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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.
21

Sedimentation of organic matter on the Hebridean slope

Perez-Castillo, Fernando January 1999 (has links)
No description available.
22

A Taxonomic Study on Lentibulariaceae of Taiwan

Chao, Yi-Shan 28 January 2004 (has links)
Utricularia is the only genus in Lentibulariaceae of Taiwan. The morphology of Utricularia is highly diverse due to the habitats variation, which results in the difficulty to identify the species of this genus. This study emphasizes the morphology of Utricularia, and combines with the information of field observation and the cultivation, to ensure the influence of environmental change on external morphology, especially the characters of stolons, rhizoids, leaves, flowers, fruits, pollens, seeds, and traps. Further, the taxonomic value of trap glands between species is discussed. There are seven species recognized in Lentibulariaceae of Taiwan; namely, U. aurea Lour., U. australis R. Br., U. bifida L., U. caerulea L., U. gibba L., U. striatula Sm., and U. uliginosa Vahl. In addition, U. minor L. and U. inflata Walter are treated as doubtful species.
23

Bose-Einstein condensation of rubidium-87 atoms in a magnetic trap /

Han, Dian-jiun, January 1998 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 140-153). Available also in a digital version from Dissertation Abstracts.
24

Κατασκευή του συστήματος φωτοπαγίδων για την έρευνα του φωτοτακτισμού θαλάσσιων οργανισμών με τον μικροελεγκτή MSP430F169

Ζέρβα, Χριστίνα 01 October 2012 (has links)
Η πλειονότητα των θαλάσσιων ασπόνδυλων οργανισμών εμφανίζει θετική απόκριση προς τις φωτεινές πηγές κατά τη διάρκεια της νύχτας, ιδιότητα που την ονομάζουμε θετικό φωτοτροπισμό. Μια ομάδα δειγματοληπτών που εκμεταλλεύεται την παραπάνω ιδιότητα (φωτοπαγίδες) έχει αρχίσει να χρησιμοποιείται εκτεταμένα στη θαλάσσια έρευνα τις τελευταίες δεκαετίες με πολύ ενθαρρυντικά αποτελέσματα. Ωστόσο, παρά την πληθώρα πλεονεκτημάτων που εμφανίζουν έναντι των παραδοσιακών μεθόδων συλλογής ασπόνδυλων οργανισμών, σε καμία περίπτωση έως τώρα δεν έχουν χρησιμοποιηθεί στη Μεσόγειο.Στην διπλωματική αυτή εργασία κατασκευάσαμε μία φωτοπαγίδα για τη λειτουργία της οποίας, προγραμματίσαμε τον μικροελεγκτή MSP430F169. Η εργασία αυτή περιλαμβάνει 4 κεφάλαια. Πιο συγκεκριμένα, στο πρώτο κεφάλαιο γίνεται αναφορά στις φωτοπαγίδες που έχουν κατασκευαστεί μέχρι τώρα καθώς και σ την συμπεριφορά των ψαριών απέναντι στο φως. Στο δεύτερο κεφάλαιο, περιγράφεται ο τρόπος λειτουργίας της φωτοπαγίδας. Στο τρίτο κεφάλαιο παρουσιάζονται βασικές έννοιες των μικροελεγκτών και περιγράφεται αναλυτικά ο προγραμματισμός του μικροελεγκτή MSP430F169 τον οποίο και χρησιμοποιήσαμε. Τέλος, δίνεται ο κώδικας του προγράμματος σύμφωνα με το οποίο προγραμματίστηκε ο MSP430F169 εκεί γίνεται και η λεπτομερής επεξήγησή του καθώς και η επεξήγηση του προγράμματος που χρησιμοποιήθηκε για την εφαρμογή του. / The majority of marine invertebrates show a positive response to the light source during the night, a property that we call positive phototropism. A group of samplers exploit the above property (light trap) has been in use extensively in marine research in recent decades with very encouraging results. However, despite the many advantages over traditional display methods for collecting invertebrates in no case has so far not been used in this dissertation Mesogeio. In this thesis we constructed a light trap for the operation of which, we programmed the microcontroller MSP430F169. This work contains 4 chapters. To be more specific, the first chapter refers to the light trap built and the behavior of fish towards the light so far . The second chapter describes how the light trap works. The third chapter presents the basic concepts of microcontrollers and describes the programming of microcontroller MSP430F169 which we used. Finally, the fourth chapter has the program code with which the MSP430F169 planned and there is a detailed code explanation and an explanation of the program which was used for its implementation.
25

