770 research outputs found
Collaborative effects in polymer translocation and the appearance of fictitious free-energy barriers
In vitro maturation of immature thymocytes into immunocompetent T cells in the absence of direct thymic influence
Peanut lectin (PNL) binds to a majority of mouse thymocytes (Thc) in suspension. By using cell affinity chromatography on a column of anti-PNL antibody, Thc populations at least 96 percent pure in PNL + or - cells, as judged by immunofluorescence, were obtained. PNL(+) cells are rich in Thy 1 and poor in H(2) antigens, cortisone sensitive, unresponsive to phytohemagglutinin (PHA), and immunologically incompetent, as judged by mixed lymphocyte reaction, popliteal lymph node graft-versus-host assay, and by testing helper activity in a primary in vitro antibody response to sheep erythrocytes; the converse is true of PNL(-) cells. Thus, PNL(+) and (-) cells appear to correspond to cortical and medullary Thc, respectively, as previously suggested. In culture, PNL(+) Thc show poor viability and a weak proliferative response to concanavalin A (Con A), except when supernate (SUP) of 24 h Con A stimulated lymph node lymphocyte cultures, or irradiated lymph node cells, are added, in which cases a strong proliferative response to the mitogen is observed. A variety of control experiments showed that the proliferating cells did not result from preferential stimulation of a few contaminating PNL(-) Thc present in the PNL(+) Thc cultures. The blasts resulting from PNL(+) Thc proliferation display mitogen-induced cytotoxicity, and give rise to a population of medium-sized lymphocytes, mostly PNL(-), poor in Thy 1 and rich in H(2) antigens, PHA responsive, and immunologically competent in the above-mentioned assays. Fresh PNL(+) Thc responded in mixed lymphocyte reaction in the presence of SUP (lectin depleted) and since incubation in SUP alone did not confer reactivity on PNL(+) Thc, it appears therefore that (a) immature Thc possess alloantigen and mitogen-specific surface receptors but lack the capacity to respond by proliferation to receptor triggering without the help of extracellular factor(s) released by mature lymphoid cells stimulated by mitogens (b) cell division is associated with the acquisition of immunological responsiveness, characteristic of mature T lymphocytes. The implications of these findings for the ontogenesis of thymus-derived lymphocytes, and for the possible traffic of Thc within and from the thymus, are discussed
UV finiteness of 3D Yang-Mills theories with a regulating mass in the Landau gauge
We prove that three-dimensional Yang-Mills theories in the Landau gauge
supplemented with a infrared regulating, parity preserving mass term are
ultraviolet finite to all orders. We also extend this result to the
Curci-Ferrari gauge.Comment: 6 page
Observables in Topological Yang-Mills Theories
Using topological Yang-Mills theory as example, we discuss the definition and
determination of observables in topological field theories (of Witten-type)
within the superspace formulation proposed by Horne. This approach to the
equivariant cohomology leads to a set of bi-descent equations involving the
BRST and supersymmetry operators as well as the exterior derivative. This
allows us to determine superspace expressions for all observables, and thereby
to recover the Donaldson-Witten polynomials when choosing a Wess-Zumino-type
gauge.Comment: 39 pages, Late
On the symmetries of BF models and their relation with gravity
The perturbative finiteness of various topological models (e.g. BF models)
has its origin in an extra symmetry of the gauge-fixed action, the so-called
vector supersymmetry. Since an invariance of this type also exists for gravity
and since gravity is closely related to certain BF models, vector supersymmetry
should also be useful for tackling various aspects of quantum gravity. With
this motivation and goal in mind, we first extend vector supersymmetry of BF
models to generic manifolds by incorporating it into the BRST symmetry within
the Batalin-Vilkovisky framework. Thereafter, we address the relationship
between gravity and BF models, in particular for three-dimensional space-time.Comment: 29 page
Let's Twist Again: N=2 Super Yang Mills Theory Coupled To Matter
We give the twisted version of N=2 Super Yang Mills theory coupled to matter,
including quantum fields, supersymmetry transformations, action and algebraic
structure. We show that the whole action, coupled to matter, can be written as
the variation of a nilpotent operator, modulo field equations. An extended
Slavnov-Taylor identity, collecting gauge symmetry and supersymmetry, is
written, which allows to define the web of algebraic constraints, in view of
the algebraic renormalization and of the extension of the non-renormalization
theorems holding for N=2 SYM theory without matter.Comment: 28 pages, final version to be published on CQ
Study of the Gribov region in Euclidean Yang-Mills theories in the maximal Abelian gauge
The properties of the Gribov region in SU(2) Euclidean Yang-Mills theories in
the maximal Abelian gauge are investigated. This region turns out to be bounded
in all off-diagonal directions, while it is unbounded along the diagonal one.
The soft breaking of the BRST invariance due to the restriction of the domain
of integration in the path integral to the Gribov region is scrutinized. Owing
to the unboundedness in the diagonal direction, the invariance with respect to
Abelian transformations is preserved, a property which is at the origin of the
local U(1) Ward identity of the maximal Abelian gauge.Comment: 15 pages, one reference added, version accepted for publication in
Phys. Rev.
THYMUS-INDEPENDENT (B) CELL PROLIFERATION IN SPLEEN CELL CULTURES OF MOUSE RADIATION CHIMERAS STIMULATED BY PHYTOHEMAGGLUTININ OR ALLOGENEIC CELLS
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