Theory of collective opinion shifts: from smooth trends to abrupt swings

We unveil collective effects induced by imitation and social pressure by analyzing data from three different sources: birth rates, sales of cell phones and the drop of applause in concert halls. We interpret our results within the framework of the Random Field Ising Model, which is a threshold model for collective decisions accounting both for agent heterogeneity and social imitation. Changes of opinion can occur either abruptly or continuously, depending on the importance of herding effects. The main prediction of the model is a scaling relation between the height h of the speed of variation peak and its width w of the form h ∼w^-κ, with κ= 2/3 for well connected populations. Our three sets of data are compatible with such a prediction, with κ≈0.62 for birth rates, κ≈0.71 for cell phones and κ≈0.64 for clapping. In this last case, we in fact observe that some clapping samples end discontinuously (w=0), as predicted by the model for strong enough imitation.     

Radiofrequency-Driven and Slow-Magic-Angle-Sample-Spinning Polarization-Transfer Techniques: A Comparative Study

The rate constant of radiofrequency-driven (RF-driven) polarization transfer and that of polarization transfer under slow-magic-angle sample spinning (S-MAS) are compared using a model system, polycrystalline α-α′-¹³C₂-phthalic acid. While the rate constant under RF irradiation in static samples strongly depends on the orientation of the internuclear vector, the rate constant under S-MAS is hardly sensitive to that orientation and, thus, depends almost exclusively on the internuclear distance. Consequently, polarization-transfer rate constants obtained under S-MAS can be interpreted more simply when used to study local order in polycrystalline or amorphous solids.     

Beta decay of 103Sn

The β decay of ¹⁰³Sn, a three-neutron-particle nucleus with respect to the ¹⁰⁰Sn core, was investigated at the GSI on-line mass separator using an array of 17 germanium crystals and a total absorption spectrometer. A total of 31 β-delayed γ-rays (29 new) of the ¹⁰³Sn →¹⁰³ In decay were observed and, on the basis of β-γ-γ coincidences, the ¹⁰³Sn decay scheme was established for the first time. By means of total absorption spectroscopy, β intensities, the Gamow-Teller strength distribution and the summed Gamow-Teller strength value of 3.5±0.5 were determined for this decay. Its half-life and Q_EC value were found to be 7.0±0.2 s and 7.64±0.7 MeV, respectively. The β-delayed proton branching ratio was measured to be 1.2±0.1%. The results are discussed in comparison with shell-model predictions based on realistic and empirical interactions.     

The calculated spectra of the azanaphthalenes

A modified INDO (intermediate neglect of differential overlap) method is used to calculate the electronic spectra of naphthalene and some mono-, di-, and tetraazanaphthalenes. The technique is capable of reproducing the better classified bands of this series within a rms error of 1000 cm⁻¹.The four lowest π-π^* bands of naphthalene are well represented; a fifth band reported at 52,600 cm⁻¹, and generally assigned ¹B_2u(π-π^*), may be ¹B_3g(π-π^*) borrowing intensity. The lowest excited singlet state calculated for quinoline is n → π^*, estimated nearly degenerate with the lowest π-π^*, while that for isoquinoline is calculated π-π^*; experimental evidence supports the π-π^* assignment in both cases, but the corresponding absorption in quinoline appears complex. Of the diazanaphthalenes examined (with two nitrogens in one benzenoid ring) all are calculated to have one n-π^* transition before the first π-π^* except phthalazine, in which two n-π^* transitions are calculated to be the lowest lying. This is in accord with experimental evidence to date, although the nature of the observation in phthalazine is reinterpreted as one ¹B₂(n-π). 1,4,5,8-tetrazanaphthalene is predicted to have a group theoretically forbidden n-π^* excited state as low as 21,000 cm⁻¹, and should prove interesting experimentally. Even though n-π^* excited states are often calculated to be the lowest lying, none of these compounds are predicted to have an “n” orbital as homo.Further interpretations of the spectra of the azanaphthalenes are made in view of the calculations. Theoretical limitations of the method employed for this study are discussed.     

Statistics of ideal randomly branched polymers in a semi-space

We investigate the statistical properties of a randomly branched 3-functional N-link polymer chain without excluded volume, whose one point is fixed at the distance d from the impenetrable surface in a 3-dimensional space. Exactly solving the Dyson-type equation for the partition function Z(N, d )= N^-θe^γN in 3D, we find the “surface” critical exponent θ = , as well as the density profiles of 3-functional units and of dead ends. Our approach enables to compute also the pairwise correlation function of a randomly branched polymer in a 3D semi-space.     

