On Toroidal Horizons in Binary Black Hole Inspirals

We examine the structure of the event horizon for numerical simulations of two black holes that begin in a quasicircular orbit, inspiral, and finally merge. We find that the spatial cross section of the merged event horizon has spherical topology (to the limit of our resolution), despite the expectation that generic binary black hole mergers in the absence of symmetries should result in an event horizon that briefly has a toroidal cross section. Using insight gained from our numerical simulations, we investigate how the choice of time slicing affects both the spatial cross section of the event horizon and the locus of points at which generators of the event horizon cross. To ensure the robustness of our conclusions, our results are checked at multiple numerical resolutions. 3D visualization data for these resolutions are available for public access online. We find that the structure of the horizon generators in our simulations is consistent with expectations, and the lack of toroidal horizons in our simulations is due to our choice of time slicing.Comment: Submitted to Phys. Rev.

Lattice Monte Carlo calculations for unitary fermions in a finite box

We perform lattice Monte Carlo simulations for up to 66 unitary fermions in a finite box using a highly improved lattice action for nonrelativistic spin 1/2 fermions. We obtain a value of $0.366^{+0.016}_{-0.011}$ for the Bertsch parameter, defined as the energy of the unitary Fermi gas measured in units of the free gas energy in the thermodynamic limit. In addition, for up to four unitary fermions, we compute the spectrum of the lattice theory by exact diagonalization of the transfer matrix projected onto irreducible representations of the octahedral group for small to moderate size lattices, providing an independent check of our few-body simulation results. We compare our exact numerical and simulation results for the spectrum to benchmark studies of other research groups, as well as perform an extended analysis of our lattice action improvement scheme, including an analysis of the errors associated with higher partial waves and finite temporal discretization.Comment: Significant revisions from previous version. Included data at a larger volume and performed an infinite volume extrapolation of the Bertsch parameter. Published versio

Nucleon-Nucleon Interactions on the Lattice

We consider the nucleon-nucleon potential in quenched and partially-quenched QCD. The leading one-meson exchange contribution to the potential is found to fall off exponentially at long-distances, in contrast with the Yukawa-type behaviour found in QCD. This unphysical component of the two-nucleon potential has important implications for the extraction of nuclear properties from lattice simulations.Comment: 6 pages LaTeX, 2 eps fig

Middle pleistocene glaciation in Patagonia dated by cosmogenic-nuclide measurements on outwash gravels

The well-preserved glacial record in Argentine Patagonia offers a ~ 1 Ma archive of terrestrial climate extremes in southern South America. These glacial deposits remain largely undated beyond the range of radiocarbon dating at ca. 40 ka. Dating old glacial deposits (> several 105 a) by cosmogenic surface exposure methods is problematic because of the uncertainty in moraine degradation and boulder erosion rates. Here, we show that cobbles on outwash terraces can reliably date ‘old’ glacial deposits in the Lago Pueyrredón valley, 47.5° S, Argentina. Favorable environmental conditions (e.g., aridity and strong winds) have enabled continuous surface exposure of cobbles and preservation of outwash terraces. The data demonstrate that nuclide inheritance is negligible and we therefore use the oldest surface cobbles to date the deposit. 10Be concentrations in outwash cobbles reveal a major glacial advance at ca. 260 ka, concurrent with Marine Isotope Stage 8 (MIS 8) and dust peaks in Antarctic ice cores. A 10Be concentration depth-profile in the outwash terrace supports the age and suggests a low terrace erosion rate of ca. 0.5 mm ka− 1. We compare these data to exposure ages obtained from associated moraines and find that surface boulders underestimate the age of the glaciation by ~ 100 ka; thus the oldest boulders in this area do not date closely moraine deposition. The 10Be concentration in moraine cobbles help to constrain moraine degradation rates. These data together with constraints from measured 26Al/10Be ratios suggest that all moraine boulders were likely exhumed after original deposition. We determine the local Last Glacial Maximum (LGM) occurred at ~ 27–25 ka, consistent with the maximum LGM in other parts of Patagonia

Clustering in mixing flows

We calculate the Lyapunov exponents for particles suspended in a random three-dimensional flow, concentrating on the limit where the viscous damping rate is small compared to the inverse correlation time. In this limit Lyapunov exponents are obtained as a power series in epsilon, a dimensionless measure of the particle inertia. Although the perturbation generates an asymptotic series, we obtain accurate results from a Pade-Borel summation. Our results prove that particles suspended in an incompressible random mixing flow can show pronounced clustering when the Stokes number is large and we characterise two distinct clustering effects which occur in that limit.Comment: 5 pages, 1 figur

