1,093 research outputs found
Multi-epoch Sub-arcsecond [Fe II] Spectroimaging of the DG Tau Outflows with NIFS. II. On the Nature of the Bipolar Outflow Asymmetry
The origin of bipolar outflow asymmetry in young stellar objects (YSOs)
remains poorly understood. It may be due to an intrinsically asymmetric outflow
launch mechanism, or it may be caused by the effects of the ambient medium
surrounding the YSO. Answering this question is an important step in
understanding outflow launching. We have investigated the bipolar outflows
driven by the T Tauri star DG Tauri on scales of hundreds of AU, using the
Near-infrared Integral Field Spectrograph (NIFS) on Gemini North. The
approaching outflow consists of a well-collimated jet, nested within a
lower-velocity disc wind. The receding outflow is composed of a
single-component bubble-like structure. We analyse the kinemat- ics of the
receding outflow using kinetic models, and determine that it is a
quasi-stationary bubble with an expanding internal velocity field. We propose
that this bubble forms because the receding counterjet from DG Tau is
obstructed by a clumpy ambient medium above the circumstellar disc surface,
based on similarities between this structure and those found in the modeling of
active galactic nuclei outflows. We find evidence of interaction between the
obscured counterjet and clumpy ambient material, which we attribute to the
large molecular envelope around the DG Tau system. An analytical model of a
momentum-driven bubble is shown to be consistent with our interpretation. We
conclude that the bipolar outflow from DG Tau is intrinsically symmetric, and
the observed asymmetries are due to environmental effects. This mechanism can
potentially be used to explain the observed bipolar asymmetries in other YSO
outflows.Comment: 16 pages, 10 figures, accepted for publication in MNRA
Turbulent mixing layers in supersonic protostellar outflows, with application to DG Tauri
Turbulent entrainment processes may play an important role in the outflows
from young stellar objects at all stages of their evolution. In particular,
lateral entrainment of ambient material by high-velocity, well-collimated
protostellar jets may be the cause of the multiple emission-line velocity
components observed in the microjet-scale outflows driven by classical T Tauri
stars. Intermediate-velocity outflow components may be emitted by a turbulent,
shock- excited mixing layer along the boundaries of the jet. We present a
formalism for describing such a mixing layer based on Reynolds decomposition of
quantities measuring fundamental properties of the gas. In this model, the
molecular wind from large disc radii provides a continual supply of material
for entrainment. We calculate the total stress profile in the mixing layer,
which allows us to estimate the dissipation of turbulent energy, and hence the
luminosity of the layer. We utilize MAPPINGS IV shock models to determine the
fraction of total emission that occurs in [Fe II] 1.644 {\mu}m line emission in
order to facilitate comparison to previous observations of the young stellar
object DG Tauri. Our model accurately estimates the luminosity and changes in
mass outflow rate of the intermediate-velocity component of the DG Tau
approaching outflow. Therefore, we propose that this component represents a
turbulent mixing layer surrounding the well-collimated jet in this object.
Finally, we compare and contrast our model to previous work in the field.Comment: 18 pages, 13 figures, accepted for publication in MNRA
Interpretations of suppression
We review the two main interpretations of suppression proposed in
the literature. The phase transition (or deconfining) scenario assumes that
below some critical value of the local energy density (or of some other
geometrical quantity which depends both on the colliding systems and on the
centrality of the collision), there is only nuclear absorption. Above this
critical value the absorptive cross-section is taken to be infinite, i.e. no
can survive in this hot region. In the hadronic scenario the
dissociates due both to nuclear absorption and to its interactions with
co-moving hadrons produced in the collision. No discontinuity exists in
physical observables. We show that an equally good description of the present
data is possible in either scenario.Comment: 12 pages, LaTeX, uses epsfig and ioplppt; review talk given by A.
