A Direct Comparison of Lyman-Alpha and Neutral Hydrogen Morphologies

The Lyman-Alpha Reference Sample (LARS) and its extension (eLARS) represent an exhaustive campaign to reverse-engineer galaxies. The main goal is to understand how \lya radiation is transported within galaxies: what fraction of it escapes, and what physical properties affect the \lya morphology and radiative transport (e.g., dust and gas content, metallicity, kinematics, properties of the producing and underlying stellar populations). Two galaxies from the sample, LARS02 and LARS09, were observed using the B and C configurations of the Very Large Array to examine the neutral hydrogen emission, which can be used to determine a galaxy\u27s neutral hydrogen (HI) structure and kinematics. Images of the \HI mass surface density and of the intensity weighted \HI velocity field were created at angular scales of $\sim$8 arcseconds, which corresponds to $\sim$5 kpc for LARS02 and $\sim$8 kpc for LARS09. Extended \HI gas is detected at high significance up to $\sim$30 kpc from the optical body of LARS02. LARS09 has a severely disturbed optical morphology; our new \HI observations reveal that LARS09 is interacting with the nearby field galaxy SDSS J082353.65+280622.2. By combining these moment maps with direct imaging of the \lya morphology from the Hubble Space Telescope, this program has produced the first direct comparison of \lya and \HI morphologies. These observations demonstrate concept for a significant observational campaign to produce similar comparisons in the remaining 40 LARS and eLARS galaxies

Model-based estimation of off-highway road geometry using single-axis LADAR and inertial sensing

This paper applies some previously studied extended Kalman filter techniques for planar road geometry estimation to the domain of autonomous navigation of off-highway vehicles. In this work, a clothoid model of the road geometry is constructed and estimated recursively based on road features extracted from single-axis LADAR range measurements. We present a method for feature extraction of the road centerline in the image plane, and describe its application to recursive estimation of the road geometry. We analyze the performance of our method against simulated motion of varied road geometries and against closed-loop detection, tracking and following of desert roads. Our method accomodates full 6 DOF motion of the vehicle as it navigates, constructs consistent estimates of the road geometry with respect to a fixed global reference frame, and requires an estimate of the sensor pose for each range measurement

Threshold games and cooperation on multiplayer graphs

Objective: The study investigates the effect on cooperation in multiplayer games, when the population from which all individuals are drawn is structured - i.e. when a given individual is only competing with a small subset of the entire population. Method: To optimize the focus on multiplayer effects, a class of games were chosen for which the payoff depends nonlinearly on the number of cooperators - this ensures that the game cannot be represented as a sum of pair-wise interactions, and increases the likelihood of observing behaviour different from that seen in two-player games. The chosen class of games are named "threshold games", and are defined by a threshold, $M > 0$, which describes the minimal number of cooperators in a given match required for all the participants to receive a benefit. The model was studied primarily through numerical simulations of large populations of individuals, each with interaction neighbourhoods described by various classes of networks. Results: When comparing the level of cooperation in a structured population to the mean-field model, we find that most types of structure lead to a decrease in cooperation. This is both interesting and novel, simply due to the generality and breadth of relevance of the model - it is likely that any model with similar payoff structure exhibits related behaviour. More importantly, we find that the details of the behaviour depends to a large extent on the size of the immediate neighbourhoods of the individuals, as dictated by the network structure. In effect, the players behave as if they are part of a much smaller, fully mixed, population, which we suggest an expression for.Comment: in PLOS ONE, 4th Feb 201

Vertical distribution and composition of phytoplankton under the influence of an upper mixed layer

The vertical distribution of phytoplankton is of fundamental importance for the dynamics and structure of aquatic communities. Here, using an advection-reaction-diffusion model, we investigate the distribution and competition of phytoplankton species in a water column, in which inverse resource gradients of light and a nutrient can limit growth of the biomass. This problem poses a challenge for ecologists, as the location of a production layer is not fixed, but rather depends on many internal parameters and environmental factors. In particular, we study the influence of an upper mixed layer (UML) in this system and show that it leads to a variety of dynamic effects: (i) Our model predicts alternative density profiles with a maximum of biomass either within or below the UML, thereby the system may be bistable or the relaxation from an unstable state may require a long-lasting transition. (ii) Reduced mixing in the deep layer can induce oscillations of the biomass; we show that a UML can sustain these oscillations even if the diffusivity is less than the critical mixing for a sinking phytoplankton population. (iii) A UML can strongly modify the outcome of competition between different phytoplankton species, yielding bistability both in the spatial distribution and in the species composition. (iv) A light limited species can obtain a competitive advantage if the diffusivity in the deep layers is reduced below a critical value. This yields a subtle competitive exclusion effect, where the oscillatory states in the deep layers are displaced by steady solutions in the UML. Finally, we present a novel graphical approach for deducing the competition outcome and for the analysis of the role of a UML in aquatic systems.Comment: 20 pages, 8 figure