Study Of Apertures And Their Influence On Fields And Multipoles In rf Ion Traps

Chattopadhyay, Madhurima 02 1900 (has links) (PDF)
This thesis presents results of investigations on fields and multipole expansion coefficients in axially symmetric (referred to as 3D)and two dimensional (2D)ion trapmass analysers. 3D mass analysers have a three-electrode geometry with two (electrically shorted) endcap electrodes and one central ring electrode. rf-only or rf/dc potential applied across the electrodes creates a linear trapping field in the central cavity of the mass analyser.2Dmass analysers have four longitudinal electrodes in which the opposite pairs of electrodes are electrically shorted. Here, rf-only or rf/dc potential applied across the pair of electrodes creates a linear trapping field and fragment ions of the analyte gas are trapped along the central axis of the mass analyser. Both these mass analysers have apertures machined on the electrodes (holes in case of 3D traps and slits in case of 2D traps) to permit entry of electrons for ionizing the analyte gas and for collection of destabilized fragment ions. This thesis is concerned with how these apertures influence the fields and multipole expansion coefficients within the traps. This thesis is divided into five chapters. Chapter 1 provides the background information which is required for the thesis. It begins with a description of the geometry of the 3D and the 2D mass analysers used in the present work.These include the quadrupole ion trap (QIT) and cylindrical ion trap (CIT) for 3D structures and the linear ion trap (LIT) and the rectilinear ion trap (RIT) for 2D structures. This is followed by a brief description of the numerical method, the boundary element method (BEM), used in the thesis. Also presented here are the Green’s function for 3D and 2D geometries. In the final section, the scope of the thesis is presented. Chapter 2 presents two approximate analytical expressions for nonlinear electric fields in the principal direction in axially symmetric (3D) and two dimensional (2D) ion trap mass analysers with apertures on the electrodes. Considered together (3D and 2D), we present composite approximations for the principal unidirectional nonlinear electric fields in these ion traps. The composite electric field E has the form E= EnoAperture + EdueToAperture where EnoAperture is the field within an imagined trap which is identical to the practical trap except that the apertures are missing; and where EdueToAperture is the field contribution due to apertures on the two trap electrodes. The field along the principal axis of the trap can in this way be well approximated for any aperture that is not too large. To derive EdueToAperture, classical results of electrostatics have been extended to electrodes with finite thickness and different aperture shapes. EnoAperture is a modified truncated multipole expansion for the imagined trap with no aperture. The first several terms in the multipole expansion are in principle exact (though numerically determined using the BEM), while the last term is chosen to match the field at the electrode. This expansion, once computed, works with any aperture in the practical trap. The composite field approximation for axially symmetric (3D) traps is checked for three geometries: the quadrupole ion trap (QIT), the cylindrical ion trap (CIT) and an arbitrary other trap. The approximation for 2D traps is verified using two geometries: the linear ion trap (LIT)and the rectilinear ion trap (RIT). In each case, for two aperture sizes (10% and 50% of the trap dimension), highly satisfactory fits are obtained. These composite approximations may be used in more detailed nonlinear ion dynamics studies than have been hitherto attempted. In Chapter 3we complement and complete the work presented in Chapter 2 by considering off-axis fields in the axially symmetric (3D) and the two dimensional (2D) ion traps whose electrodes have apertures. Our approximation has two parts. The first, EnoAperture, is the field obtained numerically for the trap under study with no apertures. We have used the boundary element method (BEM) for obtaining this field. The second part, EdueToAperture, is an analytical expression for the field contribution of the aperture. In EdueToAperture, aperture size is a free parameter. A key element in our approximation is the electrostatic field near an infinite thin plate with an aperture, and with different constant valued far field intensities on either side. Compact expressions for this field can be found using separation of variables, wherein the choice of coordinate system is crucial. This field is, in turn, used four times within our trap specific approximation. The off-axis field expressions for the 3D geometries were tested on the quadrupole ion trap (QIT) and the cylindrical ion trap (CIT), and the corresponding expressions for the 2D geometries were tested on the linear ion trap (LIT) and rectilinear ion trap (RIT). For each geometry, we have considered apertures which are 10%, 30% and 50% of the trap dimension. We have found that our analytical correction term EdueToAperture, though based on a classical small-aperture approximation, gives good results even for relatively large apertures. Chapter 4 presents approximate analytical expressions for estimating the variation in multipole expansion coefficients with the size of apertures in axially symmetric (3D) and two dimensional (2D) ion trap mass analysers. Following the approach adopted in Chapter 2 and Chapter 3 which focused on the role of apertures to fields within traps, here too, the analytical expression is a sum of two terms, An,noAperture, the multipole expansion coefficient for a trap with no apertures and An,dueToAperture, the multipole expansion coefficient contributed by the aperture. An,noAperture has been obtained numerically and An,dueToAperture is obtained from the nth derivative of the potential within the trap. The expressions derived have been tested on two 3D geometries and two 2D geometries. These include the quadrupole ion trap (QIT) and the cylindrical ion trap (CIT) for 3D geometries and the linear ion trap (LIT) and the rectilinear ion trap (RIT) for the 2D geometries. Multipole expansion coefficients A2 to A24, estimated by our analytical expressions were compared with the values obtained numerically (using the boundary element method) for aperture sizes varying up to 50% of the trap size. In all the plots presented, it is observed that our analytical expression for the variation of multipole expansion coefficients versus aperture size closely follows the trend of the numerical evaluations for the range of aperture sizes considered. The maximum relative percentage errors, which provide an estimate of the deviation of our values from those obtained numerically for each multipole expansion coefficient, are seen to be in the range of 10% to 15%. The leading multipole expansion coefficient, A2, however, is seen to be estimated very well by our expressions, with most values being within 1% of the numerically determined values, with larger deviations seen for the QIT and LIT only at larger aperture sizes. Chapter 5 presents a few concluding remarks.
26

