been conducted. Catalytic activity and specificity requirements in terms of antibody complementarity-determining regions were probed by interchanging heavy and light chain genes between antibodies that catalyze class-similar but different chemical reactions with substrates that are enantiomerically opposed. The results were that antibody-hapten binding specificity was only slightly altered, but catalytic activity was severely compromised.     

Inhibitory long-term potentiation underlies auditory conditioning of goldfish escape behaviour

Long-term potentiation (LTP), the increase in synaptic strength evoked by high-frequency stimulation, is often considered to be a cellular model for learning and memory. The validity of this model depends on the assumptions that physiological stimuli can induce LTP in vivo and that the resulting synaptic modifications correlate with behavioural changes. However, modifiable synapses are generally embedded deep in complex circuits. In contrast, the goldfish Mauthner (M)-cell and its afferent synapses are easily accessible for electrophysiological studies, and firing of this neuron is sufficient to trigger fast escape behaviour in response to sudden stimuli. We have previously shown that tetanic stimulation can induce LTP of the feedforward inhibitory synapses that control the excitability of the M-cell. Here we report that natural sensory stimulation can induce potentiation of this inhibitory connection that resembles the LTP induced by afferent tetanization. Furthermore, comparable acoustic stimulation produced a parallel decrease in the probability of the sound-evoked escape reflex. Thus we demonstrate for the first time, to our knowledge, a behavioural role for the long-term synaptic strengthening of inhibitory synapses.