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近海环境中抗生素分析样品前处理技术的研究进展
期刊论文
色谱, 2020, 卷号: 38, 期号: 1, 页码: 95-103
作者:
吕敏
;
陈令新
收藏
  |  
浏览/下载:117/0
  |  
提交时间:2020/07/08
抗生素
近海
前处理技术
综述
antibiotics
coastal
pretreatment techniques
review
The widespread and massive usage of antibiotics for the prevention and treatment of diseases in human and animals have resulted in their continuous discharge into the environment, and finally, into the coastal environment through various pathways. Accumulation of antibiotics in aquatic organisms poses a great threat to ecological and human health, especially because it facilitates the generation and spread of bacterial resistance. Given the diverse range of antibiotics with various features, as well as their presence at low concentrations in the environment, it is imperative to develop pretreatment techniques for antibiotics in various matrices. In this paper, the pretreatment methods proposed in recent decades for antibiotics in coastal water, sediment, and biota are summarized, with emphasis on commonly used methods such as solid-phase extraction, solid-liquid extraction, matrix solid-phase dispersion, and QuEChERS. Additionally, the potential factors influencing the extraction performance and clean-up efficiency are analyzed. The advantages and disadvantages of the methods and their development are finally discussed.
食用蔬菜能吸收和积累微塑料
期刊论文
科学通报, 2019, 卷号: 64, 期号: 9, 页码: 928-934
作者:
李连祯
;
周倩
;
尹娜
;
涂晨
;
骆永明
收藏
  |  
浏览/下载:63/0
  |  
提交时间:2020/06/17
微塑料
生菜
聚苯乙烯微球
吸收
积累
健康风险
microplastics
lettuce
polystyrene microbeads
uptake
accumulation
human health risk
Microplastic (MP, 100 nm-5 mm) may present an attributable risk to ecosystem and human health, and its pollution has become a global environmental concern. Despite a wealth of information on the accumulation of MPs in aquatic species, there is no information on the uptake and accumulation of MPs by higher plants. Terrestrial edible plants are directly exposed to MPs when agricultural soil was applied with organic manure, sewage sludge as fertilizer or plastic mulching. In this paper, the uptake of two sizes of polystyrene (PS) microbeads (0.2 and 1.0 mum) and then their distribution and migration in an edible plant lettuce were firstly investigated based on laboratory experiments. We used fluorescent markers to track PS microbeads in plant tissues and found fluorescence to be a sensitive and reliable detection method. Sections from untreated control lettuce showed no autofluorescence. When roots were treated with fluorescently labeled PS microbeads, the microbeads could be identified by its fluorescence. Our main study investigated the uptake of 0.2 mum beads, as few luminescence signals were observed in lettuce roots for 1.0 mum beads in our experiment. We observed that 0.2 mum fluorescent microbeads were extracellularly trapped in the root cap mucilage (which is a highly hydrated polysaccharide) and a dark green tip (which was typical of lettuce roots exposed to label PS beads) was usually visible to the naked eye. Confocal images revealed that the PS luminescence signals were mainly located in the vascular system and on the cell walls of the cortex tissue of the roots, indicated that the beads passed through the intercellular space via the apoplastic transport system. Once inside the central cylinder, the 0.2 mum PS beads were transferred from the roots to the stems and leaves via the vascular system following the transpiration stream. We also observed that the PS beads adhered to one another and self-assembled systematically into grape-like and (chain) string-like clusters in the intercellular space of the root and stem vascular tissue of lettuce plant. In contrast to the root and stem, PS beads were dispersed in the leaf tissue. Here, for the first time we provide evidence of the adherence, uptake, accumulation, and translocation of submicrometer MPs within an edible plant. Our findings highlight the previously underappreciated human exposure pathway to MPs through the consumption of contaminated crops and emphasize the need for new management strategies to control the release of MPs waste products into the terrestrial environment. Ultimately, the potential impacts of low range sized MPs on food safety of crop plants and human health need to be urgently considered.
