266 research outputs found
Degenerations and representations of twisted Shibukawa-Ueno R-operators
We study degenerations of the Belavin R-matrices via the infinite dimensional
operators defined by Shibukawa-Ueno. We define a two-parameter family of
generalizations of the Shibukawa-Ueno R-operators. These operators have finite
dimensional representations which include Belavin's R-matrices in the elliptic
case, a two-parameter family of twisted affinized Cremmer-Gervais R-matrices in
the trigonometric case, and a two-parameter family of twisted (affinized)
generalized Jordanian R-matrices in the rational case. We find finite
dimensional representations which are compatible with the elliptic to
trigonometric and rational degeneration. We further show that certain members
of the elliptic family of operators have no finite dimensional representations.
These R-operators unify and generalize earlier constructions of Felder and
Pasquier, Ding and Hodges, and the authors, and illuminate the extent to which
the Cremmer-Gervais R-matrices (and their rational forms) are degenerations of
Belavin's R-matrix
Triangular Poisson structures on Lie groups and symplectic reduction
We show that each triangular Poisson Lie group can be decomposed into Poisson
submanifolds each of which is a quotient of a symplectic manifold. The
Marsden-Weinstein-Meyer symplectic reduction technique is then used to give a
complete description of the symplectic foliation of all triangular Poisson
structures on Lie groups. The results are illustrated in detail for the
generalized Jordanian Poisson structures on SL(n).Comment: 12 pages, AMS-Late
Algebraic structure of multi-parameter quantum groups
Multi-parameter versions U_p(g) and C_p[G] of the standard quantum groups
U_q(g) and C_q[G] are considered where G is a semi-simple connected complex
algebraic group and g is the Lie algebra of G. The primitive spectrum of C_p[G]
is calculated, generalizing a result of Joseph for the standard quantum groups.
This classification is compared with the classification of symplectic leaves
for the associated Poisson structure on G.Comment: AMS Latex, 37 pages, June 1994; to appear in Advances in Mat
Ipsilateral femoral vein compression: A contraindication to thrombin injection of femoral pseudoaneurysms
AbstractDevelopment of a femoral artery pseudoaneurysm occurs in 0.6% to 3.2% of interventional procedures. Nonsurgical treatment has consisted of ultrasound scan—directed compression and, more recently, direct thrombin injection into the pseudoaneurysm cavity to achieve thrombosis. Reported complications after thrombin injection are rare. We report two cases of femoral venous compression associated with pseudoaneurysm injection and review the literature. A 76-year-old man and an 86-year-old man both underwent thrombin injection of pseudoaneurysms compressing the ipsilateral common femoral vein. Both patients were diagnosed with deep venous thrombosis and subsequently needed surgical exploration for repair of the pseudoaneurysm and release of the venous compression. At exploration, both were found to have significant inflammation surrounding the femoral vessels, which made vessel exposure challenging. Because of the venous outflow obstruction involved in femoral pseudoaneurysms with secondary venous compression and the surgical difficulty caused by surrounding inflammation, avoidance of thrombin injection in favor of early surgical intervention is suggested
Motor Adaptations to Pain during a Bilateral Plantarflexion Task: Does the Cost of Using the Non-Painful Limb Matter?
During a force-matched bilateral task, when pain is induced in one limb, a shift of load to the non-painful leg is classically observed. This study aimed to test the hypothesis that this adaptation to pain depends on the mechanical efficiency of the non-painful leg. We studied a bilateral plantarflexion task that allowed flexibility in the relative force produced with each leg, but constrained the sum of forces from both legs to match a target. We manipulated the mechanical efficiency of the non-painful leg by imposing scaling factors: 1, 0.75, or 0.25 to decrease mechanical efficiency (Decreased efficiency experiment: 18 participants); and 1, 1.33 or 4 to increase mechanical efficiency (Increased efficiency experiment: 17 participants). Participants performed multiple sets of three submaximal bilateral isometric plantarflexions with each scaling factor during two conditions (Baseline and Pain). Pain was induced by injection of hypertonic saline into the soleus. Force was equally distributed between legs during the Baseline contractions (laterality index was close to 1; Decreased efficiency experiment: 1.16±0.33; Increased efficiency experiment: 1.11±0.32), with no significant effect of Scaling factor. The laterality index was affected by Pain such that the painful leg contributed less than the non-painful leg to the total force (Decreased efficiency experiment: 0.90±0.41, P<0.001; Increased efficiency experiment: 0.75±0.32, P<0.001), regardless of the efficiency (scaling factor) of the non-painful leg. When compared to the force produced during Baseline of the corresponding scaling condition, a decrease in force produced by the painful leg was observed for all conditions, except for scaling 0.25. This decrease in force was correlated with a decrease in drive to the soleus muscle. These data highlight that regardless of the overall mechanical cost, the nervous system appears to prefer to alter force sharing between limbs such that force produced by the painful leg is reduced relative to the non-painful leg
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