9,627 research outputs found

    A nonparametric characteristics model of the demand for milk

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    Characteristics models in demand analysis capture the idea that people value goods not For the commodity itself but for the characteristics (or attributes) or embodied in the good. For example, agents may care about the fat content and the taste of different sorts of milk but not the actual type of milk. When we have fewer characteristics than types of good the theory imposes restrictions on observables. We present a revealed preference characteristics model analysis of the demand for milk in Denmark

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    My ceramic sculptures are abstracted portraits of friends and family. They reveal no clues about the age, the gender, or the physical identity of the subjects. Instead, they are abstracted character traits rendered in clay with a biomorphic sensibility. I translate a particular personality trait of a friend or family member into a tangible object and arrange those pieces referencing botanical forms. I tend to choose the negative traits that cause friction in our relationship. My work is a way of acknowledging and dealing with the struggle these traits have caused. I structure my pieces as a floral arrangement to transfer an otherwise unfavorable experience into a positive one

    Short-term Response of Holcus lanatus L. (Common Velvetgrass) to Chemical and Manual Control at Yosemite National Park, USA

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    One of the highest priority invasive species at both Yosemite and Sequoia and Kings Canyon national parks is Holcus lanatus L. (common velvetgrass), a perennial bunchgrass that invades mid-elevation montane meadows. Despite velvetgrass being a high priority species, there is little information available on control techniques. The goal of this project was to evaluate the short-term response of a single application of common chemical and manual velvetgrass control techniques. The study was conducted at three montane sites in Yosemite National Park. Glyphosate spotspray treatments were applied at 0.5, 1.0, 1.5, and 2.0% concentrations, and compared with hand pulling to evaluate effects on cover of common velvetgrass, cover of other plant species, and community species richness. Posttreatment year 1 cover of common velvetgrass was 12.1% 6 1.6 in control plots, 6.3% 6 1.5 averaged over the four chemical treatments (all chemical treatments performed similarly), and 13.6% 6 1.7 for handpulled plots. This represents an approximately 50% reduction in common velvetgrass cover in chemically- treated plots recoded posttreatment year 1 and no statistically significant reduction in hand pulled plots compared with controls. However, there was no treatment effect in posttreatment year 2, and all herbicide application rates performed similarly. In addition, there were no significant treatment effects on nontarget species or species richness. These results suggest that for this level of infestation and habitat type, (1) one year of hand pulling is not an effective control method and (2) glyphosate provides some level of control in the short-term without impact to nontarget plant species, but the effect is temporary as a single year of glyphosate treatment is ineffective over a twoyear period

    Teaching “The Essay” as a Pathway to Research and First-Year Writing

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    This session will guide attendees through teaching “the essay,” as a flexible, adaptable, customizable form. Using ignorance as a starting place, students develop research strategies that focus on their own gaps in knowledge—as opposed to relying on pre-existing certainty, bias, or opinions. By working through the essay-writing process as an exploration, students develop “high-quality ignorance,” which allows for deeper authenticity. Complex essays allow students to combine multiple rhetorical strategies—narrative, interview, immersion, argument—creating customized essays, instead of following a traditional five-paragraph format. Along the path to the final essay, they alternate writing and research, showing their inextricable connection

    Profiles and Predictors of Dating Violence Among Sexual and Gender Minority Adolescents

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    Purpose: Sexual and gender minority adolescents report higher levels of dating violence compared with their heterosexual and cisgender peers. The objectives of the present study were to (1) identify latent profiles of dating violence; (2) examine if sexual and gender minority adolescents were particularly vulnerable to certain profiles of dating violence; and (3) explore how experiences of peer victimization, discrimination, and parental maltreatment explained this greater vulnerability. Methods: High school students in Grades 9 and 11 from the 2016 Minnesota Student Survey (N = 87,532; mean age = 15.29 years, SD = 1.23) were asked about their sexual and gender identities, their gender nonconformity, their experiences of verbal, physical, and sexual dating violence victimization and perpetration, as well their experiences of childhood maltreatment, peer victimization, and gender-based and sexual minority status–based discrimination. Results: Multinomial logistic regression analysis in a three-step latent class analysis procedure suggested five profiles of dating violence victimization and perpetration across the entire sample. Sexual and gender minority adolescents were generally more likely to be in classes high in dating violence victimization, perpetration, or both, compared with their heterosexual and cisgender peers. Gender nonconformity was also associated with greater risk for being in high dating violence classes. These differences, however, were generally nonsignificant when the social stressors of childhood maltreatment, peer victimization, and experiences of discrimination were accounted for. Conclusions: Although findings suggested greater vulnerability for dating violence among sexual and gender minority adolescents, they underscore the importance of how minority stressors generally accounted for this greater vulnerability for dating violence

    Probing the catalytic activity of sulfate-derived Pristine and post-treated porous TiO2(101) anatase mesocrystals by the oxidative desulfurization of dibenzothiophenes

