Analysis of Power Absorption by Human Tissue in Deeply Implantable Medical Sensor Transponders

The use of sensor transponder systems in medicine opens valuable possibilities in therapy and diagnostics. This chapter is about physical effects by the use of sensor transponder technology for medicine applications, especially for deeply implanted passive powered sensor transponders. This chapter will inform about present and future applications. The influence of human body on the energy transmission in a sensor transponder system is shown. The dielectrical properties of human tissue are discussed. A way how to estimate losses in an analytical way and with the use of a 3D FTDT method is presented. Finally, a design example of an energy transmission for a sensor transponder is shown with a calculation of the optimal frequency and experimental results

Übertragungstechnik für passive Sensortransponder in der Medizin

Durch Sensortransponder-Systeme eröffnen sich viele neue Anwendungen in Medizin und Technik. Passive Sensortransponder benötigen dabei keine eigene Energieversorgung und sind daher insbesondere für die Implantation im menschlichen Körper geeignet. Bisher wurde bereits existierende Transpondertechnik verwendet und lediglich um eine Sensorfunktionalität erweitert. Diese Sensortransponder-Systeme sind beispielsweise bei der Therapie von Herz-Kreislauferkrankungen von besonderem Interesse. Jedoch ist der Einsatz von Sensortransponder-Systemen tief im menschlichen Körper aufgrund technischer Grenzen der Transpondertechnik bisher nicht möglich. In dieser Arbeit werden Möglichkeiten aufgezeigt, diese technischen Grenzen zu erweitern. Durch ein neues Übertragungsverfahren für Energie und Daten eröffnen sich so viele neue Einsatzmöglichkeiten für diese Technik. Zunächst wird der Einfluss des menschlichen Körpers auf die Energieübertragung zu einem passiven Transponder untersucht. Dabei wird eine Frequenz ermittelt, bei der die besten Ergebnisse zur Energiereichweite erzielt werden können. Ein einschränkender Faktor bei bisherigen Systemen ist häufig die geringe Lesereichweite. Dabei kann das Datensignal des Transponders im Empfänger nicht mehr rekonstruiert werden, auch wenn die Energiereichweite noch nicht ausgeschöpft ist. In dieser Arbeit wurden Ursachen analysiert und Verbesserungsmöglichkeiten diskutiert. Eine neue Antenne und ein neuartiges Übertragungsverfahren lösen dieses Problem. Durch die Vorteile der in dieser Arbeit entwickelten Methode ist es schließlich möglich die Lesereichweite bis zur Energiereichweite zu erweitern

First Impressions are More Important than Early Intervention Qualifying Broken Windows Theory in the Lab

Broken Windows: the metaphor has changed New York and Los Angeles. Yet it is far from undisputed whether the broken windows policy was causal for reducing crime. In a series of lab experiments we put two components of the theory to the test. We show that first impressions and early punishment of antisocial behaviour are independently and jointly causal for cooperativeness. The effect of good first impressions and of early vigilance cannot be explained with, but adds to, participants’ initial level of benevolence. Mere impression management is not strong enough to maintain cooperation. Cooperation stabilizes if good first impressions are combined with some risk of sanctions. Yet if we control for first impressions, early vigilance only has a small effect. The effect vanishes over time.

Stimuli-Responsive Polyguanidino-Oxanorbornene Membrane Transporters as Multicomponent Sensors in Complex Matrices

