On the development of a suite of tools for the analysis of Twitter discourse

Social media has become a ubiquitous avenue of natural language use that represents an enormous amount of data, which has in the last decade been used in an increasing amount of linguistic research in such topics as regional variation, stylistic variation, and identity and community construction. For a number of technical reasons, however, the collection and analysis of Twitter data for research purposes is currently prohibitively difficult, especially for studies with a particular interest in Twitter as a site of discourse creation. Existing collection tools require almost all require programming skills, and existing analytical tools are not equipped to handle the metadata that Twitter data includes, much less to leverage that metadata to highlight linguistic trends or to make large datasets navigable. In an attempt to address this problem, I have developed a web-based set of tools, called TWIG (TWItter Getter), for collecting and analyzing Twitter data. This document begins with a discussion of the basic mechanics of Twitter and its nature as a discourse context and then details the need for specialized Twitter data collection and analysis tools that focus on the needs of researchers interested in Twitter generally, and those interested in discourse specifically. The remainder of the document describes TWIG and demonstrates its use in two sample studies—one an analysis of a community’s construction of identity and values on twitter, and the second a usage-based analysis of semantic change in the construction really do be

Upwelling to Outflowing Oxygen Ions at Auroral Latitudes during Quiet Times: Exploiting a New Satellite Database

The mechanisms by which thermal O+ escapes from the top of the ionosphere and into the magnetosphere are not fully understood even with 30 years of active research. This thesis introduces a new database, builds a simulation framework around a thermospheric model and exploits these tools to gain new insights into the study of O+ ion outflows. A dynamic auroral boundary identification system is developed using Defense Meteorological Satellite Program (DMSP) spacecraft observations at 850 km to build a database characterizing the oxygen source region. This database resolves the ambiguity of the expansion and contraction of the auroral zone. Mining this new dataset, new understanding is revealed. We describe the statistical trajectory of the cleft ion fountain return flows over the polar cap as a function of activity and the orientation of the interplanetary magnetic field y-component. A substantial peak in upward moving O+ in the morning hours is discovered. Using published high altitude data we demonstrate that between 850 and 6000 km altitude, O+ is energized predominantly through transverse heating; and acceleration in this altitude region is relatively more important in the cusp than at midnight. We compare data with a thermospheric model to study the effects of solar irradiance, electron precipitation and neutral wind on the distribution of upward O+ at auroral latitudes. EUV irradiance is shown to play a dominant role in establishing a dawn-focused source population of upwelling O+ that is responsible for a pre-noon feature in escaping O+ fluxes. This feature has been corroborated by observations on platforms including the Dynamics Explorer 1 (DE-1), Polar, and Fast Auroral Snapshot SnapshoT (FAST) spacecraft. During quiet times our analysis shows that the neutral wind is more important than electron precipitation in establishing the dayside O+ upwelling distribution. Electron precipitation is found to play a relatively modest role in controlling dayside, and a critical role in controlling nightside, upwelling O+. This thesis provides a new database, and insights into the study of oxygen ion outflows during quiet times. These results and tools will be essential for researchers working on topics involving magnetosphere-ionosphere interactions

September 2017's geoeffective space weather and impacts to Caribbean radio communications during Hurricane response

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Space Weather 16 (2018): 1190-1201, doi:10.1029/2018SW001897.Between 4 and 10 September 2017, multiple solar eruptions occurred from active region AR12673. NOAA's and NASA's well‐instrumented spacecraft observed the evolution of these geoeffective events from their solar origins, through the interplanetary medium, to their geospace impacts. The 6 September X9.3 flare was the largest to date for the nearly concluded solar cycle 24 and, in fact, the brightest recorded since an X17 flare in September 2005, which occurred during the declining phase of solar cycle 23. Rapid ionization of the sunlit upper atmosphere occurred, disrupting high‐frequency communications in the Caribbean region while emergency managers were scrambling to provide critical recovery services caused by the region's devastating hurricanes. The 10 September west limb eruption resulted in the first solar energetic particle event since 2012 with sufficient flux and energy to yield a ground level enhancement. Spacecraft at L1, including DSCOVR, sampled the associated interplanetary coronal mass ejections minutes before their collision with Earth's magnetosphere. Strong compression and erosion of the dayside magnetosphere occurred, placing geosynchronous satellites in the magnetosheath. Subsequent geomagnetic storms produced magnificent auroral displays and elevated hazards to power systems. Through the lens of NOAA's space weather R‐S‐G storm scales, this event period increased hazards for systems susceptible to elevated “radio blackout” (R3‐strong), “solar radiation storm” (S3‐strong), and “geomagnetic storm” (G4‐severe) conditions. The purpose of this paper is to provide an overview of the September 2017 space weather event, and a summary of its consequences, including forecaster, post‐event analyst, and communication operator perspectives

