Development of ultrafast UTE imaging for granular systems

Ultrashort echo time (UTE) imaging is commonly used in medical MRI to image 'solid' types of tissue; to date it has not been widely used in engineering or materials science, in part due to the relatively long imaging times required. Here we show how the acquisition time for UTE can be reduced to enable a preliminary study of a fluidized bed, a type of reactor commonly used throughout industry containing short T$_{2}$$^{∗}$ material and requiring fast imaging. We demonstrate UTE imaging of particles with a T$_{2}$$^{∗}$ of only 185μs, and an image acquisition time of only 25ms. The images are obtained using compressed sensing (CS) and by exploiting the Hermitian symmetry of k-space, to increase the resolution beyond that predicted by the Nyquist theorem. The technique is demonstrated by obtaining one- and two-dimensional images of bubbles rising in a model fluidized bed reactor.HTF would like to acknowledge the financial support of the Gates Cambridge Trust. All authors would like to acknowledge the financial support of the EPSRC (EP/K008218/1, EP/F047991/1 and EP/K039318/1)

Capacity to make health care decisions: its importance in clinical practice

Background. Assessment of capacity plays a pivotal role in determining when decisions need to be made on behalf of an individual. It therefore has major clinical management implications for health care professionals and civil liberties implications for the person concerned. In many countries, there is a presumption that adults have the capacity to make health care decisions. However, in persons with a mental disability, capacity may be temporarily or permanently impaired. Methods. A selective review is presented which considers: (i) the broad approaches taken to determining capacity; (ii) the abilities commonly assessed in determining capacity; and (iii) the principles underlying health care decision-making for adults who are without capacity. Results. Capacity is a functional concept, determined by the person's ability to understand, retain, and weigh up information relevant to the decision in order to arrive at a choice, and then to communicate that choice. We have reviewed the studies that examined decision-making abilities in people with dementia, chronic mental illness or intellectual disabilities. Approaches to decision-making in adults who lack capacity include: anticipatory decisions made through advance health care statements or decisions by proxy based on ‘best interests’ or ‘substituted judgement’. Conclusions. The understanding of clinical and legal aspects of capacity is still developing. This paper examines current concepts of capacity and decision-making on behalf of those without capacity. We propose a framework, in line with current ethical and legal guidelines, as an aid to clinicians when they are seeking consent for a health care intervention.published_or_final_versio

Investigation of Void Fraction Schemes for Use with CFD-DEM Simulations of Fluidized Beds

© 2018 American Chemical Society. This paper investigates the spatial resolution of computational fluid dynamics-discrete element method (CFD-DEM) simulations of a bubbling fluidized bed for seven different void fraction schemes. Fluid grids with cell sizes of 3.5, 1.6, and 1.3 particle diameters were compared. The particle velocity maps from all of the void fraction schemes were in good qualitative agreement with the experimental data collected using magnetic resonance imaging (MRI). Refining the fluid grid improved the quantitative agreement due to a more accurate representation of flow near the gas distributor. The approach proposed by Khawaja et al. [ J. Comput. Multiphase Flows 2012, 4, 183-192 ] provided the closest match to the exact void fraction though only the particle centered method differed significantly. These results indicate that the fluid grid used for CFD-DEM simulations must be sufficiently fine to represent the inlet flow realistically and that a void fraction scheme such as that proposed by Khawaja be used

The capacity of people with a ‘mental disability’ to make a health care decision

Background. Based on the developing clinical and legal literature, and using the framework adopted in draft legislation, capacity to make a valid decision about a clinically required blood test was investigated in three groups of people with a ‘mental disability’ (i.e. mental illness (chronic schizophrenia), ‘learning disability’ (‘mental retardation’, or intellectual or developmental disability), or, dementia) and a fourth, comparison group. Methods. The three ‘mental disability’ groups (N = 20 in the ‘learning disability’ group, N = 21 in each of the other two groups) were recruited through the relevant local clinical services; and through a phlebotomy clinic for the ‘general population’ comparison group (N = 20). The decision-making task was progressively simplified by presenting the relevant information as separate elements and modifying the assessment of capacity so that responding became gradually less dependent on expressive verbal ability. Results. Compared with the ‘general population’ group, capacity to make the particular decision was significantly more impaired in the ‘learning disability’ and ‘dementia’ groups. Importantly, however, it was not more impaired among the ‘mental illness’ group. All the groups benefited as the decision-making task was simplified, but at different stages. In each of the ‘mental disability’ groups, one participant benefited only when responding did not require any expensive verbal ability. Conclusions. Consistent with current views, capacity reflected an interaction between the decision-maker and the demands of the decision-making task. The findings have implications for the way in which decisions about health care interventions are sought from people with a ‘mental disability’. The methodology may be extended to assess capacity to make other legally-significant decisions.published_or_final_versio

