2,100 research outputs found
Long-term ionospheric cooling: Dependency on local time, season, solar activity, and geomagnetic activity
Ionospheric ion temperature Ti is an excellent approximation to neutral temperature Tn in the thermosphere, especially for altitudes below 300 km. This analysis of long‒term Ti trends in the F region over different local times is based on a database of incoherent scatter radar (ISR) observations spanning more than three solar cycles during 1968–2006 at Millstone Hill and represents an extended effort to a prior study focusing on noon‒time only. This study provides important information for understanding the difference between the ISR and other results. A gross average of the Ti trend at heights of Ti ∼ Tn (200–350 km) is ∼ −4 K/decade, a cooling trend close to the Tn estimation based on the satellite neutral density data. However, there exists considerable variability in the cooling: it is strong during the day and very weak during the night with a large apparent warming at low altitudes (200–350 km); it is strong at solar minimum for both daytime and nighttime. The strongest cooling for altitudes below 375 km occurs around 90–120 solar flux units of the 10.7 cm solar flux, not at the lowest solar flux. There appears more cooling toward high magnetic activity, but this dependency is very weak. No consistent and substantial seasonal dependency across different heights was found. We speculate that a fraction of the observed cooling trend may be contributed by a gradual shifting away from the sub‒auroral region at Millstone Hill, as part of the secular change in the Earth's magnetic field. In this 39 year long series of data record, two anomalous Ti drops were noticed, and we speculate on their connection to volcano eruptions in 1982 and 1991.National Science Foundation (U.S.) (Award AGS-1042569
Day-to-day variability and solar preconditioning of thermospheric temperature over Millstone Hill
We use a continuous 30 day incoherent scatter radar experiment at Millstone Hill in October 2002 to examine day-to-day thermospheric variability in exospheric temperature T[subscript ex]. Solar flux and magnetic activity influences as the main driving factors for day-to-day variability are investigated quantitatively. Solar ultraviolet flux levels are based on the TIMED/SEE space weather product, allowing for analysis of ultraviolet flux-T[subscript ex] correlation. T[subscript ex] is most sensitive to solar EUV flux with approximately a 2 day delay at wavelengths of 27–34 nm (including 30.4 nm). In particularly, a 20–60 h time delay occurs in T[subscript ex] response to EUV flux at 27–34 nm band, with shorter delays in the morning and longer delays in the afternoon and at night. The 1 ∼ 2 day delayed T[subscript ex] response to solar ultraviolet flux and associated thermospheric solar preconditioning (“memory”) are most significant in the daily mean for the 27–34 nm band, in the diurnal and semidiurnal amplitudes for the soft X-ray flux at 0.1–7 nm, and in the diurnal amplitude for longer wavelengths. An empirical model driven only by EUV flux at 27–34 nm from 2 days in advance reproduces 90% of the observed variability in the Tex daily mean. With a 2 day time delay, solar X-ray flux at 0.1–7 nm is correlated positively with T[subscript ex] diurnal amplitude and negatively with T[subscript ex] semidiurnal amplitude. Finally, magnetic activity control, as represented by the Dst index, is weaker during the day and stronger at night and is important for the semidiurnal amplitude but not important for the daily mean.National Science Foundation (U.S.) (Award AGS-1042569
Ionospheric longitudinal variations at midlatitudes: Incoherent scatter radar observation at Millstone Hill
Incoherent scatter radar (ISR) extra-wide coverage experiments during the period of 1978–2011 at Millstone Hill are used to investigate longitudinal differences in electron density. This work is motivated by a recent finding of the US east-west coast difference in TEC suggesting a combined effect of changing geomagnetic declination and zonal winds. The current study provides strong supporting evidence of the longitudinal change and the plausible mechanism by examining the climatology of electron density Ne on both east and west sides of the radar with a longitude separation of up to 40o for different heights within 300–450 km. Main findings include: 1) The east-west difference can be up to 60% and varies over the course of the day, being positive (East side Ne > West side Ne) in the late evening, and negative (West side Ne > East side Ne) in the pre-noon. 2) The east-west difference exists throughout the year. The positive (relative) difference is most pronounced in winter; the negative (relative) difference is most pronounced in early spring and later summer. 3) The east-west difference tends to enhance toward decreasing solar activity, however, with some seasonal dependence; the enhancements in the positive and negative differences do not take place simultaneously. 4) Both times of largest positive and largest negative east-west differences in Ne are earlier in summer and later in winter. The two times differ by 12–13 h, which remains constant throughout the year. 5) Variations at different heights from 300–450 km are similar. Zonal wind climatology above Millstone Hill is found to be perfectly consistent with what is expected based on the electron density difference between the east and west sides of the site. The magnetic declination-zonal wind mechanism is true for other longitude sectors as well, and may be used to understand longitudinal variations elsewhere. It may also be used to derive thermospheric zonal winds.National Natural Science Foundation (China) (Grant 40890164)National Science Foundation (U.S.) (Grants ATM-0733510 and ATM- 6920184
