Worker Lifespan Research Articles

Life-Cycle Earnings, Education Premiums, and Internal Rates of Return

What do the education premiums look like over the life cycle? What is the impact of schooling on lifetime earnings? How does the internal rate of return compare with opportunity cost of funds? To what extent do progressive taxes attenuate the incentives to invest in education? This paper exploits Norwegian population panel data with nearly career long earnings histories to answer these important questions. We provide a detailed picture of the causal relationship between schooling and earnings over the life cycle, following individuals over their working lifespan. To account for endogeneity of schooling, we apply three commonly used identification strategies. Our estimates show that additional schooling gives higher lifetime earnings and steeper age-earnings profile, in line with predictions from human capital theory. These estimates imply an internal rate of return of around 10 percent, after taking into account income taxes and earnings-related pension entitlements. Under standard conditions, this finding suggests it was financially profitable to take additional schooling because the rates of return were substantially higher than the market interest rates. By comparison, Mincer regressions understate substantially the rates of return. We explore the reasons for this downward bias, finding that it is driven by Mincer’s assumptions of no earnings while in school and exogenous post-schooling employment.

Enhanced catalytic performance in butylene cracking by hierarchical surface silicon-rich ZSM-5

In the process of butylene catalytic cracking, the amount, location and strength of acid sites of the catalyst play an important role in suppressing the undesired reactions. Hydrothermal dealumination is widely used to adjust the acidity of catalyst. Also, the steaming treatment has a significant impact on the physico-chemical properties of the catalyst, such as leading to mesoporosity at the perimeter of zeolite crystals through dealumination process. The mesoporosity is beneficial to long working life-span of catalyst, while it can increase the external surface acid sites of ZSM-5, subsequently resulting in non-shape selective catalytic reactions on the external surface of the catalyst. Coke and large-molecular hydrocarbons or intermediates can be produced relatively easily at external surface acid sites because of the absence of spatial constraints. The external acid sites of catalyst can be deactivated through chemical liquid deposition of SiO2 onto the surface of catalyst using the tetramethoxysilane (TMOS) as silica source. Combing hydrothermal treatment and TMOS modification, a hierarchical surface silicon-rich ZSM-5 zeolite without pore-opening narrowed was prepared. Compared with the catalytic performance of untreated catalyst, this new catalyst has achieved a high total yield of propylene and ethylene and showed excellent hydrothermal stability. Side reactions and coking were restrained simultaneously during the butylene cracking process.

Lifespan differences between queens and workers are not explained by rates of molecular damage

The biological processes that underlie senescence are of universal biological importance, yet they remain poorly understood. A popular theory proposes that senescence is the result of limited investment into mechanisms involved in the prevention and repair of molecular damage, leading to an accumulation of molecular damage with age. In ants, queen and worker lifespans differ by an order of magnitude, and this remarkable difference in lifespan has been shown to be associated with differences in the expression of genes involved in DNA and protein repair. Here we use the comet assay and Western Blotting for poly-ubiquitinated proteins to explore whether these differences in expression lead to differences in the accumulation of DNA damage (comet assay) or protein damage (protein ubiquitination) with age. Surprisingly, there was no difference between queens and workers in the rate of accumulation of DNA damage. We also found that levels of ubiquitinated proteins decreased with age, as previously reported in honeybees. This is in contrast to what has been found in model organisms such as worms and flies. Overall, these results reveal that the link between investment into macromolecular repair, age-related damage accumulation and lifespan is more complex than usually recognised.

