Cyclic deformation leads to defect healing and strengthening of small-volume metal crystals

When microscopic and macroscopic specimens of metals are subjected to cyclic loading, the creation, interaction, and accumulation of defects lead to damage, cracking, and failure. Here we demonstrate that when aluminum single crystals of submicrometer dimensions are subjected to low-amplitude cyclic deformation at room temperature, the density of preexisting dislocation lines and loops can be dramatically reduced with virtually no change of the overall sample geometry and essentially no permanent plastic strain. This “cyclic healing” of the metal crystal leads to significant strengthening through dramatic reductions in dislocation density, in distinct contrast to conventional cyclic strain hardening mechanisms arising from increases in dislocation density and interactions among defects in microcrystalline and macrocrystalline metals and alloys. Our real-time, in situ transmission electron microscopy observations of tensile tests reveal that pinned dislocation lines undergo shakedown during cyclic straining, with the extent of dislocation unpinning dependent on the amplitude, sequence, and number of strain cycles. Those unpinned mobile dislocations moving close enough to the free surface of the thin specimens as a result of such repeated straining are then further attracted to the surface by image forces that facilitate their egress from the crystal. These results point to a versatile pathway for controlled mechanical annealing and defect engineering in submicrometer-sized metal crystals, thereby obviating the need for thermal annealing or significant plastic deformation that could cause change in shape and/or dimensions of the specimen.National Science Foundation (U.S.) (Grant DMR-1120901)National Science Foundation (U.S.) (DMR-1410636)Singapore-MIT Allianc

Synthesis and Broad-Spectrum Antiviral Activity of Some Novel Benzo-Heterocyclic Amine Compounds

A series of novel unsaturated five-membered benzo-heterocyclic amine derivatives were synthesized and assayed to determine their in vitro broad-spectrum antiviral activities. The biological results showed that most of our synthesized compounds exhibited potent broad-spectrum antiviral activity. Notably, compounds 3f (IC50 = 3.21–5.06 μM) and 3g (IC50 = 0.71–34.87 μM) showed potent activity towards both RNA viruses (influenza A, HCV and Cox B3 virus) and a DNA virus (HBV) at low micromolar concentrations. An SAR study showed that electron-withdrawing substituents located on the aromatic or heteroaromatic ring favored antiviral activity towards RNA viruses

Algal blooms: how are they harming models used for climate management?

18th International Conference on Harmful Algae (ICHA 2018), 21-26 October 2018, Nantes, France.-- 4 pages, 2 figuresMicroalgae blooms are generally associated with bacterial secondary producers. They produce organic matter (OM), some of which associates with the sea surface microlayer (SML). OM in the SML below the actual surface reduces fluxes of energy, including heat and momentum, and substances, including greenhouse gases, aerosols, algae, bacteria and viruses. In addition to the SML-associated OM, another OM fraction, foam (including whitecaps), often lies above the primary SML when windspeeds exceed about 5 m s-1, trapping gas bubbles. Such foam also dramatically increases albedo, reflecting solar radiation back into space, thus reducing solar heating and penetration of photosynthetically active radiation. Mean coverage of the ocean surface by foam has been measured to range between 1-6%, particularly in zones of Trade Winds. Different types of OM, and particularly their mechanical properties, depend on ambient algal abundance, as well as on taxonomic composition, as do the dynamics of foam formation and decay. Air-sea fluxes may thus be influenced by genomic control through the blooming microalgae and Darwinian-type evolution. Bacteria may also play a role. In addition, foam patches on the ocean’s surface serve as a unique microbial habitat. Such blooms, particularly when their taxonomic composition changes unpredictably, are likely to be harming the usefulness of climate models. Some of this harm might be mitigated by studying the relevant effects of these blooms on fluxes, and incorporating these effects into climate modelsJS is supported by National Nature Science Foundation of China grant (41876134) and the Changjiang Scholar Program of Chinese Ministry of Educatio

