High-temperature capacitive strain measurement system

Capacitive strain gage and signal conditioning system measures stress-induced strain and cancels thermal expansion strain at temperatures to 1,500 F (815 C). Gage does not significantly restrain or reinforce specimen

Impurity effects in few-electron quantum dots: Incipient Wigner molecule regime

Numerically exact path-integral Monte Carlo data are presented for $N\leq 10$ strongly interacting electrons confined in a 2D parabolic quantum dot, including a defect to break rotational symmetry. Low densities are studied, where an incipient Wigner molecule forms. A single impurity is found to cause drastic effects: (1) The standard shell-filling sequence with magic numbers $N=4,6,9$, corresponding to peaks in the addition energy $\Delta(N)$, is destroyed, with a new peak at N=8, (2) spin gaps decrease, (3) for N=8, sub-Hund's rule spin S=0 is induced, and (4) spatial ordering of the electrons becomes rather sensitive to spin. We also comment on the recently observed bunching phenomenon.Comment: 7 pages, 1 table, 4 figures, accepted for publication in Europhysics Letter

Magnetic confinement of massless Dirac fermions in graphene

Due to Klein tunneling, electrostatic potentials are unable to confine Dirac electrons. We show that it is possible to confine massless Dirac fermions in a monolayer graphene sheet by inhomogeneous magnetic fields. This allows one to design mesoscopic structures in graphene by magnetic barriers, e.g. quantum dots or quantum point contacts.Comment: 4 pages, 3 figures, version to appear in PR

Parameter identification in a semilinear hyperbolic system

We consider the identification of a nonlinear friction law in a one-dimensional damped wave equation from additional boundary measurements. Well-posedness of the governing semilinear hyperbolic system is established via semigroup theory and contraction arguments. We then investigte the inverse problem of recovering the unknown nonlinear damping law from additional boundary measurements of the pressure drop along the pipe. This coefficient inverse problem is shown to be ill-posed and a variational regularization method is considered for its stable solution. We prove existence of minimizers for the Tikhonov functional and discuss the convergence of the regularized solutions under an approximate source condition. The meaning of this condition and some arguments for its validity are discussed in detail and numerical results are presented for illustration of the theoretical findings

Critical Josephson current through a bistable single-molecule junction

We compute the critical Josephson current through a single-molecule junction. As a model for a molecule with a bistable conformational degree of freedom, we study an interacting single-level quantum dot coupled to a two-level system and weakly connected to two superconducting electrodes. We perform a lowest-order perturbative calculation of the critical current and show that it can significantly change due to the two-level system. In particular, the \pi-junction behavior, generally present for strong interactions, can be completely suppressed.Comment: 7 pages, 5 figures; v2: minor changes, to be published in Phys. Rev.

Transport in Double-Crossed Luttinger Liquids

We study transport through two Luttinger liquids (one-dimensional electrons interacting through a Coulomb repulsion in a metal) coupled together at {\it two} points. External voltage biases are incorporated through boundary conditions. We include density-density couplings as well as single-particle hops at the contacts. For weak repulsive interactions, transport through the wires remains undisturbed by the inter-wire couplings, which renormalise to zero. For strong repulsive interactions, the inter-wire couplings become strong. For symmetric barriers and no external voltage bias, a single gate voltage is sufficient to tune for resonance transmission in both wires. However, for asymmetric couplings or for finite external biases, the system is insulating.Comment: Latex file, 11 pages, one eps figur

Quantifying Zea mays L tassel development and correlation with anther developmental stages as a guide for experimental studies

In the study of Zea mays L early anther development, anther length is tightly correlated with developmental stage over the initial eight days of ontogeny. The developing tassel is enveloped inside the whorl of developing leaves, and the pace of its growth is environmentally sensitive. Determining the size of a young tassel without sacrific- ing the plant remains difficult. This obstacle can present problems when trying to study pre-meiotic and meiotic stages of anther development in planta or when conducting sequential sampling from the same tassel. In this study a range of exterior characteristics (leaf number, stem circumference, and tassel height above the soil line) were measured and correlated with tassel length. Anther lengths at seven tassel locations were also measured to correlate tassel length with anther development at these locations. Results indicate that tassel length can occupy a wide-range for a given exterior measurement, but also that anther development at specific tassel locations is highly reproducible for a tassel of known length. This information provides a useful guide for the study of anther development in the context of the maize tassel

Reading with Social, Digital Annotation: Encouraging Engaged Critical Reading in a Challenging Age

This design-based research study examines the pedagogical role of social, digital annotation in teaching reading as rhetorical invention, particularly the kind of invention necessary for thoughtful democratic participation in the contemporary discursive era, often described as troubled. In this dissertation study, I deployed a classroom-based intervention meant to challenge how educators in rhetoric and composition/writing studies might directly address the acute and exigent discursive struggle in the first-year composition classroom. This study ultimately finds that social, digital annotation invites significant shifts in students’ reading habits, in that Hypothes.is-based annotations yielded a far more complex, multifaceted set of reading skills, behaviors, and dispositions than the pre-intervention private annotations. The social annotation experience proved far more performative and, therefore, highly rhetorical and inventive, encouraging an agentic approach to reading that many FYC teacher-scholars crave. In addition to the performative nature of SDA (Hypothes.is, specifically), the social engagement among readers afforded by this relatively new digital tool of reading were the biggest catalysts for change. As a result, SDA may have that capacity as a technology to arrange meaning-making interactions in ways that are visible to the students themselves, shifting their perspectives on agency within reading