McLennan S.M.,State University of New York at Stony Brook |
Anderson R.B.,U.S. Geological Survey |
Bell III J.F.,Arizona State University |
Bridges J.C.,University of Leicester |
And 47 more authors.
Science | Year: 2014
Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine - rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.
Kobulnicky H.A.,University of Wyoming |
Kiminki D.C.,University of Arizona |
Lundquist M.J.,University of Wyoming |
Burke J.,University of Wyoming |
And 18 more authors.
Astrophysical Journal, Supplement Series | Year: 2014
We analyze orbital solutions for 48 massive multiple-star systems in the Cygnus OB2 association, 23 of which are newly presented here, to find that the observed distribution of orbital periods is approximately uniform in log P for P < 45 days, but it is not scale-free. Inflections in the cumulative distribution near 6 days, 14 days, and 45 days suggest key physical scales of ≃0.2, ≃0.4, and ≃1 A.U. where yet-to-be-identified phenomena create distinct features. No single power law provides a statistically compelling prescription, but if features are ignored, a power law with exponent β ≃ -0.22 provides a crude approximation over P = 1.4-2000 days, as does a piece-wise linear function with a break near 45 days. The cumulative period distribution flattens at P > 45 days, even after correction for completeness, indicating either a lower binary fraction or a shift toward low-mass companions. A high degree of similarity (91% likelihood) between the Cyg OB2 period distribution and that of other surveys suggests that the binary properties at P ≲ 25 days are determined by local physics of disk/clump fragmentation and are relatively insensitive to environmental and evolutionary factors. Fully 30% of the unbiased parent sample is a binary with period P < 45 days. Completeness corrections imply a binary fraction near 55% for P < 5000 days. The observed distribution of mass ratios 0.2 < q < 1 is consistent with uniform, while the observed distribution of eccentricities 0.1 < e < 0.6 is consistent with uniform plus an excess of e ≃ 0 systems. We identify six stars, all supergiants, that exhibit aperiodic velocity variations of 30 km s-1 attributed to atmospheric fluctuations. © 2014. The American Astronomical Society. All rights reserved..
Kitko L.A.,Pennsylvania State University |
Hupcey J.E.,Pennsylvania State University |
Gilchrist J.H.,Mt Holyoke College |
Boehmer J.P.,Heart and Vascular Institute
Heart and Lung: Journal of Acute and Critical Care | Year: 2013
Objectives: This qualitative study describes the experiences of spousal caregivers of a patient with end-stage heart failure (HF) from pre-LVAD to post-LVAD-DT implantation. Background: LVAD-DTs are implanted as permanent devices for end-stage HF patients with the goal of improving the length and quality of life. LVADs create new demands for both patients and caregivers. Methods: In-depth, semi-structured interviews of 10 spousal caregivers were thematically analyzed. Results: Throughout the process of caregiving, pre-implant through post-implant, all caregivers discussed their ability to adapt within the role as a caregiver. Adaptation as a caregiver occurred through three distinct time frames following the progression of the patient's HF and subsequent LVAD implantation: caring for a spouse with HF, decision for LVAD implantation made, and caring for a spouse with the LVAD-DT. Conclusions: Caregivers were able to adapt and develop effective strategies to incorporate the demands of caring for a spouse with an LVAD-DT, but the role remained challenging. The findings underscore the need for continued research that may be translated into effective interventions to support patient and caregivers as they live through this end-of-life trajectory. © 2013 Elsevier Inc.
