MEASUREMENT OF SUN INDUCED CHLOROPHYLL FLUORESCENCE USING HYPERSPECTRAL SATELLITE IMAGERY

Steady State ◽

Satellite Images ◽

Plant Stress ◽

Fluorescence Signal ◽

Absorption Bands ◽

Considerable Evidence ◽

Different Seasons ◽

Insight Into ◽

Accurate Indicator

Solar Induced Chlorophyll Fluorescence (SIF), can be used as an indicator of stress in vegetation. Several scientific approaches have been made and there is considerable evidence that steady state Chlorophyll fluorescence is an accurate indicator of plant stress hence a reliable tool to monitor vegetation health status. Retrieval of Chlorophyll fluorescence provides an insight into photochemical and carbon sequestration processes within vegetation. Detection of Chlorophyll fluorescence has been well understood in the laboratory and field measurement. Fluorescence retrieval methods were applied in and around the atmospheric absorption bands 02B (Red wavelength) approximately 690 nm and 02A (Far red wavelengths) 740 nm. Hyperion satellite images were acquired for the years 2012 to 2015 in different seasons. Atmospheric corrections were applied using the 6S Model. The Fraunhofer Line Discrimanator (FLD) method was applied for retrieval of SIF from the Hyperion images by measuring the signal around the absorption bands in both vegetated and non vegetated land cover types. Absorption values were extracted in all the selected bands and the fluorescence signal was detected. The relationships between NDVI and Fluorescence derived from the satellite images are investigated to understand vegetation response within the absorption bands.

Improved detection of reactive oxygen species by DCFH-DA: New insight into self-amplification of fluorescence signal by light irradiation

Sensors and Actuators B Chemical ◽

10.1016/j.snb.2021.129878 ◽

2021 ◽

Vol 339 ◽

pp. 129878

Author(s):

Daliang Yu ◽

Yingying Zha ◽

Zheng Zhong ◽

Yiming Ruan ◽

Ziwei Li ◽

...

Keyword(s):

Reactive Oxygen Species ◽

Reactive Oxygen ◽

Light Irradiation ◽

Fluorescence Signal ◽

Oxygen Species ◽

New insight into the stable grain size of nanotwinned Ni in steady-state creep: Effect of the ratio of effective-to-internal stress

International Journal of Plasticity ◽

10.1016/j.ijplas.2016.07.009 ◽

2016 ◽

Vol 85 ◽

pp. 172-189 ◽

Cited By ~ 21

Author(s):

J. Li ◽

J.Y. Zhang ◽

G. Liu ◽

J. Sun

Keyword(s):

Grain Size ◽

Steady State ◽

Internal Stress ◽

Steady State Creep ◽

Creep Effect ◽

Fluorescent chemosensors for metal ions based on 3-(2-benzoxazol-5-yl)alanine skeleton

Open Chemistry ◽

10.2478/s11532-010-0036-9 ◽

2010 ◽

Vol 8 (3) ◽

pp. 674-686 ◽

Cited By ~ 1

Author(s):

Magda Milewska ◽

Katarzyna Guzow ◽

Wiesław Wiczk

Keyword(s):

Steady State ◽

Fluorescence Spectroscopy ◽

Metal Ions ◽

Ground State ◽

Transition Metal Ions ◽

Fluorescent Chemosensors ◽

Time Resolved Fluorescence ◽

Absorption Bands ◽

Time Resolved ◽

Ratiometric Sensors

AbstractThe ability of new chelate ligands, benzoxazol-5-yl-alanine derivatives substituted in position 2 by heteroaromatic substituent, to form complexes with selected metal ions in acetonitrile are studied by means of absorption and steady-state and time-resolved fluorescence spectroscopy. Among the ligands studied, only azaaromatic derivatives form stable complexes with transition metal ions in the ground state. Their absorption bands are bathochromically shifted enabling to use those ligands as ratiometric sensors. The fluorescence of each ligand is quenched by metal ions, however, in the presence of Cd(II) and Zn(II) ions a new red shifted emission band is observed.

