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The well thermal stability and mechanical properties of geopolymer can be attributed to its predominant adhesive constituent, sodium alumino-silicate hydrate (N-A-S-H). However, the intrinsic relation between molecular structure, stoichiometry, and performance of N-A-S-H is far from being understood. Herein, the structure, thermal stability, and tensile behavior of N-A-S-H at different Si/Al ratio are investigated by means of ReaxFF molecular dynamics. The results show that, after extreme low/high temperature treatment, the atomic configuration can also recover to a large extent. The hydrolysis during high temperature treatment slightly inhibits the structure recovery. Its expansion strain at elevated temperature is much smaller than that of calcium silicate hydrate, the primary component of Portland cement. Aluminum addition diminishes alumino-silicate skeleton’s connectivity and promotes the formation of energetically unstable Al–O–Al bonds, resulting in the drop of thermal stability and mechanical properties. The consistence between simulations and experiments demonstrates the considerable function of molecular structure of N-A-S-H for the macro-performance of geopolymer. Graphical abstract: [Figure not available: see fulltext.] Sodium alumino-silicate hydrate (N-A-S-H), featuring cross-linked glassy structure, exhibits excellent thermal stability. Mechanical properties increase with Si/Al ratio.

Multiphoton upconversion super-resolution microscopy (MPUM) is a promising imaging modality, which can provide increased resolution and penetration depth by using nonlinear near-infrared emission light through the so-called transparent biological window. However, a high excitation power is needed to achieve emission saturation, which increases phototoxicity. Here, we present an approach to realize the nonlinear saturation emission under a low excitation power by a simply designed on-chip mirror. The interference of the local electromagnetic field can easily confine the point spread function to a specific area to increase the excitation efficiency, which enables emission saturation under a lower excitation power. With no additional complexity, the mirror assists to decrease the excitation power by 10-fold and facilities the achievement of a lateral resolution around 35 nm, 1/28th of the excitation wavelength, in imaging of a single nanoparticle on-chip. This method offers a simple solution for super-resolution enhancement by a predesigned on-chip device.

Upconverting stimulated emission depletion microscopy (U-STED) is emerging as an effective approach for super-resolution imaging due to its significantly low depletion power and its ability to surpass the limitations of the square-root law and achieve higher resolution. Though the compelling performance, a trade-off between the spatial resolution and imaging quality in U-STED has been recognized in restricting the usability due to the low excitation power drove high depletion efficiency. Moreover, it is a burden to search for the right power relying on trial and error as the underpinning mechanism is unknown. Here, a method is proposed that can easily predict the ideal excitation power for high depletion efficiency with the assistance of the non-saturate excitation based on the dynamic cross-relaxation (CR) energy transfer of upconversion nanoparticles. This allows the authors to employ the rate equation model to simulate the populations of each relevant energy state of lanthanides and predict the ideal excitation power for high depletion efficiency. The authors demonstrate that the resolution of STED with the assistance of nonsaturated confocal super-resolution results can easily achieve the highest resolution of sub-40 nm, 1/24th of the excitation wavelengths. The finding on the CR effect provides opportunities for population control in realizing low-power high-resolution nanoscopy.

Upconverting stimulated emission depletion microscopy (U-STED) is emerging as an effective approach for super-resolution imaging due to its significantly low depletion power and its ability to surpass the limitations of the square-root law and achieve higher resolution. Though the compelling performance, a trade-off between the spatial resolution and imaging quality in U-STED has been recognized in restricting the usability due to the low excitation power drove high depletion efficiency. Moreover, it is a burden to search for the right power relying on trial and error as the underpinning mechanism is unknown. Here, a method is proposed that can easily predict the ideal excitation power for high depletion efficiency with the assistance of the non-saturate excitation based on the dynamic cross-relaxation (CR) energy transfer of upconversion nanoparticles. This allows the authors to employ the rate equation model to simulate the populations of each relevant energy state of lanthanides and predict the ideal excitation power for high depletion efficiency. The authors demonstrate that the resolution of STED with the assistance of nonsaturated confocal super-resolution results can easily achieve the highest resolution of sub-40 nm, 1/24th of the excitation wavelengths. The finding on the CR effect provides opportunities for population control in realizing low-power high-resolution nanoscopy.