The Age-Related Effect of Job Autonomy on Depressive Symptoms Through Selective Optimization With Compensation: A Two-Wave Panel Study

Selective optimization with compensation (SOC) is an effective behavioral strategy for coping with age-related changes across the work lifespan. However, the role of work-related determinants as well as their interplay with employees' SOC use and health over time is yet unclear. Our two-wave panel study among N = 335 nurses investigated job autonomy as an antecedent of SOC at work and tested further whether SOC is effective for decreasing depressive symptoms over time. Moreover, we examined the moderating effects of age on these associations. Results of our two-wave cross-lagged panel analyses show that in older employees, job autonomy is more conducive to the use of SOC behaviors at work. Furthermore, employees' SOC use is efficient for decreasing depressive symptoms over time. Finally, we observed a significant conditional indirect effect of job autonomy on depressive symptoms through SOC for older employees, but not for younger employees. Our findings contribute to a better understanding of the underlying dynamics of job design across the work lifespan and corroborate the importance of the SOC model for lifespan perspectives on occupational health research and practice.

Extending standard testing period in honeybees to predict lifespan impacts of pesticides and heavy metals using dynamic energy budget modelling.

Concern over reported honeybee (Apis mellifera spp.) losses has highlighted chemical exposure as a risk. Current laboratory oral toxicity tests in A. mellifera spp. use short-term, maximum 96 hour, exposures which may not necessarily account for chronic and cumulative toxicity. Here, we use extended 240 hour (10 day) exposures to examine seven agrochemicals and trace environmental pollutant toxicities for adult honeybees. Data were used to parameterise a dynamic energy budget model (DEBtox) to further examine potential survival effects up to 30 day and 90 day summer and winter worker lifespans. Honeybees were most sensitive to insecticides (clothianidin > dimethoate ≫ tau-fluvalinate), then trace metals/metalloids (cadmium, arsenic), followed by the fungicide propiconazole and herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). LC50s calculated from DEBtox parameters indicated a 27 fold change comparing exposure from 48 to 720 hours (summer worker lifespan) for cadmium, as the most time-dependent chemical as driven by slow toxicokinetics. Clothianidin and dimethoate exhibited more rapid toxicokinetics with 48 to 720 hour LC50s changes of <4 fold. As effects from long-term exposure may exceed those measured in short-term tests, future regulatory tests should extend to 96 hours as standard, with extension to 240 hour exposures further improving realism.

Social regulation of ageing by young workers in the honey bee, Apis mellifera

Organisms' lifespans are modulated by both genetic and environmental factors. The lifespan of eusocial insects is determined by features of the division of labor, which itself is influenced by social regulatory mechanisms. In the honey bee, Apis mellifera, the presence of brood and of old workers carrying out foraging tasks are important social drivers of ageing, but the influence of young adult workers is unknown, as it has not been experimentally teased apart from that of brood. In this study, we test the role of young workers in the ageing of their nestmates. We measured the impact of different social contexts characterized by the absence of brood and/or young adults on the lifespan of worker nestmates in field colonies. To acquire insight into the physiological processes occurring under these contexts, we analyzed the expression of genes known to affect honey bee ageing. The data showed that young workers significantly reduced the lifespan of nestmate workers, similar to the effect of brood on its own. Differential expression of vitellogenin, major royal jelly protein-1, and methylase transferase, but not methyl farneosate epoxidase genes suggests that young workers and brood influence ageing of adult nestmate workers via different physiological pathways. We identify young workers as an essential part of the social regulation of ageing in honey bee colonies.

Пожарная опасность ограждающих деревянных конструкций с длительным сроком эксплуатации

Aim of the work presented in article is study of the effects of long-term working lifespan on the fire hazard of wooden structures with the assessment of temperature characteristics, measures of process of burning and charring of designs in standard temperature conditions of a fire in accordance with GOST 30403-2012. Carried out researches have allowed to establish features of the behavior in fire conditions and fire hazard of wooden structures of long term operation on the example of enclosing structures of uninhabited wooden object. According to the study it’s determined a significant influence of the long working lifespan of wooden structures on the rate of thermal burn-in sample, the values of speed of charring (the charring rate in combustion chamber is increased in 1.7 times), and heating intensity on the thickness of the sample. This suggests that long-term natural aging of wooden structures leads to facilitate the carbonization of the wood and accelerate the oxidation process of decarbonized balance. Special attention was paid to the temperature in the firing and thermal chambers test installation for testing samples of designs. In the experiment it was discovered that the fire activity for 45 minutes per sample of wooden structures with life of 81 years, throughout the experiment the temperature was actually more at 50 °C compared to a model of modern wooden structures in temperature test and combustion chambers. This may lead to a deterioration of the fire hazard and the environment, including improving the thermal regime and toxicological hazards in buildings and structures. Identified features needed during developing methods to reduce the fire hazard of wooden structures with long-life performance, including the development and application of fireproofing materials, selection of substances and compounds that reduce the intensity of the dissipation influence on the structure and oxidation capacity of the coal layer, as well as the intensity of the process of coal formation.

