This open access archive contains publications from University of Arizona faculty, researchers and staff, primarily open-access versions of formally published journal articles. The collection includes published articles and final accepted manuscripts submitted by UA faculty under the UA Open Access Policy. The collection also includes books, book chapters, book reviews, presentations, data, and other scholarly materials submitters have chosen to make available in the repository.

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Recent Submissions

  • Memories that Haunt: Layered Landscapes of Historical Trauma on the American Plains

    Montgomery, Lindsay M.; School of Anthropology, University of Arizona (ROUTLEDGE JOURNALS, TAYLOR & FRANCIS LTD, 2018)
    This article explores the impact of American colonization on two American Indian communities, the Cheyenne and Arapaho, through the oral histories and personal narratives of tribal members. These stories were prompted by a series of photographs collected by Jesse H. Bratley—an Indian School teacher working on the Cheyenne-Arapaho reservation at the turn of the century—which were shared with these communities in 2016. Housed at the Denver Museum of Nature and Science, Bratley’s images speak to the subtle ways that photography confirmed and conformed to the assimilationist rhetoric of the United States federal government. When shared with tribal members, Bratley’s images produced a bricolage of memories, evoking layered stories of trauma and persistence. These narratives offer new insights into the relationship between martial violence, the American Indian education system, and the inter-generational historical trauma experienced by these two communities.
  • Effects of a super absorbent polymer on soil properties and plant growth for use in land reclamation

    Abrisham, Elham Sadat; Jafari, Mohammad; Tavili, Ali; Rabii, Ahmad; Zare Chahoki, Mohammad Ali; Zare, Salman; Egan, Todd; Yazdanshenas, Habib; Ghasemian, Davood; Tahmoures, Mohammad; Univ Arizona, Dept Hydrol & Water Resources (TAYLOR & FRANCIS INC, 2018)
    Effects of the super absorbent polymer (SAP) were tested on both the soil attributes and growth properties of Seidlitzia rosmarinus in the arid Emrani region of Iran in a reclamation study. A SAP concentration gradient (SAP 0=SAP 0g dm(-3), SAP 1=SAP 1g dm(-3), and SAP 3=SAP 3g dm(-3) of soil) was coupled with 30- and 60-day irrigation intervals, and results were evaluated after two growing seasons. Results indicate that application of SAP 1 increased available water content up to 68.5% and decreased soil bulk density by 25.5% and soil infiltration rate by 21.5%. SAP enhanced growth indices and seedling establishment rates of S. rosmarinus under drought stress. In addition, the application of SAP 3 can significantly increased soil cation exchange capacity up to 31% compared to the control. This study demonstrated the increased water retention properties of SAP that leads to higher soil water storage capacity for S. rosmarinus seedlings during the first months of out-planting in arid regions. Overall, the used SAP enhanced soil and plant properties, but most assessed parameters did not differ between SAPs 1 and 3. Therefore, the 1g application rate is recommended based on technical as well as economic considerations.
  • Evaluation of dosimetric uncertainty caused by MR geometric distortion in MRI-based liver SBRT treatment planning

    Han, Silu; Yin, Fang-Fang; Cai, Jing; Univ Arizona, Dept Biomed Engn (WILEY, 2019-02-01)
    Purpose MRI-based treatment planning is a promising technique for liver stereotactic-body radiation therapy (SBRT) treatment planning to improve target volume delineation and reduce radiation dose to normal tissues. MR geometric distortion, however, is a source of potential error in MRI-based treatment planning. The aim of this study is to investigate dosimetric uncertainties caused by MRI geometric distortion in MRI-based treatment planning for liver SBRT. Materials and Methods The study was conducted using computer simulations. 3D MR geometric distortion was simulated using measured data in the literature. Planning MR images with distortions were generated by integrating the simulated 3D MR geometric distortion onto planning CT images. MRI-based treatment plans were then generated on the planning MR images with two dose calculation methods: (1) using original CT numbers; and (2) using organ-specific assigned CT numbers. Dosimetric uncertainties of various dose-volume-histogram parameters were determined as their differences between the simulated MRI-based plans and the original clinical CT-based plans for five liver SBRT cases. Results The average simulated distortion for the five liver SBRT cases was 2.77 mm. In the case of using original CT numbers for dose calculation, the average dose uncertainties for target volumes and critical structures were <0.5 Gy, and the average target volume percentage at prescription dose uncertainties was 0.97%. In the case of using assigned CT numbers, the average dose uncertainties for target volumes and critical structures were <1.0 Gy, and the average target volume percentage at prescription dose uncertainties was 2.02%. Conclusions Dosimetric uncertainties caused by MR geometric distortion in MRI-based liver SBRT treatment planning was generally small (<1 Gy) when the distortion is 3 mm.
  • Lymph nodes as barriers to T-cell rejuvenation in aging mice and nonhuman primates

    Thompson, Heather L; Smithey, Megan J; Uhrlaub, Jennifer L; Jeftić, Ilija; Jergović, Mladen; White, Sarah E; Currier, Noreen; Lang, Anna M; Okoye, Afam; Park, Byung; Picker, Louis J; Surh, Charles D; Nikolich-Žugich, Janko; Univ Arizona, Coll Med Tucson, Dept Immunobiol; Univ Arizona, Coll Med Tucson, Arizona Ctr Aging; Univ Arizona, Honors Coll (WILEY, 2019-02-01)
    In youth, thymic involution curtails production of new naive T cells, placing the onus of T-cell maintenance upon secondary lymphoid organs (SLO). This peripheral maintenance preserves the size of the T-cell pool for much of the lifespan, but wanes in the last third of life, leading to a dearth of naive T cells in blood and SLO, and contributing to suboptimal immune defense. Both keratinocyte growth factor (KGF) and sex steroid ablation (SSA) have been shown to transiently increase the size and cellularity of the old thymus. It is less clear whether this increase can improve protection of old animals from infectious challenge. Here, we directly measured the extent to which thymic rejuvenation benefits the peripheral T-cell compartment of old mice and nonhuman primates. Following treatment of old animals with either KGF or SSA, we observed robust rejuvenation of thymic size and cellularity, and, in a reporter mouse model, an increase in recent thymic emigrants (RTE) in the blood. However, few RTE were found in the spleen and even fewer in the lymph nodes, and SSA-treated mice showed no improvement in immune defense against West Nile virus. In parallel, we found increased disorganization and fibrosis in old LN of both mice and nonhuman primates. These results suggest that SLO defects with aging can negate the effects of successful thymic rejuvenation in immune defense.
  • Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code

    Masseron, T.; García-Hernández, D. A.; Mészáros, Sz.; Zamora, O.; Dell’Agli, F.; Allende Prieto, C.; Edvardsson, B.; Shetrone, M.; Plez, B.; Fernández-Trincado, J. G.; Cunha, K.; Jönsson, H.; Geisler, D.; Beers, T. C.; Cohen, R. E.; Univ Arizona, Steward Observ (EDP SCIENCES S A, 2019-02-18)
    Aims. We seek to provide abundances of a large set of light and neutron-capture elements homogeneously analyzed that cover a wide range of metallicity to constrain globular cluster (GC) formation and evolution models. Methods. We analyzed a large sample of 885 GCs giants from the SDSS IV-Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. We used the Cannon results to separate the red giant branch and asymptotic giant branch stars, not only allowing for a refinement of surface gravity from isochrones, but also providing an independent H-band spectroscopic method to distinguish stellar evolutionary status in clusters. We then used the Brussels Automatic Code for Characterizing High accUracy Spectra (BACCHUS) to derive metallicity, microturbulence, macroturbulence, many light-element abundances, and the neutron-capture elements Nd and Ce for the first time from the APOGEE GCs data. Results. Our independent analysis helped us to diagnose issues regarding the standard analysis of the APOGEE DR14 for low-metallicity GC stars. Furthermore, while we confirm most of the known correlations and anticorrelation trends (Na-O, Mg-Al, C-N), we discover that some stars within our most metal-poor clusters show an extreme Mg depletion and some Si enhancement. At the same time, these stars show some relative Al depletion, displaying a turnover in the Mg-Al diagram. These stars suggest that Al has been partially depleted in their progenitors by very hot proton-capture nucleosynthetic processes. Furthermore, we attempted to quantitatively correlate the spread of Al abundances with the global properties of GCs. We find an anticorrelation of the Al spread against clusters metallicity and luminosity, but the data do not allow us to find clear evidence of a dependence of N against metallicity in the more metal-poor clusters. Conclusions. Large and homogeneously analyzed samples from ongoing spectroscopic surveys unveil unseen chemical details for many clusters, including a turnover in the Mg-Al anticorrelation, thus yielding new constrains for GCs formation/evolution models.
  • Impact of region of diagnosis, ethnicity, age, and gender on survival in acute myeloid leukemia (AML)

