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Development and application of novel genetic transformation technologies in maize (Zea mays L.)
(2007)
Plant genetic engineering approaches are of pivotal importance to both basic and applied research. However, rapid commercialization of genetically engineered crops, especially maize, raises several ecological and environmental concerns largely related to transgene flow via pollination. In most crops, the plastid genome is inherited uniparentally in a maternal manner. Consequently, a trait introduced into the plastid genome would not be transferred to the sexually compatible relatives of the crops via pollination. Thus, beside its several other advantages, plastid transformation provides transgene containment, and therefore, is an environmentally friendly approach for genetic engineering of crop plants. Reliable in vitro regeneration systems allowing repeated rounds of regeneration are of utmost importance to development of plastid transformation technologies in higher plants. While being the world’s major food crops, cereals are among the most difficult-to-handle plants in tissue culture which severely limits genetic engineering approaches. In maize, immature zygotic embryos provide the predominantly used material for establishing regeneration-competent cell or callus cultures for genetic transformation experiments. The procedures involved are demanding, laborious and time consuming and depend on greenhouse facilities. In one part of this work, a novel tissue culture and plant regeneration system was developed that uses maize leaf tissue and thus is independent of zygotic embryos and greenhouse facilities. Also, protocols were established for (i) the efficient induction of regeneration-competent callus from maize leaves in the dark, (ii) inducing highly regenerable callus in the light, and (iii) the use of leaf-derived callus for the generation of stably transformed maize plants. Furthermore, several selection methods were tested for developing a plastid transformation system in maize. However, stable plastid transformed maize plants could not be yet recovered. Possible explanations as well as suggestions for future attempts towards developing plastid transformation in maize are discussed. Nevertheless, these results represent a first essential step towards developing chloroplast transformation technology for maize, a method that requires multiple rounds of plant regeneration and selection to obtain genetically stable transgenic plants. In order to apply the newly developed transformation system towards metabolic engineering of carotenoid biosynthesis, the daffodil phytoene synthase (PSY) gene was integrated into the maize genome. The results illustrate that expression of a recombinant PSY significantly increases carotenoid levels in leaves. The beta-carotene (pro-vitamin A) amounts in leaves of transgenic plants were increased by ~21% in comparison to the wild-type. These results represent evidence for maize to have significant potential to accumulate higher amounts of carotenoids, especially beta-carotene, through transgenic expression of phytoene synthases. Finally, progresses were made towards developing transformation technologies in Peperomia (Piperaceae) by establishing an efficient leaf-based regeneration system. Also, factors determining plastid size and number in Peperomia, whose species display great interspecific variation in chloroplast size and number per cell, were investigated. The results suggest that organelle size and number are regulated in a tissue-specific manner rather than in dependency on the plastid type. Investigating plastid morphology in Peperomia species with giant chloroplasts, plasmatic connections between chloroplasts (stromules) were observed under the light microscope and in the absence of tissue fixation or GFP overexpression demonstrating the relevance of these structures in vivo. Furthermore, bacteria-like microorganisms were discovered within Peperomia cells, suggesting that this genus provides an interesting model not only for studying plastid biology but also for investigating plant-microbe interactions.
In nature one commonly finds interacting complex oscillators which by the coupling scheme form small and large networks, e.g. neural networks. Surprisingly, the oscillators can synchronize, still preserving the complex behavior. Synchronization is a fundamental phenomenon in coupled nonlinear oscillators. Synchronization can be enhanced at different levels, that is, the constraints on which the synchronization appears. Those can be in the trajectory amplitude, requiring the amplitudes of both oscillators to be equal, giving place to complete synchronization. Conversely, the constraint could also be in a function of the trajectory, e.g. the phase, giving place to phase synchronization (PS). In this case, one requires the phase difference between both oscillators to be finite for all times, while the trajectory amplitude may be uncorrelated. The study of PS has shown its relevance to important technological problems, e.g. communication, collective behavior in neural networks, pattern formation, Parkinson disease, epilepsy, as well as behavioral activities. It has been reported that it mediates processes of information transmission and collective behavior in neural and active networks and communication processes in the Human brain. In this work, we have pursed a general way to analyze the onset of PS in small and large networks. Firstly, we have analyzed many phase coordinates for compact attractors. We have shown that for a broad class of attractors the PS phenomenon is invariant under the phase definition. Our method enables to state about the existence of phase synchronization in coupled chaotic oscillators without having to measure the phase. This is done by observing the oscillators at special times, and analyzing whether this set of points is localized. We have show that this approach is fruitful to analyze the onset of phase synchronization in chaotic attractors whose phases are not well defined, as well as, in networks of non-identical spiking/bursting neurons connected by chemical synapses. Moreover, we have also related the synchronization and the information transmission through the conditional observations. In particular, we have found that inside a network clusters may appear. These can be used to transmit more than one information, which provides a multi-processing of information. Furthermore, These clusters provide a multichannel communication, that is, one can integrate a large number of neurons into a single communication system, and information can arrive simultaneously at different places of the network.
