Dynamics of the osmotic lysis of mineral protocells and its avoidance at the origins of life.

The osmotic rupture of a cell, its osmotic lysis or cytolysis, is a phenomenon that active biological cell volume regulation mechanisms have evolved in the cell membrane to avoid. How then, at the origin of life, did the first protocells survive prior to such active processes? The pores of alkaline hydrothermal vents in the oceans form natural nanoreactors in which osmosis across a mineral membrane plays a fundamental role. Here, we discuss the dynamics of lysis and its avoidance in an abiotic system without any active mechanisms, reliant upon self-organized behaviour, similar to the first self-organized mineral membranes within which complex chemistry may have begun to evolve into metabolism. We show that such mineral nanoreactors could function as protocells without exploding because their self-organized dynamics have a large regime in parameter space where osmotic lysis does not occur and homeostasis is possible. The beginnings of Darwinian evolution in proto-biochemistry must have involved the survival of protocells that remained within such a safe regime.

Downward fingering accompanies upward tube growth in a chemical garden grown in a vertical confined geometry.

Chemical gardens are self-assembled structures of mineral precipitates enabled by semi-permeable membranes. To explore the effects of gravity on the formation of chemical gardens, we have studied chemical gardens grown from cobalt chloride pellets and aqueous sodium silicate solution in a vertical Hele-Shaw cell. Through photography, we have observed and quantitatively analysed upward growing tubes and downward growing fingers. The latter were not seen in previous experimental studies involving similar physicochemical systems in 3-dimensional or horizontal confined geometry. To better understand the results, further studies of flow patterns, buoyancy forces, and growth dynamics under schlieren optics have been carried out, together with characterisation of the precipitates with scanning electron microscopy and X-ray diffractometry. In addition to an ascending flow and the resulting precipitation of tubular filaments, a previously not reported descending flow has been observed which, under some conditions, is accompanied by precipitation of solid fingering structures. We conclude that the physics of both the ascending and descending flows are shaped by buoyancy, together with osmosis and chemical reaction. The existence of the descending flow might highlight a limitation in current experimental methods for growing chemical gardens under gravity, where seeds are typically not suspended in the middle of the solution and are confined by the bottom of the vessel.

Filament dynamics in vertical confined chemical gardens.

When confined to a Hele-Shaw cell, chemical gardens can grow as filaments, narrow structures with an erratic and tortuous trajectory. In this work, the methodology applied to studies with horizontal Hele-Shaw cells is adapted to a vertical configuration, thus introducing the effect of buoyancy into the system. The motion of a single filament tip is modeled by taking into account its internal pressure and the variation of the concentration of precipitate that constitutes the chemical garden membrane. While the model shows good agreement with the results, it also suggests that the concentration of the host solution of sodium silicate also plays a role in the growth of the structures despite being in stoichiometric excess.

Archimedean Spirals Form at Low Flow Rates in Confined Chemical Gardens.

We describe and study the formation of confined chemical garden patterns. At low flow rates of injection of cobalt chloride solution into a Hele-Shaw cell filled with sodium silicate, the precipitate forms with a thin filament wrapping around an expanding "candy floss" structure. The result is the formation of an Archimedean spiral structure. We model the growth of the structure mathematically. We estimate the effective density of the precipitate and calculate the membrane permeability. We set the results within the context of recent experimental and modeling work on confined chemical garden filaments.

Filament dynamics in planar chemical gardens.

Filaments in a planar chemical garden grow following tortuous, erratic paths. We show from statistical mechanics that this scaling results from a self-organized dispersion mechanism. Effective diffusivities as high as 10-5 m2 s-1 are measured in 2D laboratory experiments. This efficient transport is four orders of magnitude larger than molecular diffusion in a liquid, and ensures widespread contact and exchange between fluids in the chemical-garden structure and its surrounding environment.

