Refine
Year of publication
Document Type
- Article (31128)
- Part of Periodical (11550)
- Book (8266)
- Doctoral Thesis (5713)
- Part of a Book (3967)
- Working Paper (3385)
- Review (2939)
- Contribution to a Periodical (2368)
- Preprint (2084)
- Report (1560)
Language
- German (42718)
- English (29217)
- French (1060)
- Portuguese (840)
- Spanish (309)
- Croatian (302)
- Multiple languages (258)
- Italian (198)
- mis (174)
- Turkish (168)
Has Fulltext
- yes (75568) (remove)
Keywords
- Deutsch (1076)
- Literatur (868)
- taxonomy (760)
- Deutschland (553)
- Rezension (511)
- new species (449)
- Rezeption (354)
- Frankfurt <Main> / Universität (341)
- Übersetzung (326)
- Geschichte (300)
Institute
- Medizin (7691)
- Präsidium (5170)
- Physik (4464)
- Extern (2738)
- Wirtschaftswissenschaften (2686)
- Gesellschaftswissenschaften (2369)
- Biowissenschaften (2184)
- Biochemie und Chemie (1975)
- Frankfurt Institute for Advanced Studies (FIAS) (1686)
- Center for Financial Studies (CFS) (1628)
Religion sei "das Opium des Volks", das einem herz- und geistlosen "Jammertal" einen Heiligenschein verleihe. Der werde verschwinden, wenn "die Kritik des Jammertals" zur "Wahrheit des Diesseits" geführt habe, so Karl Marx 1844. Und heute: Die Religion existiert weiter, eine "wahre" Gesellschaft ist nicht verwirklicht. Im Gespräch mit vier Frankfurter Professoren erkundet der Philosoph und Publizist Rolf Wiggershaus, wie Religionsexperten das aktuelle Verhältnis von Religion und Gesellschaft sehen.
"Toleranz kommt vor Glückseligkeit" : eine Zeitreise mit der Tugend des gegenseitigen Respekts
(2016)
Toleranz ist gerade da nötig, wo sie besonders schwerfällt. Das war schon vor gut 300 Jahren so, als Denker wie der französische Philosoph Pierre Bayle in Zeiten religiöser Auseinandersetzungen den Grundstein für ein fortschrittliches Toleranz-Verständnis legten. Warum der Begriff gerade heute wieder Konjunktur hat und wie umstritten er noch immer ist, erläutert der politische Philosoph Rainer Forst im Gespräch mit Bernd Frye.
Phenology is the study of periodic life cycle events of living organisms and how these are influenced by environmental factors. Late phenological phases such as the timing of seed release and subsequent seed dispersal considerably affect ecology and evolution in plants. Since plants are mostly sessile organisms, seed dispersal is a crucial life cycle event for the ecology and evolution of plants. In fact, long-distance seed dispersal (LDD) is a very complex process in plant biology and significantly shapes the spatial and temporal dynamics of plant populations. For example, wind dispersal in plants is influenced by a variety of factors such as plant traits, habitat type and environmental conditions (e.g. wind speed). Considering the variability of wind conditions throughout the year, the timing of seed release and dispersal is known to have considerable effects on LDD. Even though late phenologies such as ripening duration and timing of seed release and subsequent dispersal are vital in estimating ecologically highly relevant LDD, these phenologies are not appropriately addressed in ecological research. The aim of this thesis is to gain insights into the factors that shape late plant phenologies. In particular, we address the following questions: which ecologically or evolutionary parameters drive the ripening process of plant species? How does the seasonal variability of wind affect the seed release phenology of plant species? How do these factors interact for plant species in different habitat types?
In order to address these questions, we applied different methodological approaches, ranging from fieldwork and monitoring phenology to computational simulation studies and statistical modeling. To study the ripening process of species, we monitored the flowering, ripening and seed release phenology of more than 100 Central European plant species. We conducted computational simulation studies for estimating LDD by wind to study the phenology of seed release and the parameters determining LDD by wind. In conjunction with phenological data from literature, we used the obtained simulation results to investigate evidence for the existence of phenological adaptations towards LDD in 165 plant species. Further, we used the results from simulation studies of LDD by wind to disentangle the effects of species, habitat types and meteorological conditions and their interactions on the spatial spread of plant species.
