Nathaniel A. Lynd

Bio: Nathaniel A. Lynd is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: Copolymer & Allyl glycidyl ether. The author has an hindex of 37, co-authored 101 publications receiving 3985 citations. Previous affiliations of Nathaniel A. Lynd include Lawrence Berkeley National Laboratory & University of California, Santa Barbara.

Tunable, high modulus hydrogels driven by ionic coacervation.

Abstract: The need for robust and responsive hydrogels in numerous pharmaceutical, biomedical, and industrial applications has motivated intense research efforts in these important polymeric materials. [ 1–6 ] The defi ning feature of hydrogels is that the vast majority of their mass consists of water, yet they still exhibit solid-like mechanical properties due to the presence of a three-dimensional network structure that, classically, is created through in situ covalent bond formation between multifunctional, reactive precursors. [ 6 , 7 ] A wide variety of chemistries have been utilized for covalent crosslinking of hydrogel-forming materials, e.g. free radical polymerization, Michael addition, and thiol-ene coupling, with the resulting hydrogels having good mechanical properties arising from the strong covalently bonded framework. [ 1 , 6–10 ] Limitations of the covalent approach are that the hydrogels are not re-moldable once formed, have limited responsiveness to external stimuli, and may require organic co-solvents/reagents during their formation. To overcome these limitations, hydrogels formed through non-covalent, physical associations arising from intermolecular interactions, in lieu of covalent crosslinks, have attracted signifi cant interest recently, particularly as responsive materials and injectable gels. [ 5 , 6 ] Typically, a drawback of such physically-associated hydrogels is their poor mechanical properties due to generally weak intermolecular interactions. [ 11 , 12 ] However, recent work by Gong et al. [ 13 ] and Yasuda et al . [ 14 ] on double network gels and Wang et al . [ 15 ] on the development of “aquamaterials” has demonstrated that signifi cant improvement in hydrogel mechanical properties is possible through careful design of the intermolecular interactions and length-scales between crosslinks or physical associations. In addressing new strategies to yield high performance, physically associated hydrogels, the role of dynamic materials formed via electrostatic interactions serves as a powerful model. While block copolyelectrolytes are widely used in the construction of hydrogel materials, the majority of these systems are based on block copolymers where the ionic blocks serve as the water soluble component and neutral, hydrophobic blocks

Influence of Polydispersity on the Self-Assembly of Diblock Copolymers

Abstract: The domain sizes and morphological boundaries in diblock copolymers have been predicted to be influenced by changes in the molecular weight distribution of one or both of the blocks. To systematically explore these effects, we prepared several sets of poly(ethylene-alt-propylene)-b-poly(dl-lactide) diblock copolymers with controlled molecular weights, compositions, and polydispersity indices. The polydispersity of the polylactide block was controlled by taking advantage of the equilibrium nature of the ring-opening polymerization of lactide. Small-angle X-ray scattering was used to evaluate the influence of block copolymer polydispersity on the equilibrium domain spacing and resultant ordered state morphology. We found that the domain spacing increased with increasing polydispersity and demonstrated that an increase in polydispersity at constant polylactide composition can result in a change in morphology for compositionally asymmetric diblock copolymers. More specifically, when the polylactide block is t...

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Designing hydrogels for controlled drug delivery.

Abstract: Hydrogel delivery systems can leverage therapeutically beneficial outcomes of drug delivery and have found clinical use. Hydrogels can provide spatial and temporal control over the release of various therapeutic agents, including small-molecule drugs, macromolecular drugs and cells. Owing to their tunable physical properties, controllable degradability and capability to protect labile drugs from degradation, hydrogels serve as a platform in which various physiochemical interactions with the encapsulated drugs control their release. In this Review, we cover multiscale mechanisms underlying the design of hydrogel drug delivery systems, focusing on physical and chemical properties of the hydrogel network and the hydrogel-drug interactions across the network, mesh, and molecular (or atomistic) scales. We discuss how different mechanisms interact and can be integrated to exert fine control in time and space over the drug presentation. We also collect experimental release data from the literature, review clinical translation to date of these systems, and present quantitative comparisons between different systems to provide guidelines for the rational design of hydrogel delivery systems.

Atom Transfer Radical Polymerization (ATRP): Current Status and Future Perspectives

Abstract: Current status and future perspectives in atom transfer radical polymerization (ATRP) are presented. Special emphasis is placed on mechanistic understanding of ATRP, recent synthetic and process development, and new controlled polymer architectures enabled by ATRP. New hybrid materials based on organic/inorganic systems and natural/synthetic polymers are presented. Some current and forthcoming applications are described.

Poly(ethylene oxide)-based electrolytes for lithium-ion batteries

Abstract: Poly(ethylene oxide) (PEO) based materials are widely considered as promising candidates of polymer hosts in solid-state electrolytes for high energy density secondary lithium batteries. They have several specific advantages such as high safety, easy fabrication, low cost, high energy density, good electrochemical stability, and excellent compatibility with lithium salts. However, the typical linear PEO does not meet the production requirement because of its insufficient ionic conductivity due to the high crystallinity of the ethylene oxide (EO) chains, which can restrain the ionic transition due to the stiff structure especially at low temperature. Scientists have explored different approaches to reduce the crystallinity and hence to improve the ionic conductivity of PEO-based electrolytes, including blending, modifying and making PEO derivatives. This review is focused on surveying the recent developments and issues concerning PEO-based electrolytes for lithium-ion batteries.