Showing papers by "Lancaster University published in 2023"

Modeling the Impact of Geomagnetically Induced Currents on Electrified Railway Signaling Systems in the United Kingdom

Abstract: Studies of space weather impacts on ground-based infrastructure have been largely focused on power networks and pipelines, but railway signaling systems are also affected, with misoperations observed in several countries. This paper advances recent theoretical work on geomagnetically induced currents in railway signaling systems by modeling realistic railway lines with parameters from current industrial standards. Focusing on two example lines in the United Kingdom with different locations and orientation, a range of uniform electric fields are simulated along each modeled line. The results show that misoperations could be caused by geomagnetic interference at disturbance levels expected to recur over timescales of several decades. We also demonstrate that the UK estimate for the geoelectric field induced by a 1 in 100-year extreme storm would be strong enough to cause widespread signal misoperations in both lines studied.

Creating 3D Objects with Integrated Electronics via Multiphoton Fabrication In Vitro and In Vivo

Abstract: 3D objects with integrated electronics are produced using an additive manufacturing approach relying on multiphoton fabrication (direct laser writing, (DLW)). Conducting polymer-based structures (with micrometer-millimeter scale features) are printed within exemplar matrices, including an elastomer (polydimethylsiloxane, (PDMS)) have been widely investigated for biomedical applications. The fidelity of the printing process in PDMS is assessed by optical coherence tomography, and the conducting polymer structures are demonstrated to be capable of stimulating mouse brain tissue in vitro. Furthermore, the applicability of the approach to printing structures in vivo is demonstrated in live nematodes (Caenorhabditis elegans). These results highlight the potential for such additive manufacturing approaches to produce next-generation advanced material technologies, notably integrated electronics for technical and medical applications (e.g., human-computer interfaces).

Spatial Authenticity and Extraordinary Experiences: Music Festivals and the Everyday Nature of Tourism Destinations

Abstract: Research taking into account the everyday nature of tourism destinations and its impact upon authenticity and attendees’ resulting extraordinary experiences is limited. Drawing upon a 3-year ethnography (including fieldnotes, photos/videos, artifact material) and interviews with festival attendees, we explore the interrelationships between authenticity and extraordinary experiences in the context of Primavera Sound music festival. Our emergent thematic categories—the festival’s indie music character, its urban and quotidian configuration, and the instrumental orientation of the festival experience—suggest the festival is firmly positioned within the structures of the indie music industry, while also being located within the confines of day-to-day urban life. Attendees seek to achieve a sense of spatial authenticity by engaging with the features of tourism destinations. We contribute to discussions about authenticity and extraordinary experiences by unpacking the everyday nature of tourism destinations, demonstrating that not all music festivals need to be “extraordinary” muddy camping events.

Improved Monitoring of Subglacial Lake Activity in Greenland

Abstract: Abstract. Subglacial lakes form beneath ice sheets and ice caps if water is available, and if bedrock and surface topography are able to retain the water. On a regional scale, the lakes modulate the timing and rate of freshwater flow through the subglacial system to the ocean by acting as reservoirs. More than one hundred hydrologically active subglacial lakes, that drain and recharge periodically, have been documented under the Antarctic ice sheet, while only a handful of active lakes have been identified in Greenland. The small size of the Greenlandic subglacial lakes puts additional demands on mapping capabilitie aiming to resolve the evolving surface topography in sufficient detail to record their temporal behavior. Here, we explore the potential for combining data from CryoSat-2, TanDEM-X, and ArcticDEM to document the evolution of four active subglacial lake sites in Greenland. The inclusion of the new data sources provides important information on lake activity, documenting that the ice surface collapse basin on Flade Isblink ice cap was 50 % (30 meters) deeper than previously recorded. We also present evidence of a new active subglacial lake in Southwest Greenland, which shows signs of being hydrologically connected to another subglacial lake in that region. These findings show how improving the measurement capabilities of subglacial lakes, improves our current understanding and knowledge of the subglacial water system and its connection to surface hydrology.

Real-time nonlinear parameter estimation and tracking control of unmanned aerial vehicles in closed-loop

Abstract: The real-time unknown parameter estimation and adaptive tracking control problems are investigated in this paper for a six degrees of freedom (6-DOF) of under-actuated quadrotor unmanned aerial vehicle (UAV). A virtual proportional derivative (PD) controller is designed to maintain the translational dynamics. Two adaptive schemes are developed to handle the attitude dynamics of the UAV with several unknown parameters. In the beginning, a classical adaptive scheme (CAS) using the certainty equivalence principle is proposed and designed. The idea is to design a controller for an ideal situation by assuming the unknown parameters were known. Then the unknown parameters are replaced by their estimation. A theoretical analysis is provided to ensure the trajectory tracking of the adaptive controller. However, an inherent drawback of this scheme is that there is no guarantee for the estimated parameters to converge to the actual values. To address this issue, a new adaptive scheme (NAS) is developed as the next step by adding a continuously differentiable function to the control structure. The proposed technique guarantees handling of the parametric uncertainties with an appropriate design manifold. A rigorous analytical proof, numerical simulation analyses, and experimental validation are presented to show the effectiveness of the proposed control design.

