67,206 research outputs found
Map of comprehensive tourist drive through Canberra [cartographic material] /
No full textOverlay printed in red showing a tourist route through Canberra, showing places of interest, overlaid on printed street map.; Base map is entitled: Map of Canberra showing development 1932 / issued by Jackson O'Sullivan in conjunction with R.R. Genge, showing streets and places of interest, with advertisments on verso. Relief shown by spot heights.; Issued for O'Sullivan's Garage, Canberra.; On map: "The red map points the way".; Also available online http://nla.gov.au/nla.map-vn1879562.Panel title: Souvenir tourist map of Australia's National Garden City Capital CanberraMap of Canberra showing development 193
The Thermal Decomposition of Fine-grained Micrometeorites, Observations from Mid-IR Spectroscopy
No full textWe analysed 44 fine-grained and scoriaceous micrometeorites. A bulk mid-IR spectrum (8–13 lm) for each grain was collected
and the entire micrometeorite population classified into 5 spectral groups, based on the positions of their absorption
bands. Corresponding carbonaceous Raman spectra, textural observations from SEM-BSE and bulk geochemical data via
EMPA were collected to aid in the interpretation of mid-IR spectra. The 5 spectral groups identified correspond to progressive
thermal decomposition. Unheated hydrated chondritic matrix, composed predominantly of phyllosilicates, exhibit smooth,
asymmetric spectra with a peak at 10 lm. Thermal decomposition of sheet silicates evolves through dehydration, dehydroxylation,
annealing and finally by the onset of partial melting. Both CI-like and CM-like micrometeorites are shown to pass
through the same decomposition stages and produce similar mid-IR spectra. Using known temperature thresholds for each
decomposition stage it is possible to assign a peak temperature range to a given micrometeorite. Since the temperature thresholds
for decomposition reactions are defined by the phyllosilicate species and the cation composition and that these variables
are markedly different between CM and CI classes, atmospheric entry should bias the dust flux to favour the survival of CIlike
grains, whilst preferentially melting most CM-like dust. However, this hypothesis is inconsistent with empirical observations
and instead requires that the source ratio of CI:CM dust is heavily skewed in favour of CM material. In addition, a small
population of anomalous grains are identified whose carbonaceous and petrographic characteristics suggest in-space heating
and dehydroxylation have occurred. These grains may therefore represent regolith micrometeorites derived from the surface
of C-type asteroids. Since the spectroscopic signatures of dehydroxylates are distinctive, i.e. characterised by a reflectance
peak at 9.0–9.5 lm, and since the surfaces of C-type asteroids are expected to be heated via impact gardening, we suggest that
future spectroscopic investigations should attempt to identify dehydroxylate signatures in the reflectance spectra of young carbonaceous
asteroid families
Synthesis, properties and structures of complexes of platinum metal halides and Group 11 metals with two distibinomethane ligands, R2SbCH2SbR2 (R = Me or Ph)
No full textThe reaction of [Ru(dmf)(6)][CF3SO3](3), LiX and Ph2SbCH2SbPh2 (dpsm) yielded trans-[RuX2(eta(1)-dpsm)(4)] (X = Cl or Br) or [RuI2(eta(1)-dpsm)(2)(eta(2)-dpsm)]. The latter was shown by an X-ray study to contain two monodentate and one chelating dpsm ligands and is the first example with any metal of a distibinomethane acting as a chelate to be authenticated crystallographically. The chelate ring is highly strained as shown by the Sb-Ru-Sb angle (74.3 degrees) and the longer Ru-Sb distances than in the eta(1)-ligands. Corresponding reactions of trans-[OsX2(dmso)(4)] and dpsm produced trans-[OsCl2(eta(1)-dpsm)(4)] and [OsBr2(eta(1)-dpsm)(2)(eta(2)-dpsm)] identified spectroscopically. The reactions of RhX3 (X = Cl, Br or I) with dpsm afford [RhX3(dpsm)(2)] which on the basis of NMR spectroscopic data contain one chelating and one monodentate dpsm ligand. Palladium(II) and platinum(II) halides form both 1 : 1 and 1 : 2 complexes with dpsm. The former are dimeric and crystal structures of [M2X4(dpsm)(2)] (M = Pt, X = Cl or Br; M = Pd, X = Br) revealed a distibine bridged structure with square-planar MX2Sb2 metal centres, one with a cis geometry, the other trans. The structures cis,trans-[X2M(mu-dpsm)(2)MX2] are the first examples of this geometry to be established crystallographically. In contrast [I2M(mu-dpsm)(2)MI2] are assigned as trans,trans isomers on the basis of spectroscopic data. Multinuclear NMR studies show that [PtX2(dpsm)(2)] (X = Cl or Br) contain eta(1)-dpsm and are a mixture of cis and trans isomers in solution, but the [PtI2(dpsm)(2)] contains only a single form, probably the trans isomer. The [PdX2(dpsm)(2)] have also been characterised and for X = Cl shown to undergo facile fragmentation in solution to form trans,trans-[Pd2Cl2(sigma-Ph)(2)(dpsm)(2)]. The complexes [M(L-L)(2)]Y (M = Cu, Ag or Au; Y = BF4 or PF6; L-L = dpsm or Me2SbCH2SbMe2) and [Rh2Cl2(CO)(2)(mu-L-L)(2)] have also been prepared. All complexes have been characterised by analysis, IR, UV-VIS, multinuclear NMR (H-1, C-13-{H-1}, Pt-195, Cu-63 and Ag-109) spectroscopies as appropriate. Comparisons are drawn between the various co-ordination modes of the distibines and those of Ph2PCH2PPh2 and related ligands
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Letter from Carl Hayden to M. J. Riordan
No full textLetter from Carl Hayden to M. J. Riordan expressing his support for Coconino County in turning over the Bright Angel Trail to the federal government
Intense aqueous alteration on C-type asteroids: Perspectives from giant fine-grained micrometeorites
No full textThis study explores the petrology of five giant (>400 lm) hydrated fine-grained micrometeorites from the Transantarctic Mountain (TAM) micrometeorite collection. For the first time, the extent and mechanisms of aqueous alteration in unmelted
