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  • 2010-2014  (68)
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  • 11
    Publication Date: 2014-10-14
    Description: New experimental data on bedform initiation under unidirectional, oscillatory, and combined flows are presented to gain quantitative insight into bedform genesis from artificially-generated defects on a flat sediment-laden bed. Planform changes revealed in time-lapse photography, allowed the study of the evolution of the downstream and upstream edges of defects from their initial geometric center. Based on this temporal data set and flow velocity profiles, it was observed that combined flow bedforms share the same bedform initiation processes as unidirectional and oscillatory flows, which are reflected directly in the generation of similar geometric patterns regardless of the hydrodynamic conditions. The development of these bed defects is strongly coupled to the direction and magnitude of the shear stress applied to the bed throughout the wave cycle. Under current-dominated combined flow conditions, no defect propagation occurred in the upstream direction, despite the presence of flow reversal. In addition, spectral analysis of the evolution of the downstream and upstream edges of the defects demonstrated that: (i) periodicity in the defect growth pattern scales with the wave period for pure oscillatory flows, (ii) wave-dominated combined flows possess a period-driven peak with respect to defect growth in experiments with relatively short wave periods, but this peak is absent in experiments possessing relatively long wave periods (T 〉15 s), and (iii) current-dominated combined flows and pure unidirectional flows do not display a period-driven peak in defect growth. These results suggest that the occurrence of long-period combined flows bedforms may be under-represented in the sedimentary record.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 12
    Publication Date: 2011-08-24
    Description: Specific regulatory states, i.e., sets of expressed transcription factors, define the gene expression capabilities of cells in animal development. Here we explore the functional significance of an unprecedented example of regulatory state conservation from the cnidarian Nematostella to Drosophila, sea urchin, fish, and mammals. Our probe is a deeply conserved cis-regulatory DNA module of the SRY-box B2 (soxB2), recognizable at the sequence level across many phyla. Transphyletic cis-regulatory DNA transfer experiments reveal that the plesiomorphic control function of this module may have been to respond to a regulatory state associated with neuronal differentiation. By introducing expression constructs driven by this module from any phyletic source into the genomes of diverse developing animals, we discover that the regulatory state to which it responds is used at different levels of the neurogenic developmental process, including patterning and development of the vertebrate forebrain and neurogenesis in the Drosophila optic lobe and brain. The regulatory state recognized by the conserved DNA sequence may have been redeployed to different levels of the developmental regulatory program during evolution of complex central nervous systems.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 13
    Publication Date: 2012-11-14
    Description: From microbial biofilm communities to multicellular organisms, 3D macroscopic structures develop through poorly understood interplay between cellular processes and mechanical forces. Investigating wrinkled biofilms of Bacillus subtilis, we discovered a pattern of localized cell death that spatially focuses mechanical forces, and thereby initiates wrinkle formation. Deletion of genes implicated in...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 14
    Publication Date: 2014-06-06
    Description: B-spline surface approximation has been widely used in many applications such as CAD, medical imaging, reverse engineering, and geometric modeling. Given a data set of measures, the surface approximation aims to find a surface that optimally fits the data set. One of the main problems associated with surface approximation by B-splines is the adequate selection of the number and location of the knots, as well as the solution of the system of equations generated by tensor product spline surfaces. In this work, we use a hierarchical genetic algorithm (HGA) to tackle the B-spline surface approximation of smooth explicit data. The proposed approach is based on a novel hierarchical gene structure for the chromosomal representation, which allows us to determine the number and location of the knots for each surface dimension and the B-spline coefficients simultaneously. The method is fully based on genetic algorithms and does not require subjective parameters like smooth factor or knot locations to perform the solution. In order to validate the efficacy of the proposed approach, simulation results from several tests on smooth surfaces and comparison with a successful method have been included.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 15
    Publication Date: 2014-04-22
    Description: The development of bedforms under unidirectional, oscillatory and combined-flows results from temporal changes in sediment transport, flow and morphological response. In such flows, the bedform characteristics (for example, height, wavelength and shape) change over time, from their initiation to equilibrium with the imposed conditions, even if the flow conditions remain unchanged. These variations in bedform morphology during development are reflected in the sedimentary structures preserved in the rock record. Hence, understanding the time and morphological development in which bedforms evolve to an equilibrium stage is critical for informed reconstruction of the ancient sedimentary record. This article presents results from a laboratory flume study on bedform development and equilibrium development time conducted under purely unidirectional, purely oscillatory and combined-flow conditions, which aimed to test and extend an empirical model developed in past work solely for unidirectional ripples. The present results yield a unified model for bedform development and equilibrium under unidirectional, oscillatory and combined-flows. The experimental results show that the processes of bedform genesis and growth are common to all types of flows, and can be characterized into four stages: (i) incipient bedforms; (ii) growing bedforms; (iii) stabilizing bedforms; and (iv) fully-developed bedforms. Furthermore, the development-path of bedform growth exhibits the same general trend for different flow types (for example, unidirectional, oscillatory and combined-flows), bedform size (for example, small versus large ripples), bedform shape (for example, symmetrical or rounded), bedform planform geometry (for example, two-dimensional versus three-dimensional), flow velocities and sediment grain sizes. The equilibrium time for a wide range of bed configurations was determined and found to be inversely proportional to the sediment transport flux occurring for that flow condition. This article is protected by copyright. All rights reserved.
