An Investigation Into The Dynamics Of Self-Acting Compressor Valves

In principle, a reciprocating compressor stage consists of a cylinder, the working volume which varies periodically due to a piston moving inside a liner. Latter is sealed by two sets of valves. On the one hand the suction valve for admitting the gas to be compressed and on the other the discharge valve for allowing the high pressure gas to be delivered to the downstream process. The typical type of valves used within compressors for refrigeration plants are reed valves. The key feature of these mentioned valves - simultaneously affecting both their sealing performance as well as the reliability - is that they are not actuated. They are held close by elastic forces and they open and close automatically, in accordance to the balance of gas pressure forces as well as the previously mentioned elastic ones. The former is primarily characterized by the static pressure difference across the closed valve and the aerodynamic drag brought about by the gas flow impinging onto the sealing reed in a partially or fully open valve. Evidently, a high degree of coupling between the gas flow and the sealing element motion, today referred to as fluid-structure interaction (FSI), can be expected. The reed and the absence of a reliable guide that would provide for the plan-parallel motion give rise to non-parallel impacts with other parts of the valve assembly, leading to dynamic stress effects. This not only complicates the prediction of the reed valve dynamics, it also causes premature sealing element fracture, decreases the compressor efficiency and ultimately leads to unscheduled maintenance shutdowns. Consequently pursuing the optimization of the reed valve movement is a necessity. The measurements of reed valve dynamics as well as their movement in compressors can be performed by commercial proximity sensors, strain gauges or in house developed sensors. Although timing and lift information is available through these methods, other modes of fluttering such as torsional movement are more difficult to be observed. This work tries to address these aspects by providing real operation data obtained in a test rig. An in-depth comparative analysis of three measurement methodologies, represented by an optical, resistive as well as an eddy current sensor system will be carried out regarding their possible adoption in a state-of-the-art refrigeration compressor. Furthermore, the acquired data will be evaluated with respect to its potential application for collecting mentioned torsional movements. In the end a comparison against a numerical approach shall be conducted

Automatic spike correction using UNIFIT 2020

The improvement of the software UNIFIT 2020 from an analysis processing software for photoelectron spectroscopy (XPS) only to a powerful tool for XPS, Auger electron spectroscopy (AES), X-ray absorption spectroscopy (XAS), and Raman spectroscopy requires new additional programme routines. Particularly, the implementation of the analysis of Raman spectra needs a well-working automatic spike correction. The application of the modified discrete Laplace operator method allows for a perfect localization and correction of the spikes and finally a successful peak fit of the spectra. The theoretical basis is described. Test spectra allow for the evaluation of the presented method. A comparison of the original and spike-corrected real measurements demonstrates the high quality of the method used

Treatment of Focal Cartilage Defects in Minipigs with Zonal Chondrocyte/Mesenchymal Progenitor Cell Constructs

Despite advances in cartilage repair strategies, treatment of focal chondral lesions remains an important challenge to prevent osteoarthritis. Articular cartilage is organized into several layers and lack of zonal organization of current grafts is held responsible for insufficient biomechanical and biochemical quality of repair-tissue. The aim was to develop a zonal approach for cartilage regeneration to determine whether the outcome can be improved compared to a non-zonal strategy. Hydrogel-filled polycaprolactone (PCL)-constructs with a chondrocyte-seeded upper-layer deemed to induce hyaline cartilage and a mesenchymal stromal cell (MSC)-containing bottom-layer deemed to induce calcified cartilage were compared to chondrocyte-based non-zonal grafts in a minipig model. Grafts showed comparable hardness at implantation and did not cause visible signs of inflammation. After 6 months, X-ray microtomography (_CT)-analysis revealed significant bone-loss in both treatment groups compared to empty controls. PCL-enforcement and some hydrogel-remnants were retained in all defects, but most implants were pressed into the subchondral bone. Despite important heterogeneities, both treatments reached a significantly lower modified O’Driscoll-score compared to empty controls. Thus, PCL may have induced bone-erosion during joint loading and misplacement of grafts in vivo precluding adequate permanent orientation of zones compared to surrounding native cartilage. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

PESTO: Proactively Secure Distributed Single Sign-On, or How to Trust a Hacked Server

