Probing the effect of UV radiation on the chemistry in circumstellar envelopes around evolved stars

Low to intermediate mass (0.8 - 8 M⊙) stars lose a substantial amount of their mass in the last phase of stellar evolution, the asymptotic giant branch (AGB) phase. Hence, they are one of the main suppliers of dust and gas in the interstellar medium and important for the enrichment of galaxies. Due to the intense mass loss, a circumstellar envelope (CSE), rich in gas and dust, forms around AGB stars. The exact mechanism(s) responsible for the mass loss is not yet fully established, although a radiatively driven dust wind appears to play a major role. <br /><br />CSEs are excellent laboratories to understand the mass loss process as well as to constrain stellar properties. It is known that ultra-violet (UV) photons play a critical role in the chemical composition and evolution of the CSEs. The UV photons that can impact the chemistry of the CSE originate, in the inner part, from stellar chromospheric activity or hot binary companions. In the outer part they come from the interstellar radiation field (ISRF). However, the ISRF is the only UV source which has been con- sidered to affect the photo-chemistry of the CSEs. It was long expected that the stellar UV emission is weak and that its effects would not be noticeable, especially not using single-dish telescope observations. Now, high-spatial resolution interferometric observa- tions and increasing number of detections of stellar UV sources indicate the importance of considering the internal UV radiation in the CSEs chemistry. <br /><br />In order to study this effect, we have started an analysis of the carbon-type AGB star, R Scl. Previous studies show a variation of the 12CO/13CO ratio in the circum- stellar envelope and a discrepancy between the circumstellar 12CO/13CO ratio and the photospheric 12C/13C ratio, which has been explained as a result of internal UV radi- ation. Our detailed radiative transfer modelling of H12CN and H13CN isotopologues around R Scl confirms this proposed scenario. This result highlights the importance of considering all the potential UV sources on the chemistry of the CSE of R Scl. <br /><br />Applying our suggested method of quantifying the effect of the internal UV radiation field to a large number of AGB stars might help to investigate the binarity rate of AGBs. This will also improve our understanding of the stellar chromospheric activity. These are both open questions in the field of research on AGB stars

UV Chemistry in the Circumstellar Envelopes of Evolved Stars

Low- and intermediate-mass stars eject a substantial amount of their material into space during a late phase of stellar evolution, the asymptotic giant branch (AGB) phase. Therefore, they impact the chemistry of the interstellar medium. Due to the intense mass loss, a circumstellar envelope (CSE), rich in gas and dust, forms around the AGB star. Observations of molecular species and dust content in CSEs help us to broaden our knowledge on late phases of stellar evolution, mass-loss processes, the CSE chemistry, and the stellar properties. For instance, observations of carbon monoxide (CO) have been extensively used to determine the mass-loss rate and the overall CSE properties. Ultraviolet (UV) photodissociation of CO from the interstellar radiation field (ISRF) is the dominant process that determines the CO distribution and extent in CSEs. Therefore, a precise calculation of the CO photodissociation rate is crucial to determine the mass-loss rates. Subsequently, the value adopted for the mass-loss rate in further modelling of the CSEs will affect the abundances derived for all other molecules. Thus, an estimation of the CO photodissociation rate affects the estimates of the amount of all the recycled material. In this thesis, we present the most updated calculations of the depth dependency of the CO photodissociation rate in CSEs using the latest laboratory measurements. Generally, it is well known that UV radiation impacts the CSE chemistry and the influence of UV radiation from the ISRF has been considered in the models of CSEs. However, there has been little discussion on the impact of internal sources of UV radiation. Recent Galaxy Evolution Explorer observations reveal the presence of strong internal UV radiation for a large sample of AGB stars. The internal UV radiation can originate from stellar chromospheric activity, a hot binary companion, and/or accretion of matter between two stars in a binary system. This thesis seeks to address the impact of both the internal and external sources of UV radiation on the CSE chemistry. To trace the impact of UV radiation, we present two approaches. First, observations of the main UV photodissociation and photoionization products, such as CI and CII. We present, for the first time, detections of CI around a UV-bright oxygen-rich AGB star, omi Ceti. In the second approach, we investigate the isotopologue ratio of molecules with different photodissociation mechanisms. We expect variations in the isotopologue ratio of molecules that dissociate through lines. However, there should not be any variation by UV radiation in the isotopologue ratio of molecules with continuum dissociation

