39,356 research outputs found
Space- and Time-Efficient Algorithm for Maintaining Dense Subgraphs on One-Pass Dynamic Streams
While in many graph mining applications it is crucial to handle a stream of
updates efficiently in terms of {\em both} time and space, not much was known
about achieving such type of algorithm. In this paper we study this issue for a
problem which lies at the core of many graph mining applications called {\em
densest subgraph problem}. We develop an algorithm that achieves time- and
space-efficiency for this problem simultaneously. It is one of the first of its
kind for graph problems to the best of our knowledge.
In a graph , the "density" of a subgraph induced by a subset of
nodes is defined as , where is the set of
edges in with both endpoints in . In the densest subgraph problem, the
goal is to find a subset of nodes that maximizes the density of the
corresponding induced subgraph. For any , we present a dynamic
algorithm that, with high probability, maintains a -approximation
to the densest subgraph problem under a sequence of edge insertions and
deletions in a graph with nodes. It uses space, and has an
amortized update time of and a query time of . Here,
hides a O(\poly\log_{1+\epsilon} n) term. The approximation ratio
can be improved to at the cost of increasing the query time to
. It can be extended to a -approximation
sublinear-time algorithm and a distributed-streaming algorithm. Our algorithm
is the first streaming algorithm that can maintain the densest subgraph in {\em
one pass}. The previously best algorithm in this setting required
passes [Bahmani, Kumar and Vassilvitskii, VLDB'12]. The space required by our
algorithm is tight up to a polylogarithmic factor.Comment: A preliminary version of this paper appeared in STOC 201
Used infant mattresses and sudden infant death syndrome in Scotland: case-control study
<P>OBJECTIVE: To examine the proposition that a used infant mattress is associated with an increased risk of sudden infant death syndrome. DESIGN: Case-control study. SETTING: Scotland (population 5.1 million, with about 53 000 births a year).</P> <P>PARTICIPANTS: 131 infants who died of sudden infant death syndrome between 1 January 1996 and 31 May 2000 and 278 age, season, and obstetric unit matched control infants.</P> <P>MAIN OUTCOME MEASURES: Routine use of an infant mattress previously used by another child and place of last sleep.</P> <P>RESULTS: Routine use of an infant mattress previously used by another child was significantly associated with an increased risk of sudden infant death syndrome (multivariate odds ratio 3.07, 95% confidence interval 1.51 to 6.22). Use of a used infant mattress for last sleep was also associated with increased risk (6.10, 2.31 to 16.12). The association was significantly stronger if the mattress was from another home (4.78, 2.08 to 11.0) than if it was from the same home (1.64, 0.64 to 4.2).</P> <P>CONCLUSION: A valid significant association exists between use of a used infant mattress and an increased risk of sudden infant death syndrome, particularly if the mattress is from another home. Insufficient evidence is available to judge whether this relation is cause and effect.</P>
Two-dimensional oscillating airfoil test apparatus
A two dimensional oscillating airfoil test apparatus is presented as a method of measuring unsteady aerodynamic forces on an airfoil or rotor blade section. The oscillating airfoil test rig, which is being built for use in an 11 X 11-foot transonic wind tunnel (speed range M = 0.4 - 1.4), will allow determination of unsteady loadings and detailed pressure distributions on representative airfoil sections undergoing simulated pitching and flapping motions. The design details of the motion generating system and supporting structure are presented. This apparatus is now in the construction phase
Unified control/structure design and modeling research
To demonstrate the applicability of the control theory for distributed systems to large flexible space structures, research was focused on a model of a space antenna which consists of a rigid hub, flexible ribs, and a mesh reflecting surface. The space antenna model used is discussed along with the finite element approximation of the distributed model. The basic control problem is to design an optimal or near-optimal compensator to suppress the linear vibrations and rigid-body displacements of the structure. The application of an infinite dimensional Linear Quadratic Gaussian (LQG) control theory to flexible structure is discussed. Two basic approaches for robustness enhancement were investigated: loop transfer recovery and sensitivity optimization. A third approach synthesized from elements of these two basic approaches is currently under development. The control driven finite element approximation of flexible structures is discussed. Three sets of finite element basic vectors for computing functional control gains are compared. The possibility of constructing a finite element scheme to approximate the infinite dimensional Hamiltonian system directly, instead of indirectly is discussed
Increasing trap stiffness with position clamping in holographic optical tweezers
We present a holographic optical tweezers system capable of position clamping multiple particles. Moving an optical trap in response to the trapped object's motion is a powerful technique for optical control and force measurement. We have now realised this experimentally using a Boulder Nonlinear Systems Spatial Light Modulator (SLM) with a refresh rate of 203Hz. We obtain a reduction of 44% in the variance of the bead's position, corresponding to an increase in effective trap stiffness of 77%. This reduction relies on the generation of holograms at high speed. We present software capable of calculating holograms in under 1ms using a graphics processor unit. © 2009 Optical Society of America
Three-nucleon interactions: A frontier in nuclear structure
Three-nucleon interactions are a frontier in understanding and predicting the
structure of strongly-interacting matter in laboratory nuclei and in the
cosmos. We present results and discuss the status of first calculations with
microscopic three-nucleon interactions beyond light nuclei. This coherent
effort is possible due to advances based on effective field theory and
renormalization group methods in nuclear physics.Comment: 7 pages, 11 figures, talk at International Symposium on New Facet of
Three-Nucleon Force (FM50), Tokyo, October, 200
Importance of Baryon-Baryon Coupling in Hypernuclei
The coupling in --hypernuclei and coupling in --hypernuclei produce novel
physics not observed in the conventional, nonstrange sector. Effects of
conversion in H are reviewed.
