210 research outputs found
On the connections between Skyrme and Yang Mills theories
Skyrme theories on S^3 and S^2, are analyzed using the generalized zero
curvature in any dimensions. In the first case, new symmetries and integrable
sectors, including the B =1 skyrmions, are unraveled. In S^2 the relation to
QCD suggested by Faddeev is discussedComment: Talk at the Workshop on integrable theories, solitons and duality.
IFT Sao Paulo July 200
Tau-functions and Dressing Transformations for Zero-Curvature Affine Integrable Equations
The solutions of a large class of hierarchies of zero-curvature equations
that includes Toda and KdV type hierarchies are investigated. All these
hierarchies are constructed from affine (twisted or untwisted) Kac-Moody
algebras~. Their common feature is that they have some special ``vacuum
solutions'' corresponding to Lax operators lying in some abelian (up to the
central term) subalgebra of~; in some interesting cases such subalgebras
are of the Heisenberg type. Using the dressing transformation method, the
solutions in the orbit of those vacuum solutions are constructed in a uniform
way. Then, the generalized tau-functions for those hierarchies are defined as
an alternative set of variables corresponding to certain matrix elements
evaluated in the integrable highest-weight representations of~. Such
definition of tau-functions applies for any level of the representation, and it
is independent of its realization (vertex operator or not). The particular
important cases of generalized mKdV and KdV hierarchies as well as the abelian
and non abelian affine Toda theories are discussed in detail.Comment: 27 pages, plain Te
Quantum effective actions from nonperturbative worldline dynamics
We demonstrate the feasibility of a nonperturbative analysis of quantum field
theory in the worldline formalism with the help of an efficient numerical
algorithm. In particular, we compute the effective action for a
super-renormalizable field theory with cubic scalar interaction in four
dimensions in quenched approximation (small- expansion) to all orders in
the coupling. We observe that nonperturbative effects exert a strong influence
on the infrared behavior, rendering the massless limit well defined in contrast
to the perturbative expectation. Our numerical method is based on a direct use
of probability distributions for worldline ensembles, preserves all Euclidean
spacetime symmetries, and thus represents a new nonperturbative tool for an
investigation of continuum quantum field theory.Comment: 33 pages, 10 figure
Negative Even Grade mKdV Hierarchy and its Soliton Solutions
In this paper we provide an algebraic construction for the negative even mKdV
hierarchy which gives rise to time evolutions associated to even graded Lie
algebraic structure. We propose a modification of the dressing method, in order
to incorporate a non-trivial vacuum configuration and construct a deformed
vertex operator for , that enable us to obtain explicit and
systematic solutions for the whole negative even grade equations
The longitudinal structure function F_L: perturbative QCD and k_T-factorization versus experimental data at fixed W
We use results for the structure functions for a gluon target having
nonzero transverse momentum square at order , obtained in our
previous paper, to compare with recent H1 experimental data for at fixwd
W values and with collinear GRV predictions at LO and NLO approximation.Comment: 10 pages, 4 figure
Renormalon Model Predictions for Power-Corrections to Flavour Singlet Deep Inelastic Structure Functions
We analyze power corrections to flavour singlet deep inelastic scattering
structure functions in the framework of the infrared renormalon model. Our
calculations, together with previous results for the non-singlet contribution,
allow to model the x-dependence of higher twist corrections to F_2, F_L and g_1
in the whole x domain.Comment: LaTeX, 25 pages, 8 eps figures included, one figure was added. Final
version for publication in Nucl.Phys.
A video guide of five access methods to the splenic flexure: the concept of the splenic flexure box
Aim: The aim of this study was to describe all the possible approaches for laparoscopic splenic flexure mobilization (SFM), each suitable for specific situations, and create an illustrated system to show SFM approaches in an easy and practical way to make it easy to learn and teach. Methods: Two different phases. First part: Cadaver-based study of the colonic splenic flexure anatomy. In order to demonstrate the different approaches, a balloon was placed through the colonic hepatic flexure in the lesser sac without sectioning any of the fixing ligaments of the splenic flexure. Second part: A real case series of laparoscopic SFM. Results: First part: 11 cadavers were dissected. Five potential approaches to SFM were found: anterior, trans-omentum, lateral, medial infra-mesocolic, and medial trans-mesocolic. The illustrative system developed was named: Splenic Flexure “Box”(SFBox). Second part: One of the types of SFM described in first part was used in five patients with colorectal cancer. Each laparoscopic approach to the splenic flexure was illustrated in a video accompanied by illustration aids delineating the access. Conclusion: With the cadaver dissection and subsequent demonstration in real-life laparoscopic surgery, we have shown five types of laparoscopic splenic flexure mobilization. The Splenic Flexure “Box” is a useful way to learn and teach this surgical maneuver
Early-onset Alzheimer's disease shows a distinct neuropsychological profile and more aggressive trajectories of cognitive decline than late-onset
Early- and late-onset Alzheimer's disease (EOAD and LOAD) share the same neuropathological traits but show distinct cognitive features. We aimed to explore baseline and longitudinal outcomes of global and domain-specific cognitive function in a well characterized cohort of patients with a biomarker-based diagnosis.In this retrospective cohort study, 195 participants were included and classified according to their age, clinical status, and CSF AD biomarker profile: 89 EOAD, 37 LOAD, 46 young healthy controls (age???65?years), and 23 old healthy controls (>65?years). All subjects underwent clinical and neuropsychological assessment, neuroimaging, APOE genotyping and lumbar puncture.We found distinct neuropsychological profiles between EOAD and LOAD at the time of diagnosis. Both groups showed similar performances on memory and language domains, but the EOAD patients displayed worsened deficits in visual perception, praxis, and executive tasks (p?<?0.05). Longitudinally, cognitive decline in EOAD was more pronounced than LOAD in the global outcomes at the expense of these non-amnestic domains. We found that years of education significantly influenced the decline in most of the neuropsychological tests. Besides, the APOE ?4 status showed a significant effect on the decline of memory-related tasks within the EOAD cohort (p?<?0.05).Age of onset is a main factor shaping the cognitive trajectories in AD patients, with younger age driving to a steeper decline of the non-memory domains. Years of education are related to a transversal decline in all cognitive domains and APOE ?4 status to a specific decline in memory performance in EOAD.© 2022 The Authors. Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association
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