We have studied the bifurcation structure of the incompressible two-dimensional Navier-Stokes equations with a special external forcing driving an array of 8×8 counterrotating vortices. The study has been motivated by recent experiments with thin layers of electrolytes showing, among other things, the formation of large-scale spatial patterns. As the strength of the forcing or the Reynolds number is raised the original stationary vortex array becomes unstable and a complex sequence of bifurcations is observed. The bifurcations lead to several periodic branches, torus and chaotic solutions, and other stationary solutions. Most remarkable is the appearance of solutions characterized by structures on spatial scales large compared to the scale of the forcing. We also characterize the different dynamic regimes by means of tracers injected into the fluid. Stretching rates and Hausdorff dimensions of convected line elements are calculated to quantify the mixing process. It turns out that for time-periodic velocity fields the mixing can be very effective.
The dynamics of noisy bistable systems is analyzed by means of Lyapunov exponents and measures of complexity. We consider both the classical Kramers problem with additive white noise and the case when the barrier fluctuates due to additional external colored noise. In case of additive noise we calculate the Lyapunov exponents and all measures of complexity analytically as functions of the noise intensity resp. the mean escape time. For the problem of fluctuating barrier the usual description of the dynamics with the mean escape time is not sufficient. The application of the concept of measures of complexity allows to describe the structures of motion in more detail. Most complexity measures sign the value of correlation time at which the phenomenon of resonant activation occurs with an extremum.
Biochemical and physiological studies of Arabidopsis thaliana Diacylglycerol Kinase 7 (AtDGK7)
(2006)
A family of diacylglycerol kinases (DGK) phosphorylates the substrate diacylglycerol (DAG) to generate phosphatidic acid (PA) . Both molecules, DAG and PA, are involved in signal transduction pathways. In the model plant Arabidopsis thaliana, seven candidate genes (named AtDGK1 to AtDGK7) code for putative DGK isoforms. Here I report the molecular cloning and characterization of AtDGK7. Biochemical, molecular and physiological experiments of AtDGK7 and their corresponding enzyme are analyzed. Information from Genevestigator says that AtDGK7 gene is expressed in seedlings and adult Arabidopsis plants, especially in flowers. The AtDGK7 gene encodes the smallest functional DGK predicted in higher plants; but also, has an alternative coding sequence containing an extended AtDGK7 open reading frame, confirmed by PCR and submitted to the GenBank database (under the accession number DQ350135). The new cDNA has an extension of 439 nucleotides coding for 118 additional amino acids The former AtDGK7 enzyme has a predicted molecular mass of ~41 kDa and its activity is affected by pH and detergents. The DGK inhibitor R59022 also affects AtDGK7 activity, although at higher concentrations (i.e. IC50 ~380 µM). The AtDGK7 enzyme also shows a Michaelis-Menten type saturation curve for 1,2-DOG. Calculated Km and Vmax were 36 µM 1,2-DOG and 0.18 pmol PA min-1 mg of protein-1, respectively, under the assay conditions. Former protein AtDGK7 are able to phosphorylate different DAG analogs that are typically found in plants. The new deduced AtDGK7 protein harbors the catalytic DGKc and accessory domains DGKa, instead the truncated one as the former AtDGK7 protein (Gomez-Merino et al., 2005).
To characterise the habitat preferences of ring ouzel (Turdus torquatus) and blackbird (T. merula) in Switzerland, we adopt species distribution modelling and predict the species’ spatial distribution. We model on two different scales to analyse in how far downscaling leads to a different set of predictors to describe the realised habitat best. While the models on macroscale (grid of one square kilometre) cover the entire country, we select a set of smaller plots for modelling on territory scale. Whereas ring ouzels occur in altitudes above 1’000 m a.s.l. only, blackbirds occur from the lowlands up to the timber line. The altitudinal range overlap of the two species is up to 400 m. Despite both species coexist on macroscale, a direct niche overlap on territory scale is rare. Small-scale differences in vegetation cover and structure seem to play a dominant role for habitat selection. On macroscale however, we observe a high dependency on climatic variables mainly representing the altitudinal range and the related forest structure preferred by the two species. Applying the models for climate change scenarios, we predict a decline of suitable habitat for the ring ouzel with a simultaneous median altitudinal shift of +440 m until 2070. In contrast, the blackbird is predicted to benefit from higher temperatures and expand its range to higher elevations.