Self-perception of older adults regarding rehabilitation with dentures / Autopercepção de idosos sobre a reabilitação com próteses dentárias

ABSTRACT Objective: To analyze the self-perception that older adults have about rehabilitation regarding their uni or bimaxillary dentures. Methods: A form was applied to investigate the sociodemographic, economic and medical-dental variables of the users, a questionnaire to assess the satisfaction level of patients with their dentures, another to investigate the technical quality of the dentures from the aesthetic-functional point of view, and the Oral Health Impact Profile (OHIP-14) to ascertain the impact of prosthetic rehabilitation on the quality of life of users. Results: The majority of the participants (65.2%) used complete bimaxillary dentures, reported dissatisfaction during chewing, while the lower dentures had unsatisfactory technical quality for the retention requirements (69.6%) and stability (69.6%). The older adults' complaints were predominantly related to the "physical pain" and "physical disability" domains. There were significant associations between general satisfaction with the dentures in use, their general technical quality and the OHIP-14 domains. Conclusion: The patient complaints were related to difficulties in their ability to chew, speak and with the retention and comfort of the lower dentures. The technical quality of the dentures had compromised retention and stability from the aesthetic-functional point of view. Dentures considered unsatisfactory caused negative impacts on the quality of life of users, especially in comfort during meals which was related to difficulty chewing and swallowing. The association between the instruments used in the study provides important tools for the performance of dental surgeons, in addition to enabling more adequate planning in the oral health services offered to the population.

RESUMO Objetivo: Analisar a autopercepção que os idosos têm sobre a reabilitação com suas próteses dentárias totais uni ou bimaxilares. Métodos: Aplicou-se um formulário para investigar as variáveis sociodemográficas, econômicas e médico-odontológicas dos usuários, um questionário para avaliar o nível de satisfação dos pacientes com seus aparelhos protéticos, outro para investigar a qualidade técnica das próteses, do ponto de vista estético-funcional, e o Oral Health Impact Profile (OHIP-14), para averiguar o impacto da reabilitação protética na qualidade de vida dos usuários. Resultados: A maioria dos participantes (65,2%) utilizava prótese total dupla, relatava insatisfação durante a mastigação, os aparelhos protéticos inferiores apresentavam qualidade técnica insatisfatória para os requisitos de retenção (69,6%) e estabilidade (69,6%). As queixas dos idosos estavam relacionadas, predominantemente, aos domínios "dor física" e "incapacidade física". Houve associações significativas entre a satisfação geral com a prótese em uso, a qualidade técnica geral das mesmas e os domínios do OHIP-14. Conclusão: As queixas dos pacientes estavam relacionadas com dificuldades na capacidade de mastigar, falar e com a retenção e o conforto das próteses totais inferiores. A qualidade técnica dessas próteses, do ponto de vista estético-funcional, apresentava retenção e estabilidade comprometidas. Os aparelhos protéticos considerados insatisfatórios causaram impactos negativos na qualidade de vida dos usuários, sobretudo, no conforto durante as refeições, o qual estava relacionado à dificuldade na mastigação e deglutição. A associação entre os instrumentos utilizados no estudo fornece ferramentas importantes para a atuação do cirurgião-dentista, além de possibilitar um planejamento mais adequado nos serviços de saúde bucal oferecidos à população.

Radial spreading of turbulent bubble plumes.

Weak bubble plumes carry liquid from the environment upwards and release it at multiple intermediate levels in the form of radial intrusive currents. In this study, laboratory experiments are performed to explore the spreading of turbulent axisymmetric bubble plumes in a liquid with linear density stratification. The thickness, volumetric flowrate and spreading rates of multiple radial intrusions of plume fluid were measured by tracking the movement of dye injected at the source of bubbles. The experimental results are compared with scaling predictions. Our findings suggest that the presence of multiple intrusions reduces their spreading rate, compared to that of a single intrusion. This work is of relevance to the spreading of methane plumes issuing from the seabed in the Arctic Ocean, above methane-hydrate deposits. The slower, multiple spreading favours the presence of methane-rich seawater close to the plume, which may reduce the dissolution of methane in the bubbles, and thus promote the direct transport of methane to the atmosphere. This article is part of the theme issue 'Stokes at 200 (part 2)'.

