New Set Of Models Research Articles

Unconventional Policies Effects on Stock Market Volatility: The MAP Approach

Abstract Taking the European Central Bank unconventional policies as a reference, we suggest a class of multiplicative error models (MEMs) tailored to analyse the impact such policies have on stock market volatility. The new set of models, called MEM with asymmetry and policy effects, keeps the base volatility dynamics separate from a component reproducing policy effects, with an increase in volatility on announcement days and a decrease unfolding implementation effects. When applied to four Eurozone markets, a model confidence set approach finds a significant improvement of the forecasting power of the proxy after the expanded asset purchase programme implementation. A multi-step ahead forecasting exercise estimates the duration of the effect; by shocking the policy variable, we are able to quantify the reduction in volatility which is more marked for debt-troubled countries.

Type Iax supernovae from deflagrations in Chandrasekhar mass white dwarfs

Context. Due to the ever increasing number of observations during the past decades, Type Ia supernovae are nowadays regarded as a heterogeneous class of optical transients consisting of several subtypes. One of the largest of these subclasses is the class of Type Iax supernovae. They have been suggested to originate from pure deflagrations in carbon-oxygen Chandrasekhar mass white dwarfs because the outcome of this explosion scenario is in general agreement with their subluminous nature. Aims. Although a few deflagration studies have already been carried out, the full diversity of the class has not been captured yet. This, in particular, holds for the faint end of the subclass. We therefore present a parameter study of single-spot ignited deflagrations in Chandrasekhar mass white dwarfs varying the location of the ignition spark, the central density, the metallicity, and the composition of the white dwarf. We also explore a rigidly rotating progenitor to investigate whether the effect of rotation can spawn additional trends. Methods. We carried out three-dimensional hydrodynamic simulations employing the LEAFS code. Subsequently, detailed nucleosynthesis results were obtained with the nuclear network code YANN. In order to compare our results to observations, we calculated synthetic spectra and light curves with the ARTIS code. Results. The new set of models extends the range in brightness covered by previous studies to the lower end. Our single-spot ignited explosions produce 56Ni masses from 5.8 × 10−3 to 9.2 × 10−2 M⊙. In spite of the wide exploration of the parameter space, the main characteristics of the models are primarily driven by the mass of 56Ni and form a one-dimensional sequence. Secondary parameters seem to have too little impact to explain the observed trend in the faint part of the Type Iax supernova class. We report kick velocities of the gravitationally bound explosion remnants from 6.9 to 369.8 km s−1. The magnitude as well as the direction of the natal kick is found to depend on the strength of the deflagration. Conclusions. This work corroborates the results of previous studies of deflagrations in Chandrasekhar mass white dwarfs. The wide exploration of the parameter space in initial conditions and viewing angle effects in the radiative transfer lead to a significant spread in the synthetic observables. The trends in observational properties toward the faint end of the class are, however, not reproduced. This motivates a quantification of the systematic uncertainties in the modeling procedure and the influence of the 56Ni-rich bound remnant to get to the bottom of these discrepancies. Moreover, while the pure deflagration scenario remains a favorable explanation for bright and intermediate luminosity Type Iax supernovae, our results suggest that other mechanisms also contribute to this class of events.

