Measurement of sigma chi c2 B(chi c2-->J/psi gamma)/sigma chi c1 B(chi c1 -->J/psi gamma) in pp collisions at square root s=1.96 TeV

We measure the ratio of cross section times branching fraction, Rp=sigma chi c2 B(chi c2-->J/psi gamma)/sigma chi c1 B(chi c1-->J/psi gamma), in 1.1 fb(-1) of pp collisions at square root s=1.96 TeV. This measurement covers the kinematic range pT(J/psi)>4.0 GeV/c, |eta(J/psi)<1.0, and pT(gamma)>1.0 GeV/c. For events due to prompt processes, we find Rp=0.395+/-0.016(stat)+/-0.015(syst). This result represents a significant improvement in precision over previous measurements of prompt chi c1,2 hadro production.     

Extremely high upper critical magnetic field of the noncentrosymmetric heavy fermion superconductor CeRhSi3

We report an extremely high upper critical field B(c2) in the noncentrosymmetric heavy fermion superconductor CeRhSi3 for a magnetic field B along the tetragonal c axis. B(c2)(T=0) possibly reaching 30 T is much higher than B(c2)(0)=7 T for B perpendicular c and greatly exceeds the paramagnetic limiting field. The strong anisotropy of B(c2)(0) with extremely high B(c2)(0) for B || c is qualitatively explained by the paramagnetic pair-breaking mechanism specific to the noncentrosymmetric superconductor. However, an unusual B(c2)(T) curve with a positive curvature for B || c cannot be explained satisfactorily by conventional orbital pair-breaking models.     

Attosecond light pulses for probing two-electron dynamics of helium in the time domain

Using attosecond light pulses to doubly ionize a two-electron wave packet of helium, we showed that the time-resolved correlated motion of the two electrons can be probed by measuring their six-dimensional momentum distributions. For simple wave packets, we showed that the measured momenta, when analyzed in appropriate coordinates, can reveal the stretching, the rotational, and the bending vibrational modes of their joint motion in momentum space, in spite of the Coulomb distortion in the final states.     

Nonlinear optical properties of polydiacetylene with donor-acceptor substitution block

The elongation finite-field (elongation-FF) method is applied to donor/acceptor substituted polydiacetylenes (PDAs) for the estimation of substituent effects on nonlinear optical (NLO) properties. The first hyperpolarizability (beta) and the second hyperpolarizability (gamma) of PDA with separated donor and acceptor substitution blocks have much larger values than those of the other substituted PDAs. For the PDAs with donor and acceptor substitution blocks, the relationship between the NLO properties and the block period is examined. It is shown, from the local density of states, that gamma of a system with a quantum well structure has a maximum value at a certain block size. This indicates that by tuning the size of proper block it is possible to achieve the largest gamma value in block polymers. Furthermore, the through-space/bond interaction analysis is performed to examine the pi-conjugation effects on the NLO properties for particular substituted PDA. It is demonstrated by our quantitative analysis that beta is affected by electron transfers in the molecule, and the quantum well structure is critical for gamma improvement.     

Efficient and accurate calculations on the electronic structure of B-type poly(dG).poly(dC) DNA by elongation method: first step toward the understanding of the biological properties of aperiodic DNA

Elongation method was applied to determine the electronic structures of B-type poly(dG).poly(dC) DNA at the ab initio molecular orbital level as a first step toward the calculation of aperiodic DNA. The discrepancy in total energy between the elongation method and a conventional calculation was negligibly small in the order of 10(-8) hartreeat. for 14 G-C base pair model. The local density of states for 10 G-C base pair model estimated by the elongation method well reproduced the results by the conventional calculation. It was found that the band gap of the whole system is mainly due to the energy difference between the valence band of guanine and the conduction band of cytosine. Moreover, the electron transfer path through stacking G-C base pairs rather than sugar-phosphate backbones has been confirmed by the authors' calculations.     

Adsorption force of polyaniline-coated polystyrene latex particles

Visible polyaniline-latex particles 13 microm in diameter were used for obtaining a quantitative relationship between the adsorption force and the electroactivity at a platinum electrode. An optical cell equipped with wire electrodes was filled with the suspension in hydrochloric acid. When electrode potential was switched between the oxidized and the reduced domains, some adsorbed particles showed color change owing to the electroactivity. The numbers of electroactive and the inactive particles in the suspension were counted, including poly(N-vinylpyrrolidone) (PVP). The ratio of the numbers was proportional to the concentration of PVP, as it was in equilibrium. The adsorbed particles were desorbed mechanically by forced flow. The numbers of the desorbed particles did not decrease with an increase in the flow velocity until threshold values. The threshold value for the electroactive particle was 10 times larger than that for the inactive ones, corresponding to 10 times larger adsorption energy of the electroactive particles than of the inactive ones. The adsorption stress was evaluated from the removal of the electropolymerized polyaniline film from the electrode. Then the adsorption area of the particle was estimated.     

