Reduced planktotrophy in larvae of <Emphasis Type="Italic">Clypeaster</Emphasis><Emphasis Type="Italic">rosaceus</Emphasis> (Echinodermata,Echiniodea)

Phylogenetic analyses have demonstrated that nonfeeding larvae have evolved from feeding larvae many times among marine invertebrates. In light of this observation, it is surprising that an intermediate strategy, a larva that can feed but is provisioned with enough energy to metamorphose without acquiring exogenous food (i.e., facultative planktotrophy), is rare. A hypothesis for the lack of facultative planktotrophic species among marine invertebrates is that the transition from feeding to nonfeeding is rapid due to this intermediate stage being evolutionarily unstable. Evidence that would support this hypothesis is if species with facultative planktotrophy have reduced food assimilation when compared with obligate planktotrophs. We studied a species with facultative planktotrophic larvae, Clypeaster rosaceus, that is very near the boundary between facultative and obligatory planktotrophy, to answer two questions: (1) does feeding during the larval stage result in energy gains in larval or juvenile stages and (2) if not, are larvae capable of assimilating exogenous food at all. Our measurements of energetics in larval and juvenile stages show that C. rosaceus larvae accumulate very little if any energy when fed, but stable isotope data indicate that larvae are able to assimilate some food. Our results are consistent with similar studies on facultative planktotrophic larvae suggesting poor food assimilation and rapid loss of larval feeding after a population evolves the ability to reach metamorphosis without feeding (lecithotrophy).     

Different policing rates of eggs laid by queenright and queenless anarchistic honey-bee workers (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.)

Worker-reproduction is rare in queenright honey-bee colonies. When workers do lay eggs, their eggs are normally eaten by other workers presumably because they lack the queen's egg-marking signal. Workers use the absence of this queen signal to enforce the queen's reproductive monopoly by policing any worker-laid eggs. In contrast, in anarchistic colonies, the majority of the males arise from worker-laid eggs. Anarchistic worker-laid eggs escape policing because workers perceive anarchistic eggs as queen-laid. However, in this study, we show that eggs laid by queenless anarchistic workers do not escape policing and have very similar removal rates to worker-laid eggs from queenless wild-type (i.e. non-anarchistic) colonies. This suggests that, under queenless conditions, eggs laid by anarchistic workers lose their chemical protection and are therefore no longer perceived as queen-laid. Hence, the egg-marking signal seems to be only applied to eggs when queen and brood are present. This suggests that in the absence of queen and brood, the biosynthetic pathway that produces the egg-marking signal is switched off.Communicated by L. Keller     

Intra-colonial foraging specialism by honey bees (Apis mellifera) (Hymenoptera:Apidae)

Summary Colonies of honey bees with two identifiable subfamilies were established. Returning foragers were captured and killed at two different sampling times. The mean volume and per cent soluble solids of crop contents were determined for each subfamily, as was the mean weight of the pollen pellets. No significant differences in nectar volume or concentration were detected between subfamilies within colonies. However, in a few colonies, significant subfamily by sampling-time interactions were present, suggesting that in these colonies subfamilies differed in their nectar and pollen collecting behavior at different times of day. The plant genera worked by pollen foragers were also determined. In four of six colonies, bees of different subfamilies were found to be majoring on different plant species (Fig. 1). Implications of this intra-colonial variance in foraging behavior for colony fitness are discussed. Offprint requests to: B.P. Oldroyd     

Formulation of a soil-pesticide transport model based on a compartmental approach

A semianalytical soil-pesticide transport model is formulated based on a compartmental approach to determine spatial and temporal variations of pesticide residues across a soil profile. The compartmental model is implemented by drawing an analogy between a series of continuous-flow stirred tank reactors and a soil horizon that consists of multiple perfectly mixed compartments. The analogy is strengthened by exploiting a relation between the compartment series and the conventional convective-dispersive equation (CDE) for vertical transport in the soil. Consequently, the number of compartments in the model formulation is not free, but dictated as a function of transport parameters. The model formulation allows consideration of arbitrary boundary value specifications and also, for some cases, spatially varying initial concentration profiles. Sorption kinetics is represented via a two-site model that involves a linear sorption isotherm and a first-order irreversible sorption or a radial diffusive penetrating model. For these three cases, analysis of the compartmental model allows the resultant concentration profiles to be expressed in terms of the Poisson distribution. When a nonlinear kinetic sorption model is used to simulate the sorption processes, an analytical solution is not found and a numerical approach is required.     

2-Chlorobenzoate biodegradation by recombinant Burkholderia cepacia under hypoxic conditions in a membrane bioreactor.

The feasibility of applying bacterial hemoglobin technology to degrade 2-chlorobenzoate (2-CBA) through co-metabolism under hypoxic conditions in a membrane bioreactor (MBR) process has been studied in the laboratory. 2-chlorobenzoate removal and chloride release rates in the MBR system varied from 99 to 78% and 98 to 73%, respectively, depending on the operation conditions. Chemical oxygen demand (COD) removal efficiencies were more than 90% at food-to-microorganism ratios ranging from 0.32 to 0.62 g/g/d, and the observed yield was 0.13 to 0.20 g biomass/g COD. The bacterial cell-floc size-distribution analysis showed that there is a significant change in bacterial floc size due to high shear stress during operation of the MBR. To characterize growth kinetics of Burkholderia cepacia strain dinitrotoluene, a mathematical model that describes co-metabolic oxidation of 2-CBA in an MBR has been developed.     