Distribution of Carrion Beetles (Coleoptera: Silphidae) in Different Geographic Regions of Virginia

Beirne, Shana Margaret 24 January 2013 (has links)
The distribution of beetles in the Family Silphidae has not been well studied in Virginia.  The primary purpose of this study was to survey silphid beetles in a more systematic manner across different geographic regions of the state, with a special consideration for Nicrophorus species.  The seasonal abundance and diversity of silphid beetles in Montgomery County, Virginia, was also examined.  Baited pitfall traps were used to sample beetle distribution and abundance, and were placed in each of the five geographical regions of Virginia in the summers of 2007 and 2008.  Traps were placed approximately one kilometer apart and were checked daily over a five day period for each of three sampling periods.  A total of 4375 silphid beetles, consisting of 11 species in four genera, were collected in ten counties with beetles in the subfamily Silphinae being predominant.  Within the Nicrophorinae, Nicrophorus tomentosus and N. orbicollis were dominant in 2007; whereas in the summer of 2008, N. tomentosus and N. pustulatus were the most commonly collected.  Contingency analyses indicated that species abundance was associated with sampling period and geographic region.  Nicrophorus americanus was not collected during either summer of surveying and only three N. carolinus were trapped in Suffolk County in the summer of 2008.  For the Montgomery County survey, a total of 3276 beetles were found between the middle of April and the middle of October.  The prevalent species within Nicrophorinae was Nicrophorus tomentosus and within the Silphinae it was Necrophila americana.  Species abundance was associated with sampling period. / Master of Science in Life Sciences
27

How competition dynamics drive access to shared scavenging opportunities amongst a group of mesocarnivores in the Rocky Mountains of Alberta