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    Mesocrystals (basically nanostructures showing alignment of nanocrystals well beyond crystal size) are attracting considerable attention for modeling and optimization of functionalities. However, for surface-driven applications (heterogeneous catalysis), only those mesocrystals with excellent textural properties are expected to fulfill their potential. This is especially true for oxidative desulfuration of dibenzothiophenes (hard to desulfurize organosulfur compounds found in fossil fuels). Here, we probe the catalytic activity of anatases for the oxidative desulfuration of dibenzothiophenes under atmospheric pressure and mild temperatures. Specifically, for this study, we have taken advantage of the high stability of the (101) anatase surface to obtain a variety of uniform colloidal mesocrystals (approximately 50 nm) with adequate orientational order and good textural properties (pores around 3-4 nm and surface areas around 200 m2/g). Ultimately, this stability has allowed us to compare the catalytic activity of anatases that expose a high number of aligned single crystal-like surfaces while differing in controllable surface characteristics. Thus, we have established that the type of tetrahedral coordination observed in these anatase mesocrystals is not essential for oxidative desulfuration and that both elimination of sulfates and good textural properties significantly improve the catalytic activity. Furthermore, the most active mesocrystals have been used to model the catalytic reaction in three-(oil-solvent-catalyst) and two-phase (solvent-catalyst) systems. Thus, we have been able to observe that the transfer of DBT from the oil to the solvent phase partially limits the oxidative process and to estimate an apparent activation energy for the oxidative desulfuration reaction of approximately 40 kJ/mol in the two-phase system to avoid mass transfer limitations. Our results clearly establish that (101) anatase mesocrystals with excellent textural properties show adequate stability to withstand several post-treatments without losing their initial mesocrystalline character and therefore could serve as models for catalytic processes different from the one studied here.Fil: Rivoira, Lorena Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; ArgentinaFil: Martinez, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación en Nanociencia y Nanotecnología; ArgentinaFil: Falcon, Horacio. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación en Nanociencia y Nanotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Beltramone, Andrea Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación en Nanociencia y Nanotecnología; ArgentinaFil: Campos-Martin, Jose M.. Consejo Superior de Investigaciones Científicas; EspañaFil: García Fierro, José Luis. Instituto de Catalisis y Petroleoquimica-csic; EspañaFil: Tartaj, Pedro. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; Españ

    Understanding the Role Thin Film Interfaces Play in Solar Cell Performance and Stability

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    As more efficient and cost-effective photovoltaic (PV) architectures are developed, solar becomes an ever more competitive and viable replacement for fossil fuels. Full grid electrification necessitates the development of efficient, reliable, cost-effective technologies - and there is room for many different kinds of PV in this expanding market. The practical challenges and constraints of terawatt PV production have brought scalability and durability into sharp scientific focus. From a materials perspective, there are commonalities in the materials questions and challenges across different PV technologies. Whereas most PV technology is referred to by the absorber layer - e.g. silicon, or perovskite solar cells, other layers in the device are equally important to performance and durability. These layers are often composed of metal oxides, and are common across device technologies - for example, interfacial layers (such as charge transport layers, CTLs), and transparent conducting oxides (TCOs) used as electrodes.This work addresses materials oxide characterization and its relationship to materials and device performance and degradation across PV technologies. Among the most promising PVs to date are two technologies with different levels of thin film incorporation: silicon heterojunction (SHJ) and perovskite PV. SHJ cells are part of the industrial Si PV portfolio, and perovskite cells are starting to be commercially produced after a decade of intensive research. However, there are well-known stability and cost limitations associated with each technology. Understanding the thin film materials science in these devices, and using that understanding to enhance device performance and stability is key to more reliable and cost effective electricity production. Under practical aging conditions, careful materials-level characterization is required to understand the degradation mechanisms of these materials and the complex effects of aging on the multilayer system. This work details the effects of practical degradation challenges such as damp heat (DH) exposure and encapsulation degradation on the stability of inorganic metal oxides in both the SHJ and perovskite thin film photovoltaic architectures. For perovskite devices, MAPbI3 films were deposited by spin coating onto a range of substrates and CTLs; substrates of glass and indium tin oxide (ITO) were paired with metal oxides (MOs) including MoOX, NiOX, and ZnO. SE and SEM were used to characterize the surface and bulk properties of the perovskite films. Results demonstrate that the underlying layers affect the rate of absorber degradation when exposed to heat and moisture. Unencapsulated SHJ cells (a subset of which were exposed to low concentrations of acetic acid under an applied voltage) were aged under DH 85°C/85% relative humidity conditions. The contact-ITO interface was examined via optical profilometry (OP), spectroscopic ellipsometry (SE), and scanning electron microscopy (SEM). SHJ cells have interfaces unique to their architecture, namely the c-Si/a-Si:H and a-Si:H/ITO interfaces at the top of the device. Examining the degradation of unencapsulated SHJ cells and comparing those results to historical degradation profiles of encapsulated SHJ cells in addition to the simulated effects of acetic acid exposure will help to decouple the effects of encapsulation on ITO stability in this architecture. It is well known that ethylene vinyl acetate (EVA) encapsulation degrades and produces acetic acid upon exposure to heat and humidity. When under an applied voltage, even small concentrations of acetic acid can quickly corrode the contact-ITO interface, leading to decreases in efficiency and increases in series resistance of the cell. Here, XPS was used to monitor the changes in the front contact of the SHJ cells during DH and acetic acid exposure. Changes to the materials will be correlated to changes in device performance under the same aging conditions

    Functional Brain Connectivity and Inhibitory Control in Older Adults: A Preliminary Study

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    According to the inhibition deficit hypothesis, the ability to inhibit unwanted or irrelevant thoughts and behaviors decreases with age, which can have a significant impact on cognitive and emotional processing. However, studies examining inhibition and age have shown mixed results, with some studies finding a decrease in inhibitory control as individuals age, while others have found no relationship. The goal of this proof-of-concept study was to examine the underlying neural mechanisms that may explain why some older adults are better than others at inhibitory control by investigating the relationship between resting-state functional connectivity (rsFC) of the salience network, a network critical for detecting and focusing attention toward relevant stimuli while ignoring irrelevant information in the environment, and a behavioral measure of inhibitory control (Stroop Task interference score) in a sample of 65 healthy older individuals (ages 65+). Results revealed no direct effect of age on Stroop performance; however, there was an indirect effect of age on Stroop performance through rsFC. These results suggest that rsFC of the salience network may be an important factor to consider when it comes to understanding individual differences in inhibitory control behavior among older adults
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