Random coil phosphorus chemical shift of deoxyribonucleic acids

Random coil phosphorus chemical shift has been studied using 16 17-nucleotide DNA sequences. Due to the presence of residual base stacking in these sequences, the temperature and sequence effects were investigated at 50 and 55 degrees C. The phosphorus chemical shifts of random coil DNA sequences have been found to be independent of temperature. Sequence effect analysis shows that the phosphorus chemical shift of a nucleotide in a random coil DNA sequence depends on both its 5'- and 3'-nearest neighbors. A trimer model has been used to establish the random coil 31P chemical shift prediction protocol which shows an accuracy of 0.02 ppm.     

Speckle reduction of endovascular optical coherence tomography using a generalized divergence measure

Endovascular optical coherence tomography (EV-OCT) is an emerging intravascular imaging technique for observing blood vessel walls. Fluctuating speckle noise, especially during rapid pull-back, can severely degrade the visibility of morphological structures. Moreover, the speckle pattern varies in different parts of the image due to beam divergence and is further complicated by interpolation through the coordinate transformation necessary for displaying the rotary scanning images, challenging the use of frequency domain analysis. In this study, a computationally efficient method using a generalized divergence regularization procedure is presented to suppress speckle noise in EV-OCT images. Results show substantial smoothing of the grainy appearance and enhanced visualization of deeper structures as demonstrated in porcine carotid arteries.     

Irreducible Characters of General Linear Superalgebra and Super Duality

We develop a new method to solve the irreducible character problem for a wide class of modules over the general linear superalgebra, including all the finite-dimensional modules, by directly relating the problem to the classical Kazhdan-Lusztig theory. Furthermore, we prove that certain parabolic BGG categories over the general linear algebra and over the general linear superalgebra are equivalent. We also verify a parabolic version of a conjecture of Brundan on the irreducible characters in the BGG category of the general linear superalgebra.     

Triple negative permeability band in plasmon-hybridized cut-wire-pair metamaterials

We expand the picture of plasmon hybridization in metamagnetic structure via numerically studying the electromagnetic coupling in the metallic cut-wire-pair super cells. It is shown that a triple negative permeability band can be achieved by systematically controlling the plasmon hybridization in such the structure. The corresponding transmission properties as well as the electromagnetic responses of the plasmon-hybridized structures were presented by using the finite integration technique simulations. Our results would reveal a promising design to obtain the multiple negative refractions based on the combination of hybridized cut-wire-pairs and continuous wires.     

Application of the sequential gradient-restoration algorithm to thermal convective instability problems

The problem of the thermal stability of a horizontal incompressible fluid layer with linear and nonlinear temperature distributions is solved by using the sequential gradient-restoration algorithm developed for optimal control problems. The hydrodynamic boundary conditions for the layer include a rigid or free upper surface and a rigid lower surface. The resulting disturbing equations are solved as a Bolza problem in the calculus of variations. The results of the study are compared with the existing works in the literature.The authors acknowledge valuable discussions with Dr. A. Miele.     

Dissipation functions and conservation laws of molecular liquids and solids

Thermodynamics of molecular liquids (anisotropic liquids, liquid crystals, etc.) and molecular solids (e.g. dielectrics, pyroelectrics, molecular crystals) are treated in a unified way, using an internal energy potentialU and a dissipation functionD. Assuming that the motion of the mass points making up the molecule is essential in determiningU we write down the appropriate field equations of motion and the entropy equation. With the assumed invariance ofU under a group of space-time transformations and the invariance ofD under rigid body uniform motions, we derive the conservation laws of mass, momentum, energy and angular momentum. In particular, we show that the total stress tensor is asymmetric.Furthermore, a symmetric stress tensor does not guarantee angular momentum conservation. The complete specification ofD leads to symmetry relations between the dissipative coefficients in an unambiguous way, without invoking the concept of so called forces and fluxes, in contrast to the conventional Onsager approach. Our formalism allows for a class of different dissipation functions, and is applicable to linear or nonlinear molecular media of arbitrary symmetry. It covers simple materials as special cases.     

Dynamics of viscous fingers in Hele-Shaw cells of liquid crystals Theory and experiment

The theoretical and experimental developments in the interfacial dynamics and the formation of viscous fingering patterns in Hele-Shaw cells of liquid crystal-air systems are summarized and discussed. These include radial and linear cells with or without grooves engraved on the cell plates. Instabilities of fingers, the role of intrinsic and extrinsic anisotropies, etc., are emphasized. In a linear cell, when the injected air is kept at constant pressure, a whole sequence of successive instabilities of fingers (hump, tip-splitting, sidewrinkling, sidebranching and DLA-like structure) is observed in a single run of the experiment. In our theory, the equations of motion of nematic flows in Hele-Shaw cells are derived from the Ericksen-Leslie equations. In the linear approximation, the equations resemble those of isotropic liquids with the presence of effective viscosities and anisotropic surface tension. Experimental observations are interpreted with the introduction of an effective control parameter which may be time dependent. Special features of viscous fingers in liquid crystals in contrast to those in isotropic liquids, such as asymmetric dendritics, displacement of the finger from the central axis of the linear cell, and reentrant sequence of patterns, are pointed out. Plausible explanations of these phenomena are given. In this newly developed field, a large number of interesting problems remain to be solved.     

Improved Stabilities of Labeling Probes for the Selective Modification of Endogenous Proteins in Living Cells and In Vivo

To date, various affinity-based protein labeling probes have been developed and applied in biological research to modify endogenous proteins in cell lysates and on the cell surface. However, the reactive groups on the labeling probes are also the cause of probe instability and nonselective labeling in a more complex environment, e. g., intracellular and in vivo. Here, we show that labeling probes composed of a sterically stabilized difluorophenyl pivalate can achieve efficient and selective labeling of endogenous proteins on the cell surface, inside living cells and in vivo. As compared with the existing protein labeling probes, probes with the difluorophenyl pivalate exhibit several advantages, including long-term stability in stock solutions, resistance to enzymatic hydrolysis and can be customized easily with diverse fluorophores and protein ligands. With this probe design, endogenous hypoxia biomarker in living cells and nude mice were successfully labeled and validated by in vivo, ex vivo, and immunohistochemistry imaging.     

Evidence for Electron Transfer between Graphene and Non-Covalently Bound π-Systems

Hybridizing graphene and molecules possess a high potential for developing materials for new applications. However, new methods to characterize such hybrids must be developed. Herein, the wet-chemical non-covalent functionalization of graphene with cationic π-systems is presented and the interaction between graphene and the molecules is characterized in detail. A series of tricationic benzimidazolium salts with various steric demand and counterions was synthesized, characterized and used for the fabrication of graphene hybrids. Subsequently, the doping effects were studied. The molecules are adsorbed onto graphene and studied by Raman spectroscopy, XPS as well as ToF-SIMS. The charged π-systems show a p-doping effect on the underlying graphene. Consequently, the tricationic molecules are reduced through a partial electron transfer process from graphene, a process which is accompanied by the loss of counterions. DFT calculations support this hypothesis and the strong p-doping could be confirmed in fabricated monolayer graphene/hybrid FET devices. The results are the basis to develop sensor applications, which are based on analyte/molecule interactions and effects on doping.