Intermolecular pi-pi interactions in solids

A parameter-free DFT/CCSD(T) correction scheme is proposed for precise calculations (close to CCSD(T) accuracy) of weakly bound molecular solids. The correction scheme has been tested for solid benzene and graphite. The CCSD(T)/CBS correction to planewave DFT calculations reproduces the experimentally determined lattice constants for solid benzene. The calculated cohesive energy of benzene (457 meV per molecule) compares well with the experimental values of the heat of sublimation (460-560 meV per molecule). For graphite, the correction yields structural parameters (a = 2.46 A, c = 6.60 A) in good agreement with experiment (a = 2.46 A, c = 6.67 A). The calculated exfoliation energy of 54 meV per atom agrees fairly well with the most recent experimental value of 52 +/- 5 meV per atom.     

Spectroscopic study of neutron shell closures via nucleon transfer in the near-dripline nucleus 23O

Neutron single particle energies have been measured in 23O using the 22O(d,p)23O*-->22O+n process. The energies of the resonant states have been deduced to be 4.00(2) MeV and 5.30(4) MeV. The first excited state can be assigned to the nu d3/2 single particle state from a comparison with shell model calculations. The measured 4.0 MeV energy difference between the nu s1/2 and nu d3/2 states gives the size of the N=16 shell gap which is in agreement with the recent USD05 ("universal" sd from 2005) shell model calculation, and is large enough to explain the unbound nature of the oxygen isotopes heavier than A=24. The resonance detected at 5.3 MeV can be assigned to a state out of the sd shell model space. Its energy corresponds to a approximately 1.3 MeV sized N=20 shell gap, therefore, the N=20 shell closure disappears at Z=8 in agreement with Monte Carlo shell model calculations using SDPF-M interaction.     

Acceptable range of speech level for both young and aged listeners in reverberant and quiet sound fields

The speech level of verbal information in public spaces should be determined to make it acceptable to as many listeners as possible, while simultaneously maintaining maximum intelligibility and considering the variation in the hearing levels of listeners. In the present study, the universally acceptable range of speech level in reverberant and quiet sound fields for both young listeners with normal hearing and aged listeners with hearing loss due to aging was investigated. Word intelligibility scores and listening difficulty ratings as a function of speech level were obtained by listening tests. The results of the listening tests clarified that (1) the universally acceptable ranges of speech level are from 60 to 70 dBA, from 56 to 61 dBA, from 52 to 67 dBA and from 58 to 63 dBA for the test sound fields with the reverberation times of 0.0, 0.5, 1.0 and 2.0 s, respectively, and (2) there is a speech level that falls within all of the universally acceptable ranges of speech level obtained in the present study; that speech level is around 60 dBA.     

Anomalous resistance ridges along filling factor nu=4i

We report anomalous structure in the magnetoresistance of SiO(2)/Si(100)/SiO(2) quantum wells. When Landau levels of opposite valleys are driven through coincidence at the Fermi level, the longitudinal resistance displays elevations at filling factors that are integer multiples of 4 (nu=4i) accompanied by suppression on either side of nu=4i. This persists when either the magnetic field or the valley splitting is swept, leading to resistance ridges running along nu=4i. The range of field over which they are observed points to the role of spin degeneracy, which is directly confirmed by their disappearance with the addition of an in-plane magnetic field. The data suggest a new type of many-body effect arising from the combined degeneracy due to the valley and the spin degrees of freedom.     

Polymerization of norbornene with a pendent sulfonyl fluoride group catalyzed by palladium complex bearing tBu3P ligand

The combination of palladium complex (^tBu₃P)Pd(Me)Cl ( 1 ) and NaB[3,5‐(CF₃)₂C₆H₃]₄ (NaBAr₄) catalyzed homopolymerization of a novel monomer, norbornene (NB) with a pendent 2‐fluorosulfonyltetrafluoroethoxymethyl chain (NBSF). Catalytic activities of 1 /NaBAr₄ were higher than those of previously reported palladium or nickel catalysts, probably, because the palladium center with electron donative ^tBu₃P ligand was barely poisoned by the sulfonyl fluoride coordination. Thus, 1 /NaBAr₄ is the current best catalyst system for NBSF polymerization. The catalyst system also gave copolymers of NB with NBSF. The obtained copolymers have high sulfonyl‐fluoride incorporation and a narrow molecular weight distribution. Present catalyst system could control incorporation ratio of NBSF by changing a feed monomer ratio with slow addition of NB solution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5133–5141, 2008     

