Late-time supernova light curves: The effect of internal conversion and Auger electrons

Energy release from radioactive decays contributes significantly to supernova light curves. Previous works, which considered the energy deposited by gamma-rays and positrons produced by 56Ni, 56Co, 57Ni, 57Co, 44Ti and 44Sc, have been quite successful in explaining the light curves of both core collapse and thermonuclear supernovae. We point out that Auger and internal conversion electrons together with the associated X-ray cascade, constitute an additional heat source. When a supernova is transparent to gamma-rays, these electrons can contribute significantly to light curves for reasonable nucleosynthetic yields. In particular, the electrons emitted in the decay of 57Co, which are largely due to internal conversion from a fortuitously low-lying 3/2- state in the daughter 57Fe, constitute an additional significant energy deposition channel. We show that when the heating by these electrons is accounted for, a slow-down in the lightcurve of SN 1998bw is naturally obtained for typical hypernova nucleosynthetic yields. Additionally, we show that for generic Type Ia supernova yields, the Auger electrons emitted in the ground-state to ground-state electron capture decay of 55Fe exceed the energy released by the 44Ti decay chain for many years after the explosion.Comment: 6 pages, 2 figures, 1 table, MNRAS in press, v2 with updated reference

Hubble Residuals of Nearby Type Ia Supernovae Are Correlated with Host Galaxy Masses

From Sloan Digital Sky Survey u'g'r'i'z' imaging, we estimate the stellar masses of the host galaxies of 70 low redshift SN Ia (0.015 < z < 0.08) from the hosts' absolute luminosities and mass-to-light ratios. These nearby SN were discovered largely by searches targeting luminous galaxies, and we find that their host galaxies are substantially more massive than the hosts of SN discovered by the flux-limited Supernova Legacy Survey. Testing four separate light curve fitters, we detect ~2.5{\sigma} correlations of Hubble residuals with both host galaxy size and stellar mass, such that SN Ia occurring in physically larger, more massive hosts are ~10% brighter after light curve correction. The Hubble residual is the deviation of the inferred distance modulus to the SN, calculated from its apparent luminosity and light curve properties, away from the expected value at the SN redshift. Marginalizing over linear trends in Hubble residuals with light curve parameters shows that the correlations cannot be attributed to a light curve-dependent calibration error. Combining 180 higher-redshift ESSENCE, SNLS, and HigherZ SN with 30 nearby SN whose host masses are less than 10^10.8 solar masses in a cosmology fit yields 1+w=0.22 +0.152/-0.143, while a combination where the 30 nearby SN instead have host masses greater than 10^10.8 solar masses yields 1+w=-0.03 +0.217/-0.108. Progenitor metallicity, stellar population age, and dust extinction correlate with galaxy mass and may be responsible for these systematic effects. Host galaxy measurements will yield improved distances to SN Ia.Comment: 16 pages, 6 figures, published in ApJ, minor change

Annihilation emission from young supernova remnants

A promising source of the positrons that contribute through annihilation to the diffuse Galactic 511keV emission is the beta-decay of unstable nuclei like 56Ni and 44Ti synthesised by massive stars and supernovae. Although a large fraction of these positrons annihilate in the ejecta of SNe/SNRs, no point-source of annihilation radiation appears in the INTEGRAL/SPI map of the 511keV emission. We exploit the absence of detectable annihilation emission from young local SNe/SNRs to derive constraints on the transport of MeV positrons inside SN/SNR ejecta and their escape into the CSM/ISM, both aspects being crucial to the understanding of the observed Galactic 511keV emission. We simulated 511keV lightcurves resulting from the annihilation of the decay positrons of 56Ni and 44Ti in SNe/SNRs and their surroundings using a simple model. We computed specific 511keV lightcurves for Cas A, Tycho, Kepler, SN1006, G1.9+0.3 and SN1987A, and compared these to the upper-limits derived from INTEGRAL/SPI observations. The predicted 511keV signals from positrons annihilating in the ejecta are below the sensitivity of the SPI instrument by several orders of magnitude, but the predicted 511keV signals for positrons escaping the ejecta and annihilating in the surrounding medium allowed to derive upper-limits on the positron escape fraction of ~13% for Cas A, ~12% for Tycho, ~30% for Kepler and ~33% for SN1006. The transport of ~MeV positrons inside SNe/SNRs cannot be constrained from current observations of the 511keV emission from these objects, but the limits obtained on their escape fraction are consistent with a nucleosynthesis origin of the positrons that give rise to the diffuse Galactic 511keV emission.Comment: 15 pages, 11 figures, accepted for publication in A&

