Fourteen research flights were conducted in the Pacific Dust Experiment (PACDEX) during April and May 2007 to sample pollution and dust outbreaks from east Asia as they traveled across the northern ...Pacific Ocean into North America and interacted with maritime storms. Significant concentrations of black carbon (BC, consisting of soot and other light‐absorbing particles measured with a soot photometer 2 instrument) and dust were observed both in the west and east Pacific Ocean from Asian plumes of dust and pollution. BC particles were observed through much of the troposphere, but the major finding is that the percentage of these particles compared with the total number of accumulation mode particles increased significantly (by a factor of 2–4) with increasing altitude, with peak values occurring between 5 and 10 km. Dust plumes had only a small impact on total cloud condensation nuclei at the sampling supersaturations but did exhibit high concentrations of ice nuclei (IN). IN concentrations in dust plumes exceeded typical tropospheric values by 4–20 times and were similar to previous studies in the Saharan aerosol layer when differences in the number concentrations of dust are accounted for. Enhanced IN concentrations were found in the upper troposphere off the coast of North America, providing a first direct validation of the transport of high‐IN‐containing dust layers near the tropopause entering the North American continent from distant sources. A source‐specific chemical transport model was used to predict dust and other aerosols during PACDEX. The model was able to predict several features of the in situ observations, including the general altitudes where BC was found and a peak in the ratio of BC to sulfate between 5 and 10 km.
The chemical link between isoprene and formaldehyde (HCHO) is a strong, nonlinear function of NOx (i.e., NO + NO2). This relationship is a linchpin for top-down isoprene emission inventory ...verification from orbital HCHO column observations. It is also a benchmark for overall photochemical mechanism performance with regard to VOC oxidation. Using a comprehensive suite of airborne in situ observations over the southeast US, we quantify HCHO production across the urban–rural spectrum. Analysis of isoprene and its major first-generation oxidation products allows us to define both a “prompt” yield of HCHO (molecules of HCHO produced per molecule of freshly emitted isoprene) and the background HCHO mixing ratio (from oxidation of longer-lived hydrocarbons). Over the range of observed NOx values (roughly 0.1–2 ppbv), the prompt yield increases by a factor of 3 (from 0.3 to 0.9 ppbv ppbv-1), while background HCHO increases by a factor of 2 (from 1.6 to 3.3 ppbv). We apply the same method to evaluate the performance of both a global chemical transport model (AM3) and a measurement-constrained 0-D steady-state box model. Both models reproduce the NOx dependence of the prompt HCHO yield, illustrating that models with updated isoprene oxidation mechanisms can adequately capture the link between HCHO and recent isoprene emissions. On the other hand, both models underestimate background HCHO mixing ratios, suggesting missing HCHO precursors, inadequate representation of later-generation isoprene degradation and/or underestimated hydroxyl radical concentrations. Detailed process rates from the box model simulation demonstrate a 3-fold increase in HCHO production across the range of observed NOx values, driven by a 100 % increase in OH and a 40 % increase in branching of organic peroxy radical reactions to produce HCHO.
Spanish learners engaged in two-way interaction gap tasks where, through social interaction, they identified and defined low-frequency vocabulary. Participants (referred to as actors to differentiate ...them from task partners) completed two such tasks. Each time, they collaborated with different partners of varying degrees of Spanish proficiency and linguistic background, either an L2 learner or a heritage speaker (HS). The purpose of the study was thus to shed light on if and how features of the collaborating partners in mixed (HS–L2) and matched (L2–L2; HS–HS) partnerships impacted vocabulary learning. Through a mixed methods analysis of the data (perception measures and qualitative responses, plus pre- and post-vocabulary tests), it was deduced that learners’ language proficiency level alone was not associated with differences in vocabulary gains. Rather, the nature of the partnerships among learners was more salient. In particular, learners in mixed partnerships had greater gains than those in matched partnerships. In addition, actors’ perceptions of the experience of working with their partner had no discernible effect on vocabulary, except for HSs who increased less when working with partners’ whose linguistic abilities they had rated as low. Pedagogical implications address learners’ social interaction in mixed language classrooms.
Language textbooks present cultural content in a typically homogeneous fashion, thereby ignoring inherent diversity both within and between cultures and reinforcing monodimensional views. ...Consequently, instructors must find ways to facilitate students’ critical engagement with and reflection on cultural representations in order to provide them with the space to more critically examine cultural heterogeneity, which is essential for effective and appropriate interactions in real settings. The current study describes novel cultural modules built around the PBS documentary series Latino Americans to be integrated into a Spanish 1 course. The modules introduced students to historical events regarding the long‐standing Latino presence in the United States and Latinos’ points of view, perceptions, and values. To ascertain the effectiveness of the modules, students’ development of intercultural sensitivity was assessed via surveys and class observations. The analysis was framed using M. Bennett's model of intercultural development. Results demonstrated students’ shifts in both ethnocentric and ethnorelative perceptions of cultural difference. Regarding ethnorelative perspectives, results suggest discrete improvements particularly as seen in the prevalence of data that support a shift toward acceptance.
The Challenge
Developing intercultural sensitivity generally requires exposure to and experience in navigating cultural difference. Is it possible to achieve this kind of development in the context of an introductory language course? What impact might the integration of culture modules based on the contributions of Latinos to U.S. history have on students’ learning outcomes?
