Distribution and dynamics of Tc-99m-pertechnetate uptake in the thyroid and other organs assessed by single-photon emission computed tomography in living mice

Background: Tc-99m pertechnetate is a well-known anion, used for clinical imaging of thyroid function. This gamma emitter is transported by the sodium iodide symporter but is not incorporated into thyroglobulin. Scintigraphy using Tc-99m pertechnetate or 123 iodide represents a powerful tool for the study of sodium iodide symporter activity in different organs of living animal models. However, in many studies that have been performed in mice, the thyroid could not be distinguished from the salivary glands. In this work, we have evaluated the use of a clinically dedicated single-photon emission computed tomography (SPECT) camera for thyroid imaging and assessed what improvements are necessary for the development of this technique. Methods: SPECT of the mouse neck region, with pinhole collimation and geometric calibration, was used for the individual measurement of Tc-99m pertechnetate uptake in the thyroid and the salivary glands. Uptake in the stomach was studied by planar whole-body imaging. Uptake kinetics and biodistribution studies were performed by sequential imaging. Results: This work has shown that thyroid imaging in living mice can be performed with a SPECT camera originally built for clinical use. Our experiments indicate that Tc-99m pertechnetate uptake is faster in the thyroid than in the salivary glands and the stomach. The decrease in Tc-99m pertechnetate uptake after injection of iodide or perchlorate as competitive inhibitors was also studied. The resulting rate decreases were faster in the thyroid than in the salivary glands or the stomach. Conclusions: We have shown that a clinically dedicated SPECT camera can be used for thyroid imaging. In our experiments, SPECT imaging allowed the analysis of Tc-99m pertechnetate accumulation in individual organs and revealed differences in uptake kinetics

Structural fatigue life investigation of a rigidly mounted aluminium fuel tank

Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Structural cracks have formed in the sub-structure of a tank that is rigidly mounted onto a truck chassis. These cracks have all formed at welds joining the various components of the aluminium sub-structure. This thesis proposes a solution methodology to address these failures. The first phase of this methodology (failure investigation) relies heavily on determining the life of the structure with fatigue life calculations. These calculations are done using the stress life method supplemented by the hot spot stress method. Experimental tests were conducted at an operational air force base to compile a composite duty cycle that is representative of the typical operation of the vehicle. This is followed by a finite element analysis which is used to calculate the scaling factor required to determine the hot spot stresses in the structure. These hot spot stresses are determined for three different crack areas and the estimated fatigue life of each of these points are calculated. The estimated fatigue lives are compared to the actual lives that were reported by the maintenance personnel, to determine a correlation factor. The comparison yields a maximum correlation factor of 9.8 and a minimum of 3.9. It is suggested that the minimum correlation factor of 3.9 is used to assess future solutions. It is also suggested to reduce the stresses by at least 37% to achieve the desired service life. Recommendations regarding the design of a repair are given. The methodology presented in this thesis provides the groundwork for a typical solution methodology that can be used at GRW Engineering. Recommendations for improvements to the method and its components are given.AFRIKAANSE OPSOMMING: Strukturele krake het ontstaan in die substruktuur van ’n tenk wat rigied gemonteer is op ’n vragmotor onderstel. Die krake het almal ontstaan op sweislaste wat die verskillende komponente van die aluminium struktuur bind. Hierdie tesis stel ’n oplossingsmetodologie voor om hierdie falings aan te spreek. Die eerste fase van hierdie metodologie (falingsondersoek) maak hewig staat op berekeninge van strukturele vermoeidheid. Hierdie berekeninge word gedoen met behulp van die ‘stress-life’ metode aangevul deur die ‘hot spot stress’ metode. Eksperimentele toetse is uitgevoer op ’n operasionele lugmagbasis om ’n saamgestelde dienssiklus te bepaal wat verteenwoordigend is van die tipiese operationele omstandighede van die voertuig. Dit word gevolg deur ’n eindige element analise wat gebruik word om die skalering faktor te bereken wat nodig is om die ‘hot spot’ spanning in die struktuur te bepaal. Hierdie ‘hot spot’ spanning word bepaal vir drie verskillende kraak gebiede ten einde die beraamde vermoeidheidslewe van elk van hierdie punte te bereken. Die beraamde vermoeidheidslewe word vergelyk met die werklike lewe wat deur die instandhoudingspersoneel berig is, om ’n korrelasie faktor te bepaal. Die vergelyking lewer ’n maksimum korrelasie faktor van 9.8 en ’n minimum van 3.9. Daar word voorgestel dat die minimum korrelasie faktor van 3.9 gebruik word in die bepaling van toekomstige oplossings. Daar word ook voorgestel dat die spanning met ten minste 37% verlaag word om die verwagte lewensduur te bereik. Aanbevelings ten opsigte van ’n verbetering aan die huidige struktuur word ook gegee. Die metodologie wat in hierdie tesis aangebied word, bied die grondslag vir ’n tipiese oplossingsmetodologie wat by GRW Engineering gebruik kan word. Aanbevelings vir verbeterings aan die metode en die verskeie komponente word ook voorgestel

