Incentives in Economic Departments: Testing Tournaments?

Existing tests of tournament theory have recently been criticized for their failure to distinguish tournaments from other theories that have similar effects like standards and marginal productivity theory (Gibbs, 1994, 1996; Prendergast, 1999). In this paper, we propose a series of empirical tests that allow to make this distinction. We use a dataset of average wages by rank in US economic departments over the period 1977-1997 and link this information to individual production data to test whether wage gaps affect the productivity and cooperative behavior of economists and to control for marginal productivity theory. We find that the wage gap is increasing along the hierarchy, even when controlling for production by rank. Moreover, wages are more sensitive to productivity for higher ranks. We find some evidence that higher wage gaps lead to higher productivity but not that wage gaps depend on the number of contestants nor that they lead to less cooperation.incentives; sorting; tournaments; standards; marginal productivity; economic departments

Overgeneralization of fear, but not avoidance, following acute stress

Research has demonstrated the spreading of fear from threat-related stimuli to perceptually similar, but innocuous, stimuli. Less is known, however, about the generalization of avoidance behavior. Given that stress is known to affect learning and memory, we were interested in the effect of acute stress on (over)generalization of fear and avoidance responses. On the first day, one geometrical shape was paired with a mild electrical stimulus (CS+), whereas another shape was not (CS-). One day later, after participants had been exposed to the Maastricht Acute Stress Test or a control task, generalization of avoidance responses and fear (shock expectancy and skin conductance responses) was tested to a range of perceptual generalization stimuli. Generalization gradients were observed across different outcome measures. Stress enhanced generalization of shock expectancy to the stimulus most similar to the CS+. Our findings confirm that stress can affect the generalization of fear, but further studies are warranted

Determining small strain shear modulus (G) of Viasvesi sand : Resonant column - Bender elements

Six samples are tested with bender element and eight samples are tested with resonant column, to respectively determine maximum shear modulus (Gmax) and shear modulus reduction curves (G/Gmax) for Viasvesi sand, which is a uniform sand. The stiffness is determined for increasing cell pressure from 50, to 100 and 300 kPa. Afterwards, the cell pressure is decreased again to 100 and 50 kPa to see if overconsolidation has any influence on Viasvesi sand. It is noticed overconsolidation has an important influence on both maximum shear stiffness and the stiffness reduction. Consolidation causes a deformation of the particle structure. Therefore, when the tested soil is unloaded, a stiffer response occurs. This stiffer response can be attributed to better localized restraints, but can also be attributed to more contacts which occur between the sand particles. The values of the maximum shear modulus and shear modulus reduction curves during loading can be important in static loadings in respectively the very small and small strain area. Additionally, during dynamic loadings, for example on- and off shore wind mills, in railway construction and during service, etc. these parameters can be useful too. Therefore it is important these parameters get determined. Additionally, the effect of overconsolidation can be useful when Viasvesi sand gets preloaded. In this case, after the preload is taken away, the soil will react stiffer and deform less. Additionally, it can be useful during excavations, where the soil body will react stiffer compared to the original soil body. The collected data with the bender elements is compared to equations of other authors during this study. During analysing the data it is noticed previously published equations are not suitable for Viasvesi sand. These equations underestimated the maximum shear stiffness. This safer estimation can be attributed to the wide range of uniformity coefficients wherefor these equations are proposed for. While the tested Viasvesi sand has a uniformity coefficient Cu of 2, the proposed equations by the other three authors are for much wider ranges of Cu, from 1.5 to 15. Therefore, a possibility exists these equations are not applicable for every type of sand. To predict the maximum shear modulus of Viasvesi sand, two equations are proposed. The reason of proposing two equations is because of some irregularities in the measurements, some data was not comparable with each other. Therefore a decision is made to propose two equations. Eventually, it is noticed both equations have an R² above 0.90 which is an acceptable accuracy. Additionally, both equations are more correct on Viasvesi sand, compared to previous noticed equations. After conducting tests, the maximum shear stiffness obtained via bender element and resonant column are plotted against each other. It is noticed the data differed not too much from each other, with R² above 0.98. Additionally, it is noticed bender element measurements estimate the maximum shear stiffness in most cases higher compared to resonant column tests

