8,713 research outputs found
Children's opinions on effective strategies to cope with bullying: the importance of bullying role and perspective
In order to find out what children would suggest as useful interventions to stop bullying, we designed a questionnaire administered to 311 children (155 boys and 156 girls; mean age = 11 years). Thirty-six items were employed to ask children how effective, in their opinion, retaliation, nonchalance and assertiveness could be in stopping bullying. Items were presented to children from three different perspectives (imagine you are the victim, the bully or a witness). We used peer reports to assess children's role in bullying. Children were grouped into bullies, followers of the bully, defenders of the victims, outsiders, victims and those not involved. The strategy most frequently chosen by all children was to cope with bullying through assertiveness. Bullies considered retaliation effective more often than their classmates, especially when they adopted the perspective of the victim or witness. Bullies did not consider assertive strategies as efficient in stopping the bully. Defenders, outsiders, victims and children not involved, on the other hand, were very much in favour of strategies aimed at solving the conflict through nonchalance or assertiveness, especially when they imagined being the bully. Girls chose assertive strategies more often than boys and younger children preferred nonchalance more often than older children, who tended to choose retaliation more often. Suggestions for intervention are made. © 2005 NFER
A Direct Upper Limit on the Density of Cosmological Dust from the Absence of an X-ray Scattering Halo around the z=4.3 QSO 1508+5714
We report on the results of a search for an intergalactic X-ray dust
scattering halo in a deep observation of the bright, high-redshift quasar QSO
1508+5714 with the Chandra X-ray Observatory. We do not detect such a halo. Our
result implies an upper limit on the density of diffuse, large-grained
intergalactic dust of Omega_ dust < 2 x 10^-6, assuming a characteristic grain
size of 1micron. The result demonstrates the sensitivity of this technique for
detecting very small amounts of intergalactic dust which are very hard to
detect otherwise. This will allow us to put important constraints on systematic
effects induced by extinction on the interpretation of the SN Ia Hubble
Diagram, as well as on the amount and properties of cosmological dust being
expelled into the intergalactic medium at early z~2 times.Comment: 14 pages, 2 figures. to appear in ApJ, vol. 651, Nov. 200
A possible dearth of hot gas in galaxy groups at intermediate redshift
We examine the X-ray luminosity of galaxy groups in the CNOC2 survey, at
redshifts 0.1 < z < 0.6. Previous work examining the gravitational lensing
signal of the CNOC2 groups has shown that they are likely to be genuine,
gravitationally bound objects. Of the 21 groups in the field of view of the
EPIC-PN camera on XMM-Newton, not one was visible in over 100 ksec of
observation, even though three of the them have velocity dispersions high
enough that they would easily be visible if their luminosities scaled with
their velocity dispersions in the same way as nearby groups' luminosities
scale. We consider the possibility that this is due to the reported velocity
dispersions being erroneously high, and conclude that this is unlikely. We
therefore find tentative evidence that groups at intermediate redshift are
underluminous relative to their local cousins.Comment: 16 pages, 5 figures, reference added in section 1, typos corrected,
published in Ap
Intermittent living; the use of ancient challenges as a vaccine against the deleterious effects of modern life - A hypothesis
Chronic non-communicable diseases (CNCD) are the leading cause of mortality in developed countries. They ensue from the sum of modern anthropogenic risk factors, including high calorie nutrition, malnutrition, sedentary lifestyle, social stress, environmental toxins, politics and economic factors. Many of these factors are beyond the span of control of individuals, suggesting that CNCD are inevitable. However, various studies, ours included, show that the use of intermittent challenges with hormetic effects improve subjective and objective wellbeing of individuals with CNCD, while having favourable effects on immunological, metabolic and behavioural indices. Intermittent cold, heat, fasting and hypoxia, together with phytochemicals in multiple food products, have widespread influence on many pathways related with overall health. Until recently, most of the employed challenges with hormetic effects belonged to the usual transient live experiences of our ancestors. Our hypothesis; we conclude that, whereas the total inflammatory load of multi-metabolic and psychological risk factors causes low grade inflammation and aging, the use of intermittent challenges, united in a 7-10 days lasting hormetic intervention, might serve as a vaccine against the deleterious effects of chronic low grade inflammation and it's metabolic and (premature) aging consequences
High-Resolution X-Ray Spectroscopy of the Accretion Disk Corona Source 4U 1822-37
