The superconducting transition temperature T(c) of bilayers comprising underdoped La(2-x)Sr(x)CuO(4) films capped by a thin heavily overdoped metallic La(1.65)Sr(0.35)CuO(4) layer, is found to increase with respect to T(c) of the bare underdoped films. The highest T(c) is achieved for x=0.12, close to the "anomalous" 1/8 doping level, and exceeds that of the optimally doped bare film. Our data suggest that the enhanced superconductivity is confined to the interface between the layers. We attribute the effect to a combination of the high pairing scale in the underdoped layer with an enhanced phase stiffness induced by the overdoped film. 相似文献
The electrical conductivity of composites of exfoliated graphite nanoplatelets (GNPs), including bromine‐doped GNP, and conjugated polyacrylonitrile has been investigated. The focal point is the dual nature of the graphite nanoparticles, which exhibit both intrinsic electrical conductivity and doping capability of semi‐conductive polymers such as conjugated polyacrylonitrile to form charge‐transfer complexes. The conductivity is particularly enhanced in conjugated polyacrylonitrile composites (e.g., with 6 wt.‐% graphite nanoplatelets) where the value rises from 1 × 10−10 to 2 × 10−3 S · cm−1, which reflects jointly the conductivity of the doped semi‐conductive polymer together with the percolation‐based conductivity of the particles.
In many Gram‐negative bacteria, lipopolysaccharide (LPS) and its lipid A moiety are pivotal for bacterial survival. Depending on its structure, lipid A carries the toxic properties of the LPS and acts as a potent elicitor of the host innate immune system via the Toll‐like receptor 4/myeloid differentiation factor 2 (TLR4/MD‐2) receptor complex. It often causes a wide variety of biological effects ranging from a remarkable enhancement of the resistance to the infection to an uncontrolled and massive immune response resulting in sepsis and septic shock. Since the bioactivity of lipid A is strongly influenced by its primary structure, a broad range of chemical syntheses of lipid A derivatives have made an enormous contribution to the characterization of lipid A bioactivity, providing novel pharmacological targets for the development of new biomedical therapies. Here, we describe and discuss the chemical aspects regarding lipid A and its role in innate immunity, from the (bio)synthesis, isolation and characterization to the molecular recognition at the atomic level. 相似文献
Molecular Diversity - Reliable prediction of anticancer potential of different substances for different cells using unambiguous algorithms is attractive alternative of experimental investigation of... 相似文献
We classify the maximal irreducible periodic subgroups of PGL(q,
), where
is a field of positive characteristic p transcendental over its prime subfield, q = p is prime, and
× has an element of order q. That is, we construct a list of irreducible subgroups G of GL(q,
) containing the centre
×1q of GL(q,
), such that G/
×1q is a maximal periodic subgroup of PGL(q,
), and if H is another group of this kind then H is GL(q,
)-conjugate to a group in the list. We give criteria for determining when two listed groups are conjugate, and show that a
maximal irreducible periodic subgroup of PGL(q,
) is self-normalising.
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Four-arm star-shaped poly(2-isopropyl-2-oxazolines) (PiPrOx4) are synthesized by cationic polymerization on t-butylcalix[4]arene macroinitiator. The obtained samples differ by polymerization degree of arms NPiPrOx = 9 and 25 and are characterized in chloroform. The behavior in aqueous solutions is studied by light scattering methods and compared with the results of investigation of eight-arm star with similar structure. Three types of particles are observed in solution of short-arm PiPrOx4 at room temperature, whereas only two particle types are present in long-arm star solution. Arm shortening leads to widening of the phase transition interval. The arm number decreasing reduces the phase transition temperature by 1°C. 相似文献
Formation of the macroscopically-infinite hydrogen-bonded water network in various aqueous systems occurs via 3D percolation transition when the probability of finding a spanning water cluster exceeds 95%. As a result, in a wide interval of water content below the percolation threshold, rarefied quasi-2D water networks span over the mesoscopic length scale. Formation and topology of spanning water networks, which affect various properties of aqueous systems, can be described within the framework of the percolation theory. 相似文献