Elastomers with excellent mechanical properties are in substantial demand for various applications, but there is always a tradeoff between their mechanical strength and stretchability. For example, ...partially replacing strong covalent crosslinking by weak sacrificial bonds can enhance the stretchability but also usually decreases the mechanical strength. To surmount this inherent tradeoff, a supramolecular strategy of introducing a zipper‐like sliding‐ring mechanism in a hydrogen‐bond‐crosslinked polyurethane network is proposed. A very small amount (0.5 mol%) of an external additive (pseudo2rotaxane crosslinker) can dramatically increase both the mechanical strength and elongation of this polyurethane network by nearly one order of magnitude. Based on the investigation of the relationship between molecular structure and mechanical properties, this enhancement is attributable to a unique molecular‐level zipper‐like ring‐sliding motion, which efficiently dissipates mechanical work in the solvent‐free network. This research not only provides a distinct and general strategy for the construction of high‐performance elastomers but also paves the way for the practical application of artificial molecular machines toward solvent‐free polyurethane networks.
A molecular zipper elastomer—the combination of ring‐sliding effects and dense hydrogen‐bonding crystal domains in a dry polymer network—results in unexpectedly substantial improvements to the elastomer mechanical performance, including stretchability and strength. The mechanism is found to be the ring‐sliding motion against hydrogen‐bonding domains upon stretching, which effectively dissipates the input mechanical energy.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Hadoop is a popular implementation of the MapReduce framework for running data-intensive jobs on clusters of commodity servers. Shuffle, the all-to-all input data fetching phase between the map and ...reduce phase can significantly affect job performance. However, the shuffle phase and reduce phase are coupled together in Hadoop and the shuffle can only be performed by running the reduce tasks. This leaves the potential parallelism between multiple waves of map and reduce unexploited and resource wastage in multi-tenant Hadoop clusters, which significantly delays the completion of jobs in a multi-tenant Hadoop cluster. More importantly, Hadoop lacks the ability to schedule task efficiently and mitigate the data distribution skew among reduce tasks, which leads to further degradation of job performance. In this work, we propose to decouple shuffle from reduce tasks and convert it into a platform service provided by Hadoop. We present iShuffle, a user-transparent shuffle service that pro-actively pushes map output data to nodes via a novel shuffle-on-write operation and flexibly schedules reduce tasks considering workload balance. Experimental results with representative workloads and Facebook workload trace show that iShuffle reduces job completion time by as much as 29.6 and 34 percent in single-user and multi-user clusters, respectively.
Spinal cord injury (SCI) often leads to permanent loss of motor, sensory, and autonomic functions.We have previously shown that neurotrophin3 (NT3)-loaded chitosan biodegradable material allowed for ...prolonged slow release of NT3 for 14 weeks under physiological conditions. Here we report that NT3-loaded chitosan, when inserted into a 1-cm gap of hemisectioned and excised adult rhesus monkey thoracic spinal cord, elicited robust axonal regeneration. Labeling of cortical motor neurons indicated motor axons in the corticospinal tract not only entered the injury site within the biomaterial but also grew across the 1-cm-long lesion area and into the distal spinal cord. Through a combination of magnetic resonance diffusion tensor imaging, functional MRI, electrophysiology, and kinematics-based quantitative walking behavioral analyses, we demonstrated that NT3-chitosan enabled robust neural regeneration accompanied by motor and sensory functional recovery. Given that monkeys and humans share similar genetics and physiology, our method is likely translatable to human SCI repair.
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A supramolecular network and its film were prepared via intermolecular hydrogen bonding of a 2rotaxane with three ureido pyrimidinone groups. Adding less polar solvents such as CHCl3 to the rotaxane ...afforded a swollen rotaxane-cross-linked network. The properties of the film obtained by drying were evaluated to characterize it.
Datacenter-scale clusters are evolving toward heterogeneous hardware architectures due to continuous server replacement. Meanwhile, datacenters are commonly shared by many users for quite different ...uses. It often exhibits significant performance heterogeneity due to multi-tenant interferences. The deployment of MapReduce on such heterogeneous clusters presents significant challenges in achieving good application performance compared to in-house dedicated clusters. As most MapReduce implementations are originally designed for homogeneous environments, heterogeneity can cause significant performance deterioration in job execution despite existing optimizations on task scheduling and load balancing. In this paper, we observe that the homogeneous configuration of tasks on heterogeneous nodes can be an important source of load imbalance and thus cause poor performance. Tasks should be customized with different configurations to match the capabilities of heterogeneous nodes. To this end, we propose a self-adaptive task tuning approach, Ant, that automatically searches the optimal configurations for individual tasks running on different nodes. In a heterogeneous cluster, Ant first divides nodes into a number of homogeneous subclusters based on their hardware configurations. It then treats each subcluster as a homogeneous cluster and independently applies the self-tuning algorithm to them. Ant finally configures tasks with randomly selected configurations and gradually improves tasks configurations by reproducing the configurations from best performing tasks and discarding poor performing configurations. To accelerate task tuning and avoid trapping in local optimum, Ant uses genetic algorithm during adaptive task configuration. Experimental results on a heterogeneous physical cluster with varying hardware capabilities show that Ant improves the average job completion time by 31, 20, and 14 percent compared to stock Hadoop (Stock), customized Hadoop with industry recommendations (Heuristic), and a profilingbased configuration approach (Starfish), respectively. Furthermore, we extend Ant to virtual MapReduce clusters in a multi-tenant private cloud. Specifically, Ant characterizes a virtual node based on two measured performance statistics: I/O rate and CPU steal time. It uses k-means clustering algorithm to classify virtual nodes into configuration groups based on the measured dynamic interference. Experimental results on virtual clusters with varying interferences show that Ant improves the average job completion time by 20, 15, and 11 percent compared to Stock, Heuristic and Starfish, respectively.
