11,519 research outputs found
Second Language Speech Intelligibility Revisited: Differential Roles of Phonological Accuracy, Visual Speech, and Iconic Gesture
Although intelligibility is a core concept in second language (L2) speech assessment and teaching research, the vast majority of previous work relies on audio-only stimuli. The current study set out to examine how linguistic and visual information jointly interact to determine the degree of speech intelligibility. Both first language (L1) and L2 English listeners were presented with stimuli that varied along 3 factors (vowel error, visual speech, and iconic gesture) and completed an orthographic transcription task. Results revealed that iconic gesture significantly increased all the listeners’ intelligibility scores when speech contained vowel errors. When speech did not contain errors, gesture increased intelligibility for L2 listeners but not L1 listeners. Visual speech had no significant effect on intelligibility in either listener group. Vowel error reduced intelligibility by approximately 20–30% for both L1 and L2 listeners. Findings suggest that visual modalities, especially gestures, have the potential to significantly affect the intelligibility of speech containing phonological errors
Extreme Supernova Models for the Superluminous Transient ASASSN-15lh
The recent discovery of the unprecedentedly superluminous transient
ASASSN-15lh (or SN 2015L) with its UV-bright secondary peak challenges all the
power-input models that have been proposed for superluminous supernovae. Here
we examine some of the few viable interpretations of ASASSN-15lh in the context
of a stellar explosion, involving combinations of one or more power inputs. We
model the lightcurve of ASASSN-15lh with a hybrid model that includes
contributions from magnetar spin-down energy and hydrogen-poor circumstellar
interaction. We also investigate models of pure circumstellar interaction with
a massive hydrogen-deficient shell and discuss the lack of interaction features
in the observed spectra. We find that, as a supernova ASASSN-15lh can be best
modeled by the energetic core-collapse of a ~40 Msun star interacting with a
hydrogen-poor shell of ~20 Msun. The circumstellar shell and progenitor mass
are consistent with a rapidly rotating pulsational pair-instability supernova
progenitor as required for strong interaction following the final supernova
explosion. Additional energy injection by a magnetar with initial period of 1-2
ms and magnetic field of 0.1-1 x 10^14 G may supply the excess luminosity
required to overcome the deficit in single-component models, but this requires
more fine-tuning and extreme parameters for the magnetar, as well as the
assumption of efficient conversion of magnetar energy into radiation. We thus
favor a single-input model where the reverse shock formed in a strong SN
ejecta-CSM interaction following a very powerful core-collapse SN explosion can
supply the luminosity needed to reproduce the late-time UV-bright plateau.Comment: 8 pages, 3 figure
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Effect of elevated CO2 and high temperature on seed-set and grain quality of rice
Hybrid vigour may help overcome the negative effects of climate change in rice. A popular rice hybrid (IR75217H), a heat-tolerant check (N22), and a mega-variety (IR64) were tested for tolerance of seed-set and grain quality to high-temperature stress at anthesis at ambient and elevated [CO2]. Under an ambient air temperature of 29 °C (tissue temperature 28.3 °C), elevated [CO2] increased vegetative and reproductive growth, including seed yield in all three genotypes. Seed-set was reduced by high temperature in all three genotypes, with the hybrid and IR64 equally affected and twice as sensitive as the tolerant cultivar N22. No interaction occurred between temperature and [CO2] for seed-set. The hybrid had significantly more anthesed spikelets at all temperatures than IR64 and at 29 °C this resulted in a large yield advantage. At 35 °C (tissue temperature 32.9 °C) the hybrid had a higher seed yield than IR64 due to the higher spikelet number, but at 38 °C (tissue temperature 34–35 °C) there was no yield advantage. Grain gel consistency in the hybrid and IR64 was reduced by high temperatures only at elevated [CO2], while the percentage of broken grains increased from 10% at 29 °C to 35% at 38 °C in the hybrid. It is concluded that seed-set of hybrids is susceptible to short episodes of high temperature during anthesis, but that at intermediate tissue temperatures of 32.9 °C higher spikelet number (yield potential) of the hybrid can compensate to some extent. If the heat tolerance from N22 or other tolerant donors could be transferred into hybrids, yield could be maintained under the higher temperatures predicted with climate change
