A simplified measurement of hydrated crystal densities of low melting points (low transition points) by solidifications of aqueous solutions

A volume change method for measuring crystal densities is described. It allows the densities of unstable hydrated crystals at room temperature to be determined, by measurements of volume changes during the solidification of aqueous solutions. NaCl x 2H2O, KCl, MgSO4 x 12H2O and K2HPO4 x 6H2O were measured by the method and their densities (SE) are 1.61+/-0.02, 1.99+/-0.05, 1.45+/-0.01 and 1.75+/-0.02 g ml(-1) respectively. Data of NaCl x 2H2O and KCl are in good agreement with the previously reported values.     

Photochemical deprotection of nitro-substituted benzenesulfenates via photoinduced electron transfer

The photochemical deprotection of alkyl 2,4-dinitrobenzenesulfenate or alkyl 2-nitrobenzenesulfenate was successfully achieved by addition of triethylamine, while it was unsuccessful without triethylamine. The sulfur-oxygen bond cleavage is thought to occur heterolytically in the sulfenate anion radical produced by photoinduced electron transfer with triethylamine.     

Geometrical characteristics of polyelectrolyte nanogel particles and their polyelectrolyte complexes studied by dynamic and static light scattering

The geometric characteristics of nanogel particles in aqueous solutions were studied by determining their ratios of radius of gyration (mean-square radius; Rg) to hydrodynamic radius (Rh), Rg/Rh, derived from static light scattering and dynamic light scattering experiments, respectively. The various nanogel samples studied included ones composed of lightly cross-linked N-isopropylacrylamide (NIPA) polymer, NIPA-based anionic or cationic copolymers, and amphoteric terpolymers. Polyelectrolyte complexes between anionic or cationic nanogels and oppositely charged polyions or nanogels having opposite charges were also studied. Most NIPA and NIPA-based polyelectrolyte nanogels in a swollen state had Rg/Rh values >0.775, which is the theoretically predicted value for a solid sphere. In a collapsed state, one may expect nanogel particles to be spherical in shape; however, this was not the case for a variety of nanogel samples, either with or without charges. These data were consistent with the idea that the surfaces of these nanogel particles were decorated with attached dangling chains. The Rg/Rh data from polyelectrolyte-nanogel complexes, however, indicated different structures from this. It was found that most of the polyelectrolyte-nanogel complex particles had Rg/Rh approximately 0.775. This suggested that the complexed nanogel particles were spherical in shape and that there were no dangling surface chains.     

Noise-Limitations of Coherence Imaging Based on Wavefront Folding Interferometry

Noise-limitations of the coherence imaging system based on the wavefront folding interferometer are studied. The signal-to-noise ratio SNR in two kinds of noise-limiting cases, the photon-noise-limit and the detector-noise-limit, is derived and are compared with the experimental results. The experimental demonstration is conducted using a wavefront folding interferometer and a single slit that provides the light source. An ensemble of ten sets of data are measured under the same conditions and the statistics of the retrieved images are computed from them. It is verified that the experimental results generally agree with the theoretical expectations.     

Structural characterization of hierarchically porous alumina aerogel and xerogel monoliths

Detailed nanostructures have been investigated for hierarchically porous alumina aerogels and xerogels prepared from ionic precursors via sol–gel reaction. Starting from AlCl₃·6H₂O and poly(ethylene oxide) (PEO) dissolved in a H₂O/EtOH mixed solvent, monolithic wet gels were synthesized using propylene oxide (PO) as a gelation initiator. Hierarchically porous alumina xerogels and aerogels were obtained after evaporative drying and supercritical drying, respectively. Macroporous structures are formed as a result of phase separation, while interstices between the secondary particles in the micrometer-sized gel skeletons work as mesoporous structures. Alumina xerogels exhibit considerable shrinkage during the evaporative drying process, resulting in relatively small mesopores (from 5.4 to 6.2 nm) regardless of the starting composition. For shrinkage-free alumina aerogels, on the other hand, the median mesopore size changes from 13.9 to 33.1 nm depending on the starting composition; the increases in PEO content and H₂O/EtOH volume ratio both contribute to producing smaller mesopores. Small-angle X-ray scattering (SAXS) analysis reveals that variation of median mesopore size can be ascribed to the change in agglomeration state of primary particles. As PEO content and H₂O/EtOH ratio increase, secondary particles become small, which results in relatively small mesopores. The results indicate that the agglomeration state of alumina primary particles is influenced by the presence of weakly interacting phase separation inducers such as PEO.     

Electronic structures of newly designed two-dimensional high-spin organic polymers

Practical two-dimensional high-spin organic polymers are newly designed and the electronic structures are examined on the basis of the ab initio two-dimensional unrestricted Hartree–Fock crystal orbital (UHF-CO) method. The present polymers can be oxidized up to six electrons per unit cell, and it is predicted that the three-electron and six-electron oxidations per unit cell lead to the high-spin organic polymers having superdegenerate band structures originating from the characteristic non-bonding crystal orbital patterns.     

Facile synthesis, crystal structures, and high-spin cationic states of all-para-brominated oligo(N-phenyl-m-aniline)s.

Syntheses of both the dimer (3) and the trimer (4) of all-para-brominated poly(N-phenyl-m-aniline)s (2c) were achieved in a one-pot procedure from the parent nonbrominated oligomers and benzyltrimethylammonium tribromide [(BTMA)Br(3)]. An X-ray crystallographic analysis revealed that 4 has a U-shaped structure, suggesting that 2c easily adopts helical structures. Furthermore, the redox properties were investigated by the UV-vis and EPR measurements. It was confirmed that the both 3 and 4 can be oxidized into the dications 3(2+) and 4(2+) with triplet spin-multiplicity.     

Coarse Metal Powder-Assisted pulsed CO2 Laser-induced Breakdown Spectroscopy for the Direct Determination of Heavy Metals in Soil

A novel method of laser-induced plasma spectroscopy utilizing a pulsed transversely excited atmospheric CO₂ laser has been developed for the high-sensitivity determination of heavy metals in soil. A coarse metal powder was used to trap the soil and to assist with plasma generation. When the CO₂ laser (10.6?µm, 1.5?J, 200?ns) was irradiated on the metal and soil powder, a high-temperature and long-lifetime luminous plasma was induced. Fine particles of soil were dissociated and were excited in the plasma region. The method was used for the rapid determination of Cr, Pb, and Hg in loam. The limits of detection for Cr, Pb, and Hg were approximately 0.8, 15, and 0.7?mg/kg, respectively.