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Showing papers by "Lawrence Berkeley National Laboratory published in 1986"


Journal ArticleDOI
TL;DR: In this article, a detailed construction of N = 8 supergravity theories in five dimensions with Yang-Mills gauge groups SO(p, 6−p), physical global symmetry SU(1, 1), and local composite symmetry USp(8).

342 citations


Journal ArticleDOI
TL;DR: The Salmonella assay has been in use for almost 15 years and can be defined as a routine test for mutagenicity and for predicting potential carcinogenicity and it is recommended that it be regularly included in all genetic testing batteries.
Abstract: The Salmonella assay has been in use for almost 15 years and can be defined as a routine test for mutagenicity and for predicting potential carcinogenicity It detects the majority of animal carcinogens and consequently plays an important role in safety assessment The test is also routinely used as the frontline screen for environmental samples (complex mixtures) isolated from air, water and food This role will continue to remain an area of growth as or because sample volumes associated with these testing areas are generally very limited and more extensive testing is generally impossible While this test, like all others, has some limitations, it is recommended that it be regularly included in all genetic testing batteries

276 citations



Journal ArticleDOI
TL;DR: Using the high resolution transmission electron microscopy techniques of weak-multibeam dark-field and direct lattice imaging, platinum particles ranging in size from 0.8 to 50 nm were imaged and their surface structure characterized as discussed by the authors.

182 citations


Journal ArticleDOI
TL;DR: In this paper, a method is developed which can assist in the determination of the optimum number of pumping wells, their rates of discharge and locations, such that further degradation of the aquifer is avoided.
Abstract: Currently a common method of aquifer cleanup is to extract the polluted ground water and, after reducing the concentration of contaminants in the water below a certain level, the treated water is either injected back into the aquifer, or if it is environmentally and economically feasible, released to a surface-water body. The proper design of such an operation is very important, both economically and environmentally. In this paper a method is developed which can assist in the determination of the optimum number of pumping wells, their rates of discharge and locations, such that further degradation of the aquifer is avoided. The complex potential theory has been used to derive the equations for the streamlines separating the capture zone of one, two, or more pumping wells from the rest of the aquifer, A series of capture-zone type curves are presented which can be used as tools for the design of aquifer cleanup projects. The use of these type curves is shown by an hypothetical field case example.

167 citations


Journal ArticleDOI
TL;DR: In this paper, evidence was given for (Me/sub 3/SiC/sub 5/H/sub 4/)/sub 3 3/UCO, the first molecular actinide complex of carbon monoxide in solution and solid phase.
Abstract: Migratory insertion of an anionic group onto coordinate carbon monoxide or an isocyanide is an important mechanistic postulate in organoactinide chemistry. In contrast to transition metals, where carbon monoxide complexes abound, only three examples of carbon monoxide coordination to uranium have been observed in matrix isolation studies at cyrogenic temperatures. These studies showed that U(CO)/sub 6/ can exist below ca. 20 K and that nu/sub CO/ of 1961 cm/sup -1/ is similar to that found for W(CO)/sub 6/, nu/sub CO/ is 1987 cm/sup -1/ under similar conditions. The nu/sub CO/ is lowered substantially from gaseous CO (nu = 2145 cm/sup -1/) which implies that uranium metal is a ..pi..-donor, though the bonds are either kinetically labile, thermodynamically weak, or both. In UF/sub 4/(CO) the nu/sub CO/ of 2182 cm/sup -1/ at 20 K/sup 2c/ shows that the tetravalent compound does not engage in ..pi..-back-bonding to CO. In another study, UO/sub 2/ has been shown to absorb CO at temperatures below 20 K; the CO stretching frequency was not measured. In this paper, evidence is given for (Me/sub 3/SiC/sub 5/H/sub 4/)/sub 3/UCO, the first molecular actinide complex of carbon monoxide in solution and solid phase. 8 references.