Stokes at 200 (part 2).

We present the second half of the papers from the Stokes200 symposium celebrating the bicentenary of George Gabriel Stokes. This article is part of the theme issue 'Stokes at 200 (part 2)'.

Chemobrionics: From Self-Assembled Material Architectures to the Origin of Life.

Self-organizing precipitation processes, such as chemical gardens forming biomimetic micro- and nanotubular forms, have the potential to show us new fundamental science to explore, quantify, and understand nonequilibrium physicochemical systems, and shed light on the conditions for life's emergence. The physics and chemistry of these phenomena, due to the assembly of material architectures under a flux of ions, and their exploitation in applications, have recently been termed chemobrionics. Advances in understanding in this area require a combination of expertise in physics, chemistry, mathematical modeling, biology, and nanoengineering, as well as in complex systems and nonlinear and materials sciences, giving rise to this new synergistic discipline of chemobrionics.

The bee Tetragonula builds its comb like a crystal.

Stingless bees of the genus Tetragonula construct a brood comb with a spiral or a target pattern architecture in three dimensions. Crystals possess these same patterns on the molecular scale. Here, we show that the same excitable-medium dynamics governs both crystal nucleation and growth and comb construction in Tetragonula, so that a minimal coupled-map lattice model based on crystal growth explains how these bees produce the structures seen in their bee combs.

Stokes at 200: a celebration of the remarkable achievements of Sir George Gabriel Stokes two hundred years after his birth.

Sir George Gabriel Stokes PRS was for 30 years an inimitable Secretary of the Royal Society and its President from 1885 to 1890. Two hundred years after his birth, Stokes is a towering figure in physics and applied mathematics; fluids, asymptotics, optics, acoustics among many other fields. At the Stokes200 meeting, held at Pembroke College, Cambridge from 15-18th September 2019, an invited audience of about 100 discussed the state of the art in all the modern research fields that have sprung from his work in physics and mathematics, along with the history of how we have got from Stokes' contributions to where we are now. This theme issue is based on work presented at the Stokes200 meeting. In bringing together people whose work today is based upon Stokes' own, we aim to emphasize his influence and legacy at 200 to the community as a whole. This article is part of the theme issue 'Stokes at 200 (Part 1)'.

Stokes, Tyndall, Ruskin and the nineteenth-century beginnings of climate science.

Although we humans have known since the first smokey campfires of prehistory that our activities might alter our local surroundings, the nineteenth century saw the first indications that humankind might alter the global environment; what we currently know as anthropogenic climate change. We are now celebrating the bicentenaries of three figures with a hand in the birth of climate science. George Stokes, John Tyndall and John Ruskin were born in August 1819, August 1820 and February 1819, respectively. We look back from the perspective of two centuries following their births. We outline their contributions to climate science: understanding the equations of fluid motion and the recognition of the need to collect global weather data together with comprehending the role in regulating terrestrial temperature played by gases in the atmosphere. This knowledge was accompanied by fears of the Earth's regression to another ice age, together with others that industrialization was ruining humankind's health, morals and creativity. The former fears of global cooling were justified but seem strange now that the balance has tipped so far the other way towards global warming; the latter, on the other hand, today seem very prescient. This article is part of the theme issue 'Stokes at 200 (Part 1)'.

