Is the Over-Education Wage Penalty Permanent?

Much has been written about the impact of over-education on wages using cross-sectional data, although there have been few studies that analyse the returns to over-education in a dynamic setting. This paper adds to the existing literature by using panel data to investigate the impact and permanence of over-education wage penalties, whilst controlling for unobserved individual heterogeneity. Our fixed effects estimates suggest that the over-education wage penalty cannot solely be explained by unobserved heterogeneity. Over-education is permanent for many workers since around 50 percent of workers over-educated in 1991 are still over-educated in 2005. However, we also show that these workers are of lower quality compared to around 25 percent who find a match within five years of being over-educated. Finally, there is a significant scarring effect for workers over-educated in 1991 since they never fully reach parity compared to those who were matched in 1991, although this is not the case for graduates who manage to find a match within 5 years.Over-education, Skills

The Neuromuscular and Mechanical Control of the Knee Joint in Patellofemoral Pain Sufferers

Results Grouped Tape Response: The mean motor unit firing exhibited an increase in the VM firing rate and a decrease in the VL firing rate within the tape condition, across both subject groups, suggesting a modification in the load bias across the Vasti muscles. The common drive, a physiological phenomenon describing common fluctuations in the motor unit firings and consequently a measure of the nervous systems signals to control pools of motor units, increased in the VM and decreased for the VL in response to the tape condition in symptomatic subjects showing that the tape may be providing enhanced feedback to the nervous system that responded by modifying the ‘control’ to the motor units. There were no changes however in the non-symptomatic subject group, perhaps suggesting their motor units were already controlled efficiently. Motor unit recruitment analyses, through regression analysis of the motor unit firing rate and knee joint moment, showed the VM motor units in the non-symptomatic subjects were recruitment at a higher firing rate in the tape condition but interestingly no change in the VL and no change in the symptomatic subjects. Both non- symptomatic and symptomatic subjects demonstrated significant reductions in transverse plane knee joint range of moment, illustrating a more controlled rotational knee joint after the application of tape. There were no significant changes found in the coronal or sagittal joint mechanics. Symptomatic subjects demonstrated a propensity to consciously control their movements, suggestively disrupting automatic motor control tasks. Symptomatic subjects presented with pain scores of 4.2/10 on the numerical rating scale. Individual Tape Response: Exploration of individuals’ response to tape, opposed to pooling data and treating as homogenous groups, exhibited a non-uniform response with variable increases, decreases and no changes across the different measurements taken. The exploration of the data with this method is in line with common clinical presentation of PFP subjects and presents rationale for new ways to view the data as to not mask the true physiological behaviours. Comparison of groups: Motor unit recruitment analyses comparing the subject groups demonstrated that symptomatic subjects had a significantly different motor unit recruitment strategy for the Vasti muscles, where the larger motor units were firing faster compared to the non-symptomatics larger motor units in both VM and VL for the same level of force. Symptomatic subjects demonstrated a lower common drive to the VM and higher common drive in the VL compared to non-symptomatic subjects, which after the application of tape became the same level as the non-symptomatics. Symptomatic subjects also exhibited significantly lower muscle activity in the GAS, BF, RF and GMed, thus suggestively increasing the muscle activity bias to the Vasti muscles. No changes were seen in the joint biomechanics or mean motor unit firing rate between the groups. Discussion These findings suggest that the nervous system offers a portfolio of solutions to control and distribute force, which can be manipulated through a common taping intervention. The results show that the motor unit firing rate in the VM increases and decreases in the VL, coupled with altered motor unit recruitment strategies thus inferring that there may be a re-distribution of force across the Vasti with the application of tape. This is interestingly complimented with an increase of common drive in the VM and decrease in the VL between subject groups. The presence and then change of common drive within the Vasti so that the motor units are firing in unison, more so with tape, and providing a tantalising prospect that the VM muscle is acting more efficiently and controlled with tape. The novel findings of the neuromuscular system and its modification were alongside the increase in torsional joint control. However, it is evident that the motor unit firing rate, common drive and motor unit recruitment present variable responses amongst individuals, offering different solutions to achieve the same goal; increasing the force and its control within the muscle. The underlying mechanism for the observed findings are unable to be expressed definitively, however it can be deduced that the application of tape presents proprioceptive feedback to the muscle that alters the motor unit pool; consequently adjusting the force and its control within and across muscles leading to an increase in knee stability. Conclusion The key implications from this work is that the application of tape can offer clinically meaningful changes to the sensory-motor control system, through the manipulation and alteration of the motor unit pool, suggestively from an enhanced proprioceptive feedback mechanism. However, researchers and clinicians should consider the individualistic responses and the potential to mask true physiological findings by assuming homogeneity within patient populations with data analyses and clinical decision processes respectively. This work offers unique and novel insights into both the behaviour of patients with Patellofemoral Pain and also the effects of a taping intervention, thus providing additional clinical understanding and also tantalizing opportunities for future work exploring musculoskeletal or neurological disorders and insight into the sensory-motor control strategies

