963 research outputs found
University Student Understanding of Evolutionary Biology's Place in the Creation/Evolution Theory
Author Institution: Department of Genetics, The Ohio State UniversityA questionnaire was used to survey 2,387 students in 10 different science courses at The Ohio State University, Columbus, Ohio. Students were questioned about their views on the creation/evolution controversy, especially their acceptance of the concept of Darwinian evolution and on the concept of equal time for creation science. Biology students in Ohio showed a surprisingly low level of acceptance for the theory of evolution, and by an 80%-to-20% rate favored the concept of equal time for competing theories of origins. Students with increased education in biology were significantly less likely to accept co-instruction of alternative theories of origins in high school. Only eight percent of students could correctly identify the concept of differential reproduction as being most consistent with Darwinian evolution, among a set of five choices. Twentyfive percent believe that scientists doubt the validity of evolution as a science, while 22% feel that teaching naturalistic theories of science may lead to a decay in American society. Age and college rank had no effect on students' answers when the amount of science education in biology was taken into account. Students who had been exposed to evolution during high school biology courses were more likely to accept the concept of Darwinian evolution. Those students who have experienced more education in biology tend to answer questions in a manner which is more favorable to evolutionary biology and less favorable to creationist ideas. Taken as a whole, the results suggest that current mass biological education is not very successful in conveying the scientific basis of evolutionary biology
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Does energy efficiency matter to home-buyers? An investigation of EPC ratings and transaction prices in England
This paper investigates whether energy performance ratings, as measured by mandatory Energy Performance Certificates (EPCs), are reflected in the sale prices of residential properties. This is the first large-scale empirical study of this topic in England involving 333,095 dwellings sold at least twice in the period from 1995 to 2012. Applying hedonic regression and an augmented repeat sales regression, we find a positive relationship between the energy efficiency rating of a dwelling and the transaction price per square metre. The price effects of superior energy performance tend to be higher for terraced dwellings and flats compared to detached and semi-detached dwellings. The evidence is less clear-cut for rates of house price growth but remains supportive of a positive association. Overall, the results of this study suggest that energy efficiency labels have a measurable and significant impact on house prices in England.The authors wish to thank the UK Department of Energy and Climate
Change (TRN 297/11/2011) for financial support. Helpful comments on
earlier drafts were received from Chris Nicholls, Jeremy Moody and two
anonymous referees of this Journal. Franz Fuerst also wishes to acknowledge
the generous support of the Cambridge University Land Society
(CULS) in enabling his research.This is the accepted manuscript of a paper published in Energy Economics Volume 48, March 2015, Pages 145–156, doi:10.1016/j.eneco.2014.12.012
Probing large-scale wind structures in Vela X-1 using off-states with INTEGRAL
Vela X-1 is the prototype of the class of wind-fed accreting pulsars in high
mass X-ray binaries hosting a supergiant donor. We have analyzed in a
systematic way ten years of INTEGRAL data of Vela X-1 (22-50 keV) and we found
that when outside the X-ray eclipse, the source undergoes several luminosity
drops where the hard X-rays luminosity goes below 3x10^35 erg/s, becoming
undetected by INTEGRAL. These drops in the X-ray flux are usually referred to
as "off-states" in the literature. We have investigated the distribution of
these off-states along the Vela X-1 ~8.9 d orbit, finding that their orbital
occurrence displays an asymmetric distribution, with a higher probability to
observe an off-state near the pre-eclipse than during the post-eclipse. This
asymmetry can be explained by scattering of hard X-rays in a region of ionized
wind, able to reduce the source hard X-ray brightness preferentially near
eclipse ingress. We associate this ionized large-scale wind structure with the
photoionization wake produced by the interaction of the supergiant wind with
the X-ray emission from the neutron star. We emphasize that this observational
result could be obtained thanks to the accumulation of a decade of INTEGRAL
data, with observations covering the whole orbit several times, allowing us to
detect an asymmetric pattern in the orbital distribution of off-states in Vela
X-1.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society (5 pages, 3 figures). A few typos fixed to match the published
versio
Discovery of a new source of rifamycin antibiotics in marine sponge actinobacteria by phylogenetic prediction
Phylogenetic analysis of the ketosynthase (KS) gene sequences of marine sponge-derived Salinispora strains of actinobacteria indicated that the polyketide synthase (PKS) gene sequence most closely related to that of Salinispora was the rifamycin B synthase of Amycolatopsis mediterranei. This result was not expected from taxonomic species tree phylogenetics using 16S rRNA sequences. From the PKS sequence data generated from our sponge-derived Salinispora strains, we predicted that such strains might synthesize rifamycin-like compounds. Liquid chromatography-tandem mass spectrometry (LC/MS/MS) analysis was applied to one sponge-derived Salinispora strain to test the hypothesis of rifamycin synthesis. The analysis reported here demonstrates that this Salinispora isolate does produce compounds of the rifamycin class, including rifamycin B and rifamycin SV. A rifamycin-specific KS primer set was designed, and that primer set increased the number of rifamycin-positive strains detected by PCR screening relative to the number detectable using a conserved KS-specific set. Thus, the Salinispora group of actinobacteria represents a potential new source of rifamycins outside the genus Amycolatopsis and the first recorded source of rifamycins from marine bacteria
Atomic carbon chains as spin-transmitters: an \textit{Ab initio} transport study
An atomic carbon chain joining two graphene flakes was recently realized in a
ground-breaking experiment by Jin {\it et al.}, Phys. Rev. Lett. {\bf 102},
205501 (2009). We present {\it ab initio} results for the electron transport
properties of such chains and demonstrate complete spin-polarization of the
transmission in large energy ranges. The effect is due to the spin-polarized
zig-zag edge terminating each graphene flake causing a spin-splitting of the
graphene bands, and the chain states. Transmission occurs when the
graphene -states resonate with similar states in the strongly hybridized
edges and chain. This effect should in general hold for any -conjugated
molecules bridging the zig-zag edges of graphene electrodes. The polarization
of the transmission can be controlled by chemically or mechanically modifying
the molecule, or by applying an electrical gate
Modulational instability of solitary waves in non-degenerate three-wave mixing: The role of phase symmetries
We show how the analytical approach of Zakharov and Rubenchik [Sov. Phys.
