Replication-Based Fault Tolerance for MPI Applications

As computational clusters increase in size, their mean time to failure reduces drastically. Typically, checkpointing is used to minimize the loss of computation. Most checkpointing techniques, however, require central storage for storing checkpoints. This results in a bottleneck and severely limits the scalability of checkpointing, while also proving to be too expensive for dedicated checkpointing networks and storage systems. We propose a scalable replication-based MPI checkpointing facility. Our reference implementation is based on LAM/MPI; however, it is directly applicable to any MPI implementation. We extend the existing state of fault-tolerant MPI with asynchronous replication, eliminating the need for central or network storage. We evaluate centralized storage, a Sun-X4500-based solution, an EMC storage area network (SAN), and the Ibrix commercial parallel file system and show that they are not scalable, particularly after 64 CPUs. We demonstrate the low overhead of our checkpointing and replication scheme with the NAS Parallel Benchmarks and the High-Performance LINPACK benchmark with tests up to 256 nodes while demonstrating that checkpointing and replication can be achieved with a much lower overhead than that provided by current techniques. Finally, we show that the monetary cost of our solution is as low as 25 percent of that of a typical SAN/parallel-file-system-equipped storage system.     

Experimental investigation of Co and Fe-Doped CuO nanostructured electrode material for remarkable electrochemical performance

The current research work presents a facile and cost–effective co-precipitation method to prepare doped (Co & Fe) CuO and undoped CuO nanostructures without usage of any type of surfactant or capping agents. The structural analysis reveals monoclinic crystal structure of synthesized pure CuO and doped-CuO nanostructures. The effect of different morphologies on the performance of supercapacitors has been found in CV (cyclic voltammetry) and GCD (galvanic charge discharge) investigations. The specific capacitances have been obtained 156 (±5) Fg^?1, 168(±5) Fg^?1 and 186 (±5) Fg^?1 for CuO, Co-doped CuO and Fe-doped CuO electrodes, respectively at scan rate of 5 mVs^?1, while it is found to be 114 (±5) Fg^?1, 136 (±5) Fg^?1 and 170 (±5) Fg^?1 for CuO, Co–CuO and Fe–CuO, respectively at 0.5 Ag^-1 as calculated from the GCD. The super capacitive performance of the Fe–CuO nanorods is mainly attributed to the synergism that evolves between CuO and Fe metal ion. The Fe-doped CuO with its nanorods like morphology provides superior specific capacitance value and excellent cyclic stability among all studied nanostructured electrodes. Consequently, it motivates to the use of Fe-doped CuO nanostructures as electrode material in the next generation energy storage devices.     

Discovery of Aporphine Analogues as Potential Antiplatelet and Antioxidant Agents: Design,Synthesis, Structure–Activity Relationships,Biological Evaluations,and in silico Molecular Docking Studies

To explore the potential of aporphine alkaloids, a novel series of functionalized aporphine analogues with alkoxy (OCH₃, OC₂H₅, OC₃H₇) functional groups at C1/C2 of ring A and an acyl (COCH₃ and COPh) or phenylsulfonyl (SO₂Ph and SO₂C₆H₄‐3‐CH₃) functionality at the N6 position of ring B of the aporphine scaffold were synthesized and evaluated for their arachidonic acid (AA)‐induced antiplatelet aggregation inhibitory activity and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free‐radical‐scavenging antioxidant activity, with acetylsalicylic acid and ascorbic acid as standard references, respectively. The preliminary structure–activity relationship related to AA‐induced platelet aggregation inhibitory activity results showed that the aporphine analogues 1‐[1,2,9,10‐tetramethoxy‐6a,7‐dihydro‐4H‐dibenzo[de,g]quinolin‐6(5H)‐yl]ethanone and 1‐[2‐(benzyloxy)‐1,9,10‐trimethoxy‐6a,7‐dihydro‐4H‐dibenzo[de,g]quinolin‐6(5H)‐yl]ethanone to be the best compounds of the series. Moreover, the DPPH free‐radical‐scavenging antioxidant activity results demonstrated that the aporphine analogues 1,2,9,10‐tetramethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, 2‐ethoxy‐1,9,10‐trimethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, 1‐ethoxy‐2,9,10‐trimethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, 2,9,10‐trimethoxy‐6‐(methylsulfonyl)‐1‐propoxy‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, and 1‐(benzyloxy)‐2,9,10‐trimethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline were the best compounds of the series. Moreover, in silico molecular docking simulation studies of the active analogues were also performed.     