Designing all-graphene nanojunctions by covalent functionalization

We investigated theoretically the effect of covalent edge functionalization, with organic functional groups, on the electronic properties of graphene nanostructures and nano-junctions. Our analysis shows that functionalization can be designed to tune electron affinities and ionization potentials of graphene flakes, and to control the energy alignment of frontier orbitals in nanometer-wide graphene junctions. The stability of the proposed mechanism is discussed with respect to the functional groups, their number as well as the width of graphene nanostructures. The results of our work indicate that different level alignments can be obtained and engineered in order to realize stable all-graphene nanodevices

The Relationship Between Resistance to the Fungal Toxin Cercosporin and Grey Leaf Spot Disease Resistance in Corn (ZEA MAYS L.)

65 leaves. Advisor: Michael E. MyszewskiThe problem. Corn is infected by the fungus "Cerospora zeae-maydis" which causes the disease Grey Leaf Spot. The fungus produces a toxin, cercosporin, whose role in the pathogenicity of the disease is not known. The first step in determining the importance of the toxin to the fungus is to screen corn inbreds to see if any disease resistant inbreds are also resistant to the toxin. Procedure. Thirteen corn inbreds were tested for their degree of resistance to the fungal toxin cercosporin. The level of tolerance to cercosporin for each inbred was then compared to the inbred's level of resistance to Grey Leaf Spot. Resistance to cercosporin was determined by measuring the increases in the conductivity of water containing leaf tissue slices following exposure to cercosporin. Ion leakage is an indicator of cellular damage, so resistant tissue would be expected ro have a lower level of conductivity increase than susceptible tissue. Resistance to Grey Leaf Spot disease had been previously determined by field test conducted by Pioneer Hi-Bred International, Inc. Findings. The ion leakage assay showed that the inbreds which were more disease resistant tended to have a lower tolerance for cercosporin than did the less disease resistant inbreds (correlation coefficient = 0.5524). Conclusion. Based on the lack of a positivc relationship between disease susceptibility and cercosporin susceptibility it was concluded that cercosporin resistance does not have a significant role in the prevention of Grey Leaf Spot infections among the tested inbreds

Type Ia Supernovae as Stellar Endpoints and Cosmological Tools

Empirically, Type Ia supernovae are the most useful, precise, and mature tools for determining astronomical distances. Acting as calibrated candles they revealed the presence of dark energy and are being used to measure its properties. However, the nature of the SN Ia explosion, and the progenitors involved, have remained elusive, even after seven decades of research. But now new large surveys are bringing about a paradigm shift --- we can finally compare samples of hundreds of supernovae to isolate critical variables. As a result of this, and advances in modeling, breakthroughs in understanding all aspects of SNe Ia are finally starting to happen.Comment: Invited review for Nature Communications. Final published version. Shortened, update

Hyperthyroidism related to McCune-Albright syndrome: report of two cases and review of the literature

