A Correlated Ab Initio Study of Linear Carbon-Chain Radicals C(sub n)H (n=2-7)

Linear carbon-chain radicals C(sub n) H for n = 2-7 have been studied with correlation consistent valence and core-valence basis sets and the coupled cluster method RCCSD(T). Equilibrium structures, rotational constants, and dipole moments are reported and compared with available experimental data. The ground state of the even-n series changes from 2Sigma(+) to 2Pi as the chain is extended. For C4H, the 2Sigma(+) state was found to lie only 72 cm(exp -1) below the 2Pi state in the estimated complete basis set limit for valence correlation. The C2H(-) and C3H(-) anions have also been characterized

AB Initio Characterization of MgCCH, MgCCH(+), and MgC2, and Pathways to their Formation in the Interstellar Medium

A study of Mg-bearing compounds has been performed in order to determine molecular properties which are critical for planning new astronomical searches and laboratory studies. The primary focus of the work is on MgCCH, MgCCH(+), and the isomers of MgC2. Only MgCCH has been identified in laboratory studies. Additional calculations have been carried out on MgH, MgNC, MgCN, and their cations in an effort to evaluate pathways to the formation of MgCCH and MgCCH(+) in the InterStellar Medium (ISM) or in circumstellar envelopes. Correlated ab initio methods and correlation-consistent basis sets have been employed. Properties including structures, rotational constants, dipole moments, and harmonic frequencies are reported. A transition state between linear MgCC and cyclic MgC2 has been characterized and was found to yield a minimal barrier (approx. 0.5 kcal/mole), indicating easy interconversion to the cyclic form. Direct reactions in the ISM between Mg or Mg(+) and HCCH are precluded by energetic considerations, but a number of ion- molecule or neutral-neutral exchange reactions between CCH and various Mg-containing species offer plausible pathways to MgCCH or MgCCH(+). Weakly bound MgH may react with CCH to form MgCCH, but MgH has not been detected. Both MgNC and MgCN have been observed, but reactions with CCH are slightly endothermic by 1-3 kcal/mole. Although MgH(+), MgNC(+), and MgCN(+) have not been detected, their reactions with CCH to form MgCCH(+) are all exothermic. With only a small barrier separating linear MgCC and cyclic MgC2, the dissociative recombination of MgCCH(+) with an electron is expected to yield cyclic MgC2, and regenerate Mg and CCH. New astronomical searches for MgCCH, MgCCH(+), cyclic MgC2, MgNC(+), and MgCN(+) will provide further insight into organo-magnesium astrochemistry

FORMATION OF THE ALMA MOLECULE HOCH2CN AND RELATED SPECIES FROM THE REACTION OF C+ WITH HCN AND HNC IN ICY GRAIN MANTLES

Density functional theory cluster calculations indicate that the intermediate HOCHNC readily forms when \chem{C^+} reacts with HCN embedded in the surface of an icy grain mantle. Subsequent H addition to HOCHNC yields the iscyano compound \chem{HOCH_2NC}. There is enough energy from the H addition for \chem{HOCH_2NC} to isomerize to \chem{HOCH_2CN} (glycolonitrile), an important prebiotic molecule that was recently detected with ALMA observations toward the solar-type protostellar source IRAS 16293-2422 B by Zeng et al. [MNRAS 2019, 484, L43]. It was found that H can also add to HOCHNC to form HOCHNCH without a barrier. The analogous reactions of \chem{C^+} with HNC in ice will also be discussed. Vibrational spectra of the various ice-bound reactants, intermediates, and products will be presented. The calculations were performed with B3LYP using aug-cc-pVDZ sets on C, N, and O and cc-pVDZ sets on H

Astrochemistry lecture and laboratory courses at the University of Illinois: Applied spectroscopy

The Department of Chemistry at the University of Illinois at Urbana-Champaign offers two courses in astrochemistry, one lecture (Chem 450) and one laboratory (Chem 451). Both courses present the opportunity for advanced undergraduate and graduate students to learn about various spectroscopic concepts as they are applied toward an exotic subject, astrochemistry. In the lecture course, each student devotes a substantial fraction of the course work to one of the known astromolecules, building a wiki page for it during the semester, presenting a brief oral description about it in class, and then finally writing a paper about it. The course covers electronic, vibrational, and rotational spectroscopy, along with Einstein coefficients, line widths, and the interpretation of actual astronomical spectra. It also covers relevant reactions and reaction networks. Students learn to use pgopher for modeling rotational spectra. The lab course focuses on the methylidyne radical (CH). It begins with its chemistry and spectroscopy and then moves on to laboratory study of its electronic spectrum as observed in a butane flame and then collected with the university's 12" f/15 Brashear refracting telescope in the campus observatory built in 1896. Students learn to use IGOR to reduce CCD data

AB INITIO CHARACTERIZATION OF SULFUR COMPOUNDS AND THEIR CHEMISTRY FOR VENUS AND THE INTERSTELLAR MEDIUM

The atmosphere of Venus is known to contain trace amounts of SO, SO$_{2}$, OCS, H$_{2}$SO$_{4}$, and possibly H$_{2}$S and elemental sulfur oligomers, S$_{n}$. Modeling studies indicate that many more compounds containing sulfur and both sulfur and chlorine may also be present, given that the known compounds are photolyzed by solar radiation in the upper atmosphere of Venus and yield reactive radical species. A large number of exotic compounds containing S, O, H, C, and/or Cl of suspected or plausible significance for Venus chemistry have been characterized at the RCCSD(T)/aug-cc-pVTZ level, yielding structures, dipole moments, and dipole polarizabilities. Representative compounds and associated chemical reactions will be discussed. Both abstraction and addition-elimination reactions have been characterized