Klein B.R.,Western Connecticut Health Network |
Brown E.N.,Mt Holyoke College |
Casden R.S.,Western Connecticut Health Network
Journal of Cataract and Refractive Surgery | Year: 2016
Purpose To evaluate spectral-domain optical coherence tomography (SD-OCT) as a strategy for identifying occult macular disease preoperatively in patients scheduled for cataract surgery with implantation of an advanced-technology intraocular lens (IOL). Setting Private practice, Danbury, Connecticut, USA. Design Retrospective consecutive case series. Methods Macular SD-OCT scans were performed on all patients scheduled for cataract surgery and Restor multifocal or toric IOL implantation over a 6-month period. All scans were reviewed for abnormalities of the retina, retinal pigment epithelium, or vitreomacular interface. For subgroup analysis, the following health information was collected: age, sex, smoking history, hypertension, heart disease, hyperlipidemia or hypercholesterolemia, and diabetes. Results Two hundred sixty-five consecutive scans from 149 patients were obtained. Macular pathology was found in 35 eyes (13.2%). The most common condition was age-related macular degeneration in 15 eyes (5.66%) followed by idiopathic epiretinal membrane in 11 eyes (4.15%). Ischemic atrophy from previously undiagnosed retinal vascular pathology was found in 5 eyes (1.89%) and edema in 3 eyes (1.13%). A subgroup analysis found a higher incidence of macular pathology in patients with a history of heart disease (30.6%, P <.001) or smoking (20.2%, P <.05), and in men (23.9%, P <.01). Media opacities precluded interpretation of 17 scans (6.42%). Conclusion Preoperative macular SD-OCT scanning was effective in identifying patients at risk for compromised visual outcomes after advanced-technology IOL surgery. Financial Disclosure None of the authors has a financial or proprietary interest in any material or method mentioned. © 2016 ASCRS and ESCRS.
Siqueira P.,University of Massachusetts Amherst |
Schrock R.,University of Massachusetts Amherst |
Millette T.,Mt Holyoke College |
Hartley T.,University of Massachusetts Amherst
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2012
The Topographic Ice Mapping Mission (TIMMi) instrument is a unique millimeter-wave interferometric radar system operating at 35 GHz (Ka-band). It was constructed, in part, to advance the technology readiness level of NASA's Surface Water and Ocean Topography (SWOT) mission, a spaceborne platform that will globally map the altimetry of Earth's water to gain insight into surface water interactions and dynamics. Previous ground deployments of TIMMi, while successful in demonstrating the abilities of the system, suffered from poor SNR due to high incidence angles. TIMMi was most recently deployed on an airborne platform to take advantage of the lower angle of incidence and to prove its capability in measuring large swaths of topography at high resolution. This paper outlines some of the challenges and considerations for adapting the smaller Ka-band system to an airborne platform, as well as some preliminary results from these datasets. © 2012 IEEE.
Evans K.A.,Curtin University Australia |
Dyar M.D.,Mt Holyoke College |
Reddy S.M.,Curtin University Australia |
Lanzirotti A.,University of Chicago |
And 2 more authors.
American Mineralogist | Year: 2014
Microscale analysis of ferrous:ferric iron ratios in silicate minerals has the potential to constrain geological processes but has proved challenging because textural information and spatial resolution are limited with bulk techniques, and in situ methods have limited spatial resolution. Synchrotron methods, such as XANES, have been hampered by the sensitivity of spectra to crystal orientation and matrix effects. In an attempt to break this nexus, biotites from Tanzania were characterized with a combination of optical microscopy, electron microprobe, Mössbauer analysis, electron backscatter diffraction (EBSD) and X-ray absorption near edge structure (XANES) spectroscopy. Pre-edge and edge characteristics of the FeKα absorption feature were compared to orientation information derived by EBSD and ferric iron content derived from Mössbauer analysis. Statistically significant correlations between measured spectral features and optic/crystallographic orientation were observed for individual samples. However, orientation corrections derived from these correlations did not reduce the uncertainty in Fe3+/Fetot. The observations are consistent with matrix- and ordering-dependency of the XANES features, and further work is necessary if a general formulation for orientation corrections is to be devised. © 2014 by Walter de Gruyter GmbH & Co. 2014.
McEnroe S.A.,Norwegian University of Science and Technology |
Robinson P.,Geological Survey of Norway |
Miyajima N.,University of Bayreuth |
Fabian K.,Geological Survey of Norway |
And 2 more authors.
