14,334 research outputs found
Indigenous demosponge spicules in a Late Devonian stromatoporoid basal skeleton from the Frasnian of Belgium
This paper records the first example of a demosponge spicule framework in a single specimen of a Devonian stromatoporoid from the Frasnian of southern Belgium. The small sample (2.5 × 2 cm) is a component in a brecciated carbonate from a carbonate mound in La Boverie Quarry 30 km east of Dinant. Because of the small size of the sample, generic identification is not confirmed, but the stromatoporoid basal skeleton is similar to the genus Stromatopora. The spicules are arranged in the calcified skeleton, but not in the gallery space, and are recrystallized as multi-crystalline calcite. The spicules fall into two size ranges: 10-20 μm diameter and 500-2000 μm long for the large ones and between 5-15 μm diameter and 50-100 μm length for the small ones. In tangential section, the spicules are circular, they have a simple structure, and no axial canal has been preserved. The large spicules are always monaxons, straight or slightly curved styles or strongyles. The spicules most closely resemble halichondrid/axinellid demosponge spicules and are important rare evidence of the existence of spicules in Palaeozoic stromatoporoids, reinforcing the interpretation that stromatoporoids were sponges. The basal skeleton may have had an aragonitic spherulitic mineralogy. Furthermore, the spicules indicate that this stromatoporoid sample is a demosponge. © 2014 Lethaia Foundation. Published by John Wiley & Sons Ltd
Two Types of K⁺ Channel Subunit, Erg1 and KCNQ2/3, Contribute to the M-Like Current in a Mammalian Neuronal Cell
The potassium M current was originally identified in sympathetic ganglion cells, and analogous currents have been reported in some central neurons and also in some neural cell lines. It has recently been suggested that the M channel in sympathetic neurons comprises a heteromultimer of KCNQ2 and KCNQ3 (Wang et al., 1998) but it is unclear whether all other M-like currents are generated by these channels. Here we report that the M-like current previously described in NG108–15 mouse neuroblastoma x rat glioma cells has two components, “fast” and “slow”, that may be differentiated kinetically and pharmacologically. We provide evidence from PCR analysis and expression studies to indicate that these two components are mediated by two distinct molecular species of K+ channel: the fast component resembles that in sympathetic ganglia and is probably carried byKCNQ2/3 channels, whereas the slow component appears to be carried by merg1a channels. Thus, the channels generating M-like currents in different cells may be heterogeneous in molecular composition
The missing complexity in seismically imaged normal faults: What are the implications for geometry and production response?
The impact of geometric uncertainty on across-fault flow behaviour at the scale of individual intra-reservoir faults is investigated in this study. A high resolution digital elevation model (DEM) of a faulted outcrop is used to construct an outcrop-scale geocellular grid capturing high-resolution fault geometries (5 m scale). Seismic forward modelling of this grid allows generation of a 3D synthetic seismic cube, which reveals the corresponding seismically resolvable fault geometries (12.5 m scale). Construction of a second geocellular model, based upon the seismically resolvable fault geometries, allows comparison with the original outcrop geometries. Running fluid flow simulations across both models enables us to assess quantitatively the impact of outcrop resolution versus seismic resolution fault geometries upon across-fault flow. The results suggest that seismically resolvable fault geometries significantly underestimate the area of across-fault juxtaposition relative to realistic fault geometries. In turn this leads to overestimates in the sealing ability of faults, and inaccurate calculation of fault plane properties such as transmissibility multipliers (TMs)
The importance of using ship bridge simulation training to enhance the competency of masters and watch-officers : a case study of the iraqi dredging fleet
Using Mendelian randomization to understand and develop treatments for neurodegenerative disease
