Radiation testing of composite materials, in situ versus ex situ effects

The effect of post irradiation test environments on tensile properties of representative advanced composite materials (T300/5208, T300/934, C6000/P1700) was investigated. Four ply (+ or - 45 deg/+ or - 45 deg) laminate tensile specimens were exposed in vacuum up to a bulk dose of 1 x 10 to the 10th power rads using a mono-energetic fluence of 700 keV electrons from a Van de Graaff accelerator. Post irradiation testing was performed while specimens were being irradiated (in situ data), in vacuum after cessation of irradiation (in vacuo data), and after exposure to air (ex situ data). Room temperature and elevated temperature effects were evaluated. The radiation induced changes to the tensile properties were small. Since the absolute changes in tensile properties were small, the existance of a post irradiation test environment effect was indeterminate

Molecular line and continuum study of the W40 cloud

The dense cloud associated with W40, one of the nearby H II regions, has been studied in millimeter-wave molecular lines and in 1.2 mm continuum. Besides, 1280 MHz and 610 MHz interferometric observations have been done. The cloud has complex morphological and kinematical structure, including a clumpy dust ring and an extended dense core. The ring is probably formed by the "collect and collapse" process due to the expansion of neighboring H II region. Nine dust clumps in the ring have been deconvolved. Their sizes, masses and peak hydrogen column densities are: $\sim 0.02-0.11$ pc, $\sim 0.4-8.1 M_{\odot}$ and $\sim (2.5-11)\times 10^{22}$ cm$^{-2}$, respectively. Molecular lines are observed at two different velocities and have different spatial distributions implying strong chemical differentiation over the region. The CS abundance is enhanced towards the eastern dust clump 2, while the NH$_3$, N$_2$H$^+$, and H$^{13}$CO$^+$ abundances are enhanced towards the western clumps. HCN and HCO$^+$ do not correlate with the dust probably tracing the surrounding gas. Number densities derived towards selected positions are: $\sim (0.3-3.2)\times 10^6$ cm$^{-3}$. Two western clumps have kinetic temperatures 21 K and 16 K and are close to virial equilibrium. The eastern clumps 2 and 3 are more massive, have higher extent of turbulence and are probably more evolved than the western ones. They show asymmetric CS(2--1) line profiles due to infalling motions which is confirmed by model calculations. An interaction between ionized and neutral material is taking place in the vicinity of the eastern branch of the ring and probably trigger star formation.Comment: 16 pages, 6 figure

Compact steep-spectrum sources from the S4 sample

We present the results of 5-GHz observations with the VLA A-array of a sample of candidate Compact Steep Spectrum sources (CSSs) selected from the S4 survey. We also estimate the symmetry parameters of high-luminosity CSSs selected from different samples of radio sources, and compare these with the larger sources of similar luminosity to understand their evolution and the consistency of the CSSs with the unified scheme for radio galaxies and quasars. The majority of CSSs are likely to be young sources advancing outwards through a dense asymmetric environment. The radio properties of CSSs are found to be consistent with the unified scheme, in which the axes of the quasars are observed close to the line of sight, while radio galaxies are observed close to the plane of the sky.Comment: accepted for publication in mnras; 8 pages, figure 1 with 21 images, and two additional figures; 2 table

VLA Observations of H I in the Helix Nebula (NGC 7293)

We report the detection of 21-cm line emission from H I in the planetary nebula NGC 7293 (the Helix). The observations, made with the Very Large Array, show the presence of a ring of atomic hydrogen that is associated with the outer portion of the ionized nebula. This ring is most probably gas ejected in the AGB phase that has been subsequently photodissociated by radiation from the central star. The H I emission spreads over about 50 km/s in radial velocity. The mass in H I is approximately 0.07 solar masses, about three times larger than the mass in molecular hydrogen and comparable with the mass in ionized hydrogen.Comment: 19 pages, 9 figure

Geologic History of Ash Hollow State Historical Park, Nebraska

Contents: Introduction Acknowledgments Cautions General Stratigraphy Oligocene Series-White River Group-Brule Formation-Whitney Member Miocene Series-Ogallala Group-Ash Hollow Formation Pliocene Series-Broadwater Formation Quaternary deposits Older colluvium and loess Younger colluvium and alluvium. General Paleontology Evidence of past life: fossils and subfossils Collecting fossils Vertebrate fossils Fossils from the Whitney Member of the Brule Formation. Plants Invertebrates Vertebrates Fossils from the Ash Hollow Formation Plants Invertebrates Vertebrates Fossils from the Broadwater Formation PlantsVertebrates Quaternary fossils Plants Invertebrates Vertebrates Additional studies of Nebraska fossils Geologic History Prehistory and History References Appendix I Appendix II Appendix III Appendix I

A graph theory-based multi-scale analysis of hierarchical cascade in molecular clouds : Application to the NGC 2264 region