The results of the relationship between plant traits, phylogeny, the ripening process and climatic factors provide insights into the basic understanding of the ripening process of plants. We identified ecological factors that shape species’ ripening phenology and seed release timing. In particular, we suggest that the species’ seed weight, life form and phylogeny shapes ripening and seed release phenology. With the statistical models on species’ temperature demands for reproduction, we introduce data that that are well suitable for parametrization and further development of plant dispersal models. The results from the simulation study based on a seasonal perspective showed that heavier seeded tree species with medium wind dispersal potential (including genera Abies, Acer, Fraxinus and Larix) have a clear synchronisation of seed abscission with periods favouring LDD. These species, which are both ecologically and economically important, showed significant synchronisation of the highest rate of seed release with high wind-speed that promoted LDD by wind in wintertime. For the tree species mentioned, we suggest strong seasonal synchronisation as evidence for phenological adaptations in order to match favourable conditions during seed release. With a closer look at the wind conditions that promote LDD by wind, our results showed considerable differences in how specific wind conditions affect LDD in different species and habitat types. We suggest that LDD by wind in species from open habitats with high wind dispersal potential is likely to be driven by thermal updrafts that are mainly driven by the sun providing energy to the ground. By contrast, LDD of heavier-seeded species from open and forested habitats is more likely to be driven by storms that produce shear-driven turbulence. The results from this thesis contribute to an increased understanding of the complete dispersal process of plants and to making more realistic projections of (future) plant distribution.
The results obtained on factors driving ripening and release phenology provide valuable insights into their ecological and phylogenetic factor constraints. The implementation of more realistic assumptions in assessing species’ dispersal potential throughout the year could help considerably in improving landscape management (e.g. timing of mowing) and in the conservation of plant populations. The evidence found for phenological adaptations towards LDD in plants is an important step in understanding the evolutionary basis of LDD in these species.
Telecommunications companies traditionally offer several tariffs from which their customers can choose the tariff that best suits their preferences. Yet, customers sometimes make choices that are not optimal for them because they do not minimize their bill for a certain usage amount. We show in this paper that companies should be very concerned about choices in which customers pick tariffs that are too small for them because they lead to a significant increase in customers churn. In contrast, this is not the case if customers choose tariffs that are too big for them. The reason is that in particular flat-rates provide customers with the additional benefit that they guarantee a constant bill amount that consumption can be enjoyed more freely because all costs are already accounted for.
Correlated activity of cortical neurons survives extensive removal of feedforward sensory input
(2016)
A fundamental property of brain function is that the spiking activity of cortical neurons is variable and that some of this variability is correlated between neurons. Correlated activity not due to the stimulus arises from shared input but the neuronal circuit mechanisms that result in these noise correlations are not fully understood. Here we tested in the visual system if correlated variability in mid-level area V4 of visual cortex is altered following extensive lesions of primary visual cortex (V1). To this end we recorded longitudinally the neuronal correlations in area V4 of two behaving macaque monkeys before and after a V1 lesion while the monkeys fixated a grey screen. We found that the correlations of neuronal activity survived the lesions in both monkeys. In one monkey, the correlation of multi-unit spiking signals was strongly increased in the first week post-lesion, while in the second monkey, correlated activity was slightly increased, but not greater than some week-by-week fluctuations observed. The typical drop-off of inter-neuronal correlations with cortical distance was preserved after the lesion. Therefore, as V4 noise correlations remain without feedforward input from V1, these results suggest instead that local and/or feedback input seem to be necessary for correlated activity.
Infections are an important cause for morbidity and mortality in pediatric acute myeloid leukemia (AML). We therefore characterized infectious complications in children treated according to the trial AML-BFM 2004. Patients with Down syndrome were excluded from the analysis. Data were gathered from the medical records in the hospital where the patients were treated. A total of 405 patients (203 girls; median age 8.4 years) experienced 1326 infections. Fever without identifiable source occurred in 56.1% of the patients and clinically and microbiologically documented infections in 17.5% and 32.4% of the patients, respectively. In all, 240 Gram-positive (112 viridans group streptococci) and 90 Gram-negative isolates were recovered from the bloodstream. Invasive fungal infection was diagnosed in 3% of the patients. Three children each died of Gram-negative bacteremia and invasive aspergillosis, respectively. As compared with the results of AML-BFM 93 with lower dose intensity, infection-related morbidity was slightly higher in AML-BFM 2004 (3.3. versus 2.8 infections per patient), whereas infection-related mortality significantly decreased (1.5% versus 5.4%; P=0.003). Specific anti-infective recommendations included in the treatment protocol, regular training courses for pediatric hematologists and increasing experience may be the reason for reduced infection-related mortality in children with AML. Further studies are needed to decrease infection-related morbidity.
