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"Zhang, R."
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Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles
Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson's ratio on torsional actuation and electronic properties.
Journal Article
إنتاج الطاقة الحيوية والوقود الحيوي من النفايات والكتلة الحيوية
توفر فصول هذا الكتاب أحدث استعراض ومسح للبحوث والتطورات التقنية، فيما يتعلق بالجيلين الثاني والثالث من الوقود الحيوي والطاقة الحيوية، كما تعرض الاتجاهات البحثية الحالية والمستقبلية في نهاية كل فصل ويغطي هذا الكتاب في المقام الأول، التحويل البيولوجي والكيميائي الحيوي لإنتاج الوقود الحيوي والطاقة الحيوية، باعتباره خيارا معلنا ورخيصا لإنتاج الوقود الحيوي والطاقة الحيوية. يعد هذا الكتاب مرجعا قيما، لطلاب المرحلة الجامعية والدراسات العليا والباحثين في الكيمياء والكيمياء الحيوية والبيئة والمجالات الهندسية وصناع القرار والمهنيين الممارسين وغيرهم من المهتمين بمجال الوقود الحيوي والطاقة الحيوية.
Book
Chemical mapping of a single molecule by plasmon-enhanced Raman scattering
Chemical mapping of a single molecule by optical means down to subnanometre resolution is achieved by spectrally matching the resonance of a nanocavity plasmon to the vibronic transitions of the molecules being studied, using tip-enhanced Raman scattering.
Inner workings of a single molecule
Raman spectroscopy is widely used to identify molecules by detecting their signature molecular vibrations. The technology has been refined to be effective at the single-molecule level by making use of strong localized plasmonic fields that can enhance spectral signals. This study goes further, with the demonstration of a technique related to 'tip-enhanced Raman scattering' (TERS) that allows precise tuning of the plasmon resonance and Raman spectral imaging with a spatial resolution below 1 nm, resolving even the inner structure of a single molecule and its configuration on the surface. The technique opens a new path to photochemistry at the single-molecule level, offering the potential to design, control and engineer the functionality of molecules on demand.
Visualizing individual molecules with chemical recognition is a longstanding target in catalysis, molecular nanotechnology and biotechnology. Molecular vibrations provide a valuable ‘fingerprint’ for such identification. Vibrational spectroscopy based on tip-enhanced Raman scattering allows us to access the spectral signals of molecular species very efficiently via the strong localized plasmonic fields produced at the tip apex
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, which is not adequate for resolving a single molecule chemically. Here we demonstrate Raman spectral imaging with spatial resolution below one nanometre, resolving the inner structure and surface configuration of a single molecule. This is achieved by spectrally matching the resonance of the nanocavity plasmon to the molecular vibronic transitions, particularly the downward transition responsible for the emission of Raman photons. This matching is made possible by the extremely precise tuning capability provided by scanning tunnelling microscopy. Experimental evidence suggests that the highly confined and broadband nature of the nanocavity plasmon field in the tunnelling gap is essential for ultrahigh-resolution imaging through the generation of an efficient double-resonance enhancement for both Raman excitation and Raman emission. Our technique not only allows for chemical imaging at the single-molecule level, but also offers a new way to study the optical processes and photochemistry of a single molecule.
Journal Article
Ground-based aerosol climatology of China: aerosol optical depths from the China Aerosol Remote Sensing Network (CARSNET) 2002–2013
Long-term measurements of aerosol optical depths (AODs) at 440 nm and Ångström exponents (AE) between 440 and 870 nm made for CARSNET were compiled into a climatology of aerosol optical properties for China. Quality-assured monthly mean AODs are presented for 50 sites representing remote, rural, and urban areas. AODs were 0.14, 0.34, 0.42, 0.54, and 0.74 at remote stations, rural/desert regions, the Loess Plateau, central and eastern China, and urban sites, respectively, and the corresponding AE values were 0.97, 0.55, 0.82, 1.19, and 1.05. AODs increased from north to south, with low values (< 0.20) over the Tibetan Plateau and northwestern China and high AODs (> 0.60) in central and eastern China where industrial emissions and anthropogenic activities were likely sources. AODs were 0.20–0.40 in semi-arid and arid regions and some background areas in northern and northeastern China. AEs were > 1.20 over the southern reaches of the Yangtze River and at clean sites in northeastern China. In the northwestern deserts and industrial parts of northeast China, AEs were lower (< 0.80) compared with central and eastern regions. Dust events in spring, hygroscopic particle growth during summer, and biomass burning contribute the high AODs, especially in northern and eastern China. The AODs show decreasing trends from 2006 to 2009 but increased ~ 0.03 per year from 2009 to 2013.
Journal Article
Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 γ-ray Galactic sources
The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10
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electronvolts) indicates the existence of the so-called PeVatrons—cosmic-ray factories that accelerate particles to PeV energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays
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. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref.
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, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.
Observations of γ-rays with energies up to 1.4 PeV find that 12 sources in the Galaxy are PeVatrons, one of which is the Crab Nebula.
