The Egyptian Cardiothoracic Surgeon (ECTS - E-Journal)
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Numerical study on mechanisms of angle-plied panels for ballistic protection
No full textThis paper investigates on the mechanisms behind the angled ply-orientation on the ballistic performances of multi-ply UHMWPE fabric panels. Finite element (FE) models have been established for the 3-ply align-laid [0/0/0] and angle-laid [0/30/60] fabric panels. Numerical analyses on the time history of projectile energy loss and panel energy absorption, panel failure time, and the stress distributions at two representative velocities are carried out for these two panels. Study results show the existence of a critical velocity for the 3-ply fabric panels. Below this critical velocity, the enhanced inter-ply isotropy in the angle-laid panel contributes to the improved energy absorption, whereas above this critical velocity, the angle-laid panel is found prone to initial stress concentration, leading to yarn premature damage on the rear ply of the panel and thus the disappearance of the advantages of the angle-laid panel. This phenomenon is supported from the FE investigation as well as from the experimental results
A study of deformation twinning in a titanium alloy by X-ray diffraction contrast tomography
No full textA near-wall domain decomposition approach in application to turbulent flow in a diffuser
No full textTurbulent flow in an asymmetric, two-dimensional diffuser is studied using a near-wall domain decomposition method and a k–εk–ε turbulence model. A one-dimensional boundary layer equation is used to transfer the boundary conditions from the wall to an interface within the flow. The boundary conditions applied to the fluid velocity and turbulent kinetic energy are of Robin type. They are mesh independent and can account for arbitrary source terms. This approach avoids the computational expense of fully simulating the turbulent boundary layers. For the first time, the technique has been applied to modelling a separated flow with an unstructured code. It is shown how the interface boundary condition on the turbulent kinetic energy allows the recirculation region in the diffuser to be captured. In contrast, the standard wall function approach, based on the log law, fails to predict any recirculation region. The only parameter required to apply the domain decomposition method is a turbulent viscosity profile across the boundary layer. Three different profiles are used in this work. It is shown how making the turbulent viscosity a function of the pressure gradient improves flow predictions for the diffuser. The results demonstrate that the method is an efficient way to simulate the boundary layers in engineering problems that include complex geometries or separating flows
British Association of Dermatologists and British Photodermatology Group guidelines for the safe and effective use of psoralen combined with ultraviolet A therapy 2015
No full textComputational hemodynamics of abdominal aortic aneurysms: Three-dimensional ultrasound versus computed tomography
No full textThe current criterion for surgical intervention in abdominal aortic aneurysms, based upon a maximal aortic diameter, is considered conservative due to the high mortality rate in case of rupture. The research community is actively investigating the use of computational mechanics tools combined with patient-specific imaging to help identify more accurate criteria. Widespread uptake of a successful metric will however be limited by the need for computed tomography, which is at present the primary image extraction method on account of the location and complex shape of the aneurysms. The use of three-dimensional ultrasound as the scanning method is more attractive on account of increased availability, reduced cost and reduced risk to patients. The suitability of three-dimensional ultrasound is assessed for this purpose in the present work; computational fluid dynamics simulations were performed on geometries obtained from the same patient using both ultrasound and computed tomography. The influence of different smoothing algorithms is investigated in the geometry preparation stage and Taubin’s low-pass filter was found to best preserve geometry features. Laminar, Newtonian, steady-state simulation analysis identified haemodynamic characteristics to be qualitatively similar in terms of wall shear stress, velocity and vorticity. The study demonstrates the potential for three-dimensional ultrasound to be integrated into a more accessible patient-specific modelling tool able to identify the need for surgical intervention of abdominal aortic aneurysms
Structural characterization of twisted gastrulation provides insights into opposing functions on the BMP signalling pathway.
