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668 results on '"GREAVES, D."'

8. Wave energy absorption by a submerged air bag connected to a rigid float

Author

Kurniawan, A., Chaplin, J. R., Hann, M. R., Greaves, D. M., and Farley, F. J. M.

Subjects
Physics - Fluid Dynamics
Abstract

A new wave energy device features a submerged ballasted air bag connected at the top to a rigid float. Under wave action, the bag expands and contracts, creating a reciprocating air flow through a turbine between the bag and another volume housed within the float. Laboratory measurements are generally in good agreement with numerical predictions. Both show that the trajectory of possible combinations of pressure and elevation at which the device is in static equilibrium takes the shape of an S. This means that statically the device can have three different draughts, and correspondingly three different bag shapes, for the same pressure. The behaviour in waves depends on where the mean pressure-elevation condition is on the static trajectory. The captured power is highest for a mean condition on the middle section., Comment: Revised version submitted to Proc R Soc A

Published
2016
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9. Wave energy absorption by a floating air bag

Author

Kurniawan, A., Chaplin, J. R., Greaves, D. M., and Hann, M. R.

Subjects
Physics - Fluid Dynamics
Abstract

A floating air bag, ballasted in water, expands and contracts as it heaves under wave action. Connecting the bag to a secondary volume via a turbine transforms the bag into a device capable of generating useful energy from the waves. Small-scale measurements of the device reveal some interesting properties, which are successfully predicted numerically. Owing to its compressibility, the device can have a heave resonance period longer than that of a rigid device of the same shape and size, without any phase control. Furthermore, varying the amount of air in the bag is found to change its shape and hence its dynamic response, while varying the turbine damping or the air volume ratio changes the dynamic response without changing the shape., Comment: Revised version submitted to Journal of Fluid Mechanics

Published
2016
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23. Resting EEG power spectra across middle to late life: associations with age, cognition, APOE-e4 carriage, and cardiometabolic burden

Author

Smith, AE, Chau, A, Greaves, D, Keage, HAD, Feuerriegel, D, Smith, AE, Chau, A, Greaves, D, Keage, HAD, and Feuerriegel, D

Abstract

We investigated how resting electroencephalography (EEG) measures are associated with risk factors for late-life cognitive impairment and dementia, including age, apolipoprotein E ɛ4 (APOE-ɛ4) carriage, and cardiometabolic burden. Resting EEG was recorded from 86 adults (50-80 years of age). Participants additionally completed the Addenbrooke's Cognitive Examination (ACE) III and had blood drawn to assess APOE-ɛ4 carriage status and cardiometabolic burden. EEG power spectra were decomposed into sources of periodic and aperiodic activity to derive measures of aperiodic component slope and alpha (7-14 Hz) and beta (15-30 Hz) peak power and peak frequency. Alpha and beta peak power measures were corrected for aperiodic activity. The aperiodic component slope was correlated with ACE-III scores but not age. Alpha peak frequency decreased with age. Individuals with higher cardiometabolic burden had lower alpha peak frequencies and lower beta peak power. APOE-ɛ4 carriers had lower beta peak frequencies. Our findings suggest that the slope of the aperiodic component of resting EEG power spectra is more closely associated with measures of cognitive performance rather than chronological age in older adults.

Published
2023

26. Mystery in western medicine

Author

Greaves, D. A.

Subjects
610.9
Abstract

This study will develop the basis for a critique of western medicine aimed at providing an analysis, starting from the proposition that any system of medicine must necessarily embody a mysterious quality. What is meant here by mystery is an all-encompassing element of indeterminacy, and so of uncertainty in both the theory and practice of medicine. This analysis will therefore begin by examining the relationship between mystery and medicine. More specific aspects of western medicine will then be considered to show how they have developed so as to produce a reinterpretation or marginalisation of all that is not quantifiable or wholly comprehensible in terms of a particular conception of rationality. The insights ignored gained from this re-evaluation will then be used to develop the outline of a different critique which will indicate ways in which western medicine should be modified in both theory and practice. This will begin the recognition that although the present justification of western medicine is flawed, a more adequate one may be found through re-examining current medical practice and re-orientating it by taking account of particular themes in other contemporary and historical systems of medicine. The unrecognised thread which unites and gives coherence to all these medical systems is the role of mystery. It must be wholeheartedly acknowledged if the current mistakes and problems of western medicine are the revealed and understood, so that more plausible moral and scientific foundations for western medicine can be established.

Published
1995

36. Exploring Waves Propagation with a Newly Developed High-Performance Code in OpenFoam using Free-Surface Capturing Approach.

Author

Mehmood, A., Graha, D. I., Langfeld, K., Greaves, D. M., Akhtar, K., and Naveed, A.

Subjects
FINITE volume method, COMPUTATIONAL fluid dynamics, FREE surfaces, LIQUID-liquid interfaces, DISCRETIZATION methods, STOKES flow
Abstract

To address the demands of contemporary research and industry, it is crucial to reduce computational costs and rely on open-source codes to simulate real-world wave propagation phenomena. As a response, we have developed an efficient solver for modeling free surfaces within the OpenFOAM computational fluid dynamics (CFD) software package. Our approach involves employing the finite volume method for discretization to solve the Laplacian of the velocity potential. Moreover, we have devised the necessary kinematic and dynamic boundary conditions to depict fluid behavior at the computational domain's boundaries and the free surface's behavior. The convergence analysis demonstrated the expected first-order accuracy of the solver as the error decreased with a reduction in grid size. Time discretization study showed good temporal convergence as decreasing the time step size resulted in lower error. Wave period comparison validated the numerical solution by comparing it with 2nd-order Stokes theory, and a close agreement was observed between the simulated and analytical wave periods. We also validated our model by comparing them with experimental data from previous studies. The comparisons showed good agreement between the numerical simulations and experimental measurements, confirming the reliability of the developed numerical model. It is pertinent to note that our solver and boundary conditions are novel, exclusive to our research and were not present in the standard OpenFOAM distribution. [ABSTRACT FROM AUTHOR]

Published
2023

45. Cannabinoid receptor 2 deficiency exacerbates inflammation and neutrophil recruitment

Author

Kapellos, T, Taylor, L, Feuerborn, A, Valaris, S, Hussain, M, Rainger, G, Greaves, D, Iqbal, A, and Needham, G

Subjects
Male, leukocyte trafficking, Neutrophils, Research, Immunity, Innate, Chemokine CXCL10, Mice, Inbred C57BL, Receptor, Cannabinoid, CB2, adhesion, Mice, Matrix Metalloproteinase 9, Cell Movement, Cell Adhesion, Animals, Humans, lipids (amino acids, peptides, and proteins), Female, Chemokine CCL4, Transcriptome, innate immunity, Cells, Cultured, Chemokine CCL2
Abstract

Cannabinoid receptor (CB)2 is an immune cell-localized GPCR that has been hypothesized to regulate the magnitude of inflammatory responses. However, there is currently no consensus as to the mechanism by which CB2 mediates its anti-inflammatory effects in vivo. To address this question, we employed a murine dorsal air pouch model with wild-type and CB2-/- 8-12-wk-old female and male C57BL/6 mice and found that acute neutrophil and lymphocyte antigen 6 complex, locus Chi monocyte recruitment in response to Zymosan was significantly enhanced in CB2-/- mice. Additionally, levels of matrix metalloproteinase 9 and the chemokines C-C motif chemokine ligand (CCL)2, CCL4, and C-X-C motif chemokine ligand 10 in CB2-/- pouch exudates were elevated at earlier time points. Importantly, using mixed bone marrow chimeras, we revealed that the proinflammatory phenotype in CB2-/- mice is neutrophil-intrinsic rather than stromal cell-dependent. Indeed, neutrophils isolated from CB2-/- mice exhibited an enhanced migration-related transcriptional profile and increased adhesive phenotype, and treatment of human neutrophils with a CB2 agonist blocked their endothelial transmigration. Overall, we have demonstrated that CB2 plays a nonredundant role during acute neutrophil mobilization to sites of inflammation and, as such, it could represent a therapeutic target for the development of novel anti-inflammatory compounds to treat inflammatory human diseases.-Kapellos, T. S., Taylor, L., Feuerborn, A., Valaris, S., Hussain, M. T., Rainger, G. E., Greaves, D. R., Iqbal, A. J. Cannabinoid receptor 2 deficiency exacerbates inflammation and neutrophil recruitment.

Published
2019

49. Focused wave interactions with floating structures: A blind comparative study

Author

Ransley, E. J., Brown, S. A., Hann, M., Greaves, D., Windt, C., Ringwood, J., Davidson, J., Schmitt, P., Yan, S., Wang, J., Ma, Q., Xie, Z., Giorgi, G., Hughes, J., Williams, A., Masters, I., Lin, Z., Chen, H., Qian, L., Ma, Z., Chen, G., Ding, H., Zang, J., van Rij, J., Yu, Y., Li, Z., Bouscasse, B., Ducrozet, G., Bingham, H., Ransley, E. J., Brown, S. A., Hann, M., Greaves, D., Windt, C., Ringwood, J., Davidson, J., Schmitt, P., Yan, S., Wang, J., Ma, Q., Xie, Z., Giorgi, G., Hughes, J., Williams, A., Masters, I., Lin, Z., Chen, H., Qian, L., Ma, Z., Chen, G., Ding, H., Zang, J., van Rij, J., Yu, Y., Li, Z., Bouscasse, B., Ducrozet, G., and Bingham, H.

Abstract

The paper presents results from the Collaborative Computational Project in Wave Structure Interaction (CCP-WSI) Blind Test Series 2. Without prior access to the physical data, participants, with numerical methods ranging from low-fidelity linear models to fully nonlinear Navier-Stokes (NS) solvers, simulate the interaction between focused wave events and two separate, taut-moored, floating structures: a hemispherical-bottomed cylinder and a cylinder with a moonpool. The ‘blind’ numerical predictions for heave, surge, pitch and mooring load, are compared against physical measurements. Dynamic time warping is used to quantify the predictive capability of participating methods. In general, NS solvers and hybrid methods give more accurate predictions; however, heave amplitude is predicted reasonably well by all methods; and a WEC-Sim implementation, with CFD-informed viscous terms, demonstrates comparable predictive capability to even the stronger NS solvers. Large variations in the solutions are observed (even among similar methods), highlighting a need for standardisation in the numerical modelling of WSI problems.

Published
2021

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