cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Formation and Eruption of a Double-decker Filament Triggered by Micro-bursts and Recurrent Jets in the Filament Channel
Creators: name: Tian, Zhanjun
name: Shen, Yuandeng
name: Liu, Yu
Publisher: name: arXiv
Year: 2018
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We present the observations of a double-decker filament to study its formation, triggering, and eruption physics. It is observed that the double-decker filament was formed by splitting of an original single filament. During the splitting process, intermittent bright point bursts are observed in the filament channel, which resulted in the generation of the upper filament branch. The eruption of the newly formed double-decker filament was possibly triggered by two recurrent two-sided loop jets in the filament channel and the continuous mass unloading from the upper filament body. The interaction between the first jet and the filament directly resulted in the unstable of the lower branch and the fast rising phase of the upper branch. The second jet occurred at the same site about three hours after the first one, which further disturbed and accelerated the rising of the lower filament branch. It is interesting that the rising lower branch overtook the upper one, and then the two branches probably merged into one filament. Finally, the whole filament erupted violently and caused a large-scale coronal mass ejection, leaving behind a pair of flare ribbons and two dimming regions on the both sides of the filament channel. We think that the intermittent bursts may directly result in the rearrangement of the filament magnetic field and therefore the formation of the double-decker filament, then the recurrent jets further caused the fully eruption of the entire filament system. The study provides convincing evidence for supporting the scenario that a double-decker filament can be formed by splitting a single filament into two branches.
description: 15 pages, 4 figures, published online in New Astronomy. https://www.sciencedirect.com/science/article/pii/S1384107618300903
Optimising secondary particle and radiation sources in high-intensity laser interaction experiments
Creators: name: Eardley, Samuel
Publisher: name: Imperial College London
Year: 2020

description: I will present data and supporting theoretical and numerical models from two experiments involving high intensity lasers interacting with matter. These experiments do not represent work at the very highest available laser intensities, rather they exploit more modest energy systems, though still able to access relativistic intensities. This work was performed with the intention of optimising the emission of secondary sources (electrons, protons and x-rays) from these laser matter interactions and, in the process, furthering our understanding of the mechanisms that produced them. This also provides a route to optimisation of experiments on near-future high-intensity lasers where the increased repetition rate provides access to large data sets, and thus enables use of techniques such as modification of the laser pulse shape via a genetic algorithm. The first experiment took place on the Astra Gemini laser at the Central Laser Facility. The 4x10^17 Wcm2 ultra short pulse laser was used to irradiate argon clusters, of radius varying from 6 nm to 11 nm. The x-ray emission of the laser irradiated clusters was observed with a set of PIN diodes and a genetic algorithm was implemented that controlled the high order spectral phase terms (up to fourth order) of the laser pulse using a Dazzler, and optimised the x-ray emission as a result. The genetic algorithm improved the x-ray emissions by a factor of ~3. The resultant laser pulse that produced the highest x-ray yield was not as one might expect the shortest pulse possible, rather it exhibited a distinct linear chirp and a low intensity foot on its leading edge. This was interpreted as the optimum laser-energy coupling to the cluster electrons requiring some initial pre-ionisation before the main pulse, along with a more subtle time varying frequency to match a transient resonance in the electrons laser absorption. The second experiment involved the Cerberus high-contrast OPCPA-Nd:Glass laser system at Imperial College. An artificial pre-pusle of I ~10^14 Wcm2 was added to the main beam of I~10^18 Wcm2 at various time delays, which subsequently irradiated 14 um aluminium foils. The x-rays, electrons and protons emitted by the target were observed by a variety of diagnostics. An enhancement in the electron and proton energies by a factor of ~5 was observed when the pre-pulse was timed to arrive 60 ps prior to the main pulse. It is theorised that this is an effect of the laser self-focusing in the short scale length pre-plasma developed at the front of the target, hence accelerating electrons with stronger fields, the enhanced electron acceleration couples into proton acceleration through the mechanism known as target normal sheath acceleration.
Open P-Branes
Creators: name: Strominger, Andrew
Publisher: name: arXiv
Year: 1995
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: It is shown that many of the $p$-branes of type II string theory and $d=11$ supergravity can have boundaries on other $p$-branes. The rules for when this can and cannot occur are derived from charge conservation. For example it is found that membranes in $d=11$ supergravity and IIA string theory can have boundaries on fivebranes. The boundary dynamics are governed by the self-dual $d=6$ string. A collection of $N$ parallel fivebranes contains $\half N(N-1)$ self-dual strings which become tensionless as the fivebranes approach one another.
description: harvmac, 8 pages
Dynamical friction in dwarf galaxies
Creators: name: Hernandez, X.
name: Gilmore, Gerard
Publisher: name: arXiv
Year: 1998
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We present a simplified analytic approach to the problem of the spiraling of a massive body orbiting within the dark halo of a dwarf galaxy. This dark halo is treated as the core region of a King distribution of dark matter particles, in consistency with the observational result of dwarf galaxies having solid body rotation curves. Thus we derive a simple formula which provides a reliable and general first order solution to the problem, totally analogous to the one corresponding to the dynamical friction problem in an isothermal halo. This analytic approach allows a clear handling and a transparent understanding of the physics and the scaling of the problem. A comparison with the isothermal case shows that in the core regions of a King sphere, dynamical friction proceeds at a different rate, and is sensitive to the total core radius. Thus, in principle, observable consequences may result. In order to illustrate the possible effects, we apply this formula to the spiraling of globular cluster orbits in dwarf galaxies, and show how present day globular cluster systems could in principle be used to derive better limits on the structure of dark halos around dwarf galaxies, when the observational situation improves. As a second application, we study the way a massive black hole population forming a fraction of these dark halos would gradually concentrate towards the centre, with the consequent deformation of an originally solid body rotation curve. This effect allows us to set limits on the fraction/mass of any massive black hole minority component of the dark halos of dwarf galaxies. In essence, we take advantage of the way the global matter distribution fixes the local distribution function for the dark matter particles, which in turn determines the dynamical friction problem.
description: 8 pages, 1 figure, Accepted in MNRAS
Insights into the behaviour of the Pliocene East Antarctic ice sheet from provenance studies of marine sediments using radiogenic isotopoes
Creators: name: Cook, Carys Patricia
Publisher: name: Imperial College London
Year: 2013

