615 research outputs found
Comparison of Sudoku Solving Skills of Preschool Children Enrolled in the Montessori Approach and the National Education Programs Yıldız Güven1, Cihat Gültekin1, A. Beyzanur Dedeoğlu1
According to Johnson-Laird (2010), sudoku, a mind game, is based on a pure deduction and reasoning processes. This study analyzed sudoku solving skills of preschool children and to ascertain whether there was a difference between children who were educated according to the Ministry of Education preschool education program and the Montessori approach. Sudoku skills of children were analyzed by gender, age, duration of preschool attendance, mother’s and father’s education level and previous experience of playing sudoku using a 12-question Sudoku Skills Measurement Tool developed for this research study.The study sample of the study consisted of 118 children (57 girls, 61 boys) aged between 54-77 months. The findings showed that there was no significant difference in sudoku skills by gender. However, sudoku skills varied with age (54-65 months and 66-77 months) in favor of older groups. Children's sudoku skills were more developed with an increase in education level of either parent. Children who had been in preschool for longer had higher sudoku scores. A previous experience of playing sudoku did not impact sudoku scores. Sudoku skills of children who were educated according to the Montessori program were more developed compared to those of children educated according to Ministry of National Education program
Shock-Driven Periodic Variability in a Low-Mass-Ratio Supermassive Black Hole Binary
We investigate the time-varying electromagnetic emission of a low-mass-ratio
supermassive black hole binary (SMBHB) embedded in a circumprimary disk, with a
particular interest in variability of shocks driven by the binary. We perform a
2D, locally isothermal hydrodynamics simulation of a SMBHB with mass ratio
and separation , using a physically self-consistent steady
disk model. We estimate the electromagnetic variability from the system by
monitoring accretion onto the secondary and using an artificial viscosity
scheme to capture shocks and monitor the energy dissipated. The SMBHB produces
a wide, eccentric gap in the disk, previously only observed for larger mass
ratios, which we attribute to our disk model being much thinner
( near the secondary) than is typical of previous works. The
eccentric gap drives periodic accretion onto the secondary SMBH on a timescale
matching the orbital period of the binary, ,
implying that the variable accretion regime of the SMBHB parameter space
extends to lower mass ratios than previously established. Shocks driven by the
binary are periodic, with a period matching the orbital period, and the shocks
are correlated with the accretion rate, with peaks in the shock luminosity
lagging peaks in the accretion rate by . We propose that
the correlation of these quantities represents a useful identifier of SMBHB
candidates, via observations of correlated variability in X-ray and UV
monitoring of AGN, rather than single-waveband periodicity alone.Comment: 12 pages, 8 figures, accepted by MNRA
Compact massive objects in Virgo galaxies: the black hole population
We investigate the distribution of massive black holes (MBHs) in the Virgo
cluster. Observations suggest that AGN activity is widespread in massive
galaxies (M>1e10 solar masses), while at lower galaxy masses star clusters are
more abundant, which might imply a limited presence of central black holes in
these galaxy-mass regimes. We explore if this possible threshold in MBH
hosting, is linked to nature, nurture, or a mixture of both. The nature
scenario arises naturally in hierarchical cosmologies, as MBH formation
mechanisms typically are efficient in biased systems, which would later evolve
into massive galaxies. Nurture, in the guise of MBH ejections following MBH
mergers, provides an additional mechanism that is more effective for low mass,
satellite galaxies. The combination of inefficient formation, and lower
retention of MBHs, leads to the natural explanation of the distribution of
compact massive ob jects in Virgo galaxies. If MBHs arrive to the correlation
with the host mass and velocity dispersion during merger-triggered accretion
episodes, sustained tidal stripping of the host galaxies creates a population
of MBHs which lie above the expected scaling between the holes and their host
mass, suggesting a possible environmental dependence.Comment: MNRAS letter
A Distinctive Disk-Jet Coupling in the Seyfert-1 AGN NGC 4051
We report on the results of a simultaneous monitoring campaign employing
eight Chandra X-ray (0.5-10 keV) and six VLA/EVLA (8.4 GHz) radio observations
of NGC 4051 over seven months. Evidence for compact jets is observed in the 8.4
