Crystallographic characteristic of the structural defects of martensite in Fe–32 at % Ni alloy

This crystallographic analysis of the structure has been based on the physical theory of large plastic deformation developed by V. V. Rybin, V. I. Vladimirov, and A. E. Romanov. The same terminology and its physical meaning as applied to plastic relaxation of elastic stress, the occurrence of which accompanies the γ→ α transformation, has been used in this study.     

The Change in the Shape of Gold–Copper Alloy Samples during a Disorder → Order Phase Transformation

Technical Physics - The changes in the linear dimensions of ZlM-80 gold–copper alloy samples (with a gold content of 80 wt %) during atomic ordering are studied. The initial disordered state...     

Effect of Annealing in a Ferromagnetic State on the Structure of an Fe–18 at % Ga Alloy

Physics of the Solid State - The atomic structure of the iron–gallium alloy containing 18 at % Ga has been studied by X-ray diffraction. The samples were annealed in the paramagnetic (T...     

Migration of γ/α Phase Boundaries As the Initial Stage of the Inverse α → γ Transformation upon Slow Heating of Fe–32 at % Ni Metastable Alloy

Technical Physics - During quenching of Fe–Ni metastable alloys with the invar composition from the austenite region, precipitating Fe3Ni disperse particles are transformed into the...     

Self-diffusion of V-48 in the FeV σ-phase and in an Fe-47 wt.% V solid solution

Self-diffusion coefficients of vanadium in the FeV -phase and in the corresponding -solid solution (Fe-47 wt.% V) measured in the temperature ranges 1002–1115 °C (-phase) and 1230–1320 °C are reported. The found results differ fundamentally and significantly from the relations in ordered and disordered solid solutions [9]. The diffusivity in -phase at the transition temperature (T _/=1200 °C) is cca 14 times lower than the diffusivity in the b.c.c. solid solution, the chemical composition of which is the same. The lowering is caused by the different values of frequency factors,D _O=0.11 cm²/s andD _O=45 cm²/s. The effect of the corresponding activation enthalpiesH =252 kJ/mole andH =293 kJ/mole is small and quite opposite. The occurence of higher activation enthalpyH in the -solid solution at temperaturesT>T _/ may be attributed to a certain amount of the f.c.c. phase coexisting in the b.c.c. matrix at concentrationsc _v>27 wt.% at sufficiently high temperatures [7]. A comparison of vanadium self-diffusion characteristics measured in the -phase to the extrapolated values obtained on the basis of the previous measurements [1] in the Fe-V primary solid solutions ₁ shows that the diffusivity ratioD ₁/D (1473 K)=33 and that the activation enthalpyH is by about 3% higher than the valuesH ₁ (eq. (5)) measured in the uniphase b.c.c. solid solutions.     

Analysis of the parameters of a smeared orientational transition at 250–260 K in C60 crystals

The orientational structural transformation in C₆₀ crystals at temperatures of 250–260 K is investigated within the theory of smeared first-order phase transitions. The parameters of this transformation are analyzed using the experimental temperature dependences of the heat capacity and the inelastic (ferroelastic) strain rate in the phase transition range. The elementary volume of the transformation (11–83 nm³) in a correlated motion of C₆₀ molecules and the spontaneous shear strain of the lattice (2.4×10^?2) upon its transformation from the simple cubic to the face-centered cubic structure are determined.     

Analysis of the bands of the B2Σ+-X2Σ+ transition in 12C16O+ and 13C16O+

The First Negative bands of ¹²C¹⁶O⁺ and ¹³C¹⁶O⁺, in the spectral region 40 000–46 000 cm⁻¹, have been photographed at a resolution sufficient to resolve the spin-doubled components. These data for ¹²C¹⁶O⁺, along with previously reported data of the same transitions, as well as microwave transitions of ¹²C¹⁶O⁺ in the ground state, have been explicitly included in a least-squares fit to determine the most precise set of molecular constants to date for the B²Σ⁺ and X²Σ⁺ states of ¹²C¹⁶O⁺. Furthermore, we report a rotational analysis of the First Negative bands of ¹³C¹⁶O⁺ for the first time. Several molecular constants characterizing ¹³C¹⁶O⁺ in the B²Σ⁺ and the X²Σ⁺ states, including spin-doubling parameters, have been determined.     

Analysis of the High-Resolution Rovibrational Spectrum of the C2H2D2-cis Molecule in the Region 1620–1780 cm–1

Russian Physics Journal - The spectrum of the cis-ethylene-d2 molecule (C2H2D2-cis) has been recorded with a Bruker IFS 120 HR Fourier spectrometer in the wavelength region 1100–2000...     