Do institutions matter?
(2006)
Contens 1 Introduction 2 Institutions and the Institutional Change 2.1 Institutions and Theoretical Concepts in Economics 2.2 Path Dependence 2.3 Inconsistence of Institutional Development 2.4 Determinants of Effectiveness 2.5 Efficiency of New Institutions 3 What is “Competition Policy”? 4 The Competition Policy in Russia as an Institution 4.1 Establishment of the Competition Policy as an Institution 4.2 Market Structure and Competition Policy 4.3 Measures of Competition Policy 4.3.1 Prohibition of Competition Restrictive Agreements or Concerted Actions 4.3.2 Abuse of Dominance 4.3.3 Merger Control 4.3.4 Restrictive Action to Competition of Administrative Bodies 4.4 Violations of the Competition Law 4.5 Problems of the Russian Competition Policy 5 Which Mistakes Russia has made with the Implementation of theCompetition Policy? 6 Is a Lacking Effectiveness of Transplanted Institutions Inevitable? 7 Concluding Remarks
The usage of nonlinear Galerkin methods for the numerical solution of partial differential equations is demonstrated by treating an example. We desribe the implementation of a nonlinear Galerkin method based on an approximate inertial manifold for the 3D magnetohydrodynamic equations and compare its efficiency with the linear Galerkin approximation. Special bifurcation points, time-averaged values of energy and enstrophy as well as Kaplan-Yorke dimensions are calculated for both schemes in order to estimate the number of modes necessary to correctly describe the behavior of the exact solutions.
A casual look at regional unemployment rates reveals that there are vast differences, which cannot be explained by different institutional settings. Our paper attempts to trace these differences in the labor market performance back to the regions' specialization in products that are more or less advanced in their product cycle. The model we develop shows how individual profit and utility maximization endogenously yields higher employment levels in the beginning. In later phases, however, employment decreases in the presence of process innovation. Our model suggests that the only way to escape from this vicious circle is to specialize in products that are at the beginning of their "economic life". The model is based on an interaction of demand and supply side forces.
Textbook wisdom says that competition yields lower prices and higher consumer surplus than monopoly. We show in two versions of a simple location-product differentiation model with and without endogenous choice of products that these two results have to be qualified. In both models, more than half of the reasonable parameter values lead to higher prices with duopoly than with monopoly. If the product characteristics are exogenous to the firms, consumers may even be be better off with monopoly in average.
The paper presents a method that determines, by standard numerical means, the type of mutual relations of fold and flip bifurcations (configured as a so-called communication area) of a map. Equation systems are developed for the computation of points where a transition between areas of different types occurs. Furthermore, it is shown that saddle area<->spring area transitions can exist which have not yet been considered in the literature. Analytical conditions of that transition are derived.
We have numerically studied the bifurcation properties of a sheet pinch with impenetrable stress-free boundaries. An incompressible, electrically conducting fluid with spatially and temporally uniform kinematic viscosity and magnetic diffusivity is confined between planes at x1=0 and 1. Periodic boundary conditions are assumed in the x2 and x3 directions and the magnetofluid is driven by an electric field in the x3 direction, prescribed on the boundary planes. There is a stationary basic state with the fluid at rest and a uniform current J=(0,0,J3). Surprisingly, this basic state proves to be stable and apparently to be the only time-asymptotic state, no matter how strong the applied electric field and irrespective of the other control parameters of the system, namely, the magnetic Prandtl number, the spatial periods L2 and L3 in the x2 and x3 directions, and the mean values B¯2 and B¯3 of the magnetic-field components in these directions.
