Now showing items 5641-5660 of 13761

    • Investigating Overdensities around z > 6 Galaxies through ALMA Observations of [C ii]

      Miller, Tim B.; Chapman, Scott C.; Hayward, Christopher C.; Behroozi, Peter S.; Bradford, Matt; Willott, Chris J.; Wagg, Jeff; Univ Arizona, Dept Astron & Steward Observ (IOP PUBLISHING LTD, 2020-01-29)
      We present a search for companion [C ii] emitters to known luminous sources at 6 < z < 6.5 in deep, archival ALMA observations. The observations are deep enough to detect sources with z similar to 6. We identify three new robust line detections from a blind search of five deep fields centered on ultraluminous infrared galaxies and QSOs. We calculate the volume density of companions and find a relative overdensity of 6(-3)(+4) when comparing to current observational constraints and theoretical predictions, respectively. These results suggest that the central sources may be highly biased tracers of mass in the early universe. We find these companion lines to have comparable properties to other known galaxies at the same epoch. All companions lie less than 650 km s(-1) and between 25 and 60 kpc (projected) from their central source. To place these discoveries in context, we employ a mock galaxy catalog to estimate the luminosity function for [C ii] during reionization and compare to our observations. The simulations support this result by showing a similar level of elevated counts found around such luminous [C ii] sources.
    • Investigating Public Facility Characteristics from a Spatial Interaction Perspective: A Case Study of Beijing Hospitals Using Taxi Data

      Kong, Xiaoqing; Liu, Yu; Wang, Yuxia; Tong, Daoqin; Zhang, Jing; Univ Arizona, Sch Geog & Dev (MDPI AG, 2017-02-06)
      Services provided by public facilities are essential to people's lives and are closely associated with human mobility. Traditionally, public facility access characteristics, such as accessibility, equity issues and service areas, are investigated mainly based on static data (census data, travel surveys and particular records, such as medical records). Currently, the advent of big data offers an unprecedented opportunity to obtain large-scale human mobility data, which can be used to study the characteristics of public facilities from the spatial interaction perspective. Intuitively, spatial interaction characteristics and service areas of different types and sizes of public facilities are different, but how different remains an open question, so we, in turn, examine this question. Based on spatial interaction, we classify public facilities and explore the differences in facilities. In the research, based on spatial interaction extracted from taxi data, we introduce an unsupervised classification method to classify 78 hospitals in 6 districts of Beijing, and the results better reflect the type of hospital. The findings are of great significance for optimizing the spatial configuration of medical facilities or other types of public facilities, allocating public resources reasonably and relieving traffic pressure.
    • Investigating reindeer pastoralism and exploitation of high mountain zones in northern Mongolia through ice patch archaeology

      Taylor, William; Clark, Julia K; Reichhardt, Björn; Hodgins, Gregory W L; Bayarsaikhan, Jamsranjav; Batchuluun, Oyundelger; Whitworth, Jocelyn; Nansalmaa, Myagmar; Lee, Craig M; Dixon, E James; et al. (PUBLIC LIBRARY SCIENCE, 2019-11-20)
      In interior Eurasia, high mountain zones are crucial to pastoral subsistence, providing seasonally productive pastures and abundant wild resources. In some areas of northern Mongolia, mountainous tundra zones also support a low-latitude population of domestic reindeer herders-a lifestyle whose origins are poorly characterized in the archaeological record of early Mongolia. Traditionally, reindeer pastoralists make significant seasonal use of munkh mus (eternal ice) for their domestic herds, using these features to cool heat-stressed animals and provide respite from insect harassment. In recent years, many of these features have begun to melt entirely for the first time, producing urgent threats to traditional management techniques, the viability of summer pastures, and reindeer health. The melting ice is also exposing fragile organic archaeological materials that had previously been contained in the patch. We present the results of horseback survey of ice patches in Baruun Taiga special protected area, providing the first archaeological insights from the region. Results reveal new evidence of historic tool production and wild resource use for fishing or other activities, and indicate that ice patches are likely to contain one of the few material records of premodern domestic reindeer use in Mongolia and lower Central Asia. The area's ancient ice appears to be rapidly melting due to changing climate and warming summer temperatures, putting both cultural heritage and traditional reindeer herding at extreme risk in the years to come.
    • Investigating Runoff Efficiency in Upper Colorado River Streamflow Over Past Centuries

