399 research outputs found

    The interaction between actin filaments and the cytoskeleton-membrane attachment site protein talin

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    Talin, a protein localized primarily in cell-matrix type adherens junctions, is involved in linking the cytoskeleton to the cell membrane. The major objectives of my study were to (1) determine the structural basis for the effect of pH and ionic strength on the direct talin-actin interaction, (2) examine the effects of other factors, such as specific phospholipids, on the talin-actin interaction, and (3) compare abilities of human platelet and avian smooth muscle talins to interact with actin. Negative staining results showed that at pH 6.4 and low ionic strength, talin extensively crosslinked actin filaments into both tight networks and bundles. Some of the bundles consisted of parallel actin filaments with an interfilament spacing of ~13 nm, and talin crossbridges spaced at ~36 nm intervals along the actin bundles. As pH and/or ionic strength was increased, talin\u27s actin bundling activity was decreased first, then its networking activity. Chemical crosslinking indicated that talin was present primarily as a dimer of two ~225 kDa subunits under all ionic conditions tested. Talin crosslinked actin filaments into networks and bundles after only five minutes of actin polymerization, with no evidence of shorter actin filaments formed in comparison to actin controls. Talin also crosslinked preformed actin filaments as well as it did actin filaments polymerized in its presence. The ~190 kDa talin fragment was able to crosslink actin filaments into networks and bundles, but required a slightly lower pH than did intact talin;The phosphoinositides, PIP2, PIP, or PI, but not IP3 or the phosphoglycerides, PS or PC, greatly inhibited the ability of talin to crosslink actin filaments. The phosphoinositides bound talin to form talin/phosphoinositide complexes, which prevented talin from effectively interacting with actin filaments. The detergent Triton X-100 or divalent cations, such as Ca2+, decreased the effect of the phosphoinositides on the talin-actin interaction;Cosedimentation assays, low shear viscometry, and negative staining showed that platelet talin interacted with actin in a fashion similar to that of smooth muscle talin. However, some differences were noted between the two talins, with platelet talin exhibiting lower actin crosslinking activity

    Some properties of Ramsey numbers

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    AbstractIn this paper, some properties of Ramsey numbers are studied, and the following results are presented. 1.(1) For any positive integers k1, k2, …, km l1, l2, …, lm (m > 1), we have r ∏i=1m ki + 1, ∏i=1m li + 1 ≥ ∏i=1m [ r (ki + 1,li + 1) − 1] + 1.2.(2) For any positive integers k1, k2, …, km, l1, l2, …, ln , we have r ∑i=1m ki + 1, ∑j=1n lj + 1 ≥ ∑i=1m∑j=1n r (ki + 1,lj + 1) − mn + 1. Based on the known results of Ramsey numbers, some results of upper bounds and lower bounds of Ramsey numbers can be directly derived by those properties

    On the clustering property of the random intersection graphs

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    A random intersection graph \mtl{\mcal{G}_{V,W,p}} is induced from a random bipartite graph \mtl{\mcal{G}^{*}_{V,W,p}} with vertices classes \mtl{V}, \mtl{W} and the edges incident between \mtl{v \in V} and \mtl{w \in W} with probability \mtl{p}. Two vertices in \mtl{V} are considered to be connected with each other if both of them connect with some common vertices in \mtl{W}. The clustering properties of the random intersection graph are investigated completely in this article. Suppose that the vertices number be \mtl{N = \mabs{V}} and \mtl{M=\mabs{W}} and \mtl{M = N^{\alpha},\ p=N^{-\beta}}, where \mtl{\alpha > 0,\, \beta > 0}, we derive the exact expressions of the clustering coefficient \mtl{C_{v}} of vertex \mtl{v} in \mtl{\mcal{G}_{V,W,p}}. The results show that if \mtl{\alpha < 2\beta} and \mtl{\alpha \neq \beta}, \mtl{C_{v}} decreases with the increasing of the graph size; if \mtl{\alpha = \beta} or \mtl{\alpha \geq 2\beta}, the graph has the constant clustering coefficients, in addition, if \mtl{\alpha > 2\beta}, the graph connecChangshui Zhangts almost completely. Therefore, we illustrate the phase transition for the clustering property in the random intersection graphs and give the condition that \mtl{\riG} being high clustering graph

    Comparison of dynamic changes of endogenous hormones between calli derived from mature and immature embryos of maize

