Combination of nuclear magnetic resonance spectroscopy and nonlinear methods to analyze the copolymerization of phosphonic acid derivatives

We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The ¹H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of r_HEMA = 1.83; r_ECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256.     

The effect of plastic deformation on Al2CuLi (T 1) precipitation

The enhancement ofT ₁ precipitation in Al-Li-Cu alloys by plastic deformation prior to aging (that is, cold work) and the subsequent increase in alloy strength is investigated. The increased understanding of the role of matrix dislocations in the nucleation and growth ofT ₁ plates, discussed in the previous paper,^[1] permits a detailed study of the phenomenon. In this paper, the effect of different levels of plastic strain on theT ₁ particle distributions as a function of aging time at 190 °C is quantified, and the subsequent influence on tensile properties is thereby described. The effect of plastic deformation is shown to decrease theT ₁ plate length and thickness, increase the number density by almost two orders of magnitude, increase the yield strength by 100 MPa, while simultaneously reaching peak strength in 20 pct of the time required without plastic deformation. Formerly Graduate Student, Department of Materials Science, University of Virginia,     

Alpha 1-adrenoceptors and calcium sources in adrenergic neurogenic contractions of rat vas deferens

1. The involvement of alpha 1-adrenoceptor subtypes in adrenergic neurogenic contractions of different type was studied in epididymal and prostatic portions of the rat vas deferens. 2. The adrenergic component of neurogenic contractions was isolated by suramin (300 microM). Twitch-like and tonic contractions were elicited by appropriate pulse patterns of electrical field stimulation, and contractions relying on intracellular calcium mobilization and calcium entry were isolated by means of nifedipine (10 microM) and ryanodine (20 microM), respectively. Increasing concentrations of 2-(2,6-dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane (WB 4101), alpha-ethyl-3,4,5-trimethoxy-alpha-(3-((2-(2-methoxyphenoxy)ethyl)- amino)-propyl)benzeneacetonitrile (HV 723), prazosin and 5-methylurapidil progressively, monophasically and with potency decreasing in that order reduced and finally abolished all types of contraction, with one exception: concentration-effect curves of 5-methylurapidil in epididymal segments in the presence of ryanodine levelled off at about 75% inhibition. In the presence of both nifedipine (10 microM) and ryanodine (20 microM), contractions were abolished. 3. Contractions elicited by exogenous noradrenaline were also studied in the presence of either nifedipine 10 microM (prostatic segments) or ryanodine 20 microM (epididymal segments). Increasing concentrations of tamsulosin, WB 4101, benoxathian, HV 723, prazosin, 5-methylurapidil and urapidil progressively, monophasically and with potency decreasing in that order reduced and eventually abolished both kinds of contraction, with two exceptions: in epididymal segments in the presence of ryanodine, the concentration-effect curve of 5-methylurapidil was biphasic and the curve of urapidil levelled off at only partial inhibition. 4. In slices prepared from the prostatic end and preincubated with [3H]-noradrenaline, WB 4101, HV 723, prazosin and 5-methylurapidil, at the highest concentrations tested against neurogenic contractions, increased only slightly the overflow of tritium elicited by trains of 50 pulses at 5 Hz. 5. It is concluded that two alpha l-adrenoceptor subtypes mediate adrenergic neurogenic contractions of rat vas deferens. The main one, pharmacologically alpha 1A, activates both calcium mobilization and entry. In addition there is a second receptor, not previously detected in the vas deferens and not corresponding to any named alpha l subtype, characterized by high and similar affinity for tamsulosin, WB 4101, benoxathian,HV 723 and prazosin and very low affinity for 5-methylurapidil and urapidil, and linked exclusively to calcium entry. Both subtypes and their respective transduction pathways also contribute to contractions elicited by exogenous noradrenaline. An alpha 1B-adrenoceptor-mediated contraction was not found under any experimental conditions.     