Timing analysis of Swift J1658.2-4242's outburst in 2018 with Insight-HXMT, NICER and AstroSat
期刊论文
Journal of High Energy Astrophysics, 2019, 卷号: 24, 页码: 30-40
作者:
HXMT
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  |  
浏览/下载:46/0
  |  
提交时间:2022/02/08
Accretion
accretion disks
Black hole physics
X-rays: binaries:
Swift J1658.2-4242
Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the observational results from a detailed timing analysis of the black hole candidate Swift J1658.2-4242 during its 2018 outburst with the observations of Hard X-ray Modulation Telescope (Insight-HXMT), Neutron Star Interior Composition Explorer (NICER) and AstroSat in 0.1-250 keV. The evolution of intensity, hardness and integrated fractional root mean square (rms) observed by Insight-HXMT and NICER are presented in this paper. Type-C quasi-periodic oscillations (QPOs) observed by NICER (0.8-3.5 Hz) and Insight-HXMT (1-1.6 Hz) are also reported in this work. The features of the QPOs are analyzed with an energy range of 0.5-50 keV. The relations between QPO frequency and other characteristics such as intensity, hardness and QPO rms are carefully studied. The timing and spectral properties indicate that Swift J1658.2-4242 is a black hole binary system. Besides, the rms spectra of the source calculated from the simultaneous observation of Insight-HXMT, NICER and AstroSat support the Lense-Thirring origin of the QPOs. The relation between QPO phase lag and the centroid frequency of Swift J1658.2-4242 reveals a near zero constant when < 4Hz and a soft phase lag at 6.68 Hz. This independence follows the same trend as the high inclination galactic black hole binaries such as MAXI J1659-152.
An analysis of first-time and repeat visitors to Korean national parks from 2007 and 2013
期刊论文
Journal of Mountain Science, 2017, 卷号: 14, 期号: 12, 页码: 2527-2539
作者:
Yunseon CHOE
;
Michael A. SCHUETT
;
Kyu-Won SIM
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  |  
浏览/下载:124/0
  |  
提交时间:2017/12/07
ThIs Paper ExamIned VIsiTors To Bukhansan NatiOnal Park In Korea Based On First-time And Repeat vIsitatiOn. Bukhansan NatiOnal Park Is Korea's Most Heavily vIsited NatiOnal Park With Annual vIsitatiOn Of Six milliOn VIsiTors In 2015. Data Used In ThIs Article Were Collected On-site In The Park In 2007 And 2013 By The Korea NatiOnal Park Service (Knps). The Study Variables Included Socio-demographics
Travel Behavior
Motivation
And Satisfaction With Park Attributes
Services And Facilities. Data Were Analyzed By Each Study Year For First-time And Repeat Visitors. Results Showed Significant Differences For Both First-time And Repeat Visitors.On Several Socio-demographic
Travel Behavior
And Motivation Variables Within Each Study Year. For Satisfaction With Park Attributes
Facilities And Services
First-time VisiTors Were Significantly Different From Repeat VisiTors On Seven Variables For Both Years. implicatiOns Are Given Regarding Programs And Services To Improve visiTor satisfactiOn And Sustain The Natural
Cultural And HisTorical Resources At Bukhansan nAtional Park And Other nAtional Parks In Korea. Future Research Suggestions Are Provided To Learn More About visiTor Characteristics
StAndards Of Quality And Preferences In The National Parks.
一种稀土取代类Dawson结构硒钨酸盐的合成及性质研究
会议论文
2015年中西部地区无机化学化工学术研讨会, 2015-04-22
作者:
李海楼[1]
;
陈利娟[2]
;
赵俊伟[3]
收藏
  |  
浏览/下载:6/0
  |  
提交时间:2019/12/23
多金属氧酸盐
硒钨氧酸盐
电化学性质Recently
exploration and synthesis of rare-earth substituted polyoxometalate derivatives have been developed as an emerging area
however
relevant reports on Dawson-like polyoxotungstate rare-earth derivatives are very rare.In this paper
we communicate the first Dawson-like ra...
中国城镇居民住房的需求与供给
研究报告
2013
邹至庄
;
牛霖琳
收藏
  |  
浏览/下载:48/0
  |  
提交时间:2013/11/08
住房需求
住房供给
联立方程
Abstract
This
paper
addresses
the
issue
of
demand
and
supply
for
residential
housing
in
urban
China
since
the
late
1980s
when
the
urban
housing
market
became
commercialized.
We
start
with
the
basic
premise
that
the
standard
theory
of
demand
for
and
supply
of
consumer
durable
goods
is
applicable
to
urban
housing
in
China
after
the
market
for
housing
was
established.
In
a
simultaneous
equations
framework
we
provide
estimates
of
income
and
price
elasticities
of
demand
and
price
elasticity
of
supply.
Analysis
of
aggregated
annual
data
from
1987
to
2006
shows
that
the
rapid
increase
of
urban
residential
housing
can
be
well
explained
by
the
forces
of
demand
and
supply
i.e.
growth
in
income
and
change
in
construction
cost
determines
the
aggregated
movement
in
housing
price
to
a
large
extent.
We
have
found
the
(long-run)
income
elasticity
of
demand
for
urban
housing
to
be
about
1
and
the
price
elasticity
of
demand
to
be
between
-0.5
and
-0.6.
