Cardiff University
  • Cardiff, Wales, United Kingdom
Recent publications
This paper proposes a maiden intelligent controller design that consists of a Fuzzy Proportional–Integral–Derivative–Double Derivative (FPIDD²) controller whose parameters are fine-tuned using the Gradient-Based Optimization algorithm (GBO). The proposed FPIDD² regulator is employed as a secondary regulator for stabilizing the combined voltage and frequency loops in a two-area interconnected power system. It has been shown that the GBO optimization algorithm outperforms other optimization strategies such as the Chimp Optimization Algorithm (ChOA), the Whale Optimization Algorithm (WOA), and the Gorilla Troops Optimization algorithm (GTO). The proposed FPIDD² controller is tested in a conventional two-area power system. Then, the investigation is expanded to a two-area hybrid system, with each area comprising a mix of traditional (thermal, gas, and hydraulic power plants) and renewable generation units (wind and solar power). Additionally, the proposed controller takes into account system nonlinearities (such as generation rate limitations, governor deadband, and communication time delays), system uncertainties, and load/renewables fluctuations. In the two tested systems, the dynamic responses of each system demonstrate that FPIDD² has a superior ability to attenuate the deviations in voltage and frequency in both areas of the system. In the studied conventional system, the proposed FPIDD² controller is compared with a PID controller tuned by the Multi-Objective Non-Linear Threshold Accepting Algorithm (MONLTA), which has been presented in the literature, and a Fuzzy PID (FPID) controller tuned by GBO. In the investigated hybrid system, the suggested FPIDD² regulator is compared to a GBO-tuned Integral Derivative-Tilted (ID-T) controller and FPID controller. As a fitness function (FF) for the GBO, the criteria of minimizing the integral time absolute error (ITAE) are applied. The results are presented in the form of MATLAB/SIMULINK time-domain simulations.
  • Shahid Ahmad
    Shahid Ahmad
  • Ghufran Ahmad
    Ghufran Ahmad
This chapter focuses on the supply and demand of water resources in Pakistan. Data on the availability and use of water in Pakistan will be used to develop a water balance for the IBIS. Because the per capita water availability is less than 1000 cubic meters (m3), Pakistan is currently categorized as a water-scarce country. However, there is a silver lining in that productivity in the agricultural sector can be doubled by using better technology and reducing the amount of land that needs to be farmed, possibly reducing the gap between supply and demand. The Indus Water Treaty of 1960 has posed serious limitations for both countries in sharing the water supply during dry years. The provinces of Pakistan agreed on the Water Apportionment Accord in 1991 to resolve the water-sharing conflict. However, there are still issues between the provinces on sharing during dry years, resulting in reduced environmental flows to the ecosystems and reduced availability for the agricultural sector. Finally, water is discussed in the regional context of South Asia which will focus on Afghanistan, Bangladesh, India, and Pakistan. A brief overview of the current scenario along with historical trends will be provided for these countries. Then, we provide the successes and gaps related to water, specifically the measures taken to deal with issues related to climate change, in the four countries.
  • Niklaas J. Buurma
    Niklaas J. Buurma
  • Scott W. Bagley
    Scott W. Bagley
Chemists know the value of looking at a reaction for clues about reaction progress and success, but what-it-looks-like has never been quantified. Reid and co-workers (C. Yan, M. Cowie, C. Howcutt, K. M. P. Wheelhouse, N. S. Hodnett, M. Kollie, M. Gildea, M. H. Goodfellow and M. Reid, Chem. Sci., 2023, 14, 5323–5331, have developed an approach that uses camera footage of reactions to obtain quantitative descriptors of changes in reaction mixtures to support kinetic analysis.
  • Julia Atayi
    Julia Atayi
  • Geophrey K. Anornu
    Geophrey K. Anornu
  • Alfred Awotwi
    Alfred Awotwi
  • [...]
