Infrared Observations During the Secondary Eclipse of HD 209458 b II. Strong Limits on the Infrared Spectrum Near 2.2 Microns

We report observations of the transiting extrasolar planet, HD 209458 b, designed to detect the secondary eclipse. We employ the method of `occultation spectroscopy', which searches in combined light (star and planet) for the disappearance and reappearance of weak infrared spectral features due to the planet as it passes behind the star and reappears. Our observations cover two predicted secondary eclipse events, and we obtained 1036 individual spectra of the HD 209458 system using the SpeX instrument at the NASA IRTF in September 2001. Our spectra extend from 1.9 to 4.2 microns with a spectral resolution of 1500. We have searched for a continuum peak near 2.2 microns (caused by CO and water absorption bands), as predicted by some models of the planetary atmosphere to be approximately 6E-4 of the stellar flux, but no such peak is detected at a level of about 3E-4 of the stellar flux. Our results represent the strongest limits on the infrared spectrum of the planet to date and carry significant implications for understanding the planetary atmosphere. In particular, some models that assume the stellar irradiation is re-radiated entirely on the sub-stellar hemisphere predict a flux peak inconsistent with our observations. Several physical mechanisms can improve agreement with our observations, including the re-distribution of heat by global circulation, a nearly isothermal atmosphere, and/or the presence of a high cloud.Comment: Accepted to the Astrophysical Journal 17 pages, 6 figure

An all-fibre PM MOPA pumped high-power OPO at 3.82 microns based on large aperture PPMgLN

We report a large aperture PPMgLN based OPO generating 21W of average output power at a slope efficiency of 45%, pumped by the output from a polarization maintaining Ytterbium doped fiber MOPA operating at 1060nm producing 58W of average output power and 20ns pulses at a repetition rate of 100kHz. A maximum of 5.5W of optical power was recorded at the idler wavelength of 3.82µm without thermal roll-off. We have experimentally verified that the pulse rise/fall time plays a significant role in the OPO conversion efficiency and that further enhancement in the OPO conversion efficiency will be possible using sub-nanosecond rise and fall times

Geometry and violent events in turbulent pair dispersion

The statistics of Lagrangian pair dispersion in a homogeneous isotropic flow is investigated by means of direct numerical simulations. The focus is on deviations from Richardson eddy-diffusivity model and in particular on the strong fluctuations experienced by tracers. Evidence is obtained that the distribution of distances attains an almost self-similar regime characterized by a very weak intermittency. The timescale of convergence to this behavior is found to be given by the kinetic energy dissipation time measured at the scale of the initial separation. Conversely the velocity differences between tracers are displaying a strongly anomalous behavior whose scaling properties are very close to that of Lagrangian structure functions. These violent fluctuations are interpreted geometrically and are shown to be responsible for a long-term memory of the initial separation. Despite this strong intermittency, it is found that the mixed moment defined by the ratio between the cube of the longitudinal velocity difference and the distance attains a statistically stationary regime on very short timescales. These results are brought together to address the question of violent events in the distribution of distances. It is found that distances much larger than the average are reached by pairs that have always separated faster since the initial time. They contribute a stretched exponential behavior in the tail of the inter-tracer distance probability distribution. The tail approaches a pure exponential at large times, contradicting Richardson diffusive approach. At the same time, the distance distribution displays a time-dependent power-law behavior at very small values, which is interpreted in terms of fractal geometry. It is argued and demonstrated numerically that the exponent converges to one at large time, again in conflict with Richardson's distribution.Comment: 21 page

Josephson effect between superconducting nanograins with discrete energy levels

We investigate the Josephson effect between two coupled superconductors, coupled by the tunneling of pairs of electrons, in the regime that their energy level spacing is comparable to the bulk superconducting gap, but neglecting any charging effects. In this regime, BCS theory is not valid, and the notion of a superconducting order parameter with a well-defined phase is inapplicable. Using the density matrix renormalization group, we calculate the ground state of the two coupled superconductors and extract the Josephson energy. The Josephson energy is found to display a reentrant behavior (decrease followed by increase) as a function of increasing level spacing. For weak Josephson coupling, a tight-binding approximation is introduced, which illustrates the physical mechanism underlying this reentrance in a transparent way. The DMRG method is also applied to two strongly coupled superconductors and allows a detailed examination of the limits of validity of the tight-binding model

High energy in-band pumped erbium doped pulse fibre laser

We demonstrate an inband, core-pumped master oscillator power amplifier (MOPA) with a maximum pulse energy of 1.56 mJ at a repetition rate of 1.25 kHz, seeded by an actively Q-switched Erbium/Ytterbium-codoped fiber (EYDF) ring laser, producing 150 ns pulses at 1562.5 nm. To maximize energy extraction whilst minimizing signal saturation effects, a 40 µm Er3+-doped larger mode area (LMA) fiber was used as the gain medium. A 1535 nm single mode fiber laser was used for in-band pumping of the LMA fiber. The output beam quality (M2) was measured to be ~1.6. This is to the best of our knowledge is the highest reported pulse energy for a pulse fiber laser at 1.5 µm with M2~1.6