The
price
elasticity
of
supply
of
the
total
stock
of
housing
is
about
0.83.
Keywords:
housing
demand
housing
supply
simultaneous
equations
Rapid Micro-Patterning of a Conductive PANI/MWNTs-Polymer Composite Using an Optically-induced Electrokinetics Chip
会议论文
IEEE Nanotechnology Materials and Devices Conference (IEEE NMDC), Honolulu, HI, OCT 16-19, 2012
作者:
Liu N(刘娜)
;
Liang WF(梁文峰)
;
Mai, John D.
;
Dong ZL(董再励)
;
Li WJ(李文荣)
收藏
  |  
浏览/下载:31/0
  |  
提交时间:2013/12/26
A flexible, dynamically programmable and low-cost method applicable to micro-patterning of a conductive polymer/carbon nanotube composite solution is significant due to the potential applications in many areas. This paper demonstrates a new micro-patterning method for fabricating electrodes from a conductive polyaniline (PANI)/MWNT composite using an optically-induced electrokinetics (OEK) chip. This method quickly patterns flexible polymeric electrodes with different geometries when a square waveform signal with amplitudes from 16-20 Volts and frequencies from 20-30 kHz are applied. The geometric dimensions of the electrodes can be varied dynamically by controlling the size and exposure time of the light pattern. The surface morphology of electrodes patterned by this method is scanned by an atomic force microscope (AFM) and a scanning electron microscope (SEM) which show that the electrodes are uniform and continuous. Furthermore, the geometric dimensions and resistances of the electrodes are measured and analyzed. Experimental results reveal that the relationship between the resistance and geometries of the electrodes obey Ohm's law and the resistivity of the electrodes is about 0.03 Omega.m.
Effect of design parameters on the reduction of top piston ring friction (EI CONFERENCE)
会议论文
2nd International Conference on Computer-Aided Design, Manufacturing, Modeling and Simulation, CDMMS 2012, September 21, 2012 - September 23, 2012, Chongqing, China
Wu B.
;
Zhang Z.
;
Wang P.
收藏
  |  
浏览/下载:132/0
  |  
提交时间:2013/03/25
In order to reduce ring-liner interface friction power loss
this paper focuses on the structure parameters of the top ring
and investigates how the value of those parameters will influence top ring-liner friction power loss and the minimum thickness of oil film at top ring-liner interface. A mixed lubrication model is developed to simulate the effect of varying design parameters on ring-liner friction. Case study shows that ring-liner friction power loss will be reduced with decreased axial ring height and barrel height. This study provides a theoretical basis for design the top ring with reduced friction power loss at ring-liner interface. (2013) Trans Tech Publications
Switzerland.
Angle measurements with laser (EI CONFERENCE)
会议论文
2012 International Conference on Measurement, Instrumentation and Automation, ICMIA 2012, September 15, 2012 - September 16, 2012, Guangzhou, China
Wang Y.
;
Yan C.
;
Gao Z.
收藏
  |  
浏览/下载:132/0
  |  
提交时间:2013/03/25
Laser is widely used in angle measurements. This paper presents several frequently used methods of angle measurement that utilize laser
including:autocollimation angle measurement
angle measurement based on internal-reflection effect
laser interference angle measurement
angle measurement with ring laser and angle measurement with CCD. The principle
actualities
application situation
superiority and defects of each method are discussed. (2013) Trans Tech Publications
Switzerland.
LABTM control system based on FPGA (EI CONFERENCE)
会议论文
2nd International Conference on Mechatronics and Applied Mechanics, ICMAM 2012, December 8, 2012 - December 9, 2012, Taiwan
Li X. F.
;
Wang X. P.
;
Qi X. D.
;
Wang Y.
;
Yu P.
收藏
  |  
浏览/下载:142/0
  |  
提交时间:2013/03/25
This paper presents the digital PI control method for design and simulation of a high precision limited angle brushless torque motor control system in Field Programmable Gate Array device (FPGA). The direct drive structures which are widely applied in many servo control fields. Matlab Xilinx System GeneratorR toolbox based on Fixed-Point Arithmetic is used to design the digital PI controller using DSP architecture
plot the responses of the control system and generate the VHDL source code. The control system model consists of a digital PI
a real LABTM
and a real absolute Inductosyn
encoder to rpm and position blocks. Through loading generated codes in process of the simulation that built by the digital discrete model
it is verified that the rising time of current loop is only 1.2ms
and rate loop is 8ms
overshoot is rarely 4.2%. Finally
the comprehensive positioning accuracy of system can reach up to 5 arc sec
and the rate jitter achieves 5% with the 4 arc sec accuracy absolute Inductosyn. (2013) Trans Tech Publications
Switzerland.
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