17 research outputs found
Bosonization in Higher Dimensions
Using the recently discovered connection between bosonization and duality
transformations (hep-th/9401105 and hep-th/9403173), we give an explicit
path-integral representation for the bosonization of a massive fermion coupled
to a U(1) gauge potential (such as electromagnetism) in d space (D=d+1
spacetime) dimensions. The bosonic theory is described by a rank d-1
antisymmetric Kalb-Ramond-type gauge potential. We construct the bosonized
lagrangian explicitly in the limit of large fermion mass. We find that the
resulting action is local for d=2 (and given by a Chern-Simons action), but
nonlocal for d larger than 3. By coupling to a statistical Chern-Simons field
for d=2, we obtain a bosonized formulation of anyons. The bosonic theory may be
further dualized to a theory involving purely scalars, for any d, and we show
this to be governed by a higher-derivative lagrangian for which the scalar
decouples from the U(1) gauge potential.Comment: (We had omitted some references and had misspelled `aficionados')
plain TeX, 11 pages, McGill-94/33, NEIP-94-006, OSLO-TP 10-9
A hydraulic feedback loop between mesendoderm cell migration and interstitial fluid relocalization promotes embryonic axis formation in zebrafish
Interstitial fluid (IF) accumulation between embryonic cells is thought to be important for embryo patterning and morphogenesis. Here, we identify a positive mechanical feedback loop between cell migration and IF relocalization and find that it promotes embryonic axis formation during zebrafish gastrulation. We show that anterior axial mesendoderm (prechordal plate [ppl]) cells, moving in between the yolk cell and deep cell tissue to extend the embryonic axis, compress the overlying deep cell layer, thereby causing IF to flow from the deep cell layer to the boundary between the yolk cell and the deep cell layer, directly ahead of the advancing ppl. This IF relocalization, in turn, facilitates ppl cell protrusion formation and migration by opening up the space into which the ppl moves and, thereby, the ability of the ppl to trigger IF relocalization by pushing against the overlying deep cell layer. Thus, embryonic axis formation relies on a hydraulic feedback loop between cell migration and IF relocalization
The holographic superconductors in higher-dimensional AdS soliton
We explore the behaviors of the holographic superconductors at zero
temperature for a charged scalar field coupled to a Maxwell field in
higher-dimensional AdS soliton spacetime via analytical way. In the probe
limit, we obtain the critical chemical potentials increase linearly as a total
dimension grows up. We find that the critical exponent for condensation
operator is obtained as 1/2 independently of , and the charge density is
linearly related to the chemical potential near the critical point.
Furthermore, we consider a slightly generalized setup the
Einstein-Power-Maxwell field theory, and find that the critical exponent for
condensation operator is given as in terms of a power parameter
of the Power-Maxwell field, and the charge density is proportional to the
chemical potential to the power of .Comment: LaTeX, 16 pages, 5 figures, typos corrected, one reference added,
version to appear in European Physical Journal
Colloquium: Mechanical formalisms for tissue dynamics
The understanding of morphogenesis in living organisms has been renewed by
tremendous progressin experimental techniques that provide access to
cell-scale, quantitative information both on theshapes of cells within tissues
and on the genes being expressed. This information suggests that
ourunderstanding of the respective contributions of gene expression and
mechanics, and of their crucialentanglement, will soon leap forward.
Biomechanics increasingly benefits from models, which assistthe design and
interpretation of experiments, point out the main ingredients and assumptions,
andultimately lead to predictions. The newly accessible local information thus
calls for a reflectionon how to select suitable classes of mechanical models.
