The Russo-Ukrainian Pre-War Crisis: A Comparative Test of Rational Choice, Expected Utility, Poliheuristic, and Prospect Theories to Explain the War\u27s Outbreak

This mixed approach study seeks to identify the most likely crisis-related decision-making strategies that President Biden, Zelensky, and Putin adopted during the Russo-Ukrainian pre-war crisis. The dissertation tests rational choice, expected utility, poliheuristic, and prospect theory frameworks against five critical decisions. The findings indicate that a Prospect Theory-based framework provides the most accurate predictions of the four models. Further, the study’s incidental finding highlights the salience of politics in decision-making, concluding that a simple lexicographic decision rule grounded in political interests accurately predicts and explains each leader’s choices more reliably and parsimoniously than the other frameworks and just as elegantly

Pulsed versus DC I-V characteristics of resistive manganites

We report on pulsed and DC I-V characteristics of polycrystalline samples of three charge-ordered manganites, Pr_{2/3}Ca_{1/3}MnO_3, Pr_{1/2}Ca_{1/2}MnO_3, Bi_{1/2}Sr_{1/2}MnO_3 and of a double-perovskite Sr_2MnReO_6, in a temperature range where their ohmic resistivity obeys the Efros-Shklovskii variable range hopping relation. For all samples, the DC I(V) exhibits at high currents negative differential resistance and hysteresis, which mask a perfectly ohmic or a moderately nonohmic conductivity obtained by pulsed measurements. This demonstrates that the widely used DC I-V measurements are usually misleading.Comment: 6 pages, 4 figures. Accepted for publication to AP

Inter-grain tunneling in the half-metallic double-perovskites Sr2_2BB'O6_6 (BB'-- FeMo, FeRe, CrMo, CrW, CrRe

The zero-field conductivities ($\sigma$) of the polycrystaline title materials, are governed by inter-grain transport. In the majority of cases their $\sigma$(T) can be described by the "fluctuation induced tunneling" model. Analysis of the results in terms of this model reveals two remarkable features: 1. For \emph{all} Sr$_2$FeMoO$_6$ samples of various microstructures, the tunneling constant (barrier width $\times$ inverse decay-length of the wave-function) is $\sim$ 2, indicating the existence of an intrinsic insulating boundary layer with a well defined electronic (and magnetic) structure. 2. The tunneling constant for \emph{all} cold-pressed samples decreases linearly with increasing magnetic-moment/formula-unit.Comment: 10 pages, 2 tables, 3 figure

Diffusion mechanisms of localised knots along a polymer

We consider the diffusive motion of a localized knot along a linear polymer chain. In particular, we derive the mean diffusion time of the knot before it escapes from the chain once it gets close to one of the chain ends. Self-reptation of the entire chain between either end and the knot position, during which the knot is provided with free volume, leads to an L^3 scaling of diffusion time; for sufficiently long chains, subdiffusion will enhance this time even more. Conversely, we propose local ``breathing'', i.e., local conformational rearrangement inside the knot region (KR) and its immediate neighbourhood, as additional mechanism. The contribution of KR-breathing to the diffusion time scales only quadratically, L^2, speeding up the knot escape considerably and guaranteeing finite knot mobility even for very long chains.Comment: 7 pages, 2 figures. Accepted to Europhys. Let

Solar H2_2 evolution in water with modified diketopyrrolopyrrole dyes immobilised on molecular Co and Ni catalyst–TiO2_2 hybrids

A series of diketopyrrolopyrrole (DPP) dyes with a terminal phosphonic acid group for attachment to metal oxide surfaces were synthesised and the effect of side chain modification on their properties investigated. The organic photosensitisers feature strong visible light absorption ($\lambda$ = 400 to 575 nm) and electrochemical and fluorescence studies revealed that the excited state of all dyes provides sufficient driving force for electron injection into the TiO$_2$ conduction band. The performance of the DPP chromophores attached to TiO$_2$ nanoparticles for photocatalytic H$_2$ evolution with co-immobilised molecular Co and Ni catalysts was subsequently studied, resulting in solar fuel generation with a dye-sensitised semiconductor nanoparticle system suspended in water without precious metal components. The performance of the DPP dyes in photocatalysis did not only depend on electronic parameters, but also on properties of the side chain such as polarity, steric hinderance and hydrophobicity as well as the specific experimental conditions and the nature of the sacrificial electron donor. In an aqueous pH 4.5 ascorbic acid solution with a phosphonated DuBois-type Ni catalyst, a DPP-based turnover number (TON$_{DPP}$) of up to 205 was obtained during UV-free simulated solar light irradiation (100 mW cm$^{-2}$ , AM 1.5G, $\lambda$ > 420 nm) after 1 day. DPP-sensitised TiO$_2$ nanoparticles were also successfully used in combination with a hydrogenase or platinum instead of the synthetic H$_2$ evolution catalysts and the platinum-based system achieved a TON$_{DPP}$ of up to 2660, which significantly outperforms an analogous system using a phosphonated Ru tris(bipyridine) dye (TON$_{Ru}$ = 431). Finally, transient absorption spectroscopy was performed to study interfacial recombination and dye regeneration kinetics revealing that the different performances of the DPP dyes are most likely dictated by the different regeneration efficiencies of the oxidised chromophores.Support by the Christian Doppler Research Association (Austrian Federal Ministry of Science, Research and Economy and National Foundation for Research, Technology and Development), the OMV Group and the Ministry of Education (Singapore) is gratefully acknowledged. RG is grateful to FRQNT for a Postdoctoral Fellowship and JRD thanks the European Science Foundation project Intersolar (291482) for support

Harmonically confined, semiflexible polymer in a channel: response to a stretching force and spatial distribution of the endpoints

We consider an inextensible, semiflexible polymer or worm-like chain which is confined in the transverse direction by a parabolic potential and subject to a longitudinal force at the ends, so that the polymer is stretched out and backfolding is negligible. Simple analytic expressions for the partition function, valid in this regime, are obtained for chains of arbitrary length with a variety of boundary conditions at the ends. The spatial distribution of the end points or radial distribution function is also analyzed.Comment: 14 pages including figure