On the possibility of coherently stimulated recombination and cosmological structure generation: recombination instability.

Possible instabilities during cosmological recombination may produce an epoch of nonlinear density growth and fractal-like structural patterns out to the horizon scale at that epoch (approximately 200 Mpc today). With this motivation, we examine the consequences of the change in effective radiative recombination reaction rate coefficients produced by intense stimulated emission. The proton-electron recombination is considered as a natural laser, leading to the formation of spatially nonuniform distributions of neutral matter earlier than the recombination epoch.

Characterization of the instability mechanisms affecting slopes on carbonatic Flysch: Alicante (SE Spain), case study

The studied Flysch sequence of Alicante occupies a widely populated area crossed by main communication routes. The slopes existing on this area usually suffer slope instabilities that cause substantial damage and a very high maintenance cost. In order to assess the type of instability mechanisms affecting these heterogeneous carbonatic slopes, in this paper a wide inventory of 194 Flysch rock slopes has been performed, reporting the existing lithologies, their competence and their relative arrangement and the geometrical relationship between bedding and the slope and the associated instability mechanism. All these data have been jointly used for performing an instability mechanisms characterization. For systematically characterizing the wide type of complex rock exposures existing in the study area, they are divided into basic units referred as lithological pattern columns to which the different observed instability mechanisms are associated. Inventoried instability mechanisms are diverse and sometimes are combined with each other. Rockfalls are a very common instability mechanism associated to the differential weathering and sapping of the marly lithologies which are present in a wide number of geometrical combinations. The other instability mechanisms closely depend on the combination of the geometrical and lithological parameters. Therefore, this work provides a new basic tool which can be easily used during preliminary project stages for knowing the instability mechanisms which can affect rock slopes excavated on carbonatic Flysch heterogeneous geological formations.

The Penetration of Financial Instability in Agricultural Credit and Leveraging. Factor Markets Working Paper No. 2, September 2011

This paper describes the aggregate rural capital markets of the EU and the main differences between the markets of its member countries. The results of our study suggest that the agricultural credit markets are still quite segmented and the segments are country- rather than currency- or region specific. Financial instability in Europe is also penetrating the agricultural sector and the variation of interest rates for agricultural credit is increasing across countries. Perhaps the most dramatic signal of growing financial instability is that the financial leverage (gearing rate) of European farms rose in 2008 by almost 4 percentage points, from 14 to 18%. The 4 percentage-point annual rise was twice the 2 percentage-point rise observed during the economic recession in the late 1980s and early 1990s. The distribution of the financial leverage of agriculture across countries does not, however, reflect the distribution of country-specific risk premiums in the manner that they are observed in government bond yields. Therefore, in those countries that have the weakest financial situation in the public sector and in which the bond markets are encumbered with high country-specific risk premiums, the agricultural sector is not directly exposed to a very large risk of increasing interest rates, since it is not so highly leveraged. For example in Greek and Spanish agriculture, the financial leverage (gearing) rate is only 0.6% and 2.2% respectively, while the highest gearing rates are found elsewhere (in Denmark), reaching 50%.

Kazakhstan: the regional success story; Tajikistan: a trial period; Uzbekistan: the major source of instability in Central Asia? OSW Study 15/2004

Kazakhstan: Kazakhstan can boast economic development like no other country in Central Asia. In contrast to other countries of the region, which have rich natural resources, Kazakhstan has managed to use its economic potential in a way that yields concrete benefits now and, at the same time, creates prospects for further sustainable economic growth. Tajikistan: Tajikistan in its present state has been built on the civil war experiences and provisions of the peace accords signed in 1997. These have had a great impact on the present form of the state, its political scene and power mechanisms. President Emomali Rakhmonov is the central figure in the state. The political system, which he has cocreated, is based on - unique in this region - political pluralism (the existence of the Islamic party), decentralisation (far-going independence of the regions and relatively limited potential of the central structures) and compromise as the basic way of resolving conflicts. Such a system has so far guaranteed stabilisation and normalisation of the country. Uzbekistan: With its geographic location, potential, ambitions and political priorities, Uzbekistan could play a leading role in Central Asia. The international community has perceived the country as the pillar of stability in the region. This perception was further reinforced after 11th September 2001 and was certainly among the factors that inspired the United States to start closer political and military cooperation with Tashkent. The administration in Washington had expected that closer contacts might galvanise political, economic and social change in Uzbekistan, thus reinforcing positive trends in other countries of the region as well. But the relations between Washington and Tashkent are in crisis (which the United States will certainly try to overcome), and we have seen rapprochement between Uzbekistan and Russia and China.

On the periphery of global jihad. The North Caucasus: the illusion of stabilisation. OSW Point of View Number 45, November 2014

The situation in the North Caucasus has stabilised, in comparison with previous years, mainly as regards the activity of the Islamic military underground. This is an effect of ideological changes among the militants which have led to a dilution of the Caucasian armed struggle and its marginalisation in global jihad, since top priority has been granted to the Middle Eastern front. The factors which have contributed to this stabilisation are the organisational crisis in the Caucasus Emirate and the outflux of militants to the Middle East, as well the successful ‘carrot and stick’ policy adopted by Moscow. However, the partial stabilisation in the Caucasus is inherently precarious, being a contingent outcome of the situation rather than the result of systemic change. The region’s pressing problems remain unresolved; and these problems are generating chronic instability and cauing the Caucasus to drift away from Russia in civilisational terms. An economic or political crisis in the Russian Federation may result in the conflicts in the Caucasus unfreezing, including a reactivation of the idea of Chechen independence as well as the idea of the Caucasus Emirate, which is a part of global jihad.