Worker lifespan is an adaptive trait during colony establishment in the long-lived ant Lasius niger

Eusociality has been recognized as a strong driver of lifespan evolution. While queens show extraordinary lifespans of 20years and more, worker lifespan is short and variable. A recent comparative study found that in eusocial species with larger average colony sizes the disparities in the lifespans of the queen and the worker are also greater, which suggests that lifespan might be an evolved trait. Here, we tested whether the same pattern holds during colony establishment: as colonies grow larger, worker lifespan should decrease. We studied the mortality of lab-reared Lasius niger workers from colonies at two different developmental stages (small and intermediate-sized) in a common garden experiment. Workers were kept in artificial cohorts that differed only with respect to the stage of the colony they were born in. We found that the stage of the birth colony affected the body size and the survival probability of the workers. The workers that had emerged from early stage colonies were smaller and had lower mortality during the first 400days of their life than the workers born in colonies at a later stage. Our results suggest that early stage colonies produce small workers with an increased survival probability. These workers are gradually augmented by larger workers with a decreased survival probability that serve as a redundant workforce with easily replaceable individuals. We doubt that the observed differences in lifespan are driven by differences in body size. Rather, we suspect that physiological mechanisms are the basis for the observed differences in lifespan.

Labour Migration to the Construction Sector in India and its Impact on Rural Poverty

The present article studies the impact of migration to the construction sector on rural poverty in India based on field survey. The survey has been carried out in two phases, the first phase involving the survey of construction workers in National Capital Region and the second phase comparing the well-being of migrant households with non migrant households in selected source villages. The study finds that at destination, workers have poor living and working conditions, lack citizenship rights, entitlements and voice. However, at the cost of hardship, low consumption levels, and possibly a smaller working life span, they manage to save a good portion of their income which they remit or take back home. At origin, migrant households report higher expenditure on consumption, residential housing, and children’s education, as well as some other assets. These differences are a result of higher employment and wage incomes among migrants. However, we were not able to control for differences in initial conditions, and life cycle and other issues, which influence both participation in migration, as well as long-term impacts.

‘In reality, i motivate myself!’. ‘Low-skilled’ workers’ motivation: between individual and societal narratives

ABSTRACT‘Education, education, education’ has been a mantra in transnational and national policies since the mid-1990s: everybody has to take part in learning activities throughout their lives in order to stay employable. Hereby lifelong learning establishes a dividing practice between active and inactive lifelong learners constituting the latter as a ‘problem’. The EU call is to make people active, with an underlying assumption of people not being motivated. This article explores how one such ‘inactive’ group, low-skilled workers, narrates motivation for learning, work and other activities through a work life span. On the basis of the Self-Determination Theory, we argue that low-skilled workers are active and motivated; however, their motivational orientation may not be towards what is considered productive activities.

Local differences in parasitism and competition shape defensive investment in a polymorphic eusocial bee.

