10,276 research outputs found
Development of the flour milling industry in Kansas
Thesis (M.A.)--University of Kansas, Economics, 1926
A Phenomenological Investigation of the Lived Experiences of Female African American Undergraduate Stem Students at an Elite Predominantly White Institution
The purpose of this qualitative study was to gain an understanding of the experiences of being a female, African American STEM undergraduate who is enrolled at an elite Predominantly White Institution and who has a mentoring relationship. A hermeneutic approach to phenomenology was used to gather data through open-ended interviews. Research questions included: What are the lived experiences of female, African American, STEM undergraduate students of the STEM community at an elite Predominantly White Institution? What are the lived experiences of high achieving female, African American, STEM undergraduate students with their mentors? Four themes emerged from the interviews: (a) Discouraging Academic Environment, (b) Minority Stress, (c) Positive Persuasions, and (d) Mentoring Support. This study concluded that African American women needed a supportive environment to thrive as an undergraduate STEM major. This support came from African American peers, informal mentoring experiences that provided psychosocial support and affirmed their ability, formal mentoring experiences that provided academic guidance, and positive verbal messages by university professors that women belong in STEM careers
Magnetic fields of intermediate mass T Tauri stars
Aims. In this paper, we aim to measure the strength of the surface magnetic
fields for a sample of five intermediate mass T Tauri stars and one low mass T
Tauri star from late-F to mid-K spectral types. While magnetic fields of T
Tauri stars at the low mass range have been extensively characterized, our work
complements previous studies towards the intermediate mass range; this
complementary study is key to evaluate how magnetic fields evolve during the
transition from a convective to a radiative core.
Methods. We studied the Zeeman broadening of magnetically sensitive spectral
lines in the H-band spectra obtained with the CRIRES high-resolution
near-infrared spectrometer. These data are modelled using magnetic spectral
synthesis and model atmospheres. Additional constraints on non-magnetic line
broadening mechanisms are obtained from modelling molecular lines in the K band
or atomic lines in the optical wavelength region.
Results. We detect and measure mean surface magnetic fields for five of the
six stars in our sample: CHXR 28, COUP 107, V2062 Oph, V1149 Sco, and Par 2441.
Magnetic field strengths inferred from the most magnetically sensitive
diagnostic line range from 0.8 to 1.8 kG. We also estimate a magnetic field
strength of 1.9 kG for COUP 107 from an alternative diagnostic. The magnetic
field on YLW 19 is the weakest in our sample and is marginally detected, with a
strength of 0.8 kG.
Conclusions. We populate an uncharted area of the pre-main-sequence HR
diagram with mean magnetic field measurements from high-resolution
near-infrared spectra. Our sample of intermediate mass T Tauri stars in general
exhibits weaker magnetic fields than their lower mass counterparts. Our
measurements will be used in combination with other spectropolarimetric studies
of intermediate mass and lower mass T Tauri stars to provide input into
pre-main-sequence stellar evolutionary models.Comment: 8 pages, 8 figures, accepted for publication in Astronomy and
Astrophysic
Modelling the molecular Zeeman effect in M-dwarfs: methods and first results
We present first quantitative results of the surface magnetic field
measurements in selected M-dwarfs based on detailed spectra synthesis conducted
simultaneously in atomic and molecular lines of the FeH Wing-Ford
transitions. A modified version of the Molecular
Zeeman Library (MZL) was used to compute Land\'e g-factors for FeH lines in
different Hund's cases. Magnetic spectra synthesis was performed with the
Synmast code. We show that the implementation of different Hund's case for FeH
states depending on their quantum numbers allows us to achieve a good fit to
the majority of lines in a sunspot spectrum in an automatic regime. Strong
magnetic fields are confirmed via the modelling of atomic and FeH lines for
three M-dwarfs YZ~CMi, EV~Lac, and AD~Leo, but their mean intensities are found
to be systematically lower than previously reported. A much weaker field
(~kG against ~kG) is required to fit FeH lines in the spectra of
GJ~1224. Our method allows us to measure average magnetic fields in very
low-mass stars from polarized radiative transfer. The obtained results indicate
that the fields reported in earlier works were probably overestimated by about
\%. Higher quality observations are needed for more definite results.Comment: Accepted by A&A, 13 pages, 7 figures, 1 tabl
The Magnetic Fields of Classical T Tauri Stars
