Effects of Additives and Templates on Calcium Carbonate Mineralization in vitro

International audienceThe review focuses on the effects of several important additives and templates controlling the calcium carbonate crystals formation and the complexity of the crystal morphologies in vitro. Additives include soluble matrices extracted from shells and pearls, amino-acids, magnesium ions and collagen among others. Templates include modified single crystal silicon, natural biominerals among others. Mechanisms proposed to explain the phenomena are not systematic, further studies are necessary to explain how organic matrices mediate calcium carbonate mineralization

On reducing mesh delay for peer-to-peer live streaming

Peer-to-peer (P2P) technology has emerged as a promising scalable solution for live streaming to large group. In this paper, we address the design of overlay which achieves low source-to-peer delay, is robust to user churn, accommodates of asymmetric and diverse uplink bandwidth, and continuously improves based on existing user pool. A natural choice is the use of mesh, where each peer is served by multiple parents. Since the peer delay in a mesh depends on its longest path through its parents, we study how to optimize such delay while meeting a certain streaming rate requirement. We first formulate the minimum delay mesh problem and show that it is NP-hard. Then we propose a centralized heuristic based on complete knowledge which serves as our benchmark and optimal solution for all the other schemes under comparison. Our heuristic makes use of the concept of power in network given by the ratio of throughput and delay. By maximizing the network power, our heuristic achieves very low delay. We then propose a simple distributed algorithm where peers select their parents based on the power concept. The algorithm makes continuous improvement on delay until some minimum delay is reached. Simulation results show that our distributed protocol performs close to the centralized one, and substantially outperforms traditional and state-of-the-art approaches

Anchor View Allocation for Collaborative Free Viewpoint Video Streaming

In free viewpoint video, a viewer can choose at will any camera angle or the so-called "virtual view" to observe a dynamic 3-D scene, enhancing his/her depth perception. The virtual view is synthesized using texture and depth videos of two anchor camera views via depth-image-based rendering (DIBR). We consider, for the first time, collaborative live streaming of a free viewpoint video, where a group of users may interactively pull and cooperatively share streams of different anchor views. There is a cost to access the anchor views from the live source, a cost to "reconfigure" the peer network due to a change in selected anchors during view switching, and a distortion cost due to the distance of the virtual views to the received anchor views at users. We optimize the anchor views allocated to users so as to minimize the overall streaming cost given by the access cost, reconfiguration cost, and view distortion cost. We first show that, if the reconfiguration cost due to view switching is negligible, the view allocation problem can be optimally and efficiently solved in polynomial time using dynamic programming. For the case of non-negligible reconfiguration cost, the problem becomes NP-hard. We thus present a locally optimal and centralized algorithm inspired by Lloyd's algorithm used in non-uniform scalar quantization. We further propose a distributed algorithm with convergence guarantee, where each peer group independently makes merge-and-split decisions with a well-defined fairness criteria. Simulation results show that our algorithms achieve low streaming cost due to its excellent anchor view allocation

Integrated transcriptomic and proteomic analyses of a molecular mechanism of radular teeth biomineralization in Cryptochiton stelleri

　Many species of chiton are known to deposit magnetite (Fe3O4) within the cusps of their heavily mineralized and ultrahard radular teeth. Recently, much attention has been paid to the ultrastructural design and superior mechanical properties of these radular teeth, providing a promising model for the development of novel abrasion resistant materials. Here, we constructed de novo assembled transcripts from the radular tissue of C. stelleri that were used for transcriptome and proteome analysis. Transcriptomic analysis revealed that the top 20 most highly expressed transcripts in the non-mineralized teeth region include the transcripts encoding ferritin, while those in the mineralized teeth region contain a high proportion of mitochondrial respiratory chain proteins. Proteomic analysis identified 22 proteins that were specifically expressed in the mineralized cusp. These specific proteins include a novel protein that we term radular teeth matrix protein1 (RTMP1), globins, peroxidasins, antioxidant enzymes and a ferroxidase protein. This study reports the first de novo transcriptome assembly from C. stelleri, providing a broad overview of radular teeth mineralization. This new transcriptomic resource and the proteomic profiles of mineralized cusp are valuable for further investigation of the molecular mechanisms of radular teeth mineralization in chitons

