Upon shearing a microscale lithographically defined graphite mesa, the sheared section retracts spontaneously to minimize interface energy. Here, we demonstrate a sixfold symmetry of the ...self-retraction and provide a first experimental estimate of the frictional force involved, as direct evidence that the self-retraction is due to superlubricity, where ultralow friction occurs between incommensurate surfaces. The effect is remarkable because it occurs reproducibly under ambient conditions and over a contact area of up to 10×10 μm2, more than 7 orders of magnitude larger than previous scanning-probe-based studies of superlubricity in graphite. By analyzing the sheared interface, we show how the grain structure of highly oriented pyrolitic graphite determines the probability of self-retraction. Our results demonstrate that such self-retraction provides a novel probe of superlubricity, and the robustness of the phenomenon opens the way for practical applications of superlubricity in micromechanical systems.
Liquid biopsy enables noninvasive and dynamic analysis of molecular or cellular biomarkers, and therefore holds great potential for the diagnosis, prognosis, monitoring of disease progress and ...treatment efficacy, understanding of disease mechanisms, and identification of therapeutic targets for drug development. In this review, the recent progress in nanomaterials, nanostructures, nanodevices, and nanosensors for liquid biopsy is summarized, with a focus on the detection and molecular characterization of circulating tumor cells (CTCs) and extracellular vesicles (EVs). The developments and advances of nanomaterials and nanostructures in enhancing the sensitivity, specificity, and purity for the detection of CTCs and EVs are discussed. Sensing techniques for signal transduction and amplification as well as visualization strategies are also discussed. New technologies for the reversible release of the isolated CTCs and EVs and for single‐CTC/EV analysis are summarized. Emerging microfluidic platforms for the integral on‐chip isolation, detection, and molecular analysis are also included. The opportunities, challenges, and prospects of these innovative materials and technologies, especially with regard to their feasibility in clinical applications, are discussed. The applications of nanotechnology‐based liquid biopsy will bring new insight into the clinical practice in monitoring and treatment of tumor and other significant diseases.
Nanotechnologies for biological detection have evolved from the individual nanomaterial and nanostructure to integrated nanobased platforms and devices. Improvements in these nanotechnologies enable efficient isolation, detection, and multifunctional analysis of circulating tumor cells and extracellular vesicles, and provide strong opportunities for the early diagnosis, real‐time monitoring, and prognosis evaluation of cancer.
Understanding the terrestrial carbon and water cycles is crucial for mitigation and adaptation for climate change. Leaf area index (LAI) is a key biophysical parameter in process-based ecosystem ...models for simulating gross primary productivity (GPP) and evapotranspiration (ET). The uncertainty in satellite-derived LAI products and their effects on the simulation of carbon and water fluxes at regional scales remain unclear. We evaluated three satellite-derived LAI products - MODIS (MCD15), GLASS, and Four-Scale Geometric Optical Model based LAI (FSGOM) over the period 2003–2012 using fine-resolution (30m) LAI data and field LAI measurements. GLASS had higher accuracy than FSGOM and MCD15 for forests, while FSGOM had higher accuracy than MCD15 and GLASS for grasslands. The three LAI products differed in magnitude, spatial patterns, and trends in LAI. We then examined the resulting discrepancies in simulated annual GPP and ET over China using a process-based, diagnostic terrestrial biosphere model. Mean annual total GPP for China's terrestrial ecosystems based on GLASS (6.32PgCyr−1) and FSGOM (6.15PgCyr−1) was 22.5% and 19.2% higher than that based on MCD15 (5.16PgCyr−1), respectively. Annual GPP based on GLASS and MCD15 increased over larger fractions of China's vegetated area (15.9% and 17.3%, respectively) than that based on FSGOM (12.6%). National annual ET based on GLASS (379.9mmyr−1) and FSGOM (374.4mmyr−1) was 7.9% and 6.3% higher than that based on MCD15 (352.1mmyr−1), respectively. Simulated ET increased in larger fractions of the vegetated area for GLASS (5.7%) and MCD15 (5.8%) than for FSGOM (3.9%). Our study shows that there were large discrepancies in LAI among satellite-derived LAI products and the biases of the LAI products could lead to substantial uncertainties in simulated carbon and water fluxes.
