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  • 1
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    Concerted electron-proton transfer in the optical excitation of hydrogen-bonded dyes [Chemistry] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-05-25
    Description: The simultaneous, concerted transfer of electrons and protons—electron-proton transfer (EPT)—is an important mechanism utilized in chemistry and biology to avoid high energy intermediates. There are many examples of thermally activated EPT in ground-state reactions and in excited states following photoexcitation and thermal relaxation. Here we report application of ultrafast excitation with absorption and Raman monitoring to detect a photochemically driven EPT process (photo-EPT). In this process, both electrons and protons are transferred during the absorption of a photon. Photo-EPT is induced by intramolecular charge-transfer (ICT) excitation of hydrogen-bonded-base adducts with either a coumarin dye or 4-nitro-4′-biphenylphenol. Femtosecond transient absorption spectral measurements following ICT excitation reveal the appearance of two spectroscopically distinct states having different dynamical signatures. One of these states corresponds to a conventional ICT excited state in which the transferring H+ is initially associated with the proton donor. Proton transfer to the base (B) then occurs on the picosecond time scale. The other state is an ICT-EPT photoproduct. Upon excitation it forms initially in the nuclear configuration of the ground state by application of the Franck–Condon principle. However, due to the change in electronic configuration induced by the transition, excitation is accompanied by proton transfer with the protonated base formed with a highly elongated +H─B bond. Coherent Raman spectroscopy confirms the presence of a vibrational mode corresponding to the protonated base in the optically prepared state.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 2
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    Towards Automated Memory Model Generation Via Event Tracing (2013)
    Oxford University Press
    Details
    Publication Date: 2013-02-02
    Description: The importance of memory performance and capacity is a growing concern for high performance computing laboratories around the world. It has long been recognized that improvements in processor speed exceed the rate of improvement in dynamic random access memory speed and, as a result, memory access times can be the limiting factor in high performance scientific codes. The use of multi-core processors exacerbates this problem with the rapid growth in the number of cores not being matched by similar improvements in memory capacity, increasing the likelihood of memory contention. In this paper, we present WMTools , a lightweight memory tracing tool and analysis framework for parallel codes, which is able to identify peak memory usage and also analyse per-function memory use over time. An evaluation of WMTools , in terms of its effectiveness and also its overheads, is performed using nine established scientific applications/benchmark codes representing a variety of programming languages and scientific domains. We also show how WMTools can be used to automatically generate a parameterized memory model for one of these applications, a two-dimensional non-linear magnetohydrodynamics application, Lare2D . Through the memory model we are able to identify an unexpected growth term which becomes dominant at scale. With a refined model we are able to predict memory consumption with under 7% error.
    Print ISSN: 0010-4620
    Electronic ISSN: 1460-2067
    Topics: Computer Science
    Published by Oxford University Press
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  • 3
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    Neural activity regulates neuronal addition [Neuroscience] (2013)
    National Academy of Sciences
    Details
    Publication Date: 2013-10-09
    Description: A striking feature of the nervous system is that it shows extensive plasticity of structure and function that allows animals to adjust to changes in their environment. Neural activity plays a key role in mediating experience-dependent neural plasticity and, thus, creates a link between the external environment, the nervous system,...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 4
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    Ti-in-zircon thermometry and crystallization modeling support hot Grenville granite hypothesis (2014)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2014-03-15
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 5
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    Carbon in Amazon forests: unexpected seasonal fluxes and disturbance-induced losses (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-12-04
    Description: The net ecosystem exchange of carbon dioxide was measured by eddy covariance methods for 3 years in two old-growth forest sites near Santarem, Brazil. Carbon was lost in the wet season and gained in the dry season, which was opposite to the seasonal cycles of both tree growth and model predictions. The 3-year average carbon loss was 1.3 (confidence interval: 0.0 to 2.0) megagrams of carbon per hectare per year. Biometric observations confirmed the net loss but imply that it is a transient effect of recent disturbance superimposed on long-term balance. Given that episodic disturbances are characteristic of old-growth forests, it is likely that carbon sequestration is lower than has been inferred from recent eddy covariance studies at undisturbed sites.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Saleska, Scott R -- Miller, Scott D -- Matross, Daniel M -- Goulden, Michael L -- Wofsy, Steven C -- da Rocha, Humberto R -- de Camargo, Plinio B -- Crill, Patrick -- Daube, Bruce C -- de Freitas, Helber C -- Hutyra, Lucy -- Keller, Michael -- Kirchhoff, Volker -- Menton, Mary -- Munger, J William -- Pyle, Elizabeth Hammond -- Rice, Amy H -- Silva, Hudson -- New York, N.Y. -- Science. 2003 Nov 28;302(5650):1554-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA. saleska@fas.harvard.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14645845" target="_blank"〉PubMed〈/a〉
