Deviations from Matthiessen's Rule for SrRuO3{\rm SrRuO_3} and CaRuO3{\rm CaRuO_3}

We have measured the change in the resistivity of thin films of ${\rm SrRuO_3}$ and ${\rm CaRuO_3}$ upon introducing point defects by electron irradiation at low temperatures, and we find significant deviations from Matthiessen's rule. For a fixed irradiation dose, the induced change in resistivity {\it decreases} with increasing temperature. Moreover, for a fixed temperature, the increase in resistivity with irradiation is found to be {\it sublinear}. We suggest that the observed behavior is due to the marked anisotropic scattering of the electrons together with their relatively short mean free path (both characteristic of many metallic oxides including cuprates) which amplify effects related to the Pippard ineffectiveness condition

Sequential low-temperature depolymerization and liquefaction of US coals

Suitable conditions for high-yield conversion of a Pittsburgh [number sign]8 (Pennsylvania) coal sample, supplied by the Argonne program and designated below as PB(PA) coal, were previously developed (see Progress Report no. 4, pp. 3--15; and Progress Report no. 6, pp- 3--4). In some recent experiments, the yield of low-boiling hydrocarbon fuel fractions (gasoline, kerosene and gas oil; b.p. up to 325[degrees]C) from this coal was further increased to a level of 70--72 wt % (MAF basis). The main emphasis of the research work during the reporting period was on the structural analysis of the depolymerized PB(PA) coal, with the uftimate objective of developing an average molecular structure for the predominant (71.5 -- 76.0 wt %) oil fraction (fr. no. 6, Figure 1) as well as for the small asphattene and asphaftol fractions (fr. no. 7 and 8, Figure 1) of this depolymerized product. The oil and asphaftene fractions of the depolymerized PB(PA) coal (Figure 1, fractions [number sign]6 and 7, respectively) were analyzed by gas chromatography/mass spectrometry (GC/MS). Figure 2 shows the reconstructed ion chromatogram for the oil fraction of the depolymerized PB(PA) coal. As seen, the bulk of the compounds present in this fraction elute in the 125--225[degrees]C range as an incompletely resolved hump. It is indicated that the oil contains a wide range of compound types

Sequential low-temperature depolymerization and liquefaction of US coals

A Beulah-Zap (North Dakota) lignite sample, designated below as BZ(ND) lignite, was obtained from the Argonne National Laboratory premium coal program. This lignite had the following ultimate analysis (MAF basis) in wt.%: C, 71.05; H, 5.58; N, 1.17; S, 1.60; 0 (diff), 20.6. The ash content (dry basis) was 6.0 wt.%. As expected, the BZ(ND) lignite had a considerably higher oxygen content ([approximately]20.6%) in comparison with that of previously studied coals (Progress Reports nos. 1--4). The BZ(ND) lignite was subjected to a previously developed stepwise depolymerization-liquefaction procedure [for details and recent applications see J. Shabtai and T. Skulthai, Proc. 1987 Internat. Confer. Coal Science, Elsevier, Amsterdam (J.A. Moulijn, K.A. Nater, and H.A.G. Chermin, Eds.), 1987, pp. 761764; and J. Shabtai, T. Skulthai, and I. Saito, Am. Chem. Soc. Div. Fuel Chem. Prepr., 31 (4), 15--23 (1986)]. The procedure, as summarized in Figure 1, consists essentially of the following sequential steps: (1) intercalation of the coal sample with catalytic amounts (5--20 %) of FeCl[sub 3] followed by mild hydrotreatment (HT) of the coal-FeCl[sub 3] intercalate; (2) base-catalyzed depolymerization (BCD) of the product from step 1, under super-critical conditions; and (3) hydroprocessing (HPR) of the depolymerized product from the two preceding steps, using a sulfided 6Co8Mo catalyst. The results obtained in processing the BZ(ND) lignite according to the above procedure are described

