Estimating topological entropy from the motion of stirring rods

Stirring a two-dimensional viscous fluid with rods is often an effective way to mix. The topological features of periodic rod motions give a lower bound on the topological entropy of the induced flow map, since material lines must `catch' on the rods. But how good is this lower bound? We present examples from numerical simulations and speculate on what affects the 'gap' between the lower bound and the measured topological entropy. The key is the sign of the rod motion's action on first homology of the orientation double cover of the punctured disk.Comment: 10 pages, 20 figures. IUTAM Procedia style (included). Submitted to volume "Topological Fluid Dynamics II.

Credit and Co-Wives : exploring empowerment in Senegal

With promises of “bottom-up” economic development and women’s empowerment, microfinance has been established as the “new orthodoxy” in mainstream development circles (Fernando 1997). This study suggests a more limited potential for microfinance to reduce poverty, however. Instead of alleviating poverty, microfinance may be improving the incomes of already established, relatively prosperous women micro-entrepreneurs. How enhanced income translates into social power for women will be a central theme of this essay. Specifically, this topic will be treated within the urban, polygamous and Senegalese context. The role that ideology plays in this process will also be crucial. Polygamy can be understood as such an ideology aiding in income’s transformation into power for women. This consideration helps make the case that women’s empowerment is a complex process that requires both female income and a value system that validates such productivity

A novel occluded RNA recognition motif in Prp24 unwinds the U6 RNA internal stem loop

The essential splicing factor Prp24 contains four RNA Recognition Motif (RRM) domains, and functions to anneal U6 and U4 RNAs during spliceosome assembly. Here, we report the structure and characterization of the C-terminal RRM4. This domain adopts a novel non-canonical RRM fold with two additional flanking α-helices that occlude its β-sheet face, forming an occluded RRM (oRRM) domain. The flanking helices form a large electropositive surface. oRRM4 binds to and unwinds the U6 internal stem loop (U6 ISL), a stable helix that must be unwound during U4/U6 assembly. NMR data indicate that the process starts with the terminal base pairs of the helix and proceeds toward the loop. We propose a mechanistic and structural model of Prp24′s annealing activity in which oRRM4 functions to destabilize the U6 ISL during U4/U6 assembly

Topological entropy and secondary folding

A convenient measure of a map or flow's chaotic action is the topological entropy. In many cases, the entropy has a homological origin: it is forced by the topology of the space. For example, in simple toral maps, the topological entropy is exactly equal to the growth induced by the map on the fundamental group of the torus. However, in many situations the numerically-computed topological entropy is greater than the bound implied by this action. We associate this gap between the bound and the true entropy with 'secondary folding': material lines undergo folding which is not homologically forced. We examine this phenomenon both for physical rod-stirring devices and toral linked twist maps, and show rigorously that for the latter secondary folds occur.Comment: 13 pages, 8 figures. pdfLaTeX with RevTeX4 macro

BESTFACT Best Practice Handbook 3

The Best Practice Handbook (BPH) gives an overview about current concepts, strategies and actions in freight transport all over Europe. It is disseminating information on successful projects and practices to increase awareness and share experiences. It is enabling knowledge transfer and supporting transferability for best practices. The third and last Best Practice Handbook focuses on the work done over the entire project, with 157 inventory cases and 60 in-depth analyses. After four years of case collection a wide field of solutions is available. The main findings of the BESTFACT cases are cross-checked and summarised for each of the cluster topics. The consistent form of collection and information provision broadens the structural understanding of best practice cases. The synthesis of cases per topic shows that under consideration of barriers and framework conditions replicable impacts are achievable. Main editors are Martin Ruesch & Simon Bohne (Rapptrans) and Jacques Leonardi (UoW). Project leader is Marcel Huschebeck (PTV)

Crystal Structure of the RNA Recognition Motif of Yeast Translation Initiation Factor eIF3b Reveals Differences to Human eIF3b

