1,960 research outputs found

    GIS and Introductory Environmental Engineering: A Way to Fold GIS into an Already-Existing Course

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    The use of Geographical Information Systems (GIS) was implemented in the upper-division undergraduate technical elective Introduction to Environmental Engineering at Harvey Mudd College. Students integrated technical engineering skills, newly-learned geographical information system (GIS) skills, and the engineering design process, all in the context of the design of a debris flow barrier for a wilderness land parcel acquired by a local conservancy group. Junior and senior general engineering students, the majority of whom had no experience with GIS, were taught ArcGIS (a GIS mapping program) in the context of an Introductory Environmental Engineering course. Students learned how to map locations, find and download geo-encoded data, and join data layers, in order to graphically present toxic release hazards near their home towns. ArcGIS skills and knowledge were assessed through completion of homework problems, and through the students’ use of GIS data, software, and mapping during the design of a debris flow barrier for a local wilderness land parcel. Assignment #1 consisted of students learning how to map and characterize toxic releases near their hometowns; these data were downloaded into a spreadsheet for later use in the ArcGIS software package. In Assignment #2, the students used ArcGIS to analyze these data for the potential of water, soil, and atmospheric transport. In addition to the homework assignments, the student team completed a team-based design project involving the characterization of the wilderness site; acquiring relevant GIS data; and studying the physics of debris flow. The team produced alternative designs for the barrier and chose the best design by applying design metrics. The alternative designs and rationale for the chosen design were presented to the board of directors of the local conservancy group. Pre- and post-assessment data were gathered to analyze the success of the learning objectives. The design project in particular was useful in evaluating the students’ skill, knowledge and ease in using the GIS tools for analysis of the wilderness land parcel

    Sensory System Responses to Human-Induced Environmental Change

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    Sensory input to the central nervous system is the primary means by which animals respond to variation in their physical and biological environments. It is well established that key threats such as habitat destruction, the introduction of non-native species, and climate change are imposing significant pressures on natural ecosystems, yet surprisingly few studies have examined how these threats impact the senses or determine species' responses to environmental change. This review focuses on how anthropogenic impacts on aquatic ecosystems can have a detrimental effect on the sensory systems of aquatic organisms and how these modalities can act to influence genetic and non-genetic (e.g., developmental) responses to environmental change, which in turn can cause knock-on effects in a range of other biological systems. Species often exhibit unique sensory specializations that are suited to their behavioral requirements; at present it is unclear whether and how sensory systems have the capacity to respond to environmental change through genetic adaptation and/or sensory plasticity, and on what timescale this might occur. Sensory systems lie at the forefront of how various species respond to environmental perturbation. As such, determining the important role they play in determining fitness is critical for understanding the effects of external processes such as habitat degradation and climate change. Given the current consensus that human impacts and environmental changes are potentially highly detrimental to the delicate balance of the biome, knowing how organisms respond, and to what degree adaptation is physiologically and behaviorally limited, warrants urgent attention

    Structure of Uranium(V) Methyl and Uranium(IV) Ylide Complexes

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    Syntheses of rare examples of U(V) methyl and U(IV) ylide complexes are reported. Reaction of the previously reported U(IV) imido complex [(C 5Me 5) 2U(py)(═NMes)] (py = pyridine, and Mes = 2,4,6-Me 3C 6H 2) with CuI forms the U(V) complex [(C 5Me 5) 2U(I)(═NMes)]. Reaction of the iodo complex with MgMe 2 produces the methyl complex [(C 5Me 5) 2U(CH 3)(═NMes)]. The methyl complex was reacted with CH 2PPh 3, surprisingly forming [(C 5Me 5) 2U(CH 2PPh 3)(═NMes)], a U(IV) ylide. This is formed from a disproportionation of a transient U(V) carbene, leading to the U(IV) ylide and a U(VI) bis(imido) complex, [(C 5Me 5) 2U(═NMes) 2]. These complexes were characterized using spectroscopic methods (nuclear magnetic resonance, infrared, and ultraviolet-visible-nean infrared), SQUID magnetometry, and X-ray crystallography, and density functional theory calculations are used to compare the U(V) methyl with the targeted U(V) carbene ligands

    Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV

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    A search for new physics is presented based on an event signature of at least three jets accompanied by large missing transverse momentum, using a data sample corresponding to an integrated luminosity of 36 inverse picobarns collected in proton--proton collisions at sqrt(s)=7 TeV with the CMS detector at the LHC. No excess of events is observed above the expected standard model backgrounds, which are all estimated from the data. Exclusion limits are presented for the constrained minimal supersymmetric extension of the standard model. Cross section limits are also presented using simplified models with new particles decaying to an undetected particle and one or two jets

    Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

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    A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

    Evidence for high bi-allelic expression of activating Ly49 receptors

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    Stochastic expression is a hallmark of the Ly49 family that encode the main MHC class-I-recognizing receptors of mouse natural killer (NK) cells. This highly polygenic and polymorphic family includes both activating and inhibitory receptor genes and is one of genome's fastest evolving loci. The inhibitory Ly49 genes are expressed in a stochastic mono-allelic manner, possibly under the control of an upstream bi-directional early promoter and show mono-allelic DNA methylation patterns. To date, no studies have directly addressed the transcriptional regulation of the activating Ly49 receptors. Our study shows differences in DNA methylation pattern between activating and inhibitory genes in C57BL/6 and F1 hybrid mouse strains. We also show a bias towards bi-allelic expression of the activating receptors based on allele-specific single-cell RT–PCR in F1 hybrid NK cells for Ly49d and Ly49H expression in Ly49h+/− mice. Furthermore, we have identified a region of high sequence identity with possible transcriptional regulatory capacity for the activating Ly49 genes. Our results also point to a likely difference between NK and T-cells in their ability to transcribe the activating Ly49 genes. These studies highlight the complex regulation of this rapidly evolving gene family of central importance in mouse NK cell function

    Combined search for the quarks of a sequential fourth generation

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    Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about +/- 20 GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions.Comment: Replaced with published version. Added journal reference and DO

    Measurement of the Z/gamma* + b-jet cross section in pp collisions at 7 TeV

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    The production of b jets in association with a Z/gamma* boson is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7 TeV and recorded by the CMS detector. The inclusive cross section for Z/gamma* + b-jet production is measured in a sample corresponding to an integrated luminosity of 2.2 inverse femtobarns. The Z/gamma* + b-jet cross section with Z/gamma* to ll (where ll = ee or mu mu) for events with the invariant mass 60 < M(ll) < 120 GeV, at least one b jet at the hadron level with pT > 25 GeV and abs(eta) < 2.1, and a separation between the leptons and the jets of Delta R > 0.5 is found to be 5.84 +/- 0.08 (stat.) +/- 0.72 (syst.) +(0.25)/-(0.55) (theory) pb. The kinematic properties of the events are also studied and found to be in agreement with the predictions made by the MadGraph event generator with the parton shower and the hadronisation performed by PYTHIA.Comment: Submitted to the Journal of High Energy Physic
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