Characterizing the chemical pathways for water formation -- A deep search for hydrogen peroxide

In 2011, hydrogen peroxide (HOOH) was observed for the first time outside the solar system (Bergman et al., A&A, 2011, 531, L8). This detection appeared a posteriori quite natural, as HOOH is an intermediate product in the formation of water on the surface of dust grains. Following up on this detection, we present a search for HOOH in a diverse sample of sources in different environments, including low-mass protostars and regions with very high column densities, such as Infrared Dark Clouds (IRDCs). We do not detect the molecule in any other source than Oph A, and derive 3$\sigma$ upper limits for the abundance of HOOH relative to H$_2$ lower than in Oph A for most sources. This result sheds a different light on our understanding of the detection of HOOH in Oph A, and shifts the puzzle to why this source seems to be special. Therefore we rediscuss the detection of HOOH in Oph A, as well as the implications of the low abundance of HOOH, and its similarity with the case of O$_2$. Our chemical models show that the production of HOOH is extremely sensitive to the temperature, and favored only in the range 20$-$30 K. The relatively high abundance of HOOH observed in Oph A suggests that the bulk of the material lies at a temperature in the range 20$-$30 K.Comment: 18 pages, 3 figures, invited refereed paper at the Faraday Discussion 16

Stability charts based on the finite element method for underground cavities in soft carbonate rocks: validation through case-study applications

Abstract. The stability of man-made underground cavities in soft rocks interacting with overlying structures and infrastructures represents a challenging problem to be faced. Based upon the results of a large number of parametric two-dimensional (2-D) finite-element analyses of ideal cases of underground cavities, accounting for the variability both cave geometrical features and rock mechanical properties, specific charts have been recently proposed in the literature to assess at a preliminary stage the stability of the cavities. The purpose of the present paper is to validate the efficacy of the stability charts through the application to several case studies of underground cavities, considering both quarries collapsed in the past and quarries still stable. The stability graphs proposed by Perrotti et al. (2018) can be useful to evaluate, in a preliminary way, a safety margin for cavities that have not reached failure and to detect indications of predisposition to local or general instability phenomena. Alternatively, for sinkholes that already occurred, the graphs may be useful in identifying the conditions that led to the collapse, highlighting the importance of some structural elements (as pillars and internal walls) on the overall stability of the quarry system

Natural and anthropogenic hazards in karst areas of Albania

International audienceIn Albania, about one quarter of the country is occupied by outcroppings of soluble rocks; thus, karst represents an important and typical natural environment. Today karst areas are seriously threatened by a number of hazards, of both natural and anthropogenic origin. Many problems are related to agricultural practices: the use of heavy machinery, ever-increasing in recent years, results at many sites in destruction of the original karst landscapes. Use of pesticides and herbicides, in addition, causes the loss of karst ecosystems of great biological relevance, as has been observed in the Dumre district, where about 80 lakes of karst origin are present in the evaporites of Permian-Triassic age. Agricultural practice performed on slopes with medium to high gradient is a further factor which greatly predispose the slopes to erosion. The cave heritage of Albania (estimated so far in about 1000 caves) is at risk because of the uncontrolled quarrying activities which determine the total or partial destruction of karst caves, including many of naturalistic, archaeological and speleological interest. Many caves have also become sites of illegal disposal of solid and liquid wastes, which causes pollution of the karst ecosystems and of the aquifer therein present, with heavy negative consequences on the quality of water. Even though most of the cases here mentioned are related to anthropogenic activities, the natural hazards, such as subsidence phenomena, floods, and the development of sinkholes, have not to be disregarded

C-banding And Fish In Chromosomes Of The Blow Flies Chrysomya Megacephala And Chrysomya Putoria (diptera, Calliphoridae).

The blow flies Chrysomya putoria and C. megacephala have 2n=12 chromosomes, five metacentric pairs of autosomes and an XX/XY sex chromosome pair. There are no substantial differences in the karyotype morphology of these two species, except for the X chromosome which is subtelocentric in C. megacephala and metacentric in C. putoria and is about 1.4 times longer in C. putoria. All autosomes were characterized by the presence of a C band in the pericentromeric region; C. putoria also has an interstitial band in pair III. The sex chromosomes of both species were heterochromatic, except for a small region at the end of the long arm of the X chromosome. Ribosomal genes were detected in meiotic chromosomes by FISH and in both species the NOR was located on the sex chromosomes. These results confirm that C. putoria was the species introduced into Brazil in 1970s, and not C. chloropyga as formerly described.96371-

Teacher Learning and Instructional Change: How Formal and On-the-Job Learning Opportunities Predict Change in Elementary School Teachers\u27 Practice

Recent education reform has emphasized the importance of teacher learning in improving classroom instruction and raising student achievement. This article focuses on teachers\u27 learning opportunities, including formal professional development and on-the-job learning that occurs through interactions with colleagues. Using data from 30 elementary schools in a mid-sized urban school district, the authors concurrently explore the relationships between teachers\u27 formal professional development and on-the-job learning opportunities and instructional change. Results suggest that formal professional development and on-the-job opportunities to learn are both significantly associated with changes in teachers\u27 instructional practice in mathematics and English language arts