description: Direct evidence for the response of Earth’s largest continental ice mass, the East Antarctic ice sheet (EAIS), to climatic warmth is extremely limited. The primary aim of this thesis is to improve understanding of the behaviour of the EAIS during the warmer-than-present Pliocene Epoch (2.58 to 5.33 million years ago). To this end, I analysed the radiogenic neodymium and strontium isotopic provenance of fine-grained (<63μm) Pliocene detrital marine sediments deposited offshore of the East Antarctic continent, which can provide information on source bedrock characteristics, continental erosional patterns and marine sediment depositional processes. In addition, I also analysed argon isotopic ages of ice-rafted hornblende grains (>150μm), to infer sites of major iceberg production events through time. Within this thesis, I present Pliocene marine sediment data from various cores drilled from the East Antarctic margin, thereby developing a detailed framework for linking provenance variability to ice sheet behaviour. My key findings have been collated into five distinct chapters, providing: i) the first evidence for significant retreat of the EAIS in the low-lying Wilkes Subglacial Basin in response to the earliest Pliocene climatic warmth; ii) insights into the benefits and pitfalls associated with utilising different tools in glaciomarine sediment provenance studies; iii) constraints on the behaviour of the EAIS and West Antarctic ice sheet during the warmth of Pleistocene super-interglacial, Marine Isotope Stage 31; iv) insights into the role of declining sea surface termperatures during the Pliocene on the flux and provenance of distally sourced ice-rafted detritus, along with evidence for potential ice sheet destabilisation events in the Aurora Subglacial Basin during Pliocene interglacials; and v) advances in understanding of the evolution of the EAIS during the Late Pliocene climatic transition, and its role in global Pliocene climate change. Hence, the findings presented within this thesis provide new and significant evidence for the behaviour of the EAIS during the Pliocene, and suggest it has in the past been more sensitive to climatic change than previously realised.
Safety and effectiveness of istradefylline in patients with Parkinson’s disease: interim analysis of a post-marketing surveillance study in Japan
Creators: name: Makio Takahashi
name: Fujita, Masaki
name: Asai, Naoko
name: Saki, Mayumi
name: Mori, Akihisa
Publisher: name: Taylor & Francis
Year: 2018
Subjects: subject: Medicine
subject: Pharmacology
subject: Sociology
subject: FOS: Sociology
subject: Immunology
subject: FOS: Clinical medicine
subject: Science Policy
subject: 111714 Mental Health
subject: FOS: Health sciences

description: Background: Istradefylline is a first-in-class, non-dopaminergic, selective adenosine A2A receptor antagonist for the treatment of Parkinson’s disease (PD) in patients experiencing the wearing-off phenomenon with levodopa (L-DOPA). The authors present an interim report from a post-marketing surveillance (PMS) evaluating the safety and effectiveness of long-term istradefylline in a real-world setting. Research design and methods: Istradefylline safety was assessed by the incidence of adverse events (AE) and adverse drug reactions (ADRs). Effectiveness was assessed using the physician’s assessment of off-time, off-time symptoms and motor dysfunction, unified PD rating scale (UPDRS) Part III score, and the physician’s global assessment. Results: This analysis evaluated 476 patients. Istradefylline was generally well tolerated, despite dyskinesia and hallucination being the most common ADRs. Reduction in off-time was observed in 38.2% of patients, off-time symptoms were improved or markedly improved in 44.7%, and motor dysfunction was improved or markedly improved in 48.5%. The mean UPDRS Part III score decreased from 33.7 to 30.3 at the end of the study. The physician’s global assessment rated the drug as effective in 61.3% of patients. Conclusions: This PMS provides useful safety and effectiveness data for long-term treatment with istradefylline in a real-world setting for patients with PD exhibiting the wearing-off phenomenon with L-DOPA.
Tenthredo lonicerae Linnaeus, 1758, spec. nov.
Creators: name: Linnaeus, Carolus
Publisher: name: Laurentius Salvius
Year: 1758
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Tenthredinidae
Tenthredo
Tenthredo lonicerae

