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.

Preeclampsia: 2-methoxyestradiol induces cytotrophoblast invasion and vascular development specifically under hypoxic conditions.

Abstract: Inadequate invasion of the uterus by cytotrophoblasts is speculated to result in pregnancy-induced disorders such as preeclampsia. However, the molecular mechanisms that govern appropriate invasion of cytotrophoblasts are unknown. Here, we demonstrate that under low-oxygen conditions (2.5% oxygen), 2-methoxyestradiol (2-ME), which is a metabolite of estradiol and is generated by catechol-o-methyltransferase (COMT), induces invasion of cytotrophoblasts into a naturally-derived, extracellular matrix. Neither low-oxygen conditions nor 2-ME alone induces the invasion of cytotrophoblasts in this system; however, low-oxygen conditions combined with 2-ME result in the appropriate invasion of cytotrophoblasts into the extracellular matrix. Cytotrophoblast invasion under these conditions is also associated with a decrease in the expression of hypoxia-inducible factor-1α (HIF-1α), transforming growth factor-β3 (TGF-β3), and tissue inhibitor of metalloproteinases-2 (TIMP-2). Pregnant COMT-deficient mice with hypoxic placentas and preeclampsia-like features demonstrate an up-regulation of HIF-1α, TGF-β3, and TIMP-2 when compared with wild-type mice; normal levels are restored on administration of 2-ME, which also results in the resolution of preeclampsia-like features in these mice. Indeed, placentas from patients with preeclampsia reveal lower levels of COMT and higher levels of HIF-1α, TGF-β3, and TIMP-2 when compared with those from normal pregnant women. We demonstrate that low-oxygen conditions of the placenta are a critical co-stimulator along with 2-ME for the proper invasion of cytotrophoblasts to facilitate appropriate vascular development and oxygenation during pregnancy.

Biomimetic self-assembly of a functional asymmetrical electronic device

Abstract: This paper introduces a biomimetic strategy for the fabrication of asymmetrical, three-dimensional electronic devices modeled on the folding of a chain of polypeptide structural motifs into a globular protein. Millimeter-size polyhedra—patterned with logic devices, wires, and solder dots—were connected in a linear string by using flexible wire. On self-assembly, the string folded spontaneously into two domains: one functioned as a ring oscillator, and the other one as a shift register. This example demonstrates that biomimetic principles of design and self-organization can be applied to generate multifunctional electronic systems of complex, three-dimensional architecture.

Indentation of polydimethylsiloxane submerged in organic solvents

Abstract: This work uses a method based on indentation to characterize a polydimethylsiloxane (PDMS) elastomer submerged in an organic solvent (decane, heptane, pentane, or cyclohexane). An indenter is pressed into a disk of a swollen elastomer to a fixed depth, and the force on the indenter is recorded as a function of time. By examining how the relaxation time scales with the radius of contact, one can differentiate the poroelastic behavior from the viscoelastic behavior. By matching the relaxation curve measured experimentally to that derived from the theory of poroelasticity, one can identify elastic constants and permeability. The measured elastic constants are interpreted within the Flory–Huggins theory. The measured permeability indicates that the solvent migrates in PDMS by diffusion, rather than by convection. This work confirms that indentation is a reliable and convenient method to characterize swollen elastomers.

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.