Acceleration waves analyzed by a new continuum model of solids incorporating microscopic thermal vibrations

Acceleration waves propagating in isotropic solids at finite temperatures are studied by applying the method of singular surfaces to a new continuum model derived statistical-mechanically from a three-dimensional lattice model. The continuum model explicitly takes into account the microscopic thermal vibrations of the constituent atoms as one of the field variables. The propagation speeds and the ratios of mechanical and thermal amplitudes for both longitudinal and transverse waves are consistently determined. The differential equations that govern the time variation of the amplitudes of the waves are also derived. The analytical results, which are valid over a wide temperature range that includes the melting point, are evaluated numerically for several materials, and their physical implications are discussed. One of the findings to be emphasized is that of the singularities of the characteristic quantities at the melting point.Received: 13 March 2003, Accepted: 20 June 2003PACS: 62.30. + d, 65.40.-bM. Sugiyama: Correspondence to Dedicated to Prof. Ingo Müller on the occasion of his 65th birthday.     

Numerical analysis of turbulent flow separation in a rectangular duct with a sharp 180‐degree turn by algebraic Reynolds stress model

Turbulent flow in a rectangular duct with a sharp 180‐degree turn is difficult to predict numerically because the flow behavior is influenced by several types of forces, including centrifugal force, pressure‐driven force, and shear stress generated by anisotropic turbulence. In particular, this type of flow is characterized by a large‐scale separated flow, and it is difficult to predict the reattachment point of a separated flow. Numerical analysis has been performed for a turbulent flow in a rectangular duct with a sharp 180‐degree turn using the algebraic Reynolds stress model. A boundary‐fitted coordinate system is introduced as a method for coordinate transformation to set the boundary conditions next to complicated shapes. The calculated results are compared with the experimental data, as measured by a laser‐Doppler anemometer, in order to examine the validity of the proposed numerical method and turbulent model. In addition, the possibility of improving the wall function method in the separated flow region is examined by replacing the log‐law velocity profile for a smooth wall with that for a rough wall. The analysis results indicated that the proposed algebraic Reynolds stress model can be used to reasonably predict the turbulent flow in a rectangular duct with a sharp 180‐degree turn. In particular, the calculated reattachment point of a separated flow, which is difficult to predict in a turbulent flow, agrees well with the experimental results. In addition, the calculation results suggest that the wall function method using the log‐law velocity profile for a rough wall over a separated flow region has some potential for improving the prediction accuracy. Copyright © 2007 John Wiley & Sons, Ltd.     

Evaluation of the DNA Alkylation Properties of a Chlorambucil-Conjugated Cyclic Pyrrole-Imidazole Polyamide

Hairpin pyrrole-imidazole polyamides (hPIPs) and their chlorambucil (Chb) conjugates (hPIP-Chbs) can alkylate DNA in a sequence-specific manner, and have been studied as anticancer drugs. Here, we conjugated Chb to a cyclic PIP (cPIP), which is known to have a higher binding affinity than the corresponding hPIP, and investigated the DNA alkylation properties of the resulting cPIP-Chb using the optimized capillary electrophoresis method and conventional HPLC product analysis. cPIP-Chb conjugate 3 showed higher alkylation activity at its binding sites than did hPIP-Chb conjugates 1 and 2 . Subsequent HPLC analysis revealed that the alkylation site of conjugate 3 , which was identified by capillary electrophoresis, was reliable and that conjugate 3 alkylates the N3 position of adenine as do hPIP-Chbs. Moreover, conjugate 3 showed higher cytotoxicity against LNCaP prostate cancer cells than did conjugate 1 and cytotoxicity comparable to that of conjugate 2 . These results suggest that cPIP-Chbs could be novel DNA alkylating anticancer drugs.     

Study of buried Si(1 1 1)-5 × 2-Au by surface X-ray diffraction

The structure of buried Si(1 1 1)-5 × 2-Au capped with amorphous Si was investigated using surface X-ray diffraction. It was found that the 5 × 2 structural periodicity is kept under the amorphous Si from the in-plane measurement. Furthermore, the intensity variation along the fractional-order rod indicates that Au atoms are located almost on the same plane.     

Automated phosphoproteome analysis for cultured cancer cells by two-dimensional nanoLC-MS using a calcined titania/C18 biphasic column.

We have developed an on-line automated system for phosphoproteome analysis using titania-based phosphopeptide enrichment followed by nanoLC-MS/MS. Titania beads were prepared by calcination of commercial chromatographic titania beads at 800 degrees C to convert the crystalline structure. The obtained rutile-form titania exhibited higher selectivity in phosphopeptide enrichment than commercial titania, even in the absence of a competitive chelating reagent for non-phosphopeptides. For phosphoproteome analysis of human cervical cancer HeLa cells, tryptic digests of the cell extracts were directly injected into this on-line system, and 696 non-redundant phosphopeptides with 671 unambiguously determined phosphorylation sites, derived from 512 phosphoproteins, were successfully identified. This is the first successful application of an on-line automated phosphoproteome analysis system to complex biological samples.     

Synthesis and structural characterization of Ni(II) complexes with the chiral CpH(PNMent) tripod ligand

Treatment of NiCl₂ with the tripod ligand (L_Ment,S_C)-1H led to (L_Ment,S_C)-[Cp(PN_Ment)NiCl] in which the potentially tridentate ligand coordinated to the metal center in a bidentate way via the cyclopentadienyl system and the phosphorus atom. In the presence of NH₄PF₆ [(L_Ment,S_C)-[Cp(PN_Ment)NiCl] readily underwent Cl/PPh₃ exchange to give (L_Ment,S_C)-[Cp(PN_Ment)NiPPh₃]PF₆. Reaction of (L_Ment,S_C)-[Cp(PN_Ment)NiCl] with 0.5 eq. of dppe afforded [{(L_Ment,S_C)-[Cp(PN_Ment)Ni]}₂dppe](PF₆)₂. (L_Ment,S_C)-[Cp(PN_Ment)NiPPh₃]PF₆ and [{(L_Ment,S_C)-[Cp(PN_Ment)Ni]}₂dppe](PF₆)₂ were characterized by NMR and MS spectroscopy, and also by single crystal X-ray diffraction. The cyclopentadienyl ligand of (L_Ment,S_C)-[Cp(PN_Ment)NiPPh₃]PF₆ shows a distortion intermediate between the ene-allyl and diene types, while the two cyclopentadienyl ligands of [{(L_Ment,S_C)-[Cp(PN_Ment)Ni]}₂dppe](PF₆)₂ have intermediate and diene distortions, respectively. According to the temperature dependent NMR spectra of (L_Ment,S_C)-[Cp(PN_Ment)NiPPh₃]PF₆ and [{(L_Ment,S_C)-[Cp(PN_Ment)Ni]}₂dppe](PF₆)₂ two different conformations of the tether in the Cp(PN_Ment)Ni system could be frozen out at low temperatures.     

Discovery of Hexagonal Structured Pd–B Nanocrystals

We report on hexagonal close-packed (hcp) palladium (Pd)–boron (B) nanocrystals (NCs) by heavy B doping into face-centered cubic (fcc) Pd NCs. Scanning transmission electron microscopy–electron energy loss spectroscopy and synchrotron powder X-ray diffraction measurements demonstrated that the B atoms are homogeneously distributed inside the hcp Pd lattice. The large paramagnetic susceptibility of Pd is significantly suppressed in Pd–B NCs in good agreement with the reduction of density of states at Fermi energy suggested by X-ray absorption near-edge structure and theoretical calculations.