Sustainable Recovery: The Multiple Benefits of Collaboration

The oil and gas industry is recovering along with the health situation and the world’s economy following one of the largest downturns in its 160-year history caused by the COVID-19 pandemic. What comes ahead brings its own challenges. The recent Intergovernmental Panel on Climate Change’s (IPCC) Working Group 1 contribution to the IPCC’s Sixth Assessment Report, Climate Change 2021: The Physical Science Basis, published in August, highlighted the “widespread and rapid acceleration of climate change,” with the 1.5°C threshold reached as early as the end of this decade. The dramatic weather events around the globe this summer (in the Northern Hemisphere) with historical temperature records on the North American Pacific Coast and in the central and eastern Mediterranean regions, and huge fires impacting those regions and others such as Siberia, were a reminder that the transformation is occurring now. In this context, the energy mix that the world uses today needs to evolve to a more rational use through energy efficiency and with a lower carbon content, starting from the use of coal. The oil and gas industry has been pioneering the development of technologies such as carbon capture and underground storage and blue hydrogen. International oil companies and national oil companies rank amongst the largest technology investors in renewables and energy storage. Renewables also have a strong potential in applications such as steam injection. Collaboration among the industry and with other peripheral sectors will be an essential ingredient to accelerate the transformation of the energy sector. I personally started in the oil and gas industry more than 4 decades ago in research and development (R&D) with a large oilfield service company, where I led a team of scientists investigating hydraulic fracturing. One of the projects was related to acid fracturing, which required the injection of a viscous non-Newtonian pad to fracture the formation and keep the fracture open, followed by acid which had a much lower viscosity. The two-fluid displacement inside the fracture led to an instability called viscous fingering. In order to understand the phenomenon, we put together a very diverse team, comprising a mathematician, an astrophysicist, a physicochemist, and a geologist. The team was unable to initially work well together and collaborate. The breakthrough came when a high-level scientist from Boston University, a specialist in critical phenomena, was added as a catalyst to the team. Within a few months, the team managed to develop and validate a model for viscous fingering using diffusion-limited aggregation and fractal theory, and its work was published in Nature and the American Physical Society’s Physical Reviews Journals. The team then developed a new set of models for wormholes created by the injection of acid through matrix acidizing and fracture acidizing which were used to create the required chemistry to ensure effectiveness of the treatments. I remain convinced that if we had not included the diversity of the skills and used a catalyst for collaboration, we would not have cracked the research code so rapidly.

Improved models for the prediction of asphalt binder dynamic shear modulus and phase angle

In this paper, new set of models for predicting the dynamic shear modulus and phase angle of asphalt binders from conventional viscosity are developed and presented. Based on theoretical considerations, suitable forms of general logistic functions are introduced to develop new models for binder dynamic shear modulus and phase angle over a wide range of temperature and loading conditions. A nonlinear optimization technique based on the Nelder-Mead optimization method is used to obtain the coefficients for the new binder dynamic shear modulus and phase angle models. The experimental binder testing database consisting of dynamic shear modulus, phase angle, frequency, viscosity measurements of thirty-two (32) unmodified and nine (9) modified binders from different sources is used in the study. A total of 7, 120 binder data points are used for the model development, evaluation and validation. The new models deliver very accurate prediction of the binder dynamic shear modulus and phase angle from the conventional steady-state viscosity indicated by very high goodness of fit using 7,120 binder data points. A new parameter termed the “reduced viscosity” is identified which produces a smooth continuous function of the binder phase angle for both modified and unmodified binders using a single viscosity shift factor. The reduced viscosity is considered as the independent variable in the new dynamic shear modulus and phase angle predictive models.

Mastery of Words and Swords: Negotiating Intellectual Masculinities in Modern China 1890s-1930s by Jun Lei (review)