Capella at the International Symposium on Strangness in Quark Matter,
Santorini (Greece), April 1997; Figs. 1 and 2 not available but can be found
in Refs. 13 and 6 respectivel
An Evaluation of Mouse and Keyboard Interaction Indicators towards Non-intrusive and Low Cost Affective Modeling in an Educational Context
AbstractIn this paper we propose a series of indicators, which derive from user's interactions with mouse and keyboard. The goal is to evaluate their use in identifying affective states and behavior changes in an e-learning platform by means of non-intrusive and low cost methods. The approach we have followed study user's interactions regardless of the task being performed and its presentation, aiming at finding a solution applicable in any domain. In particular, mouse movements and clicks, as well as keystrokes were recorded during a math problem solving activity where users involved in the experiment had not only to score their degree of valence (i.e., pleasure versus displeasure) and arousal (i.e., high activation versus low activation) of their affective states after each problem by using the Self-Assessment-Manikin scale, but also type a description of their own feelings. By using that affective labeling, we evaluated the information provided by these different indicators processed from the original user's interactions logs. In total, we computed 42 keyboard indicators and 96 mouse indicators
Ebola virus VP35 induces high-level production of recombinant TPL-2–ABIN-2–NF-κB1 p105 complex in co-transfected HEK-293 cells
Activation of PKR (double-stranded-RNA-dependent protein kinase) by DNA plasmids decreases translation, and limits the amount of recombinant protein produced by transiently transfected HEK (human embryonic kidney)-293 cells. Co-expression with Ebola virus VP35 (virus protein 35), which blocked plasmid activation of PKR, substantially increased production of recombinant TPL-2 (tumour progression locus 2)–ABIN-2 [A20-binding inhibitor of NF-κB (nuclear factor κB) 2]–NF-κB1 p105 complex. VP35 also increased expression of other co-transfected proteins, suggesting that VP35 could be employed generally to boost recombinant protein production by HEK-293 cells
Fully Transparent Gas Sensor Based on Carbon Nanotubes
In this paper, we demonstrate the feasibility of realization of transparent gas sensors based
on carbon nanotubes (CNTs). Both sensing layer and electrodes consist of CNTs deposited by spray
deposition. The transparent sensor—with a transmittance higher than 60% in both sensing layer
and electrodes—is characterized towards NH3 and CO2 and compared with a reference sensor with
the same active layer but evaporated Au electrodes. In particular, the sensitivity towards NH3 is
virtually identical for both reference and transparent sensors, whereas the transparent device exhibits
higher sensitivity to CO2 than the reference electrode. The effect of the spacing among consecutive
electrodes is also studied, demonstrating that a wider spacing in fully CNT based sensors results
in a higher sensitivity because of the higher sensing resistance, whereas this effect was not observed
in gold electrodes, as their resistance can be neglected with respect to the resistance of the CNT
sensing layer. Overall, the transparent sensors show performance comparable—if not superior—to
the traditionally realized ones, opening the way for seamlessly integrated sensors, which do not
compromise on quality.This work has been partially supported by the fellowship H2020-MSCA-IF-2017-794885-SELFSENS and
the TUM Graduate Schoo
Do Search for Dibaryonic De - Excitations in Relativistic Nuclear Reactions
Some odd characteristics are observed in the single particle distributions
obtained from interactions at momenta which are
explained as the manifestation of a new mechanism of strangeness production via
dibaryonic de-excitations. A signature of the formation of hadronic and
baryonic clusters is also reported. The di-pionic signals of the dibaryonic
orbital de-excitations are analyzed in the frame of the MIT - bag Model and a
Monte Carlo simulation.The role played by the dibaryonic resonances in
relativistic nuclear collisions could be a significant one.
Key words: Relativistic nuclear interactions negative pions, negative kaons,
di-pions , streamer chamber, dibaryons, MIT - bag model
PACS codes: 25.75.+r,14.40.Aq,14.20.Pt,12.40.AsComment: 17 pages,LATEX, preprint ICTP -243 1993,figures available by reques
Causas del bajo rendimiento académico en los alumnos y alumnas que repiten el séptimo año, en un colegio publico, diurno, del circuito 02 de Alajuela. Un estudio de casos múltiples
Trabajo final de graduación de 119 páginas en formato pdfNos acercamos al Siglo XXI y el bajo rendimiento escolar sigue siendo un tema de
gran preocupación, no obstante las múltiples investigaciones que se han llevado a cabo.
En nuestro medio existe una gran cantidad de alumnos de nivel secundario, que
presentan un bajo rendimiento escolar, el cual ha tratado de ser explicado, generalmente por
los psicólogos educacionales, como el resultado de múltiples factores.(de Garrido,
Magally,1997)
Algunos investigadores como RodrÃguez (1977), Castillo (1981) y Madams, citado
por Otárola y Rojas (1993), encontraron que hay relación entre la actitud hacia las materias
y el rendimiento académico.
Sin embargo, consideran que las causas del bajo rendimiento no son atribuibles a un
único factor, sino que se señalan factores tales como: la mala preparación de docentes y
alumnos, los contenidos programáticos que no se adaptan a la realidad educativa, la actitud que manifiestan los estudiantes y profesores hacia la asignatura y el empleo de métodos y técnicas de estudio, inadecuados y tradicionales.Universidad Estatal a Distancia de Costa Ric
Late-Season Nitrogen Applications Increase Soybean Yield and Seed Protein Concentration
Low seed and meal protein concentration in modern high-yielding soybean [Glycine max L. (Merr.)] cultivars is a major concern but there is limited information on effective cultural practices to address this issue. In the objective of dealing with this problem, this study conducted field experiments in 2019 and 2020 to evaluate the response of seed and meal protein concentrations to the interactive effects of late-season inputs [control, a liquid Bradyrhizobium japonicum inoculation at R3, and 202 kg ha−1 nitrogen (N) fertilizer applied after R5], previous cover crop (fallow or cereal cover crop with residue removed), and short- and full-season maturity group cultivars at three U.S. locations (Fayetteville, Arkansas; Lexington, Kentucky; and St. Paul, Minnesota). The results showed that cover crops had a negative effect on yield in two out of six site-years and decreased seed protein concentration by 8.2 mg g−1 on average in Minnesota. Inoculant applications at R3 did not affect seed protein concentration or yield. The applications of N fertilizer after R5 increased seed protein concentration by 6 to 15 mg g−1, and increased yield in Arkansas by 13% and in Minnesota by 11% relative to the unfertilized control. This study showed that late-season N applications can be an effective cultural practice to increase soybean meal protein concentration in modern high-yielding cultivars above the minimum threshold required by the industry. New research is necessary to investigate sustainable management practices that increase N availability to soybeans late in the season
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