Biomedical subjects

M Albiez

Publications and source records attributed to M Albiez.

5 recordsLinked to original sources

PubMed2005

Nonlinear self-trapping of matter waves in periodic potentials.

We report the first experimental observation of nonlinear self-trapping of Bose-condensed 87Rb atoms in a one-dimensional waveguide with a superimposed deep periodic potential . The trapping effect is confirmed directly by imaging the atomic spatial distribution. Increasing the nonlinearity we move the system from the diffusive regime, characterized by an expansion of the condensate, to the nonlinearity dominated self-trapping regime, where the initial expansion stops and the width remains finite. The data are in quantitative agreement with the solutions of the corresponding discrete nonlinear equation. Our results reveal that the effect of nonlinear self-trapping is of local nature, and is closely related to the macroscopic self-trapping phenomenon already predicted for double-well systems.

Journal Article↗

PubMed2004

Bright Bose-Einstein gap solitons of atoms with repulsive interaction.

We report on the first experimental observation of bright matter wave solitons for 87Rb atoms with repulsive atom-atom interaction. This counterintuitive situation arises inside a weak periodic potential, where anomalous dispersion can be realized at the Brillouin zone boundary. If the coherent atomic wave packet is prepared at the corresponding band edge, a bright soliton is formed inside the gap. The strength of our system is the precise control of preparation and real time manipulation, allowing the systematic investigation of gap solitons.

Journal Article↗

PubMed2003

Dispersion management for atomic matter waves.

We demonstrate the control of the dispersion of matter wave packets utilizing periodic potentials. This is analogous to the technique of dispersion management known in photon optics. Matter wave packets are realized by Bose-Einstein condensates of 87Rb in an optical dipole potential acting as a one-dimensional waveguide. A weak optical lattice is used to control the dispersion relation of the matter waves during the propagation of the wave packets. The dynamics are observed in position space and interpreted using the concept of effective mass. By switching from positive to negative effective mass, the dynamics can be reversed. The breakdown of the approximation of constant, as well as experimental signatures of an infinite effective mass are studied.

Journal Article↗

PubMed1989

Selective enrichment and biochemical characterization of seven human skin fibroblasts cell types in vitro.

The mitotic and postmitotic populations of the human skin fibroblast cell line HH-8 are heterogeneous when studied in vitro. There are reproducible changes in the frequencies of the mitotic fibroblasts (MF), MF I, MF II, MF III, and the postmitotic fibroblasts (PMF), PMF IV, PMF V, PMF VI, and PMF VII. For biochemical characterization, methods for selective enrichment of homogeneous populations of these seven fibroblast cell types have been established. Clonal populations with 95% purity for the mitotic fibroblasts MF I, MF II, and MF III can be raised in uniform clone types of fibroblasts (CTF) CTF I, CTF II, and CTF III. Pure clonal subpopulations of MF I type cells are present in mass populations in the range of 1-20 cumulative population doublings (CPD). Populations of mitotic fibroblasts represent nearly homogeneous populations of MF II (75-85% purity) in the range of 28-34 CPD and MF III (73-86% purity) in the range of 48-53 CPD. These populations can be easily expanded to up to 10(7)-10(8) cells. The spontaneous transition of MF III to PMF VI takes 140-180 days. In order to shorten this period and increase the proportion of distinct postmitotic types, mitotic fibroblast mass populations (CPD 30-32, MF II: 75-85% purity) have been induced by uv-irradiation to differentiate to nearly homogeneous populations of PMF IV, PMF V, PMF VI, and PMF VII within 4 to 36 days of culture. Using this method, 10(7) cells of one differentiation stage can be obtained. Spontaneously arising and experimentally selected or induced homogeneous clonal and mass populations of MF I, MF II, MF III, PMF IV, PMF V, PMF VI, and PMF VII express an identical differentiation-dependent and cell-type-specific [35S]methionine-labeled polypeptide pattern.

Cell Differentiation↗

PubMed1988

Human skin fibroblasts in vitro differentiate along a terminal cell lineage.

Secondary mitotic human skin fibroblast populations in vitro underwent 53 +/- 6 cumulative population doublings (CPD) in 302 +/- 27 days. When the growth capacity of the mitotic fibroblasts is exhausted, and if appropriate methods are applied, the fibroblasts differentiate spontaneously into postmitotic fibroblast populations, which were kept in stationary culture for up to 305 +/- 41 additional days. Mitotic and postmitotic fibroblast populations are heterogeneous populations with reproducible changes in the proportions of mitotic fibroblasts F I, F II, and F III, and postmitotic fibroblasts F IV, F V, F VI, and F VII. This process makes it evident that the fibroblasts differentiate spontaneously along a seven-stage terminal cell lineage F I-F II-F III-F IV-F V-F VI-F VII. Shifts in the frequencies of the mitotic and postmitotic fibroblasts in mass populations are accompanied by alterations in the [35S]methionine polypeptide pattern of the developing mass populations. The [35S]methionine polypeptide patterns of homogeneous subpopulations of F I, F II, F III, F IV, F V, and F VI isolated from heterogeneous mass populations reveal that the six fibroblast morphotypes studied express their cell-type-specific [35S]methionine polypeptide pattern in the heterogeneous mass populations.

Animals↗