Superconductivity in ropes of single-walled carbon nanotubes

We report measurements on ropes of single-walled carbon nanotubes (SWNT) in low-resistance contact to nonsuperconducting (normal) metallic pads, at low voltage and at temperatures down to 70 mK. In one sample, we find a 2 orders of magnitude resistance drop below 0.55 K, which is destroyed by a magnetic field of the order of 1 T, or by a dc current greater than 2.5 microA. These features strongly suggest the existence of superconductivity in ropes of SWNT.     

Cluster model of defective solid solutionsMe_{c_1 }^{(1)} Me_{c_2 }^{(2)} B_x^{(1)} B_y^{(2)}

In a cluster model of defective solid solutions the cluster components are determined and their concentration is found as a function of the defectiveness for solutions \(Me_{c_1 }^{(1)} Me_{c_2 }^{(2)} B_x^{(1)} B_y^{(2)}\) in the case of limited and unlimited solubility. An interpretation is given of the dependence of the lattice parameter, magnetic moment, and Curie point on the composition in a cluster component model, using the example of oxycarbides, oxynitrides, and solutions of certain metals in Mn₄N.     

Microscopic description of low-energy neutron scattering on a deuteron

Low-energy neutron-deuteron scattering is calculated within the collective adiabatic approach by using a few versions of realistic NN interaction. The resulting integrated cross sections for the process are in good agreement with experimental data.     

Influence of dispersion conditions and nature of the emulsifier on the dispersity and stability of artificial polymer suspensions based on polyetherimide

New methods for producing artificial polyetherimide suspensions in the presence of domestic cationic surfactants, their mixtures, and mixtures of cationic and organosilicon surfactants were proposed. The effect of the polymer concentration in the initial solution and conditions of emulsion dispersion on the stability and particle size of the final polymer suspensions is shown. The colloidal chemical properties of the obtained polymer suspensions are considered. Conclusions about the influence of the nature and concentration of surfactants on the stability of the obtained suspensions are drawn. When using a mixture of cationic and organosilicon surfactants, polymer suspensions stable during production and storage are formed, which is explained by the formation of structural mechanical and electrostatic stability barriers in the surface layers of the particles.

     

Standard bases concordant with the norm and computations in ideals and polylinear recurring sequences

Standard bases of ideals of the polynomial ring R[X] = R[x ₁, …, x _k ] over a commutative Artinian chain ring R that are concordant with the norm on R have been investigated by D. A. Mikhailov, A. A. Nechaev, and the author. In this paper we continue this investigation. We introduce a new order on terms and a new reduction algorithm, using the coordinate decomposition of elements from R. We prove that any ideal has a unique reduced (in terms of this algorithm) standard basis. We solve some classical computational problems: the construction of a set of coset representatives, the finding of a set of generators of the syzygy module, the evaluation of ideal quotients and intersections, and the elimination problem. We construct an algorithm testing the cyclicity of an LRS-family L _R (I), which is a generalization of known results to the multivariate case. We present new conditions determining whether a Ferre diagram $\mathcal{F}$ and a full system of $\mathcal{F}$ -monic polynomials form a shift register. On the basis of these results, we construct an algorithm for lifting a reduced Gröbner basis of a monic ideal to a standard basis with the same cardinality.     

Microscopic description of the reactions d + d → p + 3H and d + d → n + 3He at low energies

A collective adiabatic approach is used to explore the total and differential cross sections for the reactions d + d → p + ³H and d + d → n + ³He at incident-deuteron energies of up to 6 MeV. All substantially contributing partial waves of order not higher than that of G waves are taken into account. The experimental value of the difference of the cross sections for the above mirror reactions is reproduced theoretically under the assumption that nuclear forces obey the condition of isotopic invariance. The positions and amplitudes of the maxima in the calculated total cross sections virtually coincide with those of the corresponding experimental values. It is shown that, around the maxima of the cross sections under study, dominant contributions to them come from the P wave. The sensitivity of observables to the parameters of nucleon-nucleon interaction is analyzed.     

Defect dependence of properties of ordered ABx compounds in the cluster-component method

The possibility is shown of accounting for vacancy ordering in AB_x nonstoichiometric compounds in the cluster-component model. The example of monoxide titanium is considered.     

Decomposition kinetics in Fe–Cu dilute alloys. Monte Carlo simulation using concentration-dependent interactions

A generalization of the statistical (Monte Carlo) simulation technique for determining the structure of alloys is proposed. It takes into account the dependence of effective interactions between the atoms of a dissolved chemical element on their local concentration. Using the ab initio parametrization of the model, the decomposition of the bcc Fe–Cu alloy accompanied by the formation of Cu nanoprecipitates is studied. It is shown that the concentration dependence of effective interactions significantly affects the decomposition kinetics by displacing its onset to longer times in agreement with the experiment.