Comparison results for the Stokes equations

This paper enfolds a medius analysis for the Stokes equations and compares different finite element methods (FEMs). A first result is a best approximation result for a P1 non-conforming FEM. The main comparison result is that the error of the P2-P0-FEM is a lower bound to the error of the Bernardi-Raugel (or reduced P2-P0) FEM, which is a lower bound to the error of the P1 non-conforming FEM, and this is a lower bound to the error of the MINI-FEM. The paper discusses the converse direction, as well as other methods such as the discontinuous Galerkin and pseudostress FEMs. Furthermore this paper provides counterexamples for equivalent convergence when different pressure approximations are considered. The mathematical arguments are various conforming companions as well as the discrete inf-sup condition

All-year vehicle simulation with analysis of capacity control of R-134a and R-744 piston compressors for coach HVAC systems

The reheating of cooled air is the state-of-the-art for controlling the air-side cooling capacity in conventional omnibus HVAC systems. This method is pragmatic, albeit highly energy-inefficient. This paper deals with the structured analysis and improvement of capacity regulation for a conventional system using the example of a coach air conditioning system. Piston compressors are typically used in the air conditioning systems for conventional buses. This compressor type belongs to the group of reciprocating compressors and is a common standard in the constant displacement version for large refrigerant systems in the omnibus sector. The compressor is usually driven directly by the internal combustion engine, which is typically realized by using a V-belt and magnetic clutch. Due to the mechanical connection to the engine and the constant compressor displacement, different control strategies are necessary to realize the required variable cooling capacity. These strategies may influence each other resulting in operating conditions with varying degrees of efficiency depending on the application and refrigerant choice. This leads to the main objectives in this paper: Identifying energy-efficient methods of adapting the capacity of reciprocating piston compressors with a constant displacement volume for air conditioning systems in conventional coaches and identifying energy-saving potentials for different refrigerants and application scenarios. For this purpose, the techniques currently being used in series production for implementing capacity adaption in omnibus air conditioning systems were initially described and the procedures such as cycling-clutch operation and cylinder (bank) shutdown were explained. Subsequently, unestablished and novel methods like speed control by means of pulley transmission and continuously variable transmission (CVT), were presented. Systems were identified using a combination of established and newer methods, and the shift in performance, performance control potentials and the impact on total energy consumption were analyzed. For this purpose, a complete physical vehicle model of a coach was developed and validated. The overall model was split into the following subsystems: driving and environmental conditions as boundary conditions, driving dynamics, bus interior, refrigeration cycle, climate controller, engine cooling and heating cycle and electrical system. Special emphasis was placed on the detailed model of the air conditioning system. Monthly representative simulations for two different refrigerants (R‑134a, R‑744) and three climatically different route and journey scenarios (Germany, Portugal/Spain and India) were analysed and compared with a reference system for a conventional coach. Maximum and average annual fuel saving potentials were identified for various methods of adapting the compressor\u27s transport capacity and identifying the most efficient methods for continuous capacity control in omnibus air conditioning systems. Depending on the application and the refrigerant used, the saving potentials in primary energy were between 2.5% and 6.8% based on one year

Transient Experimental and 3D-FSI Investigation of Flapper Valve Dynamics for Refrigerant Compressors

The design of the valves for refrigerant compressors has a distinct influence on the efficiency of the refrigeration cycle. In order to predict the valve behavior for compressor optimization, flow characteristics and valve system dynamics are key factors. State of the art valve model approaches have to date ignored the retainer deflection and the influence of contact effects on fluid-structure interaction behavior. With this fact in mind, experimental valve lift investigations by means of laser vibrometry measurements were performed. In order to determine dynamic flapper valve characteristics, oscillation frequency analyses and numerical natural frequency analyses for free oscillation of the flapper valve were carried out. Additionally this paper presents an extended three-dimensional numerical discharge valve model containing a fully-coupled fluid-structure interaction (FSI) approach. The two-way mechanical coupling is carried out by a commercial CFD code combined with a commercial FEA package. The numerical results are validated using the presented experimental transient results and compared to a lumped 1D valve model. The numerical 3D-FSI results show good agreement with the experimental results and allow for further investigations of multiphysics phenomena such as adhesive effects on the flapper valve

