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This dissertation is concerned with the phenomenon of intervention effects, observed in three different domains: wh-questions, alternative questions (AltQ) and Negative Polarity Item (NPI) licensing. I propose that these three domains share some common properties, namely, they all involve focus-sensitive licensing, and are thus sensitive to an intervening focus phrase. The overview of the dissertation is as follows. In chapter 2, I discuss the phenomenon of intervention effects in wh-questions, brought to light in the discussion of German in Beck (1996), and Korean in Beck and Kim (1997). The basic idea of their analysis is that quantifiers block LF wh-movement. I show that intervention effects are observed in many other languages, too, suggesting that the intervention effect has a universal character. I then point out some problems with the analysis proposed by Beck (1996) and Beck and Kim (1997). In chapter 3, I propose a new generalization of the wh-intervention effects, namely that the core set of interveners, which is crosslinguistically stable, consists of focus phrases (and not quantifiers in general). Furthermore, I argue that the wh-intervention effect is actually an instance of the more general intervention effect, the "Focus Intervention Effect", which says that in a focus-sensitive licensing construction, no independent focus phrase may intervene between the licensor Op and the licensee XP. The underlying idea is that the Q operator is a focus-sensitive operator and that wh-phrases in-situ are dependent (i.e., semantically deficient) focus elements, which must be associated with the Q operator in order to be interpreted. An intervening independent focus operator precisely blocks that association. I further propose that the domain of focus-sensitive licensing includes not only wh-licensing, but also AltQ-licensing and NPI-licensing. In chapter 4, I show that alternative questions are also subject to the focus intervention effect, just like wh-questions. I provide evidence that the intervention effect in wh-questions and in alternative questions should receive a parallel analysis, in terms of focus-sensitivity. In chapter 5, I discuss a third construction which is sensitive to the focus intervention effect: the licensing of Negative Polarity Items (NPIs). I show that focus consistently blocks NPI licensing, with data from German and Korean. I propose that NPIs are also semantically deficient focus elements, which need to be associated with a NEG operator. Finally, chapter 6 summarizes the intervention effects and suggests some topics for future research into the precise nature of the intervention effect.
Electron tomography was used to investigate membrane proteins in a variety of contexts. A high-angle tilt holder, suitable for electron tomography was designed, constructed and characterised. 2D crystals of membrane proteins, NhaA and YidC, were examined as a resolution test, and a method established for determining planarity of crystals. A model for specific gold binding to NhaA crystals was also presented. ATP synthase, a membrane protein complex in mitochondria, were imaged in a frozen hydrated state. They were found to form ribbons of dimers at highly curved regions of the membrane. Dimers from bovine heart and rat liver were excised from the tomographic volumes and averaged. Based on the location of the dimers in the mitochondrion, a model was established whereby ATP synthase, a molecular motor driven by the proton motive force, benefits from the high curvature that it induces in the membrane. Whole yeast mitochondria, imaged by electron cryo-tomography, also contained long ribbons of dimeric ATP synthase. Multiple copies of an unknown membrane protein complex were visualised by electron cryo-tomography, excised and averaged. A general method for the identification of unknown proteins was presented to deal with this inevitable issue, as native tissues and organelles are imaged, and the structures of complexes determined in situ.
3.11.2008 - 4.11.2008 fand in Frankfurt am Main folgende Tagung statt: 21st Century Libraries: Changing Forms, Changing Challenges, Changing Objectives = 8th Frankfurt Scientific Symposium: 3.11.2008 - 4.11.2008. Sie wurde von der Universitätsbiblithek Johann Christian Senckenberg in Zusammanarbeit mit dem Deutschem Architektur Museum (Frankfurt am Main) und der Akademie der Architekten- und Stadtplanerkammer Hessen (Wiesbaden) organisiert Das 8. Frankfurt Symposium stellt den zeitgenössischen Bibliotheksbau, die Entwicklungen und die Probleme des gegenwärtigen Bibliotheksbaus zur Diskussion. Einige theoretische und technische Beiträge runden das Programm ab. Zwei zentrale Schwerpunkte des Symposiums werden die Einbindung von Bibliotheksbauten in das Stadtumfeld und die Auswirkungen gesellschaftspolitischer und technischer Entwicklungen auf die Architektur von Bibliotheken sein.
In this paper, we examine the impact of mergers among German savings banks on the extent to which these savings banks engage in small business lending. The ongoing consolidation in the banking industry has sparked concerns about the continuous availability of credit to small businesses which has been further fueled by empirical studies that partly confirm a reduction in small business lending in the aftermath of mergers. However, using a proprietary data set of German savings banks we find strong evidence that in Germany merging savings banks do not significantly change the extent to which they lend to small businesses compared to prior to the merger or compared to the contemporaneous lending by non-merging banks. We investigate the merger related effects on small business lending in Germany from a bank-level perspective. Furthermore, we estimate small business lending and its continuous adjustment process simultaneously using recent General Method of Moments (GMM) techniques for panel data as proposed by Arellano and Bond (1991).
This paper discusses the so-called commercial approach to microfinance under economic and ethical aspects. It first shows how microfinance has developed from a purely welfare-oriented activity to a commercially relevant line of banking business. The background of this stunning success is the – almost universal – adoption of the so-called commercial approach to microfinance in the course of the last decade. As the author argues, this commercial approach is the only sound approach to adopt if one wanted microfinance to have any social and developmental impact, and therefore the wide-spread “moralistic” criticism of the commercial approach, which has again and again been expressed in the 1990s, is ill-placed from an economic and an ethical perspective. However, some recent events in microfinance raise doubts as to whether the commercial approach has not, in a number of cases, gone too far. The evident example for such a development is the Mexican microfinance institution Compartamos, which recently undertook a financially extremely successful IPO. As it seems, some microfinance institutions have by now become so radically commercial that all of those social and development considerations, which have traditionally motivated work in the field of microfinance, seem to have lost their importance. Thus there is a conflict between commercial and developmental aspirations. However, this conflict is not inevitable. The paper concludes by showing that, and how, a microfinance institution can try to combine using the strengths of the capital market and at the same time maintaining its developmental focus and importance.
