Generalized bioinspired approach to a daytime radiative cooling "skin"

Energy-saving cooling materials with strong operability are desirable towards sustainable thermal management. Inspired by the cooperative thermo-optical effect in fur of polar bear, we develop a flexible and reusable cooling skin via laminating a polydimethylsiloxane film with a highly-scattering polyethylene aerogel. Owing to its high porosity of 97.9% and tailored pore size of 3.8 +- 1.4 micrometers, superior solar reflectance of 0.96 and high transparency to irradiated thermal energy of 0.8 can be achieved at a thickness of 2.7 mm. Combined with low thermal conductivity of 0.032 W/m/K of the aerogel, the cooling skin exerts midday sub-ambient temperature drops of 5-6 degrees in a metropolitan environment, with an estimated limit of 14 degrees under ideal service conditions. We envision that this generalized bilayer approach will construct a bridge from night-time to daytime radiative cooling and pave the way for economical, scalable, flexible and reusable cooling materials.Comment: 15 pages, 4 figures, of which another version has been accepted by ACS ami but not published ye

Comprehensive analysis of grazing intensity impacts alpine grasslands across the Qinghai-Tibetan Plateau: A meta-analysis

Livestock grazing is a dominant practice in alpine grasslands and plays a crucial role in the ecosystem service of the Qinghai-Tibetan Plateau. The effects of grazing on alpine grasslands highly depends on grazing intensity. Up to now, we still lack comprehensive understanding of the general responses of alpine grasslands to different grazing intensities over broad geographic scales across the Qinghai-Tibetan Plateau. Here, we conducted a meta-analysis to explore the responses of plant characteristics and soil properties to grazing intensity in alpine grasslands of the Qinghai-Tibetan Plateau based on 52 peer-reviewed literatures. The results showed that grazing did not change the belowground biomass, while significantly increased the ratio of root to shoot (P< 0.05). Light grazing exhibited no significant effects on the plant richness, Shannon-Wiener diversity, soil water content, soil bulk density, nutrients, microbial biomass carbon, and microbial biomass nitrogen (P > 0.05). Moderate grazing significantly increased the plant richness and Shannon-Wiener diversity, while significantly decreased the soil organic carbon and total nitrogen (P< 0.05). Heavy grazing significantly decreased the plant richness, Shannon-Wiener diversity, water content, soil organic carbon, total nitrogen, microbial biomass carbon, and microbial biomass nitrogen, and significantly increased the soil bulk density (P< 0.05). These findings suggest that overgrazing is closely associated with grassland degradation, and moderate grazing is a sustainable practice to provide animal production and simultaneously maintain ecological functions for alpine grasslands on the Qinghai-Tibetan Plateau

Energy recovery transport design for PKU FEL

A SRF linac based free electron laser user facility is under developed at Peking University. Energy recovery Linac technology was chosen for increase of average electron beam current, hence, increase of the free electron laser power. In this paper we present a conceptual design of beam transport line which satisfies requirement of ERL. A chicane consisting of four identical bend magnets is selected for path length adjustment up to ?? 18 degree. R56 of both arcs of the beam line is adjustable for full bunch compression. ?2007 IEEE.EI

Digital Light Processing 3D‐Printed Silica Aerogel and as a Versatile Host Framework for High‐Performance Functional Nanocomposites

Abstract Vat‐photopolymerization‐based 3D printing enables on‐demand construction of customized objects with scalable production capacity and high precision. Herein, the sol‐gel process for aerogels with digital light processing 3D printing to produce advanced functional materials possessing hierarchical pore structures and complex shapes is combined. It has revealed the temporal evolution of the photorheological behavior of acrylate‐modified silica sols in an acid‐base catalytic procedure, and confirmed that silica aerogels can be fabricated with very low acrylate content. The resulting aerogels are thermostable with intrinsic silica contents, skeletal densities, and physical characteristics similar to those of commercial silica aerogels yet distinct mechanical behaviors. More importantly, the printed silica aerogels can be used as a versatile nanoengineering platform to produce high‐performance and multifunctional interpenetrating phase nanocomposites with complex shapes through programmable post‐printing processes. Epoxy‐based nanocomposites possessing excellent mechanical performance, ionogel‐based conductive nanocomposites with decoupled electrical and mechanical properties, and anti‐swelling hydrogel‐based nanocomposites are demonstrated. The results of this study offer new guidelines for the design and fabrication of novel materials by additive manufacturing

Insights into the Correlation of Aluminum Distribution and Brönsted Acidity in H‑Beta Zeolites from Solid-State NMR Spectroscopy and DFT Calculations

Here we utilized ²⁷Al MAS/MQMAS and ³¹P MAS NMR of quantitative adsorption of trimethylphosphine oxide (TMPO) and DFT calculations to elucidate the relationship between Al distribution and Brönsted acidity of series H-Beta zeolites derived from dealumination of Al-rich H-Beta zeolite. Three types of Brönsted acid strengths corresponding to different specific Al T-sites were demonstrated. The removal of one framework Al in 5MR2–-2Al and 6MR-2Al sites led to increasing the Brönsted acid strength of dealuminated H-Beta. Our findings on such exact correlation between specific Al distributions and corresponding Brönsted acid sites may guide the controlling Al distribution to get desired acid properties through zeolite synthesis or finely tuned dealumination, which has a great impact on the catalytic activity and selectivity of zeolite catalysts

The influence of soil moisture and solar altitude on surface spectral albedo in arid area

