30 years of cosmic fullerenes

In 1985, "During experiments aimed at understanding the mechanisms by which long-chain carbon molecules are formed in interstellar space and circumstellar shells", Harry Kroto and his collaborators serendipitously discovered a new form of carbon: fullerenes. The most emblematic fullerene (i.e. C$_{60}$ "buckminsterfullerene"), contains exactly 60 carbon atoms organized in a cage-like structure similar to a soccer ball. Since their discovery impacted the field of nanotechnologies, Kroto and colleagues received the Nobel prize in 1996. The cage-like structure, common to all fullerene molecules, gives them unique properties, in particular an extraordinary stability. For this reason and since they were discovered in experiments aimed to reproduce conditions in space, fullerenes were sought after by astronomers for over two decades, and it is only recently that they have been firmly identified by spectroscopy, in evolved stars and in the interstellar medium. This identification offers the opportunity to study the molecular physics of fullerenes in the unique physical conditions provided by space, and to make the link with other large carbonaceous molecules thought to be present in space : polycyclic aromatic hydrocarbons.Comment: To appear in the Proceedings of the annual meeting of the French society of astronomy and astrophysics (SF2A 2015

Diagnostics for specific PAHs in the far-IR: searching neutral naphthalene and anthracene in the Red Rectangle

Context. In the framework of the interstellar polycyclic aromatic hydrocarbons (PAHs) hypothesis, far-IR skeletal bands are expected to be a fingerprint of single species in this class. Aims. We address the question of detectability of low energy PAH vibrational bands, with respect to spectral contrast and intensity ratio with ``classical'' Aromatic Infrared Bands (AIBs). Methods. We extend our extablished Monte-Carlo model of the photophysics of specific PAHs in astronomical environments, to include rotational and anharmonic band structure. The required molecular parameters were calculated in the framework of the Density Functional Theory. Results. We calculate the detailed spectral profiles of three low-energy vibrational bands of neutral naphthalene, and four low-energy vibrational bands of neutral anthracene. They are used to establish detectability constraints based on intensity ratios with ``classical'' AIBs. A general procedure is suggested to select promising diagnostics, and tested on available Infrared Space Observatory data for the Red Rectangle nebula. Conclusions. The search for single, specific PAHs in the far-IR is a challenging, but promising task, especially in view of the forthcoming launch of the Herschel Space Observatory.Comment: 13 pages, 13 figures, accepted for publication in A&

The role of the charge state of PAHs in ultraviolet extinction

Aims: We explore the relation between charge state of polycyclic aromatic hydrocarbons (PAHs) and extinction curve morphology. Methods: We fit extinction curves with a dust model including core-mantle spherical particles of mixed chemical composition (silicate core, $sp^2$ and $sp^3$ carbonaceous layers), and an additional molecular component. We use exact methods to calculate the extinction due to classical particles and accurate computed absorption spectra of PAHs in different charge states, for the contribution due to the molecular component, along a sample of five rather different lines of sight. Results: A combination of classical dust particles and mixtures of real PAHs satisfactorily matches the observed interstellar extinction curves. Variations of the spectral properties of PAHs in different charge states produce changes consistent with the varying relative strengths of the bump and non-linear far-UV rise.Comment: 5 pages, 3 figures, Astronomy & Astrophysics Letters, in pres

Detection of the buckminsterfullerene cation (C60+) in space

In the early 90s, C60+ was proposed as the carrier of two diffuse interstellar bands (DIBs) at 957.7 and 963.2 nm, but a firm identification still awaits gas-phase spectroscopic data. Neutral C60, on the other hand, was recently detected through its infrared emission bands in the interstellar medium and evolved stars. In this contribution, we present the detection of C60+ through its infrared vibrational bands in the NGC 7023 nebula, based on spectroscopic observations with the Spitzer space telescope, quantum chemistry calculation, and laboratory data from the literature. This detection supports the idea that C60+ could be a DIB carrier, and provides robust evidence that fullerenes exist in the gas-phase in the interstellar medium. Modeling efforts to design specific observations, combined with new gas-phase data, will be essential to confirm this proposal. A definitive attribution of the 957.7 and 963.2 nm DIBs to C60+ would represent a significant step forward in the field.Comment: To appear in "Proceedings of IAU 297 symposium on the Diffuse Interstellar Bands", eds. J. Cami and N. Cox (5 pages

On-line database of the spectral properties of polycyclic aromatic hydrocarbons

We present an on-line database of computed molecular properties for a large sample of polycyclic aromatic hydrocarbons (PAHs) in four charge states: -1, 0, +1, and +2. At present our database includes 40 molecules ranging in size from naphthalene and azulene (C10H8) up to circumovalene (C66H20). We performed our calculations in the framework of the density functional theory (DFT) and the time-dependent DFT to obtain the most relevant molecular parameters needed for astrophysical applications. For each molecule in the sample, our database presents in a uniform way the energetic, rotational, vibrational, and electronic properties. It is freely accessible on the web at http://astrochemistry.ca.astro.it/database/ and http://www.cesr.fr/~joblin/database/.Comment: Accepted for pubblication in Chem. Phys. (01/01/07