The research presented in this thesis characterizes U2AF homology motifs (UHM) and their interactions with UHM ligand motifs (ULM) in the context of splicing regulation. UHM domains are a subgroup of RNA recognition motifs (RRM) originally discovered in the proteins U2AF65 and U2AF35. Whereas canonical RRMs are usually involved in binding of RNA, UHM domains bind tryptophan containing linear protein motifs (ULM) instead. In the first article, we analyze the complex network of interactions between splicing factors and RNA that initiate the assembly of the spliceosome at the 3´ splice site of an intron. The protein U2AF65 binds a pyrimidine-rich element in introns and recruits U2snRNP by binding its protein component SF3b155. My contribution was to define the binding site of the protein U2AF65 to the intrinsically unstructured N-terminus of the scaffolding protein SF3b155. I could show that the UHM domain of U2AF65 recognizes a ULM in SF3b155, and that this binding site is not overlapping with the binding sites of other splicing factors, like p14, to SF3b155. As the U2AF65-UHM:SF3b155-ULM interaction is mutually exclusive with an interaction between U2AF65-UHM and a ULM in the splicing factor SF1, which was reported to initially recognize the branch point sequence, my results provide the molecular details on how SF3b155 replaces SF1 during spliceosomal reorganizations. In the second article, we show that overexpression of the UHM domain of the splicing factor SPF45 induces exon 6 skipping in the pre-mRNA of Fas (CD95/APO-1). I provide evidence for in vitro binding of SPF45-UHM to ULM sequences in the splicing factors U2AF65, SF1, and SF3b155. I crystallized free and SF3b155-bound SPF45 UHM and solved both structures by X-ray crystallography. The analysis of the complex interface and sequence differences in the ULMs allowed me to design mutations of SPF45-UHM, which selectively inhibit binding to distinct ULMs. After assessing the ULM binding properties in vitro, we could show that the activity of SPF45-UHM in influencing the splicing pattern of Fas relies on interactions with SF3b155 and/or SF1, but that an interaction with U2AF65 is dispensable. A mechanism for the activity of SPF45-UHM could thus be engaging in ULM interactions and thus interfering with the network of interactions that initiate the assembly of the spliceosome at the 3´splice site, as described above. In the third article, we describe an unusual flexible homodimerization mode of the UHM in the splicing factor Puf60, which enables simultaneous interactions with ULM sequences on other splicing factors. I could show that the NMR relaxation properties of Puf60-UHM are inconsistent with a model of a rigid dimer, but rather indicate a dimerization via a flexible linker. I identified a flexible loop in the peptide backbone of Puf60-UHM, and showed that mutiation of acidic residues in this loop impairs the dimerization. To analyze the dimerization interface in further detail, I solved the structure of Puf60-UHM by X-ray crystallography. The acidic residues in the flexible loop of one UHM dimer subunit mediate the dimerization by contacting basic residues on the β-sheet surface of the other dimer subunit. Differences in the four dimer interfaces observed for the eight molecules in the asymmetric unit of the crystal support the model of an undescribed, flexible mode of dimerization, and thus complement the NMR relaxation data. Furthermore, I could show that the Puf60-UHM dimer and U2AF65-UHM contact different ULM sequences on the SF3b155 N-terminus in vitro, thus providing a possible explanation for the mutual cooperative activation of Puf60 and U2AF65 in splicing assays described in the literature. The fourth article is a review about recent research on the recognition of DNA double strand breaks (DSB) by covalent histone modifications. The p53 binding protein 1 (53BP1) is a DSB sensor and a checkpoint protein for mitosis. Recent crystallographic evidence indicates that 53BP1 recognizes DSB sites by binding histone H4 dimetylated at lysine 20 (H4-K20). We provide a comprehensive overview of the atomic resolution structures that revealed how proteins can specifically recognize histone tail modifications, especially methylated lysines, to read the information stored in what is called the histone code.
We examine insurance markets with two types of customers: those who regret suboptimal decisions and those who don.t. In this setting, we characterize the equilibria under hidden information about the type of customers and hidden action. We show that both pooling and separating equilibria can exist. Furthermore, there exist separating equilibria that predict a positive correlation between the amount of insurance coverage and risk type, as in the standard economic models of adverse selection, but there also exist separating equilibria that predict a negative correlation between the amount of insurance coverage and risk type, i.e. advantageous selection. Since optimal choice of regretful customers depends on foregone alternatives, any equilibrium includes a contract which is o¤ered but not purchased.
When a spot market monopolist participates in a derivatives market, she has an incentive to deviate from the spot market monopoly optimum to make her derivatives market position more profitable. When contracts can only be written contingent on the spot price, a risk-averse monopolist chooses to participate in the derivatives market to hedge her risk, and she reduces expected profits by doing so. However, eliminating all risk is impossible. These results are independent of the shape of the demand function, the distribution of demand shocks, the nature of preferences or the set of derivatives contracts.
The focus of this thesis has been to further advance and develop existing NMR techniques for the study of protein folding. In order to do so, experimental as well as theoretical approaches have been pursued. From the theoretical side, a successful attempt to the development of a general theory for the treatment of residual dipolar couplings in the case of unfolded proteins has been undertaken. Information contained in residual dipolar couplings is especially valuable due to its long-range nature. The dynamic character of unfolded states of proteins, which may be composed of distinct subsets of conformations, renders reliable interpretation of data a non-trivial task. Statistical-coil-based approaches have been shown to be powerful in data interpretation. A consistent theory based on fundamental polymer physics, however, had not been presented so far. The herein presented model addresses this problem building on the original work by Annila and co-workers. In this work, several shortcomings have been identified. These shortcomings have been corrected here leading to a general approach for the treatment of residual dipolar couplings of unfolded proteins. More specifically, it is shown that, in the case of fully unfolded proteins aligned by a steric mechanism, basic dependencies of dipolar couplings such as on chain length and location with in the chain can be analysed in simple analytical terms. The main predictions of the model are compared to experimental data showing reasonable agreement. The presented mathematical framework is principally suited for various improvements which could include the treatment of long-range interactions and of the actual geometry of the given aligment medium. From the experimental side, bovine alpha-lactalbumin has been chosen as a model system for the development of improved time-resolved 1D NMR methods aiming at the observation of conformational transitions by kinetic means. The presented results show that high-quality data can now be obtained at protein concentrations as low as 100uM. Rate constants characterising distinct conformational transitions of up to 8/s have been measured. These are the fastest rate constants which have been reported so far for protein folding events. The NMR data supplemented by complementary biophysical data furthermore demonstrate that the folding of bovine alpha-lactalbumin is more complex than has been anticipated. All data are consistent with a triangular folding mechanism involving parallel pathways of folding for formation of the native state of the protein. Interestingly, such a folding mechanism has also been found for the highly structurally homologous protein lysoyzme from hen egg white. Evidence is presented that the guiding role of long-range interactions in the unfolded state of lysoyzme for mediating intersubdomain interactions during folding is replaced in the case of bovine alpha-lactalbumin by the Ca2+ binding site.
