Cayley Transformation and Numerical Stability of Calibration Equation

Chlorophyll-a measurements are an important factor in the water quality monitoring of surface waters, especially for determining the trophic status and ecosystem management. However, a collection of field samples for extractive analysis in a laboratory may not fully represent the field conditions. Handheld fluorometers that can measure chlorophyll-a in situ are available, but their performance in waters with a variety of potential light-interfering substances has not yet been tested. We tested a handheld fluorometer for sensitivity to ambient light and turbidity and compared these findings with EPA Method 445.0 using water samples obtained from two urban lakes in Tucson, Arizona, USA. Our results suggested that the probe was not sensitive to ambient light and performed well at low chlorophyll-a concentrations (<25 µg/L) across a range of turbidity levels (50–70 NTU). However, the performance was lower when the chlorophyll-a concentrations were >25 µg/L and turbidity levels were <50 NTU. To account for this discrepancy, we developed a calibration equation to use for this handheld fluorometer when field monitoring for potential harmful algal blooms in water bodies.

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A Calibration Equation Between Δ 48 Values of Carbonate and Temperature

Rapid Communications in Mass Spectrometry ◽

10.1002/rcm.9147 ◽

2021 ◽

Author(s):

P. K. Swart ◽

Chaojin Lu ◽

E. Moore ◽

M. Smith ◽

S. T. Murray ◽

...

Keyword(s):

Calibration Equation

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Quiescent Gap Solitons in Coupled Nonuniform Bragg Gratings with Cubic-Quintic Nonlinearity

Applied Sciences ◽

10.3390/app11114833 ◽

2021 ◽

Vol 11 (11) ◽

pp. 4833

Author(s):

Afroja Akter ◽

Md. Jahedul Islam ◽

Javid Atai

Keyword(s):

Numerical Stability ◽

Bragg Gratings ◽

Stability Boundaries ◽

Quintic Nonlinearity ◽

Numerical Stability Analysis ◽

Gap Solitons ◽

The Stability ◽

Dual Core

We study the stability characteristics of zero-velocity gap solitons in dual-core Bragg gratings with cubic-quintic nonlinearity and dispersive reflectivity. The model supports two disjointed families of gap solitons (Type 1 and Type 2). Additionally, asymmetric and symmetric solitons exist in both Type 1 and Type 2 families. A comprehensive numerical stability analysis is performed to analyze the stability of solitons. It is found that dispersive reflectivity improves the stability of both types of solitons. Nontrivial stability boundaries have been identified within the bandgap for each family of solitons. The effects and interplay of dispersive reflectivity and the coupling coefficient on the stability regions are also analyzed.

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A new method to improve the numerical stability of the hierarchical equations of motion for discrete harmonic oscillator modes

The Journal of Chemical Physics ◽

10.1063/5.0027962 ◽

2020 ◽

Vol 153 (20) ◽

pp. 204109

Author(s):

Yaming Yan ◽

Tao Xing ◽

Qiang Shi

Keyword(s):

Harmonic Oscillator ◽

Numerical Stability ◽

Equations Of Motion ◽

New Method

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In vivo calibration of the T2* cardiovascular magnetic resonance method at 1.5 T for estimation of cardiac iron in a minipig model of transfusional iron overload

Journal of Cardiovascular Magnetic Resonance ◽

10.1186/s12968-021-00715-6 ◽

2021 ◽

Vol 23 (1) ◽

Author(s):

Peter Diedrich Jensen ◽

Asbjørn Haaning Nielsen ◽

Carsten Wiberg Simonsen ◽

Ulrik Thorngren Baandrup ◽

Svend Eggert Jensen ◽

...

Keyword(s):

Rank Correlation ◽

Calibration Data ◽

Iron Loading ◽

Spearman Rank Correlation ◽

Calibration Equation ◽

Spearman Rank ◽

Cardiac Iron ◽

In Vivo Calibration ◽

Spearman Rank Correlation Coefficient

Abstract Background Non-invasive estimation of the cardiac iron concentration (CIC) by T2* cardiovascular magnetic resonance (CMR) has been validated repeatedly and is in widespread clinical use. However, calibration data are limited, and mostly from post-mortem studies. In the present study, we performed an in vivo calibration in a dextran-iron loaded minipig model. Methods R2* (= 1/T2*) was assessed in vivo by 1.5 T CMR in the cardiac septum. Chemical CIC was assessed by inductively coupled plasma-optical emission spectroscopy in endomyocardial catheter biopsies (EMBs) from cardiac septum taken during follow up of 11 minipigs on dextran-iron loading, and also in full-wall biopsies from cardiac septum, taken post-mortem in another 16 minipigs, after completed iron loading. Results A strong correlation could be demonstrated between chemical CIC in 55 EMBs and parallel cardiac T2* (Spearman rank correlation coefficient 0.72, P < 0.001). Regression analysis led to [CIC] = (R2* − 17.16)/41.12 for the calibration equation with CIC in mg/g dry weight and R2* in Hz. An even stronger correlation was found, when chemical CIC was measured by full-wall biopsies from cardiac septum, taken immediately after euthanasia, in connection with the last CMR session after finished iron loading (Spearman rank correlation coefficient 0.95 (P < 0.001). Regression analysis led to the calibration equation [CIC] = (R2* − 17.2)/31.8. Conclusions Calibration of cardiac T2* by EMBs is possible in the minipig model but is less accurate than by full-wall biopsies. Likely explanations are sampling error, variable content of non-iron containing tissue and smaller biopsies, when using catheter biopsies. The results further validate the CMR T2* technique for estimation of cardiac iron in conditions with iron overload and add to the limited calibration data published earlier.

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