The Optimal Routing of Solid Waste Collection Vehicles

Turner, Wayne C.; Hougland, E.S.

doi:10.1080/05695557508975027

Cited by 15 publications

(17 citation statements)

References 5 publications

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“…Here we have mapped two hyperfine transitions (∆F = 1) in the J = 9/2 -7/2 transition of the 2 Π 1/2 ground state. C 3 H has been observed in IRC+10216 and TMC-1 (Thaddeus et al 1985b) before its first laboratory detection (Gottlieb et al 1985(Gottlieb et al , 1986, and it has subsequently been observed toward several sources, among those are translucent molecular clouds (Turner et al 2000), a protoplanetary nebula Cernicharo 2007), andSgr B2 (McGuire et al 2013).…”

Section: Discussionmentioning

confidence: 99%

The observed chemical structure of L1544

Spezzano

Caselli

Bizzocchi

et al. 2017

A&A

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Context. Prior to star formation, pre-stellar cores accumulate matter towards the centre. As a consequence, their central density increases while the temperature decreases. Understanding the evolution of the chemistry and physics in this early phase is crucial to study the processes governing the formation of a star. Aims. We aim at studying the chemical differentiation of a prototypical pre-stellar core, L1544, by detailed molecular maps. In contrast with single pointing observations, we performed a deep study on the dependencies of chemistry on physical and external conditions. Methods. We present the emission maps of 39 different molecular transitions belonging to 22 different molecules in the central 6.25 arcmin 2 of L1544. We classified our sample in five families, depending on the location of their emission peaks within the core. Furthermore, to systematically study the correlations among different molecules, we have performed the principal component analysis (PCA) on the integrated emission maps. The PCA allows us to reduce the amount of variables in our dataset. Finally, we compare the maps of the first three principal components with the H2 column density map, and the T dust map of the core. Results. The results of our qualitative analysis is the classification of the molecules in our dataset in the following groups: (i) the c-C3H2 family (carbon chain molecules like C3H and CCS), (ii) the dust peak family (nitrogen-bearing species like N2H + ), (iii) the methanol peak family (oxygen-bearing molecules like methanol, SO and SO2), (iv) the HNCO peak family (HNCO, propyne and its deuterated isotopologues). Only HC 18 O + and 13 CS do not belong to any of the above mentioned groups. The principal component maps allow us to confirm the (anti-)correlations among different families that were described in a first qualitative analysis, but also points out the correlation that could not be inferred before. For example, the molecules belonging to the dust peak and the HNCO peak families correlate in the third principal component map, hinting on a chemical/physical correlation. Conclusions. The principal component analysis has shown to be a powerful tool to retrieve information about the correlation of different molecular species in L1544, and their dependence on physical parameters previously studied in the core.

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Section: Discussionmentioning

confidence: 99%

The observed chemical structure of L1544

Spezzano

Caselli

Bizzocchi

et al. 2017

A&A

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“…A more detailed approach would be to start with elemental abundances measured in diffuse clouds, consider both the chemistry occurring in the gas and on the surface of dust particles, allow for both adsorption on to and desorption from grains, and include the collapse of the cloud from diffuse to dense conditions (assuming that collapse is the correct direction to follow). Although such a treatment is desirable, it is our purpose here only to compare the use of the new network with comparable gas-phase treatments undertaken by astrochemists in the past (Millar et al 1997;Terzieva & Herbst 1998;Turner et al 2000).…”

Section: R E S U Lt Smentioning

confidence: 99%

Rapid neutral-neutral reactions at low temperatures: a new network and first results for TMC-1

Smith¹,

Herbst²,

Chang³

2004

Monthly Notices of the Royal Astronomical Society

257

266

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There is now ample evidence from an assortment of experiments, especially those involving the CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme) technique, that a variety of neutral–neutral reactions possess no activation energy barrier and are quite rapid at very low temperatures. These reactions include both radical–radical systems and, more surprisingly, systems involving an atom or a radical and one ‘stable’ species. Generalizing from the small but growing number of systems studied in the laboratory, we estimate reaction rate coefficients for a larger number of such reactions and include these estimates in a new network of gas‐phase reactions for use in low‐temperature interstellar chemistry. Designated osu.2003, the new network is available on the World Wide Web and will be continually updated. A table of new results for molecular abundances in the dark cloud TMC‐1 (CP) is provided and compared with results from an older (new standard model; nsm) network.

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“…Propadienylidene was first detected in the laboratory by Vrtilek et al (1990) by means of millimetrewave absorption spectroscopy in a DC discharge. It has been observed in prestellar and protostellar cores (Cernicharo et al 1991;Turner et al 2000;Kawaguchi et al 1991;Sakai & Yamamoto 2013), circumstellar envelopes (Cernicharo et al 1991), translucent clouds (Turner et al 2000), diffuse clouds (Cernicharo et al 1999;Kulczak-Jastrzȩbska et al 2012;Liszt et al 2012), and photo-dissociation regions (PDRs) (Teyssier et al 2005;Cuadrado et al 2015).…”

Section: Introductionmentioning

confidence: 99%

“…The chemistry of c and l C 3 H 2 , and that of other associated species, has previously been modeled by, e.g., Turner et al (2000) and Fossé et al (2001). Both of these works pointed out that also neutral-neutral reactions can play a part in determining the C 3 H 2 c/l ratio.…”

Section: Introductionmentioning

confidence: 99%

Understanding the C₃H₂cyclic-to-linear ratio in L1544

Sipilä

Spezzano

Caselli

2016

A&A

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Aims. We aim to understand the high cyclic-to-linear C 3 H 2 ratio (32 ± 4) that has been observed toward L1544. Methods. We combined a gas-grain chemical model with a physical model for L1544 to simulate the column densities of cyclic and linear C 3 H 2 observed toward L1544. The most important reactions for the formation and destruction of both forms of C 3 H 2 were identified, and their relative rate coefficients were varied to find the best match to the observations. Results. We find that the ratio of the rate coefficients of C 3 H + 3 + e − −→ C 3 H 2 + H for cyclic and linear C 3 H 2 must be ∼20 to reproduce the observations, depending on the branching ratios assumed for the C 3 H + 3 + e − −→ C 3 H + H 2 reaction. In current astrochemical networks it is assumed that cyclic and linear C 3 H 2 are formed in a 1:1 ratio in the aforementioned reactions. Laboratory studies and/or theoretical calculations are needed to confirm the results of our chemical modeling, which is based on observational constraints.

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The Optimal Routing of Solid Waste Collection Vehicles

Cited by 15 publications

References 5 publications

The observed chemical structure of L1544

The observed chemical structure of L1544

Rapid neutral-neutral reactions at low temperatures: a new network and first results for TMC-1

Understanding the C₃H₂cyclic-to-linear ratio in L1544

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The Optimal Routing of Solid Waste Collection Vehicles

Cited by 15 publications

References 5 publications

The observed chemical structure of L1544

The observed chemical structure of L1544

Rapid neutral-neutral reactions at low temperatures: a new network and first results for TMC-1

Understanding the C3H2cyclic-to-linear ratio in L1544

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Product

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Understanding the C₃H₂cyclic-to-linear ratio in L1544