Landscape evolution models using the stream power incision model show unrealistic behavior when <i>m</i> ∕ <i>n</i> equals 0.5

Earth Surface Dynamics ◽

10.5194/esurf-5-807-2017 ◽

2017 ◽

Vol 5 (4) ◽

pp. 807-820 ◽

Cited By ~ 5

Author(s):

Jeffrey S. Kwang ◽

Gary Parker

Keyword(s):

Steady State ◽

Landscape Evolution ◽

Drainage Area ◽

Uplift Rate ◽

Stream Power ◽

River Incision ◽

Vertical Incision ◽

Small Scales ◽

Abstract. Landscape evolution models often utilize the stream power incision model to simulate river incision: E = KAmSn, where E is the vertical incision rate, K is the erodibility constant, A is the upstream drainage area, S is the channel gradient, and m and n are exponents. This simple but useful law has been employed with an imposed rock uplift rate to gain insight into steady-state landscapes. The most common choice of exponents satisfies m ∕ n = 0.5. Yet all models have limitations. Here, we show that when hillslope diffusion (which operates only on small scales) is neglected, the choice m ∕ n = 0.5 yields a curiously unrealistic result: the predicted landscape is invariant to horizontal stretching. That is, the steady-state landscape for a 10 km2 horizontal domain can be stretched so that it is identical to the corresponding landscape for a 1000 km2 domain.

Easy insight into space-charge effects on steady-state transport in oxide films

Oxidation of Metals ◽

10.1007/bf00605111 ◽

1979 ◽

Vol 13 (5) ◽

pp. 475-479 ◽

Cited By ~ 9

Author(s):

A. T. Fromhold

Keyword(s):

Steady State ◽

Space Charge ◽

Oxide Films ◽

Space Charge Effects ◽

Charge Effects ◽

Steady-State Kinetics of Chlorophyll-Fluorescence and Light Scattering

Progress in Photosynthesis Research ◽

10.1007/978-94-009-3535-8_175 ◽

1987 ◽

pp. 745-748 ◽

Cited By ~ 2

Author(s):

Jörg Kolbowski

Keyword(s):

Steady State ◽

Light Scattering ◽

Steady State Kinetics ◽

Kinetics Of

Modification of a gas exchange system to measure active and passive chlorophyll fluorescence simultaneously under field conditions

AoB Plants ◽

10.1093/aobpla/plaa066 ◽

2020 ◽

Author(s):

Eliot W Meeker ◽

Troy S Magney ◽

Nicolas Bambach ◽

Mina Momayyezi ◽

Andrew J McElrone

Keyword(s):

Steady State ◽

Gas Exchange ◽

Near Infrared ◽

Pulse Amplitude ◽

Bottom Plate ◽

Pam Fluorometer ◽

Promising Tool ◽

Leaf Level ◽

Gas Exchange System

Abstract Solar-induced fluorescence (SIF) is a promising tool to estimate photosynthesis across scales; however, there has been limited research done at the leaf-level to investigate the relationship between SIF and photosynthesis. To help bridge this gap, a LI-COR LI-6800 gas exchange instrument was modified with a visible-near-infrared (VIS-NIR) spectrometer to measure active and passive fluorescence simultaneously. The system was adapted by drilling a hole into the bottom plate of the leaf chamber and inserting a fiber-optic to measure passive steady-state fluorescence (Ft,λ, analogous to SIF) from the abaxial surface of a leaf. This new modification can concurrently measure gas exchange, passive fluorescence, and active fluorescence over the same leaf area and will allow researchers to measure leaf-level Ft,λ in the field to validate tower-based and satellite measurements. To test the modified instrument, measurements were performed on leaves of well-watered and water stressed walnut plants at three light-levels and a constant air temperature. Measurements on these same plants were also conducted using a similarly modified Walz GFS-3000 gas exchange instrument to compare results. We found a positive linear correlation between Ft,λ measurements from the modified LI-6800 and GFS-3000 instruments. We also report a positive linear relationship between Ft,λ and normalized steady-state chlorophyll fluorescence (Ft/Fo) from the pulse-amplitude modulation (PAM) fluorometer of the LI-6800 system. Accordingly, this modification will inform the link between spectrally resolved Ft,λ and gas-exchange – leading to improved interpretation of how remotely sensed SIF tracks changes in the light reactions of photosynthesis.

