1,053 research outputs found
Differential rotation measurement of soft X-Ray corona
The aim of this paper is to study the latitudinal variation in the solar
rotation in soft X-ray corona. The time series bins are formed on different
latitude regions of the solar full disk (SFD) images that extend from 80 degree
South to 80 degree North. These SFD images are obtained with the soft X-ray
telescope (SXT) on board the Yohkoh solar observatory. The autocorrelation
analyses are performed with the time series that track the SXR flux modulations
in the solar corona. Then for each year, extending from 1992 to 2001, we obtain
the coronal sidereal rotation rate as a function of the latitude. The present
analysis from SXR radiation reveals that; (i) the equatorial rotation rate of
the corona is comparable to the rotation rate of the photosphere and the
chromosphere, (ii) the differential profile with respect to the latitude varies
throughout the period of the study; it is more in the year 1999 and least in
1994 and (iii) the equatorial rotation period varies systematically with
sunspot numbers and indicates its dependence on the phases of the solar
activity cycle.Comment: 9 Pages, 4 Figures, Accepted for Publication in MNRA
Periodicities in the coronal rotation and sunspot numbers
The present study is an attempt to investigate the long term variations in
coronal rotation by analyzing the time series of the solar radio emission data
at 2.8 GHz frequency for the period 1947 - 2009. Here, daily adjusted radio
flux (known as Penticton flux) data are used. The autocorrelation analysis
shows that the rotation period varies between 19.0 to 29.5 sidereal days (mean
sidereal rotation period is 24.3 days). This variation in the coronal rotation
period shows evidence of two components in the variation; (1) 22-years
component which may be related to the solar magnetic field reversal cycle or
Hale's cycle, and (3) a component which is irregular in nature, but dominates
over the other components. The crosscorrelation analysis between the annual
average sunspots number and the coronal rotation period also shows evidence of
its correlation with the 22-years Hale's cycle. The 22-years component is found
to be almost in phase with the corresponding periodicities in the variation of
the sunspots number.Comment: 9 pages, 5 figures, Accepted for publication in MNRA
Differential coronal rotation using radio images at 17 GHz
In the present work, we perform time-series analysis on the latitude bins of
the solar full disk (SFD) images of Nobeyama Radioheliograph (NoRH) at 17 GHz.
The flux modulation method traces the passage of radio features over the solar
disc and the autocorrelation analysis of the time-series data of SFD images
(one per day) for the period 1999-2001 gives the rotation period as a function
of latitude extending from 60 degree S to 60 degree N. The results show that
the solar corona rotates less differentially than the photosphere and
chromosphere, i.e., it has smaller gradient in the rotation rate.Comment: 5 pages, 5 figures, Accepted for publication in MNRAS letter
Pathogenic variants in the paired-related homeobox 1 gene (PRRX1) cause craniosynostosis with incomplete penetrance
Purpose
Studies previously implicated PRRX1 in craniofacial development, including demonstration of murine Prrx1 expression in the pre-osteogenic cells of the cranial sutures. We investigated the role of heterozygous missense and loss-of-function variants in PRRX1 associated with craniosynostosis.
Methods
Trio-based genome, exome or targeted sequencing were used to screen PRRX1 in patients with craniosynostosis; immunofluorescence analyses were used to assess nuclear localization of wild-type and mutant proteins.
Results
Genome sequencing identified 2 of 9 sporadically affected individuals with syndromic/multisuture craniosynostosis who were heterozygous for rare/undescribed variants in PRRX1. Exome or targeted sequencing of PRRX1 revealed a further 9/1449 patients with craniosynostosis harboring deletions or rare heterozygous variants within the homeodomain. By collaboration, seven additional individuals (four families) were identified with putatively pathogenic PRRX1 variants. Immunofluorescence analyses showed that missense variants within the PRRX1 homeodomain cause abnormal nuclear localization. Of patients with variants considered likely pathogenic, bicoronal or other multi-suture synostosis was present in 11/17 (65% of the cases). Pathogenic variants were inherited from unaffected relatives in many instances, yielding a 12.5% penetrance estimate for craniosynostosis.
Conclusion
This work supports a key role for PRRX1 in cranial suture development and shows that haploinsufficiency of PRRX1 is a relatively frequent cause of craniosynostosis
Screening for proximal coronary artery anomalies with 3-dimensional MR coronary angiography
Under 35 years of age, 14% of sudden cardiac death in athletes is caused by a coronary artery anomaly (CAA). Free-breathing 3-dimensional magnetic resonance coronary angiography (3D-MRCA) has the potential to screen for CAA in athletes and non-athletes as an addition to a clinical cardiac MRI protocol. A 360 healthy men and women (207 athletes and 153 non-athletes) aged 18–60 years (mean age 31 ± 11 years, 37% women) underwent standard cardiac MRI with an additional 3D-MRCA within a maximum of 10 min scan time. The 3D-MRCA was screened for CAA. A 335 (93%) subjects had a technically satisfactory 3D-MRCA of which 4 (1%) showed a malignant variant of the right coronary artery (RCA) origin running between the aorta and the pulmonary trunk. Additional findings included three subjects with ventral rotation of the RCA with kinking and possible proximal stenosis, one person with additional stenosis and six persons with proximal myocardial bridging of the left anterior descending coronary artery. Coronary CT-angiography (CTA) was offered to persons with CAA (the CAA was confirmed in three, while one person declined CTA) and stenosis (the ventral rotation of the RCA was confirmed in two but without stenosis, while two people declined CTA). Overall 3D MRCA quality was better in athletes due to lower heart rates resulting in longer end-diastolic resting periods. This also enabled faster scan sequences. A 3D-MRCA can be used as part of the standard cardiac MRI protocol to screen young competitive athletes and non-athletes for anomalous proximal coronary arteries
Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV
The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≥20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≤pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≤{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration
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