11-interval PFG pulse sequence for improved measurement of fast velocities of fluids with high diffusivity in systems with short T2(∗).

Magnetic resonance (MR) was used to measure SF6 gas velocities in beds filled with particles of 1.1 mm and 0.5 mm in diameter. Four pulse sequences were tested: a traditional spin echo pulse sequence, the 9-interval and 13-interval pulse sequence of Cotts et al. (1989) and a newly developed 11-interval pulse sequence. All pulse sequences measured gas velocity accurately in the region above the particles at the highest velocities that could be achieved (up to 0.1 ms(-1)). The spin echo pulse sequence was unable to measure gas velocity accurately in the bed of particles, due to effects of background gradients, diffusivity and acceleration in flow around particles. The 9- and 13-interval pulse sequence measured gas velocity accurately at low flow rates through the particles (expected velocity <0.06 ms(-1)), but could not measure velocity accurately at higher flow rates. The newly developed 11-interval pulse sequence was more accurate than the 9- and 13-interval pulse sequences at higher flow rates, but for velocities in excess of 0.1 ms(-1) the measured velocity was lower than the expected velocity. The increased accuracy arose from the smaller echo time that the new pulse sequence enabled, reducing selective attenuation of signal from faster moving nuclei.CMB acknowledges the Gates Cambridge Trust for funding his research.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.jmr.2016.01.02

The Drinfel'd twisted XYZ model

We construct a factorizing Drinfel'd twist for a face type model equivalent to the XYZ model. Completely symmetric expressions for the operators of the monodromy matrix are obtained.Comment: 15 pages, 4 figures, second preprint no. added, reference [14] added, typos correcte

Neuroimaging and other modalities to assess Alzheimer's disease in Down syndrome

People with Down syndrome (DS) develop Alzheimer's disease (AD) at higher rates and a younger age of onset compared to the general population. As the average lifespan of people with DS is increasing, AD is becoming an important health concern in this group. Neuroimaging is becoming an increasingly useful tool in understanding the pathogenesis of dementia development in relation to clinical symptoms. Furthermore, neuroimaging has the potential to play a role in AD diagnosis and monitoring of therapeutics. This review describes major recent findings from in vivo neuroimaging studies analysing DS and AD via ligand-based positron emission tomography (PET), [18F] fluorodeoxyglucose (FDG)-PET, structural magnetic resonance imaging (sMRI), and diffusion tensor imaging (DTI). Electroencephalography (EEG) and retinal imaging are also discussed as emerging modalities. The review is organized by neuroimaging method and assesses the relationship between cognitive decline and neuroimaging changes. We find that amyloid accumulation seen on PET occurs prior to dementia onset, possibly as a precursor to the atrophy and white matter changes seen in MRI studies. Future PET studies relating tau distribution to clinical symptoms will provide further insight into the role this protein plays in dementia development. Brain activity changes demonstrated by EEG and metabolic changes seen via FDG-PET may also follow predictable patterns that can help track dementia progression. Finally, newer approaches such as retinal imaging will hopefully overcome some of the limitations of neuroimaging and allow for detection of dementia at an earlier stage.This work was supported by a scholarship from the Clinical Neuroscience Training Program of Perelman School of Medicine to Natalie Neale

The incidence of healthcare use, ill health and mortality in adults with intellectual disabilities and mealtime support needs