Detecting integration of top-down information using the mismatch negativity: Preliminary evidence from phoneme restoration

The current study utilizes mismatch negativity in the phenomenon of phoneme restoration to investigate the critical debate regarding the integration of top down (lexical) and bottom up (acoustic) processing in spoken word recognition. Phoneme restoration, which occurs when phonemes missing from a speech signal are restored by the brain and may appear to be heard, was examined in a multi-standard oddball paradigm. Participants heard stimuli while watching a quiet animated film. Stimuli were divided into word and non- word conditions, with noise added to some stimuli to make them ambiguous. The many-to-one ratio of standards to deviants for generation of mismatch negativity (MMN) was achieved only if the brain could recover the missing phoneme in the ambiguous, noise-spliced stimuli. Both word and nonword conditions were compared to verify that an elicited MMN among words was contingent on involvement of the lexicon in the grouping of standards, and not some more general cognitive grouping procedure. Results from seven participants show preliminary support for the predicted effect: i.e., mismatch negativity for words but not for nonwords. This effect is contingent on phoneme restoration, and thus is consistent with recent literature suggesting that MMN is sensitive to higher information structures such as the mental lexicon. Keywords: phoneme restoration, MMN, lexical access, top-down information

Detecting integration of top-down information using the mismatch negativity: Preliminary evidence from phoneme restoration

The current study utilizes mismatch negativity in the phenomenon of phoneme restoration to investigate the critical debate regarding the integration of top down (lexical) and bottom up (acoustic) processing in spoken word recognition. Phoneme restoration, which occurs when phonemes missing from a speech signal are restored by the brain and may appear to be heard, was examined in a multi-standard oddball paradigm. Participants heard stimuli while watching a quiet animated film. Stimuli were divided into word and non- word conditions, with noise added to some stimuli to make them ambiguous. The many-to-one ratio of standards to deviants for generation of mismatch negativity (MMN) was achieved only if the brain could recover the missing phoneme in the ambiguous, noise-spliced stimuli. Both word and nonword conditions were compared to verify that an elicited MMN among words was contingent on involvement of the lexicon in the grouping of standards, and not some more general cognitive grouping procedure. Results from seven participants show preliminary support for the predicted effect: i.e., mismatch negativity for words but not for nonwords. This effect is contingent on phoneme restoration, and thus is consistent with recent literature suggesting that MMN is sensitive to higher information structures such as the mental lexicon. Keywords: phoneme restoration, MMN, lexical access, top-down informatio

Multipoint observations of compressional Pc5 pulsations in the dayside magnetosphere and corresponding particle signatures

We use Van Allen Probes (Radiation Belt Storm Probes A and B, henceforth RBSP-A and RBSP-B) and GOES-13 and GOES-15 (henceforth G-13 and G-15) multipoint magnetic field, electric field, plasma, and energetic particle observations to study the spatial, temporal, and spectral characteristics of compressional Pc5 pulsations observed during the recovery phase of a strong geomagnetic storm on 1 January 2016. From ∼ 19:00 to 23:02 UT, successive magnetospheric compressions enhanced the peak-to-peak amplitudes of Pc5 waves with 4.5\u276.0 mHz frequencies from 0\u27 2 to 10\u2715 nT at both RBSP-A and RBSP-B, particularly in the prenoon magnetosphere. Poloidal Pc4 pulsations with frequencies of ∼ 22\u2729 mHz were present in the radial Bx component. The frequencies of these Pc4 pulsations diminished with increasing radial distance, as expected for resonant Alfv n waves standing along field lines. The GOES spacecraft observed Pc5 pulsations with similar frequencies to those seen by the RBSP but Pc4 pulsations with lower frequencies. Both RBSP-A and RBSP-B observed frequency doubling in the compressional component of the magnetic field during the Pc5 waves, indicating a meridional sloshing of the equatorial node over a combined range in ZSM from 0.25 to-0:08 Re, suggesting that the amplitude of this meridional oscillation was ∼ 0.16 Re about an equatorial node whose mean position was near ZSM D∼ 0:08 Re. RBSP-A and RBSP-B HOPE (Helium Oxygen Proton Electron) and MagEIS (Magnetic Electron Ion Spectrometer) observations provide the first evidence for a corresponding frequency doubling in the plasma density and the flux of energetic electrons, respectively. Energetic electron fluxes oscillated out of phase with the magnetic field strength with no phase shift at any energy. In the absence of any significant solar wind trigger or phase shift with energy, we interpret the compressional Pc5 pulsations in terms of the mirror-mode instability

