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At least 1,387 records · Page 77

Towards the development of a standardized testing protocol for overhead island kitchen exhaust devices: Procedures, measurements and paths forward

Cooking is one of the most important sources of airborne pollutants in the indoor environments of residential buildings. Elevated concentrations of NO 2 due to cooking have been reported widely (Garret et al. 1998; Garrett et al. 1999; Mullen et al. 2016; Ryan et al. 1988; Schwab et al. 1994; J. Spengler et al. 1994; J. D. Spengler et al. 1983; Wilson et al. 1995). Many researchers have attributed elevated particulate concentrations to cooking, and some have attributed extremely high short-term concentrations of fine particles (>300 μg/m3) and ultrafine particles (>105 μg/m3) to cooking events (Abdullahi et al. 2013; Abt et al. 2000; Afshari et al. 2005; Buonanno et al. 2009; He et al. 2004; Kearney et al. 2011; Lance A. Wallace et al. 2004; See and Balasubramanian 2008; Stieb et al. 2008; Wallace and Ott 2011; Wheeler et al. 2011; Zhang et al. 2010). Cooking is also a source of other gas-phase pollutants including carbon monoxide, formaldehyde, acrolein, and other volatile organic compounds (Garret et al. 1998; Garrett et al. 1999; Logue et al. 2013; Mullen et al. 2016; Ryan et al. 1988; Schwab et al. 1994; J. Spengler et al. 1994; J. D. Spengler et al. 1983; V. Seaman et al. 2007; Wilson et al. 1995). Lastly, cooking can be a significant source of water vapor, and the water vapor produced from cooking can eventually lead to moisture-related problems (Parrott and Emmel 2003)

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Comment on "Valence state of titanium in the Wark-Lovering rim of a Leoville CAI as a record of progressive oxidation in the early Solar Nebula" by K.A. Dyl, J.I. Simon and E.D. Young

Dyl et al. (2011) state that their results confirm the conclusion of J. Simon et al. (2005) that the pyroxene in Wark-Lovering rims (Wark and Lovering, 1977) found on Ca-, Al-rich refractory inclusions has lower Ti 3+ /Ti tot ratios than the primary pyroxene in the interiors of inclusions. While true, the claim is misleading because J. Simon et al. (2005) concluded that there was no Ti 3+ in the rims, whereas Dyl et al. (2011) found Ti 3+ in 41 of 42 new rim analyses. In addition, J. Simon et al. (2005) concluded that rims formed under much more oxidizing conditions, log fO 2 ≥ IW-1, or ≥ 6-7 log units higher, than inclusion interiors. The conclusions of J. Simon et al. (2005) were disputed by S. Simon et al. (2007) and are not supported by the new data of Dyl et al. (2011). The present work is intended for clarification of this and other issues.

58 GEOSCIENCES↗

Increasing Use of Dose-Escalated External Beam Radiation Therapy for Men With Nonmetastatic Prostate Cancer

Purpose: To examine recent practice patterns, using a large national cancer registry, to understand the extent to which dose-escalated external beam radiation therapy (EBRT) has been incorporated into routine clinical practice for men with prostate cancer. Methods and Materials: We conducted a retrospective observational cohort study using the National Cancer Data Base, a nationwide oncology outcomes database in the United States. We identified 98,755 men diagnosed with nonmetastatic prostate cancer between 2006 and 2011 who received definitive EBRT and classified patients into National Comprehensive Cancer Network (NCCN) risk groups. We defined dose-escalated EBRT as total prescribed dose of ≥75.6 Gy. Using multivariable logistic regression, we examined the association of patient, clinical, and demographic characteristics with the use of dose-escalated EBRT. Results: Overall, 81.6% of men received dose-escalated EBRT during the study period. The use of dose-escalated EBRT did not vary substantially by NCCN risk group. Use of dose-escalated EBRT increased from 70.7% of patients receiving treatment in 2006 to 89.8% of patients receiving treatment in 2011. On multivariable analysis, year of diagnosis and use of intensity modulated radiation therapy were significantly associated with receipt of dose-escalated EBRT. Conclusions: Our study results indicate that dose-escalated EBRT has been widely adopted by radiation oncologists treating prostate cancer in the United States. The proportion of patients receiving dose-escalated EBRT increased nearly 20% between 2006 and 2011. We observed high utilization rates of dose-escalated EBRT within all disease risk groups. Adoption of intensity modulated radiation therapy was strongly associated with use of dose-escalated treatment.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