Khomeini and Prolonging and Normalising the Iran-Iraq War

Abstract: Chapter seven shows how Khomeini used religious language to normalise the continuation of the war. For instance, Khomeini selectively quoted from the Quran to normalise war between the two Islamic countries. This chapter also demonstrates how Khomeini rarely used the word ‘defence’ to describe the war between Iran and Iraq after the liberation of Khorramshahr. Such a labelling strategy helped Khomeini to refuse all the calls for a ceasefire. For the Ayatollah, Iran was defending itself; therefore, there was no need for a ceasefire.

Fiscal Policy—If It Moves, Tax It

Abstract: Beginning with a quote from Shakespeare, this chapter introduces the ideas of taxation and government spending. The ways in which these can be used to leverage the macroeconomy are investigated.

Identifying soil signatures from soil moisture time series via a changepoint-based approach

Abstract: Healthy soil plays a critical role in sustaining biodiversity, maintaining food production, and mitigating climate change through carbon capture. Soil moisture is an important measure of soil health that scientists model via soil drydown curves. The typical modelling process requires manually separating the soil moisture time series into segments representing the drying process and fitting exponential decay models to these segments to obtain an estimation of the key parameters. With the advancement of sensor technology, scientists can now obtain higher frequency measurements over longer periods in a larger number of locations. To enable automatic data processing and to obtain a dynamic view of the soil moisture drydown, a changepoint-based approach is developed to automatically identify structural changes in soil moisture time series.Specifically, timings of the sudden rises in soil moisture over a long time series are captured and the parameters characterising the drying processes following the sudden rises are estimated simultaneously. An algorithm based on the penalised exact linear time (PELT) method was developed to identify the changepoints and estimate the model parameters. This method can be considered as a complement to the conventional soil moisture modelling. It requires little data pre-processing and can be applied to a soil moisture time series directly. Since each drying segment has its unique parameters, the method also has the potential of capturing any temporal variations in the drying process, thus providing a more comprehensive summary of the data.The method was applied to the hourly soil moisture time series of nine field sites from the NEON data portal (https://data.neonscience.org/). Distributions and summary statistics of key model parameters, such as the exponential decay rate and the asymptotic soil moisture level, are produced for each field site. Investigating and comparing these quantities from different field sites enables the identification of soil signatures which can reflect the hydrological properties of the soil. Visualising the model parameters as a time series reveals the subtle temporal pattern of the drying process in some field sites. 

Inter-annual variability in the response of soil respiration to elevated CO2 concentrations in the atmosphere

Abstract: In this research we consider the response of soil respiration under elevated CO2 (eCO2) in an oak-dominated temperate forest. We hypothesised that under elevated CO2 (550 ppm) soil moisture would increase as a result of reduced stomatal conductance, which would in turn lead to higher soil respiration. Continuous measurements were performed on three pairs of plots near Stafford (United Kingdom). Respiration was measured diurnally for 2 minutes each time, using the LI-COR 8100A set-up, and the rate of respiration (flux rate) was calculated SoilFluxPro software. Next, an empirical model was fitted to the dataset based on hourly averages of the flux rates, soil temperature, and soil moisture. Three respiration collars per plot were averaged, thus accounting for spatial variability within the site. Model parameterization and gap filling were conducted on individual plots to calculate annual rates for 2019-2021. Cross-validation was performed by using 80% (randomly selected) of each dataset for training and the remaining 20% for testing the data against the parameters obtained by the empirical models. Preliminary results suggest that annual respiration rates were significantly higher for the eCO2 across all pairs in 2019. However, 2 out of 3 pairs in 2020 and 2021 showed significantly higher respiration for the aCO2 plots compared to eCO2, which is not in line with our hypothesis. Relationships with soil moisture and temperature help to explain what drives the difference in these fluxes. Our findings show that the relationship between higher CO2 concentrations in the atmosphere and soil respiration is not a straightforward one, which is of interest when considering the role of forest C-cycling on a global scale.

Information Economics—Well, What Do You Know?

Abstract: Beginning with a quote from Dickens, this chapter examines contexts in which information is imperfect, with particular emphasis on cases where one economic agent has superior information to another.