Ansor : Generating High-Performance Tensor Programs for Deep Learning

High-performance tensor programs are crucial to guarantee efficient execution of deep neural networks. However, obtaining performant tensor programs for different operators on various hardware platforms is notoriously challenging. Currently, deep learning systems rely on vendor-provided kernel libraries or various search strategies to get performant tensor programs. These approaches either require significant engineering effort to develop platform-specific optimization code or fall short of finding high-performance programs due to restricted search space and ineffective exploration strategy. We present Ansor, a tensor program generation framework for deep learning applications. Compared with existing search strategies, Ansor explores many more optimization combinations by sampling programs from a hierarchical representation of the search space. Ansor then fine-tunes the sampled programs with evolutionary search and a learned cost model to identify the best programs. Ansor can find high-performance programs that are outside the search space of existing state-of-the-art approaches. In addition, Ansor utilizes a task scheduler to simultaneously optimize multiple subgraphs in deep neural networks. We show that Ansor improves the execution performance of deep neural networks relative to the state-of-the-art on the Intel CPU, ARM CPU, and NVIDIA GPU by up to $3.8\times$, $2.6\times$, and $1.7\times$, respectively.Comment: Published in OSDI 202

Epigenetic modification and inheritance in sexual reversal of fish

Environmental sex determination (ESD) occurs in divergent, phylogenetically unrelated taxa, and in some species, co-occurs with genetic sex determination (GSD) mechanisms. Although epigenetic regulation in response to environmental effects has long been proposed to be associated with ESD, a systemic analysis on epigenetic regulation of ESD is still lacking. Using half-smooth tongue sole (Cynoglossus semilaevis) as a model—a marine fish that has both ZW chromosomal GSD and temperature-dependent ESD—we investigated the role of DNA methylation in transition from GSD to ESD. Comparative analysis of the gonadal DNA methylomes of pseudomale, female, and normal male fish revealed that genes in the sex determination pathways are the major targets of substantial methylation modification during sexual reversal. Methylation modification in pseudomales is globally inherited in their ZW offspring, which can naturally develop into pseudomales without temperature incubation. Transcriptome analysis revealed that dosage compensation occurs in a restricted, methylated cytosine enriched Z chromosomal region in pseudomale testes, achieving equal expression level in normal male testes. In contrast, female-specific W chromosomal genes are suppressed in pseudomales by methylation regulation. We conclude that epigenetic regulation plays multiple crucial roles in sexual reversal of tongue sole fish. We also offer the first clues on the mechanisms behind gene dosage balancing in an organism that undergoes sexual reversal. Finally, we suggest a causal link between the bias sex chromosome assortment in the offspring of a pseudomale family and the transgenerational epigenetic inheritance of sexual reversal in tongue sole fish

The goose genome sequence leads to insights into the evolution of waterfowl and susceptibility to fatty liver

BACKGROUND: Geese were domesticated over 6,000 years ago, making them one of the first domesticated poultry. Geese are capable of rapid growth, disease resistance, and high liver lipid storage capacity, and can be easily fed coarse fodder. Here, we sequence and analyze the whole-genome sequence of an economically important goose breed in China and compare it with that of terrestrial bird species. RESULTS: A draft sequence of the whole-goose genome was obtained by shotgun sequencing, and 16,150 protein-coding genes were predicted. Comparative genomics indicate that significant differences occur between the goose genome and that of other terrestrial bird species, particularly regarding major histocompatibility complex, Myxovirus resistance, Retinoic acid-inducible gene I, and other genes related to disease resistance in geese. In addition, analysis of transcriptome data further reveals a potential molecular mechanism involved in the susceptibility of geese to fatty liver disease and its associated symptoms, including high levels of unsaturated fatty acids and low levels of cholesterol. The results of this study show that deletion of the goose lep gene might be the result of positive selection, thus allowing the liver to adopt energy storage mechanisms for long-distance migration. CONCLUSIONS: This is the first report describing the complete goose genome sequence and contributes to genomic resources available for studying aquatic birds. The findings in this study are useful not only for genetic breeding programs, but also for studying lipid metabolism disorders. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13059-015-0652-y) contains supplementary material, which is available to authorized users