Thermoelectric Modeling of the Non-Ohmic Differential Conductance in a Tunnel Junction containing a Pinhole

To test the quality of a tunnel junction, one sometimes fits the bias-dependent differential conductance to a theoretical model, such as Simmons's formula. Recent experimental work by {\AA}kerman and collaborators, however, has demonstrated that a good fit does not necessarily imply a good junction. Modeling the electrical and thermal properties of a tunnel junction containing a pinhole, we extract an effective barrier height and effective barrier width even when as much as 88% of the current flows through the pinhole short rather than tunneling. A good fit of differential conductance to a tunneling form therefore cannot rule out pinhole defects in normal-metal or magnetic tunnel junctions.Comment: Revtex, 5 figure

Determination of heavy metals in corn (Zea Mays L.) using silver nanoparticles/graphene/nafion modified glassy carbon electrode

Silver nanoparticles (AgNP)/graphene/Nafion modified glassy carbon electrodes were fabricated for the determination of trace amounts of cadmium (Cd2+) and lead (Pb2+) via anodic stripping voltammetry (ASV). The electrode modifiers and the ASV parameters were optimized. The fabricated electrode was characterized by field emission scanning electron microscopy and energy dispersive x-ray spectroscopy. A linear relationship between anodic peak current and heavy metal concentration was obtained in the range of 25 parts per billion (ppb) to 250 ppb. The limit of detection of the modified electrode is 25 ppb for both Cd2+ and Pb2+, while the limits of quantitation are 155.7 ppb for Cd2+ and 159.5 ppb for Pb2+. Real sample analysis using corn plant and soil samples was performed to show the utility of the fabricated electrode in sensing applications. Trace amounts of Cd2+ and Pb2+ were found in the said samples

Elimination of Threshold Singularities in the Relation Between On-Shell and Pole Widths

In a previous communication by two of us, Phys. Rev. Lett. 81, 1373 (1998), the gauge-dependent deviations of the on-shell mass and total decay width from their gauge-independent pole counterparts were investigated at leading order for the Higgs boson of the Standard Model. In the case of the widths, the deviation was found to diverge at unphysical thresholds, m_H = 2 root{xi_V} m_V (V = W,Z), in the R_xi gauge. In this Brief Report, we demonstrate that these unphysical threshold singularities are properly eliminated if a recently proposed definition of wave-function renormalization for unstable particles is invoked.Comment: 8 pages (Latex), 1 figure (Postscript

Associated Production of Heavy Quarkonia and Electroweak Bosons at Present and Future Colliders

We investigate the associated production of heavy quarkonia, with angular-momentum quantum numbers ^{2S+1}L_J = ^1S_0, ^3S_1, ^1P_1, ^3P_J (J = 0, 1, 2), and photons, Z bosons, and W bosons in photon-photon, photon-hadron, and hadron-hadron collisions within the factorization formalism of nonrelativistic quantum chromodynamics providing all contributing partonic cross sections in analytic form. In the case of photoproduction, we also include the resolved-photon contributions. We present numerical results for the processes involving J/psi and chi_{cJ} mesons appropriate for the Fermilab Tevatron, CERN LHC, DESY TESLA, operated in the e^+ e^- and gamma gamma modes, and DESY THERA.Comment: 41 pages (Latex), 10 figures (Postscript

Associated Production of Bottomonia and Higgs Bosons at Hadron Colliders

We study the associated production of bottomonia and Higgs bosons at hadron colliders within the factorization formalism of nonrelativistic quantum chromodynamics providing all contributing partonic cross sections in analytic form. While such processes tend to be suppressed in the standard model, they may have interesting cross sections in its minimal supersymmetric extension, especially at large values of tan(beta), where the bottom Yukawa couplings are enhanced. We present numerical results for the processes involving the lighter CP-even h^0 boson and the CP-odd A^0 boson appropriate for the Fermilab Tevatron and the CERN LHC.Comment: 33 pages, 7 figures, Latex, to appear in Phys. Rev.

Fabrication and morphological characterization of Nafion thin films spin coated on silica

Nafion thin films (∼1 μm) were fabricated via the spin coating technique. Angular velocity and concentration of Nafion solution were chosen as parameters and were varied in order to determine thickness relationships. Energy-Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) characterizations were performed in order to determine elemental composition and surface morphology of the films respectively