Search

Population ageing and shrinking are demographic phenomena with far-reaching implications for sustainability in the current context of extensive and rapid urbanization. This Perspective rationalizes their interface by (a) identifying the challenges and opportunities that ageing and shrinking urban populations will have for implementing the sustainable development goals (SDGs), and (b) discussing some emerging interventions to capitalise on the opportunities and reduce the challenges to achieving sustainability. We argue that a diverse set of context-specific technological, socioeconomic, institutional and governance interventions would be needed to leverage effectively the opportunities and minimize the risks posed by ageing and shrinking urban populations for long-term sustainability.

The impact of phase structure on piezoelectric performances of &lt, 001&gt, textured Na0.5Bi0.5TiO3 (NBT) based lead-free ceramics was studied, including 0.88NBT-0.08K0.5Bi0.5TiO3-0.04BaTiO3 (88NBT) with morphotropic phase boundary (MPB) composition and 0.90NBT-0.07K0.5Bi0.5TiO3-0.03BaTiO3 (90NBT) with rhombohedral phase. Both textured ceramics exhibit a high Lotgering factor, being on the order of f~96%. The piezoelectric&nbsp, coefficients of the textured 88NBT and 90NBT ceramics are increased by 20% and 60%, respectively, comparing to their randomly oriented ceramics. The piezoelectric enhancement of 90NBT textured ceramic is three times higher than 88NBT, revealing the phase structure plays a significant role in enhancing the piezoelectric performances of textured ceramics. Of particular significance is that the 90NBT textured ceramic exhibits almost hysteresis-free strain behavior. The enhanced piezoelectric property with minimal strain hysteresis is attributed to the &lt, poled rhombohedral engineered domain configuration.

Background The increase in atmospheric CO2 is causing a number of changes in plant growth such as increases in leaf area and number, branching, plant size and biomass, and growth rate. Despite the importance of stomatal responses to CO2, little is known about the genetic and molecular mechanisms that mediate stomatal development and movement in response to CO2 levels. Deciphering the mechanisms that sense changes in CO2 and/or HCO3− concentration is critical for unraveling the role of CO2 in stomatal development movement. In Arabidopsis, CO2-induced stomatal closure is strongly Ca2+-dependent. To further dissect this signaling pathway and identify new components in the CO2 response pathway, we recorded [Ca2+]cyt changes in mutagenized Arabidopsis leaves and screened for mutants with abnormal guard cell behavior in response to CO2/HCO3−. Results We observed that 1 mM HCO3− induces [Ca2+]cys transient changes in guard cells and stomatal closure both in light and darkness. The changes in [Ca2+]cys induced by HCO3− could be detected by an aequorin-based calcium imaging system. Using this system, we identified a number of Arabidopsis mutants defective in both [Ca2+]cyt changes and the stomatal response to CO2/HCO3−. Conclusions We provide a sensitive method for isolating stomatal CO2/HCO3− response genes that function early in stomatal closure and that have a role in regulating [Ca2+]cyt. This method will be helpful in elucidating the Ca2+-dependent regulation of guard cell behavior in response to CO2/HCO3−.

A compact optical fiber sensor based on a Fabry–Perot interferometer (FPI) with an integrated fiber Bragg grating is proposed to measure pressure and temperature simultaneously. The light reflectors of the proposed FPI comprise a graphene film and a fiber end face. The sensitivities of the FPI sensor for measuring pressure and temperature are 501.4 nm/kPa and 306.2 nm/°C, respectively. Conflicting signals of pressure and temperature can cause cross-impact errors at 610 Pa/°C. The introduction of a fiber Bragg grating can effectively prevent the cross-impact of the FPI sensor. The pressure sensitivity obtained is 7.96 to 12 times higher than the previous study. The proposed fiber sensor can simultaneously measure pressure and temperature using a sensitivity matrix.

This paper aims to make clear the effects of two important parameters, namely thickness of soil layer and leaf area index of plant layer, on green roof energy and thermal performance. Based on a coupled hygrothermal transfer model validated by field experiments in Shanghai area, energy balance of plant and soil layer is analyzed. Then 18 cases are simulated for different combinations of soil thickness and leaf area index, the results show that soil thickness has a significant effect on long term thermal performance of green roof in both summer and winter, while the effect of leaf area index is only great in summer. Compared with the hypothetical case without evaporation and transpiration, it is found that evaporation of soil layer makes a greater contribution in summer but a less one in winter compared with insulation effect of soil layer. For plant layer, shading is the main cooling way of roof deck while transpiration plays a minor role. Finally, based on the simulation results of long-term thermal performance, two new indexes are proposed to evaluate the relative thermal characteristic of green roof. And the influences of soil thickness, leaf area index and evapotranspiration on the two indexes are analyzed respectively.

