Ignition of Fuel Beds by Cigarettes: A Conceptual Model to Assess Fuel Bed Moisture Content and Wind Velocity Effect on the Ignition Time and Probability

A conceptual model based on the balance of energy in a system composed of a burning cigarette, ambient flow and a porous fuel bed is proposed to study the burning of a single cigarette and the process of fuel bed dehydration, pyrolysis and its eventual ignition or combustion extinction. Model predictions of time to ignition and of the probability of ignition as a function of fuel bed moisture content and ambient flow velocity are compared with results obtained in laboratory ignition tests of straw fuel beds for various ambient conditions. According to this study, the main parameters influencing the models developed are the fuel bed and tobacco moisture content, as well as the flow velocity.

A Systematic Review on the Effect of Transcranial Direct Current and Magnetic Stimulation on Fear Memory and Extinction

Anxiety disorders are among the most prevalent mental disorders. Present treatments such as cognitive behavior therapy and pharmacological treatments show only moderate success, which emphasizes the importance for the development of new treatment protocols. Non-invasive brain stimulation methods such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) have been probed as therapeutic option for anxiety disorders in recent years. Mechanistic information about their mode of action, and most efficient protocols is however limited. Here the fear extinction model can serve as a model of exposure therapies for studying therapeutic mechanisms, and development of appropriate intervention protocols. We systematically reviewed 30 research articles that investigated the impact of rTMS and tDCS on fear memory and extinction in animal models and humans, in clinical and healthy populations. The results of these studies suggest that tDCS and rTMS can be efficient methods to modulate fear memory and extinction. Furthermore, excitability-enhancing stimulation applied over the vmPFC showed the strongest potential to enhance fear extinction. We further discuss factors that determine the efficacy of rTMS and tDCS in the context of the fear extinction model and provide future directions to optimize parameters and protocols of stimulation for research and treatment.

First Light And Reionisation Epoch Simulations (FLARES) II: The Photometric Properties of High-Redshift Galaxies

We present the photometric properties of galaxies in the First Light and Reionisation Epoch Simulations (Flares). The simulations trace the evolution of galaxies in a range of overdensities through the Epoch of Reionistion (EoR). With a novel weighting scheme we combine these overdensities, extending significantly the dynamic range of observed composite distribution functions compared to periodic simulation boxes. Flares predicts a significantly larger number of intrinsically bright galaxies, which can be explained through a simple model linking dust-attenuation to the metal content of the interstellar medium, using a line-of-sight (LOS) extinction model. With this model we present the photometric properties of the Flares galaxies for z ∈ [5, 10]. We show that the ultraviolet (UV) luminosity function (LF) matches the observations at all redshifts. The function is fit by Schechter and double power-law forms, with the latter being favoured at these redshifts by the Flares composite UV LF. We also present predictions for the UV continuum slope as well as the attenuation in the UV. The impact of environment on the UV LF is also explored, with the brightest galaxies forming in the densest environments. We then present the line luminosity and equivalent widths of some prominent nebular emission lines arising from the galaxies, finding rough agreement with available observations. We also look at the relative contribution of obscured and unobscured star formation, finding comparable contributions at these redshifts.

Small-scale clustering of nano-dust grains in supersonic turbulence

ABSTRACT We investigate the clustering and dynamics of nano-sized particles (nano dust) in high-resolution (10243) simulations of compressible isothermal hydrodynamic turbulence. It is well established that large grains will decouple from a turbulent gas flow, while small grains will tend to trace the motion of the gas. We demonstrate that nano-sized grains may cluster in a turbulent flow (fractal small-scale clustering), which increases the local grain density by at least a factor of a few. In combination with the fact that nano-dust grains may be abundant in general, and the increased interaction rate due to turbulent motions, aggregation involving nano dust may have a rather high probability. Small-scale clustering will also affect extinction properties. As an example we present an extinction model based on silicates, graphite, and metallic iron, assuming strong clustering of grain sizes in the nanometre range, could explain the extreme and rapidly varying ultraviolet extinction in the host of GRB 140506A.

How important is it to consider lineage diversification heterogeneity in in macroevolutionary studies: lessons from the lizard family Liolaemidae

Macroevolutionary studies commonly apply multiple models to test state-dependent diversification. These models track the association between states of interest along a phylogeny, but they do not consider whether independent shifts in character states are associated with shifts in diversification rates. This potentially problematic issue has received little theoretical attention, while macroevolutionary studies implementing such models in increasing larger scale studies continue growing. A recent macroevolutionary study has found that Andean orogeny has acted as a species pump driving diversification of the family Liolaemidae, a highly species-rich lizard family native to temperate southern South America.This study approaches a distribution-dependent hypothesis using the Geographic State Speciation and Extinction model (GeoSSE). However, more recent analyses have shown that there is a clear heterogeneous diversification pattern in the Liolaemidae, which likely biased the GeoSSE analysis. Specifically, we show here that there are two shifts to accelered speciation rates involving species groups that were classified as “Andean” in their distributions. We demonstrate that this GeoSSE result is meaningless when heterogeneous diversification rates are included. We use the lizard family Liolaemidae to demonstrate potential risks of ignoring clade-specific differences in diversification rates in macroevolutionary studies.

Hot star extension to the Hubble Space Telescope stellar spectral library

Context. Libraries of stellar spectra find many uses in astrophysics, from photometric calibration to stellar population synthesis. Aims. We present low resolution spectra of 40 stars from 0.2 μm (ultraviolet) to 1.0 μm (near infrared) with excellent fluxing. The stars include normal O-type stars, helium-burning stars, and post-asymptotic giant branch (PAGB) stars. Methods. Spectra were obtained with the Space Telescope Imaging Spectrograph (STIS) installed in the Hubble Space Telescope (HST) using three low resolution gratings, G230LB, G430L, and G750L. Cosmic ray hits and fringing in the red were corrected. A correction for scattered light was applied, significant only for our coolest stars. Cross-correlation was used to bring the spectra to a common, final, zero velocity wavelength scale. Finally, synthetic stellar spectra were used to estimate line of sight dust extinction to each star, and a five-parameter dust extinction model was fit, or a one-parameter fit in the case of low extinction. Results. These spectra dovetail with the similar Next Generation Stellar Library (NGSL) spectra, extending the NGSL’s coverage of stellar parameters, and extending to helium burning stars and stars that do not fuse. Conclusions. The fitted dust extinction model showed considerable variation from star to star, indicating variations in dust properties for different lines of sight. Interstellar absorption lines are present in most stars, notably Mg II.

PROBABILISTIK PUNAHNYA MYCOBACTERIUM TUBERCULOSA YANG RESISTEN TERHADAP OBAT ANTI TUBERKULOSIS RESISTENSI PRIMER, RESISTENSI TERHADAP ISONIAZID, DAN TB–MDR DI PUSKESMAS KOTA MEDAN

In this paper, probabilistic models are developed from a dynamical model of tuberculosis transmission based on a Galton-Watson branching and Negative Binomialdistribution generation with weighted probability estimation used to test an extinction model of mycobacterium germ. The values of model parameters were obtained from the medical record data at Puskesmas Kota Medan : 31 tuberculosis patients treated during February-August 2015, with 25 sensitive samples, 3 samples of RI degree, 2 samples of RII degree, and 3 samples of RIII degree. Data analysis using Galton-Watson theorem revealed the extinction point of resistant malaria parasites, that is s = 1. The successful transmission of mycobacterium bacteria is 36 people per year. The extinction probability of mycobacterium bacteria that is resistant to anti-tuberculosis drugs is ϕNB = 1.