Synthesis and Deconstruction of Polyethylene-type Materials.

Polyethylene deconstruction to reusable smaller molecules is hindered by the chemical inertness of its hydrocarbon chains. Pyrolysis and related approaches commonly require high temperatures, are energy-intensive, and yield mixtures of multiple classes of compounds. Selective cleavage reactions under mild conditions (

Polymers from Plant Oils Linked by Siloxane Bonds for Programmed Depolymerization.

The increased production of plastics is leading to the accumulation of plastic waste and depletion of limited fossil fuel resources. In this context, we report a strategy to create polymers that can undergo controlled depolymerization by linking renewable feedstocks with siloxane bonds. α,ω-Diesters and α,ω-diols containing siloxane bonds were synthesized from an alkenoic ester derived from castor oil and then polymerized with varied monomers, including related biobased monomers. In addition, cyclic monomers derived from this alkenoic ester and hydrosiloxanes were prepared and cyclized to form a 26-membered macrolactone containing a siloxane unit. Sequential ring-opening polymerization of this macrolactone and lactide afforded an ABA triblock copolymer. This set of polymers containing siloxanes underwent programmed depolymerization into monomers in protic solvents or with hexamethyldisiloxane and an acid catalyst. Monomers afforded by the depolymerization of polyesters containing siloxane linkages were repolymerized to demonstrate circularity in select polymers. Evaluation of the environmental stability of these polymers toward enzymatic degradation showed that they undergo enzymatic hydrolysis by a fungal cutinase from Fusarium solani. Evaluation of soil microbial metabolism of monomers selectively labeled with 13C revealed differential metabolism of the main chain and side chain organic groups by soil microbes.

Diffusion-Ordered Spectroscopy for Rapid and Facile Determination of Consumer Plastic Molecular Weight.

Molecular weight (MW) is a key control of plastic polymer properties and their fate in the environment. However, the primary tool used to determine plastic MW, gel permeation chromatography (GPC), has major limitations, such as low precision and accuracy, requirements for dedicated instrumentation, production of high volumes of hazardous waste, and large sample sizes. In this study, we describe, validate, and apply a diffusion-ordered spectroscopy (DOSY) method for polymer MW determinations, with a focus on applications for consumer plastics. Several experimental conditions were systematically optimized and tested to validate the DOSY method, including the selection of pulse sequences, the effect of sample concentration, cross-validation with multiple sets of external standards, and long-term instrumental stability. Validation was performed for a wide range of polymers, solvents, and temperatures, highlighting its potential for broad applicability. A preliminary screening of polystyrene and polyethylene terephthalate consumer products revealed widely varying MWs (up to two-fold) for products made of the same polymer type. A preliminary experiment was also conducted to track the decrease in polystyrene MW via photochemical chain scission reactions, finding a 20% reduction in MW after less than 1 week of irradiation. Collectively, our results demonstrate the potential for DOSY to provide high-throughput, accurate, and precise measures of polymer MW, as well as the evolution of polymer MW during environmental weathering processes, such as photochemical degradation. We conclude with a discussion of (i) the many advantages of DOSY compared to GPC, (ii) future developments to enhance the depth of information obtained from DOSY, and (iii) approaches to broaden the accessibility of this promising analytical method to the research community.

Structural competency in pre-health and health professional learning: A scoping review.

Structural competency training provides guidance to healthcare providers on recognizing and addressing structural factors leading to health inequities. To inform the evidence-based progression of structural competency curriculum development, this study was designed to map the current state of the literature on structural competency training with pre-health students, healthcare professional students, and/or healthcare professionals. We performed a scoping review and identified peer-reviewed, primary research articles assessing structural competency training interventions. The category of learners, timing of the structural competency training, types of teaching and learning activities used, instruments used to measure training outcomes, and evaluation criteria were examined. Eleven (n = 11) articles met inclusion criteria, addressing all training levels, and largely focused on medical education. Active learning strategies and researcher-developed instruments to measure training outcomes were most used. Evaluation criteria largely focused on trainees' affective reactions, utility assessments, and direct measure of the trainee learning. We suggest designing interprofessional structural competency education with an emphasis on active learning strategies and standardized training curricula. Evaluation instruments integrated at different points in the health professional learning trajectory are important for evidence-based progression in curriculum development focused on achieving structural competency.

