Background. Recent evidence suggests that decreases in morbidity and mortality in cohorts of adults infected with human immunodeficiency virus (HIV) are showing signs of reversal. We describe changes ...over time in these characteristics and in the response to treatment among children in the United Kingdom and Ireland with perinatally acquired HIV infection, many of whom are now adolescents. Methods. We analyzed prospective cohort data reported to the National Study of HIV in Pregnancy and Childhood (NSHPC) and the Collaborative HIV Paediatric Study. Results. By mid 2006, 1441 HIV-infected children were reported to NSHPC; 40% were ⩾10 years old at their most recent follow-up visit, and 34% were receiving care outside London. The proportion of children born abroad increased from 24% during 1994–1996 to 64% during 2003–2006. The percentage of total child time during which children received highly active antiretroviral therapy (HAART) increased from 36% during 1997–1999 to 61% during 2000–2002 and 63% during 2003–2006. Of children who were naive to antiretroviral therapy at the start of HAART, the percentage with an HIV-1 RNA load of <400 copies/mL after 12 months increased from 52% during 1997–1999 to 79% during 2003–2006. In multivariate analysis, only calendar time predicted virological response, whereas both younger age and lower CD4 cell percentage at HAART initiation predicted increases of >10% in the CD4 cell percentage. A total of 31% of children aged 5–14 years and 38% aged ⩾15 years at their most recent follow-up visit had been exposed to drugs from each of the 3 main HAART classes. The rate of AIDS and mortality combined decreased from 13.3 cases per 100 person-years before 1997 to 3.1 and 2.5 cases per 100 person-years, respectively, during 2000–2002 and 2003–2006; rates of hospital admission also declined during this interval. Of 18 children known to have died since 2003, 9 died within 1 month after presentation. Conclusions. Morbidity and mortality rates among HIV-infected children continue to decrease over time. Because these children are increasingly dispersed outside London, specialist care is now provided in national clinical networks. Transition pathways to adolescent and adult services and long-term observation to monitor the effects of prolonged exposure to both HIV and HAART are required.
Anaerobic degradation of the environmental pollutant toluene is initiated by the glycyl radical enzyme benzylsuccinate synthase (BSS), which catalyzes the radical addition of toluene to fumarate, ...forming benzylsuccinate. We have determined crystal structures of the catalytic α-subunit of BSS with its accessory subunits β and γ, which both bind a 4Fe-4S cluster and are essential for BSS activity in vivo. We find that BSSα has the common glycyl radical enzyme fold, a 10-stranded β/α-barrel that surrounds the glycyl radical cofactor and active site. Both accessory subunits β and γ display folds related to high potential iron—sulfur proteins but differ substantially from each other in how they interact with the α-subunit. BSSγ binds distally to the active site, burying a hydrophobic region of BSSα, whereas BSSβ binds to a hydrophilic surface of BSSα that is proximal to the active site. To further investigate the function of BSSβ, we determined the structure of a BSSαγ complex. Remarkably, we find that the barrel partially opens, allowing the C-terminal region of BSSα that houses the glycyl radical to shift within the barrel toward an exit pathway. The structural changes that we observe in the BSSαγ complex center around the crucial glycyl radical domain, thus suggesting a role for BSSβ in modulating the conformational dynamics required for enzyme activity. Accompanying proteolysis experiments support these structural observations.
The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is designed to accurately observe ultra-high-energy cosmic rays (UHECRs) and cosmic neutrinos from space with sensitivity over the full ...celestial sky. POEMMA will observe the air fluorescence produced by extensive air showers (EASs) from UHECRs and potentially UHE neutrinos above 20 EeV. Additionally, POEMMA has the ability to observe the Cherenkov signal from upward-moving EASs induced by Earth-interacting tau neutrinos above 20 PeV. The POEMMA spacecraft are designed to quickly re-orientate to follow up transient neutrino sources and obtain currently unparalleled neutrino flux sensitivity. Developed as a NASA Astrophysics Probe-class mission, POEMMA consists of two identical satellites flying in loose formation in 525 km altitude orbits. Each POEMMA instrument incorporates a wide field-of-view (45°) Schmidt telescope with an optical collecting area of over 6 sq. m. The hybrid focal surface of each telescope includes a fast (1 μs) near-ultraviolet camera for EAS fluorescence observations and an ultrafast (10 ns) optical camera for Cherenkov EAS observations. In a 5-year mission, POEMMA will provide measurements that open new multi-messenger windows onto the most energetic events in the universe, enabling the study of new astrophysics and particle physics at these extreme energies.
