Mode I Fracture Toughness of a Small-Grained Silicon Nitride: Orientation, Temperature, and Crack Length Effects

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65267/1/j.1151-2916.1999.tb02134.x.pd

Тепло-гідравлічний розрахунок мережі нафтових трубопроводів на основі двошарового бонд-графу

Purpose. Parallel synchronized calculation of networks with certain hydraulic and thermal properties of separate oil pipelines, which is possible with the use of a two-layer bond graph and a complex methods of potentials in nodes and methods loop currents in circuits. The authors propose to link two layers of graphs of the scheme using the equation of state of oil as a gas-liquid mixture, which will simplify and increase the speed of calculations. Findings. The principles of operation of the ball valve of the shut-off valve and its main differences from the flopper shutter are considered in detail. Also, the geometric parameters of the ball itself are demonstrated in detail. Examples of design are given, and the operating principle of the most common models of shut-off valves is described. Originality. The connection of the hydraulic and thermal layer of the bond-graph is realized by taking into account the average temperatures and the total heat transfer coefficient on the branches of the graph. Practical implications. The developed system of equations of the two-layer bond graph is applied to an estimation of work of networks of oil pipelines at designing and change of operational modes.Мета. Паралельний синхронізований розрахунок трубопровідних мереж з індивідуальними гідравлічними і тепловими властивостями окремих нафтопроводів, який можливий з використанням двошарового бонд-графа (зв'язкового графа) і комплексного поєднання методу потенціалів у вузлах з методом струмів у ланцюгах. Автори пропонують пов'язати два шари зв'язкового графа схеми за допомогою рівняння стану нафти як газорідинної суміші, що спростить і збільшить швидкість попередніх технологічних розрахунків. Висновки. Застосування зв'язування шарів бонд-графу щодо гідравлічних і теплових характеристик можливе із застосуванням ряду усереднених термобаричних параметрів. В цьому випадку гідравлічна ділянка може вважатися такою, на якій є середня температура і середній показник теплообміну, що дозволяє синхронізувати шари і привести їх до єдиної і уніфікованої нумерації гілок і вузлів. Прийом виявився програмно-працездатним і перевірений на практиці для моделювання та попередньої оцінки технологічних режимів роботи мережі нафтопроводів. Оригінальність. Зв'язок гідравлічного і теплового шарів бонд-графу реалізовано з урахуванням середніх температур і сумарного коефіцієнта теплопередачі на гілках графа. Практичне значення. Розроблена система рівнянь двошарового графа зв'язків (бонд-графа) застосовується для інженерної оцінки роботи мереж нафтопроводів при технологічному проектуванні і зміні режимів роботи ділянок мережі нафтопроводів

Совершенствование системы оплаты труда (на примере АО «Алмалыкский ГМК»)

Ключевые слова: мотивация труда, производительность труда, оплата труда, заработная плата, национальная экономика, рыночная экономика и т.д. Объектом исследования выступает медеплавильный завод АО "Алмалыкский ГМК". Цель данной выпускной квалификационной работы – предложить пути совершенствования системы оплаты труда на примере медеплавильного завода АО "Алмалыкский ГМК". В процессе исследования рассматриваются факторы, воздействующих на модификацию заработной платы и производительности труда в данной организации.Keywords: labor motivation, labor productivity, labor remuneration, wages, national economy, market economy, etc. The object of the study is the copper smelter of Almalyk MMC JSC. The purpose of this final qualification work is to suggest ways to improve the remuneration system on the example of the Almalyk MMC copper smelter. In the course of the research, the factors influencing the modification of wages and labor productivity in a given organization are considered

GP-9s Are Ubiquitous Proteins Unlikely Involved in Olfactory Mediation of Social Organization in the Red Imported Fire Ant, Solenopsis invicta

The red imported fire ant (RIFA), Solenopsis invicta, is an invasive species, accidentally introduced in the United States that can cause painful (sometimes life-threatening) stings to human, pets, and livestock. Their colonies have two social forms: monogyne and polygyne that have a single and multiple functional queens, respectively. A major gene (Gp-9), identified as a putative pheromone-binding protein on the basis of a modest amino acid sequence identity, has been suggested to influence the expression of colony social organization. Monogyne queens are reported to possess only the GP-9B alleles, whereas polygyne queens possess both GP-9B and GP-9b. Thus, both social forms are reported to express GP-9B, with GP-9b being a marker expressed in polygynes but it is absent in monogynes. Here, we report two types of polygyne colonies, one that does not express GP-9b (monogyne-like) and the other expressing both proteins, GP-9B and GP-9b. Given their expression pattern, GP-9s are hemolymph proteins, which are more likely to be involved in the transport of lipids and small ligands within the homocoel. GP-9B existed in two forms, one of them is phosphorylated. The helical-rich content of the protein resembles the secondary structures of a beetle hemolymph protein and moth pheromone-binding proteins. An olfactory role is unlikely given the lack of specific expression in the sensillar lymph. In marked contrast to GP-9s, a chemosensory protein, SinvCSP, is demonstrated to be specifically expressed in the antennae. Within the antennae, expression of SinvCSP is restricted to the last two segments, which are known to house olfactory sensilla