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    Mature and immature embryos of maize inbred lines 87-1 and 137 were used as explants to induce callus on improved N6 medium. The contents of endogenous hormones abscisic acid (ABA), indoleacetic acid (IAA), gibberellic acid (GA3) and cytokinins (ZR) of immature, mature embryos and their corresponding calli were detected by method of enzyme-linked immunosorbant assay (ELISA). At the beginning of culture, IAA and GA3 levels decreased rapidly and reached their lowest levels at day 7, indicating that large amounts of IAA and GA3 are needed for germination. Levels of IAA and GA3 were highest at the beginning of embryonic callus formation from immature embryos, suggesting high levels of IAA and GA3 were beneficial to induction of embryonic callus from immature embryos (CIME). The IAA, GA3 and ABA contents and ration of IAA to ABA (IAA/ABA), GA3 to ABA (GA3/ABA) in callus of mature embryos (CME) were higher than those of CIME after the 14th day from culture initiation and the changes of ratios IAA/ABA and GA3/ABA increased rapidly in CME while they remained low in CIME during the whole experimental period. This inferred that high levels of IAA, GA3 or ABA and large increases in IAA/ABA and GA3/ABA might hinder the induction and maintenance of embryonic calli from mature embryos

    Probiotics treatment ameliorated mycophenolic acid-induced colitis by enhancing intestinal barrier function and improving intestinal microbiota dysbiosis in mice

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    BackgroundMycophenolic acid (MPA)-induced colitis was still a severe side effect and challenge faced by solid transplant recipients. We aimed to explore the function and mechanism of probiotics in the treatment of MPA-induced colitis.MethodsIn this study, 15 mice (C57BL/6) were randomly assigned into three groups: control (CNTL) group (n = 5), MPA group (n = 5) and the MPA + Probiotic group (n = 5). Bifid Triple Viable capsules, which were drugs for clinical use and consisted of Bifidobacterium longum, Lactobacillus acidophilus, and Enterococcus faecalis, were used in Probiotic group. Body weight change, stool scores, colon histopathology and morphology were used to evaluate the disease severity. The intestinal mucosal barrier function was assessed by measuring the expression level of secretory immunoglobulin A (sIgA), Zonula occludens-1 (ZO-1) and Occludin. Finally, 16S rDNA sequencing and bioinformatics analysis were performed on mice feces to compare the different intestinal microbial composition and diversity among three groups.ResultsCompared with the CNTL group, the mice in MPA group showed a significantly decreased body weight, increased stool scores, shortened colon length and severe colon inflammation. However, probiotics treated MPA mice reversed the disease severity, indicating that probiotics ameliorated MPA-induced colitis in mice. Mechanistically, probiotics improved the intestinal barrier function by up-regulating the expression of sIgA, ZO-1 and Occludin. Moreover, MPA-induced colitis led to intestinal microbiota dysbiosis, including the change of Firmicutes/Bacteroidetes ratio, α- and β-diversity. But probiotic treated group showed mild change in these microbial features. Additionally, we found that Clostridiales was the most significantly different microbiota flora in MPA group.ConclusionProbiotics treatment ameliorated MPA-induced colitis by enhancing intestinal barrier function and improving intestinal microbiota dysbiosis. Clostridiales might be the dominant functional intestinal microflora and serve as the potential therapy target in MPA-induced colitis

    Prophet: Conflict-Free Sharding Blockchain via Byzantine-Tolerant Deterministic Ordering

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    Sharding scales throughput by splitting blockchain nodes into parallel groups. However, different shards' independent and random scheduling for cross-shard transactions results in numerous conflicts and aborts, since cross-shard transactions from different shards may access the same account. A deterministic ordering can eliminate conflicts by determining a global order for transactions before processing, as proved in the database field. Unfortunately, due to the intertwining of the Byzantine environment and information isolation among shards, there is no trusted party able to predetermine such an order for cross-shard transactions. To tackle this challenge, this paper proposes Prophet, a conflict-free sharding blockchain based on Byzantine-tolerant deterministic ordering. It first depends on untrusted self-organizing coalitions of nodes from different shards to pre-execute cross-shard transactions for prerequisite information about ordering. It then determines a trusted global order based on stateless ordering and post-verification for pre-executed results, through shard cooperation. Following the order, the shards thus orderly execute and commit transactions without conflicts. Prophet orchestrates the pre-execution, ordering, and execution processes in the sharding consensus for minimal overhead. We rigorously prove the determinism and serializability of transactions under the Byzantine and sharded environment. An evaluation of our prototype shows that Prophet improves the throughput by 3.11×3.11\times and achieves nearly no aborts on 1 million Ethereum transactions compared with state-of-the-art sharding

