924 research outputs found
Effects of urban green belts on the air temperature, humidity and air quality
As urbanization increases, designing green space that offers ecological benefits is an increasingly important goal of urban planning. As a linear green space in an urban environment, green belts lower air temperature, increase relative humidity, and improve air quality. To quantify the ecological effects of urban green belts and to identify a critical width for effective urban green belts, we analysed the width of urban green belts in terms of their effects on air temperature (T), relative humidity (RH), concentration of negative air ions (NAI) and bacteria rate (BR). The air T, RH and NAI from 8:00 to 18:00 and BR at 9:00 over seven days were investigated on six widths of green belts (0–10 m, 10–20 m, 20–30 m, 30–40 m, 40–50 m and over 50 m) along the west Fourth Ring Road of Beijing in April, July, October and December 2009. We found that (1) the T-RH benefits increased with the width of the green belts, and the 6 m belt had the smallest effect on T-RH, followed by the 16 m and 27 m belts, whereas the effect was obvious with the 34 m belt and conspicuous and stable with the 42 m belt (approximately 80% green coverage) (P < 0.05); (2) the critical width reference value of urban green belts for an obvious effect on the increase in NAI concentration was approximately 42 m (approximately 80% green coverage) (P < 0.05) and the NAI concentration increased with the width of green belts even in July; and (3) the positive effect on the decrease in the BR was greater than the negative effect, the BR decreased with the green belt width and the changes in the brs were stable with the 34 m belt. The results of this study may help urban planners and designers achieve urban green space designs that optimize ecological effects and cultural benefits
Experimental spectra analysis in THM with the help of simulation based on Geant4 framework
The Coulomb barrier and electron screening cause difficulties in directly
measuring nuclear reaction cross sections of charged particles in astrophysical
energies. The Trojan-horse method has been introduced to solve the difficulties
as a powerful indirect tool. In order to understand experimental spectra
better, Geant4 is employed to simulate the method for the first time. Validity
and reliability of the simulation are examined by comparing the experimental
data with simulated results. The Geant4 simulation can give useful information
to understand the experimental spectra better in data analysis and is
beneficial to the design for future related experiments.Comment: 4 pages, 5 figure
Optimal Systemic Risk Bailout: A PGO Approach Based on Neural Network
The bailout strategy is crucial to cushion the massive loss caused by
systemic risk in the financial system. There is no closed-form formulation of
the optimal bailout problem, making solving it difficult. In this paper, we
regard the issue of the optimal bailout (capital injection) as a black-box
optimization problem, where the black box is characterized as a fixed-point
system that follows the E-N framework for measuring the systemic risk of the
financial system. We propose the so-called ``Prediction-Gradient-Optimization''
(PGO) framework to solve it, where the ``Prediction'' means that the objective
function without a closed-form is approximated and predicted by a neural
network, the ``Gradient'' is calculated based on the former approximation, and
the ``Optimization'' procedure is further implemented within a gradient
projection algorithm to solve the problem. Comprehensive numerical simulations
demonstrate that the proposed approach is promising for systemic risk
management
The arabidopsis RCC1 family protein TCF1 regulates freezing tolerance and cold acclimation through modulating lignin biosynthesis
Cell water permeability and cell wall properties are critical to survival of plant cells during freezing, however the underlying molecular mechanisms remain elusive. Here, we report that a specifically cold-induced nuclear protein, Tolerant to Chilling and Freezing 1 (TCF1), interacts with histones H3 and H4 and associates with chromatin containing a target gene, BLUE-COPPER-BINDING PROTEIN (BCB), encoding a glycosylphosphatidylinositol-anchored protein that regulates lignin biosynthesis. Loss of TCF1 function leads to reduced BCB transcription through affecting H3K4me2 and H3K27me3 levels within the BCB gene, resulting in reduced lignin content and enhanced freezing tolerance. Furthermore, plants with knocked-down BCB expression (amiRNA-BCB) under cold acclimation had reduced lignin accumulation and increased freezing tolerance. The pal1pal2 double mutant (lignin content reduced by 30% compared with WT) also showed the freezing tolerant phenotype, and TCF1 and BCB act upstream of PALs to regulate lignin content. In addition, TCF1 acts independently of the CBF (C-repeat binding factor) pathway. Our findings delineate a novel molecular pathway linking the TCF1-mediated cold-specific transcriptional program to lignin biosynthesis, thus achieving cell wall remodeling with increased freezing tolerance
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