  • Maxwell Anim-Gyampo
    Maxwell Anim-Gyampo
The Volta Basin in West Africa plays a crucial role in supporting the livelihoods of millions of people, and effective management of its water resources is essential for climate change adaptation. This study utilized remote sensing technology, specifically the Gravity Recovery and Climate Experiment (GRACE), to assess terrestrial water storage (TWS) and its response to climate variability within the Volta Basin. The methodology involved integrating GRACE data with ground-based measurements, climate models, and other satellite observations to enhance the accuracy of TWS assessment. Despite numerous studies conducted within the basin, this research employed additional statistical techniques such as Independent Component Analysis (ICA) and El Niño Southern Oscillation (ENSO). It also utilized Climate Hazard Group Infrared Precipitation with Station (CHIRPS) to determine variations in TWS and climate variability observed within the Volta Basin. The results provide valuable insights into TWS dynamics, highlighting the complex interplay between precipitation patterns, groundwater storage, and surface water availability. Also, it was revealed that rainfall signals were strongest in the northernmost part of the basin, reaching a maximum value of 10 mm, while the lowest value of 5.5 mm was recorded in the southern part of the basin. Similarly, TWS signals were highest in the northern and lowest in the southern part of the basin, exhibiting values related to that of rainfall. Additionally, the highest TWS value of 250 mm was identified between 2010 and 2012. The increase in TWS during this period correlates with the occurrence of La Niña that happened between 2010 and 2012. This study offers essential information for water resource management, drought monitoring, flood forecasting, and climate change adaptation strategies not only within the Volta Basin but also in other basins across the globe.
  • Izidin El Kalak
    Izidin El Kalak
  • Robert Hudson
    Robert Hudson
  • Onur K. Tosun
    Onur K. Tosun
Exchange Traded Funds (ETFs) have often tracked indices and charged low fees so their incentives to improve firm performance are questionable although little empirical work has investigated this issue. Theoretically, however, we expect firms to perform better when held by more engaged ETFs. We develop a new measure of engagement using a weighted‐average concentration measure which captures the combined effect of the concentration of the portfolios of the ETFs investing in a firm and the ownership of the firm by those ETFs. Using ETFs' investment in US‐listed firms for the period 2000–2019, we confirm our expectations that more engaged ETFs improve firm performance.
  • Beiqin Zhang
    Beiqin Zhang
The COVID-19 pandemic has caused drastic fluctuations in the economies of various countries. Meanwhile, the governments’ ability to save the economy depends on how banks provide credit to troubled companies. Therefore, the impact of the epidemic on bank credit and inclusive finance are worth exploring. However, most of the existing studies focus on the reform of the financial and economic system, only paying attention to the theoretical mechanism analysis and effect adjustment, scant data support, and insufficient scheme landing. At the same time, with the rise and rapid development of artificial intelligence technology in recent years, all walks of life have introduced it into real scenes for multi-source heterogeneous big data analysis and decision-making assistance. Therefore, we first take the Chinese mainland as an example in this paper. By studying the impact of the epidemic on bank credit preference and the mechanism of inclusive finance, we can provide objective decision-making basis for the financial system in the post-epidemic era to better flow credit funds into various entities and form a new perspective for related research. Then, we put forward a model based on Bi-directional Long Short-term Memory Network (BiLSTM) and Attention Mechanism to predict the number of newly diagnosed cases during the COVID-19 pandemic every day. It is not only suitable for COVID-19 pandemic data characterized by time series and nonlinearity, but also can adaptively select the most relevant input data by introducing an Attention Mechanism, which can solve the problems of huge calculation and inaccurate prediction results. Finally, through experiments and empirical research, we draw the following conclusions: (1) The impact of the COVID-19 pandemic will promote enterprises to increase credit. (2) Banks provide more credit to large enterprises. (3) The epidemic has different impacts on credit in different regions, with the most significant one on central China. (4) Banks tend to provide more credit to manufacturing industries under the epidemic. (5) Digital inclusive finance plays a (positive) regulating effect on bank credit in COVID-19 pandemic. Inspired by the research results, policymakers can consider further solving the information asymmetry and strengthening the construction of a credit system, and more direct financial support policies for enterprises should be adopted. (6) By adopting the COVID-19 prediction model based on the BiLSTM-Attention network to accurately predict the epidemic situation in the COVID-19 pandemic, it can provide an important basis for the formulation of epidemic prevention and control policies.
Decarbonized power systems are critical to mitigate climate change, yet methods to achieve a reliable and resilient near-zero power system are still under exploration. This study develops an hourly power system simulation model considering high-resolution geological constraints for carbon-capture-utilization-and-storage to explore the optimal solution for a reliable and resilient near-zero power system. This is applied to 31 provinces in China by simulating 10,450 scenarios combining different electricity storage durations and interprovincial transmission capacities, with various shares of abated fossil power with carbon-capture-utilization-and-storage. Here, we show that allowing up to 20% abated fossil fuel power generation in the power system could reduce the national total power shortage rate by up to 9.0 percentages in 2050 compared with a zero fossil fuel system. A lowest-cost scenario with 16% abated fossil fuel power generation in the system even causes 2.5% lower investment costs in the network (or $16.8 billion), and also increases system resilience by reducing power shortage during extreme climatic events.
