Social Information Guides Infants' Selection of Foods

Two experiments investigated the influence of socially conveyed emotions and speech on infants' choices among food. After watching films in which two unfamiliar actresses each spoke while eating a different kind of food, 12-month-old infants were allowed to choose between the two foods. In Experiment 1, infants selected a food endorsed by a speaker of their native language who displayed positive affect over a food endorsed by a foreign-language speaker who displayed negative affect. In Experiment 2, both actresses displayed positive affect, but they spoke in different languages, and infants again selected the food associated with the speaker of their native language. The findings contrast with previous research in which infants and toddlers have shown little selectivity when presented with foods that differ in their intrinsic properties such as color, texture, and familiarity. Although infants may lack capacities for evaluating foods on their own, they do look to other people for guidance in food selection.Psycholog

Applying machine learning to improve simulations of a chaotic dynamical system using empirical error correction

Dynamical weather and climate prediction models underpin many studies of the Earth system and hold the promise of being able to make robust projections of future climate change based on physical laws. However, simulations from these models still show many differences compared with observations. Machine learning has been applied to solve certain prediction problems with great success, and recently it's been proposed that this could replace the role of physically-derived dynamical weather and climate models to give better quality simulations. Here, instead, a framework using machine learning together with physically-derived models is tested, in which it is learnt how to correct the errors of the latter from timestep to timestep. This maintains the physical understanding built into the models, whilst allowing performance improvements, and also requires much simpler algorithms and less training data. This is tested in the context of simulating the chaotic Lorenz '96 system, and it is shown that the approach yields models that are stable and that give both improved skill in initialised predictions and better long-term climate statistics. Improvements in long-term statistics are smaller than for single time-step tendencies, however, indicating that it would be valuable to develop methods that target improvements on longer time scales. Future strategies for the development of this approach and possible applications to making progress on important scientific problems are discussed.Comment: 26p, 7 figures To be published in Journal of Advances in Modeling Earth System

MacV: VCSELs for miniature atomic clocks

Compact coherent population trapping (CPT) based clocks require single-mode, low-power consumption, high-speed and polarization-stable laser sources. We report our progress in developing customized vertical cavity surface emitting laser (VCSEL) diodes designed for operating on the D1 transition of cesium, and specifically tailored for CPT-based atomic clocks. The VCSELs provide high power (>1 mW), narrow linewidths (15 dB). Preliminary spectroscopy has been observed

Increasing Maximum Gain in InAs Quantum Dot Lasers on GaAs and Si

InAs quantum-dot (QD) lasers emitting at 1300nm with nominally undoped and modulated p-type doping are studied. Modal-gain measurements indicate a higher gain can be achieved from the ground-state for a given Fermi-level separation with p-doping and a reduced temperature-dependence of threshold current for short-cavity lasers

Temperature dependent behavior of the optical gain and electroabsorption modulation properties of an InAs/GaAs quantum dot epistructure

In this work, the feasibility of a monolithically integrated laser and electroabsorption modulator based on the same active quantum dot epistructure is studied. The net modal gain and the absorption in the modulator were measured using the segmented contact method from 25 °C to 125 °C. The maximum of the net modal gain active region of the laser decreases from 10 cm -1 at 25 °C to 3.9 cm -1 at 125 °C. The non-optimized maximum extinction ratio of the modulator, 4.1 dB·mm -1 , is almost constant until 25 °C. The wavelengths at which the net modal gain and the change in absorption are maximum shifts with temperature by 0.04 eV

Impact of thermal oxidation uniformity on 150 mm GaAs- and Ge-substrate VCSELs

Vertical cavity surface emitting laser (VCSEL) devices and arrays are increasingly important in meeting the demands of today’s wireless communication and sensing systems. Understanding the origin of non-uniform wet thermal oxidation across large-area VCSEL wafers is a crucial issue to ensure highly reliable, volume-manufactured oxide-confined VCSEL devices. As VCSEL wafer diameters approach 200 mm, germanium (Ge) is emerging as an alternative substrate solution. To this end, we investigate the uniformity of 940 nm-emitting VCSEL performance across 150 mm diameter GaAs- and Ge-substrates, comparing the oxidation method in each case. Nominally identical epitaxial structures are used to evaluate the strain induced wafer bow for each substrate type with Ge exhibiting a reduction of over 100 μm in the peak-to-valley distortion when compared with GaAs. This wafer bow is found to be the principal cause of centre-to-edge oxidation non-uniformity when utilising a conduction-heated chuck furnace, in comparison to a convection-heated tube furnace. Using on-wafer testing of threshold current, differential resistance, and emission wavelength, device performance is demonstrated for the first time across a 150 mm Ge wafer, and is shown to be comparable to performance on GaAs substrates, when the effects of oxidation uniformity are removed. These results provide evidence that there is a realistic path to manufacturing high yield VCSELs, over wafer diameters approaching those used in Si-photonics, via Ge substrates

Atmospheric blocking and upper-level Rossby wave forecast skill dependence on model configuration

Weather models differ in their ability to forecast, at medium range, atmospheric blocking and the associated structure of upper-level Rossby waves. Here, we evaluate the effect of a model's dynamical core on such forecasts. Operational forecasts from the ensemble prediction systems (EPSs) of the European Centre for Medium-range Weather Forecasts (ECMWF), the Met Office (MO) and the Korean Meteorological Administration (KMA) are used. Northern hemisphere model output is analysed from winters before and after a major upgrade to the dynamical core of the MO-EPS. The KMA-EPS acts as a control as it uses the same model as the MO-EPS, but used the older dynamical core throughout. The confounding factor of resolution differences between the MO-EPS and the KMA-EPS is assessed using a MO forecast model hindcast experiment with the more recent dynamical core, but the operational resolution of the KMA-EPS. The introduction of the new dynamical core in the MO-EPS has led to increased forecast blocking frequency, at lead times of five and seven days, counteracting the typically-observed reduction in blocking frequency with lead time. Hit rates of blocking activity, onset and decay are also increased in the main blocking regions (without a corresponding increase in false positive rate). The previously-found reduction of upper-level ridge area and tropopause sharpness (measured by isentropic potential vorticity gradient) with lead time is also reduced with the new dynamical core. This dynamical core improvement (associated with a reduction in implicit damping) is thus demonstrated to be at least as effective as operational resolution improvements in improving forecasts of upper-level Rossby waves and associated blocking