Topographic Evolution and Climate Aridification during Continental Collision: Insights from Computer Simulations

How do the feedbacks between tectonics, sediment transport and climate work to shape the topographic evolution of the Earth? This question has been widely addressed via numerical models constrained with thermochronological and geomorphological data at scales ranging from local to orogenic. Here we present a novel numerical model that aims at reproducing the interaction between these processes at the continental scale. For this purpose, we combine in a single computer program: 1) a thin-sheet viscous model of continental deformation; 2) a stream-power surface-transport approach; 3) flexural isostasy allowing for the formation of large sedimentary foreland basins; and 4) an orographic precipitation model that reproduces basic climatic effects such as continentality and rain shadow. We quantify the feedbacks between these processes in a synthetic scenario inspired by the India-Asia collision and the growth of the Tibetan Plateau. We identify a feedback between erosion and crustal thickening leading locally to a <50% increase in deformation rates in places where orographic precipitation is concentrated. This climatically-enhanced deformation takes place preferentially at the upwind flank of the growing plateau, specially at the corners of the indenter (syntaxes). We hypothesize that this may provide clues for better understanding the mechanisms underlying the intriguing tectonic aneurisms documented in the Himalayas. At the continental scale, however, the overall distribution of topographic basins and ranges seems insensitive to climatic factors, despite these do have important, sometimes counterintuitive effects on the amount of sediments trapped within the continent. The dry climatic conditions that naturally develop in the interior of the continent, for example, trigger large intra-continental sediment trapping at basins similar to the Tarim Basin because they determine its endorheic/exorheic drainage. These complex climatic-drainage-tectonic interactions make the development of steady-state topography at the continental scale unlikely.     

Brownian Dynamics Computer Simulations of Quenched Lennard-Jones-like Fluids: I Morphology and Local Structural Evolution

Abstract

The structural characteristics during phase separation of a model colloidal system were investigated using Brownian dynamics simulation. The structures that formed were analysed using the radial distribution function and structure factor in separate time periods after the quench. The data were interpreted in terms of scale-invariancy and density inhomogeneities. The systems, which consisted of a gas-like phase and dense liquid or solid-like regions, developed with a highly interconnected morphology during the simulations. The aggregate morphology was sensitive to the range of the attractive part of the potential and the position in the phase diagram after the quench. The long-range 12:6 potential induced compact structures with thick filaments, whereas the systems generated using the shorter-ranged 24:12 and 36:18 potentials persisted in a more diffuse network and also evolved more slowly with time. The fractal dimensions were quite high, typically close to 3. The 24:12 and 36:18 potential systems developed regions of local crystalline order which formed contemporaneously with the more global morphological changes. In contrast, at low temperatures the particles of the longer-range 12:6 potential became trapped in glass-like states during the course of the morphological changes in the system. The value of the characteristic lengthscale with time exponent, α, was found to be dependent on the temperature, density and interaction potential and therefore cannot be described as ‘universal’.     

Simulations in Evolution. III. Randomness as a Generator of Opportunities

In Neo‐Darwinism, variation and natural selection are the two evolutionary mechanisms which propel biological evolution. Our previous reports presented a histogram model to simulate the evolution of populations of individuals classified into bins according to an unspecified, quantifiable phenotypic character, and whose number in each bin changed generation after generation under the influence of fitness, while the total population was maintained constant. The histogram model also allowed Shannon entropy (SE) to be monitored continuously as the information content of the total population decreased or increased. Here, a simple Perl (Practical Extraction and Reporting Language) application was developed to carry out these computations, with the critical feature of an added random factor in the percent of individuals whose offspring moved to a vicinal bin. The results of the simulations demonstrate that the random factor mimicking variation increased considerably the range of values covered by Shannon entropy, especially when the percentage of changed offspring was high. This increase in information content is interpreted as facilitated adaptability of the population.     

Evolution of Stronger SARS-CoV-2 Variants as Revealed Through the Lens of Molecular Dynamics Simulations

The Protein Journal - Using molecular dynamics simulations, the protein–protein interactions of the receptor-binding domain of the wild-type and seven variants of the severe acute respiratory...     

The Double Bind: Performing Arts in Hongkong

In Hongkong, local identity is muted not only by the master narrative of ‘history of Europe’, but by that of ‘Chinese history’ and ‘Chinese civilization’. This comprises a ‘double bind’ on those who write and present drama, and the dance. This paper examines the way in which the two master narratives both conflict and assist one another in the elite performing arts. It points a schematic model which tries to take account of the self-conscious efforts of some local intelligentsia to insert a specifically Hongkong dimension between the two master narratives. This cultural refiguration has much to do with the sense of instability and concern for the future which has recently gripped the island.     