Jun Lei. Mastery of Words and Swords: Negotiating Intellectual Masculinities in Modern China, s-s. Series Transnational Asian Masculinities. Hong Kong: Hong Kong University Press, . x,  pp. Hardcover HK$., ISBN ----. Jun Lei’s Mastery of Words and Swords draws on a range of literary and visual sources to analyze the complex construction of masculine identities by China’s intellectual and cultural elites during the late nineteenth and early twentieth centuries. Her study is divided into two parts, the first of which contains a pair of chapters that establish disciplinary and theoretical frameworks for the four chapter-long case studies in the second. Chapter , “Performing Chinese Masculinities on the World Stage: An Introduction,” acknowledges Kam Louie’s pioneering role in extending the study of gender in Chinese literature and culture from its original focus on women to include the consideration of masculinities as well, and draws on Louie’s influential model of traditional Chinese masculinity as constructed through the negotiation of the categories of wen (civil, literary) and wu (military, martial). The premodern prioritization of wen qualities in the masculine ideal—both for the educated elite and for most of the society whose apex they occupied—was challenged during China’s encounters with global modernity in the form of Western imperialism. Racialized colonial discourse characterized scholarly models of masculinity as effeminate and associated them with the allegedly congenital weakness of the “sick man of Asia.” Internalization of this discourse by Chinese intellectuals led to a crisis in masculinity and calls for a more militant manhood. By opening her review of this familiar story with Lu Xun’s critique of female impersonator Mei Lanfang, Lei skillfully highlights the imbrication of what she sees as some of its most significant elements: the performativity of masculinity, the concern for the gaze of a global audience, and the national stakes in gender identity. She proposes that her own contributions will be threefold. Empirically, she will offer the first systematic study Chinese masculinities during the crucial transitional periods of the late Qing and the early Republic. Methodologically, she will venture beyond canonical literary texts to examine a wider archive of literary, print, and visual culture. And theoretically, she will develop a new set of models and categories that will facilitate a response to a key question: “Can we locate agency, or any form of Reviews©  by University of Hawai‘i Press counter-orientalist discourse in reconstructing Chinese masculinities in spite of the power imbalance in the semicolonial settings?” (p. ). The second introductory chapter, “Violence and Its Antidotes: Theorizing Modern Chinese Masculinities,” casts a wide net in gathering the materials from which Lei will construct her own theoretical apparatus. Lei duly notes the need to attend both to cultural difference and to cross-cultural commonalities in “drawing on strands of scholarship within and outside of China studies, more specifically, poststructuralist theories of gender and masculinities, scholarship on cosmopolitanism, and relevant postcolonial theories of uneven transcultural exchange between the East and the West” (p. ). Balancing Judith Butler’s ideas about subjugated performativity against Erving Goffman’s more agentdriven notion of performance, she argues that the masculinities of this period were characterized by a heightened degree of performativity and staged with reference to both the “elsewhen” of the Chinese past and the “elsewhere” of the West and Japan. She then outlines two strands that will inform the remainder of the study. The first is the “brutalization of scholars,” that is, the alignment of a new scholarly identity with hypermasculine traits, including violence, both physical and discursive. This “brutalization” both emulates and serves as a form of resistance to the hegemonic militaristic masculinity of nineteenth-century Western colonialism. The second is a complementary occupation or appropriation of what she calls “feminine space,” a discursive terrain accommodating qualities, emotions, and desires disallowed by the dominant constructions of masculinity. While this “feminine space” might seem to echo or recuperate some of the qualities of premodern wen masculinity, it differs from its predecessor in being shaped by the demands and limitations of the brutalized scholar-warrior model. In chapter , “The Sick, the Weak, and the Perilous: Colonial Stereotypes and Martialized Intellectual Masculinity in Late Qing...

Yet more on a stochastic economic model: Supplement to Part 4: A model for share earnings, dividends and prices

AbstractIn this paper, we revisit the Earnings, Cover (the ratio of earnings over dividends) and Price/Earnings (P/E) Ratio models which we introduced in Part 4 of this series. Although we suggested that the significant decline in the Earnings Index over 2015-2016 might be followed by dividends and share prices, this has not happened. Instead, Earnings have risen substantially over the years 2016 to 2018. Therefore, we revise our models based on the updated data and compare the new set of models with the one in Part 4 as well as with themselves. We then compare different methods for forecasting Dividends and Share Prices.

Updating the theoretical tidal evolution constants: Apsidal motion and the moment of inertia

Context. The theoretical apsidal motion constants are key tools to investigate the stellar interiors in close eccentric binary systems. In addition, these constants and the moment of inertia are also important to investigate the tidal evolution of close binary stars as well as of exo-planetary systems. Aims. The aim of the paper is to present new evolutionary models, based on the MESA package, that include the internal structure constants (k2, k3, and k4), the radius of gyration, and the gravitational potential energy for configurations computed from the pre-main-sequence up to the first ascent giant branch or beyond. The calculations are available for the three metallicities [Fe/H] = 0.00, −0.50, and −1.00, which take the recent investigations in less metallic environments into account. This new set of models replaces the old ones, published about 15 years ago, using the code GRANADA. Methods. Core overshooting was taken into account using the mass-fov relationship, which was derived semi-empirically for models more massive than 1.2 M⊙. The differential equations governing the apsidal motion constants, moment of inertia, and the gravitational potential energy were integrated simultaneously through a fifth-order Runge-Kutta method with a tolerance level of 10−7. Results. The resulting models (from 0.8 up to 35.0 M⊙) are presented in 54 tables for the three metallicities, containing the usual characteristics of an evolutionary model (age, initial masses, log Teff, log g, and log L), the constants of internal structure (k2, k3, and k4), the radius of gyration β, and the factor α that is related with the gravitational potential energy.