On the initiation of boudinage and folding instabilities in layered elasto-visco-plastic solids - Insights from natural microstructures and numerical simulations

The present understanding of the initiation of boudinage and folding structures is based on viscosity contrasts and stress exponents, considering an intrinsically unstable state of the layer. The criterion of localization is believed to be prescribed by geometry-material interactions, which are often encountered in natural structures. An alternative localization phenomenon has been established for ductile materials, in which instability emerges for critical material parameters and loading rates from homogeneous conditions. In this thesis, conditions are sought under which this type of instability prevails and whether localization in geological materials necessarily requires a trigger by geometric imperfections. The relevance of critical deformation conditions, material parameters and the spatial configuration of instabilities are discussed in a geological context. In order to analyze boudinage geometries, a numerical eigenmode analysis is introduced. This method allows determining natural frequencies and wavelengths of a structure and inducing perturbations on these frequencies. In the subsequent coupled thermo-mechanical simulations, using a grain size evolution and end-member flow laws, localization emerges when material softening through grain size sensitive viscous creep sets in. Pinch-and-swell structures evolve along slip lines through a positive feedback between the matrix response and material bifurcations inside the layer, independent from the mesh-discretization length scale. Since boudinage and folding are considered to express the same general instability, both structures should arise independently of the sign of the loading conditions and for identical material parameters. To this end, the link between material to energy instabilities is approached by means of bifurcation analyses of the field equations and finite element simulations of the coupled system of equations. Boudinage and folding structures develop at the same critical energy threshold, where dissipative work by temperature-sensitive creep overcomes the diffusive capacity of the layer. This finding provides basis for a unified theory for strain localization in layered ductile materials. The numerical simulations are compared to natural pinch-and-swell microstructures, tracing the adaption of grain sizes, textures and creep mechanisms in calcite veins. The switch from dislocation to diffusion creep relates to strain-rate weakening, which is induced by dissipated heat from grain size reduction, and marks the onset of continuous necking. The time-dependent sequence uncovers multiple steady states at different time intervals. Microstructurally and mechanically stable conditions are finally expressed in the pinch-and-swell end members. The major outcome of this study is that boudinage and folding can be described as the same coupled energy-mechanical bifurcation, or as one critical energy attractor. This finding allows the derivation of critical deformation conditions and fundamental material parameters directly from localized structures in the field.

Fault development and interaction in distributed strike-slip shear zones: an experimental approach

Analogue model experiments using both brittle and viscous materials were performed to investigate the development and interaction of strike-slip faults in zones of distributed shear deformation. At low strain, bulk dextral shear deformation of an initial rectangular model is dominantly accommodated by left-stepping, en echelon strike-slip faults (Riedel shears, R) that form in response to the regional (bulk) stress field. Push-up zones form in the area of interaction between adjacent left-stepping Riedel shears. In cross sections, faults bounding push-up zones have an arcuate shape or merge at depth. Adjacent left-stepping R shears merge by sideways propagation or link by short synthetic shears that strike subparallel to the bulk shear direction. Coalescence of en echelon R shears results in major, through-going faults zones (master faults). Several parallel master faults develop due to the distributed nature of deformation. Spacing between master faults is related to the thickness of the brittle layers overlying the basal viscous layer. Master faults control to a large extent the subsequent fault pattern. With increasing strain, relatively short antithetic and synthetic faults develop mostly between old, but still active master faults. The orientation and evolution of the new faults indicate local modifications of the stress field. In experiments lacking lateral borders, closely spaced parallel antithetic faults (cross faults) define blocks that undergo clockwise rotation about a vertical axis with continuing deformation. Fault development and fault interaction at different stages of shear strain in our models show similarities with natural examples that have undergone distributed shear.

Strain-induced structural instability in FeRh

We perform density functional calculations to investigate the structure of the intermetallic alloy FeRh under epitaxial strain. Bulk FeRh exhibits a metamagnetic transition from a low-temperature antiferromagnetic (AFM) phase to a ferromagnetic phase at 350 K, and its strain dependence is of interest for tuning the transition temperature to the room-temperature operating conditions of typical memory devices. We find an unusually strong dependence of the structural energetics on the choice of exchange-correlation functional, with the usual local density approximation yielding the wrong ground-state structure, and generalized gradient (GGA) extensions being in better agreement with the bulk experimental structure. Using the GGA we show the existence of a metastable face-centered-cubic-like AFM structure that is reached from the ground-state body-centered-cubic-like AFM structure by following the epitaxial Bain path. We show that the behavior is well described using nonlinear elasticity theory, which captures the softening and eventual sign change of the orthorhombic shear modulus under compressive strain, consistent with this structural instability. Finally, we predict the existence of an additional unit-cell-doubling lattice instability, which should be observable at low temperature.

Stick to reality and a dream : celebrating America's young readers : a lecture for the Year of the Young Reader, presented on November 17, 1988 at the Library of Congress /

"Children's Literature Center lecture series, no. 3"--T.p. verso.

Slip casting of nuclear fuel elements.

"Contract no. AT(30-1)-2258"

Effect of rate of change of slip on the peak braking coefficient of passenger car tires. Technical report.

Mode of access: Internet.

Gaussian elimination and numerical instability /

"UILU-ENG 77 1714."

Dimensional instability of Uranium.

Report year runs ends June 30.