Economism and its Limits

Articl

The dynamical balance, transport and circulation of the Antarctic Circumpolar Current

The physical ingredients of the ACC circulation are reviewed. A picture of thecirculation is sketched by means of recent observations of the WOCE decade. Wepresent and discuss the role of forcing functions (wind stress, surfacebuoyancy flux) in the balance of the (quasi)-zonal flow, the meridionalcirculation and their relation to the ACC transport. Emphasis will be on theinterrelation of the zonal momentum balance and the meridional circulation, theimportance of diapycnal mixing and eddy processes. Finally, new model conceptsare described: a model of the ACC transport dependence on wind stress andbuoyancy flux, based on linear wave theory; and a model of the meridionaloverturning of the Southern Ocean, based on zonally averaged dynamics with eddyparameterization

Information Processing of Foreign Exchange News: Extending the Overshooting Model to Include Qualitative Information from News Sentiment

In a globalized world, the volume of international trade is based on both import and export prices, thereby making a country\u27s economy highly dependent on exchange rates. In order to study exchange rate movements, one frequently exploits the so-called Dornbusch overshooting model. However, the model is controversial from a theoretical point of view: it presupposes the processing of information, though this is not directly reflected by the underlying variables. As a remedy, this paper investigates a potential cognitive bias by including textual news content, thus adjusting for information dissemination. As such, we perform a multivariate analysis to compare the classical overshooting model with an extended variant that includes news sentiment. Our results show that news has a substantial explanatory power of 11% of the exchange rate forecasting error variance. In addition, we also find statistical evidence that a shock in news sentiment may lead to overshooting

Verfahren zur elektrochemischen Messung von Stickstoffmonoxid und S-Nitrosothiolen in Flüssigkeiten

Stickstoffmonoxid (NO) ist in den letzten Jahren als Kreislaufregulator und biologischer Botenstoff in den Mittelpunkt des Interesses gerückt. Inzwischen gilt als sicher, dass NO an vielen Schlüsselstellen, nicht nur in der Kreislaufregulation, aber dort besonders, eine prominente Rolle spielt. Das Endothel als disseminiertes Organ betrachtet ist als Produktionsort des zu Beginn der Forschungen phänomenologisch ,,endothelium derived relaxing factor" genannten NO scheinbar von größerer Bedeutung, als zunächst angenommen. Anstelle einer einfachen Gefäßauskleidung ist das Endothel Regulator vieler wichtiger Prozesse. Diskutierte Wirkungen reichen vom septischen Kreislaufversagen bei überschießender NO-Produktion, bis zur Atherosklerose bei gestörter Endothelfunktion mit verminderter NO-Produktion. Es gibt hier ,,gute" und ,,böse" Wirkungen, so das hier von einer Janusköpfigkeit, also Doppelgesichtigkeit, gesprochen wird. NO wird hier jeweils eine Schlüsselrolle als Botenstoff und Effektor zugewiesen. Bisher gibt es aber keine praktikablen Verfahren, um die effektive NO-Produktion zeitnah und in vivo zu quantifizieren. In der vorliegenden Arbeit ist im Anschluß an vorbestehenden Überlegungen und Verfahren eine Methode entwickelt worden, mit deren Hilfe Rückschlüsse auf die jeweilige Produktion und den Plasmaspiegel von NO gezogen werden können. Stickstoffmonoxid hat eine Halbwertszeit von wenigen Sekunden im Plasma. Ein wichtiges Stoffwechselprodukt aus dem Abbau des freien NO sind S-Nitrosothiole. Freies NO geht eine Verbindung mit Thiolgruppen von Plasmaproteinen ein. Diese gebundene Form von NO ist relativ stabil und gilt als Plasmaspeicher von NO. Es kann aus dieser Verbindung wieder herausgelöst werden und liegt dann wieder als freies NO vor. In der vorliegenden Arbeit werden die Grundlagen geschaffen für ein Verfahren, mit dem der Plasmaspiegel von S-Nitrosothiolen bestimmt, und Rückschlüsse auf die NO Produktion gezogen werden können. Die Methode basiert auf dem Umstand, dass man mittels Metallionen, wie beispielsweise Kupferionen, S-Nitrosothiole zur Dekomposition bringen kann. Das freigesetzte NO wurde dann mittels einer amperometrischen NO-selektiven Sonde gemessen. Die zu erwartenden Konzentrationen sind sehr gering und einer verlässlichen Messung nur bedingt zugänglich, da die Abspaltung von NO aus hochmolekularen S-Nitrosothiolen, wie dem S-Nitrosoalbumim, nur sehr langsam abläuft. Günstiger ist die Zerfallskinetik von niedermolekularen S-Nitrosoverbindungen. Daher wird der Zwischenschritt der Transnitrosylierung, der Übertragung der Nitrosylgruppe von Albumin auf einen niedermolekularen Baustein mit einer Nitrosogruppe, eingeschaltet. Die Konzentrationen des zu messenden NO bleiben aber sehr gering, so dass die Minimierung der Störeinflüsse der Methodik einen großen Teil der Arbeit einnimmt. Es konnte in dieser Arbeit nachgewiesen werden, dass S-Nitrosoalbumin mittels des beschriebenen Verfahrens quantitativ bestimmbar ist. Eine Übertragung des Verfahrens auf Messungen im Blutplasma wird der Gegenstand weiterer Forschungen sein

