Topological Field Theory and Rational Curves

We analyze the superstring propagating on a Calabi-Yau threefold. This theory naturally leads to the consideration of Witten's topological non-linear sigma-model and the structure of rational curves on the Calabi-Yau manifold. We study in detail the case of the world-sheet of the string being mapped to a multiple cover of an isolated rational curve and we show that a natural compactification of the moduli space of such a multiple cover leads to a formula in agreement with a conjecture by Candelas, de la Ossa, Green and Parkes.Comment: 20 page

The Origin, Early Evolution and Predictability of Solar Eruptions

Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from the Sun. Today, it is known that the Sun produces eruptive flares, filament eruptions, coronal mass ejections and failed eruptions; all thought to be due to a release of energy stored in the coronal magnetic field during its drastic reconfiguration. This review discusses the observations and physical mechanisms behind this eruptive activity, with a view to making an assessment of the current capability of forecasting these events for space weather risk and impact mitigation. Whilst a wealth of observations exist, and detailed models have been developed, there still exists a need to draw these approaches together. In particular more realistic models are encouraged in order to asses the full range of complexity of the solar atmosphere and the criteria for which an eruption is formed. From the observational side, a more detailed understanding of the role of photospheric flows and reconnection is needed in order to identify the evolutionary path that ultimately means a magnetic structure will erupt

Enzymatic selfpowered biosensing devices

Self-powered biosensors have been the focus of intense research due to the wide range of potential applications concerning real-time personal healthcare monitoring and disease diagnostics. The increased demand for autonomous biosensors along with the progress achieved in enzymatic fuel cells (EFCs) as power sources, hold great potential for developing new devices. Firstly, focus is given to the concepts underlying the fundamental operation of EFCs, covering both direct electron transfer and mediated electron transfer systems. As an essential step to achieve the required EFC power density performances in real applications, enzyme immobilization is critically discussed in terms of strategies to immobilize and stabilize enzymes at the electrodes of the EFCs. Highlight is then given to the progress obtained in EFCs-based biosensors. Since these devices harvest electrical power from biological systems, their unique advantages favored progress in terms of biomedical applications of self-powered biosensors. Therefore, the most recent advances in implantable, wearable and point-of-care autonomous biosensors incorporating EFCs is summarized and discussed. Key technological challenges are still present, but these devices are on track to achieve the foreseen realization of the full diagnostic potential of enzymatic fuel cells-based biosensors.One of the authors (F.T.C.M.) gratefully acknowledges Fundação para a Ciência e Tecnologia for financial support (postdoc grant reference No. SFRH/BPD/97891/2013, entitled “Biomedical devices for easier and quicker screening procedures of Alzheimer disease”). The authors from BioMark are grateful to the project IBEROS (Instituto de Bioingeniería en Red para el Envejecimiento Saludable), POCTEP/0245‐BEROS‐1‐E, PROGRAMA INTERREG 2014–2020, funded through FEDER within the cooperation region of Galicia/Spain and North of Portugal. The authors from BioMark are grateful to the project Cancer (NORTE‐01‐0145‐FEDER‐000029), entitled “Advancing cancer research: from basic knowledge to application,” funded by Norte 2020 – Programa Operacional Regional do Norte. The authors from the Centre of Biological Engineering (CEB) gratefully acknowledge the support of the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469 unit, COMPETE 2020 (POCI‐01‐0145‐FEDER‐006684), and the project entitled “MultiBiorefinery‐multi‐purpose strategies for broadband agro‐forest and fisheries by‐products valorization: a step forward for a truly integrated biorefinery” (POCI‐01‐0145‐FEDER‐016403). The authors also acknowledge financial support from the BioTecNorte operation (NORTE‐01‐0145‐FEDER‐000004), funded by the European Regional Development Fund under the scope of Norte2020 – Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio