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Showing papers by "University of Tübingen published in 1993"


Journal ArticleDOI
21 Oct 1993-Nature
TL;DR: Macrophage migration inhibitory factor (MIF) is identified as a major secreted protein released by anterior pituitary cells in response to LPS stimulation, and it is concluded that MIF plays a central role in the toxic response to endotoxaemia and possibly septic shock.
Abstract: Cytokines are critical in the often fatal cascade of events that cause septic shock. One regulatory system that is likely to be important in controlling inflammatory responses is the neuroendocrine axis. The pituitary, for example, is ideally situated to integrate central and peripheral stimuli, and initiates the increase in systemic glucocorticoids that accompanies host stress responses. To assess further the contribution of the pituitary to systemic inflammatory processes, we examined the secretory profile of cultured pituitary cells and whole pituitaries in vivo after stimulation with bacterial lipopolysaccharide (LPS). Here we identify macrophage migration inhibitory factor (MIF) as a major secreted protein release by anterior pituitary cells in response to LPS stimulation. Serum analysis of control, hypophysectomized and T-cell-deficient (nude) mice suggests that pituitary-derived MIF contributes to circulating MIF present in the post-acute phase of endotoxaemia. Recombinant murine MIF greatly enhances lethality when co-injected with LPS and anti-MIF antibody confers full protection against lethal endotoxaemia. We conclude that MIF plays a central role in the toxic response to endotoxaemia and possibly septic shock.

990 citations


Journal ArticleDOI
TL;DR: The present paper gives a survey about the various estimation methods available for the basic reproduction number Ro, which may vary considerably for different infectious diseases but also for the same disease in different populations.
Abstract: The basic reproduction number R0 is the number of secondary cases which one case would produce in a completely susceptible population. It depends on the duration of the infectious period, the probability of infecting a susceptible individual during one contact, and the number of new susceptible individuals contacted per unit of time. Therefore R0 may vary considerably for different infectious diseases but also for the same disease in different populations. The key threshold result of epidemic theory associates the outbreaks of epidemics and the persistence of endemic levels with basic reproduction numbers greater than one. Because the magnitude of R0 allows one to determine the amount of effort which is necessary either to prevent an epidemic or to eliminate an infection from a population, it is crucial to estimate R0 for a given disease in a particular population. The present paper gives a survey about the various estimation methods available.

737 citations


Journal ArticleDOI
TL;DR: In this article, the modified increment method has been applied to the calculation of oxygen isotope fractionation factors for hydroxyl-bearing silicate minerals, which can be used as a test of isotopic equilibrium or disequilibrium in natural mineral assemblages over all temperature ranges.

672 citations


Journal ArticleDOI
TL;DR: A computational model is described that takes a step toward addressing the cognitive science challenge and resolving the artificial intelligence paradox and shows how a connectionist network can encode millions of facts and rules involving n-ary predicates and variables and perform a class of inferences in a few hundred milliseconds.
Abstract: Human agents draw a variety of inferences effortlessly, spontaneously, and with remarkable efficiency – as though these inferences were a reflexive response of their cognitive apparatus. Furthermore, these inferences are drawn with reference to a large body of background knowledge. This remarkable human ability seems paradoxical given the complexity of reasoning reported by researchers in artificial intelligence. It also poses a challenge for cognitive science and computational neuroscience: How can a system of simple and slow neuronlike elements represent a large body of systemic knowledge and perform a range of inferences with such speed? We describe a computational model that takes a step toward addressing the cognitive science challenge and resolving the artificial intelligence paradox. We show how a connectionist network can encode millions of facts and rules involving n-ary predicates and variables and perform a class of inferences in a few hundred milliseconds. Efficient reasoning requires the rapid representation and propagation of dynamic bindings. Our model (which we refer to as SHRUTI) achieves this by representing (1) dynamic bindings as the synchronous firing of appropriate nodes, (2) rules as interconnection patterns that direct the propagation of rhythmic activity, and (3) long-term facts as temporal pattern-matching subnetworks. The model is consistent with recent neurophysiological evidence that synchronous activity occurs in the brain and may play a representational role in neural information processing. The model also makes specific psychologically significant predictions about the nature of reflexive reasoning. It identifies constraints on the form of rules that may participate in such reasoning and relates the capacity of the working memory underlying reflexive reasoning to biological parameters such as the lowest frequency at which nodes can sustain synchronous oscillations and the coarseness of synchronization.