Common neurodegenerative diseases are thought to arise from a combination of environmental and genetic exposures. Mendelian randomization is a powerful way to leverage existing genetic data to investigate causal relationships between risk factors and disease. In recent years, Mendelian randomization has gathered considerable traction in neurodegenerative disease research, providing valuable insights into the aetiology of these conditions. This review aims to evaluate the impact of Mendelian randomization studies on translational medicine for neurodegenerative diseases, highlighting the advances made and challenges faced. We will first describe the fundamental principles and limitations of Mendelian randomization and then discuss the lessons from Mendelian randomization studies of environmental risk factors for neurodegeneration. We will illustrate how Mendelian randomization projects have used novel resources to study molecular pathways of neurodegenerative disease and discuss the emerging role of Mendelian randomization in drug development. Finally, we will conclude with our view of the future of Mendelian randomization in these conditions, underscoring unanswered questions in this field
A utilitarian antagonist: the zombie in popular video games
This article takes as its starting point the prevalence of the zombie in video games. I argue that, although the zombie games often superficially resemble filmic texts in their use of aesthetic and narrative, they must be understood, less as a set of conventions and thematic metaphors in the way that the zombie text has been read in film and television scholarship, and more as a utilisation of the zombie as a utilitarian antagonist that facilitates and permits the pleasures of violence and fantasy in video game play. Beginning with the Resident Evil and Left 4 Dead series of games I examine the way that games necessarily update the notion zombie as mass antagonist via the need to vary gameplay activity through different styles of adversary for players. At the same time I will demonstrate that, far from simply being the province of the survival horror genre, the zombie appears across an array of game forms, game cultures and game productions. The zombie highlights the participatory nature of game culture in the array of zombie 'mods' that users create to transform existing games into zombie based games, in particular in relation to titles such as the Call of Duty series. At the other end of the production spectrum the zombie features heavily in the little studied area of online flash games where the zombie can be found in a variety of game genres and forms. The zombie here often operates as a pastiche of popular zombie narratives in survival games (The Last Stand), parodic engagements with zombie conventions (Jetpacks and Zombies) or play with the notion of zombie pandemics (the Infectionator games). Here I situate the zombie game as a aesthetic genre that works to provide an easily understandable context for such interactive genres as survival horror, text adventures, shooting games, physics games and driving games, with the popularity of these enough to drive numerous dedicated hosting and link sites such as zombiegames.net. The pastiche element of these games extends into gamers social engagement with games. Online debates over the the appropriate actions or preparation for a zombie holocaust are commonplace on the internet in such spaces as Zombieresearch.net. Whilst many of these sites feature decidedly tongue in cheek engagement with the notion of the zombie apocalypse, the users of fora for games like Left 4 Dead and Dead Island tend to debate this directly in the terms of the games themselves, discussing their relative merits or realism. Some of these games also highlight the specific pleasures of identifying the zombie as protagonist of sorts. In discussing this I will return to online gaming and the Left 4 Dead games in which players may compete online as part of the zombie horde. Such games raise major questions for the issues of identification and immersion that are said to be at the centre of the game experience. I will also explore the parodic pleasures of many flash games that situate the player in the role of spreading zombie infections. Throughout this article I aim to demonstrate that the zombie in game culture is less a cultural metaphor than a combination of utilitarian antagonist and a persistent aesthetic; a means of providing style or pleasure to many games that relies on the intertextual and flexible nature of the zombie as popular cultural phenomenon
Online tutorial – meeting students’ needs
Pretendemos dar a conhecer um estudo piloto que foi desenvolvido com alunos do ensino superior e cujo objectivo passou pelo ensejo de potenciar o trabalho colaborativo entre os mesmos, bem como as suas capacidades de pesquisa. Os recursos informáticos utilizados foram espaços virtuais de colaboração, uma vez que são espaços com grandes potencialidades ao nível da colaboração e da interacção. O grupo-alvo foi constituído por estudantes de primeiro ano do ensino superior politécnico. Os estudantes estavam divididos em turmas: um grupo a tempo inteiro e outro em pós aboral, ambos frequentando o mesmo curso e a mesma unidade curricular. A estratégia de tutória adoptada iniciou-se com a apresentação de um desafio por parte da