182 research outputs found
Excitation functions of proton induced reactions on 68Zn from threshold up to 71 MeV, with specific reference to the production of 67Cu
Experimental studies and nuclear model calculations on (p,xn) and (p,pxn) reactions on 85Rb from their threshold up to 100 MeV
Excitation functions were measured by the stacked-foil technique for the reactions Rb-85(p, pxn)Rb-89m,Rb-g83,Rb-82m.81 from their thresholds up to 100MeV. Nuclear model calculations were performed using the code ALICE-IPPE both on (p, xn) reactions reported earlier and (p, pxn) reactions described here. The experimental excitation curves and the results of nuclear model calculations were found to be qualitatively in agreement. With the exception of the (p, n) reaction above 40MeV, the theory appears to reproduce all the experimental data within deviations of about 50%. The cross section ratios for the isomeric pairs Sr-85m,Sr-g and Rb-84m,Rb-g are discussed qualitatively in terms of the spins of the states involved and the increasing projectile energy
On the derivation of the t-J model: electron spectrum and exchange interactions in narrow energy bands
A derivation of the t-J model of a highly-correlated solid is given starting
from the general many-electron Hamiltonian with account of the
non-orthogonality of atomic wave functions. Asymmetry of the Hubbard subbands
(i.e. of ``electron'' and ``hole''cases) for a nearly half-filled bare band is
demonstrated. The non-orthogonality corrections are shown to lead to occurrence
of indirect antiferromagnetic exchange interaction even in the limit of the
infinite on-site Coulomb repulsion. Consequences of this treatment for the
magnetism formation in narrow energy bands are discussed. Peculiarities of the
case of ``frustrated'' lattices, which contain triangles of nearest neighbors,
are considered.Comment: 4 pages, RevTe
Review of the some specific features of the detecting of heavy recoils
In this paper, we present the results of the first beam tests of the
detection system at the focal plane of the Dubna Gas-Filled Recoil Separator-2
(DGFRS-2), which receives beams from the DC-280 FLNR cyclotron. The high beam
intensity of Ca heavy ions from the cyclotron enables us to
obtain a number of superheavy recoils sufficient to compare both the measured
and calculated spectra of superheavy recoils implanted into a silicon detector.
A real-time algorithm to search for an Evaporation Residue (ER) --
correlated sequences is described in brief. It should be noted that the DGFRS-2
spectrometer operates in conjunction with the 48x128 strip DSSD (Double-sided
Silicon Strip Detector; 48x226 mm2) detector and a low-pressure pentane-filled
gaseous detector (1.2 Torr; 80x230 mm). A block-diagram of the spectrometer
and the event format are also presented. Special attention is paid to the
response of a low-pressure pentane-filled DeltaE multiwire proportional chamber
for recoils of Fl, synthesized in the Pu+Ca Fl +3n
complete fusion nuclear reaction. Some actual parameters of the detection
system have also been extracted from Yb + Ca, Th +
Ca, Am + Ca, U + Ca reactions. The effect
of neighbor strip charge sharing for the ohmic side of the DSSD detector is
also under consideration.Comment: 18 page
Elliptic operators on manifolds with singularities and K-homology
It is well known that elliptic operators on a smooth compact manifold are
classified by K-homology. We prove that a similar classification is also valid
for manifolds with simplest singularities: isolated conical points and fibered
boundary. The main ingredients of the proof of these results are: an analog of
the Atiyah-Singer difference construction in the noncommutative case and an
analog of Poincare isomorphism in K-theory for our singular manifolds.
As applications we give a formula in topological terms for the obstruction to
Fredholm problems on manifolds with singularities and a formula for K-groups of
algebras of pseudodifferential operators.Comment: revised version; 25 pages; section with applications expande
Large Rearrangements in Genes Responsible for Familial Adenomatous Polyposis, <i>MUTYH</i>-Associated Polyposis and PeutzâJeghers Syndrome in Russian Patients
Đim: to reveal the rate of large rearrangements in the genes responsible for familial adenomatous polyposis, MUTYH-associated polyposis and PeutzâJeghers syndrome.Materials and methods. The MLPA method was used for identification of large rearrangements. A total number of 135 patients was included in the study: 83 patients with a clinical diagnosis of âfamilial adenomatous polyposisâ, 18 â with suspected MUTYH-associated polyposis, and 34 â with a clinical diagnosis of âPeutzâJeghers syndromeâ.Results. Seven large deletions and one large duplication in the APC gene were identified in 83 patients with classic familial adenomatous polyposis, with rate of large rearrangements 9.6 % (8/83). In 18 patients with suspected MUTYH-associated polyposis, no large rearrangements were found in the MUTYH gene. Four large deletions in the STK11 gene (12 %, 4/34) were detected in 34 patients with PeutzâJeghers syndrome.Conclusion. For the first time, the expediency of including the method of detecting large rearrangements in routine DNA test list for Russian patients with various hereditary polyposis syndromes is demonstrated. Routine use of MLPA method makes it possible to increase the total frequency of detection of pathogenic variants in the APC and STK11 genes above 90 %. At the same time, the need for searching of large rearrangements in the MUTYH gene were not justified
Band spectra of rectangular graph superlattices
We consider rectangular graph superlattices of sides l1, l2 with the
wavefunction coupling at the junctions either of the delta type, when they are
continuous and the sum of their derivatives is proportional to the common value
at the junction with a coupling constant alpha, or the "delta-prime-S" type
with the roles of functions and derivatives reversed; the latter corresponds to
the situations where the junctions are realized by complicated geometric
scatterers. We show that the band spectra have a hidden fractal structure with
respect to the ratio theta := l1/l2. If the latter is an irrational badly
approximable by rationals, delta lattices have no gaps in the weak-coupling
case. We show that there is a quantization for the asymptotic critical values
of alpha at which new gap series open, and explain it in terms of
number-theoretic properties of theta. We also show how the irregularity is
manifested in terms of Fermi-surface dependence on energy, and possible
localization properties under influence of an external electric field.
KEYWORDS: Schroedinger operators, graphs, band spectra, fractals,
quasiperiodic systems, number-theoretic properties, contact interactions, delta
coupling, delta-prime coupling.Comment: 16 pages, LaTe
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