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New insights into ice accumulation at Galena Creek Rock Glacier from radar imaging of its internal structure
The ice-cored Galena Creek Rock Glacier, Wyoming, USA, has been the subject of a number of studies that sought to determine the origin of its ice. We present new observations of the rock glacier's internal structure from ground-penetrating radar to constrain ice and debris distribution and accumulation. We imaged dipping reflectors in the center of the glacier that are weak and discontinuous, in contrast to strong reflectors toward the edge of the cirque beneath large debris-avalanche chutes. These reflectors form a network of concave-up, up-glacier dipping layers. We interpret these as englacial debris bands formed by large debris falls buried by subsequent ice and snow accumulation. They are discontinuous where ice outpaces debris accumulation, but with sufficient debris accumulation an interleaved pattern of ice and debris layers can form. We propose a model in which the ice in these interleaved layers is snowfall preserved by debris-facilitated accumulation. Large debris falls that occur in early spring bury sections of the snowpack, which are then preserved through summer and incorporated into the rock glacier body over time. This study highlights the importance of sequential accumulation of ice and debris for understanding the dynamics of rock glaciers and debris-covered glaciers.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Ionospheric ion temperature climate and upper atmospheric long-term cooling
It is now recognized that Earth's upper atmosphere is experiencing a long-term cooling over the past several solar cycles. The potential impact of the cooling on societal activities is significant, but a fundamental scientific question exists regarding the drivers of the cooling. New observations and analyses provide crucial advances in our knowledge of these important processes. We investigate ionospheric ion temperature climatology and long-term trends using up-to-date large and consistent ground-based data sets as measured by multiple incoherent scatter radars (ISRs). The very comprehensive view provided by these unique observations of the upper atmospheric thermal status allows us to address drivers of strong cooling previously observed by ISRs. We use observations from two high-latitude sites at Sondrestrom (invariant latitude 73.2°N) from 1990 to 2015 and Chatanika/Poker Flat (invariant latitude 65.9°N) over the span of 1976–2015 (with a gap from 1983 to 2006). Results are compared to conditions at the midlatitude Millstone Hill site (invariant latitude 52.8°N) from 1968 to 2015. The aggregate radar observations have very comparable and consistent altitude dependence of long-term trends. In particular, the lower F region (<275 km) exhibits dayside cooling trends that are significantly higher (−3 to −1 K/yr at 250 km) than anticipated from model predictions given the anthropogenic increase of greenhouse gases. Above 275 km, cooling trends continue to increase in magnitude but values are strongly dependent on magnetic latitude, suggesting the presence of significant downward influences from nonneutral atmospheric processes.National Science Foundation (U.S.) (Awards AGS-1042569 and AGS-1343056
Flamingo Vol. III N 2
Anonymous. Cover. Picture. 0.
Anonymous. Untitled. Picture. 4.
Price, John M. Dada--Esthetic Nihilism. Prose. 5.
G.C. Tolerance. Poem. 6.
G.W.B. The Castaway. Poem. 6.
G.W.B. Cinquains. Poem. 7.
Holt, K. HORATI CARMINA, Liber I, ix. Prose. 7.
W.A.V. Untitled. Poem. 7.
A.E.R. Moods. Poem. 7.
G.W.B. Some Say The Moon. Poem. 7.
A.E.R. On Quoting The Night Has A Thousand Eyes . Poem. 7.
Anonymous. Chapel Cherubs. Prose. 8.
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Anonymous. FLIP— MIGHT I ASK YOU FOR THIS DANCE? FLAP— PLEASE DO, I\u27VE BEEN DYING TO REFUSE YOU ALL EVENING. . Picture. 9.
Anonymous. HUSBAND (SAVAGELY)— MARIA, WHERE\u27S MY CLOTHES? MARIA— GOOD HEAVENS, DEAR, I WONDER IF I USED THEM IN THE SALAD. Picture. 9.
Anonymous. Our Log Table. Prose. 9.
Anonymous. Approved Vocabulary For Fans. Prose. 9.
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F.T. GEORGE TOLD ME ALL THE SECRETS OF HIS PAST LAST NIGHT. REALLY! WHAT DID YOU THINK OF THEM? OH, I THOUGHT THEY WERE HORRIBLY DISAPPOINTING. Picture. 10.
