Structure and Dynamics of the Quasi-Liquid Layer at the Surface of Ice from Molecular Simulations

We characterized the structural and dynamical properties of the quasi-liquid layer (QLL) at the surface of ice by molecular dynamics simulations with a thermodynamically consistent water model. Our simulations show that for three low-index ice surfaces only the outermost molecular layer presents short-range and mid-range disorder and is diffusive. The onset temperature for normal diffusion is much higher than the glass temperature of supercooled water, although the diffusivity of the QLL is higher than that of bulk water at the corresponding temperature. The underlying subsurface layers impose an ordered template, which produces a regular patterning of the ice/water interface at any temperature, and is responsible for the major differences between QLL and bulk water, especially for what concern the dynamics and the mid-range structure of the hydrogen-bonded network. Our work highlights the need of a holistic approach to the characterization of QLL, as a single experimental technique may probe only one specific feature, missing part of the complexity of this fascinating system.Comment: 6 Figure

More information, better jobs? : occupational stratification and labor market segmentation in the United States' information labor force

This article examines the mix of good and bad jobs in the restructuring of United States' labor markets for information work between 1900 and 1980. ls the information sector still growing relative to other occupational sectors? What is the relative proportion of good to bad jobs in the information sector today? ls the mix of good bad jobs within the information sector changing over time? To answer these questions, we examine changes in the relative size of the information sector's labor markers and changes in five occupational strata within it - professional, semiprofessional, supervisory and upper-level sales personnel, clerks, and blue-collar workers.The information occupations mushroomed in size from 17% of the United States workforce in 1900 to over 50% in 1980. Information sector jobs vary widely in quality. Few information sector jobs are fully professional, and clerical jobs form the largest single occupational stratum. When we examined the growth of the various strata between 1900 and 1980, we found that clerical jobs became more dominant, not less dominant. But this distribution has been masked by the steady growth of information sector jobs in the highly professional and semiprofessional strata, as well as clerical jobs. The occupational stratum between clerks and semiprofessionals - the supervisory and upper-level sales workers - has steadily declined in relative size.Two lower strata - clerks and sales and supervisory workers - account for 55% of the jobs in the information sector. Our data suggest that information labor markets are divided into relatively impermeable segments. As the information sector expanded, it took on many characteristics of the overall economy. It includes a mix of jobs that are diverse in their pay, status, and power. Its internal divisions reflect patterns of segmentation that have developed elsewhere in the society - a dual labor market. Overall, the information sector has become sufficiently large that it is not an alternative to the dominant social order - it simply reproduces many of its features

Theoretical perspective in social analyses of computerization : an addendum

Since I wrote "Social Analysis of Computing" in 1979, more than 200 scholarly books and articles and several literature surveys have been published about the social dimensions of computerization. In addition, there have been interesting empirical and theoretical studies published in Danish, French, German, Italian, and Norwegian, among other languages. This addendum serves as a brief guide to some of this newer literature

Computerization and social transformations

This paper examines the relationship between the use of computer-based systems and transformations in parts of the social order. Answers to this question rest heavily on the way computer-based systems are consumed - not just produced or disseminated. The discourse about computerization advanced in many professional magazines and the mass media is saturated with talks about "revolution" - and yet, substantial social changes are often difficult to identify in carefully designed empirical studies. The paper examines qualitative case studies of computerization in welfare agencies, urban planning, accounting, marketing, and manufacturing to examine the ways that computerization alters social life in varied ways: sometimes restructuring relationships and reinforcing social relationships in other cases. The paper also examines some of the theoretical issues in studies of computerization, such as drawing boundaries. And it concludes with some observations about the sociology of computer science as an academic discipline.This paper is based on a keynote address for the annual conference of the Society for the Social Studies of Science in November, 1989

Freddie Mac and Fannie Mae: An Exit Strategy for the Taxpayer

The Fannie Mae-Freddie Mac crisis may have been the most avoidable financial crisis in history. Economists have long complained that the risks posed by the government-sponsored enterprises were large relative to any social benefits. We now realize that the overall policy of promoting home ownership was carried to excess. Even taking as given the goal of expanding home ownership, the public policy case for subsidizing mortgage finance was weak. The case for using the GSEs as a vehicle to subsidize mortgage finance was weaker still. The GSE structure serves to privatize profits and socialize losses. And even if one thought that home ownership was worth encouraging, mortgage debt was worth subsidizing, and the GSE structure was viable, allowing the GSEs to assume a dominant role in mortgage finance was a mistake. The larger they grew, the more precarious our financial markets became. Regulators should contemplate freezing the mortgage purchase activities of the GSEs while at the same time loosening the capital requirements for banks to hold low-risk mortgages. The result would almost surely be an industry much less concentrated than the current duopoly. A housing finance system that does not rely so heavily on Freddie Mac and Fannie Mae will be more robust. We have to assume that sooner or later some of the institutions involved in mortgage finance will fail. The policy should be to promote a housing finance system where mortgage risk is spread among dozens of institutions. That way, the failure of some firms can be resolved through mergers and orderly restructuring, without exposing the financial system to the sort of catastrophic risk that is represented by Fannie Mae and Freddie Mac

Reading "all about" computerization: five common genres of social analysis

This paper examines unstated, but critical, social assumptions which underlie analyses of computerization. It focuses on the popular, professional and scholarly literature which claims to describe the actual nature of computerization, the character of computer use, and the social choices and changes that result from computerization. This literature can be usefully segmented five ideal type genres: utopian, anti-utopian, social realism, social theory, and analytical reduction. Each genre is characterized and illustrated. The strengths and weaknesses of each genre are described. In the 1990s, there will be a large market for social analyses of computerization. Utopian analyses are most likely to domínate the popular and professional discourse. The empirically oriented accounts of social realism, social theory and analytical reduction, are likely to be much less common and also less commonly seen and read by computer professionals and policymakers. These genres are relatively subtle, portray a more ambiguous world, and have less rhetorical power to capture the imagination of readers. Even though they are more scientific, these empirically anchored genres don't seem to appeal to many scientists and engineers. It is ironic that computing -- often portrayed as an instrument of knowledge -- is primarily the subject of discourses whose knowledge claims are most suspect. Conversely, the discourses whose claims as valid knowledge are strongest seems to have much less appeal in the mass media and technological communities

The hormones of invertebrates

Thesis (M.A.)--Boston University, 193