Spectroscopic properties as a function of fluorine content in Eu3+:PMMA

In this work europium was used as a spectroscopic probe of the local environment about a lanthanide dopant in a fluorinated copolymer of poly(methyl methacrylate) (PMMA). Fluorination of PMMA was achieved through copolymerization with heptafluorobutyl methacrylate (HFBMA). Samples were characterized for their refractive index, glass transition temperature (T_g), and optical emissions via prism coupling, differential scanning calorimetry, and fluorescence spectroscopy respectively. The refractive index and T_gs were found to decrease linearly with fluorine content. The hypersensitivity ratio, which is defined as the ratio of integrated emission intensity between the ⁵D₀ → ⁷F₂ hypersensitive transition and ⁵D₀ → ⁷F₁ magnetic dipole transition in Eu³⁺, was found to decrease by ～60% when the HFBMA copolymer content exceeded about 75% by weight. This implies a change in the local environment about the rare earth dopant that is dependent on the copolymer concentration and is likely due to changes in solubility between the ligand and host environment. The results show that fluorination of PMMA can be useful to tailor refractive index, glass transition, and the spectroscopic properties of active dopants. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1592–1596, 2006     

Elliptical Solutions to the Standard Cosmology Model with Realistic Values of Matter Density

We have examined a solution to the FRW model of the Einstein and de Sitter Universe, often termed the standard model of cosmology, using wide values for the normalized cosmic constant (Ω_∧) and spacetime curvature (Ω _k ) with proposed values of normalized matter density. These solutions were evaluated using a combination of the third type of elliptical equations and were found to display critical points for redshift z, between 1 and 3, when Ω_∧ is positive. These critical points occur at values for normalized cosmic constant higher than those currently thought important, though we find this solution interesting because the Ω_∧ term may increase in dominance as the Universe evolves bringing this discontinuity into importance. We also find positive Ω_∧tends towards attractive at values of z which are commonly observed for distant galaxies.     

Photoemission studies of pulsed-RF plasma nitrided ultra-thin SiON dielectric layers

Results are presented of a photoemission study of the electronic structure of SiON layers formed by a pulsed-RF decoupled plasma nitration (DPN) of ultra-thin SiO₂ grown base layers approximately 1.0 nm thick. The optical thickness of these device grade nitrided dielectric layers was in the range 1.4-1.6 nm. X-ray photoelectron spectroscopy (XPS) studies indicate that the nitrogen is incorporated in a single chemical environment at concentration levels in the range 15-17%. Angle resolved XPS measurements show that the nitrogen is distributed through the layer, with the binding energy of the N 1s peak at 398.3 eV which is indicative of a Si₃N₄-like chemical species in an oxide environment. High resolution core level photoemission studies of the spin orbit stripped Si 2p⁴⁺ peak revealed full width half maximum values in the range 1.4-1.55 eV, which are significantly larger than the 1.15 eV value reported for SiO₂ layers. Synchrotron radiation photoemission studies of the valence band spectra enable the valence band off-set at the Si/SON interface to be evaluated as 2.3 eV and to infer a conduction band off-set of 2.1 eV.     

From spin flip excitations to the spin susceptibility enhancement of a two-dimensional electron gas

The g-factor enhancement of the spin-polarized two-dimensional electron gas was measured directly over a wide range of spin polarizations, using spin flip resonant Raman scattering spectroscopy on two-dimensional electron gases embedded in Cd(1-x)Mn(x)Te semimagnetic quantum wells. At zero Raman transferred momentum, the single-particle spin flip excitation, energy Z*, coexists in the Raman spectrum with the spin flip wave of energy Z, the bare giant Zeeman splitting. We compare the measured g-factor enhancement with recent spin-susceptibility enhancement theories and deduce the spin-polarization dependence of the mass renormalization.     