Optimisation Model of Dispersal Simulations on a Dendritic Habitat Network

To predict and mitigate biodiversity loss, a better understanding of species distribution and reliable dispersal models are required. A promising approach in dispersal simulation is the method of spatially explicit graph-based analysis. While graph theory is strongly connected to the field of optimisation in a variety of disciplines, the potential of optimisation has not yet been exploited in dispersal models. We introduce an optimisation model built on a graph-based dispersal simulation of an aquatic invertebrate species with a terrestrial life stage. The model simulates a directed dispersal process and investigates the fastest route to colonise predefined vacant habitat patches. The optimisation model run-time is in general an order of magnitude faster than the underlying simulation and provides the minimum time until the considered habitat patches are colonised under the given landscape structure. These results can then be used to estimate how fast newly formed habitat patches can be reached and colonised. Our model can in principle be adapted to other simulation models and can thus be seen as a pioneer of a new set of models that may support landscape conservation and restoration.

Predicting plant disease epidemics from functionally represented weather series

Epidemics are often triggered by specific weather patterns favouring the pathogen on susceptible hosts. For plant diseases, models predicting epidemics have therefore often emphasized the identification of early season weather patterns that are correlated with a disease outcome at some later point. Toward that end, window-pane analysis is an exhaustive search algorithm traditionally used in plant pathology for mining correlations in a weather series with respect to a disease endpoint. Here we show, with reference to Fusarium head blight (FHB) of wheat, that a functional approach is a more principled analytical method for understanding the relationship between disease epidemics and environmental conditions over an extended time series. We used scalar-on-function regression to model a binary outcome (FHB epidemic or non-epidemic) relative to weather time series spanning 140 days relative to flowering (when FHB infection primarily occurs). The functional models overall fit the data better than previously described standard logistic regression (lr) models. Periods much earlier than heretofore realized were associated with FHB epidemics. The findings were used to create novel weather summary variables which, when incorporated into lr models, yielded a new set of models that performed as well as existing lr models for real-time predictions of disease risk. This article is part of the theme issue 'Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes'. This issue is linked with the subsequent theme issue 'Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control'.

Strategies for integrating uncertainty in iterative geostatistical seismic inversion

Iterative geostatistical seismic inversion integrates seismic and well data to infer the spatial distribution of subsurface elastic properties. These methods provide limited assessment to the spatial uncertainty of the inverted elastic properties, overlooking alternative sources of uncertainty such as those associated with poor well-log data, upscaling, and noise within the seismic data. We have expressed uncertain well-log samples, due to bad logging reads and upscaling, in terms of local probability distribution functions (PDFs). Local PDFs are used as conditioning data to a stochastic sequential simulation algorithm, included as the model perturbation within the inversion. The problem of noisy seismic and narrow exploration of the model parameter space, particularly in the early steps of the inversion, is tackled by the introduction of a cap on local correlation coefficients (CCs) responsible for the generation of the new set of models during the next iteration. We evaluate a single geostatistical framework with application to a real case study. When compared against a conventional iterative geostatistical seismic inversion, the integration of additional sources of uncertainty increases the match between real and inverted seismic traces and the variability within the ensemble of models inverted at the last iteration. The selection of the local PDFs plays a central role in the reliability of the inverted elastic models. Avoiding high local CCs at early stages of the inversion increases convergence in terms of global correlation between synthetic and real seismic reflection data at the end of the inversion.

Development of Polarizable Gaussian Model for Molecular Mechanical Calculations I: Atomic Polarizability Parameterization To Reproduce ab Initio Anisotropy.

