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In November 2012, the 18th International Conference of Ethiopian Studies was convened in Dire Dawa, a cosmopolitan city in the eastern lowlands of Ethiopia. This event gathered more than 300 international scholars from all disciplines of the humanities and social social sciences. Under the general theme of ‘movement’ these two volumes gather a collection of 70 papers that reflect recent trends in the field of Ethiopian studies. From local studies to regional and international perspectives, these studies question long term historical processes and current social and economic transformations. A number of contributions explore and give access to fresh sources of knowledge from unpublished or rediscovered texts and documents, from recordings of oral information, or from ethnographic observation. They also review literature, challenge conventional ideas and propose critical investigations on past and present issues, such as interethnic relations, women’s role, development policies and their impact.

Investigating encounters between the Western Christianity and the Ethiopian Orthodox Church (EOC) one, of course, cannot by-pass the beginnings of the Protestant missionary endeavour in Ethiopia. The first established Protestant mission in Ethiopia was sent by the Anglican Church Missionary Society (CMS) and worked there from 1829 till 1843. This mission is interesting not only because it was the first one, but also due to its ambitious long-range objective – to reform the Ethiopian Orthodox ...

This article describes the presence of Karl Rahner in philosophical, theological, and propagandistic works published in the Soviet Union or published outside the USSR and distributed within it. Some references to Rahner appeared in self-published works without the approval of Soviet censors. These included the works of Orthodox theologians such as Sergej Želudkov and Alexander Men’. Other references to Rahner appeared in anti-religious propaganda and in works by Marxist-Leninist philosophers such as Bronislavas Juozas Kuzmickas. By 1992, the year following the collapse of the USSR, Rahner began to receive a more favorable reception in the writing of philosophers such as Elena B. Timerman.

The purpose of this work was to investigate the most important mechanical properties of the thin-walled welded straws developed by JINR (Joint Institute for Nuclear Research) COMET (COherent Muon to Electron Transition, J-PARK) group and to estimate straws lifetime as the main part of the COMET experiment tracking system. The results of the measurements, as well as the main parameters of the stand for studying the straw characteristics are given.

The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminium nucleus ($\mu-e$ conversion, $\mu^- N \to e^- N$); a lepton flavor violating process. The experimental sensitivity goal for this process in the Phase-I experiment is $3.1\times10^{-15}$, or 90 % upper limit of branching ratio of $7\times 10^{-15}$, which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the \mue conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described., Comment: A minor correction applied in Eq. 3

We evaluate the spectrum of ordered three-node substructures in food webs taking self-links (cannibalism) into account. If the order of nodes in the network cannot be neglected, 512 substructures can be distinguished. Simple statistical models of networks impose constraints on the structure that prohibit a large number of substructures completely. We analyse two variants of the widely used niche model, the original niche model and the generalised niche model, and show analytically and numerically that they exclude 344 and 320 substructures, respectively. The prohibition rules for three-node substructures in the two niche-model variants are further contrasted with a large set of empirical food webs, which reveals that up to about 30% of the three-node substructures that occur in empirical food webs are prohibited by the model algorithms.

This chapter reviews fundamentals and dynamical properties of spatial laser cavity solitons realized in broad-area vertical-cavity surface-emitting laser (VCSEL) with frequency-selective feedback from a volume Bragg grating. The solitons are stabilized by a nonlinear frequency shift induced by the strong amplitude phase coupling in semiconductor lasers. The simplest theoretical description is by a cubic complex Ginzburg-Landau equation coupled to a linear filter. The optical phase is an additional Goldstone mode for a laser soliton. Different solitons are usually mutually incoherent due to disorder resulting from cavity length fluctuations. However, we demonstrate frequency- and phase-locking overcoming the disorder and find agreement with the archetypical Adler scenario for the phase dynamics. Fast pulsing at the round-trip frequency is found after soliton switch-on demonstrating transient mode-locking of external cavity modes. An outlook is given on the asymptotic dynamics and prospects for the spatiotemporal self-localization of light.

