10,874 research outputs found
Solar wind sputtering effects in the Martian atmosphere
A Monte Carlo simulation of the sputtering of the upper atmosphere of Mars by the solar wind was performed. The calculated sputtering yields imply loss rates (molecules/cm square - sec escaping the planet) for carbon dioxide, carbon, and oxygen of R(CO2) = 2.6 X 1000000/cm square - sec, R(C) = 6.6 X 1000000/cm square - sec, and R(O) = 7.7 X 1000000/cm - sec. The total mass loss by sputtering is only about 10% of that due to chemical and photo-chemical processes, but sputtering provides a major exospheric sink for carbon. The erosion process described here preferentially removes the lighter components of the atmosphere. Calculations based on a Monte Carlo simulation suggest that for a model atmosphere, 97% of the N2 and 33% of the CO2 originally present may have been sputtered away over 4.5 X 10 to the 9th power y. In the same length of time the (15)N/(14)N isotopic ratio for the bulk atmosphere would have increased by a factor 1.7
Data Gaps in Evidence-Based Research on Small Water Enterprises in Developing Countries
This paper assess the literature on small water enterprises -- water delivery operations that predominantly provide water at the community level. A research agenda is recommended to advance knowledge on effective SWE service
Subordinate Activation Tactics: Semi-professionals and Micro-level Institutional Change in Professional Organizations
this two-year ethnographic study of the primary care departments in two U.S. hospitals examines how managers can bring about micro-level institutional change in professional practice even when such change challenges professionals’ specialized expertise, autonomy, individual responsibility, and engagement in complex work, which previous research has shown to create difficulties. In this study, managers in both hospitals attempted to implement the same patient-centered medical home (PCMH) reforms among doctors, had the same external pressures for micro-level institutional change, worked under the same organizational and reimbursement structure, and had the same contextual facilitators of micro-level institutional change present within their organizations. But managers in one hospital successfully accomplished change in professional practice while those in the other did not. I demonstrate that managers can accomplish micro-level institutional change in professional organizations using “subordinate activation tactics”—first empowering and motivating subordinate semi-professionals to activate their favorable structural position vis-à -vis the targeted professionals on behalf of managers and next giving semi-professionals positional tools to use in their daily work to minimize the targeted professionals’ concerns about the threats associated with change. Keywords: micro-level institutional change, professions, occupations, professional organizations, semi-professionals, hospitals, healthcare management, PCMH implementatio
Making the Cut: Using Status-Based Countertactics to Block Social Movement Implementation and Microinstitutional Change in Surgery
Much of the change that social movements try to accomplish requires changing practices inside organizations, yet reform implementation is difficult to achieve. This comparative case study of two hospitals demonstrates that implementing reform inside organizations may require internal reformers not only to mobilize with one another but also to stand up to internal defenders' countertactics in everyday encounters. Because reformer alliances across identity lines often require reformers with different statuses to collaborate with one another, defenders can divide reformer coalitions by linking reform practices to a status characteristic associated with lower-status reformers, denigrating higher-status reformers by associating them with these practices, and reintegrating higher-status reformers into the defender group. When status threat inside an organization is high to begin with, higher-status reformers are likely to be concerned about loss of privilege in the face of defenders' status-based countertactics and, in response, distance themselves from reform practices and align themselves with defenders to protect their identity and its rewards. This can undermine the multi-identity reformer coalition and cause change to fail. These findings regarding status-based countertactics contribute to our understanding of social movement implementation and microinstitutional change
Microscopic mechanisms of thermal and driven diffusion of non rigid molecules on surfaces
The motion of molecules on solid surfaces is of interest for technological
applications such as catalysis and lubrication, but it is also a theoretical
challenge at a more fundamental level. The concept of activation barriers is
very convenient for the interpretation of experiments and as input for Monte
Carlo simulations but may become inadequate when mismatch with the substrate
and molecular vibrations are considered. We study the simplest objects
diffusing on a substrate at finite temperature , namely an adatom and a
diatomic molecule (dimer), using the Langevin approach. In the driven case, we
analyse the characteristic curves, comparing the motion for different values of
the intramolecular spacing, both for T=0 and . The mobility of the
dimer is higher than that of the monomer when the drift velocity is less than
the natural stretching frequency. The role of intramolecular excitations is
crucial in this respect. In the undriven case, the diffusive dynamics is
considered as a function of temperature. Contrary to atomic diffusion, for the
dimer it is not possible to define a single, temperature independent,
activation barrier. Our results suggest that vibrations can account for drastic
variations of the activation barrier. This reveals a complex behaviour
determined by the interplay between vibrations and a temperature dependent
intramolecular equilibrium length.Comment: 6 pages, 5 figures, Proceeding of the EMRS 2002 Conference, to be
published in Thin Solid Film
Galaxy Clustering at z~3
Galaxies at very high redshift (z~3 or greater) are now accessible to
wholesale observation, making possible for the first time a robust statistical
assessment of their spatial distribution at lookback times approaching ~90% of
the age of the Universe. This paper summarizes recent progress in understanding
the nature of these early galaxies, concentrating in particular on the
clustering properties of photometrically selected ``Lyman break'' galaxies.
Direct comparison of the data to predictions and physical insights provided by
galaxy and structure formation models is particularly straightforward at these
early epochs, and results in critical tests of the ``biased'', hierarchical
galaxy formation paradigm.Comment: Presented at Royal Society Discussion Meeting, March 1998, "Large
Scale Structure in the Universe", 14 pages LaTeX, 7 ps figures, uses
rspublic.sty (included
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