Effect of hyperbaric oxygen on mesenchymal stem cells for lumbar fusion in vivo

<p>Abstract</p> <p>Background</p> <p>Hyperbaric oxygen (HBO) therapy has been proved in improving bone healing, but its effects on mesenchymal stem cells (MSCs) <it>in vivo </it>is not clear. The aims of this study are to clarify whether the HBO therapy has the same enhancing effect on MSCs with regard to bone formation and maturation and to ascertain whether the transplanted MSCs survive in the grafted area and contribute to new bone formation.</p> <p>Methods</p> <p>Twenty-three adult rabbits underwent posterolateral fusion at L4-L5 level. The animals were divided into three groups according to the material implanted and subsequent treatment: (1) Alginate carrier (n = 6); (2) Alginate-MSCs composite (n = 11); and (3) Alginate-MSCs composite with HBO therapy (n = 6). After 12 weeks, spine fusion was examined using radiographic examination, manual testing, and histological examination. Using a PKH fluorescence labeling system, whether the transplanted MSCs survived and contributed to new bone formation in the grafted area after HBO therapy was also examined.</p> <p>Results</p> <p>The bilateral fusion areas in each animal were evaluated independently. By radiographic examination and manual palpation, union for the Alginate, Alginate-MSCs, and Alginate-MSCs-HBO groups was 0 of 12, 10 of 22, and 6 of 12 respectively. The difference between the Alginate-MSCs and Alginate-MSCs-HBO groups was not significant (P = 0.7997). The fluorescence microscopy histological analysis indicated that the transplanted PKH67-labeled MSCs survived and partly contributed to new bone formation in the grafted area.</p> <p>Conclusions</p> <p>This study demonstrated that the preconditioned MSCs could survive and yield bone formation in the grafted area. HBO therapy did not enhance the osteogenic ability of MSCs and improve the success of spine fusion in the rabbit model. Although there was no significant effect of HBO therapy on MSCs for spine fusion, the study encourages us to research a more basic approach for determining the optimal oxygen tension and pressure that are required to maintain and enhance the osteogenic ability of preconditioned MSCs. Further controlled <it>in vivo </it>and <it>in vitro </it>studies are required for achieving a better understanding of the effect of HBO treatment on MSCs.</p

Synthesis and characterization of hypoxia-mimicking bioactive glasses for skeletal regeneration

The cellular response to hypoxia (low oxygen pressure) is vital for skeletal tissue development and regeneration. Numerous processes, including progenitor cell recruitment, differentiation and angiogenesis, are activated via the hypoxia pathway. Novel materials-based strategies designed to activate the hypoxia pathway are therefore of great interest for orthopaedic tissue engineering. Resorbable bioactive glasses (BGs) were developed to activate the hypoxia pathway by the controlled release of cobalt ions (at physiological relevant concentrations) whilst controlling BG apatite-forming ability. Two series of soda-lime-phosphosilicate glasses were synthesised with increasing concentrations of cobalt. Compositions were calculated to maintain constant network connectivity (2.13) by considering that cobalt is taking part in the network in the first series, and is acting as a network modifier in the second series. Mg2+ and Zn2+ were added to one of the Co2+-containing glasses to inhibit HCA formation. The presence of HCA formation is undesirable for the use of BG in soft tissues e. g. cartilage. Cobalt was present in both the silicate and phosphate phases of the BG. In addition, evidence was found that it plays a dual role in the silicate phase, entering the network as well as disrupting it as a network modifying oxide. Consistent with this dual role, the presence of cobalt in the BG was shown to decrease ion release. HCA formation was delayed with cobalt addition as well as incorporation of Mg2+ and Zn2+ into the BGs. Importantly, cobalt release was found to be proportional to cobalt content of the BGs enabling the controlled delivery of cobalt in therapeutically active doses

