Some regularities in the variation of the Balmer line profiles in the P Cyg spectrum

In the Coudé focus of the 2 m RCC telescope at the National Astronomical Observatory of the Bulgarian Academy of Science 47 spectrograms covering the range from 3500 to 4900 Å (about 1400 Å) with a reciprocal dispersion of 9 Å mm^–1 and a spectral resolution of 0.18 Å were obtained. The photometric and position behaviour of Balmer lines were investigated over a long time-scale, i.e. March 1981 to August 1982.The hydrogen line profiles were rectified in the way discribed by de Groot (1969). It is found that the absorption consists of three and sometimes four components. Their position behaviour may be expalined by the existence of two kinds of shells: pulsating and steadily expanding, and it is quite possible that shells of the first type may become shells of the second type in the outer parts of the P Cyg envelope.The total emission and absorption equivalent widths of the H11, H9, and H lines change with conspicuous minima and maxima. The amplitude of these variations increases with decrease in the upper quantum number. For example,W _tot ^abs change by about 38% for H and 22% for H9.Our data suggest a periodic change in the radial velocities, intensity of each separate absorption component, total equivalent widths and profiles.     

Safety-enhanced, high-rate, nonmagnetic lithium D-size cells foroceanographic and naval use

Tests were conducted to determine the performance and safety characteristics of specially designed, nonmagnetic Li/BrCl in SOCl₂ (Li/BCX) and Li/Cl₂ in SO₂Cl₂ (Li/CSC) battery cells. Discharge tests showed that D-size battery cells yield energy densities of 1.07 Wh/cc³ at currents of 0.17 A. The combination of high energy density and nonmagnetic properties allows smaller, lighter battery packs to be placed in close proximity to guidance systems without magnetic interference to the navigational systems. The safety testing results indicate that these systems possess explosion resistance and other characteristics necessary for a variety of applications     

Preparing Geographers for Interdisciplinary Research: Graduate Training at the Interface of the Natural and Social Sciences

Recent debates about the state of geography raise valuable questions about how the discipline can and should change in response to shifting institutional realities. Focusing on the breadth and interdisciplinarity of geography, these discussions often overlook the role of pedagogy—particularly graduate training—in adapting the discipline to new institutional landscapes. Drawing on experiences as current and recent geography doctoral students, we identify institutional seedlings of opportunity that can be cultivated toward a spectrum of alternative doctoral training models. These alternatives offer significant opportunities to better prepare early-career geographers for success and to solidify geography's position as a leader in interdisciplinary research.     

Energy of acoustic signals in a borehole

In the present article, the dependencies of the acoustic signal total energy and the energies of the wave packets of different types of the waves on the elastic parameters and permeability of rocks have been studied. We have considered traditional logging tools containing acoustical monopole source. Calculations were performed in a frequency range of dozens of kilohertz, typical for acoustic well logging. It was shown that in a typical high-velocity formation (v_s > v_f, where v_s and v_f are the velocities of the shear wave in the rock and of the compressional wave in the borehole fluid, respectively), the pseudo-Rayleigh waves, whose elastic properties depend mainly on the shear modulus of the rock, contributed significant energy to the total signal energy in the borehole. The energies of different wave packets depend on the permeability in different ways. The greatest sensitivity to permeability change has been shown by the acoustic signal total energy and the energy of the low-velocity part of the pseudo-Rayleigh wave packet. The theoretical analysis was illustrated by real sonic log data.     

Propagation of Elastic Compressional Waves in a Porous-Fractured Medium Saturated with Immiscible Fluids

Izvestiya, Physics of the Solid Earth - The problem of calculating the reflection and transmission coefficients of elastic P-wave incident from a porous half-space onto a fluid-filled crack is...     

Geometrical spreading factor of head waves in cased and open boreholes

Factors (coefficients) of geometrical spreading of compressional and shear head waves are calculated for an impulse multipole source of elastic oscillations in boreholes. It is shown that the length of the logging tool (i.e., the distance between the source and the nearest receiver) used for sonic measurements and the velocities of elastic waves in the medium both contribute to the factor of geometrical spreading. For a high-velocity formation (the shear wave velocity in the rock is higher than the compressional wave velocity in the fluid that fills the borehole) and a sufficiently long sonic tool with a monopole source, the coefficient of geometrical spreading is approximated by asymptotic formula 1/Z [Roever et al., 1974; Krauklis and Krauklis, 1976], where Z is the length of the tool; i.e., the amplitude of the compressional head wave decreases proportionally to the distance between the source and the receiver. In acoustically soft formations, this approximation is inapplicable even for long tools with length Z > 4 m. Waveforms in cased boreholes have a significant frequency dispersion even in case of good-quality cementing, and the factor of geometrical spreading there depends considerably on the length of the tool and the elastic properties of the rocks.     

