1,834 research outputs found
Geometry of all supersymmetric type I backgrounds
We find the geometry of all supersymmetric type I backgrounds by solving the
gravitino and dilatino Killing spinor equations, using the spinorial geometry
technique, in all cases. The solutions of the gravitino Killing spinor equation
are characterized by their isotropy group in Spin(9,1), while the solutions of
the dilatino Killing spinor equation are characterized by their isotropy group
in the subgroup Sigma(P) of Spin(9,1) which preserves the space of parallel
spinors P. Given a solution of the gravitino Killing spinor equation with L
parallel spinors, L = 1,2,3,4,5,6,8, the dilatino Killing spinor equation
allows for solutions with N supersymmetries for any 0 < N =< L. Moreover for L
= 16, we confirm that N = 8,10,12,14,16. We find that in most cases the Bianchi
identities and the field equations of type I backgrounds imply a further
reduction of the holonomy of the supercovariant connection. In addition, we
show that in some cases if the holonomy group of the supercovariant connection
is precisely the isotropy group of the parallel spinors, then all parallel
spinors are Killing and so there are no backgrounds with N < L supersymmetries.Comment: 73 pages. v2: minor changes, references adde
Syndromic Surveillance for Emerging Infections in Office Practice Using Billing Data
PURPOSE We wanted to evaluate the feasibility of conducting syndromic surveillance in a primary care office using billing data
Multiple planar coincidences with N-fold symmetry
Planar coincidence site lattices and modules with N-fold symmetry are well
understood in a formulation based on cyclotomic fields, in particular for the
class number one case, where they appear as certain principal ideals in the
corresponding ring of integers. We extend this approach to multiple
coincidences, which apply to triple or multiple junctions. In particular, we
give explicit results for spectral, combinatorial and asymptotic properties in
terms of Dirichlet series generating functions.Comment: 13 pages, two figures. For previous related work see math.MG/0511147
and math.CO/0301021. Minor changes and references update
Time-evolution of the Rule 150 cellular automaton activity from a Fibonacci iteration
The total activity of the single-seeded cellular rule 150 automaton does not
follow a one-step iteration like other elementary cellular automata, but can be
solved as a two-step vectorial, or string, iteration, which can be viewed as a
generalization of Fibonacci iteration generating the time series from a
sequence of vectors of increasing length. This allows to compute the total
activity time series more efficiently than by simulating the whole
spatio-temporal process, or even by using the closed expression.Comment: 4 pages (3 figs included
A Fascinating Polynomial Sequence arising from an Electrostatics Problem on the Sphere
A positive unit point charge approaching from infinity a perfectly spherical
isolated conductor carrying a total charge of +1 will eventually cause a
negatively charged spherical cap to appear. The determination of the smallest
distance ( is the dimension of the unit sphere) from the point
charge to the sphere where still all of the sphere is positively charged is
known as Gonchar's problem. Using classical potential theory for the harmonic
case, we show that is equal to the largest positive zero of a
certain sequence of monic polynomials of degree with integer
coefficients which we call Gonchar polynomials. Rather surprisingly,
is the Golden ratio and the lesser known Plastic number. But Gonchar
polynomials have other interesting properties. We discuss their factorizations,
investigate their zeros and present some challenging conjectures.Comment: 12 pages, 6 figures, 1 tabl
Immunodetectable cyclin D 1 is associated with oestrogen receptor but not Ki67 in normal, cancerous and precancerous breast lesions
Cyclin D1 is associated with cell cycle regulation and has more recently been shown to stimulate the transcriptional functions of the oestrogen receptor (ER). Furthermore, in normal breast there is a negative association between expression of ER and the proliferation marker Ki67 indicating that either ER positive cells are non-dividing or that the receptor is down-regulated as cells enter cycle. This important relationship breaks down in many ER-positive cancers and precancerous breast lesions where the receptor is often detected on proliferating cells. The aims of the present study were to determine the interplay between ER, Ki67 and cyclin D 1 in individual cells within the spectrum of human breast lesions ranging from normal to invasive carcinoma by using dual staining immunofluorescence. We found that in normal breast there was a strong positive association between ER and cyclin D 1 expression. In contrast there was a strong negative association between cyclin D 1 and Ki67 expression. Similar findings were seen for the other precancerous and cancerous breast lesions. Thus immunodetectable cyclin D 1 within individual cells does not appear to be associated with cell cycle progression in the benign or malignant breast but instead may have important interactions with ER. © 2001 Cancer Research Campaign http://www.bjcancer.co
Popularity-Driven Networking
We investigate the growth of connectivity in a network. In our model,
starting with a set of disjoint nodes, links are added sequentially. Each link
connects two nodes, and the connection rate governing this random process is
proportional to the degrees of the two nodes. Interestingly, this network
exhibits two abrupt transitions, both occurring at finite times. The first is a
percolation transition in which a giant component, containing a finite fraction
of all nodes, is born. The second is a condensation transition in which the
entire system condenses into a single, fully connected, component. We derive
the size distribution of connected components as well as the degree
distribution, which is purely exponential throughout the evolution.
Furthermore, we present a criterion for the emergence of sudden condensation
for general homogeneous connection rates.Comment: 5 pages, 2 figure
Multiqubit symmetric states with high geometric entanglement
We propose a detailed study of the geometric entanglement properties of pure
symmetric N-qubit states, focusing more particularly on the identification of
symmetric states with a high geometric entanglement and how their entanglement
behaves asymptotically for large N. We show that much higher geometric
entanglement with improved asymptotical behavior can be obtained in comparison
with the highly entangled balanced Dicke states studied previously. We also
derive an upper bound for the geometric measure of entanglement of symmetric
states. The connection with the quantumness of a state is discussed
Revenue divergence and competitive balance in a divisional sports league
The North American model of resource allocation in professional sports leagues is adapted for English (association) football. The theoretical relationship between revenue and competitive balance is shown to be robust with respect to changes in teams’ objectives and labour market conditions. Empirical revenue functions are reported for 1926-1999. These indicate a shift in the composition of demand favouring big-city teams and an increase in the sensitivity of revenue to performance. An analysis of match results in the FA Cup competition suggests an increase in competitive imbalance between teams at different levels of the league’s divisional hierarchy, as the theory suggests
Nurses\u27 and Patients\u27 Appraisals Show Patient Safety in Hospitals Remains a Concern
In the report To Err is Human (1999), the National Academy of Medicine called for national action to improve patient safety in hospitals. The report concluded that improving nurse work environments—assuring adequate nurse staffing and supporting nurses’ ability to care for patients—was critical to these efforts. Two decades later, have nurse work environments improved, and has that had a noticeable impact on patient safety? To find out, a research team led by LDI Senior Fellow Linda Aiken, PhD, RN surveyed more than 800,000 patients and 53,000 nurses in 535 hospitals in 2005, and again in 2016
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