QUANTUM CHEMICAL STUDY OF THE REACTION OF C+ WITH INTERSTELLAR ICE: PREDICTIONS OF VIBRATIONAL AND ELECTRONIC SPECTRA OF REACTION PRODUCTS

The C$^{+}$ cation (CII) is the dominant form of carbon in diffuse clouds and an important tracer for star formation in molecular clouds. We studied the low energy deposition of C$^{+}$ on ice using density functional theory calculations on water clusters as large as 18 H$_{2}$O. Barrierless reactions occur with water to form two dominant sets of products: HOC + H$_{3}$O$^{+}$ and CO$^{-}$ + 2H$_{3}$O$^{+}$. In order to provide testable predictions, we have computed both vibrational and electronic spectra for pure ice and processed ice clusters. While vibrational spectroscopy is expected to be able to discern that C$^{+}$ has reacted with ice by the addition of H$_{3}$O$^{+}$ features not present in pure ice, it does not provided characteristic bands that would discern between HOC and CO$^{-}$. On the other hand, predictions of electronic spectra suggest that low energy absorptions may occur for CO$^{-}$ and not HOC, making it possible to distinguish one product from the other

USE OF STUDENT-SPECIFIC MOLECULES AND THEIR SPECTROSCOPIC PROPERTIES IN PHYSICAL CHEMISTRY COURSES

Spectroscopy is a fundamental component of physical chemistry courses. To encourage students to take more interest in the critical contributions of spectroscopic properties to the subject, I assign different molecules to the students. In the second semester of a two-semester course that covers statistical and classical thermodynamics, the students draw molecules from a hat on the first day of class. They look up spectroscopic properties for their molecules on the web and use the values in various homework, quiz, and exam problems. In a one semester "principles" course, they build a closed-shell molecule from a limited set of atoms. I then provide the students with calculated values of spectroscopic properties, which they use in a term project about their molecules that covers structure, spectra, partition functions, and properties derived from partition functions

Mouse brain distribution of a carbon-11 labeled vesamicol derivative: Presynaptic marker of cholinergic neurons

The regional mouse brain distribution of a new carbon-11 labeled derivative of vesamicol, [11C]-5-(N-methylamino)benzovesamicol ([11C]MABV) is reported. Radiotracer concentrations in vivo are in the rank order of striatum>cortex>hippocampus>hypothalamus> cerebellum, consistent with reported distributions of other presynaptic cholinergic neuronal markers. In time course studies, striatum/cerebellum and cortex/cerebellum ratios for (-)-[11C]MABV continue to increase to values of 13 and 5, respectively, 75 min after i.v. injection of [11C]MABV. The specific binding in striatum and cortex is lowered by pretreatment with (+/-)-vesamicol, and shows stereoselectivity with lower uptake and lower ratios for the (+)-enantiomer. (-)-[11C]MABV is proposed as a positron-emitting radioligand for the in vivo study of presynaptic cholinergic neurons.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28961/1/0000798.pd

Tet1 Is Dispensable for Maintaining Pluripotency and Its Loss Is Compatible with Embryonic and Postnatal Development

SummaryThe Tet family of enzymes (Tet1/2/3) converts 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). Mouse embryonic stem cells (mESCs) highly express Tet1 and have an elevated level of 5hmC. Tet1 has been implicated in ESC maintenance and lineage specification in vitro but its precise function in development is not well defined. To establish the role of Tet1 in pluripotency and development, we have generated Tet1 mutant mESCs and mice. Tet1−/− ESCs have reduced levels of 5hmC and subtle changes in global gene expression, and are pluripotent and support development of live-born mice in tetraploid complementation assay, but display skewed differentiation toward trophectoderm in vitro. Tet1 mutant mice are viable, fertile, and grossly normal, though some mutant mice have a slightly smaller body size at birth. Our data suggest that Tet1 loss leading to a partial reduction in 5hmC levels does not affect pluripotency in ESCs and is compatible with embryonic and postnatal development

Creating human digital memories with the aid of pervasive mobile devices

The abundance of mobile and sensing devices, within our environment, has led to a society in which any object, embedded with sensors, is capable of providing us with information. A human digital memory, created with the data from these pervasive devices, produces a more dynamic and data rich memory. Information such as how you felt, where you were and the context of the environment can be established. This paper presents the DigMem system, which utilizes distributed mobile services, linked data and machine learning to create such memories. Along with the design of the system, a prototype has also been developed, and two case studies have been undertaken, which successfully create memories. As well as demonstrating how memories are created, a key concern in human digital memory research relates to the amount of data that is generated and stored. In particular, searching this set of big data is a key challenge. In response to this, the paper evaluates the use of machine learning algorithms, as an alternative to SPARQL, and treats searching as a classification problem. In particular, supervised machine learning algorithms are used to find information in semantic annotations, based on probabilistic reasoning. Our approach produces good results with 100% sensitivity, 93% specificity, 93% positive predicted value, 100% negative predicted value, and an overall accuracy of 97%