The activation and the spreading of deformation in a fully lamellar Ti–47 at.% Al–1 at.% Cr–0.2 at.% Si Alloy

The spreading of deformation in a lamellar Ti–47?at.% Al–1?at.% Cr–0.2?at.% Si alloy deformed under compression is studied at 25°C and 600°C. This microstructure is largely dominated by twin-related variants which are separated by either twin interfaces or thin α ₂ slabs. The alloy deforms at both temperatures by ordinary dislocations and twins. Deformation in a particular γ variant and its adjacent twin-related variant involves the same kind of glide system, either ordinary dislocations or twins. This property is found to be true for all twin-related lamellae. The occurrence of this correlated glide is explained by the introduction of the notion of pilot and driven orientations. The lamellar orientation in which the operating glide system is activated on the basis of Schmid factor considerations is termed the pilot orientation. It imposes its deformation system on to the twin-related lamella, called the driven orientation, whose deformation may not involve the slip system most favoured by the applied stress.     

Do Spectra Live in the Matrix? A Brief Tutorial on Applications of Factor Analysis to Resolving Spectral Datasets of Mixtures

Journal of Fluorescence - In spite of a rapid growth of data processing software, that has allowed for a huge advancement in many fields of chemistry, some research issues still remain problematic....     

Painlevé Analysis,Soliton Collision and B?cklund Transformation for the (3+1)-Dimensional Variable-Coefficient Kadomtsev–Petviashvili Equation in Fluids or Plasmas

In this paper, we investigate a(3+1)-dimensional generalized variable-coefficient Kadomtsev–Petviashvili equation, which can describe the nonlinear phenomena in fluids or plasmas. Painlev′e analysis is performed for us to study the integrability, and we find that the equation is not completely integrable. By virtue of the binary Bell polynomials,bilinear form and soliton solutions are obtained, and B¨acklund transformation in the binary-Bell-polynomial form and bilinear form are derived. Soliton collisions are graphically discussed: the solitons keep their original shapes unchanged after the collision except for the phase shifts. Variable coefficients are seen to affect the motion of solitons: when the variable coefficients are chosen as the constants, solitons keep their directions unchanged during the collision; with the variable coefficients as the functions of the temporal coordinate, the one soliton changes its direction.     

Improving the sensitivity of future GW observatories in the 1�C10?Hz band: Newtonian and seismic noise

The next generation gravitational wave interferometric detectors will likely be underground detectors to extend the GW detection frequency band to frequencies below the Newtonian noise limit. Newtonian noise originates from the continuous motion of the Earth??s crust driven by human activity, tidal stresses and seismic motion, and from mass density fluctuations in the atmosphere. It is calculated that on Earth??s surface, on a typical day, it will exceed the expected GW signals at frequencies below 10 Hz. The noise will decrease underground by an unknown amount. It is important to investigate and to quantify this expected reduction and its effect on the sensitivity of future detectors, to plan for further improvement strategies. We report about some of these aspects. Analytical models can be used in the simplest scenarios to get a better qualitative and semi-quantitative understanding. As more complete modeling can be done numerically, we will discuss also some results obtained with a finite-element-based modeling tool. The method is verified by comparing its results with the results of analytic calculations for surface detectors. A key point about noise models is their initial parameters and conditions, which require detailed information about seismic motion in a real scenario. We will describe an effort to characterize the seismic activity at the Homestake mine which is currently in progress. This activity is specifically aimed to provide informations and to explore the site as a possible candidate for an underground observatory. Although the only compelling reason to put the interferometer underground is to reduce the Newtonian noise, we expect that the more stable underground environment will have a more general positive impact on the sensitivity. We will end this report with some considerations about seismic and suspension noise.     

Analysis of various polarization asymmetries in the inclusive b→s?+?? decay in the fourth-generation standard model

In this study a systematical analysis of various polarization asymmetries in inclusive b→s ℓ ⁺ ℓ ⁻ decay in the standard model (SM) with four generation of quarks is carried out. We found that the various asymmetries are sensitive to the new mixing and quark masses for both of the μ and τ channels. Sizable deviations from the SM values are obtained. Hence, b→s ℓ ⁺ ℓ ⁻ decay is a valuable tool for searching physics beyond the SM, especially in the indirect searches for the fourth-generation of quarks (t′,b′).     

Is there an advantage in normalising the results of the Helicobacter pylori [13C]urea breath test for CO2 production rate in children?

