Flow coefficients v_{n} for n=2, 3, 4, characterizing the anisotropic collective flow in Au+Au collisions at sqrt[s_{NN}]=200  GeV, are measured relative to event planes Ψ_{n}, determined at large rapidity. We report v_{n} as a function of transverse momentum and collision centrality, and study the correlations among the event planes of different order n. The v_{n} are well described by hydrodynamic models which employ a Glauber Monte Carlo initial state geometry with fluctuations, providing additional constraining power on the interplay between initial conditions and the effects of viscosity as the system evolves. This new constraint can serve to improve the precision of the extracted shear viscosity to entropy density ratio η/s.

Back-to-back hadron pair yields in d+Au and p+p collisions at √s(NN)=200 GeV were measured with the PHENIX detector at the Relativistic Heavy Ion Collider. Rapidity separated hadron pairs were detected with the trigger hadron at pseudorapidity |η|<0.35 and the associated hadron at forward rapidity (deuteron direction, 3.0<η<3.8). Pairs were also detected with both hadrons measured at forward rapidity; in this case, the yield of back-to-back hadron pairs in d+Au collisions with small impact parameters is observed to be suppressed by a factor of 10 relative to p+p collisions. The kinematics of these pairs is expected to probe partons in the Au nucleus with a low fraction x of the nucleon momenta, where the gluon densities rise sharply. The observed suppression as a function of nuclear thickness, p(T), and η points to cold nuclear matter effects arising at high parton densities.

We present measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200  GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2<y<2.4) with high statistical precision and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects. In order to remove model dependent systematic uncertainties we also compare the data to a simple geometric model. The forward rapidity data are inconsistent with nuclear modifications that are linear or exponential in the density weighted longitudinal thickness, such as those from the final state breakup of the bound state.

WNT signaling activity is involved in the regulation of many cellular functions, including proliferation, migration, cell fate specification, maintenance of pluripotency and induction of tumorigenicity. Here we summarize recent progress towards understanding the regulation of canonical WNT/β-catenin signaling activity through feedback regulatory loops involving the ligands, agonists and antagonists, the availability of intracellular pools of active β-catenin and the cross-regulation of the WNT activity by β-catenin independent pathway. We also review recent findings on the role of WNT/β-catenin signaling in tissue lineage differentiation during embryogenesis and the maintenance and self renewal of embryo-derived stem cells in vitro.

Large parity-violating longitudinal single-spin asymmetries A(L)(e+)=-0.86(-0.14)(+0.30) and A(L)(e-)= 0.88(-0.71)(+0.12) are observed for inclusive high transverse momentum electrons and positrons in polarized p+p collisions at a center-of-mass energy of sqrt[s]= 500 GeV with the PHENIX detector at RHIC. These e± come mainly from the decay of W± and Z0 bosons, and their asymmetries directly demonstrate parity violation in the couplings of the W± to the light quarks. The observed electron and positron yields were used to estimate W± boson production cross sections for the e± channels of σ(pp → W+ X) × BR(W+ → e+ ν(e))= 144.1 ± 21.2(stat)(-10.3)(+3.4)(syst) ± 21.6(norm)  pb, and σ(pp → W- X) × BR(W- → e- ν[over ¯](e))= 31.7 ± 12.1(stat)(-8.2)(+10.1)(syst) ± 4.8(norm)  pb.

The translocon-associated protein (TRAP, also termed the signal sequence receptor) complex is required for the efficient translocation of secretory and membrane proteins in the endoplasmic reticulum, and is also involved in the endoplasmic reticulum stress-mediated unfolded protein response pathway. To investigate the roles of Trap-γ, a TRAP complex subunit, we generated Trap-γ knockout mice and found that mutant pups died soon after birth because of retarded embryonic organ growth, especially in the lung. The mutant placentae showed severe vascular network malformation in the labyrinth and significant reductions in blood space areas, which had an adverse effect on intrauterine embryonic growth. Placental malformation was already found by the mid-gestation-stage mutant placenta, with poor vascular endothelial cell proliferation in the chorionic plate region and increased apoptotic cell death in the labyrinth. Thus, Trap-γ appears to be required for vascular network formation in murine placental development.

Mouse embryos lacking Lhx1 (Lim1) activity display defective gastrulation and are deficient of primordial germ cells (PGCs)(Tsang et al.[2001] International Journal of Developmental Biology 45:549-555). To dissect the specific role of Lhx1 in germ cell development, we studied embryos with conditional inactivation of Lhx1 activity in epiblast derivatives, which, in contrast to completely null embryos, develop normally through gastrulation before manifesting a head truncation phenotype. Initially, PGCs are localized properly to the definitive endoderm of the posterior gut in the conditional mutant embryos, but they depart from the embryonic gut prematurely. The early exit of PGCs from the gut is accompanied by the failure to maintain a strong expression of Ifitm1 in the mesoderm enveloping the gut, which may mediate the repulsive activity that facilitates the retention of PGCs in the hindgut during early organogenesis. Lhx1 therefore may influence the localization of PGCs by modulating Ifitm1-mediated repulsive activity.

The production of e;{+}e;{-} pairs for m_{e;{+}e;{-}}<0.3 GeV/c;{2} and 1<p_{T}<5 GeV/c is measured in p+p and Au+Au collisions at sqrt[s_{NN}]=200 GeV. An enhanced yield above hadronic sources is observed. Treating the excess as photon internal conversions, the invariant yield of direct photons is deduced. In central Au+Au collisions, the excess of the direct photon yield over p+p is exponential in transverse momentum, with an inverse slope T=221+/-19;{stat}+/-19;{syst} MeV. Hydrodynamical models with initial temperatures ranging from T_{init} approximately 300-600 MeV at times of approximately 0.6-0.15 fm/c after the collision are in qualitative agreement with the data. Lattice QCD predicts a phase transition to quark gluon plasma at approximately 170 MeV.

The momentum distribution of electrons from semileptonic decays of charm and bottom quarks for midrapidity |y|<0.35 in p+p collisions at square root of s=200 GeV is measured by the PHENIX experiment at the Relativistic Heavy Ion Collider over the transverse momentum range 2<pT<7 GeV/c. The ratio of the yield of electrons from bottom to that from charm is presented. The ratio is determined using partial D/D-->e(+/-)K(-/+)X (K unidentified) reconstruction. It is found that the yield of electrons from bottom becomes significant above 4 GeV/c in pT. A fixed-order-plus-next-to-leading-log perturbative quantum chromodynamics calculation agrees with the data within the theoretical and experimental uncertainties. The extracted total bottom production cross section at this energy is sigma(bb)=3.2(-1.1)(+1.2)(stat)(-1.3)(+1.4)(syst)mub.

The double helicity asymmetry in neutral pion production for p_{T}=1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, DeltaG, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of mu;{2}=4 GeV2 a next to leading order QCD analysis gives DeltaG;{[0.02,0.3]}=0.2, with a constraint of -0.7<DeltaG;{[0.02,0.3]}<0.5 at Deltachi;{2}=9 ( approximately 3sigma) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the DeltaG constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.