Transport- reaction modeling of marine gas hydrate deposits- global results

We have developed a multi-1D numerical model of gas hydrate formation and dissolution processes in anoxic marine sediments and, by this model, we have estimated the new global gas hydrate inventory (BURWICZ E. B. et al., 2011). The reaction-transport model contains various chemical compounds (solid organic carbon, dissolved methane, inorganic carbon, and sulfates, gas hydrates, and free methane gas). The rates of POC degradation, anaerobic methane oxidation, sulfate reduction, and methanogenesis are kinetically controlled. Gas hydrate stability zone (GHSZ) is defined as a combination of pressure, temperature, and (to a smaller degree) salinity conditions. The lower boundary of the GHSZ is defined as the intersection of gas hydrate and methane gas solubilities. The diffusion equations are solved using a fully-implicit finite-differences method, while all transport processes are resolved by a Semi-Lagrangian scheme. Global input data sets (1°x1° resolution) were compiled from various oceanographic, geological and geophysical sources. The entire model was implemented in Matlab

Childhood Peer Status and the Clustering of Adverse Living Conditions in Adulthood

Within the context of the school class, children attain a social position in the peer hierarchy to which varying amounts of status are attached. Several studies have shown that children’s peer status is associated with a wide range of social and health-related outcomes. These studies commonly target separate outcomes, paying little attention to the fact that such circumstances are likely to go hand in hand. The overarching aim of the present study was therefore to examine the impact of childhood peer status on the clustering of living conditions in adulthood. Based on a 1953 cohort born in Stockholm, Sweden, multinomial regression analysis demonstrated that children who had lower peer status also had exceedingly high risks of ending up in more problem-burdened clusters as adults. Moreover, these associations remained after adjusting for a variety of family-related circumstances. We conclude that peer status constitutes a central aspect of children’s upbringing with important consequences for subsequent life chances, over and above the influences originating from the family.childhood; peer status; cohort; life course; outcome profiles; living conditions

Model Regresi Menggunakan Least Absolute Shrinkage and Selection Operator (Lasso) Pada Data Banyaknya Gizi Buruk Kabupaten/kota Di Jawa Tengah

Gizi buruk adalah bentuk terparah dari proses terjadinya kekurangan gizi yang menahun. Gizi buruk dipengaruhi oleh banyak faktor yang saling terkait. Dalam penelitian ini, dilakukan pemodelan dari faktor-faktor yang mempengaruhi gizi buruk menggunakan metode Least Absolute Shrinkage Selection and Operator (LASSO) dengan algoritma Least Angle Regression (LARS) karena pada faktor-faktor yang mempengaruhi gizi buruk terdeteksi multikolinearitas. LASSO menyusutkan koefisien regresi dari variabel bebas yang memiliki korelasi tinggi menjadi tepat pada nol atau mendekati nol. Koefisien LASSO dicari dengan menggunakan pemrograman kuadratik sehingga digunakan algoritma LARS yang lebih efisien dalam komputasi LASSO. Berdasarkan analisis yang telah dilakukan, model LASSO pada data gizi buruk Kabupaten/Kota di Jawa Tengah tahun 2014 diperoleh pada tahap kedua saat nilai s=0.02 dengan nilai MSE sebesar 0,82977. Disimpulkan bahwa variabel bayi (0-6 Bulan) yang diberi ASI Eksklusif, rumah tangga berperilaku hidup bersih dan sehat, bayi yang mendapat imunisasi Hepatitis B, bayi yang mendapat imunisasi DPT-HB3, rumah dengan sanitasi yang layak, dan rumah dengan air minum sesuai dengan syarat kesehatan berpengaruh terhadap bayi gizi buruk di Jawa Tengah tahun 2014