An analysis of astronaut performance capability in the lunar environment. Volume 1 - Performance problems and requirements for additional research

Analyzing data on expected astronaut performance in lunar environmen

An Analysis of Astronaut Performance Capability in the Lunar Environment. Volume 2 - Performance Capability Support Data

Astronaut performance capability in lunar environmen

Why Do Leaders Matter? The Role of Expert Knowledge

Why do some leaders succeed while others fail? This question is important, but its complexity makes it hard to study systematically. We draw on a setting where there are well-defined objectives, small teams of workers, and exact measures of leaders’ characteristics and organizational performance. We show that a strong predictor of a leader’s success in year T is that person’s own level of attainment, in the underlying activity, in approximately year T-20. Our data come from 15,000 professional basketball games and reveal that former star players make the best coaches. This ‘expert knowledge’ effect is large

Substitution Between Managers and Subordinates: Evidence from British Football

We use data on British football managers and teams over the 1994-2007 period to study substitution and complementarity between leaders and subordinates. We find for the Premier League (the highest level of competition) that, other things being equal, managers who themselves played at a higher level raise the productivity of less-skilled teams by more than that of highly skilled teams. This is consistent with the hypothesis that one function of a top manager is to communicate to subordinates the skills needed to succeed, since less skilled players have more to learn. We also find that managers with more accumulated professional managing experience raise the productivity of talented players by more than that of less-talented players. This is consistent with the hypothesis that a further function of successful managers in high-performance workplaces is to manage the egos of elite workers. Such a function is likely more important the more accomplished the workers are -- as indicated, in our data, by teams with greater payrolls.Productivity, leadership

Why Do Leaders Matter? The Role of Expert Knowledge

Why do some leaders succeed while others fail? This question is important, but its complexity makes it hard to study systematically. We examine an industry in which there are well-defined objectives, small teams, and exact measures of leaders’ characteristics. We show that a strong predictor of a leader’s success in year T is that person’s own level of attainment, in the underlying activity, in approximately year T-20. Our data come from 15,000 professional basketball games. The effect on team performance of the coach’s ‘expert knowledge’ is large and is discernible in the data within 12 months of his being hired.organizational performance, firms, leadership, fixed-effects, productivity

A DMRG Study of Low-Energy Excitations and Low-Temperature Properties of Alternating Spin Systems

We use the density matrix renormalization group (DMRG) method to study the ground and low-lying excited states of three kinds of uniform and dimerized alternating spin chains. The DMRG procedure is also employed to obtain low-temperature thermodynamic properties of these systems. We consider a 2N site system with spins $s_1$ and $s_2$ alternating from site to site and interacting via a Heisenberg antiferromagnetic exchange. The three systems studied correspond to $(s_1 ,s_2 )$ being equal to $(1,1/2),(3/2,1/2)$ and $(3/2,1)$; all of them have very similar properties. The ground state is found to be ferrimagnetic with total spin $s_G =N(s_1 - s_2)$. We find that there is a gapless excitation to a state with spin $s_G -1$, and a gapped excitation to a state with spin $s_G +1$. Surprisingly, the correlation length in the ground state is found to be very small for this gapless system. The DMRG analysis shows that the chain is susceptible to a conditional spin-Peierls instability. Furthermore, our studies of the magnetization, magnetic susceptibility $\chi$ and specific heat show strong magnetic-field dependences. The product $\chi T$ shows a minimum as a function of temperature T at low magnetic fields; the minimum vanishes at high magnetic fields. This low-field behavior is in agreement with earlier experimental observations. The specific heat shows a maximum as a function of temperature, and the height of the maximum increases sharply at high magnetic fields. Although all the three systems show qualitatively similar behavior, there are some notable quantitative differences between the systems in which the site spin difference, $|s_1 - s_2|$, is large and small respectively.Comment: 16 LaTeX pages, 13 postscript figure

Anisotropy effects in a mixed quantum-classical Heisenberg model in two dimensions

We analyse a specific two dimensional mixed spin Heisenberg model with exchange anisotropy, by means of high temperature expansions and Monte Carlo simulations. The goal is to describe the magnetic properties of the compound (NBu_{4})_{2}Mn_{2}[Cu(opba)]_{3}\cdot 6DMSO\cdot H_{2}O which exhibits a ferromagnetic transition at $T_{c}=15K$. Extrapolating our analysis on the basis of renormalisation group arguments, we find that this transition may result from a very weak anisotropy effect.Comment: 8 pages, 10 Postscript figure

Electronic structure of the molecule based magnet Cu PM(NO3)2 (H2O)2

We present density functional calculations on the molecule based S=1/2 antiferromagnetic chain compound Cu PM(NO3)2 (H2O)2; PM = pyrimidine. The properties of the ferro- and antiferromagnetic state are investigated at the level of the local density approximation and with the hybrid functional B3LYP. Spin density maps illustrate the exchange path via the pyrimidine molecule which mediates the magnetism in the one-dimensional chain. The computed exchange coupling is antiferromagnetic and in reasonable agreement with the experiment. It is suggested that the antiferromagnetic coupling is due to the possibility of stronger delocalization of the charges on the nitrogen atoms, compared to the ferromagnetic case. In addition, computed isotropic and anisotropic hyperfine interaction parameters are compared with recent NMR experiments