Global Sourcing under Imperfect Capital Markets

We develop a simple model to study the interactions between a supplier’s financial constraints and contract incompleteness in a vertical relationship. Production complexity increases the extent of contract incompleteness and the hold-up problem, which generates a cost when the supplier needs financial participation from the downstream firm. Vertical integration alleviates the impact of financial constraints but reduces the supplier’s incentives. We apply the model to an analysis of multinational firms’ sourcing strategies and predict that (1) complex and specific inputs are more likely to be sourced from financially developed countries and (2) multinationals are more likely to integrate suppliers located in countries with poor financial institutions, especially when trade involves complex goods. We examine and validate these predictions using firm-level trade data on multinational firms with operations in France. We provide evidence that financial development generates a comparative advantage in the supply of complex goods. Moreover, we find higher shares of intra-firm imports of complex inputs from countries with a lower level of financial development. The findings are robust to different measures of complexity and specificity, and are not driven by industry differences in fixed costs or traditional measures of external financial dependence. Quantitatively, we find that financial development is as important as contract enforcement in alleviating hold-up problems.Sourcing, FDI, financial constraints, contractual frictions.

An experimental study to discriminate between the validity of diffraction theories for off-Bragg replay

We show that experiments clearly verify the assumptions made by the first-order two-wave coupling theory for one dimensional lossless unslanted planar volume holographic gratings using the beta-value method rather than Kogelnik's K-vector closure method. Apart from the fact that the diffraction process is elastic, a much more striking difference between the theories becomes apparent particularly in the direction of the diffracted beam in off-Bragg replay. We therefore monitored the direction of the diffracted beam as a function of the off-Bragg replay angle in two distinct cases: [a] the diffracted beam lies in the plane of incidence and [b] the sample surface normal, the grating vector and the incoming beam do not form a plane which calls for the vectorial theory and results in conical scattering.Comment: Corrected Eqs. (3) & (6); 14 pages, 8 figure

Mirrors for slow neutrons from holographic nanoparticle-polymer free-standing film-gratings

We report on successful tests of holographically arranged grating-structures in nanoparticle-polymer composites in the form of 100 microns thin free-standing films, i.e. without sample containers or covers that could cause unwanted absorption/incoherent scattering of very-cold neutrons. Despite their large diameter of 2 cm, the flexible materials are of high optical quality and yield mirror-like reflectivity of about 90% for neutrons of 4.1 nm wavelength

Perceptions of Scientists Before and After Taking a Graduate Level Science Communication Course

Science education and communication students do not often see themselves as scientists although the future of science is highly dependent upon effective science communication. The purpose of this study was to determine if a science communication course could alter graduate students' perceptions of scientists and their own self-perception as a scientist. Using a semiotic approach and the Draw-A-Scientist-Test (DAST), participants were asked to draw an image of a scientist based on their perceptions on the first and last day of a 16-week course. Analysis of the images prior to the course indicated failure by students to perceive themselves as scientists. After taking the course, participants depicted being a scientist as a process and described scientists based on their roles. The participants' failure to identify themselves as scientists before the class indicates a gap in undergraduate curriculum educating students about the diversity of scientific roles within society and the academy. As such there is need for a comprehensive review of course offerings at the undergraduate level to ensure students are not only equipped with scientific knowledge but that they develop a clear understanding of who a scientist is as well as the roles of scientists.This article is published as Masambuka-Kanchewa, Fallys, and Alexa J. Lamm. "Perceptions of Scientists Before and After Taking a Graduate Level Science Communication Course." NACTA Journal 66 (2022):113-121. Copyright 2022 North American Colleges and Teachers of Agriculture. Posted with permission

Monte-Carlo simulation of neutron transmission through nanocomposite materials for neutron-optics applications

Nanocomposites enable us to tune parameters that are crucial for use of such materials for neutron-optics applications such as diffraction gratings by careful choice of properties such as species (isotope) and concentration of contained nanoparticles. Nanocomposites for neutron optics have so far successfully been deployed in protonated form, containing high amounts of $^1$H atoms, which exhibit rather strong neutron absorption and incoherent scattering. At a future stage of development, chemicals containing $^1$H could be replaced by components with more favourable isotopes, such as $^2$H or $^{19}$F. In this note, we present results of Monte-Carlo simulations of the transmissivity of various nanocomposite materials for thermal and very-cold neutron spectra. The results are compared to experimental transmission data. Our simulation results for deuterated and fluorinated nanocomposite materials predict a decrease of absorption- and scattering-losses down to about 2 % for very-cold neutrons.Comment: submitted to NIM

Neutron optical beam splitter from holographically structured nanoparticle-polymer composites

We report a breakthrough in the search for versatile diffractive elements for cold neutrons. Nanoparticles are spatially arranged by holographical means in a photopolymer. These grating structures show remarkably efficient diffraction of cold neutrons up to about 50% for effective thicknesses of only 200 micron. They open up a profound perspective for next generation neutron-optical devices with the capability to tune or modulate the neutron diffraction efficiency.Comment: 4 pages, 2 figure

Water vapour line assignments in the 9250-26 000 cm (-1) frequency range

Line parameters for water vapour in natural abundance have recently been determined for the 9250-13 000 cm(-1) region [M.-F. Wrienne, A. Jenouvrier, C. Hermans, A.C. Vandaele, M. Carleer, C. Clerbaux, P.-F. Coheur, R. Colin, S. Fally, M. Bach, J. Quant. Spectrosc. Radiat. Transfer 82 (2003) 99] and the 13 000-26 000 cm(-1) region [P.-F. Coheur, S. Fally, M. Carleer, C. Clerbaux, R. Colin, A. Jenouvrier, M.-F. Wrienne, C. Hermans, A.C. Vandaele, J. Quant. Spectrosc. Radial. Transfer 74 (2002) 493] using a high-resolution Fourier-transform spectrometer with a long-path absorption cell. These spectra are analysed using several techniques including variational line lists and assignments made. In total, over 15 000 lines were assigned to transitions involving more than 150 exited vibrational states of (H2O)-O-16. Twelve new vibrational band origins are determined and estimates for a further 16 are presented. (c) 2005 Elsevier Inc. All rights reserved

Diffraction of slow neutrons by holographic SiO_2 nanoparticle-polymer composite gratings

Diffraction experiments with holographic gratings recorded in SiO$_2$ nanoparticle-polymer composites have been carried out with slow neutrons. The influence of parameters such as nanoparticle concentration, grating thickness and grating spacing on the neutron-optical properties of such materials has been tested. Decay of the grating structure along the sample depth due to disturbance of the recording process becomes an issue at grating thicknesses of about 100 microns and larger. This limits the achievable diffraction efficiency for neutrons. As a solution to this problem, the Pendell\"{o}sung interference effect in holographic gratings has been exploited to reach a diffraction efficiency of 83% for very cold neutrons.Comment: 7 pages, 3 figures, submitted to Phys. Rev.