Understanding the mechanisms underlying cognitive control in psychosis

Background Cognitive control (CC) involves a top–down mechanism to flexibly respond to complex stimuli and is impaired in schizophrenia. Methods This study investigated the impact of increasing complexity of CC processing in 140 subjects with psychosis and 39 healthy adults, with assessments of behavioral performance, neural regions of interest and symptom severity. Results The lowest level of CC (Stroop task) was impaired in all patients; the intermediate level of CC (Faces task) with explicit emotional information was most impaired in patients with first episode psychosis. Patients showed activation of distinct neural CC and reward networks, but iterative learning based on the higher-order of CC during the trust game, was most impaired in chronic schizophrenia. Subjects with first episode psychosis, and patients with lower symptom load, demonstrate flexibility of the CC network to facilitate learning, which appeared compromised in the more chronic stages of schizophrenia. Conclusion These data suggest optimal windows for opportunities to introduce therapeutic interventions to improve CC

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

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 ‘presentness’ within the definition of presentism. The central concern raised by these critics turns on the intelligibility and theoretical usefulness of the term ‘is present’ (cf. Correia and Rosenkrantz in Thought 4:19–27, 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 ‘transientism’ 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 4:19–27, 2015). Correia and Rosenkrantz purport to show that presentism can be salvaged without making recourse to the term ‘is present’. 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 79:479–501, 2014), and Zimmerman (Philos Pap 25:115–126, 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

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.