Single Sign-On (SSO) is becoming an increasingly popular authentication method for users that leverages a trusted Identity Provider (IdP) to bootstrap secure authentication tokens from a single user password. It alleviates some of the worst security issues of passwords, as users no longer need to memorize individual passwords for all service providers, and it removes the burden of these service to properly protect huge password databases. However, SSO also introduces a single point of failure. If compromised, the IdP can impersonate all users and learn their master passwords. To remedy this risk while preserving the advantages of SSO, Agrawal et al. (CCS\u2718) recently proposed a distributed realization termed PASTA (password-authenticated threshold authentication) which splits the role of the IdP across $n$ servers. While PASTA is a great step forward and guarantees security as long as not all servers are corrupted, it uses a rather inflexible corruption model: servers cannot be corrupted adaptively and --- even worse --- cannot recover from corruption. The latter is known as proactive security and allows servers to re-share their keys, thereby rendering all previously compromised information useless. In this work, we improve upon the work of PASTA and propose a distributed SSO protocol with proactive and adaptive security (PESTO), guaranteeing security as long as not all servers are compromised at the same time. We prove our scheme secure in the UC framework which is known to provide the best security guarantees for password-based primitives. The core of our protocol are two new primitives we introduce: partially-oblivious distributed PRFs and a class of distributed signature schemes. Both allow for non-interactive refreshs of the secret key material and tolerate adaptive corruptions. We give secure instantiations based on the gap one-more BDH and RSA assumption respectively, leading to a highly efficient 2-round PESTO protocol. We also present an implementation and benchmark of our scheme in Java, realizing OAuth-compatible bearer tokens for SSO, demonstrating the viability of our approach

Preclinical Testing of New Hydrogel Materials for Cartilage Repair: Overcoming Fixation Issues in a Large Animal Model

Reinforced hydrogels represent a promising strategy for tissue engineering of articular cartilage. They can recreate mechanical and biological characteristics of native articular cartilage and promote cartilage regeneration in combination with mesenchymal stromal cells. One of the limitations of in vivo models for testing the outcome of tissue engineering approaches is implant fixation. The high mechanical stress within the knee joint, as well as the concave and convex cartilage surfaces, makes fixation of reinforced hydrogel challenging. Methods. Different fixation methods for full-thickness chondral defects in minipigs such as fibrin glue, BioGlue®, covering, and direct suturing of nonenforced and enforced constructs were compared. Because of insufficient fixation in chondral defects, superficial osteochondral defects in the femoral trochlea, as well as the femoral condyle, were examined using press-fit fixation. Two different hydrogels (starPEG and PAGE) were compared by 3D-micro-CT (μCT) analysis as well as histological analysis. Results. Our results showed fixation of below 50% for all methods in chondral defects. A superficial osteochondral defect of 1 mm depth was necessary for long-term fixation of a polycaprolactone (PCL)-reinforced hydrogel construct. Press-fit fixation seems to be adapted for a reliable fixation of 95% without confounding effects of glue or suture material. Despite the good integration of our constructs, especially in the starPEG group, visible bone lysis was detected in micro-CT analysis. There was no significant difference between the two hydrogels (starPEG and PAGE) and empty control defects regarding regeneration tissue and cell integration. However, in the starPEG group, more cell-containing hydrogel fragments were found within the defect area. Conclusion. Press-fit fixation in a superficial osteochondral defect in the medial trochlear groove of adult minipigs is a promising fixation method for reinforced hydrogels. To avoid bone lysis, future approaches should focus on multilayered constructs recreating the zonal cartilage as well as the calcified cartilage and the subchondral bone plate

Схема образования стружки при несвободном резании

Дан анализ существующих схем образования стружки при свободном и несвободном резании материалов. Предложен новый подход к описанию зоны стружкообразования при несвободном резании с единственной условной поверхностью сдвига. Решена задача аналитического описания формы условной поверхности сдвига в общем виде. Приведены примеры анализа зоны стружкообразования для острозаточенного и закругленного лезвия инструмента. Показана актуальность полученных результатов для решения задач механики процесса резания материалов лезвийными инструментами. The analysis of existing schemes chip formation with the free and non-free cutting materials. A new approach to the description of chip area with an unfree cutting with a single conventional shear surface. The problem of analytical description of the conditional form shear surfaces in general. Examples of chip area for analysis ostrozatochennogo and rounded blade tool. The urgency of the results for the solution of problems of the process of cutting edge tools of mechanics of materials

Partizipative Gestaltung von Zukunftsszenarien nachhaltiger Mobilität. Ergebnisse der Szenario-Workshops im Projekt InnaMoRuhr