    Acharya, Utkarsh H.; Halpern, Anna B.; Wu, Qian (Vicky); Voutsinas, Jenna M.; Walter, Roland B.; Yun, Seongseok; Kanaan, Mohammed; Estey, Elihu H.; Univ Arizona, Canc Ctr, Div Hematol Oncol (TAYLOR & FRANCIS INC, 2018)
    Aim: Acute myeloid leukemia (AML) is an aggressive hematopoietic clonal disorder characterized by the increased blasts and poor survival outcome, which is mainly driven by cytogenetic and molecular abnormalities. Here, we investigated the prognostic impact of other demographic parameters on the survival outcomes in AML patients. Method: We reviewed the Surveillance, Epidemiology, and End Result (SEER) database to collect demographic information, including age, diagnosis, gender, race, and geographic region in patients with non-acute promyelocytic leukemia AML, between 2004-2008. The primary end-point of our study was 3-year overall survival (OS), which was estimated by the Kaplan-Meier method and Cox regression model. Results: A total of 13,282 patients were included in our analyses. Increasing age (HR 1.2, p < .0001), male gender (HR 1.05, p = .01), and geographic region of Midwest (HR 1.07, p=.002) were associated with inferior 3-year OS in univariate analysis, and these parameters remained independent prognostic factors in multivariate analyses. Conclusions: AML is a heterogeneous myeloid neoplasm with patient outcomes largely dictated by the cytogenetics and somatic mutations. In our study, additional demographic factors, including advanced age, male gender, and geographic region of AML diagnosis were associated with OS outcome in non-APL AML patients.
  • Feasibility and acceptability of a beverage intervention for Hispanic adults: results from a pilot randomized controlled trial

