Fourier transform spectral study of BΣ-XΣ system of AlO

The spectrum of B²Σ⁺-X²Σ⁺ system of AlO has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution of 0.05 cm⁻¹. Nineteen bands of the Δv = 1, 0, −1, and −2 sequences of this band system have been analyzed for the rotational structure. Out of which seven bands, viz. 3-2, 4-3, 2-3, 3-4, 4-5, 5-6 and 6-7 have been analyzed for the first time. The rotational lines of these 19 bands along with 20 earlier analyzed bands, a total of 7200 lines, have been fitted in a simultaneous least squares fit. The study has resulted in determining more precise vibrational and rotational constants of the two states. Because of the high resolution employed it became necessary to invoke H₀ and H₁ coefficients, and a fifth order term to explain the anomalous spin-doubling observed in the v″ = 5, 6 and 7 levels of the X²Σ⁺ state.     

θ dependence of QCD at finite isospin density

We probe the θ   dependence of QCD at finite isospin chemical potential μI${\mu }_I$ using the effective chiral Lagrangian approach. The phase diagram in the θ  , μI${\mu }_I$ plane is constructed and described in detail in terms of chiral and pion condensates. The physics at θ∼π$\theta \sim \pi$ is investigated in both the normal and superfluid phase. Finally, the behaviour of the gluon condensate at finite μI${\mu }_I$ is computed.     

Room-temperature relaxation of the electrical resistance and electrical 1/fα noise observed at very low frequency in the remanent state of glass-ceramics containing magnetite nanoparticles

Slow fluctuations of the electrical resistance R have been systematically observed in three glass-ceramics containing aggregates of magnetite nanoparticles, in measurements where R was studied as a function of time at the magnetic remanence. These fluctuations are shown to be an intrinsic (i.e., not instrumental or spurious) feature of these materials. The associated electrical noise has been obtained by performing a numerical FFT transform of different segments of the R(t) curves after proper baseline subtraction. In this way, the spectral density has been investigated in the very low-frequency region (1×10^?3<f<0.2 Hz), usually not covered in standard noise measurements. The spectral density shows a 1/f^α behaviour (with α?1.6) in all cases. The results are discussed in terms of the existing models about conductance fluctuations in half-metallic oxides in the hopping regime. It is suggested that electron trapping–detrapping mechanisms (thought to be the source of electrical noise) play a relevant role in the hopping processes between adjacent nanoparticle aggregates of magnetite, which dominate the material's resistivity.     

Development of a very low energy μ+ beam at PSI

At PSI we are investigating the technique of decelerating an existing very intense secondary beam of surface ⁺ (4 MeV) to an energy of 10 eV using appropriate moderators. These ⁺ can then be used as a source of a tertiary beam of low energy muons with tunable kinetic energy between 10 eV and 10 keV.With a 1000 A layer of solid Argon deposited on an Al substrate we obtain a moderation efficiency (with respect to the number of incoming surface ⁺) of the order of 10^–4.Results of our investigations and the present status of the project are presented together with future plans and possibilities.     

The Fourier Transform Emission Spectrum of BΠ1-XΣ Band-System of InCl

The emission spectrum of the B³Π₁-X¹Σ⁺ band-system of the InCl molecule has been recorded on a Fourier transform spectrometer at an apodized resolution of 0.025 cm⁻¹. The rotational structure of 1-0, 2-1, 0-0, 0-1, 1-2, 0-2, and 1-3 bands belonging to the B³Π₁-X¹Σ⁺ transition of In³⁵Cl has been analyzed and accurate equilibrium rotational constants of the B³Π₁ state, have been obtained. Precise Λ-doubling constants of the B³Π₁ state (v=0, 1, and 2) are also reported for the first time.     

Magnetic field dependence in electron–deuteron recombination at very low relative energy

The rate coefficient for recombination of D⁺ with low energy electrons has been measured at different magnetic fields in the interaction region of the electron cooler at CRYRING. It is found that the measured recombination rate coefficient is influenced by the magnetic field. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electroproduction of π0-mesons on protons at very low values of |q 2|

The electroproduction of π⁰-mesons on protons has been measured with electrons of 1.7 and 2.1 GeV energy in the region of the nucleon resonances at \(W = \sqrt {(q + p)^2 } = 1,400 - 2,000MeV\) at rather low values of |q ²|=|(e?e′)²|=0.01–0.1 GeV² but at high values of the nucleon recoil |t|=|(p?p′)²|≈0.6–2.2 GeV² corresponding to \(\Theta _\pi ^{cm} \approx 145^ \circ - 180^ \circ\) . Up toW≈1,650 MeV the cross section for π⁰-production with virtual photons of |q ²|≈0.03 GeV² is only slightly smaller than that with real photons. ForW?1,700 MeV the cross section at |q ²|≈0.03 GeV² is on average a factor of 2 smaller than that atq ²=0 but only slightly higher than that at |q ²|≈0.3–1 GeV².     

