757 research outputs found
Serum selenium concentrations in patients with newly diagnosed lymphoid malignancies
Background. Increased mortality from lymphoid malignancies following exposure to environmental selenium has recently been reported, Moreover, conflicting results have been found in investigations examining the relationship between serum concentrations of selenium and some clinical features of malignant lymphoproliferative diseases. Methods, Serum concentrations of selenium were analyzed by atomic absorption spectrometry in fifty-nine patients with newly diagnosed chronic lymphoid malignancies and in forty control subjects. Results. Selenium concentrations were significantly lower in patients than in control subjects, However, when only patients with localized disease were compared to controls, no significant difference in serum selenium concentrations was observed. Clinical stage was inversely associated with selenium levels. High-grade non-Hodgkin's lymphoma was characterized by lower selenium levels than low-grade and intermediate-grade disease. Selenium levels were positively associated with albumin and hemoglobin, and inversely correlated with serum concentrations of beta 2-microglobulin and with erythrocyte sedimentation rate. Conclusions. The findings of this study do not suggest that a high selenium intake represents a risk factor for malignant lymphoproliferative diseases, but limitations of the investigation hamper evaluation of the results. The possible utility of determining serum concentrations of selenium in the clinical evaluation ofpatients with lymphoid malignancies merits examination in larger studies
Spectroscopy of the odd-odd fp-shell nucleus 52Sc from secondary fragmentation
The odd-odd fp-shell nucleus 52Sc was investigated using in-beam gamma-ray
spectroscopy following secondary fragmentation of a 55V and 57Cr cocktail beam.
Aside from the known gamma-ray transition at 674(5)keV, a new decay at
E_gamma=212(3) keV was observed. It is attributed to the depopulation of a
low-lying excited level. This new state is discussed in the framework of
shell-model calculations with the GXPF1, GXPF1A, and KB3G effective
interactions. These calculations are found to be fairly robust for the
low-lying level scheme of 52Sc irrespective of the choice of the effective
interaction. In addition, the frequency of spin values predicted by the shell
model is successfully modeled by a spin distribution formulated in a
statistical approach with an empirical, energy-independent spin-cutoff
parameter.Comment: accepted for publication in PR
One-neutron knockout in the vicinity of the N=32 sub-shell closure: 9Be(57Cr,56Cr+ gamma)X
The one-neutron knockout reaction 9Be(57Cr,56Cr + gamma)X has been measured
in inverse kinematics with an intermediate-energy beam. Cross sections to
individual states in 56Cr were partially untangled through the detection of the
characteristic gamma-ray transitions in coincidence with the reaction residues.
The experimental inclusive longitudinal momentum distribution and the yields to
individual states are compared to calculations that combine spectroscopic
factors from the full fp shell model and nucleon-removal cross sections
computed in a few-body eikonal approach.Comment: PRC, in pres
Cross-shell excitation in two-proton knockout: Structure of Ca
The two-proton knockout reaction Be(Ti,Ca) has
been studied at 72 MeV/nucleon. Besides the strong feeding of the Ca
ground state, the only other sizeable cross section proceeds to a 3 level
at 3.9 MeV. There is no measurable direct yield to the first excited 2
state at 2.6 MeV. The results illustrate the potential of such direct reactions
for exploring cross-shell proton excitations in neutron-rich nuclei and
confirms the doubly-magic nature of Ca
Large scale shell model calculations for odd-odd Mn isotopes
Large scale shell model calculations have been carried out for odd-odd
Mn isotopes in two different model spaces. First set of calculations
have been carried out in full shell valence space with two recently
derived shell interactions namely GXPF1A and KB3G treating Ca
as core. The second set of calculations have been performed in
valence space with the interaction treating Ca as core and
imposing a truncation by allowing up to a total of six particle excitations
from the 0f orbital to the upper orbitals for protons and
from the upper orbitals to the 0g orbital for neutron. For
low-lying states in Mn, the KB3G and GXPF1A both predicts good results
and for Mn, KB3G is much better than GXPF1A. For negative parity and
high-spin positive parity states in both isotopes interaction is
required. Experimental data on Mn is sparse and therefore it is not
possible to make any definite conclusions. More experimental data on negative
parity states is needed to ascertain the importance of 0g and higher
orbitals in neutron rich Mn isotopes.Comment: 5 pages, 4 figures, Submitted to Eur. Phys. J.
Probing shell structure and shape changes in neutron-rich sulfur isotopes through transient-field g factor measurements on fast radioactive beams of 38S and 40S
The shell structure underlying shape changes in neutron-rich nuclei near N=28
has been investigated by a novel application of the transient field technique
to measure the first-excited state g factors in 38S and 40S produced as fast
radioactive beams. There is a fine balance between proton and neutron
contributions to the magnetic moments in both nuclei. The g factor of deformed
40S does not resemble that of a conventional collective nucleus because spin
contributions are more important than usual.Comment: 10 pages, 6 figures, accepted in PR
Population of bound excited states in intermediate-energy fragmentation reactions
Fragmentation reactions with intermediate-energy heavy-ion beams exhibit a
wide range of reaction mechanisms, ranging from direct reactions to statistical
processes. We examine this transition by measuring the relative population of
excited states in several sd-shell nuclei produced by fragmentation with the
number of removed nucleons ranging from two to sixteen. The two-nucleon removal
is consistent with a non-dissipative process whereas the removal of more than
five nucleons appears to be mainly statistical.Comment: 5 pages, 6 figure
Shell structure underlying the evolution of quadrupole collectivity in S-38 and S-40 probed by transient-field g-factor measurements on fast radioactive beams
The shell structure underlying shape changes in neutron-rich nuclei between
N=20 and N=28 has been investigated by a novel application of the transient
field technique to measure the first-excited state g factors in S-38 and S-40
produced as fast radioactive beams. Details of the new methodology are
presented. In both S-38 and S-40 there is a fine balance between the proton and
neutron contributions to the magnetic moments. Shell model calculations which
describe the level schemes and quadrupole properties of these nuclei also give
a satisfactory explanation of the g factors. In S-38 the g factor is extremely
sensitive to the occupation of the neutron p3/2 orbit above the N=28 shell gap
as occupation of this orbit strongly affects the proton configuration. The g
factor of deformed S-40 does not resemble that of a conventional collective
nucleus because spin contributions are more important than usual.Comment: 10 pages, 36 figures, accepted for publication in Physical Review
Shell structure at N=28 near the dripline: spectroscopy of Si, P and S
Measurements of the N=28 isotones 42Si, 43P and 44S using one- and two-proton
knockout reactions from the radioactive beam nuclei 44S and 46Ar are reported.
The knockout reaction cross sections for populating 42Si and 43P and a 184 keV
gamma-ray observed in 43P establish that the d_{3/2} and s_{1/2} proton orbits
are nearly degenerate in these nuclei and that there is a substantial Z=14
subshell closure separating these two orbits from the d_{5/2} orbit. The
increase in the inclusive two-proton knockout cross section from 42Si to 44S
demonstrates the importance of the availability of valence protons for
determining the cross section. New calculations of the two-proton knockout
reactions that include diffractive effects are presented. In addition, it is
proposed that a search for the d_{5/2} proton strength in 43P via a higher
statistics one-proton knockout experiment could help determine the size of the
Z=14 closure.Comment: Phys. Rev. C, in pres
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