JETP {\bf 38}, 494 (1974)] to modulational instability (MI) of solitary waves
in the nonlinear Schr\"oedinger equation (NLS) can be generalised for models
with two phase symmetries. MI of three-wave parametric spatial solitons due to
group velocity dispersion (GVD) is investigated as a typical example of such
models. We reveal a new branch of neck instability, which dominates the usual
snake type MI found for normal GVD. The resultant nonlinear evolution is
thereby qualitatively different from cases with only a single phase symmetry.Comment: 4 pages with figure
Studying the accretion geometry of EXO 2030+375 at luminosities close to the propeller regime
The Be X-ray binary EXO 2030+375 was in an extended low luminosity state
during most of 2016. We observed this state with NuSTAR and Swift, supported by
INTEGRAL observations as well as optical spectroscopy with the NOT. We present
a comprehensive spectral and timing analysis of these data here to study the
accretion geometry and investigate a possible onset of the propeller effect.
The H-alpha data show that the circumstellar disk of the Be-star is still
present. We measure equivalent widths similar to values found during more
active phases in the past, indicating that the low-luminosity state is not
simply triggered by a smaller Be disk. The NuSTAR data, taken at a 3-78 keV
luminosity of ~6.8e35 erg/s (for a distance of 7.1 kpc), are well described by
standard accreting pulsar models, such as an absorbed power-law with a
high-energy cutoff. We find that pulsations are still clearly visible at these
luminosities, indicating that accretion is continuing despite the very low mass
transfer rate. In phase-resolved spectroscopy we find a peculiar variation of
the photon index from ~1.5 to ~2.5 over only about 3% of the rotational period.
This variation is similar to that observed with XMM-Newton at much higher
luminosities. It may be connected to the accretion column passing through our
line of sight. With Swift/XRT we observe luminosities as low as 1e34 erg/s
during which the data quality did not allow us to search for pulsations, but
the spectrum is much softer and well described by either a blackbody or soft
power-law continuum. This softer spectrum might be due to the fact that
accretion has been stopped by the propeller effect and we only observe the
neutron star surface cooling.Comment: 11 pages, 6 figures, accepted for publication in A&A (v2 including
language edits
Broadband X-ray spectral analysis of the Seyfert 1 galaxy GRS 1734-292
We discuss the broadband X-ray spectrum of GRS 1734-292 obtained from
non-simultaneous XMM-Newton and NuSTAR observations, performed in 2009 and
2014, respectively. GRS1734-292 is a Seyfert 1 galaxy, located near the
Galactic plane at . The NuSTAR spectrum ( keV) is dominated by
a primary power-law continuum with and a high-energy
cutoff keV, one of the lowest measured by NuSTAR in a
Seyfert galaxy. Comptonization models show a temperature of the coronal plasma
of keV and an optical depth, assuming a slab
geometry, or a similar temperature and
assuming a spherical geometry. The 2009 XMM-Newton
spectrum is well described by a flatter intrinsic continuum
() and one absorption line due to Fe\textsc{XXV}
K produced by a warm absorber. Both data sets show a modest iron
K emission line at keV and the associated Compton reflection, due
to reprocessing from neutral circumnuclear material
The 2-79 keV X-Ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton, and Chandra: A Fully Compton-thick Active Galactic Nucleus
The Circinus galaxy is one of the closest obscured active galactic nuclei (AGNs), making it an ideal target for detailed study. Combining archival Chandra and XMM-Newton data with new NuSTAR observations, we model the 2-79 keV spectrum to constrain the primary AGN continuum and to derive physical parameters for the obscuring material. Chandra's high angular resolution allows a separation of nuclear and off-nuclear galactic emission. In the off-nuclear diffuse emission, we find signatures of strong cold reflection, including high equivalent-width neutral Fe lines. This Compton-scattered off-nuclear emission amounts to 18% of the nuclear flux in the Fe line region, but becomes comparable to the nuclear emission above 30 keV. The new analysis no longer supports a prominent transmitted AGN component in the observed band. We find that the nuclear spectrum is consistent with Compton scattering by an optically thick torus, where the intrinsic spectrum is a power law of photon index Γ = 2.2-2.4, the torus has an equatorial column density of N_H = (6-10) × 10^(24) cm^(–2), and the intrinsic AGN 2-10 keV luminosity is (2.3-5.1) × 10^(42) erg s^(–1). These values place Circinus along the same relations as unobscured AGNs in accretion rate versus Γ and L_X versus L_(IR) phase space. NuSTAR's high sensitivity and low background allow us to study the short timescale variability of Circinus at X-ray energies above 10 keV for the first time. The lack of detected variability favors a Compton-thick absorber, in line with the spectral fitting results
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