Self‐Sharpening Mechanism of the Sea Urchin Tooth

The sea urchin tooth is a mosaic of calcite crystals shaped precisely into plates and fibers, cemented together by a robust calcitic polycrystalline matrix. The tooth is formed continuously at one end, while it grinds and wears at the opposite end, the sharp tip. Remarkably, these teeth enable the sea urchin to scrape and bore holes into rock, yet the teeth remain sharp rather than dull with use. Here we describe the detailed structure of the tooth of the California purple sea urchin Strongylocentrotus purpuratus, and focus on the self‐sharpening mechanism. Using high‐resolution X‐ray photoelectron emission spectromicroscopy (X‐PEEM), scanning electron microscopy (SEM), EDX analysis, nanoindentation, and X‐ray micro‐tomography, we deduce that the sea urchin tooth self‐sharpens by fracturing at discontinuities in the material. These are organic layers surrounding plates and fibers that behave as the “fault lines” in the tooth structure, as shown by nanoindentation. Shedding of tooth components at these discontinuities exposes the robust central part of the tooth, aptly termed “the stone”, which becomes the grinding tip. The precise design and position of the plates and fibers determines the profile of the tooth tip, so as the tooth wears it maintains a tip that is continually renewed and remains sharp. This strategy may be used for the top‐down or bottom‐up fabrication of lamellar materials, to be used for mechanical functions at the nano‐ and micrometer scale.     

Dynamic Behavior Sequencing for Hybrid Robot Architectures

Hybrid robot control architectures separate planning, coordination, and sensing and acting into separate processing layers to provide autonomous robots both deliberative and reactive functionality. This approach results in systems that perform well in goal-oriented and dynamic environments. Often, the interfaces and intents of each functional layer are tightly coupled and hand coded so any system change requires several changes in the other layers. This work presents the dynamic behavior hierarchy generation (DBHG) algorithm, which uses an abstract behavior representation to automatically build a behavior hierarchy for meeting a task goal. The generation of the behavior hierarchy occurs without knowledge of the low-level implementation or the high-level goals the behaviors achieve. The algorithm’s ability to automate the behavior hierarchy generation is demonstrated on a robot task of target search, identification, and extraction. An additional simulated experiment in which deliberation identifies which sensors to use to conserve power shows that no system modification or predefined task structures is required for the DBHG to dynamically build different behavior hierarchies.     

Do challenge, task experience or computer familiarity influence the learning of historical chronology from virtual environments in 8-9 year old children?

Studies examined the potential use of VEs in teaching historical chronology to 127 children of primary school age (8-9 years). The use of passive fly-through VEs had been found, in an earlier study, to be disadvantageous with this age group when tested for their subsequent ability to place displayed sequential events in correct chronological order. All VEs in the present studies included active challenge, previously shown to enhance learning in older participants. Primary school children in the UK (all frequent computer users) were tested using UK historical materials, but no significant effect was found between three conditions (Paper, PowerPoint and VE) with minimal pre-training. However, excellent (error free) learning occurred when children were allowed greater exploration prior to training in the VE. In Ukraine, with children having much less computer familiarity, training in a VE (depicting Ukrainian history) produced better learning compared to PowerPoint, but no better than in a Paper condition. The results confirmed the benefit of using challenge in a VE with primary age children, but only with adequate prior familiarisation with the medium. Familiarity may reduce working memory load and increase children’s spatial memory capacity for acquiring sequential temporal-spatial information from virtual displays.     

Performance of Ni‐based Anode‐Supported SOFCs with Doped Ceria Electrolyte at Low Temperatures Between 294 and 542°C

The performance of a conventional anode‐supported microtubular SOFC using doped ceria as an electrolyte and Ni‐based cermet as an anode is evaluated at low operating temperature between 294 and 542°C. An open‐circuit voltage (OCV) of >0.9 V is obtained at all measured operating temperatures, and power generation is observed at temperatures as low as 294°C. The power density of the cell is 0.6 W/cm² at 542°C operating temperature with 47% fuel utilization and is 5 mW/cm² at 294°C operating temperature with an open‐circuit voltage of 0.95 V. According to impedance spectroscopy, a greater influence of gas flow rate, on the cell performance, is observed at higher operating temperature.     

