The theory of power and efficiency in ecology

Some previous work on the theory of power and optimal efficiency in ecology is shown to be either incorrect or of limited applicability. The standard analysis based on Atwood's machine is not valid, and the optimal efficiency for maximum power production depends on the characteristics of the individual system. For optimally foraging aquatic organisms the theoretical efficiency is less than 50% when the hydrodynamic flow is laminar, but under turbulent conditions the optimal efficiency can rise as high as 67%. Despite these restrictions it still appears plausible that ecological efficiency should be the same for broad classes of living organisms.     

Third trimester ultrasound diagnosis of intestinal atresia following clinical evidence of polyhydramnios

Five cases of intestinal atresia were diagnosed using real-time ultrasonography following clinical evidence of polyhydramnios. No correlation was noted between ultrasound findings and the severity of the lesions. Two of the five babies died at 35 and 77 days respectively. Prematurity and presence of other abnormalities were factors in the deaths.     

Predicting particle deposition on HVAC heat exchangers

Particles in indoor environments may deposit on the surfaces of heat exchangers that are used in heating, ventilation and air conditioning (HVAC) systems. Such deposits can lead to performance degradation and indoor air quality problems. We present a model of fin-and-tube heat-exchanger fouling that deterministically simulates particle impaction, gravitational settling, and Brownian diffusion and uses a Monte Carlo simulation to account for impaction due to air turbulence. The model predicts that <2% of submicron particles will deposit on heat exchangers with air flows and fin spacings that are typical of HVAC systems. For supermicron particles, deposition increases with particle size. The dominant deposition mechanism for 1–10 μm particles is impaction on fin edges. Gravitational settling, impaction, and air turbulence contribute to deposition for particles larger than 10 μm. Gravitational settling is the dominant deposition mechanism for lower air velocities, and impaction on refrigerant tubes is dominant for higher velocities. We measured deposition fractions for 1–16 μm particles at three characteristic air velocities. On average, the measured results show more deposition than the model predicts for an air speed of 1.5 m s⁻¹. The amount that the model underpredicts the measured data increases at higher velocities and especially for larger particles, although the model shows good qualitative agreement with the measured deposition fractions. Discontinuities in the heat-exchanger fins are hypothesized to be responsible for the increase in measured deposition. The model and experiments reported here are for isothermal conditions and do not address the potentially important effects of heat transfer and water phase change on deposition.     

Modeling sorbent injection for mercury control in baghouse filters: I--model development and sensitivity analysis

A two-stage mathematical model for Hg removal using powdered activated carbon injection upstream of a baghouse filter was developed, with the first stage accounting for removal in the ductwork and the second stage accounting for additional removal caused by the retention of carbon particles on the filter. The model shows that removal in the ductwork is minimal, and the additional carbon detention time from the entrapment of the carbon particles in the fabric filter enhances the Hg removal from the gas phase. A sensitivity analysis on the model shows that Hg removal is dependent on the isotherm parameters, the carbon pore radius and tortuosity, the C/Hg ratio, and the carbon particle radius.     

Complications with using ratios for environmental data: comparing enantiomeric ratios (ERs) and enantiomer fractions (EFs)

Complications arise when ratios are used to present environmental data because ratios are an unbounded, multiplicative scale that can lead to asymmetrical (skewed) data distributions. Enantiomeric ratios (ERs), historically used in discussions of chiral signatures, often are published as mean ER+/-single-value standard deviation. Application of statistical summaries, such as the widely used sample mean and standard deviation, to skewed ratio data is misleading and often inappropriate. Comparison of statistically summarized ER and enantiomer fraction (EF) data (which are based on a bounded, additive scale) for a range of hypothetical values reveals substantial discrepancies when conversion between ER and EF formats is used. These discrepancies are largest when the ratio data are greater than one and have large variability, because the data are more skewed. In many cases, the use of fractions instead of ratios can help to minimize misrepresentation of environmental data, including chiral data. The use of nonparametric statistical summaries, e.g., median and percentiles, provides a more robust indicator of the typical value and spread for both ER and EF data.     

Shifted balance of risk and cost after autotomy affects use of cover,escape, activity,and foraging in the keeled earless lizard (<Emphasis Type="Italic">Holbrookia propinqua</Emphasis>)

Autotomy of expendable body parts is often a successful last-chance antipredatory defense for a variety of invertebrates and vertebrates, especially lizards. However, loss of a body part imposes costs and risks, some of which may be reduced by modifying subsequent behavior. I studied effects of experimentally induced autotomy of the tail in the keeled earless lizard (Holbrookia propinqua) on use of cover, escape behavior, activity, and feeding. Autotomized lizards stayed closer to plant cover than sham-autotomized lizards (having intact tails) when approached by an investigator simulating a predator. Autotomized males, but not females, fled further than sham-autotomized lizards. Autotomy did not affect the distance from an approaching predator when the lizards began to flee. After autotomy, the number of days on which lizards were active differed between sexes and lizards made fewer attempts to catch prey per unit time than lizards with intact tails. Tail loss did not affect the percentage of time spent moving. Staying closer to refuge, fleeing further after autotomy, and decreasing surface activity may compensate for decreased maximum escape speed or agility, and may reflect use of a greater margin of safety when the tail is unavailable for autotomy. Decrease in surface activity may be comparable to use of safer microhabitats reported for other lizards and damselflies subsequent to autotomy. Several possible reasons for the lower rate of feeding attempts by autotomized lizards are discussed.     

The optimal use of non-renewable resources: The theory of extraction

The traditional theory of exhaustion is revised to allow for long run capital mobility. This model is extended to include the impact of cumulative environmental damages on the optimal path of resource use. Models and optimal markets are then analyzed for cases where minerals are available over a continuum of quality and where recycling ameliorates inevitable exhaustion of non-renewable resources. Finally, the impact of technological change on long run trends in mineral prices is examined.     

Growth responses of Avicennia germinans and Batis maritima seedlings to weathered light sweet crude oil applied to soil and aboveground tissues

Environmental Science and Pollution Research - Oil spills are a significant stressor to coastal and maritime environments worldwide. The growth responses of Batis maritima and Avicennia germinans...