Two alpha(2)-adrenergic receptor subtypes, alpha(2A) and alpha(2C), inhibit transmitter release in the brain of gene-targeted mice

alpha(2)-Adrenergic receptors play an essential role in regulating neurotransmitter release from sympathetic nerves and from adrenergic neurons in the CNS. However, the role of each of the three highly homologous alpha(2)-adrenergic receptor subtypes (alpha(2A), alpha(2B), alpha(2C)) in this process has not been determined unequivocally. To address this question, the regulation of norepinephrine and dopamine release was studied in mice carrying deletions in the genes encoding the three alpha(2)-adrenergic receptor subtypes. Autoradiography and radioligand binding studies showed that alpha(2)-receptor density in alpha(2A)-deficient brains was decreased to 9 +/- 1% of the respective wild-type value, whereas alpha(2)-receptor levels were reduced to 83 +/- 4% in alpha(2C)-deficient mice. These results indicate that approximately 90% of mouse brain alpha(2)-receptors belong to the alpha(2A) subtype and 10% are alpha(2C)-receptors. In isolated brain cortex slices from wild-type mice a non-subtype-selective alpha(2)-receptor agonist inhibited release of [(3)H]norepinephrine by maximally 96%. Similarly, release of [(3)H]dopamine from isolated basal ganglion slices was inhibited by 76% by an alpha(2)-receptor agonist. In alpha(2A)-receptor-deficient mice, the inhibitory effect of the alpha(2)-receptor agonist on norepinephrine and dopamine release was significantly reduced but not abolished. Only in tissues from mice lacking both alpha(2A)- and alpha(2C)-receptors was no alpha(2)-receptor agonist effect on transmitter release observed. The time course of onset of presynaptic inhibition of norepinephrine release was much faster for the alpha(2A)-receptor than for the alpha(2C)-subtype. After prolonged stimulation with norepinephrine, presynaptic alpha(2C)-adrenergic receptors were desensitized. From these data we suggest that two functionally distinct alpha(2)-adrenergic receptor subtypes, alpha(2A) and alpha(2C), operate as presynaptic inhibitory receptors regulating neurotransmitter release in the mouse CNS

Semiklassische Quantisierung chaotischer Billardsysteme mit C4v-Symmetrie

Die Arbeit beschäftigt sich mit einem System mit C4v-Symmetrie - dem Hyperbelbillard. Die grundlegenden Ideen der Bahnsuche und die Eigenschaften des Systems werden in Kapitel 2 besprochen. Sie bilden die Voraussetzungen für die semiklassische Quantisierung. Kapitel 3 führt in die semiklassische Theorie ein und schließt mit einigen quantenmechanischen Betrachtungen. Das "Pade-Verfahren", angewandt in Kapitel 4, ist das erste semiklassische Verfahren, das die Energieeigenwerte ermitteln soll. Die Konvergenzbetrachtungen spielen dabei eine besondere Rolle. In Kapitel 5 wird ein weiteres Verfahren zur semiklassischen Quantisierung besprochen, die "harmonische Inversion", die in Kapitel 6 für die Anwendung auf kreuzkorrelierte Signale erweitert wird. Schließlich werden die Ergebnisse aller Verfahren in Kapitel 7 zusammengefaßt

Two alpha(2)-adrenergic receptor subtypes, alpha(2A) and alpha(2C), inhibit transmitter release in the brain of gene-targeted mice