MTBE, TBA, and TAME Attenuation in Diverse Hyporheic Zones

Groundwater contamination by fuel-related compounds such as the fuel oxygenates methyl tert -butyl ether (MTBE), tert -butyl alcohol (TBA), and tert -amyl methyl ether (TAME) presents a significant issue to managers and consumers of groundwater and surface water that receives groundwater discharge. Four sites were investigated on Long Island, New York, characterized by groundwater contaminated with gasoline and fuel oxygenates that ultimately discharge to fresh, brackish, or saline surface water. For each site, contaminated groundwater discharge zones were delineated using pore water geochemistry data from 15 feet (4.5 m) beneath the bottom of the surface water body in the hyporheic zone and seepage-meter tests were conducted to measure discharge rates. These data when combined indicate that MTBE, TBA, and TAME concentrations in groundwater discharge in a 5-foot (1.5-m) thick section of the hyporheic zone were attenuated between 34% and 95%, in contrast to immeasurable attenuation in the shallow aquifer during contaminant transport between 0.1 and 1.5 miles (0.1 to 2.4 km). The attenuation observed in the hyporheic zone occurred primarily by physical processes such as mixing of groundwater and surface water. Biodegradation also occurred as confirmed in laboratory microcosms by the mineralization of U- ¹⁴C-MTBE and U-¹⁴C-TBA to ¹⁴CO₂ and the novel biodegradation of U- ¹⁴C-TAME to ¹⁴CO₂ under oxic and anoxic conditions. The implication of fuel oxygenate attenuation observed in diverse hyporheic zones suggests an assessment of the hyporheic zone attenuation potential (HZAP) merits inclusion as part of site assessment strategies associated with monitored or engineered attenuation.     

Thermal expansion and spontaneous strain associated with the normal-incommensurate phase transition in melilites

The linear thermal expansions of åkermanite (Ca₂MgSi₂O₇) and hardystonite (Ca₂ZnSi₂O₇) have been measured across the normal-incommensurate phase transition for both materials. Least-squares fitting of the high temperature (normal phase) data yields expressions linear in T for the coefficients of instantaneous linear thermal expansion, $$\alpha _1 = \frac{1}{l}\frac{{dl}}{{dT}}$$ for åkermanite: $$\begin{gathered} \alpha _{[100]} = 6.901(2) \times 10^{ - 6} + 1.834(2) \times 10^{ - 8} T \hfill \\ \alpha _{[100]} = - 2.856(1) \times 10^{ - 6} + 11.280(1) \times 10^{ - 8} T \hfill \\ \end{gathered} $$ for hardystonite: $$\begin{gathered} \alpha _{[100]} = 15.562(5) \times 10^{ - 6} - 1.478(3) \times 10^{ - 8} T \hfill \\ \alpha _{[100]} = - 11.115(5) \times 10^{ - 6} + 11.326(3) \times 10^{ - 8} T \hfill \\ \end{gathered} $$ Although there is considerable strain for temperatures within 10° C of the phase transition, suggestive of a high-order phase transition, there appears to be a finite ΔV of transition, and the phase transition is classed as “weakly first order”.     

Hydrocarbon contamination on the Antarctic peninsula: III. The Bahia Paraiso—Two years after the spill

Two years after the release of 600 000 l of diesel fuel arctic into Arthur Harbor, little spill-related contamination can be detected in intertidal limpets (Nacella concinna) and subtidal sediments. Periodic releases of small amounts of material from the ship oil nearby islands, in particular the intertidal areas of Christine, Limitrophe and Humble Islands. Subtidal sediment contamination is primarily due to other local inputs such as ship, boating and station activities. Beaches were unusually contaminated after 2 yr, but quiescent weather conditions, occasional releases from the wreck, and prevailing currents may concentrate hydrocarbon contamination in relatively low energy areas. Intertidal limpets (N. concinna) collected along these beaches were also contaminated. The volatility of the fluid, the amount spilled, and the dynamic weather and current conditions in Arthur Harbor tended to minimize long-term contamination of the area.