323 research outputs found
STR-993: BEHAVIOUR OF FIRE-DAMAGED ENGINEERED TIMBER BEAMS
Recently in Canada, the national building code has been amended to include mid-rise engineered timber buildings. The code also contains an allowance for Alternative Solutions, in which taller and more complex engineered timber structures may be built with sufficient research and proof of performance. For sustainable material use in infrastructure, an environmentally conscious population is motivating the employment of new engineered timber constructions. The purpose of this study is to investigate the behaviour of timber members, specifically glulam, before and after fire damage to inform future testing of large-scale engineered timber building systems. The experiments provide valuable data with regards to the post-fire performance and resiliency of mass timber. A novel Digital Image Correlation (DIC) technique using high-resolution imagery for deformation measurement through pixel movement was used for the first time, to the knowledge of the authors, in pre- and post-fire coupon specimens. The DIC analysis proved to be accurate in introductory tests on timber coupons post-heating, with the maximum difference from the traditional instrumentation being within acceptable tolerances in a separate calibration test. The accuracy decreased in the charred coupon tests, where significant scatter in strain measurement was observed, indicating possible refinement of the technology being necessary. In both coupon sets, the unburned members were recorded to have strength 18% higher than their burned counterparts. This suggests that complex failure modes occurred within the charred specimens which caused a premature failure which is investigated herein. Overall, both burned specimens exhibited significant resiliency to a severe fire exposure
Effects of Social Isolation on Heart Rate Variabilty
The present study looked at the interaction and effects of social isolation onheart rate variability (HRV). Participants in this study includedundergraduate (N=20) students from St. Johns University and the Collegeof Saint Benedict. This study included an online survey that measuredneuroticism as well as an online program participants played calledCyberBall. After participants took the neuroticism survey they wereattached to a BioPac machine using electrodes that monitored their heartrate variability while they played two rounds CyberBall. Heart ratevariability was collected for a total of twenty minutes. We hypothesized thatsocial isolation would decrease heart rate variability
Synopsis of biological control for European fruit lecanium (Parthenolecanium corni) by parasitoids in North America and preliminary findings in hybrid hazelnut orchards
The European fruit lecanium, Parthenolecanium corni (Bouché) (Hemiptera: Coccidae) is a native insect to North America that causes significant damage to a large variety of fruit and ornamental trees worldwide. Here we provide a summary of the insect’s worldwide distribution and synopsis of all the Hymenopteran parasitoid wasps found to parasitize P. corni in North America from past literature. Additionally, a preliminary parasitoid survey of P. corni was carried out in two hybrid hazel (Corylus avellana × C. americana) plantings as hazelnuts represent a potential new crop for the region. European fruit lecanium, Parthenolecanium corni (Bouché) (Hemiptera: Coccidae), were collected over two sample days in July 2022 from two hybrid hazelnut plantings and their parasitoid fauna recorded. Parasitism rates of P. corni were estimated for hymenopterous parasitoids as well as the entomophagous fungus Ophiocordyceps clavulata (Ascomycota: Hypocreales: Ophiocordycipitaceae). Hymenopterous parasitoids were identified to the lowest taxonomic level possible. Relationships between parasitism rates (a binomial response) and P. corni density (the predictor variable) were analyzed using binomial generalized linear models. Parthenolecanium corni experienced high parasitism rates: 24.0% by hymenopteran parasitoids, and 63.4% by entomophagous fungi, giving a combined parasitism rate of 87.4%. Wasp and fungal parasitism exhibited contrasting density-dependent relationships. Plants with higher densities of scales experienced lower parasitism rates from hymenopteran parasitoids, but higher scale densities experienced higher parasitism rates from O. clavulata. Further research is needed over the whole adult female life stage of P. corni to learn more about these ecological relationships that could be of great benefit to hybrid hazelnut growers if P. corni becomes a significant pest
