On the chemistry of hydrides of N atoms and O+^+ ions

Previous work by various authors has suggested that the detection by Herschel/HIFI of nitrogen hydrides along the low density lines of sight towards G10.6-0.4 (W31C) cannot be accounted for by gas-phase chemical models. In this paper we investigate the role of surface reactions on dust grains in diffuse regions, and we find that formation of the hydrides by surface reactions on dust grains with efficiency comparable to that for H$_2$ formation reconciles models with observations of nitrogen hydrides. However, similar surface reactions do not contribute significantly to the hydrides of O$^+$ ions detected by Herschel/HIFI present along many sight lines in the Galaxy. The O$^+$ hydrides can be accounted for by conventional gas-phase chemistry either in diffuse clouds of very low density with normal cosmic ray fluxes or in somewhat denser diffuse clouds with high cosmic ray fluxes. Hydride chemistry in dense dark clouds appears to be dominated by gas-phase ion-molecule reactions.Comment: 19 pages, 4 figures, 4 tables Accepted for publication in Ap

Laboratory experiments on cohesive soil bed fluidization by water waves

Part I. Relationships between the rate of bed fluidization and the rate of wave energy dissipation, by Jingzhi Feng and Ashish J. Mehta and Part II. In-situ rheometry for determining the dynamic response of bed, by David J.A. Williams and P. Rhodri Williams. A series of preliminary laboratory flume experiments were carried out to examine the time-dependent behavior of a cohesive soil bed subjected to progressive, monochromatic waves. The bed was an aqueous, 50/50 (by weight) mixture of a kaolinite and an attapulgite placed in a plexiglass trench. The nominal bed thickness was 16 cm with density ranging from 1170 to 1380 kg/m 3, and water above was 16 to 20 cm deep. Waves of design height ranging from 2 to 8 cm and a nominal frequency of 1 Hz were run for durations up to 2970 min. Part I of this report describes experiments meant to examine the rate at which the bed became fluidized, and its relation to the rate of wave energy dissipation. Part II gives results on in-situ rheometry used to track the associated changes in bed rigidity. Temporal and spatial changes of the effective stress were measured during the course of wave action, and from these changes the bed fluidization rate was calculated. A wave-mud interaction model developed in a companion study was employed to calculate the rate of wave energy dissipation. The dependence of the rate of fluidization on the rate of energy dissipation was then explored. Fluidization, which seemingly proceeded down from the bed surface, occurred as a result of the loss of structural integrity of the soil matrix through a buildup of the excess pore pressure and the associated loss of effective stress. The rate of fluidization was typically greater at the beginning of wave action and apparently approached zero with time. This trend coincided with the approach of the rate of energy dissipation to a constant value. In general it was also observed that, for a given wave frequency, the larger the wave height the faster the rate of fluidization and thicker the fluid mud layer formed. On the other hand, increasing the time of bed consolidation prior to wave action decreased the fluidization rate due to greater bed rigidity. Upon cessation of wave action structural recovery followed. Dynamic rigidity was measured by specially designed, in situ shearometers placed in the bed at appropriate elevations to determine the time-dependence of the storage and loss moduli, G' and G", of the viscoelastic clay mixture under 1 Hz waves. As the inter-particle bonds of the space-filling, bed material matrix weakened, the shear propagation velocity decreased measurably. Consequently, G' decreased and G" increased as a transition from dynamically more elastic to more viscous response occurred. These preliminary experiments have demonstrated the validity of the particular rheometric technique used, and the critical need for synchronous, in-situ measurements of pore pressures and moduli characterizing bed rheology in studies on mud fluidization. This study was supported by WES contract DACW39-90-K-0010. (This document contains 151 pages.

Extraterrestrial applications of solar optics for interior illumination

Solar optics is a terrestrial technology that has potential extraterrestrial applications. Active solar optics (ASO) and passive solar optics (PSO) are two approaches to the transmission of sunlight to remote interior spaces. Active solar optics is most appropriate for task illumination, while PSO is most appropriate for general illumination. Research into solar optics, motivated by energy conservation, has produced lightweight and low-cost materials, products that have applications to NASA's Controlled Ecological Life Support System (CELSS) program and its lunar base studies. Specifically, prism light guides have great potential in these contexts. Several applications of solar optics to lunar base concepts are illustrated

Worship Music As Spiritual Identity: An Examination Of Music In The Liturgy Among Black And White Adventists In The United States From 1840 To 1944

The Topic This study examined Black and White Seventh-day Adventist music in the liturgy in the United States from 1840 to 1944. Little scholarly attention has been given to the development of Adventist liturgical practice, the function of music in the liturgy, and the effect of music upon the spiritual identity. This study utilized liturgical history, ritual studies, musicology, and liturgical theology to derive and compare the spiritual identity fostered through music in the liturgy by these ethnic groups. This study considered both the shared and distinct spiritual identities of Black and White Adventists, as cultivated by the music in the liturgy, and as situated in the context of the American racial climate, from the first colonies to the middle of the twentieth century. The Purpose The purpose of this study was to describe the development of spiritual identity among Black and White Seventh-day Adventist worshipers as derived from their experience of music in the Sabbath liturgy, in the United States from 1840–1944. To do so, this study created a methodology for deriving spiritual identity from music in liturgy, in order to support the thesis that music in the liturgy promotes, develops, and often establishes spiritual identity in the existential experience of the worshiper. It tested the hypothesis by situating the historical context of liturgy and music among Black and White Christians in the United States before 1840, and tracing the development of music in liturgy among Black and White Adventist Americans from 1840–1944. Within this historical development, the study explored the historical spiritual identity of these communities, as fostered through the music in the liturgy. The Sources This documentary study primarily relied on published and unpublished primary sources from the Seventh-day Adventist church, between 1840 and 1944. Primary and secondary sources provided historical context and perspective. Archives housed some of the primary sources useful in this study. Four Adventist congregations were targeted for the study, two Black and two White, respectively: Ephesus Seventh-day Adventist Church, New York City; Oakwood University Church, Huntsville, Alabama; Battle Creek Tabernacle, Battle Creek, Michigan; and Takoma Park Seventh-day Adventist Church, Takoma Park, Maryland. Bulletins of the orders of worship provided important liturgical context. Oral histories were also conducted for this research, featuring interviews with twenty-nine persons with memories of Adventist music in the liturgy in the 1920s, 30s, and 40s. Most of those interviewed for this study were members of one of the four churches. Conclusions Adventism developed within the context of American revivalism, drawing from this tradition for its early liturgical practice, including fervent singing of spirituals and gospel hymnody. Black and White Adventist pioneers augmented this milieu with their developing views on the great controversy between Christ and Satan, conditional immortality of the soul, Jesus Christ’s ministry in the heavenly sanctuary, His soon second coming, and God’s love. Adventist hymnody contributed significantly toward establishing these beliefs into their spiritual identity. Though early White Adventists were ardent abolitionists, by the late nineteenth century, few Adventists championed social justice for Black Americans. Society’s systemic racism had infected Adventist leadership, liturgy, and music publishing. In 1908, as a misappropriation of Ellen G. White’s counsel, Blacks and Whites throughout the country began worshiping in separate meeting houses. In 1944, the denomination instituted regional conferences to advance the gospel ministry among Blacks, without White oversight. Throughout the denomination’s first 100 years, Black and White Adventists worshiped through music similarly, due to a shared identity in the Adventist message. Differences in worship can be attributed to differences in the experience of privilege or oppression. Black Adventists always sang the Black spirituals and leveraged European composers, like Bach and Beethoven, in order to express their praise to God and their protest of social injustice