Coherent Raman microscopy is the method of choice for the label-free, real-time characterization of the chemical composition in biomedical samples. The common implementation relies on scanning two tightly focused laser beams across the sample, which frequently leads to sample damage and proves slow over large fields of view. The few existing wide-field techniques, for their part, feature a reduced lateral resolution and do not provide axial sectioning. To resolve these practical limitations, we developed a robust wide-field nonlinear microscope that combines random illumination microscopy (RIM) with coherent anti-Stokes Raman scattering (CARS) and sum-frequency generation (SFG) contrasts. Based on a comprehensive theoretical study, CARS-RIM provides super-resolved reconstructions and optical sectioning of the sample from the second-order statistics of multiple images obtained under different speckled illuminations. We experimentally show that multimodal CARS-RIM and SFG-RIM achieve wide-field nonlinear imaging with a 3 µm axial sectioning capability and a 300 nm transverse resolution, effectively reducing the peak intensity at the sample compared with conventional point-scanning CARS. We exemplify the label-free, highly contrasted chemical imaging potential of CARS-RIM and SFG-RIM wide-field microscopy in two dimensions, as well as three dimensions, for a variety of samples such as beads, unstained human breast tissue and a mixture of chemical compounds.
CD8⁺ T cells provide robust antiviral immunity, but how epitope-specific T cells evolve across the human lifespan is unclear. Here we defined CD8⁺ T cell immunity directed at the prominent influenza epitope HLA-A*02:01-M158–66 (A2/M158) across four age groups at phenotypic, transcriptomic, clonal and functional levels. We identify a linear differentiation trajectory from newborns to children then adults, followed by divergence and a clonal reset in older adults. Gene profiles in older adults closely resemble those of newborns and children, despite being clonally distinct. Only child-derived and adult-derived A2/M158⁺CD8⁺ T cells had the potential to differentiate into highly cytotoxic epitope-specific CD8⁺ T cells, which was linked to highly functional public T cell receptor (TCR)αβ signatures. Suboptimal TCRαβ signatures in older adults led to less proliferation, polyfunctionality, avidity and recognition of peptide mutants, although displayed no signs of exhaustion. These data suggest that priming T cells at different stages of life might greatly affect CD8⁺ T cell responses toward viral infections.
While town twinning has played a crucial role in reconciliation and reconstruction processes in Europe after World War II, urban historians have not yet paid sufficient attention to it. This special issue thus addresses this historiographical neglect through a set of case-studies that examine the role of twinned cities in post-war reconciliation and reconstruction between former enemy nations and across the ideological fault lines of the Cold War. The framework that underpins all contributions rests on the use of ‘twinned cities’ as an umbrella term to denote various forms of inter-municipal links and builds on similarly broad definitions of ‘reconciliation’ and ‘reconstruction’.
AlGaAsSb attracts significant interest for near‐infrared avalanche photodiodes (APD). The authors report a two‐order reduction in the dark current and a six‐time enhancement of gain in random alloy (RA) AlGaAsSb APD that is surface passivated by conformal coating of Al 2 O 3 via atomic layer deposition (ALD). The dark currents of the APDs with 400‐µm diameter (dry etched) at 90% breakdown voltage (0.9 V br ) are (5.5 ± 0.5) × 10 ⁻⁵ A, (2.1 ± 0.4) × 10 ⁻⁵ A, and (6.2 ± 0.8) × 10 ⁻⁷ A for non‐passivated, Si 3 N 4 passivated, and Al 2 O 3 passivated devices, respectively. The dark current at a gain of 10 for the Al 2 O 3 passivated device is 1 × 10 ⁻⁸ A which is comparable to the reported value for 100‐µm diameter mesa diodes passivated by SU‐8. Maximum gain values of 6, 12, and 35 were obtained for non‐passivated, Si 3 N 4 passivated, and Al 2 O 3 passivated devices, respectively. Moreover, punch‐through capacitance of 8 pF in a spectral response of 450 to 850 nm was obtained. Thus, Al 2 O 3 passivation can be the best solution for antimonide optoelectronic devices.
