The effects of R&D expenditures on economic growth

Meine Diplomarbeit besteht aus zwei großen Teilen: einem theoretischen und einem empirischen Teil. Der theoretische Teil beschäftigt sich mit verschiedenen Wachstumsmodellen und deren Entwicklung im Laufe der Zeit. Ich habe mich für das endogene Wachstumsmodell entschieden als Grundlage für mein Wachstumsmodells. Endogenität des technologischen Fortschrittes spielt wichtige Rolle in dieser Arbeit, weil ansonst die F&E (Forschung und Entwicklung) Ausgaben theoretisch irrelevant erscheinen würden. In meinem Modell spielt die Trennung des technologischen Fortschritts von der Steigerung der wirtschaftlichen Produktivität wichtige Rolle neben der Trennung der qualitativen Eigenschaften von den quantitativen. Die Intuition hinter diesen Trennungen sind die Folgenden: das technologische Niveau einer Wirtschaft ist eine Liste aller Erfindungen und Neuerungen die jemals von Menschen „erzeugt“ wurde. Wirtschaftliche Produktivität oder Effektivität („labor efficiency“) hängt jedoch von den verfügbaren neuen Produkten („new designs“) an den Wirtschaftsakteuren ab. Laut Annahme beeinflussen externe Effekte (wie z.B. F&E Ausgaben) den technologischen Fortschritt aber die Produktivität der Wirtschaft hängt in erster Linie von der Struktur der Wirtschaft (d.h. von der Qualität und Quantität der Produktionsfaktoren und von der Qualität der Organisierung von Produktionsprozessen) ab. In dem empirischen Teil habe ich analysiert (teilweise mit Fisher Preis und Mengenindizes) welche Typen der US-F&E Ausgaben beeinflussen signifikant auf kurze Sicht die Wirtschaftsleistung der Vereinigten Staaten (US). Es hat sich herausgestellt, dass staatliche und akademische F&E Ausgaben keine oder sehr geringe Effekten auf die sektorale Wirtschaftsleistung ausüben. Die Regressionsresultate (OLS-Schätzungen) zeigen, dass die industriellen F&E Ausgaben, insbesondere die Entwicklungs-bezogene industrielle F&E Ausgaben die größten Wirkungen auf die sektorale Wertschöpfung ausüben.In the theoretical part I presented briefly the evolution of growth models including the exogenous and endogenous models. I used in the first step the idea of endogenous growth theory, i.e. technological progress is (can be) endogenously determined, influenced in order to make the presentation of R&D expenditures plausible in the regression models. In the next step I separated the quantitative and qualitative characteristics of products and production processes from each other as well as the state of technology and labor efficiency from each other. This idea had the following intuitions: in my opinion the growth models generally emphasizes the quantitative growth, characteristics of production factors and the importance (role) of qualitative characteristics are not explicitly expressed in growth models. The separation of state of technology and labor efficiency is important because the state of technology is primarily determined by external effects like number of researchers or R&D expenditures but labor efficiency primarily depends on the available technology to production factors. Hence knowledge or technology diffusion or distribution is determined by the economic infrastructure for knowledge distribution. In the empirical part I analyzed the (short-run) relationship between the US economy and US R&D expenditures between 1953 and 2006. I used yearly nominal data (transformed by taking the natural logarithm) and Fisher indices. Consequently the estimated coefficients show an elasticity of value added with respect to the given regressor. Industrial R&D expenditures turned out to be the most plausible and significant determinants of economic performance among all types of R&D expenditures

Simulations of calcium channel block by trivalent ions: Gd3+ competes with permeant ions for the selectivity filter

Current through L-type calcium channels (CaV1.2 or dihydropyridine receptor) can be blocked by micromolar concentrations of trivalent cations like the lanthanide gadolinium (Gd 3+). These cations seem to affect both ion permeation a nd pore gating. One effect of trivalents is that the whole-cell peak current recorded after a conditioning voltage pulse depends on [Gd3+], a phenomenon called tonic block. Recently, Babich et al. (J. Gen. Physiol. 129 (2007) 461-475) proposed that tonic block is due to ions competing for a binding site when the channel is closed, and when the channel opens, Gd3+ blocks the pore to prevent the conduction of other ions; tonic block is not due to changes in gating properties, but reflects only permeation. Here, we corroborate this view by computing conductance in a model L-type calcium channel. The model not only reproduces the Gd3+ concentration dependence of the current reduction, but also the effect that substantially more Gd3+ is required to produce similar block in the presence of Sr2+ (compared to Ba2+) and even more in the presence of Ca2+. Tonic block is explained in this model by cations binding in the selectivity filter with the charge/space competition mechanism. In this mechanism, selectivity is determined by the combination of ions that most effectively screen the negative glutamates of the protein while finding space in the midst of the closely-packed carboxylate groups of the glutamate residues

