Write-Optimal Radix Tree: A Deterministic Indexing Structure for Persistent Memory Storage Systems

Department of Computer Science and EngineeringRecent interest in persistent memory (PM) has stirred development of index structures that are efficient in PM. Recent such developments have all focused on variations of the B-tree. In this paper, we show that the radix tree, which is another less popular indexing structure, can be more appropriate as an efficient PM indexing structure. This is because the radix tree structure is determined by the prefix of the inserted keys and also does not require tree rebalancing operations and node granularity updates. However, the radix tree as-is cannot be used in PM. As another contribution, we present three radix tree variants, namely, WORT (Write Optimal Radix Tree), WOART (Write Optimal Adaptive Radix Tree), and ART+CoW. Of these, the first two are optimal for PM in the sense that theyonly use one 8-byte failure-atomic write per update to guarantee the consistency of the structure and do not require any duplicate copies for logging or CoW. Extensive performance studies show that our proposed radix tree variants perform considerable better thanrecently proposed B-tree variants for PM such NVTree, wB+Tree, and FPTree for synthetic workloads as well as in implementations within Memcached.ope

DINOMO: An Elastic, Scalable, High-Performance Key-Value Store for Disaggregated Persistent Memory (Extended Version)

We present Dinomo, a novel key-value store for disaggregated persistent memory (DPM). Dinomo is the first key-value store for DPM that simultaneously achieves high common-case performance, scalability, and lightweight online reconfiguration. We observe that previously proposed key-value stores for DPM had architectural limitations that prevent them from achieving all three goals simultaneously. Dinomo uses a novel combination of techniques such as ownership partitioning, disaggregated adaptive caching, selective replication, and lock-free and log-free indexing to achieve these goals. Compared to a state-of-the-art DPM key-value store, Dinomo achieves at least 3.8x better throughput on various workloads at scale and higher scalability, while providing fast reconfiguration.Comment: This is an extended version of the full paper to appear in PVLDB 15.13 (VLDB 2023

Ga-doped Pt-Ni Octahedral Nanoparticles as a Highly Active and Durable Electrocatalyst for Oxygen Reduction Reaction

Bimetallic PtNi nanoparticles have been considered as a promising electrocatalyst for oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs) owing to their high catalytic activity. However, under typical fuel cell operating conditions, Ni atoms easily dissolve into the electrolyte, resulting in degradation of the catalyst and the membrane-electrode assembly (MEA). Here, we report gallium-doped PtNi octahedral nanoparticles on a carbon support (Ga-PtNi/C). The Ga-PtNi/C shows high ORR activity, marking an 11.7-fold improvement in the mass activity (1.24 A mgPt-1) and a 17.3-fold improvement in the specific activity (2.53 mA cm-2) compare to the commercial Pt/C (0.106 A mgPt-1 and 0.146 mA cm-2). Density functional theory calculations demonstrate that addition of Ga to octahedral PtNi can cause an increase in the oxygen intermediate binding energy, leading to the enhanced catalytic activity toward ORR. In a voltage-cycling test, the Ga-PtNi/C exhibits superior stability to PtNi/C and the commercial Pt/C, maintaining the initial Ni concentration and octahedral shape of the nanoparticles. Single cell using the Ga-PtNi/C exhibits higher initial performance and durability than those using the PtNi/C and the commercial Pt/C. The majority of the Ga-PtNi nanoparticles well maintain the octahedral shape without agglomeration after the single cell durability test (30,000 cycles). This work demonstrates that the octahedral Ga-PtNi/C can be utilized as a highly active and durable ORR catalyst in practical fuel cell applications

Ga-doped Pt-Ni Octahedral Nanoparticles as a Highly Active and Durable Electrocatalyst for Oxygen Reduction Reaction

Bimetallic PtNi nanoparticles have been considered as a promising electrocatalyst for oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs) owing to their high catalytic activity. However, under typical fuel cell operating conditions, Ni atoms easily dissolve into the electrolyte, resulting in degradation of the catalyst and the membrane-electrode assembly (MEA). Here, we report gallium-doped PtNi octahedral nanoparticles on a carbon support (Ga-PtNi/C). The Ga-PtNi/C shows high ORR activity, marking an 11.7-fold improvement in the mass activity (1.24 A mgPt-1) and a 17.3-fold improvement in the specific activity (2.53 mA cm-2) compare to the commercial Pt/C (0.106 A mgPt-1 and 0.146 mA cm-2). Density functional theory calculations demonstrate that addition of Ga to octahedral PtNi can cause an increase in the oxygen intermediate binding energy, leading to the enhanced catalytic activity toward ORR. In a voltage-cycling test, the Ga-PtNi/C exhibits superior stability to PtNi/C and the commercial Pt/C, maintaining the initial Ni concentration and octahedral shape of the nanoparticles. Single cell using the Ga-PtNi/C exhibits higher initial performance and durability than those using the PtNi/C and the commercial Pt/C. The majority of the Ga-PtNi nanoparticles well maintain the octahedral shape without agglomeration after the single cell durability test (30,000 cycles). This work demonstrates that the octahedral Ga-PtNi/C can be utilized as a highly active and durable ORR catalyst in practical fuel cell applications

