On the black hole limit of rotating discs and rings

Solutions to Einstein's field equations describing rotating fluid bodies in equilibrium permit parametric (i.e. quasi-stationary) transitions to the extreme Kerr solution (outside the horizon). This has been shown analytically for discs of dust and numerically for ring solutions with various equations of state. From the exterior point of view, this transition can be interpreted as a (quasi) black hole limit. All gravitational multipole moments assume precisely the values of an extremal Kerr black hole in the limit. In the present paper, the way in which the black hole limit is approached is investigated in more detail by means of a parametric Taylor series expansion of the exact solution describing a rigidly rotating disc of dust. Combined with numerical calculations for ring solutions our results indicate an interesting universal behaviour of the multipole moments near the black hole limit.Comment: 18 pages, 4 figures; Dedicated to Gernot Neugebauer on the occasion of his 70th birthda

A Search for Neutrinos from the Solar hep Reaction and the Diffuse Supernova Neutrino Background with the Sudbury Neutrino Observatory

A search has been made for neutrinos from the hep reaction in the Sun and from the diffus

Measurement of the Total Active 8B Solar Neutrino Flux at the Sudbury Neutrino Observatory with Enhanced Neutral Current Sensitivity

The Sudbury Neutrino Observatory (SNO) has precisely determined the total active (nu_x) 8B solar neutrino flux without assumptions about the energy dependence of the nu_e survival probability. The measurements were made with dissolved NaCl in the heavy water to enhance the sensitivity and signature for neutral-current interactions. The flux is found to be 5.21 +/- 0.27 (stat) +/- 0.38 (syst) x10^6 cm^{-2}s^{-1}, in agreement with previous measurements and standard solar models. A global analysis of these and other solar and reactor neutrino results yields Delta m^{2} = 7.1^{+1.2}_{-0.6}x10^{-5} ev^2 and theta = 32.5^{+2.4}_{-2.3} degrees. Maximal mixing is rejected at the equivalent of 5.4 standard deviations.Comment: Submitted to Phys. Rev. Let

Electron Antineutrino Search at the Sudbury Neutrino Observatory

Upper limits on the \nuebar flux at the Sudbury Neutrino Observatory have been set based on the \nuebar charged-current reaction on deuterium. The reaction produces a positron and two neutrons in coincidence. This distinctive signature allows a search with very low background for \nuebar's from the Sun and other potential sources. Both differential and integral limits on the \nuebar flux have been placed in the energy range from 4 -- 14.8 MeV. For an energy-independent \nu_e --> \nuebar conversion mechanism, the integral limit on the flux of solar \nuebar's in the energy range from 4 -- 14.8 MeV is found to be \Phi_\nuebar <= 3.4 x 10^4 cm^{-2} s^{-1} (90% C.L.), which corresponds to 0.81% of the standard solar model 8B \nu_e flux of 5.05 x 10^6 cm^{-2} s^{-1}, and is consistent with the more sensitive limit from KamLAND in the 8.3 -- 14.8 MeV range of 3.7 x 10^2 cm^{-2} s^{-1} (90% C.L.). In the energy range from 4 -- 8 MeV, a search for \nuebar's is conducted using coincidences in which only the two neutrons are detected. Assuming a \nuebar spectrum for the neutron induced fission of naturally occurring elements, a flux limit of Phi_\nuebar <= 2.0 x 10^6 cm^{-2} s^{-1}(90% C.L.) is obtained.Comment: submitted to Phys. Rev.

Elucidation of the mode of interaction in the UP1–telomerase RNA–telomeric DNA ternary complex which serves to recruit telomerase to telomeric DNA and to enhance the telomerase activity

We found that UP1, a proteolytic product of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1), both enhances and represses the telomerase activity. The formation of the UP1–telomerase RNA–telomeric DNA ternary complex was revealed by a gel retardation experiment. The interactions in the ternary and binary complexes were elucidated by NMR. UP1 has two nucleic acid-binding domains, BD1 and BD2. In the UP1–telomerase RNA binary complex, both BD1 and BD2 interact with telomerase RNA. Interestingly, when telomeric DNA was added to the binary complex, telomeric DNA bound to BD1 in place of telomerase RNA. Thus, BD1 basically binds to telomeric DNA, while BD2 mainly binds to telomerase RNA, which resulted in the formation of the ternary complex. Here, UP1 bridges telomerase and telomeric DNA. It is supposed that UP1/hnRNP A1 serves to recruit telomerase to telomeric DNA through the formation of the ternary complex. A model has been proposed for how hnRNP A1/UP1 contributes to enhancement of the telomerase activity through recruitment and unfolding of the quadruplex of telomeric DNA

Constraints on Nucleon Decay via "Invisible" Modes from the Sudbury Neutrino Observatory

Data from the Sudbury Neutrino Observatory have been used to constrain the lifetime for nucleon decay to ``invisible'' modes, such as n -> 3 nu. The analysis was based on a search for gamma-rays from the de-excitation of the residual nucleus that would result from the disappearance of either a proton or neutron from O16. A limit of tau_inv > 2 x 10^{29} years is obtained at 90% confidence for either neutron or proton decay modes. This is about an order of magnitude more stringent than previous constraints on invisible proton decay modes and 400 times more stringent than similar neutron modes.Comment: Update includes missing efficiency factor (limits change by factor of 2) Submitted to Physical Review Letter

Targeting HIV-1 Env gp140 to LOX-1 Elicits Immune Responses in Rhesus Macaques.

