In-situ synthesis of interconnected SWCNT/OMC framework on silicon nanoparticles for high performance lithium-ion batteries

AbstractIn spite of silicon has a superior theoretical capacity, the large volume expansion of Si anodes during Li+ insertion/extraction is the bottle neck that results in fast capacity fading and poor cycling performance. In this paper, we report a silicon, single-walled carbon nanotube, and ordered mesoporous carbon nanocomposite synthesized by an evaporation-induced self-assembly process, in which silicon nanoparticles and single-walled carbon nanotubes were added into the phenolic resol with F-127 for co-condensation. The ordered mesoporous carbon matrix and single-walled carbon nanotubes network could effectively accommodate the volume change of silicon nanoparticles, and the ordered mesoporous structure could also provide efficient channels for the fast transport of Li-ions. As a consequence, this hybrid material exhibits a reversible capacity of 861 mAh g−1 after 150 cycles at a current density of 400 mA g−1. It achieves significant improvement in the electrochemical performance when compared with the raw materials and Si nanoparticle anodes

Dynamics of Sediment Microbial Functional Capacity and Community Interaction Networks in an Urbanized Coastal Estuary

Coastal estuaries and bays are exposed to both natural and anthropogenic environmental changes, inflicting intensive stress on the microbial communities inhabiting these areas. However, it remains unclear how microbial community diversity and their eco-functions are affected by anthropogenic disturbances rather than natural environmental changes. Here, we explored sediment microbial functional genes dynamics and community interaction networks in Hangzhou Bay (HZB), one of the most severely polluted bays on China’s eastern coast. The results indicated key microbial functional gene categories, including N, P, S, and aromatic compound metabolism, and stress response, displayed significant spatial dynamics along environmental gradients. Sensitive feedbacks of key functional gene categories to N and P pollutants demonstrated potential impacts of human-induced seawater pollutants to microbial functional capacity. Seawater ammonia and dissolved inorganic nitrogen (DIN) was identified as primary drivers in selecting adaptive populations and varying community composition. Network analysis revealed distinct modules that were stimulated in inner or outer bay. Importantly, the network keystone species, which played a fundamental role in community interactions, were strongly affected by N-pollutants. Our results provide a systematic understanding of the microbial compositional and functional dynamics in an urbanized coastal estuary, and highlighted the impact of human activities on these communities

Efficient Multi-Scale Attention Module with Cross-Spatial Learning

Remarkable effectiveness of the channel or spatial attention mechanisms for producing more discernible feature representation are illustrated in various computer vision tasks. However, modeling the cross-channel relationships with channel dimensionality reduction may bring side effect in extracting deep visual representations. In this paper, a novel efficient multi-scale attention (EMA) module is proposed. Focusing on retaining the information on per channel and decreasing the computational overhead, we reshape the partly channels into the batch dimensions and group the channel dimensions into multiple sub-features which make the spatial semantic features well-distributed inside each feature group. Specifically, apart from encoding the global information to re-calibrate the channel-wise weight in each parallel branch, the output features of the two parallel branches are further aggregated by a cross-dimension interaction for capturing pixel-level pairwise relationship. We conduct extensive ablation studies and experiments on image classification and object detection tasks with popular benchmarks (e.g., CIFAR-100, ImageNet-1k, MS COCO and VisDrone2019) for evaluating its performance.Comment: Accepted to ICASSP202

LLMCad: Fast and Scalable On-device Large Language Model Inference

Generative tasks, such as text generation and question answering, hold a crucial position in the realm of mobile applications. Due to their sensitivity to privacy concerns, there is a growing demand for their execution directly on mobile devices. Currently, the execution of these generative tasks heavily depends on Large Language Models (LLMs). Nevertheless, the limited memory capacity of these devices presents a formidable challenge to the scalability of such models. In our research, we introduce LLMCad, an innovative on-device inference engine specifically designed for efficient generative Natural Language Processing (NLP) tasks. The core idea behind LLMCad revolves around model collaboration: a compact LLM, residing in memory, takes charge of generating the most straightforward tokens, while a high-precision LLM steps in to validate these tokens and rectify any identified errors. LLMCad incorporates three novel techniques: (1) Instead of generating candidate tokens in a sequential manner, LLMCad employs the smaller LLM to construct a token tree, encompassing a wider range of plausible token pathways. Subsequently, the larger LLM can efficiently validate all of these pathways simultaneously. (2) It employs a self-adjusting fallback strategy, swiftly initiating the verification process whenever the smaller LLM generates an erroneous token. (3) To ensure a continuous flow of token generation, LLMCad speculatively generates tokens during the verification process by implementing a compute-IO pipeline. Through an extensive series of experiments, LLMCad showcases an impressive token generation speed, achieving rates up to 9.3x faster than existing inference engines

