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

A hierarchical autonomous driver for a racing car: Real-time planning and tracking of the trajectory

The aim of this study was to develop trajectory planning that would allow an autonomous racing car to be driven as close as possible to what a driver would do, defining the most appropriate inputs for the current scenario. The search for the optimal trajectory in terms of lap time reduction involves the modeling of all the non-linearities of the vehicle dynamics with the disadvantage of being a time-consuming problem and not being able to be implemented in real-time. However, to improve the vehicle performances, the trajectory needs to be optimized online with the knowledge of the actual vehicle dynamics and path conditions. Therefore, this study involved the development of an architecture that allows an autonomous racing car to have an optimal online trajectory planning and path tracking ensuring professional driver performances. The real-time trajectory optimization can also ensure a possible future implementation in the urban area where obstacles and dynamic scenarios could be faced. It was chosen to implement a local trajectory planning based on the Model Predictive Control(MPC) logic and solved as Linear Programming (LP) by Sequential Convex Programming (SCP). The idea was to achieve a computational cost, 0.1 s, using a point mass vehicle model constrained by experimental definition and approximation of the car’s GG-V, and developing an optimum model-based path tracking to define the driver model that allows A car to follow the trajectory defined by the planner ensuring a signal input every 0.001 s. To validate the algorithm, two types of tests were carried out: a Matlab-Simulink, Vi-Grade co-simulation test, comparing the proposed algorithm with the performance of an offline motion planning, and a real-time simulator test, comparing the proposed algorithm with the performance of a professional driver. The results obtained showed that the computational cost of the optimization algorithm developed is below the limit of 0.1 s, and the architecture showed a reduction of the lap time of about 1 s compared to the offline optimizer and reproducibility of the performance obtained by the driver

Intersection types and (positive) almost-sure termination

Randomized higher-order computation can be seen as being captured by a λ-calculus endowed with a single algebraic operation, namely a construct for binary probabilistic choice. What matters about such computations is the probability of obtaining any given result, rather than the possibility or the necessity of obtaining it, like in (non)deterministic computation. Termination, arguably the simplest kind of reachability problem, can be spelled out in at least two ways, depending on whether it talks about the probability of convergence or about the expected evaluation time, the second one providing a stronger guarantee. In this paper, we show that intersection types are capable of precisely characterizing both notions of termination inside a single system of types: the probability of convergence of any λ-term can be underapproximated by its type, while the underlying derivation's weight gives a lower bound to the term's expected number of steps to normal form. Noticeably, both approximations are tight-not only soundness but also completeness holds. The crucial ingredient is non-idempotency, without which it would be impossible to reason on the expected number of reduction steps which are necessary to completely evaluate any term. Besides, the kind of approximation we obtain is proved to be optimal recursion theoretically: no recursively enumerable formal system can do better than that

À margem dos jornais: uma análise de representação das áreas de vulnerabilidade social da Grande Vitória na imprensa capixaba

O presente trabalho busca compreender como os jornais impressos A Gazeta e A Tribuna representam os fatos ocorridos nas áreas de vulnerabilidade social da Região Metropolitana da Grande Vitória, no Espírito Santo. Para selecionar as localidades analisadas foi utilizado o programa do Governo do Estado do Espírito Santo denominado Ocupação Social. Das 26 localidades contempladas pelo projeto 18 estão situadas na Região Metropolita. Em um primeiro momento parte-se das discussões em torno da imprensa como instituição social autorizada a narrar sobre o cotidiano. Entende-se o jornalismo como uma instância produtora de conteúdo regida sobre dinâmicas e rotinas próprias. Em um segundo momento há a discussão sobre a formação de territórios e territorialidades os entendendo aqui tanto fisicamente com os bairros vulneráveis como simbolicamente jornalismo como narrador social. A reflexão sobre a narrativa dos territórios culmina na discussão sobre a violência e como a imprensa é responsável por apresentá-la (e representá-la). Por fim são evidenciadas as informações obtidas por meio de uma Análise de Conteúdo sobre as coberturas dos jornais A Gazeta e A Tribuna em torno dos bairros vulneráveis no ano de 2016. A pesquisa aponta que os bairros de vulnerabilidade social são protagonistas nos conteúdos sobre a violência no Espírito Santo e que conteúdos culturais sobre os mesmo são quase que inexistentes. Há também a discussão em torno da abordagem dos dois jornais, suas semelhanças e diferenças ao noticiar esses fatos. Palavras-chave: Imprensa; Representação; Jornalismo; Vulnerabilidade Social; Grande Vitória

Calibration of the stereological estimation of the number of myelinated axons in the rat sciatic nerve: a multicenter study.