The co-effect of organic matrix from carp otolith and microenvironment on calcium carbonate mineralization

International audienceIn vitro mineralization experiment is an effective way to study the effect of organic matrix on calcium carbonate crystallization, and to reveal the relationship between organic matrix and inorganic crystal in natural biominerals. In natural biominerals, organic matrix plays an important role in crystal formation and stability, together with microenvironment changes, they can affect crystal polymorph, morphology, density, size, orientation et al. In this work, we systematically studied the effects of different organic matrices in fish otoliths, the organic matrices concentration changes, as well as the co-effect of organic matrices with temperature, pH value and Mg ion changes in the in vitro CaCO3 mineralization experiments. The organic matrix and concentration change experiments prove that water soluble matrix (WSM) plays an important role in crystal form transition. It can induce CaCO3 crystals with same crystal polymorph as the otolith from which organic matrix was extracted. The temperature change experiment proves that CaCO3 has a tendency to form calcite, vaterite, and then aragonite in priority as temperature goes up. Under different temperature, WSM from lapillus/asteriscus still has the effect to mediate different CaCO3 crystals. The pH change experiment shows that, near the neutral environment, as pH value goes up, calcites have a tendency to form crystal aggregates with more faces exposed, the organic matrix still keeps crystal mediation effect. The Mg2 + experiment shows that, Mg ion can promote aragonite formation, together with lapillus organic matrix, aragonites with different shapes are formed

The prognostic role of lactate in patients who achieved return of spontaneous circulation after cardiac arrest: A systematic review and meta-analysis

Aim: The aim of the study is to conduct a systematic review and meta-analysis of data showing the association of lactate levels with mortality and neurologic outcome in patients who achieved return of spontaneous circulation (ROSC) after cardiac arrest. Methods: An electronic search of PubMed, Embase, Web of Science, and Cochrane Library databases was conducted. Lactate levels at 0, 6, 12, 24, and 48 h after ROSC in survivors versus nonsurvivors and in good versus poor neurologic outcome patients were extracted. Continuous variable and odds ratio were applied for data analysis. Inverse-variance fixed effects model with 95% confidence interval (CI) was used depending on interstudy heterogeneity. Results: A total of 18 articles meeting the study criteria were included for systematic review and 15 for meta-analysis. The results showed that initial serum lactate levels in nonsurvivors were significantly higher than survivors (standardized mean difference [SMD] = −0.43; 95% CI = [−0.52, −0.33]; P < 0.00001), and a higher lactate level at admission was associated with increased hospital mortality. In addition, initial serum lactate levels were significantly higher in poor neurologic outcome patients than good neurologic outcome patients (SMD = −0.44; 95% CI = [−0.54, −0.34]; P < 0.00001), and initial higher lactate level was associated with poor neurologic outcome. There was a statistically significant difference in lactate levels at 6, 12, 24, and 48 h after ROSC, among survivors versus nonsurvivors and among patients presenting good neurologic outcome versus poor neurologic outcome. However, the included studies had small sample size and highly inconsistent data. Conclusions: Higher lactate levels were associated with increased mortality and poor neurologic outcome. Lower lactate levels or faster lactate clearance was associated with higher survival and good neurologic outcome

Achieving High-Bitrate Overlay Live Streaming with Proxy Helpers

overlay live streaming is challenging. We consider the design and optimization of an overlay network formed by distributed proxies for high-bitrate live streaming. The video stream is divided into substreams and pushed via multiple trees to all the proxy servers with users. To effectively overcome bandwidth bottlenecks, we employ proxy helpers to provide rich path diversity. They do not have any attached users, and hence may forward any arbitrary subset of the substreams. In this way, the helpers serve as “stepping stones ” to provide full streams to the servers. A critical issue is how to best use the proxy helpers to minimize delay meeting a certain streaming rate requirement. We first model the network by capturing various delay and bandwidth components. We formulate the problem and show that it is NP-hard. We then propose an efficient algorithm called Stepping-Stones. Our results based on simulation on real Internet topologies show that the algorithm outperforms other overlay protocols by effectively making use of helpers to achieve low delay and high streaming rate. I