Zeeman-limited Superconductivity in Crystalline Al Films

We report the evolution of the Zeeman-mediated superconducting phase diagram (PD) in ultra-thin crystalline Al films. Parallel critical field measurements, down to 50 mK, were made across the superconducting tricritical point of films ranging in thickness from 7 ML to 30 ML. The resulting phase boundaries were compared with the quasi-classical theory of a Zeeman-mediated transition between a homogeneous BCS condensate and a spin polarized Fermi liquid. Films thicker than $\sim$20 ML showed good agreement with theory, but thinner films exhibited an anomalous PD that cannot be reconciled within a homogeneous BCS framework.Comment: 8 pages, 9 figure

ORGANIZING THE ECONOMICS ACADEMY: THE EVOLUTION OF PROFESSIONAL ECONOMICS ASSOCIATIONS, 1777-2000

Scholarly societies in economics (and many other professions) are clubs that provide members with a range of club goods, many of which have broader and economically significant spillover consequences for society at large. Yet surprisingly little is known about the historical evolution or current composition of these associations. This analysis of the development of professional economics societies worldwide provides perspectives on the evolution of the economics research industry they serve. Although the origins of current economic associations can be traced at least as far back as 1777, almost all of the growth in professional economics associations has been concentrated in the past 125 years and especially between 1945 and 2000. At the beginning of the 20th century almost all economic associations were general economics societies. The fractionalization of the profession, leading to a proliferation of associations with sub-disciplinary focus began in 1920 and accelerated after 1960. By 2000, almost two thirds of all economic associations served sub-disciplines ranging from law and economics through fisheries economics to public choice and game theory. There are comparatively few economic associations in the poorest parts of the world that are often most in need of the public goods economists can provide.Professional associations, club goods, economic societies, knowledge, Teaching/Communication/Extension/Profession,

The Evolution of Economics Clubs: 1777-2000

Replaced with revised version of paper 01/30/06.Professional associations, club goods, economic societies, knowledge, Teaching/Communication/Extension/Profession, A11, A12, D71, N011,

Cost aspects of African agricultural research:

Spending per scientist declined precipitously within African agricultural R&D agencies over the past several decades. In 1991, average cost per researcher across 147 R&D agencies was $119,300 in 1985 international dollars — or US$59,500 when measured in United States rather than international dollars — 34 percent below the corresponding 1961 figure. This trend reflects the rapid growth in numbers of scientific staff compared with the slow growth in funds to support them. Comparatively low, and often shrinking, real salaries per scientist are a factor too. African scientists were paid an average of US$5,000 in 1991 (or roughly US$7,500 with fringe benefits included), while comparable average salaries for academic staff working in large public universities in the United States were $58,889 (or$72,667 with fringe benefits included. The new, agency-level data reported in this paper reveal significant variation in the costs per scientist not apparent from the country averages. There were 67 agencies (46 percent) that spent less than $100,000 per scientist per annum. Simple econometric procedures were applied to a sub-sample of 107 agencies in 21 countries to investigate reasons for the large variation in costs per scientist. The intensity of support staff per scientist and the intensity with which expatriate researchers are used are important sources of variation. Larger stations lowered the costs and having more stations raised costs, but not significantly so. An agency's organizational type had a significant influence on its costs. Semipublic agencies typically spent considerably more per scientist than government agencies with 1991 figures of$207,700 for the former, compared with around $104,600 for the latter (in 1985 international dollars). GDP per capita and various other unspecified, country-specific effects also accounted for much of the observed variation in costs per scientist.Research institutes., Research Economic aspects.,

REASSESSING PRODUCTIVITY GROWTH IN AFRICAN AGRICULTURE

This paper uses a new panel data set to examine sources of growth in African agriculture. While conventional inputs continue to be the main source of labor productivity growth in Africa, land and labor quality differentials are also significant in explaining observed cross-country productivity patterns.Productivity Analysis,

INTERNATIONAL AND INSTITUTIONAL R&D SPILLOVERS: ATTRIBUTION OF BENEFITS AMONG SOURCES FOR BRAZIL'S NEW CROP VARIETIES

In general, reported rates of return to agricultural R&D are high, but questions have been raised about upward biases in the evidence. Among the reasons for this bias, insufficient attention to attribution aspects-matching of research benefits and costs-is a pervasive problem, the magnitude of which is illustrated here with new evidence for Brazil. Over the period 1981 to 2003, varietal improvements in upland rice, edible beans, and soybeans yielded benefits attributable to research of $14.8 billion in present value (1999 prices) terms; 6.1 percent of the corresponding value of crop output. If all of those benefits were attributed to Embrapa, a public research corporation accounting for more than half Brazil's agricultural R&D spending, the benefit-cost ratio would be 78:1. If a geometric attribution rule based on genetic histories is used in conjunction with quantitative evidence on the extent of research collaborations to account for the innovative effort of others, the ratio drops substantially to 16:1 (or an internal rate of return of 38.7 percent). The sources of these gains vary markedly among crops and over time, making it hard to generalize about the international and institutional origins of varietal innovations in Brazilian agriculture during the past several decades.Brazil, agricultural R&D, attribution, soybeans, rice, beans, benefit-cost ratios, Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,