Acute exposure to sublethal doses of neonicotinoid insecticides increases heat tolerance in honey bees

The European honey bee, Apis mellifera L., is the single most valuable managed pollinator in the world. Poor colony health or unusually high colony losses of managed honey bees result from a myriad of stressors, which are more harmful in combination. Climate change is expected to accentuate the effects of these stressors, but the physiological and behavioral responses of honey bees to elevated temperatures while under simultaneous influence of one or more stressors remain largely unknown. Here we test the hypothesis that exposure to acute, sublethal doses of neonicotinoid insecticides reduce thermal tolerance in honey bees. We administered to bees oral doses of imidacloprid and acetamiprid at 1/5, 1/20, and 1/100 of LD50 and measured their heat tolerance 4 h post-feeding, using both dynamic and static protocols. Contrary to our expectations, acute exposure to sublethal doses of both insecticides resulted in higher thermal tolerance and greater survival rates of bees. Bees that ingested the higher doses of insecticides displayed a critical thermal maximum from 2 ˚C to 5 ˚C greater than that of the control group, and 67%–87% reduction in mortality. Our study suggests a resilience of honey bees to high temperatures when other stressors are present, which is consistent with studies in other insects. We discuss the implications of these results and hypothesize that this compensatory effect is likely due to induction of heat shock proteins by the insecticides, which provides temporary protection from elevated temperatures

Measurement of Inverse Pion Photoproduction at Energies Spanning the N(1440) Resonance

Differential cross sections for the process pi^- p -> gamma n have been measured at Brookhaven National Laboratory's Alternating Gradient Synchrotron with the Crystal Ball multiphoton spectrometer. Measurements were made at 18 pion momenta from 238 to 748 MeV/c, corresponding to E_gamma for the inverse reaction from 285 to 769 MeV. The data have been used to evaluate the gamma n multipoles in the vicinity of the N(1440) resonance. We compare our data and multipoles to previous determinations. A new three-parameter SAID fit yields 36 +/- 7 (GeV)^-1/2 X 10^-3 for the A^n_1/2 amplitude of the P_11.Comment: 14 pages, 8 figures, submitted to PR

Search for the lepton-family-number nonconserving decay \mu -> e + \gamma

The MEGA experiment, which searched for the muon- and electron-number violating decay \mu -> e + \gamma, is described. The spectrometer system, the calibrations, the data taking procedures, the data analysis, and the sensitivity of the experiment are discussed. The most stringent upper limit on the branching ratio of \mu -> e + \gamma) < 1.2 x 10^{-11} was obtained

Modeling Field Line Curvature Scattering Loss of 1–10 MeV Protons During Geomagnetic Storms

The proton radiation belt contains high fluxes of adiabatically trapped protons varying in energy from ∼one to hundreds of megaelectron volts (MeV). At large radial distances, magnetospheric field lines become stretched on the nightside of Earth and exhibit a small radius of curvature RC near the equator. This leads protons to undergo field line curvature (FLC) scattering, whereby changes to the first adiabatic invariant accumulate as field strength becomes nonuniform across a gyroorbit. The outer boundary of the proton belt at a given energy corresponds to the range of magnetic L shell over which this transition to nonadiabatic motion takes place, and is sensitive to the occurrence of geomagnetic storms. In this work, we first find expressions for nightside equatorial RC and field strength Be as functions of Dst and L* to fit the TS04 field model. We then apply the Tu et al. (2014, https://doi.org/10.1002/2014ja019864) condition for nonadiabatic onset to solve the outer boundary L*, and refine our expression for RC to achieve agreement with Van Allen Probes observations of 1–50 MeV proton flux over the 2014–2018 era. Finally, we implement this nonadiabatic onset condition into the British Antarctic Survey proton belt model (BAS-PRO) to solve the temporal evolution of proton fluxes at L ≤ 4. Compared with observations, BAS-PRO reproduces storm losses due to FLC scattering, but there is a discrepancy in mid-2017 that suggests a ∼5 MeV proton source not accounted for. Our work sheds light on outer zone proton belt variability at 1–10 MeV and demonstrates a useful tool for real-time forecasting

An Experimental Exploration of the QCD Phase Diagram: The Search for the Critical Point and the Onset of De-confinement

The QCD phase diagram lies at the heart of what the RHIC Physics Program is all about. While RHIC has been operating very successfully at or close to its maximum energy for almost a decade, it has become clear that this collider can also be operated at lower energies down to 5 GeV without extensive upgrades. An exploration of the full region of beam energies available at the RHIC facility is imperative. The STAR detector, due to its large uniform acceptance and excellent particle identification capabilities, is uniquely positioned to carry out this program in depth and detail. The first exploratory beam energy scan (BES) run at RHIC took place in 2010 (Run 10), since several STAR upgrades, most importantly a full barrel Time of Flight detector, are now completed which add new capabilities important for the interesting physics at BES energies. In this document we discuss current proposed measurements, with estimations of the accuracy of the measurements given an assumed event count at each beam energy.Comment: 59 pages, 78 figure

