573 research outputs found
Gradient flows without blow-up for Lefschetz thimbles
We propose new gradient flows that define Lefschetz thimbles and do not blow
up in a finite flow time. We study analytic properties of these gradient flows,
and confirm them by numerical tests in simple examples.Comment: 31 pages, 11 figures, (v2) conclusion part is expande
Quantum annealing with antiferromagnetic fluctuations
We introduce antiferromagnetic quantum fluctuations into quantum annealing in
addition to the conventional transverse-field term. We apply this method to the
infinite-range ferromagnetic p-spin model, for which the conventional quantum
annealing has been shown to have difficulties to find the ground state
efficiently due to a first-order transition. We study the phase diagram of this
system both analytically and numerically. Using the static approximation, we
find that there exists a quantum path to reach the final ground state from the
trivial initial state that avoids first-order transitions for intermediate
values of p. We also study numerically the energy gap between the ground state
and the first excited state and find evidence for intermediate values of p that
the time complexity scales polynomially with the system size at a second-order
transition point along the quantum path that avoids first-order transitions.
These results suggest that quantum annealing would be able to solve this
problem with intermediate values of p efficiently in contrast to the case with
only simple transverse-field fluctuations.Comment: 19 pages, 11 figures; Added references; To be published in Physical
Review
Shear viscosity of a highly excited string and the black hole membrane paradigm
Black hole membrane paradigm states that a certain viscous membrane seems to
be sitting on a stretched horizon of a black hole from the viewpoint of a
distant observer. We show that the shear viscosity of the fictitious membrane
can be reproduced by a highly excited string covering the stretched horizon
except for a numerical coefficient.Comment: 22 pages, no figure, minor correction
Transport coefficients of D1-D5-P system and the membrane paradigm
I discuss a correspondence between string theory and the black hole membrane
paradigm in the context of the D1-D5-P system. By using the Kubo formula, I
calculate transport coefficients of the effective string model induced by two
kinds of minimal scalars. Then, I show that these transport coefficients
exactly agree with the corresponding membrane transport coefficients of a
five-dimensional near-extremal black hole with three charges.Comment: 11 pages, no figure; v2: minor corrections, accepted for publication
in Physical Review
Effects of Orthogonal Rotating Electric Fields on Electrospinning Process
Electrospinning is a nanotechnology process whereby an external electric
field is used to accelerate and stretch a charged polymer jet, so as to produce
fibers with nanoscale diameters. In quest of a further reduction in the cross
section of electrified jets hence of a better control on the morphology of the
resulting electrospun fibers, we explore the effects of an external rotating
electric field orthogonal to the jet direction. Through extensive particle
simulations, it is shown that by a proper tuning of the electric field
amplitude and frequency, a reduction of up to a in the aforementioned
radius can be obtained, thereby opening new perspectives in the design of
future ultra-thin electrospun fibres. Applications can be envisaged in the
fields of nanophotonic components as well as for designing new and improved
filtration materials.Comment: 22 pages, 8 figure
The ets-Related Transcription Factor GABP Directs Bidirectional Transcription
Approximately 10% of genes in the human genome are distributed such that their transcription start sites are located less than 1 kb apart on opposite strands. These divergent gene pairs have a single intergenic segment of DNA, which in some cases appears to share regulatory elements, but it is unclear whether these regions represent functional bidirectional promoters or two overlapping promoters. A recent study showed that divergent promoters are enriched for consensus binding sequences of a small group of transcription factors, including the ubiquitous ets-family transcription factor GA-binding protein (GABP). Here we show that GABP binds to more than 80% of divergent promoters in at least one cell type. Furthermore, we demonstrate that GABP binding is correlated and associated with bidirectional transcriptional activity in a luciferase transfection assay. In addition, we find that the addition of a strict consensus GABP site into a set of promoters that normally function in only one direction significantly increases activity in the opposite direction in 67% of cases. Our findings demonstrate that GABP regulates the majority of divergent promoters and suggest that bidirectional transcriptional activity is mediated through GABP binding and transactivation at both divergent and nondivergent promoters
High-performance, adiabatically nanotapered fibre-chip couplers in silicon at 2 microns wavelength
Fibre optic technology connects the world through the Internet, enables
remote sensing, and connects disparate functional optical devices. Highly
confined silicon photonics promises extreme scale and functional integration.