Gestützt auf die Ergebnisse einer großangelegten Befragung aller Angehörigen der drei UA-Ruhr-Universitäten, fanden im Herbst/Winter 2021/22 fünf Szenario-Workshops mit Studierenden und Mitarbeitenden aus Technik und Verwaltung sowie aus Forschung und Lehre statt (Kap. 2). Dabei arbeitete das Team von InnaMoRuhr sechs Monate lang mit Foresight Solutions zusammen, einem Beratungshaus für zukunftsorientierte Beteiligungsverfahren, das eine Vielzahl von Methoden strategischer Vorausschau einbrachte (Kap. 3). In den ersten drei Workshops wurden vier zuvor entwickelte Ausgangsszenarien diskutiert und weiterentwickelt, die das Projektteam vorab auf Basis der Befragungsdaten entworfen hatte: Digitale Universität, vernetzte Universitäten, Fahrraduniversitäten und Universitäten als Hubs (Kap. 4). Detailliert wurden die möglichen Wirkungen und Nebenwirkungen der vier weiterentwickelten Szenarien erarbeitet – mit dem überraschenden Ergebnis, dass die digitale Universität als wünschenswerte Projektion, die in ferner Zukunft Realität werden könnte, am schlechtesten und die vernetzte Universität knapp am besten abschneidet (Kap. 5). Anders als in den ursprünglichen Planungen für das Projekt InnaMoRuhr, in denen es um Elektromobilität und Shuttle-Verbindungen zwischen den UA-Ruhr-Universitäten ging, lag der Fokus der meisten Szenarien auf dem ÖPNV und dem Radverkehr: Ein kostengünstiger und zuverlässiger ÖPNV, der zudem mit dem Radverkehr vernetzt ist, erschien vielen Teilnehmer:innen der Workshops als eine Option, die ihre Mobilitätsmuster nachhaltig verändern könnte. Ferner wurden während der ersten drei Workshops 75 fiktive Personas entwickelt, um den mobilen Alltag der Mitglieder der drei UA-Ruhr-Universitäten plastisch abzubilden, die Szenarien mit der Lebenswirklichkeit der Menschen abzugleichen und Chancen und Risiken zu identifizieren. Die den Personas zugeschriebenen Erwartungen drehten sich – neben dem dominanten Thema Mobilität – vor allem um die Veränderungen der Arbeitsorganisation (New Work), um die Flexibilität (z. B. hinsichtlich der Work-Life-Balance) sowie um mögliche Akzeptanzprobleme. So erfordern beispielsweise Kinder im eigenen Haushalt eine gewisse Flexibilität der Gestaltung von Wegeketten sowie die Fähigkeit, spontan auf unerwartete Ereignisse reagieren zu können. Insbesondere in den Punkten New Work und Flexibilität dominieren die (negativen) Befürchtungen gegenüber den (positiven) Erwartungen. Zudem ließen sich Unterschiede zwischen den Funktionsgruppen erkennen. Das überraschendste Ergebnis ist jedoch, dass das weiterentwickelte Szenario der vernetzten Universitäten bei der Konfrontation mit der Lebenswirklichkeit unterschiedlicher Gruppen aufgrund der damit verbundenen Belastungen und Herausforderungen deutlich schlechter bewertet wurde als das noch abstrakte Ausgangsszenario. Es belegte mit großem Abstand den letzten Platz (Kap. 6). Im vierten Workshop wurden acht der zuvor erstellten Personas ausgewählt, um mögliche Probleme ihrer Alltagsmobilität genauer zu beschreiben und Lösungen zu entwickeln. Zunächst wurden Maßnahmen entwickelt, die einer transformationsfreudigen Persona das Leben leichter machen. Diese wurden dann aus Sicht von transformationsskeptischen Personas bewertet – mit dem wenig überraschenden Ergebnis, dass sie leicht verhalten reagierten und von ihrer skeptischen Haltung nur schwer abzubringen waren. Interessanter waren die Überlegungen zur Skalierbarkeit der Maßnahmen. Die meisten Maßnahmen – darin waren sich die Arbeitsgruppen einig – sind im kleinen Rahmen (200 Personen pro Universität) problemlos umsetzbar, stoßen im mittleren Rahmen (2.000) auf Probleme und sind in großem Maßstab (20.000) – abgesehen von leicht skalierbaren IT-Lösungen – kaum umsetzbar (Kap. 7). Auf Grundlage der Konzepte, die in den ersten vier Workshops erarbeitet wurden, entwickelte das InnaMoRuhr-Team drei Vorschläge für Realexperimente, die im fünften Workshop intensiv diskutiert und auf ihre Machbarkeit hin überprüft wurden: Fahrradhub (mit Radabstellanlage, Werkstatt etc.), Mobilitätsbudget und E-Carsharing. Die Teilnehmenden konstruierten Prototypen in Form von 3D-Modellen und erarbeiteten konkrete Vorschläge zur Umsetzung der drei dezentralen Realexperimente, die dann von September bis Dezember 2022 im Rahmen eines Reallabors in Bochum (E-Carsharing), Dortmund (Fahrradhub) und Duisburg-Essen (Mobilitätsbudget, standortübergreifend) stattgefunden haben (Kap. 8)

