73,309 research outputs found
High quality epitaxial graphene on 4H-SiC by face-to-face growth in ultra-high vacuum
No full textEpitaxial graphene on SiC is the most promising substrate for the next generation 2D electronics, due to the possibility to fabricate 2D heterostructures directly on it, opening the door to the use of all technological processes developed for silicon electronics. To obtain a suitable material for large scale applications, it is essential to achieve perfect control of size, quality, growth rate and thickness. Here we show that this control on epitaxial graphene can be achieved by exploiting the face-to-face annealing of SiC in ultra-high vacuum. With this method, Si atoms trapped in the narrow space between two SiC wafers at high temperatures contribute to the reduction of the Si sublimation rate, allowing to achieve smooth and virtually defect free single graphene layers. We analyse the products obtained on both on-axis and off-axis 4H-SiC substrates in a wide range of temperatures (1300 °C-1500 °C), determining the growth law with the help of x-ray photoelectron spectroscopy (XPS). Our epitaxial graphene on SiC has terrace widths up to 10μm (on-axis) and 500 nm (off-axis) as demonstrated by atomic force microscopy and scanning tunnelling microscopy, while XPS and Raman spectroscopy confirm high purity and crystalline quality
Applying the causal theory of reference to intentional concepts
No full textWe argue that many recent philosophical discussions about the reference of everyday concepts of intentional states have implicitly been predicated on descriptive theories of reference. To rectify this, we attempt to demonstrate how a causal theory can be applied to intentional concepts. Specifically, we argue that some phenomena in early social development (e.g., mimicry, gaze following, and emotional contagion) can serve as reference fixers that enable children to track others' intentional states and, thus, to refer to those states. This allows intentional concepts to be anchored to their referents, even if folk psychological descriptions turn out to be false
Not losing the plot: Ken MacLeod and Iain M. Banks.
No full textThis essay appears in the first book to be devoted to the work of Ken MacLeod. It compares the science fiction of MacLeod and Iain M. Banks, who are both deemed to write political novels, yet produce very different results, to judge by Banks's Culture novels and MacLeod's Fall Revolution Quartet. The essay establishes the terms of its comparison by examining the theories of Hobbes and Arendt regarding the possibility of political action - a possibility more evident in MacLeod than in Banks. MacLeod's novels are shown to test the possibilities of action and political agency
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)
Molecular self-assembly on graphene
No full textThe formation of ordered arrays of molecules via self-assembly is a rapid, scalable route towards the realization of nanoscale architectures with tailored properties. In recent years, graphene has emerged as an appealing substrate for molecular self-assembly in two dimensions. Here, the first five years of progress in supramolecular organization on graphene are reviewed. The self-assembly process can vary depending on the type of graphene employed: epitaxial graphene, grown in situ on a metal surface, and non-epitaxial graphene, transferred onto an arbitrary substrate, can have different effects on the final structure. On epitaxial graphene, the process is sensitive to the interaction between the graphene and the substrate on which it is grown. In the case of graphene that strongly interacts with its substrate, such as graphene/Ru(0001), the inhomogeneous adsorption landscape of the graphene moiré superlattice provides a unique opportunity for guiding molecular organization, since molecules experience spatially constrained diffusion and adsorption. On weaker-interacting epitaxial graphene films, and on non-epitaxial graphene transferred onto a host substrate, self-assembly leads to films similar to those obtained on graphite surfaces. The efficacy of a graphene layer for facilitating planar adsorption of aromatic molecules has been repeatedly demonstrated, indicating that it can be used to direct molecular adsorption, and therefore carrier transport, in a certain orientation, and suggesting that the use of transferred graphene may allow for predictible molecular self-assembly on a wide range of surfaces. Understanding the behavior of monolayer and sub-monolayer films of molecules on graphene is critical to controlling the growth of these films, and exploiting them for doping, bandgap engineering, and for yet unforeseen applications. Here, the recent progress towards understanding molecular self-assembly on graphene is reviewed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Revision of the Nearctic genus Tritoxa Loew (Diptera: Ulidiidae)
No full textSinclair, Bradley J., Macleod, Alyssa M., Wheeler, Terry A. (2021): Revision of the Nearctic genus Tritoxa Loew (Diptera: Ulidiidae). Zootaxa 4920 (3): 359-379, DOI: https://doi.org/10.11646/zootaxa.4920.3.
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
Probing functional self-assembled molecular architectures with solution/solid scanning tunnelling microscopy
No full textOver the past two decades, solution/solid STM has made clear contributions to our fundamental understanding of the thermodynamic and kinetic processes that occur in molecular self-assembly at surfaces. As the field matures, we provide an overview of how solution/solid STM is emerging as a tool to elucidate and guide the use of self-assembled molecular systems in practical applications, focusing on small molecule device engineering, molecular recognition and sensing and electronic modification of 2D materials
Tritoxa californica Sinclair & Macleod & Wheeler 2021, sp. nov.