Modeling the effect of striped bass (Morone saxatilis) on the population viability of Sacramento River winter-run chinook salmon (Onchorhynchus tshawytscha)

We estimated the impact of striped bass (Morone saxatilis) predation on winter-run chinook salmon (Oncorhynchus tshawytscha) with a Bayesian population dynamics model using striped bass and winter-run chinook salmon population abundance data. Winter-run chinook salmon extinction and recovery probabilities under different future striped bass abundance levels were estimated by simulating from the posterior distribution of model parameters. The model predicts that if the striped bass population declines to 512,000 adults as expected in the absence of stocking, winter-run chinook salmon will have about a 28% chance of quasi-extinction (defined as three consecutive spawning runs of fewer than 200 adults) within 50 years. If stocking stabilizes the striped bass population at 700,000 adults, the predicted quasi-extinction probability is 30%. A more ambitious stocking program that maintains a population of 3 million adult striped bass would increase the predicted quasi-extinction probability to 55%. Extinction probability, but not recovery probability, was fairly insensitive to assumptions about density dependence. We conclude that winter-run chinook salmon face a serious extinction risk without augmentation of the striped bass population and that substantial increases in striped bass abundance could significantly increase the threat to winter-run chi-nook salmon if not mitigated by increasing winter chinook salmon survival in some other way

APPLICABILITY OF FOUR LOCALIZED-CALIBRATION METHODS IN UNDERWATER MOTION ANALYSIS

Four different localized-calibration methods were developed based on the DLT (direct linear transformation) algorithm in an effort to reduce the error due to refraction in underwater motion analysis. Their applicability in underwater motion analysis was assessed based on a simulated 3D calibration trial with 2 cameras and a hexahedral calibration frame. It was concluded from the analysis of the calibration results that (a) all methods substantially reduced the maximum reconstruction error and demonstrated the potential to minimize object space deformation, (b) localization methods based on overlapped control volumes/areas revealed superior performance than those based on distinct volumes/areas, and (c) the 2D DLT-based localization algorithm provided more accurate object space reconstruction than the 3D DLT-based algorithm

Determination of the motor unit behavior of lumbar erector spinae muscles through surface EMG decomposition technology in healthy female subjects

Introduction: The aims of this study were to determine the motor unit behavior of the erector spinae muscles and to assess whether differences exist between the dominant/non-dominant sides of the back muscles. Methods: Nine healthy women, aged 21.7 years (±0.7), performed a back extension test. Surface electromyographic decomposition data were collected from both sides of the erector spinae and decomposed into individual motor unit action potential trains. The mean firing rate for each motor unit was calculated, and a regression analysis was performed against the corresponding recruitment thresholds. Results: The mean firing rate ranged from 15.9 to 23.9 pulses per second (pps) and 15.8 to 20.6 pps on the dominant and non-dominant sides, respectively. However, the early motor unit potential s of the non-dominant lumbar erector spinae muscles were recruited at a lower firing rate. Conclusions: This technique may further our understanding of individuals with back pain and other underlying neuromuscular diseases

