Classical Swine Fever (CSF) is a highly contagious viral disease of swine that causes major losses to pig production. CSF virus is a member of the genus Pestivirus of the family Flaviviridae and is closely related antigenically to other Pestiviruses, Bovine Viral Diarrhoea (BVD) virus and Border Disease (BD) virus. In the Lao People’s Democratic Republic (Laos), CSF has been recognised as a disease that causes significant loss to the smallholder pig sector. However, there exists in Laos a deficiency in fully understanding the epidemiology and impact of CSF, together with limitations in being able to reliably detect CSF outbreaks in a timely manner. (For complete abstract open document)

The transient extensional rheology and the dynamics of elastocapillary thinning in aqueous solutions of polyethylene oxide (PEO) are studied with high-speed digital video microscopy. At long times, the evolution of the thread radius deviates from self-similar exponential decay and competition between elastic, capillary and inertial forces leads to the formation of a periodic array of beads connected by axially-uniform ligaments. This configuration is unstable and successive instabilities propagate from the necks connecting the beads and ligaments. This iterated process results in multiple generations of beads developing along the string in general agreement with predictions of Chang et al. [Phys Fluids, 11, 1717 (1999)] although the experiments yield a different recursion relation between the successive generations of beads. At long times, finite extensibility truncates the iterated instability, and slow axial translation of the bead arrays along the interconnecting threads leads to progressive coalescence before the ultimate rupture of the fluid column. Despite these dynamical complexities it is still possible to measure the steady growth in the transient extensional viscosity by monitoring the slow capillarydriven thinning in the cylindrical ligaments between beads. / Accepted for publication in JNNFM, December 2005. / NASA and the Portuguese Science Foundation

In this study, I examine pre-Hispanic and European beads from a variety of early Spanish colonial archaeological sites throughout the Peruvian Andes. I situate these materials and interactions within the history of Andean and European social networks. I demonstrate that the presence of European beads at specific archaeological sites —or contexts within sites— does not indicate that they directly belonged to European people, but were often incorporated into traditional Andean practices. Moreover, by engaging with theories of value and colonial hybridity, I argue that pre-Hispanic Spondylus shell and European glass beads were similarly valued due to the action invested in their acquisition from distant and unique places of origin. I further illustrate how the contemporaneous use of European and pre-Hispanic beads in forms of exchange, dress, and burial practices contributed to Andean and European beliefs and practices acquiring distinct meanings. These activities, with their changing significances, influenced the formation of new cultural identities and shaped Andean and European social values. / En este estudio, examino las cuentas prehispánicas y europeas recuperadas de varios sitios arqueológicos ocupados durante el colonialismo español temprano a lo largo los Andes peruanos. Al hacer esto, sitúo tales materiales e interacciones en la historia extensiva de las redes sociales andinas y europeas. Demuestro que la presencia de las cuentas europeas en sitios arqueológicos o en contextos dentro de dichos sitios no indica que directamente estas les pertenecieran a los europeos. Además, a partir de las varias teorías sobre valor por David Graeber, Mary Helms y Karl Marx, junto con ideas acerca del carácter híbrido de lo colonial, argumento que las cuentas prehispánicas de la concha de Spondylus y cuentas europeas eran similarmente valuadas debido a la acción invertida en su adquisición de tierras lejanas y orígenes únicos. Además, sostengo que el uso contemporáneo de las cuentas prehispánicas y europeas en las formas de intercambio, vestimenta y prácticas funerarias contribuyeron con las creencias y prácticas andinas y europeas al adquirir significados distintos. Estas actividades, con sus significados cambiantes, influían en la formación de nuevas identidades culturales, y conformaba los valores sociales de los andinos y europeos en un entorno español colonial emergente en los Andes.

