Efficient computation of highly oscillatory integrals by using QTT tensor approximation

We propose a new method for the efficient approximation of a class of highly oscillatory weighted integrals where the oscillatory function depends on the frequency parameter $\omega \geq 0$, typically varying in a large interval. Our approach is based, for fixed but arbitrary oscillator, on the pre-computation and low-parametric approximation of certain $\omega$-dependent prototype functions whose evaluation leads in a straightforward way to recover the target integral. The difficulty that arises is that these prototype functions consist of oscillatory integrals and are itself oscillatory which makes them both difficult to evaluate and to approximate. Here we use the quantized-tensor train (QTT) approximation method for functional $m$-vectors of logarithmic complexity in $m$ in combination with a cross-approximation scheme for TT tensors. This allows the accurate approximation and efficient storage of these functions in the wide range of grid and frequency parameters. Numerical examples illustrate the efficiency of the QTT-based numerical integration scheme on various examples in one and several spatial dimensions.Comment: 20 page

Hepatitis induced by noni juice from Morinda citrifolia: A rare cause of hepatotoxicity or the tip of the iceberg?

A 24-year-old female patient presented to her community hospital with mild elevations of serum transaminase and bilirubin levels. Because of multiple sclerosis, she was treated with interferon beta-la for 6 weeks. After exclusion of viral hepatitis due to hepatitis A-E, interferon beta-la was withdrawn under the suspicion of drug-induced hepatitis. One week later, she was admitted again to her community hospital with severe icterus. The transaminase and bilirubin levels were highly elevated, and a beginning impairment of the liver synthesis was expressed by a reduced prothrombin time. The confinement to our department occurred with a fulminant hepatitis and the suspicion of beginning acute liver failure. There was no evidence for hepatitis due to potentially hepatotoxic viruses, alcoholic hepatitis, Budd-Chiari syndrome, hemochromatosis, and Wilson's disease. In her serum there were high titers of liver-kidney microsomal type 1 autoantibody; the serum gamma globulin levels were in the normal range. Fine-needle aspiration biopsy of the liver ruled out an autoimmune hepatitis but showed signs of drug-induced toxicity. During the interview, she admitted that for `general immune system stimulation' she had been drinking Noni juice, a Polynesian herbal remedy made from a tropical fruit (Morinda citrifolia), during the past 4 weeks. After cessation of the Noni juice ingestion, her transaminase levels normalized quickly and were in the normal range within 1 month. Copyright (c) 2006 S. Karger AG, Basel

Fast Quadrature Techniques for Retarded Potentials Based on TT/QTT Tensor Approximation

We consider the Galerkin approach for the numerical solution of retarded boundary integral formulations of the three dimensional wave equation in unbounded domains. Recently smooth and compactly supported basis functions in time were introduced which allow the use of standard quadrature rules in order to compute the entries of the boundary element matrix. In this paper, we use TT and QTT tensor approximations to increase the efficiency of these quadrature rules. Various numerical experiments show the substantial reduction of the computational cost that is needed to obtain accurate approximations for the arising integral

Improved quality of life in patients with refractory or recidivant ascites after insertion of transjugular intrahepatic portosystemic shunts

Background. We have recently shown that the transjugular intrahepatic portosystemic shunt (TIPS) is more effective than paracentesis in the treatment of cirrhotic patients with severe ascites and can prolong survival in selected patients. Although an improved quality of life (QOL) has been suggested in these patients after the TIPS procedure, so far there are no data available to substantiate this assumption. Therefore, the aim of this study was to determine the effect of TIPS on the QOL in cirrhotic patients with refractory or recidivant ascites. Methods: 21 cirrhotic patients who underwent TIPS for refractory or recidivant ascites were investigated. All patients were pretreated with repeated paracentesis for at least 1 year. Before the procedure and at 3 and 6 months during follow-up, the patients themselves rated QOL, fatigue and physical performance on a visual analogue scale (range 0-100). Furthermore, QOL was determined by the QOL index (range 0-10) according to Spitzer. Results: Patients' rating of the QOL on the visual analogue scale significantly increased from 35 +/- 25 (baseline) to 64 +/- 28 (3 months), and 66 +/- 24 (6 months; p = 0.02). Similarly, the QOL index significantly increased from 6.9 +/- 2.0 (baseline) to 8.3 +/- 2.1 (3 months), and 8.6 +/- 1.7 (6 months; p < 0.001). The increase of QOL was more pronounced in patients with complete response to TIPS. Conclusions: We demonstrate that TIPS for refractory or recidivant ascites improves the QOL in patients with cirrhosis. Our data indicates that this improvement is dependent on the response to therapy. Copyright (C) 2002 S. Karger AG, Basel

THE ROLE OF TECHNOLOGY FOR SERVICE INNOVATION IN SHARING ECONOMY ORGANIZATIONS – A SERVICE-DOMINANT LOGIC PERSPECTIVE

The role and influence of information technology related to business and value creation of a firm are discussed controversially. The question how technology can drive service innovations is especially crucial in highly competitive and quickly developing areas such as digital platforms – and at the same time not well understood. This study investigates the role of information technology for service innovation in sharing economy organizations. These organizations are digital platforms that conflate physical and digital service elements. Using a service-dominant logic perspective, we conduct an interpretive multiple-case study to gain a deeper understanding for types of service innovation in this area and the different roles that IT can play in these initiatives. Our findings reveal different areas for service innovation and thereby help identifying previously unexplored interdependencies between the service ecosystem and value co-creation. We furthermore find that organizations’ choices on the role of IT are dependent on the level of heterogeneity and standardization of the mediated transactions. We derive four archetypes for the role of IT in service innovation that serve to explain how and why IT is exploited sharing economy organizations. The findings are translated into practical guidelines for managers of digital platforms

Проблеми та напрямки вдосконалення ведення обліку виробничих запасів на підприємстві

У статті розглянуто основні проблеми аналітичного обліку виробничих запасів. Досліджено напрямки вдосконалення аналітичного обліку виробничих запасів та його інформаційне забезпечення. Розглянуто шляхи використання автоматизованого обліку виробничих запасів на підприємствах, а також приведено згруповані задачі при машинній обробці інформації обліку виробничих запасів