Endothelial HO-1 induction by model TG-rich lipoproteins is regulated through a NOX4-Nrf2 pathway
Circulating levels of chylomicron remnants (CMRs) increase postprandially and their composition directly reflects dietary lipid intake. These TG-rich lipoproteins likely contribute to the development of endothelial dysfunction, albeit via unknown mechanisms. Here, we investigated how the FA composition of CMRs influences their actions on human aortic endothelial cells (HAECs) by comparing the effects of model CMRs—artificial TG-rich CMR-like particles (A-CRLPs)—containing TGs extracted from fish, DHA-rich algal, corn, or palm oils. HAECs responded with distinct transcriptional programs according to A-CRLP TG content and oxidation status, with genes involved in antioxidant defense and cytoprotection most prominently affected by n-3 PUFA-containing A-CRLPs. These particles were significantly more efficacious inducers of heme oxygenase-1 (HO-1) than n-6 PUFA corn or saturated FA-rich palm CRLPs. Mechanistically, HO-1 induction by all CRLPs requires NADPH oxidase 4, with PUFA-containing particles additionally dependent upon mitochondrial reactive oxygen species. Activation of both p38 MAPK and PPARβ/δ culminates in increased nuclear factor erythroid 2-related factor 2 (Nrf2) expression/nuclear translocation and HO-1 induction. These studies define new molecular pathways coupling endothelial cell activation by model CMRs with adaptive regulation of Nrf2-dependent HO-1 expression and may represent key mechanisms through which dietary FAs differentially impact progression of endothelial dysfunction
Lipopolysaccharide and toll-like receptor 4 in dogs with congenital portosystemic shunts
Surgical attenuation of a congenital portosystemic shunt (CPSS) results in increased portal vein perfusion, liver growth and clinical improvement. Portal lipopolysaccharide (LPS) is implicated in liver regeneration via toll-like receptor (TLR) 4 mediated cytokine activation. The aim of this study was to investigate factors associated with LPS in dogs with CPSS. Plasma LPS concentrations were measured in the peripheral and portal blood using a limulus amoebocyte lysate (LAL) assay.
LPS concentration was significantly greater in the portal blood compared to peripheral blood in dogs with CPSS (P = 0.046) and control dogs (P = 0.002). LPS concentrations in the peripheral (P = 0.012) and portal (P = 0.005) blood of dogs with CPSS were significantly greater than those of control dogs. The relative mRNA expression of cytokines and TLRs was measured in liver biopsies from dogs with CPSS using quantitative PCR. TLR4 expression significantly increased following partial CPSS attenuation (P = 0.020). TLR4 expression was significantly greater in dogs that tolerated complete CPSS attenuation (P = 0.011) and those with good portal blood flow on pre-attenuation (P = 0.004) and post-attenuation (P = 0.015) portovenography. Serum interleukin (IL)-6 concentration was measured using a canine specific ELISA and significantly increased 24 h following CPSS attenuation (P < 0.001). Portal LPS was increased in dogs with CPSS, consistent with decreased hepatic clearance. TLR4 mRNA expression was significantly associated with portal blood flow and increased following surgery. These findings support the concept that portal LPS delivery is important in the hepatic response to surgical attenuation. Serum IL-6 significantly increased following surgery, consistent with LPS stimulation via TLR4, although this increase might be non-specific
High-fat meals rich in EPA plus DHA compared with DHA only have differential effects on postprandial lipemia and plasma 8-isoprostane F-2 alpha concentrations relative to a control high-oleic acid meal: a randomized controlled trial
Background: Eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) supplementation has beneficial cardiovascular effects, but postprandial influences of these individual fatty acids are unclear. Objectives: The primary objective was to determine the vascular effects of EPA + DHA compared with DHA only during postprandial lipemia relative to control high–oleic acid meals; the secondary objective was to characterize the effects of linoleic acid–enriched high-fat meals relative to the control meal. Design: We conducted a randomized, controlled, double-blind crossover trial of 4 high-fat (75-g) meals containing 1) high–oleic acid sunflower oil (HOS; control), 2) HOS + fish oil (FO; 5 g EPA and DHA), 3) HOS + algal oil (AO; 5 g DHA), and 4) high–linoleic acid sunflower oil (HLS) in 16 healthy men (aged 35–70 y) with higher than optimal fasting triacylglycerol concentrations (mean ± SD triacylglycerol, 1.9 ± 0.5 mmol/L). Results: Elevations in triacylglycerol concentration relative to baseline were slightly reduced after FO and