| 1. |
- Arking, D. E., et al.
(author)
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Genetic association study of QT interval highlights role for calcium signaling pathways in myocardial repolarization
- 2014
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In: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 46:8, s. 826-836
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Journal article (peer-reviewed)abstract
- The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal mendelian long-QT syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals, we identified 35 common variant loci associated with QT interval that collectively explain ∼ 8-10% of QT-interval variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 new QT interval-associated loci in 298 unrelated probands with LQTS identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies new candidate genes for ventricular arrhythmias, LQTS and SCD. © 2014 Nature America, Inc.
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| 2. |
- De Medeiros, J. R., et al.
(author)
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Overview of semi-sinusoidal stellar variability with the CoRoT satellite
- 2013
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 555, s. A63-
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Journal article (peer-reviewed)abstract
- Context. To date, the CoRoT space mission has produced more than 124 471 light curves. Classifying these curves in terms of unambiguous variability behavior is mandatory for obtaining an unbiased statistical view on their controlling root-causes. Aims. The present study provides an overview of semi-sinusoidal light curves observed by the CoRoT exo-field CCDs. Methods. We selected a sample of 4206 light curves presenting well-defined semi-sinusoidal signatures. The variability periods were computed based on Lomb-Scargle periodograms, harmonic fits, and visual inspection. Results. Color-period diagrams for the present sample show the trend of an increase of the variability periods as long as the stars evolve. This evolutionary behavior is also noticed when comparing the period distribution in the Galactic center and anti-center directions. These aspects indicate a compatibility with stellar rotation, although more information is needed to confirm their root-causes. Considering this possibility, we identified a subset of three Sun-like candidates by their photometric period. Finally, the variability period versus color diagram behavior was found to be highly dependent on the reddening correction.
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| 3. |
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| 4. |
- Mota, F. de B., et al.
(author)
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Hybrid platforms of graphane-graphene 2D structures: prototypes for atomically precise nanoelectronics
- 2014
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 16:43, s. 23558-23563
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Journal article (peer-reviewed)abstract
- First-principles calculations demonstrate that line/ribbon defects, resulting from a controlled dehydrogenation in graphane, lead to the formation of low-dimensional electron-rich tracks in a monolayer. The present simulations point out that hybrid graphane-graphene nanostructures exhibit important elements, greatly required for the fabrication of efficient electronic circuits at the atomic level.
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| 5. |
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| 6. |
- Madureira, H. M. G., et al.
(author)
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System-level power consumption modeling of a SoC for WSN applications
- 2011
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In: Proceedings - 2011 IEEE 2nd International Conference on Networked Embedded Systems for Enterprise Applications.
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Conference paper (peer-reviewed)abstract
- Energy consumption is a critical issue for wireless sensor networks (WSN) because of the limited energy supply on the nodes. Therefore, performance evaluation is very important, especially at early stages of the design flow. In this work, we present the modeling and simulation of nodes composed by a typical system on chip (SoC) for WSN applications using SystemC/TLM. The SoC contains a MIPS-based processor, a memory, a bus, a timer, a transceiver and a battery. The model is intended to allow power estimation in WSN simulation. The battery module estimates the energy consumption of the node by computing the amount of electrical charge used by each block As a case study, we performed a star topology WSN simulation, showed the power consumption of each node, and presented a discussion about the computational load. This approach is flexible and can be adapted to simulate more complex systems and topologies.
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| 7. |
- Medeiros, Paulo V. C., et al.
