3,597 research outputs found
Correlations between hidden units in multilayer neural networks and replica symmetry breaking
We consider feed-forward neural networks with one hidden layer, tree
architecture and a fixed hidden-to-output Boolean function. Focusing on the
saturation limit of the storage problem the influence of replica symmetry
breaking on the distribution of local fields at the hidden units is
investigated. These field distributions determine the probability for finding a
specific activation pattern of the hidden units as well as the corresponding
correlation coefficients and therefore quantify the division of labor among the
hidden units. We find that although modifying the storage capacity and the
distribution of local fields markedly replica symmetry breaking has only a
minor effect on the correlation coefficients. Detailed numerical results are
provided for the PARITY, COMMITTEE and AND machines with K=3 hidden units and
nonoverlapping receptive fields.Comment: 9 pages, 3 figures, RevTex, accepted for publication in Phys. Rev.
Parisi Phase in a Neuron
Pattern storage by a single neuron is revisited. Generalizing Parisi's
framework for spin glasses we obtain a variational free energy functional for
the neuron. The solution is demonstrated at high temperature and large relative
number of examples, where several phases are identified by thermodynamical
stability analysis, two of them exhibiting spontaneous full replica symmetry
breaking. We give analytically the curved segments of the order parameter
function and in representative cases compute the free energy, the storage
error, and the entropy.Comment: 4 pages in prl twocolumn format + 3 Postscript figures. Submitted to
Physical Review Letter
The 'causes' of teenage pregnancy: review of South African research - Part 2
This article forms the second of a two-part series in which South African research on teenage pregnancy is reviewed. Part 1 of the series dealt with the consequences of teenage pregnancy; this paper reviews the 'causes' thereof. International literature is incorporated in the discussion by way of comparison. Contributory factors which have been investigated by South African researchers include: reproductive ignorance; the earlier occurrence of menarche; risktaking behaviour; psychological problems; peer influence; co-ercive sexual relations; dysfunctional family patterns; poor health services; socio-economic status; the breakdown of cultural traditions; and the cultural value placed on children. Preston-Whyte and colleagues present a revisionist argument, stating that early pregnancy may represent a rational life choice for certain adolescent women. The article is concluded with comments on methodological problems encountered in the South African research, and a discussion on the implications in terms of policy formulation
Hypophosphatasia
Hypophosphatasia is a rare inherited disorder characterized by defective bone and teeth mineralization, and deficiency of serum and bone alkaline phosphatase activity. The prevalence of severe forms of the disease has been estimated at 1/100 000
Baryon charge from embedding topology and a continuous meson spectrum in a new holographic gauge theory
We study a new holographic gauge theory based on probe D4-branes in the
background dual to D4-branes on a circle with antiperiodic boundary conditions
for fermions. Field theory configurations with baryons correspond to smooth
embeddings of the probe D4-branes with nontrivial winding around an S^4 in the
geometry. As a consequence, physics of baryons and nuclei can be studied
reliably in this model using the abelian Born-Infeld action. However,
surprisingly, we find that the meson spectrum is not discrete. This is related
to a curious result that the action governing small fluctuations of the gauge
field on the probe brane is the five-dimensional Maxwell action in Minkowski
space despite the non-trivial embedding of the probe brane in the curved
background geometry.Comment: 24 pages, LaTeX, 10 figures, v4: previously ignored effects of
coupling to RR-fields included, meson spectrum qualitatively changed, v5:
journal versio
Conceptual design study for heat exhaust management in the ARC fusion pilot plant
The ARC pilot plant conceptual design study has been extended beyond its
initial scope [B. N. Sorbom et al., FED 100 (2015) 378] to explore options for
managing ~525 MW of fusion power generated in a compact, high field (B_0 = 9.2
T) tokamak that is approximately the size of JET (R_0 = 3.3 m). Taking
advantage of ARC's novel design - demountable high temperature superconductor
toroidal field (TF) magnets, poloidal magnetic field coils located inside the
TF, and vacuum vessel (VV) immersed in molten salt FLiBe blanket - this
follow-on study has identified innovative and potentially robust power exhaust
management solutions.Comment: Accepted by Fusion Engineering and Desig
The interaction of lean and building information modeling in construction
