Nonlinear systems identification by combining regression with bootstrap resampling

A new parameter estimation method for nonlinear systems from time series data is proposed. For the purpose of unbiased estimation, we employ the idea of bootstrap method on regression problems. Our method can be applied into even short and noisy data and is expected to give us a robust estimation. Some benchmarks of estimating chaotic models show its practical applicability. We also try to apply this method to analysis for intermittent hormonal therapy for prostate cancer by using a mathematical model and real clinical data.     

Synthesis of uniform and dispersive calcium carbonate nanoparticles in a protein cage through control of electrostatic potential

We have synthesized calcium carbonate nanoparticles (Ca-NPs) in the cavity of a cage-shaped protein, apoferritin, by regulating the electrostatic potential of the molecule. The electrostatic potential in the cavity was controlled by pH changes resulting from changes in the dissolved carbon dioxide (CO(2)) concentration in the reaction solution. Recombinant L-apoferritin was mixed with a suspension of calcium carbonate (CaCO(3)), and the mixture was pressurized with gaseous CO(2) at 2 MPa. The pH of the solution decreased from 9.3 to 4.4; the CaCO(3) dissolved during pressurization, and then precipitated after the pressure was reduced to ambient. After repeating the pressurization/depressurization process three times, about 70% of the apoferritin molecules were found to contain nanoparticles with an average diameter of 5.8 ± 1.2 nm in their cavity. Energy-dispersive X-ray spectroscopy and electron diffraction analysis showed that the nanoparticles were calcite, one of the most stable crystal forms of CaCO(3). Electrostatic potential calculations revealed a transition in the potential in the apoferritin cavity, from negative to positive, below pH 4.4. The electrostatic potential change because of the change in pH was crucial for ion accumulation. Since the Ca-NPs synthesized by this method were coated with a protein shell, the particles were stably dispersed in solution and did not form aggregates. These Ca-NPs may be useful for medical applications such as synthetic bone scaffolds.     

Molybdenum-catalyzed transformation of molecular dinitrogen into silylamine: experimental and DFT study on the remarkable role of ferrocenyldiphosphine ligands

A molybdenum-dinitrogen complex bearing two ancillary ferrocenyldiphosphine ligands, trans-[Mo(N(2))(2)(depf)(2)] (depf = 1,1'-bis(diethylphosphino)ferrocene), catalyzes the conversion of molecular dinitrogen (N(2)) into silylamine (N(SiMe(3))(3)), which can be readily converted into NH(3) by acid treatment. The conversion has been achieved in the presence of Me(3)SiCl and Na at room temperature with a turnover number (TON) of 226 for the N(SiMe(3))(3) generation for 200 h. This TON is significantly improved relative to those ever reported by Hidai's group for mononuclear molybdenum complexes having monophosphine coligands [J. Am. Chem. Soc.1989, 111, 1939]. Density functional theory (DFT) calculations have been performed to figure out the mechanism of the catalytic N(2) conversion. On the basis of some pieces of experimental information, SiMe(3) radical is assumed to serve as an active species in the catalytic cycle. Calculated results also support that SiMe(3) radical is capable of working as an active species. The formation of five-coordinate intermediates, in which one of the N(2) ligands or one of the Mo-P bonds is dissociated, is essential in an early stage of the N(2) conversion. The SiMe(3) addition to a "hydrazido(2-)" intermediate having the NN(SiMe(3))(2) group will give a "hydrazido(1-)" intermediate having the (Me(3)Si)NN(SiMe(3))(2) group rather than a pair of a nitrido (≡N) intermediate and N(SiMe(3))(3). The N(SiMe(3))(3) generation would not occur at the Mo center but proceed after the (Me(3)Si)NN(SiMe(3))(2) group is released from the Mo center. The flexibility of the Mo-P bond between Mo and depf would play a vital role in the high catalysis of the Mo-Fe complex.     

Efficient improved extraction of tomato saponin using shock waves

In the conventional method of mixer blending extraction, the yields of the tomato-saponin, esculeoside A, in the mini and middy tomatoes were found to be 0.043% and 0.046%, respectively. In order to improve the yields, we attempted a more efficient extraction using shock waves. The yields of esculeoside A were 0.0987% in air after 1 shock, 0.0792% in air after two shots, 0.0648% in half water after 1 or 2 shocks, and 0.0599% in water after 1 or 2 shocks. The yields obtained by the proposed method were approximately twice those of the conventional mixer blending method; therefore, this method is regarded to be very efficient. Moreover, two spirosolane glycosides, tomatine and lycoperoside A, were obtained for the first time from the ripe tomato fruit in this method. To date, these compounds have not been obtained with the mixer blending method. However, whether these glycosides are produced from esculeoside A or are newly extracted from the plant organ by the shock wave is still unclear.     

Highly fluorescent M2L4 molecular capsules with anthracene shells

M(2)L(4) molecular capsules self-assembled from M(II) ions (where M = Zn, Ni, and Pd) and bent bidentate ligands constructed from anthracene fluorophores. The Ni(II) and Zn(II) capsules exhibited weak to strong blue emission unlike traditional Pd(II) cages and capsules.     

Forward plasma emission through laser–foil interaction with nanosecond lasers

Fundamental investigations of plasma diagnostics of a forward laser plasma acceleration employing laser–foil interactions were conducted for an Al-foil target irradiated with an Nd:YAG laser of 1 J/pulse with pulse width of 10 ns. Temporal evolutions of electron temperatures and densities were evaluated with electrostatic probes and spectroscopic diagnostics. From the results, it was shown that an average speed of ions in a forward direction was about 40 km/s. Also, it was shown that the plasma temperature and density were about 2.5–8 eV and 10¹⁰ cm⁻³, respectively.     

Efficient 521 nm all-fiber laser: splicing Pr(3+)-doped ZBLAN fiber to end-coated silica fiber

We demonstrated a green all-fiber laser by splicing both ends of a Pr(3+)-doped ZBLAN fiber to silica fibers, whose ends were coated with a dielectric thin film. The output power and the slope efficiency were 322 mW and 53%, respectively, and the coupled pump power of the two blue GaN pump lasers in the silica fiber core was 652 mW. We estimated that the damage threshold of the spliced structure was at least 21 MW/cm2. This splicing technique should be applicable for other wavelengths and glass fibers having low melting temperatures.     

Dielectric spectroscopy of a smectic liquid crystal

Complex dielectric spectroscopy (frequency range 5 Hz–13 MHz) has been used to analyse the frequency, temperature and bias‐field dependences of the molecular dynamics of a very high‐spontaneous‐polarization ferroelectric liquid crystalline material exhibiting SmA, SmC* and unknown SmX smectic phases. Different smectic phase transition temperatures have been observed from the study of the temperature dependence of the dielectric strength and the relaxation frequency. The phase transition temperatures (crystalline to isotropic phases) have also been described very accurately from the temperature‐dependent symmetric and asymmetric shape parameters of the relaxation function and also the dc conductivity. In a planar aligned cell, two symmetric modes (Goldstone mode and domain mode) have been observed in both the SmX and SmC* phases. One asymmetric mode (X‐mode) observed in the SmC* and SmA phases could be related to the interaction of dipoles of the ferroelectric liquid crystals being affected by the surface of the cell. The soft mode, which usually appears very close to the SmC*–SmA phase transition was not observed until the bias field was applied. The second order nature of the SmC*–SmA phase transition was revealed.