Observations and model simulations of carbon monoxide emission factors from a California highway

A series of twelve intensively monitored 1-hr CO dispersion studies were conducted near Davis, CA, in winter 1996. The experimental equipment included twelve CO sampling ports at elevations up to 50 m, three sonic anemometers, a tethersonde station, aircraft measurements of wind and temperature profile aloft, and a variety of conventional meteorological equipment. The study was designed to explore the role of vehicular exhaust buoyancy during worst-case meteorological conditions, such as low winds oriented in near-parallel alignment with the road during a surface-based nocturnal inversion. From the study, field estimates of the CO emission factor (EF) from a California vehicle fleet were computed using two different methods. The analysis suggests that the CT-EMFAC/EMFAC (EMission FACtor) models currently used to conduct federal conformity modeling significantly overpredict CO emissions for high-speed, free-flowing traffic on California highways.     

The florence floods—What the papers said

The floods of 1966 in Northern Italy provoked varying reactions from officialdom and the press. Political and administrative problems received as much coverage as the environmental effects of the disaster, but learned opinion gained a new, if rather temporary, status in the newspapers of the time. In retrospect, economic recovery seems to have occurred more rapidly than predicted in the gloomy forecasts of the time, although a clear picture of the disruption caused by the floods     

UNSATURATED FLOW THROUGH SOLID WASTE LANDFILLS: MODEL AND SENSITIVITY ANALYSIS1

ABSTRACT: The movement of precipitation water infiltrating through the material (refuse) of solid waste landfills is examined via numerical solution of the equations of continuity, and motion (Darcy's Law). The solution of the equations is obtained by a fully implicit, finite-difference scheme. Both unsaturated and saturated surface conditions are considered, making the scheme suitable for real-time simulation of net precipitation and moisture redistribution events. A sensitivity analysis showed that for unsaturated surface conditions the solution is primarily affected by hydraulic conductivity and capillary diffusivity, and is relatively independent of the space and time steps. In addition, the precipitation averaging process is shown to be critical in the correct computation of moisture transport during the time period where the transition from unsaturated to saturated conditions occurs. The model presented herein is suitable for analysis of water movement through landfills, and the design of bottom collection systems.     

A new phylogeny for basal Trechnotheria and Cladotheria and affinities of South American endemic Late Cretaceous mammals

The endemic South American mammals Meridiolestida, considered previously as dryolestoid cladotherians, are found to be non-cladotherian trechnotherians related to spalacotheriid symmetrodontans based on a parsimony analysis of 137 morphological characters among 44 taxa. Spalacotheriidae is the sister taxon to Meridiolestida, and the latter clade is derived from a primitive spalacolestine that migrated to South America from North America at the beginning of the Late Cretaceous. Meridiolestida survived until the early Paleocene (Peligrotherium) and early Miocene (Necrolestes) in South America, and their extinction is probably linked to the increasing competition with metatherian and eutherian tribosphenic mammals. The clade Meridiolestida plus Spalacotheriidae is the sister taxon to Cladotheria and forms a new clade Alethinotheria. Alethinotheria and its sister taxon Zhangheotheria, new clade (Zhangheotheriidae plus basal taxa), comprise Trechnotheria. Cladotheria is divided into Zatheria (plus stem taxa, including Amphitherium) and Dryolestida, including Dryolestidae and a paraphyletic array of basal dryolestidans (formerly classified as “Paurodontidae”). The South American Vincelestes and Groebertherium are basal dryolestidans.     

Bees use three-dimensional information to improve target detection

Bumblebee detection of a flat circular disc (two-dimensional (2D) presentation) and a disc which was presented 10 cm in front of a structured background (and thus provided three-dimensional (3D) cues) was compared. A dual choice test using a Y-maze apparatus was conducted to estimate the minimum visual angle at which the bees were able to detect the disc. At large visual angles of 15, 10 and 5° bees’ performance between the 2D and the 3D presentation did not differ. However, when the disc subtended 3° at the bee’s eye, the bees performed significantly better when 3D information was available. Overall, bees were able to detect a target subtending a 40% smaller visual angle when it was presented in front of the structured background compared to a 2D presentation. This suggests that previous reports on the limits of target detection in bees using flat stimuli might have underestimated the bees’ ability to locate small flowers under natural conditions. Bees use motion parallax, i.e. the apparent relative motion of a stationary object against a background, for perceiving the third dimension. Our data suggest that bumblebees can integrate information from at least two types of feature detectors, motion and area, to improve single target detection.