Real-time atomic force microscopy observation was carried out during crystallization in thin films of chiral poly(R-3-hydroxybutyrate-co-R-3-hydroxyhexanoate) copolymer, and the development details of single lamellae in the banded spherulites are revealed for the first time. The lamellae exhibit complicated growth behaviors:  twisting, bending, backward growth, and branching. The lamellae continuously twist to show alternating edge-on and flat-on views along the radii of the spherulites. Giant screw dislocations bring forth to the birth of new lamellae. Interaction between the leading and trailing lamellae contributes to cooperative stacking of the twisting crystals. The lamellae twist before screw dislocations appear, demonstrating that screw dislocations are not causal of twisting. All the observed twisting occurs in the right-handed sense, likely resulting from the chirality of the crystal structure. Increased crystallization temperature results in decreased magnitude of lamellar twisting and bending. Models for morphological development are discussed in the context of these observations.

We present the first results from the B-fields In STar-forming Region Observations (BISTRO) survey, using the Sub-millimetre Common-User Bolometer Array2 camera, with its associated polarimeter (POL-2), on the James Clerk Maxwell Telescope in Hawaii. We discuss the survey's aims and objectives. We describe the rationale behind the survey, and the questions thatthe survey will aim to answer. The most important of these is the role of magnetic fields in the star formation process on the scale of individual filaments and cores in dense regions. We describe the data acquisition and reduction processes for POL-2, demonstrating both repeatability and consistency with previous data. We present a first-look analysis of the first results from the BISTRO survey in the OMC1 region. We see that the magnetic field lies approximately perpendicular to the famous "integral filament" in the densest regions of that filament. Furthermore, we see an "hourglass" magnetic field morphology extending beyond the densest region of the integral filament into the less-dense surrounding material, and discuss possible causes for this. We also discuss the more complex morphology seen along the Orion Bar region. We examine the morphology of the field along the lower-density northeastern filament. We find consistency with previous theoretical models that predict magnetic fields lying parallel to low-density, non-self-gravitating filaments, and perpendicular to higher-density, self-gravitating filaments.

Massive star-forming regions with observed infall motions are good sites for studying the birth of massive stars. In this paper, 405 compact sources have been extracted from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) compact sources that also have been observed in the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey during Years 1 and 2. These observations are complemented with Spitzer GLIMPSE/MIPSGAL mid-IR survey data to help classify the elected starforming clumps into three evolutionary stages: pre-stellar, proto-stellar and UCHII regions. The results suggest that 0.05 g cm −2 is a reliable empirical lower bound for the clump surface densities required for massive-star formation to occur. The optically thick HCO + (1-0) and HNC(1-0) lines, as well as the optically thin N 2 H + (1-0) line were used to search for infall motions toward these sources. By analyzing the asymmetries of the optically thick HCO + (1-0) and HNC(1-0) lines and the mapping observations of HCO + (1-0), a total of 131 reliable infall candidates have been identified. The HCO + (1-0) line shows the highest occurrence of obvious asymmetric features, suggesting that it may be a better infall motion tracer than other lines such as HNC(1-0). The detection rates of infall candidates toward pre-stellar, proto-stellar and UCHII clumps are 0.3452, 0.3861 and 0.2152, respectively. The relatively high detection rate of infall candidates toward UCHII clumps indicates that many UCHII regions are still accreting matter. The peak column densities and masses of the infall candidates, in general, display a increasing trend with progressing evolutionary stages. However, the rough estimates of the mass infall rate show no obvious variation with evolutionary stage.