A complex aberrant karyotype consisting of multiple unrelated cytogenetic abnormalities is associated with poor prognosis in patients with acute myeloid leukemia (AML). The European Leukemia Net classification and the UK Medical Research Council recommendation provide prognostic categories that differ in the definition of unbalanced aberrations as well as the number of single aberrations. The aim of this study on 3526 AML patients was to redefine and validate a cutoff for karyotype complexity in AML with regard to adverse prognosis. Our study demonstrated that (1) patients with a pure hyperdiploid karyotype have an adverse risk irrespective of the number of chromosomal gains, (2) patients with translocation t(9;11)(p21~22;q23) have an intermediate risk independent of the number of additional aberrations, (3) patients with greater than or equal to4 abnormalities have an adverse risk per se and (4) patients with three aberrations in the absence of abnormalities of strong influence (hyperdiploid karyotype, t(9;11)(p21~22;q23), CBF-AML, unique adverse-risk aberrations) have borderline intermediate/adverse risk with a reduced overall survival compared with patients with a normal karyotype.
DNA methylation is a major regulatory process of gene transcription, and aberrant DNA methylation is associated with various diseases including cancer. Many compounds have been reported to modify DNA methylation states. Despite increasing interest in the clinical application of drugs with epigenetic effects, and the use of diagnostic markers for genome-wide hypomethylation in cancer, large-scale screening systems to measure the effects of drugs on DNA methylation are limited. In this study, we improved the previously established fluorescence polarization-based global DNA methylation assay so that it is more suitable for application to human genomic DNA. Our methyl-sensitive fluorescence polarization (MSFP) assay was highly repeatable (inter-assay coefficient of variation = 1.5%) and accurate (r2 = 0.99). According to signal linearity, only 50–80 ng human genomic DNA per reaction was necessary for the 384-well format. MSFP is a simple, rapid approach as all biochemical reactions and final detection can be performed in one well in a 384-well plate without purification steps in less than 3.5 hours. Furthermore, we demonstrated a significant correlation between MSFP and the LINE-1 pyrosequencing assay, a widely used global DNA methylation assay. MSFP can be applied for the pre-screening of compounds that influence global DNA methylation states and also for the diagnosis of certain types of cancer.
The mitochondrial cascade hypothesis of dementia assumes mitochondrial dysfunction leading to reduced energy supply, impaired neuroplasticity, and finally cell death as one major pathomechanism underlying the continuum from brain aging over mild cognitive impairment to initial and advanced late onset Alzheimer's disease. Accordingly, improving mitochondrial function has become an important strategy to treat the early stages of this continuum. The metabolic enhancer piracetam has been proposed as possible prototype for those compounds by increasing impaired mitochondrial function and related aspects like mechanisms of neuroplasticity. We here report that piracetam at therapeutically relevant concentrations improves neuritogenesis in the human cell line SH-SY5Y over conditions mirroring the whole spectrum of age-associated cognitive decline. These effects go parallel with improvement of impaired mitochondrial dynamics shifting back fission and fusion balance to the energetically more favorable fusion site. Impaired fission and fusion balance can also be induced by a reduction of the mitochondrial permeability transition pore (mPTP) function as atractyloside which indicates the mPTP has similar effects on mitochondrial dynamics. These changes are also reduced by piracetam. These findings suggest the mPTP as an important target for the beneficial effects of piracetam on mitochondrial function.
