Modal Birefringence Dependent Supercontinuum Due to Cross-Phase Modulation in a Dispersion-Flattened/Decreasing Fiber

It was found by numerical analysis that a 320 nm wide and flat spectrum at 20 dB less than the central maximum intensity is generated from cross-phase modulated soliton pulses with 3.5 ps pulse width and 2.3 W peak power, which are propagated through a 2.4km length of dispersion-flattened/decreasing fiber (DFDF). The cross-phase modulation (XPM) at a central wavelength of 1.55 μm is achieved by exciting two orthogonally polarized modes into the principal axes. The wave-vector mismatch between the orthogonal pulses can be neglected because of soliton trapping when the modal birefringence of the DFDF is less than |n_ox - n_0y| = 10⁻⁶. The effect of modal birefringence on supercontinuum generation is discussed in temporal and spectral regimes by numerical analysis.     

Short-wavelength fluorescence caused by sequential two-photon excitation of some cyanine dyes: Effect of solvent viscosity on the quantum yields

Short-wavelength (SW) fluorescence of some cyanine dyes caused by sequential two-photon excitation was studied. The fluorescence quantum yield of the SW fluorescence shows a significant dependence on the solvent viscosity, but only a small dependence on temperature. This reveals the dynamic character of the emitting state: much lower intramolecular barrier and larger solute-solvent viscous drag compared to the S₁ state in the molecular conformational change which is important as a radiationless decay channel.     

Imaging of Drop and Vapour Clouds in an Evaporating Fuel Spray by ultraviolet and visible lasers

A laser-based method was developed for the simultaneous and quantitative imaging of drop and vapour clouds in an evaporating fuel spray. The method was based on extinction of two wavelengths, that is, ultraviolet and visible laser light through the fuel spray due to absorption by the vapour and scattering by the drops. α-Methylnaphthalene was selected as an injection fuel, since it absorbs the ultraviolet laser light but does not absorb the visible laser light. Subtraction of the transmissivity of the visible laser light from that of the ultraviolet laser light made it possible to image the distribution of the vapour cloud in the evaporating fuel spray. The distribution of the drop cloud is imaged by the transmissivity of the visible laser light. The method was applied to the fuel spray injected from a nozzle of a direct injection diesel engine into high-pressure and high-temperature nitrogen gas in a bomb.     

Single‐Crystalline Optical Microcavities from Luminescent Dendrimers

Microcrystallites are promising minute mirrorless laser sources. A variety of luminescent organic compounds have been exploited along this line, but dendrimers have been inapplicable owing to their fragility and extremely poor crystallinity. Now, a dendrimer family that overcomes these difficulties is presented. First‐, second‐, and third‐generation carbazole (Cz) dendrimers with a carbon‐bridged oligo(phenylenevinylene) (COPV2) core (GnCOPV2, n=1–3) assemble to form microcrystals. The COPV2 cores align uni/bidirectionally in the crystals while the Cz units in G2‐ and G3COPV2 align omnidirectionally. The dendrons work as light‐harvesting antennas that absorb non‐polarized light and transfer it to the COPV2 core, from which a polarized luminescence radiates. Furthermore, these crystals act as laser resonators, where the lasing thresholds are strongly coupled with the crystal morphology and the orientation of COPV2, which is in contrast with the conventional amorphous dendrimers.     

High-power diode-pumped mode-locked Yb:YAG ceramic laser

A high-power diode-pumped passively mode-locked Yb:YAG ceramic laser was demonstrated. An average output power of 3.80W with a pulse duration of 433 fs at a repetition rate of 90.9MHz was obtained at a wavelength of 1050 nm using a 2% output coupler. A peak power of 96.5kW was also obtained. To the best of our knowledge, these are the highest reported average power and peak power for a diode-pumped mode-locked Yb:YAG ceramic laser.     

Fine‐Tuning of Charge‐Conversion Polymer Structure for Efficient Endosomal Escape of siRNA‐Loaded Calcium Phosphate Hybrid Micelles

For efficient delivery of siRNA into the cytoplasm, a smart block copolymer of poly(ethylene glycol) and charge‐conversion polymer (PEG‐CCP) is developed by introducing 2‐propionic‐3‐methylmaleic (PMM) amide as an anionic protective group into side chains of an endosome‐disrupting cationic polyaspartamide derivative. The PMM amide moiety is highly susceptible to acid hydrolysis, generating the parent cationic polyaspartamide derivative at endosomal acidic pH 5.5 more rapidly than a previously synthesized cis‐aconitic (ACO) amide control. The PMM‐based polymer is successfully integrated into a calcium phosphate (CaP) nanoparticle with siRNA, constructing PEGylated hybrid micelles (PMM micelles) having a sub‐100 nm size at extracellular neutral pH 7.4. Ultimately, PMM micelles achieve the significantly higher gene silencing efficiency in cultured cancer cells, compared to ACO control micelles, probably due to the efficient endosomal escape of the PMM micelles. Thus, it is demonstrated that fine‐tuning of acid‐labile structures in CCP improves the delivery performance of siRNA‐loaded nanocarriers.

     

Temperature effect on the surface phase transitions of monolayer films of C12E1 at air/water interface

The temperature-dependent conformational states of a monolayer film of ethylene glycol monododecyl ether (C₁₂E₁) at the air/water interface have been investigated using ellipsometry, surface tension, external reflection–absorption FTIR spectroscopy and two-dimensional infrared (2DIR) correlation analysis. The ellipticity coefficients and the entropy associated with C₁₂E₁ adsorption changed almost discontinuously at certain temperatures, which manifested the interfacial phase transitions. The phase transition and coexistence of two phases were further clarified using 2DIR correlation analysis with temperature perturbation. The asynchronous correlation maps revealed that both bands of asymmetric and symmetric C–H stretching vibration in one-dimensional IR were split into two components, which confirmed the coexistence of two phases at the interface.     

Comparison of Gelation in the Free‐Radical Polymerization of Triallyl Isocyanurate and its Isomer Triallyl Cyanurate

Free‐radical polymerizations of triallyl cyanurate (TAC) and its isomer triallyl isocyanurate (TAIC) were conducted in bulk at 60°C. In the polymerization of TAIC, gelation occurred at 12.4% conversion, quite early compared to 21.3% for TAC. The primary chain length of TAIC polymer, as estimated from GPC‐LALLS measurements, was quite high. Although TAIC undergoes more cyclic polymerization than TAC, its greater primary chain length causes it to gel at a lower conversion. On the other hand, the difference in the rate of polymerization between TAC and TAIC was quite small compared to that of the primary chain length. These results are discussed mechanistically in connection with the degradative chain transfer characteristics of the polymerization of allyl compounds.     

Emergent organization of oscillator clusters in coupled self-regulatory chaotic maps

Here we introduce a model of parametrically coupled chaotic maps on a one-dimensional lattice. In this model, each element has its internal self-regulatory dynamics, whereby at fixed intervals of time the nonlinearity parameter at each site is adjusted by feedback from its past evolution. Additionally, the maps are coupled sequentially and unidirectionally, to their nearest neighbor, through the difference of their parametric variations. Interestingly we find that this model asymptotically yields clusters of superstable oscillators with different periods. We observe that the sizes of these oscillator clusters have a power-law distribution. Moreover, we find that the transient dynamics gives rise to a 1/f power spectrum. All these characteristics indicate self-organization and emergent scaling behavior in this system. We also interpret the power-law characteristics of the proposed system from an ecological point of view.