Do changes in light direction affect absorption profiles in leaves?

2010 ◽  
Vol 37 (5) ◽  
pp. 403 ◽  
Author(s):  
Craig R. Brodersen ◽  
Thomas C. Vogelmann
Keyword(s):  
Cross Sections ◽  
Incident Light ◽  
Monochromatic Light ◽  
Diffuse Light ◽  
Spongy Mesophyll ◽  
Light Regimes ◽  
Direct Light ◽  
Direct Measurements ◽  
Leaf Level

Leaf anatomy plays a functional role in propagating light through the leaf; palisade mesophyll has been shown to facilitate the channelling of collimated light deeper into the spongy mesophyll. Direct measurements of the propagation of diffuse light into the leaf, however, are absent. Using chlorophyll fluorescence imaging of leaf cross-sections, we measured light absorption profiles in leaves under direct (collimated), diffuse and low-angle monochromatic light. Low-angle and diffuse light was absorbed closer to the irradiated surface than direct light perpendicular to the surface. The shapes of internal absorption profiles indicated that leaves were influenced by the directional quality of the incident light. In addition, absorption profiles revealed that leaves were not simple light absorbing objects and that cellular anatomy influences the direction of light travelling into the mesophyll. These findings also suggest a mechanism for previously measured differences in leaf level photosynthesis under opposing light regimes.

Constraint-Based Reverse Engineering From Ultrasound Cross-Sections

1997 ◽  
Author(s):  
Jai Menon ◽  
Ranjit Desai ◽  
Jay Buckey
Keyword(s):  
Reverse Engineering ◽  
Cross Sections ◽  
Biomedical Applications ◽  
Engineering Application ◽  
Volume Data ◽  
Cross Sectional ◽  
Reverse Engineer ◽  
Network Bandwidth ◽  
Complex Topology

Abstract This paper extends the “cross-sectional” approach for reverse engineering, used abundantly in biomedical applications, to the mechanical domain. We propose a combination of “projective” and cross-sectional algorithms for handling physical artifacts with complex topology and geometry. In addition, the paper introduces the concept of constraint-based reverse engineering, where the constraint parameters could include one or more of the following: time, storage (memory, disk-space), network bandwidth, Quality of Service (output-resolution), and so forth. We describe a specific reverse-engineering application which uses ultrasound (tilt-echo) imaging to reverse engineer spatial enumeration (volume) representations from cross-sectional data. The constraint here is time, and we summarize how our implementation can satisfy real-time reconstruction for distribution of the volume data on the internet. We present results that show volume representations computed from static objects. Since the algorithms are tuned to satisfy time constraints, this method is extendable to reverse engineer temporally-varying (elastic) objects. The current reverse engineering processing time is constrained by the data-acquisition (tilt-echo imaging) process, and the entire reverse engineering pipeline has been optimized to compute incremental volume representations in the order of 3 seconds on a network of four processors.

scholarly journals Evaluation of Forecasts of a Convectively Generated Bore Using an Intensively Observed Case Study from PECAN

2018 ◽  
Vol 146 (9) ◽  
pp. 3097-3122 ◽  
Author(s):  
Aaron Johnson ◽  
Xuguang Wang ◽  
Kevin R. Haghi ◽  
David B. Parsons
Keyword(s):  
Cross Sections ◽  
Turbulent Mixing ◽  
Weather Research And Forecasting ◽  
Cold Pool ◽  
Model Errors ◽  
Near Surface ◽  
Cold Pools ◽  
Convection Model

Abstract This paper presents a case study from an intensive observing period (IOP) during the Plains Elevated Convection at Night (PECAN) field experiment that was focused on a bore generated by nocturnal convection. Observations from PECAN IOP 25 on 11 July 2015 are used to evaluate the performance of high-resolution Weather Research and Forecasting Model forecasts, initialized using the Gridpoint Statistical Interpolation (GSI)-based ensemble Kalman filter. The focus is on understanding model errors and sensitivities in order to guide forecast improvements for bores associated with nocturnal convection. Model simulations of the bore amplitude are compared against eight retrieved vertical cross sections through the bore during the IOP. Sensitivities of forecasts to microphysics and planetary boundary layer (PBL) parameterizations are also investigated. Forecasts initialized before the bore pulls away from the convection show a more realistic bore than forecasts initialized later from analyses of the bore itself, in part due to the smoothing of the existing bore in the ensemble mean. Experiments show that the different microphysics schemes impact the quality of the simulations with unrealistically weak cold pools and bores with the Thompson and Morrison microphysics schemes, cold pools too strong with the WDM6 and more accurate with the WSM6 schemes. Most PBL schemes produced a realistic bore response to the cold pool, with the exception of the Mellor–Yamada–Nakanishi–Niino (MYNN) scheme, which creates too much turbulent mixing atop the bore. A new method of objectively estimating the depth of the near-surface stable layer corresponding to a simple two-layer model is also introduced, and the impacts of turbulent mixing on this estimate are discussed.

