Theoretical study on energy transfer from the excited C<Subscript>60</Subscript> to molecular oxygen

Singlet oxygen is used as an important oxidizer for various organic reactions, on the other hand, it has toxicity for the human body, since it destroys biological molecules such as DNA. Fullerene C₆₀ is known to act as a photosensitizer of singlet oxygen molecule, and it has been understood that energy transfer from the excited triplet C₆₀ to the ground triplet O₂ forming the singlet O₂ is a biologically important reaction. In the present study, we have analyzed these reaction pathways by means of the DFT (density functional theory) calculation.     

Unbiased estimators in the sense of Lehmann and their discrimination rates

Summary In this paper, we define the index of performance of unbiased estimators in the sense of Lehmann (L-unbiased), which evaluates the power for the estimators to discriminate any wrong values of a parametric function from a correct one. We shall call the indexdiscrimination rate of the estimator. The larger discrimination rate the estimator has, the more desirable it is. An upper bound of discrimination rates is obtained, which is given by thesensitivity of the probability family under consideration. The discrimination rates of several L-unbiased estimators are investigated. Moreover we discuss the conditions under which the L-unbiased estimator is improved in the sense of discrimination rate by the L-unbiased estimator depending only on a sufficient statistic. This research was supported in part by a Grant-in-Aid for Scientific Research of the Japanese Ministry of Education, Science and Culture. The Institute of Statistical Mathematics     

Proton NMR relaxation and molecular motion of long-chain cyclic paraffins in the solid state

Temperature-dependent measurements have been made on the proton NMR relaxations and proton linewidths of the cyclic paraffins (c-C₂₄H₄₈, c-C₂₈H₅₆, and c-C₁₂₈H₂₅₆) in the solid state. It is found that in c-C₂₄H₄₈ and c-C₁₂₈H₂₅₆ there exist two transitions, one due to the melting process and the other due to a rapid transition between trans and gauche conformers in a compact structure that consists of two parallel trans zigzag straight chains bridged at both ends in the crystalline state. In c-C₂₈H₅₆ there exists only the transition due to melting. Proton NMR relaxations have also been measured for c-C₄₀H₈₀ and c-C₁₆₀H₃₂₀ at room temperature, in addition to those for c-C₂₄H₄₈, c-C₂₈H₅₆, and c-C₁₂₈H₂₅₆. It is found that the extent of molecular motion decreases as the chain length increases.     

Interaction analysis of the carcinoembryonic antigen (CEA) with its monoclonal antibody immobilized on a gold surface using Fourier transform infrared reflection-absorption spectroscopy (FT-IR RAS).

A monoclonal antibody for the carcinoembryonic antigen (CEA) was immobilized on a gold chip surface covered by a self-assembled monolayer of 11-mercaptoundecanoic acid. Upon the addition of CEA, a Fourier transform infrared reflection-absorption spectroscopy (FT-IR RAS) measurement showed an increased absorption at around 1500 - 1700 cm(-1), corresponding to its amide structures. Another addition of CEA polyclonal antibody on this chip caused a further increase of the absorption in this region only after a treatment with CEA. This result shows that an antibody-fixed gold surface coupled with an FT-IR RAS measurement provides a new tool for detecting the antibody-antigen interaction.     

Release of nitric oxide and iodine to the atmosphere from the freezing of sea-salt aerosol components

The known room-temperature, solution-phase reaction between nitrite ions and iodide ions, which occurs in acidic conditions (pH < 5.5), is shown to be accelerated when neutral aqueous solutions are frozen. The reaction is proposed to occur in liquid "micropockets" within the ice structure at temperatures between the freezing point and the eutectic temperature. The products, nitric oxide and molecular iodine, are known to play significant roles in atmospheric compositional change, and therefore, the results obtained here, which are not dependent on acidification, may impact on observed snowpack chemistry. Investigation of the effect of oxygen on the chemical processing indicates that a chain reaction mechanism is operative.