Improvement of the high-speed log D assay using an injection marker for the water plug aspiration/injection method

An improved method for the high-speed assay for log D (HSLogD) employing an injection marker is described. The critical process of HSLogD is automated sampling of the water phase, which prevents contamination from the octanol phase. However, deployment of HSLogD sometimes produces incorrect and inaccurate values compared with data from closely related methods due to low solubility of compounds or instrument problems. Therefore, careful manual inspection of data is needed to confirm the results obtained by this method. To solve this problem, compounds were screened for suitability as injection markers and 2-(4-methoxyphenoxy)-4,8-dimethylquinoline was the most suitable compound examined. Introduction of the injection marker into the process successfully eliminated the need for the tedious and time-consuming manual inspection process.     

Chilling out: a cool aqueous environment promotes the formation of gas-surface complexes

SO(2), an important atmospheric pollutant, has been implicated in environmental phenomena such as acid rain, climate change, and cloud formation. In addition, SO(2) is fundamentally interesting because it forms spectroscopically identifiable complexes with water at aqueous surfaces. Vibrational sum frequency spectroscopy (VSFS) is used here to further investigate the mechanism by which SO(2) adsorbs to water at tropospherically relevant temperatures (0-23 °C). The spectral results lead to two important conclusions. SO(2) surface affinity is enhanced at colder temperatures, with nearly all of the topmost water molecules showing evidence of binding to SO(2) at 0 °C as compared to a much lower fraction at room temperature. This surface adsorption results in significant changes in water orientation at the surface, but is reversible at the temperatures examined here. Second, the SO(2) complex formation at aqueous surfaces is independent of aqueous solution acidity. One challenge in previous uptake studies was the ability to distinguish between the effects of surface adsorption as compared to bulk accommodation. The surface and vibrational specificity of these studies make this distinction possible, allowing a selective study of how the aqueous properties temperature and pH influence SO(2) surface affinity.     

Size separation of colloidally dispersed nanoparticles using a monolithic capillary column

We developed a method to separate colloidally dispersed nanoparticles on monolithic capillary columns. Silica nanoparticles were eluted according to their sizes, and the plots of the logarithm of the size of nanoparticles against their elution volume showed good linearity (r=0.992) over wide range of sizes. Because of the high porosity of the monolithic column (porosity; 88%), the column's length could be increased without clogging of the dispersed samples and the pressure in a long column (500 mm × 0.2 mm i.d.) was low, with a value of 5.8 MPa at a flow rate of 1 μL/min. We demonstrate that this method using monolithic capillary columns could be used as a powerful tool for size separation of nanometer-size materials, which will open a new pathway to quality control of nanomaterials in nanotechnology applications.     

Enantiomeric separation of asymmetric triacylglycerol by recycle high-performance liquid chromatography with chiral column

In our previous studies, we employed recycle HPLC for the separation of triacylglycerol (TAG)-positional isomers (PIs). In this study, a recycle HPLC system equipped with a polysaccharide-based chiral column was applied to the enantiomeric separation of some asymmetric TAGs having straight-chain C16-C18 acyl residues. As a result, 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (rac-PPO), 1,2-dioleoyl-3-palmitoyl-rac-glycerol (rac-OOP), and 1,2-dipalmitoyl-3-linoleoyl-rac-glycerol (rac-PPL) were resolved into their respective enantiomers. However, neither 1,2-dioleoyl-3-linoleoyl-rac-glycerol (rac-OOL), consisting of only unsaturated fatty acids, nor 1,2-dipalmitoyl-3-stearoyl-rac-glycerol (rac-PPS), consisting of only saturated fatty acids, was resolved. These results suggest that the asymmetric TAGs, used in this study, having both a palmitic acid moiety and an oleic acid (or a linoleic acid) moiety at the sn-1 or sn-3 positions are resolved by the chiral column. This new chiral separation method can be used in combination with atmospheric pressure chemical ionization mass spectrometry to determine the sn-OOP/sn-POO ratio in palm oil. This method is applicable for the chiral separation of asymmetric TAGs in palm oil.