130 citations


Journal ArticleDOI
TL;DR: These are the highest pressures for which a crystalline structure change has been directly observed in any material by x-ray diffraction, and the role of 3d core electrons in increasing the transformation pressures in Ge, as compared to Si, is emphasized.
Abstract: New phase transitions in Ge were observed by energy-dispersive x-ray diffraction techniques for pressures up to 125 GPa (1.25 Mbar) as follows: the ..beta..-Sn structure to the simple hexagonal (sh) phase at 75 +- 3 GPa and to the double hexagonal close-packed structure (dhcp) at 102 +- 5 GPa. These are the highest pressures for which a crystalline structure change has been directly observed in any material by x-ray diffraction. Total-energy pseudopotential calculations predict 84 +- 10 GPa for the ..beta..-Sn to sh phase transition and 105 +- 21 GPa for sh to hcp (not dhcp) transition. The role of 3d core electrons in increasing the transformation pressures in Ge, as compared to Si, is emphasized.

126 citations


Journal ArticleDOI
TL;DR: The rapid fall-off of dose at the end of range of heavy charged particle beams has the potential in therapeutic applications of sparing critical structures just distal to the target volume, and the effects of highly inhomogeneous regions on this desirable depth-dose characteristic are explored.
Abstract: The rapid fall-off of dose at the end of range of heavy charged particle beams has the potential in therapeutic applications of sparing critical structures just distal to the target volume. Here we explored the effects of highly inhomogeneous regions on this desirable depth-dose characteristic. The proton depth-dose distribution behind a lucite-air interface parallel to the beam was bimodal, indicating the presence of two groups of protons with different residual ranges, creating a step-like depth-dose distribution at the end of range. The residual ranges became more spread out as the interface was angled at 3 degrees, and still more at 6 degrees, to the direction of the beam. A second experiment showed little significant effect on the distal depth-dose of protons having passed through a mosaic of teflon and lucite. Anatomic studies demonstrated significant effects of complex fine inhomogeneities on the end of range characteristics. Monoenergetic protons passing through the petrous ridges and mastoid air cells in the base of skull showed a dramatic degradation of the distal Bragg peak. In beams with spread out Bragg peaks passing through regions of the base of skull, the distal fall-off from 90 to 20% dose was increased from its nominal 6 to well over 32 mm. Heavy ions showed a corresponding degradation in their ends of range. In the worst case in the base of skull region, a monoenergetic neon beam showed a broadening of the full width at half maximum of the Bragg peak to over 15 mm (compared with 4 mm in a homogeneous unit density medium). A similar effect was found with carbon ions in the abdomen, where the full width at half maximum of the Bragg peak (nominally 5.5 mm) was found to be greater than 25 mm behind gas-soft-tissue interfaces. We address the implications of these data for dose computation with heavy charged particles.

124 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined the hydrogenation of chemisorbed ethylene on platinum (111) single crystals under ultra-high vacuum using temperature programmed desorption.

123 citations


Journal ArticleDOI
TL;DR: The results suggest that liver doses in excess of 30 to 35 GyE should be limited to 30% of the liver or less when 18 GyE of whole liver radiation is delivered at 2 GyE per fraction in addition to primary radiation of the pancreas or biliary system.
Abstract: Eleven patients with carcinoma of the pancreas or biliary system received heavy charged particle radiation treatments and whole liver heavy charged particle radiation at Lawrence Berkeley Laboratory. Doses to the whole liver ranged from 10 to 24 Gray-equivalent (the biological equivalent of 10 to 24 Gray of low-LET photon radiation), whereas the dose to the primary lesion ranged from 53.5 to 70 Gray-equivalent (GyE). The fraction size was 2 to 3 GyE. The liver received partial as well as whole organ irradiation. Integral dose volume histograms for the liver were obtained in all 11 patients. An integral dose volume histogram displays on the ordinate the percentage of liver that was irradiated in excess of the dose specified on the abcissa. In this study, the clinical liver radiation tolerance of these patients is correlated with the information contained in an integral dose volume histogram. One patient developed radiation hepatitis. The integral dose volume histogram of this patient differed from the dose volume histograms of the other 10 patients. This difference was greatest in the range of doses between 30 and 40 GyE. Our results suggest that liver doses in excess of 30 to 35 GyE should be limited to 30% of the liver or less when 18 GyE of whole liver radiation is delivered at 2 GyE per fraction in addition to primary radiation of the pancreas or biliary system.

