962 research outputs found
k-Anomalies and Space-Time Supersymmetry in the Green-Schwarz Heterotic Superstring
The computation of -anomalies in the Green-Schwarz heterotic
superstring sigma-model and the corresponding Wess-Zumino consistency condition
constitute a powerful alternative approach for the derivation of manifestly
supersymmetric string effective actions. With respect to the beta-function
approach this technique presents the advantage that a result which is obtained
with the computation of beta-functions at loops can be obtained through the
calculation of -anomalies at \hbox{} loops. In this paper we
derive by a direct one-loop perturbative computation the -anomaly
associated to the Yang-Mills Chern-Simons threeform and, for the first time,
the one associated to the Lorentz Chern-Simons threeform. Contrary to what is
often stated in the literature we show that the Lorentz -anomaly gets
contributions from the integration over both the fermionic {\it and\/} bosonic
degrees of freedom of the string. A careful analysis of the absolute
coefficients of all these anomalies reveals that they can be absorbed by
setting dH={\alpha'\over4}(\trace F^2-\trace R^2), where is the
string tension, the expected result. We show that this relation ensures also
the absence of gauge and Lorentz anomalies in the sigma-model effective action.
We evidenciate the presence of infrared divergences.Comment: 50 pages, latex (uses equations.sty, feynman.tex and a4.sty),
DFPD/94/TH/4
Poor Outcome in a Mitochondrial Neurogastrointestinal Encephalomyopathy Patient with a Novel TYMP Mutation: The Need for Early Diagnosis.
Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a devastating autosomal recessive disorder due to mutations in TYMP, which cause loss of function of thymidine phosphorylase (TP), nucleoside accumulation in plasma and tissues and mitochondrial dysfunction. The clinical picture includes progressive gastrointestinal dysmotility, cachexia, ptosis and ophthalmoparesis, peripheral neuropathy and diffuse leukoencephalopathy, which usually lead to death in early adulthood. Therapeutic options are currently available in clinical practice (allogeneic hematopoietic stem cell transplantation and carrier erythrocyte entrapped TP therapy) and newer, promising therapies are expected in the near future. However, successful treatment is strictly related to early diagnosis. We report on an incomplete MNGIE phenotype in a young man harboring the novel heterozygote c.199 C>T (Q67X) mutation in exon 2, and the previously reported c.866 A>C (E289A) mutation in exon 7 in TYMP. The correct diagnosis was achieved many years after the onset of symptoms and unfortunately, the patient died soon after diagnosis because of multiorgan failure due to severe malnutrition and cachexia before any therapeutic option could be tried. To date, early diagnosis is essential to ensure that patients have the opportunity to be treated. MNGIE should be suspected in all patients who present with both gastrointestinal and nervous system involvement, even if the classical complete phenotype is lacking
The Space Filling Dirichlet 3-Brane in N=2, D=4 Superspace
We discuss a four-dimensional Volkov-Akulov supersymmetric theory on a
D3-brane with N=2 supersymmetry broken down to N=1.Comment: LaTeX2e file, espcrc2.sty, 8 pages. Based on talks given at the D. V.
Volkov Memorial Conference "Supersymmetry and Quantum Field Theory" (25-29
July, 2000, Kharkov, Ukraine). To be published in Nuclear Physics B
Conference Supplement
Sustaining Economic Exploitation of Complex Ecosystems in Computational Models of Coupled Human-Natural Networks
Understanding ecological complexity has stymied scientists for decades. Recent elucidation of the famously coined "devious strategies for stability in enduring natural systems" has opened up a new field of computational analyses of complex ecological networks where the nonlinear dynamics of many interacting species can be more realistically mod-eled and understood. Here, we describe the first extension of this field to include coupled human-natural systems. This extension elucidates new strategies for sustaining extraction of biomass (e.g., fish, forests, fiber) from ecosystems that account for ecological complexity and can pursue multiple goals such as maximizing economic profit, employment and carbon sequestration by ecosystems. Our more realistic modeling of ecosystems helps explain why simpler "maxi-mum sustainable yield" bioeconomic models underpinning much natural resource extraction policy leads to less profit, biomass, and biodiversity than predicted by those simple models. Current research directions of this integrated natu-ral and social science include applying artificial intelligence, cloud computing, and multiplayer online games
A Twistor Formulation of the Non-Heterotic Superstring with Manifest Worldsheet Supersymmetry
We propose a new formulation of the type II superstring which is
manifestly invariant under both target-space supersymmetry and worldsheet
super reparametrizations. This gives rise to a set of twistor
(commuting spinor) variables, which provide a solution to the two Virasoro
constraints. The worldsheet supergravity fields are shown to play the r\^ole of
auxiliary fields.Comment: 21p., LaTe
Reinforced feedback in virtual environment for rehabilitation of upper extremity dysfunction after stroke: preliminary data from a randomized controlled trial.
OBJECTIVES: To study whether the reinforced feedback in virtual environment (RFVE) is more effective than traditional rehabilitation (TR) for the treatment of upper limb motor function after stroke, regardless of stroke etiology (i.e., ischemic, hemorrhagic). DESIGN: Randomized controlled trial. Participants. Forty-four patients affected by stroke. Intervention. The patients were randomized into two groups: RFVE (N = 23) and TR (N = 21), and stratified according to stroke etiology. The RFVE treatment consisted of multidirectional exercises providing augmented feedback provided by virtual reality, while in the TR treatment the same exercises were provided without augmented feedbacks. Outcome Measures. Fugl-Meyer upper extremity scale (F-M UE), Functional Independence Measure scale (FIM), and kinematics parameters (speed, time, and peak). RESULTS: The F-M UE (P = 0.030), FIM (P = 0.021), time (P = 0.008), and peak (P = 0.018), were significantly higher in the RFVE group after treatment, but not speed (P = 0.140). The patients affected by hemorrhagic stroke significantly improved FIM (P = 0.031), time (P = 0.011), and peak (P = 0.020) after treatment, whereas the patients affected by ischemic stroke improved significantly only speed (P = 0.005) when treated by RFVE. CONCLUSION: These results indicated that some poststroke patients may benefit from RFVE program for the recovery of upper limb motor function. This trial is registered with NCT01955291
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