Particles Confined by Fluid Interfaces: Imaging Particle Motion, Interface Deformation and Capillary Forces

Small solid particles, confined in two-dimensions by fluid interfaces, were studied by a variety of experimental methods to understand particle motion, menisci shapes near interface-supported particles, and capillary interactions among such particles. Unwanted evaporation was circumvented by adopting non-volatile ionic liquids to create the fluid interfaces. A related application, employment of ionic liquids to float cryo-microtomed polymer sections, was also developed. The Brownian motions of nanospheres and nanorods in free-standing ionic liquid films were visualized in situ by high resolution scanning electron microscopy, which images features almost 100× smaller than possible in an optical microscope. For suspensions that are dilute and films that are thick compared to the particle diameter, the translational and rotational diffusion coefficients determined by single-particle tracking agreed with existing theoretical predictions. In thinner films, a striking and unexpected dynamical pairing of nanospheres was observed, suggesting a balance of capillary and hydrodynamic interactions. Nanospheres at high concentration displayed subdiffusive caged motion and hexagonal-lattice crystallization. Concentrated nanorods in the thinner films transiently assembled into finite stacks but did not achieve high tetratic liquid crystalline order, perhaps because of spherical impurities. A small spherical microparticles on a cylindrically curved liquid interface, to maintain constant contact angle about its wetted periphery, locally induces a quadrupolar interface deformation. Measured by optical profilometry, this deformation was compared to a recent theoretical expression, and good agreement was noted. The interface quadrupoles lead to particle capillary interactions in analogy to a 2d electrostatic quadrupoles, and as one consequence, spheres on a cylindrical interface assemble tetragonally. The assembly was monitored in the optical microscope, with particles driven to assembly as predicted, into a tetragonal lattice aligned with the underlying cylindrical axis. Lastly, ionic liquids and their mixtures with low molecular weight solvents were applied as flotation liquids for cryo-ultramicrotomy. With control of glass transition temperature and liquid viscosity, flat and ultra-thin sections were reliably floated onto transmission electron microscopy grids at cryogenic temperature. Compared to established flotation media for soft polymer systems, the required time and skill are significantly reduced, and the operator was not exposed to noxious fumes

Tumor Biology and Racial Disparities in Reconstruction After Mastectomy: A SEER Database Analysis

Introduction: Significant disparities in immediate breast reconstruction after mastectomy have persisted, and may even be increasing, despite large-scale efforts to minimize them, such as the Women’s Health and Cancer Rights Act of 1998. Immediate breast reconstruction has been shown to lead to higher rates of surgical satisfaction, minimize delay in post-operative cancer treatment, and improve the quality of life and overall well-being of mastectomy patients. However only 25-40% of eligible women in the United States receive reconstruction. The rate of reconstruction is even lower in African American and Hispanic women compared to White women. To better understand this disparity, this study uses national population-based data to examine how demographic factors, socioeconomic factors, and disease characteristics interact and affect the rate of immediate breast reconstruction (IBR) after mastectomy. Methods: Women with AJCC7 Stage 0-III breast cancer who underwent mastectomy from 2010 to 2012 were identified in the Surveillance, Epidemiology and End Results Program (SEER) database. Race, Hispanic ethnicity, age, marital status, insurance status, tumor grade, AJCC7 stage and hormone receptor/ Her2Neu profile were compared between women undergoing mastectomy with IBR and mastectomy alone using univariate and multivariate analysis. Results: We identified 51,115 women who underwent mastectomy for Stage 0-III breast cancer from 2010-2012, of whom 15,389 (30.1%) received IBR. On multivariate analysis, age (p Conclusion: The decision to undergo reconstruction after mastectomy is influenced by many factors. Our results show that even after adjusting for tumor characteristics, socioeconomic factors are independently associated with receiving IBR after mastectomy. Further research is needed to elucidate the factors that influence the decision to undergo IBR in order to eliminate these persistent disparities

Commensurate antiferromagnetic ordering in Ba(Fe{1-x}Co{x})2As2 determined by x-ray resonant magnetic scattering at the Fe K-edge