description: Tenthredo lonicerae [spec. nov.]
T. Lonicerae.
Reaum. ins. 5. t. 13. f. 8. 10.
Habitat in Lonicera.
description: Published as part of Linnaeus, Carolus, 1758, Systema Naturae per regna tria naturae: secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis, Stockholm :Laurentius Salvius on page 559, DOI: 10.5962/bhl.title.542, http://zenodo.org/record/3922206
Meso mechanics and peridynamic modelling of fibrous through thickness reinforcement at high deformation rate
Creators: name: Hijazi, Hussein
Publisher: name: Imperial College London
Year: 2019

description: Numerically modelling Z-pinned laminates is an important step in develop- ing damage tolerant structures using through thickness reinforcement such as Z-pins. This work is concerned with developing a reduced order model (ROM) capable of predicting the Z-pin bridging performance under mixed mode loading and at high deformation rates. The ROM is derived using the peridynamic formulation of the solid me- chanics equations of motion. For this purpose, rod and Timoshenko beam elements in peridynamic formulation were derived from first principles and validated against well established analytical results. The developed Tim- oshenko beam element is a non-linear element that accounts for moderate beam rotations. The rod peridynamic element is used as the basis of the Z-pin ROM model for the case of pure mode I loading. Two models were considered; the first model includes all key stages of the Z-pin response under mode I loading, i.e. bonded, debonding and frictional pull-out stages. The second model ignores the bonded and debonding stages and only considers the fric- tional pull-out stage. Both models yielded excellent prediction capabilities at different loading rates especially in terms of the energy absorbed by the Z-pin. This matched the experimental observation that most of the energy is absorbed during the frictional pull-out stage of the Z-pin response. The non-linear peridynamic beam element is used as the basis of the Z-pin ROM model for the general case of mixed mode loading. Three key external forces were considered under mixed mode loading; a lateral Win- kler foundation type force and an axial sliding and snubbing frictional forces. Ruina’s state based friction model was adopted to describe the rate depen- 2 dent behaviour of the sliding and snubbing frictional forces. The B-K failure criterion has been utilised to predict the fracture failure of the Z-pin. For this purpose, the energy release rate in peridynamic formulation has been developed. The resulting model had a number of parameters that needed to be defined. The developed model was calibrated against a subset of experimental data obtained from the literature in order to define unknown model param- eters. The calibrated model has been validated against a different subset of the experimental data. The model was able to predict the Z-pin bridging performance relatively accurately at different loading rates and mode mix- ities. More importantly, the model is very computationally efficient with a run time of the order of minutes using a non-optimised Matlab code that run on a desktop computer. This opens up the possibility of modelling Z-pinned laminates using a multi-scale approach where the ROM model is coupled with finite element packages to predict the performance of Z-pinned laminates.
Mechanisms of Obstructive Sleep Apnoea in Congestive Heart Failure
Creators: name: Carlisle, Thomas
Publisher: name: Imperial College London
Year: 2012

description: Approximately 50% of chronic heart failure (CHF) patients have obstructive sleep apnoea (OSA); however the mechanisms associated with OSA in CHF patients are incompletely understood. The overall aim of this thesis was to characterise upper airway phenotypes that may contribute to OSA in patients with CHF. Specifically, I sought to test the hypothesis that CHF patients with OSA have overnight rostral fluid shift. Pharyngeal phenotypes were measured non-invasively; pharyngeal calibre was measured using acoustic reflection, pharyngeal collapsibility using the passive critical closing pressure (Pcrit) technique, and changes in pharyngeal compliance during sleep using oesophageal pressure manometry combined with direct visualisation of the pharynx using bronchoscopy. Chapter 5 investigated differences in pharyngeal anatomy and morphology in healthy younger and older male volunteers using acoustic reflection, testing the hypothesis that older healthy males have similar pharyngeal dimensions to younger healthy males. The findings of this thesis showed that CHF patients with OSA have similar pharyngeal cross-sectional areas to CHF patients without OSA and healthy controls (Chapter 3). Pharyngeal collapsibility was also similar between groups (Chapter 4). CHF patients may be predisposed to pharyngeal collapse due to overnight attenuation of normal pharyngeal dilation during inspiration (Chapter 6). Finally, it was demonstrated that there may be differences in pharyngeal dimensions and morphology in older males compared to younger males (Chapter 5). The implications of the studies presented in this thesis are that fluid shift may be a contributing factor to OSA in CHF but the findings in this thesis suggest that its role is not likely to be dominant over more established mechanisms of OSA. Moreover, there may be no special features of CHF that explain the high prevalence of OSA in CHF.
Correspondence between the XXZ model in roots of unity and the one-dimensional quantum Ising chain with different boundary conditions
Creators: name: Alcaraz, F. C.
name: Belavin, A. A.
name: Usmanov, R. A.
Publisher: name: arXiv
Year: 2000
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We consider the integrable XXZ model with special open boundary conditions that renders its Hamiltonian ${SU(2)}_q$ symmetric, and the one-dimensional quantum Ising model with four different boundary conditions. We show that for each boundary condition the Ising quantum chain is exactly given by the Minimal Model of integrable lattice theory $LM(3, 4)$. This last theory is obtained as the result of the quantum group reduction of the XXZ model at anisotropy $Δ=(q + q^{-1})/2=\sqrt{2}/2$, with a number of sites in the latter defined by the type of boundary conditions.
description: 23 pages,LaTeX,3 tables,corrected some typos
Additional file 1 of Rosuvastatin exerts cardioprotective effect in lipopolysaccharide-mediated injury of cardiomyocytes in an MG53-dependent manner
Creators: name: Zhuang, Jiawei
name: Cheng, Gangyi
name: Huang, Jian
name: Guo, Hongwei
name: Lai, Yiquan
name: Wang, Jiamao
name: Shan, Zhonggui
name: Zheng, Shaoyi
Publisher: name: figshare
Year: 2022
Subjects: subject: Biochemistry
subject: Medicine
subject: Cell Biology
subject: Molecular Biology
subject: Physiology
subject: FOS: Biological sciences
subject: Pharmacology
subject: Chemical Sciences not elsewhere classified
subject: Immunology
subject: FOS: Clinical medicine
subject: Biological Sciences not elsewhere classified
subject: Cancer

