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Coupled double-row formation in a quasi-1D wire
Smith, L.W.,Hew, W.K.,Thomas, K.J.,Pepper, M.,Farrer, I.,Anderson, D.,Jones, G.A.C.,Ritchie, D.A. North-Holland 2010 Physica E, Low-dimensional systems & nanostructure Vol.42 No.4
We investigate one-dimensional (1D) quantum wires in the weak confinement regime, where, at certain densities, the 1D system of electrons bifurcates into two rows. We show that the two rows are coupled, forming bonding and antibonding states, and that the coupling persists in magnetic fields from 0 to 16 T. In order for a double row to form, the Coulomb interactions in the channel must overcome the confining potential, which can be achieved by tuning the density and confinement. Using a split-gate device with a top gate and back gate, we observe a transition from single-row to double-row behaviour in the weak confinement regime. We further probe the characteristics of the coupled double row regime with dc source-drain bias measurements.
Searching for Resonances in the Unbound 6Be Nucleus by Using a Radioactive 7Be Beam
채경육,D. W. Bardayan,J. C. Blackmon,M. S. Smith,A. E. Champagne,J. J. Das,R. P. Fitzgerald,D. W. Visser,V. Guimaraes,K. L. Jones,S. D. Pain,J. S. Thomas,M. S. Johnson,R. L. Kozub,R. J. Livesay,Z. Ma,C. 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.11
Knowledge of the <sup>3</sup>He(<sup>3</sup>He,<sup>2</sup><i>p</i>)<sup>4</sup>He reaction is important for understanding stellar burning and solar neutrino production. Previous measurements have found a surprisingly large rise in the cross section at low energies that could be due to a low-energy resonance in the <sup>3</sup>He + <sup>3</sup>He (<sup>6</sup>Be) system or electron screening. In the <sup>6</sup>Be nucleus, however, no excited states have been observed above the first 2<sup>+</sup> state at <i>E<sub>x</sub></i> = 1.67 MeV up to 23 MeV, even though several are expected. The <sup>2</sup>H(<sup>7</sup>Be,<sup>3</sup>H)<sup>6</sup>Be reaction has been studied for the first time to search for resonances in the <sup>6</sup>Be nucleus that may affect our understanding of the <sup>3</sup>He(<sup>3</sup>He,<sup>2</sup><i>p,</i>)<sup>4</sup>He reaction. A 100-MeV radioactive <sup>7</sup>Be beam from the Holifield Radioactive Ion Beam Facility (HRIBF) was used to bombard CD<sub>2</sub> targets, and tritons were detected by using the silicon detector array (SIDAR). A combination of reaction mechanisms appears to be necessary to explain the observed triton energy spectrum.
Chae, K.Y.,Ahn, S.,Ayres, A.,Bardayan, D.W.,Bey, A.,Greife, U.,Howard, M.E.,Jones, K.L.,Kozub, R.L.,Matoš,, M.,Moazen, B.H.,Nesaraja, C.D.,O’Malley, P.D.,Peters, W.A.,Pittman, S.T.,Smith, M.S. Elsevier 2018 Nuclear Instruments & Methods in Physics Research. Vol.900 No.-
<P><B>Abstract</B></P> <P>Direct measurements of ( α , p ) reactions of astrophysical interest with radioactive beams presents serious challenges because of the difficult nature of helium targets and the typical low intensities of the beams. To address this, a new technique has been developed for measurements of low-energy ( α , p ) reactions with heavy ion beams using an extended <SUP> 4 </SUP> He gas target and a newly developed gas recirculating system. The system was used to measure the <SUP> 4 </SUP> He(<SUP>19</SUP>F, <SUP> 1 </SUP> H)<SUP>22</SUP>Ne reaction as a demonstration. Excitation functions of the <SUP>19</SUP>F( α , p )<SUP>22</SUP>Ne and <SUP>19</SUP>F( α , <SUP> p ′ </SUP> )<SUP>22</SUP>Ne <SUP> ∗ </SUP> reactions were successfully measured to show the viability of this technique. Details of the approach and future plans are given.</P>
Smith, A.S.T.,Macadangdang, J.,Leung, W.,Laflamme, M.A.,Kim, D.H. Pergamon Press ; Elsevier Science Ltd 2017 BIOTECHNOLOGY ADVANCES Vol.35 No.1
Improved methodologies for modeling cardiac disease phenotypes and accurately screening the efficacy and toxicity of potential therapeutic compounds are actively being sought to advance drug development and improve disease modeling capabilities. To that end, much recent effort has been devoted to the development of novel engineered biomimetic cardiac tissue platforms that accurately recapitulate the structure and function of the human myocardium. Within the field of cardiac engineering, induced pluripotent stem cells (iPSCs) are an exciting tool that offer the potential to advance the current state of the art, as they are derived from somatic cells, enabling the development of personalized medical strategies and patient specific disease models. Here we review different aspects of iPSC-based cardiac engineering technologies. We highlight methods for producing iPSC-derived cardiomyocytes (iPSC-CMs) and discuss their application to compound efficacy/toxicity screening and in vitro modeling of prevalent cardiac diseases. Special attention is paid to the application of micro- and nano-engineering techniques for the development of novel iPSC-CM based platforms and their potential to advance current preclinical screening modalities.
