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Context. Interstellar dust particles, in particular carbonaceous nano-grains (like polycyclic aromatic hydrocarbons, fullerenes, and amorphous hydrogenated carbon), are critical players for the composition, energy budget, and dynamics of the interstellar medium (ISM). The dust properties, specifically the composition and size of dust grains are not static; instead, they exhibit considerable evolution triggered by variations in local physical conditions such as the density and gas temperature within the ISM, as is the case in photon-dominated regions (PDRs). The evolution of dust and its impact on the local physical and chemical conditions is thus a key question for understanding the first stages of star formation. Aims. From the extensive spectral and imaging data of the JWST PDRs4All program, we study the emission of dust grains within the Orion Bar – a well-known, highly far-UV (FUV)-irradiated PDR situated at the intersection between cold, dense molecular clouds, and warm ionized regions. The Orion Bar because of its edge-on geometry provides an exceptional benchmark for characterizing dust evolution and the associated driving processes under varying physical conditions. Our goal is to constrain the local properties of dust by comparing its emission to models. Taking advantage of the recent JWST data, in particular the spectroscopy of dust emission, we identify new constraints on dust and further previous works of dust modelling. Methods. To characterize interstellar dust across the Orion Bar, we follow its emission as traced by JWST NIRCam (at 3.35 and 4.8 μm) and MIRI (at 7.7, 11.3, 15.0, and 25.5 μm) broad band images, along with NIRSpec and MRS spectroscopic observations. First, we constrain the minimum size and hydrogen content of carbon nano-grains from a comparison between the observed dust emission spectra and the predictions of the Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS) coupled to the numerical code DustEM. Using this dust model, we then perform 3D radiative transfer simulations of dust emission with the SOC code (Scattering with OpenCL) and compare to data obtained along well chosen profiles across the Orion Bar. Results. The JWST data allows us, for the first time, to spatially resolve the steep variation of dust emission at the illuminated edge of the Orion Bar PDR. By considering a dust model with carbonaceous nano-grains and submicronic coated silicate grains, we derive unprecedented constraints on the properties of across the Orion Bar. To explain the observed emission profiles with our simulations, we find that the nano-grains must be strongly depleted with an abundance (relative to the gas) 15 times less than in the diffuse ISM. The NIRSpec and MRS spectroscopic observations reveal variations in the hydrogenation of the carbon nano-grains. The lowest hydrogenation levels are found in the vicinity of the illuminating stars suggesting photo-processing while more hydrogenated nano-grains are found in the cold and dense molecular region, potentially indicative of larger grains. [ABSTRACT FROM AUTHOR]

Although the phonological history of Tai Nüa can be roughly demonstrated through comparison of its modern dialects against their reconstructed ancestor, namely, Proto-Southwestern Tai, neither the chronology nor the pathway of the transformative sound changes can be established in detail with any certainty. This study demonstrates a more fine-grained understanding of both the chronology and pathway of the sound changes through the examination of the recently available Sino-Baiyi Manual of Translation, a Chinese-Tai Nüa section of bilingual glossary books produced for diplomatic use during the Ming Dynasty. By comparing the phonological inventory of Tai Nüa as attested in this manuscript against the pre-established list of all characterizing sound changes from Proto-Southwestern Tai to Modern Tai Nüa dialects, we chronologize all the sound changes into the pre-16th versus post-16th century changes. Employing the pre- & post-16th century changes as the demarcating criteria, we tentatively propose a tripartite chronological division of Tai Nüa into 1) Old Tai Nüa, 2) Early Modern Tai Nüa, and 3) Modern Tai Nüa dialects. [ABSTRACT FROM AUTHOR]

This study examined the effect of Aviation Turbine Fuel (ATF) exposure on tensile and flexural properties of E-Glass/epoxy composites. Specimens as per ASTM standards were made, and a portion of the specimens was coated with resin of varying thickness. Both the resin-coated and bare specimens were exposed to ATF by immersing them in the fuel till saturation. Tensile and flexural tests were carried out, and the results have been analyzed in the paper. Experimental results show that bare specimens exhibited a reduction in properties due to ATF ingression to the polymeric network and induced internal stresses, which not only degraded the reinforcement and fiber matrix adherence but created micro-cracks too in the resin at the interfaces. Resin-coated specimens limit fuel ingression, which has led to a slight reduction in properties. Fibers from the fractured surface were examined by scanning electron microscope, exhibiting slight degradation in fiber, interfacial characteristics and matrix. [ABSTRACT FROM AUTHOR]

About a thousand optical absorption features on the interstellar extinction curve popularly known as the Diffuse Interstellar Bands (DIBs) have been observed. The numbers are increasing every year, thanks to the improvement in telescope and spectroscopic technology. Ultra-high resolution spectroscopic observations and emission features corresponding to some of the DIBs suggest that, some if not all, of these features are due to large molecules. The strength of DIBs depend on the amount of reddening which is directly proportional to the amount of material present between the background star and the observer. Since, the strengths of the DIBs are not strongly correlated with each other, there must be several carriers. Time Dependent Density Functional Theory (TDDFT) calculations are useful in narrowing down molecular systems that may be further investigated in the laboratory.The observations of the unidentified infrared (UIR) bands point towards the widespread presence of Polycyclic Aromatic Hydrocarbon (PAH) molecules. Though, not a single PAH has been discovered in interstellar space, these are the largest molecules suspected to be present. PAHs are stable towards energetic environment prevailing under interstellar conditions rendering these molecules to be good candidates as DIB carriers. We report TDDFT calculations to predict electronic transitions of neutral, protonated-deuteronated and PAHs with five member rings with various sites of protonation and deuteronation. Compared to their neutral forms, these charged isoelectronic forms of PAHs are predicted to have active transitions in the visible region, which means they are suitable candidates as carriers for some of the DIBs and laboratory studies are warranted for these systems. [ABSTRACT FROM PUBLISHER]