Learning Variational Models with Unrolling and Bilevel Optimization

In this paper we consider the problem of learning variational models in the context of supervised learning via risk minimization. Our goal is to provide a deeper understanding of the two approaches of learning of variational models via bilevel optimization and via algorithm unrolling. The former considers the variational model as a lower level optimization problem below the risk minimization problem, while the latter replaces the lower level optimization problem by an algorithm that solves said problem approximately. Both approaches are used in practice, but unrolling is much simpler from a computational point of view. To analyze and compare the two approaches, we consider a simple toy model, and compute all risks and the respective estimators explicitly. We show that unrolling can be better than the bilevel optimization approach, but also that the performance of unrolling can depend significantly on further parameters, sometimes in unexpected ways: While the stepsize of the unrolled algorithm matters a lot (and learning the stepsize gives a significant improvement), the number of unrolled iterations plays a minor role

Peri-operative chemotherapy for the treatment of resectable liver metastases from colorectal cancer: A systematic review and meta-analysis of randomized trials

<p>Abstract</p> <p>Background</p> <p>The role of peri-operative chemotherapy in patients with resected stage IV colorectal cancer (CRC) remains to be defined. This study was aimed at evaluating the effectiveness of peri-operative chemotherapy in patients with resected stage IV CRC by performing a meta-analysis of relevant trials.</p> <p>Methods</p> <p>We performed a literature search to identify trials comparing patients with stage IV CRC receiving peri-operative chemotherapy and surgery with patients undergoing surgery alone. The hazard ratio (HR) was estimated to assess any survival advantage of peri-operative chemotherapy.</p> <p>Results</p> <p>Eight trials conducted on a total of 1174 patients were identified by a literature search. In these trials, HR estimates suggested that peri-operative chemotherapy yielded no survival advantage over surgery alone (HR, 0.94; 95%CI, 0.8-1.10; <it>p </it>= 0.43). In a subset analysis on intra-arterial chemotherapy alone, no survival benefit was evident (HR, 1.0; 95% CI, 0.84-1.21; <it>p </it>= 0.96; I²= 30%), whereas in the trials involving systemic chemotherapy, the difference between the groups approached statistical significance (HR, 0.74; 95% CI, 0.53-1.04; <it>p </it>= 0.08; I²= 0%). Both peri-operative treatment groups had a significant recurrence-free survival benefit (HR, 0.78; 95% CI, 0.65-0.95; <it>P </it>= 0.01 for hepatic arterial infusion; and HR, 0.75; 95% CI, 0.62-0.91; <it>p </it>= 0.003 for systemic therapy). The toxicities of chemotherapy were acceptable in most trials.</p> <p>Conclusions</p> <p>This is the first meta-analysis demonstrating the importance of peri-operative chemotherapy in the treatment of resected stage IV CRC. Although the results must be carefully interpreted because of some limitations, critical issues were identified that must be resolved by future studies.</p