Mapping the Future: Towards Oncology Curriculum Reform in Undergraduate Medical Education at a Canadian Medical School

Purpose: To evaluate (1) the quantity and quality of current undergraduate oncology teaching at a major Canadian medical school; and (2) curricular changes over the past decade, to enhance local oncology education and provide insight for other educators. Methods and Materials: Relevant 2011-2012 undergraduate curricular sessions were extracted from the University of Toronto curriculum mapping database using keywords and database identifiers. Educational sessions were analyzed according to Medical Council of Canada objectives, discussion topics, instructor qualifications, teaching format, program year, and course subject. Course-related oncology research projects performed by students during 2000 to 2012 were extracted from another internal database. Elective choices of clerks during 2008-2014 were retrieved from the institution. The 2011-2012 and 2000-2001 curricula were compared using common criteria. Results: The 2011-2012 curriculum covers 5 major themes (public health, cancer biology, diagnosis, principles of care, and therapy), which highlight 286 oncology teaching topics within 80 sessions. Genitourinary (10, 12.5%), gynecologic (8, 10.0%), and gastrointestinal cancers (7.9, 9.8%) were the most commonly taught cancers. A minority of sessions were taught by surgical oncologists (6.5, 8.1%), medical oncologists (2.5, 3.1%), and radiation oncologists (1, 1.2%). During 2000-2012, 9.0% of students (233 of 2578) opted to complete an oncology research project. During 2008-2014, oncology electives constituted 2.2% of all clerkship elective choices (209 of 9596). Compared with pre-2001 curricula, the 2012 oncology curriculum shows notable expansion in the coverage of epidemiology (6:1 increase), prevention (4:1), screening (3:1), and molecular biology (6:1). Conclusions: The scope of the oncology curriculum has grown over the past decade. Nevertheless, further work is needed to improve medical student knowledge of cancers, particularly those relevant to public health needs. Defining minimum curricular content, emphasizing content based on population needs, and ensuring educational delivery with the support and expertise of oncologists and non-oncologists will be essential next steps.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

Impact of Using Audit Data to Improve the Evidence-Based Use of Single-Fraction Radiation Therapy for Bone Metastases in British Columbia

Purpose: To assess the impact of a population-based intervention to increase the consistency and use of single-fraction radiation therapy (SFRT) for bone metastases. Methods and Materials: In 2012, an audit of radiation therapy prescriptions for bone metastases in British Columbia identified significant interphysician and -center (26%-73%) variation in the use of SFRT. Anonymous physician-level and identifiable regional cancer center SFRT use data were presented to all radiation oncologists, together with published guidelines, meta-analyses, and recommendations from practice leaders. The use of SFRT for bone metastases from 2007 through 2011 was compared with use of SFRT in 2013, to assess the impact of the audit and educational intervention. Multilevel logistic regression was used to assess the relationship between the usage of SFRT and the timing of the radiation while controlling for potentially confounding variables. Physician and center were included as group effects to account for the clustered structure of the data. Results: A total of 16,898 courses of RT were delivered from 2007 through 2011, and 3200 courses were delivered in 2013. The rates of SFRT use in 2007, 2008, 2009, 2010, 2011, and 2013 were 50.5%, 50.9%, 48.3%, 48.5%, 48.0%, and 59.7%, respectively (P<.001). Use of SFRT increased in each of 5 regional centers: A: 26% to 32%; B: 36% to 56%; C: 39% to 57%; D: 49% to 56%; and E: 73% to 85.0%. Use of SFRT was more consistent; 3 of 5 centers used SFRT for 56% to 57% of bone metastases RT courses. The regression analysis showed strong evidence that the usage of SFRT increased after the 2012 intervention (odds ratio 2.27, 95% confidence interval 2.06-2.50, P<.0001). Conclusion: Assessed on a population basis, an audit-based intervention increased utilization of SFRT for bone metastases. The intervention reversed a trend to decreasing SFRT use, reduced costs, and improved patient convenience. This suggests that dissemination of programmatic quality indicators in oncology can lead to increased utilization of evidence-based practice.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