The urea breath test (UBT) is a non-invasive diagnostic test to detect the presence of Helicobacter pylori in the stomach, and is the simplest way to confirm eradication after treatment. The test is based on the capacity of H. pylori to secrete the enzyme urease, which hydrolyses urea to ammonia and carbon dioxide. The aim of this study was to determine whether there is an advantage in expressing the results of UBTs in terms of urea hydrolysis rate (UHR), rather than breath 13C enrichment alone. Retrospective analysis of data collected between 1995 and 2002 from 260 patients undergoing UBTs was performed. The cut-offs for positive tests using breath 30-minute enrichment (E30), UHR calculated using VCO2 estimated from height and weight (H/WT) and VCO2 estimated from weight only were determined using two-graph receiver operator characteristic (TG-ROC) analysis. The cut-off points were 3.5/1000 or 38.7 ppm 13C excess, 7.04 micromol/h and 7.08 micromol/h, respectively. There was no advantage in expressing the results as UHR (theta0, Theta-zero, where sensitivity = specificity = 0.97 (UHR H/WT), 0.98 (UHR WT) and 1.00 (E30)) rather than breath 13CO2 enrichment alone. Differences in the extent of H. pylori colonisation and urease activity are more important than variation in VCO2 in determining breath 13CO2 enrichment in the UBT.     

Is there an advantage in normalising the results of the Helicobacter Pylori [13C]Urea breath test for CO2 production rate in children?

The urea breath test (UBT) is a non-invasive diagnostic test to detect the presence of Helicobacter pylori in the stomach, and is the simplest way to confirm eradication after treatment. The test is based on the capacity of H. pylori to secrete the enzyme urease, which hydrolyses urea to ammonia and carbon dioxide. The aim of this study was to determine whether there is an advantage in expressing the results of UBTs in terms of urea hydrolysis rate (UHR), rather than breath ¹³C enrichment alone. Retrospective analysis of data collected between 1995 and 2002 from 260 patients undergoing UBTs was performed. The cut-offs for positive tests using breath 30-minute enrichment (E30), UHR calculated using VCO₂ estimated from height and weight (H/WT) and VCO₂ estimated from weight only were determined using two-graph receiver operator characteristic (TG-ROC) analysis. The cut-off points were 3.5‰ or 38.7?ppm ¹³C excess, 7.04?µmol/h and 7.08?µmol/h, respectively. There was no advantage in expressing the results as UHR (θ₀, Theta-zero, where sensitivity?=?specificity?=?0.97 (UHR H/WT), 0.98 (UHR WT) and 1.00 (E30)) rather than breath ¹³CO₂ enrichment alone. Differences in the extent of H. pylori colonisation and urease activity are more important than variation in VCO₂ in determining breath ¹³CO₂ enrichment in the UBT.     

Fracture Mechanisms of Low Activation 12% Chromium Ferritic-Martensitic Steel EK-181 in the Temperature Range from –196 to 800°C

Russian Physics Journal - A comparative study of the fracture features of a promising low-activation 12% chromium ferritic-martensitic steel EK-181 after uniaxial tensile tests in the temperature...     

The effect of iron and silicon on precipitation processes in the Al-30 wt.% Zn alloy aged at 90 °C

The effect of different amounts of Fe and Si impurities in the Al-30 wt.% Zn alloy on both the continuous and the discontinuous precipitation at 90 °C was investigated by transmission electron microscopy and by X-ray diffraction. The results show that the growth of G.-P. zones and _R -precipitates as well as the rate of their transformation into the equilibrium -precipitates are unaffected by Fe and Si impurities. The experiments revealed, however, a significant retardation of the nucleation of lamellar aggregates of equilibrium phases on grain boundaries and a pronounced reduction of the growth of lamellae into the grains by the presence of Fe and Si atoms in the alloy. Their influence on the rate of cellular reaction was attributed to the impurity-drag effect on the cell-boundary motion.In conclusion we wish to express our thanks to Mr. Z.iký for his help in the X-ray diffraction measurements and to Mr. P.Vyhlídka for chemical analyses of the investigated samples.     

The low-temperature 13C and 2H spectra and relaxation rates of methyl groups depend on the azimuth of B0 in the molecular frame. Those of 1H do not. Why?

It is shown that the answer to the question asked in the title is: Because the axial symmetry axes of the H-H dipolar coupling tensors in a -CH3 group are perpendicular to the (assumed) threefold axis of the group. By contrast, those of the 13C-H dipolar and 2H quadrupolar coupling tensors are not. The use of "symmetry adapted" spin functions and of a symmetry adapted form of the (dipolar) coupling Hamiltonian greatly simplifies the analysis.