instruction:
In this task, you are given a passage which has a question and the context. You have to generate an answer to the question based on the information present in the context.
question:
Context: We study the Azospirillum brasilense tolerance to water deficit and the dynamics of adaptive process at the level of the membrane.', 'Azospirillum brasilense was exposed to polyethylene glycol (PEG) growth and PEG shock. Tolerance, phospholipids and fatty acid (FA) composition and membrane fluidity were determined. Azospirillum brasilense was able to grow in the presence of PEG; however, its viability was reduced. Cells grown with PEG showed membrane fluidity similar to those grown without, the lipid composition was modified, increasing phosphatidylcholine and decreasing phosphatidylethanolamine amounts. The unsaturation FAs degree was reduced. The dynamics of the adaptive response revealed a decrease in fluidity 20min after the addition of PEG, indicating that the PEG has a fluidizing effect on the hydrophobic region of the cell membrane. Fluidity returned to initial values after 60min of PEG exposure.\Question: Is reorganization of Azospirillum brasilense cell membrane mediated by lipid composition adjustment to maintain optimal fluidity during water deficit?
answer:
Azospirillum brasilense is able to perceive osmotic changes by changing the membrane fluidity. This effect is offset by changes in the composition of membrane phospholipid and FA, contributing to the homeostasis of membrane fluidity under water deficit.

question:
Context: Morphology and material properties are the main components of the mechanical design of organisms, with species groups developing different optimization strategies in the context of their physical environment. For intertidal and subtidal seaweeds, possessing highly flexible and extensible tissues allows individuals to bend and reconfigure in flow, thereby reducing drag. Previous research has shown that aging may compromise these qualities. Tissue age increases with distance from the blade's meristem, which differs in its position on kelps and red algae. Here, we assess whether longitudinal patterns of blade material properties differ between these two algal groups according to tissue age.", 'We performed tensile tests on tissues samples excised from various positions along the extent of blades in nine kelp species (basal growth) and 15 species of red algae (apical growth).', "We found that older tissues were less flexible and extensible than younger tissues in all species tested. As predicted, tissue near the basal meristem in kelp was more flexible and extensible than older tissue at the blade's distal end. The opposite pattern was observed for red algae, with the most flexible and extensible tissues found near the apical meristem at the distal ends of blades.\Question: Do divergent growth strategies between red algae and kelps influence biomechanical properties?
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We propose that divergent patterns in the distribution of material properties along blades may have different consequences for the performance of kelps and red algae. The positioning of younger tissues at the blade base for kelps may enable these species to attain larger body sizes in wave-swept habitats.

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Context: Modular junctions are ubiquitous in contemporary hip arthroplasty. The head-trunnion junction is implicated in the failure of large diameter metal-on-metal (MoM) hips which are the currently the topic of one the largest legal actions in the history of orthopaedics (estimated costs are stated to exceed $4 billion). Several factors are known to influence the strength of these press-fit modular connections. However, the influence of different head sizes has not previously been investigated. The aim of the study was to establish whether the choice of head size influences the initial strength of the trunnion-head connection.', 'Ti-6Al-4V trunnions (n = 60) and two different sizes of cobalt-chromium (Co-Cr) heads (28mm and 36mm; 30 of each size) were used in the study. Three different levels of assembly force were considered: 4 kN; 5 kN; and 6 kN (n = 10 each). The strength of the press-fit connection was subsequently evaluated by measuring the pull-off force required to break the connection. The statistical differences in pull-off force were examined using a Kruskal-Wallis test and two-sample Mann-Whitney U test. Finite element and analytical models were developed to understand the reasons for the experimentally observed differences.', '36mm diameter heads had significantly lower pull-off forces than 28mm heads when impacted at 4kN and 5kN (p<0.001; p<0.001), but not at 6kN (p=0.21). Mean pull-off forces at 4 kN and 5kN impaction forces were approximately 20% larger for 28mm heads compared with 36mm heads. Finite element and analytical models demonstrate that the differences in pull-off strength can be explained by differences in structural rigidity and the resulting interface pressures.\Question: Do large-diameter total hip arthroplasty modular heads require greater assembly forces for initial stability?
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This is the first study to show that 36mm Co-Cr heads have up to 20% lower pull-off connection strength compared with 28mm heads for equivalent assembly forces. This effect is likely to play a role in the high failure rates of large diameter MoM hips.Cite this article: A. R. MacLeod, N. P. T. Sullivan, M. R. Whitehouse, H. S. Gill. Large-diameter total hip arthroplasty modular heads require greater assembly forces for initial stability. Bone Joint Res 2016;5:338-346. DOI: 10.1302/2046-3758.58.BJR-2016-0044.R1.