The general assumption that brain size differences are an adequate proxy for subtler differences in brain organization turned neurobiologists toward the question why some groups of mammals such as primates, elephants, and whales have such remarkably large brains. In this meta-analysis, an extensive sample of eutherian mammals (115 species distributed in 14 orders) provided data about several different biological traits and measures of brain size such as absolute brain mass (AB), relative brain mass (RB; quotient from AB and body mass), and encephalization quotient (EQ). These data were analyzed by established multivariate statistics without taking specific phylogenetic information into account. Species with high AB tend to (1) feed on protein-rich nutrition, (2) have a long lifespan, (3) delayed sexual maturity, and (4) long and rare pregnancies with small litter sizes. Animals with high RB usually have (1) a short life span, (2) reach sexual maturity early, and (3) have short and frequent gestations. Moreover, males of species with high RB also have few potential sexual partners. In contrast, animals with high EQs have (1) a high number of potential sexual partners, (2) delayed sexual maturity, and (3) rare gestations with small litter sizes. Based on these correlations, we conclude that Eutheria with either high AB or high EQ occupy positions at the top of the network of food chains (high trophic levels). Eutheria of low trophic levels can develop a high RB only if they have small body masses.
G protein coupled receptors (GPCRs) constitute the largest family of cell-surface receptors in mammals and are key players in signal transduction. By responding to a plethora of extracellular stimuli ranging from photons to amines to fatty acids to peptides and proteins, these receptors trigger intracellular signalling cascades and regulate a variety of cellular responses. Approximately 800 genes in humans encode GPCRs which are classified according to sequence conservation into rhodopsin-like, glutamate, adhesion, frizzled/taste2 and secretin receptors. GPCRs share a seven transmembrane domain fold undergoing a conformational change upon ligand binding which is translated to the intracellular surface of the receptor thereby allowing a heterotrimeric G protein to couple. Heterotrimeric G proteins consist of a Ga, Gb and Gg subunit and dissociate into their Ga and Gbg entities upon activation by a GPCR. Subsequently, distinct signalling cascades are triggered by each G protein protomer.
Membrane proteins and GPCRs in particular, are highly important targets in drug design and development as currently approximately 60% of all marketed drugs target membrane proteins. Although these classes of proteins are of high therapeutic interest, our understanding of their mechanism of action and structure remains limited. The first structure of a human GPCR was determined in 2007 and required the development of protein engineering and innovative crystallisation techniques. Since then, approximately 130 GPCR structures of less than 40 individual receptors have been determined providing insights into the structural arrangement of the transmembrane helices, ligand binding pockets and G protein interactions. Combined with spectroscopic methods, these studies allowed a more detailed understanding of the molecular aspects of GPCR activation and signalling. Despite the tremendous advances in GPCR structural biology, certain aspects of GPCR function still remain poorly understood. Due to their size and inherent flexibility, the interaction of protein and peptide ligands with their receptors remains a challenging aspect in the structural characterisation of GPCRs. Moreover, structural information on subtype selectivity of peptide ligands continues to be scarce. To contribute functional and structural information on the molecular mechanisms of peptide interactions with GPCRs, this thesis focused on characterising receptors from the chemoattractant cluster using radioligand binding assays as well as NMR spectroscopy.
The chemoattractant cluster mainly groups the kinin, angiotensin, anaphylatoxin chemotactic complement and apelin receptors according to conserved residues in their ligand binding cavities. All receptors in this cluster bind to peptide ligands deriving from high molecular weight protein precursors upon proteolytic processing. Comparable to the conserved binding pocket of the chemoattractant receptors, the peptide ligands display a certain sequence conservation although they differ strongly in size. The largest ligands used in this thesis are the anaphylatoxins complement 3a and 5a, comprising 77 or 74 residues, respectively. Due to their size and complex fold involving three intramolecular disulphide bonds, solid phase synthesis is impossible, which prompted us to develop a modified cell-free expression system to produce these ligands in tritiated form for subsequent functional characterisation of the complement receptors. To demonstrate the versatility of the developed system, it was applied to another disulphidebond containing peptide ligand, the 21 amino acid endothelin-1. We describe a reliable and multifaceted tool to generate custom labelled peptide ligands for the structural and functional characterisation of GPCRs. The system allows the production of custom radioligands, peptides labelled for NMR studies or with fluorescent amino acids.
