Morphological analysis of photocured polyurethane acrylate networks. Correlation with viscoelastic properties

In this paper, we investigate the final morphology of photocured polyurethane acrylates based on polypropylene oxide by means of Transmission Electron Microscopy (TEM), Small Angle X‐ray Scattering (SAXS), and dynamic mechanical measurements. Two interrelated structural features on two different size scales can occur in these systems. TEM analysis demonstrates the presence of inhomogeneities on the length scale of 10–200 manometers, mostly constituted by clusters of small hard units (diacrylated diisocyanate) connected by polyacrylate chains. The bimodal shape of the dynamic mechanical relaxation spectra corroborates this two‐phase structure. Besides, a suborganization of the reacted diisocyanate hard segments inside the polyurethane acrylate matrix is revealed by SAXS measurements, depending on the nature of the hydroxylacrylate used for the synthesis of the precursor. Finally, UV‐exposure time is found to induce modifications on the viscoelastic properties of the final network, even at high double‐bond conversion: this effect can be due to a postreaction and to an increase of the crosslinking density inside the hard segments domains. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 919–937, 1999     

Evaluation of hydrogen ion concentrations in prostates from rats and dogs using fluorescent confocal microscopy

The knowledge of intracellular spatial distribution of pH in prostates in animal models reflective of human prostate may have implications for drug development upon pH dependent drug delivery and activity. Freshly dissected prostate tissues (in vitro) or the entire prostate gland (in vivo) were loaded with fluorescent dyes and viewed using confocal microscopy. Images were initially taken in tissues perfused with RPMI-1640 medium. Calibration in situ was performed with high potassium buffers of known pH containing nigericin. Acetoxymethyl ester carboxy-SNARF-1 was visible in epithelial cells (but not stroma) in rat and dog prostates. The pH of lysosomes in prostate epithelial cells was 5.2 as determined by fluorescence of Lyso Sensor Green DND-189. A method of in situ confirmation of tissue viability was developed by a secondary loading and visualization of the BCECF fluorescent dye. Besides the direct measurement of the pH in rat and dog tissues (pH ≈ 7.0), a method of pH measurement in prostate tissue (rather than in cell culture) was developed.     

Stabilization of hexagonal close-packed metallic nickel for alumina-supported systems prepared from Ni(II) glycinate

The decomposition in flowing argon of the neutral complex [Ni^II(glycinate)₂(H₂O)₂] leads to a mixture of face-centered cubic (fcc) and hexagonal close-packed (hcp) metallic nickel. The latter is the main phase when the Ni(II) complex is supported on alumina. Unlike most hexagonal Ni phases described earlier, and similar to hexagonal Ni₃C, the unit cell parameters (a=0.2493 and ) lead to Ni-Ni distances equal to those encountered in fcc Ni. TEM shows that the nanoparticles are protected by graphite layers, whose elimination by heating in hydrogen results in transformation to the fcc phase and crystal growth. Magnetic measurements provide evidence of the coexistence of superparamagnetic and ferromagnetic nanoparticles. This result is in line with the broad size distribution observed by TEM and is interpreted on the basis of the metallic character of hcp Ni particles.     

Replicated observations in metrology and testing: modelling repeated and non-repeated measurements

In order to choose the right statistical tool, a basic issue for an accurate analysis of each specific problem is to understand whether the set of replicated measurement results under examination is to be considered as pertaining to repeated measurements or not. This issue is particularly important, since most of the traditional tools are valid only for repeated measurements, but, in many cases, such as laboratory comparisons (in metrology and in testing), the measurements necessary to assess correctly the measurand value and the associated uncertainty do not represent repeated measurements. The analysis performed in this paper aims to shine some light on these issues, starting with a review of the basic concepts, such as repeatability, reproducibility, accuracy, systematic error and bias, as defined in international documents and as used in the literature. The paper shows that, currently, a full consensus on a common language and understanding has not yet been achieved, and then shows how this fact reflects on the basic data models, especially those concerning inter-comparison data.

Hybrid graphene oxide/DAB-Am-16 dendrimer: Preparation,characterization chemical reactivity and their electrocatalytic detection of l-Dopamine

Graphene oxide (GO) was chemically modified with a poly(propylene)imine Generation 3.0 dendrimer (DAB-Am-16). The characterization, structure and properties of hybrid graphene oxide/DAB-Am-16 dendrimer was studied by Raman spectroscopy, Fourier-Transforming Infrared Spectroscopy (FT-IR), X-Ray Photoelectron Spectroscopic (XPS), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Thermogravimetric analysis. After functionalized the hybrid material (GOD) can interact with copper and subsequently with hexacyanoferrate (III) ions (GODHCu). The GODHCu incorporated into a graphite paste electrode (20% w/w) was applied to an electrocatalytic detection of neurotransmitter l-dopamine using differential pulse voltammetry. The analytical curve showed a linear response in the concentration range from 1.0 × 10⁻⁷ to 1.0 × 10⁻⁵ mol L⁻¹ with a corresponding equation Y(A) = 1.706 × 10⁻⁵ + 0.862 [l-dopamine] and a correlation coefficient r² = 0.998. The detection limit was 6.36 × 10⁻⁷ mol L⁻¹ with a relative standard deviation of ±4% (n = 3) and an amperometric sensitivity of 0.862 A/mol L⁻¹.     

