Ground-Penetrating-Radar Reflection Attenuation Tomography with an Adaptive Mesh

Ground-penetrating radar (GPR) attenuation-difference analysis can be a useful tool for studying fluid transport in the subsurface. Surface-based reflection attenuation-difference tomography poses a number of challenges that are not faced by crosshole attenuation surveys. We create and analyze a synthetic attenuation-difference GPR data set to determine methods for processing amplitude changes and inverting for conductivity differences from reflection data sets. Instead of using a traditional grid-based inversion, we use a data-driven adaptive-meshing algorithm to alter the model space and to create amore even distribution of resolution. Adaptive meshing provides a method for improving the resolution of the model space while honoring the data limitations and improving the quality of the attenuation difference inversion. Comparing inversions on a conventional rectangular grid with the adaptive mesh, we find that the adaptively meshed model reduces the inversion computation time by an average of 75% with an improvement in the root mean square error of up to 15%. While the sign of the conductivity change is correctly reproduced by the inversion algorithm, the magnitude varies by as much as much as 50% from the true values. Our heterogeneous conductivity model indicates that the attenuation difference inversion algorithm effectively locates conductivity changes, and that surface-based reflection surveys can produce models as accurate as traditional crosshole surveys

2MASSJ035523.51+113337.4: A Young, Dusty, Nearby, Isolated Brown Dwarf Resembling A Giant Exoplanet

We present parallax and proper motion measurements, near-infrared spectra, and WISE photometry for the low surface gravity L5gamma dwarf 2MASSJ035523.37+113343.7 (2M0355). We use these data to evaluate photometric, spectral, and kinematic signatures of youth as 2M0355 is the reddest isolated L dwarf yet classified. We confirm its low-gravity spectral morphology and find a strong resemblance to the sharp triangular shaped $H$-band spectrum of the 10 Myr planetary-mass object 2M1207b. We find that 2M0355 is underluminous compared to a normal field L5 dwarf in the optical and MKO J,H, and K bands and transitions to being overluminous from 3-12 microns, indicating that enhanced photospheric dust shifts flux to longer wavelengths for young, low-gravity objects, creating a red spectral energy distribution. Investigating the near-infrared color magnitude diagram for brown dwarfs confirms that 2M0355 is redder and underluminous compared to the known brown dwarf population, similar to the peculiarities of directly imaged exoplanets 2M1207b and HR8799bcd. We calculate UVW space velocities and find that the motion of 2M0355 is consistent with young disk objects (< 2-3 Gyr) and it shows a high likelihood of membership in the AB Doradus association.Comment: 23 pages, 10 figures, 5 Tables, Submitted to AJ 13 May 201

Characterization of the Benchmark Binary Nltt 33370

We report the confirmation of the binary nature of the nearby, very low-mass system NLTT 33370 with adaptive optics imaging and present resolved near-infrared photometry and integrated light optical and near-infrared spectroscopy to characterize the system. VLT-NaCo and LBTI-LMIRCam images show significant orbital motion between 2013 February and 2013 April. Optical spectra reveal weak, gravity sensitive alkali lines and strong lithium 6708 ˚A absorption that indicate the system is younger than field age. VLT-SINFONI near-IR spectra also show weak, gravity sensitive features and spectral morphology that is consistent with other young, very low-mass dwarfs. We combine the constraints from all age diagnostics to estimate a system age of ∼30-200 Myr. The 1.2-4.7 µm spectral energy distribution of the components point toward Teff = 3200 ± 500 K and Teff = 3100 ± 500 K for NLTT 33370 A and B, respectively. The observed spectra, derived temperatures, and estimated age combine to constrain the component spectral types to the range M6-M8. Evolutionary models predict masses of 113 ±8 MJup and 106±7 MJup from the estimated luminosities of the components. KPNO-Phoenix spectra allow us to estimate the systemic radial velocity of the binary. The Galactic kinematics of NLTT 33370AB are broadly consistent with other young stars in the Solar neighborhood. However, definitive membership in a young, kinematic group cannot be assigned at this time and further follow-up observations are necessary to fully constrain the system’s kinematics. The proximity, age, and late-spectral type of this binary make it very novel and an ideal target for rapid, complete orbit determination. The system is one of only a few model calibration benchmarks at young ages and very low-masses.Astronom

