303 research outputs found
FIRST GRADERS AS SENSITIVE SOCIAL PARTNERS AND SKILLED READERS
This mixed methods dissertation is guided by a sociocultural framework and a pragmatist stance to contribute to early literacy scholarship about minority children. In particular, I explore the relationship between low socioeconomic status Puerto Rican children’s reading experience and their social cognition by: (1) assessing them through quantitative and qualitative measures that reveal their capacities in these areas at the end of their first grade year, and (2) documenting their reading experiences at home and at school through ethnographic qualitative methods. The analyses revealed significant positive correlations between the tests of reading and social understanding, a scarcity of conventional reading practices in the home, the predominance of a whole-class basal approach to reading in the classroom, and discrepant cross-methods findings regarding who qualifies as a reader and who has insights about the social world
Universal transport signatures of Majorana fermions in superconductor-Luttinger liquid junctions
One of the most promising proposals for engineering topological
superconductivity and Majorana fermions employs a spin-orbit coupled nanowire
subjected to a magnetic field and proximate to an s-wave superconductor. When
only part of the wire's length contacts to the superconductor, the remaining
conducting portion serves as a natural lead that can be used to probe these
Majorana modes via tunneling. The enhanced role of interactions in one
dimension dictates that this configuration should be viewed as a
superconductor-Luttinger liquid junction. We investigate such junctions between
both helical and spinful Luttinger liquids, and topological as well as
non-topological superconductors. We determine the phase diagram for each case
and show that universal low-energy transport in these systems is governed by
fixed points describing either perfect normal reflection or perfect Andreev
reflection. In addition to capturing (in some instances) the familiar
Majorana-mediated `zero-bias anomaly' in a new framework, we show that
interactions yield dramatic consequences in certain regimes. Indeed, we
establish that strong repulsion removes this conductance anomaly altogether
while strong attraction produces dynamically generated effective Majorana modes
even in a junction with a trivial superconductor. Interactions further lead to
striking signatures in the local density of states and the line-shape of the
conductance peak at finite voltage, and also are essential for establishing
smoking-gun transport signatures of Majorana fermions in spinful Luttinger
liquid junctions.Comment: 25 pages, 6 figures, v
Student Recital: Jose R. Alicea, Percussion; Ted Parge, Percussion; Pam Mosier, Accompanist; January 22, 1975
Centennial East Recital HallWednesday EveningJanuary 22, 19758:15 p.m
Percussion Recital: Jose R. Alicea, Percussion; Bon Hee Koo, Piano; Grace Pun, Piano; May 3, 1976
Centennial East Recital HallMonday EveningMay 3, 19767:00 p.m
Majorana Fermions in Equilibrium and Driven Cold Atom Quantum Wires
We introduce a new approach to create and detect Majorana fermions using
optically trapped 1D fermionic atoms. In our proposed setup, two internal
states of the atoms couple via an optical Raman transition---simultaneously
inducing an effective spin-orbit interaction and magnetic field---while a
background molecular BEC cloud generates s-wave pairing for the atoms. The
resulting cold atom quantum wire supports Majorana fermions at phase boundaries
between topologically trivial and nontrivial regions, as well as `Floquet
Majorana fermions' when the system is periodically driven. We analyze
experimental parameters, detection schemes, and various imperfections.Comment: 4 pages, 3 figures; references adde
A soft, synergy-based robotic glove for grasping assistance
This paper presents a soft, tendon-driven, robotic glove designed to augment grasp capability and provide rehabilitation assistance for postspinal cord injury patients. The basis of the design is an underactuation approach utilizing postural synergies of the hand to support a large variety of grasps with a single actuator. The glove is lightweight, easy to don, and generates sufficient hand closing force to assist with activities of daily living. Device efficiency was examined through a characterization of the power transmission elements, and output force production was observed to be linear in both cylindrical and pinch grasp configurations. We further show that, as a result of the synergy-inspired actuation strategy, the glove only slightly alters the distribution of forces across the fingers, compared to a natural, unassisted grasping pattern. Finally, a preliminary case study was conducted using a participant suffering from an incomplete spinal cord injury (C7). It was found that through the use of the glove, the participant was able to achieve a 50% performance improvement (from four to six blocks) in a standard Box and Block test
Parafermionic edge zero modes in Z_n-invariant spin chains
A sign of topological order in a gapped one-dimensional quantum chain is the
existence of edge zero modes. These occur in the Z_2-invariant Ising/Majorana
chain, where they can be understood using free-fermion techniques. Here I
discuss their presence in spin chains with Z_n symmetry, and prove that for
appropriate coupling they are exact, even in this strongly interacting system.
These modes are naturally expressed in terms of parafermions, generalizations
of fermions to the Z_n case. I show that parafermionic edge zero modes do not
occur in the usual ferromagnetic and antiferromagnetic cases, but rather only
when the interactions are chiral, so that spatial-parity and time-reversal
symmetries are broken.Comment: 22 pages. v2: small changes, added reference
Phase diagram of bismuth in the extreme quantum limit
Elemental bismuth provides a rare opportunity to explore the fate of a
three-dimensional gas of highly mobile electrons confined to their lowest
Landau level. Coulomb interaction, neglected in the band picture, is expected
to become significant in this extreme quantum limit with poorly understood
consequences. Here, we present a study of the angular-dependent Nernst effect
in bismuth, which establishes the existence of ultraquantum field scales on top
of its complex single-particle spectrum. Each time a Landau level crosses the
Fermi level, the Nernst response sharply peaks. All such peaks are resolved by
the experiment and their complex angular-dependence is in very good agreement
with the theory. Beyond the quantum limit, we resolve additional Nernst peaks
signaling a cascade of additional Landau sub-levels caused by electron
interaction
The Development of an Open Source Intelligence Gathering Exercise for Teaching Information Security & Privacy
This research-in-progress paper describes the development of a pedagogical exercise on open source intelligence gathering (OSINT). Exercise materials will include instructions, teaching notes, assessment criteria, and a preconfigured virtual machine (VM), which acts as a local web server. The VM will host multiple websites containing vulnerable information pertinent to a fictitious target organization, in effect creating a capture the flag (CTF) scenario. The exercise will not only teach students how to find public information, but also help students realize the importance of protecting such information. While this exercise is primarily geared towards those pursuing a career in information security, the exercise is appropriate for all students as it shows how personal information could be used against them, as well as their organizations
Non-Abelian statistics and topological quantum information processing in 1D wire networks
Topological quantum computation provides an elegant way around decoherence,
as one encodes quantum information in a non-local fashion that the environment
finds difficult to corrupt. Here we establish that one of the key
operations---braiding of non-Abelian anyons---can be implemented in
one-dimensional semiconductor wire networks. Previous work [Lutchyn et al.,
arXiv:1002.4033 and Oreg et al., arXiv:1003.1145] provided a recipe for driving
semiconducting wires into a topological phase supporting long-sought particles
known as Majorana fermions that can store topologically protected quantum
information. Majorana fermions in this setting can be transported, created, and
fused by applying locally tunable gates to the wire. More importantly, we show
that networks of such wires allow braiding of Majorana fermions and that they
exhibit non-Abelian statistics like vortices in a p+ip superconductor. We
propose experimental setups that enable the Majorana fusion rules to be probed,
along with networks that allow for efficient exchange of arbitrary numbers of
Majorana fermions. This work paves a new path forward in topological quantum
computation that benefits from physical transparency and experimental realism.Comment: 6 pages + 17 pages of Supp. Mat.; 10 figures. Supp. Mat. has doubled
in size to establish results more rigorously; many other improvements as wel
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