Abstract Establishing a general model of heterogeneous ice nucleation has long been challenging because of the surface water structures found on different substrates. Identifying common water clusters, regardless of the underlying substrate, is one of the key steps toward solving this problem. Here, we demonstrate the presence of a common water cluster found on both hydrophilic Pt(111) and hydrophobic Cu(111) surfaces using scanning tunneling microscopy and non-contact atomic force microscopy. Water molecules self-assemble into a structure with a central flat-lying hexagon and three fused pentagonal rings, forming a cluster consisting of 15 individual water molecules. This cluster serves as a critical nucleus during ice nucleation on both surfaces: ice growth beyond this cluster bifurcates to form two-dimensional (three-dimensional) layers on hydrophilic (hydrophobic) surfaces. Our results reveal the inherent similarity and distinction at the initial stage of ice growth on hydrophilic and hydrophobic close-packed metal surfaces; thus, these observations provide initial evidence toward a general model for water-substrate interaction.
Abstract. The yield of particle mass in secondary organic aerosol (SOA) formed by dark ozonolysis was measured for 0.3–22.8 ppbv of reacted α-pinene. Most experiments were conducted using a continuous-flow chamber, allowing nearly constant SOA concentration and chemical composition for several days. For comparison, some experiments were also conducted in batch mode. Reaction conditions were 25°C, 40% RH, dry (NH4)SO4 seed particles, and excess 1-butanol. The organic particle loading was independently measured by an aerosol mass spectrometer and a scanning mobility particle sizer, and the two measurements agreed well. The observations showed that SOA formation occurred for even the lowest reacted α-pinene concentration of 0.3 ppbv. The particle mass yield was 0.09 at 0.15 μg m−3, increasing to 0.27 at 40 μg m−3. Compared to some results reported in the literature, the yields were 80 to 100% larger for loadings above 2 μg m−3. At lower loadings, the yields had an offset of approximately +0.07 from those reported in the literature. To as low as 0.15 μm−3, the yield curve had no inflection point toward null yield, implying the formation of one or several products having vapor pressures below this value. These observations of increased yields, especially for low loadings, are potentially important for accurate prediction by chemical transport models of organic particle concentrations in the ambient atmosphere.
Synthetic aperture sonar (SAS) is an emerging technology capable of providing high resolution seafloor imaging, which has the appealing property of range and frequency independent spatial resolution. However, for SAS systems with low frequency signals in shallow water environments, there are strong sea surface and bottom reflected wideband multipath components that interfere with the desired echo signal. Based upon a small vertically-displaced hydrophone array, several spatial processing algorithms have already been proposed for multipath reduction. Unfortunately, all of these algorithms are only applicable to narrowband signals, while wideband signals are always utilized in low-to-medium-frequency SAS systems for achieving high range resolution. Thus there is a great demand to solve the wideband multipath rejection problem in SAS systems. This paper discusses wideband multipath mitigation using a small vertical array and presents a steered robust Capon beamforming (SRCB) approach, together with conventional delay-and-sum beamforming (DSB), for shallow water wideband multipath rejection in SAS imaging. The designed performance improvements, mainly measured by direct-to-multipath-ratio (DMR) enhancements, are verified by numerical simulations. In addition, the limitations of these algorithms are also discussed.
Abstract Chemotherapy remains as the first-choice treatment option for triple-negative breast cancer (TNBC). However, the limited tumor penetration and low cellular internalization efficiency of current nanocarrier-based systems impede the access of anticancer drugs to TNBC with dense stroma and thereby greatly restricts clinical therapeutic efficacy, especially for TNBC bone metastasis. In this work, biomimetic head/hollow tail nanorobots were designed through a site-selective superassembly strategy. We show that nanorobots enable efficient remodeling of the dense tumor stromal microenvironments (TSM) for deep tumor penetration. Furthermore, the self-movement ability and spiky head markedly promote interfacial cellular uptake efficacy, transvascular extravasation, and intratumoral penetration. These nanorobots, which integrate deep tumor penetration, active cellular internalization, near-infrared (NIR) light-responsive release, and photothermal therapy capacities into a single nanodevice efficiently suppress tumor growth in a bone metastasis female mouse model of TNBC and also demonstrate potent antitumor efficacy in three different subcutaneous tumor models.
Abstract As the most effective way to manage the surge in municipal solid waste (MSW) and global energy issues, waste‐to‐energy (WTE) incineration plants have been actively promoted by the Chinese government, and the public‐private partnership (PPP) procurement model is widely used to improve management efficiency. However, risk events have occurred frequently in this industry due to a lack of practice experience and to poor risk management. To investigate the potential risk factors in PPP WTE incineration projects in China, this paper aims to identify critical risk factors by assessing their severity and occurrence probability. Opinions of industry experts were collected via an empirical questionnaire survey. The respondents were invited to rate a total of 18 risk factors that impact the success of PPP WTE projects as gleaned from previous research. The overall results ranked risk factors based on risk impact and showed that public opposition, government decision making, defective legal and regulatory systems, environmental pollution, lack of supporting infrastructure, and government credit are the top six risk factors affecting the sustainable development of PPP WTE incineration projects. In addition, the causes and consequences of each critical risk factor are comprehensively analyzed. Lastly, practical and managerial implications are analyzed in terms of their management of these critical risks. The originality of this research lies in thoroughly identifying potential implicit risk factors according to the current social background using an empirical questionnaire survey based on case study findings. The results of this study are expected to improve risk management and facilitate the sustainable development of the PPP WTE incineration industry in China.
Building digital government is an important means for the government to improve the public service ability and optimize the business environment, which directly affects the production and operation activities of micro-enterprises. Based on the panel data of listed enterprises and municipal government portal website performance in China, this paper empirically investigates the impact of digital government development on enterprise total factor productivity (TFP) and the moderating effect of the local government’s attention distribution. The research results showed that digital government development significantly improved the enterprise TFP, and this conclusion remained unchanged after a series of robustness tests using instrumental variables, one-stage lag of explained variables, and debiased machine learning models. We also found that the greater the pressure faced by local governments and the longer the chief officials’ tenure, the more attention local governments paid to building digital government, and the more obvious the role of digital government development in promoting enterprise TFP. Heterogeneity test results showed that the information disclosure, online service, and public participation all had a positive effect on enterprise TFP, while the user experience had no effect on it. Digital government development had a more obvious role in promoting enterprise TFP of central and western regions, non-SOEs, and technology-intensive enterprises. Moreover, reducing enterprise rent-seeking, attracting new enterprise entry, and increasing enterprise R&D investment are important mechanisms for digital government development to improve enterprise TFP.
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