864 research outputs found

    Aerosol radiative forcing from the 2010 Eyjafjallajökull volcanic eruptions

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    The data set from this article is available through Deep Blue Data: https://doi.org/10.7302/pz7e-r328Although the 2010 volcanic eruptions of Eyjafjallajökull did not exert a large climate forcing, several features of their emissions favored weaker aerosol cooling or stronger warming than commonly attributed to volcanic events. These features include a high ratio of fine ash to SO2, occurrence near reflective surfaces exposed to strong insolation, and the production of very little stratospheric sulfate. We derive plausible ranges of optical properties and top-of-atmosphere direct radiative forcing for aerosol emissions from these events and find that shortwave cooling from sulfate was largely offset by warming from ash deposition to cryospheric surfaces and longwave warming from atmospheric ash and sulfate. Shortwave forcing from atmospheric ash was slightly negative in the global mean under central estimates of optical properties, though this forcing term was uniquely sensitive to the simulated distribution of clouds. The forcing components sum to near climate-neutral global mean 2010 instantaneous (−1.9mW m−2) and effective (−0.5mW m−2) radiative forcing, where the latter is elevated by high efficacy of snow-deposited ash. Ranges in net instantaneous (−7.3 to +2.8mW m−2) and effective (−7.2 to +4.9mW m−2) forcing derived from sensitivity studies are dominated by uncertainty in ash shortwave absorptivity. Forcing from airborne ash decayed quickly, while sulfate forcing persisted for several weeks and ash deposits continued to darken snow and sea ice surfaces for months following the eruption. Despite small global forcing, monthly averaged net forcing exceeded 1 W m−2in some regions. These findings indicate that ash can be an important component of climate forcing from high-latitude volcanic eruptions and in some circumstances may exceed sulfate forcing.National Science Foundation (NSF)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/162596/1/Flanner_AerosolRadiativeForcing_JGRa_2014.pdfDescription of Flanner_AerosolRadiativeForcing_JGRa_2014.pdf : ArticleSEL

    Limitation of finite element analysis of poroelastic behavior of biological tissues undergoing rapid loading

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    The finite element method is used in biomechanics to provide numerical solutions to simulations of structures having complex geometry and spatially differing material properties. Time-varying load deformation behaviors can result from solid viscoelasticity as well as viscous fluid flow through porous materials. Finite element poroelastic analysis of rapidly loaded slow-draining materials may be ill-conditioned, but this problem is not widely known in the biomechanics field. It appears as instabilities in the calculation of interstitial fluid pressures, especially near boundaries and between different materials. Accurate solutions can require impractical compromises between mesh size and time steps. This article investigates the constraints imposed by this problem on tissues representative of the intervertebral disc, subjected to moderate physiological rates of deformation. Two test cylindrical structures were found to require over 10(4) linear displacement-constant pressure elements to avoid serious oscillations in calculated fluid pressure. Fewer Taylor–Hood (quadratic displacement–linear pressure elements) were required, but with complementary increases in computational costs. The Vermeer–Verruijt criterion for 1D mesh size provided guidelines for 3D mesh sizes for given time steps. Pressure instabilities may impose limitations on the use of the finite element method for simulating fluid transport behaviors of biological soft tissues at moderately rapid physiological loading rates

    Precollege nanotechnology education: A different kind of thinking

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    The introduction of nanotechnology education into K-12 education has happened so quickly that there has been little time to evaluate the approaches and knowledge goals that are most effective to teach precollege students. This review of nanotechnology education examines the instructional approaches and types of knowledge that frame nanotechnology precollege education. Methods used to teach different forms of knowledge are examined in light of the goal of creating effective and meaningful instruction. The developmental components needed to understand concepts such as surface area to volume relationships as well as the counterintuitive behavior of nanoscale materials are described. Instructional methods used in precollege nanotechnology education and the levels at which different nanoscale topics are introduced is presented and critiqued. Suggestions are made for the development of new nanotechnology educational programs that are developmental, sequenced, and meaningful

    Recognition of reptile predator scent is innate in an endangered lizard species

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    Chemical cues can alert prey to the presence of predators before the predator is within visual proximity. Recognition of a predator’s scent is therefore an important component of predator awareness. We presented predator and control scents to wild, wild-born captive, and predator-naive captive-born pygmy bluetongue lizards to determine (1) whether lizards respond to reptile chemical cues differently from controls, (2) whether captive lizards respond more strongly to a known predator than to other predatory reptiles, (3) whether captive-born lizards recognise predators innately, whether captive-born lizards have reduced predator recognition compared with wild lizards and whether time spent in captivity reduces responses to predators, and (4) whether the avoidance response to predator detection differs between naive and experienced lizards. There was no significant difference in the number of tongue flicks to predator scent among wild, wild-born and captive-born lizards, suggesting that predator detection is innate in the pygmy bluetongue lizard and time in captivity did not reduce predator recognition. The number of tongue flicks directed towards brown snake scent was significantly higher than that to the novel and water controls for all lizard origins. Lizards of all origins continued to bask in the presence of predator scents, suggesting that chemical cues alone may be insufficient to instigate an avoidance response and other cues may be required.Tara L. Daniell, Mark N. Hutchinson, Phil Ainsley and Michael G. Gardne

