The use of natural and archeological analogues for understanding the long-term behavior of nuclear glasses

The knowledge of the long-term behavior of nuclear waste in anticipation of ultimate disposal in a deep geological formation is of prime importance in a waste management strategy. If phenomenological models have been developed to predict the long-term behavior of these materials, validating these models remains a challenge, when considering the time scale of radioactive decay of radionuclides of environmental concern, typically 10⁴–10⁵ yrs. Here we show how natural or archaeological analogues provide critical constraints not only on the phenomenology of glass alteration and the mechanisms involved, but also on the ability of experimental short-term data to predict long-term alteration in complex environments.     

A search for planetary system candidates

We report on our search for possible planetary system candidates in a volume-limited sample of 62 nearby A stars. Since the evolutionary lifetimes of A stars ( 10⁹ yrs) roughly correspond to the era of planet formation and subsequent heavy bombardment in our solar system, our study could provide valuable insight into the origin of our own Solar System. From our ground-based visual and IUE high-resolution spectroscopy of all the northern nearby A stars, we have identified at least 12 stars with circumstellar gas. Combining these results with our previous IRAS survey we are probing the link between stars with circumstellar gas and those showing circumstellar dust disks. Our aim is not just to identify stars with gas, or stars with both gas and dust, but to identify systems with dynamic spectral activity similar to Pic, a well known proto-planetary system candidate. By measuring the gas dynamics in the disks of these Pic-like stars, we can begin to study the physics of accretion disks of young evolving systems.     

Toxicity of polynuclear aromatic hydrocarbons to the polychaete Neanthes arenaceodentata

The toxicity of ten polynuclear aromatic hydrocarbons (PNAs) to Neanthes arenaceodentata was studied in replicate 96 h bioassays with specific hydrocarbons in solution. Relative solubilities for each PNA were derived in short-term equilibration experiments. Disappearance of representative di-, tri, tetra- and pentacyclic-aromatic hydrocarbons from test solutions was also characterized by ultraviolet spectrophotometry. PNA toxicity and residence time in test solutions were directly related to molecular weight (MW), while relative solubility is inversely related to MW. 96 h TL_m values for the diaromatic PNAs naphthalene, 2,6-dimethylnaphthalene, and 2,3,6-trimethylnaphthalene were 3.8, 2.6 and 2.0 ppm, respectively. Phenanthrene, fluorene and 1-methylphenanthrene (triaromatics) exhibited 96 h TL_m values of 0.6, 1.0 and 0.3 ppm, respectively. None of the tetra- and pentacyclic-aromatics (chrysene, 3,4-benzo(a)pyrene, 1,2,5,6-dibenzanthracene) were toxic up to the highest concentration tested (1 ppm), excepting fluoranthene, with a 96 h TL_m of 0.5 ppm. PNA toxicity appears to be related to both solubility and residence time in test solutions.     

High resolution scans of Comet Kohoutek in the vicinity of 5015, 5890, and 6563 Å

High resolution scans were made of Comet Kohoutek (1973f) using the McMath solar telescope at Kitt Peak National Observatory. The data were taken on January 1 and 4, 1974 UT, just after the comet perihelion. Hα emission (～4.1 × 10²⁷ photon sec^?1) was observed from the head of the Comet. An upper limit on the He I(5015) radiation was determined to be less than 2% of the observed Hα emission. The Na D1/D2 line intensities on both nights were approximately 0.5, indicating an optically thin emission region.     

Wave and turbulence structure in a disturbed nocturnal inversion

Acoustic sounder and tower data obtained at the Boulder Atmospheric Observatory (BAO) are used to examine several features of the wave and turbulence structure associated with a disturbed nocturnal inversion. General features, including mean fields and Richardson number, for the case selected for this study are presented. Spectral analysis of the tower data reveals a separation of energy into wavelike and turbulent fluctuations. Analysis of the heat flux, however, shows upward counter-gradient fluxes in the vicinity of a low-level jet and near the top of the inversion. Cospectral analysis shows that the major contribution to the upward heat flux occurs at frequencies that would normally be considered characteristic of waves. In some cases, the upward flux is associated with a phase shift between vertical velocity w and fluctuating temperature θ different from the quadrature relation that would be expected of internal waves. Time series analysis reveals that these unexpected positive fluxes occur in relatively short bursts. Analysis of time series of θ and w in other cases, as well as inspection of acoustic sounder records, shows that sometimes such upward fluxes can result from a combination of wave motion and horizontal temperature advection. In this case the advection is associated with a shallow cold front.     