Analysis of data from sensitive U.S. monitoring stations for the Fukushima Dai-ichi nuclear reactor accident

The March 11, 2011 9.0 magnitude undersea megathrust earthquake off the coast of Japan and subsequent tsunami waves triggered a major nuclear event at the Fukushima Dai-ichi nuclear power station. At the time of the event, units 1, 2, and 3 were operating and units 4, 5, and 6 were in a shutdown condition for maintenance. Loss of cooling capacity to the plants along with structural damage caused by the earthquake and tsunami resulted in a breach of the nuclear fuel integrity and release of radioactive fission products to the environment. Fission products started to arrive in the United States via atmospheric transport on March 15, 2011 and peaked by March 23, 2011. Atmospheric activity concentrations of 131I reached levels of 3.0 * 10*2 Bqm*3 in Melbourne, FL. The noble gas 133Xe reached atmospheric activity concentrations in Ashland, KS of 17 Bqm*3. While these levels are not health concerns, they were well above the detection capability of the radionuclide monitoring systems within the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty.

Biegalski, Steven R.↗

Effective Half-Life of Caesium-137 in Various Environmental Media at the Savannah River Site

During the operational history of the Savannah River Site (SRS), many different radionuclides have been released from site facilities into the SRS environment. However, only a relatively small number of pathways, most importantly 137 Cs in fish and deer, have contributed significantly to doses and risks to the public. The “effective” half-lives (T e ) of 137 Cs (which include both physical decay and environmental dispersion) in Savannah River floodplain soil and vegetation and in fish and white-tailed deer from the SRS were estimated using long-term monitoring data. For 1974–2011, the T e s of 137 Cs in Savannah River floodplain soil and vegetation were 17.0 years (95% CI = 14.2–19.9) and 13.4 years (95% CI = 10.8–16.0), respectively. These T e s were greater than in a previous study that used data collected only through 2005 as a likely result of changes in the flood regime of the Savannah River. Field analyses of 137 Cs concentrations in deer collected during yearly controlled hunts at the SRS indicated an overall T e of 15.9 years (95% CI = 12.3–19.6) for 1965–2011; however, the T e for 1990–2011 was significantly shorter (11.8 years, 95% CI = 4.8–18.8) due to an increase in the rate of 137 Cs removal. The shortest T e s were for fish in SRS streams and the Savannah River (3.5–9.0 years), where dilution and dispersal resulted in rapid 137 Cs removal. Long-term data show that T e s are significantly shorter than the physical half-life of 137 Cs in the SRS environment but that they can change over time. Therefore, it is desirable have a long period of record for calculating Tes and risky to extrapolate T e s beyond this period unless the processes governing 137 Cs removal are clearly understood.

