Herd Behaviour in Occupational Choice

In this paper we examine why many professional labor markets are disturbed by cycles in the supply of new workers. We present a model where cycles in labor supply are the consequence of herd behavior in occupational choice. We also present evidence from nearly 150 West German labor markets which supports the herd behavior model of labor supply cycles.analysis of education, occupational choice, professional labor markets

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

Land value as a function of distance from the CBD : the case of the eastern suburbs of Pretoria

The greater the benefit derived from using a piece of land for any particular purpose the higher the price the prospective riser is willing to pay. The demand for land is thus a reflection of the utility derived from its use by current or potential users. The ability to compete for sites depends on whether they have the means to benefit from accessibility and complementarity within the urban framework. Conventional theory states that productivity determines urban rent, which is the highest at the place of maximum accessibility, i.e. the central business district (CBD). This paper review selected residential location theories and the factors influencing location decisions. Using selected eastern suburbs of Pretoria, the paper tries to determine whether residential land values decrease as distance from the CBD increase as theory suggests

Land value as a function of distance from the CBD : the case of the eastern suburbs of Pretoria

The greater the benefit derived from using a piece of land for any particular purpose the higher the price the prospective riser is willing to pay. The demand for land is thus a reflection of the utility derived from its use by current or potential users. The ability to compete for sites depends on whether they have the means to benefit from accessibility and complementarity within the urban framework. Conventional theory states that productivity determines urban rent, which is the highest at the place of maximum accessibility, i.e. the central business district (CBD). This paper review selected residential location theories and the factors influencing location decisions. Using selected eastern suburbs of Pretoria, the paper tries to determine whether residential land values decrease as distance from the CBD increase as theory suggests

Flow intermittency affects structural and functional properties of macroinvertebrate communities in alpine streams

Flow regime is a major determinant of the structure and functioning of aquatic ecosystems. Under climate change, flow intermittency is becoming more prevalent in glaciated alpine catchments, but the effects of increasing dryness on aquatic biodiversity remain largely unknown. We characterised flow intermittency patterns in 30 streams of a glaciated alpine catchment over 15 months and separated these streams into four intermittency categories: perennial streams, winter-drying streams, moderately intermittent streams with occasional drying in summer, and periodically intermittent streams with extensive dry periods throughout the year. We then examined how these drying patterns affected structural and functional properties of benthic macroinvertebrate communities, and whether these changes were primarily deterministic or stochastic. At the taxonomic level, we observed a response at the highest intermittency levels, with α diversity lower and β diversity higher in periodically intermittent streams than in other stream types. This result suggested that local biota were well adapted to intermediate intermittency levels (mostly during winter) but not to high intermittency during summer. In contrast, functional diversity indices at the α and β levels (based on trait abundances) did not differ across intermittency categories. Considering the moderate level of functional redundancy, we interpreted this as an indication that changes in taxonomic diversity may have resulted primarily from stochastic processes. Analysis of community and trait composition indicated that deterministic selection may indeed have occurred with increased intermittency, but this process was likely to be minor in comparison to stochastic extinctions. Notably, community evenness was highest in periodically intermittent streams and lowest in perennial streams, suggesting that frequent drying prevented competitive exclusion. Our results suggested that most macroinvertebrate populations are resilient to intermediate intermittency levels but are filtered at high intermittency, irrespective of their resilience capacities. However, more research is needed to clarify the specific roles of different facets of flow regimes, specifically frequency, duration, and timing of intermittency. Understanding the consequences of responses in diversity and community evenness with increasing intermittency on the functional properties of communities will allow better prediction of the future ecological status of alpine stream networks to ongoing environmental change

Long-lasting effects of experimental flow intermittency on alpine stream macroinvertebrates (Val Roseg, Switzerland)

Changing weather patterns and receding glaciers are predicted to increase flow intermittency in alpine streams. If aquatic macroinvertebrate communities largely comprise taxa adapted to perennial flows, an increase in flow intermittency substantially reduces biodiversity and affects functional processes. We conducted a before-after-control-impact field experiment to examine how macroinvertebrate communities in an alpine headwater stream responded to and recovered from a repeated experimental increase in flow intermittency. Flow in one channel was manipulated to simulate increased summer intermittency (June-September) over two consecutive years, whilst an adjacent channel served as a control. We monitored the density of benthic macroinvertebrates, periphyton and organic matter at approximately monthly intervals over three years during the snow-free period. Before manipulation, both channels had similar ecological properties. The flow manipulation reduced the overall macroinvertebrate density, and especially the proportional rheophile density, across both years. Recovery of the macroinvertebrate community following experimental flow intermittency took more than a year, and longer than our study period. This could be due to long aquatic life stages, dispersal limitation and biotic interactions. We conclude that climate-induced changes in alpine stream flow regimes can lead to a fundamental shift in macroinvertebrate assemblages through local extinctions, mostly of rheophilic species.ISSN:0018-8158ISSN:1573-511

Long-lasting effects of experimental flow intermittency on alpine stream macroinvertebrates (Val Roseg, Switzerland)

International audienceChanging weather patterns and receding glaciers are predicted to increase flow intermittency in alpine streams. If aquatic macroinvertebrate communities largely comprise taxa adapted to perennial flows, an increase in flow intermittency substantially reduces biodiversity and affects functional processes. We conducted a before-after-control-impact field experiment to examine how macroinvertebrate communities in an alpine headwater stream responded to and recovered from a repeated experimental increase in flow intermittency. Flow in one channel was manipulated to simulate increased summer intermittency (June-September) over two consecutive years, whilst an adjacent channel served as a control. We monitored the density of benthic macroinvertebrates, periphyton and organic matter at approximately monthly intervals over three years during the snow-free period. Before manipulation, both channels had similar ecological properties. The flow manipulation reduced the overall macroinvertebrate density, and especially the proportional rheophile density, across both years. Recovery of the macroinvertebrate community following experimental flow intermittency took more than a year, and longer than our study period. This could be due to long aquatic life stages, dispersal limitation and biotic interactions. We conclude that climate-induced changes in alpine stream flow regimes can lead to a fundamental shift in macroinvertebrate assemblages through local extinctions, mostly of rheophilic species