The role of psychometrics in individual differences research in cognition: A case study of the AX-CPT

Investigating individual differences in cognition requires addressing questions not often thought about in standard experimental designs, especially regarding the psychometric properties of the task. Using the AX-CPT cognitive control task as a case study example, we address four concerns that one may encounter when researching the topic of individual differences in cognition. First, we demonstrate the importance of variability in task scores, which in turn directly impacts reliability, particularly when comparing correlations in different populations. Second, we demonstrate the importance of variability and reliability for evaluating potential failures to replicate predicted correlations, even within the same population. Third, we demonstrate how researchers can turn to evaluating psychometric properties as a way of evaluating the feasibility of utilizing the task in new settings (e.g., online administration). Lastly, we show how the examination of psychometric properties can help researchers make informed decisions when designing a study, such as determining the appropriate number of trials for a task

Gradual Certified Programming in Coq

Expressive static typing disciplines are a powerful way to achieve high-quality software. However, the adoption cost of such techniques should not be under-estimated. Just like gradual typing allows for a smooth transition from dynamically-typed to statically-typed programs, it seems desirable to support a gradual path to certified programming. We explore gradual certified programming in Coq, providing the possibility to postpone the proofs of selected properties, and to check "at runtime" whether the properties actually hold. Casts can be integrated with the implicit coercion mechanism of Coq to support implicit cast insertion a la gradual typing. Additionally, when extracting Coq functions to mainstream languages, our encoding of casts supports lifting assumed properties into runtime checks. Much to our surprise, it is not necessary to extend Coq in any way to support gradual certified programming. A simple mix of type classes and axioms makes it possible to bring gradual certified programming to Coq in a straightforward manner.Comment: DLS'15 final version, Proceedings of the ACM Dynamic Languages Symposium (DLS 2015

On formal verification of arithmetic-based cryptographic primitives

Cryptographic primitives are fundamental for information security: they are used as basic components for cryptographic protocols or public-key cryptosystems. In many cases, their security proofs consist in showing that they are reducible to computationally hard problems. Those reductions can be subtle and tedious, and thus not easily checkable. On top of the proof assistant Coq, we had implemented in previous work a toolbox for writing and checking game-based security proofs of cryptographic primitives. In this paper we describe its extension with number-theoretic capabilities so that it is now possible to write and check arithmetic-based cryptographic primitives in our toolbox. We illustrate our work by machine checking the game-based proofs of unpredictability of the pseudo-random bit generator of Blum, Blum and Shub, and semantic security of the public-key cryptographic scheme of Goldwasser and Micali.Comment: 13 page

‘Faster counting while walking' as a predictor of falls in older adults

Objective: to establish whether changes in a spoken verbal task performance while walking compared with being at rest could predict falls among older adults. Design: prospective cohort study of 12 months' duration. Setting: twenty-seven senior housing facilities. Participants: sample of 187 subjects aged 75-100 (mean age 84.8±5.2). During enrollment, participants were asked to count aloud backward from 50, both at rest and while walking and were divided into two groups according to their counting performance. Information on incident falls during the follow-up year was monthly collected. Measurements: the number of enumerated figures while sitting on a chair and while walking, and the first fall that occurred during the follow up year. Results: the number of enumerated figures under dual-task as compared to single task increased among 31.5% of the tested subjects (n=59) and was associated with lower scores in MMSE (P=0.034), and higher scores in Geriatric Depression Scale (P=0.007) and Timed Up & Go (P=0.005). During the 12 months follow-up, 54 subjects (28.9%) fell. After adjusting for these variables, the increase in counting performance was significantly associated with falls (adjusted OR = 53.3, P < 0.0001). Kaplan-Meier distributions of falls differed significantly between subjects who either increased or decreased their counting performance (P < 0.0001). Conclusions: faster counting while walking was strongly associated with falls, suggesting that better performance in an additional verbal counting task while walking might represent a new way to predict falls among older adult

Population synthesis of radio and gamma-ray millisecond pulsars from the Galactic disk

We present results of a population synthesis of millisecond pulsars from the Galactic disk. Excluding globular clusters, we model the spatial distribution of millisecond pulsars by assuming their birth in the Galactic disk with a random kick velocity and evolve them to the present within the Galactic potential. We assume that normal and millisecond pulsars are standard candles described with a common radio luminosity model that invokes a new relationship between radio core and cone emission suggested by recent studies. In modeling the radio emission beams, we explore the relativistic effects of time delay, aberration and sweepback of the open field lines. While these effects are essential in understanding pulse profiles, the phase-averaged flux is adequately described without a relativistic model. We use a polar cap acceleration model for the gamma-ray emission. We present the preliminary results of our recent study and the implications for observing millisecond pulsars with GLAST and AGILE.Comment: 38 pages, 10 figures, accepted in ApJ - new versio

Arbuscular mycorrhizal colonization in black poplar roots after defoliation by a non-native and a native insect

A major goal in ecology is to understand how interactions among organisms influence ecosystem services. This work compares the effects of two Lepidoptera defoliators, one non-native (Hyphantria cunea) and one native (Lymantria dispar) to Europe, on the colonization of black poplar (the Populus nigra clone "Jean Pourtet") roots by an arbuscular mycorrhizal (AM) symbiotic fungus (Funneliformis mosseae) in a pot experiment. The effects of defoliation have also been assessed on the expression of fungal and plant genes playing a role during symbiosis. Both control and defoliated poplars have shown a low level of mycorrhization. Additionally, neither the non-native nor the native insect seem to strongly affect the AM colonization, at least at the time of observation (eight days from the end of the defoliation). Concerning the gene expression analysis, our results suggest that defoliation does not influence neither the expression of genes coding for a fungal and a plant phosphate transporter nor that of a gene coding for a fungal ATPase, and that there were no differences between defoliation carried out by the non-native and the native insect. \ua9 SISEF

Isolated pulsar spin evolution on the P-Pdot Diagram

We look at two contrasting spin-down models for isolated radio pulsars and, accounting for selection effects, synthesize observable populations. While our goal is to reproduce all of the observable characteristics, in this paper we pay particular attention to the form of the spin period vs. period derivative (P-Pdot) diagram and its dependence on various pulsar properties. We analyse the initial spin period, the braking index, the magnetic field, various beaming models, as well as the pulsar's luminosity. In addition to considering the standard magnetic dipole model for pulsar spin-down, we also consider the recent hybrid model proposed by Contopoulos & Spitkovsky. The magnetic dipole model, however, does a better job of reproducing the observed pulsar population. We conclude that random alignment angles and period dependent luminosity distributions are essential to reproduce the observed P-Pdot diagram. We also consider the time decay of alignment angles, and attempt to reconcile various models currently being studied. We conclude that, in order to account for recent evidence for the alignment found by Weltevrede & Johnston, the braking torque on a neutron star should not depend strongly on the inclination. Our simulation code is publically available and includes a web-based interface to examine the results and make predictions for yields of current and future surveys.Comment: 9 pages, 4 figure