Testing the ability of males and females to respond to altered songs in the dueting green lacewing, Chrysoperla plorabunda (Neuroptera: Chrysopidae)

Green lacewings in the carnea group of Chrysoperla engage in species-specific heterosexual duets using low-frequency substrate-borne signals. Within each species, both sexes sing nearly identical songs. Songs are the principal barriers to hybridization between sympatric species in the complex. Here, we investigated the responsiveness of males and females of Chrysoperla plorabunda to synthesized, prerecorded songs that differed from the species mean in the period between repeated volleys of abdominal vibration. We tested 15–16 males and 15–16 females using playbacks of two signals that gradually increased or decreased in volley period, starting at the species mean. We found that (1) duets during courtship are accurate, interactive, and adjustable by each participant; (2) in staged duets, both sexes respond best to song tempos near the mean volley period of their population, but can nonetheless maintain duets with signals of nearly twice, or half, the normal volley period; (3) individuals fine-tune their adjustments to signals of different volley periods by changing their own volley duration and latent period, or less often by inserting extra volleys or skipping every other volley; (4) males are significantly better at matching signals of changing tempo than females; and (5) the range of song responsiveness of C. plorabunda does not overlap the natural range of volley periods found in Chrysoperla adamsi, an acoustically similar sibling species, thus reaffirming strong behavioral isolation. In sum, the precise, almost unbreakable heterosexual duets characteristic of song species of the carnea group result from tight mutual feedback between partners. Effective reproductive isolation between species can be based on song differences alone.     

Relationship of diversity and habitat area in North Pacific plastic-associated rafting communities

Plastic and other anthropogenic debris (e.g., rubber, tar) augment natural floating substrates (e.g., algal rafts, pumice) in the open ocean, allowing “islands” of substrate-associated organisms to persist in an otherwise unsuitable habitat. We examined a total of 242 debris objects collected in the eastern Pacific in 2009 and 2011 (32–39°N, 130–142°W) and the western Pacific in 2012 (19–41°N, 143–156°E). Here, we ask: (a) What taxa are associated with plastic rafts in the North Pacific? and (b) Does the number of taxa associated with plastic debris vary with the size of the debris “island?” We documented 95 rafting taxa from 11 phyla. We identified several potentially invasive plastic-associated rafting taxa, including the coral pathogen Halofolliculina spp. In concordance with classic species–area curves, the number of rafting taxa was positively correlated with the size of the raft. Our findings suggest that diversity patterns on plastic debris are compatible with the concept of island biogeography.     

Appraisal and Modification Of West-Gaeke Method For Sulfur Dioxide Determination

The West-Gaeke method has been shown to be feasible for detecting changes in SO₂ concentration greater than 10%. Reliable results can be obtained if one makes up stock solutions of the pararosaniline dye from the same powder batch at the same time. Gum arabic stabilizes the SOvtetrachloromercurate complex at concentrations of SO₂ > 8 μg/ml.     

Heterogeneous demand for ecologically sustainable products on ensuring environmental sustainability in South Africa

Environmental Economics and Policy Studies - There is an urgent need for the development of environmentally sustainable products market in developing economies, particularly in South Africa due to...     

Correction to: Heterogeneous demand for ecologically sustainable products on ensuring environmental sustainability in South Africa

Environmental Economics and Policy Studies - The original article can be found online.     

A Review of Techniques Available for Estimating Short-Term NO2 concentrations

The Environmental Protection Agency is reviewing the need for a short-term NO₂ standard based on an averaging time of three hours or less. State Implementation plans and New Source Reviews will require air quality simulation techniques capable of estimating ambient NO₂ concentrations. There is a need for multi-source (urban) models and for point source models.

A review of currently available techniques for the estimation of NO₂ concentrations resulting from NO_x point sources is presented. The available methods include simple screening techniques and refined reactive plume models. The screening techniques first use a standard gaussian dispersion model to estimate the maximum 1 hr NO_x concentration caused by the source. The second step involves estimating the fraction of this NO* concentration occurring as NO₂.

Reactive plume models numerically simulate the simultaneous effects of dispersion and chemistry on NO₂ concentrations. Organic as well as inorganic reactions are incorporated. Reactive plume models should be used, where screening techniques indicate the potential for violation of the NO₂ standard.

Current generation reactive plume models neglect the effect of turbulent concentration fluctuation on NO₂ formation and use inappropriately large dispersion coefficients to estimate plume concentrations. Approaches being developed to resolve these problems are discussed.     

Performance of a Pulse-Jet Filter At High Filtration Velocity II. Filter Cake Redeposition

Pulse-jet filter cleaning is ineffective to the extent that collected dust redeposits rather than falls to the hopper. Dust tracer techniques were used to measure the amount of redeposition in a pilot scale pulse-jet filter. A mathematical model based on experimental results was developed to describe dust transfer from bag to bag, redeposition on the pulsed bag itself, and migration to the dust hopper. Dust redeposition upon the pulsed bag increased markedly with increasing filtration velocity, whereas migration and redeposition on bags adjacent to the pulsed bag decreased. For high velocity pulse-jet filters to operate at lowest possible pressure drop, filter cake redeposition must be minimized.     

Reducing Air Pollutant Emissions at Airports by Controlling Aircraft Ground Operations

Potential reductions in air pollutant emissions were determined for four strategies to control aircraft ground operations at two case study airports, Los Angeles and San Francisco International Airports. Safety, cost, and fuel savings associated with strategy implementation were examined.

Two strategies, aircraft towing and shutdown of one engine during taxi operations, provided significant emission reductions. However, there are a number of safety problems associated with aircraft towing. The shutdown of one engine while taxiing was found to be the most viable strategy because of substantial emission reductions, cost benefits resulting from fuel savings, and no apparent safety problems.