description: Additional file 1: One-way ANOVA with the Tukey’s post-hoc test of cytokine levels, western blotting analysis of MG53 knockdown on the expression levels of signaling components supplementar, and raw data of western blotting.
Consensus of Maximum Likelihood Bootstrap Analysis of Type II MADS-box gene sequences
Creators: name: Sigel, Erin
Publisher: name: figshare
Year: 2018
Subjects: subject: Botany
subject: Evolutionary Biology
subject: FOS: Biological sciences
subject: 60405 Gene Expression (incl. Microarray and other genome-wide approaches)
subject: Plant Biology

description: Supplemental Figure for Sigel et al. 2018. Overlapping patterns of gene expression between gametophyte and sporophyte phases in the fern Polypodium amorphum. Frontiers in Plant Science. doi:10.3398/fpls.2018.01450Maximum likelihood bootstrap consensus tree of Type II MADS-box sequences. Numbers at nodes indicate bootstrap support values.
Oral history interview with Paul F. Godley, 1951
Publisher: name: Columbia University
Year: 2020
Subjects: Telegraph
Morse code
Radio--History

description: In this interview with Ernest Hill, Paul Godley discusses his family's lineage on both parents' sides, his relationship with father, time spent with brother, interest in communications and college experience. Godley describes his home life and the need to move frequently due to his father's fundraising work for the church. Godley delves into his first interest in communications when he was about five years old when telephone lines were installed near his home. He explains how he learned to telegraph as a result of "tinkering" he and his brother did with equipment on the farm. After receiving a telegraph machine, Godley taught himself to setup a line and Morse code. Godley describes his awareness of Marconi's accomplishments, which inspired him to pursue his interest, and the professors at Defiance College who supported his work and expanded his professional network. Godley discusses his experience on the denominational college campus. He describes summer employment and fill-in work on the telegraph that he did as an undergraduate. Godley also discusses how he became further interested in communications and communications problems, including wireless communications
More Dual String Pairs From Orbifolding
Creators: name: Gao, H. B.
Publisher: name: arXiv
Year: 1995
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We construct more dual pairs of type II-heterotic strings in four dimensions with $N=2,1$ spacetime supersymmetry. On the type II side the construction utilizes the various possible choices of K3 automorphisms with fixed points which transform the holomorphic two-form nontrivially, and rotation plus translation on $T^2$. The Calabi-Yau orbifolds so obtained have non-zero Euler numbers, so quantum corrections exist on the type IIA strings. The heterotic string (asymmetric) orbifold duals are found which depend on going to the enhanced symmetry points. Some aspects of the construction are discussed including the role of the singularity and the possibility of going beyond the adiabatic argument. Many of these examples have also orientifold analogs.
description: LaTex, 13 pages
Online Spatio-Temporal Learning and Prediction for Adaptive Robotic Systems : applications in tactile classification and learning assistance by demonstration
Creators: name: Soh, Harold Soon Hong
Publisher: name: Imperial College London
Year: 2013

