8,057 research outputs found
A new approach to planning in vitro and in vivo experiments for cardiovascular stents. (2) Planning of experiments
No full textCopyright @ 2000 Pacini Editore SpAWithin our overall project to improve the design of stents in terms of reduced rates of re-stenosis, there are three main methods, namely computer simulation and in vitro and in vivo experiments. These methods are closely integrated using contemporary design procedures described below, especially to accommodate patient-to-patient variation. Clinical experience shows that a small variation has considerable effects on flow characteristics of stents and in engineering terms may be described as a ‘geometric risk factor’. The Robust Engineering Design procedure readily incorporates this factor which may thus become a component feature in our experimental planning. We envisage that this approach could be applied to other invasive implants with a view to enhancing their quality
Preservation of ancient DNA in thermally damaged archaeological bone
No full textNoEvolutionary biologists are increasingly relying on ancient DNA from archaeological animal bones to study processes such as domestication and population dispersals. As many animal bones found on archaeological sites are likely to have been cooked, the potential for DNA preservation must be carefully considered to maximise the chance of amplification success. Here, we assess the preservation of mitochondrial DNA in a medieval cattle bone assemblage from Coppergate, York, UK. These bones have variable degrees of thermal alterations to bone collagen fibrils, indicative of cooking. Our results show that DNA preservation is not reliant on the presence of intact collagen fibrils. In fact, a greater number of template molecules could be extracted from bones with damaged collagen. We conclude that moderate heating of bone may enhance the retention of DNA fragments. Our results also indicate that ancient DNA preservation is highly variable, even within a relatively recent assemblage from contexts conducive to organic preservation, and that diagenetic parameters based on protein diagenesis are not always useful for predicting ancient DNA survival
Impact Earth! Protecting the UK and further afield from impacts by Near-Earth objects
No full textMark Burchell, Gareth Collins and Massimiliano Vasile report on an RAS Specialist Discussion Meeting dedicated to investigating the effects of potentially hazardous objects colliding with the Eart
Self-compression of 4.9 µm pulses to sub-40 fs with 2 mJ energy in Zinc Sulfide
No full textNonlinear self-compression of few-cycle multi-mJ pulses at 4.9 µm in ZnS is presented. 80 fs input pulses are compressed to 37 fs with 2.1 mJ energy at a 1 kHz repetition rate. © 2024 The Author(s
Bounds for finite primitive complex linear groups
No full textIn 1878, Jordan showed that a finite complex linear group must possess a normal abelian subgroup whose index is bounded by a function of the degree n alone. In this paper, we study primitive groups; when n >12, the optimal bound is (n+1)!, achieved by the symmetric group of degree n+1. We obtain the optimal bounds in smaller degree also. Our proof uses known lower bounds for the degrees of the faithful representations of each quasisimple group, for which the classification of finite simple groups is required. In a subsequent paper [M.J. Collins, On Jordan's theorem for complex linear groups, J. Group Theory 10 (2007) 411–423] we will show that (n+1)! is the optimal bound in general for Jordan's theorem when n≥71
Correction to: Chamoun et al., Bacterial pathogenesis and interleukin-17: interconnecting mechanisms of immune regulation, host genetics, and microbial virulence that influence severity of infection
No full textChamoun MN, Blumenthal A, Sullivan MJ, Schembri MA, Ulett GC. 2018. Bacterial pathogenesis and interleukin-17: interconnecting mechanisms of immune regulation, host genetics, and microbial virulence that influence severity of infection. Critical Reviews in Microbiology. https://doi.org/10.1080/1040841X.2018.1426556.
When the above article was first published online, the below three corrections were missed.
The author ‘Antje Blumenthal’ was wrongly affiliated to the affiliation “cSchool of Chemistry and Molecular Biosciences, and Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Australia”. Now this affiliation has been removed for this author.
The affiliation ‘bTranslational Research Institute, The University of Queensland Diamantina Institute, Woolloongabba, Australia’ of the author ‘Antje Blumenthal’ should read ‘bThe University of Queensland Diamantina Institute, Translational Research Institute, Brisbane, Australia’.