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Howard, Lillis. The Engaged Homo. Poem. 10.
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Ubersax. AS OTHERS MIGHT SEE US—CLEVELAND HALL TO A CUBIST. Picture. 11.
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Anonymous. SECOND FROM THE RIGHT— WHAT\u27S THAT DESERTED OLD BUILDING OVER THERE? DITTO LEFT— MUST BE WHERE THEY USED TO MAKE HAIRPINS. Picture. 11.
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E.T.B. Broadway Bizarre. Prose. 12.
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E.B. The First One. Picture. 13.
Anonymous. It\u27s done. Prose. 14.
W.G.M. Mother. Prose. 15.
Anonymous. Our Daily Mud. Prose. 15.
G.C. Optimism. Poem. 15.
Bridge. Denison Comics. Picture. 16.
Anonymous. Our Asinetic Appreciation Corner. Prose. 18.
Anonymous. STILL LIFE OF A NEAR-BEER AT THE TURNING POINT. Picture. 18.
Rine, Russell. Stewed and Hashed. Poem. 18.
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Mercer, Hod. OUR OWN IDEA OF SOMETHING AESTHETIC. Picture. 19.
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Anonymous. Such Is Life. Poem. 19.
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Grayce. THE FLIGHT IS ON—THE FESTIVAL IS HERE. Picture. 20.
W.G.K. Eutopia Regained. Prose. 20.
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Anonymous. Oh You Nine Weeks. Poem. 20.
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Anonymous. THAT MAUSOLEUM HAS BEEN CONDEMNED BY THE BUILDING INSPECTOR. WHAT\u27S WRONG WITH IT? IT HASN\u27T ANY FIRE ESCAPES. Picture. 20.
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Lampoon. Cut Rates. Prose. 28.
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Gargoyle. Putting It Fairly. Prose. 29.
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Sun Dial. The Stuffed Kind. Prose. 30.
Student Life. Untitled. Prose. 30.
Malteaser. Heard in EC. Class. Prose. 30.
Nashville Tennessean. Untitled. Prose. 30.
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Gargoyle. Two is a Crowd. Prose. 31.
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Spatial heterogeneity of the cytosol revealed by machine learning-based 3D particle tracking
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McLaughlin, G. A., Langdon, E. M., Crutchley, J. M., Holt, L. J., Forest, M. G., Newby, J. M., & Gladfelter, A. S. (2020). Spatial heterogeneity of the cytosol revealed by machine learning-based 3D particle tracking. Molecular Biology of the Cell, 31(14), 1498-1511, doi:10.1091/mbc.E20-03-0210.The spatial structure and physical properties of the cytosol are not well understood. Measurements of the material state of the cytosol are challenging due to its spatial and temporal heterogeneity. Recent development of genetically encoded multimeric nanoparticles (GEMs) has opened up study of the cytosol at the length scales of multiprotein complexes (20-60 nm). We developed an image analysis pipeline for 3D imaging of GEMs in the context of large, multinucleate fungi where there is evidence of functional compartmentalization of the cytosol for both the nuclear division cycle and branching. We applied a neural network to track particles in 3D and then created quantitative visualizations of spatially varying diffusivity. Using this pipeline to analyze spatial diffusivity patterns, we found that there is substantial variability in the properties of the cytosol. We detected zones where GEMs display especially low diffusivity at hyphal tips and near some nuclei, showing that the physical state of the cytosol varies spatially within a single cell. Additionally, we observed significant cell-to-cell variability in the average diffusivity of GEMs. Thus, the physical properties of the cytosol vary substantially in time and space and can be a source of heterogeneity within individual cells and across populations.We would like to thank the 2016 Physiology course and Christina Termini at the Marine Biological Laboratory in Woods Hole, MA, Gregory Brittingham, and Marcus Roper for initial experiments and perspectives on pipeline. We thank David Adalsteinsson for help with DataTank software and many conversations about image analysis on large datasets. We thank Emmanual Levy (Weizmann Institute) for providing plasmids encoding synthetic phase separating peptides. This work was supported by Google Cloud, the National Science Foundation (NSF), the National Institutes of Health (NIH), and the Natural Sciences and Engineering Research Council of Canada (NSERC). ASG, EML, and GAM were supported by the NSF (RoLs: 1840273), HHMI faculty scholar award and the NIH (R01GM081506). JMN was supported by the NSERC (RGPIN-2019-06435, RGPAS-2019-00014, DGECR-2019-00321) and the NSF (DMS-171474). MGF was supported by the NSF (DMS-1816630, DMS-1664645). LJH was supported by the NIH (R01GM132447)
A meta-study of qualitative research examining determinants of children’s independent active free play
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