Fluorescence derivatization of single-walled carbon nanotubes for analysis by means of conventional CE-LIF

Single-walled carbon nanotubes (SWNTs) are now widely used in many fields, and while many analytical methods for SWNTs have been reported, there are few practical analytical methods that combine the necessary levels of selectivity and sensitivity. We have developed a highly sensitive separation method for fluorescence-derivatized SWNTs by means of conventional CE with laser-induced fluorescence. First, SWNTs were dispersed using a triphenylene derivative into the water, and the excess dispersant was removed by nitric acid treatment. The dispersed SWNTs were then derivatized with a fluorescence reagent, 4-aminofluorescein. Finally, the derivatized SWNTs were analyzed using a conventional apparatus CE-LIF detection. The SWNTs migrated within 20 min. The detection sensitivity of SWNTs was improved by about 170 times with LIF detection as compared with UV detection. We anticipate that the derivatized SWNTs can also be detected with high sensitivity using LC.     

Stereocontrolled synthesis of substituted bicyclic ethers through oxy-Favorskii rearrangement: total synthesis of (±)-communiol E

The potential of the oxy-Favorskii rearrangement to form branched cis-fused bicyclic ethers was explored. Both tertiary and quaternary centers were constructed in highly stereospecific manners. Methanol and primary amines were effective nucleophiles for the rearrangement. The total synthesis of (±)-communiol E was achieved based on this method.     

Photochemical dynamics of indolylmaleimide derivatives

On-the-fly nonadiabatic ab initio molecular dynamics simulations have been carried out for three anionic species of indolylmaleimides (3-(1H-3-indolyl)-2,5-dihydro-1H-2,5-pyrroledione, IM) to clarify the mechanisms of photochemical reactions. The results are obtained for (i) a monovalent anion with a deprotonated indole NH group (IM(-)'), (ii) a monovalent anion with a deprotonated maleimide NH group (IM(-)') and (iii) a divalent anion with doubly deprotonated indole and the maleimide NH groups (IM(2-)). Quantum chemical calculations are treated at the three state averaged complete-active space self-consistent field level for 6 electrons in 5 orbitals with the cc-pVDZ basis set (CAS (6, 5) SCF/cc-pVDZ). Molecular dynamics simulations are performed with electronically nonadiabatic transitions included using the Zhu-Nakamura version of the trajectory surface hopping (ZN-TSH) method. It is found that the nonadiabatic transitions occur accompanied by the stretching and shrinking motions of the N(7)-C(8) bond in the case of IM(-)' and the C(11)-N(12) bond in IM(2-) rather than the twisting motion of the dihedral angle. We also found that the ultrafast S(2)→ S(1) nonadiabatic transitions occur through the conical intersection (CoIn) right after photoexcitation to S(2) in IM(-)' and IM(2-). Furthermore, the S(1)→ S(0) nonadiabatic transitions are found to take place in IM(-)'. It is concluded that IM(2-) would mainly contribute to the photoemission, because the S(1)← S(0) and S(2)← S(0) transitions of IM(-)' are dipole-forbidden transitions and, moreover, IM(2-) is found to be the only species to stay in the S(1) state without non-radiative decay.     

Communication structure,trust and the free rider problem

Despite the recent wave of interest in the social and physical sciences regarding “complexity,” relatively title attention has been given to the logical foundation of complexity measurement. With this in mind, a number of fairly simple, “reasonable” axioms for the measurement of network complexity are here presented, and some of the implications of these axioms are considered. It is shown that the only family of graph complexity measures satisfying the “reasonable” axioms is of limited theoretical utility, and hence that those seeking more interesting measures of complexity must be willing to sacrifice at least one intuitively reasonable constraint. Several existing complexity measures are also described, and are differentiated from one another on an axiomatic basis. Finally, some suggestions are offered regarding future efforts at measuring graph complexity.     

Order parameter profiles in one component systems with a temperature gradient

Order parameter profiles are investigated under heat flow in a certain class of one-component systems in the neighborhood of a second order phase transition. A surface transition is also discussed, which occurs at a cooler boundary.     

Picosecond time-resolved observation of photoinduced charge separation from the singlet excited state of porphyrin-quinone model systems

The charge transfer state formed from the S₁ state of porphyrin-p-benzoquinone (BQ) model systems in solution has been observed combining octaethylporphyrin and BQ by methylene chains of various lengths. The lifetime of the electron transfer state depends upon the length of the methylene chain and the nature of the solvent.     

Effect of ionic interaction on linear and nonlinear viscoelastic properties of ethylene based ionomer melts

The effect of ionic interaction on linear and nonlinear viscoelastic properties was investigated using poly(ethylene-co-methacrylic acid) (E/MAA) and its ionomers which were partially neutralized by zinc or sodium. Dynamic shear viscosity and step-shear stress relaxation studies were performed. Stress relaxation moduli G(t, y) of the E/MAA and its sodium or zinc ionomers were factorized into linear relaxation moduli G°(t) and damping functions h(y). The relaxation modulus at the smallest strain in each ionomer agreed with the linear relaxation modulus calculated from storage modulus G and loss modulus G. In the linear region, the ionic interaction shifted the relaxation time longer with keeping the same relaxation time distribution as E/MAA. In the nonlinear region, the ionic interaction had no influence on h(y) when the ion content was low. At higher ion content, however, the ion bonding enhanced the strain softening of h(y).