The Gas Temperature of Starless Cores in Perseus

In this paper we study the determinants of starless core temperatures in the Perseus molecular cloud. We use NH3 (1,1) and (2,2) observations to derive core temperatures (T_kin) and data from the COMPLETE Survey of Star Forming Regions and the c2d Spitzer Legacy Survey for observations of the other core and molecular cloud properties. The kinetic temperature distribution probed by NH3 is in the fairly narrow range of 9 - 15 K. We find that cores within the clusters IC348 and NGC1333 are significantly warmer than "field" starless cores, and T_kin is higher within regions of larger extinction-derived column density. Starless cores in the field are warmer when they are closer to class O/I protostars, but this effect is not seen for those cores in clusters. For field starless cores, T_kin is higher in regions in which the 13CO linewidth and the 1.1mm flux from the core are larger, and T_kin is lower when the the peak column density within the core and average volume density of the core are larger. There is no correlation between T_kin and 13CO linewidth, 1.1mm flux, density or peak column density for those cores in clusters. The temperature of the cloud material along the line of sight to the core, as measured by CO or far-infrared emission from dust, is positively correlated with core temperature when considering the collection of cores in the field and in clusters, but this effect is not apparent when the two subsamples of cores are considered separately.Comment: Accepted to ApJ; 13 pages, including 3 tables and three figure

Construction and Measurements of an Improved Vacuum-Swing-Adsorption Radon-Mitigation System

In order to reduce backgrounds from radon-daughter plate-out onto detector surfaces, an ultra-low-radon cleanroom is being commissioned at the South Dakota School of Mines and Technology. An improved vacuum-swing-adsorption radon mitigation system and cleanroom build upon a previous design implemented at Syracuse University that achieved radon levels of $\sim$0.2$\,$Bq$\,$m$^{-3}$. This improved system will employ a better pump and larger carbon beds feeding a redesigned cleanroom with an internal HVAC unit and aged water for humidification. With the rebuilt (original) radon mitigation system, the new low-radon cleanroom has already achieved a $>$$\,$300$\times$ reduction from an input activity of $58.6\pm0.7$$\,$Bq$\,$m$^{-3}$ to a cleanroom activity of $0.13\pm0.06$$\,$Bq$\,$m$^{-3}$.Comment: 5 pages, 4 figures, Proceedings of Low Radioactivity Techniques (LRT) 2015, Seattle, WA, March 18-20, 201

Time-resolved infrared absorption spectroscopy applied to photoinduced reactions: how and why

Abstract: Time-resolved infrared (IR) spectroscopy is a widely used technique in the investigation of photoinduced reactions, given its capabilities of providing structural information about the presence of intermediates and the reaction mechanism. Despite the fact that it is used in several fields since the ‘80s, the communication between the different scientific communities (photochemists, photobiologists, etc.) has been to date quite limited. In some cases, this lack of communication happened—and still happens—even inside the same scientific community (for instance between specialists in ultrafast ps/fs IR and those in “fast” ns/µs/ms IR). Even more surprising is the difficulty of non-specialists to understand the potential of time-resolved IR spectroscopy, despite the fact that IR spectroscopy is normally taught to all chemistry and material science students, and to several biology and physics students. This tutorial review aims at helping to solve these issues, first by providing a comprehensive but reader-friendly overview of the different techniques, and second, by focusing on five “case studies” (from photobiology, gas-phase photocatalysis, photochemistry, semiconductors and metal-carbonyl complexes). We are confident that this approach can help the reader—whichever is its background—to understand the capabilities of time-resolved IR spectroscopy to study the mechanism of photoinduced reactions. Graphical Abstract: [Figure not available: see fulltext.

Determining the Mass of Dark Matter Particles with Direct Detection Experiments

In this article I review two data analysis methods for determining the mass (and eventually the spin-independent cross section on nucleons) of Weakly Interacting Massive Particles with positive signals from direct Dark Matter detection experiments: a maximum likelihood analysis with only one experiment and a model-independent method requiring at least two experiments. Uncertainties and caveats of these methods will also be discussed.Comment: 24 pages, 10 figures, 1 reference added, typos fixed, published version, to appear in the NJP Focus Issue on "Dark Matter and Particle Physics

