9,978 research outputs found
An Evolutionary Artificial Neural Network approach for spatio-temporal wave height time series reconstruction
This paper proposes a novel methodology for recovering missing time series data, a crucial task for
subsequent Machine Learning (ML) analyses. The methodology is specifically applied to Significant
Wave Height (SWH) time series in the field of marine engineering. The proposed approach involves two
phases. Firstly, the SWH time series for each buoy is independently reconstructed using three transfer
function models: regression-based, correlation-based, and distance-based. The distance-based transfer
function exhibits the best overall performance. Secondly, Evolutionary Artificial Neural Networks
(EANNs) are utilised for the final recovery of each time series, using as inputs highly correlated buoys
that have been intermediately recovered. The EANNs are evolved considering two metrics, the novel
squared error relevance area, which balances the importance of extreme and around-mean values, and
the well-known mean squared error. The study considers SWH time series data from 15 buoys in two
coastal zones in the United States. The results demonstrate that the distance-based transfer function
is generally the best transfer function, and that EANNs outperform a range of state-of-the-art ML
techniques in 12 out of the 15 buoys, with a number of connections comparable to linear models.
Furthermore, the proposed methodology outperforms the two most popular approaches for time
series reconstruction, BRITS and SAITS, for all buoys except one. Therefore, the proposed methodology
provides a promising approach, which may be applied to time series from other fields, such as wind
or solar energy farms in the field of green energy
Radio observations of NGC 6388: an upper limit on the mass of its central black hole
We present the results of deep radio observations with the Australia
Telescope Compact Array (ATCA) of the globular cluster NGC 6388. We show that
there is no radio source detected (with a r.m.s. noise level of 27 uJy) at the
cluster centre of gravity or at the locations of the any of the Chandra X-ray
sources in the cluster. Based on the fundamental plane of accreting black holes
which is a relationship between X-ray luminosity, radio luminosity and black
hole mass, we place an upper limit of 1500 M_sun on the mass of the putative
intermediate-mass black hole located at the centre of NGC 6388. We discuss the
uncertainties of this upper limit and the previously suggested black hole mass
of 5700 M_sun based on surface density profile analysis.Comment: 6 pages, 2 figures, accepted for publication in MNRA
Spatial and temporal clustering of dengue virus transmission in Thai villages.
BackgroundTransmission of dengue viruses (DENV), the leading cause of arboviral disease worldwide, is known to vary through time and space, likely owing to a combination of factors related to the human host, virus, mosquito vector, and environment. An improved understanding of variation in transmission patterns is fundamental to conducting surveillance and implementing disease prevention strategies. To test the hypothesis that DENV transmission is spatially and temporally focal, we compared geographic and temporal characteristics within Thai villages where DENV are and are not being actively transmitted.Methods and findingsCluster investigations were conducted within 100 m of homes where febrile index children with (positive clusters) and without (negative clusters) acute dengue lived during two seasons of peak DENV transmission. Data on human infection and mosquito infection/density were examined to precisely (1) define the spatial and temporal dimensions of DENV transmission, (2) correlate these factors with variation in DENV transmission, and (3) determine the burden of inapparent and symptomatic infections. Among 556 village children enrolled as neighbors of 12 dengue-positive and 22 dengue-negative index cases, all 27 DENV infections (4.9% of enrollees) occurred in positive clusters (p < 0.01; attributable risk [AR] = 10.4 per 100; 95% confidence interval 1-19.8 per 100]. In positive clusters, 12.4% of enrollees became infected in a 15-d period and DENV infections were aggregated centrally near homes of index cases. As only 1 of 217 pairs of serologic specimens tested in positive clusters revealed a recent DENV infection that occurred prior to cluster initiation, we attribute the observed DENV transmission subsequent to cluster investigation to recent DENV transmission activity. Of the 1,022 female adult Ae. aegypti collected, all eight (0.8%) dengue-infected mosquitoes came from houses in positive clusters; none from control clusters or schools. Distinguishing features between positive and negative clusters were greater availability of piped water in negative clusters (p < 0.01) and greater number of Ae. aegypti pupae per person in positive clusters (p = 0.04). During primarily DENV-4 transmission seasons, the ratio of inapparent to symptomatic infections was nearly 1:1 among child enrollees. Study limitations included inability to sample all children and mosquitoes within each cluster and our reliance on serologic rather than virologic evidence of interval infections in enrollees given restrictions on the frequency of blood collections in children.ConclusionsOur data reveal the remarkably focal nature of DENV transmission within a hyperendemic rural area of Thailand. These data suggest that active school-based dengue case detection prompting local spraying could contain recent virus introductions and reduce the longitudinal risk of virus spread within rural areas. Our results should prompt future cluster studies to explore how host immune and behavioral aspects may impact DENV transmission and prevention strategies. Cluster methodology could serve as a useful research tool for investigation of other temporally and spatially clustered infectious diseases
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Lessons Learned and Next Steps in Energy Efficiency Measurement and Attribution: Energy Savings, Net to Gross, Non-Energy Benefits, and Persistence of Energy Efficiency Behavior
This white paper examines four topics addressing evaluation, measurement, and attribution of direct and indirect effects to energy efficiency and behavioral programs: Estimates of program savings (gross); Net savings derivation through free ridership / net to gross analyses; Indirect non-energy benefits / impacts (e.g., comfort, convenience, emissions, jobs); and, Persistence of savings
A Long, Hard Look at the Low-Hard State in Accreting Black Holes
We present the first results of coordinated multi-wavelength observations of
the Galactic black hole GX 339-4 in a canonical low-hard state, obtained during
its 2004 outburst. XMM-Newton observed the source for 2 revolutions, or
approximately 280 ksec; RXTE monitored the source throughout this long stare.