Growth—Growing Pains

Abstract: Beginning with a quote from Trollope, this chapter examines the sources of long-term economic growth.

Higher Education Edtech Policy Recommendations and Principles 1.0

Abstract: This webinar will present the first version of policy recommendations for policymakers, universities, Edtech companies, and investors in Edtech. The recommendations are coming from the ESRC-funded research project on new forms of value in Edtech.

Catalog of noninteracting tight-binding models with two energy bands in one dimension

Abstract: We classify Hermitian tight-binding models describing noninteracting electrons on a one-dimensional periodic lattice with two energy bands. To do this, we write a generalized Rice-Mele model with two orbitals per unit cell, including all possible complex-valued long-range hoppings consistent with Hermicity. We then apply different forms of time-reversal, charge-conjugation and chiral symmetry in order to constrain the parameters, resulting in an array of possible models in different symmetry classes. For each symmetry class, we define a single, canonical form of the Hamiltonian and identify models that are related to the canonical form by an off-diagonal unitary transformation in the atomic basis. The models have either symmorphic or nonsymmorphic nonspatial symmetries (time $T$, chiral and charge-conjugation). The nonsymmorphic category separates into two types of state of matter: an insulator with a $\mathbb{Z}_2$ topological index in the absence of nonsymmorphic time-reversal symmetry or, in the presence of nonsymmorphic time-reversal symmetry, a metallic state. The latter is an instance of Kramer's degeneracy with one degeneracy point in the Brillouin zone as opposed to no degeneracy points in symmorphic systems with $T^2 = 1$ and two in symmorphic systems with $T^2 = - 1$.

Detecting Changes in Covariance via Random Matrix Theory

Abstract: A novel method is proposed for detecting changes in the covariance structure of moderate dimensional time series. This nonlinear test statistic has a number of useful properties. Most importantly, it is independent of the underlying structure of the covariance matrix. We discuss how results from Random Matrix Theory, can be used to study the behavior of our test statistic in a moderate dimensional setting (i.e., the number of variables is comparable to the length of the data). In particular, we demonstrate that the test statistic converges point wise to a normal distribution under the null hypothesis. We evaluate the performance of the proposed approach on a range of simulated datasets and find that it outperforms a range of alternative recently proposed methods. Finally, we use our approach to study changes in the amount of water on the surface of a plot of soil which feeds into model development for degradation of surface piping.

Vitamin A: Physiology, dietary sources and requirements

Abstract: Vitamin A (retinol) is essential for many physiological functions throughout the body. Its physiology comprises processes and biochemical reactions in the intestine (absorption), liver (uptake, storage, metabolism, secretion and elimination), and numerous target organs and epithelial cells, especially the eye, immune system, and reproductive systems. The retina utilizes a specific metabolite, 11-cis-retinal, for vision. All-trans-retinoic acid is produced by well-controlled metabolic processes in nearly all tissues, where it functions in the regulation of gene expression. The nuclei of cells in nearly all tissues contain nuclear retinoic acid receptors that function homeostatically to regulate the biological functions of vitamin A.

Theoretical Frameworks

Abstract: This chapter introduces a theoretical framework for the study of Khomeini’s corpus during the war, which is a combination of CDA (Critical Discourse Analysis) and CMT (Critical Metaphor analysis and CMT). This book’s theoretical framework is examined in five stages. The first stage introduces cognitive approaches, constructivist discourse analysis and poststructuralist discourse analysis as the main three potential alternative approaches to CDA. However, after explaining why these approaches cannot be used to analyse Khomeini’s discourse, in stage two CDA is presented as the first part of the theoretical framework of this book. Despite all its advantages, CDA fails to recognise the importance of cognitive approaches (Chilton in Manipulation and ideologies in the twentieth century. John Benjamins Publishing Company, 2005; Koller in Metaphor and gender in business media discourse: A critical cognitive study. Palgrave Macmillan, 2004). Therefore, to cover this lapse, stage three suggests that cognitive metaphors should be added to CDA as a complementary theory. Stage four introduces the theoretical framework of the research: a combination of the CDA and CMT. Finally, stage five justifies the use of CDA and CMT as two “Western theories” in a non-Western case study. Although a combination of CDA and CMT per se is not new, the theoretical framework introduced in this chapter mainly focuses on the political aspects of language rather than its linguistic aspects.

