9,028 research outputs found
Before and Beyond Divergence: A New Look at the Economic History of China and Europe [Book Review]
Before and Beyond Divergence is a model of collaboration and academic production: between two disciplinesâeconomics and history and between two area specialistsâan economic historian of Europe and a socioeconomic historian of China
What Explains Vietnam's Exceptional Performance in Education Relative to Other Countries? Analysis of the Young Lives Data from Ethiopia, Peru, India and Vietnam
Vietnamâs strong performance on the 2012 and 2015 PISA assessments has led to interest in what explains the strong academic performance of Vietnamese students. Analysis of the PISA data has not shed much light on this issue. This paper analyses a much richer data set, the Young Lives data for Ethiopia, India (Andhra Pradesh and Telangana), Peru and Vietnam, to investigate the reasons for the strong academic performance of 15-year-olds in Vietnam. Differences in observed child and household characteristics explain 37-39 percent of the gap between Vietnam, and Ethiopia, while observed school variables explain only about 3-4 additional percentage points (although an important variable, math teachersâ pedagogical skills, is not available for Ethiopia). Differences in observed child and household characteristics explain very little of the gaps between Vietnam and India and between Vietnam and Peru, yet one observed school variable has a large explanatory effect: primary school math teachersâ pedagogical skills. It explains about 10-12 percent of the gap between Vietnam and India, raising the overall explained portion to 14-21 percent of the gap. For Peru, it explains most (65-84 percent) of the gap
Bayesian inference on random simple graphs with power law degree distributions
We present a model for random simple graphs with power law (i.e., heavy-tailed) degree dis- tributions. To attain this behavior, the edge probabilities in the graph are constructed from BertoinâFujitaâRoynetteâYor (BFRY) random variables, which have been recently utilized in Bayesian statistics for the construction of power law models in several applications. Our construction readily extends to capture the structure of latent factors, similarly to stochastic block- models, while maintaining its power law degree distribution. The BFRY random variables are well approximated by gamma random variables in a variational Bayesian inference routine, which we apply to several network datasets for which power law degree distributions are a natural assumption. By learning the parameters of the BFRY distribution via probabilistic inference, we are able to automatically select the appropriate power law behavior from the data. In order to further scale our inference procedure, we adopt stochastic gradient ascent routines where the gradients are computed on minibatches (i.e., sub- sets) of the edges in the graph.J. Lee and S. Choi were partly supported by an Institute for Information & Communications Technology Promotion (IITP) grant, funded by the Korean government (MSIP) (No.2014- 0-00147, Basic Software Research in Human-level Life- long Machine Learning (Machine Learning Center)) and Naver, Inc. C. Heaukulani undertook this work in part while a visiting researcher at the Hong Kong University of Science and Technology, who along with L. F. James was funded by grant rgc-hkust 601712 of the Hong Kong Special Administrative Region.
EPSRC Grant EP/N014162/1
ATI Grant EP/N510129/
A method for evaluating the murine pulmonary vasculature using micro-computed tomography
AbstractBackgroundSignificant mortality and morbidity are associated with alterations in the pulmonary vasculature. While techniques have been described for quantitative morphometry of whole-lung arterial trees in larger animals, no methods have been described in mice. We report a method for the quantitative assessment of murine pulmonary arterial vasculature using high-resolution computed tomography scanning.MethodsMice were harvested at 2 weeks, 4 weeks, and 3 months of age. The pulmonary artery vascular tree was pressure perfused to maximal dilation with a radio-opaque casting material with viscosity and pressure set to prevent capillary transit and venous filling. The lungs were fixed and scanned on a specimen computed tomography scanner at 8-ÎŒm resolution, and the vessels were segmented. Vessels were grouped into categories based on lumen diameter and branch generation.ResultsRobust high-resolution segmentation was achieved, permitting detailed quantitation of pulmonary vascular morphometrics. As expected, postnatal lung development was associated with progressive increase in small-vessel number and arterial branching complexity.ConclusionsThese methods for quantitative analysis of the pulmonary vasculature in postnatal and adult mice provide a useful tool for the evaluation of mouse models of disease that affect the pulmonary vasculature
Small-sized dichroic atomic vapor laser lock
Two, lightweight diode laser frequency stabilization systems designed for
experiments in the field are described. A significant reduction in size and
weight in both models supports the further miniaturization of measurement
devices in the field. Similar to a previous design, magnetic-field lines are
contained within a magnetic shield enclosing permanent magnets and a Rb cell,
so that these DAVLL systems may be used for magnetically sensitive instruments.