We introduce guanidinium-containing synthetic polymers based on polyguanidino-oxanorbornenes (PGONs) as anion transporters in lipid bilayers that can be activated and inactivated by chemical stimulation. According to fluorogenic anion export experiments with vesicles, PGON transporters are most active in neutral bilayers near their phase transition, with EC50's in the nanomolar range. Six times higher effective transporter concentrations were measured with aminonaphthalene-1,3,6-trisulfonate than with 5(6)-carboxyfluorescein, demonstrating the importance of anion binding for transport and excluding nonspecific efflux. Negative surface potentials efficiently annihilate transport activity, while inside-negative membrane potentials slightly increase it. These trends demonstrate the functional importance of counterions to hinder the binding of hydrophilic counterions and to minimize the global positive charge of the transporter-counterion complexes. Strong, nonlinear increases in activity with polymer length reveal a significant polymer effect. Overall, the characteristics of PGONs do not match those of similar systems (for example, polyarginine) and hint toward an interesting mode of action, clearly different from nonspecific leakage caused by detergents. The activity of PGONs increases in the presence of amphiphilic anions such as pyrenebutyrate (EC50 = 70 microM), while several other amphiphilic anions tested were inactive. PGONs are efficiently inactivated by numerous hydrophilic anions including ATP (IC 50 = 150 microM), ADP (IC50 = 460 microM), heparin (IC50 = 1.0 microM), phytate (IC50 = 0.4 microM), and CB hydrazide (IC50 = 26 microM). The compatibility of this broad responsiveness with multicomponent sensing in complex matrices is discussed and illustrated with lactate sensing in sour milk. The PGON lactate sensor operates together with lactate oxidase as a specific signal generator and CB hydrazide as an amplifier for covalent capture of the pyruvate product as CB hydrazone (IC50 = 1.5 microM)

Vergleich der signalverstärkten farbkodierten Duplexsonographie fokaler Leberläsionen mit anderen bildgebenden Verfahren: eine Betrachtung anhand des Patientengutes der Universitätsklinik Rostock

Aus der spezifischen Gewebe- und Gefäßstruktur resultiert ein veränderliches Echoverhalten mit charakterisierenden Merkmalen und typischem Anflutungsverhalten. Die Ergebnisse der signalverstärken FKDS (Levovist®) wurden mit der Angiographie, CT und MRT bzw. der Histologie verglichen. Durch die Kombination von Aussagen einer dynamischen und schnittbildgebenden Untersuchung und die Anwendung eines Signalverstärkers erreicht die FKDS eine höhere diagnostische Sicherheit und kann so an die Aussagekraft einer CT oder MRT bzw. der Angiographie heranreichen

Time-resolved Monitoring of Enzyme Activity with Ultrafast Hyper-CEST Spectroscopy

We propose a method to dynamically monitor the progress of an enzymatic reaction using NMR of hyperpolarized ^(129)Xe in a host-guest system. It is based on a displacement assay originally designed for fluorescence experiments that exploits the competitive binding of the enzymatic product on the one hand and a reporter dye on the other hand to a supramolecular host. Recently, this assay has been successfully transferred to NMR, using xenon as a reporter, cucurbit[6]uril as supramolecular host, and Hyper-CEST as detection technique. Its advantage is that the enzyme acts on the unmodified substrate and only the product is detected through immediate inclusion into the host. We here apply a method that drastically accelerates the acquisition of Hyper-CEST spectra in vitro using magnetic field gradients. This allows monitoring the dynamic progress of the conversion of lysine to cadaverine with a temporal resolution of ~30 s. Moreover, the method only requires to sample the very early onset of the reaction (<0.5 % of substrate conversion where the host itself is required only at μM concentrations) at comparatively low reaction rates, thus saving enzyme material and reducing NMR acquisition time. The obtained value for the specific activity agrees well with previously published results from fluorescence assays. We furthermore outline how the Hyper-CEST results correlate with xenon T_2 measurements performed during the enzymatic reaction. This suggests that ultrafast Hyper-CEST spectroscopy can be used for dynamically monitoring enzymatic activity with NMR

Time Scales of Auditory Habituation in the Amygdala and Cerebral Cortex

Habituation is a fundamental form of learning manifested by a decrement of neuronal responses to repeated sensory stimulation. In addition, habituation is also known to occur on the behavioral level, manifested by reduced emotional reactions to repeatedly presented affective stimuli. It is, however, not clear which brain areas show a decline in activity during repeated sensory stimulation on the same time scale as reduced valence and arousal experience and whether these areas can be delineated from other brain areas with habituation effects on faster or slower time scales. These questions were addressed using functional magnetic resonance imaging acquired during repeated stimulation with piano melodies. The magnitude of functional responses in the laterobasal amygdala and in related cortical areas and that of valence and arousal ratings, given after each music presentation, declined in parallel over the experiment. In contrast to this long-term habituation (43 min), short-term decreases occurring within seconds were found in the primary auditory cortex. Sustained responses that remained throughout the whole investigated time period were detected in the ventrolateral prefrontal cortex extending to the dorsal part of the anterior insular cortex. These findings identify an amygdalocortical network that forms the potential basis of affective habituation in human