scholarly journals The impact of episodic outflow feedback on stellar multiplicity and the star formation efficiency

2020 ◽  
Vol 500 (3) ◽  
pp. 3594-3612
Author(s):  
P F Rohde ◽  
S Walch ◽  
S D Clarke ◽  
D Seifried ◽  
A P Whitworth ◽  
...  
Keyword(s):  
Star Formation ◽  
Hydrodynamic Simulations ◽  
The Core ◽  
Subgrid Model ◽  
High Incidence ◽  
Smoothed Particle ◽  
The Mean ◽  
Smoothed Particle Hydrodynamic ◽  
Formation Efficiency ◽  
The Impact

ABSTRACT The accretion of material on to young protostars is accompanied by the launching of outflows. Observations show that accretion, and therefore also outflows, are episodic. However, the effects of episodic outflow feedback on the core scale are not well understood. We have performed 88 smoothed particle hydrodynamic simulations of turbulent dense $1 \, {{\mathrm{M}}}_{\odot }$ cores to study the influence of episodic outflow feedback on the stellar multiplicity and the star formation efficiency (SFE). Protostars are represented by sink particles, which use a subgrid model to capture stellar evolution, inner-disc evolution, episodic accretion, and the launching of outflows. By comparing simulations with and without episodic outflow feedback, we show that simulations with outflow feedback reproduce the binary statistics of young stellar populations, including the relative proportions of singles, binaries, triples, etc. and the high incidence of twin binaries with q ≥ 0.95; simulations without outflow feedback do not. Entrainment factors (the ratio between total outflowing mass and initially ejected mass) are typically ∼7 ± 2, but can be much higher if the total mass of stars formed in a core is low and/or outflow episodes are infrequent. By decreasing both the mean mass of the stars formed and the number of stars formed, outflow feedback reduces the SFE by about a factor of 2 (as compared with simulations that do not include outflow feedback).

scholarly journals STAR FORMATION AND FEEDBACK IN SMOOTHED PARTICLE HYDRODYNAMIC SIMULATIONS. II. RESOLUTION EFFECTS

2010 ◽  
Vol 717 (1) ◽  
pp. 121-132 ◽  
Author(s):  
Charlotte R. Christensen ◽  
Thomas Quinn ◽  
Gregory Stinson ◽  
Jillian Bellovary ◽  
James Wadsley
Keyword(s):  
Star Formation ◽  
Hydrodynamic Simulations ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamic

scholarly journals Star formation and feedback in smoothed particle hydrodynamic simulations – I. Isolated galaxies

2006 ◽  
Vol 373 (3) ◽  
pp. 1074-1090 ◽  
Author(s):  
Greg Stinson ◽  
Anil Seth ◽  
Neal Katz ◽  
James Wadsley ◽  
Fabio Governato ◽  
...  
Keyword(s):  
Star Formation ◽  
Hydrodynamic Simulations ◽  
Isolated Galaxies ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamic

The Angular Momentum Problem in CDM Cosmolgies: The End of the Beginning?

2003 ◽  
Vol 208 ◽  
pp. 227-236
Author(s):  
H.M.P. Couchman ◽  
R.J. Thacker
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Hydrodynamic Simulations ◽  
Plausible Model ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamic ◽  
Disc Galaxies ◽  
Scale Length

We show, by adopting a plausible model for star formation and energetic feedback in cosmological simulations of galaxy formation, that we are able to alleviate the angular momentum problem which has bedeviled many previous attempts to generate realistic disc galaxies in Cold Dark Matter cosmogonies. This paper highlights the “cooling catastrophe” as manifest in numerical cosmology and describes a simple prescription for modelling the sub-resolution physics of star formation and feedback in Smoothed Particle Hydrodynamic simulations. We show results for angular momentum and disc scale length for simulations with and without feedback.

scholarly journals Association between stress and bilateral symmetrical alopecia in free-ranging Formosan macaques in Mt. Longevity, Taiwan

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chen-Chih Chen ◽  
Ai-Mei Chang ◽  
Ming-Shan Tsai ◽  
Yen-Hua Huang ◽  
Kurtis Jai-Chyi Pei ◽  
...  
Keyword(s):  
Total Population ◽  
Causative Factor ◽  
Population Status ◽  
Adrenocortical Activity ◽  
High Incidence ◽  
Normal Hair ◽  
The Mean ◽  
The Individual ◽  
Free Ranging ◽  
The Impact

