Chemical order and crystallographic texture of FePd:Cu thin alloy films

FePd thin films have been recently considered as promising material for high-density magnetic storage devices. However, it is necessary to find a proper method of fabrication for the (001)-textured and chemically well-ordered alloy. In this paper, we present the detailed investigations of lattice parameters, chemical order degree, grain sizes and crystallographic texture, carried out on FePd alloys with 10 at.% of Cu addition. The initial [Cu(0.2 nm)/Fe(0.9 nm)/Pd(1.1 nm)]x5 multilayers were thermally evaporated in an ultra-high vacuum on MgO(100), Si(100), Si(111) and Si(100) covered by 100 nm thick layer of amorphous SiO2. In order to obtain homogeneous FePd:Cu alloy, the multilayers were annealed in two different ways. First, the samples were rapidly annealed in nitrogen atmosphere at 600oC for 90 seconds. Next, the long annealing in a high vacuum for 1 hour at 700oC was done. This paper focuses on quantitative investigations of the chemical order degree and crystallographic texture of ternary FePd:Cu alloys deposited on four different substrates. In order to obtain both quantities we have taken a novel approach to consider the problem of dopant atoms located in the FePd structure. The studies of the structure were done using X-Ray Diffraction (XRD) performed with synchrotron radiation and pole figures measurements. We have found that the addition of Cu changes the FePd lattice parameters and lattice distortion. We have also shown, that using different substrates it is possible to obtain a FePd:Cu alloy with different chemical order and texture. Moreover, it was observed that texture category is substrate dependent

Study of structure and antireflective properties of LaF3/HfO2/SiO2 and LaF3/HfO2/MgF2 trilayers for UV applications

Abstract The aim of this paper is to study antireflective properties of the tree-layer systems LaF3/HfO2/SiO2 and LaF3/HfO2/MgF2 deposited on heated optical glass substrates. The films were evaporated by the use two deposition techniques. In first method oxide films were prepared by means of e-gun evaporation in vacuum of 5 × 10−5 mbar in the presence of oxygen. The second was used for the deposition of fluoride films. They were obtained by means of thermal source evaporation. Simulation of reflectance was performed for 1M2H1L (Quarter Wavelength Optical Thickness) film stack on an optical quartz glass with the refractive index n = 1.46. The layer thickness was optimized to achieve the lowest light scattering from glass surface covered with dioxide and fluoride films. The values of the interface roughness were determined through atomic force microscopy measurements. The essence of performed calculation was to find minimum reflectance of light in wide ultraviolet region. The spectral dispersion of the refractive index needed for calculations was determined from ellipsometric measurements using the spectroscopic ellipsometer M2000. Additionally, the total reflectance measurements in integrating sphere coupled with Perkin Elmer 900 spectrophotometer were performed. These investigations allowed to determine the influence of such film features like surface and interface roughness on light scattering

Evidence for the Existence of an Effective Interfacial Tension between Miscible Fluids: Isobutyric Acid-Water and 1-Butanol-Water in a Spinning-Drop Tensiometer

We report definitive evidence for an effective interfacial tension between two types of miscible fluids using spinning-drop tensiometry (SDT). Isobutyric acid (IBA) and water have an upper critical solution temperature (UCST) of 26.3 degrees C. We created a drop of the IBA-rich phase in the water-rich phase below the UCST and then increased the temperature above it. Long after the fluids have reached thermal equilibrium, the drop persists. By plotting the inverse of the drop radius cubed (r(-3)) vs the rotation rate squared (omega(2)), we confirmed that an interfacial tension exists and estimated its value. The transition between the miscible fluids remained sharp instead of becoming more diffuse, and the drop volume decreased with time. We observed droplet breakup via the Rayleigh-Tomotika instability above the UCST when the rotation rate was decreased by 80%, again demonstrating the existence of an effective inter-facial tension. When pure IBA was injected into water above the UCST, drops formed inside the main drop even as the main drop decreased in volume with time. We also studied 1-butanol in water below the solubility limit. Effective interfacial tension values measured over time were practically constant, while the interface between the two phases remains sharp as the volume of the drop declines. The effective interfacial tension was found to be insensitive to changes in temperature and always larger than the equilibrium interfacial tension. Although these results may not apply to all miscible fluids, they clearly show that an effective interfacial tension can exist and be measured by SDT for some systems

