2,345 research outputs found
Self-Dual Conformal Supergravity and the Hamiltonian Formulation
In terms of Dirac matrices the self-dual and anti-self-dual decomposition of
a conformal supergravity is given and a self-dual conformal supergravity theory
is developed as a connection dynamic theory in which the basic dynamic variabes
include the self-dual spin connection i.e. the Ashtekar connection rather than
the triad. The Hamiltonian formulation and the constraints are obtained by
using the Dirac-Bergmann algorithm.
PACS numbers: 04.20.Cv, 04.20.Fy,04.65.+
The prevalence of insomnia in the general population in China: A meta-analysis
This is the first meta-analysis of the pooled prevalence of insomnia in the general population of China. A systematic literature search was conducted via the following databases: PubMed, PsycINFO, EMBASE and Chinese databases (China National Knowledge Interne (CNKI), WanFang Data and SinoMed). Statistical analyses were performed using the Comprehensive Meta-Analysis program. A total of 17 studies with 115,988 participants met the inclusion criteria for the analysis. The pooled prevalence of insomnia in China was 15.0% (95% Confidence interval [CI]: 12.1%-18.5%). No significant difference was found in the prevalence between genders or across time period. The pooled prevalence of insomnia in population with a mean age of 43.7 years and older (11.6%; 95% CI: 7.5%-17.6%) was significantly lower than in those with a mean age younger than 43.7 years (20.4%; 95% CI: 14.2%-28.2%). The prevalence of insomnia was significantly affected by the type of assessment tools (Q = 14.1, P = 0.001). The general population prevalence of insomnia in China is lower than those reported in Western countries but similar to those in Asian countries. Younger Chinese adults appear to suffer from more insomnia than older adults
Boxicity and separation dimension
A family of permutations of the vertices of a hypergraph is
called 'pairwise suitable' for if, for every pair of disjoint edges in ,
there exists a permutation in in which all the vertices in one
edge precede those in the other. The cardinality of a smallest such family of
permutations for is called the 'separation dimension' of and is denoted
by . Equivalently, is the smallest natural number so that
the vertices of can be embedded in such that any two
disjoint edges of can be separated by a hyperplane normal to one of the
axes. We show that the separation dimension of a hypergraph is equal to the
'boxicity' of the line graph of . This connection helps us in borrowing
results and techniques from the extensive literature on boxicity to study the
concept of separation dimension.Comment: This is the full version of a paper by the same name submitted to
WG-2014. Some results proved in this paper are also present in
arXiv:1212.6756. arXiv admin note: substantial text overlap with
arXiv:1212.675
Image-guided Radiotherapy to Manage Respiratory Motion: Lung and Liver.
Organ motion as a result of respiratory and cardiac motion poses significant challenges for the accurate delivery of radiotherapy to both the thorax and the upper abdomen. Modern imaging techniques during radiotherapy simulation and delivery now permit better quantification of organ motion, which in turn reduces tumour and organ at risk position uncertainty. These imaging advances, coupled with respiratory correlated radiotherapy delivery techniques, have led to the development of a range of approaches to manage respiratory motion. This review summarises the key strategies of image-guided respiratory motion management with a focus on lung and liver radiotherapy
Eigenvector Expansion and Petermann Factor for Ohmically Damped Oscillators
Correlation functions in ohmically damped
systems such as coupled harmonic oscillators or optical resonators can be
expressed as a single sum over modes (which are not power-orthogonal), with
each term multiplied by the Petermann factor (PF) , leading to "excess
noise" when . It is shown that is common rather than
exceptional, that can be large even for weak damping, and that the PF
appears in other processes as well: for example, a time-independent
perturbation \sim\ep leads to a frequency shift \sim \ep C_j. The
coalescence of () eigenvectors gives rise to a critical point, which
exhibits "giant excess noise" (). At critical points, the
divergent parts of contributions to cancel, while time-independent
perturbations lead to non-analytic shifts \sim \ep^{1/J}.Comment: REVTeX4, 14 pages, 4 figures. v2: final, 20 single-col. pages, 2
figures. Streamlined with emphasis on physics over formalism; rewrote Section
V E so that it refers to time-dependent (instead of non-equilibrium) effect
Spectrum of Sizes for Perfect Deletion-Correcting Codes
One peculiarity with deletion-correcting codes is that perfect
-deletion-correcting codes of the same length over the same alphabet can
have different numbers of codewords, because the balls of radius with
respect to the Levenshte\u{\i}n distance may be of different sizes. There is
interest, therefore, in determining all possible sizes of a perfect
-deletion-correcting code, given the length and the alphabet size~.