121 citations


Journal ArticleDOI
TL;DR: In this paper, the interaction of H2 and CO with Pd SiO 2 promoted with La2O3, CeO2, Pr6O11, Nd2O 3, and Sm 2O3 has been investigated using temperature-programmed desorption and temperatureprogrammed surface reaction.

Journal ArticleDOI
TL;DR: In this article, the total energies of simple metal clusters (sodium, magnesium, and aluminium) containing up to 100 valence electrons were calculated in the spherical jellium approximation using the local density functional scheme.

Journal ArticleDOI
TL;DR: In this paper, the authors classify the d = 3 anti-de Sitter and d = 2 conformal superalgebras and give a general construction of their positive energy unitary representations.

Journal ArticleDOI
TL;DR: Inclusion of the spin- orbit interaction using the vector part of the pseudopotential in first order reproduces the measured spin-orbit splittings in Ge as well as the rare-gas solids and agrees with all-electron calculations.
Abstract: In this Brief Report, we give the expressions required for using the vector (spin-orbit) part of the ab initio pseudopotential in a crystalline calculation. Inclusion of the spin-orbit interaction using the vector part of the pseudopotential in first order reproduces the measured spin-orbit splittings in Ge as well as the rare-gas solids and agrees with all-electron calculations.

Journal ArticleDOI
TL;DR: The charged-particle multiplicity distributions are almost Poissonian and narrower than have been reported by other e/sup +/e/sup -/ experiments in this energy range, and give further support to the idea of independent jet fragmentation.
Abstract: This paper presents the charged-particle multiplicity distributions for e/sup +/e/sup -/ annihilation at ..sqrt..s = 29 GeV measured in the High Resolution Spectrometer. The data, which correspond to an integrated luminosity of 185 pb/sup -1/, were obtained at the SLAC e/sup +/e/sup -/ storage ring PEP. The techniques used to correct the observed prong numbers are discussed. The multiplicity distribution of the charged particles has a mean value = 12.87 +- 0.03 +- 0.30, a dispersion D/sub 2/ = 3.67 +- 0.02 +- 0.18, and an f/sub 2/ moment of 0.60 +- 0.02 +- 0.18. Results are also presented for a two-jet sample selected with low sphericity and aplanarity. The charged-particle distributions are almost Poissonian and narrower than have been reported by other e/sup +/e/sup -/ experiments in this energy range. The mean multiplicity increases with the event sphericity, and for the sample of threefold-symmetric three-jet events, a value of = 16.3 +- 0.3 +- 0.7 is found. No correlation is observed between the multiplicities in the two hemispheres when the events are divided into two jets by a plane perpendicular to the thrust axis. This result is in contrast with the situation in soft hadronic collisions, where a strongmore » forward-backward correlation is measured. For the single jets, a mean multiplicity of 6.43 +- 0.02 +- 0.15 and a dispersion value of D/sub 2/ = 2.55 +- 0.02 +- 0.13 are found. These values give further support to the idea of independent jet fragmentation. The multiplicity distributions are well fit by the negative-binomial distribution.« less

Journal ArticleDOI
TL;DR: In this article, a photoelectron spectra of rotationally cold C2H2 and C2D2 was obtained with improved resolution, permitting the first three electronic states of the ions to be characterized in greater detail.
Abstract: The 584 A photoelectron spectra of rotationally cold C2H2 and C2D2 were obtained with improved resolution, permitting the first three electronic states of the ions to be characterized in greater detail. Temperature‐dependent studies led to a definitive assignment of the low intensity features in the X 2∏u state, yielding ν4=837±12 cm−1 for C2H+2 and ν4=702±12 cm−1 for C2D+2. The ν5 origin of the Renner–Teller multiplet was identified. In the case of C2D+2, a Fermi resonance with this multiplet contributed intensity to the ν1 mode, facilitating its evaluation at 2572±16 cm−1. The C2h geometry of the A 2Ag state was determined from the two previously unobserved bending progressions, assigned to ν4 and ν5B, and evaluated at 492±12 and 605±12 cm−1 for C2H+2 and 339±12 and 516±12 cm−1 for C2D+2, respectively. A more extensive vibrational progression than previously evident, comprised of irregular spectral features indicative of nonadiabatic effects, was observed for the B 2∑+u state. Autocorrelation functions were derived from the spectra for all three electronic states, and the two electronically excited states exhibit an ultrafast decay on a 10−14 s time scale. The A 2Ag state decays within one period of bending vibration, while the B 2∑+u state survives only 14 fs, corresponding to a single period of symmetric stretching motion.

