50 research outputs found
Sexual dimorphism in myocardial acylcarnitine and triglyceride metabolism
Figure S1. Concentrations of non-esterified fatty acid moieties in NOD and Wistar rats by sex. (PPTX 163 kb
Genomic and metabolic disposition of non-obese Type 2 Diabetic rats to increased myocardial fatty acid metabolism
Lipotoxicity of the heart has been implicated as a leading cause of morbidity in Type 2 Diabetes Mellitus (T2DM). While numerous reports have demonstrated increased myocardial fatty acid (FA) utilization in obese T2DM animal models, this diabetic phenotype has yet to be demonstrated in non-obese animal models of T2DM. Therefore, the present study investigates functional, metabolic, and genomic differences in myocardial FA metabolism in non-obese type 2 diabetic rats. The study utilized Goto-Kakizaki (GK) rats at the age of 24 weeks. Each rat was imaged with small animal positron emission tomography (PET) to estimate myocardial blood flow (MBF) and myocardial FA metabolism. Echocardiograms (ECHOs) were performed to assess cardiac function. Levels of triglycerides (TG) and non-esterified fatty acids (NEFA) were measured in both plasma and cardiac tissues. Finally, expression profiles for 168 genes that have been implicated in diabetes and FA metabolism were measured using quantitative PCR (qPCR) arrays. GK rats exhibited increased NEFA and TG in both plasma and cardiac tissue. Quantitative PET imaging suggests that GK rats have increased FA metabolism. ECHO data indicates that GK rats have a significant increase in left ventricle mass index (LVMI) and decrease in peak early diastolic mitral annular velocity (E’) compared to Wistar rats, suggesting structural remodeling and impaired diastolic function. Of the 84 genes in each the diabetes and FA metabolism arrays, 17 genes in the diabetes array and 41 genes in the FA metabolism array were significantly up-regulated in GK rats. Our data suggest that GK rats’ exhibit increased genomic disposition to FA and TG metabolism independent of obesity
Thermionic Energy Conversion in the Twenty-First Century: Advances and Opportunities for Space and Terrestrial Applications
Thermionic energy conversion (TEC) is the direct conversion of heat into electricity by the mechanism of thermionic emission, the spontaneous ejection of hot electrons from a surface. Although the physical mechanism has been known for over a century, it has yet to be consistently realized in a manner practical for large-scale deployment. This perspective article provides an assessment of the potential of TEC systems for space and terrestrial applications in the twenty-first century, overviewing recent advances in the field and identifying key research challenges. Recent developments as well as persisting research needs in materials, device design, fundamental understanding, and testing and validation are discussed
Low-Frequency Electronic Noise in the Aluminum Gallium Oxide Schottky Barrier Diodes
We report on the low-frequency electronic noise in
(AlGa)O Schottky barrier diodes. The noise spectral density
reveals 1/f dependence, characteristic of the flicker noise, with superimposed
Lorentzian bulges at the intermediate current levels (f is the frequency). The
normalized noise spectral density in such diodes was determined to be on the
order of 10 cm/Hz (f=10 Hz) at 1 A/cm current density. At the
intermediate current regime, we observed the random telegraph signal noise,
correlated with the appearance of Lorentzian bulges in the noise spectrum. The
random telegraph signal noise was attributed to the defects near the Schottky
barrier. The defects can affect the local electric field and the potential
barrier, and correspondingly, impact the electric current. The obtained results
help to understand noise in Schottky barrier diodes made of ultra-wide-band-gap
semiconductors and can be used for the material and device quality assessment.Comment: 16 pages, 6 figure
Optical and Acoustic Phonons in Turbostratic and Cubic Boron Nitride Thin Films on Diamond Substrates
We report an investigation of the bulk optical, bulk acoustic, and surface
acoustic phonons in thin films of turbostratic boron nitride (t-BN) and cubic
boron nitride (c-BN) grown on B-doped polycrystalline and single-crystalline
diamond (001) and (111) substrates. The characteristics of different types of
phonons were determined using Raman and Brillouin-Mandelstam light scattering
spectroscopies. The atomic structure of the films was determined using
high-resolution transmission electron microscopy (HRTEM) and correlated with
the Raman and Brillouin-Mandelstam spectroscopy data. The HRTEM analysis
revealed that the cubic boron nitride thin films consisted of a mixture of c-BN
and t-BN phases, with c-BN being the dominant phase. It was found that while
visible Raman spectroscopy provided information for characterizing the t-BN
phase, it faced challenges in differentiating the c-BN phase either due to the
presence of high-density defects or the overlapping of the Raman features with
those from the B-doped diamond substrates. In contrast, Brillouin-Mandelstam
spectroscopy clearly distinguishes the bulk longitudinal and surface acoustic
phonons of the c-BN thin films grown on diamond substrates. Additionally, the
angle-dependent surface Brillouin-Mandelstam scattering data show the peaks
associated with the Rayleigh surface acoustic waves, which have higher phase
velocities in c-BN films on diamond (111) substrates. These findings provide
valuable insights into the phonon characteristics of the c-BN and diamond
interfaces and have important implications for the thermal management of
electronic devices based on ultra-wide-band-gap materials.Comment: 27 pages; 4 figure