AbstractSince 2013, a high incidence of bilateral symmetrical alopecia has been observed in free-ranging Formosan macaques (Macaca cyclopis) in Mt. Longevity, Taiwan. We hypothesized that stress induces alopecia in this population. To verify our hypothesis, we evaluated the histopathological characteristics of skin biopsy and used a validated enzyme immunoassay (EIA) for fecal glucocorticoid metabolite (FGM) analysis, which act as an indicator of stress experienced by the individual. Follicular densities were lower (2.1–3.0 mm2) in individuals with symmetrical alopecia than in those with normal hair conditions (4.7 mm2). Furthermore, anagen to catagen/telogen ratios were lower in individuals with alopecia (0–1.4) than in those with normal hair (4.0). The histopathological characteristics of alopecia were similar to those of telogen effluvium, which indicates that stress is one of the possible etiologies. On the basis of the analytical and biological validation of EIAs for FGM analysis, 11β-hydroxyetiocholanolone was considered suitable for monitoring adrenocortical activity in both sexes of Formosan macaques. The mean concentrations (standard error; sample size) of 11β-hydroxyetiocholanolone were 2.02 (0.17; n = 10) and 1.41 (0.10; n = 31) μg/g for individuals with and without alopecia, respectively. Furthermore, the results of logistic regression analysis show that 11β-hydroxyetiocholanolone (p = 0.012) concentration was positively associated with alopecia. Thus, stress was the most likely to trigger symmetrical alopecia in Formosan macaques in Mt. Longevity. Although stress can decrease the fitness of an individual, considering the population status of Formosan macaques in Taiwan is stable and alopecia was only observed in our study area, which is isolated from other populations, the impact on the total population of Formosan macaque in Taiwan is limited. Nonetheless, stress-induced immunosuppression and alopecia might affect the local abundance and increase zoonosis risk due to frequent human–macaque contact in Mt. Longevity. Future studies are suggested to focus on the causative factor of stress and the effects of stress and alopecia on the health and welfare in the Formosan macaques.

Numerical Simulation of Wave Breaking Over a Submerged Step with SPH Method

2018 ◽  
Vol 01 (02) ◽  
pp. 1840005 ◽  
Author(s):  
Hongjie Wen ◽  
Bing Ren ◽  
Guoyu Wang ◽  
Yumeng Zhao
Keyword(s):  
Wave Breaking ◽  
Sph Method ◽  
Vertical Distributions ◽  
Sph Model ◽  
Smoothed Particle ◽  
Mean Water Level ◽  
The Mean ◽  
Wave Maker ◽  
Wave Induced ◽  
Smoothed Particle Hydrodynamic

Wave breaking over a submerged step with a steep front slope and a wide horizontal platform is studied by smoothed particle hydrodynamic (SPH) method. By adding a momentum source term and a velocity attenuation term into the governing equation, a nonreflective wave maker system is introduced in the numerical model. A suitable circuit channel is specifically designed for the present SPH model to avoid the nonphysical rise of the mean water level on the horizontal platform of the submerged step. The predicted free surface elevations and the spatial distributions of wave height and wave setup over the submerged step are validated using the corresponding experimental data. In addition, the vertical distributions of wave-induced current over the submerged step are also investigated at both low and high tides.

Analysis of Contact Mechanics and Smoothed Particle Hydrodynamic Simulations of Viscoelastic Polymer Sine Waves

2015 ◽  
Author(s):  
Nick Cramer ◽  
Janet Chao ◽  
Travis Tollefson ◽  
M. Teodorescu
Keyword(s):  
United States ◽  
Head And Neck ◽  
Contact Mechanics ◽  
The United States ◽  
Head And Neck Cancers ◽  
Malignant Neoplasms ◽  
Invasive Procedures ◽  
Hydrodynamic Simulations ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamic

According the American Cancer Society’s data, in 2013, an estimated 53,640 people developed head and neck cancers [1], which accounts for about 3% to 5% of all cancers in the United States. Removing head and neck malignant neoplasms is one of the first stages towards patient recovery. However, these types of invasive procedures often lead to disfiguring scars and resections with functional and aesthetical drawbacks (see Figure 1).

Sign in / Sign up

Export Citation Format

Share Document