Synthesis and properties of thermotropic liquid-crystalline polyesters containing 9,10-diphenylanthracene moiety in the main chain

We synthesized thermotropic liquid-crystalline polyesters in which 9,10-diphenylanthracene moieties are incorporated into the main chain type of polyester forming the chiral smectic C (Sm C*). The polymers were prepared by the isopropyltitanate-catalyzed reaction of biphenyldicarboxylic acid and the corresponding diols, with different ratios of diol of 9,10-diphenylanthracene moiety to the alkane diols (1, 5, and 10 mol %) under nitrogen atmosphere. The polymers exhibited thermotropic liquid crystals despite the presence of a bulky diphenylanthracene moiety in the main chain. The circular dichroism spectra revealed that a Sm C* phase was formed in the polymer with 1 mol % of anthracene moiety, although only an Sm A phase was formed in the other polymers. This is the first example of a Sm C* polyester containing a diphenylanthracene moiety in the main chain. Furthermore, we measured the optical properties of the polymers and found that they exhibited very high fluorescent efficiency. The fluorescence spectra of the thin film differed from that of a CH₂Cl₂ solution.     

Electrodeposition of Se on carbon-supported Pt nanoparticles by cyclic voltammetry

Cyclic voltammetry (CV) is a powerful and popular electrochemical technique widely used to study the surface structure of materials through the electrochemical behaviors. Herein CV is utilized to study the electrochemical deposition of selenium (Se) on carbon black-supported Pt nanostructures. We synthesized carbon-loaded platinum nanoparticles (Pt/C) by microwave method and studied the electrochemical behavior of selenium on them. Through the experiment of changing the reverse potential, the corresponding relationship between the Se deposition peak and stripping peak was clarified and the deposition and stripping process of Se was proposed. Meanwhile, we synthesized cubic and octahedral nanocrystals of Pt, and used CV to study the Se deposition on these nanosctructures supported by carbon. It was found that the relative intensity of UPD peaks on Pt is different, as Pt_cube@C is dominated by (100) and Pt_oct@C electrode is dominated by (111) while Pt@C falls in between.

     

In vivo estimation of optical properties of rat liver using single-reflectance fiber probe during ischemia and reperfusion

Optical Review - To quantify the changes in optical properties of in vivo rat liver tissue, we applied diffuse reflectance spectroscopy (DRS) system using single-reflectance fiber probe during...     

Practical aspects of (1)H transverse paramagnetic relaxation enhancement measurements on macromolecules

The use of (1)H transverse paramagnetic relaxation enhancement (PRE) has seen a resurgence in recent years as method for providing long-range distance information for structural studies and as a probe of large amplitude motions and lowly populated transient intermediates in macromolecular association. In this paper we discuss various practical aspects pertaining to accurate measurement of PRE (1)H transverse relaxation rates (Gamma(2)). We first show that accurate Gamma(2) rates can be obtained from a two time-point measurement without requiring any fitting procedures or complicated error estimations, and no additional accuracy is achieved from multiple time-point measurements recorded in the same experiment time. Optimal setting of the two time-points that minimize experimental errors is also discussed. Next we show that the simplistic single time-point measurement that has been commonly used in the literature, can substantially underestimate the true value of Gamma(2), unless a relatively long repetition delay is employed. We then examine the field dependence of Gamma(2), and show that Gamma(2) exhibits only a very weak field dependence at high magnetic fields typically employed in macromolecular studies. The theoretical basis for this observation is discussed. Finally, we investigate the impact of contamination of the paramagnetic sample by trace amounts (5%) of the corresponding diamagnetic species on the accuracy of Gamma(2) measurements. Errors in Gamma(2) introduced by such diamagnetic contamination are potentially sizeable, but can be significantly reduced by using a relatively short time interval for the two time-point Gamma(2) measurement.     

Temperature dependence of the lattice locations of boron implanted in germanium

The β-NMR of the probe atom ¹²B implanted in In-doped germanium was measured as a function of temperature. As a result, three resonances were observed: sharp and broad resonances around the Larmor frequency and a resonance split by the electric quadrupole interaction. It was found that the appearance of the resonances is similar to the case of Si host (Izumikawa et al. Hyperfine Interact. 136/137:559–605, 2001). The quadrupole coupling constant for the split resonance was deduced as ∣eqQ/h∣ = 252(3) kHz under the assumption that it has <111> axial symmetry. And furthermore, assuming that the defect atom jumps thermally between the identical defect sites, the activation energy of the jump was deduced as 0.4 ± 0.1 eV.     

Detecting Counterion Dynamics in DNA–Protein Association

Due to a high density of negative charges on its surface, DNA condenses cations as counterions, forming the so-called “ion atmosphere”. Although the release of counterions upon DNA–protein association has been postulated to have a major contribution to the binding thermodynamics, this release remains to be confirmed through a direct observation of the ions. Herein, we report the characterization of the ion atmosphere around DNA using NMR spectroscopy and directly detect the release of counterions upon DNA–protein association. NMR-based diffusion data reveal the highly dynamic nature of counterions within the ion atmosphere around DNA. Counterion release is observed as an increase in the apparent ionic diffusion coefficient, which directly provides the number of counterions released upon DNA–protein association.     

Hiding information using a checkered pattern

Visual cryptography is expected to have various applications since it has potential for visual decoding. However, there are still few practical applications. One reason for this is the difficulty of superposition to decode. To solve the alignment difficulty, we propose an information hiding method which can be physically decode by superimposing a checkered pattern. Superimposing a checkered pattern can also be considered as a kind of image sampling process, and a decoding experiment using an ordinary compact digital camera is presented.