[en] The superfluid density for He₄ films adsorbed in two different geometries has been studied. With Vycor glass, using a third sound technique, phonons with a T₂ temperature dependence have been observed. These are attributed to the cylindrical nature of the Vycor pores. Also observed were rotons with a 5 K energy gap. The observations were in substantial agreement with calculations by Padmore and others for two-dimensional rotons. Also studied were He₄ films adsorbed in porous Vycor glass near their critical points using an Andronikashvili method. The superfluid density was found to vary as a power law in reduced temperature with an exponent equal to the bulk value. This three-dimensional critical behavior was attributed to the three-dimensional interconnectedness of the Vycor substrate. For He₄ films using a Mylar substrate with an Andronikashvili method, profound differences in the nature of the superfluid transition have been observed. A sharply changing superfluid density at the transition was seen along with a peak in the superfluid dissipation. By interpreting the data through a dynamic theory, the Kosterlitz-Thouless picture of superfluidity in two dimensions was supported. Good numerical agreement with the universal constant predicted by the theory was obtained

[en] The concentrations of copper in the abiotic and biotic compartments of freshwater ecosystems, and the effects on biota of increased amounts of copper in the water and sediments are reviewed. Data compiled and discussed include the quantities and physicochemical forms of copper in the water column, the concentrations of copper in the bed-load sediments and interstitial waters, and the concentrations of copper in primary producers, molluscs, crustacea, aquatic insects, other invertebrates, and fishes. In addition, the acute and sublethal effects of copper on the same groups of biota are presented, as well as data on copper concentration factors. This information can be used to: (1) determine the ranges of copper concentrations that occur in nature for different types of ecosystems; (2) identify ecosystems that are or may be impacted by copper released from industrial and urban sources; and (3) assess the effects of biota of the use of copper alloys in nuclear power station cooling systems

[en] Copper concentrations were measured in the soluble and particulate fractions of water samples and bedload sediments collected in intake and discharge areas of the Surry and Salem Nuclear Power Stations during normal operations. Additional samples of water and suspended particles were collected during startup of Unit 2 at the Salem Power Station. In water samples collected from Surry, total copper ranged from 6.5 to 24.7 and labile copper from 0.5 to 2.9 μg/L; in those from Salem, total copper ranged from 6.7 to 10.6 and labile from 0.9 to 3.8 μg/L. At both sites the highest total copper concentration was measured in January 1979 during a period of high runoff. In general, differences between influent and effluent waters were small; the maximum was 4.2 μg Cu/L. Copper concentration in the water during startup of Unit 2 of Salem was high initially (>2500 μg Cu/L) but was almost entirely in the particulate fraction; labile copper was only 0.6 μg/L. The apparent complexing capacity (ACC) of the waters from Surry ranged from 6 to 40 and those from Salem from 5 to 60 μg Cu/L. Ranges in dissolved organic carbon were smaller, 2.9 to 5.1 and 2.2 to 5.0 mg C/L for Surry and Salem, respectively, and showed no relationship with ACC. Ultrafiltration of discharge waters indicated that, in most samples, the largest fraction of copper in the untreated water was in the >10,000 <100,000 molecular weight fraction; in waters treated to destroy dissolved organic carbon, it was generally in the >100,000 molecular weight fraction.Copper concentrations in intact bedload sediments from the intake area of Surry ranged from 2.3 to 26 and of Salem from 36 to 74 μg/g dry weight; those in the discharge area of Surry ranged from 13 to 30 and of Salem from 3 to 67. We noted considerable spatial heterogeneity both at the intake and discharge areas, and higher copper concentrations in the <62-μm fraction than in intact sediments

[en] This year is the 10th anniversary of the discovery of the first high-transition temperature (T_c) superconducting compounds. Since then, these materials have taught us much new physics. Few issues have been s hotly debated as the controversy about flux lattice melting. Two recent papers by Kes and co-workers at the University of Leiden drive right to the heart of this issue. The superconducting state, in general, does not like magnetic fields. To avoid the presence of a magnetic field in its interior, a superconductor responds in interesting ways. There are two important critical fields for a superconductor that define its response. The first is the lower critical field H_cl; for fields less than this value, superconductors expel the applied field (the Meissner effect). The second is the upper critical field H_c2; for fields above this value, superconductivity is destroyed. The high-T_c superconductors are examples of what are called open-quotes strongly type IIclose quotes materials, those for which H_c2>>H_cl. All of the technologically important superconductors are of this type, and so their study is essential if applications are to be realized. This article goes on to discuss the research, background, and future of these. 4 refs., 1 fig