      Woodhouse, Connie A.; Pederson, Gregory T.; Univ Arizona, Sch Geog & Dev; Univ Arizona, Tree Ring Res Lab (AMER GEOPHYSICAL UNION, 2018-01-05)
      With increasing concerns about the impact of warming temperatures on water resources, more attention is being paid to the relationship between runoff and precipitation, or runoff efficiency. Temperature is a key influence on Colorado River runoff efficiency, and warming temperatures are projected to reduce runoff efficiency. Here, we investigate the nature of runoff efficiency in the upper Colorado River (UCRB) basin over the past 400 years, with a specific focus on major droughts and pluvials, and to contextualize the instrumental period. We first verify the feasibility of reconstructing runoff efficiency from tree-ring data. The reconstruction is then used to evaluate variability in runoff efficiency over periods of high and low flow, and its correspondence to a reconstruction of late runoff season UCRB temperature variability. Results indicate that runoff efficiency has played a consistent role in modulating the relationship between precipitation and streamflow over past centuries, and that temperature has likely been the key control. While negative runoff efficiency is most common during dry periods, and positive runoff efficiency during wet years, there are some instances of positive runoff efficiency moderating the impact of precipitation deficits on streamflow. Compared to past centuries, the 20th century has experienced twice as many high flow years with negative runoff efficiency, likely due to warm temperatures. These results suggest warming temperatures will continue to reduce runoff efficiency in wet or dry years, and that future flows will be less than anticipated from precipitation due to warming temperatures.
    • Investigating Systematic Reviews Outside Health Sciences

      Slebodnik, Maribeth; Hermer, Janice; Pardon, Kevin; University of Arizona Health Sciences Library; Arizona State University Library (2018-06)
      Originally developed for medicine and related fields in support of evidence-based practice, systematic reviews (SRs) are now published in other fields. We investigated non-health sciences disciplines that are publishing systematic reviews. We searched the Scopus database for articles with “systematic review*” in the title or abstract. Results were limited to review articles. Articles were examined by reviewers to determine if they a) were classified as SRs by the authors, b) written in English and c) addressed a non-health sciences topic. We reconciled differences for articles on which there was not initial consensus, and grouped remaining articles according to Scopus subject areas. Our filtered result set included 952 self-described systematic reviews outside the health science disciplines. We then examined a random sample of 90 articles and compared each article's methodology to health sciences systematic review criteria. Our results show that the non-health science disciplines with the highest number of self described systematic reviews appear to be the social sciences, environmental science, business, computer science and engineering. Details about inclusion/exclusion criteria and the databases used were often included. A majority of our sample did not clearly describe the search strategy or use published SR protocols as a basis for methodology. Librarians were consulted in only 3 of 90 articles we examined.
    • Investigating the effect of teacher mediation on student expressed reasoning

      Moreira, Patricia; Marzabal, Ainoa; Talanquer, Vicente; Univ Arizona, Dept Chem & Biochem (ROYAL SOC CHEMISTRY, 2019-07-01)
      Understanding how chemistry teachers' interventions shape the reasoning that students express after a lesson is critical to support prospective and in-service teachers as they work with students' ideas in the classroom. In this qualitative research study, we analysed changes in the reasoning expressed by 10th grade students in a Chilean school in their written explanations about freezing point depression before and after a lesson on the topic. We also investigated how the teacher's interventions shaped the type of reasoning expressed by participating students. Our findings revealed significant shifts in the types of explanations generated after the lesson. A significant number of students transitioned from relational to simple causal reasoning in their pre- and post-lesson explanations. After the lesson most of the explanations were based on the activities of one or more of the system's entities. Analysis of teacher-student interactions during the observed lesson suggests that the teacher's mediation played a central role in the shift towards simple causal reasoning with centralized causality that was observed. The teacher in our study was more skilled at eliciting students' ideas than at helping students develop them with proper scaffolding. Thus, the observed classroom talk could not be considered as accountable talk, as most of the key ideas were introduced, selected, or reshaped by the teacher.
    • Investigating the effects of adding hybrid nanoparticles, graphene and boron nitride nanosheets, to octadecane on its thermal properties

