324 research outputs found

    Signatures of Steady Heating in Time Lag Analysis of Coronal Emission

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    Among the many ways of investigating coronal heating, the time lag method of Viall & Klimchuk (2012) is becoming increasingly prevalent as an analysis technique complementary to those traditionally used. The time lag method cross correlates light curves at a given spatial location obtained in spectral bands that sample different temperature plasmas. It has been used most extensively with data from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory. We have previously applied the time lag method to entire active regions and surrounding quiet Sun and create maps of the results (Viall & Klimchuk 2012; Viall & Klimchuk 2015). We find that the majority of time lags are consistent with the cooling of coronal plasma that has been impulsively heated. Additionally, a significant fraction of the map area has a time lag of zero. This does not indicate a lack of variability. Rather, strong variability must be present, and it must occur in phase in the different channels. We have shown previously that these zero time lags are consistent with the transition region response to coronal nanoflares (Viall & Klimchuk 2015; Bradshaw & Viall 2016), but other explanations are possible. A common misconception is that the zero time lag indicates steady emission resulting from steady heating. Using simulated and observed light curves, we demonstrate here that highly correlated light curves at zero time lag are not compatible with equilibrium solutions. Such light curves can only be created by evolution.Comment: 10 pages, 3 figures. Accepted to ApJ July 5 201

    Nanoflare Properties throughout Active Regions: Comparing SDO/AIA Observations with Modeled Active Region Light Curves

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    Coronal plasma in active regions is typically measured to be at temperatures near ~1-3 MK. Is the majority of the coronal plasma in hydrostatic equilibrium, maintained at these temperatures through a form of quasi-steady heating, or is this simply a measure of the average temperature of widely varying, impulsively heated coronal plasma? Addressing this question is complicated by the fact that the corona is optically thin: many thousands of flux tubes which are heated completely independently are contributing to the total emission along a given line of sight. There is a large body of work focused on the heating of isolated features - coronal loops - which are impulsively heated, however it is the diffuse emission between loops which often comprises the majority of active region emission. Therefore in this study we move beyond isolated features and analyze all of the emission in an entire active region from all contributing flux tubes. We investigate light curves systematically using SDO/AIA observations. We also model the active region corona as a line-of-sight integration of many thousands of completely independently heated flux tubes. The emission from these flux tubes may be time dependent, quasi-steady, or a mix of both, depending on the cadence of heat release. We demonstrate that despite the superposition of randomly heated flux tubes, different distributions of nanoflare cadences produce distinct signatures in light curves observed with multi-wavelength and high time cadence data, such as those from SDO/AIA. We conclude that the majority of the active region plasma is not maintained in hydrostatic equilibrium, rather it is undergoing dynamic heating and cooling cycles. The observed emission is consistent with heating through impulsive nanoflares, whose energy is a function of location within the active region

    The feasibility of conducting manual image segmentation of 3D sonographic images of axillary lymph nodes

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    School of Allied Medical Professions ScholarshipThe current standards of axillary lymph node staging following cancer diagnosis involve significant ionization, morbidity, and cost. While sonography has not yet been used in this capacity, three dimensional ultrasound has been used in the modeling of breast tumors with some success. This study was interested in determining whether 3D ultrasound could be used to manually segment axillary lymph node images in order to determine a reliable volume for later possible clinical significance. Fourteen volunteers were collected and one to three of their axillary lymph nodes imaged using a 4D16L GE transducer, specially designed to make volume measurements. Each node was then manually segmented using a deformable snake by two licensed sonographers and one untrained student and their volume results compared. Between the licensed sonographers for nodes 1, 2, and 3 correlations of r = 0.9 were achieved. Between the student and Sonographer A correlations of r = 0.6, 0.9, and 0.9, respectively, were accomplished, while with Sonographer B the correlations were r = 0.5, 0.9, and 0.9. This demonstrated the feasibility and validity of this technology, as well as indicated the importance of increased operator training. Three dimensional ultrasound should not be ruled out as a non-ionizing, less invasive alternative in lymph node staging. Advisor: Dr. Kevin EvansNo embarg

    Medication Administration In Child Care: A Comparison Of State Child Care Center Regulations With National Health And Safety Standards

