Enhancing Students' Understanding of Risk and Geologic Hazards Using a Dartboard Model

This article describes the use of a model to express the magnitude-frequency relationships of natural hazards. The model consists of a dartboard whose rings can be drawn to represent magnitude, exceedence probability, average recurrence interval, or other statistical information. Students are engaged by "playing" the dart game through conducting a thought experiment, actually throwing at a physical dartboard, or simulating events based on a computer program. This type of model is applicable to any sequence of events that can be described by random sampling. It helps emphasize the random nature of such events, and provides a means for presenting hazard recurrence information in an easily visible form. In addition, it helps mitigate students' misconceptions about risk and average recurrence intervals, and provides a way to teach probability concepts without the use of sophisticated mathematics. Educational levels: Graduate or professional

Global Climate Change: Impact and Remediation

This "clicker case" is a continuation of another case study "Global Climate Change: Evidence and Causes". Students assume the role of an intern working for a U.S. senator to learn about the effects of global climate change as well as technologies and practices available to remediate the impact of climate effects. The case was designed for use in a one-semester introductory biology course taken primarily by freshmen and sophomores to fulfill a general education requirement, but could be used in any introductory biology course or in an ecology or environmental science course. It consists of a PowerPoint presentation (2.2MB) presented in class that is punctuated by multiple-choice questions students respond to using personal responses systems, or "clickers." The case can be adapted for use without these technologies. Educational levels: High school, Undergraduate lower division

F-18-FDG and C-11-choline positron emission tomography in human esophago-gastric cancer : prediction of response to therapy

Peer reviewedPublisher PD

Time-Domain Separation of Optical Properties From Structural Transitions in Resonantly Bonded Materials

The extreme electro-optical contrast between crystalline and amorphous states in phase change materials is routinely exploited in optical data storage and future applications include universal memories, flexible displays, reconfigurable optical circuits, and logic devices. Optical contrast is believed to arise due to a change in crystallinity. Here we show that the connection between optical properties and structure can be broken. Using a unique combination of single-shot femtosecond electron diffraction and optical spectroscopy, we simultaneously follow the lattice dynamics and dielectric function in the phase change material Ge2Sb2Te5 during an irreversible state transformation. The dielectric function changes by 30% within 100 femtoseconds due to a rapid depletion of electrons from resonantly-bonded states. This occurs without perturbing the crystallinity of the lattice, which heats with a 2 ps time constant. The optical changes are an order-of-magnitude larger than those achievable with silicon and present new routes to manipulate light on an ultrafast timescale without structural changes

An Integrated Approach to Studying Rare Neuromuscular Diseases Using Animal and Human Cell-Based Models.

As sequencing technology improves, the identification of new disease-associated genes and new alleles of known genes is rapidly increasing our understanding of the genetic underpinnings of rare diseases, including neuromuscular diseases. However, precisely because these disorders are rare and often heterogeneous, they are difficult to study in patient populations. In parallel, our ability to engineer the genomes of model organisms, such as mice or rats, has gotten increasingly efficient through techniques such as CRISPR/Cas9 genome editing, allowing the creation of precision human disease models. Suc

Does Atrazine Influence Larval Development and Sexual Differentiation in Xenopus laevis?

Debate and controversy exists concerning the potential for the herbicide atrazine to cause gonadal malformations in developing Xenopus laevis. Following review of the existing literature the U.S. Environmental Protection Agency required a rigorous investigation conducted under standardized procedures. X. laevis tadpoles were exposed to atrazine at concentrations of 0.01, 0.1, 1, 25, or 100 μg/l from day 8 postfertilization (dpf) until completion of metamorphosis or dpf 83, whichever came first. Nearly identical experiments were performed in two independent laboratories: experiment 1 at Wildlife International, Ltd. and experiment 2 at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB). Both experiments employed optimized animal husbandry procedures and environmental conditions in validated flow-through exposure systems. The two experiments demonstrated consistent survival, growth, and development of X. laevis tadpoles, and all measured parameters were within the expected ranges and were comparable in negative control and atrazine-treated groups. Atrazine, at concentrations up to 100 μg/l, had no effect in either experiment on the percentage of males or the incidence of mixed sex as determined by histological evaluation. In contrast, exposure of larval X. laevis to 0.2 μg 17β-estradiol/l as the positive control resulted in gonadal feminization. Instead of an even distribution of male and female phenotypes, percentages of males:females:mixed sex were 19:75:6 and 22:60:18 in experiments 1 and 2, respectively. These studies demonstrate that long-term exposure of larval X. laevis to atrazine at concentrations ranging from 0.01 to 100 μg/l does not affect growth, larval development, or sexual differentiation

