Search

The effects of tensile strain and contact transmissivity on the performance limits of monolayer molybdenum disulfide ( MoS 2) nanoscale n-channel MOSFETs are studied using a semi-classical Monte Carlo method. Density functional theory calculations were performed to parametrize the electronic band structure of MoS 2 subject to tensile and shear strain. Tensile strain decreases the bandgap, increases the inter-valley band-edge energy separation between the light-mass K-valleys and heavier-mass Q-valleys, and decreases the K-valley effective mass in a way that depends on the direction and the amount of the applied strain. Biaxial tensile strain and uniaxial tensile strain along the x- or y-directions are found to have the largest effect. In bulk materials, low-field phonon-limited electron mobility is enhanced, peak and saturation drift velocities are increased, and high-field negative differential resistance becomes more pronounced. Both 200 and 15 nm gate length MoS 2 MOSFETs with end-contacts with ideal (unity) and more realistic (significantly sub-unity) contact interface transmissivity were simulated. These MoS 2 devices exhibited substantial sensitivity to strain with ideal contact transmissivity, and more so for the 15 nm quasi-ballistic device scale than 200 nm long-channel devices. However, the results showed much less strain sensitivity for devices with more realistic contact transmissivities, which may be good or bad depending on whether strain-insensitive or strain-sensitive performance is desired for a particular application and may be possible to modify with improved contact geometries. [ABSTRACT FROM AUTHOR]

Pancreas volume, as measured by magnetic resonance imaging (MRI), is smaller in individuals with newly-diagnosed type 1 diabetes (T1D) and declines over the first year after diagnosis. However, the repeatability and reproducibility of these MRI measurements is not established, and for MRI to be utilized to measure pancreas volume, the variation between measurements of pancreas volume must be determined. To determine the test-retest repeatability of pancreas volume measurements by MRI, we performed two or three same-day repeat MRIs in the same individuals with or without T1D (n = 8, mean age 24 y, range 11-40 y). A single radiologist, blinded to whether the subject had T1D or not, outlined the pancreas on these repeat images. Pancreas volume was determined by multiplying the area of the pancreatic regions of interest by the MRI slice volume (5 mm). The repeatability of test-retest scans had an intraclass correlation coefficient (ICC) of 0.979 (95% CI 0.928 to 0.996). To determine the inter-reader reliability of pancreas volume measurements, the pancreas was independently outlined by two board-certified radiologists (n = 11). Comparing results from multiple radiologists yielded an ICC of 0.931 (95% CI 0.776 to 0.981), with greater differences in measurement in larger pancreases (p < 0.005). The mean DICE coefficient, a measurement of the degree overlap between pancreas regions of interest between the two readers, was 0.77. These data show that measurements of pancreas volume obtained using MRI are both repeatable and reproducible across multiple readers with ICCs corresponding to excellent clinical significance (ICC > 0.9). These results indicate that MRI measurements of T1D pancreatic volume can be reliably determined and could be useful for clinical investigation. Disclosure: J.M. Williams: None. M.A. Hilmes: None. B.T. Archer: None. L. Du: None. H. Kang: None. W.E. Russell: None. D.J. Moore: None. A.C. Powers: None. J. Virostko: None. Funding: JDRF (3-SRA-2015-102-M-B) [ABSTRACT FROM AUTHOR]