Degradable and Recyclable Polyesters from Multiple Chain Length Bio- and Waste-Sourceable Monomers.

Monomers sourced from waste or biomass are often mixtures of different chain lengths; e.g. catalytic oxidation of polyethylene waste yields mixtures of dicarboxylic acids (DCAs). Yet, polyesters synthesized from such monomer mixtures have rarely been studied. We report polyesters based on multiple linear aliphatic DCAs, present in chain length distributions that vary in their centers and ranges. We demonstrate that these materials can adopt high-density polyethylene-like solid state structures, and are ductile (e.g. Et 610 MPa), allowing for injection molding, or film and fiber extrusion. Melting and crystallization points of the polyesters show no odd-even effects as dipoles cannot favorably align in the crystal, similar to traditional odd carbon numbered, long-chain DCA polyesters. Biodegradation studies of 13 C-labelled polyesters in soil reveal rapid mineralization, and depolymerization by methanolysis indicates suitability for closed-loop recycling.

Biodegradable High-Density Polyethylene-like Material.

We report a novel polyester material generated from readily available biobased 1,18-octadecanedicarboxylic acid and ethylene glycol possesses a polyethylene-like solid-state structure and also tensile properties similar to high density polyethylene (HDPE). Despite its crystallinity, high melting point (Tm =96 °C) and hydrophobic nature, polyester-2,18 is subject to rapid and complete hydrolytic degradation in in vitro assays with isolated naturally occurring enzymes. Under industrial composting conditions (ISO standard 14855-1) the material is biodegraded with mineralization above 95 % within two months. Reference studies with polyester-18,18 (Tm =99 °C) reveal a strong impact of the nature of the diol repeating unit on degradation rates, possibly related to the density of ester groups in the amorphous phase. Depolymerization by methanolysis indicates suitability for closed-loop recycling.

Synergy between Sunlight, Titanium Dioxide, and Microbes Enhances Cellulose Diacetate Degradation in the Ocean.

Sunlight chemically transforms marine plastics into a suite of products, with formulation─the specific mixture of polymers and additives─driving rates and products. However, the effect of light-driven transformations on subsequent microbial lability is poorly understood. Here, we examined the interplay between photochemical and biological degradation of fabrics made from cellulose diacetate (CDA), a biobased polymer used commonly in consumer products. We also examined the influence of ∼1% titanium dioxide (TiO2), a common pigment and photocatalyst. We sequentially exposed CDA to simulated sunlight and native marine microbes to understand how photodegradation influences metabolic rates and pathways. Nuclear magnetic resonance spectroscopy revealed that sunlight initiated chain scission reactions, reducing CDA's average molecular weight. Natural abundance carbon isotope measurements demonstrated that chain scission ultimately yields CO2, a newly identified abiotic loss term of CDA in the environment. Measurements of fabric mass loss and enzymatic activities in seawater implied that photodegradation enhanced biodegradation by performing steps typically facilitated by cellulase. TiO2 accelerated CDA photodegradation, expediting biodegradation. Collectively, these findings (i) underline the importance of formulation in plastic's environmental fate and (ii) suggest that overlooking synergy between photochemical and biological degradation may lead to overestimates of marine plastic persistence.

Cancer content and social media platform influence young adult cancer caregivers' social support on social media.

PURPOSE: To determine how social media platform and cancer content is associated with the presence of social support in responses to young adult cancer caregivers' (YACC) posts. DESIGN: We retrospectively collected YACC's Facebook and/or Instagram posts and all responses from the first six months of caregiving. SAMPLE: Eligible YACC were 18-39, caring for a cancer patient diagnosed 6 months-5 years prior, spoke English, and used social media weekly. METHODS: Social media posts and responses were manually coded for five social support types, then transformed to depict the proportion of responses per post representing each type of support. Using mixed-effects models, we compared the distributions of responses with social support types by platform (Facebook vs. Instagram) and cancer content (no vs. yes). FINDINGS: More responses contained emotional support on Instagram than Facebook (B = 0.25, Standard Error (SE)=0.09, p = 0.007). More responses with cancer content contained -validation support (B = 0.20, SE = 0.07, p = 0.002), but fewer contained emotional (B=-0.17, SE = 0.07, p = 0.02) and instrumental support (B=-0.06, SE = 0.02, p = 0.001) than posts without cancer content. CONCLUSIONS: Studying the responsiveness of social media followers by platform and cancer content provides a foundation for intervention development. IMPLICATIONS FOR PSYCHOSOCIAL PROVIDERS: Emphasizing the suitability of different social media platforms for particular support seeking behaviors is essential.

