Атомно-абсорбционное определение содержания кремния в природных водах

Показана возможность определения содержания кремния в природных и подземных водах различной минерализации методом атомной абсорбции с зеемановской коррекцией неселективного поглощения фона. Высокая селективность метода позволяет определять содержания кремния без предварительной подготовки проб даже в высокоминерализованных образцах подземных вод (в частности, в пластовых водах)

РОЛЬ ПСИХОЛОГИЧЕСКИХ АСПЕКТОВ ПЕДАГОГИЧЕСКОГО ПРОЦЕССА В ФОРМИРОВАНИИ БУДУЩЕГО СПЕЦИАЛИСТА

В условиях формирования в Украине рыночной экономики увеличивается роль системы высшего образования как фактора социально -экономического роста через обеспечение рынка труда молодыми квалифицированными специалистами , произво дительный труд которых влияет на темпы выхода из глубокого кризиса . При вступлении молодежи на рынок труда сложились особенно жесткие условия в связи с ее низкой конкурентоспособностью . Это обусловлено действием следующих факторов : недостатком профессиональных знаний , умений и навыков ; необходимостью предоставления молодым людям дополнительных льгот ; трудо вой нестабильностью молодежи , связанной с увольнениями в связи с призывом в вооруженные силы , уходом на учебу , длительными отпусками в связи с рождением и воспитанием детей ; инфантильностью части молодежи , привыкшей основные жиз ненные блага получать бесплатно от родителей и государства ; несоответствием психологических , мыслительных , поведенческих качеств студентов требованиям , предъявляемым к молодым специалистам

Chemical and natural stressors combined::from cryptic effects to population extinction

In addition to natural stressors, populations are increasingly exposed to chemical pollutants released into the environment. We experimentally demonstrate the loss of resilience for Daphnia magna populations that are exposed to a combination of natural and chemical stressors even though effects on population size of a single stressor were cryptic, i.e. hard to detect statistically. Data on Daphnia population demography and along with model-based exploration of our predator-prey system revealed that direct trophic interactions changed the population size-structure and thereby increased population vulnerability to the toxicant which acts in a size selective manner. Moreover, population vulnerability to the toxicant increases with predator size and predation intensity whereas indirect trait-mediated interactions via predator kairomones may buffer chemical effects to a certain extent. Our study demonstrates that population size can be a poor endpoint for risk assessments of chemicals and that ignoring disturbance interactions can lead to severe underestimation of extinction risk

Sprachliche Verfahren des Wissensmanagements im Kriminalroman : Ein Beitrag zur dynamischen Texttheorie

