Hydrodynamic signatures of stationary Marangoni-driven surfactant transport

We experimentally study steady Marangoni-driven surfactant transport on the interface of a deep water layer. Using hydrodynamic measurements, and without using any knowledge of the surfactant physico-chemical properties, we show that sodium dodecyl sulphate and Tergitol 15-S-9 introduced in low concentrations result in a flow driven by adsorbed surfactant. At higher surfactant concentration, the flow is dominated by the dissolved surfactant. Using Camphoric acid, whose properties are {\it a priori} unknown, we demonstrate this method's efficacy by showing its spreading is adsorption dominated

Force Distributions in Frictional Granular Media

We report a joint experimental and theoretical investigation of the probability distribution functions (pdf's) of the normal and tangential (frictional) forces in amorphous frictional media. We consider both the joint pdf of normal and tangential forces together, and the marginal pdf's of normal forces separately and tangential forces separately. A maximum entropy formalism is utilized for all these cases after identifying the appropriate constraints. Excellent agreements with both experimental and simulational data are reported. The proposed joint pdf (which appears new to the literature) predicts giant slip events at low pressures, again in agreement with observations.Comment: 13 pages, 15 figure

HTA: A Scalable High-Throughput Accelerator for Irregular HPC Workloads

We propose a new architecture called HTA for high throughput irregular HPC applications with little data reuse. HTA reduces the contention within the memory system with the help of a partitioned memory controller that is amenable for 2.5D implementation using Silicon Photonics. In terms of scalability, HTA supports 4 × higher number of compute units compared to the state-of-the-art GPU systems. Our simulation-based evaluation on a representative set of HPC benchmarks shows that the proposed design reduces the queuing latency by 10% to 30%, and improves the variability in memory access latency by 10% to 60%. Our results show that the HTA improves the L1 miss penalty by 2.3 × to 5 × over GPUs. When compared to a multi-GPU system with the same number of compute units, our simulation results show that the HTA can provide up to 2 × speedup

LLM: Realizing Low-Latency Memory by Exploiting Embedded Silicon Photonics for Irregular Workloads

As emerging workloads exhibit irregular memory access patterns with poor data reuse and locality, they would benefit from a DRAM that achieves low latency without sacrificing bandwidth and energy efficiency. We propose LLM (Low Latency Memory), a codesign of the DRAM microarchitecture, the memory controller and the LLC/DRAM interconnect by leveraging embedded silicon photonics in 2.5D/3D integrated system on chip. LLM relies on Wavelength Division Multiplexing (WDM)-based photonic interconnects to reduce the contention throughout the memory subsystem. LLM also increases the bank-level parallelism, eliminates bus conflicts by using dedicated optical data paths, and reduces the access energy per bit with shorter global bitlines and smaller row buffers. We evaluate the design space of LLM for a variety of synthetic benchmarks and representative graph workloads on a full-system simulator (gem5). LLM exhibits low memory access latency for traffics with both regular and irregular access patterns. For irregular traffic, LLM achieves high bandwidth utilization (over 80% peak throughput compared to 20% of HBM2.0). For real workloads, LLM achieves 3 × and 1.8 × lower execution time compared to HBM2.0 and a state-of-the-art memory system with high memory level parallelism, respectively. This study also demonstrates that by reducing queuing on the data path, LLM can achieve on average 3.4 × lower memory latency variation compared to HBM2.0

Distributed Adaptive Attitude Synchronization of Multiple Spacecraft

This paper addresses the distributed attitude synchronization problem of multiple spacecraft with unknown inertia matrices. Two distributed adaptive controllers are proposed for the cases with and without a virtual leader to which a time-varying reference attitude is assigned. The first controller achieves attitude synchronization for a group of spacecraft with a leaderless communication topology having a directed spanning tree. The second controller guarantees that all spacecraft track the reference attitude if the virtual leader has a directed path to all other spacecraft. Simulation examples are presented to illustrate the effectiveness of the results.Comment: 13 pages, 11 figures. To appear in SCIENCE CHINA Technological Science

Molecular Analysis of Serum and Bronchoalveolar Lavage in a Mouse Model of Influenza Reveals Markers of Disease Severity That Can Be Clinically Useful in Humans

