The effect of γ radiation on the determination of the antineutrino angular distribution from experiments on the β decay of polarized neutrons

In experiments on the β decay of polarized neutrons where only the electron and proton momentum distributions are observed and the γ radiation is not registered, the asymmetry factor B of the antineutrino angular distribution cannot be obtained rigorously — the value of B is only estimated on the average by taking into consideration the expectation (mean) value 〈B〉 and the rms deviation ΔB. The resulting unavoidable ambiguities in the determination of B amount to several percent, which is significant for the present-day experimental attempts to obtain B to very high precision ∼(0.1–1)%. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 10, 681–685 (25 May 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

The effect of α, β crystalline structure on the mechanical properties of polypropylene

In order to study the effect of the α,β crystalline structure of polypropylene (PP) on its mechanical properties, it is necessary to prepare samples with variable α/β-phase content but with constant crystallinity and constant spherulite size. With this objective, heat treatment was first defined to be applied to an isotactic PP containing a β nucleating agent in order to achieve these conditions. Then study of the effect of the β-phase content on the tensile properties and fracture behaviour has been done at room temperature. The mechanical properties at fracture were assessed by three-point bending tests and were analysed on the basis of the “Essential Work of Fracture” (EWF). The results show that the elongation at fracture under tensile stress and the “near” Plane-Strain Essential Work of Fracture, w _Ie, increase substantially with the β-phase content. Besides, Young's modulus and the yield stress in tensile tests decrease slowly with the β-phase content. Finally, these results are analysed taking account the differences in structure of the α and β spherulites. Received 18 September 2000 and Received in final form 19 December 2000     

The effect of frenkel defects on the electronic structure of 1T−TiSe2

Using a tight binding formalism the wave vector resolved electronic density of states has been calculated in the coherent potential approximation for an 1 T–TiSe₂ crystal containing Frenkel defects. Additional structure originating from disorder is discussed. An extra peak in the A direction at 1.5 eV binding energy can be traced back to a resonance caused by titanium vacancies.     

The effect of laser surface treatment of Al-Si alloy on the surface hardness and structure

In this paper, some samples of Al-Si alloy with various silicon content were treated by laser beam. The effects on structure, hardness and substructure of samples were investigated. The experimental results show that the primary crystal Al and eutectic silicon in the laser treated samples is got thinning obviously, the mosaic dimension is decreased and the dislocation density is increased.     

The effect of fluorine substitutions on the refractive index properties for π-conjugated calamitic nematic materials

In order to reveal the effect of fluorine substitutions on the refractive index properties for calamitic nematic materials, we carried out a comparative study with respect to non-fluorinated and two types of laterally fluorinated 1,4-bis[4-(hexyloxy)phenyl]ethynylbenzene molecules. Phase transition behaviours were investigated by differential scanning calorimetry and polarised optical microscopy. Additionally, extraordinary and ordinary refractive index and birefringence were evaluated from each single component system. All the analogues exhibited high birefringence values beyond 0.3 at 550 nm, of which an analogue with a fluorine substitution at the central benzene ring showed the highest Δn-value of 0.43. With respect to an analogue with the highest level of fluorination, Δn as well as n_e and n_o values were declined due to decreased order parameter and diluted molecular density. Not only the mesomorphic behaviours but also optical properties strongly relied on the manner of fluorine substitution including the number and position.     

The influence of pressure on the Mössbauer effect

A study was made of the pressure dependence of the intensity of the Mössbauer line, and the dependence of this quantity on the specific volume of the crystal, which has the same form for all these crystals in the first approximation, was derived for regular atomic crystals in the Grüneisen approximation. The change in intensity of the Mössbauer line due to pressure can be converted, except for a multiplication factor, to a change in intensity of this line caused by a change in temperature.     

The power of distinguished limits: A comment on ‘On the two-dimensional instability of square-wave detonations’

The stability of both Chapman-Jouguet and overdriven square-wave detonations is investigated in the limit of a large detonation Mach number and a ratio of specific heats close to one.     

