Supersoft Norbornene-Based Thermoplastic Elastomers with High Strength and Upper Service Temperature.

With over 6 million tons produced annually, thermoplastic elastomers (TPEs) have become ubiquitous in modern society, due to their unique combination of elasticity, toughness, and reprocessability. Nevertheless, industrial TPEs display a tradeoff between softness and strength, along with low upper service temperatures, typically ≤100 °C. This limits their utility, such as in bio-interfacial applications where supersoft deformation is required in tandem with strength, in addition to applications that require thermal stability (e.g., encapsulation of electronics, seals/joints for aeronautics, protective clothing for firefighting, and biomedical devices that can be subjected to steam sterilization). Thus, combining softness, strength, and high thermal resistance into a single versatile TPE has remained an unmet opportunity. Through de novo design and synthesis of novel norbornene-based ABA triblock copolymers, this gap is filled. Ring-opening metathesis polymerization is employed to prepare TPEs with an unprecedented combination of properties, including skin-like moduli (<100 kPa), strength competitive with commercial TPEs (>5 MPa), and upper service temperatures akin to high-performance plastics (≈260 °C). Furthermore, the materials are elastic, tough, reprocessable, and shelf stable (≥2 months) without incorporation of plasticizer. Structure-property relationships identified herein inform development of next-generation TPEs that are both biologically soft yet thermomechanically durable.

Multimorphic Materials: Spatially Tailoring Mechanical Properties via Selective Initiation of Interpenetrating Polymer Networks.

Access to multimaterial polymers with spatially localized properties and robust interfaces is anticipated to enable new capabilities in soft robotics, such as smooth actuation for advanced medical and manufacturing technologies. Here, orthogonal initiation is used to create interpenetrating polymer networks (IPNs) with spatial control over morphology and mechanical properties. Base catalyzes the formation of a stiff and strong polyurethane, while blue LEDs initiate the formation of a soft and elastic polyacrylate. IPN morphology is controlled by when the LED is turned "on", with large phase separation occurring for short time delays (≈1-2 min) and a mixed morphology for longer time delays (>5 min), which is supported by dynamic mechanical analysis, small angle X-ray scattering, and atomic force microscopy. Through tailoring morphology, tensile moduli and fracture toughness can be tuned across ≈1-2 orders of magnitude. Moreover, a simple spring model is used to explain the observed mechanical behavior. Photopatterning produces "multimorphic" materials, where morphology is spatially localized with fine precision (<100 µm), while maintaining a uniform chemical composition throughout to mitigate interfacial failure. As a final demonstration, the fabrication of hinges represents a possible use case for multimorphic materials in soft robotics.

Polymeric multimaterials by photochemical patterning of crystallinity.

An organized combination of stiff and elastic domains within a single material can synergistically tailor bulk mechanical properties. However, synthetic methods to achieve such sophisticated architectures remain elusive. We report a rapid, facile, and environmentally benign method to pattern strong and stiff semicrystalline phases within soft and elastic matrices using stereo-controlled ring-opening metathesis polymerization of an industrial monomer, cis-cyclooctene. Dual polymerization catalysis dictates polyolefin backbone chemistry, which enables patterning of compositionally uniform materials with seamless stiff and elastic interfaces. Visible light-induced activation of a metathesis catalyst results in the formation of semicrystalline trans polyoctenamer rubber, outcompeting the formation of cis polyoctenamer rubber, which occurs at room temperature. This bottom-up approach provides a method for manufacturing polymeric materials with promising applications in soft optoelectronics and robotics.

Selective Separation of Lithium Chloride by Organogels Containing Strapped Calix[4]pyrroles.

Reported herein are two functionalized crown ether strapped calix[4]pyrroles, H1 and H2. As inferred from competitive salt binding experiments carried out in nitrobenzene-d5 and acetonitrile-d3, these hosts capture LiCl selectively over four other test salts, viz. NaCl, KCl, MgCl2, and CaCl2. Support for the selectivity came from density functional theory (DFT) calculations carried out in a solvent continuum. These theoretical analyses revealed a higher innate affinity for LiCl in the case of H1, but a greater selectivity relative to NaCl in the case of H2, recapitulating that observed experimentally. Receptors H1 and H2 were outfitted with methacrylate handles and subject to copolymerization with acrylate monomers and cross-linkers to yield gels, G1 and G2, respectively. These two gels were found to adsorb lithium chloride preferentially from an acetonitrile solution containing a mixture of LiCl, NaCl, KCl, MgCl2, and CaCl2 and then release the lithium chloride in methanol. The gels could then be recycled for reuse in the selective adsorption of LiCl. As such, the present study highlights the use of solvent polarity switching to drive separations with potential applications in lithium purification and recycling.