HE 0557-4840: Ultra-Metal-Poor and Carbon-Rich

We report the discovery and high-resolution, high-S/N spectroscopic analysis of the ultra-metal-poor red giant HE 0557-4840, which is the third most heavy-element-deficient star currently known. Its atmospheric parameters are T eff = 4900 K, log g = 2.2

Searches for Metal-Poor Stars from the Hamburg/ESO Survey using the CH G-band

We describe a new method to search for metal-poor candidates from the Hamburg/ESO objective-prism survey (HES) based on identifying stars with apparently strong CH G-band strengths for their colors. The hypothesis we exploit is that large over-abundances of carbon are common among metal-poor stars. The selection was made by considering two line indices in the 4300A region, applied directly to the low-resolution prism spectra. This work also extends a previously published method by adding bright sources to the sample. The spectra of these stars suffer from saturation effects, compromising the index calculations and leading to an undersampling of the brighter candidates. Visual inspection and classification of the spectra from the HES plates yielded a list of 5,288 new metal-poor candidates, which are presently being used as targets for medium-resolution spectroscopic follow-up. Estimates of the stellar atmospheric parameters, as well as carbon abundances, are now available for 117 of the first candidates, based on follow-up medium-resolution spectra obtained with the SOAR 4.1m and Gemini 8m telescopes. We demonstrate that our new method improves the metal-poor star fractions found by our pilot study by up to a factor of three in the same magnitude range, as compared with our pilot study based on only one CH G-band index. Our selection scheme obtained roughly a 40% success rate for identification of stars with [Fe/H] < -1.0; the primary contaminant is late-type stars with near solar abundances and, often, emission line cores that filled in the CaII K line on the prism spectrum. Because the selection is based on carbon, we greatly increase the numbers of known CEMP stars from the HES with intermediate metallicities -2.0 < [Fe/H] < -1.0, which previous survey efforts undersampled. There are eight newly discovered stars with [Fe/H] < -3.0 in our sample, including two with [Fe/H] < -3.5.Comment: 18 pages, 13 figures; accepted for publication in A

A comprehensive analysis of the faecal microbiome and metabolome of Strongyloides stercoralis infected volunteers from a non-endemic area.

Data from recent studies support the hypothesis that infections by human gastrointestinal (GI) helminths impact, directly and/or indirectly, on the composition of the host gut microbial flora. However, to the best of our knowledge, these studies have been conducted in helminth-endemic areas with multi-helminth infections and/or in volunteers with underlying gut disorders. Therefore, in this study, we explore the impact of natural mono-infections by the human parasite Strongyloides stercoralis on the faecal microbiota and metabolic profiles of a cohort of human volunteers from a non-endemic area of northern Italy (S+), pre- and post-anthelmintic treatment, and compare the findings with data obtained from a cohort of uninfected controls from the same geographical area (S-). Analyses of bacterial 16S rRNA high-throughput sequencing data revealed increased microbial alpha diversity and decreased beta diversity in the faecal microbial profiles of S+ subjects compared to S-. Furthermore, significant differences in the abundance of several bacterial taxa were observed between samples from S+ and S- subjects, and between S+ samples collected pre- and post-anthelmintic treatment. Faecal metabolite analysis detected marked increases in the abundance of selected amino acids in S+ subjects, and of short chain fatty acids in S- subjects. Overall, our work adds valuable knowledge to current understanding of parasite-microbiota associations and will assist future mechanistic studies aimed to unravel the causality of these relationships