123,646 research outputs found
Supplementary Materials for Schell et al. 2022
No full textSupplementary Materials for Schell et al. 2022. Genetics. Genetic Basis of a Spontaneous Mutation's Expressivit
Shape-invariant anisotropic Gaussian Schell-model beams: a complete characterization
No full textWe present a complete analysis of shape-invariant anisotropic Gaussian Schell-model beams, generalizing the shape-invariant beams introduced earlier by Gori and Guattari (1983) and the recently discovered twisted Gaussian Schell-model beams. We show that the set of all shape-invariant Gaussian Schell-model beams forms a six-parameter family embedded within the ten-parameter family of all anisotropic Gaussian Schell-model beams. These shape-invariant beams are generically anisotropic and possess a saddlelike phase front in addition to a twist phase in such a way that the tendency of the latter to twist the beam in the course of propagation is exactly countered by the former. The propagation characteristics of these beams turn out to be surprisingly simple and are akin to those of coherent Gaussian beams. They are controlled by a single parameter that plays the role of the Rayleigh range; its value is determined by an interplay among the beam widths, transverse coherence lengths, and the strength of the twist parameter. The positivity requirement on the cross-spectral density is shown to be equivalent to an upper bound on the twist parameter. The entire analysis is carried out by use of the Wigner distribution, which reduces the problem to a purely algebraic one involving matrices, thus rendering the complete solution immediately transparent
Shape-invariant anisotropic Gaussian Schell-model beams: a complete characterization
No full textWe present a complete analysis of shape-invariant anisotropic Gaussian Schell-model beams, which generalizes the shape-invariant beams introduced earlier by Gori and Guattari [Opt. Commun. 48, 7 (1983)] and the recently discovered twisted Gaussian Schell-model beams. We show that the set of all shape-invariant Gaussian Schell-model beams forms a six-parameter family embedded within the ten-parameter family of all anisotropic Gaussian Schell-model beams. These shape-invariant beams are generically anisotropic and possess a saddlelike phase front in addition to a twist phase in such a way that the tendency of the latter to twist the beam in the course of propagation is exactly countered by the former. The propagation characteristics of these beams turn out to be surprisingly simple and are akin to those of coherent Gaussian beams. They are controlled by a single parameter that plays the role of the Rayleigh range; its value is determined by an interplay among the beam widths, transverse coherence lengths, and the strength of the twist parameter. The positivity requirement on the cross-spectral density is shown to be equivalent to an upper bound on the twist parameter. The entire analysis is carried out by use of the Wigner distribution, which reduces the problem to a purely algebraic one involving 4×4 matrices, thus rendering the complete solution immediately transparent
Using transformation to study the mechanism of action of plant hormones
No full textSchell Jozef St. Using transformation to study the mechanism of action of plant hormones. In: Bulletin de la Classe des sciences, tome 9, n°7-12, 1998. pp. 361-367
Si Tian'anmen m'était conté... [Mandate of Heaven, de Orville Schell]
No full textMarsouin Jacques. Si Tian'anmen m'était conté... [Mandate of Heaven, de Orville Schell]. In: Perspectives chinoises, n°26, 1994. pp. 71-72
Si Tian'anmen m'était conté... [Mandate of Heaven, de Orville Schell]
No full textMarsouin Jacques. Si Tian'anmen m'était conté... [Mandate of Heaven, de Orville Schell]. In: Perspectives chinoises, n°26, 1994. pp. 71-72
Twisted Gaussian schell-model beams
No full textWe introduce a new class of partially coherent axially symmetric Gaussian Schell-model (GSM) beams incorporating a new twist phase quadratic in configuration variables. This phase twists the beam about its axis during propagation and is shown to be bounded in strength because of the positive semidefiniteness of the crossspectral density. Propagation characteristics and invariants for such beams are derived and interpreted, and two different geometric representations are developed. Direct effects of the twist phase on free propagation as well as in parabolic index fibers are demonstrated. Production of such twisted GSM beams, starting with Li-Wolf anisotropic GSM beams, is described
Twisted Gaussian Schell-model beams
No full textWe introduce a new class of partially coherent axially symmetric Gaussian Schell-model (GSM) beams incorporating a new twist phase quadratic in configuration variables. This phase twists the beam about its axis during propagation and is shown to be bounded in strength because of the positive semidefiniteness of the cross-spectral density. Propagation characteristics and invariants for such beams are derived and interpreted, and two different geometric representations are developed. Direct effects of the twist phase on free propagation as well as on parabolic index fibers are demonstrated. Production of such twisted GSM beams, starting with Li-Wolf anisotropic GSM beams, is described