However, the optical modes of silicon nanowire waveguides and optical fibres
are very different, making efficient fibre-chip coupling a challenge. Vertical
grating couplers, the dominant coupling method today, have limited optical
bandwidth and are naturally out-of-plane. Here we demonstrate a new method that
is low-loss, broadband, easily manufacturable, and naturally planar. We
adiabatically couple a tapering silicon nanowire waveguide to a conic
nanotapered optical fibre, measuring transmission between 2.0 and 2.2 micron
wavelength. The silicon chip is fabricated at a commercial foundry and then
post-processed to release the tapering nanowires. We estimate an optimal
per-coupler transmission of -0.48 dB (maximum; 95% confidence interval [+0.46,
-1.68] dB) and a 1-dB bandwidth of 295 nm . With automated measurements, we
quantify the device tolerance to lateral misalignment, measuring a flat
response within +/- 0.968 micron. This design can enable low-loss modular
systems of integrated photonics irrespective of material and waveband.Comment: 6 pages, 3 figure
Antenatal care and skilled delivery service utilisation in Somali pastoral communities of Eastern Ethiopia
To assess maternal health care service utilisation and associated factors in Somali pastoral communities of eastern Ethiopia.; Community-based cross-sectional study complemented by qualitative assessments in Adadle district, Somali region, eastern Ethiopia, among 450 women in six kebeles from August to September 2016. Logistic regression was used to assess factors associated with antenatal care use and skilled delivery care use, controlling for confounders.; About 27% [95%CI 22.8-31.2%] of women used antenatal care, and 22.6% [95%CI 18.7-26.5%] received skilled delivery service. None of the respondents reported post-natal care. About 43% reported that they had no knowledge of antenatal care, and 46% did not perceive delivery at a health facility as important. Pastoral lifestyle, husband's educational status, women's attitude towards health care service and financial support from the husband were significantly associated with antenatal care utilisation. Health professionals' attitudes, perceptions of institutional delivery, antenatal care utilisation and information about exemptions from maternal health care fees were associated with skilled delivery service utilisation.; Improving community awareness of antenatal care, employing female health professionals and culturally adapted guidelines could improve skilled delivery utilisation. In a patriarchal society, involving male partners in all maternal health issues is essential to increase use of maternal health services and to decrease maternal mortality
Universality and superiority in preference for chromatic composition of art paintings
Color composition in paintings is a critical factor affecting observers' aesthetic judgments. We examined observers' preferences for the color composition of Japanese and Occidental paintings when their color gamut was rotated. In the experiment, observers were asked to select their preferred image from original and three hue-rotated images in a four-alternative forced choice paradigm. Despite observers' being unfamiliar with the presented artwork, the original paintings (0 degrees) were preferred more frequently than the hue-rotated ones. Furthermore, the original paintings' superiority was observed when the images were divided into small square pieces and their positions randomized (Scrambled condition), and when the images were composed of square pieces collected from different art paintings and composed as patchwork images (Patchwork condition). Therefore, the original paintings' superiority regarding preference was quite robust, and the specific objects in the paintings associated with a particular color played only a limited role. Rather, the original paintings' general trend in color statistics influenced hue-angle preference. Art paintings likely share common statistical regulations in color distributions, which may be the basis for the universality and superiority of the preference for original paintings.- We thank Dr. Yukinori Misaki at Kagawa National Institute of Technology, Japan and Ms. Nobuyo Okada and Ms. Kanako Maruchi at Toyohashi City Museum of Art and History, Japan for assisting in the measurement of art paintings. This work was supported by JSPS KAKENHI Grant Number JP19H01119 and 20H05956, and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020
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