    Silicon-based Integrated Microarray Biochips for Biosensing and Biodetection Applications

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    The silicon-based integrated microarray biochip (IMB) is an inter-disciplinary research direction of microelectronics and biological science. It has caught the attention of both industry and academia, in applications such as deoxyribonucleic acid (DNA) and immunological detection, medical inspection and point-of-care (PoC) diagnosis, as well as food safety and environmental surveillance. Future biodetection strategies demand biochips with high sensitivity, miniaturization, integration, parallel, multi-target and even intelligence capabilities. In this chapter, a comprehensive investigation of current research on state-of-the-art silicon-based integrated microarray biochips is presented. These include the electrochemical biochip, magnetic tunnelling junction (MTJ) based biochip, giant magnetoresistance (GMR) biochip and integrated oscillator-based biochip. The principles, methodologies and challenges of the aforementioned biochips will also be discussed and compared from all aspects, e.g., sensitivity, fabrication complexity and cost, compatibility with silicon-based complementary metal-oxide-semiconductor (CMOS) technology, multi-target detection capabilities, signal processing and system integrations, etc. In this way, we discuss future silicon-based fully integrated biochips, which could be used for portable medical detection and low cost PoC diagnosis applications

    Polymer nanocomposites: Synthetic and natural fillers a review

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    This paper reviews current research, techniques for characterization and trends on the field of nanocomposites. Nanocomposites are new materials made with fillers which have nanosize. These materials have a big potential for applications in the automotive and aerospace industry as well as in construction, electrical applications and food packing. There is a tremendous interest for using bionanoparticles like cellulose microfibrils or whiskers to be applied in the new era of biocomposites

    Maximizing Drilling Performance with Real-Time surveillance system Based on Parameters Optimization Algorithm

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    With deeper exploration and development of hydrocarbon reservoirs, a novel drilling parameters optimization algorithm, named as Navigation Optimization (NAVO) based on mechanical specific energy (MSE) theory, was investigated to continually improve the rate of penetration (ROP) and drilling performance. From the perspectives of rock mechanics and conservation of energy, the relationship among drilling parameters, ROP and MSE has been derived from comprehensive analysis of optimized drilling mechanism. Based on the R.Teale MSE model, the specific energy concept, considering the effect of hydraulics energy on rock breaking efficiency, is further extended based on the hydro-mechanical specific energy (HMSE). With the principle of maximum ROP and minimum HMSE, drilling parameter recommendation model was established, and a real-time drilling optimization system was developed and named as DrillNAV. The DrillNAV system could monitor all dynamic drilling parameters during drilling operations and feed back the advisory for drillers in real time. A pilot test showed the use of DrillNAV provided about 35% higher ROP with identification of downhole vibrations. It showed that NAVO algorithm can optimize drilling parameters in real time, which can be used to drilling performance evaluation and rock breaking analysis so as to raise the ROP and reduce drilling cost.Key Words: Navigation optimization; Hydro-mechanical Specific energy; Drilling parameter recommendation; DrillNAV systemWith deeper exploration and development of hydrocarbon reservoirs, a novel drilling parameters optimization algorithm, named as Navigation Optimization (NAVO) based on mechanical specific energy (MSE) theory, was investigated to continually improve the rate of penetration (ROP) and drilling performance. From the perspectives of rock mechanics and conservation of energy, the relationship among drilling parameters, ROP and MSE has been derived from comprehensive analysis of optimized drilling mechanism. Based on the R.Teale MSE model, the specific energy concept, considering the effect of hydraulics energy on rock breaking efficiency, is further extended based on the hydro-mechanical specific energy (HMSE). With the principle of maximum ROP and minimum HMSE, drilling parameter recommendation model was established, and a real-time drilling optimization system was developed and named as DrillNAV. The DrillNAV system could monitor all dynamic drilling parameters during drilling operations and feed back the advisory for drillers in real time. A pilot test showed the use of DrillNAV provided about 35% higher ROP with identification of downhole vibrations. It showed that NAVO algorithm can optimize drilling parameters in real time, which can be used to drilling performance evaluation and rock breaking analysis so as to raise the ROP and reduce drilling cost
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