Shell model calculation of the beta- and beta+ partial halflifes of 54Mn and other unique second forbidden beta decays

The nucleus 54Mn has been observed in cosmic rays. In astrophysical environments it is fully stripped of its atomic electrons and its decay is dominated by the beta- branch to the 54Fe ground state. Application of 54Mn based chronometer to study the confinement of the iron group cosmic rays requires knowledge of the corresponding halflife, but its measurement is impossible at the present time. However, the branching ratio for the related beta+ decay of 54Mn was determined recently. We use the shell model with only a minimal truncation and calculate both beta+ and beta- decay rates of 54Mn. Good agreement for the beta+ branch suggests that the calculated partial halflife of the beta- decay, (4.94 \pm 0.06) x 10^5 years, should be reliable. However, this halflife is noticeably shorter than the range 1-2 x 10^6 y indicated by the fit based on the 54Mn abundance in cosmic rays. We also evaluate other known unique second forbidden beta decays from the nuclear p and sd shells (10Be, 22Na, and two decay branches of 26Al) and show that the shell model can describe them with reasonable accuracy as well.Comment: 4 pages, RevTeX, 2 figure

Overcoming barriers to collective action through transboundary water negotiation along the Blue Nile River

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Urban Studies and Planning, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 179-186).We are headed towards a global water crisis. While technological advancements may help reduce this gap, achieving global water security will also require establishing self-enforcing agreements negotiated among countries that share transboundary rivers. At its core, transboundary water governance is a type of collective action problem (Olson 1965), in which sovereign actors must cooperate to achieve a collective interest. In this research, I attempt to delineate common procedural and context-specific barriers to collective action within transboundary water negotiations in the Nile River Basin. I compare efforts by three countries -- Egypt, Ethiopia, and Sudan --to pursue collective action in two separate, but related, face-to-face negotiations related to water use: the basin-wide negotiations on the Nile Basin Cooperative Framework Agreement (1997 - 2010) and the ongoing project-specific negotiations on the Grand Ethiopian Renaissance Dam which started in 2011. Between 2015 and 2018, I interviewed over 50 Egyptian, Ethiopian, and Sudanese negotiators; transboundary water scholars and academics; and journalists and reviewed primary and secondary documents to identify the perceived barriers within these negotiation processes. The conventional approach to treaty-making is through negotiations among state actors.I argue that while many barriers related to the number of actors and degree of heterogeneity among them (as defined by differences in their capacity, access to information, preferences, beliefs, and identities) can be addressed through procedural interventions, non-procedural interventions by both state- and non-state actors are necessary to reduce these barriers at different scales (e.g., between negotiators or between negotiators and the public) in the short-, medium-, and long-term. Furthermore, I argue that multi-track water diplomacy is increasingly necessary in the Nile Basin due to several context-specific factors: the 'securitization' of water, frequent political transitions, and lack of public trust. Based on this research, I offer a list of procedural- and non-procedural interventions that can be employed by state- and non-state actors to reduce different types of barriers.Although reducing these barriers will not guarantee collective action, I argue that these interventions can create a more enabling environment in which collective action can occur.by Yasmin Zaerpoor.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Urban Studies and Plannin

Distributed Object Transportation on a Desired Path Based on Constrain-and-Move Strategy

In this paper, a distributed strategy to move objects on different arbitrary paths in a 2D plane is proposed and analyzed. This algorithm which is based on Constrain-and-Move strategy [1] , organizes the robots in two groups. The object manipulation task also is decomposed to two different tasks. The task given to one group is control of linear velocity and that assigned to the other group is control of angular velocity of the object. The independence of these tasks makes the design of the distributed architecture of the team possible. To calculate each robot’s desired velocity, a simple method using Constrain-and-Move strategy and robot’s local sensors is developed. To prevent small errors in the robot sensory system from affecting the system performance, limited compliance is assumed in robot arms. The basic behaviors of the robots are presented. Moreover, simulation results are given to verify the proposed strategy. 1

Breaking out of carbon lock-in: Malaysia’s path to decarbonization

Malaysia has made an ambitious commitment to reduce the intensity of its carbon emissions, notably a 40% reduction (compared to 2005 levels) by 2020 and a 45% reduction (compared to 2005 levels) by 2030. As with other developing countries, Malaysia’s challenge is to decarbonize its energy-centric economy in the face of population growth pressures and substantial levels of poverty. Drawing on extensive interviews with both public and private stakeholders, we examine how Malaysia has launched its transition to a decarbonized development path. Based on our multi-year analysis, we identify key breakout factors, including behavioral transformations, institutional shifts, and action by a broad network of actors that have allowed Malaysia to begin decarbonizing its economy. At the same time, we note that federal-state friction, limited government capacity, the absence of a centralized management agency, the lack of international funding, incipient environmental awareness, and numerous barriers to investment in renewable energy reinforce carbon lock-in. Our analysis suggests ways in which other rapidly developing countries can learn from Malaysia’s initial successes and challenges. ©202

Verification of isomerism and direct measurement of half-lives in Au-184

The existence of two decaying isomers in 184Au was confirmed through direct observation of the variation of decay rates with time. The ordering of the low- and high-spin isomers was verified by the decay studies. The isomers are identified as a low-spin (probably 2+) state at an energy of 69 keV with a half-life of 48±1 sec and a high-spin (probably 5+) ground state with a half-life of 21±1 sec