916 research outputs found
Using graphical and pictorial representations to teach introductory astronomy students about the detection of extrasolar planets via gravitational microlensing
The detection and study of extrasolar planets is an exciting and thriving
field in modern astrophysics, and an increasingly popular topic in introductory
astronomy courses. One detection method relies on searching for stars whose
light has been gravitationally microlensed by an extrasolar planet. In order to
facilitate instructors' abilities to bring this interesting mix of general
relativity and extrasolar planet detection into the introductory astronomy
classroom, we have developed a new Lecture-Tutorial, "Detecting Exoplanets with
Gravitational Microlensing." In this paper, we describe how this new
Lecture-Tutorial's representations of astrophysical phenomena, which we
selected and created based on theoretically motivated considerations of their
pedagogical affordances, are used to help introductory astronomy students
develop more expert-like reasoning abilities.Comment: 10 pages, 10 figures, accepted for publication in the American
Journal of Physic
Relative roles of climate and emissions changes on future tropospheric oxidant concentrations
Role of climate feedback on methane and ozone studied with a coupled ocean-atmosphere-chemistry model.
Flight-based chemical characterization of biomass burning aerosols within two prescribed burn smoke plumes
Biomass burning represents a major global source of aerosols impacting direct radiative forcing and cloud properties. Thus, the goal of a number of current studies involves developing a better understanding of how the chemical composition and mixing state of biomass burning aerosols evolve during atmospheric aging processes. During the Ice in Clouds Experiment-Layer Clouds (ICE-L) in the fall of 2007, smoke plumes from two small Wyoming Bureau of Land Management prescribed burns were measured by on-line aerosol instrumentation aboard a C-130 aircraft, providing a detailed chemical characterization of the particles. After ~2–4 min of aging, submicron smoke particles, produced primarily from sagebrush combustion, consisted predominantly of organics by mass, but were comprised primarily of internal mixtures of organic carbon, elemental carbon, potassium chloride, and potassium sulfate. Significantly, the fresh biomass burning particles contained minor mass fractions of nitrate and sulfate, suggesting that hygroscopic material is incorporated very near or at the point of emission. The mass fractions of ammonium, sulfate, and nitrate increased with aging up to ~81–88 min and resulted in acidic particles. Decreasing black carbon mass concentrations occurred due to dilution of the plume. Increases in the fraction of oxygenated organic carbon and the presence of dicarboxylic acids, in particular, were observed with aging. Cloud condensation nuclei measurements suggested all particles >100 nm were active at 0.5% water supersaturation in the smoke plumes, confirming the relatively high hygroscopicity of the freshly emitted particles. For immersion/condensation freezing, ice nuclei measurements at −32 °C suggested activation of ~0.03–0.07% of the particles with diameters greater than 500 nm
The impact of developer team sizes on the structural attributes of software
It is established that the internal quality of software is a key determinant of the total cost of ownership of that software. The objective of this research is to determine the impact that the development team’s size has on the internal structural attributes of a codebase and, in doing so, we consider the impact that the team’s size may have on the internal quality of the software that they produce. In this paper we leverage the wealth of data available in the open-source domain by mining detailed data from 1000 projects in Google Code and, coupled with one of the most established of object-oriented metric suites, we isolate and identify the effect that the development team size has on internal structural attributes of the software produced. We will find that some measures of functional decomposition are enhanced when we compare projects authored by fewer developers against those authored by a larger number of developers while measures of cohesion and complexity are degraded
Ex-nihilo II: Examination Syllabi and the Sequencing of Cosmology Education
Cosmology education has become an integral part of modern physics courses.
Directed by National Curricula, major UK examination boards have developed
syllabi that contain explicit statements about the model of the Big Bang and
the strong observational evidence that supports it. This work examines the
similarities and differences in these specifications, addresses when cosmology
could be taught within a physics course, what should be included in this
teaching and in what sequence it should be taught at different levels.Comment: 9 pages. Accepted for publication in a special issue of Physics
Educatio
A comparison of two schemes for the convective transport of chemical species in a Lagrangian global chemistry model
Clinoform architecture and along-strike variability through an exhumed erosional to accretionary basin margin transition
Exhumed basin margin‐scale clinothems provide important archives for understanding process interactions and reconstructing the physiography of sedimentary basins. However, studies of coeval shelf through slope to basin‐floor deposits are rarely documented, mainly due to outcrop or subsurface dataset limitations. Unit G from the Laingsburg depocentre (Karoo Basin, South Africa) is a rare example of a complete basin margin scale clinothem (>60 km long, 200 m‐high), with >10 km of depositional strike control, which allows a quasi‐3D study of a preserved shelf‐slope‐basin floor transition over a ca. 1200 km2 area. Sand‐prone, wave‐influenced topset deposits close to the shelf‐edge rollover zone can be physically mapped down dip for ca. 10 km as they thicken and transition into heterolithic foreset/slope deposits. These deposits progressively fine and thin over 10s of km farther down dip into sand‐starved bottomset/basin floor deposits. Only a few km along strike, the coeval foreset/slope deposits are bypass‐dominated with incisional features interpreted as minor slope conduits/gullies. The margin here is steeper, more channelized, and records a stepped profile with evidence of sand‐filled intraslope topography, a preserved base‐of‐slope transition zone and sand‐rich bottomset/basin‐floor deposits. Unit G is interpreted as part of a composite depositional sequence that records a change in basin margin style from an underlying incised slope with large sand‐rich basin‐floor fans to an overlying accretion‐dominated shelf with limited sand supply to slope and basin‐floor. The change in margin style is accompanied with decreased clinoform height/slope and increased shelf width. This is interpreted to reflect a transition in subsidence style from regional sag, driven by dynamic topography/inherited basement configuration, to early foreland basin flexural loading. Results of this study caution against reconstructing basin margin successions from partial datasets without accounting for temporal and spatial physiographic changes, with potential implications on predictive basin evolution models
Tropospheric ozone and El Niño–Southern Oscillation: Influence of atmospheric dynamics, biomass burning emissions, and future climate change
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