GHz radio band; This builds on mounting evidence that jet production may be
prevalent even in radio-quiet Seyferts. Assuming comparatively negligible local
diffuse emission in the nucleus, the results also demonstrate an inverse
correlation of L_radio proportional to L_X-ray ^(-0.72+/-0.04) . Current
research linking the mass of supermassive black holes and stellar-mass black
holes in the "low/hard" state to X-ray luminosities and radio luminosities
suggest a "fundamental plane of accretion onto black holes" that has a positive
correlation of L_radio proportional to L_X-ray^(0.67+/-0.12) . Our simultaneous
results differ from this relation by more than 11 sigma, indicating that a
separate mode of accretion and ejection may operate in this system. A review of
the literature shows that the inverse correlation seen in NGC 4051 is seen in
three other black hole systems, all of which accrete at near 10% of their
Eddington luminosity, perhaps suggesting a distinct mode of disk-jet coupling
at high Eddington fractions. We discuss our results in the context of disk and
jets in black holes and accretion across the black hole mass scale.Comment: 12 pages, 9 figure
Illness tracking in SARS-CoV-2 tested persons using a smartphone app: a non-interventional, prospective, cohort study
There are few data on the range and severity of symptoms of SARS-CoV-2 infection or the impact on life quality in infected, previously healthy, young adults such as Swiss Armed Forces personnel. It is also unclear if an app can be used to remotely monitor symptoms in persons who test positive. Using a smartphone app called ITITP (Illness Tracking in Tested Persons) and weekly pop-up questionnaires, we aimed to evaluate the spectrum, duration, and impact of symptoms reported after a positive SARS-CoV-2 test according to sex, age, location, and comorbidities, and to compare these to responses from persons who tested negative. We followed up 502 participants (57% active participation), including 68 (13.5%) positive tested persons. Hospitalisation was reported by 6% of the positive tested participants. We found that positives reported significantly more symptoms that are typical of COVID-19 compared to negatives. These symptoms with odds ratio (OR > 1) were having difficulty breathing (OR 3.35; 95% CI: 1.16, 9.65; p = 0.03), having a reduced sense of taste (OR 5.45; 95% CI: 1.22, 24.34; p = 0.03) and a reduced sense of smell (OR 18.24; 95% CI: 4.23, 78.69; p < 0.001). Using a random forest model, we showed that tiredness was the single symptom that was rated as having a significant impact on daily activities, whereas the other symptoms, although frequent, had less impact. The study showed that the use of an app was feasible to remotely monitor symptoms in persons infected with SARS-CoV-2 and could be adapted for other settings and new pandemic phases such as the current Omicron wave
Spectroastrometry of rotating gas disks for the detection of supermassive black holes in galactic nuclei. II. Application to the galaxy Centaurus A (NGC 5128)
We measure the black hole mass in the nearby active galaxy Centaurus A (NGC
5128) using a new method based on spectroastrometry of a rotating gas disk. The
spectroastrometric approach consists in measuring the photocenter position of
emission lines for different velocity channels. In a previous paper we focused
on the basic methodology and the advantages of the spectroastrometric approach
with a detailed set of simulations demonstrating the possibilities for black
hole mass measurements going below the conventional spatial resolution. In this
paper we apply the spectroastrometric method to multiple longslit and integral
field near infrared spectroscopic observations of Centaurus A. We find that the
application of the spectroastrometric method provides results perfectly
consistent with the more complex classical method based on rotation curves: the
measured BH mass is nearly independent of the observational setup and spatial
resolution and the spectroastrometric method allows the gas dynamics to be
probed down to spatial scales of ~0.02", i.e. 1/10 of the spatial resolution
and ~1/50 of BH sphere of influence radius. The best estimate for the BH mass
based on kinematics of the ionized gas is then log(MBH (sin i)^2/M\odot)=7.5
\pm 0.1 which corresponds to MBH = 9.6(+2.5-1.8) \times 10^7 M\odot for an
assumed disk inclination of i = 35deg. The complementarity of this method with
the classic rotation curve method will allow us to put constraints on the disk
inclination which cannot be otherwise derived from spectroastrometry. With the
application to Centaurus A, we have shown that spectroastrometry opens up the
possibility of probing spatial scales smaller than the spatial resolution,