Global polarization of Ξ and Ω hyperons has been measured for the first time in Au + Au collisions at √sNN = 200 GeV. The measurements of the Ξ− and ... hyperon polarization have been performed by ...two independent methods, via analysis of the angular distribution of the daughter particles in the parity violating weak decay Ξ → Λ + π, as well as by measuring the polarization of the daughter Λ hyperon, polarized via polarization transfer from its parent. The polarization, obtained by combining the results from the two methods and averaged over Ξ− and ... is measured to be ⟨PΞ⟩ = 0.47 ± 0.10(stat) ± 0.23(syst)% for the collision centrality 20%–80%. The ⟨PΞ⟩ is found to be slightly larger than the inclusive Λ polarization and in reasonable agreement with a multiphase transport model. The ⟨PΞ⟩ is found to follow the centrality dependence of the vorticity predicted in the model, increasing toward more peripheral collisions. The global polarization of Ω, ⟨PΩ⟩ = 1.11 ± 0.87(stat) ± 1.97(syst)% was obtained by measuring the polarization of daughter Λ in the decay Ω → Λ + K, assuming the polarization transfer factor CΩΛ = 1.
Measurements of the production of forward jets from transversely polarized proton collisions at s=500 GeV conducted at the Relativistic Heavy Ion Collider (RHIC) are reported. Our measured jet cross ...section is consistent with hard scattering expectations. Our measured analyzing power for forward jet production is small and positive, and provides constraints on the Sivers functions that are related to partonic orbital angular momentum through theoretical models.
According to the CPT theorem, which states that the combined operation of charge conjugation, parity transformation and time reversal must be conserved, particles and their antiparticles should have ...the same mass and lifetime but opposite charge and magnetic moment. Here, we test CPT symmetry in a nucleus containing a strange quark, more specifically in the hypertriton. This hypernucleus is the lightest one yet discovered and consists of a proton, a neutron and a Λ hyperon. With data recorded by the STAR detector1–3 at the Relativistic Heavy Ion Collider, we measure the Λ hyperon binding energy BΛ for the hypertriton, and find that it differs from the widely used value4 and from predictions5–8, where the hypertriton is treated as a weakly bound system. Our results place stringent constraints on the hyperon–nucleon interaction9,10 and have implications for understanding neutron star interiors, where strange matter may be present11. A precise comparison of the masses of the hypertriton and the antihypertriton allows us to test CPT symmetry in a nucleus with strangeness, and we observe no deviation from the expected exact symmetry.The STAR collaboration reports a measurement of the mass difference and binding energy of the hypertriton and its antiparticle. This work constrains the hyperon–nucleon interaction and allows us to test the CPT theorem in a nucleus with strangeness.
We report precision measurements of hypernuclei $^3_ΛH$ and $^4_ΛH$ lifetimes obtained from Au + Au collisions at $\sqrt{sNN}$ = 3.0 GeV and 7.2 GeV collected by the STAR experiment at the ...Relativistic Heavy Ion Collider, and the first measurement of $^3_ΛH$ and $^4_ΛH$ midrapidity yields in Au + Au collisions at $\sqrt{sNN}$ = 3.0 GeV. $^3_ΛH$ and $^4_ΛH$, being the two simplest bound states composed of hyperons and nucleons, are cornerstones in the field of hypernuclear physics. Their lifetimes are measured to be 221 ± 15 (stat) ± 19 (syst) ps for $^3_ΛH$ and 218 ± 6 (stat) ± 13 (syst) ps for $^4_ΛH$. The pT-integrated yields of $^3_ΛH$ and $^4_ΛH$ are presented in different centrality and rapidity intervals. It is observed that the shape of the rapidity distribution of $4_ΛH$ is different for 0%–10% and 10%–50% centrality collisions. Thermal model calculations, using the canonical ensemble for strangeness, describes the $^3_ΛH$ yield well, while underestimating the $^4_ΛH$ yield. Transport models, combining baryonic mean-field and coalescence (jam) or utilizing dynamical cluster formation via baryonic interactions (phqmd) for light nuclei and hypernuclei production, approximately describe the measured $^3_ΛH$ and $^4_ΛH$ yields. Our measurements provide means to precisely assess our understanding of the fundamental baryonic interactions with strange quarks, which can impact our understanding of more complicated systems involving hyperons, such as the interior of neutron stars or exotic hypernuclei.