No full textTritoxa californica sp. nov. (Figs 6, 14, 15, 24) urn:lsid:zoobank.org:act: 0350D4DB-7407-4C19-941A-31B9951299EB Type material. HOLOTYPE ♂, labelled: “ CALIF: Plumas Co. / Little Long Valley / Creek [39°52′06″N 120°42′08″W], 6000′ 6 mi. E./ Spring Garden/ VIII-4-10-1977 ”; “ Malaise Trap / 8A-6P/ M. Wasbauer / Collector”; “ HOLOTYPE / Tritoxa / californica Sinclair,/ MacLeod & Wheeler” (CSCA). PARATYPES: USA. California: El Dorado Co., Pollack Pines [38°45′41″N 120°35′12″W], 2.ix.1986, Jackson trap, peach, D. Bolster (1♂, CSCA); Nipa Co., Angwin, 38.575°N 122.453°W, 17.ix.2008, McPhail trap, T. Samansky (1♂, 1♀, CSCA); Same data as holotype (1♂, 2♀, CSCA); Santa Cruz Co., Big Basin SP [37°10′21″N 122°13′21″W], 13.ix.1966, E.L. Sleeper (1♂, CAS); Trinity Co. [40.66°N 123.12°W], 13.vi.1934 (1♂, CAS); Tuolumne Co., 2.7 mi E Smoky Jack [37°49′3.72″N 119°42′45.61″W], Summer 1962, Frick trap on Prunus emarginata, D.P. Allen (1♂, CSCA). Possible additional material. USA. California: El Dorado Co., Placerville [38°43′47″N 120°47′55″W], 26.vi.1953, P.H. Arnaud (1♂, USNM) [genitalia lost]; Sagehen Ck Field Stn., 15 km N Truckee, 39°25.89′N 120°14.61′W, 16.viii.1999, J. Savage (1♀, LEM); Nevada Co., Sagehen Ck [39°25′57″N 120°14′13″W], 2.vii.1968, R. W. Pinger (1♀, USNM). Diagnosis. This species has the general appearance of Tritoxa cuneata, but is distinguished by the short, oblique discal hyaline crossband not extending beyond level of crossvein r-m in cell dm, inner surstylus with tight cluster of 4–5 thick prensisetae and phallus is shorter, with two loops. Description. Entirely yellowish brown to brown, abdomen darker brown bands. Head: ocellar triangle dark brown to black, microtrichose; frons yellowish brown to brown; parafrontal silvery microtrichia stripe very narrow, limited to extreme margin of eye, continuous with very narrow microtrichose parafacial; gena slightly darker brown below narrowest part of lower eye margin; postocular microtrichia slightly wider than parafrontal microtrichose stripe in lateral view, extending from base to middle of eye; face concolourous with face laterally, slightly paler medially; supracervical setulae very pale. Antenna with postpedicel greyish brown, yellowish brown on inner and medially surfaces. Proboscis with yellowish brown palpus. Thorax: yellowish brown; scutum mostly thinly microtrichose without pair of vittae; lateral margin of scutum and postpronotal lobe broadly shiny; scutellum concolourous with scutum; mediotergite without distinct stripe; pleura shiny, anepisternum and katepisternum lightly clothed in whitish microtrichia when viewed obliquely; whitish microtrichia above fore coxa; 2 anepisternal setae. Wing (Fig. 6) entirely brown, slightly tapered apically, with 3 hyaline crossbands; some faded or paler regions between bands; costal cell without hyaline band at humeral break, with narrow hyaline band at extreme apex of cell in line with discal hyaline crossband; oblique subbasal hyaline crossband very short, extending to basal fifth of cell dm; discal hyaline crossband short, continuous from R 1, reaching posterior margin of cell dm, not extending beyond level of crossvein r-m in cell dm; subapical hyaline crossband nearly straight, anterior end not extending proximal to crossvein r-m; crossvein dm-m straight to slightly arched; anal lobe developed; calypter with white margin. Abdomen: yellowish brown. Male terminalia (Figs 14, 15): inner surstylus with tight cluster of 4–5 thick prensisetae, inner margin concave; outer surstylus slender, slightly tapered and arched, slightly longer than length of inner surstylus, with narrow apex (Fig. 10); subepandrial sclerite with strong dark setae. Cercus with short setae; apical margin slightly pointed. Phallus short, with 2 loops. Distribution. This species is known exclusively from northern California (Fig. 24). Remarks. See comments under T. cuneata.Published as part of Sinclair, Bradley J., Macleod, Alyssa M. & Wheeler, Terry A., 2021, Revision of the Nearctic genus Tritoxa Loew (Diptera: Ulidiidae), pp. 359-379 in Zootaxa 4920 (3) on pages 361-362, DOI: 10.11646/zootaxa.4920.3.3, http://zenodo.org/record/447808
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
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