Relative efficacy of intrinsic and extant parameters for modeling biodegradation of synthetic organic compounds in activated sludge: dynamic systems.

The utility of intrinsic and extant kinetic parameters for simulating the dynamic behavior of a biotreatment system coupled with a distributed, unstructured, balanced microbial growth model were evaluated against the observed response of test reactors to transient loads of synthetic organic compounds (SOCs). Biomass from a completely mixed activated-sludge (CMAS) system was tested in fed-batch reactors, while a sequencing batch reactor (SBR) was tested by measuring SOC concentrations during the fill and react period. Both the CMAS system and the SBR were acclimated to a feed containing biogenic substrates and several SOCs, and the transient loading tests were conducted with biogenic substrates along with one or more SOCs. Extant parameters more closely reflect the steady-state degradative capacity of activated-sludge biomass than intrinsic parameters and, hence, were expected to be better predictors of system performance. However, neither extant nor intrinsic parameters accurately predicted system response and neither parameter set was consistently superior to the other. Factors that may have contributed to the inability of the model to predict system response were identified and discussed. These factors included the role of abiotic processes in SOC removal, disparity in the bases used to evaluate parameter estimates (substrate mineralization) and reactor performance (substrate disappearance), inhibitory substrate interactions under the severe loading conditions of the SBR, changes in the physiological state of the biomass during the transient loading tests, and the presumed correlation between the competent biomass concentration and the influent SOC concentration.     

Modeling of NO x Emissions from Oil Refinery Furnaces

The current paper investigates the possibility of establishing an empirically based model for predicting the emission rate of nitrogen oxides (NO _x ) from oil refinery furnaces, in order to continually track emissions with respect to environmental licence limits. Model input data were collected by direct stack monitoring using an electrochemical cell NO _x analyser, as well as a range of telemetry sensors to obtain refinery process parameters. Principal Component Analysis (PCA), in conjunction with Partial Least Squares (PLS) regression was then used to build a series of models able to predict NO _x emissions from the furnaces. The models produced were proven to be robust, with a relatively high accuracy, and are able to predict NO _x levels over the range of operating conditions which were sampled. It was found that due to structural/operational variations a separate model is usually required for each furnace. The models can be integrated with the refinery operating system to predict NO _x emission rates on a continuous basis. Two models representing structurally different furnaces are considered in this paper. This revised version was published online in July 2006 with corrections to the Cover Date.     

Different motivations for knowledge sharing and hiding: The role of motivating work design

Little research to date has focused on understanding employee motivation to share and hide knowledge. Using self‐determination theory, we tested the premise that knowledge sharing and hiding might be differentially motivated and that work design characteristics might influence the motivation to share knowledge with colleagues. In a panel survey of Australian knowledge workers and in a Chinese knowledge‐intensive organization, we asked knowledge workers, using time‐lagged designs, about perceptions of work design, motivation to share knowledge, and self‐reported knowledge sharing and hiding behaviors. Results, largely replicated across both samples, indicated that cognitive job demands and job autonomy were positively related to future reports of knowledge‐sharing frequency and usefulness via autonomous motivation to share knowledge. Unexpectedly, task interdependence was positively related to the three forms of knowledge hiding (evasive and rationalized hiding, and playing dumb) via external regulation to share knowledge. Implications for the design of jobs that motivate knowledge sharing and demotivate knowledge hiding are discussed.     

The useful field of view assessment predicts simulated commercial motor vehicle driving safety

Objective: The Useful Field of View (UFOV) assessment, a measure of visual speed of processing, has been shown to be a predictive measure of motor vehicle collision (MVC) involvement in an older adult population, but it remains unknown whether UFOV predicts commercial motor vehicle (CMV) driving safety during secondary task engagement. The purpose of this study is to determine whether the UFOV assessment predicts simulated MVCs in long-haul CMV drivers.

Method: Fifty licensed CMV drivers (M_age = 39.80, SD = 8.38, 98% male, 56% Caucasian) were administered the 3-subtest version of the UFOV assessment, where lower scores measured in milliseconds indicated better performance. CMV drivers completed 4 simulated drives, each spanning approximately a 22.50-mile distance. Four secondary tasks were presented to participants in a counterbalanced order during the drives: (a) no secondary task, (b) cell phone conversation, (c) text messaging interaction, and (d) e-mailing interaction with an on-board dispatch device.

Results: The selective attention subtest significantly predicted simulated MVCs regardless of secondary task. Each 20 ms slower on subtest 3 was associated with a 25% increase in the risk of an MVC in the simulated drive. The e-mail interaction secondary task significantly predicted simulated MVCs with a 4.14 times greater risk of an MVC compared to the no secondary task condition. Subtest 3, a measure of visual speed of processing, significantly predicted MVCs in the email interaction task. Each 20 ms slower on subtest 3 was associated with a 25% increase in the risk of an MVC during the email interaction task.

Conclusions: The UFOV subtest 3 may be a promising measure to identify CMV drivers who may be at risk for MVCs or in need of cognitive training aimed at improving speed of processing. Subtest 3 may also identify CMV drivers who are particularly at risk when engaged in secondary tasks while driving.