652 citations


Journal ArticleDOI
TL;DR: A revised system of abbreviated names is proposed for xyloglucan-derived oligosaccharides, where each (1→4)-linked β-D-glucosyl residue (and the reducing terminal n- glucose moiety) of the backbone is given a one-letter code according to its substituents.
Abstract: A revised system of abbreviated names is proposed for xyloglucan-derived oligosaccharides. Each (1→4)-linked β-D-glucosyl residue (and the reducing terminal n-glucose moiety) of the backbone is given a one-letter code according to its substituents. The name of the oligosaccharide consists of these code letters listed in sequence from non-reducing to reducing terminus of the backbone

554 citations


Journal ArticleDOI
TL;DR: G glycogen in astrocytes can be considered as a store for lactate rather than for glucose, and gluconolactone or 2-deoxyglucose which prevent glycogen breakdown in astroglial cells after glucose deprivation, allow to discriminate between lactate generated from glycogen and lactate from other sources.

516 citations


Journal ArticleDOI
TL;DR: Se sequencing of the iron(II) transport genes revealed regions of homology to ATPases, which indicates that ferrous iron uptake may be ATP driven.
Abstract: Escherichia coli has an iron(II) transport system (feo) which may make an important contribution to the iron supply of the cell under anaerobic conditions. Cloning and sequencing of the iron(II) transport genes revealed an open reading frame (feoA) possibly coding for a small protein with 75 amino acids and a membrane protein with 773 amino acids (feoB). The upstream region of feoAB contained a binding site for the regulatory protein Fur, which acts with iron(II) as a corepressor in all known iron transport systems of E. coli. In addition, a Fnr binding site was identified in the promoter region. The FeoB protein had an apparent molecular mass of 70 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and was localized in the cytoplasmic membrane. The sequence revealed regions of homology to ATPases, which indicates that ferrous iron uptake may be ATP driven. FeoA or FeoB mutants could be complemented by clones with the feoA or feoB gene, respectively. Images

438 citations


Journal ArticleDOI
TL;DR: An improved chemiluminescence-based RNA/DNA detection procedure offering a widely applicable alternative to the conventional 32P labeling employed in molecular biology is described, delineating a system consistently superior to radioactivity.

418 citations


Journal ArticleDOI
TL;DR: The data suggest that boswellic acids are specific, non-redox inhibitors of leukotriene synthesis either interacting directly with 5-lipoxygenase or blocking its translocation.

411 citations


Journal ArticleDOI
TL;DR: It is postulate that a decrease in cellular hydration in liver and skeletal muscle triggers the protein catabolic states that accompany various diseases.

405 citations


Journal ArticleDOI
TL;DR: An overlap-free “window” within which pipistrelles may detect potential prey and which allows predictions of minimum distances to prey and clutter-producing objects is proposed.
Abstract: We studied the echolocation and hunting behavior of three aerial insectivorous species of bats (Vespertilionidae: Pipistrellus) in the field in order to characterize the signals used by the bats and to determine how call structure varies in relation to habitat structure (“uncluttered” versus “cluttered” space). We documented free-flying, naturally foraging wild pipistrelles in various habitats using multiflash stereophotography combined with simultaneous sound recordings. Then we reconstructed the bat's flight position in three-dimensional space and correlated it with the corresponding echolocation sequences. In all three species of pipistrelles, signal structure varied substantially. In echolocation sequences of the search phase we found a consistent association of signal types with habitat types. In uncluttered habitats (obstacles more than 5 m from the bat) pipistrelles emitted almost exclusively narrowband signals with bandwidths less than 15 kHz. In cluttered habitats (obstacles less than 5 m from the bat) they switched to signals with bandwidths of more than 15 kHz. Wideband signals were also used when the bats were turning in cluttered and uncluttered spaces and for an instant after turning away from obstacles. Prey detection occured only when the outgoing signal did not overlap with the returning echo from potential prey. The bats also avoided overlap of echoes from potential prey and obstacles. Based on the results of this study, we propose an overlap-free “window” within which pipistrelles may detect potential prey and which allows predictions of minimum distances to prey and clutter-producing objects.

