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At least 73 records · Page 4

Nanofabrication with Metallopolymers: Recent Developments and Future Perspectives

We found that synthetic polymers containing metals and metal centers have experienced rapid growth in the last two decades. Metal-containing polymers and these have an unprecedented role to play in modern high-tech applications including nanomanufacturing, sensing, separation and catalysis. Advancement in synthetic strategies for macromolecules has enabled the synthesis of novel, exotic and use-inspired metallopolymers. Using state-of-the-art design strategies, it is now possible to perform targeted synthesis of macromolecules with varied complexity that contain a range of metal centers either in the backbone or in the side chains of the organic moiety. Moreover, the presence of an inorganic element (metals and metal centers) in organic moieties has led to a number of new physicochemical properties while implementing novel functionality to the polymer matrix. This review covers nanotechnology influenced by distinctive features of metal-containing macromolecular systems, particularly in developing flexible, functional materials.

36 MATERIALS SCIENCE↗

Resilient remediation: Addressing extreme weather and climate change, creating community value

Devastating hurricanes experienced in recent years demonstrated that extreme weather and climate change can jeopardize contaminated land remediation and harm public health and the environment. Since early 2016, the Sustainable Remediation Forum (SURF) has led research and organized knowledge exchanges to examine (1) the impacts of climate change and extreme weather events on hazardous waste sites, and (2) how we can mitigate these impacts and create value for communities. The SURF team found that climate change and extreme weather events can undermine the effectiveness of the approved site remediation, and can also affect contaminant toxicity, exposure, organism sensitivity, fate and transport, long-term operations, management, and stewardship of remediation sites. Further, failure to consider social vulnerability to climate change could compromise remediation and adaptation strategies. SURF's recommendations for resilient remediation build on resources and drivers from state, national, and international sources, and marry the practices of sustainable remediation and climate change adaptation. They outline both general principles and site-specific protocols and provide global examples of mitigation and adaptation strategies. Opportunities for synergy include vulnerability assessments that benefit and build on established hazardous waste management law, policy, and practices. SURF's recommendations can guide owners and project managers in developing a site resiliency strategy. Resilient remediation can help expedite cleanup and redevelopment, decrease public health risks, and create jobs, parks, wetlands, and resilient energy sources. Resilient remediation and redevelopment can also positively contribute to achieving international goals for sustainable land management, climate action, clean energy, and sustainable cities.

54 ENVIRONMENTAL SCIENCES↗

Simulated Biomass Sorghum GHG Reduction Potential is Similar to Maize

Policy support for cellulosic biofuels is contingent on their achieving much greater reductions in life-cycle greenhouse gas emissions than corn starch ethanol. Biomass sorghum has been suggested as a genetically and agronomically tractable feedstock species to augment near-term cellulosic feedstock production. This study used DayCent modeling to investigate biomass sorghum production emissions relative to corn with and without stover utilization at 3,265 across the rainfed United States. Sorghum produced greater average feedstock dry matter (15.6±1.4 vs. 14.8±2.2 Mg ha -1 yr -1 ) and slightly lower estimated ethanol energy yields (10.6±1.0 vs. 11.8±2.9 MJ m -2 yr -1 ) as corn grain with 75% stover collection. The high biomass removals in both the sorghum and corn stover scenarios led to soil organic carbon losses on 90% and 100% of sites, respectively. Average feedstock production emissions intensities were similar between sorghum and corn with 75% stover removal (17.6±2.8 vs. 18.8±3.0 g CO 2 e MJ -1 ), but were notably lower under sorghum for sites in the southwestern study region (13.6±3.0 vs. 22.5±3.1 g CO 2 e MJ -1 ). Futhermore, these results suggest that biomass sorghum produces cellulosic feedstock with similar emissions to corn grain and at current yield levels is unlikely to meet the Renewable Fuel Standard emissions reduction threshold for cellulosic biofuels.