In Table 3, the sentence ‘Benefit of manipulating IL-17 levels to improve immunization strategies M. tuberculosis’ should read “Benefit of manipulating IL-17 levels to improve immunization strategies against M. tuberculosis”.No Full Tex
Generation of 22-mJ, 2.0-ps Pulses from a 1-kHz Ho:YLF Regenerative Chirped Pulse Amplifier
No full textWe report a CW-pumped Ho:YLF regenerative amplifier (RA) delivering pulses with 22.5-mJ energy and 2.0-ps duration at 1 kHz. The RA emitting at 2051 nm is broadband-seeded and implemented in a chirped pulse amplification system. © 2024 The Author(s
Deep learning approaches for segmenting Bruch's membrane opening from OCT volumes
No full textAutomated segmentation of the eye's morphological features in OCT datasets is fundamental to support rapid clinical decision making and to avoid time-consuming manual segmentation of the images. In recent years, deep learning (DL) techniques have become a commonly employed approach to tackle image analysis problems. This study provides a description of the development of automated DL segmentation methods of the Bruch's membrane opening (BMO) from a series of OCT cross-sectional scans. A range of DL techniques are systematically evaluated, with the secondary goal to understand the effect of the network input size on the model performance. The results indicate that a fully semantic approach, in which the whole B-scan is considered with data augmentation, results in the best performance, achieving high levels of similarity metrics with a dice coefficient of 0.995 and BMO boundary localization with a mean absolute error of 1.15 pixels. The work further highlights the importance of fully semantic methods over patch-based techniques in the classification of OCT regions.Full Tex
Elastohydrodynamics of the eyelid wiper
No full textThis paper presents an elastohydrodynamic model of the human eyelid wiper. Standard lubrication theory is applied to the fluid layer between the eyelid wiper and ocular surface. The role of the lubrication film is to reduce the shear stresses by preventing solid to solid contact between the eyelid wiper and ocular surface. For the lubrication film to be effective, it is required that the orientation of the eyelid wiper changes between the opening and closing phases of a blink. In order to model this, the hydrodynamic model is coupled with an elastic mattress model for the soft tissue of the eyelid wiper and ocular surface. This leads to a one-dimensional non-linear partial differential equation governing the fluid pressure in the lubrication film. In order to solve the differential equation, a loading condition or constraint equation must be specified. The resulting system is then solved numerically. The model allows predictions of the tear film flux from under the upper eyelid, as well as normal and shear stresses acting on the ocular surface. These factors are important in relation to dry eye syndrome, deformation of the cornea and contact lens design. It is found that the pressure and shear stress under the eyelid act across a length of approximately 0.1 mm which is consistent with clinical observations. It order to achieve a flow of tears from under the upper eyelid during a blink, the model requires that the normal force the eyelid applies to the ocular surface during the closing phase of the blink is significantly higher than during the opening phase of the blink
Retinal OFF-Pathway Overstimulation Leads to Greater Accommodation-Induced Choroidal Thinning
No full textPURPOSE. To examine the interactions between accommodation and overstimulation of the retinal ON- and OFF-pathways, and their association with changes in choroidal thickness (ChT) and vascularity. METHODS. Optical coherence tomography imaging of the choroid of twenty young adults (ages 25 ± 5 years) was performed before and after a series of 30-minute-long viewing tasks, including reading a bright text on dark background (ON-pathway overstimulation) and dark text on bright background (OFF-pathway overstimulation), and a control task of viewing a movie with unbiased ON-/OFF-pathway activation. The viewing tasks were performed with relaxed, and 5 diopter (D) accommodation (induced by soft contact lenses) demands. Both reading texts were matched for the mean luminance (35 cd/m2), luminance contrast (87%), and letter size (approximately 11.8 arc minutes). The change in ChT from baseline associated with contrast polarity and accommodation was examined using linear mixed model analysis. RESULTS. The subfoveal ChT decreased significantly by -7 ± 1 μm with 5 D accommodation compared with relaxed accommodation (-3 ± 1 μm; P < 0.001), and by -9 ± 1 μm with OFF-pathway compared with ON-pathway overstimulation (-4 ± 1 μm; P = 0.002) and the control condition (-2 ± 1 μm; P < 0.001). Overstimulation of the OFF-pathway, but not the ON-pathway, resulted in a significantly greater choroidal thinning compared with the control condition, both at relaxed (-7 ± 1 μm; P = 0.003) and 5 D (-11 ± 1 μm; P = 0.005) accommodation levels. Similar changes were also observed for macular total, stromal, and luminal ChT. CONCLUSIONS. Retinal OFF-pathway stimulation enhanced the choroidal thinning associated with accommodation, thereby providing a potential mechanism that involves accommodation and the retinal OFF-signaling pathway, linking near work and myopia.Full Tex
- …
