2,277 research outputs found
Cheating With Honor
The intent of this paper is to understand what leads a student to cheat within the context of a small (enrollment below 2,000 students) liberal arts college. The development of a model will examine cheating from three categories highlighted in the literature: demographics, college culture, and the perception of cheating. Demographics capture relevant personal attributes of a student such as gender, GPA, and major. Cultural variables include variables for the presence of an honor code and participation in a sport or social organization, which provide that student with a unique cultural experience. Perception variables deal with the perceptions the students have developed about cheating based on the academic culture within which they operate, such as student perception of cheating on campus, perception of peer behavior, and perceived faculty involvement
The Impact of Honor Codes on Academic Cheating Within Liberal Arts Colleges
Many researchers study the subject of collegiate cheating by focusing on demographic characteristics of cheaters at schools of varying sizes. Other researchers examine whether collegiate honor codes can abate rampant cheating. A third group studies whether perceptions of what students believe to be cheating behaviors affects actual cheating. This paper incorporates previous research and develops a model of academic cheating based on three sets of incentives - moral, social and economic – and how they affect self-reported cheating behaviors at liberal arts colleges. An on-line survey was administered to students from three liberal arts colleges in spring 2008. The nearly 700 respondents provide a robust data set with nearly half of the respondents coming from institutions with honor codes in place. Econometric models using ordinary least squares highlight the determinants of cheating and whether honor codes are efficacious. The results will be useful in the national dialogue regarding college cheating
The Impact of Honor Codes and Perceptions of Cheating on Academic Cheating Behaviors, Especially for MBA Bound Undergraduates
Researchers studying academic dishonesty in college often focus on demographic characteristics of cheaters and discuss changes in cheating trends over time. To predict cheating behavior, some researchers examine the costs and benefits of academic cheating, while others view campus culture and the role which honor codes play in affecting behavior. This paper develops a model of academic cheating based on three sets of incentives - moral, social and economic—and how they affect cheating behaviors. An on-line survey comprising 61 questions was administered to students from three liberal arts colleges in the USA in spring 2008, yielding 700 responses, with half from colleges with honor codes. Econometric modelling indicates that students ultimately seeking MBA degrees, and those who lack a perception of what constitutes cheating, undertake more cheating, regardless of whether an honor code is in place. Additionally, unless an honor code is embraced by the college community, the existence of an honor code by itself will not reduce cheating
A Numerical Relativity Waveform Surrogate Model for Generically Precessing Binary Black Hole Mergers
A generic, non-eccentric binary black hole (BBH) system emits gravitational
waves (GWs) that are completely described by 7 intrinsic parameters: the black
hole spin vectors and the ratio of their masses. Simulating a BBH coalescence
by solving Einstein's equations numerically is computationally expensive,
requiring days to months of computing resources for a single set of parameter
values. Since theoretical predictions of the GWs are often needed for many
different source parameters, a fast and accurate model is essential. We present
the first surrogate model for GWs from the coalescence of BBHs including all
dimensions of the intrinsic non-eccentric parameter space. The surrogate
model, which we call NRSur7dq2, is built from the results of numerical
relativity simulations. NRSur7dq2 covers spin magnitudes up to and mass
ratios up to , includes all modes, begins about orbits
before merger, and can be evaluated in . We find the
largest NRSur7dq2 errors to be comparable to the largest errors in the
numerical relativity simulations, and more than an order of magnitude smaller
than the errors of other waveform models. Our model, and more broadly the
methods developed here, will enable studies that would otherwise require
millions of numerical relativity waveforms, such as parameter inference and
tests of general relativity with GW observations.Comment: 10 pages, 5 figures; Added report numbe
Low mass binary neutron star mergers : gravitational waves and neutrino emission
Neutron star mergers are among the most promising sources of gravitational
waves for advanced ground-based detectors. These mergers are also expected to
power bright electromagnetic signals, in the form of short gamma-ray bursts,
infrared/optical transients, and radio emission. Simulations of these mergers
with fully general relativistic codes are critical to understand the merger and
post-merger gravitational wave signals and their neutrinos and electromagnetic
counterparts. In this paper, we employ the SpEC code to simulate the merger of
low-mass neutron star binaries (two neutron stars) for a set of
three nuclear-theory based, finite temperature equations of state. We show that
the frequency peaks of the post-merger gravitational wave signal are in good
agreement with predictions obtained from simulations using a simpler treatment
of gravity. We find, however, that only the fundamental mode of the remnant is
excited for long periods of time: emission at the secondary peaks is damped on
a millisecond timescale in the simulated binaries. For such low-mass systems,
the remnant is a massive neutron star which, depending on the equation of
state, is either permanently stable or long-lived. We observe strong
excitations of l=2, m=2 modes, both in the massive neutron star and in the form
of hot, shocked tidal arms in the surrounding accretion torus. We estimate the
neutrino emission of the remnant using a neutrino leakage scheme and, in one
case, compare these results with a gray two-moment neutrino transport scheme.
