To study how microbes establish themselves in a mammalian gut environment, we colonized germ-free mice with microbial communities from human, zebrafish, and termite guts, human skin and tongue, soil, and estuarine microbial mats. Bacteria from these foreign environments colonized and persisted in the mouse gut; their capacity to metabolize dietary and host carbohydrates and bile acids correlate...

The phenomenological model that all quark and lepton mass matrices have the same zero texture, namely their (1,1), (1,3) and (3,1) components are zeros, is discussed in the context of SO(10) Grand Unified Theories (GUTs). The mass matrices of type I for quarks are consistent with the experimental data in the quark sector. For the lepton sector, consistent fitting to the data of neutrino oscilla...

It is generally believed that the cosmological constant problem is the most severe hierarchy problem in particle physics. The hierarchy problem has been formulated since 1975 in connection with grand unified theories(GUTs). GUTs introduce two scales which differ by a factor of 10. At the classical Lagrangian level, there appear parameters which are of order 10 GeV. But loop corrections and spon...