Journal ArticleDOI
TL;DR: In vivo 1H NMR spectra of small volumes‐of‐interest (VOI) were localized in human soleus muscle and compared with volume selective spectraof subcutaneous fat tissue and femoral yellow bone marrow to provide comparability.
Abstract: In vivo 1H NMR spectra of small volumes-of-interest (VOI) were localized in human soleus muscle (8 ml) and compared with volume selective spectra of subcutaneous fat tissue and femoral yellow bone marrow (2 ml). All examinations were performed by the double spin echo (PRESS) localization technique. To provide comparability, spectra of different tissues were recorded using identical sequence timing. Clearly improved resolution of the lipid signals of muscle tissue was obtained using long echo times TE > 200 ms. The spectra of muscle tissue exhibit lipid signals that stem from two compartments with a difference of their resonance frequencies of about 0.2 ppm (Larmor frequency difference 12-13 Hz at 1.5 T). The existence of two fatty acid compartments is supported by measurements of the relaxation times and line shape analysis. Both compartments contain fatty acids or triglycerides with similar composition. Probably one compartment corresponds to fat cells within muscle tissue, the other compartment with lower Larmor frequency is located within muscle cells.

Journal ArticleDOI
TL;DR: Pyragas as discussed by the authors proposed a method for chaos control by a small time-continuous perturbation, which is realized experimentally by a specially designed analogue circuit using a simple delay line.

Journal ArticleDOI
TL;DR: An improvement of the continued fraction technique is presented for a very accurate numerical determination of the asymptotic behavior of quasinormal frequencies with very large imaginary parts of Schwarzschild black holes.
Abstract: We present an improvement of the continued fraction technique for the numerical calculation of quasinormal modes of Schwarzschild black holes. On this basis it becomes possible to compute quasinormal frequencies with arbitrary imaginary parts. We use this technique for a very accurate numerical determination of the asymptotic behavior of quasinormal frequencies with very large imaginary parts [Im(\ensuremath{\omega})\ensuremath{\gg}100].

Journal ArticleDOI
TL;DR: It is demonstrated that axotomy initializes a cascade of microglia-mediated autodestructive retinal responses, which culminate in degradation of “sick,” but obviously viable neurons, and postulate that the retinal microglial system has a key role in recognizing and eliminating severed neurons.
Abstract: To monitor the cascade of events initiated by injury of adult neurons, and to explore whether and how neighboring microglial cells contribute to the degradation of lesioned neurons, axotomy-induced ganglion cell degeneration was investigated in adult rats. Suppression of macrophage and microglia activity during the weeks following transection of the optic nerve was performed with the immunoglobulin-derived tripeptide Thr-Lys-Pro, which is a macrophage inhibitory factor (MIF) and retards the activity of cells of monocytic origin. Single or repeated injection of MIF into the vitreous body during and after transection of the optic nerve resulted in significant retardation of axotomy-induced ganglion cell degradation in the retina as detected by specific labeling with the retrogradely transported fluorescent dye 4Di-10ASP. MIF specifically altered the morphology of labeled microglial cells from a ramified to an oval, less ramified shape, indicating that these cells were targets of its activity. Injection of the tetrapeptide macrophage stimulating factor, also known as tuftsin (Thr-Lys-Pro-Arg), revealed effects opposite to those described for the MIF: it increased the number of labeled microglial cells and enhanced the devastating effects of axotomy on ganglion cells. The viability of rescued ganglion cells in retinas treated with the various drugs was assessed both in vivo and in vitro. (1) Intravitreal injection of MIF to prevent degradation of neurons combined with transplantation of autologous peripheral nerve grafts, which facilitate regrowth of the transected neurites, revealed that significantly more ganglion cells contributed to axonal regeneration (17.1%) than in untreated controls (9.5%). (2) Explantation of retinas that were pretreated with MIF in situ revealed higher incidence of axonal outgrowth in organ cultures than untreated control explants or retinas treated with either the basic fibroblast growth factor or brain-derived neurotrophic factor. The present results demonstrate that axotomy initializes a cascade of microglia-mediated autodestructive retinal responses, which culminate in degradation of "sick," but obviously viable neurons. We postulate that the retinal microglial system has a key role in recognizing and eliminating severed neurons.

