Transporting and Storing High-Level Nuclear Waste in the U.S.—Insights from a Mathematical Model

The nuclear industry in the United States of America has accumulated about 70,000 metric tons of high-level nuclear waste over the past decades; at present, this waste is temporarily stored close to the nuclear power plants. The industry and the Department of Energy are now facing two related challenges: (i) will a permanent geological repository, e.g., Yucca Mountain, become available in the future, and if yes, when?; (ii) should the high-level waste be transported to interim storage facilities in the meantime, which may be safer and more cost economic? This paper presents a mathematical transportation model that evaluates the economic challenges and costs associated with different scenarios regarding the opening of a long-term geological repository. The model results suggest that any further delay in opening a long-term storage increases cost and consolidated interim storage facilities should be built now. We show that Yucca Mountain’s capacity is insufficient and additional storage is necessary. A sensitivity analysis for the reprocessing of high-level waste finds this uneconomic in all cases. This paper thus emphasizes the urgency of dealing with the high-level nuclear waste and informs the debate between the nuclear industry and policymakers on the basis of objective data and quantitative analysis.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität BerlinBMBF, 01LN1704A, Nachwuchsgruppe Globaler Wandel: CoalExit - Die Ökonomie des Kohleausstiegs - Identifikation von Bausteinen für Rahmenpläne zukünftiger regionaler Strukturwande

Plant mechanosensitive ion channels: an ocean of possibilities

Mechanosensitive ion channels, transmembrane proteins that directly couple mechanical stimuli to ion flux, serve to sense and respond to changes in membrane tension in all branches of life. In plants, mechanosensitive channels have been implicated in the perception of important mechanical stimuli such as osmotic pressure, touch, gravity, and pathogenic invasion. Indeed, three established families of plant mechanosensitive ion channels play roles in cell and organelle osmoregulation and root mechanosensing - and it is likely that many other channels and functions await discovery. Inspired by recent discoveries in bacterial and animal systems, we are beginning to establish the conserved and the unique ways in which mechanosensitive channels function in plants

Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences

Plants can use ammonium (NH4+) as the sole nitrogen source, but at high NH4+ concentrations in the root medium, particularly in combination with a low availability of K+, plants suffer from NH4+ toxicity. To understand the role of K+ transporters and non-selective cation channels in K+/NH4+ interactions better, growth, NH4+ and K+ accumulation and the specific fluxes of NH4+, K+, and H+ were examined in roots of barley (Hordeum vulgare L.) and Arabidopsis seedlings. Net fluxes of K+ and NH4+ were negatively correlated, as were their tissue concentrations, suggesting that there is direct competition during uptake. Pharmacological treatments with the K+ transport inhibitors tetraethyl ammonium (TEA+) and gadolinium (Gd3+) reduced NH4+ influx, and the addition of TEA+ alleviated the NH4+-induced depression of root growth in germinating Arabidopsis plants. Screening of a barley root cDNA library in a yeast mutant lacking all NH4+ and K+ uptake proteins through the deletion of MEP1–3 and TRK1 and TRK2 resulted in the cloning of the barley K+ transporter HvHKT2;1. Further analysis in yeast suggested that HvHKT2;1, AtAKT1, and AtHAK5 transported NH4+, and that K+ supplied at increasing concentrations competed with this NH4+ transport. On the other hand, uptake of K+ by AtHAK5, and to a lesser extent via HvHKT2;1 and AtAKT1, was inhibited by increasing concentrations of NH4+. Together, the results of this study show that plant K+ transporters and channels are able to transport NH4+. Unregulated NH4+ uptake via these transporters may contribute to NH4+ toxicity at low K+ levels, and may explain the alleviation of NH4+ toxicity by K+

Opening and Closing of KcnkØ Potassium Leak Channels Is Tightly Regulated

Potassium-selective leak channels control neuromuscular function through effects on membrane excitability. Nonetheless, their existence as independent molecular entities was established only recently with the cloning of KCNKØ from Drosophila melanogaster. Here, the operating mechanism of these 2 P domain leak channels is delineated. Single KCNKØ channels switch between two long-lived states (one open and one closed) in a tenaciously regulated fashion. Activation can increase the open probability to ∼1, and inhibition can reduce it to ∼0.05. Gating is dictated by a 700-residue carboxy-terminal tail that controls the closed state dwell time but does not form a channel gate; its deletion (to produce a 300-residue subunit with two P domains and four transmembrane segments) yields unregulated leak channels that enter, but do not maintain, the closed state. The tail integrates simultaneous input from multiple regulatory pathways acting via protein kinases C, A, and G

Investigations on the Biosynthesis of Ansamitocin and Production of Secondary Metabolites by microbial Interaction

