Study on Transverse Horizontal Error Calculation and Alignment Fitting for Newly Built Railway

The design alignment of newly built railway is described by sorted linked lists consisting of straight line element, circular curve element and transition curve element. Based on this description this article studies the method for calculating transverse horizontal errors of structure centers of newly built railway. The article also studies the method for fitting newly built railway alignment, that is based on fitting straight line element and circular curve element using the least squares method and then resolving the transition curve element.

Culture of Mesenchymal Stem Cells on Nanosheets Assembled at the Surface of Liquid Microcarriers.

PhD ThesisMesenchymal stem cells (MSC) are one of the prevalent cell types for potential clinical utility including cell therapies and tissue engineering. In order to meet massive demand for clinical usage, a large scale in vitro cell expansion is required. The culture of adherent cells like MSCs is typically thought to require cell spreading on a rigid substrate to sustain the formation of stable focal adhesions and the assembly of a contractile cytoskeleton. More recent studies suggest that cells may also actively respond to external stimuli despite the lack of bulk mechanics on underlying substrates, bringing liquid-liquid interface, which offers attractive features for the development of novel stem cell technologies as a potential culture platform. In particular, liquid emulsions can provide surface area comparable to current solid-microcarriers used in industry for cell culture, emulsion are also more advantageous in avoiding harsh enzymatic digestion for cell harvesting. The relative cheaper cost and potential recyclability also make emulsions a promising substrate for next generation platform for in vitro cell expansion. In this thesis, we aim at developing a protein nanosheet-assembled liquid-liquid interface with tuneable interfacial mechanical properties for the expansion of MSCs. In particular we focus on development of a protein-nanosheet stabilised oil in water (O/W) emulsion as a carrier for long-term cell culture. Chapter one presents fundamental knowledge of this research, starting with a general description of integrin mediated cell adhesion and mechanotransduction, followed by an introduction to self-assembled polyelectrolyte multilayers (PEMs) for cell culture. The third part discusses the generation of emulsions by highlighting the important role of agitation and emulsifiers in its formation. Special attention is paid to the stability of the emulsion. In the final section of this chapter, we investigate the current cell expansion techniques with a major focus on microcarrier-based bioreactor systems. In Chapter two, we focus on the design and characterisation of poly-L-lysine (PLL) nanosheets at the liquid-liquid interface between fluorinated oil and PBS. The impact of pro-surfactant, solution pH and IV PLL molecular weight on PLL assembly at the interface are investigated. In particular, we focus on the impact on the interfacial mechanical properties, characterised by interfacial rheology. Upon the adjustment of these parameters, controllable PLL nanosheets with interfacial moduli of a wide range are obtained. Chapter three demonstrates the culture of MSC on the interfaces prepared in chapter two. Cell adhesion is studied by imaging focal adhesion markers and actin, demonstrating that MSC adhesion at our liquid-liquid interface is mediated by classical integrin/acto-myosin machinery. Cellular proliferation is also found on such nanosheets, showing the effects of pro-surfactant and nanosheet mechanics on the ultimate cell output. Similar findings are also displayed by other non-fluorinated oil systems. Furthermore, we summarise interfacial mechanical properties of the nanosheets and the corresponding proliferation data, showing MSC proliferation at the liquid-liquid interface is seemingly regulated by the stress retention of the self-assembled PLL nanosheets. In chapter four, O/W emulsion stabilised by the PLL assembled nanosheets is employed as a novel platform for the culture of MSCs. Based on the emulsion stability and cell proliferation, the optimum emulsion is selected to conduct long-term culture of MSCs and compared with commercially available microcarriers and tissue culture polystyrene (TPS, tissue culture treated). During this process cellular adhesion and morphology are monitored; the expression of MSC surface markers are characterised, whilst the stemness and multi-lineage differentiation potential are all characterised. These characterisations demonstrate minor difference in MSC phenotypes on three different platforms, suggesting the emulsion could be a potential candidate for the in vitro expansion of MSCs. Chapter five summarises the main findings and conclusions of this thesis, addresses the challenges of the project and provides possible directions and improvements for future research

SOCIAL PREFERENCES AND OPEN SOURCE SOFTWARE DEVELOPMENT

Open source software (OSS), and open innovation in general, has received increasing attention from both researchers and practitioners. Based on recent literature on social preference from behavior economics, we propose a finite-horizon dynamic model to study the interactions between OSS developers who are either purely self-interested or conditional cooperators. We find that selfinterested developers who are predicted to free ride under conventional analysis may contribute to a public good, and the existence of purely these developers may, under certain conditions, even benefit the provision of a public good. We further analyze how code architecture affects OSS development outcome and propose that a higher level of code modularity leads to more code contributions overall, due to the strategic behavior of self-interested developers. However, a right mix of the two types of developers plays a critical role for modular design to make an impact. The findings bear important theoretical as well as practical implications and provide guidelines for OSS development and the collective innovation in general

CODE ARCHITECTURE AND OPEN SOURCE SOFTWARE DEVELOPMENT

A model is developed to study how the code architecture affects open source software (OSS) development. The model incorporates the resource heterogeneity and diverse motivations of various groups of programmers as well as the strategic interactions among them. We argue that the major advantage brought by a modular architecture of OSS code base is that it reduces both the cognitive cost and the coordination cost associated with OSS development, thus allowing programmers more easily to locate, manage, and contribute to the code base. We show that in OSS development, while modular architecture can potentially increase code contribution, it does not necessarily reduce free-riding; in fact it may well increase free-riding due to the strategic interactions among the programmers. We further empirically test the predictions using the SourceForge OSS development data, and the results confirm our theoretical predictions. The findings bear important theoretical as well as practical implications and provide guidelines for practitioners of OSS development and the collective innovation in general

The relationship between post-procedural platelet count and left ventricular aneurysm in patients with acute anterior ST-segment elevation myocardial infarction following primary percutaneous coronary intervention

Background: Left ventricular aneurysm (LVA) relates to worse prognosis in patients with myocardial infarction despite successful reperfusion treatment. There is no evidence that early detectable biomarkers can predict the risk for the future development of LVA. Aim: The aim of our study was to investigate the possible predictive value of periprocedural haematological parameters for LVA. Methods: A total of 281 patients with acute anterior ST-segment elevation myocardial infarction (STEMI) who underwent primary percutaneous coronary intervention (pPCI) were enrolled. Haematological parameters were measured on admission before pPCI and between 8 and 12 h after pPCI, separately. The development of LVA was evaluated at one-year follow-up. The patients were then divided into two groups: an LVA group and a non-LVA group. Univariate and multivariate logistic regression analyses were performed to find the predictors of LVA. Results: A total of 34 (12.1%) patients developed LVA at one-year follow-up after pPCI. Multivariate analyses revealed that a 10 × 109/L increase in platelet count 12 h after pPCI (odds ratio [OR] 1.092, 95% confidence interval [CI] 1.015–1.188, p = 0.039), peak cardiac troponin I (OR 1.107, 95% CI 1.003–1.215, p = 0.000), and left ventricular ejection fraction (OR 0.853, 95% CI 0.772–0.943, p = 0.002) were independent risk factors for LVA. For the prediction of LVA, platelet count 12 h after pPCI at a cut-off value > 197 × 109/L yielded a receiver operating characteristic-area under the curve (ROC-AUC) of 0.635 (82.3% sensitivity, 44.1% specificity). Conclusions: Platelet count after pPCI was significantly associated with the development of LVA in anterior STEMI patients and may be available for early risk stratification of future LVA formation