      Tafrishi, Hossein; Sadeghzadeh, Sadegh; Molaei, Fatemeh; Siavoshi, Hossein; Univ Arizona, Min & Geol Engn Dept (ROYAL SOC CHEMISTRY, 2020-04-14)
      Octadecane is an alkane that is used to store thermal energy at ambient temperature as a phase change material. A molecular dynamics study was conducted to investigate the effects of adding graphene and a boron nitride nanosheet on the thermal and structural properties of octadecane paraffin. The PCFF force field for paraffin, AIREBO potential for graphene, Tersoff potential for the boron nitride nanosheet, and Lennard-Jones potential for the van der Waals interaction between the nanoparticles and n-alkanes were used. Equilibrium and nonequilibrium molecular dynamics simulations were used to study the nano-enhanced phase change material properties. Results showed that the nanocomposite had a lower density change, more heat capacity (except at 300 K), more thermal conductivity, and a lower diffusion coefficient in comparison with pure paraffin. Additionally, the nanocomposite had a higher melting point, higher phonon density of state and radial distribution function peaks.
    • Investigating the Impact of Gadolinium-Based Contrast Agents on the Corrected QT Interval

      Gress, Kyle L.; Gallo, Tyler; Urits, Ivan; Geng, Xue; Viswanath, Omar; Kaye, Alan D.; Woosley, Raymond L.; Univ Arizona, Div Clin Data Analyt, Coll Med; Univ Arizona, Med, Coll Med (CUREUS INC, 2020-08)
      Introduction The manufacturing labels for all currently marketed gadolinium-based MRI contrast agents describe adverse cardiac events reported during post-market use. The goal of this study was to determine prolongation of the rate-corrected QT interval occurs in the immediate setting after gadolinium-based MRI contrast agent injection. Methods This study enrolled adults scheduled to have a gadolinium-based MRI contrast agent injection as part of a diagnostic MRI. A single-lead electrocardiogram was recorded using the AliveCor Kardia (R) ECG (Mountain View, CA) device before and after injection. The rate-corrected QT interval was subsequently measured by two independent investigators. The QT interval was corrected for rate using the two most common formulas, originally cited by Bazett and Fridericia. These rate-corrected QT intervals from before and after gadolinium-based MRI contrast agent injection were compared using the Wilcoxon signed-rank test paired analysis. Results A total of 24 consenting adults had electrocardiogram that were free of motion artifact. The mean age of the final patient cohort was 59.4 years. There was an equal split of 12 men and 12 women. The mean pre-injection, rate-corrected QT interval, corrected using Bazett's formula, was 395 msec. The mean post-injection, rate-corrected QT interval, corrected using Bazett's formula, was 396 msec. The corrections using Fridericia's formula were 384 and 381 msec, respectively. There was no statistically significant change in Bazett-corrected QT interval (QTcB) when pre-injection and post-injection values were directly compared. Discussion The results of the present investigation support the conclusion that gadolinium-based MRI contrast agents do not commonly affect rate-corrected QT interval in routine clinical use. While the frequency of rate-corrected QT interval prolongation might be overstated, the severity of adverse events is definitively not. A role for concomitant rate-corrected QT interval-prolonging drugs or unidentified rare factors such as genetic predisposition cannot be ruled out. The limitations of this study include its relatively small size and the implementation of a single- lead electrocardiogram to measure rate-corrected QT interval. Conclusion The present investigation revealed that significant rate-corrected QT interval prolongation, while previously reported in as many as 55% of patients after gadolinium-based MRI contrast agent injection, is not a common occurrence in the routine clinical setting.
    • Investigating the multiwavelength behaviour of the flat spectrum radio quasar CTA 102 during 2013–2017