Since independence from British colonial rule, Uganda has had a turbulent political history characterised by putsches, dictatorship, contested electoral outcomes, civil wars and a military invasion. There were eight changes of government within a period of twenty-four years (from 1962-1986), five of which were violent and unconstitutional. This paper identifies factors that account for these recurrent episodes of political violence and state collapse. While colonialism bequeathed the country a negative legacy including a weak state apparatus, ethnic division, skewed development, elite polarisation and a narrow economic base, post-colonial leaders have on the whole exacerbated rather than reversed these trends. Factors such as ethnic rivalry, political exclusion, militarisation of politics, weak state institutions, and unequal access to opportunities for self-advancement help to account for the recurrent cycles of violence and state failure prior to 1986. External factors have also been important, particularly the country’s politically turbulent neighbourhood, the outcome of political instability and civil conflict in surrounding countries. Neighbourhood turbulence stemming from such factors as civil wars in Congo and Sudan has had spill-over effects in that it has allowed insurgent groups geographical space within which to operate as well as provided opportunities for the acquisition of instruments of war with which to destabilise the country. Critical to these processes have been the porosity of post-colonial borders and the inability by the Ugandan state to exercise effective control over its entire territory. By demonstrating the interplay between internal and external factors in shaping Uganda’s postcolonial experience, the paper makes an important shift away from conventional explanations that have focused disproportionately on internal processes. Lastly, the paper provides pointers to areas of further research such as the economic foundations of conflict that should ultimately strengthen our understanding of factors that combine to make state-making fail or succeed.
The animated statues, robots and monsters in German Romantic narratives, as I will argue throughout, tell us something about the Romantic conception of the mutually embedded relationship between art and life. In the works of the German Romantics, the theme of artificial humans thus has an essentially autopoetic, or selfreflexive, function (cf. Schmitz-Emans 1993, 168f). It corresponds in exemplary fashion with Friedrich Schlegel´s idea of transcendental poetry, which should always be “poetry and simultaneously the poetry of poetry” (Schlegel [1985], 50). In the theme of artificial life as well as in transcendental poetry, the observation of the world is integrally bound up with the observation of art and the self (cf. Kremer [1996], 8ff).
The timing of feedback to early visual cortex in the perception of long-range apparent motion
(2008)
When 2 visual stimuli are presented one after another in different locations, they are often perceived as one, but moving object. Feedback from area human motion complex hMT/V5+ to V1 has been hypothesized to play an important role in this illusory perception of motion. We measured event-related responses to illusory motion stimuli of varying apparent motion (AM) content and retinal location using Electroencephalography. Detectable cortical stimulus processing started around 60-ms poststimulus in area V1. This component was insensitive to AM content and sequential stimulus presentation. Sensitivity to AM content was observed starting around 90 ms post the second stimulus of a sequence and most likely originated in area hMT/V5+. This AM sensitive response was insensitive to retinal stimulus position. The stimulus sequence related response started to be sensitive to retinal stimulus position at a longer latency of 110 ms. We interpret our findings as evidence for feedback from area hMT/V5+ or a related motion processing area to early visual cortices (V1, V2, V3).
This paper is one of the first to analyse political influence on state-owned savings banks in a developed country with an established financial market: Germany. Combining a large dataset with financial and operating figures of all 457 German savings banks from 1994 to 2006 and information on over 1,250 local elections during this period we investigate the change in business behavior around elections. We find strong indications for political inflence: the probability that savings banks close branches, lay-off employees or engage in merger activities is significantly reduced around elections. At the same time they tend to increase their extraordinary spendings, which include support for social and cultural events in the area, on average by over 15%. Finally, we find that savings banks extend significantly more loans to their corporate and private customers in the run-up to an election. In further analyses, we show that the magnitude of political influence depends on bank specific, economical and political circumstances in the city or county: political influence seems to be facilitated by weak political majorities and profitable banks. Banks in economically weak areas seem to be less prone to political influence.
In this paper, we investigate how bank mergers affect bank revenues and present empirical evidence that mergers among banks have a substantial and persistent negative impact on merging banks’ revenues. We refer to merger related negative effects on banks’ revenues as dissynergies and suggest that they are a result of organizational diseconomies, the loss of customers and the temporary distraction of management from day-to-day operations by effecting the merger. For our analyses we draw on a proprietary data set with detailed financials of all 457 regional savings banks in Germany, which have been involved in 212 mergers between 1994 and 2006. We find that the negative impact of a merger on net operating revenues amounts to 3% of pro-forma consolidated banks’ operating profits and persists not only for the year of the merger but for up to four years post-merger. Only thereafter mergers exhibit a significantly superior performance compared to their respective pre-merger performance or the performance of their non-merging peers. The magnitude and persistence of merger related revenue dissynergies highlight their economic relevance. Previous research on post-merger performance mainly focuses on the effects from mergers on banks’ (cost) efficiency and profitability but fails to provide clear and consistent results. We are the first, to our knowledge, to examine the post-merger performance of banks’ net operating revenues and to empirically verify significant negative implications of mergers for banks’ net operating revenues. We propose that our finding of negative merger related effects on banks’ operating revenues is the reason why previous research fails to show merger related gains.
Background The successful use of zirconia ceramics in orthopedic surgery led to a demand for dental zirconium-based implant systems. Because of its excellent biomechanical characteristics, biocompatibility, and bright tooth-like color, zirconia (zirconium dioxide, ZrO2) has the potential to become a substitute for titanium as dental implant material. The present study aimed at investigating the osseointegration of zirconia implants with modified ablative surface at an ultrastructural level. Methods A total of 24 zirconia implants with modified ablative surfaces and 24 titanium implants all of similar shape and surface structure were inserted into the tibia of 12 Gottinger minipigs. Block biopsies were harvested 1 week, 4 weeks or 12 weeks (four animals each) after surgery. Scanning electron microscopy (SEM) analysis was performed at the bone implant interface. Results Remarkable bone attachment was already seen after 1 week which increased further to intimate bone contact after 4 weeks, observed on both zirconia and titanium implant surfaces. After 12 weeks, osseointegration without interposition of an interfacial layer was detected. At the ultrastructural level, there was no obvious difference between the osseointegration of zirconia implants with modified ablative surfaces and titanium implants with a similar surface topography. Conclusion The results of this study indicate similar osseointegration of zirconia and titanium implants at the ultrastructural level.
