724 research outputs found
Measurement-based Close-in Path Loss Modeling with Diffraction for Rural Long-distance Communications
In this letter, we investigate rural large-scale path loss models based on
the measurements in a central area of South Korea (rural area) in spring. In
particular, we develop new close-in (CI) path loss models incorporating a
diffraction component. The transmitter used in the measurement system is
located on a hill and utilizes omnidirectional antennas operating at 1400 and
2250 MHz frequencies. The receiver is also equipped with omnidirectional
antennas and measures at positions totaling 3,858 (1,262 positions for LOS and
2,596 positions for NLOS) and 4,957 (1,427 positions for LOS and 3,530
positions for NLOS) for 1400 and 2250 MHz, respectively. This research
demonstrates that the newly developed CI path loss models incorporating a
diffraction component significantly reduce standard deviations (STD) and are
independent of frequency, especially for LOS beyond the first meter of
propagation, making them suitable for use with frequencies up to a
millimeter-wave.Comment: 5 pages, 5 figure
Prediction of Alzheimer's disease pathophysiology based on cortical thickness patterns
AbstractIntroductionRecent studies have shown that pathologically defined subtypes of Alzheimer's disease (AD) represent distinctive atrophy patterns and clinical characteristics. We investigated whether a cortical thicknessābased clustering method can reflect such findings.MethodsA total of 77 AD subjects from the Alzheimer's Disease Neuroimaging Initiative 2 data set who underwent 3-T magnetic resonance imaging, [18F]-fluorodeoxyglucose-positron emission tomography (PET), [18F]-Florbetapir PET, and cerebrospinal fluid (CSF) tests were enrolled. After clustering based on cortical thickness, diverse imaging and biofluid biomarkers were compared between these groups.ResultsThree cortical thinning patterns were noted: medial temporal (MT; 19.5%), diffuse (55.8%), and parietal dominant (P; 24.7%) atrophy subtypes. The P subtype was the youngest and represented more glucose hypometabolism in the parietal and occipital cortices and marked amyloid-beta accumulation in most brain regions. The MT subtype revealed more glucose hypometabolism in the left hippocampus and bilateral frontal cortices and less performance in memory tests. CSF test results did not differ between the groups.DiscussionCortical thickness patterns can reflect pathophysiological and clinical changes in AD
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