Separation into spectral and nonlinear complex-eigenvalue problems is shown to be an effective and flexible approach to soliton laser models. The simplest such model, a complex Ginzburg-Landau model with cubic nonlinearity, has no stable solitonic solutions. We show that coupling it to a resonant linear system is a simple and general route to stabilization, which encompasses several previous instances in both space- and time-domains. Graphical solution in the complex eigenvalue plane provides valuable insight into the similarities and differences of such models, and into the interpretation of related experiments. It can also be used predictively, to guide analysis, numerics and experiment., This work was supported in part by the EU FET Open Project FunFACS. P.V. Paulau acknowledges financial support from MEC (Spain) and FEDER (EU) through project No. FIS2007- 60327 FISICOS. We gratefully acknowledge helpful discussions with many FunFACS partner collaborators and colleagues, in particular Andrew Scroggie, Gian-Luca Oppo and Thorsten Ackemann.

The analysis of small recurrent substructures, so called network motifs, has become a standard tool of complex network science to unveil the design principles underlying the structure of empirical networks. In many natural systems network nodes are associated with an intrinsic property according to which they can be ordered and compared against each other. Here, we expand standard motif analysis to be able to capture the hierarchical structure in such ordered networks. Our new approach is based on the identification of all ordered 3-node substructures and the visualization of their significance profile. We present a technique to calculate the fine grained motif spectrum by resolving the individual members of isomorphism classes (sets of substructures formed by permuting node-order). We apply this technique to computer generated ensembles of ordered networks and to empirical food web data, demonstrating the importance of considering node order for food-web analysis. Our approach may not only be helpful to identify hierarchical patterns in empirical food webs and other natural networks, it may also provide the base for extending motif analysis to other types of multi-layered networks., Comment: 10 pages, 5 figures, submitted to Scientific Reports

A system consisting of two thin films interacting resonantly with a light field is considered. The model formulated for such a system is based on the approximation of two-level atoms and takes into account the peculiarities of the semiconductor medium, in particular, the effect of the ratio of dispersions of real and imaginary parts of the susceptibility (α-factor). It is shown that the inclusion of the α-factor leads to an additional nonlinearity and a considerable modification of the set of steady states of the system. The effect of α-factor on the dynamic regimes emerging in the system is discussed.

We predict the formation of a stable solitary rectangular pulse in semiconductor quantum dot media. The formation of such a pulse occurs when a quantum dot system is pumped in a way, where the s shell excitation exhibits gain while the p shell absorbs. We provide formulas to describe the rectangular pulse by the systems material parameters. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This article analyzes the properties of rotationally symmetric self-localized solutions with different radial quantum numbers in the simplest one- and two-component reaction-diffusion systems. The consideration is made in one and two dimensions with the focus on the fundamental and first higher-order solutions showing zero and one intersections of the radial profile with zero. It is demonstrated that the solution with one intersection does not exist for the case of the quadratic-cubic nonlinearity, while the cubic-quintic extension of the models does allow existence. I show additionally that the cubic-quintic reaction diffusion system supports the existence and stability of the states with zero quantum numbers, as well as their antistates, state-antistate pairs, and clusters, which can be interpreted as the states with nonzero azimuthal quantum number.

We observe vortex solitons and dissipative azimuthons in a vertical-cavity surface-emitting laser with feedback, and demonstrate evolution between these states under parameter variation. Stable vortices and azimuthons also exist in a simple model.

We study the conditions under which species competition, as described by competitive Lotka- Volterra models in a homogeneous niche space, can support localized states, i.e. patches of species with enhanced population surrounded by species with smaller densities. Using some approximations we show analytically and numerically that for strong enough self-interaction, such states exist and are stable, representing self-enhanced populations arising from the interactions, and not by any preferred niche location or better fitness. These structures can be thought as portions of stable periodic density patterns (which are also supported by the system), inserted in the background of homogeneous density of species., We acknowledge financial support from FEDER and MINECO (Spain) through Grant No. FIS2012-30634 INTENSE@COSYP, and from Comunitat Autónoma de les Illes Balears. D.G. acknowledges support from CSIC (Spain) through Grant No. 201050I016.

We study the interaction of phase singularities with homogeneous Neumann boundaries in one, two, and three spatial dimensions for the complex Ginzburg-Landau equation. The existence of a boundary-induced drift attractor, well known for spiral waves in two spatial dimensions, is demonstrated for scroll waves in three spatial dimensions. We find that a cylindrical Neumann boundary can lock a scroll ring, thus preventing the collapse of its closed filament.