We have studied the bifurcations in a three-dimensional incompressible magnetofluid with periodic boundary conditions and an external forcing of the Arnold-Beltrami-Childress (ABC) type. Bifurcation-analysis techniques have been applied to explore the qualitative behavior of solution branches. Due to the symmetry of the forcing, the equations are equivariant with respect to a group of transformations isomorphic to the octahedral group, and we have paid special attention to symmetry-breaking effects. As the Reynolds number is increased, the primary nonmagnetic steady state, the ABC flow, loses its stability to a periodic magnetic state, showing the appearance of a generic dynamo effect; the critical value of the Reynolds number for the instability of the ABC flow is decreased compared to the purely hydrodynamic case. The bifurcating magnetic branch in turn is subject to secondary, symmetry-breaking bifurcations. We have traced periodic and quasi- periodic branches until they end up in chaotic states. In particular detail we have analyzed the subgroup symmetries of the bifurcating periodic branches, which are closely related to the spatial structure of the magnetic field.
This paper analyses the structural change in Russia during the transition from the planned to a market economy. With regard to the famous three sector hypothesis, broad economic sectors were formed as required by this theory. The computation of their shares at GNP at market prices using Input-Output tables, and the adjustment of results from distortions, generated as side effects of tax avoidance practices, shows results that clearly reject claims that Russia would be on the road to a post-industrial service economy. Instead, at least until 2001, a tendency of "primarisation" could be observed, that presents Russia closer to less-developed countries.
Instability in competition
(2005)
In this paper we show that Puu (2002) does not provide a stable solution to the location game, according to his own definition of stability. If the usual two-stage game is considered, where in the first stage a location is chosen once and forever, and in the second stage prices are determined, the equilibrium proves stable for a sizeable interval of parameters, however. Even though this procedure is most common in analyzing Hotelling's location problem, it is not satisfying because it exhibits an inconsistent informational structure. The search for a better concept of stability is imperative.
Traveltime residuals for worldwide seismic stations are calculated. We use P and S waves from earthquakes in SE-Asia at teleseismic and regional distances. The obtained station residuals help to enhance earthquake localisation. Furthermore we calculated regional source dependent station residuals. They show a systematic dependence of the locality of the source. These source dependent residuals reflect heterogenities along the path and can be used for a refinement of earthquake localisation.
This volume presents annotation guidelines that have been developed in the context of the SFB 632, a collaborative research center entitled "Information Structure: the Linguistic Means for Structuring Utterances, Sentences and Texts". An important result of the SFB 632 are the SFB corpora from more than 20 typologically different languages, which have been annotated according to the guidelines presented here. The ultimate target of the data and its annotations is to support the study of Information Structure. Information Structure involves all levels of grammar and, hence, the present guidelines cover relevant aspects of all these levels: - Phonology - Morphology - Syntax - Semantics - Information Structure These levels are dealt with in individual chapters, containing tagset declarations with obligatory and optional tags, detailed annotation instructions, and illustrative examples. The volume also presents an evaluation of inter-annotator agreement of Syntax and Information Structural annotation.
Table of contens 1 Introduction 2 The concept of sustainability 2.1 Ecological sustainability 2.2 Social sustainability 2.3 Economic sustainability 2.4 The sustainability strategy of the german government 3 Effects of energy use on the enviromment 4 Requirements of the SSGG for energy policy 4.1 Ecological implications of thr SSGG 4.2 Social and economic requirements of the SSGG 5 The German Renewable Energies Act 5.1 Objectives 5.2 Design and mechanisms 5.3 Fees-in tariffs 6 Does the EEG meet the sustainability requirements of the SSGG? 6.1 Management rules 6.2 Social sustainability 6.3 Economic sustainability 6.4 Development tendencis 7 Possible amendments for more sustainability 7.1 Changing the promotional system 7.2 A European regulation
Social segregation in cities takes place where different household groups exist and when, according to Schelling, their location choice either minimizes the number of differing households in their neighborhood or maximizes their own group. In this contribution an evolutionary simulation based on a monocentric city model with externalities among households is used to discuss the spatial segregation patterns of four groups. The resulting complex spatial patterns can be shown as graphic animations. They can be applied as initial situation for the analysis of the effects a rent control has on segregation.
Optimal spatial patterns of two, three and four segregated household groups in a monocentric city
(2004)
Usually, in monocentric city models the spatial patterns of segregated household groups are assumed to be ring-shaped, while early in the 1930ies Hoyt showed that wedge-shaped areas empirically predominate. This contribution presents a monocentric city model with different household groups generating positive externalities within the groups. At first, border length is founded as a criterion of optimality. Secondly, it is shown that mixed patterns of concentric and wedge-shaped areas represent multiple equilibria if more than two groups of households are being considered. The welfare optimal segregated pattern depends on the relative purchasing power of different household groups.