Single Molecule DNA Detection with an Atomic Vapor Notch Filter

The detection of single molecules has facilitated many advances in life- and material-sciences. Commonly, it founds on the fluorescence detection of single molecules, which are for example attached to the structures under study. For fluorescence microscopy and sensing the crucial parameters are the collection and detection efficiency, such that photons can be discriminated with low background from a labeled sample. Here we show a scheme for filtering the excitation light in the optical detection of single stranded labeled DNA molecules. We use the narrow-band filtering properties of a hot atomic vapor to filter the excitation light from the emitted fluorescence of a single emitter. The choice of atomic sodium allows for the use of fluorescent dyes, which are common in life-science. This scheme enables efficient photon detection, and a statistical analysis proves an enhancement of the optical signal of more than 15% in a confocal and in a wide-field configuration.Comment: 9 pages, 5 figure

Time of harvesting soybeans : in relation to soil improvement and protein content of the hay

Cover title.Includes bibliographical references

Ein Open Source Ansatz zur akustischen Detektion holzbewohnender Insekten

Bioakustik ist eine vielversprechende Methode, um Veränderungen in Ökosystemen besser zu verstehen, geeignete Massnahmen zu beschliessen und deren Wirksamkeit zu überprüfen. Diese Arbeit beschäftigt sich mit holzbewohnenden Insekten, die in Zeiten von globalen Lieferketten und Klimaveränderungen eine essenzielle Bedrohung für heimische Bäume und Ökosysteme darstellen können. Als Modellorganismus wurden kleine Holzbohrer Xyleborus saxesenii gewählt. Der Fokus liegt aber nicht auf der Biologie, sondern auf den physikalischen Grundlagen und der Technik zur bioakustischen Beobachtung von holzbewohnenden Insekten. Die physikalischen Grundlagen über Schall im Holz und der elektronischen Hilfsmittel sind in einem theoretischen Teil zusammengefasst und werden in einem Experiment umgesetzt. Ein wichtiger Anspruch hierbei war, dass die verwendeten Hard- und Softwares Open Source lizenziert sind. Der Kern der praktischen Arbeit ist die Entwicklung eines Vorverstärkers, mit dem ein piezoelektrischer Wandler als Körperschallmikrofon mit einem AudioMoth Rekorder verwendet werden kann. Die Datenauswertung wird in dieser Arbeit nur qualitativ gemacht, weitere Automatisierungen werden theoretisch diskutiert.Bioacoustics is a promising method to better understand changes in ecosystems, to decide on appropriate measures and to evaluate their effectiveness. This work focuses on wood-inhabiting insects that pose an essential threat to native trees and ecosystems in times of global supply chains and climate change. Fruit tree pinhole borer Xyleborus saxesenii were chosen as the model organism. The focus of this work is not on biology, but on physical principles and technology for bioacoustics observation of wood-inhabiting Insects. The physical basics about sound propagation in wood and the electronic instruments are summarized in a theoretical part and implemented in an experiment. An important requirement here was to use open source licensed hardware and software. The core of the practical work is the development of a preamplifier, with which a piezoelectric transducer can be used as a structure-borne sound microphone with an AudioMoth recorder. Data analysis is done only qualitatively in this work, further automations are discussed theoretically