Load imbalance is a major source of overhead in parallel programs such as MapReduce. Due to the uneven distribution of input data, tasks with more data become stragglers and delay the overall job ...completion. Running Hadoop in a private cloud opens up opportunities for expediting stragglers with more resources but also introduces problems that often outweigh the performance gain: (1) performance interference from co-running jobs may create new stragglers; (2) there exists a semantic gap between the Hadoop task management and resource pool-based virtual cluster management preventing tasks from using resources efficiently. In this paper, we strive to make Hadoop more resilient to data skew and more efficient in cloud environments. We present FlexSlot, a usertransparent task slot management scheme that automatically identifies map stragglers and resizes their slots accordingly to accelerate task execution. FlexSlot adaptively changes the number of slots on each virtual node to balance the resource usage so that the pool of resources can be efficiently utilized. FlexSlot further improves mitigation of data skew with an adaptive speculative execution strategy. Experimental results show that FlexSlot effectively reduces job completion time up to 47.2 percent compared to stock Hadoop and two recently proposed skew mitigation and speculative execution approaches.
Clinical evaluations of long-term outcomes in the early-stage spinal cord injury (SCI) focus on macroscopic motor performance and are limited in their prognostic precision. This study was designed to ...investigate the sensitivity of the magnetic resonance imaging (MRI) indexes to the data-driven gait process after SCI. Ten adult female rhesus monkeys were subjected to thoracic SCI. Kinematics-based gait examinations were performed at 1 (early stage) and 12 (chronic stage) months post-SCI. The proportion of stepping (PS) and gait stability (GS) were calculated as the outcome measures. MRI metrics, which were derived from structural imaging (spinal cord cross-sectional area, SCA) and diffusion tensor imaging (fractional anisotropy, FA; axial diffusivity, λ//), were acquired in the early stage and compared with functional outcomes by using correlation analysis and stepwise multivariable linear regression. Residual tissue SCA at the injury epicenter and residual tissue FA/remote normal-like tissue FA were correlated with the early-stage PS and GS. The extent of lesion site λ///residual tissue λ// in the early stage after SCI was correlated with the chronic-stage GS. The ratios of lesion site λ// to residual tissue λ// and early-stage GS were predictive of the improvement in the PS at follow-up. Similarly, the ratios of lesion site λ// to residual tissue λ// and early-stage PS best predicted chronic GS recovery. Our findings demonstrate the predictive power of MRI combined with the early data-driven gait indexes for long-term outcomes. Such an approach may help clinicians to predict functional recovery accurately.
•BPHs were prepared into LM-1 (<1 kDa) and HM-2 (1–30 kDa) fractions.•HM-2 promoted fermentation of soy sauce aroma-producing yeast Z. rouxii.•HM-2 promoted the accumulation of intracellular K+ and ...glycerol.•HM-2 improved cell membrane integrity and decreased intracellular ROS.
Supplementation of protein hydrolysate is an important strategy to improve the salt tolerance of soy sauce aroma-producing yeast. In the present study, Tartary buckwheat protein hydrolysates (BPHs) were prepared and separated by ultrafiltration into LM-1 (<1 kDa) and HM-2 (1–300 kDa) fractions. The supplementation of HM-2 fraction could significantly improve cell growth and fermentation of soy sauce aroma-producing yeast Zygosaccharomyces rouxii As2.180 under high salt (12%, w/w) conditions. However, the LM-1 fraction inhibited strain growth and fermentation. The addition of HM-2 promoted yeast cell accumulation of K+, removal of cytosolic Na+ and accumulation of glycerol. Furthermore, the HM-2 fraction improved the cell membrane integrity and mitochondrial membrane and decreased intracellular ROS accumulation of the strain. The above results indicated that the supplementation of BPHs with a molecular weight of 1–300 kDa is a potentially effective and feasible strategy for improving the salt tolerance of soy sauce aroma-producing yeast Z. rouxii.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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