A Conservative Discontinuous Galerkin Scheme With O(N-2) Operations In Computing Boltzmann Collision Weight Matrix

In the present work, we propose a deterministic numerical solver for the homogeneous Boltzmann equation based on Discontinuous Galerkin (DG) methods. The weak form of the collision operator is approximated by a quadratic form in linear algebra setting. We employ the property of >shifting symmetry> in the weight matrix to reduce the computing complexity from theoretical O(N-3) down to O(N-2), with N the total number of freedom for d-dimensional velocity space. In addition, the sparsity is also explored to further reduce the storage complexity. To apply lower order polynomials and resolve loss of conserved quantities, we invoke the conservation routine at every time step to enforce the conservation of desired moments (mass, momentum and/or energy), with only linear complexity. Due to the locality of the DG schemes, the whole computing process is well parallelized using hybrid OpetiMP and MPI. The current work only considers integrable angular cross-sections under elastic and/or inelastic interaction laws. Numerical results on 2-D and 3-D problems are shown.Mathematic

Estudio comparativo de capas de TiO2depositadas por PLD a presión atmosférica y nebulización pirolítica

Las nanocapas cerámicas son ampliamente estudiadas por su interés en aplicaciones tecnológicas. Estos recubrimientos pueden conformar celdas solares, superficies de transmisión, emisión o reflexión selectiva de luz, entre otras tantas aplicaciones. En este trabajo se presenta una comparación entre películas delgadas de TiO2 depositadas por ablación láser pulsado (PLD) y por nebulización pirolítica (sol-gel spray-pyrolisis, SP). La caracterización de las nanocapas se realizó empleando diversas técnicas como microscopía electrónica de barrido (SEM), espectrometría de dispersión de energía de Rayos X (EDS), microscopia de Fuerza Atómica (AFM), Difracción de Rayos X y espectroscopia Raman.TiO 2 layers and nanolayers are widely studied due to its technological applications. This material could be used in solar cells, transmission, emission or selective reflection, among other applications. In this paper, we show a characterization of layers of TiO 2 grown by two different methods, Pulsed Laser Deposition (PLD) at atmospheric pressure and spray pyrolysis (SP). The samples were characterized by SEM, EDS, AFM, XRD and Raman Spectrometry.Fil: Tejerina, Matías Rubén. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Gamba, Martina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Ponce Cabrera, L.. San Petersburg Electrotechnical University; RusiaFil: Alvira, Fernando Carlos. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Congenital pancreatoblastoma: a case report

The literature describes 15 cases of congenital pancreatoblastoma (PB): 5 had prenatal diagnosis, none had metastases at diagnosis, 7 were associated with BeckwitheWiedemann syndrome (BWS). In 13 cases resection was radical, while in 2 there were macroscopic residues. Only one patient underwent chemotherapy after distant recurrence. All children are alive except one who died because of problems related to BWS. Our goal is to describe the approach adopted in an infant with congenital PB treated in our center. After a prenatal third semester diagnosis of abdominal anechoic lesion, the radiological investigations (ultrasound, MRI) performed at birth described a cystic lesion of unclear nature. We proceeded to laparoscopic exploration, transformed into open approach after the detection of a lesion located in the body of the pancreas; this lesion was resected, preserving the head and tail of pancreas. The histological diagnosis showed a completely excised PB. After excluding metastatic lesions, we decided to perform only careful follow-up without chemotherapy. The follow-up at 12 months is negative. Although PB is a malignant tumor that requires a multidisciplinary treatment, the congenital cases seem to have a less aggressive biological behavior. The treatment, therefore, in case of complete resection, could be only surgical, followed by a careful follow-up. These forms are often associated with congenital BWS, but in our case the patient did not have the typical characteristics of the syndrome

Octonic Electrodynamics

In this paper we present eight-component values "octons", generating associative noncommutative algebra. It is shown that the electromagnetic field in a vacuum can be described by a generalized octonic equation, which leads both to the wave equations for potentials and fields and to the system of Maxwell's equations. The octonic algebra allows one to perform compact combined calculations simultaneously with scalars, vectors, pseudoscalars and pseudovectors. Examples of such calculations are demonstrated by deriving the relations for energy, momentum and Lorentz invariants of the electromagnetic field. The generalized octonic equation for electromagnetic field in a matter is formulated.Comment: 12 pages, 1 figur