Product Formulation Controls the Impact of Biofouling on Consumer Plastic Photochemical Fate in the Ocean.

The photodegradation rates of floating marine plastics govern their environmental lifetimes, but the controls on this process remain poorly understood. Photodegradation of these materials has so far been studied under ideal conditions in the absence of environmental factors such as biofouling, which may slow photochemical transformation rates through light screening. To investigate this interaction, we incubated different plastics in continuous flow seawater mesocosms to follow (i) the extent of biofilm growth on the samples and (ii) decreases in light transmittance through the samples over time. We used consumer products with high relevance (e.g., shopping bags, water bottles, and packaging materials) and with different formulations, referring to primary polymers (polyethylene (PE) and polyethylene terephthalate (PET)) and inorganic additives (titanium dioxide (TiO2)). The behavior of consumer-relevant formulations was compared to those of pure PE and PET films, revealing that the relative effects of UV- and, to a lesser extent, visible-light screening differ based on the formulation of the product. Pure PE showed greater relative UV-transmittance decreases (Δ = -34% through the entire sample, accounting for biofilm on both sides of the plastic film) than PET (Δ = -20%) and PE products with TiO2 (Δ = < -10%). Our results demonstrate that even with biofouling, photodegradation remains a highly relevant process for the fate of marine plastics. However, we expect photodegradation rates of plastics in the ocean to be slower than those measured in laboratory studies, due to light screening by biofilms, and the specific formulation of plastic products is a key determinant of the extent of this effect.

The Mechanism of Rhodium-Catalyzed Allylic C-H Amination.

Herein, the mechanism of catalytic allylic C-H amination reactions promoted by Cp*Rh complexes is reported. Reaction kinetics experiments, stoichiometric studies, and DFT calculations demonstrate that the allylic C-H activation to generate a Cp*Rh(π-allyl) complex is viable under mild reaction conditions. The role of external oxidants in the catalytic cycle is elucidated. Quantum mechanical calculations, stoichiometric reactions, and cyclic voltammetry experiments concomitantly support an oxidatively induced reductive elimination process of the allyl fragment with an acetate ligand proceeding through a Rh(IV) intermediate. Stoichiometric oxidation and bulk electrolysis of the proposed π-allyl intermediate are also reported to support these analyses. Lastly, evidence supporting the amination of an allylic acetate intermediate is presented. We show that Cp*Rh(III)2+ behaves as a Lewis acid catalyst to complete the allylic amination reaction.

Quantification of Synthetic Polyesters from Biodegradable Mulch Films in Soils.

Soil biodegradable mulch films composed of the polyester polybutylene adipate-co-terephthalate (PBAT) are being increasingly used in agriculture. Analytical methods to quantify PBAT in field soils are needed to assess its soil occurrence and fate. Here, we report an analytical method for PBAT in soils that couples Soxhlet extraction or accelerated solvent extraction (ASE) with quantitative protonnuclear magnetic resonance (q-1H NMR) spectroscopy detection. The 1H NMR peak areas of aromatic PBAT protons increased linearly with PBAT concentrations dissolved in deuterated chloroform (CDCl3), demonstrating accurate quantitation of PBAT by q-1H NMR. Spike-recovery experiments involving PBAT addition to model sorbents and soils showed increased PBAT extraction efficiencies into chloroform (CHCl3) with methanol (MeOH) as cosolvent, consistent with MeOH competitively displacing PBAT from H-bond donating sites on mineral surfaces. Systematic variations in solvent composition and temperatures in ASE revealed quantitative PBAT extraction from soil with 90/10 volume % CHCl3/MeOH at 110-120 °C. Both Soxhlet extraction and ASE resulted in the complete recovery of PBAT added to a total of seven agricultural soils covering a range of physicochemical properties, independent of whether PBAT was added to soils dissolved in CHCl3, as film, or as particles. Recovery was also complete for PBAT added to soil in the form of a commercial soil biodegradable mulch film with coextractable polylactic acid (PLA). The presented analytical method enables accurate quantification and biodegradation monitoring of PBAT in agricultural field soils.