Apart from the modulation of GPCR activity by orthosteric ligands, GPCR signalling has long been described to be regulated by allosteric ligands including peptides, small molecules and ions. In this thesis, the influence of sodium ions on the activity state of the chemoattractant cluster receptors and in particular on the apelin, bradykinin 2 and angiotensin II type 1 receptors was examined. In recent high resolution crystal structures an allosteric sodium ion pocket beneath the orthosteric ligand binding cavity was identified and residues contributing to the coordination of sodium ions are conserved throughout the chemoattractant cluster receptors. This allosteric sodium ion coordinated within the transmembrane domain bundle has been described to negatively influence the affinity of agonists but not of antagonists. It was found that sodium ions have distinct influences on the affinity state as well as the available number of binding sites of the chemoattractant receptors. In case of the apelin and bradykinin 2 receptors, sodium ions drastically reduced the number of available binding sites whereas the affinity of peptide ligands to the bradykinin 2 receptors remained constant and the ligand binding affinities to the apelin receptor were completely abolished. In contrast, the angiotensin II type 1 receptor affinity state towards the endogenous peptide ligand angiotensin II is highly dependent on the presence of sodium ions, whereas binding of the synthetic peptide antagonist Sar1-Ile8-angiotensin II remained unaffected by the sodium ion concentration. As differential effects irrespective of the efficacy class but dependent on the amino acid composition of the applied ligands are observed, it can be concluded that electrostatic interactions between charged residues of the peptide ligands and amino acids on the extracellular surface of the receptors are influenced by sodium ions thereby adding another layer of complexity on GPCR signalling.
To elucidate the structure-function relationship of ligand selectivity between the kinin receptors, the structure of desArg10-kallidin (DAK) bound to the bradykinin 1 receptor was determined using solid state NMR (SSNMR) in the course of this thesis. The kinin peptides DAK and bradykinin bind with high affinity and high selectivity to either the bradykinin 1 or bradykinin 2 receptor, respectively. The binding pockets of the receptors are highly conserved and the two peptide ligands only differ in one amino acid at their N- and C-termini whereas the remaining eight amino acids are fully conserved. DAK adopts a U-shaped structure when bound to the bradykinin 1 receptor which resembles a horse shoe-like conformation. Using 2D TEDOR spectroscopy it could furthermore be demonstrated that positively charged residues at the N-terminal part of the peptide engage in ionic interactions with negatively charged amino acids on the extracellular surface of the bradykinin 1 receptor. In contrast, bradykinin displays a distinct b-turn at the C-terminus and an S-shaped conformation of the N-terminal segment when bound to the bradykinin 2 receptor. By using SSNMR to study the binding mode of DAK on the bradykinin 1 receptor we could determine that subtype selectivity between the kinin receptors is conferred by distinct conformational restraints within the peptide ligands and by the formation of specific ionic interaction between charged residues on the peptide and receptor, respectively.
In brief, this thesis contributes structural and functional data on the binding mechanisms and binding mode of different peptide-ligand GPCRs helping to understand subtype selectivity and allosteric modulation of the chemoattractant cluster receptors. In addition, a versatile cell-free expression system was developed that allows the custom synthesis of isotopically labelled peptides containing disulphide bonds for the functional characterisation of GPCRs.
Melt segregation inside the earth consists of two different processes: 1) Generation of partially molten rock and 2) separation of melt, produced from partially molten rock, from the solid residual matrix. This thesis focuses on the later process. The 2 phase flow dynamics combines the study of flow dynamics of melt and matrix. Several studies have given the background theoretical frameworks for the flow dynamics of melt inside the earth. [McKenzie, 1984] summarizes the studies of [Ahern and Turcotte, 1979; Frank, 1968; Sleep, 1975] and gives a complete set of governing equations for the 2-phase flow problem.
[Bercovici et al., 2001] gives a general formulation considering the univariate system of equations related to matrix and melt flow which includes the interfacial surface force. The assumption of melt having negligible viscosity compare to the matrix has been abandoned. Therefore, based on these formulations, we have constructed our numerical model and thereafter a fortran code PERCOL2D to get an insight of melt percolation process through porous media. Additionally, we have used the Helmhotz decomposition, which splits a smooth and rapidly decaying vector field into an irrotational vector field and an incompressible vector field [Srámek, 2007], for matrix and fluid viscosity in order to lower the number of linearly independent variables to minimize the computational complications. The melt residing at inter-granular areas of lithosphere, forms an interconnected network even at low porosity. Therefore, being less dense than the matrix, melt moves up through porous media due to its buoyancy. Compaction of matrix, which occurs to compensate the melt separation, is considered in this thesis, where the effective bulk and shear viscosity of matrix are function of melt fraction. We have effective bulk viscosity of matrix as inversely proportional to melt fraction. Porosity dependence of effective bulk and shear viscosity leads to stronger melt focusing in highly porous region like mid ocean ridges [Katz, 2008] since the ratio of bulk and shear viscosity is smaller (< 10) than the constant viscosity case for the porous waves having non dimensional amplitude 5% or higher. Moreover, it is observed in [Richard et al., 2012] that the solitary wave formed in porosity dependent viscous matrix settings are steeper than the one formed in the constant matrix viscosity setting.
