233 research outputs found
Identification of Ion Transport Compartments in Turtle Urinary Bladder
To identify the turtle urinary bladder cells involved in Na and Cl absorption and Hand HCO3 secretion cellular electrolyte concentrations and uptake of Br and Solutrast were determined using electron microprobe analysis. Whereas inhibition of transepithelial Na transport by ouabain (reversion of short circuit current) led to a pronounced K-Na exchange in granular, and most of the basal cells, surface CA-cells and some basal cells were ouabain insensitive. Surface CA-cells could be divided into a large Cl-rich and a small Cl-poor population. Since the ouabain-induced K-Na exchange could be completely prevented by blocking passive luminal Na entry by amiloride, granular and most of the basal cells seem to form a syncytial Na transport compartment. Luminal uptake of Br only occurred in Cl-poor surface CA-cells, indicating the sole responsibility of these cells for electrogenic and electroneutral Cl absorption and HCO3 secretion.
Serosal Br was taken up into all cell types. Whereas H secretion and serosal Br uptake into all cell types could be inhibited by 4-isothiocyano-4\u27-acetamido-2,2\u27-disulfonic stilbene (SITS), blockade of H secretion by lowering luminal pH to 4.5 diminished Br uptake only in Cl-rich surface CA-cells. Theses results indicate: a) Only Cl-rich surface CA-cells have a serosal anion exchanger involved in H secretion and b) granular and basal cells also possess a serosal anion exchanger, possibly responsible for cellular pH regulation.
Luminal endocytosis of the I-containing Solutrast was observed in apical regions of Cl-rich surface CA-cells after inhibition of H secretion, but not under steady-state conditions, indicating a transport related but not a constitutive endo-exocytosis
Garvey-Kelson Relations for Nuclear Charge Radii
The Garvey-Kelson relations (GKRs) are algebraic expressions originally
developed to predict nuclear masses. In this letter we show that the GKRs
provide a fruitful framework for the prediction of other physical observables
that also display a slowly-varying dynamics. Based on this concept, we extend
the GKRs to the study of nuclear charge radii. The GKRs are tested on 455 out
of the approximately 800 nuclei whose charge radius is experimentally known. We
find a rms deviation between the GK predictions and the experimental values of
only 0.01 fm. This should be contrasted against some of the most successful
microscopic models that yield rms deviations almost three times as large.
Predictions - with reliable uncertainties - are provided for 116 nuclei whose
charge radius is presently unknown.Comment: 4 pages and 3 figure
Computer program for the relativistic mean field description of the ground state properties of even-even axially deformed nuclei
A Fortran program for the calculation of the ground state properties of
axially deformed even-even nuclei in the relativistic framework is presented.
In this relativistic mean field (RMF) approach a set of coupled differential
equations namely the Dirac equation with potential terms for the nucleons and
the Glein-Gordon type equations with sources for the meson and the
electromagnetic fields are to be solved self-consistently. The well tested
basis expansion method is used for this purpose. Accordingly a set of harmonic
oscillator basis generated by an axially deformed potential are used in the
expansion. The solution gives the nucleon spinors, the fields and level
occupancies, which are used in the calculation of the ground state properties.Comment: 18 pages, LaTex, 6 p.s figures, To appear in Comput. Phys. Commu
Saturation properties and incompressibility of nuclear matter: A consistent determination from nuclear masses
Starting with a two-body effective nucleon-nucleon interaction, it is shown
that the infinite nuclear matter model of atomic nuclei is more appropriate
than the conventional Bethe-Weizsacker like mass formulae to extract saturation
properties of nuclear matter from nuclear masses. In particular, the saturation
density thus obtained agrees with that of electron scattering data and the
Hartree-Fock calculations. For the first time using nuclear mass formula, the
radius constant =1.138 fm and binding energy per nucleon = -16.11
MeV, corresponding to the infinite nuclear matter, are consistently obtained
from the same source. An important offshoot of this study is the determination
of nuclear matter incompressibility to be 288 28 MeV using
the same source of nuclear masses as input.Comment: 14 latex pages, five figures available on request ( to appear in Phy.
Rev. C
Charge radii and structural evolution in Sr, Zr, and Mo isotopes
The evolution of the ground-state nuclear shapes in neutron-rich Sr, Zr, and
Mo isotopes, including both even-even and odd-A nuclei, is studied within a
self-consistent mean-field approximation based on the D1S Gogny interaction.