Atmospheric Correction for Tower-Based Solar-Induced Chlorophyll Fluorescence Observations at O2-A Band

Remote Sensing ◽

10.3390/rs11030355 ◽

2019 ◽

Vol 11 (3) ◽

pp. 355 ◽

Cited By ~ 6

Author(s):

Xinjie Liu ◽

Jian Guo ◽

Jiaochan Hu ◽

Liangyun Liu

Keyword(s):

Atmospheric Correction ◽

Field Measurements ◽

Correction Method ◽

Oxygen Absorption ◽

Atmospheric Transmission ◽

Absorption Bands ◽

Transfer Path ◽

The Difference ◽

Atmospheric Transmittance

Solar-induced chlorophyll fluorescence (SIF) has been proven to be an efficient indicator of vegetation photosynthesis. To investigate the relationship between SIF and Gross Primary Productivity (GPP), tower-based continuous spectral observations coordinated with eddy covariance (EC) measurements are needed. As the strong absorption effect at the O2-A absorption bands has an obvious influence on SIF retrieval based on the Fraunhofer Line Discrimination (FLD) principle, atmospheric correction is required even for tower-based SIF observations made with a sensor tens of meters above the canopy. In this study, an operational and simple solution for atmospheric correction of tower-based SIF observations at the O2-A band is proposed. The aerosol optical depth (AOD) and radiative transfer path length (RTPL) are found to be the dominant factors influencing the upward and downward transmittances at the oxygen absorption band. Look-up tables (LUTs) are established to estimate the atmosphere transmittance using AOD and RTPL based on the MODerate resolution atmospheric TRANsmission 5 (MODTRAN 5) model simulations, and the AOD is estimated using the ratio of the downwelling irradiance at 790 nm to that at 660 nm (E790/E660). The influences of the temperature and pressure on the atmospheric transmittance are also compensated for using a corrector factor of RTPL based on an empirical equation. A series of field measurements were carried out to evaluate the performance of the atmospheric correction method for tower-based SIF observations. The difference between the SIF retrieved from tower-based and from ground-based observations decreased obviously after the atmospheric correction. The results indicate that the atmospheric correction method based on a LUT is efficient and also necessary for more accurate tower-based SIF retrieval, especially at the O2-A band.

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

Ultrasonic measurement of self-loosening in bolted joints

10.1177/0954406211429758 ◽

2011 ◽

Vol 226 (7) ◽

pp. 1869-1884 ◽

Cited By ~ 7

Author(s):

MB Marshall ◽

R Lewis ◽

T Howard ◽

H Brunskill

Keyword(s):

Steady State ◽

Ultrasonic Measurement ◽

Bolted Joints ◽

Catastrophic Failure ◽

Interface Pressure ◽

Rapid Reduction ◽

Contact Conditions ◽

Joint Integrity ◽

Clamping Pressure ◽

Self-loosening of bolted joints in response to vibration can lead to the catastrophic failure of a range of engineering components and structures. Many techniques employed to study this phenomenon focus on directly measuring the pre-load remaining in the bolt itself, and offer little insight into the behaviour of the clamped interface. In this study, a non-intrusive ultrasonic reflection-based technique is used to first characterize interface pressure in the joint, and then determine the rate at which relaxation occurs. A key advantage of the technique is that it does not require the modification of the contact conditions, and rather utilizes the spring-like behaviour of a rough surface interface when subject to ultrasonic excitation. A series of different bolt torques were investigated, along with the inclusion of both plain and spring washers under the bolt head. All test samples were subjected to an oscillating fixed–displacement vibration cycle. An initial rapid reduction in interface clamping pressure was observed, followed by a more steady-state period. Increasing bolt torque was seen to enhance joint integrity, whereas both the plain and spring washers showed little improvement. The spring washer was observed to extend the secondary steady-state phase of loosening, though as the majority of pre-load was removed prior to this period any change was largely unbeneficial.