At the molecular level, polymers are long chains in which the emergent material properties are dictated by the movement, arrangement, and interactions of these chains. Key factors that contribute to how the polymer chains move and rearrange are the molecular identity and arrangement, crystallinity, and molecular weight. Generally, the monomer identity influences the final application of the polymer by dictating many properties, such as the glass transition temperature (Tg). 12 As the Tg represents a softening of the material, it is a prime factor in determining the final polymer application. Flexible molecules in the backbone, which can relax faster, may result in low Tg materials with applications such as PE bags or rubber (i.e. polybutadiene). 13 Meanwhile, rigid molecules or molecules that result in stronger interchain interactions (and relax on longer timescales) can result in high Tg materials, ideal for reinforced applications. In general, when materials are at temperatures below the Tg, the polymer chains are kinetically arrested, exhibiting higher strengths. Even though monomer identity is often the largest contribution to Tg, it is not the only factor, as molecular weight, 14 tacticity, 15 and crystallinity 16 also contribute. While nearly all polymers exhibit a Tg characteristic of their amorphous region, semi-crystalline polymers will also exhibit concomitant melting behaviour crystalline in their crystalline regions, making them semi-crystalline. Crystallinity has a direct impact on polymer properties, as increases in crystallinity augment the strength of the final product and reduce the permeability of liquids and gases. Co-monomers (e.g., isophthalic acid in poly(ethylene terephthalate) (PET)) are often used to lower or completely remove crystallinity to make polymers easier to process or more transparent. 17 Finally, molecular weight, and the distributions of molecular weights, have some effect on the thermomechanical polymer properties (e.g., increasing molecular weight leads to higher Tg, modulii, etc.). However, over a critical molecular weight, nearly all thermomechanical polymer properties are constant. The exception to this generalization is the viscosity of a polymer melt, which scales with the molecular weight to the 3-3.5 power (η ~ MW 3-3.5 ) and also encapsulates properties such as diffusivity. These factors together contribute to polymer recalcitrance by limiting polymer mobility and accessibility to chemical linkages, posing a challenge for catalytic plastics deconstruction.

Mixed plastics waste represents an abundant and largely untapped feedstock for the production of valuable products. The chemical diversity and complexity of these materials, however, present major barriers to realizing this opportunity. In this work, we show that metal-catalyzed autoxidation depolymerizes comingled polymers into a mixture of oxygenated small molecules that are advantaged substrates for biological conversion. We engineer a robust soil bacterium, Pseudomonas putida , to funnel these oxygenated compounds into a single exemplary chemical product, either β-ketoadipate or polyhydroxyalkanoates. This hybrid process establishes a strategy for the selective conversion of mixed plastics waste into useful chemical products.

This study tested the principle that 68 Ga-DOTATATE PET/CT may be used to select children with primary refractory or relapsed high-risk neuroblastoma for treatment with 177 Lu-DOTATATE and evaluated whether this is a viable therapeutic option for those children. Methods: Between 2008 and 2010, 8 children with relapsed or refractory high-risk neuroblastoma were studied with 68 Ga-DOTATATE PET/CT. The criterion of eligibility for 177 Lu-DOTATATE therapy was uptake on the diagnostic scan equal to or higher than that of the liver. Results: Of the 8 children imaged, 6 had abnormally high uptake on the 68 Ga-DOTATATE PET/CT scan and proceeded to treatment. Patients received 2 or 3 administrations of 177 Lu-DOTATATE at a median interval of 9 wk and a median administered activity of 7.3 GBq. Of the 6 children treated, 5 had stable disease by the response evaluation criteria in solid tumors (RECIST). Of these 5 children, 2 had an initial metabolic response and reduction in the size of their lesions, and 1 patient had a persistent partial metabolic response and reduction in size of the lesions on CT, although the disease was stable by RECIST. One had progressive disease. Three children had grade 3 and 1 child had grade 4 thrombocytopenia. No significant renal toxicity has been seen. Conclusion: 68 Ga-DOTATATE can be used to image children with neuroblastoma and identify those suitable for molecular radiotherapy with 177 Lu-DOTATATE. We have shown, for what is to our knowledge the first time, that treatment with 177 Lu-DOTATATE is safe and feasible in children with relapsed or primary refractory high-risk neuroblastoma. We plan to evaluate this approach formally in a phase I-II clinical trial.

Lignin is the largest source of renewable aromatic compounds, making the recovery of aromatic compounds from this material a significant scientific goal. Recently, many studies have reported on lignin depolymerization and upgrading strategies. Electrochemical approaches are considered to be low cost, reagent free, and environmentally friendly, and can be carried out under mild reaction conditions. In this Review, different electrochemical lignin conversion strategies, including electrooxidation, electroreduction, hybrid electro‐oxidation and reduction, and combinations of electrochemical and other processes (e. g., biological, solar) for lignin depolymerization and upgrading are discussed in detail. In addition to lignin conversion, electrochemical lignin fractionation from biomass and black liquor is also briefly discussed. Finally, the outlook and challenges for electrochemical lignin conversion are presented.

Because populations of channel catfish Ictalurus punctatus have been difficult to sample in small impoundments, we determined whether tandem hoop net series (three nets tied in series and baited with cheese) fished for 3 d could effectively sample these populations. In 2000 we compared seasonal catch rates (catch per unit effort (CPUE), defined as the number of fish caught per series) and length frequencies (total length (TL); mm) of channel catfish captured with two types of tandem series (long versus short bridles) and monitored the mortality of channel catfish along with the CPUE and mortality of bycatch in five lakes. Mean CPUE ranged from 12 to 194 fish/series for channel catfish and from 5 to 101 fish/series for bycatch among series types, lakes, and sampling periods. Mean CPUE for channel catfish and bycatch was similar between series types and did not consistently vary with sampling period. Length frequencies of channel catfish were usually similar between series types. Mortality was low for both channel catfish (0.3% of total catch) and bycatch (8%). In 2001, using short‐bridled series, we assessed gear size bias in one lake; sampled 66 lakes that are stocked annually with channel catfish fingerlings at rates of 12, 37, or 74/ha; and estimated the sample sizes required for precise estimates of mean CPUE and accurate estimates of size structure. Hoop nets failed to capture channel catfish less than 250 mm TL in proportion to their abundance. Mean CPUE among 62 lakes ranged from 0.5 to 369.7 channel catfish/series and increased with stocking rate. Four lakes were excluded because of the high catch and mortality of turtles. Mean TL ranged from 276 to 463 mm among the lakes and decreased with stocking rate. For moderate precision (coefficient of variation (100·SE/mean) = 0.2) of mean CPUE, from 12 to nearly 50 series were required, and length measurements from 300 fish were necessary for accurate assessments of size structure. Tandem hoop netting provided adequate samples of channel catfish in most small impoundments, but obtaining precise estimates of CPUE may be difficult; moreover, turtle mortality can be problematic in some lakes.