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1. Synthesis and characterization of modular polyphosphonate homopolymers and copolymers

   https://doi.org/10.1002/pol.20200066  

   Totsch, Timothy R.; Stanford, Victoria L.; Klep, Oleksander; Burdette, Mary K.; Grant, Benjamin; Foulger, Stephen H.; Gray, Gary M. (June 2020, Journal of Polymer Science)

   Abstract Linear polyphosphonates with the generic formula –[P(Ph)(X)OR′O]_n– (X = S or Se) have been synthesized by polycondensations of P(Ph)(NEt₂)₂and a diol (HOR′OH = 1,4‐cyclohexanedimethanol, 1,4‐benzenedimethanol, tetraethylene glycol, or 1,12‐dodecanediol) followed by reaction with a chalcogen. Random copolymers have been synthesized by polycondensations of P(Ph)(NEt₂)₂and mixture of two of the diols in a 2:1:1 mol ratio followed by reaction with a chalcogen. Block copolymers with the generic formula –[P(Ph)(X)OR′O]_(x + 2)–[P(Ph)(X)OR′O]_(x + 3)– (X = S or Se) have been synthesized by the polycondensations of Et₂N[P(Ph)(X)OR′O]_(x + 2)P(Ph)NEt₂oligomers with HOR′O[P(Ph)(X)OR′O]_(x + 3)H oligomers followed by reaction with a chalcogen. The Et₂N[P(Ph)(X)OR′O]_(x + 2)P(Ph)NEt₂oligomers are prepared by the reaction of an excess of P(Ph)(NEt₂)₂with a diol while the HOR′O[P(Ph)(X)OR′O]_(x + 3)H oligomers are prepared by the reaction of P(Ph)(NEt₂)₂with an excess of the diol. In each case the excess, x is the same and determines the average block sizes. All of the polymers were characterized using¹H,¹³C{¹H}, and³¹P{¹H} NMR spectroscopy, TGA, DSC, and SEC.³¹P{¹H} NMR spectroscopy demonstrates that the random and block copolymers have the expected arrangements of monomers and, in the case of block copolymers, verifies the block sizes. All polymers are thermally stable up to ~300°C, and the arrangements of monomers in the copolymers (block vs. random) affect their degradation temperatures andT_gprofiles. The polymers have weight average MWs of up to 3.8 × 10⁴ Da. 

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2. Spatial and temporal variability in summertime dissolved carbon dioxide and methane in temperate ponds and shallow lakes

   https://doi.org/10.1002/lno.12362  

   Ray, Nicholas E.; Holgerson, Meredith A.; Andersen, Mikkel Rene; Bikše, Jānis; Bortolotti, Lauren E.; Futter, Martyn; Kokorīte, Ilga; Law, Alan; McDonald, Cory; Mesman, Jorrit P.; et al (May 2023, Limnology and Oceanography)

   Abstract Small waterbodies have potentially high greenhouse gas emissions relative to their small footprint on the landscape, although there is high uncertainty in model estimates. Scaling their carbon dioxide (CO₂) and methane (CH₄) exchange with the atmosphere remains challenging due to an incomplete understanding and characterization of spatial and temporal variability in CO₂and CH₄. Here, we measured partial pressures of CO₂(pCO₂) and CH₄(pCH₄) across 30 ponds and shallow lakes during summer in temperate regions of Europe and North America. We sampled each waterbody in three locations at three times during the growing season, and tested which physical, chemical, and biological characteristics related to the means and variability ofpCO₂andpCH₄in space and time. Summer means ofpCO₂andpCH₄were inversely related to waterbody size and positively related to floating vegetative cover;pCO₂was also positively related to dissolved phosphorus. Temporal variability in partial pressure in both gases weas greater than spatial variability. Although sampling on a single date was likely to misestimate mean seasonalpCO₂by up to 26%, mean seasonalpCH₄could be misestimated by up to 64.5%. Shallower systems displayed the most temporal variability inpCH₄and waterbodies with more vegetation cover had lower temporal variability. Inland waters remain one of the most uncertain components of the global carbon budget; understanding spatial and temporal variability will ultimately help us to constrain our estimates and inform research priorities. 

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3. Variability and Controls on δ ¹⁸ O, d‐excess, and ∆′ ¹⁷ O in Southern Peruvian Precipitation

   https://doi.org/10.1029/2020JD034009  

   Aron, Phoebe G.; Poulsen, Christopher J.; Fiorella, Richard P.; Levin, Naomi E.; Acosta, Rene P.; Yanites, Brian J.; Cassel, Elizabeth J. (December 2021, Journal of Geophysical Research: Atmospheres)

   Abstract The isotopic composition of precipitation is used to trace water cycling and climate change, but interpretations of the environmental information recorded in central Andean precipitation isotope ratios are hindered by a lack of multi‐year records, poor spatial distribution of observations, and a predominant focus on Rayleigh distillation. To better understand isotopic variability in central Andean precipitation, we present a three‐year record of semimonthly δ¹⁸O_pand δ²H_pvalues from 15 stations in southern Peru and triple oxygen isotope data, expressed as ∆′¹⁷O_p, from 32 precipitation samples. Consistent with previous work, we find that elevation correlates negatively with δ¹⁸O_pand that seasonal δ¹⁸O_pvariations are related to upstream rainout and local convection. Spatial δ¹⁸O_pvariations and atmospheric back trajectories show that both eastern‐ and western‐derived air masses bring precipitation to southern Peru. Seasonal d‐excess_pcycles record moisture recycling and relative humidity at remote moisture sources, and both d‐excess_pand ∆′¹⁷O_pclearly differentiate evaporated and non‐evaporated samples. These results begin to establish the natural range of unevaporated ∆′¹⁷O_pvalues in the central Andes and set the foundation for future paleoclimate and paleoaltimetry studies in the region. This study highlights the hydrologic understanding that comes from a combination of δ¹⁸O_p, d‐excess_p, and ∆′¹⁷O_pdata and helps identify the evaporation, recycling, and rainout processes that drive water cycling in the central Andes. 

