Subsonic high-angle-of-attack aerodynamic characteristics of a cone and cylinder with triangular cross sections and a cone with a square cross section

Experiments were conducted in the 12-Foot Pressure Wind Tunnel at Ames Research Center on three models with noncircular cross sections: a cone having a square cross section with rounded corners and a cone and cylinder with triangular cross sections and rounded vertices. The cones were tested with both sharp and blunt noses. Surface pressures and force and moment measurements were obtained over an angle of attack range from 30 deg to 90 deg and selected oil-flow experiments were conducted to visualize surface flow patterns. Unit Reynolds numbers ranged from 0.8x1,000,000/m to 13.0x1,000,000/m at a Mach number of 0.25, except for a few low-Reynolds-number runs at a Mach number of 0.17. Pressure data, as well as force data and oil-flow photographs, reveal that the three dimensional flow structure at angles of attack up to 75 deg is very complex and is highly dependent on nose bluntness and Reynolds number. For angles of attack from 75 deg to 90 deg the sectional aerodynamic characteristics are similar to those of a two dimensional cylinder with the same cross section

Robust multipoint water-fat separation using fat likelihood analysis

Fat suppression is an essential part of routine MRI scanning. Multiecho chemical-shift based water-fat separation methods estimate and correct for Bo field inhomogeneity. However, they must contend with the intrinsic challenge of water-fat ambiguity that can result in water-fat swapping. This problem arises because the signals from two chemical species, when both are modeled as a single discrete spectral peak, may appear indistinguishable in the presence of Bo off-resonance. In conventional methods, the water-fat ambiguity is typically removed by enforcing field map smoothness using region growing based algorithms. In reality, the fat spectrum has multiple spectral peaks. Using this spectral complexity, we introduce a novel concept that identifies water and fat for multiecho acquisitions by exploiting the spectral differences between water and fat. A fat likelihood map is produced to indicate if a pixel is likely to be water-dominant or fat-dominant by comparing the fitting residuals of two different signal models. The fat likelihood analysis and field map smoothness provide complementary information, and we designed an algorithm (Fat Likelihood Analysis for Multiecho Signals) to exploit both mechanisms. It is demonstrated in a wide variety of data that the Fat Likelihood Analysis for Multiecho Signals algorithm offers highly robust water-fat separation for 6-echo acquisitions, particularly in some previously challenging applications. © 2011 Wiley Periodicals, Inc

‘It’s where I belong’: what does it mean to age in place from the perspective of people aged 80 and above? A longitudinal qualitative study (wave one)

\ua9 The Author(s) 2024.Background: Most people want to remain at home as they age. Ageing in place – remaining at home and connected to the community – is a national and international policy priority; however, to better understand how policy might be implemented, a more nuanced understanding is required about older adults’ lived experiences of ageing in place, especially the experiences of those aged 80 and above. Objective: To describe and explore the social processes which enable ageing in place from the perspective of community-dwelling older people (80+). Methods: Forty-six respondents (80–100+ years) participated in the first wave of a longitudinal qualitative study set in North East England. Semi-structured interviews were conducted in participants’ homes between June 2022 and January 2023. Interviews were analysed using reflexive thematic analysis. Results: Participants positioned their homes as a place of freedom and as the antithesis of a ‘care home’. Remaining in place was important for all participants; a key priority for them was to remain physically active to enable this. However, many participants faced significant hurdles to remaining in place. These were primarily related to health and mobility issues. Some participants were able to overcome such barriers by drawing on financial resources and available social networks. Conclusion: The home is central to understanding older peoples’ (80+) experiences of ageing. In a socio-political context which promotes ageing in place, the social factors shaping experiences of ageing in place must be considered. This involves attending to the challenges of later life, particularly health and especially mobility and physical function. Currently, those with resources (social and economic) are better equipped to respond to such challenges, thus potentially exacerbating widening inequalities in ageing. By foregrounding the perspectives of those ageing in place alongside social factors shaping their experiences, our study has important implications for policy and health and social care. We show that a more equitable allocation of resources is vital to fulfil the ageing in place policy agenda. Furthermore, we highlight a need to recognise commitments to ageing in place displayed by people aged 80 and above, especially when remaining in place becomes difficult to achieve