Keep calm and carry on:The relations between narrative coherence, trauma, social support, psychological well-being, and cortisol responses

In order to explain trauma resilience, previous research has been investigating possible risk and protective factors, both on an individual and a contextual level. In this experimental study, we examined narrative coherence and social support in relation to trauma resilience. Participants were asked to write about a turning point memory, after which they did the Maastricht Acute Stress Test, our lab analog of a traumatic event. Following, half of the participants received social support, whereas the other half did not. Afterwards, all participants wrote a narrative on the traumatic event. Moment-to-moment fluctuations in psychological and physiological well-being throughout the experiment were investigated with state anxiety questionnaires and cortisol measures. Results showed that narratives of traumatic experiences were less coherent than narratives of turning point memories. However, contrary to our predictions, coherence, and, in particular, thematic coherence, related positively to anxiety levels. Possibly, particular types of thematic coherence are a non-adaptive form of coping, which reflect unfinished attempts at meaning-making and are more similar to continuous rumination than to arriving at a resolution. Furthermore, coherence at baseline could not buffer against the impact of trauma on anxiety levels in this study. Contrary to our hypotheses, social support did not have the intended beneficial effects on coherence, neither on well-being. Multiple explanations as to why our support manipulation remained ineffective are suggested. Remarkably, lower cortisol levels at baseline and after writing about the turning point memory predicted higher coherence in the trauma narratives. This may suggest that the ability to remain calm in difficult situations does relate to the ability to cope adaptively with future difficult experiences. Clinical and social implications of the present findings are discussed, and future research recommendations on the relations between narrative coherence, social support, and trauma resilience are addressed

Noninvasive monitoring of radiotherapy-induced microvascular changes using dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) in a colorectal tumor model

To examine dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with a macromolecular contrast agent (P792) to visualize effects of radiotherapy (RT) on microvascular leakage in a colorectal cancer model.Journal Articleinfo:eu-repo/semantics/publishe

Dopaminergic and noradrenergic modulation of stress-induced alterations in brain activation associated with goal-directed behaviour

BACKGROUND: Acute stress is thought to reduce goal-directed behaviour, an effect purportedly associated with stress-induced release of catecholamines. In contrast, experimentally increased systemic catecholamine levels have been shown to increase goal-directed behaviour. Whether experimentally increased catecholamine function can modulate stress-induced reductions in goal-directed behaviour and its neural substrates, is currently unknown. AIM: To assess whether and how experimentally induced increases in dopamine and noradrenaline contribute to the acute stress effects on goal-directed behaviour and associated brain activation. METHODS: One hundred participants underwent a stress induction protocol (Maastricht acute stress test; MAST) or a control procedure and received methylphenidate (MPH) (40 mg, oral) or placebo according to a 2 × 2 between-subjects design. In a well-established instrumental learning paradigm, participants learnt stimulus–response–outcome associations, after which rewards were selectively devalued. Participants’ brain activation and associated goal-directed behaviour were assessed in a magnetic resonance imaging scanner at peak cortisol/MPH concentrations. RESULTS: The MAST and MPH increased physiological measures of stress (salivary cortisol and blood pressure), but only MAST increased subjective measures of stress. MPH modulated stress effects on activation of brain areas associated with goal-directed behaviour, including insula, putamen, amygdala, medial prefrontal cortex, frontal pole and orbitofrontal cortex. However, MPH did not modulate the tendency of stress to induce a reduction in goal-directed behaviour. CONCLUSION: Our neuroimaging data suggest that MPH-induced increases in dopamine and noradrenaline reverse stress-induced changes in key brain regions associated with goal-directed behaviour, while behavioural effects were absent. These effects may be relevant for preventing stress-induced maladaptive behaviour like in addiction or binge eating disorder

