939 research outputs found
D-brane superpotentials and RG flows on the quintic
The behaviour of D2-branes on the quintic under complex structure
deformations is analysed by combining Landau-Ginzburg techniques with methods
from conformal field theory. It is shown that the boundary renormalisation
group flow induced by the bulk deformations is realised as a gradient flow of
the effective space time superpotential which is calculated explicitly to all
orders in the boundary coupling constant.Comment: 24 pages, 1 figure, v2:Typo in (3.14) correcte
Symmetries of perturbed conformal field theories
The symmetries of perturbed conformal field theories are analysed. We explain
which generators of the chiral algebras of a bulk theory survive a perturbation
by an exactly marginal bulk field. We also study the behaviour of D-branes
under current-current bulk deformations. We find that the branes always
continue to preserve as much symmetry as they possibly can, i.e. as much as is
preserved in the bulk. We illustrate these findings with several examples,
including permutation branes in WZW models and B-type D-branes in Gepner
models.Comment: 30 pages, 3 figures. V2: Small error in eq. (2.14) correcte
Matrix factorisations and D-branes on K3
D-branes on K3 are analysed from three different points of view. For
deformations of hypersurfaces in weighted projected space we use geometrical
methods as well as matrix factorisation techniques. Furthermore, we study the
D-branes on the T^4/\Z_4 orbifold line in conformal field theory. The behaviour
of the D-branes under deformations of the bulk theory are studied in detail,
and good agreement between the different descriptions is found.Comment: 35 pages, no figure
Characterization and differentiation of the tumor microenvironment (TME) of orthotopic and subcutaneously grown head and neck squamous cell carcinoma (HNSCC) in immunocompetent mice
For the development and evaluation of new head and neck squamous cell carcinoma (HNSCC) therapeutics, suitable, well-characterized animal models are needed. Thus, by analyzing orthotopic versus subcutaneous models of HNSCC in immunocompetent mice, we evaluated the existence of adenosine-related immunosuppressive B- and T lymphocyte populations within the tumor microenvironment (TME). Applying the SCC VII model for the induction of HNSCC in immunocompetent C3H/HeN mice, the cellular TME was characterized after tumor initiation over time by flow cytometry. The TME in orthotopic grown tumors revealed a larger population of tumor-infiltrating lymphocytes (TIL) with more B cells and CD4+ T cells than the subcutaneously grown tumors. Immune cell populations in the blood and bone marrow showed a rather distinct reaction toward tumor induction and tumor location compared to the spleen, lymph nodes, or thymus. In addition, large numbers of immunosuppressive B- and T cells were identified within the TME but also in secondary lymphoid organs, independently of the tumor initiation site. The altered immunogenic TME may influence the response to any treatment attempt. Moreover, when analyzing the TME and other lymphoid organs of tumor-bearing mice, we observed conditions reflecting largely those of patients suffering from HNSCC suggesting the C3H/HeN mouse model as a suitable tool for studies aiming to target immunosuppression to improve anti-cancer therapies
On the nature of long-range contributions to pair interactions between charged colloids in two dimensions
We perform a detailed analysis of solutions of the inverse problem applied to
experimentally measured two-dimensional radial distribution functions for
highly charged latex dispersions. The experiments are carried out at high
colloidal densities and under low-salt conditions. At the highest studied
densities, the extracted effective pair potentials contain long-range
attractive part. At the same time, we find that for the best distribution
functions available the range of stability of the solutions is limited by the
nearest neighbour distance between the colloidal particles. Moreover, the
measured pair distribution functions can be explained by purely repulsive pair
potentials contained in the stable part of the solution.Comment: 6 pages, 5 figure
Three-body interactions in colloidal systems
We present the first direct measurement of three-body interactions in a
colloidal system comprised of three charged colloidal particles. Two of the
particles have been confined by means of a scanned laser tweezers to a
line-shaped optical trap where they diffused due to thermal fluctuations. Upon
the approach of a third particle, attractive three-body interactions have been
observed. The results are in qualitative agreement with additionally performed
nonlinear Poissson-Boltzmann calculations, which also allow us to investigate
the microionic density distributions in the neighborhood of the interacting
colloidal particles
The matrix factorisations of the D-model
The fundamental matrix factorisations of the D-model superpotential are found
and identified with the boundary states of the corresponding conformal field
theory. The analysis is performed for both GSO-projections. We also comment on
the relation of this analysis to the theory of surface singularities and their
orbifold description.Comment: 23 pages, LaTe
Topological defects for the free boson CFT
Two different conformal field theories can be joined together along a defect
line. We study such defects for the case where the conformal field theories on
either side are single free bosons compactified on a circle. We concentrate on
topological defects for which the left- and right-moving Virasoro algebras are
separately preserved, but not necessarily any additional symmetries. For the
case where both radii are rational multiples of the self-dual radius we
classify these topological defects. We also show that the isomorphism between
two T-dual free boson conformal field theories can be described by the action
of a topological defect, and hence that T-duality can be understood as a
special type of order-disorder duality.Comment: 43 pages, 4 figure
Topology and Organization of the Salmonella typhimurium Type III Secretion Needle Complex Components
The correct organization of single subunits of multi-protein machines in a three dimensional context is critical for their functionality. Type III secretion systems (T3SS) are molecular machines with the capacity to deliver bacterial effector proteins into host cells and are fundamental for the biology of many pathogenic or symbiotic bacteria. A central component of T3SSs is the needle complex, a multiprotein structure that mediates the passage of effector proteins through the bacterial envelope. We have used cryo electron microscopy combined with bacterial genetics, site-specific labeling, mutational analysis, chemical derivatization and high-resolution mass spectrometry to generate an experimentally validated topographic map of a Salmonella typhimurium T3SS needle complex. This study provides insights into the organization of this evolutionary highly conserved nanomachinery and is the basis for further functional analysis
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