Observations of complex-terrain flows using acoustic sounders: Experiments,topography, and winds

Acoustic sounders have now been used extensively in a series of noctural drainage flow experiments carried out by the U.S. Department of Energy's Atmospheric Studies in Complex Terrain (ASCOT) program. Doppler acoustic sounders, located in three different valleys during the sequence of experiments, reveal drainage-wind profiles that depend strongly on the ambient meteorological conditions and the elevation of each observing site relative to surrounding terrain. In elevated sites that drain easily, Doppler-sounder derived wind profiles show a simply-structured flow; in lower lying areas, subject to topographic constriction and cold-air pooling, and where Archimedean forces are comparable to those due to synoptic and mesoscale pressure gradients, the wind profiles show considerable vertical and temporal variation. In particular, in the Geysers area of northern California, the seabreeze and the depth of the Pacific Coast marine inversion affect not only the initiation of drainage winds but also their subsequent evolution.     

Wind-tunnel simulation of field dispersion tests (by the U.K. health and safety executive) of water-spray curtains

Field trials of water-spray curtain tests performed by the (British) Health and Safety Executive and designated by HSE 41 and HSE 46 were modeled at a scale ratio of 1:28.9 in an atmospheric boundary-layer wind tunnel. The tests confirmed that dense clouds of carbon dioxide gas were significantly diluted by additional air entrained by the water curtain. Linear and logarithmic scatter diagrams of concentrations measured at equivalent scaled points produced correlations of 0.87 and 0.97, respectively. Results confirm the use of Froude-number modeling of both the dense gas cloud and water spray droplet fluid dynamics.Professor, Colorado State University.Research Associate, Colorado State University.Senior Scientist, Factory Mutual Research Corp., Boston, Mass.     

Spatially resolved absolute spectrophotometry of Saturn: 3390 to 8080 Å

Absolute spectrophotometry of four regions on the visible disk of Saturn (north and south polar regions, equatorial band, south “temperate” region) from 3390 to 8080 Å is reported. Spectral resolution is 10 Å in the interval 3390–6055 Å, and 20 Å; aperture size is 1.92 arcsec. The explicit purpose of our observations was to provide ground-based photometric calibration for the Pioneer Saturn Imaging Photopolarimeter (IPP). We also compare our data with earlier spectrophotometric measurements of Saturn (R.L. Younkin and G. Munch, 1963,Mem. Soc. Roy. Sci. Liege7, 123–136; W.M. Irvine and A.P. Lane, 1971,Icarus16, 10–26; T.B. McCord, T.V. Johnson, and J.H. Elias, 1971,Astrophys. J.165, 413–424) and with the M. Podolak and R.EE. Danielson (1977)Icarus30, 479–492) parameterization of “Axel Dust.” The latter reproduces the broad features but not the details of the observed spectral reflectivity (I/F). We find that large depths of clear molecular hydrogen (>14 km-am in the temperate regions) are needed to match the observed upturn in reflectivity shortward of 3800 Å.     

Whither Parity? The Need for a Comprehensive Curriculum in Human‐Environment Geography

If human‐environment geography is central to the discipline, then human‐environment courses should be a sizable segment of the undergraduate curriculum. Undergraduate educational offerings are inadequate, however, meaning that geography departments are shortchanging their majors, missing opportunities to attract and inform the general student body, and failing to meet the needs of future K–12 educators. Unless geography provides satisfactory human‐environment education, it will likely have much less impact on twenty‐first‐century environmental science.