441 research outputs found
We \u27ll Have A Jubilee In My Old Kentucky Home
https://digitalcommons.library.umaine.edu/mmb-vp/2632/thumbnail.jp
A quantitative evaluation of physical and digital approaches to centre of mass estimation
Centre of mass is a fundamental anatomical and biomechanical parameter. Knowledge of centre of mass is essential to inform studies investigating locomotion and other behaviours, through its implications for segment movements, and on whole body factors such as posture. Previous studies have estimated centre of mass position for a range of organisms, using various methodologies. However, few studies assess the accuracy of the methods that they employ, and often provide only brief details on their methodologies. As such, no rigorous, detailed comparisons of accuracy and repeatability within and between methods currently exist. This paper therefore seeks to apply three methods common in the literature (suspension, scales and digital modelling) to three 'calibration objects' in the form of bricks, as well as three birds to determine centre of mass position. Application to bricks enables conclusions to be drawn on the absolute accuracy of each method, in addition to comparing these results to assess the relative value of these methodologies. Application to birds provided insights into the logistical challenges of applying these methods to biological specimens. For bricks, we found that, provided appropriate repeats were conducted, the scales method yielded the most accurate predictions of centre of mass (within 1.49 mm), closely followed by digital modelling (within 2.39 mm), with results from suspension being the most distant (within 38.5 mm). Scales and digital methods both also displayed low variability between centre of mass estimates, suggesting they can accurately and consistently predict centre of mass position. Our suspension method resulted not only in high margins of error, but also substantial variability, highlighting problems with this method
Centimeter to decimeter hollow concretions and voids in Gale Crater sediments, Mars
Voids and hollow spheroids between ∼1 and 23 cm in diameter occur at several locations along the traverse of the Curiosity rover in Gale crater, Mars. These hollow spherical features are significantly different from anything observed in previous landed missions. The voids appear in dark-toned, rough-textured outcrops, most notably at Point Lake (sols 302-305) and Twin Cairns Island (sol 343). Point Lake displays both voids and cemented spheroids in close proximity; other locations show one or the other form. The spheroids have 1-4 mm thick walls and appear relatively dark-toned in all cases, some with a reddish hue. Only one hollow spheroid (Winnipesaukee, sol 653) was analyzed for composition, appearing mafic (Fe-rich), in contrast to the relatively felsic host rock. The interior surface of the spheroid appears to have a similar composition to the exterior with the possible exceptions of being more hydrated and slightly depleted in Fe and K. Origins of the spheroids as Martian tektites or volcanic bombs appear unlikely due to their hollow and relatively fragile nature and the absence of in-place clearly igneous rocks. A more likely explanation to both the voids and the hollow spheroids is reaction of reduced iron with oxidizing groundwater followed by some re-precipitation as cemented rind concretions at a chemical reaction front. Although some terrestrial concretion analogs are produced from a precursor siderite or pyrite, diagenetic minerals could also be direct precipitates for other terrestrial concretions. The Gale sediments differ from terrestrial sandstones in their high initial iron content, perhaps facilitating a higher occurrence of such diagenetic reactions
Gas Metallicities in the Extended Disks of NGC 1512 and NGC 3621. Chemical Signatures of Metal Mixing or Enriched Gas Accretion?