Improved antigenicity against HIV-1 envelope (Env) protein is needed to elicit vaccine-induced protective immunity in humans. Here we describe the first tests in non-human primates (NHPs) of Env gp140 protein fused to a humanized anti-LOX-1 recombinant antibody for delivering Env directly to LOX-1-bearing antigen presenting cells, especially dendritic cells (DC). LOX-1, or 1ectin-like oxidized low-density lipoprotein (LDL) receptor-1, is expressed on various antigen presenting cells and endothelial cells, and is involved in promoting humoral immune responses. The anti-LOX-1 Env gp140 fusion protein was tested for priming immune responses and boosting responses in animals primed with replication competent NYVAC-KC Env gp140 vaccinia virus. Anti-LOX-1 Env gp140 vaccination elicited robust cellular and humoral responses when used for either priming or boosting immunity. Co-administration with Poly ICLC, a TLR3 agonist, was superior to GLA, a TLR4 agonist. Both CD4+ and CD8+ Env-specific T cell responses were elicited by anti-LOX-1 Env gp140, but in particular the CD4+ T cells were multifunctional and directed to multiple epitopes. Serum IgG and IgA antibody responses induced by anti-LOX-1 Env gp140 against various gp140 domains were cross-reactive across HIV-1 clades; however, the sera neutralized only HIV-1 bearing sequences most similar to the clade C 96ZM651 Env gp140 carried by the anti-LOX-1 vehicle. These data, as well as the safety of this protein vaccine, justify further exploration of this DC-targeting vaccine approach for protective immunity against HIV-1

A cellular trafficking signal in the SIV envelope protein cytoplasmic domain is strongly selected for in pathogenic infection

The HIV/SIV envelope glycoprotein (Env) cytoplasmic domain contains a highly conserved Tyr-based trafficking signal that mediates both clathrin-dependent endocytosis and polarized sorting. Despite extensive analysis, the role of these functions in viral infection and pathogenesis is unclear. An SIV molecular clone (SIVmac239) in which this signal is inactivated by deletion of Gly-720 and Tyr-721 (SIVmac239ΔGY), replicates acutely to high levels in pigtail macaques (PTM) but is rapidly controlled. However, we previously reported that rhesus macaques and PTM can progress to AIDS following SIVmac239ΔGY infection in association with novel amino acid changes in the Env cytoplasmic domain. These included an R722G flanking the ΔGY deletion and a nine nucleotide deletion encoding amino acids 734–736 (ΔQTH) that overlaps the rev and tat open reading frames. We show that molecular clones containing these mutations reconstitute signals for both endocytosis and polarized sorting. In one PTM, a novel genotype was selected that generated a new signal for polarized sorting but not endocytosis. This genotype, together with the ΔGY mutation, was conserved in association with high viral loads for several months when introduced into naïve PTMs. For the first time, our findings reveal strong selection pressure for Env endocytosis and particularly for polarized sorting during pathogenic SIV infection in vivo

Molecular Architectures of Trimeric SIV and HIV-1 Envelope Glycoproteins on Intact Viruses: Strain-Dependent Variation in Quaternary Structure

The initial step in target cell infection by human, and the closely related simian immunodeficiency viruses (HIV and SIV, respectively) occurs with the binding of trimeric envelope glycoproteins (Env), composed of heterodimers of the viral transmembrane glycoprotein (gp41) and surface glycoprotein (gp120) to target T-cells. Knowledge of the molecular structure of trimeric Env on intact viruses is important both for understanding the molecular mechanisms underlying virus-cell interactions and for the design of effective immunogen-based vaccines to combat HIV/AIDS. Previous analyses of intact HIV-1 BaL virions have already resulted in structures of trimeric Env in unliganded and CD4-liganded states at ∼20 Å resolution. Here, we show that the molecular architectures of trimeric Env from SIVmneE11S, SIVmac239 and HIV-1 R3A strains are closely comparable to that previously determined for HIV-1 BaL, with the V1 and V2 variable loops located at the apex of the spike, close to the contact zone between virus and cell. The location of the V1/V2 loops in trimeric Env was definitively confirmed by structural analysis of HIV-1 R3A virions engineered to express Env with deletion of these loops. Strikingly, in SIV CP-MAC, a CD4-independent strain, trimeric Env is in a constitutively “open” conformation with gp120 trimers splayed out in a conformation similar to that seen for HIV-1 BaL Env when it is complexed with sCD4 and the CD4i antibody 17b. Our findings suggest a structural explanation for the molecular mechanism of CD4-independent viral entry and further establish that cryo-electron tomography can be used to discover distinct, functionally relevant quaternary structures of Env displayed on intact viruses