The Experts below are selected from a list of 74709 Experts worldwide ranked by ideXlab platform

Marcel R Haas - One of the best experts on this subject based on the ideXlab platform.

  • disentangling galaxy environment and host halo mass
    Monthly Notices of the Royal Astronomical Society, 2012
    Co-Authors: Marcel R Haas, Joop Schaye, Akila Jeesondaniel
    Abstract:

    The properties of both observed galaxies and dark matter haloes in simulations depend on their environment. The term “environment” has, however, been used to describe a wide variety of measures that may or may not correlate with each other. Popular measures of environment include, for example, the distance to the N th nearest neighbour, the number density of objects within some distance, or, for the case of galaxies only, the mass of the host dark matter halo. Here we use results from the Millennium simulation and a semi-analytic model for galaxy formation to quantify the relations between different measures of environment and halo mass. We show that the Environmental Parameters used in the observational literature are in effect measures of halo mass, even if they are measured for a fixed stella r mass. The strongest correlation between Environmental density and halo mass arises when the number of objects is counted out to a distance of 1.5 ‐ 2 times the virial radius of the host h alo and when the galaxies/haloes are required to be relatively bright/massive. For observational studies this virial radius is no t easily determined, but the number of neighbours out to 1 ‐ 2 h −1 Mpc gives a similarly strong correlation with halo mass. For the distance to the N th nearest neighbour the (anti-)correlation with halo mass is nearly as strong provided N > 2. We demonstrate that this Environmental Parameter becomes insensitive to halo mass if it is constructed from dimensionless quantities. This can be achieved by scaling the minimum luminosity/mass of neighbours to that of the object that the environment is determined for and by dividing the distance to a length scale associated with either the neighbour or the galaxy under consideration. We show how such a halo mass independent Environmental Parameter can be defin ed for both observational and numerical studies. The results presented here will help fut ure studies to disentangle the effects of halo mass and external environment on the properties of galaxies and dark matter haloes.

  • disentangling galaxy environment and host halo mass
    arXiv: Cosmology and Nongalactic Astrophysics, 2011
    Co-Authors: Marcel R Haas, Joop Schaye, Akila Jeesondaniel
    Abstract:

    [Abridged] The properties of observed galaxies and dark matter haloes in simulations depend on their environment. The term environment has been used to describe a wide variety of measures that may or may not correlate with each other. Popular measures of environment include the distance to the N'th nearest neighbour, the number density of objects within some distance, or the mass of the host dark matter halo. We use results from the Millennium simulation and a semi-analytic model for galaxy formation to quantify the relations between environment and halo mass. We show that the Environmental Parameters used in the observational literature are in effect measures of halo mass, even if they are measured for a fixed stellar mass. The strongest correlation between environment and halo mass arises when the number of objects is counted out to a distance of 1.5-2 times the virial radius of the host halo and when the galaxies/haloes are required to be relatively bright/massive. For observational studies the virial radius is not easily determined, but the number of neighbours out to 1-2 Mpc/h gives a similarly strong correlation. For the distance to the N'th nearest neighbour the correlation with halo mass is nearly as strong provided N>2. We demonstrate that this Environmental Parameter becomes insensitive to halo mass if it is constructed from dimensionless quantities. This can be achieved by scaling the minimum luminosity/mass of neighbours to that of the object in question and by dividing the distance to a length scale associated with either the neighbour or the galaxy under consideration. We show how such a halo mass independent Environmental Parameter can be defined for observational and numerical studies. The results presented here will help future studies to disentangle the effects of halo mass and external environment on the properties of galaxies and dark matter haloes.

Mirjam Fröhlich - One of the best experts on this subject based on the ideXlab platform.