alpha(2)-Adrenergic receptors play an essential role in regulating neurotransmitter release from sympathetic nerves and from adrenergic neurons in the CNS. However, the role of each of the three highly homologous alpha(2)-adrenergic receptor subtypes (alpha(2A), alpha(2B), alpha(2C)) in this process has not been determined unequivocally. To address this question, the regulation of norepinephrine and dopamine release was studied in mice carrying deletions in the genes encoding the three alpha(2)-adrenergic receptor subtypes. Autoradiography and radioligand binding studies showed that alpha(2)-receptor density in alpha(2A)-deficient brains was decreased to 9 +/- 1% of the respective wild-type value, whereas alpha(2)-receptor levels were reduced to 83 +/- 4% in alpha(2C)-deficient mice. These results indicate that approximately 90% of mouse brain alpha(2)-receptors belong to the alpha(2A) subtype and 10% are alpha(2C)-receptors. In isolated brain cortex slices from wild-type mice a non-subtype-selective alpha(2)-receptor agonist inhibited release of [(3)H]norepinephrine by maximally 96%. Similarly, release of [(3)H]dopamine from isolated basal ganglion slices was inhibited by 76% by an alpha(2)-receptor agonist. In alpha(2A)-receptor-deficient mice, the inhibitory effect of the alpha(2)-receptor agonist on norepinephrine and dopamine release was significantly reduced but not abolished. Only in tissues from mice lacking both alpha(2A)- and alpha(2C)-receptors was no alpha(2)-receptor agonist effect on transmitter release observed. The time course of onset of presynaptic inhibition of norepinephrine release was much faster for the alpha(2A)-receptor than for the alpha(2C)-subtype. After prolonged stimulation with norepinephrine, presynaptic alpha(2C)-adrenergic receptors were desensitized. From these data we suggest that two functionally distinct alpha(2)-adrenergic receptor subtypes, alpha(2A) and alpha(2C), operate as presynaptic inhibitory receptors regulating neurotransmitter release in the mouse CNS

Biokraftstoff-Zertifizierungssysteme ISCC und REDcert : Darstellung, Vergleich und kritische Diskussion

Seit Jahren wird die Biokraftstoffproduktion weltweit mit ihren beiden Haupttreibstoffen, Bioethanol und Biodiesel, immer bedeutender. In 31 Ländern existieren auf nationaler Ebene Beimischungsverpflichtungen für Biokraftstoffe. Die Situation auf dem Biokraftstoffmarkt wird weltweit durch staatliche Förderung beeinflusst. Dies trifft auch auf die Biokraftstoffpolitik der EU zu. Im Jahre 2009 erfolgte die letzte große Änderung dieser Politik, die seit Januar 2011 unter anderem die Nachhaltigkeitszertifizierung von Biokraftstoffen vorschreibt. Die Berücksichtigung des Nachhaltigkeitsgedankens in Verbindung mit der Entwicklung der EU-Biokraftstoffförderung entstand als Folge der Kritik an den Biokraftstoffen: Biokraftstoffe vernichten Regenwald, seien zur Bekämpfung des Klimawandels ungeeignet und lassen die Bevölkerung in Entwicklungsländern hungern. Nach der Darstellung der relevanten rechtlichen Grundlagen und einem Überblick über die Nachhaltigkeitszertifizierung folgt ein Vergleich der beiden bislang in Deutschland zugelassenen Zertifizierungssysteme für Biokraftstoffe International SustainabilityandCarbonCertification (ISCC) und RenewableEnergyDirectiveCertification (REDcert). Beide Systeme werden auf Unterschiede und Gemeinsamkeiten untersucht. Dabei werden jeweils die rechtliche Grundlage, die Biokraftstoff-Nachhaltigkeitsverordnung (Biokraft-NachV), und die von der für Nachhaltigkeitszertifizierungssysteme zuständigen Behörde, der Bundesanstalt für Landwirtschaft und Ernährung (BLE), gemachten Ausführungen zur Biokraft-NachV einbezogen. Anhand der Kritikpunkte, dass Biokraftstoffe klimatisch unsinnig seien, wertvolle Ökosysteme vernichten würden und negative Auswirkungen besonders auf Menschen in Entwicklungsländern hätten, folgt eine kritische Diskussion der Nachhaltigkeitszertifizierungauf Basis der Erneuerbaren Energien Richtlinie (EER), die mögliche Schwächen und Chancen aufzeigt

Diffusion Monte Carlo calculations for the ground states of atoms and ions in neutron star magnetic fields

