Some Observations on Permafrost Distribution at a Lake in the Mackenzie Delta, N.W.T., Canada

Reports investigations of the thawing effect of water on permafrost in northern Mackenzie District during Apr 1961. Holes were drilled under the center of a small, shallow lake with a mean bottom temperature higher than 32 degrees F and at various distances to the west of the lake. Hand probings were made near the edge of the lake, soil and water samples taken, ground temperatures measured, altitude and various terrain surveys made. It was found that the sediments below the center of the lake were unfrozen to bedrock; but the position of the permafrost table rose progressively toward shore and the thawing effect was confined to the ground lying under the lake. The thermal effect of the lake however, extended for some distance beyond

Absolute electrical impedance tomography (aEIT) guided ventilation therapy in critical care patients: simulations and future trends

Thoracic electrical impedance tomography (EIT) is a noninvasive, radiation-free monitoring technique whose aim is to reconstruct a cross-sectional image of the internal spatial distribution of conductivity from electrical measurements made by injecting small alternating currents via an electrode array placed on the surface of the thorax. The purpose of this paper is to discuss the fundamentals of EIT and demonstrate the principles of mechanical ventilation, lung recruitment, and EIT imaging on a comprehensive physiological model, which combines a model of respiratory mechanics, a model of the human lung absolute resistivity as a function of air content, and a 2-D finite-element mesh of the thorax to simulate EIT image reconstruction during mechanical ventilation. The overall model gives a good understanding of respiratory physiology and EIT monitoring techniques in mechanically ventilated patients. The model proposed here was able to reproduce consistent images of ventilation distribution in simulated acutely injured and collapsed lung conditions. A new advisory system architecture integrating a previously developed data-driven physiological model for continuous and noninvasive predictions of blood gas parameters with the regional lung function data/information generated from absolute EIT (aEIT) is proposed for monitoring and ventilator therapy management of critical care patients

Written accounts of living With epilepsy or psychogenic nonepileptic seizures: A thematic comparison

This study examines the subjective experience of living with epilepsy or psychogenic nonepileptic seizures (PNES) by thematically comparing individuals' written accounts of their condition. Five key differences emerged. Theme 1: "Seizure onset" revealed differences in how individuals think about and ruminate over the possible causes of their condition. Theme 2: "Emotive tone" demonstrated that writings of those with epilepsy reflected stable emotions (no intense emotional reactions), whereas those of writers with PNES reflected anxiety and low mood. Theme 3: "Seizure symptoms" showed differences in the conceptualization of seizures. Theme 4: "Treatment" explored differences in the diagnostic journey and experiences of health care professionals. Theme 5: "Daily life" revealed that those with epilepsy perceived sequelae and seizures as something that must be fought, whereas those with PNES tended to describe their seizures as a place they enter and something that has destroyed their lives. The findings have implications for treatment and management

Phylogenetic placement and the timing of diversification in Australia's endemic Vachellia (Caesalpinioideae, Mimosoid Clade, Fabaceae) species

The genus Vachellia Wight & Arn. has a pantropical distribution, with species being distributed through Africa, the Americas, Asia and Australia. The relationships among the lineages from Africa and America are well understood, but the phylogenetic placement and evolutionary origins of the Australian species of Vachellia are not known. We, therefore, sequenced four plastid genes from representatives of each of the nine Australian species of Vachellia, and used Bayesian inference to assess the phylogenetic placement of these lineages, and a relaxed molecular clock to assess the timing of diversification. The Australian species of Vachellia form a well-supported monophyletic clade, with molecular-dating analysis suggesting a single dispersal into Australia 6.5 million years ago (95% range 13.9-2.7 million years ago). Diversification of the Australian clade commenced more recently, c. 3.1 million years ago (95% range 9.2-1.2 million years ago), perhaps driven by the increased aridification of Australia at this time. The closest relatives to the Australian Vachellia were not from the Malesian bioregion, suggesting either a long-distance dispersal from Africa, or two separate migrations through Asia. These results not only improve our understanding of the biogeography of Vachellia species, but also have significant implications for the biological control of invasive Vachellia species in Australia. © 2020 CSIRO

Influence of confinement on the orientational phase transitions in the lamellar phase of a block copolymer melt under shear flow

In this work we incorporate some real-system effects into the theory of orientational phase transitions under shear flow (M. E. Cates and S. T. Milner, Phys. Rev. Lett. v.62, p.1856 (1989) and G. H. Fredrickson, J. Rheol. v.38, p.1045 (1994)). In particular, we study the influence of the shear-cell boundaries on the orientation of the lamellar phase. We predict that at low shear rates the parallel orientation appears to be stable. We show that there is a critical value of the shear rate at which the parallel orientation loses its stability and the perpendicular one appears immediately below the spinodal. We associate this transition with a crossover from the fluctuation to the mean-field behaviour. At lower temperatures the stability of the parallel orientation is restored. We find that the region of stability of the perpendicular orientation rapidly decreases as shear rate increases. This behaviour might be misinterpreted as an additional perpendicular to parallel transition recently discussed in literature.Comment: 25 pages, 4 figures, submitted to Phys. Rev.