On the determination of dynamic surface tensions by means of a modified bubble pressure method

A method for the determination of the dynamic surface tension of surfactant solutions is presented which allows to cover adsorption times down to 10 seconds. This method is based on the determination of the pressure inside two communicating bubbles. There is no deformation of the solution/air interface during the experimental procedure. Hence, in evaluating the kinetic data no surface area enlargement has to be taken into account. An automatically operating procedure should allow to cover adsorption times down to approximately one second and should improve the measuring accuracy substantially. Experimental investigations with aqueous n-decanoic acid solutions using the method proposed provided evidence that decanoic acid is adsorbed by a diffusioncontrolled mechanism.     

Phase and Interfacial Tension Behavior of Certain Model Gas Condensates: Measurements and Modeling

This contribution reports on the phase and interfacial tension behavior of some model high-temperature–high-pressure gas condensates. On the one hand these types of gas condensate are becoming a subject of major interest for the oil industry, while on the other their phase and interfacial tension behavior have not been very well studied. For two different model gas condensates, both composed of the three n-alkanes, methane, butane, and decane, experimental results on their fluid phase behavior have been obtained in the temperature region 270 < T (K) < 490 and up to pressures as high as 24 MPa. Also, critical points of the two mixtures have been determined experimentally. Both mixtures show an extended retrograde region. Using the Peng–Robinson equation of state, the phase behavior of the two mixtures was modeled. In addition, the interfacial tension behavior of the model gas condensates was modeled. For that purpose, the Cahn–Hilliard theory was applied in combination with the Peng–Robinson equation of state. Satisfactory results were obtained.     

Speckle interferometry for measurement of continuous deformations

Improvements of a method for measurement of continuous displacements and deformations with digital phase shifting speckle pattern interferometry are presented. The method is based on an algorithm that, with the knowledge of the initial phase, only needs one image at a time to evaluate continuos phase changes due to object deformations. In the improved method, the initial random phase of the speckle pattern is evaluated using a number of phase-shifted images before the deformation under study. This is used for increasing the accuracy of the initial phase estimation and reducing influences from image noise and other measurement disturbances. The phase-shifted speckle patterns are used as references for comparison with the speckle patterns of the deformed object, thereby increasing the reliability and accuracy of the phase estimations of the deformed patterns. The technique can be used for measuring deformations such as transients and other dynamic events, heat expansion as well as other phenomena where it is difficult to accomplish phase shifting during deformation.     

Structure and stability of the anatase TiO2 (101) and (001) surfaces

Well-defined (101) and (001) surfaces of anatase TiO₂ were studied for the first time by secondary-electron imaging and low-energy electron diffraction. Initially, both surfaces show a crystalline structure corresponding to the bulk anatase phase, buried under an atomically thin contamination layer. After mild sputtering with 500 eV Ne⁺ ions, we have observed a surface phase transition from tetragonal anatase to face-centered cubic titanium monoxide TiO. Subsequent annealing at 900 K restores the (1×1) anatase structure at the (101) surface. On the (001) surface, however, a (1×4) reconstruction appears. The unreconstructed structure can be recovered by exposing the surface to oxygen. These observations demonstrate the stability of the anatase surfaces and illustrate the feasibility of preparing and investigating clean surfaces of this technological important form of TiO₂.     

Nonclassical properties and algebraic characteristics of negative binomial states in quantized radiation fields

We study the nonclassical properties and algebraic characteristics of the negative binomial states introduced by Barnett recently. The ladder operator formalism and displacement operator formalism of the negative binomial states are found and the algebra involved turns out to be the SU(1,1) Lie algebra via the generalized Holstein-Primarkoff realization. These states are essentially Perelomov's SU(1,1) coherent states. We reveal their connection with the geometric states and find that they are excited geometric states. As intermediate states, they interpolate between the number states and geometric states. We also point out that they can be recognized as the nonlinear coherent states. Their nonclassical properties, such as sub-Poissonian distribution and squeezing effect are discussed. The quasiprobability distributions in phase space, namely the Q and Wigner functions, are studied in detail. We also propose two methods of generation of the negative binomial states. d 32.80.Pj Optical cooling of atoms; trapping Received 8 May 1999 and Received in final form 8 November 1999