Performing arts medicine.

Arts medicine has come of age, resulting from 3 important developments over the past decade: improved methods of diagnosis and treatment, an awareness that artists suffer from special problems related to their occupation and lifestyle, and the establishment of health programs emphasizing an interdisciplinary approach to these patients. We focus on the patterns of illness afflicting performing artists, specifically dancers, singers, actors, and instrumental musicians, and explain some of the things a health care team can do in treating these patients. The conditions governing these patients'' lives--early exposure to high expectations of excellence, incessant demands for perfection, long periods of intense practicing, fierce competition, high levels of anxiety associated with performance, and uncertain careers--need to be understood. Levels of disease and disability are remarkably high, but artists often ignore symptoms. We discuss the musculoskeletal, neurologic, vocal, psychological, and other syndromes found among performers and some of the difficulties in treating them. The prevention of injury, conservative management, collaboration with teachers, and a psychotherapeutic approach are desirable. Arts medicine programs for professional consultation exist in several major cities of the United States and abroad. Although research is needed regarding the effectiveness of health care services for performing artists, the scientific literature devoted to this field is growing.     

Mechanosensitive Channels: Insights from Continuum-Based Simulations

Mechanotransduction plays an important role in regulating cell functions and it is an active topic of research in biophysics. Despite recent advances in experimental and numerical techniques, the intrinsic multiscale nature imposes tremendous challenges for revealing the working mechanisms of mechanosensitive channels. Recently, a continuum-mechanics-based hierarchical modeling and simulation framework has been established and applied to study the mechanical responses and gating behaviors of a prototypical mechanosensitive channel, the mechanosensitive channel of large conductance (MscL) in bacteria Escherichia coli (E. coli), from which several putative gating mechanisms have been tested and new insights are deduced. This article reviews these latest findings using the continuum mechanics framework and suggests possible improvements for future simulation studies. This computationally efficient and versatile continuum-mechanics-based protocol is poised to make contributions to the study of a variety of mechanobiology problems.     

Performing Place: Staging Identity with the Kuranda Amphitheatre

This paper is part of a wider study exploring the politics of place and identity in Kuranda, the small North Queensland town in which my extended family has been settled for the past 25 years. I focus on activities associated with the Kuranda amphitheatre as an attempt by people in Kuranda to define their place and their community in the context of a shire in which they felt ‘out of place’. The amphitheatre is for Kuranda people more than just a venue for the performing arts. It is a place where ideas of ‘community’ get played out and contested, where place is performed, and where experiences of ‘the difference within’ are produced. I argue that, whether they be on the stage or off it, performances are not the mere reflection, nor even a representation, of given structurally and/or cognitively encoded identities. Rather, they are generative phenomena, experientially constitutive of such identities.     

Simulations of a protein translocation pore: SecY

SecY is the central channel protein of the SecYEbeta translocon, the structure of which has been determined by X-ray diffraction. Extended (15 ns) MD simulations of the isolated SecY protein in a phospholipid bilayer have been performed to explore the relationship between protein flexibility and the mechanisms of channel gating. In particular, principal components analysis of the simulation trajectory has been used to probe the intrinsic flexibility of the isolated SecY protein in the absence of the gamma-subunit (SecE) clamp. Analysis and visualization of the principal eigenvectors support a "plug and clamshell" model of SecY channel gating. The simulation results also indicate that hydrophobic gating at the central pore ring prevents leakage of water and ions through the channel in the absence of a translocating peptide.     

Korean Fan Dance for Fun: Performing Alterity in Contemporary Japan

ABSTRACT

This paper focuses on performances of Korean folk culture in Japanese schools and communities to analyse how minority identities are constructed. Korean minority education in Japan has taken up the challenge of reversing the stigma attached to former colonial subjects, employing a range of tangible props what Twine (1999 Twine, France Winddance. 1999. Bearing Blackness in Britain: The Meaning of Raical Difference for White Birth Mothers of African-Descent Children. Social Identities, 5(2):185–210. doi: 10.1080/13504639951554[Taylor & Francis Online] , [Google Scholar]) calls ‘racial literacy’ which prepares racial minority children to cope with and challenge racism at large. While embodying identity expression through Korean folk dance performances is an effective strategy, it faces constraints from larger social forces. Korean dance and music performances do little to challenge the dominance of mainstream values. These performances are embedded in everyday family, school, and community practices and paradoxically reproduce existing gender roles, broader pedagogical ideologies, and social structures. This ethnographic case study disentangles contradictions in minority education and shows commitment to alterity accompanies disavowal of alterity in relation to the hegemonic Japanese culture and society.