Für die Textlinguistik ist der Kriminalroman als Untersuchungsgegenstand ausgesprochen lehrreich, weil darin zwei textlinguistische Parameter besonders markant ausgeprägt sind, nämlich der Wissensaufbau und das darauf bezogene Referieren. Ziel der vorliegenden Arbeit ist es, die sprachlichen Verfahren des Wissensmanagements im Kriminalroman aus textlinguistischer Sicht einer pragmatischen und referenzsemantischen Untersuchung zu unterziehen. Dieser Zielsetzung entsprechend werden in der Arbeit unter anderem die folgenden Thesen aufgestellt und anhand ausgewählter Textbeispiele plausibel gemacht: (1) Im Kriminalroman ist ein spezifisches Wissensmanagement nachweisbar, durch welches sich der Kriminalroman von anderen Texttypen unterscheidet, und (2) Die Art und Weise, wie Wissen in Texten typischerweise aufgebaut, strukturiert und vermittelt wird, kann als Spezifikum eines Texttyps gelten. Am Beispiel des Kriminalromans wird gezeigt, dass Formen des krimispezifischen Wissensmanagements und die dafür verwendeten charakteristischen sprachlichen Verfahren zu den konstituierenden Besonderheiten des Texttyps gehören. Als Grundlage für die Untersuchung dient ein Textkorpus mit mehr als 100 deutschsprachigen Krimis, das sowohl Originalwerke als auch Übersetzungen umfasst. Bei der Untersuchung liegt der Fokus vor allem auf Verfahren des systematischen Wissensaufbaus und der Wissensentwicklung sowie dem Zusammenspiel von Wissensvermittlung und Formen des Referierens. Theoretische Grundlage der Arbeit ist eine funktionale und dynamische Texttheorie. Der Ausgangspunkt bildet demnach die Grundidee, dass das Wissensmanagement ein zentraler Aspekt der Textorganisation ist, der eng mit anderen Aspekten zusammenhängt und mit diesen auf vielfältige Weise zusammenwirkt. Ausgehend von den Annahmen, dass die Grundfunktion des Kriminalromans darin besteht, durch die Erzeugung von Spannung den Leser zu unterhalten, und dass Spannungserzeugung im Wesentlichen durch den Wissensaufbau geleistet wird, werden grundlegende Mittel und Strategien des Wissensmanagements im Kriminalroman beschrieben. Zum theoretischen Rahmen der Arbeit gehören auch eine handlungstheoretische Referenztheorie, literaturwissenschaftliche Krimi-Forschung und Erzähltheorien sowie Schreibratgeber für Krimis, in denen erfolgreiche Krimiautoren reflexiv Darstellungsstrategien und Erfolgsrezepte beschreiben. Bei der Untersuchung wird die Ergiebigkeit textlinguistischer Methoden und Ansätze im Zuge einer umfassenden sprachlichen Analyse des Wissensmanagements im Genre Kriminalroman erwiesen. Diese Arbeit stellt insbesondere einen Beitrag zur dynamischen Texttheorie dar. Anhand einer Fallstudie von Andrea Maria Schenkels "Tannöd", bei der das Verfahren der Wissensbuchführung in Form eines Leseprotokolls mit anschließender Mikroanalyse zum Einsatz kommt, werden die Wissensdynamik in "Tannöd" und die jeweils verfügbaren Wissensstände und Wissensressourcen zu unterschiedlichen Text-Zeitpunkten modelliert. Dadurch wird der Grundgedanke einer dynamischen Texttheorie veranschaulicht, nämlich dass sich mit jedem neuen "Zug", jeder neuen Texthandlung, der "Spielstand" bzw. Wissensstand verändert. Diese Fallstudie belegt, dass der Kriminalroman ein besonders markantes Beispiel für den dynamischen Aspekt des Wissensaufbaus in Texten ist. Der Wissensaufbau ist ein Parameter der Textorganisation, der bisher in der Diskussion von Texttypologien noch nicht ausreichend Beachtung gefunden hat. Die Untersuchung von Krimis ist damit auch ein besonders lohnendes Untersuchungsfeld für die Weiterentwicklung der textlinguistischen Theoriebildung

Third order nonlinear susceptibility of InN at near band-gap wavelengths

The authors report room-temperature measurements of the third order nonlinear susceptibility modulus ∫ (3) ∫ of thick (∼600 nm) InN layers. Transmission measurements provide a room-temperature value for the optical band gap of the samples slightly above 1500 nm. Third order nonlinear optical susceptibility has been measured using degenerate four wave mixing experiments at wavelengths near and above band gap. ∫ (3) ∫ values of (4.2-10) × 10-10 esu were measured at this wavelength range. The associated relaxation time of the generated population grating at 1500 nm was measured. The obtained value of 4.8 ps is consistent with a nonradiative recombination mechanism. © 2007 American Institute of Physics.Peer Reviewe

Double trouble at high density::Cross-level test of ressource-related adaptive plasticity and crowding-related fitness.

Population size is often regulated by negative feedback between population density and individual fitness. At high population densities, animals run into double trouble: they might concurrently suffer from overexploitation of resources and also from negative interference among individuals regardless of resource availability, referred to as crowding. Animals are able to adapt to resource shortages by exhibiting a repertoire of life history and physiological plasticities. In addition to resource-related plasticity, crowding might lead to reduced fitness, with consequences for individual life history. We explored how different mechanisms behind resource-related plasticity and crowding-related fitness act independently or together, using the water flea Daphnia magna as a case study. For testing hypotheses related to mechanisms of plasticity and crowding stress across different biological levels, we used an individual-based population model that is based on dynamic energy budget theory. Each of the hypotheses, represented by a sub-model, is based on specific assumptions on how the uptake and allocation of energy are altered under conditions of resource shortage or crowding. For cross-level testing of different hypotheses, we explored how well the sub-models fit individual level data and also how well they predict population dynamics under different conditions of resource availability. Only operating resource-related and crowding-related hypotheses together enabled accurate model predictions of D. magna population dynamics and size structure. Whereas this study showed that various mechanisms might play a role in the negative feedback between population density and individual life history, it also indicated that different density levels might instigate the onset of the different mechanisms. This study provides an example of how the integration of dynamic energy budget theory and individual-based modelling can facilitate the exploration of mechanisms behind the regulation of population size. Such understanding is important for assessment, management and the conservation of populations and thereby biodiversity in ecosystems

Modelling foraging behaviour in the insect predator Notonecta maculata using the individuals approach