    Garcia, David O; Morrill, Kristin E; Aceves, Benjamin; Valdez, Luis A; Rabe, Brooke A; Bell, Melanie L; Hakim, Iman A; Martinez, Jessica A; Thomson, Cynthia A; Univ Arizona, Mel & Enid Zuckerman Coll Publ Hlth, Dept Hlth Promot Sci; Univ Arizona, Dept Nutr Sci; Univ Arizona, Mel & Enid Zuckerman Coll Publ Hlth; Univ Arizona, Canc Ctr (CAMBRIDGE UNIV PRESS, 2019-03-01)
    Objective To assess the feasibility and acceptability of a beverage intervention in Hispanic adults. Design Eligible individuals identified as Hispanic, were 18-64 years old and had BMI 30.0-50.0 kg/m(2). Participants were randomized 2:2:1 to one of three beverages: Mediterranean lemonade (ML), green tea (GT) or flavoured water control (FW). After a 2-week washout period, participants were asked to consume 32 oz (946 ml) of study beverage daily for 6 weeks and avoid other sources of tea, citrus, juice and sweetened beverages; water was permissible. Fasting blood samples were collected at baseline and 8 weeks to assess primary and secondary efficacy outcomes. Setting Tucson, AZ, USA. Participants Fifty-two participants were recruited over 6 months; fifty were randomized (twenty-one ML, nineteen GT, ten FW). Study population mean (sd) age 44.6 (sd 10.2) years, BMI 35.9 (4.6) kg/m(2); 78 % female. Results Forty-four (88 %) completed the 8-week assessment. Self-reported adherence was high. No significant change (95 % CI) in total cholesterol (mg/dl) from baseline was shown -1.7 (-14.2, 10.9), -3.9 (-17.2, 9.4) and -13.2 (-30.2, 3.8) for ML, GT and FW, respectively. Mean change in HDL-cholesterol (mg/dl) -2.3 (-5.3, 0.7; ML), -1.0 (-4.2, 2.2; GT), -3.9 (-8.0, 0.2; FW) and LDL-cholesterol (mg/dl) 0.2 (-11.3, 11.8; ML), 0.5 (-11.4, 12.4; GT), -9.8 (-25.0, 5.4; FW) were also non-significant. Fasting glucose (mg/dl) increased significantly by 5.2 (2.6, 7.9; ML) and 3.3 (0.58, 6.4; GT). No significant change in HbA1c was demonstrated. Due to the small sample size, potential confounders and effect modifiers were not investigated. Conclusions Recruitment and retention figures indicate that a larger-scale trial is feasible; however, favourable changes in cardiometabolic biomarkers were not demonstrated.
  • Methods of optimizing and evaluating geometrical lightguides with microstructure mirrors for augmented reality displays

    Xu, Miaomiao; Hua, Hong; Univ Arizona, Coll Opt Sci, 3D Visualizat & Imaging Syst Lab (OPTICAL SOC AMER, 2019-02-18)
    Waveguide or lightguide technology has been widely used in the state-of-the-art, see-through, near-eye displays to reduce system weight and form factor. Although a few of the current products use a geometrical lightguide as an optical combiner, its design and performance assessment methods have been barely discussed. In this paper, by taking into account the factors affecting retinal image quality, we presented novel methods for quantifying and evaluating the optical performances and artifacts of geometrical lightguides based on microstructure mirror arrays, and proposed new merit functions and a novel process for systematic optimization of such lightguides. A lightguide design example implementing the evaluation and optimization methods are demonstrated, and the resulted lightguide is then further utilized as a combiner for the design of a lightweight, glasses-like, see-through, near-eye display. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
  • Non-equilibrium dynamics in the dual-wavelength operation of vertical external-cavity surface-emitting lasers

    Kilen, I.; Hader, J.; Koch, S. W.; Moloney, J. V.; Univ Arizona, Coll Opt Sci; Univ Arizona, Dept Math (OPTICAL SOC AMER, 2019-02-18)
    Microscopic many-body theory coupled with Maxwell's equation is used to study dual-wavelength operation in vertical external-cavity surface-emitting lasers. The intrinsically dynamic nature of coexisting emission wavelengths in semiconductor lasers is associated with characteristic non-equilibrium carrier dynamics, which causes significant deformations of the quasi-equilibrium gain and carrier inversion. Extended numerical simulations are employed to efficiently investigate the parameter space to identify the regime for dual-wavelength operation. Using a frequency selective intracavity etalon, two families of modes are stabilized with dynamical interchange of the strongest emission peaks. For this operation mode, anti-correlated intensity noise is observed in agreement with the experiment. A method using effective frequency selective filtering is suggested for stabilization of genuine dual-wavelength output. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
  • Approximating geodesics via random points

