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AI for Cosmology
Published in Volker Knecht, AI for Physics, 2023
Kilian Hikaru Scheutwinkel, Daniel Grün, Bernard Jones, Jimena González Lozano, Volker Knecht
The expansion of space is obvious from the redshift of prominent spectral absorption or emission lines in the light from distant galaxies and the time dilation in the light decay of supernova luminosity curves. The redshift is attributed to the Doppler effect: a change in frequency of a wave in relation to an observer who is moving relative to the wave source.
Applications in Astronomy
Published in Sylvia Frühwirth-Schnatter, Gilles Celeux, Christian P. Robert, Handbook of Mixture Analysis, 2019
Michael A. Kuhn, Eric D. Feigelson
All of these early studies treated galaxy clustering as an isotropic process. But this assumption was radically invalidated as larger telescopes devoted observing time to galaxy redshift surveys. Redshifts represent an approximate measure of galaxy distance in the expanding universe and, when combined with location in the sky, give a three-dimensional view of the galaxy distribution. When about 1000 redshifts were obtained, the distribution was found to resemble “a slice through the suds in the kitchen sink”. The language of galaxy clustering changed: “clusters” were now viewed as the intersections of “filaments”, “sheets” and “Great Walls” of galaxies that surround “voids”. The volume by Martínez & Saar (2002) lays the foundation between three-dimensional galaxy statistics and cosmological theory.
Composition of Global Environment
Published in Takashiro Akitsu, Environmental Science, 2018
Redshift refers to a phenomenon in which, in astronomy, the spectrum of light from observation objects (including not only visible light but also all wavelength electromagnetic waves) shifts to the long wavelength side (closer to red in visible light). The Doppler effect is a phenomenon in which the frequency of a wave is observed differently due to the existence of the relative velocity between the source (sound source, light source, etc.) of the wave (sound source, electromagnetic wave, etc.) and the observer.
Visible-light-driven TiO2@Fe2O3/Chitosan nanocomposite with promoted photodegradation of meropenem and imipenem antibiotics by peroxymonosulfate
Published in Environmental Technology, 2023
Mehdi Ahmadmoazzam, Hamed Akbari, Amir Adibzadeh, Sudabeh Pourfadakari, Hesam Akbari
Utilising UV-vis DRS, the optical characteristics of the produced nanocomposites were studied. Figure 1B exhibits the UV–vis absorption spectra of pure TiO2 and Fe2O3, TiO2@Fe2O3, and TiO2@Fe2O3/chitosan nanocomposite. The findings showed that the TiO2 sample could only absorb in the UV area with an absorption edge below 400 nm. However, it revealed that modified TiO2 with Fe2O3 and their coating on chitosan has increased and amended the optical features of TiO2. It causes a redshift to an increased wavelength that includes a visible light region (380–700 nm) regarding to the band-gap hematite excitation. The d-d transition from the ground state to the excited state of Fe3+ might be responsible for the peak wavelength of roughly 470 nm for TiO2@Fe2O3/chitosan nanocomposite [21]. The inclusion of Fe3+ into the Fe2O3 lattice and Ti4+ in the produced TiO2@Fe2O3/chitosan nanocomposite was verified by DRS UV-vis spectra analyses.
Excited-state intramolecular double proton transfer mechanism associated with solvent polarity for 9,9-dimethyl-3,6-dihydroxy-2,7-bis(4,5-dihydro-4,4-dimethyl-2-oxazolyl)fluorene compound
Published in Molecular Physics, 2022
Liying Song, Xuan Meng, Jinfeng Zhao, Haiyun Han, Daoyuan Zheng
Infrared vibrational spectroscopy is also an effective method which can analyse the variations of functional groups in molecules [72]. In this case, we employ it to investigate the transformation of double hydrogen bonds in S1 and S0 states of the system under different solvents. The calculated results are shown in Figure 3. It was noteworthy that the peak positions from S0 to S1 state of hydroxyl groups were red-shifted in all three solvents. This was another indication that the hydrogen bonding was enhanced in the excited state. The vibrational spectra were mostly measured in solution, so it was also worthwhile to investigate how solvent effects affect the vibrational spectra of the hydrogen bonds. The redshift was 211–3036 cm−1 from 3247 cm−1 in cyclohexane, 163–3046 cm−1 from 3209 cm−1 in chloroform, and 155–3019 cm−1 from 3174 cm−1 in acetonitrile. The wavelength of the redshift showed that the hydrogen bond was most redshifted in the cyclohexane solvent. Thus, it was again demonstrated that the hydrogen bonding was enhanced the most in the nonpolar solvent. Since hydrogen bond enhancement is the most significant change in the ESIPT process, we speculate that the system prefers to undergo proton transfer in nonpolar solvents.
Augmenting the internal quantum efficiency of GaN-based green light-emitting diodes by sandwiching active region with p-AlGaN layers
Published in Journal of Modern Optics, 2020
Muhammad Usman, Abdur-Rehman Anwar, Munaza Munsif, Shahzeb Malik, Noor Ul Islam, Tariq Jamil
Figure 5 shows the comparison of emission spectra at maximum current density. The emission spectra show that the light output of all the LEDs is in the green regime i.e. ∼513 nm to ∼522 nm. The full width at half maximum of the emission spectrum of LED-I, -II and -III is increased with the increase of current density. Similarly, the redshift of the wavelength and broadening is observed. This could be attributed to high lattice mismatch induced in the active region between p-Al0.05Ga0.95N QB and In0.3Ga0.7N QW. The LED-III exhibits highest peak of emission spectra as compared to LED-I and II. The enhancement of emission rate is attributed to the better radiative recombination (improved overlapping of the electron-hole wavefunction).