1,673 research outputs found
Safe Spaces on Campus: An Examination of Student and Faculty Perceptions
Creating and maintaining a positive school climate is paramount for student well-being. This climate is marked by a teaching and learning environment that can foster positive student outcomes, such as academic achievement, and decrease negative student outcomes, such as absenteeism (Thapa, Cohen, Guffey, & Higgins-D’Alessandro, 2013). One approach to creating a positive and inclusive school climate that welcomes diversity is the development of safe spaces or safe zones on campus. Given the lack of scholarly literature that addresses this topic, the current study explores safe spaces from the perspective of college students and faculty at a liberal arts institution
Microaggressions on Campus: An Examination of Student Perceptions
Creating and maintaining a positive school climate is paramount for student well-being. Microaggressions, or subtle forms of prejudice, in the classroom setting can present a barrier to cultivating such a climate and contribute to a host of negative consequences for impacted students. This study explores student perceptions of the prevalence and types of microaggressions at a private, liberal arts college in South-Central Pennsylvania. Data from student surveys will be examined to develop a better understanding of this topic and generate discussions about maintaining a positive and inclusive school climate that welcomes diversity
The discovery of the optical/IR counterpart of the 12s transient X-ray pulsar GS 0834-43
We report the discovery of the optical/infra-red counterpart of the 12.3s
transient X-ray pulsar GS0834-43. We re-analysed archival ROSAT PSPC
observations of GS0834-43, obtaining two new refined positions, about 14" and
18" away from the previously published one, and a new spin period measurement.
Within the new error circles we found a relatively faint (V=20.1) early type
reddened star (V-R=2.24). The optical spectrum shows a strong Halpha emission
line. The IR observations of the field confirm the presence of an IR excess for
the Halpha-emitting star (K'=11.4, J-K'=1.94) which is likely surrounded by a
conspicuous circumstellar envelope. Spectroscopic and photometric data indicate
a B0-2 V-IIIe spectral-type star located at a distance of 3-5kpc and confirm
the Be-star/X-ray binary nature of GS0834-43.Comment: 6 pages. Accepted for publication in MNRA
Unravelling the enigmatic origin of calcitic nanofibres in soils and caves: purely physicochemical or biogenic processes?
Calcitic nanofibres are ubiquitous habits of sec- ondary calcium carbonate (CaCO3 ) accumulations observed in calcareous vadose environments. Despite their widespread occurrence, the origin of these nanofeatures remains enig- matic. Three possible mechanisms fuel the debate: (i) purely physicochemical processes, (ii) mineralization of rod-shaped bacteria, and (iii) crystal precipitation on organic templates. Nanofibres can be either mineral (calcitic) or organic in na- ture. They are very often observed in association with needle fibre calcite (NFC), another typical secondary CaCO3 habit in terrestrial environments. This association has contributed to some confusion between both habits, however they are truly two distinct calcitic features and their recurrent asso- ciation is likely to be an important fact to help understanding the origin of nanofibres. In this paper the different hypotheses that currently exist to explain the origin of calcitic nanofibres are critically reviewed. In addition to this, a new hypothe- sis for the origin of nanofibres is proposed based on the fact that current knowledge attributes a fungal origin to NFC. As this feature and nanofibres are recurrently observed together, a possible fungal origin for nanofibres which are associated with NFC is investigated. Sequential enzymatic digestion of the fungal cell wall of selected fungal species demonstrates that the fungal cell wall can be a source of organic nanofibres. The obtained organic nanofibres show a striking morpho- logical resemblance when compared to their natural coun- terparts, emphasizing a fungal origin for part of the organic
nanofibres observed in association with NFC. It is further hy- pothesized that these organic nanofibres may act as templates for calcite nucleation in a biologically influenced mineraliza- tion process, generating calcitic nanofibres. This highlights the possible involvement of fungi in CaCO3 biomineraliza- tion processes, a role still poorly documented. Moreover, on a global scale, the organomineralization of organic nanofi- bres into calcitic nanofibres might be an overlooked process deserving more attention to specify its impact on the biogeo- chemical cycles of both Ca and C
Swift J201424.9+152930: discovery of a new deeply eclipsing binary with 491 s and 3.4 h modulations
We report on the discovery of a new X-ray pulsator, Swift J201424.9+152930
(Sw J2014). Owing to its X-ray modulation at 491 s, it was discovered in a
systematic search for coherent signals in the archival data of the Swift X-ray
Telescope. To investigate the nature of Sw J2014, we performed multi-wavelength
follow-up observations with space-borne (Swift and XMM-Newton) and ground-based
(the 1.5-m Loiano Telescope and the 3.6-m Telescopio Nazionale Galileo)
instruments. The X-ray spectrum of Sw J2014 can be described by a hard and
highly absorbed power law. The optical observations made it possible to single
out the optical counterpart to this source, which displays several variable
emission lines and total eclipses lasting ~20 min. Total eclipses of similar
length were observed also in X-rays. The study of the eclipses, allowed us to
infer a second periodicity of 3.44 h, which we interpret as the orbital period
of a close binary system. We also found that the period has not significantly
changed over a ~7 yr timespan. Based on the timing signatures of Sw J2014, and
its optical and X-ray spectral properties, we suggest that it is a close binary
hosting an accreting magnetic white dwarf. The system is therefore a
cataclysmic variable of the intermediate polar type and one of the very few
