Assessment of pollen rewards by foraging bees

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.The removal of pollen by flower-visiting insects is costly to plants, not only in terms of production, but also via lost reproductive potential. Modern angiosperms have evolved various reward strategies to limit these costs, yet many plant species still offer pollen as a sole or major reward for pollinating insects. 2. The benefits plants gain by offering pollen as a reward for pollinating are defined by the behaviour of their pollinators, some of which feed on the pollen at the flower, while others collect pollen to provision offspring. 3. We explore how pollen impacts on the behaviour and foraging decisions of pollen-collecting bees, drawing comparisons with what is known for nectar rewards. This question is of particular interest since foraging bees typically do not ingest pollen during collection, meaning the sensory pathways involved in evaluating this resource are not immediately obvious. 4. Previous research focussed on whether foraging bees can determine the quality of pollen sources offered by different plant species, and attempted to infer the mechanisms underpinning such evaluations, mainly through observations of collection preferences in the field 5. More recent experimental research has started to focus on if pollen itself can mediate the detection of, and learning about, pollen sources and associated floral cues. 6. We review advancements in the understanding of how bees forage for pollen and respond to variation in pollen quality, and discuss future directions for studying how this ancestral floral food reward shapes the behaviour of pollinating insects

Simulations of preindustrial, present-day, and 2100 conditions in the NASA GISS composition and climate model G-PUCCINI

International audienceA model of atmospheric composition and climate has been developed at the NASA Goddard Institute for Space Studies (GISS) that includes composition seamlessly from the surface to the lower mesosphere. The model is able to capture many features of the observed magnitude, distribution, and seasonal cycle of trace species. The simulation is especially realistic in the troposphere. In the stratosphere, high latitude regions show substantial biases during period when transport governs the distribution as meridional mixing is too rapid in this model version. In other regions, including the extrapolar tropopause region that dominates radiative forcing (RF) by ozone, stratospheric gases are generally well-simulated. The model's stratosphere-troposphere exchange (STE) agrees well with values inferred from observations for both the global mean flux and the ratio of Northern (NH) to Southern Hemisphere (SH) downward fluxes. Simulations of preindustrial (PI) to present-day (PD) changes show tropospheric ozone burden increases of 11% while the stratospheric burden decreases by 18%. The resulting tropopause RF values are ?0.06 W/m2 from stratospheric ozone and 0.40 W/m2 from tropospheric ozone. Global mean mass-weighted OH decreases by 16% from the PI to the PD. STE of ozone also decreased substantially during this time, by 14%. Comparison of the PD with a simulation using 1979 pre-ozone hole conditions for the stratosphere shows a much larger downward flux of ozone into the troposphere in 1979, resulting in a substantially greater tropospheric ozone burden than that seen in the PD run. This implies that reduced STE due to stratospheric ozone depletion may have offset as much as 2/3 of the tropospheric ozone burden increase from PI to PD. However, the model overestimates the downward flux of ozone at high Southern latitudes, so this estimate is likely an upper limit. In the future, the tropospheric ozone burden increases by 101% in 2100 for the A2 scenario including both emissions and climate changes. The primary reason is enhanced STE, which increases by 124% (168% in the SH extratropics, and 114% in the NH extratropics). Climate plays a minimal role in the SH increases, but contributes 38% in the NH. Chemistry and dry deposition both change so as to reduce tropospheric ozone, partially in compensation for the enhanced STE, but the increased ozone influx dominates the burden changes. The net RF due to projected ozone changes is 0.8 W/m2 for A2. The influence of climate change alone is ?0.2 W/m2, making it a substantial contributor to the net RF. The tropospheric oxidation capacity increases seven percent in the full A2 simulation, and 36% due to A2 climate change alone

Comparison of Temperature-Dependent Hadronic Current Correlation Functions Calculated in Lattice Simulations of QCD and with a Chiral Lagrangian Model