Synthesis and mechanical properties of iron-filled carbon nanotubes

Carbon forms the basis of a variety of compounds. The allotropic forms of carbon include graphene, fullerenes, graphite, carbon nanotubes and diamond. All these structures possess unique physical and chemical properties. This work focusses on the usage of carbon nanotubes (CNT), especially iron-filled CNT. An industrial application of CNT requires the understanding of the growth mechanism and the control of the synthesis process parameters. Regarding iron-filled CNT the shell formation as well as the filling process has to be understood in order to control the CNT morphology and distribution and dimension of the iron filling. The thesis involves two topics - synthesis of CNT and characterization of their mechanical properties. Chapter 2 of the present work deals with the synthesis of iron-filled CNT. In this thesis all experiments and the discussion about the growth process were conducted with respect to the demands of magnetic force microscopy probes. The experimental work was focused on the temperature profile of the furnace, the aluminum layer of the substrate, the precursor mass flow and their impact on the morphology of in-situ iron-filled CNT. By selecting appropriate process parameters for the temperature, sample position, gas flow and by controlling the precursor mass flow, CNT with a continuous filling of several microns in length were created. Existing growth models have been analyzed and controversially discussed in order to explain the formation of typical morphologies of in-situ filled CNT. In this work a modified growth model for the formation of in-situ filled CNT has been suggested. The combined-growth-mode model is capable to explain the experimental results. Experiments which were conducted with respect to the assumptions of this model, especially the role of the precursor mass flow, resulted in the formation of long and continuous iron nanowires encapsulated inside multi-walled CNT. The modified growth model and the synthesis results showed, that besides the complexity of the parameter interaction, a control of the morphology of in-situ iron-filled CNT is possible. In chapter 3 the measurements of mechanical properties of in-situ iron-filled CNT are presented. Two different experimental methods and setups were established, whereby one enabled a static bending measurement inside a TEM and another a dynamical excitation of flexural vibration of CNT inside SEM. For the first time mechanical properties and in particular the effective elastic modulus Eb of in-situ iron-filled CNT were determined based on the Euler-Bernoulli beam model (EBM). This continuum mechanic model can be applied to describe the mechanical properties of CNT and especially MWCNT in consideration of the restriction that CNT represent a macro molecular structure built of nested rolled-up graphene layers. For evaluation and determination of the elastic modulus the envelope of the resonant vibrating state was evaluated by fitting the EBM to the experimental data. The experiments also showed, that at the nanoscale the properties of sample attachment have to be taken into account. Thus, instead of a rigid boundary condition a torsion spring like behavior possessing a finite stiffness was used to model an one side clamped CNT. The extended data evaluation considering the elastic boundary conditions resulted in an average elastic modulus of Eb = 0.41 ± 0.11 TPa. The low standard deviation gives evidence for the homogeneity of the grown material. To some extend a correlation between the formation process, the morphology and the mechanical properties has been discussed. The obtained results prove the usability of this material as free standing tips for raster scanning microscopy and especially magnetic force microscopy. The developed methods provide the basis for further investigations of the CNT and the understanding of mechanical behavior in greater detail

Characterization of antimicrobial resistance in Aeromonas and Vibrio isolated in Canada from fish and seafood

