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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

The effect of native forest dynamics upon the arrangements of species in oak forests-analysis of heterogeneity effects at the example of epigeal arthropods

Langer, Marco January 2011 (has links)
The heterogeneity in species assemblages of epigeal spiders was studied in a natural forest and in a managed forest. Additionally the effects of small-scale microhabitat heterogeneity of managed and unmanaged forests were determined by analysing the spider assemblages of three different microhabitat structures (i. vegetation, ii. dead wood. iii. litter cover). The spider were collected in a block design by pitfall traps (n=72) in a 4-week interval. To reveal key environmental factors affecting the spider distribution abiotic and biotic habitat parameters (e.g. vegetation parameters, climate parameters, soil moisture) were assessed around each pitfall trap. A TWINSPAN analyses separated pitfall traps from the natural forest from traps of the managed forest. A subsequent discriminant analyses revealed that the temperature, the visible sky, the plant diversity and the mean diameter at breast height as key discriminant factors between the microhabitat groupings designated by the TWINSPAN analyses. Finally a Redundant analysis (RDA) was done revealing similar environmental factors responsible for the spider species distribution, as a good separation of the different forest types as well as the separation of the microhabitat groupings from the TWINSPAN. Overall the study revealed that the spider communities differed between the forest types as well as between the microhabitat structures and thus species distribution changed within a forest stand on a fine spatial scale. It was documented that the structure of managed forests affects the composition of spider assemblages compared to natural forests significantly and even small scale-heterogeneity seems to influence the spider species composition. / Um die Anpassungsfähigkeit von Organismen, bei sich ändernden Umweltbedingungen, sicher zu stellen, spielt die Erhaltung der Biologischen Vielfalt auf allen ökosystemaren Ebenen eine entscheidende Rolle. Eben diese Anpassungsfähigkeit kann durch waldbauliche Maßnahmen einschränkt werden, und zur Instabilität des Systems führen. Daher kommt der Untersuchung von aus der Nutzung genommenen Naturwaldzellen eine immer größere Bedeutung zu. Einerseits um die potentiell natürliche Diversität in Naturwäldern mit der in Wirtschaftswäldern zu vergleichen, andererseits um die ökologischen Zusammenhänge in einer natürlichen Waldentwicklung zu verstehen. Ziel diese Studie war es eben diese natürlichen Waldynamiken auf das Artengefüge von Spinnen (Araneae) zu untersuchen. Dabei sollte Mithilfe eines experimentellen Fangdesigns, auch der kleinräumige Einfluss von Strukturheterogenität untersucht werden.
12

Organic farming and generalist predator communities

Birkhofer, Klaus. Unknown Date (has links)
Techn. University, Diss., 2007--Darmstadt.
13

Entwicklung von Fertigungstechnologien zur Herstellung biomimetischer faserbasierter Scaffolds aus Kollagen für das Tissue Engineering und die regenerative Medizin

Tonndorf, Robert 14 June 2022 (has links)
Die enormen Fortschritte und Erkenntnisse der Medizin und der damit einhergehenden gestiegenen mittleren globalen Lebenserwartung von indes knapp 75 Jahren fußen auch auf den medizinischen Entwicklungen des 20. Jahrhunderts, da durch diese z. B. infektiöse und onkologische Erkrankungen, Diabetes, Bluthochdruck, Herzinsuffizienz, Magengeschwüre, Depressionen, Hämophilie und andere Krankheiten erfolgreich therapiert werden können. Die entwickelten Therapiemethoden beruhten im Wesentlichen auf chirurgischen und intensivmedizinischen Neuerungen, chemischen Wirkstoffen, belastungsfähigen Implantaten und extrakorporalen Systemen. Im 21. Jahrhundert hingegen sind medizinische Neuerungen im molekularbiologischen Bereich zu erwarten, wie beispielsweise in der Zellbiologie, DNA-Analyse und -Transfer oder in der regenerativen Medizin. In Letzterer werden autologe regenerative Mechanismen als therapeutisches Prinzip genutzt, um funktionsgestörte Zellen, Gewebe und Organe entweder durch den biologischen Ersatz oder durch die Anregung körpereigener Regenerations- und Reparaturprozesse zu erhalten bzw. wiederherzustellen.
14

Effect of forests structure and small-scale environmental conditions on the community of epigeic arthropods (Carabidae, Araneae)