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4. Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley

   https://doi.org/10.1051/0004-6361/202348180  

   Bonfanti, A; Brady, M; Wilson, T G; Venturini, J; Egger, J A; Brandeker, A; Sousa, S G; Lendl, M; Simon, A E; Queloz, D; et al (February 2024, Astronomy & Astrophysics)

   Context. TOI-732 is an M dwarf hosting two transiting planets that are located on the two opposite sides of the radius valley. Inferring a reliable demographics for this type of systems is key to understanding their formation and evolution mechanisms. Aims. By doubling the number of available space-based observations and increasing the number of radial velocity (RV) measurements, we aim at refining the parameters of TOI-732 b and c. We also use the results to study the slope of the radius valley and the density valley for a well-characterised sample of M-dwarf exoplanets. Methods. We performed a global Markov chain Monte Carlo analysis by jointly modelling ground-based light curves and CHEOPS and TESS observations, along with RV time series both taken from the literature and obtained with the MAROON-X spectrograph. The slopes of the M-dwarf valleys were quantified via a support vector machine (SVM) procedure. Results. TOI-732b is an ultrashort-period planet (P= 0.76837931_-0.00000042^+0.0000039days) with a radiusR_b= 1.325_-0.058^+0.057R_⊕, a massM_b= 2.46 ± 0.19M_⊕, and thus a mean densityρ_b= 5.8_-0.8^+1.0g cm^-3, while the outer planet atP= 12.252284 ± 0.000013 days hasR_c= 2.39_-0.11^+0.10R_⊕,M_c= 8.04_-0.48^+0.50M_⊕, and thusρ_c= 3.24_-0.43^+0.55g cm^-3. Even with respect to the most recently reported values, this work yields uncertainties on the transit depths and on the RV semi-amplitudes that are smaller up to a factor of ~1.6 and ~2.4 for TOI-732 b and c, respectively. Our calculations for the interior structure and the location of the planets in the mass-radius diagram lead us to classify TOI-732 b as a super-Earth and TOI-732 c as a mini-Neptune. Following the SVM approach, we quantified d logR_p,valley/ d logP= -0.065_-0.013^+0.024, which is flatter than for Sun-like stars. In line with former analyses, we note that the radius valley for M-dwarf planets is more densely populated, and we further quantify the slope of the density valley as d log ρ^_valley/ d logP= -0.02_-0.04^+0.12. Conclusions. Compared to FGK stars, the weaker dependence of the position of the radius valley on the orbital period might indicate that the formation shapes the radius valley around M dwarfs more strongly than the evolution mechanisms. 

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5. Effects of anaerobic HRT and VFA loading on the kinetics and stoichiometry of enhanced biological phosphorus removal

   https://doi.org/10.1002/wer.1544  

   Coats, Erik R.; Deyo, Brent; Brower, Nicole; Brinkman, Cynthia K. (March 2021, Water Environment Research)

   Abstract Enhanced biological phosphorus removal (EBPR) can recover significant quantities of wastewater phosphorus. However, this resource recovery process realizes limited use largely due to process stability concerns. The research evaluated the effects of anaerobic HRT (τ_AN) and VFA concentration—critical operational parameters that can be externally controlled—on EBPR performance. Evaluated alone, τ_AN(1–4 h) exhibited no statistical effect on effluent phosphorus. However, PHA increased with VFA loading and biomass accumulated more phosphorus. Regarding resiliency, under increasing VFA loads PAOs hydrolyzed more phosphorus to uptake/catabolize VFAs; moreover, PHA synthesis normalized to VFA loading increased with τ_AN, suggesting fermentation. Kinetically, PAOs exhibited a Monod‐like relationships for qPHA_ANand qVFA_ANas a function of anaerobic P release; additionally, qP_AEexhibited a Monod‐like relationship with end‐anaerobic PHA concentration. A culminating analysis affirmed the relationship between enhanced aerobic P uptake, and net P removal, with a parameter (phosphorus removal propensity factor) that combines influent VFA concentration with τ_AN. Practitioner pointsEvaluated alone τ_ANexhibits no statistical effect on effluent phosphorus in an EBPR configuration.Increased PHA synthesis, associated with increased VFAs and/or extended τ_AN,enhances aerobic phosphorus removal.PHA synthesis normalized to VFA loading increased with τ_AN, suggesting fermentation in the EBPR anaerobic zone.Aerobic phosphorus uptake increases linearly with anaerobic phosphorus release, with the slope exceeding unity.Increased VFAs can be substituted for shorter anaerobic HRTs, and vice versa, to enhance EBPR performance. 

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