54 ENVIRONMENTAL SCIENCES↗

Urea-Functionalized M4L6 Cage Receptors: Self-Assembly, Dynamics, and Anion Recognition in Aqueous Solutions

We present an extensive study of a novel class of de novo designed tetrahedral M{sub 4}L{sub 6} (M = Ni, Zn) cage receptors, wherein internal decoration of the cage cavities with urea anion-binding groups, via functionalization of the organic components L, led to selective encapsulation of tetrahedral oxoanions EO{sub 4}{sup -} (E = S, Se, Cr, Mo, W, n = 2; E = P, n = 3) from aqueous solutions, based on shape, size, and charge recognition. External functionalization with tBu groups led to enhanced solubility of the cages in aqueous methanol solutions, thereby allowing for their thorough characterization by multinuclear ({sup 1}H, {sup 13}C, {sup 77}Se) and diffusion NMR spectroscopies. Additional experimental characterization by electrospray ionization mass spectrometry, UV-vis spectroscopy, and single-crystal X-ray diffraction, as well as theoretical calculations, led to a detailed understanding of the cage structures, self-assembly, and anion encapsulation. We found that the cage self-assembly is templated by EO{sub 4}{sup -} oxoanions (n {ge} 2), and upon removal of the templating anion the tetrahedral M{sub 4}L{sub 6} cages rearrange into different coordination assemblies. The exchange selectivity among EO{sub 4}{sup -} oxoanions has been investigated with {sup 77}Se NMR spectroscopy using {sup 77}SeO{sub 4}{sup 2-} as an anionic probe, which found the following selectivity trend: PO{sub 4}{sup 3-} CrO{sub 4}{sup 2-} > SO{sub 4}{sup 2-} > SeO{sub 4}{sup 2-} > MoO{sub 4}{sup 2-} > WO{sub 4}{sup 2-}. In addition to the complementarity and flexibility of the cage receptor, a combination of factors have been found to contribute to the observed anion selectivity, including the anions charge, size, hydration, basicity, and hydrogen-bond acceptor abilities.

10 SYNTHETIC FUELS↗

In the search for extraterrestrial life

The study of stellar, planetary and galactic evolution leads to the conclusion that the phenomenon of life must be coursing through the universe. It is estimated, by means of telescopic sampling, that there are billions of stars capable of having those photochemical reactions necessary for the origin of life. One approach in the search for other life would be to deploy men and instruments in spacecraft. Radio contact with other civilizations is another approach. Finally, the question might be approached by considering life as an inevitable consequence of the evolution of matter. A survey of Martian characteristics shows the possibility of life there to be dubious. The possibility of life in other parts of the galaxy is supported by a fundamental conclusion of living matter that all organisms have a common chemical ancestry. The experiment of Urey and Miller, wherein four amino acids were obtained by subjecting a mixture of methane, ammonia, and water to an electric arc, is believed to duplicate the initial organic syntheses which led to the emergence of life on earth.

Ponnamperuma, C.↗

Review of results on Halley's comet

Since its recovery in 1982, Comet Halley has been the focus of an unparalleled global scientific effort of exploration. Remote and in situ measurements were conducted from the ground, from earth orbit, from Venus orbit, from interplanetary space, and from the comet itself. Many discoveries, such as the presence of an unexpectedly large and dark nucleus or the abundance of organic material, have led to major changes in the ideas about the general nature of comets. In this report, results of various studies are summarized.

Rahe, Jurgen↗

Can the chirality of the ISM be measured

Many moderately complex carbon-based molecules of the type associated with biological systems can exist in one of two mirror-image forms (left-handed and right-handed), which can be distinguished on the basis of their influence on the state of polarization of a light beam. Both forms are possible in nature; yet in living organisms it is invariably the rule that one of these two species predominates. This gives rise to a net chirality. One possible explanation for the net chirality is that the early earth was somehow seeded from the ISM with an excess of chiral organic compounds which led to the development of life forms which are based on left-handed amino acids and right-handed sugars. Molecular spectroscopy of the interstellar medium (ISM) has revealed a complex variety of molecular species similar to those thought to have been available in the oceans and atmospheres of the earth at the time life formed. The detection of such molecules demonstrates the generality of the chemical processes occurring in both environments. If this generality extends to the processes which produce chirality, it may be possible to detect a net chirality in the ISM. This is of particular interest because determining whether or not net chirality exists elsewhere in the universe is an essential aspect of understanding how life developed on earth and how widely distributed it might be. Researchers report preliminary results of a feasibility study to determine whether or not a net chirality in the ISM can be measured. If laboratory results identify candidate chiral molecules that might exist in the ISM, the next step in this feasibility study will be to estimate the detectability of the chiral signature in astrophysical environments.