ITQ-37 a chiral zeolite framework following the SrSi2 net and containing 30-ring extra-large gyroidal channels

[EN] The synthesis of crystalline molecular sieves with pore dimensions that fill the gap between microporous and mesoporous materials is a matter of fundamental and industrial interest(1-3). The preparation of zeolitic materials with extralarge pores and chiral frameworks would permit many new applications. Two important steps in this direction include the synthesis(4) of ITQ-33, a stable zeolite with 18 x 10 x 10 ring windows, and the synthesis(5) of SU-32, which has an intrinsically chiral zeolite structure and where each crystal exhibits only one handedness. Here we present a germanosilicate zeolite (ITQ-37) with extralarge 30-ring windows. Its structure was determined by combining selected area electron diffraction ( SAED) and powder X-ray diffraction (PXRD) in a charge-flipping algorithm(6). The framework follows the SrSi2 (srs) minimal net(7) and forms two unique cavities, each of which is connected to three other cavities to form a gyroidal channel system. These cavities comprise the enantiomorphous srs net of the framework. ITQ-37 is the first chiral zeolite with one single gyroidal channel. It has the lowest framework density (10.3 T atoms per 1,000 angstrom(3)) of all existing 4-coordinated crystalline oxide frameworks, and the pore volume of the corresponding silica polymorph would be 0.38 cm(3) g(-1).This project is supported by the CICYT ( Project MAT 2006-14274-C02-01 and Prometeo 2008 GV), the Swedish Research Council (VR) and the Swedish Governmental Agency for Innovation Systems (VINNOVA). J.S. and C. B. are supported by post-doctoral grants from the Carl-Trygger and Wenner-Gren foundations respectively. M. M. thanks ITQ for a scholarship.Sun, J.; Bonneau, C.; Cantin Sanz, A.; Corma Canós, A.; Díaz Cabañas, MJ.; Moliner Marin, M.; Zhang, D.... (2009). ITQ-37 a chiral zeolite framework following the SrSi2 net and containing 30-ring extra-large gyroidal channels. Nature. 458(7242):1154-1158. https://doi.org/10.1038/nature07957S115411584587242Davis, M. E. Ordered porous materials for emerging applications. Nature 417, 813–821 (2002)Corma, A. State of the art and future challenges of zeolites as catalysis. J. Catal. 216, 298–312 (2003)Férey, G. Materials science: the simplicity of complexity—rational design of giant pores. Science 291, 994–995 (2001)Corma, A., Díaz-Cabañas, M. J., Jorda, J. L., Martínez, C. & Moliner, M. High-throughput synthesis and catalytic properties of a molecular sieve with 18- and 10-member rings. Nature 443, 842–845 (2006)Tang, L. Q. et al. A zeolite family with chiral and achiral structures built from the same building layer. Nature Mater. 7, 381–385 (2008)Baerlocher, McCusker, L. B. & Palatinus, L. Charge flipping combined with histogram matching to solve complex crystal structures from powder diffraction data. Z. Kristallogr. 222, 47–53 (2007)Delgado-Friedrichs, O., O’Keeffe, M. & Yaghi, O. M. Three-periodic nets and tilings: regular and quasiregular nets. Acta Crystallogr. A 59, 22–27 (2003)Schröder, G. E., Fogden, A. & Hyde, S. T. Bicontinuous geometries and molecular self-assembly: comparison of local curvature and global packing variation in genus-three cubic, tetragonal and rhombohedral surfaces. Eur. Phys. J. B 54, 509–524 (2006)Taylor, W. H. The structure of analcite (NaAlSi2O6.H2O). Z. Kristallogr. 74, 1–19 (1930)Gier, T. E., Bu, X., Feng, P. & Stucky, G. D. Synthesis and organization of zeolite-like materials with three-dimensional helical pores. Nature 395, 154–157 (1998)Zou, X., Conradsson, T., Klingstedt, M., Dadachov, M. S. & O’Keeffe, M. A mesoporous germanium oxide with crystalline pore walls and its chiral derivative. Nature 437, 716–719 (2005)Cantín, Á., Corma, A., Díaz-Cabañas, M. J., Jorda, J. L. & Moliner, M. Rational design and HT techniques allow the synthesis of new IWR zeolite polymorphs. J. Am. Chem. Soc. 128, 4216–4217 (2006)Gramm, F. et al. Complex zeolite structure solved by combining powder diffraction and electron microscopy. Nature 444, 79–81 (2006)Baerlocher, Ch et al. Structure of the polycrystalline zeolite catalyst IM-5 solved by enhanced charge flipping. Science 315, 1113–1116 (2007)Baerlocher, Ch et al. Ordered silicon vacancies in the framework structure of the zeolite catalyst SSZ-74. Nature Mater. 7, 631–635 (2008)Grosse-Kunstleve, R. W., McCusker, L. B. & Baerlocher, Ch Powder diffraction data and crystal chemical information combined in an automated structure determination procedure for zeolites. J. Appl. Cryst. 30, 985–995 (1997)Palatinus, L. & Chapuis, G. Superflip—a computer program for the solution of crystal structures by charge flipping in arbitrary dimensions. J. Appl. Cryst. 40, 786–790 (2007)Zou, X. D., Sukharev, Y. & Hovmöller, S. Quantitative measurement of intensities from electron diffraction patterns for structure determination—new features in the program system ELD. Ultramicroscopy 52, 436–444 (1993)O'Keeffe, M., Peskov, M. A., Ramsden, S. J. & Yaghi, O. M. The Reticular Chemistry Structure Resource (RCSR) database of, and symbols for, crystal nets. Acc. Chem. Res. 41, 1782–1798 (2008)Climent, M. J., Corma, A. & Velty, A. Zeolites for the production of fine chemicals. Synthesis of the fructone fragance. J. Catal. 196, 345–351 (2000)Climent, M. J., Corma, A. & Velty, A. Design of a solid catalyst for the synthesis of a molecule with a orange blossom scent. Green Chem. 4, 565–569 (2002)Climent, M. J., Corma, A. & Velty, A. Synthesis of hyacinth, vanilla and orange blossom fragrances. The benefit of using zeikutes and delaminated zeolites as catalysts. Appl. Catal. Gen. 263, 155–161 (2004)Hovmöller, S. CRISP: Crystallographic image processing on a personal computer. Ultramicroscopy 41, 121–135 (1992)Young, R. A. The Rietveld Method 1–39 (IUCr Book Serials, Oxford Univ. Press, 1993)Delgado-Friedrichs, O. & O'Keeffe, M. Identification and symmetry computation for crystal nets. Acta Crystallogr. A 59, 351–360 (2003)Delgado-Friedrichs, O. Data structures and algorithms for tilings. I. Theor. Comput. Sci. 303, 431–445 (2003)Blatov, V. A. Multipurpose crystallochemical analysis with the program package TOPOS. IUCr Comp. Commun. Newsl. 7, 4–38 (2006