54 ENVIRONMENTAL SCIENCES↗

Validation and Testing of ENDF/B-VII Decay Data

The nuclear decay library developed for the ORIGEN code was upgraded from ENDF/B-VI.8 to -VII.0 and released in the SCALE nuclear modeling and simulation code system in 2011. Experience with the ENDF/B-VII.0 library identified serious errors and performance issues in the evaluated decay sublibrary. Initially, errors were identified in the decay scheme for the 238U series, leading to large discrepancies in the gamma emission rate for uranium. Further testing of the fission product decay data revealed significant performance issues with ENDF/B-VII.0 relative to the previous release of ENDF/B-VI. To address the performance issues, the decay data library in SCALE was upgraded to ENDF/B-VII.1 and released as an update for users in 2013. This paper describes the practical impact of the ENDF/B-VII.0 decay data performance issues on common code applications, and the validation and testing performed on the updated ORIGEN libraries developed from the ENDF/B-VII.1 sublibrary.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Correlation between Asian Dust and Specific Radioactivities of Fission Products Included in Airborne Samples in Tokushima, Shikoku Island, Japan, Due to the Fukushima Nuclear Accident

Radioactive fission product {sup 131}I released from the Fukushima Daiichi Nuclear Power Plants (FD-NPP) was first detected on March 23, 2011 in an airborne aerosol sample collected at Tokushima, Shikoku Island, located in western Japan. Two other radioactive fission products, {sup 134}Cs and {sup 137}Cs were also observed in a sample collected from April 2 to 4, 2011. The maximum specific radioactivities observed in this work were about 2.5 to 3.5 mBq×m{sup -3} in a airborne aerosol sample collected on April 6. During the course of the continuous monitoring, we also made our first observation of seasonal Asian Dust and those fission products associated with the FDNPP accident concurrently from May 2 to 5, 2011. We found that the specific radioactivities of {sup 134}Cs and {sup 137}Cs decreased drastically only during the period of Asian Dust. And also, it was found that this trend was very similar to the atmospheric elemental concentration (ng×m{sup -3}) variation of stable cesium ({sup 133}Cs) quantified by elemental analyses using our developed ICP-DRC-MS instrument.

54 ENVIRONMENTAL SCIENCES↗

First isolation of Aedes flavivirus in the Western Hemisphere and evidence of vertical transmission in the mosquito Aedes (Stegomyia) albopictus (Diptera: Culicidae)

We report here the first evidence of vertical transmission of Aedes flavivirus (AEFV) and its first isolation in the Western Hemisphere. AEFV strain SPFLD-MO-2011-MP6 was isolated in C6/36 cells from a pool of male Aedes albopictus mosquitoes that were reared to adults from larvae collected in southwest Missouri, USA, in 2011. Electron micrographs of the virus showed virions of approximately 45 nm in diameter with morphological characteristics associated with flaviviruses. The genomic sequence demonstrated that AEFV-SPFLD-MO-2011-MP6 shares a high degree of nucleotide and amino acid sequence identity with the AEFV Narita-21 strain, isolated in Japan in 2003. Intracerebral inoculation of newborn mice with the virus failed to produce observable illness or death and the virus did not replicate in vertebrate cells, consistent with a lack of vertebrate host range. - Highlights: ► The first report of Aedes flavivirus (AEFV) in the Western Hemisphere. ► The first evidence of vertical transmission of AEFV in mosquitoes. ► The first electron micrograph of AEFV. ► The first attempt to infect animals with AEFV.

60 APPLIED LIFE SCIENCES↗

Contiguous US summer maximum temperature and heat stress trends in CRU and NOAA Climate Division data plus comparisons to reanalyses

Abstract Warming is a major climate change concern, but the impact of high maximum temperatures depends upon the air’s moisture content. Trends in maximum summertime temperature, moisture, and heat index are tracked over three time periods: 1900–2011, 1950–2011, and 1979–2011; these trends differ notably from annual temperature trends. Trends are emphasized from two CRU datasets (CRUTS3.25 and CRUTS4.01) and two reanalyses (ERA-20C and 20CRv2). Maximum temperature trends tend towards warming that is stronger over the Great Lakes, the interior western and the northeastern contiguous United States. A warming hole in the Midwest generally decreases in size and magnitude when heat stress trends are calculated because the region has increasing moisture. CRU and nearly all reanalyses find cooling in the northern high plains that is not found in NOAA Climate Division trends. These NOAA trends are captured better by CRUTS401. Moistening in the northeast amplifies the heat stress there. Elsewhere the moisture trends are less clear. Drying over northern Texas (after 1996) in CRUTS401 translates into decreasing heat stress there (less so in CRUTS325). Though other reanalyses are not intended for long-term trends, MERRA-2 and ERA-Interim match observed trends better than other reanalyses.