Perfil e evolução da mortalidade por causas externas em Joinville (SC), 2003 a 2016 / Profile and trend in mortality due to external causes in Joinville (SC) from 2003 to 2016

Resumo Introdução A mortalidade por causas externas está entre as principais causas de óbito no mundo, com acentuada expressão em faixas etárias jovens. Objetivo Descrever o perfil das mortes por causas externas em município do Sul do país e verificar sua tendência nos últimos anos. Método Estudo retrospectivo dos óbitos por causas externas usando os coeficientes de mortalidade por sexo, grupo etário e causa da morte com análise por regressão quasi Poisson. Resultados O coeficiente de mortalidade foi de 46,3 por 100 mil habitantes, predominando os acidentes por transporte terrestre (40%) e agressões (30,5%). Identificou-se aumento de 53% nos coeficientes de mortalidade, com variações segundo sexo, grupo etário e tipo. Conclusão Necessitam-se intensificar políticas públicas conforme as especificidades na determinação dos tipos de morte em cada grupo etário.

Abstract Background Mortality due to external causes is among of the leading causes of death worldwide, with great expression in young age groups. Objective: To describe the profile of deaths from external causes in a southern municipality of Brazil and verify its trend in the last years. Method It was carried out a retrospective study of external causes deaths using mortality rates by gender, age group and cause of with quasi Poisson regression analysis. Results Mortality coefficient was 46 per 100,000 inhabitants prevailing transport accidents (40%) and aggressions (30.5%). Increase of 53% in mortality rate was detected with variations by gender, age group and type. Conclusion Social policies are necessary encompassing intersectoral actions and taking into account the specificities in determination of each age group's types of death.

Intrinsic concentration cycles and high ion fluxes in self-assembled precipitate membranes.

Concentration cycles are important for bonding of basic molecular building components at the emergence of life. We demonstrate that oscillations occur intrinsically in precipitation reactions when coupled with fluid mechanics in self-assembled precipitate membranes, such as at submarine hydrothermal vents. We show that, moreover, the flow of ions across one pore in such a prebiotic membrane is larger than that across one ion channel in a modern biological cell membrane, suggesting that proto-biological processes could be sustained by osmotic flow in a less efficient prebiotic environment. Oscillations in nanoreactors at hydrothermal vents may be just right for these warm little pores to be the cradle of life.

Self-Assembling Ice Membranes on Europa: Brinicle Properties, Field Examples, and Possible Energetic Systems in Icy Ocean Worlds.

Brinicles are self-assembling tubular ice membrane structures, centimeters to meters in length, found beneath sea ice in the polar regions of Earth. We discuss how the properties of brinicles make them of possible importance for chemistry in cold environments-including that of life's emergence-and we consider their formation in icy ocean worlds. We argue that the non-ice composition of the ice on Europa and Enceladus will vary spatially due to thermodynamic and mechanical properties that serve to separate and fractionate brines and solid materials. The specifics of the composition and dynamics of both the ice and the ocean in these worlds remain poorly constrained. We demonstrate through calculations using FREZCHEM that sulfate likely fractionates out of accreting ice in Europa and Enceladus, and thus that an exogenous origin of sulfate observed on Europa's surface need not preclude additional endogenous sulfate in Europa's ocean. We suggest that, like hydrothermal vents on Earth, brinicles in icy ocean worlds constitute ideal places where ecosystems of organisms might be found.

Exploding Chemical Gardens: A Phase-Change Clock Reaction.

Chemical gardens and clock reactions are two of the best-known demonstration reactions in chemistry. Until now these have been separate categories. We have discovered that a chemical garden confined to two dimensions is a clock reaction involving a phase change, so that after a reproducible and controllable induction period it explodes.

Filiform corrosion as a pressure-driven delamination process.

Filiform corrosion produces long and narrow trails on various coated metals through the detachment of the coating layer from the substrate. In this work, we present a combined experimental and theoretical analysis of this process with the aim to describe quantitatively the shape of the cross-section, perpendicular to the direction of propagation, of the filaments produced. For this purpose, we introduce a delamination model of filiform corrosion dynamics and show its compatibility with experimental data where the coating thickness has been varied systematically.

Differences in the diagnosis of primary cutaneous melanoma in the public and private healthcare systems in Joinville, Santa Catarina State, Brazil.

