A generalized exchange-correlation functional: the Neural-Networks approach

A Neural-Networks-based approach is proposed to construct a new type of exchange-correlation functional for density functional theory. It is applied to improve B3LYP functional by taking into account of high-order contributions to the exchange-correlation functional. The improved B3LYP functional is based on a neural network whose structure and synaptic weights are determined from 116 known experimental atomization energies, ionization potentials, proton affinities or total atomic energies which were used by Becke in his pioneer work on the hybrid functionals [J. Chem. Phys. ${\bf 98}$, 5648 (1993)]. It leads to better agreement between the first-principles calculation results and these 116 experimental data. The new B3LYP functional is further tested by applying it to calculate the ionization potentials of 24 molecules of the G2 test set. The 6-311+G(3{\it df},2{\it p}) basis set is employed in the calculation, and the resulting root-mean-square error is reduced to 2.2 kcal$\cdot$mol$^{-1}$ in comparison to 3.6 kcal$\cdot$mol$^{-1}$ of conventional B3LYP/6-311+G(3{\it df},2{\it p}) calculation.Comment: 10 pages, 1figur

Analysis of landscape influencing factors of urban waterfront greenways based on the scenic beauty estimation method, taking Tongjian Lake in Hangzhou as an example

In order to assess the unique beauty of Tongjian Lake in Hangzhou, 80 sample photographs were selected for landscape beauty degree assessment using the Scenic Beauty Estimation method. The 14 characteristic influencing factors of landscape photos were extracted according to the Scenic Beauty Estimation value, and the influencing factors with insignificant differences and small bias correlation coefficients were eliminated through multiple linear regression analysis. The results showed that the main factors affecting the expression of the beauty of Tongjian Lake were water ecology, greenway morphology, landscape openness, water area ratio, vegetation color richness, and vignette matching. Combining the abovementioned analysis results, the two-dimensional plan, isometric map, and three-dimensional space are combined to show the main factors in a visual way, and on this basis, the corresponding optimization strategy is proposed. It provides a reference for future urban waterfront greenway landscape creation

Seaweed polysaccharide relieves hexavalent chromium-induced gut microbial homeostasis

Heavy metals released in the environment pose a huge threat to soil and water quality, food safety and public health. Additionally, humans and other mammals may also be directly exposed to heavy metals or exposed to heavy metals through the food chain, which seriously threatens the health of animals and humans. Chromium, especially hexavalent chromium [Cr (VI)], as a common heavy metal, has been shown to cause serious environmental pollution as well as intestinal damage. Thus, increasing research is devoted to finding drugs to mitigate the negative health effects of hexavalent chromium exposure. Seaweed polysaccharides have been demonstrated to have many pharmacological effects, but whether it can alleviate gut microbial dysbiosis caused by hexavalent chromium exposure has not been well characterized. Here, we hypothesized that seaweed polysaccharides could alleviate hexavalent chromium exposure-induced poor health in mice. Mice in Cr and seaweed polysaccharide treatment group was compulsively receive K2Cr2O7. At the end of the experiment, all mice were euthanized, and colon contents were collected for DNA sequencing analysis. Results showed that seaweed polysaccharide administration can restore the gut microbial dysbiosis and the reduction of gut microbial diversity caused by hexavalent chromium exposure in mice. Hexavalent chromium exposure also caused significant changes in the gut microbial composition of mice, including an increase in some pathogenic bacteria and a decrease in beneficial bacteria. However, seaweed polysaccharides administration could ameliorate the composition of gut microbiota. In conclusion, this study showed that seaweed polysaccharides can restore the negative effects of hexavalent chromium exposure in mice, including gut microbial dysbiosis. Meanwhile, this research also lays the foundation for the application of seaweed polysaccharides

Integrated Approach for Low-Cost and Sensitive Multiplex Pathogen Detection on 3D Paper-Based Microfluidic Devices