Size-dependent optical properties of colloidal PbS quantum dots

We quantitatively investigate the size-dependent optical properties of colloidal PbS nanocrystals or quantum dots (Qdots) by combining-the Qdot absorbance spectra with detailed elemental analysis of the Qdot suspensions. At high energies, the molar extinction coefficient epsilon increases With the Not volume d(3) and agrees with theoretical calculations using the Maxwell-Garnett effective medium theory and bulk values for the Qdot dielectric function. This demonstrates that quantum confinement has no influence on E in this spectral range, and it provides an accurate method to calculate the Qdot concentration. Around the band gap, epsilon only increases with d(1.3), and values are comparable to the epsilon of PbSe Qdots. The data are related to the oscillator strength f(if) of the band gap transition and results agree well with theoretical tight-binding calculations, predicting a linear dependence of f(if) on d. For both PbS and PbSe Qdots, the exciton lifetime tau is calculated from f(if). We find values ranging between 1 and 3 mu s, in agreement with experimental literature data from time-resolved luminescence spectroscopy. Our results provide a thorough general framework to calculate and understand the optical properties of suspended colloidal quantum dots. Most importantly, it highlights the significance of the local field factor in these systems

Differentiation between peri-anastomotic inflammatory changes and local recurrence following neoadjuvant radiochemotherapy surgery for colorectal cancer using visual and semiquantitative analysis of PET-CT data

Aim. The aim of this study was to evaluate the usefulness of visual and semiquantitative [F-18]fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) data for the diagnosis of peri-anastomotic colorectal cancer recurrence, taking into account the time period between surgery and [F-18]FDG PET-CT scanning. Methods. The study population consisted of 70 patients who had prior preoperative radiochemotherapy and surgical resection of the primary tumor and who underwent whole body [F-18]FDG PET-CT scanning for the detection of recurrent disease. Visual and semiquantitative (SUVmax) analysis of [F-18]FDG uptake at the peri-anastomosis was performed. The final diagnosis was based on pathological proof or clinical and/or imaging follow-up data. Results. On visual reading, 27 patients exhibited increased [F-18]FDG uptake at the peri-anastomosis. Of these, 11 (41%) patients had a local tumor recurrence and 16 (59%) had no recurrent tumor. Among the 43 patients without increased [F-18]FDG uptake at the peri-anastomosis, none had local tumor recurrence. On semiquantitation, SUVmax in patients with and without a local recurrence overlapped. However, when the time period between surgery and [F-18]FDG PET-CT scanning was taken into account, overlap of SUVmax was mainly observed within a postoperative period of <= 12 months; thereafter, a threshold SUVmax of 3.2 discriminated between benign and malignant lesions in all but one patient. Conclusion. In our series, visually increased [F-18]FDG uptake at the peri-anastomosis was 100% sensitive but non-specific (73% specificity) for the diagnosis of local tumor recurrence. On the other hand, normal [F-18]FDG uptake at the peri-anastomosis precluded a local tumor recurrence (a negative predictive value of 100%). In addition, semiquantitative (SUVmax) analysis of [F-18]FDG uptake at the peri-anastomosis may increase specificity (up to 97%), while preserving maximum sensitivity, if the postoperative period is >12 months

Acute stress differentially affects spatial configuration learning in high and low cortisol-responding healthy adults

Background: Stress and stress hormones modulate memory formation in various ways that are relevant to our understanding of stress-related psychopathology, such as posttraumatic stress disorder (PTSD). Particular relevance is attributed to efficient memory formation sustained by the hippocampus and parahippocampus. This process is thought to reduce the occurrence of intrusions and flashbacks following trauma, but may be negatively affected by acute stress. Moreover, recent evidence suggests that the efficiency of visuo-spatial processing and learning based on the hippocampal area is related to PTSD symptoms. Objective: The current study investigated the effect of acute stress on spatial configuration learning using a spatial contextual cueing task (SCCT) known to heavily rely on structures in the parahippocampus. Method: Acute stress was induced by subjecting participants (N = 34) to the Maastricht Acute Stress Test (MAST). Following a counterbalanced within-subject approach, the effects of stress and the ensuing hormonal (i.e., cortisol) activity on subsequent SCCT performance were compared to SCCT performance following a no-stress control condition. Results: Acute stress did not impact SCCT learning overall, but opposing effects emerged for high versus low cortisol responders to the MAST. Learning scores following stress were reduced in low cortisol responders, while high cortisol-responding participants showed improved learning. Conclusions: The effects of stress on spatial configuration learning were moderated by the magnitude of endogenous cortisol secretion. These findings suggest a possible mechanism by which cortisol responses serve an adaptive function during stress and trauma, and this may prove to be a promising route for future research in this area