Gamma-ray spectroscopy of Cr

A study of low-lying states in the self-conjugate nucleus ⁴⁸Cr has been performed with the reaction ⁴⁰Ca(¹⁰B, pnγ)⁴⁸Cr. Several techniques of γ-ray spectroscopy have been used: activity measurements, γ-ray angular distributions, γ-γ coincidences, p-n-γ triple coincidences, and recoil-distance lifetime measurements. The following level energies, spin-parity assignments, and lifetimes have been found: 752.4±0.5 keV, 2₁⁺, τ_m = 9.7±2.6 ps; 1858.7±0.7 keV, 4₁⁺, τ_m = 1.5_−0.5^+2.0 ps; 3532.7±1.2 keV, (6₁⁺); 4064.3±1.3 keV, ( 4), τ_m < 60 ps. The 2₁⁺ state in ⁴⁸Cr is found to have the lowest excitation energy and highest E2 transition strength (33±9 W.u.) among the 2₁⁺ states of even nuclei in the 1f shell.     

Two-dimensional wetting with binary disorder: a numerical study of the loop statistics

We numerically study the wetting (adsorption) transition of a polymer chain on a disordered substrate in 1+1 dimension. Following the Poland-Scheraga model of DNA denaturation, we use a Fixman-Freire scheme for the entropy of loops. This allows us to consider chain lengths of order N ∼10⁵ to 10⁶, with 10⁴ disorder realizations. Our study is based on the statistics of loops between two contacts with the substrate, from which we define Binder-like parameters: their crossings for various sizes N allow a precise determination of the critical temperature, and their finite size properties yields a crossover exponent φ=1/(2-α) ≃0.5. We then analyse at criticality the distribution of loop length l in both regimes l ∼O(N) and 1 ≪l ≪N, as well as the finite-size properties of the contact density and energy. Our conclusion is that the critical exponents for the thermodynamics are the same as those of the pure case, except for strong logarithmic corrections to scaling. The presence of these logarithmic corrections in the thermodynamics is related to a disorder-dependent logarithmic singularity that appears in the critical loop distribution in the rescaled variable λ=l/N as λ↦1.     

Central configurations of nested rotated regular tetrahedra

In this paper we prove that there are only two different classes of central configurations with convenient masses located at the vertices of two nested regular tetrahedra: either when one of the tetrahedra is a homothecy of the other one, or when one of the tetrahedra is a homothecy followed by a rotation of Euler angles α=γ=0 and β=π of the other one.We also analyze the central configurations with convenient masses located at the vertices of three nested regular tetrahedra when one them is a homothecy of the other one, and the third one is a homothecy followed by a rotation of Euler angles α=γ=0 and β=π of the other two.In all of these cases we have assumed that the masses on each tetrahedron are equal but masses on different tetrahedra could be different.     

Low-spin states of doubly odd 184Au

Low-spin states of ¹⁸⁴Au have been studied using the β⁺/EC decay of ¹⁸⁴Hg. γ-ray and conversion-electron singles spectra were recorded with ¹⁸⁴Hg mass-separated sources. For γ-γ-t and X-γ-t coincidence measurements, mercury nuclei were produced in the ¹⁴⁸Sm + ⁴⁰Ar reaction and transported by a He-jet system. The electron spectra were recorded from ¹⁸⁴Hg sources produced at ISOLDE. A level scheme of ¹⁸⁴Au including 48 transitions is proposed. The experimental results are interpreted in the frame of a semi-microscopic axial-rotor-plus-two-quasiparticle model developed in the context of the HF+BCS approximation.     

The possible test of the calculations of nuclear matrix elements of the (ββ)0ν-decay

The existing calculations of the nuclear matrix elements of the neutrinoless double β-decay differ by about a factor three. This uncertainty prevents quantitative interpretation of the results of experiments searching for this process. We suggest here that the observation of the neutrinoless double β-decay of several nuclei could allow to test calculations of the nuclear matrix elements through the comparison of the ratios of the calculated lifetimes with experimental data. It is shown that the ratio of the lifetimes is very sensitive to different models.     

Modified scaling relation for the random-field Ising model

We investigate the low-temperature critical behavior of the three-dimensional random-field Ising ferromagnet. By a scaling analysis we find that in the limit of temperature T → 0 the usual scaling relations have to be modified as far as the exponent α of the specific heat is concerned. At zero temperature, the Rushbrooke equation is modified to α + 2β + γ = 1, an equation which we expect to be valid also for other systems with similar critical behavior. We test the scaling theory numerically for the three-dimensional random-field Ising system with Gaussian probability distribution of the random fields by a combination of calculations of exact ground states with an integer optimization algorithm and Monte Carlo methods. By a finite-size scaling analysis we calculate the critical exponents ν ≈ 1.0, β ≈ 0.05,

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≈ 2.9, γ ≈ 1.5 and α ≈ −0.55.     

Hot particles in industrial waste and mining tailings

Industrial waste was studied concerning its radioactive pollution. Using known properties of the solid state nuclear track detector CR-39 we found among a high concentration of more or less homogeneously distributed single α-tracks discrete spots of very high enrichments of α-particles created by so called hot particles. We will report about the α-activity, the concentration of hot particles and about their ability to be air borne.     