Linear Theory of Electron-Plasma Waves at Arbitrary Collisionality

The dynamics of electron-plasma waves are described at arbitrary collisionality by considering the full Coulomb collision operator. The description is based on a Hermite-Laguerre decomposition of the velocity dependence of the electron distribution function. The damping rate, frequency, and eigenmode spectrum of electron-plasma waves are found as functions of the collision frequency and wavelength. A comparison is made between the collisionless Landau damping limit, the Lenard-Bernstein and Dougherty collision operators, and the electron-ion collision operator, finding large deviations in the damping rates and eigenmode spectra. A purely damped entropy mode, characteristic of a plasma where pitch-angle scattering effects are dominant with respect to collisionless effects, is shown to emerge numerically, and its dispersion relation is analytically derived. It is shown that such a mode is absent when simplified collision operators are used, and that like-particle collisions strongly influence the damping rate of the entropy mode.Comment: 23 pages, 10 figures, accepted for publication on Journal of Plasma Physic

Sorting of multiple molecular species on cell membranes

Eukaryotic cells maintain their inner order by a hectic process of distillation of molecular factors taking place on the surface of their lipid membranes. To understand the properties of this molecular sorting process, a physical model of the process has been recently proposed [arXiv:1811.06760], based on (a) the phase separation of a single, initially dispersed molecular species into spatially localized sorting domains on the lipid membrane, and (b) domain-induced membrane bending leading to the nucleation of submicrometric lipid vesicles, naturally enriched in the molecules of the engulfed sorting domain. The analysis of the model has shown the existence of an optimal region of the parameter space where sorting is most efficient. Here, the model is extended to account for the simultaneous distillation of a pool of distinct molecular species. We find that the mean time spent by sorted molecules on the membrane increases with the heterogeneity of the pool (i.e., the number of distinct molecular species sorted) according to a simple scaling law, and that a large number of distinct molecular species can in principle be sorted in parallel on a typical cell membrane region without significantly interfering with each other. Moreover, sorting is found to be most efficient when the distinct molecular species have comparable homotypic affinities. We also consider how valence (i.e., the average number of interacting neighbors of a molecule in a sorting domain) affects the sorting process, finding that higher-valence molecules can be sorted with greater efficiency than lower-valence molecules

Congenital pancreatoblastoma: a case report

The literature describes 15 cases of congenital pancreatoblastoma (PB): 5 had prenatal diagnosis, none had metastases at diagnosis, 7 were associated with BeckwitheWiedemann syndrome (BWS). In 13 cases resection was radical, while in 2 there were macroscopic residues. Only one patient underwent chemotherapy after distant recurrence. All children are alive except one who died because of problems related to BWS. Our goal is to describe the approach adopted in an infant with congenital PB treated in our center. After a prenatal third semester diagnosis of abdominal anechoic lesion, the radiological investigations (ultrasound, MRI) performed at birth described a cystic lesion of unclear nature. We proceeded to laparoscopic exploration, transformed into open approach after the detection of a lesion located in the body of the pancreas; this lesion was resected, preserving the head and tail of pancreas. The histological diagnosis showed a completely excised PB. After excluding metastatic lesions, we decided to perform only careful follow-up without chemotherapy. The follow-up at 12 months is negative. Although PB is a malignant tumor that requires a multidisciplinary treatment, the congenital cases seem to have a less aggressive biological behavior. The treatment, therefore, in case of complete resection, could be only surgical, followed by a careful follow-up. These forms are often associated with congenital BWS, but in our case the patient did not have the typical characteristics of the syndrome

An intramolecular oxa-Michael reaction on α,β-unsaturated α-amino-δ-hydroxycarboxylic acid esters. Synthesis of functionalized 1,3-dioxanes

A highly diastereoselective intramolecular oxa-Michael reaction on α,β-unsaturated α-amino-δ-hydroxycarboxylic acid esters is presented; 1,3-dioxanes functionalized in positions 2,4 and 6 were obtained in good yields and with excellent selectivities; an experimental and computational study was carried out to understand the reaction course in terms of yields and selectivities. This reaction proceeds under mild reaction conditions using highly electrophilic aldehydes and ketones