•Sorghum accumulates dhurrin (cyanide) and nitrate; forage can be toxic.•Partitioning of N to cyanide and nitrate was measured in FACE studies.•Cyanide, nitrate accumulation depended on tissue type, ...plant age and irrigation.•Drought effected increases in cyanide and nitrate were not moderated at high CO2.•Risk of toxicity likely to increase with climate change but not directly from rising CO2.
Sorghum Sorghum bicolor (L.) Moench is the world’s fifth most important crop, grown for forage, grain, and as a biofuel. Fast growing and drought tolerant, it is increasingly being planted as a climate change-ready alternative to maize. All parts of the sorghum plant except the grain contain the cyanogenic glucoside dhurrin, which breaks down to release hydrogen cyanide (prussic acid) when plant tissue is disrupted. Fresh forage, hay and silage may be toxic to stock when derived from plants that are young, droughted or heavily fertilized. Sorghum also stores nitrate, which can cause nitrite toxicity. The impact of elevated CO2 on dhurrin and nitrate concentration is unknown. It is important to understand how global environmental change will affect composition in order to be able to predict the safety of the crop in coming decades. Sorghum was grown experimentally at elevated CO2 in two free-air CO2 enrichment (FACE) experiments at ambient and elevated CO2 (ca. 550ppm) and either irrigated regularly or only once after sowing in consecutive years and sampled at different stages of development. Since FACE-grown sorghum has been shown to have improved water status we hypothesized that they would contain less dhurrin. We found the most important factors governing cyanide concentration were (in decreasing order): plant age, irrigation treatment and tissue type. For nitrate, tissue type was by far the most important factor, followed by plant age, and then irrigation treatment. The concentration of CO2 in the atmosphere had no significant effect on the total nitrogen concentration, or the concentrations of cyanide and nitrate. As sorghum is becomes more widely used for forage, it will be important to have simple methods to assess the cyanide levels in the field or to develop new, low cyanogenic varieties to ensure that it is safe for grazing.
We report a new measurement of D0-meson production at mid-rapidity (| y | < 1) in Au + Au collisions at $\sqrt{s}$$_ {NN}$ = 200 GeV utilizing the heavy flavor tracker, a high resolution silicon ...detector at the STAR experiment. Invariant yields of D0 mesons with transverse momentum pT ≲ 9 GeV / c are reported in various centrality bins (0–10%, 10–20%, 20–40%, 40–60%, and 60–80%). Blast-wave thermal models are used to fit the D0-meson pT spectra to study D0 hadron kinetic freeze-out properties. The average radial flow velocity extracted from the fit is considerably smaller than that of light hadrons (π, K, and p), but comparable to that of hadrons containing multiple strange quarks (Φ, Ξ -) , indicating that D0 mesons kinetically decouple from the system earlier than light hadrons. The calculated D0 nuclear modification factors reaffirm that charm quarks suffer a large amount of energy loss in the medium, similar to those of light quarks for pT > 4 GeV/c in central 0–10% Au + Au collisions. At low pT, the nuclear modification factors show a characteristic structure qualitatively consistent with the expectation from model predictions that charm quarks gain sizable collective motion during the medium evolution. The improved measurements are expected to offer new constraints to model calculations and help gain further insights into the hot and dense medium created in these collisions.
Atmospheric CO2 concentration (C(a)) continues to rise. An imperative exists, therefore, to elucidate the interactive effects of elevated C(a) and drought on plant water relations of wheat (Triticum ...aestivum L.). A spring wheat (cv. Yecora Rojo) crop was exposed to ambient (Control: 370 micromol mol(-1)) and free-air CO2 enrichment (FACE: ambient + 180 micromol mol(-1)) under ample (Wet), and reduced (Dry), water supplies (100 and 50% replacement of evapotranspiration, respectively) over a 2-yr study. Our objective was to characterize and quantify the responses of 26 edaphic, gas exchange, water relations, carbohydrate pool dynamics, growth, and development parameters to rising C(a) and drought. Increasing C(a) minimized the deleterious effects of soil-water depletion by increasing drought avoidance (i.e., lower stomatal conductance and transpiration rate, and growth and development of a more robust root system) and drought tolerance (i.e., enhanced osmoregulation and adaptation of tissue) mechanisms, resulting in a 30% reduction in water stress-induced midafternoon depressions in net assimilation rate. An elevated C(a)-based increase in daily and seasonal carbon gain resulted in a positive feedback between source capacity (shoots) and sink demand (roots). Devoid of a concomitant rise in global temperature resulting from the rise in C(a), improved water relations for a herbaceous, cool-season, annual, C3 cereal monocot grass (i.e., wheat) are anticipated in a future high-CO2 world. These findings are applicable to other graminaceous species of a similar function-type as wheat common to temperate zone grassland prairies and savannas, especially under dryland conditions.
