This review paper on amorphous calcium phosphates (ACPs) provides an update on several aspects of these compounds which have led to many studies and some controversy since the 1970s, particularly ...because of the lack of irrefutable proof of the occurrence of an ACP phase in mineralised tissues of vertebrates. The various synthesis routes of ACPs with different compositions are reported and the techniques used to characterise this phase are reviewed. We focus on the various physico-chemical properties of ACPs, especially the reactivity in aqueous media, which have been exploited to prepare bioactive bone substitutes, particularly in the form of coatings and cements for orthopaedic applications and composites for dental applications.
Highlights • Our work is the first to show that RvD1 and RvE1 are potent inhibitors of LPS-induced TNF-α, IL-6 and IL-1β gene expression. • RvD1 and RvE1 are modulators of microglial phenotype in ...vitro. • RvE1 regulates NFκB signaling pathway. • RvD1 regulates miRNAs expression.
This work presents a detailed analysis of the flow structures relevant to extreme wall shear stress events for turbulent pipe flow direct numerical simulation data at a friction Reynolds number ...$\textit {Re}_{\tau} \approx 1000$. The results reveal that extreme positive wall-friction events are located below an intense sweep (Q4) event originated from a strong quasi-streamwise vortex at the buffer region. This vortex transports high streamwise momentum from the overlap and the outer layers towards the wall, giving rise to a high-speed streak within the inner region. This vortical structure also relates to regions with extreme wall-normal velocity. Consequently, the conditional fields of turbulence production and viscous dissipation exhibit peaks whose magnitudes are approximately 25 times higher than the ensemble mean quantities in the vicinity of the extreme positive events. An analysis of the turbulent inertia force reveals that the energetic quasi-streamwise vortex acts as an essential source of momentum at the near-wall region. Similarly, extremely rare backflow events are studied. An examination of the wall-normal vorticity and velocity vector fields shows an identifiable oblique vortical structure along with two other large-scale roll modes. These counter-rotating motions contribute to the formation of backflow events by transporting streamwise momentum from the inner to the outer region, creating a large-scale meandering low-speed streak. It is found that extreme events are clustered below large-scale structures of positive streamwise momentum that interact with near-wall low-speed streaks, related to regions densely populated with vortical structures. Finally, a three-dimensional model is proposed to conceptualise the flow dynamics associated with extreme events.
Tomato production in South Africa is threatened by the emergence of tomato curly stunt virus (ToCSV), a monopartite Begomovirus transmitted by the whitefly vector Bemisia tabaci (Genn.). We ...investigated the role of sequence differences present in the 3' intergenic region (IR) and the V2 coding region on the differing infectivity of ToCSV sequence variant isolates V30 and V22 in the model host Nicotiana benthamiana. Using virus mutant chimeras, we determined that the development of the upward leaf roll symptom phenotype is mediated by sequence differences present in the 3' IR containing the TATA-associated composite element. Sequence differences present in the V2 coding region are responsible for modulating disease severity and symptom recovery in V22-infected plants. Serine substitution of V22 V2 Val27 resulted in a significant increase in disease severity with reduced recovery, the first study to demonstrate the importance of this V2 residue in disease development. Two putative ORFs, C5 and C6, were identified using in silico analysis and detection of an RNA transcript spanning their coding region suggests that these ORFs may be transcribed during infection. Additional virus-derived RNA transcripts spanning multiple ORFs and crossing the boundaries of recognised polycistronic transcripts, as well as the origin of replication within the IR, were detected in ToCSV-infected plants providing evidence of bidirectional readthrough transcription. From our results, we conclude that the diverse responses of the model host to ToCSV infection is influenced by select sequence differences and our findings provide several avenues for further investigation into the mechanisms behind these responses to infection.
•Dietary n-3 LC-PUFA supplementation modulates hippocampal oxylipins profile.•Dietary n-3 LC-PUFA supplementation decreases hippocampal pro-inflammatory cytokines induced by LPS.•Oxylipin profile ...depending on dietary intake could orchestrate inflammatory response to LPS.
