Time-of-Flight Based Calibration of an Ultrasonic Computed Tomography System

The paper presents a novel method for calibration of measuring geometry and of individual signal delays of transducers in ultrasonic computed tomography (USCT) systems via computational processing of multiple time-of-flight measurements of ultrasonic (US) impulses. The positions and time-delay parameters of thousands of ultrasonic transducers inside the USCT tank are calibrated by this approach with a high precision required for the tomographic reconstruction; such accuracy cannot be provided by any other known method. Although utilising similar basic principles as the global positioning system (GPS), the method is importantly generalised in treating all transducer parameters as the to-be calibrated (floating) unknowns, without any a-priori known positions and delays. The calibration is formulated as a non-linear least-squares problem, minimizing the differences between the calculated and measured time-of-arrivals of ultrasonic pulses. The paper provides detailed derivation of the method, and compares two implemented approaches (earlier calibration of individual transducers with the new approach calibrating rigid transducer arrays) via detailed simulations, aimed at testing the convergence properties and noise robustness of both approaches. Calibration using real US signals is described and, as an illustration of the utility of the presented method, a comparison is shown of two image reconstructions using the tomographic US data from a concrete experimental USCT system measuring a 3D phantom, without and after the calibration

Vitamin D stimulates (Na+ + K+)-ATPase activity in chick small intestine

AbstractVitamin D3 and 1,25-dihydroxyvitamin D3 raise (Na+ + K+)-ATPase activity (ouabain-sensitive 86Rb+ uptake) in cultured embryonic and 4-week-old chick small intestine. Vitamin D stimulation of the sodium pump, which requires genomic action of the sterol, may lead to enhanced Ca2+ extrusion via a basolateral Na+/Ca2+ exchange mechanism, and, in addition, may provide a proliferative signal in undifferentiated enterocytes

Asynchronous haptic simulation of contacting deformable objects with variable stiffness

International audienceAbstract--This paper presents a new asynchronous approach for haptic rendering of deformable objects. When stiff nonlinear deformations take place, they introduce important and rapid variations of the force sent to the user. This problem is similar to the stiff virtual wall for which a high refresh rate is required to obtain a stable haptic feedback. However, when dealing with several interacting deformable objects, it is usually impossible to simulate all objects at high rates. To address this problem we propose a quasi-static framework that allows for stable interactions of asynchronously computed deformable objects. In the proposed approach, a deformable object can be computed at high refresh rates, while the remaining deformable virtual objects remain computed at low refresh rates. Moreover, contacts and other constraints between the different objects of the virtual environment are accurately solved using a shared Linear Complementarity Problem (LCP). Finally, we demonstrate our method on two test cases: a snap-in example involving non-linear deformations and a virtual thread interacting with a deformable object

Metabotropic Glutamate Receptors – Regulation of Acute and Chronic Stress-Related Behavior and Physiology

