scholarly journals Recommendations for spectral fitting of SO<sub>2</sub> from MAX-DOAS measurements

2020 ◽  
Author(s):  
Zoë Y. W. Davis ◽  
Robert McLaren
Keyword(s):  
Light Path ◽  
True Error ◽  
Pass Filter ◽  
Spectral Fitting ◽  
Actinic Light ◽  
True Value ◽  
Ambient Measurements ◽  
Absorption Features ◽  
So2 Absorption ◽  
Actinic Light Intensity

Abstract. Fitting SO2 dSCDs from MAX-DOAS measurements of scattered sunlight is challenging because actinic light intensity is low in wavelength regions where the SO2 absorption features are strongest. SO2 dSCDs were fit with different wavelength windows (λlow to λhigh) from ambient measurements with calibration cells of 2.2 × 1017 and 2.2 × 1016 molec cm−2 inserted in the light path at different viewing elevation angles. SO2 dSCDs were the least accurate and fit errors were the largest for fitting windows with λlow  312 nm. The SO2 dSCDs also exhibited an inverse relationship with the SO2 absorption cross-section for fitting windows with λlow  400 nm. Deviation of the SO2 dSCD from the true value depended on the SO2 concentration for some fitting windows rather than exhibiting a consistent bias. Uncertainties of the SO2 dSCD reported by the fit algorithm were significantly less than the true error for many windows, particularly for the measurements without the filter or offset function. For retrievals with the filter or offset function, increasing λhigh > 320 nm tended to decrease the reported fit uncertainty but did not increase the accuracy. Based on the results of this study, a short-pass filter and a fitting window of 307.5 

scholarly journals Recommendations for spectral fitting of SO<sub>2</sub> from miniature multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements

2020 ◽  
Vol 13 (7) ◽  
pp. 3993-4008
Author(s):  
Zoë Y. W. Davis ◽  
Robert McLaren
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Differential Optical Absorption Spectroscopy ◽  
Stray Light ◽  
Optical Absorption Spectroscopy ◽  
Ocean Optics ◽  
Pass Filter ◽  
True Value ◽  
Absorption Features ◽  
So2 Absorption

Abstract. Fitting sulfur dioxide (SO2) differential slant column densities (dSCDs) from multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of scattered sunlight is challenging because actinic light intensity is low in the wavelength regions where the SO2 absorption features are strongest. SO2 dSCDs were fit with different wavelength windows (λlow to λhigh) from ambient measurements with calibration cells of 2.2×1017 and 2.2×1016 molec. cm−2 inserted in the light path at different viewing elevation angles using an Ocean Optics USB2000 spectrometer in a miniature MAX-DOAS instrument. SO2 dSCDs were the least accurate, and fit errors were highest for fitting windows with λlow < 307 or λlow > 312 nm. The SO2 dSCDs also exhibited an inverse relationship with the depth of the differential features in the SO2 absorption cross section for fitting windows with λlow < 307 nm. Spectra measured at low viewing elevation angles (i.e., α=2∘) exhibited less accurate SO2 dSCDs for the same fitting windows compared with higher angles. The use of a 400 nm short-pass filter or a polynomial to account for stray light (the offset function) increased the accuracy of the SO2 dSCDs for many different fitting windows, decreased fit errors, and decreased the dSCDs' dependence on the depth of the SO2 differential absorption features. These results suggest that the radiance at shorter wavelengths was increased by stray light. The inaccuracies at lower fitting wavelengths were increased by stray light originating from light with λ > 400 nm. Deviation of the SO2 dSCD from the true value depended on the SO2 concentration for some fitting windows rather than exhibiting a consistent bias. Uncertainties in the SO2 dSCD reported by the fit algorithm were more than 50 % less than the true error for many windows, particularly for the measurements without the filter or offset function. For retrievals with the filter or offset function, increasing λhigh > 320 nm tended to decrease the reported fit uncertainty but did not increase the accuracy. Based on the results of this study, a short-pass filter and a fitting window of 307.5 < λ < 319 nm are recommended for the retrieval of SO2 SCDs from miniature MAX-DOAS measurements. If a filter is not available or conflicts with other species to be determined (e.g., NO2 or HCHO), the offset function should be enabled, and a fit window 307.5 < λ < 319 nm is still recommended.