Noise analysis for 3-point chemical shift-based water-fat separation with spectral modeling of fat

Purpose: To model the theoretical signal-to-noise ratio (SNR) behavior of 3-point chemical shift-based water-fat separation, using spectral modeling of fat, with experimental validation for spin-echo and gradient-echo imaging. The echo combination that achieves the best SNR performance for a given spectral model of fat was also investigated. Materials and Methods: Cramér-Rao bound analysis was used to calculate the best possible SNR performance for a given echo combination. Experimental validation in a fatwater phantom was performed and compared with theory. In vivo scans were performed to compare fat separation with and with out spectral modeling of fat. Results: Theoretical SNR calculations for methods that include spectral modeling of fat agree closely with experimental SNR measurements. Spectral modeling of fat more accurately separates fat and water signals, with only a slight decrease in the SNR performance of the water-only image, although with a relatively large decrease in the fat SNR performance. Conclusion: The optimal echo combination that provides the best SNR performance for water using spectral modeling of fat is very similar to previous optimizations that modeled fat as a single peak. Therefore, the optimal echo spacing commonly used for single fat peak models is adequate for most applications that use spectral modeling of fat. © 2010 Wiley-Liss, Inc

Identifying and understanding digital exclusion: a mixed-methods study

\ua9 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.Many of our transactions and interactions are now exclusively online; however, whilst we live in a world which is becoming ubiquitously digital, digital exclusion remains a complex societal issue. This study aimed to identify the scale and characteristics of ‘digitally excluded’ individuals in one borough in North East England and investigate factors influencing experiences of digital exclusion. A two-phase, sequential explanatory mixed-methods design was used. Phase One utilised a survey which was sent to every household in the borough (N = >98,000). The surveys (N = 9181) were analysed using exploratory univariate analysis, followed by a two-staged regression model. Of those responses, 1130 individuals (12.3%) were identified as digitally excluded. Older adults with disability, no or low-level education, and residing in specific (micro) geographical areas, were at higher risk of digital exclusion. Smaller household sizes and lower income also contributed to digitally exclusion. To further enhance inclusivity, three focus groups were conducted with groups who were identified as being at higher risk of digital exclusion (N = 10). Discussions highlighted the complexities of digital exclusion and digital use across communities and within individual circumstances. Digital exclusion is multi-factored and complex. It requires regional institutions and local communities to collaborate in an integrated governance framework to improve digital inclusion

Warm gas at 50 AU in the disk around Herbig Be star HD 100546

The disk atmosphere is one of the fundamental elements of theoretical models of a protoplanetary disk. However, the direct observation of the warm gas (>> 100 K) at large radius of a disk (>> 10 AU) is challenging, because the line emission from warm gas in a disk is usually dominated by the emission from an inner disk. Our goal is to detect the warm gas in the disk atmosphere well beyond 10 AU from a central star in a nearby disk system of the Herbig Be star HD 100546. We measured the excitation temperature of the vibrational transition of CO at incremental radii of the disk from the central star up to 50 AU, using an adaptive optics system combined with the high-resolution infrared spectrograph CRIRES at the VLT. The observation successfully resolved the line emission with 0".1 angular resolution, which is 10 AU at the distance of HD 100546. Population diagrams were constructed at each location of the disk, and compared with the models calculated taking into account the optical depth effect in LTE condition. The excitation temperature of CO is 400-500 K or higher at 50 AU away from the star, where the blackbody temperature in equilibrium with the stellar radiation drops as low as 90 K. This is unambiguous evidence of a warm disk atmosphere far away from the central star.Comment: 7 pages, 5 figures, A&A in pres

Infrared High-Resolution Spectroscopy of Post-AGB Circumstellar Disks. I. HR 4049 - The Winnowing Flow Observed?

