5 research outputs found
Detection of Intra-day Variability Timescales of Four High Energy Peaked Blazars with XMM-Newton
We selected a sample of 24 XMM-Newton light curves (LCs) of four high energy
peaked blazars, PKS 0548-322, ON 231, 1ES 1426+428 and PKS 2155-304. These data
comprise continuous light curves of 7.67h to 18.97h in length. We searched for
possible quasi-periodic oscillations (QPO) and intra-day variability (IDV)
timescales in the LCs of these blazars. We found a likely QPO in one LC of PKS
2155-304 which was reported elsewhere (Lachowicz et al. 2009). In the remaining
23 LCs we found hints of possible weak QPOs in one LC of each of ON 231 and PKS
2155-304, but neither is statistically significant. We found IDV timescales
that ranged from 15.7 ks to 46.8 ks in 8 LCs. In 13 LCs any variability
timescales were longer than the length of the data. Assuming the possible weak
QPO periods in the blazars PKS 2155-304 and ON 231 are real and are associated
with the innermost portions of their accretion disk, we can estimate that their
central black hole masses exceed 1.2 10 M. Emission
models for radio-loud active galactic nuclei (AGN) that could explain our
results are briefly discussed.Comment: 13 emulateapj pages, 2 tables, 4 figures, accepted for publication in
The Astrophysical Journa
The Effect of Cadmium on Sleep Parameters Assessed in Polysomnographic Studies: A Case–Control Study
Cadmium is a heavy metal that accumulates in the body due to environmental and occupational exposure. The main form of environmental exposure to cadmium is related to cigarette smoking. The primary aim of this study was to evaluate the effect of cadmium on numerous sleep parameters with the use of polysomnography. The secondary aim of this study was to investigate if environmental exposure to cadmium is a risk factor for the intensity of sleep bruxism (SB). Methods: A total of 44 adults underwent a full night of polysomnographic examination. The polysomnograms were assessed according to guidelines set out by the American Academy of Sleep Medicine (AASM). The concentration of cadmium in the blood and urine was determined spectrophotometrically. Results: The polysomnographic examination confirmed that cadmium, age, male gender and smoking status are independent risk factors for an increase in the apnea–hypopnea index (AHI). Cadmium alters sleep architecture by favoring sleep fragmentation and decreasing the duration of the rapid eye movement (REM) phase of sleep. However, cadmium exposure is not a risk factor for the development of sleep bruxism. Conclusions: In summary, this study demonstrates that cadmium affects sleep architecture and is a risk factor for the development of obstructive sleep apnea; however, it does not affect sleep bruxism