Exploring mammalian preimplantation development and pluripotency
No full textOur current understanding of how stem cells arise and transition during embryonic development has been limited by analysis tools that have lacked single-cell, whole-genome resolution. This thesis emphasizes the use of novel techniques and cutting-edge technology to better evaluate the biological underpinning of stem cell dynamics in both mouse and human. Development relies on stem cells to establish different lineage potentials from the same starting material. Stem cell populations are produced during embryogenesis at multiple stages, existing in various cellular states. These cells have unique self-renewal properties that allow them to divide without differentiating. Stem cell plasticity becomes more restricted as development progresses. A totipotent stem cell state arises after fertilization once embryo cells can generate exact copies of themselves. Totipotent cells maintain the competency for specification into both embryonic (organism) and extraembryonic (placenta and yolk sack) lineages. Once the mammalian blastocyst is formed, the embryonic lineage is maintained exclusively in epiblast (EPI) cells. Both pre- and postimplantation EPI cells are considered pluripotent stem cells, which lack the capacity for generating extraembryonic tissues but maintain full competency to develop into all embryonic germ lineages. During embryogenesis EPI cells transition through several definable pluripotent states, several of which can be maintained in vitro. This thesis focuses on utilizing better methods for evaluating how well in vitro stem cell culture systems recapitulate endogenous developmental cell types.In Paper I we assessed pre- and postimplantation mouse embryonic stem cells and compared their allelic and transcriptional profiles with developing in vivo cell types. We were able to make unprecedented observations of X chromosome inactivation (XCI) dynamics, elucidating evidence that in vitro mouse XCI does not follow the perceived dogma that preimplantation stem cells express two fully active X chromosomes. By assessing the full length of each X chromosome with allelic resolution we found that XCI is initiated heterogeneously in preimplantation female stem cells with an observable elongated transition between stem cell states. In Paper II we screen two states of human pluripotent stem cells and preimplantation human embryos to define cell surface markers that attempts to effectively separate preimplantation from postimplantation epiblast. The markers provide a sorting method for state conversions. Paper III and IV complement one another in their intent to define the limits of mouse totipotency using transcriptomics and implementation of functional aggregation assays that effectively evaluate lineage specification and commitment. We determined when the first lineage segregation is defined and used an assortment of molecular tools to evaluate embryonic and extraembryonic contribution. This establishes a benchmark for defining totipotency.Together the findings presented in this thesis add significant contribution toward an improved understanding of mammalian embryonic development and stem cell biology.List of scientific papersI. Chen G, SCHELL JP**, Benitez JA, Petropoulos S,Yilmaz M, Reinius B, Alekseenko Z, Shi L, Hedlund E, Lanner F, Sandberg R, Deng Q. (2016). Single-cell analyses of X Chromosome inactivation dynamics and pluripotency during differentiation. Genome Research. 26(10):1342-1354. *First author, **Second author. https://doi.org/10.1101/gr.201954.115 II. Collier AJ*, Panula SP*, SCHELL JP**, Chovanec P, Plaza Reyes A, Petropoulos S, Corcoran AE, Walker R, Douagi I, Lanner F, Rugg-Gunn PJ. (2017). Comprehensive Cell Surface Protein Profiling Identifies Specific Markers of Human Naive and Primed Pluripotent States. Cell Stem Cell. 20(6):874-890.e7. *First author, **Second author. https://doi.org/10.1016/j.stem.2017.02.014 III. Posfai E, Petropoulos S, de Barros F, SCHELL JP, Jurisica I, Sandberg R, Lanner F, Rossant J. (2017). Position- and Hippo signalling-dependent plasticity during lineage segregation in the early mouse embryo. Elife. 6:e22906. https://doi.org/10.7554/eLife.22906 IV. Posfai E*, SCHELL JP*, Adrian Janiszewski*,Isidora R, Murray A, Bradshaw B, Pardon T, Bakkali M, Talon I, Geest N, Kumar P, To S, Petropoulos S, Jurisicova A, Pasque V, Lanner F, Rossant J. (2020). Defining Totipotency Using Criteria of Increasing Stringency. bioRxiv. *First author. [Manuscript] https://doi.org/10.1101/2020.03.02.972893</p
Louisa Schell, Susan Migden Socolow (Ed.), The Countryside in Colonial Latin America
No full textLangue Frédérique. Louisa Schell, Susan Migden Socolow (Ed.), The Countryside in Colonial Latin America. In: Caravelle, n°69, 1997. Ports d'Amérique latine. pp. 280-282
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