The spatial properties of small star-clusters suggest that they may originate from a fragmentation cascade of the cloud for which there might be traces up to a few dozen of kAU. Our goal is to investigate the multi-scale spatial structure of gas clumps, to probe the existence of a hierarchical cascade and to evaluate its possible link with star production in terms of multiplicity. From the Herschel emission maps of NGC 2264, clumps are extracted using getsf software at each of their associated spatial resolution, respectively [8.4, 13.5, 18.2, 24.9, 36.3]". Using the spatial distribution of these clumps and the class 0/I Young Stellar Object (YSO) from Spitzer data, we develop a graph-theoretic analysis to represent the multi-scale structure of the cloud as a connected network. From this network, we derive three classes of multi-scale structure in NGC 2264 depending on the number of nodes produced at the deepest level: hierarchical, linear and isolated. The structure class is strongly correlated with the column density $N_{\rm H_2}$ since the hierarchical ones dominate the regions whose N$_{\rm H_2} > 6 \times 10^{22}$cm$^{-2}$. Although the latter are in minority, they contain half of the class 0/I YSOs proving that they are highly efficient in producing stars. We define a novel statistical metric, the fractality coefficient F that measure the fractal index describing the scale-free process of the cascade. For NGC 2264, we estimate F = 1.45$\pm$0.12. However, a single fractal index fails to fully describe a scale-free process since the hierarchical cascade starts at a 13 kAU characteristic spatial scale. Our novel methodology allows us to correlate YSOs with their multi-scale gaseous environment. This hierarchical cascade that drives efficient star formation is suspected to be both hierarchical and rooted by the larger-scale gas environment up to 13 kAU

Monitoring of ultrafine particles in French regional air quality network

Monitoring of ultrafine particles (UFP) in the ambient air is ongoing since 2012 in France. A national working group was created in 2014, including nowadays five French regional air quality monitoring networks. The main instrument selected to monitor UFP is the particle sizer “UFP-3031” (TSI Inc.). It measures the particle number concentration between 20 and 800 nm with six size channels. Two intercomparisons were organized in 2014 and 2015, which evaluated the accuracy of this instrument through a comparison with other techniques (such as Scanning Mobility Particle Sizer, SMPS), and through uncertainty calculations. Recently, several networks have been also equipped with CPC (condensation particle counter) to be able to measure the total UFP number concentration from 7 nm. This work presents the main results of short and long-term measurement of UFP which have been carried out in various environments: urban/traffic sites, near heavy industry zones (Dunkerque and Fos-sur-Mer in northern and southern France, respectively), near harbor area (Nice)… For urban/ traffic environment, the number concentration and size distribution are compared at the national level; it appears that they vary significantly depending on the influence of road traffic around the site. The concentration levels near traffic sites are at least twice than in the urban area, especially for UFP smaller than 50 nm. Additionally, the UFP measurement also makes it possible to improve the identification of specific sources and to understand the atmospheric physicochemical phenomena. The relationship between UFP and industrial emissions, ferries, forest fires was clearly identified in different places in France. During summer, the UFP monitoring also shows the formation of new particles (between 20-30 nm or smaller) in the afternoon, due to photochemical reactions. From 2019, the French national strategy on UFP will start putting a particular emphasis on the impact of UFP on human health

Star formation around the H II region Sh2-235

We present a picture of star formation around the H ii region Sh2-235 (S235) based upon data on the spatial distribution of young stellar clusters and the distribution and kinematics of molecular gas around S235. We observed 13CO (1-0) and CS (2-1) emission toward S235 with the Onsala Space Observatory 20-m telescope and analysed the star density distribution with archival data from the Two Micron All-Sky Survey (2MASS). Dense molecular gas forms a shell-like structure at the southeastern part of S235. The young clusters found with 2MASS data are embedded in this shell. The positional relationship of the clusters, the molecular shell and the H ii region indicates that expansion of S235 is responsible for the formation of the clusters. The gas distribution in the S235 molecular complex is clumpy, which hampers interpretation exclusively on the basis of the morphology of the star-forming region. We use data on kinematics of molecular gas to support the hypothesis of induced star formation, and distinguish three basic types of molecular gas components. The first type is primordial undisturbed gas of the giant molecular cloud, the second type is gas entrained in motion by expansion of the H ii region (this is where the embedded clusters were formed) and the third type is a fast-moving gas, which might have been accelerated by winds from the newly formed clusters. The clumpy distribution of molecular gas and its kinematics around the H ii region implies that the picture of triggered star formation around S235 can be a mixture of at least two possibilities: the 'collect-and-collapse' scenario and the compression of pre-existing dense clumps by the shock wave. Journal compilation © 2008 RAS

Star formation around the H II region Sh2-235

We present a picture of star formation around the H ii region Sh2-235 (S235) based upon data on the spatial distribution of young stellar clusters and the distribution and kinematics of molecular gas around S235. We observed 13CO (1-0) and CS (2-1) emission toward S235 with the Onsala Space Observatory 20-m telescope and analysed the star density distribution with archival data from the Two Micron All-Sky Survey (2MASS). Dense molecular gas forms a shell-like structure at the southeastern part of S235. The young clusters found with 2MASS data are embedded in this shell. The positional relationship of the clusters, the molecular shell and the H ii region indicates that expansion of S235 is responsible for the formation of the clusters. The gas distribution in the S235 molecular complex is clumpy, which hampers interpretation exclusively on the basis of the morphology of the star-forming region. We use data on kinematics of molecular gas to support the hypothesis of induced star formation, and distinguish three basic types of molecular gas components. The first type is primordial undisturbed gas of the giant molecular cloud, the second type is gas entrained in motion by expansion of the H ii region (this is where the embedded clusters were formed) and the third type is a fast-moving gas, which might have been accelerated by winds from the newly formed clusters. The clumpy distribution of molecular gas and its kinematics around the H ii region implies that the picture of triggered star formation around S235 can be a mixture of at least two possibilities: the 'collect-and-collapse' scenario and the compression of pre-existing dense clumps by the shock wave. Journal compilation © 2008 RAS