Study of VUV emission and γ-ray responses of Nd:BaF2 scintillaotor

Nd³⁺ 1%, 5% and 10% doped BaF₂ single crystals were grown by the micro-pulling down method. Photoluminescence properties, including excitation and emission spectra and luminescence decay were measured under synchrotron radiation excitation at the Superlumi station in HASYLAB at DESY (Hamburg, Germany). The Nd³⁺ related 5d-4f emission lines peaking around 180 nm, 230 nm, and 260 nm, identified as the 5d–⁴I_j, 5d–⁴F_j, and 5d–²G_j transitions, were observed under 140–168 nm excitation. In photoluminescence decay under the 160 nm excitation, the dominant component decay time is about 12, 2.5 and 1.2 ns for Nd³⁺ 1%, 5% and 10% concentration, respectively. The decay time shortening is explained by the concentration quenching effect. Transmittance of Nd1% sample is about 80% for wavelengths above 185 nm. Finally, gamma-ray responses, non-proportionality and energy resolution of Nd1% sample were compared with the undoped BaF₂ scintillator. The light yield of the Nd1%:BaF₂ is about 93% of that of undoped BaF₂. ^©2009 Elsevier Ltd. All rights reserved.     

The hydrogel containing a novel vesicle‐like soft crosslinker,a “trilayered” polymeric micelle,shows characteristic rheological properties

We have developed a novel hydrogel that is formed from a crosslinkable trilayered polymeric micelle and a polyamine for the sustained release of hydrophilic compounds. This hydrogel is quite unique because the vesicle‐like structure of the trilayered polymeric micelle acts as not only a crosslinker of the hydrogel but also a container of hydrophilic compounds. The hydrogel is rapidly formed by mixing both the trilayered polymeric micelle solution and the polyamine solution. The gelation property of the hydrogel, such as the storage modulus, can be changed by tuning the molecular weights, concentrations, and pH of the dissolving solvent of the hydrogel's constituent components. Furthermore, it is clarified that the structural difference among the micelles acting as crosslinkers affects the gelation property of the hydrogel. Amazingly, the hydrogel that is formed from the trilayered polymeric micelles possessing a vesicle‐like flexible structure exhibits a higher storage modulus than the hydrogel that is formed from the bilayered polymeric micelles possessing a highly packed, hard structure. Our results demonstrates that a microscopic structural difference of crosslinkers can induce a macroscopic (and, in some cases, an interesting and unexpected) change in the properties of the resulting hydrogels. For medical applications, the hydrogel proposed in the present article can encapsulate the hydrophilic compounds so that the hydrogel can be available as the material for their sustained release. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Silver Ion Mediated Desulfurization-Condensation of Glucosyl Isothiocyanate With Hydroxy Acids

ABSTRACT

Desulfurization-condensation of 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate with α-hydroxy acids and salicylic acid in the presence of silver trifluoroacetate and triethylamine gave glucosylamino heterocycles in good yields, while the reaction with β-hydroxy acids afforded N-glucosyl olefinic amides with the evolution of carbon dioxide.     

Anion-directed formation and degradation of an interlocked metallohelicate

Although there are many examples of catenanes, those of more complex mechanically interlocked molecular architectures are rare. Additionally, little attention has been paid to the degradation of such interlocked systems into their starting complexes, although formation and degradation are complementary phenomena and are equally important. Interlocked metallohelicate, [(Pd(2)L(4))(2)](8+) (2(8+)), is a quadruply interlocked molecular architecture consisting of two mechanically interlocked monomers, [Pd(2)L(4)](4+) (1(4+)). 2(8+) has three internal cavities, each of which encapsulates one NO(3)(-) ion (1:3 host-guest complex, 2?(NO(3)|NO(3)|NO(3))(5+)) and is characterized by unusual thermodynamic stability. However, both the driving force for the dimerization and the origin of the thermodynamic stability remain unclear. To clarify these issues, BF(4)(-), PF(6)(-), and OTf(-) have been used to demonstrate that the dimerization is driven by the anion template effect. Interestingly, the stability of 2(8+) strongly depends on the encapsulated anions (2?(NO(3)|NO(3)|NO(3))(5+) ? 2?(BF(4)|BF(4)|BF(4))(5+)). The origins of this differing thermodynamic stability have been shown through detailed investigations to be due to the differences in the stabilization of the interlocked structure by the host-guest interaction and the size of the anion. We have found that 2-naphthalenesulfonate (ONs(-)) induces the monomerization of 2?(NO(3)|NO(3)|NO(3))(5+) via intermediate 2?(ONs|NO(3)|ONs)(5+), which is formed by anion exchange. On the basis of this finding, and using p-toluenesulfonate (OTs(-)), the physical separation of 2?(NO(3)|NO(3)|NO(3))(5+) and 1(4+) as OTs(-) salt was accomplished.     