Ziesche, Tim 23 June 2016 (has links) (PDF)
Forests are more than a stand of trees in the landscape. They represent a complex, functional system of interacting and often interdependent biological, physical and chemical components (Kimmins 1997). In the past, complex interactions were increasingly recognized over time as food webs, abiotic processes and biotic feedbacks since then defined as the forest ecosystem. Trees grow in a world of multitrophic interactions (van der Putten et al. 2001). One component of this functional system is represented in several aspects by spiders and insects, as they contribute considerably to the biodiversity and ecosystem functioning in forest habitats (Watt et al. 1997). There is knowledge on the community composition of several forests of different stand type or tree species composition referring to soil dwelling arthropods. Moreover, studies often highlight the orientation of single arthropod species on abiotic factors or the composition of species assemblages in case studies; these represent ecologically well described groups that can be used as indicators of habitat quality (Pearce and Venier 2006; Cardoso et al. 2004). Evidence on the scale of interactions between the species and their environment are rare. This applies particularly to examples based on fine spatial and temporal scales.
15

Ants and spiders in grassland food webs / Top-down control and intraguild interactions / Ameisen und Spinnen in Grasland Nahrungsnetzen / Top-down Wirkung und Intraguilden Interaktionen

Sanders, Dirk 24 January 2008 (has links)
No description available.
16

Effect of forests structure and small-scale environmental conditions on the community of epigeic arthropods (Carabidae, Araneae)

Ziesche, Tim 12 April 2016 (has links)
Forests are more than a stand of trees in the landscape. They represent a complex, functional system of interacting and often interdependent biological, physical and chemical components (Kimmins 1997). In the past, complex interactions were increasingly recognized over time as food webs, abiotic processes and biotic feedbacks since then defined as the forest ecosystem. Trees grow in a world of multitrophic interactions (van der Putten et al. 2001). One component of this functional system is represented in several aspects by spiders and insects, as they contribute considerably to the biodiversity and ecosystem functioning in forest habitats (Watt et al. 1997). There is knowledge on the community composition of several forests of different stand type or tree species composition referring to soil dwelling arthropods. Moreover, studies often highlight the orientation of single arthropod species on abiotic factors or the composition of species assemblages in case studies; these represent ecologically well described groups that can be used as indicators of habitat quality (Pearce and Venier 2006; Cardoso et al. 2004). Evidence on the scale of interactions between the species and their environment are rare. This applies particularly to examples based on fine spatial and temporal scales.:Zusammenfassung 1 Summary 4 Chapter 1 General Introduction 7-19 1.1 Arthropods as a permanent component of forest ecosystems 7 1.2 Spiders and carabids in forest ecosystems 10 1.3 Are spiders and carabids in ecosystems dispensable? – functional diversity in natural antagonists 13 1.4 Objectives 20 Chapter 2 Influence of environmental parameters on small-scale distribution of soil-dwelling spiders in forests: what makes the difference, tree species or microhabitat? 23 2.1 Abstract 23 2.2 Introduction 24 2.3 Methods and materials 25 2.4 Results 32 2.5 Discussion 45 2.6 Conclusions 51 Chapter 3 Microhabitat heterogeneity in temperate forests: is distance to stems affecting ground-dwelling spider communities? 61 3.1 Abstract 61 3.2 Introduction 62 3.3 Materials and Methods 63 3.4 Results 68 3.5 Discussion 77 Chapter 4 The impacts of seasonality, forest type and succession on the community structure of temperate-forest ground beetles. 88 4.1 Abstract 88 4.2 Introduction 90 4.3 Methods and materials 92 4.4 Results 98 4.5 Discussion 113 4.6 Conclusions 120 Chapter 5 Is the age of forest habitats affecting the reproductive rate of generalist predatory ground beetle species? 129 5.1 Abstract 129 5.2 Introduction 131 5.3 Methods and materials 133 5.4 Results 138 5.5 Discussion 150 5.6 Conclusions 153 Chapter 6 General Discussion 161 6.1 Management effect 169 6.2 Future prospect 170 Liste der Veröffentlichtungen 173-174 Danksagung
17

Development of new hybrid yarn construction from recycled carbon fibers (rCF) for high performance composites: Part-II: Influence of yarn parameters on tensile properties of composites

