234 research outputs found
3-D Kinematics of the HH 110 jet
We present new results on the kinematics of the jet HH 110. New proper motion
measurements have been calculated from [SII] CCD images obtained with a time
baseline of nearly fifteen years. HH 110 proper motions show a strong asymmetry
with respect to the outflow axis, with a general trend of pointing towards the
west of the axis direction. Spatial velocities have been obtained by combining
the proper motions and radial velocities from Fabry-Perot data. Velocities
decrease by a factor ~3 over a distance of ~10 cm, much shorter than the
distances expected for the braking caused by the jet/environment interaction.
Our results show evidence of an anomalously strong interaction between the
outflow and the surrounding environment, and are compatible with the scenario
in which HH 110 emerges from a deflection in a jet/cloud collision.Comment: (1)Universitat de Barcelona; (2)UNAM; (3)UPC; (4)University of
Hawaii; (5)Southern Astrophysical Research Telescope. 9 pages; 7 Figures
Accepted by A&
Observations and simulations of recurrent novae: U Sco and V394 CrA
Observations and analysis of the Aug. 1987 outburst of the recurrent nova V394 CrA are presented. This nova is extremely fast and its outburst characteristics closely resemble those of the recurrent nova U Sco. Hydrodynamic simulations of the outbursts of recurrent novae were performed. Results as applied to the outbursts of V394 CrA and U Sco are summarized
On the Hydrodynamic Interaction of Shock Waves with Interstellar Clouds. II. The Effect of Smooth Cloud Boundaries on Cloud Destruction and Cloud Turbulence
The effect of smooth cloud boundaries on the interaction of steady planar
shock waves with interstellar clouds is studied using a high-resolution local
AMR technique with a second-order accurate axisymmetric Godunov hydrodynamic
scheme. A 3D calculation is also done to confirm the results of the 2D ones. We
consider an initially spherical cloud whose density distribution is flat near
the cloud center and has a power-law profile in the cloud envelope. When an
incident shock is transmitted into a smooth cloud, velocity gradients in the
cloud envelope steepen the smooth density profile at the upstream side,
resulting in a sharp density jump having an arc-like shape. Such a ``slip
surface'' forms immediately when a shock strikes a cloud with a sharp boundary.
For smoother boundaries, the formation of slip surface and therefore the onset
of hydrodynamic instabilities are delayed. Since the slip surface is subject to
the Kelvin-Helmholtz and Rayleigh-Taylor instabilities, the shocked cloud is
eventually destroyed in cloud crushing times. After complete cloud
destruction, small blobs formed by fragmentation due to hydrodynamic
instabilities have significant velocity dispersions of the order of 0.1 ,
where is the shock velocity in the ambient medium. This suggests that
turbulent motions generated by shock-cloud interaction are directly associated
with cloud destruction. The interaction of a shock with a cold HI cloud should
lead to the production of a spray of small HI shreds, which could be related to
the small cold clouds recently observed by Stanimirovic & Heiles (2005). The
linewidth-size relation obtained from our 3D simulation is found to be
time-dependent. A possibility for gravitational instability triggered by shock
compression is also discussed.Comment: 62 pages, 16 figures, submitted to Ap
Evolution of non-kin cooperation:social assortment by cooperative phenotype in guppies
© 2019 The Authors. Cooperation among non-kin constitutes a conundrum for evolutionary biology. Theory suggests that non-kin cooperation can evolve if individuals differ consistently in their cooperative phenotypes and assort socially by these, such that cooperative individuals interact predominantly with one another. However, our knowledge of the role of cooperative phenotypes in the social structuring of real-world animal populations is minimal. In this study, we investigated cooperative phenotypes and their link to social structure in wild Trinidadian guppies (Poecilia reticulata). We first investigated whether wild guppies are repeatable in their individual levels of cooperativeness (i.e. have cooperative phenotypes) and found evidence for this in seven out of eight populations, a result which was mostly driven by females. We then examined the social network structure of one of these populations where the expected fitness impact of cooperative contexts is relatively high, and found assortment by cooperativeness, but not by genetic relatedness. By contrast, and in accordance with our expectations, we did not find assortment by cooperativeness in a population where the expected fitness impact of cooperative contexts is lower. Our results provide empirical support for current theory and suggest that assortment by cooperativeness is important for the evolution and persistence of non-kin cooperation in real-world populations
Odor and Odorous Chemical Emissions from Animal Buildings: Part 1. Project Overview, Collection Methods, and Quality Control