Surface Electromyography of the foot: a protocol for sensor placement

Background The use of surface EMG (sEMG) to record muscle activity is common place yet due to restrictions in technology studies on the intrinsic foot muscles have been limited or only fine wire instruments have been used. Aim This paper looks at the potential reliability of a sEMG protocol for assessing the intrinsic foot muscles. Methods Six intrinsic muscles were defined using ultrasound and muscle function testing. A protocol for sensor placement was created with repeatability and reliability testing of the protocol conducted by three separate testers on three subjects over two different time frames. Inter tester and Inter session repeatability and reliability was measured with ICC and percentage standard error of measurement. Results Although there was good correlation between Extensor Digitorum Brevis, Dorsal Interossei, Abductor Digiti Minimi and Flexor Digitorum Brevis there was increased variability and poor correlation for Flexor hallucis Brevis and Abductor Hallucis. The percentage standard error of measurement did not support the high ICC values indicating a lower precision of measurement. Significance Variability between testers and sessions shows an inconsistent reliability of sEMG and further work is required with protocols focussing on grouping muscles to improve the understanding of the intrinsic foot muscles

Research Tools to Investigate Movements, Migrations, and Life History of Sturgeons (Acipenseridae), with an Emphasis on Marine-Oriented Populations

Worldwide, sturgeons (Acipenseridae) are among the most endangered fishes due to habitat degradation, overfishing, and inherent life history characteristics (long life span, late maturation, and infrequent spawning). As most sturgeons are anadromous, a considerable portion of their life history occurs in estuarine and marine environments where they may encounter unique threats (e.g., interception in non-target fisheries). Of the 16 marine-oriented species, 12 are designated as Critically Endangered by the IUCN, and these include species commercially harvested. We review important research tools and techniques (tagging, electronic tagging, genetics, microchemistry, observatory) and discuss the comparative utility of these techniques to investigate movements, migrations, and life-history characteristics of sturgeons. Examples are provided regarding what the applications have revealed regarding movement and migration and how this information can be used for conservation and management. Through studies that include Gulf (Acipenser oxyrinchus desotoi) and Green Sturgeon (A. medirostris), we illustrate what is known about well-studied species and then explore lesser-studied species. A more complete picture of migration is available for North American sturgeon species, while European and Asian species, which are among the most endangered sturgeons, are less understood. We put forth recommendations that encourage the support of stewardship initiatives to build awareness and provide key information for population assessment and monitoring

Growth in within graduate wage inequality: the role of subjects, cognitive skill dispersion and occupational concentration

UK graduate wage inequality has increased over the previous three decades. This paper demonstrates that most of the growth has occurred within degree subjects, with the largest occurring in non-STEM subjects. The paper therefore investigates two potential explanations. The first is the increase in the variance of childhood cognitive test scores amogst graduates in the same subject. This increase differs across subjects, and is again in the non-STEM subjects where the variance of test scores has increased the most, especially during the second period of rapid higher education expansion in the 1990s. The second potential explanation explored is the fall in the occupational concentration of subjects. Graduates of some subjects (like Medicine and Education) are highly concentrated into only a few jobs whereas others are much more widely dispersed. Generally, all subjects have become more widely dispersed across occupations over time, but some more so than others. The paper then shows that both of these factors have played a role in explaining growing graduate wage inequality within subjects, though the largest is by far from the widening in the variance of test scores. The path of graduate wage inequality would have been relatively flat without the accompanying increase in the variance of cognitive skills

Research Tools to Investigate Movements, Migrations, and Life History of Sturgeons (Acipenseridae), with an Emphasis on Marine-Oriented Populations

Worldwide, sturgeons (Acipenseridae) are among the most endangered fishes due to habitat degradation, overfishing, and inherent life history characteristics (long life span, late maturation, and infrequent spawning). As most sturgeons are anadromous, a considerable portion of their life history occurs in estuarine and marine environments where they may encounter unique threats (e.g., interception in non-target fisheries). Of the 16 marine-oriented species, 12 are designated as Critically Endangered by the IUCN, and these include species commercially harvested. We review important research tools and techniques (tagging, electronic tagging, genetics, microchemistry, observatory) and discuss the comparative utility of these techniques to investigate movements, migrations, and life-history characteristics of sturgeons. Examples are provided regarding what the applications have revealed regarding movement and migration and how this information can be used for conservation and management. Through studies that include Gulf (Acipenser oxyrinchus desotoi) and Green Sturgeon (A. medirostris), we illustrate what is known about well-studied species and then explore lesser-studied species. A more complete picture of migration is available for North American sturgeon species, while European and Asian species, which are among the most endangered sturgeons, are less understood. We put forth recommendations that encourage the support of stewardship initiatives to build awareness and provide key information for population assessment and monitoring