Imaging defects and their evolution in a metal–organic framework at sub-unit-cell resolution

© 2019, The Author(s), under exclusive licence to Springer Nature Limited. Defect engineering of metal–organic frameworks (MOFs) offers promising opportunities for tailoring their properties to specific functions and applications. However, determining the structures of defects in MOFs—either point defects or extended ones—has proved challenging owing to the difficulty of directly probing local structures in these typically fragile crystals. Here we report the real-space observation, with sub-unit-cell resolution, of structural defects in the catalytic MOF UiO-66 using a combination of low-dose transmission electron microscopy and electron crystallography. Ordered ‘missing linker’ and ‘missing cluster’ defects were found to coexist. The missing-linker defects, reconstructed three-dimensionally with high precision, were attributed to terminating formate groups. The crystallization of the MOF was found to undergo an Ostwald ripening process, during which the defects also evolve: on prolonged crystallization, only the missing-linker defects remained. These observations were rationalized through density functional theory calculations. Finally, the missing-cluster defects were shown to be more catalytically active than their missing-linker counterparts for the isomerization of glucose to fructose

Small and mighty: adaptation of superphylum Patescibacteria to groundwater environment drives their genome simplicity.

BackgroundThe newly defined superphylum Patescibacteria such as Parcubacteria (OD1) and Microgenomates (OP11) has been found to be prevalent in groundwater, sediment, lake, and other aquifer environments. Recently increasing attention has been paid to this diverse superphylum including > 20 candidate phyla (a large part of the candidate phylum radiation, CPR) because it refreshed our view of the tree of life. However, adaptive traits contributing to its prevalence are still not well known.ResultsHere, we investigated the genomic features and metabolic pathways of Patescibacteria in groundwater through genome-resolved metagenomics analysis of > 600 Gbp sequence data. We observed that, while the members of Patescibacteria have reduced genomes (~ 1 Mbp) exclusively, functions essential to growth and reproduction such as genetic information processing were retained. Surprisingly, they have sharply reduced redundant and nonessential functions, including specific metabolic activities and stress response systems. The Patescibacteria have ultra-small cells and simplified membrane structures, including flagellar assembly, transporters, and two-component systems. Despite the lack of CRISPR viral defense, the bacteria may evade predation through deletion of common membrane phage receptors and other alternative strategies, which may explain the low representation of prophage proteins in their genomes and lack of CRISPR. By establishing the linkages between bacterial features and the groundwater environmental conditions, our results provide important insights into the functions and evolution of this CPR group.ConclusionsWe found that Patescibacteria has streamlined many functions while acquiring advantages such as avoiding phage invasion, to adapt to the groundwater environment. The unique features of small genome size, ultra-small cell size, and lacking CRISPR of this large lineage are bringing new understandings on life of Bacteria. Our results provide important insights into the mechanisms for adaptation of the superphylum in the groundwater environments, and demonstrate a case where less is more, and small is mighty

