71 research outputs found
Baxter Operators and Hamiltonians for "nearly all" Integrable Closed gl(n) Spin Chains
We continue our systematic construction of Baxter Q-operators for spin
chains, which is based on certain degenerate solutions of the Yang-Baxter
equation. Here we generalize our approach from the fundamental representation
of gl(n) to generic finite-dimensional representations in quantum space. The
results equally apply to non-compact representations of highest or lowest
weight type. We furthermore fill an apparent gap in the literature, and provide
the nearest-neighbor Hamiltonians of the spin chains in question for all cases
where the gl(n) representations are described by rectangular Young diagrams, as
well as for their infinite-dimensional generalizations. They take the form of
digamma functions depending on operator-valued shifted weights.Comment: 26 pages, 1 figur
A Shortcut to the Q-Operator
Baxter's Q-operator is generally believed to be the most powerful tool for
the exact diagonalization of integrable models. Curiously, it has hitherto not
yet been properly constructed in the simplest such system, the compact spin-1/2
Heisenberg-Bethe XXX spin chain. Here we attempt to fill this gap and show how
two linearly independent operatorial solutions to Baxter's TQ equation may be
constructed as commuting transfer matrices if a twist field is present. The
latter are obtained by tracing over infinitely many oscillator states living in
the auxiliary channel of an associated monodromy matrix. We furthermore compare
and differentiate our approach to earlier articles addressing the problem of
the construction of the Q-operator for the XXX chain. Finally we speculate on
the importance of Q-operators for the physical interpretation of recent
proposals for the Y-system of AdS/CFT.Comment: 41 pages, 2 figures; v2: references added; v3: version published in
J. Stat. Mec
Ct-Guided Pancreatic Percutaneous Fine-needle Biopsy in Differential Diagnosis Between Pancreatic Cancer and Chronic Pancreatitis
Differential diagnosis between pancreatic cancer and chronic pancreatitis is still difficult to establish. In
63 patients with suspected pancreatic neoplasm we performed: serum CA 19-9 assessment, abdominal
ultrasound, CT scan and CT-guided pancreatic percutaneous fine-needle biopsy. The conclusive diagnosis
was pancreatic cancer in 40 patients and chronic pancreatitis in 23 patients. With regard to the differential
diagnosis, sensitivity and specificity were respectively 80% and 78% for serum CA 19-9, 75% and 65% for
abdominal US, 85% and 70% for CT scan, 00% and 87% for percutaneous fine-needle biopsy. We
conclude that CT-guided percutaneous fine-needle biopsy is the most reliable method for differential
diagnosis between pancreatic cancer and chronic pancreatitis
Baxter Q-Operators and Representations of Yangians
We develop a new approach to Baxter Q-operators by relating them to the
theory of Yangians, which are the simplest examples for quantum groups. Here we
open up a new chapter in this theory and study certain degenerate solutions of
the Yang-Baxter equation connected with harmonic oscillator algebras. These
infinite-state solutions of the Yang-Baxter equation serve as elementary,
"partonic" building blocks for other solutions via the standard fusion
procedure. As a first example of the method we consider sl(n) compact spin
chains and derive the full hierarchy of operatorial functional equations for
all related commuting transfer matrices and Q-operators. This leads to a
systematic and transparent solution of these chains, where the nested Bethe
equations are derived in an entirely algebraic fashion, without any reference
to the traditional Bethe ansatz techniques.Comment: 27 pages, 5 figures; v2: typos fixed, references updated and adde
Proteomics Reveals Novel Oxidative and Glycolytic Mechanisms in Type 1 Diabetic Patients' Skin Which Are Normalized by Kidney-Pancreas Transplantation
Background: In type 1 diabetes (T1D) vascular complications such as accelerated atherosclerosis and diffused macro-/microangiopathy are linked to chronic hyperglycemia with a mechanism that is not yet well understood. End-stage renal disease (ESRD) worsens most diabetic complications, particularly, the risk of morbidity and mortality from cardiovascular disease is increased several fold. Methods and Findings: We evaluated protein regulation and expression in skin biopsies obtained from T1D patients with and without ESRD, to identify pathways of persistent cellular changes linked to diabetic vascular disease. We therefore examined pathways that may be normalized by restoration of normoglycemia with kidney-pancreas (KP) transplantation. Using proteomic and ultrastructural approaches, multiple alterations in the expression of proteins involved in oxidative stress (catalase, superoxide dismutase 1, Hsp27, Hsp60, ATP synthase δ chain, and flavin reductase), aerobic and anaerobic glycolysis (ACBP, pyruvate kinase muscle isozyme, and phosphoglycerate kinase 1), and intracellular signaling (stratifin-14-3-3, S100-calcyclin, cathepsin, and PPI rotamase) as well as endothelial vascular abnormalities were identified in T1D and T1D+ESRD patients. These abnormalities were reversed after KP transplant. Increased plasma levels of malondialdehyde were observed in T1D and T1D+ESRD patients, confirming increased oxidative stress which was normalized after KP transplant. Conclusions: Our data suggests persistent cellular changes of anti-oxidative machinery and of aerobic/anaerobic glycolysis are present in T1D and T1D+ESRD patients, and these abnormalities may play a key role in the pathogenesis of hyperglycemia-related vascular complications. Restoration of normoglycemia and removal of uremia with KP transplant can correct these abnormalities. Some of these identified pathways may become potential therapeutic targets for a new generation of drugs