Plusieurs études ont examiné la sensibilité aux antimicrobiens chez les bactéries d’organismes provenant de produits issus de l’aquaculture ou de leur environnement. Aucune information n’est cependant disponible concernant la résistance aux antimicrobiens dans les bactéries de la flore de poissons ou de fruits de mer vendus au détail au Canada. C’est particulièrement vrai en ce qui a trait aux bactéries des genres Aeromonas et Vibrio, dont certaines espèces sont des agents pathogènes zoonotiques connus. Au cours de cette étude, la sensibilité aux antimicrobiens d’isolats d’Aeromonas spp. et de Vibrio spp. provenant de poissons et de crevettes domestiques et importés a été mesurée à l’aide de techniques de micro dilution en bouillon et/ou de diffusion sur disque. Les classes d’antimicrobiens examinés comprenaient les tétracyclines (TET), les inhibiteurs de la voie des folates (sulfadiméthoxine-triméthoprime, SXT), le florfenicol (FLO), et les quinolones (acide nalidixique / enrofloxacine, NA/ENO). Des valeurs seuils épidémiologiques pour Aeromonas et Vibrio ont été établies en utilisant la méthode d’interprétation normalisée des données de résistance provenant de diffusion sur disque. La recherche de gènes de résistance associés au profil de résistance des isolats a été effectuée en utilisant des PCRs et des puces ADN. Le nombre d’isolats résistants aux divers antimicrobiens parmi les 201 isolats d’Aeromonas et les 185 isolats de Vibrio étaient respectivement les suivants: TET (n=24 et 10), FLO (n=1 et 0), SXT (n=2 et 8), NA (n=7 et 5) et ENO (n= 5 et 0). Diverses associations de gènes tet(A), tet(B), tet(E), floR, sul1, sul2, et intI1 ont été détectées, les gènes tet(E), intI1, sul2 et tet(B) étant les plus communs. Les espèces d’Aeromonas et de Vibrio isolées de poissons au détail et de fruits de mer peuvent héberger une variété de gènes de résistance, bien que peu fréquemment. Le risque que représente ces gènes de résistance reste à évaluer en considérant le potentiel infectieux des bactéries, l’utilisation des ces agents antimicrobiens pour le traitement des maladies en aquaculture et en médecine humaine et leur rôle en tant que réservoir de la résistance antimicrobienne.Multiple studies have examined antimicrobial susceptibility in bacteria from aquacultured products microorganisms and their environment. However, no information is available concerning antimicrobial resistance in bacterial flora of fish and seafood available at the retail level in Canada. This is particularly true for the common aquatic commensals, Aeromonas and Vibrio, for which some species are known zoonotic pathogens. In the course of this study, the antimicrobial susceptibility among Aeromonas spp. and Vibrio spp. from domestic and imported fish and seafood was characterized. Aeromonas and Vibrio spp. isolates cultured from finfish and shrimp samples were evaluated for antimicrobial susceptibility by broth microdilution and/or disk diffusion techniques. Antimicrobial classes examined in detail included: tetracyclines (TET), folate pathway inhibitors (sulfadimethoxine-trimethoprim, SXT), florfenicol (FLO), and the quinolones (nalidixic acid / enrofloxacin, NA/ENO). Epidemiological cut-off values (ECV’s) for Aeromonas/Vibrio were established using normalized resistance interpretation (NRI) of disk diffusion data. Isolates were further examined by PCR and microarray for genes associated with their antimicrobial resistance. Of 201 Aeromonas and 185 Vibrio isolates, those classified as resistant were as follows, respectively: TET (n=24 and 10), FLO (n=1 and 0), SXT (n=2 and 8), NA (n=7 and 5) and ENO (n=5 and 0). Various combinations of tet(A), tet(B), tet(E), floR, sul1, sul2 and intI1 genes were detected with tet(E), intI1, sul2 and tet(B) being the most common. Vibrio and Aeromonas species isolated from retail fish and seafood sources can harbor a variety of resistance determinants, although their occurrence is not high. The risk represented by these resistances remains to be evaluated in view of the potential for bacterial infection and their role as a reservoir for antimicrobial resistance

Beyond Difference Scores: Testing Models of Speed of Information-Processing Using Confirmatory Factor Analysis

This study has two parts: Part I discusses the limitations of difference scores and exploratory factor analysis for representing speed of information-processing stages in the context of a reanalysis of a study by Vernon (1983). Vernon interpreted the differences between objectively measured reaction times on various simple cognitive tasks as components of speed of information processing. Correlations were calculated among these differences and subjected to exploratory factor analysis. The factors obtained from this analysis were interpreted by Vernon in terms of short-term and long-term memory processing constructs. The use of difference scores, however, implies an additive model allowance for random error, which correlations between these differences. that does not make leads to spurious The application of exploratory factor analysis to among these differences compounds uncover latent variables the problem because it admits many alternative interpretations which cannot be tested against one another for goodness-of-fit to the data. Confirmatory factor analysis addresses these problems. This thesis demonstrates that the correlations between the difference scores can be accounted for in terms of factors obtained from factor analysis of the original reaction time data. These factors lead to an alternative interpretation of the results which is contrasted with Vernon\u27s interpretation. Part II of this study illustrates the use of confirmatory factor analysis with this kind of data. An attempt to test the assumptions of Vernon\u27s difference score model with confirmatory factor analysis did not succeed because the implied model was too constrained for the statistical program we were using; consequently, the program could not find a starting solution. In order to demonstrate how confirmatory factor analysis can be used to test models of speed of cognitive processing, Part II partially replicates a study by Lansman, Donaldson, Hunt, & Yantis (1982). This research analyzed a simple cognitive reaction time task that was examined in detail by Vernon. Donaldson (1983) used the Lansman et al. data to compare difference scores and part correlational techniques with a general approach based on analysis of covariance structures to demonstrate how the components of cognitive processes can be explicated using confirmatory factor analysis

