2,942 research outputs found
Black-odorous water bodies annual dynamics in the context of climate change adaptation in Guangzhou City, China
Black-odorous water (BOW) in urban areas has brought detrimental ecological effects and posed a threat to the health of surrounding residents. Identifying BOWs in urban areas is difficult because they are usually small in area, and discontinuous in spatial distribution. The efforts to adapt to climate change in cities have a direct connection to urban environment and may affect the dynamics of BOWs, but their relationship has seldom been addressed in previous research. This research builds a new urban BOW detection model using Gaofen (GF) images and ground-level in-situ water quality data to detect the spatiotemporal dynamics of BOWs in Guangzhou City's main urban area from 2016 to 2020, when comprehensive climate adaptation strategy has been implemented as a pilot metropolitan area in China. Spatial analysis in the study area with a total of 97 focused rivers revealed a decreasing trend in BOW occurrence (from 85.57% in 2016 to 21.65% in 2020) in the context of climate change adaptation efforts. Redundancy analysis between BOWs occurrence and environmental factors showed that across the entire study area, the contributions of anthropogenic factors (highest proportion at 14.3% for the area percentage of built-ups) to BOW, such as population density, agricultural water use, domestic water use, and so on, distinctly stronger than climatic drivers (largest contribution of 4.4% for temperature). The results suggested that climate change adaptation efforts help to decrease BOW occurrence in the study area, while exploring the response mechanism between climate change adaptation measures and the changes of BOWs is necessary in the future research. The findings were conducive to the development of targeted measures to decrease the occurrence of urban BOWs while improving adaptability of the city to climate change
Chiral effect in plane isotropic micropolar elasticity and its application to chiral lattices
In continuum mechanics, the non-centrosymmetric micropolar theory is usually
used to capture the chirality inherent in materials. However when reduced to a
two dimensional (2D) isotropic problem, the resulting model becomes non-chiral.
Therefore, influence of the chiral effect cannot be properly characterized by
existing theories for 2D chiral solids. To circumvent this difficulty, based on
reinterpretation of isotropic tensors in a 2D case, we propose a continuum
theory to model the chiral effect for 2D isotropic chiral solids. A single
material parameter related to chirality is introduced to characterize the
coupling between the bulk deformation and the internal rotation which is a
fundamental feature of 2D chiral solids. Coherently, the proposed continuum
theory is also derived for a triangular chiral lattice from a homogenization
procedure, from which the effective material constants of the lattice are
analytically determined. The unique behavior in the chiral lattice is
demonstrated through the analyses of a static tension problem and a plane wave
propagation problem. The results, which cannot be predicted by the non-chiral
model, are validated by the exact solution of the discrete model.Comment: 33 pages, 7 figure
Bacterial diversity in the intestine of sea cucumber Stichopus japonicus
The intestinal bacterial diversity of Stichopus japonicus was investigated using 16S ribosomal RNA gene (rDNA) clone library and Polymerase Chain Reaction/Denaturing Gradient Gel Electrophoresis (PCR-DGGE). The clone library yielded a total of 188 clones, and these were sequenced and classified into 106 operational taxonomic units (OTUs) with sequence similarity ranging from 88 to 100%. The coverage of the library was 77.4%, with approximately 88.7% of the sequences affiliated to Proteobacteria. Gammaproteobacteria and Vibrio sp. were the predominant groups in the intestine of S. japonicus. Some bacteria such as Legionella sp., Brachybacterium sp., Streptomyces sp., Propionigenium sp. and Psychrobacter sp were first identified in the intestine of sea cucumber
Analysis of oscillations of atmospheric neutrinos
We briefly review the current status of standard oscillations of atmospheric
neutrinos in schemes with two, three, and four flavor mixing. It is shown that,
although the pure \nu_\mu-->\nu_\tau channel provides an excellent 2\nu fit to
the data, one cannot exclude, at present, the occurrence of additional
subleading \nu_\mu-->\nu_e oscillations (3\nu schemes) or of sizable
\nu_\mu-->\nu_s oscillations (4\nu schemes). It is also shown that the wide
dynamical range of energy and pathlength probed by the Super-Kamiokande
experiment puts severe constraints on nonstandard explanations of the
atmospheric neutrino data, with a few notable exceptions.Comment: Talk at the 19th International Conference on Neutrino Physics and
Astrophysics - Neutrino 2000 (Sudbury, Ontario, Canada, 16-21 June 2000
Impacts of environmental factors and human disturbance on composition of roadside vegetation in Xishuangbanna National Nature Reserve of Southwest China
AbstractVegetation-disturbance-environment relationships in Xishuangbanna Nature Reserve (XNR) was examined using multivariate analysis to understand the impacts of environmental factors and human disturbance on vegetation along the highway corridor. The results show that native forests were the best habitat for protected/endangered species and native species. The exotic plants Eupatorium odoratum and Eupatorium adenophora were found primarily in secondary forests and their presence was positively associated with altitude and soil potassium concentrations. The distribution of two protected plants, Phoebe nanmu and Pometia tomentosa, was negatively associated with road disturbance. Understanding the complex effects of environmental factors and human disturbance is key for developing conservation and restoration strategies for roadside plant ecosystems
Multiple time scales and the empirical models for stochastic volatility
The most common stochastic volatility models such as the Ornstein-Uhlenbeck
(OU), the Heston, the exponential OU (ExpOU) and Hull-White models define
volatility as a Markovian process. In this work we check of the applicability
of the Markovian approximation at separate times scales and will try to answer
the question which of the stochastic volatility models indicated above is the
most realistic. To this end we consider the volatility at both short (a few
days) and long (a few months)time scales as a Markovian process and estimate
for it the coefficients of the Kramers-Moyal expansion using the data for
Dow-Jones Index. It has been found that the empirical data allow to take only
the first two coefficients of expansion to be non zero that define form of the
volatility stochastic differential equation of Ito. It proved to be that for
the long time scale the empirical data support the ExpOU model. At the short
time scale the empirical model coincides with ExpOU model for the small
volatility quantities only.Comment: 19 pages, 6 figure
Higher Derivative Corrections to Locally Black Brane Metrics
In this paper we generalize the construction of locally boosted black brane
space time to higher derivative gravities. We consider the Gauss-Bonnet term
(with coefficient ) as a toy example. We find the solution to the
corrected Einstein equations to first order in the boundary
derivative expansion. This allows us to find the corrections to the
boundary stress tensor in the presence of the Gauss-Bonnet term in the bulk
action. We therefore obtain the ratio of shear viscosity to entropy which
agrees with other methods of computation in the literature.Comment: 0+17 page
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