      D’Ammando, F; Raiteri, C M; Villata, M; Acosta-Pulido, J A; Agudo, I; Arkharov, A A; Bachev, R; Baida, G V; Benítez, E; Borman, G A; et al. (OXFORD UNIV PRESS, 2019-10-09)
      We present a multiwavelength study of the flat-spectrum radio quasar CTA 102 during 2013-2017. We use radio-to-optical data obtained by the Whole Earth Blazar Telescope, 15 GHz data from the Owens Valley Radio Observatory, 91 and 103 GHz data from the Atacama Large Millimeter Array, near-infrared data from the Rapid Eye Monitor telescope, as well as data from the Swift (optical-UV and X-rays) and Fermi (gamma-rays) satellites to study flux and spectral variability and the correlation between flux changes at different wavelengths. Unprecedented gamma-ray flaring activity was observed during 2016 November-2017 February, with four major outbursts. A peak flux of (2158 +/- 63) x 10(-8) ph cm(-2) s(-1), corresponding to a luminosity of (2.2 +/- 0.1) x10(50) erg s(-1), was reached on 2016 December 28. These four gamma-ray outbursts have corresponding events in the near-infrared, optical, and UV bands, with the peaks observed at the same time. A general agreement between X-ray and gamma-ray activity is found. The gamma-ray flux variations show a general, strong correlation with the optical ones with no time lag between the two bands and a comparable variability amplitude. This gamma-ray/optical relationship is in agreement with the geometrical model that has successfully explained the low-energy flux and spectral behaviour, suggesting that the long-term flux variations are mainly due to changes in the Doppler factor produced by variations of the viewing angle of the emitting regions. The difference in behaviour between radio and higher energy emission would be ascribed to different viewing angles of the jet regions producing their emission.
    • Investigating the physical properties of transiting hot Jupiters with the 1.5-m Kuiper Telescope

      Turner, Jake D.; Leiter, Robin M.; Biddle, Lauren I.; Pearson, Kyle A.; Hardegree-Ullman, Kevin K.; Thompson, Robert M.; Teske, Johanna K.; Cates, Ian T.; Cook, Kendall L.; Berube, Michael P.; et al. (OXFORD UNIV PRESS, 2017-12)
      We present new photometric data of 11 hot Jupiter transiting exoplanets (CoRoT-12b, HATP-5b, HAT-P-12b, HAT-P-33b, HAT-P-37b, WASP-2b, WASP-24b, WASP-60b, WASP-80b, WASP-103b and XO-3b) in order to update their planetary parameters and to constrain information about their atmospheres. These observations of CoRoT-12b, HAT-P-37b and WASP-60b are the first follow-up data since their discovery. Additionally, the first near-UV transits of WASP-80b and WASP-103b are presented. We compare the results of our analysis with previous work to search for transit timing variations (TTVs) and a wavelength dependence in the transit depth. TTVs may be evidence of a third body in the system, and variations in planetary radius with wavelength can help constrain the properties of the exoplanet's atmosphere. For WASP-103b and XO-3b, we find a possible variation in the transit depths which may be evidence of scattering in their atmospheres. The B-band transit depth of HAT-P-37b is found to be smaller than its near-IR transit depth and such a variation may indicate TiO/VO absorption. These variations are detected from 2-4.6s, so follow-up observations are needed to confirm these results. Additionally, a flat spectrum across optical wavelengths is found for five of the planets (HAT-P-5b, HAT-P-12b, WASP-2b, WASP-24b and WASP-80b), suggestive that clouds may be present in their atmospheres. We calculate a refined orbital period and ephemeris for all the targets, which will help with future observations. No TTVs are seen in our analysis with the exception of WASP-80b and follow-up observations are needed to confirm this possible detection.
    • Investigating the Puzzling Synchrotron Behaviour of Mrk 421