Pendleton, Y.↗

Final report: ES11: The 23rd Annual Workshop on Electronic Structure Methods

ES11: the 23rd Annual Workshop on Electronic Structure Methods was held from June 6-9, 2011 at the University of Pennsylvania. The local organizing committee (see Section II) led by PI Andrew M. Rappe supervised the organization of the conference, before, during, and after the meeting itself. The national organizing committee set the technical program of talks, and provided support and advice in various ways. The conference was well-attended (see Section III). An important feature of this conference was a series of panel discussions (see Section IV) to discuss the field of electronic structure and to set new directions. The technical program was of extraordinarily high quality (see Section V). The host institution, the University of Pennsylvania, provided a supportive environment for this meeting (see Section VI).

99 GENERAL AND MISCELLANEOUS↗

Burning conditions and transportation pathways determine biomass-burning aerosol properties in the Ascension Island marine boundary layer

Abstract. African biomass-burning aerosol (BBA) in the southeast Atlantic Ocean (SEA) marine boundary layer (MBL) is an important contributor to Earth's radiation budget, yet its representation remains poorly constrained in regional and global climate models. Data from the Layered Atlantic Smoke Interactions with Clouds (LASIC) field campaign on Ascension Island (7.95° S, 14.36° W) provide insight into how burning conditions, fuel type, transport pathways, and atmospheric processing affect the chemical, microphysical, and optical properties of BBA between June and September 2017. A total of 10 individual plume events characterize the seasonal evolution of the BBA properties. Early-season inefficient fires, determined by low refractory black carbon to above-background carbon monoxide mixing ratios (rBC : ΔCO), led to enhanced concentrations of organic- and sulfate-rich aerosols. Mid-season efficient fires, determined by higher rBC : ΔCO values, led to rBC-enriched BBA. A mix of efficient and inefficient fires later in the season resulted in conflicting BBA properties. Prolonged transport (∼ 10 d) through the MBL and lower free troposphere (FT) facilitated chemical and aqueous-phase processing, which led to a reduction in organic aerosol mass concentrations. This resulted in lower organic aerosol (OA) to rBC (OA : rBC) mass ratios (2–5) in the MBL compared to higher values (5–15) in the nearby FT. These atmospheric and cloud oxidation processes yield more light-absorbing BBA and explain the notably low single-scattering albedo at 530 nm (SSA530) values (< 0.80) observed in the MBL. This study establishes a robust correlation between SSA530 and OA : rBC across the MBL and FT, underscoring the dependency of optical properties on chemical composition.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Two-Step Resonance-Enhanced Desorption Laser Mass Spectrometry for In Situ Analysis of Organic-Rich Environments

A wide diversity of planetary surfaces in the solar system represent high priority targets for in situ compositional and contextual analysis as part of future missions. The planned mission portfolio will inform our knowledge of the chemistry at play on Mars, icy moons, comets, and primitive asteroids, which can lead to advances in our understanding of the interplay between inorganic and organic building blocks that led to the evolution of habitable environments on Earth and beyond. In many of these environments, the presence of water or aqueously altered mineralogy is an important indicator of habitable environments that are present or may have been present in the past. As a result, the search for complex organic chemistry that may imply the presence of a feedstock, if not an inventory of biosignatures, is naturally aligned with targeted analyses of water-rich surface materials. Here we describe the two-step laser mass spectrometry (L2MS) analytical technique that has seen broad application in the study of organics in meteoritic samples, now demonstrated to be compatible with an in situ investigation with technique improvements to target high priority planetary environments as part of a future scientific payload. An ultraviolet (UV) pulsed laser is used in previous and current embodiments of laser desorption/ionization mass spectrometry (LDMS) to produce ionized species traceable to the mineral and organic composition of a planetary surface sample. L2MS, an advanced technique in laser mass spectrometry, is selective to the aromatic organic fraction of a complex sample, which can provide additional sensitivity and confidence in the detection of specific compound structures. Use of a compact two-step laser mass spectrometer prototype has been previously reported to provide specificity to key aromatic species, such as PAHs, nucleobases, and certain amino acids. Recent improvements in this technique have focused on the interaction between the mineral matrix and the organic analyte. The majority of planetary targets of astrobiological interest are characterized by the presence of water or hydrated mineral phases. Water signatures can indicate a history of available liquid water that may have played an important role in the chemical environment of these planetary surfaces and subsurfaces. The studies we report here investigate the influence of water content on the detectability of organics by L2MS in planetary analog samples.

