Gender differences in response to contingent rewards: Evidence from a natural experiment of junior tennis

We investigate gender differences in responding to contingent rewards by exploiting a natural experiment in junior tennis tournaments in Florida where the ranking point system was revised to induce more players to play doubles. The new point system increased the points earned from wins in singles matches significantly if the two thirds or more of players in their sex/age group chose to play doubles. We examine three types of potential responses to the new system: (1) a ‘positive’ response of playing doubles more by singles winners, (2) a ‘subversive’ response of playing doubles less by singles losers, and (3) a ‘slack’ response of playing loosely in their doubles matches by singles winners. We find strong evidence on the positive response among boys and top-ranked girls but no evidence for subversive and slack responses

Conductance Fluctuations Near the Two-Dimensional Metal-Insulator Transition

Measurements of conductance $G$ on short, wide, high-mobility Si-MOSFETs reveal both a two-dimensional metal-insulator transition (MIT) at moderate temperatures (1 $<~ T <$ 4~K) and mesoscopic fluctuations of the conductance at low temperatures ($T~ <$ 1~K). Both were studied as a function of chemical potential (carrier concentration $n_s$) controlled by gate voltage ($V_g$) and magnetic field $B$ near the MIT. Fourier analysis of the low temperature fluctuations reveals several fluctuation scales in $V_g$ that vary non-monotonically near the MIT. At higher temperatures, $G(V_g,B)$ is similar to large FETs and exhibits a MIT. All of the observations support the suggestion that the MIT is driven by Coulomb interactions among the carriers.Comment: 4 pages, LaTeX, physica.sty (slightly modified prabib.sty), Submitted to the 1997 Conference on Electronic Properties of Two-Dimensional System

REMOVED: Explaining the Ultra-High Water Flow Rates Observed in Carbon Nanotube Membranes

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Spatial risk for a superspreading environment: Insights from six urban facilities in six global cities across four continents

Introduction: This study sets out to provide scientific evidence on the spatial risk for the formation of a superspreading environment. Methods: Focusing on six common types of urban facilities (bars, cinemas, gyms and fitness centers, places of worship, public libraries and shopping malls), it first tests whether visitors' mobility characteristics differ systematically for different types of facility and at different locations. The study collects detailed human mobility and other locational data in Chicago, Hong Kong, London, São Paulo, Seoul and Zurich. Then, considering facility agglomeration, visitors' profile and the density of the population, facilities are classified into four potential spatial risk (PSR) classes. Finally, a kernel density function is employed to derive the risk surface in each city based on the spatial risk class and nature of activities. Results: Results of the human mobility analysis reflect the geographical and cultural context of various facilities, transport characteristics and people's lifestyle across cities. Consistent across the six global cities, geographical agglomeration is a risk factor for bars. For other urban facilities, the lack of agglomeration is a risk factor. Based on the spatial risk maps, some high-risk areas of superspreading are identified and discussed in each city. Discussion: Integrating activity-travel patterns in risk models can help identify areas that attract highly mobile visitors and are conducive to superspreading. Based on the findings, this study proposes a place-based strategy of non-pharmaceutical interventions that balance the control of the pandemic and the daily life of the urban population

Editorials

Continuing medical education in obstetrics and gynaecologyThe present and future of obstetrics and gynaecology in South AfricaThe case for an increased tobacco tax in South AfricaImplications of bacterial resistance for the use of beta-lactam agents in clinical practiceQuality of care - and debateAlcohol and brain damag