Quantifying effects of long-range transport of air pollutants over Delhi using back-trajectories and satellite NO₂ data

Abstract: Abstract. Exposure to air pollution is a leading public health risk factor in India, especially over densely populated Delhi and the surrounding Indo-Gangetic Plain. During the post-monsoon months, the prevailing north-westerly winds are known to influence aerosol pollution events in Delhi, by advecting pollutants from agricultural fires as well as from local sources. Here we investigate the year-round impact of meteorology on gaseous nitrogen oxides (NOx = NO + NO2), a hazardous primary air pollutant for health, which can lead to the formation of secondary aerosols and ozone. We use bottom-up NOx emission inventories (anthropogenic and fire) and high-resolution satellite measurement based tropospheric column NO2 (TCNO2) data, from S5P on-board TROPOMI, alongside a back-trajectory model (ROTRAJ) to investigate the balance of local and external sources influencing air pollution changes in Delhi, with a focus on different emission sectors. Our analysis shows that accumulated emissions (i.e. integrated along the trajectory path, allowing for chemical loss) are highest under westerly, north-westerly and northerly flow during pre- (February–March) and post- (October–January) monsoon periods. During the pre-monsoon period, the residential and transport sectors together account for more than 50 % of the total accumulated emissions, which are dominated by local sources (90 %) under easterly winds and by non-local sources (> 70 %) under north-westerly winds. The high accumulated emissions estimated during the pre-monsoon season under north-westerly wind directions are likely to be driven by high NOx emissions locally and in nearby regions (since NOx lifetime is reduced and the boundary layer is relatively deeper in this period). During the post-monsoon period non-local (60 %) transport emissions are the largest contributor to the total accumulated emissions as high emissions, coupled with a relatively long NOx atmospheric lifetime and shallow boundary-layer aid the build-up of emissions along the trajectory path. Analysis of surface daily NO2 observations indicates that high pollution episodes (> 90th percentile) occur predominantly in the post-monsoon and more than 75 % of high pollution events are primarily caused by non-local sources. Overall, we find that in the post-monsoon period, there is a substantial import of NOx pollution into Delhi with a large contribution from the transport sector. This work indicates that the advection of highly polluted air originating from outside Delhi is of concern for the population and air quality mitigation strategies need to be adopted not only in Delhi but in the surrounding regions to successfully control this issue. In addition, our analysis suggests that the largest benefits to Delhi NOx air quality would be seen with targeted reductions in emissions from the transport sector, particularly during post-monsoon months.

“Confronting time out of joint. . . – On economic rationality and imagination”

Abstract: It is often suggested that today we are living in the “end times.” Confronted by a perpetual incursion of major global crises, we increasingly find ourselves incapable of meaningfully relating to the present, let alone to the future. The forever deferred “end” throws the very idea of time out of joint. Unable to advance, our imagination retreats, with retrograde tendencies taking over both culture and politics. From incessant movie prequels and sequels, through the re-emergence of populist fascist politics, all the way to the return of Cold War rhetoric, we witness our reality becoming increasingly substituted by a string of peculiar rehashings and reunions. History, as we knew it, is no longer “made”; we strain to cling to the past, equating the future with dystopia. Crucially, this problematique of the fading of temporality is not new. In fact, it has got a history of its own. This paper explores our current (a)temporal whereabouts by reflecting upon them from the perspective of their historical trajectory. It does this by revisiting the work of André Gorz—a thinker whose contributions equip us with the insights needed to confront time out of joint effectively and embrace the idea of future. The article argues that the roots of today’s temporal malaise can be found in the process of “economicization,” which subordinated the notion of utopia to its principles, thereby nullifying it. Examining the effects of the unbridled reign of economic rationality over our imagination, it calls for a temporal intervention by means of ecological rationality.

Nitrate retention and subsidy in oligotrophic mountain stream-lake networks

Abstract: With human activity rapidly accelerating the global nitrogen cycle, aquatic environments are facing increasing eutrophication and ecosystem damage. Oligotrophic headwater streams are particularly susceptible to nutrient pollution, which is affecting biodiversity, ecosystem services and water quality. However, not much in known about biogeochemical nitrogen cycling in these remote environments. This research presents seasonal data for nitrate concentrations and stable isotope signatures from oligotrophic mountain stream-lake networks in the English Lake District, UK. While phosphate concentrations were frequently below detection limit, nitrate was present throughout the year with concentrations ranging from 0.01 to 0.49 mg N L-1. Dual isotope analysis of δ15N-NO3 and δ18O-NO3 identified atmospheric deposition as an important nutrient source to the ecosystem and provided information on the fate of nitrate moving through hydrologically connected stream-lake networks. Some mountain lakes removed up to 69% of nitrate delivered by the inflow stream, while others were substantial sources compared to upstream concentrations. This contrasting lake response was consistent throughout the year, with in-lake nitrate subsidy being observed in systems where concentrations in the inflow stream dropped below 0.25 mg N L-1. These findings suggest that dominant biogeochemical processes may be controlled by nutrient load, and ecosystem response could potentially change with increasing nutrient pollution.