On the Interpretation of the l-v Features in the Milky Way Galaxy

We model the gas dynamics of barred galaxies using a three-dimensional, high-resolution, $N$-body+hydrodynamical simulation and apply it to the Milky Way in an attempt to reproduce both the large-scale structure and the clumpy morphology observed in Galactic H\emissiontype{I} and CO $l-v$ diagrams. Owing to including the multi-phase interstellar medium, self-gravity, star-formation and supernovae feedback, the clumpy morphology, as well as the large-scale features, in observed $l-v$ diagrams are naturally reproduced. We identify in our $l-v$ diagrams with a number of not only large-scale peculiar features such as the '3-kpc arm', '135-km s$^{-1}$ arm' and 'Connecting arm' but also clumpy features such as `Bania clumps', and then link these features in a face-on view of our model. We give suggestions on the real structure of the Milky Way and on the fate of gas clumps in the central region.Comment: accepted to PAS

Exploring the lived experiences of hearing mothers of Deaf children in Lebanon: A phenomenological study

The conceptualization of deafness is predominantly centered around two perspectives: the medical model which pathologizes hearing loss and congenital deafness as something to fix, and the sociocultural model which views deafness as a cultural identity. Deaf communities have their own distinct culture, values, history, art, language and mode of communication. However, not every deaf person necessarily identifies with these communities. The purpose of this study was to explore hearing mothers’ experiences of raising a Deaf child in Lebanon. Five participants were recruited through the Lebanese Center for the Deaf. The mothers had a Deaf child aged 10 to 15 years old at the time of the interview. The study aimed to formulate themes portraying the lived experience of these mothers and examine their meaning-making through an in-depth phenomenological approach. The research method adopted is an interpretative phenomenological analysis. The superordinate themes are: ‘Mother’s reaction to her child’s deafness: from denial to finding solutions’, ‘Mother’s meaning-making and acceptance of deafness’, ‘Societal and family reactions to deafness, ‘guilt towards other children and informal support received’, ‘Challenges faced and journey with the medical field: from diagnosis to rehabilitation’, and ‘The choice of education and communication strategies implemented’. The findings present the mothers’ meaning-making and formulation of motherhood through the grieving process upon hearing the diagnosis. The responsibility and inevitable decisions taken by the mothers created tremendous uneasiness. The choice of hearing devices, schools, and communication strategies affected the child’s development and interactions. Suggestions for practice and future research pertains to the formal and informal support offered to mothers and their families following their needs. Further research is needed to explore the lived experiences of people in the Deaf community in Lebanon and their families to improve services presented by practitioners in contact with this population

Post-traumatic stress disorders, depression, and anxiety in unaccompanied refugee minors exposed to war-related trauma: a systematic review

This systematic review gathers data from the existing literature on the prevalence and course of psychiatric disorders among unaccompanied refugee minors (URMs). The databases PsychINFO, PubMed, Scopus and Web of Science were searched and reference lists of papers were also manually examined to identify relevant articles. Peer-reviewed journal articles included focused on the mental health of URMs, who were forced to leave their place of residence because of threats of wars. A narrative synthesis was done to analyse the data presented in the studies. Results from the fifteen studies included in the review highlighted the high prevalence of post-traumatic stress disorders (PTSD), depression, and anxiety among URMs. The association between internalizing disorders and exposure to trauma, and time since displacement were examined. Separation from family members, death of parents and close relatives, level of exposure to armed conflicts, and threats to a person were the most frequent stressful life events (SLE) among URMs before migration. Although the number of research done on this vulnerable population is increasing overtime, the review highlights the need for further examination of refugee mental health and the factors affecting symptoms of PTSD, depression, and anxiety

Valley current characterization of high current density resonant tunnelling diodes for terahertz-wave applications

We report valley current characterisation of high current density InGaAs/AlAs/InP resonant tunnelling diodes (RTDs) grown by metal-organic vapour phase epitaxy (MOVPE) for THz emission, with a view to investigate the origin of the valley current and optimize device performance. By applying a dual-pass fabrication technique, we are able to measure the RTD I-V characteristic for different perimeter/area ratios, which uniquely allows us to investigate the contribution of leakage current to the valley current and its effect on the PVCR from a single device. Temperature dependent (20 – 300 K) characteristics for a device are critically analysed and the effect of temperature on the maximum extractable power (PMAX) and the negative differential conductance (NDC) of the device is investigated. By performing theoretical modelling, we are able to explore the effect of typical variations in structural composition during the growth process on the tunnelling properties of the device, and hence the device performance

Molecular Dynamics Simulation of Sympathetic Crystallization of Molecular Ions

It is shown that the translational degrees of freedom of a large variety of molecules, from light diatomic to heavy organic ones, can be cooled sympathetically and brought to rest (crystallized) in a linear Paul trap. The method relies on endowing the molecules with an appropriate positive charge, storage in a linear radiofrequency trap, and sympathetic cooling. Two well--known atomic coolant species, ${}^9{\hbox{Be}}^+$ and ${}^{137}{\hbox{Ba}}^+$, are sufficient for cooling the molecular mass range from 2 to 20,000 amu. The large molecular charge required for simultaneous trapping of heavy molecules and of the coolant ions can easily be produced using electrospray ionization. Crystallized molecular ions offer vast opportunities for novel studies.Comment: Accepted for publication in Phys. Rev.

The dynamics of spiral arms in pure stellar disks

It has been believed that spirals in pure stellar disks, especially the ones spontaneously formed, decay in several galactic rotations due to the increase of stellar velocity dispersions. Therefore, some cooling mechanism, for example dissipational effects of the interstellar medium, was assumed to be necessary to keep the spiral arms. Here we show that stellar disks can maintain spiral features for several tens of rotations without the help of cooling, using a series of high-resolution three-dimensional $N$-body simulations of pure stellar disks. We found that if the number of particles is sufficiently large, e.g., $3\times 10^6$, multi-arm spirals developed in an isolated disk can survive for more than 10 Gyrs. We confirmed that there is a self-regulating mechanism that maintains the amplitude of the spiral arms. Spiral arms increase Toomre's $Q$ of the disk, and the heating rate correlates with the squared amplitude of the spirals. Since the amplitude itself is limited by the value of $Q$, this makes the dynamical heating less effective in the later phase of evolution. A simple analytical argument suggests that the heating is caused by gravitational scattering of stars by spiral arms, and that the self-regulating mechanism in pure-stellar disks can effectively maintain spiral arms on a cosmological timescale. In the case of a smaller number of particles, e.g., $3\times 10^5$, spiral arms grow faster in the beginning of the simulation (while $Q$ is small) and they cause a rapid increase of $Q$. As a result, the spiral arms become faint in several Gyrs.Comment: 18 pages, 19 figures, accepted for Ap