Inhuman shields - children caught in the crossfire of domestic violence

Background. Child abuse is a worldwide scourge. One of its most devastating manifestations is non-accidental head injury (NAHI).Methods. This is a retrospective chart review of children presenting to the Red Cross Children's Hospital trauma unit with a diagnosis of NAHI over a 3-year period.Results. Sixty-eight children were included in the study and 2 different groups were identified. Fifty-three per cent of the children were deliberately injured (median age 2 years), while 47% were allegedly not the intended target of the assailant (median age 9 months). The assailant was male in 65% of the intentional assaults and male in 100% of the unintentional assaults, with the intended adult victim female in 85% of the latter cases. Overall, 85% of the assaults were committed in the child's own home.Conclusions. The high proportion of cases in which a young child was injured unintentionally suggests that these infants effectively become shields in assaults committed by adults. In this context any attempts to deal with child abuse must also address the concurrent intimate partner violence

Development of methods for optimisation of complex 3D weave geometries

The development of 3D weaves has resulted in the ability to produce near net shaped preforms, with the additional advantage over unidirectional lay-ups and 2D weaves of greater delamination resistance provided by through-thickness reinforcement. 3D weaving can allow the post-weave formation of bifurcations to form the web and flange of structural components. The mechanical properties of 3D woven components are highly dependent on the weave architecture, allowing the mechanical performance of the component to be tailored to its specific application. Given the number of design parameters to be varied, the design space is potentially infinite. This work focuses on the development of methods to find the optimum weave geometry of a unit cell based on the numerical evaluation of objective functions.This work demonstrates the development of methods to optimise 3D woven textile geometry, using the University of Nottingham’s open-source software TexGen [1] to automatically generate each weave based on the input from a global optimisation algorithm. Methods of varying a number of the parameters will be reported alongside their geometric and physical constraints. Finally, the facility to automatically generate a wide range of weaves, with the ability to vary parameters as desired for input either directly into an optimisation algorithm or for further pre-processing is demonstrated

Structured computer-based training in the interpretation of neuroradiological images

Computer-based systems may be able to address a recognised need throughout the medical profession for a more structured approach to training. We describe a combined training system for neuroradiology, the MR Tutor that differs from previous approaches to computer-assisted training in radiology in that it provides case-based tuition whereby the system and user communicate in terms of a well-founded Image Description Language. The system implements a novel method of visualisation and interaction with a library of fully described cases utilising statistical models of similarity, typicality and disease categorisation of cases. We describe the rationale, knowledge representation and design of the system, and provide a formative evaluation of its usability and effectiveness

Development of methods for optimisation of complex 3D weave geometries

The development of 3D weaves has resulted in the ability to produce near net shaped preforms, with the additional advantage over unidirectional lay-ups and 2D weaves of greater delamination resistance provided by through-thickness reinforcement. 3D weaving can allow the post-weave formation of bifurcations to form the web and flange of structural components. The mechanical properties of 3D woven components are highly dependent on the weave architecture, allowing the mechanical performance of the component to be tailored to its specific application. Given the number of design parameters to be varied, the design space is potentially infinite. This work focuses on the development of methods to find the optimum weave geometry of a unit cell based on the numerical evaluation of objective functions. This work demonstrates the development of methods to optimise 3D woven textile geometry, using the University of Nottingham’s open-source software TexGen [1] to automatically generate each weave based on the input from a global optimisation algorithm. Methods of varying a number of the parameters will be reported alongside their geometric and physical constraints. Finally, the facility to automatically generate a wide range of weaves, with the ability to vary parameters as desired for input either directly into an optimisation algorithm or for further pre-processing is demonstrated

Growth, microstructure, and failure of crazes in glassy polymers

We report on an extensive study of craze formation in glassy polymers. Molecular dynamics simulations of a coarse-grained bead-spring model were employed to investigate the molecular level processes during craze nucleation, widening, and breakdown for a wide range of temperature, polymer chain length $N$, entanglement length $N_e$ and strength of adhesive interactions between polymer chains. Craze widening proceeds via a fibril-drawing process at constant drawing stress. The extension ratio is determined by the entanglement length, and the characteristic length of stretched chain segments in the polymer craze is $N_e/3$. In the craze, tension is mostly carried by the covalent backbone bonds, and the force distribution develops an exponential tail at large tensile forces. The failure mode of crazes changes from disentanglement to scission for $N/N_e\sim 10$, and breakdown through scission is governed by large stress fluctuations. The simulations also reveal inconsistencies with previous theoretical models of craze widening that were based on continuum level hydrodynamics