No surviving evolved companions to the progenitor of supernova SN 1006

Type Ia supernovae are thought to occur as a white dwarf made of carbon and oxygen accretes sufficient mass to trigger a thermonuclear explosion$^{1}$. The accretion could occur slowly from an unevolved (main-sequence) or evolved (subgiant or giant) star$^{2,3}$, that being dubbed the single-degenerate channel, or rapidly as it breaks up a smaller orbiting white dwarf (the double- degenerate channel)$^{3,4}$. Obviously, a companion will survive the explosion only in the single-degenerate channel$^{5}$. Both channels might contribute to the production of type Ia supernovae$^{6,7}$ but their relative proportions still remain a fundamental puzzle in astronomy. Previous searches for remnant companions have revealed one possible case for SN 1572$^{8,9}$, though that has been criticized$^{10}$. More recently, observations have restricted surviving companions to be small, main-sequence stars$^{11,12,13}$, ruling out giant companions, though still allowing the single-degenerate channel. Here we report the result of a search for surviving companions to the progenitor of SN 1006$^{14}$. None of the stars within 4' of the apparent site of the explosion is associated with the supernova remnant, so we can firmly exclude all giant and subgiant companions to the progenitor. Combined with the previous results, less than 20 per cent of type Iae occur through the single degenerate channel.Comment: Published as a letter in Nature (2012 September 27

Revan-degree indices on random graphs

Given a simple connected non-directed graph $G=(V(G),E(G))$, we consider two families of graph invariants: $RX_\Sigma(G) = \sum_{uv \in E(G)} F(r_u,r_v)$ (which has gained interest recently) and $RX_\Pi(G) = \prod_{uv \in E(G)} F(r_u,r_v)$ (that we introduce in this work); where $uv$ denotes the edge of $G$ connecting the vertices $u$ and $v$, $r_u$ is the Revan degree of the vertex $u$, and $F$ is a function of the Revan vertex degrees. Here, $r_u = \Delta + \delta - d_u$ with $\Delta$ and $\delta$ the maximum and minimum degrees among the vertices of $G$ and $d_u$ is the degree of the vertex $u$. Particularly, we apply both $RX_\Sigma(G)$ and R$X_\Pi(G)$ on two models of random graphs: Erd\"os-R\'enyi graphs and random geometric graphs. By a thorough computational study we show that \left and \left, normalized to the order of the graph, scale with the average Revan degree \left; here \left denotes the average over an ensemble of random graphs. Moreover, we provide analytical expressions for several graph invariants of both families in the dense graph limit.Comment: 16 pages, 10 figure

In vitro Study of the Survival, Reproduction and Morphology of Daphnia pulicaria irradiated with a Low Energy Laser

Daphnia is a genus of crustaceans that is representative of freshwater communities. The species exhibit a high sensitivity to a wide range of toxic compounds so that they have been used internationally as biomonitors in toxicity tests to evaluate ecosystem conditions such as water quality. It is also a model genus in genetics, epigenetics and reproductive ecology. In this work, we used Daphnia pulicaria as a model to measure the effects of low-energy laser irradiation on survival, reproduction, and morphology variables of parental organisms and their offspring. We used (1) a single clone line of organisms to eliminate interindividual genetic variability; (2) individuals from more than 50 generations after the clone line was established, and offspring from the third brood onwards to dissipate maternal and epigenetic effects, and (3) neonates, those individuals of the species that have less than 48 hours of life, because they are the most sensitive stage to optical stimuli. We analyzed number of deaths, longevity, age at first reproduction, number of offspring per week, number of total offspring during all their life cycle, body size, size of the antennules, and length of the apical spine of the 4th and 5th brood of the irradiated individuals, who were exposed to a blue laser stimulus of 405 nm for 25 minutes with a power of 40 mW at a distance of 50 cm, compared to those of the control (non-irradiated) group

Future scenarios and opportunities for interventional radiology in the post COVID-19 era

ABSTRACT Pandemic outbreak has led health systems worldwide into a rapid reorganization in response to coronavirus infections, forcing interventional radiology units to adapt. Interventional procedures have evolved in number, type and setting and have arguably been optimized as a direct consequence of this pandemic; a result that will undoubtedly lead to radical change within the specialty. This paper explores the future of interventional radiology from various perspectives, and forecasts the new opportunities that will be presented, from the adaptation of the interventional radiology staff and angiography suite, to the immunological environment, and through to digital medical education. We analyze the economic impact and the future relationship we can expect with the rest of the medical industry

An Examination of Cesarean and Vaginal Birth Histories Among Hispanic Women Entering Prenatal Care in Two California Counties with Large Immigrant Populations

Repeat cesarean delivery (CD) rates among US Hispanic women are the highest of all racial/ethnic groups (90%). Vaginal birth after cesarean (VBAC) is an alternative delivery method, but requires medical records documentation of a non-vertical incision and favorable conditions in the current pregnancy. VBAC rates for Hispanic women are extremely low. This study explores the birth histories and medical records access among Hispanic women in California, taking into account the potential role of immigration on access to VBAC. Study aims are to describe for a sample of Hispanic women: (1) CD and VBAC histories as well as history of vaginal delivery preceding CD; and (2) medical records access, among women who had previous births in Mexico. Chart review was conducted for prenatal patients from three safety net clinics in two California counties with large Mexican migrant populations between August, 2003 and February 2004—during which VBAC was widely available in these two counties to determine: obstetric histories, CD details, birthplace and whether or not medical records had been requested/obtained for CD. 355 multiparous Hispanic women were included. Thirty-three percent had a previous CD, almost two-thirds (64%) had only one CD. Over half of the women (55%) with 2+ births and CD history also reported a vaginal birth history. Medical records for CD were infrequently requested (29%). Of those requested, records were received for 77% of women with a US CD, compared with 13% of women with Mexican CD histories. Policies to address: (1) VBAC opportunities for low risk women, such as those with prior vaginal births and one CD, and (2) overcoming limited medical records access, could mitigate against unnecessary CD and associated medical expenditures and risks for future complications

Derivatives of Mithramycin and Methods of Making and Uses Thereof

The invention, in one aspect, generally relates to mithramycin derivatives from mutated Streptomyces argillaceus and their production. The invention also relates using the derivatives for the treatment of various diseases. Finally, the invention relates to a mutated Streptomyces argillaceus useful in the production of the mithramycin derivatives

Weighing Risk Factors for Female Victimization in the Context of Romantic Relationship Initiation

Research has paid little attention to the link between the characteristics of the relational context where adolescents are likely to initiate their romantic relationships and teen dating violence (TDV). Hence, the findings are still scattered. This study examined different risks in the female teenagers’ relational context (peer group characteristics, participants’ risky activities, and pressure to start dating) and their TDV victimization, which had not been previously studied in the Spanish population. The moderating role of parental monitoring strategies was also analyzed. Participants were 1248 Spanish female teenagers who completed measures of the aforementioned factors. Highly victimized girls reported having more deviant and older male peers, receiving more pressure to start dating, and using more alcohol and drugs than participants with low victimization did. High parental monitoring was only effective to prevent TDV victimization in low-risk relational contexts. The findings extend prior research by providing evidence of the risk of pressure to start dating and low effectiveness of parental monitoring against high-risk peers. They also highlight the need to reduce specific risks for TDV in the adolescent relational context