A Self-Supervised Feature Map Augmentation (FMA) Loss and Combined Augmentations Finetuning to Efficiently Improve the Robustness of CNNs

Deep neural networks are often not robust to semantically-irrelevant changes in the input. In this work we address the issue of robustness of state-of-the-art deep convolutional neural networks (CNNs) against commonly occurring distortions in the input such as photometric changes, or the addition of blur and noise. These changes in the input are often accounted for during training in the form of data augmentation. We have two major contributions: First, we propose a new regularization loss called feature-map augmentation (FMA) loss which can be used during finetuning to make a model robust to several distortions in the input. Second, we propose a new combined augmentations (CA) finetuning strategy, that results in a single model that is robust to several augmentation types at the same time in a data-efficient manner. We use the CA strategy to improve an existing state-of-the-art method called stability training (ST). Using CA, on an image classification task with distorted images, we achieve an accuracy improvement of on average 8.94% with FMA and 8.86% with ST absolute on CIFAR-10 and 8.04% with FMA and 8.27% with ST absolute on ImageNet, compared to 1.98% and 2.12%, respectively, with the well known data augmentation method, while keeping the clean baseline performance.Comment: Accepted at ACM CSCS 2020 (8 pages, 4 figures

Out-of-Cycle Update of the US/UK World Magnetic Model for 2015-2020

In early 2018, the World Magnetic Model 2015-2020 (WMM2015) was predicted to exceed its performance specification error tolerances by the end of 2018 or early 2019. Specifically, the grid variation root-mean-square error was about to exceed the 1 degree specification (MIL-PRF89500A) due to fast fluid flows in the Earth’s outer core, especially in the North polar region. An out-of-cycle update of the WMM2015 was developed and released in early 2019 (WMM2015v2) to address this performance degradation. There was a pre-release in September 2018 and this technical note confirms the information provided in that pre-release. It also provides a description of the new model (section 1), how it was produced (section 2) and its uncertainties (section 3). How to Use this Note: A complete description of the WMM2015 is provided in the WMM2015 Technical Report (Chulliat et al., 2015; WMM2015-TR hereafter (http://nora.nerc.ac.uk/id/eprint/510709/)). This new technical note should be seen as an addendum to the WMM2015-TR. It is organized in the same manner as the WMM2015-TR in order to facilitate the retrieval of information by users. It only includes information that is new for the out-of-cycle update, hereafter referred to as WMM2015v2

Long-term results of pancreas transplantation under tacrolimus immunosuppression

Background. The long-term safety and efficacy of tacrolimus in pancreas transplantation has not yet been demonstrated. The observation of prolonged pancreatic graft function under tacrolimus would indicate that any potential islet toxicity is short-lived and clinically insignificant. We report herein the results of pancreas transplantation in patients receiving primary tacrolimus immunosuppression for a minimum of 2 years. Methods. From July 4, 1994 until April 18, 1996, 60 patients received either simultaneous pancreas- kidney transplant (n=55), pancreas transplant only (n=4), or pancreas after kidney transplantation (n=1). Baseline immunosuppression consisted of tacrolimus and steroids without antilymphocyte induction. Azathioprine was used as a third agent in 51 patients and mycophenolate mofetil in 9. Rejection episodes within the first 6 months occurred in 48 (80%) patients and were treated with high-dose corticosteroids. Antilymphocyte antibody was required in eight (13%) patients with steroid-resistant rejection. Results. With a mean follow-up of 35.1±5.9 months (range: 24.3-45.7 months), 6-month and 1-, 2-, and 33-year graft survival is 88%, 82%, 80%, and 80% pancreas) and 98%, 96%, 93%, and 91% (kidney), respectively. Six-month and 1-, 2-, and 3-year patient survival is 100%, 98%, 98%, and 96.5%. Mean fasting glucose is 91.6±13.8 mg/dl, and mean glycosylated hemoglobin is 5.1±0.7% (normal range: 4.3-6.1%). Mean tacrolimus dose is 6.5±2.6 mg/day and mean prednisone dose 2.0±2.9 mg/day at follow-up. Complete steroid withdrawal was possible in 31 (65%) of the 48 patients with functioning pancreases. Conclusions. These data show for the first time that tacrolimus is a safe and effective long-term primary agent in pancreas transplantation and provides excellent long-term islet function without evidence of toxicity while permitting steroid withdrawal in the majority of patients