Results 1 to 10 of about 13,043 (174)

n-Alkanes formed by methyl-methylene addition as a source of meteoritic aliphatics [PDF]

Communications Chemistry
Aliphatics prevail in asteroids, comets, meteorites and other bodies in our solar system. They are also found in the interstellar and circumstellar media both in gas-phase and in dust grains.
P. Merino, L. Martínez, G. Santoro, J. I. Martínez, K. Lauwaet, M. Accolla, N. Ruiz del Arbol, C. Sánchez-Sánchez, A. Martín-Jimenez, R. Otero, M. Piantek, D. Serrate, R. Lebrón-Aguilar, J. E. Quintanilla-López, J. Mendez, P. L. De Andres, J. A. Martín-Gago   +16 more
doaj   +2 more sources

The dust disk of HR4049 [PDF]

, 2002
We present the Spectral Energy Distribution of HR 4049 based on literature data and new continuum measurements at 850 micron. The SED shows variable absorption in the UV, and a large IR excess, both caused by circumstellar dust.
Bakker, Beintema, Buss, C. Dominik, C. P. Dullemond, Chen, Chiang, Cuzzi, de Graauw, Dominik, Draine, Dullemond, Geballe, Guillois, H. van Winckel, J. Cami, Jeffreys, Johnson, Joshi, Kenyon, Kessler, Lamers, Mellema, Miyake, Monier, Pringle, Roddier, Sahai, Savage, Tielens, van Winckel, van Winckel, Waelkens, Waelkens, Waelkens, Waters, Waters, Zuckerman   +37 more
core   +31 more sources

AGB Stars and Their Circumstellar Envelopes. I. the VULCAN Code

Universe, 2021
The interplay between AGB interiors and their outermost layers, where molecules and dust form, is a problem of high complexity. As a consequence, physical processes like mass loss, which depend on the chemistry of the circumstellar envelope, are often ...
Sergio Cristallo, Luciano Piersanti, David Gobrecht, Lucio Crivellari, Ambra Nanni   +4 more
doaj   +1 more source

Grain Growth and Dust Segregation Revealed by Multiwavelength Analysis of the Class I Protostellar Disk WL 17

The Astrophysical Journal, 2023
The first step toward planet formation is grain growth from (sub)micrometer to millimeter/centimeter sizes. Grain growth has been reported not only in Class II protoplanetary disks but also in Class 0/I protostellar envelopes.
Ilseung Han, Woojin Kwon, Yusuke Aso, Jaehan Bae, Patrick Sheehan   +4 more
doaj   +1 more source

Prebiotic Synthesis and Isomerization in Interstellar Analog Ice: Glycinal, Acetamide, and Their Enol Tautomers

Angewandte Chemie, Volume 135, Issue 12, March 13, 2023., 2023
Out of the cold: Ammonia (NH3) and acetaldehyde (CH3CHO) are exposed to galactic cosmic ray proxies while frozen at 5 K to simulate the environment of an interstellar molecular cloud. Reactants undergo dissociation and radical recombination to produce glycinal (NH2CH2CHO) and acetamide (CH3CONH2) prior to tautomerization to 2‐aminoethenol (HOCHCHNH2 ...
Joshua H. Marks, Jia Wang, N. Fabian Kleimeier, Andrew M. Turner, André K. Eckhardt, Ralf I. Kaiser   +5 more
wiley   +2 more sources

Slow Neutron-Capture Process: Low-Mass Asymptotic Giant Branch Stars and Presolar Silicon Carbide Grains

Universe, 2022
Presolar grains are microscopic dust grains that formed in the stellar winds or explosions of ancient stars that died before the formation of the solar system.
Nan Liu, Sergio Cristallo, Diego Vescovi
doaj   +1 more source

Asymptotic Giant Branch Stars and presolar grains [PDF]

EPJ Web of Conferences, 2020
Starting from the recognition that radioactive isotopes were present alive in the Early Solar System, inducing composition anomalies from their decay, and through the discovery that other important anomalies affected also stable species, we shall discuss
Busso Maurizio, Palmerini Sara, Vescovi Diego   +2 more
doaj   +1 more source

Effects of Barnett Magnetic Dipole–Dipole Interaction on Grain Growth and Destruction

The Astrophysical Journal, 2023
Rapidly spinning magnetic grains can acquire large magnetic dipole moments due to the Barnett effect. Here we study the new effect of Barnett magnetic dipole–dipole interaction on grain–grain collisions and grain growth, assuming that grains are spun up ...
Thiem Hoang, Bao Truong
doaj   +1 more source

Kinetics of the tautomerization of thioimidic acids R−C(SH)NH → R−C(S)NH2: For R = H, F, HO, CN, NC, H2N, HC(O), HC(S), HC≡ C, CH3, CF3, H2C=CH, HOCH2, H2NCH2,CH3C(O), C2H5, (CH3)2CH, C6H5

International Journal of Chemical Kinetics, Volume 55, Issue 11, Page 731-742, November 2023., 2023
Abstract The kinetics of the tautomerization of thio‐imidic acids RC(SH)NH were determined at low (50–300 K) and high (500–1500 K) temperatures as R was varied to encompass mono‐ and diatomic species H, F, HO, NC, CN through H2N, HC(O), HC(S), HC≡ C, H3C, F3C, HOCH2, H2C=CH, CH3C(O), H2NCH2 and including ethyl, isopropyl and phenyl groups. The presence
Judith Würmel, John M. Simmie
wiley   +1 more source

Substituent effects in the tautomerization of imidic acids R−C(OH)=NH → R−C(O)NH2: Kinetic implications for the formation of peptide bonds in the interstellar medium

International Journal of Chemical Kinetics, Volume 55, Issue 7, Page 381-391, July 2023., 2023
Abstract A number of amides, RC(O)NH2, have been detected spectroscopically in the space between the stars. Naturally the study of how these are formed is an important question on the path of chemical evolution from the elements C, H, N, O, P, … to life because the so‐called peptide‐bond −C(O)−NH− is a key linkage in poly‐amino acids or proteins.
Judith Würmel, John M. Simmie
wiley   +1 more source