The Role of Natural Calcium Oxalate Crystals in Plant Defense Against Chewing Insects

Calcium oxalate is the most abundant insoluble mineral found in plants and it is common among many plant families. Calcium oxalate crystals in plants can appear as irregular rectangles, spiked balls, or needles. The formidable appearance of these crystals has lead to speculation that they might serve as a form of pest control by deterring chewing insects. We utilized mutant plant lines to assess the effects of plant calcium oxalate crystals on the survival and feeding habits of chewing insects. We have taken advantage of calcium oxalate-deficient (cod) mutants of the barrel medic, Medicago truncatula Calcium oxalate crystals accumulate in wildtype M. truncatula leaves along the vascular strands of secondary veins. Results demonstrate that beet army-worm, Spodoptera exigua, larvae that feed on M. truncatula cod mutants with reduced levels of calcium oxalate crystals grow faster and larger than insects that feed on normal wildtype plants. Pupae formed by larvae raised on cod plants are significantly larger than those raised on the wildtype plants. The results of two-way choice tests indicate that older( 4\u27h instar or later) S. exigua larvae prefer to feed on leaves lacking calcium oxalate, whereas young larvae (2nd instar or earlier) show no feeding preference. This development-specific feeding preference is perhaps due to the feeding habits of the herbivore; young larvae typically feed between secondary veins, away from areas where the calcium oxalate crystals are localized. Accumulation of RNA transcripts encoding wound-inducible gene products is normal in the cod mutants, suggesting that these plants are not altered in their ability to sense or respond to wounding by insect herbivores. Because calcium oxalate crystals seem to serve as a feeding deterrent to insects, understanding how they are made and distributed could ultimately lead to novel, environmentally sound strategies for improving insect resistance in crop plant species

A 3–D Chemistry Transport Model for Titan’s Thermosphere

A 3–D model of the atmospheric chemistry of Saturn's moon Titan has been constructed which incorporates some of the latest advances of 1–D Titan chemistry models as well as 3–D GCMs for Titan in simplified-enough way that integrations covering many Earth years are numerically feasible. The thermosphere, with its shorter transport and chemistry time scales, reasonably simple circulation, and basic 3–D coverage of the moon with Cassini INMS observations, is the primary focus of this study. The model is first validated as far as possible against the observations, showing that it performs quite well for most species, given the general margins of error and uncertainties inherent in Titan modeling. Winds are not seen to have the same overriding influence on concentrations as an earlier study using a pre-Cassini GCM wind field suggested (Doege et al., 2008), but nonetheless many species such as ethane exhibit sensitivity to advection and a chemistry transport model with advection does improve the fit to observations over a model with only diffusive transport. Overall it is found that state-of-the-art GCMs for Titan deliver winds realistic enough for the chemistry model to correctly reproduce the basic shapes of chemical species distributions with a variety of chemical lifetimes. In some instances, the limitations of the Cassini measurements become apparent and model results point to difficulties and uncertainties with the INMS data retrieval process (e.g. for C4H6) that would be less conspicuous by analyzing only Cassini observations without a model. Then some specific scientific topics are explored, namely the influence of the Solar cycle and of vertically-propagating tidal waves. As the Cassini measurements so far cover a period of decreasing and generally below-average Solar activity, Solar minimum conditions are particularly of interest, because chemistry models for Titan have so far normally been run for Solar average UV output. It is found that some species such as propane react strongly to changes in Solar irradiance and the resulting concentrations of primary photolysis products. However, chemical distributions remain recognizable from the Control experiment and accounting for the Solar cycle does not resolve remaining issues with chemistry schemes for Titan's atmosphere. Atmospheric tidal waves which are forced mainly in the lower atmosphere also influence the thermosphere significantly, therefore the possbility that chemical concentrations might be measurably affected by these waves is explored with the model. The conclusion is drawn that the effects of such waves through their temperature perturbations alone, while they are easily detectable in the model, might be too weak to identify them in Cassini measurements

Convex risk measures for portfolio optimization and concepts of flexibility

Due to their axiomatic foundation and their favorable computational properties convex risk measures are becoming a powerful tool in financial risk management. In this paper we will review the fundamental structural concepts of convex risk measures within the framework of convex analysis. Then we will exploit it for deriving strong duality relations in a generic portfolio optimization context. In particular, the duality relationship can be used for designing new, efficient approximation algorithms based on Nesterov's smoothing techniques for non-smooth convex optimization. Furthermore, the presented concepts enable us to formalize the notion of flexibility as the (marginal) risk absorption capacity of a technology or (available) resource

Risk management of power portfolios and valuation of flexibility

Risk management by applying operational flexibility is becoming a key issue for production companies. This paper discusses how a power portfolio can be hedged through its own production assets. In particular we model operational flexibility of a hydro pump storage plant and show how to dispatch it to hedge against adverse movements in the portfolio. Moreover, we present how volume risk, which is not hedgeable with standard contracts from power exchanges, can be managed by an intelligent dispatch policy. Despite the incompleteness of the market we quantify the value of this operational flexibility in the framework of coherent risk measure

Estimativa da taxa natural de desemprego do Brasil a partir de uma análise da estrutura do mercado de trabalho