New Findings What is the central question of this study? Gonadal hormones modulate cerebrovascular function while insulin‐like growth factor 1 (IGF‐1) facilitates exercise‐mediated cerebral angiogenesis; puberty is a critical period of neurodevelopment alongside elevated gonadal hormone and IGF‐1 activity: but whether exercise training across puberty enhances cerebrovascular function is unkown. What is the main finding and its importance? Cerebral blood flow is elevated in endurance trained adolescent males when compared to untrained counterparts. However, cerebrovascular reactivity to hypercapnia is faster in trained vs. untrained children, but not adolescents. Exercise‐induced improvements in cerebrovascular function are attainable as early as the first decade of life. Abstract Global cerebral blood flow (gCBF) and cerebrovascular reactivity to hypercapnia () are modulated by gonadal hormone activity, while insulin‐like growth factor 1 facilitates exercise‐mediated cerebral angiogenesis in adults. Whether critical periods of heightened hormonal and neural development during puberty represent an opportunity to further enhance gCBF and is currently unknown. Therefore, we used duplex ultrasound to assess gCBF and in n = 128 adolescents characterised as endurance‐exercise trained (males: n = 30, females: n = 36) or untrained (males: n = 29, females: n = 33). Participants were further categorised as pre‐ (males: n = 35, females: n = 33) or post‐ (males: n = 24, females: n = 36) peak height velocity (PHV) to determine pubertal or ‘maturity’ status. Three‐factor ANOVA was used to identify main and interaction effects of maturity status, biological sex and training status on gCBF and . Data are reported as group means (SD). Pre‐PHV youth demonstrated elevated gCBF and slower mean response times than post‐PHV counterparts (both: P ≤ 0.001). gCBF was only elevated in post‐PHV trained males when compared to untrained counterparts (634 (43) vs. 578 (46) ml min ⁻¹ ; P = 0.007). However, mean response time was faster in pre‐ (72 (20) vs. 95 (29) s; P ≤ 0.001), but not post‐PHV ( P = 0.721) trained youth when compared to untrained counterparts. Cardiorespiratory fitness was associated with gCBF in post‐PHV youth ( r ² = 0.19; P ≤ 0.001) and mean response time in pre‐PHV youth ( r ² = 0.13; P = 0.014). Higher cardiorespiratory fitness during adolescence can elevate gCBF while exercise training during childhood primes the development of cerebrovascular function, highlighting the importance of exercise training during the early stages of life in shaping the cerebrovascular phenotype.
The Conley index of an isolated invariant set is a fundamental object in the study of dynamical systems. Here we consider smooth functions on closed submanifolds of Euclidean space and describe a framework for inferring the Conley index of any compact, connected isolated critical set of such a function with high confidence from a sufficiently large finite point sample. The main construction of this paper is a specific index pair which is local to the critical set in question. We establish that these index pairs have positive reach and hence admit a sampling theory for robust homology inference. This allows us to estimate the Conley index, and as a direct consequence, we are also able to estimate the Morse index of any critical point of a Morse function using finitely many local evaluations.
Purpose Although a long-term goal of cancer therapy always has been the development of agents that selectively destroy cancer cells, more recent trends have been to seek secondary agents that sensitize cancer cells to existing treatment regimens. In this regard, the present study explored the possibility of using small molecule inhibitors of p38MAPK/MK2 stress signaling pathways as potential agents to enhance the sensitivity of cancer cells with abrogated G1 checkpoint to the DNA damaging agent etoposide by specifically targeting the DNA damage-induced G2 cell cycle checkpoint. Methods We have applied CCK8 and FACS-based viability assays and cell cycle analysis to investigate the effect of small molecules SB203580 and MK2.III on the sensitivity of small cell lung cancer cells (SCLC) that lack the G1 checkpoint to the DNA damaging agent Etoposide when used in combination. We have also assessed the effectiveness of combination chemotherapy on tumor xenograft suppression with etoposide and MK2.III in immunosuppressed mice. In addition, additional CCK8 cell viability analysis of the MDA-MB-231 breast cancer cell line, and SW620, and SW480 colorectal cancer cell lines was performed. Results Results suggest that etoposide produces a profound effect on the cell cycle profile of cells in a manner that is consistent with the degree of cell viability that is seen using the viable cell assay. Results of the co-treatment experiments revealed that the p38/MK2 kinase inhibitors SB203580 and MK2.III both enhanced the DNA-damaging effects of etoposide on NCI-H69 cell viability in vitro. Results revealed that in vivo MK2.III was able to act as a chemosensitizer when used in combination with etoposide making NCI-H69 lung cancer cells sensitive to chemotherapeutic drug by 45% compared to single usage of the drug. We also report that MK2.III sensitizes metastatic cell lines SW-620 and MDA-MB-231 to etoposide but does not increase the sensitivity of non-metastasizing SW-480 colorectal cells to DNA damaging agent in vitro. Conclusion Findings reported in this study provide evidence that specific inhibitors of MK2 may indeed improve overall cancer therapy; however, their effectiveness depends on cell types.