The diffusion quantum Monte Carlo method is extended to solve the old theoretical physics problem of many-electron atoms and ions in intense magnetic fields. The feature of our approach is the use of adiabatic approximation wave functions augmented by a Jastrow factor as guiding functions to initialize the quantum Monte Carlo prodecure. We calcula te the ground state energies of atoms and ions with nuclear charges from Z= 2, 3, 4, ..., 26 for magnetic field strengths relevant for neutron stars.Comment: 6 pages, 1 figure, proceedings of the "9th International Conference on Path Integrals - New Trends and Perspectives", Max-Planck-Institut fur Physik komplexer Systeme, Dresden, Germany, September 23 - 28, 2007, to be published as a book by World Scientific, Singapore (2008

Energy levels of light atoms in strong magnetic fields

In this review article we provide an overview of the field of atomic structure of light atoms in strong magnetic fields. There is a very rich history of this field which dates back to the very birth of quantum mechanics. At various points in the past significant discoveries in science and technology have repeatedly served to rejuvenate interest in atomic structure in strong fields, broadly speaking, resulting in three eras in the development of this field; the historical, the classical and the modern eras. The motivations for studying atomic structure have also changed significantly as time progressed. The review presents a chronological summary of the major advances that occurred during these eras and discusses new insights and impetus gained. The review is concluded with a description of the latest findings and the future prospects for one of the most remarkably cutting-edge fields of research in science today.Comment: 37 pages, 16 figures, 1 tabl

Crowdsourcing, open innovation and collective intelligence in the scientific method : a research agenda and operational framework

Open Access PublikationThe lonely researcher trying to crack a problem in her office still plays an important role in fundamental research. However, a vast exchange, often with participants from different fields is taking place in modern research activities and projects. In the “Research Value Chain” (a simplified depiction of the Scientific Method as a process used for the analyses in this paper), interactions between researchers and other individuals (intentional or not) within or outside their respective institutions can be regarded as occurrences of Collective Intelligence. “Crowdsourcing” (Howe 2006) is a special case of such Collective Intelligence. It leverages the wisdom of crowds (Surowiecki 2004) and is already changing the way groups of people produce knowledge, generate ideas and make them actionable. A very famous example of a Crowdsourcing outcome is the distributed encyclopedia „Wikipedia“. Published research agendas are asking how techniques addressing “the crowd” can be applied to non-profit environments, namely universities, and fundamental research in general. This paper discusses how the non-profit “Research Value Chain” can potentially benefit from Crowdsourcing. Further, a research agenda is proposed that investigates a) the applicability of Crowdsourcing to fundamental science and b) the impact of distributed agent principles from Artificial Intelligence research on the robustness of Crowdsourcing. Insights and methods from different research fields will be combined, such as complex networks, spatially embedded interacting agents or swarms and dynamic networks. Although the ideas in this paper essentially outline a research agenda, preliminary data from two pilot studies show that nonscientists can support scientific projects with high quality contributions. Intrinsic motivators (such as “fun”) are present, which suggests individuals are not (only) contributing to such projects with a view to large monetary rewards

Experimental Investigation of a SOFC Off-Gas Combustor for Hybrid Power Plant Usage with Low Heating Values Realised by Natural Gas Addition

Rising power demands and the increasing importance of decentralised energy production based on renewable resources require gas turbine systems with flexible energy conversion. Therefore, a suitable hybrid power plant demonstrator with a high temperature fuel cell is being set up at the German Aerospace Centre (DLR). This facility requires burner concepts for low calorific gases capable of combusting the exhaust products of the fuel cell system anode side, here referred to as SOFC (solid oxide fuel cell) off-gas. The combustor behaviour for the demonstrator system is investigated in the current work using an atmospheric combustor test rig at DLR. Additionally, a strategy for stabilisation of the flame in operating points with very low heating values (LHV) via addition of natural gas into the SOFC off-gas before entering the combustor is tested in view of expected impacts on efficiency and other critical system parameters. The combustion system is furthermore investigated in view of CO emissions