description: Successful biological systems adapt to change. Humans, for example, are capable of continual self-improvement and gain new skills with experience. Similar online learning characteristics would enable robotic systems to autonomously improve their capabilities over time. In this thesis, we focus on the problem of iteratively learning from multivariate time-series; the "raw material" that we use to make inferences about the future. We adopt a combined approach: gaining inspiration from biological systems, in particular recurrent neural networks, and merging these ideas with recent advances in statistical machine learning. The resulting algorithm --- the online echo-state Gaussian process (OESGP) --- learns in an online manner, produces predictive distributions and attains state-of-the-art results on a variety of benchmark problems. We further extend this method to networks of "infinite size" through a recursive kernel with automatic relevance determination. This allows for online optimisation of the hyper-parameters through stochastic natural gradient descent, which improves adaptability and alleviates the problem of reservoir parameter specification. Using this online infinite ESGP (OIESGP) as a building block, we address two challenging problems in robotics: online tactile learning using the iCub humanoid platform and smart mobility assistance on the ARTY smart wheelchair. For the former, we develop online generative and discriminative classifiers that learn new objects "on-the-fly" and refine older models with new sensory input. For the latter, we adopt a novel approach by applying imitation learning to derive assistive policies. We present an OIESGP-based probabilistic mixture model for learning when and how to appropriately assist, and demonstrate its effectiveness in simulation and real-world experiments with human subjects.
Prospects for measuring Inflation parameters with the CMB
Creators: name: Souradeep, Tarun
name: Bond, J. Richard
name: Knox, Lloyd
name: Efstathiou, George
name: Turner, Michael S.
Publisher: name: arXiv
Year: 1998
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We present the status of our study into the feasibility of estimating the parameters of inflation from planned satellite observations of the anisotropy of the cosmic microwave background (CMB).We describe a perturbative procedure for studying inflation models with soft departures from scale free spectra and find that in this case the parameters of inflation are likely to be well determined. We also demonstrate that radical departures from scale free initial perturbations with broad features in $k$-space can be be measured by Planck. However, allowing for very fine features in $k$-space can very strongly compromise the ability to measure cosmological parameters.
description: 3 pages, 2 figures, LaTeX (sprocl.sty), To appear in the Proceedings of COSMO-97, Ambleside, England, September 1997, (Ed. L. Roszkowski,World Scientific)
Oral history interview with Paul E. Hile 1974
Publisher: name: Columbia University
Year: 2019
Subjects: Supervisors, Industrial
Manufacturing processes
Quality control

description: Engineering degree, Colorado University; Lithograph Department, Continental Can; pressman training; Enamel Plate Control Laboratory; manufacturing research service representative; introduction of statistical quality control; manager, quality control division; solder techniques; division resident inspector; adoption of aluminium cans; conoweld.
Oral history interview with Paul Haas, 1990
Publisher: name: Columbia University
Year: 2020
Subjects: Hemophilia--History.--United States
Hemophilia--Social aspects
Hemophilia--Political aspects
AIDS (Disease)--History.--United States
Hemophilia in children

description: Discovery that son had hemophilia; self-education and choices made regarding how to raise sons with hemophilia; involvement with local hemophilia chapter; involvement with Ohio state hemophilia advisory committee and work with Charles Carman; service on the Board of Directors of the NHF; questions of cost of and reimbursement for hemophilia care products; early emphasis as NHF President on local chapter involvement; advent of AIDS and of dramatic increase in costs of hemophilia products during tenure as President; aspects of the "hemophilia community(ies)"; questions regarding role and image of NHF regarding relationship of hemophilia to HIV; mix of lay and medical persons in NHF leadership; sources of funding for NHF; education versus research issues at NHF; tripartite leadership model between NHF, Centers for Disease Control (CDC), and Maternal Child Health Bureau (MCHB); "four pillars" of the NHF (staff, chapter leadership, medical leadership, and lay volunteers); need of local chapters to take the next step in dissemination of information; issues of denial in hemophilia community
Additional file 1 of Targeting NEK2 impairs oncogenesis and radioresistance via inhibiting the Wnt1/β-catenin signaling pathway in cervical cancer
Creators: name: Xu, Tie
name: Zeng, Yulan
name: Shi, Linli
name: Yang, Qin
name: Chen, Yeshan
name: Wu, Gang
name: Li, Guiling
name: Xu, Shuangbing
Publisher: name: figshare
Year: 2020
Subjects: subject: Biochemistry
subject: Cell Biology
subject: Genetics
subject: FOS: Biological sciences
subject: Molecular Biology
subject: Physiology
subject: Biological Sciences not elsewhere classified
subject: Cancer
subject: Computational Biology

description: Additional file 1: Table S1. Sequences of primers used for Real-time quantitative PCR.
title: MatK impacts differential chloroplast translation by limiting spliced tRNA‐K(UUU) abundance
Creators: name: Muino, Jose M.
name: Ruwe, Hannes
name: Qu, Yujiao
name: Maschmann, Sascha
name: Chen, Wei
name: Zoschke, Reimo
name: Ohler, Uwe
name: Kaufmann, Kerstin
name: Schmitz‐Linneweber, Christian
Publisher: name: Humboldt-Universität zu Berlin
Year: 2024
Subjects: subject: chloroplast
subject: tRNA
subject: translation regulation
subject: splicing
subject: intron maturase
subject: IEP
subject: 570 Biologie