NEUTRONICS MODELING AND SIMULATION OF SHARPFOR FAST REACTOR ANALYSIS
W. S. YANG,M. A. SMITH,C. H. LEE,A. WOLLABER,D. KAUSHIK,A. S. MOHAMED 한국원자력학회 2010 Nuclear Engineering and Technology Vol.42 No.5
This paper presents the neutronics modeling capabilities of the fast reactor simulation system SHARP, which ANL isdeveloping as part of theU.S. DOE’s NEAMS program. We discuss the three transport solvers (PN2ND, SN2ND, and MOCFE)implementedin the UNIC code along with the multigroup cross section generation code MC2-3. We describe the solution methodsand modelingcapabilities, and discuss the improvement needs for each solver, focusing on massively parallel computation.We present the performance test results against various benchmark problems and ZPR-6 and ZPPR critical experiments. We alsodiscuss weakand strong scalability results for the SN2ND solver on the ZPR-6 critical assembly benchmarks.
Smith, S. B.,Go, G. W.,Johnson, B. J.,Chung, K. Y.,Choi, S. H.,Sawyer, J. E.,Silvey, D.T.,Gilmore, L. A.,Ghahramany, G.,Kim, K. H. Oxford University Press 2012 Journal of animal science Vol.90 No.8
<P>We have demonstrated that among carcass adipose tissue depots, brisket subcutaneous adipose tissue contains the greatest concentration of MUFA and lowest concentration of SFA. Therefore, we hypothesized that brisket subcutaneous adipose tissue depots would exhibit greater adipogenic gene expression over time than other major subcutaneous adipose tissue depots. Four Angus steers, each at 9, 12, 14, and 16 mo of age, were harvested and fresh subcutaneous adipose tissue samples were collected from over the brisket, chuck, rib, loin, sirloin, round, flank, and plate. Relative gene expression for C/EBPβ, PPARγ, carnitine palmitoyltransferase-1 beta (CPT-1β), stearoyl-coenzyme A desaturase (SCD), AMP-activated protein kinase alpha (AMPKα), and G-coupled protein receptor 43 (GPR43) was analyzed by quantitative real-time PCR. Expression of C/EBPβ, PPARγ, and CPT-1β was greatest at 12 to 14 mo of age (all P < 0.0001) and declined to very low abundance by 16 mo of age in all depots. Expression of PPARγ and CPT-1β was greater (P < 0.03) in flank, rib, and sirloin subcutaneous adipose tissues than in brisket and round adipose tissues. The expression of the SCD gene did not differ among the 4 age groups (P = 0.95). The palmitoleic:stearic acid ratio (an estimate of SCD activity) was greater (P < 0.001) in the subcutaneous adipose tissues from brisket, plate, and round than in the loin, rib, and sirloin. Conversely, subcutaneous adipose tissue from the loin, rib, and sirloin had greater (P < 0.001) SCD gene expression than the brisket, plate, and round. In general, subcutaneous adipose tissues with the highest concentration of MUFA and least SFA consistently exhibited the least SCD gene expression and adipogenic gene expression. We conclude that MUFA in the brisket and other depots with large SCD indices were deposited before 9 mo of age, during a time when the subcutaneous adipocytes were highly differentiated.</P>
Woo, W.,An, G.B.,Kingston, E.J.,DeWald, A.T.,Smith, D.J.,Hill, M.R. Elsevier Science 2013 ACTA MATERIALIA Vol.61 No.10
Spatial variations of residual stresses were determined through the thickness of 70mm thick ferritic steel welds created using low (1.7kJmm<SUP>-1</SUP>) and high (56kJmm<SUP>-1</SUP>) heat inputs. Two-dimensional maps of the longitudinal residual stress were obtained by using the contour method. The results were compared to neutron diffraction measurements through the thickness at different locations from the weld centerline. The deep hole drilling technique was utilized to confirm the maximum stress locations and magnitudes. The results show that significant tensile stresses (~90% of yield strength) occur along the weld centerline near the top surface (within 10% of the depth) in the low heat-input specimen. Meanwhile, in the high heat-input weld, the peak stress moved towards the heat-affected zone at a depth of ~40% of the thickness. Finally, the influence of residual stresses on potential fracture behavior of the welded joints is discussed.