Journal ArticleDOI
TL;DR: The reliability and validity of these scales were determined in a sample of 120 chronic pain patients suffering from various rheumatic disorders, 213 patients who suffered from chronic back pain, 44 patients with temporomandibular pain and dysfunction and 38 healthy controls.

Journal ArticleDOI
TL;DR: The purpose of the present study was to describe the development of the efferent projections of the cochlear nucleus (CN), the first central relay station in the ascending auditory pathway of mammals.
Abstract: Although the connections of the auditory brainstem nuclei are well described in adult mammals, almost nothing is known concerning how and when these connections develop. The purpose of the present study was to describe the development of the efferent projections of the cochlear nucleus (CN), the first central relay station in the ascending auditory pathway of mammals. We used two tracers in rats aged between embryonic day 15 (E15) and postnatal day 14 (P14; birth in the rat is at E22 = P0). The carbocyanine dye DiI was applied into the CN in aldehyde-fixed tissue. The second tracer, biocytin, was applied into the ventral acoustic stria in an in vitro slice preparation. The ontogeny of the efferent projections from the CN could be divided into three periods. The first period (E15–E17) is characterized by axonal outgrowth. Axons traverse nuclei in the superior olivary complex and the lateral lemniscus and finally grow up into the inferior colliculus, but axon collaterals do not from during this period. The second period (E18–P5) is marked by pronounced collateral branching of CN fibers in auditory brainstem nuclei. Collateralisation in the contralateral inferior colliculus starts shortly before that in the ipsilateral superior olivary complex. The remaining auditory nuclei become successively innervated, as indicated by collaterals found in them. During the third period (P5–P14) terminal structures mature further, as shown by the morphological changes of the calyces of Held in the medial nucleus of the trapezoid body. In conclusion, our results show that the efferent connections from the cochlear nucleus form over a period of almost two weeks and are laid down without forming aberrant internuclear connections. On a nuclear level, an adult-like projection pattern is already achieved one week prior to the onset of physiological hearing. © 1993 Wiley-Liss, Inc.

Journal ArticleDOI
TL;DR: The present data indicate that the pathway mediating PPI impinges upon the primary acoustic startle circuit through an inhibitory cholinergic projection from the PPTg to the PnC.
Abstract: The amplitude of the acoustic startle response (ASR) is markedly reduced when the startle eliciting pulse is preceded by a weak, non-startling stimulus at an appropriate lead time, usually about 100 ms. This phenomenon is termed prepulse inhibition (PPI) and has received considerable attention in recent years as a model of sensorimotor gating. We report here on experiments which were undertaken in order to investigate some of the neural mechanisms of PPI. We focused on the characterization of the cholinergic innervation of the pontine reticular nucleus, caudal part (PnC), an obligatory relay station in the primary startle pathway. The combination of retrograde tracing with choline acetyltransferase-immunocytochemistry revealed a cholinergic projection from the pedunculopontine tegmental nucleus (PPTg) and laterodorsal tegmental nucleus (LDTg) to the PnC. Extracellular recording from single PnC units, combined with microiontophoretic application of the acetylcholine (ACh) agonists acetyl-β-methylcholine (AMCH) and carbachol revealed that ACh inhibits the majority of acoustically responsive PnC neurons. Neurotoxic lesions of the cholinergic neurons of the PPTg significantly reduced PPI without affecting the ASR amplitude in the absence of prepulses. No effect on long-term habituation of the ASR was observed. The present data indicate that the pathway mediating PPI impinges upon the primary acoustic startle circuit through an inhibitory cholinergic projection from the PPTg to the PnC.

