354 research outputs found
Atlas models of equity markets
Atlas-type models are constant-parameter models of uncorrelated stocks for
equity markets with a stable capital distribution, in which the growth rates
and variances depend on rank. The simplest such model assigns the same,
constant variance to all stocks; zero rate of growth to all stocks but the
smallest; and positive growth rate to the smallest, the Atlas stock. In this
paper we study the basic properties of this class of models, as well as the
behavior of various portfolios in their midst. Of particular interest are
portfolios that do not contain the Atlas stock.Comment: Published at http://dx.doi.org/10.1214/105051605000000449 in the
Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute
of Mathematical Statistics (http://www.imstat.org
Atom Chips: Fabrication and Thermal Properties
Neutral atoms can be trapped and manipulated with surface mounted microscopic
current carrying and charged structures. We present a lithographic fabrication
process for such atom chips based on evaporated metal films. The size limit of
this process is below 1m. At room temperature, thin wires can carry more
than 10A/cm current density and voltages of more than 500V. Extensive
test measurements for different substrates and metal thicknesses (up to 5
m) are compared to models for the heating characteristics of the
microscopic wires. Among the materials tested, we find that Si is the best
suited substrate for atom chips
Deterministic quantum teleportation between distant atomic objects
Quantum teleportation is a key ingredient of quantum networks and a building
block for quantum computation. Teleportation between distant material objects
using light as the quantum information carrier has been a particularly exciting
goal. Here we demonstrate a new element of the quantum teleportation landscape,
the deterministic continuous variable (cv) teleportation between distant
material objects. The objects are macroscopic atomic ensembles at room
temperature. Entanglement required for teleportation is distributed by light
propagating from one ensemble to the other. Quantum states encoded in a
collective spin state of one ensemble are teleported onto another ensemble
using this entanglement and homodyne measurements on light. By implementing
process tomography, we demonstrate that the experimental fidelity of the
quantum teleportation is higher than that achievable by any classical process.
Furthermore, we demonstrate the benefits of deterministic teleportation by
teleporting a dynamically changing sequence of spin states from one distant
object onto another
Characterization of infectious and defective cloned avian hepadnavirus genomes
The infectivity in vivo, replication competence in vitro, and expression of viral genes of several molecularly cloned duck hepatitis B virus (DHBV) genomes were investigated. In addition, replication competence, core protein expression, and secretion of viral proteins were investigated for a grey heron hepatitis B virus genome. Except two, all DHBV isolates tested induced a systemic infection in Pekin ducks when injected as cloned viral DNA into the liver. After transfection of chicken hepatoma cells, both defective DHBV genomes expressed intracellular nucleocapsid and pre-S envelope proteins and secreted DHBs/pre-S particles into the medium. One of the defective DHBV genomes and HHBV produced within the cells replicative intermediates encapsidated in core particles and secreted virions, whereas the other defective DHBV genome did not and was unable to efficiently encapsidate the RNA pregenome. Comparative sequence analysis was performed to identify potential amino acid changes in viral proteins of both defective DHBV genomes. The data obtained demonstrate that most cloned avian hepadnaviruses are infectious or replication competent and suggest defects in envelope, polymerase or encapsidation function, respectively, in two cloned DHBV genomes
Electrical and Structural Properties of \u3ci\u3ep-n\u3c/i\u3e Junctions in cw Laser Annealed Silicon
Depth profiles of the electrical quality of ion implanted and cw laser annealed p-n junctions in silicon are obtained for the first time by secondary ion mass spectroscopy. A comparison with the crystallographic properties of the surface and the junction as observed by Nomarski optical microscopy as well as cross-sectional and plan view transmission electron microscopy is made. Samples containing slip dislocations show better insulation and a lower reverse bias current across the p-n junction as compared to samples with a perfect surface in agreement with current-voltage characteristics. Small dislocation loops located at the junction are found to degrade the junction quality
How many independent bets are there?
