425 research outputs found
Acoustic Signals of \u3ci\u3eGraminella Nigrifrons\u3c/i\u3e (Homoptera: Cicadellidae)
The deltocephaline leafhopper, Graminella nigrifrons, produces low intensity sub- strate transmitted vibrations (signals) to facilitate location of virgin females by males during courtship. In the laboratory, signals produced on maize leaves were received by a phonographic cartridge, amplified, and analyzed on an oscillograph and sonograph. Male calls, that are produced spontaneously, are complex, consisting of three consecutive sections. Section 1 consists of ca. 3 sec of irregular clicks. Section 2 has ca. 4 sec of repeated phrases consisting of a continuous series of 0.4 sec chirps and a roll. Section 3 consists of ca. 5 sec of an intermittent series of 0.2 sec chirps and a roll. Female calls are produced in response to male calls. Female calls are simple compared to male calls and consist of ca. 4-5 sec of low frequency clicking. Signal patterns of G. nigrifrons are compared to those of other leafhoppers and evolutionary scenarios are presented to account for the observed gender differences in signals
Zea diploperennis: A Primitive Relative Offers New Traits to Improve Corn
Four years ago, a young Mexican botanist made what may someday be recognized as the botanical find of the century. Rafael Guzmán, a student at the University of Guadalajara, was searching for one of the wild relatives of corn in the mountains of southern Mexico. Guzmán was looking for Zea perennis, a perennial teosinte thought to be extinct in the wild since the early 1920\u27s. This primitive corn relative was considered more of a botanical curiosity than a boon to mankind. As a tetraploid, perennial teosinte produces sterile offspring when crossed with corn, a diploid species. Guzmán found perennial teosinte growing in a remote mountain site
Influence of Honey Bee, Apis mellifera, Hives and Field Size on Foraging Activity of Native Bee Species in Pumpkin Fields
The purpose of this study was to identify bee species active in pumpkin fields in New York and to estimate their potential as pollinators by examining their foraging activity. In addition, we examined whether foraging activity was affected by either the addition of hives of the honey bee, Apis mellifera L., or by field size. Thirty-five pumpkin (Cucurbita spp.) fields ranging from 0.6 to 26.3 ha, 12 supplemented with A. mellifera hives and 23 not supplemented, were sampled during peak flowering over three successive weeks in 2008 and 2009. Flowers from 300 plants per field were visually sampled for bees on each sampling date. A. mellifera, Bombus impatiens Cresson, and Peponapis pruinosa (Say) accounted for 99% of all bee visits to flowers. A. mellifera and B. impatiens visited significantly more pistillate flowers than would be expected by chance, whereas P. pruinosa showed no preference for visiting pistillate flowers. There were significantly more A. mellifera visits per flower in fields supplemented with A. mellifera hives than in fields not supplemented, but there were significantly fewer P. pruinosa visits in supplemented fields. The number of B. impatiens visits was not affected by supplementation, but was affected by number of flowers per field. A. mellifera and P. pruinosa visits were not affected by field size, but B. impatiens visited fewer flowers as field size increased in fields that were not supplemented with A. mellifera hives. Declining A. mellifera populations may increase the relative importance of B. impatiens in pollinating pumpkins in New Yor
Integration of airborne and ground observations of nitryl chloride in the Seoul metropolitan area and the implications on regional oxidation capacity during KORUS-AQ 2016
Nitryl chloride (ClNO2) is a radical reservoir species that releases chlorine radicals upon photolysis. An integrated analysis of the impact of ClNO2 on regional photochemistry in the Seoul metropolitan area (SMA) during the Korea-United States Air Quality Study (KORUS-AQ) 2016 field campaign is presented. Comprehensive multiplatform observations were conducted aboard the NASA DC-8 and at two ground sites (Olympic Park, OP; Taehwa Research Forest, TRF), representing an urbanized area and a forested suburban region, respectively. Positive correlations between daytime Cl2 and ClNO2 were observed at both sites, the slope of which was dependent on O3 levels. The possible mechanisms are explored through box model simulations constrained with observations. The overall diurnal variations in ClNO2 at both sites appeared similar but the nighttime variations were systematically different. For about half of the observation days at the OP site the level of ClNO2 increased at sunset but rapidly decreased at around midnight. On the other hand, high levels were observed throughout the night at the TRF site. Significant levels of ClNO2 were observed at both sites for 4-5 h after sunrise. Airborne observations, box model calculations, and back-trajectory analysis consistently show that these high levels of ClNO2 in the morning are likely from vertical or horizontal transport of air masses from the west. Box model results show that chlorine-radical-initiated chemistry can impact the regional photochemistry by elevating net chemical production rates of ozone by 25% in the morning
The potential role of methanesulfonic acid (MSA) in aerosol formation and growth and the associated radiative forcings
Atmospheric
marine aerosol particles impact Earth's albedo and climate. These particles
can be primary or secondary and come from a variety of sources, including sea
salt, dissolved organic matter, volatile organic compounds, and
sulfur-containing compounds. Dimethylsulfide (DMS) marine emissions
contribute greatly to the global biogenic sulfur budget, and its oxidation
products can contribute to aerosol mass, specifically as sulfuric acid and
methanesulfonic acid (MSA). Further, sulfuric acid is a known nucleating
compound, and MSA may be able to participate in nucleation when bases are
available. As DMS emissions, and thus MSA and sulfuric acid from DMS
oxidation, may have changed since pre-industrial times and may change in a
warming climate, it is important to characterize and constrain the climate
impacts of both species. Currently, global models that simulate aerosol size
distributions include contributions of sulfate and sulfuric acid from DMS
oxidation, but to our knowledge, global models typically neglect the impact
of MSA on size distributions.