A set of atomic polarizability parameters for a new polarizable Gaussian model (pGM) has been developed with the goal to accurately reproduce the polarizability anisotropy, taking advantage of its ability to attenuate all short-range electrostatic interactions, by fitting the ab initio molecular polarizability tensors ( A pq) calculated at the B3LYP/aug-cc-pVTZ level. For comparison, we also rederived the parameters for three Thole models in which the 1-2 (bonded), 1-3 (separated by two bonds), and 1-4 (separated by three bonds) interactions are fully included. The average percent errors (APEs) of molecular polarizability tensors for 4842 molecules or dimers are 2.98, 3.76, 3.28, and 3.82% for the pGM, Thole linear, Thole exponential, and Thole Amoeba models, respectively, with atom-type independent, universal screening factors (USF). The APEs are reduced further to 2.30, 2.69, 2.25, and 2.48% for the four corresponding polarizable models with atom-type dependent, variable screening factors (VSF). It is encouraging that the pGM with variable screening factors achieved APEs of 1.83 for 1155 amino acid analogs, dipeptides, and tetrapeptides, 1.39 for 28 nucleic acid bases, 0.708 for 1464 water clusters, and 1.99 for 85 dimers of water and biological building blocks. Compared to the new set of models, the APEs of the old Thole models that were fitted to isotropic molecular polarizabilities are 8.7% for set A (without the 1-2 and 1-3 interactions) and 6.3% for set D (with the 1-2 and 1-3 interactions) models, respectively. MPAD, a metric of molecular polarization anisotropy difference based on the diagonal terms of molecular polarizability tensors was defined and applied to assess the polarizable models in reproducing the ab initio molecular polarization anisotropy. The MPADs are 3.71, 4.70, 4.11, and 4.77% for the pGM, Thole linear, Thole exponential, and Thole Amoeba USF models, respectively. The APEs are reduced further to 2.85, 3.58, 2.90, and 3.15% for the four corresponding VSF models. Thus, the new pGM and Thole models notably improve molecular polarization anisotropy. Since pGM attenuates all short-range electrostatic interactions, its application is expected to improve stability in charge fitting, energy, and force calculations and the accuracy of multibody polarization.

Models for Predicting Average Bubble Diameter and Volumetric Bubble Flux in Deep Fluidized Beds

The average bubble diameter and volumetric bubble flux give indications about the overall bed expansion in a fluidized bed. As these properties depend on the particle properties and fluidized bed regime, their accurate predictions have been a challenge. A new set of models for predicting the average bubble properties within the bubbling and slugging regimes in a deep fluidized bed is proposed, where bubble flux is modeled by G=U0−c(U0Umf)aUmf, bubble diameter is modeled by db=0.848G0.66D0.34 and transition velocity is modeled by UbsUmf=1+2.33Umf−0.027(φ0.35ctat−1)(h0D)−0.588. The models are developed using the information obtained from an experimental setup equipped with a dual-plane electrical capacitance tomography and a porous distributor plate. Although they are empirical, the proposed models are based on the two-phase theory used in describing the bubble flow in a fluidized bed. These models have been validated, and the results show that they can be used to predict the behavior in different regimes ...

The development of bankruptcy prediction models in modern Russian economy

The paper focuses on problems of bankruptcy prediction models in Russia. This issue gains more and more relevance in recent years, in the light of falling incomes of population. The bankruptcy prediction models are widely used to predict bankruptcy. However, they might have low accuracy. In that regard, there is an active discussion in the foreign literature. In Russia there is a growing number of models developed, however so far no detailed studies to assess their efficiency. There are several objectives of the current study: a detailed review of domestic literature to reveal the flaws of existing models; design of a new set of models accounting to analyzed flaws; suggestions for future research. The estimation of Russian models revealed their inefficiency, due to data instability problem, poor financial reports quality, insufficient sample size, and distortion effect of “black accounting” and criminal bankruptcy practices. The set of models offered was proved to be efficient and robust. As the way of further model improvement it was suggested to distinguish between possible scenarios of failure (including liquidation, merger and “freezing”) using statistical classification methods. The Benfords Law analysis was introduced to separate companies falsifying financial statements. The application showed this method as promising.

