University of Texas at Dallas

About: University of Texas at Dallas is a education organization based out in Richardson, Texas, United States. It is known for research contribution in the topics: Population & Computer science. The organization has 14986 authors who have published 35589 publications receiving 1293714 citations. The organization is also known as: UT-Dallas & UT Dallas.

Impurities and Electronic Property Variations of Natural MoS2 Crystal Surfaces.

Abstract: Room temperature X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICPMS), high resolution Rutherford backscattering spectrometry (HR-RBS), Kelvin probe method, and scanning tunneling microscopy (STM) are employed to study the properties of a freshly exfoliated surface of geological MoS2 crystals. Our findings reveal that the semiconductor 2H-MoS2 exhibits both n- and p-type behavior, and the work function as measured by the Kelvin probe is found to vary from 4.4 to 5.3 eV. The presence of impurities in parts-per-million (ppm) and a surface defect density of up to 8% of the total area could explain the variation of the Fermi level position. High resolution RBS data also show a large variation in the MoSx composition (1.8 < x < 2.05) at the surface. Thus, the variation in the conductivity, the work function, and stoichiometry across small areas of MoS2 will have to be controlled during crystal growth in order to provide high quality uniform materials for future device fa...

Thermal conductivity of multi-walled carbon nanotube sheets: radiation losses and quenching of phonon modes.

Abstract: The extremely high thermal conductivity of individual carbon nanotubes, predicted theoretically and observed experimentally, has not yet been achieved for large nanotube assemblies. Resistances at tube–tube interconnections and tube–electrode interfaces have been considered the main obstacles for effective electronic and heat transport. Here we show that, even for infinitely long and perfect nanotubes with well-designed tube–electrode interfaces, excessive radial heat radiation from nanotube surfaces and quenching of phonon modes in large bundles are additional processes that substantially reduce thermal transport along nanotubes. Equivalent circuit simulations and an experimental self-heating 3ω technique were used to determine the peculiarities of anisotropic heat flow and thermal conductivity of single MWNTs, bundled MWNTs and aligned, free-standing MWNT sheets. The thermal conductivity of individual MWNTs grown by chemical vapor deposition and normalized to the density of graphite is much lower (κMWNT = 600 ± 100 W m−1 K−1) than theoretically predicted. Coupling within MWNT bundles decreases this thermal conductivity to 150 W m−1 K−1. Further decrease of the effective thermal conductivity in MWNT sheets to 50 W m−1 K−1 comes from tube–tube interconnections and sheet imperfections like dangling fiber ends, loops and misalignment of nanotubes. Optimal structures for enhancing thermal conductivity are discussed.

PEGylation and zwitterionization: pros and cons in the renal clearance and tumor targeting of near-IR-emitting gold nanoparticles.

Abstract: PEGylation is the most common and successful surface-chemistry strategy for reducing nonspecific accumulation and prolonging blood circulation of inorganic nanoparticles (NPs), so that the NPs can effectively target tumors through well-known “enhanced permeability and retention (EPR)” effect.[1] These strengths fundamentally arise from the fact that poly(ethylene glycol) (PEG) moiety on the particle surface creates steric hindrance for the serum protein (opsonin) adsorption and slows down the NP uptake by the reticuloendothelial system (RES) organs (liver, spleen etc.).[2] However, the majority of PEGylated NPs still end up in RES organs after the circulation,[3] resulting in low targeting specificity (defined as the amount of NPs in tumor vs that in liver).[4] For instance, even though PEGylated AuNPs with a 2 nm core size can circulate in the body at a high concentration, they were found to severely accumulate in the liver (78 %ID/g) and spleen (15.2 %ID/g) at 24 h post-injection (p.i.).[5] Such long-term severe accumulation in RES potentially induces health hazards, hampering their clinical translation. Therefore, developing PEGylated inorganic NPs that not only can retain strong EPR effect but also can be eliminated from the urinary system like clinically used small molecular contrast agents[6] is highly desired but remains a big challenge.

The perception of face gender: the role of stimulus structure in recognition and classification.

Abstract: The perception of face gender was examined in the context of extending “face space” models of human face representations to include the perceptual categories defined by male and female faces. We collected data on the recognizability, gender classifiability (reaction time to classify a face as male/female), attractiveness, and masculinity/femininity of individual male and female faces. Factor analyses applied separately to the data for male and female faces yielded the following results. First, for both male and female faces, the recognizability and gender classifiability of faces were independent—a result inconsistent with the hypothesis that both recognizability and gender classifiability depend on a face’s “distance” from the subcategory gender prototype. Instead, caricatured aspects of gender (femininity/masculinity ratings) related to the gender classifiability of the faces. Second, facial attractiveness related inversely to face recognizability for male, but not for female, faces—a result that resolves inconsistencies in previous studies. Third, attractiveness and femininity for female faces were nearly equivalent, but attractiveness and masculinity for male faces were not equivalent. Finally, we applied principal component analysis to the pixel-coded face images with the aim of extracting measures related to the gender classifiability and recognizability of individual faces. We incorporated these model-derived measures into the factor analysis with the human rating and performance measures.