A collaborative approach to learning programming: a hybrid learning model

The use of cooperative working as a means of developing collaborative skills has been recognised as vital in programming education. This paper presents results obtained from preliminary work to investigate the effectiveness of Pair Programming as a collaborative learning strategy and also its value towards improving programming skills within the laboratory. The potential of Problem Based Learning as a means of further developing cooperative working skills along with problem solving skills is also examined and a hybrid model encompassing both strategies outlined

The Difficulty of Getting High Escape Fractions of Ionizing Photons from High-redshift Galaxies: a View from the FIRE Cosmological Simulations

We present a series of high-resolution (20-2000 Msun, 0.1-4 pc) cosmological zoom-in simulations at z~6 from the Feedback In Realistic Environment (FIRE) project. These simulations cover halo masses 10^9-10^11 Msun and rest-frame ultraviolet magnitude Muv = -9 to -19. These simulations include explicit models of the multi-phase ISM, star formation, and stellar feedback, which produce reasonable galaxy properties at z = 0-6. We post-process the snapshots with a radiative transfer code to evaluate the escape fraction (fesc) of hydrogen ionizing photons. We find that the instantaneous fesc has large time variability (0.01%-20%), while the time-averaged fesc over long time-scales generally remains ~5%, considerably lower than the estimate in many reionization models. We find no strong dependence of fesc on galaxy mass or redshift. In our simulations, the intrinsic ionizing photon budgets are dominated by stellar populations younger than 3 Myr, which tend to be buried in dense birth clouds. The escaping photons mostly come from populations between 3-10 Myr, whose birth clouds have been largely cleared by stellar feedback. However, these populations only contribute a small fraction of intrinsic ionizing photon budgets according to standard stellar population models. We show that fesc can be boosted to high values, if stellar populations older than 3 Myr produce more ionizing photons than standard stellar population models (as motivated by, e.g., models including binaries). By contrast, runaway stars with velocities suggested by observations can enhance fesc by only a small fraction. We show that "sub-grid" star formation models, which do not explicitly resolve star formation in dense clouds with n >> 1 cm^-3, will dramatically over-predict fesc.Comment: 17 pages, 16 figures, MNRAS in pres

Abell 1201: a Minor merger at second core passage

We present an analysis of the structures and dynamics of the merging cluster Abell~1201, which has two sloshing cold fronts around a cooling core, and an offset gas core approximately 500kpc northwest of the center. New Chandra and XMM-Newton data reveal a region of enhanced brightness east of the offset core, with breaks in surface brightness along its boundary to the north and east. This is interpreted as a tail of gas stripped from the offset core. Gas in the offset core and the tail is distinguished from other gas at the same distance from the cluster center chiefly by having higher density, hence lower entropy. In addition, the offset core shows marginally lower temperature and metallicity than the surrounding area. The metallicity in the cool core is high and there is an abrupt drop in metallicity across the southern cold front. We interpret the observed properties of the system, including the placement of the cold fronts, the offset core and its tail in terms of a simple merger scenario. The offset core is the remnant of a merging subcluster, which first passed pericenter southeast of the center of the primary cluster and is now close to its second pericenter passage, moving at ~1000 km/s. Sloshing excited by the merger gave rise to the two cold fronts and the disposition of the cold fronts reveals that we view the merger from close to the plane of the orbit of the offset core.Comment: accepted by Ap

Missing binary outcomes under covariate-dependent missingness in cluster randomised trials.

Missing outcomes are a commonly occurring problem for cluster randomised trials, which can lead to biased and inefficient inference if ignored or handled inappropriately. Two approaches for analysing such trials are cluster-level analysis and individual-level analysis. In this study, we assessed the performance of unadjusted cluster-level analysis, baseline covariate-adjusted cluster-level analysis, random effects logistic regression and generalised estimating equations when binary outcomes are missing under a baseline covariate-dependent missingness mechanism. Missing outcomes were handled using complete records analysis and multilevel multiple imputation. We analytically show that cluster-level analyses for estimating risk ratio using complete records are valid if the true data generating model has log link and the intervention groups have the same missingness mechanism and the same covariate effect in the outcome model. We performed a simulation study considering four different scenarios, depending on whether the missingness mechanisms are the same or different between the intervention groups and whether there is an interaction between intervention group and baseline covariate in the outcome model. On the basis of the simulation study and analytical results, we give guidance on the conditions under which each approach is valid. © 2017 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd

Protein Kinase A Subunit α Catalytic and A Kinase Anchoring Protein 79 in Human Placental Mitochondria

Components of protein phosphorylation signalling systems have been discovered in mitochondria and it has been proposed that these molecules modulate processes including oxidative phosphorylation, apoptosis and steroidogenesis

Traveling waves for a model of the Belousov-Zhabotinsky reaction

Following J.D. Murray, we consider a system of two differential equations that models traveling fronts in the Noyes-Field theory of the Belousov-Zhabotinsky (BZ) chemical reaction. We are also interested in the situation when the system incorporates a delay $h\geq 0$. As we show, the BZ system has a dual character: it is monostable when its key parameter $r \in (0,1]$ and it is bistable when $r >1$. For $h=0, r\not=1$, and for each admissible wave speed, we prove the uniqueness of monotone wavefronts. Next, a concept of regular super-solutions is introduced as a main tool for generating new comparison solutions for the BZ system. This allows to improve all previously known upper estimations for the minimal speed of propagation in the BZ system, independently whether it is monostable, bistable, delayed or not. Special attention is given to the critical case $r=1$ which to some extent resembles to the Zeldovich equation.Comment: 23 pages, to appear in the Journal of Differential Equation

Robot navigation in dense human crowds: Statistical models and experimental studies of human–robot cooperation

We consider the problem of navigating a mobile robot through dense human crowds. We begin by exploring a fundamental impediment to classical motion planning algorithms called the “freezing robot problem”: once the environment surpasses a certain level of dynamic complexity, the planner decides that all forward paths are unsafe, and the robot freezes in place (or performs unnecessary maneuvers) to avoid collisions. We argue that this problem can be avoided if the robot anticipates human cooperation, and accordingly we develop interacting Gaussian processes, a prediction density that captures cooperative collision avoidance, and a “multiple goal” extension that models the goal-driven nature of human decision making. We validate this model with an empirical study of robot navigation in dense human crowds (488 runs), specifically testing how cooperation models effect navigation performance. The multiple goal interacting Gaussian processes algorithm performs comparably with human teleoperators in crowd densities nearing 0.8 humans/m^2, while a state-of-the-art non-cooperative planner exhibits unsafe behavior more than three times as often as the multiple goal extension, and twice as often as the basic interacting Gaussian process approach. Furthermore, a reactive planner based on the widely used dynamic window approach proves insufficient for crowd densities above 0.55 people/m^2. We also show that our non-cooperative planner or our reactive planner capture the salient characteristics of nearly any dynamic navigation algorithm. Based on these experimental results and theoretical observations, we conclude that a cooperation model is critical for safe and efficient robot navigation in dense human crowds