NuSTAR discovery of a cyclotron line in the accreting X-ray pulsar IGR J16393-4643
The high-mass X-ray binary and accreting X-ray pulsar IGR J16393-4643 was
observed by NuSTAR in the 3-79 keV energy band for a net exposure time of 50
ks. We present the results of this observation which enabled the discovery of a
cyclotron resonant scattering feature with a centroid energy of 29.3(+1.1/-1.3)
keV. This allowed us to measure the magnetic field strength of the neutron star
for the first time: B = (2.5+/-0.1)e12 G. The known pulsation period is now
observed at 904.0+/-0.1 s. Since 2006, the neutron star has undergone a
long-term spin-up trend at a rate of P' = -2e-8 s/s (-0.6 s per year, or a
frequency derivative of nu' = 3e-14 Hz/s ). In the power density spectrum, a
break appears at the pulse frequency which separates the zero slope at low
frequency from the steeper slope at high frequency. This addition of angular
momentum to the neutron star could be due to the accretion of a quasi-spherical
wind, or it could be caused by the transient appearance of a prograde accretion
disk that is nearly in corotation with the neutron star whose magnetospheric
radius is around 2e8 cm.Comment: Accepted for publication in the Astrophysical Journal, 7 pages, 8
figures, 2 table
Broadband X-ray Properties of the Gamma-ray Binary 1FGL J1018.6-5856
We report on NuSTAR, XMM-Newton and Swift observations of the gamma-ray
binary 1FGL J1018.6-5856. We measure the orbital period to be 16.544+/-0.008
days using Swift data spanning 1900 days. The orbital period is different from
the 2011 gamma-ray measurement which was used in the previous X-ray study of An
et al. (2013) using ~400 days of Swift data, but is consistent with a new
gamma-ray solution reported in 2014. The light curve folded on the new period
is qualitatively similar to that reported previously, having a spike at phase 0
and broad sinusoidal modulation. The X-ray flux enhancement at phase 0 occurs
more regularly in time than was previously suggested. A spiky structure at this
phase seems to be a persistent feature, although there is some variability.
Furthermore, we find that the source flux clearly correlates with the spectral
hardness throughout all orbital phases, and that the broadband X-ray spectra
measured with NuSTAR, XMM-Newton, and Swift are well fit with an unbroken
power-law model. This spectrum suggests that the system may not be
accretion-powered.Comment: 8 pages, 4 figures. Accepted for publication in Ap
Human Consumption of Microplastics
Microplastics are ubiquitous across ecosystems, yet the exposure risk to humans is unresolved. Focusing on the American diet, we evaluated the number of microplastic particles in commonly consumed foods in relation to their recommended daily intake. The potential for microplastic inhalation and how the source of drinking water may affect microplastic consumption were also explored. Our analysis used 402 data points from 26 studies, which represents over 3600 processed samples. Evaluating approximately 15% of Americans’ caloric intake, we estimate that annual microplastics consumption ranges from 39000 to 52000 particles depending on age and sex. These estimates increase to 74000 and 121000 when inhalation is considered. Additionally, individuals who meet their recommended water intake through only bottled sources may be ingesting an additional 90000 microplastics annually, compared to 4000 microplastics for those who consume only tap water. These estimates are subject to large amounts of variation; however, given methodological and data limitations, these values are likely underestimates
Looking at A 0535+26 at low luminosities with NuSTAR
We report on two NuSTAR observations of the HMXB A 0535+26 taken toward the
end of its normal 2015 outburst at very low keV luminosities of
erg/s and erg/s which are
complemented by 9 Swift observations. The data clearly confirm indications seen
in earlier data that the source's spectral shape softens as it becomes fainter.
