Crystalline water ice on the Kuiper belt object (50000) Quaoar

Igneous processes in the small bodies of the Solar System II: Small satellites and dwarf planets

Evidence of hot and cold igneous processes has been reported in small satellites and dwarf planets of the Solar System. Olivine and pyroxenes were detected in the spectral bands of both small satellites and dwarf planets. The aqueously altered form of olivine and serpentine has been detected in the spectrums of Ceres and Miranda hinting at possible hydrothermal processes in their interiors. Once more, the ubiquitous distribution of 26Al in the planetary nebula, then evolving in the protoplanetary disk, contributed to the primordial widespread heating. Volcanism, or cryovolcanism, then developed only in those bodies where long-lived radiogenic elements, and/or tidal processes, were available.

Rapid crystallization of amorphous solid water by porosity induction

Rapid crystallization of amorphous solid water via acetonitrile diffusion–desorption induced porosity in the window of 128–134 K under ultrahigh vacuum.

A Photoionization Reflectron Time-of-Flight Mass Spectrometric Study on the Detection of Ethynamine (HCCNH2 ) and 2H-Azirine (c-H2 CCHN)

Ices of acetylene (C₂ H₂ ) and ammonia (NH₃ ) were irradiated with energetic electrons to simulate interstellar ices processed by galactic cosmic rays in order to investigate the formation of C₂ H₃ N isomers. Supported by quantum chemical calculations, experiments detected product molecules as they sublime from the ices using photoionization reflectron time-of-flight mass spectrometry (PI-ReTOF-MS). Isotopically-labeled ices confirmed the C₂ H₃ N assignments while photon energies of 8.81 eV, 9.80 eV, and 10.49 eV were utilized to discriminate isomers based on their known ionization energies. Results indicate the formation of ethynamine (HCCNH₂ ) and 2H-azirine (c-H₂ CCHN) in the irradiated C₂ H₂ :NH₃ ices, and the energetics of their formation mechanisms are discussed. These findings suggest that these two isomers can form in interstellar ices and, upon sublimation during the hot core phase, could be detected using radio astronomy.

Nucleophilic Substitution in Solution: Activation Strain Analysis of Weak and Strong Solvent Effects

We have quantum chemically studied the effect of various polar and apolar solvents on the shape of the potential energy surface (PES) of a diverse collection of archetypal nucleophilic substitution reactions at carbon, silicon, phosphorus, and arsenic by using density functional theory at the OLYP/TZ2P level. In the gas phase, all our model SN 2 reactions have single-well PESs, except for the nucleophilic substitution reaction at carbon (SN 2@C), which has a double-well energy profile. The presence of the solvent can have a significant effect on the shape of the PES and, thus, on the nature of the SN 2 process. Solvation energies, charges on the nucleophile or leaving group, and structural features are compared for the various SN 2 reactions in a spectrum of solvents. We demonstrate how solvation can change the shape of the PES, depending not only on the polarity of the solvent, but also on how the charge is distributed over the interacting molecular moieties during different stages of the reaction. In the case of a nucleophilic substitution at three-coordinate phosphorus, the reaction can be made to proceed through a single-well [no transition state (TS)], bimodal barrier (two TSs), and then through a unimodal transition state (one TS) simply by increasing the polarity of the solvent.

The prediction of far-infrared spectra for planetary nitrile ices using periodic density functional theory with comparison to thin film experiments

The application of high accuracy periodic DFT calculations to replicate laboratory thin film spectra allowing the assignment of vibrational far-infrared modes in nitrile-bearing planetary ices.

B-DNA model systems in non-terran bio-solvents: implications for structure, stability and replication

We have computationally analyzed a comprehensive series of Watson–Crick and mismatched B-DNA base pairs, in the gas phase and in several solvents, including toluene, chloroform, ammonia, methanol and water, using dispersion-corrected density functional theory and implicit solvation.

