The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems II: CO Fourth Positive Emission and Absorption

We exploit the high sensitivity and moderate spectral resolution of the $HST$-Cosmic Origins Spectrograph to detect far-ultraviolet spectral features of carbon monoxide (CO) present in the inner regions of protoplanetary disks for the first time. We present spectra of the classical T Tauri stars HN Tau, RECX-11, and V4046 Sgr, representative of a range of CO radiative processes. HN Tau shows CO bands in absorption against the accretion continuum. We measure a CO column density and rotational excitation temperature of N(CO) = 2 +/- 1 $\times$ 10$^{17}$ cm$^{-2}$ and T_rot(CO) 500 +/- 200 K for the absorbing gas. We also detect CO A-X band emission in RECX-11 and V4046 Sgr, excited by ultraviolet line photons, predominantly HI LyA. All three objects show emission from CO bands at $\lambda$ $>$ 1560 \AA, which may be excited by a combination of UV photons and collisions with non-thermal electrons. In previous observations these emission processes were not accounted for due to blending with emission from the accretion shock, collisionally excited H$_{2}$, and photo-excited H2; all of which appeared as a "continuum" whose components could not be separated. The CO emission spectrum is strongly dependent upon the shape of the incident stellar LyA emission profile. We find CO parameters in the range: N(CO) 10$^{18-19}$ cm$^{-2}$, T_{rot}(CO) > 300 K for the LyA-pumped emission. We combine these results with recent work on photo- and collisionally-excited H$_{2}$ emission, concluding that the observations of ultraviolet-emitting CO and H2 are consistent with a common spatial origin. We suggest that the CO/H2 ratio in the inner disk is ~1, a transition between the much lower interstellar value and the higher value observed in solar system comets today, a result that will require future observational and theoretical study to confirm.Comment: 12 pages, 7 figures, 3 tables. ApJ - accepte

A Frame-Based Language in Information Retrieval

With the advent of the information society, many researchers are turning to artificial intelligence techniques to provide effective retrieval over large bodies of textual information. Yet any AI system requires a formalism for encoding its knowledge about the objects of its knowledge, the world, and the intelligence that it is designed to manifest. In the CODER system, the mission of which is to provide an environment for experiments in applying AI to information retrieval, that formalism is provided by a single well defined factual representation language. Designed as a flexible tool for retrieval research, the CODER factual representation language is a hybrid AI language involving a system of strong types for attribute values, a frame system, and a system of Prolog-like relational structures. Inheritance is enforced throughout, and the semantics of type subsumption and object matching formally defined. A collection of type and object managers called the knowledge administration complex implements this common language for storing knowledge and communicating it within the system. Of the three types of knowledge structures in the language, the frame facility has proven most useful in the retrieval domain. The factual representation language is implemented in Prolog as a set of predicates accessible to all system modules. Each level of knowledge representation (elementary primitives, frames, and relations) has a type manager; the frame and relation levels also have object managers. Storage of complete knowledge objects (statements in the factual representation language) is supported by a system or external knowledge bases. One paper discusses the frame construct itself, the implementation of the knowledge administration complex and external knowledge bases. and the use of the construct in retrieval research. The paper closes with a discussion of the utility of the language in experiments

Integrated Access to a Large Medical Literature Database

Project INCARD (INtegrated CARdiology Database) has adapted the CODER (COmposite Document Expert/effective/extended Retrieval) system and LEND (Large External Network object oriented Database) to provide integrated access to a large collection of bibliographic citations, a full text document in cardiology, and a large thesaurus of medical terms. CODER is a distributed expert-based information system that incorporates techniques from artificial intelligence, information retrieval, and human-computer interaction to support effective access to information and knowledge bases. LEND is an object-oriented database which incorporates techniques from information retrieval and database systems to support complex objects, hypertext/hypermedia and semantic network operations efficiently with very large sets of data. LEND stores the CED lexicon, MeSH thesaurus, MEDLARS bibliographics records on cardiology, and the syllabus for the topic Abnormal Human Biology (Cardiology Section) taught at Columbia University. Together, CODER/LEND allow efficient and flexible access to all of this information while supporting rapid "intelligent" searching and hypertext-style browsing by both novice and expert users. This report gives statistics on the collections, illustrations of the system's use, and details on the overall architecture and design for Project INCARD

Building the CODER Lexicon: The Collins English Dictionary and Its Adverb Definitions

The CODER (COmposite Document Expert/extended/effective Retrieval) project is an investigation of the applicability of artificial intelligence techniques to the information retrieval task of analyzing, storing, and retrieving heterogeneous collections of "composite documents." In order to support some of the processing desired, and to allow experimentation in information retrieval and natural language processing, a lexicon was constructed from the machine readable Collins dictionary of the English Language. After giving background, motivation, and a survey of related work, the Collins lexicon is discussed. Following is a description of the conversion process, the format of the resulting Prolog database, and characteristics of the dictionary and relations. To illustrate what is present and to explain how it relates to the files produced from Webster's Seventh New Collegiate Dictionary, a number of comparative charts are given. Finally, a summary of adverb definitions is presented, together with a description of defining formula that usually indicate the type of the adverb. Ultimately it is hoped that definitions for adverbs and other words will be parsed so that the relational lexicon being constructed will include many additional relationships and other knowledge about words and their usage