The resulting data offer the best view yet obtained of the inner accretion flow
geometry in the low-hard state, which is thought to be analogous to the
geometry in low-luminosity active galactic nuclei. The XMM-Newton spectra
clearly reveal the presence of a cool accretion disk component, and a
relativistic Fe K emission line. The results of fits made to both components
strongly suggest that a standard thin disk remains at or near to the innermost
stable circular orbit, at least in bright phases of the low-hard state. These
findings indicate that potential links between the inner disk radius and the
onset of a steady compact jet, and the paradigm of a radially-recessed disk in
the low-hard state, do not hold universally. The results of our observations
can best be explained if a standard thin accretion disk fuels a corona which is
closely related to, or consistent with, the base of a compact jet. In a brief
examination of archival data, we show that Cygnus X-1 supports this picture of
the low/hard state. We discuss our results within the context of disk-jet
connections and prevailing models for accretion onto black holes.Comment: 13 pages, 10 figures (6 in color), ApJ, in pres
Colocation and role of polyphosphates and alkaline phosphatase in apatite biomineralization of elasmobranch tesserae
AbstractElasmobranchs (e.g. sharks and rays), like all fishes, grow continuously throughout life. Unlike other vertebrates, their skeletons are primarily cartilaginous, comprising a hyaline cartilage-like core, stiffened by a thin outer array of mineralized, abutting and interconnected tiles called tesserae. Tesserae bear active mineralization fronts at all margins and the tesseral layer is thin enough to section without decalcifying, making this a tractable but largely unexamined system for investigating controlled apatite mineralization, while also offering a potential analog for endochondral ossification. The chemical mechanism for tesserae mineralization has not been described, but has been previously attributed to spherical precursors, and alkaline phosphatase (ALP) activity. Here, we use a variety of techniques to elucidate the involvement of phosphorus-containing precursors in the formation of tesserae at their mineralization fronts. Using Raman spectroscopy, fluorescence microscopy and histological methods, we demonstrate that ALP activity is located with inorganic phosphate polymers (polyP) at the tessera–uncalcified cartilage interface, suggesting a potential mechanism for regulated mineralization: inorganic phosphate (Pi) can be cleaved from polyP by ALP, thus making Pi locally available for apatite biomineralization. The application of exogenous ALP to tissue cross-sections resulted in the disappearance of polyP and the appearance of Pi in uncalcified cartilage adjacent to mineralization fronts. We propose that elasmobranch skeletal cells control apatite biomineralization by biochemically controlling polyP and ALP production, placement and activity. Previous identification of polyP and ALP shown previously in mammalian calcifying cartilage supports the hypothesis that this mechanism may be a general regulating feature in the mineralization of vertebrate skeletons
Single-molecular real-time deep sequencing reveals the dynamics of multi-drug resistant haplotypes and structural variations in the hepatitis C virus genome
While direct-acting antivirals (DAAs) for hepatitis C virus (HCV) have dramatically progressed, patients still suffer from treatment failures. For the radical eradication of HCV, a deeper understanding of multiple resistance-associated substitutions (RASs) at the single-clone level is essential. To understand HCV quasispecies and their dynamics during DAA treatment, we applied single-molecule real-time (SMRT) deep sequencing on sera from 12 patients with genotype-1b HCV infections with DAA treatment failures, both pre- and post-treatment. We identified >3.2 kbp sequences between NS3 and NS5A genes of 187, 539 clones in total, classifying into haplotype codes based on the linkage of seven RAS loci. The number of haplotype codes during the treatment, per sample, significantly decreased from 14.67 ± 9.12 to 6.58 ± 7.1, while the number of nonsynonymous codons on the seven RAS loci, per clone, significantly increased from 1.50 ± 0.92 to 3.64 ± 0.75. In five cases, the minority multi-drug resistant haplotypes at pre-treatment were identical to the major haplotypes at relapse. Moreover, various structural variations (SVs) were detected and their dynamics analysed. These results suggest that SMRT deep sequencing is useful for detecting minority haplotypes and SVs, and to evaluate the dynamics of viral genomes at the single-clone level
Soft error rate estimation in deep sub-micron CMOS
Soft errors resulting from the impact of charged particles are emerging as a major issue in the design of reliable circuits at deep sub-micron dimensions. In this paper, we model the sensitivity of individual circuit classes to single event upsets using predictive technology models over a range of CMOS device sizes from 90 nm down to 32 nm. Modeling the relative position of particle strikes as injected current pulses of varying amplitude and fall time, we find that the critical charge for each technology is an almost linear function both of the fall time of the injected current and the supply voltage. This simple relationship will simplify the task of estimating circuit-level soft error rate (SER) and support the development of an efficient SER modeling and optimization tool that might eventually be integrated into a high level language design flow
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