864 research outputs found
Succeeding in Introduction to Physical Science: Is Mathematics Background Important?
Most college students complete courses in physical and life science as general education requirements. Although the level of difficulty of these survey courses is relatively low compared to upper-level science courses, a number of students still struggle to pass them. The purpose of this research was to investigate (a) the nature of mathematics background of students enrolling in physical science courses; (b) the change in mathematics ability of students at the end of the semester; and (c) what is the relationship between mathematics background and course completion and success. A 15-item test of basic mathematics skills was administered as a pre-test and post-test to students in two sections of Introduction to Physical Science at Arkansas Tech University. Results show that more than half of the students performed deficiently or failed the pre-test, that students who finished the course did not gain any significant knowledge in mathematics, that students who eventually withdrew from the course performed worst in the pre-test than students who persisted, and that there is a statistically significant relationship between pre- and post-test scores and students\u27 final grades in the course
Factors Associated With Students Graduating With STEM Degrees at a Military Academy: Improving Success by Identifying Early Obstacles
The United States is not graduating enough science, technology, engineering, and mathematics (STEM) majors for the increasing number of available employment opportunities and national security needs. The purpose of this study was to quantify the magnitude of STEM attrition at the United States Air Force Academy (USAFA), a military service academy and one of the three commissioning sources of officers for the United States Air Force. Also, the study identified factors associated with STEM attrition among students. Despite strong academic preparation, of the students who reported their intention to major in a STEM discipline as incoming freshmen, 36.4% switched and graduated with a nonSTEM degree. Two binary logistic regressions revealed that the best predictors associated with students graduating with a STEM major were their initial intention and motivation to major in these disciplines upon arrival at the USAFA and course grades in Calculus I, Calculus-based General Physics I, and Applications of Chemistry I. These findings suggest that, as in many other universities, students motivated to major in STEM may switch out if they struggle with prerequisite quantitative courses
Identifying academically at-risk incoming freshmen at a private university in Uruguay: Psychometric evaluation of a mathematics diagnostic test
This study determined to what extent the mathematics diagnostic test (MDT) used at the Catholic University of Uruguay (CUU) was psychometrically appropriate. Also, after removing “red-flagged” items, the study measured to what extent MDT scores correlated with academic success. It was found that five MDT items (out of 30) did not meet the guidelines and were discarded. The score on the remaining items showed the highest correlation with the number of mathematics courses completed, confirming that students with low MDT-Revised scores might need additional academic support to remain in the engineering program
The AMIGA sample of isolated galaxies: VIII. The rate of asymmetric HI profiles in spiral galaxies
(abridged) Measures of the HI properties of a galaxy are among the most
sensitive interaction diagnostic at our disposal. We report here on a study of
HI profile asymmetries (e.g., lopsidedness) in a sample of some of the most
isolated galaxies in the local Universe. This presents us with an excellent
opportunity to quantify the range of intrinsic HI asymmetries and provides us
with a zero-point calibration for evaluating these measurements in less
isolated samples. We characterize the HI profile asymmetries and search for
correlations between HI asymmetry and their environments, as well as their
optical and far infrared (FIR) properties. We use high signal-to-noise global
HI profiles for galaxies in the AMIGA project (http://amiga.iaa.csic.es). We
restrict our study to N=166 galaxies with accurate measures of the HI shape
properties. We quantify asymmetries using a flux ratio parameter. The asymmetry
parameter distribution of our isolated sample is well described by a Gaussian
model. The width of the distribution is sigma=0.13, and could be even smaller
(sigma=0.11) if instrumental errors are reduced. Only 2% of our carefully
vetted isolated galaxies sample show an asymmetry in excess of 3sigma. By using
this sample we minimize environmental effects as confirmed by the lack of
correlation between HI asymmetry and tidal force (one-on-one interactions) and
neighbor galaxy number density. On the other hand, field galaxy samples show
wider distributions and deviate from a Gaussian curve. As a result we find
higher asymmetry rates (~10-20%) in such samples. We find evidence that the
spiral arm strength is inversely correlated with the HI asymmetry. We also find
an excess of FIR luminous galaxies with larger HI asymmetries that may be
spirals associated with hidden accretion events. Our sample presents the
smallest fraction of asymmetric HI profiles compared with any other yet
studied.Comment: 18 pages, 17 figures, accepted for publication in A&
Collider production of Electroweak resonances from photon-photon states
We estimate production cross sections for 2-body resonances of the
Electroweak Symmetry Breaking sector (in and rescattering)
from scattering. We employ unitarized Higgs Effective Field
Theory amplitudes previously computed coupling the two photon channel to the
EWSBS. We work in the Effective Photon Approximation and examine both
collisions at energies of order 1-2 TeV (as relevant for future lepton
machines) and collisions at LHC energies. Dynamically generating a spin-0
resonance around 1.5 TeV (by appropriately choosing the parameters of the
effective theory) we find that the differential cross section per unit ,
is of order 0.01 fbarn/TeV at the LHC. Injecting a spin-2 resonance
around 2 TeV we find an additional factor 100 suppression for up to 200
GeV. The very small cross sections put these processes, though
very clean, out of reach of immediate future searches.Comment: 36 pages, 20 plot
Detecting Repetitions and Periodicities in Proteins by Tiling the Structural Space
The notion of energy landscapes provides conceptual tools for understanding
the complexities of protein folding and function. Energy Landscape Theory
indicates that it is much easier to find sequences that satisfy the "Principle
of Minimal Frustration" when the folded structure is symmetric (Wolynes, P. G.