Recently, pathogenic microorganisms have aroused wide public concern for their potential to cause serious diseases in humans, animals and agricultural crops. Although DNA microarrays are commonly used for pathogen detection, the approach is sophisticated, time-consuming and requires expensive equipment, limiting its application in resource-poor settings. Herein we present a novel, low-cost, paper-based microfluidic approach for multiplexed DNA detection of Giardia Lamblia, S. aureus, and Entamoeba, by “on-chip” isothermal DNA amplification and hybridization. Paper-based microfluidics offers a novel, sensitive and low-cost alternative for Point-of-Care Diagnostics for the Developing Countries. The project described utilizes Loop-mediated Isothermal Amplification (LAMP), a novel isothermal DNA amplification method using six primers to amplify a target DNA sequence specific to each pathogen. ssDNA probes covalently-immobilized at three separate detection zones then bind their complementary CY3-labeled amplification products. Currently, the flow speed in our paper-based device has been optimized to reach the detection zones quickly after amplification and with as little as 15 µl of reagents. The integration of both the amplification and hybridization steps in one multiplexed paper device will allow for on-site testing of pathogens with minimal device fabrication costs, less reagent consumption, no need for expensive laboratory equipment, and minimal expertise requirements to retrieve highly-sensitive genetic testing. As such, our paper-based microfluidic device will potentially bring sophisticated DNA testing to people in regions with limited healthcare infrastructure and adequate laboratory facilities, but with a high demand for in situ diagnosis and treatment

Water Hammer Protection Characteristics and Hydraulic Performance of a Novel Air Chamber with an Adjustable Central Standpipe in a Pressurized Water Supply System

Water scarcity is an urgent issue for social and economic development in arid and semi-arid areas. Constructing long-distance pressurized water supply projects is a commonly used measure to solve water scarcity problems in these areas. With the increasing complexity of long-distance pressurized water supply projects, the issue of water hammer protection has become more and more prominent. Air chambers have been widely used to solve the issue of water hammer accidents. In this paper, we propose a novel air chamber with an adjustable central standpipe, and then analyze the hydraulic performance, as well as the water hammer protection characteristics, of the proposed novel air chamber using numerical simulations. The influences of the inner length, the diameter of the central standpipe, and the diameter of the bottom connecting pipe on the hydraulic performance of the air chamber are also studied. Then, the optimization of the relevant parameters of the central standpipe for the proposed air chamber is conducted. In addition, the volumes of the proposed air chamber and conventional air chambers are compared

Association between sleep duration and high blood pressure in adolescents: a systematic review and meta-analysis

Context: Sleep has been assessed as a risk factor for health consequences. Among adults, excessively longer and shorter sleep durations are associated with high blood pressure (BP), but knowledge of the association between sleep duration and high BP among adolescents is limited. Objectives: To estimate the associations between sleep duration and high BP in adolescents. Methods: PubMed, Web of Science, and Cochrane databases were searched for eligible publications up until 20 November 2017. This study reviewed the reference lists from retrieved articles to search for relevant studies. Pooled odds ratios (ORs) were calculated using a random-effects meta-analysis. Sub-group and sensitivity analyses were conducted to identify heterogeneity. Publication bias was evaluated using Egger’s test. Results: Seven studies involving 21,150 participants were included, with ages ranging from 10–18 years. For primary analysis, compared with the reference sleep duration, the pooled OR for high BP was 1.51 (95% confidence interval [CI] = 1.04–2.19) for the short sleep duration overall. For long sleep duration, the pooled OR was 1.04 (95% CI = 0.78–1.38). Further sub-group analysis showed that short sleep duration had a higher risk of incident high BP in males (OR = 1.55, 95% CI = 1.24–1.93) than in females (OR = 1.23, 95% CI = 0.47–3.22). Conclusions: Among adolescents, and particularly male adolescents, short sleep duration may be a risk factor for high BP. More attention should be given to this lifestyle factor