cosmic dust are evaluated and quantified. We use a range of criteria, previously defined for use on hydrated chondrites, including phyllosilicate fraction, matrix geochemistry and micro textures. Collectively, these micrometeorites represent
2.22 mm2 of intensely altered hydrated chondritic matrix (with petrologic subtypes of <1.2 in the scheme of Howard et al. (2015)) and reveal a range of alteration styles. Two particles are found to contain pseudomorphic chondrules with thick fine-grained rims, while another micrometeorite contains several aqueously altered CAIs. Their outlines range from welldefined to indistinct, demonstrating that the advanced stages of aqueous alteration progressively remove evidence of coarse-grained components. The remaining two micrometeorites entirely lack coarse-grained components but are similarly altered. Thus, the combined chondrule-to-matrix ratio among these giant micrometeorites is extremely low (6.45 area%), and significantly below the average ratio found in typical CM or CR chondrites (20%, Weisberg et al., 2006). Our findings are consistent with previous analyses from smaller Antarctic micrometeorites, which suggest that chondrules (and CAIs) derived from hydrated carbonaceous chondrite parent bodies are underrepresented among the micrometeorite flux, even when considering contributions from coarse-grained micrometeorites. Therefore, to explain the relative paucity of anhydrous material, we propose that the flux of fine-grained micrometeorites is primarily derived from intensely aqueously altered, primitive C-type asteroids, which have lost the majority of their refractory coarse-grained components by replacement with secondary phyllosilicate minerals
Flying too close to the Sun – The viability of perihelion-induced aqueous alteration on periodic comets
No full textComets are typically considered to be pristine remnants of the early solar system. However, by definition they evolve significantly over their lifetimes through evaporation, sublimation, degassing and dust release. This occurs once they enter the inner solar system and are heated by the Sun. Some comets (e.g. 1P/Halley, 9P/Tempel and Hale-Bopp) as well as chondritic porous cosmic dust – released from comets – show evidence of minor aqueous alteration resulting in the formation of phyllosilicates, carbonates or other secondary phases (e.g. Cu-sulphides, amphibole and magnetite). These observations suggest that (at least some) comets experienced limited interaction with liquid water under conditions distinct from the alteration histories of hydrated chondritic asteroids (e.g. the CM and CR chondrites). This synthesis paper explores the viability of perihelion-induced heating as a mechanism for the generation of highly localised subsurface liquid water and thus mild aqueous alteration in periodic comets. We draw constraints from experimental laboratory studies, numerical modelling, spacecraft observations and microanalysis studies of cometary micrometeorites. Both temperature and pressure conditions necessary for the generation and short-term (hour-long) survival of liquid water are plausible within the immediate subsurface (<0.5 m depth) of periodic comets with small perihelia (<1.5 A.U.), low surface permeabilities and favourable rotational states (e.g. high obliquities and/or slow rotational periods). We estimate that solar radiant heating may generate liquid water and perform aqueous alteration reactions in 3–9% of periodic comets. An example of an ideal candidate is 2P/Encke which has a small perihelion (0.33 A.U.), a high obliquity and a short orbital period. This comet should therefore be considered a high priority candidate in future spectroscopic studies of comet surfaces. Small quantities of phyllosilicate generated by aqueous alteration may be important in cementing together grains in the subsurface of older dormant comets, thereby explaining observations of unexpectedly high tensile strength in some bodies. Most periodic comets which currently pass close to the Sun are dormant, having experienced surface heating, significant cometary activity and dust release in the past. These bodies may be responsible for the partially hydrated cometary micrometeorites we find at the Earth's surface and their aqueous alteration histories may have been produced by perihelion-induced subsurface heating. This is in contrast to radiogenic and impact heating that operated during the early solar system on asteroids. This study has implications for the alteration history of the active asteroid Phaethon, the target of JAXA's DESTINY+ mission
Radical cyclisations of methylenecyclopropyl azetidinones-synthesis of novel tricyclic ?-lactams
No full textAddition of lithium bis(methylenecyclopropyl)cuprates to acetoxy azetidinones gives methylenecyclopropyl azetidinones, which can be converted to various radical cyclisation precursors. Attempted 4-exo cyclisation of 3 led only to reduced product, while cyclisation of 5, using CuCl/bipy, gave a carbacephem, via a 5-exo cyclisation, but in low yield. Cyclisation of 6 and 7, however, gave novel tricyclic ?-lactams, as the result of 7-endo cyclisation, in good yield, and a cyclisation of bromide 23 led to the tricyclic ?-lactam 24, via a radical cascade sequence
Letter from M. J. Riordan, Arizona Lumber and Timber Company, to Carl Hayden
No full textLetter from M. J. Riordan to Carl Hayden expressing his opposition to the federal government's takeover of Bright Angel Trail
Measurement of the time-dependent CP asymmetry in B0 -> J/ψ KS0 decays
No full textThis Letter reports a measurement of the CP violation observables SJ/ψK0S and CJ/ψK0S in the decay channel B0→J/ψK0S performed with 1.0 fb−1 of pp collisions at s√=7 TeV collected by the LHCb experiment. The fit to the data yields SJ/ψK0S=0.73±0.07(stat)±0.04(syst) and CJ/ψK0S=0.03±0.09(stat)±0.01(syst). Both values are consistent with the current world averages and within
expectations from the Standard Model
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