2,053 research outputs found
School Counselors Involvement and Opportunities to Advocate Against Racialized Punitive Practices
Given the increase of violence against Black, Indigenous, People of Color (BIPOC), there is no doubt a need to tackle racialized violence in schools. This phenomenological study draws on semi-structured interviews with school counselors to explore their experiences and practices to disrupt the racialized disciplinary practices that disproportionally target Black, Indigenous, and Students of Color. We draw on theories of racialized organizations and organizational routines to better understand how school counselors make sense of their practices in racialized disciplinary practices that dehumanize and criminalized youth of color. Findings from this study revealed two themes: 1) school counselorsâ perceived neutrality towards disciplinary practices and 2) school counselorsâ advocacy in racialized school discipline practices. This study offers some implications for professional school counseling organization, counselor educators, and school counselors to inform their anti-racist pedagogy to dismantle racialized punitive practices in schools
IM Normae: The Death Spiral of a Cataclysmic Variable?
We present a study of the orbital light curves of the recurrent nova IM Normae since its 2002 outburst. The broad
âeclipsesâ recur with a 2.46 hr period, which increases on a timescale of 1.28(16) Ă 106 yr. Under the assumption
of conservative mass transfer, this suggests a rate near 10â7 Me yrâ1
, and this agrees with the estimated accretion
rate of the postnova, based on our estimate of luminosity. IM Nor appears to be a close match to the famous
recurrent nova T Pyxidis. Both stars appear to have very high accretion rates, sufficient to drive the recurrent-nova
events. Both have quiescent light curves, which suggest strong heating of the low-mass secondary, and very wide
orbital minima, which suggest obscuration of a large âcoronaâ around the primary. And both have very rapid
orbital period increases, as expected from a short-period binary with high mass transfer from the low-mass
component. These two stars may represent a final stage of novaâand cataclysmic variableâevolution, in which
irradiation-driven winds drive a high rate of mass transfer, thereby evaporating the donor star in a paroxysm of
nova outburst
Superhumps and spin-period variations in the intermediate polar RX J2133.7+5107
We report the results of long-term time series photometry on RX J2133.7+5107, an intermediate polar distinguished by its long orbital period (7.14 h) and rapid rotation (571 s) of its white dwarf. The light curves show the presence of a conspicuous modulation with a 6.72-h period, 6.1 ± 0.1 per cent shorter than the orbital period, which we interpret as a (negative) superhump associated with the nodal precession of the accretion disc. This detection may prove a challenge to the idea that superhumps are limited to binaries of short orbital period. Our rotational timings over the 7 yr spanned by our observations show spin-up at a rate of 3.41(2) ms yr-1 or, equivalently, on a time-scale
|P/P?|=0.17Ă106
yr. The latter is sensibly shorter than the time-scale of spin period variations reported for other intermediate polars, possibly due to a greater accretion rate.We thank the National Science Foundation for support of this research (AST-1211129 and AST-1615456), and NASA through HST-G0-13630. EdM acknowledges financial support from the Ministerio de Educacion, Cultura y Deporte (Spain) under the Mobility Program Salvador de Madariaga (PRX15/00521)
BK Lyncis: The Oldest Old Nova?... And a Bellwether for Cataclysmic-Variable Evolution
We summarize the results of a 20-year campaign to study the light curves of
BK Lyncis, a nova-like star strangely located below the 2-3 hour orbital period
gap in the family of cataclysmic variables. Two apparent "superhumps" dominate
the nightly light curves - with periods 4.6% longer, and 3.0% shorter, than
P_orb. The first appears to be associated with the star's brighter states
(V~14), while the second appears to be present throughout and becomes very
dominant in the low state (V~15.7).
Starting in the year 2005, the star's light curve became indistinguishable
from that of a dwarf nova - in particular, that of the ER UMa subclass.
Reviewing all the star's oddities, we speculate: (a) BK Lyn is the remnant of
the probable nova on 30 December 101, and (b) it has been fading ever since,
but has taken ~2000 years for the accretion rate to drop sufficiently to permit
dwarf-nova eruptions. If such behavior is common, it can explain other puzzles
of CV evolution. One: why the ER UMa class even exists (because all members can
be remnants of recent novae). Two: why ER UMa stars and short-period novalikes
are rare (because their lifetimes, which are essentially cooling times, are
short). Three: why short-period novae all decline to luminosity states far
above their true quiescence (because they're just getting started in their
postnova cooling). Four: why the orbital periods, accretion rates, and
white-dwarf temperatures of short-period CVs are somewhat too large to arise
purely from the effects of gravitational radiation (because the unexpectedly
long interval of enhanced postnova brightness boosts the mean mass-transfer
rate). These are substantial rewards in return for one investment of
hypothesis: that the second parameter in CV evolution, besides P_orb, is time
since the last classical-nova eruption.Comment: PDF, 46 pages, 4 tables, 10 figures; in preparation; more info at
http://cbastro.org
On the application of a diffusive memristor compact model to neuromorphic circuits
Memristive devices have found application in both random access memory and neuromorphic circuits. In particular, it is known that their behavior resembles that of neuronal synapses. However, it is not simple to come by samples of memristors and adjusting their parameters to change their response requires a laborious fabrication process. Moreover, sample to sample variability makes experimentation with memristor-based synapses even harder. The usual alternatives are to either simulate or emulate the memristive systems under study. Both methodologies require the use of accurate modeling equations. In this paper, we present a diffusive compact model of memristive behavior that has already been experimentally validated. Furthermore, we implement an emulation architecture that enables us to freely explore the synapse-like characteristics of memristors. The main advantage of emulation over simulation is that the former allows us to work with real-world circuits. Our results can give some insight into the desirable characteristics of the memristors for neuromorphic applications
SDSS J162520.29+120308.7 â a new SU Ursae Majoris star in the period gap
We report results of an extensive world-wide observing campaign devoted to the recently discovered dwarf nova
SDSS J162520.29+120308.7 (SDSS J1625). The data were obtained during the July 2010 eruption of the star and in August and
September 2010 when the object was in quiescence. During the July 2010 superoutburst, SDSS J1625 clearly displayed superhumps
with a mean period of Psh = 0.095942(17) days (138.16 ± 0.02 min) and a maximum amplitude reaching almost 0.4 mag. The superhump
period was not stable, decreasing very rapidly at a rate of ËP = â1.63(14) Ă 10â3 at the beginning of the superoutburst and
increasing at a rate of ËP = 2.81(20) Ă 10â4 in the middle phase. At the end of the superoutburst, it stabilized around the value of
Psh = 0.09531(5) day.
During the first twelve hours of the superoutburst, a low-amplitude double wave modulation was observed whose properties are
almost identical to early superhumps observed in WZ Sge stars. The period of early superhumps, the period of modulations observed
temporarily in quiescence, and the period derived from radial velocity variations are the same within measurement errors, allowing
us to estimate the most probable orbital period of the binary to be Porb = 0.09111(15) days (131.20 ± 0.22 min). This value clearly
indicates that SDSS J1625 is another dwarf nova in the period gap. Knowledge of the orbital and superhump periods allows us to
estimate the mass ratio of the system to be q â 0.25. This high value poses serious problems for both the thermal and tidal instability
(TTI) model describing the behaviour of dwarf novae and for some models explaining the origin of early superhumps
- âŠ