INTRODUCTION: McCune-Albright syndrome is a sporadic disease clinicaly characterized by polyostotic fibrous dysplasia, café-au-lait cutaneous spots and hyperfunctional endocrinopathies, such as precocious puberty, hyperthyroidism, acromegaly and others. The biologic physiopathology of the disease is based on an activating mutation of the gene for the Gs protein which mediates the activation of adenyl cyclase and subsequent gland autonomous secretion. The thyroid gland is usually involved in this disease, being hyperthyroidism the second most common endocrinopathy seen after precocious puberty. OBJECTIVE: Revision of the literature since 1937 to 1997, adding our casuistic and discussing the adequate treatment for the hyperthyroidism in the syndrome. RESULTS: Among 85 cases identified with the syndrome, hyperthyroidism treatment was described in 26 of them. Fifteen were submitted to surgery (total thyroidectomy), 6 were submitted to iodotherapy and 5 were treated with antithyroid drugs (ATD - propylthiouracil, carbimazole or methimazole). In some cases, treatment association was done. CONCLUSION: McCune-Albright syndrome is a rare disease, combining polyostotic fibrous dysplasia, café-au-lait cutaneous spots and hyperfunctional endocrinopathies. Cases with hyperthyroidism are treated iniatially clinically, but definitive ablation with surgery or radioiodine treatment is the most indicated option.INTRODUÇÃO: A síndrome de McCune Albright é uma doença rara, clinicamente definida pela combinação de displasia fibrosa poliostótica, manchas café-com-leite e endocrinopatias com hiperfunção, como puberdade precoce, hipertireoidismo, acromegalia e outras. A fisiopatologia biomolecular baseia-se em uma mutação ativadora do gene para a subunidade alfa da proteína de membrana Gs, que estimula a produção intracelular de AMPc, conferindo secreção autônoma à glândula em particular. A glândula tireóide é freqüentemente envolvida nesta doença, sendo o hipertireoidismo a segunda endocrinopatia mais comum após a puberdade precoce. OBJETIVO: Realizar uma revisão da literatura no período de 1937 a 1997, incluindo nossa casuística, e discutir o tratamento utilizado para o hipertireoidismo nesta síndrome. RESULTADOS: Do total de 85 casos, em 26 com hipertireoidismo se descreve o tipo de tratamento utilizado. Entre esses, 15 foram submetidos à cirurgia (tireoidectomia total), seis foram submetidos à iodoterapia e cinco foram submetidos a tratamento com drogas antitireoidianas (DAT - propiltiuracil, carbimazol ou metimazol), pois em alguns houve associação dos tratamentos citados anteriormente. CONCLUSÃO: A síndrome de McCune-Albright é uma doença rara, que inclui displasia fibrosa poliostótica, manchas café-com-leite e endocrinopatias com hiperfunção. Os casos acompanhados com hipertireoidismo são inicialmente tratados clinicamente com DAT, porém a ablação cirúrgica ou com radioiodoterapia é a opção definitiva mais indicada.Universidade Federal de São Paulo (UNIFESP) Departamento de Otorrinolaringologia e Cirurgia de Cabeça e PescoçoUNIFESP, Depto. de Otorrinolaringologia e Cirurgia de Cabeça e PescoçoSciEL

The epidemiology of mild cognitive impairment (MCI) and Alzheimer’s disease (AD) in community-living seniors: protocol of the MemoVie cohort study, Luxembourg

BACKGROUND: Cognitive impairment and Alzheimer’s disease (AD) are increasingly considered a major public health problem. The MemoVie cohort study aims to investigate the living conditions or risk factors under which the normal cognitive capacities of the senior population in Luxembourg (≥ 65 year-old) evolve (1) to mild cognitive impairment (MCI) – transitory non-clinical stage – and (2) to AD. Identifying MCI and AD predictors undeniably constitutes a challenge in public health in that it would allow interventions which could protect or delay the occurrence of cognitive disorders in elderly people. In addition, the MemoVie study sets out to generate hitherto unavailable data, and a comprehensive view of the elderly population in the country. METHODS/DESIGN: The study has been designed with a view to highlighting the prevalence in Luxembourg of MCI and AD in the first step of the survey, conducted among participants selected from a random sample of the general population. A prospective cohort is consequently set up in the second step, and appropriate follow-up of the non-demented participants allows improving the knowledge of the preclinical stage of MCI. Case-control designs are used for cross-sectional or retrospective comparisons between outcomes and biological or clinical factors. To ensure maximal reliability of the information collected, we decided to opt for structured face to face interviews. Besides health status, medical and family history, demographic and socio-cultural information are explored, as well as education, habitat network, social behavior, leisure and physical activities. As multilingualism is expected to challenge the cognitive alterations associated with pathological ageing, it is additionally investigated. Data relative to motor function, including balance, walk, limits of stability, history of falls and accidents are further detailed. Finally, biological examinations, including ApoE genetic polymorphism are carried out. In addition to standard blood parameters, the lipid status of the participants is subsequently determined from the fatty acid profiles in their red blood cells. The study obtained the legal and ethical authorizations. DISCUSSION: By means of the multidisciplinary MemoVie study, new insights into the onset of cognitive impairment during aging should be put forward, much to the benefit of intervention strategies as a whole