The UniProt-GO Annotation database in 2011

The GO annotation dataset provided by the UniProt Consortium (GOA: http://www.ebi.ac.uk/GOA) is a comprehensive set of evidenced-based associations between terms from the Gene Ontology resource and UniProtKB proteins. Currently supplying over 100 million annotations to 11 million proteins in more than 360 000 taxa, this resource has increased 2-fold over the last 2 years and has benefited from a wealth of checks to improve annotation correctness and consistency as well as now supplying a greater information content enabled by GO Consortium annotation format developments. Detailed, manual GO annotations obtained from the curation of peer-reviewed papers are directly contributed by all UniProt curators and supplemented with manual and electronic annotations from 36 model organism and domain-focused scientific resources. The inclusion of high-quality, automatic annotation predictions ensures the UniProt GO annotation dataset supplies functional information to a wide range of proteins, including those from poorly characterized, non-model organism species. UniProt GO annotations are freely available in a range of formats accessible by both file downloads and web-based views. In addition, the introduction of a new, normalized file format in 2010 has made for easier handling of the complete UniProt-GOA data se

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Models of classroom assessment for course-based research experiences

Course-based research pedagogy involves positioning students as contributors to authentic research projects as part of an engaging educational experience that promotes their learning and persistence in science. To develop a model for assessing and grading students engaged in this type of learning experience, the assessment aims and practices of a community of experienced course-based research instructors were collected and analyzed. This approach defines four aims of course-based research assessment—(1) Assessing Laboratory Work and Scientific Thinking; (2) Evaluating Mastery of Concepts, Quantitative Thinking and Skills; (3) Appraising Forms of Scientific Communication; and (4) Metacognition of Learning—along with a set of practices for each aim. These aims and practices of assessment were then integrated with previously developed models of course-based research instruction to reveal an assessment program in which instructors provide extensive feedback to support productive student engagement in research while grading those aspects of research that are necessary for the student to succeed. Assessment conducted in this way delicately balances the need to facilitate students’ ongoing research with the requirement of a final grade without undercutting the important aims of a CRE education

Utilizing Electrical Conductivity for Characterizing Hydrogeologic Properties

A variety of methods utilizing geophysical tools have been developed to characterize fundamental subsurface material properties. Relationships between measured values and material properties are often defined through empirical equations. Mapping fluid distribution and movement within an aquifer can help to identify changes in porosity and permeability and to define preferential flow paths. I relate changes in fluid type and properties within pore spaces to changes in measured electrical properties, specifically electrical conductivity. In synthetic and field experiments, ground-penetrating radar (GPR) is used to map the location and movement of conductive salt tracers introduced into high porosity sand layers. Conductivity increases the attenuation of the GPR signal. Using a novel surface-based time-lapse tomographic approach, increases in GPR attenuation can be mapped to areas of increased conductivity. Electrical conductivity can also be used with low frequency methods. In a laboratory experiment, I use converted electric to elastic energy in a method called electroseismics to image fluid boundaries between water and a NAPL (non-aqueous phase liquid) with acoustic energy. Acoustic energy originates from the top and bottom of the introduced NAPL layer allowing for the imaging of very thin contaminant layers. Both methods show that time-lapse data collection can reveal subtle changes in the concentration and location of fluids within the pore space that may otherwise be missed

The Effect of Tissue Structure and Soil Chemistry on Trace Element Uptake in Fossils