Synthesis of diameter controlled carbon nanotubes using self-assembled catalyst nanoparticles

Vertically-aligned diameter-controlled carbon nanotubes (CNTs) are synthesised by the plasma enhanced chemical vapour deposition (PECVD) method using multi-layers of self-assembled catalytic ligand-coated iron oxide nanoparticles. We find that the mono-dispersed nanoparticles play a vital role for the production of diameter-controlled CNTs. A new growth model is also proposed based on the experimental results. The present results may make a great contribution to the development and design of mechanical, electronic and biomedical devices, in which diameter-controlled CNTs are utilised.     

Component Crystallization and Physical Collapse during Freeze-Drying of L-Arginine-Citric Acid Mixtures

Component crystallization and physical collapse during freeze-drying of aqueous solutions containing protein-stabilizing L-arginine and citric acid mixtures were studied. Freeze-drying microscopy (FDM) and thermal analysis of the solute-mixture frozen solutions showed collapse onset at temperatures (T(c)) approximately 10°C higher than their T(g)'s (glass transition temperatures of the maximally freeze-concentrated solute phase). Experimental freeze-drying of these solutions at a low chamber pressure showed the occurrence of physical collapse at shelf temperatures close to or slightly higher than the T(c). Slower ice sublimation at higher chamber pressures induced the physical collapse from lower shelf temperatures. The large effect of chamber pressures on the collapse-inducing shelf temperatures confirmed significance of the sublimation-related heat loss on the sublimation interface temperature during the primary drying. Drying of the single-solute L-arginine solution resulted in cake-structure solids composed of its anhydrous crystal. Thermal and powder X-ray diffraction (PXRD) analysis suggested slow crystal nucleation of L-arginine dihydrate in the frozen solutions. Characterization of the frozen solutions and freeze-dried solids should enable rational formulation design and process control of amino acid-containing lyophilized pharmaceuticals.     

Optimal photosensitizers for photodynamic therapy of infections should kill bacteria but spare neutrophils

Photodynamic therapy (PDT) for localized microbial infections exerts its therapeutic effect both by direct bacterial killing and also by the bactericidal effects of host neutrophils stimulated by PDT. Therefore, PDT-induced damage to neutrophils must be minimized, while direct photoinactivation of bacteria is maintained to maximize the therapeutic efficacy of antimicrobial PDT in vivo. However, there has been no study in which the cytocidal effect of PDT on neutrophils was investigated. In this study, the cytocidal effects of PDT on neutrophils were evaluated using different antimicrobial photosensitizers to find suitable candidate photosensitizers for antimicrobial PDT. PDT on murine peripheral-blood neutrophils was performed in vitro using each photosensitizer at a concentration that exerted a maximum bactericidal effect on methicillin-resistant Staphylococcus aureus, and morphological alteration and viability of neutrophils were studied. Most neutrophils were viable (>80%) after PDT using toluidine blue-O (TB) or methylene blue (MB), while neutrophils showed morphological change and their viabilities were decreased (<70%) after PDT using other photosensitizers (erythrosine B, rose bengal, crystal violet, Photofrin, new methylene blue and Laserphyrin). These results suggest that PDT using TB or MB can preserve host neutrophils while exerting a significant therapeutic effect on in vivo localized microbial infection.     

Studies on rotational barriers of N-C axially chiral compounds: increase in the rotational barrier by aromatization

The rotational barriers in axially chiral quinolin-2-one and quinazolin-2-one possessing N-(ortho-tert-butyl)phenyl group were found to significantly increase in comparison with those of corresponding dihydroquinolin-2-one and dihydroquinazolin-2-one. Analysis of transition state structure during N-Ar bond rotation based on DFT calculation indicates that the increase in the rotational barrier is due to considerable distortion of the nitrogen-containing heterocyclic part.