Constrained sintering kinetics of 3YSZ films

This article was published in the Journal of the European Ceramic Society [© Elseview Ltd.] and the definitive version is available at: http://dx.doi.org/10.1016/j.jeurceramsoc.2011.05.0443YSZ green layers approximately 10 μm thick were screen-printed onto 3YSZ substrates and their constrained sintering kinetics were measured at 1100–1350 °C using an optical dilatometer. The densification rates of the same powder in the form of pellets and free-standing films were also measured. The constrained densification rate was greatly retarded compared with the free densification rate at a given temperature and density. The retardation increased with increasing density and temperature and could not be properly accounted for by existing theories of constrained sintering. As a result the apparent activation energy is much lower for constrained sintering (135 ± 20 kJ mol−1) than for free sintering (660 ± 30 kJ mol−1). It is proposed that this is because the constrained microstructure exhibits larger and more widely separated pores at the higher temperatures

Quantitative Analyse des Kniegelenkknorpels von Marathonläufern, Marathon-Debütanten und etablierten Wettkampfläufern, mittels 3D-Magnetresonanztomographie

Die weltweit steigende Teilnehmerzahl bei Volks- und Marathonläufen zeigt, dass sich das Langstreckenlaufen in den letzten Jahren zum Volkssport entwickelt hat [Merz, 2004]. Das Streben vieler Freizeitläufer, außergewöhnliche sportliche Leistungen zu erbringen und beim Marathon an die eigenen Grenzen zu stoßen, birgt jedoch auch die Gefahr von Überlastungsreaktionen und Verletzungen besonders des Kniegelenks [Hohmann et al., 2005]. In welchem Maße die Belastungen beim Langstreckenlaufen physiologische Grenzen überschreiten und damit den hyalinen Gelenkknorpel schädigen sowie die Gonarthroseentstehung begünstigen, konnte bislang noch nicht eindeutig geklärt werden. Ziel unserer Studie war es, den hyalinen Knorpel im Kniegelenk zu quantifizieren (Knorpelvolumen und -dicke), um auf dieser Grundlage Rückschlüsse auf ein möglicherweise erhöhtes Arthroserisiko bei Marathonläufern ziehen zu können. Zu diesem Zweck erfolgte die Untersuchung aller Probanden, mit einem weit verbreiteten MRT-Gerät (1.5 T Magnetom Symphony, Siemens). Spezielle MRT-Sequenzen (qMRT) in Kombination mit digitalen Bildbearbeitungsprogrammen ermöglichen eine exakte drei-dimensionale Analyse der quantitativen Knorpelparameter Volumen und mittlerer Dicke im Kniegelenk. Bei den Wettkampfanfängern (5 Frauen und 6 Männer; 39.5 ± 4.8 Jahre; 75.9 ± 18.2 kg; BMI 25.1 ± 3.5 kg/m2) erfolgten die MRT-Messungen zu Beginn ihrer sechsmonatigen Vorbereitung auf den Frankfurt-Marathon und in den ersten Tagen nach dem Rennen. Die durchschnittliche Laufleistung der Marathon-Debütanten, die im Schnitt seit 3 Jahren freizeitmäßig joggten, lag bei 34 km/Woche während des sechsmonatigen Marathontrainings. Die fortgeschrittenen Wettkampfläufer (12 Männer; 37.9 ± 7.4 Jahre; 75.2 ± 5.4 kg; BMI 23 ± 1.3 kg/m2) wurden vor und nach einem Trainings- und Wettkampfjahr untersucht, in dem sie ein durchschnittliches Laufpensum von 67 km pro Woche absolvierten. Eine validierte T1-gewichtete Gradientenechosequenz mit Wasseranregungstechnik (FLASH: TR = 49 ms, TE = 10.3 ms, FA = 30°, Auflösung = 0.156 mm x 0.156 mm, Schichtdicke 1.5 mm, Matrix = 512 Pixels x 512 Pixels, Bildausschnitt [FOV] = 160 mm x 160 mm) diente zur Akquisition koronarer Datensätze des femoralen und tibialen Knorpels (jeweils laterales und mediales Kompartiment) und transversaler Datensätze des patellaren Gelenkknorpels. Nach manueller Segmentierung und 3D-Rekonstruktion erfolgte die Analyse der quantitativen Knorpelparameter. Die Veränderungen von Knorpelvolumen und mittlerer Knorpeldicke im Zeitverlauf wurden prozentual dargestellt und die Signifikanz mittels gepaartem T-Test berechnet. Bei den Wettkampfanfängern zeigte sich keine signifikante Reduktion der Knorpeldicke oder des Knorpelvolumens, lediglich am lateralen Femur war eine signifikante Reduktion von Knorplvolumen (-3.2 ± 3.0 %, p = 0.012) und mittlerer Knorpeldicke (-1.7 ± 1.6 %, p = 0.010) zu finden. Da jedoch die Schwankungen vom Knorpelvolumen im Tagesverlauf und nach 50 Kniebeugen größer sind als die prozentualen Veränderungen am lateralen Femur, kann die berechnete signifikante