Dissolution dominating calcification process in polar pteropods close to the point of aragonite undersaturation

Thecosome pteropods are abundant upper-ocean zooplankton that build aragonite shells. Ocean acidification results in the lowering of aragonite saturation levels in the surface layers, and several incubation studies have shown that rates of calcification in these organisms decrease as a result. This study provides a weight-specific net calcification rate function for thecosome pteropods that includes both rates of dissolution and calcification over a range of plausible future aragonite saturation states (Omega_Ar). We measured gross dissolution in the pteropod Limacina helicina antarctica in the Scotia Sea (Southern Ocean) by incubating living specimens across a range of aragonite saturation states for a maximum of 14 days. Specimens started dissolving almost immediately upon exposure to undersaturated conditions (Omega_Ar,0.8), losing 1.4% of shell mass per day. The observed rate of gross dissolution was different from that predicted by rate law kinetics of aragonite dissolution, in being higher at Var levels slightly above 1 and lower at Omega_Ar levels of between 1 and 0.8. This indicates that shell mass is affected by even transitional levels of saturation, but there is, nevertheless, some partial means of protection for shells when in undersaturated conditions. A function for gross dissolution against Var derived from the present observations was compared to a function for gross calcification derived by a different study, and showed that dissolution became the dominating process even at Omega_Ar levels close to 1, with net shell growth ceasing at an Omega_Ar of 1.03. Gross dissolution increasingly dominated net change in shell mass as saturation levels decreased below 1. As well as influencing their viability, such dissolution of pteropod shells in the surface layers will result in slower sinking velocities and decreased carbon and carbonate fluxes to the deep ocean

Laminar degeneration of frontal and temporal cortex in Parkinson disease dementia

To investigate cortical laminar degeneration in Parkinson’s disease (PD) with dementia (PDD). Changes in density of α-synuclein-immunoreactive Lewy bodies (LB), Lewy neurites (LN), and Lewy grains (LG) together with surviving neurons, abnormally enlarged neurons (EN), vacuoles, and glial cell nuclei were measured across cortical laminae of frontal and temporal cortex in fifteen cases of PDD using quantitative methods and polynomial curve-fitting. Most frequently, LB and LN were distributed across all laminae, while LG were distributed in upper cortical laminae. Low densities of EN were present in most cases distributed across all cortical laminae. Densities of vacuoles and glia were greatest in upper and lower cortical laminae, respectively. In most gyri, there were no spatial correlations between the densities of LB, LN, and LG. Cortical degeneration of frontal and temporal lobes in PDD affects all cortical laminae. Laminar distributions may result from the spread of α-synuclein pathology from subcortical regions and subsequent spread via the cortico-cortical pathways. This spread may be a major factor in the development of dementia in PD

Clustering of tau-immunoreactive pathology in chronic traumatic encephalopathy

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disorder which may result from repetitive brain injury. A variety of tau-immunoreactive pathologies are present, including neurofibrillary tangles (NFT), neuropil threads (NT), dot-like grains (DLG), astrocytic tangles (AT), and occasional neuritic plaques (NP). In tauopathies, cellular inclusions in the cortex are clustered within specific laminae, the clusters being regularly distributed parallel to the pia mater. To determine whether a similar spatial pattern is present in CTE, clustering of the tau-immunoreactive pathology was studied in the cortex, hippocampus, and dentate gyrus in 11 cases of CTE and 7 cases of Alzheimer’s disease neuropathologic change (ADNC) without CTE. In CTE: (1) all aspects of tau-immunoreactive pathology were clustered and the clusters were frequently regularly distributed parallel to the tissue boundary, (2) clustering was similar in two CTE cases with minimal co-pathology compared with cases with associated ADNC or TDP-43 proteinopathy, (3) in a proportion of cortical gyri, estimated cluster size was similar to that of cell columns of the cortico-cortical pathways, and (4) clusters of the tau-immunoreactive pathology were infrequently spatially correlated with blood vessels. The NFT and NP in ADNC without CTE were less frequently randomly or uniformly distributed and more frequently in defined clusters than in CTE. Hence, the spatial pattern of the tau-immunoreactive pathology observed in CTE is typical of the tauopathies but with some distinct differences compared to ADNC alone. The spread of pathogenic tau along anatomical pathways could be a factor in the pathogenesis of the disease

Water incident related hospital activity across England between 1997/8 and 2003/4: a retrospective descriptive study