Die vorliegende Arbeit ist in vier Themenabschnitte gegliedert. Das Hauptaugenmerk befasst sich mit Biosyntheseuntersuchungen zum Ansamitocin, einem hochpotenten, cytostatischen Naturstoff der Maytansinfamilie. Zum Einen erfolgte heterologe Expression verschiedener Diketidvorläufer des Ansamitocin P-3 in Corynebakterium glutamicum. Mittels Fütterungsexperimenten unter Verwendung stammeigener sowie stammfremder Startereinheiten des Ansamitocins konnten einige Diketide per HPLC-ESI-MS nachgewiesen werden. Zum Anderen war die Vorläufer-dirigierte Biosynthese durch Fütterung verschiedener stammfremder Biosynthesevorläufer zum 20-Desmethoxyansamitocin mit der Actinosynnema pretiosum-Knockout-Mutante HGF073 ein Teil der Untersuchungen zur Ansamitocin-Biosynthese. Dieses Derivat konnte im Rahmen dieser Arbeit erstmals durch Optimierung der Fermentations-, Fütterungs- und Isolierungsmethoden in ausreichender Menge für umfassende analytische Zwecke bereitgestellt und die biologische Aktivität vergleichend zum Ansamitocin P-3 getestet werden.Ein zweiter Themenbereich dieser Arbeit befasst sich ebenfalls mit der Substanzklasse der Maytansine. Der aus einer maytansinproduzierenden Pflanze isolierte Stamm Kitasatospora putterlickiae F98-18 (AK LEISTNER, Bonn) reagiert bei Interaktion mit dem Schimmelpilz Mucor sp. mit der Produktion eines neuen Metaboliten. Bei den umfassenden Isolierungsarbeiten zeigte sich ein rascher Zerfall dieses neuen Metaboliten. Als offensichtliches Zerfallsprodukt konnte Anthranilsäure identifiziert werden.Der dritte Zweig dieser Arbeit besteht aus Untersuchungen des Stammes Streptomyces antimycoticus FZB53 (überlassen von E. KOCH, Biologische Bundesanstalt für Land- und Forstwirtschaft (BBA), Darmstadt), der in einem Screeningprogramm der BBA gegen verschiedene phytopathogene Bakterien und Pilze aufgrund seiner starken Aktivität aufgefallen ist. Die Isolierung des aktiven Prinzips ergab nach Fermentationsvariation überraschenderweise zwei Substanzen: Einen Polyether aus der Nigericin-Familie sowie Geldanamycin.Ein viertes Themengebiet dieser Arbeit beschäftigt sich mit der Wirkung des Pilzes Piriformospora indica auf Pflanzen, welcher in Studien (AK KARLOVSKY) ein verzweigtes Wurzelwachstum der Modellpflanze Arabidopsis thaliana ausgelöst hat. Als verantwortlicher Metabolit konnte mithilfe von MS-Analyse der Pilz-Kulturfiltrat-Extrakte das Pflanzenhormon Auxin nachgewiesen werden

Freedom Gas to Europe: Scenarios Analyzed Using the Global Gas Model

State-of-the-art, open access numerical modeling of imperfectly competitive energy markets offers a sound and transparent way to address topical research questions in energy and commodity markets. We use an open access equilibrium model, the Global Gas Model (GGM), and sector-specific, politically motivated scenarios to investigate the prospects for sales of liquefied natural gas (LNG) from the U.S. into the European energy market. We discuss the risks and opportunities for U.S. LNG and derive implications for policy, business, and finance in the energy sector. We find that Europe is not an attractive market for US LNG in the base case and in scenarios of moderate support of U.S. LNG flows into Europe. In these scenarios, Asia offers higher prices for US LNG and draws substantially higher import volumes. Our modeling results show that the interconnectedness of global gas markets due to an abundance of LNG import capacity in Europe and other regions—particularly Asia—allows for adjustments to global trade patterns that mitigate the consequences of regional disturbances

Molecular mechanisms and regulation of plant ion channels

Plant ion channel activities are rapidly modulated in response to several environmental and endogenous stimuli. Electrophysiological as well as pharmacological studies provide strong evidence that ion channels are essential for the induction of specific cellular responses and that they are themselves subject to regulation by a variety of cellular factors. Genes anal cDNAs of several plant ion channels have been identified in recent years giving access to molecular mechanisms of such regulatory processes. Cloned inwardly rectifying potassium channels have been investigated in various heterologous expression systems. Two other ion channel classes, namely members of the 'two-pore' K+ channel family as well as of the anion-conducting chloride channel (CIC) family, have been cloned, but a direct link to corresponding plasma membrane or endomembrane ion channel conductances has not been demonstrated yet. Analysis of cellular expression patterns of plant ion channel genes in combination with transgenic approaches now gives access to a detailed ex planta/in planta correlation of channel function, as has recently been demonstrated for proteins of the K-in(+) channel family. This review summarizes current knowledge on molecular structures and some features of structure-function relationships of plant ion channels

New structure and function in plant K+ channels: KCO1, an outward rectifier with a steep Ca2+ dependency.

Potassium (K+) channels mediating important physiological functions are characterized by a common pore-forming (P) domain. We report the cloning and functional analysis of the first higher plant outward rectifying K+ channel (KCO1) from Arabidopsis thaliana. KCO1 belongs to a new class of 'two-pore' K+ channels recently described in human and yeast. KCO1 has four putative transmembrane segments and tandem calcium-binding EF-hand motifs. Heterologous expression of KCO1 in baculovirus-infected insect (Spodoptera frugiperda) cells resulted in outwardly rectifying, K+-selective currents elicited by depolarizing voltage pulses in whole-cell measurements. Activation of KCO1 was strongly dependent on the presence of nanomolar concentrations of cytosolic free Ca2+ [Ca2+]cyt. No K+ currents were detected when [Ca2+]cyt was adjusted to <150 nM. However, KCO1 strongly activated at increasing [Ca2+]cyt, with a saturating activity observed at approximately 300 nM [Ca2+]cyt. KCO1 single channel analysis on excised membrane patches, resulting in a single channel conductance of 64 pS, confirmed outward rectification as well as Ca2+-dependent activation. These data suggest a direct link between calcium-mediated signaling processes and K+ ion transport in higher plants. The identification of KCO1 as the first plant K+ outward channel opens a new field of structure-function studies in plant ion channels