Deuterated formaldehyde in rho Ophiuchi A

From mapping observations of H2CO, HDCO, and D2CO, we have determined how the degree of deuterium fractionation changes over the central 3'x3' region of rho Oph A. The multi-transition data of the various H2CO isotopologues, as well as from other molecules (e.g., CH3OH and N2D+) present in the observed bands, were analysed using both the standard type rotation diagram analysis and, in selected cases, a more elaborate method of solving the radiative transfer for optically thick emission. In addition to molecular column densities, the analysis also estimates the kinetic temperature and H2 density. Toward the SM1 core in rho Oph A, the H2CO deuterium fractionation is very high. In fact, the observed D2CO/HDCO ratio is 1.34+/-0.19, while the HDCO/H2CO ratio is 0.107+/-0.015. This is the first time, to our knowledge, that the D2CO/HDCO abundance ratio is observed to be greater than 1. The kinetic temperature is in the range 20-30 K in the cores of rho Oph A, and the H2 density is (6-10)x10^5 cm-3. We estimate that the total H2 column density toward the deuterium peak is (1-4)x10^23 cm-2. As depleted gas-phase chemistry is not adequate, we suggest that grain chemistry, possibly due to abstraction and exchange reactions along the reaction chain H2CO -> HDCO -> D2CO, is at work to produce the very high deuterium levels observed.Comment: 17 pages, 11 figures, accepted for publication in Astronomy & Astrophysic

The evolutionary state of the southern dense core Cha-MMS1

Aims: Our goal is to set constraints on the evolutionary state of the dense core Cha-MMS1 in the Chamaeleon I molecular cloud. Methods: We analyze molecular line observations carried out with the new submillimeter telescope APEX. We look for outflow signatures around the dense core and probe its chemical structure, which we compare to predictions of models of gas-phase chemistry. We also use the public database of the Spitzer Space Telescope (SST) to compare Cha-MMS1 with the two Class 0 protostars IRAM 04191 and L1521F, which are at the same distance. Results: We measure a large deuterium fractionation for N2H+ (11 +/- 3 %), intermediate between the prestellar core L1544 and the very young Class 0 protostar L1521F. It is larger than for HCO+ (2.5 +/- 0.9 %), which is probably the result of depletion removing HCO+ from the high-density inner region. Our CO(3-2) map reveals the presence of a bipolar outflow driven by the Class I protostar Ced 110 IRS 4 but we do not find evidence for an outflow powered by Cha-MMS1. We also report the detection of Cha-MMS1 at 24, 70 and 160 microns by the instrument MIPS of the SST, at a level nearly an order of magnitude lower than IRAM 04191 and L1521F. Conclusions: Cha-MMS1 appears to have already formed a compact object, either the first hydrostatic core at the very end of the prestellar phase, or an extremely young protostar that has not yet powered any outflow, at the very beginning of the Class 0 accretion phase.Comment: Accepted by Astronomy & Astrophysics as a letter, to appear in the special issue on the APEX first result

PIP-II SSR2 Cavities Fabrication and Processing Experience

The Proton Improvement Plan-II (PIP-II [1]) linac will include 35 Single Spoke Resonators type 2 (SSR2). A preproduction SSR2 cryomodule will contain 5 jacketed cavities. Several units are already manufactured and prepared for cold testing. In this work, data collected from the fabrication, processing and preparation of the cavities will be presented and the improvements implemented after the completion of the first unit will be highlighted

H2CO and CH3OH maps of the Orion Bar photodissociation region

A previous analysis of methanol and formaldehyde towards the Orion Bar concluded that the two molecular species may trace different physical components, methanol the clumpy material, and formaldehyde the interclump medium. To verify this hypothesis, we performed multi-line mapping observations of the two molecules to study their spatial distributions. The observations were performed with the IRAM-30m telescope at 218 and 241 GHz, with an angular resolution of ~11''. Additional data for H2CO from the Plateau de Bure array are also discussed. The data were analysed using an LVG approach. Both molecules are detected in our single-dish data. Our data show that CH3OH peaks towards the clumps of the Bar, but its intensity decreases below the detection threshold in the interclump material. When averaging over a large region of the interclump medium, the strongest CH3OH line is detected with a peak intensity of ~0.06K. Formaldehyde also peaks on the clumps, but it is also detected in the interclump gas. We verified that the weak intensity of CH3OH in the interclump medium is not caused by the different excitation conditions of the interclump material, but reflects a decrease in the column density of methanol. The abundance of CH3OH relative to H2CO decreases by at least one order of magnitude from the dense clumps to the interclump medium.Comment: 11 pages, accepted for publication in A&

Preliminary 3-D finite element analysis of the triggering mechanism of an occasional reactivation of a large landslide in stiff clays

In December 2013 a large landslide occurred along a clay slope located at the south-western outskirts of the Montescaglioso village (Basilicata, Southern Italy) as a consequence of intense and prolonged rainfalls that presumably caused a significant increment of the pore water pressures in the slope. The slope is formed of stiff clays belonging to the formation of the Subappennine Blue Clays, which are over-consolidated and characterized by medium plasticity. According to aerial photos dating back to 1950s, the slope was already affected by previous landslide processes, so that the examined landslide process can be classified as an occasional reactivation according to the well-known classification of Cruden & Varnes (1996). Also, during the last decades several man-made actions in the area resulted in strong changes in the original water surface network that could have played some role in the slope reactivation. Based on displacement data, obtained from a monitoring system installed few days after the phenomenon, and still in function, at present the landslide does not show relevant signs of activity. Preliminary 2-D and 3-D finite element analyses have been carried out to investigate the factors that controlled the mechanism of reactivation of the landslide. The numerical model has been setup based on the available topographical, geological and geomorphological information, the geotechnical properties of the involved soils and the information concerning the piezometric regime in the slope. The results indicate that the mobilized shear strength of the clays ranges between the typical post-peak and residual values for this type of material and confirmed that the strong increment of the pore water pressures in the slope induced by the exceptional rainfalls occurred in the previous days can be identified as the main triggering factor of the reactivation