Fracture data and stress-strain behavior of rocks in triaxial compression

Test results are reported for a recently completed experimental research program on rocks subjected to triaxial compression. Sandstone, marble, granite and shale specimens were tested at confining pressures as high as 90,000 psi corresponding to mean stresses of up to 143,000 psi. Recognizing that the largest potential experimental error in such tests results from making strain and load measurements external to the vessel, special load and strain-measuring devices were designed and fabricated for use inside the pressure vessel. The specimens were carefully machined cylinders with length-to-diameter ratios of two and with diameters ranging from 4/16 in. to 1 in. The confining pressure was held constant during each run, but varied from 0 to 90,000 psi over the tests. Results are reported in the form of:

1. Stress-strain curves for individual specimens
2. Maximum shear stress at fracture vs. mean-stress curves for each rock type tested
3. Tabulation of results for 59 specimens

A number of tests were run on granite specimens which had been previously fractured. Results from these tests showed good agreement with tests on intact granite, providing the confining pressure was above 30,000 psi.     

Rheological properties of wheat flour doughs

Summary A comparative study was made of the large deformation and rupture properties of doughs from a medium strength and a weak wheat flour. Experiments were made by stretching, at a uniform rate, dough rings immersed in a liquid of matching density to prevent the rings from deforming under their own weight. Data were obtained on doughs differing in water content at temperatures from 5 to 45 °C and extension rates from 0.132 to 52.6 inches per minute.Essentially, the tensile properties of each dough could be represented by four characteristic functions, each dependent on only one of the variables: strain, time, temperature, and water content. The strain function (), equaled (In)/, where is the extension ratio, for extensions up to about 90% and, in some instances, up to nearly 200%. Thus, over extended ranges of strain, isochronal stress-strain data (representing comparable states of stress relaxation) gave a direct proportionality between true stress and theHencky strain, _H=In; the proportionality constant is the constant strain rate modulus,F (t^*), evaluated at the (isochronal) timet ^*. The modulusF(t,T,W — a function of timet, temperatureT, and water absorptionW-equals (T/T ₀)F (t ^*,T ₀,W ₀) (t/t ^* a _T a _W)ⁿ, wheren is a negative constant characteristic of the flour,F (t ^*,T ₀,W ₀) is the modulus at timet ^* at the reference temperatureT ₀ for a dough having the reference water absorptionW ₀;a _T anda _W are shift factors that account for the change of relaxation times with temperature and water content. The factor ay obeyed theArrhenius equation and gave activation energies of about 7.7 and 22.8 kcal for doughs from the medium strength and weak flour, respectively. Rupture data obtained at different temperatures and extension rates were superposed by usinga _T data and also were represented by failure envelopes. The shift factora _W appears to depend somewhat on temperature, especially for the weaker flour.Differences in the rheological behavior of doughs from the two flours were evident in: (1) the range over which the isochronal stress-strain behavior could be linearized; (2) the magnitude of the characteristic exponentn; (3) the magnitude and the temperature dependence of the moduli; (4) the activation energies; (5) the effect of temperature ona _W; and (6) several characterizing plots prepared to represent rupture data.