Synthetic Studies toward Bazzanin K: Regioselective and Chemoselective Three-Component Suzuki Coupling.

The terphenyl substructure of the chiral cyclophane natural product bazzanin K was constructed. The key step involved sequential Suzuki couplings of a nonsymmetric dibromobenzene, which can be performed as a two-step process or as a one-pot three-component coupling. The key step represented a regioselective coupling of a dibromobenzene, as well as a chemoselective coupling of phenyl bromides in the presence of phenyl chlorides. Terphenyl intermediates displayed atropdiastereoisomerism, and they were converted to a single phenanthrene target by way of ring-closing metathesis.

Large-scale Generation of Patterned Bubble Arrays on Printed Bi-functional Boiling Surfaces.

Bubble nucleation control, growth and departure dynamics is important in understanding boiling phenomena and enhancing nucleate boiling heat transfer performance. We report a novel bi-functional heterogeneous surface structure that is capable of tuning bubble nucleation, growth and departure dynamics. For the fabrication of the surface, hydrophobic polymer dot arrays are first printed on a substrate, followed by hydrophilic ZnO nanostructure deposition via microreactor-assisted nanomaterial deposition (MAND) processing. Wettability contrast between the hydrophobic polymer dot arrays and aqueous ZnO solution allows for the fabrication of heterogeneous surfaces with distinct wettability regions. Heterogeneous surfaces with various configurations were fabricated and their bubble dynamics were examined at elevated heat flux, revealing various nucleate boiling phenomena. In particular, aligned and patterned bubbles with a tunable departure frequency and diameter were demonstrated in a boiling experiment for the first time. Taking advantage of our fabrication method, a 6 inch wafer size heterogeneous surface was prepared. Pool boiling experiments were also performed to demonstrate a heat flux enhancement up to 3X at the same surface superheat using bi-functional surfaces, compared to a bare stainless steel surface.

Mobility and speciation of arsenic in the coal fly ashes collected from the Savannah River Site (SRS).

Arsenic (As) leaching from coal fly ash stockpiled at waste disposal sites is a source of environmental concern. An array of techniques including batch extraction and column leaching tests, in combination with speciation analysis of chemically specific As species, was employed to evaluate the mobility of As in fly ashes collected from the U.S. DOE Savannah River Site. The results obtained using the U.S. EPA Toxicity Characteristic Leaching Procedure (TCLP), a two-step sequential extraction technique, and continuous column leaching experiments suggest that only a small portion of total As in the fly ashes was mobile, but mobilizable As could be a considerable fraction (3.1-43%), varying inversely with alkalinity of fly ash. Speciation analysis by using phosphate extraction suggests that arsenate (As(V)) was the major extractable species in the fly ash samples. During the column leaching experiment, however, it was observed that arsenite (As(III)) was an important species leached out of the fly ashes, indicating species conversion during the leaching process. The matrix-bound As(V) within the fly ash, once being released from the solid matrix, could be converted to As(III) during its transport inside the column. The pHs of leachates and fly ashes (both acidic in column leaching experiments here) could be related to the dominance of As(III) in the effluents.

Neurosurgery at Medical College of Georgia, Georgia Regents University in Augusta (1956-2013).

: The neurosurgery service at the Medical College of Georgia, Georgia Regents University at Augusta has a rich history spanning almost 6 decades. Here, we review the development of neurological surgery as a specialty in Augusta and the history of the Department of Neurosurgery at Georgia Regents University. This article describes some of the early neurosurgeons in the city and those who have contributed to the field and helped to shape the department. Our functional and stereotactic program is emphasized. Our surgical epilepsy program dates back more than a half-century and remains a highly experienced program. We also describe our affiliation with the medical illustration graduate program, which was the first to be accredited and remains 1 of 4 such programs in the world. Finally, we list our alumni, former faculty, and current faculty, as well as the major accomplishments in our first decade as a full department.