Accurate simulation estimates of phase behaviour in ternary mixtures with prescribed composition

This paper describes an isobaric semi-grand canonical ensemble Monte Carlo scheme for the accurate study of phase behaviour in ternary fluid mixtures under the experimentally relevant conditions of prescribed pressure, temperature and overall composition. It is shown how to tune the relative chemical potentials of the individual components to target some requisite overall composition and how, in regions of phase coexistence, to extract accurate estimates for the compositions and phase fractions of individual coexisting phases. The method is illustrated by tracking a path through the composition space of a model ternary Lennard-Jones mixture.Comment: 6 pages, 3 figure

Ionic selectivity in L-type calcium channels by electrostatics and hard-core repulsion

A physical model of selective “ion binding” in the L-type calcium channel is constructed, and consequences of the model are compared with experimental data. This reduced model treats only ions and the carboxylate oxygens of the EEEE locus explicitly and restricts interactions to hard-core repulsion and ion–ion and ion–dielectric electrostatic forces. The structural atoms provide a flexible environment for passing cations, thus resulting in a self-organized induced-fit model of the selectivity filter. Experimental conditions involving binary mixtures of alkali and/or alkaline earth metal ions are computed using equilibrium Monte Carlo simulations in the grand canonical ensemble. The model pore rejects alkali metal ions in the presence of biological concentrations of Ca2+ and predicts the blockade of alkali metal ion currents by micromolar Ca2+. Conductance patterns observed in varied mixtures containing Na+ and Li+, or Ba2+ and Ca2+, are predicted. Ca2+ is substantially more potent in blocking Na+ current than Ba2+. In apparent contrast to experiments using buffered Ca2+ solutions, the predicted potency of Ca2+ in blocking alkali metal ion currents depends on the species and concentration of the alkali metal ion, as is expected if these ions compete with Ca2+ for the pore. These experiments depend on the problematic estimation of Ca2+ activity in solutions buffered for Ca2+ and pH in a varying background of bulk salt. Simulations of Ca2+ distribution with the model pore bathed in solutions containing a varied amount of Li+ reveal a “barrier and well” pattern. The entry/exit barrier for Ca2+ is strongly modulated by the Li+ concentration of the bath, suggesting a physical explanation for observed kinetic phenomena. Our simulations show that the selectivity of L-type calcium channels can arise from an interplay of electrostatic and hard-core repulsion forces among ions and a few crucial channel atoms. The reduced system selects for the cation that delivers the largest charge in the smallest ion volume

Structural transformation of sulfidized zerovalent iron and its impact on long-term reactivity

Sulfidized nanoscale zerovalent iron (S-nZVI), synthesized via two-step synthesis using Na2S, is an emerging in situ material for groundwater remediation, composed of a metallic iron core and iron sulfide shell. The shell efficiently transfers electrons from the core to its surface for contaminant reduction, while simultaneously protecting the core from anoxic corrosion. However, what controls the S-nZVI longevity is poorly understood. In this study, we characterized at high resolution the structure of S-nZVI and assessed its reactivity with trichloroethene (TCE) with increasing aging. Our data of freshly synthesized material show that the S-nZVI shell primarily consists of ∼5 nm-thick nanocrystalline mackinawite (FeSm) with structural imperfections and heterogeneous crystal orientations. As S-nZVI was aged in anoxic artificial groundwater for up to 180 days, the shell remained mostly intact, while the iron core significantly corroded, resulting in hollow particle structures. We interpret that FeSm defects caused the deterioration of the core. Between 0 and 120 days of aging, rate constants for TCE reduction decreased by only ∼41%. This shows that FeSm remained accessible for TCE reduction; but as the core became depleted, the reduction rate decreased. Re-spiking experiments with TCE oxidized ∼1/4 of the core while the FeSm structure was unaffected. This indicates that the FeSm does not oxidize during TCE reduction, but merely transfers the electron from the core. Overall, these results demonstrate that S-nZVI is able to sustain its reactivity over extended periods due to the persistence of FeSm against oxidation, while its defects control the extent of core corrosion

