Adaptive radiation of <i>Pseudomonas fluorescens</i> SBW25 in experimental microcosms provides an understanding of the evolutionary ecology and molecular biology of A-L interface biofilm formation

Combined experimental evolutionary and molecular biology approaches have been used to investigate the adaptive radiation of Pseudomonas fluorescens SBW25 in static microcosms leading to the colonisation of the air-liquid interface by biofilm–forming mutants such as the Wrinkly Spreader. In these microcosms, the ecosystem engineering of the early wild-type colonists establish the niche space for subsequent WS evolution and colonisation. Random WS mutations occurring in the developing population that de-regulate diguanylate cyclases and c-di-GMP homeostasis result in cellulose-based biofilms at the air-liquid interface. These structures allow Wrinkly Spreaders to intercept O2 diffusing into the liquid column and limit the growth of competitors lower down. As the biofilm matures, competition increasingly occurs between WS lineages, and niche divergence within the biofilm may support further diversification before system failure when the structure finally sinks. A combination of pleiotropic and epistasis effects, as well as secondary mutations, may explain variations in WS phenotype and fitness. Understanding how mutations subvert regulatory networks to express intrinsic genome potential and key innovations providing a selective advantage in novel environments is key to understanding the versatility of bacteria, and how selection and ecological opportunity can rapidly lead to substantive changes in phenotype and in community structure and function

Actinide-rich and Actinide-poor rr-Process Enhanced Metal-Poor Stars do not Require Separate rr-Process Progenitors

The astrophysical production site of the heaviest elements in the universe remains a mystery. Incorporating heavy element signatures of metal-poor, $r$-process enhanced stars into theoretical studies of $r$-process production can offer crucial constraints on the origin of heavy elements. In this study, we introduce and apply the "Actinide-Dilution with Matching" model to a variety of stellar groups ranging from actinide-deficient to actinide-enhanced to empirically characterize $r$-process ejecta mass as a function of electron fraction. We find that actinide-boost stars do not indicate the need for a unique and separate $r$-process progenitor. Rather, small variations of neutron richness within the same type of $r$-process event can account for all observed levels of actinide enhancements. The very low-$Y_e$, fission-cycling ejecta of an $r$-process event need only constitute 10-30% of the total ejecta mass to accommodate most actinide abundances of metal-poor stars. We find that our empirical $Y_e$ distributions of ejecta are similar to those inferred from studies of GW170817 mass ejecta ratios, which is consistent with neutron-star mergers being a source of the heavy elements in metal-poor, $r$-process enhanced stars.Comment: 14 pages, 11 figures, Submitted to Ap

A Giant Sample of Giant Pulses from the Crab Pulsar

We observed the Crab pulsar with the 43-m telescope in Green Bank, WV over a timespan of 15 months. In total we obtained 100 hours of data at 1.2 GHz and seven hours at 330 MHz, resulting in a sample of about 95000 giant pulses (GPs). This is the largest sample, to date, of GPs from the Crab pulsar taken with the same telescope and backend and analyzed as one data set. We calculated power-law fits to amplitude distributions for main pulse (MP) and interpulse (IP) GPs, resulting in indices in the range of 2.1-3.1 for MP GPs at 1.2 GHz and in the range of 2.5-3.0 and 2.4-3.1 for MP and IP GPs at 330 MHz. We also correlated the GPs at 1.2 GHz with GPs from the Robert C. Byrd Green Bank Telescope (GBT), which were obtained simultaneously at a higher frequency (8.9 GHz) over a span of 26 hours. In total, 7933 GPs from the 43-m telescope at 1.2 GHz and 39900 GPs from the GBT were recorded during these contemporaneous observations. At 1.2 GHz, 236 (3%) MP GPs and 23 (5%) IP GPs were detected at 8.9 GHz, both with zero chance probability. Another 15 (4%) low-frequency IP GPs were detected within one spin period of high-frequency IP GPs, with a chance probability of 9%. This indicates that the emission processes at high and low radio frequencies are related, despite significant pulse profile shape differences. The 43-m GPs were also correlated with Fermi gamma-ray photons to see if increased pair production in the magnetosphere is the mechanism responsible for GP emission. A total of 92022 GPs and 393 gamma-ray photons were used in this correlation analysis. No significant correlations were found between GPs and gamma-ray photons. This indicates that increased pair production in the magnetosphere is likely not the dominant cause of GPs. Possible methods of GP production may be increased coherence of synchrotron emission or changes in beaming direction.Comment: 33 pages, 10 figures, 6 tables, accepted for publication in Ap

Case Report of Exercise to Attenuate Side Effects of Treatment for Pancreatic Cancer

Treatments for pancreatic cancer can have debilitating side effects including fatigue, weight loss, and cardiac toxicity, resulting in functional loss and psychological distress. Exercise has been proposed as a therapy to counteract physical and psychological detriments. The case: A 47-year-old male undergoing chemotherapy for stage 3 locally advanced pancreatic cancer. He was cycling during hospital chemotherapy infusions (6 fortnightly cycles of FOLFIRINOX: 5-FU 2, 400 mg/m2, over 48 h: irinotecan 180 mg/m2, oxaliplatin 85 mg/m2, no 5-FU bolus) plus 12 weeks of twice weekly aerobic and resistance exercise. Over 12 weeks, body composition was maintained, and physical function improved, with specific increases in muscular strength of up to 50% and aerobic capacity improving by 9%. Moreover, quality of life, fatigue, psychological distress, and sleep quality improved by 38, 113, 50, and 9%, respectively. Additionally, the participant experienced more severe side effects in week 6, when he did not cycle to a high intensity during hospital infusion and had less total weekly exercise. After cycle 6 (week 11), chemotherapy was halted, and a Whipple resection procedure was successfully performed. It can be concluded that regular aerobic and resistance exercise plus exercise during infusion can attenuate expected decline in physical and mental health with pancreatic cancer treatment and may reduce treatment side effects and have favourable effects on prognosis