Single Crystals of Globular Molecules from the Melt

This thesis is an investigation of the possibility of growing single crystals of dl-camphene, d-camphor, and cyclohexanol. These are organic compounds, characterized by globular molecules , which form plastic crystals immediately below their melting point. Single crystals were desired in order to study, by ultra-sound techniques, properties pertinent to the evaluation of the elastic constants of these crystals. Primary emphasis was placed on growing crystals of dl-camphene, since it is conveniently handled at room temperatures. Methods of growth from the melt were chosen because of the relatively fast growth rates, compared to vapor or solution techniques. Secondary considerations were simplicity of the apparatus and the final geometry of the crystals, with the cylindrical shape being well suited for the ultrasonic measurements

Prevalence and diversity of Chlamydiales in Swiss ruminant farms.

Chlamydia and Chlamydia-related bacteria are known to infect various organisms and may cause a wide range of diseases, especially in ruminants. To gain insight into the prevalence of these bacteria in the ruminant environment, we applied a pan-Chlamydiales PCR followed by sequencing to 72 ruminant environmental samples from water, feed bunks and floors. Chlamydiales from four family-level lineages were detected indicating a high biodiversity of Chlamydiales in ruminant farms. Parachlamydiaceae were detected in all three types of environmental samples and was the most abundant family-level taxon (60%). In contrast, only one bacterium from each of the following family-level lineages was identified: Chlamydiaceae, Criblamydiaceae and Simkaniaceae. The observed high prevalence of Parachlamydiaceae in water samples may suggest water as the main source of contamination for ruminants as well as their environment due to spoilage. The absence of reported infections in the investigated ruminant farms might indicate that either detected Chlamydiales are of reduced pathogenicity or infective doses have not been reached

Crescent and star shapes of members of the Chlamydiales order: impact of fixative methods.

Members of the Chlamydiales order all share a biphasic lifecycle alternating between small infectious particles, the elementary bodies (EBs) and larger intracellular forms able to replicate, the reticulate bodies. Whereas the classical Chlamydia usually harbours round-shaped EBs, some members of the Chlamydia-related families display crescent and star-shaped morphologies by electron microscopy. To determine the impact of fixative methods on the shape of the bacterial cells, different buffer and fixative combinations were tested on purified EBs of Criblamydia sequanensis, Estrella lausannensis, Parachlamydia acanthamoebae, and Waddlia chondrophila. A linear discriminant analysis was performed on particle metrics extracted from electron microscopy images to recognize crescent, round, star and intermediary forms. Depending on the buffer and fixatives used, a mixture of alternative shapes were observed in varying proportions with stars and crescents being more frequent in C. sequanensis and P. acanthamoebae, respectively. No tested buffer and chemical fixative preserved ideally the round shape of a majority of bacteria and other methods such as deep-freezing and cryofixation should be applied. Although crescent and star shapes could represent a fixation artifact, they certainly point towards a diverse composition and organization of membrane proteins or intracellular structures rather than being a distinct developmental stage

Deer as a potential wildlife reservoir for Parachlamydia species.

Wildlife populations represent an important reservoir for emerging pathogens and trans-boundary livestock diseases. However, detailed information relating to the occurrence of endemic pathogens such as those of the order Chlamydiales in such populations is lacking. During the hunting season of 2008, 863 samples (including blood, conjunctival swabs, internal organs and faeces) were collected in the Eastern Swiss Alps from 99 free-living red deer (Cervus elaphus) and 64 free-living roe deer (Capreolus capreolus) and tested using ELISA, PCR and immunohistochemistry for members of the family Chlamydiaceae and the genus Parachlamydia. Parachlamydia spp. were detected in the conjunctival swabs, faeces and internal organs of both species of deer (2.4% positive, with a further 29.5% inconclusive). The very low occurrence of Chlamydiaceae (2.5%) was in line with serological data (0.7% seroprevalence for Chlamydia abortus). Further investigations are required to elucidate the zoonotic potential, pathogenicity, and distribution of Parachlamydia spp. in wild ruminants

Development of a new chlamydiales-specific real-time PCR and its application to respiratory clinical samples.

Originally composed of the single family Chlamydiaceae, the Chlamydiales order has extended considerably over the last several decades. Chlamydia-related bacteria were added and classified into six different families and family-level lineages: the Criblamydiaceae, Parachlamydiaceae, Piscichlamydiaceae, Rhabdochlamydiaceae, Simkaniaceae, and Waddliaceae. While several members of the Chlamydiaceae family are known pathogens, recent studies showed diverse associations of Chlamydia-related bacteria with human and animal infections. Some of these latter bacteria might be of medical importance since, given their ability to replicate in free-living amoebae, they may also replicate efficiently in other phagocytic cells, including cells of the innate immune system. Thus, a new Chlamydiales-specific real-time PCR targeting the conserved 16S rRNA gene was developed. This new molecular tool can detect at least five DNA copies and show very high specificity without cross-amplification from other bacterial clade DNA. The new PCR was validated with 128 clinical samples positive or negative for Chlamydia trachomatis or C. pneumoniae. Of 65 positive samples, 61 (93.8%) were found to be positive with the new PCR. The four discordant samples, retested with the original test, were determined to be negative or below detection limits. Then, the new PCR was applied to 422 nasopharyngeal swabs taken from children with or without pneumonia; a total of 48 (11.4%) samples were determined to be positive, and 45 of these were successfully sequenced. The majority of the sequences corresponded to Chlamydia-related bacteria and especially to members of the Parachlamydiaceae family

Presence of Chlamydiales DNA in ticks and fleas suggests that ticks are carriers of Chlamydiae.