    Davis, Erik; Sethuraman, Sunder; Univ Arizona, Dept Math (INST MATHEMATICAL STATISTICS, 2019-06)
    Given a cost functional F on paths gamma in a domain D subset of R-d, in the form 1 F(gamma) = integral(1)(0) f (gamma(t), gamma(t)) dt , it is of interest to approximate its minimum cost and geodesic paths. Let X-1,...X-n be points drawn independently from D according to a distribution with a density. Form a random geometric graph on the points where X-i and X-j are connected when 0 < vertical bar X-i - X-j vertical bar < epsilon, and the length scale epsilon = epsilon(n) vanishes at a suitable rate. For a general class of functionals F, associated to Finsler and other distances on D, using a probabilistic form of Gamma convergence, we show that the minimum costs and geodesic paths, with respect to types of approximating discrete cost functionals, built from the random geometric graph, converge almost surely in various senses to those corresponding to the continuum cost F, as the number of sample points diverges. In particular, the geodesic path convergence shown appears to be among the first results of its kind.
  • Partial sample average approximation method for chance constrained problems

    Cheng, Jianqiang; Gicquel, Céline; Lisser, Abdel; Univ Arizona, Dept Syst & Ind Engn (SPRINGER HEIDELBERG, 2019-06)
    In this paper, we present a new scheme of a sampling-based method to solve chance constrained programs. The main advantage of our approach is that the approximation problem contains only continuous variables whilst the standard sample average approximation (SAA) formulation contains binary variables. Although our approach generates new chance constraints, we show that such constraints are tractable under certain conditions. Moreover, we prove that the proposed approach has the same convergence properties as the SAA approach. Finally, numerical experiments show that the proposed approach outperforms the SAA approach on a set of tested instances.
  • Knowing the Great Plains Weather: Field Life and Lay Participation on the American Frontier during the Railroad Era

    Vetter, Jeremy; Univ Arizona, Dept Hist (DUKE UNIV PRESS, 2019-06)
    On the US Great Plains frontier in the late nineteenth century, perhaps no area of scientific knowledge was more contested than the weather, which connected with debates around the long-term climate of this semiarid region. Observation of the weather was shared across the divide between scientists and lay people, illustrating an early historical predecessor of enlisting citizen scientists to help in the production of knowledge. Situating this example of lay participation in the larger context of diverse modes of field practice during the railroad era, this article examines the production of weather knowledge on the Great Plains frontier, especially in Kansas, to explore some important stages in the process of coordinating lay observers, including the ground-level practices of organizing lay people into networks for producing knowledge, and marginalizing and discrediting folk knowledge about the weather that was autonomous from the authorized scientific community. The author argues for greater attention to the historical emergence of crucial hierarchical, structured aspects of lay participation in science, inflected by the Chinese concept of shi, in contrast to the recently common focus on flattened, collaborative networks.
  • Arsenic‑induced BRCA1 CpG promoter methylation is associated with the downregulation of ERα and resistance to tamoxifen in MCF7 breast cancer cells and mouse mammary tumor xenografts

    Selmin, Ornella I; Donovan, Micah G; Skovan, Bethany; Paine-Murieta, Gillian D; Romagnolo, Donato F; Univ Arizona, Dept Nutr Sci; Univ Arizona, Canc Biol Grad Interdisciplinary Program (SPANDIDOS PUBL LTD, 2019-03-01)
    A significant percentage (similar to 30%) of estrogen receptor- (ER)-positive tumors become refractory to endocrine therapies; however, the mechanisms responsible for this resistance remain largely unknown. Chronic exposure to arsenic through foods and contaminated water has been linked to an increased incidence of several tumors and long-term health complications. Preclinical and population studies have indicated that arsenic exposure may interfere with endocrine regulation and increase the risk of breast tumorigenesis. In this study, we examined the effects of sodium arsenite (NaAsIII) exposure in ER-positive breast cancer cells in vitro and in mammary tumor xenografts. The results revealed that acute (within 4 days) and long-term (10 days to 7 weeks) in vitro exposure to environmentally relevant doses reduced breast cancer 1 (BRCA1) and ER expression associated with the gain of cyclin D1 (CCND1) and folate receptor 1 (FOLR1), and the loss of methylenetetrahydrofolate reductase (MTHFR) expression. Furthermore, long-term exposure to NaAsIII induced the proliferation and compromised the response of MCF7 cells to tamoxifen (TAM). The in vitro exposure to NaAsIII induced BRCA1 CpG methylation associated with the increased recruitment of DNA methyltransferase 1 (DNMT1) and the loss of RNA polymerase II (PolII) at the BRCA1 gene. Xenografts of NaAsIII-preconditioned MCF7 cells (MCF7NaAs(III)) into the mammary fat pads of nude mice produced a larger tumor volume compared to tumors from control MCF7 cells and were more refractory to TAM in association with the reduced expression of BRCA1 and ER, CpG hypermethylation of estrogen receptor 1 (ESR1) and BRCA1, and the increased expression of FOLR1. These cumulative data support the hypothesis that exposure to As-III may contribute to reducing the efficacy of endocrine therapy against ER-positive breast tumors by hampering the expression of ER and BRCA1 via CpG methylation, respectively of ESR1 and BRCA1.
  • Seasonal Prediction of North Atlantic Accumulated Cyclone Energy and Major Hurricane Activity