The "quiet life hypothesis (QLH)" posits that banks enjoy the advantages of market power in terms of foregone revenues or cost savings. We suggest a unified approach to measure competition and efficiency simultaneously to test this hypothesis. We estimate bank-specific Lerner indices as measures of competition and test if cost and profit efficiency are negatively related to market power in the case of German savings banks.We find that both market power and average revenues declined among these banks between 1996 and 2006. While we find clear evidence supporting the QLH, estimated effects of the QLH are small from an economical perspective.
Motivated by the recent discussion of the declining importance of deposits as banks´ major source of funding we investigate which factors determine funding costs at local banks. Using a panel data set of more than 800 German local savings and cooperative banks for the period from 1998 to 2004 we show that funding costs are not only driven by the relative share of comparatively cheap deposits of bank´s liabilities but among other factors especially by the size of the bank. In our empirical analysis we find strong and robust evidence that, ceteris paribus, smaller banks exhibit lower funding costs than larger banks suggesting that small banks are able to attract deposits more cheaply than their larger counterparts. We argue that this is the case because smaller banks interact more personally with customers, operate in customers´ geographic proximity and have longer and stronger relationships than larger banks and, hence, are able to charge higher prices for their services. Our finding of a strong influence of bank size on funding costs is also in an in- ternational context of great interest as mergers among small local banks - the key driver of bank growth - are a recent phenomenon not only in European banking that is expected to continue in the future. At the same time, net interest income remains by far the most important source of revenue for most local banks, accounting for approximately 70% of total operating revenues in the case of German local banks. The influence of size on funding costs is of strong economic relevance: our results suggest that an increase in size by 50%, for example, from EUR 500 million in total assets to EUR 750 million (exemplary for M&A transactions among local banks) increases funding costs, ceteris paribus, by approximately 18 basis points which relates to approx. 7% of banks´ average net interest margin.
We study the relation between cognitive abilities and stockholding using the recent Survey of Health, Ageing and Retirement in Europe (SHARE), which has detailed data on wealth and portfolio composition of individuals aged 50+ in 11 European countries and three indicators of cognitive abilities: mathematical, verbal fluency, and recall skills. We find that the propensity to invest in stocks is strongly associated with cognitive abilities, for both direct stock market participation and indirect participation through mutual funds and retirement accounts. Since the decision to invest in less information-intensive assets (such as bonds) is less strongly related to cognitive abilities, we conclude that the association between cognitive abilities and stockholding is driven by information constraints, rather than by features of preferences or psychological traits.
We investigate whether information sharing among banks has affected credit market performance in the transition countries of Eastern Europe and the former Soviet Union, using a large sample of firm-level data. Our estimates show that information sharing is associated with improved availability and lower cost of credit to firms. This correlation is stronger for opaque firms than transparent ones and stronger in countries with weak legal environments than in those with strong legal environments. In cross-sectional estimates, we control for variation in country-level aggregate variables that may affect credit, by examining the differential impact of information sharing across firm types. In panel estimates, we also control for the presence of unobserved heterogeneity at the firm level, as well as for changes in macroeconomic variables and the legal environment.
The single most important policy-induced innovation in the international financial system since the collapse of the Bretton-Woods regime is the institution of the European Monetary Union. This paper provides an account of how the process of financial integration has promoted financial development in the euro area. It starts by defining financial integration and how to measure it, analyzes the barriers that can prevent it and the effects of their removal on financial markets, and assesses whether the euro area has actually become more integrated. It then explores to which extent these changes in financial markets have influenced the performance of the euro-area economy, that is, its growth and investment, as well as its ability to adjust to shocks and to allow risk-sharing. The paper concludes analyzing further steps that are required to consolidate financial integration and enhance the future stability of financial markets.
Various concurrency primitives have been added to sequential programming languages, in order to turn them concurrent. Prominent examples are concurrent buffers for Haskell, channels in Concurrent ML, joins in JoCaml, and handled futures in Alice ML. Even though one might conjecture that all these primitives provide the same expressiveness, proving this equivalence is an open challenge in the area of program semantics. In this paper, we establish a first instance of this conjecture. We show that concurrent buffers can be encoded in the lambda calculus with futures underlying Alice ML. Our correctness proof results from a systematic method, based on observational semantics with respect to may and must convergence.
Life-threatening fungal infections are becoming increasingly common for immunocompromised patients such as those with AIDS, or those undergoing organ transplantation or chemotheraphy, as well as for other health-vulnerable patients. Excellent targets for antifungal drugs are chitin synthases, which are essential for survival of the fungus and lacking in humans. To design new antifungal drugs, knowledge of the three-dimensional structure and mechanism of action of chitin synthases are crucial. Chitin synthases are members of an important family of enzymes that synthesize structural polysaccharides, such as cellulose, β(1,3)-glucan, β(1,4)-mannan and hyaluronan. Therefore, chitin synthases could be used as a model system to understand these more complex enzymes, which are also of major medical and commercial importance. Chitin synthase 2 from Saccharomyces cerevisiae (ScChS2), the protein under study, is an integral membrane protein that synthesizes the primary septum between mother and daughter cells in budding yeast. It is essential for proper cell separation and expected to be highly regulated. An important aspect is that ScChS2 shows 55% sequence identity and is functionally analogous to chitin synthase 1 from the human opportunistic pathogen Candida albicans, this enzyme is also essential for cell survival (Munro, Winter et al. 2001). ...
What is the energy function guiding behavior and learningµ Representationbased approaches like maximum entropy, generative models, sparse coding, or slowness principles can account for unsupervised learning of biologically observed structure in sensory systems from raw sensory data. However, they do not relate to behavior. Behavior-based approaches like reinforcement learning explain animal behavior in well-described situations. However, they rely on high-level representations which they cannot extract from raw sensory data. Combinations of multiple goal functions seems the methodology of choice to understand the complexity of the brain. But what is the set of possible goals. ...
