Vergleichende bilaterale magnetresonanztomographische Untersuchung der Hufregion im Niederfeld-MRT

Durch die Einführung der MRT-Untersuchung am stehenden sedierten Pferd ist deren Anzahl deutlich angestiegen. Hierbei stellen sich neue Fragen und Herausforderungen bezüglich der Einschätzung der Vielzahl an auftretenden Signalveränderungen. Es ergeben sich aber auch neue Möglichkeiten bezüglich der statistischen Auswertung von Befunden mit aussagekräftigen Fallzahlen. In dieser Studie sollte daher untersucht werden, wie Signalveränderungen statistisch verwendbar beschrieben und eingestuft werden können. Weiterhin sollte die Verteilung der Befunde insgesamt und bei der bilateralen Untersuchung der Vordergliedmaßen bestimmt werden. Mögliche Rückschlüsse auf deren klinische Bedeutung sollten gezogen werden. Hierzu wurden 120 bilaterale Niederfeld-MRT-Untersuchungen der Hufregion (240 Gliedmaßen) am stehenden Pferd durch zwei Tierärzte gesichtet und eine Befundbeschreibung mit einem Einstufungsschema (Grade 1-4) entsprechend dem vorgefundenen Spektrum an Signalveränderungen erstellt. Durch Anwendung und Zusammenfassung 66 wiederholte Diskussion der verschiedenen Kriterien im 1. Bewertungsdurchgang wurden die Beschreibungen und Grade auf Grundlage bestehender Literatur ausgearbeitet. In einem 2. Bewertungsdurchgang wurden die Strukturen eingestuft und die Ergebnisse statistisch ausgewertet. Hierbei wurden die generellen Häufigkeiten der Signalabweichungen erfasst und deren Zusammenhang zum Auftreten von unilateralen oder bilateralen Lahmheiten beachtet. Signalabweichungen am Strahlbein, der Tiefen Beugesehne und dem Hufgelenk standen deutlich im Vordergrund. Hierbei waren Strahlbeinveränderungen signifikant häufiger bei beidseitig lahmen Pferden zu finden, während Sehnenveränderungen deutlich häufiger bei einseitig lahmen Pferden vorgefunden wurden. Hufgelenkveränderungen wurden hingegen nicht signifikant vermehrt bei bilateralen oder unilateralen Lahmheiten festgestellt. Die Fesselbein-Strahlbein-Hufbeinbänder zeigten eine Häufung von Signalabweichungen bei lahmen Gliedmaßen, wobei diese vermehrt in Zusammenhang mit starken Veränderungen des Strahlbeins zu beobachten waren. Bei den übrigen Strukturen ließ sich kein statistisch aussagekräftiger Zusammenhang feststellen, da die Fallzahlen mit dem deutlichsten Befund an diesen Strukturen zu gering für eine Auswertung waren. Die entstandene Befundbeschreibung mit Einstufungsschema ermöglicht Vergleiche der MRT-Veränderungen z.B. mit klinischen Parametern. Signalabweichungen bestimmter Strukturen konnten statistisch eindeutig mit dem Auftreten und der Art der Lahmheit in Verbindung gebracht werden, während dies bei anderen Strukturen nicht möglich war. Hieraus ergeben sich Hinweise für die Einschätzung der Befunde und ihrer klinischen Relevanz. Insbesondere geringgradige Befunde sollten vorsichtig bewertet werden, da diese auch häufig bei nicht lahmen Gliedmaßen auftraten. Weitere statistische Vergleiche mit klinischen Parametern sind möglich und notwendig um das Krankheitsbild des „Equinen palmaren Fußsyndroms“ weiter zu untersuchen.As a result of adopting MRI examinations for standing sedated horses their number has increased significantly. In this respect there are new questions and challenges being faced regarding estimating the huge number of occurring signal changes. New possibilities also arise regarding the statistical analysis of findings with convincing number of examined cases. In this study therefore it should be investigated how signal changes can be suitably described and classified statistically. Furthermore, the distribution of the findings as a whole and in the bilateral investigations of the forelimbs should be ascertained. Possible conclusions should be drawn regarding their clinical significance. Concerning this, 120 bilateral low-field-MRI examinations of the foot (240 limbs) on a standing horse were looked at by two veterinarians and a description of the analysis with a classification scheme (grades 1-4) corresponding to the existing spectrum of signal changes was compiled. By applying and repeatedly discussing the various Summary 68 criteria in the first evaluation round the descriptions and grades were worked out on the basis of existing literature. In a second evaluation round the structures were classified and the results statistically evaluated. In this regard the general frequency of signal deviations was recorded and its connection to the occurrence of unilateral or bilateral lameness was observed. Signal deviations at the navicular bone, deep digital flexor tendon and the coffin joint noticeably prevailed. In this respect changes to the navicular bone were found significantly more frequently in bilaterally lame horses while changes in tendons were found significantly more often in unilaterally lame horses. In contrast, changes in the coffin joint were not significantly more in bilateral or unilateral lameness. The collateral sesamoidean ligaments showed an accumulation of signal deviations at lame limbs, whereby this was observed more frequently in connection with pronounced changes of the navicular bone. In the remaining structures no statistically significant connection was found as the number of examined cases with the most significant results at these structures was too low for an evaluation. The related description of the findings with a classification scheme enables comparisons of MRI changes e.g. with clinical parameters. Signal deviations of certain structures were found to be clearly statistically associated with the occurrence and type of lameness, while this was not possible at other structures. This provides useful information for evaluating findings and their clinical relevance. Low-grade findings should be interpreted with caution since these also occurred frequently at non-lame limbs Further statistical comparisons with clinical parameters are possible and necessary in order to further examine the clinical picture of the equine palmar foot syndrome

