151 research outputs found
Quantum Pair Creation of Soliton Domain Walls
A large body of experimental evidence suggests that the decay of the false
vacuum, accompanied by quantum pair creation of soliton domain walls, can occur
in a variety of condensed matter systems. Examples include nucleation of charge
soliton pairs in density waves [eg. J. H. Miller, Jr. et al., Phys. Rev. Lett.
84, 1555 (2000)] and flux soliton pairs in long Josephon junctions. Recently,
Dias and Lemos [J. Math. Phys. 42, 3292 (2001)] have argued that the mass
of the soliton should be interpreted as a line density and a surface density,
respectively, for (2+1)-D and (3+1)-D systems in the expression for the pair
production rate. As the transverse dimensions are increased and the total mass
(energy) becomes large, thermal activation becomes suppressed, so quantum
processes can dominate even at relatively high temperatures. This paper will
discuss both experimental evidence and theoretical arguments for the existence
of high-temperature collective quantum phenomena
Dominant Folding Pathways of a WW Domain
We investigate the folding mechanism of the WW domain Fip35 using a realistic
atomistic force field by applying the Dominant Reaction Pathways (DRP)
approach. We find evidence for the existence of two folding pathways, which
differ by the order of formation of the two hairpins. This result is consistent
with the analysis of the experimental data on the folding kinetics of WW
domains and with the results obtained from large-scale molecular dynamics (MD)
simulations of this system. Free-energy calculations performed in two
coarse-grained models support the robustness of our results and suggest that
the qualitative structure of the dominant paths are mostly shaped by the native
interactions. Computing a folding trajectory in atomistic detail only required
about one hour on 48 CPU's. The gain in computational efficiency opens the door
to a systematic investigation of the folding pathways of a large number of
globular proteins
The Presidency and the Executive Branch in Latin America: What We Know and What We Need to Know
The presidential politics literature depicts presidents either as all- powerful actors or figureheads and seeks to explain outcomes accordingly. Th e president and the executive branch are nonetheless usually treated as black boxes, particularly i n developing countries, even though the presidency has evolved into an extremely complex branch of government. While these developments have been studied in the U nited States, far less i s known in other countries, particularly in Latin America, where presi dential systems have been considered the source of all goods and evils. To help close the knowledge gap and explore differences in policymaking characteristics not only between Latin America and the US but also across Latin American countries, this paper s ummarizes the vast literature on the organization and resources of the Executive Branch in the Americas and sets a research agenda for the study of Latin American presidencies.Fil: Bonvecchi, Alejandro. Universidad Torcuato Di Tella. Departamento de Ciencia Política y Estudios Internacionales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Scartascini, Juan Carlos. Banco Interamericano de Desarrollo; Estados Unido
Is Social Assistance Contributing to Higher Informality in Turkey?
Although still low for European standards, investments in Social Assistance (SA) transfers in Turkey have been increasing in recent years. The government is expanding access to subsidized health for individuals in the informal sector through a rapid expansion of the Green Card program. Generous non-contributory programs, such as the Green Card, may create perverse incentives for individuals to join or remain in the informal sector as they can access free services without paying taxes and/or contributions, thus potentially being able to get higher “net” labor earnings than in the formal sector. Despite the fact that the Green Card is a large and generous program offered to individuals in the informal sector, empirical analysis in this report does not find an actual impact of the program (or of its rapid expansion) on informality. The reason behind this finding is the existence of a very large differential in wages between formal and informal workers explained by differences worker’s productivity. Low-wage workers facing the possibility to move from the informal sector to the formal sector would have strong incentives to do so even if this would imply losing all SA benefits. As such, the expected monetary and job security gains of having a formal job dominate those of having an informal job even after accounting for SA transfers
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