George M. Whitesides

Bio: George M. Whitesides is an academic researcher from Harvard University. The author has contributed to research in topics: Microcontact printing & Self-assembled monolayer. The author has an hindex of 240, co-authored 1739 publications receiving 269833 citations. Previous affiliations of George M. Whitesides include University of California, Davis & University of Texas at Austin.

Heterogeneous, platinum-catalyzed hydrogenation of (diolefin)dialkylplatinum(II) complexes: kinetics

Abstract: (Diolefin)dialkylplatinum(II) complexes ((Ol/sub 2/)PtR/sub 2/) are rapidly reduced by dihydrogen in the presence of platinum black catalyst: the organic groups are converted to alkanes, and the platinum(II) to platinum(0). This platinum(0) is incorporated into the surface of the platinum black catalyst. The reaction is a heterogeneous process catalyzed by platinum(0). Its rate is strongly influenced by mass transport and by the surface area of the catalyst. It is poisoned by dineopentylmercury, di-n-octyl sulfide, and tri-tert-butylphosphine. Because the catalyst surface is constantly renewed by deposition of platinum, the reaction is, however, less sensitive to poisoning than more familiar platinum-catalyzed reactions such as hydrogenation of olefins. The form of the kinetic rate law observed for reduction of (1,5-cyclooctadiene)dimethylplatinum(II) depends on the reaction conditions. Two limiting kinetic regimes are observed. In one, mass transport of dihydrogen to the catalyst surface is rate-limiting; in the second, a reaction occurring on the platinum surface is rate-limiting. The activation energy for reaction in the mass transport limited regime is approx. 3 kcalmol and that in the reaction rate limited regime is approx. 15 kcalmol. In neither regime is there a kinetic isotope effect: nu/sub H/sub 2//nu/sub D/sub 2// approx. = 1.0. Examination of the relative ratesmore » of reaction of a series of (diolefin)dialkylplatinum(II) complexes indicates that the structure of the diolefin has a greater influence on the rate of reaction than does that of the alkyl group. Competitive experiments show that rates are influenced by adsorption of the (Ol/sub 2/)PtR/sub 2/ complex to the catalyst.« less

Nuclear Magnetic Resonance Spectroscopy. Temperature Dependence of the Spectrum of Fluorocyclooctatetraene

Abstract: The fluorine n.m.r. spectrum of fluorocyclootatetraene has been shown to be temperature dependent between 30 and 65o. This is attributed to changes in the rate of an inversion-bond-shift process which is slow on the n.m.r. time scale at low temperatures. The free energy of activation for inversion is approximately 12 kcal/mole at -33o.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

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。

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Large-scale pattern growth of graphene films for stretchable transparent electrodes

Abstract: Problems associated with large-scale pattern growth of graphene constitute one of the main obstacles to using this material in device applications. Recently, macroscopic-scale graphene films were prepared by two-dimensional assembly of graphene sheets chemically derived from graphite crystals and graphene oxides. However, the sheet resistance of these films was found to be much larger than theoretically expected values. Here we report the direct synthesis of large-scale graphene films using chemical vapour deposition on thin nickel layers, and present two different methods of patterning the films and transferring them to arbitrary substrates. The transferred graphene films show very low sheet resistance of approximately 280 Omega per square, with approximately 80 per cent optical transparency. At low temperatures, the monolayers transferred to silicon dioxide substrates show electron mobility greater than 3,700 cm(2) V(-1) s(-1) and exhibit the half-integer quantum Hall effect, implying that the quality of graphene grown by chemical vapour deposition is as high as mechanically cleaved graphene. Employing the outstanding mechanical properties of graphene, we also demonstrate the macroscopic use of these highly conducting and transparent electrodes in flexible, stretchable, foldable electronics.

Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites

Abstract: Multilayer films of organic compounds on solid surfaces have been studied for more than 60 years because they allow fabrication of multicomposite molecular assemblies of tailored architecture. However, both the Langmuir-Blodgett technique and chemisorption from solution can be used only with certain classes of molecules. An alternative approach—fabrication of multilayers by consecutive adsorption of polyanions and polycations—is far more general and has been extended to other materials such as proteins or colloids. Because polymers are typically flexible molecules, the resulting superlattice architectures are somewhat fuzzy structures, but the absence of crystallinity in these films is expected to be beneficial for many potential applications.