Individuals and groups of 2, 3, 4, or 5 people solved 2 letters-to-numbers problems that required participants, on each trial, to identify the coding of 10 letters to 10 numbers by proposing an ...equation in letters, receiving the answer in letters, proposing a hypothesis, and receiving feedback on the correctness of the hypothesis. Groups of 3, 4, and 5 people proposed more complex equations and had fewer trials to solution than the best of an equivalent number of individuals. Groups of 3, 4, and 5 people had fewer trials to solution than 2-person groups but did not differ from each other. These results suggest that 3-person groups are necessary and sufficient to perform better than the best individuals on highly intellective problems.
Recently, there has been increasing attention to and importance placed on qualified health claims both on industry and policy fronts. All parties have been advocating for broader qualified health ...claims to improve the information that consumers possess so that they can make more informed decisions. This research attempts to inform this discussion by examining consumer responses to qualified health claims and the scientific certainty that supports the health claim. The results of this study have important implications for consumers who are prospective buyers of these products as well as policymakers and industry members.
As part of an overall 'biodiversity crisis', many amphibian populations are in decline throughout the world. Numerous factors have contributed to these declines, including habitat destruction, ...pathogens, increasing ultraviolet (UV) radiation, introduced non-native species and contaminants. In this paper we review the contribution of increasing UV radiation and environmental contamination to the global decline of amphibian populations. Both UV radiation and environmental contaminants can affect amphibians at all life stages. Exposure to UV radiation and to certain contaminants can kill amphibians and induce sublethal affects in embryos, larvae and adults. Moreover, UV radiation and contaminants may interact with one another synergistically. Synergistic interactions of UV radiation with contaminants can enhance the detrimental effects of the contaminant and UV radiation.
To increase our understanding of the events that lead to HIV-1 genome packaging, we examined the dynamics of viral RNA and Gag-RNA interactions near the plasma membrane by using total internal ...reflection fluorescence microscopy. We labeled HIV-1 RNA with a photoconvertible Eos protein via an RNA-binding protein that recognizes stem-loop sequences engineered into the viral genome. Near-UV light exposure causes an irreversible structural change in Eos and alters its emitted fluorescence from green to red. We studied the dynamics of HIV-1 RNA by photoconverting Eos near the plasma membrane, and we monitored the population of photoconverted red-Eos-labeled RNA signals over time. We found that in the absence of Gag, most of the HIV-1 RNAs stayed near the plasma membrane transiently, for a few minutes. The presence of Gag significantly increased the time that RNAs stayed near the plasma membrane: most of the RNAs were still detected after 30 min. We then quantified the proportion of HIV-1 RNAs near the plasma membrane that were packaged into assembling viral complexes. By tagging Gag with blue fluorescent protein, we observed that only a portion, ∼13 to 34%, of the HIV-1 RNAs that reached the membrane were recruited into assembling particles in an hour, and the frequency of HIV-1 RNA packaging varied with the Gag expression level. Our studies reveal the HIV-1 RNA dynamics on the plasma membrane and the efficiency of RNA recruitment and provide insights into the events leading to the generation of infectious HIV-1 virions.
Nascent HIV-1 particles assemble on plasma membranes. During the assembly process, HIV-1 RNA genomes must be encapsidated into viral complexes to generate infectious particles. To gain insights into the RNA packaging and virus assembly mechanisms, we labeled and monitored the HIV-1 RNA signals near the plasma membrane. Our results showed that most of the HIV-1 RNAs stayed near the plasma membrane for only a few minutes in the absence of Gag, whereas most HIV-1 RNAs stayed at the plasma membrane for 15 to 60 min in the presence of Gag. Our results also demonstrated that only a small proportion of the HIV-1 RNAs, approximately 1/10 to 1/3 of the RNAs that reached the plasma membrane, was incorporated into viral protein complexes. These studies determined the dynamics of HIV-1 RNA on the plasma membrane and obtained temporal information on RNA-Gag interactions that lead to RNA encapsidation.
It has been observed that language learners struggle to gain access to the metaphorical structures that are part of the target language and culture. In this study, six Spanish L2 learners and nine ...Spanish heritage speakers from the United States completed a study abroad program in Spain in which language instruction was supplemented with a module on the subject of metaphors. This article seeks to describe this module and present learners’ perceptions of its implementation and of the learnings resulting from it, as reflected in learners’ weekly reflections and exit questionnaire. The analysis of these data indicated that most participants became aware of metaphors in every-day language. However, they were not fully able to produce metaphors themselves. Pedagogical implications of this experience include differentiated metaphor instruction for heritage speakers and L2 learners, and fostering not just metaphor awareness but competence.
By comparing photoemission spectroscopy with a nonperturbative dynamical mean field theory extension to many-body ab initio calculations, we show in the prominent case of pentacene crystals that an ...excellent agreement with experiment for the bandwidth, dispersion, and lifetime of the hole carrier bands can be achieved in organic semiconductors, provided that one properly accounts for the coupling to molecular vibrational modes and the presence of disorder. Our findings rationalize the growing experimental evidence that even the best band structure theories based on a many-body treatment of electronic interactions cannot reproduce the experimental photoemission data in this important class of materials.
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