Coupling the non-gravitational forces and Modified Newton Dynamics for cometary orbits

In recent work (Milgrom 2009, Blanchet & Novak 2011), the authors showed that MOdified Newton Dynamics (MOND) have a non-negligible secular perturbation effect on planets with large semi-major axes (gaseous planets) in the Solar System. Some comets also have a very eccentric orbit with a large semi-major axis (Halley family comets) going far away from the Sun (more than 15 AU) in a low acceleration regime where they would be subject to MOND perturbation. They also approach the Sun very closely (less than 3 AU) and are affected by the sublimation of ices from their nucleus, triggering so-called non-gravitational forces. The main goal of this paper is to investigate the effect of MOND perturbation on three comets with various orbital elements (2P/Encke, 1P/Halley and 153P/Ikeya-Zhang) and then compare it to the non-gravitational perturbations. It is motivated by the fact that when fitting an outgassing model for a comet, we have to take into account all of the small perturbing effects to avoid absorbing these effects into the non-gravitational parameters. Otherwise, we could derive a completely wrong estimation of the outgassing. For this work, we use six different forms of MOND functions and compute the secular variations of the orbital elements due to MOND and non-gravitational perturbations. We show that, for comets with large semi-major axis, the MONDian effects are not negligible compared to the non-gravitational perturbations

Anatomy of a reindeer dissected in Copenhagen in 1672 by Niels Stensen as reported by Thomas Bartholin. I. Introduction by Troels Kardel. II. Translation by Paul Maquet

A report by Professor Thomas Bartholin on the dissection of a reindeer performed in 1672 by his former student Niels Stensen as Royal Anatomist in Copenhagen is presented in English translation with biographical introduction and bibliographical notes. The report is most likely the first of its kind being an early contribution to comparative anatomy

Aspectos neuropsicológicos associados à presença de sintomas depressivos em crianças escolarizadas

O propósito do estudo foi estimar a presença de sintomatologia depressiva em una mostra não clínica de crianças escolarizadas e descrever o funcionamento neuropsicológico de crianças com sintomatologia depressiva para compará-lo com um grupo de características demográficas similares sem sintomatologia depressiva. Para tal fim aplicou-se o Inventário para a depressão infantil (Children Depression Inventory, CDI) a 312 crianças escolarizados entre 9 e 12 anos. Com base nos resultados foram selecionadas 62 crianças, que foram distribuídas em dois grupos: um com sintomatologia depressiva e outro sem sintomas. A avaliação neuropsicológica incluiu: Teste de caras, Cancelamento do A, Teste de traçados (TMT) A e B, Figura de Rei, Stroop e Teste de aprendizagem verbal para crianças (CVLT). O CDI mostrou que 13.78% das crianças apresenta sintomatologia depressiva. A avaliação neuropsicológica mostrou diferenças significativas somente na tarefa de conflito do Stroop. Isto sugere que a nível subclínico está afetada a capacidade para inibir respostas automáticas.El propósito del estudio fue estimar la presencia de sintomatología depresiva en una muestra no clínica de niños escolarizados y describir el funcionamiento neuropsicológico de niños con sintomatología depresiva para compararlo con un grupo de características demográficas similares sin sintomatología depresiva. Para tal fin se aplicó el Inventario para la depresión infantil (Children Depression Inventory, CDI) a 312 niños escolarizados entre 9 y 12 años. Con base en los resultados se seleccionaron 62 niños los cuales se distribuyeron en dos grupos: uno con sintomatología depresiva y otro sin síntomas. La evaluación neuropsicológica incluyó: Test de caras, Cancelación de la A, Test de trazados (TMT) A y B, Figura de Rey, Stroop y Test de aprendizaje verbal para niños (CVLT). El CDI mostró que el 13.78% de los niños presenta sintomatología depresiva. La evaluación neuropsicológica arrojó únicamente diferencias significativas en la tarea de conflicto del Stroop. Esto sugiere que a nivel subclínico está afectada la capacidad para inhibir respuestas automáticas.The purpose of this study was to estimate the presence of depressive symptoms in a nonclinical sample of school children and describe the neuropsychological functioning of children with depressive symptoms to compare them with a similar demographic group without depressive symptoms. To this end the Child Depression Inventory (Children Depression Inventory, CDI) was administered to 312 school children aged between 9 and 12. Based on the results 62 children were selected and distributed into two groups: one with depressive symptoms and one without symptoms. Neuropsychological assessment included: the Perceptions and Differences Test -FACES, the Cancelación de la A [A Cancellation Test], the Trail Making Test (TMT) forms A and B, the Rey Figure Test, the Stroop Test and the California Verbal Learning Test for Children (CVLT). The CDI showed that 13.78% of children have symptoms of depression. Neuropsychological assessment showed only significant differences in the conflict task of the Stroop Test. This suggests that the ability to inhibit automatic responses is affected at a subclinical level

Meteor hurricane at Mars on 2014 October 19 from comet C/2013 A1

International audienceComet C/2013 A1 will make a very close approach with the planet Mars on 2014 October 19. For this event, we compute the density of cometary dust particles around the Mars Express spacecraft, in order to assess the real risk for space probes. We also estimate the zenithal hourly rate (ZHR) and discuss observational opportunities for the resulting Martian meteor shower. We find, for a surface of 2.7 m 2 , that the Mars Express spacecraft will experience approximately 10 impacts from particles larger than 100 µm in size. The fluence per square metre is found to be 3.5 during the encounter. The equivalent ZHR is computed to be ZHR 4.75 × 10 9 h −1 , making this event the strongest meteor storm ever predicted. We call this event a 'meteor hurricane', which we define to be a meteor shower with ZHR exceeding 10 6 h −1

Leidenfrost drops on a heated liquid pool

We show that a volatile liquid drop placed at the surface of a non-volatile liquid pool warmer than the boiling point of the drop can experience a Leidenfrost effect even for vanishingly small superheats. Such an observation points to the importance of the substrate roughness, negligible in the case considered here, in determining the threshold Leidenfrost temperature. A theoretical model based on the one proposed by Sobac et al. [Phys. Rev. E 90, 053011 (2014)] is developed in order to rationalize the experimental data. The shapes of the drop and of the substrate are analyzed. The model notably provides scalings for the vapor film thickness. For small drops, these scalings appear to be identical to the case of a Leidenfrost drop on a solid substrate. For large drops, in contrast, they are different and no evidence of chimney formation has been observed either experimentally or theoretically in the range of drop sizes considered in this study. Concerning the evaporation dynamics, the radius is shown to decrease linearly with time whatever the drop size, which differs from the case of a Leidenfrost drop on a solid substrate. For high superheats, the characteristic lifetime of the drops versus the superheat follows a scaling law that is derived from the model but, at low superheats, it deviates from this scaling by rather saturating

Theory of attosecond delays in laser-assisted photoionization

We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum--continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. This makes clear that the observed time-delays is a sum of two components: a one-photon Wigner-like delay and an universal delay that originates from the probing process itself.Comment: 15 pages, 10 figures, special issue 'Attosecond spectroscopy' Chem. Phy

Phase of harmonics from strongly driven two-level atoms

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