Summary form only given. Laser cavity solitons (LCS) are transverse, nonlinear, self-localized and dissipative states that possess both translational and phase invariance. LCS interaction and synchronisation properties in broad-area semiconductor lasers have the potential for massive parallelism and the formation of complex arrays. Phase-locked bound states of solitons have been predicted in mode-locked lasers for the temporal case [1] and in lasers with saturable absorbers for the spatial case [2]. Corresponding phase-quadrature states have been observed in fibre lasers [1].Here we present a different kind of soliton locking. We demonstrate experimentally and theoretically Adlertype locking and synchronization of spatial LCS in a vertical-cavity surface-emitting laser (VCSEL) with an external volume Bragg grating (VBG) that provides frequency-selective feedback (see left panel of Fig.1) [3]. In particular we explain the role played by defects resulting from fluctuations during the epitaxial growth process. The experiment has been performed with a temperature tuned 981 nm VCSEL of 200 μm circular aperture and a VBG with a single reflection peak at 981.1 nm, and a peak reflectivity of 99% [3]. The external cavity for the frequency-selective feedback is arranged in a self-imaging configuration that maintains the high Fresnel number of the VCSEL cavity (see the left panel of Fig. 1). This potentially enables large parallelism of solitons and hence the prospect of synchronisation in large disordered networks.A piezo-electric transducer was used to minutely tilt the external cavity's end reflector (VBG) with respect to the optical axis. The differential change of the external cavity length for the two LCS leads to a differential change in feedback phase. In this way the detuning between two LCS can be tuned. During the scan, a region of frequency and phase locking appears, identified in the right panel of Fig. 1 by the region of high fringe visibility in the far field. This illustrates that locking - once achieved - is a robust phenomenon. We have theoretically and numerically investigated the interaction of pinned LCS upon the change of the difference in the depth of the trapping defects for both class-B semiconductor [4] and Ginzburg-Landau [5] models. In the locking region we recover an Adler scenario, where the fringe phase varies smoothly and quasilinearly with the detuning of the external cavity (see the red curve in the right panel of Fig. 1). The transitions to and from frequency and phase-locking are rather abrupt. Finally we discuss theoretical and experimental spectra in the locked and unlocked regions and the effect of the external cavity modes. Independent switching and erasure of locked and unlocked LCS is demonstrated.

We report the observation of single and multiple vortex solitons in a self-focusing dissipative system, a broad-area vertical-cavity surface-emitting laser (VCSEL) with frequency-selective feedback by a volume Bragg grating. They are bistable and the transitions between different soliton structures are analysed. The observations qualitatively verify theoretical predictions based on simplified models for a semiconductor laser with frequency-selective feedback. © 2013 IOP Publishing Ltd., JG gratefully acknowledge support from CONACYT, YN from an EPSRC DTG and a Macquarie University Research Excellence Scholarship. DG acknowledges financial support from the Spanish MINECO and FEDER under grant FISICOS (FIS2007-60327). PVP acknowledges support from SFB 910.

Edited by B. A. Malomed., Self-localized states or dissipative solitons have the freedom of translation in systems with a homogeneous background. When compared to cavity solitons in coherently driven nonlinear optical systems, laser cavity solitons have the additional freedom of the optical phase. We explore the consequences of this additional Goldstone mode and analyze experimentally and numerically frequency and phase locking of laser cavity solitons in a vertical-cavity surface-emitting laser with frequency-selective feedback. Due to growth-related variations of the cavity resonance, the translational symmetry is usually broken in real devices. Pinning to different defects means that separate laser cavity solitons have different frequencies and are mutually incoherent. If two solitons are close to each other, however, their interaction leads to synchronization due to phase and frequency locking with strong similarities to the Adler-scenario of coupled oscillators., P.V.P. acknowledges support from SFB 910; C.M., and Y.N. from EPSRC DTA; P.C. from MICINN and Feder (FIS2007-60327, FISICOS, TEC2009-14101, DeCoDicA). Y.N. and C.M. were supported by EPSRC DTA/DTG grants.