scholarly journals Physiological performance by growth rate, pigment and protein content of the brown seaweed Sargassum filipendula (Ochrophyta: Fucales) induced by moderate UV radiation exposure in the laboratory

2020 ◽  
Vol 84 (1) ◽  
pp. 59
Author(s):  
Luz K. Polo ◽  
Fungyi Chow
Keyword(s):  
Growth Rate ◽  
Uv Radiation ◽  
Brown Seaweed ◽  
Physiological Parameters ◽  
Absorption Bands ◽  
Visible Absorption ◽  
Photosynthetic Organisms ◽  
Antioxidant Defence System ◽  
Sargassum Filipendula ◽  
Ecosystem Studies

UV radiation is a factor affecting the distribution and physiology of photosynthetic organisms in an aquatic ecosystem. Studies with macroalgae indicate diverse biological disturbances in response to UV radiation. This work aimed to study sensitivity of the brown macroalga Sargassum filipendula exposed to UV radiation: PAR (control), PAR+UVA+UVB(++) and PAR+UVA(++)+UVB. Changes in the physiological parameters growth rate, total soluble proteins, photosynthetic pigments and the UV-vis absorbing compounds were analysed after T0, T4, T7 and T10 (days) of UV exposure. Physiological parameters showed little variation between treatments and over time, suggesting that moderate UV radiation doses could regulate resistance responses to re-establish the cellular homoeostasis condition through activation of an antioxidant defence system, such as an overproduction of phenolic compounds. Responses recorded in S. filipendula would be related to acclimation mechanisms against acute UV radiation stress, triggering resistance responses to avoid serious damage to the metabolic machinery, activating control systems to maintain hormesis, and homoeostasis of deleterious actions of reactive species, similar to the phenomenon known as preparation for oxidative stress. Finally, UV-visible absorption spectra showed absorption bands evidencing the presence of mainly UV-absorbing compounds with photoprotective function, such as phlorotannins, flavonoids and carotenoids, which could provide adaptive advantages for organisms exposed to UV radiation.

Meso-aryl-ß-pyrrolic positions interactions in meso-tetraarylporphyrins: Flat arylporphyrins and building blocks for oligoporphyrins

2004 ◽  
Vol 08 (02) ◽  
pp. 111-119 ◽  
Author(s):  
Henry J. Callot ◽  
Romain Ruppert ◽  
Christophe Jeandon ◽  
Sébastien Richeter
Keyword(s):  
Building Blocks ◽  
Absorption Bands ◽  
Visible Absorption ◽  
Aryl Ring ◽  
Porphyrin Macrocycle ◽  
Uv Visible

Aryl groups bound to the meso positions of porphyrins often react with neighboring groups, in particular ß-acyl groups to give highly diversified monomeric and dimeric new functionalized porphyrins. The products, whose meso-aryl ring approaches coplanarity with the porphyrin macrocycle, show large shifts of UV-visible absorption bands and various potentialities for building external chelating moieties and assembling oligoporphyrins.

In Situ and Ex Situ Ellipsometric Characterization of Oxygen Plasma and UV Radiation Effects on Spacecraft Materials

1997 ◽  
Vol 502 ◽  
Author(s):  
C. L. Bungay ◽  
T. E. Tiwald ◽  
M. J. DeVries ◽  
B. J. Dworak ◽  
John A. Woollam
Keyword(s):  
Uv Radiation ◽  
Oxygen Plasma ◽  
Index Of Refraction ◽  
Uv Absorption ◽  
Ex Situ ◽  
Absorption Bands ◽  
Space Applications ◽  
Growth Trends ◽  
Ellipsometry Data