primitive asteroids↗

Lipid–enhanced Oilcane does not impact soil carbon dynamics compared with wild–type Sugarcane

The carbon neutral potential of bioenergy relies in part on the ability of feedstocks to sequester carbon (C) in the soil. Sugarcane is one of the most widely used bioenergy crops, yet there remain unknowns about how it impacts soil C dynamics. In addition, Oilcane, a genetically modified version of Sugarcane has been produced to accumulate more energy-dense oils and less soluble lignin, which enhances conversion efficiency but may also impact soil C cycling. Thus, our objectives were to examine the impact of Sugarcane litter decomposition on soil C formation and losses and determine if the genetic modifications to produce Oilcane alter these dynamics. To do this, we incubated bagasse (processed stem litter) and leaf litter from Sugarcane and Oilcane in microcosms with forest soil for 11 weeks. We used differences in natural abundance δ 13 C between C 3 forest soil and C 4 litter to trace the fate of the litter into respiratory losses as well as stable and unstable soil C pools. Our results show that genetic modifications to Oilcane did not substantially alter soil C dynamics. Sugarcane and Oilcane litter both led to net soil C gains dominated by an accumulation of the added litter as unstable, particulate organic C (POC). Oilcane litter led to small but significantly greater net soil C gains than Sugarcane litter due to greater POC formation, but the formation of stable, mineral associated organic matter (MAOC) did not differ between crop types. Sugarcane and Oilcane had opposing effects on tissue type where Sugarcane bagasse formed more MAOC, while Oilcane leaves preferentially remained as POC which may have important management implications. These results suggest that genetic modifications to Sugarcane will not significantly impact soil C dynamics; however, this may not be universal to other crops particularly if modifications lead to greater differences in litter chemistry.

09 BIOMASS FUELS↗

An Open-Access Nuclear Knowledge and Innovation Toolkit to Make Use of Nuclear World and Increase Collaboration

Nuclear engineering began as an urgent weapons development program in the early 1940s, involving work in enrichment, reactor design, shielding design, and isotope production. This work led to investigations of peaceful uses of nuclear technology, including nuclear power production and applications of radiation. Such peaceful technologies, often derived from experience gained through the weapons program, often maintained some level or attitude of secrecy. As the field continued to develop, that secrecy led to different specializations developing with different sets of terminology and methods of computation. For example, radiation safety used buildup and shielding factors while reactor designers use diffusivity and cross sections. Impressive amounts of work went into theory and application development in each sub-field over the next few decades, with much of the work left without adequate documentation or with important documentation made only within the organization. This situation has led to a loss of knowledge and experience, a lack of collaboration across nuclear sub-fields, and immense amounts of time and effort spent on redundant work. This paper proposes an open-access system that combines preserving and passing on the knowledge in all nuclear sub-fields with tools to make that knowledge useful, referred to as the Nuclear Knowledge and Innovation Toolkit (NuKIT). Knowledge would be captured in user-entered and expert-verified databases of reactors, applications of radiation, isotope production methods, and other pertinent nuclear information complete with technical information and tags that can be used to organize and investigate the data. Tools include community tools like forums and the ability to create collaborative projects; visualization and presentation tools; and an online programming system that allows code sharing, collaborative editing, database manipulation, and integration with all other tools. Finally, NuKIT is envisioned to include commercialization tools to allow freelance work and to compensate data entry/moderation work to help encourage participation. Eventually, integration with industry-standard tools like MCNP, SCALE, etc. is expected. This paper will present some proposed work in the context of its use for isotopes and radiation application, as well as possible work to be done in the context of the Combined Materials Experimental Toolkit (CoMET) being developed by the Nuclear Science User Facilities (NSUF) program. It should be noted that any work done towards this system, by any group, will advance the full system. It should also be noted that similar work previously done can be integrated into NuKIT.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Advanced Modeling and Process-Materials Co-Optimization Strategies for Swing Adsorption Based Gas Separations