  • Hypoxia and stem cell-based engineering of mesenchymal tissues
    Biotechnology progress, 2017
    Co-Authors: Mirjam Fröhlich, Warren L. Grayson, Teng Ma, Gordana Vunjak-novakovic
    Abstract:

    Stem cells have the ability for prolonged self-renewal and differentiation into mature cells of various lineages, which makes them important cell sourcesfor tissue engineering applications. Their remarkable ability to replenish and differentiate in vivo is regulated by both intrinsic and extrinsic cellular mechanisms. The anatomical location where the stem cells reside, known as the "stem cell niche or microenvironment," provides signals conducive to the maintenance of definitive stem cell properties. Physiologicalcondition including oxygen tension is an important component of the stem cell microenvironment and has been shown to play a role in regulatingboth embryonic and adult stem cells. This review focuses on oxygen as a signaling molecule and the way it regulates the stem cells' development into mesenchymal tissues in vitro. The physiological relevance of low oxygen tension as an Environmental Parameter that uniquely benefits stem cells' expansion and maintenance is described along with recent findings on the regulatory effects of oxygen on embryonic stem cells and adult mesenchymal stem cells. The relevance to tissue engineering is discussed in the context ofthe need to specifically regulate the oxygen content in the cellular microenvironment in order to optimize in vitro tissue development.

  • hypoxia and stem cell based engineering of mesenchymal tissues
    Biotechnology Progress, 2009
    Co-Authors: Warren L. Grayson, Mirjam Fröhlich, Gordana Vunjaknovakovic
    Abstract:

    Stem cells have the ability for prolonged self-renewal and differentiation into mature cells of various lineages, which makes them important cell sources for tissue engineering applications. Their remarkable ability to replenish and differentiate in vivo is regulated by both intrinsic and extrinsic cellular mechanisms. The anatomical location where the stem cells reside, known as the “stem cell niche or microenvironment,” provides signals conducive to the maintenance of definitive stem cell properties. Physiological condition including oxygen tension is an important component of the stem cell microenvironment and has been shown to play a role in regulating both embryonic and adult stem cells. This review focuses on oxygen as a signaling molecule and the way it regulates the stem cells' development into mesenchymal tissues in vitro. The physiological relevance of low oxygen tension as an Environmental Parameter that uniquely benefits stem cells' expansion and maintenance is described along with recent findings on the regulatory effects of oxygen on embryonic stem cells and adult mesenchymal stem cells. The relevance to tissue engineering is discussed in the context of the need to specifically regulate the oxygen content in the cellular microenvironment in order to optimize in vitro tissue development. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009

Warren L. Grayson - One of the best experts on this subject based on the ideXlab platform.

  • Hypoxia and stem cell-based engineering of mesenchymal tissues
    Biotechnology progress, 2017
    Co-Authors: Mirjam Fröhlich, Warren L. Grayson, Teng Ma, Gordana Vunjak-novakovic
    Abstract:

    Stem cells have the ability for prolonged self-renewal and differentiation into mature cells of various lineages, which makes them important cell sourcesfor tissue engineering applications. Their remarkable ability to replenish and differentiate in vivo is regulated by both intrinsic and extrinsic cellular mechanisms. The anatomical location where the stem cells reside, known as the "stem cell niche or microenvironment," provides signals conducive to the maintenance of definitive stem cell properties. Physiologicalcondition including oxygen tension is an important component of the stem cell microenvironment and has been shown to play a role in regulatingboth embryonic and adult stem cells. This review focuses on oxygen as a signaling molecule and the way it regulates the stem cells' development into mesenchymal tissues in vitro. The physiological relevance of low oxygen tension as an Environmental Parameter that uniquely benefits stem cells' expansion and maintenance is described along with recent findings on the regulatory effects of oxygen on embryonic stem cells and adult mesenchymal stem cells. The relevance to tissue engineering is discussed in the context ofthe need to specifically regulate the oxygen content in the cellular microenvironment in order to optimize in vitro tissue development.