Use of Transcription when Assessing Children's Speech: Australian Speech-Language Pathologists' Practices, Challenges, and Facilitators.

OBJECTIVE: There is currently limited knowledge on the useof transcription in the management of children with speech sound disorders (SSD) by speech-language pathologists in Australia. This study explored the use of transcription, the facilitators, and challenges of transcription use, and differences in the use of detailed transcription with various client groups. Method and Participants: Eighty-four participants (speech-language pathologists working in Australia) completed an online exploratory survey which included closed and open-ended questions. RESULTS: 95% of participants reported using transcription. The three most commonly reported strategies/resources were transcription charts (81%), self-practice (68%), and websites (42%). Transcription challenges included the use of two vowel notation systems, reduced proficiency in transcription, service delivery issues, sampling/recording issues, and issues with using transcription to communicate. Finally, results from this survey found that participants use detailed transcription more often when recording the speech of children with childhood apraxia of speech and craniofacial impairment compared to using transcription to document the speech of children who have SSD of unknown origin. Most participants (91%) had not attended transcription professional development. CONCLUSIONS: These findings have implications for the university training of speech-language pathologists and for the establishment of professional development courses for practising speech-language pathologists in Australia.

Regioselective Cp*Ir(III)-Catalyzed Allylic C-H Sulfamidation of Allylbenzene Derivatives.

In this study we report the development of the regioselective Cp*Ir(III)-catalyzed allylic C-H sulfamidation of allylbenzene derivatives, using azides as the nitrogen source. The reaction putatively proceeds through a Cp*Ir(III)-π-allyl intermediate and demonstrates exclusive regioselectivity for the branched position of the π-allyl. The reaction performs well on electron-rich and electron-deficient allylbenzene derivatives and is tolerant of a wide range of functional groups, including carbamates, esters, and ketones. The proposed mechanism for this reaction proceeds via C-N reductive elimination from a Cp*Ir(V) nitrenoid complex at the branched position of the π-allyl.

Oxidation of Reduced Peat Particulate Organic Matter by Dissolved Oxygen: Quantification of Apparent Rate Constants in the Field.

Peat particulate organic matter (POM) is an important terminal electron acceptor for anaerobic respiration in northern peatlands provided that the electron-accepting capacity of POM is periodically restored by oxidation with O2 during peat oxygenation events. We employed push-pull tests with dissolved O2 as reactant to determine pseudo-first-order rate constants of O2 consumption ( kobs) in anoxic peat soil of an unperturbed Swedish ombrotrophic bog. Dissolved O2 was rapidly consumed in anoxic peat with a mean kobs of 2.91 ± 0.60 h-1, corresponding to an O2 half-life of ∼14 min. POM dominated O2 consumption, as evidenced from approximately 50-fold smaller kobs in POM-free control tests. Inhibiting microbial activity with formaldehyde did not appreciably slow O2 consumption, supporting abiotic O2 reduction by POM moieties, not aerobic respiration, as the primary route of O2 consumption. Peat preoxygenation with dissolved O2 lowered kobs in subsequent oxygen consumption tests, consistent with depletion of reduced moieties in POM. Finally, repeated oxygen consumption tests demonstrated that anoxic peat POM has a high reduction capacity, in excess to 20 µmol electrons donated per gram POM. This work demonstrates rapid abiotic oxidation of reduced POM by O2, supporting that short-term oxygenation events can restore the capacity of POM to accept electrons from anaerobic respiration in temporarily anoxic parts of peatlands.

Intermolecular Allylic C-H Etherification of Internal Olefins.

Herein we report on the development of an oxidative allylic C-H etherification reaction, utilizing internal olefins and alcohols as simple precursors. Key advances include the use of RhCp* complexes to promote the allylic C-H functionalization of internal olefins and the compatibility of the oxidative conditions with oxidatively sensitive alcohols, enabling the direct etherification reaction. Preliminary mechanistic studies, consistent with C-H functionalization as the rate determining step, are presented.

Chemically Recyclable and Biodegradable Vulcanized Rubber.