First successful case of in vitro fertilization-embryo transfer with venom immunotherapy for hymenoptera sting allergy

BACKGROUND: To describe immune and endocrine responses in severe hymenoptera hypersensitivity requiring venom immunotherapy (VIT) during in vitro fertilization (IVF). CASE PRESENTATION: A 39-year old patient was referred for history of multiple miscarriage and a history of insect sting allergy. Four years earlier, she began subcutaneous injection of 100 mcg mixed vespid hymenoptera venom/venom protein every 5–6 weeks. The patient had one livebirth and three first trimester miscarriages. Allergy treatment was maintained for all pregnancies ending in miscarriage, although allergy therapy was discontinued for the pregnancy that resulted in delivery. At our institution ovulation induction incorporated venom immunotherapy (VIT) during IVF, with a reduced VIT dose when pregnancy was first identified. Serum IgE was monitored with estradiol during ovulation induction and early pregnancy. Response to controlled ovarian hyperstimulation was favorable while VIT was continued, with retrieval of 12 oocytes. Serum RAST (yellow jacket) IgE levels fluctuated in a nonlinear fashion (range 36–54%) during gonadotropin therapy and declined after hCG administration. A healthy female infant was delivered at 35 weeks gestation. The patient experienced no untoward effects from any medications during therapy. CONCLUSION: Our case confirms the safety of VIT in pregnancy, and demonstrates RAST IgE can remain <60% during IVF. With proper monitoring, VIT during IVF can be safe and appropriate for selected patients and does not appear to adversely affect blastocyst implantation, early embryo development or perinatal outcome. Further studies will be needed to develop VIT guidelines specifically applicable to IVF

Combining Different Motivation and Cognitive Supports in Undergraduate Biology in Different Contexts: Lessons Learned

Researchers acknowledge that students’ learning and achievement requires both effective cognition and the motivation to apply it. In addition, both cognition and motivation are multidimensional, each involving different processes that may be less or more salient in different contexts. However, most basic research and intervention studies focus on either cognition OR motivation, and commonly only target a single process. We designed an intervention to investigate the role of different combinations of cognitive and motivational supports in first-year undergraduate introductory biology courses. We sought an online delivery approach with minimal burden on the instructor that can accompany any such course. Building on prior research, we selected four types of cognitive supports and three types of motivational supports. Cognitive supports: Priming Prior Knowledge, Demonstrating Worked Examples, Instructing Study Strategies and Scaffolding Organization of Lectures. Motivational supports: Self-Efficacy Promoting Feedback, Value Enhancement Through Relevance Writing, and Perceived Cost Alleviation Through Persuasion. The intervention study was designed to test the effects of different combinations of these cognition and motivation supports. Initial development began in 2015-2016 with post-iterative experiments in 2017. Overall, there were 3,092 undergraduate student participants, tested in 10 studies at 3 universities over 4 years. Students were randomly assigned to either a no-treatment control condition or one of 17 combinations of cognition and motivation intervention modules delivered via the Internet, each over the course of a semester. A meta-analysis of the overall effect of all interventions on grades across the 10 studies was positive (g = .30), with significant moderation of fidelity (i.e., students’ access; g = .24) and research phase (stronger effect in later administrations; g = .26). Moreover, certain combinations had little effect across administrations (e.g., any combination with Priming Prior Knowledge). However, the development and testing process also pointed to contextual and situational factors that influenced the effect of mostly effective interventions. For example, in one institution, Scaffolding Organization of Lectures through thematically segmenting lecture videos had the unintended consequence of students stopping lecture attendance. Or, in one institution but not in others, students “crammed” on the supports, which undermined the effect and required modifying the intervention in order to regulate timely access in that institution. Additionally, for yet to be explored reasons, successful combinations of modules were more effective in certain administrations in some institutions than in others. Finally, in certain administrations, there were unanticipated direct effects of motivational modules on cognitive biological reasoning, and cognitive modules on motivational beliefs The current study demonstrated that, when aggregated across context, time, and participants, a “hands-off” administration of a combination of certain cognitive and motivational supports can meaningfully improve undergraduate students’ motivation, biological reasoning, and course grades, with a stronger effect than a cognitive or motivation intervention alone. In addition, however, the findings point to important contextual as well as potentially unpredictable factors as moderating the effect of such interventions. “Evidence-based practice” might need to be considered a “first-step” in a systematic design process of catering any intervention to the particular educational context

