Top-quark-mass enhancement in a seesaw-type quark mass matrix

We investigate the implications of a seesawtype mass matrix, i.e.,M _f?m _LM _F ^?1 m _R, for quarks and leptonsf under the assumption that the matricesm _L andm _R are common to all flavors (up-/down- and quark-/lepton-sectors) and the matricesM _F characterizing the heavy fermion sectors have the form [(unit matrix)+b _f (a democratic matrix)] whereb _f is a flavor parameter. We find that by adjusting the complex parameterb _f, the model can provide thatm _t?m _b while at the same time keepingm _u～m _d without assuming any parameter with hierarchically different values betweenM _U andM _D. The model with three adjustable parameters under the “maximal” top-quark-mass enhancement can give reasonable values of five quark-mass ratios and four KM matrix parameters.     

U(3)-family nonet Higgs boson and its phenomenology

In a model where quark and lepton masses and family-mixings are caused not by a variety of Yukawa couplingsy _ij (i,j=1, 2, 3: family indices) with one vacuum expectation value (VEV)ν=〈φ _L ⁰ 〉₀, but by a variety of VEV’s of a U(3)-family nonet Higgs bosonφ _L ,v _i ^j =〈φ _Li ^0j 〉₀, with a single coupling constant, the following problems are investigated: what constraints on the Higgs potential are imposed in order to provide realistic quark and lepton mass spectra and mixings and what constraints on the Higgs boson masses are required in order to suppress unwelcome flavor-changing neutral current effects. Lower bounds of the physical Higgs boson masses ofφ _L are deduced from the present experimental data and new physics from the present scenario is speculated.     

A synthetic library of cell-permeable molecules.

Small molecules that induce or stabilize the association of macromolecules have proven to be useful effectors of a wide variety of biological processes. To date, all examples of such chemical inducers of dimerization have involved known ligands to well-characterized proteins. The generality of this approach could be broadened by enabling the discovery of heterodimerizers that target known macromolecules having no established ligand, or heterodimerizers that produce a novel biologic response in screens having no predetermined macromolecular target. Toward this end, we report the construction of a diversified library of synthetic heterodimerizers consisting of an invariant ligand that targets the FK506-binding protein (AP1867) attached to 320 substituted tetrahydrooxazepines (THOXs). The THOX components were generated by a combination of liquid- and solid-phase procedures employing sequential Mitsonobu displacements to join two structurally diversified olefin-containing monomers, followed by ruthenium-mediated olefin metathesis to effect closure of the seven-membered ring. The 320 resin-bound THOX ligands were coupled in parallel to AP1867, and the products were released from the resin to yield candidate heterodimerizers in sufficient yield and purity to be used directly in biologic testing. A representative panel of 25 candidate heterodimerizers were tested for their ability to pass through the membrane of human fibrosarcoma cells, and all were found to possess activity in this tissue culture system. These studies pave the way for further studies aimed at using small-molecule inducers of heterodimerization to effect novel biological responses in intact cells.     

Taste masking of propiverine hydrochloride by conversion to its free base

The aim of the present study was to mask the bitterness of propiverine hydrochloride (P-4) by converting it to propiverine free base. Fine granules comprising the free base, which was converted from P-4 by desalination, were prepared. By using Fourier transform infrared spectroscopy, thermogravimetry-differential thermal analysis, and powder X-ray diffraction spectra, we confirmed that P-4 had been converted into propiverine free base by desalination during the manufacturing process. Furthermore, the conversion into free base appeared to result in decreased solubility, and both the taste testing sensor and tasting volunteers determined that it masked the bitterness of P-4. On using the gustatory sensation test, the bitterness of the P-4 fine granules was confirmed to be weakened. The dissolution rate and bioavailability of fine granules of the free base were compared with tablets of P-4. The dissolution rate and bioavailability of the fine granules and tablets were almost the same. We successfully masked the taste of P-4 by converting it into free base using a manufacturing process that was suitable for commercial manufacturing.     

Additional insights into luminescence process of polycyclic aromatic hydrocarbons with carbonyl groups: photophysical properties of secondary N-alkyl and tertiary n,n-dialkyl carboxamides of naphthalene, anthracene, and pyrene

Here we report the substitution effects of N-alkyl and N,N-dialkyl carboxamide groups on the fluorescence properties of polycyclic aromatic hydrocarbon chromophores, so as to control their fluorescence properties. The fluorescence properties of compounds obtained using solvents with different polarities showed very little change, indicating that the modified compounds do not form charge transfer states. TD-DFT calculations and measurements performed at low temperature (78 K) and in viscous solvents revealed that the N-alkyl and N,N-dialkyl carboxamide groups tend to reduce the contributions from intersystem crossing and increase those from internal conversion. Considering that the fluorescence mechanism of low-fluorescence carbonyl compounds such as aldehyde and ketone is dominated by intersystem crossing and that of high-luminescence carbonyl compounds such as carboxylic acid and ester is dominated by a radiative process, it can be said that the photophysical process of N-alkyl and N,N-dialkyl carboxamides is novel. In addition, the calculation results for excited states indicated that such contributions can be controlled by selecting the appropriate polycyclic aromatic hydrocarbon or amide structure, in addition to solvent viscosity and temperature.     

Amorphous silicon diamond based heterojunctions with high rectification ratio

We have fabricated and characterized diamond based heterojunctions composed of homoepitaxial diamond (B-doped film: p type) and hydrogenated amorphous silicon (a-Si:H film: n-type). All devices include an intrinsic amorphous silicon interface (i-a-Si:H). (J–V) characteristics of a-Si:H heterojunctions measured from 300 K to 460 K present a very high rectification ratio (in the range 10⁸–10⁹) and a current density of 10 mA/cm² under 2 V of forward bias. The reverse current up to ? 4 V is below the detection limit in the whole temperature range. The devices present two regimes of operation indicating that more than one mechanism governs the carrier transport. These characteristics are compared with a Schottky barrier diode (SBD) using a tungsten carbide metal on top of the p-type diamond as a Schottky contact. The SBD device exhibits J–V characteristic with an ideality factor n close to one and the heterojunction follows this trend for low bias voltages whereas for bias voltage above 1 V a second regime with larger ideality factors n ~ 3.6 is observed. These results point out the prominent role of transport mechanisms at heterointerface between the a-Si:H layers and the p-type doped diamond which degrades the current injection. The breakdown voltage reached ? 160 V indicating the good quality of the deposited layers.     

Synthesis of beta-analogues of C-mannosyltryptophan, a novel C-glycosylamino acid found in proteins

alpha-C-Mannosyltryptophan (alpha-C-Man-Trp) has been found to be a novel post-translational modification of tryptophan found from some biologically important glycoproteins. In order to analyze the biological functions of alpha-C-Man-Trp, we have developed an efficient synthetic strategy for alpha-C-Man-Trp and its glucose and galactose analogues, starting from alpha-C-glycosidation of the corresponding hexapyranoside derivatives with tinacetylene. According to the synthetic routes, we describe here syntheses of beta-anomers of C-Man-Trp, and its glucose and galactose analogues from the corresponding beta-C-glycosylacetylenes. During this study, we have developed a highly stereocontrolled synthesis of beta-C-mannosylacetylene that is required for the synthesis of beta-C-Man-Trp, while the precedented method gave an anomeric mixture of the C-mannosylacetylene. The synthetic C-Man-Trp and its analogues were analyzed by HPLC.