A small-world network has been suggested to be an efficient solution for achieving both modular and global processing-a property highly desirable for brain computations. Here, we investigated functional networks of cortical neurons using correlation analysis to identify functional connectivity. To reconstruct the interaction network, we applied the Ising model based on the principle of maximum entropy. This allowed us to assess the interactions by measuring pairwise correlations and to assess the strength of coupling from the degree of synchrony. Visual responses were recorded in visual cortex of anesthetized cats, simultaneously from up to 24 neurons. First, pairwise correlations captured most of the patterns in the population´s activity and, therefore, provided a reliable basis for the reconstruction of the interaction networks. Second, and most importantly, the resulting networks had small-world properties; the average path lengths were as short as in simulated random networks, but the clustering coefficients were larger. Neurons differed considerably with respect to the number and strength of interactions, suggesting the existence of "hubs" in the network. Notably, there was no evidence for scale-free properties. These results suggest that cortical networks are optimized for the coexistence of local and global computations: feature detection and feature integration or binding.
Background One of the central issues in ecology is the question what allows sympatric occurrence of closely related species in the same general area? The non-biting midges Chironomus riparius and C. piger, interbreeding in the laboratory, have been shown to coexist frequently despite of their close relatedness, similar ecology and high morphological similarity. Methodology/Principal Findings In order to investigate factors shaping niche partitioning of these cryptic sister species, we explored the actual degree of reproductive isolation in the field. Congruent results from nuclear microsatellite and mitochondrial haplotype analyses indicated complete absence of interspecific gene-flow. Autocorrelation analysis showed a non-random spatial distribution of the two species. Though not dispersal limited at the scale of the study area, the sister species occurred less often than expected at the same site, indicating past or present competition. Correlation and multiple regression analyses suggested the repartition of the available habitat along water chemistry gradients (nitrite, conductivity, CaCO3), ultimately governed by differences in summer precipitation regime. Conclusions We show that these morphologically cryptic sister species partition their niches due to a certain degree of ecological distinctness and total reproductive isolation in the field. The coexistence of these species provides a suitable model system for the investigation of factors shaping the distribution of closely related, cryptic species.
Introduction : extent, processes and evolutionary impact of interspecific hybridization in animals
(2008)
Since the time of Charles Darwin, studies of interspecific hybridization have been a major focus for evolutionary biologists. Although this phenomenon has often been viewed as problematic in the fields of ecology, taxonomy and systematics, it has become a primary source of data for studies on speciation and adaptation. Effects from genetic/evolutionary processes, such as recombination and natural selection, usually develop over extended periods of time; however, they are accelerated in cases of hybridization. Interspecific hybrids exhibit novel genomes that are exposed to natural selection, thus providing a key to unravel the ultimate causes of adaptation and speciation. Here we provide firstly a historic perspective of hybridization research, secondly a novel attempt to assess the extent of hybridization among animals and thirdly an overview of the reviews and case studies presented in this theme issue.
Using (13)C spin relaxation NMR in combination with molecular dynamic (MD) simulations, we characterized internal motions within double-stranded DNA on the pico- to nano-second time scale. We found that the C-H vectors in all cytosine ribose moieties within the Dickerson-Drew dodecamer (5´-CGCGAATTCGCG-3´) are subject to high amplitude motions, while the other nucleotides are essentially rigid. MD simulations showed that repuckering is a likely motional model for the cytosine ribose moiety. Repuckering occurs with a time constant of around 100 ps. Knowledge of DNA dynamics will contribute to our understanding of the recognition specificity of DNA-binding proteins such as cytosine methyltransferase.
Targeting signals direct proteins to their extra- or intracellular destination such as the plasma membrane or cellular organelles. Here we investigated the structure and function of exceptionally long signal peptides encompassing at least 40 amino acid residues. We discovered a two-domain organization ("NtraC model") in many long signals from vertebrate precursor proteins. Accordingly, long signal peptides may contain an N-terminal domain (N-domain) and a C-terminal domain (C-domain) with different signal or targeting capabilities, separable by a presumably turn-rich transition area (tra). Individual domain functions were probed by cellular targeting experiments with fusion proteins containing parts of the long signal peptide of human membrane protein shrew-1 and secreted alkaline phosphatase as a reporter protein. As predicted, the N-domain of the fusion protein alone was shown to act as a mitochondrial targeting signal, whereas the C-domain alone functions as an export signal. Selective disruption of the transition area in the signal peptide impairs the export efficiency of the reporter protein. Altogether, the results of cellular targeting studies provide a proof-of-principle for our NtraC model and highlight the particular functional importance of the predicted transition area, which critically affects the rate of protein export. In conclusion, the NtraC approach enables the systematic detection and prediction of cryptic targeting signals present in one coherent sequence, and provides a structurally motivated basis for decoding the functional complexity of long protein targeting signals.
Exported proteases of Helicobacter pylori (H. pylori) are potentially involved in pathogen-associated disorders leading to gastric inflammation and neoplasia. By comprehensive sequence screening of the H. pylori proteome for predicted secreted proteases, we retrieved several candidate genes. We detected caseinolytic activities of several such proteases, which are released independently from the H. pylori type IV secretion system encoded by the cag pathogenicity island (cagPAI). Among these, we found the predicted serine protease HtrA (Hp1019), which was previously identified in the bacterial secretome of H. pylori. Importantly, we further found that the H. pylori genes hp1018 and hp1019 represent a single gene likely coding for an exported protein. Here, we directly verified proteolytic activity of HtrA in vitro and identified the HtrA protease in zymograms by mass spectrometry. Overexpressed and purified HtrA exhibited pronounced proteolytic activity, which is inactivated after mutation of Ser205 to alanine in the predicted active center of HtrA. These data demonstrate that H. pylori secretes HtrA as an active protease, which might represent a novel candidate target for therapeutic intervention strategies.
A mild synthetic method for N-formyl-Met-Leu-Phe-OH (1) is described. After Fmoc solid phase peptide synthesis, on-bead formylation and HPLC purification, more than 30 mg of the fully 13C/15N-labelled tripeptide 1 could be isolated in a typical batch. This peptide can be easily crystallised and is therefore well suited as a standard sample for setting up solid-state NMR experiments.
Infliximab is a monoclonal antibody directed against TNF-alpha. It has been approved for use in rheumatoid arthritis, ankylosing spondylitis, inflammatory bowel disease, psoriatic arthritis and plaque-type psoriasis. In case reports, positive effects on pustular variants of psoriasis have also been reported. However, paradoxically, manifestation of pustular psoriasis and plaque-type psoriasis has been reported in patients treated with TNF antagonists including infliximab for other indications. Here, we report on 5 patients with chronic plaque-type psoriasis who developed palmoplantar pustulosis during or after discontinuation of infliximab therapy. In two of the five cases, manifestation of palmoplantar pustulosis was not accompanied by worsening of plaque-type psoriasis. Possibly, site-specific factors or a differential contribution of immunological processes modulated by TNF inhibitors to palmoplantar pustulosis and plaque-type psoriasis may have played a role.