Journal ArticleDOI
TL;DR: Automated infrared photoretinoscopy proved to be very convenient and easy to handle in both children and adults and there was a striking inter‐individual variability in the maximum possible speed of accommodation and near to far accommodation.
Abstract: 1. To study the relationship between accommodation under natural viewing conditions, age and refractive errors, we have measured time courses of accommodation in thirty-nine human subjects aged 5-49 years using a newly developed technique. The technique is based on infrared photoretinoscopy and involves fully automated on-line image processing of digitized video images of the eyes with a sampling rate of 5.3 Hz. 2. The distance between the subject and the video camera was about 1.3 m. Head movements of the subject required little restriction because the eyes were automatically tracked in the video image by the computer program. All subjects were tested under binocular viewing conditions. 3. Both refraction of the right eye and pupil diameter were measured with a precision of 0.2-0.4 dioptres (D) and 0.1 mm, respectively, and were plotted on-line. The data were subsequently automatically analysed. 4. Automated infrared photoretinoscopy proved to be very convenient and easy to handle in both children and adults. 5. The maximal speed of accommodation for a target at a distance of 5 D declined in the subjects with age (from up to 21.7 D s-1 for accommodation and 32.7 D s-1 for subsequent accommodation to a distant target ('near to far accommodation') in children down to 2-18 D s-1 in adults). There was a striking inter-individual variability in the maximum possible speed of accommodation and near to far accommodation. 6. Speed of accommodation and of near to far accommodation was correlated for each subject. However, in most of the subjects, the process of near to far accommodation was faster than accommodation (P < 0.005, if averaged over all subjects). This correlation was independent of age. 7. The accommodation-induced pupillary constriction (pupillary near response) was absent in children for a 4 D target; even at 10 D, there was no reliable pupillary response. The pupillary near response increased to about 1.6 mm D-1 of accommodation at the age of 47. Since a pupillary near response could still be elicited in presbyopic subjects unable to accommodate, the ratio of pupillary constriction per dioptre of accommodation approached infinity. 8. The magnitude of the pupillary near response was highly variable even among subjects of the same age but was typical for each subject. There was a correlation (P < 0.01) to refractive error: corrected myopes had weaker pupillary near responses than emmetropes or hyperopes.(ABSTRACT TRUNCATED AT 400 WORDS)

Journal ArticleDOI
TL;DR: Results are consistent with animal studies and earlier case reports indicating that intact cerebellar structures are necessary for the acquisition of classically conditioned motor responses.
Abstract: We explored classical conditioning in human subjects who had lesions in their cerebellar circuitry. Seven patients with damage to cerebellar structures and matched control subjects underwent simple delay tone-airpuff conditioning. Eyelid conditioned response (CR) acquisition was severely disrupted in the patient group, whereas autonomic CRs and slow cortical potentials developing between conditioned stimulus (CS) and the unconditioned stimulus (UCS) were unaffected. Results are consistent with animal studies and earlier case reports indicating that intact cerebellar structures are necessary for the acquisition of classically conditioned motor responses.

Journal ArticleDOI
TL;DR: An imporant relationship between clinical disease and an increase in cerebral Gd‐DTPA MRI activity was confirmed, and a relationship with long‐term disability was suggested, but cannot be confirmed without longer follow‐up of these patients.
Abstract: It is now well established that clinically stable patients with relapsing–remitting multiple sclerosis have ongoing disease activity when evaluated by serial gadolinium–enhanced (Gd-DTPA) magnetic resonance imaging (MRI) scans. Despite this, the relationship between clinical disease and MRI lesions, though suspected, has not been extensively documented. The relationship between Gd-DTPA MRI lesions, and clinical disease was examined in this study of 9 patients with mild relapsing–remitting multiple sclerosis (Expanded Disability Status Scale [EDSS] <3.5) who had 24 to 37 monthly Gd-DTPA MRI scans, neurological examinations, and EDSS score assignments. The area and frequency of Gd-DTPA lesions were examined during months with and without clinical worsening as measured by EDSS. Forty-one episodes of clinical worsening were noted during the study. A significant association was observed between these periods of clinical worsening and MRI parameters, including increases in total number, number of new lesions, and the total area of enhancement. Logistic regression analysis showed a signficant effect of the number and area of Gd-DTPA MRI lesions on both the onset and continuation of clinical worsening, confirming an imporant relationship between clinical disease and an increase in cerebral Gd-DTPA MRI activity. A relationship with long-term disability was suggested, but cannot be confirmed without longer follow-up of these patients.

