3,741 research outputs found
On the dialog between experimentalist and modeler in catchment hydrology
The dialog between experimentalist and modeler in catchment hydrology has been minimal to date. The experimentalist often has a highly detailed yet highly qualitative understanding of dominant runoff processes—thus there is often much more information content on the catchment than we use for calibration of a model. While modelers often appreciate the need for 'hard data' for the model calibration process, there has been little thought given to how modelers might access this 'soft' or process knowledge. We present a new method where soft data (i.e., qualitative knowledge from the experimentalist that cannot be used directly as exact numbers) are made useful through fuzzy measures of model-simulation and parameter-value acceptability. We developed a three-box lumped conceptual model for the Maimai catchment in New Zealand, a particularly well-studied process-hydrological research catchment. The boxes represent the key hydrological reservoirs that are known to have distinct groundwater dynamics, isotopic composition and solute chemistry. The model was calibrated against hard data (runoff and groundwater-levels) as well as a number of criteria derived from the soft data (e.g. percent new water, reservoir volume, etc). We achieved very good fits for the three-box model when optimizing the parameter values with only runoff (Reff=0.93). However, parameter sets obtained in this way showed in general a poor goodness-of-fit for other criteria such as the simulated new-water contributions to peak runoff. Inclusion of soft-data criteria in the model calibration process resulted in lower Reff-values (around 0.84 when including all criteria) but led to better overall performance, as interpreted by the experimentalist’s view of catchment runoff dynamics. The model performance with respect to soft data (like, for instance, the new water ratio) increased significantly and parameter uncertainty was reduced by 60% on average with the introduction of the soft data multi-criteria calibration. We argue that accepting lower model efficiencies for runoff is 'worth it' if one can develop a more 'real' model of catchment behavior. The use of soft data is an approach to formalize this exchange between experimentalist and modeler and to more fully utilize the information content from experimental catchments
Thermal photon production in high-energy nuclear collisions
We use a boost-invariant one-dimensional (cylindrically symmetric) fluid
dynamics code to calculate thermal photon production in the central rapidity
region of S+Au and Pb+Pb collisions at SPS energy ( GeV/nucleon).
We assume that the hot matter is in thermal equilibrium throughout the
expansion, but consider deviations from chemical equilibrium in the high
temperature (deconfined) phase. We use equations of state with a first-order
phase transition between a massless pion gas and quark gluon plasma, with
transition temperatures in the range MeV.Comment: revised, now includes a_1 contribution. revtex, 10 pages plus 4
figures (uuencoded postscript
Correlation measurements in high-multiplicity events
Requirements for correlation measurements in high--multiplicity events are
discussed. Attention is focussed on detection of so--called hot spots,
two--particle rapidity correlations, two--particle momentum correlations (for
quantum interferometry) and higher--order correlations. The signal--to--noise
ratio may become large in the high--multiplicity limit, allowing meaningful
single--event measurements, only if the correlations are due to collective
behavior.Comment: MN 55455, 20 pages, KSUCNR-011-92 and TPI-MINN-92/47-T (revised).
Revised to correct typo in equation (30), and to fill in a few steps in
calculations. Now published as Phys. Rev. C 47 (1993) 232
PadrĂŁo de frugivoria por Tapirus terrestris na Mata Atlântica do norte do EspĂrito Santo, Brasil
A anta Tapirus terrestris (Linnaeus, 1758), Ăşltimo representante da megafauna PleistocĂŞnica na regiĂŁo Neotropical, representa um importante grupo funcional, pois se alimentam de uma grande variedade de espĂ©cies vegetais, especialmente frutos. No entanto, o padrĂŁo de frugivoria da espĂ©cie pode variar entre diferentes áreas. Dessa forma, nosso interesse foi investigar o grau de frugivoria da espĂ©cie em duas diferentes áreas no estado do EspĂrito Santo e a sua importância para a dinâmica florestal. Para isso, foram coletadas amostras fecais, atravĂ©s de busca ativa em diferentes ambientes na Reserva BiolĂłgica do CĂłrrego do Veado (Rebio CĂłrrego do Veado) e na Reserva Particular do PatrimĂ´nio Natural Recanto das Antas (RPPN Recanto das Antas), durante o perĂodo de janeiro de 2011 a novembro de 2013. ApĂłs a triagem do material biolĂłgico, as sementes foram individualizadas, classificadas quanto Ă s caracterĂsticas e grupos ecolĂłgicos e identificadas atĂ© o menor nĂvel taxonĂ´mico possĂvel. Foi