We report new magnetic field measurements for 14 classical T Tauri stars
(CTTSs). We combine these data with one previous field determination in order
to compare our observed field strengths with the field strengths predicted by
magnetospheric accretion models. We use literature data on the stellar mass,
radius, rotation period, and disk accretion rate to predict the field strength
that should be present on each of our stars according to these magnetospheric
accretion models. We show that our measured field values do not correlate with
the field strengths predicted by simple magnetospheric accretion theory. We
also use our field strength measurements and literature X-ray luminosity data
to test a recent relationship expressing X-ray luminosity as a function of
surface magnetic flux derived from various solar feature and main sequence star
measurements. We find that the T Tauri stars we have observed have weaker than
expected X-ray emission by over an order of magnitude on average using this
relationship. We suggest the cause for this is actually a result of the very
strong fields on these stars which decreases the efficiency with which gas
motions in the photosphere can tangle magnetic flux tubes in the corona.Comment: 25 pages, 5 figure
NMR surface relaxivity in a time-dependent porous system
We demonstrate an unexpected decay-recovery behaviour in the time-dependent
NMR relaxation times of water confined within a hydrating
porous material. Our observations are rationalised by considering the combined
effects of decreasing material pore size and evolving interfacial chemistry,
which facilitate a transition between surface-limited and diffusion-limited
relaxation regimes. Such behaviour necessitates the realisation of temporally
evolving surface relaxivity, highlighting potential caveats in the classical
interpretation of NMR relaxation data obtained from complex porous systems.Comment: 12 pages, 2 figure
Human Behavior Models for Agents in Simulators and Games: Part I: Enabling Science with PMFserv
This article focuses on challenges to improving the realism of socially intelligent agents and attempts to reflect the state of the art in human behavior modeling with particular attention to the impact of personality/cultural values and affect as well as biology/stress upon individual coping and group decision-making. The first section offers an assessment of the state of the practice and of the need to integrate valid human performance moderator functions (PMFs) from traditionally separated sub-fields of the behavioral literature. The second section pursues this goal by postulating a unifying architecture and principles for integrating existing PMF theories and models. It also illustrates a PMF testbed called PMFserv created for implementating and studying how PMFs may contribute to such an architecture. To date it interconnects versions of PMFs on physiology and stress (Janis-Mann, Gillis-Hursh, others); personality, cultural and emotive processes (Damasio, Cognitive Appraisal-OCC, value systems); perception (Gibsonian affordance); social processes (relations, identity, trust, nested intentionality); and cognition (affect- and stress-augmented decision theory, bounded rationality). The third section summarizes several usage case studies (asymmetric warfare, civil unrest, and political leaders) and concludes with lessons learned. Implementing and inter-operating this broad collection of PMFs helps to open the agenda for research on syntheses that can help the field reach a greater level of maturity. Part II presents a case study in using PMFserv for rapid scenario composability and realistic agent behavior
A prototype system for observing the Atlantic Meridional Overturning Circulation - scientific basis, measurement and risk mitigation strategies, and first results
The Atlantic Meridional Overturning Circulation (MOC) carries up to one quarter of the global northward heat transport in the Subtropical North Atlantic. A system monitoring the strength of the MOC volume transport has been operating since April 2004. The core of this system is an array of moored sensors measuring density, bottom pressure and ocean currents. A strategy to mitigate risks of possible partial failures of the array is presented, relying on backup and complementary measurements. The MOC is decomposed into five components, making use of the continuous moored observations, and of cable measurements across the Straits of Florida, and wind stress data. The components compensate for each other, indicating that the system is working reliably. The year-long average strength of the MOC is 18.7±5.6 Sv, with wind-driven and density-inferred transports contributing equally to the variability. Numerical simulations suggest that the surprisingly fast density changes at the western boundary are partially linked to westward propagating planetary wave
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