This project devised a computational framework for simultaneously co-optimizing pressure swing adsorption process designs along with the sorbent materials (specifically, metal-organic frameworks) to be employed in the associated packed bed columns. The materials optimization aspect involved search over a design space that can describe the material’s molecular structure, while the process optimization aspect considered various process degrees of freedom for steps arising in various cycle configurations. This framework was demonstrated on the separation of nitrogen and carbon dioxide, which arises ubiquitously in a multitude of post-combustion carbon capture and “blue” hydrogen production applications. Our results led to metal-organic framework molecular descriptor choices that are predicted to outperform standard structures used in practice, providing guidance for future metal-organic framework synthesis efforts.

20 FOSSIL-FUELED POWER PLANTS↗

Mechanism of electronic-excitation transfer in organic light-emitting devices based on semiconductor quantum dots

The results of an experimental study of organic light-emitting diodes (LEDs) with luminescent layers based on two types of CdSe/CdS semiconductor quantum dots (QDs) with an average CdSe core diameter of 3 and 5 nm and a characteristic CdS shell thickness of 0.5 nm are presented. The dependences of the LED efficiency on the QD concentration are determined. The experimental data are used to determine the mechanism of electronic-excitation transfer from the organic matrix to the semiconductor QDs. Ways of optimizing the design of the LEDs in order to improve their efficiency are suggested on this basis.

36 MATERIALS SCIENCE↗

Redox Fluctuations and Organic Complexation Govern Uranium Redistribution from U(IV)-Phosphate Minerals in a Mining-Polluted Wetland Soil, Brittany, France

Wetlands have been proposed to naturally attenuate U transfers in the environment via U complexation by organic matter and potential U reduction. However, U mobility may depend on the identity of particulate/dissolved uranium source materials and their redox sensitivity. Here, we examined the fate of uranium in a highly contaminated wetland (up to 4500 mg·kg –1 U) impacted by former mine water discharges. Bulk U L III -EXAFS and (micro-)XANES combined with SEM-EDXS analyses of undisturbed soil cores show a sharp U redox boundary at the water table, together with a major U redistribution from U(IV)-minerals to U(VI)-organic matter complexes. Above the water table, U is fully oxidized into mono- and bidentate U(VI)-carboxyl and monodentate U(VI)-phosphoryl complexes. Minute amounts of U(VI)-phosphate minerals are also observed. Below the water table, U is fully reduced and is partitioned between U(IV)-phosphate minerals (i.e., ningyoite and a lermontovite-like phase), and bidentate U(IV)-phosphoryl and monodentate U(IV)-carboxyl complexes. Such a U redistribution from U-minerals inherited from mine water discharge deposits could result from redox cycling nearby the water table fluctuation zone. In conclusion, oxidative dissolution of U(IV)-phosphate minerals could have led to U(VI)-organic matter complexation, followed by subsequent reduction into U(IV)-organic complexes. However, uranium(IV) minerals could have been preserved in permanently waterlogged soil.

54 ENVIRONMENTAL SCIENCES↗

Molecular Architecture and Reactivity of Organic Acids on Kaolinite and Gamma-Alumina

Interactions at mineral surfaces impact the environmental fate of organic materials. Their complexity led us to investigate simpler systems, the interaction of salicylic or myristic acid with ?-alumina or kaolinite from aqueous or hexane solution using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The stability of all the adsorbed materials against removal by water or hexane raises the question of whether this may be a first step toward carbon sequestration. To gain insight, we used fully-loaded samples to explore the exchange of each with its deuterated equivalent and possible displacement by the other acid. Myristic shows almost total exchange on the surface of kaolinite and partial exchange on ?-alumina. All displacement sample spectra always showed presence of both organics. The spectrum of salicylic acid, but not that of myristic acid, was unchanged when applied first.