Firstly some 1D numerical experiments with PERCOL2D have been carried out using fixed and periodic boundary conditions for zero source term (i.e. no melting or no freezing) and negligible surface tension.
3 series of model setups with different initial conditions have been carried out varying the width, non-dimensional amplitude and the background porosity value of the initial input of porous wave.
A mathematical derivation for 1D solitary wave solution for the two phase flow through porosity dependent compacting media, is obtained in this thesis which is different than the study of [Barcilon and Lovera, 1989; Barcilon and Richter, 1986; Scott and Stevenson, 1984; Spiegelman, 1993a,b] as the effective viscosity of matrix is constant there.
Although [Simpson and Spiegelman, 2011] gives the solitary wave solutions in 1D, 2D and 3D considering the porosity dependent effective viscosity of the matrix, but using the small background porosity approximation, they neglect the background porosity (i.e φ0) and therefore the effect of variation of compaction lengths, which causes variation in the shape and dynamics of the solitary wave. Therefore, the study [This thesis, Richard et al., 2012] can be used for more general purpose. Solitary waves in varying viscous medium, are steeper (cf fig.5.1) compared to the one in constant viscous medium and their speed decreases as an inverse function of the background porosity. Additionally, this analytical solution is used in our code PERCOL2D and also in FDCON for numerical benchmarking (1D) of PERCOL2D.
The role of melt grain contiguity is considered in the revised viscosity formulation [Schmeling et al., 2012] based on elastic moduli theory of a fluid filled poro-elastic medium. This formulation is used in this thesis to produce a comparative dispersion relationship between speed of the wave and the non dimensional amplitude of porous wave, based on both the viscosity formulations (fig. 6.20) where one can see that the model based on [Bercovici et al., 2001] formulation, converges to the same dispersion relationship obtained from [Simpson and Spiegelman, 2011]. Whereas, the dispersion relationship using [Schmeling et al., 2012] formulations, shows time-dependent decrease of phase velocity with increasing amplitude and it is not yet clear that whether these solutions converge to steady state porosity waves before the porosity becomes 1.
Amid increasing regulation, structural changes of the market and Quantitative Easing as well as extremely low yields, concerns about the market liquidity of the Eurozone sovereign debt markets have been raised. We aim to quantify illiquidity risks, especially such related to liquidity dry-ups, and illiquidity spillover across maturities by examining the reaction to illiquidity shocks at high frequencies in two ways:
a) the regular response to shocks using a variance decomposition and,
b) the response to shocks in the extremes by detecting illiquidity shocks and modeling those as ultivariate Hawkes processes.
We find that:
a) market liquidity is more fragile and less predictable when an asset is very illiquid and,
b) the response to shocks in the extremes is structurally different from the regular response.
In 2015 long-term bonds are less liquid and the medium-term bonds are liquid, although we observe that in the extremes the medium-term bonds are increasingly driven by illiquidity spillover from the long-term titles.
Most defined contribution pension plans pay benefits as lump sums, yet the US Treasury has recently encouraged firms to protect retirees from outliving their assets by converting a portion of their plan balances into longevity income annuities (LIA). These are deferred annuities which initiate payouts not later than age 85 and continue for life, and they provide an effective way to hedge systematic (individual) longevity risk for a relatively low price. Using a life cycle portfolio framework, we measure the welfare improvements from including LIAs in the menu of plan payout choices, accounting for mortality heterogeneity by education and sex. We find that introducing a longevity income annuity to the plan menu is attractive for most DC plan participants who optimally commit 8-15% of their plan balances at age 65 to a LIA that starts paying out at age 85. Optimal annuitization boosts welfare by 5-20% of average retirement plan accruals at age 66 (assuming average mortality rates), compared to not having access to the LIA. We also compare the optimal LIA allocation versus two default options that plan sponsors could implement. We conclude that an approach where a fixed fraction over a dollar threshold is invested in LIAs will be preferred by most to the status quo, while enhancing welfare for the majority of workers.