  • hypoxia and stem cell based engineering of mesenchymal tissues
    Biotechnology Progress, 2009
    Co-Authors: Warren L. Grayson, Mirjam Fröhlich, Gordana Vunjaknovakovic
    Abstract:

    Stem cells have the ability for prolonged self-renewal and differentiation into mature cells of various lineages, which makes them important cell sources for tissue engineering applications. Their remarkable ability to replenish and differentiate in vivo is regulated by both intrinsic and extrinsic cellular mechanisms. The anatomical location where the stem cells reside, known as the “stem cell niche or microenvironment,” provides signals conducive to the maintenance of definitive stem cell properties. Physiological condition including oxygen tension is an important component of the stem cell microenvironment and has been shown to play a role in regulating both embryonic and adult stem cells. This review focuses on oxygen as a signaling molecule and the way it regulates the stem cells' development into mesenchymal tissues in vitro. The physiological relevance of low oxygen tension as an Environmental Parameter that uniquely benefits stem cells' expansion and maintenance is described along with recent findings on the regulatory effects of oxygen on embryonic stem cells and adult mesenchymal stem cells. The relevance to tissue engineering is discussed in the context of the need to specifically regulate the oxygen content in the cellular microenvironment in order to optimize in vitro tissue development. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009

Gordana Vunjak-novakovic - One of the best experts on this subject based on the ideXlab platform.

  • Hypoxia and stem cell-based engineering of mesenchymal tissues
    Biotechnology progress, 2017
    Co-Authors: Mirjam Fröhlich, Warren L. Grayson, Teng Ma, Gordana Vunjak-novakovic
    Abstract:

    Stem cells have the ability for prolonged self-renewal and differentiation into mature cells of various lineages, which makes them important cell sourcesfor tissue engineering applications. Their remarkable ability to replenish and differentiate in vivo is regulated by both intrinsic and extrinsic cellular mechanisms. The anatomical location where the stem cells reside, known as the "stem cell niche or microenvironment," provides signals conducive to the maintenance of definitive stem cell properties. Physiologicalcondition including oxygen tension is an important component of the stem cell microenvironment and has been shown to play a role in regulatingboth embryonic and adult stem cells. This review focuses on oxygen as a signaling molecule and the way it regulates the stem cells' development into mesenchymal tissues in vitro. The physiological relevance of low oxygen tension as an Environmental Parameter that uniquely benefits stem cells' expansion and maintenance is described along with recent findings on the regulatory effects of oxygen on embryonic stem cells and adult mesenchymal stem cells. The relevance to tissue engineering is discussed in the context ofthe need to specifically regulate the oxygen content in the cellular microenvironment in order to optimize in vitro tissue development.

Gordana Vunjaknovakovic - One of the best experts on this subject based on the ideXlab platform.

  • hypoxia and stem cell based engineering of mesenchymal tissues
    Biotechnology Progress, 2009
    Co-Authors: Warren L. Grayson, Mirjam Fröhlich, Gordana Vunjaknovakovic
    Abstract:

    Stem cells have the ability for prolonged self-renewal and differentiation into mature cells of various lineages, which makes them important cell sources for tissue engineering applications. Their remarkable ability to replenish and differentiate in vivo is regulated by both intrinsic and extrinsic cellular mechanisms. The anatomical location where the stem cells reside, known as the “stem cell niche or microenvironment,” provides signals conducive to the maintenance of definitive stem cell properties. Physiological condition including oxygen tension is an important component of the stem cell microenvironment and has been shown to play a role in regulating both embryonic and adult stem cells. This review focuses on oxygen as a signaling molecule and the way it regulates the stem cells' development into mesenchymal tissues in vitro. The physiological relevance of low oxygen tension as an Environmental Parameter that uniquely benefits stem cells' expansion and maintenance is described along with recent findings on the regulatory effects of oxygen on embryonic stem cells and adult mesenchymal stem cells. The relevance to tissue engineering is discussed in the context of the need to specifically regulate the oxygen content in the cellular microenvironment in order to optimize in vitro tissue development. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009