The excellent performance and stability of perovskite solar cells (PSCs) based on quasi-2D Ruddlesden–Popper perovskites (RPPs) holds promise for their commercialization. Further improvement in the performance of 2D PSCs requires a detailed understanding of the microstructure of the quasi-2D perovskite films. Based on scanning transmission electron microscopy (STEM), time-resolved photoluminescence, and transient absorption measurements, a new sandwich-like structural model is proposed to describe the phase distribution of RPPs. In contrast to the conventional gradient distribution, it is found that small-n RPPs are sandwiched between large-n RPP phase layers at the front and back sides owing to crystallization initiated from both interfaces during film formation. This sandwich-like distribution profile facilitates excitons funneling from the film interior to both surfaces for dissociation while free carriers transport via large-n channels that permeate the film to ensure efficient charge collection by the corresponding electrodes, which is favorable for high-performance photovoltaics. This discovery provides a new fundamental understanding of the operating principles of 2D PSCs and has valuable implications for the design and optimization strategies of optoelectronic devices based on quasi-2D RPPs films.

Introducing layered quasi-2D perovskite phases into a conventional 3D perovskite light-absorbing matrix is a promising strategy for overcoming the limited environmental stability of 3D perovskite solar cells. Here, we present a simple drop-casting method for preparing hybrid perovskite films comprising both quasi-2D and quasi-3D phases, formed using phenylethylammonium or iso-butylammonium as spacer cations. The film morphology, phase purity, and crystal orientation of the hybrid quasi-2D/3D perovskite films are improved significantly by applying a simple N2 blow-drying step, together with inclusion of methylammonium chloride as an additive. An enhanced power conversion efficiency of 16.0% is achieved using an iso-butylammonium-based quasi-2D/3D perovskite layer which, to our knowledge, is the highest recorded to date for a quasi-2D/3D perovskite solar cells containing a non-spin-cast perovskite layer prepared under ambient laboratory conditions.

A mild and simple method was developed to synthesize a highly efficient photocatalyst comprised of Ce-doped ZnO rods and optimal synthesis conditions were determined by testing samples with different Ce/ZnO molar ratios calcined at 500 °C for 3 hours via a one-step pyrolysis method. The photocatalytic activity was assessed by the degradation of a common dye pollutant found in wastewater, rhodamine B (RhB), using a sunlight simulator. The results showed that ZnO doped with 3% Ce exhibits the highest RhB degradation rate. To understand the crystal structure, elemental state, surface morphology and chemical composition, the photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and inductively coupled plasma emission spectroscopy (ICP), respectively. The newly developed, robust, field-only surface integral method was employed to explore the relationship between the remarkable catalytic effect and the catalyst shape and porous microstructure. The computational results showed that the dipole-like field covers the entire surface of the rod-like Ce-doped ZnO photocatalyst and is present over the entire range of wavelengths considered. The optimum degradation conditions were determined by orthogonal tests and range analysis, including the concentration of RhB and catalyst, pH value and temperature. The results indicate that the pH value is the main influential factor in the photocatalytic degradation process and the optimal experimental conditions to achieve the maximum degradation rate of 97.66% in 2 hours are as follows: concentration (RhB) = 10 mg/L, concentration (catalyst) = 0.7 g/L, pH 9.0 and T = 50 °C. These optimum conditions supply a helpful reference for large-scale wastewater degradation containing the common water contaminant RhB.

© Cambridge University Press 2016. Introduction: The nature and scale of demand for national infrastructure services is driven by long-term changes in population, the economy, technology, society and the environment. However, how those factors affect the longer-term demand for infrastructure is not straightforward. Investment in infrastructure will be challenged by a number of fundamental long-term trends that include demographic developments (e.g. ageing and urbanisation), increasing constraints on public finances, environmental factors (climate change), technological progress (especially in the area of information and communication technology), trends in governance (particularly decentralisation), an expanding role for the private sector and an increasing need to maintain and upgrade existing infrastructures (OECD, 2007). Chapter 1 highlighted the relationship between infrastructure and the economy. However, the causation between infrastructure availability, economic growth and productivity remains subject to much uncertainty because the relationships between infrastructure and the economy are multiple and complex (Kessides, 1993; Serven, 1996; O'Fallon, 2003; Prud'Homme, 2004; Bourguignon and Pleskovic, 2005; Straub, 2011). Moreover, it is not necessarily generally the case that growth in the economy and population results in increasing demand for infrastructure services. For example, in the transport sector the notion of ‘peak car’ (Le Vine et al., 2009; Millard-Ball and Schipper, 2010), asserts that car ownership and usage may have plateaued (Chapter 5); and, the quantity of solid waste which needs to be dealt with by infrastructure has been decoupled from economic growth over time (Chapter 8). Nonetheless, it is clear that a growing population and economy are important factors that influence demand for infrastructure services, even while the relationship between these underlying factors and demand is changing. Moreover, it is not just aggregate demand that is