Polarization due to rotational distortion in the bright star Regulus

Polarization in stars was first predicted by Chandrasekhar 1 , who calculated a substantial linear polarization at the stellar limb for a pure electron-scattering atmosphere. This polarization will average to zero when integrated over a spherical star but could be detected if the symmetry was broken, for example, by the eclipse of a binary companion. Nearly 50 years ago, Harrington and Collins 2 modelled another way of breaking the symmetry and producing net polarization—the distortion of a rapidly rotating hot star. Here we report the first detection of this effect. Observations of the linear polarization of Regulus, with two different high-precision polarimeters, range from +42 ppm at a wavelength of 741 nm to –22 ppm at 395 nm. The reversal from red to blue is a distinctive feature of rotation-induced polarization. Using a new set of models for the polarization of rapidly rotating stars, we find that Regulus is rotating at $$96.{5}_{-0.8}^{+0.6} \% $$ of its critical angular velocity for break-up, and has an inclination greater than 76.5°. The rotation axis of the star is at a position angle of 79.5 ± 0.7°. The conclusions are independent of, but in good agreement with, the results of previously published interferometric observations of Regulus 3 . The accurate measurement of rotation in early-type stars is important for understanding their stellar environments 4 and the course of their evolution 5 . The polarization resulting from electron scattering in a stellar atmosphere has been detected towards the rapidly spinning star Regulus. Deformation of the star from spherical allows this effect to be seen, fulfilling a prediction from around 50 years ago.

A modular set of synthetic spectral energy distributions for young stellar objects

In this paper, I present a new set of synthetic spectral energy distributions (SEDs) for young stellar objects (YSOs) spanning a wide range of evolutionary stages, from the youngest deeply embedded protostars to pre-main-sequence stars with few or no disks. These models include significant improvements on the previous generation of published models: in particular, the new models cover a much wider and more uniform region of parameter space, do not include highly model-dependent parameters, and include a number of improvements that make them more suited to modeling far-infrared and sub-mm observations of forming stars. Rather than all being part of a single monolithic set of models, the new models are split up into sets of varying complexity. The aim of the new set of models is not to provide the most physically realistic models for young stars, but rather to provide deliberately simplified models for initial modeling, which allows a wide range of parameter space to be explored. I present the design of the model set, and show examples of fitting these models to real observations to show how the new grid design can help us better understand what can be determined from limited unresolved observations. The models, as well as a Python-based fitting tool are publicly available to the community.

Implementation of new physics models for low energy electrons in liquid water in Geant4-DNA

A new alternative set of elastic and inelastic cross sections has been added to the very low energy extension of the Geant4 Monte Carlo simulation toolkit, Geant4-DNA, for the simulation of electron interactions in liquid water. These cross sections have been obtained from the CPA100 Monte Carlo track structure code, which has been a reference in the microdosimetry community for many years. They are compared to the default Geant4-DNA cross sections and show better agreement with published data.In order to verify the correct implementation of the CPA100 cross section models in Geant4-DNA, simulations of the number of interactions and ranges were performed using Geant4-DNA with this new set of models, and the results were compared with corresponding results from the original CPA100 code. Good agreement is observed between the implementations, with relative differences lower than 1% regardless of the incident electron energy.Useful quantities related to the deposited energy at the scale of the cell or the organ of interest for internal dosimetry, like dose point kernels, are also calculated using these new physics models. They are compared with results obtained using the well-known Penelope Monte Carlo code.

Theoretical Aspects of GPCR-Ligand Complex Pharmacology.