The composition of the protosolar disk and the formation conditions for comets

Conditions in the protosolar nebula have left their mark in the composition of cometary volatiles, thought to be some of the most pristine material in the solar system. Cometary compositions represent the end point of processing that began in the parent molecular cloud core and continued through the collapse of that core to form the protosun and the solar nebula, and finally during the evolution of the solar nebula itself as the cometary bodies were accreting. Disentangling the effects of the various epochs on the final composition of a comet is complicated. But comets are not the only source of information about the solar nebula. Protostellar disks around young stars similar to the protosun provide a way of investigating the evolution of disks similar to the solar nebula while they are in the process of evolving to form their own solar systems. In this way we can learn about the physical and chemical conditions under which comets formed, and about the types of dynamical processing that shaped the solar system we see today. This paper summarizes some recent contributions to our understanding of both cometary volatiles and the composition, structure and evolution of protostellar disks.Comment: To appear in Space Science Reviews. The final publication is available at Springer via http://dx.doi.org/10.1007/s11214-015-0167-

Residential PM2.5 exposure and the nasal methylome in children

Rationale: PM2.5-induced adverse effects on respiratory health may be driven by epigenetic modifications in airway cells. The potential impact of exposure duration on epigenetic alterations in the airways is not yet known. Objectives: We aimed to study associations of fine particulate matter PM2.5 exposure with DNA methylation in nasal cells. Methods: We conducted nasal epigenome-wide association analyses within 503 children from Project Viva (mean age 12.9 y), and examined various exposure durations (1-day, 1-week, 1-month, 3-months and 1-year) prior to nasal sampling. We used residential addresses to estimate average daily PM2.5 at 1 km resolution. We collected nasal swabs from the anterior nares and measured DNA methylation (DNAm) using the Illumina Methylation EPIC BeadChip. We tested 719,075 high quality autosomal CpGs using CpG-by-CpG and regional DNAm analyses controlling for multiple comparisons, and adjusted for maternal education, household smokers, child sex, race/ethnicity, BMI z-score, age, season at sample collection and cell-type heterogeneity. We further corrected for bias and genomic inflation. We tested for replication in a cohort from the Netherlands (PIAMA). Results: In adjusted analyses, we found 362 CpGs associated with 1-year PM2.5 (FDR < 0.05), 20 CpGs passing Bonferroni correction (P < 7.0 x 10(-8)) and 10 Differentially Methylated Regions (DMRs). In 445 PIAMA participants (mean age 16.3 years) 11 of 203 available CpGs replicated at P < 0.05. We observed differential DNAm at/ near genes implicated in cell cycle, immune and inflammatory responses. There were no CpGs or regions associated with PM2.5 levels at 1-day, 1-week, or 1-month prior to sample collection, although 2 CpGs were associated with past 3-month PM2.5. Conclusion: We observed wide-spread DNAm variability associated with average past year PM2.5 exposure but we did not detect associations with shorter-term exposure. Our results suggest that nasal DNAm marks reflect chronic air pollution exposure

Robustness of N₂H⁺ as tracer of the CO snowline

Context. Snowlines in protoplanetary disks play an important role in planet formation and composition. Since the CO snowline is difficult to observe directly with CO emission, its location has been inferred in several disks from spatially resolved ALMA observations of DCO⁺ and N₂H⁺. Aims. N₂H⁺ is considered to be a good tracer of the CO snowline based on astrochemical considerations predicting an anti-correlation between N₂H⁺ and gas-phase CO. In this work, the robustness of N₂H⁺ as a tracer of the CO snowline is investigated. Methods. A simple chemical network was used in combination with the radiative transfer code LIME to model the N₂H⁺ distribution and corresponding emission in the disk around TW Hya. The assumed CO and N₂ abundances, corresponding binding energies, cosmic ray ionization rate, and degree of large-grain settling were varied to determine the effects on the N₂H⁺ emission and its relation to the CO snowline. Results. For the adopted physical structure of the TW Hya disk and molecular binding energies for pure ices, the balance between freeze-out and thermal desorption predicts a CO snowline at 19 AU, corresponding to a CO midplane freeze-out temperature of 20 K. The N₂H⁺ column density, however, peaks 5–30 AU outside the snowline for all conditions tested. In addition to the expected N₂H⁺ layer just below the CO snow surface, models with an N₂/CO ratio 0.2 predict an N₂H⁺ layer higher up in the disk due to a slightly lower photodissociation rate for N₂ as compared to CO. The influence of this N₂H⁺ surface layer on the position of the emission peak depends on the total CO and N₂ abundances and the disk physical structure, but the emission peak generally does not trace the column density peak. A model with a total (gas plus ice) CO abundance of 3 × 10−6 with respect to H₂ fits the position of the emission peak previously observed for the TW Hya disk. Conclusions. The relationship between N₂H⁺ and the CO snowline is more complicated than generally assumed: for the investigated parameters, the N₂H⁺ column density peaks at least 5 AU outside the CO snowline. Moreover, the N₂H⁺ emission can peak much further out, as far as ∼50 AU beyond the snowline. Hence, chemical modeling, as performed here, is necessary to derive a CO snowline location from N₂H⁺ observations

Measurements of psi(2S) decays to octet baryon-antibaryon pairs

With a sample of 14 million psi(2S) events collected by the BESII detector at the Beijing Electron Positron Collider (BEPC), the decay channels psi(2S)->p p-bar, Lambda Lambda-bar, Sigma0 Sigma0-bar, Xi Xi-bar are measured, and their branching ratios are determined to be (3.36+-0.09+-0.24)*10E-4, (3.39+-0.20+-0.32)*10E-4, (2.35+-0.36+-0.32)*10E-4, (3.03+-0.40+-0.32)*10E-4, respectively. In the decay psi(2S)->p p-bar, the angular distribution parameter alpha is determined to be 0.82+-0.17+-0.04.Comment: 8 pages, 8 figure