269 research outputs found
The SO(N) principal chiral field on a half-line
We investigate the integrability of the SO(N) principal chiral model on a
half-line, and find that mixed Dirichlet/Neumann boundary conditions (as well
as pure Dirichlet or Neumann) lead to infinitely many conserved charges
classically in involution. We use an anomaly-counting method to show that at
least one non-trivial example survives quantization, compare our results with
the proposed reflection matrices, and, based on these, make some preliminary
remarks about expected boundary bound-states.Comment: 7 pages, Late
Supersymmetric WZW Model on Full and Half Plane
We study classical integrability of the supersymmetric U(N) model
with the Wess-Zumino-Witten term on full and half plane. We demonstrate the
existence of nonlocal conserved currents of the model and derive general
recursion relations for the infinite number of the corresponding charges in a
superfield framework. The explicit form of the first few supersymmetric charges
are constructed. We show that the considered model is integrable on full plane
as a concequence of the conservation of the supersymmetric charges. Also, we
study the model on half plane with free boundary, and examine the conservation
of the supersymmetric charges on half plane and find that they are conserved as
a result of the equations of motion and the free boundary condition. As a
result, the model on half plane with free boundary is integrable. Finally, we
conclude the paper and some features and comments are presented.Comment: 12 pages. submitted to IJMP
Special Theory of Relativity through the Doppler Effect
We present the special theory of relativity taking the Doppler effect as the
starting point, and derive several of its main effects, such as time dilation,
length contraction, addition of velocities, and the mass-energy relation, and
assuming energy and momentum conservation, we discuss how to introduce the
4-momentum in a natural way. We also use the Doppler effect to explain the
"twin paradox", and its version on a cylinder. As a by-product we discuss
Bell's spaceship paradox, and the Lorentz transformation for arbitrary
velocities in one dimension.Comment: 20 pages, 1 figur
Estratégia de resistência: a comercialização digital de produtoras de café do Norte Pioneiro do Paraná, Brasil.
Resumo: Esse trabalho é uma síntese de um estudo mais abrangente sobre a inserção econômica de produtoras de café da região do Norte Pioneiro- PR. Esse processo ocorreu através de ações desenvolvidas por meio da criação de um coletivo de mulheres e da comercialização digital do café. Nesse trabalho destaca-se aspectos da trajetória das mulheres atuantes no projeto, os interesses em torno da comercialização de café, os meios de comercialização adotados pelas mulheres. A análise envolveu a aplicação de um conjunto de técnicas da metodologia qualitativa. Foram realizadas visitas às unidades de produção do projeto café e também, entrevistas com base em um roteiro semiestruturado. Constatou-se avanços na comercialização gerado pelos meios digitais, principalmente no período da pandemia da Covid 19, substituindo meios de comercialização presenciais e concluí que os meios digitais estimularam a promoção social e econômica das mulheres. O conhecimento gerado subsidia a formulação de políticas públicas
Integrable Boundary Conditions for the O(N) Nonlinear Model
We discuss the new integrable boundary conditions for the O(N) nonlinear
model and related solutions of the boundary Yang-Baxter equation,
which were presented in our previous paper hep-th/0108039.Comment: 9 pages. To appear in the proceedings of the NATO Advanced Research
Workshop on "Statistical Field Theories", Como, Italy, 18-23 June 2001. v2:
typos correcte
On the Beta Function for Anisotropic Current Interactions in 2D
By making use of current-algebra Ward identities we study renormalization of
general anisotropic current-current interactions in 2D. We obtain a set of
algebraic conditions that ensure the renormalizability of the theory to all
orders. In a certain minimal prescription we compute the beta function to all
orders.Comment: 7 pages, 6 figures. v2: References added and typos corrected; v3:
cancellation of finite parts more accurately state
Embelin as Lead Compound for New Neuroserpin Polymerization Inhibitors