Evaluation of Pool-based Testing Approaches to Enable Population-wide Screening for COVID-19

Background: Rapid testing for an infection is paramount during a pandemic to prevent continued viral spread and excess morbidity and mortality. This study aimed to determine whether alternative testing strategies based on sample pooling can increase the speed and throughput of screening for SARS-CoV-2. Methods: A mathematical modelling approach was chosen to simulate six different testing strategies based on key input parameters (infection rate, test characteristics, population size, testing capacity etc.). The situations in five countries (US, DE, UK, IT and SG) currently experiencing COVID-19 outbreaks were simulated to reflect a broad variety of population sizes and testing capacities. The primary study outcome measurements that were finalised prior to any data collection were time and number of tests required; number of cases identified; and number of false positives. Findings: The performance of all tested methods depends on the input parameters, i.e. the specific circumstances of a screening campaign. To screen one tenth of each country's population at an infection rate of 1% - e.g. when prioritising frontline medical staff and public workers -, realistic optimised testing strategies enable such a campaign to be completed in ca. 29 days in the US, 71 in the UK, 25 in Singapore, 17 in Italy and 10 in Germany (ca. eight times faster compared to individual testing). When infection rates are considerably lower, or when employing an optimal, yet logistically more complex pooling method, the gains are more pronounced. Pool-based approaches also reduces the number of false positive diagnoses by 50%. Interpretation: The results of this study provide a clear rationale for adoption of pool-based testing strategies to increase speed and throughput of testing for SARS-CoV-2. The current individual testing approach unnecessarily wastes valuable time and resources.Comment: Revision; 16 pages, 3 figures, 2 tables, 2 supplementary figure

Infrared Nonlinear Optics

Contains reports on one research project.U.S. Air Force - Office of Scientific Research (Grant AFOSR-76-2894

A single-use chromatographic purification platform for viral gene transfer vectors & viral vaccines

In steric exclusion chromatography (SXC), a crude sample is mixed with polyethylene glycol (PEG) and fed onto a single-use cellulose column. In this operation, selectivity is influenced strongly by the target species’ size, so SXC is well suited for purification of virus particles. The purified product is recovered at physiological pH and conductivity. We have observed recoveries above 95% for several cell culture-based virus particles used as viral gene transfer vectors or as viral vaccines, including: adeno-associated virus (AAV), Modified Vaccinia Ankara (MVA) virus, influenza virus, and yellow fever virus. Preliminary data for purification of lentiviruses suggests recoveries exceeding 60%. Host cell DNA and protein depletion are typically above 90% and infectivity is not compromised thanks to the inert character of PEG towards biomolecules and the mild elution conditions. Several AAV serotypes and display mutants were produced using HEK cells and purified with up to 95% recovery. Elution fractions had ≤2×1014 viral genomes·L−1 and, depending on the specific AVV particle, the purified viruses successfully transduced or induced gene knockdown in vitro. Elution pools from MVA virus produced in continuous bioreactors with an avian cell line contained about 3.7×109 infectious virions measured by TCID50. For influenza virus, four strains were produced in MDCK cells. Full recovery of all strains was observed using identical SXC conditions for both infectious and chemically inactivated viruses. The column capacity in terms of the viral hemagglutinin antigen was \u3e 50 mg·m−2. In the case of yellow fever virus, two attenuated strains were produced in Vero cells. Here, full recovery of infective titers was also achieved: the elution fraction was concentrated more than 100-fold to a titer of \u3e6×109 plaque forming units (≈100 000 doses). In summary, SXC capture with PEG and unmodified cellulose membranes seems to perform very well for a broad range of viruses from different production processes. Thanks to the high degree of success in a relatively narrow operational range, SXC can drastically reduce process development. The high recoveries obtained so far, enable subsequent polishing operations with minimum risk to low overall process yields