The role of coupling suppression in the
--hypernuclei due to Pauli blocking is highlighted, and the
implications for the structure of B are explored.
Suppression of conversion in He is hypothesized as the reason that the
matrix element is small. Measurement of H is
proposed to investigate the full interaction. The
implication for analog states is discussed.Comment: 17 pages LATEX, 1 figure uuencoded postscrip
Understanding the role of promoters in catalysis: operando XAFS/DRIFTS study of CeO<sub>x</sub>/Pt/Al<sub>2</sub>O<sub>3</sub> during CO oxidation
A combined operando XAFS/DRIFTS study on CeOx/Pt/Al2O3 catalysts has been performed during CO oxidation and provides insights into the changes in nanoparticle structure and adsorbed species during the reaction profile. The onset of CO2 formation is shown to be concurrent with a rapid re-oxidation of the Pt nanoparticles, evidenced by XAFS spectroscopy, and the loss of bridge bonded CO adsorbed on Pt, as shown by simultaneous DRIFTS acquisition. The continued appearance of linear bound CO on the catalyst surface is shown to remain long after catalytic light off. The interaction of Pt and CeOx is evidenced by the improved performance towards CO oxidation, compared to the non-CeOx modified Pt/Al2O3, and changes in the CO adsorption properties on Pt previously linked to Pt-CeO2 interfaces
A systematic review of worldwide cancer nursing research: 1994 to 2003
Kelly contributed to the conduct and choice of papers for the study, carried out a systematic review of one sixth of all the papers, contributed to the conclusion and helped to edit the final version of this paper
Labeless and reversible immunosensor assay based upon an electrochemical current-transient protocol
A novel labeless and reversible immunoassay based upon an electrochemical
current-transient protocol is reported which offers many advantages in
comparison to classical immuno-biochemical analyses in terms of simplicity,
speed of response, reusability and possibility of multiple determinations.
Conducting polypyrrole films containing antibodies against 1) Bovine Serum
Albumin (BSA) and 2) Digoxin were deposited on the surface of platinum
electrodes to produce conductive affinity matrices having clearly defined
binding characteristics. The deposition process has been investigated using 125I
labelled anti-digoxin to determine optimal fabrication protocols. Antibody
integrity and activity, together with non-specific binding of antigen on the
conducting matrix have also been investigated using tritiated digoxin to probe
polypyrrole/anti-digoxin films. Amperometric responses to digoxin were recorded
in flow conditions using these films, but the technique was limited in use
mainly due to baseline instability. Anti-BSA - polypyrrole matrices were
investigated in more detail in both flow and quiescent conditions. No observable
response was found in flow conditions, however under quiescent conditions (in
non-stirred batch cell), anti-BSA – polypyrrole films have been demonstrated to
function as novel quantitative chronoamperometric immuno-biosensors when
interrogated using a pulsed potential waveform. The behaviour of the electrodes
showed that the antibody/antigen binding and/or interaction process underlying
the response observed was reversible in nature, indicating that the electrodes
could be used for multiple sensing protocols. Calibration profiles for BSA
demonstrated linearity for a concentration range of 0-50 ppm but tended towards
a plateau at higher concentrations. Factors relating to replicate sensor
production, sample measurement and reproducibility are discuss
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