iDO: Compiler-Directed Failure Atomicity for Nonvolatile Memory

This paper presents iDO, a compiler-directed approach to failure atomicity with nonvolatile memory. Unlike most prior work, which instruments each store of persistent data for redo or undo logging, the iDO compiler identifies idempotent instruction sequences, whose re-execution is guaranteed to be side-effect-free, thereby eliminating the need to log every persistent store. Using an extension of prior work on JUSTDO logging, the compiler then arranges, during recovery from failure, to back up each thread to the beginning of the current idempotent region and re-execute to the end of the current failure-Atomic section. This extension transforms JUSTDO logging from a technique of value only on hypothetical future machines with nonvolatile caches into a technique that also significantly outperforms state-of-The art lock-based persistence mechanisms on current hardware during normal execution, while preserving very fast recovery times

Improved Battery Performance of Nanocrystalline Si Anodes Utilized by Radio Frequency (RF) Sputtered Multifunctional Amorphous Si Coating Layers

Despite the high theoretical specific capacity of Si, commercial Li-ion batteries (LIBs) based on Si are still not feasible because of unsatisfactory cycling stability. Herein, amorphous Si (a-Si)-coated nanocrystalline Si (nc-Si) formed by versatile radio frequency (RF) sputtering systems is proposed as a promising anode material for LIBs. Compared to uncoated nc-Si (retention of 0.6% and Coulombic efficiency (CE) of 79.7%), the a-Si-coated nc-Si (nc-Si@a-Si) anodes show greatly improved cycling retention (C_50th/C_first) of ∼50% and a first CE of 86.6%. From the ex situ investigation with electrochemical impedance spectroscopy (EIS) and cracked morphology during cycling, the a-Si layer was found to be highly effective at protecting the surface of the nc-Si from the formation of solid-state electrolyte interphases (SEI) and to dissipate the mechanical stress upon de/lithiation due to the high fracture toughness

Defect-Free Erbium Silicide Formation Using an Ultrathin Ni Interlayer

An ultrathin Ni interlayer (∼1 nm) was introduced between a TaN-capped Er film and a Si substrate to prevent the formation of surface defects during thermal Er silicidation. A nickel silicide interfacial layer formed at low temperatures and incurred uniform nucleation and the growth of a subsequently formed erbium silicide film, effectively inhibiting the generation of recessed-type surface defects and improving the surface roughness. As a side effect, the complete transformation of Er to erbium silicide was somewhat delayed, and the electrical contact property at low annealing temperatures was dominated by the nickel silicide phase with a high Schottky barrier height. After high-temperature annealing, the early-formed interfacial layer interacted with the growing erbium silicide, presumably forming an erbium silicide-rich Er–Si–Ni mixture. As a result, the electrical contact property reverted to that of the low-resistive erbium silicide/Si contact case, which warrants a promising source/drain contact application for future high-performance metal–oxide–semiconductor field-effect transistors

Real-world outcomes with immuno-oncology therapies in advanced melanoma: Final results of the OPTIMIzE registry study

Aim: The OPTIMIzE registry study evaluated real-world outcomes in patients with advanced melanoma receiving immuno-oncology therapies. Materials and methods: Data were collected for patients treated with anti-programmed death 1 (PD-1) monotherapy (nivolumab or pembrolizumab; n = 147) or nivolumab plus ipilimumab (n = 81) from 2015-2017 and followed for ≥3 years. Results: Nivolumab plus ipilimumab versus anti-PD-1 monotherapy was associated with a nonsignificantly lower risk of death (adjusted HR: 0.83; 95% CI: 0.54-1.28; p = 0.41), higher disease control rate (72 vs 56%; p = 0.04), and stable quality of life, but more grade 3-4 treatment-related adverse events (54 vs 26%; p \u3c 0.0001). Conclusion: These results support the use of immuno-oncology therapy in advanced melanoma