Evidence for dust evolution within the Taurus Complex from Spitzer images

We present Spitzer images of the Taurus Complex (TC) and take advantage of the sensitivity and spatial resolution of the observations to characterize the diffuse IR emission across the cloud. This work highlights evidence of dust evolution within the translucent sections of the archetype reference for studies of quiescent molecular clouds. We combine Spitzer 160 um and IRAS 100 um observations to produce a dust temperature map and a far-IR dust opacity map at 5' resolution. The average dust temperature is about 14.5K with a dispersion of +/-1K across the cloud. The far-IR dust opacity is a factor 2 larger than the average value for the diffuse ISM. This opacity increase and the attenuation of the radiation field (RF) both contribute to account for the lower emission temperature of the large grains. The structure of the TC significantly changes in the mid-IR images that trace emission from PAHs and VSGs. We focus our analysis of the mid-IR emission to a range of ecliptic latitudes where the zodiacal light residuals are small. Within this cloud area, there are no 8 and 24 um counterparts to the brightest 160 um emission features. Conversely, the 8 and 24 um images reveal filamentary structure that is strikingly inconspicuous in the 160 um and extinction maps. The IR colors vary over sub-parsec distances across this filamentary structure. We compare the observed colors with model calculations quantifying the impact of the RF intensity and the abundance of stochastically heated particles on the dust SED. To match the range of observed colors, we have to invoke variations by a factor of a few of both the interstellar RF and the abundance of PAHs and VSGs. We conclude that within this filamentary structure a significant fraction of the dust mass cycles in and out the small size end of the dust size distribution.Comment: 43 pages, 13 figures, accepted for publication in Ap

A (sub)millimetre study of dense cores in Orion B9

We aim to further constrain the properties and evolutionary stages of dense cores in Orion B9. The central part of Orion B9 was mapped at 350 micron with APEX/SABOCA. A sample of nine cores in the region were observed in C17O(2-1), H13CO+(4-3) (towards 3 sources), DCO+(4-3), N2H+(3-2), and N2D+(3-2) with APEX/SHFI. These data are used in conjunction with our previous APEX/LABOCA 870-micron dust continuum data. Many of the LABOCA cores show evidence of substructure in the higher-resolution SABOCA image. In particular, we report on the discovery of multiple very low-mass condensations in the prestellar core SMM 6. Based on the 350-to-870 micron flux density ratios, we determine dust temperatures of ~7.9-10.8 K, and dust emissivity indices of ~0.5-1.8. The CO depletion factors are in the range ~1.6-10.8. The degree of deuteration in N2H+ is ~0.04-0.99, where the highest value (seen towards the prestellar core SMM 1) is, to our knowledge, the most extreme level of N2H+ deuteration reported so far. The level of HCO+ deuteration is about 1-2%. We also detected D2CO towards two sources. The detection of subcondensations within SMM 6 shows that core fragmentation can already take place during the prestellar phase. The origin of this substructure is likely caused by thermal Jeans fragmentation of the elongated parent core. A low depletion factor and the presence of gas-phase D2CO in SMM 1 suggest that the core chemistry is affected by the nearby outflow. The very high N2H+ deuteration in SMM 1 is likely to be remnant of the earlier CO-depleted phase.Comment: 20 pages, 10 figures, 10 tables. Accepted for publication in Astronomy and Astrophysic

Influence of Operational Parameters on Photocatalytic Degradation of Linuron in Aqueous TiO2 Pillared Montmorillonite Suspension

TiO2 pillared clay was prepared by intercalation of titan polyoxocation into interlamelar space of an Algerian montmorillonite and used for the photocatalytic degradation of the linuron herbicide as a target pollutant in aqueous solution. The TiO2 pillared montmorillonite (Mont-TiO2) was characterized by X-ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD), X-Ray fluorescence (XRF), scanning electronic microscopy (SEM), thermogravimetry and differential thermal analysis (TG-DTA), Fourier transformed infra-red (FT-IR), specific area and porosity determinations. This physicochemical characterization pointed to successful TiO2 pillaring of the clay. The prepared material has porous structure and exhibit a good thermal stability as indicated by its surface area after calcination by microwave. The effects of operating parameters such as catalyst loading, initial pH of the solution and the pollutant concentration on the photocatalytic efficiency and COD removal  were evaluated. Under initial pH of the solution around seven, pollutant concentration of 10 mg/L and 2.5 g/L of catalyst at room temperature, the degradation efficiency and COD removal of linuron was best then the other operating conditions. It was observed that operational parameters play a major role in the photocatalytic degradation process. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

From AMANDA to IceCube

The first string of the neoteric high energy neutrino telescope IceCube successfully began operating in January 2005. It is anticipated that upon completion the new detector will vastly increase the sensitivity and extend the reach of AMANDA to higher energies. A discussion of the IceCube's discovery potential for extra-terrestrial neutrinos, together with the prospects of new physics derived from the ongoing AMANDA research will be the focus of this paper. Preliminary results of the first antarctic high energy neutrino telescope AMANDA searching in the muon neutrino channel for localized and diffuse excess of extra-terrestrial neutrinos will be reviewed using data collected between 2000 and 2003. Neutrino flux limits obtained with the all-flavor dedicated UHE and cascade analyses will be described. A first neutrino spectrum above one TeV in agreement with atmospheric neutrino flux expectations and no extra-terrestrial contribution will be presented, followed by a discussion of a limit for neutralino CDM candidates annihilating in the center of the Sun.Comment: 15 pages, 8 figures Invited talk contribution at 5th International Conference on Non-accelerator New Physics (NANP 05), Dubna, Russia, 20-25 Jun 200