Many colonial animals rely for their defense on a soldier caste. Adaptive colony demography theory predicts that colonies should flexibly adjust the investment in different worker castes depending on the colony needs. For example, colonies should invest more in defensive workers (e.g., soldiers) in dangerous environments. However, evidence for this prediction has been mixed. We combined descriptive and experimental approaches to examine whether defensive investment and worker size are adjusted to local ecology in the only known bee with polymorphic workers, Tetragonisca angustula. Colonies of this species are defended by a morphologically specialized soldier caste. Our study included three populations that differed in the density of food competition and the occurrence of a parasitic robber bee. We found that colonies coexisting with robber bees had on average 43% more soldiers defending the nest entrance, while colonies facing stronger foraging competition had soldiers that were -6-7% smaller. We then experimentally relocated colonies to areas with different levels of competition. When released from intense food competition, body sizes of guards and foragers increased. After introducing chemical robber bee cues at nest entrances, we found both a short-term and a long-term up-regulation of the number of soldiers defending the colony. Active soldier numbers remained high after the experiment for a duration equivalent to 2-3 worker life spans. How information about past parasite threat is stored in the colony is currently unknown. In summary, T. angustula adjusts both the number and the body size of active soldiers to local ecological conditions. Competitor density also affects forager (or minor) size, an important colony trait with potential community ecological consequences. Our study supports adaptive colony demography theory in a eusocial bee and highlights the importance of colony threats and competition as selective forces shaping colony phenotype.

Creative capital accumulation and the advancement of India's creative economy

Despite the relevance of Richard Florida's ideas about the role of creative capital in promoting the creative economy of developing nations like India, there is no theoretical research on these topics in the extant literature. Therefore, we focus on an arbitrary region in a developing country like India and then analyze the creative capital accumulation decision faced by workers in this region who aspire to membership in the so-called creative class. Specifically, we compute the present discounted value of a worker's lifetime earnings as a function of the primitives of the problem. Next, we solve for the level of education that maximizes the lifetime earnings function. Finally, we describe how this optimal level of education is affected by changes in the lifespan of workers, the interest rate, and by the growth rate of the wage function.

The Importance of a Precise Definition, Comprehensive Model, and Critical Discussion of Successful Aging at Work

It is crucial to advance understanding of the concept of successful aging at work to guide rigorous future research and effective practice. Drawing on the gerontology and life-span developmental literatures, I recently proposed a definition and theoretical framework of successful aging at work that revolve around employees increasingly deviating from average developmental trajectories across the working life span. Based on sustainability, person–job fit, and proactivity theories, Kooij suggested an alternative perspective that emphasizes the active role of employees for successful aging at work. In this article, I compare the 2 approaches and attempt a partial integration. I highlight the importance of a precise definition, comprehensive model, and critical discussion of successful aging at work. Furthermore, I suggest that person–environment fit variables other than person–job fit (e.g., person–organization fit) and adapting to person–environment misfit may also contribute to successful aging at work. Finally, I argue that proactive behaviors must have age-differential effects on work outcomes to be considered personal resources for successful aging at work.

Curcumin Stimulates Biochemical Mechanisms of Apis Mellifera Resistance and Extends the Apian Life-Span

Abstract We examined the influence of curcumin-supplemented feeding on worker lifespan, Nosema resistance, key enzyme activities, metabolic compound concentrations and percentage of the global DNA methylation. Two worker groups (Apis mellifera) were set up: 1) control group; workers were fed ad libitum with sucrose syrup; 2) workers were fed with the syrup with the addition of curcumin. Dead workers were removed every two days and the Nosema spp. infection levels were assessed. Hemolymph was taken from living workers for biochemical analyses. The global DNA methylation level was analysed using DNA from worker heads and thoraces. The bees that consumed curcumin lived longer and were less infested with Nosema spp. The curcumin-treated workers had higher concentrations of proteins, non-enzymatic biomarkers (triglycerides, glucose, cholesterol, Mg2+ and Ca2+), uric acid and creatinine, as well as elevated activities of antioxidant enzymes (SOD , GPx, CAT , GST ), neutral proteases, protease inhibitors, enzymatic biomarkers (AST , ALT , ALP ). The concentrations of albumin and urea, and the activities of acidic and alkaline proteases were higher in the control group. Curcumin decreased global DNA methylation levels especially in older bees in which the natural, age-related level increase was observed. Most of the parameters increased over the apian youth and adulthood, and decreased in older bees. The decrease was markedly delayed in the bees fed with curcumin. Curcumin appeared to be an unexpectedly effective natural bio-stimulator, improving apian health and vitality. This multifactorial effect is caused by the activation of many biochemical processes involved in the formation of apian resistance.