Livestock facilities have historically generated public concerns due to their emissions of odorous air and various chemical pollutants. Odor emission factors and identification of principal odorous chemicals are needed to better understand the problem. Applications of odor emission factors include inputs to odor setback models, while chemical emission factors may be compared with regulation thresholds as a means of demonstrating potential health impacts. A companion study of the National Air Emissions Monitoring Study (NAEMS) included measurements necessary for establishing odor and chemical emission factors for confined animal feeding operations. This additional investigation was conducted by the University of Minnesota, Iowa State University, West Texas A&M Agri-Life Center, and Purdue University. The objectives were to (1) determine odor emission rates across swine and dairy facilities and seasons using common protocols and standardized olfactometry methods, (2) develop a chemical library of the most significant odorants, and (3) correlate the chemical library with the olfactometry results. This document describes the sampling and quality assurance methods used in the measurement and evaluation of odor and chemical samples collected at two freestall dairy farms, one sow (gestation/farrowing) facility, and one finishing pig site. Odor samples were collected in Tedlar bags and chemical samples were collected in sorbent tubes at barn inlet and exhaust locations using the NAEMS multiple-location gas sampling systems. Quality assurance protocols included interlaboratory comparison tests, which were evaluated to identify variations between olfactometry labs. While differences were observed, the variations among the labs and samples appeared random and the collected odor data were considered reliable at a 0.5% level of statistical significance. Overall, the study took advantage of groundbreaking opportunities to collect and associate simultaneous odor and chemical information from swine and dairy buildings while maintaining accordance with standard methods and comparability across laboratories
Model experiment of magnetic field amplification in laser-produced plasmas via the Richtmyer-Meshkov instability
A model experiment of magnetic field amplification (MFA) via the Richtmyer-Meshkov instability (RMI) in supernova remnants (SNRs) was performed using a high-power laser. In order to account for very-fast acceleration of cosmic rays observed in SNRs, it is considered that the magnetic field has to be amplified by orders of magnitude from its background level. A possible mechanism for the MFA in SNRs is stretching and mixing of the magnetic field via the RMI when shock waves pass through dense molecular clouds in interstellar media. In order to model the astrophysical phenomenon in laboratories, there are three necessary factors for the RMI to be operative: a shock wave, an external magnetic field, and density inhomogeneity. By irradiating a double-foil target with several laser beams with focal spot displacement under influence of an external magnetic field, shock waves were excited and passed through the density inhomogeneity. Radiative hydrodynamic simulations show that the RMI evolves as the density inhomogeneity is shocked, resulting in higher MFA
Recommended from our members
Consensus Statement on the Pathology of IgG4-Related Disease
IgG4-related disease is a newly recognized fibro-inflammatory condition characterized by several features: a tendency to form tumefactive lesions in multiple sites; a characteristic histopathological appearance; and—often but not always—elevated serum IgG4 concentrations. An international symposium on IgG4-related disease was held in Boston, MA, on 4–7 October 2011. The organizing committee comprising 35 IgG4-related disease experts from Japan, Korea, Hong Kong, the United Kingdom, Germany, Italy, Holland, Canada, and the United States, including the clinicians, pathologists, radiologists, and basic scientists. This group represents broad subspecialty expertise in pathology, rheumatology, gastroenterology, allergy, immunology, nephrology, pulmonary medicine, oncology, ophthalmology, and surgery. The histopathology of IgG4-related disease was a specific focus of the international symposium. The primary purpose of this statement is to provide practicing pathologists with a set of guidelines for the diagnosis of IgG4-related disease. The diagnosis of IgG4-related disease rests on the combined presence of the characteristic histopathological appearance and increased numbers of IgG4+ plasma cells. The critical histopathological features are a dense lymphoplasmacytic infiltrate, a storiform pattern of fibrosis, and obliterative phlebitis. We propose a terminology scheme for the diagnosis of IgG4-related disease that is based primarily on the morphological appearance on biopsy. Tissue IgG4 counts and IgG4:IgG ratios are secondary in importance. The guidelines proposed in this statement do not supplant careful clinicopathological correlation and sound clinical judgment. As the spectrum of this disease continues to expand, we advocate the use of strict criteria for accepting newly proposed entities or sites as components of the IgG4-related disease spectrum
Enhanced brightness of a laser-driven X-ray and particle source by microstructured surfaces of silicon targets
The production of intense X-ray and particle sources is one of the most remarkable aspects of high energy laser interaction with a solid target. Wide application of these laser-driven secondary sources requires a high yield, which is partially limited by the amount of laser energy absorbed by the target. Here, we report on the enhancement of laser absorption and X-ray and particle flux by target surface modifications. In comparison to targets with flat front surfaces, our experiments show exceptional laser-to-target performance for our novel cone-shaped silicon microstructures. The structures are manufactured via laser-induced surface structuring. Spectral and spatial studies of reflectance and X-ray generation reveal significant increases of the silicon Kα line and a boost of the overall X-ray intensity, while the amount of reflected light decreases. Also, the proton and electron yields are enhanced, but both temperatures remain comparable to those of flat foil targets. We support the experimental findings with 2D particle in cell simulations to identify the mechanisms responsible for the strong enhancement. Our results demonstrate how custom surface structures can be used to engineer high power laser-plasma sources for future applications
- …