Strong Terahertz Radiation via Rapid Polarization Reduction in Photoinduced Ionic-To-Neutral Transition in Tetrathiafulvalene-p-Chloranil.

Terahertz lights are usually generated through the optical rectification process within a femtosecond laser pulse in noncentrosymmetric materials. Here, we report a new generation mechanism of terahertz lights based upon a photoinduced phase transition, in which an electronic structure is rapidly changed by a photoirradiation. When a ferroelectric organic molecular compound, tetrathiafulvalene-p-chloranil, is excited by a femtosecond laser pulse, the ionic-to-neutral transition is driven and simultaneously a strong terahertz radiation is produced. By analyzing the terahertz electric-field waveforms and their dependence on the polarization direction of the incident laser pulse, we demonstrate that the terahertz radiation originates from the ultrafast decrease of the spontaneous polarization in the photoinduced ionic-to-neutral transition. The efficiency of the observed terahertz radiation via the photoinduced phase transition mechanism is found to be much higher than that via the optical rectification in the same material and in a typical terahertz emitter, ZnTe.

Pd2 MnGa Metamagnetic Shape Memory Alloy with Small Energy Loss.

Metamagnetic shape memory alloys (MMSMAs) are attractive functional materials owing to their unique properties such as magnetostrain, magnetoresistance, and the magnetocaloric effect caused by magnetic-field-induced transitions. However, the energy loss during the martensitic transformation, that is, the dissipation energy, Edis , is sometimes large for these alloys, which limits their applications. In this paper, a new Pd2 MnGa Heusler-type MMSMA with an extremely small Edis and hysteresis is reported. The microstructures, crystal structures, magnetic properties, martensitic transformations, and magnetic-field-induced strain of aged Pd2 MnGa alloys are investigated. A martensitic transformation from L21 to 10M structures is seen at 127.4 K with a small thermal hysteresis of 1.3 K. The reverse martensitic transformation is induced by applying a magnetic field with a small Edis (= 0.3 J mol-1 only) and a small magnetic-field hysteresis (= 7 kOe) at 120 K. The low values of Edis and the hysteresis may be attributed to good lattice compatibility in the martensitic transformation. A large magnetic-field-induced strain of 0.26% is recorded, indicating the proposed MMSMA's potential as an actuator. The Pd2 MnGa alloy with low values of Edis and hysteresis may enable new possibilities for high-efficiency MMSMAs.

Dynamic changes of genome sizes and gradual gain of cell-specific distribution of C4 enzymes during C4 evolution in genus Flaveria.

C4 plants are believed to have evolved from C3 plants through various C3 -C4 intermediate stages in which a photorespiration-dependent CO2 concentration system known as C2 photosynthesis operates. Genes involved in the C4 cycle were thought to be recruited from orthologs present in C3 species and developed cell-specific expression during C4 evolution. To understand the process of establishing C4 photosynthesis, we performed whole-genome sequencing and investigated expression and mesophyll- or bundle-sheath-cell-specific localization of phosphoenolpyruvate carboxylase (PEPC), NADP-malic enzyme (NADP-ME), pyruvate, orthophosphate dikinase (PPDK) in C3 , C3 -C4 intermediate, C4 -like, and C4 Flaveria species. While genome sizes vary greatly, the number of predicted protein-coding genes was similar among C3 , C3 -C4 intermediate, C4 -like, and C4 Flaveria species. Cell-specific localization of the PEPC, NADP-ME, and PPDK transcripts was insignificant or weak in C3 -C4 intermediate species, whereas these transcripts were expressed cell-type specific in C4 -like species. These results showed that elevation of gene expression and cell-specific control of pre-existing C4 cycle genes in C3 species was involved in C4 evolution. Gene expression was gradually enhanced during C4 evolution, whereas cell-specific control was gained independently of quantitative transcriptional activation during evolution from C3 -C4 intermediate to C4 photosynthesis in genus Flaveria.

Effects of cell culture scaffold stiffness on cell membrane damage induced by sonoporation.

PURPOSE: As basic studies to realize in vivo sonoporation, rates of cell membrane damage during sonoporation were evaluated using monolayer cells cultured on scaffolds with different degrees of stiffness. METHODS: Four types of scaffolds, constructed using collagen gel, 10 and 30 % acrylamide gels, and a coverslip, were used for cultivation of monolayer cells. Young's moduli measured using an atomic force microscope were in the range 0.09-8.6 kPa for the gel scaffolds, whereas Young's modulus for living cells was 4.5 kPa. Cells with attached microbubbles were exposed to one-shot pulsed ultrasound of 8.0/-1.3 MPa in peak positive/negative pressures with durations of 3, 100, and 10,000 cycles. RESULTS: Cell membrane damage was visualized by fluorescence microscopy using propidium iodide. The 3-cycle ultrasound pulse had no significant effect; however, the rates of damage caused by 100-cycle and 10,000-cycle pulses showed a strong tendency for higher rates of damage with a higher Young's modulus. CONCLUSION: The experimental results indicate that the stiffness of the underlying layer of adherent cells should be considered as an essential parameter of the sonoporation condition and that the optimum exposure conditions for in vivo sonoporation should be determined with consideration of the physical properties of underlying tissues.