Investment Horizons and Price Indeterminacy in Financial Markets

We examine how different investment horizons, and consequently the number of hands through which a security passes during its life, affect prices in a laboratory market populated by overlapping generations of investors. We find that (i) price deviations are larger in markets populated only by short-horizon investors compared to markets with long-horizon investors; (ii) for a given maturity of security, price deviations increase as investment horizons shrink (and frequency of transfers increases); and (iii) short investment horizons create upward pressure on prices when liquidity is high and downward pressure when liquidity is low

Success Factors of Communities for User Driven Content: the Case of Ciao.com

Virtual communities that produce “user driven content ” are a relatively new phenomenon. In this study we present the findings of an exploratory empirical study that focus on the success factors that stimulate content production from the perspective of community members. One main finding is that methods or tools that advance the transparency of what is going on in the community platform results in more content production. This accents the importance of new tools like RSS for example. Furthermore an ambiguous role of sociological motives was found. On the one hand there is statistical evidence that sociological motives and content production activities are closely linked. But on the other hand our descriptive data indicates only very weak sociological forces at work. We discuss some causes that may explain this result. KEYWORDS: Virtual communities, user driven content, exploratory empirical stud

Frequency-adaptive control of a three-phase single-stage grid-connected photovoltaic system under grid voltage sags

The low-voltage ride-through service is carried out in this paper according to the voltage profile described by the IEC 61400-21 European normative when short-duration voltage sags happen, and some instantaneous reactive power is delivered to the grid in accordance with the Spanish grid code; the mandatory limitation of the amplitude of the three-phase inverter currents to its nominal value is carried out with a novel control strategy, in which a certain amount of instantaneous constant active power can also be delivered to the grid when small or moderate voltage sags happen. A Multiple second order generalized integrator frequency-locked loop synchronization algorithm is employed in order to estimate the system frequency without harmonic distortions, as well as to output the positive- and the negative- sequence of the {\alpha}\b{eta} quantities of the three-phase grid voltages when balanced and unbalanced voltage sags happen in a frequency-adaptive scheme. The current control is carried out in the stationary reference frame, which guarantees the cancellation of the harmonic distortions in the utility grid currents using a Harmonic compensation structure, and the implementation of a constant active power control in order to protect the DC link capacitor from thermal stresses avoiding the appearance of large harmonic distortions at twice the fundamental frequency in the DC link voltage. A case study of a three-phase single-stage grid-connected PV system with a maximum apparent power about 500 kVA is tested with several simulations using MATLAB/SIMULINK firstly, and secondly, with some experiments using the Controller hardware-in-the-loop (CHIL) simulation technique for several types of voltage sags in order to do the final validation of the control algorithms

Application of gas diffusion electrodes in bioeconomy: An update

The transition of today's fossil fuel based chemical industry toward sustainable production requires improvement of established production processes as well as development of new sustainable and bio-based synthesis routes within a circular economy. Thereby, the combination of electrochemical and biotechnological advantages in such routes represents one important keystone. For the electrochemical generation of reactants from gaseous substrates such as O2 or CO2, gas diffusion electrodes (GDE) represent the electrodes of choice since they overcome solubility-based mass transport limitations. Within this article, we illustrate the architecture, function principle and fabrication of GDE. We highlight the application of GDE for conversion of CO2 using abiotic catalysts for subsequent biosynthesis as well as the application of microbial catalysts at GDE for CO2 conversion. The reduction of oxygen at GDE is summarized for the application of oxygen depolarized cathodes in microbial fuel cells and generation of H2O2 to drive enzymatic reactions. Finally, engineering aspects such as scale-up and the modeling of GDE-based processes are described. This review presents an update on the application of GDE in bio-based production systems and emphasizes their large potential for sustainable development of new pathways in bioeconomy