Resumo: O presente trabalho se propõe a estimar a taxa natural de desemprego do Brasil a partir da análise da estrutura do mercado de trabalho, em comparação às estimativas baseadas no aparato teórico da Curva de Phillips. Para tanto inicialmente são analisadas as principais teorias produzidas sobre o desemprego, como a teoria de salário eficiência, de insidersoutsiders e formação de sindicatos e as consequências de benefícios oficiais como estabelecimento de um salário mínimo e os pagamentos de seguro desemprego. Estas teorias explicam o comportamento otimizador dos agentes e sua consequência para a eterminação do salário de equilíbrio. A taxa natural de desemprego é uma variável não observável, estimada a partir do sistema de equações construído de acordo com o modelo de barganha salarial de Blanchard. Neste sistema de equações são inseridas variáveis estruturais do mercado de trabalho, de acordo com a teoria apresentada no início do trabalho. A estimação empírica é feita por meio da ransformação das equações em forma de estado espaço, cuja estimação é feita por máxima verossimilhança com informação completa. O trabalho contorna o problema da mudança de metodologia da principal pesquisa do emprego do país, a PME, em 2002 de acordo com o sugerido por da Silva Filho (2008). Para fins de comparação de resultados também é feita a estimação da NAIRU, pela metodologia mais radicional da Curva de Phillips. Os resultados mostram aderência da taxa observada de desemprego à taxa natural, embora esta apresente grande variabilidade e determinados parâmetros em desacordo com o reconizado pela teoria econômica

Bewältigungsverhalten bei Eltern von Kindern mit geistiger Behinderung: Quantitative und qualitative Untersuchung von Bewältigungsmustern

In der vorliegenden Untersuchung wurde überprüft, welche Bewältigungsstrategien Eltern von Kindern mit einer geistigen Behinderung in ihrem Alltag anwenden. Dabei lag der Fokus auf der Frage, welche Bewältigungsmuster, also Kombinationen verschiedener Strategien, unterschieden werden können, und wodurch diese gekennzeichnet sind. Das Bewältigungsverhalten wurde mit dem Fragebogen Soziale Orientierungen von Eltern behinderter Kinder (SOEBEK, Krause & Petermann, 1997) erhoben. Nach einer kurzen Einführung (Kapitel 1) fasst der Theorieteil der Arbeit (Kapitel 2) den gegenwärtigen Forschungsstand zur elterlichen Anpassung an die geistige Behinderung eines Kindes zusammen. Aus einer resilienzorientierten Perspektive ist es von Interesse, mit welchen Haltungen, kognitiven, emotionalen, aber auch Handlungsstrategien Eltern den Belastungen und Herausforderungen entgegentreten, die sich durch die geistige Behinderung ihres Kindes ergeben können. Der empirische Teil der Arbeit gliedert sich in drei Abschnitte. Im ersten Studienteil (Kapitel 3) wurden mittels Clusteranalysen bei den Eltern von 325 Kindern mit einer geistigen Behinderung verschiedene Muster von Bewältigungsverhalten differenziert. Anschließend wurde untersucht, welche weiteren Charakteristika Familien mit den jeweiligen Bewältigungsmustern aufweisen, sowohl soziodemographisch als auch hinsichtlich Familienfunktionalität, Familienkohärenzgefühl und Stressbelastung. Zur qualitativen Vertiefung der Ergebnisse wurden im zweiten Studienteil (Kapitel 4) teilstrukturierte Interviews mit den Eltern von fünf Kindern mit geistiger Behinderung durchgeführt, deren Bewältigungsstrategien den zuvor charakterisierten Mustern entsprachen. In einem dritten Untersuchungsteil (Kapitel 5) wurden Fachpersonen befragt, die in Beratungseinrichtungen für Eltern von Kindern mit geistiger Behinderung arbeiten. Ihnen wurden die zuvor analysierten Bewältigungsmuster vorgelegt und um eine Einschätzung des jeweiligen Beratungsbedarfs gebeten. Eine Integration der Ergebnisse aus den drei Studienteilen, im Sinne von Schlussfolgerungen für die Beratungspraxis schließt sich in Kapitel 6 an. Ein Fazit findet sich in Kapitel 7

Rot- und Braunalgen: Rote Liste und Artenliste Sachsens

Rot- und Braunalgen gelten als Indikatorarten für die Gewässergüte. Durch die Abnahme vorrangig der saprobiellen Belastung der Gewässer in Sachsen nach 1990 hat sich ihre Bestandssituation allgemein verbessert. Dennoch sind fast drei Viertel der 17 in Sachsen vorkommenden Rot- und Braunalgenarten als ausgestorben oder gefährdet einzuschätzen. Die Rote Liste enthält eine Checkliste, Verbreitungskarten und gibt einen Überblick über die Gefährdungssituation der einzelnen Arten

Rote Liste und Artenliste Sachsens - Armleuchteralgen

Bei den Armleuchteralgen (Characeae) handelt es sich um eine gut abgrenzbare Gruppe von Wasserpflanzen, die sich hervorragend zur Bioindikation von Gewässern eignet. Nach Erscheinen der letzten Roten Liste und Artenliste Sachsens (2008) konnte der Kenntnisstand über diese Artengruppe in Sachsen deutlich erweitert werden. Die aktuelle Rote Liste und Artenliste Sachsens – Armleuchteralgen wurde gemeinsam von LfULG und BfUL herausgegeben. Redaktionsschluss: 31.01.201