    Keywords: Brazil ; Carbon/*analysis/metabolism ; Carbon Dioxide/*analysis/metabolism ; Confidence Intervals ; *Ecosystem ; Oxygen Consumption ; Photosynthesis ; Rain ; *Seasons ; *Trees/growth & development/metabolism ; Wood
    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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  • 6
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    Drug-based modulation of endogenous stem cells promotes functional remyelination in vivo (2015)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2015-04-22
    Description: Multiple sclerosis involves an aberrant autoimmune response and progressive failure of remyelination in the central nervous system. Prevention of neural degeneration and subsequent disability requires remyelination through the generation of new oligodendrocytes, but current treatments exclusively target the immune system. Oligodendrocyte progenitor cells are stem cells in the central nervous system and the principal source of myelinating oligodendrocytes. These cells are abundant in demyelinated regions of patients with multiple sclerosis, yet fail to differentiate, thereby representing a cellular target for pharmacological intervention. To discover therapeutic compounds for enhancing myelination from endogenous oligodendrocyte progenitor cells, we screened a library of bioactive small molecules on mouse pluripotent epiblast stem-cell-derived oligodendrocyte progenitor cells. Here we show seven drugs function at nanomolar doses selectively to enhance the generation of mature oligodendrocytes from progenitor cells in vitro. Two drugs, miconazole and clobetasol, are effective in promoting precocious myelination in organotypic cerebellar slice cultures, and in vivo in early postnatal mouse pups. Systemic delivery of each of the two drugs significantly increases the number of new oligodendrocytes and enhances remyelination in a lysolecithin-induced mouse model of focal demyelination. Administering each of the two drugs at the peak of disease in an experimental autoimmune encephalomyelitis mouse model of chronic progressive multiple sclerosis results in striking reversal of disease severity. Immune response assays show that miconazole functions directly as a remyelinating drug with no effect on the immune system, whereas clobetasol is a potent immunosuppressant as well as a remyelinating agent. Mechanistic studies show that miconazole and clobetasol function in oligodendrocyte progenitor cells through mitogen-activated protein kinase and glucocorticoid receptor signalling, respectively. Furthermore, both drugs enhance the generation of human oligodendrocytes from human oligodendrocyte progenitor cells in vitro. Collectively, our results provide a rationale for testing miconazole and clobetasol, or structurally modified derivatives, to enhance remyelination in patients.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4528969/" 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/PMC4528969/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Najm, Fadi J -- Madhavan, Mayur -- Zaremba, Anita -- Shick, Elizabeth -- Karl, Robert T -- Factor, Daniel C -- Miller, Tyler E -- Nevin, Zachary S -- Kantor, Christopher -- Sargent, Alex -- Quick, Kevin L -- Schlatzer, Daniela M -- Tang, Hong -- Papoian, Ruben -- Brimacombe, Kyle R -- Shen, Min -- Boxer, Matthew B -- Jadhav, Ajit -- Robinson, Andrew P -- Podojil, Joseph R -- Miller, Stephen D -- Miller, Robert H -- Tesar, Paul J -- F30 CA183510/CA/NCI NIH HHS/ -- F30CA183510/CA/NCI NIH HHS/ -- NS026543/NS/NINDS NIH HHS/ -- NS030800/NS/NINDS NIH HHS/ -- NS085246/NS/NINDS NIH HHS/ -- P30 CA043703/CA/NCI NIH HHS/ -- P30CA043703/CA/NCI NIH HHS/ -- R01 NS026543/NS/NINDS NIH HHS/ -- R01 NS030800/NS/NINDS NIH HHS/ -- R21 NS085246/NS/NINDS NIH HHS/ -- T32 GM007250/GM/NIGMS NIH HHS/ -- T32 GM008056/GM/NIGMS NIH HHS/ -- T32GM008056/GM/NIGMS NIH HHS/ -- UL1 TR000439/TR/NCATS NIH HHS/ -- England -- Nature. 2015 Jun 11;522(7555):216-20. doi: 10.1038/nature14335. Epub 2015 Apr 20.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA. ; Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA. ; 1] Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA [2] Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA [3] Department of Stem Cell Biology and Regenerative Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA. ; PerkinElmer, 940 Winter Street, Waltham, Massachusetts 02451, USA. ; Center for Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA. ; Drug Discovery Center, University of Cincinnati College of Medicine, Cincinnati, Ohio 45237, USA. ; National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, Maryland 20850, USA. ; Department of Microbiology-Immunology and Interdepartmental Immunobiology Center, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Avenue, Chicago, Illinois 60611, USA. ; 1] Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA [2] Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25896324" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Differentiation/drug effects ; Cerebellum/drug effects/metabolism/pathology ; Clobetasol/*pharmacology ; Demyelinating Diseases/drug therapy/metabolism/pathology ; Disease Models, Animal ; Encephalomyelitis, Autoimmune, Experimental/drug therapy/metabolism/pathology ; Female ; Germ Layers/drug effects/metabolism/pathology ; Humans ; Lysophosphatidylcholines ; MAP Kinase Signaling System ; Male ; Mice ; Miconazole/*pharmacology ; Mitogen-Activated Protein Kinases/metabolism ; Multiple Sclerosis/*drug therapy/*metabolism/pathology ; Myelin Sheath/*drug effects/*metabolism ; Oligodendroglia/cytology/drug effects/metabolism ; Phenotype ; Pluripotent Stem Cells/cytology/*drug effects/metabolism ; Receptors, Glucocorticoid/metabolism ; Regeneration/drug effects ; Tissue Culture Techniques