scholarly journals Accuracy and Reproducibility of Acoustic Tomography Significantly Increase with Precision of Sensor Position

2017 ◽  
Vol 2 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Steffen Rust
Keyword(s):  
Risk Assessment ◽  
Norway Spruce ◽  
Cross Sections ◽  
Acoustic Tomography ◽  
Model Operator ◽  
Sensor Position ◽  
Complex Shapes ◽  
Source Of Error ◽  
Sensor Positions

Acoustic tomograms are widely used in tree risk assessment. They should be accurate,repeatable and comparable between consecutive measurements. Previous work has failed to address the effects of different approaches to record sensor positions, operators and models of tomograph on the resulting tomograms.In this study, three operators used the two most common sonic tomographmodels to measure seven cross-sections of Norway spruce trees, whichwere felled after the measurement. We evaluated the effects of model, operator, and different approaches to measure sensor positions on the quality of the tomograms.The largest source of error was the position of sensors, affectingestimated stress wave velocity, the shape of the tomogram, and the sizeof the defect.To produce accurate and repeatable tomograms of trees with complex shapes,it is essential to measure the sensor positions precisely.

scholarly journals The colorimetric properties of the spectrum

1931 ◽  
Vol 108 (759) ◽  
pp. 576-576 ◽  
Keyword(s):  
Distribution Curve ◽  
National Physical Laboratory ◽  
Group Of Seven ◽  
Physical Laboratory ◽  
Luminosity Functions ◽  
Direct Measurements ◽  
Energy Distribution Curve ◽  
The Mean ◽  
General Method

The paper describes an investigation carried out at the National Physical Laboratory to determine the colorimetric properties of a group of seven subjects as obtained from direct measurements of the trichromatic coefficients of the spectrum on a trichromatic colorimeter. The “spectral distribution curves of the primaries,” by means of which the colorimetric quality of a heterochromatic stimulus may be computed from its energy distribution curve, are obtained by combining the experimentally determined trichromatic coefficients with the International Standard visibility curve. This procedure is a simplification, applicable to the mean results of a normal group, of a general method by which the chromatic and luminosity functions of any subject or group of subjects can be determined from one set of observations. The general method is described in an Appendix.

Image processing algorithms in the assessment of grain damage degree

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wojciech Maliga ◽  
Włodzimierz Dudziński ◽  
Magdalena Łabowska ◽  
Jerzy Detyna ◽  
Marcin Łopusiewicz ◽  
...  
Keyword(s):  
Image Processing ◽  
Cross Sections ◽  
Three Dimensional ◽  
Sample Volume ◽  
Three Dimensional Model ◽  
Time Intervals ◽  
Damage Degree ◽  
Grain Damage ◽  
Analyse Sample

Abstract Objectives The paper presents preliminary results on the assessment of algorithms used in image processing of the grain damage degree. The purpose of the work is developing a tool allowing to analyse sample cross-sections of rye germs. Methods The analysis of the grain cross-sections was carried out on the basis of a series their photos taken at equal time intervals at a set depth. The cross-sections will be used to create additional virtual cross-sections allowing to analyse the whole sample volume. The ultimate plan is to generate two cross-sections perpendicular to each other. Based on volumetric data read from the sample section, a three-dimensional model of an object will be generated. Results The analysis of model surface will allowed us to detect possible grain damage. The developed method of preparing the research material and the proprietary application allowed for the identification of internal defects in the biological material (cereal grains). Conclusions The presented methodology may be used in the agri-food industry in the future. However, much research remains to be done. These works should primarily aim at significantly reducing the time-consuming nature of individual stages, as well as improving the quality of the reconstructed image.