The benefits of portfolio diversification is a central tenet implicit to
modern financial theory and practice. Linked to diversification is the notion
of breadth. Breadth is correctly thought of as the number of in- dependent bets
available to an investor. Conventionally applications us- ing breadth
frequently assume only the number of separate bets. There may be a large
discrepancy between these two interpretations. We uti- lize a simple
singular-value decomposition (SVD) and the Keiser-Gutman stopping criterion to
select the integer-valued effective dimensionality of the correlation matrix of
returns. In an emerging market such as South African we document an estimated
breadth that is considerably lower than anticipated. This lack of
diversification may be because of market concentration, exposure to the global
commodity cycle and local currency volatility. We discuss some practical
extensions to a more statistically correct interpretation of market breadth,
and its theoretical implications for both global and domestic investors.Comment: Less technical rewrite. 12 Pages, 6 Figures (.eps
Mesoscopic atomic entanglement for precision measurements beyond the standard quantum limit
Squeezing of quantum fluctuations by means of entanglement is a well
recognized goal in the field of quantum information science and precision
measurements. In particular, squeezing the fluctuations via entanglement
between two-level atoms can improve the precision of sensing, clocks,
metrology, and spectroscopy. Here, we demonstrate 3.4 dB of metrologically
relevant squeezing and entanglement for ~ 10^5 cold cesium atoms via a quantum
nondemolition (QND) measurement on the atom clock levels. We show that there is
an optimal degree of decoherence induced by the quantum measurement which
maximizes the generated entanglement. A two-color QND scheme used in this paper
is shown to have a number of advantages for entanglement generation as compared
to a single color QND measurement.Comment: 6 pages+suppl, PNAS forma
Cross-Boarder Teaching and Collaboration
Since the publication of Best Practices for Legal Education, the globalization of both legal education and law practice has exploded. Today’s lawyers increasingly serve border-crossing clients or clients who present with transnational legal issues. As law schools expand their international programs, and enroll increasing numbers of non-U.S. law students, law students transcend cultural and legal borders. As a result, they deepen their understanding of—and sharpen their critical perspective on—their own national systems. Similarly, U.S. law teachers are increasingly called to engage in border-crossing teaching and other academic pursuits. Best Practices did not address these issues. The primary aim of this chapter of Building on Best Practices: Transforming Legal Education in a Changing World (Lexis 2015) is to identify best practices for law teachers engaged with non-U.S. or “international” learners who study or train in a U.S.-style learning environment, either in the United States or abroad.
This chapter also addresses collaboration of U.S. law teachers with their counterparts abroad in such areas as developing innovative teaching and clinical legal education, training and research. It identifies eight guiding principles that cut across types of international learning and then applies these principles to three specific contexts: 1) teaching international students in U.S. law school settings; 2) integrating international students in U.S.-based clinics; and 3) collaborating in legal education and reform efforts with law teachers abroad.https://digitalcommons.law.uw.edu/faculty-chapters/1001/thumbnail.jp
Two-dimensional array of microtraps with atomic shift register on a chip
Arrays of trapped atoms are the ideal starting point for developing registers
comprising large numbers of physical qubits for storing and processing quantum
information. One very promising approach involves neutral atom traps produced
on microfabricated devices known as atom chips, as almost arbitrary trap
configurations can be realised in a robust and compact package. Until now,
however, atom chip experiments have focused on small systems incorporating
single or only a few individual traps. Here we report experiments on a
two-dimensional array of trapped ultracold atom clouds prepared using a simple
magnetic-film atom chip. We are able to load atoms into hundreds of tightly
confining and optically resolved array sites. We then cool the individual atom
clouds in parallel to the critical temperature required for quantum degeneracy.
Atoms are shuttled across the chip surface utilising the atom chip as an atomic
shift register and local manipulation of atoms is implemented using a focused
laser to rapidly empty individual traps.Comment: 6 pages, 4 figure
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