Journal ArticleDOI
TL;DR: In this article, progress in testing semiconductor drift detectors is reported, and it is shown that they are becoming versatile and reliable detectors for position and energy measurements, mainly due to new electronics better matched to different detectors.
Abstract: Progress in testing semiconductor drift detectors is reported. Generally better position and energy resolutions were obtained than resolutions published previously. The improvement is mostly due to new electronics better matched to different detectors. It is shown that semiconductor drift detectors are becoming versatile and reliable detectors for position and energy measurements.

Journal ArticleDOI
TL;DR: It is found that the H+O3→HO+O2 reaction proceeds along a nonplanar pathway in which the H atom descends vertically to the plane containing the ozone molecule to form an HO3 intermediate which then undergoes fragmentation.
Abstract: The key features of the H+O3 potential energy surface have been determined using ab initio quantum mechanical methods. The electronic wave function used is a multiconfiguration Hartree–Fock wave function which provides a qualitatively correct description of various reactive channels. It is found that the H+O3→HO+O2 reaction proceeds along a nonplanar pathway in which the H atom descends vertically to the plane containing the ozone molecule to form an HO3 intermediate which then undergoes fragmentation. No planar transition state for a direct O‐atom abstraction could be located. The radical–radical O+HO2 reaction was found to have no energy barrier to formation of HO3 which was determined to subsequently decompose to HO+O2. The H‐atom abstraction reaction O+HO2→OH+O2 was found to have a small activation energy. The dynamical implications of these findings are discussed. The results are consistent with the observed vibrational excitation of the OH product in the H+O3 reaction. The key features of the H+O3 p...



Journal ArticleDOI
TL;DR: In the presence of TiO2, as a support or promoter, a portion of the TiO 2 is reduced to TiOx moieties which decorate the surfaces of the Pd particles as discussed by the authors.

Journal ArticleDOI
TL;DR: In this paper, a series of cross-hole acoustic measurements made between four horizontal boreholes drilled from a near-surface underground opening situated in a basaltic rock mass were evaluated to assess the extent of blast damage around the opening.
Abstract: Results are presented of a series of cross-hole acoustic measurements made between four horizontal boreholes drilled from a near-surface underground opening situated in a basaltic rock mass. The objectives of the program were to assess the extent of blast damage around the opening, and to evaluate the rock mass characteristics and their spatial variation around the opening. The acoustic velocity and attenuation data are indicative of an anisotropic, jointed rock mass, with a greater intensity of jointing along travel paths in the horizontal than the vertical direction. Low acoustic P- and S-velocities are indicative of blast damage and of zones of intense jointing or fracturing. In this case blast damage extends to approximately 1.5 m from the face. Attenuation data appear to be less sensitive in distinguishing between the blast-damaged zone and intense vertical jointing and fracturing in the virgin rock mass. Taken together with field data, laboratory measurements of P- and S-wave velocities on intact core samples suggest that the rock mass is probably water saturated.

Journal ArticleDOI
TL;DR: In this paper, the initial stages of the Pd-GaAs reactions are studied by high resolution transmission electron microscopy, electron diffraction and energy-dispersive analysis of X-rays.

Journal ArticleDOI
TL;DR: In this paper, the authors solved the class of anomalous two-dimensional theories and proved that the spectrum is not relativistic in physical gauges, and that anomalous models in covariant gauges are equivalent to adding Wess-Zumino terms.