Functional Gene Array-Based Ultrasensitive and Quantitative Detection of Microbial Populations in Complex Communities.

While functional gene arrays (FGAs) have greatly expanded our understanding of complex microbial systems, specificity, sensitivity, and quantitation challenges remain. We developed a new generation of FGA, GeoChip 5.0, using the Agilent platform. Two formats were created, a smaller format (GeoChip 5.0S), primarily covering carbon-, nitrogen-, sulfur-, and phosphorus-cycling genes and others providing ecological services, and a larger format (GeoChip 5.0M) containing the functional categories involved in biogeochemical cycling of C, N, S, and P and various metals, stress response, microbial defense, electron transport, plant growth promotion, virulence, gyrB, and fungus-, protozoan-, and virus-specific genes. GeoChip 5.0M contains 161,961 oligonucleotide probes covering >365,000 genes of 1,447 gene families from broad, functionally divergent taxonomic groups, including bacteria (2,721 genera), archaea (101 genera), fungi (297 genera), protists (219 genera), and viruses (167 genera), mainly phages. Computational and experimental evaluation indicated that designed probes were highly specific and could detect as little as 0.05 ng of pure culture DNAs within a background of 1 μg community DNA (equivalent to 0.005% of the population). Additionally, strong quantitative linear relationships were observed between signal intensity and amount of pure genomic (∼99% of probes detected; r > 0.9) or soil (∼97%; r > 0.9) DNAs. Application of the GeoChip to a contaminated groundwater microbial community indicated that environmental contaminants (primarily heavy metals) had significant impacts on the biodiversity of the communities. This is the most comprehensive FGA to date, capable of directly linking microbial genes/populations to ecosystem functions.IMPORTANCE The rapid development of metagenomic technologies, including microarrays, over the past decade has greatly expanded our understanding of complex microbial systems. However, because of the ever-expanding number of novel microbial sequences discovered each year, developing a microarray that is representative of real microbial communities, is specific and sensitive, and provides quantitative information remains a challenge. The newly developed GeoChip 5.0 is the most comprehensive microarray available to date for examining the functional capabilities of microbial communities important to biogeochemistry, ecology, environmental sciences, and human health. The GeoChip 5 is highly specific, sensitive, and quantitative based on both computational and experimental assays. Use of the array on a contaminated groundwater sample provided novel insights on the impacts of environmental contaminants on groundwater microbial communities

Nearly a decade-long repeatable seasonal diversity patterns of bacterioplankton communities in the eutrophic Lake Donghu (Wuhan, China).

Uncovering which environmental factors govern community diversity patterns and how ecological processes drive community turnover are key questions related to understand the community assembly. However, the ecological mechanisms regulating long-term variations of bacterioplankton communities in lake ecosystems remain poorly understood. Here we present nearly a decade-long study of bacterioplankton communities from the eutrophic Lake Donghu (Wuhan, China) using 16S rRNA gene amplicon sequencing with MiSeq platform. We found strong repeatable seasonal diversity patterns in terms of both common (detected in more than 50% samples) and dominant (relative abundance >1%) bacterial taxa turnover. Moreover, community composition tracked the seasonal temperature gradient, indicating that temperature is a key environmental factor controlling observed diversity patterns. Total phosphorus also contributed significantly to the seasonal shifts in bacterioplankton composition. However, any spatial pattern of bacterioplankton communities across the main lake areas within season was overwhelmed by their temporal variabilities. Phylogenetic analysis further indicated that 75%-82% of community turnover was governed by homogeneous selection due to consistent environmental conditions within seasons, suggesting that the microbial communities in Lake Donghu are mainly controlled by niche-based processes. Therefore, dominant niches available within seasons might be occupied by similar combinations of bacterial taxa with modest dispersal rates throughout different lake areas