Performance Pay and Multidimensional Sorting - Productivity, Preferences and Gender

This paper studies the impact of incentives on worker self-selection in a controlled laboratory experiment. Subjects face the choice between a fixed and a variable payment scheme. Depending on the treatment, the variable payment is a piece rate, a tournament or a revenue-sharing scheme. We find that output is higher in the variable pay schemes (piece rate, tournament, and revenue sharing) compared to the fixed payment scheme. This difference is largely driven by productivity sorting. In addition personal attitudes such as willingness to take risks and relative self-assessment as well as gender affect the sorting decision in a systematic way. Moreover, self-reported effort is significantly higher in all variable pay conditions than in the fixed wage condition. Our lab findings are supported by an additional analysis using data from a large and representative sample. In sum, our findings underline the importance of multi-dimensional sorting, i.e., the tendency for different incentive schemes to systematically attract people with different individual characteristics

Improved methods for detecting gravitational waves associated with short gamma-ray bursts

In the era of second generation ground-based gravitational wave detectors, short gamma-ray bursts (GRBs) will be among the most promising astrophysical events for joint electromagnetic and gravitational wave observation. A targeted search for gravitational wave compact binary merger signals in coincidence with short GRBs was developed and used to analyze data from the first generation LIGO and Virgo instruments. In this paper, we present improvements to this search that enhance our ability to detect gravitational wave counterparts to short GRBs. Specifically, we introduce an improved method for estimating the gravitational wave background to obtain the event significance required to make detections; implement a method of tiling extended sky regions, as required when searching for signals associated to poorly localized GRBs from Fermi Gamma-ray Burst Monitor or the InterPlanetary Network; and incorporate astrophysical knowledge about the beaming of GRB emission to restrict the search parameter space. We describe the implementation of these enhancements and demonstrate how they improve the ability to observe binary merger gravitational wave signals associated with short GRBs.Comment: 13 pages, 6 figure

<i>‘What retention’ means to me</i>: the position of the adult learner in student retention

Studies of student retention and progression overwhelmingly appear adopt definitions that place the institution, rather than the student, at the centre. Retention is most often conceived in terms of linear and continuous progress between institutionally identified start and end points. This paper reports on research that considered data from 38 in-depth interviews conducted with individuals who had characteristics often associated with non-traditional engagement in higher education who between 2006 and 2010 had studied an ‘Introduction to HE’ module at one distance higher education institution, some of whom had progressed to further study at that institution, some of whom had not. The research deployed a life histories approach to seek a finer grained understanding of how individuals conceptualise their own learning journey and experience, in order to reflect on institutional conceptions of student retention. The findings highlight potential anomalies hidden within institutional retention rates – large proportions of the interview participants who were not ‘retained’ by the institution reported successful progression to and in other learning institutions and environments, both formal and informal. Nearly all described positive perspectives on lifelong learning which were either engendered or improved by the learning undertaken. This attests to the complexity of individuals’ lives and provides clear evidence that institution-centric definitions of retention and progression are insufficient to create truly meaningful understanding of successful individual learning journeys and experiences. It is argued that only through careful consideration of the lived experience of students and a re-conception of measures of retention, will we be able to offer real insight into improving student retention

Predicting population-level risk effects of predation from the responses of individuals.

Fear of predation produces large effects on prey population dynamics through indirect risk effects that can cause even greater impacts than direct predation mortality. As yet, there is no general theoretical framework for predicting when and how these population risk effects will arise in specific prey populations, meaning that there is often little consideration given to the key role predator risk effects can play in understanding conservation and wildlife management challenges. Here, we propose that population predator risk effects can be predicted through an extension of individual risk trade-off theory and show for the first time that this is the case in a wild vertebrate system. Specifically, we demonstrate that the timing (in specific months of the year), occurrence (at low food availability), cause (reduction in individual energy reserves), and type (starvation mortality) of a population-level predator risk effect can be successfully predicted from individual responses using a widely applicable theoretical framework (individual-based risk trade-off theory). Our results suggest that individual-based risk trade-off frameworks could allow a wide range of population-level predator risk effects to be predicted from existing ecological theory, which would enable risk effects to be more routinely integrated into consideration of population processes and in applied situations such as conservation

NXY-059, a Failed Stroke Neuroprotectant, Offers No Protection to Stem Cell-Derived Human Neurons

Background: Developing new medicines is a complex process where understanding the reasons for both failure and success takes us forward. One gap in our understanding of most candidate stroke drugs before clinical trial is whether they have a protective effect on human tissues. NXY-059 is a spin-trap reagent hypothesized to have activity against the damaging oxidative biology which accompanies ischemic stroke. Re-examination of the preclinical in vivo dataset for this agent in the wake of the failed SAINT-II RCT highlighted the presence of a range of biases leading to overestimation of the magnitude of NXY-059\u27s effects in laboratory animals. Therefore, NXY-059 seemed an ideal candidate to evaluate in human neural tissues to determine whether human tissue testing might improve screening efficiency. Materials and Methods: The aim of this randomized and blinded study was to assess the effects of NXY-059 on human stem cell-derived neurons in the presence of ischemia-like injury induced by oxygen glucose deprivation or oxidative stress induced by hydrogen peroxide or sodium nitroprusside. Results: In MTT assays of cell survival, lactate dehydrogenase assays of total cell death and terminal deoxynucleotidyl transferase dUTP nick end labeling staining of apoptotic-like cell death, NXY-059 at concentrations ranging from 1 µm to 1 mm was completely without activity. Conversely an antioxidant cocktail comprising 100 µm each of ascorbate, reduced glutathione, and dithiothreitol used as a positive control provided marked neuronal protection in these assays. Conclusion: These findings support our hypothesis that stroke drug screening in human neural tissues will be of value and provides an explanation for the failure of NXY-059 as a human stroke drug

Methanol Masers as Tracers of Circumstellar Disks

We show that in many methanol maser sources the masers are located in lines, with a velocity gradient along them which suggests that the masers are situated in edge-on circumstellar, or protoplanetary, disks. We present VLBI observations of the methanol maser source G309.92+0.48, in the 12.2 GHz transition, which confirm previous observations that the masers in this source lie along a line. We show that such sources are not only linear in space but, in many cases, also have a linear velocity gradient. We then model these and other data in both the 6.7 GHz and the 12.2 GHz transition from a number of star formation regions, and show that the observed spatial and velocity distribution of methanol masers, and the derived Keplerian masses, are consistent with a circumstellar disk rotating around an OB star. We consider this and other hypotheses, and conclude that about half of these methanol masers are probably located in edge-on circumstellar disks around young stars. This is of particular significance for studies of circumstellar disks because of the detailed velocity information available from the masers.Comment: 38 pages, 13 figures accepted by Ap

Non-locking screw insertion:No benefit seen if tightness exceeds 80% of the maximum torque

Screws are the most commonly used orthopaedic implant, however they are frequently overtightened when inserted. Using screw, bone and screw hole characteristics, maximum torque for a screw hole is predicted prior to insertion. Using this, optimum tightness as a percentage of the maximum torque is investigated as functions of compression and pullout forces. This data set provides the raw data for these investigations. The methodology is described in detail in the related manuscript: Fletcher, J., Ehrhardt, B., MacLeod, A., Whitehouse, M., Gill, H. & Preatoni, E. 2019. Non-locking screw insertion: No benefit seen if tightness exceeds 80% of the maximum torque. Clinical Biomechanics. https://doi.org/10.1016/j.clinbiomech.2019.07.009Biomechanical testing using juvenile bovine bone'R' software, v3.3.3 (R: A language and environment for statistical computing. R Foundation for Statistical Computing)