Mechanical behavior of double-aged AA8090

The short-transverse fracture toughness of AA8090 is dramatically improved by double aging treatments, which produce a transition from coarse planar slip to homogeneous deformation. Although the fracture mode remains intergranular, stress concentrations across the weak, highangle boundaries are reduced by homogeneous deformation, ultimately increasing fracture toughness. This behavior is attributed to dissolution of the shearable phase(δ’) and growth of the strong precipitate (S’). Predictions of slip distribution agree fairly well with observed deformation behavior. A number of tempers with improved strength-toughness relationships were developed, and fatigue crack growth behavior in laboratory air was not affected by double aging.     

Enhanced assessment of ageing phenomena in steel structures based on materials data and non‐destructive testing

The increasing amount of ageing civil steel infrastructure requests an enhanced assessment of this infrastructure in terms of determining its residual fatigue life in a more realistic way than this has been done in the past. Often the relevant materials data for cyclic loading of such an ageing infrastructure is not available and its retrieval turns out to be relatively cumbersome bearing the urgency in data availability and continuous cost pressure in mind. This article addresses different approaches and techniques on how materials data for cyclic loading can be obtained at a fraction of the effort compared to state‐of‐the‐art techniques, considering load increase tests, non‐destructive testing techniques and finally even a stepped bar specimen allowing a complete set of materials data (stress‐strain behaviour and stress‐ and strain‐life curve) to be obtained with a single specimen in the end only. Options for ’digitizing’ materials data evaluation are discussed and some prospect on application of those novel approaches and techniques in damage accumulation assessments on real steel infrastructure is provided.     

Ermittlung des elektromagnetischen Feldes von Mehrleiteranordnungen mit kreiszylindrischer Geometrie der Einzelleiter

Übersicht Das elektromagnetische Feld läßt sich im TEM-Fall in einer beliebigen Transversalebene aus einer Partikulärlösung der Poissongleichung, dem Coulomb-Integral, bestimmen. Im Falle kreiszylindrischer Leiter entsteht ein lineares Gleichungssystem zur Bestimmung der Fourierkoeffizienten der unbekannten Oberflächenstromdichteverteilungen bei gegebenen Leiterspannungen. Mit den Fourierkoeffizienten kann auch die Feldverteilung außerhalb der Leiter bestimmt werden. Die elektrischen und magnetischen Feldlinien werden mit Hilfe von Potentialfunktionen dargestellt. Als Beispiel werden die elektromagnetischen Felder von Grundanregungen der geschirmten symmetrischen Dreileiteranordnung in der Transversalebene betrachtet.

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Electromagnetic field investigation of multiconductor transmission lines by means of circular cylindrical conductors

Contents The TEM-field is determined by means of Coulombintegral, as a particular solution of Poisson's equation. After Fourier series expansion a linear equation system relates the Fourier coefficients of the surface current density on the circular cylindrical conductors to the applied voltage excitations on the conductors. The Fourier coefficients are required for determining the field distribution outside conductors. Then, by means of potential functions the electric and magnetic field distributions through flux lines are also obtained. For instance, the electromagnetic fields for some excitations of the shielded balanced three-conductor transmission line in transverse plane are considered.

     

Preprecipitation in Al/Zn/Mg alloys studied by hardness and small-angle X-ray scattering measurements

Small-angle X-ray scattering techniques and hardness measurements have been used to study preprecipitation in two Al/Zn/Mg alloys containing the same Zn content (2.46 at. %) but different Mg contents. Changes in Guinier-Preston (G-P) zone size are observed to follow the same pattern as changes in hardness. It is also observed that a critical zone size is required for the nucleation of the intermediate precipitate,'; the size being dependent on the Mg content. The role of Mg as a reversible-vacancy trap is also established.     

Deformation behavior and texture development in beta Ti-V alloys

Beta phase titanium-vanadium alloys in the composition range 20 to 40 wt pct vanadium were studied to determine the dependence of mechanical properties and texture formation on deformation modes. Changes in twinning probability and slip characteristics with vanadium content are reflected in wide variations in sheet textures in both as-rolled and rolled and recrystallized samples. These sheet textures exhibit strongly anisotropic strength properties which may be qualitatively related to the type of texture.