The ballistic acceleration of a supercurrent in a superconductor

One of the most primitive but elusive current-voltage (I-V) responses of a superconductor is when its supercurrent grows steadily after a voltage is first applied. The present work employed a measurement system that could simultaneously track and correlate I(t) and V(t) with sub-nanosecond timing accuracy, resulting in the first clear time-domain measurement of this transient phase where the quantum system displays a Newtonian like response. The technique opens doors for the controlled investigation of other time dependent transport phenomena in condensed-matter systems.Comment: 4 pages, 3 figure

First Principles Study of Work Functions of Double Wall Carbon Nanotubes

Using first-principles density functional calculations, we investigated work functions (WFs) of thin double-walled nanotubes (DWNTs) with outer tube diameters ranging from 1nm to 1.5nm. The results indicate that work function change within this diameter range can be up to 0.5 eV, even for DWNTs with same outer diameter. This is in contrast with single-walled nanotubes (SWNTs) which show negligible WF change for diameters larger than 1nm. We explain the WF change and related charge redistribution in DWNTs using charge equilibration model (CEM). The predicted work function variation of DWNTs indicates a potential difficulty in their nanoelectronic device applications.Comment: 11 pages, 3 figures, to appear as rapid communication on Physical Review

Strong and Electromagnetic Decays of Two New Lambdac∗Lambda_c^* Baryons

Two recently discovered excited charm baryons are studied within the framework of Heavy Hadron Chiral Perturbation Theory. We interpret these new baryons which lie 308 \MeV and 340 \MeV above the $\Lambda_c$ as $I=0$ members of a P-wave spin doublet. Differential and total decay rates for their double pion transitions down to the $\Lambda_c$ ground state are calculated. Estimates for their radiative decay rates are also discussed. We find that the experimentally determined characteristics of the $\Lambda_c^*$ baryons may be simply understood in the effective theory.Comment: 16 pages with 4 figures not included but available upon request, CALT-68-191

An exploration of the nature of teacher/peer feedback interactions on pre-sessional English for academic purposes (EAP) courses in UK higher education.

This research concerns itself with the exploration of methods used to support student-writers‘ learning opportunities, as employed by teachers and by their students in teacher-student writing conferences; particularly the cadences of role construction and negotiation of viewpoints between peers in student-student writing conferences, within the context of English for Academic Purposes (EAP) programmes‘ pre-sessional writing courses in a UK university. The author poses two distinct questions: first, what methods are employed in the supporting of students‘ learning processes in terms of teacher-student writing conferences? Second, what tactics are taken in peers‘ role construction and viewpoint negotiation in student-student writing conferences? The study utilises a Conversation Analysis-informed methodology and interrogates its research data: namely audio/video recordings of 32 spoken teacher-feedback sessions and nine spoken peer-feedback sessions taken over a period of six months. Data analyses in this study reveal the massive importance that writing conferences play in jointly constructing the student‘s critical judgment and knowledge in preparation for academic literacy development. The study explores a number of interactional strategies used by teachers in support of student learning; giving special attention to the ―scaffolding technique‖, and how it assists students by maintaining their interest and enthusiasm for their studies, and by creating a shared frame through the teacher appearing to share responsibility for the learning, like an accomplice to the student. The study also considers the role of student-student interactions in promoting and developing learners‘ supporting arguments through engaging in the sheer complexity of these sessions. Overall, the study suggests and emphasises the importance of teachers and the requirement for them to create and to maintain opportunities for productive dialogue activities—as with writing conferences—by using an array of interactional strategies, all of which lead to students‘ joint and active participation for solving any problems that they may encounter during their journey to higher education, equipping them with all the knowledge and know-how that they need for their future studies

Analytical treatment of SUSY Quasi-normal modes in a non-rotating Schwarzschild black hole

We use the Fock-Ivanenko formalism to obtain the Dirac equation which describes the interaction of a massless 1/2-spin neutral fermion with a gravitational field around a Schwarzschild black hole (BH). We obtain approximated analytical solutions for the eigenvalues of the energy (quasi-normal frequencies) and their corresponding eigenstates (quasi-normal states). The interesting result is that all the excited states [and their supersymmetric (SUSY) partners] have a purely imaginary frequency, which can be expressed in terms of the Hawking temperature. Furthermore, as one expects for SUSY Hamiltonians, the isolated bottom state has a real null energy eigenvalue.Comment: Version to be published in European Physical Journal

COMMUNITY CHOICES AND HOUSING DECISIONS: A SPATIAL ANALYSIS OF THE SOUTHERN APPALACHIAN HIGHLANDS

This paper examines land development using an integrated approach that combines residential decisions about choices of community in the Southern Appalachian region with the application of the GIS (Geographical Information System). The empirical model infers a distinctive heterogeneity in the characteristics of community choices. The results also indicate that socioeconomic motives strongly affect urban housing decisions while environmental amenities affect those of rural housing.Public Economics,

Stability of inflating branes in a texture

We investigate the stability of inflating branes embedded in an O(2) texture formed in one extra dimension. The model contains two 3-branes of nonzero tension, and the extra dimension is compact. When the gravitational perturbation is applied, the vacuum energy which is responsible for inflation on the branes stabilizes the branes if the symmetry-breaking scale of the texture is smaller than some critical value. This critical value is determined by the particle-hierarchy scale between the two branes, and is smaller than the 5D Planck-mass scale. The scale of the vacuum energy can be considerably low in providing the stability. This stability story is very different from the flat-brane case which always suffers from the instability due to the gravitational perturbation.Comment: 16 pages, 5 eps figures, revte

Systematic Study of Theories with Quantum Modified Moduli

We begin the process of classifying all supersymmetric theories with quantum modified moduli. We determine all theories based on a single SU or Sp gauge group with quantum modified moduli. By flowing among theories we have calculated the precise modifications to the algebraic constraints that determine the moduli at the quantum level. We find a class of theories, those with a classical constraint that is covariant but not invariant under global symmetries, that have a singular modification to the moduli, which consists of a new branch.Comment: 21 pages, ReVTeX (or Latex, etc), corrected typos and cQMM discusio