The Euclidean-time hadronic current correlation functions, $G_P(\tau, T)$ and $G_V(\tau, T)$, of pseudoscalar and vector currents have recently been calculated in lattice simulations of QCD and have been used to obtain the corresponding spectral functions. We have used the Nambu-Jona-Lasinio (NJL) model to calculate such spectral functions, as well as the Euclidean-time correlators, and have made a comparison to the lattice results for the correlators. We find evidence for the type of temperature dependence of the NJL coupling parameters that we have used in previous studies of the mesonic confinement-deconfinement transition. We also see that the spectral functions obtained when using the maximum-entropy-method (MEM) and the lattice data differ from the spectral functions that we calculate in our chiral model. However, our results for the Euclidean-time correlators are in general agreement with the lattice results, with better agreement when our temperature-dependent coupling parameters are used than when temperature-independent parameters are used for the NJL model. We also discuss some additional evidence for the utility of temperature-dependent coupling parameters for the NJL model. For example, if the constituent quark mass at T=0 is $352 {MeV}$ in the chiral limit, the transition temperature is $T_c=208 {MeV}$ for the NJL model with a standard momentum cutoff parameter. (If a Gaussian momentum cutoff is used, we find $T_c=225 {MeV}$ in the chiral limit, with $m=368 {MeV}$ at T=0.) The introduction of a weak temperature dependence for the coupling constant will move the value of $T_c$ into the range 150-170 MeV, which is more in accord with what is found in lattice simulations of QCD with dynamical quarks

Continuous measurements of greenhouse gases and atmospheric oxygen at the Namib Desert atmospheric observatory

A new coastal background site has been established for observations of greenhouse gases (GHGs) in the central Namib Desert at Gobabeb, Namibia. The location of the site was chosen to provide observations for a data-poor region in the global sampling network for GHGs. Semi-automated continuous measurements of carbon dioxide, methane, nitrous oxide, carbon monoxide, atmospheric oxygen, and basic meteorology are made at a height of 21 m a.g.l., 50 km from the coast at the northern border of the Namib Sand Sea. Atmospheric oxygen is measured with a differential fuel cell analyzer (DFCA). Carbon dioxide and methane are measured with an early-model cavity ring-down spectrometer (CRDS); nitrous oxide and carbon monoxide are measured with an off-axis integrated cavity output spectrometer (OA-ICOS). Instrument-specific water corrections are employed for both the CRDS and OA-ICOS instruments in lieu of drying. The performance and measurement uncertainties are discussed in detail. As the station is located in a remote desert environment, there are some particular challenges, namely fine dust, high diurnal temperature variability, and minimal infrastructure. The gas handling system and calibration scheme were tailored to best fit the conditions of the site. The CRDS and DFCA provide data of acceptable quality when base requirements for operation are met, specifically adequate temperature control in the laboratory and regular supply of electricity. In the case of the OA-ICOS instrument, performance is significantly improved through the implementation of a drift correction through frequent measurements of a reference cylinder

A device for feasible fidelity, purity, Hilbert-Schmidt distance and entanglement witness measurements

A generic model of measurement device which is able to directly measure commonly used quantum-state characteristics such as fidelity, overlap, purity and Hilbert-Schmidt distance for two general uncorrelated mixed states is proposed. In addition, for two correlated mixed states, the measurement realizes an entanglement witness for Werner's separability criterion. To determine these observables, the estimation only one parameter - the visibility of interference, is needed. The implementations in cavity QED, trapped ion and electromagnetically induced transparency experiments are discussed.Comment: 6 pages, 3 figure

