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 …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

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。

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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Hydrogels that undergo a volume phase transition in response to an external stimulus are of great interest because of their possible use as actuator materials. The performance of an actuator material is normally characterized by its force–stroke curve, but little is known about the force–stroke behavior of hydrogels. We use the theory of the ideal elastomeric gel to predict the force–stroke curves of a temperature-sensitive hydrogel and introduce an experimental method for measuring the curve. The technique is applied to PNIPAm hydrogels with low cross-link densities. The maximum force generated by the hydrogel increases with increasing cross-link density, while the maximum stroke decreases. The force–stroke curves predicted by the theory of the ideal elastomeric gel are in very good agreement with the experimental curves.

https://dash.harvard.edu/bitstream/handle/1/14023007/Force%20and%20stroke%20of%20a%20hydrogel%20actuator_1.pdf?sequence=1

Force and stroke of a hydrogel actuator

We applied strain ranging from 1% compressive to ∼0.3% tensile to a-Si:H TFTs on polyimide foils by bending them inward or outward, or by stretching them in a microstrain tester. We also applied strain to a-Si:H TFTs by deforming a flat substrate into a spherical dome. In each case, compression lowered and tension raised the on-current and hence the electron field-effect mobility. We conclude that compressive strain broadens both the valence and conduction band tails of the a-Si:H channel material, and thus reduces the effective electron mobility. We show that the mobility can be used as an indicator of local mechanical strain.

Field-effect mobility of amorphous silicon thin-film transistors under strain

Subject to compression, elastic materials may undergo bifurcation of various kinds. A homogeneous material forms creases, whereas a bilayer consisting of a stiff film and a compliant substrate forms wrinkles. Here, we show several new types of bifurcation behavior for bilayers consisting of films and substrates of comparable elastic moduli. Depending on the ratios of moduli and thicknesses of the two materials, the critical strain for the onset of creases can be either smaller or larger than that for the onset of wrinkles. When the critical strain for the onset of creases is lower than that of wrinkles, creases can be subcritical or supercritical. When the critical strain for the onset of wrinkles is lower than that of creases, wrinkles can further channel to creases at a strain much lower than the critical strain for the onset of creases in a homogeneous material. Experiments, conducted with bilayer polydimethylsiloxane (PDMS) structures subject to compressive loading, show that the different types of bifurcation behavior agree with the theoretical predictions.

/pdf/bifurcation-diagrams-for-the-formation-of-wrinkles-or-sdzc0o8rpk.pdf

Bifurcation Diagrams for the Formation of Wrinkles or Creases in Soft Bilayers

When a gas is injected into a bubble in an elastomer, the bubble may first expand gradually, and then snap suddenly to a large size. This snap-through instability is analyzed here using a model that accounts for both the surface tension and the limiting stretch of the elastomer. In a state of equilibrium, the pressure in the bubble counteracts three contributions: the ambient pressure due to the environment outside the elastomer, the Laplace pressure due to the surface tension of the elastomer, and the additional pressure due to the elasticity of the elastomer. The Laplace pressure is large for a small bubble, but falls as the bubble expands. The additional pressure due to elasticity increases as the bubble expands, and rises steeply when the surface of the bubble approaches the limiting stretch of the elastomer. We show that the bubble snaps only if a sufficient amount of gas can rush into the bubble at the onset of instability.

Snap-through Expansion of a Gas Bubble in an Elastomer

Two clean and flat wafers can adhere spontaneously. The technique has recently led to novel electronic and optoelectronic devices. The adhesion arises from short-range interatomic forces between wafer surfaces, which can be represented by a reduction in surface energy associated with the transformation of two surfaces into one interface. The wafers, however, are seldom perfectly flat; the misfit has to be accommodated by elastic distortion, plastic deformation, or mass transport. We model elastic accommodation in this paper. The distortion causes the wafers to gain elastic energy. If the surface reduction dominates over the elastic energy gain, the wafers will bond. We solve the three dimensional elastic field in the misfit wafers analytically. The conditions for bonding are established, and practical implications discussed.

Zhigang Suo

Papers

Force and stroke of a hydrogel actuator

Field-effect mobility of amorphous silicon thin-film transistors under strain

Bifurcation Diagrams for the Formation of Wrinkles or Creases in Soft Bilayers

Snap-through Expansion of a Gas Bubble in an Elastomer

A model of wafer bonding by elastic accommodation