Background: Adrenal chromaffin cells and sympathetic neurons both originate from the neural crest, yet signals that trigger chromaffin development remain elusive. Bone morphogenetic proteins (BMPs) emanating from the dorsal aorta are important signals for the induction of a sympathoadrenal catecholaminergic cell fate. Results: We report here that BMP-4 is also expressed by adrenal cortical cells throughout chick embryonic development, suggesting a putative role in chromaffin cell development. Moreover, bone morphogenetic protein receptor IA is expressed by both cortical and chromaffin cells. Inhibiting BMP-4 with noggin prevents the increase in the number of tyrosine hydroxylase positive cells in adrenal explants without affecting cell proliferation. Hence, adrenal BMP-4 is likely to induce tyrosine hydroxylase in sympathoadrenal progenitors. To investigate whether persistent BMP-4 exposure is able to induce chromaffin traits in sympathetic ganglia, we locally grafted BMP-4 overexpressing cells next to sympathetic ganglia. Embryonic day 8 chick sympathetic ganglia, in addition to principal neurons, contain about 25% chromaffin-like cells. Ectopic BMP-4 did not increase this proportion, yet numbers and sizes of "chromaffin" granules were significantly increased. Conclusions: BMP-4 may serve to promote specific chromaffin traits, but is not sufficient to convert sympathetic neurons into a chromaffin phenotype.
Self-inactivating gammaretroviral vectors for the gene therapy of chronic granulomatous disease
(2008)
Chronic granulomatous disease (CGD) is a rare inherited primary immunodeficiency characterized by defective intracellular oxidative killing of ingested invading microbes by PMN and monocytes. It is caused by mutations in one of the four genes coding for the essential subunits of the NADPH oxidase (gp91phox, p47phox, p67phox and p22phox). Approximately 75% of the CGD cases are due to mutations in the gp91phox gene. If regular care and conventional therapy fail, the recommended therapy is allogeneic bone marrow transplantation (BMT), but only if a matched donor is available. A therapeutic option for patients lacking suitable donors is the genetic modification of autologous hematopoietic stem cells. The gene therapy offers an interesting alternative to BMT since it implies a less invasive treatment and represents a possibly unique curative option for patients with no suitable donor. Gammaretroviral vectors were already used in some gene therapy trials for CGD and other immunodeficiencies showing relevant clinical benefit. However, these trials uncovered an unexpected mutagenic side effect. If the retrovial integration ocurrs near to, or into proto-oncogenes this might lead to clonal dominance or even malignant transformation (Hacein-Bey-Abina et al., 2003a; Ott et al., 2006). Therefore, there was a need to further improve the safety of these vectors and to this end the self-inactivating gammaretroviral vectors were engineered. Non essential sequences for virus infectivity and integration, which might influence the surrounding gene expression, were deleted in these vectors. In the first set of experiments, a series of SIN gamma retroviral vectors was cloned driving the expression of the wild-type gp91phox cDNA under the control of a viral constitutive SFFV promoter. However initial studies with these vectors failed because the titers of the virus produced by transient transfection protocols were extremely low (<5x105 TU/ml). Therefore, a codon optimization of the gp91phox cDNA was considered as an alternative. The codon optimized synthetic gp91phox gene was used to construct a SIN gammaretroviral vector, again under the control of the SFFV promoter (Schambach et al., 2006c). With this vector an increase in titer was observed compared to the native gp91phox sequence, which was due to the improved transcription in 293T transfected cells. The enhancement of the synthetic gp91phox transcription led to a higher internal transcript production and protein expression. An enhanced superoxide production in transduced myelomonocytic X-CGD PLB-985 populations was also detected. All these data indicate that the synthetic gp91phox might represent an excellent alternative to those former constructs expressing the native gp91phox transgene. Since it was postulated that the SFFV promoter could still cause transactivation of neighboring genes due to its strength (Modlich et al., 2006), three different non-viral promoters were tested, one constitutive (the EFs promoter) and two myeloid-specific promoters (the c-fes and MRP8 promoter). The three SIN gammaretroviral vectors were able to generate high titers after transient transfection of 293T packaging cells, to efficiently transduce the X-CGD PLB-985 cell line and to reconstitute the NADPH oxidase activity to a high degree. In mouse transplantation experiments, the EFs promoter showed a high variable transgene expression in the different lineages analyzed, and the c-fes promoter showed also a ubiquitinous expression. In contrast, the MRP8 promoter showed a high myeloid specificity since gp91phox expression in mSca-1+ cells and lymphoid B cells from transplanted mice was extremly low and even absent. However, the lowest levels of transgene expression were observed in the myeloid populations both in bone marrow and peripheral blood with this vector. When the oxidase reconstitution ability of these promoters was tested, the numbers of superoxide producing cells obtained were similar than those observed in the clinical X-CGD trial conducted by the groups of Dr. M. Grez and Prof. R. A. Seger (over 35% in one patient and ~15% in the second), which led to the eradication of therapy refractory infections (Ott et al., 2006). Between the three constructs, the MRP8 promoter was less effective in restoring the NADPH oxidase activity than the EFs and c-fes promoters. The c-fes promoter reached the highest levels of DHR reactive cells in the highest number of mice. Overall, these data showed that between all constructs tested, the c-fes containing construct in combination with the codon optimized gp91phox sequence showed the best performance within the SIN gammaretroviral backbone. It generated the highest titers in combination with a better NADPH oxidase reconstituting ability. One main goal in the development of SIN gammaretroviral vectors is reducing the genotoxic effect due to random vector integration. An improved gene transfer and expression, and a constant performance are also highly desirable. The present study shows that the c-fes SIN vector in combination with the synthetic gp91phox may be considered as an effective gene therapy strategy for the restoration of the NADPH oxidase activity in CGD. It allows the use of a cellular promoter generating adequate physiological levels of the therapeutic protein and reduces the number of vector copies required for a therapeutic effect.