Superconductors with Magnetic Impurities: Instantons and Sub-gap States

When subject to a weak magnetic impurity potential, the order parameter and quasi-particle energy gap of a bulk singlet superconductor are suppressed. According to the conventional mean-field theory of Abrikosov and Gor'kov, the integrity of the energy gap is maintained up to a critical concentration of magnetic impurities. In this paper, a field theoretic approach is developed to critically analyze the validity of the mean field theory. Using the supersymmetry technique we find a spatially homogeneous saddle-point that reproduces the Abrikosov-Gor'kov theory, and identify instanton contributions to the density of states that render the quasi-particle energy gap soft at any non-zero magnetic impurity concentration. The sub-gap states are associated with supersymmetry broken field configurations of the action. An analysis of fluctuations around these configurations shows how the underlying supersymmetry of the action is restored by zero modes. An estimate of the density of states is given for all dimensionalities. To illustrate the universality of the present scheme we apply the same method to study `gap fluctuations' in a normal quantum dot coupled to a superconducting terminal. Using the same instanton approach, we recover the universal result recently proposed by Vavilov et al. Finally, we emphasize the universality of the present scheme for the description of gap fluctuations in d-dimensional superconducting/normal structures.Comment: 18 pages, 9 eps figure

A global Mars dust composition refined by the Alpha-Particle X-ray Spectrometer in Gale Crater

Modern Martian dust is similar in composition to the global soil unit and bulk basaltic Mars crust, but it is enriched in S and Cl. The Alpha Particle X-ray Spectrometer (APXS) on the Mars Science Laboratory Curiosity rover analyzed air fall dust on the science observation tray (o-tray) in Gale Crater to determine dust oxide compositions. The o-tray dust has the highest concentrations of SO3 and Cl measured in Mars dust (SO3 8.3%; Cl 1.1 wt %). The molar S/Cl in the dust (3.35 ± 0.34) is consistent with previous studies of Martian dust and soils (S/Cl = 3.7 ± 0.7). Fe is also elevated ~25% over average Mars soils and the bulk crust. These enrichments link air fall dust with the S-, Cl-, and Fe-rich X-ray amorphous component of Gale Crater soil. Dust and soil have the same S/Cl, constraining the surface concentrations of S and Cl on a global scale

Haloperidol and Ziprasidone for Treatment of Delirium in Critical Illness

BACKGROUND: There are conflicting data on the effects of antipsychotic medications on delirium in patients in the intensive care unit (ICU). METHODS: In a randomized, double-blind, placebo-controlled trial, we assigned patients with acute respiratory failure or shock and hypoactive or hyperactive delirium to receive intravenous boluses of haloperidol (maximum dose, 20 mg daily), ziprasidone (maximum dose, 40 mg daily), or placebo. The volume and dose of a trial drug or placebo was halved or doubled at 12-hour intervals on the basis of the presence or absence of delirium, as detected with the use of the Confusion Assessment Method for the ICU, and of side effects of the intervention. The primary end point was the number of days alive without delirium or coma during the 14-day intervention period. Secondary end points included 30-day and 90-day survival, time to freedom from mechanical ventilation, and time to ICU and hospital discharge. Safety end points included extrapyramidal symptoms and excessive sedation. RESULTS: Written informed consent was obtained from 1183 patients or their authorized representatives. Delirium developed in 566 patients (48%), of whom 89% had hypoactive delirium and 11% had hyperactive delirium. Of the 566 patients, 184 were randomly assigned to receive placebo, 192 to receive haloperidol, and 190 to receive ziprasidone. The median duration of exposure to a trial drug or placebo was 4 days (interquartile range, 3 to 7). The median number of days alive without delirium or coma was 8.5 (95% confidence interval [CI], 5.6 to 9.9) in the placebo group, 7.9 (95% CI, 4.4 to 9.6) in the haloperidol group, and 8.7 (95% CI, 5.9 to 10.0) in the ziprasidone group (P=0.26 for overall effect across trial groups). The use of haloperidol or ziprasidone, as compared with placebo, had no significant effect on the primary end point (odds ratios, 0.88 [95% CI, 0.64 to 1.21] and 1.04 [95% CI, 0.73 to 1.48], respectively). There were no significant between-group differences with respect to the secondary end points or the frequency of extrapyramidal symptoms. CONCLUSIONS: The use of haloperidol or ziprasidone, as compared with placebo, in patients with acute respiratory failure or shock and hypoactive or hyperactive delirium in the ICU did not significantly alter the duration of delirium. (Funded by the National Institutes of Health and the VA Geriatric Research Education and Clinical Center; MIND-USA ClinicalTrials.gov number, NCT01211522 .)