54 ENVIRONMENTAL SCIENCES↗

Hot-spot mix in ignition-scale implosions on the NIF

Ignition of an inertial confinement fusion (ICF) target depends on the formation of a central hot spot with sufficient temperature and areal density. Radiative and conductive losses from the hot spot can be enhanced by hydrodynamic instabilities. The concentric spherical layers of current National Ignition Facility (NIF) ignition targets consist of a plastic ablator surrounding a thin shell of cryogenic thermonuclear fuel (i.e., hydrogen isotopes), with fuel vapor filling the interior volume [S. W. Haan et al., Phys. Plasmas 18, 051001 (2011)]. The Rev. 5 ablator is doped with Ge to minimize preheat of the ablator closest to the DT ice caused by Au M-band emission from the hohlraum x-ray drive [D. S. Clark et al., Phys. Plasmas 17, 052703 (2010)]. Richtmyer-Meshkov and Rayleigh-Taylor hydrodynamic instabilities seeded by high-mode () ablator-surface perturbations can cause Ge-doped ablator to mix into the interior of the shell at the end of the acceleration phase [B. A. Hammel et al., Phys. Plasmas 18, 056310 (2011)]. As the shell decelerates, it compresses the fuel vapor, forming a hot spot. K-shell line emission from the ionized Ge that has penetrated into the hot spot provides an experimental signature of hot-spot mix. The Ge emission from tritium-hydrogen-deuterium (THD) and deuterium-tritium (DT) cryogenic targets and gas-filled plastic-shell capsules, which replace the THD layer with a mass-equivalent CH layer, was examined. The inferred amount of hot-spot-mix mass, estimated from the Ge K-shell line brightness using a detailed atomic physics code [J. J. MacFarlane et al., High Energy Density Phys. 3, 181 (2006)], is typically below the 75-ng allowance for hot-spot mix [S. W. Haan et al., Phys. Plasmas 18, 051001 (2011)]. Predictions of a simple mix model, based on linear growth of the measured surface-mass modulations, are consistent with the experimental results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Improvements to laser wakefield accelerated electron beam stability, divergence, and energy spread using three-dimensional printed two-stage gas cell targets

High intensity, short pulse lasers can be used to accelerate electrons to ultra-relativistic energies via laser wakefield acceleration (LWFA) [T. Tajima and J. M. Dawson, Phys. Rev. Lett. 43, 267 (1979)]. Recently, it was shown that separating the injection and acceleration processes into two distinct stages could prove beneficial in obtaining stable, high energy electron beams [Gonsalves et al., Nat. Phys. 7, 862 (2011); Liu et al., Phys. Rev. Lett. 107, 035001 (2011); Pollock et al., Phys. Rev. Lett. 107, 045001 (2011)]. Here, we use a stereolithography based 3D printer to produce two-stage gas targets for LWFA experiments on the HERCULES laser system at the University of Michigan. We demonstrate substantial improvements to the divergence, pointing stability, and energy spread of a laser wakefield accelerated electron beam compared with a single-stage gas cell or gas jet target.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

The preliminary results: Internal seismic velocity structure imaging beneath Mount Lokon

