2,335 research outputs found
Extreme alpha-clustering in the 18O nucleus
The structure of the 18O nucleus at excitation energies above the alpha decay
threshold was studied using 14C+alpha resonance elastic scattering. A number of
states with large alpha reduced widths have been observed, indicating that the
alpha-cluster degree of freedom plays an important role in this N not equal Z
nucleus. However, the alpha-cluster structure of this nucleus is very different
from the relatively simple pattern of strong alpha-cluster quasi-rotational
bands in the neighboring 16O and 20Ne nuclei. A 0+ state with an alpha reduced
width exceeding the single particle limit was identified at an excitation
energy of 9.9+/-0.3 MeV. We discuss evidence that states of this kind are
common in light nuclei and give possible explanations of this feature.Comment: 4 pages, 2 figures, 1 table. Resubmission with minor changes for
clarity, including removal of one figur
Adiabatic Transfer of Electrons in Coupled Quantum Dots
We investigate the influence of dissipation on one- and two-qubit rotations
in coupled semiconductor quantum dots, using a (pseudo) spin-boson model with
adiabatically varying parameters. For weak dissipation, we solve a master
equation, compare with direct perturbation theory, and derive an expression for
the `fidelity loss' during a simple operation that adiabatically moves an
electron between two coupled dots. We discuss the possibility of visualizing
coherent quantum oscillations in electron `pump' currents, combining quantum
adiabaticity and Coulomb blockade. In two-qubit spin-swap operations where the
role of intermediate charge states has been discussed recently, we apply our
formalism to calculate the fidelity loss due to charge tunneling between two
dots.Comment: 13 pages, 8 figures, to appear in Phys. Rev.
Presentism remains
Here I examine some recent attempts to provide a new way of thinking about the philosophy of time that question the central role of âpresentnessâ within the definition of presentism. The central concern raised by these critics turns on the intelligibility and theoretical usefulness of the term âis presentâ (cf. Correia and Rosenkrantz in Thought 4:19â27, 2015; Deasy in Nous, 2017. https://doi.org/10.1111/nous.12109; Williamson in Modal logic as metaphysics, OUP, Oxford, 2013). My overarching aim is to at least challenge such concerns. I begin with arguments due to Deasy (Nous, 2017. https://doi.org/10.1111/nous.12109). Deasy develops a view that he calls âtransientismâ and that he takes to be a well-motivated version of presentism. I show that both this way of thinking about presentism and the argument supposedly motivating it all fail. I then move to an argument due to Correia and Rosenkrantz (Thought 4:19â27, 2015). Correia and Rosenkrantz purport to show that presentism can be salvaged without making recourse to the term âis presentâ. I demonstrate that their arguments fail. I then move on to a view, proposed and defended by Merricks (Truth and ontology, OUP, Oxford, 2007), Tallant (Erkenntnis 79:479â501, 2014), and Zimmerman (Philos Pap 25:115â126, 1996), and show that it has the wherewithal to meet the challenges raised by Williamson (Modal logic as metaphysics, OUP, Oxford, 2013) who, as noted above, raises genuine concerns about our capacity to define presentism
An argument for the use of Aristotelian method in bioethics
The main claim of this paper is that the method outlined and used in Aristotle's Ethics is an appropriate and credible one to use in bioethics. Here âappropriateâ means that the method is capable of establishing claims and developing concepts in bioethics and âcredibleâ that the method has some plausibility, it is not open to obvious and immediate objection. It begins by suggesting why this claim matters and then gives a brief outline of Aristotle's method. The main argument is made in three stages. First, it is argued that Aristotelian method is credible because it compares favourably with alternatives. In this section it is shown that Aristotelian method is not vulnerable to criticisms that are made both of methods that give a primary place to moral theory (such as utilitarianism) and those that eschew moral theory (such as casuistry and social science approaches). As such, it compares favourably with these other approaches that are vulnerable to at least some of these criticisms. Second, the appropriateness of Aristotelian method is indicated through outlining how it would deal with a particular case. Finally, it is argued that the success of Aristotle's philosophy is suggestive of both the credibility and appropriateness of his method.</p
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