showing deep eclipses.Comment: 12 pages, 8 figures, 5 tables; minor changes to match the final MNRAS
versio
XTE J1946+274 = GRO J1944+26: An Enigmatic Be/X-ray Binary
XTE J1946+274 = GRO J1944+26 is a 15.8 s Be/X-ray pulsar discovered
simultaneously in 1998 September with the Burst and Transient Source Experiment
(BATSE) on the Compton Gamma Ray Observatory (CGRO) and the All-Sky Monitor
(ASM) on the Rossi X-ray Timing Explorer (RXTE). Here we present new results
from BATSE and {\em RXTE} including a pulse timing analysis, spectral analysis,
and evidence for an accretion disk. Our pulse timing analysis yielded an
orbital period of 169.2 days, a moderate eccentricity of 0.33, and implied a
mass function of 9.7 M_sun. We observed evidence for an accretion disk, a
correlation between measured spin-up rate and flux, which was fitted to obtain
a distance estimate of 9.5 +/- 2.9 kpc. XTE J1946+274 remained active from 1998
September - 2001 July, undergoing 13 outbursts that were not locked in orbital
phase. Comparing RXTE PCA observations from the initial bright outburst in 1998
and the last pair of outbursts in 2001, we found energy and intensity dependent
pulse profile variations in both outbursts and hardening spectra with
increasing intensity during the fainter 2001 outbursts. In 2001 July, optical
Halpha observations indicate a density perturbation appeared in the Be disk as
the X-ray outbursts ceased. We propose that the equatorial plane of the Be star
is inclined with respect to the orbital plane in this system and that this
inclination may be a factor in the unusual outburst behavior of the system.Comment: 18 pages, 15 figures, To appear in ApJ v584, Feb 20, 2003 issu
The identification of the optical/IR counterpart of the 15.8-s transient X-ray pulsar XTE J1946+274
We report on the discovery of the optical/IR counterpart of the 15.8s
transient X-ray pulsar XTE J1946+274. We re-analysed archival BeppoSAX
observations of XTE J1946+274, obtaining a new refined position (a circle with
22" radius at 90% confidence level). Based on this new position we carried out
optical and infra-red (IR) follow-up observations. Within the new error circle
we found a relatively optical faint (B=18.6) IR bright (H=12.1) early type
reddened star (V--R=1.6). The optical spectra show strong H-alpha and H-beta
emission lines. The IR photometric observations of the field confirm the
presence of an IR excess for the H-alpha--emitting star (K=11.6, J--H=0.6)
which is likely surrounded by a circumstellar envelope. Spectroscopic and
photometric data indicate a B0--1V--IVe spectral-type star located at a
distance of 8--10kpc and confirm the Be-star/X-ray binary nature of XTE
J1946+274.Comment: Accepted for publication on A&A (7 pages and 4 figures
The Agile Alert System For Gamma-Ray Transients
In recent years, a new generation of space missions offered great
opportunities of discovery in high-energy astrophysics. In this article we
focus on the scientific operations of the Gamma-Ray Imaging Detector (GRID)
onboard the AGILE space mission. The AGILE-GRID, sensitive in the energy range
of 30 MeV-30 GeV, has detected many gamma-ray transients of galactic and
extragalactic origins. This work presents the AGILE innovative approach to fast
gamma-ray transient detection, which is a challenging task and a crucial part
of the AGILE scientific program. The goals are to describe: (1) the AGILE
Gamma-Ray Alert System, (2) a new algorithm for blind search identification of
transients within a short processing time, (3) the AGILE procedure for
gamma-ray transient alert management, and (4) the likelihood of ratio tests
that are necessary to evaluate the post-trial statistical significance of the
results. Special algorithms and an optimized sequence of tasks are necessary to
reach our goal. Data are automatically analyzed at every orbital downlink by an
alert pipeline operating on different timescales. As proper flux thresholds are
exceeded, alerts are automatically generated and sent as SMS messages to
cellular telephones, e-mails, and push notifications of an application for
smartphones and tablets. These alerts are crosschecked with the results of two
pipelines, and a manual analysis is performed. Being a small scientific-class
mission, AGILE is characterized by optimization of both scientific analysis and
ground-segment resources. The system is capable of generating alerts within two
to three hours of a data downlink, an unprecedented reaction time in gamma-ray
astrophysics.Comment: 34 pages, 9 figures, 5 table
The AGILE real-time analysis pipelines in the multi-messenger era
In the multi-messenger era, space and ground-based observatories usually
develop real-time analysis (RTA) pipelines to rapidly detect transient events
and promptly share information with the scientific community to enable
follow-up observations. These pipelines can also react to science alerts shared
by other observatories through networks such as the Gamma-Ray Coordinates
Network (GCN) and the Astronomer's Telegram (ATels). AGILE is a space mission
launched in 2007 to study X-ray and gamma-ray phenomena. This contribution
presents the technologies used to develop two types of AGILE pipelines using
the RTApipe framework and an overview of the main scientific results. The first
type performs automated analyses on new AGILE data to detect transient events
and automatically sends AGILE notices to the GCN network. Since May 2019, this
pipeline has sent more than 50 automated notices with a few minutes delay since
data arrival. The second type of pipeline reacts to multi-messenger external
alerts (neutrinos, gravitational waves, GRBs, and other transients) received
through the GCN network and performs hundreds of analyses searching for
counterparts in all AGILE instruments' data. The AGILE Team uses these
pipelines to perform fast follow-up of science alerts reported by other
facilities, which resulted in the publishing of several ATels and GCN
circulars.Comment: 8 pages, 3 figures, Proceedings of the 37th International Cosmic Ray
Conference (ICRC 2021), Berlin, German
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