(Abridged) We have obtained spectra of 135 HII regions located in the inner
and extended disks of the spiral galaxies NGC 1512 and NGC 3621, spanning the
range of galactocentric distances 0.2-2 x R25 (from 2-3 kpc to 18-25 kpc). We
find that the excitation properties of nebulae in the outer (R>R25) disks are
similar to those of the inner disks, but on average younger HII regions tend to
be selected in the bright inner disks. Reddening by dust is not negligible in
the outer disks, and subject to significant large-scale spatial variations. For
both galaxies the radial abundance gradient flattens to a constant value
outside of the isophotal radius. The outer disk O/H abundance ratio is highly
homogeneous, with a scatter of only ~0.06 dex. Based on the excitation and
chemical (N/O ratio) analysis we find no compelling evidence for variations in
the upper initial mass function of the ionizing clusters of extended disks. The
O/H abundance in the outer disks of the target galaxies corresponds to 35% of
the solar value (or higher, depending on the metallicity diagnostic). This
conflicts with the notion that metallicities in extended disks of spiral
galaxies are necessarily low. The observed metal enrichment cannot be produced
with the current level of star formation. We discuss the possibility that metal
transport mechanisms from the inner disks lead to metal pollution of the outer
disks. Gas accretion from the intergalactic medium, enriched by outflows,
offers an alternative solution.Comment: Accepted for publication in the Astrophysical Journa
A Three-Dimensional Taxonomy of Achievement Emotions
We present a three-dimensional taxonomy of achievement emotions that considers valence, arousal, and object focus as core features of emotions occurring in achievement settings. By distinguishing between positive and negative emotions (valence), activating and deactivating emotions (arousal), and activity emotions, prospective outcome emotions, and retrospective outcome emotions (object focus), the taxonomy has a 2 × 2 × 3 structure representing 12 groups of achievement emotions. In four studies across different countries (N = 330, 235, 323, and 269 participants in Canada, the US, Germany, and the UK, respectively), we investigated the empirical robustness of the taxonomy in educational (Studies 1-3) and work settings (Study 4). An expanded version of the Achievement Emotions Questionnaire was used to assess 12 key emotions representing the taxonomy. Consistently across the four studies, findings from multilevel facet analysis and structural equation modeling documented the importance of the three dimensions for explaining achievement emotions. In addition, based on hypotheses about relations with external variables, the findings show clear links of the emotions with important antecedents and outcomes. The Big Five personality traits, appraisals of control and value, and context perceptions were predictors of the emotions. The 12 emotions, in turn, were related to participants’ use of strategies, cognitive performance, and self-reported health problems. Taken together, the findings provide robust evidence for the unique positions of different achievement emotions in the proposed taxonomy, as well as unique patterns of relations with external variables. Directions for future research and implications for policy and practice are discussed
Landscape-scale benefits of protected areas for tropical biodiversity
We are indebted to numerous local communities, PA and government agency staff, research assistants, and other partners for supporting the field data collection. Research permissions were granted by appropriate forestry and conservation government departments in each country. Special thanks is given to the Sarawak State Government, Sarawak Forestry Corporation, Forest Department Sarawak, Sabah Biodiversity Centre, the Danum Valley Management Committee, the Forest Research Institute Malaysia (FRIM), the Smithsonian Institute and the Tropical Ecology Assessment and Monitoring (TEAM) network, Sarayudh Bunyavejchewin, and Ronglarp Sukmasuang. Support was provided by the United Nations Development Programme, NASA grants NNL15AA03C and 80NSSC21K0189, National Geographic Society’s Committee for the Research and Exploration award #9384–13, the Australian Research Council Discovery Early Career Researcher Award DECRA #DE210101440, the Universiti Malaysia Sarawak, the Ministry of Higher Education Malaysia, Nanyang Technological University Singapore, the Darwin Initiative, Liebniz-IZW, and the Universities of Aberdeen, British Columbia, Montana, and Queensland.Peer reviewedPostprin
Quantum state preparation and macroscopic entanglement in gravitational-wave detectors
Long-baseline laser-interferometer gravitational-wave detectors are operating
at a factor of 10 (in amplitude) above the standard quantum limit (SQL) within
a broad frequency band. Such a low classical noise budget has already allowed
the creation of a controlled 2.7 kg macroscopic oscillator with an effective
eigenfrequency of 150 Hz and an occupation number of 200. This result, along
with the prospect for further improvements, heralds the new possibility of
experimentally probing macroscopic quantum mechanics (MQM) - quantum mechanical
behavior of objects in the realm of everyday experience - using
gravitational-wave detectors. In this paper, we provide the mathematical
foundation for the first step of a MQM experiment: the preparation of a
macroscopic test mass into a nearly minimum-Heisenberg-limited Gaussian quantum
state, which is possible if the interferometer's classical noise beats the SQL
in a broad frequency band. Our formalism, based on Wiener filtering, allows a
straightforward conversion from the classical noise budget of a laser
interferometer, in terms of noise spectra, into the strategy for quantum state
preparation, and the quality of the prepared state. Using this formalism, we
consider how Gaussian entanglement can be built among two macroscopic test
masses, and the performance of the planned Advanced LIGO interferometers in
quantum-state preparation
Searching for a Stochastic Background of Gravitational Waves with LIGO
The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.Comment: 37 pages, 16 figure
Serial O-(2-[18F]fluoroethyl)-L-tyrosine PET for monitoring the effects of intracavitary radioimmunotherapy in patients with malignant glioma
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