In Canada, one in five people suffers from arthritis, of which the most common type is osteoarthritis (OA). OA is a group of joint diseases that cause pain and loss of range of motion and for which there is currently no cure. OA can be caused by numerous factors such as aging, genetics, environmental elements, and abnormal joint biomechanics (e.g., injury, obesity). These diseases are degenerative and lead to the progressive breakdown of joint cartilage, as well as changes in the underlying bone and other tissues of the joint over a period of years to decades. Articular cartilage incorporates a single type of resident cells, termed chondrocyte cells. These cells are entrapped within a dense extracellular matrix that limits their ability to proliferate and migrate to a site of injury, while the absence of blood vessels in the cartilage, amongst other factors, hinders the ability of progenitor cells to reach the site of injury, contributing to a limited capacity for intrinsic regeneration of the damaged tissue following an injury. As such, efforts to develop tissue engineering strategies that combine a biomaterial with bioactive signals to induce cells with the chondrogenic potential to regenerate tissue have been pursued actively. In this thesis, we investigate the potential of one such cartilage tissue engineering approach, whereby chondrocytes are encapsulated with alginate hydrogels incorporating inorganic polyphosphate (polyP), a promising chondrogenic signal. The driving hypothesis of the work was that polyanionic polyP would crosslink within the alginate hydrogel meshwork by ionic bonds with the multivalent cations used to form the hydrogel. Initial efforts focussed on optimizing the sterile chondrocyte encapsulation protocol for alginate beads, chondrocyte culture conditions to reduce proliferation – a response that is associated with dedifferentiation and a pathological state – and protocol for the incorporation of polyP in alginate bead when using calcium as a cationic crosslinker. We observed that polyP release from the calcium-alginate bead exhibited an important burst release to nearly 80% of the initial polyP loading within 24 hours of incubation in the culture medium. Increasing the alginate concentration led to approximately a 2.5-fold increase in polyP retention following the burst release. Subsequent incubation showed a more controlled release for at least 1 week. Efforts to reduce hydrogel swelling and increase its stability by substituting Ca2+ by Sr2+ as a crosslinker did not reduce the release rate during the burst release phase, nor did it increase the polyP retention following this initial stage. Other divalent cations including Mg2+ and Co2+, and pre-loading the polyP-alginate solution with a small concentration of Ca2+ did not impact the release profile either. Chondrocytes encapsulated in calcium- and strontium-alginate beads showed decreased DNA content and increased sulfated glycosaminoglycan accumulation at 1 week when polyP was incorporated in the beads compared to controls without polyP; however, this effect was lost at longer time points. These results suggest that this new material may find applications as a vehicle for the short-term delivery of polyP in joints and other tissues. Further efforts to improve the polyP release profile from alginate beads lead to promising results with the use of polyethylenimine (PEI) as a cationic tethering molecule between polyP and alginate. This thesis aims to generate novel biomaterials that can be used to stimulate cartilage tissue regeneration and to eventually develop a treatment strategy for OA. The work presented here will serve as a basis for continued efforts to ensure the prolonged retention of exogenous polyP into the joint.

Magnetic biosensors detect biological targets through sensing the stray field of magnetic beads which label the targets. Commonly, magnetic biosensors employ the “sandwich” method to immobilize biological targets, i.e., the targets are sandwiched between a bio-functionalized sensor surface and bio-functionalized magnetic beads. This method has been used very successfully in different application, but its execution requires a rather elaborate procedure including several washing and incubation steps. This dissertation investigates a new magnetic biosensor concept, which enables a simple and effective detection of biological targets. The biosensor takes advantage of the size difference between bare magnetic beads and compounds of magnetic beads and biological targets. First, the detection of super-paramagnetic beads via magnetic tunnel junction (MTJ) sensors is implemented. Frequency modulation is used to enhance the signal-to-noise ratio, enabling the detection of a single magnetic bead. Second, the concept of the magnetic biosensor is investigated theoretically. The biosensor consists of an MTJ sensor, which detects the stray field of magnetic beads inside of a trap on top of the MTJ. A microwire between the trap and the MTJ is used to attract magnetic beads to the trapping well by applying a current to it. The MTJ sensor’s output depends on the number of beads inside the trap. If biological targets are in the sample solution, the beads will form bead compounds consisting of beads linked to the biological targets. Since bead compounds are larger than bare beads, the number of beads inside the trapping well will depend on the presence of biological targets. Hence, the output of the MTJ sensor will depend on the biological targets. The dependences of sensor signals on the sizes of the MTJ sensor, magnetic beads and biological targets are studied to find the optimum constellations for the detection of specific biological targets. The optimization is demonstrated for the detection of E. coli, and similar optimization processes can be performed for the detection of other biological targets. Third, we demonstrate the new magnetic biosensor concept using a mechanical trap capable of detecting nucleic acids via the size difference between bare magnetic beads and bead compounds. The bead compounds are formed through linking nonmagnetic beads of 1 µm in diameter and magnetic beads of 2.8 µm in diameter by the target nucleic acids. The purpose of the nonmagnetic beads is to increase the size of the compounds, since the nucleic acid is very small compared to the magnetic beads. Alternatively, smaller magnetic beads could be used but their detection would be more challenging. Finally, an enhanced version of the magnetic biosensor concept is developed using an electromagnetic trap for the detection of E. coli. The trap is formed by a current-carrying microwire that attracts magnetic beads into a virtual sensing space. As in the case of the mechanical trap, the sensor signal depends on the number of beads inside of the sensing space. The distance which magnetic beads can be detected from by the MTJ sensor defines the sensing space. The results showed that the output signal depends on the concentration of E. coli in the sample solution and that individual E. coli bacterium inside the sensing space could be detected using super-paramagnetic beads that are 2.8 µm in diameter. In summary, this dissertation investigates a new magnetic biosensor concept, which detects biological targets via the size difference between bare magnetic beads and compounds of magnetic beads and biological targets. The new method is extremely simple and enables the detection of biological targets in two simple steps and within a short time. The concept is demonstrated for the detection of nucleic acid and E. coli.

