278,856 research outputs found
QED Penguin Contributions To Isospin Splittings of Heavy-Light Quark Systems
Recent experiments show that the isospin-violating mass splitting of the B
mesons is very small, but the best fits with a QCD sum rule analysis give a
splitting of at least 1.0 MeV. The isospin-violating mass splittings of the
charmed mesons, on the other hand, are in agreement with experiment. In this
letter we show that the inclusion of 2 kind QED penguin diagrams can
account for this discrepancy within the errors in the QCD sum rule method.Comment: 9 pages, latex, 2 figure
Studies of human dynamic space orientation using techniques of control theory
Three-dimensional contact analog display system development for use in surface, subsurface, air, and space vehicle
Studies of human dynamic space orientation using techniques of control theory Status report
Human dynamic space orientation using control theory technique
Studies of human dynamic space orientation using techniques of control theory Status report, Jun. 1967 - Jun. 1968
Human dynamic space orientation using techniques of control theor
Learning algorithms for multi-class pattern classification and problems associated with on-line handwritten character recognition
On-line handwritten alphanumeric character recognition system and learning algorithm for multiclass pattern classificatio
Lunar surface mining for automated acquisition of helium-3: Methods, processes, and equipment
In this paper, several techniques considered for mining and processing the regolith on the lunar surface are presented. These techniques have been proposed and evaluated based primarily on the following criteria: (1) mining operations should be relatively simple; (2) procedures of mineral processing should be few and relatively easy; (3) transferring tonnages of regolith on the Moon should be minimized; (4) operations outside the lunar base should be readily automated; (5) all equipment should be maintainable; and (6) economic benefit should be sufficient for commercial exploitation. The economic benefits are not addressed in this paper; however, the energy benefits have been estimated to be between 250 and 350 times the mining energy. A mobile mining scheme is proposed that meets most of the mining objectives. This concept uses a bucket-wheel excavator for excavating the regolith, several mechanical electrostatic separators for beneficiation of the regolith, a fast-moving fluidized bed reactor to heat the particles, and a palladium diffuser to separate H2 from the other solar wind gases. At the final stage of the miner, the regolith 'tailings' are deposited directly into the ditch behind the miner and cylinders of the valuable solar wind gases are transported to a central gas processing facility. During the production of He-3, large quantities of valuable H2, H2O, CO, CO2, and N2 are produced for utilization at the lunar base. For larger production of He-3 the utilization of multiple-miners is recommended rather than increasing their size. Multiple miners permit operations at more sites and provide redundancy in case of equipment failure
A retrospective segmentation analysis of placental volume by magnetic resonance imaging from first trimester to term gestation
Background
Abnormalities of the placenta affect 5–7% of pregnancies. Because disturbances in fetal growth are often preceded by dysfunction of the placenta or attenuation of its normal expansion, placental health warrants careful surveillance. There are limited normative data available for placental volume by MRI.
Objective
To determine normative ranges of placental volume by MRI throughout gestation.
Materials and methods
In this cross-sectional retrospective analysis, we reviewed MRI examinations of pregnant females obtained between 2002 and 2017 at a single institution. We performed semi-automated segmentation of the placenta in images obtained in patients with no radiologic evidence of maternal or fetal pathology, using the Philips Intellispace Tumor Tracking Tool.
Results
Placental segmentation was performed in 112 women and had a high degree of interrater reliability (single-measure intraclass correlation coefficient =0.978 with 95% confidence interval [CI] 0.956, 0.989; P<0.001). Normative data on placental volume by MRI increased nonlinearly from 6 weeks to 39 weeks of gestation, with wider variability of placental volume at higher gestational age (GA). We fit placental volumetric data to a polynomial curve of third order described as placental volume = –0.02*GA3 + 1.6*GA2 – 13.3*GA + 8.3. Placental volume showed positive correlation with estimated fetal weight (P=0.03) and birth weight (P=0.05).
Conclusion
This study provides normative placental volume by MRI from early first trimester to term gestation. Deviations in placental volume from normal might prove to be an imaging biomarker of adverse fetal health and neonatal outcome, and further studies are needed to more fully understand this metric. Assessment of placental volume should be considered in all routine fetal MRI examinations
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