The chiral magnetic effect (CME) refers to charge separation along a strong magnetic field due to imbalanced chirality of quarks in local parity and charge-parity violating domains in quantum ...chromodynamics. The experimental measurement of the charge separation is made difficult by the presence of a major background from elliptic azimuthal anisotropy. This background and the CME signal have different sensitivities to the spectator and participant planes, and could thus be determined by measurements with respect to these planes. We report such measurements in Au+Au collisions at a nucleon-nucleon center-of-mass energy of 200 GeV at the Relativistic Heavy-Ion Collider. It is found that the charge separation, with the flow background removed, is consistent with zero in peripheral (large impact parameter) collisions. Some indication of finite CME signals is seen with a significance of 1–3 standard deviations in mid-central (intermediate impact parameter) collisions. Furthermore, significant residual background effects may, however, still be present.
We present results from a harmonic decomposition of two-particle azimuthal correlations measured with the STAR detector in Au+Au collisions for energies ranging from sqrts_{NN}=7.7 to 200 GeV. The ...third harmonic v_{3}^{2}{2}=⟨cos3(ϕ_{1}-ϕ_{2})⟩, where ϕ_{1}-ϕ_{2} is the angular difference in azimuth, is studied as a function of the pseudorapidity difference between particle pairs Δη=η_{1}-η_{2}. Nonzero v_{3}^{2}{2} is directly related to the previously observed large-Δη narrow-Δϕ ridge correlations and has been shown in models to be sensitive to the existence of a low viscosity quark gluon plasma phase. For sufficiently central collisions, v_{3}^{2}{2} persist down to an energy of 7.7 GeV, suggesting that quark gluon plasma may be created even in these low energy collisions. In peripheral collisions at these low energies, however, v_{3}^{2}{2} is consistent with zero. When scaled by the pseudorapidity density of charged-particle multiplicity per participating nucleon pair, v_{3}^{2}{2} for central collisions shows a minimum near sqrts_{NN}=20 GeV.
We report the beam energy and collision centrality dependence of fifth and sixth order cumulants (C_{5}, C_{6}) and factorial cumulants (κ_{5}, κ_{6}) of net-proton and proton number distributions, ...from center-of-mass energy (sqrts_{NN}) 3 GeV to 200 GeV Au+Au collisions at RHIC. Cumulant ratios of net-proton (taken as proxy for net-baryon) distributions generally follow the hierarchy expected from QCD thermodynamics, except for the case of collisions at 3 GeV. The measured values of C_{6}/C_{2} for 0%-40% centrality collisions show progressively negative trend with decreasing energy, while it is positive for the lowest energy studied. These observed negative signs are consistent with QCD calculations (for baryon chemical potential, μ_{B}≤110 MeV) which contains the crossover transition range. In addition, for energies above 7.7 GeV, the measured proton κ_{n}, within uncertainties, does not support the two-component (Poisson+binomial) shape of proton number distributions that would be expected from a first-order phase transition. Taken in combination, the hyperorder proton number fluctuations suggest that the structure of QCD matter at high baryon density, μ_{B}∼750 MeV at sqrts_{NN}=3 GeV is starkly different from those at vanishing μ_{B}∼24 MeV at sqrts_{NN}=200 GeV and higher collision energies.
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