Hare: a file system for non-cache-coherent multicores

Hare is a new file system that provides a POSIX-like interface on multicore processors without cache coherence. Hare allows applications on different cores to share files, directories, and file descriptors. The challenge in designing Hare is to support the shared abstractions faithfully enough to run applications that run on traditional shared-memory operating systems, with few modifications, and to do so while scaling with an increasing number of cores. To achieve this goal, Hare must support features (such as shared file descriptors) that traditional network file systems don't support, as well as implement them in a way that scales (e.g., shard a directory across servers to allow concurrent operations in that directory). Hare achieves this goal through a combination of new protocols (including a 3-phase commit protocol to implement directory operations correctly and scalably) and leveraging properties of non-cache-coherent multiprocessors (e.g., atomic low-latency message delivery and shared DRAM). An evaluation on a 40-core machine demonstrates that Hare can run many challenging Linux applications (including a mail server and a Linux kernel build) with minimal or no modifications. The results also show these applications achieve good scalability on Hare, and that Hare's techniques are important to achieving scalability.Quanta Computer (Firm

Size-Effect of Pd-(Poly(N-vinyl-2-pyrrolidone)) Nanocatalysts on Selective Hydrogenation of Alkynols with Different Alkyl Chains

We have studied the effect of unsupported Pd nanoparticle (NP) size in the selective C C semi-hydrogenation of alkynols with different alkyl chains, i.e., C-16 in dehydroisophytol (DIP) (to isophytol (IP)) vs C-1 in 2-methyl-3-butyn-2-ol (MBY) (to 2-methyl-3-buten-2-ol (MBE)). The Pd NPs were synthesized via colloidal technique with poly(N-vinyl-2-pyrrolidone) (PVP) as stabilizing agent where a range of crystal sizes (2.1-9.8 nm; confirmed by HRTEM) was generated. Both reactions show antipathetic structure sensitivity consistent with higher specific activity (TOF) over larger Pd NPs where the structure sensitivity effect is more pronounced for NPs = 88%) selectivity to the target alkenol product at almost complete (98%) conversion. Increased IP selectivity (S-IP; (XDIP=98%) ca. 95%) was observed over smaller (2.1-3.0 nm) Pd NPs while ca. 98% selectivity to MBE (S-MBE; XDIP=98%) is obtained irrespective of particle size. The kinetic results were consistent with a Langmuir-Hinshelwood model. The observed Pd NPs size effect on catalytic response is ascribed to a contribution of Pd electronic surface modifications, fraction of Pd-plane active sites and the steric effects which impact akynol/alkenol adsorption constants. The results obtained in this work provide a powerful tool for catalyst design for industrial applications