    Print ISSN: 0037-0746
    Electronic ISSN: 1365-3091
    Topics: Geosciences
    Published by Wiley
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  • 16
    Publication Date: 2014-11-12
    Description: The two-photon absorption (TPA) coefficient β and the nonlinear index of refraction n 2 for bulk cuprous oxide (Cu 2 O) direct gap semiconductor single crystal have been measured by using a balance-detection Z-scan single beam technique, with an excellent signal to noise ratio. Both coefficients were measured at 790 nm using a 65 fs laser pulse at a repetition rate of 90.9 MHz, generated by a Ti:Sapphire laser oscillator. The experimental values for β were explained by using a model that includes allowed-allowed, forbidden-allowed, and forbidden-forbidden transitions. It was found that the forbidden-forbidden transition is the dominant mechanism, which is consistent with the band structure of Cu 2 O. The low value for β found in bulk, as compared with respect to thin film, is explained in terms of the structural change in thin films that result in opposite parities of the conduction and valence band. The n 2 is also theoretically calculated by using the TPA dispersion curve and the Kramers-Kronig relations for nonlinear optics.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 17
    Publication Date: 2014-08-13
    Description: Author(s): V. S. Manko and H. García-Compeán The Gaussian curvature of the two-surface r=0, t=const is calculated for the Kerr–de Sitter and Kerr–Newman–de Sitter solutions, yielding nonzero analytical expressions for both cases. The results obtained on the one hand exclude the possibility for that surface to be a disk and, on the other hand, ... [Phys. Rev. D 90, 047501] Published Tue Aug 12, 2014
    Keywords: General relativity, gravitation
    Print ISSN: 0556-2821
    Electronic ISSN: 1089-4918
    Topics: Physics
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  • 18
    Publication Date: 2011-12-02
    Description: Long gamma-ray bursts (GRBs) are the most dramatic examples of massive stellar deaths, often associated with supernovae. They release ultra-relativistic jets, which produce non-thermal emission through synchrotron radiation as they interact with the surrounding medium. Here we report observations of the unusual GRB 101225A. Its gamma-ray emission was exceptionally long-lived and was followed by a bright X-ray transient with a hot thermal component and an unusual optical counterpart. During the first 10 days, the optical emission evolved as an expanding, cooling black body, after which an additional component, consistent with a faint supernova, emerged. We estimate its redshift to be z = 0.33 by fitting the spectral-energy distribution and light curve of the optical emission with a GRB-supernova template. Deep optical observations may have revealed a faint, unresolved host galaxy. Our proposed progenitor is a merger of a helium star with a neutron star that underwent a common envelope phase, expelling its hydrogen envelope. The resulting explosion created a GRB-like jet which became thermalized by interacting with the dense, previously ejected material, thus creating the observed black body, until finally the emission from the supernova dominated. An alternative explanation is a minor body falling onto a neutron star in the Galaxy.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thone, C C -- de Ugarte Postigo, A -- Fryer, C L -- Page, K L -- Gorosabel, J -- Aloy, M A -- Perley, D A -- Kouveliotou, C -- Janka, H T -- Mimica, P -- Racusin, J L -- Krimm, H -- Cummings, J -- Oates, S R -- Holland, S T -- Siegel, M H -- De Pasquale, M -- Sonbas, E -- Im, M -- Park, W-K -- Kann, D A -- Guziy, S -- Garcia, L Hernandez -- Llorente, A -- Bundy, K -- Choi, C -- Jeong, H -- Korhonen, H -- Kubanek, P -- Lim, J -- Moskvitin, A -- Munoz-Darias, T -- Pak, S -- Parrish, I -- England -- Nature. 2011 Nov 30;480(7375):72-4. doi: 10.1038/nature10611.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉IAA - CSIC, Glorieta de la Astronomia s/n, 18008 Granada, Spain. cthoene@iaa.es〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22129726" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 19
    Publication Date: 2014-01-07