Quantitative Analysis of Protein–Protein Interactions by Native Page/Fluorimaging

We have developed a new quantitative native PAGE mobility shift assay, which allows for the measurement of binding affinities for interacting protein pairs, one of which is fluorescently labelled. We have used it to examine recognition of the Simian virus 40 (SV40) large tumour T-antigen (T-ag) nuclear localisation sequence (NLS) by members of the importin (Imp) superfamily of nuclear transport proteins. We demonstrate that the T-ag NLS binds to the Imp α/β heterodimer in NLS-dependent manner, determining that it binds with eight-fold higher affinity (340 nM), when compared to Imp α alone, consistent with autoinhibition of Imp αwhen not complexed with Imp β. The mobility shift assay is able to detect nM binding affinities, making it a sensitive and useful tool to analyse protein–protein interactions in solution.     

Hartree–Fock versus quantum Monte Carlo study of persistent current in a one-dimensional ring with single scatterer

We calculate the persistent current of interacting spinless electrons in a one-dimensional ring containing a single δ barrier. We use the self-consistent Hartree–Fock method and the quantum Monte Carlo method which gives fully correlated solutions. Our Hartree–Fock method treats the non-local Fock term in a local approximation and also exactly (if the ring is not too large). Treating the Fock term exactly we attempt to support our previous Hartree–Fock result obtained in the local approximation, in particular the persistent current behaving like I∝L^-1-α, where L is the ring length and α>0 is the power depending only on the electron–electron interaction. Finally, we use the Hartree–Fock solutions as an input for our quantum Monte Carlo calculation. The Monte Carlo results exhibit only small quantitative differences from the Hartree–Fock results.     

Formation of frozen α-AgI in superionic glass matrices at ambient temperature by rapid quenching

Superionic conducting phase of α-AgI, which is thermodynamically stable only above 147°C, was successfully frozen at ambient temperature in various kinds of glass matrices in the systems AgI---Ag₂O---M_xO_y (M_xO_y=B₂O₃, GeO₂,P₂O₅ and MoO₃) by a rapid quenching technique. The larger composition regions where α-AgI was frozen were observed in the systems with B₂O₃ and GeO₂ than in the systems with P₂O₅ and MoO₃. Since the glasses with B₂O₃ and GeO₂ have higher glass transition temperature than those with P₂O₅ and MoO₃, the former glasses have higher viscosities at 147° C. The former matrix glasses have stronger effect to depress the α-β transformation of AgI rather than the latter glasses in the course of rapid quenching of melts.     

Electron heating in a submicron-size n GaAs wire

We have studied electron heating in a submicron-size GaAs wire from 4.2 K to 50 K. We find that the energy relaxation rate for the electrons is of the form τ_E⁻¹ = α + βT_eⁿ where α, β are constants and T_e is the electron temperature. We associate the temperature-independent term with a quasi-elastic surface scattering process in which an electron losses 1% of its energy at each collision. The temperature dependent term may be due to electron-phonon scattering. It is possible to fit the data to 2 < n < 3.     

Spin and isospin effects in the NN → NKΛ reaction near threshold

The spin and isospin structure of the amplitudes and observables for K⁺Λ production in nucleon-nucleon collisions in the near-threshold region is analysed. Five experiments are required in order to isolate the amplitudes, up to an overall phase and two discrete ambiguities, in a model-independent way. It is shown that, with reasonable values for the relative strengths of the π and ρ terms in a meson-exchange model, one expects production on the neutron to be significantly stronger than that on the proton. Negative values of the spin-transfer coefficient D_NN are also predicted due to π-ρ interference.     

Ring puckering progressions in the infrared CH2 scissoring region of several deuterated analogs of trimethylene sulfide

Band progressions were observed in the CH₂ scissoring region of the infrared spectra of trimethylene sulfide (TMS) and three of its deuterated analogs (viz., α - d₂, β - d₂, and α, α′ - d₄). These absorptions are assigned to combination tones of CH₂ scissoring fundamentals with the ring puckering mode and its overtones. The scissoring vibrations of the α- and β-methylene groups were identified. Some comments are made regarding the potential governing the puckering mode in the excited states of other vibrations.     

Automated photoelasticity: weighted least-squares determination of field stresses

The three-wavelength approach to phase-stepping photoelasticity as developed by the author is extended to determine automatically full-field stress tensor values. The only need for the user to calibrate the results is to give the material fringe value and the value of a stress at a single point. Four phase-stepped images illuminated by three wavelengths of light, that differ by prescribed increments, are collected using a semi-circular polariscope and an RGB CCD camera. A ramped phase map for the isochromatic parameter (α) is produced in the wrapped range −π/2<απ/2 that can be calibrated automatically. The value of the isoclinic angle (θ) is determined in the wrapped range −π/4<θπ/4. A discrete cosine transform algorithm has been developed to separate the stresses into Cartesian components. A convenience of the method is that accurate results can be obtained using a least-squares error minimisation process. The results obtained from experimental testing of a disc-in-compression specimen using transmission photoelasticity presented in comparison with theoretical solutions demonstrate the accuracy of the new approach.