557 research outputs found
Calculating the nuclear mass at finite angular momenta
Mean field methods to calculate the nuclear mass are extended into the high
spin regime to calculate the nuclear binding energy as a function of proton
number, neutron number and angular momentum. Comparing the trend as a function
of mass number for a selection of high-spin states, a similar agreement between
theory and experiment is obtained as for ground state masses.Comment: 4 pages, 3 figure
Polarization Effects in Superdeformed Nuclei
A detailed theoretical investigation of polarization effects in superdeformed
nuclei is performed. In the pure harmonic oscillator potential it is shown that
when one particle (or hole) with the mass single-particle quadrupole moment
q_{nu} is added to a superdeformed core, the change of the electric quadrupole
moment can be parameterized as q_{eff}=e(bq_{nu}+a), and analytical expressions
are derived for the two parameters, and . Simple numerical expressions
for q_{eff}(q_\nu}) are obtained in the more realistic modified oscillator
model. It is also shown that quadrupole moments of nuclei with up to 10
particles removed from the superdeformed core of 152Dy can be well described by
simply subtracting effective quadrupole moments of the active single-particle
states from the quadrupole moment of the core. Tools are given for estimating
the quadrupole moment for possible configurations in the superdeformed A
150-region.Comment: 28 pages including 9 figure
Identical Bands in Superdeformed Nuclei: A Relativistic Description
Relativistic Mean Field Theory in the rotating frame is used to describe
superdeformed nuclei. Nuclear currents and the resulting spatial components of
the vector meson fields are fully taken into account. Identical bands in
neighboring Rare Earth nuclei are investigated and excellent agreement with
recent experimental data is observed.Comment: 11 pages (Latex) and 4 figures (available upon request)
TUM-ITP-Ko93/
Obtainable Sizes of Topologies on Finite Sets
We study the smallest possible number of points in a topological space having
k open sets. Equivalently, this is the smallest possible number of elements in
a poset having k order ideals. Using efficient algorithms for constructing a
topology with a prescribed size, we show that this number has a logarithmic
upper bound. We deduce that there exists a topology on n points having k open
sets, for all k in an interval which is exponentially large in n. The
construction algorithms can be modified to produce topologies where the
smallest neighborhood of each point has a minimal size, and we give a range of
obtainable sizes for such topologies.Comment: Final version, to appear in Journal of Combinatorial Theory, Series
Quasiperiodic Tip Splitting in Directional Solidification
We report experimental results on the tip splitting dynamics of seaweed
growth in directional solidification of succinonitrile alloys with
poly(ethylene oxide) or acetone as solutes. The seaweed or dense branching
morphology was selected by solidifying grains which are oriented close to the
{111} plane. Despite the random appearance of the growth, a quasiperiodic tip
splitting morphology was observed in which the tip alternately splits to the
left and to the right. The tip splitting frequency f was found to be related to
the growth velocity V as a power law f V^{1.5}. This finding
is consistent with the predictions of a tip splitting model that is also
presented. Small anisotropies are shown to lead to different kinds of seaweed
morphologies.Comment: 4 pages, 7 figures, submitted to Physical Review Letter
Enhancing reductive cleavage of aromatic carboxamides
[GRAPHICS] A set of aromatic and especially heteroaromatic N-benzyl carboxamides, derived from naphthalene, pyridine, pyrazine, and quinoline, and the corresponding tert-butyl acylcarbamates have been synthesized and studied by cyclic voltammetry with respect to facilitated reduction. The latter undergo regiospecific cleavage of their C(O)-N bonds under very mild reductive conditions with formation of Boc-protected (benzyl)amine in most cases in nearly quantitative yields, Examples of preparative cleavage by controlled potential electrolysis, activated aluminum, and NaBH4 are given
Microscopic Study of Superdeformed Rotational Bands in 151Tb
Structure of eight superdeformed bands in the nucleus 151Tb is analyzed using
the results of the Hartree-Fock and Woods-Saxon cranking approaches. It is
demonstrated that far going similarities between the two approaches exist and
predictions related to the structure of rotational bands calculated within the
two models are nearly parallel. An interpretation scenario for the structure of
the superdeformed bands is presented and predictions related to the exit spins
are made. Small but systematic discrepancies between experiment and theory,
analyzed in terms of the dynamical moments, J(2), are shown to exist. The
pairing correlations taken into account by using the particle-number-projection
technique are shown to increase the disagreement. Sources of these systematic
discrepancies are discussed -- they are most likely related to the yet not
optimal parametrization of the nuclear interactions used.Comment: 32 RevTeX pages, 15 figures included, submitted to Physical Review
Intracellular Fas ligand in normal and malignant breast epithelium does not induce apoptosis in Fas-sensitive cells
Fas ligand (FasL) is expressed on some cancers and may play a role in the immune evasion of the tumour. We used immuno-histochemistry to study the expression of Fas and FasL in tissue samples from breast cancer patients, as well as normal breast tissue. Our results show that Fas and FasL are co-expressed both in normal tissue and in breast tumours. Fas and FasL mRNA were expressed in fresh normal and malignant breast tissue, as well as cultured breast epithelium and breast cancer cell lines. Flow cytometry analysis of live cells failed to detect FasL on the surface of normal or malignant breast cells; however, both stained positive for FasL after permeabilization. Fas was detected on the surface of normal breast cells and T47D and MCF-10A cell lines but only intracellularly in other breast cell lines tested. Neither normal breast epithelium nor breast cell lines induced Fas-dependent apoptosis in Jurkat cells. Finally, 20 tumour samples were stained for apoptosis. Few apoptotic cells were detected and there was no increase in apoptotic cells on the borders between tumour cells and lymphocytes. We conclude that FasL is expressed intracellularly in both normal and malignant breast epithelium and unlikely to be important for the immune evasion of breast tumours. © 2000 Cancer Research Campaign http://www.bjcancer.co
Time-odd mean fields in the rotating frame: microscopic nature of nuclear magnetism
The microscopic role of nuclear magnetism in rotating frame is investigated
for the first time in the framework of the cranked relativistic mean field
theory. It is shown that nuclear magnetism modifies the expectation values of
single-particle spin, orbital and total angular momenta along the rotational
axis effectively creating additional angular momentum. This effect leads to the
increase of kinematic and dynamic moments of inertia at given rotational
frequency and has an impact on effective alignments.Comment: 16 pages, 4 figures, submitted to Physical Review
- …