We describe x-ray resonant magnetic diffraction measurements at the Fe K-edge of both the parent BaFe2As2 and superconducting Ba(Fe0.953Co0.047)2As2 compounds. From these high-resolution measurements we conclude that the magnetic structure is commensurate for both compositions. The energy spectrum of the resonant scattering is in reasonable agreement with theoretical calculations using the full-potential linear augmented plane wave method with a local density functional.Comment: 5 pages, 3 figures; accepted for publication in Phys. Rev. B Rapid Com

Anomalous kinetics of attractive A+B→0A+B \to 0 reactions

We investigate the kinetics of $A+B \to 0$ reaction with the local attractive interaction between opposite species in one spatial dimension. The attractive interaction leads to isotropic diffusions inside segregated single species domains, and accelerates the reactions of opposite species at the domain boundaries. At equal initial densities of $A$ and $B$, we analytically and numerically show that the density of particles ($\rho$), the size of domains ($\ell$), the distance between the closest neighbor of same species ($\ell_{AA}$), and the distance between adjacent opposite species ($\ell_{AB}$) scale in time as $\rho \sim t^{-1/3}$, $\ell_{AA} \sim t^{1/3}$, and $\ell \sim \ell_{AB} \sim t^{2/3}$ respectively. These dynamical exponents form a new universality class distinguished from the class of uniformly driven systems of hard-core particles.Comment: 4 pages, 4 figure

Parallel Manipulator-Gripper for Mobile Manipulating UAVs

Unmanned Aerial Vehicles (UAVs) are originally developed for military, but have been developed over time to time for valuable roles in surveillance, work-assistant, and intelligence for both civilian and military operations. The ability of UAVs that manipulate or carry objects can expand the type of tasks achieved by unmanned aerial systems. High degree of freedom robots with dexterous arm can lead to various applications. Most of manipulators are serial, each motor on each joint affects on stabilizing UAVs. Our lab , DASL , has presented parallel mechanism manipulator for UAVs. It results in less impact on center of gravity(CoG) of UAVs and high precise manipulation. Thus, this work focuses on 6 degree-of-freedom parallel manipulator and gripper(PMG) concept for unmanned aerial vehicles that can be used for multiple purposes. Depending on the purpose, the grasper module on the manipulator’s end-effector changes. The design and mechanism is proposed, and the final results are also given

A Control Switch for Prothrombinase: Characterization of a Hirudin-Like Pentapeptide From the COOH Terminus of Factor VA Heavy Chain That Regulates the Rate and Pathway for Prothrombin Activation

Membrane-bound factor Xa alone catalyzes prothrombin activation following initial cleavage at Arg(271) and prethrombin 2 formation (pre2 pathway). Factor Va directs prothrombin activation by factor Xa through the meizothrombin pathway, characterized by initial cleavage at Arg(320) (meizo pathway). We have shown previously that a pentapeptide encompassing amino acid sequence 695-699 from the COOH terminus of the heavy chain of factor Va (Asp-Tyr-Asp-Tyr-Gln, DYDYQ) inhibits prothrombin activation by prothrombinase in a competitive manner with respect to substrate. To understand the mechanism of inhibition of thrombin formation by DYDYQ, we have studied prothrombin activation by gel electrophoresis. Titration of plasma-derived prothrombin activation by prothrombinase, with increasing concentrations of peptide, resulted in complete inhibition of the meizo pathway. However, thrombin formation still occurred through the pre2 pathway. These data demonstrate that the peptide preferentially inhibits initial cleavage of prothrombin by prothrombinase at Arg(320). These findings were corroborated by studying the activation of recombinant mutant prothrombin molecules rMZ-II (R155A/R284A/R271A) and rP2-II (R155A/R284A/R320A) which can be only cleaved at Arg(320) and Arg(271), respectively. Cleavage of rMZ-II by prothrombinase was completely inhibited by low concentrations of DYDYQ, whereas high concentrations of pentapeptide were required to inhibit cleavage of rP2-II. The pentapeptide also interfered with prothrombin cleavage by membrane-bound factor Xa alone in the absence of factor Va increasing the rate for cleavage at Arg(271) of plasma-derived prothrombin or rP2-II. Our data demonstrate that pentapeptide DYDYQ has opposing effects on membrane-bound factor Xa for prothrombin cleavage, depending on the incorporation of factor Va in prothrombinase