Using data collected from a specially designed experiment at the Dunhuang Station (40°10′N, 94°31′E, 1150 m) from September 2017 to September 2018, we have characterized the influences of soil moisture and solar altitude on surface spectral albedo in an arid area. The specific settings of our experiment allowed us to minimize the influences of underlying surface, cloud cover, aerosol and weather conditions, and thus highlight the influence of soil moisture and solar altitude. During the timespan of the experiment, we observed the annual mean surface albedo of global radiation (GR), ultraviolet radiation (UV), visible radiation (VIS) and near-infrared radiation (NIR) to be 0.24, 0.11, 0.24 and 0.25. A significantly negative linear correlation between surface albedo and soil moisture was identified, with the correlation coefficients between GR, UV, VIS, NIR and soil moisture being −0.68, −0.75, −0.70 and −0.61. In addition, we identified an exponential relationship between surface albedo and solar altitude. The exponential regression coefficients are −0.21, −0.077, −0.53 and −0.21, respectively. From these analyses, we derived a new two-factor parametric formula for depicting the influence of soil moisture and solar altitude on surface spectral albedo. Using observation data, we demonstrate that the formula recapitulates the real-world relationship between soil moisture, solar altitude and surface spectral albedo with little deviation. These findings may help us gain a deeper understanding of improving land surface parameterizations and have potential implications for solar energy research and applications

LncRNA expression profile and ceRNA analysis in tomato during flowering.

Long non-coding RNAs (lncRNAs) are a class of non-coding RNAs that play essential regulatory roles in various developmental processes and stress responses. However, the functions of lncRNAs during the flowering period of tomato are largely unknown. To explore the lncRNA profiles and functions during flowering in tomato, we performed strand-specific paired-end RNA sequencing of tomato leaves, flowers and roots, with three biological replicates. We identified 10919 lncRNAs including 248 novel lncRNAs, of which 65 novel lncRNAs were significantly differentially expressed (DE) in the flowers, leaves, and roots. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were carried out to identify the cis target gene of DE lncRNAs. The results showed that the lncRNAs might play an important role in the growth, development, and apoptosis of flowering tomato plant by regulating the formation of intima in flower tissues, binding to various molecules, influencing metabolic pathways, and inducing apoptosis. Moreover, we identified the interaction between 32, 78, and 397 kinds of miRNAs, lncRNAs, and mRNAs. The results suggest that the lncRNAs can regulate the expression of mRNA during flowering period in tomato by forming competitive endogenous RNA, and further regulate various biological metabolism pathways in tomato

Diffusion tensor imaging study of early white matter integrity in HIV-infected patients: A tract-based spatial statistics analysis

Objective: HIV preferentially affects brain, especially white matter (WM). We used diffusion tensor imaging (DTI) and tract-based spatial statistics (TBSS) to analyze early changes of the white matter in HIV-infected patients with normal appearance on conventional MRI. Methods: Diffusion tensor imaging data of 20 HIV-infected (HIV+) subjects not receiving cART (HIV+/cART−), 20 HIV+ subjects receiving stable cART (HIV+/cART+) for at least 12 consecutive weeks prior to study, and 20 HIV negative (HIV−) controls with matched age and sex. Using TBSS analysis method, the voxel-based differences in fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) of the global white matters were respectively compared between the HIV+/cART− group and the HIV− group, the HIV+/cART+ group and the HIV- group, the HIV+/cART− group and the HIV+/cART+ group. The correlation analysis was performed between diffusion parameters in brain regions with significant difference and CD4+ counts in the HIV+ group. Results: There were no statistical significances in white matter values (FA, MD, AD, RD) between HIV+/cART− group and HIV+/cART+ group. Compared with HIV− controls, HIV+/cART− patients showed significant increased MD in genu of corpus callosum (GCC), body of corpus callosum (BCC), splenium of corpus callosum (SCC), fornix (FOR) , bilateral anterior limb of internal capsule (ALIC), anterior corona radiate (ACR), superior corona radiate (SCR), posterior corona radiate (PCR), external capsule (EC), cingulum (cingulate gyrus) (CIN-CG), cingulum (hippocampus) (CIN–H), superior longitudinal fasciculus (SLF), right retrolenticular part of internal capsule (RIC), left posterior thalamic radiation (PTR); significant increased AD in GCC, BCC, SCC, FOR, bilateral ALIC, posterior limb of internal capsule (PLIC), RIC, ACR, SCR, PCR, EC, CIN-CG, CIN–H, SLF; significant increased RD in GCC, BCC, SCC, bilateral ALIC, ACR, SCR, PCR, PTR, EC, SLF, left CIN-CG (all P < 0. 05); No areas with FA changes were found. Compared with HIV- controls, HIV+/cART+ patients showed significant increased MD in GCC, BCC, SCC, FOR, bilateral ALIC, ACR, SCR, PCR, PTR, EC, CIN-CG, SLF, right PLIC, RIC, left CIN-H; significant increased AD in GCC, BCC, SCC, FOR, bilateral ALIC, PLIC, ACR, SCR, PCR, EC, CIN-CG, SLF, left RIC, right PTR; significant increased RD in GCC, BCC, SCC, bilateral ACR, SCR, PCR(all P < 0. 05); the difference of FA in every region was not significant between the two groups. In HIV+/cART− group, significant negative correlations were found between DTI indices (MD, RD values) and CD4+ counts in significant clusters (r = −0. 457, p = 0. 034; r = −0. 494, p = 0. 027). Conclusion: Multiple cerebral white matter fiber tracts are damaged in HIV-infected patients without cognitive impairment. Quantitative analysis of DTI using TBSS is valuable in evaluating changes of HIV-associated white matter microstructures