A possible origin of the middle phase of polyphasic chlorophyll fluorescence transient

2003 ◽  
Vol 30 (5) ◽  
pp. 571 ◽  
Author(s):  
Ban-Dar Hsu ◽  
Kuen-Lin Leu
Keyword(s):  
Chlorophyll Fluorescence ◽  
Chlorophyll Concentration ◽  
Light Path ◽  
Middle Phase ◽  
Fluorescence Transient ◽  
Actinic Light ◽  
Light Gradient ◽  
Initial Rise ◽  
Chlorophyll Fluorescence Transient ◽  
Photosynthetic Activities

The rise of the chlorophyll fluorescence of a whole leaf as induced by high-intensity actinic light comprises three distinct phases, and is termed the O–J–I–P polyphasic rise. The initial rise (the O–J phase) was found to be the most sensitive to light intensity, being slower and smaller with decreasing irradiation. The leaf was also found to be transparent for chlorophyll fluorescence to a considerable extent, so that the fluorescence originating from deep inside the sample could still be detected. In contrast, the actinic light used to induce fluorescence was strongly absorbed by chlorophylls, so that a steep light gradient was created along the light path. The fluorescence transient of a leaf, thus, was always a mixture of the fluorescence from the surface of the sample as well as that from the inside of the sample, whose O–J phase is slower as it is induced by a weaker actinic light. We have provided evidence suggesting that, in an intact leaf, the middle phase of the measured polyphasic fluorescence transient (the J–I phase) might actually reflect the initial rise of the transient coming from the abaxial layer of the leaf. Moreover, if the polyphasic fluorescence transient is used as an analytical tool for accessing information on the photosynthetic activities of leaves, the factors of concentration and thickness of the sample must be taken into account. To obtain the 'true' fluorescence transient of a sample, both the chlorophyll concentration and thickness of the sample must be kept as low as possible.

Data Filter Performance for Rocket Thrust Measurement System

2014 ◽  
Vol 629 ◽  
pp. 240-245
Author(s):  
Nor Hafizah Abdullah ◽  
Tengku Farah Wahida Ku Chik ◽  
Fairul Azmin Zaraini
Keyword(s):  
Measurement System ◽  
Measurement Data ◽  
Data Interpretation ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Filter Performance ◽  
True Value ◽  
Low Pass ◽  
Thrust Measurement ◽  
Rocket Thrust

This research focuses on the electrical noise coming from the sensor: load cell which is being used in rocket thrust measurement system. The aim is to investigate the noise contained in the measurement data. Fast Fourier Transform (FFT) is used as an indicator for appropriate cut off frequency in filtering data. Low Pass Filter is used as the measurement of thrust for it produces steady-state signal and acceptable transient response. Results confirmed that there are significant differences for Signal Noise Ratio (SNR) value between filtered and unfiltered data. Data noise has an impact to the true value of the expected results that affects data interpretation. It is shown that the influence of noise on the measurement data has been successfully reduced by the method used.

scholarly journals XMM-Newton RGS spectra of four Seyfert 1 galaxies

2006 ◽  
Vol 2 (S238) ◽  
pp. 335-336
Author(s):  
M. V. Cardaci ◽  
M. Santos-Lleó ◽  
A. I. Díaz
Keyword(s):  
High Resolution ◽  
Column Density ◽  
Active Nucleus ◽  
X Ray ◽  
Spectral Fitting ◽  
Absorbing Material ◽  
Absorption Features ◽  
Reflection Grating ◽  
High Column

AbstractUsing the spectral fitting technique we have studied the components contributing to the soft X-ray spectra of four AGN. The selected objects are the Seyfert 1 galaxies: HE 1143-1810, Mkn 110, CTS A08.12 and ESO 359-G19. The high-resolution X-ray spectra analysed were taken with the Reflection Grating Spectrometers on board the XMM-Newton satellite. In contrast to the results for other well-studied Seyfert 1 galaxies, we have found that the spectra of the four galaxies lack of significant absorption features. Hence, there are no signs of high-column-density partially-ionised absorbing material in the vicinity of the active nucleus in these galaxies.