Photochemical Chiral Symmetry Breaking in Alanine

We introduce a general theoretical approach for the simulation of photochemical dynamics under the influence of circularly polarized light to explore the possibility of generating enantiomeric enrichment through polarized-light-selective photochemistry. The method is applied to the simulation of the photolysis of alanine, a prototype chiral amino acid. We show that a systematic enantiomeric enrichment can be obtained depending on the helicity of the circularly polarized light that induces the excited-state photochemistry of alanine. By analyzing the patterns of the photoinduced fragmentation of alanine we find an inducible enantiomeric enrichment up to 1.7%, which is also in good correspondence to the experimental findings. Our method is generally applicable to complex systems and might serve to systematically explore the photochemical origin of homochirality.

Large enantiomeric excesses in primitive meteorites and the diverse effects of water in cosmochemical evolution

Carbonaceous chondrites are meteoritic fragments of asteroids that avoided the geological reprocessing of larger planets and allow laboratory probing of early solar-nebula materials. Among these, Renazzo-type (CR) chondrites found in Antarctica appear remarkably pristine and are distinguished by abundant organic materials and water-soluble molecules such as amino acids and ammonia. We present a comprehensive analysis of the organic composition of selected CR meteorites of different petrographic classification and compare compounds' abundance and distribution as they may relate to asteroidal aqueous processing and concomitant evolution of the mineral phases. We found that several CR compounds such as amino acids and sugar alcohols are fully represented in stones with no or minimal water exposure indicating a formation that, if solar, preceded parent body processes. The most pristine CRs also revealed natal enantiomeric excesses (ee) of up to 60%, much larger than ever recorded. However, aqueous alteration appears to affect CR soluble organic composition and abundances, in particular some diastereomeric amino acids may gauge its extent by the consequent racemization of their ee.

The impact of recent advances in laboratory astrophysics on our understanding of the cosmos

An emerging theme in modern astrophysics is the connection between astronomical observations and the underlying physical phenomena that drive our cosmos. Both the mechanisms responsible for the observed astrophysical phenomena and the tools used to probe such phenomena-the radiation and particle spectra we observe-have their roots in atomic, molecular, condensed matter, plasma, nuclear and particle physics. Chemistry is implicitly included in both molecular and condensed matter physics. This connection is the theme of the present report, which provides a broad, though non-exhaustive, overview of progress in our understanding of the cosmos resulting from recent theoretical and experimental advances in what is commonly called laboratory astrophysics. This work, carried out by a diverse community of laboratory astrophysicists, is increasingly important as astrophysics transitions into an era of precise measurement and high fidelity modeling.

Most Used Codons per Amino Acid and per Genome in the Code of Man Compared to Other Organisms According to the Rotating Circular Genetic Code

My previous theoretical research shows that the rotating circular genetic code is a viable tool to make easier to distinguish the rules of variation applied to the amino acid exchange; it presents a precise and positional bio-mathematical balance of codons, according to the amino acids they codify. Here, I demonstrate that when using the conventional or classic circular genetic code, a clearer pattern for the human codon usage per amino acid and per genome emerges. The most used human codons per amino acid were the ones ending with the three hydrogen bond nucleotides: C for 12 amino acids and G for the remaining 8, plus one codon for arginine ending in A that was used approximately with the same frequency than the one ending in G for this same amino acid (plus *). The most used codons in man fall almost all the time at the rightmost position, clockwise, ending either in C or in G within the circular genetic code. The human codon usage per genome is compared to other organisms such as fruit flies (Drosophila melanogaster), squid (Loligo pealei), and many others. The biosemiotic codon usage of each genomic population or 'Theme' is equated to a 'molecular language'. The C/U choice or difference, and the G/A difference in the third nucleotide of the most used codons per amino acid are illustrated by comparing the most used codons per genome in humans and squids. The human distribution in the third position of most used codons is a 12-8-2, C-G-A, nucleotide ending signature, while the squid distribution in the third position of most used codons was an odd, or uneven, distribution in the third position of its most used codons: 13-6-3, U-A-G, as its nucleotide ending signature. These findings may help to design computational tools to compare human genomes, to determine the exchangeability between compatible codons and amino acids, and for the early detection of incompatible changes leading to hereditary diseases.

