Novel non-local behaviour of quasi-3D Wide Quantum Wells

We investigate the high magnetic field regime of wide quantum wells (WQW) for the case of a many valley host semiconductor. The complete system is described within a modified Landauer-Buettiker formalism and we demonstrate that a parallel contribution of two electron systems in different valleys of the band structure can lead to an edge channel related non-local behaviour even in the 3D-regime. From the obtained general result we derive also a simplified model which applies for the case of much different dissipation. It represents the most dissipative system by an Ohmic resistor network and the less dissipative system by an EC-system.Comment: postscript file including 3 figs, 4 page

Anomalous magnetotransport in wide quantum wells

We present magneto transport experiments of quasi 3D PbTe wide quantum wells. A plateau-like structure in the Hall resistance is observed, which corresponds to the Shubnikov de Haas oscillations in the same manner as known from the quantum Hall effect. The onsets of plateaux in Rxy do not correspond to 2D filling factors but coincide with the occupation of 3D (bulk-) Landau levels. At the same time a non-local signal is observed which corresponds to the structure in Rxx and Rxy and fulfils exactly the Onsager-Casimir relation (Rij,kl(B) = Rkl,ij(-B)). We explain the behaviour in terms of edge channel transport which is controlled by a permanent backscattering across a system of "percolative EC - loops" in the bulk region. Long range potential fluctuations with an amplitude of the order of the subband splitting are explained to play an essential role in this electron system.Comment: postscript file including 3 figs, 5 page

Magnetotransport in wide parabolic PbTe quantum wells

The 3D- and 2D- behaviour of wide parabolic PbTe single quantum wells, which consist of PbTe p-n-p-structures, are studied theoretically and experimentally. A simple model combines the 2D- subband levels and the 3D-Landau levels in order to calculate the density of states in a magnetic field perpendicular to the 2D plane. It is shown that at a channel width of about 300nm on can expect to observe 3D- and 2D-behaviour at the same time. Magnetotransport experiments in selectively contacted Hall bar samples are performed at temperatures down to T = 50 mK and at magnetic fields up to B = 17 T.Comment: postscript file including 2 figs, 4 pages, Paper presented at EP2DS-XI, Nottingham 199

Conductance Fluctuations in PbTe Wide Parabolic Quantum Wells

We report on conductance fluctuations which are observed in local and non-local magnetotransport experiments. Although the Hall bar samples are of macroscopic size, the amplitude of the fluctuations from the local measurements is close to e^2/h. It is shown that the fluctuations have to be attributed to edge channel effects.Comment: postscript file including 3 figs, 3 pages, Paper presented at 3rd Int. Symposium on "New Phenomena in Mesoscopic Structures" in Maui, Hawaii 199

Antidepressants and age

Antidepressants as a commodity have been remarkably little-studied by economists. This study shows in new data for 27 European countries that 8% of people (and 10% of those middle-aged) take antidepressants each year. The probability of antidepressant use is greatest among those who are middle-aged, female, unemployed, poorly educated, and divorced or separated. A hill-shaped age pattern is found. The adjusted probability of using antidepressants reaches a peak -- approximately doubling -- in people‟s late 40s. This finding is consistent with, and provides a new and independent form of corroboration of, recent claims in the research literature that human well-being follows a U-shape through life

International happiness

This paper describes the findings from a new, and intrinsically interdisciplinary, literature on happiness and human well-being. The paper focuses on international evidence. We report the patterns in modern data; we discuss what has been persuasively established and what has not; we suggest paths for future research. Looking ahead, our instinct is that this social-science research avenue will gradually merge with a related literature -- from the medical, epidemiological, and biological sciences -- on biomarkers and health. Nevertheless, we expect that intellectual convergence to happen slowly

What makes an entrepreneur?

This article uses various micro data sets to study entrepreneurship. Consistent with the existence of capital constraints on potential entrepreneurs, the estimates imply that the probability of self-employment depends positively upon whether the individual ever received an inheritance or gift. When directly questioned in interview surveys, potential entrepreneurs say that raising capital is their principal problem. Consistent with our theoretical model's predictions, the self-employed report higher levels of job and life satisfaction than employees. Childhood psychological test scores, however, are not strongly correlated with later self-employment

Is Well-being U-Shaped over the Life Cycle?

Recent research has argued that psychological well-being is U-shaped through the life cycle. The difficulty with such a claim is that there are likely to be omitted cohort effects (earlier generations may have been born in, say, particularly good or bad times). Hence the apparent U may be an artifact. Using data on approximately 500,000 Americans and Europeans, this paper designs a test that makes it possible to allow for different birth-cohorts. A robust U-shape of happiness in age is found. Ceteris paribus, well-being reaches a minimum, on both sides of the Atlantic, in people's mid to late 40s. The paper also shows that in the United States the well-being of successive birth-cohorts has gradually fallen through time. In Europe, newer birth-cohorts are happier.