619 research outputs found
Quasifission at extreme sub-barrier energies
With the quantum diffusion approach the behavior of the capture cross-section
is investigated in the reactions Mo + Mo, Ru +
Ru, Pd + Pd, and Kr + Sn at deep
sub-barrier energies which are lower than the ground state energies of the
compound nuclei. Because the capture cross section is the sum of the complete
fusion and quasifission cross sections, and the complete fusion cross section
is zero at these sub-barrier energies, one can study experimentally the unique
quasifission process in these reactions after the capture.Comment: 3 pages, 3 figure
Azimuthal asymmetries in QCD hard scattering: infrared safe but divergent
We consider high-mass systems of two or more particles that are produced by
QCD hard scattering in hadronic collisions. We examine the azimuthal
correlations between the system and one of its particles. We point out that the
perturbative QCD computation of such azimuthal correlations and asymmetries can
lead to divergent results at fixed perturbative orders. The fixed-order
divergences affect basic (and infrared safe) quantities such as the total cross
section at fixed (and arbitrary) values of the azimuthal-correlation angle
. Examples of processes with fixed-order divergences are heavy-quark
pair production, associated production of vector bosons and jets, dijet and
diboson production. A noticeable exception is the production of high-mass
lepton pairs through the Drell--Yan mechanism of quark-antiquark annihilation.
However, even in the Drell--Yan process, fixed-order divergences arise in the
computation of QED radiative corrections. We specify general conditions that
produce the divergences by discussing their physical origin in fixed-order
computations. We show lowest-order illustrative results for
asymmetries (with ) in top-quark pair production and associated
production of a vector boson and a jet at the LHC. The divergences are removed
by a proper all-order resummation procedure of the perturbative contributions.
Resummation leads to azimuthal asymmetries that are finite and computable. We
present first quantitative results of such a resummed computation for the
asymmetry in top-quark pair production at the LHC.Comment: 43 pages, 5 eps figure
Enzyme activities in brown forest soils after introduction of Bacillus thuringiensis-based bioinsecticides
Much attention in the complex of forest pest control methods nowadays is devoted to the application of biological preparations, especially to bacterial formulations produced on the base of Bacillus thuringiensis (BT) that in addition to their high biological effectiveness against injurious insects are safe for man, homoiоtherms, beneficial insects and fish. As is known only 20-40% of sprayed preparation influences directly on pests while its 60-80% by different ways eventually penetrates into the soil. Taking into account also the fact that usage norm of commercial bacterial preparations makes up to 1-3 kg ha^-1^ and that preparation powder contains 45-100 billion viable spores g^-1^ it becomes evident that as a result of spraying huge quantity of bacterial stimulants introduces into the forest soils. In this connection a goal was set to determine the impact of some separately applied domestic insecticides of BT species (BT кб-1, BT кб-2, BT(SAR)-49, BT(SAR)-54, BT(SAR)-86, BT subsp. thuringiensis) introduced into the brown forest soils after spraying on soil enzymatic activity (invertase, urease) defining its fertility. Studies were conducted in 2010 under laboratory conditions. The results obtained indicate that in soils sprayed and non-sprayed by bioinsecticides the activities of invertase and urease undergo to changes from May to August. Maximal activities in soils were registered in June (25.641mg C~6~H~12~O~6~ g^-1^ for invertase and 12.254 mg NH~3~ g^-1^ for urease) and minimal – in May (20.643 mg C~6~H~12~O~6~ g^-1^ for invertase) and in August (9.297 mg NH~3~ g^-1^ for urease) at the average for all variants. By statistical analysis of study results it has been established that there aren’t any significant differences between indices of enzyme activities in sprayed and non-sprayed by biopesticides soils. Study results have led us to the assumption that tested insecticides don’t influence adversely on enzyme activities of brown forest soils and can be widely used in the field of plant protection
Production of exotic isotopes in complete fusion reactions with radioactive beams
The isotopic dependence of the complete fusion (capture) cross section is
analyzed in the reactions
Xe+Ca with stable and
radioactive beams. It is shown for the first time that the very neutron-rich
nuclei W can be reached with relatively large cross sections by
complete fusion reactions with radioactive ion beams at incident energies near
the Coulomb barrier. A comparison between the complete fusion and fragmentation
reactions for the production of neutron-rich W and neutron-deficient Rn
isotopes is performed.Comment: 13 pages, 6 figures, accepted in PR
Disagreement between capture probabilities extracted from capture and quasi-elastic backscattering excitation functions
Experimental quasi-elastic backscattering and capture (fusion) excitation
functions are usually used to extract the s-wave capture probabilities for the
heavy-ion reactions. We investigated the
O+Sn,Sm,Pb systems at energies near and below
the corresponding Coulomb barriers and concluded that the probabilities
extracted from quasi-elastic data are much larger than the ones extracted from
fusion excitation functions at sub and deep-sub barrier energies. This seems to
be a reasonable explanation for the known disagreement observed in literature
for the nuclear potential diffuseness derived from both methods.Comment: 9 pages, 3 figure
Andragogical and heuthagogical methods for theory and practice of the teaching in engineering university
The article describes the potentiality of andragogical and heuthagogical technologies for increasing the teaching efficiency in the engineering universityΠ ΡΡΠ°ΡΡΠ΅ ΡΠ°ΡΡΠΌΠ°ΡΡΠΈΠ²Π°ΡΡΡΡ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΠΈ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΡ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΠΉ Π°Π½Π΄ΡΠ°Π³ΠΎΠ³ΠΈΠΊΠΈ ΠΈ ΡΠ²ΡΠ°Π³ΠΎΠ³ΠΈΠΊΠΈ Π΄Π»Ρ ΠΏΠΎΠ²ΡΡΠ΅Π½ΠΈΡ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΠΈ ΠΏΡΠ΅ΠΏΠΎΠ΄Π°Π²Π°Π½ΠΈΡ Π² ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ½ΠΎΠΌ Π²ΡΠ·
To the center of cold spot with Planck
The structure of the cold spot, of a non-Gaussian anomaly in the cosmic
microwave background (CMB) sky first detected by Vielva et al. is studied using
the data by Planck satellite. The obtained map of the degree of stochasticity
(K-map) of CMB for the cold spot, reveals, most clearly in 100 GHz band, a
shell-type structure with a center coinciding with the minima of the
temperature distribution. The shell structure is non-Gaussian at a 4\sigma
confidence level. Such behavior of the K-map supports the void nature of the
cold spot. The applied method can be used for tracing voids that have no
signatures in redshift surveys.Comment: A & A (in press), 4 pages, 5 figures; to match the published versio
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