scholarly journals EPR, UV-Visible, and Near-Infrared Spectroscopic Characterization of Dolomite

2008 ◽  
Vol 2008 ◽  
pp. 1-8 ◽  
Author(s):  
S. Lakshmi Reddy ◽  
R. L. Frost ◽  
G. Sowjanya ◽  
N. C. G. Reddy ◽  
G. Siva Reddy ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Spectroscopic Characterization ◽  
Distorted Octahedron ◽  
Spectral Studies ◽  
Indian Origin ◽  
Absorption Studies ◽  
Light Green

Dolomite mineral samples having white and light green colors of Indian origin have been characterized by EPR, optical, and NIR spectroscopy. The optical spectrum exhibits a number of electronic bands due to presence of Fe(III) ions in the mineral. From EPR studies, the parameters ofgfor Fe(III) andg,A, andDfor Mn(II) are evaluated and the data confirm that the ions are in distorted octahedron. Optical absorption studies reveal that Fe(III) is in distorted octahedron. The bands in NIR spectra are due to the overtones and combinations of water molecules. Thus EPR and optical absorption spectral studies have proven useful for the study of the solid state chemistry of dolomite.

Optical Absorption Spectroscopy of DNA-Wrapped HiPco Carbon Nanotubes

2019 ◽  
Vol 943 ◽  
pp. 95-99
Author(s):  
Li Jun Wang ◽  
Kazuo Umemura
Keyword(s):  
Carbon Nanotubes ◽  
Aqueous Solution ◽  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Optical Characterization ◽  
Optical Absorption Spectroscopy ◽  
Double Stranded Dna

Optical absorption spectroscopy provides evidence for individually dispersed carbon nanotubes. A common method to disperse SWCNTs into aqueous solution is to sonicate the mixture in the presence of a double-stranded DNA (dsDNA). In this paper, optical characterization of dsDNA-wrapped HiPco carbon nanotubes (dsDNA-SWCNT) was carried out using near infrared (NIR) spectroscopy and photoluminescence (PL) experiments. The findings suggest that SWCNT dispersion is very good in the environment of DNA existing. Additionally, its dispersion depends on dsDNA concentration.

Bayesian Spectroscopic Characterization of Directly Imaged Planets and Brown Dwarfs and Implications for Ultracool Model Atmospheres

2021 ◽  
Author(s):  
Zhoujian Zhang ◽  
Michael Liu ◽  
Mark Marley ◽  
Michael Line ◽  
William Best
Keyword(s):  
Physical Properties ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Spectroscopic Characterization ◽  
Cool Temperature ◽  
Brown Dwarf ◽  
Modeling Framework ◽  
High Quality ◽  
Model Predictions

<p>Spectroscopic characterization of imaged exoplanets and brown dwarfs is essential for understanding their atmospheres, formation, and evolution, but such work is challenged by the unavoidably simplified model atmospheres needed to interpret spectra. While most previous work has focused on single or at most a few objects, comparing a large collection of spectra to models can uncover trends in data-model inconsistencies needed to improve model predictions, thereby leading to robust properties from exoplanet and brown dwarf spectra. Therefore, we are conducting a systematic analysis of a valuable but underutilized resource: the numerous high-quality spectra of (directly imaged and free-floating) exoplanets and brown dwarfs already accumulated by the community.<span class="Apple-converted-space"> </span></p> <p>Focusing on the cool-temperature end, we have constructed a Bayesian modeling framework using the new Sonora-Bobcat model atmospheres and have applied it to study near-infrared low-resolution spectra of >50 late-T imaged planets and brown dwarfs (≈600-1200K, ≈10-70 M<sub>Jup</sub>) and infer their physical properties (effective temperature, surface gravity, metallicity, radii, mass). By virtue of having such a large sample of high-quality spectra, our analysis identifies the systematic offsets between observed and model spectra as a function of wavelength and physical properties to pinpoint specific shortcomings in model predictions. We have also found that the spectroscopically inferred metallicities, ages, and masses of our sample all considerably deviate from expectations, suggesting the physical and chemical assumptions made within these models need to be improved to fully interpret data. Our work has established a systematic validation of cloudless model atmospheres to date and we discuss extending such analysis to wider temperature and wavelength (e.g., JWST) ranges, as well as finding new planetary-mass and brown dwarf benchmarks, in order to validate ultracool model atmospheres over larger parameter space.</p>

scholarly journals Quantitative Characterization of Arnicae flos by RP-HPLC-UV and NIR Spectroscopy