Geophysical Journal International | Year: 2016
Recent high-resolution aeromagnetic surveys in South Norway have revealed numerous remanent anomalies over Mesoproterozoic metamorphic rocks. Studies on the nature of the minerals that are the remanent carriers has led to discoveries of titanohematite samples with unusual magnetic properties caused by nanoscale exsolution lamellae with their related lamellar magnetism. Here we focus on a rock unit dominated by quartz-plagioclase-biotite granulite containing titanohematite grains with a strong lattice-preferred orientation parallel to regional foliation. When samples with their natural remanent magnetization (NRM), acquired nearly 1 billion years ago, are cooled to 10 K and hysteresis loops measured, these loops show bi-modal exchange bias caused by the magnetism induced within the ilmenite by antiferromagnetic coupling with the adjacent lamellar NRM. By contrast when the samples are cooled in a strong magnetic field (1.5 Tesla), this results in unimodal lamellar magnetism, and, below the TN of ilmenite it adopts a consistent negative orientation, giving rise to unimodal negative exchange bias of >500 mT. The results presented here cover the chemical and magnetic properties, Mossbauer results and transmission electron microscopy of the titanohematite and ilmenite lamellae. Initial magnetic experiments indicated the shifts found in the exchangebias experiments were directly related to the orientation of the sample to the applied field and the initial state of the NRM. In most samples with these unusual magnetic properties, ilmenite lamellae could not be seen in an optical or a scanning electron microscope. However magnetic experiments gave proof of the presence of ilmenite, later confirmed by Mössbauer spectroscopy. Several attempts were made to identify ilmenite in TEM studies, finally successful in showing ilmenite lamellae parallel to (001) of hematite with thicknesses ~1.2 to 1.7 nmand aspect ratios 7-13. Here we compare new TEM images and the magnetic behaviour of these samples to the MOD2 samples that previously showed extraordinary exchange bias properties, and investigate further the nature of these magnetic minerals. © The Authors 2016.
Biermann J.,Mt Holyoke College |
Van Tuyl A.,Lakehead University
Electronic Journal of Combinatorics | Year: 2013
Given any finite simplicial complex Δ, we show how to construct from a colouring X of Δ a new simplicial complex ΔX that is balanced and vertex decomposable. In addition, the h-vector of ΔX is precisely the f-vector of Δ. Our construction generalizes the "whiskering" construction of Villarreal, and Cook and Nagel. We also reverse this construction to prove a special case of a conjecture of Cook and Nagel, and Constantinescu and Varbaro on the h-vectors of flag complexes.
Revealed I.,University of Minnesota |
Yuwono V.M.,University of Minnesota |
Burrows N.D.,University of Minnesota |
Soltis J.A.,Mt Holyoke College |
Lee Penn R.,University of Minnesota
Journal of the American Chemical Society | Year: 2010
(Figure Presented) Oriented aggregation is a special case of aggregation in which nanocrystals self-assemble and form new secondary single crystals. This process has been suggested to proceed via an intermediate state known as the mesocrystal, in which the nanocrystals have parallel crystallographic alignment but are spatially separated. We present the first direct observations of mesocrystals with size and shape similar to product oriented aggregates by employing cryo-TEM to directly image the particles in aqueous suspension. The cryo-TEM images reveal that mesocrystals not only form but also transform to the final single crystal product while in the dispersed state. Further, high-resolution cryo-TEM images demonstrate that the mesocrystals are composed of spatially separated and crystallographically aligned nanocrystals. Copyright © 2010 American Chemical Society.
Cassey A.J.,Washington State University |
Schmeiser K.N.,Mt Holyoke College
Annals of Regional Science | Year: 2013
Precise characterization of informational trade barriers is neither well documented nor understood. Using Russian customs data, we document that regional destination-specific export spillovers exist for developing countries, extending a result that was only known for developed countries. This result suggests behavior responding to a destination barrier. To account for this fact, we build on a monopolistic competition model of trade by postulating an externality in the international transaction of goods. We test the model's prediction on region-level exports using Russian data and find improvement over gravity-type models without agglomeration. This finding has important development implications in that export policy that considers current trade partners may be more effective than policy that focuses only on the exporting country's industries. Furthermore, our findings can be considered in the burgeoning literature refining transaction costs beyond the traditional iceberg cost. © 2012 Springer-Verlag.