Propagation of thin plastic zones in the vicinity of a normally separating crack

A problem of the development of a plastic zone in the vicinity of a physical cut in the plain strain and stress states is posed and solved on the basis of a discrete deformation model under the assumption of an ideal elastoplastic medium. The Tresca yield condition and the ultimate plasticity condition are used in studying the plane stress state. The dependence of the plastic zone length on the external load is compared with a similar dependence obtained on the basis of the Leonov-Panasyuk-Dugdale model. In contrast to the Leonov-Panasyuk-Dugdale model, the distributions of stresses and lengths of plastic zones in the plane strain and stress states are found to be substantially different if elastic compressibility and compressive-tensile stresses along the cut direction are taken into account.     

Proton-proton and deuteron-deuteron correlations in interactions of relativistic helium nuclei with protons

The reactions⁴Hep pp+X,³Hep pp+X and⁴Hep ddp have been investigated and the correlation function has been measured for protons and deuterons with small relative momenta. Strong positive correlation has been observed for protons related mainly to the final state interactions in¹S₀ state. The root mean square radius of the proton source calculated from the correlation function has been found to be equal to (1.7±0.3) fm and (2.1±0.3) fm for⁴He and³He respectively. It agrees with the known radii of these nuclei.We would like to thank Dr R. Lednicky for discussion, helpful suggestions and for making available the computer program that calculates the theoreticalpp correlation function. The authors also thank Dr D.H. Boal for providing the results of the two-deuteron correlation function calculations.     

Formation of long-lived “colored” spiroantrooxazine isomers incorporated into fluoroplast F-42 matrix in a supercritical carbon dioxide medium

It has been demonstrated that formation of isomeric “colored” merocyanine forms B and B _x of indoline spiroantrooxazine (SAO) introduced into Fluoroplast F-42 matrix from supercritical carbon dioxide (SC-CO₂) depends on the volume concentration of toluene in the medium, which plays a role of an aromatic electron donor cosolvent. It also has been shown that observed dependencies of changes in the content of introduced photochrome forms, forming in the Fluoroplast F-42 matrix, can be described by a scheme which reflects the redistribution kinetics of SAO molecules between the medium (SC-CO₂) and the polymer. In this case, the “blue” form B is formed by SAO molecules solvated by toluene, which localize at specific fragments of the matrix and form triple SAO/F-42/toluene complexes. The “Red” form B _x is formed under the coordination of desolvated SAO molecules, which transfer into the matrix from the SC-CO₂ medium, near F-42 matrix fragments.     

Structure and properties of polymeric ethyne-hexacarbonyldicobalt π complexes

A polymeric ethyne-hexacarbonyldicobalt π complex was prepared by the reaction of poly-p-diethynylbenzene with Co₂(CO)₈. The conformations in which the polymer chains can exist and the conformations in which the ?C≡CH and-Ph-groups can form π complexes with Co₂(CO)₈ were revealed by analysis of Stuart-Briegleb molecular models. The IR spectra of the polymeric complexes were analyzed, and their thermal degradation in air was examined.     

The top quark, others new phenomena observed at the CDF in {ie359-1} collisions at √s = 1.96 TeV (Review)

Upgraded Tevatron luminosity in Run-II (started 2001) has opened a new level of modern heavy-quark studies compared to that one of Run-I. Now top event samples contain hundreds of event statistics for investigation. This review mainly covers the mass measurements of the top quark produced at √s = 1.96 TeV in {ie359-2} collisions at the Collider Detector of Fermilab with the integrated luminosity samples up to 1 fb^?1. As an example of the top quark mass measurements we consider so-called Matrix Element method in “lepton + jets” and “dilepton” channels of the top-quark decay. The CDF top quark mass obtained in lepton +jets mode is the world most precise single measurement of this important physics parameter. The review summarizes the essential results of the CDF top-quark mass measurement achieved and published for the recent 2003–2008 period. We consider also b-quark baryon discoveries like Σ _b , Σ _b ^* , Θ _b as well as first observation of {ie359-3} oscillations. Let us mention here that a CDF/JINR-group created significant contribution to the new CDF complex and physics investigation.     

The deuteron D-state probability

A method of direct determination of the deuteron D-state probability from the experiment, based on the d ↑ p → ppn reaction analyzis is suggested. Using the known results on the vector analyzing power in elastic NN-scattering, the values of the overall nucleon polarization and the deuteron vector polarization have been obtained. The probability of the deuteron D-state is estimated to be w _D = 0.078 ± 0.046.     

Some special features of the momentum spectrum of protons produced in <Superscript>16</Superscript>O<Emphasis Type="Italic">p</Emphasis> collisions at a momentum of 3.25 GeV/<Emphasis Type="Italic">c</Emphasis> per nucleon

The momentum features of protons originating from ¹⁶Op collisions at a momentum of 3.25 GeV/c per nucleon are analyzed. It is shown that the degree of excitation of the fragmenting nucleus affects predominantly the shape of the momentum spectrum of protons emitted into the backward hemisphere in the rest frame of the projectile nucleus and partly the shape of the spectra of protons emitted into the forward hemisphere and formed via the mechanisms of Fermi breakup and evaporation.     

Determining the thermomechanical characteristics of the separation process

The crack growth condition was obtained in [1, 2] from energy considerations and holds for arbitrary nonlinearly elastic materials. This condition is reduced to determining the trajectory-independent transition from one of the shores of the mathematical cut to the other shore in the J-integral. The time when the J-integral attains the critical value corresponds to the initiation of crack motion. In the present paper, we consider the steady-state strip separation process starting from the fundamental thermodynamic relation. The strip material behavior is determined both at the stage of stable (in general, elastoplastic) loading and at the stage of Drucker unsdtable strain until the time at which the interaction between particles ceases. We single out a domain of unstable material strain, i.e., an interaction layer whose initial width is assumed to be a universal constant of the material [3]. The proposed approach permits expressing the material surface energy via the critical thermomechanical parameters (determined from the complete strain diagram) and the interaction layer thickness. We obtain expressions for the critical values of J-integrals. The critical values of J-integrals [4–6] corresponding to nonlinearly elastic and ideally plastic materials follow from general considerations. We have shown that the possibility of using J-integrals as elastoplastic separation criteria depends on the layer thickness of an irreversibly strained material. If the corresponding thickness is independent of the boundary conditions and the body geometry, then it is possible to use the value of the J-integral as a separation criterion; this corresponds to the Irwin-Orowan quasibrittle fracture approach.