Journal ArticleDOI
TL;DR: In this paper, the authors discuss tourism development theories with respect to their spatio-temporal implications in the Third World and propose a model of tourist space in developing countries, which acknowledges the influence of the existing social and economic structures in these countries at all stages of tourism development, differentiates the tourism industry into two sectors, and recognizes the spatial segregation and different economic impacts of the sectors.

Journal ArticleDOI
TL;DR: The convergence theory of multigrid methods for self-adjoint and coercive linear elliptic boundary value problems reached a mature, if not its final state, in the early 1990s as mentioned in this paper.
Abstract: Multigrid methods are the fastest known methods for the solution of the large systems of equations arising from the discretization of partial differential equations. For self-adjoint and coercive linear elliptic boundary value problems (with Laplace's equation and the equations of linear elasticity as two typical examples), the convergence theory reached a mature, if not its final state. The present article reviews old and new developments for this type of equation and describes the recent advances.

Journal ArticleDOI
TL;DR: In this article, the authors argue that existing definitions and operationalizations are problematic, and the few empirical studies that have examined the impact of grief work have yielded equivocal results, and that grief work is not a universal concept.
Abstract: The article challenges the longstanding belief in the importance of “grief work” for adjustment to bereavement (the grief work hypothesis). It examines claims made in theoretical formulations and principles of grief counseling and therapy concerning the necessity of working through loss. Empirical evidence is reviewed, and cross-cultural findings are described to document alternative patterns of coping with grief. It is argued that there are grounds for questioning the hypothesis: 1) existing definitions and operationalizations are problematic; 2) the few empirical studies that have examined the impact of grief work have yielded equivocal results; 3) grief work is not a universal concept. Limitations of the grief work hypothesis as an explanation of coping with bereavement are identified and a differential approach is suggested. Implications for counseling and therapy are discussed.

Journal ArticleDOI
TL;DR: A possible involvement of the PDFMe neurons in the circadian pacemaking system of Drosophila is suggested, which is identical with those of neurons containing the period protein which is essential for circadian rhythmicity.
Abstract: Antisera against the crustacean pigment-dispersing hormone (p-PDH) were used in immunocytochemical preparations to investigate the anatomy of PDH-immunorea ctive neu­ rons in the nervous system of wild-type Drosophila melanogaster and in that of several brain mutants of this species, some of which express altered circadian rhythmicity. In the wild-type and in all rhythmic mutants (small optic lobes, sine oculis, small optic lobes;sine oculis), eight cell bodies at the anterior base of the medulla (PDFMe neurons) exhibit intense PDH-like immunoreactivity. Four of the eight somata are large and four are smaller. The four large PDFMe neurons have wide tangential arborizations in the medulla and send axons via the posterior optic tract to the contralateral medulla. Fibers from the four small PDFMe neurons ramify in the median protocerebrum dorsal to the calyces of the mushroom bodies. Their terminals are adjacent to other PDH-immunoreactive somata (PDFCa neurons) which send axons via the median bundle into the tritocerebrum. The results suggest a possible involvement of the PDFMe neurons in the circadian pacemaking system of Drosophila. The location and size of the PDFMe neurons are identical with those of neurons containing the period protein which is essential for circadian rhythmicity. Changes in the arborizations of the PDFMe neurons in small optic lobes;sine oculis mutants are suited to explain the splitting in the locomotor rhythm of these flies. In the arrhythmic mutant, disconnected, the PDFMe neurons are absent. The arrhythmic mutant per0, however, shows normal PDH immunoreactivity and therefore, does not prevent the expression of PDH-like peptides in these neurons. 1993 Wiley-Lias, Inc.