[en] The high resolution Bitter pattern technique has been used to reveal the structure of the array of flux lines which is present when single crystal samples of the high Tc superconductor YBa₂Cu₃O₇ are placed in a magnetic field. At 4.2 K with the magnetic field parallel to the c axis, the patterns formed are strongly reminiscent of the analogous structures in ordinary type II superconductors. The structures typically consist of flux spots with short range hexagonal correlations. The patterns are interpreted to consist of singly quantized vortices. Very uniform patterns are observed in thin, flat samples cooled in a constant field. Sampling the spot density yields a vortex density consistent with a flux quantum of hc/2e. Experiments at 77 K, the only other temperature studied, showed no spatially varying magnetic structure. Recent mechanical measurements which are sensitive to the bulk modulus and dissipation within the vortex lattice show evidence for a mobility transition near 75 K, which would be consistent with this observation. This is believed to stem from materials properties rather than some more fundamental property of the new superconductors. 9 references

[en] Published in summary form only

[en] As part of a cooperatively sponsored HAZWRAP and Lawrence Livermore National Laboratory (LLNL) project to evaluate field-based methods to measure retardation factors, we investigated some aspects of the variability associated with measuring the concentrations of perchloroethylene (PCE) within the saturated unconsolidated alluvial sediments beneath LLNL. Using the depth-sampling technique developed at LLNL, we are describing the relationship of VOC spatial variability to various sediment characteristics such as geophysical log results, grain size distribution, cation exchange capacity, total organic carbon, permeability, bulk density, skeletal density, and porosity. Using this information an algorithm is being developed to calculate representative field-based partitioning coefficients (Ka) and retardation factors (R). A critical parameter used in the algorithm is the total mass of PCE present in a saturated sediment sample. The two major sources of sediment PCE concentration variability examined were those associated with (1) the analytical extraction methods and (2) the spatial changes in fine-grained materials within permeable and confining sediments. To evaluate desorption efficiency during headspace extraction (EPA Method 3810) for VOC analyses (EPA Method 8010), a bulk thermal desorption chamber (BTDC) was constructed and calibrated. The BTDC extraction provided a reference method against which generally used EPA extraction methods such as headspace were compared. Compared to untreated control surrogate sediment samples, BTDC extraction efficiencies of better than 94 percent were obtained. The results of PCE comparisons between adjacent sediment samples indicated that there was no significant difference between headspace extraction techniques and the BTDC. We used both headspace and BTDC analytical results to describe the vertical distribution of PCE in four adjacent boreholes. 14 refs., 6 figs., 2 tabs

[en] We report the phase diagram for magnetic fluxoids in two-dimensional In/InO/sub x/ superconducting films. The films are sputtered directly onto high-Q silicon oscillators. The melting of the vortex lattice is signaled by a peak in the attenuation and a shift of the resonant frequency of the oscillator, caused by the rapid change in mobility of the vortex array. The zero-field limit of the melting temperature can be fitted by the Kosterlitz-Thouless model. However, the magnetic field dependences disagree with the current theoretical picture

[en] We have measured the moment of inertia of hcp ⁴He crystals from 25 mK to 2 K. With a precision of five parts in 10⁶ we find no evidence for a nonclassical rotational inertia. This indicates that if a supersolid exists, it has a rho/sub s//rho of less than 5 x 10^-6, a transition temperature of less than 25 mK, or a critical velocity of less than 5 μm/sec

[en] The mechanical response, comprising longitudinal sound velocity and damping, of amorphous In/InO/sub x/ is studied as a function of normal state sheet resistance. The films are sputtered directly onto a high Q oscillator fabricated from single crystal silicon. With a resonant frequency near 3 KHz, the oscillators have Q's of 10⁵ and a frequency stability of 10^-8. This allows for a unique measurement of the dynamics of magnetic vortices, induced by a field perpendicular to the plane of the sample. The melting of the vortex lattice is signaled by a peak in the attenuation and a frequency shift of the silicon oscillator. The zero field melting temperature and the magnitude of the frequency shift are described by a model of Kosterlitz-Thouless melting due to D.S. Fisher. The temperature dependence of the melting does not agree with this calculation