Every year in the United Kingdom, 10,000 people will die from accidental injury and the treatment of these injuries will cost the NHS £2 billion and the consequences of injuries received at home cost society a further £25 billion [1]. Non-fatal injuries result in 720,000 people being admitted to hospital a year and more than six million visits to accident and emergency departments each year [2]. Drowning is the second leading cause of unintentional injury mortality globally behind road traffic injuries. It is estimated that a total of 409, 272 people drown each year [3]. This equates to a global incident rate of 7.4 deaths per 100, 000 people worldwide and relates to a further 1.3 million Disability Adjusted Life Years (DALYs) which are lost as a result of premature death or disability [4]. 'Death' represents only the tip of the injury "iceberg" [5]. For every life lost from an injury, many more people are admitted to hospital, attend accident and emergency departments or general practitioners, are rescued by search and rescue organisations or resolve the situation themselves. It is estimated that 1.3 million people are injured as a result of near drowning episodes globally and that many more hundreds of thousands of people are affected through incidents and near misses but there are no accurate data [4]. The United Kingdom has reported a variable drowning fatality rate, the injury chart book reports a rate of 1.0 – 1.5 per 100,000 [6] and other studies suggest a rate as low as 0.5 per 100, 000 population [7] for accidental drowning and submersion, based on the International Classification of Disease 10 code W65 – 74, however, the problem is even greater and these Global Burden of Disease (GDB) figures are an underestimate of all drowning deaths, since they exclude drownings due to cataclysms (floods), water related transport accidents, assaults and suicide [3]. A recent study in Scotland highlighted this underestimation in drowning fatality data and found that the overall death rate due to drownings in Scotland 3.26 per 100,000 [8]. Even though drowning fatality rates in the United Kingdom vary, little is known about the people who are admitted to hospital after an incident either in or on water. This paper seeks to address this gap in our knowledge through the investigation of the data available on those admitted to NHS hospitals in England

Framework For Improving Complex System Performance

This paper introduces a framework for improvement of complex system performance. Complex systems are besieged with conditions marked by increasing uncertainty, emergence, and ambiguity. Additionally, demands for increased productivity, resource efficiencies, and performance improvement make new approaches paramount for modern systems engineers. In response, a framework to improve complex system performance is developed. Following an introduction, the paper pursues four objectives: (1) introduction of Complex System Governance (CSG) as a foundation to describe essential system functions, (2) suggest system `pathologies\u27 as an explanation for deep system performance issues, (3) exploration of system performance improvement as a function of `requisite variety\u27 to compensate for deep system issues, and (4) introduce a framework for complex system performance improvement using system pathologies as `unab-sorbed variety\u27. The paper closes with some challenges for further development of the framework for deployment and application guidance for practitioners

Prioritized Sweeping Neural DynaQ with Multiple Predecessors, and Hippocampal Replays

During sleep and awake rest, the hippocampus replays sequences of place cells that have been activated during prior experiences. These have been interpreted as a memory consolidation process, but recent results suggest a possible interpretation in terms of reinforcement learning. The Dyna reinforcement learning algorithms use off-line replays to improve learning. Under limited replay budget, a prioritized sweeping approach, which requires a model of the transitions to the predecessors, can be used to improve performance. We investigate whether such algorithms can explain the experimentally observed replays. We propose a neural network version of prioritized sweeping Q-learning, for which we developed a growing multiple expert algorithm, able to cope with multiple predecessors. The resulting architecture is able to improve the learning of simulated agents confronted to a navigation task. We predict that, in animals, learning the world model should occur during rest periods, and that the corresponding replays should be shuffled.Comment: Living Machines 2018 (Paris, France

Percepção de autoeficácia, assertividade sexual e uso do preservativo em jovens colombianos

El uso correcto y consistente del condón en las relaciones sexuales es un procedimiento altamente eficaz para la prevención del VIH/SIDA, así como para otras infecciones de transmisión sexual (ITS). Algunos estudios reportan que las habilidades psicosociales y de interrelación favorecen el desarrollo de prácticas sexuales protegidas, como con el uso de preservativos. El objetivo del presente estudio fue determinar en qué medida la percepción de autoeficacia y la asertividad sexual predicen el uso del condón en las relaciones sexuales en un grupo de jóvenes. Se realizó un estudio descriptivo correlacional y predictivo con una muestra de 631 jóvenes con edades entre 19 y 26 años que reportaron haber tenido relaciones o ser activos sexualmente. Los resultados muestran que la percepción de autoeficacia y la asertividad sexual fueron fuertes predictores del uso del condón en las relaciones sexuales de las mujeres, mientras que para el caso de los hombres, solo la asertividad sexual predijo su uso.O uso correto e consistente do preservativo nas relações sexuais é um procedimento altamente eficaz para a prevenção do HIV/ Aids, bem como para outras infecções de transmissão sexual (ITS). Alguns estudos mostram que as habilidades psicossociais e de inter-relação favorecem o desenvolvimento de práticas sexuais protegidas, como com o uso do preservativo. O objetivo do presente estudo foi determinar em que medida a percepção de autoeficácia e a assertividade sexual predizem o uso do preservativo nas relações sexuais em um grupo de jovens. Realizou-se um estudo descritivo correlacional e preditivo com uma amostra de 631 jovens com idades entre 19 e 26 anos que relataram ter tido relações ou ser ativos sexualmente. Os resultados mostram que a percepção de autoeficácia e a assertividade sexual foram fortes indicadores do uso do preservativo nas relações sexuais das mulheres, enquanto para o caso dos homens, só a assertividade sexual predisse seu uso.The correct and consistent use of condoms during sexual intercourse is a highly effective procedure for the prevention of HIV / AIDS as well as other sexually transmitted infections (STIs). Some studies report that psychosocial skills and interaction promote the development of safe sexual relations by using condoms. The objective of this study was to determine to what extent the perception of self-efficacy and sexual assertiveness predicts condom use in sexual activity in a group of young people. The study was descriptive correlational and predictive.The sample consisted of 645 young people aged between 19 and 26 years who reported having had sex or being sexually active. Results showed that, unlike men, the perception of selfefficacy coupled with sexual assertiveness are strong predictors of condom use in women's sexual relations, whereas for men only sexual assertiveness predicts condom use in sexual relations