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Zusammenfassung Es wurde eine Vergleichsuntersuchung betreffend große Verformungen und Brucheigenschaften von Teigen aus zwei Weizenmehltypen durchgeführt. Die Versuche wurden in der Weise ausgeführt, daß man Teigringe, die in eine Flüssigkeit von entsprechender Dichte eingetaucht waren, um zu verhindern, daß sich die Ringe unter der Wirkung ihres eigenen Gewichtes verformten, mit gleichbleibender Geschwindigkeit streckte. Es wurden Werte für verschiedene Teige ermittelt, die sich durch ihren Wassergehalt unterschieden, und zwar bei Temperaturen von 5–45 °C und Dehnungsgeschwindigkeiten von 0,132–52,6 Zoll pro Minute.Die Zugeigenschaften eines jeden Teiges konnten im wesentlichen durch vier charakteristische Funktionen dargestellt werden, von denen jede lediglich von einer der Veränderlichen: Verformung, Zeit, Temperatur und Wassergehalt abhing. Die Verformungsfunktion () war gleich (In)/, worin das Dehnungsverhältnis bedeutet, und zwar für Dehnungen bis zu ungefähr 90%, in einigen Fällen sogar bis zu fast 200%. Somit ergab sich über einem ausgedehnten Verformungsbereich für die isochronen Kraft-Dehnungs-Werte (die vergleichbare Zustände der Spannungsrelaxation darstellen) eine direkte Proportionalität zwischen wahrer Spannung undHencky- Verformung, _H=In; die Proportionalitätskonstante ist der ModulF (t^*), genommen bei konstanter Verformungsgeschwindigkeit und der (isochronen) Zeit t^*. Der ModulF (t, T, W)eine Funktion der Zeitt, der TemperaturT und der WasserabsorptionW — läßt sich darstellen durch (T/T ₀)F (t ^*,T ₀,W ₀ ) (t/t ^* a _T a _W)ⁿ, worinn eine für das Mehl charakteristische negative Konstante undF (t ^*,T ₀,W ₀) der Modul zur Zeitt ^* bei der BezugstemperaturT ₀ ist für einen Teig, der die Bezugs-WasserabsorptionW ₀ hat;a _T unda _W sind Verschiebungsfaktoren, die der Veränderung der Relaxationszeiten mit der Temperatur und dem Wassergehalt Rechnung tragen. Der Faktor ay gehorcht derArrhenius-Gleichung und ergibt Aktivierungsenergien von ungefähr 7,7 bzw. 22,8 kcal für die Teige der beiden Mehltypen. Bruchwerte, die bei verschiedenen Temperaturen und verschiedenen Dehnungsgeschwindigkeiten erhalten wurden, ließen sich durch Verwendung vona _T-Daten überlagern und durch eine Brucheinhüllende (failure envelope) darstellen. Der Verschiebungsfaktora _W scheint etwas von der Temperatur abzuhängen, und zwar besonders bei dem schwächeren Mehl.Unterschiede im rheologischen Verhalten von Teigen aus den beiden Mehlsorten bestanden offensichtlich in Bezug auf: (1) den Bereich, über den das isochrone Kraft-Dehnungs-Verhalten linearisiert werden konnte, (2) die Größe des charakteristischen Exponentenn, (3) die Größe und die Temperaturabhängigkeit der Moduln, (4) die Aktivierungsenergien, (5) die Wirkung der Temperatur aufa _W und (6) einige graphische Darstellungen zur Charakterisierung der Bruchwerte.

     

Local liquid velocity measurements in air-water bubbly flow

Local measurements of axial liquid velocity were performed for vertical upward air-water bubbly flow in a 101.6-mm inner-diameter round pipe by using a laser Doppler anemometer (LDA) and a hot-film anemometer (HFA). The data reduction approaches for both the LDA and HFA are discussed in detail. A threshold scheme with the information of local void fraction and velocity distribution in single-phase flow was applied to the LDA to approximately discriminate liquid velocity signals from those of the bubble interface velocity. Furthermore, a formulation was given to account for the effect of the bubble relative velocity on the liquid in the front and wake regions of the bubbles. For the HFA, an amplitude threshold scheme and a slope criterion were used to extract liquid velocity information. To reduce the measurement uncertainty, the experiments were performed in flow conditions where the area-averaged void fraction was less than 20%. The experimental results showed satisfactory agreement between the liquid volumetric flow rates calculated by area integration of the local liquid velocity and void fraction measurements, and the measured value by a magnetic flow meter. Also, the area-averaged relative velocity between the gas and liquid phases obtained from the current measurements agreed well with previous research.     

The correlation between surface temperature and subsurface velocity during evaporative convection

The cross-correlation between surface temperature and subsurface velocity is presented for water undergoing evaporative convection. The surface temperature measurements were obtained via quantitative infrared imaging, and the velocity measurements were obtained using a two-component laser Doppler velocimetry (LDV) system. The water surface was covered with a surfactant monolayer, which did not impede evaporation. The largest measured correlation coefficient was 0.375. Correlation coefficients obtained after shifting the velocity and temperature time traces with respect to each other revealed a peak in the correlation coefficient very close to a zero time shift. The significance of these results and their implications for the remote sensing of underwater objects via infrared imaging are discussed. Received: 2 April 2001/Accepted: 30 November 2001     

Comments on the paper “On the derivation of the constitutive equation of the simple fluid from that of a simple material” by R.R. Huilgol

Huilgol's paper [1] is discussed critically. It is shown that there are significant errors in each section of the paper. His argument depends critically on a refusal to recognize that when a statement is made that a functional of a tensor function is invariant under a group of transformations, these transformations must be constants and that otherwise the statement is meaningless. Furthermore, he consistently ignores the contradictions to which this refusal leads.