description: The protein levels of chloroplast photosynthetic genes and genes related to the chloroplast genetic apparatus vary to adapt to different conditions. However, the underlying mechanisms governing these variations remain unclear. The chloroplast intron Maturase K is encoded within the trnK intron and has been suggested to be required for splicing several group IIA introns, including the trnK intron. In this study, we used RNA immunoprecipitation followed by high-throughput sequencing (RIP-Seq) to identify MatK's preference for binding to group IIA intron domains I and VI within target transcripts. Importantly, these domains are crucial for splice site selection, and we discovered alternative 5′-splice sites in three MatK target introns. The resulting alternative trnK lariat structure showed increased accumulation during heat acclimation. The cognate codon of tRNA-K(UUU) is highly enriched in mRNAs encoding ribosomal proteins and a trnK-matK over-expressor exhibited elevated levels of the spliced tRNA-K(UUU). Ribosome profiling analysis of the overexpressor revealed a significant up-shift in the translation of ribosomal proteins compared to photosynthetic genes. Our findings suggest the existence of a novel regulatory mechanism linked to the abundance of tRNA-K(UUU), enabling the differential expression of functional chloroplast gene groups.
Hybrid nanopore field-effect transistors for controlling single-molecule transport and selective sensing of small molecules
Creators: name: Xue, Liang
Publisher: name: Imperial College London
Year: 2020

description: Single-molecule methods have been rapidly developing with the appealing prospect of transforming conventional analytical techniques. The selective recognition of proteins and small molecules is a major motivation in developing single-molecule detection and diagnostic techniques. However, challenges remain especially in improving detection sensitivity, selectivity and controlling molecular transport. This is compounded by the complexities in selectively detecting small molecules in biological fluids. In this thesis, we address these limitations by showing a direct fabrication method for an analytical sensor that integrates the advantages of nanopores, field-effect transistors (FET) and selective recognition of target analytes, for simultaneous single-molecule detection and manipulation of DNA, proteins and small molecules such as neurotransmitters. In the first part of this thesis, a controlled and easy fabrication method for nanopore field-effect transistors was developed in terms of electrodeposition, facilitating the implementation of fabricated analytical sensors for the gating of molecular transport. It was demonstrated that the perfect alignment of nanopore and FET enables the gating of molecular transport across nanopore to be switched on/off in real-time. More importantly, surface functionalization of the gate electrode can be used to fine-tune transport properties enabling more active control over translocation velocity and capture rates by orders of magnitude. Based on the established sensing platform, a novel sensing strategy was presented for selective sensing of proteins and neurotransmitters at the single-molecule level. Aptamers were attached to the surface of the gate electrode for selectively recognizing different analytes. Our results elucidated that, protein-aptamer interactions are able to generate unique fingerprints allowing for monitoring and extracting real-time binding affinity by target-induced conformational changes. The gating of binding affinity was revealed in terms of controlling protein transport. Importantly, by enhancing the affinity of aptamers, selective single-molecule detection of neurotransmitters at fM concentration was demonstrated in biological fluids such as human serum. The selective detection of neurotransmitters has yet to be achieved using solid-state nanopores. This approach was proved to be versatile for different types of neurotransmitters, including dopamine, serotonin and acetylcholine. Further development of such a strategy may enable the improvement of nanopore sensors towards different 4 biologically important applications such as protein fingerprinting and multiplexed sensing of different molecular targets. An outlook was made on a range of sensing modes developed on this multifunctional platform with different dynamic ranges for in-vivo monitoring of neuron activities using functionalised nanopipettes.
D-branes from M-branes
Creators: name: Townsend, P. K.
Publisher: name: arXiv
Year: 1995
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: The 2-brane and 4-brane solutions of ten dimensional IIA supergravity have a dual interpretation as Dirichlet-branes, or `D-branes', of type IIA superstring theory and as `M-branes' of an $S^1$-compactified eleven dimensional supermembrane theory, or M-theory. This eleven-dimensional connection is used to determine the ten-dimensional Lorentz covariant worldvolume action for the Dirichlet super 2-brane, and its coupling to background spacetime fields. It is further used to show that the 2-brane can carry the Ramond-Ramond charge of the Dirichlet 0-brane as a topological charge, and an interpretation of the 2-brane as a 0-brane condensate is suggested. Similar results are found for the Dirichlet 4-brane via its interpretation as a double-dimensional reduction of the eleven-dimensional fivebrane. It is suggested that the latter be interpreted as a D-brane of an open eleven-dimensional supermembrane.
description: Version to appear in Physics Letters B. Incorporates minor revisions to previous revised version. 16 pp
Large Marginal Deformations in String Field Theory
Creators: name: Sen, Ashoke
name: Zwiebach, Barton
Publisher: name: arXiv
Year: 2000
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We use the level truncation scheme to obtain accurate descriptions of open bosonic string field configurations corresponding to large marginal deformations such as background Wilson lines. To do so, we solve for all fields as functions of the massless string field, and confirm that the effective potential of the massless field becomes increasingly flat as the level of approximation is increased. Surprisingly, as a result of the merging of two branches of the solution - one originating at zero tachyon vev and the other originating at the tachyonic vacuum - this effective potential exists only for a finite range of values of the massless field. We use the D1 to D0 brane marginal transition on a circle to explore the possibility that this finite range corresponds to the infinite range of the conformal field theory parameter describing marginal deformations, but are unable to arrive at a definitive conclusion.
description: 34 pages, 4 figures, LaTeX
A Joint Eulerian-Lagrangian Method for the Solution of Multi-Scale Flow Problems
Creators: name: Pettit, Michael
Publisher: name: Imperial College London
Year: 2013