Abnahme nicht als relevanter Knorpelverlust oder -verschleiß interpretiert werden. Die fortgeschrittenen Wettkampfläufer wiesen in keinem der fünf Knorpelkompartimente des Kniegelenks (laterale und mediale Tibia, lateraler und medialer Femur und Patella) eine signifikante Zu- oder Abnahme der Knorpelparameter auf. Die Ergebnisse dieser Studie legen den Schluss nahe, dass die andauernden und hohen axialen Lasten beim Langstreckenlaufen, vom Kniegelenksknorpel der Marathon-Debütanten und etablierten Wettkampfläufer gut toleriert werden. Insgesamt liefert die quantitative Analyse der Knorpelmorphologie im Kniegelenk keine Anhaltspunkte für ein erhöhtes Risiko der vorzeitigen Arthroseentstehung bei Marathonläufern.The worldwide rising number of participants in marathons demonstrates, that long-distance running has become a very popular sport in recent years. The attempt of many recreational runners to perform extraordinarily in sports and to experience their limits in marathon competitions could increase the risk of overloading reactions and injuries especially of the knee joint. Whether the repetitive load impact associated with long-distance running exceeds physiological limits and causes cartilage damage and thus increases the risk of osteoarthritis remains controversial. The aim of this study was to provide quantitative data of the hyaline articular cartilage of the knee joint (cartilage volume and thickness) in order to allow conclusions regarding a possibly increased osteoarthritis risk for marathon runners (marathon-debutants and advanced competition runners). To examine the assumption of increased risks the participants underwent magnetic resonance imaging (1.5 T Magnetom Symphony, Siemens). Special MRI- pulse sequences allowed in combination with digital image analysing tools an exact three-dimensional examination of the quantitative cartilage volume and thickness of the knee joint. The group of marathon-debutants (5 female and 6 male; 39.5 ± 4.8 years; 75.9 ± 18.2 kg; BMI 25.1 ± 3.5 kg/m2) underwent a MRI examination six month before participating in their first marathon, the Frankfurt-Marathon. The second examination was carried out a few days after the competition. During the six months training period the average running distance of the members of this group, who had on average 3 years of jogging experience, was 34 km / week. The advanced runners (12 male; 37.9 ± 7.4 years; 75.2 ± 5.4 kg; BMI 23 ± 1.3 kg/m2) were examined by MRI before and after their competition year. They prepared their marathons with a mean running distance of 67 km / week. MRI was performed using a validated T1-weighted spoiled gradient echo sequence with selective water excitation (FLASH: TR = 49 ms, TE = 10.3 ms, FA = 30°, in plane resolution = 0.156 mm x 0.156 mm, slice thickness = 1.5 mm, matrix = 512 pixel x 512 pixel, FOV = 160 mm x 160 mm) to acquire coronal data sets of the femoral und tibial cartilage and transversal data sets of the patellar articular cartilage. After manual segmentation and three-dimensional reconstruction the quantitative cartilage parameters were determined. The change of cartilage volume and mean thickness within the time between the two examinations was derived and the statistical significance was evaluated by using an paired t-test. The articular cartilage of the marathon-debutants showed no significant reduction of volume and thickness, only the lateral femur exhibited a significant decrease of the cartilage volume (-3.2 ± 3.0 %, p = 0.012) and mean thickness (-1.7 ± 1.6 %, p = 0.010). However, the variations of cartilage volume in the course of the day and after 50 knee bends are larger than the percentage changes of the lateral femur so that the calculated significant reduction can not be interpreted as relevant cartilage decrease or wear. In the group of advanced competition runners no significant increase or decrease of the quantitative cartilage parameters of the knee joint was found. The results of our study indicate that continuous and high axial loads during long-distance running of both, marathon-debutants and advanced competitors, are well tolerated by the articular cartilage of the knee. In conclusion, the quantitative analysis of the cartilage morphology in the knee joint of marathon runners showed no evidence for an increased risk of an early onset of osteoarthritis