We review both mechanical ingredientssuggested by the current knowledge of
tissue behaviour, and modelling methods that can helpgenerate a rheological
diagram or a constitutive equation. We distinguish cell scale ("intra-cell")and
tissue scale ("inter-cell") contributions. We recall the mathematical framework
developpedfor continuum materials and explain how to transform a constitutive
equation into a set of partialdifferential equations amenable to numerical
resolution. We show that when plastic behaviour isrelevant, the dissipation
function formalism appears appropriate to generate constitutive equations;its
variational nature facilitates numerical implementation, and we discuss
adaptations needed in thecase of large deformations. The present article
gathers theoretical methods that can readily enhancethe significance of the
data to be extracted from recent or future high throughput
biomechanicalexperiments.Comment: 33 pages, 20 figures. This version (26 Sept. 2015) contains a few
corrections to the published version, all in Appendix D.2 devoted to large
deformation
Lethal giant larvae 2 regulates development of the ciliated organ Kupffer's vesicle
Motile cilia perform crucial functions during embryonic development and throughout adult life. Development of organs containing motile cilia involves regulation of cilia formation (ciliogenesis) and formation of a luminal space (lumenogenesis) in which cilia generate fluid flows. Control of ciliogenesis and lumenogenesis is not yet fully understood, and it remains unclear whether these processes are coupled. In the zebrafish embryo, lethal giant larvae 2 (lgl2) is expressed prominently in ciliated organs. Lgl proteins are involved in establishing cell polarity and have been implicated in vesicle trafficking. Here, we identified a role for Lgl2 in development of ciliated epithelia in Kupffer's vesicle, which directs left-right asymmetry of the embryo; the otic vesicles, which give rise to the inner ear; and the pronephric ducts of the kidney. Using Kupffer's vesicle as a model ciliated organ, we found that depletion of Lgl2 disrupted lumen formation and reduced cilia number and length. Immunofluorescence and time-lapse imaging of Kupffer's vesicle morphogenesis in Lgl2-deficient embryos suggested cell adhesion defects and revealed loss of the adherens junction component E-cadherin at lateral membranes. Genetic interaction experiments indicate that Lgl2 interacts with Rab11a to regulate E-cadherin and mediate lumen formation that is uncoupled from cilia formation. These results uncover new roles and interactions for Lgl2 that are crucial for both lumenogenesis and ciliogenesis and indicate that these processes are genetically separable in zebrafish
Planar cell polarity signalling regulates cell adhesion properties in progenitors of the zebrafish laterality organ
Organ formation requires the precise assembly of progenitor cells into a functional multicellular structure. Mechanical forces probably participate in this process but how they influence organ morphogenesis is still unclear. Here, we show that Wnt11- and Prickle1a-mediated planar cell polarity (PCP) signalling coordinates the formation of the zebrafish ciliated laterality organ (Kupffer's vesicle) by regulating adhesion properties between organ progenitor cells (the dorsal forerunner cells, DFCs). Combined inhibition of Wnt11 and Prickle1a reduces DFC cell-cell adhesion and impairs their compaction and arrangement during vesicle lumen formation. This leads to the formation of a mis-shapen vesicle with small fragmented lumina and shortened cilia, resulting in severely impaired organ function and, as a consequence, randomised laterality of both molecular and visceral asymmetries. Our results reveal a novel role for PCP-dependent cell adhesion in coordinating the supracellular organisation of progenitor cells during vertebrate laterality organ formation
Multitier mechanics control stromal adaptations in the swelling lymph node.
Lymph nodes (LNs) comprise two main structural elements: fibroblastic reticular cells that form dedicated niches for immune cell interaction and capsular fibroblasts that build a shell around the organ. Immunological challenge causes LNs to increase more than tenfold in size within a few days. Here, we characterized the biomechanics of LN swelling on the cellular and organ scale. We identified lymphocyte trapping by influx and proliferation as drivers of an outward pressure force, causing fibroblastic reticular cells of the T-zone (TRCs) and their associated conduits to stretch. After an initial phase of relaxation, TRCs sensed the resulting strain through cell matrix adhesions, which coordinated local growth and remodeling of the stromal network. While the expanded TRC network readopted its typical configuration, a massive fibrotic reaction of the organ capsule set in and countered further organ expansion. Thus, different fibroblast populations mechanically control LN swelling in a multitier fashion