Bell, Elicia 01 September 2021 (has links)
Mesocarnivores occupy critical functional roles in regulating ecosystems and maintaining biodiversity. In the Canadian Rocky Mountains, mustelid species depend heavily on carrion as an important dietary contribution, particularly in winter when resources are scarce. In diverse mesocarnivore communities such as this, sympatric species must balance energetic resource acquisitions through scavenging with avoidance of costly competition dynamics, in a manner that optimizes energetic gain through risk aversion. We examined the nature of spatial-temporal interactions between wolverine (Gulo gulo), American marten (Martes Americana), and short-tailed weasel (Mustela erminea) in the Willmore Wilderness Park in western Alberta. Data were collected from camera traps (n = 59) baited with a simulated scavenging opportunity during winter months between 2006 to 2008. The spatial-temporal dimensions of intraguild competition were evaluated using a multi-model approach. Zero-inflated negative binomial (ZINB) or zero-inflated Poisson (ZIP) regression models were used to identify the competitive and environmental factors that affected (1) species presence/absence and (2) how intensely a species would spatiotemporally optimize a carrion site. A time-to-event analysis was used to quantify the directionality of fine-scale (hourly) reactionary behavioural responses of species to potential sources of competition. An extension of this group of models, the Cox proportional hazard (CPH) model was used to further reveal the relative influence of external environmental variables (i.e. diel period, landcover, and snow depth) on temporal spacing. Pairing CPH and ZINB/ZIP models enables us to recognize the relative contribution of fine-scale spatial and temporal behavioural responses to competitors in shaping coexistence strategies. Our results suggest that facultative scavengers adopt different coexistence mechanisms based on the interspecific competitor and environmental conditions they encounter at carrion sites. We found that carrion use was impacted for all species by competition and snow depth. Marten scavenging behaviours were additionally impacted by habitat character. We also found evidence of fine-scale temporal attraction between marten and wolverine, thought to indicate a shared net-energetic gain at scavenging sites. Our results suggest that mesocarnivore scavengers are likely to adopt spatiotemporal mechanisms to facilitate carrion resource partitioning and adapt to conditions specific to carcass placement in a spatially complex environment. Given their vital ecological roles, it is important that we recognize the ability of individual mustelid species to exploit scavenging opportunities and identify the external factors that influence coexistence. Understanding the factors that drive access to these ephemeral resources will provide valuable information for anticipating impacts of climate change on facultative scavengers in the boreal forests of western Canada. / Graduate / 2022-08-23
28

Effectiveness of colored pan traps in assessing apiformes diversity in two sandhill plant communities in central Florida

Russell, Phillip Joseph 01 January 2004 (has links)
No description available.
29

Frequency Perturbation In Non-Linear Paul Traps

Sevugarajan, S 10 1900 (has links) (PDF)
No description available.
30

Evaluation of a Common Carp (Cyprinus carpio L.) Exclusion and Trapping Device for Use in Aquatic Plant Founder Colony Establishment

Williams, Paul Edwin 05 1900 (has links)
The focus of this study was to design and evaluate a trapping system that would reduce populations of common carp within water bodies in conjunction with establishment of native aquatic macrophytes founder colonies. A pond study and field study were conducted. A pond study was performed at the Lewisville Aquatic Ecosystem Research Facility, located in Lewisville, Texas, followed by a field study within a constructed wetland located in southern Dallas, Texas. For the pond study, twelve funnel traps were constructed (four reps of each type: control, dual-walled and ring cage). Two anti-escape devices were tested with funnels including steel fingers and hinged flaps. Ring cage and dual-walled treatments were planted using native pondweeds, while controls were left unplanted (additional bait and a drift fence scenarios were also tested). Common carp were introduced into the study pond. Chi-square statistical analyses were utilized and showed ring cage treatments using fingers as well as the use of a drift fence to be most effective. Following completion of the pond study, the two most effective treatments (controls and ring cages) were tested within the Dallas, Texas wetland; no carp were caught during the field test.

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