16,521 research outputs found
Search for, and study of, paleozoic impact ejecta: Progress made during the past year
Nodule-like objects which the author believes to be impact bombs had been found in Middle Ordovician rocks of southeastern Wisconsin and northern Illinois. In northern Illinois, rock fragments containing oolith-like spherules, which the author believes to be solidified impact droplets, and numerous large bubble-holes, had been found at the same stratigraphic level. The discovery of bomb-like nodules in Lower Ordovician rocks of southeastern Wisconsin was reported. Bomb-type nodules associated with droplet-type spherules have been found in Lower Ordovician rocks of central Pennsylvania. These discoveries, in the authors opinion, suffice to show that impact ejecta are widespread in marine sediments of Ordovician age and are likely to be widespread also in marine sediments of other ages. Unfortunately, according to the author, there is little indication so far that this evidence has been accepted as valid by the concerned scientific community
Monte Carlo Evaluation of Non-Abelian Statistics
We develop a general framework to (numerically) study adiabatic braiding of
quasiholes in fractional quantum Hall systems. Specifically, we investigate the
Moore-Read (MR) state at filling factor, a known candidate for
non-Abelian statistics, which appears to actually occur in nature. The
non-Abelian statistics of MR quasiholes is demonstrated explicitly for the
first time, confirming the results predicted by conformal field theories.Comment: 4 pages, 4 figure
Student experiences of technology integration in school subjects: A comparison across four middle schools
This research examined student perspectives on their in-school, subject specific, technology use in four U.S. public schools. Considering students’ perspectives may provide a significant reframing of adult-created rhetoric of the utopian power of digital technologies for changing teaching and learning. A survey and focus group interviews were administered to 6th and 7th students (n=1,544) in four public middle schools, with varying demographics, that rely on local funding. These four schools revealed moderate use of many well-established digital technologies, such as word processing, presentation software, and quiz games. Students voiced outright hatred for teacher-directed PowerPoint-supported lectures, the most prominent technology activity students experienced, yet reported enjoying creation activities. The students in the rural school with a Hispanic-majority and high economically disadvantaged population reported much lower technology use. Discussion frame the digital inequities in the four schools and emphasizes the need for awareness and inclusion of students’ digital experiences to form any trajectory toward establishing digital equity and learning in schools
Backpack carrier Patent
Backpack carrier with retractable legs suitable for lunar exploration and convertible to rescue vehicl
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Dust cycles and storms in a Mars GCM
A number of different dust lifting parameterizations have been used to model the injection of dust from the Martian surface into the atmosphere, and the form of the resulting dust cycles and dust storms produced are found to be highly dependent on the precise form of the parameterization used, provided that it includes some threshold dependence, and particularly where radiatively active dust transport is employed. This talk will review the most interesting results from previous work. We have recently altered a key factor which particularly affects the dust lifting due to near-surface wind stress, however, so we will also present results using the new dust lifting formulation, and make some comparisons
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GCM simulations of the martian water cycle
Results from the Viking Orbiter Mars Atmospheric
Water Detectors (MAWD) have long been the definitive
data set for observations of the Martian water cycle
(Farmer et al., 1977). The ongoing Mars Global Surveyor
Thermal Emission Spectrometer (TES) observations
are providing new insights into the current water
cycle, with detailed longitude-latitude dependence of
water vapour (Figure 1) and water cloud (Figure 2) with
time, as well as information on vertical distribution of
water vapour and ice cloud (Smith, 2001). The described
results are derived from an ongoing project to model the
currentwater cycle using the Oxford version of the European
Mars General Circulation Model (MGCM) (Forget
et al., 1999), which was developed in colaboration with
LMD, Paris
Virtual reality in theatre education and design practice - new developments and applications
The global use of Information and Communication Technologies (ICTs) has already established new approaches to theatre education and research, shifting traditional methods of knowledge delivery towards a more visually enhanced experience, which is especially important for teaching scenography. In this paper, I examine the role of multimedia within the field of theatre studies, with particular focus on the theory and practice of theatre design and education. I discuss various IT applications that have transformed the way we experience, learn and co-create our cultural heritage. I explore a suite of rapidly developing communication and computer-visualization techniques that enable reciprocal exchange between students, theatre performances and artefacts. Eventually, I analyse novel technology-mediated teaching techniques that attempt to provide a new media platform for visually enhanced information transfer. My findings indicate that the recent developments in the personalization of knowledge delivery, and also in student-centred study and e-learning, necessitate the transformation of the learners from passive consumers of digital products to active and creative participants in the learning experience
The stellar mass-halo mass relation of isolated field dwarfs: a critical test of CDM at the edge of galaxy formation
We fit the rotation curves of isolated dwarf galaxies to directly measure the
stellar mass-halo mass relation () over the mass range . By accounting for cusp-core
transformations due to stellar feedback, we find a monotonic relation with
little scatter. Such monotonicity implies that abundance matching should yield
a similar if the cosmological model is correct. Using the 'field
galaxy' stellar mass function from the Sloan Digital Sky Survey (SDSS) and the
halo mass function from the Cold Dark Matter Bolshoi simulation, we
find remarkable agreement between the two. This holds down to M, and to M if we
assume a power law extrapolation of the SDSS stellar mass function below M.
However, if instead of SDSS we use the stellar mass function of nearby galaxy
groups, then the agreement is poor. This occurs because the group stellar mass
function is shallower than that of the field below M,
recovering the familiar 'missing satellites' and 'too big to fail' problems.
Our result demonstrates that both problems are confined to group environments
and must, therefore, owe to 'galaxy formation physics' rather than exotic
cosmology.
Finally, we repeat our analysis for a Warm Dark Matter cosmology,
finding that it fails at 68% confidence for a thermal relic mass of keV, and keV if we use the power law extrapolation
of SDSS. We conclude by making a number of predictions for future surveys based
on these results.Comment: 22 pages; 2 Tables; 10 Figures. This is the version accepted for
publication in MNRAS. Key changes: (i) added substantially more information
on the surveys used to measure the stellar mass functions; (ii) added tests
of the robustness of our results. Results and conclusions unchanged from
previously. Minor typos corrected from previous versio
Non-Abelian quantized Hall states of electrons at filling factors 12/5 and 13/5 in the first excited Landau level
We present results of extensive numerical calculations on the ground state of
electrons in the first excited (n=1) Landau level with Coulomb interactions,
and including non-zero thickness effects, for filling factors 12/5 and 13/5 in
the torus geometry. In a region that includes these experimentally-relevant
values, we find that the energy spectrum and the overlaps with the trial states
support the previous hypothesis that the system is in the non-Abelian k = 3
liquid phase we introduced in a previous paper.Comment: 5 pages (Revtex4), 7 figure
Neural signature of fictive learning signals in a sequential investment task
Reinforcement learning models now provide principled guides for a wide range of reward learning experiments in animals and humans. One key learning (error) signal in these models is experiential and reports ongoing temporal differences between expected and experienced reward. However, these same abstract learning models also accommodate the existence of another class of learning signal that takes the form of a fictive error encoding ongoing differences between experienced returns and returns that "could-have-been-experienced" if decisions had been different. These observations suggest the hypothesis that, for all real-world learning tasks, one should expect the presence of both experiential and fictive learning signals. Motivated by this possibility, we used a sequential investment game and fMRI to probe ongoing brain responses to both experiential and fictive learning signals generated throughout the game. Using a large cohort of subjects (n = 54), we report that fictive learning signals strongly predict changes in subjects' investment behavior and correlate with fMRI signals measured in dopaminoceptive structures known to be involved in valuation and choice
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