Background: Management of influenza, a major contributor to the worldwide disease burden, is complicated by lack of reliable methods for early identification of susceptible individuals. Identification of molecular markers that can augment existing diagnostic tools for prediction of severity can be expected to greatly improve disease management capabilities. Methodology/Principal Findings: We have analyzed cytokines, proteome flux and protein adducts in bronchoalveolar lavage (BAL) and sera from mice infected with influenza A virus (PR8 strain) using a previously established non-lethal model of influenza infection. Through detailed cytokine and protein adduct measurements of murine BAL, we first established the temporal profile of innate and adaptive responses as well as macrophage and neutrophil activities in response to influenza infection. A similar analysis was also performed with sera from a longitudinal cohort of influenza patients. We then used an iTRAQ-based, comparative serum proteome analysis to catalog the proteome flux in the murine BAL during the stages correlating with “peak viremia,” “inflammatory damage,” as well as the “recovery phase.” In addition to activation of acute phase responses, a distinct class of lung proteins including surfactant proteins was found to be depleted from the BAL coincident with their “appearance” in the serum, presumably due to leakage of the protein following loss of the integrity of the lung/epithelial barrier. Serum levels of at least two of these proteins were elevated in influenza patients during the febrile phase of infection compared to healthy controls or to the same patients at convalescence. Conclusions/Significance: The findings from this study provide a molecular description of disease progression in a mouse model of influenza and demonstrate its potential for translation into a novel class of markers for measurement of acute lung injury and improved case management.Singapore. National Research FoundationSingapore-MIT Alliance for Research and Technology (ID-IRG research program

Meniscal T1rho and T2 measured with 3.0T MRI increases directly after running a marathon

PURPOSE: To prospectively evaluate changes in T1rho and T2 relaxation time in the meniscus using 3.0 T MRI in asymptomatic knees of marathon runners and to compare these findings with those of age-matched healthy subjects. MATERIAL AND METHODS: Thirteen marathon runners underwent 3.0 T MRI including T1rho and T2 mapping sequences before, 48-72 h after, and 3 months after competition. Ten controls were examined at baseline and after 3 months. All images were analyzed by two musculoskeletal radiologists identifying and grading cartilage, meniscal, ligamentous. and other knee abnormalities with WORMS scores. Meniscal segmentation was performed to generate T1rho and T2 maps in six compartments. RESULTS: No differences in morphological knee abnormalities were found before and after the marathon. However, all marathon runners showed a significant increase in T1rho and T2 values after competition in all meniscus compartments (p < 0.0001), which may indicate changes in the biochemical composition of meniscal tissue. While T2 values decreased after 3 months T1rho values remained at a high level, indicating persisting changes in the meniscal matrix composition after a marathon. CONCLUSION: T2 values in menisci have the potential to be used as biomarkers for identifying reversible meniscus matrix changes indicating potential tissue damage. T1rho values need further study, but may be a valuable marker for diagnosing early, degenerative changes in the menisci following exercise

A Bacterial Acetyltransferase Destroys Plant Microtubule Networks and Blocks Secretion

The eukaryotic cytoskeleton is essential for structural support and intracellular transport, and is therefore a common target of animal pathogens. However, no phytopathogenic effector has yet been demonstrated to specifically target the plant cytoskeleton. Here we show that the Pseudomonas syringae type III secreted effector HopZ1a interacts with tubulin and polymerized microtubules. We demonstrate that HopZ1a is an acetyltransferase activated by the eukaryotic co-factor phytic acid. Activated HopZ1a acetylates itself and tubulin. The conserved autoacetylation site of the YopJ / HopZ superfamily, K289, plays a critical role in both the avirulence and virulence function of HopZ1a. Furthermore, HopZ1a requires its acetyltransferase activity to cause a dramatic decrease in Arabidopsis thaliana microtubule networks, disrupt the plant secretory pathway and suppress cell wall-mediated defense. Together, this study supports the hypothesis that HopZ1a promotes virulence through cytoskeletal and secretory disruption

Increasing microtubule acetylation rescues axonal transport and locomotor deficits caused by LRRK2 Roc-COR domain mutations

​Leucine-rich repeat kinase 2 (​LRRK2) mutations are the most common genetic cause of Parkinson’s disease. ​LRRK2 is a multifunctional protein affecting many cellular processes and has been described to bind microtubules. Defective microtubule-based axonal transport is hypothesized to contribute to Parkinson’s disease, but whether ​LRRK2 mutations affect this process to mediate pathogenesis is not known. Here we find that ​LRRK2 containing pathogenic Roc-COR domain mutations (R1441C, Y1699C) preferentially associates with deacetylated microtubules, and inhibits axonal transport in primary neurons and in Drosophila, causing locomotor deficits in vivo. In vitro, increasing microtubule acetylation using deacetylase inhibitors or the tubulin acetylase ​αTAT1 prevents association of mutant ​LRRK2 with microtubules, and the deacetylase inhibitor ​trichostatin A (​TSA) restores axonal transport. In vivo knockdown of the deacetylases ​HDAC6 and ​Sirt2, or administration of ​TSA rescues both axonal transport and locomotor behavior. Thus, this study reveals a pathogenic mechanism and a potential intervention for Parkinson’s disease