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  • Articles  (29)
  • Wiley  (22)
  • American Association for the Advancement of Science (AAAS)  (6)
  • American Chemical Society (ACS)
  • MDPI Publishing
  • Physics  (20)
  • Natural Sciences in General  (15)
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  • Articles  (29)
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  • 1
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    A physically-based analytical model of flood-frequency curves (2016)
    Wiley
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    Publication Date: 2016-08-03
    Description: Predicting magnitude and frequency of floods is a key issue in hydrology, with implications in many fields ranging from river science and geomorphology to the insurance industry. In this paper, a novel physically-based approach is proposed to estimate the recurrence intervals of seasonal flow maxima. The method links the extremal distribution of streamflows to the stochastic dynamics of daily discharge, providing an analytical expression of the seasonal flood-frequency curve. The parameters involved in the formulation embody climate and landscape attributes of the contributing catchment, and can be estimated from daily rainfall and streamflow data. Only one parameter, which is linked to the antecedent wetness condition in the watershed, needs to be calibrated on the observed maxima. The performance of the method is discussed through a set of applications in four rivers featuring heterogeneous daily flow regimes. The model provides reliable estimates of seasonal maximum flows in different climatic settings and is able to capture diverse shapes of flood-frequency curves emerging in erratic and persistent flow regimes. The proposed method exploits experimental information on the full range of discharges experienced by rivers. As a consequence, model performances do not deteriorate when the magnitude of events with return times longer than the available sample size is estimated. The approach provides a framework for the prediction of floods based on short data series of rainfall and daily streamflows that may be especially valuable in data scarce regions of the world.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    CH4 concentrations over the Amazon from GOSAT consistent with in situ vertical profile data (2016)
    Wiley
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    Publication Date: 2016-08-28
    Description: The Amazon Basin contains large wetland ecosystems which are important sources of methane (CH 4 ). Space-borne observations of atmospheric CH 4 can provide constraints on emissions from these remote ecosystems, but lack of validation precludes robust estimates. We present the first validation of CH 4 columns in the Amazon from the Greenhouse gases Observing SATellite (GOSAT) using aircraft measurements of CH 4 over five sites across the Amazon Basin. These aircraft profiles, combined with stratospheric results from the TOMCAT chemical transport model, are vertically integrated allowing direct comparison to the GOSAT XCH 4 measurements (the column averaged dry air mole fraction of CH 4 ). The measurements agree within uncertainties or show no significant difference at three of the aircraft sites, with differences ranging from -1.9 ppb to 6.6 ppb, whilst at two sites GOSAT XCH 4 is shown to be slightly higher than aircraft measurements, by 8.1 ppb and 9.7 ppb. The seasonality in XCH 4 seen by the aircraft profiles is also well captured (correlation coefficients from 0.61 to 0.90). GOSAT observes elevated concentrations in the north-west corner of South America in the dry season and enhanced concentrations elsewhere in the Amazon Basin in the wet season; with the strongest seasonal differences coinciding with regions in Bolivia known to contain large wetlands. Our results are encouraging evidence that these GOSAT CH 4 columns are generally in good agreement with in situ measurements and understanding the magnitude of any remaining biases between the two will allow more confidence in the application of XCH 4 to constrain Amazonian CH 4 fluxes.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Climatic and landscape controls on effective discharge (2015)
    Wiley
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    Publication Date: 2015-10-14