HLS compared with the HOS control (P < 0.05). The characteristic decrease from baseline in plasma nonesterified fatty acids after a mixed meal was inhibited after AO (Δ 0–3 h, P < 0.05). HLS increased the augmentation index compared with the other test meals (P < 0.05), although the digital volume pulse–reflection index was not significantly different. Plasma 8-isoprostane F(2α) analysis revealed opposing effects of FO (increased) and AO (reduced) compared with the control (P < 0.05). No differences in nitric oxide metabolites were observed. Conclusions: These data show differential postprandial 8-isoprostane F(2α) responses to high-fat meals containing EPA + DHA–rich fish oil compared with DHA-rich AO, but these differences were not associated with consistent effects on postprandial vascular function or lipemia. More detailed analyses of polyunsaturated fatty acid–derived lipid mediators are required to determine possible divergent functional effects of single meals rich in either DHA or EPA. This trial was registered at clinicaltrials.gov as NCT01618071
Searching for the expelled hydrogen envelope in Type I supernovae via late-time H-alpha emission
We report the first results from our long-term observational survey aimed at
discovering late-time interaction between the ejecta of hydrogen-poor Type I
supernovae and the hydrogen-rich envelope expelled from the progenitor star
several decades/centuries before explosion. The expelled envelope, moving with
a velocity of ~10 -- 100 km s, is expected to be caught up by the
fast-moving SN ejecta several years/decades after explosion depending on the
history of the mass-loss process acting in the progenitor star prior to
explosion. The collision between the SN ejecta and the circumstellar envelope
results in net emission in the Balmer-lines, especially in H-alpha. We look for
signs of late-time H-alpha emission in older Type Ia/Ibc/IIb SNe having
hydrogen-poor ejecta, via narrow-band imaging. Continuum-subtracted H-alpha
emission has been detected for 13 point sources: 9 SN Ibc, 1 SN IIb and 3 SN Ia
events. Thirty-eight SN sites were observed on at least two epochs, from which
three objects (SN 1985F, SN 2005kl, SN 2012fh) showed significant temporal
variation in the strength of their H-alpha emission in our DIAFI data. This
suggests that the variable emission is probably not due to nearby H II regions
unassociated with the SN, and hence is an important additional hint that
ejecta-CSM interaction may take place in these systems. Moreover, we
successfully detected the late-time H-alpha emission from the Type Ib SN 2014C,
which was recently discovered as a strongly interacting SN in various (radio,
infrared, optical and X-ray) bands.Comment: 8 pages, 7 figures, accepted in Ap
Exact relativistic stellar models with liquid surface. I. Generalizing Buchdahl's polytrope
A family of exact relativistic stellar models is described. The family
generalizes Buchdahl's n=1 polytropic solution. The matter content is a perfect
fluid and, excluding Buchdahl's original model, it behaves as a liquid at low
pressures in the sense that the energy density is non-zero in the zero pressure
limit. The equation of state has two free parameters, a scaling and a stiffness
parameter. Depending on the value of the stiffness parameter the fluid
behaviour can be divided in four different types. Physical quantities such as
masses, radii and surface redshifts as well as density and pressure profiles
are calculated and displayed graphically. Leaving the details to a later
publication, it is noted that one of the equation of state types can quite
accurately approximate the equation of state of real cold matter in the outer
regions of neutron stars. Finally, it is observed that the given equation of
state does not admit models with a conical singularity at the center.Comment: 19 pages, 12 figures (16 eps files), LaTeX2e with the standard
packages amssymb, amsmath, graphicx, subfigure, psfra
Attosecond pulse shaping around a Cooper minimum
High harmonic generation (HHG) is used to measure the spectral phase of the
recombination dipole matrix element (RDM) in argon over a broad frequency range
that includes the 3p Cooper minimum (CM). The measured RDM phase agrees well
with predictions based on the scattering phases and amplitudes of the
interfering s- and d-channel contributions to the complementary photoionization
process. The reconstructed attosecond bursts that underlie the HHG process show
that the derivative of the RDM spectral phase, the group delay, does not have a
straight-forward interpretation as an emission time, in contrast to the usual
attochirp group delay. Instead, the rapid RDM phase variation caused by the CM
reshapes the attosecond bursts.Comment: 5 pages, 5 figure
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