Intracavity laser absorption spectroscopy of AuO: Identification of the BΣ-XΠ3/2 transition

The visible electronic spectrum of AuO has been recorded at rotational resolution using intracavity laser absorption spectroscopy. Six vibrational bandheads have been identified, and three of the bands have been analyzed and assigned as bands of a newly identified B²Σ⁻-X²Π_3/2 transition of AuO. The molecular parameters for the newly identified B²Σ⁻ state are presented.     

Effect of indium doping on the electrical switching behaviour of Ge–Te glasses

Bulk Ge₁₅Te_85?x In _x (1?≤?x?≤?11) series of glasses have been found to exhibit a threshold switching behaviour for an input current of 2?mA. An initial decrease is seen in the switching voltages (V _T) with the addition of indium, which is due to the higher metallicity of indium. An increase is seen in V _T above 3 at.% of indium, which proceeds until 8 at.%, with a change in slope (lower to higher) seen around 7 at.%. Beyond x?=?8, a reversal in trend is exhibited in the variation of V _T, with a well-defined minimum around x?=?9 at.%. Based on the composition dependence of V _T, it is proposed that Ge₁₅Te_85?x In _x glasses exhibit an extended rigidity percolation threshold. The composition, x?=?3, at which the V _T starts to increase and the composition, x?=?7, at which a slope change is exhibited correspond to the onset and completion, respectively, of the extended stiffness transition. Thermal studies and photoconductivity measurements also support the idea of an extended rigidity percolation in Ge₁₅Te_85?x In _x glasses. In addition, the minimum seen in V _T at x?=?9 is associated with the chemical threshold (CT) of this glassy system.     

Optimization of hydrostatic pressure at varied sonication conditions – power density,intensity, very low frequency – for isothermal ultrasonic sludge treatment

This work aims at investigating for the first time the key sonication (US) parameters: power density (D_US), intensity (I_US), and frequency (F_S) – down to audible range, under varied hydrostatic pressure (P_h) and low temperature isothermal conditions (to avoid any thermal effect).The selected application was activated sludge disintegration, a major industrial US process. For a rational approach all comparisons were made at same specific energy input (ES, US energy per solid weight) which is also the relevant economic criterion.The decoupling of power density and intensity was obtained by either changing the sludge volume or most often by changing probe diameter, all other characteristics being unchanged. Comprehensive results were obtained by varying the hydrostatic pressure at given power density and intensity. In all cases marked maxima of sludge disintegration appeared at optimum pressures, which values increased at increasing power intensity and density. Such optimum was expected due to opposite effects of increasing hydrostatic pressure: higher cavitation threshold then smaller and fewer bubbles, but higher temperature and pressure at the end of collapse.In addition the first attempt to lower US frequency down to audible range was very successful: at any operation condition (D_US, I_US, P_h, sludge concentration and type) higher sludge disintegration was obtained at 12 kHz than at 20 kHz. The same values of optimum pressure were observed at 12 and 20 kHz.At same energy consumption the best conditions – obtained at 12 kHz, maximum power density 720 W/L and 3.25 bar – provided about 100% improvement with respect to usual conditions (1 bar, 20 kHz). Important energy savings and equipment size reduction may then be expected.     

Influence of ageing on the low cycle fatigue behaviour of an Al–Mg–Si alloy

Abstract

The low cycle fatigue (LCF) performance of AA6063 Al–Mg–Si alloy at under-aged (UA), peak-aged (PA) and over-aged (OA) conditions has been examined to understand the micromechanism of fatigue and the associated dynamic structural changes in this alloy. The LCF behaviour of the differently aged AA6063 alloys has been studied at strain amplitudes ranging between 0.2 and 1.0% under strain control mode. The UA state exhibits pronounced cyclic hardening unlike the PA and the OA states at strain amplitudes greater than 0.4%. The PA and the OA states show hardening only for a few cycles followed by prolonged softening. Characterisations of the micro- and the sub-structural alterations due to LCF establish that the phenomenon of dynamic precipitation results in cyclic hardening the UA alloy. The softening of PA alloy occurs due to shearing of precipitates and that in the OA alloy takes place owing to reversibility of slip by the formation and annihilation of the Orowan loops around the β (Mg₂Si) precipitates. Analyses of the hysteresis loops reveal Masing, nearly-Masing and non-Masing behaviour in the UA, OA and PA states, respectively. Analyses of the asymmetry factor of the hysteresis loops assist to infer that the Masing behaviour in the UA alloy is due to dislocation–dislocation interactions, whereas the nearly-Masing behaviour in the OA alloy and the non-Masing behaviour in the PA alloy are the consequence of varying degrees of dislocation–precipitate interactions associated with inhomogeneous deformation.     