Lean construction and Building Information Modeling are quite different initiatives, but both are having profound impacts on the construction industry. A rigorous analysis of the myriad specific interactions between them indicates that a synergy exists which, if properly understood in theoretical terms, can be exploited to improve construction processes beyond the degree to which it might be improved by application of either of these paradigms independently. Using a matrix that juxtaposes BIM functionalities with prescriptive lean construction principles, fifty-six interactions have been identified, all but four of which represent constructive interaction. Although evidence for the majority of these has been found, the matrix is not considered complete, but rather a framework for research to
explore the degree of validity of the interactions. Construction executives, managers, designers and developers of IT systems for construction can also benefit from the framework as an aid to recognizing the potential synergies when planning their lean and BIM adoption strategies
Regulation of neutrophil senescence by microRNAs
Neutrophils are rapidly recruited to sites of tissue injury or infection, where they protect against invading pathogens. Neutrophil functions are limited by a process of neutrophil senescence, which renders the cells unable to respond to chemoattractants, carry out respiratory burst, or degranulate. In parallel, aged neutrophils also undergo spontaneous apoptosis, which can be delayed by factors such as GMCSF. This is then followed by their subsequent removal by phagocytic cells such as macrophages, thereby preventing unwanted inflammation and tissue damage. Neutrophils translate mRNA to make new proteins that are important in maintaining functional longevity. We therefore hypothesised that neutrophil functions and lifespan might be regulated by microRNAs expressed within human neutrophils. Total RNA from highly purified neutrophils was prepared and subjected to microarray analysis using the Agilent human miRNA microarray V3. We found human neutrophils expressed a selected repertoire of 148 microRNAs and that 6 of these were significantly upregulated after a period of 4 hours in culture, at a time when the contribution of apoptosis is negligible. A list of predicted targets for these 6 microRNAs was generated from http://mirecords.biolead.org and compared to mRNA species downregulated over time, revealing 83 genes targeted by at least 2 out of the 6 regulated microRNAs. Pathway analysis of genes containing binding sites for these microRNAs identified the following pathways: chemokine and cytokine signalling, Ras pathway, and regulation of the actin cytoskeleton. Our data suggest that microRNAs may play a role in the regulation of neutrophil senescence and further suggest that manipulation of microRNAs might represent an area of future therapeutic interest for the treatment of inflammatory disease
Comparison of bar strengths in optical and near-infrared for the OSUBSGS sample
We use a gravitational bar torque method to compare bar strengths (the
maximum tangential force normalized by radial force) in B and H-band images of
152 galaxies from the Ohio State University Bright Spiral Galaxy Survey. Our
main motivation is to check how much the difference in the rest-frame
wavelength could affect comparisons of bar strengths in low and high redshift
observations. Between these two bands we find an average bar strength ratio
Q_B/H= 1.25 which factor is nearly independent of the morphological type. We
show that Q_B/H > 1 is mostly due to reduced bulge dilution of radial forces in
the B-band. The bar torque method needs an estimate for the vertical scale
height of the galaxy, based on the radial scale length of the disk and the
galaxy's morphological type. Since these two might not always be possible to
determine at high redshifts in a reliable manner, we also checked that similar
results are obtained with vertical scale heights estimated from the radii
corresponding to the K-band surface brightness of 20 mag/arcsec^2. Also, we
made a simple test of the usability of the bar torque method at high redshifts
by checking the effects of image degradation (nearest neighbour sampling
without any adjustment of noise levels): we found that the estimated bar
strengths varied by +/- 10% at most as long as the total extent of the bar was
at least 10 pixels. Overall, we show that the gravitational bar torque method
should provide a proficient tool for quantifying bar strengths also at high
redshifts.Comment: 15 pages, 9 figures, 1 table, accepted to MNRA
Impact of rural-to-urban migration on family and gender values in China
Drawing on data from the 2006 China General Social Survey, propensity score matching was used to investigate the impact of rural-to-urban migration on family and gender values in China at distinct stages of the migratory process. Little evidence of ideational difference is found between rural natives who intend to migrate to urban areas and those who intend to stay in rural China. However, rural-to-urban migration has significant, diverse and gendered impacts on various domains of family and gender values at distinct migratory stages. The results also cast light on the important roles played by hukou status and various forms of socioeconomic and cultural status, such as education and occupation, in mediating the impact of rural-to-urban migration on family and gender values. The ideational impact of migration is shown to be shaped by China’s distinctive institutional features
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