Journal ArticleDOI
TL;DR: A detailed film analysis shows that orientation flights in solitary wasps of the genus Cerceris consist of a systematic behavioural sequence: after lift-off from the nest entrance, wasps fly in ever increasing arcs around the nest.
Abstract: Bees and wasps are known to use a visual representation of the nest environment to guide the final approach to their nest. It is also known that they acquire this representation during an orientation flight performed on departure. A detailed film analysis shows that orientation flights in solitary wasps of the genus Cerceris consist of a systematic behavioural sequence: after lift-off from the nest entrance, wasps fly in ever increasing arcs around the nest. They fly along these arcs obliquely to their long axis and turn so that the nest entrance is held in the left or right visual field at retinal positions between 30° and 70° from the midline. Horizontal distance from the nest and height above ground increase throughout an orientation flight so that the nest is kept at retinal elevations between 45° and 60° below the horizon. The wasps' rate of turning is constant at between 100°/s and 200°/s independent of their distance from the nest and their ground velocity increases with distance. The consequence of this is that throughout the flight wasps circle at a constant angular velocity around the nest. Orientation flights are strongly influenced by landmark lay-out. Wasps adjust their flight-path and their orientation in a way that allows them to fixate the nest entrance and to hold the closest landmark in their frontal visual field. The orientation flight generates a specific topography of motion parallax across the visual field. This could be used by wasps to acquire a series of snapshots that all contain the nest position, to acquire snapshots of close landmarks only (distance filtering), to exclude shadow contours from their visual representation (figure-ground discrimination) or to gain information on the distance of landmarks relative to the nest.

Journal ArticleDOI
TL;DR: Spectral interferometry has been used to monitor the swelling of polymers caused by organic gases or hydrocarbons in waste water as well as the adsorption and interaction of antigens and antibodies in immunoreactions.
Abstract: Spectral interferometry is presented as a tool to monitor the swelling of polymers caused by organic gases or hydrocarbons in waste water as well as the adsorption and interaction of antigens and antibodies in immunoreactions. Modern diode-array technology allows the consequent observation of changes in optical pathlength on a fractional nanometer scale with subsecond repetition times. The theory of multiple-reflection principles in white-light interferometry determines the possibilities and limitations of this method. The optical set-up and some applications in gas sensing and label-free immunosensing are discussed with respect to the sensitivity, selectivity and limits of detection at present.

Journal ArticleDOI
TL;DR: In this article, two-step nucleophilic hydroalkylations, hydroar-ylations as well as hydrostannylations of fullerene-60 (1) and fulleren-70 (2) lead to defined organodihydrofullerenes C60HR and C70HR.
Abstract: Controlled two-step nucleophilic hydroalkylations, hydroar-ylations as well as hydrostannylations of fullerene-60 (1) and fullerene-70 (2) lead to defined organodihydrofullerenes C60HR and C70HR. NMR investigations show that only one isomer of each organodihydrofullerene with Cs symmetry is formed. In all cases the addition takes place at a double bond separating two six-membered rings of the fullerene core. In this way a variety of organodihydrofullerenes also carrying functional groups have been synthesized.

Journal ArticleDOI
TL;DR: Surprisingly, and by mechanisms not yet defined, hyperpolarization of the cell also reduces agonist-induced accumulation of inositol 1,4,5-trisphosphate, and the Ca2+ sensitivity of the contractile apparatus.

Journal ArticleDOI
TL;DR: Investigation of the regulation of excitability in cortical networks, as indicated by surface-negative slow cortical potentials (SCPs), is impaired in epileptic patients and to what extent training of SCP self-regulation by means of biofeedback and instrumental learning procedures might affect seizure frequency found significant increases in SCP control.