Ionic Interactions in Biological and Physical Systems: a Variational Treatment

Chemistry is about chemical reactions. Chemistry is about electrons changing their configurations as atoms and molecules react. Chemistry studies reactions as if they occurred in ideal infinitely dilute solutions. But most reactions occur in nonideal solutions. Then everything (charged) interacts with everything else (charged) through the electric field, which is short and long range extending to boundaries of the system. Mathematics has recently been developed to deal with interacting systems of this sort. The variational theory of complex fluids has spawned the theory of liquid crystals. In my view, ionic solutions should be viewed as complex fluids. In both biology and electrochemistry ionic solutions are mixtures highly concentrated (~10M) where they are most important, near electrodes, nucleic acids, enzymes, and ion channels. Calcium is always involved in biological solutions because its concentration in a particular location is the signal that controls many biological functions. Such interacting systems are not simple fluids, and it is no wonder that analysis of interactions, such as the Hofmeister series, rooted in that tradition, has not succeeded as one would hope. We present a variational treatment of hard spheres in a frictional dielectric. The theory automatically extends to spatially nonuniform boundary conditions and the nonequilibrium systems and flows they produce. The theory is unavoidably self-consistent since differential equations are derived (not assumed) from models of (Helmholtz free) energy and dissipation of the electrolyte. The origin of the Hofmeister series is (in my view) an inverse problem that becomes well posed when enough data from disjoint experimental traditions are interpreted with a self-consistent theory.Comment: As prepared for Faraday Discussion, Pavel Jungwirth Organizer, 3 - 5 September 2012, Queens College Oxford, UK on Ion Specific Hofmeister Effects. Version 2 has significant typo corrections in eq. 1 and eq. 4, and has been reformatted to be easier to rea

A highly reactive precursor in the iron sulfide system

Iron sulfur (Fe–S) phases have been implicated in the emergence of life on early Earth due to their catalytic role in the synthesis of prebiotic molecules. Similarly, Fe–S phases are currently of high interest in the development of green catalysts and energy storage. Here we report the synthesis and structure of a nanoparticulate phase (FeSnano) that is a necessary solid-phase precursor to the conventionally assumed initial precipitate in the iron sulfide system, mackinawite. The structure of FeSnano contains tetrahedral iron, which is compensated by monosulfide and polysulfide sulfur species. These together dramatically affect the stability and enhance the reactivity of FeSnano

Protein structure and ionic selectivity in calcium channels: Selectivity filter size, not shape, matters

Calcium channels have highly charged selectivity filters (4 COO − groups) that attract cations in to balance this charge and minimize free energy, forcing the cations (Na + and Ca 2+) to compete for space in the filter. A reduced model was developed to better understand the mechanism of ion selectivity in calcium channels. The charge/space competition (CSC) mechanism implies that Ca 2+ is more efficient in balancing the charge of the filter because it provides twice the charge as Na + while occupying the same space. The CSC mechanism further implies that the main determinant of Ca 2+ versus Na + selectivity is the density of charged particles in the selectivity filter, i.e., the volume of the filter (after fixing the number of charged groups in the filter). In this paper we test this hypothesis by changing filter length and/or radius (shape) of the cylindrical selectivity filter of our reduced model. We show that varying volume and shape together has substantially stronger effects than varying shape alone with volume fixed. Our simulations show the importance of depletion zones of ions in determining channel conductance calculated with the integrated Nernst–Planck equation. We show that confining the protein side chains with soft or hard walls does not influence selectivity

Development of Fe-B Based Bulk Metallic Glasses: Morphology of Residual Phases in Fe50Ni16Mo6B18Zr10 Glass

Iron-boron based bulk metallic glasses (BMG) development has been initiated using Fe40Ni38Mo4B18 as precursor. Addition of zirconium up to 10 atomic % along with the reduction of Ni proportion improves the glass forming ability (GFA), which is optimum when Ni is suppressed in the alloy. However melting instability occurred during the materials fabrication resulting in the formation of residual crystalline phases closely related to the amorphous phase. Microstructure study shows an evolution from amorphous structure to peculiar acicular structure, particularly for Fe50Ni16Mo6B18Zr10, suggesting the amorphous structure as interconnected atomic sheets like “atomic mille feuilles” whose growth affects the alloys’ GFA