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.

Mesoscale Self-Assembly: Capillary Interactions When Positive and Negative Menisci Have Similar Amplitudes

Abstract: This paper describes the two-dimensional self-assembly of hexagonal plates at the interface between perfluorodecalin and water. The plates were prepared with five different permutations of hydrophobic and hydrophilic faces. The shapes and amplitudes of the menisci that form on the faces of the plates determine the magnitude of the lateral capillary forces through which they interact. The amplitudes of the menisci also influencethrough their out-of-plane componentsthe position and orientation of the plate relative to the plane of the liquid−liquid interface. In these experiments, the plates were made of poly(dimethylsiloxane) (PDMS) (ρ = 1.05 g/cm3) containing aluminum oxide (ρ = 4.00 g/cm3); this dopant adjusted the density of the plates, the extent to which they sank into the liquid−liquid interface, and thus the structure of their menisci. The plates studied had densities of 1.05 to 1.86 g/cm3. This work complements previous papers (Bowden, N.; Choi I. S.; Grzybowski, B. A.; Whitesides, G. M. J. Am. Che...

Mechanism of formation of 1,2,3,4-tetramethylnaphthalene from 2-butyne and triphenyltris(tetrahydrofuran) chromium(III)

Abstract: \\bstract: Reacrion of triphenyltris(tetrahydrofuran)chromium(III) (f) with 2-butyne y'ields, inter alia, 1,2,3,4' tetremerhylnaphthalene (2). A free or metal-complexed tetramethylcyclobutadiene has been exclr-rded as an inter-mediare rn rhis reaction by the observation that 1,2-dimethyl-3,4-di(methyl-rir)naphthalene (6) is not a product of I and 2-burl ne-1,1,1-d3 (3). Examination of the relative yields of 1,2,3,4,5-pentamethylnaphthalene (15) and 1,2,3,' .1.6-pentamerhylnaphthalene (16) tbrmed in reaction of 2-butyne with trio -tolyl-, tri'nr-tolyl-, and trip -tolyltris-(terrahldroiuren)chromium(III) demonstrates thiit a iong-lived aryne-chromium complex is also not an intermedi-atc in fhe:e cyclizations. Labeling and kineric isotope experiments using partially deuterated derivatives of 1 fur-rhcr drse rcdir bcnzyne complexes as intermediates in the tbrmation of 2. The reaction of trimesityltris(tetrahydro-iurrn)chronrrumtlll) with 2-butyne to torm cis-2-mesitylbut-2-ene suggests that an initial step in these reactions may be rnserrron ot'2-butyne into a carbon-chromium bond rvirh formation of an intermediate vinylic chromium reagent (2{r. The additional observations that 2-biphenylmagnesium bromide and trichlorotris(tetrahydrofuran)chro-mrum(lll) relct to form 5-(2-biphenyl)dibenzchromole (29), and that this chromocyclc reacts with 2-butyne to yield 9.lr.t-dimcthylphenanrhrene, impliclte an analogous chromocycle 3,4-dimethyt-5-phenylbenzchromole (34) in the l'ormarron of 2. Taken togethei with further deuterium exchange and labeling experiments. thcse obscrvations lead ro rhc proposal thar the reaction of I with 2-buryne proceeds by initial insertion of one molccule ol'2-butyne into a phcnll-chromium bond of l, cyclization of thc resulting vinylic chromium contpound rvith elimination of benzene to iorm chromocycle 34, anci reaction of the chromocycle with a second molecule of 2-butyne to yield 2 (Scheme VII). rclooliuonrerizetion of acetylene by transition ntetal clitllvsts pror ides the basis for a number of useiul orslnic sl'ntheses.3 Attenrpts to establish mechanisms ior this class of reactions have been hindered by' dif'hculties in identifying the active organometallic catalvsts. Although a variety of structures have been postulated tor these catalysts, it has proved possible to isollte and characterize mechanistically significant reection intermcdiates or by-products in only a small number oi reactions.{'; Precedcnts derived from the ertensir elv explored chemistry of transition-metal acety-lenc conrplexes suggest that these cyclooligomerization reactions are initiated by coordination of one or more molecules of acetylenic substrate to a metal atom or metal atonr cluster of the catalyst. s'6 The process(es) b1' which the coordinated acetylenes are subsequently conr erted to product has been variously suggested to involr e metallocyclic, r'z's ?r-allylic,s\"'e'r0 or cyclo-butadienes' r0-r3 intermediates. or to proceed by a con-certecl \" n-ntulticenter\" rcaction pat[. t t' t3 Of these suggested and not necessarily exclusive mechanistns, only the …

Emergence of reconfigurable wires and spinners via dynamic self-assembly

Abstract: Dissipative colloidal materials use energy to generate and maintain structural complexity. The energy injection rate, and properties of the environment are important control parameters that influence the outcome of dynamic self-assembly. Here we demonstrate that dispersions of magnetic microparticles confined at the air-liquid interface, and energized by a uniaxial in-plane alternating magnetic field, self-assemble into a variety of structures that range from pulsating clusters and single-particle-thick wires to dynamic arrays of spinners (self-assembled short chains) rotating in either direction. The spinners emerge via spontaneous breaking of the uniaxial symmetry of the energizing magnetic field. Demonstration of the formation and disaggregation of particle assemblies suggests strategies to form new meso-scale structures with the potential to perform functions such as mixing and sensing.

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.