Historical records that before the 17{sup th} century, Mount Lokon had been dormant for approximately 400 years. In the years between 1350 and 1400, eruption ever recorded in Empung, came from Mount Lokon’s central crater. Subsequently, in 1750 to 1800, Mount Lokon continued to erupt again and caused soil damage and fall victim. After 1949, Mount Lokon dramatically increased in its frequency: the eruption interval varies between 1 – 5 years, with an average interval of 3 years and a rest interval ranged from 8 – 64 years. Then, on June 26{sup th}, 2011, standby alert set by the Center for Volcanology and Geological Hazard Mitigation. Peak activity happened on July 4{sup th}, 2011 that Mount Lokon erupted continuously until August 28{sup th}, 2011. In this study, we carefully analyzed micro-earthquakes waveform and determined hypocenter location of those events. We then conducted travel time seismic tomographic inversion using SIMULPS12 method to detemine Vp, Vs and Vp/Vs ratio structures beneath Lokon volcano in order to enhance our subsurface geological structure. During the tomographic inversion, we started from 1-D seismic velocities model obtained from VELEST33 method. Our preliminary results show low Vp, low Vs, and high Vp/Vs are observed beneath Mount Lokon-Empung which are may be associated with weak zone or hot material zones. However, in this study we used few station for recording of micro-earthquake events. So, we suggest in the future tomography study, the adding of some seismometers in order to improve ray coverage in the region is profoundly justified.

58 GEOSCIENCES↗

Assessing Component Effects in Formulation Systems

The purpose of Snee (2011) was to discuss and illustrate how using Six Sigma concepts and approaches can lead to a better understanding of formulation systems. Central to the recommended approach is estimating and interpreting the effects of the components in the formulation on the response variable. Knowledge of components that have no effect, small or large effects (positive or negative), and similar effects is very helpful in understanding how the formulation system works. This understanding helps one decide 1) which components having large effects should be increased or decreased, and 2) what to do about components with no effects or similar effects. Correspondence between the authors following Snee (2011), along with further review of the literature, have pointed out that the approaches discussed in Snee (2011), and the interpretation of component effects in general, need further clarification. That is the focus of this article.

component effect directions↗

SDSS-III: MASSIVE SPECTROSCOPIC SURVEYS OF THE DISTANT UNIVERSE, THE MILKY WAY, AND EXTRA-SOLAR PLANETARY SYSTEMS

Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of the Milky Way, and the population of giant planets around other stars. In keeping with SDSS tradition, SDSS-III will provide regular public releases of all its data, beginning with SDSS Data Release 8 (DR8), which was made public in 2011 January and includes SDSS-I and SDSS-II images and spectra reprocessed with the latest pipelines and calibrations produced for the SDSS-III investigations. This paper presents an overview of the four surveys that comprise SDSS-III. The Baryon Oscillation Spectroscopic Survey will measure redshifts of 1.5 million massive galaxies and Ly{alpha} forest spectra of 150,000 quasars, using the baryon acoustic oscillation feature of large-scale structure to obtain percent-level determinations of the distance scale and Hubble expansion rate at z < 0.7 and at z {approx} 2.5. SEGUE-2, an already completed SDSS-III survey that is the continuation of the SDSS-II Sloan Extension for Galactic Understanding and Exploration (SEGUE), measured medium-resolution (R = {lambda}/{Delta}{lambda} {approx} 1800) optical spectra of 118,000 stars in a variety of target categories, probing chemical evolution, stellar kinematics and substructure, and the mass profile of the dark matter halo from the solar neighborhood to distances of 100 kpc. APOGEE, the Apache Point Observatory Galactic Evolution Experiment, will obtain high-resolution (R {approx} 30,000), high signal-to-noise ratio (S/N {>=} 100 per resolution element), H-band (1.51 {mu}m < {lambda} < 1.70 {mu}m) spectra of 10{sup 5} evolved, late-type stars, measuring separate abundances for {approx}15 elements per star and creating the first high-precision spectroscopic survey of all Galactic stellar populations (bulge, bar, disks, halo) with a uniform set of stellar tracers and spectral diagnostics. The Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) will monitor radial velocities of more than 8000 FGK stars with the sensitivity and cadence (10-40 m s{sup -1}, {approx}24 visits per star) needed to detect giant planets with periods up to two years, providing an unprecedented data set for understanding the formation and dynamical evolution of giant planet systems. As of 2011 January, SDSS-III has obtained spectra of more than 240,000 galaxies, 29,000 z {>=} 2.2 quasars, and 140,000 stars, including 74,000 velocity measurements of 2580 stars for MARVELS.

