Publications

The advent of RoCE (RDMA over Converged Ethernet) has led to a significant increase in the use of RDMA in datacenter networks. To achieve good performance, RoCE requires a lossless network which is in turn achieved by enabling Priority Flow Control (PFC) within the network. However, PFC brings with it a host of problems such as head-of-the-line blocking, congestion spreading, and occasional deadlocks. Rather than seek to fix these issues, we instead ask: is PFC fundamentally required to support RDMA over Ethernet?

Abstract Atherosclerosis, a chronic vascular disease, is characterized by deposition of fatty substances and accumulation of immune cells in susceptible regions of arteries. Increasing evidence show that abnormal metabolic conditions, such as dyslipdemia and diabetes, induce immune cell activation and inflammation, which play crucial roles in progression of atherosclerosis. However, molecular linkers of metabolic disorder, immune activation and atherosclerosis are not well understood. Here we report that ligands for NKG2D, an immune-activating receptor, were upregulated in multiple tissues and organs under atherosclerotic disease condition, particularly in atherosclerotic lesion and liver. Preventing NKG2D/ligands interaction significantly reduced atherosclerotic lesion formation and systemic inflammation. In addition, preventing NKG2D/ligand interaction alleviated abnormal metabolic conditions by suppressing liver inflammation. Our data clearly show that NKG2D/ligand interaction plays critical roles in the progression of atherosclerosis and might be potential targets against atherosclerosis.

A detailed exploration and systematic evaluation of V₂O₅ as a cathode material for multi-valent batteries using first-principles.

Abstract Magnetotactic bacteria (MTB) are ubiquitous aquatic microorganisms that form intracellular nanoparticles of magnetite (Fe 3 O 4 ) or greigite (Fe 3 S 4 ) in a genetically controlled manner. Magnetite and greigite synthesis requires MTB to transport a large amount of iron from the environment which is subsequently concentrated in organelles called magnetosomes for crystal precipitation and maturation. X-ray absorption analysis of MTB suggests that the intracellular iron is mainly contained within the crystals, thus preventing potential toxic effects of free iron. In contrast, recent mass spectrometry studies suggest that MTB may contain a large amount of iron that is not precipitated in crystals. Here, we attempt to resolve these descrepancies by performing chemical and magnetic assays to quantify the different iron pools in the magnetite-forming strain Magnetospirillum magneticum AMB-1 cultivated at varying iron concentrations. AMB-1 mutants showing defects in crystal precipitation were also characterized following the same approach. All results show that magnetite represents at most 30 % of the total intracellular iron under our experimental conditions. We further examined the iron speciation and subcellular localization in AMB-1 using the fluorescent indicator FIP-1 that is designed for detection of labile Fe(II). Staining with this probe suggests that unmineralized reduced iron is found in the cytoplasm and associated with magnetosomes. Our results demonstrate that, under our experimental conditions, AMB-1 is able to accumulate a large pool of iron distinct from magnetite. Finally, we discuss the biochemical and geochemical implications of these results. Importance Magnetotactic bacteria (MTB) are a group of microorganisms producing iron-based intracellular magnetic crystals. They represent a model system for studying iron homeostasis and biomineralization in bacteria. MTB contain an important mass of iron, about 10 to 100 higher than other bacterial model such as Escherichia coli , suggesting efficient iron uptake and storage systems. Accordingly, MTB have been proposed to significantly impact the iron biogeochemical cycle in sequestering a large amount of soluble iron into crystals. Recently, several studies proposed that MTB could also accumulate iron in a reservoir distinct from their crystals. Here, we present a chemical and magnetic methodology for quantifying the fraction of the total cellular iron contained in the magnetic crystals of the magnetotactic strain Magnetospirillum magneticum AMB-1. Comparison of the mass of iron contained in the different cellular pools showed that most of the bacterial iron is not contained in AMB-1 crystals. We then adapted protocols for the fluorescent detection of Fe(II) in bacteria, and showed that iron could be detected outside of crystals using fluorescence assays. This work suggests a more complex picture for iron homeostasis in MTB than previously thought. Because iron speciation controls its solubility, our results also provide important insights into the geochemical impact of MTB. A large pool of unmineralized iron in MTB could be more easily released in the environment than magnetite, thus limiting iron sequestration into MTB crystals.

Calcium dodecahydro-closo-dodecaborate, CaB12H12, was calculated to have a percolating Ca migration path with low activation barrier (650 meV). The formation of Ca vacancies required for diffusion was calculated to be thermodynamically feasible by substitution of Ca with Al, Bi, or a number of trivalent rare-earth cations

The maximum free-electron concentration is observed to increase dramatically with the nitrogen content $x$ in heavily Se-doped ${\mathrm{Ga}}_{1\ensuremath{-}3x}{\mathrm{In}}_{3x}{\mathrm{N}}_{x}{\mathrm{As}}_{1\ensuremath{-}x}$ $(0<~x<0.033)$ films. For example, an electron concentration of $7\ifmmode\times\else\texttimes\fi{}{10}^{19} {\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ was observed at $x=0.033;$ a value more than 20 times larger than that observed in GaAs films grown under similar conditions. It is shown that the increase is caused by a combination of two effects: (1) a downward shift of the conduction band and (2) an increase of the electron effective mass caused by flattening of the conduction-band minimum. Both these effects are due to modifications to the conduction-band structure caused by an anticrossing interaction of a localized $N$ state and the conduction band of the III-V host.

Paleomagnetic studies of the 91 Ma Ecstall pluton and other Cretaceous plutons of British Columbia imply large northward tectonic movements (>2000 km) may have occurred during the tectonic evolution of western North America. However, more recent studies have shown that the eastern edge of the Ecstall pluton experienced considerable mineralogical changes as younger Eocene plutons, such as the ∼58 Ma Quottoon Pluton, were emplaced along its margins. We investigated changes in the rock magnetic properties associated with this reheating event by examining isolated grains of intergrown ilmenite and hematite, the primary paleomagnetic recorder in the Ecstall pluton. Measurements of hysteresis properties, low‐temperature remanence, and room temperature isothermal remanent magnetization acquisition and observations from magnetic force microscopy and off‐axis electron holography indicate that samples fall into three groups. The groups are defined by the presence of mineral microstructures that are related to distance from the Quotoon plutonic complex. The two groups closest to the Quottoon Pluton contain magnetite within hematite and ilmenite lamellae. Reheating of the Ecstall pluton led to an increase in coercivity and magnetization, as well as to development of mixed phase hysteresis. These results indicate that shallow paleomagnetic directions from the western Ecstall pluton are not affected by reheating and are therefore likely to record original field conditions at the time of pluton emplacement. In the absence of structural deformation, these shallow inclinations are consistent with large‐scale northward translation suggested by the Baja–British Columbia hypothesis.