1,320 research outputs found
Magnetically asymmetric interfaces in a (LaMnO)/(SrMnO) superlattice due to structural asymmetries
Polarized neutron reflectivity measurements of a ferromagnetic
[(LaMnO)/(SrMnO)] superlattice reveal a modulated
magnetic structure with an enhanced magnetization at the interfaces where
LaMnO was deposited on SrMnO (LMO/SMO). However, the opposite
interfaces (SMO/LMO) are found to have a reduced ferromagnetic moment. The
magnetic asymmetry arises from the difference in lateral structural roughness
of the two interfaces observed via electron microscopy, with strong
ferromagnetism present at the interfaces that are atomically smooth over tens
of nanometers. This result demonstrates that atomic-scale roughness can
destabilize interfacial phases in complex oxide heterostructures.Comment: 5 pages, 4 figure
“I just want to be skinny.”: A content analysis of tweets expressing eating disorder symptoms
There is increasing concern about online communities that promote eating disorder (ED) behaviors through messages and/or images that encourage a “thin ideal” (i.e., promotion of thinness as attractive) and harmful weight loss/weight control practices. The purpose of this paper is to assess the content of body image and ED-related content on Twitter and provide a deeper understanding of EDs that may be used for future studies and online-based interventions. Tweets containing ED or body image-related keywords were collected from January 1-January 31, 2015 (N = 28,642). A random sample (n = 3000) was assessed for expressions of behaviors that align with subscales of the Eating Disorder Examination (EDE) 16.0. Demographic characteristics were inferred using a social media analytics company. The comprehensive research that we conducted indicated that 2,584 of the 3,000 tweets were ED-related; 65% expressed a preoccupation with body shape, 13% displayed issues related to food/eating/calories, and 4% expressed placing a high level of importance on body weight. Most tweets were sent by girls (90%) who were ≤19 years old (77%). Our findings stress a need to better understand if and how ED-related content on social media can be used for targeting prevention and intervention messages towards those who are in-need and could potentially benefit from these efforts.</div
Ground-based monitoring of comet 67P/Churyumov-Gerasimenko gas activity throughout the <i>Rosetta</i> mission
Simultaneously to the ESA Rosetta mission, a world-wide ground-based campaign provided measurements of the large scale activity of comet 67P/Churyumov-Gerasimenko through measurement of optically active gas species and imaging of the overall dust coma. We present more than two years of observations performed with the FORS2 low resolution spectrograph at the VLT, TRAPPIST, and ACAM at the WHT. We focus on the evolution of the CN production, as a tracer of the comet activity. We find that it is asymmetric with respect to perihelion and different from that of the dust. The CN emission is detected for the first time at 1.34 au pre-perihelion and production rates then increase steeply to peak about two weeks after perihelion at (1.00±0.10) ×1025 molecules s−1, while the post-perihelion decrease is more shallow. The evolution of the comet activity is strongly influenced by seasonal effects, with enhanced CN production when the Southern hemisphere is illuminated
The engineering classroom is still relevant
Citation: Fitzsimmons, E. J., Tucker-Kulesza, S. E., Li, X., Jeter, W., & Fallin, J. R. (2016). The engineering classroom is still relevant.Attrition in engineering is a complex issue with dynamically linked variables related to teaching methods in the classroom, student learning behaviors, and student perceptions of difficult material. Extensive research has been conducted in order to understand common, yet ineffective teaching practices in engineering that result in the loss of numerous future engineers. The objective of this study was to determine student actions necessary to achieve a desired grade in any engineering course, regardless of course delivery method and instructor effectiveness in the classroom. An anonymous survey was disseminated and logistic regression models were developed in order to determine relationships between self-regulated learning behaviors and final grades in seven freshman to senior engineering classes taught by civil engineering faculty. A total of five prediction models were developed for each letter grade, with the failing grade "F" serving as the baseline condition, or null model. The models found three significant variables that affect a student's final grade: regular class attendance, note-taking during class, and if he or she could keep up with the instructor during lecture. These interactive learning behaviors were all identified as critical for success, defining success as receiving an "A" in an engineering course. The combination of students taking notes and attending class showed the highest probability of a student receiving an "A." Results of this study have been summarized into a graphic that the authors show and discuss during the first class with students. This powerful graphic shows students what they can do in classes of all levels of civil engineering to succeed in their ever-changing learning environment. © American Society for Engineering Education, 2016
Extreme asteroids in the Pan-STARRS 1 Survey
Using the first 18 months of the Pan-STARRS 1 survey we have identified 33
candidate high-amplitude objects for follow-up observations and carried out
observations of 22 asteroids. 4 of the observed objects were found to have
observed amplitude mag. We find that these high amplitude
objects are most simply explained by single rubble pile objects with some
density-dependent internal strength, allowing them to resist mass shedding even
at their highly elongated shapes. 3 further objects although below the cut-off
for 'high-amplitude' had a combination of elongation and rotation period which
also may require internal cohesive strength, depending on the density of the
body. We find that none of the 'high-amplitude asteroids' identified here
require any unusual cohesive strengths to resist rotational fission. 3
asteroids were sufficiently observed to allow for shape and spin pole models to
be determined through light curve inversion. 45864 was determined to have
retrograde rotation with spin pole axes and asteroid 206167 was found to have best fit spin
pole axes , . An additional
object not initially measured with mag, 49257, was determined to
have a shape model which does suggest a high-amplitude object. Its spin pole
axes were best fit for values .
