7,912 research outputs found
A comparative study of experimental configurations in synchrotron pair distribution function
The identification and quantification of amorphous components and nanocrystalline phases
with very small crystal sizes, smaller than ~3 nm, within samples containing crystalline phases is
very challenging. However, this is important as there are several types of systems that contain these
matrices: building materials, glass-ceramics, some alloys, etc. The total scattering synchrotron pair
distribution function (PDF) can be used to characterize the local atomic order of the nanocrystalline
components and to carry out quantitative analyses in complex mixtures. Although the resolution in
momentum transfer space has been widely discussed, the resolution in the interatomic distance space
has not been discussed to the best of our knowledge. Here, we report synchrotron PDF data collected at
three beamlines in different experimental configurations and X-ray detectors. We not only discuss the
effect of the resolution in Q-space, Qmax ins of the recorded data and Qmax of the processed data, but we
also discuss the resolution in the interatomic distance (real) space. A thorough study of single-phase
crystalline nickel used as standard was carried out. Then, selected cement-related samples including
anhydrous tricalcium and dicalcium silicates, and pastes derived from the hydration of tricalcium
silicate and yeâelimite with bassanite were analyzed.This work is part of the PhD of Mr. Jesus D. Zea-Garcia. This work was supported by Spanish MINECO and FEDER [BIA2017-82391-R research project and I3 [IEDI-2016-0079] program]
Improved Orbital Parameters And Transit Monitoring For HD 156846b
HD 156846b is a Jovian planet in a highly eccentric orbit (e = 0.85) with a period of 359.55 days. The pericenter passage at a distance of 0.16 AU is nearly aligned to our line of sight, offering an enhanced transit probability of 5.4% and a potentially rich probe of the dynamics of a cool planetary atmosphere impulsively heated during close approach to a bright star (V = 6.5). We present new radial velocity (RV) and photometric measurements of this star as part of the Transit Ephemeris Refinement and Monitoring Survey. The RV measurements from the Keck-High Resolution Echelle Spectrometer reduce the predicted transit time uncertainty to 20 minutes, an order of magnitude improvement over the ephemeris from the discovery paper. We photometrically monitored a predicted transit window under relatively poor photometric conditions, from which our non-detection does not rule out a transiting geometry. We also present photometry that demonstrates stability at the millimagnitude level over its rotational timescale
On the nature of continuous physical quantities in classical and quantum mechanics
Within the traditional Hilbert space formalism of quantum mechanics, it is
not possible to describe a particle as possessing, simultaneously, a sharp
position value and a sharp momentum value. Is it possible, though, to describe
a particle as possessing just a sharp position value (or just a sharp momentum
value)? Some, such as Teller (Journal of Philosophy, 1979), have thought that
the answer to this question is No -- that the status of individual continuous
quantities is very different in quantum mechanics than in classical mechanics.
On the contrary, I shall show that the same subtle issues arise with respect to
continuous quantities in classical and quantum mechanics; and that it is, after
all, possible to describe a particle as possessing a sharp position value
without altering the standard formalism of quantum mechanics.Comment: 26 pages, LaTe
A Decidable Multi-agent Logic for Reasoning About Actions, Instruments, and Norms
We formally introduce a novel, yet ubiquitous, category of norms: norms of instrumentality. Norms of this category describe which actions are obligatory, or prohibited, as instruments for certain purposes. We propose the Logic of Agency and Norms (LAN) that enables reasoning about actions, instrumentality, and normative principles in a multi-agent setting. Leveraging LAN , we formalize norms of instrumentality and compare them to two prevalent norm categories: norms to be and norms to do. Last, we pose principles relating the three categories and evaluate their validity vis-Ă -vis notions of deliberative acting. On a technical note, the logic will be shown decidable via the finite model property
Quantum Cryptography
Quantum cryptography is a new method for secret communications offering the
ultimate security assurance of the inviolability of a Law of Nature. In this
paper we shall describe the theory of quantum cryptography, its potential
relevance and the development of a prototype system at Los Alamos, which
utilises the phenomenon of single-photon interference to perform quantum
cryptography over an optical fiber communications link.Comment: 36 pages in compressed PostScript format, 10 PostScript figures
compressed tar fil
Where would we be without counterfactuals?
Huw Price gives his inaugural lecture as Bertrand Russell Professor of Philosophy. Bertrand Russellâs celebrated essay âOn the Notion of Causeâ was first delivered to the Aristotelian Society on 4 November 1912, as Russellâs Presidential Address. The piece is best known for a passage in which its author deftly positions himself between the traditional metaphysics of causation and the British crown, firing broadsides in both directions: âThe law of causalityâ, Russell declares, âLike much that passes muster in philosophy, is a relic of a bygone age, surviving, like the monarchy, only because it is erroneously supposed to do no harm.â To mark the lectureâs centenary, we offer a contemporary view of the issues Russell here puts on the table, and of the health or otherwise, at the end of the essayâs first century, of his notorious conclusion
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