Effects of LED Monochromatic Light Quality of Different Colors on Fucoxanthin Content and Expression Levels of Related Genes in Phaeodactylum Tricornutum

2019 ◽  
Vol 39 (9) ◽  
pp. 0917001 ◽  
Author(s):  
徐润洁 Runjie Xu ◽  
龚一富 Yifu Gong ◽  
陈文婷 Wenting Cheng ◽  
李申睿 Shenrui Li ◽  
陈若莹 Ruoying Chen ◽  
...  
Keyword(s):  
Phaeodactylum Tricornutum ◽  
Light Quality ◽  
Monochromatic Light ◽  
Expression Levels

Untersuchungen zur Wirkung von monochromatischer Vakuum-UV-Strahlung auf DNS

1969 ◽  
Vol 24 (6) ◽  
pp. 722-728 ◽  
Author(s):  
K. U. Berger
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Electron Emission ◽  
Vacuum Ultraviolet ◽  
Monochromatic Light ◽  
Ionization Probability ◽  
Thin Layers ◽  
Inactivation Mechanism ◽  
Grating Monochromator ◽  
Vacuum Uv

Inactivation cross sections of infectious ΦΧ-174-DNA in the extreme vacuum-ultraviolet were determined by irradiation of thin layers with monochromatic light down to 584 Å by means of a powerful grating-monochromator, the elements of which are described. Comparison of inactivation and light-induced electron emission shows that light of quantum energies below 7 eV inactivates by excitation only, whereas above 10.2 eV ionization is the predominant inactivation mechanism. Because of the satisfactory agreement of the curves for inactivation and electron emission, it is conducted that the remarkable increase of the inactivation cross section in the region of the short wavelength vacuum-uv is due to increasing ionization probability.

scholarly journals Relation between Changes in Photosynthetic Rate and Changes in Canopy Level Chlorophyll Fluorescence Generated by Light Excitation of Different Led Colours in Various Background Light

2019 ◽  
Vol 11 (4) ◽  
pp. 434 ◽  
Author(s):  
Linnéa Ahlman ◽  
Daniel Bånkestad ◽  
Torsten Wik
Keyword(s):  
Steady State ◽  
Light Quality ◽  
Incident Light ◽  
Red Light ◽  
Intensity Level ◽  
Potential Candidate ◽  
Light Emitting ◽  
Background Light ◽  
Light Regimes ◽  
The Difference

Using light emitting diodes (LEDs) for greenhouse illumination enables the use of automatic control, since both light quality and quantity can be tuned. Potential candidate signals when using biological feedback for light optimisation are steady-state chlorophyll a fluorescence gains at 740 nm, defined as the difference in steady-state fluorescence at 740 nm divided by the difference in incident light quanta caused by (a small) excitation of different LED colours. In this study, experiments were conducted under various background light (quality and quantity) to evaluate if these fluorescence gains change relative to each other. The light regimes investigated were intensities in the range 160–1000 μ mol   m − 2   s − 1 , and a spectral distribution ranging from 50% to 100% red light. No significant changes in the mutual relation of the fluorescence gains for the investigated LED colours (400, 420, 450, 530, 630 and 660 nm), could be observed when the background light quality was changed. However, changes were noticed as function of light quantity. When passing the photosynthesis saturate intensity level, no further changes in the mutual fluorescence gains could be observed.

scholarly journals Methoden zur Bestimmung von Wirkungsquerschnitten für Spinaustausch und Depolarisation indirekt optisch gepumpter Atome

1971 ◽  
Vol 26 (10) ◽  
pp. 1571-1577
Author(s):  
A. Assfalg ◽  
J. Fricke ◽  
J. Haas ◽  
E. Lüscher
Keyword(s):  
Phase Angle ◽  
Cross Sections ◽  
Nuclear Spin ◽  
Spin Exchange ◽  
Light Transmission ◽  
Primary System ◽  
Buffer Gas ◽  
Secondary System ◽  
Spin Depolarization

Abstract Two methods are described to derive cross sections for spin exchange and spin depolarization of an indirectly pumped alkali vapor with zero nuclear spin. Either pulsed or sinusoidally modulated radiofrequency can be used to destroy the polarization of the indirectly pumped (secondary) system, while the intensity of the transmitted pumping light is observed. Cross sections follow from the indirectly produced depolarization of the primary system i. e. from the change in pumping light transmission or from the phase angle between the rf modulation and the intensity oscillations of the transmitted light. The quality of the two methods is tested by deriving cross sections for spin exchange between Cs and Rb and for depolarization of Rb in Argon buffer gas.

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