extending the measured MBH range to new domains which are currently not
accessible: smaller BHs in the local universe and similar BHs in more distant
galaxies
An Over-Massive Black Hole in the Compact Lenticular Galaxy NGC1277
All massive galaxies likely have supermassive black holes at their centers,
and the masses of the black holes are known to correlate with properties of the
host galaxy bulge component. Several explanations have been proposed for the
existence of these locally-established empirical relationships; they include
the non-causal, statistical process of galaxy-galaxy merging, direct feedback
between the black hole and its host galaxy, or galaxy-galaxy merging and the
subsequent violent relaxation and dissipation. The empirical scaling relations
are thus important for distinguishing between various theoretical models of
galaxy evolution, and they further form the basis for all black hole mass
measurements at large distances. In particular, observations have shown that
the mass of the black hole is typically 0.1% of the stellar bulge mass of the
galaxy. The small galaxy NGC4486B currently has the largest published fraction
of its mass in a black hole at 11%. Here we report observations of the stellar
kinematics of NGC 1277, which is a compact, disky galaxy with a mass of 1.2 x
10^11 Msun. From the data, we determine that the mass of the central black hole
is 1.7 x 10^10 Msun, or 59% its bulge mass. Five other compact galaxies have
properties similar to NGC 1277 and therefore may also contain over-sized black
holes. It is not yet known if these galaxies represent a tail of a
distribution, or if disk-dominated galaxies fail to follow the normal black
hole mass scaling relations.Comment: 7 pages. 6 figures. Nature. Animation at
http://www.mpia.de/~bosch/blackholes.htm
Dynamical Measurements of Black Hole Masses in Four Brightest Cluster Galaxies at 100 Mpc
We present stellar kinematics and orbit superposition models for the central
regions of four Brightest Cluster Galaxies (BCGs), based upon integral-field
spectroscopy at Gemini, Keck, and McDonald Observatories. Our integral-field
data span radii from < 100 pc to tens of kpc. We report black hole masses,
M_BH, of 2.1 +/- 1.6 x 10^10 M_Sun for NGC 4889, 9.7 + 3.0 - 2.6 x 10^9 M_Sun
for NGC 3842, and 1.3 + 0.5 - 0.4 x 10^9 M_Sun for NGC 7768. For NGC 2832 we
report an upper limit of M_BH < 9 x 10^9 M_Sun. Stellar orbits near the center
of each galaxy are tangentially biased, on comparable spatial scales to the
galaxies' photometric cores. We find possible photometric and kinematic
evidence for an eccentric torus of stars in NGC 4889, with a radius of nearly 1
kpc. We compare our measurements of M_BH to the predicted black hole masses
from various fits to the relations between M_BH and stellar velocity
dispersion, luminosity, or stellar mass. The black holes in NGC 4889 and NGC
3842 are significantly more massive than all dispersion-based predictions and
most luminosity-based predictions. The black hole in NGC 7768 is consistent
with a broader range of predictions.Comment: 24 pages, 18 figures. Accepted for publication in Ap
A Radio Relic And A Search For The Central Black Hole In The Abell 2261 Brightest Cluster Galaxy
We present VLA images and HST/STIS spectra of sources within the center of the brightest cluster galaxy (BCG) in Abell 2261. These observations were obtained to test the hypothesis that its extremely large, flat core reflects the ejection of its supermassive black hole. Spectra of three of the four most luminous knots embedded in the core were taken to test whether one may represent stars bound to a displaced massive black hole. The three knots have radial velocity offsets dV \u3c ~150 km/s from the BCG. Knots 2 and 3 show kinematics, colors, and stellar masses consistent with infalling low-mass galaxies or larger stripped cluster members. Large errors in the stellar velocity dispersion of Knot 1, however, mean that we cannot rule out the hypothesis that it hosts a high-mass black hole. A2261-BCG has a compact, relic radio-source offset by 6.5 kpc (projected) from the optical core\u27s center, but no active radio core that would pinpoint the galaxy\u27s central black hole to a tight 10 GHz flux limit 48 Myr ago, with an equipartition condition magnetic field of 15 uG. These observations are still consistent with the hypothesis that the nuclear black hole has been ejected from its core, but the critical task of locating the supermassive black hole or demonstrating that A2261-BCG lacks one remains to be done
Epicardial fat volume is inversely correlated with the degree of diastolic dysfunction and outcome in patients with heart failure with preserved ejection fraction
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