description: Numerical convection schemes in a time-dependent Computational Fluid Dynamics simulation suffer from numerical diffusion, where a transported scalar quantity experiences a total diffusivity greater than any physical diffusivity due to the viscosity of the surrounding fluid. This work aims to develop and test a novel convection method, combining the Eulerian and Lagrangian frameworks, to eliminate numerical diffusion. A conserved scalar quantity is decomposed into low- and high-frequency components. The low-frequency field is transported in the Eulerian framework using a high-order Central Differencing Scheme, which has a negligible numerical diffusivity and good cost efficiency, but exhibits oscillatory behaviour around sharp changes in gradient. The high-frequency information is described with (computationally expensive) massless Lagrangian particles, where the prescribed particle 'density' provides a balance between accuracy and computational cost. Particles are convected by interpolating the underlying velocity field on to the particle position, while particle diffusion is described using a stochastic Wiener process. After transport an Eulerian representation of the Lagrangian particle field is constructed and added to the low-frequency scalar component, to recover the overall transported field. Formulations of the joint Eulerian-Lagrangian method for Direct Numerical Simulation and Large-Eddy Simulation are proposed. Re-initialisation (particle addition) and particle removal are implemented to maintain accuracy and to reduce the computational cost of the method. The accuracy of the Lagrangian reconstruction is improved through the development and application of localised filtering and deconvolution algorithms. The method is applied in two and three dimensions, where it is effective in removing numerical diffusion, but introduces noise into the scalar field due to the point-like nature of the particles. While the method is at least twice as expensive as traditional Eulerian simulations at the same grid resolution, it is capable of delivering better accuracy and considerably greater cost efficiency than Eulerian simulations at higher resolutions.
Revealing attractive electron-electron interaction in a quantum dot by full counting statistics
Creators: name: Kleinherbers, Eric
name: Stegmann, Philipp
name: König, Jürgen
Publisher: name: arXiv
Year: 2018
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Recent experiments [Nature 521, 196 (2015) and Nat. Commun. 8, 395 (2017)] have presented evidence for electron pairing in a quantum dot beyond the superconducting regime. Here, we show that the impact of an attractive electron-electron interaction on the full counting statistics of electron transfer through a quantum dot is qualitatively different from the case of a repulsive interaction. In particular, the sign of higher-order (generalized) factorial cumulants reveals more pronounced correlations, which even survive in the limit of fast spin relaxation.
description: 14 pages, 5 figures
Controls on the flow regime and thermal structure of the subduction zone mantle wedge: a systematic 2-D and 3-D investigation
Creators: name: Le Voci, Giuseppe
Publisher: name: Imperial College London
Year: 2013

description: Arc volcanism at subduction zones is likely regulated by the mantle wedge’s flow regime and thermal structure and, hence, numerous studies have attempted to quantify the princi- pal controls on mantle wedge conditions. In this thesis, we build on these previous studies by undertaking the first systematic 2-D and 3-D numerical investigations, across a wide parameter-space, into how hydration, thermal buoyancy and toroidal flow around the slab edge influence the wedge’s flow regime and associated thermal structure. We find that small- scale convection (SSC), resulting from Rayleigh-Taylor instabilities, or drips, off the base of the overriding lithosphere, is a typical occurrence, if: (i) viscosities are < 5 × 1018 Pa s; and (ii) hydrous weakening of wedge rheology extends at least 100-150 km from the forearc cor- ner. In 2-D models, instabilities generally take the form of ‘drips’. In 3-D, two separate, but interacting, longitudinal Richter roll systems form (with their axes aligned perpendicular to the trench), the first below the arc region and the second below the back-arc region. These instabilities result in transient and spatial temperature fluctuations of 100-150K, which are sufficient to influence melting, the stability of hydrous minerals and the dehydration of crustal material. Furthermore, they are efficient at eroding the overriding lithosphere, par- ticularly in 3-D and, thus, provide a means to explain observations of high heat flow and thin back-arc lithosphere at many subduction zones. A preliminary study into the effects of a finite-width slab on the wedge’s flow regime, which allows for toroidal flow around the slab edge, highlights that the toroidal cell can locally increase or decrease temperatures suf- ficiently to either enhance or shut down wet melting, while a hydrated wedge corner may channel trench-parallel flow. The dynamic complexities of wedge flow revealed by our mod- els may help explain the diversity in geophysical and geochemical subduction signatures.
Nano and hierarchical composites with high CNT loading fractions
Creators: name: Herceg, Tomi
Publisher: name: Imperial College London
Year: 2013