Predation is considered to significantly alter dynamics and diversity of aquatic communities. The current thesis was therefore aimed at assessing mechanisms behind the predation by the backswimmer Notonecta maculata in the context of ecology, ethology and physiology. Moreover, a foraging model was developed, parameterized and evaluated on the basis of individual foraging behaviour, for application in ecology and ecotoxicology. An iterative process of model development thereby provided insights into several research questions. In a first step the ecological and ecotoxicological relevance of backswimmer predation was examined. Therefore, population dynamics of Daphnia magna was observed under predation pressure, xenobiotic stress and a combination of both predation and chemical disturbance. The experiment revealed that size selective predation of the backswimmers did alter population demography, which in turn led to higher vulnerability of D. magna population to toxic stress. The results mentioned above have raised the question to what extend the functional response and size selectivity of juvenile backswimmers changes with predator instar. Therefore, ecological parameters that were considered influential in prey selection were quantified experimentally and subsequently led to the parameterization of an individuals model to be used for the prediction of predation rates. Testing the model against independent data revealed that prey selection in backswimmer might not be determined by active preference, but by passive selectivity mediated by variations in the components of predation. Application of the model revealed that predation rates in juvenile backswimmers are reduced under dark conditions compared to light. These differences are accounted for by the presence/absence of light and are not regulated by any endogenous circadian rhythm. Behavioural observations led to the conclusion that in the dark backswimmers probably detect prey items at a shorter distance as compared to light and that the resulting reduction in the encounter rate is compensated by gaining a higher amount of food per item during a lengthier, more thorough handling of the prey. Comparing model output to independent functional response data did support this hypothesis. In order to account for variations in food availability, and thus allow for long term prediction of predation rates, the model was extended by a physiological component. Therefore, behavioural observations on the components of predations were correlated with gut state of the predator. Moreover, the empirical results showed that food-deprived backswimmers attack their prey more frequently and that they extract more biomass from a single prey item than their well-fed conspecifics do. Model application provided further evidence for compensatory feeding under variable environmental conditions. In the current study, proximate factors in the foraging behaviour were identified and implemented in a simulation model. The model developed here is able to adequately predict size selectivity and long term predation rates of juvenile backswimmers under laboratory conditions. A major future task will be the generalization of mechanistic rules that will allow predictions for a broad range of species

Modelling foraging behaviour in the insect predator Notonecta maculata using the individuals approach

Predation is considered to significantly alter dynamics and diversity of aquatic communities. The current thesis was therefore aimed at assessing mechanisms behind the predation by the backswimmer Notonecta maculata in the context of ecology, ethology and physiology. Moreover, a foraging model was developed, parameterized and evaluated on the basis of individual foraging behaviour, for application in ecology and ecotoxicology. An iterative process of model development thereby provided insights into several research questions. In a first step the ecological and ecotoxicological relevance of backswimmer predation was examined. Therefore, population dynamics of Daphnia magna was observed under predation pressure, xenobiotic stress and a combination of both predation and chemical disturbance. The experiment revealed that size selective predation of the backswimmers did alter population demography, which in turn led to higher vulnerability of D. magna population to toxic stress. The results mentioned above have raised the question to what extend the functional response and size selectivity of juvenile backswimmers changes with predator instar. Therefore, ecological parameters that were considered influential in prey selection were quantified experimentally and subsequently led to the parameterization of an individuals model to be used for the prediction of predation rates. Testing the model against independent data revealed that prey selection in backswimmer might not be determined by active preference, but by passive selectivity mediated by variations in the components of predation. Application of the model revealed that predation rates in juvenile backswimmers are reduced under dark conditions compared to light. These differences are accounted for by the presence/absence of light and are not regulated by any endogenous circadian rhythm. Behavioural observations led to the conclusion that in the dark backswimmers probably detect prey items at a shorter distance as compared to light and that the resulting reduction in the encounter rate is compensated by gaining a higher amount of food per item during a lengthier, more thorough handling of the prey. Comparing model output to independent functional response data did support this hypothesis. In order to account for variations in food availability, and thus allow for long term prediction of predation rates, the model was extended by a physiological component. Therefore, behavioural observations on the components of predations were correlated with gut state of the predator. Moreover, the empirical results showed that food-deprived backswimmers attack their prey more frequently and that they extract more biomass from a single prey item than their well-fed conspecifics do. Model application provided further evidence for compensatory feeding under variable environmental conditions. In the current study, proximate factors in the foraging behaviour were identified and implemented in a simulation model. The model developed here is able to adequately predict size selectivity and long term predation rates of juvenile backswimmers under laboratory conditions. A major future task will be the generalization of mechanistic rules that will allow predictions for a broad range of species