Simulations of secondary Farley-Buneman instability driven by a kilometer-scale primary wave: anomalous transport and formation of flat-topped electric fields

Since the 1950s, high frequency and very high frequency radars near the magnetic equator have frequently detected strong echoes caused ultimately by the Farley‐Buneman instability (FBI) and the gradient drift instability (GDI). In the 1980s, coordinated rocket and radar campaigns made the astonishing observation of flat‐topped electric fields coincident with both meter‐scale irregularities and the passage of kilometer‐scale waves. The GDI in the daytime E region produces kilometer‐scale primary waves with polarization electric fields large enough to drive meter‐scale secondary FBI waves. The meter‐scale waves propagate nearly vertically along the large‐scale troughs and crests and act as VHF tracers for the large‐scale dynamics. This work presents a set of hybrid numerical simulations of secondary FBIs, driven by a primary kilometer‐scale GDI‐like wave. Meter‐scale density irregularities develop in the crest and trough of the kilometer‐scale wave, where the total electric field exceeds the FBI threshold, and propagate at an angle near the direction of total Hall drift determined by the combined electric fields. The meter‐scale irregularities transport plasma across the magnetic field, producing flat‐topped electric fields similar to those observed in rocket data and reducing the large‐scale wave electric field to just above the FBI threshold value. The self‐consistent reduction in driving electric field helps explain why echoes from the FBI propagate near the plasma acoustic speed.NSF grants PHY-1500439 and AGS-1755350 and NASA grant NNX14AI13G supported the research presented in this work. This work used TACC and XSEDE computational resources supported by the National Science Foundation grant ACI-1053575. This paper did not use any data; simulation runs are archived on the TACC Ranch system. The authors thank one anonymous reviewer for helpful comments. (PHY-1500439 - NSF; AGS-1755350 - NSF; NNX14AI13G - NASA; ACI-1053575 - National Science Foundation)Published version2019-07-0

On Graph Refutation for Relational Inclusions

We introduce a graphical refutation calculus for relational inclusions: it reduces establishing a relational inclusion to establishing that a graph constructed from it has empty extension. This sound and complete calculus is conceptually simpler and easier to use than the usual ones.Comment: In Proceedings LSFA 2011, arXiv:1203.542

ASMs and Operational Algorithmic Completeness of Lambda Calculus

We show that lambda calculus is a computation model which can step by step simulate any sequential deterministic algorithm for any computable function over integers or words or any datatype. More formally, given an algorithm above a family of computable functions (taken as primitive tools, i.e., kind of oracle functions for the algorithm), for every constant K big enough, each computation step of the algorithm can be simulated by exactly K successive reductions in a natural extension of lambda calculus with constants for functions in the above considered family. The proof is based on a fixed point technique in lambda calculus and on Gurevich sequential Thesis which allows to identify sequential deterministic algorithms with Abstract State Machines. This extends to algorithms for partial computable functions in such a way that finite computations ending with exceptions are associated to finite reductions leading to terms with a particular very simple feature.Comment: 37 page

Levantamento de hospedeiros e parasitóides de Anastrepha spp. (Diptera: Tephritidae) no município de Boa Vista, Estado de Roraima.

Resumo 937-1

Socio-demographic and clinical characterization of patients with obsessive-compulsive tic-related disorder (OCTD) : An Italian multicenter study

© Copyright by Pacini Editore SrlIn the DSM-5 a new "tic-related" specifier for obsessive compulsive disorder (OCD) has been introduced, highlighting the importance of an accurate characterization of patients suffering from obsessive-compulsive tic-related disorder ("OCTD"). In order to characterize OCTD from a socio-demographic and clinical perspective, the present multicenter study was carried out. The sample consists of 266 patients, divided in two groups with lifetime diagnoses of OCD and OCTD, respectively. OCTD vs OCD patients showed a significant male prevalence (68.5% vs 48.5%; p < .001), a higher rate of psychiatric comorbidities (69.4 vs 50%; p < .001) - mainly with neurodevelopmental disorders (24 vs 0%; p < .001), a lower education level and professional status (middle school diploma: 25 vs 7.6%; full-Time job 44.4 vs 58%; p < .001). Moreover, OCTD vs OCD patients showed significantly earlier age of OCD and psychiatric comorbidity onsets (16.1 ± 10.8 vs 22.1 ± 9.5 years; p < .001, and 18.3 ± 12.8 vs 25.6 ± 9.4: p < .001, respectively). Patients with OCTD patients were treated mainly with antipsychotic and with a low rate of benzodiazepine (74.2 vs 38.2% and 20.2 vs 31.3%, respectively; p < .001). Finally, OCTD vs OCD patients showed higher rates of partial treatment response (58.1 vs 38%; p < .001), lower rates of current remission (35.5 vs 54.8%; p < .001) and higher rates of suicidal ideation (63.2 vs 41.7%; p < .001) and attempts (28.9 vs 8.3%; p < .001). Patients with OCTD report several unfavorable socio-demographic and clinical characteristics compared to OCD patients without a history of tic. Additional studies on larger sample are needed to further characterize OCTD patients from clinical and therapeutic perspectives.Peer reviewedFinal Published versio

A Formalization of the Theorem of Existence of First-Order Most General Unifiers

This work presents a formalization of the theorem of existence of most general unifiers in first-order signatures in the higher-order proof assistant PVS. The distinguishing feature of this formalization is that it remains close to the textbook proofs that are based on proving the correctness of the well-known Robinson's first-order unification algorithm. The formalization was applied inside a PVS development for term rewriting systems that provides a complete formalization of the Knuth-Bendix Critical Pair theorem, among other relevant theorems of the theory of rewriting. In addition, the formalization methodology has been proved of practical use in order to verify the correctness of unification algorithms in the style of the original Robinson's unification algorithm.Comment: In Proceedings LSFA 2011, arXiv:1203.542

Origin of atomic clusters during ion sputtering

Previous studies have shown that the size distributions of small clusters ( n&#60;=40 n = number of atoms/cluster) generated by sputtering obey an inverse power law with an exponent between -8 and -4. Here we report electron microscopy studies of the size distributions of larger clusters ( n&#62;=500) sputtered by high-energy ion impacts. These new measurements also yield an inverse power law, but one with an exponent of -2 and one independent of sputtering yield, indicating that the large clusters are produced when shock waves, generated by subsurface displacement cascades, ablate the surface