The cross-linked nature of vulcanized rubbers as used in tire and many other applications prohibits an effective closed-loop mechanical or chemical recycling. Moreover, vulcanization significantly retards the material's biodegradation. Here, we report a recyclable and biodegradable rubber that is generated by the vulcanization of amorphous, unsaturated polyesters. The elastic material can be broken down via solvolysis into the underlying monomers. After removal of the vulcanized repeat units, the saturated monomers, constituting the major share of the material, can be recovered in overall recycling rates exceeding 90%. Respirometric biodegradation experiments by 13CO2 tracking under environmental conditions via the polyesters' diol monomer indicated depolymerization and partial mineralization of the vulcanized polyester rubbers.

Correlation of Enzymatic Depolymerization Rates with the Structure of Polyethylene-Like Long-Chain Aliphatic Polyesters.

Long-chain aliphatic polyesters are emerging sustainable materials that exhibit polyethylene-like properties while being amenable to chemical recycling and biodegradation. However, varying polyester chemical structures results in markedly different degradation rates, which cannot be predicted from commonly correlated bulk polyester properties, such as polymer melting temperature. To elucidate these structure-degradability relationships, long-chain polyesters varying in their monomer composition and crystallinity were subjected to enzymatic hydrolysis, the rates of which were quantified via detection of formed monomers. Copolymers with poorly water-soluble, long-chain diol monomers (e.g., 1,18-octadecanediol) demonstrated strongly reduced depolymerization rates compared to copolymers with shorter chain length diol monomers. This was illustrated by, e.g., the 20× faster hydrolysis of PE-4,18, consisting of 1,4-butanediol and 1,18-octadecanedicarboxylic acid monomers, relative to PE-18,4. The insoluble long-chain diol monomer released upon hydrolysis was proposed to remain attached to the bulk polymer surface, decreasing the accessibility of the remaining ester bonds to enzymes for further hydrolysis. Tuning of polyester crystallinity via the introduction of branched monomers led to variable hydrolysis rates, which increased by an order of magnitude when crystallinity decreased from 72% to 45%. The results reported enables the informed design of polyester structures with balanced material properties and amenability to depolymerization.

Cadherin-11 contributes to the heterogenous and dynamic Wnt-Wnt-ß-catenin pathway activation in Ewing sarcoma.

Ewing sarcoma is the second most common bone cancer in children, and while patients who present with metastatic disease at the time of diagnosis have a dismal prognosis. Ewing sarcoma tumors are driven by the fusion gene EWS/Fli1, and while these tumors are genetically homogenous, the transcriptional heterogeneity can lead to a variety of cellular processes including metastasis. In this study, we demonstrate that in Ewing sarcoma cells, the canonical Wnt/ß-Catenin signaling pathway is heterogeneously activated in vitro and in vivo, correlating with hypoxia and EWS/Fli1 activity. Ewing sarcoma cells predominantly express ß-Catenin on the cell membrane bound to CDH11, which can respond to exogenous Wnt ligands leading to the immediate activation of Wnt/ß-Catenin signaling within a tumor. Knockdown of CDH11 leads to delayed and decreased response to exogenous Wnt ligand stimulation, and ultimately decreased metastatic propensity. Our findings strongly indicate that CDH11 is a key component of regulating Wnt//ß-Catenin signaling heterogeneity within Ewing sarcoma tumors, and is a promising molecular target to alter Wnt//ß-Catenin signaling in Ewing sarcoma patients.

Characterization of transcriptional heterogeneity and novel therapeutic targets using single cell RNA-sequencing of primary and circulating Ewing sarcoma cells.

Ewing sarcoma is the second most common bone cancer in children, accounting for 2% of pediatric cancer diagnoses. Patients who present with metastatic disease at the time of diagnosis have a dismal prognosis, compared to the >70% 5-year survival of those with localized disease. Here, we utilized single cell RNA-sequencing to characterize the transcriptional landscape of primary Ewing sarcoma tumors and surrounding tumor microenvironment (TME). Copy-number analysis identified subclonal evolution within patients prior to treatment. Primary tumor samples demonstrate a heterogenous transcriptional landscape with several conserved gene expression programs, including those composed of genes related to proliferation and EWS targets. Single cell RNA-sequencing and immunofluorescence of circulating tumor cells at the time of diagnosis identified TSPAN8 as a novel therapeutic target.