Symmetry and the Energy Landscapes of Biomolecules. Proc. Natl. Acad. Sci.
U.S.A. 1996, 93, 14249-14255). Similarly, repeats and structural mosaics may be
fundamentally related to landscapes with multiple embedded funnels. Here we
present analytical tools to detect and compare structural repetitions in
protein molecules. By an exhaustive analysis of the distribution of structural
repeats using a robust metric we define those portions of a protein molecule
that best describe the overall structure as a tessellation of basic units. The
patterns produced by such tessellations provide intuitive representations of
the repeating regions and their association towards higher order arrangements.
We find that some protein architectures can be described as nearly periodic,
while in others clear separations between repetitions exist. Since the method
is independent of amino acid sequence information we can identify structural
units that can be encoded by a variety of distinct amino acid sequences
The central parsecs of M87: jet emission and an elusive accretion disc
We present the first simultaneous spectral energy distribution (SED) of M87
core at a scale of 0.4 arcsec () across the electromagnetic
spectrum. Two separate, quiescent, and active states are sampled that are
characterized by a similar featureless SED of power-law form, and that are thus
remarkably different from that of a canonical active galactic nuclei (AGN) or a
radiatively inefficient accretion source. We show that the emission from a jet
gives an excellent representation of the core of M87 core covering ten orders
of magnitude in frequency for both the active and the quiescent phases. The
inferred total jet power is, however, one to two orders of magnitude lower than
the jet mechanical power reported in the literature. The maximum luminosity of
a thin accretion disc allowed by the data yields an accretion rate of , assuming 10% efficiency. This power
suffices to explain M87 radiative luminosity at the jet-frame, it is however
two to three order of magnitude below that required to account for the jet's
kinetic power. The simplest explanation is variability, which requires the core
power of M87 to have been two to three orders of magnitude higher in the last
200 yr. Alternatively, an extra source of power may derive from black hole
spin. Based on the strict upper limit on the accretion rate, such spin power
extraction requires an efficiency an order of magnitude higher than predicted
from magnetohydrodynamic simulations, currently in the few hundred per cent
range.Comment: 18 pages, 6 figures. Accepted for publication in MNRA
A variable active galactic nucleus at z = 2.06 triply-imaged by the galaxy cluster MACS J0035.4−2015
Support by grant 2020750 from the United States-
Israel Binational Science Foundation (BSF) and grant 2109066
from the United States National Science Foundation (NSF), and
by the Ministry of Science and Technology, Israel. J.C. acknowl-
edges funding from the ‘FirstGalaxies’ Advanced Grant from the
European Research Council (ERC) under the European Union’s
Horizon 2020 research and innovation program (Grant agreement
No. 789056). E.C.L. acknowledges support of an STFC Webb
Fellowship (ST/W001438/1). K.K. acknowledges the support by
JSPS KAKENHI Grant Number JP17H06130 and the NAOJ ALMA
Scientific Research Grant Number 2017–06B. D.E. acknowledges
support from a Beatriz Galindo senior fellowship (BG20/00224)
from the Spanish Ministry of Science and Innovation, projects
PID2020-114414GB-100 and PID2020-113689GB-I00 financed by
MCIN/AEI/10.13039/501100011033, project P20-00334 financed
by the Junta de Andaluc´ıa, and project A-FQM-510-UGR20 of
the FEDER/Junta de Andaluc´ıa-Consejer´ıa de Transformaci ´on
Econ ´omica, Industria, Conocimiento y Universidades. G.E.M. ac-
knowledges financial support from the Villum Young Investiga-
tor grant 37440 and 13160 and the The Cosmic Dawn Center
(DAWN), funded by the Danish National Research Foundation
under grant No. 140. F.E.B. acknowledges support from ANID-
Chile BASAL CATA FB210003, FONDECYT Regular 1200495 and
1190818, and Millennium Science Initiative Program–ICN12 009.
