Abstract
We report the discovery of three stars that, along with the prototype LP 40−365, form a distinct class of chemically peculiar runaway stars that are the survivors of thermonuclear ...explosions. Spectroscopy of the four confirmed LP 40−365 stars finds ONe-dominated atmospheres enriched with remarkably similar amounts of nuclear ashes of partial O- and Si-burning. Kinematic evidence is consistent with ejection from a binary supernova progenitor; at least two stars have rest-frame velocities indicating they are unbound to the Galaxy. With masses and radii ranging between 0.20 and 0.28 M$\odot$ and between 0.16 and 0.60 R$\odot$, respectively, we speculate these inflated white dwarfs are the partly burnt remnants of either peculiar Type Iax or electron-capture supernovae. Adopting supernova rates from the literature, we estimate that ∼20 LP 40−365 stars brighter than 19 mag should be detectable within 2 kpc from the Sun at the end of the Gaia mission. We suggest that as they cool, these stars will evolve in their spectroscopic appearance, and eventually become peculiar O-rich white dwarfs. Finally, we stress that the discovery of new LP 40−365 stars will be useful to further constrain their evolution, supplying key boundary conditions to the modelling of explosion mechanisms, supernova rates, and nucleosynthetic yields of peculiar thermonuclear explosions.
Tidal disruption and subsequent accretion of planetesimals by white dwarfs can reveal the elemental abundances of rocky bodies in exoplanetary systems. Those abundances provide information on the ...composition of the nebula from which the systems formed, which is analogous to how meteorite abundances inform our understanding of the early Solar System. We report the detection of lithium, sodium, potassium, and calcium in the atmosphere of the white dwarf Gaia DR2 4353607450860305024, which we ascribe to the accretion of a planetesimal. Using model atmospheres, we determine abundance ratios of these elements, and, with the exception of lithium, they are consistent with meteoritic values in the Solar System. We compare the measured lithium abundance with measurements in old stars and with expectations from Big Bang nucleosynthesis.
CONTEXT.— Previous studies have documented that cancer patients tend to overestimate
the probability of long-term survival. If patient preferences about the trade-offs
between the risks and benefits ...associated with alternative treatment strategies
are based on inaccurate perceptions of prognosis, then treatment choices may
not reflect each patient's true values. OBJECTIVE.— To test the hypothesis that among terminally ill cancer patients an
accurate understanding of prognosis is associated with a preference for therapy
that focuses on comfort over attempts at life extension. DESIGN.— Prospective cohort study. SETTING.— Five teaching hospitals in the United States. PATIENTS.— A total of 917 adults hospitalized with stage III or IV non–small
cell lung cancer or colon cancer metastatic to liver in phases 1 and 2 of
the Study to Understand Prognoses and Preferences for Outcomes and Risks of
Treatments (SUPPORT). MAIN OUTCOME MEASURES.— Proportion of patients favoring life-extending therapy over therapy
focusing on relief of pain and discomfort, patient and physician estimates
of the probability of 6-month survival, and actual 6-month survival. RESULTS.— Patients who thought they were going to live for at least 6 months were
more likely (odds ratio OR, 2.6; 95% confidence interval CI, 1.8-3.7)
to favor life-extending therapy over comfort care compared with patients who
thought there was at least a 10% chance that they would not live 6 months.
This OR was highest (8.5; 95% CI, 3.0-24.0) among patients who estimated their
6-month survival probability at greater than 90% but whose physicians estimated
it at 10% or less. Patients overestimated their chances of surviving 6 months,
while physicians estimated prognosis quite accurately. Patients who preferred
life-extending therapy were more likely to undergo aggressive treatment, but
controlling for known prognostic factors, their 6-month survival was no better. CONCLUSIONS.— Patients with metastatic colon and lung cancer overestimate their survival
probabilities and these estimates may influence their preferences about medical
therapies.
Tidal disruption and subsequent accretion of planetesimals by white dwarfs can reveal the elemental abundances of rocky bodies in exoplanetary systems. Those abundances provide information on the ...composition of the nebula from which the systems formed, which is analogous to how meteorite abundances inform our understanding of the early Solar System. In this work, we report the detection of lithium, sodium, potassium, and calcium in the atmosphere of the white dwarf Gaia DR2 4353607450860305024, which we ascribe to the accretion of a planetesimal. Using model atmospheres, we determine abundance ratios of these elements, and, with the exception of lithium, they are consistent with meteoritic values in the Solar System. We compare the measured lithium abundance with measurements in old stars and with expectations from Big Bang nucleosynthesis.