The effect of thermal treatment on the atomic structure of core–shell PtCu nanoparticles in PtCu/C electrocatalysts

Physics of the Solid State - PtCu/C electrocatalysts with bimetallic PtCu nanoparticles were synthesized by successive chemical reduction of Cu2+ and Pt(IV) in a carbon suspension prepared based on...     

The effect of the irradiation of germanium with α-particles on the recombination of current carriers

A study was made of the effect of irradiation with -particles on surface recombination on germanium. An approximative evaluation of the results showed that the position of the energy level of the recombination centre produced by irradiation lies near to the upper edge of the valence band or the lower edge of the conduction band. A value of roughly 3. 10^–12 cm² was obtained for the effective recombination surface produced by the absorption of one -particle.     

The effect of Sc on the superconductivity of the BaYCu oxides

The oxide compounds of Ba_0.6Y_0.4−xSc_xCu (x=0.05−0.35) have been prepared. It was found that the superconducting transition temperatures of the samples vary with the contents of Sc and when Sc>0.325, the samples become nonsuperconducting.     

The Hamiltonian systems on the Poisson structure of the quasi-classical limit of GL q (∞)

We consider the Hamiltonian systems on the Poisson structure of GL() which is introduced from the quantum group GL _q () by the so-called quasi-classical limit of GL _q (). Furthermore, we show that the Toda lattice hierarchy is a Hamiltonian system of this structure.     

The effect of nitrobenzene on the Raman spectra of ribonuclease in aqueous solution

The Raman spectra of the native ribonuclease treated with nitrobenzene in aqueous solution have been obtianed. The conformation of the main chain and the side chain in ribonuclease were studied. Among the amide Ⅰ and amide Ⅲ bands, the characters of β-sheet and random coil structures are clear. The disulfide bridges assume the gauche-gauche-gauche conformation. The parts of tyrosine residue are buried. It indicates that nitrobenzene treatment on protein aqueous solution is an efficient means for obtaining better Raman spectra.     

The effect of the superconducting–normal proximity on the Josephson tunneling of high-Tc superconductors

The Josephson coupling between two identical high-temperature superconductors was studied theoretically based on a superconducting–normal (SN) bilayer model with s+id-wave pairing in the S layer. It is indicated that due to the proximity effect between S and N layers as the interlayer hopping t_⊥ decreases, the product of the tunneling current through the junction and the normal-state resistance of the junction can be substantially reduced from the value described by the Ambegaokar–Baratoff (AB) theory. Our theoretical result is in good agreement with the experiments.     

The effect of high-frequency acoustic wave vibration pattern on HKUST’s multi-level pore structure

The physical properties of materials are critical to their functionality, and the ability to control these properties using external forces is a significant challenge. In this study, we investigate the effect of three high frequency acoustic wave vibration patterns on the structure and morphology of MOF particles. Our results indicate that while regular vibration patterns generated by SAW can alter particle morphology, hybrid waves and Lamb waves with irregular vibration patterns can synthesise MOF crystals with multi-level pores. The vibration pattern of acoustic waves is shown to be a critical factor in controlling the particle morphology process. These results provide new insights into the precise control of crystal structure and the theory of crystallisation by particle attachment (CPA).     

Baseline drift effect on the performance of neutron and γ ray discrimination using frequency gradient analysis

Frequency gradient analysis (FGA) effectively discriminates neutrons and γ rays by examining the frequency-domain features of the photomultiplier tube anode signal. This approach is insensitive to noise but is inevitably affected by the baseline drift similar to other pulse shape discrimination methods. The baseline drift effect is attributed to factors such as power line fluctuation, dark current, noise disturbances, hum, and pulse tail in front-end electronics. This effect needs to be elucidated and quantified before the baseline shift can be estimated and removed from the captured signal. Therefore, the effect of baseline shift on the discrimination performance of neutrons and γ rays with organic scintillation detectors using FGA is investigated in this paper. The relationship between the baseline shift and discrimination parameters of FGA is derived and verified by an experimental system consisting of an americium-beryllium source, a BC501A liquid scintillator detector, and a 5 GSample/s 8-bit oscilloscope. The theoretical and experimental results both show that the estimation of the baseline shift is necessary, and the removal of baseline drift from the pulse shapes can improve the discrimination performance of FGA.     