docente. Após o desafio lançado os estudantes pesquisaram acerca da temática e partilharam, no Diigo, os links/documentos que encontraram e consideraram serem pertinentes para o desenvolvimento do tema. No final, os estudantes tinham que escrever um artigo acerca do tema, tendo em conta as pesquisas desenvolvidas, as leituras efectuadas e as discussões colaborativas realizadas. Para facilitar o desenvolvimento de uma compreensão partilhada, os estudantes, além de disponibilizarem e comentarem a informação no Diigo, também participaram em sessões virtuais de discussão na plataforma Second Life®. O estudo piloto conduzido, e descrito neste documento, permitiu reunir indicadores sobre as mais valias das ferramentas online utilizadas, nomeadamente no que se refere ao grau e qualidade da participação, colaboração e interacção dos estudantes, aliados à inexistência de constrangimentos de ordem temporal e/ou física.This article will present a pilot study
that was developed with students from higher
education on approaches to increase the
collaborative work between students, and to enhance
their research skills. The methodology we are
evaluating is designed around collaborative virtual
spaces which offer some benefits for deeper
collaboration and interaction. The target group was
students from the 1st year of a Higher Level Course.
One group of students was in full-time education and
a second group was mature students in part-time
education. Both groups are engaged on an identical
course.
The tutorial strategy adopted began with the teacher
setting the class a challenge. Students were then
invited to research the question and post whatever
links/documents they consider relevant using a Diigo
group, and comment on what they found (using the
share and comment capabilities). The task for
students was to write an article about the topic based
on their research, readings and collaborative
discussions. To facilitate the development of a
shared understanding the students posted
information and participated in virtual on-line
meetings (Second Life®).
The pilot study implemented, and described in this
article, demonstrated some gains from the use of
online tools, in particular related with the level and
quality of participation, collaboration and interaction
among students. The use of virtual environments
allows students to participate in richer interactions at
times that are more convenient to their work/study
patterns, with no physical restrictionsinfo:eu-repo/semantics/publishedVersio
A comparative study of the dynamic critical behavior of the four-state Potts like models
We investigate the short-time critical dynamics of the Baxter-Wu (BW) and
Turban (3TU) models to estimate their global persistence exponent . We conclude that this new dynamical exponent can be useful in detecting
differences between the critical behavior of these models which are very
difficult to obtain in usual simulations. In addition, we estimate again the
dynamical exponents of the four-state Potts (FSP) model in order to compare
them with results previously obtained for the BW and 3TU models and to decide
between two sets of estimates presented in the current literature. We also
revisit the short-time dynamics of the 3TU model in order to check if, as
already found for the FSP model, the anomalous dimension of the initial
magnetization could be equal to zero
Influence of Rotations on the Critical State of Soil Mechanics
The ability of grains to rotate can play a crucial role on the collective
behavior of granular media. It has been observed in computer simulations that
imposing a torque at the contacts modifies the force chains, making support
chains less important. In this work we investigate the effect of a gradual
hindering of the grains rotations on the so-called critical state of soil
mechanics. The critical state is an asymptotic state independent of the initial
solid fraction where deformations occur at a constant shear strength and
compactness. We quantify the difficulty to rotate by a friction coefficient at
the level of particles, acting like a threshold. We explore the effect of this
particle-level friction coefficient on the critical state by means of molecular
dynamics simulations of a simple shear test on a poly-disperse sphere packing.
We found that the larger the difficulty to rotate, the larger the final shear
strength of the sample. Other micro-mechanical variables, like the structural
anisotropy and the distribution of forces, are also influenced by the
threshold. These results reveal the key role of rotations on the critical
behavior of soils and suggest the inclusion of rotational variables into their
constitutive equations.Comment: 9 pages, 8 figures, Accepted for publication in Computer Physics
Communication
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