A bstract. W e present prelim inary results ofan o -line search fornon-triggered gam m a-ray bursts(G RBs)in the BATSE daily recordsforabout5.7 yearsofobservations. W efound m oreG RB-likeeventsthan theyield ofthesim ilarsearch ofK om m ersetal.(1998)and extended theLog N -log P distribution down to 0.1 ph cm 2 s .The indication ofaturnoverofthelogN -logP ata sm allP is notcon rm ed:the distribution isstraightat1.5 decades with the powerlaw index -.6 and cannotbe tted with a standard candlecosm ologicalm odel.

The article discusses the methods of teaching higher mathematics, arising at the modern level of education in our country. The author relies on his experience working at the Faculty of Information Technologies of the Moscow State Psychological and Pedagogical University.

The emergence of the pairing effect of identical nucleons in the j = 9/2 state in low-lying excited states of nuclei near 90Zr (N = 50, Z = 40) is discussed. Multiplets of states with seniority s ≥ 2, the splitting of which is determined by the proton pairing energy, are clearly visible in the nuclear spectra for a chain of N = 50 isotones. A comparison of the spectra of ground state multiplets, calculated in the δ-interaction approximation, with experimental data and results from other theoretical calculations shows this approach can be used to describe the structure of spectra and level positions with high J values.

The cross sections of partial photoneutron reactions for 98Mo were evaluated. These cross sections are free from the shortcomings of various methods for neutron multiplicity determination used at the beams of quasimonoenergetic annihilation photons and bremsstrahlung radiation. New data on the cross sections of reactions (γ, 1n), (γ, 2n), and (γ, 3n) were obtained using the experimental–theoretical method for evaluation of cross sections of partial reactions satisfying the introduced physical reliability criteria. It is demonstrated that considerable deviations of the experimental cross sections from the evaluated ones result from an inaccurate sorting of neutrons between channels with a multiplicity of 1, 2, and 3.

The ground state multiplet structure for nuclei over the wide range of mass number A was calculated in δ-approximation and different mass relations for pairing energy were analysed in this work. Correlation between the calculated multiplet structure and experimental data offers a guideline in deciding between mass relations for nucleon pairing.

The pairing interaction of neutrons and protons in calcium isotopes and N = 28 isotones is considered. Ground state multiplets formed by neutrons and protons on the 1f 7/2 subshell with seniority values ν = 2, 3, 4 are investigated. Good agreement between the multiplet splitting value and nucleon pairing energies is shown not only for multiplets with seniorities ν = 2, but for higher seniority values as well.

Pairing forces between nucleons in an atomic nucleus strongly influence its structure. One of the manifestations of pair interaction is the ground state multiplet (GSM) formation in the spectrum of low-lying excited states of even–even nuclei. The value of GSM splitting is determined by the value of pair interaction of nucleons; for each isotope, it can be estimated on the basis of experimental nuclear masses. The quality of this estimate is characterized by the degree of reproduction of GSM levels in the nucleus. The GSM systematics in even–even nuclei with a pair of identical nucleons in addition to the filled nuclear core is considered on the basis of delta interaction.

In addition to the results obtained earlier for the isotopes 188,189Os, experimental data on the photodisintegration of the isotopes 186,190,192Os are analyzed on the basis of specially introduced objective criteria of reliability of data on the cross sections for partial photoneutron reactions. It is found that the (γ, 1n), (γ, 2n), and (γ, 3n) cross sections for each isotope satisfy differently or, on the contrary, do not satisfy the data-reliability criteria. In many cases, the multiplicity transition functions specified as the ratios F i = σ(γ, in)/σ(γ, xn) of the cross sections for the (γ, in) partial reactions to the neutron-yield reaction cross section σ(γ, xn) = σ(γ, 1n) + 2σ(γ, 2n) + 3σ(γ, 3n) +... have values that are physically unreliable by definition. It is shown that ambiguities in the dependence of significant systematic uncertainties in experimentally determined neutron multiplicities on the measured kinetic energies is the reason for this. The dependence of these uncertainties on the energy spectra of neutrons is analyzed. For the isotopes 186,190,192Os, new evaluated data satisfying the data-reliability criteria are obtained for the cross sections for partial and total photoneutron reactions.

The pairing interaction between nucleons has a strong effect on the structure of an atomic nucleus. The most precise estimate of the magnitude of pairing forces is obtained by determining it for every isotope, based on the masses of the nuclei. The quality of this estimate is characterized by the degree of reconstruction for levels of the nucleus ground state multiplet (GSM). In this work, GSMs for even-even nuclei with pairs of identical nucleons over a filled core are considered on the basis of the delta interaction. Calculations of the GSM structure for isobar nuclei A = 42 and A = 134 show that analyzing GSM in the case of np pairing yields additional information on the correlation between isoscalar and isovector components in the structure of pairing forces.

Experimental data on 91,94Zr photodisintegration that were obtained in a beam of quasimonoenergetic annihilation photons by the method of neutron multiplicity sorting are analyzed. It is found that the cross sections for the (γ, 1n), (γ, 2n), and (γ, 3n) reactions on both isotopes do not meet the objective data-reliability criteria formulated earlier. Within the experimental–theoretical method for evaluating partial-reaction cross sections that satisfy these criteria, new data on the cross sections for the aforementioned partial reactions, as well as for the (γ, sn) = (γ, 1n) + (γ, 2n) + (γ, 3n) +... total photoneutron reaction, are obtained for the isotopes 91,94Zr.

In addition to the results obtained earlier for the isotopes Os, experimental data on the photodisintegration of the isotopes Os are analyzed on the basis of specially introduced objective criteria of reliability of data on the cross sections for partial photoneutron reactions. It is found that the (γ, 1n), (γ, 2n), and (γ, 3n) cross sections for each isotope satisfy differently or, on the contrary, do not satisfy the data-reliability criteria. In many cases, the multiplicity transition functions specified as the ratios Fi = σ(γ, in)/σ(γ, xn) of the cross sections for the (γ, in) partial reactions to the neutron-yield reaction cross section σ(γ, xn) = σ(γ, 1n) + 2σ(γ, 2n) + 3σ(γ, 3n) + . . . have values that are physically unreliable by definition. It is shown that ambiguities in the dependence of significant systematic uncertainties in experimentally determined neutron multiplicities on the measured kinetic energies is the reason for this. The dependence of these uncertainties on the energy spectra of neutrons is analyzed. For the isotopes Os, new evaluated data satisfying the data-reliability criteria are obtained for the cross sections for partial and total photoneutron reactions. DOI: 10.1134/S1063778815060150