Washington and the North Korean Nuclear Crisis: From Muddling Multilateralism to Sanctions?

Peter M. Beck,Meredith J. Sumpter 통일연구원 2005 International journal of korean unification studie Vol.14 No.1

The viability of the Six-Party Talks as a medium to resolve the nuclear crisis increasingly is being called into question, particularly as Pyongyang claims to be reprocessing a second batch of spent fuel rods from its Yongbyon reactor and rumors swirl that the North is preparing to test a nuclear device. North Korea is proving adept at finding reasons to refuse to come back to the table, above all waiting for the “right conditions” to be met and now demanding the multilateral talks becomes a broader forum for “nuclear disarmament.” Washington has been trying to nudge the process along in vain, so far failing to convince the other four governments to buy into its North Korea approach. At this point, the only thing China, Japan, Russia, and South Korea seem to agree on is that the Bush Administration should be more “flexible.” Indeed Washington seems to be in a difficult position these days, together with its fraying relations with South Korea, a key ally in the region and one whose favorable relations are crucial to a constructive resolution of the nuclear issue. Clearly, the present North Korea policy of the second Bush Administration is in need of some serious adjustments if it is to have any hope of stopping the North’s nuclear breakout. After examining the second Bush Administration’s North Korea team, this paper explores the divergences within the Six-Party framework and considers the United States’ role in the multilateral talks. The paper concludes with suggestions for attempting a breakthrough, including the activation of a special envoy or third country to help bridge the deep mistrust between Washington and Pyongyang. The viability of the Six-Party Talks as a medium to resolve the nuclear crisis increasingly is being called into question, particularly as Pyongyang claims to be reprocessing a second batch of spent fuel rods from its Yongbyon reactor and rumors swirl that the North is preparing to test a nuclear device. North Korea is proving adept at finding reasons to refuse to come back to the table, above all waiting for the “right conditions” to be met and now demanding the multilateral talks becomes a broader forum for “nuclear disarmament.” Washington has been trying to nudge the process along in vain, so far failing to convince the other four governments to buy into its North Korea approach. At this point, the only thing China, Japan, Russia, and South Korea seem to agree on is that the Bush Administration should be more “flexible.” Indeed Washington seems to be in a difficult position these days, together with its fraying relations with South Korea, a key ally in the region and one whose favorable relations are crucial to a constructive resolution of the nuclear issue. Clearly, the present North Korea policy of the second Bush Administration is in need of some serious adjustments if it is to have any hope of stopping the North’s nuclear breakout. After examining the second Bush Administration’s North Korea team, this paper explores the divergences within the Six-Party framework and considers the United States’ role in the multilateral talks. The paper concludes with suggestions for attempting a breakthrough, including the activation of a special envoy or third country to help bridge the deep mistrust between Washington and Pyongyang.

Ultrathin Planar Graphene Supercapacitors

Yoo, Jung Joon,Balakrishnan, Kaushik,Huang, Jingsong,Meunier, Vincent,Sumpter, Bobby G.,Srivastava, Anchal,Conway, Michelle,Mohana Reddy, Arava Leela,Yu, Jin,Vajtai, Robert,Ajayan, Pulickel M. American Chemical Society 2011 Nano letters Vol.11 No.4

<P>With the advent of atomically thin and flat layers of conducting materials such as graphene, new designs for thin film energy storage devices with good performance have become possible. Here, we report an “in-plane” fabrication approach for ultrathin supercapacitors based on electrodes comprised of pristine graphene and multilayer reduced graphene oxide. The in-plane design is straightforward to implement and exploits efficiently the surface of each graphene layer for energy storage. The open architecture and the effect of graphene edges enable even the thinnest of devices, made from as grown 1−2 graphene layers, to reach specific capacities up to 80 μFcm<SUP>−2</SUP>, while much higher (394 μFcm<SUP>−2</SUP>) specific capacities are observed multilayer reduced graphene oxide electrodes. The performances of devices with pristine as well as thicker graphene-based structures are examined using a combination of experiments and model calculations. The demonstrated all solid-state supercapacitors provide a prototype for a broad range of thin-film based energy storage devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-4/nl200225j/production/images/medium/nl-2011-00225j_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl200225j'>ACS Electronic Supporting Info</A></P>

Decoding Liquid Crystal Oligomer Phase Transitions: Toward Molecularly Engineered Shape Changing Materials

Guo, Yuanhang,Lee, Jieun,Son, Jinha,Ahn, Suk-kyun,Carrillo, Jan-Michael Y.,Sumpter, Bobby G. American Chemical Society 2019 Macromolecules Vol.52 No.18