      Carnerero, Maria; Raiteri, Claudia; Villata, Massimo; Acosta Pulido, Jose; Smith, Paul; Larionov, Valeri; Univ Arizona, Steward Observ (MDPI AG, 2016-11-04)
      We investigate the multiwavelength behaviour of the high-energy peaked BL Lac object (HBL) Mrk 421 at redshift z = 0.031 in the period 2007-2015. We use optical photometric, spectroscopic, and polarimetric data and near-infrared data obtained by 35 observatories participating in the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT), as well as by the Steward Observatory Support of the Fermi Mission. We also employ high-energy data from the Swift (UV and X-rays) satellite to study correlations among emission in different bands.
    • Investigating the relationship between (3200) phaethon and (155140) 2005 UD through telescopic and laboratory studies

      Kareta, T.; Reddy, V.; Pearson, N.; Sanchez, J.A.; Harris, W.M.; Lunar and Planetary Laboratory, University of Arizona (Web Portal IOP, 2021)
      The relationship between the near-Earth objects (3200) Phaethon and (155140) 2005 UD is unclear. While both are parents to meteor showers (the Geminids and Daytime Sextantids, respectively) and have similar visiblewavelength reflectance spectra and orbits, dynamical investigations have failed to find any likely method to link the two objects in the recent past. Here we present the first near-infrared reflectance spectrum of 2005 UD, which shows it to be consistently linear and red-sloped, unlike Phaethon's very blue and concave spectrum. Searching for a process that could alter some common starting material to both of these end states, we hypothesized that the two objects had been heated to different extents, motivated by their near-Sun orbits, the composition of Geminid meteoroids, and previous models of Phaethon's surface. We thus set about building a new laboratory apparatus to acquire reflectance spectra of meteoritic samples after heating to higher temperatures than available in the literature to test this hypothesis and were loaned a sample of the CI chondrite Orgueil from the Vatican Meteorite Collection for testing. We find that while Phaethon's spectrum shares many similarities with different CI chondrites, 2005 UD's does not. We thus conclude that the most likely relationship between the two objects is that their similar properties are only by coincidence as opposed to a parent-fragment scenario, though the ultimate test will be when JAXA's DESTINY+ mission visits one or both of the objects later this decade. We also discuss possible paths forward to understanding Phaethon's properties from dynamical and compositional grounds. © 2021. The Author(s).
    • Investigating various products of IMERG for precipitation retrieval over surfaces with and without snow and ice cover

      Arabzadeh, A.; Behrangi, A.; Department of Hydrology and Atmospheric Sciences, University of Arizona; Department of Geosciences, University of Arizona (MDPI AG, 2021)
      Precipitation rate from various products of the integrated multisatellite retrievals for GPM (IMERG) and passive microwave (PMW) sensors are assessed with respect to near-surface wet-bulb temperature (Tw), precipitation intensity, and surface type (i.e., with and without snow and ice on the surface) over the contiguous United States (CONUS) and using ground radar product as reference precipitation. IMERG products include precipitation estimates from infrared (IR), combined PMW, and combination of PMW and IR. It was found that precipitation estimates from PMW products generally have higher skills than IR over snow-and ice-free surfaces. Over snow-and ice-covered surfaces: (1) most PMW products show higher correlation coefficients than IR, (2) at cold temperatures (e.g., Tw &lt; −10◦C), PMW products tend to underestimate and IR product shows large overestimations, and (3) PMW sensors show higher overall skill in detecting precipitation occurrence, but not necessarily at very cold Tw. The results suggest that the current approach of IMERG (i.e., replacing PMW with IR precipitation estimates over snow-and ice-surfaces) may need to be revised. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
    • Investigation and mitigation of noise contributions in a compact heterodyne interferometer