BACKGROUND: Cutaneous melanoma accounts for up to 80% of deaths caused by skin cancer. Diagnostic suspicion and access to medical care and early intervention in suspected cases is vital to the patient's prognosis. OBJECTIVES: To compare demographic and histopathological characteristics of primary cutaneous melanoma diagnosed in the public healthcare system (Sistema Único de Saúde SUS) and the private system in Joinville, Santa Catarina State, Brazil. METHODS: This cross-sectional retrospective study analyzed primary cutaneous melanoma cases recorded from 2003 to 2014 in the resident population of Joinville. Ethical approval was obtained from the local Research Ethics Committee. RESULTS: 893 cases of primary cutaneous melanoma were identified. Patients in the private system were mostly younger, while there were more elderly patients in the public healthcare system (p <0.001). There was no statistically significant association between type of care (public/private) and gender or presence of multiple primary cutaneous melanomas. Histological diagnosis of superficial spreading melanoma was more common in patients treated in private healthcare, while nodular melanoma was more frequent in patients in the public healthcare system (p <0.001). Mean Breslow depth in patients treated in private healthcare was 1.35mm, compared to 2.72mm in the public system (p <0.001). STUDY LIMITATIONS: This was a retrospective study using secondary databases. CONCLUSIONS: thin cutaneous melanoma (in situ cutaneous melanoma and Breslow T1) showed the strongest association with the private healthcare system, while thick cutaneous melanoma was more frequent in the public system (Breslow category T3 and T4) (p <0.001).

Reactive convective-dissolution in a porous medium: stability and nonlinear dynamics.

We investigate the effects of a dissolution reaction, A(aq) + B(s) → C(aq), on the gravitational instability and nonlinear dynamic behaviour of a diffusive boundary layer in a porous medium. Our linear stability and numerical results reveal that, unexpectedly, even when the density contribution of the soluble product C is smaller than that of the dissolved solute A, the chemical reaction can destabilize the layer and accelerate the onset of convection. However, for a very light product, the reaction stabilizes the layer. We show that these widely disparate characteristics of the reactive-diffusive layer are outcomes of the nonlinear competition between two reaction effects, the destabilizing sharpening of the solute concentration gradient and associated increase in the solute diffusive flux, and the stabilizing replacement of the solute by a less dense product near the interface.

Differences in the diagnosis of primary cutaneous melanoma in the public and private healthcare systems in Joinville, Santa Catarina State, Brazil

Abstract: Background: Cutaneous melanoma accounts for up to 80% of deaths caused by skin cancer. Diagnostic suspicion and access to medical care and early intervention in suspected cases is vital to the patient's prognosis. Objectives: To compare demographic and histopathological characteristics of primary cutaneous melanoma diagnosed in the public healthcare system (Sistema Único de Saúde SUS) and the private system in Joinville, Santa Catarina State, Brazil. Methods: This cross-sectional retrospective study analyzed primary cutaneous melanoma cases recorded from 2003 to 2014 in the resident population of Joinville. Ethical approval was obtained from the local Research Ethics Committee. Results: 893 cases of primary cutaneous melanoma were identified. Patients in the private system were mostly younger, while there were more elderly patients in the public healthcare system (p <0.001). There was no statistically significant association between type of care (public/private) and gender or presence of multiple primary cutaneous melanomas. Histological diagnosis of superficial spreading melanoma was more common in patients treated in private healthcare, while nodular melanoma was more frequent in patients in the public healthcare system (p <0.001). Mean Breslow depth in patients treated in private healthcare was 1.35mm, compared to 2.72mm in the public system (p <0.001). Study limitations: This was a retrospective study using secondary databases. Conclusions: thin cutaneous melanoma (in situ cutaneous melanoma and Breslow T1) showed the strongest association with the private healthcare system, while thick cutaneous melanoma was more frequent in the public system (Breslow category T3 and T4) (p <0.001).