Conclusion Scale Integration Based on the results of spike-field coherence, the underlying process of shortterm memory seems to involve networks of different sizes within and, most probably, beyond prefrontal cortex. Spikes, which were generated by single neurons, cooperate with local field potentials, which were the slower fluctuations of the environment. Although differences among behavioral conditions appear to be based on rather few instances of phase-locked spikes, the task-related effects on spike-field coherence are highly reliable and cannot be explained by chance, as the comparison of results from experimental and simulated data shows. The differential locking of prefrontal neuron populations with two different frequency bands in their input signals suggests that neuronal activity underlying short-term memory in prefrontal cortex transiently engages cortical circuits on different spatial scales, probably in order to coordinate distributed processes. NeuroXidence method and Synchronizedfiring Based on the results of the calibration datasets, for bi- and multi-variate cases, the extension of NeuroXidence remains its sensitivity and reliability of detecting coordinate firing events for different processes. Based on this extension of NeuroXidence, we demonstrated that in monkey’s prefrontal cortex during short-term memory task, encoding and maintenance of the information rely on the formation of neuronal assemblies characterized by precise and reliable synchronization of spiking activity on a millisecond time scale, which is consistent with the results from spike-spike coherence. The task and performance dependent modulation of synchrony reflects the dynamic formation of group of neurons has large effect on short-term-memory.
Development of chromium(VI)-free defect etching solutions for application on silicon substrates
(2008)
Spectroscopic responses of the potentiometric probe 2-(4-(dimethylamino)styryl)-1-methylpyridinium iodide (DASPMI) were investigated in living cells by means of a time- and space-correlated single photon counting technique. Spatially resolved fluorescence decays from single mitochondria or only a very few organelles of XTH2 cells exhibited three-exponential decay kinetics. Based on DASPMI photophysics in a variety of solvents, these lifetimes were attributed to the fluorescence from the locally excited state, intramolecular charge transfer state, and twisted intramolecular charge transfer state. A considerable variation in lifetimes among mitochondria of different morphologies and within single cells was evident, corresponding to high physiological variations within single cells. Considerable shortening of the short lifetime component ({tau}1) under a high-membrane-potential condition, such as in the presence of ATP and/or substrate, was similar to quenching and a dramatic decrease of lifetime in polar solvents. Under these conditions {tau}2 and {tau}3 increased with decreasing contribution. Inhibiting respiration by cyanide resulted in a notable increase in the mean lifetime and a decrease in mitochondrial fluorescence. Increased DASPMI fluorescence under conditions that elevate the mitochondrial membrane potential has been attributed to uptake according to Nernst distributions, delocalization of {pi}-electrons, quenching processes of the methyl pyridinium moiety, and restricted torsional dynamics at the mitochondrial inner membrane. Accordingly, determination of anisotropy in DASPMI-stained mitochondria in living cells revealed a dependence of anisotropy on the membrane potential. The direct influence of the local electric field on the transition dipole moment of the probe and its torsional dynamics monitor changes in mitochondrial energy status within living cells.
A series of production and perception experiments investigating the prosody and well-formedness of special sentences, called Wide Focus Partial Fronting (WFPF), which consist of only one prosodic phrase and a unique initial accented argument, are reported on here. The results help us to decide between different models of German prosody. The absence of pitch height difference on the accent of the sentence speaks in favor of a relative model of prosody, in which accents are scaled relative to each other, and against models in which pitch accents are scaled in an absolute way. The results also speak for a model in which syntax, but not information structure, influences the prosodic phrasing. Finally, perception experiments show that the prosodic structure of sentences with a marked word order needs to be presented for grammaticality judgments. Presentation of written material only is not enough, and falsifies the results.
Focus asymmetries in Bura
(2008)
This article presents the central aspects of the focus system of Bura (Chadic), which exhibits a number of asymmetries: Grammatical focus marking is obligatory only with focused subjects, where focus is marked by the particle án following the subject. Focused subjects remain in situ and the complement of án is a regular VP. With nonsubject foci, án appears in a cleft-structure between the fronted focus constituent and a relative clause. We present a semantically unified analysis of focus marking in Bura that treats the particle as a focusmarking copula in T that takes a property-denoting expression (the background) and an individual-denoting expression (the focus) as arguments. The article also investigates the realization of predicate and polarity focus, which are almost never marked. The upshot of the discussion is that Bura shares many characteristic traits of focus marking with other Chadic languages, but it crucially differs in exhibiting a structural difference in the marking of focus on subjects and non-subject constituents.
The term cephalic sensory organ (CSO) is used for specialised structures in the head region of adult Opisthobranchia. These sensory organs show a high diversity in form and function, and the gross morphology of these organs differs considerably among taxa. They can be identified as cephalic shields, oral veils, Hancocks organs, lip organs, rhinophores or oral tentacles. Because of this extremely high diversity, the homology and the evolution of these organs have not been clarified yet. My intention was to use neuroanatomical data sets in order to find putative homologous CSOs. In this study, I will show data about immunohistochemical neurotransmitter content and cellular innervation patterns and their applicability as morphological characters for the homologisation of structures. I support earlier investigations that neurotransmitter content is often related to function. In contrast, axonal tracing patterns can be used to homologise nerves. Overall the aim of this study was to reconstruct the evolution of the CSOs of the Opisthobranchia, by projecting our neuroanatomical data sets onto a molecular phylogeny.