Theory of biopolymer stretching at high forces

We provide a unified theory for the high force elasticity of biopolymers solely in terms of the persistence length, $\xi_p$, and the monomer spacing, $a$. When the force f>\fh \sim k_BT\xi_p/a^2 the biopolymers behave as Freely Jointed Chains (FJCs) while in the range \fl \sim k_BT/\xi_p < f < \fh the Worm-like Chain (WLC) is a better model. We show that $\xi_p$ can be estimated from the force extension curve (FEC) at the extension $x\approx 1/2$ (normalized by the contour length of the biopolymer). After validating the theory using simulations, we provide a quantitative analysis of the FECs for a diverse set of biopolymers (dsDNA, ssRNA, ssDNA, polysaccharides, and unstructured PEVK domain of titin) for $x \ge 1/2$. The success of a specific polymer model (FJC or WLC) to describe the FEC of a given biopolymer is naturally explained by the theory. Only by probing the response of biopolymers over a wide range of forces can the $f$-dependent elasticity be fully described.Comment: 20 pages, 4 figure

Dithieno[2,3-d;2',3'-d]benzo[2,1-b;3,4-b']dithiophene: a novel building-block for a planar copolymer

A planar heteroacene building block, dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;3,4-b′]dithiophene (DTmBDT), is reported via a facile synthetic procedure.</p

Reversible stretching of homopolymers and random heteropolymers

We have analyzed the equilibrium response of chain molecules to stretching. For a homogeneous sequence of monomers, the induced transition from compact globule to extended coil below the $\theta$-temperature is predicted to be sharp. For random sequences, however, the transition may be smoothed by a prevalence of necklace-like structures, in which globular regions and coil regions coexist in a single chain. As we show in the context of a random copolymer, preferential solvation of one monomer type lends stability to such structures. The range of stretching forces over which necklaces are stable is sensitive to chain length as well as sequence statistics.Comment: 14 pages, 4 figure

Cilia at the node of mouse embryos sense fluid flow for left-right determination via Pkd2

Unidirectional fluid flow plays an essential role in the breaking of left-right (L-R) symmetry in mouse embryos, but it has remained unclear how the flow is sensed by the embryo. We report that the Ca2+ channel Polycystin-2 (Pkd2) is required specifically in the perinodal crown cells for sensing the nodal flow. Examination of mutant forms of Pkd2 shows that the ciliary localization of Pkd2 is essential for correct L-R patterning. Whereas Kif3a mutant embryos, which lack all cilia, failed to respond to an artificial flow, restoration of primary cilia in crown cells rescued the response to the flow. Our results thus suggest that nodal flow is sensed in a manner dependent on Pkd2 by the cilia of crown cells located at the edge of the node.CREST of the Japan Science and Technology Corporation; NIH [P30 DK090744]; Human Frontier Science Program [ST00246/2003C]; Deutsche Forschungsgemeinschaft [PE 853/2]; Japan Society for the Promotion of Science; American Heart Association [R10682]info:eu-repo/semantics/publishedVersio

Self-Aligned Bilayers for Flexible Free-Standing Organic Field-Effect Transistors

[Image: see text] Free-standing and flexible field-effect transistors based on 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene)/polystyrene bilayers are obtained by well-controlled phase separation of both components. The phase separation is induced by solvent vapor annealing of initially amorphous blend films, leading to crystallization of TIPS-pentacene as the top layer. The crystallinity and blend morphology strongly depend on the molecular weight of polystyrene, and under optimized conditions, distinct phase separation with a well-defined and trap-free interface between both fractions is achieved. Due to the distinct bilayer morphology, the resulting flexible field-effect transistors reveal similar charge carrier mobilities as rigid devices and additionally pronounced environmental and bias stress stabilities. The performance of the flexible transistors remains stable up to a strain of 1.8%, while above this deformation, a close relation between current and strain is observed that is required for applications in strain sensors

Utilizing Tissue Microarrays for Medium-Throughput Validation of Antibodies Against Immune Markers

https://openworks.mdanderson.org/sumexp21/1201/thumbnail.jp