Several sources of variability can affect stereological estimates. Here we measured the impact of potential sources of variability on numerical stereological estimates of myelinated axons in the adult rat sciatic nerve. Besides biological variation, parameters tested included two variations of stereological methods (unbiased counting frame versus 2D-disector), two sampling schemes (few large versus frequent small sampling boxes), and workstations with varying degrees of sophistication. All estimates were validated against exhaustive counts of the same nerve cross sections to obtain calibrated true numbers of myelinated axons (gold standard). In addition, we quantified errors in particle identification by comparing light microscopic and electron microscopic images of selected consecutive sections. Biological variation was 15.6%. There was no significant difference between the two stereological approaches or workstations used, but sampling schemes with few large samples yielded larger differences (20.7%±3.7% SEM) of estimates from true values, while frequent small samples showed significantly smaller differences (12.7%±1.9% SEM). Particle identification was accurate in 94% of cases (range: 89–98%). The most common identification error was due to profiles of Schwann cell nuclei mimicking profiles of small myelinated nerve fibers. We recommend sampling frequent small rather than few large areas, and conclude that workstations with basic stereological equipment are sufficient to obtain accurate estimates. Electron microscopic verification showed that particle misidentification had a surprisingly variable and large impact of up to 11%, corresponding to 2/3 of the biological variation (15.6%). Thus, errors in particle identification require further attention, and we provide a simple nerve fiber recognition test to assist investigators with self-testing and training

An Exploration of Young Australian Women's Smoking Cessation Goals across the Trajectory of Pregnancy and Post Birth

Objective: Young pregnant women are more likely than other pregnant women to smoke tobacco during pregnancy and post birth. This study explored young women’s perceptions of the factors which impact their smoking cessation goals throughout pregnancy and post birth. Methods: This qualitative descriptive study was performed at two metropolitan obstetric hospitals in Western Australia. Forty three women aged 16 to 24 years old who reported smoking tobacco at their first antenatal visit were interviewed at each scheduled antenatal visit and every two weeks up to six weeks post birth. Interviews were subjected to thematic analysis. Results: A total of 244 interviews were performed; a mean of six interviews per woman (four in pregnancy and two post birth). Four overarching themes across three time periods were identified: the baby; the social bond of smoking; the chaotic nature of life; and access to social support. Pregnant women had a foetus-centric approach to cessation. Post birth those who sustained cessation held this belief for their newborn, whilst those who relapsed did not. The social bond of smoking highlighted smoking as the norm. Initially, women sought out non-smokers to support them. A partner’s smoking status post birth appeared pivotal to remaining tobacco free. The chaotic nature of life, reflected through multiple stressful, negative events, challenged women in achieving their smoking cessation goals. Women who sought social support appeared to stay smoke free post birth. Conclusion: The longitudinal nature of this study provides new insight into complex issues faced by this marginalised group of young, pregnant, tobacco smokers throughout the journey of pregnancy and post birth. Findings enhance our understanding of the complex real life issues some young pregnant Australian smokers face and may be considered when women focused smoking cessation interventions are developed

Partnering for sustainability in agri-food supply chains: the case of Barilla Sustainable Farming in the Po Valley

This is the final version. Available on open access from Springer via the DOI in this recordAvailability of data and materials: Not applicableThe objective of the paper is to understand the process of designing a multi-stakeholder partnership in the adoption of sustainable innovations in value chains. More specifically, the focus is on the design of feasible types of horizontal agreements and contractual formulas to be implemented in the agri-food supply chain in order to introduce sustainable agricultural practices. To this purpose, the Barilla Sustainable Farming initiative, which is currently in the first phase of designing an MSP, is used as a case study.European Union Horizon 202