Formation of hydroxylamine (NH2OH) in electron-irradiated ammonia-water ices

We investigated chemical and physical processes in electron-irradiated ammonia-water ices at temperatures of 10 and 50 K. Chemically speaking, the formation of hydroxylamine (NH(2)OH) was observed in electron-irradiated ammonia-water ices. The synthesis of molecular hydrogen (H(2)), molecular nitrogen (N(2)), molecular oxygen (O(2)), hydrazine (N(2)H(4)), and hydrogen peroxide (H(2)O(2)), which was also monitored in previous irradiation of pure ammonia and water ices, was also evident. These newly formed species were trapped inside of the ices and were released into the gas phase during the warm-up phase of the sample after the irradiation. A quantitative analysis of the data showed that the production rates of the newly formed species at 10 K are higher compared to those at 50 K. Our studies also suggest that hydroxylamine is likely formed by the recombination of amino (NH(2)) with hydroxyl (OH) radicals inside of the ices. Considering the physical effects on the ice sampled during the irradiation, the experiments provided compelling evidence that the crystalline ammonia-water ice samples can be partially converted to amorphous ices during the electron irradiation; similar to the chemical processes, the irradiation-induced amorphization of the ices is faster at 10 K than that at 50 K--a finding which is similar to electron-irradiated crystalline water ices under identical conditions. However, the amorphization of water in water-ammonia ices was found to be faster than that in pure water ices at identical temperatures.

[Virtual tissue. Quaoaring]

Virtual tissue can be generated by employing various methods. First steps en route to virtual tissue may encompass the generation of virtual cells. One such approach termed Quaoaring was applied to produce artificial erythrocytes and these were both discocyte and echinocyte in shape. The results were subsequently compared with data gleaned from scanning electron microscopy and atomic force microscopy. Quaoaring has, however, proved to be unsuccessful in creating convincing objects, particularly those which should be echinocytic in appearance.

Morphological study into the temperature dependence of solid ammonia under astrochemical conditions using vacuum ultraviolet and Fourier-transform infrared spectroscopy

The authors present the results of a morphological study of solid ammonia using both Fourier-transform infrared and vacuum ultraviolet (VUV) spectroscopy. Dramatic changes in the VUV and infrared spectra at temperatures between 65 and 85 K provide a deeper insight into the structure of ammonia ice particularly with the observation of an exciton transition at 194 nm (6.39 eV) in the VUV spectrum, revealing a structure that is composed of crystallites. A complementary structure is observed in the IR spectrum at 1100 cm(-1) which is assigned to the symmetric deformation of ammonia molecules at the surfaces of the crystallites. Such spectral signatures may be used to identify the environment within which the ammonia ice is formed and provide a new route for obtaining information on the physical and chemical conditions occurring within the interstellar medium, on the surfaces of planetary bodies, and in Kuiper belt objects.

Mechanistical studies on the formation of isotopomers of hydrogen peroxide (HOOH), hydrotrioxy (HOOO), and dihydrogentrioxide (HOOOH) in electron-irradiated H218O/O2 ice mixtures

In order to investigate the chemical reactions inside water-oxygen ice mixtures in extreme environments, and to confirm the proposed reaction mechanisms in pure water ice, we conducted a detailed infrared spectroscopy and mass spectrometry study on the electron irradiation of H(2)(18)O/O(2) ice mixtures. The formation of molecular hydrogen, isotopically substituted oxygen molecules (18)O(18)O and (16)O(18)O, ozone ((16)O(16)O(16)O, (16)O(16)O(18)O, and (16)O(18)O(16)O), hydrogen peroxide (H(18)O(18)OH, H(16)O(16)OH and H(16)O(18)OH), hydrotrioxy (HOOO), and dihydrogentrioxide (HOOOH) were detected. Kinetic models and reaction mechanisms are proposed to form these molecules in water and oxygen-rich solar system ices.

VUV spectroscopy and photo-processing of astrochemical ices: an experimental study

In order to understand much of the chemistry that underpins astronomical phenomena (e.g. star and planet formation) it is essential to probe the physico-chemistry of ice surfaces under astronomical conditions. The physical properties and chemical reactivity of such icy surfaces depends upon its morphology. Thus it is necessary to explore how the morphology of astrochemical ices is influenced by their local environment (e.g. temperature and pressure) and the mechanisms by which they are processed. In this paper we report the results of a series of experiments to explore the morphology of a variety of molecular ices using VUV spectroscopy. Spectral signatures are found that may allow the morphology of such ices to be identified.