Over the past 50 years in pharmacology, an understanding of seven transmembrane (7TMR) function has been gained from the comparison of experimental data to receptor models. These models have been constructed from building blocks composed of systems consisting of series and parallel mass action binding reactions. Basic functions such as the the isomerization of receptors upon ligand binding, the sequential binding of receptors to membrane coupling proteins, and the selection of multiple receptor conformations have been combined in various ways to build receptor systems such as the ternary complex, extended ternary complex, and cubic ternary complex models for 7TMR function. Separately, the Black/Leff operational model has furnished an extremely valuable method of quantifying drug agonism. In the past few years, incorporation of the basic allosteric nature of 7TMRs has led to additional useful models of functional receptor allosteric mechanisms; these models yield valuable methods for quantifying allosteric effects. Finally, molecular dynamics has provided yet another new set of models describing the probability of formation of multiple receptor states; these radically new models are extremely useful in the prediction of functionally selective drug effects.

The FRUITY database on AGB stars: past, present and future

We present and show the features of the FRUITY database, an interactive web- based interface devoted to the nucleosynthesis in AGB stars. We describe the current available set of AGB models (largely expanded with respect to the original one) with masses in the range 1.3≤M/M⊙≤3.0 and metallicities –2.15 ≤[Fe/H]≤+0.15. We illustrate the details of our s-process surface distributions and we compare our results to observations. Moreover, we introduce a new set of models where the effects of rotation are taken into account. Finally, we shortly describe next planned upgrades.

EVOLUTION, NUCLEOSYNTHESIS, AND YIELDS OF AGB STARS AT DIFFERENT METALLICITIES. III. INTERMEDIATE-MASS MODELS, REVISED LOW-MASS MODELS, AND THE pH-FRUITY INTERFACE

We present a new set of models for intermediate mass AGB stars (4.0, 5.0 and, 6.0 Msun) at different metallicities (-2.15<=Fe/H]<=+0.15). This integrates the existing set of models for low mass AGB stars (1.3<=M/M<=3.0) already included in the FRUITY database. We describe the physical and chemical evolution of the computed models from the Main Sequence up to the end of the AGB phase. Due to less efficient third dredge up episodes, models with large core masses show modest surface enhancements. The latter is due to the fact that the interpulse phases are short and, then, Thermal Pulses are weak. Moreover, the high temperature at the base of the convective envelope prevents it to deeply penetrate the radiative underlying layers. Depending on the initial stellar mass, the heavy elements nucleosynthesis is dominated by different neutron sources. In particular, the s-process distributions of the more massive models are dominated by the \nean~reaction, which is efficiently activated during Thermal Pulses. At low metallicities, our models undergo hot bottom burning and hot third dredge up. We compare our theoretical final core masses to available white dwarf observations. Moreover, we quantify the weight that intermediate mass models have on the carbon stars luminosity function. Finally, we present the upgrade of the FRUITY web interface, now also including the physical quantities of the TP-AGB phase of all the models included in the database (ph-FRUITY).

CARBON-RICH PRESOLAR GRAINS FROM MASSIVE STARS: SUBSOLAR 12 C/ 13 C AND 14 N/ 15 N RATIOS AND THE MYSTERY OF 15 N

Carbon-rich grains with isotopic anomalies compared to the Sun are found in primitive meteorites. They were made by stars, and carry the original stellar nucleosynthesis signature. Silicon carbide grains of Type X and C, and low-density graphites condensed in the ejecta of core-collapse supernovae. We present a new set of models for the explosive He shell and compare them with the grains showing 12C/13C and 14N/15N ratios lower than solar. In the stellar progenitor H was ingested into the He shell and not fully destroyed before the explosion. Different explosion energies and H concentrations are considered. If the SN shock hits the He-shell region with some H still present, the models can reproduce the C and N isotopic signatures in C-rich grains. Hot-CNO cycle isotopic signatures are obtained, including a large production of 13C and 15N. The short-lived radionuclides 22Na and 26Al are increased by orders of magnitude. The production of radiogenic 22Ne from the decay of 22Na in the He shell might solve the puzzle of the Ne-E(L) component in low-density graphite grains. This scenario is attractive for the SiC grains of type AB with 14N/15N ratios lower than solar, and provides an alternative solution for SiC grains originally classified as nova grains. Finally, this process may contribute to the production of 14N and 15N in the Galaxy, helping to produce the 14N/15N ratio in the solar system.