We investigate neutrino masses and mixings within the framework of the Zee mass matrix, with three lepton flavors. It is shown that the bi-maximal solution is the only possibility to reconcile atmospheric and solar neutrino data, within this ansatz. We obtain two almost degenerate neutrinos, which are mixtures of all three neutrino flavors, with heavy masses ≃ ∆m 2 atm . The predicted mass of the lightest neutrino, which should consist mostly of ν µ and ν τ , is ≃ ∆m 2 ⊙ /(2 ∆m 2 atm ).

In the context of Calabi-Yau string models we explore the origin of characteristic pattern of quark-lepton masses and the CKM matrix. The discrete $R$-symmetry $Z_K \times Z_2$ is introduced and the $Z_2$ is assigned to the $R$-parity. The gauge symmetry at the string scale, $SU(6) \times SU(2)_R$, is broken into the standard model gauge group at a very large intermediate energy scale. At energies below the intermediate scale down-type quarks and also leptons are mixed with unobserved heavy states, respectively. On the other hand, there are no such mixings for up-type quarks. Due to the large mixings between light states and heavy ones we can derive phenomenologically viable fermion mass hierarchies and the CKM matrix. Mass spectra for intermediate-scale matter beyond the MSSM are also determined. Within this framework proton lifetime is long enough to be consistent with experimental data. As for the string scale unification of gauge couplings, however, consistent solutions are not yet found.Comment: 49 pages, 1 figure, Latex Revised version includes discussion on FCNC problems. Final version to appear in Prog. Theor. Phys. Vol.96 No.

We study the explicit CP violation of the Higgs sector in the minimal supersymmetric standard model with a gauge singlet Higgs field. The magnitude of CP violation is discussed in the limiting cases of x ≫ v 1 , v 2 and x ≪ v 1 , v 2 , where x and v 1,2 denote VEV of singlet and doublet Higgs scalars, respectively. Our numerical predictions of the electric dipole moments of electron and neutron lie around the present experimental upper limits. It is found that the large CP violation effect reduces the magnitude of the lightest Higgs boson mass in the order of a few ten GeV.

Ultrasonographic assessment of bladder wall thickness is a sensitive screening tool for the diagnosis of urodynamic risk factors for upper urinary tract deterioration in children with myelodysplasia.

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