Etiology and pharmacotherapy of stress-related psychiatric conditions and comorbid somatic pathologies are nowadays areas of high unmet medical need and intense research. It is widely accepted that stressors holding a chronic and psychosocial component represent the most acknowledged risk factor. The L-glutamatergic system represents the primary excitatory neurotransmitter system of the mammalian brain and mGlu receptors acting as important pre- and postsynaptic regulators of neurotransmission provide a mechanism by which fast synaptic responses through iGlu receptors can be fine-tuned. During the last decades, research on mGlu receptors advanced remarkably and much attention was given to the mGlu5 and mGlu7 subtypes in acute stress, fear and depression-related behavior and physiology (see Introduction). As the most widely distributed throughout the mammalian brain, the presynaptic mGlu7 receptor is an important regulator of glutamatergic function and postulated to be critical for both normal CNS functioning and a range of stress-related disorders. Although genetic and pharmacological approaches have helped to understand mGlu7’s function in a host of behavioral and physiological processes, available allosteric ligands have often yielded disparate results despite displaying similar pharmacological properties in vitro. The recent discovery of XAP044 raised great hope to resolve this discrepancy. XAP044 was characterized as the first mGlu7-selective full antagonist that blocks the receptor’s signaling pathways by binding to its large VFTD, but not to allosteric sites within the transmembrane domain. Thus, XAP044 presumably binds via a novel mechanism compared to that from known selective ligands. It was part of the present PhD thesis to characterize this novel compound XAP044 in vivo in a broad battery of acute stress tests for depression, fear and anxiety in mice. It was shown that XAP044 is systemically active and demonstrates a wide spectrum of anti-stress, antidepressant and anxiolytic-like efficacy, strongly supporting pharmacological blockade of mGlu7 as a promising mode of action for future treatment of stress-related disorders of emotion in man. Also the mGlu5 subtype has become a recent focus for drug discovery efforts (see Introduction). Due to its physical and functional association with the postsynaptic NMDA receptor the mGlu5 subtype is considered as a good target to modulate NMDA receptor function. This is an important consideration as, for instance, the NMDA receptor antagonist ketamine – despite showing rapid and sustained efficacy in clinical depression trials – is also associated with severe cognition-altering and dissociative effects. To date, several mGlu5 NAMs have been reported to have therapeutic potential for numerous conditions including clinical depression and anxiety disorders. A recent study revealed the mGlu5 NAM basimglurant as a promising antidepressant drug with the potential to also alleviate comorbidities such as anxiety and pain. Despite the overall well-established link between mGlu5 and mGlu7 and acute stress-related behavior and physiology, the roles these receptors play in chronic stress-related conditions is only little explored. The CSC paradigm represents a powerful animal model as it displays harmful behavioral, physiological and immunological changes induced by chronic psychosocial stress. Those consequences are relevant for the development of psychiatric, somatic and/or gastrointestinal disorders in humans and the question whether mGlu5 and mGlu7 have the potential to exert control on these pathological consequences is of great interest, and it may suggest future therapeutic strategies for the treatment of chronic stress-related disorders in humans, i.e. a wide clinical application spectrum. In a first step of the present PhD thesis, the molecular changes were assessed that occur within the mGlu receptor system in response to CSC exposure. Here, an increase by trend of mGlu5 mRNA was found in the hypothalamus. Additional saturation binding analysis revealed increased mGlu5 protein binding specifically in the hippocampus. Furthermore, robust downregulation of mGlu7 mRNA was found specifically in the PFC. In contrast, mGlu2 and mGlu3 were not dysregulated upon CSC exposure. Taken together, the present results indicate specific CSC-induced alterations of mGlu5 and mGlu7 expression in stress-sensitive brain regions involved in the regulation of behavior and HPA axis functionality, and thus provide early evidence towards a role of specific mGlu receptor subtypes in chronic psychosocial stress-induced pathophysiology. In a next step, the influence of genetic ablation of mGlu7 on behavioral, physiological and immunological consequences of CSC was analyzed to reveal the potential role of the endogenous mGlu7 receptor during chronic psychosocial stress. Indeed, genetic ablation of mGlu7 relieved multiple CSC induced alterations; mGlu7 deficient mice were protected against the CSC-induced anxiety-prone phenotype as well as against several CSC-induced physiological and immunological consequences such as HPA axis dysfunction and colonic inflammation, respectively. These findings point to a distinct role of mGlu7 in modulating a wide range of affective and somatic alteration that occur upon CSC exposure. Moreover, the stress-protective phenotype of genetic mGlu7 ablation suggests mGlu7 pharmacological blockade to be a possible treatment strategy for chronic stress-related emotional and somatic conditions in man. In the last part of the present thesis, the potentially beneficial role of genetic and pharmacological mGlu5 inhibition on CSC-induced alterations (the same broad range as presented above) was analyzed. Interestingly, also mGlu5 deficient mice were protected against a variety of CSC-induced physiological and behavioral changes, including the newly established CSC-induced increase in SIH response. Moreover, the effects of the mGlu5 NAM CTEP, a close analogue to the clinically active drug basimglurant with long half-life in rodents, were studied on a wider range of CSC-affected parameters. Here, CTEP relieved in a dose-dependent manner various CSC-induced consequences such as HPA axis dysfunction, immunological alterations and colonic inflammation, suggesting that mGlu5 is a relevant mediator for a wide range of alterations induced by chronic psychosocial stress and a potentially valuable drug target for the treatment of stress-related somatic pathologies. In conclusion, the present PhD thesis provides clear evidence for the importance of especially the mGlu5 and mGlu7 subtypes in the regulation of acute and chronic stress-related behavior and physiology, lending further support towards future development of mGlu5- and mGlu7-selective antagonists and their administration as therapy for stress-related psychiatric and somatic disorders in humans

Gewalt in rechtsradikaler Literatur - eine Betrachtung von (Selbst-) Darstellungen Rechtsradikaler im Verlauf der 20er und 30er Jahre

In dieser Hausarbeit vergleiche ich diachron die Legitimation de in Freikorpsliteratur der 20er und 30er Jahre dargestellten Gewalt

Haptic Rendering Based on RBF Approximation from Dynamically Updated Data

In this paper, an extension of our previous research focused on haptic rendering based on interpolation from precomputed data is presented. The technique employs the radial-basis function (RBF) interpolation to achieve the accuracy of the force response approximation, however, it assumes that the data used by the interpolation method are generated on-the-fly during the haptic interaction. The issue caused by updating the RBF coefficients during the interaction is analyzed and a force-response smoothing strategy is proposed

Low temperature fullerene encapsulation in single wall carbon nanotubes: synthesis of N@C60_{60}@SWCNT

High filling of single wall carbon nanotubes (SWCNT) with C$_{60}$ and C$_{70}$ fullerenes in solvent is reported at temperatures as low as 69 $^{o}$C. A 2 hour long refluxing in n-hexane of the mixture of the fullerene and SWCNT results in a high yield of C$_{60}$,C$_{70}$@SWCNT, fullerene peapod, material. The peapod filling is characterized by TEM, Raman and electron energy loss spectroscopy and X-ray scattering. We applied the method to synthesize the temperature sensitive (N@C$_{60}$:C$_{60}$)@SWCNT as proved by electron spin resonance spectroscopy. The solvent prepared peapod samples can be transformed to double walled nanotubes enabling a high yield and industrially scalable production of DWCNT