Dielectric properties of sol–gel synthesized SrTiO3/(Ba0.7Sr0.3)TiO3 and SrTiO3/Ba(Zr0.3Ti0.7)O3 thin film heterostructures

The paper presents synthesis of Ba_0.7Sr_0.3TiO₃ (BST), BaZr_0.3Ti_0.7O₃ (BZT) and SrTiO₃ (ST) thin films and their heterostructures using modified Pechini method. The La_0.7Sr_0.3MnO₃ has been used as a conducting bottom layer to form metal ferroelectric metal capacitor. The thin films are spin coated on SiO₂/n-Si(100) substrates. The thin films thus deposited are characterized for crystal structure, morphology, dielectric, complex impedance and admittance properties. Deposition of surface layer ST is observed to reduce loss tangent tan δ of BST and BZT thin films, still maintaining equivalent magnitude of figure of merit γ. The results on dielectric properties are analyzed in terms of the Maxwell–Wagner model and Koop’s phenomenological theory.     

An investigation into surface energetics of rice hull ash particles using Inverse Gas Chromatography (IGC)

Silanol groups that are present on the surface of rice hull ash or silica ash fillers can positively influence the reinforcing character of the filler. However, being hydrophilic, they present the problem of aggregation and moisture absorption. Physicochemical contributions to reinforcement, provided by silanol groups, influence the filler-polymer and filler-filler interactions. In this study, we investigated the surface energetics of silica ash particles and the effect of chemical surface modification on the free surface energy of silica ash particles was studied.Inverse Gas Chromatography (IGC), a successful evaluation technique for the surface energy of solids, has been used at infinite dilution to determine the nature of surface interaction of various probes with a silica ash surface. The Gibbs free energies and enthalpies of specific interactions were also determined to estimate the acid-base characteristics of the surface of silica ash particles. The influence of heat treatment and surface modification upon the physicochemical parameters was also investigated. It was found that the silica ash surface is acidic in nature. Modification of the surface, by hydrophobization using silane agents, reduces the specific component of surface energy and could be expected to positively affect the reinforcing character. Surface modification reduced the specific component of surface energy by 80% and positively affects the filler-matrix interaction.     

Transient Turbulent Flow in a Liquid-Metal Model of Continuous Casting,Including Comparison of Six Different Methods

Computational modeling is an important tool to understand and stabilize transient turbulent fluid flow in the continuous casting of steel to minimize defects. The current work combines the predictions of two steady Reynolds-averaged Navier–Stokes (RANS) models, a “filtered” unsteady RANS model, and two large eddy simulation (LES) models with ultrasonic Doppler velocimetry (UDV) measurements in a small-scale liquid GaInSn model of the continuous casting mold region fed by a bifurcated well-bottom nozzle with horizontal ports. Both mean and transient features of the turbulent flow are investigated. LES outperformed all models while matching the measurements, except in locations where measurement problems are suspected. The LES model also captured high-frequency fluctuations, which the measurements could not detect. Steady RANS models were the least accurate methods. Turbulent velocity variation frequencies and energies decreased with distance from the nozzle port regions. Proper orthogonal decomposition analysis, instantaneous velocity patterns, and Reynolds stresses reveal that velocity fluctuations and flow structures associated with the alternating-direction swirl in the nozzle bottom lead to a wobbling jet exiting the ports into the mold. These turbulent flow structures are responsible for patterns observed in both the time average flow and the statistics of their fluctuations.