We confirm the complex geometry of the neutrino emission, also observed in
previous simulations with neutrino leakage, and show explicitly the presence of
important differences in the neutrino luminosity, disk composition, and outflow
properties between the neutrino leakage and transport schemes.Comment: Accepted by PRD; 23 pages; 24 figures; 4 table
Descriptive analysis of preschool physical activity and sedentary behaviors - a cross sectional study of 3-year-olds nested in the SKOT cohort
Abstract Background Further collection of surveillance data is warranted, particularly in preschool populations, for optimizing future public health promotion strategies. This study aims to describe physical activity (PA) and sedentary behavior (SB) across different settings, including time in and out of daycare, and to determine the proportion of children complying with suggested PA recommendations in a high income country. Methods Valid PA was assessed in 231 children (36.4 ± 1.1 months) with the Actigraph GT3X accelerometer, and information regarding date and time of dropping-off/picking-up children in daycare was provided by parents. Mean total PA (i.e., counts per minute (CPM)), moderate-to-vigorous physical activity (MVPA), SB time, and non-SB time was generated and compared across settings. Post hoc, PA and SB were examined in subgroups of low-active (1st quartile) and high-active (4th quartile) children. Results Overall, boys and girls spent 1.4 ± 0.3 h/day and 1.2 ± 0.4 h/day in MVPA, respectively. Likewise, boys and girls accumulated 6.7 ± 0.8 h and 6.8 ± 0.9 h of SB time per day, respectively. Higher PA levels consistently co-occurred with lower SB time in the daycare setting. Girls accumulated less SB time in daycare than before and after daycare (β = −12.2%, p < 0.001 & β = −3.8%, p < 0.001, respectively). In boys, daycare-days contained more PA and less SB than non-daycare-days (CPM: β =29, p = 0.046, %MVPA: β = 0.83, p = 0.007, %SB: β = −2.3, p < 0.001, respectively). All children fulfilled recommendations of at least 3 h of daily non-SB. Eighty-nine percent of boys and 72% of girls met the daily 1-h MVPA recommendation for 5 year-olds. Lower proportions of children, especially boys, fulfilled MVPA recommendation on days with no daycare attendance. Generally, large mean differences in MVPA and SB were observed across all settings between the most active and the least active children, and only 7% of the low-active girls and 59% of the low-active boys fulfilled MVPA recommendations. Conclusions Overall, the majority of children fulfilled MVPA guidelines for 5 year-olds, and all children complied with suggested recommendations of 180 min of daily activity. Daycare time was found to represent an important setting for PA. Substantial and consistent differences observed in the amount of time spent physically active between high- and low-active children across all settings indicate substantial variations in young children’s PA levels irrespective of the context
Neutron star-black hole mergers with a nuclear equation of state and neutrino cooling: Dependence in the binary parameters
We present a first exploration of the results of neutron star-black hole
mergers using black hole masses in the most likely range of
, a neutrino leakage scheme, and a modeling of the neutron
star material through a finite-temperature nuclear-theory based equation of
state. In the range of black hole spins in which the neutron star is tidally
disrupted (), we show that the merger consistently
produces large amounts of cool (), unbound,
neutron-rich material (). A comparable
amount of bound matter is initially divided between a hot disk () with typical neutrino luminosity , and a cooler tidal tail. After a short period of rapid
protonization of the disk lasting , the accretion disk cools
down under the combined effects of the fall-back of cool material from the
tail, continued accretion of the hottest material onto the black hole, and
neutrino emission. As the temperature decreases, the disk progressively becomes
more neutron-rich, with dimmer neutrino emission. This cooling process should
stop once the viscous heating in the disk (not included in our simulations)