In this paper, we determine completely the spectrum of possible sizes for
perfect -ary 1-deletion-correcting codes of length three for all , and
perfect -ary 2-deletion-correcting codes of length four for almost all ,
leaving only a small finite number of cases in doubt.Comment: 23 page
DNA hybridization to mismatched templates: a chip study
High-density oligonucleotide arrays are among the most rapidly expanding
technologies in biology today. In the {\sl GeneChip} system, the reconstruction
of the target concentration depends upon the differential signal generated from
hybridizing the target RNA to two nearly identical templates: a perfect match
(PM) and a single mismatch (MM) probe. It has been observed that a large
fraction of MM probes repeatably bind targets better than the PMs, against the
usual expectation from sequence-specific hybridization; this is difficult to
interpret in terms of the underlying physics. We examine this problem via a
statistical analysis of a large set of microarray experiments. We classify the
probes according to their signal to noise () ratio, defined as the
eccentricity of a (PM, MM) pair's `trajectory' across many experiments. Of
those probes having large () only a fraction behave consistently with
the commonly assumed hybridization model. Our results imply that the physics of
DNA hybridization in microarrays is more complex than expected, and they
suggest new ways of constructing estimators for the target RNA concentration.Comment: 3 figures 1 tabl
The lesbian, gay, bisexual and transgender community online: discussions of bullying and self-disclosure in YouTube videos
Computer-mediated communication has become a popular platform for identity construction and experimentation as well as social interaction for those who identify as lesbian, gay, bisexual or transgender (LGBT). The creation of user-generated videos has allowed content creators to share experiences on LGBT topics. With bullying becoming more common amongst LGBT youth, it is important to obtain a greater understanding of this phenomenon. In our study, we report on the analysis of 151 YouTube videos which were identified as having LGBT- and bullying-related content. The analysis reveals how content creators openly disclose personal information about themselves and their experiences in a non-anonymous rhetoric with an unknown public. These disclosures could indicate a desire to seek friendship, support and provide empathy
Scaling, Propagation, and Kinetic Roughening of Flame Fronts in Random Media
We introduce a model of two coupled reaction-diffusion equations to describe
the dynamics and propagation of flame fronts in random media. The model
incorporates heat diffusion, its dissipation, and its production through
coupling to the background reactant density. We first show analytically and
numerically that there is a finite critical value of the background density,
below which the front associated with the temperature field stops propagating.
The critical exponents associated with this transition are shown to be
consistent with mean field theory of percolation. Second, we study the kinetic
roughening associated with a moving planar flame front above the critical
density. By numerically calculating the time dependent width and equal time
height correlation function of the front, we demonstrate that the roughening
process belongs to the universality class of the Kardar-Parisi-Zhang interface
equation. Finally, we show how this interface equation can be analytically
derived from our model in the limit of almost uniform background density.Comment: Standard LaTeX, no figures, 29 pages; (to appear in J. Stat. Phys.
vol.81, 1995). Complete file available at
http://www.physics.helsinki.fi/tft/tft.html or anonymous ftp at
ftp://rock.helsinki.fi/pub/preprints/tft
High-reflectivity, high-Q micromechanical membranes via guided resonances for enhanced optomechanical coupling
Using Fano-type guided resonances (GRs) in photonic crystal (PhC) slab
structures, we numerically and experimentally demonstrate optical reflectivity
enhancement of high-Q SiNx membrane-type resonators used in
membrane-in-the-middle optomechanical (OM) systems. Normal-incidence
transmission and mechanical ringdown measurements of 50-nm-thick PhC membranes
demonstrate GRs near 1064 nm, leading to a ~ 4\times increase in reflectivity
while preserving high mechanical Q factors of up to ~ 5 \times 10^6. The
results would allow improvement of membrane-in-the-middle OM systems by virtue
of increased OM coupling, presenting a path towards ground state cooling of
such a membrane and observations of related quantum effects
- …