Antecedents of the expectation of remaining in nursing until retirement age

To identify job-related resources which strengthen nurses' expectation of remaining in the same job until retirement age. The dramatic shortage of qualified nurses in industrialized countries makes it necessary to take steps to retain nurses at work at all career stages. The study introduces to the nursing literature the construct 'expectation of remaining in the same job until retirement age' as an early indicator of attitudes responsible for employees leaving the job prematurely. Longitudinal questionnaire survey. In 2010, a longitudinal study was carried out and data were collected from 387 nurses aged 21-63 years. To ensure predictive validity, the dependent variable was assessed again in 2011 after a time lag of 6 months. Data were analysed applying multiple regression analyses. The expectation of remaining in the same job until retirement age is positively related to work-time control, role clarity and colleague support. Supervisor support exerts an indirect effect via job resources. Vitality partially mediates the relationship between job resources and the expectation of remaining in the same job until retirement age. Most importantly, as hypothesized, the analysed relationships are different for younger (<30 years), middle-aged (30-50 years) and older (>50 years) nurses. Our findings suggest that interventions that seek to retain nurses should promote different job resources along the working life span to strengthen nurses' vitality in all age groups. Future research should apply age-differentiated measures to unveil work conditions that improve the retention of nurses.

Waste Management in the Stingless Bee Melipona beecheii Bennett (Hymenoptera: Apidae)

Waste management is important in insect societies because waste can be hazardous to adults, brood and food stores. The general organization of waste management and the influence of task partitioning, division of labor and age polyethism on waste processing were studied in three colonies of the tropical American stingless bee Melipona beecheii Bennett in Yucatan, Mexico. Waste generated in the colony (feces, old brood cells, cocoons, dead adults and brood) was collected by workers throughout the nest and taken to specific waste dumps within the nest. During the day, workers based at the waste dumps formed waste pellets, which they directly transferred in 93% of cases, to other workers who subsequently removed them from the nest. This is an example of task partitioning and is hypothesized to improve nest hygiene as has been found in leafcutting ants, Atta. To investigate division of labor and age polyethism we marked a cohort of 144 emerging workers. Workers forming waste pellets were on average 31.2±6.5 days old (±SD, N= 40, range of 18-45 days). The life span of M. beecheii workers was 49.0±14.0 days (N= 144). There was no difference in the life span of workers who formed (52.2±11.6 days, N= 40) or did not form (49.9±11.5 days, N= 97) waste pellets, suggesting that waste work did not increase mortality. Although waste was probably not hazardous to adults and brood, because the dumps are located outside the brood chamber, its presence inside the nests can attract phorid flies and predators, which can harm the colony.

Genotype effect on lifespan following vitellogenin knockdown

Honey bee workers display remarkable flexibility in the aging process. This plasticity is closely tied to behavioral maturation. Workers who initiate foraging behavior at earlier ages have shorter lifespans, and much of the variation in total lifespan can be explained by differences in pre-foraging lifespan. Vitellogenin (Vg), a yolk precursor protein, influences worker lifespan both as a regulator of behavioral maturation and through anti-oxidant and immune functions. Experimental reduction of Vg mRNA, and thus Vg protein levels, in wild-type bees results in precocious foraging behavior, decreased lifespan, and increased susceptibility to oxidative damage. We sought to separate the effects of Vg on lifespan due to behavioral maturation from those due to immune and antioxidant function using two selected strains of honey bees that differ in their phenotypic responsiveness to Vg gene knockdown. Surprisingly, we found that lifespans lengthen in the strain described as behaviorally and hormonally insensitive to Vg reduction. We then performed targeted gene expression analyses on genes hypothesized to mediate aging and lifespan: the insulin-like peptides (Ilp1 and 2) and manganese superoxide dismutase (mnSOD). The two honey bee Ilps are the most upstream components in the insulin-signaling pathway, which influences lifespan in Drosophila melanogaster and other organisms, while manganese superoxide dismutase encodes an enzyme with antioxidant functions in animals. We found expression differences in the llps in fat body related to behavior (llp1 and 2) and genetic background (Ilp2), but did not find strain by treatment effects. Expression of mnSOD was also affected by behavior and genetic background. Additionally, we observed a differential response to Vg knockdown in fat body expression of mnSOD, suggesting that antioxidant pathways may partially explain the strain-specific lifespan responses to Vg knockdown.