    Description: The effective discharge constitutes a key concept in river science and engineering. Notwithstanding many years of studies, a full understanding of the effective discharge determinants is still challenged by the variety of values identified for different river catchments. The present paper relates the observed diversity of effective discharge to the underlying heterogeneity of flow regimes. An analytic framework is proposed, which links the effective ratio (i.e. the ratio between effective discharge and mean streamflow) to the empirical exponent of the sediment rating curve and to the streamflow variability, as resulting from climatic and landscape drivers. The analytic formulation predicts patterns of effective ratio versus streamflow variability observed in a set of catchments of the continental United States, and helps in disentangling the major climatic and landscape drivers of sediment transport in rivers. The findings highlight larger effective ratios of erratic hydrologic regimes (characterized by high flow variability) compared to those exhibited by persistent regimes, which are attributable to intrinsically different streamflow dynamics. The framework provides support for the estimate of effective discharge in rivers belonging to diverse climatic areas.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    The application of heat-deproteinization to the morphological study of cortical bone: A contribution to the knowledge of the osteonal structure (2016)
    Wiley
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    Publication Date: 2016-06-11
    Description: ABSTRACT Observation of heat-deproteinized cortical bone specimens in incident light enabled the high definition documentation of the osteonal pattern of diaphyseal Haversian bone. This prompted a study to compare these images with those revealed by polarized light microscopy, carried out either on decalcified or thin, undecalcified, resin-embedded sections. Different bone processing methods can reveal structural aspects of the intercellular matrix, depending on the light diffraction mode: birefringency in decalcified sections can be ascribed to the collagen fibrils orientation alone; in undecalcified sections, to both the ordered layout of collagen and the inorganic phase; in the heat-deproteinized samples, exclusively to the hydroxyapatite crystals aggregation mode. The elemental chemical analysis documented low content of carbon and hydrogen, no detectable levels of nitrogen and significantly higher content of calcium and phosphorus in heat-deproteinized samples, as compared with dehydrated controls. In both samples, the X-ray diffraction (XRD) pattern did not show any significant difference in pattern of hydroxyapatite, with no peaks of any possible decomposition phases. Scanning electron microscopic (SEM) morphology of heat-deproteinized samples could be documented with the fracturing technique facilitated by the bone brittleness. The structure of crystal aggregates, oriented in parallel and with marks of time periods, was documented. Comparative study of deproteinized and undecalcified samples showed that the matrix inorganic phase did not undergo a coarse grain thermal conversion until it reached 500°C, maintaining the original crystals structure and orientation. Incident light stereomicroscopy, combined with SEM analysis of deproteinized bone fractured surfaces, is a new enforceable technique which can be used in morphometric studies to improve the understanding of the osteonal dynamics. Microsc. Res. Tech., 2016 . © 2016 Wiley Periodicals, Inc.
    Print ISSN: 1059-910X
    Electronic ISSN: 1097-0029
    Topics: Natural Sciences in General
    Published by Wiley
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  • 5
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    Contribution of regional sources to atmospheric methane over the Amazon Basin in 2010 and 2011 (2016)
    Wiley
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    Publication Date: 2016-02-07
    Description: We present an assessment of methane (CH 4 ) atmospheric concentrations over the Amazon Basin for 2010 and 2011 using a 3-D atmospheric chemical transport model, two wetland emission models and new observations made during bi-weekly flights made over four locations within the Basin. We attempt to constrain Basin-wide CH 4 emissions using the observations, and, since 2010 was an unusually dry year, we assess the effect of this drought on Amazonian methane emissions. We find that South American emissions contribute up to 150 ppb to concentrations at the sites, mainly originating from within the Basin. Our atmospheric model simulations agree reasonably well with measurements at three of the locations (0.28 ≤ r 2 ≤ 0.63, mean bias ≤ 9.5 ppb). Attempts to improve the simulated background CH 4 concentration through analysis of simulated and observed sulphur hexafluoride concentrations do not improve the model performance, however. Through minimisation of seasonal biases between the simulated and observed atmospheric concentrations, we scale our prior emission inventories to derive total Basin-wide methane emissions of 36.5-41.1 Tg(CH 4 )/yr in 2010 and 31.6-38.8 Tg(CH 4 )/yr in 2011. These totals suggest that the Amazon contributes significantly (up to 7%) to global CH 4 emissions. Our analysis indicates that factors other than precipitation, such as temperature variations or tree mortality, may have affected microbial emission rates. However, given the uncertainty of our emission estimates, we cannot say definitively whether the non-combustion emissions from the region were different in 2010 and 2011, despite contrasting meteorological conditions between the two years.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Seasonality and inter-annual variability of CH4 fluxes from the eastern Amazon Basin inferred from atmospheric mole fraction profiles (2015)