      Zhang, Y.; Hines, A.S.; Valdes, G.; Guzman, F.; Wyant College of Optical Sciences, The University of Arizona (MDPI AG, 2021)
      We present a noise estimation and subtraction algorithm capable of increasing the sensitivity of heterodyne laser interferometers by one order of magnitude. The heterodyne interferometer is specially designed for dynamic measurements of a test mass in the application of sub-Hz inertial sensing. A noise floor of 3.31 × 10−11 m/√Hz at 100 mHz is achieved after applying our noise subtraction algorithm to a benchtop prototype interferometer that showed a noise level of 2.76 × 10−10 m/√Hz at 100 mHz when tested in vacuum at levels of 3 × 10−5 Torr. Based on the previous results, we investigated noise estimation and subtraction techniques of non-linear optical pathlength noise, laser frequency noise, and temperature fluctuations in heterodyne laser interferometers. For each noise source, we identified its contribution and removed it from the measurement by linear fitting or a spectral analysis algorithm. The noise correction algorithm we present in this article can be generally applied to heterodyne laser interferometers. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
    • Investigation of a Monte Carlo simulation and an analytic-based approach for modeling the system response for clinical I-123 brain SPECT imaging

      Auer, Benjamin; Zeraatkar, Navid; De Beenhouwer, Jan; Kalluri, Kesava; Kuo, Philip; Furenlid, Lars R.; King, Michael A.; Univ Arizona, Dept Med Imaging (SPIE-INT SOC OPTICAL ENGINEERING, 2019-05-28)
      The use of accurate system response modeling has been proven to be an essential key of SPECT image reconstruction, with its usage leading to overall improvement of image quality. The aim of this work was to investigate the imaging performance using an XCAT brain perfusion phantom of two modeling strategies, one based on analytic techniques and the other one based on GATE Monte-Carlo simulation. In addition, an efficient forced detection approach to improve the overall simulation efficiency was implemented and its performance was evaluated. We demonstrated that accurate modeling of the system matrix generated by Monte-Carlo simulation for iterative reconstruction leads to superior performance compared to analytic modeling in the case of clinical I-123 brain imaging. It was also shown that the use of the forced detection approach provided a quantitative and qualitative enhancement of the reconstruction.
    • Investigation of a possible malaria epidemic in an illegal gold mine in French Guiana: an original approach in the remote Amazonian forest

      Douine, Maylis; Sanna, Alice; Hiwat, Helene; Briolant, Sébastien; Nacher, Mathieu; Belleoud, Didier; Le Tourneau, François Michel; Bogreau, Hervé; De Laval, Franck; Univ Arizona, IGLOBES (BMC, 2019-03-22)
      Background: In April 2017, Suriname's Ministry of Health alerted French Guiana's Regional Health Agency (RHA) about an increase of imported malaria cases among people coming from an illegal gold mining site called Sophie, in French Guiana, a French overseas territory located in the Amazonian forest. Methods: Due to safety issues and the remoteness of Sophie, the RHA requested the collaboration of the French Armed Forces for the epidemiological investigation. A medical unit, and six soldiers to ensure the security of the mission, were transported by helicopter. Results: During the investigation, two malaria episodes were diagnosed among 46 persons. Twenty-six of them were from Sophie, where PCR-Plasmodium prevalence was estimated at 60% (15/26). This result was concordant with previous studies revealing high malaria endemicity in the gold miner population. The increase of imported cases in Suriname may have resulted from decreased access to under-the-counter anti-malarials and increased migration of gold miners to Suriname following a decline of the profitability of gold mining in a context of increased repression against illegal mining by the French army. Conclusion: This investigation of a suspicious malaria epidemic confirms the importance of malaria among illegal gold miners. Their mobility along the Guiana Shield and their health-seeking behaviour are likely to spread malaria in populations for which significant efforts are undertaken to fight against this disease. Fighting malaria in this population remains more relevant than ever. A pilot study (Malakit project) is currently in progress to evaluate the efficacy of kits for self-diagnosis and self-treatment.
    • Investigation of aerosol-cloud interactions under different absorptive aerosol regimes using Atmospheric Radiation Measurement (ARM) southern Great Plains (SGP) ground-based measurements