An Architecture for Personality-based, Nonverbal Behavior in Affective Virtual Humanoid Character

As humans we perceive other humans as individually different based – amongst other things – on a consistent pattern of affect, cognition, and behavior. Here we propose a biologically and psychologically grounded cognitive architecture for the control of nonverbal behavior of a virtual humanoid character during dynamic interactions with human users. Key aspects of the internal states and overt behavior of the virtual character are modulated by high-level personality parameters derived from the scientific literature. The virtual character should behave naturally and consistently while responding dynamically to the environment's feedback. Our architecture strives to yield consistent patterns of behavior though personality traits that have a modulatory influence at different levels of the hierarchy. These factors affect on the one hand high-level components such as ‘emotional reactions’ and ‘coping behavior’, and on the other hand low-level parameters such as the ‘speed of movements and repetition of gestures. Psychological data models are used as a reference to create a map between personality factors and patterns of behavior. We present a novel hybrid computational model that combines the control of discrete behavior of the virtual character moving through states of the interaction with continuous updates of the emotional state of the virtual character depending on feedback from interactions with the environment. To develop and evaluate the hybrid model, a testing scenario is proposed that is based on a turn-taking interaction between a human participant and a 3D representation of the humanoid character. We believe that our work contributes to individualized, and ultimately more believable humanoid artifacts that can be deploy in a wide range of application scenarios

Simulink toolbox for real-time virtual character control

Building virtual humans is a task of formidable complexity. We believe that, especially when building agents that interact with biological humans in real-time over multiple sensorial channels, graphical, data flow oriented programming environments are the development tool of choice. In this paper, we describe a toolbox for the system control and block diagramming environment Simulink that supports the construction of virtual humans. Available blocks include sources for stochastic processes, utilities for coordinate transformation and messaging, as well as modules for controlling gaze and facial expressions

Photodissociation of CO in the outflow of evolved stars

Context. Ultraviolet (UV) photodissociation of carbon monoxide (CO) controls the abundances and distribution of CO and its photodissociation products. This significantly influences the gas-phase chemistry in the circumstellar material around evolved stars. A better understanding of CO photodissociation in outflows also provides a more precise estimate of mass-loss rates. Aims. We aim to update the CO photodissociation rate in an expanding spherical envelope assuming that the interstellar radiation field (ISRF) photons penetrate through the envelope. This will allow us to precisely estimate the CO abundance distributions in circumstellar envelope around evolved stars. Methods. We used the most recent CO spectroscopic data to precisely calculate the depth dependency of the photodissociation rate of each CO dissociating line. We calculated the CO self- and mutual-shielding functions in an expanding envelope. We investigated the dependence of the CO profile on the five fundamental parameters mass-loss rate, the expansion velocity, the CO initial abundance, the CO excitation temperature, and the strength of the ISRF. Results. Our derived CO envelope size is smaller than the commonly used radius derived by Mamon et al. 1988. The difference between results varies from 1% to 39% and depends on the H2 and CO densities of the envelope. We list two fitting parameters for a large grid of models to estimate the CO abundance distribution. We demonstrate that the CO envelope size can differ between outflows with the same effective content of CO, but different CO abundance, mass-loss rate, and the expansion velocity as a consequence of differing amounts of shielding by H2 and CO. Conclusions. Our study is based on a large grid of models employing an updated treatment of the CO photodissociation, and in it we find that the abundance of CO close to the star and the outflow density both can have a significant effect on the size of the molecular envelope. We also demonstrate that modest variations in the ISRF can cause measurable differences in the envelope extent