Foods ◽  
2018 ◽  
Vol 8 (1) ◽  
pp. 9
Author(s):  
Daniela Ivanova ◽  
Vera Deneva ◽  
Dimitrina Zheleva-Dimitrova ◽  
Vesela Balabanova-Bozushka ◽  
Daniela Nedeltcheva ◽  
...  
Keyword(s):  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Sesquiterpene Lactones ◽  
Nir Spectroscopy ◽  
Spectral Distortion ◽  
Active Components ◽  
Quantitative Characterization ◽  
Convolution Window ◽  
Spectra Processing

The possibility of applying near-infrared (NIR) spectroscopy to monitor 13 active components (phenolic acids, flavonoids, and sesquiterpene lactones) in Arnicae flos was studied. The preprocessing of the spectra were performed by using the conventional Golay-Savitzky procedure and the newly developed step-by-step filter. The results obtained show that the step-by-step filter derivatives provide a better signal-to-noise ratio at a lower convolution window. Better calibration for the content of protocatechuic acid, chlorogenic acid, caffeic acid, p-cumaric acid, ferulic acid, isoquercitrin, and quercetin were obtained by step-by-step filter derivatives, compared to the direct raw spectra processing and the Golay-Savitzky approach. Although the step-by-step filter substantially reduces the spectral distortion, the convolution procedure leads to loss of spectral points in the red end of the spectral curve. Probably for this reason this approach shows better calibration only in seven of the monitored 13 active components.

scholarly journals Spectroscopic characterization of the protocluster of galaxies around 7C 1756+6520 at z ~ 1.4

2018 ◽  
Vol 618 ◽  
pp. A128 ◽  
Author(s):  
V. Casasola ◽  
L. Magrini ◽  
F. Combes ◽  
E. Sani ◽  
J. Fritz ◽  
...  
Keyword(s):  
Near Infrared ◽  
Radio Galaxy ◽  
High Redshift ◽  
Theoretical Models ◽  
Spectroscopic Characterization ◽  
Emission Lines ◽  
Peculiar Velocities ◽  
Long Time ◽  
High Fraction

Aims. The aim of this paper is the spectroscopic study of 13 galaxies belonging to the field of the protocluster associated with the radio galaxy 7C 1756+6520 at z = 1.4156. In particular, we focus on the characterization of the nuclear activity. Methods. This analysis has been performed on rest-frame optical spectra taken with the Large Binocular Telescope, using the spectrograph LUCI, which is operative in the near-infrared domain. The adopted spectral coverage allowed us to observe emission lines such as Hα, Hβ, [O III]λ 5007 Å, and [N II]λ 6583 Å at the redshift of the central radio galaxy. We observed the central part of the protocluster, which is suitable to include the radio galaxy, several spectroscopically confirmed active galactic nuclei (AGN) belonging to the protocluster, and other objects that might be members of the protocluster. Results. For four previously identified protocluster members, we derived the redshift by detecting emission lines that have never detected before for these galaxies. We identified a new protocluster member and eight new possible protocluster members. The stacked spectrum of the galaxies in which we detected the [O III]λ 5007 Å emission line revealed the second line of the [O III] doublet at 4959 Å and the Hβ line, which confirms that they belong to the protocluster. By collecting all members identified so far in this work and other members from the literature, we defined 31 galaxies, including the central radio galaxy, around the redshift 1.4152 ± 0.056. This corresponds to peculiar velocities ≲5000 km s−1 with respect to the radio galaxy. The position versus velocity phase-space diagram suggests that three AGN of the protocluster and the central radio galaxy might be a virialized population that has been coexisting for a long time in the densest core region of this forming structure. This protocluster is characterized by a high fraction of AGN (~23%). For one of them, AGN1317, we produced two so-called Baldwin, Phillips & Terlevich (BPT) diagrams. The high fraction of AGN and their distribution within the protocluster seem to be consistent with predictions of some theoretical models on AGN growth and feedback. These models are based on galaxy interactions and ram pressure as triggers of AGN activity. Conclusions. The high fraction of AGN belonging to the protocluster suggests that they were likely triggered at the same time, maybe by the ongoing formation of the protocluster. Observations of AGN in this protocluster and in other distant clusters will help clarifying whether the resulting high fraction of AGN is unusual or typical for such structures at high redshift. Our next step will be analyses of previously acquired high-resolution radio data of the central radio galaxy to derive information on the nature of the radio galaxy and connect it with its cosmic evolution.