Evidence for Height and Immune Function Trade-offs Among Preadolescents in a High Pathogen Population

Background In an energy-limited environment, caloric investments in one characteristic should trade-off with investments in other characteristics. In high pathogen ecologies, biasing energy allocation towards immune function over growth would be predicted, given strong selective pressures against early-life mortality. Methodology In the present study, we use flow cytometry to examine trade-offs between adaptive immune function (T cell subsets, B cells), innate immune function (natural killer cells), adaptive to innate ratio and height-for-age z scores (HAZ) among young children (N = 344; aged 2 months–8 years) in the Bolivian Amazon, using maternal BMI and child weight-for-height z scores (WHZ) as proxies for energetic status. Results Markers of adaptive immune function negatively associate with child HAZ, a pattern most significant in preadolescents (3+ years). In children under three, maternal BMI appears to buffer immune and HAZ associations, while child energetic status (WHZ) moderates relationships in an unexpected direction: HAZ and immune associations are greater in preadolescents with higher WHZ. Children with low WHZ maintain similar levels of adaptive immune function, but are shorter compared to high WHZ peers. Conclusions Reduced investment in growth in favor of immunity may be necessary for survival in high pathogen contexts, even under energetic constraints. Further, genetic and environmental factors are important considerations for understanding variation in height within this population. These findings prompt consideration of whether there may be a threshold of investment into adaptive immunity required for survival in high pathogen environments, and thus question the universal relevance of height as a marker of health. Lay Summary Adaptive immune function is negatively associated with child height in this high pathogen environment. Further, low weight-for-height children are shorter but maintain similar immune levels. Findings question the relevance of height as a universal health marker, given that costs and benefits of height versus immunity may be calibrated to local ecology

Warm-based basal sediment entrainment and far-field Pleistocene origin evidenced in central Transantarctic blue ice through stable isotopes and internal structures

Stable isotopes of water (δ18O and δ2H) were measured in the debris-laden ice underlying an Antarctic blue ice moraine, and in adjoining Law Glacier in the central Transantarctic Mountains. Air bubble content and morphology were assessed in shallow ice core samples. Stable isotope measurements plot either on the meteoric waterline or are enriched from it. The data cluster in two groups: the ice underlying the moraine has a δ2H:δ18O slope of 5.35 ± 0.92; ice from adjoining portions of Law Glacier has a slope of 6.69 ± 1.39. This enrichment pattern suggests the moraine's underlying blue ice entrained sediment through refreezing processes acting in an open system. Glaciological conditions favorable to warm-based sediment entrainment occur 30–50 km upstream. Basal melting and refreezing are further evidenced by abundant vapor figures formed from internal melting of the ice crystals. Both the moraine ice and Law Glacier are sufficiently depleted of heavy isotopes that their ice cannot be sourced locally, but instead must be derived from far-field interior regions of the higher polar plateau. Modeled ice flow speeds suggest the ice must be at least 80 ka old, with Law Glacier's ice possibly dating to OIS 5 and moraine ice older still

How Instructors Can Enhance Biology Students\u27 Motivation, Learning, and Grades Through Brief Relevance Writing and Worked-Example Interventions

The high failure rate of students in gateway science, technology, engineering, and mathematics (STEM) courses has been a persistent problem for biology programs nationwide. Common wisdom contends that addressing this problem requires major curricular overhauls. While desirable, such large systematic changes are often expensive or impractical. We propose an alternative approach: supplementing the regular instruction with brief online modules targeting specific cognitive (learning) and motivational mechanisms. We conducted an intervention study to test the effects of different combinations of cognitive and motivational modules on undergraduate introductory biology students\u27 learning, motivation, achievement, and intentions to remain in science. Introductory biology students at three research universities were randomly assigned to a no-treatment control condition or one of several combinations of cognition motivation modules. In this article, we describe the modules that are easiest for instructors to integrate with existing course content: worked examples (demonstrations of biology problem solving) and relevance writing (brief open-ended writing assignments about connections of biology concepts to one\u27s life). Increased student engagement in these modules led to higher motivation, biology reasoning, and course grades. These findings support the effectiveness of delivering brief online supplemental modules on students\u27 success in introductory biology courses. This easily implemented intervention can utilize online tools such as Blackboard, Canvas, or Moodle and provides an option when major changes to course instruction are not practical