We present a preliminary analysis of the X-ray spectrum of the accretion disk
corona source, 4U 1822-37, obtained with the High Energy Transmission Grating
Spectrometer onboard the Chandra X-ray Observatory. We detect discrete emission
lines from photoionized iron, silicon, magnesium, neon, and oxygen, as well as
a bright iron fluorescence line. Phase-resolved spectroscopy suggests that the
recombination emission comes from an X-ray illuminated bulge located at the
predicted point of impact between the disk and the accretion stream. The
fluorescence emission originates in an extended region on the disk that is
illuminated by light scattered from the corona.Comment: 12 pages, 6 figures; Accepted for publication in ApJ Letter
Evidence for the importance of resonance scattering in X-ray emission line profiles of the O star Puppis
We fit the Doppler profiles of the He-like triplet complexes of \ion{O}{7}
and \ion{N}{6} in the X-ray spectrum of the O star Puppis, using
XMM-Newton RGS data collected over ks of exposure. We find that they
cannot be well fit if the resonance and intercombination lines are constrained
to have the same profile shape. However, a significantly better fit is achieved
with a model incorporating the effects of resonance scattering, which causes
the resonance line to become more symmetric than the intercombination line for
a given characteristic continuum optical depth . We discuss the
plausibility of this hypothesis, as well as its significance for our
understanding of Doppler profiles of X-ray emission lines in O stars.Comment: 29 pages, 8 figures, revised version accepted by Ap
Changes in lower limb muscle function and muscle mass following exercise-based interventions in patients with chronic obstructive pulmonary disease : a review of the English-language literature
Chronic obstructive pulmonary disease (COPD) patients often experience lower limb muscle dysfunction and wasting. Exercise-based training has potential to improve muscle function and mass, but literature on this topic is extensive and heterogeneous including numerous interventions and outcomemeasures. This reviewuses a detailed systematic approach to investigate the effect of this wide range of exercise-based interventions on muscle function and mass. PUBMED and PEDro databases were searched. In all, 70 studies (n = 2504 COPD patients) that implemented an exercise-based intervention and reported muscle strength, endurance, or mass in clinically stable COPD patients were critically appraised. Aerobic and/or resistance training, high-intensity interval training, electrical or magnetic muscle stimulation, whole-body vibration, andwater-based training were investigated. Muscle strength increased in 78%, muscle endurance in 92%, and muscle mass in 88% of the cases where that specific outcome was measured. Despite large heterogeneity in exercise-based interventions and outcome measures used, most exercise-based trials showed improvements in muscle strength, endurance, and mass in COPD patients. Which intervention(s) is (are) best for which subgroup of patients remains currently unknown. Furthermore, this literature review identifies gaps in the current knowledge and generates recommendations for future research to enhance our knowledge on exercise-based interventions in COPD patients
On the Putative Detection of z>0 X-ray Absorption Features in the Spectrum of Markarian 421
In a series of papers, Nicastro et al. have reported the detection of z>0
OVII absorption features in the spectrum of Mrk421 obtained with the Chandra
Low Energy Transmission Grating Spectrometer (LETGS). We evaluate this result
in the context of a high quality spectrum of the same source obtained with the
Reflection Grating Spectrometer (RGS) on XMM-Newton. The data comprise over
955ks of usable exposure time and more than 26000 counts per 50 milliAngstrom
at 21.6 Angstroms. We concentrate on the spectrally clean region (21.3 < lambda
< 22.5 Angstroms) where sharp features due to the astrophysically abundant OVII
may reveal an intervening, warm--hot intergalactic medium (WHIM). We do not
confirm detection of any of the intervening systems claimed to date. Rather, we
detect only three unsurprising, astrophysically expected features down to the
Log(N_i)~14.6 (3 sigma) sensitivity level. Each of the two purported WHIM
features is rejected with a statistical confidence that exceeds that reported
for its initial detection. While we can not rule out the existence of fainter,
WHIM related features in these spectra, we suggest that previous discovery
claims were premature. A more recent paper by Williams et al. claims to have
demonstrated that the RGS data we analyze here do not have the resolution or
statistical quality required to confirm or deny the LETGS detections. We show
that our careful analysis resolves the issues encountered by Williams et al.
and recovers the full resolution and statistical quality of the RGS data. We
highlight the differences between our analysis and those published by Williams
et al. as this may explain our disparate conclusions.Comment: 19 pages/7 figures/4 tables. 060424 submitted to ApJ 060522
re-submitted following ApJ reques
- âŠ