Patterns of biomedical science production in a sub-Saharan research center

<p>Abstract</p> <p>Background</p> <p>Research activities in sub-Saharan Africa may be limited to delegated tasks due to the strong control from Western collaborators, which could lead to scientific production of little value in terms of its impact on social and economic innovation in less developed areas. However, the current contexts of international biomedical research including the development of public-private partnerships and research institutions in Africa suggest that scientific activities are growing in sub-Saharan Africa. This study aims to describe the patterns of clinical research activities at a sub-Saharan biomedical research center.</p> <p>Methods</p> <p>In-depth interviews were conducted with a core group of researchers at the Medical Research Unit of the Albert Schweitzer Hospital from June 2009 to February 2010 in Lambaréné, Gabon. Scientific activities running at the MRU as well as the implementation of ethical and regulatory standards were covered by the interview sessions.</p> <p>Results</p> <p>The framework of clinical research includes transnational studies and research initiated locally. In transnational collaborations, a sub-Saharan research institution may be limited to producing confirmatory and late-stage data with little impact on economic and social innovation. However, ethical and regulatory guidelines are being implemented taking into consideration the local contexts. Similarly, the scientific content of studies designed by researchers at the MRU, if local needs are taken into account, may potentially contribute to a scientific production with long-term value on social and economic innovation in sub-Saharan Africa.</p> <p>Conclusion</p> <p>Further research questions and methods in social sciences should comprehensively address the construction of scientific content with the social, economic and cultural contexts surrounding research activities.</p

Условия формирования и перспективы обнаружения россыпных месторождений пылевидного золота в Украине

Изложены тезисы новой гипотезы гравитационной дифференциации мельчайших твердых частиц в жидкой и твердой, но дезинтегрированной средах. На этой основе прогнозируется образование россыпей пылевидного золота в дельтах Дона, Днепра, Днестра и Дуная, а также на прилегающих к ним частям шельфа Азово-Черноморского бассейна. Приведены доказательства биогенного и хемогенного генезиса некоторой части пылевидного золота. Приведен подсчет результата прогнозных ресурсов самородного мельчайшего золота по трем открытым автором россыпям на шельфе Черного моря, равный в сумме 25 т металла. Они были открыты только благодаря применению устройства “Говерла”.Викладено тези нової гіпотези гравітаційної диференціації дрібних твердих часток у твердому, але дезінтегрированому середовищі. На цій основі прогнозується утворення розсипів пилеподібного золота в дельтах Дону, Дніпра, Дністра й Дунаю, а також на прилеглих до них частинах шельфу Азово-Чорпоморського басейну. Наведено докази біогенного й хемогенного генезису деякої частини пилеподібного золота. Наведено результат підрахунку прогнозних ресурсів самородного найдрібні-шого золота по трьох відкритих автором розсипах на шельфі Чорного моря, які дорівнюють 25т металу. Розсипи були відкриті тільки завдяки використанню пристрою “Говерла”.It is expounded thesises for the new theory about gravitational differentiation of title rocky particles inside rocky environment. On this basis it is forecasted formation of gold flour placers in the deltas of Don, Dnieper, Dniester and Danube, and also on the adjoining part of the Azov-Black Sea shelf. There are introduced the evidence of biogenetical and chemogenetical genesis of some part of the gold flour. It is represented the prognosical resources of three gold placers which was discovered by author on the Black Sea shelf only due to using his device “Goverla”. They are amount to 25 ton of gold flour

Futterbau im Ökologischen Landbau - Futterbauerhebungen im Ökologischen Landbau – Vegetationsperiode 2005

Im Rahmen des Projektes „Unternehmensauswertung Ökologischer Landbau“ der Sächsischen Landesanstalt für Landwirtschaft wurden 16 ökologisch wirtschaftende Landwirtschaftsbetriebe über drei Wirtschaftsjahre betriebswirtschaftlich ausgewertet und einzelne Betriebszweige analysiert. Sechs der 16 Betriebe waren milchviehhaltende, sechs weitere mutterkuhhaltende Betriebe sowie weitere vier reine Marktfruchtbaubetriebe. Die Analysen bezogen sich auf den Marktfruchtbau, den Futterbau sowie die Milchvieh- bzw. Mutterkuhhaltung. Im Bereich des Futterbaus wurden die Erzeugungskosten einzelner Futtermittelarten ermittelt und die Einzelfuttermittel bewertet. Dabei stellte sich im Laufe der Analyse heraus, dass die Betriebsleiterangaben zu den Futterbauverfahren, insbesondere zu den Erträgen, häufig sehr ungenau waren. Teilweise waren keine Mengenaufzeichnungen im Betrieb vorhanden, teilweise wurden nur einfach zählbare Futtermittel quantitativ erfasst (Heuballen, Silageballen), jedoch nicht die in Fahrsilos gelagerten Futtermittel. Die Angaben zu den Einzelgewichten der zählbaren Futtermittel waren häufig geschätzt. Dies führte zu Grundfutterkosten, die nur bedingt belastbar sind. Besondere Schwierigkeiten bereitete die extreme Witterung des Jahres 2003. Viele Betriebsleiter konnten lediglich angeben, dass wesentlich weniger Futter gewachsen ist als in durchschnittlichen Jahren. Genauere Angaben zu Ertragseinbußen konnten nur diejenigen Betriebsleiter machen, die einen Antrag auf Dürrebeihilfe gestellt hatten, weil im Zuge des Antragsverfahrens die Erträge des Jahres 2003 ermittelt und mit den Erträgen der letzten drei Jahre verglichen wurden. Diese Erfahrung führte zu der Entscheidung, innerhalb des Projektes „Unternehmensauswertung Ökologischer Landbau“ genauere Erhebungen im Futterbau durchzuführen. Ziel der Untersuchung war daher vor allem die Erfassung der Nutzungen und die Ermittlung der Futtermittelmengen über eine Vegetationsperiode