The role of hydrogen bonds in Baeyer-Villiger reactions

Various Baeyer-Villiger (B-V) oxidation reactions were examined by density functional theory calculations. Proton movements in transition states (TSs) of the two key steps, the nucleophilic addition of a peroxyacid molecule to a ketone (TS1) and the migration-cleavage of O-O (TS3), were discussed. A new TS of a hydrogen-bond rearrangement in the Criegee intermediate (TS2) was found. The hydrogen-bond directionality requires a trimer of the peroxyacid molecules at the nucleophilic addition of a peroxyacid molecule to a ketone TS (TS1). At the migration-cleavage of O-O TS (TS3), also three peroxyacid molecules are needed. Elementary processes of the B-V reaction were determined by the use of the (acetone and (H-CO-OOH)n, n=3) system. The geometries of the nucleophilic addition of a peroxyacid molecule to a ketone TS (TS1) and the migration-cleavage of O-O TS (TS3) in the trimer (n=3) participating are nearly insensitive to the substituent on the peroxyacid. The directionality is satisfied in those geometries. The migration-cleavage of O-O TS (TS3) was found to be rate-determining in reactions, [Me2C=O+(H-CO-OOH)3], [Me2C=O+(F3C-CO-OOH)3], and [Me2C=O+(MCPBA)3]. In contrast, the nucleophilic addition of a peroxyacid molecule to a ketone (TS1) is rate-determining in the reaction, [Ph(Me)C=O+(H-CO-OOH)3].     

Label- and marker-free gene detection based on hybridization-induced conformational flexibility changes in a ferrocene-PNA conjugate probe

We report a strategy for label-free and marker-free gene detection transducing the hybridization event to an electrochemical signal based on the hybridization-induced conformational flexibility change in probe structure. The probe structure was designed to possess a ferrocene moiety as a reporter part and a cysteine moiety as an anchor part at each end of a peptide nucleic acid (PNA) as a recognition part. Electrochemical examination of probe-modified gold electrodes revealed that the ferrocene moiety was placed at the flexible end of the linear probe chain. Upon hybridization with a complementary target DNA, the resultant rigid duplex restricted the ferrocene motion to the electrode surface, causing a decrease in the observed current. The target DNA was detected with the detection limit of 1.44 x 10(-11) M. Thus the probe functioned as a 'self-reporting probe' and detection of the target DNA was demonstrated without the need for external indicators. Moreover, the sensor electrode was able repeatedly to detect the target DNA by the process of regeneration and could discriminate a mismatched DNA.     

Synthesis of Pd complexes combined with photosensitizing of a ruthenium(II) polypyridyl moiety through a series of substituted bipyrimidine bridges. Substituent effect of the bridging ligand on the photocatalytic dimerization of alpha-methylstyrene

Mononuclear ruthenium complexes and dinuclear Ru...Pd complexes having a series of 2,2'-bipyrimidine ligands, [(bpy)2Ru(Ln)]2+ [Ln = 2,2'-bipyrimidine (L1), 5,5'-dimethyl-2,2'-bipyrimidine (L2), 5,5'-dibromo-2,2'-bipyrimidine (L3), 4,4'-dimethyl-2,2'-bipyrimidine (L4), and 4,4',6,6'-tetramethyl- 2,2'-bipyrimidine (L5)] and [(bpy)2Ru(Ln)PdL]m+ [Ln = L1-L3; PdL = PdMeCl (m = 2) and PdMe(solvent) (m = 3)], are prepared, and the obtained complexes are characterized by means of spectroscopic and crystallographic methods. Introduction of the substituents on the bipyrimidine ligands led to the substantial differences in their electrochemical and photophysical properties. Density functional theory calculations have been performed to understand the substituent effect on the ground-state molecular orbital energy level. Reactivity studies on the catalytic dimerization of alpha-methylstyrene revealed that the Pd complex having a Br-substituted bipyrimidine ligand were much more active than those of the corresponding Pd complexes having methyl-substituted or nonsubstituted bipyrimidine ligands.