Luxury goods, used in mediaeval long distance trade ca. AD 900-1250, found an important market among the Iron Age peoples of southern Africa. Indirect evidence of this trade can be seen in the form of archaeological collections of glass beads at sites throughout Africa and Southeast Asia. Thousands of beads have been found at Iron Age sites in the eastern Transvaal Lowveld and at inland sites along the Limpopo Valley and in Botswana. Similar looking types of beads, referred to as small seed beads, were also used in the Muslim mercantile networks and maritime trade in the Indian Ocean, and have been found at coeval sites throughout Southeast Asia, particularly at entrepot ports in India, eastern and western Malaysia and Thailand. At the commencement of the Iron Age occupation of southern African sites, glass beads of any kind were very rare. From ca. AD 900-1000, Islamic influences spread southward along the African east coast. This coincided with the marked increase of glass beads found in southern Africa. Their presence is direct evidence of foreign industry, external trade and contact. The beads are widely believed to have originated in India, and to have been distributed through Arab traders in the Indian Ocean. Exports would have included gold, possibly ivory, and other raw materials. Archaeology has much to contribute towards documenting these activities. The identity and location of the bead sources is important to an understanding of early contact and economic and political developments in southern Africa. The trade connection coincided with the beginning of a critical sequence of events in the cultural history of southern Africa, which culminated in the formation of an incipient state at Great Zimbabwe (AD 1250-1450) from precursors at Mapungubwe and related sites. This period corresponds in time with an important episode in Islamic history, when Muslims conquered Egypt and the Fatimids moved their capital eastwards, in AD 969, from Tunisia to al-Qahira (Cairo) next to the well-established cosmopolitan port entrepot of al- Fustat (now old Cairo). Texts, chronicles, glass weights, scribal notes and receipts confirm that it was already a successful industrial centre with a history of glass-making when the Fatimids gained control of Egypt. In this thesis I have addressed two aspects of research to investigate the trade networks associated with internal and foreign contact: (1) the manufacturing origins of the beads, and, (2) who brought them to southern Africa. Glass material from Egypt, Palestine, Syria and Southeast Asia was used for comparison, and as possible source material. Scientific techniques were used to confirm these operations. The beads were described, classified, and sampled selectively for physical and chemical analysis. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine the rare earth elements (REE) composition. The results show that a particular glass, used to make beads in Egypt, is the same as that used to make some of the beads found at sites in the northern and eastern Transvaal. They document the existence of a trade link with the Mediterranean via the Red Sea 1000 years ago. Until now, both the origin of this contact and the extent of indigenous responses were largely unknown. These findings cast a different light on maritime trade along the east coast of Africa from a millennium ago. Bibliography: pages 175-190.

Abstract Superabsorbent water beads have found many uses as household decorative items, crafts, and other industrial uses. We report a case of ingestion of several LiquiBlock Rainbow brand superabsorbent beads by a ten month old girl leading to small bowel obstruction requiring laparotomy and removal of the beads.

Two possible ways for increasing the rate of separation for magnetic bead separation has been observed. Increasing NP concentration by 2.5x gave a slight increase in rate of separation while 1.5x and 2.0x concentration increase resulted in a slight decrease in rate of separation. Synthesizing the magnetic beads under the influence of an external magnetic field also showed promising results. In a literature review, several types of magnetic beads and technologies are discussed, and how there is a great future potential for magnetic beads in the isolation of several types of biomolecules. It is concluded that the market for magnetic beads for cell isolation is expanding greatly with many different applications and expects to be worth 14.64 billion USD by 2025.

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Pavement markings are vital for safely navigating roadways. The nighttime visibility of pavement markings is enhanced by addition of retroreflective glass beads, most of which are made from recycled glass. Concern has been raised over the presence of heavy metals in glass beads used in pavement markings and their effect on human and environmental health. Based upon the potential risk associated with the presence of arsenic and lead in the glass beads, two Bills are currently being considered before the 112th Congress of the United States of America seeking to set a maximum permissible limit for the amount of arsenic and lead in glass beads used within pavement marking systems on domestic roadways. This study was designed to support legislative decision making by providing data necessary for risk assessment. The experiments carried out provide: an analysis of glass bead metal content and extractability; an evaluation of the relationship between arsenic content of the glass beads and their retroreflective performance; an evaluation of analytical methods used to measure the total bead metal content; and an analysis of samples of glass bead and soil mixture from a glass bead storage site used to determine site-specific metal concentrations in the soil media. Mean arsenic content, measured using the Pacific Northwest National Laboratory's KOH fusion digestion, in all the glass beads examined ranged from 11 ppm to 82 ppm, while mean lead content, measured using KOH fusion digestion, ranged from below quantification limit to 199 ppm. Total metal content measurements indicated a high amount of variability in the glass bead samples; most likely associated with the use of recycled glass feed during manufacturing. The relationship between the retroreflective performance and the arsenic content of the glass beads was analyzed and a weak but positive correlation was observed between the two factors. However, a more detailed study is required to evaluate the relationship between arsenic content and retroreflectivity. Different methods to evaluate the total metal content in glass beads were compared; it is recommended that any analytical method may be used, as long as the standard reference material is reproduced within the range of concentration expected in the glass beads. In the analysis of the field site samples of soil containing glass beads obtained from a glass bead storage and transfer facility, the mass content of beads in the soil varied from a mean of 19% to 78% depending on the location within the facility. However, a detailed analysis with larger number of samples must be performed to evaluate the effect of glass beads on the total arsenic content of the soil.