Anatomical suitability of abdominal aortic aneurysms for endovascular repair

BACKGROUND: Aortic aneurysm anatomy is crucial when considering patients for endovascular repair. The aim of this study was to determine the proportion of patients with aortic aneurysm suitable for endovascular repair with three different graft-stent systems. METHODS: Spiral computed tomographic angiography was used to assess the anatomy of 154 abdominal aortic aneurysms. Measurements were made of aneurysm neck length and diameter, renal artery to aortic bifurcation length, common iliac artery diameter and length, and external iliac artery diameter. Aneurysms were assessed for anatomical suitability for currently available aortoaortic, aortobi-iliac and aortouni-iliac devices. RESULTS: Six patients (4 per cent) had a distal aortic neck suitable for implantation of a straight aortic graft. Fifteen patients (10 per cent) had arterial anatomy suitable for implantation of a bifurcated graft and 85 (55 per cent) patients were suitable for endovascular repair with an aortouni-iliac graft. The primary reasons for unsuitability were: proximal neck length less than 1.5 cm (44 patients), proximal neck diameter greater than 3.0 cm (12), and angulation of the proximal neck (three). A further ten patients were considered unsuitable for an aortouni-iliac graft because of bilateral common iliac artery aneurysms (four), tortuous iliac arteries (four) and narrow external iliac arteries (two). CONCLUSION: The aortouni-iliac device has the widest applicability of the currently available endovascular systems but open repair remains the only option for a large proportion of patients.     

Characterization of titanium alloy implant surfaces with improved dissolution resistance

The present work sets out to investigate the structure and chemistry of surface treated oxides (either aged in boiling water or air-heated) with improved dissolution resistance compared to conventionally passivated surfaces. X-ray photoelectron spectroscopy (XPS) has demonstrated a significant reduction in oxidized aluminium associated with an ageing-based surface treatment. Angle-dependent XPS has revealed an increase in amphoteric-OH surface sites for the thermal treatments. Atomic force microscopy (AFM) investigation suggests that these sites play a role in the improved proteinadsorption properties of these surfaces. These observations form the basis of a model which describes the influence of surface oxide on the kinetics of metal ion dissolution.     

ATTRITION IN THE BUBBLING ZONE OF A STEADY-STATE FLUIDIZED BED

This paper describes the kinetics of attrition in the bubbling zone of a fluidized bed and focuses on the development of an equation for attrition in continuous fluidized beds operating at steady state.

Laboratory data describing batch attrition of a limestone sorbent are applied to the integrated equations to describe overall attrition rate in a full-scale continuous system.     

All‐Hex Mesh Generation via Volumetric PolyCube Deformation

While hexahedral mesh elements are preferred by a variety of simulation techniques, constructing quality all‐hex meshes of general shapes remains a challenge. An attractive hex‐meshing approach, often referred to as sub‐mapping, uses a low distortion mapping between the input model and a PolyCube (a solid formed from a union of cubes), to transfer a regular hex grid from the PolyCube to the input model. Unfortunately, the construction of suitable PolyCubes and corresponding volumetric maps for arbitrary shapes remains an open problem. Our work introduces a new method for computing low‐distortion volumetric PolyCube deformations of general shapes and for subsequent all‐hex remeshing. For a given input model, our method simultaneously generates an appropriate PolyCube structure and mapping between the input model and the PolyCube. From these we automatically generate good quality all‐hex meshes of complex natural and man‐made shapes.     

Determination of Dextrose Equivalent Value and Number Average Molecular Weight of Maltodextrin by Osmometry

ABSTRACT:  Dextrose equivalent (DE) value is the most common parameter used to characterize the molecular weight of maltodextrins. Its theoretical value is inversely proportional to number average molecular weight ( M_n ), providing a theoretical basis for correlations with physical properties important to food manufacturing, such as: hygroscopicity, the glass transition temperature, and colligative properties. The use of freezing point osmometry to measure DE and M_n  was assessed. Measurements were made on a homologous series of malto-oligomers as well as a variety of commercially available maltodextrin products with DE values ranging from 5 to 18. Results on malto-oligomer samples confirmed that freezing point osmometry provided a linear response with number average molecular weight. However, noncarbohydrate species in some commercial maltodextrin products were found to be in high enough concentration to interfere appreciably with DE measurement. Energy dispersive spectroscopy showed that sodium and chloride were the major ions present in most commercial samples. Osmolality was successfully corrected using conductivity measurements to estimate ion concentrations. The conductivity correction factor appeared to be dependent on the concentration of maltodextrin. Equations were developed to calculate corrected values of DE and M_n  based on measurements of osmolality, conductivity, and maltodextrin concentration. This study builds upon previously reported results through the identification of the major interfering ions and provides an osmolality correction factor that successfully accounts for the influence of maltodextrin concentration on the conductivity measurement. The resulting technique was found to be rapid, robust, and required no reagents.     