Trace element profiles for common divalent cations (Sr, Zn, Ba), rare-earth elements (REE), Y, U, and Th were measured in fossil bones and teeth from the c. 25 ka Merrell locality, Montana, USA, by using laser-ablation ICP-MS. Multiple traverses in teeth were transformed into 2-D trace element maps for visualizing structural influences on trace element uptake. Trace element compositions of different soils from the fossil site were also analyzed by solution ICP-MS, employing progressive leaches that included distilled H2O, 0.1 M acetic acid, and microwave digestion in concentrated HCl–HNO3. In teeth, trace element uptake in enamel is 2–4 orders of magnitude slower than in dentine, forming an effective trace element barrier. Uptake in dentine parallel to the dentine–enamel interface is enhanced by at least 2 orders of magnitude compared to transverse, causing trace element “plumes” down the tooth core. In bone, U, Ba and Sr are nearly homogeneous, implying diffusivities 5 orders of magnitude faster than in enamel and virtually complete equilibration with host soils. In contrast all REE show strong depletions inward, with stepwise linear segments in log-normal or inverse complementary error function plots; these data require a multi-medium diffusion model, with about 2 orders of magnitude difference in slowest vs. fastest diffusivities. Differences in REE diffusivities in bone (slow) vs. dentine (fast) reflect different partition coefficients (Kd’s). Although acid leaches and bulk digestion of soils yield comparable fossil–soil Kd’s among different elements, natural solutions are expected to be neutral to slightly basic. Distilled H2O leachates instead reveal radically different Kd’s in bone for REE than for U–Sr–Ba, suggest orders of magnitude lower effective diffusivities for REE, and readily explain steep vs. flat profiles for REE vs. U–Sr–Ba, respectively. Differences among REE Kd’s and diffusivities may explain inward changes in Ce anomalies. Acid washes and bulk soil compositions yield misleading Kd’s for many trace elements, especially the REE, and H2O-leaches are preferred. Patterns of trace element distributions indicate diagenetic alteration at all scales, including enamel, and challenge the use of trace elements in paleodietary studies

The Establishment of a Geophysics Field Camp in Northern Thailand

As a participant in SEG\u27s Geoscientists Without Borders program, wehave developed a geophysics field camp in northern Thailand totrain students and professionals from throughout Southeast Asia in field-basedgeophysical methods. Over the past two years, faculty, technicians, professionals,and students from 18 institutions and 11 countries have acquired,processed, and interpreted geophysical data at field sites in andaround Chiang Mai, Thailand. Participation from undergraduate students, graduate students,and private and public sector geoscience professionals provides a broadbase of experience, background, and insight. Our training has providedopportunities for cross-cultural collaboration and education, and a greater useof field-based geophysical methods for academic, private sector, and governmentagencies throughout Southeast Asia

The Nubian Swell

We use the name Nubian Swell to refer to a complex, east-west trending structural high in southern Egypt and northern Sudan. This 500 km wide zone of uplifted Neoproterozoic crystalline basement and Paleozoic sediments and parallel troughs extend westward for more than 800 km from the flanks of the Red Sea Hills. The Nile in this region is called the Cataract Nile and is in a youthful stage, particularly in northern Sudan where it is incised in the Neoproterozoic crystalline basement. The northern Cataract Nile flows through the rapids of the Batn el Hajar or \u27Belly of Stones\u27 region, characterized by structurally controlled 90⁰ turns, frequent bifurcation and disruption by several cataracts, and near-absence of floodplains. Orbital imaging radar has advanced our understanding of the Nubian Swell, through the discovery and mapping of paleochannels and faults that indicate tectonic uplift during Cenozoic time. Earthquakes in southern Egypt during the early 1980s provide evidence that portions of the Nubian Swell are still tectonically active, with recent seismic activity concentrated where E-W trending structures intersect N-S trending structures of the Aswan corridor. We conclude that the Nubian Swell is an important tectonic feature of North Africa, with episodic but continuing uplift