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We question the assumption of serial attention shifts and the assumption that saccade programs are initiated or canceled only after stage one of word identification. Evidence: (1) Fixation durations prior to skipped words are not consistently higher compared to those prior to nonskipped words. (2) Attentional modulation of microsaccade rate might occur after early visual processing. Saccades are probably triggered by attentional selection.
Computational models such as E-Z Reader and SWIFT are ideal theoretical tools to test quantitatively our current understanding of eye-movement control in reading. Here we present a mathematical analysis of word skipping in the E-Z Reader model by semianalytic methods, to highlight the differences in current modeling approaches. In E-Z Reader, the word identification system must outperform the oculomotor system to induce word skipping. In SWIFT, there is competition among words to be selected as a saccade target. We conclude that it is the question of competitors in the “game” of word skipping that must be solved in eye movement research.
We consider a nonparametric survival model with random censoring. To test whether the hazard rate has a parametric form the unknown hazard rate is estimated by a kernel estimator. Based on a limit theorem stating the asymptotic normality of the quadratic distance of this estimator from the smoothed hypothesis an asymptotic ®-test is proposed. Since the test statistic depends on the maximum likelihood estimator for the unknown parameter in the hypothetical model properties of this parameter estimator are investigated. Power considerations complete the approach.
The dependence between survival times and covariates is described e.g. by proportional hazard models. We consider partly parametric Cox models and discuss here the estimation of interesting parameters. We represent the ma- ximum likelihood approach and extend the results of Huang (1999) from linear to nonlinear parameters. Then we investigate the least squares esti- mation and formulate conditions for the a.s. boundedness and consistency of these estimators.
We give a survey on procedures for testing functions which are based on quadratic deviation measures. The following problems are considered: Testing whether a density function lies in a parametric class of functions, whether continuous random variables are independent; testing cell probabilities and independence in sparse data sets; testing the parametric fit of a regression homoscedasticity in a regression model and testing the hazard rate in survival models with censoring and with and without covariates.
Content: I. The nature and form of international law 1. The acceptance of the existence of an international legal order 2. The legal position of the individual in international law II. Obligations of states in the protection of international human rights 1. Treaty-based human rights obligations 2. The nature of treaty-based human rights obligations 3. The ”absolute” and ”objective” character of human rights treaty obligations 4. Human rights conventions as self-contained regimes 5. The problem of characterisation of human rights obligations of states III. Human rights obligations arising from general principles of international law 1. Obligations erga omnes and human rights norms 2. The outlawing of genocide as obligation erga omnes 3. Protection from slavery as obligation erga omnes 4. The outlawing of acts of aggression as obligation erga omnes 5. Protection from racial discrimination as obligation erga omnes 6. The basic rights of the human person as obligation erga omnes 7. Jus Cogens and the search for peremptory norms of human rights 8. International crimes and human rights norms 9. The relationship between the concepts: erga omnes, jus cogens, international crime and human rights IV. International instruments for the coercive enforcement of state obligations to ‘respect and ensure’ human rights 1. Countermeasures as consequences of breach of treaties in international law 2. Application of reprisals for the enforcement of treaty-based human rights obligations 3. Intervention for the protection of human rights in international law 4. Intervention by the Security Council for the protection of human rights: the situation before the East-West détente 5. Humanitarian intervention after the end of the Cold War 6. The legal nature of ECOWAS intervention in the Liberian Civil War 7. The legality of NATO’s intervention in Kosovo 8. Some instances of intervention with mixed motives V. Non-forceful measures for the enforcement of states’ human rights obligations 1. Economic and financial pressure as means of enforcing states’ obligation to respect and observe human rights 2. The application of the clausula rebus sic stantibus for the protection of human rights 3. The enforcement of human rights through the World Bank 4. The enforcement of human rights through the ILO 5. Diplomatic recognition as an instrument for securing a state's respect and promotion of human rights 6. Refusal to comply with an extradition agreement as a means of enforcing a state’s human rights obligations 7. Denial of immunity as a means of enforcing a state’s human rights obligations 8. Publicity as an instrument for the enforcement of human rights VI. Judicial enforcement of state obligations to ‘respect and ensure’ human rights 1. Enforcement of human rights through International Criminal Tribunals 2. The International Criminal Tribunal for Yugoslavia 3. The International Criminal Tribunal for Rwanda 4. The International Special Court of Sierra Leone Résumé
Biogenic amines and their receptors regulate and modulate many physiological and behavioural processes in animals. In vertebrates, octopamine is only found in trace amounts and its function as a true neurotransmitter is unclear. In protostomes, however, octopamine can act as neurotransmitter, neuromodulator and neurohormone. In the honeybee, octopamine acts as a neuromodulator and is involved in learning and memory formation. The identification of potential octopamine receptors is decisive for an understanding of the cellular pathways involved in mediating the effects of octopamine. Here we report the cloning and functional characterization of the first octopamine receptor from the honeybee, Apis mellifera . The gene was isolated from a brain-specific cDNA library. It encodes a protein most closely related to octopamine receptors from Drosophila melanogaster and Lymnea stagnalis . Signalling properties of the cloned receptor were studied in transiently transfected human embryonic kidney (HEK) 293 cells. Nanomolar to micromolar concentrations of octopamine induced oscillatory increases in the intracellular Ca2+ concentration. In contrast to octopamine, tyramine only elicited Ca2+ responses at micromolar concentrations. The gene is abundantly expressed in many somata of the honeybee brain, suggesting that this octopamine receptor is involved in the processing of sensory inputs, antennal motor outputs and higher-order brain functions.
Dopamine is found in many invertebrate organisms, including insects, however, the mechanisms through which this amine operates remain unclear. We have expressed two dopamine receptors cloned from honey bee (AmDOP1 and AmDOP2) in insect cells (Spodoptera frugiperda), and compared their pharmacology directly using production of cAMP as a functional assay. In each assay, AmDOP1 receptors required lower concentrations of dopamine and 6,7-ADTN for maximal activation than AmDOP2 receptors. Conversely, butaclamol and cis(Z)-flupentixol were more potent at blocking the cAMP response mediated through AmDOP2 than AmDOP1 receptors. Expression of AmDOP1, but not AmDOP2, receptors significantly increased levels of cAMP even in the absence of ligand. This constitutive activity was blocked by cis(Z)-flupentixol. This work provides the first evidence of a constitutively activated dopamine receptor in invertebrates and suggests that although AmDOP1 and AmDOP2 share much less homology than their vertebrate counterparts, they display a number of functional parallels with the mammalian D1-like dopamine receptors.
Electro-chemical signal transduction is the basis of communication between n eurons and their target cells. An important group of neuroactive substances that are released by action potentials from neurons are the biogenic amines. These a re small organic molecules that bind to specific receptors located in the target cell membrane. Once activated these receptors cause changes in the intracellula r concentration of second messengers, i.e. cyclic nucleotides, phosphoinositides , or Ca2+, leading to slow but long-lasting cellular responses. Biochemical, pha rmacological, physiological, and molecular biological approaches have unequivoca lly shown that biogenic amines are important regulators of cellular function in both vertebrates and invertebrates. In this review, we will concentrate on the p roperties of two biogenic amines and their receptors that were originally identi fied in invertebrates: tyramine and octopamine.