Journal Article
Bulk tissue cell type deconvolution with multi-subject single-cell expression reference
Knowledge of cell type composition in disease relevant tissues is an important step towards the identification of cellular targets of disease. We present MuSiC, a method that utilizes cell-type specific gene expression from single-cell RNA sequencing (RNA-seq) data to characterize cell type compositions from bulk RNA-seq data in complex tissues. By appropriate weighting of genes showing cross-subject and cross-cell consistency, MuSiC enables the transfer of cell type-specific gene expression information from one dataset to another. When applied to pancreatic islet and whole kidney expression data in human, mouse, and rats, MuSiC outperformed existing methods, especially for tissues with closely related cell types. MuSiC enables the characterization of cellular heterogeneity of complex tissues for understanding of disease mechanisms. As bulk tissue data are more easily accessible than single-cell RNA-seq, MuSiC allows the utilization of the vast amounts of disease relevant bulk tissue RNA-seq data for elucidating cell type contributions in disease.
Bulk tissue RNA-seq data reveals transcriptomic profiles but masks the contributions of different cell types. Here, the authors develop a new method for estimating cell type proportions from bulk tissue RNA-seq data guided by multi-subject single-cell expression reference.
Journal Article
miR-506 acts as a tumor suppressor by directly targeting the hedgehog pathway transcription factor Gli3 in human cervical cancer
Although significant advances have recently been made in the diagnosis and treatment of cervical carcinoma, the long-term survival rate for advanced cervical cancer remains low. Therefore, an urgent need exists to both uncover the molecular mechanisms and identify potential therapeutic targets for the treatment of cervical cancer. MicroRNAs (miRNAs) have important roles in cancer progression and could be used as either potential therapeutic agents or targets. miR-506 is a component of an X chromosome-linked miRNA cluster. The biological functions of miR-506 have not been well established. In this study, we found that miR-506 expression was downregulated in approximately 80% of the cervical cancer samples examined and inversely correlated with the expression of Ki-67, a marker of cell proliferation. Gain-of-function and loss-of-function studies in human cervical cancer, Caski and SiHa cells, demonstrated that miR-506 acts as a tumor suppressor by inhibiting cervical cancer growth
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. Further studies showed that miR-506 induced cell cycle arrest at the G1/S transition, and enhanced apoptosis and chemosensitivity of cervical cancer cell. We subsequently identified Gli3, a hedgehog pathway transcription factor, as a direct target of miR-506 in cervical cancer. Furthermore, Gli3 silencing recapitulated the effects of miR-506, and reintroduction of Gli3 abrogated miR-506-induced cell growth arrest and apoptosis. Taken together, we conclude that miR-506 exerts its anti-proliferative function by directly targeting Gli3. This newly identified miR-506/Gli3 axis provides further insight into the pathogenesis of cervical cancer and indicates a potential novel therapeutic agent for the treatment of cervical cancer.
Journal Article
Organization of the human intestine at single-cell resolution
The intestine is a complex organ that promotes digestion, extracts nutrients, participates in immune surveillance, maintains critical symbiotic relationships with microbiota and affects overall health
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. The intesting has a length of over nine metres, along which there are differences in structure and function
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. The localization of individual cell types, cell type development trajectories and detailed cell transcriptional programs probably drive these differences in function. Here, to better understand these differences, we evaluated the organization of single cells using multiplexed imaging and single-nucleus RNA and open chromatin assays across eight different intestinal sites from nine donors. Through systematic analyses, we find cell compositions that differ substantially across regions of the intestine and demonstrate the complexity of epithelial subtypes, and find that the same cell types are organized into distinct neighbourhoods and communities, highlighting distinct immunological niches that are present in the intestine. We also map gene regulatory differences in these cells that are suggestive of a regulatory differentiation cascade, and associate intestinal disease heritability with specific cell types. These results describe the complexity of the cell composition, regulation and organization for this organ, and serve as an important reference map for understanding human biology and disease.
Intestinal cell types are organized into distinct neighbourhoods and communities within the healthy human intestine, with distinct immunological niches.
Journal Article
Assessing intratumor heterogeneity and tracking longitudinal and spatial clonal evolutionary history by next-generation sequencing
Cancer is a disease driven by evolutionary selection on somatic genetic and epigenetic alterations. Here, we propose Canopy, a method for inferring the evolutionary phylogeny of a tumor using both somatic copy number alterations and single-nucleotide alterations from one or more samples derived from a single patient. Canopy is applied to bulk sequencing datasets of both longitudinal and spatial experimental designs and to a transplantable metastasis model derived from human cancer cell line MDA-MB-231. Canopy successfully identifies cell populations and infers phylogenies that are in concordance with existing knowledge and ground truth. Through simulations, we explore the effects of key parameters on deconvolution accuracy and compare against existing methods. Canopy is an open-source R package available at https://cran.r-project.org/web/packages/Canopy/.
Journal Article