Space based astronomy: Teacher's guide with activities

This curriculum guide uses hands-on activities to help students and teachers understand the significance of space-based astronomy - astronomical observations made from outer space. The guide contains few of the traditional activities found in many astronomy guides such as constellation studies, lunar phases, and planetary orbits. Instead, it tells the story of why it is important to observe celestial objects from outer space and how to study the entire electromagnetic spectrum. The guide begins with a survey of astronomy related NASA spacecraft. This is followed by a collection of activities in four units: (1) the atmospheric filter; (2) the electromagnetic spectrum; (3) collecting electromagnetic radiation; and (4) down to Earth. A curriculum index identifies the curriculum areas each activity addresses. The guide concludes with a glossary, reference list, a NASA Resources list, and an evaluation card. It is designed for students in grades 5 through 8

Effects of rapid urbanisation on the urban thermal environment between 1990 and 2011 in Dhaka Megacity, Bangladesh

This study investigates the influence of land-use/land-cover (LULC) change on land surface temperature (LST) in Dhaka Megacity, Bangladesh during a period of rapid urbanisation. LST was derived from Landsat 5 TM scenes captured in 1990, 2000 and 2011 and compared to contemporaneous LULC maps. We compared index-based and linear spectral mixture analysis (LSMA) techniques for modelling LST. LSMA derived biophysical parameters corresponded more strongly to LST than those produced using index-based parameters. Results indicated that vegetation and water surfaces had relatively stable LST but it increased by around 2 °C when these surfaces were converted to built-up areas with extensive impervious surfaces. Knowledge of the expected change in LST when one land-cover is converted to another can inform land planners of the potential impact of future changes and urges the development of better management strategies

Temperature and Chemistry Effects in Porous-Media Electrokinetics

ABSTRACTElectrokinetic phenomena in brine-saturated porous media, such as electroosmosis (fluid-flow induced by applied electric fields) and streaming current (the complementary process) depend on the density of ions adsorbed on the pore surface and the characteristic thickness of the diffuse space-charge layer λ. These, in turn, depend on brine chemistry, ambient temperature and possibly other parameters. We report on a series of measurements of natural rock and synthetic glass-bead samples: for one sample group, we varied the temperature over 0–50 ° C; for another, we changed the brine cation species. We find that the electrokinetic coefficients depend only weakly on temperature; this is shown to follow from the expected trends in λ, η, and σ. The chemistry dependence follows qualitatively but not quantitatively the predictions of the Debye-Hiickel approximation.</jats:p

Electrokinetic Phenomena in Porous Media

ABSTRACTElectrokinetic phenomena, such as electroosmosis (fluid-flow induced by applied electric fields) and streaming potential (the complementary process) are known to exist in brine-saturated porous media, but are very difficult to measure. With modern instrumentation and an ac method, we can now determine these transport coefficients accurately, and use them to characterize the permeability k1, the effective throat radius Re, and the electric potential at the slip-plane, or ζ-potential. Our study shows that permeability can be determined by two different means: by combining the dc values of the streaming potential, electroosmotic pressure and conductivity; or from the frequency response of ac electroosmosis alone. The high sensitivity of the method allows us to measure k over the 0.1–10,000 millidarcy range with less than lOkPa applied pressure. This article reviews some of the basics of electrokinetics and describes our methods. We also discuss effects of brine salinity and possible effects due to the fractal nature of the pore surface.</jats:p

Dynamics of Air-Water Contact Lines and Interfaces Near the Pinning Threshold

ABSTRACTWe report a study of the dynamics of capillary rise of water in glass tubes and glass bead packs. The water column height h is measured as a function of time t byvideo imaging. Analyzing the late time data in terms of critical pinning, dh/dt ∞ (P – Pc)β, we find an anomalously large exponent β for interfaces in bead packs and β ≈ 1 for contact lines in capillary tubes. Repetitive rise and fall experiments in capillary tubes suggests that thinning of the wetting film plays an important role in the dynamics. We discuss these findings in light of recent theories and experiments.</jats:p