18,411 research outputs found
Transit times through the cycle phases of jejunal crypt cells of the mouse
Mean transit times as well as variances of the transit times through the individual phases of the cell cycle have been determined for the crypt epithelial cells of the jejunum of the mouse. To achieve this the fraction of labelled mitoses (FLM) technique has been modified by double labelling with [3H] and [14C]thymidine. Mice were given a first injection of [3H]thymidine, and 2 hr later a second injection of [14C]thymidine. This produces a narrow subpopulation of purely 3H-labelled cells at the beginning of G2-phase and a corresponding subpopulation of purely 14C-labelled cells at the beginning of the S-phase. When these two subpopulations progress through the cell cycle, one obtains FLM waves of purely 3H- and purely 14C-labelled mitoses. These waves have considerably better resolution than the conventional FLM-curves. From the temporal positions of the observed maxima the mean transit times of the cells through the individual phases of the cycle can be determined. Moreover one obtains from the width of the individual waves the variances of the transit times through the individual phases. It has been found, that the variances of the transit times through successive phases are additive. This indicates that the transit times of cells through successive phases are independently distributed. This statistical independence is an implicit assumption in most of the models applied to the analysis of FLM curves, however there had previously been no experimental support of this assumption. A further result is, that the variance of the transit time through any phase of the cycle is proportional to the mean transit time. This implies that the progress of the crypt epithelial cells is subject to an equal degree of randomness in the various phases of the cycle
Radiative Penguin Decays of B Mesons: Measurements of B -> K* gamma, B -> K2*(1430) gamma, and Search for B0 -> phi gamma
Electromagnetic radiative penguin decays of the B meson were studied with the
BaBar detector at SLAC's PEP-II asymmetric-energy B Factory. Branching
fractions and isospin asymmetry of the decay B -> K* gamma, branching fractions
of B -> K2*(1430) gamma, and a search for B0 -> phi gamma are presented. The
decay rates may be enhanced by contributions from non-standard model processes.Comment: 5 pages, 3 figures, presented at the 2004 Meeting of the Division of
Particles and Fields of the American Physical Society, Riverside, CA, USA,
August 26-31, 2004, submitted to International Journal of Modern Physics
Structure formation by cosmic strings with a cosmological constant
Final published version.Comment: 4 Page
Superconducting phase formation in random neck syntheses: a study of the Y-Ba-Cu-O system by magneto-optics and magnetometry
Magneto-optical imaging and magnetization measurements were applied to
investigate local formation of superconducting phase effected by a random neck
synthesis in Y-Ba-Cu-O system. Polished pellets of strongly inhomogeneous
ceramic samples show clearly the appearance of superconducting material in the
intergrain zones of binary primary particles reacted under different
conditions. Susceptibility measurements allows evaluation of superconducting
critical temperature, which turned out to be close to that of optimally doped
YBCO.Comment: 6 pages, 11 figure
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