No full textTwisted gastrulation (Tsg) and chordin are secreted glycoproteins that function together as BMP (bone morphogenetic protein) antagonists to regulate BMP growth factor signalling. Chordin binds to BMPs, preventing them from interacting with their receptors and Tsg is known to strengthen this inhibitory complex. Tsg also acts as a BMP agonist by promoting cleavage of chordin by tolloid-family proteinases. Here we explore the structural mechanism through which Tsg exerts this dual activity. We have characterized the nanoscale structure of human Tsg using in-solution biomolecular analysis and show that Tsg is a globular monomer with a flattened cross shape. Tsg has a high proportion of N-linked glycans, in relation to its molecular weight, which supports a role in solubilising BMPs. Tsg binds with high affinity to the C-terminal region of chordin and was also able to inhibit BMP-7 signalling directly but did not have an effect on BMP-4 signalling. Although both Tsg and mammalian tolloid are involved in chordin cleavage, no interaction could be detected between them using surface plasmon resonance. Together these data suggest that Tsg functions as a BMP-agonist by inducing conformational change in chordin making it more susceptible to tolloid cleavage and as a BMP-antagonist either independently or via a chordin-mediated mechanism. Following single cleavage of chordin by tolloids, Tsg continues to strengthen the inhibitory complex, supporting a role for partially cleaved chordin in BMP regulation
Care-limiting decisions in acute stroke and association with survival: analyses of UK national quality register data
No full textBackground: Prognosis after intracerebral hemorrhage (ICH) is poor and care-limiting decisions may worsen outcomes. Aims: To determine whether in current UK stroke practice, key acute care decisions are associated with stroke subtype (ICH/ischemic) and whether these decisions are independently associated with survival. Methods:We extracted data describing all stroke patients included in a UK quality register between 1 April 2013 and 31 March 2014. Key care decisions in our analyses were transfer to higher level care on admission and palliation in the first 72 h. We used multivariable regression models to test for associations between stroke subtype (ICH/ischemic), key care decisions, and survival. Results: A total of 65,818 patients were included in the final analysis. After ICH (n¼7020/65,818, 10.7%), 10.5% were palliated on the day of admission and 19.3% by 72 h (vs. 0.7% and 3.3% for ischemic stroke). Although a greater proportion were admitted directly to higher level care after ICH (3.7% vs. 1.5% for ischemic stroke), ICH was not independently associated with the decision to admit to higher level care (adjusted odds ratio (OR): 1.12, 95% confidence interval (95%CI): 0.95–1.31, p¼0.183). However, ICH was strongly associated with the decision to commence palliative care on the day of admission (OR: 7.27, 95%CI: 6.31–8.37, p<0.001). Palliative care was independently associated with risk of death by 30 days regardless of stroke subtype. Conclusions: When compared to ischemic stroke, patients with ICH are much more likely to commence palliative care during the first 72 h of their care, independent of level of consciousness, age, and premorbid health
Exploring socio-cultural values of ecosystem service categories in the Central Alps: the influence of socio-demographic factors and landscape type
No full textThe socio-cultural assessment of ecosystem services has been proposed as a promising tool for eliciting people’s preferences towards ecosystem services. Despite an increasing integration of the socio-cultural perspective in ecosystem service research, little knowledge exists about linkages between landscape and the socio-cultural values people assign to ecosystem services. This paper combines a socio-cultural valuation approach with the use of landscape pictures to analyse and compare people’s perceived importance of the provisioning, regulating, and cultural ecosystem service categories across three landscape types (i.e. larch meadows, spruce forests, and hay meadow). A survey with 470 tourists visiting the region of South Tyrol (Italy) was conducted to link people’s perceived importance to their socio-demographic background and to the landscape types explored. The results show that regulating ecosystem services are preferred over provisioning and cultural services, whereby environmental awareness is found to be more influential than formal education levels regarding the perceived importance of regulating services. The results further demonstrate that cultural background is an important driver in determining people’s perceived importance of cultural services. The underlying landscape types, however, exert an even stronger influence on people’s socio-cultural valuation of ecosystem service categories. This finding suggests that the focus of most ecosystem services assessments on the study area as a whole risks mistakenly attributing differences in people’s socio-cultural values to socio-demographic characteristics only. A better knowledge of the spatial integration of socio-cultural values, however, could help with anticipating the consequences of changes in the landscape and provide better guidance for future landscape planning