obtido um esforço amostral de 130 dias, resultando em 325 amostras fecais coletadas, sendo 53,2% da Rebio CĂłrrego do Veado e 46,8% da RPPN Recanto das Antas. Do total de amostras, 41,8% estavam depositadas dentro ou prĂłximas a corpos dágua e 58,2% na serrapilheira/substrato seco. A dieta da anta foi composta por 94,1% de fibras e 5,9% de frutos. Foram encontradas duas vezes mais amostras contendo sementes na RPPN Recanto das Antas do que na Rebio CĂłrrego do Veado. Das 30 morfoespĂ©cies encontradas nas amostras, 15 foram identificadas em nĂvel especĂfico, as quais estĂŁo distribuĂdas em oito famĂlias. As famĂlias mais representativas foram Anacardiaceae, Fabaceae e Myrtaceae. As espĂ©cies mais freqĂĽentemente encontradas nas amostras foram Spondias macrocarpa Engl. e S. venulosa (Engl.) Engl. Do total de sementes encontradas 60% apresentam dispersĂŁo zoocĂłrica e 46,7% sĂŁo sementes grandes e muito grandes e 50% possuem fruto do tipo carnoso. Das morfoespĂ©cies encontradas, sete foram registradas em ambas as unidades de conservação, 21 foram encontradas apenas na RPPN Recanto das Antas e duas foram encontradas na Rebio CĂłrrego do Veado. Isso pode indicar que o ambiente na RPPN Recanto das Antas pode fornecer mais frutos que na Rebio CĂłrrego do Veado, o que pode ser um resultado do histĂłrico de perturbações da Ăşltima
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reserva. Na dĂ©cada de 1980, 80% da Rebio CĂłrrego do Veado foi queimada em um incĂŞndio e, atualmente, o entorno da reserva Ă© composto principalmente por pastagens. Ao contrário, a RPPN Recanto das Antas, apesar de sua área ter sofrido extração seletiva na dĂ©cada de 50, está inserida no maior remanescente de Mata Atlântica do EspĂrito Santo. Ainda que a anta possua uma dieta composta por uma variedade de frutos nas áreas de estudo, ela aparenta ser menos frugĂvora do que em outras áreas da Mata Atlântica. Contudo, Ă© evidente a importância de T. terrestris na dispersĂŁo de um grande nĂşmero de espĂ©cies vegetais, especialmente as espĂ©cies com sementes grandes, aumentando o recrutamento de espĂ©cies de plantas que nĂŁo sĂŁo dispersadas por outras espĂ©cies animais
EXPlainistry: Creating Documentation, Explanations, and Animated Visualizations of Chemistry Experiments Supported by Information and Communication Technology to Help School Students Understand Molecular-Level Interactions
Given that students are constantly communicating and documenting special experiences in their social and private lives with digital devices, we suggest that this behavior could be used to record and deepen learning experiences-such as visualizing reactions at the molecular level-in a chemistry class. An example would be the creation of stop-motion videos to aid the visualization process for the documentation of experiments. This approach makes use of well-established techniques for documentation and visualization (e.g., static models or pictures) and combines them with dynamic approaches (e.g., animations) in order to enhance explanations of chemical experiments. Here, we describe how we use this approach to augment the novel teaching method, EXPlainistry (experiments explained in chemistry) with 5th to 12th graders, and consider how it helps students use ICT (information and communications technology) in order to document, explain, and visualize experiments in chemistry education
The Starburst Nature of Lyman-Break Galaxies: Testing UV Extinction with X-rays
We derive the bolometric to X-ray correlation for a local sample of normal
and starburst galaxies and use it, in combination with several UV reddening
schemes, to predict the 2--8 keV X-ray luminosity for a sample of 24
Lyman-break galaxies in the HDF/CDF-N. We find that the mean X-ray luminosity,
as predicted from the Meurer UV reddening relation for starburst galaxies,
agrees extremely well with the Brandt stacking analysis. This provides
additional evidence that Lyman-break galaxies can be considered as scaled-up
local starbursts and that the locally derived starburst UV reddening relation
may be a reasonable tool for estimating the UV extinction at high redshift. Our
analysis shows that the Lyman-break sample can not have far-IR to far-UV flux
ratios similar to nearby ULIGs, as this would predict a mean X-ray luminosity
100 times larger than observed, as well as far-IR luminosities large enough to
be detected in the sub-mm. We calculate the UV reddening expected from the
Calzetti effective starburst attenuation curve and the radiative transfer
models of Witt & Gordon for low metallicity dust in a shell geometry with
homogeneous or clumpy dust distributions and find that all are consistent with
the observed X-ray emission. Finally, we show that the mean X-ray luminosity of
the sample would be under predicted by a factor of 6 if the the far-UV is
unattenuated by dust.Comment: 7 pages, 3 figures. Accepted for publication in A
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