Dielectric properties of potassium–sodium niobate ceramics at low frequencies

ABSTRACT

A study of the effects of ageing history on the electrical properties of lead-free ferroelectric ceramics of (K_0.5Na_0.5)(Nb_1?xSb_x)O₃ + 0.5 mol% MnO₂ and (K_0.5Na_0.5)(Nb_1?xTa_x)O₃ + 0.5 mol%MnO₂ for x = 0.05 is reported. The samples after storage at a constant temperature have been subject to infra-low-frequency electric field and radiation. Differences of the photoelectric response between the two examined compounds were found and the restoration of polarisation in the aged ceramic materials by cycles of applied field is discussed.     

Preparation and characterization of low density polystyrene/TiO2 core–shell particles for electronic paper application

In order to reduce the density mismatch between TiO₂ and the low dielectric medium and improve the dispersion stability of the electrophoretic particles in the low dielectric medium for electrophoretic display application, polystyrene/titanium dioxide (PS/TiO₂) core–shell particles were prepared via in-situ sol–gel method by depositing TiO₂ on the PS particle which was positively charged with 2-(methacryloyloxy)ehyl trimethylammonium chloride (DMC). The morphology and average particle size of PS/TiO₂ core–shell particles were observed by transmission electron microscopy (TEM), scanning electron microscope (SEM) and particle size analyzer. It was found that density of PS/TiO₂ core–shell particles were reduced obviously and the particles can suspend in the low dielectric medium of low density. The PS/TiO₂ core–shell particles can endure ultrasonic treatment because of the interaction between TiO₂ and PS. Zeta potential and electrophoretic mobility of the fabricated core–shell particles in a low dielectric medium with charge control agent was measured to be −44.3 mV and −6.07 × 10⁻⁶ cm²/Vs, respectively, which presents potential in electronic paper application.     

Fore-aft asymmetry of the 2H(n,γ)3H at very low energies

We have used the recent effective field theory (EFT) which is constructed from two-and three-nucleon interactions, using minimal substitution in the momentum dependence of these interactions. We present the calculations of the fore-aft asymmetry of γ-rays in the reaction ²H(n,γ)³H which are based on EFT up to next-to-next-to leading order (N²LO). The results are compared with the recently reported calculations and measurements of the fore-aft asymmetry of γ-rays from neutron-deuteron radiative capture. The calculated fore-aft asymmetry of the nd radiative capture process above deuteron breakup threshold is in good agreement with the available experimental data up to 20 MeV.     

The 1-v″ bands progression of the BΣ → XΣ system of CO

The B²Σ⁺ → X²Σ⁺ (0-1, 2, 3, 4 progression) electronic transition of ¹²C¹⁷O⁺ was first observed and analyzed by Szajna and Ke¸pa [Spectrochim. Acta A 65 (2006) 1014-1020]. We have now extended our previous studies. The use of high resolution conventional spectroscopic techniques has allowed first rotational analysis of the 1-2, 1-3, 1-4 and 1-5 bands of the first negative system in the 37,000-43,000 cm⁻¹ spectral region. Approximately 500 transition wavenumbers were measured with an estimated accuracy of 0.005 cm⁻¹. The present data were combined with the previous measurements to yield an improved set of molecular constants for the B²Σ⁺(v′ = 0, 1) and X²Σ⁺(v″ = 1, 2, 3, 4, 5). The v′ = 1 and v″ = 5 vibrational levels were observed for the first time and the main molecular constants are (in cm⁻¹, one standard deviation in parentheses)

B2Σ+		X2Σ+
B1 = 1.710792(20)		B5 = 1.825694(23)
D1 = 7.799(15) × 10−6		D5 = 6.085(21) × 10−6
γ1 = 1.9491(37) × 10−2		γ5 = [8.381] × 10−3

Full-size table