We report new STAR measurements of the single-spin asymmetries AL for W+ and W− bosons produced in polarized proton-proton collisions at s=510 GeV as a function of the decay-positron and ...decay-electron pseudorapidity. The data were obtained in 2013 and correspond to an integrated luminosity of 250 pb−1. The results are combined with previous results obtained with 86 pb−1. A comparison with theoretical expectations based on polarized lepton-nucleon deep-inelastic scattering and prior polarized proton-proton data suggests a difference between the u¯ and d¯ quark helicity distributions for 0.05<x<0.25. In addition, we report new results for the double-spin asymmetries ALL for W±, as well as AL for Z/γ* production and subsequent decay into electron-positron pairs.
We report on the first measurements of J/ψ production at very low transverse momentum (pT<0.2 GeV/c) in hadronic Au+Au collisions at sNN=200 GeV and U+U collisions at sNN=193 GeV. Remarkably, the ...inferred nuclear modification factor of J/ψ at midrapidity in Au+Au (U+U) collisions reaches about 24 (52) for pT<0.05 GeV/c in the 60%–80% collision centrality class. This noteworthy enhancement cannot be explained by hadronic production accompanied by cold and hot medium effects. In addition, the dN/dt distribution of J/ψ for the very low pT range is presented for the first time. The distribution is consistent with that expected from the Au nucleus and shows a hint of interference. Comparison of the measurements to theoretical calculations of coherent production shows that the excess yield can be described reasonably well and reveals a partial disruption of coherent production in semicentral collisions, perhaps due to the violent hadronic interactions. Incorporating theoretical calculations, the results strongly suggest that the dramatic enhancement of J/ψ yield observed at extremely low pT originates from coherent photon-nucleus interactions. In particular, coherently produced J/ψ's in violent hadronic collisions may provide a novel probe of the quark-gluon plasma.
We introduce two-particle pt correlations as a function of event centrality for Au+Au collisions at √sNN = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV at the Relativistic Heavy Ion Collider ...using the STAR detector. These results are compared to previous measurements from CERES at the Super Proton Synchrotron and from ALICE at the Large Hadron Collider. The data are compared with UrQMD model calculations and with a model based on a Boltzmann-Langevin approach incorporating effects from thermalization. The relative dynamical correlations for Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV reveal a power law dependence on the number of participant nucleons 3 and agree with the results for Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV from ALICE. As the collision energy is lowered from $\sqrt{s_{NN}}$ = 200 GeV to 7.7 GeV, the centrality dependence of the relative dynamical correlations departs from the power law behavior observed at the higher collision energies. In central collisions, the relative dynamical correlations increase with collision energy up to $\sqrt{s_{NN}}$ = 200 GeV in contrast to previous measurements that showed little dependence on the collision energy.
Nonmonotonic variation with collision energy (sqrts_{NN}) of the moments of the net-baryon number distribution in heavy-ion collisions, related to the correlation length and the susceptibilities of ...the system, is suggested as a signature for the quantum chromodynamics critical point. We report the first evidence of a nonmonotonic variation in the kurtosis times variance of the net-proton number (proxy for net-baryon number) distribution as a function of sqrts_{NN} with 3.1 σ significance for head-on (central) gold-on-gold (Au+Au) collisions measured solenoidal tracker at Relativistic Heavy Ion Collider. Data in noncentral Au+Au collisions and models of heavy-ion collisions without a critical point show a monotonic variation as a function of sqrts_{NN}.
The longitudinal spin transfer DLL to Λ and Λ hyperons produced in high-energy polarized proton-proton collisions is expected to be sensitive to the helicity distribution functions of strange quarks ...and antiquarks of the proton, and to longitudinally polarized fragmentation functions. We report an improved measurement of DLL from data obtained at a center-of-mass energy of √s = 200 GeV with the STAR detector at RHIC. The data have an approximately twelve times larger figure of merit than prior results and cover |η| < 1.2 in pseudorapidity with transverse momenta pT up to 6 GeV / c. In the forward scattering hemisphere at largest pT, the longitudinal spin transfer is found to be DLL = −0.036 ± 0.048 (stat) ± 0.013 (sys) for Λ hyperons and DLL = 0.032 ± 0.043 (stat) ± 0.013 ( sys ) for Λ antihyperons. The dependences on η and pT are presented and compared with model evaluations.
We report on the first measurement of charm-strange meson $D_s^{\pm}$ production at midrapidity in Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV from the STAR experiment. The yield ratio ...between strange ($D_{s}^{\pm}$) and non-strange ($D^{0}$) open-charm mesons is presented and compared to model calculations. A significant enhancement, relative to a PYTHIA simulation of $p$+$p$ collisions, is observed in the $D_{s}^{\pm}/D^0$ yield ratio in Au+Au collisions over a large range of collision centralities. Model calculations incorporating abundant strange-quark production in the quark-gluon plasma (QGP) and coalescence hadronization qualitatively reproduce the data. The transverse-momentum integrated yield ratio of $D_{s}^{\pm}/D^0$ at midrapidity is consistent with a prediction from a statistical hadronization model with the parameters constrained by the yields of light and strange hadrons measured at the same collision energy. These results suggest that the coalescence of charm quarks with strange quarks in the QGP plays an important role in $D_{s}^{\pm}$ meson production in heavy-ion collisions.
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