Refractive index of silicon at γ ray energies

For x rays the real part of the refractive index, dominated by Rayleigh scattering, is negative and converges to zero for higher energies. For γ rays a positive component, related to Delbrück scattering, increases with energy and becomes dominating. The deflection of a monochromatic γ beam due to refraction was measured by placing a Si wedge into a flat double crystal spectrometer. Data were obtained in an energy range from 0.18?MeV to 2?MeV. The data are compared to theory, taking into account elastic and inelastic Delbrück scattering as well as recent results on the energy dependence of the pair creation cross section. Probably a new field of γ optics with many new applications opens up.     

The effect of gamma-ray irradiation on the electrical conductivity of CuO–PbO glasses

The effect of gamma-ray irradiation on the dc electrical conductivity of CuO–PbO glasses has been studied as a function of temperature. A 33% CuO–67% PbO glass composition has been prepared, using the melt-quenching technique. The samples have been irradiated to a dose of 0.5 MGy using a ⁶⁰Co γ-source. The electrical conductivity of this glass composition was investigated before and after gamma-ray irradiation. The values of the dc electrical conductivity have been measured from 303 to 373 K, and the activation energy of samples before and after gamma irradiation has been calculated. The observed data show that the electrical conductivity increases with temperature and following gamma irradiation. The electrical conductivity of CuO–PbO can be interpreted in terms of mixed ionic–electronic conduction.     

Baseline drift effect on the performance of neutron and γ ray discrimination using frequency gradient analysis

Frequency gradient analysis (FGA) effectively discriminates neutrons and γ rays by examining the frequency-domain features of the photomultiplier tube anode signal. This approach is insensitive to noise but is inevitably affected by the baseline drift similar to other pulse shape discrimination methods. The baseline drift effect is attributed to factors such as power line fluctuation, dark current, noise disturbances, hum, and pulse tail in front-end electronics. This effect needs to be elucidated and quantified before the baseline shift can be estimated and removed from the captured signal. Therefore, the effect of baseline shift on the discrimination performance of neutrons and γ rays with organic scintillation detectors using FGA is investigated in this paper. The relationship between the baseline shift and discrimination parameters of FGA is derived and verified by an experimental system consisting of an americium-beryllium source, a BC501A liquid scintillator detector, and a 5 GSample/s 8-bit oscilloscope. The theoretical and experimental results both show that the estimation of the baseline shift is necessary, and the removal of baseline drift from the pulse shapes can improve the discrimination performance of FGA.     

Effects of γ rays irradiation on structure and property of TiO2 thin films

TiO₂ thin films were deposited on a glass substrate by the radio frequency magnetron sputtering method, and annealed for 2 h at temperatures of 550°C. Then, ⁶⁰Co γ rays with different doses were used to irradiate the resulting TiO₂ thin films. The surface features of films before and after irradiation were observed by scanning electron microscope (SEM). Simultaneously, the crystal structure and optical properties of films before and after irradiation were studied by X-ray diffraction (XRD), UV–VIS transmission spectrum and Photoluminescence (PL) spectrum, respectively. The SEM analysis shows that the film is smooth with tiny particles on the film surface, and non-crystallization trend was clear after irradiated with γ rays. The XRD results indicated that the structure of the film at the room temperature mainly exists in the form of amorphous and mixed crystal at a sputtering power of 200 W, and non-crystallinity was more obvious after irradiation. Obvious difference can be found for the transmissibility of the irradiated and pre irradiation TiO₂ films by the UV-VIS spectra. The color becomes light yellow, and the new absorption edge also appeared at about 430 nm. PL spectra and photocatalysis experiments indicate that the photocatalysis degradation rate of the TiO₂ films on methylthionine chloride solution irradiated with the maximum dose can be increased to 90%.