    Davis, Kyle; Zeng, Xubin; Univ Arizona, Dept Hydrol & Atmospher Sci (AMER METEOROLOGICAL SOC, 2019-02)
    Building upon our previous seasonal hurricane prediction model, here we develop two statistical models to predict the number of major hurricanes (MHs) and accumulated cyclone energy (ACE) in the North Atlantic basin using monthly data from March to May for an early June forecast. The input data include zonal pseudo-wind stress to the 3/2 power, sea surface temperature in the North Atlantic, and, depending on the magnitude of the Atlantic multidecadal oscillation index, the multivariate ENSO index. From 1968 to 2017, these models have a mean absolute error of 0.96 storms for MHs and 30 units for ACE. When tested over an independent period from 1958 to 1967, the models show a 22% improvement for MHs and 16% for ACE over a no-skill metric based on a 5-yr running average. Both the MH and ACE results show consistent improvements over those produced by three other centers using statistical-dynamical hybrid models and a 5-yr running average prediction over the period 2000-17 for MHs (2003-17 for ACE) in a simulated real-time prediction. These improvements vary from 25% to 37% for MHs and from 15% to 37% for ACE. While most forecasting centers called for a slightly above-average hurricane season in May/June 2017, our models predicted in June 2017 a very active season, in much better agreement with observations.
  • The Massive and Distant Clusters of WISE Survey. I. Survey Overview and a Catalog of >2000 Galaxy Clusters at z ≃ 1

    Gonzalez, Anthony H.; Gettings, Daniel P.; Brodwin, Mark; Eisenhardt, Peter R. M.; Stanford, S. A.; Wylezalek, Dominika; Decker, Bandon; Marrone, Daniel P.; Moravec, Emily; O’Donnell, Christine; Stalder, Brian; Stern, Daniel; Abdulla, Zubair; Brown, Gillen; Carlstrom, John; Chambers, Kenneth C.; Hayden, Brian; Lin, Yen-Ting; Magnier, Eugene; Masci, Frank J.; Mantz, Adam B.; McDonald, Michael; Mo, Wenli; Perlmutter, Saul; Wright, Edward L.; Zeimann, Gregory R.; Univ Arizona, Steward Observ (IOP PUBLISHING LTD, 2019-02)
    We present the Massive and Distant Clusters of WISE Survey (MaDCoWS), a search for galaxy clusters at 0.7 less than or similar to z less than or similar to 1.5 based upon data from the Wide-field Infrared Survey Explorer (WISE) mission. MaDCoWS is the first cluster survey capable of discovering massive clusters at these redshifts over the full extragalactic sky. The search is divided into two regions-the region of the extragalactic sky covered by Pan-STARRS (delta > - 30 degrees) and the remainder of the southern extragalactic sky at delta < -30 degrees for which shallower optical data from the SuperCOSMOS Sky Survey is available. In this paper, we describe the search algorithm, characterize the sample, and present the first MaDCoWS data release-catalogs of the 2433 highest amplitude detections in the WISE-Pan-STARRS region and the 250 highest amplitude detections in the WISE-SuperCOSMOS region. A total of 1723 of the detections from the WISE-Pan-STARRS sample have also been observed with the Spitzer Space Telescope, providing photometric redshifts and richnesses, and an additional 64 detections within the WISE-SuperCOSMOS region also have photometric redshifts and richnesses. Spectroscopic redshifts for 38 MaDCoWS clusters with IRAC photometry demonstrate that the photometric redshifts have an uncertainty of sigma(z)/(1 + z) similar or equal to 0.036. Combining the richness measurements with Sunyaev-Zel'dovich observations of MaDCoWS clusters, we also present a preliminary mass-richness relation that can be used to infer the approximate mass distribution of the full sample. The estimated median mass for the WISE-Pan-STARRS catalog is M-500 = 1.6(-0.8)(+0.7) x 10(14) M-circle dot, with the Sunyaev-Zel'dovich data confirming that we detect clusters with masses up to M-500 similar to 5 x 10(14) M-circle dot (M-200 similar to 10(15) M-circle dot).
  • Electron Monte Carlo simulations of nanoporous Si thin films—The influence of pore-edge charges