Longitudinal Spin Transfer to Λ\Lambda and Λˉ\bar{\Lambda} Hyperons in Polarized Proton-Proton Collisions at s\sqrt{s} = 200 GeV

The longitudinal spin transfer, $D_{LL}$, from high energy polarized protons to $\Lambda$ and $\bar{\Lambda}$ hyperons has been measured for the first time in proton-proton collisions at $\sqrt{s} = 200 \mathrm{GeV}$ with the STAR detector at RHIC. The measurements cover pseudorapidity, $\eta$, in the range $|\eta| < 1.2$ and transverse momenta, $p_\mathrm{T}$, up to $4 \mathrm{GeV}/c$. The longitudinal spin transfer is found to be $D_{LL}= -0.03\pm 0.13(\mathrm{stat}) \pm 0.04(\mathrm{syst})$ for inclusive $\Lambda$ and $D_{LL} = -0.12 \pm 0.08(\mathrm{stat}) \pm 0.03(\mathrm{syst})$ for inclusive $\bar{\Lambda}$ hyperons with $= 0.5$ and $= 3.7 \mathrm{GeV}/c$. The dependence on $\eta$ and $p_\mathrm{T}$ is presented.Comment: 5 pages, 4 figure

Measurements of Dihadron Correlations Relative to the Event Plane in Au+Au Collisions at sNN=200\sqrt{s_{NN}}=200 GeV

Dihadron azimuthal correlations containing a high transverse momentum (\pt) trigger particle are sensitive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium, i.e. jet-quenching. Previous measurements revealed a strong modification to dihadron azimuthal correlations in Au+Au collisions with respect to \pp\ and \dAu\ collisions. The modification increases with the collision centrality, suggesting a path-length dependence to the jet-quenching effect. This paper reports STAR measurements of dihadron azimuthal correlations in mid-central (20-60\%) Au+Au collisions at \snn=200~GeV as a function of the trigger particle's azimuthal angle relative to the event plane, \phis=|\phit-\psiEP|. The azimuthal correlation is studied as a function of both the trigger and associated particle \pt. The subtractions of the combinatorial background and anisotropic flow, assuming Zero Yield At Minimum (\zyam), are described. The away-side correlation is strongly modified, and the modification varies with \phis, which is expected to be related to the path-length that the away-side parton traverses. The pseudo-rapidity (\deta) dependence of the near-side correlation, sensitive to long range \deta correlations (the ridge), is also investigated. The ridge and jet-like components of the near-side correlation are studied as a function of \phis. The ridge appears to drop with increasing \phis while the jet-like component remains approximately constant. ...Comment: 50 pages, 39 figures, 6 table

Studies of di-jet survival and surface emission bias in Au+Au collisions via angular correlations with respect to back-to-back leading hadrons

We report first results from an analysis based on a new multi-hadron correlation technique, exploring jet-medium interactions and di-jet surface emission bias at RHIC. Pairs of back-to-back high transverse momentum hadrons are used for triggers to study associated hadron distributions. In contrast with two- and three-particle correlations with a single trigger with similar kinematic selections, the associated hadron distribution of both trigger sides reveals no modification in either relative pseudo-rapidity or relative azimuthal angle from d+Au to central Au+Au collisions. We determine associated hadron yields and spectra as well as production rates for such correlated back-to-back triggers to gain additional insights on medium properties.Comment: By the STAR Collaboration. 6 pages, 2 figure

Observation of the antimatter helium-4 nucleus

High-energy nuclear collisions create an energy density similar to that of the universe microseconds after the Big Bang, and in both cases, matter and antimatter are formed with comparable abundance. However, the relatively short-lived expansion in nuclear collisions allows antimatter to decouple quickly from matter, and avoid annihilation. Thus, a high energy accelerator of heavy nuclei is an efficient means of producing and studying antimatter. The antimatter helium-4 nucleus ($^4\bar{He}$), also known as the anti-{\alpha} ($\bar{\alpha}$), consists of two antiprotons and two antineutrons (baryon number B=-4). It has not been observed previously, although the {\alpha} particle was identified a century ago by Rutherford and is present in cosmic radiation at the 10% level. Antimatter nuclei with B < -1 have been observed only as rare products of interactions at particle accelerators, where the rate of antinucleus production in high-energy collisions decreases by about 1000 with each additional antinucleon. We present the observation of the antimatter helium-4 nucleus, the heaviest observed antinucleus. In total 18 $^4\bar{He}$ counts were detected at the STAR experiment at RHIC in 10$^9$ recorded Au+Au collisions at center-of-mass energies of 200 GeV and 62 GeV per nucleon-nucleon pair. The yield is consistent with expectations from thermodynamic and coalescent nucleosynthesis models, which has implications beyond nuclear physics.Comment: 19 pages, 4 figures. Submitted to Nature. Under media embarg