•Satellite-derived LAI products (MCD15, GLASS, FSGOM) exhibited large discrepancies.•These LAI products had substantial differences in magnitude, patterns, and trends.•These LAI products led to large uncertainty and discrepancies in modeled GPP and ET.•GLASS and FSGOM led to in much higher annual GPP and ET estimates compared to MCD15.•More accurate LAI products will improve regional carbon and water flux simulations.
In-plane and vertically stacked heterostructures of graphene and hexagonal boron nitride (h-BN-G and G/h-BN, respectively) are both recent focuses of graphene research. However, targeted synthesis of ...either heterostructure remains a challenge. Here, via chemical vapour deposition and using benzoic acid precursor, we have achieved the selective growth of h-BN-G and G/h-BN through a temperature-triggered switching reaction. The perfect in-plane h-BN-G is characterized by scanning tunnelling microscopy (STM), showing atomically patched graphene and h-BN with typical zigzag edges. In contrast, the vertical alignment of G/h-BN is confirmed by unique lattice-mismatch-induced moiré patterns in high-resolution STM images, and two sets of aligned selected area electron diffraction spots, both suggesting a van der Waals epitaxial mechanism. The present work demonstrates the chemical designability of growth process for controlled synthesis of graphene and h-BN heterostructures. With practical scalability, high uniformity and quality, our approach will promote the development of graphene-based electronics and optoelectronics.
Abstract Macrophages are involved in all phases of scaffold induced tissue regeneration, orchestrating the transition from an inflammatory to regenerative phenotype to guide all other cell types to ...complete the wound healing process when a tissue defect advances beyond the critical size. Therefore, harnessing macrophages by scaffolds is important for facilitating tissue regeneration in situ . In this work we utilized the superparamagnetic scaffold upon magnetization as a mechanostimulation platform to apply forces directly to macrophages grown in the scaffold, aiming to figure out whether the functions of macrophages related to bone tissue regeneration can be mechanomodulated and to elucidate the underlying mechanisms. We showed the first evidence that upon magnetization the interaction of superparamagnetic scaffolds to macrophages drove them to polarize towards an M2-like phenotype by inhibiting TLR2/4 activation and enhancing VEGFR2 activation, thereby inhibiting secretion of the pro-inflammatory cytokines IL-1β, TNF-α and MCP-1, as well as the osteoclast differentiation cytokines MMP-9 and TRAP, and up-regulating VEGF and PDGF. The conditioned media enhanced the osteogenesis of osteoblasts and the angiogenesis of endothelial cells.
With the potential wide uses of nanoparticles such as carbon nanotubes in biomedical applications, and the growing concerns of nanotoxicity of these engineered nanoparticles, the importance of ...nanoparticle–protein interactions cannot be stressed enough. In this study, we use both experimental and theoretical approaches, including atomic force microscope images, fluorescence spectroscopy, CD, SDS-PAGE, and molecular dynamics simulations, to investigate the interactions of single-wall carbon nanotubes (SWCNTs) with human serum proteins, and find a competitive binding of these proteins with different adsorption capacity and packing modes. The π-π stacking interactions between SWCNTs and aromatic residues (Trp, Phe, Tyr) are found to play a critical role in determining their adsorption capacity. Additional cellular cytotoxicity assays, with human acute monocytic leukemia cell line and human umbilical vein endothelial cells, reveal that the competitive bindings of blood proteins on the SWCNT surface can greatly alter their cellular interaction pathways and result in much reduced cytotoxicity for these protein-coated SWCNTs, according to their respective adsorption capacity. These findings have shed light toward the design of safe carbon nanotube nanomaterials by comprehensive preconsideration of their interactions with human serum proteins.