Hengstermann, M., Hasan, M. M. B., Abdkader, A., Cherif, Ch. 05 November 2019 (has links)
This article reports the successful manufacturing of hybrid yarns from virgin staple CF (40 or 60 mm) or recycled staple CF (rCF) by mixing with polyamide 6 (PA 6) fibers of defined length. The hybrid yarns are produced using an optimized process route of carding, drawing, and flyer machine. Furthermore, the influence of CF length, CF type (i.e. virgin or rCF), CF volume content, and twist of the yarn are also investigated regarding the tensile properties of unidirectionally laid (UD) thermoplastic composites. The results show that CF length, yarn twist, and CF content of composites play a big role on the tensile properties of thermoplastic composites. From the comparison of tensile strength of UD composites produced from 40 and 60mm virgin staple CF, it can be seen that the increase of yarn twist decreases the tensile strength. However, the effect of twist on the tensile properties of UD composites manufactured from 40mm virgin staple CF is insignificant. The tensile strength of UD thermoplastic composites manufactured from the hybrid yarn with 40 and 60mm virgin staple CF and rCF is found to be 771 ± 100, 838 ± β1, and 801 ± 53.4 MPa, respectively, in the case of 87 T/m containing 50 volume% CF.
18

Development of new hybrid yarn construction from recycled carbon fibers for high performance composites: Part-I: basic processing of hybrid carbon fiber/polyamide 6 yarn spinning from virgin carbon fiber staple fibers

Hengstermann, M., Raithel, N., Abdkader, A., Hasan, M. M. B., Cherif, Ch. 18 September 2019 (has links)
The availability of a considerable amount of waste carbon fiber (CF) and the increased pressure to recycle/reuse materials at the end of their life cycle have put the utilization of recycled CF (rCF) under the spotlight. This article reports the successful manufacturing of hybrid yarns consisting of staple CF cut from virgin CF filament yarn and polyamide 6 fibers of defined lengths (40 and 60 mm). Carding and drawing are performed to prepare slivers with improved fiber orientation and mixing for the manufacturing of hybrid yarns. The slivers are then spun into hybrid yarns on a flyer machine. The investigations reveal the influence of fiber length and mixing ratio on the quality of the card web, slivers and on the strength of the hybrid yarns. The findings based on the results of this research work will help realize value-added products from rCF on an industrial scale in the near future.
19

Indirect measures of associations and psychopathology: applications to Spider Phobia

Ellwart, Thomas 28 March 2004 (has links) (PDF)
To study of cognitive fear networks and associations, indirect experimental paradigms like the Implicit Association Test (IAT, Greenwald et al., 1998) or the Extrinsic Affective Simon Task (EAST, De Houwer, 2003) may be helpful, as they promise to assess the structure of specific associations using a performance based approach without having to ask the participant for a verbal report. Three studies investigated the usefulness and characteristics of IAT and EAST. The aim of the first study was to measure fear associations towards spiders among spider phobic and non-phobic participants as well as in a group of spider enthusiasts. Results indicate that the IAT paradigm is sensitive to the strength of fear relevant associations and able to predict anxious behavior beyond the predictions of direct measures such as questionnaires. The second study focused on some of the mechanisms that underlie IAT effects. With a newly developed masked IAT, these experiments investigated the influences of individual stimuli and superordinate categories on IAT performance. Besides theoretical implications, the results also provide practical, relevant applications for the use of IAT experiments. A third study applied the EAST to investigate how different context conditions lead to differential activation of cognitive schemata in fear of spiders. One can conclude that the impact of automatic threat associations depends on the activated context, and that the EAST is suitable for the assessment of fear associations and their current activation level. This dissertation leads to the conclusion that the performance based methodology of the IAT and EAST is a useful and practical approach to reflect fear associations in phobia indirectly. At this point, the use of indirect measures is still at its beginning, and requires intensive methodological and theoretical efforts. These paradigms, however, may become useful for possible implications in psychopathology and other fields of psychology.
20

Habitatpotentiale im Ackerbereich: Endergebnisse des LfULG-FuE-Projekts: Habitatpotentiale im Ackerbereich: Konzipierung und Erprobung schlagintegrierter Artenschutzmaßnahmen im LVG Köllitsch

Rapp, Charlotte, Muster, Christoph, Brunk, Ingo, Gebert, Jörg 28 February 2022 (has links)
Die Broschüre informiert über ein Projekt zur Umsetzung von einer angepassten Ackerrandbewirtschaftung zur Erhöhung des Habitatpotentials für Tiere und Pflanzen. Am Ackerrand wurden auf 9 m breiten Streifen die Effekte von Weiter Reihe und Untersaat von Luzerne untersucht. Es konnte nachgewiesen werden das mit den Maßnahmen mehr Laufkäfer und Spinnen den Acker besiedeln. Die Wirkung der Maßnahmenstreifen waren höher wenn sie an Landschaftselemente angrenzten. Die Publikation richtet sich an Landwirte, Berater und Naturschützer und soll zur Nachahmung der entsprechenden Maßnahmen einladen. Redaktionsschluss: 18.01.2022

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