ABSTRACTAtomic Oxygen (AO) and ultraviolet (UV) radiation contribute (including synergistically) to degradation of spacecraft materials in Low Earth Orbit (LEO). NASA is, therefore, interested in determining what effects the harsh LEO environment has on materials exposed to it, as well as develop materials that are more AO and UV resistant. The present work involves the study of AO and UV effects on polyarylene ether benzimidazole (PAEBI) with in situ and ex situ spectroscopic ellipsometry. PAEBI is a polymer proposed for space applications due to its reported ability to form a protective phosphorous oxide on the surface when exposed to AO. In our experiments PAEBI was exposed to UV radiation from a xenon lamp while in situ ellipsometry data were acquired. The effects of UV radiation were modeled as an exponentially graded layer on the surface of bulk PAEBI. The change in UV absorption spectra, depth profile of the index of refraction, and growth trends of the UV irradiated PAEBI were all studied in these experiments. In addition, PAEBI was exposed to an oxygen plasma to simulate the synergistic effects of AO and UV. Ellipsometry data were acquired in-line with both a UV-Visible ellipsometer and an infrared ellipsometer. The change in UV absorption bands and index of refraction due to synergistic AO/UV, as well as the growth trends of the oxide layer were studied.

Initial Reaction Intermediates in the Oxidation of Ascorbic Acid by Nitrous Acid

1981 ◽  
Vol 44 (1) ◽  
pp. 28-32 ◽  
Author(s):  
JAY B. FOX ◽  
ROSEMARY N. FIDDLER ◽  
AARON E. WASSERMAN
Keyword(s):  
Nitric Oxide ◽  
Ascorbic Acid ◽  
Nitrous Acid ◽  
Organic Radicals ◽  
Initial Reaction ◽  
Reaction Intermediates ◽  
Absorption Bands ◽  
Visible Absorption ◽  
Decomposition Products

Nitrite and ascorbate react to form nitric oxide at pH 5.5. In the initial stages of the reaction, seven intermediates can be identified spectrally and chromatographically; these include two colorless nitroso derivatives which contain 30–60% of the initial nitrite, two nitroso reductant derivatives absorbing at 345 and 412 nm, diketogulonic acid and two further decomposition products. None of the intermediates was paramagnetic; except for diketogulonic acid, all decomposed rapidly during or after isolation. Based on the order of appearance of the ultraviolet and visible absorption bands in the reaction mixtures, the observed characteristics of the intermediates, and the lack of organic radicals, a sequence is proposed for the initial steps in the oxidation of ascorbic acid by nitrous acid.

scholarly journals PISCES-v2: an ocean biogeochemical model for carbon and ecosystem studies

2015 ◽  
Vol 8 (2) ◽  
pp. 1375-1509 ◽  
Author(s):  
O. Aumont ◽  
C. Ethé ◽  
A. Tagliabue ◽  
L. Bopp ◽  
M. Gehlen
Keyword(s):  
Growth Rate ◽  
Marine Ecosystem ◽  
Trophic Levels ◽  
Full Description ◽  
Biogeochemical Model ◽  
Ecosystem Studies ◽  
Ocean Biogeochemical Model ◽  
Iron Chemistry ◽  
Steady State Simulation

Abstract. PISCES-v2 is a biogeochemical model which simulates the lower trophic levels of marine ecosystem (phytoplankton, microzooplankton and mesozooplankton) and the biogeochemical cycles of carbon and of the main nutrients (P, N, Fe, and Si). The model is intended to be used for both regional and global configurations at high or low spatial resolutions as well as for short-term (seasonal, interannual) and long-term (climate change, paleoceanography) analyses. There are twenty-four prognostic variables (tracers) including two phytoplankton compartments (diatoms and nanophytoplankton), two zooplankton size-classes (microzooplankton and mesozooplankton) and a description of the carbonate chemistry. Formulations in PISCES-v2 are based on a mixed Monod–Quota formalism: on one hand, stoichiometry of C/N/P is fixed and growth rate of phytoplankton is limited by the external availability in N, P and Si. On the other hand, the iron and silicium quotas are variable and growth rate of phytoplankton is limited by the internal availability in Fe. Various parameterizations can be activated in PISCES-v2, setting for instance the complexity of iron chemistry or the description of particulate organic materials. So far, PISCES-v2 has been coupled to the NEMO and ROMS systems. A full description of PISCES-v2 and of its optional functionalities is provided here. The results of a quasi-steady state simulation are presented and evaluated against diverse observational and satellite-derived data. Finally, some of the new functionalities of PISCES-v2 are tested in a series of sensitivity experiments.

