Recent Invasions of the Gulf of Maine: Three Contrasting Ecological Histories

Introduced species are common members of estuarine communities where their role as competitors and predators is of concern, This paper examines the invasion of Gulf of Maine benthic habitats by the ecologically similar alien invertebrates Styela clava, Botrylloides diegensis , and Membranipora membranacea .
Styela clava increased slowly in abundance at study sites in Beverly, Massachusetts and Portsmouth, New Hampshire. We found no evidence of competitive dominance by S. clava , even though it is the competitive dominant in similar habitats elsewhere. Botrylloides diegensis rapidly became a dominant species after its arrival in the Great Bay Estuary, but this dominance was short-lived. B. diegensis persists in the estuary as an early colonist of primary space and as an epibiont on secondary substrates in established communities. Membranipora membranacea became the dominant epiphyte on laminarian kelps within two years. Although M. membranacea overgrew the native epiphytes Obelia geniculata and Electra pilosa in the overwhelming majority of encounters these native species are more common on other algal hosts. Therefore, competitive dominance is not likely a factor in the successful invasion of the Gulf of Maine by M. membranacea .
These species provide evidence for opposing views of the role of competition in mediating community invasion. We show that ecological similarity among species is not an accurate criterion to predict either the mechanism of invasion or the means of persistence. In addition, these data indicate that biological invasions must be examined on broad spatial and temporal scales; short-term or narrowly focused studies can lead to incorrect conclusions.     

Lifting technique and abdominal belt usage: a biomechanical, physiological and subjective investigation

Some 10 male subjects carried out a repetitive lifting task for 15 min under four conditions on separate days. Subjects used either a squat lifting or a stoop lifting technique with or without an abdominal belt on each day. Measurements of spinal shrinkage, heart rate, perceived exertion and regional body pain were made under each condition. Although there was a significant difference in spinal shrinkage under all lifting conditions compared with shrinkage during 15 min of quiet standing (4.36 ± 2.24 vs. 1.13 ± 1.18 mm), there were no significant differences in shrinkage between the conditions. The subjects' heart rates were higher during the squat lift than the stoop lift (123 vs. 97 beats/min; p < 0.001). While the squat lift was perceived to be the safest lift by 90% of the subjects, 60% regarded this lift as the least preferred method (with or without the belt). Although all 10 subjects perceived the safest lifting method to involve the use of the belt, 50% rated the belt as their least preferred lifting condition. The findings cast doubt on the efficacy and acceptability of both abdominal belts and the practice of training workers in ‘safe’ lifting techniques and indicate that individual characteristics and preferences need to be considered when attempting to improve the safety of manual handling operations in industry.     

Photocatalytic oxidation of volatile organic compounds using fluorescent visible light

Photocatalytic oxidation (PCO) of volatile organic compounds (VOCs) is a highly attractive alternative technology for purification and deodorization of indoor air. The main objectives of this study were to demonstrate that a common fluorescent visible light (FVL) lamp can be used to effectively remove by PCO low concentrations of VOCs from slightly contaminated air and to provide some fundamental and technical details on the process. The target VOC was n-butanol, which is a standard reference odorant. Its PCO was studied under a long residence time in a 3.7-L cylindrical reactor with commercial titanium dioxide (TiO2) as the reference photocatalyst and using mostly FVL for illumination. For comparison only, a UV (black) light lamp was used. The gas-phase products were detected and quantified online by gas chromatography (GC). The effects of reactor residence time, of inlet concentration, and of the relative light intensity on the efficiency of the process were also evaluated. At a high n-butanol concentration (0.1 vol %), butanal and propanal were identified as the intermediate products of the process; ethanal appeared when the initial concentration was < or = 850 ppm(v). This indicates that PCO leading to CO2 and H2O is relatively slow and proceeds in a stepwise manner. Although the efficiency of the process with an FVL lamp was significantly lower than when using a UV black light, complete PCO of low concentrations was achieved for 100 ppm(v). In a search for a material with photoactivation extended to higher wavelengths or increased photoactivity, several samples of transition metal- or silver ion-doped (2 atomic %) TiO2 as well as SrTi(1-x-)Fe(x)O3 (x = 0.1 and 0.15) perovskites were included in the study. None of these materials was more active than pure TiO2. The results of this study open new horizons in the area of in door air quality (IAQ) control.     