There has been growing evidence that vegetation greenness has been increasing in many parts of the northern middle and high latitudes including China during the last three to four decades. However, ...the effects of increasing vegetation greenness particularly afforestation on the hydrological cycle have been controversial. We used a process-based ecosystem model and a satellite-derived leaf area index (LAI) dataset to examine how the changes in vegetation greenness affected annual evapotranspiration (ET) and water yield for China over the period from 2000 to 2014. Significant trends in vegetation greenness were observed in 26.1% of China's land area. We used two model simulations driven with original and detrended LAI, respectively, to assess the effects of vegetation 'greening' and 'browning' on terrestrial ET and water yield. On a per-pixel basis, vegetation greening increased annual ET and decreased water yield, while vegetation browning reduced ET and increased water yield. At the large river basin and national scales, the greening trends also had positive effects on annual ET and had negative effects on water yield. Our results showed that the effects of the changes in vegetation greenness on the hydrological cycle varied with spatial scale. Afforestation efforts perhaps should focus on southern China with larger water supply given the water crisis in northern China and the negative effects of vegetation greening on water yield. Future studies on the effects of the greenness changes on the hydrological cycle are needed to account for the feedbacks to the climate.
•Sustainability assessment of deep-sea mining transport plans.•Both qualitative and quantitative indicators exist in the evaluation process.•A proposed integrated multi-criteria decision-making ...method and its application to evaluate sustainable DSM transport plans.•Environmental impact indicators and technical feasibility indicators coupling.
Deep-sea mining (DSM) is an emerging interdisciplinary and cross-domain research topic. So far, there is no an effective, viable approach to evaluate the comprehensive performance, i.e., sustainability, of DSM transport plans integrating the technological feasibility, economic profitability, and environmental and social impacts. Considering the following characteristics and complexities of this problem: (i) both qualitative and quantitative criteria exist in the evaluation process, and (ii) some of the evaluation criteria might be dependent upon each other, the multi-criteria decision-making (MCDM) method is selected to address this typical multiple attribute decision-making problem. The objective of this paper is to propose a suitable MCDM method for evaluating sustainable DSM transport plans based on a systematic literature review. This research compares the existing MCDM methods, describes the characteristics of DSM transport plans, and discusses a proposed integrated MCDM approach and its application to evaluate sustainable DSM transport plans.
Photodegradation of rhodamine B in the presence of H2O2 by visible light over α‐Fe2O3 architectures has been investigated (see picture; left to right: 1D nanorods, 2D nanoplates, 3D nanocubes). A ...link between the exposed facets of α‐Fe2O3 architectures and their photoreactivity is established, following {110}>{012}≫{001}.
Visible light (λ > 420 nm) induced photocatalytic degradation of rhodamine B (RhB) in the presence of H2O2 by one-dimensional (1D) nanorods of goethite (α-FeOOH) and hematite (α-Fe2O3) has been ...investigated, and results were compared to those of micrometer-sized rods. α-FeOOH nanorods were self-assembled by oriented attachment of α-FeOOH primary nanoparticles, while porous α-Fe2O3 rods were prepared by thermal dehydration of respective α-FeOOH precursors via a topotactic transformation. The as-prepared samples were characterized by powder X-ray diffraction, micro-Raman spectroscopy, diffuse reflectance UV−visible spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption−desorption, high-angle annular dark-field scanning transmission electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. Nanosized α-FeOOH and α-Fe2O3 particles appeared to be more active than microsized ones in terms of surface area normalized reaction rate, suggesting intrinsic photocatalytic properties of nanorods as compared to microrods in both α-FeOOH and α-Fe2O3. In addition, α-Fe2O3 nanorods exhibited the greatest activity among the as-prepared samples. The observed photocatalytic performance by iron oxide particles was attributed to the synergetic effects of the particle composition, size, porosity, and the variations of local structure. The results from current study will be potentially applicable to a range of naturally abundant semiconducting minerals and compounds (e.g., metal oxyhydroxides and metal oxides).
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