High-resolution infrared spectroscopy in the 2.3-4.6 micron region is reported for the peculiar A supergiant, single-lined spectroscopic binary HR 4049. Lines from the CO fundamental and first overtone, OH fundamental, and several H2O vibration-rotation transitions have been observed in the near-infrared spectrum. The spectrum of HR 4049 appears principally in emission through the 3 and 4.6 micron region and in absorption in the 2 micron region. The 4.6 micron spectrum shows a rich 'forest' of emission lines. All the spectral lines observed in the 2.3-4.6 micron spectrum are shown to be circumbinary in origin. The presence of OH and H2O lines confirm the oxygen-rich nature of the circumbinary gas which is in contrast to the previously detected carbon-rich material. The emission and absorption line profiles show that the circumbinary gas is located in a thin, rotating layer near the dust disk. The properties of the dust and gas circumbinary disk and the spectroscopic orbit yield masses for the individual stars, M_AI~0.58 Msolar and M_MV~0.34 Msolar. Gas in the disk also has an outward flow with a velocity of $\gtrsim$ 1 km/s. The severe depletion of refractory elements but near-solar abundances of volatile elements observed in HR 4049 results from abundance winnowing. The separation of the volatiles from the grains in the disk and the subsequent accretion by the star are discussed. Contrary to prior reports, the HR 4049 carbon and oxygen isotopic abundances are typical AGB values: 12C/13C=6^{+9}_{-4} and 16O/17O>200.Comment: 42 pages, 14 figures, Accepted by Ap

Phase and amplitude correction for multi-echo water-fat separation with bipolar acquisitions

Purpose: To address phase and amplitude errors for multi-point water-fat separation with bipolar acquisitions, which efficiently collect all echoes with alternating read-out gradient polarities in one repetition. Materials and Methods: With the bipolar acquisitions, eddy currents and other system nonidealities can induce inconsistent phase errors between echoes, disrupting water-fat separation. Previous studies have addressed phase correction in the read-out direction. However, the bipolar acquisitions may be subject to spatially high order phase errors as well as an amplitude modulation in the read-out direction. A method to correct for the 2D phase and amplitude errors is introduced. Low resolution reference data with reversed gradient polarities are collected. From the pair of low-resolution data collected with opposite gradient polarities, the two-dimensional phase errors are estimated and corrected. The pair of data are then combined for water-fat separation. Results: We demonstrate that the proposed method can effectively remove the high order errors with phantom and in vivo experiments, including obliquely oriented scans. Conclusion: For bipolar multi-echo acquisitions, uniform water-fat separation can be achieved by removing high order phase errors with the proposed method. © 2010 Wiley-Liss, Inc

Quantification of hepatic steatosis with 3-T MR imaging: Validation in ob/ob mice

Purpose: To validate quantitative imaging techniques used to detect and measure steatosis with magnetic resonance (MR) imaging in an ob/ob mouse model of hepatic steatosis. Materials and Methods: The internal research animal and resource center approved this study. Twenty-eight male ob/ob mice in progressively increasing age groups underwent imaging and were subsequently sacrificed. Six ob /+ mice served as control animals. Fat fraction imaging was performed with a chemical shift-based water-fat separation method. The following three methods of conventional fat quantification were compared with imaging: lipid extraction and qualitative and quantitative histologic analysis. Fat fraction images were reconstructed with single- and multiple-peak spectral models of fat and with and without correction for T2* effects. Fat fraction measurements obtained with the different reconstruction methods were compared with the three methods of fat quantification, and linear regression analysis and two-sided and two-sample t tests were performed. Results:Lipid extraction and qualitative and quantitative histologic analysis were highly correlated with the results of fat fraction imaging (r2 = 0.92, 0.87, 0.82, respectively). No significant differences were found between imaging measurements and lipid extraction (P = .06) or quantitative histologic (P = .07) measurements when multiple peaks of fat and T2* correction were included in image reconstruction. Reconstructions in which T2* correction, accurate spectral modeling, or both were excluded yielded lower agreement when compared with the results yielded by other techniques. Imaging measurements correlated particularly well with histologic grades in mice with low fat fractions (intercept, -1.0% ± 1.2 [standard deviation ]). Conclusion: MR imaging can be used to accurately quantify fat in vivo in an animal model of hepatic steatosis and may serve as a quantitative biomarker of hepatic steatosis. © RSNA, 2010