      Zheng, Xiaojian; Xi, Baike; Dong, Xiquan; Logan, Timothy; Wang, Yuan; Wu, Peng; Univ Arizona, Dept Hydrol & Atmospher Sci (COPERNICUS GESELLSCHAFT MBH, 2020-03-24)
      The aerosol indirect effect on cloud microphysical and radiative properties is one of the largest uncertainties in climate simulations. In order to investigate the aerosol-cloud interactions, a total of 16 low-level stratus cloud cases under daytime coupled boundary-layer conditions are selected over the southern Great Plains (SGP) region of the United States. The physicochemical properties of aerosols and their impacts on cloud microphysical properties are examined using data collected from the Department of Energy Atmospheric Radiation Measurement (ARM) facility at the SGP site. The aerosol-cloud interaction index (ACI(r)) is used to quantify the aerosol impacts with respect to cloud-droplet effective radius. The mean value of ACI(r) calculated from all selected samples is 0.145 +/- 0.05 and ranges from 0.09 to 0.24 at a range of cloud liquid water paths (LWPs; LWP = 20-300 g m(-2)). The magnitude of ACI(r) decreases with an increasing LWP, which suggests a diminished cloud microphysical response to aerosol loading, presumably due to enhanced condensational growth processes and enlarged particle sizes. The impact of aerosols with different light-absorbing abilities on the sensitivity of cloud microphysical responses is also investigated. In the presence of weak light-absorbing aerosols, the low-level clouds feature a higher number concentration of cloud condensation nuclei (N-CCN) and smaller effective radii (r(e)), while the opposite is true for strong light-absorbing aerosols. Furthermore, the mean activation ratio of aerosols to CCN (N-CCN/N-a) for weakly (strongly) absorbing aerosols is 0.54 (0.45), owing to the aerosol microphysical effects, particularly the different aerosol compositions inferred by their absorptive properties. In terms of the sensitivity of cloud-droplet number concentration (N-d) to N-CCN, the fraction of CCN that converted to cloud droplets (N-d/N-CCN) for the weakly (strongly) absorptive regime is 0.69 (0.54). The measured ACI(r) values in the weakly absorptive regime are relatively higher, indicating that clouds have greater microphysical responses to aerosols, owing to the favorable thermodynamic condition. The reduced ACI(r) values in the strongly absorptive regime are due to the cloud-layer heating effect induced by strong light-absorbing aerosols. Consequently, we expect larger shortwave radiative cooling effects from clouds in the weakly absorptive regime than those in the strongly absorptive regime.
    • Investigation of Charon's Craters With Abrupt Terminus Ejecta, Comparisons With Other Icy Bodies, and Formation Implications

      Robbins, Stuart J.; Runyon, Kirby; Singer, Kelsi N.; Bray, Veronica J.; Beyer, Ross A.; Schenk, Paul; McKinnon, William B.; Grundy, William M.; Nimmo, Francis; Moore, Jeffrey M.; et al. (AMER GEOPHYSICAL UNION, 2018-01)
      On the moon and other airless bodies, ballistically emplaced ejecta transitions from a thinning, continuous inner deposit to become discontinuous beyond approximately one crater radius from the crater rim and can further break into discrete rays and secondary craters. In contrast, on Mars, ejecta often form continuous, distinct, and sometimes thick deposits that transition to a low ridge or escarpment that may be circular or lobate. The Martian ejecta type has been variously termed pancake, rampart, lobate, or layered, and in this work we refer to it as abrupt termini ejecta (ATE). Two main formation mechanisms have been proposed, one requiring interaction of the ejecta with the atmosphere and the other mobilization of near-surface volatiles. ATE morphologies are also unambiguously seen on Ganymede, Europa, Dione, and Tethys, but they are not as common as on Mars. We have identified up to 38 craters on Charon that show signs of ATE, including possible distal ramparts and lobate margins. These ejecta show morphologic and morphometric similarities with other moons in the solar system, which are a subset of the properties observed on Mars. From comparison of these ejecta on Charon and other solar system bodies, we find the strongest support for subsurface volatile mobilization and ejecta fluidization as the main formation mechanism for the ATE, at least on airless, icy worlds. This conclusion comes from the bodies on which they are found, an apparent preference for certain terrains, and the observation that craters with ATE can be near to similarly sized craters that only have gradational ejecta.
    • Investigation of confocal microscopy for differentiation of renal cell carcinoma versus benign tissue. Can an optical biopsy be performed?