    Hao, Qing; Xiao, Yue; Univ Arizona, Dept Aerosp & Mech Engn (AMER INST PHYSICS, 2019-02-14)
    Electron transport within nanostructures can be important for various engineering applications, such as thermoelectrics and nanoelectronics. In theoretical studies, electron Monte Carlo simulations are widely used as an alternative approach to solving the electron Boltzmann transport equation, where the energy-dependent electron scattering, exact structure shape, and detailed electric field distribution can be fully incorporated. In this work, such electron Monte Carlo simulations are employed to predict the electrical conductivity of periodic nanoporous Si films that have been widely studied for thermoelectric applications. The focus is on the influence of pore-edge charges on the electron transport. The results are further compared to our previous analytical modeling [Hao et al., J. Appl. Phys. 121, 094308 (2017)], where the pore-edge electric field has its own scattering rate to be added to the scattering rates of other mechanisms. Published under license by AIP Publishing.
  • Differential colorimetry measurements of fluctuation growth in nanofilms exposed to large surface thermal gradients

    Fiedler, Kevin R.; McLeod, Euan; Troian, Sandra M.; Univ Arizona, Coll Opt Sci (AMER INST PHYSICS, 2019-02-14)
    Slender liquid nanofilms exposed to large surface thermal gradients are known to undergo thickness fluctuations, which rapidly self-organize into arrays of nanoprotrusions with a separation distance of tens of microns. We previously reported good agreement between measurements of the characteristic spacing and the wavelength of the most unstable mode predicted by a linear stability analysis based on a long wavelength thermocapillary model. Here, we focus on differential colorimetry measurements to quantify early time out-of-plane growth of protrusions for peak heights spanning 20 to 200 nm. Analysis of peak heights based on shape reconstruction reveals robust exponential growth. Good quantitative agreement of the growth rates with the thermocapillary model is obtained using a single fit constant to account for material parameters of nanofilms that could not be measured directly. These findings lend further support to the conjecture that the array protrusions uncovered almost two decades ago likely stem from a linear instability, whose growth rate is controlled by thermocapillary forces counterbalanced by capillary forces. Published under license by AIP Publishing.
  • Non-averaged regularized formulations as an alternative to semi-analytical orbit propagation methods