The brain is highly enriched in long chain polyunsaturated fatty acids (LC-PUFAs) that display immunomodulatory properties in the brain. At the periphery, the modulation of inflammation by LC-PUFAs occurs through lipid mediators called oxylipins which have anti-inflammatory and pro-resolving activities when derived from n-3 LC-PUFAs and pro-inflammatory activities when derived from n-6 LC-PUFAs. However, whether a diet rich in LC-PUFAs modulates oxylipins and neuroinflammation in the brain has been poorly investigated. In this study, the effect of a dietary n-3 LC-PUFA supplementation on oxylipin profile and neuroinflammation in the brain was analyzed. Mice were given diets deficient or supplemented in n-3 LC-PUFAs for a 2-month period starting at post-natal day 21, followed by a peripheral administration of lipopolysaccharide (LPS) at adulthood. We first showed that dietary n-3 LC-PUFA supplementation induced n-3 LC-PUFA enrichment in the hippocampus and subsequently an increase in n-3 PUFA-derived oxylipins and a decrease in n-6 PUFA-derived oxylipins. In response to LPS, n-3 LC-PUFA deficient mice presented a pro-inflammatory oxylipin profile whereas n-3 LC-PUFA supplemented mice displayed an anti-inflammatory oxylipin profile in the hippocampus. Accordingly, the expression of cyclooxygenase-2 and 5-lipoxygenase, the enzymes implicated in pro- and anti-inflammatory oxylipin synthesis, was induced by LPS in both diets. In addition, LPS-induced pro-inflammatory cytokine increase was reduced by dietary n-3 LC-PUFA supplementation. These results indicate that brain n-3 LC-PUFAs increase by dietary means and promote the synthesis of anti-inflammatory derived bioactive oxylipins. As neuroinflammation plays a key role in all brain injuries and many neurodegenerative disorders, the present data suggest that dietary habits may be an important regulator of brain cytokine production in these contexts.
This investigation characterises the time response and the transient turbulence dynamics undergone by rapidly decelerating turbulent pipe flows. A series of direct numerical simulations of ...decelerating flows between two steady Reynolds numbers were conducted for this purpose. The statistical analyses reveal that rapidly decelerating turbulent flows undergo four coherent, unambiguous transitional stages: inertial (stage I), a dramatic change of sign in the viscous force associated with the decay of the viscous shear stress at the wall together with a mild turbulence decay in the viscous sublayer; friction recovery (stage II), a recovery in viscous force and progressive decay in the turbulent inertia at the near-wall region; turbulence decay (stage III), a balanced decay in both turbulent inertia and viscous force at the near-wall and overlap regions; core relaxation (stage IV), slow turbulence decay at the core region. The FIK identity derived by Fukagata, Iwamoto and Kasagi (Phys. Fluids, vol. 14, 2002, L73–L76) was used to understand further how the flow dynamics influence the time response of the skin friction coefficient ($C_f$). The results show that although $C_f$ plateaus during the fourth stage, the turbulent contribution keeps decaying, undershoots and finally recovers to attain its final steady value. The time evolution of the azimuthal vorticity ($\omega _\theta$) flux reveals that as the flow is decelerated, a layer of negative $\omega _\theta$ is produced at the wall during the flow excursion. As time progresses, this negative vorticity propagates in the wall-normal direction, attenuating the pre-existing vorticity and producing a decay in the turbulence levels.
The transient dynamics of accelerating turbulent pipe flow has been examined using direct numerical simulation (DNS) data sets with a high spatiotemporal resolution, starting from low and moderate ...Reynolds numbers. The time-dependent evolution of the mean flow dynamics reveals that internal flows, during and after a rapid increase in the flow rate, experience four unambiguous transient stages: inertial, pre-transition, transition and core relaxation before they reach their final steady-state. The first stage is characterised by a rapid and substantial increment in the viscous forces within the viscous sublayer, together with the frozen behaviour of the existing turbulent eddies. The pre-transitional stage reveals a weak response of the turbulent inertia within the near-wall region, together with a rapid reduction in the viscous forces. At the third stage, termed transition, balanced growth in the magnitude of both the turbulent and the viscous forces within $y^{+0} \lesssim 50$ is observed. The final stage, referred to as core relaxation, shows a quasi-steady behaviour at $y^{+0} < 50$ and reveals the slow propagation of turbulence from the near-wall region into the wake region. A decomposition of the skin friction coefficient ($C_f$), using an FIK identity suitable for unsteady pipe flow, shows a progressive increment in the turbulent contribution during the core-relaxation period. Simultaneously, the unsteady contribution decreases proportionally, maintaining a plateau in $C_f$. The principal mechanism responsible for this slow regeneration in the wake is a temporal turbulence stratification at the inner region of the flow, together with a quiescent core, which maintains geometric coherence across extensive periods.
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