Impact Theory Pdf

[Jodee Bouman]

Accordingto a hypothesis developed by UA alumni William Hartmann and Donald Davis, the moon was formed from a debris blown off primordial Earth by a giant impact during Earth's formation. Their 1974 paper introduced what is now the leading theory of lunar origin.

Left: A page from the Rectified Lunar Atlas, showing the edge of the Mare Orientale impact crater, discovered by William Hartmann during his time as a graduate student at the University of Arizona. Right: The Orientale basin, as imaged by the Lunar Reconnaissance Orbiter in 2010.

The Giant Impact Theory seems to account for the most obvious characteristics of the moon today: No atmosphere, little water and no iron core. Additionally, returned Apollo samples have shown that lunar rocks are chemically indistinguishable from Earth rocks.

On the surface, pun intended, this confirms the 1974 theory. However, computer simulations show that the standard giant impact would create a moon made of the impacting planet Theia, not the Earth, said lunar expert Erik Asphaug, UA professor of planetary sciences.

Simulations also seem to show that the larger the giant impact, the more the moon is made primarily of the impactor. So, another recent study suggests that instead of one Theia, a succession of smaller impactors formed a series of smaller moons, each one more Earth-like in composition, that coalesced into the moon.

If Theia kept going, the outcome could be a moon formed mostly out of Earth. Or, if Theia was a wayward icy planet, such a hit and run would vaporize Theia, resolving the Earth-rock problem and explaining why Theia is no more.

Andrews-Hanna is excited about the data that has been collected on the moon since the Giant Impact Theory was proposed, including topography, gravity, visible images, spectral data, samples, seismic data, thermal data and electromagnetic data.

Recall that intended impact defines the results your organization will hold itself accountable for achieving. Since your organization will ideally measure its progress against the intended impact statement you develop, it is important to get specific:

In parallel to this intended impact work, YW Boston also took a hard look at its theory of change: HOW, at a high level, the organization would achieve that impact. Hallmarks of a strong theory of change include:

Ultimately, YW Boston arrived at a theory of change anchored in the belief that increasing the number of women of color in leadership positions would require both supporting women and girls of color directly and creating more inclusive work environments. More specifically, YW Boston would cultivate the pipeline of future women leaders of color while at the same time dismantling systemic racism in the institutions in which they work.

In working with scores of nonprofits over the past two decades, Bridgespan teams have noted three especially important practices that can help set intended impact and theory of change work up for success: engaging stakeholders systematically and genuinely; pressure testing drafts of your intended impact and theory of change; and building in opportunities for flexibility and continued learning.

Developing an intended impact and theory of change begins with aspirational visioning: what is the change you will hold yourselves accountable for advancing in the world and how can you use your capabilities and expertise to help accelerate that change? While such exercises soar on generative, expansive thinking, the work ultimately needs to be grounded in real world data and experience. That means pressure testing and refining your early drafts, as part of a highly iterative process.

Pressure testing is all about identifying areas where there are gaps in logic, where you feel less confident, and where further learning and research is required. This is an opportunity for you and your team, in collaboration with your stakeholders (see above), to take on the mindset of a skeptic.

Clarity on intended impact and theory of change can also help support accountability and measurement by enabling your organization to track progress against the impact goals you set out to achieve. YW Boston is partnering with a local university on an assessment tool for organizational change around diversity and inclusion. It is also investing in a new measurement approach for its goal of increasing the number of women of color in leadership positions in Boston.

A number of different circumstances or events can trigger a refresh of your intended impact and theory of change. Often, it is a first step in undertaking a strategic planning process. But sometimes there are specific triggers:

Please fill out the form below to download the toolkit. We use the information we collect to help us improve our content and to inform our funders about the impact of our work. We will never share your personal information with any third party without your permission. If you'd rather not share your information, you can download a PDF of the toolkit directly by clicking here.

The disparate impact theory has long been viewed as one of the most important and controversial developments in antidiscrimination law. In this article, Professor Selmi assesses the theory's legacy and challenges much of the conventional wisdom. Professor Selmi initially charts the development of the theory, including a close look at Griggs v. Duke Power Co. and Washington v. Davis, to demonstrate that the theory arose to deal with specific instances of past discrimination rather than as a broad theory of equality. In the next section, Professor Selmi reviews the success of the theory in the courts through an empirical analysis and concludes that the theory has had a strikingly limited impact outside of the context of written employment tests and is, in fact, an extremely difficult theory on which to succeed. In the final section, Professor Selmi contends that whatever gains the disparate impact theory has produced could likely have been obtained through other means, particularly in large urban cities, and that the theory may have had the unintended effect of limiting our conception of intentional discrimination. Disparate impact theory has always been seen as beginning where intentional discrimination ends, and by pushing an expansive theory of impact we were left with a truncated theory of intentional discrimination, one that continues to turn on animus and motive. Rather than a new legal theory of discrimination, what was needed, Professor Selmi concludes, was a greater societal commitment to remedying inequities and the ultimate mistake behind the theory was a belief that legal theory could do the work that politics could not.

"The Giant Impact Hypothesis is very good in explaining most of the moon's features," said lead study author Daniel Herwartz, an isotope geochemist at the University of Gttingen in Germany. [How the Moon Formed: A Timeline (Gallery)]

Initially, the scientists looked at lunar rocks that were blasted off the moon by cosmic impacts and landed on Earth as meteorites. However, these samples were contaminated by the oxygen isotopes in water from Earth.

"This group of meteorites has a very, very similar isotopic composition to the Earth," Herwartz said. "Such a composition of Theia would explain why no isotopic differences for oxygen or any other isotope system had been detected to date."

The authors highlight three major challenges faced by Corridors stakeholders: developing a shared understanding of collective impact work, maintaining organizational competencies in a coordinated system, and using data to support collective impact work. They also consider whether the incentives for collective impact are sufficient to drive the work despite the funding and capacity constraints faced by participating organizations. Thus, the brief provides a lens for understanding why well-intentioned collective impact efforts may not take root.

Although we endeavor to make our web sites work with a wide variety of browsers, we can only support browsers that provide sufficiently modern support for web standards. Thus, this site requires the use of reasonably up-to-date versions of Google Chrome, FireFox, Internet Explorer (IE 9 or greater), or Safari (5 or greater). If you are experiencing trouble with the web site, please try one of these alternative browsers. If you need further assistance, you may write to he...@aps.org.

The work of two previous papers is extended and a theory of pressure broadening is developed which treats the perturbers quantum mechanically and allows for inelastic collisions, degeneracy, and overlapping lines. The impact approximation is used. It consists in assuming that it takes, on the average, many collisions to produce an appreciable disturbance in the wave function of the atom, and it results in an isolated line having a Lorentz shape. Validity criteria are given. When the approximation is valid, it is allowable to replace the exact, fluctuating interaction of the perturbers with the atom by a constant effective interaction. The effective interaction is expressed in terms of the one-perturber quantum mechanical transition amplitudes on and near the energy shell and its close relationship to the scattering matrix is stressed. The calculation of the line shape in terms of the effective interaction is the same as when the perturbers move on classical paths. Results are written explicitly for isolated lines. If the interaction of the perturbers with the final state can be neglected, the shift and width are proportional to the real and imaginary part of the forward elastic scattering amplitude, respectively. By the optical theorem, the width can also be written in terms of the total cross section. When the interaction in the final state cannot be neglected, the shift and width are still given in terms of the elastic scattering amplitudes, in a slightly more complicated fashion. Finally, rules are given for taking into account rotational degeneracy of the radiating states.

3a8082e126