Pyrolysis of cellulose under ammonia leads to nitrogen-doped nanoporous carbon generated through methane formation.

Here, we present a simple one-step fabrication methodology for nitrogen-doped (N-doped) nanoporous carbon membranes via annealing cellulose filter paper under NH3. We found that nitrogen doping (up to 10.3 at %) occurs during cellulose pyrolysis under NH3 at as low as 550 °C. At 700 °C or above, N-doped carbon further reacts with NH3, resulting in a large surface area (up to 1973.3 m(2)/g). We discovered that the doped nitrogen, in fact, plays an important role in the reaction, leading to carbon gasification. CH4 was experimentally detected by mass spectrometry as a product in the reaction between N-doped carbon and NH3. When compared to conventional activated carbon (1533.6 m(2)/g), the N-doped nanoporous carbon (1326.5 m(2)/g) exhibits more than double the unit area capacitance (90 vs 41 mF/m(2)).

George W. Smith, M.D. (1916-1964).

Dr. George W. Smith is credited with developing the Smith-Robinson procedure, the automatic drill, the vessel-encircling aneurysm clip, and treatment of tic douloureux with stilbamidine. His contributions to neurosurgery were unfortunately truncated by his untimely death. This article highlights his career and his contributions.

Mercury characterization in a soil sample collected nearby the DOE Oak Ridge Reservation utilizing sequential extraction and thermal desorption method.

A new attempt to characterize Hg speciation and to evaluate Hg mobility in soils was made by applying operationally defined speciation techniques coupled with fractionation of soil components to a soil sample collected just outside the Y-12 boundary of the Oak Ridge Reservation (ORR) site. The soil sample was fractionated based on redoximorphic features and particle size and a sequential extraction procedure and thermal desorption technique were then applied to the fractionated soil components. The redoximorphic concentration component was observed to have higher Hg concentrations than the redoximorphic depletion component in the soil, and fine particles contained higher concentrations of Hg compared with coarse particles. The preliminary results of using thermal desorption as well as the sequential extraction procedure suggested that Hg0 and other "easily" vaporized Hg species accounted for 10-30% of total Hg in the soil. Sequential extraction analysis showed that both soluble and bioavailable Hg fractions were relatively small proportions whereas the organic matter bound mercury fraction constituted the major form of Hg species in the sample. The results suggest that Hg retained in the redoximorphic concentrations was less volatile and labile than Hg in the redoximorphic depletions possibly due to the strong binding affinity of Fe/Mn oxides and organic matter to Hg.

Field testing of particulate matter continuous emission monitors at the DOE Oak Ridge TSCA incinerator. Toxic Substances Control Act.

A field study to evaluate the performance of three commercially available particulate matter (PM) continuous emission monitors (CEMs) was conducted in 1999-2000 at the US Department of Energy (DOE) Toxic Substances Control Act (TSCA) Incinerator. This study offers unique features that are believed to enhance the collective US experience with PM CEMs. The TSCA Incinerator is permitted to treat PCB-contaminated RCRA hazardous low-level radioactive wastes. The air pollution control system utilizes MACT control technology and is comprised of a rapid quench, venturi scrubber, packed bed scrubber, and two ionizing wet scrubbers in series, which create a saturated flue gas that must be conditioned by the CEMs prior to measurement. The incinerator routinely treats a wide variety of wastes including high and low BTU organic liquids, aqueous, and solid wastes. The various possible combinations for treating liquid and solid wastes may present a challenge in establishing a single, acceptable correlation relationship for individual CEMs. The effect of low-level radioactive material present in the waste is a unique site-specific factor not evaluated in previous tests. The three systems chosen for evaluation were two beta gauge devices and a light scattering device. The performance of the CEMs was evaluated using the requirements in draft Environmental Protection Agency (EPA) Performance Specification 11 (PS11) and Procedure 2. The results of Reference Method 5i stack tests for establishing statistical correlations between the reference method data and the CEMs responses are discussed.