Retention behavior of oligomeric proanthocyanidins in hydrophilic interaction chromatography

A novel method was developed for the separation of proanthocyanidins (PAs; oligomeric flavan-3-ols) by hydrophilic interaction chromatography (HILIC) using an amide-silica column eluting with an aqueous acetonitrile mobile phase. The best separation was achieved with a linear gradient elution of acetonitrile-water at ratios of 9:1 to 5:5 (v/v) for 60 min at a flow rate of 1.0 ml/min. Under these HPLC conditions, a mixture of natural oligomeric PAs (from apple) was separated according to degree of polymerization (DP) up to decamers. The DP of each separated oligomer was confirmed by LC/electrospray ionization MS. In further HILIC separation studies of 15 different flavan-3-ol and oligomeric PA (up to pentamer) standards with an isocratic elution of acetonitrile-water (84:16), a high correlation was observed between the logarithm of retention factors (log k) and the number of hydroxyl groups in their structures. The coefficient of this correlation (r2=0.9501) was larger than the coefficient (r2=0.7949) obtained from the correlation between log k and log P(o/w) values. These data reveal that two effects, i.e. hydrogen bonding between the carbamoyl terminal on the column and the hydroxyl group of solute oligomer and hydrophilicity based on the high-order structure of oligomeric PAs, corporately contribute to the separation, but the hydrogen bonding effect is predominant in our HILIC separation mode.     

Cervical spondylosis: Evaluation of microstructural changes in spinal cord white matter and gray matter by diffusional kurtosis imaging

Introduction

We investigated microstructural changes in the spinal cord, separately for white matter and gray matter, in patients with cervical spondylosis by using diffusional kurtosis imaging (DKI).

Methods

We studied 13 consecutive patients with cervical myelopathy (15 affected sides and 11 unaffected sides). After conventional magnetic resonance (MR) imaging, DKI data were acquired by using a 3 T MR imaging scanner. Values for fractional anisotropy (FA), apparent diffusion coefficient (ADC), and mean diffusional kurtosis (MK) were calculated and compared between unaffected and affected spinal cords, separately for white matter and gray matter.

Results

Tract-specific analysis of white matter in the lateral funiculus showed no statistical differences between the affected and unaffected sides. In gray matter, only MK was significantly lower in the affected spinal cords than in unaffected spinal cords (0.60 ± 0.18 vs. 0.73 ± 0.13, P = 0.0005, Wilcoxon’s signed rank test).

Conclusions

MK values in the spinal cord may reflect microstructural changes and gray matter damage and can potentially provide more information beyond that obtained with conventional diffusion metrics.     

Effect of distribution of powder size on estimation of critical current densities in polycrystalline Sr0.6K0.4Fe2As2 superconductors

The effect of distribution of powder size on the estimation of intra-grain critical current density was investigated for polycrystalline samples of Sr_0.6K_0.4Fe₂As₂ with and without addition of Ag 20 wt.%. It turned out that the value of intra-grain critical current density calculated using the average of powder size J_cl is more overestimated than that calculated taking account of the distribution of powder size J_clP as the distribution of powder size is widened, since the magnetic moment drastically increases due to the larger contribution from larger particles. From the distribution of powder size obtained by the microscopic observation using SEM, the factor of overestimation of J_cl/J_clP is found to be larger than two in both samples. Moreover, the distribution of powder size in the Ag-added sample is found to be smaller than that of pure sample. Therefore, the factor of overestimation of J_cl is considered to be smaller in the Ag-added sample. It is recommended to take account of the distribution of powder size for precise estimation of intra-grain critical current density.     

Probing the Majorana nature of TeV-scale radiative seesaw models at collider experiments

A general feature of TeV-scale radiative seesaw models, in which tiny neutrino masses are generated via loop corrections, is an extended scalar (Higgs) sector. Another feature is the Majorana nature; e.g., introducing right-handed neutrinos with TeV-scale Majorana masses under the discrete symmetry, or otherwise introducing some lepton number violating interactions in the scalar sector. We study phenomenological aspects of these models at collider experiments. We find that, while properties of the extended Higgs sector of these models can be explored to some extent, the Majorana nature of the models can also be tested directly at the International Linear Collider via the electron–positron and electron–electron collision experiments.     

Scanning laser microscope for imaging nanostructured superconductors

The nanofabrication of superconductors yields various interesting features in superconducting properties. A variety of different imaging techniques have been developed for probing the local superconducting profiles. A scanning pulsed laser microscope has been developed by the combination of the XYZ piezo-driven stages and an optical fiber with an aspheric focusing lens. The scanning laser microscope is used to understand the position-dependent properties of a superconducting MgB₂ stripline of length 100 μm and width of 3 μm under constant bias current. Our results show that the superconducting stripline can clearly be seen in the contour image of the scanning laser microscope on the signal voltage. It is suggested from the observed image that the inhomogeneity is relevant in specifying the operating conditions such as detection efficiency of the sensor.     

Synthesis of well‐defined functionalized polymers and star branched polymers by means of living anionic polymerization using specially designed 1,1‐diphenylethylene derivatives

This article covers precise syntheses of well‐defined chain‐end and in‐chain functionalized polymers, multi‐functionalized polymers with a definite number of functional groups, star‐branched and graft polymers by recently developed methodologies using specially designed 1,1‐diphenylethylene (DPE) derivatives. The DPE derivatives include various substituted DPE derivatives with functional groups and their derivatives, DPE‐functionalized DPE derivatives, and well‐defined DPE‐functionalized macromonomers. The synthetic utility and importance of these DPE derivatives are described via such polymer syntheses.     

Photobleaching Kinetics and Effect of Solvent in the Photophysical Properties of Indocyanine Green for Photodynamic Therapy

Indocyanine green is an attractive molecule for photodynamic therapy due to its near infrared absorption, resulting in a higher tissue penetration. However, its quantum yields of the triplet and singlet state have been reported to be low and then, reactive oxygen species are unlikely to be formed. Aiming to understand the ICG role in photodynamic response, its photobleaching behavior in solution has been studied under distinct conditions of CW laser irradiation at 780 and 808 nm, oxygen saturations and solvents. Sensitizer bleaching and photoproduct formation were measured by absorption spectroscopy and analyzed using the PDT bleaching macroscopic model to extract physical parameters. ICG photobleaching occurs even at lower oxygen concentrations, indicating that the molecule presents more than one way of degradation. Photoproducts were produced even in solution of less than 4 % oxygen saturation for both solvents and excitation wavelengths. Also, the amplitude of absorption related to J-dimers was increased during irradiation, but only in 50 % PBS solution. The formation of photoproducts was enhanced in the presence of J-type dimers under low oxygen concentration, and the quantum yields of triplet and singlet states were one order of magnitude and two times higher, respectively, when compared to ICG in distilled H₂O.     

Color Formation and Gelation of Xyloglucan Upon Addition of Iodine Solutions

Summary: We developed a novel thermo‐reversible gelation system by mixing xyloglucan with an iodine solution. Xyloglucan dissolves in water to produce a colorless solution. However, the addition of iodine solution induces color and gelation; heating causes the gel to melt and become colorless. According to results from spectroscopic and small‐angle X‐ray scattering experiments, the gelation mechanism was proposed to involve two xyloglucan chains that associate side‐by‐side and incorporate iodine and/or iodide ions.

Xyloglucan gel prepared by mixing xyloglucan and iodine solution and heating to 60 °C, followed by cooling.