First Principles Analysis of Electron-Phonon Interaction in Graphene

The electron-phonon interaction in monolayer graphene is investigated by using density functional perturbation theory. The results indicate that the electron-phonon interaction strength is of comparable magnitude for all four in-plane phonon branches and must be considered simultaneously. Moreover, the calculated scattering rates suggest an acoustic phonon contribution that is much weaker than previously thought, revealing the role of optical phonons even at low energies. Accordingly it is predicted, in good agreement with a recent measurement, that the intrinsic mobility of graphene may be more than an order of magnitude larger than the high values reported in suspended samples.Comment: 12 pages, 4 figure

Reconfigurable ferromagnetic liquid droplets.

Solid ferromagnetic materials are rigid in shape and cannot be reconfigured. Ferrofluids, although reconfigurable, are paramagnetic at room temperature and lose their magnetization when the applied magnetic field is removed. Here, we show a reversible paramagnetic-to-ferromagnetic transformation of ferrofluid droplets by the jamming of a monolayer of magnetic nanoparticles assembled at the water-oil interface. These ferromagnetic liquid droplets exhibit a finite coercivity and remanent magnetization. They can be easily reconfigured into different shapes while preserving the magnetic properties of solid ferromagnets with classic north-south dipole interactions. Their translational and rotational motions can be actuated remotely and precisely by an external magnetic field, inspiring studies on active matter, energy-dissipative assemblies, and programmable liquid constructs

Zero field magnetic phase transitions and anomalous low temperature upturn in resistivity of single crystalline α-TmAlB4

In this study, pure α-TmAlB4 (YCrB4structure)single crystals were grown with no β-TmAlB4 (ThMoB4structure) intergrowth, and zero magnetic fieldtransitions were confirmed through specific heat capacity, magnetization, and electric resistivity measurements. The anomalous magnetic transition was found at approximately 6.2 K with long range antiferromagnetictransition at 5.6 K. The difference in field dependence between these two transitions indicates that they do not share a common magnetic origin. In addition, we investigated electrical resistivity down to 20 mK, and found upturn behavior at around 0.8 K. The low temperature upturn anomaly in resistivity was not found for other compounds of investigation for RAlB4 (R=rare earth elements), which suggests that an α-RAlB4system has a significantly different ground state, compared to a β-RAlB4 system

The Origin of the Intrinsic Scatter in the Relation Between Black Hole Mass and Bulge Luminosity for Nearby Active Galaxies

We investigate the origin of the intrinsic scatter in the correlation between black hole mass (MBH) and bulge luminosity [L(bulge)] in a sample of 45 massive, local (z < 0.35) type~1 active galactic nuclei (AGNs). We derive MBH from published optical spectra assuming a spherical broad-line region, and L(bulge) from detailed two-dimensional decomposition of archival optical Hubble Space Telescope images. AGNs follow the MBH-L(bulge) relation of inactive galaxies, but the zero point is shifted by an average of \Delta log MBH ~ -0.3 dex. We show that the magnitude of the zero point offset, which is responsible for the intrinsic scatter in the MBH-L(bulge) relation, is correlated with several AGN and host galaxy properties, all of which are ultimately related to, or directly impact, the BH mass accretion rate. At a given bulge luminosity, sources with higher Eddington ratios have lower MBH. The zero point offset can be explained by a change in the normalization of the virial product used to estimate MBH, in conjunction with modest BH growth (~ 10%--40%) during the AGN phase. Galaxy mergers and tidal interactions appear to play an important role in regulating AGN fueling in low-redshift AGNs.Comment: To appear in ApJ; 67 pages, 56 figures, 4 tables, version with full resolution figures at http://users.ociw.edu/mjkim/papers/scatter.pd