Bailey, Diana↗

Head and Neck Margin Reduction With Adaptive Radiation Therapy: Robustness of Treatment Plans Against Anatomy Changes

Purpose: We set out to investigate loss of target coverage from anatomy changes in head and neck cancer patients as a function of applied safety margins and to verify a cone beam computed tomography (CBCT)–based adaptive strategy with an average patient anatomy to overcome possible target underdosage. Methods and Materials: For 19 oropharyngeal cancer patients, volumetric modulated arc therapy treatment plans (2 arcs; simultaneous integrated boost, 70 and 54.25 Gy; 35 fractions) were automatically optimized with uniform clinical target volume (CTV)–to–planning target volume margins of 5, 3, and 0 mm. We applied b-spline CBCT–to–computed tomography (CT) deformable registration to allow recalculation of the dose on modified CT scans (planning CT deformed to daily CBCT following online positioning) and dose accumulation in the planning CT scan. Patients with deviations in primary or elective CTV coverage >2 Gy were identified as candidates for adaptive replanning. For these patients, a single adaptive intervention was simulated with an average anatomy from the first 10 fractions. Results: Margin reduction from 5 mm to 3 mm to 0 mm generally led to an organ-at-risk (OAR) mean dose (D{sub mean}) sparing of approximately 1 Gy/mm. CTV shrinkage was mainly seen in the elective volumes (up to 10%), likely related to weight loss. Despite online repositioning, substantial systematic errors were present (>3 mm) in lymph node CTV, the parotid glands, and the larynx. Nevertheless, the average increase in OAR dose was small: maximum of 1.2 Gy (parotid glands, D{sub mean}) for all applied margins. Loss of CTV coverage >2 Gy was found in 1, 3, and 7 of 73 CTVs, respectively. Adaptive intervention in 0-mm plans substantially improved coverage: in 5 of 7 CTVs (in 6 patients) to <2 Gy of initially planned. Conclusions: Volumetric modulated arc therapy head and neck cancer treatment plans with 5-mm margins are robust for anatomy changes and show a modest increase in OAR dose. Margin reduction improves OAR sparing with approximately 1 Gy/mm at the expense of target coverage in a subgroup of patients. Patients at risk of CTV underdosage >2 Gy in 0-mm plans may be identified early in treatment using dose accumulation. A single intervention with an average anatomy derived from CBCT effectively mitigates discrepancies.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

One-step synthesis of layered yttrium hydroxides in immiscible liquid–liquid systems: Intercalation of sterically-bulky hydrophobic organic anions and doping of europium ions

Inorganic–organic layered rare-earth compounds were synthesized on the basis of a biphasic liquid–liquid system in one pot. Layered yttrium hydroxides (LYHs) were chosen as a host material for the intercalation of hydrophobic organic guest anions such as benzoate, sebacate, or laurate. In a typical synthesis, an organic phase dissolving carboxylic acid was placed in contact with an equal amount of an aqueous phase dissolving yttrium nitrate n-hydrate and urea. At elevated temperatures up to 80 °C, urea was hydrolyzed to release hydroxyl anions which were used to form yttrium hydroxide layers. LYHs were then precipitated with the intercalation of carboxylate anions delivered from the organic phase under the distribution law. The structure and the morphology of the LYHs could be modulated by the intercalated anions. Doped with Eu{sup 3+} ions, the LYHs exhibited red photoluminescence which was enhanced by the intercalated anions due to the antenna effect. - Graphical abstract: The Eu{sup 3+}-doped layered yttrium hydroxide exhibits intense red photoluminescence after intercalation of benzoate ions. Display Omitted - Highlights: • Immiscible biphasic liquid systems were introduced to synthesize layered yttrium hydroxides. • The temperature of the biphasic systems does not exceed 80 °C in one step of the synthesis. • Hydrophobic organic anions were intercalated between the hydroxide layers in one pot. • Structure and morphology of the hydroxides were modulated by changing the kind of organic anions. • Eu{sup 3+}-doping led to red luminescence from the hydroxides in association with the intercalated organic anions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