Cerebrospinal fluid markers before and after shunting in patients with secondary and idiopathic normal pressure hydrocephalus

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to explore biochemical changes in the cerebrospinal fluid (CSF) induced by shunt surgery and the relationship between these changes and clinical improvement.</p> <p>Methods</p> <p>We measured clinical symptoms and analysed lumbar CSF for protein content, neurodegeneration and neurotransmission markers in patients with secondary (SNPH, n = 17) and idiopathic NPH (INPH, n = 18) before and 3 months after shunt surgery. Patients were divided into groups according to whether or not there was improvement in clinical symptoms after surgery.</p> <p>Results</p> <p>Preoperatively, the only pathological findings were elevated neurofilament protein (NFL), significantly more so in the SNPH patients than in the INPH patients, and elevated albumin content. Higher levels of NFL correlated with worse gait, balance, wakefulness and neuropsychological performance. Preoperatively, no differences were seen in any of the CSF biomarkers between patients that improved after surgery and those that did not improve. Postoperatively, a greater improvement in gait and balance performance correlated with a more pronounced reduction in NFL. Levels of albumin, albumin ratio, neuropeptide Y, vasoactive intestinal peptide and ganglioside GD3 increased significantly after shunting in both groups. In addition, Gamma amino butyric acid increased significantly in SNPH and tau in INPH.</p> <p>Conclusion</p> <p>We conclude that a number of biochemical changes occur after shunt surgery, but there are no marked differences between the SNPH and INPH patients. The results indicate that NFL may be a marker that can predict a surgically reversible state in NPH.</p

BET-inhibition by JQ1 promotes proliferation and self-renewal capacity of hematopoietic stem cells

Although inhibitors of bromodomain and extra terminal domain (BET) proteins show promising clinical activity in different hematologic malignancies, a systematic analysis of the consequences of pharmacological BET inhibition on healthy hematopoietic (stem) cells is urgently needed. We found that JQ1 treatment decreases the numbers of pre-, immature and mature B cells while numbers of early pro-B cells remain constant. In addition, JQ1 treatment increases apoptosis in T cells, all together leading to reduced cellularity in thymus, bone marrow and spleen. Furthermore, JQ1 induces proliferation of long-term hematopoietic stem cells, thereby increasing stem cell numbers. Due to increased numbers, JQ1-treated hematopoietic stem cells engrafted better after stem cell transplantation and repopulated the hematopoietic system significantly faster after sublethal myeloablation. As quantity and functionality of hematopoietic stem cells determine the duration of life-threatening myelosuppression, BET inhibition might benefit patients in myelosuppressive conditions

The Short Rise and Long Fall of heterodox Economics in germany After the 1970s: Explorations in a Scientific Field of Power and Struggle.

In the context of ongoing criticisms of the lack of pluralism in economics, the present article aims to discuss the development of ‘heterodox’ economics since the 1970s. Following Lakatos’s concept of scientific research programs (srp), and concentrating on the situation in Germany, the article will discuss classifications of economics, and will specify the understanding of diversity in the light of ‘axiomatic variations’ of the economic mainstream. This will form the basis for the subsequent description of the development of heterodoxy in Germany, with special reference to the founding of new universities and the reform movements in the 1970s. It can be shown that the heterodox scene flourished in this period, but that this pluralization remained fragmented and short-lived; by the 1980s at the latest heterodoxy was again on its way to marginalization. The history of heterodoxy in Germany thus presents itself as an unequal ‘battle of the paradigms,’ and can only be told as the story of a failure