<P>This work details an integrated investigation of liquid crystal (LC) oligomers that combines experiments and molecular dynamics simulations to obtain a detailed understanding of the molecular structure of LC oligomers and the mechanism underlying their phase transition temperatures. We synthesized and characterized a series of LC oligomers prepared from different lengths of methylene spacers in the reactive LC monomers and <I>n</I>-alkylamine chain extenders <I>via</I> the <I>aza</I>-Michael addition reaction. In parallel, we performed isothermal-isobaric (<I>NPT</I>) ensemble coarse-grained molecular dynamics (CG-MD) simulation of analogue mesogens that are connected to flexible spacers and extenders at varying temperatures, spacer lengths, and extender lengths. This approach allowed the effect of length in the flexible spacer as well as in the chain extender on the nematic-isotropic transition temperature (<I>T</I><SUB>ni</SUB>) to be determined. The results showed that increasing the length of the extender decreases <I>T</I><SUB>ni</SUB> for LC oligomers and amplifies the decrease of <I>T</I><SUB>ni</SUB> in LC oligomers when the spacer length is short. We infer that the combination of spacer and extender changes the shape anisotropy of LC oligomers, changing the packing behavior of constituent mesogens, thus affecting their ability to transition from the isotropic to the nematic phase. The detailed molecular structure-property relationships formulated enable prescribing design rules for LC oligomers geared toward molecularly engineered shape changing materials.</P> [FIG OMISSION]</BR>

Nanoporous poly(3-hexylthiophene) thin film structures from self-organization of a tunable molecular bottlebrush scaffold

Ahn, S. k.,Carrillo, J. M.,Keum, J.,Chen, J.,Uhrig, D.,Lokitz, B.,Sumpter, B.,MichaelKilbey, S. Royal Society of Chemistry 2017 Nanoscale Vol.9 No.21

<P>The ability to widely tune the design of macromolecular bottlebrushes provides access to self-assembled nanostructures formed by microphase segregation in melt, thin film and solution that depart from structures adopted by simple linear copolymers. A series of random bottlebrush copolymers containing poly (3-hexylthiophene) (P3HT) and poly(D, L-lactide) (PLA) side chains grafted on a poly(norbornene) backbone were synthesized via ring-opening metathesis polymerization (ROMP) using the grafting through approach. P3HT side chains induce a physical aggregation of the bottlebrush copolymers upon solvent removal by vacuum drying, primarily driven by attractive p-p interactions; however, the amount of aggregation can be controlled by adjusting side chain composition or by adding linear P3HT chains to the bottlebrush copolymers. Coarse-grained molecular dynamics simulations reveal that linear P3HT chains preferentially associate with P3HT side chains of bottlebrush copolymers, which tends to reduce the aggregation. The nanoscale morphology of microphase segregated thin films created by casting P3HTPLA random bottlebrush copolymers is highly dependent on the composition of P3HT and PLA side chains, while domain spacing of nanostructures is mainly determined by the length of the side chains. The selective removal of PLA side chains under alkaline conditions generates nanoporous P3HT structures that can be tuned by manipulating molecular design of the bottlebrush scaffold, which is affected by molecular weight and grafting density of the side chains, and their sequence. The ability to exploit the unusual architecture of bottlebrushes to fabricate tunable nanoporous P3HT thin film structures may be a useful way to design templates for optoelectronic applications or membranes for separations.</P>

Assessing the Predictive Power of Density Functional Theory in Finite-Temperature Hydrogen Adsorption/Desorption Thermodynamics

Ihm, Yungok,Park, Changwon,Jakowski, Jacek,Morris, James R.,Shim, Ji Hoon,Kim, Yong-Hyun,Sumpter, Bobby G.,Yoon, Mina American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.45

<P>Density functional theory (DFT) has been widely employed to study the gas adsorption properties of surface-based or nanoscale structures. However, recent indications raise questions about the trustworthiness of some literature values, especially in terms of the DFT exchange-correlation (XC) functional. Using hydrogen adsorption on metalloporphyrin-incorporated graphenes (MPIGs) as an example, we diagnosed the trustworthiness of DFT results, meaning the range of expected variations in the DFT prediction of experimentally measurable quantities, in characterizing the gas adsorption/desorption thermodynamics. DFT results were compared in terms of XC functionals and vibrational effects that have been overlooked in the community. We decomposed free energy associated with gas adsorption into constituting components (binding energy, zero-point energy, and vibrational free energy) to systematically analyze the origin of deviations associated with the most commonly adopted DFT functionals in the field. We then quantify the deviations in the measurable quantities, such as operating temperature or pressure for hydrogen adsorption/desorption depending on the level of approximations. Using chemical potential change associated with gas adsorption as a descriptor, we identify the required calculational accuracy of DFT to predict the room-temperature hydrogen storage material.</P> [FIG OMISSION]</BR>