The Mini-DAVLL system (49 mm long) uses a vapor cell (20 mm long), and does not
require cell heaters. An even smaller Micro-DAVLL system (9mm long) uses a
micro-fabricated cell (3 mm square), and requires heaters. These new systems
show no degradation in performance with regard to previous designs, while
considerably reducing dimensions.Comment: 13 pages, 11 figures, published versio
Measuring health-related quality of life outcomes in bladder cancer patients using the Bladder Cancer Index (BCI)
BACKGROUND. Health-related quality of life (HRQOL) has not been adequately measured in bladder cancer. A recently developed reliable and disease-specific quality of life instrument (Bladder Cancer Index, BCI) was used to measure urinary, sexual, and bowel function and bother domains in patients with bladder cancer managed with several different interventions, including cystectomy and endoscopic-based procedures. METHODS. Patients with bladder cancer were identified from a prospective bladder cancer outcomes database and contacted as part of an Institutional Review Board-approved study to assess treatment impact on HRQOL. HRQOL was measured using the BCI across stratified treatment groups. Bivariate and multivariable analyses adjusted for age, gender, income, education, relationship status, and follow-up time were performed to compare urinary, bowel, and sexual domains between treatment groups. RESULTS. In all, 315 bladder cancer patients treated at the University of Michigan completed the BCI in 2004. Significant differences were seen in mean BCI function and bother scores between cystectomy and native bladder treatment groups. In addition, urinary function scores were significantly lower among cystectomy patients treated with continent neobladder compared with those treated with ileal conduit (all pairwise P < .05). CONCLUSIONS. The BCI is responsive to functional and bother differences in patients with bladder cancer treated with different surgical approaches. Significant differences between therapy groups in each of the urinary, bowel, and sexual domains exist. Among patients treated with orthotopic continent urinary diversion, functional impairments related to urinary incontinence and lack of urinary control account for the low observed urinary function scores. Cancer 2007. © 2007 American Cancer Society.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55989/1/22556_ftp.pd
Pion Breather States in QCD
We describe a class of pionic breather solutions (PBS) which appear in the
chiral lagrangian description of low-energy QCD. These configurations are
long-lived, with lifetimes greater than fm/c, and could arise as
remnants of disoriented chiral condensate (DCC) formation at RHIC. We show that
the chiral lagrangian equations of motion for a uniformly isospin-polarized
domain reduce to those of the sine-gordon model. Consequently, our solutions
are directly related to the breather solutions of sine-gordon theory in 3+1
dimensions. We investigate the possibility of PBS formation from multiple
domains of DCC, and show that the probability of formation is non-negligible.Comment: 9 pages, 4 figure
Can codimension-two branes solve the cosmological constant problem?
It has been suggested that codimension-two braneworlds might naturally
explain the vanishing of the 4D effective cosmological constant, due to the
automatic relation between the deficit angle and the brane tension. To
investigate whether this cancellation happens dynamically, and within the
context of a realistic cosmology, we study a codimension-two braneworld with
spherical extra dimensions compactified by magnetic flux. Assuming Einstein
gravity, we show that when the brane contains matter with an arbitrary equation
of state, the 4D metric components are not regular at the brane, unless the
brane has nonzero thickness. We construct explicit 6D solutions with thick
branes, treating the brane matter as a perturbation, and find that the universe
expands consistently with standard Friedmann-Robertson-Walker (FRW) cosmology.
The relation between the brane tension and the bulk deficit angle becomes
for a general equation of state. However, this
relation does not imply a self-tuning of the effective 4D cosmological constant
to zero; perturbations of the brane tension in a static solution lead to
deSitter or anti-deSitter braneworlds. Our results thus confirm other recent
work showing that codimension-two braneworlds in nonsupersymmetric Einstein
gravity do not lead to a dynamical relaxation of the cosmological constant, but
they leave open the possibility that supersymmetric versions can be compatible
with self-tuning.Comment: Revtex4, 17 pages, references added, typos corrected, minor points
clarified. Matches published versio
Don't bleach chaotic data
A common first step in time series signal analysis involves digitally
filtering the data to remove linear correlations. The residual data is
spectrally white (it is ``bleached''), but in principle retains the nonlinear
structure of the original time series. It is well known that simple linear
autocorrelation can give rise to spurious results in algorithms for estimating
nonlinear invariants, such as fractal dimension and Lyapunov exponents. In
theory, bleached data avoids these pitfalls. But in practice, bleaching
obscures the underlying deterministic structure of a low-dimensional chaotic
process. This appears to be a property of the chaos itself, since nonchaotic
data are not similarly affected. The adverse effects of bleaching are
demonstrated in a series of numerical experiments on known chaotic data. Some
theoretical aspects are also discussed.Comment: 12 dense pages (82K) of ordinary LaTeX; uses macro psfig.tex for
inclusion of figures in text; figures are uufile'd into a single file of size
306K; the final dvips'd postscript file is about 1.3mb Replaced 9/30/93 to
incorporate final changes in the proofs and to make the LaTeX more portable;
the paper will appear in CHAOS 4 (Dec, 1993
Two-dimensional Dirac fermions in a topological insulator: transport in the quantum limit
Pulsed magnetic fields of up to 55T are used to investigate the transport
properties of the topological insulator Bi_2Se_3 in the extreme quantum limit.
For samples with a bulk carrier density of n = 2.9\times10^16cm^-3, the lowest
Landau level of the bulk 3D Fermi surface is reached by a field of 4T. For
fields well beyond this limit, Shubnikov-de Haas oscillations arising from
quantization of the 2D surface state are observed, with the \nu =1 Landau level
attained by a field of 35T. These measurements reveal the presence of
additional oscillations which occur at fields corresponding to simple rational
fractions of the integer Landau indices.Comment: 5 pages, 4 figure
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