Highly charged interface trap states in PbS1−x govern electro-thermal transport

This work describes our discovery of the dominant role of highly charged interfaces on the electrothermal transport properties of PbS, along with a method to reduce the barrier potential for charge carriers by an order of magnitude. High temperature thermoelectrics such as PbS are inevitably exposed to elevated temperatures during postsynthesis treatment as well as operation. However, we observed that as the material was heated, large concentrations of sulfur vacancy (VS..) sites were formed at temperatures as low as 266 degrees C. This loss of sulfur doped the PbS n-type and increased the carrier concentration, where these excess electrons were trapped and immobilized at interfacial defect sites in polycrystalline PbS with an abundance of grain boundaries. Sulfur deficient PbS0.81 exhibited a large barrier potential for charge carriers of 0.352 eV, whereas annealing the material under a sulfur-rich environment prevented VS.. formation and lowered the barrier by an order of magnitude to 0.046 eV. Through ab initio calculations, the formation of VS.. was found to be more favorable on the surface compared to the bulk of the material with a 1.72 times lower formation energy barrier. These observations underline the importance of controlling interface-vacancy effects in the preparation of bulk materials comprised of nanoscale constituents.U. S. National Science Foundation [CAREER-1553987, REU-1560098]; UConn Research Foundation [PD17-0137]; U.S. Department of Energy Office of Science [89233218CNA000001]; GE Graduate Fellowship for Innovation; XSEDE through the computational resource allocation [TG-DMR170031]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Viscoelasticity Imaging of Biological Tissues and Single Cells Using Shear Wave Propagation

Changes in biomechanical properties of biological soft tissues are often associated with physiological dysfunctions. Since biological soft tissues are hydrated, viscoelasticity is likely suitable to represent its solid-like behavior using elasticity and fluid-like behavior using viscosity. Shear wave elastography is a non-invasive imaging technology invented for clinical applications that has shown promise to characterize various tissue viscoelasticity. It is based on measuring and analyzing velocities and attenuations of propagated shear waves. In this review, principles and technical developments of shear wave elastography for viscoelasticity characterization from organ to cellular levels are presented, and different imaging modalities used to track shear wave propagation are described. At a macroscopic scale, techniques for inducing shear waves using an external mechanical vibration, an acoustic radiation pressure or a Lorentz force are reviewed along with imaging approaches proposed to track shear wave propagation, namely ultrasound, magnetic resonance, optical, and photoacoustic means. Then, approaches for theoretical modeling and tracking of shear waves are detailed. Following it, some examples of applications to characterize the viscoelasticity of various organs are given. At a microscopic scale, a novel cellular shear wave elastography method using an external vibration and optical microscopy is illustrated. Finally, current limitations and future directions in shear wave elastography are presented

Estimation and prediction of avoidable health care costs of cardiovascular diseases and type 2 diabetes through adequate dairy food consumption: a systematic review and micro simulation modeling study

Background: Recent evidence from prospective cohort studies show a relationship between consumption of dairy foods and cardiovascular diseases (CVDs) and type 2 diabetes mellitus (T2DM). This association highlights the importance of dairy foods consumption in prevention of these diseases and also reduction of associated healthcare costs. The aim of this study was to estimate avoidable healthcare costs of CVD and T2D through adequate dairy foods consumption in Iran. Methods: This was a multistage modelling study. We conducted a systematic literature review in PubMed and EMBASE to identify any association between incidence of CVD and T2DM and dairy foods intake, and also associated relative risks. We obtained age- and sex-specific dairy foods consumption level and healthcare expenditures from national surveys and studies. Patient level simulation Markov models were constructed to predict the disease incidence, patient population size and associated healthcare costs for current and optimal dairy foods consumption at different time horizons (1, 5, 10 and 20 years). All parameters including costs and transition probabilities were defined as statistical distributions in the models, and all analyses were conducted by accounting for first and second order uncertainty. Results: The systematic review results indicated that dairy foods consumption was inversely associated with incidence of T2DM, coronary heart disease (CHD) and stroke. We estimated that the introduction of a diet containing 3 servings of dairy foods per day may produce a $0.43 saving in annual per capita healthcare costs in Iran in the first year due to saving in cost of CVD and T2DM treatment. The estimated savings in per capita healthcare costs were$8.42, $39.97 and$190.25 in 5, 10 and 20-years’ time, respectively. Corresponding total aggregated avoidable costs for the entire Iranian population within the study time horizons were $33.83,$661.31, $3,138.21 and$14,934.63 million, respectively. Conclusion: Our analysis demonstrated that increasing dairy foods consumption to recommended levels would be associated with reductions in healthcare costs. Further randomized trial studies are required to investigate the effect of dairy foods intake on cost of CVD and T2DM in the population

Thermal, Electrical, and Electrochemical Characterizations of Advanced Nanomaterials for Energy Conversion and Storage Applications

Archival abstract submitte

Boron neutron capture therapy for the treatment of lung cancer and assessment of dose received by organs at risk

Recent studies on boron neutron capture therapy (BNCT) have focused on investigating the appropriate neutron sources based on accelerators for neutron production, such as 7Li(p,n)7 Be. The therapeutic abilities of BNCT have been studied for the possible treatment of lung cancer using thermal and epithermal neutron beams. For neutron transport, the Monte Carlo N-particle transport code was used, and doses in the organs of different Oak Ridge National Laboratory phantoms were evaluated. The right lung was meshed with voxels to obtain depth-dose distributions using 1 eV, 10 eV, 100 eV, 1 keV, 5 keV, 8 keV and 10 keV energy sources. These results suggest that BNCT with an epithermal neutron beam can be used to treat lung cancer. By evaluating the biological dose rate and dose-depth distribution curves in healthy tissues and tumors by simulating a lung phantom, the quantities in the phantom were also evaluated. Our calculations show that with increasing boron concentration applied to the tumor, the dose is increased and the 100 eV energy source has the greatest effect on the tumor dose