    Wiley
    Details
    Publication Date: 2015-11-25
    Description: The Amazon Basin is an important region for global CH 4 emissions. It hosts the largest area of humid tropical forests, and around 20% of this area is seasonally flooded. In a warming climate it is possible that CH 4 emissions from the Amazon will increase both as a result of increased temperatures and precipitation. To examine if there are indications of first signs of such changes we present here a 13-year (2000-2013) record of regularly measured vertical CH 4 mole fraction profiles above the eastern Brazilian Amazon, sensitive to fluxes from the region upwind of Santarém (SAN), between SAN and the Atlantic coast. Using a simple mass balance approach, we find substantial CH 4 emissions with an annual average flux of 52.8±6.8 mg CH 4 m -2 day -1 over an area of approximately 1 million km 2 . Fluxes are highest in two periods of the year: in the beginning of the wet season and during the dry season. Using a CO:CH 4 emission factor estimated from the profile data, we estimated an influence of biomass burning around 15% of the total flux in dry season, indicating that biogenic emissions dominate the CH 4 flux. This 13-year record shows that CH 4 emissions upwind of SAN varied over the years, with highest emissions in 2008 (around 25% higher than in 2007), mainly during the wet season, representing 19% of the observed global increase.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Shared motor error for multiple eye movements (1997)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1997-06-13
    Description: Most natural actions are accomplished with a seamless combination of individual movements. Such coordination poses a problem: How does the motor system orchestrate multiple movements to produce a single goal-directed action? The results from current experiments suggest one possible solution. Oculomotor neurons in the superior colliculus of a primate responded to mismatches between eye and target positions, even when the animal made two different types of eye movements. This neuronal activity therefore does not appear to convey a command for a specific type of eye movement but instead encodes an error signal that could be used by multiple movements. The use of shared inputs is one possible strategy for ensuring that different movements share a common goal.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krauzlis, R J -- Basso, M A -- Wurtz, R H -- New York, N.Y. -- Science. 1997 Jun 13;276(5319):1693-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9180078" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Eye Movements/*physiology ; Fixation, Ocular/physiology ; Macaca mulatta ; Motor Neurons/*physiology ; Pursuit, Smooth/physiology ; Saccades/physiology ; Superior Colliculi/cytology/*physiology ; Visual Pathways
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Genetic and molecular basis of drug resistance and species-specific drug action in schistosome parasites (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-11-23
    Description: Oxamniquine resistance evolved in the human blood fluke (Schistosoma mansoni) in Brazil in the 1970s. We crossed parental parasites differing ~500-fold in drug response, determined drug sensitivity and marker segregation in clonally derived second-generation progeny, and identified a single quantitative trait locus (logarithm of odds = 31) on chromosome 6. A sulfotransferase was identified as the causative gene by using RNA interference knockdown and biochemical complementation assays, and we subsequently demonstrated independent origins of loss-of-function mutations in field-derived and laboratory-selected resistant parasites. These results demonstrate the utility of linkage mapping in a human helminth parasite, while crystallographic analyses of protein-drug interactions illuminate the mode of drug action and provide a framework for rational design of oxamniquine derivatives that kill both S. mansoni and S. haematobium, the two species responsible for 〉99% of schistosomiasis cases worldwide.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4136436/" 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/PMC4136436/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Valentim, Claudia L L -- Cioli, Donato -- Chevalier, Frederic D -- Cao, Xiaohang -- Taylor, Alexander B -- Holloway, Stephen P -- Pica-Mattoccia, Livia -- Guidi, Alessandra -- Basso, Annalisa -- Tsai, Isheng J -- Berriman, Matthew -- Carvalho-Queiroz, Claudia -- Almeida, Marcio -- Aguilar, Hector -- Frantz, Doug E -- Hart, P John -- LoVerde, Philip T -- Anderson, Timothy J C -- 098051/Wellcome Trust/United Kingdom -- 5R21-AI072704/AI/NIAID NIH HHS/ -- 5R21-AI096277/AI/NIAID NIH HHS/ -- C06 RR013556/RR/NCRR NIH HHS/ -- HHSN272201000005I/PHS HHS/ -- R01 AI097576/AI/NIAID NIH HHS/ -- R01-AI097576/AI/NIAID NIH HHS/ -- R21 AI072704/AI/NIAID NIH HHS/ -- R21 AI096277/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 2013 Dec 13;342(6164):1385-9. doi: 10.1126/science.1243106. Epub 2013 Nov 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Departments of Biochemistry and Pathology, University of Texas Health Science Center, San Antonio, TX 78229, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24263136" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Drug Resistance/*genetics ; Gene Knockdown Techniques ; Genetic Linkage ; Helminth Proteins/*genetics ; Humans ; Molecular Sequence Data ; Mutation ; Oxamniquine/*pharmacology ; Phylogeny ; Protein Conformation ; Quantitative Trait Loci ; RNA Interference ; Schistosoma mansoni/*drug effects/*genetics ; Schistosomicides/*pharmacology ; Sulfotransferases/chemistry/classification/*genetics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    Appetite-suppressing effects of urocortin, a CRF-related neuropeptide (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-09-13
    Description: The neuropeptide corticotropin-releasing factor (CRF) is well known to act on the central nervous system in ways that mimic stress and result in decreases in exploration, increases in sympathetic activity, decreases in parasympathetic outflow, and decreases in appetitive behavior. Urocortin, a neuropeptide related to CRF, binds with high affinity to the CRF2 receptor, is more potent than CRF in suppressing appetite, but is less potent than CRF in producing anxiety-like effects and activation. Doses as low as 10 nanograms injected intracerebroventricularly were effective in decreasing food intake in food-deprived and free-feeding rats. These results suggest that urocortin may be an endogenous CRF-like factor in the brain responsible for the effects of stress on appetite.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Spina, M -- Merlo-Pich, E -- Chan, R K -- Basso, A M -- Rivier, J -- Vale, W -- Koob, G F -- 1 F05 TW05262/TW/FIC NIH HHS/ -- DK 26741/DK/NIDDK NIH HHS/ -- New York, N.Y. -- Science. 1996 Sep 13;273(5281):1561-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neuropharmacology, Scripps Research Institute, 10666 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8703220" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Appetite/*drug effects ; Appetite Depressants/administration & dosage/metabolism/*pharmacology ; Behavior, Animal/drug effects ; Blood Pressure/drug effects ; Carrier Proteins/metabolism ; Corticotropin-Releasing Hormone/administration & dosage/metabolism/*pharmacology ; Dose-Response Relationship, Drug ; Eating/drug effects ; Fasting ; Injections, Intraventricular ; Motor Activity/drug effects ; Rats ; Rats, Wistar ; Receptors, Corticotropin-Releasing Hormone/metabolism ; Urocortins ; Urotensins/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    Effect of different implant abutment surfaces on OBA-09 epithelial cell adhesion (2017)
    Wiley
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    Publication Date: 2017-08-31
    Description: For the long-term success of implants, it is necessary to achieve a direct contact between the implant and the subjacent bone. To avoid bacterial penetration that could adversely affect the initial wound healing as well as the long-term behavior of the implants, an early tissue barrier must form that is able to protect the biological peri-implant structures. Given the need of an effective tissue early barrier around dental implants, the present study evaluated, in vitro, the influence of physical and chemical characteristics of two implant abutment surfaces on gingival epithelial cells (OBA-9) adhesion. To this end, titanium (Ti) and zirconia (ZrO 2 ) disk-shaped specimens were used mimicking the abutment components surfaces, while bovine enamel (BE) and glass cover slips (GCS) disks served as positive and negative controls, respectively. Roughness and surface free energy (SFE) of all materials were evaluated previously to cellular adhesion step. In sequence, the effect of each material on cells morphology and viability was analyzed after 1 and 24 hr. The results showed that roughness and SFE had no effect on the cell viability data or on their interaction ( p = .559), independent of a post-contact analysis of 1 or 24 hr. However, cells attachment and spreading increased after 24 hr on Ti and ZrO 2 than BE, corresponding to the highest SFE values. SFE appears to be an important property interfering on the quality of the soft tissue surrounding dental implants. These data can be considered a trigger point for developing new material surfaces. Titanium and zirconia substrates disclosed hydrophobic properties and admitted the highest surface free energy values when in comparison to enamel. Well-attached/spreading cells were observed on implant abutment materials.
    Print ISSN: 1059-910X
    Electronic ISSN: 1097-0029
    Topics: Natural Sciences in General
    Published by Wiley
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