Sequential low-temperature depolymerization and liquefaction of US coals

Results obtained in the studies with BS(IL) coal as feed can be summarized as follows: (1) The low-temperature depolymerization - liquefaction procedure, summarized in Figure 1, is easily adaptable and applicable to a high-sulfur, Burning Star (Illinois No. 6) coal sample. The final product obtained consists of a fully desulfurized, light hydrocarbon oil. (2)Suitable processing conditions for each step of the stepwise depolymerization - liquefaction of the above coal were determined. (3)Direct hydroprocessing of the Burning Star (Illinois No. 6) coal with sulfided catalysts is ineffective for its conversion into a light hydrocarbon product. In accordance with the research program the depolymerized, THF-soluble coal products will be subjected to detailed analysis for the purpose of deriving average molecular structures for the oil, asphaltene and asphaltol fractions. The data obtained will be used to develop a structural model for the BS(IL) coal

THE TIGHT-BINDING APPROACH TO THE DIELECTRIC RESPONSE IN THE MULTIBAND SYSTEMS

Starting from the random phase approximation for the weakly coupled multiband tightly-bounded electron systems, we calculate the dielectric matrix in terms of intraband and interband transitions. The advantages of this representation with respect to the usual plane-wave decomposition are pointed out. The analysis becomes particularly transparent in the long wavelength limit, after performing the multipole expansion of bare Coulomb matrix elements. For illustration, the collective modes and the macroscopic dielectric function for a general cubic lattice are derived. It is shown that the dielectric instability in conducting narrow band systems proceeds by a common softening of one transverse and one longitudinal mode. Furthermore, the self-polarization corrections which appear in the macroscopic dielectric function for finite band systems, are identified as a combined effect of intra-atomic exchange interactions between electrons sitting in different orbitals and a finite inter-atomic tunneling.Comment: 20 pages, LaTeX, no figure

Magnetic susceptibility of insulators from first principles

We present an {\it ab initio} approach for the computation of the magnetic susceptibility $\chi$ of insulators. The approach is applied to compute $\chi$ in diamond and in solid neon using density functional theory in the local density approximation, obtaining good agreement with experimental data. In solid neon, we predict an observable dependence of $\chi$ upon pressure.Comment: Revtex, to appear in Physical Review Lette

Turning G Proteins On and Off Using Peptide Ligands

Intracellular Gα subunits represent potential therapeutic targets for a number of diseases. Here we describe three classes of new molecules that modulate G protein signaling by direct targeting of Gα. Using messenger RNA display, we have identified unique peptide sequences that bind Gα_(i1). Functionally, individual peptides were found that either enhance or repress basal levels of G protein-activated inwardly rectifying potassium (GIRK) channel signaling, a downstream effector of G protein activation, indicating that the peptides directly turn G proteins on or off in vivo. A third functional class acts as a signaling attenuator; basal GIRK channel activity is unaffected but responses to repeated G protein activation are reduced. These data demonstrate that G protein-directed ligands can achieve physiological effects similar to those resulting from classical receptor targeting and may serve as leads for developing new classes of therapeutics

Shale Oil Value Enhancement Research. Quarterly Report, June 1 - August 31, 1993

All tasks are on schedule, or ahead of schedule. Particular progress has been made in identifying industrial entities, commodities and specialty products of target interest for shale oil-derived products. There is clearly a major emphasis worldwide on new chemicals and shale oil-derived structures are similar to many of these chemicals of interest. Details of the mathematical modeling, programming and algorithm development have progressed with excellent results. Considerable effort will be required to interface these with the output of the gc/ms but we are receiving excellent support from Hewlett Packard in this regard. The ability to concentrate particularly valuable compounds with reasonable projected cost processes continues to show promise. In one system, a single-stage extraction recovered 87% of the total nitrogen in an extract representing only 33% of the fraction. Special attention is being paid to both nitrogen types and oxygen types. The raffinates from the polar solvent extractions will be evaluated for their oil and wax contents. All of the start-up infrastructure is now in place. Subcontracts have been initiated and equipment and supplies have been procured. We are now planning a major push to reach some general findings by early in 1994. From these findings, we will be prepared to focus on experimental verification of process design needed for the second program phase