On Approximating Solitary Wave Solutions for the Classical Euler Equations

In this paper, we use a method based on Hirota substitution or the Wronskian method to find approximate solitary wave solutions to the classical Euler equations. This method uses a small parameter lambda as the basis of approximation, a parameter derived from the form of prospective solutions we consider, rather than the standard small parameters alpha and beta. The L-infinity norm and asymptotic notation are used to measure the accuracy of the approximation rather than finding the error explicitly

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Manifold spirals, disc-halo interactions and the secular evolution in N-body models of barred galaxies

The manifold theory of barred-spiral structure provides a dynamical mechanism explaining how spiral arms beyond the ends of galactic bars can be supported by chaotic flows extending beyond the bar's co-rotation zone. We discuss its applicability to N-body simulations of secularly evolving barred galaxies. In these simulations, we observe consecutive `incidents' of spiral activity, leading to a time-varying disc morphology. Besides disc self-excitations, we provide evidence of a newly noted excitation mechanism related to the `off-centering' effect: particles ejected in elongated orbits at major incidents cause the disc center-of-mass to recoil and be set in a wobble-type orbit with respect to the halo center of mass. The time-dependent m=1 perturbation on the disc by the above mechanism correlates with the excitation of new incidents of non-axisymmetric activity beyond the bar. At every new excitation, the manifolds act as dynamical avenues attracting particles which are directed far from corotation along chaotic orbits. The fact that the manifolds evolve morphologically in time, due to varying non-axisymmetric perturbations, allows to reconcile manifolds with the presence of multiple patterns and frequencies in the disc. We find a time-oscillating pattern speed profile $\Omega_p(R)$ at distances R between the bar's corotation, at resonance with the succession of minima and maxima of the non-axisymmetric activity beyond the bar. Finally, we discuss disc thermalization, i.e., the evolution of the disc velocity dispersion profile and its connection with disc responsiveness to manifold spirals.Comment: 20 pages, 22 figures. Accepted for publication in MNRA

Charge Symmetry Breaking in 500 MeV Nucleon-Trinucleon Scattering

Elastic nucleon scattering from the 3He and 3H mirror nuclei is examined as a test of charge symmetry violation. The differential cross-sections are calculated at 500 MeV using a microsopic, momentum-space optical potential including the full coupling of two spin 1/2 particles and an exact treatment of the Coulomb force. The charge-symmetry-breaking effects investigated arise from a violation within the nuclear structure, from the p-nucleus Coulomb force, and from the mass-differences of the charge symmetric states. Measurements likely to reveal reliable information are noted.Comment: 5 page

Disorder Effect On The Anisotropic Resistivity Of Phosphorene Determined By A Tight-binding Model

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)In this work we develop a compact multiorbital tight-binding model for phosphorene that accurately describes states near the main band gap. The model parameters are adjusted using as reference the band structure obtained by a density functional theory calculation with the hybrid HSE06 functional. We use the optimized tight-binding model to study the effects of disorder on the anisotropic transport properties of phosphorene. In particular, we evaluate how the longitudinal resistivity depends on the lattice orientation for two typical disorder models: dilute scatterers with high potential fluctuation amplitudes, mimicking screened charges in the substrate, and dense scatterers with lower amplitudes, simulating weakly bounded adsorbates. We show that the intrinsic anisotropy associated to the band structure of this material, although sensitive to the type and intensity of the disorder, is robust.9416FAPESP [2015/12974-5]DOE [DE-FG02-07ER46354]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Zigzag Phosphorene Nanoribbons: One-dimensional Resonant Channels In Two-dimensional Atomic Crystals

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)We theoretically investigate phosphorene zigzag nanoribbons as a platform for constriction engineering. In the presence of a constriction at one of the edges, quantum confinement of edge-protected states reveals conductance peaks, if the edge is uncoupled from the other edge. If the constriction is narrow enough to promote coupling between edges, it gives rise to Fano-like resonances as well as antiresonances in the transmission spectrum. These effects are shown to mimic an atomic chain like behavior in a two dimensional atomic crystal.719831990FAPESP [2012/19060-0, 2012/50259-8, 2010/50646-6]CNPqFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

A Whole CLOTTA Pain: A Case of IVC Thrombosis Presenting as Severe Abdominal Pain in a Patient with Anti-Phospholipid Syndrome

Background: Anti-phospholipid syndrome (APS) is an immune-mediated condition characterized by the presence of antiphospholipid antibodies in the setting of venous and arterial thrombosis and or pregnancy loss [1]. APS can be a primary syndrome or can be associated with connective tissue diseases such as systemic lupus erythematosus. The goal of treatment in patients with APS is to decrease the risk of thromboembolic events and the standard of care is warfarin therapy. We describe a case of a 42-year-old gentleman with a history of APS on anticoagulation with apixaban who presented to the hospital with severe abdominal pain secondary to infrarenal IVC thrombosis. This case highlights the importance of appropriate anticoagulation in patients with APS. Case Presentation: A 42-year-old man with a past medical history of APS presented to the hospital with a 7-day history of bilateral, dull, non-radiating, generalized abdominal pain. He denied any associated diarrhea, constipation, changes in urination, fever, nausea, or vomiting. Physical examination was notable for tachycardia with HR 110s, BP 150/100 mmHg, and a distended, tender abdomen with visible abdominal varicosities. Labs revealed a WBC 20,000 th/uL, creatinine of 2.0 mg/dL, AST 15 IU/L, ALT 20 IU/L, alkaline phosphatase 101gm/dL, INR of 1.12, and a PTT of 62.2 secs. CT abdomen and pelvis without contrast showed severe narrowing and occlusion of the infrarenal inferior vena cava over a length of 6-7 cm with dilated tortuous varices. Liver US demonstrated normal-appearing flow in hepatic veins and the intrahepatic IVC. The patient was evaluated by surgery however recommendations were made to treat the patient medically with a heparin drip with a bridge to warfarin. Discussion: Anticoagulation therapy in patients with APS is important as these patients can develop severe, life-threatening thrombotic events. Warfarin therapy is superior to direct oral anticoagulant (doac) therapy in preventing thrombotic events in these patients. Given the episode of thrombosis on doac therapy, our patient will be on lifelong warfarin therapy with an INR goal of 3.5. He has not had a recurrence of thrombotic events

Microbiologically Influenced Corrosion in Aluminium Alloys 7075 and 2024

Aluminum and its alloys are central materials for the aircraft industry. Aluminum alloys (AA) 7075 and 2024 are widely used both in the structures and in brittle sections of the airplanes. The presence of the alloying elements in these metals makes them susceptible to localized corrosion at the same time vulnerable to bacterial attachment. A great number of reports on aircraft deterioration are related to microbial growth by contamination inside fuel storage tanks and aircraft wing tanks; this phenomenon is known as microbiologically influenced corrosion (MIC). As expected, corrosion and biocorrosion increase maintenance costs and time of the aircraft in the hangar. Therefore, the growing interest is to shed light on these issues and develop future inhibition methods. In this chapter, we will give an overview of microbiologically influenced corrosion associated with AA 2024 and 7075 by consortia and bacteria. Three mechanisms of biocorrosion in aluminium alloys have been described. In addition, some alternatives methods to battle the effect of biocorrosion will be shown, these methods are based on green compound which blocking of attached of bacteria and promote the detachment of biofilm, being these a tendency of the last innovation way to inhibit this kind of phenomenon