Way to increase the efficiency of a reactions: steady and unsteady state catalysis

In the lecture on the example of the process of benzene hydrogenation taking into account the presence of thiophene in the feed gas was discussed approaches to the developing of the unsteady state kinetic model and process optimization. On the base of the kinetic model the theoretical analysis of the reactor performance under unsteady state conditions and unsteady state was carried out.It is shown that for periodic reactor operation an average conversion was up to several times higher than the steady state value

Ultrathin Solar Cell With Magnesium-Based Optical Switching for Window Applications

Photovoltaic windows that can be switched between transparent and energy harvesting mode can be realized by using ultrathin solar absorbers embedded in an optical nanocavity. In the present work, we use a 5 nm thick amorphous germanium absorber integrated in a magnesium-based thin film optical cavity, which switches from an absorptive to a transparent state due to hydrogen absorption. We analyze the influence of the mirror layer thickness on the light absorption, photocurrent generation, and transmission as well as color neutrality of the device. The optical properties are studied by 1-D transfer-matrix method by changing Mg thickness between 0 and 100 nm, then compared to the experimental results of fabricated devices. When the thickness of Mg increases, the switchable average transparency varies between 25% and 0%, while the power conversion efficiency rises up to 2.3%. The applicability of the device is tested by modeling the annual power generation in realistic scenarios. The influence of the cardinal orientation and the seasons on the switchable photovoltaic window implemented in a building facade with the abovementioned parameters is analyzed for different switching scenarios

Maintenance of Leukemia-Initiating Cells Is Regulated by the CDK Inhibitor Inca1

Functional differences between healthy progenitor and cancer initiating cells may provide unique opportunities for targeted therapy approaches. Hematopoietic stem cells are tightly controlled by a network of CDK inhibitors that govern proliferation and prevent stem cell exhaustion. Loss of Inca1 led to an increased number of short-term hematopoietic stem cells in older mice, but Inca1 seems largely dispensable for normal hematopoiesis. On the other hand, Inca1-deficiency enhanced cell cycling upon cytotoxic stress and accelerated bone marrow exhaustion. Moreover, AML1-ETO9a-induced proliferation was not sustained in Inca1-deficient cells in vivo. As a consequence, leukemia induction and leukemia maintenance were severely impaired in Inca1−/− bone marrow cells. The re-initiation of leukemia was also significantly inhibited in absence of Inca1−/− in MLL—AF9- and c-myc/BCL2-positive leukemia mouse models. These findings indicate distinct functional properties of Inca1 in normal hematopoietic cells compared to leukemia initiating cells. Such functional differences might be used to design specific therapy approaches in leukemia

Proteinase-Activated Receptor 1 (PAR1) Regulates Leukemic Stem Cell Functions

External signals that are mediated by specific receptors determine stem cell fate. The thrombin receptor PAR1 plays an important role in haemostasis, thrombosis and vascular biology, but also in tumor biology and angiogenesis. Its expression and function in hematopoietic stem cells is largely unknown. Here, we analyzed expression and function of PAR1 in primary hematopoietic cells and their leukemic counterparts. AML patients' blast cells expressed much lower levels of PAR1 mRNA and protein than CD34+ progenitor cells. Constitutive Par1-deficiency in adult mice did not affect engraftment or stem cell potential of hematopoietic cells. To model an AML with Par1-deficiency, we retrovirally introduced the oncogene MLL-AF9 in wild type and Par1−/− hematopoietic progenitor cells. Par1-deficiency did not alter initial leukemia development. However, the loss of Par1 enhanced leukemic stem cell function in vitro and in vivo. Re-expression of PAR1 in Par1−/− leukemic stem cells delayed leukemogenesis in vivo. These data indicate that Par1 contributes to leukemic stem cell maintenance