    Description: Performing genetic studies in multiple human populations can identify disease risk alleles that are common in one population but rare in others, with the potential to illuminate pathophysiology, health disparities, and the population genetic origins of disease alleles. Here we analysed 9.2 million single nucleotide polymorphisms (SNPs) in each of 8,214 Mexicans and other Latin Americans: 3,848 with type 2 diabetes and 4,366 non-diabetic controls. In addition to replicating previous findings, we identified a novel locus associated with type 2 diabetes at genome-wide significance spanning the solute carriers SLC16A11 and SLC16A13 (P = 3.9 x 10(-13); odds ratio (OR) = 1.29). The association was stronger in younger, leaner people with type 2 diabetes, and replicated in independent samples (P = 1.1 x 10(-4); OR = 1.20). The risk haplotype carries four amino acid substitutions, all in SLC16A11; it is present at ~50% frequency in Native American samples and ~10% in east Asian, but is rare in European and African samples. Analysis of an archaic genome sequence indicated that the risk haplotype introgressed into modern humans via admixture with Neanderthals. The SLC16A11 messenger RNA is expressed in liver, and V5-tagged SLC16A11 protein localizes to the endoplasmic reticulum. Expression of SLC16A11 in heterologous cells alters lipid metabolism, most notably causing an increase in intracellular triacylglycerol levels. Despite type 2 diabetes having been well studied by genome-wide association studies in other populations, analysis in Mexican and Latin American individuals identified SLC16A11 as a novel candidate gene for type 2 diabetes with a possible role in triacylglycerol metabolism.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4127086/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4127086/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉SIGMA Type 2 Diabetes Consortium -- Williams, Amy L -- Jacobs, Suzanne B R -- Moreno-Macias, Hortensia -- Huerta-Chagoya, Alicia -- Churchhouse, Claire -- Marquez-Luna, Carla -- Garcia-Ortiz, Humberto -- Gomez-Vazquez, Maria Jose -- Burtt, Noel P -- Aguilar-Salinas, Carlos A -- Gonzalez-Villalpando, Clicerio -- Florez, Jose C -- Orozco, Lorena -- Haiman, Christopher A -- Tusie-Luna, Teresa -- Altshuler, David -- F32 HG005944/HG/NHGRI NIH HHS/ -- P01 HL045522/HL/NHLBI NIH HHS/ -- P30 AG038072/AG/NIA NIH HHS/ -- R01 CA144034/CA/NCI NIH HHS/ -- R01 CA55069/CA/NCI NIH HHS/ -- R01 CA80205/CA/NCI NIH HHS/ -- R01 DK042273/DK/NIDDK NIH HHS/ -- R01 DK047482/DK/NIDDK NIH HHS/ -- R01 DK057295/DK/NIDDK NIH HHS/ -- R01 HG006399/HG/NHGRI NIH HHS/ -- R01DK053889/DK/NIDDK NIH HHS/ -- R01HL24799/HL/NHLBI NIH HHS/ -- R35 CA53890/CA/NCI NIH HHS/ -- U01DK085526/DK/NIDDK NIH HHS/ -- England -- Nature. 2014 Feb 6;506(7486):97-101. doi: 10.1038/nature12828. Epub 2013 Dec 25.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24390345" target="_blank"〉PubMed〈/a〉
    Keywords: African Continental Ancestry Group/genetics ; Alleles ; Animals ; Asian Continental Ancestry Group/genetics ; Cohort Studies ; Diabetes Mellitus, Type 2/*genetics ; Endoplasmic Reticulum/genetics ; European Continental Ancestry Group/genetics ; Female ; Genetic Predisposition to Disease/*genetics ; Genome-Wide Association Study ; Haplotypes/genetics ; HeLa Cells ; Humans ; Indians, North American/genetics ; Lipid Metabolism/genetics ; Liver/cytology/metabolism ; Male ; Mexico ; Monocarboxylic Acid Transporters/*genetics ; Neanderthals/genetics ; Polymorphism, Single Nucleotide/*genetics ; RNA, Messenger/genetics/metabolism ; Triglycerides/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 20
    Publication Date: 2014-06-12
    Description: In probabilistic seismic-hazard analysis (PSHA), seismic source zone (SSZ) models are widely used to account for the contribution to the hazard from earthquakes not directly correlated with geological structures. Notwithstanding the impact of SSZ models in PSHA, the theoretical framework underlying SSZ models and the criteria used to delineate the SSZs are seldom explicitly stated and suitably documented. In this paper, we propose a methodological framework to develop and document SSZ models, which includes (1) an assessment of the appropriate scale and degree of stationarity, (2) an assessment of seismicity catalog completeness-related issues, and (3) an evaluation and credibility ranking of physical criteria used to delineate the boundaries of the SSZs. We also emphasize the need for SSZ models to be supported by a comprehensive set of metadata documenting both the unique characteristics of each SSZ and the criteria used to delineate its boundaries. This procedure ensures that the uncertainties in the model can be properly addressed in the PSHA and that the model can be easily updated whenever new data are available. The proposed methodology is illustrated using the SSZ model developed for the Azores–West Iberian region in the context of the Seismic Hazard Harmonization in Europe project (project SHARE) and some of the most relevant SSZs are discussed in detail. Online Material: Tables describing characteristics and boundaries of the seismic source zones.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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