79 ASTRONOMY AND ASTROPHYSICS↗

OUTBURST DUST PRODUCTION OF COMET 29P/SCHWASSMANN-WACHMANN 1

Multi-aperture photometry of Comet 29P/Schwassmann-Wachmann 1 was conducted on Johnson-Cousins R-band observations spanning 2011 May 1-9 and 2012 June 6-July 3. The comet was observed in outburst on 2011 May 3 and 2012 July 1, during which its brightness increased by 2.2 and 2.1 mag, respectively, as measured through a 10 arcsec aperture. Dust production before and after each outburst is calculated using the parameter Af {rho}, which is converted to a lower limit on the dust production rate based on dust models and derived nuclear properties from other studies. Both outbursts are accompanied by large increases in dust production, Af {rho} by a factor of {approx}6.5-7 and dust production rate by a factor of {approx}18-23. In addition, variations in the dust brightness profile of the coma are examined during the events. The profile is observed to steepen significantly at the beginning of each outburst and then slowly return to pre-outburst values, mirroring the behavior of Af {rho}. The start of an outbound 'ripple' of dust in the profile might be observed as the comet returns to its pre-outburst state, although this cannot be confirmed. Using a simple model of the 2011 May 3 outburst, an estimated lower limit of (2.6 {+-} 0.7) Multiplication-Sign 10{sup 8} kg of dust was released during the event. If this is representative of a typical outburst of 29P, then it is estimated that outbursts account for a lower limit of 80{sub -30}{sup +20}% of the total material ejected by the comet per year.

79 ASTRONOMY AND ASTROPHYSICS↗

ENIGMATIC RECURRENT PULSATIONAL VARIABILITY OF THE ACCRETING WHITE DWARF EQ LYN (SDSS J074531.92+453829.6)

Photometric observations of the cataclysmic variable EQ Lyn (SDSS J074531.92+453829.6), acquired from 2005 October to 2006 January, revealed high-amplitude variability in the range 1166-1290 s. This accreting white dwarf underwent an outburst in 2006 October, during which its brightness increased by at least five magnitudes, and it started exhibiting superhumps in its light curve. Upon cooling to quiescence, the superhumps disappeared and it displayed the same periods in 2010 February as prior to the outburst within the uncertainties of a couple of seconds. This behavior suggests that the observed variability is likely due to nonradial pulsations in the white dwarf star, whose core structure has not been significantly affected by the outburst. The enigmatic observations begin with an absence of pulsational variability during a multi-site campaign conducted in 2011 January-February without any evidence of a new outburst; the light curve is instead dominated by superhumps with periods in the range of 83-87 minutes. Ultraviolet Hubble Space Telescope time-series spectroscopy acquired in 2011 March reveals an effective temperature of 15,400 K, placing EQ Lyn within the broad instability strip of 10,500-16,000 K for accreting pulsators. The ultraviolet light curve with 90% flux from the white dwarf shows no evidence of any pulsations. Optical photometry acquired during 2011 and Spring 2012 continues to reflect the presence of superhumps and an absence of pulsations. Subsequent observations acquired in 2012 December and 2013 January finally indicate the disappearance of superhumps and the return of pulsational variability with similar periods as previous data. However, our most recent data from 2013 March to May reveal superhumps yet again with no sign of pulsations. We speculate that this enigmatic post-outburst behavior of the frequent disappearance of pulsational variability in EQ Lyn is caused either by heating the white dwarf beyond the instability strip due to an elevated accretion rate, disrupting pulsations associated with the He II instability strip by lowering the He abundance of the convection zone, free geometric precession of the entire system, or appearing and disappearing disk pulsations.

79 ASTRONOMY AND ASTROPHYSICS↗