Near-Infrared Time-Resolved Optical Absorption Studies of the Reaction of Fully Reduced CytochromecOxidase with Dioxygen†

Biochemistry ◽  
2001 ◽  
Vol 40 (8) ◽  
pp. 2332-2339 ◽  
Author(s):  
Istvan Szundi ◽  
Guang-Ling Liao ◽  
Ólöf Einarsdóttir
Keyword(s):  
Optical Absorption ◽  
Near Infrared ◽  
Time Resolved ◽  
Absorption Studies

Crystallographic and spectroscopic characterization of a natural Zn-rich spinel approaching the endmember gahnite (ZnAl2O4) composition

2013 ◽  
Vol 77 (7) ◽  
pp. 2941-2953 ◽  
Author(s):  
V. D’Ippolito ◽  
G. B. Andreozzi ◽  
F. Bosi ◽  
U. Hålenius ◽  
L. Mantovani ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Spectroscopic Characterization ◽  
Structural Formula ◽  
Unit Cell Dimension ◽  
X Ray Diffraction ◽  
Crystal Chemical Analysis ◽  
X Ray ◽  
Intervalence Charge Transfer ◽  
Oxide Spinel

AbstractThe crystal chemistry of a natural, gem-quality, blue-grey Zn-rich spinel crystal from Jemaa, Kaduna State, Nigeria, was studied using electron microprobe, single-crystal X-ray diffraction, optical absorption and Raman spectroscopies. The composition of the crystal approaches the gahnite endmember (ZnAl2O4), ∼94 mol.%, with the remainder being dominated by a hercynite component (FeAl2O4). The unit-cell dimension is 8.0850(3) Å and the tetrahedral and octahedral bond distances are determined as T–O 1.9485(6) Å and M–O 1.9137(3) Å. Crystal chemical analysis resulted in the empirical structural formula T(Zn0.94Fe2+0.03Al0.03)M (Al1.96Fe2+0.03Fe3+0.01)O4, which shows Zn and Al almost fully ordered in the tetrahedrally and octahedrally coordinated T and M sites, respectively. Raman spectra obtained using the excitation of the blue 473.1 nm line of a Nd:YAG laser display three of the five Raman-active modes predicted for the general oxide spinel group of minerals. These are the Eg mode at 420.6 cm–1 and the T2g modes at 510 cm–1 and 661 cm–1, due to vibrations in the AlO6 octahedra. Optical absorption spectra recorded in the UV/VIS-NIR-MIR range 2000 29000 cm–1 show a dominant absorption band at ∼5000 cm–1 which is caused by spin-allowed electronic d–d transitions in Fe2+ located at the T sites. The blue-grey hue exhibited by the sample is mainly due to spin-forbidden electronic transitions in TFe2+ and to MFe2+ ↔MFe3+ intervalence charge transfer, and the poor saturation of the colour is due to the small concentration of Fe2+ and Fe3+.

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