Oscillator Construction of su(n|m) Q-Operators
We generalize our recent explicit construction of the full hierarchy of
Baxter Q-operators of compact spin chains with su(n) symmetry to the
supersymmetric case su(n|m). The method is based on novel degenerate solutions
of the graded Yang-Baxter equation, leading to an amalgam of bosonic and
fermionic oscillator algebras. Our approach is fully algebraic, and leads to
the exact solution of the associated compact spin chains while avoiding Bethe
ansatz techniques. It furthermore elucidates the algebraic and combinatorial
structures underlying the system of nested Bethe equations. Finally, our
construction naturally reproduces the representation, due to Z. Tsuboi, of the
hierarchy of Baxter Q-operators in terms of hypercubic Hasse diagrams.Comment: 24 pages, 4 figures; v2: references adde
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Inotuzumab Ozogamicin Murine Analog–Mediated B-Cell Depletion Reduces Anti-islet Allo- and Autoimmune Responses
B cells participate in the priming of the allo- and autoimmune responses, and their depletion can thus be advantageous for islet transplantation. Herein, we provide an extensive study of the effect of B-cell depletion in murine models of islet transplantation. Islet transplantation was performed in hyperglycemic B-cell–deficient(μMT) mice, in a purely alloimmune setting (BALB/c into hyperglycemic C57BL/6), in a purely autoimmune setting (NOD.SCID into hyperglycemic NOD), and in a mixed allo-/autoimmune setting (BALB/c into hyperglycemic NOD). Inotuzumab ozogamicin murine analog (anti-CD22 monoclonal antibody conjugated with calicheamicin [anti-CD22/cal]) efficiently depleted B cells in all three models of islet transplantation examined. Islet graft survival was significantly prolonged in B-cell–depleted mice compared with control groups in transplants of islets from BALB/c into C57BL/6 (mean survival time [MST]: 16.5 vs. 12.0 days; P = 0.004), from NOD.SCID into NOD (MST: 23.5 vs. 14.0 days; P = 0.03), and from BALB/c into NOD (MST: 12.0 vs. 5.5 days; P = 0.003). In the BALB/c into B-cell–deficient mice model, islet survival was prolonged as well (MST: μMT = 32.5 vs. WT = 14 days; P = 0.002). Pathology revealed reduced CD3+ cell islet infiltration and confirmed the absence of B cells in treated mice. Mechanistically, effector T cells were reduced in number, concomitant with a peripheral Th2 profile skewing and ex vivo recipient hyporesponsiveness toward donor-derived antigen as well as islet autoantigens. Finally, an anti-CD22/cal and CTLA4-Ig–based combination therapy displayed remarkable prolongation of graft survival in the stringent model of islet transplantation (BALB/c into NOD). Anti-CD22/cal–mediated B-cell depletion promotes the reduction of the anti-islet immune response in various models of islet transplantation
A Novel Clinically Relevant Strategy to Abrogate Autoimmunity and Regulate Alloimmunity in NOD Mice
OBJECTIVE - To investigate a new clinically relevant immunoregulatory strategy based on treatment with murine Thymoglobulin mATG Genzyme and CTLA4-Ig in NOD mice to prevent alloand autoimmune activation using a stringent model of islet transplantation and diabetes reversal. RESEARCH DESIGN AND METHODS - Using allogeneic islet transplantation models as well as NOD mice with recent onset type 1 diabetes, we addressed the therapeutic efficacy and immunomodulatory mechanisms associated with a new immunoregulatory protocol based on prolonged low-dose mATG plus CTLA4-Ig. RESULTS - BALB/c islets transplanted into hyperglycemic NOD mice under prolonged mATG+CTLA4-Ig treatment showed a pronounced delay in allograft rejection compared with untreated mice (mean survival time: 54 vs. 8 days, P < 0.0001). Immunologic analysis of mice receiving transplants revealed a complete abrogation of autoimmune responses and severe downregulation of alloimmunity in response to treatment. The striking effect on autoimmunity was confirmed by 100% diabetes reversal in newly hyperglycemic NOD mice and 100% indefinite survival of syngeneic islet transplantation (NOD.SCID into NOD mice). CONCLUSIONS - The capacity to regulate alloimmunity and to abrogate the autoimmune response in NOD mice in different settings confirmed that prolonged mATG+CTLA4-Ig treatment is a clinically relevant strategy to translate to humans with type 1 diabetes
Spectral Parameters for Scattering Amplitudes in N=4 Super Yang-Mills Theory
49 pages, 20 figures; v2: typos fixedPlanar N=4 Super Yang-Mills theory appears to be a quantum integrable four-dimensional conformal theory. This has been used to find equations believed to describe its exact spectrum of anomalous dimensions. Integrability seemingly also extends to the planar space-time scattering amplitudes of the N=4 model, which show strong signs of Yangian invariance. However, in contradistinction to the spectral problem, this has not yet led to equations determining the exact amplitudes. We propose that the missing element is the spectral parameter, ubiquitous in integrable models. We show that it may indeed be included into recent on-shell approaches to scattering amplitude integrands, providing a natural deformation of the latter. Under some constraints, Yangian symmetry is preserved. Finally we speculate that the spectral parameter might also be the regulator of choice for controlling the infrared divergences appearing when integrating the integrands in exactly four dimensions.Peer reviewe
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