In this study, we use the GEOS-Chem-TOMAS (GC-TOMAS) global aerosol
microphysics model to determine the impact on aerosol size distributions and
subsequent aerosol radiative effects from including MSA in the size-resolved
portion of the model. The effective equilibrium vapor pressure of MSA is
currently uncertain, and we use the Extended Aerosol Inorganics Model (E-AIM)
to build a parameterization for GC-TOMAS of MSA's effective volatility as a
function of temperature, relative humidity, and available gas-phase bases,
allowing MSA to condense as an ideally nonvolatile or semivolatile species or
too volatile to condense. We also present two limiting cases for MSA's
volatility, assuming that MSA is always ideally nonvolatile (irreversible
condensation) or that MSA is always ideally semivolatile (quasi-equilibrium
condensation but still irreversible condensation). We further present
simulations in which MSA participates in binary and ternary nucleation with
the same efficacy as sulfuric acid whenever MSA is treated as ideally
nonvolatile. When using the volatility parameterization described above (both
with and without nucleation), including MSA in the model changes the global
annual averages at 900 hPa of submicron aerosol mass by 1.2 %, N3
(number concentration of particles greater than 3 nm in diameter) by
−3.9 % (non-nucleating) or 112.5 % (nucleating), N80 by 0.8 %
(non-nucleating) or 2.1 % (nucleating), the cloud-albedo aerosol indirect
effect (AIE) by −8.6 mW m−2 (non-nucleating) or −26 mW m−2
(nucleating), and the direct radiative effect (DRE) by −15 mW m−2
(non-nucleating) or −14 mW m−2 (nucleating). The sulfate and
sulfuric acid from DMS oxidation produces 4–6 times more submicron mass than
MSA does, leading to an ∼10 times stronger cooling effect in the DRE.
But the changes in N80 are comparable between the contributions from MSA and
from DMS-derived sulfate/sulfuric acid, leading to comparable changes in the
cloud-albedo AIE.
Model–measurement comparisons with the Heintzenberg et al. (2000) dataset
over the Southern Ocean indicate that the default model has a missing source
or sources of ultrafine particles: the cases in which MSA participates in
nucleation (thus increasing ultrafine number) most closely match the
Heintzenberg distributions, but we cannot conclude nucleation from MSA is the
correct reason for improvement. Model–measurement comparisons with
particle-phase MSA observed with a customized Aerodyne high-resolution
time-of-flight aerosol mass spectrometer (AMS) from the ATom campaign show
that cases with the MSA volatility parameterizations (both with and without
nucleation) tend to fit the measurements the best (as this is the first use
of MSA measurements from ATom, we provide a detailed description of these
measurements and their calibration). However, no one model sensitivity case
shows the best model–measurement agreement for both Heintzenberg and the
ATom campaigns. As there are uncertainties in both MSA's behavior (nucleation
and condensation) and the DMS emissions inventory, further studies on both
fronts are needed to better constrain MSA's past, current, and future impacts
upon the global aerosol size distribution and radiative forcing.</p
Atmospheric Acetaldehyde: Importance of Air-Sea Exchange and a Missing Source in the Remote Troposphere.
We report airborne measurements of acetaldehyde (CH3CHO) during the first and second deployments of the National Aeronautics and Space Administration (NASA) Atmospheric Tomography Mission (ATom). The budget of CH3CHO is examined using the Community Atmospheric Model with chemistry (CAM-chem), with a newly-developed online air-sea exchange module. The upper limit of the global ocean net emission of CH3CHO is estimated to be 34 Tg a-1 (42 Tg a-1 if considering bubble-mediated transfer), and the ocean impacts on tropospheric CH3CHO are mostly confined to the marine boundary layer. Our analysis suggests that there is an unaccounted CH3CHO source in the remote troposphere and that organic aerosols can only provide a fraction of this missing source. We propose that peroxyacetic acid (PAA) is an ideal indicator of the rapid CH3CHO production in the remote troposphere. The higher-than-expected CH3CHO measurements represent a missing sink of hydroxyl radicals (and halogen radical) in current chemistry-climate models
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