Am 27. Dezember 2015 verabschiedete der Ständige Ausschuss des Nationalen Volkskongresses das erste Antiterrorgesetz in der Geschichte der Volksrepublik China (VRC). Damit wurde eine über 25 Jahre erarbeitete umfangreiche Antiterrorstrategie zu Papier gebracht und mit ihr endlich eine verbindliche rechtliche Definition von „Terrorismus.“ Bereits gängige Praktiken wie öffentliche Medienzensur oder die Verpflichtung von Telekommunikationsunternehmen und Internetprovidern zur Bereitstellung von Inhaltsdaten wurden formalisiert und verschärft, sowie auch die Mobilisierung zivilgesellschaftlicher Organisationen auf eine rechtliche Grundlage gestellt. Allerdings stellt das Gesetz nur den finalen, formalen Schritt einer fünfundzwanzigjährigen Entwicklung dar. Tatsächlich kämpft Beijing seit Anfang der 1990er Jahre in der Provinz Xinjiang mit einer Mischung aus separatistisch und islamistisch motivierter politischer Gewalt, an deren Spitze seit spätestens 2008 das East Turkestan Independence Movement (ETIM) steht. ETIM weist ideell und organisatorisch eine Nähe zu Al Qaeda auf, und arbeitet transnational mit der Islamischen Bewegung Usbekistans, Tehrik-i-Taliban (Pakistan) und der al-Nusra Front (Syrien) zusammen...
Systemic co-jumps
(2016)
The simultaneous occurrence of jumps in several stocks can be associated with major financial news, triggers short-term predictability in stock returns, is correlated with sudden spikes of the variance risk premium, and determines a persistent increase (decrease) of stock variances and correlations when they come along with bad (good) news. These systemic events and their implications can be easily overlooked by traditional univariate jump statistics applied to stock indices. They are instead revealed in a clearly cut way by using a novel test procedure applied to individual assets, which is particularly effective on high-volume stocks.
This paper addresses whether and to what extent econometric methods used in experimental studies can be adapted and applied to financial data to detect the best-fitting preference model. To address the research question, we implement a frequently used nonlinear probit model in the style of Hey and Orme (1994) and base our analysis on a simulation stud. In detail, we simulate trading sequences for a set of utility models and try to identify the underlying utility model and its parameterization used to generate these sequences by maximum likelihood. We find that for a very broad classification of utility models, this method provides acceptable outcomes. Yet, a closer look at the preference parameters reveals several caveats that come along with typical issues attached to financial data, and that some of these issues seems to drive our results. In particular, deviations are attributable to effects stemming from multicollinearity and coherent under-identification problems, where some of these detrimental effects can be captured up to a certain degree by adjusting the error term specification. Furthermore, additional uncertainty stemming from changing market parameter estimates affects the precision of our estimates for risk preferences and cannot be simply remedied by using a higher standard deviation of the error term or a different assumption regarding its stochastic process. Particularly, if the variance of the error term becomes large, we detect a tendency to identify SPT as utility model providing the best fit to simulated trading sequences. We also find that a frequent issue, namely serial correlation of the residuals, does not seem to be significant. However, we detected a tendency to prefer nesting models over nested utility models, which is particularly prevalent if RDU and EXPO utility models are estimated along with EUT and CRRA utility models.
Microeconomic modeling of investors behavior in financial markets and its results crucially depends on assumptions about the mathematical shape of the underlying preference functions as well as their parameterizations. With the purpose to shed some light on the question, which preferences towards risky financial outcomes prevail in stock markets, we adopted and applied a maximum likelihood approach from the field of experimental economics on a randomly selected dataset of 656 private investors of a large German discount brokerage firm. According to our analysis we find evidence that the majority of these clients follow trading pattern in accordance with Prospect Theory (Kahneman and Tversky (1979)). We also find that observable sociodemographic and personal characteristics such as gender or age don't seem to correlate with specific preference types. With respect to the overall impact of preferences on trading behavior, we find a moderate impact of preferences on trading decisions of individual investors. A classification of investors according to various utility types reveals that the strength of the impact of preferences on an investors' rading behavior is not connected to most personal characteristics, but seems to be related to round-trip length.