    Uniqueness in Discrete Tomography of Delone Sets with Long-Range Order

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    We address the problem of determining finite subsets of Delone sets ΛRd\varLambda\subset\R^d with long-range order by XX-rays in prescribed Λ\varLambda-directions, i.e., directions parallel to non-zero interpoint vectors of Λ\varLambda. Here, an XX-ray in direction uu of a finite set gives the number of points in the set on each line parallel to uu. For our main result, we introduce the notion of algebraic Delone sets ΛR2\varLambda\subset\R^2 and derive a sufficient condition for the determination of the convex subsets of these sets by XX-rays in four prescribed Λ\varLambda-directions.Comment: 15 pages, 2 figures; condensed and revised versio

    SAperI: Approaching Gender Gap Using Spatial Ability Training Week in High-School Context

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    The purpose of this paper is to describe the structure of a girls summer school, “SAperI – Spatial Ability per l’Ingegneria” (in English, “Knowledge – Spatial Ability for Engineering”), and to illustrate its impact on spatial ability development and future career preferences on those who participated in the week long summer school compared to a control group that did not participate.The 5 days school,organized by Politecnico di Torino (Italy), was included in a larger project addressing 17 years old high-school students. Thirtyseven girls actively took part in a summer school, while 167 students (both males and females) were tested as a controlled group.For those who attended the summer school, significant gains were observed in four measures of spatial ability - mental rotation, spatialvisualization, mental cutting and paper folding. For a minority of participants, scores on one of these tests, paper folding, were lower when measured at the end of the summer school but this was an exception. Furthermore, when tested several months after the summer school, the gains in spatial ability that were made during the course were maintained indicating stability over time with regard to the improvement in spatial ability.In terms of the experience of taking the course, the feedback provided was very positive and all but one participant would recommend the summer school to othergirls at this stage of high school

    The role of proteomics in defining the human embryonic secretome

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    Non-invasive gamete and embryo assessment is considered an important focus in assisted reproductive technologies (ART). Currently, the selection of embryos for transfer is based on morphological indices. Though successful, the field of ART would benefit from a non-invasive quantitative method of viability determination. Omics technologies, including transcriptomics, proteomics and metabolomics, have already begun providing evidence that viable gametes and embryos possess unique molecular profiles with potential biomarkers that can be utilized for developmental and/or viability selection. Unlike the human genome that is relatively fixed and steady throughout the human body, the human proteome, estimated at over a million proteins, is more complex, diverse and dynamic. It is the proteins themselves that contribute to the physiological homeostasis in any cell or tissue. Of particular interest in ART is the secretome, those proteins that are produced within the embryo and secreted into the surrounding environment. Defining the human embryonic secretome has the potential to expand our knowledge of embryonic cellular processes, including the complex dialogue between the developing embryo and its maternal environment, and may also assist in identifying those embryos with the highest implantation potential. Advances in proteomic technologies have allowed the non-invasive profiling of the human embryonic secretome with ongoing research focused on correlation with outcome. From a clinical perspective, embryo selection based on morphological assessment and non-invasive analysis of the human embryonic secretome may improve IVF success and lead to routine single embryo transfers

    Unsupervised system to classify SO2 pollutant concentrations in Salamanca, Mexico

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    Salamanca is cataloged as one of the most polluted cities in Mexico. In order to observe the behavior and clarify the influence of wind parameters on the Sulphur Dioxide (SO2) concentrations a Self-Organizing Maps (SOM) Neural Network have been implemented at three monitoring locations for the period from January 1 to December 31, 2006. The maximum and minimum daily values of SO2 concentrations measured during the year of 2006 were correlated with the wind parameters of the same period. The main advantages of the SOM Neural Network is that it allows to integrate data from different sensors and provide readily interpretation results. Especially, it is powerful mapping and classification tool, which others information in an easier way and facilitates the task of establishing an order of priority between the distinguished groups of concentrations depending on their need for further research or remediation actions in subsequent management steps. For each monitoring location, SOM classifications were evaluated with respect to pollution levels established by Health Authorities. The classification system can help to establish a better air quality monitoring methodology that is essential for assessing the effectiveness of imposed pollution controls, strategies, and facilitate the pollutants reduction

    The role and importance of gene polymorphisms in the development of atherosclerosis

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    The development of atherosclerosis is a multifactorial process. The purpose of the study was to examine three genetic polymorphisms playing a role in the metabolic processes underlying the disease. We compared the data of 348 atherosclerotic non-diabetic patients with 260 atherosclerotic diabetic patients and 384 healthy controls. We analyzed the prevalence of myocardial infarction and stroke in three different groups of patients carrying different polymorphisms. It was proved that if the mutant TT eNOS Glu298ASP variant is present, a significantly higher number of myocardial infarctions can be observed than in patients carrying heterozygote GT or normal GG genotype. We proved that in the case of MTHFR 677CT heterozygote variants, the occurrence of myocardial infarction is significantly higher and the difference is also significant in case of the 677TT homozygote variant. It was verified that among patients with the mutant TNF-α AA genotype the occurrence of cardiovascular events was significantly higher. Screening the genetically high risk groups on the long run should be considered as an early detection opportunity that may give better chances for prevention and treatment. Understanding the inflammatory mechanisms of the atherosclerosis may give new therapeutical targets to pharmacologists

    An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics

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    For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
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