Magnetic field effects as a result of the radical pair mechanism are unlikely in redox enzymes

Environmental exposure to electromagnetic fields is potentially carcinogenic. The radical pair mechanism is considered the most feasible mechanism of interaction between weak magnetic fields encountered in our environment and biochemical systems. Radicals are abundant in biology, both as free radicals and reaction intermediates in enzyme mechanisms. The catalytic cycles of some flavin-dependent enzymes are either known or potentially involve radical pairs. Here, we have investigated the magnetic field sensitivity of a number of flavoenzymes with important cellular roles. We also investigated the magnetic field sensitivity of a model system involving stepwise reduction of a flavin analogue by a nicotinamide analogue—a reaction known to proceed via a radical pair. Under the experimental conditions used, magnetic field sensitivity was not observed in the reaction kinetics from stopped-flow measurements in any of the systems studied. Although widely implicated in radical pair chemistry, we conclude that thermally driven, flavoenzyme-catalysed reactions are unlikely to be influenced by exposure to external magnetic fields.     

The effects of variable nitrogen application on barley starch structure under drought stress

Under well‐watered conditions, agronomic yield increases have been observed to correlate with nitrogen supply. Thus there is a need for proper fertilizer regimes to increase both metabolic and regulatory processes during kernel development in cereal crops. However, the impact of varying levels of nitrogen application on starch biosynthesis, structure and properties in grain under drought stress is not well known. This study examines the impact of different nitrogen application rates, in conjunction with drought stress, on starch biosynthesis in barley (Hordeum vulgare L.) grain. The proportions of short amylopectin branches and long amylose branches in the grain of Fitzroy and Grout were higher under drought stress with high nitrogen. This suggests that starch biosynthesis was affected, probably owing to early termination of grain fill. These changes in the long branches can affect starch properties, such as the rates of enzymatic degradation, and hence fermentability and nutritional value. In contrast, the chain length distribution (CLD) of the debranched starch from the grain grown under favourable conditions (Hermitage) did not show the same level of qualitative variations among the nitrogen treatments. The similar CLDs between these grain samples suggest that starch biosynthesis was not negatively impacted by the different nitrogen applications. However, with the grain under drought stress conditions, the results indicate that starch biosynthesis and quality could be impacted by nitrogen application. This has the potential to give rise to beneficial structural changes that are useful for some value‐added products. Copyright © 2015 The Institute of Brewing & Distilling     

Speeding up systems biology simulations of biochemical pathways using condor

Systems biology is a scientific field that uses computational modelling to study biological and biochemical systems. The simulation and analysis of models of these systems typically explore behaviour over a wide range of parameter values; as such, they are usually characterised by the need for nontrivial amounts of computing power. Grid computing provides access to such computational resources. In previous research, we created the grid‐enabled biochemical networks simulation environment to attempt to speed up system biology simulations over a grid (the UK National Grid Service and ScotGrid). Following on from this work, we have created the simulation modelling of the epidermal growth factor receptor microtubule‐associated protein kinase pathway utility, a standalone simulation tool dedicated to the modelling and analysis of the epidermal growth factor receptor microtubule‐associated protein kinase pathway. This builds on experiences from biochemical networks simulation environment by decoupling the simulation modelling elements from the Grid middleware. This new utility enables us to interface with different grid technologies. This paper therefore describes the new SIMAP utility and an empirical investigation of its performance when deployed over a desktop grid based on the high throughput computing middleware Condor. We present our results based on a case study with a model of the mammalian ErbB signalling pathway, a pathway strongly linked to cancer. Copyright © 2013 John Wiley & Sons, Ltd.     

Changes in total body bone mineral density following a common bone health plan with two versions of a unique bone health supplement: a comparative effectiveness research study

Background  

The US Surgeon General's Report on Bone Health suggests America's bone-health is in jeopardy and issued a "call to action" to develop bone-health plans that: (1) improve nutrition, (2) increase health literacy and, (3) increase physical activity. This study is a response to this call to action.     

Temporo-spatial model construction using the MML and software framework

Development of complex temporo-spatial biological computational models can be a time consuming and arduous task. These models may contain hundreds of differential equations as well as realistic geometries that may require considerable investment in time to ensure that all model components are correctly implemented and error free. To tackle this problem, the Modeling Markup Languages (MML) and software framework is a modular XML/HDF5-based specification and toolkits that aims to simplify this process. The main goal of this framework is to encourage reusability, sharing and storage. To achieve this, the MML framework utilizes the CellML specification and repository, which comprises an extensive range of curated models available for use. The MML framework is an open-source project available at http://mml.gsbme.unsw.edu.au.