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 7
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    Ti-in-zircon thermometry and crystallization modeling support hot Grenville granite hypothesis (2014)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2014-02-28
    Description: Quantitative modeling of crystallization histories using the program rhyolite-MELTS indicates that zircon crystallization in 1.0 to 1.2 Ga Grenville granitoids with Zr concentrations of 300–1200 ppm begins at 930–1000 °C, and always after onset of crystallization of most other phases (pyroxenes, feldspars, quartz, apatite, ilmenite). Zircon saturation temperatures, calculated from whole-rock compositions and Zr concentrations for modeled samples, range from 835 to 997 °C. Zircon in the two samples with the highest Zr (1201 and 829 ppm) analyzed by sensitive high-resolution ion microprobe (SHRIMP) yielded Ti contents of 10–77 ppm, corresponding to Ti-in-zircon temperatures as high as 1035 °C and 915 °C, respectively. These are among the highest Ti-in-zircon temperatures recorded in magmatic rocks. The modeling and SHRIMP data support the hypothesis that high-Zr Grenville granites are hot granites, and support tectonic models that invoke high-temperature (〉900 °C) crustal conditions for generation of Grenville magmas.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 8
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    Parameterizing air-sea gas transfer velocity with dissipation (2017)
    Wiley
    Details
    Publication Date: 2017-03-18
    Description: The air-sea gas transfer velocity k is frequently estimated as an empirical function of wind speed. However, it is widely recognized that k depends on processes other than wind speed alone. The small-eddy model, which describes periodic events of small eddies disturbing the sea surface with water from below, suggests a direct relation between k and the dissipation rate of turbulent kinetic energy ε at the air-sea interface. This relation has been proven both in laboratories and in the field in various freshwater and coastal environments, but to date has not been verified in open ocean conditions. Here, concurrent North Atlantic field observations of ε and eddy covariance measurements of DMS and CO 2 air-sea gas flux are presented. Using ε measurements, we compare the small-eddy model at various depths to previously published observations. Extrapolating the measured ε profiles to the thickness of the viscous sublayer allows us to formulate a function of k that depends solely on the water side friction velocity , which can be inferred from direct eddy covariance measurements of the air side friction velocity . These field observations are generally consistent with the theoretical small-eddy model. Utilizing a variable Schmidt number exponent in the model, rather than a constant value of yields improved agreement between model and observations. This article is protected by copyright. All rights reserved.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    New methodology merging seismic, geologic, and engineering data to predict completion performance (2017)
    Society of Exploration Geophysicists (SEG)
    Details
    Publication Date: 2017-03-03
    Description: Previous work in hydraulic fracture performance identifies rock quality and completion quality as key drivers of good production; however, quantifying rock quality in a systematic method along the wellbore is a difficult task. Novel methodologies are developed for calculating rock-quality measurements along the wellbore using seismic data calibrated to geologic information encompassing petrophysical and geomechanical parameters and merging these metrics with stage-level engineering observations. Far-field wellbore seismic attributes correlate with stage completion performance and are promising predictors for improved well design. Further, these integrated attributes may contribute to the fundamental understanding of the hydraulic fracturing process and to the development of more robust and powerful computation models of overall well performance.
    Print ISSN: 1070-485X
    Electronic ISSN: 1938-3789
    Topics: Geosciences
    Published by Society of Exploration Geophysicists (SEG)
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  • 10
    Electronic Resource
    Electronic Resource
    Dynamical coupling of wind and ocean waves through wave-induced air flow (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 422 (2003), S. 55-58 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Understanding the physical mechanisms behind the generation of ocean waves by wind has been a longstanding challenge. Previous studies have assumed that ocean waves induce fluctuations in velocity and pressure of the overlying air that are synchronized with the waves, and numerical models have ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature01382
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    Paper (German National Licenses)
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