A Common Origin for Neutrino Anarchy and Charged Hierarchies

The generation of exponential flavor hierarchies from extra-dimensional wavefunction overlaps is re-examined. We find, surprisingly, that coexistence of anarchic fermion mass matrices with such hierarchies is intrinsic and natural to this setting. The salient features of charged fermion and neutrino masses and mixings can thereby be captured within a single framework. Both Dirac and Majorana neutrinos can be realized. The minimal phenomenological consequences are discussed, including the need for a fundamental scale far above the weak scale to adequately suppress flavor-changing neutral currents. Two broad scenarios for stabilizing this electroweak hierarchy are studied, warped compactification and supersymmetry. In warped compactifications and "Flavorful Supersymmetry," where non-trivial flavor structure appears in the new TeV physics, Dirac neutrinos are strongly favored over Majorana by lepton flavor violation tests. We argue that this is part of a more general result for flavor-sensitive TeV-scale physics. Our scenario strongly suggests that the supersymmetric flavor problem is not solved locally in the extra dimension, but rather at or below the compactification scale. In the supersymmetric Dirac case, we discuss how the appearance of light right-handed sneutrinos considerably alters the physics of dark matter.Comment: Comparison with the Froggatt-Nielsen mechanism omitted. Some clarifications added. This is the version accepted by PRL with a longer abstract

Ginsenoside-Rg1 mediates a hypoxia-independent upregulation of hypoxia-inducible factor-1α to promote angiogenesis

Hypoxia-inducible factor (HIF-1) is the key transcription regulator for multiple angiogenic factors and is an appealing target. Ginsenoside-Rg1, a nontoxic saponin isolated from the rhizome of Panax ginseng, exhibits potent proangiogenic activity and has the potential to be developed as a new angiotherapeutic agent. However, the mechanisms by which Rg1 promotes angiogenesis are not fully understood. Here, we show that Rg1 is an effective stimulator of HIF-1α under normal cellular oxygen conditions in human umbilical vein endothelial cells. HIF-1α steady-state mRNA was not affected by Rg1. Rather, HIF-1α protein synthesis was stimulated by Rg1. This effect was associated with constitutive activation of phosphatidylinositol 3-kinase (PI3K)/Akt and its effector p70 S6 kinase (p70S6K), but not extracellular-signal regulated kinase 1/2. We further revealed that HIF-1α induction triggered the expression of target genes, including vascular endothelial growth factor (VEGF). The use of small molecule inhibitors LY294002 or rapamycin to inhibit PI3K/Akt and p70S6K activities, respectively, resulted in diminished HIF-1α activation and subsequent VEGF expression. RNA interference-mediated knockdown of HIF-1α suppressed Rg1-induced VEGF synthesis and angiogenic tube formation, confirming that the effect was HIF-1α specific. Similarly, the angiogenic phenotype could be reversed by inhibition of PI3K/Akt and p70S6K. These results define a hypoxia-independent activation of HIF-1α, uncovering a novel mechanism for Rg1 that could play a major role in angiogenesis and vascular remodeling

Amide-controlled, one-pot synthesis of tri-substituted purines generates structural diversity and analogues with trypanocidal activity

Anovel one-pot synthesis of tri-substituted purines and the discovery of purine analogues with trypanocidal activity are reported. The reaction is initiated by a metal-free oxidative coupling of primary alkoxides and diaminopyrimidines with Schiff base formation and subsequent annulation in the presence of large N,N-dimethylamides (e.g.N,N-dimethylpropanamide or larger). This synthetic route is in competition with a reaction previously-reported by our group1, allowing the generation of a combinatorial library of tri-substituted purines by the simple modification of the amide and the alkoxide employed. Among the variety of structures generated, two purine analogues displayed trypanocidal activity against the protozoan parasite Trypanosoma brucei with IC50 , 5 mM, being each of those compounds obtained through each of the synthetic pathways.J.J.D.M. thanks Spanish Ministerio de Economı´a y Competitividad for a Ramon y Cajal Fellowship. A.U.B. thanks MRC IGMM for an academic fellowship. This work was partially supported by Grant SAF2011-30528 to J.A.G.S.

Spin-Wave Theory On Finite Lattices: Application To The J1-J2 Heisenberg Model

We present a new method for a systematic spin-wave expansion for the quantum fluctuations of a generic spin Hamiltonian in a finite lattice, where the inverse spin magnitude 1/S is a well-defined expansion parameter. The first two leading contributions of the spin-spin correlation function are evaluated for the J1-J2 Heisenberg model. Very good agreement between our finite-size predictions and the exact diagonalization and Monte Carlo results is found for J2/J1 < 0.2 and S = 1/2, thus confirming the existence of antiferromagnetic long-range order in this J region. For J2/J1 > 0.3 the expansion is poorly converging, suggesting a possible breakdown of the spin-wave approximation. Here our calculation seems consistent with a possible spin liquid ground state

REALIZATION OF A SPIN LIQUID IN A 2-DIMENSIONAL QUANTUM ANTIFERROMAGNET

The ground state properties of the two dimensional spatially anisotropic Heisenberg model are investigated by use of field theory mappings, spin-wave expansion, and Lanczos technique. Evidence for a disorder transition induced by anisotropy at about J(y)/J(x) < 0.1 is shown. We argue that the disordered phase is gapless and its long wavelength properties can be interpreted in terms of decoupled one dimensional chains

Modulating microstructure and magnetic properties of BaFe12O19 thin films by using Pt and yttria stabilized zirconia underlayers

The c-axis oriented barium ferrite thin films were prepared by radio frequency magnetron sputtering on silicon substrates with a metal underlayer Pt (111) as well as an oxide underlayer yttria stabilized zirconia (YSZ). Microstructural studies (scanning electron microscopy, atomic force microscopy, and magnetic force microscopy) showed that the magnetic grains in BaM film have a strong relationship with the grains in the underlayer. The Pt underlayer is more effective in forming micrometer-sized and multidomain magnetic grains, which have high saturation magnetization but small coercivity and remanence of the BaM film. On the contrary, the YSZ underlayer is favorable to obtain nanometer-sized and monodomain magnetic grains, which lead to a slight decrease in saturation magnetization but dramatically increase coercivity and remanence of the BaM film. Hence, with careful selection of underlayer, it is feasible to obtain suitable magnetic grain size and domain structure of BaM films to satisfy special requirements