balances the cooling. These mergers of neutron star-black hole binaries with
black hole masses and black hole spins high
enough for the neutron star to disrupt provide promising candidates for the
production of short gamma-ray bursts, of bright infrared post-merger signals
due to the radioactive decay of unbound material, and of large amounts of
r-process nuclei.Comment: 20 pages, 19 figure
Post-merger evolution of a neutron star-black hole binary with neutrino transport
We present a first simulation of the post-merger evolution of a black
hole-neutron star binary in full general relativity using an energy-integrated
general relativistic truncated moment formalism for neutrino transport. We
describe our implementation of the moment formalism and important tests of our
code, before studying the formation phase of a disk after a black hole-neutron
star merger. We use as initial data an existing general relativistic simulation
of the merger of a neutron star of 1.4 solar mass with a black hole of 7 solar
mass and dimensionless spin a/M=0.8. Comparing with a simpler leakage scheme
for the treatment of the neutrinos, we find noticeable differences in the
neutron to proton ratio in and around the disk, and in the neutrino luminosity.
We find that the electron neutrino luminosity is much lower in the transport
simulations, and that the remnant is less neutron-rich. The spatial
distribution of the neutrinos is significantly affected by relativistic
effects. Over the short timescale evolved, we do not observe purely
neutrino-driven outflows. However, a small amount of material (3e-4Msun) is
ejected in the polar region during the circularization of the disk. Most of
that material is ejected early in the formation of the disk, and is fairly
neutron rich. Through r-process nucleosynthesis, that material should produce
high-opacity lanthanides in the polar region, and could thus affect the
lightcurve of radioactively powered electromagnetic transients. We also show
that by the end of the simulation, while the bulk of the disk is neutron-rich,
its outer layers have a higher electron fraction. As that material would be the
first to be unbound by disk outflows on longer timescales, the changes in Ye
experienced during the formation of the disk could have an impact on the
nucleosynthesis outputs from neutrino-driven and viscously-driven outflows.
[Abridged]Comment: 29 pages, 25 figure
Evolution of the Magnetized, Neutrino-Cooled Accretion Disk in the Aftermath of a Black Hole Neutron Star Binary Merger
Black hole-torus systems from compact binary mergers are possible engines for
gamma-ray bursts (GRBs). During the early evolution of the post-merger remnant,
the state of the torus is determined by a combination of neutrino cooling and
magnetically-driven heating processes, so realistic models must include both
effects. In this paper, we study the post-merger evolution of a magnetized
black hole-neutron star binary system using the Spectral Einstein Code (SpEC)
from an initial post-merger state provided by previous numerical relativity
simulations. We use a finite-temperature nuclear equation of state and
incorporate neutrino effects in a leakage approximation. To achieve the needed
accuracy, we introduce improvements to SpEC's implementation of
general-relativistic magnetohydrodynamics (MHD), including the use of
cubed-sphere multipatch grids and an improved method for dealing with
supersonic accretion flows where primitive variable recovery is difficult. We
find that a seed magnetic field triggers a sustained source of heating, but its
thermal effects are largely cancelled by the accretion and spreading of the
torus from MHD-related angular momentum transport. The neutrino luminosity
peaks at the start of the simulation, and then drops significantly over the
first 20\,ms but in roughly the same way for magnetized and nonmagnetized
disks. The heating rate and disk's luminosity decrease much more slowly
thereafter. These features of the evolution are insensitive to grid structure
and resolution, formulation of the MHD equations, and seed field strength,
although turbulent effects are not fully convergedComment: 17 pages, 18 figure
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