Expressing Personality Through Non-verbal Behaviour in Real-Time Interaction

The attribution of traits plays an important role as a heuristic for how we interact with others. Many psychological models of personality are analytical in that they derive a classification from reported or hypothesised behaviour. In the work presented here, we follow the opposite approach: Our personality model generates behaviour that leads an observer to attribute personality characteristics to the actor. Concretely, the model controls all relevant aspects of non-verbal behaviour such as gaze, facial expression, gesture, and posture. The model, embodied in a virtual human, affords to realistically interact with participants in real-time. Conceptually, our model focuses on the two dimensions of extra/introversion and stability/neuroticism. In the model, personality parameters influence both, the internal affective state as well as the characteristic of the behaviour execution. Importantly, the parameters of the model are based on empirical findings in the behavioural sciences. To evaluate our model, we conducted two types of studies. Firstly, passive experiments where participants rated videos showing variants of behaviour driven by different personality parameter configurations. Secondly, presential experiments where participants interacted with the virtual human, playing rounds of the Rock-Paper-Scissors game. Our results show that the model is effective in conveying the impression of the personality of a virtual character to users. Embodying the model in an artificial social agent capable of real-time interactive behaviour is the only way to move from an analytical to a generative approach to understanding personality, and we believe that this methodology raises a host of novel research questions in the field of personality theory

Analyzing the Global Trend of Publications on Laryngeal Mask Airway

Background: Bibliometrics evaluates the scientific publications in different fields from different aspects. However, the bibliometric state of global research publications on Laryngeal Mask Airway (LMA), as a main progressive medical field, is unknown. Aim: This study aimed to conduct a bibliometric analysis and scientific visualization for inspecting some main bibliometric indicators of the research publications in the field. Methods: This study is a descriptive cross-sectional applied study that used bibliometric techniques. MeSH-retrieved synonyms for LMA were searched in Scopus and the bibliometric indicators of retrieved papers in the field were measured and visualized in Excel and VOSviewer. Results: In total, 9,783 papers were published on LMA during 1952-2021, starting from one paper in 1952 and amounted to 255 in 2021. With ups and downs in the annual publication growth, steady trend was seen in the growth coefficient of publications (R²=.1652). The first to third ranks in publishing countries belonged to the United States with 1,783 papers (18.22%), the United Kingdom with 1,632 papers (16.68%) and Japan with 729 papers (7.45%), respectively. Among active research institutes, Cairns Hospital from Australia ranked first with publishing 284 papers, followed by the University of Queensland again from Australia with publishing 141 papers and Royal United Hospital from England with 117 published papers, respectively. Anaesthesia ranked first highly-publishing journal with 1,049 published papers, followed by Anesthesia and Analgesia with 487 published papers and Pediatric Anaesthesia with 448 published documents. Anaesthesia was the main cited source, too. The top three highly-frequent keywords were laryngeal mask airway (N=223), equipment (N=132) and airway management (N=116), respectively. Co-occurred keywords were in four subject clusters.&nbsp;&nbsp; &nbsp; Conclusion: This study is the first to give a relatively comprehensive bibliometric analysis and visualization of the global research publication and a guide for researchers and research policy-makers in LMA, as a progressive medical discipline

Evaluating the Performance of Forecasting Models for Portfolio Allocation Purposes with Generalized GRACH Method

Portfolio theory assumes that investors accept risk. This means thatin the equal rate of return on the two assets, the assets were chosenthat have a lower risk level. Modern portfolio theory is accepted byinvestors who believe that they are not cope with the market. Sothey keep many different types of securities in order to access theoptimum efficiency rate that is close to the rate of return on market.One way to control investment risk is establishing the portfolioshares. There are many ways to choose the optimal portfolioshares. Among these methods in this study we use loss functions.For this, we choose all firms from the year2011to the end of 2015that had been a member in the Tehran Stock Exchange. The resultsof this research show that the likelihood functions have the bestperformance in Forecasting the optimal portfolio allocationprob-lem