© Cambridge University Press 2016. Introduction: The nature and scale of demand for national infrastructure services is driven by long-term changes in population, the economy, technology, society and the environment. However, how those factors affect the longer-term demand for infrastructure is not straightforward. Investment in infrastructure will be challenged by a number of fundamental long-term trends that include demographic developments (e.g. ageing and urbanisation), increasing constraints on public finances, environmental factors (climate change), technological progress (especially in the area of information and communication technology), trends in governance (particularly decentralisation), an expanding role for the private sector and an increasing need to maintain and upgrade existing infrastructures (OECD, 2007). Chapter 1 highlighted the relationship between infrastructure and the economy. However, the causation between infrastructure availability, economic growth and productivity remains subject to much uncertainty because the relationships between infrastructure and the economy are multiple and complex (Kessides, 1993; Serven, 1996; O'Fallon, 2003; Prud'Homme, 2004; Bourguignon and Pleskovic, 2005; Straub, 2011). Moreover, it is not necessarily generally the case that growth in the economy and population results in increasing demand for infrastructure services. For example, in the transport sector the notion of ‘peak car’ (Le Vine et al., 2009; Millard-Ball and Schipper, 2010), asserts that car ownership and usage may have plateaued (Chapter 5); and, the quantity of solid waste which needs to be dealt with by infrastructure has been decoupled from economic growth over time (Chapter 8). Nonetheless, it is clear that a growing population and economy are important factors that influence demand for infrastructure services, even while the relationship between these underlying factors and demand is changing. Moreover, it is not just aggregate demand that is

© Cambridge University Press 2016. Introduction: The nature and scale of demand for national infrastructure services is driven by long-term changes in population, the economy, technology, society and the environment. However, how those factors affect the longer-term demand for infrastructure is not straightforward. Investment in infrastructure will be challenged by a number of fundamental long-term trends that include demographic developments (e.g. ageing and urbanisation), increasing constraints on public finances, environmental factors (climate change), technological progress (especially in the area of information and communication technology), trends in governance (particularly decentralisation), an expanding role for the private sector and an increasing need to maintain and upgrade existing infrastructures (OECD, 2007). Chapter 1 highlighted the relationship between infrastructure and the economy. However, the causation between infrastructure availability, economic growth and productivity remains subject to much uncertainty because the relationships between infrastructure and the economy are multiple and complex (Kessides, 1993; Serven, 1996; O'Fallon, 2003; Prud'Homme, 2004; Bourguignon and Pleskovic, 2005; Straub, 2011). Moreover, it is not necessarily generally the case that growth in the economy and population results in increasing demand for infrastructure services. For example, in the transport sector the notion of ‘peak car’ (Le Vine et al., 2009; Millard-Ball and Schipper, 2010), asserts that car ownership and usage may have plateaued (Chapter 5); and, the quantity of solid waste which needs to be dealt with by infrastructure has been decoupled from economic growth over time (Chapter 8). Nonetheless, it is clear that a growing population and economy are important factors that influence demand for infrastructure services, even while the relationship between these underlying factors and demand is changing. Moreover, it is not just aggregate demand that is

Deafferentation pain secondary to brachial plexus avulsion, spinal cord injury, and other peripheral nerve injuries is often refractory to conventional treatments. Stimulation of the primary motor cortex (M1) has been proven to be an effective treatment for intractable deafferentation pain. The mechanisms underlying the attenuation of deafferentation pain by motor cortex stimulation remain hypothetical.