NODAL Secures Pluripotency upon Embryonic Stem Cell Progression from the Ground State

Naive mouse embryonic stem cells (ESCs) can develop multiple fates, but the cellular and molecular processes that enable lineage competence are poorly characterized. Here, we investigated progression from the ESC ground state in defined culture. We utilized downregulation of Rex1::GFPd2 to track the loss of ESC identity. We found that cells that have newly downregulated this reporter have acquired capacity for germline induction. They can also be efficiently specified for different somatic lineages, responding more rapidly than naive cells to inductive cues. Inhibition of autocrine NODAL signaling did not alter kinetics of exit from the ESC state but compromised both germline and somatic lineage specification. Transient inhibition prior to loss of ESC identity was sufficient for this effect. Genetic ablation of Nodal reduced viability during early differentiation, consistent with defective lineage specification. These results suggest that NODAL promotes acquisition of multi-lineage competence in cells departing naive pluripotency.This research was funded by the Wellcome Trust (091484/Z/10/Z). The Cambridge Stem Cell Institute receives core support from the Wellcome Trust and the Medical Research Council (G1100526). C.M. was funded by a BBSRC studentship (961424). A.S. is a Medical Research Council Professor

Associations between migration experience and perceived mental health in optimal ageing: evidence from the Sardinian Blue Zone

The effect of migration on perceived mental health has not been examined in older migrants after their return to their places of origin. This study was mainly aimed at evaluating the perceived mental health of older people who experienced migration and permanent resident peers living in the Sardinian Blue Zone (i.e. one of the four areas of exceptional longevity in the world). Forty-eight community-based older participants (32 males and 16 females) with and without a migration experience were recruited in two villages of the Sardinian Blue Zone and completed a battery of self-report inventories assessing psychological well-being, negative mood, and ego resilience. Older individuals who experienced migration reported higher ego resilience and exhibited greater resources used to manage positive emotionality (i.e. openness to life experiences). Moreover, compared to the normative data, both the groups reported higher psychological well-being and fewer depressive symptoms. Finally, no significant associations were found between the length of migration and each mental health index. In conclusion, resilience seems to represent a psychological trait that helps to manage stressful events and contributes to the preservation of perceived mental health in late adulthood

Mental Health and Religiosity in the Sardinian Blue Zone: Life Satisfaction and Optimism for Aging Well

This study evaluated the impact of the sociocultural context on dispositional optimism and resilience, life satisfaction, and religiosity in late adulthood. Moreover, the associations between those psychological measures and religiosity were investigated. Ninety-five older individuals recruited in the Sardinian Blue Zone and Cagliari completed a battery of tools assessing cognitive and mental health, and religiosity. Life satisfaction correlated with resilience and religiosity, whereas resilience correlated with optimism. Furthermore, participants of the rural area reported greater optimism and life satisfaction than peers living in the urban area. In conclusion, optimism and hedonic well-being favor optimal aging in the Blue Zone

Hedonic and eudaimonic well-being in late adulthood: lessons from Sardinia’s Blue Zone

This study was conducted to investigate whether socio-cultural context (i.e., urban versus rural), perceived physical health, marital status, and satisfaction with family and non-family ties predicted hedonic and eudaimonic well-being in late adulthood and to examine the impact of the socio-cultural context on well-being, physical health and satisfaction with family and non-family ties by controlling age.One hundred and one community-dwelling participants aged between 68 and 94 were enrolled in the Sardinian Blue Zone—an area of exceptional longevity located in Sardinia, an Italian island in the Mediterranean Sea—and in the city of Cagliari—the regional capital. All participants completed a battery of tools assessing global cognitive efficiency, hedonic (i.e., SPANE and Satisfaction with Life Scales) and eudaimonic (i.e., Flourishing Scale) well-being, perceived physical health, and satisfaction with family and non-family ties. Hedonic and eudaimonic well-being were associated with several variables: marital status, socio-cultural context, and perceived physical health predicted 24% of the variance in the SPANE condition, 52% of the variance in the Satisfaction with Life condition was predicted by the socio-cultural context and satisfaction with family ties, whereas 39% of the Flourishing index was predicted by the socio-cultural context and physical health. Finally, the participants in the Sardinian Blue Zone reported better mental well-being and satisfaction with family and non-family ties than older people living in Cagliari. In conclusion, a socio-cultural context in which positive relationships in late adulthood are strengthened contributes to the promotion of mental health in late adulthood