Neutron separation energies and charge radii are calculated and compared with
available data. A correlation between a shape transition and a discontinuity in
those observables is found microscopically. While in Sr and Zr isotopes the
steep behavior observed in the isotopic dependence of the charge radii is a
consequence of a sharp prolate-oblate transition, the smooth behavior found in
Mo isotopes has its origin in an emergent region of triaxiality.Comment: 6 pages, 7 figures, to be published in Phys. Lett.
Accurate spectroscopy of Sr atoms
We report the frequency measurement with an accuracy in the 100 kHz range of
several optical transitions of atomic Sr : at 689 nm, at 688 nm and at 679 nm. Measurements are performed with
a frequency chain based on a femtosecond laser referenced to primary frequency
standards. They allowed the indirect determination with a 70 kHz uncertainty of
the frequency of the doubly forbidden 5s^2^1S_0- 5s5p^3P_0 transition of
Sr at 698 nm and in a second step its direct observation. Frequency
measurements are performed for Sr and Sr, allowing the
determination of , and isotope shifts, as well as the
hyperfine constants.Comment: 12 pages, 16 figure
Rare-Earth Nuclei: Radii, Isotope-Shifts and Deformation Properties in the Relativistic Mean Field Theory
A systematic study of the ground-state properties of even-even rare earth
nuclei has been performed in the framework of the Relativistic Mean-Field (RMF)
theory using the parameter set NL-SH. Nuclear radii, isotope shifts and
deformation properties of the heavier rare-earth nuclei have been obtained,
which encompass atomic numbers ranging from Z=60 to Z=70 and include a large
range of isospin. It is shown that RMF theory is able to provide a good and
comprehensive description of the empirical binding energies of the isotopic
chains. At the same time the quadrupole deformations obtained in
the RMF theory are found to be in good agreement with the available empirical
values. The theory predicts a shape transition from prolate to oblate for
nuclei at neutron number N=78 in all the chains. A further addition of neutrons
up to the magic number 82 brings about the spherical shape. For nuclei above
N=82, the RMF theory predicts the well-known onset of prolate deformation at
about N=88, which saturates at about N=102. The deformation properties display
an identical behaviour for all the nuclear chains. A good description of the
above deformation transitions in the RMF theory in all the isotopic chains
leads to a successful reproduction of the anomalous behaviour of the empirical
isotopic shifts of the rare-earth nuclei. The RMF theory exhibits a remarkable
success in providing a unified and microscopic description of various empirical
data.Comment: Revtex (50 pages) and 24 figures (available upon request), Nuclear
Physics A (in press
Experimental Multi-state Quantum Discrimination in the Frequency Domain with Quantum Dot Light
The quest for the realization of effective quantum state discrimination
strategies is of great interest for quantum information technology, as well as
for fundamental studies. Therefore, it is crucial to develop new and more
efficient methods to implement discrimination protocols for quantum states.
Among the others, single photon implementations are more advisable, because of
their inherent security advantage in quantum communication scenarios. In this
work, we present the experimental realization of a protocol employing a
time-multiplexing strategy to optimally discriminate among eight non-orthogonal
states, encoded in the four-dimensional Hilbert space spanning both the
polarization degree of freedom and photon energy. The experiment, built on a
custom-designed bulk optics analyser setup and single photons generated by a
nearly deterministic solid-state source, represents a benchmarking example of
minimum error discrimination with actual quantum states, requiring only linear
optics and two photodetectors to be realized. Our work paves the way for more
complex applications and delivers a novel approach towards high-dimensional
quantum encoding and decoding operations
A Dirac-Hartree-Bogoliubov approximation for finite nuclei
We develop a complete Dirac-Hartree-Fock-Bogoliubov approximation to the
ground state wave function and energy of finite nuclei. We apply it to
spin-zero proton-proton and neutron-neutron pairing within the
Dirac-Hartree-Bogoliubov approximation (we neglect the Fock term), using a
zero-range approximation to the relativistic pairing tensor. We study the
effects of the pairing on the properties of the even-even nuclei of the
isotopic chains of Ca, Ni and Sn (spherical) and Kr and Sr (deformed), as well
as the =28 isotonic chain, and compare our results with experimental data
and with other recent calculations.Comment: 43 pages, RevTex, 13 figure
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