Tidal disruption and subsequent accretion of planetesimals by white dwarfs can reveal the elemental abundances of rocky bodies in exoplanetary systems. Those abundances provide information on the ...composition of the nebula from which the systems formed, which is analogous to how meteorite abundances inform our understanding of the early Solar System. In this work, we report the detection of lithium, sodium, potassium, and calcium in the atmosphere of the white dwarf Gaia DR2 4353607450860305024, which we ascribe to the accretion of a planetesimal. Using model atmospheres, we determine abundance ratios of these elements, and, with the exception of lithium, they are consistent with meteoritic values in the Solar System. We compare the measured lithium abundance with measurements in old stars and with expectations from Big Bang nucleosynthesis.
An excess incidence of brain cancer in male farmers has been noted in several studies, but few studies have focused on women. The National Institute for Occupational Safety and Health Upper Midwest ...Health Study evaluated effects of rural exposures for 341 female glioma cases and 528 controls, all adult (18-80 years of age) nonmetropolitan residents of Iowa, Michigan, Minnesota, and Wisconsin. On average, controls lived longer on farms than did cases. After adjusting for age, age group, education, and farm residence, no association with glioma was observed for exposure to arsenicals, benzoic acids, carbamates, chloroacetanilides, dinitroanilines, inorganics, organochlorines, organophosphates, phenoxys, triazines, or urea-based or estrogenic pesticides. An increased risk of glioma was observed for carbamate herbicides but was not statistically significant (odds ratio = 3.0; 95% confidence interval, 0.9-9.5). No association was observed between glioma and exposure to 12 widely used specific pesticides, after adjustment for age, age group, education, and any other pesticide exposure. These results were not affected after exclusion of proxy respondents (43% of cases, 2% of controls). Women were less likely than men to have applied pesticides, but more likely to have laundered pesticide-contaminated clothes. Storing pesticides in the house was associated with a statistically non-significant increased risk. Results show that exposure to pesticides was not associated with an increased risk of intracranial gliomas in women. Other farm-related factors could be etiologic factors and will be discussed in future reports.
Summary
Development of antibodies (Ab) that inhibit the procoagulant function of factor VIII (fVIII) seriously complicates the treatment of hemophilia A patients. It also causes acquired hemophilia, ...a rare yet serious autoimmune disease. The design of effective fVIII-specific tolerizing procedures will require elucidation of the role of the different CD4
+
T cell subsets that drive inhibitor synthesis. To examine the contribution of Th1 and Th2 cells in the anti-fVIII Ab response, we measured the concentration of Th1- and Th2-driven anti-fVIII IgG subclasses in 17 patients with severe hemophilia A and 18 patients with acquired hemophilia. We found that both congenital and acquired hemophilia patients had similar and comparable proportions of Th1- and Th2-induced anti-fVIII Ab, suggesting a more important role of Th1 cells in the immune response to fVIII than previously appreciated. The distribution of anti-fVIII IgG subclasses was stable for periods of up to six months. More intense anti-fVIII Ab responses and higher inhibitor titers correlated with a predominance of Th2-driven subclasses. In contrast, Th1-driven anti-fVIII Ab were predominant in patients who had low anti-fVIII Ab concentrations, even when this was the result of successful immune tolerance or immunosuppressive therapy, which had caused drastic reduction or disappearance of inhibitors.
Thus, synthesis of Th2-driven inhibitors occurs when the anti-fVIII Ab response is intense, while Th1 cells may be involved in the long-term maintenance of anti-fVIII Ab synthesis.
The objectives of the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial are to determine in screenees ages 55–74 at entry whether screening with flexible sigmoidoscopy (60-cm ...sigmoidoscope) can reduce mortality from colorectal cancer, whether screening with chest X-ray can reduce mortality from lung cancer, whether screenng men with digital rectal examination (DRE) plus serum prostate-specific antigen (PSA) can reduce mortality from prostate cancer, and whether screening women with CA125 and transvaginal ultrasound (TVU) can reduce mortality from ovarian cancer. Secondary objectives are to assess screening variables other than mortality for each of the interventions including sensitivity, specificity, and positive predictive value; to assess incidence, stage, and survival of cancer cases; and to investigate biologic and/or prognostic characterizations of tumor tissue and biochemical producs as intermediate endpoints. The design is a multicenter, two-armed, randomized trial with 37,000 females and 37,000 males in each of the two arms. In the intervention arm, the PSA and CA125 tests are performed at entry, then annually for 5 years. The DRE, TVU, and chest X-ray exams are performed at entry and then annually for 3 years. Sigmoidoscopy is performed at entry and then at the 5-year point. Participants in the control arm follow their usual medical care practices. Participants will be followed for at least 13 years from randomization to ascertain all cancers of the prostate, lung, colorectum, and ovary, as well as deaths from all causes. A pilot phase was undertaken to assess the randomization, screening, and data collection procedures of the trial and to estimate design parameters such as compliance and contamination levels. This paper describes eligibility, consent, and other design features of the trial, randomization and screening procedures, and an outline of the follow-up procedures. Sample-size calculations are reported, and a data analysis plan is presented.
