4,437 research outputs found
Largest Empty Circle Centered on a Query Line
The Largest Empty Circle problem seeks the largest circle centered within the
convex hull of a set of points in and devoid of points
from . In this paper, we introduce a query version of this well-studied
problem. In our query version, we are required to preprocess so that when
given a query line , we can quickly compute the largest empty circle
centered at some point on and within the convex hull of .
We present solutions for two special cases and the general case; all our
queries run in time. We restrict the query line to be horizontal in
the first special case, which we preprocess in time and
space, where is the slow growing inverse of the Ackermann's
function. When the query line is restricted to pass through a fixed point, the
second special case, our preprocessing takes time and space. We use insights from the two special cases to solve the
general version of the problem with preprocessing time and space in and respectively.Comment: 18 pages, 13 figure
A two-coil mutual inductance technique to study matching effect in disordered NbN thin films
Although matching effects in superconducting anti-dot arrays have been
studied extensively through magneto-resistance oscillations, these
investigations have been restricted to a very narrow temperature window close
to the superconducting transition. Here we report a "two coil" mutual
inductance technique, which allows the study of this phenomenon deep in the
superconducting state, through a direct measurement of the magnetic field
variation of the shielding response. We demonstrate how this technique can be
used to resolve outstanding issues on the origin of matching effects in
superconducting thin films with periodic array of holes grown on anodized
alumina membranes
Spin Filtering and Entanglement Swapping through Coherent Evolution of a Single Quantum Dot
We exploit the non-dissipative dynamics of a pair of electrons in a large
square quantum dot to perform singlet-triplet spin measurement through a single
charge detection and show how this may be used for entanglement swapping and
teleportation. The method is also used to generate the AKLT ground state, a
further resource for quantum computation. We justify, and derive analytic
results for, an effective charge-spin Hamiltonian which is valid over a wide
range of parameters and agrees well with exact numerical results of a realistic
effective-mass model. Our analysis also indicates that the method is robust to
choice of dot-size and initialization errors, as well as decoherence introduced
by the hyperfine interaction.Comment: 5 pages, 3 figure
Biophysical evidence for intrinsic disorder in the C-terminal tails of the epidermal growth factor receptor (EGFR) and HER3 receptor tyrosine kinases
The epidermal growth factor receptor (EGFR)/ErbB family of receptor tyrosine kinases includes oncogenes important in the progression of breast and other cancers, and they are targets for many drug development strategies. Each member of the ErbB family possesses a unique, structurally uncharacterized C-terminal tail that plays an important role in autophosphorylation and signal propagation. To determine whether these C-terminal tails are intrinsically disordered regions, we conducted a battery of biophysical experiments on the EGFR and HER3 tails. Using hydrogen/deuterium exchange mass spectrometry, we measured the conformational dynamics of intracellular half constructs and compared the tails with the ordered kinase domains. The C-terminal tails demonstrate more rapid deuterium exchange behavior when compared with the kinase domains. Next, we expressed and purified EGFR and HER3 tail-only constructs. Results from circular dichroism spectroscopy, size exclusion chromatography with multiangle light scattering, dynamic light scattering, analytical ultracentrifugation, and small angle X-ray scattering each provide evidence that the EGFR and HER3 C-terminal tails are intrinsically disordered with extended, non-globular structure in solution. The intrinsic disorder and extended conformation of these tails may be important for their function by increasing the capture radius and reducing the thermodynamic barriers for binding of downstream signaling proteins
Origin of Matching Effect in Anti-dot Array of Superconducting NbN Thin Films
We investigate the origin of matching effect observed in disordered
superconducting NbN thin films with periodic array of holes. In addition to the
periodic variation in the electrical resistance just above the superconducting
transition temperature, Tc0, we find pronounced periodic variations with
magnetic field in all dynamical quantities which can be influenced by flux-line
motion under an external drive such as the magnetic shielding response and the
critical current which survive in some samples down to temperatures as low as
0.09Tc0. In contrast, the superconducting energy gap, D which is a true
thermodynamic quantity does not show any periodic variation with magnetic
fields for the same films. Our results show that commensurate pinning of the
flux line lattice driven by vortex-vortex interaction is the dominant mechanism
for the observed matching effects in these superconducting anti-dot films
rather than Little-Parks like quantum interference effect.Comment: 18 pages, 6 figure
Inhibition of the EGF receptor by binding of MIG6 to an activating kinase domain interface.
Members of the epidermal growth factor receptor family (EGFR/ERBB1, ERBB2/HER2, ERBB3/HER3 and ERBB4/HER4) are key targets for inhibition in cancer therapy. Critical for activation is the formation of an asymmetric dimer by the intracellular kinase domains, in which the carboxy-terminal lobe (C lobe) of one kinase domain induces an active conformation in the other. The cytoplasmic protein MIG6 (mitogen-induced gene 6; also known as ERRFI1) interacts with and inhibits the kinase domains of EGFR and ERBB2 (refs 3-5). Crystal structures of complexes between the EGFR kinase domain and a fragment of MIG6 show that a approximately 25-residue epitope (segment 1) from MIG6 binds to the distal surface of the C lobe of the kinase domain. Biochemical and cell-based analyses confirm that this interaction contributes to EGFR inhibition by blocking the formation of the activating dimer interface. A longer MIG6 peptide that is extended C terminal to segment 1 has increased potency as an inhibitor of the activated EGFR kinase domain, while retaining a critical dependence on segment 1. We show that signalling by EGFR molecules that contain constitutively active kinase domains still requires formation of the asymmetric dimer, underscoring the importance of dimer interface blockage in MIG6-mediated inhibition
Data Structures for Halfplane Proximity Queries and Incremental Voronoi Diagrams
We consider preprocessing a set of points in convex position in the
plane into a data structure supporting queries of the following form: given a
point and a directed line in the plane, report the point of that
is farthest from (or, alternatively, nearest to) the point among all points
to the left of line . We present two data structures for this problem.
The first data structure uses space and preprocessing
time, and answers queries in time, for any . The second data structure uses space and
polynomial preprocessing time, and answers queries in time. These
are the first solutions to the problem with query time and
space.
The second data structure uses a new representation of nearest- and
farthest-point Voronoi diagrams of points in convex position. This
representation supports the insertion of new points in clockwise order using
only amortized pointer changes, in addition to -time
point-location queries, even though every such update may make
combinatorial changes to the Voronoi diagram. This data structure is the first
demonstration that deterministically and incrementally constructed Voronoi
diagrams can be maintained in amortized pointer changes per operation
while keeping -time point-location queries.Comment: 17 pages, 6 figures. Various small improvements. To appear in
Algorithmic
Evaluation: Perspectives of Students and Graduates
Women\u27s studies, now in its second phase, is making its presence felt within institutions, developing a new curriculum, and building a new body of intellectual knowledge. Women\u27s studies\u27 original purpose continues: to change the sexist and other biased values, practices, and structures within and outside traditional educational spheres.
How much change has occurred? Impact within colleges, high schools, and women\u27s centers is easier to judge than effect in other arenas . Outside educational institutions, impact may be observed through two channels: first, the ties which programs explicitly make with community groups; second, students who graduate and choose not to continue their formal education. Although we assume that students are changed by their women\u27s studies experience, we often do not know what happens to them after leaving. Do they become involved in social change? Or do they feel their education has not influenced what they are now doing? The answers to these questions measure the strengths and deficiencies of women\u27s studies and provide one solid basis on which to build the curriculum during its second phase
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