In the course of this project to date no large super-fast rotators ( h) have been identified.Comment: 31 pages; accepted by A
Delta Doping of Ferromagnetism in Antiferromagnetic Manganite Superlattices
We demonstrate that delta-doping can be used to create a dimensionally
confined region of metallic ferromagnetism in an antiferromagnetic (AF)
manganite host, without introducing any explicit disorder due to dopants or
frustration of spins. Delta-doped carriers are inserted into a manganite
superlattice (SL) by a digital-synthesis technique. Theoretical consideration
of these additional carriers show that they cause a local enhancement of
ferromagnetic (F) double-exchange with respect to AF superexchange, resulting
in local canting of the AF spins. This leads to a highly modulated
magnetization, as measured by polarized neutron reflectometry. The spatial
modulation of the canting is related to the spreading of charge from the doped
layer, and establishes a fundamental length scale for charge transfer,
transformation of orbital occupancy and magnetic order in these manganites.
Furthermore, we confirm the existence of the canted, AF state as was predicted
by de Gennes [P.-G. de Gennes, Phys. Rev. 118, 141 (1960)], but had remained
elusive
Lithium peroxide test program Final report
Experimental design and performance data on carbon dioxide and oxygen control for portable life support system using lithium peroxid
Col-OSSOS: Colors of the Interstellar Planetesimal 1I/`Oumuamua
The recent discovery by Pan-STARRS1 of 1I/2017 U1 (`Oumuamua), on an unbound
and hyperbolic orbit, offers a rare opportunity to explore the planetary
formation processes of other stars, and the effect of the interstellar
environment on a planetesimal surface. 1I/`Oumuamua's close encounter with the
inner Solar System in 2017 October was a unique chance to make observations
matching those used to characterize the small-body populations of our own Solar
System. We present near-simultaneous g, r, and J photometry
and colors of 1I/`Oumuamua from the 8.1-m Frederick C. Gillett Gemini North
Telescope, and photometry from the 4.2 m William Herschel Telescope. Our
grJ observations are directly comparable to those from the
high-precision Colours of the Outer Solar System Origins Survey (Col-OSSOS),
which offer unique diagnostic information for distinguishing between outer
Solar System surfaces. The J-band data also provide the highest signal-to-noise
measurements made of 1I/`Oumuamua in the near-infrared. Substantial, correlated
near-infrared and optical variability is present, with the same trend in both
near-infrared and optical. Our observations are consistent with 1I/`Oumuamua
rotating with a double-peaked period of hours and being a
highly elongated body with an axial ratio of at least 5.3:1, implying that it
has significant internal cohesion. The color of the first interstellar
planetesimal is at the neutral end of the range of Solar System and
solar-reflectance colors: it is like that of some dynamically excited objects
in the Kuiper belt and the less-red Jupiter Trojans.Comment: Accepted to ApJ
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Electrically heated ex-reactor pellet-cladding interaction (PCI) simulations utilizing irradiated Zircaloy cladding. [PWR]
In a program sponsored by the Fuel Systems Research Branch of the US Nuclear Regulatory Commission, a series of six electrically heated fuel rod simulation tests were conducted at Pacific Northwest Laboratory. The primary objective of these tests was to determine the susceptibility of irradiated pressurized-water reactor (PWR) Zircaloy-4 cladding to failures caused by pellet-cladding mechanical interaction (PCMI). A secondary objective was to acquire kinetic data (e.g., ridge growth or relaxation rates) that might be helpful in the interpretation of in-reactor performance results and/or the modeling of PCMI. No cladding failures attributable to PCMI occurred during the six tests. This report describes the testing methods, testing apparatus, fuel rod diametral strain-measuring device, and test matrix. Test results are presented and discussed
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