4,707 research outputs found
Wave-Packet Scattering off the Kink-Solution
We investigate the propagation of a wave--packet in the model. We
solve the time-dependent equation of motion for two distinct initial
conditions: The wave-packet in a trivial vacuum background and in the
background of the kink soliton solution. We extract the scattering matrix from
the wave-packet in the kink background at very late times and compare it with
the result from static potential scattering in the small amplitude
approximation. We vary the size of the initial wave-packet to identify
non-linear effects as, for example, the replacement of the center of the kink.Comment: 15 pages, 7 figures (from 14 eps files), 4 tables, Int. J. Mod. Phys.
A, in prin
Endocytic Function, Glycosaminoglycan Specificity, and Antibody Sensitivity of the Recombinant Human 190-kDa Hyaluronan Receptor for Endocytosis (HARE)
The human hyaluronan receptor for endocytosis (hHARE) mediates the endocytic clearance of hyaluronan (HA) and chondroitin sulfate from lymph fluid and blood. Two hHARE isoforms (190 and 315 kDa) are present in sinusoidal endothelial cells of liver, spleen, and lymph nodes (Zhou, B., McGary, C. T., Weigel, J. A., Saxena, A., and Weigel, P. H. (2003) Glycobiology 13, 339–349). Here we report the specificity and function of the 190-kDa HARE, expressed without the larger isoform, in Flp-In 293 cell lines (190hHARE cells). Like the native protein, recombinant hHARE contains ~25 kDa of N-linked oligosaccharides, binds HA in a ligand blot assay, cross-reacts with three anti-rat HARE monoclonal antibodies, and is inactivated by reduction. The 190hHARE cell lines mediated rapid, continuous 125I-HA endocytosis and degradation for \u3e1 day. About 30–50% of the total cellular receptors were on the cell surface, and their recycling time for reutilization was ~8.5 min. The average Kd for the binding of HA to the 190-kDa hHARE at 4 °C was 7 nm with 118,000 total HA binding sites per cell. Competition studies at 37 °C indicated that the 190- kDa hHARE binds HA and chondroitin better than dermatan sulfate and chondroitin sulfates A, C, D, and E, but it does not bind to heparin, heparan sulfate, or keratan sulfate. Although competition was observed at 37 °C, none of the glycosaminoglycans tested, except HA, competed for 125I-HA binding by 190hHARE cells at 4 °C. Anti-HARE monoclonal antibodies #30 and #154, which do not inhibit 125I-HA uptake mediated by the 175-kDa rat HARE, partially blocked HA endocytosis by the 190-kDa hHARE. We conclude that the 190-kDa hHARE can function independently of other hHARE isoforms to mediate the endocytosis of multiple glycosaminoglycans. Furthermore, the rat and human small HARE isoforms have different glycosaminoglycan specificities and sensitivities to inhibition by cross-reacting antibodies
The Human Hyaluronan Receptor for Endocytosis (HARE/Stabilin-2) Is a Systemic Clearance Receptor for Heparin
The hyaluronic acid receptor for endocytosis (HARE; also designated Stabilin-2) mediates systemic clearance of hyaluronan and chondroitin sulfates from the vascular and lymphatic circulations. The internalized glycosaminoglycans are degraded in lysosomes, thus completing their normal turnover process. Sinusoidal endothelial cells of human liver, lymph node, and spleen express two HARE isoforms of 315 and 190 kDa. Here we report that the 190- and 315-kDa HARE isoforms, expressed stably either in Flp-In 293 cell lines or as soluble ectodomains, specifically bind heparin (Hep). The Kd for Hep binding to purified 190- and 315-kDa HARE ectodomains was 17.2 ± 4.9 and 23.4 ± 5.3 nm, respectively. Cells expressing HARE readily and specifically internalized 125I-streptavidin-biotin-Hep complexes, which was inhibited \u3e70% by hyperosmolar conditions, confirming that uptake is mediated by the clathrin-coated pit pathway. Internalization of Hep occurred for many hours with an estimated HARE recycling time of ~12 min. Internalized fluorescent streptavidin-biotin-Hep was present in a typical endocytic vesicular pattern and was delivered to lysosomes. We conclude that HARE in the sinusoidal endothelial cells of lymph nodes and liver likely mediates the efficient systemic clearance of Hep and many different Hep-binding protein complexes from the lymphatic and vascular circulations
Fermion Energies in the Background of a Cosmic String
We provide a thorough exposition, including technical and numerical details,
of previously published results on the quantum stabilization of cosmic strings.
Stabilization occurs through the coupling to a heavy fermion doublet in a
reduced version of the standard model. We combine the vacuum polarization
energy of fermion zero-point fluctuations and the binding energy of occupied
energy levels, which are of the same order in a semi-classical expansion.
Populating these bound states assigns a charge to the string. We show that
strings carrying fermion charge become stable if the electro-weak bosons are
coupled to a fermion that is less than twice as heavy as the top quark. The
vacuum remains stable in our model, because neutral strings are not
energetically favored. These findings suggests that extraordinarily large
fermion masses or unrealistic couplings are not required to bind a cosmic
string in the standard model.Comment: 38 pages, 6 figures, version accepted for publication in Phys Rev
Soliton Models for the Nucleon and Predictions for the Nucleon Spin Structure
In these lectures the three flavor soliton approach for baryons is reviewed.
Effects of flavor symmetry breaking in the baryon wave--functions on axial
current matrix elements are discussed. A bosonized chiral quark model is
considered to outline the computation of spin dependent nucleon structure
functions in the soliton picture.Comment: 12 pages, Lectures presented at the Advanced Study Institute Symmetry
and Spin, Prague, 2001, to appear in the proceedings. References correcte
On the strange vector form factors of the nucleon in the NJL soliton model
Within the Nambu--Jona--Lasinio model strange degrees of freedom are
incorporated into the soliton picture using the collective approach of Yabu and
Ando. The form factors of the nucleon associated with the nonet vector current
are extracted. The numerical results provide limits for the strange magnetic
moment: . For the strange magnetic form factor of the
nucleon the valence quark and vacuum contributions add coherently while there
are significant cancellations for the strange electric form factor.Comment: 9 pages, one figure, postscript file submitted as uuencoded
compressed fil
Chiral Quark Model
In this talk I review studies of hadron properties in bosonized chiral quark
models for the quark flavor dynamics. Mesons are constructed from
Bethe--Salpeter equations and baryons emerge as chiral solitons. Such models
require regularization and I show that the two--fold Pauli--Villars
regularization scheme not only fully regularizes the effective action but also
leads the scaling laws for structure functions. For the nucleon structure
functions the present approach serves to determine the regularization
prescription for structure functions whose leading moments are not given by
matrix elements of local operators. Some numerical results are presented for
the spin structure functions.Comment: Talk presented at the workshop QCD 2002, IIT Kanpur, Nov. 2002, 10
pages, proceedings style files include
On photoexcitation of baryon antidecuplet
We show that the photoexcitation of the baryon antidecuplet, suggested by the
soliton classification of low-lying baryons, is strongly suppressed on the
proton target. The process occurs mostly on the neutron target. This
qualitative prediction can be useful in identifying the non-exotic members of
the antidecuplet in the known baryon spectrum. We also analyze the
interrelation between photocouplings of various baryon multiplets in the
soliton picture and in the nonrelativistic quark model.Comment: 9 pages, one Latex figur
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