The Chlamydiales order includes the Chlamydiaceae, Parachlamydiaceae, Waddliaceae, Simkaniaceae, Criblamydiaceae, Rhabdochlamydiaceae, Clavichlamydiaceae, and Piscichlamydiaceae families. Members of the Chlamydiales order are obligate intracellular bacteria that replicate within eukaryotic cells of different origins including humans, animals, and amoebae. Many of these bacteria are pathogens or emerging pathogens of both humans and animals, but their true diversity is largely underestimated, and their ecology remains to be investigated. Considering their potential threat on human health, it is important to expand our knowledge on the diversity of Chlamydiae, but also to define the host range colonized by these bacteria. Thus, using a new pan-Chlamydiales PCR, we analyzed the prevalence of Chlamydiales DNA in ticks and fleas, which are important vectors of several viral and bacterial infectious diseases. To conduct this study, 1340 Ixodes ricinus ticks prepared in 192 pools were collected in Switzerland and 55 other ticks belonging to different tick species and 97 fleas belonging to different flea species were harvested in Algeria. In Switzerland, the prevalence of Chlamydiales DNA in the 192 pools was equal to 28.1% (54/192) which represents an estimated prevalence in the 1340 individual ticks of between 4.0% and 28.4%. The pan-Chlamydiales qPCR was positive for 45% (25/55) of tick samples collected in Algeria. The sequencing of the positive qPCR amplicons revealed a high diversity of Chlamydiales species. Most of them belonged to the Rhabdochlamydiaceae and Parachlamydiaceae families. Thus, ticks may carry Chlamydiales and should thus be considered as possible vectors for Chlamydiales propagation to both humans and animals

Self-sensing cellulose structures with design-controlled stiffness

Robots are often used for sensing and sampling in natural environments. Within this area, soft robots have become increasingly popular for these tasks because their mechanical compliance makes them safer to interact with. Unfortunately, if these robots break while working in vulnerable environments, they create potentially hazardous waste. Consequently, the development of compliant, biodegradable structures for soft, eco-robots is a relevant research area that we explore here. Cellulose is one of the most abundant biodegradable materials on earth, but it is naturally very stiff, which makes it difficult to use in soft robots. Here, we look at both biologically and kirigami inspired structures that can be used to reduce the stiffness of cellulose based parts for soft robots up to a factor of 19 000. To demonstrate this, we build a compliant force and displacement sensing structure from microfibrillated cellulose. We also describe a novel manufacturing technique for these structures, provide mechanical models that allow designers to specify their stiffness, and conclude with a description of our structure's performance

Structural and physical properties of layered oxy-arsenides LnRuAsO (Ln = La, Nd, Sm, Gd)

Polycrystalline samples of LaRuAsO, NdRuAsO, SmRuAsO, and GdRuAsO have been synthesized and studied using powder x-ray diffraction, electrical transport, magnetization, and heat capacity measurements. Variations in structural properties across the series reveal a trend toward more ideal tetrahedral coordination around Ru as the size of the rare earth element is reduced. The lattice parameters of these Ru compounds show a more anisotropic response to variation in Ln than their Fe analogues, and significant anisotropy in thermal expansion is also observed. Transport measurements show metallic behavior, and carrier concentrations near 10^21 - 10^22 electrons per cm^3 are inferred from simple analysis of Hall effect measurements. Anomalies in resistivity, magnetization, and heat capacity indicate antiferromagnetic ordering of rare earth moments at 5 K for GdRuAsO, 4.5 K for SmRuAsO, and <2 K for NdRuAsO. Magnetization measurements on LaRuAsO show no evidence of a magnetic moment on Ru. Observed behaviors are compared to those reported for similar Fe and Ru compounds

Maximizing lentiviral vector gene transfer in the CNS.

Gene transfer is a widely developed technique for studying and treating genetic diseases. However, the development of therapeutic strategies is challenging, due to the cellular and functional complexity of the central nervous system (CNS), its large size and restricted access. We explored two parameters for improving gene transfer efficacy and capacity for the selective targeting of subpopulations of cells with lentiviral vectors (LVs). We first developed a second-generation LV specifically targeting astrocytes for the efficient expression or silencing of genes of interest, and to better study the importance of cell subpopulations in neurological disorders. We then made use of the retrograde transport properties of a chimeric envelope to target brain circuits affected in CNS diseases and achieve a broad distribution. The combination of retrograde transport and specific tropism displayed by this LV provides opportunities for delivering therapeutic genes to specific cell populations and ensuring high levels of transduction in interconnected brain areas following local administration. This new LV and delivery strategy should be of greater therapeutic benefit and opens up new possibilities for the preclinical development of gene therapy for neurodegenerative diseases