The JWST Galactic Center Survey -- A White Paper

The inner hundred parsecs of the Milky Way hosts the nearest supermassive black hole, largest reservoir of dense gas, greatest stellar density, hundreds of massive main and post main sequence stars, and the highest volume density of supernovae in the Galaxy. As the nearest environment in which it is possible to simultaneously observe many of the extreme processes shaping the Universe, it is one of the most well-studied regions in astrophysics. Due to its proximity, we can study the center of our Galaxy on scales down to a few hundred AU, a hundred times better than in similar Local Group galaxies and thousands of times better than in the nearest active galaxies. The Galactic Center (GC) is therefore of outstanding astrophysical interest. However, in spite of intense observational work over the past decades, there are still fundamental things unknown about the GC. JWST has the unique capability to provide us with the necessary, game-changing data. In this White Paper, we advocate for a JWST NIRCam survey that aims at solving central questions, that we have identified as a community: i) the 3D structure and kinematics of gas and stars; ii) ancient star formation and its relation with the overall history of the Milky Way, as well as recent star formation and its implications for the overall energetics of our galaxy's nucleus; and iii) the (non-)universality of star formation and the stellar initial mass function. We advocate for a large-area, multi-epoch, multi-wavelength NIRCam survey of the inner 100\,pc of the Galaxy in the form of a Treasury GO JWST Large Program that is open to the community. We describe how this survey will derive the physical and kinematic properties of ~10,000,000 stars, how this will solve the key unknowns and provide a valuable resource for the community with long-lasting legacy value.Comment: This White Paper will be updated when required (e.g. new authors joining, editing of content). Most recent update: 24 Oct 202

Development of Microporous Structure and its Application to Optical Film for Cellulose Triacetate Containing Diisodecyl Adipate

Phase separation in plasticized cellulose triacetate (CTA) films is investigated to produce a microporous film that can be used in optical devices. Hot-stretched CTA films containing diisodecyl adipate (DIDA) show negative orientation birefringence similar to the hot-stretched pure CTA. After extracting DIDA from the stretched films by immersion into an organic solvent, however, the films exhibit positive birefringence. Moreover, the magnitude of the birefringence increases with the wavelength, known as extraordinary dispersion, which is an essential property in the preparation of an ideal quarter-wave plate. Numerous ellipsoidal pores with micro-scale were detected in the film after the immersion, indicating that DIDA were segregated and formed ellipsoidal domains in the CTA matrix during annealing and stretching. These results indicate that extraordinary wavelength dispersion is given by the combinations of orientation birefringence from CTA and form birefringence from micropores. Furthermore, it was found that annealing time and stretching condition affect the phase separation as well as the shape and size of pores

Interphase transfer of tackifier between immiscible rubbers

Interphase transfer of a coumarone-indene tackifier between natural rubber (NR) and poly(isobutylene) (PIB) was studied. The laminated sheets composed of NR with the tackifier and PIB with the tackifier were annealed at various temperatures to promote the interphase transfer of the tackifier. After separating the post-annealing sheets, the infrared spectra were measured to evaluate the tackifier content in each rubber sheet. It was found that a large amount of the tackifier resided in PIB after annealing at -20 °C, whereas the tackifier moved to NR at 40 °C. Consequently, the NR sheet exhibited lower glass transition temperature T_g after annealing at -20 °C and higher T_g when annealed at 40 °C. The differential scanning calorimetry measurements revealed that the crystallization of NR was responsible for the tackifier transfer. This phenomenon should be noted of interest because the matrix of their blend shows low T_g at low ambient temperature and high T_g at high temperature when NR is the matrix of the blend

Thermal Expansion Behavior of Antiplasticized Polycarbonate

Thermal expansion behavior and viscoelastic properties of antiplasticized polycarbonate (PC) are studied employing p-terphenyl (p-tPh) as an antiplasticizer. The rheological characterization reveals that the free volume fraction at the glass transition temperature and thermal expansion coefficient of the free volume in the rubbery region are unchanged by the p-tPh addition. However, the linear coefficient of thermal expansion in the glassy region is found to be reduced, which can be attributed to the reduction of free volume in the glassy state. Since the antiplasticized PC exhibits high modulus with a low thermal expansion coefficient, its suitability as a replacement for inorganic glasses will be considered

Surface localization of poly(methyl methacrylate) in a miscible blend with polycarbonate

A new method to localize poly(methyl methacrylate) (PMMA) at the surface of a miscible blend with polycarbonate (PC) is demonstrated. Low-molecular-weight PMMA, which is found to be miscible with PC, is used in this study. After annealing the PC/PMMA blend in a temperature gradient, PMMA is found to localize on the high-temperature side, as detected by infrared spectroscopy and molecular weight measurements. Furthermore, the sample exhibits good transparency even after annealing. This phenomenon is notable because it is applicable to enhancing the anti-scratch properties of PC

Localization of Nanofibers on Polymer Surface Using Interface Transfer Technique

A new method to localize polymer nanofibers on a polymer surface was verified using interface transfer technique of nanofibers between immiscible polymer pairs. Nanofibers of poly(butylene terephthalate) (PBT) were prepared in a molten polypropylene (PP) by melt stretching and subsequent quenching. The obtained composite of PP containing PBT nanofibers was compressed into a flat sheet and piled with a sheet of high-density polyethylene (HDPE). During annealing procedure of the piled sheets at the temperature between Tm’s of PP and PBT, PBT nanofibers were transferred from PP to HDPE. Consequently, PBT fibers was confirmed on the surface of HDPE. Similarly, polytetrafluoroethylene (PTFE) nanofibers dispersed in a molten PLA, which were obtained by mechanical blending process, were found to move to PP during annealing procedure at the temperature between Tm’s of PLA and PTFE. This movement leads to the modification of surface tension for PP. Furthermore, the piled sheets of PP/PBT and HDPE as well as those of PLA/PTFE and PP were easily separated each other because of the immiscible nature