    Amato, Davide; Bombardelli, Claudio; Baù, Giulio; Morand, Vincent; Rosengren, Aaron J.; Univ Arizona, Dept Aerosp & Mech Engn (SPRINGER, 2019-05)
    This paper is concerned with the comparison of semi-analytical and non-averaged propagation methods for Earth satellite orbits. We analyze the total integration error for semi-analytical methods and propose a novel decomposition into dynamical, model truncation, short-periodic, and numerical error components. The first three are attributable to distinct approximations required by the method of averaging, which fundamentally limit the attainable accuracy. In contrast, numerical error, the only component present in non-averaged methods, can be significantly mitigated by employing adaptive numerical algorithms and regularized formulations of the equations of motion. We present a collection of non-averaged methods based on the integration of existing regularized formulations of the equations of motion through an adaptive solver. We implemented the collection in the orbit propagation code THALASSA, which we make publicly available, and we compared the non-averaged methods with the semi-analytical method implemented in the orbit propagation tool STELA through numerical tests involving long-term propagations (on the order of decades) of LEO, GTO, and high-altitude HEO orbits. For the test cases considered, regularized non-averaged methods were found to be up to two times slower than semi-analytical for the LEO orbit, to have comparable speed for the GTO, and to be ten times as fast for the HEO (for the same accuracy). We show for the first time that efficient implementations of non-averaged regularized formulations of the equations of motion, and especially of non-singular element methods, are attractive candidates for the long-term study of high-altitude and highly elliptical Earth satellite orbits.
  • A social identity threat perspective on being the target of generosity from a higher status other

    Sandstrom, Gillian M.; Schmader, Toni; Croft, Alyssa; Kwok, Navio; Univ Arizona (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2019-05)
    Both giving and receiving money have emotional benefits, but when gifts of value are made in the context of socioeconomic differences, there might also be emotional costs. Four studies (and an internal meta-analysis) tested the idea that receiving a generous gift from someone higher in perceived socioeconomic status (SES) signals social identity threat. In Study 1 (N = 218), participants on average, but especially those with relatively lower SES, reported experiencing more self-conscious negative affect when receiving a generous amount of money (vs. an even split) from a higher status giver in a dictator game. This effect was mediated by feeling pitied by the giver. Studies 2 (N = 331) and 3 (N = 426) revealed similar effects with recalled real-world experiences of receiving a generous gift from higher SES givers. Studies 3 and 4 (N = 142) revealed evidence for serial mediation, with lower relative SES predicting status awareness, status awareness predicting attributions of pity, and attributions of pity in turn predicting self-conscious negative affect. Effects were not significantly moderated by needing or requesting the money, suggesting that acts of generosity across the status divide readily signal social devaluation for those with lower perceived status. Findings have practical and conceptual implications for prosocial giving in a system of social and economic inequality.
  • The impact of physical proximity and attachment working models on cardiovascular reactivity: Comparing mental activation and romantic partner presence

    Bourassa, Kyle J.; Ruiz, John M.; Sbarra, David A.; Univ Arizona, Dept Psychol (WILEY, 2019-05)
    Close relationships, especially high-quality romantic relationships, are consistently associated with positive physical health outcomes. Attenuated cardiovascular reactivity is one physiological mechanism implicated in explaining these effects. Drawing on attachment and social baseline theories, this experimental study evaluated two potential affiliative cues as mechanisms through which romantic relationships may attenuate cardiovascular reactivity to a laboratory-based stressor. Prior to a cold pressor task, 102 participants were randomly assigned to either have their partner physically present, call upon a mental representation of their partner, or think about their day during the stressor. Consistent with our preregistered hypotheses, participants in both the partner present and mental activation conditions had significantly lower blood pressure (BP) reactivity during the cold pressor task compared to control participants for both systolic (d = -0.54) and diastolic BP (d = -0.53), but no significant differences emerged for heart rate or heart rate variability. Although participants in the partner present and mental activation conditions had similar BP reactivity to the cold pressor task, those in the partner present condition reported significantly less pain as a result of the task. The difference in BP reactivity by condition was moderatedBP reactivity was greater for people with lower self-reported relationship satisfaction. The results suggest that accessing the mental representation of a romantic partner and a partner's presence each buffer against exaggerated acute stress responses to a similar degree. Romantic relationships are associated with positive physical health, and cardiovascular reactivity (CVR) is one mechanism that may explain these effects. The current study provided evidence that having a partner present or imagining a partner's support resulted in significantly lower systolic and diastolic blood pressure compared to people thinking about their day. Results suggest that accessing the mental representation of a romantic partner and a partner's presence reduces CVR to stressful tasks in a similar way.

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