Kultur ist. Beiträge der Empirischen Kulturwissenschaft in Tübingen

»Denn was nützt alle Kultur, die nicht mehr ist als ›nur‹ Kultur?« fragte Hermann Bausinger einmal provokant. In diesem Lesebuch zum 50-jährigen Institutsjubiläum sondieren die Autor*innen jeweils in ihren eigenen Forschungsfeldern am LUI, was »Kultur« als Forschungsperspektive und Gegenstand für sie bedeutet. Gemeinsam ist allen Beiträgen das Ziel, (jungen) Kulturwissenschaftler*innen und (Alltags-)Kulturinteressierten nahezubringen, warum es sich lohnt, die Welt mit und durch Kultur zu sehen, zu beschreiben und zu analysieren

Utilisation de bactériophages pour contrôler les populations de Aeromonas salmonicida résistantes aux antibiotiques

La furonculose, causée par la bactérie Aeromonas salmonicida, représente une des principales causes de mortalité chez les salmonidés d’élevage. L’antibiothérapie constitue l’approche la plus largement répandue pour contrer les effets néfastes de cette maladie. Cependant, le développement de bactéries résistantes aux antibiotiques représente un problème de plus en plus préoccupant. La présente recherche a visé à explorer une nouvelle option pour lutter contre la furonculose, soit la possibilité d’utiliser des bactériophages comme moyen de prévention pour contrôler les populations de A. salmonicida. La sensibilité de 19 souches de A. salmonicida, résistantes à aucun, un, deux ou trois antibiotiques, a été évaluée vis‑à‑vis de 12 bactériophages. Les résultats ont montré que les souches de A. salmonicida résistantes aux antibiotiques utilisés dans l’industrie piscicole canadienne sont aussi sensibles à de nombreux bactériophages, tout comme des souches sensibles aux antibiotiques. Il serait donc possible d’envisager un traitement préventif à base de bactériophages pour lutter contre la furonculose chez les salmonidés d’élevage.Aquaculture represents an increasingly important source of food fish worldwide. The aquaculture industry currently produces between 25 and 30% of all seafood for human consumption. In Canada, salmonids (salmon, rainbow trout, arctic char and brook trout) account for the majority of food fish production. Furonculosis involving the bacterium Aeromonas salmonicida is one of the most important infections observed in salmonid farms. An A. salmonicida infection results either in morbidity and mortality with few clinical signs, or in weakened fish with skin ulcers that make them unmarketable for human consumption. The A. salmonicida bacterium uses a number of mechanisms to counteract the natural barrier of the immune system. Bacterial growth is encouraged by an increase in the ambient temperature and in the concentration of organic matter in the water.During recent years, a relationship between therapeutic failures and the development of bacterial resistance to antibiotics has been reported in salmonid farms. This problem is complicated by the fact that only four antibiotics are authorized for the aquaculture industry in Canada. One consequence of this increasing resistance is a renewed interest in alternative therapies and prevention. Bacteriophages (bacterial viruses) may represent one such alternative. In recent decades, interest in bacteriophages as antibacterial agents has been growing in the Americas and in Asia. Some researchers have tried to exploit the potential of bacteriophages to reduce bacterial populations in infections affecting humans, while others have tried to identify uses in veterinary medicine.The overall objective of this research was to explore a new treatment against furonculosis infection based on the use of bacteriophages to inhibit growth of A. salmonicida cells. In this study, we looked at 19 strains of A. salmonicida, resistant to zero, one, two or three antibiotics, and evaluated their sensitivity to 12 bacteriophages. The results showed that the antibiotic-resistant strains were sensitive to as many bacteriophages as were the bacterial strains sensitive to antibiotics. They also showed that all the A. salmonicida strains were sensitive to several bacteriophages and, conversely, that several bacteriophages were effective against all the A. salmonicida strains. It may thus be possible to consider a preventive treatment using bacteriophages to fight against furonculosis in salmonid farms