Familial encephalopathy with neuroserpin inclusion bodies (FENIB) is a severe and lethal neurodegenerative disease. Upon specific point mutations in the SERPINI1gene-coding for the human protein neuroserpin (NS) the resulting pathologic NS variants polymerize and accumulate within the endoplasmic reticulum of neurons in the central nervous system. To date, embelin (EMB) is the only known inhibitor of NS polymerization in vitro. This molecule is capable of preventing NS polymerization and dissolving preformed polymers. Here, we show that lowering EMB concentration results in increasing size of NS oligomers in vitro. Moreover, we observe that in cells expressing NS, the polymerization of G392E NS is reduced, but this effect is mediated by an increased proteasomal degradation rather than polymerization impairment. For these reasons we designed a systematic chemical evolution of the EMB scaffold aimed to improve its anti-polymerization properties. The effect of EMB analogs against NS polymerization was assessed in vitro. None of the EMB analogs displayed an anti-polymerization activity better than the one reported for EMB, indicating that the EMB\u2013NS interaction surface is very specific and highly optimized. Thus, our results indicate that EMB is, to date, still the best candidate for developing a treatment against NS polymerizatio
Embelin as lead compound for new neuroserpin polymerization inhibitors
Familial encephalopathy with neuroserpin inclusion bodies (FENIB) is a severe and lethal neurodegenerative disease. Upon specific point mutations in the SERPINI1gene-coding for the human protein neuroserpin (NS) the resulting pathologic NS variants polymerize and accumulate within the endoplasmic reticulum of neurons in the central nervous system. To date, embelin (EMB) is the only known inhibitor of NS polymerization in vitro. This molecule is capable of preventing NS polymerization and dissolving preformed polymers. Here, we show that lowering EMB concentration results in increasing size of NS oligomers in vitro. Moreover, we observe that in cells expressing NS, the polymerization of G392E NS is reduced, but this effect is mediated by an increased proteasomal degradation rather than polymerization impairment. For these reasons we designed a systematic chemical evolution of the EMB scaffold aimed to improve its anti-polymerization properties. The effect of EMB analogs against NS polymerization was assessed in vitro. None of the EMB analogs displayed an anti-polymerization activity better than the one reported for EMB, indicating that the EMB–NS interaction surface is very specific and highly optimized. Thus, our results indicate that EMB is, to date, still the best candidate for developing a treatment against NS polymerization
Effects of formalin fixation on polarimetric properties of brain tissue: fresh or fixed?
Imaging Mueller polarimetry (IMP) appears as a promising technique for real-time delineation of healthy and neoplastic tissue during neurosurgery. The training of machine learning algorithms used for the image post-processing requires large data sets typically derived from the measurements of formalin-fixed brain sections. However, the success of the transfer of such algorithms from fixed to fresh brain tissue depends on the degree of alterations of polarimetric properties induced by formalin fixation (FF).
Comprehensive studies were performed on the FF induced changes in fresh pig brain tissue polarimetric properties.
Polarimetric properties of pig brain were assessed in 30 coronal thick sections before and after FF using a wide-field IMP system. The width of the uncertainty region between gray and white matter was also estimated.
The depolarization increased by 5% in gray matter and remained constant in white matter following FF, whereas the linear retardance decreased by 27% in gray matter and by 28% in white matter after FF. The visual contrast between gray and white matter and fiber tracking remained preserved after FF. Tissue shrinkage induced by FF did not have a significant effect on the uncertainty region width.
Similar polarimetric properties were observed in both fresh and fixed brain tissues, indicating a high potential for transfer learning
Circulation Statistics in Three-Dimensional Turbulent Flows
We study the large limit of the loop-dependent characteristic
functional , related
to the probability density function (PDF) of the circulation around a closed
contour . The analysis is carried out in the framework of the
Martin-Siggia-Rose field theory formulation of the turbulence problem, by means
of the saddle-point technique. Axisymmetric instantons, labelled by the
component of the strain field -- a partially annealed variable in
our formalism -- are obtained for a circular loop in the plane, with
radius defined in the inertial range. Fluctuations of the velocity field around
the saddle-point solutions are relevant, leading to the lorentzian asymptotic
behavior . The
subleading correction and the asymmetry between right and left PDF tails due to
parity breaking mechanisms are also investigated.Comment: Computations are discussed in a more detailed way; accepted for
publication in Physical Review
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