      Phung, Michael C.; Rouse, Andrew R.; Pangilinan, Jayce; Bell, Robert C.; Bracamonte, Erika R.; Mashi, Sharfuddeen; Gmitro, Arthur F.; Lee, Benjamin R.; Univ Arizona, Dept Urol, Coll Med; Univ Arizona, Dept Med Imaging, Coll Med; et al. (ELSEVIER SINGAPORE PTE LTD, 2020-10)
      Objective: Novel optical imaging modalities are under development with the goal of obtaining an "optical biopsy" to efficiently provide pathologic details. One such modality is confocal microscopy which allows in situ visualization of cells within a layer of tissue and imaging of cellular-level structures. The goal of this study is to validate the ability of confocal microscopy to quickly and accurately differentiate between normal renal tissue and cancer. Methods: Specimens were obtained from patients who underwent robotic partial nephrectomy for renal mass. Samples of suspected normal and tumor tissue were extracted from the excised portion of the kidney and stained with acridine orange. The stained samples were imaged on a Nikon E600 C1 Confocal Microscope. The samples were then submitted for hematoxylin and eosin processing and read by an expert pathologist to provide a gold-standard diagnosis that can later be compared to the confocal images. Results: This study included 11 patients, 17 tissue samples, and 118 confocal images. Of the 17 tissue samples, 10 had a gold-standard diagnosis of cancer and seven were benign. Of 118 confocal images, 66 had a gold-standard diagnosis of cancer and 52 were benign. Six confocal images were used as a training set to train eight observers. The observers were asked to rate the test images on a six point scale and the results were analyzed using a web based receiver operating characteristic curve calculator. The average accuracy, sensitivity, specificity, and area under the empirical receiver operating characteristic curve for this study were 91%, 98%, 81%, and 0.94 respectively. Conclusion: This preliminary study suggest that confocal microscopy can be used to distinguish cancer from normal tissue with high sensitivity and specificity. The observers in this study were trained quickly and on only six images. We expect even higher performance as observers become more familiar with the confocal images. (C) 2020 Editorial Office of Asian Journal of Urology. Production and hosting by Elsevier B.V.
    • Investigation of frequency-dependent attenuation coefficients for multiple solids using a reliable pulse-echo ultrasonic measurement technique

      Zhang, Guangdong; Li, Xiongbing; Zhang, Shuzeng; Kundu, Tribikram; Department of Civil & Architectural Engineering & Mechanics, University of Arizona (Elsevier B.V., 2021-03-14)
      A well-established narrowband pulse-echo technique is employed and improved further to investigate the frequency-dependent ultrasonic wave attenuation in various solids. During attenuation coefficient measurement, the diffraction correction is introduced to minimize wave beam-spreading loss, and frequency domain signals are used to minimize both the effects of downward shift of frequency and the error in determining the amplitude of time-domain signals. The frequency-dependent attenuation curves for 19 frequently-used solid materials are obtained using this method in the frequency range 1–25 MHz. It is observed from the measurement results of these materials that the attenuation can vary linearly or nonlinearly with the signal frequency, and the potential impact factors of the attenuation-frequency relationship are discussed. The experimental results presented in this paper is expected to provide a good reference for researchers interested in developing and using frequency-dependent attenuation coefficients of materials that are currently missing in the literature. © 2021 Elsevier Ltd