It's widely accepted that green roof systems exhibit varying thermal performances compared with common roofs, nonetheless, there are lack of indexes to characterize this difference with regards to internal mechanisms. In light of this condition, this paper presents two new indexes, namely insulation factor ( φ ) and comprehensive temperature regulation factor ( β ) based on insulation and passive cooling effect of the green roof. In order to predict long-term thermal performance of green roof in Shanghai area, a coupled heat and moisture transfer model is developed and validated by measurement data. Based on this model, green roof thermal performances are simulated under different indoor temperatures, and two indexes under different seasons are calculated. The results demonstrate that φ changes little around the year while β varies greatly. To make clear the variation rule of these two indexes, a sensitivity test is carried out. It's observed that thermal resistance of substrate layer and corresponding common roof are the main influence parameters of φ , while β is affected mostly by leaf area index, surface reflectivity and emissivity of substrate layer and common roof. In practice, these two indexes could be used to evaluate the relative thermal performance of different types of green roof against corresponding common roof.

This work provides a comparative study of the dielectric and piezoelectric properties of randomly oriented and textured 0.88Na0.5Bi0.5TiO3-0.08K0.5Bi0.5TiO3-0.04BaTiO3 (88NBT) ceramics. Textured ceramics were fabricated by template grain growth (TGG) method using NaNbO3 (NN) for templates. For textured ceramics with 4 wt% NN templates, a Lotgering factor of 96% and piezoelectric coefficient d33 of 185 pC/N were obtained. Compared to the randomly oriented ceramics, textured ceramics show lower strain hysteresis (H = 7.6%), higher unipolar strain of 0.041% with corresponding large signal piezoelectric coefficient d33* of 200 pm/V at applied field of 2 kV/mm. This enhancement can be explained by the grain orientation along &lt, 001&gt, direction by texturing, where an engineered domain configuration is formed after polarization, leading to decreased hysteresis and increased piezoelectric property.

Green roofs have been recognized as an effective way to increase urban green space and improve building micro-environment. This paper investigated the thermal and energy performance of an extensive green roof under free-floating 1 and air-conditioned conditions in Shanghai, a coastal city with hot and humid summer. A field experiment was conducted on two full-scale rooms of a building from 30/07/2014 to 31/08/2014. One room was covered by a green roof while the other one was covered by a common roof. The results show that solar radiation has the strongest correlation with green roof’s cooling effect, and the correlation between solar radiation and heat flux through green roof is negative in free-floating condition but positive under air-conditioned condition. Outdoor temperature is the most correlated factor of green roof’s temperatures but the least correlated one for green roof’s cooling effect. Energy balance analysis indicates that evapotranspiration and long wave radiation dissipate most of heat gain for green roof, and soil water content has a significant impact on energy balance. This paper presents the basic thermal characteristic of extensive green roof in Shanghai and also make it possible for further validation of hygrothermal transfer model of green roof system.

This paper presents an ultrahigh sensitive pressure and temperature sensor based on a Fabry-Perot interferometer (FPI) using a graphene diaphragm. The cavity of the FPI is the gap between the end-face of fiber Bragg gratings (FBG) and the graphene diaphragm. To prevent the serious cross-impact of pressure and temperature, a FBG is used to replace the single mode fiber. The sensitivities of pressure are 17.4698nm/kPa and 0.0267pm/kPa for FPI and FBG, respectively. The sensitivities of temperature are 5.075nm/°C and 10.9pm/°C, for FPI and FBG, respectively. The resolutions for pressure and temperature measurement are ±0.0267kPa and ±0.459°C with the wavelength resolution of 5pm. The experimental results show that the sensor is able to measure pressure and temperature simultaneously and accurately by a matrix on sensitivity. The proposed sensor can be applied on wide applications such as ocean exploration, biomedical science, and microfluidic, etc.

We propose modified laser Doppler imaging for real-time monitoring anomalous changes of blood flow. The imaging works based on the moving red blood cell concentration obtained with undersampled method.

We propose a full-field optical method for the label-free and quantitative mapping of the velocities of red blood cells (RBCs) in capillaries. It integrates spatiotemporal demodulation and an autocorrelation algorithm, and measures RBC velocity according to the ratio of RBC length to lag time. Conventionally, RBC length is assumed to be a constant and lag time is taken as a variable, while our method treats both of them as variables. We use temporal demodulation and the Butterworth spatial filter to separate RBC signal from background signal, based on which we obtain the RBC length by image segmentation and lag time by autocorrelation analysis. The RBC velocity calculated now is more accurate. The validity of our method is verified by an in vivo experiment on a mouse ear. Owing to its higher image signal-to-noise ratio, our method can be used for mapping RBC velocity in the turbid tissue case.