Microstructural effects on fracture toughness in AA7010 plate

The influence of recrystallization and quench rate after solution treatment on the fracture toughness of 7010 aluminum plate has been studied in longitudinal-transverse (L-T) and short-longitudinal (S-L) orientations for T76-type heat treatments. Extensive fractographic analysis was carried out to identify the failure mechanisms, including simultaneous scanning electron microscope (SEM) observation of fracture surfaces and underlying microstructures. A slow quench rate was strongly detrimental because it modified the dominant failure mode from a relatively high energy primary void growth mechanism to lower energy transgranular shear and grain boundary ductile failure in the L-T and S-L orientations, respectively. Low energy failure was associated with coarse ν precipitation during the quench in both L-T and S-L orientation tests, with intragranular and intersubgranular particles contributing to L-T quench sensitivity, and intergranular particles contributing to S-L sensitivity. Partial recrystallization was generally detrimental, with recrystallized grains being shown to be a preferential crack path. The commonly supposed susceptibility of recrystallized grains to intergranular failure did not explain this behavior, particularly in fast quench materials, as recrystallized grains primarily failed by transgranular void growth from the large intermetallics with which they were intrinsically associated. Exceptional S-L orientation quench sensitivity was observed in unrecrystallized material and attributed to a synergistic interaction between heterogeneous boundary precipitation and the specific location of coarse intermetallics along grain boundaries in the unrecrystallized condition. Quantitative assessment of individual contributions to overall fracture resistance is discussed for cases where multiple failure mechanisms occur, highlighting the importance of interacting and noninteracting mechanisms.     

Using angular dispersion of gradient direction for detecting edgeribbons

Edges in a scene generally project to smooth continuous curves nearly everywhere in the image, which results in low angular deviation of the intensity gradients in small neighborhoods straddling edges. Angular deviation is shown to be a measure of SNR. A theoretical analysis of angular deviation arising due to independent and identically distributed N(0, σ²) random noise is presented. Angular deviation thresholds for neighborhood sizes from 3×3 to 11×11 pixels are determined both from this analysis and numerical examples. The proposed gradient angular dispersion detection algorithm detects edge elements by comparing the measured angular deviation with values computed for the minimum acceptable SNR. Low values of deviation violate the `no edge' hypothesis. The algorithm is shown to make good use of the limited dynamic range of the imaging system. The sensitivity and selectivity of the strategy are both shown to be high     

Outcomes following acute hospital care for stroke or hip fracture: how useful is an assessment of anxiety or depression for older people?

OBJECTIVE: To investigate the association between severe life events and mental health outcomes following acute hospital care for older patients with acute stroke or fractured neck of femur. DESIGN: Prospective longitudinal survey of stroke and hip fracture patients admitted to hospital from admission to 6-month follow-up. SETTING: Six district general hospitals, three in the North and three in the South of England. PARTICIPANTS: 642 patients admitted to hospital with an acute stroke (268) or hip fracture (374) resident in a private household at 6 months follow-up. MAIN OUTCOME MEASURES: Hospital Anxiety and Depression Scale, cognitive items of the Survey Psychiatric Assessment Scale, Clackmannan Disability Scale, Severe Life Events Inventory, Wenger Social Support Network Typology. RESULTS: 47% of 6-month survivors of stroke or hip fracture resident in private households had a possible psychiatric illness: dementia (13%), anxiety or depression (41%). 57% had severe or very severe disability and 48% experienced additional life events (17% two or more) after hospital admission. Severe disability was strongly associated with a higher prevalence of anxiety (p < 0.0005) or depression (p < 0.0001). Social contact was associated with a lower prevalence of anxiety (p < 0.01) or depression (p < 0.0001) and social support network type was strongly associated with depression (p < 0.001) but not anxiety (p = 0.096). Number of severe life events was associated with anxiety (p < 0.001) but not depression (p = 0.058). CONCLUSION: Disability is probably a more robust outcome measure than assessments of mental health for older people in uncontrolled studies.