Chemokines: A New Dendritic Cell Signal for T Cell Activation

Dendritic cells (DCs) are the main inducers and regulators of cytotoxic T lymphocyte (CTL) responses against viruses and tumors. One checkpoint to avoid misguided CTL activation, which might damage healthy cells of the body, is the necessity for multiple activation signals, involving both antigenic as well as additional signals that reflect the presence of pathogens. DCs provide both signals when activated by ligands of pattern recognition receptors and “licensed” by helper lymphocytes. Recently, it has been established that such T cell licensing can be facilitated by CD4+ T helper cells (“classical licensing”) or by natural killer T cells (“alternative licensing”). Licensing regulates the DC/CTL cross-talk at multiple layers. Direct recruitment of CTLs through chemokines released by licensed DCs has recently emerged as a common theme and has a crucial impact on the efficiency of CTL responses. Here, we discuss recent advances in our understanding of DC licensing for cross-priming and implications for the temporal and spatial regulation underlying this process. Future vaccination strategies will benefit from a deeper insight into the mechanisms that govern CTL activation

Persistent Identification for Conferences

Persistent identification of entities plays a major role in the progress of digitization of many fields. In the scholarly publishing realm there are already persistent identifiers (PID) for papers (DOI), people (ORCID), organisation (GRID, ROR), books (ISBN) but there is no generally accepted PID system for scholarly events such as conferences or workshops yet. This article describes the relevant use cases that motivate the introduction of persistent identifiers for conferences. The use cases were mainly derived from interviews, discussions with experts and their previous work. As primary stakeholders who are involved in the typical conference event life cycle researchers, conference organizers, and data consumers were identified. The resulting list of use cases illustrates how PIDs for conference events will improve the current situation for these stakeholders and help with problems they are facing today

Are behavioral and electrophysiological measures of impulsivity useful for predicting entrepreneurship?

We examine the association between several behavioral and electrophysiological indices of impulsivity-related constructs and multiple entrepreneurial constructs. Specifically, we investigate if these behavioral and electrophysiological measures are more useful as predictors of entrepreneurship than self-reported measures of impulsivity. Our findings are based on two datasets (n = 133 and n = 142) and indicate that behavioral and electrophysiological impulsivity measures are not robustly associated with entrepreneurship constructs, in contrast to selfreported measures of impulsivity. Though disappointing at first, our findings pave the way for future research on the relevance of behavioral and electrophysiological measures for entrepreneurship

Data-Driven Regionalization of Decarbonized Energy Systems for Reflecting Their Changing Topologies in Planning and Optimization

The decarbonization of energy systems has led to a fundamental change in their topologysince generation is shifted to locations with favorable renewable conditions. In planning, this changeis reflected by applying optimization models to regions within a country to optimize the distributionof generation units and to evaluate the resulting impact on the grid topology. This paper proposesa globally applicable framework to find a suitable regionalization for energy system models witha data-driven approach. Based on a global, spatially resolved database of demand, generation,and renewable profiles, hierarchical clustering with fine-tuning is performed. This regionalizationapproach is applied by modeling the resulting regions in an optimization model including asynthesized grid. In an exemplary case study, South Africa’s energy system is examined. The resultsshow that the data-driven regionalization is beneficial compared to the common approach of usingpolitical regions. Furthermore, the results of a modeled 80% decarbonization until 2045 demonstratethat the integration of renewable energy sources fundamentally changes the role of regions withinSouth Africa’s energy system. Thereby, the electricity exchange between regions is also impacted,leading to a different grid topology. Using clustered regions improves the understanding and analysisof regional transformations in the decarbonization process

Early Adolescent Friendship Selection Based on Externalizing Behavior: the Moderating Role of Pubertal Development. The SNARE Study

Abstract This study examined friendship (de-)selection processes in early adolescence. Pubertal development was examined as a potential moderator. It was expected that pubertal development would be associated with an increased tendency for adolescents to select their friends based on their similarities in externalizing behavior engagement (i.e., delinquency, alcohol use, and tobacco use). Data were used from the first three waves of the SNARE (Social Network Analysis of Risk behavior in Early adolescence) study (N = 1144; 50 % boys; M age = 12.7; SD = 0.47), including students who entered the first year of secondary school. The hypothesis was tested using Stochastic Actor-Based Modeling in SIENA. While taking the network structure into account, and controlling for peer influence effects, the results supported this hypothesis. Early adolescents with higher pubertal development were as likely as their peers to select friends based on similarity in externalizing behavior and especially likely to remain friends with peers who had a similar level of externalizing behavior, and thus break friendship ties with dissimilar friends in this respect. As early adolescents are actively engaged in reorganizing their social context, adolescents with a higher pubertal development are especially likely to lose friendships with peers who do not engage in externalizing behavior, thus losing an important source of adaptive social control (i.e., friends who do not engage in externalizing behavior)

The Role of Privacy in Digitalization – Analyzing Perspectives of German Farmers

Technological progress can disrupt domains and change the way we work and collaborate. This paper presents a qualitative study with 52 German farmers that investigates the impact of the ongoing digitalization process in agriculture and discusses the implications for privacy research. As in other domains, the introduction of digital tools and services leads to the data itself becoming a resource. Sharing this data with products along the supply chain is favored by retailers and consumers, who benefit from traceability through transparency. However, transparency can pose a privacy risk. Having insight into the business data of others along the supply chain provides an advantage in terms of market position. This is particularly true in agriculture, where there is already a significant imbalance of power between actors. A multitude of small and medium-sized farming businesses are opposed by large upstream and downstream players that drive technological innovation. Further weakening the market position of farmers could lead to severe consequences for the entire sector. We found that on the one hand, privacy behaviors are affected by adoption of digitalization, and on the other hand, privacy itself influences adoption of digital tools. Our study sheds light on the emerging challenges for farmers and the role of privacy in the process of digitalization in agriculture