Journal ArticleDOI
TL;DR: In this article, the optical second-harmonic generation from the Rh(111) crystal surface was investigated and the surface was covered with alkali atoms, and the results established the surface specificity of secondharmonic generating to the topmost 1 or 2 atomic layers of alkali metals.

Journal ArticleDOI
11 Jul 1986-Science
TL;DR: Semiclassical theory provides a useful picture of quantum features (interference in product state distribution, generalized tunneling phenomena, and others) in these more complex systems.
Abstract: Semiclassical theory finds use in chemical physics both as a computational method and as a conceptual framework for interpreting quantum features in experiments and in numerical quantum calculations. The semiclassical description of one-dimensional dynamical systems is essentially a solved problem for eigenvalue and scattering situations and for general topologies of potential functions (simple potential wells, multiple wells, multiple barriers, and so forth). Considerable progress has also been made in generalizing semiclassical theory to multidimensional dynamical systems (such as inelastic and reactive scattering of atoms and molecules and vibrational energy levels of polyatomic molecules), and here, too, it provides a useful picture of quantum features (interference in product state distribution, generalized tunneling phenomena, and others) in these more complex systems.

Journal ArticleDOI
TL;DR: Neovascular glaucoma developed in 22 of 169 uveal melanoma patients treated with helium ion irradiation and occurred more commonly in larger tumors; the incidence was not affected by tumor location, presence of subretinal fluid, nor rate of tumor regression.

Journal ArticleDOI
TL;DR: Intracellular recordings of the light responses of bipolar cells were made in the isolated perfused retina of the larval tiger salamander by microelectrodes filled with a 1% solution of the enzyme horseradish peroxidase (HRP).
Abstract: Intracellular recordings of the light responses of bipolar cells were made in the isolated perfused retina of the larval tiger salamander by microelectrodes filled with a 1% solution of the enzyme horseradish peroxidase (HRP). Two classes of bipolar cell were identified in terms of their responses to luminous spots and annuli centered upon their receptive fields: on-center cells, which depolarized in response to a centered spot and hyperpolarized in response to a concentric annulus, and off-center cells, which responded with the opposite polarities. Physiologically identified cells were labelled with HRP by iontophoretic injection and prepared for light microscopy. Examples of each of the three classes of bipolar cell described in Cajal's study of the amphibian retina were found amongst the labelled cells. The only morphological feature found to correlate with the physiological classification was the stratum at which the axon of the cell arborized in the inner plexiform layer. The axons of on-center cells arborized in the more proximal sublamina b, while those of off-center cells arborized in the more distal sublamina a. This is consistent with earlier findings in the retinae of the cat and the carp.

Journal ArticleDOI
TL;DR: The present experimental constraints on the existence of light charged and neutral electroweak scalar particles are summarized and the production cross sections of the other expected scalars are computed and decay signatures are explored.
Abstract: The present experimental constraints on the existence of light charged and neutral electroweak scalar particles are summarized. Within the context of an explicit extended technicolor model, we discuss prospects for the detection of light scalars in p\ifmmode\bar\else\textasciimacron\fi{}p collisions at energies up to 2 TeV, in ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ collisions at energies up to the ${Z}^{0}$ mass, and in fixed-target hadron-hadron collisions. In addition the production cross sections of the other expected scalars are computed and decay signatures are explored.

Journal ArticleDOI
TL;DR: In this paper, the pyrochlore phase was calculated to be Pb/sub 2.25/Mg/sub 0.79/O/sub 7.27/Nb/ sub 1.
Abstract: Lead-magnesium niobate ceramics were processed with excess MgO and by precalcining MgO and Nb/sub 2/O/sub 5/. Transmission electron microscopy revealed submicrometer MgO inclusions in the perovskite phase. The pyrochlore phase exists as submicrometer rectangular crystals in an amorphous PbO matrix. The composition of the pyrochlore phase was calculated to be Pb/sub 2.25/Mg/sub 0.27/Nb/sub 1.79/O/sub 7/.