This is the final published version. It first appeared at http://onlinelibrary.wiley.com/doi/10.1111/jir.12167/full.Background\ud Adults with intellectual disabilities (ID) experience a wide range of eating, drinking and/or swallowing (EDS) problems, for which they receive diverse mealtime support interventions. Previous research has estimated that dysphagia (difficulty swallowing) affects 8% of all adults with ID and that 15% require some form of mealtime support. People with ID (whether they require mealtime support or not) also experience a greater burden of ill-health and die younger than their peers in the general population with no ID.\ud \ud Methods\ud Using an exploratory, population-based cohort study design, we set out to explore health-related outcomes in adults with ID who receive mealtime support for any eating, drinking or swallowing problem, by establishing the annual incidence of healthcare use, EDS-related ill-health, and all-cause mortality. This study was conducted in two counties in the East of England.\ud \ud Results\ud In 2009, 142 adults with mild to profound ID and a need for any type of mealtime support were recruited for a baseline survey. At follow-up one year later, 127 individuals were alive; eight had died; and seven could not be contacted. Almost all participants had one or more GP consultations each year (85-95%) and, in the first year, 20% reportedly had one or more emergency hospitalisations. Although their annual number of GP visits was broadly comparable to that of the general population, one-fifth of this population?s primary healthcare use was directly attributable to EDS-related ill-health. Respiratory infections were the most common cause of morbidity, and the immediate cause of all eight deaths, while concerns about nutrition and dehydration were surprisingly minor. Our participants had a high annual incidence of death (5%) and, with a standardised mortality ratio of 267, their observed mortality was more than twice that expected in the general population of adults with ID (not selected because of mealtime support for EDS problems).\ud \ud Conclusions\ud All Annual Health Checks now offered to adults with ID should include questions about respiratory infections and EDS functioning, in order to focus attention on EDS problems in this population. This has the potential to reduce life-threatening illness

The Early Presentation of Dementia in People with Down Syndrome: a Systematic Review of Longitudinal Studies

Adults with Down syndrome (DS) are at a very high risk of developing early onset Alzheimer's disease (AD) due to trisomy of chromosome 21. AD is preceded by a prolonged prodromal "pre-clinical" phase presenting with clinical features that do not fulfil the diagnostic criteria for AD. It is important to clinically characterise this prodromal stage to help early detection of the disease as neuropathology of AD is almost universal by the fifth decade in DS. There is a lack of knowledge of the trajectory of decline associated with the onset of dementia in this population and early signs may be overlooked or misdiagnosed, negatively affecting the quality of life of those affected and the use of early pharmacological or psychosocial interventions. The objective of this systematic review is to evaluate the published literature on longitudinal data in order to identify the cognitive and behavioural changes occurring during the prodromal and early stages of AD in this population. Fifteen peer-reviewed articles met the inclusion criteria, including a total number of 831 participants, with the duration between baseline and follow up varying from 1 year to 47 years. Results suggest that, compared to the general population for which short-term (episodic) memory loss is the most common indicator associated with the onset of AD, in people with DS, executive dysfunction and Behavioural and Psychological Symptoms of Dementia (BPSD) are commonly observed during pre-clinical and early stages and may precede memory loss. The review highlights the importance of using a broad spectrum of assessments in the context of heterogeneity of symptoms. Theoretical and practical implications are discussed, as well as the need for further research.This systematic review is part of a larger research study funded by the Baily Thomas Charitable Fund, Addenbrookes Charitable Trust and the Health Foundation. Queens’ College Cambridge contributed via a grant which enabled the dissemination of these findings at BNA 2015 Festival of Neuroscience in Edinburgh

Measurements of the velocity distribution for granular flow in a Couette cell

© 2018 American Physical Society. In this paper, magnetic resonance velocimetry is used to measure the spatially resolved velocity and velocity fluctuations for granular flow in a Couette cell for four different particle sizes. The largest particles studied (dp=1.7mm) showed significant slip at the inner wall. The remaining particles showed no slip and all exhibit the same behavior in the profiles of the mean velocity and variance of velocity. The measurements demonstrate that the velocity and variance in velocity scale with the inner wall velocity U; the variance does not scale with U2. The experimental data were compared with a kinetic theory based model of granular flow and a hydrodynamic model. It was found that the shear rate scales with an exponent of 1.5-2.0 with respect to the velocity fluctuations (uy2), compared with the value of 1.0 expected from kinetic theory. The difference in the exponent is consistent with the effect of collective dynamics as described by the hydrodynamic model