Worker senescence and the sociobiology of aging in ants.

Senescence, the decline in physiological and behavioral function with increasing age, has been the focus of significant theoretical and empirical research in a broad array of animal taxa. Preeminent among invertebrate social models of aging are ants, a diverse and ecologically dominant clade of eusocial insects characterized by reproductive and sterile phenotypes. In this review, we critically examine selection for worker lifespan in ants and discuss the relationship between functional senescence, longevity, task performance, and colony fitness. We did not find strong or consistent support for the hypothesis that demographic senescence in ants is programmed, or its corollary prediction that workers that do not experience extrinsic mortality die at an age approximating their lifespan in nature. We present seven hypotheses concerning how selection could favor extended worker lifespan through its positive relationship to colony size and predict that large colony size, under some conditions, should confer multiple and significant fitness advantages. Fitness benefits derived from long worker lifespan could be mediated by increased resource acquisition, efficient division of labor, accuracy of collective decision-making, enhanced allomaternal care and colony defense, lower infection risk, and decreased energetic costs of workforce maintenance. We suggest future avenues of research to examine the evolution of worker lifespan and its relationship to colony fitness, and conclude that an innovative fusion of sociobiology, senescence theory, and mechanistic studies of aging can improve our understanding of the adaptive nature of worker lifespan in ants.

Differences in the resource intake of two sympatric Australian stingless bee species

Tetragonula carbonaria and Austroplebeia australis are two species of eusocial stingless bees with phylogeographically different origins that can occur sympatrically on the Australian east coast. We studied their foraging activity and resource intake and found pronounced differences between species. Tetragonula carbonaria showed consistently higher flight activity (resulting in a higher sugar intake per minute) and thus likely collected more resin and more pollen from a broader plant spectrum than A. australis. In contrast, the smaller A. australis colonies tended to collect a narrower resource spectrum and focused on high-quality resources (i.e., nectar of significantly higher sugar concentrations). Tetragonula carbonaria colonies also gained more weight over the study period than A. australis colonies, but colony growth may nevertheless be similar between the two species, albeit resulting from differences in resource allocation and exploitation as well as worker lifespan. Given their overlapping geographic ranges, T. carbonaria and A. australis may have evolved different patterns with regard to the use of resources to avoid exploitative competition between species or due to constraints imposed by their different phylogeographic origins.

Simple Modification Measurement of Photodegradability of Polymers by using Photo-induced Chemiluminescence Technique

Polymers and organic materials that are exposed to sunlight undergo photooxidation, which leads to deterioration of their physical properties. To allow adequate performance under outdoor conditions, synthetic polymers require additives such as antioxidants and UV absorbers. A major problem with optimising polymer formulations to maximise their working life span is that accelerated weathering tests are empirical. The conditions differ significantly from real weathering situations, and samples require lengthy irradiation period. Degradation may not be apparent in the early stages of exposure, although this is when products such as hydroperoxides are formed which later cause acceleration of oxidation. A simple way of quantifying the number of free radicals presents in organic materials following exposure to light or heat is by measuring chemiluminescence (CL) emission. Most polymers emit CL when they undergo oxidative degradation, and it originates from the bimolecular reaction of macroperoxy radicals which creates an excited carbonyl.