Type Ia supernovae are among the most scientifically valuable objects in modern astronomy, especially as “standard candles” for measuring cosmic distances. Despite their importance, the nature of ...supernova Ia progenitors remains a mystery—they arise either from a single white dwarf star gradually accreting mass from a companion, or from the merger of two white dwarfs. However, not all white dwarf binary mergers result in a runaway thermonuclear reaction. Should these potential progenitor systems lack the conditions necessary for supernova detonation, they may instead produce a variety of single-star merger products, such as strongly magnetic, massive, fast-rotating, and metal-polluted white dwarfs. These remnants often exhibit unexpected and interesting physics that manifests in their spectral and photometric activity; thus, one best identifies white dwarf merger remnants by investigating the small fraction of white dwarfs that are photometrically variable due to surface activity instigated in interactions. In particular, the most rapidly variable white dwarfs invoke a potential merger origin due to the remnant being spun-up through conservation of angular momentum during the merger process.To explore this exotic stellar subset, I identify the most rapidly variable white dwarfs observed with the Kepler space telescope, Transiting Exoplanet Survey Satellite (TESS), and Gaia mission. I then collect time-series ground-based spectroscopy using the 4.1-m Southern Astrophysical Research (SOAR) Telescope on Cerro Pach´on, Chile, to obtain snapshots of the physics driving the variability. This method uncovers a diverse array of behaviors exhibited by peculiar stars that comprise the menagerie of “failed” Ia supernovae.By executing this observation strategy, I established a new class of variable white dwarfs which present rotationally modulated hydrogen Balmer emission with magnetic Zeeman splitting (class DAHe), and which are now a major focus of the worldwide white dwarf community. I also explored the broader relation between white dwarf mass and rotation rate using detailed stellar modeling analysis, and contributed to discoveries of other types of white dwarf merger and partial supernova detonation remnants. These studies offer valuable context for understanding stellar evolution, stellar interactions, and the supernova Ia progenitor question.
Since several studies indicated that farmers and agricultural workers had an excess risk of brain cancer, the National Institute for Occupational Safety and Health initiated the Upper Midwest Health ...Study to examine risk of intracranial glioma in the non-metropolitan population. This population-based, case-control study evaluated associations between gliomas and rural and farm exposures among adults (ages 18 to 80) in four upper midwestern states (Iowa, Michigan, Minnesota, Wisconsin). At diagnosis/selection, participants lived in non-metropolitan counties where the largest population center had fewer than 250,000 residents. Cases were diagnosed 1 January 1995 through 31 January 1997. Over 90% of 873 eligible ascertained cases and over 70% of 1670 eligible controls consented to participate. Participants and nonparticipants, evaluated for "critical questions" on main and refusant questionnaires, differed significantly in farming and occupational experience, ethnicity, education, and lifestyle. The 1,175 controls were more likely than the 798 cases to have reported ever drinking alcohol (77% vs. 73%, adjusted odds ratio (OR) 0. 73, 95% confidence interval (CI) 0.59-0.92) and having had panoramic dental x-rays (34% vs. 29%, OR 0. 75, CI 0.61-0.92). Controls spent a greater percentage of their lives in non-metropolitan counties (78% vs. 75%, OR 0.81, CI 0.67-1.09). Among ever-farmers, controls were more likely to have had exposure to farm insecticides (57% vs. 50%, OR 0.75, CI 0.59-0.95) and farm animals (96% vs. 91%, OR 0.48, CI 0.25-0.90). Moving to a farm as an adolescent (ages 11 to 20) vs. as an adult was associated with a greater risk of glioma. In our study sample, farm or rural residence and summary farm exposures were associated with decreased glioma risk. However, nonparticipation by never-farming eligible controls could have affected results. Comparisons of farm chemical exposures may clarify associations between farming and glioma that others have reported.
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