The Dynamical Masses, Densities, and Star Formation Scaling Relations of Lyman Alpha Galaxies

We present the first dynamical mass measurements for Lyman alpha galaxies at high redshift, based on velocity dispersion measurements from rest-frame optical emission lines and size measurements from HST imaging, for a sample of nine galaxies drawn from four surveys. These measurements enable us to study the nature of Lyman alpha galaxies in the context of galaxy scaling relations. The resulting dynamical masses range from 1e9 to 1e10 solar masses. We also fit stellar population models to our sample, and use them to plot the Lyman alpha sample on a stellar mass vs. line width relation. Overall, the Lyman alpha galaxies follow well the scaling relation established by observing star forming galaxies at lower redshift (and without regard for Lyman alpha emission), though in 1/3 of the Lyman alpha galaxies, lower-mass fits are also acceptable. In all cases, the dynamical masses agree with established stellarmass-linewidth relation. Using the dynamical masses as an upper limit on gas mass, we show that Lyman alpha galaxies resemble starbursts (rather than "normal" galaxies) in the relation between gas mass surface density and star formation activity, in spite of relatively modest star formation rates. Finally, we examine the mass densities of these galaxies, and show that their future evolution likely requires dissipational ("wet") merging. In short, we find that Lyman alpha galaxies are low mass cousins of larger starbursts.Comment: Submitted to The Astrophysical Journal. 23 pp including three figures and four table

New Evidence of Discrete Scale Invariance in the Energy Dissipation of Three-Dimensional Turbulence: Correlation Approach and Direct Spectral Detection

We extend the analysis of [Zhou and Sornette, Physica D 165, 94-125, 2002] showing statistically significant log-periodic corrections to scaling in the moments of the energy dissipation rate in experiments at high Reynolds number ($\approx 2500$) of three-dimensional fully developed turbulence. First, we develop a simple variant of the canonical averaging method using a rephasing scheme between different samples based on pairwise correlations that confirms Zhou and Sornette's previous results. The second analysis uses a simpler local spectral approach and then performs averages over many local spectra. This yields stronger evidence of the existence of underlying log-periodic undulations, with the detection of more than 20 harmonics of a fundamental logarithmic frequency $f = 1.434 \pm 0.007$ corresponding to the preferred scaling ratio $\gamma = 2.008 \pm 0.006$.Comment: 9 RevTex4 papes including 8 eps figure

High power femtosecond source based on passively mode-locked 1055nm VECSEL and Yb-fibre power amplifier

We report 5 ns pulses at 160 W average power and 910 repetition rate from a passively mode-locked VECSEL source seeding an Yb-doped fibre power amplifier. The amplified pulses were compressed to 291 fs duration

"Boring formal methods" or "Sherlock Holmes deduction methods"?

This paper provides an overview of common challenges in teaching of logic and formal methods to Computer Science and IT students. We discuss our experiences from the course IN3050: Applied Logic in Engineering, introduced as a "logic for everybody" elective course at at TU Munich, Germany, to engage pupils studying Computer Science, IT and engineering subjects on Bachelor and Master levels. Our goal was to overcome the bias that logic and formal methods are not only very complicated but also very boring to study and to apply. In this paper, we present the core structure of the course, provide examples of exercises and evaluate the course based on the students' surveys.Comment: Preprint. Accepted to the Software Technologies: Applications and Foundations (STAF 2016). Final version published by Springer International Publishing AG. arXiv admin note: substantial text overlap with arXiv:1602.0517

An Evaluation of the Efficacy of GraphoGame Rime for Promoting English Phonics Knowledge in Poor Readers

© Copyright © 2020 Ahmed, Wilson, Mead, Noble, Richardson, Wolpert and Goswami. Here, we report further analysis of data drawn from a Randomized Controlled Trial (RCT) run in the United Kingdom designed to evaluate the efficacy of an adaptive software game to aid the learning of English phonics, GraphoGame Rime. We evaluate the efficacy of GraphoGame Rime for the “top half” of players in the RCT, children aged 6 to 7 years who played above the group mean play progress point (95 children). We also analyze three sub-groupings of this cohort. The GraphoGame family of games in different languages was originally designed to support children at family risk of dyslexia, hence we analyzed data for the subgroup of the GraphoGame Rime children who were struggling in school and had Individual Education Plans (IEPs). Secondly, we analyzed data from the younger children in the RCT, born in the Spring and Summer months, as international studies of GraphoGame have found the strongest effects during the first year of reading tuition and our participants were in their second year of reading tuition. Finally, we analyzed GraphoGame Rime data from players in schools rated as “requiring improvement.” Schools that are found to be “requiring improvement” in the United Kingdom are encouraged to use additional teaching strategies to achieve better outcomes. GraphoGame Rime is relatively cheap to acquire and easy to implement, hence if it offers significant gains over “business-as-usual” this would be a valulable additional strategy for such schools. We find that GraphoGame Rime is more effective than “business-as-usual” in developing knowledge of English phonics for all of the groupings analyzed. We conclude that the supplementary use of GraphoGame Rime in addition to ongoing classroom literacy instruction can benefit children in learning phonic decoding and spelling skills.Wellcome Trus