The smooth, exponential rollover at high energies present in the first
observation evolves to a much more abrupt steepening of the spectrum at
keV. The continuum evolution can be well described with emission from a
magnetized accretion column, modeled using the compmag model modified by an
additional Gaussian emission component for the fainter observation. Between the
two observations, the optical depth changes from to
, the electron temperature remains constant, and there is
an indication that the column decreases in radius. Since the energy resolved
pulse profiles remain virtually unchanged in shape between the two
observations, the emission properties of the accretion column, however, reflect
the same accretion regime. This conclusion is also confirmed by our result that
the energy of the cyclotron resonant scattering feature (CRSF) at
keV is independent of the luminosity, implying that the magnetic field in the
region in which the observed radiation is produced is the same in both
observations. Finally, we also constrain the evolution of the continuum
parameters with rotational phase of the neutron star. The width of the CRSF
could only be constrained for the brighter observation. Based on Monte-Carlo
simulations of CRSF formation in single accretion columns, its pulse phase
dependence supports a simplified fan beam emission pattern. The evolution of
the CRSF width is very similar to that of the CRSF depth, which is in
disagreement with expectations.Comment: 14 pages, 11 figures, 3 tables, accepted for publication in A&
NuSTAR Discovery of a Cyclotron Line in the Be/X-ray Binary RX J0520.5-6932 During Outburst
We present spectral and timing analysis of NuSTAR observations of RX
J0520.56932 in the 3-79 keV band collected during its outburst in January
2014. The target was observed on two epochs and we report the detection of a
cyclotron resonant scattering feature with central energies of keV and keV during the two
observations, respectively, corresponding to a magnetic field of G. The 3-79 keV luminosity of the system during the two epochs
assuming a nominal distance of 50 kpc was and
. Both values are much higher
than the critical luminosity of
above which a radiation dominated shock front may be expected. This adds a new
object to the sparse set of three systems that have a cyclotron line observed
at luminosities in excess of . A broad
( keV) Fe emission line is observed in the spectrum at a
central energy of keV in both epochs. The pulse profile
of the pulsar was observed to be highly asymmetric with a sharply rising and
slowly falling profile of the primary peak. We also observed minor variations
in the cyclotron line energy and width as a function of the rotation phase.% As
in observations of other cyclotron absorption line sources, there is a small
() phase difference between the peak of the cyclotron
energy variation and the peak of the flux variation.Comment: 9 pages, 4 figures, 6 tables. Accepted to Ap
A NuSTAR observation of the reflection spectrum of the low mass X-ray binary 4U 1728-34
We report on a simultaneous NuSTAR and Swift observation of the neutron star
low-mass X-ray binary 4U 1728-34. We identified and removed four Type I X-ray
bursts during the observation in order to study the persistent emission. The
continuum spectrum is hard and well described by a black body with 1.5
keV and a cutoff power law with 1.5 and a cutoff temperature of 25
keV. Residuals between 6 and 8 keV provide strong evidence of a broad Fe
K line. By modeling the spectrum with a relativistically blurred
reflection model, we find an upper limit for the inner disk radius of . Consequently we find that km,
assuming M=1.4{\mbox{\rm\,M_{\mathord\odot}}} and . We also find an
upper limit on the magnetic field of G.Comment: 9 pages, 8 figure
Hard X-ray Morphological and Spectral Studies of The Galactic Center Molecular Cloud Sgr B2: Constraining Past Sgr A* Flaring Activity
Galactic Center (GC) molecular cloud Sgr B2 is the best manifestation of an
X-ray reflection nebula (XRN) reprocessing a past giant outburst from the
supermassive black hole Sgr A*. Alternatively, Sgr B2 could be illuminated by
low-energy cosmic ray electrons (LECRe) or protons (LECRp). In 2013, NuSTAR for
the first time resolved Sgr B2 hard X-ray emission on sub-arcminute scales. Two
prominent features are detected above 10 keV - a newly emerging cloud
G0.66-0.13 and the central 90" radius region containing two compact cores Sgr
B2(M) and Sgr B2(N) surrounded by diffuse emission. It is inconclusive whether
the remaining level of Sgr B2 emission is still decreasing or has reached a
constant background level. A decreasing Fe K emission can be best
explained by XRN while a constant background emission can be best explained by
LECRp. In the XRN scenario, the 3-79 keV Sgr B2 spectrum can well constrain the
past Sgr A* outburst, resulting in an outburst spectrum with a peak luminosity
of derived from the
maximum Compton-scattered continuum and the Fe K emission consistently.
The XRN scenario is preferred by the fast variability of G0.66-0.13, which
could be a molecular clump located in the Sgr B2 envelope reflecting the same
Sgr A* outburst. In the LECRp scenario, we derived the required CR ion power
and the CR ionization rate
. The Sgr B2 background level
X-ray emission will be a powerful tool to constrain GC CR population.Comment: 17 pages, 6 figures, submitted to Ap
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