Improved Method of Neutron Activation Analysis for Microleakage Studies

Improvements in the neutron activation technique for studying microleakage were achieved by selecting more suitable tracers and by using a more accurate method for evaluation of the activation data. Dysprosium was the most suitable tracer; it provided the least variation in the results and allowed the fastest activation and counting procedure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66594/2/10.1177_00220345740530022901.pd

Banana streak badnavirus (BSV) in South Africa : incidence, transmission and the development of an antibody based detection system

Various research efforts have focused on Banana streak badnavirus (BSV), the causal agent of banana streak disease (BSD), since the discovery of endogenous sequences of the virus in the nuclear genome of several Musa (banana and plantain) species. In vitro propagation of Musa was identified as one of the main activation triggers of integrated BSV sequences to cause systemic (episomal) BSD. This was especially observed in B genome-containing tetraploid hybrids. Although, the South African banana industry is based on Cavendish varieties, some plantations with tetraploid hybrids have been established. In order to investigate the occurrence of episomally expressed BSV, a survey was done in the Kiepersol area of South Africa and episomal BSV was detected in six out of seven locations sampled. No episomal BSV was detected in the Cavendish cultivars sampled in close proximity to BSV infected cultivars. To determine the risk of vector-assisted spread of endogenous BSV, which has become episomally activated after tissue culture, transmission studies with local mealybug species (Planococcus citri (Risso), P. ficus (Signoret), Dysmicoccus brevipes (Cockerell) and Pseudococcus longispinus (Targioni-Tozzetti)) were conducted under controlled conditions. Virus-free FHIA-21 was multiplied in vitro and resulting progeny with, putatively episomally activated BSV, served as sources for mealybug-assisted transmissions to Cavendish. Activated, episomal BSV was transmitted by three mealybug species to Cavendish. Transmission with P. ficus was demonstrated for the first time. Limited antiserum stocks against BSV occur worldwide and detection of the virus remains crucial for the safe movement of Musa germplasm between continents. Antiserum is needed in order to detect the episomal form of the virus that causes BSD. Using conventional immunization methodology, antisera against a wide spectrum of BSV isolates were produced. Twenty diverse BSV isolates were characterized by IC-PCR and selected as sources for the production of the polyclonal antiserums in two animal species. An effective triple antibody sandwich (TAS) enzyme linked immunosorbent assay (ELISA) system; able to detect various serologically different species of BSV was developed. BSV was screened with a synthetically manufactured phage displayed antibody library; however, no satisfactory polyclonal or monoclonal antibodies were obtianed in using this approach.Dissertation (MSc (Microbiology))--University of Pretoria, 2007.Microbiology and Plant Pathologyunrestricte

Initial Leakage Under Pit and Fissure Sealants Assessed by Neutron Activation

An improved neutron activation method and a model system were used to study microleakage associated with three pit and fissure sealants. Both the sealant and the etching procedure were evaluated on enamel surfaces as well as in prepared model pits. Leakage was reduced to 3 to 4 μg for all three materials, and the etching process was relatively ineffective in forming an initial seal.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66699/2/10.1177_00220345740530062501.pd

Misleading signatures of quantum chaos

The main signature of chaos in a quantum system is provided by spectral statistical analysis of the nearest neighbor spacing distribution and the spectral rigidity given by $\Delta_3(L)$. It is shown that some standard unfolding procedures, like local unfolding and Gaussian broadening, lead to a spurious increase of the spectral rigidity that spoils the $\Delta_3(L)$ relationship with the regular or chaotic motion of the system. This effect can also be misinterpreted as Berry's saturation.Comment: 4 pages, 5 figures, submitted to Physical Review

Novel RNA modifications in the nervous system: form and function

Modified RNA molecules have recently been shown to regulate nervous system functions. This mini-review and associated mini-symposium provide an overview of the types and known functions of novel modified RNAs in the nervous system, including covalently modified RNAs, edited RNAs, and circular RNAs. We discuss basic molecular mechanisms involving RNA modifications as well as the impact of modified RNAs and their regulation on neuronal processes and disorders, including neural fate specification, intellectual disability, neurodegeneration, dopamine neuron function, and substance use disorders

Human-machine networks: Towards a typology and profiling framework

© Springer International Publishing Switzerland 2016. In this paper we outline an initial typology and framework for the purpose of profiling human-machine networks, that is, collective structures where humans and machines interact to produce synergistic effects. Profiling a humanmachine network along the dimensions of the typology is intended to facilitate access to relevant design knowledge and experience. In this way the profiling of an envisioned or existing human-machine network will both facilitate relevant design discussions and, more importantly, serve to identify the network type. We present experiences and results from two case trials: a crisis management system and a peerto- peer reselling network. Based on the lessons learnt from the case trials we suggest potential benefits and challenges, and point out needed future work

On the equivalence between hierarchical segmentations and ultrametric watersheds

We study hierarchical segmentation in the framework of edge-weighted graphs. We define ultrametric watersheds as topological watersheds null on the minima. We prove that there exists a bijection between the set of ultrametric watersheds and the set of hierarchical segmentations. We end this paper by showing how to use the proposed framework in practice in the example of constrained connectivity; in particular it allows to compute such a hierarchy following a classical watershed-based morphological scheme, which provides an efficient algorithm to compute the whole hierarchy.Comment: 19 pages, double-colum

A technique for thoracic duct-portal vein anastomosis in the dog

A technique for effecting a thoracic duct-portal vein anastomosis in dogs is described.The journals have been scanned in colour with a HP 5590 scanner; 600 dpi. Adobe Acrobat v.11 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Transport Properties of the Quark-Gluon Plasma -- A Lattice QCD Perspective

Transport properties of a thermal medium determine how its conserved charge densities (for instance the electric charge, energy or momentum) evolve as a function of time and eventually relax back to their equilibrium values. Here the transport properties of the quark-gluon plasma are reviewed from a theoretical perspective. The latter play a key role in the description of heavy-ion collisions, and are an important ingredient in constraining particle production processes in the early universe. We place particular emphasis on lattice QCD calculations of conserved current correlators. These Euclidean correlators are related by an integral transform to spectral functions, whose small-frequency form determines the transport properties via Kubo formulae. The universal hydrodynamic predictions for the small-frequency pole structure of spectral functions are summarized. The viability of a quasiparticle description implies the presence of additional characteristic features in the spectral functions. These features are in stark contrast with the functional form that is found in strongly coupled plasmas via the gauge/gravity duality. A central goal is therefore to determine which of these dynamical regimes the quark-gluon plasma is qualitatively closer to as a function of temperature. We review the analysis of lattice correlators in relation to transport properties, and tentatively estimate what computational effort is required to make decisive progress in this field.Comment: 54 pages, 37 figures, review written for EPJA and APPN; one parag. added end of section 3.4, and one at the end of section 3.2.2; some Refs. added, and some other minor change