Determination of the distribution of halocarbons in the tropical upper troposphere and stratosphere
(2008)
The aim of this thesis was to investigate distributions of 32 volatile chlorinated and/or brominated halocarbons that are currently believed to be present in the tropical upper troposphere and stratosphere and to contribute to stratospheric ozone depletion and also to global warming. For this purpose an analytical system was established, which is capable to measure ultra-low concentrated atmospheric trace gases. A quadrupole Mass Spectrometric (MS) Detector was attached to an existing Gas Chromatograph with pre-concentration system and Electron Capture Detector (ECD). The characterisation of the chromatographic system was significantly enhanced by the subsequent identification of 48 additional volatile organic compounds. Furthermore a Gaussian fit algorithm, which was developed in the workgroup, was applied to the chromatographic signals. This algorithm was proven to reflect peaks quantitatively and to enhance the performance of the integration process – especially the reproducibilities for peaks with a low signal to noise ratio. As it is known that the Electron Capture Detector responds nonlinear the new MS detector was checked for such behaviour and found to respond linear. In logical consistency the complete quantification process including e.g. pre-concentration of trace gases and signal integration can be considered as linear responding within the investigated parameter ranges. Moreover, the long term stability of the targeted halocarbons was proven inside the calibration standard containers over a period of 25 months. Many substances were also found to be stable inside the containers used for storage of air samples but a number of substances showed significant concentration changes. These were mainly CH3Cl (methyl chloride), CH3Br (methyl bromide), CH2Cl2 (dichloromethane), CHCl3 (chloroform), CCl4 (tetrachloromethane), C2Cl4 (tetrachloroethene), CH3CCl3 (methyl chloroform), CH2ClCH2Cl (1,2-dichloroethane) und C2H5Cl (chloroethane). But the number of affected substances and also the corresponding concentration changes varied between the individual containers. A systematic investigation of the influence of possible causes (e.g. air sampling methods, container materials) is recommended. Results from both internal detectors were compared and revealed biases and disadvantages of the ECD caused by its lower selectivity and its nonlinear response behaviour. Consequently the MS detector was chosen for the quantification of atmospheric trace gases. The quantification process was performed relative to externally calibrated air standards. To assess the uncertainties connected with different absolute calibration scales cross-comparisons between calibration standards of three different laboratories were carried out. Most substances’ calibrations agreed within the measurement uncertainties but significant differences were observed for CF2ClBr (H1211), CH3Cl (methyl chloride), CH2Cl2 (dichloromethane), CHCl3 (chloroform), CCl4 (tetrachloromethane) and CH3CCl3 (methyl chloroform). As five of these substances were also observed to show concentration changes inside sample containers it is likely, that such changes are responsible for calibration differences. In addition to the detailed assessment of uncertainties connected with the analytical quantification process a set of air samples was available for measurements. These samples mainly originated from the upper troposphere and lower and middle stratosphere in the tropics and the determined halocarbon quantities were used to investigate their distributions in the respective atmospheric regions. In detail, the altitudinal distributions and interrelations of 17 long-lived halocarbons in the tropical stratosphere were determined and compared with those of other stratospheric regions. Tracer-tracer-correlations of these substances in the tropical stratosphere were found to differ from those in mid- and high-latitudes. Characteristic fit functions relative to CF2Cl2 (F12) which are valid for the tropical stratosphere in 2005 were derived as well as time-independent fit functions of fractional release factors (FRFs) relative to the mean age of air. Both sets of correlations could be used for the parameterisation and evaluation of models and also to reassess the Global Warming Potentials (GWPs) of the corresponding halocarbons which might affect future climate predictions. However, the data set on halocarbons in the tropical stratosphere is still insufficient to investigate the variability of tracer-tracer-correlations and FRFs caused by dynamical and photochemical processes. Therefore it is important for future research to perform additional measurements there and – if possible – to extend the measurements to the upper tropical stratosphere in order to characterise the sink of those halocarbons that are still present in these altitudes. In addition, the amount of chlorine and bromine present in the form of organic compounds inside and above the main stratospheric entrance region (the Tropical Tropopause Layer, TTL) was quantified in the frame of a case study. This was possible because of a cooperation with scientists from the University of East Anglia which carried out measurements of six additional halocarbons leading to a total of 28 quantified target substances. Ten of these substances have short atmospheric lifetimes compared with the mean transport times of tropospheric air to the stratosphere (i.e. lifetimes below 0.5 years) and show non-uniform distributions in the upper troposphere. The contribution of these substances to stratospheric ozone depletion is subject of an ongoing scientific debate. In the performed case study a fraction range of short-lived halocarbons of 6 – 8 % (0.98 – 1.25 ppt) relative to the sum of bromine from organic substances and of 1.1 – 1.4 % (36.6 – 47.1 ppt) for the corresponding sum of chlorine was calculated to enter the stratosphere above Brazil in June 2005. Moreover by combining the data with tropospheric reference data and age of air observations the abundances of inorganic chlorine and bromine (Cly and Bry) were derived. At an altitude of 34 km an amount of 3062 ppt of Cly and 17.5 ppt of Bry from organic source gases was calculated. The latter is significantly lower than Bry mixing ratios inferred from quasisimultaneous BrO measurements at 33 km altitude above Brazil (Dorf, 2005, Dorf et al., 2008). But at the University of East Anglia indications for the presence of unknown brominated organic substances in the TTL were found which might cause this difference. Finally, a major result of this thesis adds to the knowledge of the composition of the troposphere as three Chlorofluorocarbons (CFCs) were first observed. Trifluorochloroethene, 3-chloropentafluoropropene and 4,4-dichlorohexafluoro-1-butene were found in air samples collected at the Taunus Observatory near Frankfurt (Main) and the Jungfraujoch High Altitude Research Station in Switzerland (Laube and Engel, 2008). Identification was possible because of an air plume containing high concentrations of these substances. It is suggested that the abundances found on this occasion originated from a local source. The atmospheric lifetimes of these substances are expected to be rather short as they contain a double bond. A quantitative calibration could only be derived for trifluorochloroethene but not for the other species by now. Thus, a relative sensitivity method was derived to get a first indication of the observed atmospheric abundances. All three CFCs could also be detected in air masses representative of background conditions, though with much lower concentrations. These species and some of their degradation products are toxic and could also be relevant for stratospheric and tropospheric ozone depletion. It is important to find out more about their atmospheric distributions, lifetimes, sinks and sources and their ability to reach the stratosphere to assess their possible influence on the global atmosphere. This will be done in the frame of the project "CLEARFOGG – Checking Layers of the Earths AtmospheRe For halogenated Ozone-depleting and Greenhouse Gases". This research project aims to perform a systematic scan of the atmosphere because there are indications for the presence of a number of halogenated organic compounds which are unknown by now. It was recently decided to be funded by the British National Environmental Research Council and will be carried out at the University of East Anglia mainly by the author of this thesis.
Freeze (1992) argued on the basis of data from several different languages that there is a close relationship between existential sentences (stating the existence of an entity) and locative sentences (stating the location of an entity). Freeze (1992) proposes that they are both derived from the same base structure and that the surface differences are rather due to the distinct information structures.This paper argues against this position with the data from Serbian existentials, which show clear syntactic differences from the locatives. Thus, the close relationship between existential and locative sentences that Freeze (1992) observes is conceptual, but not (necessarily) part of the syntax of the language. In order to account for the data, we propose that existential sentences originate from a different syntactic predication structure than the locative ones. The existential meaning arises, as we will show, from the interaction of this predication structure with the structure and meaning of the noun phrase.
The ACL 2008 Workshop on Parsing German features a shared task on parsing German. The goal of the shared task was to find reasons for the radically different behavior of parsers on the different treebanks and between constituent and dependency representations. In this paper, we describe the task and the data sets. In addition, we provide an overview of the test results and a first analysis.