description: One of the major challenges in the field of nanocomposites has been to distribute and disperse high loading fractions of carbon nanotubes (CNT) in epoxy resins through a route that is scalable to high throughput. Furthermore, CNTs have been employed as an additional constituent in advanced carbon fibre composite materials to improve their poor matrix dominated properties in the drive to manufacture lighter and stronger composite structures. Attempts to produce epoxy based hierarchical composites (HC) with high CNT loadings by introducing nanoreinforcement in the resin have been plagued by processing difficulties related to viscosity and infiltration. Nonetheless, introducing just a few weight percent of CNTs into the matrix of continuous carbon fibre composites has been shown to enhance fracture toughness and compression performance. As such, this thesis tackles an effective way to combine carbon fibre, thermosetting resin and CNTs into hierarchical composites with high loadings of nanoreinforcement. To this end, a readily scalable powder based processing route was developed to produce epoxy based polymer nanocomposites (PNC) with a maximum CNT loading of 18.4 wt% (11.5 vol%). Due to the excellent CNT distribution and dispersion achieved during processing, some practically relevant physical and mechanical properties were enhanced even at the highest CNT loadings: 67 S/m and 0.77 W/ m•K electrical and thermal conductivities, respectively, and 5.5 GPa Young’s modulus. Analytical micromechanical models to validate reinforcement due to CNTs were also explored. The nanocomposite powder was also employed as a constituent in a wet powder impregnation process to produce carbon fibre based HC laminates containing as much as 5.5 vol% CNTs (11.5 vol% CNTs in the matrix). The processing parameters were optimised to yield a laminate with 55% fibre volume fraction, making it suitable for structural applications. The through thickness electrical conductivity of the HC containing 5.5 vol% CNTs improved by an order of magnitude; however, the largest enhancement in interlaminar fracture toughness (20%) was observed at an intermediate loading of 2 vol% CNTs. The mechanical underperformance at high CNT loadings was attributed to the heterogeneous microstructure observed to different extents in both PNCs and HCs, and a number of solutions related to material selection and processing design were proposed.
Modelling of turbulent combustion using the Rate-Controlled Constrained Equilibrium (RCCE) - Arti cial Neural Networks (ANNs) approach
Creators: name: Chatzopoulos, Athanasios
Publisher: name: Imperial College London
Year: 2013

description: The objective of this work is the formulation, development and implementation of Artificial Neural Networks (ANNs) to turbulent combustion problems, for the representation of reduced chemical kinetics. Although ANNs are general and robust tools for simulating dynamical systems within reasonable computational times, their employment in combustion has been limited. In previous studies, ANNs were trained with data collected from either the test case of interest or from a similar problem. To overcome this training drawback, in this work, ANNs are trained with samples generated from an abstract problem; the laminar flamelet equation, allowing the simulation of a wide range of problems. To achieve this, the first step is to reduce a detailed chemical mechanism to a manageable number of variables. This task is performed by the Rate-Controlled Constrained Equilibrium (RCCE) reduction method. The training data sets consist of the composition of points with random mixture fraction, recorded from flamelets with random strain rates. The training, testing and simulation of the ANNs is carried out via the Self-Organising Map - Multilayer Perceptrons (SOM-MLPs) approach. The SOM-MLPs combination takes advantage of a reference map and splits the chemical space into domains of chemical similarity, allowing the employment of a separate MLP for each sub-domain. The RCCE-ANNs tabulation is used to replace conventional chemistry integration methods in RANS computations and LES of real turbulent flames. In the context of RANS the interaction of turbulence and combustion is described by using a PDF method utilising stochastic Lagrangian particles. In LES the sub-grid PDF is represented by an ensemble of Eulerian stochastic fields. Test cases include non-premixed and partially premixed turbulent flames in both non-piloted and piloted burner configurations. The comparison between RCCE-ANNs, real-time RCCE and experimental measurements shows good overall agreement in reproducing the overall flame structure and a significant speed-up of CPU time by the RCCE-ANN method.
Some properties of unstable monopoles in Super-QCD
Creators: name: Barbon, J. L. F.
name: Ramgoolam, S.
Publisher: name: arXiv
Year: 1995
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We study embeddings of the Prasad-Sommerfield monopole solution in SU(N) Super-QCD (N>2), where the role of the Higgs field is played by the squarks in the fundamental representation. Classically, the resulting configurations live in a phase with unbroken SU(k) subgroups of SU(N) (as a result they are not topologically stable). The structure of zero modes is such that they can be naturally interpreted as massive chiral superfields with R charge one and baryon number zero, transforming in the adjoint representation of a dual gauge group defined using the Goddard-Nuyts-Olive (GNO) framework. We discuss the possible applications of these monopoles to N=1 duality, and more generally the possibility of relating GNO-type dual gauge groups to those appearing in N=1 duality.
description: 15 pages. harvmac
Chaotic behaviour on invariant sets of linear operators
Creators: name: Murillo-Arcila, Marina
name: Peris, Alfredo
Publisher: name: arXiv
Year: 2012
Subjects: subject: Functional Analysis (math.FA)
subject: Dynamical Systems (math.DS)
subject: FOS: Mathematics
subject: 47A16

description: We study hypercyclicity, Devaney chaos, topological mixing properties and strong mixing in the measure-theoretic sense for operators on topological vector spaces with invariant sets. More precisely, our purpose is to establish links between the fact of satisfying any of these properties on certain invariant sets, and the analogous property on the closed span of the invariant set. We also give examples that illustrate these results.
description: The measure-theoretic part of the paper is now a new article entitled "Strong mixing measures for linear operators and frequent hypercyclicity". The topological part is being completed with further results