Constricted Boron Nanotubes

The recent discovery of pure boron nanotubes raises questions about their detailed atomic structure. Previous simulations predicted tubular structures with smooth or puckered surfaces. Here, we present some novel results based on ab initio simulations of bundled single-wall zigzag boron nanotubes (ropes). Besides the known smooth and puckered modifications, we found new forms that are radially constricted, and which seem to be energetically superior to the known isomers. Furthermore, those structures might be interpreted as intermediate states between ideal tubular phases and the known bulk phases based on boron icosahedra.Comment: 11 pages, 4 figure

Ab initio density functional investigation of B_24 cluster: Rings, Tubes, Planes, and Cages

We investigate the equilibrium geometries and the systematics of bonding in various isomers of a 24-atom boron cluster using Born-Oppenheimer molecular dynamics within the framework of density functional theory. The isomers studied are the rings, the convex and the quasiplanar structures, the tubes and, the closed structures. A staggered double-ring is found to be the most stable structure amongst the isomers studied. Our calculations reveal that a 24-atom boron cluster does form closed 3-d structures. All isomers show staggered arrangement of nearest neighbor atoms. Such a staggering facilitates $sp^2$ hybridization in boron cluster. A polarization of bonds between the peripheral atoms in the ring and the planar isomers is also seen. Finally, we discuss the fusion of two boron icosahedra. We find that the fusion occurs when the distance between the two icosahedra is less than a critical distance of about 6.5a.u.Comment: 8 pages, 9 figures in jpeg format Editorially approved for publication in Phys. Rev.

A New Class of Boron Nanotube

The configurations, stability and electronic structures of a new class of boron sheet and related boron nanotubes are predicted within the framework of density functional theory. This boron sheet is sparser than those of recent proposals. Our theoretic results show that the stable boron sheet remains flat and is metallic. There are bands similar to the p-bands in graphite near the Fermi level. Stable nanotubes with various diameters and chiral vectors can be rolled from the sheet. Within our study, only the thin (8, 0) nanotube with a band gap of 0.44 eV is semiconducting, while all the other thicker boron nanotubes are metallic, independent of their chirality. It indicates the possibility, in the design of nanodevices, to control the electronic transport properties of the boron nanotube through the diameter

Molar pregnancy and co-existent foetus: A report of two cases

Molar pregnancy with a co-existent foetus will lead to preterm labour, severe preeclampsia or bleeding in most of the cases and may need urgent intervention. However, if it does not become complicated with preeclampsia or preterm Labour, the outcome is usually good, with minimal post partum complications and so such pregnancies can be managed with watchful waiting and close observation. The first case was a 29 year-old at 19 weeks of gestation, with hypertension, oedema and severe epigastric pain. Karyotypic assessment of the contents of the uterus revealed a 46-XX foetus with no chromosomal abnormality, as well as the molar placenta also suggesting a complete mole with 46-XX. The second case was a 19 year old woman in labour. A pathological study of the delivered contents of the uterus revealed a complete hydatidiform mole and a normal placenta

Variegated firm finance and global production networks : car component manufacturers in Hungary and Eastern Germany

PhD ThesisThis study explores the financial dimension of global production networks, a major lacuna in global production networks theory only recently beginning to be addressed. It conceptually challenges accounts of capitalism as a uniform process by evidencing spatially variegated practices of capital sourcing by car component manufacturers in Hungary and Eastern Germany. It aims to determine how such patterns can be explained and understood by the firms’ agency and embeddedness both in variegated forms of capitalism and, through ownership, within global production networks. The study further aims to assess potential implications on the firms’ governance and on local and regional development prospects. The research applies a mixed-methods approach combining quantitative analysis of data collected from publicly available sources with qualitative data from secondary sources. Based on a conceptual framework combining existing literature on variegated capitalism, global production networks and geographies of firm finance, it analyses the capital sources of around 160 Hungarian and 160 Eastern German car component manufacturers in the light of their location, size and ownership, arguing that financing practices (i) are not uniform but variegated, depending on historical, socio-institutional and political/regulatory contexts of regions in which firms operate, and on the firms’ agency also shaping this context and (ii) are shaped by the firms’ integration and relative position within networks of firms, shareholders, financial institutions and capital market investors. The thesis empirically evidences geographical variegation in the capital sourcing patterns of the firms analysed and provides empirical evidence of variegation at regional levels. It highlights the important financial dimensions of global production networks by showing how firms owned by other firms within a global production network are financed in a way fundamentally different from those that are not. It also contributes to a better theorisation of less studied variegations of capitalism such as formerly state-socialist regions, supporting calls for a more fine-grained and nuanced analysis of geographies of finance both at and beneath the national level

Investigating the role of antibody dysregulation in lung disease

Antibodies play a critical role in providing long-term immunity against pathogens. They are also required for the maintenance of commensal homeostasis at mucosal surfaces. However, their dysregulation can result in the generation of autoantibody, resulting in autoimmune disease and a shift away from a protective function to a more pathogenic role. There is growing evidence to support the dysregulation of antibody responses in chronic lung diseases such as interstitial lung disease, chronic obstructive pulmonary disease and, more recently, COVID-19. The aim of this thesis was to investigate how dysregulated antibody responses contribute to the pathogenesis of ILD and to pulmonary changes in individuals with persistent respiratory symptoms following COVID-19. Total antibody and autoantibody responses were characterised in a cohort of patients with IPF, CHP, CTD-ILD and healthy controls. A broad autoantibody signature was identified in approximately half of patients that was absent in healthy controls. Additionally, this signature was specific to the airways as autoantibody was not detected systemically. Analysis of antibody coating of airway bacteria revealed a loss of binding by antibody in patients with IPF compared to healthy controls, despite local increases in antibodies against taxa whose abundances are commonly elevated in IPF airways. Patients with IPF had increases in lung B cells. Further, approximately half of patients with IPF had extensive B cell aggregates within the lung parenchyma that co-localised with CXCL13, highlighting the lungs as a potential local niche for the generation of dysregulated antibody. Dysregulated antibody responses were also a feature in post- COVID patients and were associated with worse lung function.. Collectively, these findings confirm a dysregulation of antibody responses in ILD and post-COVID airways in the absence of systemic changes and highlight the importance of airway sampling, particularly in determining future therapeutic strategies for lung fibrosis.Open Acces

A Computational Fluid-Structure Interaction Method for Simulating Supersonic Parachute Inflation

Following the successful landing of the Curiosity rover on the Martian surface in 2012, NASA/JPL conducted the low-density supersonic decelerator (LDSD) missions to develop large diameter parachutes to land the increasingly heavier payloads being sent to the Martian surface. Unexpectedly, both of the tested parachutes failed far below their design loads. It became clear that there was an inability to model and predict loads that occur during supersonic parachute inflation. In this dissertation, a new computational method that was developed to provide NASA with the capability to simulate supersonic parachute inflation is presented and validated. The method considers the loose coupling of two different immersed boundary methods with a nonlinear finite element solver. Following validation on canonical FSI problems, methods to simulate the permeability of parachute broadcloth and to identify and enforce contact in parallel are presented and validated. The coupled solvers are first applied to the supersonic parachute problem on a sub-scale MSL parachute and capsule geometry, and subsequently, a full-scale test flight from the Advanced Supersonic Parachute Inflation Research Experiments (ASPIRE) is simulated. To the best of the author’s knowledge, these are the first FSI simulations to match the ASPIRE flight test data