3,407 research outputs found
Signal quality measures for unsupervised blood pressure measurement
Accurate systolic and diastolic pressure estimation, using automated blood pressure measurement, is difficult to achieve when the transduced signals are contaminated with noise or interference, such as movement artifact. This study presents an algorithm for automated signal quality assessment in blood pressure measurement by determining the feasibility of accurately detecting systolic and diastolic pressures when corrupted with various levels of movement artifact. The performance of the proposed algorithm is compared to a manually annotated reference scoring (RS). Based on visual representations and audible playback of Korotkoff sounds, the creation of the RS involved two experts identifying sections of the recorded sounds and annotating sections of noise contamination. The experts determined the systolic and diastolic pressure in 100 recorded Korotkoff sound recordings, using a simultaneous electrocardiograph as a reference signal. The recorded Korotkoff sounds were acquired from 25 healthy subjects (16 men and 9 women) with a total of four measurements per subject. Two of these measurements contained purposely induced noise artifact caused by subject movement. Morphological changes in the cuff pressure signal and the width of the Korotkoff pulse were extracted features which were believed to be correlated with the noise presence in the recorded Korotkoff sounds. Verification of reliable Korotkoff pulses was also performed using extracted features from the oscillometric waveform as recorded from the inflatable cuff. The time between an identified noise section and a verified Korotkoff pulse was the key feature used to determine the validity of possible systolic and diastolic pressures in noise contaminated Korotkoff sounds. The performance of the algorithm was assessed based on the ability to: verify if a signal was contaminated with any noise; the accuracy, sensitivity and specificity of this noise classification, and the systolic and diastolic pressure differences between the result obtained from the algorithm and the RS. 90% of the actual noise contaminated signals were correctly identified, and a sample-wise accuracy, sensitivity and specificity of 97.0%, 80.61% and 98.16%, respectively, were obtained from 100 pooled signals. The mean systolic and diastolic differences were 0.37 ± 3.31 and 3.10 ± 5.46 mmHg, respectively, when the artifact detection algorithm was utilized, with the algorithm correctly determined if the signal was clean enough to attempt an estimation of systolic or diastolic pressures in 93% of blood pressure measurements
The low abundance of CpG in the SARS-CoV-2 genome is not an evolutionarily signature of ZAP
The zinc finger antiviral protein (ZAP) is known to restrict viral replication by binding to the CpG rich regions of viral RNA, and subsequently inducing viral RNA degradation. This enzyme has recently been shown to be capable of restricting SARS-CoV-2. These data have led to the hypothesis that the low abundance of CpG in the SARS-CoV-2 genome is due to an evolutionary pressure exerted by the host ZAP. To investigate this hypothesis, we performed a detailed analysis of many coronavirus sequences and ZAP RNA binding preference data. Our analyses showed neither evidence for an evolutionary pressure acting specifically on CpG dinucleotides, nor a link between the activity of ZAP and the low CpG abundance of the SARS-CoV-2 genome
Earth Radiation Budget Experiment (ERBE) scanner instrument anomaly investigation
The results of an ad-hoc committee investigation of in-Earth orbit operational anomalies noted on two identical Earth Radiation Budget Experiment (ERBE) Scanner instruments on two different spacecraft busses is presented. The anomalies are attributed to the bearings and the lubrication scheme for the bearings. A detailed discussion of the pertinent instrument operations, the approach of the investigation team and the current status of the instruments now in Earth orbit is included. The team considered operational changes for these instruments, rework possibilities for the one instrument which is waiting to be launched, and preferable lubrication considerations for specific space operational requirements similar to those for the ERBE scanner bearings
On the influence of the Sun on the rapid variability of compact extragalactic sources
Starting from December 2004, a program for the monitoring of intraday
variable sources at a frequency of 5 GHz was performed at the Urumqi
Observatory. The analysis of the variability characteristics of the
flat-spectrum radio source AO 0235+164 revealed the existence of an annual
cycle in the variability amplitude. This appears to correlate with the solar
elongation of the source. A thorough analysis of the results of the MASIV IDV
survey --- which provides the variability characteristics of a large sample of
compact radio sources --- confirms that there is a small but detectable
component of the observed fractional modulation which increases with decreasing
solar elongation. We discuss the hypothesis that the phenomenon is related to
interplanetary scintillation.Comment: 10 pages, 12 figures and 2 tables. Accepted for publication in
Astronomy and Astrophysic
A seasonal cycle and an abrupt change in the variability characteristics of the intraday variable source S4 0954+65
The BLLac object S4 0954+65 is one of the main targets of the Urumqi
monitoring program targeting IntraDay Variable (IDV) sources. Between August
2005 and December 2009, the source was included in 41 observing sessions,
carried out at a frequency of 4.8 GHz. The time analysis of the collected light
curves, performed by applying both a structure function analysis and a
specifically developed wavelet-based algorithm, discovered an annual cycle in
the variability timescales, suggesting that there is a fundamental contribution
by interstellar scintillation to the IDV pattern of the source. The combined
use of the two analysis methods also revealed that there was a dramatic change
in the variability characteristics of the source between February and March
2008, at the starting time of a strong outburst phase. The analysis' results
suggest that the flaring state of the source coincides with the appearance of
multiple timescales in its light curves, indicating that changes in the
structure of the relativistically moving emitting region may strongly influence
the variability observed on IDV timescales.Comment: 9 pages, 8 figures and 3 tables. Accepted for publication in
Astronomy and Astrophysic
Local and non-local equivalent potentials for p-12C scattering
A Newton-Sabatier fixed energy inversion scheme has been used to equate
inherently non-local p-C potentials at a variety of energies to pion
threshold, with exactly phase equivalent local ones. Those energy dependent
local potentials then have been recast in the form of non-local Frahn-Lemmer
interactions.Comment: 15 pages plus 9 figures submitted to Phys. Rev.
PMN J1838-3427: A new gravitationally lensed quasar
We report the discovery of a new double-image quasar that was found during a
search for gravitational lenses in the southern sky. Radio source PMN
J1838-3427 is composed of two flat-spectrum components with separation 1", flux
density ratio 14:1 and matching spectral indices, in VLA and VLBA images.
Ground-based BRI images show the optical counterpart (total I=18.6) is also
double with the same separation and position angle as the radio components. An
HST/WFPC2 image reveals the lens galaxy. The optical flux ratio (27:1) is
higher than the radio value probably due to differential extinction of the
components by the lens galaxy. An optical spectrum of the bright component
contains quasar emission lines at z=2.78 and several absorption features,
including prominent Ly-alpha absorption. The lens galaxy redshift could not be
measured but is estimated to be z=0.36 +/- 0.08. The image configuration is
consistent with the simplest plausible models for the lens potential. The flat
radio spectrum and observed variability of PMN J1838-3427 suggest the time
delay between flux variations of the components is measurable, and could thus
provide an independent measurement of H_0.Comment: 23 pages, incl. 6 figures, to appear in A.J.; replaced with accepted
version; minor changes to text, improved figure
- …