Formation of Cosmic Dust Bunnies

Planetary formation is an efficient process now thought to take place on a relatively short astronomical time scale. Recent observations have shown that the dust surrounding a protostar emits more efficiently at longer wavelengths as the protoplanetary disk evolves, suggesting that the dust particles are coagulating into fluffy aggregates, "much as dust bunnies form under a bed." One poorly understood problem in this coagulation process is the manner in which micron-sized, charged grains form the fractal aggregate structures now thought to be the precursors of protoplanetary disk evolution. This study examines the characteristics of such fractal aggregates formed by the collision of spherical monomers and aggregates where the charge is distributed over the aggregate structure. The aggregates are free to rotate due to collisions and dipole-dipole electrostatic interactions. Comparisons are made for different precursor size distributions and like-charged, oppositelycharged, and neutral grains

The Economic Value of Water: Results of a Workshop in Caracas, Venezuela, November 2000

In November 2000 a small workshop of 14 people met in Caracas, Venezuela, to discuss the value\u27 of water. The meeting was sponsored by the International Water Resources Network (IWRN), the Organization of American States (OAS), The Nature Conservancy, the University of New Mexico, and the National Oceanic and Atmospheric Administration (NOAA). The meeting was hosted by Jose Ochoa-Iturbe, Director of the School of Civil Engineering at the Universidad Catolica Andres Bello. The participants represented a mix of academics, water administrators, government officials and NGOs (non-governmental organizations) from around the Americas. Although many of the participants are economists, multiple disciplines and perspectives were represented. The meeting occurred as part of a process for stimulating discussion about water issues in the Americas. During and after IWRN\u27s Dialog III in Panama, the participants at a session on water valuation discussed the need for an intermediate meeting that would keep the discussion moving forward. The feeling was that the time interval between Dialogs was too long and significant time was spent at each Dialog repeating conversations that had occurred before. An intermediate conference was organized in Caracas to fill that need. This document was produced as a result of the Caracas meeting and is meant to serve as an input to IWRN\u27s Dialog IV in Brazil. The document should not be looked on as the final word but as an intermediate step meant to stimulate additional discussion

High-accuracy waveforms for binary black hole inspiral, merger, and ringdown

The first spectral numerical simulations of 16 orbits, merger, and ringdown of an equal-mass non-spinning binary black hole system are presented. Gravitational waveforms from these simulations have accumulated numerical phase errors through ringdown of ~0.1 radian when measured from the beginning of the simulation, and ~0.02 radian when waveforms are time and phase shifted to agree at the peak amplitude. The waveform seen by an observer at infinity is determined from waveforms computed at finite radii by an extrapolation process accurate to ~0.01 radian in phase. The phase difference between this waveform at infinity and the waveform measured at a finite radius of r=100M is about half a radian. The ratio of final mass to initial mass is M_f/M = 0.95162 +- 0.00002, and the final black hole spin is S_f/M_f^2=0.68646 +- 0.00004.Comment: 15 pages, 11 figures; New figure added, text edited to improve clarity, waveform made availabl

Learning to see the infinite: Measuring visual literacy skills in a 1st-year seminar course

Visual literacy, defined as the ability to interpret, negotiate, and make meaning from information presented in an image, was a stated learning objective for the fall 2009 iteration of a first-year seminar course. To help students develop visual literacy skills, they received formal instruction throughout the semester and completed a series of carefully designed learning activities. The effects of these interventions were measured using a pre-/post-semester methodology where students were asked to look at two different—but stylistically similar—paintings and write a response to the following two questions: what do you see and what do you think it means? Students’ responses were analyzed based on the visual evidence recorded, and 2) the strength of their arguments using Toulmin’s argument model. After instructional interventions, paired t-tests indicate that students made significantly more basic and advanced observations, offered more supporting visual evidence for their best-supported claims, and made stronger connections between their claims and the visual evidence

Effect of Local Norms on Racial and Ethnic Representation in Gifted Education

Educators have sought to understand and address the disproportional representation of students from certain student subgroups in gifted education. Most gifted identification decisions are made with national comparisons where students must score above a certain percentage of test takers. However, this approach is not always consistent with the overall goal of gifted education. Scholars have long argued for the use of local normative criteria to increase the diversity of students identified for gifted services, and although some districts across the country have applied such recommendations, little research has been carried out. In this study, we use a large data set to assess the extent to which identifying gifted students with either school-level norms or a combination of national and school-level norms would improve gifted education representation rates for students who are from African American and Latinx families. A preprint of this registered report and this project’s preregistration documentation are available at https://osf.io/z2egy/

Genetic dissection of MHC-associated susceptibility to Lepeophtheirus salmonis in Atlantic salmon

Background: Genetic variation has been shown to play a significant role in determining susceptibility to the salmon louse, Lepeophtheirus salmonis. However, the mechanisms involved in differential response to infection remain poorly understood. Recent findings in Atlantic salmon (Salmo salar) have provided evidence for a potential link between marker variation at the major histocompatibility complex (MHC) and differences in lice abundance among infected siblings, suggesting that MHC genes can modulate susceptibility to the parasite. In this study, we used quantitative trait locus (QTL) analysis to test the effect of genomic regions linked to MHC class I and II on linkage groups (LG) 15 and 6, respectively. Results: Significant QTL effects were detected on both LG 6 and LG 15 in sire-based analysis but the QTL regions remained unresolved due to a lack of recombination between markers. In dam-based analysis, a significant QTL was identified on LG 6, which accounted for 12.9% of within-family variance in lice abundance. However, the QTL was located at the opposite end of DAA, with no significant overlap with the MHC class II region. Interestingly, QTL modelling also revealed evidence of sex-linked differences in lice abundance, indicating that males and females may have different susceptibility to infection. Conclusion: Overall, QTL analysis provided relatively weak support for a proximal effect of classical MHC regions on lice abundance, which can partly be explained by linkage to other genes controlling susceptibility to L. salmonis on the same chromosom

Aircraft Exceedances Vary According to Time of Day and Workload

The Flight Operational Quality Assurance (FOQA) programs have been implemented in US and Europe to identify anomalous flights based on data recorded on board an aircraft in an effort to improve flight safety. Numerous methods have been developed to support the analysis of FOQA data. However, it is unclear how FOQA data relates to the performance of the pilot. We sought to characterize the frequency and type of flight exceedances extracted from FOQA data during a controlled pilot schedule in order to determine whether patterns of exceedances related to human control of the aircraft would change according to scheduling factors