The configurations of ground heat exchangers (GHEs) play a significant role in the efficiency and sustainability of ground-source heat pump (GSHP) systems. However, there is a knowledge gap in understanding the performance differences between the horizontal and vertical GSHP systems in the same project under various heating and cooling demands. In this study, a technical performance comparison between GSHP systems coupled with horizontal ground loops and vertical boreholes under three scenarios of heating-to-cooling ratios (6 : 1, 2.4 : 1, and 1 : 1) was conducted. The simulations were based on a coupled thermal–hydraulic model for unsaturated soils that takes into account realistic ground surface boundary, GHE boundary, and the dynamics of heat pump efficiency. The GHEs were designed based on an experimental site located on the campus of a UK university. Results showed significant differences in the development of fluid temperatures and coefficient of performance (COP) of heat pumps between the horizontal and vertical GSHP systems due to the differences in the soil profiles and temperature boundaries. Both the fluid temperatures and heat pump COPs in the horizontal GSHP system reached a steady annual cycle after 2 years regardless of the heating-to-cooling ratios. For the vertical system, a general downward trend in the fluid temperatures and the COP of the heat pump in the heating mode can be found when a heating-to-cooling ratio was 6 : 1 or 2.4 : 1, while an overall upward trend in the fluid temperatures and the COP of the heat pump in the heating mode can be noted in the case of 1 : 1 heating-to-cooling ratio. Additionally, the heat pump operating in the cooling mode was off most of the time when a heating-to-cooling ratio was 6 : 1 or 2.4 : 1, while a declining trend in the COP of the heat pump in the cooling mode was exhibited in the case of a heating-to-cooling ratio of 1 : 1. The technical comparison reveals that the heating-to-cooling ratios would significantly affect the efficiency and sustainability of both GSHP systems.
In this short article we review the contribution of Sergey Naboko to the theory of boundary triples and outline some of its uses in applied mathematics. We also describe the benefits to our own mathematical careers which came from working with Sergey Naboko, starting with a brief history of our collaborations with him.
In eukaryotes, histone paralogues form obligate heterodimers such as H3/H4 and H2A/H2B that assemble into octameric nucleosome particles. Archaeal histones are dimeric and assemble on DNA into ‘hypernucleosome’ particles of varying sizes with each dimer wrapping 30 bp of DNA. These are composed of canonical and variant histone paralogues, but the function of these variants is poorly understood. Here, we characterise the structure and function of the histone paralogue MJ1647 from Methanocaldococcus jannaschii that has a unique C-terminal extension enabling homotetramerisation. The 1.9 Å X-ray structure of a dimeric MJ1647 species, structural modelling of the tetramer, and site-directed mutagenesis reveal that the C-terminal tetramerization module consists of two alpha helices in a handshake arrangement. Unlike canonical histones, MJ1647 tetramers can bridge two DNA molecules in vitro. Using single-molecule tethered particle motion and DNA binding assays, we show that MJ1647 tetramers bind ~60 bp DNA and compact DNA in a highly cooperative manner. We furthermore show that MJ1647 effectively competes with the transcription machinery to block access to the promoter in vitro. To the best of our knowledge, MJ1647 is the first histone shown to have DNA bridging properties, which has important implications for genome structure and gene expression in archaea.
Institution pages aggregate content on ResearchGate related to an institution. The members listed on this page have self-identified as being affiliated with this institution. Publications listed on this page were identified by our algorithms as relating to this institution. This page was not created or approved by the institution. If you represent an institution and have questions about these pages or wish to report inaccurate content, you can contact us here.
24,958 members
Frank C Langbein
  • School of Computer Science and Informatics
Richard James Stanton
  • Cardiff Institute of Infection & Immunity
Barend H. J. de Graaf
  • Department of Molecular and Cell Biology
Museum Avenue, CF10 3AX, Cardiff, Wales, United Kingdom
Head of institution
Professor Colin Riordan
+44 (0)29 2087 4000
+44(0) 2920 874000