(author)
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Benzene, coronene, and circumcoronene adsorbed on gold, and a gold cluster adsorbed on graphene: Structural and electronic properties
- 2012
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In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 85:20, s. 205423-
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Journal article (peer-reviewed)abstract
- Density functional theory (DFT) calculations were performed in order to investigate the stability and the electronic structure of graphene-gold interfaces. Two configurations were studied: a gold cluster interacting with graphene and different polycyclic aromatic hydrocarbon (PAH) molecules, namely, C6H6 (benzene), C24H12 (coronene), and C54H18 (circumcoronene) adsorbed on an Au(111) surface. Nonlocal interactions were accounted for by using the semiempirical DFT-D2 method of Grimme. A limited set of calculations were also performed by using the first-principles van der Waals density functional method (vdW-DF). Adsorption distances around 3 angstrom and electronic charge transfer values of about (3-13) x 10(-3)e(-) per carbon atom were predicted for all systems. No major changes resulting from the adsorption of the gold cluster were detected in the graphenes density of states. The DFT-D2 results involving the adsorption of the PAH molecules on gold show an estimated binding energy of 73 meV per carbon atom, as well as an electronic charge loss of 0.10 x 10(-2) e(-), also per carbon atom, for an extended graphene sheet adsorbed on a gold surface. The modeling of the adsorption of C6H6 molecule on a gold surface suggests that the vdW-DF method provides more accurate results for the binding energies of such systems, in comparison to pure DFT calculations, which do not take the nonlocal interactions into account, as well as to simulations employing the DFT-D2 method.
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| 8. |
- Medeiros, Paulo V. C., et al.
(author)
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Effects of extrinsic and intrinsic perturbations on the electronic structure of graphene : Retaining an effective primitive cell band structure by band unfolding
- 2014
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In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 89:4, s. 041407-1-041407-4
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Journal article (peer-reviewed)abstract
- We use a band unfolding technique to recover an effective primitive cell picture of the band structure of graphene under the influence of different types of perturbations. This involves intrinsic perturbations, such as structural defects, and external ones, comprising nitrogen substitutions and the inclusion of graphene in adsorbed systems. In such cases, the band unfolding provides a reliable and efficient tool for quantitatively analyzing the effect of doping and defects on the electronic structure of graphene. We envision that this approach will become a standard method in the computational analysis of graphene's electronic structure in related systems.
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| 9. |
- Oliveira, Micael J. T., et al.
(author)
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Optical and Magnetic Excitations of Metal-Encapsulating Si Cages : A Systematic Study by Time-Dependent Density Functional Theory
- 2014
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:21, s. 11377-11384
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Journal article (peer-reviewed)abstract
- A systematic study of the optical and magnetic excitations of 12 MSi12 and four MSi10 transition metal encapsulating Si cages has been carried out by employing real time time-dependent density functional theory. Criteria for the choice of transition metals (M) are clusters stability, synthesizability, and diversity. It was found that both the optical absorption and the spin-susceptibility spectra are mainly determined by, in decreasing order of importance, (1) the cage shape, (2) the group in the Periodic Table to which M belongs, and (3) the period of M in the Periodic Table. Cages with similar structures and metal species that are close to each other in the Periodic Table possess spectra sharing many similarities; for example, the optical absorption spectra of the MSi12 (M = V, Nb, Ta, Cr, Mo, and W), which are highly symmetric and belong to groups 4 and 5 of the Periodic Table, all share a very distinctive peak at around 4 eV. In all cases, although some of the observed transitions are located at the Si skeleton of the cages, the transition metal species is always significant for the optical absorption and the spin-susceptibility spectra. Our results provide fingerprint data for identification of gas-phase MSi12 and MSi10 by optical absorption spectroscopy.
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| 10. |
- Preve, Daniel, et al.
(author)
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Linear programming-based estimators in simple linear regression
- 2011
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In: Journal of Econometrics. - : Elsevier BV. - 0304-4076 .- 1872-6895. ; 165:1, s. 128-136
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Journal article (peer-reviewed)abstract
- In this paper we introduce a linear programming estimator (LPE) for the slope parameter in a constrained linear regression model with a single regressor. The LPE is interesting because it can be superconsistent in the presence of an endogenous regressor and, hence, preferable to the ordinary least squares estimator (LSE). Two different cases are considered as we investigate the statistical properties of the LPE. In the first case, the regressor is assumed to be fixed in repeated samples. In the second, the regressor is stochastic and potentially endogenous. For both cases the strong consistency and exact finite-sample distribution of the LPE is established. Conditions under which the LPE is consistent in the presence of serially correlated, heteroskedastic errors are also given. Finally, we describe how the LPE can be extended to the case with multiple regressors and conjecture that the extended estimator is consistent under conditions analogous to the ones given herein. Finite-sample properties of the LPE and extended LPE in comparison to the LSE and instrumental variable estimator (IVE) are investigated in a simulation study. One advantage of the LPE is that it does not require an instrument.
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