K.K.K. acknowledges support from the Knut and Alice Wallenberg
Foundation.We report the discovery of a triply imaged active galactic nucleus (AGN), lensed by the galaxy cluster MACS J0035.4−2015 (z d = 0.352). The object is detected in Hubble Space Telescope imaging taken for the RELICS program. It appears to have a quasi-stellar nucleus consistent with a point-source, with a de-magnified radius of re ≲ 100 pc. The object is spectroscopically confirmed to be an AGN at z spec = 2.063 ± 0.005 showing broad rest-frame UV emission lines, and detected in both X-ray observations with Chandra and in ALCS ALMA band 6 (1.2 mm) imaging. It has a relatively faint rest-frame UV luminosity for a quasar-like object, MUV, 1450 = −19.7 ± 0.2. The object adds to just a few quasars or other X-ray sources known to be multiply lensed by a galaxy cluster. Some diffuse emission from the host galaxy is faintly seen around the nucleus, and there is a faint object nearby sharing the same multiple-imaging symmetry and geometric redshift, possibly an interacting galaxy or a star-forming knot in the host. We present an accompanying lens model, calculate the magnifications and time delays, and infer the physical properties of the source. We find the rest-frame UV continuum and emission lines to be dominated by the AGN, and the optical emission to be dominated by the host galaxy of modest stellar mass M✶ ≃ 109.2 M⊙. We also observe some variation in the AGN emission with time, which may suggest that the AGN used to be more active. This object adds a low-redshift counterpart to several relatively faint AGN recently uncovered at high redshifts with HST and JWST.Horizon 2020 Framework Programme
H2020Consejería de Transformación Económica, Industria, Conocimiento y Universidades
13160, 37440Science and Technology Facilities Council ST/W001438/1 STFCEuropean Research Council
ERCFondo Nacional de Desarrollo Científico y Tecnológico
1190818, 1200495, ICN12_009 FONDECYTMinisterio de Ciencia e Innovación
MCIN/AEI/10.13039/501100011033, P20-00334, PID2020-113689GB-I00, PID2020-114414GB-100 MICINNHorizon 2020
789056European Regional Development Fund
ERDFJunta de Andalucía
A-FQM-510-UGR2
HI asymmetry in the isolated galaxy CIG 85 (UGC 1547)
We present the results from the Giant Metrewave Radio Telescope (GMRT)
interferometric HI and 20 cm radio continuum observations of CIG 85, an
isolated asymmetric galaxy from the AMIGA (Analysis of the Interstellar Medium
of Isolated GAlaxies) sample. Despite being an isolated galaxy, CIG 85 showed
an appreciable optical and HI spectral asymmetry and therefore was an excellent
candidate for resolved HI studies to understand the reasons giving rise to
asymmetries in isolated galaxies. The galaxy was imaged in HI and 20 cm radio
continuum using the GMRT. For a detailed discussion of the results we also made
use of multi-wavelength data from archival SDSS, GALEX and Halpha imaging. We
find the HI in CIG 85 to have a clumpy, asymmetric distribution which in the NW
part is correlated with optical tail like features, but the HI velocity field
displays a relatively regular rotation pattern. Evaluating all the
observational evidence, we come to a conclusion that CIG 85 is most likely a
case of a disturbed spiral galaxy which now appears to have the morphology of
an irregular galaxy. Although it is currently isolated from major companions,
the observational evidence is consistent with HI asymmetries, a highly
disturbed optical disk and recent increase in star formation having been caused
by a minor merger, remnants of which are now projected in front of the optical
disk. If this is correct, the companion will be fully accreted by CIG 85 in the
near future.Comment: 10 pages, 9 figures, accepted in A&
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