BACKGROUND: The multi-subunit eukaryotic initiation factor3 (eIF3) plays a central role in the initiation step of protein synthesis in eukaryotes. One of its large subunits, eIF3b, serves as a scaffold within eIF3 as it interacts with several other subunits. It harbors an RNA Recognition Motif (RRM), which is shown to be a non-canonical RRM in human as it is not capable to interact with oligonucleotides, but rather interacts with eIF3j, a sub-stoichiometric subunit of eIF3. PRINCIPAL FINDING: We have analyzed the high-resolution crystal structure of the eIF3b RRM domain from yeast. It exhibits the same fold as its human ortholog, with similar charge distribution on the surface interacting with the eIF3j in human. Thermodynamic analysis of the interaction between yeast eIF3b-RRM and eIF3j revealed the same range of enthalpy change and dissociation constant as for the human proteins, providing another line of evidence for the same mode of interaction between eIF3b and eIF3j in both organisms. However, analysis of the surface charge distribution of the putative RNA-binding β-sheet suggested that in contrast to its human ortholog, it potentially could bind oligonucleotides. Three-dimensional positioning of the so called "RNP1" motif in this domain is similar to other canonical RRMs, suggesting that this domain might indeed be a canonical RRM, conferring oligonucleotide binding capability to eIF3 in yeast. Interaction studies with yeast total RNA extract confirmed the proposed RNA binding activity of yeast eIF3b-RRM. CONCLUSION: We showed that yeast eIF3b-RRM interacts with eIF3j in a manner similar to its human ortholog. However, it shows similarities in the oligonucleotide binding surface to canonical RRMs and interacts with yeast total RNA. The proposed RNA binding activity of eIF3b-RRM may help eIF3 to either bind to the ribosome or recruit the mRNA to the 43S pre-initiation complex

Modular protein-RNA interactions regulating mRNA metabolism: a role for NMR

Here we review the role played by transient interactions between multi-functional proteins and their RNA targets in the regulation of mRNA metabolism, and we describe the important function of NMR spectroscopy in the study of these systems. We place emphasis on a general approach for the study of different features of modular multi-domain recognition that uses well-established NMR techniques and that has provided important advances in the general understanding of post-transcriptional regulation

Loans and Leaving: Migration and the Expansion of Microcredit in Cambodia

Over the last decade, the expansion of microfinance institutions (MFIs) has dramatically shifted the availability of credit across the developing world. This recent development provides an opportunity to examine the relationship between household labor migration and access to and use of formal credit. Both theories of migration and the expectations of formal credit providers have suggested that labor migration and credit are substitute solutions to the demand for capital in the developing world, with the implication that greater access to formal financial services may stem migration out of rural places. Using household survey data from Cambodia, an MFI-saturated country, we find that households using formal credit and households with greater access to formal credit are more likely to have labor migrants than households without access. This association persists across size of loan, purpose of loan, remittances behavior, and for domestic migrations. These findings complicate our understanding of the relationship between credit and migration, and call for a greater recognition of the importance of context in framing migration behavior

Against Three Arguments for a Free Market in Healthcare

Healthcare is not like other commodities. Central features of healthcare undermine the benefits of a free market. A free market in healthcare fails to exhibit the same virtues as markets in other goods and services. Proponents of free markets in healthcare often argue for their position based on efficiency, moral hazard, and innovation. I will address these arguments in turn to show that each one relies on unstable assumptions and unstated definitions. According to the first argument, competitive free markets are efficient, so a free market in healthcare would be efficient; I demonstrate that free markets in healthcare are not competitive and thus do not promote efficiency. The second arguments states that in a healthcare free market, patients must pay for medical services, so will not use more healthcare than they need; I point out that on a medical definition of “appropriate use of healthcare,” a free market fails to solve the problem of overuse and may introduce a problem of underuse. The third argument asserts that through competitive pressure and profit-based motivations, free markets foster innovation; I will argue that the on a free market, companies can only generate profitable innovations, which may leave research deficiencies in crucial areas of healthcare. The way in which healthcare is distributed impacts the lives of the people who must access medical services: ostensibly everyone at some time or another. This project seeks to carefully examine and question the assumptions that underlie arguments in favor of a free market in healthcare in the hopes that a considered, informed debate can shape a better healthcare system