Combustion characteristics of spent catalyst and paper sludge in an internally circulating fluidized-bed combustor

Combustion of spent vacuum residue hydrodesulfurization catalyst and incineration of paper sludge were carried out in thermo-gravimetric analyzer and an internally circulating fluidized-bed (ICFB) reactor. From the thermo-gravimetric analyzer-differential thermo-gravimetric curves, the pre-exponential factors and activation energies are determined at the divided temperature regions, and the thermo-gravimetric analysis patterns can be predicted by the kinetic equations. The effects of bed temperature, gas velocity in the draft tube and annulus, solid circulation rate, and waste feed rate on combustion efficiency of the wastes have been determined in an ICFB from the experiments and the model studies. The ICFB combustor exhibits uniform temperature distribution along the bed height with high combustion efficiency (>90%). The combustion efficiency increases with increasing reaction temperature, gas velocity in the annulus region, and solid circulation rate and decreases with increasing waste feed rate and gas velocity in the draft tube. The simulated data from the kinetic equation and the hydrodynamic models predict the experimental data reasonably well.     

Unraveling the impact of workforce age diversity on labor productivity: The moderating role of firm size and job security

Previous literature has suggested both positive and negative effects of age diversity on labor productivity: positive because of the potential knowledge complementarities between employees of different ages and negative because of the age‐related value differences that might reduce cohesion and cooperation, hampering firm performance. Using a Belgian sample of 5892 organizational observations (2008–2011), we unraveled these countervailing effects in two ways. First, we built on prior studies to suggest that the effect of age diversity depends on the particular shape of the age distribution: positive when it is heterogeneous (i.e., variety) and negative when it is polarized (i.e., polarization). This was supported by our findings. Second, we explored the moderating impact of two contextual contingencies, firm size and job security. As expected, the positive effect of age variety is reinforced in large firms and in firms where job security is high. Although firm size also emphasizes the negative effect of age polarization on productivity, job security, unexpectedly, does not moderate this relationship. Our study offers a valuable contribution to the literature as it reveals the boundary conditions of the competing implications of age diversity and, thus, allows one to account for the inconclusive findings reported in previous literature. Copyright © 2015 John Wiley & Sons, Ltd.     

Sex differences in mass loss rate and growth efficiency in Antarctic fur seal (Arctocephalus gazella) pups at Macquarie Island

We investigated the relationship between the mass gained by a pup during a period of maternal attendance (as an index of milk intake) and the duration of the preceding foraging trip in relation to the mass-specific rate of mass loss during fasting periods and the growth rate of Antarctic fur seal (Arctocephalus gazella) pups at Macquarie Island. We found that (1) serially weighed male pups grew significantly faster than females pups and that (2) fasting female pups lost mass at a significantly higher rate (2.55% day⁻¹) than male pups (2.12% day⁻¹) of the same mass; (3) during periods of maternal attendance, there were no intersexual differences in the amount of mass gained by pups of the same size, hence (4) female pups required a higher daily mass gain to grow at the same rate as male pups. Our results show that intersexual differences in growth rate may be accounted for by intersexual differences in mass-specific rate of mass loss, because females lost 0.42% more of their total mass per day (i.e. 4.2 g kg⁻¹ day⁻¹) compared with male pups of the same body mass. Despite intersexual differences in growth rates, our results indicate equality of maternal expenditure between the sexes. Intersexual differences in the rate of mass loss may be due to differences in the metabolic rate, activity level and/or body composition of male and female pups. Received: 19 August 1998 / Received in revised form: 19 April 1999 / Accepted: 19 April 1999     

Failure rate evaluation with influencing factors

A new methodology for failure rate evaluation with influencing factors is proposed. A quantitative part allows integrating potential available data from feedback. Then, a qualitative analysis deals with influencing factors such as design, environment, and use to provide more coherent and argued results. The main idea is to use some criteria to fix the failure rate within a prior interval, according to the influencing factor states. To this end, the system is broken up into main component groups. When a component group is susceptible to an influencing factor, its baseline failure rate is multiplied by the relevant influencing coefficient. A seven-step methodology is presented to define the model, identify and rate the influencing factors, set indicator functions taking the uncertainties into account, and calculate the influencing coefficients. The proposed methodology is global enough to be usable for a large number of safety instrumented systems and influencing factors. For example, an application regarding safety pressure relief valves is given. The prospect is for more efficient risk management by acting both on systems and influencing factors.