Is the Informal Sector Constrained from the Demand Side? Evidence for Six West African Capitals

Employing a unique dataset that covers households from six West African capitals, this paper provides new evidence on the demand for informal sector products and services. We first investigate whether demand linkages exist between formal and informal products and distribution channels, and whether there is an overlapping customer base, which would imply that both formal sector wage earners and informal workers buy both formal and informal products using both formal and informal distribution channels. In a second step, we estimate demand elasticities based on Engel curves. We find a strongly overlapping customer base and strong demand-side linkages between the formal and informal sector, with the exception that informal goods are hardly bought through formal distribution channels. The estimated demand elasticities tend to show that rising incomes are associated with a lower propensity to consume informal sector goods and to use informal distribution channels. We therefore conclude that the informal sector in West Africa is likely to be constrained from the demand side. --Informal sector,formal-informal linkages,Engel curve estimates,West Africa

Herstellung und Charakterisierung von Nanodots in dünnen Blockcopolymerfilmen

Die in Blockcopolymeren beobachtete Mikrophasenseparation ermöglicht die Herstellung von periodischen Strukturen mit einer charakteristische Länge kleiner 100 nm. In der vorliegenden Arbeit wurden dünne Blockcopolymerfilme als Template zur Herstellung von metallischen, keramischen bzw. polymeren Nanodots untersucht. Derartige Nanodots könnten in magnetischen Datenspeichern, Superkondensatoren oder als photonische Kristalle eingesetzt werden.The microphase seregation observed in block copolymers enables the generation of mesoscopic structures with characteristic lengths below 100 nm on a large scale. In this thesis, thin block copolymer films were investigated as templates for the synthesis of metallic, ceramic and polymeric nanodots. Such nanodots could be used in magnetic data storage devices, supercapacitors or photonic crystals

Migration Experience, Aspirations and the Brain Drain: Theory and Empirical Evidence

Böhme MH, Glaser T. Migration Experience, Aspirations and the Brain Drain: Theory and Empirical Evidence. Working Papers in Economics and Management. Vol 14-2014. Bielefeld: Bielefeld University, Department of Business Administration and Economics; 2014.We develop a theoretical model of human skill formation and emigration. We extend the existing brain drain models, by partly endogenizing the heterogeneity of individuals, by introducing aspirations. Emigration of an individual will result in a migration experience, which increases the migrant's aspirations. This will induce her to invest more in the education of her children back home. We find that this aspirations effect increases the average skill level in the society for a given migration rate. We show that the optimal migration rate that maximizes the post-migration skill-rate of the population is higher if we allow for the aspirations effect of migration. We use panel data from Indonesia to demonstrate that a migration experience has an aspirations increasing effect and calibrate our model accordingly. Our results suggest that there are potentially more countries than previously thought which could benefit from migration

Tuning the Properties and Self-Healing Behavior of Ionically Modified Poly(isobutylene-co-isoprene) Rubber

The focus of this work is on the nature of self-healing of ionically modified rubbers obtained by reaction of brominated poly(isobutylene-co-isoprene) rubber (BIIR) with various alkylimidazoles such as 1-methylimidazole, 1-butylimidazole, 1-hexylimidazole, 1-nonylimidazole, and 1-(6-chlorohexyl)-1H-imidazole. Based on stress-strain and temperature dependent DMA measurements, a structural influence of the introduced ionic imidazolium moieties on the formation of ionic clusters and, as a consequence, on the mechanical strength and self-healing behavior of the samples could be evidenced. These results are fully supported by a molecular-level assessment of the network structure (cross-link and constraint density) and the dynamics of the ionic clusters using an advanced proton low-field NMR technique. The results show distinct correlations between the macroscopic behavior and molecular chain dynamics of the modified rubbers. In particular, it is shown that the optimization of material properties with regard to mechanical and self-healing behavior is limited by opposing tendencies. Samples with reduced chain dynamics exhibit superior mechanical behavior but lack on self-healing behavior. In spite of these limitations, the overall performance of some of our samples including self-healing behavior exceeds distinctly that of other self-healing rubbers described in the literature so far

Viscosity and Diffusion: Crowding and Salt Effects in Protein Solutions

We report on a joint experimental-theoretical study of collective diffusion in, and static shear viscosity of solutions of bovine serum albumin (BSA) proteins, focusing on the dependence on protein and salt concentration. Data obtained from dynamic light scattering and rheometric measurements are compared to theoretical calculations based on an analytically treatable spheroid model of BSA with isotropic screened Coulomb plus hard-sphere interactions. The only input to the dynamics calculations is the static structure factor obtained from a consistent theoretical fit to a concentration series of small-angle X-ray scattering (SAXS) data. This fit is based on an integral equation scheme that combines high accuracy with low computational cost. All experimentally probed dynamic and static properties are reproduced theoretically with an at least semi-quantitative accuracy. For lower protein concentration and low salinity, both theory and experiment show a maximum in the reduced viscosity, caused by the electrostatic repulsion of proteins. The validity range of a generalized Stokes-Einstein (GSE) relation connecting viscosity, collective diffusion coefficient, and osmotic compressibility, proposed by Kholodenko and Douglas [PRE 51, 1081 (1995)] is examined. Significant violation of the GSE relation is found, both in experimental data and in theoretical models, in semi-dilute systems at physiological salinity, and under low-salt conditions for arbitrary protein concentrations

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

Guidelines for the Use of Household Interview Duration Analysis in CAPI Survey Management Guidelines for the Use of Household Interview Duration Analysis in CAPI Survey Management *

Abstract: This paper provides evidence based guidance for practical survey work, namely choosing interviewers and their workload. Analyzing a survey of 3568 households obtained through computer assisted personal interviews (CAPI) we find that interviewers learn considerably while the survey progresses. Time requirements for field work increase concavely with sample size which allows larger samples to be realized with a given budget than would be expected in planning such projects with simplistic cost estimates. We find a decrease of interview duration of almost 50 percent which translates into a significant increase of the average hourly wage the interviewers receive. These learning effects cease after around 20 interviews. Based on our results we recommend targeting interviewer training by age and technology-affinity of interviewers for CAPI surveys. An updated version is forthcoming in Field Methods