A spectroscopic study of the solvent dependent processes of the anils of benzaldehyde and salicylaldehyde

1982 ◽  
Vol 60 (13) ◽  
pp. 1727-1737 ◽  
Author(s):  
Jerry W. Lewis ◽  
Camille Sandorfy
Keyword(s):  
Hydrogen Bond ◽  
Ground State ◽  
Spectral Characteristics ◽  
Infrared And Raman Spectra ◽  
Absorption Data ◽  
Absorption Bands ◽  
Visible Absorption ◽  
Raman Spectral ◽  
Dependent Processes ◽  
Electronic Ground

The ultraviolet–visible, infrared, and Raman spectral characteristics of some anils of benzaldehyde and salicylaldehyde in several solvents have been investigated. The ultraviolet–visible absorption data indicate that in solvents with a proton donating ability less than or equal to trifluoroethanol a single equilibrium exists in solutions of N-(2-hydroxybenzylidene)aniline, whereas in solvents with a proton donating ability equal to or greater than hexafluoroisopropanol more than one equilibrium occurs. The infrared spectra of this compound dissolved in trifluoroethanol do not show new absorption bands in the 1700–1500 cm−1 region; however, new absorption bands in this region do appear when hexafluoroisopropanol is employed as solvent. From these data it is inferred that the first equilibrium involves the breaking of the chelate hydrogen bond and the second equilibrium involves actual protonation of N-(2-hydroxybenzylidene)aniline in the electronic ground state. A comparison of the infrared and Raman spectra of the title compounds is also made and alternate assignments for several observed bands in the 1700–1500 cm−1 region are proposed.

Spectroelectrochemical Study of some μ3-Oxo-μ-acetato Trinuclear Rhodium(III) and Iridium(III) Complexes

1995 ◽  
Vol 50 (4) ◽  
pp. 551-557 ◽  
Author(s):  
Kenta Takahashi ◽  
Keisuke Umakoshi ◽  
Akihiro Kikuchi ◽  
Yoichi Sasaki ◽  
Masato Tominaga ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption Spectrum ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Visible Region ◽  
Absorption Bands ◽  
Visible Absorption ◽  
The One ◽  
Species Being

New trinuclear rhodium(III) complexes, [Rh3(μ3-O)(μ-CH3COO)6(L)3]+ (L = imidazole (Him), 1-methylimidazole (Meim), and 4-methylpyridine (Mepy)) have been prepared. The Him, Meim, and Mepy complexes show reversible one-electron oxidation waves at E1/2 = +1.12, +1.12, and +1.28 V vs Ag/AgCl, respectively, in acetonitrile. Electronic absorption spectra of the one electron oxidized species of these complexes and [Rh3(μ3-O)(μ-CH3COO)6(py)3]+ (py = pyridine) (E1/2 = +1.32 V ) were obtained by spectroelectrochemical techniques. While the Rh3(III,III,III) states show no strong visible absorption, the Rh3(III,III,IV ) species give a band at ca. 700 nm (ε = 3390-5540 mol dm-3 cm-1). [Ir3(μ3-O)(μ-CH3COO)6(py)3]+ with no strong absorption in the visible region, shows two reversible one-electron oxidation waves at +0.68 and +1.86 V in acetonitrile. The electronic absorption spectrum of the one-electron oxidized species (Ir3(III,III,IV )) also shows some absorption bands (688 nm (ε, 5119), 1093 (2325) and 1400 (ca. 1800)). It is suggested that the oxidation removes an electron from the fully occupied anti-bonding orbital based on metal-dπ-μ3-O-pπ interactions, the absorption bands of the (III,III,IV ) species being assigned to transitions to the anti-bonding orbital.

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