Density-based discrimination of protein and RNA in the ribosome

1992 ◽  
Vol 50 (1) ◽  
pp. 464-465
Author(s):  
Joachim Frank
Keyword(s):  
Transfer Function ◽  
Spatial Frequency ◽  
Three Dimensional ◽  
Wiener Filter ◽  
Dark Field Image ◽  
Dark Field ◽  
Frequency Range ◽  
Bright Field ◽  
Contrast Transfer Function ◽  
Pass Filter

Cryo-electron microscopy combined with single-particle reconstruction techniques has allowed us to form a three-dimensional image of the Escherichia coli ribosome.In the interior, we observe strong density variations which may be attributed to the difference in scattering density between ribosomal RNA (rRNA) and protein. This identification can only be tentative, and lacks quantitation at this stage, because of the nature of image formation by bright field phase contrast. Apart from limiting the resolution, the contrast transfer function acts as a high-pass filter which produces edge enhancement effects that can explain at least part of the observed variations. As a step toward a more quantitative analysis, it is necessary to correct the transfer function in the low-spatial-frequency range. Unfortunately, it is in that range where Fourier components unrelated to elastic bright-field imaging are found, and a Wiener-filter type restoration would lead to incorrect results. Depending upon the thickness of the ice layer, a varying contribution to the Fourier components in the low-spatial-frequency range originates from an “inelastic dark field” image. The only prospect to obtain quantitatively interpretable images (i.e., which would allow discrimination between rRNA and protein by application of a density threshold set to the average RNA scattering density may therefore lie in the use of energy-filtering microscopes.

MOTIF YANG BERPENGARUH PADA PROSES KEJIWAAN TOKOH SAM DALAM NOVEL SEBENING SYAHADAT KARYA DIVA SR

2020 ◽  
Vol 8 (2) ◽  
pp. 10
Author(s):  
Dandy Ashghor Dawudi ◽  
Kamidjan Kamidjan ◽  
Agus Sulton
Keyword(s):  
Research Method ◽  
Descriptive Analysis ◽  
Research Process ◽  
Cultural Factors ◽  
Qualitative Approach ◽  
Literature Study ◽  
Love Story ◽  
True Value ◽  
Analysis Technique ◽  
Qualitative Descriptive

This research takes the object of Sebening Syahadat by Diva SR, this work is a novel that tells the story of the journey ofa teenager named Sam who is in the process ofsearching for identity. The journey is filled with interesting twits and turns embelissed with a love story that is very suitable if consumed by the younger generation who are learning to find identit. This study aims to reveal the value motives that led Sam’s character in finding his identity, which expected to be a material for reflection for readers, especially young people who are in the process of discovering his identity, the scope of the problem in this study is to reveal the value motives that affect the character’s psyche. Sam is told to have a rascal character.The research method used in this study took a descriptive qualitative approach, data colletion used was a literature study technique with stages of reading, note taking, coding for futher analysis. The analysis technique used is qualitative descriptive analysis technique.The result of the research in this research process indicate that the mental process of Sam’s character influenced by several factors, including: a. Motives in cultural factors (Situasional Factors), b. The motive for love begins with admiration for the attitude of someone who is full of noble values of character, c. The motive of curiosity and fulfillment of his needs for true value.

The True Value of LASERs

1995 ◽  
Vol 5 (6) ◽  
pp. 8.2-9
Author(s):  
Bruce Fox
Keyword(s):  
True Value
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