Assessment of Sprint Parameters in Top Speed Interval in 100 m Sprint—A Pilot Study Under Field Conditions

Improving performances in sprinting requires feedback on sprint parameters such as step length and step time. However, these parameters from the top speed interval (TSI) are difficult to collect in a competition setting. Recent advances in tracking technology allows to provide positional data with high spatio-temporal resolution. This pilot study, therefore, aims to automatically obtain general sprint parameters, parameters characterizing, and derived from TSI from raw speed. In addition, we propose a method for obtaining the intra-cyclic speed amplitude in TSI. We analyzed 32 100 m-sprints of 7 male and 9 female athletes (18.9 ± 2.8 years; 100 m PB 10.55–12.41 s, respectively, 12.18–13.31 s). Spatio-temporal data was collected with a radio-based position detection system (RedFIR, Fraunhofer Institute, Germany). A general velocity curve was fitted to the overall speed curve (vbase), TSI (upper quintile of vbase values) was determined and a cosine term was added to vbase within TSI (vcycle) to capture the cyclic nature of speed. This allowed to derive TSI parameters including TSI amplitude from the fitted parameters of the cosine term. Results showed good approximation for vbase (error: 5.0 ± 1.0%) and for vcycle (2.0 ± 1.0%). For validation we compared spatio-temporal TSI parameters to criterion values from laser measurement (speed) and optoelectric systems (step time and step length) showing acceptable RMSEs for mean speed (0.08 m/s), for step time (0.004 s), and for step length (0.03 m). Top speed interval amplitude showed a significant difference between males (mean: 1.41 m/s) and females (mean: 0.71 m/s) and correlations showed its independence from other sprint parameters. Gender comparisons for validation revealed the expected differences. This pilot study investigated the feasibility of estimating sprint parameters from high-quality tracking data. The proposed method is independent of the data source and allows to automatically obtain general sprint parameters and TSI parameters, including TSI amplitude assessed here for the first time in a competition-like setting

β-Catenin Promotes the Differentiation of Epidermal Langerhans Dendritic Cells

The epithelial signaling protein and transcriptional regulator β-catenin has recently been implicated in hematopoietic dendritic cell (DC) differentiation as well as in DC-mediated tolerance. We here observed that epidermal Langerhans cells (LCs) but not interstitial/dermal DCs express detectable β-catenin. LCs are unique among the DC family members in that LC networks critically depend on epithelial adhesion molecules as well as on the cytokine transforming growth factor-β1 (TGF-β1). However, despite the important functions of LCs in the immune system, the molecular mechanisms governing LC differentiation and maintenance remain poorly defined. We found that TGF-β1 induces β-catenin in progenitor cells undergoing LC differentiation and that β-catenin promotes LC differentiation. Vitamin D, another epidermal signal, enhanced TGF-β1-mediated β-catenin induction and promoted the expression of multiple epithelial genes by LCs. Moreover, full-length vitamin D receptor (VDR) promoted, whereas a truncated VDR diminished, the positive effects of ectopic β-catenin on LC differentiation. Therefore, we here identified β-catenin as a positive regulator of LC differentiation in response to TGF-β1 and identified a functional interaction between β-catenin and VDR in these cells

Prevalence of Drug-Resistant HIV-1 Variants in Untreated Individuals in Europe: Implications for Clinical Management

BackgroundInfection with drug-resistant human immunodeficiency virus type 1 (HIV-1) can impair the response to combination therapy. Widespread transmission of drug-resistant variants has the disturbing potential of limiting future therapy options and affecting the efficacy of postexposure prophylaxis penta increase-spacing 1>MethodsWe determined the baseline rate of drug resistance in 2208 therapy-naive patients recently and chronically infected with HIV-1 from 19 European countries during 1996-2002 ResultsIn Europe, 1 of 10 antiretroviral-naive patients carried viruses with ⩾1 drug-resistance mutation. Recently infected patients harbored resistant variants more often than did chronically infected patients (13.5% vs. 8.7%; P=.006). Non-B viruses (30%) less frequently carried resistance mutations than did subtype B viruses (4.8% vs. 12.9%; P<.01). Baseline resistance increased over time in newly diagnosed cases of non-B infection: from 2.0% (1/49) in 1996-1998 to 8.2% (16/194) in 2000-2001 ConclusionsDrug-resistant variants are frequently present in both recently and chronically infected therapy-naive patients. Drug-resistant variants are most commonly seen in patients infected with subtype B virus, probably because of longer exposure of these viruses to drugs. However, an increase in baseline resistance in non-B viruses is observed. These data argue for testing all drug-naive patients and are of relevance when guidelines for management of postexposure prophylaxis and first-line therapy are update