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    The purpose of this thesis was to review the 50 state and D.C. child care center regulations (N=51) and compare with medication administration standards in Caring for Our Children (CFOC)- National Health and Safety Performance Standards: Guidelines for Out-of-Home Child Care Programs, 3rd edition (CFOC). A data collection instrument, which included the seven standards directly related to medication administration in early care and education programs (ECE), was developed and reviewed by a team of national experts to measure compliance of state regulations with the standards. None of the states\u27 regulations (N=51) met the criteria for all seven standards. Most of the states (98%) met some criteria for standards on medication administration (98%), labeling, storage, disposal (98%), contents of medication record (98%), and maintenance of records (84%). However, only a few states\u27 regulations included some of the criteria for training of caregivers (27%), a medication policy (22%), and records of injury (12%). Most state child care regulations do not meet CFOC standards to ensure safe medication administration to children in ECE programs

    5 Tips to Healthy Eating in College

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    This pamphlet informs the audience about the principles of healthy defaults, as well as tips for eating healthy in a college dining hall setting.https://dune.une.edu/an_studedres/1159/thumbnail.jp

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    Inherent length-scales of periodic solar wind number density structures

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    [1] We present an analysis of the radial length-scales of periodic solar wind number density structures. We converted 11 years (1995–2005) of solar wind number density data into radial length series segments and Fourier analyzed them to identify all spectral peaks with radial wavelengths between 72 (116) and 900 (900) Mm for slow (fast) wind intervals. Our window length for the spectral analysis was 9072 Mm, approximately equivalent to 7 (4) h of data for the slow (fast) solar wind. We required that spectral peaks pass both an amplitude test and a harmonic F-test at the 95% confidence level simultaneously. From the occurrence distributions of these spectral peaks for slow and fast wind, we find that periodic number density structures occur more often at certain radial length-scales than at others, and are consistently observed within each speed range over most of the 11-year interval. For the slow wind, those length-scales are L ∼ 73, 120, 136, and 180 Mm. For the fast wind, those length-scales are L ∼ 187, 270 and 400 Mm. The results argue for the existence of inherent radial length-scales in the solar wind number density

    Are periodic solar wind number density structures formed in the solar corona?

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    [1] We present an analysis of the alpha to proton solar wind abundance ratio (AHe) during a period characterized by significant large size scale density fluctuations, focusing on an event in which the proton and alpha enhancements are anti-correlated. In a recent study using 11 years (1995–2005) of solar wind observations from the Wind spacecraft, N. M. Viall et al. [2008] showed that periodic proton density structures occurred at particular radial length-scales more often than others. The source of these periodic density structures is a significant and outstanding question. Are they generated in the interplanetary medium, or are they a relic of coronal activity as the solar wind was formed? We use AHe to answer this question, as solar wind elemental abundance ratios are not expected to change during transit. For this event, the anti-phase nature of the AHe variations strongly suggests that periodic solar wind density structures originate in the solar corona

    Relative occurrence rates and connection of discrete frequency oscillations in the solar wind density and dayside magnetosphere

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    [1] We present an analysis of the occurrence distributions of statistically significant apparent frequencies of periodic solar wind number density structures and dayside magnetospheric oscillations in the f = 0.5–5.0 mHz range. Using 11 years (1995–2005) of solar wind data, we identified all spectral peaks that passed both an amplitude test and a harmonic F test at the 95% confidence level in 6-hour data segments. We find that certain discrete frequencies, specifically f = 0.7, 1.4, 2.0, and 4.8 mHz, occur more often than do other frequencies over those 11 years. We repeat the analysis on discrete oscillations observed in 10 years (1996–2005) of dayside magnetospheric data. We find that certain frequencies, specifically f = 1.0, 1.5, 1.9, 2.8, 3.3, and 4.4 mHz, occur more often than do other frequencies over those 10 years. Many of the enhancements found in the magnetospheric occurrence distributions are similar to those found in the solar wind. Lastly, we counted the number of times the same discrete frequencies were identified as statistically significant using our two spectral tests on corresponding solar wind and magnetospheric 6-hour time series. We find that in 54% of the solar wind data segments in which we identified a spectral peak, at least one of the same discrete frequencies was statistically significant in the corresponding magnetospheric data segment. Our results argue for the existence of inherent apparent frequencies in the solar wind number density that directly drive global magnetospheric oscillations at the same discrete frequencies, although the magnetosphere also oscillates through other physical mechanisms
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